COPOLYMER, LUBRICATING OIL VISCOSITY MODIFIER, AND LUBRICATING OIL COMPOSITION

摘要

Disclosed are: a lubricating oil composition having excellent low-temperature properties; a lubricating oil viscosity modifier which is intended to be contained in the lubricating oil composition; and a specific copolymer which constitutes the lubricating oil viscosity modifier. Specifically disclosed is a copolymer which has a constituent unit derived from ethylene and a constituent unit derived from an a-olefin having 3 to 20 carbon atoms and meets the following requirements (1) to (5): (1) Tm lies within the range from -20 to 100ºC; (2) Tm and the density (D) (g/cm3) have the relationship represented by the formula (1); (3) Mw/Mn as measured by GPC lies within the range from 1.6 to 5.0; (4) the half-width value (?Thalf) of the melting peak as measured by DSC is 90ºC or lower; and (5) ?Thalf and Tm have the relationship represented by the formula (2). Tm = 1073 x D - 893 (1) ?Thalf = -0.71 x Tm + 101.4 (2)