| abstract |
The present invention relates to a process for the preparation of diisocyanates corresponding to the formula n n OCN--R--NCO n n wherein n R denotes a (cyclo)aliphatic hydrocarbon group with up to 15 carbon atoms n by phosgenation of the corresponding diamines represented by the formula n n H.sub.2 N--R--NH.sub.2 n n in the gas phase, characterized in that n (a) the diamines in vapor form, optionally diluted with an inert gas or with the vapors of an inert solvent, and phosgene are separately heated to temperatures of about 200° to 600° C. and continuously reacted together in a cylindrical reaction chamber which is free from moving parts and heated to about 200° to 600° C., while a turbulent flow is maintained in the reaction chamber. n (b) the gas mixture continuously leaving the reaction chamber is passed through an inert solvent for the diisocyanate which is maintained at a temperature above the decomposition temperature of the carbamic acid chloride corresponding to the diamine, and n (c) the diisocyanate which is dissolved in the inert solvent is purified by distillation. |