| 摘要 |
PROBLEM TO BE SOLVED: To obtain a viscosity index improver which generates a small amt. of caulking by selecting a copolymer having structural units derived from an alkyl methacrylate and a specific monomer as the essential units. SOLUTION: This improver is a copolymer having structural units derived from an alkyl methacrylate and a monomer selected from among a conjugated diene, (a substd.) acetylene, an alkyl vinyl ether, and an alkyl allyl ether as the essential units. An engine oil contg. this improver can reduce the amt. of caulking to the same level or lower of an engine oil contg. a conventionally used OCP viscosity index improver, has a low TBS viscosity and a high viscosity index, and thus can satisfy the requirement of automobiles, low fuel consumption. |
