Abstract: This aqueous dispersion contains monomer emulsion particles comprising a monomer component, wherein the monomer component contains (A) at least one monomer X selected from the group consisting of styrene-based monomers and alkyl (meth)acrylates including an alkyl group having 4 to 12 carbon atoms, (B) a nonionic emulsifier, (C) an aliphatic organic acid (alkyl ester) having 15 or more carbon atoms, and (D) a lipophilic active component, and the mean particle size of the monomer emulsion particles is 10 to 200 nm.

Abstract: A viscosity index improver comprising a copolymer having a unit (a) derived from a maleimide monomer and a unit (b) derived from a macromonomer, wherein viscosity measured by the following method is 8000 mPa·s or less. Viscosity measurement method: A solution composed of 78 mass % of a Group III base oil (viscosity index: 122, kinematic viscosity at 40° C.: 19.6 mm2/s) on the American Petroleum Institute (API) classification and 22 mass % of the copolymer is measured with a viscometer (TVB-10 manufactured by Toki Sangyo Co., Ltd., rotor: SPINDLE No. M3, rotation speed: 6 rpm) at 25° C.

Abstract: A viscosity index improver comprising a copolymer having a unit (a) derived from a maleimide monomer and a unit (b) derived from a macromonomer, wherein viscosity measured by the following method is 8000 mPa·s or less. Viscosity measurement method: A solution composed of 78 mass % of a Group III base oil (viscosity index: 122, kinematic viscosity at 40° C.: 19.6 mm2/s) on the American Petroleum Institute (API) classification and 22 mass % of the copolymer is measured with a viscometer (TVB-10 manufactured by Toki Sangyo Co., Ltd., rotor: SPINDLE No. M3, rotation speed: 6 rpm) at 25° C.