The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 01, 1994
Filed:
Apr. 02, 1993
Gerd Bohmholdt, Marl, DE;
Wilhelm Heitmann, Herne, DE;
Peter Kirchner, Bochum, DE;
Hans-Werner Michalczak, Herne, DE;
Huels Aktiengesellschaft, Marl, DE;
Abstract
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.