Process for the production of isocyanates, preferably diisocyanates and polyisocyanates with solvent recirculation

摘要

The present invention relates to a process for the production of isocyanates, preferably diisocyanates and polyisocyanates of the diphenylmethane series (MDI), by reacting an amine with phosgene in the liquid phase or in the gas phase to form the corresponding isocyanates, subsequent removal of the solvent in at least two steps to obtain at least two solvent streams, individual treatment of the at least two solvent streams, and recirculation of at least a portion of the solvent streams.

主权项

1. A process for the continuous preparation of producing an isocyanate, the process comprising:
(a) preparing an isocyanate and solvent-containing reaction solution by reacting at least one amine with phosgene in a solvent, to obtain a reaction solution comprising an isocyanate and solvent; (b) separating crude isocyanate from the isocyanate and solvent-containing reaction solution at a pressure ≧ambient pressure, to obtain a crude isocyanate stream and a first solvent stream; (c) recycling at least a portion of the first solvent stream into the reacting (a); and (d) separating the crude isocyanate stream at a pressure ≦ambient pressure, to obtain a purified isocyanate stream and a second solvent stream at a pressure ≦ambient pressure, (e) optionally purifying at least a portion of the second solvent stream to obtain a second purified solvent stream having a water content of ≦100 ppm, based on the weight of the second purified solvent stream, and (f) recycling at least a portion of the second purified solvent stream into step (a).