Synthesis of Dimeryl Diisocyanate (DDI) Curing Agent Using Triphosgene Reagent

Dimeryl diisocyanate (DDI) is a cycloaliphatic diisocyanate with a high molecular weight and a long carbon chain. The long carbon chain decrease the activity of N=C=O groups in the structure of this molecule. In this research, the synthesis of dimeryl diisocyanate (DDI) using triphosgene reagent has been investigated. Thus, in the first step, the reaction of acid dimer with thionyl chloride at ambient temperature has led to acyl chloride compound with 98% yield, and in the second step, by blowing ammonia gas, the dimeramide product was obtained with 78% yield. Then reduction of dimer amide using sodium borohydride reagent afforded dimer amine product with 52% yield. In the final step, using triphosgene reagent has led to the formation of dimeryl diisocyanate (DDI) with 62% yield. The products of different stages of the reaction were characterized using IR, 1HNMR and 13CNMR.