| abstract |
The invention relates to a method for the production of methylenedi(phenylamine) by reacting aniline with formaldehyde in the presence of acid catalysts. The method is characterized in that aniline and optionally an acid catalyst are treated in a semi-continuos method; formaldehyde and optionally an acid catalyst are fed through a mixing organ in a circuit in which aniline, optionally an acid catalyst and optionally an already added formaldehyde are circulated and tempering the reaction mixture at a temperature of over 75 DEG C after feeding at least 50 % of the total amount of formaldehyde. The invention also relates to a method for the production of polyisocyanates by phosgenating the amines thus obtained and the polyisocyanates obtained according to this method. |