Process for the continuous thermal cleavage of carbamic acid esters and preparation of isocyanates from the products thereof
US4386033A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 16, 1981 |
| Grant date | May 31, 1983 |
| Priority date | — |
| Expiry date | Dec 16, 2001 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P20/582
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.