| 摘要 |
PROBLEM TO BE SOLVED: To provide a viscosity index improver containing a polymethacrylate-based polymer having a high viscosity index and good shear stability and also showing sufficient solubility to lubricant base oil, and a lubricant oil composition using the polymethacrylate-based viscosity index improver.SOLUTION: Provided is a viscosity index improver comprising a polymer obtained by polymerizing: (a) alkyl(meth)acrylate having a 1 to 5C aliphatic hydrocarbon group; (b) alkyl(meth)acrylate having a 6 to 40C aliphatic hydrocarbon group; and (c)a maleimide-based monomer represented by General Formula (1) as essential components, in which the (c) component and the unit quantity derived from a styrene-based monomer lie in specified ranges, and also, the weight average molecular weight lies in a specified range, and also provided is a lubricant oil composition comprising lubricant oil and the viscosity index improver.SELECTED DRAWING: None |
