Grease composition and rolling bearing

Abstract

A grease composition includes a base oil, a thickener, and zirconium oxide particles. The base oil is a poly-α-olefin. The zirconium oxide particles have a median diameter D50 of 0.6 μm to 4 μm. A content of the zirconium oxide particles is 2% by mass to 15% by mass with respect to a total amount of the base oil and the thickener.

What is claimed is: 
     
         1 . A grease composition comprising:
 a base oil;   a thickener; and   zirconium oxide particles, wherein   the base oil is a poly-α-olefin,   the zirconium oxide particles have a median diameter D 50  of 0.6 μm to 4 μm, and   a content of the zirconium oxide particles is 2% by mass to 15% by mass with respect to a total amount of the base oil and the thickener.   
     
     
         2 . The grease composition according to  claim 1 , wherein the thickener is a diurea represented by the following structural formula (1):
   R 1 —NHCONH—R 2 —NHCONH—R 3   (1)
   
       wherein, in the formula (1), R 1  and R 3  are each independently a functional group represented by the following formula (2) and R 2  is —C 6 H 4 —CH 2 —C 6 H 4 —; 
       
         
           
           
               
               
           
         
         a bonding position of each —C 6 H 4 — contained in R 2  with N is a 4-position when the bonding position of —C 6 H 4 — with —CH 2 —is considered as a 1-position; and 
         in the formula (2), R 4  is an alkyl group having 1 to 12 carbon atoms. 
       
     
     
         3 . The grease composition according to  claim 1 , wherein the content of the thickener is 10% by mass to 30% by mass with respect to the total amount of the base oil and the thickener. 
     
     
         4 . The grease composition according to  claim 1 , further comprising at least one of a rust inhibitor and an antioxidant. 
     
     
         5 . A rolling bearing in which the grease composition according to  claim 1  is sealed.