Patent ID: 6977043
Filing Date: 2005-12-20
Classification: B01D,D01D,D01F

Abstract:
1. A method of producing a hollow fiber membrane from a perfluorinated thermoplastic polymer having a skinned inner surface and a porous structure throughout the remainder of the membrane comprising; a) dissolving a perfluorinated thermoplastic polymer in a solvent that forms an upper critical solution temperature solution with said polymer, b) extruding said solution through an annular die, a portion of said die being submerged in a cooling bath, and maintained at a temperature sufficiently high to prevent said solution from prematurely cooling, c) simultaneously supplying a stream of pressurized fluid to the central portion of the die, d) extruding said solution into a cooling bath, e) cooling said solution to below the upper critical solution temperature to cause separation into two phases by liquid-liquid phase separation, said phases being a polymer rich solid phase, and a solvent rich liquid phase, to form a gel fiber, f) extracting said solvent from said gel fiber to form a hollow fiber membrane having a substantially non-porous inner surface and a substantially porous structure through the remainder of the fiber, g) drying said porous hollow fiber membrane.