Microporous membranes and uses thereof

• US 6,258,276 B1
• Filed: 10/18/1996
• Issued: 07/10/2001
• Est. Priority Date: 10/18/1996
• Status: Expired due to Term

• Current Assignee: Mcmaster University
• Original Assignee: Mcmaster University
• Inventors: Dickson, James M., Childs, Ronald F., Mika, Alicja M.
• Primary Examiner(s): Therkorn, Ernest G.
• Application Number:
  US08/733,792
• Time in Patent Office: 1,726 Days
• Field of Search: 210/638, 210/651, 210/653, 210/654, 210/683, 210/684, 210/685, 210/641
• US Class Current: 210/638
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 2323/40 in-situ membrane formation
• CPC Class Codes: B01D 2325/14 Membrane materials having negatively charged functional groups
• CPC Class Codes: B01D 2325/16 Membrane materials having positively charged functional groups
• CPC Class Codes: B01D 2325/26 Electrical properties
• CPC Class Codes: B01D 2325/42 Ion-exchange membranes
• CPC Class Codes: B01D 61/027 Nanofiltration
• CPC Class Codes: B01D 61/243 Dialysis
• CPC Class Codes: B01D 61/362 Pervaporation
• CPC Class Codes: B01D 61/44 Ion-selective electrodialysis
• CPC Class Codes: B01D 67/0006 by chemical reactions in-situ polymerisation, polycondensation, cross-linking or reaction for manufacturing composite membranes B01D69/125
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 69/106 Membranes in the pores of a support, e.g. polymerized in the pores or voids
• CPC Class Codes: B01D 69/107 Organic support material
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: H01M 8/1023 having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• CPC Class Codes: H01M 8/1058 characterised by a porous support having no ion-conducting properties
• CPC Class Codes: H01M 8/1072 by chemical reactions, e.g. insitu polymerisation or insitu crosslinking
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

Charged membranes comprise a porous substrate and a cross-linked polyelectrolyte or hydrogel located in the pores of the substrate and are useful in a variety of membrane separation processes, including pressure driven membrane separation, diffusion dialysis, Donnan dialysis, electrodialysis, electrochemical synthesis and prevaporation. Certain of the membranes are novel.

Claims

1. In a membrane separation process for water softening selected from the group consisting of pressure driven membrane separation, diffusion dialysis, Donnan dialysis and electrodialysis,, the improvement which comprises employing a charged membrane which preferentially rejects multivalent ions over monovalent ions and suitable for operation at ultra-low pressure, said charged membrane comprising a porous substrate and a cross-linked polyelectrolyte or hydrogel located in the pores of the substrate.

2. The process of claim 1 wherein said membrane separation process comprises a pressure-driven membrane separation to effect selective removal of multivalent cations from an aqueous medium containing monovalent cations and multivalent cations.

3. The process of claim 2 which is effected at a pressure of 70 psig.

4. The process of claim 3 wherein said membrane comprises a microporous substrate in the pores of which is in situ polymerized vinylpyridine combined with about 0.25 to about 1 wt. % of total monomers by divinylbenzene.

5. The process of claim 4 wherein amine groups in the polyelectrolyte are quaternized.

6. The process of claim 1 wherein the polyelectrolyte or hydrogel is formed in the pores of the substrate by in situ polymerization of a monomer or a mixture of monomers with a cross-linking agent, the monomer or at least one of the monomers of the monomer mixture being selected from those monomers which contain a functional group that provides an ion-exchange site and those which contain a group which is susceptible to a reaction by which such functional groups are subsequently introduced to in situ-formed polymer.

7. The process of claim 1 wherein the polyelectrolyte or hydrogel is formed in the pores of substrate by, first, in situ polymerization of a monomer or a mixture of monomers, the monomer or at least one of the monomers of the monomer mixture being selected from those monomers which contain a functional group that provides an ion-exchange site and those which contain a group which is susceptible to a chemical reaction by which such functional groups are subsequently introduced to the in situ-formed polymer, and, subsequently, cross-linking in situ-formed polymer.

8. The process of claim 1 wherein the polyelectrolyte is a copolymer of vinylpyridine and a monomer selected from divinylbenzene and divinylpyridine.

9. The process of claim 8 wherein the polyvinylpyridine is quaternized with an alkyl or aryl substituted alkyl halide or sulphate.

10. The process of claim 1 wherein the substrate is a microporous polyolefin substrate.

11. The process of claim 10 wherein the polyolefin is polypropylene or polyethylene.

12. The process of claim 1 wherein the properties of the bound polyelectrolyte or hydrogel are modified for a specific membrane and separation process by selection of the degree and type of cross-linking of the polyelectrolyte or hydrogel.

13. The process of claim 1 wherein said porous substrate is a microporous polypropylene substrate and said polyelectrolyte or hydrogel located in the pores of the microporous polypropylene substrate is poly(4-vinylpyridine) cross-linked with divinylbenzene and N-methylated with dimethyl sulfate.