Patent ID: 9695115
Date: 2017-07-04
CPC Classifications: C07C,Y02P

Claim:
1. A continuous method for preparing an isocyanate by (i) reacting the corresponding primary amine with phosgene in stoichiometric excess in a reaction chamber, wherein the reaction is carried out either in the liquid phase in the presence of an inert solvent or in the gas phase, such that a crude product 1 is obtained comprising the desired isocyanate, inert solvent, secondary components having a boiling point below that of the isocyanate (low boilers), secondary components having a boiling point above that of the isocyanate (high boilers), hydrogen chloride and unreacted phosgene, (ii) separating the crude product 1 into a liquid product stream 2 containing the desired isocyanate and into a gaseous product stream 3, (iii) working-up the liquid product stream 2, wherein inert solvent, low boilers, high boilers, hydrogen chloride and phosgene are removed from the desired isocyanate, characterized in that the low boilers, the hydrogen chloride and the phosgene are removed in step (iii) within a period of 30 second to 60 minutes following the separation of the crude product 1 in step (ii) into the product streams 2 and 3, and the temperature of the product stream 2 is always maintained below or equal to 250° C., and wherein in the case where the reaction is carried out in the gas phase, the isocyanate is liquefied after leaving the reaction chamber by adding an inert solvent to the process product.