US 5,489,406 AGranted

Method of making polyvinylidene fluoride membrane

AssigneeMemtec Limited

InventorsThomas W. Beck, Matthew B. Lee, Richard D. Grant, Robert J. W. Streeton

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Abstract

A method of making a porous polymeric material by heating a mixture comprising polyvinylidene fluoride and a solvent system initially comprising a first component that is a latent solvent for polyvinylidene fluoride and a second component that is a non-solvent for polyvinylidene fluoride wherein, at elevated temperature, polyvinylidene fluoride dissolves in the solvent system to provide an optically clear solution. The solution is then rapidly cooled so that non-equilibrium liquid-liquid phase separation takes place to form a continuous polymer rich phase and a continuous polymer lean phase with the two phases being intermingled in the form of bicontinuous matrix of large interfacial area, and cooling is continued until the polymer rich phase solidifies. The polymer lean phase is removed from the solid polymeric material. A porous material so prepared is characterised by a lacey or filamentous structure consisting of a plurality of polymer strands (1) connected together at a number of locations (2) spaced apart along each strand.

Claims12

Dependent claims

A method of making a porous polymeric hollow fiber membrane comprising the steps of:

(a) heating a mixture comprising polyvinylidene fluoride (PVdF) and a solvent system, initially comprising a first component that is a latent solvent for PVdF and a second component that is a non-solvent for PVdF, wherein at elevated temperature PVdF dissolves in the solvent system to provide an optically clear solution,
(b) introducing said solution into an extrusion head adapted to form the solution into a hollow fiber membrane form extruded co-axially with a lumen-forming fluid, a coating liquid that is introduced around the outer surface of the hollow fiber and a cooling liquid that is introduced around the coating liquid,
(c) rapidly cooling the solution so that non-equilibrium liquid-liquid phase separation takes place to form a continuous polymer rich phase and a continuous polymer lean phase with the two phases being intermingled to form a bicontinuous matrix of large interfacial area;
(d) continuing cooling until the polymer rich phase solidifies to form a porous hollow fiber membrane, and
(e) removing the solvent system from said porous hollow fiber membrane.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/946,496Filed 8 Dec 1992 · continuation in part
Priority: AU PK00369 May 1990
Granted: 6 Feb 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

C08J 9/28
Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof: by elimination of a liquid phase…
B01D 67/00113
Casting solutions therefor: pretreatment of the casting solutions, e.g. thermal treatment or ageing
B01D 67/0027
By mechanical treatment, e.g. pore-stretching: by stretching
B01D 67/003
By inducing porosity into non porous precursor membranes: by selective elimination of components, e.g. by leaching

Family

Serial536,650Parent of this continuation-in-part · filed 9 Jul 1990
Serial536,649Parent of this continuation · filed 9 Jul 1990
Serial941,376Parent of this continuation-in-part · filed 4 Sep 1992
US 5,277,851 AParent of this continuation-in-part · filed 11 Jan 1994
US 5,318,417 AParent of this continuation-in-part · filed 7 Jun 1994
US 5,489,406 AThis patent

From the US filing history. Foreign family members aren’t listed.