Poly(meth)acrylate viscosity index improver, and lubricating oil composition and lubricating oil additive containing said viscosity index improver

Abstract

The present invention provides a poly(meth)acrylate-based viscosity index improver comprising a polymer chain comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2), wherein Mw is 100000 or more, and Mw/Mn, is 1.6 or less. [R 1 represents hydrogen or a methyl group, and R 2 represents a group represented by the following formula (3), and R 3 represents a C1 to C18 alkyl group that is straight-chain or has a branch having 5 or less carbon atoms. m and n are integers which satisfy m≧5, n≧4, and m+n≦31.]

1 . A poly(meth)acrylate-based viscosity index improver comprising a polymer chain comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),
 wherein a weight-average molecular weight Mw is 100000 or more, and a ratio of the weight-average molecular weight Mw to a number average molecular weight Mn, Mw/Mn, is 1.6 or less.   
       
         
           
           
               
               
           
         
         
           [In the formulas (1) and (2), R 1  represents hydrogen or a methyl group, and R 2  represents a group represented by the following formula (3), and R 3  represents a C1 to C18 alkyl group that is straight-chain or has a branch having 5 or less carbon atoms. 
         
       
       
         
           
           
               
               
           
         
         
           In the formulas (3), m and n are integers which satisfy m≧5, n≧4, and m+n≦31.] 
         
       
     
     
         2 . A poly(meth)acrylate-based viscosity index improver comprising a polymer chain comprising a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2),
 wherein a weight-average molecular weight Mw is less than 100000, and a ratio of the weight-average molecular weight Mw to a number average molecular weight Mn, Mw/Mn, is 1.6 or less.   
       
         
           
           
               
               
           
         
         
           [In the formulas (1) and (2), R 1  represents hydrogen or a methyl group, and R 2  represents a group represented by the following formula (3), and R 3  represents a C1 to C18 alkyl group that is straight-chain or has a branch having 5 or less carbon atoms. 
         
       
       
         
           
           
               
               
           
         
         
           In the formula (3), m and n are integers which satisfy m≧5, n≧4, and m+n≦31.] 
         
       
     
     
         3 . A lubricating oil additive comprising the poly(meth)acrylate-based viscosity index improver according to  claim 1 . 
     
     
         4 . A lubricating oil composition comprising:
 a lubricating base oil; and   the poly(meth)acrylate-based viscosity index improver according to  claim 1 .   
     
     
         5 . A lubricating oil additive comprising the poly(meth)acrylate-based viscosity index improver according to  claim 2 . 
     
     
         6 . A lubricating oil composition comprising:
 a lubricating base oil; and   the poly(meth)acrylate-based viscosity index improver according to  claim 2 .