| 摘要 |
PROBLEM TO BE SOLVED: To obtain a viscosity index improver which can heighten viscosity even when added in a small amount, is excellent in oxidation resistance and shear stability, and has a reduced temp. dependence of viscosity by polymerizing a free radical-polymerizable monomer using a specific chain transfer agent. SOLUTION: The improver comprises a (co)polymer obtained by polymerizing a free radical-polymerizable monomer using a free radical-polymerization initiator and a chain transfer agent free radical polymerization represented by the formula (wherein Q is a polyvalent organic group; A is a 1-8C alkylene; Z is a chain transfer group; p and q each is 0 or 1, provided that at least either is not 1; m is 2-100; and the groups in the respective [ ]s may be the same or different). This improver is reduced in sludge formation and is capable of increasing viscosity even when added in a small amount. It is excellent in oxidation resistance and shear stability and has a reduced temp. dependence of viscosity. |
