Process for preparing polymethylene polyphenyl polycarbamates
申请人:MITSUI TOATSU CHEMICALS, Inc.
公开号:EP0032733A1
公开(公告)日:1981-07-29
This invention relates to a process for preparing diphenylmethane dicarbamates and polymethylene polyphenyl polycarbamates by reacting an N-phenyl carbamic acid ester with formaldehyde or a formaldehyde-producing substance in which the reaction is carried out in a substantially homogeneous system by using a ferric halide compound as the catalyst and in which, after completion of the reaction, water or an aqueous solution of a hydrohalogenic acid is added to the reaction mixture and the resulting aqueous phase containing the ferric halide compound is separated and recovered to reuse the catalyst.