Grease Composition For Use In Constant Velocity Joints

Abstract

In order to provide for a grease composition which has a good compatibility with boots made of rubber or thermoplastic elastomer, and which also gives low wear and low friction, a grease composition for use in constant velocity joints is suggested, comprising a) a base oil composition; b) at least one tri-nuclear molybdenum compound of the formula Mo 3 S k L n Q z , wherein L are independently selected ligands having organo groups with a sufficient number of carbon atoms to render the compound soluble or dispersible in the oil, n is from 1 to 4, k varies from 4 though 7, Q is selected from the group of neutral electron donating compounds such as amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5 and includes non-stoichiometric values; c) at least one urea derivative thickener.

1 . A grease composition for use in constant velocity joints comprising:
 a) a base oil composition;   b) at least one tri-nuclear molybdenum compound of the formula
   Mo 3 S k L n Q z , 
   wherein L are independently selected ligands having organo groups with a sufficient number of carbon atoms to render the compound soluble or dispersible in the oil, n is from 1 to 4, k varies from 4 though 7, Q is selected from the group of neutral electron donating compounds such as amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5 and includes non-stoichiometric values;   c) at least one urea derivative thickener.   
     
     
         2 . A grease composition according to  claim 1 , characterised in that the urea derivative thickener is selected from the group comprising di-urea and/or polyurea compounds and mixtures of said compounds with calcium-based thickeners. 
     
     
         3 . A grease composition according to  claim 1 , further comprising at least one zinc dithiophosphates, molybdenum dithiocarbamate and/or molybdenum dithiophosphates. 
     
     
         4 . A grease composition according to  claim 3 , characterised in that the amount of zinc dithiophosphates, molybdenum dithiophosphates and/or molybdenum dithiocarbamates is in a range of between 0.1% by weight to 5% by weight, referred to the total amount of the grease composition. 
     
     
         5 . A grease composition according to  claim 4 , characterised in that the weight percent added, referred to the total amount of the grease composition, of each of zinc dithiophosphates, molybdenum dithiophosphates and/or molybdenum dithiocarbamates is essentially identical. 
     
     
         6 . A grease composition according to  claim 1 , further comprising an agent having at least one anti-oxidation agent, corrosion inhibitor, anti-wear-agent wax, friction modifier and/or extreme pressure agent (EP agent). 
     
     
         7 . A grease composition according to  claim 1 , comprising 50% by weight to 98.9% by weight of the base oil composition, 0.1% by weight to 5% by weight of at least one tri-nuclear molybdenum compound, 1% by weight to 25% by weight of at least one urea derivative thickener, in each case referred to the total amount of the grease composition. 
     
     
         8 . A grease composition according to  claim 1 , comprising 70% by weight to 92% by weight of the base oil composition, 0.3% by weight to 2% by weight of the least one tri-nuclear molybdenum compound, 4.5% by weight to 20% by weight of the least one urea derivative thickener, 1.5% by weight to 3.5% by weight of at least one molybdenum dithiocarbamate, 0.5% by weight to 3% by weight of the least one zinc dithiophosphate, and 0.5% by weight to 2% by weight of at least one wax. 
     
     
         9 . A grease composition according to  claim 3 , characterised in that the weight percent added, referred to the total amount of the grease composition, of tri-nuclear molybdenum compounds is essentially identical with the weight percent of each one of zinc dithiophosphates, molybdenum dithiophosphates and/or molybdenum dithiocarbamates added. 
     
     
         10 . A grease composition according to  claim 3 , characterised in that the weight percent added, referred to the total amount of the grease composition, of tri-nuclear molybdenum compounds is four to ten times lower than the weight percent of the total amount of zinc dithiophosphates, molybdenum dithiophosphate and/or molybdenum dithiocarbamate added. 
     
     
         11 . A grease composition according to  claim 1 , characterised in that the sliding friction coefficient is at most 0.08.