Lubricant composition and lubricating method

Abstract

Provided is a lubricating oil composition containing a refined paraffinic mineral oil (A) and an alkylbenzene (B) having a flash point of 160° C. or higher, and having a flash point of 250° C. or higher. The lubricating oil composition has a high flash point of 250° C. or higher and has an excellent long lifetime to such an extent that the lubricating oil composition can maintain excellent oxidation stability even in long-term use in high-temperature environments.

1 : A lubricating oil composition, comprising:
 (A) a refined paraffinic mineral oil (A); and   (B) an alkylbenzene (B) having a flash point of 160° C. or higher, and having a flash point of 250° C. or higher.   
     
     
         2 : The lubricating oil composition according to  claim 1 , further comprising:
 (C) an anti-foaming agent (C) comprising a polyacrylate-based anti-foaming agent (C1).   
     
     
         3 : The lubricating oil composition according to  claim 2 , wherein a weight average molecular weight of the polyacrylate-based anti-foaming agent (C1) is from 10,000 to 200,000. 
     
     
         4 : The lubricating oil composition according to  claim 2 , wherein:
 the anti-foaming agent (C) further comprises a silicone-based anti-foaming agent; and   a content of a silicone-based anti-foaming agent based on a total amount of the anti-foaming agent (C) is 10% by mass or less.   
     
     
         5 : The lubricating oil composition according to  claim 1 , further comprising:
 (D) an antioxidant (D) comprising an amine-based antioxidant (D1).   
     
     
         6 : The lubricating oil composition according to  claim 5 , wherein the amine-based antioxidant (D1) comprises a diphenylamine compound (D11) and a phenyl-naphthylamine compound (D12). 
     
     
         7 : The lubricating oil composition according to  claim 6 , wherein a content ratio of the component (D11) to the component (D12) [D11/D12] is from 0.1/1 to 1/1 by mass ratio. 
     
     
         8 : The lubricating oil composition according to  claim 5 , wherein:
 the amine-based antioxidant (D1) comprises a phenylenediamine-based antioxidant; and   a content of the phenylenediamine-based antioxidant based on a total amount of the amine-based antioxidant (D1) is 10% by mass or less.   
     
     
         9 : The lubricating oil composition according to  claim 1 , wherein a flash point of the refined paraffinic mineral oil (A) is 250° C. or higher. 
     
     
         10 : The lubricating oil composition according to  claim 1 , wherein a content of the refined paraffinic mineral oil (A) is from 60 to 99.9% by mass, based on a total amount of the lubricating oil composition. 
     
     
         11 : The lubricating oil composition according to  claim 1 , wherein a kinematic viscosity at 40° C. of the refined paraffinic mineral oil (A) is from 20 to 300 mm 2 /s. 
     
     
         12 : The lubricating oil composition according to  claim 1 , wherein a content of the alkylbenzene (B) is from 0.1 to 10% by mass, based on a total amount of the lubricating oil composition. 
     
     
         13 : The lubricating oil composition according to  claim 1 , wherein a kinematic viscosity at 40° C. of the alkylbenzene (B) is from 45 to 80 mm 2 /s. 
     
     
         14 : The lubricating oil composition according to  claim 1 , wherein:
 the alkylbenzene (B) comprises an alkylnaphthalene; and   a content of the alkylnaphthalene is 10 parts by mass or less relative to 100 parts by mass of a total amount of the alkylbenzene (B).   
     
     
         15 : A lubricating method, comprising lubricating a machine with a lubricating oil composition comprising:
 (A) a refined paraffinic mineral oil (A); and   (B) an alkylbenzene (B) having a flash point of 160° C. or higher, and has a flash point of 250° C. or higher.