Method for making semi-permeable polymer membranes

• US 5,275,766 A
• Filed: 10/30/1992
• Issued: 01/04/1994
• Est. Priority Date: 10/30/1992
• Status: Expired due to Term

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Gadkaree, Kishor P., Hersh, Leroy S.
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US07/968,661
• Time in Patent Office: 431 Days
• Field of Search: 264/22, 264/41, 264/210.3, 264/210.4, 264/211.19, 264/340, 264/344
• US Class Current: 264/423
• CPC Class Codes: B01D 2323/02 Hydrophilization
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2325/38 Hydrophobic membranes
• CPC Class Codes: B01D 67/003 by selective elimination of components, e.g. by leaching
• CPC Class Codes: B01D 67/009 with wave-energy, particle-radiation or plasma
• CPC Class Codes: B01D 71/522 Aromatic polyethers
• CPC Class Codes: B01D 71/5221 Polyaryletherketone
• CPC Class Codes: B29C 2793/0045 Perforating
• CPC Class Codes: B29C 59/14 by plasma treatment plasma tubes per se H01J
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: C08J 9/26 by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out

Abstract

A method for making a semi-permeable microporous polymer sheet, useful as a separation membrane or the like, including extruding a melt-blended mixture of a high-temperature thermoplastic polymer and a leachable glass to form sheet and then leaching the glass from the sheet to leave a microporous relict polymer network, wherein the permeability of the sheet is improved by plasma-etching the surface of the sheet before or after leaching. Hydrophilic or hydrophobic porous membranes may be provided.

Claims

1. A method for making a semi-permeable microporous polymer sheet having an intercommunicating pore structure which comprises the steps of blending a batch mixture of a thermoplastic polymer and a finely divided leachable glass to form a two-phase glass-polymer blend material, extruding the glass-polymer blend material through a die to form a sheet having a sheet surface and comprising a continuous polymer network and an intercommunicating glass phase, and thereafter leaching the intercommunicating glass phase from the sheet without disruption of the polymer network, wherein:

prior to or subsequent to leaching, the sheet surface is exposed to a plasma of an energy at least sufficient to etch thermoplastic polymer from the sheet surface, for a time at least sufficient to increase the area of leachable glass or intercommunicating pore structure exposed at the sheet surface, thus to provide a microporous polymer sheet having an intercommunicating pore structure.

2. A method in accordance with claim 1 wherein the polymer is composed at least predominantly of a high-temperature polymer selected from the group consisting of polyether ketones, polyether amides, polysulfones, liquid crystal polymers, and mixtures, copolymers or other combinations thereof.

3. A method in accordance with claim 2 wherein the batch mixture comprises about 65-95% of glass and 5-35% of polymer by weight, and wherein the leachable glass is selected from the group consisting of alkali phosphate, borate, halophosphate, halide and oxyhalide glasses.

4. A method in accordance with claim 3 wherein the leachable glass is a halophosphate glass comprising, in mole percent, about 25-55% P₂ O₅, 10-40% R₂ O, wherein R is at least one alkali metal selected from the group consisting of sodium, potassium and lithium and 10-40% ZnCL₂.

5. A method in accordance with claim 3 wherein the leachable glass is an alkali phosphate glass comprising, in mole percent, about 35-70% P₂ O₅, 25-65% R₂ O, wherein R is at least one alkali metal selected from the group consisting of sodium, potassium and lithium, and 0-10% of oxides selected from the group consisting of Al₂ O₃ and B₂ O₃.

6. A method in accordance with claim 5 wherein the alkali phosphate glass has a glass transition temperature in the range of about 200°

-350°

C. and a composition which consists essentially, in mole percent, of about 40-55% P₂ O₅, 45-55% R₂ O, wherein R is at least one alkali metal selected from the group consisting of sodium, potassium and lithium, and 0-10% of Al₂ O₃.

7. A method in accordance with claim 1 wherein the plasma comprises an element, mixture or compound selected from the group consisting of oxygen, air, H₂ O, N₂ O, hydrogen, and ammonia.

8. A method in accordance with claim 7 wherein the plasma comprises oxygen.

9. A method in accordance with claim 7 wherein the sheet surface is exposed to the plasma prior to leaching.

10. A method in accordance with claim 8 wherein the sheet surface is exposed to the plasma subsequent to leaching.

11. A method in accordance with claim 1 wherein the polymer is composed at least predominantly of a polymer selected from the group consisting of polyether ether ketones.