Grease composition

Abstract

Provided is a lubricating grease used for lubricating mechanical elements having a reciprocating sliding ball interposed therebetween and maintaining flaking resistance even under a high load in mechanical elements having a reciprocating sliding ball interposed therebetween. The present invention therefore provides a grease composition comprising a base oil (a), a diurea compound (b), an amide compound (c), and a thiophosphorous compound or a thiophosphoric acid ester compound (d), wherein the diurea compound (b) includes a compound represented by Formula (1) R 1 —NHCONH—R 2 —NHCONH—R 3 (1) wherein R 1 and R 3 represent an acyclic aliphatic hydrocarbon group having from 8 to 20 carbon atoms, and R 2 represents a diphenylmethane group.

We claim: 
     
         1 . A grease composition comprising a base oil (a), a diurea compound (b), an amide compound (c), and a thiophosphorous compound or a thiophosphoric acid ester compound (d), wherein the diurea compound (b) includes a compound represented by Formula (1)
   R 1 —NHCONH—R 2 —NHCONH—R 3   (1)
   
       wherein R 1  and R 3  represent an acyclic aliphatic hydrocarbon group having from 8 to 20 carbon atoms, and R 2  represents a diphenylmethane group. 
     
     
         2 . A grease composition according to  claim 1 , wherein the diurea compound (b) includes a diurea compound (b) in which R 1  and R 3  in Formula 1 are either an acyclic aliphatic hydrocarbon group having from 8 to 12 carbon atoms or an acyclic aliphatic hydrocarbon group having from 14 to 20 carbon atoms. 
     
     
         3 . A grease composition according to  claim 1 , further comprising a saturated or an unsaturated fatty acid having from 4 to 18 carbon atoms or a metal salt thereof (e). 
     
     
         4 . A grease composition according to  claim 1 , further comprising an amine compound (f) represented by Formula (2)
   R 4 —NH—R 5 —NH 2   (2)
   
       wherein R 4  represents a saturated or an unsaturated hydrocarbon group having from 5 to 18 carbon atoms, and R 5  represents a saturated or an unsaturated hydrocarbon group having from 2 to 3 carbon atoms. 
     
     
         5 . A grease composition according to  claim 1 , wherein the amide compound (c) includes an amide compound (c) represented by Formula (3) or Formula (4)
   R 6 —CO—NH 2   (3)
     R 6 —CO—NH—R 7 —NH—CO—R 6   (4)
   
       wherein R 6  represents a saturated or an unsaturated hydrocarbon group having from 15 to 17 carbon atoms, and R 7  represents a methylene group or an ethylene group. 
     
     
         6 . A grease composition according to  claim 1 , wherein the thiophosphorous compound includes a thiophosphorous compound represented by Formula (5), and the thiophosphoric acid ester compound includes a thiophosphoric acid ester compound represented by Formula (6)
   (R 8 S) 3 P  (5)
     (R 9 O) 3 PS  (6)
   
       wherein R 8  represents a saturated or an unsaturated hydrocarbon group having from 8 to 18 carbon atoms or an aryl group having from 6 to 18 carbon atoms and wherein R 9  represents a saturated or an unsaturated hydrocarbon group having from 8 to 18 carbon atoms or an aryl group having from 6 to 18 carbon atoms.