RECENT STUDIES OF SELF-CONDENSATION AND CO-CONDENSATION OF MELAMINE-FORMALDEHYDE RESINS - CURE AT LOW-TEMPERATURES

Self-condensation: recent research on the chemical pathways by which alcoholated melamine-formaldehyde (MF) resins react with themselves and on the product structures is summarized. Model compound studies suggest that NCH2N bridges are less stable than widely thought unless they are in hexahydro-1,3,5-triazine ring structures. In acyclic structures they are probably less stable than NCH2OCH2N bridges. Co-condensation: studies of how the composition of MF resins influences the rates of reaction with poly(ol) co-reactant show that MF resins that contain very low levels of NH and/or NNCH2OH functionality are quite reactive. Reactivities of a variety of poly(ester) and acrylic co-reactants were studied. By combining reactive MF resins with reactive co-reactants one can formulate high solids enamels that cure by co-condensation in 30 min at 50 to 65-degrees-C with 0.5 parts per hundred (phr) of p-toluenesulfonic acid (p-TSA) catalyst. Cure at 25-degrees-C appears feasible with higher catalyst levels.