Abstract: The present invention relates to a process for producing diamines and polyamines of the diphenylmethane series (MDA) by reacting aniline and formaldehyde in the presence of an acid catalyst, wherein the aniline contains in total less than 0.5 wt. %, based on the total weight of aniline, of one or more compounds which contain at least one carbonyl group or of one or more compounds that are formed by reaction of these compounds which contain at least one carbonyl group with aniline.

Abstract: The invention relates to a method for determining the isomer composition in an isocyanate isomer mixture, wherein a spectrum of the isomer mixture is recorded and the spectrum is entered into a chemometric calibration model.

Abstract: The present invention relates to a process for producing diamines and polyamines of the diphenylmethane series (MDA) by reacting aniline and formaldehyde in the presence of an acid catalyst, wherein the aniline contains in total less than 0.5 wt. %, based on the total weight of aniline, of one or more compounds which contain at least one carbonyl group or of one or more compounds that are formed by reaction of these compounds which contain at least one carbonyl group with aniline.

Abstract: The invention provides an improved process for preparing diamines and polyamines from the diphenylmethane series by reacting aniline and formaldehyde in the presence of an acid catalyst, the improvement involving the aniline containing less than about 3 wt. % of diamines and polyamines from the diphenylmethane series, based on the weight of the aniline.

Abstract: The invention provides an improved process for preparing diamines and polyamines from the diphenylmethane series by reacting aniline and formaldehyde in the presence of an acid catalyst, the improvement involving the aniline containing less than about 3 wt. % of diamines and polyamines from the diphenylmethane series, based on the weight of the aniline.

Abstract: The invention relates to a process for the production of di- and polyisocyanates of the diphenylmethane series and mixtures thereof, in which aniline and formaldehyde are reacted in the presence of an acid catalyst to form di- and polyamines of the diphenylmethane series; the di- and polyamines of the diphenylmethane series are phosgenated, optionally in the presence of a solvent, to obtain a crude di- and polyisocyanate; from the crude di- and polyisocyanate, at least one fraction containing at least 5 wt. % 3-ring and multi-ring MDI and at least one fraction containing at least 95 wt. % 2-ring MDI are separated by distillation, and the acidities of the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt. % 2-ring MDI are determined analytically; and an acidic compound is added to the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt.

Abstract: The present invention relates to a process for the preparation of di- and polyamines of the diphenylmethane series, and to the preparation of di- and poly-isocyanates of the diphenylmethane series from these di- and poly-amines. The di- and poly-amines of the diphenylmethane series are prepared by the reaction of aniline and formaldehyde in the presence of hydrochloric acid. In with the present invention, the hydrochloric acid employed contains less than 0.001 wt. % of metal ions which are divalent and/or more than divalent.

Abstract: The present invention relates to a process for the preparation of di- and polyamines of the diphenylmethane series, and to the preparation of di- and polyisocyanates of the diphenylmethane series from these di- and poly-amines. The di- and poly-amines of the diphenylmethane series are prepared by the reaction of aniline and formaldehyde in the presence of hydrochloric acid. In with the present invention, the hydrochloric acid employed contains less than 0.001 wt. % of metal ions which are divalent and/or more than divalent.

Abstract: The invention relates to a process for the production of di- and polyisocyanates of the diphenylmethane series and mixtures thereof, in which aniline and formaldehyde are reacted in the presence of an acid catalyst to form di- and polyamines of the diphenylmethane series; the di- and polyamines of the diphenylmethane series are phosgenated, optionally in the presence of a solvent, to obtain a crude di- and polyisocyanate; from the crude di- and polyisocyanate, at least one fraction containing at least 5 wt. % 3-ring and multi-ring MDI and at least one fraction containing at least 95 wt. % 2-ring MDI are separated by distillation, and the acidities of the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt. % 2-ring MDI are determined analytically; and an acidic compound is added to the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt.

Abstract: The invention relates to a method for determining the isomer composition in an isocyanate isomer mixture, wherein a spectrum of the isomer mixture is recorded and the spectrum is entered into a chemometric calibration model.

Abstract: Polyisocyanates of the diphenylmethane series are produced by a) reacting aniline and formaldehyde in the presence of an acidic catalyst to produce a polyamine, b) neutralizing the reaction mixture from step a) with a base at a temperature of more than 110° C. or neutralizing the reaction mixture from step a) with a base and heating the neutralized mixture to a temperature of more than 110° C., and c) phosgenating the polyamine from step b) to convert it to the corresponding polyisocyanate.

Abstract: The invention relates to a process for the preparation of polyamines of the diphenylmethane series, comprising

Abstract: The present invention concerns a process for the production of methylenedianiline (MDA) having a high monomer content.

Abstract: Polyisocyanates of the diphenylmethane series are produced by a) reacting aniline and formaldehyde in the presence of an acidic catalyst to produce a polyamine, b) neutralizing the reaction mixture from step a) with a base at a temperature of more than 110° C. or neutralizing the reaction mixture from step a) with a base and heating the neutralized mixture to a temperature of more than 110° C., and c) phosgenating the polyamine from step b) to convert it to the corresponding polyisocyanate.