Circulation process for the production of aliphatic and cycloaliphatic diisocyanates

US5087739A · kind A · utility

Assignee

• Huels Aktiengesellschaft · DE

Inventors

• Gerd Bohmholdt · Marl, DE
• Josef Disteldorf · Herne, DE
• Peter Kirchner
• Hans-Werner Michalczak · Herne, DE

Key dates

• Filing date: May 28, 1991
• Grant date: Feb 11, 1992
• Expiry date: May 28, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C263/04
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

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.