The present invention aims to provide a viscosity index improver composition and a lubricating oil composition having a low HTHS viscosity at 100°C, an excellent shear stability, and an excellent low temperature viscosity. The present invention relates to, for example, a viscosity index improver composition (C), containing: a copolymer (A) containing a polyolefin-based monomer (a) represented by the following formula (1) as a constituent monomer; a copolymer (B) containing a (meth)acrylic acid alkyl ester (c) having a C12-C15 straight-chain or branched alkyl group and a (meth)acrylic acid alkyl ester (d) having a C16-C20 straight-chain or branched alkyl group as constituent monomers; and a base oil, wherein a weight average molecular weight ratio (A)/(B)} of the copolymer (A) to the copolymer (B) is 2 to 55, and a weight ratio (A/B) of the copolymer (A) to the copolymer (B) constituting the viscosity index improver composition (C) is 5 to 100:
本发明旨在提供一种粘度指数改进剂组合物和一种润滑油组合物,其在 100°C 时具有较低的 H
THS 粘度、出色的剪切稳定性和出色的低温粘度。例如,本发明涉及一种粘度指数改进剂组合物(C),其中含有一种共聚物 (A),其组成单体包含由下式 (1) 表示的聚烯烃基单体 (a);一种共聚物 (B),其组成单体包含具有 C12-C15 直链或支链烷基的(甲基)
丙烯酸烷基酯 (c) 和具有 C16-C20 直链或支链烷基的(甲基)
丙烯酸烷基酯 (d);和基础油,其中共聚物(A)与共聚物(B)的重量平均分子量比(A)/(B)}为 2 至 55,构成粘度指数改进剂组合物(C)的共聚物(A)与共聚物(B)的重量比(A/B)为 5 至 100: