Cationic electrocoating compositions, method of making, and use

Abstract

An electrodepositable composition that has: (A) an active hydrogen-containing cationic resin, electrodepositable on a cathode, having: (1) a polyepoxide; (2) an oxygen-substituted diamine compound having the following formula: ##STR1## where n is an integer from 2 to 4; and where R.sup.1 or R.sup.2 are the same or different and either one or both contain at least one oxygen and are alkyl, cycloalkyl, substituted alkyl, or substituted cycloalkyl having from 1 to 6 carbon atoms, or R.sup.1 and R.sup.2 are alkanol groups having from 2 to 6 carbon atoms, or R.sup.1, R.sup.2, and the N atom form a cyclic group which is substituted or unsubstituted such as morpholine and 1-(3-aminopropyl) imidazole; and (B) at least partially blocked isocyanate or polyisocyanate curing agent. The diamine compound of Formula I can be used alone or in conjunction with one or more secondary amines, nonhydroxy group containing amines and/or amines with ring structures. Optionally, the polyepoxide can be chain extended with active hydrogen-containing compounds other than polyoxyalkylene polyamines. Also provided is a method of producing an active hydrogen-containing cationic resin composition, electrodepositable on a cathode, comprised of (a) mixing together in a suitable reaction vessel a polyepoxide, or the precursors of the polyepoxide, a polycarboxylic acid, a blocked isocyanate curing agent; (b) adding to the mixture of (a) a base catalyst and the diamine compound of Formula I; (c) polymerizing the mixture of (b) to form a resinous composition; and (d) neutralizing the resinous composition of (c) by adding the resinous composition to a dilute mixture of acid and water to form an aqueous dispersed electrodepositable cationic resin composition.