Process for producing polyolefin membrane with integrally asymmetrical structure

US7429343B2 · kind B2 · utility

Assignee

• Membrana GmbH · DE

Inventors

• Erich Kessler · Kelsterbach, DE
• Thomas Batzilla · Miltenberg, DE
• Friedbert Wechs · Bad Mergentheim, DE
• Frank Wiese · Huntsville, US

Key dates

• Filing date: Jan 8, 2003
• Grant date: Sep 30, 2008
• Expiry date: Jan 23, 2024

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01D2325/026
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

Process for producing an integrally asymmetrical hydrophobic polyolefinic membrane with a sponge-like, open-pored, microporous support structure and a separation layer with a denser structure, using a thermally induced liquid-liquid phase separation process. A solution of at least one polyolefin is extruded to form a shaped object. The solvent used is one for which the demixing temperature of a solution of 25% by weight of the polyolefin in this solvent is 10 to 70° C. above the solidification temperature. After leaving the die, the shaped object is cooled using a liquid cooling medium that does not dissolve the polymer up to the die temperature, until the phase separation and solidification of the high-polymer-content phase take place. The integrally asymmetrical membrane producible in this manner has a porosity of greater than 30% to 75% by volume, a sponge-like, open-pored, microporous support layer without macrovoids and with on average isotropic pores, and on at least one of its surfaces a separation layer with pores <100 nm, if any. The membrane is preferably used for gas separation or gas transfer processes, in particular for oxygenation of blood.