| 摘要 |
<p>It is disclosed that, in the process for producing polymethylene polyphenyl polycarbamates through the reaction of N-phenyl carbamate with formaldehyde or a formaldehyde-supplying substance in the presence of an acid catalyst, if the reaction is carried out in the concurrent presence of at least one compound or a mixture of at least two compounds selected from the group consisting of N-carboalkoxy (or cycloalkoxy)-2-oxa-4-aza-naphthalenes, bis(N-carboalkoxy(or cycloalkoxy)-anilino)-methanes and N,N'-dicarboalkoxy (or cycloalkoxy)aminobenzyl-anilines, the object product, polymethylene polyphenyl polycarbamate, can be obtained at a high yield. According to the present invention, also a more economical and easily aperable process for producing polymethylene polyphenyl polycarbamate is provided, by the recycling use of the named compound or compounds which have been concurrently present in the reaction system and after the reaction separated and recovered from the reaction product, and also by the recycling use of the aqueous acid solution which has been used as the catalyst, without the interceding removal of organic impurities formed in the reaction but simply with the adjustment of its acid concentration to the predetermined level.</p> |
