A method for preparing graft polymer dispersions having broad particle size distribution without wildly fluctuating viscosities is disclosed. The method comprises:
(a) preparing intermediate graft polyol dispersions containing 30 percent by weight or less solids to achieve a broad distribution of partial sizes in a continuous process by feeding a sufficient amount of an ethylenically unsaturated monomer and a free radical initiator into a flow reactor at a temperature sufficient to promote polymerization, and
(b) charging the intermediate graft polymer dispersion of (a) to a semi-batch reactor as seeds for further grafting to increase the solids content of the dispersion to above 30 percent by weight by feeding an effective amount of an ethylenically unsaturated monomer and a free radical initiator into the semi-batch reactor at a temperature sufficient to promote the growth of the seeds, whereby the seed particles generally grow larger but retain the characteristic of broad size distribution. The graft polymer so formed is useful in the production of polyurethanes.
本发明公开了一种制备接枝聚合物分散体的方法,该分散体具有较宽的粒度分布,且粘度不会剧烈波动。该方法包括
(a) 在足以促进聚合的温度下,将足量的
乙烯基不饱和单体和自由基
引发剂送入流动反应器中,制备固体含量为 30% (重量百分比)或更少的中间接枝多元醇分散体,以便在连续工艺中实现广泛的部分尺寸分布,以及
(b) 在半间歇反应器中加入适量的
乙烯基不饱和单体和自由基
引发剂,在足以促进种子生长的温度下,将(a)中的中间接枝聚合物分散体作为种子加入半间歇反应器中,以进一步接枝,从而将分散体的固体含量提高到 30%以上(按重量计),种子颗粒一般会变大,但仍保持宽尺寸分布的特性。这样形成的接枝聚合物可用于生产聚
氨酯。