Process of recovering .epsilon.-caprolactam from PA-6 synthesis extract water

US6093788A · kind A · utility

Assignee

• Lurgi Zimmer GmbH · DE

Inventors

• Claus Born · Ingelheim am Rhein, DE
• Stefan Deibert · Offenbach am Main, DE
• Jurgen Schiwek · Hanau, DE
• Konrad Wolf · Walzbachtal, DE

Key dates

• Filing date: Oct 9, 1998
• Grant date: Jul 25, 2000
• Expiry date: Oct 9, 2018

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G69/18
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

The invention comprises a process of producing .epsilon.-caprolactam from extract water of polycaprolactam obtained by hydrolytic polymerization, wherein PA1 (i) the extract water is concentrated by distillation of water, PA1 (ii) from the concentrated extract water from stage (i) an extract of .epsilon.-caprolactam and oligomers including dimers is obtained by separating an .epsilon.-caprolactam/water vapor mixture, PA1 (iii) the extract from stage (ii) is depolymerized in the presence of a catalyst and superheated steam, where a vapor mixture of .epsilon.-caprolactam and water is obtained, and PA1 (iv) from the .epsilon.-caprolactam/water vapor mixtures of process stages (ii) and (iii) .epsilon.-caprolactam with a dimer content of .ltoreq.0.2 wt-% is obtained by distillation of water.