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:
Feb. 08, 1994
Filed:
Nov. 06, 1992
Andreas Hauner, Cologne, DE;
Hans-Joachim Hennig, Leverkusen, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
A process for the continuous catalyst-free production of polyisocyanates by thermal decomposition of the N-substituted carbamic acid esters corresponding to the polyisocyanates, in which the carbamic acid esters to be decomposed, in the form of a 5 to 90% by weight solution in an inert high-boiling solvent, are heated to a temperature of 100.degree. to 400.degree. C. and are subsequently introduced with expansion as a sidestream into a distillation column (4), in the sump of which a pressure of 0.001 to 5 bar and a temperature of 150.degree. to 400.degree. C. are maintained so that the high boiler is kept boiling in the sump, and the decomposition products are simultaneously condensed continuously and selectively at the head of the distillation column. The high boiler, which optionally contains impurities, is continuously removed via the sump outlet in a quantity substantially corresponding to the quantity of high boiler introduced into the column as solvent for the carbamic acid ester.