Cathodic electrocoating compositions containing acid-functional aminoplast and flexibilized, epoxy-free, aminated resin

Claim 1

A cathodic electrocoating composition comprising, in aqueous dispersion: (a) a cathodically electrodepositable, at least partially cationized binder resin comprising a major proportion by weight of a reaction product of a 1,2-epoxide-functional resin and a monoamino alcohol having at least one reactive hydrogen on the amino nitrogen, said reaction product being substantially devoid of reactive epoxide groups and having an average of at least about two reactive hydroxyl groups and an average of at least about 1/2 directly or indirectly pendant 5 to 20 carbon atom hydrocarbon radical per molecule; (b) from about 0.05 to about 1 weight parts, per weight part of said binder resin, of an acid-functional aminoplast resin (i) cathodically co-electrodepositable with said binder resin from said aqueous dispersion to form an intermediate product comprising an intimate mixture of the cathodically electrodeposited forms of said binder resin and said aminoplast resin, (ii) co-reactive in said intermediate product with the cathodically electrodeposited form of said binder resin, upon heating, to transform said intermediate product into a cured resinous product. (iii) having at least about 0.0001 equivalent of titratable acid functionality of pK a not greater than about 5 per gram of said aminoplast resin, and (iv) not soluble in the aqueous medium of said dispersion, and (c) from about 20 to about 150 milliequivalents, per 100 grams of (a) and (b), of an anion of a water-soluble acid to enhance and stabilize the cationization of said binder resin; said aqueous dispersion having a pH of from about 2 to about 7 and being substantially free of any water-soluble acid which will be retained in water-soluble form in said cured resinous product and of anions thereof.