Manufacture of vesiculated polymer granules

In a process for preparing vesiculated crosslinked polyester granules by polymerizing the oil phase of a water-in-oil-in-water emulsion formed from (a) a polymerizable water-immiscible oil phase composed of an ethylenically unsaturated monomer and a polyester obtained from the condensation of one or more polyhydric alcohols and one or more polycarboxylic acids, at least one of said alcohols or acids being unsaturated, (b) an aqueous phase, containing a base having a dissociation exponent of less than 8 in which said oil phase is dispersed to from a water-in-oil-in-water emulsion, and (c) distributed in at least one of said phases a free-radical polymerization initiator with or without a polymerization promoter,

• wherein the improvement comprises effecting the polymerization of said oil phase essentially instantaneously and substantially immediately following the formation of said water-in-oil-in-water emulsion by
• i. contacting said oil phase at a temperature from 10.degree. to 40.degree.C. with said aqueous phase at a temperature from 65.degree. to 95.degree.C.
• said oil phase containing a free-radical polymerization initiator capable of activation at a temperature from 65.degree. to 95.degree.C. in the presence of water,
• said aqueous phase containing in addition to said base at least one emulsion stabilizing agent selected from the group consisting of surface active agents and nonflocculating polymeric thickeners,
• ii. recovering the product thereby formed as an aqueous slurry of said vesiculated cross-linked polyester granules.