CONTINUOUS MULTI-STAGE PROCESS FOR THE PREPARATION OF (CYCLO)ALIPHATIC DIISOCYANATES

摘要

23443-494 CONTINUOUS MULTI-STAGE PROCESS FOR THE PREPARATION OF (CYCLO)ALIPHATIC DIISOCYANATES The invention relates to a multi-stage process for the continuous phosgene-free preparation of (cyclo)aliphatic diisocyanates. The process comprises conversion of (cyclo)aliphatic diamines of the formula H2N-R1-NH2, wherein R1 represents a straight-chain or branched aliphatic hydrocarbon radical having from 6 to 12 carbon atoms or an optionally substituted cycloaliphatic hydrocarbon radical having 6 to 13 carbon atoms into the corresponding (cyclo) alkylenebisureas in a distillation reactor. The bisureas are further reacted with a primary alcohol having 3 to 5 carbon atoms in a pressurised distillation reactor to obtain the corresponding (cyclo)alkylene biscarbamates. The latter are thermally cleaved in the presence of a catalyst in a combined cleavage and rectifying column into the (cyclo)alkylene diisocyanates and alcohol in the liquid phase without using solvents. Compared with similar known processes, the process of the invention avoids the exposure of the reaction intermediates and products to high temperatures and ensures higher yields and lower energy consumption.