Surfactant-free polymer emulsion coating composition and method for preparing same

Claim 1

A two-stage method for preparing a surfactant-free polymer emulsion product which comprises, in a first stage, (1) forming a mixture of polymerizable monomers comprising, by weight from about 3 to about 15% of a carboxylic acid or anhydride selected from the group consisting of acrylic, methacrylic and maleic acid and their anhydrides and the C 1 -C 8 alkyl half esters of maleic acid, from about 30 to about 97% of a C 1 -C 8 alkyl acrylate or C 1 -C 8 alkyl methacrylate, from 0 to about 25% of a C 2 -C 4 hydroxy alkyl ester of a carboxylic acid or acrylamide or methacrylamide and from 0 to about 35% styrene, (2) polymerizing said mixture in the presence of a polymerization catalyst, a suitable solvent, and optionally a molecular weight regulator to form a polymer having an average molecular weight of from about 3000 to about 50,000, (3) neutralizing the polymer with an amine or base to the extent required to make the polymer water-dispersible and (4) forming a dispersion of the polymer in water, and, in a second stage, (5) forming a second mixture of polymerizable monomers comprising, by weight, from about 40 to about 100% of a C 1 -C 8 alkyl acrylate or C 1 -C 8 alkyl methacrylate, from about 0 to about 25% of a C 2 -C 4 hydroxyalkyl ester of a carboxylic acid or acrylamide or methacrylamide and from about 0 to about 35% of styrene, (6) combining said second monomer mixture and a polymerization catalyst with the dispersion produced in step (4), the proportion of the second stage monomer mixture combined being such as to comprise from about 20 to about 80% of the total weight of the first and second stage monomer mixtures, and (7) heating the mixture so formed to effect polymerization and produce the polymer emulsion product.