Water-swellable crosslinked polymeric microgel particles and aqueous dispersions of organic film-forming resins containing the same

Claim 1

A polymeric microgel composition comprising discrete particles of crosslinked, aqueous emulsion polymerized copolymer comprising: a. at least one polymerizable carboxylic acid group-free polymerizable vinyl monomer selected from the group consisting of polymerizable vinyl aromatic monomers, methacrylate ester monomers, nitrile monomers, vinyl halide monomers, mixtures thereof, and mixtures thereof with minor amounts of vinyl ester monomers and alkyl acrylate monomers in an amount of sufficient to provide a major portion of said copolymer; b. from about 10 to 50%, based on the total monomer weight, of at least one polymerizable vinyl monomer selected from the group consisting of αβ-ethylenically unsaturated carboxylic acid monomers and mixtures thereof, said carboxylic acid monomers being substantially nongelling when copolymerized with said acid group-free monomers in an aqueous emulsion; and c. from a small amount sufficient to crosslink the microgel particles up to about 5%, based on the total monomer weight, of a difunctional cross-linking monomer having at least two polymerizable double bonds; said microgel particles being water-swellable and exhibiting a stability in aqueous media of at least one week when an aqueous dispersion of said microgel particles of about 20% solids content is maintained at 140° F.