| 摘要 |
Disclosed is a viscosity index improver in the form of a high-concentration non-aqueous dispersion of a low-viscosity olefinic polymer and a method of preparing the same. The improver comprises (1) an olefinic polymer, (2) a compound of (i) or (ii), (i) being a compound having at least one segment comprising A and B wherein A is a residue of a compound substantially composed of a hydrocarbon having a weight average molecular weight of 500 to 500,000 and having hydroxyl and/or carboxyl and/or carbonyl and/or amino and/or dithiocarboxyl group(s) and B is a residue of a compound having carboxyl and/or hydroxyl and/or isocyanate and/or amino and/or ketomine group(s), said A and B being bonded through at least one linkage selected from ester linkage, thioester linkage, urethane linkage, urea linkage, amide linkage, imide linkage and ether linkage, and (ii) being a reaction product of AA and BB wherein AA is an olefinic polymer having a weight average molecular weight of 500 to 500,000 and added with ethylenic unsaturated dicarboxylic acid(s) and BB is a compound having at least one group selected from mercapto group, amino group, ketimine group, hydroxy group and isocyanate group, said AA and BB being bonded through at least one linkage selected from thioester linkage, amide linkage, imide linkage and ester linkage, and (3) a medium which does not substantially dissolve or which scarcely dissolves the said olefinic polymer.
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