Grease composition for automobile wheel bearing

Abstract

The present invention provides a grease composition for automobile wheel bearings, which contains (a) an urea thickener represented by general formula (1): R 1 —NHCONH—R 2 —NHCONH—R 3 (wherein R 1 and R 3 may be the same or different from each other and are each independently an aromatic hydrocarbon group having 6 to 12 carbon atoms, and R 2 represents an aromatic hydrocarbon group having 6 to 15 carbon atoms); (b) an organic molybdenum compound; and (c) a base oil. The composition of the present invention can extend the flaking life and lubrication life, and reduce the fretting wear.

1 . A grease composition for automobile wheel bearings, comprising: 
 (a) an urea thickener represented by general formula (1):      R 1 —NHCONH—R 2 —NHCONH—R 3    (1)    wherein R 1  and R 3  may be the same or different from each other and each independently represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, and R 2  represents an aromatic hydrocarbon group having 6 to 15 carbon atoms;    (b) an organic molybdenum compound; and    (c) a base oil.    
   
   
       2 . The grease composition of  claim 1 , wherein the urea thickener (a) is a compound represented by formula (1-1) or (1-2):  
     
       
         
         
             
             
         
       
     
   
   
       3 . The grease composition of  claim 1 , wherein the urea thickener (a) is contained in an amount of 2 to 35% by mass with respect to the mass of the base oil.  
   
   
       4 . The grease composition of  claim 1 , wherein the organic molybdenum compound (b) is a molybdenum dithiocarbamate.  
   
   
       5 . The grease composition of  claim 4 , wherein the organic molybdenum compound (b) is a molybdenum dithiocarbamate represented by formula (2):  
       [R 4 R 5 N—CS—S] 2 —Mo 2 O m S n    (2)  
     wherein R 4  and R 5 , which may be the same or different and each independently represents a straight-chain or branched alkyl group having 1 to 24 carbon atoms; and m ranges from 0 to 3 and n ranges from 4 to 1, provided that m+n=4.  
   
   
       6 . The grease composition of  claim 1 , wherein the organic molybdenum compound (b) is contained in an amount of 0.1 to 10% by mass in the composition.  
   
   
       7 . The grease composition of  claim 1 , wherein the organic molybdenum compound (b) is contained in an amount of 1 to 5% by mass in the composition.  
   
   
       8 . The grease composition of  claim 1 , wherein the base oil (c) is a mixture comprising 20 to 50% of a synthetic oil and 80 to 50% of a mineral oil.  
   
   
       9 . The grease composition of  claim 8 , wherein the synthetic oil is a synthetic hydrocarbon oil.  
   
   
       10 . A grease composition for automobile wheel bearings, comprising: 
 (a) an urea thickener represented by formula (1-1) or (1-2) in an amount of 10 to 25% by mass with respect to the total mass of the composition;                          (b) a molybdenum dithiocarbamate in an amount of 1 to 5% by mass with respect to the total mass of the composition; and    (c) a mixed base oil consisting of 60% of a mineral oil and 40% of a synthetic hydrocarbon oil.