Process for the preparation of poliisocianatos of methane with reduced chromatic value series.

摘要

Process for the preparation of diphenylmethane series poliisocianatos with reduced chromatic value.The invention relates to a process for the preparation of poliisocinatos of diphenylmethane series, in which the) aniline and formaldehyde are converted, in the presence of an acid catalyst.In polyamines and below (b) the reaction mixture is neutralized with a base at a temperature higher than 110 198 C or the reactional mixture is heated after neutralization with a base at a temperature of SuPerior to 110 198 C and then (c) the polyamine is converted, by means of fosgenau00e7u00e3o in the corresponding poliisocianatos.