Method of preparing membranes from blends of polymers

• US 5,910,274 A
• Filed: 09/04/1997
• Issued: 06/08/1999
• Est. Priority Date: 10/11/1994
• Status: Expired due to Fees

• Current Assignee: L'Air Liquide SA
• Original Assignee: Praxair Technology Incorporated (Linde Plc)
• Inventors: Bikson, Benjamin, Nelson, Joyce Katz, Macheras, James Timothy
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US08/923,821
• Time in Patent Office: 642 Days
• Field of Search: 264/41, 264/102, 264/178 F, 264/184, 264/209.1, 264/559, 264/561, 264/562, 264/563
• US Class Current: 264/41
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/00111 Polymer pretreatment in the casting solutions
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 69/085 Details relating to the spinneret
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: B01D 71/643 Polyether-imides
• CPC Class Codes: B01D 71/76 Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 rubbers in general B01D71/24
• CPC Class Codes: B01D 71/80 Block polymers
• CPC Class Codes: B01D 71/82 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
• CPC Class Codes: Y10T 428/2967 Synthetic resin or polymer
• CPC Class Codes: Y10T 428/2969 Polyamide, polyimide or polyester
• CPC Class Codes: Y10T 428/2973 Particular cross section
• CPC Class Codes: Y10T 428/2975 Tubular or cellular
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated

Abstract

Improved anisotropic fluid separation membranes are prepared from blends of polymers with surface energy differences. The membranes are formulated by processes wherein low surface energy polymer with desirable fluid separation and permeation characteristics is preferentially concentrated in the surface discriminating layer of the membrane.

Claims

1. A process for making an anisotropic gas separation membrane, said process comprising:

(a) forming a blend of at least two polymers in at least one solvent, wherein at least one of said polymers being a low surface energy polymer having a measured surface energy that is at least 10% lower than the measured surface energy of the other polymers in the blend;

(b) extruding said blend, as a hollow fiber, through a gaseous atmosphere and into a liquid medium wherein said fiber solidifies as an anisotropic gas separation membrane; and

(c) recovering the solidified fiber anisotropic gas separation membrane, wherein said low surface energy polymer comprises less than 20% by weight of the overall membrane material and is concentrated in a surface discriminating layer.

2. The process according to claim 1, wherein said low surface energy polymer comprises polyimide, polyester or polycarbonate.

3. The process according to claim 1, wherein said low surface energy polymer contains siloxane or fluorocarbon groups.

4. The process according to claim 1, wherein the bulk of said membrane material comprises a polyetherimide or polysulfone.

5. The process according to claim 2, wherein said gaseous atmosphere is maintained at a subatmospheric pressure.

6. The process according to claim 1, wherein said membrane is a hollow fiber membrane.

7. The process of claim 1, wherein said low surface energy polymer comprises less than 10% by weight of the overall membrane material.

8. The process of claim 1, wherein said low surface energy polymer comprises less than 5% by weight of the overall membrane material.