Multi-stage opacifying polymer particles containing non-polymeric acid absorbed therein.

摘要

Multi-stage polymer particles containing one or more void space(s) therein are produced by sequential emulsion polymerization of at least one earlier polymer stage, encapsulation of said polymer stages with at least a final polymer stage, contacting said polymer particles with a non-polymerizable carboxylic acid to permit the acid to be absorbed onto at least one of said earlier polymer stages and swelling the polymer particles by contacting the particles with an aqueous base. When dried the particles contain void space(s) therein which produce(s) opacity in compositions in which the particles are contained.