Process for the manufacture of aromatic di- and/or polyisocyanates

摘要

This invention pertains to a process for the preparation of an aromatic di- and/or polyisocyanate comprising the steps of A. preparing an aromatic di- and/or polyurethane by 1. reacting a primary aromatic di- and/or polyamine with an O-alkyl carbamate at temperatures greater than 100 DEG C.; 2. separating the ammonia and other by-products from the aromatic di- and/or polyurethane; B. heating and the aromatic di- and/or polyurethane at temperatures of from 175 DEG C. to 600 DEG C.; and C. isolating the di- and/or polyisocyanate resulting from step B.