Lubricating oil composition and method for using lubricating oil composition

Abstract

A lubricating oil composition including a base oil (X) having a tertiary carbon atom at a content of 8.0 at % or more based on the total carbon of hydrocarbons and an antioxidant (Y) having an amine-based antioxidant (A), a phenol-based antioxidant (B), and a phosphor-based antioxidant (C). The amine-based antioxidant (A) includes a diphenylamine compound (A1) represented by the following general formula (a1):where Ra1 and Ra2, na1 and na2 are defined in the disclosure.

1 . A lubricating oil composition comprising:
 a base oil (X) comprising tertiary carbon atom at a content of 8.0 at % or more based on the total carbon of hydrocarbons; and   an antioxidant (Y) comprising an amine-based antioxidant (A), a phenol-based antioxidant (B), and a phosphor-based antioxidant (C),   wherein the amine-based antioxidant (A) comprises a diphenylamine compound (A1) represented by the following general formula (a1):   
       
         
           
           
               
               
           
         
       
       wherein R a1  and R a2  are each independently an alkyl group having 1 to 30 carbon atoms, na1 and na2 are each independently an integer of 1 to 5, wherein when na1 is 2 or more, a plurality of Rai's may be the same, or may be different from each other, and in the case where na2 is 2 or more, a plurality of R a2 's may be the same, or may be different from each other,
 the phenol-based antioxidant (B) comprises a hindered phenol compound (B1) having an ester structure, and 
 the total content [(A1)+(B1)+(C)] of the diphenylamine compound (A1), the hindered phenol compound (B1) having an ester structure, and the phosphor-based antioxidant (C) based on the total amount of the lubricating oil composition is greater than 1.0 mass % and 2.0 mass % or less. 
 
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the total content [(A1)+(B1)] of the diphenylamine compound (A1) and the hindered phenol compound (B1) having an ester structure is 0.9 mass % or more based on the total amount of the lubricating oil composition. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the content of the diphenylamine compound (A1) is 0.3 mass % to 1.8 mass % based on the total amount of the lubricating oil composition. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the amine-based antioxidant (A) further comprises a naphthylamine compound (A2) represented by the following general formula (a2): 
       
         
           
           
               
               
           
         
         wherein R a3  is an alkyl group having 1 to 30 carbon atoms, na3 is an integer of 1 to 5, and when na3 is 2 or more, a plurality of R a3 's may be the same or may be different from each other. 
       
     
     
         5 . The lubricating oil composition according to  claim 4 , wherein the total content [(A1)+(A2)] of the diphenylamine (A1) and the naphthylamine (A2) is 0.8 mass % or more and lower than 2.0 mass % based on the total amount of the lubricating oil composition. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the hindered phenol compound (B1) having an ester structure is one or more selected from the group consisting of a compound (B1-1) represented by the following general formula (b1-1) and a compound (B1-2) represented by the following general formula (b1-2): 
       
         
           
           
               
               
           
         
         wherein R b1  is an alkylene group having 1 to 5 carbon atoms, and R b2  is an alkyl group having 1 to 25 carbon atoms; 
       
       
         
           
           
               
               
           
         
         wherein R b3  and R b4  are each independently an alkylene group having 1 to 5 carbon atoms, and m is an integer of 2 to 4. 
       
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein the phosphor-based antioxidant (C) comprises a phosphor atom-containing compound (C1) having a phenol structure represented by the following general formula (c1): 
       
         
           
           
               
               
           
         
         wherein R c1 , R c2 , R c3  and R c4  are each independently a hydrogen atom or an alkyl group having 1 to 30 carbon atoms. 
       
     
     
         8 . The lubricating oil composition according to  claim 1 , further comprising one or more of lubricating oil additive selected from the group consisting of an extreme pressure agent, a detergent dispersant, a pour point depressant, a viscosity index improver, a rust inhibitor, a metal deactivator, an anti-foaming agent and a friction modifier. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the content of the base oil (X) is 90.0 mass % or more based on the total amount of the lubricating oil composition. 
     
     
         10 . The lubricating oil composition according to  claim 1 , which is used for one or more device selected from the group consisting of a turbine, a compressor and a hydraulic device. 
     
     
         11 . A method for using the lubricating oil composition according to  claim 1 , in one or more device selected from the group consisting of a turbine, a compressor and a hydraulic device.