Continuous preparation of polycaprolactam wherein constant composition is maintained

US4429107A · kind A · utility

Assignee

• BASF SE

Inventors

• Hugo Strehler · Bischofswerda, DE
• Werner Hoerauf · Ludwigshafen, DE
• Guenter Valentin · Ludwigshafen, DE
• Friedrich Urbanek

Key dates

• Filing date: Aug 24, 1982
• Grant date: Jan 31, 1984
• Expiry date: Aug 24, 2002

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G69/16
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

An improved process for the continuous preparation of polycaprolactam, in which .epsilon.-caprolactam is partially polymerized, with the addition of a water-containing agent and acetic acid or propionic acid as a chain regulator, at a nylon-forming temperature, in a mechanically mixed zone in a vertical tubular reactor through which the reaction mixture flows downwards, and is then polymerized further, in additional heat exchange zones, until the desired degree of polymerization is reached, and polycaprolactam is then discharged as a melt, wherein a gaseous mixture of caprolactam, water and acetic acid or propionic acid is removed at the top of the tubular reactor and is fed to the middle of a column, water is removed at the top of the column, the bottom of the column is maintained at from 125.degree. to 145.degree. C., and the mixture obtained at the bottom of the column, and comprising caprolactam, acetic acid or propionic acid and a small amount of water, is recycled to the top of the tubular reactor.