Grease composition

Abstract

Provided is a grease composition containing a base oil (A) and a urea-based thickener (B), the base oil (A) containing a poly-α-olefin (PAO), the urea-based thickener (B) being one or more selected from diurea compounds represented by the general formula (b1): R1—NHCONH—R3—NHCONH—R2 (b1), when a content of the chain hydrocarbon group in R1 and R2 in the general formula (b1) is X molar equivalents and a content of the alicyclic hydrocarbon group in R1 and R2 in the general formula (b1) is Y molar equivalents, the grease composition satisfying the following Requirement (1) and having an increased cone penetration at a low temperature (−40° C.): Requirement (1): having a X/Y ratio of 2/1 to 10/1.

1 : A grease composition, comprising:
 a base oil comprising a poly-α-olefin; and   a urea-based thickener comprising at least one compound selected from diurea compounds of formula (b1), R 1 —NHCONH—R 3 —NHCONH—R 2 , where R 1  and R 2  are each independently a monovalent chain hydrocarbon group or alicyclic hydrocarbon group having 6 to 24 carbon atoms, R 1  and R 2  may be the same as or different from each other, R 3  is a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and a X/Y ratio in a range of 2/1 to 10/1 where a content of the chain hydrocarbon group in R 1  and R 2  is X molar equivalents and a content of the alicyclic hydrocarbon group in R 1  and R 2  is Y molar equivalents.   
     
     
         2 : The grease composition according to  claim 1 , wherein the chain hydrocarbon group in R 1  and R 2  is a saturated chain hydrocarbon group. 
     
     
         3 : The grease composition according to  claim 1 , wherein the alicyclic hydrocarbon group in R 1  and R 2  is a saturated alicyclic hydrocarbon group. 
     
     
         4 : The grease composition according to  claim 1 , wherein the grease composition has a worked penetration in a range of 240 to 300 at 25° C. 
     
     
         5 : The grease composition according to  claim 1 , wherein the grease composition has an unworked penetration of 150 or more at −40° C. 
     
     
         6 : The grease composition according to  claim 1 , wherein the base oil has a 40° C. kinematic viscosity in a range of 10 mm 2 /s to 40 mm 2 /s. 
     
     
         7 : The grease composition according to  claim 1 , wherein the base oil further comprises an ester-based synthetic oil. 
     
     
         8 : The grease composition according to  claim 7 , wherein the ester-based synthetic oil is in an amount of 20% by mass or less based on a total amount of the base oil. 
     
     
         9 : The grease composition according to  claim 7 , wherein the ester-based synthetic oil has a 40° C. kinematic viscosity in a range of 10 mm 2 /s to 40 mm 2 /s. 
     
     
         10 : The grease composition according to  claim 1 , wherein the grease composition further comprises an acidic phosphate ester. 
     
     
         11 : The grease composition according to  claim 10 , wherein the acidic phosphate ester is in an amount in a range of 1.0% by mass to 3.0% by mass based on a total amount of the grease composition. 
     
     
         12 : A grease composition for lubricating a sliding mechanism in which a metal material and a rubber material slide, comprising:
 the grease composition of  claim 1 .   
     
     
         13 : A method of lubrication, comprising:
 applying the grease composition of  claim 1  to a sliding mechanism in which a metal material and a rubber material slide.   
     
     
         14 : A method for producing a grease composition, comprising:
 synthesizing a urea-based thickener in a base oil comprising a poly-α-olefin,   wherein the urea-based thickener includes at least one compound selected from diurea compounds of formula (b1), R 1 —NHCONH—R 3 —NHCONH—R 2 , where R 1  and R 2  are each independently a monovalent chain hydrocarbon group or alicyclic hydrocarbon group having 6 to 24 carbon atoms, R 1  and R 2  may be the same as or different from each other, R 3  is a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and a X/Y ratio in a range of 2/1 to 10/1 where a content of the chain hydrocarbon group in R 1  and R 2  is X molar equivalents and a content of the alicyclic hydrocarbon group in R 1  and R 2  is Y molar equivalents.   
     
     
         15 : The grease composition according to  claim 2 , wherein the alicyclic hydrocarbon group in R 1  and R 2  is a saturated alicyclic hydrocarbon group. 
     
     
         16 : The grease composition according to  claim 2 , wherein the grease composition has a worked penetration in a range of 240 to 300 at 25° C. 
     
     
         17 : The grease composition according to  claim 2 , wherein the grease composition has an unworked penetration of 150 or more at −40° C. 
     
     
         18 : The grease composition according to  claim 2 , wherein the base oil has a 40° C. kinematic viscosity in a range of 10 mm 2 /s to 40 mm 2 /s. 
     
     
         19 : The grease composition according to  claim 2 , wherein the base oil further comprises an ester-based synthetic oil. 
     
     
         20 : The grease composition according to  claim 19 , wherein the ester-based synthetic oil is in an amount of 20% by mass or less based on a total amount of the base oil.