Process for the preparation of mixtures of di- and polyisocyanates of the diphenylmethane series with a high amount of 4,4'-methylenediphenyldiisocyanate and 2,4'-methylenediphenyldiisocyanate

摘要

A fraction of diisocyanates of the diphenylmethane series is produced by reacting aniline and formaldehyde in the presence of an acid catalyst; phosgenating diamines and polyamines of diphenylmethane series containing binuclear methylenediphenyl diamine to produce a crude diisocyanate and polyisocyanate; and separating from crude diisocyanate and polyisocyanate, a fraction containing >=95 wt.% binuclear methylenediphenyl diisocyanate. Production of a fraction of diisocyanates of the diphenylmethane series containing >=95 wt.% binuclear methylenediphenyl diisocyanate by: (1) reacting aniline and formaldehyde in the presence of an acid catalyst to produce diamines and polyamines of the diphenylmethane series containing binuclear methylenediphenyl diamine; (2) phosgenating the diamines and polyamines of the diphenylmethane series containing binuclear methylenediphenyl diamine to produce a crude diisocyanate and polyisocyanate; and (3) separating from the crude diisocyanate and polyisocyanate, a fraction containing >=95 wt.% binuclear methylenediphenyl diisocyanate comprising greater than 60 wt.% 4,4'-methyl diisocyanate (MDI), 4-35 wt.% 2,4'-MDI, 0.01-10 wt.% 2,2'-MDI relative to the mass of the fraction; and not >20 ppm phenyl isocyanate in a single distillation step. Independent claims are also included for: (1) production of a diphenylmethane diisocyanate mixture comprising blending the separated fraction with a mixture containing an aromatic isocyanate; and (2) production of a polymer comprising reacting the separated fraction and/or the blend of separated fraction with a mixture containing an aromatic isocyanate with a polyol.