A new curing agent for self-curable system of aqueous-based PU dispersion

Anionic aqueous-based polyurethane (PU) dispersion consists of carboxyl group that served as an internal emulsifier stabilizing aqueous PU dispersion and also a reactive site toward curing agent. A model reaction of a mono-azetidine-containing compound and trimethylacetic acid (TMAA) demonstrated that an amino ester bond formation between azetidine and carboxylic acid. A di-azetidine containing compound (HDDA-AZT) was prepared and served as a curing agent, which was synthesized by a Michael addition reaction of azetidine (AZT) to hexanediol diacrylate (HDDA). Anionic aqueous PU dispersion was treated with HDDA-AZT as a latent curing agent and becoming a self-curable aqueous PU system. A cross-linked PU resin was obtained from this self-curing PU system on drying at ambient temperature. The performance properties of these self-cured PU resins proved that cross-linking behaviors with this new curing agent, HDDA-AZT.