Huels Aktiengesellschaft

Peter Kirchner

Josef Disteldorf

Hans-Werner Michalczak

Gerd Bohmholdt

Wilhelm Heitmann

Hans-Jurgen Haage

Hubert Libera

A continuous multistage process for the preparation of (cyclo)aliphatic diisocyanates comprising a) condensing urea with a (cyclo)aliphatic diamine in the presence of an alcohol solvent to make a (cyclo)alkylenebisurea in a distillation reactor; b) reacting the crude (cyclo)alkylenebisurea with alcohol in a pressurized distillation reactor to make (cyclo)biscarbamate; c) removing the ammonia formed in the pressurized distillation reactor; d) cleaving the (cyclo)biscarbamate in the presence of a catalyst in a combined cleavage and rectifying column to make crude (cyclo)alkylene diisocyanate; e) reacting a diverted portion of the cleavage products with the alcohol to form a recycling mixture; f) and distilling the crude (cyclo)alkylene diisocyanate formed in step d.

Continuous multi-stage process for the preparation of (cyclo) aliphatic

A circulation process for the production of (cyclo)aliphatic diisocyanates, in which the biscarbamate is produced from diamines, by-products from the thermal cracking, urea, and alcohol in the presence of N-unsubstituted carbamates and dialkyl carbonates, and with separation of NH.sub.3 ; the subsequent cracking of the biscarbamate is carried out in the liquid phase without solvent; the diisocyanate and alcohol are condensed; the diisocyanate is subjected to a purifying distillation; and a portion of the cracking reaction mixture is discharged with the by-products formed and recycled to the biscarbamate production step after prior reaction with the crude alcohol formed, effectively utilizes the by-products formed in the cracking step and is an industrially practical and economical process.

Circulation process for the production of aliphatic and cycloaliphatic

A stabilizer system for stabilization of polyolefins against light, heat, and oxidative degradation, comprising:

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Bochum, Germany

Peter Kirchner