Lubricating oil composition for an internal combustion engine

Abstract

The lubricating oil composition for an internal combustion engine of the invention contains (A) a lubricant base oil composed of a mineral oil and/or a synthetic oil, (B) a boron-containing alkenylsuccinimide and/or a boron-containing alkylsuccinimide in an amount of 0.001 to 0.1% by mass as a boron-equivalent amount based on the total amount of the composition, and (C) a poly(meth)acrylate in an amount of 0.1 to 30% by mass based on the total amount of the composition, and the poly(meth)acrylate has Mw of 100,000 to 700,000 and Mw/X of 30,000 or more, in which the weight-average molecular weight thereof is represented by Mw and the mean carbon number of the alkyl groups therein, as measured through 13 C-NMR, is represented by X.

1 . A lubricating oil composition for an internal combustion engine, the composition comprising:
 (A) a lubricant base oil comprising a mineral oil, a synthetic oil, or both;   (B) a boron-containing alkenylsuccinimide, a boron-containing alkylsuccinimide, or both, in an amount of 0.001 to 0.1% by mass as a boron-equivalent amount based on a total amount of the composition; and   (C) a poly(meth)acrylate in an amount of 0.1 to 30% by mass based on the total amount of the composition, the poly(meth)acrylate having Mw of 100,000 to 700,000 and Mw/X of 30,000 or more, wherein a weight-average molecular weight thereof is represented by Mw, and a mean carbon number of alkyl groups therein, as measured through  13 C-NMR, is represented by X.   
     
     
         2 . The lubricating oil composition for an internal combustion engine according to  claim 1 , wherein Mw/X is 30,000 to 200,000. 
     
     
         3 . The lubricating oil composition for an internal combustion engine according to  claim 1 , wherein the poly(meth)acrylate (C) is a non-dispersive poly(meth)acrylate. 
     
     
         4 . The lubricating oil composition for an internal combustion engine according to  claim 1 , wherein a viscosity index of the lubricant base oil (A) is 90 or more. 
     
     
         5 . The lubricating oil composition for an internal combustion engine according to  claim 1 , comprising a mineral oil having a paraffin content (% C P ) according to ring analysis of 60% or more. 
     
     
         6 . The lubricating oil composition for an internal combustion engine according to  claim 1 , further comprising at least one selected from the group consisting of
 (D) a zinc dithiophosphate, and   (E) an alkali metal detergent or an alkaline earth metal detergent.   
     
     
         7 . The lubricating oil composition for an internal combustion engine according to  claim 6 , wherein the composition comprises the zinc dithiophosphate (D) in an amount of 0.01 to 0.15% by mass as a phosphorus-equivalent amount, and the alkali metal detergent or the alkaline earth metal detergent (E) in an amount of 0.1 to 0.3% by mass as a metal-equivalent amount, based on the total amount of the composition. 
     
     
         8 . The lubricating oil composition for an internal combustion engine according to  claim 1 , wherein the composition has a kinematic viscosity at 100° C. of 4 to 17 mm 2 /s. 
     
     
         9 . A method of producing a lubricating oil composition for an internal combustion engine, the method comprising blending (B) a boron-containing alkenylsuccinimide, a boron-containing alkylsuccinimide, or both, in an amount of 0.001 to 0.1% by mass as a boron-equivalent amount based on the total amount of the composition, and (C) a poly(meth)acrylate in an amount of 0.1 to 30% by mass based on the total amount of the composition, into (A) a lubricant base oil comprising a mineral oil, a synthetic oil, or both,
 wherein the poly(meth)acrylate (C) has a Mw of 100,000 to 700,000 and Mw/X of 30,000 or more, in which a weight-average molecular weight thereof is represented by Mw and a mean carbon number of alkyl groups therein, as measured through  13 C-NMR, is represented by X.