High impact rubber-modified polystyrene - using di:acyl peroxide mixt. as initiator in pre:copolymerisation; avoiding use of mol. wt. regulator

摘要

Impact-resistant graft copolymers of styrene and synthetic rubber are prepd. by (a) dissolving rubber in styrene at is not >75 degrees C, (b) prepolymerising the soln. at increased temp. in presence of a softener and a peroxide activator, 25-40% conversion of the styrene, and (c) polymerisation of the prepolymer in suspension in an aq. medium in a ratio by vol. of pre-polymer:water of 5-10:3, and at is not >140 degrees C, in presence of peroxide activators, and a stabiliser system contg. 0.15-1.5 wt.% of tri-Ca phosphate, 0.003-0.02% of a mixt. of Na salts of sec. alkyl sulphates of formula R-OSO3Na, where R is an 8-18C hydrocarbon gp. and 0.15-0.35% of K2CO3. Pre-polymerisation is at 75-85 degrees C, using as activator a mixt. of diacyl peroxides of 3-12C aliphatic acids in the ratio:2-8% diacyl peroxides (I) of 3-5C acids, 80-89% dicacyl peroxides (II) of 6-9C acids, and 7-14% diacyl peroxides (III) of 10-20C acids. The prepolymerisation is rapid, and can be controlled without the use of mol. wt. regulators. Accurate metering of the peroxide mixt. is possible. Dispersion of the prepolymer in the suspension polymerisationa stage is facilitated.