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°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.
一种制备平均粒径小的高稳定、细粒度、低粘度聚合物多元醇的连续工艺,其中第一步制备中间体的方法是:(1)
苯乙烯和
丙烯腈混合物在(2)聚氧亚烷基聚醚多元醇和(3)大单体的混合物中,在(4)自由基
引发剂存在下进行反应、(5) 具有中等链转移活性的溶剂,以及 (6) 反应调节剂,温度至少为 100°C,使中间体含有较高含量的大单体,相对于多元醇混合物至少约为 12%,最好至少约为 15%,中间体的固体含量按重量计小于约 30%,最好小于约 25%,至少约为 15%。然后,中间体作为进一步聚合的种子,在一个或多个搅拌罐反应器中与
苯乙烯和
丙烯腈的混合物在多元醇和大单体(可选)中串联,在溶剂、
引发剂和反应调节剂的存在下进一步反应,反应调节剂分布在其余的反应器中。