Lubricant composition

Abstract

The present invention relates to a lubricating oil composition containing a mineral oil (A) containing 30% by mass or more of a bright stock (A1) on the basis of the total amount of the lubricating oil composition, wherein the lubricating oil composition further contains a synthetic oil (B) and a phosphoric acid ester (C), the content of the synthetic oil (B) is less than 70% by mass on the basis of the total amount of the lubricating oil composition, the content of the phosphoric acid ester (C) as expressed in terms of a phosphorus atom is 0.050 to 0.200% by mass on the basis of the total amount of the lubricating oil composition, and a viscosity index is 150 or more, thereby providing a lubricating oil composition having low temperature dependence and favorable lubricating characteristics even in the case of using the mineral oil containing a bright stock.

1 . A lubricating oil composition comprising 30% by mass or more of a mineral oil (A) containing a bright stock (A1) on the basis of the total amount of the lubricating oil composition, wherein
 the lubricating oil composition further comprises a synthetic oil (B) and a phosphoric acid ester (C),   the content of the synthetic oil (B) is less than 70% by mass on the basis of the total amount of the lubricating oil composition,   the content of the phosphoric acid ester (C) as expressed in terms of a phosphorus atom is 0.050 to 0.200% by mass on the basis of the total amount of the lubricating oil composition, and   a viscosity index is 150 or more.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein a kinematic viscosity at 100° C. of the bright stock (A1) is 28.0 mm 2 /s or more. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein a content proportion of the bright stock (A1) in the mineral oil (A) is 5 to 70% by mass on the basis of the total amount of the mineral oil (A). 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the content of the synthetic oil (B) is 10% by mass or more and less than 70% by mass on the basis of the total amount of the lubricating oil composition. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein a viscosity index of the synthetic oil (B) is 130 or more. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein a kinematic viscosity at 100° C. of the synthetic oil (B) is 80 to 180 mm 2 /s. 
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein the synthetic oil (B) contains a poly-α-olefin (B1). 
     
     
         8 . The lubricating oil composition according to  claim 1 , wherein the phosphoric acid ester (C) contains a compound (C1) selected from an acidic phosphoric acid ester and an amine salt of an acidic phosphoric acid ester. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the phosphoric acid ester (C) contains a compound (C1) selected from an acidic phosphoric acid ester and an amine salt of an acidic phosphoric acid ester and a neutral phosphoric acid ester (C2). 
     
     
         10 . The lubricating oil composition according to  claim 9 , wherein a content ratio [(C2)/(C1)] of the neutral phosphoric acid ester (C2) to the compound (C1) is 2.0 to 40 in terms of a mass ratio. 
     
     
         11 . The lubricating oil composition according to  claim 1 , further comprising a sulfur atom-containing extreme pressure agent,
 the content of the sulfur atom-containing extreme pressure agent as expressed in terms of a sulfur atom being less than 0.12% by mass on the basis of the total amount of the lubricating oil composition.   
     
     
         12 . The lubricating oil composition according to  claim 1 , which is used for an oil-air lubrication system.