Oil-blocker copolymers, viscosity improvers for lubricating oils and lubricating oil composition

摘要

The present invention provides an olefin block copolymer for a viscosity index improver capable of preparing a lubricating oil composition having excellent low temperature properties and excellent balance between viscosity and shear stability, a viscosity index improver and a lubricating oil composition comprising the viscosity index improver. ??The olefin block copolymer has a ratio Mw/Mn of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of not more than 1.5, and comprises: (i) a polymer block comprising ethylene and an alpha -olefin of 3 to 20 carbon atoms, having a molar ratio (ethylene/ alpha -olefin) of ethylene units to alpha -olefin units of from 20/80 to 65/35 and having an Mw value of 50,000 to 2,000,000, and (ii) a polymer block comprising ethylene and an alpha -olefin of 3 to 20 carbon atoms, having a molar ratio (ethylene/ alpha -olefin) of ethylene units to alpha -olefin units of from 70/30 to 85/15 and having an Mw value of 10,000 to 400,000.