Grease composition and mechanical part

Abstract

The invention provides a grease composition containing a base oil, a thickener and an additive, characterized in that the base oil has a kinetic viscosity at 40° C. of 50 to 200 mm 2 /s; the thickener contains a diurea compound represented by formula (I): R 1 —NHCONH—R 2 —NHCONH—R 3 (wherein R 2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 1 and R 3 , which may be the same or different, represent cyclohexyl group or a straight-chain or branched alkyl group having 8 to 22 carbon atoms); and the additive is at least one selected from the group consisting of a metal salt of naphthenic acid, a salt of a fatty acid having 6 to 10 carbon atoms and an aliphatic amine having 6 to 10 carbon atoms, and a metal salt of an organic sulfonic acid. The composition of the invention shows excellent anti-fretting properties under the conditions of ordinary temperature to low temperature (e.g., −50° C., preferably about −40° C.).

1 . A grease composition comprising a base oil, a thickener and an additive, wherein;
 the base oil has a kinetic viscosity at 40° C. of 50 to 200 mm 2 /s;   the thickener comprises a diurea compound represented by formula (I):
   R 1 —NHCONH—R 2 —NHCONH—R 3   (I)
 
   
       (wherein R 2  is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 1  and R 3 , which may be the same or different, represent cyclohexyl group or a straight-chain or branched alkyl group having 8 to 22 carbon atoms); and
 the additive is at least one selected from the group consisting of a metal salt of naphthenic acid, a salt of a fatty acid having 6 to 10 carbon atoms and an aliphatic amine having 6 to 10 carbon atoms, and a metal salt of an organic sulfonic acid. 
 
     
     
         2 . The grease composition of  claim 1 , wherein the metal salt of naphthenic acid is at least one selected from the group consisting of zinc cyclopentanoate and zinc cyclohexanoate; the amine salt is a salt of a straight-chain fatty acid having 6 to 10 carbon atoms and a straight-chain aliphatic amine having 6 to 10 carbon atoms; and the metal salt of an organic sulfonic acid is at least one selected from the group consisting of calcium dinonylnaphthalenesulfonate, zinc dinonylnaphthalenesulfonate and barium dinonylnaphthalenesulfonate. 
     
     
         3 . The grease composition of  claim 1 , wherein the metal salt of naphthenic acid is contained in an amount of 0.5 to 5.0 mass %, the amine salt is contained in an amount of 1.5 to 5.0 mass %, and the metal salt of an organic sulfonic acid is contained in an amount of 1.5 to 5.0 mass %, with respect to the total mass of the grease composition. 
     
     
         4 . A mechanical part in which the grease composition of  claim 1  is packed.