| abstract |
The object of the present invention is to provide a stable water-dispersible resin, using a reduced amount of an organic solvent or not using any organic solvent, and to provide an aqueous coating composition comprising the water-dispersible resin and capable of forming on metallic substrates a protective film having excellent characteristics. The invention provides a method for preparing a water-dispersing resin comprising: (1) preparing an aqueous dispersion of a modified epoxy resin having at least two quaternary ammonium carboxylate groups in one molecule, from an epoxy resin having a least two 1,2-epoxy groups in one molecule and having an epoxy equivalent of from 100 to 5,000, (2) polymerizing, in the aqueous dispersion, at least one unsaturated monomer component that indispensably comprises an unsaturated compound having at least one unsaturated group and at least one carboxyl group in one molecule, and (3) adding to the resulting polymer from 0.2 to 3.0 moles, per carboxyl equivalent of the polymer, of ammonia, a primary amine, a secondary amine, a tertiary amine or an inorganic alkaline substance to thereby neutralize the carboxyl groups of the polymer. |