VISCOSITY INDEX IMPROVER, METHOD FOR PRODUCING SAME, AND OIL COMPOSITION

摘要

The present invention provides: a viscosity index improver having an excellent effect of improving a viscosity index and a high-temperature high-shear viscosity of an oil; and others. The viscosity index improver according to the present invention comprises a hydrogenation product of a copolymer which contains (a) a structural unit derived from an aromatic vinyl compound and (b) a structural unit derived from a conjugated diene, wherein (b1) a farnesene-derived structural unit is contained in an amount of 1 to 100 mass% and (b2) a structural unit derived from a conjugated diene other than farnesene is contained in an amount of 0 to 99 mass% both relative to the total amount of (b) the structural unit derived from a conjugated diene, and 50 mol% or more of carbon-carbon double bonds in (b) the structural unit derived from a conjugated diene are hydrogenated.