PROCESS FOR PREPARING POLYMETHYLENE POLYPHENYL POLYCARBAMATES

摘要

In the preparation of polymethylene polyphenyl polycarbamates by reacting an N-phenyl carbamic acid ester with formaldehyde or a formaldehyde-producing compound in the presence of water and an acid catalyst, the acid catalyst is used in the form of its aqueous solution having an acid catalyst concentration, at the start of the reaction, of at least 10% by weight and in an amount, at the start of the reaction, of from 0.01 to 100 moles per mole of the N-phenyl carbamic acid ester, and the reaction is carried out at a temperature of from 20 to 150.degree.C. After completion of the reaction, the aqueous acid catalyst solution containing small amounts of organic impurities may be recovered, subjected to adjustment of its acid catalyst concentration, and then reused directly for a subsequent reaction.