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OSP-New Group V Base Fluid for Manufacture
OSP-New Group V Base Fluid for Manufacture of Sulfonate Greases
Govind Khemchandani, Ph. D.1, Perry Byrd2, & Jeff St. Aubin3
1 ἀe Dow Chemical Company Freeport, Texas 77541, USA gvkhemchandani@dow.com 2Mid-South Sales, Inc Jonesboro, Arkansas 3Chemtool Incorporated Rockton, IL
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]. ἀis 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]. ἀese 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]. ἀe 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 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. ἀerefore, 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
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
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. ἀe 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
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. ἀe base thickener is derived from a calcium sulfonate having a total base number of 300-400. ἀese 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. ἀe 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
ἀe 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. ἀey 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 ἀickened 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
