| 摘要 |
The invention relates to a process for preparing an impact-resistant translucent rubber-modified polystyrene and poly(alkyl)-styrene by a two-stage process in which - in the first stage - a batch consisting of styrene, ringalkylated styrene, side-chain-alkylated styrene or a mixture thereof and at least one rubbery polymer conforming to the formula P-(SH)X, where x denotes the number of thiol groups per rubber molecule and is an integer from 1 to 5 and P is a polymer of more than 80% conjugated dienes, and having an average molecular weight (average as measured by gel permeation chromatography) in the range from 20,000 to 200,000 is polymerized thermally or in the presence of free radical initiators, with stirring in the absence of a solvent for from 3 to 6 hours, to a conversion of from 20 to 40%, based on the monomer, stirring being carried out in such a way that thereafter the flexible phase dispersed in the polystyrene has a median particle diameter of from 0.1 to 0.8 .mu.m, and - in the second stage - the product thus obtained is dispersed, after the addition of a free radical initiator, in an aqueous phase which contains suspending assistants and buffer salts, and polymerization is effected in the course of from 5 to 15 hours to a conversion of from 95 to 99.95%, based on the monomer. This process makes it possible, on the one hand, to prepare translucent impactresistant polystyrenes or polyalkylstyrenes using rubers based on polybutadiene, and, on the other hand, to prepare non-translucent products having improved properties. |
