Modified aminoplast crosslinkers and powder coating compositions containing such crosslinkers

A method for preparing a crosslinking agent, the method comprising the following steps:

• (I) combining the following reactants:
• (a) at least one aminoplast resin;
• (b) at least one compound having active hydrogen groups reactive with aminoplast resin (a), said compound selected from at least one of:
• (i) compounds having the following structure (I):
• wherein X is aromatic and is selected from the group consisting of substituted phenyl groups, unsubstituted or substituted naphthyl, unsubstituted or substituted anthracyl, unsubstituted or substituted pyrene, and unsubstituted or substituted benzofuranyl;
• R1, R2, and R3 can be the same or diffaent and each independently represents H, (cyclo)alkyl having from 1 to 12 carbon atoms, aryl, alkaryl, aralkyl, or an active hydrogen-containing group, provided that at least one of R1, R2, and R3 represents an active hydrogen-containing group which is reactive with the aminoplast resin (A)
• (ii) compounds having the following structure (II) or (III):
• where R′ and R″ are the same or different and each independently represents an aromatic group or an alkyl group having 1 to 12 carbon atoms;
• and
• (iii) compounds different from (i) and (ii) and having a melting point of at least 80° C. selected from borneol, norborneol, isoborneol, 5-norbornen-2-ol, 1-adamantanemethanol, 1-adamatanol and 2-methyl-2-adamantanol to form a reaction admixture;
• (II) heating the reaction admixture to a temperature ranging from 90° C. to 135° C.;
• and
• (III) maintaining the temperature achieved in (II) for a time sufficient to obtain an ungelled reaction product having a glass transition temperature of at least 10° C. which is essentially free of active hydrogen-containing groups as detennined by infrared spectroscopy.

A method for preparing a crosslinking agent, the method comprising the following steps:

• (I) combining the following reactants:
• (a) at least one aminoplast resin comprising (alkoxyalkyl) aminotriazine having one or less non-alkylated NH bond per triazine ring;
• and
• (b) at least one compound selected from benzoin, isoborneol, and mixtures thereof,
• (II) heating the reaction admixture to a temperature ranging from 90° C. to 135° C.;
• and
• (III) maintaining the temperature achieved in (II) for a time sufficient to obtain an ungelled reaction product having a glass transition temperature of at least 10° C. which is essentially free of active hydrogen-containing groups as determined by infrared spectroscopy.