Abstract:
The invention relates to a method for producing diphenylmethandiamine, comprising the steps of a) reacting aniline with formaldehyde in the presence of an acid, b) neutralizing most of the acid with ammonia and/or aqueous ammonia solution, c) separating the reaction mixture from step b) into an aqueous and an organic phase, d) neutralizing the remaining part of the acid in the organic phase with aqueous alkali hydroxide solution, e) separating the reaction mixture from step d) into an aqueous and an organic phase, f) treating the aqueous phase obtained in step c) or optionally the unified aqueous phases from steps c) and e) with at least one oxide or hydroxide of an alkaline earth metal, and g) separating the ammonia obtained in step f).
Abstract:
The invention relates to a method for partially or completely separating a substance mixture consisting of hydrogen chloride and phosgene, optionally of solvents and optionally of low-boiling fractions and inert substances such as those that normally arise during the production of isocyanates by reacting amines with phosgene. The inventive method is characterized in that a partial or complete condensation of phosgene is firstly carried out followed by a distillation or stripping inside a column for removing the hydrogen chloride from the bottom product phosgene and lastly, a washing of the top product hydrogen chloride with the process solvent for absorbing the phosgene in the process solvent is carried out. A subsequent purification by means of adsorption on activated carbon or other appropriate methods can be used for removing solvent remnants.
Abstract:
The invention relates to a method for producing isocyanates by reacting amines with phosgene inside a reactor followed by separating the isocyanate out from the reaction mixture exiting the reactor and purifying this isocyanate. The invention is characterized in that the isocyanate is separated out and purified in a column with a top pressure of 1 to 950 mbar, preferably 5 to 50 mbar, particularly preferred 10 to 20 mbar, with a bottom temperature of 90 to 250 °C, preferably 120 to 170 °C, particularly preferred 130 to 150 °C, and that the pure isocyanate flow is withdrawn in liquid or gaseous form, preferably in a side-stream of the column.
Abstract:
The invention relates to a method for producing isocyanates by reacting primary amines with phosgene in a solvent, the solvent containing a dialkyl carbonate.
Abstract:
The invention relates to a method for the continuous production of polyisocyanates by reaction of organic amines with phosgene, characterised in that the reaction occurs in at least three stages, whereby the first stage is in a mixing unit, the second stage in at least one residence time unit and the third stage in at least one material separating apparatus and the pressure in each subsequent stage is lower than in the previous stage.
Abstract:
The invention relates to a method for producing isocyanates by reacting amines with phosgene in the presence of inert organic solvents inside a reactor and by subsequently processing the reaction mixture exiting the reactor. The invention is characterized in that the separating out of the solvent ensues in a two-step or multi-step, preferably two-step distillation process, and the solvent is separated out in a first apparatus under a pressure of 0.1 to 15 bar and in a second or other apparatuses under a pressure of 1 to 900 mbar. The condensation heat of the solvent vapor from the first apparatus is used for partially or completely vaporizing solvent in the second apparatus.
Abstract:
The invention relates to a method for producing polyisocyanates by reacting primary amines with phosgene, comprising the following steps: a) mixing the amine with the phosgene; b) reacting the amine with the phosgene in a reactor, inside of which the mixture stays for a period of time and, optionally; c) transferring the discharge from the reactor from step b) into a distillation column. The invention is characterized in that the reactor cited in step b) is provided in the form of a tubular reactor.