Preparation of mixtures of di - and poliisocianatos of diphenylmethane series with high contents of 4,4 '- metilenodifenildiisocianato and 2,4' - metilenodifenildiisocianato

摘要

Preparation of mixtures of di - and poliisocianatos series with high levels of diphenylmethane 4,4 and 39, 39 metilenodifenildiisocianato 2,4 - metilenodifenildiisocianato ".The present invention relates to a process for the preparation of a fraction of the diphenylmethane diisocyanates series containing at least 95% by weight of metilenodifenildiisocianato binuclear,In which) aniline and formaideu00eddo are reagidos in the presence of an acid catalyst to form di - and polyamines of the diphenylmethane series containing metilenodifenildiamina binuclear and (b) the di - and polyamineS of the diphenylmethane series containing metilenodifenildiamina binuclear are eventually fosgenadas in the presence of a solvent.And that is a di - and poliisocianato gross and (c) of di - and poliisocianato crude is separated a fraction containing at least 95% by weight of metilenodifenildiisocianato binuclear containing 4,4 39 MDI greater than 60% by weight, a content of 2,4 '- MDI 39 4 to 35% by weight and a content of 2,2' - MDI 39 of 0.01 to 10% by weight,With the mass fraction and a maximum of 20 ppm fenilisocianato and possibly up to a maximum of 50 ppm of solvent.With the separation of a fraction is carried out in a single stage distillation separation of components with low boiling point may be connected in series and / or connected downstream.