Cathodic electrocoating compositions containing branched epoxy amine resins

摘要

An improved aqueous cathodic electrocoating composition of an aqueous carrier having dispersed therein a film forming binder of (1) an epoxy resin-amine adduct and (2) a blocked polyisocyanate crosslinking agent; wherein the improvement is the use of a branched epoxy resin to form the adduct which is the reaction product of a polyhydric phenol and a branched epoxy macromonomer formed by the self condensation of an epoxy resin in the presence of a catalyst; the branched epoxy resin has an epoxy equivalent weight of about 700-2,000 and provides an electrocoating composition that has improved throw power and that forms coatings that have improved corrosion resistance in comparison to conventional electrocoating compositions formed from linear epoxy resins.