Patent ID: 8546606

Claim:
A process for preparing polyisocyanates by reacting primary amines with phosgene, which comprises the steps a) mixing an amine with phosgene, b) reacting said amine with said phosgene in a residence reactor wherein the residence reactor in step b) is configured as a tube reactor comprising horizontal segments, vertical segments, or a combination thereof, which are connected to one another by sections which have a diameter less than the diameter of the narrowest horizontal or vertical segment and wherein said phosgene and said amine comprise a flowing medium comprises a mixture of a gaseous and/or vapor phase and a liquid, wherein said gaseous and/or vapor phase comprises phosgene and wherein said amine and phosgene are reacted at a temperature of from 60 to 200° C. and an absolute pressure of from 0.9 to 400 bar.