U.S. 8,168,700 B2
PPG Industries has been granted a patent for an electrodepositable coating composition comprised of a resinous phase dispersed in an aqueous medium. The resinous phase is comprised of (a) an active hydrogen-containing, cationic salt group-containing resin; and (b) an at least partially blocked polyisocyanate curing agent,
the improvement is comprised of the inclusion in the electrodepositable coating composition of an organotin catalyst for effecting cure between the resin (a) and the curing agent (b), wherein the catalyst is comprised of the following structure (I):
[R1][R2]—Sn═O  (I)
where R1 and R2 are the same or different, and each independently represents a monovalent hydrocarbon group, wherein the sum of the carbon atoms of R1 and R2 is greater than 8, the 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); wherein the catalyst is dispersed in the resin (a) and/or the curing agent (b) of the resinous phase prior to the resinous phase being dispersed in the aqueous medium; 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.