Impact polymer process

Claim 1

In a method for the preparation of impact or rubber reinforced alkenyl aromatic polymers wherein a polymerizable monomer composition is mass or mass-suspension polymerized in the presence of up to about 25 weight percent solvent based on the weight of the reaction mixture of a dissolved reinforcing polymer with agitation until the reinforcing polymer separates from the polymerizable monomer mixture as a plurality of particles to thereby result in phase inversion, wherein the polymerizable composition has from about 40 to 98 percent by weight of an alkenyl aromatic monomer, from about 0 to 45 weight percent of an olefinically unsaturated monomer copolymerizable with the alkenyl aromatic monomer and from about 2 to 40 weight percent of a rubbery butadiene reinforcing polymer having a glass temperature not higher than 0° C., the polymer containing at least 60 weight percent butadiene polymerized therein and up to 40 percent by weight of one or more ethylenically unsaturated monomers polymerized therein, the improvement which comprises polymerizing the composition until separation of reinforcing polymer from the mixture occurs, the mixture containing 40 to 98 weight percent of the desired amount of reinforcing polymer, and polymerizing the composition until at least an additional 10 percent amount of monomer has been converted to polymer, adding to the mixture with agitation a monomer solution containing from 60 to 2 weight percent of the total reinforcing polymer of a rubbery butadiene reinforcing polymer, the addition being made after separation of the particles or phase inversion and after sufficient additional polymerization has occurred such that phase reinversion does not occur.