| 摘要 |
A continuous process for the preparation of highly stable, finely divided, low viscosity polymer polyols of small average particle size wherein in the first step an intermediate is prepared by reacting (1) a mixture of at least two ethylenically unsaturated monomers, preferably styrene and acrylonitrile, in a mixture comprising (2) a base polyol and (3) a macromer in the presence of (4) a free radical initiator, (5) a solvent having moderate chain transfer activity, and, optionally, (6) a reaction moderator at a temperature of at least 100.degree.C, such that the intermediate contains at least about 12% by weight of macromer, based on the weight of the base polyol and macromer, and a solids content of at least about 15% by weight and less than about 30% by weight, based on the weight of the base polyol, macromer and ethylenically unsaturated monomers. The intermediate, which functions as a seed for further polymerization, is then further reacted, in one or more stirred-tank reactors in series, in a mixture of at least two ethylenically unsaturated monomers, preferably styrene and acrylonitrile, in a base polyol and, optionally, a macromer, in the presence of solvent, initiator and a reaction moderator which are distributed among the remaining reactors.
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