The present invention relates to a process for the manufacture of diisocyanates
by phosgenation of the corresponding diamines in which the vaporous diamines, optionally
rarefied with an inert gas or with the vapors of an inert solvent, and phosgene
are heated separately to temperatures of about 200 C. to about 600
C. and mixed and reacted in a tube reactor characterized in that a number n2
of nozzles directed parallel to the axis of the tube reactor are arranged in the
tube reactor, the diamine-containing stream being fed into the tube reactor through
the n nozzles and the phosgene stream being fed into the tube reactor through the
remaining free space.