Gas transfer membrane

• US 7,819,956 B2
• Filed: 06/30/2005
• Issued: 10/26/2010
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC (Xylem, Inc.)
• Original Assignee: Siemens Water Technologies Corp (Siemens AG)
• Inventors: Muller, Heinz-Joachim
• Primary Examiner(s): Greene; Jason M
• Application Number:
  US11/571,100
• Publication Number:
  US 20070157812A1
• Time in Patent Office: 1,944 Days
• Field of Search: 96/4, 96/8, 96/10, 96/11, 96/6, 95/45, 95/46, 95/48, 95/50, 95/54, 210/640, 210/650, 210/490, 210/500.21, 210/500.23, 210/500.27, 555/24, 55D/IG.5
• US Class Current: 96/6
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2323/18 Pore-control agents or pore formers
• CPC Class Codes: B01D 2323/22 Specific non-solvents or non-solvent system
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 2325/02834 more than 0.1 and up to 1 µm
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 2325/38 Hydrophobic membranes
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 67/0018 Thermally induced processes [TIPS]
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 67/003 by selective elimination of components, e.g. by leaching
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• 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 71/32 containing fluorine atoms
• CPC Class Codes: Y10S 55/05 Methods of making filter

Abstract

Porous polymeric membranes formed from a hydrophobic polymer, such as halar having membrane pores of a size sufficient to permit gas and/or vapor permeation 0.05 μm to 5 μm without permitting the flow of a hydrophilic fluid across the membrane. Pore distribution is uniform and porosity is high, in some cases up to 80%. Membranes may be in the form of a flay sheet or hollow fibre for example and can be used in a variety of applications such as stripping HF gas, degassing of caustic solution, chlorine gas/alkaline filtration, degassing tap water to remove dissolved chlorine. Processes used to make such membranes can be carried out using relatively non toxic solvents such as citric acid ethyl ester or glycerol triacetate.

Claims

1. A hydrophobic porous polymeric gas transfer membrane comprising poly(ethylene chlorotrifluoroethylene), having membrane pores in the range of 0.05 microns to 5 microns, a porosity of 70% to 80%, and a wall thickness of 150 microns to 250 microns, wherein the pores permit the flow of gas and/or vapour across the gas transfer membrane without permitting the flow of a hydrophilic fluid across the membrane.

2. The porous polymeric membrane according to claim 1, wherein membrane pore size is chosen so as to permit gas and/or vapour permeation without permitting the flow of liquid water molecules.

3. The porous polymeric membrane according to claim 1, wherein membrane pore size is chosen in combination with membrane material polarity to provide a gas filtration membrane.

4. The porous polymeric membrane according to claim 1 wherein the pore sizes are in the range 0.1 μ

m to 1 μ

m.

5. The porous polymeric membrane according to claim 4, wherein the pore sizes are in the range 0.1 μ

m to 0.5 μ

m.

6. The porous polymeric membrane according to claim 1, in the form of a flat sheet.

7. The porous polymeric membrane according to claim 1, in the form of a hollow fibre membrane.

8. The porous polymeric membrane according to claim 1, used in one or more processes selected from the group consisting of transmembrane distillation, osmotic distillation, degassing, drying, adsorption, and bubbleless membrane aeration.

9. The porous polymeric membrane according to claim 1, for use as a gas filtration membrane.

10. The porous polymeric membrane according to claim 1, for use in stripping HF gas.

11. The porous polymeric membrane according to claim 1, for use in degassing of caustic solution.

12. The porous polymeric membrane according to claim 1, for use in chlorine gas/alkaline filtration.

13. The porous polymeric membrane according to claim 1, for use in degassing tap water to remove dissolved chlorine.

14. The porous polymeric membrane according to claim 1, for use in a membrane contactor.

15. The porous polymeric membrane according to claim 1, free from toxic solvent residue.