Patent ID: 6127325
Filing Date: 2000-10-03
Classification: C10M,C10N

Abstract:
A viscosity index improver comprising a graft copolymer having a molecular weight in the range of between about 10,000 to 2,000,000 as the weight average; said graft copolymer having a structural unit formed by an oil-soluble polymer (a) containing an olefin polymer and a structural unit formed by a peroxy bond-containing polymer (b) obtained from a monomer represented by the formulas (1), (2) or (3) as follows: ##STR6## wherein R.sub.1 represents a hydrogen atom or a methyl group; R.sub.2 represents a hydrogen atom or a methyl group; R.sub.3 and R.sub.4 each represent an alkyl group having 1 to 4 carbon atoms; R.sub.5 represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group or an alkyl-substituted phenyl group; and n is 1 to 5; ##STR7## wherein R.sub.6 represents a hydrogen atom or a methyl group; R.sub.7 represents a hydrogen atom or a methyl group; R.sub.8 and R.sub.9 each represent an alkyl group having 1 to 4 carbon atoms; R.sub.10 represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group or an alkyl-substituted phenyl group; and n is 0 to 4; ##STR8## wherein R.sub.11 represents a hydrogen atom or a methyl group; R.sub.12 and R.sub.13 each represent an alkyl group having 1 to 4 carbon atoms; R.sub.14 represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group or an alkyl-substituted phenyl group;or a polymer (c) obtained by copolymerizing the peroxy bond-containing copolymer (b) with a monomer being selected from the group consisting of the tertiary nitrogen-containing monomers and monomers containing either or both of a hydroxyl group and an ether bond, said tertiary nitrogen-containing monomers being selected from the group consisting of vinylpyrrolidone, vinylpyridine, vinylimidazol, dimethylaminoethyl(meth)acrylate, dimethylaminopropyl(meth)acrylate, dimethylaminoethyl(meth)acrylamide, dimethyl(meth)acrylamide and (meth)acrylonitrile, said hydroxyl or ether bond containing monomers are alkyl(meth)acrylates of the formula: ##STR9## wherein R.sub.15 is a hydrogen atom or a methyl group, R.sub.16 is a C.sub.1 -C.sub.6 alkyl group having at least one hydroxyl group or a group of the following formula: ##STR10## wherein R.sub.17 and R.sub.18 each represent a hydrogen atom or a methyl group, R.sub.19 is a hydrogen atom or a C.sub.1 -C.sub.3 alkyl group, and n is an integer of 1 to 60; the weight ratio of the oil-soluble polymer (a) to the peroxy bond containing polymer (b) or (c) being in the range of 5 to 95 to 95 to 5.