GB1445238A - Preparation of grafted copolymers - Google Patents

Abstract

1445238 Graft polymerization process OKHTINSKOE NAUCH-PROIZVODSTVENNOE OBIEDINENIE "PLASTPOLIMER" USSR 31 July 1974 33804/74 Heading C3G A graft polymer is produced by (i) dissolving a synthetic rubber in styrene or vinyl toluene at a temperature of 20‹ to 80‹ C., (ii) heating the solution to 85‹ to 125‹ C. in the presence of a plasticizer and a molecular weight regulator until the conversion of the styrene or vinyl toluene is from 25 to 40% and (iii) subjecting the polymer to suspension polymerization in an aqueous medium, the volume ratio of prepolymer : aqueous phase being from 5 : 3 to 10: 3, at a temperature up to 140‹C. in the presence of an initiator and a stabilizing system consisting of (a) 0À15 to 1À5% by weight of tricalcium phosphate, (b) 0À003 to 0À02% of a sodium alkyl sulphate of formula where R is a C 8 to C 18 -alkyl group, and (c) 0À15 to 0À35% of calcium carbonate, the proportions of the stabilizing system components being based on the total weight of the aqueous phase and the calcium carbonate component being introduced into the suspension polymerization mixture at a temperature of not more than 90‹ C. Examples are given in which (1) butadiene rubber, styrene-butadiene rubber or styrenebutadiene block copolymer is grafted with styrene in the presence of liquid petrolatum, benzoyl peroxide and lauryl mercaptan, the resulting prepolymer being polymerized in an aqueous medium containing Ca 3 (PO 4 ) 2 , sodium alkyl sulphonate, tert. butyl perbenzoate and benzoyl peroxide, CaCO 3 being added when the temperature attains 90‹ C.; (2) butadiene rubber is grafted as in (1) with o- and p-vinyltoluene; (3) the procedure as in (1) is repeated, except that prepolymerization is carried out in the absence of an initiator at 120‹ C. until monomer conversion is 25 to 30%.