Emulsion of polyurethane having thermosetting properties. I. Preparation

A method of preparation of an urethane emulsion which provides thermosetting film is described here. By reacting a urethane prepolymer containing terminal isocyanate groups with diethylenetriamine in the presence of ketones, poly(urethane-urea-amine) was prepared. In other organic solvents, however, gelation occurred immediately and preparation of polyurethane-urea-amine was not successful. The function of ketone was ascribed to the tentative formation of a Schiff base between the primary amino group of diethylenetriamine and ketone in situ, and the reaction of primary amine with isocyanate was partly masked to prevent gelation. Then the free amino group is generated when the polymer is treated with epichlorohydrin and the reaction occurs between them. After the solution was neutralized with an aqueous acid, the solvent was removed in vacuo to give a stable self-emulsifiable thermosetting urethane emulsion. Typical mechanical properties of film from this urethane emulsion are also given here.