Lubricating oil composition for shock absorber

Abstract

The lubricating oil composition for a shock absorber of the present invention contains (A) a base oil containing a mineral oil and/or a synthetic oil, (B) a tertiary amine represented by the following general formula (I), (C) a zinc dithiophosphate represented by the following general formula (II), and (D) a phosphorus acid ester amine salt, wherein R 1 and R 2 each independently represent an aliphatic hydrocarbon group having from 1 to 5 carbon atoms, and R 3 represents an aliphatic hydrocarbon group having from 12 to 24 carbon atoms, in the general formula (I), wherein R 4 to R 7 each independently represent one selected from an alkyl group and an alkenyl group each having from 1 to 24 carbon atoms, in the general formula (II).

1 . A lubricating oil composition for a shock absorber, comprising (A) a base oil composed of a mineral oil and/or a synthetic oil, (B) a tertiary amine represented by the following general formula (I), (C) a zinc dithiophosphate represented by the following general formula (II), and (D) a phosphorus acid ester amine salt, 
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  each independently represent an aliphatic hydrocarbon group having from 1 to 5 carbon atoms, and R 3  represents an aliphatic hydrocarbon group having from 12 to 24 carbon atoms in the general formula (I), 
       
       
         
           
           
               
               
           
         
         wherein R 4  to R 7  each independently represent one selected from a linear, branched or cyclic alkyl group having from 1 to 24 carbon atoms and a linear, branched or cyclic alkenyl group having from 1 to 24 carbon atoms in the general formula (II). 
       
     
     
         2 . The lubricating oil composition for a shock absorber according to  claim 1 , wherein R 1  and R 2  each are independently selected from a linear, branched or cyclic alkyl group having from 1 to 5 carbon atoms and a linear, branched or cyclic alkenyl group having from 1 to 5 carbon atoms, and R 3  is selected from a linear, branched or cyclic alkyl group having from 12 to 24 carbon atoms and a linear, branched or cyclic alkenyl group having from 12 to 24 carbon atoms in the general formula (I). 
     
     
         3 . The lubricating oil composition for a shock absorber according to  claim 2 , wherein R 3  in the general formula (I) is a linear, branched or cyclic alkyl group having from 16 to 20 carbon atoms. 
     
     
         4 . The lubricating oil composition for a shock absorber according to  claim 3 , wherein R 3  in the general formula (I) is a stearyl group. 
     
     
         5 . The lubricating oil composition for a shock absorber according to  claim 1 , wherein R 4  to R 7  in the general formula (II) each are independently one selected from a linear, branched or cyclic alkyl group having from 10 to 20 carbon atoms and a linear, branched or cyclic alkenyl group having from 10 to 20 carbon atoms. 
     
     
         6 . The lubricating oil composition for a shock absorber according to  claim 1 , wherein the phosphorus acid ester amine salt (D) is an amine salt of an acidic phosphoric acid ester represented by the following general formula (III): 
       
         
           
           
               
               
           
         
         wherein R 11  is selected from a hydrogen atom, a linear, branched or cyclic alkyl group having from 8 to 24 carbon atoms and a linear, branched or cyclic alkenyl group having from 8 to 24 carbon atoms, and R 12  is selected from a linear, branched or cyclic alkyl group having from 8 to 24 carbon atoms and a linear, branched or cyclic alkenyl group having from 8 to 24 carbon atoms in the general formula (III). 
       
     
     
         7 . The lubricating oil composition for a shock absorber according to  claim 6 , wherein R 11  and R 12  in the general formula (III) each are independently an alkyl group having from 16 to 20 carbon atoms or an alkenyl group having from 16 to 20 carbon atoms. 
     
     
         8 . The lubricating oil composition for a shock absorber according to  claim 1 , which comprises from 0.01 to 3% by mass of the tertiary amine (B). 
     
     
         9 . The lubricating oil composition for a shock absorber according to  claim 1 , which comprises from 0.01 to 3% by mass of the zinc dithiophosphate (C). 
     
     
         10 . The lubricating oil composition for a shock absorber according to  claim 1 , which is a lubricating oil composition for a shock absorber for cars. 
     
     
         11 . The lubricating oil composition for a shock absorber according to  claim 1 , wherein R 1  and R 2  in the general formula (I) each have 1 or 2 carbon atoms.