Latex paints with microemulsion modifier and process for their preparation

摘要

An aqueous ambient dry paint coating based on an addition copolymer matrix polymer containing an oligomer selected from a polyurethane or a polyester having a Tg below -20^oC and a number average molecular weight between 200 and 20,000, where the coating is free of organic coalescing solvents. The matrix polymer comprises emulsion copolymerized ethylenic monomers. In a preferred process, the oligomer is produced by forming an aqueous micro-preemulsion of oligomer in water by high shear mixing of oligomer and water containing 40% to 70% by weight oligomer and at temperatures between about 20^oC and 100^oC to provide an aqueous pre-emulsion having an organic phase droplet size less than 10 microns. The polymeric binder can be produced also by mixing the oligomer with the ethylenic monomers to form an organic mixture of monomer and oligomer, providing an aqueous micro dispersion of the organic mixture phase droplet size less than 5 microns, and copolymerizing the monomer to produce a vinyl acetate polymer containing oligomer. The polymeric binder system is free of coalescing organic solvent.