Method and device for evaporating polymer solutions of thermoplastic polymers, and a polycarbonate which can be obtained by evaporation

US6545122B1 · kind B1 · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Thomas Elsner · Düsseldorf, DE
• Jürgen Heuser · Krefeld, DE
• Christian Kords · Krefeld, DE

Key dates

• Filing date: Oct 19, 2001
• Grant date: Apr 8, 2003
• Expiry date: Oct 19, 2021

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01D19/0005
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

Described is a multi-stage, continuous process for evaporating and concentrating feed polymer solutions. In a first stage (a) of the process, the feed polymer solution is concentrated by passing it through one of (i) a combination of a tubular heat exchanger with one of a thin-film evaporator and a coiled tube evaporator, and (ii) a tubular heat exchanger. Each evaporator of (i) having a downstream separator. In a further stage (b), the intermediate polymer solution of the first stage is further concentrated and degassed to form a product polymer in a tubular heat exchanger having a downstream separator. The tubular heat exchanger of the further stage has an inside diameter of from 5 to 30 mm, and a length of from 0.5 to 4 m, and the throughput per heat exchanger tube being from 5 to 30 kg/h, based on the polymer. An entrainer is introduced into a delivery device located downstream from the separator of further stage (b). The product concentrated/degassed polymer of further stage (b) is then isolated and optionally granulated. Also described is an apparatus for evaporating and concentrating feed polymer solutions.