AN AMINOPLAST BASED CROSSLINKING AGENT, METHOD OF PREPARATION THEREOF AND A CURABLE POWDER COATING COMPOSITION CONTAINING SAID CROSSLINKING AGENT

摘要

The present invention provides an aminoplast based crosslinking agent having reactive benzoxazine groups comprising the ungelled reaction product of the following reactants: (a) at least one mono-hydroxy aromatic compound having the following structure (I): wherein R1 represents a monovalent hydrocarbon group, COOR5 where R5 represents H or a monovalent hydrocarbon group, NO2, halogen or XR4, where X represents O or S and R4 represents a monovalent hydrocarbon group having 1 to 8 carbon atoms; R3, R3', R2 and R2' can be the same or different and each independently represents a substituent selected from H, a monovalent hydrocarbon group, COOR5, NO2, halogen and XR4, provided that at least one of R3 and R3' is H; or when R3' is non-hydrogen substituted and R3' is H, RI and R2 taken together, R1 and R2' taken together, or R2 and R3 taken together represent fused aliphatic or aromatic ring structures, or when R3' is non-hydrogen substituted and R3 is H, R1 and R2 taken together, RI and R2' taken together, or R2' and R3' taken together represent fused aliphatic or aromatic ring structures; and (b) at least one aminotriazine compound having one or less non-alkylated NH group, present in a molar ratio of reactant (a) to reactant (b) ranging from 1.0 to 3.0: 1.0, provided that where reactant (a) is a single ring monohydroxy aromatic compound, the molar ratio of reactant (a) to reactant (b) ranges from 1.0 to less than 1.8:1.0 and from greater than 2.2 to 3.0:1.0, wherein said crosslinking agent is essentially free of hydroxyl functionality and has a glass transition temperature of at least 40°C. The invention also relates to a method of preparation of said crosslinking agent and to a curable powder coating composition containing the crosslinking agent.