Method of making organic solvent free aqueous coating compositions of acrylic polymer latex, water soluble emulsion-polymerized acrylic polymer, and aminoplast

摘要

Water-based paints having improved properties and application characteristics are disclosed. The paint, exclusive of optional components such as pigments, particulate fillers and catalysts, comprises a liquid, continuous aqueous phase. About 30 to about 50% by weight of this phase exclusive of the aforecited optional components, is made up of a mixture of (a) an amino resin crosslinking agent; (b) a mixture of at least two copolymers of acrylic monomers; and (c) an amine. The balance is water or, in certain embodiments, water and an organic solvent. The mixture of copolymers comprises (1) about 5 to about 50, preferably about 10 to about 30, parts by weight of a "solution polymer", i.e., a carboxy-functional copolymer of acrylic monomers that (i) is at least partially neutralized with an amine, (ii) is soluble in said aqueous phase, (iii) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (iv) has Tg in the range of -15 DEG to 50 DEG C., and (2) about 50 to about 95, preferably about 70 to about 90, parts by weight of an "emulsion polymer", i.e., a copolymer of acrlic monomers having carboxy, hydroxy or carboxy and hyroxy functionality that (i) is essentially insoluble in said continuous phase, (ii) has average molecular weight (Mn) in the range of about 3,000 to about 20,000 and (iii) has Tg of -15 DEG to 50 DEG C. The amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weight of solution polymer and the weight of emulsion polymer. The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7 to about 10, most commonly in the range of about 7.1 to about 8.5. The invention claimed is directed to a method for producing such paints wherein both the solution polymer and the emulsion polymer are produced by emusion polymerization.