May / June 2015 NLGI Spokesman

NLGI

SPOKESMAN

Serving the Grease Industry Since 1933 – VOL. 79, NO. 2, MAY/JUNE 2015

In this issue . . .

6 Meeting the Challenges Posed by Environmentally Acceptable Lubricants 10

Blends: Friend or Foe? Base oil Blends for Grease Formulations

20

OSP-New Group V Base Fluid for Manufacture of Sulfonate Greases

26

Alkylated Naphthalenes

NLGI 2015-2016 BOARD OF DIRECTORS Photo taken at the 82nd Annual Meeting, Coeur d’Alene, Idaho, 2015

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VICE-PRESIDENT:

Bruce M. Urban FMC-Lithium Division 2801 Yorkmont Rd., Ste. 300 Charlotte, NC 28208

David Como Dow Corning Corp.

P.O. Box 0994 Midland, MI 48686

SECRETARY:

TREASURER:

Kim Smallwood Citgo Petroleum Corp.

1293 Eldridge Pkwy.

Houston, TX 77077

Joe Kaperick Afton Chemical Corporation 500 Spring St. Richmond, VA 23218-2158

PAST-PRES./ADVISORY:

EXECUTIVE DIRECTOR:

Chuck Coe Grease Technology Solutions LLC 7010 Bruin Ct. Manassas, VA 20111

Kimberly Hartley NLGI International Headquarters 249 SW Noel, Suite 249 Lee’s Summit, MO 64063

DIRECTORS Barbara Bellanti Battenfeld Grease & Oil Corp. of NY P.O. Box 728 • 1174 Erie Ave. N. Tonawanda, NY 14120-0728 Richard Burkhalter Covenant Engineering Services 140 Corporate Place Branson, MO 65616 Faith Cordo King Industries, Inc. Science Road Norwalk, CT 06852 Gary Dudley Exxon Mobil Corporation 3225 Gallows Road Room 7C1906 Fairfax, VA 22037 Gian L. Fagan Chevron Lubricants 100 Chevron Way Room 71-7338 Richmond, CA 94802-0627 Jim Hunt Tiarco Chemical 1300 Tiarco Drive Dalton, GA 30720 Tyler Jark Lubricating Specialties Co. 8015 Paramount Blvd.

Pico Rivera, CA 90660 Dr. Anoop Kumar Royal Manufacturing Co., LP 516 S, 25th West Ave. Tulsa, Oklahoma 74127 Wayne Mackwood Chemtura 199 Benson Rd. Middlebury, CT 06749

Dennis Parks Texas Refinery Corp.

One Refinery Place Ft. Worth, TX 76101 Tom Schroeder Axel Americas, LLC P.O. Box 12337 Kansas City, MO 64116 Raj Shah Koehler Instrument Co. 85 Corporate Dr. Holtsville, NY 11716-1796 Dr. Huafeng “Bill” Shen Bel-Ray Co. P.O. Box 526 Farmingdale, NJ 07727 Terry Smith Lubrication Engineers, Inc. P.O. Box 16447 Wichita, KS 67216 Thomas W. Steib The Elco Corporation 1000 Belt Line Street Cleveland, OH 44109 Lisa Tocci Lubes ’n’ Greases 6105 Arlington Blvd., Suite G Falls Church, VA 22044 William (Bill) Ward The Lubrizol Corporation 29400 Lakeland Blvd.

Mail Drop 051E Wickliffe, OH 44092 Ruiming “Ray” Zhang R.T. Vanderbilt Company, Inc. 30 Winfield St. Norwalk, CT 06855

Dwaine (Greg) Morris Shell Lubricants 526 S. Johnson Drive Odessa, MO 64076

TECHNICAL COMMITTEE CO-CHAIRS:

CHAIR, SESSION PLANNING:

Joe Kaperick Afton Chemical Corporation 500 Spring St. Richmond, VA 23218-2158

Joe Kaperick Afton Chemical Corporation 500 Spring St. Richmond, VA 23218-2158

NLGI

OFFICERS PRESIDENT:

SPOKESMAN

Serving the Grease Industry Since 1933 – VOL. 79, NO. 2, MAY/JUNE 2015

5 6

NLGI 2015-16 Board of Directors Meeting the Challenges Posed by Environmentally Acceptable Lubricants: Thickener Systems for Unsaturated Polyol Ester Based Oils Mark Wilkinson &

Steve Nolan, R S Clare & Co Ltd Liverpool, England

10 Blends: Friend or Foe? Base oil Blends for Grease Formulations

Mehdi Fathi-Najafi, Linda Malm, René Abrahams, Luis BastardoZambrano, Nynas AB, Sweden

20 OSP-New Group V Base Fluid for Manufacture

of Sulfonate Greases Govind Khemchandani, Ph. D.1, Perry

Byrd2, & Jeff St. Aubin3. 1The Dow Chemical Company Freeport, Texas 77541, USA. gvkhemchandani@dow.com 2 Mid-South Sales, Inc Jonesboro, Arkansas 3 Chemtool Incorporated, Rockton, IL

26 Alkylated Naphthalenes Maureen E. Hunter, Ph.D.

King Industries, Inc., Norwalk, CT

44 Advertiser’s Index

David Turner 22110 Stone Cross Court Katy, TX 77450

SERVICE INDUSTRY ASSISTANCE COMMITTEE CHAIR: Jim Hunt Tiarco Chemical 1300 Tiarco Drive Dalton, GA 30720

EDITORIAL REVIEW COMMITTEE CHAIR: Joe Kaperick Afton Chemical Corporation 500 Spring St. Richmond, VA 23218-2158

ON THE COVER NLGI 2015-2016 BOARD OF DIRECTORS. See page 5.

Published bi-monthly by NLGI. (ISSN 0027-6782) KIMBERLY HARTLEY, Editor NLGI International Headquarters 249 SW Noel, Suite 249, Lee’s Summit, MO 64063 USA Phone (816) 524-2500, FAX: (816) 524-2504 Web site: http://www.nlgi.org — E-mail: nlgi@nlgi.org One-year subscriptions: U.S.A. $65.00; Canada $80.00; International $109.00; Airmail $147.00. Claims for missing issues must be made within six months for foreign subscribers and three months for domestic. Periodicals postage paid at Kansas City, MO. The NLGI Spokesman is indexed by INIST for the PASCAL database, plus by Engineering Index and Chemical Abstracts Service. Microfilm copies are available through University Microfilms, Ann Arbor, MI. The NLGI assumes no responsibility for the statements and opinions advanced by contributors to its publications. Views expressed in the editorials are those of the editors and do not necessarily represent the official position of NLGI. Copyright 2015, NLGI. Postmaster: Send address corrections to the above address.

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12/10/14 6:23 PM

NLGI 2015-2016 BOARD OF DIRECTORS Photo taken at the 82nd Annual Meeting, Coeur d’Alene, Idaho, 2015

Kneeling: Anoop Kumar, Royal Manufacturing; Dr. Huafeng “Bill” Shen, Bel-Ray Co.; Ruiming “Ray” Zhang, R.T. Vanderbilt; Gian Fagan, Chevron Lubricants; Raj Shah, Koehler Instrument; David Como, Dow Corning Corp. (Vice President); Faith Corbo, King Industries Standing: Terry Smith, Lubrication Engineers; Tom Steib, ἀ e Elco Corp.; Tom Schroeder, Axel Americas; Lisa Tocci, Lubes’n’Greases; Duane (Greg) Morris, Exxon Mobil Corp.; Jim Hunt, Tiarco Chemical; Wayne Mackwood, Chemtura; Barbara Bellanti, Battenfeld Grease & Oil; Joe Kaperick, Afton Chemical Corp. (Treasurer); Bruce Urban, FMC-Lithium (President); Chuck Coe, Grease Technology Solutions (Past President/Advisory); Kim Smallwood, CITGO (Secretary); David Turner, CITGO (Co-Chair Technical Committee); Tyler Jark, Lubrication Specialties; Dick Burkhalter, Covenant Engineering; Dennis Parks, Texas Refinery; Gary Dudley, Shell Canada Not pictured: Bill Ward, ἀ e Lubrizol Corp.

-5NLGI SPOKESMAN, MAY/JUNE 2015

6:23 PM

Meeting the Challenges Posed by Environmentally Acceptable Lubricants: Thickener Systems for Unsaturated Polyol Ester Base Oils Mark Wilkinson & Steve Nolan R S Clare & Co Ltd Liverpool, Englandt

Introduction

ἀ ere has been an increasing and continuing trend in recent years towards biodegradable, low ecotoxicity greases. ἀ e recent introduction of the Vessel General Permit (2013) regulations, which mandate the use of Environmentally Acceptable Lubricants, has focussed the grease industry’s attention on the issue of formulating such greases.

A wide range of biodegradable base oils has been available for many years. However, substantial market penetration has been limited by a combination of commercial and technical challenges. ἀ e commercial challenge has been the high price of most biodegradable base oils; high performance esters, such as the fully saturated diesters used in high-

temperature applications, are several times as expensive as typical Group I or Group II mineral oils. Even with regulation requiring the use of biodegradable base oils, such a price difference will present a substantial commercial obstacle to their use. ἀ e most commercially attractive – in other words, the cheapest – biodegradable base oils are vegetable oils and their synthetic analogues, the TMP esters. Vegetable oils have been assumed to present difficult technical challenges for manufacturers; the poor thermal and oxidative stability of the polyunsaturated component has deterred investigation of their use as bases for lithium soap greases.

Synthetic TMP oleate appears to offer a useful compromise for such greases, with better stability than -6VOLUME 79, NUMBER 2

vegetable oils and lower price than saturated diesters.

An alternative approach would be to reduce the thermal stress on the oil by use of a different soap.

A lithium/calcium mixed base soap would typically reduce the maximum temperature required during processing by 10-15 °C; using an anhydrous calcium soap would reduce the temperature by 50 °C or more compared to a pure lithium soap. Where the grease is not intended to be subjected to high temperatures – and this will include most marine applications impacted by the VGP regulations – such thickener systems would seem to be appropriate.

We have therefore decided to

NLGI investigate the formulation and behaviors of three base oils: rapeseed oil as a typical lowcost commercial vegetable oil, high oleic sunflower oil as a mid-range low polyunsaturated vegetable oil, and trimethylolpropane trioleate as the high stability synthetic analogue. ἀ ese have been prepared in combination with three thickener systems: a pure lithium 12-hydroxystearate soap, a mixed base lithium/calcium 12-hydroxystearate soap, and a pure anhydrous calcium 12-hydroxystearate soap.

Our initial intent was to concentrate on the physical properties of the basic greases – penetration, shear stability, oil separation, etc. - and to investigate the impact of adjustments in the soap formation step of the manufacturing process, especially with regard to the mixed base grease. However, some unanticipated – indeed, rather surprising – initial results led us to focus more on the stability and performance of the pure lithium grease.

Initial Formulations

All nine of the initial greases were intended to be prepared to a common formulation. ἀ e stages were: • 600g of base oil and 80g of commercial 12-hydroxystearic acid heated to 90°C with stirring on a hotplate • A suspension of the base (either 10g of calcium hydroxide, 5g of calcium hydroxide and 5.7g of lithium hydroxide monohydrate, or 11.4g of lithium hydroxide monohydrate) in 20g of water added to the oil/acid mix • ἀe temperature was held at 90-95°C for 2 hours to ensure complete reaction of the base and acid • ἀe temperature was increased to 130°C and held for 30 minutes to dry the soap • ἀe temperature was increased to completely melt / dissolve the soap (150°C for the pure calcium soap, 195°C for the mixed base soap, 205°C for the pure lithium soap) and held for 15 minutes • ἀe grease was shock chilled by addition of 310g of base oil and allowed to cool to 100°C • ἀe grease was sheared at 1500 rpm in a mixer for 15 minutes and allowed to stand overnight before testing.

Initial Results

(Limited to visual observations and basic test data – much further data to follow in final paper) ἀ e first unanticipated result was that it appears that conventional production method cannot form an anhydrous calcium grease in either of the vegetable oils. ἀ e calcium 12-hydroxystearate, upon melting, will not dissolve or disperse in, even at elevated temperatures; it remains as a viscous and separate phase. Addition of the chilling oil

-7NLGI SPOKESMAN, MAY/JUNE 2015

NLGI

precipitated the soap as a solid. As a result, no testing of the physical properties was possible or meaningful. It was possible, with difficulty, to produce a grease-like consistency with the calcium soap in TMP trioleate; however, the soap dispersed very poorly and the consistency of the end product was semi-fluid, with an unworked penetration of ??? mm/10. ἀ e mixed base soaps did disperse adequately at 195°C, and formed a grease on shock chilling. ἀ e greases were less solid than we had initially expected, although this was less of a surprise following the pure calcium soap results. ἀ e unworked penetration results for the greases are: Lithium/calcium in rapeseed oil: 338 mm/10 Lithium/calcium in high oleic sunflower oil:

331 mm/10

Lithium/calcium in TMP trioleate:

319 mm/10

ἀe lithium soaps formed well. ἀ e unworked penetration results for the greases are: Lithium in rapeseed oil: 271 mm/10 Lithium in high oleic sunflower oil:

259 mm/10

Lithium in TMP trioleate:

264 mm/10

ἀe se soaps provided us with our second unanticipated result. ἀ ere was much less discoloration due to thermal and oxidative damage than we had anticipated; despite the higher processing temperature, the pure lithium soap greases appeared to be in better condition than the mixed base soap greases. ἀ e rapeseed oil grease had only discolored slightly, and the high oleic sunflower oil grease showed no sign of discoloration.

-8VOLUME 79, NUMBER 2

NLGI

Second Phase results

Following the initial results, we decided to refocus our investigation on the properties and performance of the pure lithium soap greases, since it seemed that they offered the best possibility of a conventional grease using these polyol base oils. (more data to be assembled – rheology, wear & weld, basic antioxidant packages & performance, spectroscopy)

Conclusion

(to be expanded as later data develops) It seems that the optimal soap thickener for vegetable oils and synthetic polyol analogues, despite the high temperatures involved, is a pure lithium soap. Conventional manufacturing techniques are adequate, and oxidation appears to be much less of a problem than has been expected. High oleic base stocks, both synthetic and vegetable, appear very well suited for use within the normal temperature ranges expected of a conventional simple lithium greases. Common commodity vegetable oils such as rapeseed oil appear to offer an economical option for greases that are not expected to be exposed to temperatures much above ambient, and approach cost parity with mineral oil formulations.

-9NLGI SPOKESMAN, MAY/JUNE 2015

Blends:

Friend or Foe?

Base oil Blends for Grease Formulations Mehdi Fathi-Najafi* Linda Malm, René Abrahams Luis Bastardo-Zambrano *Corresponding author

Nynas AB Sweden

Abstract

ἀ e introduction of Group II and III base stocks, with better oxidation stability and higher viscosity index than Group I base stocks, will create two main drawbacks; lack of solvency (solvent power) and lack of high viscosity.

Highly naphthenic oils have been regarded as an excellent solution to these drawbacks. Put simply, it is possible to “kill two birds with one stone”. Nynas has, during the last years, in a number of publications offered some practical solutions to these forthcoming obstacles.

ἀ e purpose of this work is to compare “side by side” three base oil blends where GrI, GrII and GrIII, in combination with naphthenic, were used for preparation of lubricating greases. Since the target viscosity was 150 mm2/s at 40 ºC, a naphthenic oil was used in order to reach this viscosity. Key parameters in this study were frictional and thermal stability of the base oil blends, as well as low temperature flowability, elastomer compatibility and rheological properties of the corresponding greases. Last but not least, an attempt was made to minimize the thickener content level. ἀ e prepared base oil blends have been thoroughly characterized. ἀ e overall results obtained, reveal some interesting aspects of the use of Gr II as a substitute to Gr I for preparation of greases. ἀ e outcome of this work emphasizes that blends should be regarded as a great opportunity for grease formulators who are looking for some further development of their current formulations and furthermore, the lubricating grease based on the blend of paraffinic Gr II and naphthenic oil performs better than others.

1. Introduction

ἀ e base oil industry has been going through fundamental changes in the last decade. ἀ ese changes have been marked by the rapid growth in production capacity for Group II and Group III base oils. ἀ e total production of Gr I is estimated to fall to about 40% of the total base oil production by the year 2020. ἀi s global rationalization of Group I production, and its potential impact on the future availability of paraffinic bright stock, has led several lubricant formulators to start evaluating alternative products. Lubricating greases are, by far, one of the product types that strongly depend on highly viscous oils, especially for industrial and automobile applications. ἀ ere are of course a few alternatives to bright stocks, such as synthetic oils. But they are expensive, and furthermore, in some applications such as in the case of elastomer compatibility, PAO would probably cause some problems.

Mineral oils used by grease manufacturers can be divided into two major groups, naphthenic oils and paraffinic oils. Of course both categories of base oils have their own advantages and disadvantages. ἀ e most important advantages of the naphthenic oils over the paraffinic oils, with the same viscosity and similar aromatic content, are better low-temperature flowability and better solvency. ἀ e contribution of having base oils with good solvency towards the thickener is that less thickener is needed to obtain a certain consistency of the finished product.

It is notable that the higher soap content in greases

- 10 VOLUME 79, NUMBER 2

NLGI produced from paraffinic oils may contribute to the mechanical stability. A typical NLGI grade 2 lithium grease, based on a solvent neutral 500 (SN500) Gr I oil, may contain 11-13wt% thickener; while 6-8% thickener is required for an equivalent viscosity oil of naphthenic nature. ἀ e authors believe that the surplus of Group II and Group III base oils is one among a number of market trends that brings some great opportunities to the grease formulators, if they look for blends where naphthenic oils are regarded as part of the solution for a sustainable formulation. A number of key parameters important for the performance of the finished product could be obtained within reasonable cost.

2. Preparation and Characterization of the Base Oils

ἀ e target for this study was to compare different oil mixtures, where the main focus was on the possible synergies of the blends between paraffinic oils and naphthenic oil. For this reason, three base oil blends have been prepared by using three paraffinic base oils, representing Gr I, Gr II and Gr III, with one naphthenic oil. ἀ e paraffinic oils had different viscosities at 40 ºC; subsequently different wt% of the naphthenic oil was used to obtain 150 mm2/s in viscosity at 40 ºC. ἀ e characterizations of the base oil blends cover a wide range of tests.

Table 1 shows the characteristics of the three base oil blends that have been used for preparation of greases in this study.

Table 1 shows the characteristics of the base oil blends - 11 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI As can be seen in the Table 1, the viscosity of the blends at 100 ºC varies within 1 mm2/s, which is close enough to be regarded as equivalent to each other. It is notable that main impact of the naphthenic oil on the blends could be traced in the parameters such as sulphur content, pour point and aniline point.

2.1 ἀ ermal stability of the base oil blends

ἀ e short term thermal stability of the base oil

blends were studied by an in- house method. ἀ e method consists of two parts; the first one with copper catalyst (8 grams copper wire) and the second one without. ἀ e test duration was 48 hrs, however by loading two samples of each blend, the thermal stability could be controlled after half time or 24 hrs.100 grams of each blend were put in an open beaker in an oven at 100 ºC. ἀ en the samples are analyzed, based on change of weight, total acid number (TAN) and colour.

Table 2 shows the obtained results for all three blends Weight loss: although the weight loss of Blend B and C seems to be slightly better than Blend A, the overall conclusion should be more or less very good for all three blends.

Colour change: ἀ e colour was measured according to ASTM D 1500. All Blends with copper catalyst behave similar to each other, namely they ended up to almost the same colour, 7 to 8. However, blends without copper catalyst aged differently. Blend B shows less colour change, 0.6 after 48 hrs. followed by Blend A and Blend C, 1.2 and 1.4 respectively. ἀi s colour change may be addressed to the amount of naphthenic oil used in these preparations, since in the last two blends the wt.% of naphthenic oils are higher than in Blend B.

Total Acid Number (TAN): TAN for all blends without copper catalyst are good; however the change of TAN for Blend B is about one third of the other two blends.

2.2 Tribological measurements of the base oil blends

A mini traction machine (MTM2, PCS Instruments) has been used to measure the frictional properties of the base oil blends in a mixed rolling/sliding contact.

A load is applied to a steel ball, and with a force transducer the frictional force is measured as the ball is in contact with a steel disc. ἀ e Slide to Roll Ratio (SRR) is defined as the percentage ratio between the

- 12 VOLUME 79, NUMBER 2

NLGI sliding speed (difference between the ball speed and the disc speed) and the mean speed.

Consequently, 0 % is pure rolling and 200 % is pure sliding. Furthermore, by measuring the traction (friction) as a function of the mean speed at constant SRR, a Stribeck curve can be obtained.

Figure 1. Picture of the ball on the disc (MTM)

In this study, the friction measurements were performed in a steel/steel contact at 820 MPa and a steel ball with a diameter of 19.05 mm (3/4”) was used. Both the steel ball and the disc where of AISI 52100 steel and had a smooth finish with a roughness less than 0.01 µm (Ra).

Four repeat runs were measured, each one after the other,

Figure 2. discribes Stribeck curve

and the mean value of the measurements is displayed.

Two tests for each base oil blend were performed and very good agreement was observed for the tests. ἀ e temperature was kept constant at 40 ºC for all MTM measurements.

Figure 3 shows the traction coefficient as a function of slide to roll ratio, measured at 40 ºC - 13 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI Based on the obtained data, described in Figure 3, all three base oil blends show almost similar frictional behaviour at running conditions.

A Stribeck curve was obtained by measuring the Traction coefficient of the blends as a function of speed at constant SRR (50%), see Figure 4. ἀi s Figure indicates a slightly lower traction coefficient for blend B. Electrical Contact Resistance (ERC): ERC describes the degree of separation between the Ball and the Disc

in a MTM. Hence, when they are fully separated from each other the voltage at the disc will be the same as the applied one (15 V) and if they are fully separated (100%) e.g. by base oil, then the balance resistor will be 0 V. Based on the measured ECR, at different speeds, for the three blends, see Figure 5, a better performance for the Blend B at lower speeds can be observed. ἀi s measurement reveals that the film thickness of Blend A and C are reduced significantly at lower speeds.

Figure 4 shows the traction coefficient as a function of speed, measured at 40 ºC

Figure 5 shows the separation of disc and ball during the Stribeck run.

- 14 VOLUME 79, NUMBER 2

NLGI

3. Preparation and Characterization of the Greases

ἀ e three base oil blends (A, B and C) have been used for preparation of lithium based greases in an open kettle.

Grease A corresponds with base oil Blend A, Grease B with base oil Blend B and finally Grease C with base oil Blend C. In order to make the comparison easier, each blend was used during the entire production of the grease, meaning a blend was used in both cooking and cooling stages.

Table 4 shows some of the typical characteristics for the lithium based greases produced with the blends.

Based on the obtained results shown in Table 4, some conclusions may be drawn. Firstly, the moderate level of soap combined with good mechanical stability after 100,000 strokes, although Grease C shows about 25% less soap thanks to higher amount of naphthenic oil; secondly the excellent oxidation stability of all the greases.

the oil and the thickener differently. ἀ us, flowability of the grease sample under controlled conditions can generate valuable information, such as the storage or elastic modulus (G´) of the grease, which could be interpreted as the real consistency of the grease, at the applied temperature.

ἀ e four ball wear tests were carried out by applying a load of 400 N for 60 minutes. ἀ e rotational speed was higher 1400 rpm instead for 1200 rpm which is recommended in ASTM D 2266 which may increase the wear scar, however, the measured wear scar for all three greases are in-line within the expected wear scar for a naked lithium based grease.

3.1.1. Strain Sweep:

3.1. Rheological measurements

It is well known that lubricating grease is a viscoelastic material, in other words a material with a viscous part (the base oil) and an elastic part (the thickener).

Parameters such as temperature and shear stress affect

In an attempt to compare the dynamic (Shear) stability of the greases rheologically, a strain sweep program was applied in which the frequency and the temperature were kept constant (10 rad/s and 25 °C respectively), and the strain was increased logarithmically from 0.01 to 1000%.

As can be seen in Figure 6 G´ for C, at the starting point, is significantly lower than the other two greases, 13179 (Pa) versus 21794 (Pa) for Grease A and 21626 (Pa) for Grease B, which reflects the level of the thickener content of the greases.

- 15 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI Furthermore, the Linear Viscoelastic Region of Grease A is slightly wider than for Grease B and significantly wider than for the Grease C, which indicates the better shear stability of Grease A. ἀi s can also be verified by comparing the Flow point of the Greases, see Table 5.

Table 5 shows the measured Elastic modulus at various stages of the oscillatory tests ἀ e Flow point is obtained when G´=G´´ and/or the phase angle reaches 45 º. At this point the structure of the grease is destroyed and it starts to flow. ἀ e higher flow point, the more shear stable the grease is supposed to be. Hence based on the measured data, Grease A is more shear stable than Grease B and C. Furthermore, Grease B and C show the same shear stability despite having significantly different thickener content (about 24% less for Grease C). It is notable that this result doesn’t support the shear stability of the greases after 100000 strokes, see Table 4.

Figure 6 describes the elastic (storage) modulus and the viscous modulus as a function of the strain for the greases.

- 16 VOLUME 79, NUMBER 2

NLGI 3.1.2. Temperature sweep:

ἀ e low temperature behaviour of the greases was investigated by using a temperature sweep program, from +40 to -25 °C. ἀ en the change of G´ as a function of temperature was measured.

Based on the measured storage modulus, Figure 7, all three greases more or less show the same good behaviour down to about -17 ºC, however, as the temperature is dropped further Grease A shows a steep increase of the elastic modulus, or in other words the consistency of

Grease A increases faster than the other greases below -17 ºC, while this deviation could not be found in the case of the other two greases (B & C).

Using pour point of the base oil as a tool in order to predicate the performance of a lubricant questioned in the past [4] and the authors recommend rheological measurements should be used instead which is in-line with the finding in e.g. Figure 7.

Figure 7. ἀ e measured elastic modulus as a function of temperature Based on the measured storage modulus, Figure 7, all three greases more or less show the same good behaviour down to about -17 ºC, however, as the temperature is dropped further Grease A shows a steep increase of the elastic modulus, or in other words the consistency of Grease A increases faster than the other greases below -17 ºC, while this deviation could not be found in the case of the other two greases (B & C).

Using pour point of the base oil as a tool in order to

predicate the performance of a lubricant questioned in the past [4] and the authors recommend rheological measurements should be used instead which is in-line with the finding in e.g. Figure 7.

4. Flow Pressure measurements

In order to simulate the pumpability of the greases, the flow pressure (FP) of the greases at two different temperatures (-20 ºC and -35 ºC) have been measured, according to DIN 51805. ἀ e test setup consists of

- 17 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI a conical nozzle that is filled with grease. ἀ e nozzle is placed in the measuring instrument, equilibrated for 2-3 hours at a desired temperature, and then an increasing pressure is applied to the nozzle. ἀ e threshold pressure at which grease starts to flow through the nozzle is recorded.

Table 6 shows the low temperature properties of the greases based on different temperatures.

Based on the Rheological study and Flow pressure measurements, all the combinations show very good low temperature properties. However, Grease C (based on Gr III + Naphthenic Oil) shows superior low temperature behavior, followed by Grease B (Gr II + Naphthenic oil), when compared with Grease A (Gr I + Naphthenic).

5. Elastomer compatibility

Chloroprene rubber is one of the most common elastomers used in constant velocity joints application.

Hence, the rubber interactions with the lithium grease, based on the three Blends, were conducted through total immersion of the rubber sample in the greases. ἀ e test duration was 168 hours at 100 ºC. ἀ e change in hardness and weight of the chloroprene rubber samples was measured. Hardness is a measurement of a rubber’s ability to resist penetration of a specified metal rod with a specifically shaped tip or end. In order to measure the change in hardness of the rubber, the IRHD (International Rubber Hardness Degrees) method was used. ἀ e scale runs from 0 to 100 degrees were 0 is an extremely soft material and 100 is an extremely hard material. Common rubber values are 30-85 degrees.

Previous publications have shown that the Aniline point of the oil has significant influence on the interaction between the oil, the corresponding grease and the rubber.

For example, in the case of Nitrile butadiene rubber, an oil with low aniline point is recommended, while high

aniline point is desired for Chloroprene rubber. ἀi s part of the work confirms that recommendation. Oil Blend B, used for Grease B, has the highest aniline point (116 ºC), and this is reflected in the obtained results, see Figures 7 and 8.

Figure 7 and 8 show the impact of different greases on Chloroprene rubber after various time at 100 ºC.

6. Summary

ἀr ee base oil blends have been prepared by using a naphthenic oil and three paraffinic oils, one from each group (Gr I, Gr II and Gr III). ἀ e characterization of the blends emphasizes that all three blends have similar properties. However, the thermal stability test which is in fact a static test, and MTM measurements, indicate slightly better performance for Blend B, which contains paraffinic Gr II oil. ἀ e three lithium based greases, which are corresponding with the three base oil blends, show good performance in a number of tests. In the rubber compatibility test, Blend B shows less impact, and therefore should be regarded as a better candidate.

Regarding the low temperature behavior of the greases, Grease C seems to be a better product. According to the rheological measurements, see Figure 6, Grease A appeared to be more shear stable than Grease B and Grease C.

- 18 VOLUME 79, NUMBER 2

NLGI

ἀi s study emphasizes the potential of taking advantage of the ongoing fundamental change within the base oil industry, which has created, and will continue to create, new opportunities to upgrade the current (old) grease formulations, by using blends of paraffinic oils, preferably Gr II, and naphthenic oil. ἀ e surplus of paraffinic Gr II oil, and availability of severely processed naphthenic oils, offers a cost effective solution with extended performance for demanding applications such as in the automobile industry.

Reference

[1] Salomonsson, L., et. al, Oil/ἀic kener interaction of chloroprene and nitrilebutadiene rubber with lubricating greases and base oil. Lubricating oil, 2006.

21(54).

[2] Serra-Holm V., Development of a novel naphthenic base oil for application in CVJ greases, NLGI 73rd Annual Meeting, October 2006, FL (US).

[3] Sullivan, T., Tighter base oil supply expected in Europe. Lube report 2012.

[4] Fathi-Najafi, M., et al., Low temperature tribology. A study of the influence of base oil characteristics on friction behaviour under low temperature conditions. EUROGREASE, 2012.

[5] Bastardo-Zambrano L. et.al, Base oil blends to meet the new demands of the lubricant industry, Lubes Magazine No.115 June 2013 [6] Fathi-Najafi M. et.al, When the going gets tough... A heavy specialty oil for grease formulations (Part II), NLGI 80th Annual Meeting, June 2013, AZ (US).

[7] http://www.pcs-instruments.com/mtm/accessories/mtm-ecr. shtml#page=page-1

- 19 NLGI SPOKESMAN, MAY/JUNE 2015

OSP-New Group V Base Fluid for Manufacture of Sulfonate Greases Govind Khemchandani, Ph. D.1, Perry Byrd2, & Jeff St. Aubin3 ἀ e Dow Chemical Company Freeport, Texas 77541, USA gvkhemchandani@dow.com

1

INTRODUCTION

Oil-soluble polyalkylene glycols (OSPs), a new group V base fluid derived from downstream derivatives of butylene oxide (BO), have been designed to provide good solubility in API (American Petroleum Institute) Groups I to IV base oils [1-4]. ἀi s new class of group V base fluid now can be used as a co-base oil in hydrocarbon base fluids, which is not possible with conventional polyalkylene glycols (PAGs). OSPs have high viscosity indices (VI), good low temperature properties, low coefficients of friction and low aniline points. OSPs help to improve the deposit control of compositions derived from mineral oil when used as co-base oil. A combination of low aniline point and deposit control ability of OSPs were leveraged to make lithium and lithium complex greases [5-7].

Recent innovations in equipment design have resulted in components operating at higher speeds, producing increased power output, and as a direct result, operating at

higher continuous temperatures.

Under these severe conditions, protecting equipment is stretching the limits of conventional grease technology [8]. ἀ ese new tribomachines create new opportunities for grease formulators to use their skills in developing products based on new base fluids, thickeners and superior additive systems. Without change in base stocks or thickeners, avenues for performance advances become limited [9]. ἀ e quest for better performing synthetic grease prompted the authors to develop ‘over based calcium sulfonate (OBCS)’ grease derived from OSP base stock and super sulfonate thickener.

OBJECTIVE

Conventional PAGs are used for making greases with inorganic and organic thickeners for specific applications [10]. However, Calcium Sulfonate Complex Grease is suitable for a wide range of applications, since it has various excellent inherent properties in the sulfonate matrix [11]. Basic technology for the - 20 VOLUME 79, NUMBER 2

Mid-South Sales, Inc Jonesboro, Arkansas 3 Chemtool Incorporated Rockton, IL 2

manufacture of Calcium Sulfonate Complex Grease was established in early 1980’s. Improvements in the formulation and manufacturing process have been made thereafter and one can find several patents and reports [12, 13]. However, Calcium Sulfonate Grease was included in ‘NLGI Global Grease Survey’ as a separate category [14] in year 2000.

Since then many excellent research papers have appeared describing their use in steel mills, automotive and construction heavy equipment [15].

In the components of grease, base oil accounts for about 75-95 percent, meaning that the performance of grease is largely determined by the characteristics of base oil. ἀ erefore, grease cannot be any better than its base oil [16]. Consequently, before selecting any base oil, its characteristics should be examined in detail for its desired application.

References 1 to 6 describe many excellent characteristics of OSPs for grease making. Further continued research on OSPs has indicated novel

characteristics which are worth considering for choosing OSPs as base fluid for synthetic grease formulations [17].

NOVEL PROPERTIES of OSPs

Table 1 describes the physical properties of OSP base oils that can be used for Over based Calcium Sulfonate (OBCS) Greases. Two important inherent characteristics of OSPs are: 1. improving hydrolytic stability of natural and synthetic esters 2. acting as a corrosion performance booster in ASTM D 665 B test

Table 1: OSPs – Typical Properties OSPs – Ester Hydrolytic Stability Improvers Vegetable oils are used for biodegradable greases since they offer high VIs, biodegradability and renewability. For more demanding applications synthetic esters are used However, it is well known that in environments where water or moisture ingress into the fluid occurs, esters are prone to hydrolysis leading to acid generation and fluid degradation. One method of minimizing this degradation is to include an OSP into the ester formulation. Table 2 illustrates the improvement in hydrolytic stability using an OSP at a treat level of 10% in sunflower oil and also a synthetic polyol ester.

Table 2: Improvement in Hydrolytic Stability of esters using OSPs Hydrolytic Stability: Modified ASTM D2619 – extended time - 21 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI

NLGI OSPs and Corrosion Improvement

Industrial lubricant formulations based on conventional PAGs that are derived from ethylene oxide and propylene oxide copolymers, offer excellent performance versus Original Equipment Manufacturer (OEM) specifications. However one weakness is their inability to meet the requirements of the well known salt water corrosion test (ASTM D665B). OSPs have been found to improve the corrosion performance of conventional PAG formulations (Table 3) in the ASTM D 665B test, when added at a 0.5% treat level. Test results are shown in Figure 1. Rust free cylindrical steel test rods are shown and the photos demonstrate that the inclusion of the OSP helps to boost the corrosion protection properties of the fluid. ἀ e main objective of the project was to determine if suitable OBCS grease can be made with OSP meeting general specifications suited to applications that involve water, heat and load.

Table 3: OSPs as Corrosion Inhibitor Boosters in Conventional PAGs

Figure 1: Steel Cylindrical Test Rods

- 22 VOLUME 79, NUMBER 2

NLGI OSP based OBCS Formulation and Performance Tests

Many advances have taken place in improving manufacture and preparation of sulfonate greases [18, 19]. A state of the art method was used for preparing an OSP based OBCS grease. OSP-320 was chosen as the base fluid for preparing an OBCS grease.

Calcium sulfonate greases begin with an over based sulfonate. ἀ e base thickener is derived from a calcium sulfonate having a total base number of 300-400. ἀ ese

over based sulfonates contain calcium carbonate in an amorphous state. To make grease, the calcium carbonate is converted to a crystalline state by the use of a polar activator. ἀ e basic calcium sulfonate properties predominate in these greases yielding good inherent rust inhibition and extreme pressure protection. High dropping points are the results of the OSP, calcium sulfonate/carbonate complex. After adding an antioxidant to the gelled sulfonate grease, the results shown in table 4 were obtained.

Table 4: Typical Properties: OSP based OBCS Grease

Figure 2: Wear Profile of OSP based OBCS Grease, ASTM D 5707

- 23 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI

Figure 3: Friction Profile of OSP-based OBCS Grease, ASTM D 5707

Figure 4: EP Property OSP-based OBCS Grease, ASTM D 5706 - 24 VOLUME 79, NUMBER 2

RESULTS & DISCUSSION

ἀ e data on the OSP based OBCS grease showed product with excellent EP/AW characteristics, extremely high drop point, and very good oxidation stability as indicated by PDSC and ASTM D 942 tests. It has acceptable mechanical shear stability and excellent water resistance capability as indicated by the water wash out value of 0.7%. SRV test data show additional EP and low wear properties of OSP based OBCS grease with low coefficient of friction under chosen conditions of SRV test. High drop points greater than 300⁰C can be achieved easily with the use of OSP. In light of the results obtained from this work, we can conclude that high performance OBCS grease can be made with OSPs as base fluid using common manufacturing methods for complex sulfonate greases.

In earlier work [11] researchers made three complex sulfonate greases using diester, polyol ester and PAG as a base fluid. ἀ ey were unable to make stable grease and found half the functional life of greases compared to reference grease. OSPs now offer grease formulators an option to make stable high performing synthetic grease with OSP’s excellent inherent properties of improving hydrolytic stability of esters and boosting corrosion protection of PAGs.

CONCLUSIONS

• Formulators and researchers can now use Oil Soluble Polyalkylene Glycols as primary base oil, a co-base oil or as an additive in grease formulations.

• OSPs can provide good friction control and higher Oxidation Induction Time (OIT) values for greases.

REFERENCES

1. Neil Canter, “New Type of Polyalkylene Glycol”, Tribology and Lubrication Technology, October 2010, pp10-11 2. Govind Khemchandani, “Characteristics of New Oil Soluble Polyalkylene Glycols”, STLE Houston Chapter, February 9, 2011 3. Martin Greaves et al. “New Oil Soluble Polyalkylene Glycols”, STLE, Las Vegas, May 19, 2010 4. Lisa Tocci, “Building a Better Base Fluid, Lubes N Greases”, November 2013, pp.30-32 5. Govind Khemchandani, “New Oil Soluble Polyalkylene Glycol for Making High Performance

Grease,” NLGI, Volume 76, Number 2, pp 36-41 6. Govind Khemchandani, “Characteristics of OSPbased Lithium Complex Grease,” NLGI, 80th Annual Meeting, June 15-18, 2013, Tuscon, Arizona 7. E. Blancas-Sanchez, C. Galeano-Guerra, M. Oyervides Muñiz, J. Chavez-Contreras, “Comparative Analysis of OSP, Mineral, PAO and POE based Lithium Complex Greases: A Rheological Approach”, STLE, May 17-21, Orlando, 2014 8. John Lorimor, “Synthetic Greases Poised for Growth”, Compoundings, Vol. 63 No.8, August 2013 9. Tim Sullivan, Averse to Change, Lubes N Grease, Europe-Middle East-Africa, Aug 2012, pp 20-24 10. US Patent US 2011/0160110 A1, Lubricating Grease Composition, June 30, 2011 11. Y. Kimura et al, “Study of Synthetic Oil based Calcium Sulfonate Complex Greases”, NLGI 72nd Annual Meeting, Oct30-Nov1, San Antonio, TX 12. Elidaes, T. I. “One Step Process for Preparation of Over based Calcium Sulfonate Grease and ἀic kened Compositions”, US Patent 4,597,880 (1996) 13. Olson, W. D., Muir, R. J. et al. “Sulfonate Grease Improvement” US Patent 5,338,467 (1994) 14. Jeff St. Aubin, “Calcium Sulfonate Greases”, NLGI Advanced Grease Course, June 12, 2012, Palm Beach, Florida 15. Lubricating Grease Guide, Chapter 4, pp 51-58, 2006 Edition 16. Lou Robin et al, “A Study of Composition and Technology of Complex Lithium Grease”, NLGI, October 26-29, 1997 17. Martin Greaves, New Oil Soluble Polyalkylene Glycols & Practical Aspect of Formulating Advanced Lubricants”, Uniti Tech congress, Stuttgart, Germany, April19th, 2013 18. W. Mackwood, R. Muir, “Calcium Suffocate Grease One Decade Later”, 65th NLGI Annual Meeting, Naples, FL, October 25-28, 1998 19. Gareth Fish et al. “Calcium Sulfonate Grease Revisited”, NLGI, 78th Annual Meeting, June 11-14, 2011, Desert Palm, California

- 25 NLGI SPOKESMAN, MAY/JUNE 2015

Alkylated Naphthalenes Author: Maureen E. Hunter, Ph.D. King Industries, Inc., Science Road, Norwalk, CT, 06852 USA mhunter@kingindustries.com

Greases are used in numerous applications requiring a broad range of operating temperatures and special requirements, and the base oil used can impart improved characteristics to the grease. Alkylated naphthalenes are a unique class of synthetic fluids with outstanding thermooxidative and hydrolytic stability, low volatility, and good solubility characteristics. ἀ e flexibility of this technology to achieve a balance of physical and chemical properties will be discussed. Physical property and performance test data will be presented for both liquid lubricants and greases with alkylated naphthalenes as the sole base fluid and as a modifier for other primary base fluids. Grease work has focused on the advantages of using alkylated naphthalenes to reduce the amount of thickener, improve grease clarity and smoothness, and impart significant resistance to oxidation.

INTRODUCTION

Alkylated naphthalenes are high performance synthetic fluids that were first developed during WWII but were never commercialized. In the last 20 years, with advanced processing technology and raw material availability, alkylated naphthalenes have emerged as cost-competitive, high-performance basestocks. ἀ ese unique synthetic fluids were first used in engine oils and more recently in all types of industrial lubricants and greases. ἀ ey are primarily used as base oil modifiers with other synthetic base oils or Group II and III mineral oils. ἀ ey are used to enhance the thermal and oxidative stability and/or

additive performance to extend the lifetime of high performance lubricants. ἀ e basic structure of an alkylated naphthalene is shown in figure 1, where the core consists of two fused six-membered rings with the alkyl groups attached. It is because of the ability of this electron-rich conjugated naphthalene ring to absorb energy, resonate, and disperse energy, much like antioxidants do, that alkylated naphthalenes inherently have excellent thermo-oxidative stability. To make alkylated naphthalenes, naphthalene is reacted with an alkylating agent (alcohols, alkyl halides, or olefins) in the presence of an acid catalyst and this produces a mixture of alkylated naphthalenes having different numbers of alkyl groups on the naphthalene ring. ἀ e reaction is shown in figure 2. ἀ e physical properties of alkylated naphthalenes depend on: • ἀ e number of carbons in the alkyl group, which is controlled by raw material selection.

• ἀ e degree of branching of the alkyl group, which is controlled by raw material selection.

• ἀe number of alkyl groups on the naphthalene ring, which is controlled by chemical processing.

Figure 3 shows by gas chromatograph the distribution of an alkylated naphthalene mixture showing MAN (mono alkylated naphthalene), DAN (di alkylated naphthalene),

- 26 VOLUME 79, NUMBER 2

NLGI and PAN (poly alkylated naphthalene) with three or more alkyl groups on the naphthalene ring (1). Table 1 describes the physical properties of alkylated naphthalenes made with linear and branched alkyl groups of the same carbon number (2). MLAN is a mono linear alkylated naphthalene, so it has one linear alkyl group on the naphthalene ring.

MBAN is a mono branched alkylated naphthalene, so it has one branched alkyl group on the naphthalene ring. PLAN is a poly linear alkylated naphthalene, so it consists of 2 two or more linear alkyl groups on the naphthalene ring, and PBAN is a poly branched alkylated naphthalene, so it consists of two or more branched alkyl groups on the naphthalene ring.

From the table, one can see that: • Viscosity increases with increasing number of alkyl groups and with chain branching. So the mono linear alkylated naphthalene has the lowest viscosity.

• Viscosity index (VI) increases with the number of alkyl groups, and linear alkyl groups have better viscosity index because it is easier for them to coil up at low temperatures and expand at high temperatures compared to the branched alkyl chains. Branched alkyl groups are more rigid especially at lower temperatures and this destroys the viscosity index.

• Pour point increases with increasing number of alkyl groups and branching. Mono linear alkylated naphthalenes have the best (lowest) pour points.

• Aniline point, which is a measure of the polarity of a substance

and its ability to solubilize polar material, increases with increasing number of alkyl groups but decreases with branching. ἀ e lower the number the better the ability to solubilize polar material.

• Flash points are good for all. In the American Petroleum Institute (API) categories for base oils, as shown in table 2, alkylated naphthalenes are part of the Group V category. Group I, II, and III are paraffinic oils refined from petroleum crude oil with increasing severity of refinement.

Group IV base oils are poly-alphaolefins (PAO). Group V is the catch-all for base oils not included in the other categories. Figure 4 shows the structure of an alkylated naphthalene compared to other synthetic lubricants, including a PAO, a polyol ester, and a diester.

Compared to mineral oils, PAOs, esters, and polyalkylene glycols (PAG), alkylated naphthalenes have several performance advantages, as shown in table 3. ἀ ey provide superior thermooxidative stability because of the electron-rich naphthalene ring and its ability to resonate and disperse energy. Alkylated naphthalenes have inherent hydrolytic stability because they do not contain any functional groups that can hydrolyze. ἀ ey have good seal swelling properties - better than Group II and III mineral oils and PAOs. ἀ ey have better additive solubility than Group II and III mineral oils and PAOs, and this is again because of the aromatic ring of the alkylated naphthalene. ἀ ey also have - 27 NLGI SPOKESMAN, MAY/JUNE 2015

good low pour points and greater film thickness and film strength, which can reduce friction. As previously mentioned, another property used to characterize oils is aniline point. ἀi s is an indirect measure of the polarity of a substance and its ability to solubilize polar materials. A low aniline point is indicative of a fluid with high polarity and good solubilizing characteristics. As shown in figure 5, the aniline point of alkylated naphthalenes is between esters, which have high polarity, and mineral oils and PAOs, which are non-polar.

So alkylated naphthalenes can be used to help solubilize additives in non-polar base stocks, and, like esters, are often added to PAOs. However, alkylated naphthalenes do not incorporate hydrolytic instability or compete with additives for the surface as esters can. ἀ e mono alkylated naphthalenes are more polar than the poly alkylated naphthalenes.

In today’s marketplace, alkylated naphthalenes are available with a diverse ISO viscosity range from 22-193 cSt at 40°C, as shown in table 4. In general, as the viscosity increases: • Viscosity index increases • Aniline point increases, which means the solubility decreases • Volatility decreases significantly • Pour point increases • Flash point increases • Oxidative stability remains excellent • ἀe rmal stability remains excellent

NLGI Several alkylated naphthalenes are also approved by the U.S. FDA for use as H1 “Lubricants with Incidental Food Contact” per 21 CFR 178.3570, where they can be used up to 100% if needed to achieve the desired technical effect. Some are NSF listed as HX-1 additives. ἀ e primary areas of application for alkylated naphthalenes include: • Automotive and Stationary Engine Oils • Automotive and Industrial Gear Oils 3 • High Temperature Chain Lubricants • Paper Machine Oils • Hydraulic Oils • Circulating Oils / Turbine Oils / R&O Oils • Screw Compressor Oils • Heat Transfer Oils • Automotive and Industrial Greases

EXPERIMENTAL

In this paper, alkylated naphthalenes are evaluated both as neat fluids and as base oil modifiers using the following tests (3).

• ἀ ermal Stability - Federal Test Method 3411 - Cincinnati Milacron - ASTM D 2070 • ἀ ermo-oxidative Stability - Panel Coker - Federal Test Method 791-3462 - Rotating Pressure Vessel Oxidation Test (RPVOT) ASTM D 2272 - Pressure Differential Scanning Calorimetry (PDSC) ASTM D 6186 • Hydrolytic Stability - Beverage Bottle Test - ASTM D 2619 • Volatility • Low Temperature Performance - Viscosity vs. Temperature with VI and PPD • Friction - FZG - ASTM D 5182 • EHD (Elastohydrodynamic) Film ἀic kness and Pressure-Viscosity Coefficient • Seal Swell - Volume Change and Hardness Change - ASTM D 4289 and ASTM D 471 • Grease - Pressure Differential Scanning Calorimetry (PDSC) -

ASTM D 5483

RESULTS AND DISCUSSION

ἀ ermal Stability Federal Test Method 3411 In Federal Test Method 3411, samples are held at 274°C for 96 hours in the presence of a steel coupon in a sealed glass tube. ἀ e test evaluates the change in viscosity, increase in acid number, steel coupon weight loss, steel coupon appearance, and appearance of the oil. Table 5 shows that neat samples of AN-15, AN- 19, and AN-23 did not undergo any significant decomposition using this test method. A 7 cSt Group III base oil was also evaluated and compared to 20% modifications with AN-15, a trimethylolpropane (TMP) ester, and a diester. Table 6 shows that the Group III oil modified with the alkylated naphthalene exhibited excellent performance while the oils containing the esters resulted in thick, dark deposits and, in one case, extensive degradation of the metal.

Cincinnati Milacron - ASTM D 2070

Cincinnati Milacron testing was also conducted. In this test, 200 ml of the test fluid is held at 135°C for 7 days in the presence of copper and steel rods. Measurements include sludge formation, copper rod rating, steel rod rating, change in viscosity, and change in acid number.

Even though the test is normally run at 135°C, testing was conducted at higher temperatures. Table 7 shows that when tested at 150°C, AN-15, AN-19, and AN-23 all showed good performance with little change. Table 8 shows the test results at 200°C comparing AN-15 to a PAO blended to the same viscosity. Even though the sludge was equivalent, the PAO experienced a very high viscosity increase. At 225°C, table 9 shows that both these fluids resulted in equivalent sludge, but again the PAO experienced a very high viscosity increase, even with the addition of 1.5% of a package containing antioxidants, a yellow metal deactivator, and a rust inhibitor.

ἀ ermo-oxidative Stability

Panel Coker - FTM 791-3462 In Panel Coker testing, oil is splashed against a test panel at elevated temperatures and the amount of coke deposited on the panel is determined by weight. As shown in table 10, modifying a PAO with 10% of AN-8,

- 28 VOLUME 79, NUMBER 2

NLGI AN-15, and AN-19 significantly reduced the amount of coke formed. ἀ e neat PAO resulted in 9 mg of coke, while the PAO modified with alkylated naphthalene resulted in much less. ἀi s is also evident by the pictures showing the 100% PAO result on the left and the PAO modified with 10% AN-15 on the right.

Rotating Pressure Vessel Oxidation Test (RPVOT) ASTM D 2272

RPVOT testing was conducted where 50 g of test fluid and 5 ml of water with a copper coil catalyst are pressurize to 90 psi with oxygen and then held at 150°C. ἀ e time required for the pressure to drop to 25 psi is defined as the lifetime of the sample. Table 11 shows that neat fluids of AN-15, AN-19, and AN-23 showed superior thermo-oxidative stability compared to a PAO of equal viscosity to the AN-15. ἀ e alkylated naphthalenes also showed very good additive response, resulting in very high RPVOT lifetimes compared to the PAO when additized with 0.2% of di-tertiary butyl phenol (DTBP) and alkylated di-phenyl amine (ADPA) antioxidants versus the PAO. ἀi s was especially noted with the ADPA. ἀ e excellent thermo-oxidative stability of alkylated naphthalene is the result of the electron-rich naphthalene ring, which can scavenge radicals, resonate, and disperse the energy. Table 12 shows the AN-8 being used to boost the RPVOT performance of a Group III oil containing 0.7% of an R&O package. Replacing 15% of the Group III oil with alkylated naphthalene increases the oxidation lifetime from 1339 to 1926 minutes but also significantly reduces the sludge in the Cincinnati Milacron test.

Pressurized Differential Scanning Calorimetry (PDSC) - ASTM D 6186

PDSC measures the oxidation induction time to an onset of an exotherm under specific conditions. Testing was conducted using 2 mg samples at 500 psi and 160°C. An ISO VG 46 Group II oil was compared to the Group II oil modified with 20% of AN-8, AN-15, and AN-19, as shown in figure 6. ἀ e addition of the alkylated naphthalene increased the oxidation induction time and reduced the rate of oxidation. ἀ e degree of improvement depended upon which alkylated naphthalene was used.

Also tested was a PAO modified with 20% AN-8 with and without antioxidant. Figure 7 shows that the oil

combination exhibited good additive response, increasing the oxidation induction time with 0.2% alkylated diphenyl amine (ADPA) and alkylated phenyl alpha naphthylamine (APANA).

Hydrolytic Stability

Beverage Bottle Test - ASTM D 2619 In the Hydrolytic Stability Beverage Bottle test, a 75 g sample, 25 g of distilled water, and a copper test strip are sealed in a Coca-Cola bottle. ἀ e bottle is rotated for 48 hours in an oven at 93°C. Measurements include total acidity of the water, copper loss, appearance of the copper strip, and the acid number change of the oil. Two neat alkylated naphthalenes, AN-15 and AN-19, were tested and showed excellent hydrolytic stability, as shown in table 13. As mentioned earlier, alkylated naphthalenes do not contain functional groups that tend to hydrolize.

Figure 8 shows the beneficial effect of adding 10% AN-15 to an ISO VG 46 Group II base oil compared to adding a diester and a polyol ester. ἀ e esters are hydrolytically unstable and this results in high acid values of the water layer.

Volatility

Thin film testing was conducted using 2 g of fluid in an aluminum pan for 24 hours at temperatures of 200°C, 225°C, and 250°C. As shown in table 14, AN-15 showed less volatility at the lower temperatures than a PAO of equal viscosity. A second alkylated naphthalene, AN-19, also resulted in good volatility. Table 15 shows that a 40 cSt PAO had higher volatility than the AN-19, and when 20% of the alkylated napthalene was added to the PAO, the volatility was brought down to the level of the alkylated naphthalene alone. For comparison, an ester at 20% in the PAO resulted in significantly higher volatility.

Low Temperature Performance

Viscosity versus temperature profiles were run as shown in figure 9. ἀ e upper line is for an 8 cSt PAO containing 20% viscosity index (VI) improver. When 20% of the PAO is replaced with AN-8, the viscosity temperature profile is improved, and further improvement is realized with the addition of 0.3% of a pour point depressant (PPD). FZG

- 29 NLGI SPOKESMAN, MAY/JUNE 2015

Friction Performance - ASTM D 5182

In the standard FZG test, gears are run at increasing load stages at a constant speed of 1450 rpm for 21,700 revolutions (about 15 minutes) per load stage until scuffing occurs. Figure 10 shows the results of a modified procedure where the first 6 load stages were run in accordance to the ASTM method. ἀ en Load Stage 7 was applied for an 8-hour duration and the temperature difference between the gear box and the room was determined. AN-15 was compared to a mineral oil and PAO of similar viscosity, each containing 0.3% of an AW additive. AN-15 showed less frictional heat than the mineral oil and was equivalent to the PAO. EHD (Elastohydrodynamic) Film ἀic kness and PressureViscosity Coefficient A WAM machine was used where a optical interferometer measures fluid film thickness between a rotating Pyrex disc and a smooth 2 cm free wheeling steel ball. ἀ e load applied was 44.4N, and optical measurements to determine film thickness were made at a rolling velocity of 2 m/sec and temperatures of 45°C and 100°C. From the film thickness data, pressure-viscosity coefficients were calculated using the Hamrock-Dowson formula for point contacts. Pressureviscosity coefficients are a good measure of film forming capability to protect the metal surface at different speeds and temperatures in rolling contact zones. An alkylated napthalene and a polyolester of the same viscosity were tested, and the film thicknesses and pressure-viscosity coefficients are reported in table 16. ἀ e alkylated naphthalene resulted in thicker films and superior (higher) pressure-viscosity coefficients showing better film forming capability.

Seal Swell Performance - ASTM D 4289 and ASTM D 471

Neat AN-19 was tested with three different seal materials using the ASTM D 4298 test. Table 17 shows that AN-19 imparted seal swell to the different elastomers.

Using a nitrile seal material, a 20% addition of AN-15 to a 7 cSt Group III oil was compared to the Group III alone using ASTM D 471. Figure 11 shows that the alkyated naphthalene was able to impart seal swell properties to the non-polar Group III base oil. Greases Made with Alkylated Naphthalenes Lithium 12-hydroxystearate greases made with AN-15 and PAO of a similar viscosity were also evaluated. ἀ e grease made with the alkylated

naphthalene had several improved properties over the grease made with the PAO, as shown in table 18. ἀ e grease made with AN-15 required less thickener – 7% compared to 12% for the PAO grease. Less thickener can result in improved low temperature properties. ἀ e alkylated naphthalene grease was also more transparent than the PAO grease. ἀi s can be seen in figure 12 and is probably because the alkylated naphthalene acts as a bridging solvent, reducing the opaqueness of the grease. ἀ e AN-15 grease was also a smoother grease than the PAO grease probably because the alkylated naphthalene acts as a highly effective dispersant. ἀ e AN-15 grease also resulted in superior thermal gravimetric analysis and PDSC performance, liberating very small amounts of heat.

Pressurized Differential Scanning Calorimetry (PDSC) - ASTM D 5483

PDSC testing was conducted using greases made with the same lithium 12-hydroxystearate thickener but with blends of different oil ratios of AN-15 and PAO. In this test, 2 mg of grease was place in an aluminum test pan and the temperature was ramped at 100°C/min to the test temperature. ἀ en the sample was allowed to equilibrate at the test temperature for 2 minutes. ἀ e oxygen valve was opened, and the system was pressurized to 500 psi within 2 minutes. When equilibrated, the oxygen was adjusted to a flowrate of 100 ml/min. Note that the oxidation induction time is measured from the time when the oxygen valve is opened. Figure 13 shows the temperature ramp to the test temperature, the 2 minute equilibration, and the opening of the oxygen valve, which always causes a spike. Figure 14 shows PDSC test results at 180°C. ἀ e temperature ramp, the 2 minute equilibration, the oxygen valve opening, and the spike can clearly be seen followed by whatever happens afterwards. ἀ e grease made with 100% Group III oil was the least stable and oxidized immediately and quickly. ἀ e grease made with 100% PAO was better but also oxidized quickly. Modifying the PAO with 10% AN-15 imparted oxidation resistance to the grease. And modifying the PAO with 50% alkylated naphthalene imparted significant oxidation resistance making the grease completely stable and equivalent to the grease made with 100% alkylated naphthalene.

- 30 VOLUME 79, NUMBER 2

CONCLUSIONS

So why use alkylated naphthalenes? Alkylated naphthalenes are high performance synthetic fluids available in a diverse ISO viscosity range from 22-193 cSt for flexibility in designing lubricants for specific applications. ἀ ey have many superior performance properties over other oils and are able to impart these advantages when added to other oils and greases. ἀ ey provide excellent thermal and thermo-oxidative stability because of the electron-rich naphthalene ring and its ability to resonate and disperse energy. Alkylated naphthalenes have inherent hydrolytic stability because they do not contain functional groups that can hydrolyze. ἀ ey have good seal swelling properties - better than Group II and III mineral oils and PAOs. ἀ ey have better additive solubility than Group II and III mineral oils and PAOs and less surface competition than seen with polar esters. Alkylated naphthalenes have good pressureviscosity coefficients, film thickness, and film strength,

which can reduce friction. ἀ ey also have good low pour points. Greases made with alkylated naphthalenes also have several advantages over greases made with PAO, including less required thickener, improved transparency, and a smoother texture. Alkylated naphthalenes also have superior thermo-oxidative stability than PAO and are able to impart this stability to PAO greases.

REFERENCES

1. Hourani, M.J., Hessell, E.T., Abramshe, R.A., and Liang, J.G., “Alkylated Naphthalenes as High Performance Synthetic Fluids,” Tribology Transactions, 50: 82-87, 2007.

2. Hessell, E.T. and Abramshe, R.A., “Alkylated Naphthalenes as High Performance Synthetic Fluids,” Journal of Synthetic Lubrication, 20-2, 2003.

3. ASTM Annual Books of ASTM Standards, Volumes 05.01, 05.02, and 05.03, Petroleum

Figure 1: Alkylated Naphthalene Structure ἀ e core naphthalene system consists of two fused six-membered rings with a electron rich conjugated π system.

R1 to R8 are independently a linear or branched alkyl group or hydrogen

Figure 2: Alkylated Naphthalene Synthesis Physical properties depend on: - Number of carbons in the alkyl group (Controlled by raw material selection) - Degree of branching of the alkyl group (Controlled by raw material selection) - Number of alkyl groups on the naphthalene ring (Controlled by chemical processing)

NLGI

Figure 3: Gas Chromatography of an Alkylated Naphthalene Mixture Showing the Distribution GC separates compounds by boiling point.

Table 1: Physical Properties of Alkylated Naphthalenes Linear and branched alkyl groups are of the same carbon number.

- 32 VOLUME 79, NUMBER 2

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Table 2: API Base Oil Categories Group I: Solvent refined paraffinic base stocks Group II: Mildly hydrotreated paraffinic base stocks Group III: Severely hydrotreated paraffinic base stocks Group V: Esters, glycols, silicones, alkylated aromatics, phosphate esters

Figure 4: Generalized Structures of Alkylated Naphthalenes vs. Other Synthetics

- 33 NLGI SPOKESMAN, MAY/JUNE 2015

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Table 3: Comparison of Some Lubricant Base Fluids

Figure 5: Aniline Point

- 34 VOLUME 79, NUMBER 2

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Table 4: Alkylated Naphthalene Properties

Table 5: ἀ ermal Stability (FTM 3411) 274ºC for 96 hours with steel coupon in sealed glass tube

- 35 NLGI SPOKESMAN, MAY/JUNE 2015

Table 6: ἀ ermal Stability (FTM 3411) 274ºC for 96 hours with steel coupon in sealed glass tube A 7 cSt Group III base stock has been modified with different Group V base stocks.

Table 7: ἀ ermal Stability - Modified Cincinnati Milacron ASTM D 2070 Copper and steel rods in 200 ml test oil (Test run at 150ºC, 7 days) Original test procedure is run at 135ºC, 7 days.

Table 8: ἀ ermal Stability - Modified Cincinnati Milacron ASTM D 2070 Copper and steel rods in 200 ml test oil (Test run at 150ºC, 7 days) Original test procedure is run at 135ºC, 7 days. * PAO is 114 cSt @ 40°C - Blend adjusted to equal viscosity of AN-15.

Table 9: ἀ ermal Stability - Modified Cincinnati Milacron ASTM D 2070 Copper and steel rods in 200 ml test oil (Test run at 150°C, 7 days) Original test procedure is run at 135ºC, 7 days ** PAO - 114 cSt @ 40°C - Blend adjusted to equal viscosity of AN-15. *** Additive Package containing antioxidants, yellow metal deactivator, and rust inhibitor.

Table 10: ἀ ermal Stability - Panel Coker FTM 791-3462 Temperature Conditions: Test Panel: 200°C Oil Sample: 140°C

Table 11: ἀ ermo-oxidative Stability - RPVOT ASTM D 2272

- 37 NLGI SPOKESMAN, MAY/JUNE 2015

NLGI

Table 12: Group III (ISO VG 46) vs. Group III Modified with Alkylated Naphthalene

Figure 6: ἀ ermooxidative Stability PDSC ASTM D 6186 Isothermal @ 160ºC, 500 psi Oxygen Group II vs. 20% Alkylated Naphthalene in Group II

- 38 VOLUME 79, NUMBER 2

NLGI Figure 7: ἀ ermooxidative Stability – PDSC ASTM D 6186 Isothermal @ 160ºC, 500 psi Oxygen 20% AN-8 in PAO 4 cSt with 0.2% Antioxidant

Table 13: Hydrolytic Stability – Beverage Bottle Test ASTM D 2619 Neat Alkylated Naphthalenes

Figure 8: Hydrolytic Stability – Beverage Bottle Test ASTM D 2619 Group II Base Oil (ISO VG 46) Modified with 10% of Different Group V Base Stocks

- 39 NLGI SPOKESMAN, MAY/JUNE 2015

Table 14: ἀ in Film Volatility 2 grams in aluminum pan for 24 hours

Table 15: ἀ in Film Volatility 2 grams in aluminum pan for 24 hours

Figure 9: Low Temperature Viscosity Profile

- 40 VOLUME 79, NUMBER 2

Figure 10: Friction Study – FZG Modified ASTM D 5182 Test Oils with 0.3% AW additive

Table 16: EHD Film ἀ ickness and PressureViscosity Coefficient

Table 17: Seal Swell - ASTM D 4289 (Neat AN-19)

- 41 NLGI SPOKESMAN, MAY/JUNE 2015

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Figure 11: Seal Swell - ASTM D 471

Table 18: AN-15 vs. PAO 10 in Li-12-OH Grease Lithium 12-Hydroxystearte NLGI #2

- 42 VOLUME 79, NUMBER 2

Figure 12: Grease Color / Appearance Alkylated Naphthalene Less thickener = improved low temperature properties Bridging solvent = reduced opaqueness Effective dispersant = smooth grease

Figure 13: ἀ ermo-oxidative Stability – PDSC ASTM 5483 Explanation

Figure 14: ἀ ermo-oxidative Stability – PDSC ASTM D 5483 at 180ºC

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