Patent ID: 7387718

Claim:
A method of preparing a cationic electrodeposition coating composition, the method comprising: preparing a polyisocyanate curing agent including partially blocked isocyanate functional groups, wherein the polyisocyanate curing agent is prepared by reacting an isocyanate with a trimethylol propane in a molar ratio of about 3:1 and blocking the isocyanate with a blocking agent including diethylmalonate and an auxiliary blocking agent in a molar ratio of about 8:2; preparing a cationic electrodeposition resin by reacting (a) about 40 to about 60% by weight of a cationic electrodeposition synthetic resin prepared by an epoxy-amino addition reaction, (b) about 2 to about 5% by weight of an acrylic cationic resin having an amino group and (c) about 30 to about 50% by weight of the curing agent; preparing an aqueous dispersion of the cationic electrodeposition resin by dispersing the cationic electrodeposition resin in an aqueous medium containing about 0.5 to about 3% by weight of zinc acetate; and adding about 0.5 to about 3% by weight of ethylene glycol monohexyl ether to the aqueous dispersion of the cationic electrodeposition resin.