Water resistant grease composition

Abstract

A grease with improved water resistance is based on a combination of a polyamide thixotrope with a water insoluble thickener, preferably a lithium soap/complex thickener and an antioxidant/corrosion inhibitor/antiwear additive package. The improvement is maintained when highly effective or aggressive rust inhibitors which normally tend to degrade water wash out resistance are present in the grease. Another advantage is that resistance to fretting is significantly improved to the extent that the greases containing these components are capable of achieving a high level of resistance to false brinelling. The greases are particularly useful for application in wind turbine bearings.

What is claimed is: 
     
         1 . A grease composition which comprises: a lubricating base oil, a water insoluble thickener, and a thixotropic polyamide. 
     
     
         2 . The grease composition according to  claim 1  in which the polyamide comprises a reaction product of (i) a long chain (C 8 -C 20 ) carboxylic acid derivative and (ii) an alkylene amine having at least two primary amine groups. 
     
     
         3 . The grease composition according to  claim 2  in which the polyamide comprises a diamide which is a reaction product of a C 10 -C 20  carboxylic acid and a C 2 -C 4  alkylene diamine. 
     
     
         4 . The grease composition according to  claim 3  in which the polyamide comprises a diamide which is a reaction product of a C 10 -C 20  straight chain fatty carboxylic acid and a C 2 -C 4  alkylene diamine. 
     
     
         5 . The grease composition according to  claim 4  in which the polyamide comprises a diamide which is derived from ethylene diamine, decanoic acid and 12-hydroxyoctadeanoic acid. 
     
     
         6 . The grease composition according to  claim 4  in which the polyamide comprises a diamide which is mixture of N,N′-ethane-1,2-diylbis(decanamide), 12-hydroxy-N-[2(1-oxydecyl) amino]ethyloctadecanamide and N,N′-1,2-diylbis(12-hydroxyoctadecanamide). 
     
     
         7 . The grease composition according  claim 1  in which the thickener comprises an aluminum, barium, calcium or lithium soaps, or an aluminum, barium, calcium or lithium salt/soap complex. 
     
     
         8 . The grease composition according  claim 7  in which the thickener comprises a lithium salt/soap complex. 
     
     
         9 . The grease composition according  claim 1  in which the thickener comprises an inorganic clay thickener. 
     
     
         10 . The grease composition according  claim 1  in which the lubricating base oil comprises a poly alpha olefin. 
     
     
         11 . The grease composition according  claim 10  in which the lubricating base oil comprises a poly alpha (C 8 -C 12 ) olefin. 
     
     
         13 . The grease composition according  claim 10  in which the lubricating base oil comprises a poly alpha (C 8 -C 12 ) olefin having a kinematic viscosity of 2 to 10 cSt and a poly alpha (C 8 -C 12 ) olefin having a kinematic viscosity of 100 to 200 cSt. 
     
     
         14 . The grease composition according  claim 1  which comprises at least one of a corrosion inhibitor, an antioxidant and an antiwear agent. 
     
     
         15 . The grease composition according  claim 14  in which the corrosion inhibitor comprises an amine phosphate derived from a tertiary alkylamine and acid phosphate moiety derived from a phosphoric acid represented by the formula. R 1 O(R 2 O)P(O)OH, where R 1  is hydrogen or C 10 -C 20  hydrocarbyl and R 2  is hydrocarbyl and R 1  and R 2  may be the same or different. 
     
     
         16 . The grease composition according  claim 14  which comprises an imidazoline rust inhibitor. 
     
     
         17 . The grease composition according  claim 16  in which the imidazoline rust inhibitor comprises a long chain alkyl or alkenyl (C 8 -C 20 ) imidazoline. 
     
     
         18 . The grease composition according  claim 17  in which the imidazoline rust inhibitor comprises 2-oleyl imidazoline. 
     
     
         19 . The grease composition according  claim 1  which has a rating in the Riffel Test of maximum scar less than 10μ, average scar less than 3μ and corrosion not more than 3. 
     
     
         20 . The grease composition according  claim 1  which has a water resistance (ASTM D 1264) of not more than 10%. 
     
     
         21 . The grease composition according  claim 1  which has an oil separation (ASTM D 6184) less than 5%. 
     
     
         22 . The grease composition according  claim 1  which has a low-temperature starting torque (ASTM D 1478, −40° C.) not more than 4,000 g-cm. 
     
     
         23 . A grease composition having improved water resistance, mechanical grease stability and low temperature performance which comprises:
 (i) a synthetic hydrocarbon base oil,   (ii) a lithium complex thickener,   (iii) a thixotropic, water-insoluble, oil-insoluble polyamide co-thickener derived from at least one C 8 -C 20  monocarboxylic fatty acid and a C 2 -C 6  alkylene diamine,   (iv) a corrosion inhibitor   (v) an antioxidant, and   (vi) an antiwear agent.   
     
     
         24 . The grease composition according to  claim 23  in which:
 (i) the base oil comprises a polyalpha olefin), 
 (ii) the thixotropic polyamide co-thickener is derived from decanoic acid, 12-hydroxystearic acid and ethylene diamine, and 
 (iii) the corrosion inhibitor comprises an amine phosphate and/or an alkyl imidazoline. 
 
     
     
         25 . The grease composition according to  claim 24  which comprises:
 (i) from 70 to 85 wt % of the base oil, 
 (ii) from 6 to 14 wt % of the lithium complex thickener, 
 (iii) from 0.1 to 5 wt % of the polyamide co-thickener. 
 
     
     
         26 . A grease composition having improved water washout resistance and anticorrosion characteristics having a water washout resistance (D 1264) not more than 15%, low-temperature torque starting torque (ASTM D 1478, −40° C.) not more than 4,000 g-cm, and oil separation (ASTM D6184) less than 8. 
     
     
         27 . The grease according to  claim 26  having a water washout resistance (D 1264) not more than 10%, and low-temperature torque starting torque (ASTM D 1478, −40° C.) not more than 3,000 g-cm, and an oil separation (ASTM D 6184) less than 5%. 
     
     
         28 . The grease according to  claim 26  having a water washout resistance (D 1264) not more than 15%, low-temperature torque starting torque (ASTM D 1478, −30° C.) not more than 2,000 g-cm, and an oil separation (ASTM D 6184) less than 8%. 
     
     
         29 . The grease according to  claim 26  having an Oil separation (ASTM D 6184) less than 5%. 
     
     
         30 . The grease according to  claim 26  having a negative change in penetration in the Wet Roll test (ASTM D 7342-2 (Procedure B, 10% DI at room temperature). 
     
     
         31 . A method of making a grease composition having improved water resistance, mechanical grease stability and low temperature performance which comprises providing the following components:
 (i) a synthetic hydrocarbon base oil,   (ii) a lithium complex thickener,   (iii) a thixotropic, water-insoluble, oil-insoluble polyamide co-thickener derived from at least one C 8 -C 20  monocarboxylic fatty acid and a C 2 -C 6  alkylene diamine,   (iv) a corrosion inhibitor   (v) an antioxidant, and   (vi) an antiwear agent,   
       and mixing the components to form a grease. 
     
     
         32 . The method according to  claim 31  in which:
 (i) the base oil comprises a poly(alpha olefin), 
 (ii) the thixotropic polyamide co-thickener is derived from decanoic acid, 12-hydroxystearic acid and ethylene diamine, and 
 (iii) the corrosion inhibitor comprises an amine phosphate and/or an alkyl imidazoline. 
 
     
     
         33 . The method according to  claim 32  which comprises:
 (i) from 70 to 85 wt % of the base oil, 
 (ii) from 6 to 14 wt % of the lithium complex thickener, 
 (iii) from 0.1 to 5 wt % of the polyamide co-thickener.