Lubricant composition

Abstract

Provided is a lubricating oil composition having excellent wear resistance, the lubricating oil composition containing a base oil (A), an overbased metal detergent (B), a sulfur-phosphorus extreme pressure agent (C) having a carboxylic acid ester group, and a sulfur-phosphorus extreme pressure agent (D) having a carboxy group at an end.

1 . A lubricating oil composition, comprising:
 a base oil;   an overbased metal detergent;   a sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group; and   a sulfur-phosphorus extreme pressure agent having a carboxy group at an end.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the overbased metal detergent is at least one of an overbased calcium sulfonate with a base number of 100 mgKOH/g or more and an overbased calcium salicylates with a base number of 100 mgKOH/g or more. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group is a thiophosphoric acid ester having a carboxylic acid ester group. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group is a thiophosphoric acid ester of formula (1), 
       
         
           
           
               
               
           
         
         where R1 to R3 each independently are a hydrocarbon group having 3 to 20 carbon atoms, and L1 is a linear or branched alkylene group having 1 to 8 carbon atoms. 
       
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is a thiophosphoric acid ester having a carboxy group at an end. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is a thiophosphoric acid ester of formula (2), 
       
         
           
           
               
               
           
         
         where R4 and R5 each independently are a hydrocarbon group having 3 to 20 carbon atoms, and L2 is a linear or branched alkylene group having 1 to 8 carbon atoms. 
       
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein a ratio between a content of the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group and a content of the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is in a range of 50 to 95% by mass in terms of a mass ratio of the content of the sulfur-phosphorus extreme pressure agent to a total content of the sulfur-phosphorus extreme pressure agent and sulfur-phosphorus extreme pressure agent. 
     
     
         8 . The lubricating oil composition according to  claim 1 , wherein an organometallic extreme pressure agent has a content of less than 0.1% by mass based on a whole amount of a hydraulic oil composition. 
     
     
         9 . The lubricating oil composition according to  claim 1 , further comprising:
 a hindered phenol-based antioxidant.   
     
     
         10 . The lubricating oil composition according to  claim 1 , further comprising:
 an amine-based antioxidant.   
     
     
         11 . The lubricating oil composition according to  claim 1 , further comprising:
 an imide compound.   
     
     
         12 . (canceled) 
     
     
         13 . A lubrication method for lubricating an apparatus equipped with a sliding member having a phosphate coating on at least a part of a sliding surface, comprising:
 applying the lubricating oil composition of  claim 1  to the sliding member in the apparatus.   
     
     
         14 . The lubricating oil composition according to  claim 2 , wherein the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group is a thiophosphoric acid ester having a carboxylic acid ester group. 
     
     
         15 . The lubricating oil composition according to  claim 2 , wherein the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group is a thiophosphoric acid ester of formula (1), 
       
         
           
           
               
               
           
         
         where R1 to R3 each independently are a hydrocarbon group having 3 to 20 carbon atoms, and L1 is a linear or branched alkylene group having 1 to 8 carbon atoms. 
       
     
     
         16 . The lubricating oil composition according to  claim 2 , wherein the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is a thiophosphoric acid ester having a carboxy group at an end. 
     
     
         17 . The lubricating oil composition according to  claim 2 , wherein the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is a thiophosphoric acid ester of formula (2), 
       
         
           
           
               
               
           
         
         where R4 and R5 each independently are a hydrocarbon group having 3 to 20 carbon atoms, and L2 is a linear or branched alkylene group having 1 to 8 carbon atoms. 
       
     
     
         18 . The lubricating oil composition according to  claim 2 , wherein a ratio between a content of the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group and a content of the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is in a range of 50 to 95% by mass in terms of a mass ratio of the content of the sulfur-phosphorus extreme pressure agent to a total content of the sulfur-phosphorus extreme pressure agent and sulfur-phosphorus extreme pressure agent. 
     
     
         19 . The lubricating oil composition according to  claim 2 , wherein an organometallic extreme pressure agent has a content of less than 0.1% by mass based on a whole amount of a hydraulic oil composition. 
     
     
         20 . The lubricating oil composition according to  claim 3 , wherein the sulfur-phosphorus extreme pressure agent having a carboxylic acid ester group is a thiophosphoric acid ester of formula (1), 
       
         
           
           
               
               
           
         
         where R1 to R3 each independently are a hydrocarbon group having 3 to 20 carbon atoms, and L1 is a linear or branched alkylene group having 1 to 8 carbon atoms. 
       
     
     
         21 . The lubricating oil composition according to  claim 3 , wherein the sulfur-phosphorus extreme pressure agent having a carboxy group at an end is a thiophosphoric acid ester having a carboxy group at an end.