Grease composition

Abstract

A grease composition with high wear resistance, comprising a base oil, a thickener and a poly(meth)acrylate derivative.

1 . A grease composition comprising a base oil, a thickener and poly(meth)acrylate which contains hydroxyl groups. 
     
     
         2 . A grease composition according to  claim 1 , wherein the thickener comprises a urea compound formed by the reaction between an isocyanate and a primary amine. 
     
     
         3 . A grease composition according to  claim 1 , wherein the thickener comprises a urea compound selected from the group consisting of:
 a diurea compound obtained by the reaction between a diisocyanate and a primary monoamine;   a tetraurea compound obtained by the reaction between a diisocyanate, a primary diamine and a primary monoamine; and   a triurea-monoureathane compound obtained by the reaction between a diisocyanate, a primary diamine, a primary monoamine and a monoalcohol.   
     
     
         4 . A grease composition according to  claim 1 , wherein the thickener comprises an alkyl diurea compound represented by general formula (I):
   R 1 —NHCONH—R 2 —NHCONH—R 3   (I)
   
       wherein R 1  and R 3  each represents a C 8-12  aliphatic hydrocarbon group, and R 2  represents a C 6-15  divalent aromatic group. 
     
     
         5 . A grease composition according to  claim 1 , wherein the poly(meth)acrylate which contains hydroxyl groups is a copolymer comprising, as constituent monomers, an alkyl(meth)acrylate having a C 1-20  alkyl group, and a hydroxyl-group-containing vinyl monomer. 
     
     
         6 . A grease composition according to  claim 5 , wherein the alkyl(meth)acrylate having a C 1-20  alkyl group is an alkyl(meth)acrylate having a C 8-20  alkyl group. 
     
     
         7 . A grease composition according to  claim 5 , wherein the hydroxyl-group-containing vinyl monomer is selected from the group consisting of: hydroxyalkyl(C 2-6 ) (meth)acrylates, mono- or di-hydroxyalkyl(C 1-4 )-substituted (meth)acrylamides, vinyl alcohol (formed by the hydrolysis of vinyl acetate units), C 3-12  alkenols, C 4-12  alkene diols, hydroxyalkyl(C 1-6 ) alkenyl(C 3-10 ) ethers, hydroxyl-group-containing aromatic monomers, polyhydric alcohols, and vinyl monomers containing a polyoxyalkylene chain and hydroxyl group(s). 
     
     
         8 . A grease composition according to  claim 5 , wherein the copolymer further comprises, as constituent monomers, a monomer containing a nitrogen atom selected from the group consisting of: nitro-group-containing monomers, vinyl monomers containing primary, secondary or tertiary amino groups, amphoteric vinyl monomers and monomers containing a nitrile group. 
     
     
         9 . A grease composition according to  claim 1 , wherein the poly(meth)acrylate containing hydroxyl groups has a hydroxyl value of from 20 to 50. 
     
     
         10 . A grease composition according to  claim 1 , comprising from 60-95 mass % of the base oil, from 1-20 mass % of the thickener, and from 2-20 mass % of the poly(meth)acrylate which contains hydroxyl groups, taking the total grease composition as 100 mass %. 
     
     
         11 . A grease composition according to  claim 4 , wherein R 1  and R 3  each represent a C 8  aliphatic hydrocarbon group, and R 2  represents a diphenylmethane group. 
     
     
         12 . A grease composition according to  claim 4 , wherein either R 1  or R 3  represents a C 8  aliphatic hydrocarbon group, while the other from amongst R 1  and R 3  represents a C 12  aliphatic hydrocarbon group, and wherein R 2  represents a diphenylmethane group. 
     
     
         13 . A grease composition according to  claim 1 , wherein the thickener comprises:
 a first alkyl diurea compound represented by general formula (II):
   R 1 —NHCONH—R 2 —NHCONH—R 1   (II); and
 
   a second alkyl diurea compound represented by general formula (III):
   R 3 —NHCONH—R 2 —NHCONH—R 3   (III),
 
   
       wherein R 1  represents a C 8  aliphatic hydrocarbon group, R 2  represents a diphenylmethane group and R 3  represents a C 12  aliphatic hydrocarbon group. 
     
     
         14 . A grease composition according to  claim 1 , wherein the thickener comprises:
 a first alkyl diurea compound (a) selected from the group consisting of:
 (a1) an alkyl diurea compound represented by general formula (II):
   R 1 —NHCONH—R 2 —NHCONH—R 1   (II)
 
 
 (a2) an alkyl diurea compound represented by general formula (III):
   R 3 —NHCONH—R 2 —NHCONH—R 3   (III); and
 
 
 (a3) a combination of (a1) and (a2); and 
   a second alkyl diurea compound (b) represented by general formula (IV):
   R 1 —NHCONH—R 2 —NHCONH—R 3   (IV)
 
   
       wherein R 1  represents a C 8  aliphatic hydrocarbon group, R 2  represents a diphenylmethane group, and R 3  represents a C 12  aliphatic hydrocarbon group. 
     
     
         15 . A grease composition according to  claim 5 , wherein the alkyl(meth)acrylate having a C 1-20  alkyl group is selected from the group consisting of: an alkyl (meth)acrylate with a C 1-4  alkyl group, an alkyl(meth)acrylate having a C 8-20  alkyl group; and an alkyl (meth)acrylate with a C 5-7  alkyl group. 
     
     
         16 . A grease composition according to  claim 5 , wherein the alkyl(meth)acrylate having a C 1-20  alkyl group is an alkyl(meth)acrylate having a C 10-20  alkyl group. 
     
     
         17 . A method of lubrication comprising:
 applying a grease composition to a surface in relative movement to another surface, wherein the grease composition comprises a base oil, a thickener and poly(meth)acrylate which contains hydroxyl groups.   
     
     
         18 . A method of lubrication according to  claim 17 , wherein the thickener comprises a diurea compound obtained by the reaction between a diisocyanate and a primary monoamine. 
     
     
         19 . A method of lubrication according to  claim 17 , wherein the poly(meth)acrylate which contains hydroxyl groups is a copolymer comprising, as constituent monomers, an alkyl(meth)acrylate having a C 1-20  alkyl group, and a hydroxyl-group-containing vinyl monomer. 
     
     
         20 . A method of lubrication according to  claim 17 , wherein the alkyl(meth)acrylate having a C 1-20  alkyl group is an alkyl(meth)acrylate having a C 8-20  alkyl group.