Process for making stable solvent-free, aqueous epoxy resin dispersions

Claim 1

An improved process for preparing a stable aqueous dispersion having no particles large in size than 5 microns or an aqueous, low organic solvent fine particle emulsion of an epoxy resin having a molecular weight from about 4,000 to about 100,000 useful in forming water-dilutable, heat-curable coating compositions with aminoplast or phenoplast curing systems, which comprises dissolving said epoxy resin in an organic solvent to prepare a 40 to 80% by weight solution, said organic solvent containing from 1 to 25% by weight based on the epoxy resin of a nonionic surfactant and said organic solvent having a boiling point below 160° C. and being selected from the group consisting of aromatic hydrocarbons, esters, ethers, alcohols, ketones, halogenated aromatic hydrocarbons and mixtures thereof, adding with stirring sufficient water to give a mixture containing from 30 to 50% by weight water, subjecting the resulting mixture to homogenizing action using a colloid mill, homogenizer or other high speed, high shear mixer, removing essentially all the organic solvent present by vacuum distillation at a temperature under 40° C. and with a pressure of about 5 to 100 mm Hg to give an essentially solvent free aqueous dispersion having from about 40 to 65 weight percent epoxy resin, from about 0.5 to 13 weight percent nonionic surfactant and from about 35 to 60 weight percent water; or removing from 40 to 70 percent of the organic solvent by vacuum distillation under 40° C. and with a pressure of about 5 to 100 mm Hg to give a low organic solvent aqueous emulsion having about 35 to 65 weight percent epoxy resin, from about 0.5 to 13 weight percent nonionic surfactant, from about 8 to 20 weight percent organic solvent and from about 35 to 60 weight percent water, wherein the improvement comprises using as the nonionic surfactant a dispersing agent selected from the group consisting of the polyoxyethylene esters of fatty, rosin and tall oil acids having 8 to 20 carbon atoms in the acid moiety and having from 5 to 50 moles of poly(ethylene oxide) per acid molecule.