Patent ID: 7497936

Claim:
In a method for preparing an electrodepositable coating composition comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising: (a) an active hydrogen-containing, cationic salt group-containing resin; (b) an at least partially blocked polyisocyanate curing agent; and (c) an organotin catalyst for effecting the cure of the resin (a) and the curing agent (b), said method comprising the steps of (1) preparing the resin (a) from a mixture of reactive components in the absence of the aqueous medium; (2) preparing the at least partially blocked polyisocyanate curing agent (b) separate from the resin (a) by reacting a polyisocyanate and a blocking agent; (3) admixing the resin (a) and the curing agent (b) to form a resinous admixture; (4) blending an organic and/or inorganic acid with the resinous admixture to form an acidified admixture; and (5) dispersing the acidified admixture of (4) in the aqueous medium, the improvement comprising incorporating the organotin catalyst (c) into the mixture of reactive components during the preparation of the resin (a) in step (1), wherein the catalyst (c) comprises the following structure (I): [R 1 ][R 2 ]−Sn=O (I) where R 1 and R 2 are the same or different, and each independently represents a monovalent hydrocarbon group wherein the sum of the carbon atoms in R 1 and R 2 is greater than 8, said catalyst being present in the electrodepositable coating composition in an amount sufficient to effect cure of the electrodepositable composition at a temperature at or below 340° F. (171.1° C.); and wherein the resinous phase is not subjected to a grinding or milling operation; and wherein there is no other curing catalyst in the resinous phase.