| 摘要 |
PROBLEM TO BE SOLVED: To obtain an olefin block copolymer to become a viscosity index improver for providing a lubricating oil composition having excellent low- temperature properties and an excellent balance between viscosity and shear stability, the viscosity index improver and the lubricating oil composition containing the viscosity index improver. SOLUTION: This olefin block copolymer comprises a polymer block (i) obtained from ethylene and a 3-20Cα-olefin and having the molar ratio of ethylene unit toα-olefin unit (ethylene/α-olefin) in the range of 20/80-65/35 and 50,000-2,000,000 Mw and a polymer block (ii) from ethylene and a 3-20Cα-olefin and having the molar ratio of ethylene unit toα-olefin unit (ethylene/α- olefin) in the range of 70/30-85/15 and 10,000-400,000 Mw and has <=1.5 Mw/Mn. |
