Preparation of insoluble polymer powders which are only slightly swellable

Abstract From the Canadian patent

Insoluble polymer powders which are only slightly swellable are prepared by polymerization of N-vinylpyrrolidone or a mixture of (a) an Nvinylcarboxamide, acrylamide, methacrylamide acrylic acid, methacrylic acid, acrylates methacrylates and/or a vinyl, ester and (b) from 0.1 to 10% by weight based on the, total amount of monomers of, as a crosslinking agent, a compound possessing two or more ethylenically unsaturated double bonds, in a powder bed in the presence of a heat-transfer medium and in the absence of oxygen and polymerization initiators, at from 90 to 220°C the powder, state being maintained, the reaction mass being circulated and the heat-transfer medium evaporated from the …