Polyurea/Calcium Sulfonate Complex Grease Composition for Use in Constant Velocity Joints

Abstract

The present application relates to polyurea/calcium sulfonate complex grease composition for use in constant velocity joints. The invention discloses a lubricating grease with thixotropy and a preparation method thereof. The lubricating grease comprises a polyurea/high base number calcium sulfonate composite thickener, colloidally dispersed calcium carbonate solid particles in the form of calcite, a calcium borate or calcium borate composite, a calcium soap of fatty acid having 12 to 24 carbon atoms, an organic molybdenum compound, and an antioxidant. The above components are uniformly dispersed in an oil phase medium. The content of high base number calcium sulfonate in the lubricating grease is less than 22 wt %.

1 . The polyurea/calcium sulfonate complex grease for constant velocity joints comprising the following components (a) to (d):
 (a) a base oil;   (b) a thickener;   (c) an organic molybdenum compound; and   (d) an antioxidant.   
     
     
         2 . The grease as claimed in  claim 1 , wherein the component (a) is a mixed mineral and synthetic oil. 
     
     
         3 . The grease as claimed in  claim 1 , wherein the component (a) is a mineral oil. 
     
     
         4 . The grease as claimed in  claim 1 , wherein the component (a) is a synthetic oil. 
     
     
         5 . The grease as claimed in  claim 1 , wherein the grease comprises: 70 wt % or more oleaginous medium in which there is homogeneously dispersed:
 less than 22 wt % calcium sulfonate complex thickener comprising fine particles of crystalline calcium carbonate in calcite form;   0.5 to 6.5 wt % polyurea thickener;   0.05 to 3 wt % calcium borate or a calcium borate complex;   0.5 to 3.5 wt % calcium soap of C 12-24  aliphatic fatty acids;   0.1 to 1 wt % organic molybdenum compound;   0.5 to 2 wt % antioxidant; and   0 to 3 wt % lime or calcium hydroxide from lime or calcium hydroxide not consumed in the reactions during the preparation of grease,   wherein all percentages are weight % based on the total weight of the grease.   
     
     
         6 . The grease as claimed in  claim 1 , wherein the component (b) is a polyurea/calcium sulfonate complex thickener. 
     
     
         7 . The grease as claimed in  claim 5 , wherein the calcium soap of C 12-24  aliphatic fatty acids comprises a calcium soap of C 12-24  hydroxy fatty acids. 
     
     
         8 . The grease as claimed in  claim 7 , wherein the calcium soap of C 12-24  hydroxy fatty acids comprises a calcium soap of hydroxystearic acid. 
     
     
         9 . The grease as claimed in  claim 5 , wherein the polyurea thickener is obtained by reaction of a diisocyanate and one or more amine containing compounds. 
     
     
         10 . The grease as claimed in  claim 9 , wherein the diisocyanate comprises 4,4′-diphenylmethane diisocyanate. 
     
     
         11 . The grease as claimed in  claim 9 , wherein the one or more amine containing compounds comprises one or more of octylamine, stearyl amine, or cyclohexyl amine. 
     
     
         12 . The grease as claimed in  claim 1 , wherein the component (c) is molybdenum di-thiophosphates. 
     
     
         13 . The grease as claimed in  claim 1 , wherein the component (d) is one or a mixture of dialkyldiphenylamine, phenyl-α-naphthylamine, di-tert-butyl-p-cresol, and 2-naphthol. 
     
     
         14 . A process for preparing the polyurea/calcium sulfonate complex grease of  claim 1 , the process comprising mixing an overbased calcium sulfonate, a base oil, a C 12-24  fatty acid such as 12-hydroxylstearic acid, water, dodecylbenzene sulfonic acid, boric acid and a carboxylic acids having from 1 to 7 carbon atoms, in a sealed reactor while heating under elevated pressure; venting the reactor and then heating to remove water and volatiles; then adding additional base oil, diisocyanate and one or more amines, heating to effect reaction to form a polyurea/calcium sulfonate complex thickener and removal of volatiles; and then adjusting the final properties of the grease by adding extra base oil and/or additives, followed by any additional processing steps. 
     
     
         15 . The process as claimed in  claim 14 , wherein after calcite formation and before addition of the polyurea forming components, additional hydroxy stearic acid and/or boric acid, water, and an appropriate amount of lime are optionally added and mixed at temperatures of about 280° F.