Process for separating low molecular weight compounds from an impure thermoplastic polymer or mixture

US5459168A · kind A · utility

Assignee

• Fried Krupp AG Hoesch-Krupp · DE

Inventors

• Hedi B. Nasr · Gelsenkirchen, DE
• Manfred Grabow · Ratingen, DE
• Klaus Reimann · Eindhoven, NL

Key dates

• Filing date: Aug 19, 1994
• Grant date: Oct 17, 1995
• Expiry date: Aug 19, 2014

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29K2105/26
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A process for treating an impure thermoplastic polymer, including raw and recycled polymers, during extrusion to separate low molecular weight compounds therefrom, including: introducing a separating agent into plasticized impure thermoplastic polymer passing through a first high pressure zone, the low molecular weight compounds of the plasticized polymer being at least partially soluble in the separating agent; extracting at least a part of the low molecular weight compounds from the plasticized polymer into the separation agent during passage of the plasticized polymer through an extraction zone; removing the separating agent charged with low molecular weight compounds from the extruder as the plasticized polymer passes through a low pressure zone having a residual pressure, P, which is lower the introductory pressure, P.sub.e, and for which 1 bar.gtoreq.P.gtoreq.P.sub.c ; collecting the charged separating agent as it is removed from the extruder; thermal vacuum treating the plasticized polymer as it passes through a last low pressure zone to vacuum degas the plasticized polymer at a pressure, P.sub.v, for which P.sub.v <0.5 bar and thereby further remove separating agent and low…