| abstract |
PROBLEM TO BE SOLVED: To provide a viscosity index improver excellent in compatibility with GTL base oil and excellent in viscosity index improving ability. A (meth) acrylic acid alkyl ester (a1) having an alkyl group having 1 and / or 2 carbon atoms, a (meth) acrylic acid alkyl ester (a2) having an alkyl group having 12 and / or 13 carbon atoms, (Meth) acrylic acid alkyl ester (a3) having an alkyl group having 14 and / or 15 carbon atoms and (meth) acrylic acid alkyl ester having one or more alkyl groups selected from alkyl groups having 16 to 24 carbon atoms (A4) is an essential constituent monomer, and (a1) is 5 to 26%, (a2) is 10 to 70%, and (a3) is 10 to 60% based on the total mass of (a1) to (a4). And a viscosity index improver for a GTL base oil comprising the copolymer (A) in which (a4) is 5 to 35%. [Selection figure] None |