Verfahren zur Herstellung von MDI, insbesondere von 2.4'-MDI

摘要

The invention relates to a method for producing MD1, comprising the following steps: A) aniline and formaldehyde are made to react in the presence of an acid to form methylene(diphenyldiamene) and polymethylene polyphenylene polyamine, the mol ratio of acid to amine being a maximum of 0.2; b) the mixture obtained in step A) is reacted with phosgene to form methylene (diphenyldiisocyanate) and polymethylene polyphenylene polyisocyanate; C) the mixture obtained in step B) is separated into monomer MDI and polymer MDI; and D) the monomer MDI obtained in step C) is separated from 2,4'- MDI.