PAPERmaking! Vol.10 No.2 2024

PAPERmaking!

The e-magazine for the Fibrous Forest Products Sector

Produced by:

The Paper Industry Technical Association Publishers of:

Paper Technology International®

Volume 10 / Number 2 / 2024

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

CONTENTS: FEATURE ARTICLES: 1. Paperboard: Relating papermaking process parameters to paperboard properties.

2. Tissue: Simulation of sheet moulding during TAD processing.

3. Chemistry: ASA for better sizing – a review.

4. Environment: CO2 emissions accounting of Chinese paper industry.

5. Water Treatment: Quality evaluation of water disclosure of Chinese paper mills.

6. Sustainabililty: Recycling various papermaking wastes as eco-friendly slurry.

7. Wood Panel: Antibacterial Medium-Density Fibreboard (MDF) production.

8. Packaging: Barrier coating and tray forming of paperboard.

9. Social Media: Using X (Twitter) for business.

10. Eye Health: Easy steps to keep your eyes healthy.

11. Sitting Posture: Tips for improving posture at your computer desk.

12. AI in the Office: Possible uses of AI to improve the office environment.

SUPPLIERS NEWS SECTION: News / Products / Services: • • •

Section 1 – PITA CORPORATE MEMBERS AFT / ARCHROMA / VALMET Section 2 – PITA NON-CORPORATE MEMBERS ANDRITZ / VOITH Section 3 – NON-PITA SUPPLIER MEMBERS KADANT / KONECRANES / SICK Advertisers: ABB

DATA COMPILATION: Events: PITA Courses & International Conferences / Exhibitions Installations: Overview of equipment orders and installations between Feb. and June.

Research Articles: Recent peer-reviewed articles from the technical paper press.

Technical Abstracts: Recent peer-reviewed articles from the general scientific press.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Contents

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Relating papermaking process parameters to properties of paperboard with special attention to through‑ thickness design MIKAEL NYGÅRDS1,2 A biaxial stress state has been proposed to formulate a failure criterion for paperboard during bending. About 100 paperboards have been splitted, such that top, middle, and bottom plies have been free-laid and tested in the machine direction, cross-machine direction as well as in out-of-plane direction (ZD). The purpose was to determine the failure stresses and its dependency of papermaking parameters: density, degree of orientation, and fiber length for each layer. A linear model to predict the geometrical strength of a plies was suggested.

Analytically simulations of different paperboard structures behavior during bending were performed. The density of the middle ply affected the location of the failure position in ZD, as well as the maximum bending moment. The impact of orientation and degree of anisotropy was simulated, which can be used to optimize the ZD property gradient by tweaking the properties, and hence optimize paperboard performance.

Contact information: 1 BillerudKorsnäs, 801 81 Gävle, Sweden.

2 Solid Mechanics, Department of Engineering Mechanics, KTH, 100 44 Stockholm, Sweden.

MRS Advances (2022) 7:789–798 https://doi.org/10.1557/s43580-022-00282-7 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 11

Article 1 – Paperboard Properties

MRS Advances (2022) 7:789–798 https://doi.org/10.1557/s43580-022-00282-7

ORIGINAL PAPER

Relating papermaking process parameters to properties of paperboard with special attention to through‑thickness design Mikael Nygårds1,2 Received: 23 March 2022 / Accepted: 26 April 2022 / Published online: 6 May 2022 © The Author(s) 2022

Abstract A biaxial stress state has been proposed to formulate a failure criterion for paperboard during bending. About 100 paperboards have been splitted, such that top, middle, and bottom plies have been free-laid and tested in the machine direction, cross-machine direction as well as in out-of-plane direction (ZD). The purpose was to determine the failure stresses and its dependency of papermaking parameters: density, degree of orientation, and fiber length for each layer. A linear model to predict the geometrical strength of a plies was suggested. Analytically simulations of different paperboard structures behavior during bending were performed. The density of the middle ply affected the location of the failure position in ZD, as well as the maximum bending moment. The impact of orientation and degree of anisotropy was simulated, which can be used to optimize the ZD property gradient by tweaking the properties, and hence optimize paperboard performance.

Introduction In the papermaking process, fibers with different fiber length are mixed into a pulp. In the process, it is possible to steer a paperboard machine to control the density by refining and by chemical additives in different plies in a paperboard. It is also possible to steer the orientation of the fiber by controlling the headbox outlet speed in relation to the moving web.

Hence, by utilizing papermaking parameters paperboards can be engineered to have different properties in the plies of a multiply paperboard.

The product paperboard is characterized with respect to its bending stiffness, thickness, or grammage. To optimize these properties and the paperboard functionality the through-thickness (ZD) profile can be engineered. The straightforward path to optimize the bending stiffness would be to make a paperboard with and I-beam structure. However, when a paperboard is folded an I-beam structure might not be optimal to comply with the stress state that arise. One complicating factor is that the in-plane tensile and compression behavior is different for paperboard [1]. Depending on

* Mikael Nygårds Mikael.nygards@billerudkorsnas.com 1

BillerudKorsnäs, 801 81 Gävle, Sweden

2

Solid Mechanics, Department of Engineering Mechanics, KTH, 100 44 Stockholm, Sweden

how the ZD profile is engineered different failure mechanisms can be activated when a paperboard is folded.

Before a paperboard becomes a package, it needs to be converted; creasing is used to score the paperboard such that it will fold along pre-defined lines [2]. For optimal converting behavior it is important to control where the intentional damage created during creasing develops. This put additional requirements on the paperboard design that can be considered for optimal folding performance.

The key element to design paperboard properties in the ZD is to utilize multiply board structures, such that at least three plies can have different properties. To evaluate how the effect of the papermaking process in each ply, it is necessary to freelay the plies and perform testing, where the intention is to isolate the constituent plies, and test each of them separately.

While multiply paperboard has been available for a long time, effective and rigorous methods to free-lay (or isolate) the plies have not been available until recently. Initially surface grinding was used [3], and the technique has also successfully been used to determine properties of top, middle, and bottom plies [4–7].

The technique works to determine properties, but is dependent on good calibration of the machinery, and is very time consuming. A more time efficient machine has been developed

by Fortuna Gmbh [8], where a rotating knife is placed after a nip. With this technique top, middle, and bottom plies can be free-laid in a very time efficient procedure. The machine has also been used to characterize properties of plies [9–11].

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Vol.:(0123456789)

790

M. Nygårds

The aim of this work would be to implement analytical models that can be used to predict the performance of paperboards. It will be based on how it is constructed in the thickness direction using the properties of three plies in the paperboard structures. This will be done by utilizing laminate theory Fellers and Carlsson [12] and Fellers [13], and Timoshenko beam bending [14] to construct a model that can predict the maximal bending moment for paperboards based on papermaking variables such as density, fiber orientation, and fiber length.

Theoretical background In the analysis, we will assume that in-plane tensile and outof-plane shear stresses will contribute to failure during folding. With laminate theory, it is possible to calculate how a multilayer structure respond to external forces, which helps us to develop a ZD structure with accurate bending stiffness.

Elastic bending Bending stiffness of paperboard is normally measured by twopoint bending, when the bending arm is L = 50 mm [15]. With this configuration the shear stress component is negligible.

Bending of a homogenous cantilever beam with a rectangular cross section will be performed with a bending moment Mb per unit width. A tensile stress will arise on the convex side of the beam, and compressive stresses on the concave side.

The theoretical framework for evaluation of the bending stiffness for multiply paperboards have been derived by Fellers and Carlsson [12] and Fellers [13]. By using the definition of bending moment, integrating the elastic stress in the beam and by utilizing strain compatibility the bending moment for a homogenous beam with thickness, t, and rectangular cross section the bending moment becomes h∕2

Sb =

∫ −h∕2

Ez2 dz =

Et3 .

12

(1)

In the two-point bending setup, one end of the paperboard is clamped, and the other end is loaded by a concentrated load.

The bending moment then decreases linearly as the distance x from the clamped end increase. If small deformations are assumed during the bending stiffness measurements, then the maximum deflection δ becomes

𝛿=

F b l3 .

3Sb

(2)

Then bending stiffness which is evaluated as the steepest slope of a F − δ plot, becomes

13

ΔF b S = Δ𝛿 b

( 3) l .

3

(3)

If the angle, θ, is measured in degrees the bending stiffness is given by ( ) ΔF b 60l2 Sb = .

(4) Δ𝜃 𝜋 The two-point bending is commonly used as a quality control in industry. Then w = 38 mm wide samples are bent, and L = 50 mm is used. For this test, the force, PSb, that is read on the testing device is often interpreted as the bending moment of the paperboard

PSb =

15𝜋wSb .

60L2

(5)

Multi-ply paperboards consist of several plies, which can represent layers in a laminate. With a multi-ply model, it would be possible to calculate the bending stiffness. The model can be used to make predictions, and hence extend the design space for multi-ply paperboards. The ability to make calculations is beneficial for optimization, since it can give an indication of the choice of raw material, grammage, and ply layout. For multi-ply paperboard the same strategy as for homogenous plies are applied. However, it needs to be accounted for that the plies are not located along the neutral line. Then bending stiffness for a multi-ply structure can then be expressed as

Sb = D −

B2 , A

where ∑ ) ( A= Ek × zk − zk−1 ,

(6)

(7)

B=

( ) 1∑ Ek × z2k − z2k−1 , 2

(8)

D=

( ) 1∑ Ek × z3k − z3k−1 , 3

(9)

zk = zk−1 + tk for k = 1, 2, … , N,

(10)

where Ek is the elastic modulus of ply k, which might be in either MD or CD. The ply coordinates zk (Fig. 9) (k = 0, 1, 2, …., N) where N is the number of plies, are calculated as

z0 = −

t for k = 0, 2

(11)

where t is the total thickness of the paperboard. The bending stiffness is dependent of the thickness and grammage of the different plies.

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Relating papermaking process parameters to properties of paperboard with special attention…

Maximum bending moment during folding Two-point bending, or a cantilever configuration is often used to measure the bending stiffness of paper and paperboard. Folding of a paperboard will give an initial linear response associated with the bending stiffness. Thereafter, a peak bending moment will be reached, which is followed by a non-linear response as the paperboard is folded 90°.

To evaluate bending stiffness the standard span is L = 50 mm. This ensures that the shear component during folding is small. On the other hand, a span of only L = 10 mm is used when folding both uncreased and creased paperboards. To analyze the stress state in the paperboard during folding a Timoshenko beam analysis [14] can be applied to uncreased paperboard samples, see further Nygårds [16].

The stress state then consists of two components, an in-plane tensile/compressive stress, σx, and an out-of-plane shear stress, τxz, which is expressed as

𝜎x =

M z PL PL z = 12 3 z = 12 b 3 , I w t wt

and

P 𝜏xz = 2I

(12)

stress state. Here the difference is however smaller than a factor 2 in density, hence the effect should be neglectable compared to other assumptions. It also has a large dependency of thickness. In thick paperboard, and paperboards with low τf or high σf the shear stress component will become larger than the normal stress component.

This means that it will contribute to failure, basically the paperboard will shear and cause failure. L = 10 m is an idealized lab setting, bending of paperboards can occur, with shorter bending arm, L, the shear component will be even more important. The conclusion from this is that the out-of-plane shear properties affect the folding behavior for paperboard grades, yet it can be disregarded for nonpaper materials.

Because of the biaxial stress state, a failure criterion needs to be formulated. The idea here is to keep it simple to enable predictions of failure. It should also cover the simple mechanisms that have been observed, which are: • Normalized stress components should be used.

• If the normal stress is positive, shearing will be more

difficult since the fibers are stretched.

( 2 ) ( ) d 3 P z2 2 1−4 2 , −z = 4 2t w t

• If the normal stress is negative, shearing will be easier

(13)

where t is the sample thickness, w the width, and z the distance from the neutral line of the specimen. For most materials, the shear component will be small, and can be neglected.

However, due to the orthotropy in paper materials, where the in-plane stiffness and strength are much greater than the out-of-plane stiffness and strength, the shear component will impact the behavior. For this purpose, it will be of interest to evaluate the stress components in relation to its measured failure stresses, σf and τf, accordingly

𝜎x PL z , = 12 w 𝜎 f t3 𝜎f

(14)

and

( ) 𝜏xz 3 P z2 = 1−4 2 . 𝜏f 2t𝜏f w t

(15)

In the analysis, it was assumed that the failure stress is homogenous in the thickness direction, hence the paperboard does not have a property gradient. This is an obvious simplification in the case of multiply paperboard, which will not have a homogeneous stress distribution in the thickness direction. It shows that within the normal limit of failure properties there is shift of dominating stress component. However, it should also be emphasized that if there is large difference in properties of the outer plies and the middle ply, this will also affect the parabolic shear

since the paperboard ply can buckle.

• For simplicity no mixed terms are accounted for.

Using the assumptions above it was assumed that

| 𝜎 𝜏 | f = || f − f || = 1, | 𝜎 (z) 𝜏 (z) |

(16)

where σf(z) and τf(z) are the failure stresses that are different in the different plies. Out-of-plane shear strength is needed to evaluate the folding behavior. Normally out-of-plane shear strength can be associated with breaking of bonds within the sheets. In the literature out-of-plane shear properties are often lacking. Instead, ZD strength is most often measured strength value. A fair approximation base on the work by Stenberg et al. [17] is

𝜏 f (z) = 3 ∗ 𝜎ZD (z).

(17)

Hence, the failure criterion can be express as ) ( 3 PL || 12 z2 || f (z) = 1 − 4 2 | = 1. | f 3z − f w || 𝜎 (z)t t || 6𝜎ZD (z)tL

(18)

The failure criterion has been plotted in Fig. 1 for some different combinations of uniform failure stresses σ f and f f 𝜎ZD . This show that as 𝜎ZD decreases the failure mechanism is changing from in-plane tension/compression, i.e., failure close to the outer surfaces, that is dominated by the network structure to out-of-plane shear, i.e., failure within the paperboard, that is dominated by bond strength.

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Fig. 1 The failure criterion plotted for a 400 μm paperboard with different normal and shear failure stresses. In bending the paperboards will fail in the z-position, where the normalized stress is maximal

Results Properties of free‑laid plies Paperboards from a series of trial productions have been splitted (Fortuna [8] to free-lay the top, middle, and bottom plies.

About 100 paperboards with various properties was used in the study. The paperboards were selected to have variation in the different plies to represent the limits with respect to density, fiber orientation etc. within each layer. The plies have been characterized with respect to physical properties and tensile tests to measure density, degree of anisotropy, strength, and stiffness within each layer. The in-plane tensile properties were measured using ISO 1924-2, while the ZD tensile test was measured using ISO 15754. Normally the variation of strength is about 10% when whole paperboard is tested, which is due to the inhomogeneous fiber structure that can have density variations. When free-laid plies are tested, the strength variation is about the same. However, the splitting procedure is also a source of variation, since thickness of the free-laid plies can vary between splits. The aim here has been to try to position the splitting position to the middle of the interface. However, the interface has a thickness of 10–20 mm, hence some fibers from the neighboring ply will still be found on the free-laid ply. The variation of strength properties would then be about 10% and is the main reason to the variations seen in Figs. 2, 3, 4, 5. The data will be used to formulate simplified models that can be used to make qualitative analytical predictions, in these we will not consider variation at this time. Of interest will be to identify the importance of papermaking parameters

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such as density, fiber orientation, and fiber length to predict strength and stiffness.

Since paperboard is orthotropic the geometrical mean strength is often calculated from the strength in the machine direction (MD) and cross-machine direction (CD) [18], √ b b 𝜎0 = 𝜎MD 𝜎CD ..

(19) In this work several paperboards have been tested, a different feature between the paperboards was the fiber orientation.

From tensile testing of paperboards with different fiber orientation it was established that as the MD/CD strength ratio varied; in fact, the tensile strengths in MD and CD were invariant, see Fig. 2, where the top, middle, bottom plies have the same behavior as the whole paperboard.

The strength of a paperboard in arbitrary direction was expressed as (20)

𝜎 = 𝜎0 A,

where A is the degree of anisotropy, which by rearranging Eq. (19) the strengths in MD and CD can be expressed as � b b 𝜎MD ⎧ 𝜎MD for MD, where ≥1 b b ⎪ 𝜎 𝜎CD , A = ⎨ � CD (21) b b ⎪ 𝜎bCD for CD, where 𝜎MD < 1 b ⎩ 𝜎 𝜎 MD

CD

𝜎b

= 1. At where σ0 is the strength of an isotropic sheet, at 𝜎MD b CD

this stage it can be concluded that the Eqs. (20–21) can be

793

Relating papermaking process parameters to properties of paperboard with special attention…

2.50

2.00

Normalized failure stress σ/σ0GM

Fig. 2 Tensile strength as function degree of anisotropy for the whole paperboard and the free-laid plies

1.50

1.00

0.50

Board MD 0.00 1.000 1.100

Board CD 1.200

TP MD 1.300

TP CD

MP MD

1.400

1.500

MP CD 1.600

BP MD 1.700

BP CD 1.800

1.900

2.000

Degree of anisotropy, A

Fig. 3 Strength of free-laid plies as function of density

50.0 σ 0/Lfiber [MPa/mm]

45.0 40.0 35.0 30.0 25.0 20.0 15.0 10.0

400

500

600

700 3 Density [kg/m ]

800

900

1000

900

MP BP TP 1000

4000.0 3500.0

EGM/Lfiber [MPa/mm]

Fig. 4 The geometrical mean in MD and CD elastic modulus normalized with fiber length show a liner relation with density

MP BP TP

3000.0 2500.0 2000.0 1500.0 1000.0 500.0 0.0

400

500

used to make fair approximations about the fiber orientation effect on the plies.

The density of the paperboard plies as well as the fiber length will affect the strength properties. If the strength σ0

600

700 Density [kg/m3]

800

was plotted versus density one can see that the strengths of the three plies became grouped into different clusters.

The difference could be explained by the difference in fiber length of the fibers used in the different plies. Here, we

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M. Nygårds

Fig. 5 ZD strength of whole paperboards plotted versus the density of middle plies

400 380

ZD strength [kPa]

360 340 320 300 280 260 240

420

440

460

assume that the following average fiber lengths apply to the different plies: • Bottom ply Lfiber = 2.0 mm, • Middle ply Lfiber = 1.3 mm, • Top ply Lfiber = 1.5 mm.

This is essentially a curve-fitting of the data, but it has a physical relevance. The bottom plies were made of softwood fibers, the top plies had different mixtures of hardwood and softwood fibers, while the middle plies had mixtures of softwood, hardwood, broke, and CTMP. All these measurements were also in agreement with measurement of average fiber length for headbox pulp samples. However, due to the large number of paperboards tested, there are samples the deviate from these fiber lengths. Then one gets the plot in Fig. 3, where the ration σ0/Lfiber has been plotted for three plies. In Fig. 3 it was obvious that the density and σ0/Lfiber were different for the different plies. By doing a linear regression it became evident that the failure stress, 𝜎0 , of the ply data in Fig. 3 can be simplified into a simple equation

𝜎0 = 0.03𝜌Lfiber .

(22)

The aim of plotting the tensile properties of the free-laid plies was to find relations to different parameters that easily can be controlled during machine trials. This was identified to be density, fiber length, and fiber orientation (here expressed as a function of the MD/CD strength ratio). Based on this, simple expression was found that can be implemented in the derived stress state during folding. Here we found that the tensile strength can be expressed as:

𝜎 = 0.03𝜌Lfiber A.

(23)

Normally the tensile strength and tensile stiffness is correlated in paper materials. In Fig. 4, it should be noted

13

480

500

Density [kg/m3]

520

540

560

that the ratio tensile stiffness/fiber length also has almost a linear correlation with density for the free-lied plies.

There is a deviation for the top ply at high densities. This should be due to the long fiber length that cause greater entanglement between the fibers, and lead to fiber failure rather than bond failure where the fibers are torn out of the fiber network. To make a simple model of stiffness in relation to strength it can be assumed that

E = 3.0𝜌Lfiber A.

(24)

Typically, ZD tensile tests are performed on the whole paperboard. This is since testing on free-laid middle plies can show smaller ZD strength values, because damage can be initiated during the splitting operation. Therefore, we will present ZD strength tested on whole paperboard, but it will be presented against the middle ply density, since this is most physically relevant since the ZD tensile failures occurs in the middle ply. In Fig. 5, the ZD strength density can be seen, and a linear trend can be observed, yet there is variation. A linear trend would be expected since ZD tensile strength correlates with the number of bonds in the fiber network. Formations effects that give local variation of density, as well of ply strength in relation to interface strength will, however, contribute to the observed variation. For the modeling purpose it will however be relevant to assume that denser middle plies give higher ZD strength, that based on the data in Fig. 5 can be assumed to follow f 𝜎ZD = 0.7 ∗ 10−3 𝜌 MPa.

(25)

Based on properties of the free-laid sheets it has been possible to develop models that express the failure stresses as function of the papermaking parameters: density, fiber orientation, and fiber length, which are parameters that can be altered during the papermaking process. The derived

Relating papermaking process parameters to properties of paperboard with special attention…

models are now inserted in the failure envelope (Eq. 18), hence ( ) z2 || 833t2 PL || 400 1 − 4 2 | = 1. z− f = 3 | (26) L wt 𝜌 || Lfiber A t || Or expressed in MD and CD √ | √ b )| ( | 𝜎CD 833t2 z2 || PL | 400 √ √ z − 1 − 4 2 | = 1, (27) fMD = 3 | b L wt 𝜌 || Lfiber t || 𝜎MD | |

√ | √ b ( )| | 2 | 2 𝜎 z 833t PL | 400 √ | MD 1 − 4 2 | = 1. (28) z√ b − fCD = 3 | | L wt 𝜌 || Lfiber t 𝜎CD | | |

Modeling of bending of paperboard structures

Paperboard structures do not have uniform through-thickness (ZD) profiles, instead the idea is to have a ZD- profile to optimize performance. In papermaking one can easily change the density, fiber length, and orientation of each ply, which was also observed in Figs. 2, 3, 4. Based on this information some artificial paperboard structures will be constructed to visualize potential problems that can arise during bending. For this purpose, the laminate theory and bending analysis equations were implemented in an Excel sheet. To show how the concept works, the laminate theory was first used to optimize the bending stiffness of an artificial symmetric paperboard with grammage 250 g/m2, degree

795

of anisotropy, A = 1 in all plies. In the simulations the effect of different grammage in the plies was investigated, and the impact of density of the middle ply as well as fiber length in the middle ply. When the density of the middle ply is low the paperboard thickness is high (Fig. 6).

When Lfiber = 1.0 mm was used, a rather weak middle ply was simulated; a local maximum was found, where the bending stiffness can be optimized with respect to grammage in the outer plies. The simulations showed that the maximum bending stiffness have about 25–30% of the grammage in the outer plies. However, simulations with Lfiber = 2.0 mm, which represent a middle ply with high elastic modulus. For this case, it was observed that the middle ply contributes considerably to the bending stiffness of the paperboard, and therefore the bending stiffness increase with increasing grammage in the middle plies. Hence, the effect of the increased thickness due to more grammage in the middle ply was larger than the effect of separating the denser outer plies.

This was an interesting observation since many paperboard products are within the property range used. It is hence not necessarily true that maximum bending stiffness is achieved with 30% outer plies.

The bending stiffness analysis showed that the bending stiffness can be optimized by altering the grammages of outer plies, and the maximum ratio between bending stiffness and grammage of the paperboard can be found.

However, there are also other parameters that depend on the grammage of the outer plies, such as printing and surface properties. Therefore, other parameters than bending stiffness also contribute to optimal paperboard performance. For the upcoming simulation of paperboard folding, we have

Fig. 6 Optimization of bending stiffness simulating paperboards with different densities in the middle ply, as well as different fiber lengths Lfiber = 1 mm (solid lines) corresponding to EMP = 900 MPa and Lfiber = 2 mm (dotted lines) corresponding to EMP = 1800 MPa

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constructed a paperboard, where data was taken from Fig. 3.

This is a asymmetric paperboard with different densities 600, 500, and 750 kg/m3 for the bottom, middle, and top plies, respectively, and fiber lengths 2, 1.3, and 1.5 mm in the plies. The grammages (83, 250, and 50 g/m2) were chosen such that the paperboard thickness became h = 400 μm and based on the properties of the plies the failure stress during bending was estimated and put into the stress state Eqs. (14–15). With the chosen material parameters, the normal stress is still dominating, but it should be seen that the largest normalized stress can be found in the middle ply, close to the interfaces. This indicates that tensile failure can occur in the middle ply before it can be seen in the outer plies. The normalized shear stress was smaller than the normal stress, but it was not neglectable. This can be seen when the proposed failure criterion was plotted (Fig. 7) it was noted that the fmax is located along the bottom interface, where we hence expect failure to occur when the maximum bending moment has been reached. If a higher bending moment is desired for the paperboard, then the highest prioritization should be to increase the strength of the bottom interface, thereafter the top interface should be strengthened.

The fact that the failure criterion f is largest in the middle ply suggest that the failure will occur there during bending, and that modifications of the middle ply will alter the value and position of the failure criterion. In paperboard making, it is common to work with the middle ply to alter the properties of the paperboard. If the density of Fig. 7 Failure criterion based on the unsymmetrical paperboard that was constructed

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the middle ply is changed the in-plane and ZD strength of the middle ply will change, which will alter the failure criterion. In Fig. 8, the middle ply density has been varied from 250 to 750 kg/m3. It should be noted when the density is around 500 kg/m3 the failure criterion is roughly the same in the middle ply and the outer plies with this parameter set. This must be optimal; the middle ply has then been made bulkier without compromising the maximum bending moment. As the density is decreased the risk of failure in the middle ply increases, which will also lower the maximum bending moment. And when the middle ply is denser the largest risk of failure is within the outer plies and dominated by the normal component.

In the previous plots (Figs. 7, 8) the failure criterion has been shown for A = 1, i.e., when the paperboard is in-plane isotropic. At a paperboard machine more fibers are often oriented in MD. This will alter the shape of the failure criterion. In fact, the orientation of different plies can be altered to minimize the risk of failure, and hence increase the maximum bending moment. If the orientation of the outer plies varies from A = 1 to A = 2 one can see that it is the CD direction that will have the largest risk of failure, see Fig. 9. This is since the failure stress in MD will increase more when the fibers are oriented in MD. In Fig. 9, it can also be seen that a similar effect occurs when the orientation of the middle ply is changed, the risk of failure during folding increase with increased MD orientation.

Relating papermaking process parameters to properties of paperboard with special attention…

797

Fig. 8 Effect on the failure envelope of having different density in the middle ply

Discussion and conclusion The development of analytical models can help us to better understand how paperboards behave under different loading conditions. One alternative approach would be to develop finite element models to do the same kind of analysis. Both methods have their respective advantages and drawbacks. The main advantage with the model presented

here is that it quickly can correlate papermaking parameters to potential risks and do simple parameter studies; this by utilizing Excel.

Splitting and free laying of the top, middle, and bottom plies of paperboards that had been produced during different trial gave us a good database to develop phenomenological models of strength that was dependent on density, degree of anisotropy, and fiber length. Typical values from this data set were used to perform simulation of folding of paperboard.

Fig. 9 Effect on the failure envelope of orientation: (left) bottom and top plies, (right) middle ply

13

798

M. Nygårds

It was evident the greatest risk for failure often was within the middle ply. Moreover, if the density is lowered, the risk of failure due to insufficient middle ply density increases.

Hence by having good control of the densities in the different plies it would be possible to balance where the weakest point in the through-thickness direction should be located, and how much stronger the outer plies need to be for optimal performance. Hence, it is not the strength of the individual ply that is important, it is the relation to the other plies that gives optimal performance.

While it could be concluded that an efficient way to increase the bending stiffness of a paperboard was to decrease the density of the middle ply. When the density is decreased from 500 to 400 kg/m3 the bending stiffness increase about 50%. However, the analysis also show that this will result in a 20% drop in ZD strength. The drop in ZD strength will also affect the maximum bending moment that the paperboard can carry, which in turn will affect the box compression. Hence, lightweight will reduce quality of the paperboard, which is not acceptable.

An alternative approach is then to work with the strength profile in the through-thickness direction. Instead, it would be possible to work with the density gradient in the paperboard, which can be controlled by drainage of the paperboard during production. The analysis done here showed that it would be advantageous to increase the strength of the lower part of the middle ply to increase the maximum bending moment of the paperboard. In addition, the orientation of the different plies can be utilized to optimize the paperboard performance; the plies can be oriented more or less in the MD to minimize the largest stresses that arise in the through-thickness direction.

Acknowledgements The work has been financed by internal resources from BillerudKorsnäs, for which the author is grateful. BillerudKorsnäs acknowledge the possibility offered to publish results within the scientific community.

Funding Open access funding provided by Royal Institute of Technology.

Data availability This manuscript has no additional data available.

Declarations Conflict of interest There are not potential conflicts of interest behind the work presented here.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes

13

were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/.

References 1. M. Nygårds, J. Sundström, Comparison and analysis of in-plane compression and bending failure in paperboard. Nord. Pulp Pap. Res. J. 31(3), 432–440 (2016) 2. D.W. Coffin, M. Nygårds, Creasing and folding, Advances in Paper Science and Technology: Trans. 16th Fundamental Research Symposium (2018) 3. M. Östlund, S. Östlund, C. Fellers, Experimental determination of residual stresses in paperboard. Exp. Mech. 45, 493–497 (2005) 4. M. Nygårds, Experimental techniques for characterization of elasticplastic material properties in paperboard. Nord. Pulp Pap. Res. J. 23(4) (2008) 5. A. Hagman, M. Nygårds, Short compression testing of multi-ply paperboard, influence from shear strength. Nord. Pulp Pap. Res. J. 31(1), 123–134 (2016) 6. H. Huang, M. Nygårds, A simplified material model for finite element analysis of paperboard creasing. Nord. Pulp Pap. Res. J. 25(4), 502–509 (2010) 7. H. Huang, M. Nygårds, Numerical and experimental investigation of paperboard folding. Nord. Pulp Pap. Res. J. 26(4), 452–467 (2011) 8. Fortuna GmbH, Splitting Machine AB 320 P, Fortuna GmbH, Eisenbahnstraße 15, D-71263 Weil der Stadt (2004) 9. G. Marin, In-plane fracture of paperboard, Master thesis, KTH Royal Institute of Technology, Solid Mechanics, Stockholm (2014) 10. J. Tryding, G. Marin, M. Nygårds, P. Mäkelä, G. Ferrari, Experimental and theoretical analysis of in-plane cohesive testing of paperboard. Int. J. Damage Mech. 26(6), 895–918 (2016) 11. A.N. Giashi, T. Gereke, T. Mbarek, C. Cherif, Novel dynamic test methods for paperboard composite structures. Exp. Tech. (2021). https://​doi.​org/​10.​1007/​s40799-​021-​00496-8 12. Fellers, Carlsson, Bending stiffness, with special reference to paperboard. In: Handbook of Physical Testing of Paper, Vol 1, Chapter 5: 233–256 (1983) 13. C. Fellers, Laminate theory for papermakers, in Paper Products Physics and Technology (Walter de Gruyter, 2009), pp. 287–314 14. S. Timoshenko, Theory of Elasticity. Engineering Societies Monographs, ed. by H. W. Craver (McGraw-Hill, New York, 1934) 15. ISO 2493-2, Paper and board—determination of bending resistance—part 2: Taber-type tester, Technical Committee: ISO/TC 6/ SC 2 (2011) 16. M. Nygårds, Behavior of corners in carton board boxes, in Mechanics of Paper Products, 2nd edn. ed. by S. Östlund (Walter de Gruyer GmbH, Berlin, 2021) 17. N. Stenberg, C. Fellers, S. Östlund, Plasticity in the thickness direction of paperboard under combined shear and normal loading. Trans. ASME 123, 184–190 (2001) 18. Htun, Fellers, The invariant mechanical properties of oriented handsheets. Tappi 65(4), 113–117 (1982)

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Simulation of Sheet Molding during Through Air Drying of Tissue Paper within a Papermaking Framework K. REZK & B. SJÖSTRAND A way to improve product performance of tissue grade paper products is to replace the press section with a Through Air Drying (TAD) section which is a technique where paper sheets are moulded into a structured fabric by vacuum boxes and transferred over one or more TAD cylinders with steam heated displacement drying. The process of sheet molding is modelled with Comsol Multiphysics where the computational model is setup with a 2-dimensional representation of the paper sheet. The tissue sample with randomly distributed fibre positions is generated using a MATLAB script written in the Livelink interface with Comsol. The process is simulated with the Moisture Flow multiphysics interface. The comprising physical modules are the Laminar Flow and the Moisture Transport in Air modules. Respectively, these modules calculate the velocity and pressure field of the moist air as well as the relative humidity, which is a rewrite of the concentration of water in air. The fibres in the sheet are modelled as porous media where the fibres contain both moist air and liquid water in equilibrium. In this paper, a basis weight at roughly 20 g/m 2 is simulated and compared to laboratory data. The aim of the model is to estimate solid content in the paper sheet over vacuum time as well as energy demand and required airflow through the structure.

Contact information: Pro2BE, the research environment for Processes and products for a circular forest-based bioeconomy, Department of engineering and chemical sciences, Karlstad University, Karlstad, Sweden.

COMSOL Conference 2023, Munich Open Source

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 8

Article 2 – Simulation of TAD

Simulation of Sheet Molding during Through Air Drying of Tissue Paper within a Papermaking Framework K. Rezk1, B. Sjöstrand1 1. Pro2BE, the research environment for Processes and products for a circular forest-based bioeconomy, Department of engineering and chemical sciences, Karlstad University, Karlstad, Sweden

Abstract A way to improve product performance of tissue grade paper products is to replace the press section with a Through Air Drying (TAD) section which is a technique where paper sheets are moulded into a structured fabric by vacuum boxes and transferred over one or more TAD cylinders with steam heated displacement drying. The process of sheet molding is modelled with Comsol Multiphysics where the computational model is setup with a 2-dimensional representation of the paper sheet. The tissue sample with randomly distributed fibre positions is generated using a MATLAB script written in the Livelink interface with Comsol. The process is simulated with the Moisture Flow multiphysics interface. The comprising physical modules are the Laminar Flow and the Moisture Transport in Air modules. Respectively, these modules calculate the velocity and pressure field of the moist air as well as the relative humidity, which is a rewrite of the concentration of water in air. The fibres in the sheet are modelled as porous media where the fibres contain both moist air and liquid water in equilibrium. In this paper, a basis weight at roughly 20 g/m2 is simulated and compared to laboratory data. The aim of the model is to estimate solid content in the paper sheet over vacuum time as well as energy demand and required airflow through the structure.

Keywords: CFD, Dewatering, Moisture transport, tissue paper, through air dying.

These studies show that a prolonged dwell time would increase dryness to a certain level. To reach a higher dryness level, increased vacuum pressure is necessary.

Introduction Water removal during paper and board manufacturing is an energy intensive process. The dewatering process in paper and board manufacturing generally consists of four stages with progressively high energy demand [1, 2]. The first stage comprises water removal with gravity or centrifugal forces where water escapes without additional energy input and then with help of static elements in the geometry of the paper machine, followed by low and high vacuum pressure. In the second stage of vacuum exposure, where higher levels of vacuum pressure are applied through suction boxes [2-8]. Most of the suspended water is removed during gravitational and vacuum dewatering [9]. The third stage is performed in the press section by compressing the paper in one or more press nips [10]. The last stage, which far exceeds the other stages in energy demand, is comprised by thermal drying where remaining water in fibres are evaporated on steam-heated cylinders [9, 11]. Hence, improving the mechanical dewatering processes prior to the thermal stage could reduce major production cost.

Numerous researchers have conducted theoretical and numerical analysis on various aspects on vacuum dewatering such as single-flow mechanics in fibrous porous media where permeation through compressible fiber beds, permeability in various representative fiber structures were studied as well as penetrated air volume calculated and compared to experimental data [26-30]. Some attempts on simulating the two-phase flow behavior during the early stage of dewatering of the unbound water where progression on estimating the dwell time and dry content with varying pressure pulses has been conducted in [16, 31, 32]. While there are improvements that need to me made on the estimation of the dewatering rate, the penetrated air volume showed excellent agreement with experimental data.

Fluid inertia as well as spatial heterogeneity has been studied for moderate Reynolds number in various fiber arrangements by [33-37]. Moreover, the influence on the permeability based on sample size, boundary conditions, homogeneity and isotropy were studied. The relations are used to predict permeability for various fiber arrangements and porosity levels.

A number of researchers have studied vacuum dewatering experimentally using laboratory equipment as well using pilot scale machines [2-8, 12-21]. Process parameters that influence sheet dryness such as applied vacuum, dwell time and basis weight have been analysed.[4, 6, 13, 22-25]

1

A way to improve product performance of tissue grade paper products is to replace the press section with a Through Air Drying (TAD) section which is a technique where paper sheets are moulded into a structured fabric by vacuum boxes and transferred over one or more TAD cylinders with steam heated displacement drying (Tysén 2018, Tysén et al. 2015; 2018). Much like conventional papermaking machines, where the Yankee cylinder is the most energy requiring step, the TAD cylinders have by far the highest energy demand. Hence, improving the drying rate in the molding process is necessary from an energy demand standpoint. The process of sheet molding is modelled with Comsol Multiphysics where the computational model is setup with a 2dimensional representation of the paper sheet. The tissue sample with randomly distributed fibre positions is generated using a MATLAB script written in the Livelink interface with Comsol. The process is simulated with the Moisture Flow multiphysics interface. The comprising physical modules are the Laminar Flow and the Moisture Transport in Air modules. The purpose of this paper is to gain a better understanding of driving as well as limiting mechanisms of moisture transport in porous media concept of TAD molding system. The aim is to develop a first draft of a computational model that can simulate the change in solid content

Figure 1. 2-dimensional representation of paper sheet model in Comsol. The upper SEM image is from the study [20].

The basis weight (g/m2) is a standard measurement in paper manufacturing and it represent the weight of the paper in relation to a standard size. More specifically, it is the ratio between the mass of dry substance and the surface area of the sample. 𝐵𝑊 =

𝑁𝜌𝐿 𝑆

(1)

Where 𝜌𝐿 coarseness or length density (kg/m) of a fibre, 𝑁 is the number of fibres, whereas 𝑆 (m) is the height of the sample.

Modelling continua in porous media Porous materials such as networks of wood fibres has a complex solid structure and is highly discontinues from a continuum theory perspective, see Fig. (2). This is resolved by viewing the modelled structure as a porous media in several layers, that is, the wood fibres are interpreted as a mixture of different materials (solids and fluids) with measurable quantities in a macroscopic field.

Theory / Numerical Set Up Wood fibres for papermaking and paper sheets are both hygroscopic materials and, as such, contain bound water within the sheet network structure and within fibre walls. The network of fibres in a sheet as well as the fibres themselves can be viewed as porous media and understanding the physics and characteristics of fluid transport is key in numerically assessing water removal rate. Physical effects such as fluid flow and transport of fluids in different phases is considered. Heat transfer is excluded from these simulations at this stage as evaporative cooling is assumed to have neglectable effects on the drying process.

Figure 2. A 2-dimensional schematic representation of the structure of a single wood fibre and, on smaller scales, bundles of microfibrils.

Computational domain The computational model is setup with a 2dimensional representation of the paper sheet. The tissue sample with randomly distributed fibre positions is generated using a MATLAB script written in the Livelink interface with Comsol. The script creates fibres and randomly position them throughout the domain, which represents the paper, see Fig. 1. The code can be set to create fibres comprising of various basis weights and paper sheet porosities. In this paper, a sheet comprising of a basis weight at 18 g/m2 and a porosity at approximately 0.7 were simulated and analysed. Ten different structures were created in the Livelink Matlab script.

Governing Equations / Numerical Model At the start of the simulation process, the fibres are saturated with water, although surrounded by moist air. As air flows through the paper sheet, the fibres are dried due to moisture mitigation from the core of the fibre to the surface through convection and capillary forces. At the surface, water is evaporated though forced convection and vapour diffusion. The process is simulated with the Moisture Flow Multiphysics interface. The comprising physical modules are the Laminar Flow and the Moisture Transport in Air modules.

2

contain the maximum amount of water. The relative permeability varies between zero and one for each phase depending on the water content within the fibre walls. The total permeability is, hence, the product of the intrinsic and relative permeability.

Pore space in the paper model The penetrating airflow is modelled with the continuity and Navier stokes equations in COMSOL Multiphysics 6.1, see Eqs. (2) and (3), 𝜕𝜌 𝜕𝑡

+

𝜕(𝜌𝑢𝑖 )

𝜕(𝜌𝑢𝑖 ) 𝜕𝑡

𝜕𝑥𝑖

=0

+ 𝜌𝑢𝑗

𝜕𝑢𝑖 𝜕𝑥𝑗

𝑘𝑔 = 𝑘𝑔𝑖 𝑘𝑔𝑟 { 𝑘𝑤 = 𝑘𝑤𝑖 𝑘𝑤𝑟

(2) =−

𝜕𝑝 𝜕𝑥𝑖

+

𝜕 𝜏 − 𝜌𝑔𝑖 𝜕𝑥𝑗 𝑖𝑗

The equations that describe the relative permeability for each phase are described in Eq. (9) and (10). [38]

(3)

where 𝜏𝑖𝑗 is the deviatoric stress tensor which includes the bulk viscosity due to compressibility in the air, see Eq. (4). 𝜏𝑖𝑗 = 𝜇 (

𝜕𝑢𝑖

𝜕𝑥𝑗

𝜕𝑢𝑗

+

𝜕𝑥𝑖

2

𝜕𝑢𝑘

3

𝜕𝑥𝑘

− 𝜇

{

𝛿𝑖𝑗 )

{

(4)

𝜕𝑡

+ 𝑀𝑣 𝑢𝑗

𝜕𝑐 𝜕𝑥𝑗

− 𝑀𝑣 𝐷𝑣

𝜕2 𝑐

2 = 𝐺

𝜕𝑥𝑗

𝜅

𝜕𝑝

𝑘𝑤𝑟 = 0

, 𝑖𝑓 𝑆𝑤 < 𝑆𝑖𝑟

𝜕𝑡

(10)

+ 𝜌𝑔 𝑢𝑔,𝑗

𝜕𝜔𝑣 𝜕𝑥𝑗

+

𝜕𝑔𝑤 𝜕𝑥𝑗

+ 𝜌𝑔 𝑢𝑙,𝑗

𝜕𝜌𝑙 𝜕𝑥𝑗

+

𝜕𝑔𝑙𝑐 𝜕𝑥𝑗

=𝐺

(11) (5)

where 𝑔𝑤 (kg/(m·s)), see Eq. (12), is the vapor transport in the gaseous phase in the wood fibre. As the Millington and Quirk equation is used calculate the effective diffusivity in see Eq. (12). The capillary flux term 𝑔𝑙𝑐 (kg/(m·s)), see Eq. (13), is described as the relative humidity gradient of the moisture content and an added diffusivity term 𝐷𝑤 (m2/s), see Eq. (14). [38] The moisture content, 𝑊(𝜑𝑣 ), is a function of the relative humidity, see Eq. (15).

(6)

𝜇 𝜕𝑥𝑖

) , 𝑖𝑓 𝑆𝑤 > 𝑆𝑖𝑟

1−𝑆𝑖𝑟

(9)

1.1

𝑘𝑤𝑟 = ( 𝑤

𝜕𝑊(𝜑𝑣 )

𝑔𝑤 = −𝜌𝑔 𝐷𝑒𝑓𝑓

Porous media modelling in wood fibre The wood fibres are typically hygroscopic materials and, as such, should be modelled as a porous media.

The fibres contain two phases in equilibrium, which is the liquid water and the moist air. The driving force for transportation of each phase is vapor diffusion and convection in air, as well as capillary flow and convection for water. Assuming that the inertial forces in the fibres are neglectable, Darcy’s correction model is used to relate pressure gradients to the volume averaged superficial velocity 〈𝑢𝑖 〉 = − 𝑖𝑗

, 𝑖𝑓 𝑆𝑤 >

Fluid transport in and between wood fibres is described with the following equation

where 𝑀𝑣 (kg/mol) is the molar mass of water vapour, 𝐷𝑣 (m2/s) is the vapor diffusion in air coefficient and 𝐺 (kg/m3s) is the moisture source or sink term. The concertation term in in Eq. (5) is related to the relative humidity with the vapor saturation concentration. 𝑐 = 𝜑𝑣 𝑐𝑠𝑎𝑡

𝑘𝑔𝑟 = 0

1 1.1 1

The intrinsic permeability for wood fibres are used from [38].

The moisture transport in the air is described with a modified advection diffusion model shown in Eq. (5), 𝜕𝑐

𝑘𝑔𝑟 = 1 − 1.1𝑆𝑤 , 𝑖𝑓 𝑆𝑤 < 𝑆 −𝑆𝑖𝑟 3

Turbulence modelling was excluded from the simulations due to small length scales in the order of 10e-6 m and, hence, leading to low Reynolds numbers.

𝑀𝑣

(8)

𝑔𝑙𝑐 = −𝐷𝑤

𝜕𝜔𝑣

(12)

𝜕𝑥𝑗

𝜕𝑊(𝜑𝑣 ) 𝜕𝜑𝑣 𝜕𝜑𝑣

𝐷𝑤 = 1 ∙ 10−8 𝑒

∙

𝜕𝑥𝑗 2𝑤(𝜑𝑣 ) ) (1−𝜀𝑝 )𝜌𝑓

(13)

(−2.8+

𝑊(𝜑𝑣 ) = 𝜀𝑝 (𝜌𝑙 𝑠𝑙 + 𝜌𝑔 𝜔𝑔 (1 − 𝑠𝑙 ))

(14) (15)

The liquid saturation, 𝑠𝑙 , is a dimensionless parameter and it describes the amount of water left within the pores, 𝜀𝑝 is the porosity of the wood fibres and 𝜔𝑔 is vapour mass fraction.

(7)

where 𝜅𝑖𝑗 (m2) is permeability coefficient and 𝜇 (Pa·s) is the dynamic viscosity. The permeability is typically decomposed into intrinsic permeability and relative permeability for multiphase flow in porous media according to [38]. The intrinsic parameter represents the permeability of liquid or gas in an entirely saturated state, i.e. the pores in the fibre

Model simplifications Some of the major assumptions this model relies on is: • Aligned fibre positions due to 2dimensional representation of the paper sheet

3

• •

diameter of a single fibre as well as typical gap distance between adjacent fibres.

The forming and deformation of the fibre web during the TAD molding process is excluded Zero unbound water remaining in the paper sheet model.

A direct linear system solver was used coupled with an implicit second order backward differentiation formula (BDF) solver. The direct solver is called PARDISO which handles sparse linear systems using LU factorization to compute a solution. More information on the solver is found in COMSOL documentation. The BDF solver performs time stepping using a backward differentiation with a maximum order of accuracy of 2, which is the degree of the interpolating polynomial.

Initial and boundary conditions Initially, the fibres are saturated with water and the pore structure of the paper sheet contains air. The boundary conditions of the 2-dimensional representation is presented in Fig. (3)

Figure 4. Grid resolution and geometrical properties of the paper sheet model.

Figure 3. The properties of the computational domain and boundary conditions.

Results and Discussion The results are comprised by presenting the solid content of the fibre web over time. Fig. (5) presents four snapshots of the solid content at times 0, 5, 10 and 20 ms. Local variations of the solid content are observed at 20 ms which is a result of adjacent fibres blocking the airflow and hence, reducing the influence of convective mass transport. Considering that the fibre web is viewed in two dimensions, the air blockage should be overrepresented and thus, causing larger variations of the airflow. This notion is supported in [33] which concluded that flow resistance in the isotropic fibre arrangement in space is lower than the in-plane isotropic orientation and disordered unidirectional fibre arrangements at creeping flow conditions for low to moderate

Pressure was applied at the inlet and outlet boundary in which the vacuum level was set at 30 kPa at the outlet and reference pressure at 0 Pa was set at the inlet. Symmetry was set at the vertical boundaries as the fibre structure of the domain which was considered characteristic. Key input parameters for the simulation model are presented in Table (1).

Table 1: Key input data to the simulation model

Parameter data Permeability Porosity Vapor-air diffusion Vacuum pressure Density fibre

Size 4.8e-8 [m2] 0.55 [-] 2.6e-5 [m2/s] -30 [kPa] 1340 [kg/m3]

Mesh setup and solver settings An unstructured mesh grid containing triangle elements was created for the paper models, see Fig. (4). The grid is solved in a finite element space where a set of basis functions are used to create piecewise linear relations between the mesh elements and convert them to weak formulations for them to be solved. Moreover, geometrical features such as the

4

Conclusions The first draft of the simulation model shows promising results in terms estimating average solid content over dwell time. At least that is the case up until roughly 15 ms. Based in laboratory results, the solid content rate seems to converge to an upper limit value, which is not the case for the simulation model.

Hence, experiments indicate that there is a physical limit on the dewatering rate. The surface moisture vaporization needs to by analysed further as theory suggest that there should be an increased resistance to surface vaporization as the moisture level decreases in the porous media. However, since the dryness levels during the TAD molding process ranges about 5-6% from start to finish, it should have a neglectable affect as there is still a lot of bound water in the fibre. Other limiting factors that are not considered at the moment are:

Figure 5. Colour plot representing solid content in in the fibre structure

The averaged solid content for the entire fibre web is presented in Fig. (5)

• •

•

Including the TAD wire which add blockage to the airflow as well as absorbs water from the fibres Analysing the TAD molding process in a 3dimensional space which should have an overall reduction in blockage due to an added dimension where the flow can travel.

Including the deformation of the fibre web during the molding process. Perhaps the poroelastic physics interface could be utilized to analyse both the deformation of the fibre web as the fluid transport of the porous media simultaneously.

Acknowledgements

Figure 6. Solid content comparison to laboratory trials performed by [20]

The authors are grateful for the financial support of the Knowledge foundation, Grant No. 2022-0024, as well as generous in-kind contributions from Albany International Inc., Karlstad University and Valmet AB.

The solid content from the simulation model is compared to lab-scale data from [20], for early TAD molding the simulation model show great coherence with the laboratory results. After some time, the laboratory results deviate from the linear behaviour and display diminishing returns. A few additions need to be added to the models to capture the diminishing returns. In a first approach to establish a numerical model of the TAD molding process, the influence of web deformation was excluded which eliminates both compressibility of the sheet which leads to decreasing permeability and also the rewetting phenomena, which are important factors to consider for a comprehensive model [39, 40]. The TAD fabric is likewise excluded from the simulations. According to [12] machine clothing such as forming fabrics affects the dewatering rate and magnitude through three main parameters, fabric caliper, void volume and air permeability. Similar dependence on the process is assumed to be influenced by TAD fabrics. Adding some of these to the numerical models, it is hypothesized to better simulate both laboratory and pilot scale results.

References [1] Hubbe MA, Sjostrand B, Nilsson L, Koponen A, McDonald JD. Rate-limiting Mechanisms of Water Removal during the Formation, Vacuum Dewatering, and Wet-pressing of Paper Webs: A Review. Bioresources. 15(4) (2020) 9672-755, [2] Ramaswamy S. Vacuum dewatering during paper manufacturing. Dry Technol. 21(4) (2003) 685-717, https://doi.org/10.1081/Drt-120019058 [3] Attwood BW. A study of vacuum box operation. Paper Technology. 3(5) (1962) T144-T53, [4] Neun JA. Performance of High-Vacuum Dewatering Elements in the Forming Section. Tappi J. 77(9) (1994) 133-8, [5] Neun JA. High-vacuum dewatering of newsprint. Tappi J. 79(9) (1996) 153-7,

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[6] Räisänen K, Karrila, S., Maijala, A. Vacuum dewatering optimization with different furnishes. Pap Puu-Pap Tim. 78(8) (1996) 455-, [7] Baldwin L. High vacuum dewatering. Paper Technology. 38(4) (1997) 23-8, [8] Räisänen KO. Vacuum systems. In: Gullichsen HPJ, editor. Papermaking part 1: Stock preparation and wet end 2000. p. 417-30.

[9] Sjöstrand B. Vacuum Dewatering of Cellulosic Materials: Karlstad University; 2020.

[10] Wahlstrom B. Wet pressing in the 20th century: Evolution, understanding and future. Pulp Pap-Canada. 102(12) (2001) 81-8, [11] Kuhasalo A, Niskanen, J., Paltakari, J., Karlsson, M. Introduction to paper drying and principles and structure of a dryer section. In: Gullichsen PJ, editor. Papermaking part 2, Drying 2000. p. 16-53.

[12] Granevald R, Nilsson LS, Stenstrom S. Impact of different forming fabric parameters on sheet solids content during vacuum dewatering.

Nord Pulp Pap Res J. 19(4) (2004) 428-33, https://doi.org/DOI 10.3183/npprj-2004-19-04p428-433 [13] Pujara J, Siddiqui MA, Liu Z, Bjegovic P, Takagaki SS, Li PY, et al. Method to characterize the air flow and water removal characteristics during vacuum dewatering. Part I - Experimental method.

Dry Technol.

26(3) (2008) 334-40, https://doi.org/10.1080/07373930801898091 [14] Aslund P, Vomhoff H. Method for studying the deformation of a fibre web during a suction pulse. Nord Pulp Pap Res J. 23(4) (2008) 398-402, https://doi.org/DOI 10.3183/npprj-2008-23-04p398-402 [15] Sjöstrand B, Barbier, C., & Nilsson, L. .

Influence on sheet dewatering by structural differences in forming fabrics. Paper Conference and Trade Show Cincinnati, Ohio, USA2016. p. 76776.

[16] Sjostrand B, Barbier C, Nilsson L. Modeling the influence of forming fabric structure on vacuum box dewatering. Tappi J. 16(8) (2017) 477-83, https://doi.org/Doi 10.32964/Tj16.8.477 [17] Sjostrand B, Barbier C, Ullsten H, Nilsson L. Dewatering of Softwood Kraft Pulp with Additives of Microfibrillated Cellulose and Dialcohol Cellulose. Bioresources. 14(3) (2019) 6370-83, https://doi.org/10.15376/biores.14.3.63706383 [18] Rahman H, Engstrand P, Sandstrom P, Sjostrand B. Dewatering properties of low grammage handsheets of softwood kraft pulps modified to minimize the need for refining. Nord Pulp Pap Res J. 33(3) (2018) 397-403, https://doi.org/10.1515/npprj-2018-3037 [19] Sjostrand B, Brolinson A. Addition of Polyvinylamine in Chemi-thermomechanical Pulp and Kraft Pulp and the Effects on Dewatering, Strength, and Air Permeance. Bioresources. 17(3) (2022) 4098-115, https://doi.org/10.15376/biores.17.3.4098-4115

[20] Sjostrand B, Danielsson M, Lestelius M. Method for Studying Water Removal and Air Penetration during Through Air Drying of Tissue in Laboratory Scale. Bioresources. 18(2) (2023) 307388, https://doi.org/10.15376/biores.18.2.3073-3088 [21] Sjostrand B. Progression of Vacuum Level in Successive Vacuum Suction Boxes in a Paper Machine-Impact on Dewatering Efficiency and Energy Demand-A Laboratory Study. Bioresources.

18(2) (2023) 3642-53, https://doi.org/10.15376/biores.18.2.3642-3653 [22] Britt KW, Unbehend JE. Water Removal during Paper Formation. Tappi J. 68(4) (1985) 1047, [23] Granevald R. Vacuum dewatering of lowgrammage paper webs and fabrics.: Karlstad University; 2005.

[24] Aslund P, Vomhoff H, Waljanson A. The deformation of chemical and mechanical pulp webs during suction box dewatering. Nord Pulp Pap Res J. 23(4) (2008) 403-8, https://doi.org/DOI 10.3183/npprj-2008-23-04-p403-408 [25] Pujara J, Siddiqui MA, Liu Z, Bjegovic P, Takagaki SS, Li PY, et al. Method to characterize the air flow and water removal characteristics during vacuum dewatering. Part II - Analysis and characterization. Dry Technol. 26(3) (2008) 341-8, https://doi.org/10.1080/07373930801898125 [26] Jackson GW, James DF. The Permeability of Fibrous Porous-Media. Can J Chem Eng. 64(3) (1986) 364-74, https://doi.org/DOI 10.1002/cjce.5450640302 [27] Zhu S, Pelton RH, Collver K. Mechanistic Modeling of Fluid Permeation through Compressible Fiber Beds. Chem Eng Sci. 50(22) (1995) 3557-72, https://doi.org/Doi 10.1016/00092509(95)00205-J [28] Nilsson L, Stenstrom S. A study of the permeability of pulp and paper. Int J Multiphas Flow. 23(1) (1997) 131-53, https://doi.org/Doi 10.1016/S0301-9322(96)00064-X [29] Matthews GP. Computer modelling of fluid permeation in porous coatings and paper - an overview. Nord Pulp Pap Res J. 15(5) (2000) 47685, https://doi.org/DOI 10.3183/npprj-2000-15-05p476-485 [30] Nilsson L. Stepwise Development of a Mathematical Model for Air Flow in Vacuum Dewatering of Paper. Dry Technol. 32(13) (2014) 1587-97, https://doi.org/10.1080/07373937.2014.909844 [31] Rezk K, Nilsson L, Forsberg J, Berghel J. Modelling of water removal during a paper vacuum dewatering process using a Level-Set method. Chem Eng Sci. 101 (2013) 543-53, https://doi.org/10.1016/j.ces.2013.07.005 [32] Rezk K, Nilsson L, Forsberg J, Berghel J. Simulation of Water Removal in Paper Based on a 2D Level-Set Model Coupled with Volume Forces Representing Fluid Resistance in 3D Fiber Distribution. Dry Technol. 33(5) (2015) 605-15, https://doi.org/10.1080/07373937.2014.967401 6

[33] Rezk K, Forsberg J, Nilsson L, Berghel J. Characterizing flow resistance in 3-dimensional disordered fibrous structures based on Forchheimer coefficients for a wide range of Reynolds numbers.

Appl Math Model. 40(21-22) (2016) 8898-911, https://doi.org/10.1016/j.apm.2016.05.036 [34] Yazdchi K, Luding S. Towards unified drag laws for inertial flow through fibrous materials.

Chem Eng J. 207 (2012) 35-48, https://doi.org/10.1016/j.cej.2012.06.140 [35] Koch DL, Ladd AJC. Moderate Reynolds number flows through periodic and random arrays of aligned cylinders. J Fluid Mech. 349 (1997) 31-66, https://doi.org/Doi 10.1017/S002211209700671x [36] Yazdchi K, Srivastava S, Luding S. Microstructural effects on the permeability of periodic fibrous porous media. Int J Multiphas Flow.

37(8) (2011) 956-66, https://doi.org/10.1016/j.ijmultiphaseflow.2011.05.

003 [37] Yazdchi K, Srivastava S, Luding S. Micromacro relations for flow through random arrays of cylinders. Compos Part a-Appl S. 43(11) (2012) 2007-20, https://doi.org/10.1016/j.compositesa.2012.07.020 [38] Datta AK. Porous media approaches to studying simultaneous heat and mass transfer in food processes. II: Property data and representative results. J Food Eng. 80(1) (2007) 96-110, https://doi.org/10.1016/j.jfoodeng.2006.05.012 [39] Mcdonald JD, Kerekes RJ. Estimating limits of wet pressing on paper machines. Tappi J. 16(2) (2017) 81-7, https://doi.org/Doi 10.32964/Tj16.2.81 [40] Sjostrand B, Barbier C, Nilsson L. Rewetting after high vacuum suction boxes in a pilot paper machine. Nord Pulp Pap Res J. 30(4) (2015) 667-72, https://doi.org/DOI 10.3183/npprj-2015-3004-p667-672

7

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Alkenyl Succinic Anhydride: The Question of Covalent Bonding and Chemistry Considerations for Better Sizing—Review YAO NTIFAFA1, LEBO XU1, SARA BOLLINGER1, YUN JI2, & PETER W. HART1 Alkenyl Succinic Anhydride (ASA) is a sizing agent used in papermaking to increase the water repellency of paper. Almost 60 years after the introduction of the chemical in papermaking, scientists still have differing views on how ASA interacts with cellulose. Several experiments were conducted to bring more clarity to the ASA sizing mechanism, especially on the contentious question of ASA-cellulose covalent bonding or the esterification reaction between ASA and cellulose during papermaking. Herein, research papers and patents, including experiments and results, from the 1960s to 2020 were reviewed. Our investigation revealed that the ester bond formation between ASA and cellulose is insignificant and is not a prerequisite for sizing effectiveness; the main ASA-related material found in sized paper is hydrolyzed ASA or both hydrolyzed ASA and ASA salt. In addition, ASA emulsion stability and ASA emulsion retention are important for sizing efficiency improvement.

Contact information: 1 WestRock, 2742 Charles City Road, Richmond, VA 23231, USA. 2 Department of Chemical Engineering, University of North Dakota, Grand Forks, ND 58202, USA. Polymers 2023, 15, 2876. https://www.mdpi.com/2073-4360/15/13/2876 Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 16

Article 3 – Sizing Agents

polymers Review

Alkenyl Succinic Anhydride: The Question of Covalent Bonding and Chemistry Considerations for Better Sizing—Review Yao Ntifafa 1, *,† , Lebo Xu 1,† , Sara Bollinger 1,† , Yun Ji 2,† and Peter W. Hart 1,† 1 2

* †

WestRock, 2742 Charles City Road, Richmond, VA 23231, USA; peter.hart@westrock.com (P.W.H.) Department of Chemical Engineering, University of North Dakota, Grand Forks, ND 58202, USA Correspondence: yao.ntifafa@westrock.com These authors contributed equally to this work.

Abstract: Alkenyl Succinic Anhydride (ASA) is a sizing agent used in papermaking to increase the water repellency of paper. Almost 60 years after the introduction of the chemical in papermaking, scientists still have differing views on how ASA interacts with cellulose. Several experiments were conducted to bring more clarity to the ASA sizing mechanism, especially on the contentious question of ASA-cellulose covalent bonding or the esterification reaction between ASA and cellulose during papermaking. Herein, research papers and patents, including experiments and results, from the 1960s to 2020 were reviewed. Our investigation revealed that the ester bond formation between ASA and cellulose is insignificant and is not a prerequisite for sizing effectiveness; the main ASA-related material found in sized paper is hydrolyzed ASA or both hydrolyzed ASA and ASA salt. In addition, ASA emulsion stability and ASA emulsion retention are important for sizing efficiency improvement.

Keywords: Alkenyl Succinic Anhydride (ASA); cellulose; paper sizing; covalent bonding; sizing agent stability; sizing agent retention

Citation: 2023, Ntifafa, Y.;xXu, L.; PEER REVIEW Polymers 15, FOR Bollinger, S.; Ji, Y.; Hart, P.W. Alkenyl Succinic Anhydride: The Question of Covalent Bonding and Chemistry Considerations for Better Sizing—Review. Polymers 2023, 15, 2876. https://doi.org/10.3390/

1. Introduction

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The objective of paper sizing is to delay wetting by reducing the fiber absorbency.

Alkenyl Succinic Anhydride (ASA) was introduced as a sizing agent in papermaking in 1963 emulsion particles are retained[1]. in ASA the forming paper compound sheet at thewith wetcyclic end and forming

by Wurzburg and Mazzarella is an organic dicarboxylic section.

Sizing development mostly happens in the dryer section, where the particles anhydride and a tetrafurandione (Figure 1). The chemical is light yellow color, oil-like, break down to ASAliquid in contact with the fibers [9,10]. non-soluble in release water, and at room temperature [2,3].

polym15132876 Academic Editor: Lili Wang Received: 13 June 2023 Revised: 23 June 2023 Accepted: 25 June 2023 Published: 29 June 2023

Copyright: © 2023 by the authors.

Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://

Figure1.1.Scheme Schemeof ofester esterbond bondformation formationbetween betweenASA ASAand andcellulose. cellulose.

Figure

Today, common internal (e.g., alum/rosin, AKD [Alkyl ketene dimer] The proposed and widelysizing cited chemicals ASA sizing mechanism is the formation of an ester or and ASA) are introduced into a pulp slurry at the wet end during the papermaking process. covalent bond between ASA molecules and fibers.

Figure 1 illustrates the ester bond for4.0/). mation between ASA and fiber (cellulose). However, during the last 60 years of papermaking research, this popular mechanism has been questioned. Several scientists are still uncertain about the binding mechanism between ASA and cellulose. In addition, most sciPolymers 2023, 15, 2876. https://doi.org/10.3390/polym15132876 https://www.mdpi.com/journal/polymers entists agree that ASA hydrolyzes in water during the papermaking process (Figure 2) [7,11–13]. creativecommons.org/licenses/by/

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Alum/rosin sizing is commonly used for acidic papermaking with a typical pH range from 4.0 to 5.5. In this pH range, alum forms the right aluminum species to either react with soap rosin or to retain dispersed rosin (DRS) for sizing development. AKD and ASA are used in alkaline papermaking processes, where ASA has a higher reactivity to cellulosic fiber compared to AKD. Moreover, ASA has also been reported to be applied in acidic paper-making conditions [4–8].

Due to the insolubility of ASA in water, ASA oil needs to be emulsified before adding to the wet end for homogenous distribution in pulp slurries. The emulsifier can be starchbased (cationic starch) or polymer-based (polyacrylamide). Typical ASA emulsion particle Figure 1. Scheme of ester bond formation between ASA and cellulose. size is around 1 µm. The ASA emulsion has a short shelf life, and thus the chemical is typically emulsified on-site in the mill and dosed to the wet end as soon as possible. The The proposed widely cited ASA paper sizingsheet mechanism theand formation emulsion particles areand retained in the forming at the wetisend forming of an e section.

Sizing development mostly happens in the dryer section, where the particles break covalent bond between ASA molecules and fibers. Figure 1 illustrates the ester bon down to release ASA in contact with the fibers [9,10]. mation between ASA and fiber (cellulose). However, during the last 60 years of pape The proposed and widely cited ASA sizing mechanism is the formation of an ester or ing research, this popular mechanism has been scientists covalent bond between ASA molecules and fibers.

Figurequestioned.

1 illustrates theSeveral ester bond forma- are s certain about the binding mechanism between ASA and cellulose.

In addition, mo tion between ASA and fiber (cellulose). However, during the last 60 years of papermaking research, this popular mechanism has beeninquestioned.

Severalthe scientists are still uncertain entists agree that ASA hydrolyzes water during papermaking process (Fig about the binding mechanism between ASA and cellulose.

In addition, most scientists [7,11–13]. agree that ASA hydrolyzes in water during the papermaking process (Figure 2) [7,11–13].

Figure 2. Scheme of the formation of hydrolyzed ASA.

Figure 2. Scheme of the formation of hydrolyzed ASA.

The covalent bonding question becomes a heated debate between scientists who support the ester bond formation as the primary sizing mechanism and scientists who believe The covalent bonding question becomes a heated debate between scientists wh ester bonding is almost nonexistent and does not play a major role in paper sizing. Due to port the esteraround bond formation the primary sizing and scientists the confusion the covalentas bonding questions, manymechanism authors prefer to use the ex- who b ester bonding is accepted”, almost nonexistent and does not play a major role in paper sizing. pressions “widely “generally accepted”, “generally understood”, “traditionally”, or “assume” in reference to the ASA-cellulose covalent bond formation the confusion around the covalent bonding questions, many [7,12,14–19]. authors prefer to use In this review, patents and research papers with experimental data wereunderstood”, reviewed to pressions “widely accepted”, “generally accepted”, “generally “tra understand the ASA sizing mechanism since 1963. In addition, chemistry considerations ally”, or “assume” in reference to the ASA-cellulose covalent bond formation [7,12,1 for better application of ASA are briefly discussed.

In this review, patents and research papers with experimental data were revie 2. Debate on the ASAASA Sizing Mechanism in Papermaking understand sizing mechanism since 1963. In addition, chemistry consider Prior to the introduction of ASA to the papermaking process in the 1960s, the additive for better application of ASA are briefly discussed. was used in the textile industry to impart water repellency to cellulosic fabrics. Patent 2,903,382 by Robert Berls [20] in 1959 provided details on how to make hydrophobic cellulosic fabric using ASA. Different types of ASA with chains from 19 to 35 carbon atoms were dissolved in solvent such as isopropanol, benzene, toluene, chloroform, carbon tetrachloride, ammonia, morpholine, and water emulsions. The fabric was dipped into the resulting solution then heat cured. The recommended ASA concentration was from 0.7%

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to 2.5% (14 to 50 lb/t) of the weight of the fabric. The spray test method of the American Association of Textile Chemists and Colorists A.S.T.M. Designation: D583-54 was used to evaluate water repellency. There was no mention of esterification reaction nor covalent bonding in the claim. In addition, the ASA application is like wax application to textile fiber for hydrophobicity, as claimed in patent 2,759,851 in 1956 by Fluck, Pluckemin, and Logan [21].

In 1963, Wurzburg and Mazzarella [1] mixed ASA with different derivatives of starch to form an emulsion. It was claimed that the application of the ASA emulsion on fiber made the sheet hydrophobic. The patent demonstrated the sizing process with the use of the ASA emulsion and the addition of alum, aluminum chloride, long chain fatty amines, sodium aluminate, polyacrylamide, animal glue, polyamide polymers, primary amine starch derivatives, secondary amine starch derivatives, tertiary amine starch derivatives, and quaternary amine starch derivatives.

The author recommended to use 0.5 to 2 parts by weight of cationic starch per 1 part of the sizing agent to obtain adequate results. Different dosages from 0.25% to 2% (5 to 40 lb/t) of the sizing agent were used in 14 different examples to support the claim. Uranine dye and ink dip tests were used to prove the hydrophobicity of the sheets. There was no disclosure of covalent or ester bonding between ASA and cellulose in the patent document.

Cuculo [22] at NC State University tried to esterify succinic anhydride with cellulose in 1971. First, successful results were obtained from the reaction between viscose rayon cellulose and succinamic acid. The samples were baked in succinamic acid at 136 ◦ C, 183 ◦ C, and 207 ◦ C, water-washed, and then treated with 3% sodium sulfate to form sodium cellulose-hemisuccinate. The degree of substitutions for the reactions were, respectively, 0.03, 0.24, and 0.25. The author concluded that the degree of the substitution of reaction depends strongly on the reaction temperature. Second, when succinic anhydride in water was used under comparable conditions to those of the succinamic acid, the author stated that there was no evidence of ester formation. The reported reaction yield with succinamic acid was 36%, and the author mentioned that ammonia copiously evolved during the reaction. The recommended temperature using the succinamic acid is above 150 ◦ C. McCarthy and Stratton [23] studied the reaction between cotton linters pulp and ASA in 1986. In one study, the cotton linters and ASA were reacted in N,N-dimethyl formamide with triethyl amine as a catalyst. In another study, the cotton linter pulp (washed in chloroform-ethanol solution for 48 h and air dry for several hours) and a high concentration of ASA (1.5% or 30 lb/ton) were reacted. Poly(1,2-dimethyl-5-vinylpyridinium bromide), or DMVPB, was used as ASA retention aid. In both studies, FTIR data showed the formation of ester bonds, however the efficiency of these reactions was not reported. In McCarthy’s thesis in 1987 [24], the author showed by FTIR that ASA reacted with ethanol to form ester bonds. It is not known if part of the ASA formed ester bonds with ethanol rather than cellulose since the pulp was washed 48 h with chloroform-ethanol solution.

Wan [25] studied the mechanism of ASA sizing in 1988 using C 14-labelled tetradecenyl succinic anhydride (TDSA) and tetradecenyl succinic acid (TDSAcid). TDSA and TDSAcid emulsions were made using starch as an emulsifier at a 1:3 ratio. The emulsions containing 1.3% total solid was charged to the pulp to make 60 g/m2 hand-sheets. The C14labelled technique was used to quantify the ASA component in the sheets after chloroform extraction. The results showed that unreacted ASA is predominantly found in the sheet and about 25% of ASA can produce sizing and is not extractable with chloroform.

According to the author, the retained ASA could be explained by covalent bonding due to three reasons. First, the continuous increasing in sizing at room temperature suggests the reduction in moisture allows the ASA to react with the hydroxyls of cellulose. Second, the ASA molecule, which is under constant reorientation during the sizing process, would undergo hydrolysis if at any time the hydrophilic part of the molecule is exposed to moisture. The retained molecule can be assumed to be held by stronger irreversible bond forces. Third, the inability of the ASAcid (hydrolyzed form of ASA in the dicarboxylic acid form) to size hand-sheets demonstrates that hydrogen bonding is not the mechanism of

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ASA sizing, thus covalent bonding must be the mechanism. The author concluded that this evidence suggests that unextractable ASA is bound to cellulose via covalent bonding. In addition, according to the author, solvent sized sheets gave better sizing than conventional emulsion sized sheets due to the absence of water that induces hydrolysis.

Nishiyama et al. [26] used a series of extraction, impregnation, and cellulase treatment experiments to study the ASA bonding mechanism under common papermaking conditions in 1996. Pulp and ASA-starch emulsion containing 0.2% (4 lb/ton) ASA were used to make 60 g/m2 hand-sheets. Chloroform, water-acetone, and dimethyl sulfoxide (DMSO) were used to extract the hand-sheets and cellulase was used to isolate the ASA residues.

The measurement of the extracts by gas chromatography showed that not all ASA was extractable, and the NMR data showed no presence of formed ester linkage between the ASA and the hydroxyl group of cellulose. When an old ASA emulsion, which has no chance to form ester linkages with cellulose, was used, the extraction results also showed not all ASA was extractable. The authors concluded that a small amount of ASA is physically entangled in the cellulose network without forming covalent bonds.

Impregnation of filter papers with acetone solutions of ASA, non-reactive ASAcid, and non-reactive ASAcid methyl esters were also studied. Sizing occurred in all cases, but no ester linkages between ASA and cellulose-OH were found to exist.

To ensure that ester bonds were not formed then destroyed by the cellulase isolation and analytical techniques employed, the tests were repeated using cellulase treatment stable conditions. These conditions ensured any ester linkages between cellulose-OH and ASA would not be cleaved during isolation and analysis. These tests were repeated using sample A which is ASA-alum-sized hand-sheets, sample B which is ASA-PAE-sized handsheets, and sample C which is PAE-treated hand-sheets. The residues after the enzymatic treatment were 1.4, 0.7, and 1.1% for the samples A, B, and C, respectively. The analysis of the residues showed the samples A and B contain 10% and 15% ASA, respectively. Further analysis of the residues of samples A and B was conducted; the FTIR data showed that most ASA components do not form ester bonds with cellulose, and the predominant components of ASA in the sheets A and B are in the form of ASAcid. The author concluded after the extraction, impregnation, and cellulase treatment studies that the ASA sizing mechanism should not be explained by the formation of ester linkages.

In 2000, Akira [27] studied the extracts of ASA-sized hand-sheets with ASA content of 2.2 mg/g. Pulp and ASA-starch emulsion containing 0.2% ASA was used to make the 60 g/m2 hands-sheets. A series of extractions using water, chloroform, 1% Tween 80 at 20 ◦ C, and 1% Tween 80 at 70 ◦ C were performed. The extracted sheets were analyzed with pyrolysis gas chromatography–mass spectrometry (GCMS). The amount of ASA retained in the sheet was respectively 1.7 mg/g, 0.6 mg/g, 0.3 mg/g, and almost zero for the listed extraction conditions, respectively. According to the author, the extraction results showed that virtually no covalent bonds between ASA and hydroxyl groups of cellulose were present in the hand-sheet. These results also indicated that chloroform is not a suitable solvent to completely extract ASA even though the ASA is present only by physical interactions without forming covalent bond with cellulose.

Moreover, to understand the efficient state of the ASA, three types of hand-sheets containing 0.4% (8 lb/t) ASA were made with different ASA emulsions: fresh emulsion, fresh emulsion and pulp stirred for 3 days, and 3-days-old emulsion. Only the fresh emulsion paper exhibited a sizing effect. SEM data showed large flocs of ASAcid in the two sets of sheets made with either stirred or old emulsion. The set made with fresh emulsion had well dispersed ASA contained within the sheet. The author concluded that fresh ASA emulsion spread over the fiber surface and promotes hydrophobicity.

In 2002, Yu and Garnier [28] concluded from their work that ASA and cellulose are covalently bonded. In the experiment, cellulose film was regenerated from cellulose acetate on glass. ASA vapor was deposited on the substrate in an airtight adsorption cell, which was heated in an oven at a preset temperature and then quenched. The contact angle was measured immediately, and the measurement revealed the substrate was hydrophobic.

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According to the authors, the presence of the OH groups, the temperature dependence of the reaction, the non-decrease in hydrophobicity (even after chloroform extraction), and the time frame (hour) of the reaction are typical for the formation of covalent bond by esterification.

Acha et al. [29] studied the reaction between ASA and wood flour in 2003. The esterification reaction was carried out by immersing the wood flour with an average diameter of 57 µm in 96 g/L (9.6% or 192 lb/ton) ASA in acetone solution; 4-dimethylaminopyridine was used as a catalyst. The mixture was refluxed at 56.5 ◦ C for 4 h. The product was dried at 70 ◦ C in an oven and later washed intensively with distilled water to remove unreacted reagents before it was dried again at 70 ◦ C under vacuum to constant weight. The esterified product was later mixed with unsaturated polyester (UPE) based on bisphenol A-fumarate cross-linked with styrene for molding; benzoyl peroxide was used as an initiator, and polymethyl methacrylate was used as a thermoplastic modifier.

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), a saponification test, and an acid value test were used to analyze qualitatively and quantitatively the esterified products. The results showed that esterification did occur. The yield was 166 g ASA for 1 kg treated wood flour (16.6%).

In 2006, Wang [30] studied ASA sizing mechanism by comparing FT-IR spectra between ASA-sized hand-sheets, synthesized ASA-cellulose compound, hydrolyzed ASA, hydrolyzed ASA-sodium salt, hydrolyzed ASA-calcium salt, and hydrolyzed ASA-aluminum salt. The amount of ASA charged to the studied hand-sheets was 0.5% or 10 lb/t oven-dried pulp. The results showed no covalent bonding between the ASA and the cellulose. In addition, the results suggested that the sizing material found in ASA-sized hand-sheet was mainly hydrolyzed ASA and its salt. The paper also demonstrated that to size hand-sheets directly with hydrolyzed-ASA emulsion resulted in low sizing degree. Nevertheless, after dipping hydrolyzed-ASA-sized hand-sheets in an alum solution, the sizing degree could be brought up to the level close to ASA emulsion sized paper.

Hundhausen et al. [31] studied the reaction of ASA and particleboard chips in 2010.

The objective was to investigate if ASA bonds to the surface of the chips to repel water. The chips were dried to 1% moisture content and then were wetted with 3% or 60 lb/t ASA (based on the oven dry wood). The samples were processed in a rotating reactor at 130 ◦ C and 1013 mbar for 1 h at 12 rpm.

FTIR analysis before and after the treatment revealed that esterification did not occur and both hydrolyzed and non-hydrolyzed ASA were located on the chip surface after curing in the reactor. In addition, FTIR measurement of the chips after Soxhlet extraction did not show any ASA signal, which indicated that the ASA did not esterify and was completely removed by the solvent during the extraction.

Furthermore, ASA-ethyl acetate and ASA dimethyl sulfoxide (DMSO) solutions were applied to veneers. It turned out that the ASA was completely removed after extraction when it was applied in ethyl acetate but not completely in DMSO; the covalently bound ASA could not be extracted. The unextractable amount, or the yield of the reaction, is not known. According to the authors, the ASA esterification with cellulose depends on the solvent that provides certain mobility and orientation to the sizing agent. DMSO leads to esterification but its high boiling point (189 ◦ C) and its poor miscibility with ASA make it disadvantageous. Water emulsions would hamper the ASA penetration into the wood; xylene is a better candidate but harmful for human health.

Masumi et al. [32] used Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to study the ASA sizing mechanism in 2012. ToF-SIMS is a surface-sensitive analytical method that uses a pulsed ion beam to remove molecules from the very outermost surface of the sample. ToF-SIMS collected on an ASA-sized paper sample was compared to the spectra collected from ASA, ASA/water mixture, ASA/NaOH solution, cellulose, and synthesized ASA-cellulose compound. The results indicated that the form of ASA in ASAsized paper was different from that in ASA-cellulose compound, which did not support an ester bonding hypothesis. The ToF-SIMS from ASA/NaOH solution was close to that from

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ASA-sized paper. This suggested the ASA in ASA-sized paper was likely hydrolyzed ASA or its salt.

In 2015, Li et al. [33] studied the anchorage of ASA on cellulose by dipping cellulose film and filter paper in both acetone-ASA solution and ASA emulsion. The cellulose film was generated by immersing cellulose acetate film in 0.5% sodium methoxide in methanol for 12 h. The film was repeatedly rinsed with running deionized water and methanol, air-dried, and stored in a desiccator. The filter paper used was a commercial ash-free filter paper. The ASA-acetone dipping solution contained 1% (20 lb/ton) of ASA and the ASA emulsion, which also contained 1% ASA, was prepared by using laponite as particle stabilizers after being modified by urea, alanine, tetramethylammonium chloride and melamine or in combination with poly-aluminum sulfate (PAS).

The FTIR and the XPS results showed the presence of covalent bonds between ASA and cellulose. The authors concluded that sizing is due to the formation of the ester bond.

The ASA-acetone sizing solution performed better than the ASA emulsion co-stabilized by laponite and PAS due to the absence of water, which tends to produce hydrolyzed ASA more easily. Although the yield of the esterification is not known, the authors suggest that the amount of extractable ASA species in the paper is higher than the amount anchored.

In addition, laponite and PAS co-stabilized emulsions lead to high sizing performance but greatly depend on the use of aluminum sulfate. According to the author, the added aluminum sulfate may improve the retention of ASA or anchor the hydrolyze ASA to the cellulose.

Lackinger et al. [34] attempted to provide proof in favor or against covalent binding of ASA to cellulose in 2015. To avoid the interaction of starch, filter paper was soaked in acetone solutions with various levels of ASA (blank, 1, 5, 10, and 25%) and dried under different conditions (room temperature, drum dryer at 115 ◦ C, drum dryer at 115 ◦ C, and oven at 125 ◦ C). The COOH-selective fluorescent labeling for cellulosic material and the gel permeation chromatography (GPC) with a multi-detector setup for covalently bound sizing agent detection approach was used to provide profiles of carboxyl groups along the molecular weight distribution. The result showed that only about 0.5% of the total ASA covalently bonded to cellulose. Furthermore, hand-sheets were made with 0.2% ASA emulsion in starch, and the correlation between the small amount of covalently bonded ASA and the sizing efficiency of the sheets were studied. The results indicated that there was no correlation between the amount of covalently bonded ASA and sizing efficiency.

The authors concluded from the two sets of experiments that ester bonds between ASA and cellulose were a small fraction and were not a prerequisite for sizing.

In 2016, Porkert [35] worked on the localization of ASA in the sheet using confocal white light microscopy and the dye Sudan Red 7B. Preliminary experiments using thin layer chromatography and FTIR were conducted to ensure that the dye does not affect the processability and the performance of ASA and ASA emulsions. Dyed ASA dosages of 0%, 0.05%, 0.1%, 0.2%, 0.3%, and 0.4% were applied to 100 g/m2 hand-sheets and the shades were correlated to each value. Different sheets were mapped to study the relation between size performance and the homogeneity of the ASA distributions under different dosages and conditions. Some of the conditions are reactive ASA emulsion, cationic and anionic hydrolyzed ASA emulsions, ASA-Starch ratio, and emulsion age.

The study revealed that the ASA sizing mechanism depends on the distribution of the ASA in the sheet. There is a direct correlation between the agglomeration of ASA and sizing performance: the more agglomerates, the weaker the sizing. The application of reactive ASA led to uniform distribution, which results in better sizing performance. Cationic and anionic hydrolyzed ASAs have higher agglomerates thus low sizing performance. Better size distribution and performance were obtained at ASA/starch ratio of 1:1 for low dosage of 0.05% (1 lb/ton) ASA. Concerning the aging, the first 20 min gave the best performance for low and high dosages.

According to the author, the distribution of ASA supports the sizing mechanism based on homogenous molecular distribution and orientation. Hydrophobization is solely

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based on the physical distribution and orientation of the ASA molecules within the sheet.

In addition, the application of reactive ASA is the key element to obtain homogenous distribution as the application of the hydrolyzed ASA led to agglomerations. Furthermore, the esterification reaction between ASA and cellulose is very unlikely to happen during the papermaking process, and the phenomena of size reversion, size reactivation, and size migration exclude any significant extent of esterification but are only explainable by intraand inter-molecular mobilities.

The objective of Wulz [36] in 2020 was to hydrophobize the surface of paper by vapor deposition of ASA, palmitoyl chloride, TFAA/Ac2O (trifluoroacetic anhydride/acetic anhydride), and TFAA/Acetic acid mixtures and hexamethyldisilazane (HMDS). Unsized and untreated papers were used for the experiment. The papers were stored at 23 ◦ C and 50% humidity for at least 24 h. The gas phase ASA deposition was performed at 50 ◦ C and 100 ◦ C at 20 mbar for 2 h. The experiment with ASA did not lead to hydrophobicity, however the experiment with other additives led to hydrophobicity via formation of ester bonds. Due to the poor hydrophobization of the ASA gas phase deposition, no further research was carried out with ASA, and no FTIR data were collected.

There is no doubt that ASA sizes paper. However, the sizing mechanism, especially the covalent bond formation between the ASA and cellulose is a divergence point among scientists, researchers, and papermakers. The covalent bond theory is often used by vendors to explain sizing development. However, the assessment of the available data over the last 60 years shows that the formation of covalent bond is insignificant in ASA-sized paper.

Hydrolyzed ASA and or ASA salts are the fundamental elements found in sized paper.

Catalysts and or organic solvents can be used to initiate esterification, but such conditions are unrealistic in papermaking.

3. Overview of the ASA Mechanism A summary of the proposed reaction mechanisms for ASA sizing suggest that multiple potential pathways exist. The first proposed sizing mechanism is bonded ASA molecules to cellulose via esterification. Though some research using organic solvent, high temperature, or catalyst showed the evidence of ester bond formation, most studies conducted close to commercial papermaking conditions yielded scientific evidence supporting hydrolyzed ASA as the major sizing material in a sized paper. However, the direct application of hydrolyzed ASA to the pulp or the application (coating) of hydrolyzed ASA to the paper does not achieve sizing. Thus, the type of sizing material and the uniform distribution or structure of the sizing material significantly contributes to sizing development [26,27,35,37].

Figure 3 shows the main steps of the ASA sizing process; the oil (ASA) is first emulsified and then applied to the pulp. The pulp is drained and pressed to form a sheet. Sizing is developed after the sheet is dried.

In commercial paper mills, common ASA application consists of preparing the ASA emulsion, which is later added to the pulp at a point close to the fan pump. The mixture is moved to the headbox where the average consistency of the pulp is about 1%, and the predominant component is water, not organic solvent. Although other materials such as alum, PAE (Polyamide Epichlorohydrin), GCC (Ground Calcium Carbonate), CPAM (cationic polyacrylamide), etc., are added to the furnish depending on the paper grade and the papermaker, the predominant component remains water, and the chance of the formation of hydrolyzed ASA is high. The slurry is dewatered then dried in the dryer section of the machine to develop sizing, i.e., the resistance to liquid penetration of the sheet (Figure 3).

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Figure 3. Scheme of ASA sizing process.

commercial FigureThe 3. Scheme of ASApapermaking sizing process.process is more complex than laboratory hand-sheet

making, and the chance of covalent bond formation is even lower than the already low laboratory results due to the following reasons: In commercial paper mills, common ASA application consists of preparing the ASA

Laboratory in theclose mill to (deionized water The vs. white • emulsion, which water is laterquality addedistosuperior the pulptoatthat a point the fan pump. mixture water) [35,38,39]. is moved to the headbox where the average consistency of the pulp is about 1%, and the • Laboratory ASA dosage is usually that used in the mill, predominant component is water, not higher organicthan solvent.

Although other[23,30,31,33–35]. materials such as • In some studies, ASA is applied in organic solvents (DMVPB, DMSO, acetone, toluene, alum, PAE (Polyamide Epichlorohydrin), GCC (Ground Calcium Carbonate), CPAM (catchloroform, ethanol, xylene, ethyl acetate . . . ) that are not found on paper machines to ionic polyacrylamide), etc., are added to the furnish depending on the paper grade and create idealized systems [23,30,31,33–35]. the papermaker, the predominant component remains water, and the chance of the for• One additive (ASA) is usually studied in the laboratory to prevent the influence mation of hydrolyzed ASA is high. The slurry is dewatered then dried in the dryer section of other variables while in real papermaking processes many organics, inorganics, of the additives machine and to develop sizing,compete i.e., the with resistance todwell liquidwith penetration sheet (Figeven bacteria ASA to the fiber. of In the short, there ure 3).are more uncontrolled variables in field experiments than in lab ones [39,40]. commercial papermaking process is more than laboratory hand-sheet • The Lastly, in laboratory studies, sometimes the pulpcomplex or the substrate has a special treatmaking, and the chance of covalent bond formation is even lower than the already ment not found in the mill. Such treatment can be ethanol or methanol wash of the pulplow laboratory duealthough to the following or theresults substrate, it is well reasons: known that these solvents esterify with ASA, and their leftovers in the pulp can of FTIR results [23,26,33,41,42].

Laboratory water quality is mislead superiorthe tointerpretation that in the mill (deionized water vs. white The covalent bond theory was not believed or developed or affirmed by the inventors water) [35,38,39]. and Mazzarella inisthe available patent It ismill, assumed that if a • Wurzburg Laboratory ASA dosage usually higher thandocument that used[1]. in the [23,30,31,33–35]. strong catalyst, a special condition, or an aid that promotes covalent bonding between • In some studies, ASA is applied in organic solvents (DMVPB, DMSO, acetone,the toluASAene, andchloroform, the celluloseethanol, is addedxylene, to the process in the paper it might be on possible ethyl acetate…) thatmill, are not found papertomaformchines covalent bonds idealized between ASA and cellulose.

Some of these catalysts are triethylamine, to create systems [23,30,31,33–35]. methanesulfonic, sulfuric acid, and 4-dimethylaminopyridine [23,26,29,43]. As of now, such • One additive (ASA) is usually studied in the laboratory to prevent the influence of aids are missing in paper mills and the amount of covalent bond between ASA and cellulose other variables while in real papermaking processes many organics, inorganics, adis very low. Covalent bonding is not a prerequisite and does not play a major role in the ditives and even bacteria compete with ASA to dwell with the fiber. In short, there sizing. In addition, the contact between ASA and starch in a real papermaking process is are more uncontrolled variables in field experiments than in lab ones far more intimate and extensive than the contact with cellulose [26,34,44].

The[39,40]. “nebule” of • starch Lastly, in laboratory studies, sometimes the pulp or the substrate has specialthe treatthat vehiculates ASA on the paper machine will eventually break anda release ment not found starch in the does mill. not Such treatment canthe beburst, ethanol or methanol of the additive.

Assuming evaporate after which is realistic,wash another pulp or the substrate, although it is well known that these solvents esterify with ASA, selectivity mechanism will be needed to explain the reason why ASA chooses to bond and their leftovers in the pulp can mislead the interpretation of FTIR results with cellulose instead of starch, which is in closer contact for the assumed esterification reaction.

Furthermore, even if paper mills start using strong catalysts or solvents or a [23,26,33,41,42].

•

special for ASA cellulose esterification, choice these materials needs Thecondition covalent bond theory was not believed orcareful developed orofaffirmed by the inventors to be made with respect to the reaction selectivity, so ASA “droplets” enveloped in starch Wurzburg and Mazzarella in the available patent document [1]. It is assumed that if a (emulsion) do not react with the starch itself or lignin (coniferyl alcohol and sinapyl alcohol)

strong catalyst, a special condition, or an aid that promotes covalent bonding between the ASA and the cellulose is added to the process in the paper mill, it might be possible to

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or other additives or residual wood extractives (fatty alcohols) in the pulp [45–48] but mainly with cellulose and hemicellulose.

After careful review of the past research efforts both supporting and refuting ester bonding of ASA to cellulose, it is believed that, under routine papermaking conditions, the esterification level is almost null in the papermaking process. Future research efforts need to find aids such as harmless catalysts or solvents that promote better yield of esterification, especially in water and on commercial paper machines. Higher esterification yield should be beneficial for the paper sizing process. We believe high yield covalent bonding equates to strong chemical bonds, which will reduce certain amounts of size reversion due to migration, re-orientation, or fugitive ASA molecules.

4. Chemistry Considerations for Better ASA Sizing Application Sizing performance is a function of size distribution, retention, and development. For an ASA sizing program, though there was debate on the sizing development mechanism, a few researchers agreed that better ASA emulsion stability and higher retention improves sizing results [27,30,37,49–51]. Some chemistry considerations for better ASA stability and retention are provided herein.

•

Emulsion Stability (better distribution)

ASA emulsion is made from ASA (oil) and an emulsifier such as cationic starch or polymer in water. Typically, concentrated emulsifier is first diluted with process water to a targeted low concentration. Then, ASA oil is introduced to make the emulsion in high shear equipment. When cationic starch is used as an emulsifier, the most efficient size response is obtained when the mass of the starch is up to 6 times the mass of the ASA; this range obviously depends on the paper grade that is being made and other additives that are being used. In general, it is recommended to keep the mass ratio of the cationic starch to ASA at 4:1 and the particle size about 1 µm [12,35,44,52,53]. pH and temperature of the process water can affect the stability of ASA emulsion.

It is known that ASA is hydrolyzed rapidly at alkaline water pH. The hydrolyzed ASA has been demonstrated to agglomerate, leading to inefficient distribution of the sizing agent [26,30]. Therefore, maintaining the process water pH at neutral or a slightly acidic range can ensure stable emulsion particle size and better distribution. Alum, citric acid, and adipic acid are generally used to adjust pH [12,14,53–55]. Higher temperature generally accelerates chemical reactions, including ASA hydrolysis. If the machine temperature is high, it is better to add ASA emulsion close to the headbox to minimize contact time. In addition, a mill using on-site cooked starch as an emulsifier should pay attention to the starch temperature going to the ASA emulsion process. The optimal temperature for the emulsification process should be determined for better sizing response [2,50,56].

Conductivity is another important water parameter to consider for emulsion (colloidal) stability. High conductivity, due to high electrolyte concentration, collapses the starch or the polymer chain in aqueous solution and leads to unstable emulsion, which in turn leads to poor size distribution [57,58]. The impact of the ionic strength of the process water on the emulsifier can happen at different locations such as the emulsifier dilution point or the ASA emulsion dilution point (push water). For example, if ground water is used for emulsifier dilution, depending on mill location, high hardness (Ca2+ or Mg2+ ) or salinity may impair the emulsifier. Pulping soda carry over is a typical ion source for a virgin machine. Recycle machines may experience unexpected conductivity shock due to salt coming with recycled material.

•

Emulsion Shelf Life

The shelf life of ASA emulsion is another important factor to control after the ASAemulsifier ratio, pH, temperature, conductivity, shear, and other water quality parameters are in their appropriate ranges. In general, the emulsion is used as soon as possible, or less than an hour after it is formed, to prevent the hydrolysis of ASA. Several studies have shown that 20 to 30 min is the best shelf life of an ASA-starch emulsion [6,9,35,59,60].

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The emulsion starts forming large aggregates after 30 min and becomes hydrophilic; the hydrolysis of ASA accelerates and the use of such emulsion forms agglomerates on the paper surface, which lead to inefficient sizing. Knowing the shelf life also gives the ability to estimate how far from the headbox the emulsion must be injected into the pulp for better sizing performance.

ASA sizing certainly reduces the paper tendency to absorb liquid; however, the short shelf life of the ASA emulsion is one of its application drawbacks. There are some novel chemistries to stabilize and extend the emulsion shelf life. Anionic polyacrylamide (APAM), maleated sunflower oil high oleic (MSOHO), urea, combination of laponite and polyaluminum sulfate (PAS), combination of chitosan and montmorillonite, ethyl oleate succinic anhydride (EOSA), methyl oleate-succinic anhydride (MOSA) and lauric arginate/cellulose nanocrystal nanorods (LAE/CNC) can extend the emulsion shelf life from several hours up to a day. More information is needed on large scale availability for industrial use of these products, their environmental impacts, and side effects on the papermaking process [9,60–66].

The decrease in sizing performance versus the age of ASA emulsion is known [67] but how the change in the ASA-emulsifier ratio, pH, temperature, conductivity, and shear of the emulsion individually or collectively affects the aging process is not known. More work needs to be done to understand key factors and at what proportion they influence the rapid ageing or the short life of an ASA emulsion.

•

Emulsion Retention

The retention of ASA emulsion was reported mainly based on charge attraction mechanism between anionic cellulose, amphoteric ASA emulsion particles, cationic polymers, and cationic aluminum compounds. The ASA molecule and the fiber surface are negatively charged while, at the proper pH, the aluminum species supplied by the alum and PAC are positively charged. In addition, the use of alum or PAC puts more cationic charge on the ASA emulsion, which is easily retained on the anionic fiber surface. These two additives improve the sizing due to higher retention, better anchoring, and alignment of ASA to the fiber [52,68,69].

When properly used in papermaking, alum improves retention, drainage, neutralizes anionics, controls pH, and improves runnability. PAC and sodium aluminate are also used as sources of aluminum ions. PAC is known to size at higher pH, improve sizing efficiency, control pitch, reduce or eliminate barium sulfate (BaSO4 ) deposits, while sodium aluminate is known to size at higher pH with less corrosion, and increases retention and paper strength. Alum and PAC are commonly used for ASA applications; in addition, alum is suitable for acidic paper making, while PAC can be used in neutral or alkaline paper making [70–73].

Alum was first used in paper sizing in combination with rosin in 1807 by Moritz Friedrich Illig. The chemical was later used in AKD and ASA sizing applications. Alum is known to form a bridge between cellulose and the sizing agent depending on the pH and the species of the aluminum ions available. As shown in Figure 4, alum generally will exist in one of three dominant species: Al3+ (pH less than 4.3), Al8 (OH)20 4+ (pH 4.3–5.0), or Al(OH)3 (pH 5.0–8.0). The adsorption of the aluminum ions Al3+ to the fiber occurs at low pH and understanding the pH regions of alum is paramount for ASA addition and retention [8,57,74,75].

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known to form a bridge between cellulose and the sizing agent depending on the pH a the species of the aluminum ions available. As shown in Figure 4, alum generally will ex in one of three dominant species: Al3+ (pH less than 4.3), Al8(OH)204+ (pH 4.3–5.0), Al(OH)3 (pH 5.0–8.0). The adsorption of the aluminum ions Al3+ to the fiber occurs at lo pH and understanding the pH regions of alum is paramount for ASA addition 11 of 15and rete tion [8,57,74,75].

FigureFigure 4. Distribution ofofHydrolyzed Aluminum as a Function of(III) pH. Al × (III) 1.024× 10−3 M, 4. Distribution Hydrolyzed Aluminum (III)(III) as a Function of pH. Al = 1.0 10−=3 M, h (Adopted fromfrom Rubin and [76]). h (Adopted Rubin andHayden Hayden [76]).

ASA salt, mainly aluminum-ASA salt, is one of the predominant forms of ASA found

ASA salt, mainly aluminum-ASA salt, is one of the predominant forms of ASA fou in the sheet beside the hydrolyzed ASA. The use of alum enables the formation of the nonin thetacky sheetaluminum beside the ASA.over Thethe use of alum enables the formation of the no salthydrolyzed which is preferred sticky calciumor magnesium-ASA salt. tackyInaluminum salt preferred over the sticky calciumor magnesium-ASA sa addition, the usewhich of alumiscontrols the deposit of hydrolyzed ASA, and the aluminum salt of thethe hydrolyzed ASA may interact with the anionic charges on cellulose to improve In addition, use of alum controls the deposit of hydrolyzed ASA, and the aluminu sizing. Furthermore, the application of alum can anchor free hydrolyzed ASA to the fiber as salt of the hydrolyzed ASA may interact with the anionic charges on cellulose to impro a metal salt to reduce, to delay, or to reverse size reversion due to migration, reorientation sizing. the application of alum can anchor free hydrolyzed ASA to the fib or Furthermore, fugitivity [26,52,67,75]. as a metalThe saltdosage to reduce, toordelay, to reverse size reversion duethe to papermaking migration, reorien of alum PAC isor critical as it can improve or impair process and paper properties.

It is reported that 0.5% alum based on dry pulp is generally tion or fugitivity [26,52,67,75]. sufficient [75].

However, a preliminary alum or PAC application optimization study be The dosage of alum or PAC is critical as it can improve or impair thewill papermaki ideal for each paper mill to determine the dosage, injection location, and the sizing efficiency. process and paper properties. It is reported that 0.5% alum based on dry pulp is genera An excessive use of alum can lead to deposits on the paper machine, loss of sizing, and sufficient a preliminary alumaluminate or PAC application optimization loss of[75]. sheetHowever, strength. Alum, PAC, or sodium deposits require downtime forstudy w cleanup; analysis has shown these depositsthe are dosage, mainly aluminum hydroxide [Al(OH) be ideal for each paper mill that to determine injection location, and3 ]the sizi and complex aluminum hydroxides [Al (OH) (SO )nH O, Al (OH) Cl nH O], which can x y x y 2 2 paper 2 efficiency. An excessive use of alum can lead 4to deposits on the machine, loss be found on the primary screens, machine chest, headbox, blades, and vacuum box [73]. sizing, and loss of sheet strength. Alum, PAC, or sodium aluminate deposits requ In addition, excessive use of alum has little effect on sizing at low concentrations but downtime for sizing cleanup; analysis has shown these deposits are mainly aluminum h decreased at higher concentrations.

The that overuse of alum has a degradative effect on droxide [Al(OH) 3 ] and complex aluminum hydroxides [Al x (OH) y (SO 4 )nH 2 paper as it becomes more acidic and undergoes acid hydrolysis that causes cellulose chain scission resulting in the loss paper strength [8,52,68,70].

Alx(OH) yCl2nH 2O], which canofbe found on the primary screens, machine chest, headbo Finally, excessive use of defoamer and certain biocides hasofanalum adverse oneffect sizing on sizi blades, and vacuum box [73]. In addition, excessive use haseffect little performance. It is known the excessive application of defoamer, especially at the wet at lowend, concentrations but decreased sizing at higher concentrations. The overuse of alu destroys sizing [58,77,78], but it is not well understood if the defoamer or the biocide has a prevents degradative effect on paper as it becomes acidic undergoes hydroly ASA from anchoring to cellulose or if thesemore chemicals justand attack and ruin theacid sizing agent. Quaternary ammonium saltresulting biocide is known to cause adversestrength effects on[8,52,68,70]. sizing that causes cellulose chain scission in the loss of paper Finally, excessive use of defoamer and certain biocides has an adverse effect on sizi performance. It is known the excessive application of defoamer, especially at the wet en

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while organosulfur and isothiazoline has almost no effect on sizing performance. More investigations are needed to determine the mechanism by which defoamers or biocides negatively affect ASA. 5. Conclusions Several experiment-result papers and patents about the ASA application were reviewed from 1963 to 2020.

•

• •

• • •

•

It was believed that ASA formed covalent bonding with cellulose during the papermaking process. Nevertheless, most recent scientific evidence supports that the major sizing material in a sized paper is hydrolyzed ASA and its salts.

The amount of covalent bonds between ASA and the fiber is very low and is not a requirement to sizing development.

Hydrolyzed ASA contributes to the sizing performance; however, the direct application of hydrolyzed ASA to the pulp or the application of hydrolyzed ASA to the sheet leads to flocculation and does not achieve sizing.

The pH, temperature, conductivity, and the ASA-emulsifier ratio are critical for ASA emulsion stability.

Alum or PAC, when properly used improve sizing performance.

The shelf life of the ASA emulsion is about 20 to 30 min. More work is needed to understand how the change in ASA concentration, ASA-starch ratio, temperature, and pH individually or collectively affects the ageing process.

The use of novel chemistries to stabilize or extend ASA emulsion shelf life should be investigated for large scale availability, health and environmental impacts, and repercussions on the papermaking process.

Author Contributions: Writing—original draft preparation, Y.N. and L.X.; writing—review and editing, Y.N., L.X., S.B., Y.J., and P.W.H.; supervision, P.W.H. and Y.J.; project administration, P.W.H.; funding acquisition, Y.J. All authors have read and agreed to the published version of the manuscript.

Funding: This research was supported by WestRock. The publication cost was provided by the Chemical Engineering Department of the University of North Dakota.

Data Availability Statement: No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Acknowledgments: The authors want to thank Nichole Kilgore, Data Scientist at WestRock, for her constant help in providing needed articles for this review paper.

Conflicts of Interest: The authors declare no conflict of interest.

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

CO2 Emissions Accounting and Carbon Peak Prediction of China’s Papermaking Industry JIAMENG YANG1, YUCHEN HUA1, JIARONG YE1, SHIYING XU1 & ZHIYONG (JOHN) LIU2 China has been the world’s largest producer and consumer of paper products. In the context of the “carbon peaking and carbon neutrality goals”, China’s papermaking industry which is traditionally a high energyconsuming and high-emissions industry, desperately needs a nationally appropriate low-carbon development path. From the consumption-side perspective, this paper calculates the CO2 emissions of China’s papermaking industry from 2000 to 2019 by using carbon emission nuclear algorithm, grain-straw ratio, firstorder attenuation method, and STIRFDT decomposition model, etc., to further explore the core stages and basic patterns affecting the industry’s carbon peaking. The results show that the total CO 2 emissions of China’s papermaking industry showed an upward trend from 2000–2013, stable from 2013–2017, and a steady but slight decline from 2017–2019. Meanwhile, the total CO2 emissions of the full life cycle of paper products in China have decreased to a certain extent in the raw material acquisition, pulp, and paper making and shipping stages, with only the waste paper disposal stage showing a particular upward trend. We find that from 2000 to 2019, China’s CO2 emissions in the pulping and papermaking stage of paper products accounted for 68% of the total emissions in the whole life cycle, of which 59% was caused by coal consumption. Moreover, the scenario prediction shows that improving the energy structure and increasing the waste paper recovery rate can reduce the CO 2 emissions of the industry, and it is more significant when both work. Based on this and the four core stages of CO 2 emissions of the papermaking industry we proposed ways to promote CO2 emissions peaking of China’s paper products.

Contact information: 1 College of Economics and Management, Nanjing Forestry University, Nanjing 210037, China.

2 Networks Financial Institute, Donald W. Scott College of Business, Indiana State University, 30 N 7th St., Terre Haute, IN 47809, USA. Forests 2022, 13, 1856. https://doi.org/10.3390/f13111856 This is an open access article under the CC BY-licence 4.0

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 22

Article 4 – Emissions Accounting

Article

CO2 Emissions Accounting and Carbon Peak Prediction of China’s Papermaking Industry Jiameng Yang 1, * , Yuchen Hua 1 , Jiarong Ye 1 , Shiying Xu 1 and Zhiyong (John) Liu 2 1 2

*

Citation: Yang, J.; Hua, Y.; Ye, J.; Xu, S.; Liu, Z. CO2 Emissions Accounting and Carbon Peak Prediction of China’s Papermaking Industry.

College of Economics and Management, Nanjing Forestry University, Nanjing 210037, China Networks Financial Institute, Donald W. Scott College of Business, Indiana State University, 30 N 7th St., Terre Haute, IN 47809, USA Correspondence: yjm@njfu.edu.cn

Abstract: China has been the world’s largest producer and consumer of paper products. In the context of the “carbon peaking and carbon neutrality goals”, China’s papermaking industry which is traditionally a high energy-consuming and high-emissions industry, desperately needs a nationally appropriate low-carbon development path. From the consumption-side perspective, this paper calculates the CO2 emissions of China’s papermaking industry from 2000 to 2019 by using carbon emission nuclear algorithm, grain-straw ratio, first-order attenuation method, and STIRFDT decomposition model, etc., to further explore the core stages and basic patterns affecting the industry’s carbon peaking. The results show that the total CO2 emissions of China’s papermaking industry showed an upward trend from 2000–2013, stable from 2013–2017, and a steady but slight decline from 2017–2019.

Meanwhile, the total CO2 emissions of the full life cycle of paper products in China have decreased to a certain extent in the raw material acquisition, pulp, and paper making and shipping stages, with only the waste paper disposal stage showing a particular upward trend. We find that from 2000 to 2019, China’s CO2 emissions in the pulping and papermaking stage of paper products accounted for 68% of the total emissions in the whole life cycle, of which 59% was caused by coal consumption.

Moreover, the scenario prediction shows that improving the energy structure and increasing the waste paper recovery rate can reduce the CO2 emissions of the industry, and it is more significant when both work. Based on this and the four core stages of CO2 emissions of the papermaking industry we proposed ways to promote CO2 emissions peaking of China’s paper products.

Forests 2022, 13, 1856. https:// doi.org/10.3390/f13111856

Keywords: paper and paper products; LCA; CO2 emissions; carbon peaking

Academic Editors: Chul-Hee Lim and Moonil Kim Received: 7 October 2022

1. Introduction

Accepted: 3 November 2022

Since the 21st century, global problems such as lack of resources, environmental damage, and climate change have become increasingly prominent. China has overtaken the United States as the world’s largest CO2 emitter since 2009 [1], and in 2019, China’s CO2 emissions were higher than the combined CO2 emissions of the United States and European Union (EU) countries, with a global share of 29.37% [2]. According to China’s Intended Nationally Determined Contributions (INDC) commitment, they “Strive to achieve carbon peaking by 2030 and carbon neutrality by 2060”. Energy saving and carbon reduction have become essential tasks to help achieve the “carbon peaking and carbon neutrality goals” in the coming period. The papermaking industry presents an energy-intensive sector, which accounted for approximately 1.4% of total national manufacturing energy consumption in 2021 [3]. China is the world’s largest producer and consumer of paper and paperboard [4,5], and the types and quantities of paper products are increasing with the growth of the population and the improvement of people’s living standards. National paper and paperboard production reaches 112.60 × 106 tons in 2020, up 4.60% from 2019 [6]. Currently, China’s papermaking industry is still in the rising stage of industrial development and energy consumption, and the corresponding CO2 emissions continue to increase with the increase

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Copyright: © 2022 by the authors.

Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Forests 2022, 13, 1856. https://doi.org/10.3390/f13111856

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in paper products production [7]. Hence, scientific accounting of CO2 emissions from the whole life cycle of paper products can provide an information reference for the development of China’s paper product CO2 emission life cycle database and related standard guidelines, which is of positive significance to the green transformation development of the papermaking industry.

Currently, the methods used by scholars to account for CO2 emissions from the production process of paper products mainly include the carbon emission factor method, inputoutput method, and life cycle assessment. Fleiter et al., Zhang et al., and Wang et al. [8–10] all used the carbon emission factor method provided in the Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories to account for the CO2 emissions generated by the pulp and paper production process of paper companies as well as the industry. Pulping and papermaking are the main processes in paper product production, yet the waste treatment processes are also crucial. Wang et al. [11] measured the CO2 emissions of pulp making, alkali recovery, and wastewater treatment processes in papermaking enterprises in Shandong and Jiangsu provinces using the carbon emission factor method, and the results showed that CO2 emissions per unit of straw pulp were the highest, followed by wood pulp, and waste pulp was the lowest. Chen et al. [12] estimated energy consumption and CO2 emissions of the Chinese papermaking industry from a supply chain perspective supplemented by the energy input/output method, involving the main processes of forest cultivation, logging, pulp, and paper production. Accounting found that the total CO2 emissions of China’s papermaking industry in 2011 was 149.74 × 106 t, with unit CO2 emissions of about 1543 kg/t paper, much higher than the 200 kg/t paper in the Netherlands and 204 kg/t paper in Sweden in the same period (We need to note that the energy mix in China is very different from that in Europe. China is a country rich in coal resources, but less in oil and natural gas resources, and the development and use of new energy in the overall energy system is not yet in a dominant position, contrary to the widespread use of renewable energy in European plants. Therefore, China is one of a few countries in the world whose energy production and consumption is dominated by coal. These differences are also directly reflected in the difference in carbon emissions from the paper industry). Zhao et al. [13] accounted and analyzed the implicit carbon flows and CO2 emissions in the production and operation of Stora Enso (Guangxi), an integrated forest-paper enterprise, based on the multi-level input/output method of the forest-pulppaper supply chain, and proposed relevant ways to reduce CO2 emissions in the enterprise.

In addition, Furszyfer Del Rio et al. [14] presented the main determinants of energy and CO2 emissions emerging from the papermaking industry and barriers to decarbonization of the papermaking industry based on a socio-technical utilization perspective.

Life cycle assessment (LCA) is a method to quantitatively evaluate the resource consumption and environmental impact of a product throughout its life cycle, from the acquisition of raw materials, the production of the product to the disposal of the product after use, etc. It is a product-oriented environmental load quantification tool and is increasingly used in the papermaking industry. In terms of theoretical exploration, Li et al. [15] used life cycle theory to construct an analytical framework for CO2 emission accounting of paper products in the papermaking industry; Liu et al. [16] analyzed the carbon source and carbon sink flow of paper enterprises in the context of forest-paper integration; Ma et al. [17] constructed a carbon footprint evaluation system for products in the papermaking industry and evaluated the application of carbon footprint in the papermaking industry and enterprises. Tang and Zheng [18,19] divided the life cycle of paper products into four stages from the perspective of market consumption: input period, growth period, maturity period, and decline period, and based on the characteristics of each stage, the development stages of paper products and their characteristics were judged through the analysis of indexed data such as types of paper products, production volume, consumption, and degree of industry competition, etc. As for empirical studies, Lopes et al. and Dias et al. [20,21] used the LCA method to evaluate the environmental impact of the papermaking industry in Portugal. Gemechu et al. [22] used the LCA method to calculate and analyze the green-

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house gas emissions from virgin wood pulp and waste pulp papermaking processes, and found that waste pulp papermaking produced fewer greenhouse gases. Chen et al. [23] analyzed the 2010 and 2015 life cycle CO2 emissions of paper products in China. The scope covered in their study was relatively complete, including forest plantation, pulp and paper making, transportation, waste paper recycling and pulp making, incineration, and landfill.

However, their analysis did not include non-wood pulp raw materials in the production process, and the CO2 emissions from the pulp and papermaking process accounted for as much as 86.33% of their results. It is worthwhile to note that the process of paper making is generally divided into two types: wet paper and drying process. Currently, China is still dominated by the former, but the latter is also developing. Different processes are used to produce different types of paper. The types of paper produced in China mainly include corrugated paper, containerboard, printing paper, and newsprint. The array of paper product categories varies from country to country.

In summary, scholars’ research results on CO2 emission accounting in the papermaking industry are relatively abundant and they provide an essential reference for the study of this paper. However, studies on CO2 emissions of paper products are basically based on the production-side perspective, mainly accounting for CO2 emissions of the pulp and paper production process. With the development of trade globalization, the import and export trade of paper products has become more and more frequent, and it is easy to ignore the spatial transfer of CO2 emissions in the trade by accounting only from the production side. At the same time, the existing research also needs to deepen further the determination of the system boundary of the whole life cycle of the papermaking industry.

Accordingly, this paper combines the perspective of consumer responsibility to provide a more complete estimation of CO2 emissions of Chinese paper products from 2000 to 2019, from various stages in the whole life cycle, including raw material acquisition, pulp and paper production, trade and transportation, waste paper disposal, and export. On this basis, the impact of relevant policies on CO2 emissions in the papermaking industry is discussed at both macro and micro levels, and then specific paths are proposed to promote the industry’s “carbon peaking”.

2. Materials and Methods 2.1. System Boundary and CO2 Emission Source Determination 2.1.1. System Boundary CO2 emissions from the perspective of consumer responsibility are based on the carbon footprint idea, accounting for the total amount of greenhouse gas emissions from products or services consumed by enterprises and individuals in the process of transportation, production, and consumption, which is equivalent to the production-side CO2 emissions minus the CO2 emissions of exported products plus the CO2 emissions of imported products, where the difference between the CO2 emissions of imported and exported products is the implied CO2 emissions of product trade [24–26]. In order to comprehensively and systematically quantify the CO2 emissions of paper products at all stages of production and consumption, this paper adopts the whole life cycle accounting method and proposes a system boundary for CO2 emissions accounting of paper products, as shown in Figure 1.

The system boundary is the sub-interface between the system and the environment.

The environment of the whole life cycle CO2 emission system of paper products includes resources and energy input, and CO2 output. The whole life cycle of paper products is mainly divided into four stages within the system: raw material acquisition stage, pulp and paper stage, waste paper disposal stage, and transportation stage. Considering the data acquisition problem, CO2 generated by paper and paperboard in domestic consumption is not included in the accounting system. Under the perspective of consumer responsibility, and based on the principle of who consumes who bears, part of the CO2 emissions from paper and paperboard exported from China (including production and transportation) are borne by the importing country, and this part should be subtracted from the accounting process. In addition, China imports mainly wood pulp and waste paper which are semi-

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finished products, and still need to be processed in China. Thus, the CO2 emissions from Forests 2022, 13, x FOR PEER REVIEW 4 of 22 this part are divided into the pulp and paper stage and the transportation stage, which are

included in the accounting system.

Figure Figure1.1.CO CO22 emission emission accounting accounting boundary boundary of of paper paper products productsin inthe thewhole wholelife lifecycle. cycle.

2.1.2. The CO2system Emission Source Determination boundary is the sub-interface between the system and the environment.

(1) The raw material acquisition China’s paper system raw materials are currently domiThe environment of the whole lifestage. cycle CO 2 emission of paper products includes natedand by waste pulp followed by2 output. wood pulp, consuming theis resources energy input, and CO The with wholenon-wood life cycle pulp of paper products lowest percentage.

Non-wood pulp originates from mainly divided into four stages within the system: rawdomestic materialproduction, acquisitionwhile stage,waste pulp wood pulp originate from domestic production and imports.

The CO 2 and pulp paperand stage, waste paper disposal stage, and transportation stage.

Considering the emissions from the production or import of the three raw materials are defined in data acquisition problem, CO2 generated by paper and paperboard in domestic consumpbelow. in the accounting system. Under the perspective of consumer respontion Table is not 1included (2) The pulp and on paper stage. This stageconsumes is the process of pulp processing produce sibility, and based the principle of who who bears, part of the COto 2 emissions which involves CO2 emissions frompaper paperand andpaperboard, paperboard exported from China (including including productionfuel andcombustion transportaemissions, chemical decomposition emissions, and electricity and heat consumption tion) are borne by the importing country, and this part should be subtracted from the emissions.

The research boundary the pulp and paper based on paper the accountaccounting process.

In addition, China of imports mainly woodstage pulpis and waste which ing standards for greenhouse gas emissions from the papermaking industry defined are semi-finished products, and still need to be processed in China. Thus, the CO 2 emisthe “Greenhouse Gas Emissions Accounting Methodology and Reporting Guidesionsinfrom this part are divided into the pulp and paper stage and the transportation stage, lines for Paper and Paper Products Producers in China (for Trial Implementation)”. which are included in the accounting system.

Additionally, the amount of CO2 emissions due to fuel combustion was accounted for to Zhang et al.

[9], and Peng et al. [27].

2.1.2.according CO2 Emission Source Determination (3) The waste paper disposal stage. Drawing on the research results of Gonzalez(1) Garcia The raw stage. chu China’s paper the rawcore materials currently domiet material al., Ghoseacquisition et al., and Geme [22,28,29], aspectsare of raw material innated by waste pulp followed by wood pulp, with non-wood pulp consuming the put, production, and product output in the transportation phase of paper products are lowest percentage.

Non-wood pulpAmong originates domesticinput production, while included in the accounting boundary. them,from raw material transportation waste pulp and wood pulp originate from domestic production and imports. includes pulp raw materials from domestic origin or foreign imports transportedThe to COpulp 2 emissions from the production or import of the three raw materials are defined the and paper enterprises and after the use of waste paper recycling transported in the Table 1 below. to pulp and paper enterprises recycling; product output transportation includes (2) finished The pulppaper and paper stage. Thisfrom stagethe is the process of pulp processing to produce and paperboard production enterprises transported to the paper and paperboard, which involves CO 2 emissions including fuel combustion paper products suppliers, distributors, individual consumers or export transported to emissions, chemical decomposition emissions, and electricity and heat consumption emissions. The research boundary of the pulp and paper stage is based on the accounting standards for greenhouse gas emissions from the papermaking industry defined in the “Greenhouse Gas Emissions Accounting Methodology and Reporting Guidelines for Paper and Paper Products Producers in China (for Trial

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(4)

other countries. Under the consumer responsibility principle, CO2 emissions from the export transportation of paper and paperboard should be borne by the importing country of paper and paperboard, and this part of CO2 emissions is not included in the transportation phase of paper products. Due to the availability of data, CO2 emissions from the export transportation of the product to the consumer are difficult to calculate, and the part of the production process that involves transportation from the workshop is neglected.

The transportation stage. China’s waste paper disposal mainly has three ways: landfill, incineration, and recycling [23]. Waste paper recycling and utilization is an important part of the closed-loop material flow of “resource consumption-products-renewable resources” in the papermaking industry, and the CO2 generated from recycling is included in the transportation stage. For the convenience of estimation, it is assumed that the waste paper is landfilled or incinerated in the open air without fixed concentration points, and methane recovery is not considered in the landfilling process, so the CO2 released in the landfilling or incineration process is mainly accounted for in the waste paper disposal stage.

Table 1. Three sources of raw materials and definition of CO2 emissions.

Raw Materials

Origins

Notes

Domestic timber harvesting and transportation

The proportion of foreign imported wood used for furniture manufacturing is high, and only a small portion of it is used for pulp and paper making, so the CO2 generated from the transportation of this part of imported wood is negligible. The CO2 generated in the process of forest plantation can be absorbed by its own photosynthesis, so we do not calculate CO2 emissions from forest plantation, but only calculate CO2 emissions from domestic harvesting of wood for pulp and paper production.

Foreign wood pulp import

Wood pulp imported from abroad is mainly involved in transportation distance and transportation volume, so CO2 generated from imported wood pulp is included in the transportation phase for calculation.

Non-wood pulp

Domestic production

Among non-wood pulp, rice-wheat straw pulp has always accounted for the highest percentage [6], so we mainly calculate the CO2 emissions from the rice-wheat straw pulp feedstock acquisition process, and then estimate the CO2 emissions from the non-wood pulp feedstock acquisition process based on the percentage of rice-wheat straw pulp.

Waste paper pulp

Domestic recycling and foreign import of waste paper

Both domestic waste paper recycling and foreign waste paper import mainly involve transportation, so this portion of CO2 emissions are included in the transportation phase.

Wood pulp

2.2. Calculation Method 2.2.1. Accounting for CO2 Emissions in the Raw Material Acquisition Stage Timber Harvesting Process The acquisition of wood pulp raw materials (wood harvesting process) involves three processes: logging for timber, skidding, and transportation. The accounting of CO2 emissions from this process is based on the carbon emission factor method of the National Greenhouse Gas Emissions Inventory Guidelines. The formula is as follows.

1

Logging and timbering operations: Ch = ed × Eh = ed × Wh × Wah

(1)

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In Equation (1), Ch is the CO2 emission from logging and timbering operation activities (106 t), ed is the CO2 emission factor of diesel fuel (tCO2 /t), Eh is the energy consumption of logging and timbering (106 t), Wh is the volume of paper logging (m3 ), and Wah is the average fuel consumption of chainsaw in logging operation (t/m3 ).

2

Mechanical ropeway skidding operations: Cm = ed × Em = ed × Wm × Wam × Lm

(2)

In Equation (2), Cm is the CO2 emission of ropeway skidding operation activity (106 t), Em is the energy consumption of ropeway skidding (106 t), Wm is the volume of skidding (m3 ), Wam is the average fuel consumption of mechanical ropeway skidding (t/m3 .km), and Lm is the length of ropeway (km).

3

Material transport operations: Cl = ed × El = ed × Wl × Wat × Ll

(3)

In Equation (3), Cl is the CO2 emission from the vehicle timber transport activity (106 t), El is the energy consumption of timber transport (106 t), Wl is the volume of timber transported (m3 ), Wat is the average fuel consumption of timber transport (t/m3 .km), and Ll is the distance of timber transport (km). Assuming no damage to wood during skidding and transportation, i.e., Wh = Wm = Wl . The final CO2 emissions during the wood pulp raw material acquisition stage are Cw = Ch + Cm + Cl .

The Process of Obtaining Raw Materials for Rice and Wheat Straw Pulp Rice-wheat straw pulp is one of the important ways to utilize straw as raw material.

CO2 emissions from this process include: 1 CO2 from the use of agricultural chemicals (fertilizers, pesticides); 2 CO2 from the consumption of diesel fuel for irrigation [30], tilling and harvesting with agricultural machinery, etc. Refer to the grain/straw ratio method.

The formula is as follows. i

Cn = n−1 × ∑i=1 ARi × ci × A

(4)

In Equation (4), A is the area of rice planted for papermaking, Cn is the CO2 emission in the non-wood pulp raw material acquisition stage (106 t), n is the ratio of rice-wheat straw pulp production to total non-wood pulp production, ARi is the i-th agricultural input per hectare of rice planted area (t/hm2 , kW-h/hm2 ). According to the statistics of the China Rural Statistical Yearbook, agricultural inputs include nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, compound fertilizer, herbicide, insecticide, fungicide, diesel, agricultural film, rice seed and electricity. ci is the CO2 emission factor of the i-th agricultural input (tCO2 /t, tCO2 /kW-h). CO2 emissions in the raw material acquisition stage of the final paper product C A = Cw + Cn .

2.2.2. Accounting for CO2 Emissions in the Pulp and Paper Stage The pulp and paper stage mainly generates CO2 emissions from energy consumption.

In this paper, the carbon emission nuclear algorithm is used to calculate CO2 emissions based on the energy consumption of the pulp and paper stage and the CO2 emission factor of energy, the formula is as follows. j

CB = ∑ c j = ∑ e j × f j

(5)

j =1

In Equation (5), CB is the CO2 emission of the pulp and paper stage (106 t), c j is the CO2 emission of various energy sources consumed in this stage (106 t), and e j is the physical quantity of various energy sources consumed (106 t, m3 , kW-h). According to the statistical

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caliber of China Statistical Yearbook, the energy consumed in the pulp and paper stage includes coal, coke, crude oil, gasoline, kerosene, diesel, fuel oil, natural gas, and electricity. f j is the CO2 emission coefficient of each energy source (tCO2 /t, tCO2 /m3 , tCO2 /kW-h).

2.2.3. Accounting for CO2 Emissions in the Waste Paper Disposal Stage The accounting method on transportation CO2 emissions mainly refers to the idea of the STIRPAT factor decomposition model [31,32], Which is based on constructing an accounting model of energy consumption in the transportation process of paper products, and then combining it with the carbon emission factor method. To account for CO2 consumption during the transportation of paper products, the formula is as follows.

CT = ∑ F ×

K E K E × µi C × i × µi = ∑ F × × i = F × D × = ∑ F × D × ϕj F K F K K

(6)

In Equation (6), CT is the total CO2 emission during the transportation of paper products (106 t), F is the freight volume of paper products (106 t); K is the turnover of paper products (106 t.km), and KF is the transportation distance of paper products (km), expressed as D; Ei is the consumption of the i-th energy source during the transportation of paper products (106 t), and EKi is the consumption of various energy sources per 106 t of paper products in 1km-transportation (t/106 t.km), µi is the CO2 emission coefficient of C each energy source, K is the CO2 emission per 106 t of paper product in 1km-transportation 6 (tCO2 /10 t.km), i.e., the CO2 emission coefficient of transportation mode, expressed as ϕ j , j is the jth transportation mode. For the convenience of calculation, ϕ j is set constant for each transportation mode.

(1)

CO2 emission accounting method for the transportation process of imported paper raw materials

In international trade, the distance of cargo transportation is mostly measured by the shortest spherical distance between the capitals of the two trading countries [33,34], but this is generally applicable to air transportation methods, and if used as a distance measure for waterway transportation, it will greatly underestimate the actual distance of cargo transportation [35]. Due to the low cost and high volume of waterway transportation, Chinese paper raw material imports are mainly transported by waterway. To make up for the shortcomings of this international transport distance measure, the traditional international trade transport distance is split into the international and domestic distance measures [35], and in this paper, the transport distance of paper raw material import is divided into two parts with the main Chinese port as the transit point, the first part is the international distance transported from the paper raw material exporting country to the main Chinese port, and the second part is the domestic distance transported from the main Chinese port to the paper and paperboard main production provinces in China. The two paper raw materials (pulp and waste paper) source countries are not exactly the same and they are from numerous source countries, hence, for ease of accounting, we only set China’s largest port of international trade—Shanghai—for the international distance in the destination, the largest port of paper raw materials exporting countries as the starting place. The actual water transport distance between these two places is the international distance of paper raw materials imports. As for the domestic distance, according to reality, we set Qingdao port, Tianjin port, Shanghai port, Xiamen port, and Shenzhen port as the main ports of paper raw material imports [36]. The main provinces of paper and paperboard production follow the nearest and only principle, i.e., it will be from the nearest port and only from this port to import pulp and waste paper. Therefore, the actual distance between the main ports and the provincial capitals of the main paper and paperboard-producing provinces is the domestic distance. In summary, the formula for accounting for CO2 emissions during the transportation of imported paper raw materials is as follows.

α β C I = ∑α=1 Fp × Dα × ϕ1 + ∑ β=1 Fw × Dβ × ϕ1 + Fp + Fw × D N × ϕ2

(7)

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In Equation (7), C I is the total CO2 emission of paper raw material import transportation (106 t), Fp and Fw are the import volume of pulp and waste paper respectively (106 t), and the sum of both is the total import volume of paper raw material (106 t), Dα and Dβ are the water transportation distance between the largest port of the αth pulp exporting country and the βth waste paper exporting country and Shanghai port respectively (km), and ϕ1 is the CO2 emission coefficient of waterway transportation mode (tCO2 /106 t.km). Since it is difficult to obtain specific data on the volume of pulp and waste paper transported by the main paper and paperboard producing provinces from each major port, D N is the average distance (km) of the actual distance between all major ports to the provincial capitals of the main paper and paperboard-producing provinces, and based on the average distance, we set that the domestic transport process is dominated by rail transport, and ϕ2 is the CO2 emission factor of the rail transport mode.

(2)

CO2 emission accounting method for domestic waste paper recycling and transportation process

Paper and paper products are involved in almost every aspect of everyone’s life, and within the Chinese region, the consumer market is nationwide, with waste paper generally originating from China’s 31 provinces, autonomous regions, and municipalities (Hong Kong, Macau, and Taiwan of China are not counted). The recovered waste paper is transported to 16 paper and paperboard-producing provinces with complicated and irregular transportation routes. Therefore, this paper sets 31 provinces, autonomous regions, and municipalities directly under the Central Government to follow the principle of proximity and uniqueness, i.e., only transport to the nearest major paper and paperboardproducing province. Taking the actual distance between these two provincial capitals as the transportation distance of waste paper recycling, and the transportation mode is also mainly railroad transportation, the CO2 emission accounting formula of the domestic waste paper recycling transportation process is as follows.

Cz = Fw × Dw × ϕ2

(8)

In Equation (8), Cz is CO2 emissions from domestic waste paper recycling transportation (106 t). Since specific data on the amount of waste paper shipped to the main paper and paperboard production sites in each province and city are not available, Fw is the total amount of waste paper recovered (106 t) and, Dw is the average distance (km) between the source of all recovered waste paper and the provincial capitals of the main paper and paperboard production sites.

2.2.4. Accounting for CO2 Emissions in the Transportation Stage In order to ensure the consistency of methods and data sets in the time series and minimize accounting errors, the first-order attenuation method is used to estimate the CO2 emissions from waste paper open landfill and incineration.

(1)

Open landfill

Open-air landfills mainly release CH4 , and the accounting converts CH4 emissions into CO2 emissions, with the following accounting formula.

C J = MSWm × DOC × DOC f × MCF × F ×

16 12

Cd = MSWm × DOC × DOC f × (1 − MCF × F ) ×

(9) 44 12

(10)

In Equations (9) and (10), MSWm is the volume of waste paper landfill (106 t), DOC is the proportion of decomposable organic carbon (%) (how many kg of carbon per kg of landfill waste paper), DOC f is the proportion of decomposable DOC (%), MCF is the CH4 correction factor for aerobic decomposition (%), F is the proportion of CH4 in landfill gas 16 44 (%), 12 is CH4 /C molecular weight ratio, and 12 is the CO2 /C molecular weight ratio.

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(2)

Open burning

Assuming that the waste paper is burned completely in the open air, releasing mainly CO2 gas and producing very little CO, the CO2 emissions from this part are accounted for by the following formula.

Cv = MSWs × CF × FCF × OF ×

44 12

(11)

In Equation (11), MSWs is the waste paper incineration volume (106 t), CF is the carbon content of waste paper (%), FCF is the fossil carbon percentage of waste paper (%), and OF is the oxidation factor.

2.2.5. Accounting Methods for Export Paper and Paperboard CO2 Emissions From a consumer responsibility perspective, CO2 emissions from the production and other processes of paper and paperboard exported from China should be borne by the importing country and not counted as part of the whole life cycle CO2 emissions of Chinese paper products. The formula for accounting for CO2 emissions from this portion of paper and paperboard is as follows.

CO = Uc × PB (12) In Equation (12), CO is the CO2 emissions of paper and paperboard exported (106 t), Uc is the CO2 emissions per unit of paper and paperboard production (t CO2 /t), and PB is the volume of paper and paperboard exported from China (106 t).

2.3. List of Data and Sources (1)

(2)

The raw material acquisition stage. The amount of wood used in the process of acquiring wood pulp is equivalent to the amount of timber used for paper making, data of which is taken from the “China Forestry Statistical Yearbook 2000–2020” (national production of major timber and bamboo). The average fuel consumption for logging for timber, skidding, and transporting timber was referred to the data in the research results of Yuan Zhou et al. [37], and the cableway length and distance for transporting timber were adopted from the field research conducted by Zhang et al. [38] on southern plantation forests. As for the non-wood pulp acquisition process, non-wood pulp and rice-wheat straw pulp production data were drawn from the “China Papermaking Industry Annual Report (2001–2020). The parameters of the amount of straw resources consumed per unit of rice-wheat straw pulp output were referred to the data of Zhang [39] who investigated the non-wood pulp production lines of Yongfengyu enterprises. Paper straw availability coefficient and straw collectability coefficient were adopted from the research results of Sun et al. and Li Zhongzheng [40,41]. The straw-to-grain ratio (straw coefficient) was selected as the average of the straw coefficient of rice in China by Wang [42]; data on total rice production and total planted area in China during the study period were obtained from the China Rural Statistical Yearbook (2000–2020) [43] (planted and farmed area and production of major agricultural products). Statistics on various agricultural inputs during rice cultivation and cultivation up to harvesting were taken from the National Compilation of Information on Costs and Returns of Agricultural Products (2001–2020) [44]. The CO2 emission factors of agricultural inputs such as fertilizers, pesticides, agricultural films, and seeds were obtained from the data of Huang et al., Wang et al., and Xue et al. [30,45,46], respectively.

The pulp and paper stage. Energy consumption data for the study period was obtained from the China Statistical Yearbook (2000–2020) [3]. Energy types were classified into nine categories according to the China Energy Yearbook: coal, coke, crude oil, gasoline, kerosene, diesel, fuel oil, natural gas, and electricity, and the CO2 emission coefficients of various energy sources were adopted from the Guide to Provincial Greenhouse Gas Inventory Preparation (for Trial Implementation) [47]. The electricity CO2 emission

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(3)

(4)

factor is the average value of CO2 emissions per unit of electricity supply in the six regions of China and Hainan Province in the reference list.

The transportation stage. Data on pulp and waste paper imports and country of import for the study period were obtained from the UN Trade Database https:// comtrade.un.org/data (accessed on 25 December 2021). China needs to import large amounts of paper raw materials from abroad. The pulp or paper scrap exporting countries with the highest export volumes and the sum of their export volumes accounting for more than 90% of China’s total pulp or paper scrap imports were selected as the main importers of paper raw materials into China. The distance between the largest port of the importing country and the Chinese port of Shanghai was referred to as the water transport distance as indicated on the website of the International Cargo Exchange https://www.searates.com (accessed on 25 December 2021). For the main paper and paperboard-producing provinces, we referred to the “China Papermaking Industry 2000–2020 Annual Report” [6] and selected 16 provinces and cities such as Shandong, Zhejiang, Guangdong, and Jiangsu, whose combined production of paper and paperboard accounted for more than 95% of the total paper and paperboard production in China during the study period. The actual distance data between the main importing ports to the provincial capitals of the main paper and paperboard production areas and to the provincial capitals of main waste paper recycling sites were based on the Baidu map, and ArcGIS was used to calculate the spherical distance between points. The data on waste paper recycling volume were obtained from the China Paper Yearbook (2000–2020) [48], and the CO2 emission factors of each transportation mode were referred to the “European Communities Trade Mark Association’s Guidelines for Measuring and Managing CO2 Emission from Freight Transport Operations” [31].

The waste paper disposal stage. There is relatively less literature available about the percentage of waste paper recycling, landfill, and incineration. In our paper, the proportion of landfill and incineration of domestic waste to the total domestic waste disposal in China from 2000 to 2020, respectively, was used as the landfill rate and incineration rate of waste paper, from which the amount of landfill and incineration of waste paper was derived [23]. Data on domestic waste disposal in China during the study period were obtained from the China Statistical Yearbook of Urban Construction (2000–2020) [49] (information on the national urban sanitation subgroup). The data parameters such as DOC f utilized in the accounting process were referred to as the National Greenhouse Gas Emission Inventory Guidelines and the Provincial Greenhouse Gas Inventory Preparation Guidelines (for Trial Implementation) [47].

Some additional notes are in place here. The China Forestry Statistical Yearbook (2017–2020) no longer separately counts wood used for paper making. The wood used for paper making during 2017–2019 is forecasted by the average year-on-year growth from 2012–2016. For the reason of limitations in data acquisition, the shipping distance from Shanghai port to other regions in Asia is calculated by the average shipping distance from Shanghai port to the largest ports in Japan, South Korea, Thailand, and Singapore. China Urban Construction Statistical Yearbook 2000 does not count the domestic waste landfill rate and incineration rate, and the domestic waste landfill rate and incineration rate in 2000 are extrapolated by the data in 2001.

A list of data parameters and a summary of values used in the whole life cycle carbon accounting of paper products were included in Table 2 below.

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Table 2. Summary of data parameters related to CO2 emissions of paper products.

Data Parameters

Value

Data Parameters

Value

Paper straw availability coefficient (t/t) Straw collectability coefficient (t/t) Grain/straw ratio (t/t) Agricultural film CO2 emission factor (tCO2 /t) Rice seed CO2 emission factor (tCO2 /t) Nitrogen fertilizer CO2 emission factor (tCO2 /t) Phosphate fertilizer CO2 emission factor (tCO2 /t) Potash CO2 emission factors (tCO2 /t) Compost CO2 emission factor (tCO2 /t) Herbicide CO2 emission factor (tCO2 /t) Pesticide CO2 emission factor (tCO2 /t) Fungicide CO2 emission factor (tCO2 /t) DOC MCF CF

0.4500 0.8300 1.0400 22.7200 1.8400 1.5300 1.6300 0.6500 1.7700 10.1500 16.6100 10.5700 40% 50% 50%

Coal CO2 emission factors (tCO2 /t) Coke CO2 emission factor (tCO2 /t) Crude oil CO2 emission factor (tCO2 /t) Gasoline CO2 emission factor (tCO2 /t) Kerosene CO2 emission factor (tCO2 /t) Diesel CO2 emission factors (tCO2 /t) Fuel oil CO2 emission factor (tCO2 /t) Natural gas CO2 emission factor (tCO2 /m3 ) Electricity CO2 Emission Factor (tCO2 /kW-h) Rail transport CO2 emission factors (t/t.km) waterway transport CO2 emission factors (t/t.km) DOCf F FCF OF

1.9003 2.8604 3.0202 2.9251 3.0179 3.0959 3.1705 0.0022 0.0010 0.0220 0.0140 50% 50% 90% 100%

3. Results 3.1. Overall CO2 Emission Status The results of accounting for each stage of the whole life cycle of CO2 emissions of paper products are combined to estimate the CO2 emissions of the whole life cycle of paper products in China, as shown in Figure 2. The CO2 emissions of each stage are, in descending order, pulp and paper stage (average share of about 67.95%) > waste paper disposal stage (19.26%) > raw material disposal stage (5.70%) > transportation stage (3.84%) > export paper and board (3.23%). The pulp and paper making and waste paper disposal stages are the main sources of CO2 emissions for the whole life cycle of paper products, accounting for more than 90%. The growth of CO2 emissions from exported paper and paperboard means a gradual increase in CO2 emissions transferred from abroad to China, in Forests 2022, 13, x FOR PEER REVIEWwhich not only increases the pressure of energy conservation and emission reduction 12 of 22 China but also exacerbates the contradiction between the lack of paper raw materials and the excess production of paper and paperboard in China’s papermaking industry.

Figure 2.

2. CO CO22emissions emissionsfrom fromthe thelife lifecycle cycleof ofpaper paperproducts productsfrom from the the perspective perspective of of consumer consumer Figure responsibility. responsibility.

3.2. CO2 Emission Status of the Raw Material Acquisition Stage In the raw material acquisition stage, the CO2 emissions from acquiring non-wood pulp are much higher than those from acquiring wood pulp, see Figure 3. China is also gradually reducing the use of non-wood pulp raw materials, which is in the direction of improving the raw material structure of papermaking in China, and we expect that the

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Figure 2. CO2 emissions from the life cycle of paper products from the perspective of consumer 12 of 21 responsibility.

3.2. CO2 Emission Status of the Raw Material Acquisition Stage 3.2. CO2 Emission Status of the Raw Material Acquisition Stage In the raw material acquisition stage, the CO2 emissions from acquiring non-wood In the raw material acquisition stage, the CO2 emissions from acquiring non-wood pulp are much higher than those from acquiring wood pulp, see Figure 3. China is also pulp are much higher than those from acquiring wood pulp, see Figure 3. China is also gradually reducing the use of non-wood pulp raw materials, which is in the direction of gradually reducing the use of non-wood pulp raw materials, which is in the direction of improving the raw material structure of papermaking in China, and we expect that the improving the raw material structure of papermaking in China, and we expect that the CO2 emissions from acquiring non-wood pulp will continue to show a significant decline.

CO2 emissions from acquiring non-wood pulp will continue to show a significant decline.

Figure3.3.CO CO2 2emissions emissionsfrom fromthe theraw rawmaterial materialacquisition acquisitionstage. stage.

Figure

From the the accounting accounting results, results, the the CO CO22 emissions emissionsfrom from wood wood pulp pulp acquisition acquisition rose rose From slightly from 2000–2019, and the opposite for non-wood pulp.

Since the CO emissions 2 slightly from 2000–2019, and the opposite for non-wood pulp. Since the CO2 emissions from non-wood pulp always accounted for the largest proportion, accounting for more from non-wood pulp always accounted for the largest proportion, accounting for more than 95% from 2000–2019, the total CO emissions from the raw material acquisition stage than 95% from 2000–2019, the total CO22emissions from the raw material acquisition stage continued to decline with the decline in CO emissions from non-wood pulp acquisition. continued to decline with the decline in CO22emissions from non-wood pulp acquisition.

Among them, around 2010, the CO2 emissions of the raw material acquisition stage rose Among them, around 2010, the CO2 emissions of the raw material acquisition stage rose significantly, mainly due to the continued high prices of imported wood pulp and imported significantly, mainly due to the continued high prices of imported wood pulp and waste paper, resulting in a year-on-year decline in imports and a rise in domestic demand for non-wood pulp. 2013 onwards, the adjustment of the raw material structure of paper production has to some extent reduced the pressure on CO2 emissions. During the two “2011–2019 Five-Year Plan” period, the proportion of non-wood pulp has been reduced from 13.71% to 6.03% so that the CO2 emissions of this phase exhibit a certain downward trend. In terms of wood harvesting and transportation, the highest CO2 emissions are from transporting wood, followed by skidding, and the lowest is from harvesting wood; in terms of CO2 emissions from various agricultural inputs used in rice cultivation for paper production, fertilizer accounts for 41%, electricity consumption for irrigation accounts for 26%, and CO2 emissions from diesel and pesticide inputs account for 8–9%, and the CO2 emissions from the above agricultural inputs in total account for more than 85% of the total emissions from cultivation.

3.3. CO2 Emissions Status of Pulp and Paper Stage From an overall perspective, CO2 emissions from the pulp and paper stage rose from 64.21 × 106 t in 2000 to 151.61 × 106 t in 2019, with an average annual compound growth rate of 4.38% (Figure 4), which is higher than the average annual compound growth rate of 3.79% of China’s total CO2 emissions [2]. While the UK’s CO2 emissions at that stage in 2014 have been reduced by 42% compared to 2008 [50]. Compared to some European countries, CO2 emissions from the pulp and paper production process in China are still on an increasing trend.

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64.21 × 106 t in 2000 to 151.61 × 106 t in 2019, with an average annual compound growth rate of 4.38% (Figure 4), which is higher than the average annual compound growth rate of 3.79% of China’s total CO2 emissions [2]. While the UK’s CO2 emissions at that stage in 2014 have been reduced by 42% compared to 2008 [50]. Compared to some European countries, CO2 emissions from the pulp and paper production process in China are13still of 21 on an increasing trend.

Figure4.4.CO CO2 2emissions emissionsfrom fromenergy energyconsumption consumptionininthe thepulp pulpand andpaper paperstage. stage.

Figure

Specifically, from 2000–2016, coal, which accounts for more than 75% of total energy Specifically, from 2000–2016, coal, which accounts for more than 75% of total energy consumption, accounted for the highest proportion of CO2 emissions in the pulp and consumption, accounted for the highest proportion of CO2 emissions in the pulp and papaper stage, basically remaining at around 60% and still on an upward trend. With per stage, basically remaining at around 60% and still on an upward trend. With the imthe implementation of China’s “13th five-year plan” in 2016–2019, the energy structure plementation of China’s “13th five-year plan” in 2016–2019, the energy structure adjustadjustment has increased, and the proportion of CO2 emissions from coal in the pulp and ment has increased, and the proportion of CO2 emissions from coal in the pulp and paper paper stage has been reduced to 49.4% by 2019. In 2013, there was a phase peak of CO stage has been reduced to 49.4% by 2019. In 2013, there was a phase peak of CO2 emissions2 emissions in the pulp and paper stage, which was attributed to the large increase in coal in the pulp and paper stage, which was attributed to the large increase in coal consumpconsumption during this stage, and a slow decline in the Chinese coal price index during tion during this stage, and a slow decline in the Chinese coal price index during the same the same period, followed by a steep downward trend after the summer, until late in the period, followed by a steep downward trend after the summer, until late in the “12th Five“12th Five-Year Plan” [51]. The CO2 emissions share of electricity is above 35%, growing Year CO 2 emissions share 6of electricity is above 35%, growing from 22.65 6 t in fromPlan” 22.65[51]. × 10The 2000 to 71.04 × 10 t in 2019, with an average annual compound ×growth 106 t inrate 2000ofto 71.04 × 106 t in 2019, an average compound growth rate of 5.88%, higher than thatwith of coal at 3.24%.annual The sum of CO2 emissions from 5.88%, higher than that of coalfor at more 3.24%.than The95% sumofofthe COtotal 2 emissions from coal and electriccoal and electricity accounts CO2 emissions from the entire ity accounts for more than 95% of the total CO 2 emissions from the entire pulp and paper pulp and paper stage, while the sum of CO2 emissions from natural gas and other energy sources accounts for just under 4%. Moreover, according to the European Papermaking Industry Federation CEPI (Confederation of European Paper Industries) [52], data show that in 2016 the European papermaking industry biomass energy consumption reached 58.82%, natural gas consumption accounted for about 33.43%, while coal accounted for only 3.96%. In particular, in the Dutch papermaking industry by 2009 natural gas energy consumption accounted for about 97% [53]. This shows that the energy consumption structure of the pulp and paper stage of China’s papermaking industry is still dominated by coal and electricity, and the energy structure adjustment is yet to be strengthened.

3.4. CO2 Emissions Status of the Transportation Stage CO2 emissions from the input of paper raw materials during the transportation phase of paper products mainly include wood pulp, waste paper imports, and domestic waste paper recycling. The results are shown in Figure 5.

Overall, from 2000 to 2020, the total CO2 emissions from the whole life cycle transportation process of paper products increased from 1.59 × 106 t to a maximum value of 11.16 × 106 t within 2017 and then gradually declined to 8.07 × 106 t in 2020. The high dependence on paper raw material imports is one of the main reasons for the increase in CO2 emissions during the whole life cycle transportation of paper products. In 2010, CO2 emissions from transportation declined significantly due to high international pulp and waste paper prices and the accordingly reduced imports of paper raw materials. Comparing the CO2 emissions of pulp and waste paper import and transportation from 2000–2017, the gap between the two has gradually narrowed. On the one hand, due to the gradual increase in China’s waste paper recycling rate, there has been a fluctuating decline in waste paper

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stage, while the sum of CO2 emissions from natural gas and other energy sources accounts imports.

On the hand,according due to thetotight forestry resources, the external for just under 4%.other Moreover, the European Papermaking Industrydependence Federation on wood pulp remains high and isPaper temporarily difficult improve, so the CO2 the emissions CEPI (Confederation of European Industries) [52], to data show that in 2016 Euroof wood pulp import and transportation may continue to rise in the future.

Influenced pean papermaking industry biomass energy consumption reached 58.82%, natural gas by the “Implementation Plan for 33.43%, Prohibiting thecoal Entry of Foreign Waste3.96%. and Promoting consumption accounted for about while accounted for only In particthe Reform of Solid Waste Import Management System” released in 2017, the structure of ular, in the Dutch papermaking industry by 2009 natural gas energy consumption acimported raw materials for the papermaking industry is adjusted in 2018–2020, with the counted for about 97% [53]. This shows that the energy consumption structure of the pulp gappaper between pulp waste paper gradually expanding showing opposite pattern and stage of and China’s papermaking industry is still and dominated byancoal and electricto that of 2000–2017.

2000–2020, China’s waste paper recycling rate increases from 29.5% ity, and the energy structure adjustment is yet to be strengthened. to 46.5%, and CO2 emissions from domestic waste paper recycling transport are slowly 6 t in 2000 to 0.41 × 106 t in 2020. Compared with paper raw increasing, from 0.08 × of 10the 3.4.

CO2 Emissions Status Transportation Stage material import transport, domestic waste paper recycling transport is shorter in distance CO2 emissions from the input of paper raw materials during the transportation phase and the recycling volume is lower than the sum of pulp and waste paper import volume in of paper products mainly include wood pulp, waste paper imports, and domestic waste the same period, resulting in its CO2 emissions being much lower than the CO2 emissions paper recycling. The results are shown in Figure 5. from paper raw material import transport in the same period.

Figure5.5.CO CO2 2emissions emissionsfrom fromthe thetransportation transportationofofChinese Chinesepaper paperproducts. products.

Figure

3.5. CO2 Emissions Status of Waste Paper Disposal Stage Overall, from 2000 to 2020, the total CO2 emissions from the whole life cycle transThe process amount of of paper CO2 released the waste waste paper incinportation productsfrom increased frompaper 1.59 ×landfill 106 t toand a maximum value of eration segments of the life cycle of paper products in China is shown in Figure 6.

At 6 6 11.16 × 10 t within 2017 and then gradually declined to 8.07 × 10 t in 2020. The high depresent, the total amount of harmless domestic waste disposal in the country has been pendence on paper raw material imports is one of the main reasons for the increase in CO2 rising significantly bylife year, and the development trend of incineration volume is emissions during theyear whole cycle transportation of paper products.

In 2010, CO 2 emissimilar to it, while the sanitary landfill volumedue is growing very slowly. In Figure CO2 sions from transportation declined significantly to high international pulp and 6, waste emissions from waste paper incineration rise and those from landfill fall, with the former paper prices and the accordingly reduced imports of paper raw materials. Comparing the increasing at a compound annual growth rate (CAGR) of 22.17% and surpassing the latter CO 2 emissions of pulp and waste paper import and transportation from 2000–2017, the since 2013. emissionsnarrowed. from the waste paper phase also increased, gap betweenThe thetotal two CO has2 gradually On the one disposal hand, due to the gradual inwith a CAGR of 7.76%. In comparison, the CO2 emissions per unit of waste paper landfill crease in China’s waste paper recycling rate, there has been a fluctuating decline in waste are about 0.55 t, while the CO2 emissions per unit of waste paper incineration are about paper imports. On the other hand, due to the tight forestry resources, the external depend1.65 t, so the landfill of waste paper is more conducive to the low carbon development of ence on wood pulp remains high and is temporarily difficult to improve, so the CO2 emispaper products compared to incineration. sions of wood pulp import and transportation may continue to rise in the future. Influenced by the “Implementation Plan for Prohibiting the Entry of Foreign Waste and Promoting the Reform of Solid Waste Import Management System” released in 2017, the structure of imported raw materials for the papermaking industry is adjusted in 2018– 2020, with the gap between pulp and waste paper gradually expanding and showing an

Forests 2022, 13, 1856

compound annual growth rate (CAGR) of 22.17% and surpassing the latter since 2013. The total CO2 emissions from the waste paper disposal phase also increased, with a CAGR of 7.76%. In comparison, the CO2 emissions per unit of waste paper landfill are about 0.55 t, while the CO2 emissions per unit of waste paper incineration are about 1.65 t, so the landfill of waste paper is more conducive to the low carbon development of paper products 15 of 21 compared to incineration.

Figure6.

6.CO CO22emissions emissionsfrom fromthe thewaste wastepaper paperdisposal disposalof ofChinese Chinesepaper paperproducts. products.

Figure

3.6. Export Paper and Paperboard CO Emissions Status 3.6. Export Paper and Paperboard CO22Emissions Status From a consumer responsibility perspective, CO2 emissions from exported paper From a consumer responsibility perspective, CO2 emissions from exported paper and and paperboard should be subtracted from the full life-cycle CO2 emissions of the paper paperboard should be subtracted from the full life-cycle CO2 emissions of the paper prodproduct, which are shown in Table 3. uct, which are shown in Table 3.

Table 3. CO2 emissions from exported paper and board.

Table 3. CO2 emissions from exported paper and board.

Year Year

Paper Paperand andPaperboard Paperboard 6 Export ExportVolume Volume(10 (106t)t)

2000 2000 2001 2001 2002 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

0.72 0.72 0.76 0.76 0.85 0.85 1.29 1.25 1.94 3.41 4.61 4.03 4.05 4.33 5.09 5.13 6.11 6.81 6.45 7.33 6.99 6.18 6.86

of Paper Emissions the Production of 2 Emissions CO2CO Emissions per per UnitUnit of Paper and Emissions fromfrom the Production of Paper 6 and Board Produced (tCO /t) Paper Paperboard for Export Board Produced (tCO 2/t) 2 andand Paperboard for Export (106(10 t) t) 2.11 1.52 2.11 1.52 2.06 1.57 2.06 1.57 1.90 1.62 1.90 1.62 1.74 2.24 1.95 2.43 1.90 3.69 1.81 6.17 1.58 7.30 1.52 6.11 1.44 5.83 1.45 6.29 1.43 7.28 1.39 7.14 1.58 9.63 1.48 10.05 1.42 9.18 1.43 10.50 1.44 10.07 1.50 9.30 1.41 9.66

3.7. Discussion of the Limitations of Our Analytical Results The whole-life cycle CO2 emissions of paper products accounted for in this paper are conservative estimates, and the results of the study are subject to some limitations, mainly including: (1) With regard to the system accounting boundary, CO2 emissions generated from the consumption of paper and paperboard, CO2 emissions generated from road construction and repair and production and maintenance of transportation

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equipment during the whole life cycle transportation of paper products are not included in the accounting system because of the difficulty in obtaining data. (2) In terms of accounting methods, when accounting for CO2 emissions from domestic waste paper recycling in the transportation stage, it is assumed that the waste paper generated in each of the 16 major paper and paperboard-producing provinces is recycled for pulping within the province, and the distance of this part of waste paper recycling is 0, resulting in negligible CO2 emissions; the waste paper from the remaining 15 (non-major paper and paperboard producing) provinces is recycled and transported to the nearest major paper and paperboard producing province (region or city), and the distance between the provincial capitals of the two provinces is taken as the distance of waste paper recycling, which may be slightly lower than the actual transportation distance, resulting in lower CO2 emissions from waste paper recycling and transportation. (3) Some data parameters (such as CO2 emissions coefficients of different transportation modes) are adopted from relevant European research data, while there are certain differences between the development of China and Europe, which will affect the accuracy of the relevant parameters used. In addition, this paper sets the CO2 emissions coefficients related to each stage of the study period unchanged, but the corresponding CO2 emissions coefficients may decrease with the improvement of the technology level in various aspects, which will lead to some errors in the accounting results.

(4) Regarding the accounting method of CO2 emissions used, there are relevant references for CO2 emissions accounting methods listed in our paper. Among similar studies, CO2 emissions accounting studies from the perspective of different pulp types are relatively consistent with the results of this paper [7,27]. In addition, the CO2 emissions trend of the papermaking industry in this article is consistent with the overall situation of CO2 emissions of the manufacturing industry in China [54], while reflecting the industrial characteristics of low carbon development, transformation, and upgrading of the papermaking industry.

4. Forecast of LCA CO2 Emissions Scenarios for Paper Products in China Since the pulp and paper and waste paper disposal stage is the main stage of the whole life cycle of CO2 emissions of paper products, reduction in CO2 emissions in the process of pulp and paper and waste paper disposal is the key link to low carbon development of paper products in China. Accordingly, this paper further predicts the whole life cycle of CO2 emissions of paper products in China from 2020 to 2035 using scenario analysis.

Among them, the baseline scenario uses curve fitting to predict CO2 emissions at each stage of the whole life cycle of paper products, i.e., CO2 emissions are predicted for each stage of the whole life cycle, and then aggregated into the total CO2 emissions of the whole life cycle of paper products. Low-carbon scenario I only improves the waste paper recovery rate, otherwise the same as the baseline scenario; low-carbon scenario II only improves the energy consumption structure in the pulp and paper stage, otherwise the same as the baseline scenario; low-carbon scenario III improves both the energy structure and waste paper recovery rate, otherwise the same as the baseline scenario. In terms of scenario parameters, the paper recycling problem is complex and comprehensive, which is reflected in the fact that paper recycling cannot achieve a high recycling rate under the existing circumstances due to the economic structure, paper characteristics, and recycling algorithms in China. In this paper, we set the optimization criteria in the scenario prediction by combining the policy proposal and the impact of the “waste separation” policy on CO2 emissions in the waste paper disposal stage. Low carbon scenario I sets China’s waste paper recycling rate to 74% in 2035 with reference to Europe’s waste paper recycling rate of 74% in 2020, and assumes a linear increase in the waste paper recycling rate from 2020 to 2035. For the low carbon scenario II, with reference to the requirements in the outline of the “14th five-year plan” and the 2035 visionary goals for national economic and social development of the People’s Republic of China issued by the National Development and Reform Commission, the proportion of non-fossil energy consumption in 2035 is set to be about 20% [55], the proportion of coal consumption is within 49%, natural gas is more than 13%, and oil is about 16% [56]. The total energy consumption of the papermaking industry

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recycling rate of 74% in 2020, and assumes a linear increase in the waste paper recycling rate from 2020 to 2035. For the low carbon scenario II, with reference to the requirements in the outline of the “14th five-year plan” and the 2035 visionary goals for national economic and social development of the People’s Republic of China issued by the National Development and Reform Commission, the proportion of non-fossil energy consumption 17 of 21 in 2035 is set to be about 20% [55], the proportion of coal consumption is within 49%, natural gas is more than 13%, and oil is about 16% [56]. The total energy consumption of the papermaking thisthe scenario is obtained from the output value in this scenario isindustry obtainedin from industrial output value andindustrial energy intensity, while and energy intensity, while the energy structure is set to change linearly, where the inthe energy structure is set to change linearly, where the industrial output value is fitted dustrial output value is fitted to the model curve using SPSS software.

To avoid the effect to the model curve using SPSS software. To avoid the effect of energy intensity effect on of energy intensity effect on CO2 emissions reduction, the energy intensity is assumed to CO 2 emissions reduction, the energy intensity is assumed to be the same as in 2016. The be the same as in 2016.

Theare scenario are shown in Figure 7. scenario projection results shownprojection in Figure results 7.

Figure 7.

7. Prediction Prediction of ofof paper products under the the lowlow carbon scenario.

Figure of CO CO22 emissions emissionsfrom fromlife lifecycle cycle paper products under carbon scenario.

From the predicted results, under the existing policy, CO2 emissions from paper products China’s papermaking industry will peak around about 223 from × 106paper t, and Frominthe predicted results, under the existing policy,2025 CO2atemissions 6 the peak trend will be very smooth, with CO emissions fluctuating only within 1 × 6 2 products in China’s papermaking industry will peak around 2025 at about 223 × 10 t, 10 andt from 2023 to 2026.

Invery general, improving the energy mix and increasing the recycling the peak trend will be smooth, with CO 2 emissions fluctuating only within 1 × 106 t rate of waste paper can curb CO emissions throughout theincreasing life cycle of products.

2 from 2023 to 2026. In general, improving the energy mix and thepaper recycling rate The projections of the baseline scenario show that, under the existing policy background, of waste paper can curb CO2 emissions throughout the life cycle of paper products. The the systematic and continuous adjustment of the industrial structure of the papermaking projections of the baseline scenario show that, under the existing policy background, the industry in China since the “12th Five-Year Plan” has achieved significant results. The emissions reduction effect of low-carbon scenario II based on energy consumption structure is better than that of low-carbon scenario I based on waste paper recycling rate, and the difference in CO2 emissions reduction between the two is relatively minor. The projection results of low carbon scenario III show that simultaneously improving the energy mix and increasing the waste paper recycling rate are more effective in reducing total CO2 emissions.

Compared with the baseline scenario, the CO2 emissions reduction of the whole life cycle of paper products from 2021–2035 increases from 49.04 × 106 t to 86.82 × 106 t, which is close to the CO2 emissions of the pulp and paper stage in 2003–2004, and the emissions reduction contribution rate is also as high as 41.63% in 2035, which is more effective than the effect of low carbon scenarios I and II. In a low-carbon context, the papermaking industry, as a traditional high-energy-consuming and high-emissions industry, can achieve a faster and more effective low-carbon development path.

5. Conclusions From two dimensions and four stages of reducing CO2 emissions and increasing carbon sequestration, we propose the following emissions reduction strategy for the whole life cycle of paper products (Figure 8).

(1)

The raw material acquisition stage. Combined with the CO2 emissions accounting and scenario prediction results in this paper, the pulp and paper stage is the stage with the largest share of emissions in the papermaking industry (over 70%). Its energy structure adjustment is the top priority for the low-carbon development of the papermaking industry. Specifically, we propose the following: Firstly, increase the application of cogeneration technology in the papermaking industry. Through cogeneration technology, paper companies can use the steam generated for power generation

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18 of 21

(2)

(3)

(4)

in pulp and paper production through temperature and pressure reduction, which can significantly improve the utilization rate of energy and reduce the production costs of paper companies. In this regard, in the European papermaking industry cogeneration power accounted for 96% of the total electricity consumption, China’s corresponding proportion on this is less than 50%, hence, the development potential is enormous. Secondly, increase the application of biomass energy. The raw material of the papermaking industry mainly comes from plants. After extracting fiber from plants, in the pulping process by converting the remaining organic matter into biomass energy efficiently, it can significantly reduce the consumption of fossil energy and reduce the emissions of CO2 . In Europe, paper mills have been able to achieve a non-fossil energy consumption ratio of more than 57% by efficiently converting organic matter from paper residues into biomass energy. For example, biodiesel produced by UPM in Finland from the by-products of pulp production can reduce CO2 emissions by 80% [57]. Some Japanese paper companies make full use of their own biomass resources, while purchasing waste rubber and wood from society and treating municipal waste, so that 100% of their energy consumption is biomass energy, thereby reducing the CO2 generated by energy consumption.

The pulp and paper stage. This stage requires greater efforts to sort waste in recycling.

For example, the three types of waste paper—old newspapers, books, and cardboard boxes—contain different varieties of pulp, and the mechanical and chemical pulp obtained from their recycling has different properties. If a large amount of chemical pulp is mixed into the mechanical pulp, the corrugated boxes produced will become soft and lose their original load-bearing and pressure-resistant capacity. So, the stronger and more detailed the classification of all types of waste paper, the higher the value it will produce. With China’s waste paper nearing the limit of recyclable volume, greater recycling and sorting efforts can provide new ideas for reducing CO2 emissions.

The waste paper disposal stage. Although “the policy of banning waste imports” has led to a significant reduction in CO2 emissions from imports, the imbalance between supply and demand has led to high prices of waste paper raw materials and serious adulteration, so many paper companies have had to revise their waste paper acquisition quality standards, which has had a series of adverse effects on the papermaking industry. In response to the problem, it is recommended “the policy of banning waste imports” to refine the import of solid waste to avoid “one-size-fits-all”.

From the perspective of circular economy and environmental protection, China’s own exports take away the packaging and instructions and other paper products through the import of the way to recycle is a more scientific and more environmentally friendly choice.

The transportation stage. First, increasing sustainable management of forests. With the certification of forest certification organizations, we can effectively reduce CO2 emissions by supervising and managing the entire value chain from forest management to paper product production then to consumer recycling. Second, promote the “forest-pulp-paper integration” model, effectively reducing CO2 emissions from the raw material acquisition stage of the aggregation and transportation operations.

Third, promote the optimal rotation period system for forests, choose suitable tree species according to local conditions and maintain a reasonable forest age structure so that the forest can absorb the maximum amount of CO2 . Fourth, to reduce the use of non-wood pulp in the proportion of rice-wheat straw pulp. The use of rice-wheat straw pulp is an important reason for the relatively large proportion of CO2 emissions in the pulp and paper stage. Promoting the clean production of reed raw materials and other pulp and paper can effectively reduce CO2 emissions. In addition, the use of bamboo pulp and paper is also an effective path to reduce CO2 emissions.

a faster and more effective low-carbon development path.

5. Suggested Paths to Promote Low-Carbon Development in the Papermaking Industry Forests 2022, 13, 1856

From two dimensions and four stages of reducing CO2 emissions and increasing car19 of 21 bon sequestration, we propose the following emissions reduction strategy for the whole life cycle of paper products (Figure 8).

Figure 8. Low carbon development route map for the whole life cycle of papermaking industry.

Figure 8. Low carbon development route map for the whole life cycle of papermaking industry.

(1) To Theachieve raw material acquisition stage. Combined 2 emissions accounting the Sustainable Development Goalswith and the the CO emission reduction targets and scenario prediction results in this paper, the pulp and paper stagetoisstudy the stage in the INDC framework for China’s papermaking industry we will need more with the largest share of emissions in the papermaking industry (over 70%). enaspects beyond our current article’s focus on CO2 emissions. The outlook from Its “a tree” is the priority for the low-carbon of the to “a ergy piecestructure of paper”adjustment suggests that thetop whole industry chain involvesdevelopment more than just CO2 papermaking industry.

Specifically, we propose the following: Firstly, increase the emissions. In the future, we look forward to conducting more research on forests, natural application technology in the papermaking Through cogas, and biomassof to cogeneration promote sustainable development and achieveindustry. clean production. generation technology, paper companies can use the steam generated for genNowadays, China’s papermaking industry is gradually developing intopower an industry eration in pulp and paper production through temperature and pressure reduction, with recyclable resources, low energy consumption, and low emissions, but there is still a significantly improve the utilization rate efficiency of energy and reduce to thedeveloped produclarge which gap incan industrial structure and energy utilization compared tion costs of paper companies.

In this regard, in the European papermaking industry countries’ papermaking industry. For a long time to come, China’s low-carbon development for 96%ofofgreen the total electricity consumption, China’s path cogeneration must alwayspower adhereaccounted to the concept development, synergize technology, corresponding proportion on this is less than 50%, hence, the development potential management, finance, and other multiple means. is enormous. Secondly, increase the application of biomass energy. The raw material of Contributions: the papermaking industry Yang) mainly comes from plants.

After extracting fiber from J.Y. (Jiameng conceptualization, formal analysis, validation, superAuthor in the pulping process by converting the remaining into biovision;plants, Y.H. methodology, data curation, writing—original draft; J.Y.organic (Jiarongmatter Ye) investigation, mass energy efficiently, it candraft; significantly reduce the writing—review consumption ofand fossil energy visualization; S.X. writing—original Z.L. formal analysis, editing.

All authors have read and agreed to the published version of the manuscript.

Funding: This research was financially supported by the Major project of National Social Science Foundation of China (Grant No. 20&ZD092).

Data Availability Statement: Not applicable.

Conflicts of Interest: The authors declare no conflict of interest.

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Quality evaluation of water disclosure of Chinese papermaking enterprises based on accelerated genetic algorithm CHAORAN HE1, JUQIN SHEN2, JIAWEI XU1, FUHUA SUN2 & BING WANG3 As the carrier of enterprise water resources management disclosure, water information disclosure is a means of expression of enterprises’ environmental responsibility. First, a corporate water information disclosure quality evaluation index system and evaluation method are established, and with the help of the projection tracing method of accelerated genetic algorithm, 27 paper companies in China are selected as a sample and the disclosure quality level is analyzed empirically. Then, the analysis is carried out in terms of three changes in vertical trends, horizontal trends and changes in laws, regulations and policies, and the results show that Chinese paper and paper product enterprises have low quality of water information disclosure, weak disclosure content and low voluntary disclosure. Finally, feasible suggestions are made based on the evaluation of disclosure issues.

Contact information: 1 Business School, Hohai University, Nanjing 210098, China.

2 College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China.

3 Xuchang Bureau of Hydrology and Water Resources Investigation, Xuchang 461000, China. www.nature.com/scientificreports, (2023) 13:12225. https://doi.org/10.1038/s41598-023-39307-y Creative Commons Attribution 4.0 International License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Article 5 – Quality Evaluation of Water

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Quality evaluation of water disclosure of Chinese papermaking enterprises based on accelerated genetic algorithm Chaoran He 1, Juqin Shen 2, Jiawei Xu 1, Fuhua Sun 2* & Bing Wang 3 As the carrier of enterprise water resources management disclosure, water information disclosure is a means of expression of enterprises’ environmental responsibility. First, a corporate water information disclosure quality evaluation index system and evaluation method are established, and with the help of the projection tracing method of accelerated genetic algorithm, 27 paper companies in China are selected as a sample and the disclosure quality level is analyzed empirically. Then, the analysis is carried out in terms of three changes in vertical trends, horizontal trends and changes in laws, regulations and policies, and the results show that Chinese paper and paper product enterprises have low quality of water information disclosure, weak disclosure content and low voluntary disclosure.

Finally, feasible suggestions are made based on the evaluation of disclosure issues.

As an important traditional manufacturing industry, the paper industry is closely related to social development and ecological environment, and is also an important part of water consumption. As a disclosure carrier of corporate water resources management, water information disclosure describes the relevant information of corporate water use and drainage through monetary performance or volume, and discloses non-financial reports on corporate water management, strategy and other business risks and opportunities to stakeholders (The CEO Water Mandate, 2014), which occupies an important part of environmental information disclosure. With the intensification of global climate change and the increasing strain on industrial water use, the importance of corporate water information disclosure has made Chinese enterprises have begun to pay attention to their own water resource management, and gradually integrate water resource management into high-level supervision (Carbon Disclosure Project China, 2020). The research field of water resources management mainly focuses on the influence of macro factors on enterprise water resources management from the perspective of ­economics1, the strategy of corporate water resources from the perspective of ­management2, the improvement of enterprise water resources accounting capacity from the perspective of water management ­accounting3, and the development of comprehensive framework of enterprise water management ­accounting4. Whether in practice or theoretical research, water environment issues have gradually been paid attention to by enterprises. Green development with the goal of "water-saving priority" has become one of the important directions for the development of the paper and paper products industry.

According to the statistics compiled by the China Environmental Statistical Yearbook, the wastewater discharge of the paper industry accounted for 12.3% in 2020, second only to chemical raw materials and chemical products manufacturing, and is the second largest industry in China’s industrial wastewater discharge. Although the Administrative Measures for the Legal Disclosure of Enterprise Environmental Information reviewed by the Ministry of Ecology and Environment clarifies the accurate and complete disclosure of environmental information by enterprises. However, in the actual enterprise report disclosure, the information disclosure on water consumption, total groundwater withdrawal control and wastewater emission reduction is far lower than expected, and there are problems such as incomplete and inconsistent water information disclosure and weak water performance disclosure. Water information disclosure by enterprises not only promotes the transformation of enterprises from extensive management to refined management mode, but also optimizes the water resource management mechanism of enterprises, which is more important for sustainable water resources ­management5.

With the increasing attention of society to the environment, the information disclosure of listed companies has

1

Business School, Hohai University, Nanjing 210098, China. 2College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China. 3Xuchang Bureau of Hydrology and Water Resources Investigation, Xuchang 461000, China. *email: ccranhh@163.com

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www.nature.com/scientificreports/ transitioned from voluntary disclosure to mandatory disclosure, and carbon emission information must be disclosed in the content requirements of environmental information disclosure according to law, but there are few related contents related to water information disclosure, and there are no clear requirements. As a result, enterprises cannot deal with the "internal and external response" problem of water information disclosure, that is, the imbalanced ecological contradiction between enterprises and nature, and human society. In the process of papermaking production and sales activities, enterprises gradually expose the low water efficiency and slow update and iteration of water-saving technology, resulting in high production water costs, and increasing the risk of enterprises taking the social responsibility of ecological water as a marketing strategy and public relations means of "greenwashing"; It cannot meet the individualization of stakeholders and their needs, and it is not conducive to the role of the market in allocating r­ esources6.

In view of the water information disclosure reports of existing enterprises, how to scientifically and objectively evaluate the quality of enterprise water information disclosure, and the disclosure of enterprise water information has become a hot spot for scholars. At present, the establishment of an applicable model of enterprise water information disclosure quality has become the most urgent need at present, this paper constructs an evaluation index system of enterprise water information disclosure by sorting out relevant literature and results at home and abroad, and at the same time, based on the quality characteristics of enterprise accounting information disclosure as a research framework. Finally, the improved projection tracing model is used to analyze the water information disclosure quality of paper and paper products enterprises and obtain the final evaluation value. This paper and paper products industry is trying to analyze whether China’s paper and paper products industry has got rid of water-consuming production methods, aiming to better summarize the current results and problems of intensive water conservation in China’s paper and paper products industry.

The theoretical contribution of this paper is fourfold, first, the study is based on the high water consumption and high pollution light industry—Paper and paper products industry as an example, the introduction of sustainable development theory and environmental accounting theory and other research methods, through theoretical analysis from internal factors and external factors two perspectives a comprehensive and systematic analysis of the connotation of enterprise water information disclosure, The impact of corporate water disclosure on the evaluation of the company’s own water environment and corporate value is explored to provide a theoretical basis for corporate water management and sustainable innovation; then, that is, a corporate water disclosure indicator evaluation system is constructed, which will help stakeholders to assess the understanding of optimal management of water resources within the company, bridging the gap between existing studies in the evaluation of the quality of corporate water disclosure; Next, this paper constructs a model based on projection tracing method, which can overcome the interference of subjective factors and improve the performance of computing more accurately and scientifically, and improve the algorithm as an accelerated genetic algorithm encoded with real numbers, so as to speed up the convergence speed, improve the accuracy and robustness of the model, and finally find the best projection value of the sample, rank the quality of corporate water disclosure, and solve the subsequent corporate water disclosure laying the foundation for solving the problem; Finally, this paper systematically proposed enterprise water information disclosure index system, based on the quality characteristics of enterprise environmental accounting information, from the four principles of relevance, reliability, effectiveness and comparability, to build a new paper and paper products enterprise water information disclosure Indicator system, enrich the existing literature of water information disclosure system in each level of indicators, improve the practicality of enterprise water information disclosure, and thus has a theoretical contribution to provide planning and decision-making for the sustainable and high-quality development of enterprise water resources cycle.

The rest of the paper is structured as follows: Sect. “Literature reviews” provides an overview of the factors and quality evaluation methods that affect the disclosure of corporate water information. The third section constructs the enterprise water information disclosure quality evaluation index system and model, scores based on the four principles of accounting information quality, and adopts the improved projection tracing model method. In the fourth section, the horizontal and vertical process changes of water information quality of China’s A-share papermaking and paper products enterprises are analyzed using weight indicators and final evaluation values.

Finally, the research conclusions are drawn and recommendations are made for the future water management of the enterprise.

Literature reviews

Only high-quality disclosure of water resources information can enterprises achieve long-term sustainable development. Most of the domestic and international literature focus on the current situation of corporate water information disclosure and the impact mechanism, expressed in the company’s internal and external factors.

From the perspective of internal factors, corporate water disclosure is motivated by "internal incentives" and "own risk" c­ onsiderations7,8. Internal incentives are mainly in the form of corporate governance and business performance. Liu et al.9 used a sample of 781 listed companies to clarify that water information disclosure through financing constraints can significantly improve financial quality, thus establish a good reputation and help enterprises develop capital markets for green credit; Japanese scholars Burritt et al.10 conducted an empirical study on 100 enterprises’ water information disclosure and explored the impact of corporate water risk awareness, media exposure, and ownership dispersion on corporate water disclosure behavior. Malik et al.11 constructed environmental information disclosure level indicators based on listed companies in China to analyze the significance of the environment on corporate performance at macro and micro levels. Liao et al.12, Clarkso et al.13 and M ­ artinez14 found that corporate information disclosure was significantly and negatively related to environmental performance. It means that enterprises found to have poor business performance in the early stage should disclose environmental information promptly to avoid future penalties for not fully disclosing it.

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www.nature.com/scientificreports/ Risk is mainly manifested in the enterprise’s own risk. Zkou et al.15 study selected 334 listed companies in China’s high-water risk industry. The results show that water information disclosure is not significantly correlated with enterprise systemic risk, but helps enterprises to attenuate systemic risk. Most of the listed companies’ business development is financed by external financing. The "green credit" policy launched by the regulatory authorities combines environmental and financial risks, raising higher standards for corporate environmental governance.

It can be seen that corporate water information disclosure is more focused on water resources in terms of saving operating costs and improving short-term earnings.

From the perspective of external factors, generally manifested as direct pressure (government) and indirect pressure (media or market), driven by the results of pressure, corporate disclosure of water information is not only a requirement for stakeholders and companies to fulfill their social and environmental obligations, but also a requirement to achieve sustainable and high-quality national and corporate development. Deng Mingjun et al.16 analyzed the motivation mechanism of corporate water information disclosure, explained the mechanism of corporate water information disclosure regulation and realization mechanism, and called on relevant authorities to set quantifiable and enforceable evaluation criteria for critical regulations such as "significant corporate water-related impact" and "significant corporate water-related litigation". We call on relevant authorities to set quantifiable and clearly enforceable evaluation criteria for critical provisions such as "company water-related material impact" and "company water-related material litigation, Walid and ­Mohamed17. Taking a sample of 1166 non-financial companies in the CDP report, the empirical test of how national policies and legal systems can help strengthen the level of water information disclosure of enterprises, and Shen Juqin et al.18 constructed a water information phi level indicator system in line with China’s national conditions, and verified the sensitivity of social monitoring to water information disclosure through model testing, indicating that under external environmental governance, the public and the government attach great importance to the environment and the use of information.information utilization status, and increased the willingness of enterprises to actively disclose.

Xu Jianling et al.19 and Zeng et al.20, using a sample of listed companies in highly water-sensitive industries, confirmed that the effect of water information disclosure on corporate risk containment was strengthened by means of media exposure through the news. Media coverage generates reputational pressure to a certain extent, forcing firms to fulfill their environmental responsibilities. Thus, external monitoring plays a leading role in environmental governance, with the public monitoring pollutant emissions and the government compensating for market "failures" and providing subsidies and incentives in tax and credit policies, so that water conservation is elevated to the strategic level of corporate water management actions to achieve high-quality economic development and sustainable and harmonious social and environmental development.

The choice of different evaluation methods will have an impact on the accuracy of the evaluation. Scholars at home and abroad have studied the content of water disclosure through empirical research, and the relevant research results provide more options for improving the level of corporate water disclosure. And there is no unified standard for evaluating and measuring water information disclosure quality, and many scholars have explored various ways to measure the quality of corporate water information disclosure. Liu CY et al.21 and Yu ­HC9 took the data of Chinese listed companies as a sample, and after mathematical and statistical analysis of the disclosed water information, based on the relevant information disclosed in the annual reports of enterprises, to The "quantitative + qualitative" approach was used to analyze the factors affecting water information disclosure by listed companies based on the coding of water disclosure items by the Global Reporting Initiative (GRI). Liang et al.22 uses the NCA and fsQCA approach to study the joint roles of environmental regulations and other internal and external factors on the quality of environmental information disclosure. Liu ­Xuewen23 used a combination of fuzzy comprehensive evaluation and hierarchical analysis methods to construct a water environmental information disclosure index system for heavily polluting listed companies, which provided a reference for the evaluation method of enterprise water information disclosure quality, ­Kleinman24 uses Formal Concept Analysis (FCA) to study water disclosure and water stewardship in the U.S. food and beverage industry.Plumle et al.25 and Clarkson et al.26 evaluated by "content analysis method" and constructed environmental information disclosure indexes for analysis and evaluation, and the study of environmental information disclosure and quality evaluation. As we can see, domestic and foreign scholars are still exploring the methods of information disclosure quality evaluation. After the promulgation of the revised Environmental Protection Law in China, what are the main contents of water information disclosed by enterprises to the relevant departments, and what is the impact of the environmental laws and regulations, and policies introduced by the government on enterprises’ disclosure of information about water resources? What is the quality of water information disclosure for high water-consuming manufacturing industries? Do manufacturing enterprises record information on water consumption, withdrawal, and consumption generated in the supply chain? The existing literature fails to explain well enough to answer the more profound questions behind corporate water information disclosure.

Given the above theoretical and practical limitations, and to implement the ecological civilization construction of intensive and sustainable use of water resources, this paper studies the paper and paper products industry, a typical high water-consuming enterprise in the manufacturing industry, digs deeper and analyzes the disclosure of water information of listed enterprises, and adopts the mainstream method of content analysis to quantify the water information of enterprises. The content of the disclosure, combined with the projection tracing model of accelerated genetic algorithm, to establish a scientific and practical quality evaluation system in line with the paper and paper products enterprises, through the evaluation of the value of high and low ranking, analysis of the quality of enterprise water information disclosure, so as to force enterprises to accelerate the development of green transformation and innovation, to provide experience and methodological guidance to achieve sustainable and high-quality development of the paper industry.

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Methods

Evaluation index system construction. Currently, China has not yet issued a responsibility report on water information disclosure, and has been in the stage of voluntary disclosure. The enterprise water information disclosure system is not perfect. The system is not sound and generally puts the data related to water disclosure into the annual report of listed enterprises, social responsibility report, and sustainable development report, resulting in the lack of uniform standards when enterprises make the disclosure. There are differences. Based on the existing studies (Morikawa et al. and Zeng Huixiang et al.), this paper selects the four basic principles of "relevance", "reliability", "validity", and "comparability" based on the quality characteristics of corporate accounting information disclosure.

Relevance is a corporate environmental report to provide evaluation information useful to users of water resources, and companies through water environmental assets, water environmental liabilities, water environmental costs, and water environmental management impact. This water-related information to stakeholders to meet the information needs of interested parties; reliability is used to test the quality of water information disclosure, usually using third-party audit or system certification to assess this reliability is used to test the quality of water information disclosure, and third-party audits or systematic certification are often used to evaluate this information. Currently, the water information disclosure audit has not been established, so the water risk assessment, environmental violations penalties, environmental honors, patented green technology, and corporate environmental emergency plans are selected to reflect the truth and objectivity of corporate water information disclosure; validity is the daily production and operation activities of enterprises to provide information about water resources clean production status, water and environmental performance comparison, production process equipment, and staff related education and training, etc. Reflect the importance of enterprise water information disclosure, as well as enterprise transformation of water-saving equipment to show the efforts made by enterprises in energy conservation and emission reduction, to eliminate investors’ doubts about whether the enterprise production process is green and environmentally friendly, the indicators to choose the enterprise water resources management performance evaluation, enterprise water conservation measures secondary indicators for effectiveness; comparability refers to different enterprises, different periods of time can be compared with each other information. Annual reports, social responsibility reports, and environmental reports as disclosure vehicles. Disclosure information will involve the degree of detailed water information disclosure, a horizontal comparison of the report’s content. Content analysis method, "quantitative + qualitative" method, the number and quality of disclosure analysis, each quality dimension assigned a value range of [0 – 3], the higher the score, on behalf of the paper and paper products enterprises more detailed water information disclosure standard. The results are shown in Table 1.

Among the secondary indicators of enterprise water information disclosure quality, we selected water recycling efficiency, enterprise COD emissions, environmental information exchange with stakeholders, enterprise daily water management system plans, goals and strategies, and enterprise water management performance evaluation programs as key indicators for evaluation, which reflect the key aspects of enterprise water use, water conservation measures, water discharge and wastewater treatment performance. By focusing on these key indicators, companies can better understand their core water management issues and take targeted improvement measures.

(1) Water recycling efficiency can promote the sustainable use of water resources. By improving water recycling, enterprises can reduce the over-exploitation of natural water bodies and save production costs. By optimizing the recycling technology of water resources, enterprises can demonstrate their innovative ability in resource management and competitive advantages in sustainable development, and enhance their brand image and market competitiveness. (2) COD emissions from enterprises is an important indicator for internationally common detection of the content of organic matter in water bodies and the pollution level of water quality.

Monitoring COD emissions helps enterprises identify potential water environmental risks, timely identify the source of water pollution, adjust treatment plans and ensure the safety of discharged water quality. By reducing COD emissions, enterprises can reduce wastewater generation and treatment costs, improve resource utilization efficiency, and achieve the dual benefits of energy saving and cost saving. (3) Communicating environmental information with stakeholders is a social responsibility that enterprises should undertake, reflecting their concern for environmental protection and sustainable development. On the one hand, it can improve the transparency of information disclosure and convey to stakeholders the performance and responsibility of the enterprise in water resources management, which helps to enhance the reputation of the enterprise. On the other hand, by communicating environmental information disclosure with stakeholders and introducing their opinions and suggestions, it increases the diversity and legitimacy of decision making to help enterprises better respond to the expectations of society. (4) An enterprise’s daily water management system plan, objectives and strategies can clarify the enterprise’s goals and directions in water resources management and provide guidance for the development of specific action plans and strategies in water resources management. At the same time, it provides a set of systematic strategies and measures to help companies manage and use water resources effectively. In addition, by developing a daily water management system plan, objectives and strategies, companies are better able to identify and manage the risks associated with water management. This helps companies comply with relevant laws and regulations and reduce the legal risks they face due to non-compliance with discharge or excessive discharge of pollutants from water bodies. (5) Enterprise water management performance evaluation provides a quantitative assessment of the enterprise’s internal water management practices. Through information on the status of clean production of water resources, comparative water and environmental performance, production processes and equipment, and employee education and training related to water conservation, companies can identify problems and opportunities for improvement, which can help them understand the effectiveness and efficiency of their water management and promote continuous improvement and optimization of water management strategies.

The results are shown in Table 1.

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Guideline indicators

Tier 1 indicators

Water environment assets (A1)

Water environment liabilities (A2)

Relevance

Secondary indicators

Evaluation criteria

Water source (B1)

For the area where the water source is sufficient, take the value of 3, generally take the value of 2. For local water shortage 1, water scarcity takes the value of 0

Water recycling efficiency (B2)

Quantitative and qualitative disclosure of water pollution control and emission reduction information to take the value of 3, quantitative hit 2, qualitative hit 1, otherwise take the value of 0

Environmental investment (B3)

Quantitative and qualitative disclosure of water pollution control and emission reduction information to take the value of 3, quantitative hit 2, qualitative hit 1, otherwise take the value of 0

Water resources tax or environmental protection tax (B4)

Disclosure of the amount of taxes paid quantitative and qualitative disclosure of water pollution control, and emission reduction information is taken as quantitative hit 2, qualitative hit 1, otherwise the value of 0

Wastewater abatement treatment expenditure (B5)

Quantitative and qualitative disclosure of water pollution control and emission reduction information to take the value of 3, quantitative hit 2, qualitative hit 1, otherwise take the value of 0

Enterprise water consumption (B6)

Quantitative and qualitative disclosure of water consumption row information to take the value of 3, quantitative hit 2, qualitative hit 1; otherwise, take the value of 0

Enterprise wastewater discharge (B7)

Quantitative and qualitative disclosure of wastewater discharge information takes the value of 3, quantitative hit 2, qualitative hit 1; otherwise, it takes the value of 0

Enterprise COD emissions (B8)

Quantitative and qualitative disclosure of COD information takes the value of 3, quantitative hit 2, qualitative hit 1, otherwise it takes the value of 0

Enterprise daily water management system plans, goals and strategies (B9)

Disclosure of the company to develop water resources objectives and the completion of the system and other quantitative and qualitative disclosure of water pollution control and emission reduction information to take the value of 3, quantitative hit 2, qualitative hit 1, otherwise take the value of 0

Environmental information exchange with stakeholders (B10)

Disclosure of environmental information exchange with environmental protection departments at all levels, suppliers, vendors, the public, industry peers, and employees quantitative and qualitative disclosure of water pollution control and emission reduction information take the value of 3, qualitative hit 2, quantitative hit 1, otherwise, take the value of 0

Water risk assessment (B11)

Searching Baidu library and news reports, information such as positive news reports on the existence of physical risk, regulatory risk, and reputational risk of enterprises take the value of 1, negative reports otherwise 0

Penalties for environmental violations (B12)

Disclosure of company environmental penalty information takes the value of 1; otherwise, it is 0

Environmental honors (B13)

Get environmental protection and water conservation honor to take the value of 2, general environmental protection honor for 1, otherwise take the value of 0

Green patented technology (B14)

The value of the green patent is 1; otherwise, it is 0

Enterprise environmental emergency plan (B15)

Disclosure of information on the company’s emergency mechanism, emergency measures, and programs for major environmental emergencies takes a value of 3 in detail, 2 for quantitative, and 1 for qualitative. Otherwise, it takes the value of 0

Enterprise water management performance evaluation (B16)

Qualitative and quantitative disclosure of information on the status of clean production of water resources, comparative performance of the water environment, production processes and equipment, as well as staffrelated education and training is valued at 3, quantitative hit 2, qualitative hit 1; otherwise, it is valued at 0

Enterprise water conservation measures program (B17)

Qualitative and quantitative disclosure of detailed water conservation measures take the value of 3, quantitative hit 2, qualitative hit 1; otherwise, take the value of 0

Corporate annual report (B18)

Qualitative and quantitative disclosure of relevant water information to take the value of 3, quantitative hit 2, qualitative hit 1; otherwise, take the value of 0

Social responsibility report (B19)

Qualitative and quantitative disclosure of relevant water information to take the value of 3, quantitative hit 2, qualitative hit 1; otherwise, take the value of 0

Environmental report (B20)

Qualitative and quantitative disclosure of relevant water information to take the value of 3, quantitative hit 2, qualitative hit 1; otherwise, take the value of 0

Water environment costs (A3)

Water environment management (A4)

Reliability

Validity

Comparability

Water environment regulation (A5)

Water environment performance (A6)

Disclosure vehicle (A7)

Table 1. Enterprise water information disclosure quality index system.

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www.nature.com/scientificreports/ Corporate water information data from the annual reports, social responsibility reports, and sustainability reports of listed companies in Juchao Consulting and Hexun.com, green patent data from China "CSMAR Solution V4.4", water risk assessment based on the Annual Report and Baidu News Database.

Model specification. The projection tracing model was first proposed and conducted by U.S. professors

­ ruskal27,28 in the 1970s as an operational model for cluster analysis to solve the problem of high-dimensional K data, many of which do not satisfy the assumption of normality and need to be solved by a robust or nonparametric method. It mainly involves projecting high-dimensional data onto a low-dimensional subspace by some combination, using a projection indicator function to describe the probability size of a certain classification ranking structure of the original system, finding the projection value that makes the projection indicator function optimal, and then analyzing the characteristics of the classification structure of high-dimensional data according to that projection ­value29. This method is used in water quality evaluation, land resource carrying capacity, and enterprise accounting information quality evaluation. In this paper, a projection tracing model based on an accelerated genetic algorithm is used to evaluate the quality of corporate water information disclosure. The specific process of model construction is as ­follows30.

Step 1: Normalization of sample indicators. Let the sample set of each indicator value be {x ∗ (i, j)|i = 1, 2, · · · , n; j = 1, 2, · · · , p}, Among them x ∗ (i, j) is the value of the Jth indicator for the ith sample, N is the number of samples, and P is the number of indicators in the sample. For the larger and better indicators, the normalization criteria were applied to the indicators using Eq. (1).

x(i, j) =

x ∗ (i, j) − xmin (j) , xmax (j) − xmin (j)

(1)

which xmin (j), xmax (j) are the minimum and maximum values of the Jth index value in the sample set, respectively, x(i, j) is the sequence of indicator eigenvalues normalized.

Step 2: Construct the projection indicator function. The projection tracing method is to project the P-dimensional data {x(i, j)|j = 1, 2, · · · , p} into the low-dimensional space, Integrated into a one-dimensional projection with a = (a(1), a(2), . . . , a(p)) as the projection direction z(i).

z(i) =

p

a(j)x(i, j), i = 1, 2, · · · , n

(2)

j=1

Then the one-dimensional scatterplot is classified according to Eq. (2) as a unit length vector for the projection function expressed as (3)

Q(a) = Sz Dz ,

Sz =

Dz =

n (z(i) − Ez)2 i=1 n−1

n n

,

(R − rij )u(R − rij ),

(4)

(5)

i=1 j=1

where Sz is the standard deviation of the projection z(i),Dz is the local density of the projection z(i); Ez is the mean of the projection, R is the window radius of the local scatter density. rij denotes the distance between samples, rij = |Zi − Zj |,u(R − rij ) is a first-order unit step function, When R − rij ≥ 0, Its value is 1; R − rij < 0, Its value is 0.

Step 3: Optimize the projection direction. After determining the sample index value, the Q(a) maximum direction is estimated as the best projection direction,

max Q(a) = s(z) · d(z),

s.t.

p

a2 (j) = 1,

(6) (7)

j=1

Step 4: Optimal alignment of samples. According to the optimal projection direction, the projection eigenvalue z(i) of each evaluation index combined is calculated.

The genetic algorithm introduces the simulated biological evolution process into the middle algorithm, which is first converted into genetic space. After composing individuals or chromosomes according to the structure of biological evolution, the computational process is optimized by binary coding without restricting the objective function and constraints. Compared with traditional and projection tracking models, its advantages are (1) accelerated genetic algorithms are able to search and improve solutions in the space of feasible solutions, thus improving the multi-dimensional spatial movement tendency of feasible solutions, exploring diverse solutions, and discovering high-quality projections, which can improve the accuracy and robustness of the model, (2) avoiding the drawbacks of traditional projection tracking models that fall into local extremes and early global Scientific Reports | Vol:.(1234567890)

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Figure 1. Dynamic evolution of the quality of water disclosure by paper and paper product companies, 2017–2021.

convergence. It has inherent parallelism and global superiority seeking capability. (3) Accelerated genetic algorithms are able to speed up convergence in each generation iteration and improve the efficiency of finding optimal projections by using genetic operations such as crossover and mutation to complete the optimization process in a limited amount of time. In this paper, an accelerated genetic algorithm is used to solve complex nonlinear optimization, improve the algorithm’s performance in finding the best, and solve the high-dimensional global optimum problem. The basic procedure is as ­follows31,32.

First, the encoding of model real numbers is constructed, and linear optimization is performed: x(j) = a(j) + y(j)(b(j) − a(j)), (j = 1, 2..., p); Then, the initial parent basic group is produced, and N initial string structure data are randomly generated. {x ∗ (i, j)|i = 1, 2, · · · , n; j = 1, 2, · · · , p}, A further population of N individuals is generated for evolutionary sorting {f (i)|i = 1, 2, · · · , n; }{y(i, j)|i = 1, 2, · · · , n; j = 1, 2, · · · , p}; Assessment of the degree of adaptation. The merits and demerits of the individual or solution.

F(i) = 1/(f 2 (i) + 0.001); and select the next generation of individuals.

After selecting good individuals from each chromosome, the cycle was repeated—forming a new individual PS (i) = F(i)/ ni=1 F(i).

By cross-operation, Y2 (i, j) = u1 y(i1 , j) + (1 − u1 )y(i2 , j) < 0.5

Y2 (i, j) = u2 y(i1 , j) + (1 − u2 )y(i2 , j), u3 ≥ 0.5.

Mutation operation Y3 (i, j) = u(j), um < pm (i);Y3 (i, j) = u(j), um ≥ pm (i); Finally iterate. The cycle is repeated until the best individual in the group of N individuals is found and the operation is finished.

Results and discussions

Vertical changes in water disclosure for paper and paper product companies. Using 2017–2021 (excluding ST, ST*, and current year listed companies) as sample data, a projection tracing model with an accelerated genetic algorithm was used to analyze the change in the trend of information disclosure about water resources in listed companies of paper and paper products. MATLAB 2022 was used to program the data, and the parents’ initial population size was 200, the crossover probability was 0. 8, the variation probability was 0.1, the number of outstanding individuals was selected as 20, and the number of accelerations was 20. Obtain the best projection direction of the indicator a∗ = (0.1157, 0.2559, 0.1702, 0.1985, 0.2042, 0.3147, 0.2496, 0.3384, 0.1782, 0.2317, 0.1436, 0.1964, 0.1240, 0.2079, 0.1993, 0.2215, 0.2676, 0.2359, 0.2617, 0.2178), and to obtain the value of the investment evaluation of each sample corresponding to the disclosure of water resources information (Fig. 1).

Changes in the vertical projection value of water information disclosure of paper and paper product companies. From the characteristics of the projection value change trend of water information

disclosure of paper and paper product enterprises over the years, the projection value of each subsystem shows a staggered state of increase and decrease. Among them, the change trend of the disclosure carrier projection value shows a gradual decrease, as shown in Fig. 1. Water environment regulation, water environment assets, water environment management projection value in 2017 to 2019 overall steadily increasing, especially the water environment assets projection value from 0.4802 to 0.6778, 2019–2021, except for the disclosure carrier and water environment management projection value, showing a slow decline after a continuous increase, mainly Scientific Reports |

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www.nature.com/scientificreports/ because of the " COVID-19", in order to reduce the spread of the virus, some localities implemented blockade and quarantine measures, which restricted the daily operations of enterprises, and as the epidemic was controlled, the Chinese government enacted policy measures to stimulate economic growth in order to promote economic recovery and development. As a result, various projection values gradually continued to rise during this period. The disclosure carrier and water environment management showed a gradual decline in the projection value of enterprise water information disclosure, decreasing from 0.7963 and 0.4724 in 2017 to 0.5833 and 0.3946, respectively. Although in 2020, the government issued the Opinions on Further Improving the Quality of Listed Companies (hereinafter referred to as "Opinions") and the Measures for the Administration of the Legal Disclosure of Enterprise Environmental Information, which put forward the principle of "the disclosure of information on listed companies". The government issued the "Opinions on Further Improving the Quality of Listed Companies" (hereinafter referred to as "Opinions") and the "Measures for the Administration of Legal Disclosure of Corporate Environmental Information" in 2020, which put forward the requirement of "improving the quality of information disclosure" to further optimize and regulate the activities of legal disclosure of corporate environmental information. However, the disclosure content does not clearly regulate the disclosure of enterprise water information, focusing more on the ecological and environmental information of the production process and carbon emission information of enterprises. Because it is not mandatory for enterprises to disclose information on water consumption, sewage discharge, etc., resulting in paper companies to disclose less content about water resources in the relevant reports, so the disclosure carrier and water environment management projection value continued to decrease from 2017 to 2021, indicating that there are certain risks in the process of using water resources.

From the dynamic evolutionary change characteristics of the projection value, the following five influencing factors are mainly summarized (1) From the analysis of tax policy factors, the Chinese government has implemented a series of tax reduction and fee reduction policies for paper enterprises, aiming to help enterprises develop green, promote transformation and upgrading and environmental protection. For the purchase and installation of qualified wastewater treatment equipment, they can enjoy the VAT reduction policy, and the expenditure related to the purchase and installation of wastewater treatment equipment by enterprises can be included in the cost or offset against income tax. In addition, the Chinese tax law stipulates that enterprises purchasing fixed assets (such as wastewater treatment equipment) can charge depreciation expenses according to certain depreciable life. The depreciation expense can reduce the tax burden of enterprises and promote the return of investment. While enjoying tax benefits, in order to restrain the ecological and environmental problems caused by the discharge of enterprise pollutants, the Chinese government started the environmental protection tax on January 1, 2018, to force environmental polluters to reduce pollution and prompt enterprises to transform and upgrade through the imposition of environmental protection tax; (2) from the analysis of technological innovation and application factors, Chinese paper enterprises adopt more efficient and environmentally friendly pulp production technologies, paper-making equipment and processes in the production process. To improve the efficiency, quality and paper manufacturing efficiency, quality and diversity of pulp production. This reduces environmental pollution and resource consumption. (3) From the analysis of industrial structure transformation factors, Chinese paper companies gradually promote the digital and intelligent transformation of paper-making process equipment and apply technologies such as information technology, big data analysis and artificial intelligence in order to move toward high-quality development of comprehensive strength. Through the implementation of intelligent manufacturing and water supply chain management, they have improved the efficiency of water recycling and daily water management, and explored a new path to develop a circular economy; (4) from the analysis of environmental governance investment factors, as social awareness of environmental protection increases, more and more enterprises are aware of the importance of environmental governance and take on environmental responsibility. Some paper enterprises have a certain awareness of environmental governance and corporate social responsibility, and voluntarily increase the investment in environmental governance funds. For example, Jingxing Paper and Rongsheng Environmental, according to the annual report information statistics 2017–2019, the amount of investment in environmental protection increased from 66.35 million yuan to 127.3296 million yuan, the investment in environmental governance funds can not only promote water-saving technology innovation and improvement, improve the efficiency and effectiveness of water environmental management, but also reduce resource waste and pollution emissions, reduce costs and increase efficiency, and increase the competitive advantage of enterprises. Among other things, banks and financial institutions provide certain support to environment-friendly enterprises, including the provision of green credit and financing channels.

This injects "living water" into the cash flow of paper enterprises and supports them to carry out environmental management. (5) In terms of public participation, Chinese paper companies have established a series of public participation mechanisms for external corporate management, such as public hearings, media coverage and third-party assessments. These mechanisms provide channels and platforms for public participation, enabling the public to directly participate in the environmental decision-making and management of the company and enhancing public participation. In terms of internal management, the company organizes and holds employee water conservation education and publicity activities, community involvement activities and public welfare projects to promote public attention and participation in the paper-making enterprise.

Changes in horizontal projection values of water information disclosure of paper and paper product companies. Considering that 2020 is the closing year of China’s 13th Five-Year Plan, the paper

and products enterprises in 2020 are taken as the research unit, following the above approach, Exploring the characteristics of corporate water disclosure in 2020, obtaining the best projection direction of the indicator a∗ = (0.2195, 0.2680, 0.1435, 0.1894, 0.2933, 0.2490, 0.1891, 0.2856, 0.2298, 0.1802, 0.2925, 0.2066, 0.2313,

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Figure 2. Projection weights of first-level evaluation indicators.

0.2621, 0.1265, 0.1465, 0.2870, 0.1631, 0.1314, 0.2424). In turn, the distribution ratio of each index dimension of the paper company is obtained.

The value of each vector in the best projection direction represents each indicator’s corresponding weight, and each indicator’s importance in evaluating the quality of corporate water disclosure can be derived by ranking.

As can be seen from Fig. 2, the weight of the first-level evaluation indicators is ranked from largest to smallest as water environmental supervision (A5), water environmental costs (A3), water environmental assets (A1), disclosure vehicle (A7), water environmental performance (A6), water environmental management (A4), water environmental liabilities (A2), of which the total contribution of the three indicator dimensions of water environmental supervision, water environmental costs, and water environmental assets is more than 50%. It can be seen that listed companies in the paper industry should improve the information disclosure quality of these three indicators, which have a greater impact on the overall quality of corporate water information disclosure. The greater the indicator’s weight represents a greater impact on the quality of corporate water disclosure, specifically in the secondary indicators. Table 2 shows the degree of impact of each indicator in detail. Four indicators, such as wastewater abatement treatment, water risk assessment, enterprise COD emissions, and enterprise water conservation measures program, have higher weight values and have the greatest impact on the quality of water information disclosure of paper enterprises. In addition, it can also be more intuitive to see the water information disclosure quality evaluation value projection value of paper-listed enterprises, as shown in Table 3. In order to qualitatively evaluate the quality of water disclosure of enterprises, concerning relevant literature s­ tudies33, this study uses a 4-level grading scale to evaluate (Table 4), and the projection values are divided into intervals, (~ , 1.6], [1.6, 2.4], [2.4, 3.2], [3.2, ~) indicating poor, average, better, and excellent.

From the evaluation values (see Table 3), we can see that the top three companies are "Jingxing Paper", "Minfeng Special Paper" and " Rong sheng Environmental Protection Paper", with evaluation values of 3.7901, 3.7072, and 2.9978, respectively. In the original information, these three companies issued not only independent social responsibility reports, but also disclosed independent annual environmental reports, describing in detail the content of environmental accounting, including investment in clean production, governance costs, environmental research and development expenditure and investment in environmental education and training; water resources management performance. Including water consumption, sewage discharge methods, whether the number of emissions and emission concentrations comply with national standards, water conservation program measures, water environment management, including internal environmental management system, system and clean production status, environmental protection supervision letter work, and other content. Among them, Jing xing Paper publicly disclosed in the 2020 environmental report to exchange water environmental information with stakeholders, effectively allowing public participation in the enterprise’s water environmental protection work, timely follow-up and feedback on problems, and the establishment of a set of internal water environmental management system in line with the enterprise, and got 95% of stakeholders in 2020 to evaluate Jingxing Pape’s

Evaluation indicators

Best projection direction

Evaluation indicators

Best projection direction

Evaluation indicators

Best projection direction

Evaluation indicators

Best projection direction

B1

0.2195

B6

0.2490

B11

0.2925

B16

0.1465

B2

0.2680

B7

0.1891

B12

0.2066

B17

0.2870

B3

0.1435

B8

0.2856

B13

0.2313

B18

0.1631

B4

0.1894

B9

0.2298

B14

0.2621

B19

0.1314

B5

0.2933

B10

0.1802

B15

0.1265

B20

0.2424

Table 2. Optimal projection directions for the secondary evaluation indicators of water information disclosure for paper companies in 2020.

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Code

Company name

Rate the value

Ranking

Code

Company name

Rate the value

Ranking

002067

Jingxing Paper

3.7901

1

002228

Hexing Packaging Printing

1.2537

16

600235

Minfeng Special Paper

3.7072

2

600963

Yueyang Forest & Paper

1.2382

17

603165

Rongsheng Environmental Protection Paper

2.9978

3

002303

Mys Environmental Protec1.2355 tion & Technology

18

002078

Sun Paper

2.4780

4

600793

Yibin Paper

1.2311

19

000488

Chenming Paper

2.4610

5

002831

YUTO Packaging Technology

1.2181

20

002012

Kan Specialities Material

2.4550

6

002521

Qifeng New Material

1.2167

21

0.7507

22

600433

Guanhao High-Tech

2.2351

7

603863

Songyang Recycle Resources

600308

Huatai Paper

2.1004

8

002799

Global Printing

0.6766

23

600966

Bohui Paper

1.6854

9

603687

Great Shengda Packing

0.6217

24

600567

Shanying intl

1.6685

10

603022

Xintonglian Packaging

0.5863

25

0.5541

26

002511

C&s Paper

1.6631

11

002565

Shunho New Materials Technology

600103

Qingshan Paper

1.6581

12

603607

Jinghua Laser Technology

0.5355

27

600356

Hengfeng Paper

1.6333

13

–

–

–

–

000815

MCC Meili Paper

1.2662

14

–

–

–

–

603733

Xianhe Limited Ltd

1.2556

15

–

–

–

–

Table 3. Evaluation value of water information disclosure quality of paper companies.

c

Grade

Number of companies

Percentage of

< 1.6

Bad

14

51.85%

1.6 ~ 2.4

General

7

25.93%

2.4 ~ 3.2

better

4

14.81%

> 3.2

Excellent

2

7.41%

Table 4. Quality rating of water information disclosure of paper companies.

environmental information good. It indicates that the enterprise has a strong voluntary disclosure of water information and values the direct impact of water management on its sustainable and high-quality development.

From the grade rating (see Table 4), the maximum value of 27 paper enterprises is 3.7901. The minimum value is 0.5355. The average value is 1.6360, the variance is 0.804, and the standard deviation is 0.8966, indicating that the quality of water information disclosure of paper enterprises varies greatly. The difference is a bifurcated phenomenon. Only two enterprises (7.41%) that reach the excellent grade, better and general enterprises, have 11, respectively, accounting for 14.81% and 25.93%. In contrast, the majority of enterprises are bad grades, a total of 14, accounting for half of the overall proportion of 51.85%. It can be seen that most paper enterprises are missing water information disclosure content, facing low-quality of water information disclosure, and the need to improve the enthusiasm for enterprise water information disclosure.

In terms of the nature of enterprises (see Fig. 3), although the maximum projection value of SOEs is smaller than the maximum projection value of non-SOEs, the overall disclosure of SOEs is slightly higher than that of non-SOEs. Minfeng Special Paper proposes an environmental management grid in the disclosure information, establishes a special environmental management committee, incorporates the results of monthly supervision and inspection into the monthly performance assessment, and the disclosure information also makes special explanations about the situation of letters and visits during the period of Central Ecological and Environmental Protection Inspectors. In addition, Guanhao High-Tech has prepared annual sustainability reports in accordance with the Global Sustainability Reporting Standards (GRI Standards) of the Global Sustainability Standards Board, and implement the concept of efficient use of water resources and strict protection of the environment, relatively speaking, SOEs are subject to more stringent regulation and supervision in their operations. The government, as the major shareholder of SOEs, usually requires more information disclosure from SOEs to ensure a fair, just and transparent market environment. At the same time, SOEs are more sensitive to the government’s environmental policies and have better execution, especially those that have been listed for a longer period of time, pay more attention to fulfilling their social responsibility, achieving high-quality development, and carrying out environmental protection and ecological sustainability, and their image and reputation have a direct impact on the country’s image.

Regionally (see Fig. 4), A-share listed paper and paper products companies are concentrated in 11 provinces (municipalities and autonomous regions), with Zhejiang Province and Shandong Province generally having a higher composite rating value of 2.1947 and 1.9883 than other regions. Shanghai, as China’s economic and financial center, has a dominant position in industry. However, Shanghai’s water resources are mainly dependent Scientific Reports | Vol:.(1234567890)

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Figure 3. Evaluation of the nature of the enterprise of the quality of water information disclosure of paper companies.

Figure 4. Regional evaluation of paper companies’ water information disclosure quality enterprises. on external water diversions and water management may focus more on meeting industrial and urban water supply needs, with relatively little attention to water information disclosure, which, combined with the fact that some water information may involve commercially sensitive information or privacy issues, may limit the scope and content of water information disclosure, resulting in a low overall rating value. From the perspective of raw materials, Heilongjiang has abundant forest resources, while Fujian and Zhejiang have abundant bamboo resources, and Guangdong and Zhejiang also have abundant waste paper resources. The abundance of these raw material resources provides convenience and cost advantages for local paper enterprises; from the perspective of water sources, Ningxia and Shaanxi land belongs to the structural water shortage, and Shanghai, although located in the coastal area, belongs to the supply and demand water shortage. In addition to these three places, Scientific Reports |

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www.nature.com/scientificreports/ the rest of the regions are abundant in water resources, which makes it convenient for enterprises to use water locally and also meet the production water needs of industrial enterprises; from the perspective of geographical advantageous location, Guangdong, Zhejiang, Shandong and Shanghai are located in the coastal areas of China, which makes it easy to trade with domestic and foreign markets. Provides convenient conditions for logistics and sales of paper enterprises; from the perspective of market demand, Shandong and Shanghai areas, the demand for packaging paper, printing paper, etc. is large, which provides local paper enterprises with broad market opportunities and potential. From the perspective of technological innovation, Zhejiang Province has strong technical strength and innovation capability in the field of specialty paper and printing paper, Guangdong Province has strong technical advantages in the field of paper processing and packaging, Shandong Province is the first in pulp and paper production nationwide, and its regional enterprises jointly complete the "high-performance wood chemical pulp green preparation and high-value utilization of key technologies and industrialization "project won the 2020 National Science and Technology Progress Second Prize, the only award-winning project in the paper industry; from the perspective of environmental policy regulation, six provincial governments have long supported and encouraged the paper industry, promoting industrial development through policy, financial and tax support. These provinces may enjoy certain preferential policies in terms of policy support.

Analysis of legal regulations and policy influencing factors. During the period 2017–2021, several

laws, regulations and policy documents have been introduced in China related to environmental protection in the paper industry. The following are some of the important laws, regulations and policies that have prompted companies to pay more attention to water environmental issues and take more effective management measures, thus driving up indicators. In 2015, the State Council promulgated the Water Pollution Prevention and Control Action Plan and the Ten Articles of Water, which provide for the principles, responsibilities, legal liabilities and supervision of water environmental protection; in 2017, the Water Pollution Prevention and Control Law was revised to Prevention and control was regulated, for the paper industry wastewater discharge standards, sewage permit system, water environmental monitoring and assessment and other aspects of the corresponding requirements; 2019 the National Development and Reform Commission, the Ministry of Water Resources jointly issued a "National Water Conservation Action Plan" for industrial enterprises to put forward "water conservation and emission reduction" and "Science and technology innovation" and other closely related, paper enterprises from the technical adjustment of the paper industry industrial transformation, increased investment in environmental protection and water-saving equipment, the construction of a new model of diversification of enterprise water-saving services, so as to achieve the transformation of the results of green water-saving technology as soon as possible. The government from the policy and regulations to further strengthen the protection of water sources and limit the discharge of polluted water sources, for enterprise water resources management and water information disclosure to provide planning and guidance. The two go hand in hand to promote the paper industry intensive water conservation, to the green, low-carbon direction, in the 2020 implementation of the "2020 in accordance with the law to promote backward production capacity exit work program" policy documents to the paper industry and other heavy polluting enterprises were strictly in accordance with the law to eliminate backward products, so that overcapacity contradictions are eased, reducing the discharge of industrial wastewater in the production process, indicating that the paper industry has always Adhere to the policy guidance of green and sustainable development, and actively improve and upgrade water-saving technology to reduce production costs and sewage discharge. In the same year, the Law of the People’s Republic of China on the Prevention of Environmental Pollution by Solid Waste was introduced, which clearly stipulates that China will gradually achieve zero solid waste imports. The continuous adjustment and retrenchment of the waste paper import policy has led to the concentration of enterprises’ foreign waste quotas in large enterprises, the decline of foreign waste ratios year by year, and the rising cost of raw materials. In addition, China has issued a series of policy documents on environmental protection and environmental impact assessment of construction projects, such as the China Agenda for Sustainable Development 2030 and the Law of the People’s Republic of China on Environmental Impact Assessment, which provide guidance and measures to regulate the procedures and contents of environmental protection and environmental impact assessment. Therefore, under the guidance and promotion of national laws and regulations and policy documents, we should strengthen the regulation and restraint of enterprise water pollutant discharge and encourage enterprises to voluntarily disclose water information in order to realize the optimal allocation and intensive, economical and safe use of enterprise water resources.

Conclusions

In order to better evaluate the level of enterprise water information disclosure quality, this paper constructs a water information disclosure quality index system for paper and paper products enterprises, which improves and supplements the previous evaluation indexes. The projection tracing model is used to analyze A-share paper and product enterprises. Meanwhile, in order to overcome the shortcomings of the traditional model of projection tracing, an improved model based on accelerated genetic algorithm is proposed, which improves the accuracy and robustness of the model. Finally, the effectiveness and adaptability of the method is demonstrated through a case study of water disclosure quality evaluation of 27 paper companies in China, which provides ideas for the study of corporate water disclosure quality evaluation. Our study shows that (1) corporate water disclosure quality indicators include four basic criteria: "relevance", "reliability", "validity" and "comparability", as well as the selection of water recycling efficiency, corporate COD emissions, environmental information exchange with stakeholders, corporate daily water management system plans, goals and strategies, and corporate water management performance evaluation programs as key indicators for evaluation. (2) Introducing accelerated genetic algorithm in the traditional projection tracing model to construct the best projection weights and evaluation values to more accurately and reliably analyze the dynamic evolutionary trend changes of information disclosure related Scientific Reports | Vol:.(1234567890)

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www.nature.com/scientificreports/ to water resources in paper and paper product enterprises. (3) Analysis of the vertical trend changes of weights and evaluation values from 2017 to 2021 reveals that the disclosure of information about water resources in paper and paper products enterprises shows fluctuations and increases in 2017, but after 2019, enterprises disclose information about water resources tends to slow down, and in the disclosure carrier, relevant reports gradually compress the details of information disclosure about water, which is related to relevant environmental policy changes and enterprise disclosure awareness Weakness is related. And from the tax policy, from technological innovation and application factors, industrial structure transformation, environmental investment governance and social public participation in five categories of influencing factors, a detailed analysis of the trend of change in paper enterprises, (4) from the 2021 weight and rating value of the horizontal trend change analysis, in the rating level, the number of excellent enterprises is less, indicating that enterprises are not high enthusiasm for voluntary disclosure of water resources information, enterprise water information The overall quality of disclosure quality results are less satisfactory; the nature of enterprises, state-owned enterprises slightly better than non-state enterprises, mainly because of the stronger policy sensitivity of state-owned enterprises and its image and reputation of the direct impact on the image of the country; from a regional perspective, Zhejiang Province and Shandong Province in the overall enterprise water information quality evaluation system performance is better, its advantages in raw materials, water resources, geographic location, market demand, technology and innovation and environmental policy rules, while Shanghai and Shaanxi Province evaluation value is at a lower level, mainly by the geographical environment to limit access to water resources, as well as enterprises involved in commercially sensitive information or privacy issues, reluctance to actively disclose water-related information factors. It is worth noting that although the projection tracing imitation with the introduction of genetic algorithm overcomes the subjective factors of the evaluation method to a certain extent, the subjectivity brought by the content analysis method still cannot be avoided. This paper tries to establish a scientific, complete and effective evaluation index system, which will help to achieve the comprehensiveness of the evaluation index and make the definition of the evaluation results clearer and more accurate through the continuous in-depth research conducted by future scholars and thus improve the objectivity of the evaluation results.

We note that these results have some implications for understanding corporate water information disclosure, first, to raise awareness and improve the construction of the legal and regulatory system. In recent years, a number of laws and regulations have been promulgated in environmental protection, but. However, the legal system for environmental information disclosure, especially water information disclosure, is still under development.

Specific measurement indicators regarding water information disclosure need to be continuously improved, and specific requirements and content forms for water information disclosure should be introduced as soon as possible. Enterprises in the water information disclosure, daily need to measure, and collect data and timely collation of information. The process will increase the cost of certain fees, due to the lack of mandatory disclosure of enterprise water information, resulting in the disclosure of enthusiasm is not high. The government should lead enterprises to carry out water-saving technology upgrades, promote enterprise green technology innovation, and reduce enterprise water and environmental risks. At the same time, the government’s specific system continues to adapt to changes in the implementation of the enterprise to the reality, to give enterprises a certain amount of financial assistance, so that the ecologically sustainable development of enterprises have a material basis for the protection of positive water information disclosure of enterprises, through green financial means to promote the construction of enterprise water information disclosure system, to mobilize the initiative of enterprises.

In addition, there is a need to improve the system, and the ability to play the main corporate governance.

Enterprises are the main body of water information disclosure, in the pursuit of profit maximization at the same time, shoulders social responsibility, high water-sensitive industries should be a more spontaneous initiative to disclose water information, but from the report, only three enterprises independently disclose information related to water information in the annual environmental report, one enterprise independently discloses the annual sustainability report, there are enterprises did not disclose social responsibility report. From the disclosure of information, to the disclosure of formal content, the quality varies, only the disclosure of better indicator data, so that stakeholders have one-sided cognitive enterprise water environment status. Enterprises combine their own reality and the requirements of relevant departments to establish an internal control system for environmental management, responsible for information collection, collation, review and release, to ensure the authenticity and reliability of data disclosure, the main person in charge of the enterprise to enhance the sense of responsibility, the enterprise water resources information disclosure as an important work well arranged and deployed, the enterprise management of water resources information disclosure with business work with the same arrangements, with the implementation, and finally detailed to each The management of the enterprise will arrange and implement the disclosure of water resources information together with the business work, and finally, it will be detailed to each staff position, encourage the staff to actively participate in the activities of information disclosure, and give job promotion and material rewards to the staff who are complete and comprehensive in the information disclosure.

Data availability

Upon publication of the paper, the datasets used and analyzed during the study are available from the corresponding author upon reasonable request.

Received: 23 March 2023; Accepted: 23 July 2023

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Account. Finance 51, 2–49. https://​doi.​org/​10.​1111/j.​1467-​629X.​2010.​00387.x (2011).

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Acknowledgements

Key technology research on the evaluation and improvement of the management level of Yangtze River thousand flowing water resources assets based on the Yangtze River protection needs, grant number B200204019.

Author contributions

Conceptualization, Formal analysis, Writing – original draft, C.H.; Methodology, Writing – original draft, J.S.; Writing – review & editing, J.X.; Data preprocessing, Software, F.S. Diagrams, Data collection and recording, B.W. All authors reviewed and approved the final manuscript.

Competing interests

The authors declare no competing interests.

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry TENG YI, SHUENN-REN LIOU & WEN-YIH KUO Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated. For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect. Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.

Contact information: Department of Architecture, National Cheng Kung University, 701 No. 1, East District, Tainan 701401, Taiwan.

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Article 6 – Sustanability

sustainability Article

Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry Teng Yi *, Shuenn-Ren Liou

and Wen-Yih Kuo Department of Architecture, National Cheng Kung University, 701 No. 1, East District, Tainan 701401, Taiwan * Correspondence: n78083503@gs.ncku.edu.tw; Tel.: +886-(06)-275-7575 (ext. 54122)

Abstract: Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated.

For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect.

Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.

Keywords: alkali-activated binder; wastes in papermaking; blast furnace slag; compressive strength; flexibility; texture

Citation: Yi, T.; Liou, S.-R.; Kuo, W.-Y. Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry. Sustainability 2022, 14, 13536. https://doi.org/ 10.3390/su142013536 Academic Editors: Rui Zhao, Tianxue Yang and Sebastiano Patti Received: 19 September 2022 Accepted: 17 October 2022 Published: 19 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Copyright: © 2022 by the authors.

Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

1. Introduction In 2021, the global output of paper products was 90.2 million tons, which continues to grow due to the COVID-19 pandemic [1]. In addition, approximately 3 billion USD is spent each year on waste disposal from the paper industry and related expenses. For a mediumsized mill, the cost is close to 7 million USD [2]. The waste in papermaking includes many solid wastes such as chips from wood processing, lime muds from kraft pumping, bottom ash in the recovery boiler, and paper sludges from on-site sewage treatment [3,4].

Several programs have been developed to manage these wastes. For example, biomass materials such as wood chips and water treatment sludge could be partially added as fuel to fuel boilers of paper mills [5]. However, this process created additional air and water pollution while supplying electricity to the paper manufacturing process [6]. Some other solid wastes, such as lime sludge, were difficult to reuse as fuel. These materials were usually landfilled with the ashes from incineration [7], causing occupancy of the waste plant and posing the risk of soil and water contamination [8]. Therefore, it is necessary to select suitable resource-based methods to reprocess these wastes without increasing or shifting the environmental burden.

By investigating the main components of waste in papermaking [9], the conversion of waste into building materials could be a suitable solution [10]. Among the solid wastes, lime mud replaced the raw materials of ordinary Portland cement by calcination, with a maximum replacement ratio of 20% [11,12]. The paper sludge thermally activated at 600–750 ◦ C replaced 10% of cement as the cementitious binder [13]. In addition, 15% of wood chip ash from paper mills could be used as a raw material for the cementitious binder [14]. Although these methods helped convert waste into building materials, they still caused some energy consumption and environmental impact [15]. In addition, some studies investigated the use of bottom ashes as aggregates [16].

Sustainability 2022, 14, 13536. https://doi.org/10.3390/su142013536

https://www.mdpi.com/journal/sustainability

Sustainability 2022, 14, 13536

some energy consumption and environmental impact [15]. In addition, some studies investigated the use of bottom ashes as aggregates [16].

Alkali-activated cementitious materials are formed by mixing aluminosilicate mate2 of 11 rials with alkali metal silicate solutions and alkali activators [17,18]. Among them, alkaliactivated slag has received wide attention for its low CO2 emission, high compressive strength, durability, and fire resistance [19]. Recently, more emphasis has been placed on the potential for solidifying waste from alkali-activated furnace slag [20–24]. materials Alkali-activated cementitious materials are formedblast by mixing aluminosilicate This study aimed to analyze the possibility of alkali-activating the mixture them, of wastes with alkali metal silicate solutions and alkali activators [17,18]. Among alkaliand blast furnace slag (BFS) in papermaking.

Moreover, the effects of different wastes on activated slag has received wide attention for its low CO2 emission, high compressive the physical and mechanical the slurry are discussed.

In thishas study, different strength, durability, and fireproperties resistanceof[19].

Recently, more emphasis been placed on single-type papermaking wastes (SPW) were mixed with BFS and alkali-activated at amthe potential for solidifying waste from alkali-activated blast furnace slag [20–24]. bientThis conditions.

The compressive strengths and stress-time curves were used to analyze study aimed to analyze the possibility of alkali-activating the mixture of wastes the optimized component proportion of waste replacement BFS.ofOn this basis, differand blast furnace slag (BFS)and in papermaking.

Moreover, the effects different wastes on the ent types of wastes were selected as paper waste mixture (PWM) for further analysis to physical and mechanical properties of the slurry are discussed. In this study, different singleensure a balance between the proportion of wastes in the mixtures, compressive strengths, type papermaking wastes (SPW) were mixed with BFS and alkali-activated at ambient and flexibilities. The effect of organic materials, such as wood chips, was also discussed. conditions. The compressive strengths and stress-time curves were used to analyze the This study provided an appropriate alkali equivalent (AE) for the alkali activators.

optimized component and proportion of waste replacement BFS. On this basis, different types of wastes were selected as paper waste mixture (PWM) for further analysis to ensure 2. Materials and Methods a balance between the proportion of wastes in the mixtures, compressive strengths, and The BFS used in this study was the experimental raw material provided by China flexibilities. The effect of organic materials, such as wood chips, was also discussed. This Steel in Taiwan, with the label S6000, packed in 20 kg sealed bags. The papermaking study provided an appropriate alkali equivalent (AE) for the alkali activators.

wastes were provided by the Chung Hwa Paper Corporation in eastern Taiwan. Among lime mud collected from the caustic kiln, paper sludge was collected during 2.them, Materials and was Methods the sewage treatment process, and the bottom ash was collected from the recovery boilers.

The BFS used in this study was the experimental raw material provided by China Steel All the papermaking wastes were directly collected from the same batch of paper, with in Taiwan, with the labelmaterial S6000, packed sealed bags. papermaking wastes iswere 150 kg samples of each packed in in 20 sixkg sealed bags.

TheThe sample of raw materials provided by the Chung Hwa Paper Corporation in eastern Taiwan.

Among shown in Figure 1. Those four materials were dried to constant weight at 110 them, °C andlime mud was collected the0.282 caustic sludge was collected provided during the sieved with a meshfrom size of mm.kiln, The paper main chemical components bysewage the treatment process, and the bottom ash was collected from the recovery boilers.

All the manufacturer are shown in Table 1. papermaking wastes were directlyofcollected from the same batch ofmaterial paper, with 150 kg Considering the simplification the alkali-activated cementitious producsamples of each material packed in six sealed bags.

The sample of raw materials is shown tion and the convenience of storage and transportation, sodium silicate powder was used ◦ C and sieved with a in Figure 1.

Those four materials were dried to constant weight at 110 to prepare activators. The composition of sodium silicate powder was 46.07% of SiO2 and mesh size mm. main chemical components provided by the manufacturer 51.35% of of Na0.282 2O. The AEThe of the activators was 10%, the silicate modulus (Ms) of the acti- are shown in Table 1. vators was 0.93, and the water-binder ratio (W/B) was 0.5.

Figure1.

1. The The material material diagram. (c)(c) Paper sludge. (d) (d) Bottom ash.ash.

Figure diagram.(a) (a)BFS. BFS.(b) (b)Lime Limemud. mud.

Paper sludge.

Bottom

Table 1. Chemical composition of paper industrial wastes and BFS. Item

SiO2 (wt. %)

CaO (wt. %)

Al2 O3 (wt. %)

SO3 (wt. %)

Fe2 O3 (wt. %)

L.O.I (wt. %)

Other (wt. %)

BFS lime mud paper sludge bottom ash

28.1 – – 33.5

53.7 71.6 18.2 16.7

13.2 – – 14.1

– 16.2 3.7 5.2

0.5 3.4 0.5 7.9

– 3.2 74.2 18.2

4.5 1.5 2.1 4.4

Legend: SiO2 —Silicon dioxide; CaO—Calcium oxide; Al2 O3 —Aluminum oxide; SO3 —Sulphur trioxide; Fe2 O3 —Ferric oxide; L.O.I—Loss on ignition; wt.%—weight percentage.

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The experimental procedures included the preparation of the activator or material mixture, preparation of slurry, casting of specimens, and testing. Firstly, the alkali activator solution was prepared by mixing sodium silicate powder and water, then sealed and 3 of 11 cooled to room temperature. Meanwhile, the raw materials were weighed in the required quantity and thoroughly mixed for 1 min. Subsequently, the mixture of dry materials was added to an alkali activator and mixed for another 10 min to finish the slurry. According Considering simplification of the alkali-activated cementitious to ASTM C109, thethe specimens for compressive strength tests were cast material in 50 mmproduction × 50 mm the molds convenience of layers storage transportation, silicate used ×and 50 mm with two of and mortar, followed by sodium compaction and powder vibrationwas to elimto prepare activators.

Theinitial composition of sodiumwere silicate powder 46.07% SiO2 inate air bubbles.

After the setting, specimens sealed with was plastic films of to preand 51.35% of Na O. The AE of the activators was 10%, the silicate modulus (Ms) of the vent moisture loss.2In this study, samples were de-molded after 24 h of casting and stored activators was 0.93, and the water-binder ratio (W/B) was 0.5. in a control box at 20 °C and 95% relative humidity. Considering the experimental design Thenumber experimental procedures the preparation the separately activator ortested material and the of samples, three ofincluded each experimental seriesof were on mixture, preparation of slurry, and testing.curves Firstly, activator the compressive strengths at 3,casting 7, and of 28 specimens, days; the stress-time atthe dayalkali 28 were recsolution was prepared byand mixing silicate and water,2 then sealed and cooled orded.

The specific steps test sodium parameters arepowder shown in Figure and the experiment’s to room temperature.

Meanwhile, the raw materials were weighed in the required quantity process records in the laboratory are shown in Figure 3. and thoroughly mixed for 1 min. Subsequently, the mixture of dry materials was added to an alkali activator and mixed another 10 min to finish the slurry. According to ASTM Table 1. Chemical composition of for paper industrial wastes and BFS. C109, the specimens for compressive strength tests were cast in 50 mm × 50 mm × 50 mm SiO CaO Al2O SO3 Fe2O 3 L.O.I Otherair moldsItem with two layers of2 mortar, followed by3 compaction and vibration to eliminate ( wt. % ) ( wt. % ) ( wt. % ) ( wt. % ) ( wt. % ) ( wt. % ) ( %) bubbles. After the initial setting, specimens were sealed with plastic films towt. prevent BFSloss. In this28.1 53.7 were 13.2 -- after 240.5 -- and stored 4.5 in moisture study, samples de-molded h of casting a control box at 20 ◦ C -and 95%71.6 relative humidity.

Considering design lime mud -16.2 3.4the experimental 3.2 1.5 and the number three of each experimental on the paper sludge of samples, -18.2 -3.7series were 0.5 separately 74.2 tested2.1 compressive strengths at 3, 7, and 28 days; the stress-time curves at day 28 were recorded. bottom ash 33.5 16.7 14.1 5.2 7.9 18.2 4.4 The specific steps and test parameters are shown in2O Figure 2 and the experiment’s process Legend: SiO2—Silicon dioxide; CaO—Calcium oxide; Al 3—Aluminum oxide; SO3—Sulphur trirecords the laboratory are shownon inignition; Figure 3. oxide; Fe2in O3—Ferric oxide; L.O.I—Loss wt.%—weight percentage.

Figure 2. Experimental steps and test item.

Figure 2. Experimental steps and test item.

Sustainability 14, 13536 Sustainability 2022, 2022, 14, x FOR PEER REVIEW

4 of 124 of 11

(a)

(b)

Figure 3. The process record in theinlaboratory. (a) The mixing process. (b) The Figure 3.experiments The experiments process record the laboratory. (a) material The material mixing process. (b) The performance test. test. performance

3. Results Discussion 3. Results and and Discussion classified thesubstitution BFS substitution from in wastes in papermaking into two ThisThis studystudy classified the BFS from wastes papermaking into two pathpathways: SPW substitution and PWM substitution.

In both pathways, the effects of these ways: SPW substitution and PWM substitution. In both pathways, the effects of these wastes on mechanical properties and texture were investigated.

The suitable AE values wastes on mechanical properties and texture were investigated. The suitable AE values analyzed. werewere also also analyzed.

3.1. Effect of Single-Type Paper Waste (SPW) Substitution Proportion 3.1. Effect of Single-Type Paper Waste (SPW) Substitution Proportion The experiment parameters of the SPW substitution are shown in Table 2 and the The experiment parameters of the SPW substitution are shown in Table 2 and the compressive strengths of samples are illustrated in Figure 4. The compressive strengths for compressive strengths of samples are illustrated in Figure 4. The compressive strengths different experimental series ranged from 14.5 MPa to 73.7 MPa after 28 days of curing. In for different experimental series ranged from 14.5 MPa to 73.7 MPa after 28 days of curing. terms of the SPW substitution proportion, the highest compressive strength was 73.7 MPa, In terms of the SPW substitution proportion, the highest compressive strength was 73.7 in which BFS was partially substituted by 10% of the lime mud. The weakest compressive MPa, in which BFS was partially substituted by 10% of the lime mud. The weakest comstrength was 14.5 MPa, in which wood chips partially replaced 30% of BFS. Under the same pressive strength was 14.5 MPa, in which wood chips partially replaced 30% of BFS. Unsubstitution ratio, the compressive strength of lime mud, paper sludge, bottom ash, and der the same substitution ratio, the compressive strength of lime mud, paper sludge, botwood chips sequentially decreased. The early strength illustrated that the compressive tom ash, and wood chips sequentially decreased. The early strength illustrated that the strengths of the sample increased rapidly from 0 to 7 days, almost exceeding 85% of the compressive strengths of the increased rapidly from 0 strength to 7 days,values almostofexceeding final strength.

Except forsample the decrease in the compressive samples with 85% the of the final strength.

Except for the decrease in the compressive strength values of addition of sawdust from 7 to 28 days, the trend of strength development remained samples with the addition of sawdust from 7 to 28 days, the trend of strength development relatively constant, with some values fluctuating. remained relatively constant, with some values fluctuating.

Table 2. Experimental parameters of SPW substitution proportion.

Table 2. Experimental parameters of SPW substitution proportion.

Solid Materials wt.%

SolidLime Materials wt.% Paper Bottom Wood Ms AE W/B Chip LimeMud BottomAshPaperSludgeWood AE Ms W/B BFS S0 100 Mud – Ash – Sludge – Chip – S9L1 90 10 – – – S0 S8L2 100 -- 20 -- – --- – 80 – 70 – S9L1 S7L3 90 10 30 -- – --- – 0.5 S9B1 90 – 10 – – S8L2 80 20 ---S8B2 80 – 20 – – S7L3 S7B3 70 30 – -- 30 --- – 70 – 10% 0.93 0.5 90 S9B1 S9P1 90 -- – 10 – -- 10 -- – S8P2 80 – – 20 – S8B2 S7P3 80 -- – 20 – -- 30 -- – 10% 0.93 70 0.6 90 – S7B3 S9W1 70 -- – 30 – --- 10 S8W2 80 – – – 20 S9P1 S7W3 90 -- – -- – 10 – -- 30 70 S8P2 80 equivalent;--Ms—Silicate -- modulus; 20W/B—Water-binder -Legend: AE—Alkali ratio; wt.%—weight percentage.

0.6 S7P3 70 --30 -S9W1 90 ---10 Experiment

Experiment No. No.

BFS

S8W2 S7W3 Sustainability 2022, 14, 13536

80 70

---

---

---

20 30

5 of 11 Legend: AE—Alkali equivalent; Ms—Silicate modulus; W/B—Water-binder ratio; wt.%—weight percentage.

Figure Figure4.

4.The Thecompressive compressivestrength strengthof ofSPW SPW substitution substitution proportion. proportion.

When When paper paper sludge sludge and and wood wood chips chips were were used used as as partial partial substitutes substitutes for for BFS, BFS, the the highest28-day 28-daycompressive compressivestrengths strengthswere were 41.1 MPa and 28.8 MPa, respectively. highest 41.1 MPa and 28.8 MPa, respectively.

ThisThis reresult could attributed thehigh highcontent contentofoforganic organicimpurities, impurities,which whichdisrupted disruptedthe the sult could bebe attributed totothe polymerization of of the thecement cement [25].

[25].In Inaddition, addition,the thehighest highestcompressive compressivestrength strengthof ofbottom bottom polymerization ash was was 39.4 39.4 MPa, MPa, which which substituted substituted BFS BFS after after 28 28 days days of of curing. curing. Compared Compared to to other other ash wastes, bottom bottom ash ash had had some some volume volume expansion expansion except except for for the the reduction reduction in in the ratio wastes, the w/b w/b ratio ofthe theslurry slurry[21].

[21].Although Althoughthe thevolume volumeexpansion expansionreduced reducedthe theself-shrinkage self-shrinkageofofthe theslurry, slurry, of cracks were were also also generated generated in in this this process, process, degrading degrading the the mechanical mechanical properties properties of of the the cracks material [16]. material [16].

In S8L2 S8L2 and andS8P2, S8P2,the thedevelopment developmentof ofcompressive compressivestrengths strengthsfrom from77toto28 28days daysapapIn proached 20% 20% of of the the final final strength. strength. Since Sincethe thereactivity reactivityof ofthe thelime lime mud mud and and the the paper paper proached sludge isis poorer poorer than than BFS, BFS, the the weakening weakening of of compressive compressive strength strength was was reflected reflected by by the the sludge decreased development rate of compressive strength with an increasing ratio.

Furthermore, decreased development rate of compressive strength with an increasing ratio. Furtherthe strengths on dayon 28day showed a significant decrease of moreof than 10 MPa comparimore, the strengths 28 showed a significant decrease more than in 10 the MPa in the son between S8M2 and S7M3 or S8P2 and S7P3 (11.5 MPa and 14.0 MPa, respectively).

This comparison between S8M2 and S7M3 or S8P2 and S7P3 (11.5 MPa and 14.0MPa, respecresult indicated that if the total proportion of lime mud and the paper sludge exceeded 20%, tively). This result indicated that if the total proportion of lime mud and the paper sludge the polymerization in cementitiousin materials was incomplete [26],incomplete significantly decreasing exceeded 20%, the polymerization cementitious materials was [26], signifithe compressive strength.

This result was similar to previous reports [11,12].

However, cantly decreasing the compressive strength. This result was similar to previous reports the other reports have expressed different opinionsdifferent [27,28] due to different pretreatment [11,12].

However, the other reports have expressed opinions [27,28] due to difof slurry raw materials.

Therefore, a total weight of 20% could be considered a suitable ferent pretreatment of slurry raw materials. Therefore, a total weight of 20% could be conproportion, which allowed the partial substitution of the lime mud or paper sludge for BFS. sidered a suitable proportion, which allowed the partial substitution of the lime mud or Considering the optimization of compressive strength, the stress-time curve of BFS paper sludge for BFS. replaced by 20% of the waste was selected as the study object. According to Figure 5, the Considering the optimization of compressive strength, the stress-time curve of BFS stress-time curves for partial substitution of BFS with lime mud or bottom ash showed the replaced by 20% of the waste was selected as the study object. According to Figure 5, the characteristics of brittle materials. Moreover, the shapes of the curves were similar, with a stress-time curves for partial substitution of BFS with lime mud or bottom ash showed the linear increase in yield strength and a sharp decrease at the peak. This variation suggested characteristics of brittle materials. Moreover, the shapes of the curves were similar, with that the samples were crushed and lost the stress intensity at the peak. Only the peak points a linear increase in yield strength and a sharp decrease at the peak. This variation of the curves differed between them, indicating that lime mud or bottom ash could not change the characteristics of brittle materials, resulting in the alkali activation of BFS. In the partial substitution of BFS with paper sludge or wood chips, the curves decreased slowly at the peak. This change indicated that the samples still exceeded the yield strength in some respects. Based on these results, paper sludge or wood chips could significantly change the properties of alkali-activated BFS from brittle to ductile [29].

Sustainability 2022, 14, 13536

suggested that the samples were crushed and lost the stress intensity at the peak. Only the peak points of the curves differed between them, indicating that lime mud or bottom ash could not change the characteristics of brittle materials, resulting in the alkali activation of BFS. In the partial substitution of BFS with paper sludge or wood chips, the curves decreased slowly at the peak. This change indicated that the samples still exceeded the 6 of 11 yield strength in some respects. Based on these results, paper sludge or wood chips could significantly change the properties of alkali-activated BFS from brittle to ductile [29].

Figure 5.

5. The The stress stress curve curve of of the the slurry slurry with with the the 20% 20% proportion proportion of of SPW SPW substituted substituted for for BFS. BFS. Figure

3.2. Effect of Paper Waste Mixture (PWM) Proportion 3.2. Effect of Paper Waste Mixture (PWM) Proportion Due to the experimental results of the partial substitution of BFS with SPW, the lime Due to the experimental results of the partial substitution of BFS with SPW, the lime mud and paper sludge were considered suitable materials for partial substitution. The mud and paper sludge were considered suitable materials for partial substitution. The experiment parameters of the PWM substitution are shown in Table 3. The effect of the experiment parameters of the PWM on substitution arestrength shown in Table 3. Theineffect of the proportion of various waste mixtures compressive was discussed this section. proportion of various waste mixtures on compressive strength was discussed in this secBased on the results, the proportion of BFS in the mixed powder can be further reduced. tion. Based on the results, the proportion of BFS in the mixed powder can be further reduced.

Table 3. Experimental parameters of PWM substitution proportion.

As shown in Figure 6, the compressive strengths of BFS substituted with waste mixSolid to Materials tures showed a similar trend that ofwt.% BFS substituted with SPW. The compressive Experiment Lime Paperday 7 and AEfluctuatedMs W/B strengthNo. rapidly increased to a maximum around from 7 to 28 days.

BFS Mud Sludge When the BFS was substituted by waste mixtures with a weight proportion of 50%, the PWM4-1 60 30 MPa. It 10 highest compressive strength was 23.1 was evident that the compressive strength PWM4-2 60 20 20 decreased with decreasing proportion of lime mud in the waste mixtures. For every 5% PWM5-1 50 40 10 reduction in the proportion of lime mud, the average compressive strength decreased by PWM5-2 50 35 15 10% 0.93 0.5 nearlyPWM5-3 2.5 MPa. 50 30 20 PWM5-4 50 25 25 TablePWM5-5 3. Experimental parameters of PWM 50 20 substitution 30 proportion.

Legend: AE—Alkali equivalent; Ms—Silicate modulus; W/B—Water-binder ratio; wt.%—weight percentage.

Solid Materials wt.% Experiment Lime Paper AE Ms W/B No. BFS 6, the compressive strengths of BFS substituted with waste mixAs shown in Figure Mud Sludge tures showed a similar trend to that of BFS substituted with SPW. The compressive strength PWM4-1 60 30 10 rapidly increased to a maximum around day 7 and fluctuated from 7 to 28 days. When PWM4-2 60 by waste mixtures 20 20 proportion of 50%, the highest the BFS was substituted with a weight 10% 0.93 0.5 PWM5-1 50 40 compressive strength was 23.1 MPa. It was evident that10 the compressive strength decreased PWM5-2 50 35 in the waste mixtures.

15 with decreasing proportion of lime mud For every 5% reduction in the proportion of lime mud, the average compressive strength decreased by nearly 2.5 MPa.

PWM5-3 PWM5-4 PWM5-5 Sustainability 2022, 14, 13536

50 50 50

30 25 20

20 25 30

7 of 11 Legend: AE—Alkali equivalent; Ms—Silicate modulus; W/B—Water-binder ratio; wt.%—weight percentage.

Figure The compressive strength PWMsubstitution substitutionproportion. proportion.

Figure 6. 6.

The compressive strength ofof PWM

Figure7,7,the thestress-time stress-timecurves curves did did not not drop drop abruptly InInFigure abruptly at atthe thepeak peakininthe thesubstitution substituof BFS with mixed wastes. the lime lime mud mudininwaste wastemixtures mixtures tion of BFS with mixed wastes.When When the the proportion proportion of of the exceeded 10% of the total weight, curve optimization was performed.

As the proportion exceeded 10% of the total weight, curve optimization was performed. As the proportion papersludge sludgeininwaste wastemixtures mixturesincreased, increased,the theslope slopeofofthe thecurve curveflattened flattenedout outatatthe the ofofpaper yield stress, suggesting that the flexibility of samples was optimized with the increase of yield stress, suggesting that the flexibility of samples was optimized with the increase of paper sludge. When the proportion of paper sludge increased to 1% of the total weight, the paper sludge. When the proportion of paper sludge increased to 1% of the total weight, slope of the curve over the yield point changed from −2.5 to −1, indicating a prominent Sustainability 2022, 14, x FOR PEER REVIEW 8 of 12 the slope of the curve over the yield point changed from −2.5 to −1, indicating a prominent enhancement of flexibility. Therefore, the stress-time curve was optimized when the paper enhancement of flexibility. Therefore, the stress-time curve was optimized when the paper sludge accounted for 20% of the total mixture weight. sludge accounted for 20% of the total mixture weight.

Figure 7. The stress curve of the slurry with the 50% proportion of PWM substituted for BFS. Figure 7. The stress curve of the slurry with the 50% proportion of PWM substituted for BFS.

3.3. Texture Change of PWM Slurry Considering the optimization of slurry texture and compressive strength, the wood chips were added to the slurry as seen in Table 4. Both wood chips and paper sludge improved the property of the stress-time curve. In addition, 5% of wood chips were used to gradually replace the paper sludge in the mixing proportion of up to 20% of the total

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3.3. Texture Change of PWM Slurry Considering the optimization of slurry texture and compressive strength, the wood chips were added to the slurry as seen in Table 4. Both wood chips and paper sludge improved the property of the stress-time curve. In addition, 5% of wood chips were used to gradually replace the paper sludge in the mixing proportion of up to 20% of the total weight. It can be seen from Figure 8 that when wood chips were added from 10% (PWM3-3) to 15% (PWM3-4) of the total weight, the compressive strength was at a steady stage (nearly 25 MPa), with both stony and woody textures starting to appear clearly on the surface of the mud (Figure 9). Considering the possibility of adding wood chips as decoration materials, it is appropriate to add 15% of wood chips and 5% of paper sludge to the mixture.

Table 4. Experimental parameters of PWM3 series substitution proportion.

Experiment No.

BFS

PWM3-1 PWM3-2 PWM3-3 Sustainability 2022, 14, x FOR PEER REVIEW PWM3-4 Sustainability 2022, 14, x FOR PEER REVIEW PWM3-5

70 70 70 70 70

Solid Materials wt.% Lime Paper Mud Sludge 10 10 10 10 10

20 15 10 5 0

Wood Chips 0 5 10 15 20

AE

Ms

W/B

10%

0.93

0.5 9 of 12 9 of 12

Legend: AE—Alkali equivalent; Ms—Silicate modulus; W/B—Water-binder ratio; wt.%—weight percentage.

Figure 8. The compressive strength of PWM3 series.

Figure 8.

8. The The compressive compressive strength strength of of PWM3 PWM3 series. series.

Figure

Figure 9. The change of texture in terms of PWM.

Figure 9. The change of texture in terms of PWM. Figure 9. The change of texture in terms of PWM.

3.4. Effect of Declining Alkali Equivalent

Given simplified for producing alkali-activated cementitious materials 3.4. Effect of the Declining Alkaliprocess Equivalent and the convenience of storing and transporting materials, only sodium silicate powGiven the simplified process for producingraw alkali-activated cementitious materials der was used to prepare alkali activators in this study.

Therefore, the silicate modulus and the convenience of storing and transporting raw materials, only sodium silicate pow-

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3.4. Effect of Declining Alkali Equivalent Given the simplified process for producing alkali-activated cementitious materials and the convenience of storing and transporting raw materials, only sodium silicate powder was used to prepare alkali activators in this study. Therefore, the silicate modulus (Ms) of alkali activators was a constant value and the ingredient of alkali activators could only be adjusted by AE. Considering the pulp waste proportion, the compressive strength, and the optimization of slurry texture, three kinds of slurries were selected as the samples to investigate the most suitable value of AE. Based on the results of the BFS substitution with waste mixtures in papermaking, the lime mud significantly improved the compressive strength of the slurry. Moreover, two SPW test groups and one PWM test group were used for AE adjustment. The waste substitutions were S7L3, S8L2, and PWM3-4. The content of AE in the activator decreased from 10% to 2%.

The effects of AE on the compressive strengths are shown in Figure 10. When the content of AE exceeded 6%, the compressive strength increased as the AE decreased.

The reason was the presence of excessive hydroxyl ions in the slurry, which could form carbonate on the sample surface by evaporation of water [19]. In addition, this reaction led to the destruction of the colloidal structure. With 6% of AE, the compressive strength reached its peak. This result is consistent with the best AE interval in a previous study Sustainability 2022, 14, x FOR PEER REVIEW 10 of [30].

12 However, S8L2 and PWM3-4 failed to harden after 24 h and could not be de-molded. This result suggested that the alkalinity of the activator was not sufficient to fully stimulate the activity of the BFS and lime mud, resulting in a dramatic decrease in compressive strength. strength. the 6%, AE was 6%, the compressive could approach more thanafter 65 Since theSince AE was the compressive strength strength could approach more than 65 MPa MPa afterof28curing. days of curing.

28 days

Figure10.

10.The Theeffect effectofofdifferent differentAE AEon onthe thecompressive compressivestrength. strength.

Figure

4. Conclusions 4. Conclusions This study evaluated the potential of various wastes in papermaking to be alkaliThis evaluated the potential various wastes in papermaking to be alkaliactivatedstudy as cementitious materials in of terms of mechanical properties, flexibility, and activated as cementitious materials in terms mechanical boundary properties,of flexibility, and samsample texture.

The results expanded theofknowledge paper waste reuse ple texture. The results expanded the knowledge boundary of paper waste reuse and demonstrated the potential advantages of using papermaking wastes as building materials (e.g., toughness enhancement and wood texture). Some experimental data (e.g., 6% AE, 20% waste addition) can also be used as a reference for the actual transformation of wastes in papermaking. However, the experimental findings have limitations in terms of

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and demonstrated the potential advantages of using papermaking wastes as building materials (e.g., toughness enhancement and wood texture). Some experimental data (e.g., 6% AE, 20% waste addition) can also be used as a reference for the actual transformation of wastes in papermaking. However, the experimental findings have limitations in terms of generalization because the compositions of papermaking wastes from different sources vary considerably. The conclusions of this study are as follows: (1)

(2)

(3) (4)

According to the experimental results, the compressive strength showed a huge span of 14.5~73.7 MPa after curing for 28 days. When the BFS was partially substituted by the same proportion of wastes, the compressive strength decreased sequentially from the lime mud, paper sludge, bottom ash, and wood chips. The effect of the mixture of the lime mud and paper sludge on the compressive strength showed that for every 5% reduction in the proportion of lime mud, the strength decreased by nearly 2.5 MPa. From the stress-time curves, neither the lime mud nor the bottom ash contributed to the flexibility of the slurry. On the contrary, the paper sludge and wood chips significantly optimized the slurries. In order to strike a balance between the compressive strength and the flexibility proportion, 20% of the waste substitution should be preliminarily determined as the suitable proportion.

Considering the possibility of adding wood chips as decoration materials, 15% of wood chips and 5% of paper sludge are appropriate proportions in the mixture.

For the alkali-activated mixture of wastes and BFS, 6% of AE was the best ratio for the activator with the silicate modulus (Ms) fixed at 0.9.

Author Contributions: T.Y.: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing—original draft. S.-R.L.: Funding acquisition, Project administration, Supervision, Resources, Writing—review and editing. W.-Y.K.: Supervision, Resources, Writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding: This research was funded by Ministry of Education of Taiwan, grant number H108-AA09.

Data Availability Statement: https://www.researchgate.net/publication/364358812_data_for_Research_ on_Recycling_Various_Wastes_in_Papermaking_as_Eco-Friendly_Slurry (accessed on 18 September 2022).

Acknowledgments: We thank the CHP for materials provision, and NCKU C-Hub for space and instruments.

Conflicts of Interest: The authors declare no conflict of interest.

Nomenclature BFS SPW PWM AE Ms W/B wt.%

blast furnace slag the single-type papermaking wastes the paper waste mixture alkali equivalent silicate modulus water-binder ratio weight percentage

References 1.

2.

3.

4.

5.

Lombard, B. Cepi Preliminary Statistics Report 2021; Confederation of European Paper Industries: Brussels, Belgium, 2022; p. 2.

Available online: https://www.cepi.org/statistics/ (accessed on 23 February 2022).

Kilinc, M.B. Epicellulyse XT (Xerophilic Technology)-Paper Mill Sludge (Waste) to Energy & amp; Organic Fertilizer. Available online: https://sdgs.un.org/partnerships/epicellulyse-xt-xerophilic-technology-paper-mill-sludge-waste-energyorganic-fertilizer (accessed on 18 September 2022).

Suhr, M.; Klein, G.; Kourti, I.; Gonzalo, M.R.; Santonja, G.G.; Roudier, S.; Sancho, L.D. Best Available Techniques (Bat) Reference Document for the Production of Pulp, Paper and Board; Publications Office of the European Union: Luxembourg, 2015; Volume 906.

Monte, M.C.; Fuente, E.; Blanco, A.; Negro, C. Waste management from pulp and paper production in the European Union. Waste Manag. 2009, 29, 293–308. [CrossRef] [PubMed] Gavrilescu, D. Energy from biomass in pulp and paper mills. Environ. Eng. Manag. J. 2008, 7, 537–546. [CrossRef]

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Resour. Conserv. Recycl. 2018, 134, 48–60. [CrossRef] Kaur, R.; Tyagi, R.D.; Zhang, X. Review on pulp and paper activated sludge pretreatment, inhibitory effects and detoxification strategies for biovalorization. Environ. Res. 2020, 182, 109094. [CrossRef] [PubMed] Martins, F.M.; Martins, J.M.; Ferracin, L.C.; da Cunha, C.J. Mineral phases of green liquor dregs, slaker grits, lime mud and wood ash of a Kraft pulp and paper mill. J. Hazard. Mater. 2007, 147, 610–617. [CrossRef] de Azevedo, A.R.G.; Alexandre, J.; Pessanha, L.S.P.; Manhães, R.d.S.T.; de Brito, J.; Marvila, M.T. Characterizing the paper industry sludge for environmentally-safe disposal. Waste Manag. 2019, 95, 43–52. [CrossRef] Buruberri, L.H.; Seabra, M.P.; Labrincha, J.A. Preparation of clinker from paper pulp industry wastes. J. Hazard. Mater. 2015, 286, 252–260. [CrossRef] Singh, S.K.; Singh, A.; Singh, B.; Vashistha, P. Application of thermo-chemically activated lime sludge in production of sustainable low clinker cementitious binders. J. Clean. Prod. 2020, 264, 121570. [CrossRef] Ferreiro, S.; Frías, M.; Vigil de la Villa, R.; Sánchez de Rojas, M.I. The influence of thermal activation of art paper sludge on the technical properties of blended Portland cements. Cem. Concr. Compos. 2013, 37, 136–142. [CrossRef] Ukrainczyk, N.; Vrbos, N.; Koenders, E.A.B. Reuse of woody biomass ash waste in cementitious materials. Chem. Biochem. Eng. Q. 2016, 30, 137–148. [CrossRef] Yi, T.; Liou, S.-R.; Kuo, W.-Y. The Interaction Effects of the Parameters on Optimization Design in Paper Production Waste Usage on Alkali-Activated Slag with Taguchi Method. J. Renew. Mater. 2022, 10, 1753–1772. [CrossRef] Wyrzykowski, M.; Ghourchian, S.; Sinthupinyo, S.; Chitvoranund, N.; Chintana, T.; Lura, P. Internal curing of high performance mortars with bottom ash. Cem. Concr. Compos. 2016, 71, 1–9. [CrossRef] Wang, S.-D.; Scrivener, K.L.S. Hydration products of alkali activated slag cement. Cem. Concr. Res. 1995, 25, 561–571. [CrossRef] Xu, H.; Van Deventer, J.S.J. The geopolymerisation of alumino-silicate minerals. Int. J. Miner. Process. 2000, 59, 247–266. [CrossRef] Chen, J.-H. Silicon-Contained Waste as a Raw Material of Inorganic Polymers. Ph. D. Thesis, National Cheng Kung University, Tainan City, Taiwan, 2009.

Huang, K.; Fan, X.; Gan, M.; Ji, Z. Use of Municipal Solid Waste Incinerator (MSWI) Fly Ash in Alkali Activated Slag Cement. In Characterization of Minerals, Metals, and Materials 2019; Springer: Berlin/Heidelberg, Germany, 2019; pp. 401–410.

Gao, X.; Yuan, B.; Yu, Q.L.; Brouwers, H.J.H. Characterization and application of municipal solid waste incineration (MSWI) bottom ash and waste granite powder in alkali activated slag. J. Clean. Prod. 2017, 164, 410–419. [CrossRef] Kang, S.-P.; Kwon, S.-J.J.C.; Materials, B. Effects of red mud and alkali-activated slag cement on efflorescence in cement mortar.

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[CrossRef] Long, W.-J.; Tan, X.-W.; Xiao, B.-X.; Han, N.-X.; Xing, F. Effective use of ground waste expanded perlite as green supplementary cementitious material in eco-friendly alkali activated slag composites. J. Clean. Prod. 2019, 213, 406–414. [CrossRef] Choi, H.; Choi, Y.C. Setting characteristics of natural cellulose fiber reinforced cement composite. Constr. Build. Mater. 2021, 271, 121910. [CrossRef] Dai, X.; Aydin, S.; Yücel Yardimci, M.; Qiang, R.E.N.; Lesage, K.; De Schutter, G. Rheology, early-age hydration and microstructure of alkali-activated GGBFS-Fly ash-limestone mixtures. Cem. Concr. Compos. 2021, 124, 104244. [CrossRef] de Azevedo, A.R.G.; Alexandre, J.; Xavier, G.d.C.; Pedroti, L.G. Recycling paper industry effluent sludge for use in mortars: A sustainability perspective. J. Clean. Prod. 2018, 192, 335–346. [CrossRef] Saeli, M.; Senff, L.; Tobaldi, D.M.; Carvalheiras, J.; Seabra, M.P.; Labrincha, J.A. Unexplored alternative use of calcareous sludge from the paper-pulp industry in green geopolymer construction materials. Constr. Build. Mater. 2020, 246, 118457. [CrossRef] Silva, G.; Kim, S.; Bertolotti, B.; Nakamatsu, J.; Aguilar, R.J.C.; Materials, B. Optimization of a reinforced geopolymer composite using natural fibers and construction wastes. Constr. Build. Mater. 2020, 258, 119697. [CrossRef] Shi, C.; Roy, D.; Krivenko, P. Alkali-Activated Cements and Concretes; CRC Press: Boca Raton, FL, USA, 2003.

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Production of environmentally friendly and antibacterial MDF (Medium-density fiberboard) surfaces with green synthesized nano silvers ARIFE KÜBRA YONTAR1,3 SINEM ÇEVIK2,3 & SEYMA AKBAY4 The study involves modifying green nano silver particles (AgNP) synthesized from the extracts of Cannabis Sativa seeds onto Medium-Density Fiberboard (MDF) surfaces. Microstructural examinations and chemical analyses of the produced surfaces were performed with Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). A peak at 415nm was found in the UV–Vis spectrophotometer analysis range of the aqueous media containing green synthesized silver nanoparticles. The average size of AgNPs was found to be 45nm by particle size distribution analysis. Performance tests of the modified surfaces revealed that the abrasion and scratch resistance of the coating containing 1% AgNP increased twice and that all modified surfaces were resistant to staining. With nano silver modification, energy efficiency was achieved by shortening the gelation (drying) time of the surfaces coming out of the bath by one and a half minutes during coating production. Nano silver-modified MDF surfaces have shown antibacterial properties that are at least 1000 times more effective. MDF surface coatings modified with new-generation plant-based nanoparticles can prevent and reduce bacterial diseases that can be contaminated by the environment. The production of MDF surfaces that provide low energy consumption and antibacterial properties with green production will be possible.

Contact information: 1 Department Mechanical and Metal Technologies, Ondokuz Mayis University, 55300, Samsun, Turkey.

2 Department of Metallurgical and Materials Engineering, Ondokuz Mayis University, 55270, Samsun, Turkey.

3 Department of Nanoscience and Nanotechnology, Ondokuz Mayis University, Atakum 55139, Samsun, Turkey.

4 CAMSAN ORDU ĂGAÇ SANAY˙I˙I VE T˙IC. Inc., 52000, Ordu, Turkey.

Inorganic Chemistry Communications 159 (2024) 111865 https://doi.org/10.1016/j.inoche.2023.111865 Creative Commons Attribution 4.0 License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 13

Article 7 – Antibacterial MDF

Inorganic Chemistry Communications 159 (2024) 111865

Contents lists available at ScienceDirect

Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche

Short communication

Production of environmentally friendly and antibacterial MDF (Medium-density fiberboard) surfaces with green synthesized nano silvers Arife Kübra Yontar a, c, *, Sinem Çevik b, c, Şeyma Akbay d a

Department Mechanical and Metal Technologies, Ondokuz Mayis University, 55300, Samsun, Turkey Department of Metallurgical and Materials Engineering, Ondokuz Mayis University, 55270, Samsun, Turkey c Department of Nanoscience and Nanotechnology, Ondokuz Mayis University, Atakum 55139, Samsun, Turkey d CAMSAN ORDU AĞAÇ SANAYİİ VE TİC. Inc., 52000, Ordu, Turkey b

A R T I C L E I N F O

A B S T R A C T

Keywords: Green synthesis Nano silver Antibacterial MDF coating Mechanical strength

The study involves modifying green nano silver particles (AgNP) synthesized from the extracts of Cannabis Sativa seeds onto Medium-Density Fiberboard (MDF) surfaces. Microstructural examinations and chemical analyses of the produced surfaces were performed with Scanning Electron Microscope (SEM) and Energy Dispersive Spec­ troscopy (EDS). A peak at 415 nm was found in the UV–Vis spectrophotometer analysis range of the aqueous media containing green synthesized silver nanoparticles. The average size of AgNPs was found to be 45 nm by particle size distribution analysis. Performance tests of the modified surfaces revealed that the abrasion and scratch resistance of the coating containing 1 % AgNP increased twice and that all modified surfaces were resistant to staining. With nano silver modification, energy efficiency was achieved by shortening the gelation (drying) time of the surfaces coming out of the bath by one and a half minutes during coating production. Nano silver-modified MDF surfaces have shown antibacterial properties that are at least 1000 times more effective.

MDF surface coatings modified with new-generation plant-based nanoparticles can prevent and reduce bacterial diseases that can be contaminated by the environment. The production of MDF surfaces that provide low energy consumption and antibacterial properties with green production will be possible.

1. Introduction

moisture in the environment, it provides suitable conditions for bacterial growth [4,5]. MDFs are generally used as coated with polymers such as Polyvinyl chloride and melamine and special papers for aesthetic appearance and protection. In this way, moisture retention and disin­ tegration of the fibers are prevented, while their resistance to fire and chemicals is increased [6]. Unfortunately, until today, MDF surfaces did not provide antibacterial effects and were the source of many moldrelated diseases. Generally, people become ill with infectious diseases by coming into direct or indirect contact with pathogenic microorgan­ isms [7]. For this reason, minimizing the bacterial growth on the sur­ faces of MDF and similar products used in hospitals and food areas is of great importance for public health. In recent years, it has come to the fore to add antibacterial properties to the surfaces of these wood-based products. Various studies have been carried out on antibacterial MDF surfaces, but they are not sufficient [8–11]. The diversification of these studies and their preparation with natural ingredients that do not show toxic effects are critical for both the environment and human health.

Antibacterial properties for MDF and all other surfaces can be achieved

Infections and diseases, especially those of hospital origin, pose a worldwide health risk and cause serious deaths yearly [1]. A report in the Lancet noted that approximately 1.27 million deaths in 2019 were caused by AMR bacteria, which include six leading pathogens such as Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae, Acinetobacter baumannii, Klebsiella pneumonia, and Pseudomonas aeruginosa [2]. Current global pandemics have raised public awareness of developing new antimicrobial surfaces and coatings that can stop microbial contamination and prevent the spread of infection-causing bacteria [3]. Medium-density fiberboard (MDF) is widely used as a wood substrate in furniture and wood products due to its unique grain and texture, easy processing, lightweight and high strength. MDF products are frequently used in flooring, furniture and building mate­ rials, tables, counters, cutlery etc. and have a place in our daily lives in many areas, including hospitals and health institutions. MDF is very sensitive to rot and mold, and since it has a structure that can absorb * Corresponding author.

E-mail address: kubra.demirbas@omu.edu.tr (A. Kübra Yontar).

https://doi.org/10.1016/j.inoche.2023.111865 Received 26 October 2023; Received in revised form 23 November 2023; Accepted 9 December 2023 Available online 10 December 2023 1387-7003/© 2023 Elsevier B.V. All rights reserved.

A. Kübra Yontar et al.

Inorganic Chemistry Communications 159 (2024) 111865

Fig. 1. Production of silver nanoparticles by green synthesis method.

with metallic nanoparticles. Among the metallic nanoparticles, silver nanoparticles (AgNPs) have been widely used in antibacterial surface applications due to their antibacterial, antifungal, antioxidant, anticancer and anti-inflammatory effects [12,13]. However, due to the toxic chemicals and harmful reactions used in AgNP production, they become harmful to the environment and human health. Green synthesis, which has replaced the sol–gel method, sono chemical method, thermal decomposition method, pulsed laser deposition and pyrolysis process methods in recent years, provides the production of silver nanoparticles at low cost with a minimal toxic effect by using natural ingredients [14,15]. It is also known that green synthesized AgNPs have superior effects compared to those produced by other methods. They have also been proven to be potentially pathogenic antibacterial agents against a variety of Gram-positive and Gram-negative bacteria, including Salmo­ nella epidermidis, Streptococcus pyogens, Escherichia coli, Bacillus subtilis, Vibrio parahaemolyticus, Salmonella Typhimurium, Pseudo­ monas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae [16–18]. They owe all these impressive properties to plant extracts.

Many natural resources such as plants, fungi and algae can be used as initiators in green synthesis production [19,20]. Herbs are the most effective ones ever known. Flowers, leaves, stems, roots and bulbs of plants are used for green synthesis. They take part in the green synthesis reaction as starting agents by obtaining the extracts of the used part of the plants in water [21,22]. Flavonoids, carboxyl groups, beneficial acids, hydroxyl groups and all other secondary metabolites in plants reduce Ag+ ions in aqueous solution and provide AgNP synthesis and prevent agglomeration of these nanoparticles [23–25]. Silver nano­ particles synthesized using extracts of Cannabis Sativa seeds are known

to have small sizes and high antibacterial effects [21,23]. Silver nano­ particles synthesized using extracts of Cannabis Sativa seeds are known to have small sizes and high antibacterial effects. This is because Cannabis Sativa contains high levels of Cannabinoids, Terpenes, Organic Acids, Phenolic Compounds and Flavonoids [26–29].

In this current study, the curing time was improved and the anti­ bacterial effect was achieved by modifying green synthesized AgNPs with extracts of Cannabis sativa seeds on MDF surfaces. MDF surfaces, which are produced at high rates in the wood industry and used in many places in daily life, have been made resistant to bacteria. In this way, it is aimed to reduce diseases caused by mold and bacteria and improve the quality of human life. In addition, the fact that the raw materials used for the production of nanoparticles are natural will ensure that the anti­ bacterial MDF surfaces produced are environmentally and climate friendly.

2. Experimental methods and materials 2.1. Materials Silver nanoparticles were synthesized using plant extracts and silver nitrate (AgNO3). Silver nitrate (AgNO3) salt (99 %) was purchased from Sigma Aldrich. Cannabis sativa seeds were obtained from the local market. Melamine and UC 205 coded BLACK colored papers used in the surface coating of MDFs were specially supplied by ÇAMSAN A.Ş. The materials used in all other MDF surface coating processes and the MDF itself are company-specific materials that ÇAMSAN A.Ş. provides for its own production. This coating solution consists of melamine glue, 2

A. Kübra Yontar et al.

Inorganic Chemistry Communications 159 (2024) 111865

Fig. 2. MDF coating manufacturing process with AgNP modification.

hardener, wetting agent, release agent, and antiblocanticust chemicals.

The proportion of melamine glue varies between 99 and 100 %.

passing the solution through filter paper. As shown in Fig. 1, when the color of the water changed from clear to light brown, it was understood that the seed extracts were released into the water. In order to compare the antibacterial, mechanical and other performance properties with nano silver modification on MDF surfaces, silver solutions were used at the rates of 1,3 and 5 % by weight on the surfaces to be coated. The green synthesis method was used to prepare individual nano silver solutions at these ratios. Basically, silver nitrate solution is prepared first for green synthesis. These nano silver solutions, which will be added to the coating solution, which will be 40 mL in total, were prepared with 7 mL of distilled water. While preparing nano silver solutions, 0.4 g for 1 %, 1.2 g for 3 % and 2 g for 5 % silver nitrate were used. Silver nitrates were added to 7 mL of pure water in separate beakers and mixed for 15 min in a magnetic stirrer to ensure complete dissolution. After adding 3 mL of Cannabis Sativa seeds extracts into silver nitrate solutions, stirring continued for 10 min. When the reaction solution turned from light yellow to dark gray, the synthesis process was complete and mixing was stopped. Thus, as shown in Fig. 1, silver nanoparticles were synthesized with plant extracts.

2.2. Green synthesis of silver nanoparticles Cannabis Sativa seeds contain carboxylic acids, oleic acid, antioxi­ dants, terpenoids, flavonoids, alkaloids and canniprene [30,31]. These biomolecules found in plants are called secondary metabolites and generally act as both reductants and stabilizers in the green synthesis and nanoparticle production mechanism. Hydroxyl groups (OH) found in plant biomolecules such as amino acids, alkaloids, proteins, poly­ phenols, flavonoids, enzymes, tannins, carbohydrates and saponins provide the stabilization and reduction of silver ions (Ag+) to Ag0.

Further reduction to Ag + leads to the formation of silver nuclei, resulting in the synthesis of AgNPs. Ag+ ions as OH groups bind to the carbon atoms of aromatic rings of plants, which is the mechanism that enables the reduction of Ag+ into nanoparticles [33–35]. The first step required for green synthesis of nanosilver is the preparation of the plant extract. First, Cannabis Sativa seeds were crushed in a mortar until they reached an average size of 500 μm. Then the seed pieces were thrown into 200 mL of distilled water. Water was preferred in obtaining the extract of Cannabis Sativa seeds. Because, by using water and heat together, results as effective as alcohol extraction can be achieved. With temperature, the components and oils found in plants can rapidly diffuse into water. As a greener and more economical method, the use of water in the preparation of plant extracts is highly preferred [36–38]. After heating at 90˚C for 20 min, the water containing the seeds was kept at room temperature for 12 h. Finally, the plant extracts were obtained by

2.3. Production of antibacterial MDFs An antibacterial effective product was produced with silver nano­ particle modification on MDF surfaces. In the MDF surface coating process, the production stages of which are shown in Fig. 2, the first step was the modification of AgNPs into melamine. A solution of 10 mL of green synthesized nanosilver particles was added to 30 mL of melamine and mixed for 10 min until it became homogeneous. Then, after pouring 3

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Inorganic Chemistry Communications 159 (2024) 111865

Fig. 3. Results of characterization analyzes, (A) UV–Vis spectrophotometer, (B) Particle Size Measurement, and (C) X-Ray Diffraction Analysis.

the melamine mixture into a glass container, A4 size MDF coating papers were slowly placed in the bath. The solution was distributed over the entire surface with the help of a brush so that the paper could absorb the solution homogeneously. After the paper had absorbed all the solution, it was placed in the second bath. In the second bath, a chemical solution consisting of binders and hardeners of ÇAMSAN company’s own recipe was used. After the second bath, the papers were placed on the MDF surfaces and compressed at 190 ◦ C in a hot press. The MDFs were dried to ensure that the paper and all components adhere to the surface completely. After the drying process, the final antibacterial effective MDF product was created. A total of 4 MDF samples were produced together with the control sample named R. Sample A is 1 %, sample B is 3 % and sample C is 5 % nano silver modified surfaces.

deviation. The wavelength range for Ag-NPs is 300 to 700 nm, and this was detected by UV–Vis spectrophotometer analysis performed 48 h after biosynthesis (Perkin Elmer, Lambda 25). In the range of 10◦ ≤ 2θ ≥ 80◦ at room temperature, XRD was performed at a rate of 2◦ /min using a Rigaku Smart Lab CuKα radiation monochromatic filter. XRD analyses of silver and plant extract added films and only plant added films were carried out separately and the presence and crystallite sizes of silver nanoparticles were investigated. Debye-Scherer’s equation(1) was used to calculate the crystallite size and microstrain of silver nanoparticles.

Debye-Scherer’s equation is; D = Kλ/βcosθ

(2)

where D is the Crystallites size (nm), λ the X-ray wavelength (k = 0.1541 nm), K the so-called shape or geometry factor which usually takes a value of about 0.9 (Scherer constant), β the full width at half maximum (FWHM) of diffraction peak and ‘‘θ’’ the diffraction angle. MDF surface microstructure and EDS chemical mapping were examined using an 80 mm2 X-MAX detector and an EDS attachment on a JEOL 7001F Field Emission (FE) Scanning Electron Microscope (SEM).

2.4. Characterizations Particle size measurement analysis was performed to calculate the average sizes of nano silvers produced by green synthesis with Master­ sizer 3000 laser technology (ISO-13320). By adjusting the particle size distribution histogram to the log-normal distribution function, the average particle size for silver nanoparticles has been calculated which is represented as in Eq(1) [32]; ( ) D ( ) ln2 D0 1 f (D) = ] (1) exp[− 2σ 2 √2πσD

2.5. Performance tests MDF is the process of coating the surface of the boards under high pressure and heat by impregnating and drying decorative papers in glued baths. They are available in various thicknesses and features and are often used in areas such as furniture, interior design, countertops, floor coverings, wall panels. The key features of HPL are: resistance to

where D corresponds to average particle size and σD is the standard 4

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Inorganic Chemistry Communications 159 (2024) 111865

Fig. 4. SEM images of all nanosilver modified and non-modified MDF samples.

physical abrasion, scratching and impact, variety of finishes, and resis­ tance to stains and chemicals. All performance tests were carried out in accordance with TSE EN 438–2 standard. This standard is used to evaluate the performance of coating materials and to determine the compliance of products with quality standards. In this way, it is aimed to offer reliable and quality coating materials to consumers. Three per­ formance tests were performed for antibacterial MDF surfaces modified with AgNP. The first of these is the stain resistance test. The stain tests of MDF products used in living areas were carried out by dripping the substances that are used extensively in daily life and cause stains. Sub­ stances are cleaned from the surface by washing after being kept on the surface for one day in contact with oxygen and in environments where

contact with oxygen is cut off. It is checked whether there is any trace, swelling, color change on the surface. The substances used in the test and leaving significant stains are as follows; acetone, vinegar, hydrogen peroxide, trioxidant, coffee and bleach. The second test is the wear resistance measurement. For the wear test, a 50 x 50 mm MDF sample is cut. Abrasion test is done by rotating the test specimen with cylindrical wheels covered with sandpaper and applied load. The wheels cause an annular wear on the surface of the sample. The test is continued until there is a certain amount of wear and the results are given over the number of revolutions. The first wear point occurs when the pattern in the sample is clearly visible or a solid color appears so that 3/4 of the substrate is visible. When approximately 95 % wear occurs on 5

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Inorganic Chemistry Communications 159 (2024) 111865

Fig. 5. EDS mapping results of nanosilver modified and non-modified MDF surfaces.

patterned/unpatterned MDF, the number of revolutions at the last wear point is recorded. The third test was the scratch resistance test. For the scratch test, a 50 x 50 mm MDF sample is cut and placed in the test device. The scratch tip of this tester is diamond and double scratches are created starting from 1 N force up to 2, 4, 6 N. Each double scratch is adjusted to 1–2 mm between itself, and 3–5 mm between double scratches. The test is continued until the maximum load value required to produce a continuous surface scratch is determined. In addition, the gelation times of polymeric adhesives used in the production of surface coatings with nano silver reinforcement in 3 different ratios were also calculated. This is the time required for the solution to cure after being absorbed into the paper and hot pressed. Gelling time covers a large part of the time spent on total production. Therefore, by shortening this period, time and energy savings can be achieved in production.

2.6. Antibacterial activity AgNPs and modified MDF surfaces with plant extracts were tested for their antibacterial activities using a version of the Japanese Industrial Standard JIS Z 2801. Staphylococcus aureus (NCTC-13552) and Escherichia coli (ATCC 25922) bacteria had been grown at a concen­ tration of 5 x 105 CFU/mL, and 1 x 1 cm test samples were inserted within. As a control, a culture with 5 x 105 CFU/mL that was created without a sample was employed. Samples were shaken in Eppendorf tubes for 4 h at 100 rpm. The sample was vortexed after spending 30 s in an ultrasonic water bath to separate the bacteria that were sticking to the surface. Transferring 100 L of suspension into 900 L of physiological saline (FTS) served as the dilution process. Plate Count Agar (PCA)-filled petri plates were split into eight equal portions, and 25 μL of each dilution was seeded. Three duplicates of each experiment were per­ formed. The antibacterial activity value of colony-forming units (CFU) 6

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was measured after incubation for 24 h at 37 ◦ C. The growth difference between the culture treated with coated filters and the positive control was assessed logarithmically and documented.

Table 1 Stain resistance of nanosilver modified MDF coatings.

3. Results and discussion

AgNP Modified MDF Samples

Stain resistance

1%

Outdoor (in contact with oxygen) Vinegar (Suitable) Acetone (Suitable) Coffee (Suitable) Bleach (Suitable) H2O2 Suitable (Slight discoloration) Vinegar (Suitable) Acetone (Suitable) Coffee (Suitable) Bleach (Suitable) H2O2Suitable (Slight discoloration) Vinegar (Suitable) (Light Stain) Acetone (Suitable) Bleach (Suitable) Coffee (Suitable) H2O2 (Suitable)

3.1. Characterizations of silver nanoparticles UV–Vis spectroscopy has been utilized to clarify the optical proper­ ties and demonstrate the generation of AgNPs after green synthesis.

Fig. 3 (A) demonstrates that the most intense wavelength for silver nanoparticles is around 415 nm, 72 h after green synthesize. The peak observed in the UV–Visible spectrum is strongly affected by the size, shape, and morphology of the created AgNP. Earlier studies has shown that the visible zone of spherical-shaped AgNP fluctuates in wavelength with amplitude from 400 to 470 nm under UV–Visible spectroscopy [39–44]. The varying sizes and shapes of AgNP cause a wide range of absorption bands to appear. Average sizes and standard derivation values of silver nanoparticles produced by green synthesis are shown in the graph given in Fig. 3 (B). The average nanoparticle size and standard deviation were found to be 45 nm and 1.59 nm, respectively. UV–Vis spectroscopy and particle size measurement analyzes revealed that nano silver particles could be successfully synthesized in small sizes.

3%

5%

Closed to external environment (no contact with oxygen) Vinegar (Suitable) Acetone (Suitable) Coffee (Suitable) Bleach (Suitable) H2O3 (Suitable) Vinegar (Suitable) Acetone (Suitable) Coffee (Suitable) Bleach (Suitable) (Light Stain) H2O3 (Suitable) Vinegar (Suitable) Acetone (Suitable) Bleach (Suitable) Coffee (Suitable) H2O3 (Suitable)

Table 2 Wear, scratch resistance and curing times of nanosilver modified MDF surface coatings.

3.2. X-ray diffraction analysis of MDF surfaces Crystal phases, nature and average crystal size values of MDF coating surfaces were measured and calculated by XRD analysis. In particular, XRD revealed the crystal structure of AgNP synthesized with Cannabis Sativa seed extracts and polymeric coating material in Fig. 3. XRD pattern of MDF surfaces revealed the sharp diffraction peaks at 30.68◦ , 36◦ , 43.62◦ , and 63.18◦ , indexed as (2 2 0), (3 1 1), (2 0 0) and, (2 2 0) Bragg’s reflection planes. These peaks correspond to FCC lattice struc­ ture and crystalline nature as indexed in JCPDS-04–0783 [45,46]. This crystal structure of our AgNPs parallels the XRD pattern of silver nanoparticles synthesized from plant extract in similar studies [47–52].

The unassigned peaks were considered to have formed because of the crystallization of other organic compounds in the Cannabis Sativa seeds extract. The wide-ranging main crystal peaks appearing at 23◦ are pre­ dicted to arise mainly from the coating resin and added cross-linkers, and these peaks have also been revealed in similar studies [53–55].

Debye-Scherrer formula (1) was used to calculate the crystallite size on MDF surfaces containing synthesized green AgNPs. Calculation of crystallite size of all samples was based on the four strongest peaks observed in the XRD pattern. The crystallite size was found to be 12.26, 9.58 and 6.13 nm for samples A, B and C, respectively. Crystallite size is known to belong to a consistently diffracted area and does not have the same meaning as particle size [56,57]. The lowest crystallite sizes in sample C, which contains the highest amount of AgNP, are due to nanoparticles. It was calculated that the crystallite size decreased with increasing AgNP content. The addition of AgNP suppresses the growth of polymer particles in the melamine resin present in the MDF coating.

Thus, it creates a retarding effect that reduces the crystallite size.

Moreover, reducing the crystallite size leads to an increase in the surface area, which improves the antibacterial effect. The higher polymer ratio in the coating content causes the polymer grains and crystals to grow rapidly upon cooling and the crystallite sizes to increase [58–61].

Agnps Modified Samples (%) %1

Abrasion Resistance (İp + Fp)/2 (>150)

Scratch Resistance (>1.75 N)

Cycle

N

275

3

Gel Time (Curing Time)

1st Bath Melamine, Formaldehyde Glue And Hardener Control Sample: 3 Minutes 42 Seconds Agnps Modified: 3 Minutes 32 Seconds

%3

250

3

Control Sample: 3 Minutes 40 Seconds Agnps Modified: 3 Minutes 33 Seconds

%5

165

3

Control Sample: 3 Minutes 43 Seconds Agnps Modified: 3 Minutes

2nd Bath

Control Sample: 3 Minutes 16 Seconds Agnps Modified: 1 Minute 53 Seconds Control Sample: 3 Minutes 18 Seconds Agnps Modified: 1 Minute 40 Seconds Control Sample: 3 Minutes 15 Seconds Agnps Modified: 1 Minute 20 Seconds

edge section of the MDF sample. The layer on the top layer is the coating consisting of paper, resin and nanosilver particles applied to the MDF surface. EDS analysis was performed to determine the coating content and nanosilver presence on the coating surfaces. Fig. 5 shows the results of the EDS mapping analyses. Fig. 5 (R) shows the EDS mapping of the uncoated MDF surface, and Fig. 5 (A), (B), and (C) of the AgNP modified coating surfaces. The elements present on the surfaces are shown sepa­ rately for the regions they are found in the mapping results with different colors. EDS results of the sample without coating revealed that

3.3. Microstructural characterzation of MDF surfaces SEM analysis was performed to examine the nanosilver distribution on the coating surfaces. Fig. 4 shows the microstructure images of the MDF sample without any coating and the MDF coating surfaces modified with nanosilver. Fig. 4 (R) shows the surface of an uncoated MDF sample. Fig. 4 (A), (B) and (C) show the microstructures of the coating surfaces containing 1 %, 3 % and 5 % nanosilver. Fig. 4 (D) shows the 7

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Inorganic Chemistry Communications 159 (2024) 111865

Fig. 6. MDF surface images after performance tests, (A) MDF surface before tests, (B) application of stain resistance tests, (C) surface after stain resistance tests, (D) surfaces after wear test and, (E) furfaces after scratch test.

it contained C, O, Ca and K elements coming from the structure of the wood and binders used in MDF production. It is known that the Pd element comes from the coating applied to the sample to provide con­ ductivity for SEM imaging. In addition, it can be seen from the SEM image that the R sample does not contain nano silver and melamine resin added coating. In Fig. 4 (A), (B) and (C) images, the coating surface applied to the MDF surface under high temperature pressure and the nano silver particles dispersed on the surface are clearly visible. It is shown in Fig. 5 (A), (B) and (C) EDS results that the added nano silver particles are distributed homogeneously on all MDF surfaces. It is esti­ mated that the N, Fe, Si, Al and Ti elements appearing in the EDS mapping results come from the melamine resin coating content and the plants used in nano silver synthesis [62,63]. The image of the MDF coating layer in Fig. 4 (D) shows that the total veneer thickness is 1 mm.

This layer is the layer containing paper, melamine and nano silver.

been tested and Table 1 shows their status against each contaminant.

Whether the contaminants are suitable for the stains they leave on the surface or whether they are stained is also recorded. Fig. 6 (A) shows the coating surfaces before the staining test. In Fig. 6 (B), the application of the staining tests is shown, and in Fig. 6 (C), the surfaces are shown separately for each pollutant after the staining test. The slightly light gray areas visible on all post-test surfaces are not due to staining, but due to the reflection of light from rough surfaces with the nano silver ad­ ditive. After the staining test, it was determined that the nano silver treated surfaces were only slightly sensitive to hydrogen peroxide, bleach and vinegar. These staining amounts are at negligible levels. This result proved that nano silver reinforcement does not reduce the resis­ tance of the coating against different pollutants and chemicals. In order to examine the effects of nanosilver on the mechanical strength of MDF coating surfaces, abrasion and scratch tests were carried out and the results are shown in Table 2. According to TSE EN 438–2 standards, the control values are 150 cycles for wear resistance and 1.75 N for scratch resistance. Performance test results were compared according to these values. It has been determined that silver nanoparticle reinforcement increases the mechanical strength of all MDF coating surfaces above their standard values. However, sample A with 1 % AgNP added showed the highest wear resistance with 275 cycles. It has a wear resistance almost twice the standard value. As the nanoparticle ratio increased,

3.4. Performance tests The results of performance tests of silver nanoparticle treated and non-treated MDF surfaces are shown in Tables 1 and 2. Staining resis­ tance tests were carried out both in an open air environment with ox­ ygen and in a vacuum environment with no contact with oxygen. The resistance of the surfaces to staining with different contaminants has 8

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Fig. 7. Growth of bacterial colonies images, (A) %1 AgNPs modified MDF surface, (B) %3 AgNPs modified MDF surface, and (C) %5 AgNPs modified MDF surface and (D) antibacterial effect comparisons in logarithmic growth difference (CFU. mL− 1) graph.

wear resistance decreased. It is thought that this may be due to increased nanoparticle agglomeration and the melamine coating showing higher slip behavior in some regions. It is possible that nanoparticles cannot bond sufficiently with melamine, which may increase the amount of wear on the surface. Scratch resistance was found to be 3 N in all sam­ ples. In other words, a strength approximately twice the standard value was achieved. The curing times of the coating solutions prepared with nanosilver reinforcement were determined for each ratio. Table 2 shows the curing times of the control and AgNP modified samples after both baths. In the production of coatings, two different baths containing melamine mixture are prepared to ensure that the papers adhere to the surface and to improve the surfaces both aesthetically and mechanically.

The time it takes for the polymeric gel layer of the binder mixture on the surfaces immersed in the baths to dry is called gelation time. These gelation times were calculated for each nanoparticle doping ratio. With

the nano silver particle additive, the curing time after the second bath was shortened by 1 min. Moreover, by increasing the nano silver rate, the time could be shortened by 30 s. In this way, the time spent in production can be shortened and the daily production amount can be increased by applying more MDF surface coatings. Shortening the gelation time was achieved by reducing the amount of water by filling the gaps in the polymeric coating of nano silver particles. As the amount of water that had to evaporate during drying decreased, gelation occurred faster.

3.5. Antibacterial activity of MDF surfaces Fig. 7 (A), (B) and (C) shows the growth amounts of Staphylococcus aureus and Escherichia coli bacteria colonies on agar on nanosilveradded MDF coating surfaces. The lowest growth rate was obtained in

Table 3 Antibacterial effect comparisons in logarithmic growth difference (CFU. mL− 1).

Bacteria

Control

A Sample Concentration after incubation (CFU. mL− 1)

Log10 – reduction

B Sample Concentration after incubation (CFU. mL− 1)

Log10 – reduction

C Sample Concentration after incubation (CFU. mL− 1)

Log10 – reduction

E. coli

5± 0,5x107 5 ± 0,2 × 107

5,0 ± 0,2 × 104

4,09

4,2 ± 0,2 × 101

5,29

1,2 ± 0,2 × 101

6,69

4,0 ± 0,2 × 103

3

6,1 ± 0,5 × 101

3,69

8,1 ± 0,5 × 101

4,79

S.

aureus

9

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sample C with 5 % AgNP-doped coating surface. As the amount of nanosilver increased, bacterial growth decreased at a higher rate. With the values given in Fig. 7(D) and Table 3, it has been proven that nano silver additive has an antibacterial effect of at least 1000 times on MDF surfaces. Green synthesized nano silver modification even at a rate of 1 % in MDF coatings can provide a high antibacterial effect to all wood products used in daily life. The effective antibacterial activity mecha­ nism of AgNPs is explained by destroying cell membranes, causing intracellular damage, altering genetic material, and causing oxidative stress in the bacterial cell. With their small size, nanoparticles have a large surface area that allows them to adhere to the cell wall, penetrate the cell, and cause bacterial death by causing a deterioration in mem­ brane permeability and leakage of cell contents. Silver ions released from AgNPs into surfaces, tissues, and environments serve as a reservoir for antimicrobial activity [64–66]. Another predicted mechanism is that the ability of silver nanoparticles to adhere to the bacterial cell wall is due to the electrostatic interaction between positively charged silver ions and the negatively charged surface of the cell membrane. Due to these electrostatic attractions, silver nanoparticles can cross the cell membrane and change its molecular composition and permeability. This causes the bacterial cell contents to disperse and the membrane to rupture [67]. It has also been proven by previous studies that AgNPs are more effective against Gram-negative bacteria (Escherichia coli) than Gram-positive bacteria (Staphylococcus aureus). This effect is thought to be due to changes in the membrane structures of different bacterial pathogens. Positively charged nanosilver is likely to have a higher electrostatic interaction with the negatively charged E.coli bacterial wall and therefore has a higher effect, ensuring bacterial growth and death [68]. The fact that the cell wall of E.coli bacteria is thinner than the wall of S.aureus bacteria explains the higher effectiveness of AgNPs [69]. Nano silvers synthesized with the extract of Cannabis Sativa seeds showed 1.5 times higher effectiveness against E.coli bacteria than S. aurues bacteria, and this effect has also been demonstrated in other studies [70–74]. Nano silvers synthesized with the extract of Cannabis Sativa seeds have lower toxicity, while on the other hand, they show a higher antibacterial effect with the components coming from the essence. Thus, MDF surfaces with both natural content and antibacterial effect could be produced. Nano silvers synthesized with the extract of Cannabis Sativa seeds have lower toxicity [75], while on the other hand, they show a higher antibacterial effect with the components coming from the extract [76–79]. Thus, MDF surfaces with both natural content and antibacterial effect could be produced.

Funding The Unit of Scientific Research Projects, Ondokuz Mayıs University funded this study with the following project codes PYO. MUH.1908.21.001. The production of MDF surfaces and the perfor­ mance tests of the surfaces were carried out in CAMSAN ORDU AĞAÇ SANAYİİ VE TİC. Inc./Turkey.

CRediT authorship contribution statement Arife Kübra Yontar: Conceptualization, Methodology, Data cura­ tion, Investigation, Writing – original draft. Sinem Çevik: Conceptual­ ization, Funding acquisition, Investigation, Project administration, Resources, Supervision, Writing – review & editing. Şeyma Akbay: Data curation, Formal analysis, Investigation, Resources, Visualization.

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability Data will be made available on request.

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4. Conclusions The aim of the study was to produce MDF surface coatings with improved mechanical strength, gelation time and high antibacterial ef­ fect. Moreover, the aim was to create MDF surfaces with clean content by providing these effects with nano silver particles naturally synthe­ sized with plant extracts. In the study, by modifying nano silvers syn­ thesized with Cannabis Sativa seed extracts into MDF surface coatings, products with 2 times higher abrasion and scratch resistance than standard surfaces, resistant to staining and high antibacterial effect were created. With green synthesized nano silver, productivity is increased by shortening the waiting time during production and the curing period that causes time loss. All tests revealed that the 1 % AgNP added MDF surface had both high mechanical strength and high antibacterial ef­ fects. As a result, it has been proven that MDF surfaces with superior properties can be produced with 1 % green synthesized nano silver ad­ ditive. With this study, a new way has been developed for the production of low energy consumption, environmentally friendly and multifunc­ tional MDF surfaces. Also, it will provide antibacterial production of wooden surfaces used in daily life in hospitals, homes, offices and all health institutions. In this way, it will be possible to reduce and elimi­ nate various diseases transmitted from the environment.

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12

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Barrier, converting, and tray-forming properties of paperboard packaging materials coated with waterborne dispersions ANDREA MARINELLI1, JOHANNA LYYTIKÄINEN2, PANU TANNINEN2, BARBARA DEL CURTO1 & VILLE LEMINEN2 In this work, different food-contact experimental and commercial aqueous polymeric dispersions were applied to paperboard via rod coating technology to achieve <5% non-cellulosic content. Barrier (water, moisture and grease), mechanical (tensile and bending) and converting (heat-sealing and creasing) properties were analysed before tray formation trials on pilot-scale equipment. Dispersion-coated samples were compared against polyethylene terephthalate (PET) extrusion-coated paperboard, the principal industrial material used for food trays. Results show that, within the investigated properties, waterborne dispersions can achieve similar barrier properties compared with PET, yet at lower dry coat grammage (12 g/m2 vs. 40 g/m2 of PET-coated paperboard). Additionally, the investigated coatings heat-sealed at temperatures as low as 80–90°C, almost 100°C less than PET; however, lower seal forces could be achieved (15–20 N/(25 mm) vs. 23 N/(25 mm) of PET-coated paperboard). Paperboard delamination occurred at the highest seal forces. Dispersion-coated trays were obtained at 4.5–5.0% blank moisture content. Formed trays at industrial processing parameters showed critical coating damage during converting due to tensile stresses. This work shows that milder processing conditions allow a reduction in coat defects.

Contact Details: 1 Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy.

2 Lappeenranta-Lahti University of Technology LUT, Lappeenranta, Finland.

Packag Technol Sci. 2024;37:149–165. https://onlinelibrary.wiley.com/doi/full/10.1002/pts.2784 This work is licensed under the Creative Commons Attribution License

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 18

Article 8 – Barrier Coating and Tray Forming

Received: 12 September 2023

Revised: 7 November 2023

Accepted: 13 November 2023

DOI: 10.1002/pts.2784

RESEARCH ARTICLE

Barrier, converting, and tray-forming properties of paperboard packaging materials coated with waterborne dispersions Andrea Marinelli 1 Barbara Del Curto

Johanna Lyytikäinen 2

| 1

|

Ville Leminen

|

Panu Tanninen 2

|

2

1

Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milan, Italy

Abstract In this work, different food-contact experimental and commercial aqueous polymeric

2

Lappeenranta-Lahti University of Technology LUT, Lappeenranta, Finland

dispersions were applied to paperboard via rod coating technology to achieve <5% non-cellulosic content. Barrier (water, moisture and grease), mechanical (tensile and

Correspondence Andrea Marinelli, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan 20131, Italy.

Email: andrea.marinelli@polimi.it

bending) and converting (heat-sealing and creasing) properties were analysed before tray formation trials on pilot-scale equipment. Dispersion-coated samples were compared against polyethylene terephthalate (PET) extrusion-coated paperboard, the principal industrial material used for food trays. Results show that, within the investigated properties, waterborne dispersions can achieve similar barrier properties compared with PET, yet at lower dry coat grammage (12 g/m2 vs. 40 g/m2 of PET-coated paperboard). Additionally, the investigated coatings heat-sealed at temperatures as low as 80–90 C, almost 100 C less than PET; however, lower seal forces could be achieved (15–20 N/(25 mm) vs. 23 N/(25 mm) of PET-coated paperboard). Paperboard delamination occurred at the highest seal forces. Dispersion-coated trays were obtained at 4.5–5.0% blank moisture content. Formed trays at industrial processing parameters showed critical coating damage during converting due to tensile stresses.

This work shows that milder processing conditions allow a reduction in coat defects.

KEYWORDS

aqueous dispersions, barrier properties, coating, converting, food packaging, mechanical properties, paperboard trays

1

|

recycling yields2,3. Indeed, previous studies4–6 reported how DCs can

I N T RO DU CT I O N

be recycled, showing lower reject fractions. However, it was only Dispersion coating (DC) is an interesting technology that, despite

recently that testing methodologies were standardized or developed

being known for some decades, has only recently gained increased

for a European harmonization7,8; besides, such recycling methodolo-

interest from the industry. Most of the commercialized coated

gies are constantly adapting to address issues linked to the new pack-

fibre-based packaging is extrusion-coated or laminated. Only a few

aging sold on the market. By potentially avoiding slot screening during

1

products are currently dispersion-coated . One advantage of the DC

recycling, thin coating and filler fragments might reach the secondary

technology is that it can achieve a lower final dry coat grammage

raw material (i.e., recycled material) or add up in the water circuits at

compared with extrusion coating and lamination, reducing the non-

the paper mill9. Related to microplastics, this potential issue is

cellulosic content of the packaging. This might lead to higher fibre

currently under discussion, possibly hindering the application of

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2023 The Authors. Packaging Technology and Science published by John Wiley & Sons Ltd. Packag Technol Sci. 2024;37:149–165.

wileyonlinelibrary.com/journal/pts

149

MARINELLI ET AL.

numerous coatings that are brittle, fragment in tiny particles during

dispersion coat grammages representing less than 5% of the total

repulping, and detach from fibres.

packaging weight, that is, maximum non-cellulosic content that might 10–12

inside coating formula-

constitute an insignificant part of the packaging unit, hence possibly

tions and different latex polymeric nature, generally based on styrene-

considered as monomaterial by EU member countries40. Therefore, the

Previous studies focused on fillers

10–14

butadiene and styrene acrylates latexes

. Recent research focused

on biobased polymers15–19; still, in many cases, they feature lower

aim is to assess if and in which cases the use of lightweight DCs (<5% w/w non-cellulosic content) might substitute PET-coated substrates.

barrier properties as against synthetic counterparts, higher cost, and are challenging to scale up in their production process for an industrial technology transfer20,21.

2

M A T E R I A L S A N D M ET H O D S

|

Nowadays, there are many commercially available aqueous dispersion grades, some of which were already applied and tested on

2.1

Materials

|

paper substrates22. Most grades are based on synthetic latexes because of higher industrial availability and easier production pro-

2.1.1

|

Substrate

cesses, though academic and industry efforts to shift to bio-based counterparts must be acknowledged15,16,23.

StoraEnso (Helsinki, Finland) Trayforma 350 g/m2 paperboard

Besides a complete barrier properties characterization, the pro-

(UC) (average measured grammage was 348.5 g/m2) was used as the

cessing of fibre-based substrates might affect coating integrity, hence

basis substrate. UC is a three-layer 457 ± 4 μm thick bleached sul-

the final packaging performance24–27. Therefore, the evaluation of

phate pulp paperboard, featuring chemithermomechanical pulp in the

processing effects on the barrier properties, and the actual process-

middle layer. All the layers are Alkyl Ketene Dimer (AKD) sized. Sizing

ability of such coatings is of extreme interest.

improves the hydrophobic behaviour of the substrate.

Creasing is a method that creates a groove in the processed mate-

Moreover, StoraEnso (Helsinki, Finland) Trayforma PET 40

rial. It aims to locally decrease bending stiffness to generate preferential

extrusion-coated substrate (grammage: 350 + 40 g/m2, UC + PET,

folding lines28(p916). Different methods were reported to obtain creases,

respectively) (PET) was tested as reference commercial material,

both in the flatbed die-cutting process29,30 – commonly used in large-

representing the commonest material used at an industrial scale to

scale production – and with creasing wheels mounted on sample

produce, for example, paperboard trays. The paperboard substrate of

makers30–32 to study, for example, both creasing patterns and crease

Trayforma PET 40 is UC.

orientation. Additionally, previous studies discussed the effect of crease rule and groove width on the processed material's thickness29,32.

Heat-sealing, in contrast, is aimed at bonding two surfaces thanks to the action of temperature, pressure and time. Previous literature

2.1.2 | Experimental aqueous dispersions formulation

focused on both flexible33,34 and rigid35 packaging. Different seal bar geometries can be used, especially for flexible packaging, whereas rigid

Two experimental formulations were produced at a lab scale involving

packaging commonly adopts a flat bar. A successful heat seal is

HPH 39 highly crosslinked carboxylated styrene-butadiene latex

required to ensure spill-proof packaging as well as sufficient adhesion

(Tg ffi 0 C, dry solid content 54%) as binder – which was kindly pro-

to ensure unintentional package opening. Aqueous dispersions provide

vided by Trinseo (Horgen, Switzerland) – and CamCoat 80 kaolin

inferior heat-seal strength compared with laminated counterparts36.

(63% of the particles <2 μm in size) from Amberger Kaolinwerke

Multiple converting properties might be involved in a single forming

(Hirschau, Germany) as filler:

process like paperboard 3D forming (referred to as drawing) to achieve a final packaging structure, for example, trays. Former studies explored

• H39K 80, containing 80:20 latex: pigment ratio – dry weight ratio;

several parameters affecting output quality, including packaging geome-

• H39K 60, containing 60:40 latex: pigment ratio – dry weight ratio.

try, substrate moisture content, blank holding force, creasing depth and creasing width31,35,37–39. In summary, multiple process parameters must

Coating preparation followed the procedure described in previous

be finely tuned to guarantee that both the substrate and the coating

publications22,24. PCC Exol SA (Brzeg Dolny, Poland) kindly provided

layer do not crack; this would allow for a material-coating configuration

Exolat C40 sodium polyacrylate, used as a dispersant (0.16% dry

that might compete under both economic and environmental perspec-

weight on dry pigment weight). NaOH 1 M was used to adjust the pH

tives against polymeric packaging counterparts, as well as against fibre-

level to 8. At first, a water-based kaolin slurry was produced by adding

based solutions with higher non-cellulosic content.

kaolin powder, dispersant and NaOH inside deionized water. The

In this work, the authors explored the production and characteriza-

slurry was continuously stirred with a turbine-type stirrer at 1200 rpm

tion of both experimental mineral-filled and commercial aqueous disper-

for at least 1 h. The final solid content of the slurry was 63%. Follow-

sions on paperboard. The authors aimed for a broad characterization,

ing, the kaolin slurry was mixed with HPH 39 latex (the amounts were

going from barrier properties to converting properties and tray forming

according to the defined dry weight ratio) and stirred at 500 rpm for

to be compared with polyethylene terephthalate (PET)-coated paper-

30 min with the turbine type stirrer, adjusting the pH to 8 with NaOH.

board, currently the leading industrial material. This study involved dry

Experimental formulations had 50% solid content.

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150

T A B L E 1 Properties of the dispersion coatings involved in this study.

Coating

Tg [ C]

Solid content [%]

pH

Ford cup #4 viscosity [s]

a

H39K 80

50

0

8

12

H39K 60

50

0a

8

11

SA-B

46

31.7

8

>60

SAP-H

51

12.1

7

18

a

Tg of HPH 39 (neat latex used in the coating formulation).

Before any use, experimental formulations were stirred with a

coated samples and the measured one of UC. The pinhole test was

magnetic anchor for at least 1 h to ensure proper homogeneity. H39K

assessed according to the procedure defined in BS EN 13676:200141

80 and H39K 60 were applied wet-on-wet to prepare double-layer

with a 25 cm2 testing apparatus. Five replicates were tested for each

coated samples.

coating material. Additionally, Bendtsen roughness according to DIN 53108, and air permeability were measured using a Lorentzen & Wettre (Kista, Sweden) SE 114 Bendtsen Paper Roughness and Air

2.1.3

|

Commercial aqueous dispersions

Permeability Tester 10 measurements for each coating, as well as for UC. The pressure was 1.47 kPa for both roughness and air perme-

In this work, two commercial aqueous dispersions were investigated.

ability tests; the latter was measured over an area of 10 cm2.

Such dispersions were already part of previous research for single-

A Biolin Scientific AB Attension Theta Optical Tensiometer

layer coated paper packaging22,24. Adopting a previous nomenclature,

(Göteborg, Sweden) was used to measure the sessile drop contact

the specific grades studied in this context were:

angle of both coated and uncoated substrates. A total of seven measurements were averaged for each sample. The deionized water drop-

• SA-B: styrene acrylate DC developed to provide barrier performance.

Solid content is 46% (on a weight basis), whereas Tg is 31.7 C.

let volume was 3 μl. The contact angle was measured 1 s after the application of the drop.

• SAP-H: heat-sealable styrene acrylate-based DC with 6% pigment by weight. Solid content is 51% (on a weight basis), whereas Tg is 12.1 C.

2.2.2

|

Mechanical properties

Considering a wet-on-wet double-layer coating investigation,

A total of 20 samples (measuring 140 by 15 mm) – 10 alongside MD,

three distinct configurations were produced and tested: SA-B, SAP-H

and the same number alongside CD – were tensile tested according to

and SAP-H over SA-B to make the coated substrates heat-sealable.

BS ISO 1924-3:200542 using a Lorentzen & Wettre (Kista, Sweden)

Table 1 reports the properties of both experimental and commercial DCs.

SE 064 Tensile tester. The testing length was 100 mm, whereas the crossheads speed was 100 mm/min.

A total of 20 samples (100 by 38 mm) – 10 alongside machine direction and the same amount alongside cross direction (CD) – were

2.2

|

Methods

bending tested using a Lorentzen & Wettre (Kista, Sweden) SE 160 Bending Tester. The bending resistance (0–15 ) and two-point

2.2.1 | Sample preparation and preliminary characterization

bending stiffness (0–5 ) were measured according to BS ISO 2493-1:201043 and ISO 5628:201944, respectively. For both tests, the bending length was 50 mm.

The top side of UC was double coated along the machine direction

Before their testing, both grammage (see Section 2.2.1) and thick-

(MD) using a 20 μm (wet film thickness) wire drawdown coater

ness were determined for both tensile and bending tests; the

mounted on an Erichsen (Hemer, Germany) Coatmaster 510 auto-

thickness was obtained using a Messmer Büchel (The Netherlands)

mated coater. The machine was equipped with a vacuum suction plate

49–56 Micrometer, averaging 20 measurements.

to improve UC flatness on the coating plane. The coating speed was 50 mm/s, and no additional mass weighed on the coating rod. The second coat layer was applied wet-on-wet over the first one, that is,

2.2.3

|

Barrier properties

without oven-drying the first layer. Drying occurred in a VWR (Leuven, Belgium) Venti-line 180 Prime oven at 120 C for 90 s.

Unless elsewhere specified, coated samples were conditioned at

23 ± 1 C and 50 ± 2% relative humidity for at least 24 h before any

Conditioned samples were tested for water absorptiveness (Cobb test), Water Vapour Transmission Rate (WVTR) and Oil and Grease Resistance (OGR).

further characterization and tests. The average dry coat grammage

Cobb 1800 (i.e., 30 min) test was performed according to the

was determined as the difference between the grammage of the

methodology defined in BS EN ISO 535:201445 on five samples over

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151

MARINELLI ET AL.

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an area of 25 cm2. Water absorptiveness is defined as the weight increase of the sample due to water uptake during the test, divided by the testing area. The result is then converted to g/m2. Lower water absorptiveness values indicate higher water barrier properties.

WVTR, instead, followed the evaluation procedure defined in BS ISO 2528:201746 using cups filled with 35.0 ± 0.1 g of silica gel. Three samples for each coating material were tested; the testing area was 20 cm2. WVTR is defined as the amount of water vapour absorbed by silica gel at a steady state. It was calculated as the slope of mass increase in time, divided by the testing area. The result is reported in g/(m2 day).

Lower WVTR values show higher water vapour barrier performance.

OGR followed a similar methodology to the one defined in BS ISO 16532-1:200847. Evaluation times and setup were the same (50 g

FIGURE 1

Heat sealing investigation matrix.

weights with a diameter of 30 mm), but the testing temperature was 60 C. This allowed harsher testing conditions for the substrates, simu-

The equipment mounted flat 25 mm wide tools; the top one – moved

lating contact with hot greasy food. Given the temperature, dyed palm

by two pneumatic cylinders – was heated, whereas the bottom one, a

kernel oil was liquid, and the amount applied to the samples was

flexible tool, was kept at room temperature.

0.1 ml. A total of five samples for each coating were tested and the

A 23 full-factorial design of experiments (DoE) including a central

results were averaged. The outcomes were reported as defined in BS

point was designed adopting as variables temperature, dwell time and

ISO 16532-1:200847.

pressure. A schematic representation of such DoE is reported in Figure 1. The number of replicates was five. The reader should consider that the pressure in Figure 1 represents the cylinder pressure

2.2.4

|

Creasing

that allows a sample-specific pressure of 2, 2.5 and 3 MPa, respectively.

Each aqueous dispersion configuration underwent creasing with a

Heat-sealed

samples

were

subsequently

T-peel

three-rule tool developed at LUT and already presented in a single-

tested – unsupported peel testing, according to ASTM F88/F88M-

rule version in previous work48. The tool was mounted on a Shimadzu

2149 – using a Shimadzu (Kyoto, Japan) Autograph AGS-X machine

(Kyoto, Japan) Autograph AGS-X machine. It features three equally

with pneumatic clamps. The pre-test speed was 50 mm/min until

spaced 2 pt. (0.706 mm) rules that differ in length and whose corners

reaching 0.2 N. Afterwards, the speed was 300 mm/min until the end

are rounded — total length is almost 43 mm, excluding rounding. On

of the test. T-peel test curves were analysed to determine peak force,

the bottom, the authors used a 0.5 mm deep and 1.4 mm wide creas-

average force in the seal area, and peel energy in the seal area. Linear

ing matrix, leading to a creasing factor μ of 1.5 (see Tanninen et al.32

Pareto charts provided heat-sealing relevance for the analysed pro-

for the equation to calculate μ).

cessing parameters. Since low dry coat grammages might negatively

The creasing pre-load was set to 10 N. The speed was constant at

affect the heat-seal ability of rough substrates, the authors also con-

5 mm/min for the pre-test and actual creasing. The authors assessed

sidered the dry coat grammage of the single specimens as a factor to

the effect of two different creasing strokes (0.5 mm and 0.6 mm,

be included in Pareto charts. Indeed, the aim was to assess if small

respectively) for both MD and CD fibre orientation of every double-

changes in the coat grammage could affect the heat-sealing

coated layer configuration, leading to a crease depth of around 90–

performance.

120 μm.

A Keyence (Osaka, Japan) VR-3200 wide-area 3D measurement system determined the real crease depth. For each sample, 11 multi-

2.2.6

|

Tray forming

line profiles were equally spaced (0.5 mm distant) and averaged for each crease line.

Tray forming behaviour was assessed for H39K 80, H39K 60, and SA-

Next, possible coating damage was evaluated through an OGR

B + SAP-H coated paperboard. For comparison, the PET-coated

test, as described in Section 2.2.3. Five samples were tested for each

paperboard was also investigated to ensure that the processing condi-

creasing condition and each coating configuration. ORG testing of five

tions corresponded to industrial production ones. Tray blanks were

uncreased samples provided reference resistance time.

produced using commercial die-cutting equipment with 1/9 foodstuff container – nomenclature according to BS EN 631–1:199350 – die and matrix. Matrix groove width and depth were 1.4 mm and 0.5 mm,

2.2.5

|

Heat sealing

respectively; creasing rules were 2 pt. wide (0.706 mm) and 23 mm high, like for the creasing tests defined in Section 2.2.4. The crease

An RDM Test Equipment (Hertfordshire, England) HSB-1 heat sealer

pattern featured creases that were radial toward the rotation axis of

was used to seal 25 by 130 mm coated strips with facing coated sides.

the tray corner, as discussed in previous research32. The blanks were

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152

FIGURE 2

Tray blank after creasing.

TABLE 2

Tray forming parameters.

Parameter

Units

Min

Max

Blank moisture content

[%]

4.0

5.6

Blank holding force

[kN]

0.546

1.014

Temperature

[ C]

100

120

Pressing speed

[mm/s]

45

90

Subsequently, coat defects due to press-formation were qualitatively evaluated using E131-dyed water and ethanol.

die-cut with the longer side aligned to the Machine Direction (MD) to provide higher tray stiffness (Figure 2).

Berry trays (142 mm 94 mm 50 mm) were press-formed from

conditioned

tray

blanks,

with

main

dimensions

of

211.3 mm 167.3 mm, varying blank moisture content (MC), blank holding force (BHF), temperature, and pressing speed — dwell time was constant to 0.6 s. PET blanks were formed maintaining the MC within the 8–9% range. The moisture content was assessed by testing 5 g of material with an Adam Equipment (Milton Keynes, UK) PMB 53 Moisture Analyzer. Parameters ranged as reported in Table 2 and

F I G U R E 3 Average dry coat grammage for each coating investigated in this work.

their effect was assessed following the previously mentioned sequence. Such specific order was because of preliminary tests, which showed a sticking behaviour of both H39K 80 and H39K 60. Dynamic

2.2.7

|

Statistical analysis

friction tests at different MC (i.e., 2.4%, 7.4% and 11.0%, due to different conditioning environments) were performed on three samples

Graph representation was performed with MS Excel (all error bars

for each coating, to be tested along MD. Dynamic friction equipment

represent standard deviation), whereas statistical analysis of the heat

consisted of a 0.2 kg sled stuck to a sample-coated side facing a

sealing experiments (see Section 2.2.5) was carried out using Minitab

smooth stainless steel sliding plane.

21.3.1. Linear Pareto charts were produced to evaluate the relevance

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153

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T A B L E 3 Average number of pinholes measured for each coating grade, both commercial and experimental.

Coating

Average number of pinholes

PET

0

H39K 80

2

H39K 60

0

SA-B

0

SAP-H

1

SA-B + SAP-H

0

F I G U R E 5 Dispersion-coated, uncoated, and PET-coated paperboard measured contact angle.

microbubbles incorporated in the aqueous dispersion during mixing since both experimental formulations feature no defoamers.

Bendtsen roughness is reported in Figure 4. UC and PET-coated samples achieved the highest results, whereas aqueous dispersions reached, on average, 200 ml/min roughness, meaning more than 55% reduction. It must be observed how, in general, H39K 60 showed higher Bendtsen roughness compared with H39K 80, which was attributed to increased kaolin content, which is coarser compared with latex particles that film-form22,51.

Regarding air permeability, UC showed 4.23 ± 0.23 μm/(Pa s) air F I G U R E 4 Bendtsen roughness of the coated side of different aqueous dispersion-coated paperboard. Uncoated and PET-coated paperboard are included, too.

permeability, whereas all the DCs and PET achieved results that were almost null (≤0.002 ± 0.001 μm/(Pa s)).

Contact angle (Figure 5) clearly shows how experimental kaolin-containing styrene-butadiene coatings feature highly hydrophilic surface52, without statistically significant difference due to dif-

of temperature, time, pressure and dry coat grammage processing

ferent kaolin amounts. On the contrary, uncoated paperboard

parameters for heat-sealing.

achieved the highest value (127 ), highlighting the hydrophobic nature due to sizing agents. Interestingly, the SA-B + SAP-H coated paperboard featured a contact angle that was close to the SA-B one; this

3

|

RESULTS

suggests that the wet-on-wet coating allows the two coating layer particles to interdiffuse before drying.

3.1 | Sample preparation and preliminary characterization 3.2

|

Mechanical properties

Coated paperboard was successfully obtained. Average dry coat grammages for each material under investigation are reported in Figure 3.

Tensile and bending test results are reported in Figure 6 and Figure 7,

Differently from what was expected, dry coat grammage for a double

respectively. The results differed depending on substrate fibre align-

20 μm wet thickness coating achieved an average of 12 g/m2. This

ment, that is, MD or CD. MD alignment provided, as predictable,

might be attributed to paperboard surface sizing, repelling to some

higher tensile strength, average maximum force, as well as bending

extent the waterborne dispersion spread with the rod coater.

resistance and stiffness due to parallel fibre alignment in tensile tests

Generally, coated substrates showed few or no pinholes, as reported in Table 3. H39K 80 pinholes were explained by

and orthogonal alignment to the bending axis—up to threefold values compared with CD.

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154

F I G U R E 6 Tensile test results for both UC, PET, and dispersion-coated paperboard: a) tensile strength; b) strain at break; c) average maximum force; d) tensile energy absorption.

No significant difference could be observed in the investigated

even SAP-H, a commercial heat-sealable grade, showed a water

parameters because of different DC because of either close average

absorption that was 50% lower compared with H39K 80. On the

value or standard deviation–as it is for bending stiffness (Figure 7.b).

other hand, SA-B achieved similar results compared with PET-coated

Such results are coherent with previous findings53,54. The rationale is

paperboard, as well as SA-B + SAP-H coating configuration.

in the low dry coat grammage compared with the substrate one, with

Coherently to previous studies22,55–57, the presence of kaolin in

the former accounting for less than 5% of the total grammage. The

the formulation proved to be of low benefit for improved water bar-

previous statement might be supported by the results for PET-coated

rier properties because of its hydrophilic nature58. In particular, higher

substrate, generally showing better mechanical performance to both

kaolin content generally led to increased water absorption. However,

MD and CD. Indeed, the PET grammage fraction is slightly more than

in terms of magnitude, such results differ from previous results22,24

10% of the total grammage.

with the same coatings but different substrate, especially for experimental coatings, where higher dry coat grammage led to even worse relative performance.

3.3

|

Barrier properties

WVTR (Figure 9), once again, showed how SA-B provided performances similar to PET (both less than 20 g/(m2 day), whereas experi-

Cobb1800 test results are reported in Figure 8. Experimental formula-

mental formulations achieved results around 40 g/(m2 day), with

tion provided minimal barrier compared with other coatings. Indeed,

H39K 60 showing slightly lower WVTR, similarly to what described

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MARINELLI ET AL.

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FIGURE 7

Bending test results for UC, PET, and dispersion-coated paperboard: a) bending resistance; b) bending stiffness.

F I G U R E 8 Water absorptiveness (Cobb1800 test) results of the investigated coatings.

elsewhere22. Waterborne dispersions showed barrier properties improvement ranging from 80–95%. Still, coat weight should be con-

F I G U R E 9 Moisture permeability (WVTR) results of the investigated coatings.

sidered when discussing results, since aqueous dispersions involved in this study led to less than half coat grammage than it was for PET. Both SA-B and experimental coatings achieved performance similar to

respectively) showed the worst resistance, only up to 4 h. On the

previous studies with similar dry coat grammage12,55,59.

contrary, both experimental formulations and SA-B + SAP-H configu-

Grease barrier resistance, expressed as minutes to spot dyed

ration were able to resist up to 24 h at 60 C. Nonetheless, the best

grease on the uncoated side of the samples, is reported in Table 4. UC

result, that is, similar to PET, was achieved with SAP-H, which was

samples showed no OGR. The oil penetrates through the material in a

able to resist for more than 24 h.

couple of seconds after its application on the surface. As a general

Despite similar results achieved on paper substrates22,24, the test-

statement, the different dispersions provided widely variably perfor-

ing conditions involved in this research were harsher because of

mance. Indeed, SA-B, which was the best-performing material for

higher penetration rates caused by higher test temperature (i.e., 60 C

both water absorption and moisture barrier (Figure 8 and Figure 9,

instead of 23 C).

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156

Overall, DCs achieved properties that were sometimes similar to

between 6 and 24 h. PET sample was the only material that did not

PET, but at a reduced dry coat grammage. This means that, from a

show dye colour leftovers on the coat side, highlighting that – at least

barrier point of view, dispersion-coated substrates might represent

to some extent – the coating absorbs dyed grease. Such results are

more sustainable solutions since they decrease the non-cellulosic

coherent with similar previous literature29.

content.

Generally, samples failed because of general permeation through the coatings (Figure 10.c), suggesting once again the possible presence of pores that were filled by dyed grease. However, pores' dimen-

3.4

|

Creasing

sion might be small, since colour was homogeneous and coat porosity was

Results for creased samples are reported in Table 5, which also spec-

not

observed

at

high

magnification

scanning

electron

microscope22.

ifies failure mode. PET provided the best performance, alongside SAP-

Nevertheless, as a general statement, samples were not affected

H; still, H39K 80 and H39K 60 showed interesting results, resisting

by stroke or fibre orientation apart from SA-B + SAP-H, which failed because of several crease defects as of Figure 10.a and Figure 10.b.

Such behaviour underlines a multi-DCs coat that is more brittle com-

T A B L E 4 Grease permeability of the investigated coatings. Unless specified, the results unit is minutes.

Uncreased UC

PET

H39K 80

H39K 60

SA-B

SAP-H

SA-B + SAP-H

pared with aqueous dispersions used on their own. Single aqueous dispersions behaved similarly to extrusion-coated and laminated materials rather than cracking60 at the studied crease depths.

Therefore, crease stroke should be further reduced for SA-B

Test result

0

+ SAP-H, limiting creasing-induced defects. However, stroke reduc-

Min-Max [min]

All <1

tion means – like increasing crease rule width – shallower creases,

Test result

>24 h

which are detrimental for leakproof seals31,35. Additionally, given

Min-Max [min]

All >1440

the measured data, it seems that crease tip-related defects are more

Test result

6 < X < 24 h

likely to be witnesses as against the ones along the crease line. The

Min-Max [min]

All ≤1440

reason lies in crease rule tips, which generally undergo a filing process

Test result

6 < X < 24 h

that might leave some dents that can damage thin coat layers

Min-Max [min]

All ≤1440

more easily.

Test result

240

Min-Max [min]

240–270

Test result

>24 h

Min-Max [min]

All >1440

Test result

6 < X < 24 h

Min-Max [min]

All ≤1440

3.5

|

Heat-sealing

Peel test results of heat-sealed samples are shown in Figure 11. H39K 60 and SA-B + SAP-H coated substrates behaved following the same trend, whereas H39K 80 did not vary as much as the others did. This

T A B L E 5 Grease permeability of the investigated coatings after creasing. Different strokes and fibre orientation were considered.

Additionally, failure modes are reported. Unless specified, the results unit is minutes.

PET

H39K 80

H39K 60

SA-B

SAP-H

SA-B + SAPH

Stroke

0.5

0.5

0.6

0.6

Orientation

MD

CD

MD

CD

Failure mode n.a.

Test result

>24 h

>24 h

>24 h

>24 h

Min-Max [min]

All >1440

All >1440

All >1440

All >1440

Test result

6 < X < 24 h

6 < X < 24 h

6 < X < 24 h

6 < X < 24 h

Min-Max [min]

All 1440

All 1440

All 1440

All 1440

Permeation through coating

Test result

6 < X < 24 h

6 < X < 24 h

6 < X < 24 h

6 < X < 24 h

Min-Max [min]

150–1440

330–1440

All 1440

150–1440

Permeation through coating (rare crease tip damage) Permeation through coating

Test result

180

180

150

180

Min-Max [min]

All 180

180–210

70–210

130–180

Test result

>24 h

>24 h

>24 h

>24 h

Min-Max [min]

All >1440

All >1440

1440– > 1440

1440– > 1440

Test result

6 < X < 24 h

6 < X < 24 h

360

360

Min-Max [min]

180–1440

24–1440

30–1440

26–1440

n.a. (rare crease tip damage)

Crease tip damage (+some along crease)

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F I G U R E 1 0 Pictures of the backside of the samples that show observed failure modes: a) coat defect along the crease line; b) coat defect because of the crease tip; and c) no coat defect because of creasing, but grease permeation through the coating.

FIGURE 11 energy.

Peel test results for each heat-seal set of temperature, dwell time and pressure: a) average force; b) maximum force; c) seal

might be explained by lower kaolin content that cannot shield native

and, equivalently, to peel energies in the sealed area ≥450 mJ and

latex stickiness, as previously reported24.

maximum forces ≥18 N. Consequently, it could be stated how the

Similar to previous works24,33, two main failure modes were

ranges investigated in this work were not correct to spot out a change

retrieved: a separation along the coat-coat interface, and a crack for-

in H39K 80 behaviour, hence too high set of temperature, time and

mation in the sealant followed by paperboard delamination (i.e., fibre

pressure. Additionally, peel energy values should not be considered

tear). Indicatively, the latter mode occurred at average forces ≥10 N —

meaningful when associated with paperboard delamination. The

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158

F I G U R E 1 2 Linear Pareto charts of the standardized effects of heat-seal parameters, plus dry coat grammage: a) H39K 80; b) H39K 60; c) SAP-H. Factors with a score higher than the reference value (2.021, red dashed line) are statistically evident factors.

F I G U R E 1 3 Maximum heat-seal force registered for samples sealed at different temperatures (dwell time: 1.5 s; equipment pressure: 0.21 MPa).

159

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MARINELLI ET AL.

MARINELLI ET AL.

F I G U R E 1 4 Dynamic friction results for H39K 80, H39K 60, and SA-B + SAP-H at different moisture contents.

reason lies in the energy contribution, which is not due to coatto-coat interface separation; instead, the external energy provided by the system is mainly associated with fibre separation.

Linear Pareto charts for both processing parameters and dry coat grammage (Figure 12) highlight different statistically significant parameters for each material, given the same DoE. For H39K 80, it seems to be a matter of dry coat grammage. However, taking a closer look at the results for such coating (Figure 11), the change in sealing parameters appeared negligible in the measured outcomes. Indeed, almost every sample showed paperboard delamination (fibre tearing) during the peel test, underlining a coat-to-coat interface bonding that is stronger than the one of bulk paperboard, regardless of temperature, time and pressure applied during heat-sealing34.

H39K 60 and SAP-H, instead, undoubtedly show the importance of time, plus temperature, notwithstanding the lower magnitude of the latter. Coherently with previous work24 and despite higher substrate grammage (i.e., thickness), similar time range, and higher specific pressures (0.4 to 0.6 MPa versus 2 to 3 MPa of the current work), time was the most crucial parameter to obtain heat-sealed samples.

The effect of time was discussed in previous work33 to be crucial at lower temperatures because of thermal insulation properties of cellulosic substrates. As of Figure 11, data is coherent with such argument for all the investigated properties at 80 C and 100 C comparing samples sealed at 1 s and 2 s, with a sharper difference at lower sealing

F I G U R E 1 5 Blank breakage during tray forming. Higher moisture content increases friction, leading to blank adhesion to the male mould.

pressures. With a good approximation, also pressure was a significant parameter according to Pareto charts.

interface — despite some PET-paperboard interface bonding being

The authors compared the heat-seal ability of dispersion-coated

damaged at higher temperatures. Higher maximum forces for PET-

paperboard with the one of PET-coated paperboard. As of Figure 13,

coated paperboard could be explained by the higher coat

maximum seal force clearly shows how aqueous dispersions are capa-

grammage – as well as the tough nature of the material – that pro-

ble of sealing at temperatures that are around 100 C lower than PET

vided higher Tensile Energy Absorption (Figure 6), that is, it was able

ones. This represents a crucial advantage, leading to lower energy

to withstand peeling without breaking nor transferring the stress to

consumption, hence lowering production costs. Additionally, a major

paperboard fibres which, in turn, resists to a lower extent compared

difference in peeling behaviour is that DCs generally fail by paper-

with coat–coat bond at the sealing interface (as observed for disper-

board delamination, whereas PET separates at the coat-coat

sion coated substrates). Recent research36 showed how dispersion-

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160

coated paper could withstand maximum forces that were almost 50%

carboxyl groups, leading to reduced Tg61,62. H39K 80 and H39K

less than PE-coated similar substrates. In this work, the authors expe-

60 gap was explained by higher kaolin content, which reduced the

rienced similar behaviour, though the seal strength gap was consider-

equivalent latex (hence, fewer carboxyl groups) facing the sliding

ably less, ranging from 10% to 20%. Although seal strength at a

plane, thus limiting friction. The lower friction coefficient achieved by

given set of sealing parameters is mainly driven by the polymeric

the presence of pigment is also coherent with previous findings63,64.

nature, as well as possible pigment amount and fibre tear resistance, it

Additionally, the friction coefficient was aligned with Bendtsen rough-

should be considered that coat grammage might play a role in such

ness values (Figure 4); indeed, H39K 60 features a rougher surface,

lower strength, as suggested by Figure 12.c.

hence fewer contact points to stick to the smooth steel surface.

Despite friction, coated paperboard trays were successfully achieved. The processing window in terms of MC for the experimental

3.6

|

Tray forming

formulations was limited to 4.5–5.0%, whereas SA-B + SAP-H could be formed even at 5.6% — female mould: 100 C; BHF: 0.780 kN;

Different materials showed different dynamic friction coefficients, as

pressing speed: 90 mm/s; dwell time: 0.6 s. Each coating material

reported in Figure 14. It is clear how moisture plays a crucial role in

could not form at a lower MC (i.e., 4.0%). Such results differ from typi-

determining the friction coefficient, with increasing MC leading to

cal paperboard forming MC, which previous research reported to be

increased friction. Friction increased linearly with MC (for H39K

around 8.0–9.0%38,65,66. Indeed, both trials at MC of 4.0% and prelim-

80 and SA-B + SAP-H, R ≥ 0.98) in the investigated moisture con-

inary tray forming at higher moisture content (>6.0%) showed highly

tent range. Such behaviour might find a similar explanation as in previ-

adhesive behaviour on the male mould, which led to material break-

2

33

ous research , since water increases paperboard thermal conduction,

age, as documented in Figure 15. Therefore, all the following proces-

hence helping coating softening. Additionally, previous works dis-

sing was carried out at a blank MC of 4.5–5.0% for all the coatings

cussed the hydroplasticizing effect of moisture on polymeric coating

involved.

F I G U R E 1 6 Dyed water and ethanol defects in the corners for H39K 80, H39K 60, and SA-B + SAP-H coated paperboard trays: a) H39K 80, water; b) H39K 60, water; c) SA-B + SAP-H, water; d) H39K 80, ethanol; e) H39K 60, ethanol; f) SA-B + SAP-H, ethanol. All trays were produced at 100 C, 0.780 kN BHF, 90 mm/s, 0.6 s dwell time.

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161

MARINELLI ET AL.

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F I G U R E 1 7 Effect of forming speed on coat defects for SA-B + SAP-H formed trays (dyed ethanol): a) 45 mm/s; b) 90 mm/s. Other forming parameters were 120 C, 1.014 kN BHF, and 0.6 s dwell time.

BHF is associated with friction, too. Increasing BHF leads to

On the contrary, the PET sample trays showed no defects or sticking

increased normal forces applied on the blank, hence friction. How-

behaviour within the investigated parameter range, highlighting how

ever, BHF is also proportional to the smoothness of the flange —

the processing arrangement corresponded to the ones adopted for

which is, in turn, crucial for trays that need to be heat-sealed35. H39K

industrial production. Nonetheless, it must be noted that the PET

60 and SA-B + SAP-H could be processed at a BHF of 1.014 kN,

coating was much thicker compared with dispersion-coated counter-

whereas H39K 80 failed, badly sticking to the mould. Once again,

parts, allowing possible higher tensile resistance.

higher pigment content seemed to help limit friction coefficient and stickiness.

No marked difference was observed because of BHF and temperature parameter effects for the investigated ranges. Nevertheless,

The effect of processing temperature correlates to the thermal

lower pressing speed showed significantly fewer defects, highlighting

properties of the coatings. Higher mould temperature leads to

how higher speed helped damage the thin DCs (Figure 17). Addition-

increased chain mobility, which, in turn, helps the heat-sealing of the

ally, taking a closer look at the defects, stained areas clearly show

creases and adhesion to other substrates in general. SA-B + SAP-H

transversal cracks to the crease lines, suggesting damages caused by

trays were formed without any issues when mould temperature

axial deformation.

increased from 100 C to 120 C at both BHF of 0.780 kN and 1.014 kN. Similarly, H39K 80 and H39K 60 could be formed at 120 C at a BHF of 0.780 kN. Unfortunately, despite kaolin content, a BHF of

4

|

CONC LU SIONS

1.014 kN led to mould sticking for H39K 60 at 120 C. Additionally, both H39K 80 and H39K 60 were tray-formed at a BHF of 0.546 kN

This work provided encouraging results from multiple points of view

to have further data to assess forming speed.

to sustain a narrow yet possible material substitution to reduce non-

From a material perspective, forming speed is primarily associated

cellulosic content in paperboard-based packaging.

with deformation rate and latex softening (because of an extended

SA-B aqueous dispersion provided water and moisture barrier

contact time with the heated mould). The former, given other factors

properties that were similar to PET, whereas SAP-H for grease barrier.

to be constant, influences the brittle or plastic behaviour of the coat-

Experimental dispersions, on the contrary, featured intermediate

ing, with higher speeds that can be associated with more fragile

values, apart from water barrier properties. Nevertheless, the results

behaviour due to less time for the polymeric chains to flow without

were satisfying because of the lower dry coat grammage involved for

breaking. At 45 mm/s forming speed (120 C, BHF of 0.780 kN and

dispersions as against PET.

1.014 kN for SA-B + SAP-H, and 0.546 kN and 0.780 kN for H39K

The investigated creasing depth range did not affect the coating

80 and H39K 60), all the materials could be tray formed without stick-

integrity of both experimental formulations (i.e., H39K 80 and H39K

ing occurrence. Lower speed seemed to have a negligible effect on

60) and SAP-H, generally leaving grease permeation values intact.

the adhesion and blocking effect of the investigated coated

Some damages were observed with SA-B and SA-B + SAP-H,

paperboard.

highlighting a more fragile behaviour at room temperature.

Despite successful tray forming at the given parameters' range,

Aqueous dispersion-coated paperboard could be heat sealed at

dyed water and ethanol generally highlighted quite damaged coatings

temperatures that were up to 100 C lower compared with conven-

(Figure 16). The main damaged areas were the corners and the flange.

tional PET-coated paperboard, representing a better choice to reduce

Specifically, the flange showed defects in the area exposed to tensile

power consumption. Such behaviour appeared to be proportional to

stresses (convex coated side), leaving fewer damages to the concave

the Tg of each polymeric fraction. Despite lower seal strength, such

coated side. Moreover, despite lower sticking behaviour, H39K

materials may be used in applications where a temperature-sensitive

60 was more damaged compared with H39K 80. The reason lies

content is involved. Unfortunately, the peel mechanism for strongly

within lower latex continuity in highly pigmented formulations that

sealed samples was paperboard delamination, suggesting early coating

lead to early breakage, similar to filled polymer matrix composites67.

breakage, whereas PET separates at the heat-sealed interface.

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162

Paperboard dispersion-coated trays could be manufactured; however, moisture content was reduced to 4.5–5.0% to prevent blanks from sticking to the equipment. Although this is an atypical procedure to prepare the materials for processing, it strongly affected coating blocking behaviour. Still, tray forming speed damaged coat integrity.

Lower formation speed and higher temperature proved to qualitatively reduce coat cracking, though fine-tuning is required to achieve a flawless converted coated paperboard tray. Overall, dispersioncoated substrates showed good machinability.

The present study provided further insights into the relationship between coating properties and their influence on process parameters, posing an additional basis for future research.

ACKNOWLEDGEMEN TS The authors would like to thank the companies for supplying materials as well as Antti Pesonen for assisting in the laboratory experiments.

DATA AVAI LAB ILITY S TATEMENT The data that support the findings of this study are available from the corresponding author upon reasonable request.

ORCID Andrea Marinelli

https://orcid.org/0000-0002-2646-8686

Johanna Lyytikäinen Panu Tanninen Barbara Del Curto Ville Leminen

https://orcid.org/0000-0002-2241-762X

https://orcid.org/0000-0001-6570-5253 https://orcid.org/0000-0002-0125-0226

https://orcid.org/0000-0001-5854-3321

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2019;166:206-214. doi:10.1016/J.POLYMER.2019.01.074 63. Hubbe MA, Gill RA. Fillers for papermaking: a review of their properties, usage practices, and their mechanistic role. BioResources. 2016; 11(1):2886-2963. doi:10.15376/biores.11.1.2886-2963 64. Rättö P, Barbier C, Rigdahl M. An investigation of the friction properties of coated paper. Nord Pulp Pap Res J. 2000;15(5):351-356. doi: 10.3183/npprj-2000-15-05-p351-356

65. Kettle J. Moisture and fluid transport. In: Niskanen K, ed. Paper physics (papermaking science and technology). 2nd ed. Finnish Paper Engineers' Association/Paperi ja Puu Oy; 2008:265-294.

66. Tanninen P, Lindell H, Saukkonen E, Backfolk K. Thermal and mechanical durability of starch-based dual polymer coatings in the press forming of paperboard. Packag Technol Sci. 2014;27(5):353363. doi:10.1002/pts.2036 67. Faruk O, Bledzki AK, Fink HP, Sain M. Biocomposites reinforced with natural fibers: 2000-2010. Prog Polym Sci. 2012;37(11):1552-1596. doi:10.1016/j.progpolymsci.2012.04.003

How to cite this article: Marinelli A, Lyytikäinen J, Tanninen P, Del Curto B, Leminen V. Barrier, converting, and tray-forming properties of paperboard packaging materials coated with waterborne dispersions. Packag Technol Sci. 2024;37(3): 149‐165. doi:10.1002/pts.2784

10991522, 2024, 3, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/pts.2784 by Test, Wiley Online Library on [16/04/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

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Volume 10, Number 2, 2024

Pros and Cons of “X (Twitter)” for Business: Maximizing Opportunities and Overcoming Challenges In today’s digital landscape, social media platforms have become indispensable for businesses seeking to establish a strong online presence. Among these platforms, “X (Twitter)” has emerged as a powerful tool for connecting with audiences, increasing brand exposure, and driving engagement. However, like any tool, “X (Twitter)” has both its advantages and disadvantages for businesses. In this article, we will explore the pros and cons of using “X (Twitter)” for business. By understanding these factors, you can make informed decisions and effectively leverage “X (Twitter)” potential to maximize your business’s success.

By Yoel Israel 11 July 2023 https://wadidigital.com/blog/pros-and-cons-of-twitter-for-business/

Page 1 of 2

Article 9 – Using X (Twitter) for Business

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

Advantages of using “X (Twitter)” for Business When it comes to leveraging “X (Twitter)” for business, there are several compelling advantages that make it a valuable platform for brands. Let’s delve into the pros in more detail: Wide Reach and Brand Exposure “X (Twitter)” boasts a massive user base, offering businesses an extensive platform to reach a global audience. With millions of active users, businesses can significantly increase brand visibility and awareness.

The viral nature of “X (Twitter)” allows brand messages to spread rapidly, exposing your business to new customers and markets.

Real-Time Marketing Opportunities “X (Twitter)” real-time nature enables businesses to tap into trending topics and hashtags, leveraging current events and popular conversations to promote their products or services. By engaging in real-time marketing, businesses can stay relevant and capture the attention of their target audience.

Customer Engagement and Feedback “X (Twitter)” facilitates direct interaction between businesses and customers, providing a platform for valuable engagement and feedback. Customers can easily reach out to brands, share their experiences, ask questions, and provide feedback. This real-time engagement not only builds trust and fosters customer loyalty but also enables businesses to address concerns promptly and improve their offerings based on customer feedback.

Influencer Marketing and Partnerships “X (Twitter)” offers excellent opportunities for influencer marketing, allowing businesses to collaborate with relevant industry influencers. By partnering with influencers aligned with their brand values, businesses can reach a larger audience, gain credibility, and drive conversions effectively.

Disadvantages of using “X (Twitter)” for Business Now, let’s explore the cons of using “X (Twitter)” for business, which is important to consider: Information Overload and Noise With the vast number of tweets flooding users’ timelines, businesses face the challenge of standing out amidst the noise. It can be difficult to capture users’ attention and make an impact in such a crowded environment. Thoughtful content creation and strategic approaches are necessary to cut through the clutter.

Negative Publicity and Crisis Management While “X (Twitter)” provides ample opportunities for positive brand exposure, it also poses the risk of negative publicity. Negative sentiments and crises can spread quickly on the platform, potentially damaging a brand’s reputation. Effective crisis management strategies and timely responses are crucial to mitigate damage and maintain a positive brand image.

Limited Message Length and Context The character limit on “X (Twitter)” poses a challenge for businesses aiming to convey complex messages.

Crafting concise yet impactful tweets while providing sufficient context can be difficult. However, this limitation also encourages businesses to communicate their core value proposition succinctly, promoting clarity and engagement.

Time and Resource Commitment Successful management of an “X (Twitter)” presence requires dedicated time and resources. Consistently posting, engaging with followers, and creating relevant content demand a significant commitment. Without proper planning and resource allocation, businesses may struggle to maintain an active and effective presence on the platform.

Conclusion: “X (Twitter)” offers businesses a wealth of opportunities to connect with audiences, increase brand exposure, and foster customer engagement. Understanding the advantages and disadvantages of using “X (Twitter)” is crucial for developing a well-rounded strategy that aligns with your goals and resources. By leveraging “X (Twitter)” wide reach, real-time marketing potential, customer engagement, and influencer partnerships, businesses can tap into a vast network of opportunities. However, it’s equally important to address the challenges of information overload, crisis management, limited message length, and time/resource commitment. With careful planning and a deep understanding of the platform, businesses.

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Article 9 – Using X (Twitter) for Business

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

How to Keep Your Eyes Healthy Don't take your eyes for granted. Take these easy steps to keep your peepers healthy.

Medically Reviewed by Whitney Seltman, OD on June 14, 2022 Written by WebMD Editorial Contributors https://www.webmd.com/eye-health/good-eyesight

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 3

Article 10 – Eye Health

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

1. Eat Well Good eye health starts with the food on your plate. Nutrients like omega-3 fatty acids, lutein, zinc, and vitamins C and E might help ward off age-related vision problems like macular degeneration and cataracts. To get them, fill your plate with: Green leafy vegetables like spinach, kale, and collards Salmon, tuna, and other oily fish Eggs, nuts, beans, and other nonmeat protein sources Oranges and other citrus fruits or juices Oysters and pork A well-balanced diet also helps you stay at a healthy weight. That lowers your odds of obesity and related diseases like type 2 diabetes, which is the leading cause of blindness in adults.

2. Quit Smoking It makes you more likely to get cataracts, damage to your optic nerve, and macular degeneration, among many other medical problems. If you've tried to kick the habit before only to start again, keep at it. The more times you try to quit, the more likely you are to succeed. Ask your doctor for help.

3. Wear Sunglasses The right pair of shades will help protect your eyes from the sun's ultraviolet (UV) rays. Too much UV exposure boosts your chances of cataracts and macular degeneration.

Choose a pair that blocks 99% to 100% of UVA and UVB rays. Wraparound lenses help protect your eyes from the side. Polarized lenses reduce glare while you drive, but don’t necessarily offer added protection.

If you wear contact lenses, some offer UV protection. It's still a good idea to wear sunglasses for an extra layer.

4. Use Safety Eyewear If you use hazardous or airborne materials on the job or at home, wear safety glasses or protective goggles.

Sports like ice hockey, racquetball, and lacrosse can also lead to eye injury. Wear eye protection. Helmets with protective face masks or sports goggles with polycarbonate lenses will shield your eyes.

5. Look Away From the Computer Screen Staring at a computer or phone screen for too long can cause: • • • • • •

Eyestrain Blurry vision Trouble focusing at a distance Dry eyes Headaches Neck, back, and shoulder pain

To protect your eyes: • • • • • • •

Make sure your glasses or contacts prescription is up to date and good for looking at a computer screen.

If your eye strain won’t go away, talk to your doctor about computer glasses.

Move the screen so your eyes are level with the top of the monitor. That lets you look slightly down at the screen.

Try to avoid glare from windows and lights. Use an anti-glare screen if needed.

Choose a comfortable, supportive chair. Position it so that your feet are flat on the floor.

If your eyes are dry, blink more or try using artificial tears.

Rest your eyes every 20 minutes. Look 20 feet away for 20 seconds. Get up at least every 2 hours and take a 15-minute break.

6. Visit Your Eye Doctor Regularly Everyone needs a regular eye exam, even young children. It helps protect your sight and lets you see your best.

Page 2 of 3

Article 10 – Eye Health

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

Eye exams can also find diseases, like glaucoma, that have no symptoms. It's important to spot them early on, when they're easier to treat.

Depending on your eye health needs, you can see one of two types of doctors: • •

Ophthalmologists are medical doctors who specialize in eye care. They can provide general eye care, treat eye diseases, and perform eye surgery.

Optometrists have had 4 years of specialized training after college. They provide general eye care and can diagnose and treat most eye diseases. They don't do eye surgery.

A comprehensive eye exam might include: • • • • •

Talking about your personal and family medical history Vision tests to see if you’re nearsighted, farsighted, have an astigmatism (a curved cornea that blurs vision), or presbyopia (age-related vision changes) Tests to see how well your eyes work together Eye pressure and optic nerve tests to check for glaucoma External and microscopic examination of your eyes before and after dilation

You might also need other tests.

Page 3 of 3

Article 10 – Eye Health

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

10 Tips For Proper Sitting Posture At A Computer Desk In the modern workplace, many workers spend more than 50% of their workday in a seated position. This is why learning the proper sitting posture is so important.

Our bodies were built to move and yet we are spending an increasing amount of time in sedentary environments that minimize our physical activity levels, and also require us to sit for prolonged periods of time.

Sitting with poor posture can lead to: – Neck and back pain – Forward head posture – Rounded shoulders – Hyperkyphosis – Anterior pelvic tilt – Bulging discs – Muscle stiffness – Decreased mobility – Poor balance – Decreased athletic performance According to the Cleveland Clinic, good posture involves positioning your body to walk, stand, sit, or lie in a position that places the least amount of strain on the supporting muscles and ligaments of your body.

Benefits of proper posture include: – Keeps bones and joints in proper alignment to encourage efficient use of muscles.

– Helps reduce abnormal wear and tear on joint surfaces.

– Decreases the stress on the spinal ligaments.

– Prevents abnormal spinal positions.

– Prevents muscle fatigue.

– Prevents injury including strains, sprains, and overuse injuries.

– Contributes to a good appearance.

– Improves self-esteem.

Dr. Shaina McQuilkie, DC, July 3, 2023 https://backintelligence.com/proper-sitting-posture-at-a-desk/

Page 1 of 5

Article 11 – Sitting Posture at a Desk

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

1. Keep your pelvis neutral with your buttocks against the back of your chair.

Proper sitting posture at a desk begins at your pelvis. You want to sit with your pelvis in a neutral position, with your buttocks against the back of the chair.

You might be wondering… how do I sit with a neutral pelvis? The first step to finding a neutral pelvis is begins with finding your sitz bones. These bones are the most prominent bones that you’ll feel in your buttocks when you place your hands underneath your buttocks.

Once you find these bones, round your lower back into a slouched position and tuck your pelvis under – the sitz bones will start to feel flat under your hands. Now, tilt your pelvis forward by arching your lower back.

Your sitz bones will leave your hands and all of your weight will move to the back of your thighs.

A neutral pelvis is midway between the slouched and tilted forward positions. In a neutral pelvis posture, your sitz bones will feel pointy.

Sitting with your pelvis in a neutral position, with your buttocks positioned against the back of your chair, will help to prevent your pelvis from tilting forwards (anterior pelvis tilt), or backwards (posterior pelvic tilt).

2. Keep your ears, shoulders, and hips aligned.

The natural curves of your spine are maintained by keeping your ears, shoulders, and hips aligned. Any deviation from this position will cause shifting of the natural curves of your spine, which places excess stress on the spine resulting in pain, and also increases your risk of injury.

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Article 11 – Sitting Posture at a Desk

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

3. Maintain the normal low back curve (Use a back support) Your back should have a small curve in the lower back, which is where your lordortic curve is. Without support, your back tends to curve in the opposite direction, which is known as kyphosis (hunchback), which leaves your lower back vulnerable to injuries including sprains and strains, and disc herniation. A rolled up towel, or a small pillow, is a simple solution that can be used to provide support to the lower back.

4. Keep your hips and knees at 90 degrees.

When sitting at your desk, try to keep your knees almost aligned with your hips. This position helps to keep a neutral spine position. Sitting in a chair that’s too low positions your knees above your hips, while sitting perched higher up positions your hips significantly higher than your knees. Both of these positions place excessive stress on your back and can lead to back pain and stiffness.

5. Evenly distribute your weight over both hips (avoid leaning to one side).

It can be tempting to lean to the side when you’re sitting at your desk, but this bad habit causes your spine to curve, which can lead to issues such as sprains and strains, scoliosis, and disc herniation. Ensure that your weight is evenly distributed over both hips when in a seated position.

Page 3 of 5

Article 11 – Sitting Posture at a Desk

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

6. Keep both feet flat on the ground (use foot stool if necessary).

When you cross your legs, or if just your toes are touching the floor, you put stress on the large supportive muscles of your back, pelvis and hip and you also interfere with proper blood flow. Another issue with a crossed-leg position is that it puts added pressure on your lower back and forces you to lean slightly to one side, causing and imbalanced pelvis.

7. Keep your forearms parallel with the floor, resting on your desk.

Keeping your forearms parallel with the floor, resting on your desk helps to reduce the amount of stress on the joints of your upper extremities. Ensure that you place your keyboard and mouse at appropriate distances from your body so that you don’t have to continually reach forwards to use them. If you have to stretch your arms to reach you keyboard and/or mouse, your shoulders will start to rotate forward which can lead to rounded shoulders posture as well as upper back pain.

8. Place your computer monitor 18-24 inches from your face with the top 1/3 of monitor at eye level.

If your computer monitor is positioned incorrectly, you’ll be placing excess strain on your neck because you’ll have to be constantly looking up or down. This puts you at risk for injuries such as neck strains and sprains, cervical disc herniation, and headaches.

Page 4 of 5

Article 11 – Sitting Posture at a Desk

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

9. Regularly check that your head is not protruding forward.

You’ll really want to be aware of this bad habit and make a conscious effort to avoid it. Research has found that for every inch your head moves forward, there’s an extra 10 pounds of weight placed on your neck!

Protruding your head forward when seated can lead to forward head posture, which can results in an array of health issues including neck and back pain, muscle spasms, arthritis of the neck, restricted breathing, headaches and migraine, insomnia, sleep apnea, chronic fatigue, numbness and tingling in your arms and hands, and temporal mandibular joint (TMJ) pain.

10. Take periodic breaks & Stretch out.

Try to take a short break from sitting at least once every hour to move around your office. This can help to relieve pain and prevent muscle tightness. During your breaks, you can try doing simple stretches to relieve muscle tightness and improve blood flow. Simple exercises that can be done in your office include: – Neck range of motion (flexion, lateral flexion, and rotation) – Shoulder shrugs – Calf raises – Ankle pumps – Lunges – Doorway stretch

In Conclusion If you’re like many people, you spent countless hours seated at your desk and you may be suffering with aches and pains due to poor posture. Bad sitting habits, such as slouching or crossing your legs, can have a detrimental impact on the health of your spine. Fortunately, these bad habits can be corrected by following the tips outlines above. Simple changes to your workspace and your sitting posture can go a long way to improving the health of your spine.

Page 5 of 5

Article 11 – Sitting Posture at a Desk

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

The best AI productivity tools in 2024 As the dust settles on last year's AI storm, ChatGPT is just one of hundreds of powerful tools in the game.

From new intelligent features on apps you already love, to entirely new platforms with jaw-dropping functionality, there's an AI-powered solution to nearly every productivity problem.

I've been playing around with AI tools for a while now, and I've continued to update this list with lots of research and testing from me and the team at Zapier. With that, here are 37 AI productivity tools that will change the way you work.

The best AI productivity tools by category • • • • • • • • • • • • • •

Chatbots (ChatGPT, Claude, Bing AI, Zapier Central) Content creation (Jasper, Copy.ai, Anyword) Grammar checkers and rewording tools (Grammarly, Wordtune, ProWritingAid) Video creation and editing (Descript, Wondershare Filmora, Runway) Image generation (DALL·E 3, Midjourney, Stable Diffusion) Voice and music generation (Murf, Splash Pro, AIVA) Knowledge management and AI grounding (Mem, Notion AI Q&A, Personal AI) Task and project management (Asana, Any.do, BeeDone) Transcription and meeting assistants (Fireflies, Airgram, Krisp) Scheduling (Reclaim, Clockwise, Motion) Email inbox management (SaneBox, Mailbutler, EmailTree) Slide decks and presentations (Decktopus, Beautiful.ai, Slidesgo) Automation (Zapier) Other AI productivity tools

How I selected the best AI productivity app in each category My AI app database is at 270 entries right now. I'm absolutely sure there are way more out there, with many new apps being launched every week.

Full transparency: I've had a chance to take a look at most of them, but I haven't tested them all (yet). The list you're about to see contains a collection of great AI productivity tools tested by Zapier's app review team, myself included. If there's a particular category you like, check out the best apps lists we've put together for them—or if we're still in the process of writing that list, run a quick Google search to find more options.

While all these apps are getting better every day, they're far from perfect: be sure to always check AI's work with your human brain. With that being said, please keep all hands and legs inside the vehicle—it's time to explore.

By Miguel Rebelo · January 25, 2024 https://zapier.com/blog/best-ai-productivity-tools/

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 7

Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

1. AI chatbots The best place to start is the category that brought AI to the mainstream. AI chatbots allow you to chat with an AI large language model, letting you ask questions and get answers in a conversational style. The best chatbots use advanced reasoning and logic, write code, and make mathematical calculations.

ChatGPT ChatGPT is the current industry leader, and the first chatbot that set the scene on fire. It's powered by OpenAI's GPT-3 and GPT-4 models, and it's surprisingly flexible and very easy to use. Learn how to use ChatGPT, understand how it works, and discover how to use it to write marketing copy, do market research, or write sales emails. When you connect ChatGPT to Zapier, you can automate ChatGPT, so you can access the power of the AI chatbot from within any of your favorite apps.

Claude Anthropic's safe and creative chatbot, Claude has impressive memory: it can remember up to 150,000 words in each conversation. This makes it useful to have long, step-by-step discussions of a problem or to upload a PDF and ask questions.

Bing AI (Microsoft Copilot) Microsoft's close relationship with OpenAI was a positive step to Bing Search: it can search the web and generate answers based on the results. It's also connected to DALL·E 3, so if you ask for images, you'll get four visual variations of your prompt. Microsoft is bringing all its AI features into a single name—Microsoft Copilot—so look out for that rebranding across its product line.

Zapier Central Zapier Central is an experimental AI workspace where you can teach bots to work across thousands of apps.

But the interface is a chatbot, which means that creating your own AI agent is as simple as using ChatGPT. Tell your bot what to do when it's triggered, how to process or summarize data, and which actions it should take. You can trigger behaviors on demand, when new data comes through any app in your tech stack, or when you use a specific keyword in a message to the bot. It's AI chat, automation, and data analysis all in one place.

2. AI apps for content creation Entire movies have been made about writer's block. These apps are here to break it. By entering your prompts, starting from templates, or using recipes, you can use AI models as a co-writer, helping you put together first drafts faster.

Jasper Jasper is a powerful AI content creation platform, favoring users who need a high volume of content. It packs dozens of templates to help you get started, connects to the internet to find research and sources, and also lets you generate images with AI. All your content creation needs are covered here. You can also connect Jasper to thousands of other apps using Zapier.

Copy.ai Copy.ai is a slower-paced option, acting as a writing co-pilot. Each of your prompts generates a list of options, and it's up to you to pull the best ones into your document. This is better for writing tasks that require more ideation and iteration, such as copywriting.

Anyword Anyword helps marketers create content by breaking the generation process down step by step. First, you add your prompt to generate a few titles. Then, you can pick your favorite and see a generated outline. Once you tweak that outline to what you want to cover, you can move forward to generating the final piece.

3. AI apps for text enhancement Spell-checking has been around for a long time, but AI is changing the game. Before, it only detected spelling and basic structure errors. Now, it can spot tone and complex language and offer suggestions to make your writing clearer.

Grammarly Grammarly is the mainstream spell- and structure-checking app. It's a complete solution that keeps your English on point, lets you adjust your tone, and suggests shortcuts to simplify wordy or complex phrases. It

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

has plenty of extensions and integrations, so you can use it almost anywhere there's a text box. It has generative text features, too.

Wordtune Wordtune helps you find plenty of wording alternatives to improve your text. When you input the text you want to check, you can easily browse synonyms, ask to rewrite entire sentences, and adapt the suggestions into a final draft.

ProWritingAid ProWritingAid is a direct competitor of Grammarly, offering plenty of statistics to help you track grammar, style, and spelling scores. One of the main advantages here is its lifetime plan, helping you leverage all these features without adding a new recurring bill.

4. AI apps for video generation and editing While full-blown video generation is still coming together, there's already a set of video tools that leverage AI to enhance video, remove backgrounds accurately, and even paint a few new images into each frame.

Descript Descript transcribes your videos into a script. Then, instead of using a timeline to trim the audio and video tracks, you edit the text script. As you do so, the video gets trimmed automatically. The rest of the editing works in a similar way, cutting the time to edit your talking head videos. When you connect Descript to Zapier, you can automate the work better suited for computers, so you can focus on the creative side of things.

Wondershare Filmora Wondershare Filmora has been around for a long time. Now, it also brings to the table a set of AI features that let you remove backgrounds, denoise low-quality clips, and improve sound quality. All this with the classic video editing user experience, so you'll never feel lost.

Runway Runway is a video magic wand. It has a set of interesting features that helps you generate video with AI, train your own AI models, and paint parts of frames using text prompts. The learning curve is very rewarding, and the app is growing at a great pace. Be sure to check it out.

5. AI apps for image generation An image is worth a thousand words, but you don't need so many to generate a beautiful one with AI. These image generators take a text prompt and deliver the results—and this can be anywhere between mind-blowing to nightmare-inducing. They're both hugely entertaining and highly useful.

DALL·E 3 DALL·E 3 is an image generator by OpenAI, the creators of ChatGPT. It's very simple to use—it runs in ChatGPT—and it produces interesting results, no matter if you've just started writing image prompts or are already a master. A great choice to begin exploring the realm of AI image generation. You can connect DALL·E to Zapier to do things like automatically create images from transcripts, chat messages, or any other apps you use.

Midjourney Midjourney is impressive. Anything you throw at it generates incredible results—even if sometimes they're slightly off the mark. The fact that you have to use Discord to access it feels unintuitive at first, but once you get the hang of it, you'll be spending hours turning your imagination into colorful pixels.

Stable Diffusion DreamStudio, powered by the Stable Diffusion AI model, is versatile and offers plenty of controls to help you prompt your way to the results you want. You'll have to invest a bit more time and learn how to control the model, but the reward is well worth it.

6. Voice and music generators YouTubers and other social media creators sometimes struggle to get original assets for their content. Good thing AI is here to (re)mix everything with AI voice generators and AI music generators.

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

Murf Short on voiceover talent? Murf offers over 120 voices in 20 languages to turn your text into voice. With simple controls to change pitch, emphasis, and pauses, you'll have a quick way to add narration to your latest social media post or training video.

Splash Pro Moving on to music generation, Splash Pro is one of the few apps that accepts a text prompt. I recommend you try out the Improve button before sending it—you'll get more interesting results. The engine generates up to five music samples per prompt. If you like one of them, you can either ask for variations or move on to creating the full song.

AIVA AIVA also deals with music, but takes a different approach. Instead of a text prompt, there are three ways you can start generating: • • •

By picking a style, from epic orchestral to cinematic cyberpunk By chord progression By uploading an audio reference as inspiration

Once ready, you can edit the result in a timeline editor, adding or removing instrument tracks as you feel your way into the final version.

7. AI apps for knowledge management and grounding AI is also a powerful search tool. When you connect it to your personal data, workspace, or second brain, it can find anything you need and put it into a natural language answer. Much better than sifting through your notes for hours, right? This is the gist of grounding: keeping an AI model close to your facts—not up there flying with the hallucinations.

Mem Mem uses AI to tag and connect the notes you take, so you don't have to spend time organizing them. You can just gather bits and pieces of information, store them, and trust that Mem's AI features will keep everything connected and organized. When the time comes to search for those notes, you can browse the automatic tags and use the search bar to find all you wrote about each topic that matters to you. Keep feeding your intelligent second brain by connecting Mem to Zapier, improving data transmission and opening up more automation opportunities.

Notion AI Q&A Notion is a strong workspace for organizing your knowledge, but even if you're disciplined, important pages will still fall through the cracks. Not anymore with Notion AI Q&A: grounded on your data, it generates answers and points you to the sources, revealing that lost insight you recorded in a meeting years ago. You can connect Notion to Zapier to streamline things even more.

Personal AI While Mem and Notion focus on notes and documents, Personal AI focuses on messaging. The data you upload into the app is turned into memory blocks. Then, whenever someone messages you, your personal AI generates a reply based on your data: you can edit the details or tap to send it right away. When you feel your AI model knows enough about you, you can turn on AI Autopilot, which will make others feel like they're talking to a ChatGPT-like version of you. You can help Personal AI learn about you by connecting it to Zapier and sending it memories from the apps where you spend the most time.

8. AI task and project management When you have a good plan, collaboration and execution is easier. AI can help getting more clarity on what to do, optimize processes, and help you cross every single task off your list.

Asana A project management heavyweight, Asana adds a wide range of useful AI-powered features. Smart goals use historical data to come up with better goals for the quarter. It identifies project risks and workflow blockers, so you can tackle trouble before it happens. And it provides answers to anything related to your projects, helping you gain more visibility into what is (or isn't) happening. You can automate Asana even more by connecting it to Zapier, so it can talk to thousands of other apps.

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

Any.do It's natural not to know the entire task lineup of a project. If you have trouble figuring out all the steps to get from zero to complete, Any.do generates tasks for you. Whenever you're writing them down, you can take a look at AI suggestions and click to enlarge your list. Connect Any.do to Zapier to automate all your task management processes.

BeeDone BeeDone is a quirky option directed at those of us who need a little excitement to get things done (I'm 100% guilty here). Based on principles put forward by Cal Newport and James Clear (among other productivity greats), the app turns boring tasks into little games, offering rewards whenever you move forward. It keeps track of your habits, offers an AI assistant to guide you, and you can spin the Task Roulette if you feel like tackling a random one from your list.

9. AI transcription apps and meeting assistants Taking notes in meetings may reduce your focus, so why not scrap that activity entirely? AI transcription/meeting assistant apps are great to turn voice into text, letting you browse it later. This will help you be more present in your meetings and, at the same time, be able to thoroughly analyze the transcription later.

Fireflies Fireflies is great to transcribe all your meetings, tracking the conversation topics along the way. It has its own bot called Fred that can handle summarizing the meeting's contents, generating text, and searching through your history to meet your query.

Airgram Airgram has all the core transcription features too. But it also adds AI data extraction on top of it, helping you extract bits of information, such as currencies, people, or places from unstructured data.

Krisp Krisp is actually an audio optimization tool that reduces background noise to help you sound better in meetings.

While you can use it to improve your podcast or other important recordings, you can also use it to assist you in your meetings by transcribing everything.

10. AI apps for scheduling No one loves the back and forth of setting up meetings, or any of the extra work tied to scheduling your work for the day. In an ideal world, you'd just look at your calendar, hop on meetings, and start your tasks at the marked date and time. We're getting closer to that, as AI can already take some trouble out of scheduling your work and your life.

Reclaim Reclaim does a great job protecting your habits, so you never miss your weekly fitness objectives or your reading targets. More than that, it'll defend the time you need to complete important tasks by rearranging your schedule.

Clockwise Clockwise is better for teams, promising to save you one hour per week—and to show you that it works, it'll schedule a one-hour break shortly after you start using it. You can adjust the settings to create your ideal day where work, breaks, and meetings live in harmony.

Motion Motion focuses on project management, helping you keep track of all the tasks you still have to complete. By tweaking each task priority, you'll be telling the AI engine when it should land on the calendar and how to place the other tasks around it.

11. AI apps for email and inbox management People spend about one month per year managing their work email inbox—no, I didn't make this up. With so many messages to follow up on, it can feel like email is driving you away from what really moves your work forward. You can start cutting the admin time here by using an AI email assistant to categorize, generate reply drafts, and keep everything up to date.

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

SaneBox SaneBox starts by scanning your inbox, understanding who you usually communicate with, which newsletters you receive, and what useless emails arrive every day. Based on that, it can help you delete unwanted emails, prioritize important messages, and add tags to keep things organized.

Mailbutler Mailbutler has the full suite of generative AI tools in the email compose window: Smart Compose, Respond, Summarize, and Improve. An extension for Gmail, Apple Mail, and Outlook, it extracts the contact information of people in your inbox, so you don't have to organize them manually. And, if you usually forget to note down your tasks, it analyzes all the emails you get and extracts any detected tasks into the sidebar.

EmailTree EmailTree is a solution for customer support teams, helping you organize your inbox, follow up on messages, and automate a few replies. It does this by processing the emails you receive and suggesting the follow-up action that makes the most sense. It's then up to you to trigger it.

12. AI apps for presentations and slide decks Your magnetic stage presence is what people came for, but they stayed because of your beautiful slide deck.

Clean and beautiful slides support your performance, keep your audience engaged, and help you drive in the points that you're making. The problem? Creating a solid slide deck can take a decent chunk of time, especially if you're starting from scratch. Can AI help?

Decktopus Decktopus is simple and fun to use. You enter what your presentation should be about, the target audience, and the objective. It'll put together a full presentation with text and slides, with plenty of magic buttons scattered around the user interface, helping you change images or generate text. Great for starting with a solid first draft and honing it into a powerful final version.

Beautiful.ai Beautiful.ai delivers on its name's promise. It simplifies the process of putting together a beautiful slide deck, with all the layouts and styles figured out. Pick the colors, find royalty-free images in the library, and start putting together your presentation. If you have data that changes frequently, you can update it by using sliders and tables. The values will then change dynamically on the presentation.

Slidesgo Slidesgo will let you pick the topic, writing tone, and a general template. AI generates the whole presentation for you, and from there, you can add your own content, customize each slide, and use AI to write, generate images, or generate a new slide.

13. AI apps for automation Each of these AI productivity tools is impressive on its own, but when you want to integrate AI into your daily workflows, that means connecting AI to the other tools you already use.

Zapier Zapier lets you automate faster by using natural language to create workflows that connect thousands of apps.

Describe what you want to automate, and Zapier will draft a workflow that you can easily customize. You can even use Zapier to build your own custom chatbot. Zapier connects to OpenAI, ChatGPT, Jasper, Hugging Face, and thousands of other apps, so you can combine the magic of AI with the power of automation to accelerate the work that matters most.

Other AI productivity apps If you like trying out more niche apps, here are some extra ones to keep an eye out for.

• • • •

3D modeling: Generate the third dimension with Spline AI, 3DFY.ai, and Meshcapade.

AI agents: Automate tasks with AI using AI Agent, AgentGPT, and HyperWrite Assistant.

Research: Take a deep dive with aomni, genei, and Consensus.

AI app builders: Quickstart your interface and databases with Softr, PowerApps, and AppSheet (or try an AI website builder).

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY®

Volume 10, Number 2, 2024

AI for productivity: the AI-powered you I'm a full-blown AI enthusiast. Even still, I like to think that these are merely tools. They save you time, spark ideas, and offer new angles. Remember to always use your judgment and keep your attention on the objective of what you're working on.

Another big risk: losing too much time feeding prompts to the AI, or generating so much output that it becomes difficult to edit, manipulate, and put together. Sharpen your cutting and editing skills to curb the excess, and you'll do great.

With all that in mind, it's time to enjoy. Try out these tools, and see why AI is the next big productivity leap.

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Article 12 – Using AI in the Office

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Products & Services & News PITA CORPORATE SUPPLIER MEMBERS Page 2 ABB advert “ABB MES for Pulp & Paper” Page 3 AFT MaxEdge600 refiner Page 4 AFT IoT data processing and reporting Page 5 Archroma Cartaseal® OGB F10 barrier coating Page 6 Valmet Low friction doctor blades Page 7 Valmet Valmet DNAe for process automation

PITA NON-CORPORATE SUPPLIER MEMBERS Page 9 Andritz HPC carbon capture technology Page 10 Voith SolarFlow Green suction roll cover

NON-PITA SUPPLIER MEMBERS Page 11 Kadant Page 12 Konecranes Page 14 SICK

VeriFlex™ oscillation system roll cleaning system X-series industrial crane series OD7000 displacement sensor

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Page 2 of 14

Products & Services

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

AFT EXPANDS MAXEDGE REFINER PRODUCT LINE The MaxEdge™ refiner family has a new member: Meet the MaxEdge600, capable of handling process capacities over 600 t/d.

With this latest design, AFT is expanding its product range to higher production rates, offering energy efficient refining technology combined with patented Finebar® segments.

Since launching the MaxEdge refiner, AFT has been continuously developing the refiner series by integrating more control and IoT features. With AFTLinx™ service, we are providing more comprehensive and faster support to ensure efficient and optimized refiner operation.

For more on MaxEdge Technology: https://ow.ly/FL3j50Reju4 .

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Volume 10, Number 2, 2024

AFT DEVELOPS IOT DATA PROCESSING AND REPORTING USING ISLET Aikawa Fiber Technologies (AFT) and Islet Group have collaborated to improve AFT's IoT data processing and reporting. Islet's team created a modern data and analytics platform using Microsoft Fabric, able to meet AFT’s current needs and expandable for the future.

AFT is a global supplier of equipment, engineered components, and IoT solutions for the pulp and paper industry. IoT refers to systems that are based on the automatic data transfer performed by technical devices and the remote monitoring via the Internet. With the right tools, information can be processed into an easily usable form - and with the help of a data network, automatic, real-time analytics can be used to organize massive amounts of data into usable key figures and snapshot reports.

From manual reporting to scalable architecture AFTLinx™ Service was developed as a diagnostic service that collects equipment-specific operating data to improve its productivity and performance - with assistance from AFT specialists who analyze the instrument information.

In the solution implemented by Islet, both current needs and future expansion of AFTLinx service were taken into account. AFT’s data platform and reporting will be expanded in stages by bringing in data from other operational systems. The architecture was implemented using specific Microsoft models, which have become industry standards.

"Our collaboration with AFT has been very inspiring. With the new data and analytics platform, AFT can now fully utilize the potential of IoT data and get real-time information that helps them make better decisions. The new platform not only meets AFT's current needs but is also expandable for future needs. This gives AFT the opportunity to scale and develop operations more flexibly. We are pleased to be able to support AFT's journey towards datadriven business." - Janne Anttila, CBO Data & Analytics, Islet Group.

Islet is a full-service provider Islet Group serves as AFT's Cloud Solution Partner (CSP) for IoT. The collaboration covers the information platform, reporting, analytics, and low-code application development, as well as the maintenance of the overall solution.

"Islet’s team of experts has created a modern and efficient data and analytics platform for us, enabling real-time reporting. Islet's role as a partner and their innovative approach has been crucial in the development and maintenance of the data platform, reporting, analytics, and overall solution. We are very satisfied with our collaboration with Islet and look forward to continuing working with them." – Timo Koivisto, VP, Technology, AFT.

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

ARCHROMA LAUNCHES CARTASEAL® OGB F10, A SUPERIOR PFAS-FREE BARRIER COATING FOR OIL AND GREASE APPLICATIONS Archroma, a global leader in specialty chemicals towards sustainable solutions, announces the launch of the latest innovation in their Cartaseal® portfolio, Cartaseal® OGB F10.

Cartaseal® OGB F10 is a superior water-based oil and grease resistant barrier coating that enables papermakers to provide high-quality and sustainable packaging by replacing fluoro based substances and polyethylene with a recyclable and repulpable coating. It is FDA and BfR compliant, making it suitable for the manufacturing of paper and board for food and nonfood contact.

Key features and benefits of Cartaseal® OGB F10 include: •

Superior oil and grease barrier: Offers unparalleled protection against oil and grease, ensuring the integrity and freshness of packaged goods. Its advanced formulation guarantees maximum resistance, providing peace of mind for both manufacturers and consumers.

•

Exceptional resistance even when folding: Provides superior oil and grease resistance (OGR) for folding box board and flexible paper packaging application, without compromising on performance.

•

Recyclable and repulpable: Facilitates easy recycling and repulping processes, contributing to a more sustainable packaging lifecycle. In addition, as it contains biobased raw materials, Cartaseal® OGB F10 supports brands and papermakers in their journey towards sustainability by minimizing reliance on oil-based substances.

"We are excited to introduce Cartaseal® OGB F10 to the market, our latest barrier solution that addresses key challenges in the packaging industry while upholding our commitment to sustainability," said Sameer Singla, CEO PP&C at Archroma. "With its unmatched oil and grease resistance, exceptional foldability, and sustainability features, Cartaseal® OGB F10 represents a significant advancement in packaging technology, empowering businesses to meet evolving consumer demands while reducing their environmental footprint."

Cartaseal® OGB F10 sets a new standard for packaging excellence, offering a comprehensive solution that prioritizes functionality, sustainability, and performance.

Archroma remains committed to driving innovation and sustainability across the value chain, empowering businesses to embrace greener practices and meet evolving consumer demands.

For information about Cartaseal® OGB F10 and Archroma's comprehensive range of packaging solutions, please visit https://www.archroma.com/innovations/cartaseal-ogbf10

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Products & Services

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

VALMET INTRODUCES SUSTAINABLE LOW-FRICTION DOCTOR BLADES TO REDUCE ENERGY CONSUMPTION AT THE DRYER SECTION OF BOARD AND PAPER MACHINES Valmet is introducing new low-friction doctor blades to respond to customers’ energy savings and decreased doctor blade usage sustainability requirements. The new low-friction doctor blades are suitable for dryer sections in all paper and board machines regardless of the original equipment manufacturer.

“We are always striving to help our customers diminish their environmental impact with our products. As their name suggests, the new low-friction doctor blades have a low coefficient of friction, leading to significant energy savings at the dryer section. The new blades also contribute to cleaner dryer cylinders and, thanks to increased blade lifetime, to less doctor blade usage,” says Pasi Viitasalo, Global Technology Manager for paper process parts at Valmet.

The new doctor blades are made of epoxy resin with glass and/or carbon glass fiber reinforcements. Special attention in research and development was paid to functional fillers for low friction.

Valmet has conducted a series of successful customer trials with the new blades. “Based on the data given to us by a European customer, the new doctor blades decreased the absolute electric consumption of dryer section electric motors by more than 26%. This results in annual energy savings that are as much as 950 MWh at that mill. When it comes to CO 2 emissions, the reduction is 190 ton per year,” says Viitasalo.

Valmet’s doctoring offering includes a complete portfolio of doctor blades, holders and other accessories.

Read more about Valmet doctoring solutions: Doctoring solutions for board and paper making

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

VALMET REACHES A SIGNIFICANT MILESTONE FOR AUTOMATION SYSTEMS BUSINESS BY LAUNCHING VALMET DNAE, THE NEXT GENERATION DISTRIBUTED CONTROL SYSTEM Valmet is taking process automation further by introducing the next-generation distributed control system (DCS), the Valmet DNAe. The fully web-based process control system comes with a new cybersecure system architecture, control software and hardware, engineering and analytics tools, helping customers improve efficiency, productivity, sustainability and safety of their operations.

“The new Valmet DNAe represents a major milestone in process automation. It provides a solid platform for moving towards more digitalized, autonomous operations, helping our customers thrive in the changing business environment. In the development of this new system, we have focused on usability and performance, with a modular approach that enables upgrade paths also from our previous system generations,” says Emilia TorttilaMiettinen, President, Automation Systems business line at Valmet.

The launch is a major step in the company’s roadmap for growing its automation business further and in bringing unrivalled future-proof automation solutions to a wide base of process industries globally. With this new system, the company will have an excellent opportunity to continue expanding the footprint of its automation systems business worldwide.

Designed to support the work of all process automation user groups Valmet DNAe is developed with a design philosophy to empower people to perform and collaborate better across the organization. The system provides a common user interface for controls, analytics, configuration, and maintenance. Intuitive workflows simplify operations and enable users to manage larger process areas with less effort. Advanced analytics tools enable turning real-time and historical data into actionable insights. Additionally, the new web-based configuration environment provides a unified environment for all engineering needs from office to field, enhancing flexibility in configuration and maintenance tasks. These features are designed to increase the operational efficiency of our customers.

A high-performing DCS advancing digitalization and autonomous operations Valmet DNAe has been engineered for demanding process control, emphasizing performance and availability. The system empowers users to seamlessly run industrial applications on-premise, at the edge server, or in the cloud. It features a scalable redundant data platform, granting easy and controlled access to all data. The system architecture is cybersecure by design, with role-based access control, authentication, audit trail and encryption mechanisms for proactive prevention of cyber threats. With smooth OT/IT (Operational technology / Information technology) connectivity through secure communication interfaces with external systems, Valmet DNAe establishes a robust base for advancing digitalization and autonomous operations.

Step-by-step upgrade paths for cost-efficient system evolution In alignment with Valmet’s lifetime systems compatibility promise, a leading principle in Valmet DNAe’s development has been to make it easy for Valmet’s existing process automation customers to benefit from the latest technology.

The new Valmet DNAe Distributed Control System shares its web-based user interface, analytics tools, and common hardware with the previous generation of Valmet DNA. Page 7 of 14

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Additionally, Valmet also introduces a new modular controller and a single-channel I/O as new hardware options for Valmet DNAe. “The lifecycle approach enables flexible step-by-step upgrade paths for a sustainable and cost-efficient system evolution. We have already delivered over 200 new generation user interface upgrade projects to various industries. The first full Valmet DNAe systems have also been successfully delivered to customers. An important part of Valmet's strategy is to cover a wide base of global process industries in the automation business, and with this new system, we will have an excellent opportunity to continue expanding the footprint of our DCS business globally,” says Torttila-Miettinen.

Read more: https://www.valmet.com/automation/control-systems/dnae

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

ANDRITZ EXPANDS CARBON CAPTURE OFFERING WITH HPC TECHNOLOGY International technology group ANDRITZ has expanded its technology portfolio for carbon capture through a licensing agreement with US-based Eickmeyer & Associates, Inc. The cooperation gives ANDRITZ access to Eickmeyer’s hot potassium carbonate (HPC) technology known under the brand name CATACARB®. It complements the technologies used by ANDRITZ to offer complete carbon capture plants to a wide range of industries.

ANDRITZ’s technology portfolio already includes amine-based absorption/desorption and membrane separation. The addition of the state-of-the-art CATACARB process, which has been proven in various applications around the world, will enable ANDRITZ to respond more flexibly to individual customer requirements. Based on its extensive experience in designing flue gas treatment systems, ANDRITZ is well positioned to efficiently integrate carbon capture units into existing and planned flue gas treatment plants.

“We are very pleased to enter into this cooperation with Eickmeyer. Both our companies are committed to advancing carbon capture technologies and helping industries transition to a greener future,” says Harald Reissner, Senior Vice President of Clean Air Technologies at ANDRITZ. “The HPC technology perfectly complements our product portfolio and helps us to serve an even broader customer base with solutions tailored to their needs.”

Gary Buckholz, CEO and President of Eickmeyer & Associates, Inc., adds: “Industries need solutions that enable them to maintain competitive operations in a carbon-constrained world.

This partnership will further promote the use of our leading-edge technology that aligns with global sustainability goals.”

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

VOITH: BIO-BASED SOLARFLOW GREEN SUCTION PRESS ROLL COVER ENSURES MORE SUSTAINABLE PAPER PRODUCTION With SolarFlow Green, Voith is setting yet another standard for paper manufacturing products made of renewable raw materials. The suction press roll cover is certified according to the internationally recognized DIN CERTCO standard for bio-based products. The cover combines all the advantages of the proven SolarFlow technology while simultaneously reducing the carbon footprint. This innovation is in line with Voith’s long-standing commitment and ambitious goals to promote sustainability in both paper manufacturing and its own production.

SolarFlow Green is a premium polyurethane roll cover and boasts a maximum void volume that remains constant over a long operating period.

“Achieving a high dry content is extremely important to us. Thanks to SolarFlow Green, we were able to implement our customized surface design, resulting in a high void volume and maximum dewatering in the press section. We achieve this using resourcefriendly, sustainable materials. It’s a winning combination for us.” Robin Linney, Palm Paper plant manager at King’s Lynn The polyurethane material with its biobased component also gives the press roll cover a high degree of stability that can withstand extreme nip conditions. This enables not only fast machine speeds with a high dry content but also low energy consumption at the same time.

“With SolarFlow Green, we are the first manufacturer with the ability to offer our customers a suction press roll cover made of biobased materials that has been certified

by DIN CERTCO. We look forward to working together with our customers to make paper production even more sustainable and resource-friendly in the future.” Dr. Christina Bauer, Global Product Manager for Press Roll Covers at Voith.

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

KADANT SOLUTIONS LAUNCHES THE VERIFLEX™ OSCILLATION SYSTEM FOR ROLL CLEANING Kadant Solutions, a division of Kadant Inc. (NYSE: KAI), announced the launch of the VeriFlex™ oscillation system which provides compact and reliable oscillation for the VeriLite™ roll cleaner assembly. The VeriFlex oscillation system enhances roll cleaning effectiveness and extends blade life in a variety of industrial processing applications.

“Highly effective roll cleaning is critical to performance in industrial applications where installation space is often limited,” stated Marcelo Deboni, applications and product manager for Kadant Solutions. “From our extensive doctoring and roll cleaning experience, we know how much more effective roll cleaning can be when a blade is oscillated. The VeriFlex oscillation system reduces the space requirement of conventional oscillators by use of our proven pneumatic Varimatic™ 500 oscillator along with an innovative flex element design.”

Design simplicity is a key feature of the VeriFlex oscillation system, which uses low-pressure compressed air and eliminates the need for external controls. The addition of the VeriFlex oscillation system provides enhanced roll cleaning through oscillation, particularly in more challenging or critical roll cleaning applications.

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Products & Services

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

KONECRANES LAUNCHES SMART, STANDARD IN INDUSTRIAL CRANES

CONNECTED

CRANE:

SETTING

A

NEW

Konecranes today launched its flagship Konecranes X-series industrial crane, the successor to its popular CXT model with a new compact design and safe, reliable technology that — thanks to its wireless upgrade capabilities — can adapt to customer needs now and in the future.

"The new flagship crane builds on a quarter-century of success for the CXT, which was launched in 2000 and to date has sold well over 100,000 units globally," said Jussi Luokomaa, Product Manager, ISE EMEA, Konecranes. "We expect to see good demand for the Konecranes X-series across multiple industries including general manufacturing, making it a core product for the company for years to come."

Connectivity for enhanced performance The Konecranes X-series stands out not only for its lean, state-of-the-art electrical architecture but also for its connectivity. Designed to be safe, compact and reliable, it can flexibly adjust to future customer requirements, maximizing the investment's value. This adaptability is enabled by smart, connected components, allowing seamless software upgrades "over the air"— a first in the standard crane industry.

Customers have the option to initially purchase the crane and easily upgrade to additional Smart Features, enabling seamless incorporation of functionalities as business needs evolve.

Additionally, troubleshooting and software updates can be conveniently conducted from floor level, minimizing potential downtime. With a focus on user-friendly design, the crane features a new ergonomic CANMAN radio with an integrated display, providing operators with freedom of movement and essential information at their fingertips, while also offering stepless control for safer and more precise lifting experiences.

Equipped with TRUCONNECT Remote Monitoring, the Konecranes X-series provides vital insights into crane usage and operation. This data, combined with maintenance information, empowers businesses to make informed decisions regarding maintenance schedules, safety and productivity enhancements. This innovation in connectivity underscores Konecranes' commitment to enhancing productivity, reducing downtime, and leading in digital services, reflecting the growing importance of connected equipment in material handling. To date, Konecranes has 53,600 pieces of connected equipment globally.

A great crane needs a great hoist What further distinguishes the Konecranes X-series crane is the new Konecranes S-series low headroom hoist. This compact hoist features excellent approach dimensions and smooth stepless lifting with a load-dependent lifting motor, enhancing the user experience and reducing cycle times. The use of strong, lightweight, durable synthetic rope improves safety and handling compared to steel wire rope.

Commitment to Sustainability The X-series shows how Konecranes is shaping next generation material handling for a smarter, safer and better world. Through sustainable design and material choices, such as a more compact and efficient motor and synthetic rope, the X-series drives efficiency improvements. Features like a thrust rocker reduce steel consumption, and an optimized belt drive reduces wear, minimizing the overall environmental impact. The optimized design, with synthetic rope and guide rollers, enhances performance and extends equipment lifespan Page 12 of 14

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Volume 10, Number 2, 2024

while also reducing maintenance needs. Additionally, the implementation of inverter lifting technology ensures precise motor speed control, minimizing energy waste. With the X-series, Konecranes delivers a reliable solution while having an emphasis on sustainability. The Design for Environment (DfE) approach guided product development, aiming to minimize environmental impact throughout the product lifecycle.

A strong focus on customers and commitment to business growth and continuous improvement make Konecranes a material handling industry leader. This is underpinned by investments in digitalization and technology, plus our work to make material flows more efficient with solutions that decarbonize the economy and advance circularity and safety.

Konecranes is now taking orders for the crane and expects the first deliveries to begin in Q4 2024 in Europe, Middle East and Africa, with deliveries in other regions to follow later.

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

SICK OD7000 PRECISION SENSOR FOR DEMANDING MICRON MEASUREMENTS Developed for ultra-high precision in the micron range, SICK’s innovative and compact OD7000 displacement sensor reliably measures tiny distances in consumer goods and packaging applications cost-effectively. Comprising a separate controller and sensor head that are both extremely compact, the OD7000 is purpose-built to fit into the tightest machine spaces.

The SICK OD7000 is a 1D laser distance sensor that measures differences in height accurately even on challenging materials. Its tiny light spot precisely targets the object and outputs a precise measurement regardless of the colour or surface material and even measures curved surfaces accurately.

Challenging Applications The SICK OD7000’s chromatic confocal technology enables highly-precise measurement on a wide range of materials, from black to transparent, diffuse, reflective, and even curved surfaces. The SICK OD7000 can inspect, for example, whether a target object is smooth or is positioned correctly. It can measure holes or check if a material has the desired thickness.

Using one sensor head, it can measure up to three very thin layers simultaneously, even if the material is transparent.

It is therefore ideal for precise measurement duties in packaging, food and beverage/consumer goods applications, even for challenging applications such as detecting deviations in thin, embossed films, measuring the thickness of dark-coloured glass, or the thickness of multi-ply toilet and tissue papers.

Meticulous Development “SICK has worked hard and taken some time to develop the OD7000 meticulously,” explains Nick Hartley, SICK’s UK Product Manager for Distance Measurement. “The result is a highlyprecise instrument that offers manufacturers with some of the most challenging measurement requirements a real opportunity to output precise data, without complicated set-ups or superexpensive equipment.

“Using a 1D laser distance sensor with the performance of the OD7000 enables machine integrations to achieve high levels of material inspection and thickness determination, that might otherwise only be possible with much more expensive equipment.”

Easy to Set up and Install Two controller types both with EtherNet interface and a choice of 3 sensor heads span measurement ranges of 600μm, 4mm, and 10mm with corresponding resolutions of 25nm, 180nm, and 400nm.

The OD7000’s engineering tool has an easy-to-use graphic interface that allows the user to visualise the installation and configure the controller rapidly, while additional settings are available for more advanced applications. The OD7000 also offers serial RS-232 / RS-422 or Ethernet TCP/IP interfaces as standard.

One of the OD7000’s controllers offers the further cost and space-saving benefit of being able to define an encoder input as a trigger for the output of measurement data, so that a separate encoder is not required as part of the machine set-up. The SICK OD7000 has a 10 kHz maximum sampling frequency, meaning all variants offer the same high performance, enabling stock control to minimise inventories.

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Products & Services

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FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

CALENDAR OF EVENTS – 2024 PITA TRAINING COURSES Ian Padley

Modern Papermaking

17-18 Sept.

Jo Thorne

EPR Permits

16 Oct.

Mark Smith

Introduction to Wet End Chemistry

12-13 Nov.

Papierzentrum Gernsback

Fundamentals of Papermaking

26-28 Nov.

INTERNATIONAL CONFERENCES & EXHIBITIONS PRIMA 2024

Vienna, Austria

2 Sept.

Specialty Papers Europe

Vienna, Austria

3-4 Sept.

Paper Arabia

Dubai, UAE

3-5 Sept.

Paper Middle East

Cairo, Egypt

8-10 Sept.

ProPaper

Dubai, UAE

17-19 Sept.

MIAC

Lucca, Italy

9-11 Oct.

ProPaper

Dar Es Salaam, Tanzania

7-9 Nov.

Paper Middle East

Jeddah, Saudi Arabia

18-20 Nov.

Technologie Kring

Apeldoorn, Netherlands

20-21 Nov.

Tissue World

Istanbul, Türkiye

20-21 Nov.

DITP

Postojna, Slovenia

20-21 Nov.

Paperex South India

Chennai, India

5-7 Dec.

Page 1 of 1 Events

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024 Installations The following pages contain a summary of the various installations and orders from around the world of papermaking, wood panel and saw mills, and bio-power generation, received between the start of March 2024 and the end of June 2024.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Installations

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Adara Pakkaus Valkeakoski Finland

SUPPLIER Valmet

Africaine Paper Mills Rouiba near Algiers Algeria

Toscotec

Al Dhafra Paper Manufacturing Company Abu Dhabi United Arab Emirates

Valmet

Alkim Kagit Kemalpasa Izmir Turkey Anagren Pack Uzbekistan

Runtech

Andhra Paper Limited Kadiyam Mill Andhra Pradesh India Anon Asia-Pacific region

Valmet

Bellmer

Valmet

Page 2 of 10

ORDER DESCRIPTION To supply a Valmet IQ Warp Control system and an IQ Moisturizer, which is used to correct all kinds of warping, decrease cracking tendency and optimize glue consumption (Corrugator).

To supply new rewinder line to process near 2,800mm width parent reels using two unwind stands; also a complete service package with erection supervision, training, commissioning, and start-up assistance.

To deliver dewatering element ceramics made of wear-resistant material offering long and trouble-free operation and optimized dewatering in the forming section.

To deliver a vacuum system rebuild (PM2).

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To supply a new white top line, capacity 120tpd, to fit their 4.25m testliner and fluting machine.

To deliver a new tissue production line.

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To supply both a papermaking line and a paper machine rebuild. One order includes a complete papermaking line from stock preparation to reel and winders, a comprehensive automation solution package as well as spare parts and consumables packages. The other order includes a paper machine rebuild with automation and services. Both will produce uncoated woodfree grades.

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Anon Kyushu area Japan

SUPPLIER ABB

Anon Paper Mill Germany Arauco global operations

PCF Maintenance

Arauco Trupan Chile

Sunds Fibertech

Assocarta Italy

AFRY

Cartiera del Vignaletto Zevio Tissue Mill Verona Italy Cartiera Fornaci Fagnano Olona Italy Cordenons Italy

Toscotec

Crown Paper Mill Dammam area Saudi Arabia

Valmet

DL E&C Co., Ltd. Yeosu South Korea E.ON Steven’s Croft biomass power station Lockerbie Scotland

BMH Technology Oy

Opturion

ABB

Sael

Valmet

Page 3 of 10

ORDER DESCRIPTION To supply a L&W Autoline with modules to measure Air Permeance, Thickness, Tensile, Burst P Lower and Grammage.

The team is also providing two standalone instruments for tensile and tear, and a lab management system (LMS).

To supply two press felt cleaners with moisture and permeability measuring.

To build, commission and support a supply chain optimisation solution, based on its proven optimisation platform.

To supply a complete resin dosing and injection system, including automation and startup.

To define a decarbonisation strategy for the pulp and paper sector that is in line with EU framework, country-specific conditions, and technological advancements.

To supply upgrade of the cogeneration plant and air systems of the mill’s PM4 and PM5.

Placed an order for L&W Autoline paper testing equipment.

To rebuild the coating machine and install a new soft calender, and reconstruct the electrical control system of Coater 2.

To supply an Advantage DCT 200 tissue line, including an extensive automation package, flow control valves and Industrial Internet solutions.

To deliver a biomass handling system to a combined heat and power (CHP) plant.

To deliver a boiler rebuild.

Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Ence Navia Pulp Biofactory Spain

SUPPLIER BTG

Five Continents Special Paper Hanchuan Hubei Province China GHC Jinjiang Quanzhou City China

A.Celli

Göteborg Energi AB Riskulla site Mölndal Sweden

Valmet

Grigeo Baltwood Lithuania

Sunds Fibertech

Guangxi Xiangsheng Household Material Technology Co, Ltd. Xiangsheng High-End Green Household Furnishing Industrial Park China

Siempelkamp

A.Celli

Page 4 of 10

ORDER DESCRIPTION Have entered into a comprehensive three-year lifecycle and maintenance agreement to maintain the full functionality of its instruments.

To supply a paper rewinder to process T-paper and highstrength corrugated paper.

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Has partnered with Reicofil to integrate a winder, slitter and packaging system into a spunbond nonwoven line supplied by Reicofil.

To provide a 50MW pellet-fired heating plant, which will be integrated into the existing district heating system. The delivery includes a boiler system with wood pellet storage and milling, wood dust dosing, and a flue gas cleaning system featuring Valmet's Bag House Filter and Selective Catalytic Reduction (SCR) system.

To supply a major upgrade of the press in line number two.

The installation will include new Columns and sleeves, Cylinder renovation with Pistons, Press table guides, along with the delivery of a new top table and heating platens. The Multi Opening Press Line No.2 has a pressing format of 5’7” x 18’.

To supply a new super strength particleboard line. The “super strength” feature of the new particleboard line is characterised by the use of elongated flakes in the core layer, which significantly enhances bending strength. This technological advancement will support the production of durable and high-quality particleboards tailored to meet diverse market demands.

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE lndah Kiat Pulp & Paper TBK Karawang Jawa Barat Indonesia

SUPPLIER Andritz

Ittihad Paper Mill Abu Dhabi UAE

Valmet

Klabin global

WEG

Koskisen Sawmill Järvelä Finland

MiCROTEC

Kuantum Papers Limited Punjab India

Valmet

Page 5 of 10

ORDER DESCRIPTION To supply a complete old corrugated containers line including a reject treatment system with design capacity of 2,000bdmt/d, to process a mixture of OCC, mixed waste and up to 30% American OCC as raw material to produce testliner.

To deliver a comprehensive selection of field services both prior to and during the Ittihad Paper Mill’s annual shutdown.

Valmet will perform a machine alignment check as well as inspection and maintenance of several paper machine sections and parts such as Valmet Disc Filter, OptiFlo Gap headbox, Valmet SymBelt Shoe Press Roll, OptiSizer Film, OptiCalender Hard and OptiWin Drum two-drum base winders.

Valmet will also be responsible for the planning and management of the shutdown.

To supply an IoT solution for asset management of a paper machine, including intelligent WEGscan sensors, and asset management software WEG Motion Fleet Management (MFM).

To supply a new log sorting line with a multi-sensor scanner that utilizes laser, colour, and X-ray channels to provide a highprecision real 360° shape of the log with a wealth of data for log sorting and cutting optimisation.

To deliver a recovery boiler upgrade (for the older of the two boilers). The delivery consists of key pressure parts, such as the lower furnace rebuild and a new economizer replacing the cascade evaporator, new Valmet design airports, liquor guns, and other boiler related auxiliaries and associated systems.

Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Lecta Zaragoza Mill Spain

SUPPLIER Valmet

Levent Kâğıt ve Tic. A.S. Paper Mill Kemalpasa Izmir Turkey Lignatherm AG Küssnacht am Rigi Switzerland Middle East Paper Company Jeddah Saudi Arabia

Runtech

Middle East Paper Company Jeddah Saudi Arabia

Voith

Metsä Group ‘Muoto Production Plant’ Rauma Finland Metsä Group ‘Muoto Production Plant’ Rauma Finland

A-insinöörit Suunnittelu Ltd

Metsä Group ‘Muoto Production Plant’ Rauma Finland

SRV

Metsä Group ‘Muoto Production Plant’ Rauma Finland Metsä Group Äänekoski bioproduct mill Finland

Valmet

Andritz

AFRY

Elomatic

Andritz

Page 6 of 10

ORDER DESCRIPTION To upgrade the fibreline including a new log feeding system and a Valmet Chip Cutter for wood handling, a cooking modification with Valmet OptiBin solution and Valmet Chip Pumps, a new screening room, an additional washing stage with a new Valmet TwinRoll Press, and an Oxygen Delignification stage modification.

Signed a 5-year care agreement for the vacuum system.

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To supply a pressurised refining system for a new insulation board production plant.

Signed a contract for detailed engineering services and project management consultancy concerning MEPCO’s upcoming paper machine project.

Has signed an engineering and supply contract to manufacture, supply, and supervise the installation of a new containerboard machine (PM5).

Has been selected as the plant construction design partner for the project.

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To be the main design partner for the design of the factory structure and facilities and will assist in the cost planning and construction schedule.

To act as project management contractor for the construction project and will also be the engineering design partner for the building services.

To act as process engineer for the fibre product in the project.

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To build a demo plant for developing new lignin products.

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Metsä Group Kemi Finland Metsä Tissue Project ”The Future Mill” Mariestad Sweden

SUPPLIER Fortum Recycling & Waste

Moorim Paper Moorim Ulsan, Moorim Jinju & Moorim Daegu Mills South Korea Munksjo Caieiras Ltda Brazil

Voith

Nordic Paper various sites in Sweden Norway and Canada

AFRY

Northwood Tissue Ltd. Chesterfield Derbyshire UK Novopan del Ecuador Quito Ecuador

Andritz

Papelera Reyes Lima Peru

Voith

Valmet

Runtech

Dieffenbacher

Page 7 of 10

ORDER DESCRIPTION To dismantle and demolish the old pulp mill which closed in Autumn 2023.

To provide two complete tissue converting lines including packaging solutions; the order follows the earlier announced delivery of a Valmet Advantage DCT 200 tissue making line to the same mill. Both deliveries are part of Metsä Tissue’s expansion and modernisation project “The Future Mill”, aiming at world-class environmental and operational performance.

To supply a range of fabrics and sleeves; the order was placed through the Voith Paper Webshop.

To deliver ropeless tail threading (to offer more fluent and faster tail threading and improved operator safety).

To supply the digital solution AFRY PaperLine to replace the existing production support system with a new MES-system; this includes migration of existing data to the new system and start-up.

To supply a new PrimeDry Hood and an air system for a tissue machine rebuild.

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To deliver a new 30MW energy plant equipped with advanced reciprocating grate technology to combust waste wood, including a big crusher and rechipper, both designed to reprocess waste wood for combustion.

To supply clothing for the company’s third tissue paper machine, including the forming fabrics and the press felts.

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Papresa Errentería Paper Mill Spain

SUPPLIER Valmet

Papeteries du Cotentin Orval sur Sienne Mill Normandy France Papierfabrik Palm Aalen & Wörth Mills Germany PT. Cikarang Listrindo Tbk Babelan Indonesia PT. Pabrik Kertas Indonesia Surabaya Indonesia

Toscotec

Roseburg Forest Products Dillard Oregon USA Shandong Jin Tian He Paper Co., Ltd China

IMA Schelling Group

Sichuan Fengsheng Paper Technology Leshan City Sichuan province China Silvan near Diyarbakir Southeast Anatolia Region Türkiye

A.Celli

Valmet

Valmet

Andritz

GAW

Andritz

Page 8 of 10

ORDER DESCRIPTION To deliver a Bale Tester which is a reliable and real-time measuring system for recovered paper, providing an opportunity to reduce operational costs and to improve the recycled fibre line performance. The Valmet Bale Tester measures the moisture and other contaminants, such as plastic and ash of the recovered paper, after which the information is automatically stored in the mill’s database, analysed, and further utilised for optimising the production process.

Purchased a steel Yankee dryer and a complete highperformance steam and condensate plant (PM3).

Signed a one-year Performance Agreement to further improve the performance of PM5 and PM6.

To add biomass co-firing to coalfired circulating fluidised bed boiler (power supplier).

To rebuild two existing OCC (old corrugated containers) lines, increasing capacity to increased to 500t/d.

To install automated panel cutting and packaging solution (MDF plant).

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To supply coating colour preparation and working stations to the new PM13 for production of food grade folding boxboard.

To supply a Film Size Press and Suction Press Rolls for the new machine (PM1).

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To equip this hydropower plant with four 40MW turbines, four generators, associated hydropower plant equipment, and a 154kV switchyard system.

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Sioen Technical Felts Liège Belgium

SUPPLIER Andritz

Siteks Sismanlar Tekstil San. ve Tic. A.S Tekirdag Turkiye

Andritz

Södra Cell Mönsterås Mill Sweden

Valmet

Södra Mörrum pulp mill Sweden Södra Cell Värö Pulp Mill Sweden

Andritz

Solidus Solutions Bad Nieuweschans Netherlands Stora Enso Oulu Mill Finland

PCF

Stora Enso Oulu Mill Finland

Enersense

Suzano S.A. (site not yet decided)

Spinnova

Sylvamo Mogi Guaçu SP Brazil Waraq Paper Manufacturers Dammam Saudi Arabia

Hergen

ABB

Caverion

PCF Maintenance

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ORDER DESCRIPTION To add a complete needlepunch line for production of technical fabrics used mainly in industrial applications such as pipe lining (CIPP), acoustics and filtration.

To supply a complete needlepunch line for production of insulation felt products in the automotive and construction sectors.

To deliver a new digester top separator that will lengthen the lifespan of the digester originally installed in 1979.

To upgrade flue gas treatment systems.

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To implement optimisation control; delivery includes extended functionality for the ABB Ability™ System 800xA® distributed control system (DCS) through the implementation of advanced process control (APC) for the bleaching process.

To supply one tail cutter with rotating knife.

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To deliver work related to process electrics and instrumentation installations; the work is related to the project, where one of the production lines in the Oulu mill is converted into a consumer packaging board line.

Has made an agreement with Andritz Oy for the mechanical installation works of a new debarking line.

Has signed a Letter of Intent (LOI) regarding a potential new production facility for woodbased SPINNOVA® fibre (preliminary capacity 20,000tpy).

To supply a rewinder, which will be installed on its PM3.

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To deliver three dryer fabric cleaners (PM3), and two dryer cleaners (PM1).

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Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

COMPANY, SITE Wisewoods Co Ltd Khao Yoi province of Phetchaburi Thailand Yueli Machinery Taiwan Zhejiang Jiding New Material Technology China

SUPPLIER Dieffenbacher

ORDER DESCRIPTION To supply a CEBRO MDF plant.

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PCF

To supply two HP water tail cutters for dryer section.

To supply a paper rewinder to process decoration paper master rolls.

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A.Celli

Page 10 of 10

Installations

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PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Research Articles Most journals and magazines devoted to the paper industry contain a mixture of news, features and some technical articles. Very few contain research items, and even fewer of these are peer-reviewed.

This listing contains the most recent articles from three of the remaining specialist English language journals alongside one Korean journal and one Japanese journal, all of which publish original peer-reviewed research: • • • • •

IPPITA JOURNAL (Peer-reviewed and other) JAPAN TAPPI JOURNAL (English abstract only) JOURNAL OF KOREA TAPPI (English abstract only) NORDIC PULP & PAPER RESEARCH JOURNAL TAPPI JOURNAL

Notes: 1. JAPAN TAPPI JOURNAL is a members-only journal that contains excellent research articles – abstracts are in English but articles are in Japanese.

2. JOURNAL OF KOREA TAPPI is an excellent open-access research journal – abstracts are in English but articles are in Korean.

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry.

Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

Page 1 of 5

Research Articles

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

IPPTA JOURNAL, Vol.36(1), 2024 1.

Achieving New Benchmarks in Field of Energy Efficiency and Sustainability in Pulp & Paper Industry 2.

AI-Ml Driven Control Of Effluent Treatment Plants For Sustainable Pulp And Paper Mill Operations 3.

Carbon Neutrality And Emissions Reduction 4.

Energy Efficiency & Optimization 5.

Energy Efficiency in Chilled Water System & Compressed Air System 6.

Energy Saving Efforts And Results In TNPL 7.

Fostering energy and environment through de-carbonization by agro residue 8.

Fostering the future of energy and environment in Seshasayee Paper and Boards Ltd, Unit: Erode 9.

Green Energy A Reality For Integrated Pulp And Paper Mill 10. Improvement in Energy Efficiency and Energy Conservation Initiatives at Khanna Paper Mills Limited 11. Innovation in Effluent Colour Reduction and Generation of Vermi Compost from Lignin Sludge 12. Innovative Power Enhancement Scheme In Extraction Condensing Steam Turbines of Cpp In Orient Paper Mills 13. New MCA Generator 14. Ozone Oxidation for brighter Pulp & Blue Water 15. Potassium Hydroxide Pulping of Rice Straw 16. Revolutionizing Green Practices: Role of Bio-Methanation Technology’s Transformative Role in Pulp & Paper Mills for net zero emissions and sustainable future 17. Saving Energy through Synergistic Innovation with Digitalization 18. Significance & Role of Biotechnological Applications in Environmental & Energy Sustainability in Pulp & Paper Industry – An Overview 19. Solutions for a carbon neutral pulp and paper production 20. Sustainable Practices for Environmental Stewardship 21. Trash to Treasure – Bio-Cng from Recycled-Based Paper Mill Waste 22. Valorization of Pulp and Paper Mill Bio-Residues to Biochar for Environmental and Business Sustainability in Totality JAPAN TAPPI JOURNAL, VOL.78(3), March 2024 Automation Technology and IoT/DX 1.

Report of the 47th Automation Technology Seminar 2.

Digitization Made Innovative Operation Management ―The Need to Digitize Timeseries in Formation 3.

Recent Generator Online Insulation Diagnosis 4.

Automated Plant Operation Using AI that Imitates Manual Operation 5.

A Small Scale Advanced Control Solution to Utilize Sensors and Analyzers Topics & Information 6.

Case Study：Degitalization of Raw Material Yard―Degital Data Utilization and Visualizaiton by BI × IoT Technology 7.

DX Brought by Control AI ―Winner of the Prime Minister’s Award 8.

Corporate Profile & Product Information（50）AQUAS CORPORATION Research Report 9.

Characteristics of CNF-reinforced PA6 for PBF 3D Printers

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Research Articles

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

JAPAN TAPPI JOURNAL, VOL.78(4), April 2024 1.

‘Mpression Smart Motor Sensor’ Lecture on Predictive Maintenance Solution: Services for Low-voltage Three-phase Cage Induction Motors 2.

NDT Assessment of Boiler Pipe’s Wall Thinning Using 3D Scanner: Current Technology and Future Trajectory 3.

Paralign Revolutionary Roll Parallelism Measurement Technology, Enables Measurement with Higher Accuracy Than Previously Possible ―Introduction of Roll Parallelism Measurement Technology Using a Laser Ring Gyro 4.

Age of Renovation Somay-Q will be Responsible for 5.

Traditional and State of the art cost reduction approach in abroad -- 5th generation automated paper testing machine 6.

The latest information of softness measurement by acoustic and stress 7.

Performance evaluation of low attracting insects between sunlight type LEDs, high CRI LEDs, and white LEDs. 8.

Key Points for Manipulation of Several Data and Effective Measures Concerning with Pest Management 9.

Report on the Results of the Fiscal 2023 Follow-up Survey on “JPA’s Carbon Neutrality Action Plan” and Related Information on Measures against Global Warming in the Japanese Paper Industry 10. Creation of polycaprolactone–wood pulp composites and the evaluation of degradability in soil 11. Introduction of Research Laboratories（156）Laboratory of Plant Biomass Chemistry, Faculty of Agriculture, Niigata University 12. Research Report（Original Paper）- Creation of Poly caprolactone-wood Pulp Composites and the Evaluation of Degradability in Soil 13. Pulp and Paper Mills in Japan（105）Ohe Mill, Marusumi Paper Co., Ltd JAPAN TAPPI JOURNAL, VOL.78(5), May 2024 Biorefinery and Plastics substitution 1.

Pine-based Resin Use in Paper for Sustainability 2.

Valmet’s Biorefinery Technologies for Products from Wood-resources towards Decarbonization 3.

Effective Treatment of Organic Liquid Waste Such as Shochu Liquid Waste ―Introduction of Miyazaki Model 4.

Development of the Bio-Asphalt Mixture Utilizing Kraft Lignin 5.

Development of Cellophane Recycling Technology 6.

Paper Packaging Materials to Substitute for Film Topics & Information 7.

Valmet’s New Recovery Boiler and Effective Utilization of Existing Boilers After New Recovery Boiler Construction 8.

Our Efforts to the Energy Plants in the Pulp and Paper Industry 9.

Anti-Scaling Technique of Black Liquor Evaporator Using High Power Ultrasonic Technology 10. Confront the Surge in Energy Prices ! An Organizational Approach to Maximize the Value of Factory Energy Management Systems 11. Application of Superheated Steam Drying to Pulp and Paper Industries 12. Research Projects of Universities and Government Research Institutes Research Report 13. Safety Assessment of Bamboo-derived Cellulose Nanofibers in Food for Healthy Adults：A Long-term, Open-label Ingestion Trial

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Research Articles

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

14. Pulp and Paper Mills in Japan（106）Mishima Mill, Tokushu Tokai Paper Co., Ltd. JOURNAL OF KOREA TAPPI, Vol.56(1), February 2024 1.

Determinants of Pulp Producer Prices in Korea: Focused on Exchange Rate and Import Prices 2.

Interpretation of Carboxymethylation in Cellulose Pretreatment by 1H-NMR Spectroscopy 3.

A Study on Production of Soil Covering Materials Using Waste Paper and Citrus Pomace 4.

Manufacturing of Solid Substrates Using Waste Paper Fiber and Biochar 5.

Changes in Properties of Various Deep Eutectic Solvents According to Water Mixing Ratio and Temperature Changes JOURNAL OF KOREA TAPPI, Vol.56(2), April 2024 1.

Dynamic Causal Relationship between Imported Pulp and Wood Chip Prices 2.

Effect of Mechanical-Chemical Pretreatment at Room Temperature on Properties of Cellulose and Cellulose Solution 3.

Preparation of Hydrophobic Cellulose Beads using Cellulose Dissolved in TEAH/Urea Solvent and AKD 4.

The Characteristics of Wet-laid Nonwoven Sheet Using Lyocell/Wood Pulp Fibers 5.

A Study on the Post-treatments of Citrus Pomace-based Soil Covering Materials for Improving Functional Properties NORDIC PULP & PAPER RESEARCH JOURNAL, Vol.39(1), 2024 1.

Biorefining: Organic acid fractionation of hardwoods planted in social forestry 2.

Paper Technology: Effect of fine fibers on secondary fibers and recycled paper 3.

Paper Chemistry: Increased recyclability of wet strengthened liquid packaging board, through synergetic effects of combining CMC and PAE – a case study in full scale 4.

Packaging: Printable active packaging film with Pelargonium graveolens oil 5.

Chemical Technology/Modifications: Water uptake as a fuel for soft actuators from cellulose 6.

Miscellaneous: Nanofibers/reduced graphene oxide/polypyrrole for Highperformance electrode material 7.

Miscellaneous: Chemical properties, crystallinity, and fiber biometry of Jabon (Anthocephalus cadamba) wood for pulp raw material: the effect of age and position 8.

Miscellaneous: Penetration and spreading of graphene oxide ink in rice paper enabling its unique expressiveness in Chinese paintings NORDIC PULP & PAPER RESEARCH JOURNAL, Vol.39(2), 2024 9.

Biorefining: Advances and prospects for adsorption-driven valorization of newspapers using activated carbon: a short review 10. Biorefining: Influence of spent liquor obtained from SO2–ethanol–water (SEW) fractionation of Eucalyptus on drifting sands stabilization 11. Paper Technology: Drying characteristics and thin layer drying model of semimature rice paper 12. Paper Technology: Monitoring solids content development in pilot-scale through air drying of tissue paper 13. Paper Technology: Strength and thermal insulation properties of foam-formed ceramic fiber paper with different reinforcement methods Page 4 of 5

Research Articles

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

14. Paper Physics: Heterogeneity characterization of commercial structural papers 15. Paper Chemistry: Production of recycled paper using harmless municipal sludge as a new biomass filler 16. Environmental Impact: Preparation and characterization of nanocellulose acetate and acrylate polymer composite membrane 17. Environmental Impact: Fabrication of modified lignin-based liquid mulching film and its potential application 18. Environmental Impact: Modification of polyvinyl alcohol with 2-hydroxypropionic acid and cross-linking with glutaraldehyde for the preparation of biodegradable mulch paper and its properties 19. Recycling: Research on the brightening effect of miscible wetting additives on fly ash coatings 20. Nanotechnology: Nanofibrillated pulps from Amazonian species as a potential raw material for ecological packaging 21. Chemical Technology/Modifications: Effect of in-situ mineralization of calcium carbonate on the aging resistance of Wikstroemia bast fiber 22. Miscellaneous: Utilization of rice straw for parallel production of sugars rich extract and paper TAPPI JOURNAL, March 2024 1.

Editorial: Special issues in March and May TAPPI Journal focus on the latest pulp manufacture and engineering research 2.

Life cycle carbon analysis of packaging products containing nonwood residues: A case study on linerboard and corrugating medium 3.

Life cycle carbon analysis of packaging products containing purposely grown nonwood fibers: A case study on the use of switchgrass pulp for linerboard and corrugating medium 4.

Effect of high sulfate content on viscosity of recovery boiler molten smelt 5.

Effects of varying total titratable alkali and causticizing efficiency targets on kraft pulp mill productivity 6.

Factors affecting phosphorus uptake/dissolution during slaking and causticizing TAPPI JOURNAL, April 2024 1.

Editorial: Celebrating an industry giant: Dr. Peter W. Hart 2.

A true green cover for industrial waste landfills 3.

Characterizing rheological behavior and fluidization of highly refined furnishes 4.

Surface modification of TiO2 with MPS and its effects on the wettability and physical properties of Kawayan Kiling (Bambusa vulgaris Schrad ex. Wendl) handsheets 5.

Effect of pressure and time on water absorption of coated paperboard based on a modified Cobb test method TAPPI JOURNAL, May 2024 1. Editorial: Surface energy in printing is the focus of runner-up 2. Remembering Dr. Peter W. Hart: Dedicated leader, mentor, friend 3. Polyvinylamine as a wet-end additive: Effects of pH and anionic contamination 4. Enhancing tissue wet pressing performance and dry end material efficiency for cost savings 5. Z-directional testing of paperboard in combined tensile and compression loading 6. Utilization of Areca leaf residues for sustainable production of greyboard

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Research Articles

PAPERmaking!

FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL®

Volume 10, Number 2, 2024

Technical Abstracts The general peer-reviewed scientific and engineering press consists of several thousand journals, conference proceedings and books published annually. In among the multitude of articles, presentations and chapters is a small but select number of items that relate to papermaking, environmental and waste processing, packaging, moulded pulp and wood panel manufacture. The abstracts contained in this report show the most recently published items likely to prove of interest to our readership, arranged as follows:

Page 2

Coating Environment

Page 3

Fillers Moulded Pulp

Page 4

Nano-Science

Page 5

Packaging Technology Paper Chemicals

Page 6

Papermaking Pulp Testing

Page 7

Tissue

Page 8

Waste Treatment

Page 9

Wood Panel

The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International® and the PITA Annual Review, both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating.

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Volume 10, Number 2, 2024

COATING “Oil- and water-resistant paper coatings: A review”, Sumanta Basak, Milind Shrinivas Dangate & Shanmugha Samy, Progress in Organic Coatings, Vol.186, January 2024, 107938. Paper coatings based on petroleum-based compounds such as fluoro-compounds, polyethylene, and waxes are utilized to alter the properties of paper, such as wettability and oil and water transport. Although such polymers promote surface water resistance, their unfavorable qualities—poor recycling and lack of biodegradability— have led to their decline. However, using such non-renewable and non-biodegradable materials not only poses a threat to the environment and human health but also releases greenhouse gases. In addition, the use of plastic and fossil-fuel-based materials as barrier coatings in paper-based packaging boxes makes recycling difficult, enhancing overall recycling costs and causing environmental concerns about the waste created due to lack of biodegradation. Due to increasing worries about using petroleum-based polymeric packaging compounds and coatings and rising consumer demands for items with nutritive quality and prolonged shelf life, studies on alternative packaging materials are getting more popular. On the other hand, fresh techniques for environmentally friendly coatings may be constructed by employing biological polymers like polyesters, amino acids, and carbohydrates. These biopolymer coatings are powerful oil and water protectors that can substitute chemical-based paper and paperboard coatings. They could also stop inadvertent water transfer in food products. Nevertheless, many biopolymers may encounter challenges during manufacturing due to the material's innate water-holding capacity, crystallinity, and fragility, which precludes their usage in industrial applications.

For that reason, it will be preferable to use polymer blends by combining them with other polymers, fillers, and plasticizers to enhance coating efficacy. This review paper will cover a detailed analysis of the water and oil resistance characteristics of several synthetic and naturally occurring polymers and their composites used as paper coatings for food packaging applications. The combination of polymers and their modifications with various agents and fillers can be utilized to build coatings that enhance the water and oil resistance of papers. There are also discussions about different coating techniques and the various solvents used to prepare coating solutions.

ENVIRONMENT “Sustainable Papermaking in China: Assessing Provincial Economic and Environmental Performance of Pulping Technologies”, Qian-long Han, Hai-long Zhao, Guo-xia Wei, Yu-wen Zhu*, Tong Li, Mao Xu, Xin Guo, Hui-zhen Shi, Yi Lian, & Han-qiao Liu, ACS Sustainable Chem. Eng. 2024, 12(11), 4517–4529. There are 100 million tonnes of carbon emissions from China’s paper industries, which attracts growing interest in their sustainability under the dual-carbon targets. Reasonable technological upgrading, waste paper recycling, and waste resource utilization can positively affect the sustainable development of paper manufacturing. Hence, the environmental and economic performance of paper from four pulping technologies (chemical mechanical, chemical, biomechanical, and waste paper pulping) were analyzed via Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methods. LCA results show that paper from chemical pulp is optimal, reducing 591.6–1385.7kg CO2 equiv/t compared to others. LCC results indicate paper from biomechanical pulp has the highest economic benefits, with net profits outperforming others by $52.2–84.6/t. Moreover, environmental differences were investigated for papermaking wastes (black liquor (BL) and paper sludge (PS)) management options. The 80% caustic combustion of BL has the best environmental benefits, saving 154.3–331.6 kg of CO2 equiv/t compared to other methods. The production of paperboard from PS is more environmentally friendly, causing 200 kg of CO 2 equivalent/t less emissions than landfill. Finally, various waste paper recovery rates (60%, Page 2 of 10

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70%, and 80%) and technology substitution scenarios were designed from the provincial perspective. The results indicate that the current carbon emissions and energy consumption (CEEC) of paper from wood pulp are 13.51Mt CO 2 equiv and 7.05 million GJ, respectively. Based on an 80% recovery rate and the adoption of advanced pulping technologies, the national CEEC can be reduced by 32.4% and 50.06%, respectively. In economic terms, advanced pulping technology application can increase total revenue by 30.2%. With the implementation of the optimal waste management programs, the national CEEC can be reduced by 27.8% and 65.3%, respectively.

FILLERS “Production of recycled paper using harmless municipal sludge as a new biomass filler”, Hao Sun , Xiyu Chen , Lingjun Wei EMAIL logo , Jieyu Cui , Wanlu Zhang & Longfei Liu, Nordic Pulp & Paper Research Journal, https://doi.org/10.1515/npprj2024-0007. Due to a shortage of resources, exploring new biomass fillers has become critical for paper making. In this study, we reported an eco-friendly strategy for fabricating low-cost and efficient recycled paper with high mechanical properties using corrugated cardboard waste paper and harmless municipal sludge (HMS). First, the characteristics of HMS, including the particle size, pH, specific surface area, organic functional groups and organic component content, were analyzed. Then, the influence of the amount of HMS on the properties of the recycled paper was studied. Finally, the strengthening mechanism of biomass filling recycled paper was discussed. The results showed that HMS, a biomass filler for recycled paper preparation, exhibited excellent physical and chemical properties, with a median particle size of 6.395μm, a surface area of 39.974m 2 g−1 and organic functional groups. The tensile index of the recycled paper with 30% HMS was 13.10Nm/g, which was 16.4% greater than that of the unfilled paper and showed better thermal stability. This excellent performance could be attributed to the uniform distribution of HMS on the fiber surface, which improved the accessibility of hydrogen bond formation between fibers. Thus, this study proved that HMS was an excellent biomass filler for producing recycled paper.

MOULDED PULP “Development of a beverage carton closure cap based on 100% wood pulp fibres”, Gary Chinga-Carrasco, Jost Ruwoldt, Eva Pasquier, Marianne Øksnes Dalheim & Martin K. Wieser, Journal of Cleaner Production, Vol.445, 15 March 2024, 141339.

Single-use plastic products have been identified as an environmental challenge. When such products are not recycled, they may end up in nature and thus cause, e.g., marine littering. Thermoformed wood pulp fibre products are gaining more interest to replace fossil plastic products. However, beverage caps made of wood pulp fibres are challenging due to the hygroscopic nature of wood fibres, i.e., they absorb water, deform and loose functionality. Hence, the purpose of this study was to develop a fibre-based beverage cap that could replace plastic tethered cap systems. Both unbleached and bleached Kraft pulp and chemo-thermo-mechanical pulp (CTMP) fibres were tested in thermoforming trials, using tailor-made metal moulds. The results showed that Kraft pulp fibres formed denser structures, with more limited water absorption, compared to CTMP. The mechanical properties of thermoformed specimens were suitable for the application, i.e., the strength, modulus and elongation were between 32 and 36 MPa, 4–4.9 GPa and 1.6–1.9%, respectively, depending on the type of pulp fibre. Additionally, in order to secure that the caps were functional in relevant conditions in contact with liquids (water or milk), the caps were surface modified by silylation and esterification to increase the liquid barrier. The results indicate that surface esterification increased the contact angle to 95°. On the other hand, the surface-modified caps could not entirely limit the liquid absorption over longer Page 3 of 10

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periods of time (>∼1 h) when the caps were directly exposed to liquid. However, the liquid barrier was satisfactory when the products were exposed to increased relative humidity in refrigerated conditions (relative humidity >76% and temperature <7 °C).

“Investigation of a lignocellulose fiber hornification treatment for improving the functionality of apple pomace-based pulp for molded pulp packaging”, Emma Gordy, Jooyeoun Jung & Yanyun Zhao, International Journal of Biological Macromolecules, Vol.263(Pt.1), April 2024, 130265. Transfer molded pulp packaging (TMPP) is a viable alternative to single use plastic packaging. TMPP is typically produced from recycled newspapers, but the availability of this feedstock material is declining. Apple pomace (AP) pulp, primarily composed of cellulose, hemicellulose, lignin, and pectin, can be used as the primary component of TMPP, but its high water retention value (WRV) and separation from other pulps (recycled cardboard (CB) in this study) limits its utilizations in TMPP. A pressing and thermal drying cellulose hornification treatment followed by a repulping step was implemented to reduce pulp WRV and enhance AP and CB fiber entanglements. 11%, 20%, and 25% reductions in WRV were achieved through 1 t-force pressing and drying at 120°C for 2.5, 15, or 27.5min, named mild, medium, and strong hornification treatments, respectively. Increased AP and CB fiber entanglements were observed via microscopy with rising hornification drying times. The medium hornification treatment was identified as the optimal treatment for reducing pulp WRV and reducing pulp separation without decreasing pulp sheet tensile strength. This study introduced and validated a novel processing technique for improved functionality of AP-based pulp for packaging applications.

NANO-SCIENCE “The effect of pre-treatment and process conditions on the gas barrier properties of fibrillated cellulose films and coatings: A review”, Robyn Hill, Jon Phipps, Richard Greenwood, David Skuse, & Zhenyu Jason Zhang, Carbohydrate Polymers, Vol.337, 1 August 2024, 122085. Microfibrillated cellulose (MFC) is a bio-material produced by disintegrating cellulose fibres into fibrillar components. MFC could offer a sustainable solution to packaging needs since it can form an excellent barrier to oxygen. However, a comprehensive understanding of how MFC characteristics impact barrier properties of MFC films or coatings is required. This article critically reviews how the extent of separation of fibres into fibrils—and any resulting changes to the crystallinity and degree of polymerisation of cellulose—influences gas barrier properties of MFC films or coatings.

Findings from publications investigating the barrier performance of MFC prepared through different processes intending to increase the effectiveness of fibrillation are evaluated and compared. The effects of processing conditions or chemical pre-treatments on barrier properties of MFC films or coatings are then discussed. A comparison of reported results showed that morphology and size polydispersity of the cellulose strongly influence the barrier properties of MFC. However, changing the MFC production process to decrease fibril diameter and polydispersity can result in changes to cellulose crystallinity; reduction in fibril length; introduction of bulky functional groups; or increased fibril surface charge: all of which could have a negative impact on the barrier properties of the final films or coatings.

“A review on the enhancement of circular economy aspects focusing on nanocellulose composites”, Muhammad Adlan Azka, Adib Adam, S.M. Ridzuan, S.M. Sapuan & Abdul Habib, International Journal of Biological Macromolecules, Vol.269(Pt.1), June 2024, 132052. Researchers are now focusing on using the circular economy model to manufacture nanocellulose composites due to growing environmental Page 4 of 10

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issues related to waste management. The circular economy model offers a sustainable solution to the problem by optimizing resource efficiency and waste management by reducing waste, maintaining value over time, minimizing the use of primary resources, and creating closed loops for goods, components, and materials. With the use of the circular economy model, waste, such as industrial, agricultural, and textile waste, is used again to produce new products, which can solve waste management issues and improve resource efficiency. In order to encourage the use of circular economy ideas with a specific focus on nanocellulose composites, this review examines the concept of using circular economy, and explores ways to make nanocellulose composites from different types of waste, such as industrial, agricultural, and textile waste. Furthermore, this review investigates the application of nanocellulose composites across multiple industries. In addition, this review provides researchers useful insights of how circular economics can be applied to the development of nanocellulose composites, which have the goal of creating a flexible and environmentally friendly material that can address waste management issues and optimize resource efficiency.

PACKAGING TECHNOLOGY “Biodegradable active coating from chitosan/astaxanthin crosslinked with genipin to improve water resistance, moisture and oxygen barrier and mechanical properties of Kraft paper”, Patthrare Inthamat, Thomas Karbowiak, Wirongrong Tongdeesoontorn & Ubonrat Siripatrawan, International Journal of Biological Macromolecules, Vol.254(Pt.2), January 2024, 127816. An active chitosan-based coating with an addition of a natural antioxidant and a natural crosslinker has been applied to improve the performance of Kraft paper. Coatings, including chitosan (CS), CS crosslinked with 1.5% genipin (CS-1.5G), CS containing 1% astaxanthin (CSA) and CSA crosslinked with 1% genipin (CSA-1G) were coated on Kraft paper. Uncoated and coated papers were then evaluated for water content (WC), water vapor permeability (WVP), contact angle, oxygen permeability (OP), tensile strength (TS), bursting strength and elongation at break (EAB). Results indicated that the coating improved the properties of Kraft paper. When compared with CS-coated paper, WC and WVP of CSA-1G-coated paper decreased significantly by 40% and 24%, respectively. The lowest OP was also observed in CSA-1G-coated paper. CSA- and CSA-1G-coated paper had contact angle values >100°, indicating hydrophobic nature of coated paper surface. All coatings largely improved TS of the paper (by 182–224%) whereas CS-1.5G and CSA-1G significantly improved the bursting strength of the paper. The developed genipin-crosslinked chitosanbased coating enriched with astaxanthin can improve the functional properties of Kraft paper and thus will facilitate the usage of the paper for food packaging applications.

PAPER CHEMICALS “A comprehensive comparison between synthetic and bio-based wet-strength additives for paper manufacturing”, Varsha Singh, Satish Kumar Bachala, Manisha Madan, Arihant Ahuja & Vibhore Kumar Rastogi, Cellulose, Vol.31, 4645–4679, (2024). Wet-strength additives are vital in maintaining the structural integrity of paper and paper-based products in wet conditions. Most wet-strength additives are synthetically produced and pose environmental and human health risks. Therefore, there is a growing interest in developing natural and environment-friendly wet-strength additives for paper.

However, the unavoidable replacement of these harmful wet-strength additives with greener materials to achieve similar wet-strength without compromising product performance, with the added option of sustainability, is challenging. This review discusses up-to-date conventional synthetic, natural, and other wet-strength additives used in developing wet-strength in paper-based products. A detailed description of the additive’s Page 5 of 10

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reaction mechanisms and working principles for achieving the required wet-strength is also analyzed. Moreover, a detailed comparative literature review of the physio-chemical properties of these wet-strength additives is also discussed. Finally, the paper also discusses the challenges associated with bio-based additives in improving the wetstrength of paper-based products, comparing the well-established synthetic wet-strength additives.

PAPERMAKING “Surface Modification of Adsorbents for Removing Microstickies from Papermaking Whitewater”, Kunrui Xu, Wenxuan Mo, Fengshan Zhang, Carl J. Houtman, Jinquan Wan, & Bo Li, Ind. Eng. Chem. Res., 63(17), 7950–7957 (2024). Adhesion and agglomeration of small sticky particles, i.e., microstickies, onto paper and paper machines cause serious problems for recycling mills. Because associations between materials with similar surface energies are strongest, we propose an “adhesives collect stickies” strategy to physically remove microstickies from whitewater systems. We characterized deposits from a commercial paper machine and observed a large amount of acrylate-based materials. Based on this observation, we chose to graft glycidyl methacrylate (GMA) to surfaces of polypropylene (PP) to make it more similar to the deposited stickies, which will encourage association by van der Waals forces and interdiffusion. The modified material efficiently collected acrylic adhesive particles suspended in water (58.3%) and particles found in paper mill whitewater (40.6%). Additionally, a flow cell incorporating layers of modified mats of fibers shows good efficiency (40.6–49.4%) for collecting stickies at steady flow rates. This strategy may provide a method for removing microstickies without disturbing the chemical environment of the papermaking system.

PULP “Flax biorefining for paper production”, L. Verónica Cabañas-Romero, Oriol Cusola, Carolina Buruaga-Ramiro, Cristina Valls, M. Blanca Roncero & Susana V. Valenzuela, Cellulose, Vol.31, 4497–4508, (2024). In this work, we assessed the potential of Cel6D, a recently reported exocellulase from Paenibacillus barcinonensis, as a biorefining agent for flax pulp. Pulp fibers were treated with this enzyme, Cel9B (an endocellulase previously shown to possess biorefining action) and the two in combination.

Samples of biorefined flax pulp were mechanically refined to obtain handsheets. All three biorefining treatments decreased air permeance in the handsheets. Cel9B increased tensile index and folding endurance, and the Cel6D − Cel9B combination increased tensile index and burst index but also resulted in markedly decreased tear index and folding endurance. On the other hand, Cel6D increased tensile index and burst index; also, more importantly, it increased tear resistance, albeit slightly, relative to the other two treatments.

The results of this work can be useful to understand the differential effects of exocellulases and endocellulases as biorefining tools and open up new avenues for exploring their use in other biotechnological applications.

TESTING “Optical measurement of paper moisture content with application in paper pressing”, Hooman Mahdavi, Boris Stoeber & Sheldon Green, Cellulose, Vol.31, 2557–2570, (2024). We present a novel non-contact method for measuring the moisture content of paper. In the method, paper is illuminated obliquely by light from an IR LED, and the light reflected from the paper is imaged by a short-wave infrared (SWIR) camera.

Owing to the high absorptivity of liquid water to light in the 1400–1500nm wavelength range, the intensity of light reflected off the paper diminishes sharply with increasing moisture content. We show that for a variety of paper samples (Whatman paper, NBSK, Page 6 of 10

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NBHK, tissue paper) and moisture contents of up to 200%, there is a monotonic relationship between reflectivity and moisture content. This relationship is independent of the wood species used to make the paper, but does differ between wood-based papers and cotton-based papers. As this method involves an optical camera, the spatio-temporal distribution of moisture content in paper can be measured. The method was validated by separately measuring moisture content in paper gravimetrically for both uniform and nonuniform moisture distributions. The measurement technique was applied to a simulated pressing operation where the inferred moisture content distribution changes with the applied pressure.

“Classification Analysis of Copy Papers Using Infrared Spectroscopy and Machine Learning Modeling”, Yong-Ju Lee, Tai-Ju Lee & Hyoung Jin Kim, BioResources, Vol.19(1), p160, (2024). The evaluation and classification of chemical properties in different copypaper products could significantly help address document forgery. This study analyzes the feasibility of utilizing infrared spectroscopy in conjunction with machine learning algorithms for classifying copy-paper products. A dataset comprising 140 infrared spectra of copy-paper samples was collected. The classification models employed in this study include partial least squares-discriminant analysis, support vector machine, and Knearest neighbors. The key findings indicate that a classification model based on the use of attenuated-total-reflection infrared spectroscopy demonstrated good performance, highlighting its potential as a valuable tool in accurately classifying paper products and ensuring assisting in solving criminal cases involving document forgery.

“Alternative methods to evaluate flocculation of particles in papermaking suspensions”, Juan Cecchini, Antti I. Koponen, Olli-Ville Laukkanen & Ari Jäsberg, Proceedings of TAPPICon 2024, April 28-May 1, 2024, Cleveland OH, USA. When dealing with papermaking fibre suspensions, particle aggregation takes place already before the paper web is formed. The particle aggregation depends on several aspects including particle mass concentration (consistency), particle collisions, electrochemical interactions promoted by chemical additives, etc. Due to its importance, fibre suspension aggregation (or flocculation) has been studied for a long time in papermaking, and several methods have been developed for this purpose. The traditional techniques include e.g.

Focused Beam Reflectance Microscopy (FBRM) and High-Speed Video Imaging (HSVI).

Recently, a new optical method, Optical Coherence Tomography (OCT) has emerged for flocculation and aggregation analysis. The advantages of OCT are the possibility to study opaque suspensions, its micron-level resolution and its high data acquisition speed. OCT measurements can be combined with rheological measurements, allowing simultaneous measurement of both the time evolution of the aggregate size and the suspension viscosity. In this work, we used this approach to study the flocculation of suspensions of various papermaking furnishes. We analyzed the time evolution of the aggregate size and the fibre suspension viscosity when the studied papermaking suspensions were treated with a Highly Refined Furnish (HRF, this furnish contains a significant amount of MFC type fibrils) together with chemical additives. We show how such studies can lead to a better understanding of the impact of flocculation on the produced paper web on such quantities as formation, drainage potential and strength behavior.

TISSUE “Impact of Air Jet Impingement Technology on the Strength of Tissue Paper”, Reczulski, Mariusz; Pospiech, Piotr; Troszczyńska, Kinga & Bieńkowska, Maria, BioResources, 2024, Vol.19(1), p1190. Impinging air jets can be used to dewater, heat, and dry the web of tissue paper. High velocities of the air jets degrade the paper, and Page 7 of 10

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appropriate adjustments to the jet velocity and the distance of the nozzle from the surface of the wet web are crucial to obtain the highest quality product. This work investigated the correlation between the velocity of the air jet and the strength of paper subjected to the impingement method. Papers with an initial moisture content of 20% and various pulp mixes were tested, and the physical properties of papers were explored. After impinging an air jet, different tensile strength limits were obtained in the machine and cross directions. The paper had lower apparent density and higher roughness compared to classical pressing. The dependence of tensile strength and roughness on the fibers composition also was determined. Increasing the amount of eucalyptus fibers in impingement dewatered paper resulted in a decrease in its tensile strength and roughness. The value of elongation before breaking was the highest for softwood papers after the impingement method. The maximum velocity of an air jet that can be used to dewater or dry paper without the risk of damage to the papers was determined.

WASTE TREATMENT “Enhancing anaerobic digestion of actual papermaking wastewater with addition of Fenton sludge”, Xianbao Wang, Xiang Li, Yili Xie, Jialu Zhang, Jiarong Ran, Minting Zhang, Lixin Zhang, Anlong Zhang & Chao Zhu, Journal of Water Process Engineering, Vol.63, June 2024, 105520. The effect of Fenton sludge on anaerobic digestion of actual papermaking wastewater was investigated in this study. The results showed the iron in the Fenton sludge primarily exists in the form of needle-like iron oxide (FeOOH) and showed high electron transfer capability. Fenton sludge promoted electron transport in anaerobic digestion and electron transport system activity increased by 59%.

Fenton sludge enhanced the metabolic activity of anaerobic microorganisms, especially that of the hydrogenotrophic methanogens, the content of coenzyme F420 increased by 48.9%. Besides, the microbial community structure in anaerobic digestion was affected by Fenton sludge, the quantity of microorganisms increased significantly. The dissimilatory iron-reducing bacteria (Desulfobacterota) and hydrogenotrophic methanogens (Methanobacterium and Methanolinea) were enriched, which promoted the methane production. As a result, the anaerobic digestion performance of papermaking wastewater was promoted significantly by adding Fenton sludge, the organic matter removal efficiency and methane production increased by 11.17% and 15.12%. This study provided an effective solution for the optimisation of anaerobic treatment of actual refractory organic wastewater.

“Modeling greenhouse gas emissions from biological wastewater treatment process with experimental verification: A case study of paper mill”, Jiahui Han, Yin Liu, Wenqing Li, Feini Huang, Wenhao Shen, Tianlong Liu, Jean-Pierre Corriou & Panagiotis Seferlis, Science of The Total Environment, Vol.924, 10 May 2024, 171637. Wastewater treatment plants (WWTPs) have been regarded as the main sources of greenhouse gas (GHG) emissions. This study compares the influent characteristics of industrial wastewater represented by the WWTP of paper mill and that of domestic sewage represented by the Benchmark Simulation Model No.1 (BSM1) under stormy weather. The various sources of GHG emissions from the two processes are calculated, and the contribution of each source to the total GHG emissions is assessed. Firstly, based on the mass balance analysis and the recognized emission factors, a GHG emission calculation model was established for the on-site and off-site GHG emission sources from the WWTP of paper mill. Simultaneously, a GHG emission experimental model was established by determining the dissolved concentrations of carbon dioxide (CO 2) and nitrous oxide (N2O) in the papermaking wastewater, to verify the accuracy of the developed GHG calculation model. Subsequently, an optimum aeration rate for the paper mill was investigated to Page 8 of 10

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comply with the discharging norms. Under the optimum aeration rate of 10h −1, the obtained calculation accuracies of CO2 and N2O emissions were 94.6% and 91.1%, respectively. The mean total GHG emission in the WWTP of paper mill was 550kg CO 2eq·h−1, of which 44.6% came from the on-site emission sources and 55.4% from the offsite emission sources. It was also uncovered that the electrical consumption for aeration was the largest contributor to the total GHG emissions with a proportion of 25.2%, revealing that the control strategy of the aeration rate is highly significant in reducing GHG emissions in WWTP of paper mills.

WOOD PANEL “Characterization of randomly oriented strand boards manufactured from juvenile wood of underutilized wood species”, Tomáš Pipíška, Marek Nociar, Pavel Král, Jozef Ráheľ, Pavlo Bekhta, Roman Réh, Ľuboš Krišťák, Miroslav Jopek, Barbora Pijáková, Rupert Wimmer & Milan Šernek, European Journal of Wood and Wood Products, (2024). The wood-based panel industry in Europe, which is dominated by the use of Norway spruce, will face new challenges due to environmental changes and the bark-beetle calamity, which started a new era of forestry. To explore the possibility of replacing spruce with other wood species, juvenile wood of nine underutilized wood species (Scots pine, European larch, poplar, willow, alder, birch, European beech, English oak and hornbeam) were used to make randomly oriented strand boards (OSBs). Singlelayer OSBs were produced with 3% pMDI resin and 0.5% wax. Standard physical and mechanical properties were measured. The bending strength (MOR) values showed that there was no statistically significant difference between the values for, on the one hand, spruce (34.6MPa) and, on the other, larch (25.9MPa), poplar (25.2MPa), willow (27.8MPa), alder (34.3MPa) or birch (27.1MPa). A similar trend was found for the boards modulus of elasticity (MOE). The highest MOE values of 5,185MPa and 4,472MPa were found for spruce and alder, respectively. There was no significant difference between spruce and other wood species in internal bond strength. Boards made from high-density wood species showed better physical performance, whereas those made from low-density wood species (except pine) gave better mechanical properties. Strand-generalized characteristics, such as the slenderness ratio and specific surface, were analyzed for all investigated physical and mechanical properties. European larch, poplar, willow, and alder are potential wood species for manufacturing OSBs in future without mixing species, as they can replace spruce in the wood-based panel industry.

“Sensitivity study of measured wooden board thermal properties on solid heat transfer model predictions”, Vojtěch Šálek, Lucie Hasalová, Vojtěch Štejfa, Adam Pivák, Petr Hejtmánek, Jiří Ira & Milan Jahoda, Fire Safety Journal, Vol.143, February 2024, 104055. This work presents experimental investigation on specific heat capacity and thermal conductivity as a function of temperature and vertical density profile over the sample cross section of oriented strand board, particle board, medium density fibreboard, and plywood. A possibility of introducing an universal set of parameters describing various EWPs by averaging the parameters of the four studied materials obtained in this work is investigated. A one-dimensional heat transfer simulation sensitivity study is performed using the experimentally measured values. The study aims to investigate the effect of using spatial- and temperature-dependent properties compared to constant values and to study the importance of these parameters and their combination in predicting onedimensional heat transfer below the thermal decomposition temperature of engineered wood products.

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Volume 10, Number 2, 2024

“Life cycle assessment of wood-based panels: A review”, Daniele Costa, João Serra, Paula Quinteiro & Ana Cláudia Dias, Journal of Cleaner Production, Vol.444, 10 March 2024, 140955. Wood-based panels are products used in various applications with the potential to replace energy-intensive materials while promoting carbon sequestration. This article aims to systematically review the scientific literature assessing the impacts of wood-based panel manufacturing from a life cycle perspective. It intends to identify different methodological choices and challenges, compare impacts on the climate change impact category and provide recommendations for future assessments. The reviewed articles were identified using search strings in the Web of Science and Scopus databases, focusing on the different wood-based panel sub-types (veneer sheets, plywood, particleboard or chipboard, fibreboard). In total, 53 articles were selected for qualitative and 36 for quantitative synthesis. Most articles were published in the United States of America, Spain, Brazil or China, which are among the largest wood-based panel producers. This study's assessment shows that the published articles' methodological choices varied widely, specifically concerning the functional unit, system boundaries, procedures to deal with multifunctionality, biogenic carbon modelling and impact assessment methods. Further, its quantitative synthesis reveals considerable variability in the results, even within the same panel subtype. Laminated veneer lumber tends to be the least carbon-intensive wood-based panel. However, a lack of uniformity in previous articles' methodological choices precludes comparisons of results. For this reason, elaborating Product Environmental Footprint Category Rules (PEFCR) for wood-based panels to harmonize methodological choices is critical for obtaining comparable results regarding multiple environmental impact categories.

“Enhancing oriented strand board performance using wheat straw for eco-friendly construction”, Hani Abobakr, Marya Raji, Hamid Essabir, Mohammed Ouadi Bensalah, Rachid Bouhfid & Abou el kacem Qaiss, Construction and Building Materials, Vol.417, 23 February 2024, 135135. Wheat straw is an abundant and cheap agricultural by-product. This research aims to produce an outperform-oriented strand board utilizing wheat straw for sustainable construction. The produced rectangular specimens via the compression molding process were tested in terms of mechanical, hygroscopic, morphological, and sound isolation performances. The results compared to the commercial (OSB) EN 300: 2006 standard showed excellent mechanical properties in wheat straw-based panels with a density of 0.60g.cm−3, with a remarkable 44.61% increase in flexural strength and 42.2% improvement in Young's modulus over woodbased OSB. Taking into consideration the hygroscopic properties, wheat straw-based boards showed superior swelling resistance, with WS-OSB-0.45 leading the way with a 23% reduction compared to commercial OSB. Water absorption was inversely related to density, with WS-OSB-0.60 reducing water absorption by 8.9% compared to commercial OSB. The contact angle measurements showed that wheat straw-based panels (WS-OSB0.60 at 106° and WS-OSB-0.45 at 100.4°) had more hydrophobic surfaces than commercial OSB (88.1°). The wheat straw-based OSB panels, especially WS-OSB-0.45, achieved remarkable sound reduction, with an overall sound reduction value of 35.2dB, outperforming WS-OSB-0.6 (34.9dB) and commercial OSB (34dB). These results demonstrate the viability of using wheat straw residues as an environmentally friendly alternative to wood in the production of panels for building, furniture manufacturing, and equipment packaging applications.

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Technical Abstracts