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:
May. 31, 1983
Filed:
Dec. 16, 1981
Klaus Konig, Leverkusen, DE;
Peter Heitkamper, Dormagen, DE;
Bayer Aktiengesellschaft, Bayerwerk, DE;
Abstract
A carbamic acid ester corresponding to the formula R.sup.1 --NH--CO--OR.sup.2 is thermally cleaved to form isocyanate R.sup.1 --NCO and alcohol R.sup.2 --OH fractions. This cleavage is accomplished by boiling the carbamic acid ester, condensing the vapor given off in a first fractionation column, and condensing the vapor from the first fractionation column in a second fractionation column. The boiling of the carbamic acid ester is carried out in a manner such that the average dwell time in the reaction vessel is from 1 to 20 hours, the temperature is from 160.degree. to 260.degree. C. and the pressure is from 0.001 to 2 bar. The isocyanate fraction obtained by this cleavage process may be used as a starting material for a transurethanation reaction in which a lower boiling isocyanate R.sup.3 --NCO is produced. The radicals R.sup.1, R.sup.2, and R.sup.3 are defined herein.