Grease composition

Abstract

Provided are a grease composition which inhibits simultaneously a bearing wear and a fretting wear under a high load to make it possible to elongate a life of the bearing; a grease composition which can inhibit a fretting wear caused by a change in a load in a thrust direction in addition to an usual fretting wear caused by small vibration in an oscillating direction; and a grease composition which is excellent in low-temperature characteristics. The grease compositions contain a base oil and a thickener, wherein the base oil contains a poly-α-olefin (component A) which has a kinetic viscosity of 300 mm 2 /s or more at 40° C. and which is produced by using a metallocene catalyst.

1 . A grease composition, comprising:
 a base oil comprising a poly-α-olefin (component A) having a kinetic viscosity of 300 mm 2 /s or more at 40° C. and that is produced by a metallocene catalyst; and   a thickener.   
     
     
         2 . The grease composition of  claim 1 , wherein the kinetic viscosity of the component A at 40° C. is 600 mm 2 /s or more. 
     
     
         3 . The grease composition of  claim 1 , comprising, based on a total mass of the composition, 20% by mass or more of the component A. 
     
     
         4 . The grease composition of  claim 1 , wherein the base oil has a kinetic viscosity of 150 to 2000 mm 2 /s at 40° C. and a worked penetration of 220 to 385. 
     
     
         5 . The grease composition  claim 1 , wherein the base oil further comprises a second component (B) having a kinetic viscosity of 70 mm 2 /s or less at 40° C. in a proportion of 10 to 70% by mass, based on a total mass of the composition. 
     
     
         6 . The grease composition of  claim 1 , comprising, based on a total mass of the composition, 17% by mass or less of the thickener. 
     
     
         7 . The grease composition of  claim 1 , wherein the thickener is a soap base thickener. 
     
     
         8 . The grease composition of  claim 5 , wherein the thickener is obtained by reacting a carboxylic acid with an alkali in the component B. 
     
     
         9 . The grease composition of  claim 1 , further comprising an extreme pressure additive comprising sulfur in a proportion of 0.01 to 10% by mass, based on a total mass of the composition. 
     
     
         10 . A method of inhibiting bearing wear, the method comprising:
 applying the grease composition of  claim 1 , to at least one selected from the group consisting of a main bearing and a pitch bearing of a wind power generation apparatus,   wherein the main bearing contacts a main shaft with which a blade of the wind power generation apparatus is connected, and the pitch bearing contacts a blade shaft mounted in the blade.   
     
     
         11 . The grease composition of  claim 1 , wherein the kinetic viscosity of the component A at 40° C. is 1000 mm 2 /s or more. 
     
     
         12 . The grease composition of  claim 1 , wherein the base oil further comprises a second component (B) having a kinetic viscosity in a range from 10 to 50 mm 2 /s at 40° C. in a proportion of 10 to 70% by mass, based on a total mass of the composition. 
     
     
         13 . The grease composition of  claim 1 , wherein the base oil further comprises a second component (B) having a kinetic viscosity in a range from 20 to 45 mm 2 /s at 40° C. in a proportion of 10 to 70% by mass, based on a total mass of the composition. 
     
     
         14 . The grease composition of  claim 1 , wherein the base oil further comprises a second component (B) having a kinetic viscosity in a range from 20 to 40 mm 2 /s at 40° C. in a proportion of 10 to 70% by mass, based on a total mass of the composition. 
     
     
         15 . The grease composition of  claim 1 , wherein the base oil has a kinetic viscosity of 200 to 1000 mm 2 /s at 40° C. and a worked penetration of 220 to 385. 
     
     
         16 . The grease composition of  claim 1 , wherein the base oil has a kinetic viscosity of 300 to 700 mm 2 /s at 40° C. and a worked penetration of 220 to 385. 
     
     
         17 . The grease composition of  claim 1 , comprising, based on a total mass of the composition, 30% by mass or more of the component A. 
     
     
         18 . The grease composition of  claim 1 , comprising, based on a total mass of the composition, 50% by mass or more of the component A. 
     
     
         19 . The grease composition of  claim 5 , comprising, based on a total mass of the composition:
 45 to 85% by mass of component (A); and   10 to 70% by mass of component (B).   
     
     
         20 . The grease composition of  claim 5 , comprising, based on a total mass of the composition:
 45 to 85% by mass of component (A); and   20 to 50% by mass of component (B).