Polyureas of high molecular weight were obtained by the direct polycondensation reaction of carbon dioxide with diamines at 40°C for several hours under a pressure of carbon dioxide (below 30 atm) by use of diphenyl phosphite in pyridine. Optimal temperature and pressure were 40°C and 20 atm of carbon dioxide. The polycondensation reaction was also affected by solvents and type and amounts of tertiary amines. Pyridine was most effective as tertiary amine and solvent as well. Of the phosphorous compounds used, triaryl phosphites and diphenyl phosphite were most effective, but trialkyl phosphites failed to give polymer. The reaction was assumed to proceed via a carbamyl N‐phosphonium salt of pyridine formed by dephenoxylation of phosphites. Similarly, polythioureas were prepared by heating a mixture of carbon disulfide, diamines, and diphenyl phosphite in pyridine at 40°C for 6 hr under nitrogen.
SynopsisSelective formation of biscarbamates from diphenyl carbonate (DPC) and diamines and the preparation of polyurethanes from the carbamates and diols under mild conditions were studied. The reaction of DPC and diamines was significantly affected by catalysts, biscarbamates being exclusively prepared in high yields in the presence of %-hydroxypyridine. The polycondensation reaction of the biscarbamates with diols was facilitated by catalysts such as metal salts; among the catalysts examined magnesium chloride in pyridine gave the best results. Metal chlorides in pyridine also promoted the reaction of DPC with aromatic amines to give the corresponding ureas, and the direct synthesis of polyureas was achieved by the polycondensation of DPC with diamines in the presence of the chloride.
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