| abstract |
(57) [Summary]nDispersant Viscosity Index Improver Linear diblock copolymer or radial or star block copolymer, wherein each arm of the linear diblock copolymer and the radial or star block copolymer has a total number average molecular weight of 7500-250,000, respectively. And a conjugated diene block having a number average molecular weight of 5,000 to 200,000 and a vinyl aromatic hydrocarbon block having a number average molecular weight of 2,500 to 100,000, wherein the copolymer has a vinyl aromatic content of 5 to 50% by weight. Such copolymers having a hydrocarbon content and having from 5 to 10 N-vinylimidazole functional groups per polymer chain grafted to the copolymer, a process for preparing the same, and such a dispersant viscosity index improvement Oil composition containing additive and additive concentrate |