| abstract |
The present invention is directed to a polymeric isocyanate modified epoxy blocked sulfonic acid ester as a catalyst for the crosslinking of polymers having hydroxyl, carboxyl, and amide functional groups with a crosslinking agent and resin compositions containing the same. More particularly, the present invention is directed to a polymeric isocyanate modified epoxy blocked sulfonic acid ester with a molecular weight of about 1000 preferably prepared from a sulfonic acid, an epoxy resin and a mono- or di- isocyanate and resin compositions containing the polymeric isocyanate modified epoxy blocked sulfonic acid ester catalyst. The catalyst when used in the crosslinking or curing of hydroxyl, carboxyl or amide containing polymers with an acid catalyzed amino-formaldehyde crosslinking agent, such as hexamethoxymethylmelamine ("HMMA"), produced polymeric film coatings which have superior hardness, impact resistance, adhesion, improved blister resistance, salt spray characteristics and flexibility. |