SUPPORTED HOLLOW FIBER MEMBRANE

• US 20120156485A1
• Filed: 12/15/2010
• Published: 06/21/2012
• Est. Priority Date: 12/15/2010
• Status: Active Grant

• Current Assignee: BL Technologies Inc. (Ashland Global Holdings, Inc.)
• Original Assignee: General Electric Company
• Inventors: Palinkas, Attila, Szabo, Robert, Marschall, Marcell
• Granted Patent: US 8,529,814 B2
• Time in Patent Office: Days
• US Class Current: 428/365
• CPC Class Codes: B01D 2323/225 Use of supercritical fluids
• CPC Class Codes: B01D 2325/40 Fibre reinforced membranes
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 69/087 Details relating to the spinning process
• CPC Class Codes: B01D 69/0871 Fibre guidance after spinning through the manufacturing apparatus
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/0021 combined with joining, lining or laminating
• CPC Class Codes: B29C 48/06 Rod-shaped
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/11 comprising two or more partially or fully enclosed cavities, e.g. honeycomb-shaped
• CPC Class Codes: B29C 48/151 Coating hollow articles
• CPC Class Codes: B29C 48/18 the components being layers
• CPC Class Codes: B29C 48/2883 of preformed parts, e.g. inserts fed and transported generally uninfluenced through the extruder or inserts fed directly to the die
• CPC Class Codes: B29C 48/295 in gaseous form
• CPC Class Codes: B29C 48/32 with annular openings, e.g. for forming tubular articles
• CPC Class Codes: B29C 48/34 Cross-head annular extrusion nozzles, i.e. for simultaneously receiving moulding material and the preform to be coated
• CPC Class Codes: B29C 48/908 characterised by calibrator surface, e.g. structure or holes for lubrication, cooling or venting
• CPC Class Codes: B29C 48/919 using a bath, e.g. extruding into an open bath to coagulate or cool the material
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29K 2023/06 : PE, i.e. polyethylene
• CPC Class Codes: B29K 2067/003 : PET, i.e. poylethylene terephthalate
• CPC Class Codes: B29K 2105/04 : cellular or porous
• CPC Class Codes: B29K 2313/00 : Use of textile products or fabrics as reinforcement B29K2105/06 takes precedence
• CPC Class Codes: B29L 2031/755 : Membranes, diaphragms
• CPC Class Codes: Y10T 428/2915 : including textile, cloth or fabric

Abstract

A hollow fiber membrane is made by covering a tubular supporting structure with a membrane dope and converting the membrane dope into a solid porous membrane wall. Optionally, a textile reinforcing structure in the form of a circular knit may be added around the supporting structure before it is covered in dope. The reinforcing structure thereby becomes embedded in the membrane wall. The supporting structure may be soluble in a non-solvent of the membrane wall, for example water, and may be removed from the membrane. Alternatively, the supporting structure may be porous. A porous supporting structure may be made by a non-woven textile process, a sintering process within an extrusion machine, or by extruding a polymer mixed with a second component. The second component may be a soluble solid or liquid, a super-critical gas, or a second polymer that does not react with the first polymer.

Claims

1. A method of making a hollow fiber membrane comprising the steps of,

a) providing a tubular supporting structure;

b) forming a textile reinforcing structure in the form of a circular knit around the supporting structure;

c) covering the textile reinforcing structure with a membrane dope; and

,

d) converting the membrane dope into a solid porous membrane wall.

2. The method of claim 1 further comprising a step of dissolving the tubular supporting structure after step d).

3. The method of claim 2 wherein the tubular supporting structure is water soluble.

4. The method of claim 1 wherein step b) comprises passing the supporting structure through a circular warp knitting machine.

5. The method of claim 4 wherein the textile reinforcing structure is formed around the supporting structure under tension.

6. The method of claim 1 wherein step c) comprises passing the supporting structure and reinforcing structure through the inlet of a coating head, wherein the inlet is centered within a membrane dope outlet.

7. The method of claim 6 wherein step b) comprises passing the supporting structure through a circular warp knitting machine in line with the coating head.

8. The method of claim 1 wherein the supporting structure is porous.

9. The method of claim 8 wherein step a) comprises extruding a mixture of a thermoplastic membrane polymer and a second material selected from the group consisting of a) a super-critical gas, b) a water soluble solid or liquid, and c) a polymer that is non-reactive with the membrane polymer.

10. The method of claim 8 wherein the supporting structure is a non-woven material.

11. The method of claim 8 wherein step a) comprises extruding semi-molten granules of a polymer.

19. A hollow fiber membrane produced according to the method of claim 1.

12. A method of making a hollow fiber membrane comprising the steps of,

a) providing a porous tubular supporting structure;

b) covering the supporting structure with a membrane dope; and

,

c) converting the membrane dope into a solid porous membrane wall.

13. The method of claim 12 wherein step a) comprises extruding a mixture of a thermoplastic membrane polymer and super-critical carbon dioxide gas.

14. The method of claim 12 wherein step a) comprises extruding a mixture of a thermoplastic membrane polymer and a water soluble solid or liquid.

15. The method of claim 12 wherein step a) comprises extruding a mixture of a thermoplastic membrane polymer and a second polymer that is non-reactive with the membrane polymer, followed by stretching the extrusion to create cracks between the two polymers.

16. The method of claim 12 wherein the supporting structure is a non-woven material.

17. The method of claim 12 wherein step a) comprises extruding semi-molten granules of a polymer under pressure through an annular die.

18. The method of claim 12 further comprising a step of forming a textile reinforcing structure in the form of a circular knit around the supporting structure after step a) and before step b).

20. A hollow fiber membrane produced according to the method of claim 12.