Process for the manufacture of impact-resistant polyvinyl aromatic compound

Claim 1

In the continuous process for the manufacture of an impact-resistant polyvinyl-aromatic compound by the bulk polymerization of a solution of a vinyl-aromatic monomer in admixture with an elastomeric polymer and in the optional presence of up to 20% by weight of hydrocarbon diluent, calculated on the starting vinyl-aromatic monomer, where said solution is successively passed through an agitated pre-polymerication zone, a backmixed intermediate polymerization zone and an unstirred final polymerization zone, the improvement which comprises reacting said solution in an intermediate zone having from 2 to 4 reactors, inclusive, wherein the reaction mixture is maintained in each reactor in substantially homogeneous condition by agitation, and heat of polymerization is removed from each reactor by evaporation of vaporizable components of the mixture, and wherein the monomer conversion in said intermediate zone is advanced from a range of about 20% to about 35% entering the first intermediate reactor to a range of about 65% to about 85% leaving the last intermediate reactor, and controlling the conversion in said intermediate zone so that the difference in the percent of conversion in successive reactors in said zone does not exceed 25%.