In situ process for making a bimodal HIPS having both high gloss and high impact strength

摘要

A continuous bulk polymerization process for making a high gloss, high impact strength polystyrene based resin having a bimodal particle size distribution containing capsule particles having an average size of 0.2 to 0.6 microns and cellular particles having an average particle size of 1.2 to 8.0 microns. The process comprises three reaction zones in series where styrene and a styrene-butadiene copolymer are fed to the first reaction zone which is maintained at pre-phase inversion conditions and no particles are allowed to form. The capsule particles form in the second reaction zone which is maintained at post-phase inversion conditions. Polybutadiene is introduced into the third reaction zone which is also maintained at post-phase inversion conditions. The cellular morphology particles form in the third reaction zone. The resultant bimodal particle size polymer mixture may be subjected to devolitilization after the third reaction zone or, alternatively, the mixture can be subjected to further polymerization in one or more finishing reactors prior to polymerization.