Continuous process for the preparation of highly stable, finely divided, low viscosity polymer polyols of small average particle size

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 styrene and acrylonitrile in a mixture of (2) a polyoxyalkylene polyether 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 DEG C, such that the intermediate contains a high level of macromer, at least about 12% and preferably at least about 15% with respect to the polyol mixture and the solids content of the intermediate is less than about 30%, preferably less than about 25% and at least about 15% by weight. The intermediate, which functions as a seed for further polymerization, is then further reacted in one or more stirred-tank reactors in series with a mixture of styrene and acrylonitrile in a polyol and optionally a macromer, in the presence of solvent, initiator and a reaction moderator which are distributed among the remaining reactors.