| abstract |
PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent in shear stability, viscosity index improving ability and low temperature viscosity. A viscosity index improver comprising a copolymer (A) having an alkyl (meth) acrylate (a1) represented by the general formula (1) as an essential constituent monomer. [Chemical 8] In the formula, R 1 is a hydrogen atom or a methyl group; the carbon number in — (CH 2 ) 2 — [CH (R 2 )] n—CH 3 is 14 to 40, and R 2 is a hydrogen atom or carbon. N is an integer of 4 to 36, and at least one of n R 2 is an alkyl group of 1 to 3 carbon atoms; A 1 is a carbon number of 2 M is an integer of 0 or 1-20. [Selection figure] None |