| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a viscosity index improver that has, for lubricating oil composition, high metal friction reduction capability, excellent shear stability, low HTHS viscosity, and hardly increases the low temperature viscosity.SOLUTION: Provided is a viscosity index improver containing a copolymer obtained from, as essential constituent monomer, a monomer (a) of the following formula (1), and a monomer (b) of a particular formula; the monomer (b) can be obtained by esterification reaction between one terminal hydroxyl group-containing (co)polymer obtained by introducing hydroxyl group into one terminal of hydrocarbon polymer, and (meth)acrylic acid. [p is a number 0 or 1; r is an integer of 0 to 20].</p> |
