Abstract:
The invention relates to a method for controlling the viscosity of a mixture (125; 210) containing at least two components having different viscosities, comprising the following steps: • (a) determining the viscosity (132; 222) of the mixture (125; 210) by means of ultrasound measurements, • (b) standardizing the determined viscosity (132; 222) to standard conditions, • (c) comparing the standardized viscosity (14) with a specified target value (134; 224), • (d) adjusting the viscosity of the mixture (125; 210) by increasing or decreasing the fraction of at least one component of the mixture.
Abstract:
The invention relates to a process for preparing methylene diphenyl diisocyanate, comprising (a) the phosgenation of di- and/or polycyclic methylene diphenyl diamine, (b) the separation of the crude methylene diphenyl diisocyanate obtained into di- and polycyclic isomers, (c) the purification and/or separation of the mixture of bicyclic isomers of methylene diphenyl diisocyanate obtained, and (d) the storage of the mixtures obtained in step (c) or in step (b), wherein a portion of the stored mixtures is used again by means of recycling in at least one of steps (b) and (c).
Abstract:
The invention relates to a method for producing isocyanates through reaction of the corresponding amines with phosgene in the liquid phase, optionally in the presence of at least one inert medium, in which first the amine and the phosgene are mixed in a mixing chamber (1) to form a reaction mixture and the reaction mixture is fed to a reactor, wherein the amine is added through an opening (3) that is disposed coaxially to the mixing chamber (1) and wherein the phosgene is added through feed openings (5) in at least two planes (7, 9) disposed perpendicular to the axis (11) of the mixing chamber (1), or the phosgene is added through the opening (3) that is coaxial to the mixing chamber and the amine is added through the feed openings (5) in at least two planes (7, 9) disposed perpendicular to the axis (11) of the mixing chamber (1). At least one plane (9) is disposed upstream in the main flow direction of the reaction mixture and at least one plane (7) is disposed downstream relative to the opening (3) disposed coaxially to the mixing chamber (1). The average residence time of the reaction mixture in the mixing chamber (1) is no more than 20 ms.