Patent ID: 9593075
Date: 2017-03-14
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 carded out either in the liquid phase in the presence of an inert solvent or in the gas phase, wherein a stream comprising a liquid inert solvent is added to the process product after leaving the reaction chamber, 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.