Abstract: A process for the preparation of polyetherols, comprising the following steps: a) reaction of at least one starter compound with at least one alkylene oxide and a catalyst to give a crude polyetherol and b) removal of low molecular weight byproducts from the crude polyetherol from step a), wherein the crude polyetherol is treated with a stripping gas in a column having internals.

Abstract: The invention relates to a process for distillatively preparing TDA from a reactant stream comprising TDA, high boilers and low boilers in a dividing wall column in which a dividing wall is disposed in the longitudinal direction of the column to form an upper combined column region (2), a lower combined column region (3), a feed section (4) having a rectifying section (5) and stripping section (6), and also a withdrawal section (7) having a rectifying section (9) and stripping section (8), which comprises the following steps: a. feeding the reactant stream (13) into the feed section (4) of the dividing wall column (1); b. drawing off a low boiler fraction via the top of the column (11); c. drawing off TDA via a side draw (14) in the withdrawal section (7) of the dividing wall column (1); d. drawing off a low boiler fraction via the bottom of the column (12).

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: A process is provided for preparing light-colored isocyanates which can be used for preparing urethane compounds, in particular polyurethanes, for example polyurethane foams.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: A process for working up distillation residues from the synthesis of tolylene diisocyanate by reaction of the distillation residues with water comprises reacting the TDI distillation residues with water in a continuous or semicontinuous process in a backmixed reactor in the presence of hydrolysate.

Abstract: In a process for preparing mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates having a reduced content of chlorinated by-products and a reduced iodine color number by two-stage reaction of the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, separation of the excess phosgene and solvent after the phosgenation is complete and thermal treatment of the reaction product, the mass ratios of phosgene to hydrogen chloride in the residence time apparatus of the second stage of the phosgenation are at the same time 10-30:1 in the liquid phase and 1-10:1 in the gas phase.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: Organic diurethanes and/or polyurethanes are prepared by reacting organic diamines and/or polyamines (a) with urea and/or alkyl cabamates (b) and alcohols (c) in the presence of soluble zirconium compounds, preferably zirconium alkoxides, zirconium acetate or zirconium acetylacetonate, as catalyst (d). They can be used for preparing diisocyanates and/or polyisocyanates by thermal dissociation.

Abstract: The invention relates to a process for the preparation of amines by hydrogenation of nitro compounds, which comprises carrying out the hydrogenation in a vertical reactor whose length is greater than its diameter, having a downward-facing jet nozzle arranged in the upper region of the reactor through which the starting materials and the reaction mixture are fed in, and having an outlet at any desired point of the reactor, through which the reaction mixture is fed back to the jet nozzle in an external circuit by means of a conveying means, and having flow reversal in the lower region of the reactor.

Abstract: Organic diurethanes and/or polyurethanes are prepared by reacting organic diamines and/or polyamines (a) with urea and/or alkyl cabamates (b) and alcohols (c) in the presence of soluble zirconium compounds, preferably zirconium alkoxides, zirconium acetate or zirconium acetylacetonate, as catalyst (d). They can be used for preparing diisocyanates and/or polyisocyanates by thermal dissociation.