Patent ID: 7718588

Claim:
A lubricating oil additive comprising at least one acrylic block copolymer having a weight-average molecular weight of 10,000 to 1,000,000 and a molecular weight distribution (ratio (Mw/Mn) of a weight-average molecular weight (Mw) to a number-average molecular weight (Mn)) of 1.3 or below, wherein the block copolymer comprises (meth)acrylic acid alkyl ester units consisting of(meth)acrylic acid alkyl ester units having a C 1-3 alkyl group as polymer block A and (meth)acrylic acid alkyl ester units selected from the group consisting of n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, lauryl methacrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and tridecyl acrylate as polymer block B; and the block copolymer has at least one kind of a structure selected from the group consisting of (A−B) a , (A−B) b −A, and (B−A) c −B, wherein a, b, and c independently represent an integer of 1 to 10.