Charge-modified hydrophobic membrane materials and method for making the same

• US 5,004,543 A
• Filed: 06/21/1988
• Issued: 04/02/1991
• Est. Priority Date: 06/21/1988
• Status: Expired due to Term

• Current Assignee: Millipore Corporation
• Original Assignee: Millipore Corporation
• Inventors: Wang, David, Pluskal, Malcolm G., Steuck, Michael J.
• Primary Examiner(s): SPEAR JR, FRANK
• Application Number:
  US07/209,307
• Time in Patent Office: 1,015 Days
• Field of Search: 210/500.39, 210/638, 210/490, 210/500.23, 210/500.36, 210/500.29, 427/244, 427/245, 427/246, 427/307
• US Class Current: 210/490
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 67/0093 Chemical modification
• CPC Class Codes: G01N 27/44717 Arrangements for investigating the separated zones, e.g. localising zones

Abstract

A hydrophobic material having a crosslinked, cationic charge-modifying coating such that the majority of the ion exchange capacity of the material is provided by fixed formal positive charge groups is disclosed. The material is produced by contacting a hydrophobic substrate with a mildly alkaline, aqueous organic solvent solution into which has been dissolved a cationic charge-modifying agent. The charge-modifying agent comprises a water soluble, organic polymer having a molecular weight of greater than about 1000, wherein the polymer chain contains both fixed formal positive charge groups and halohydrin groups.

Materials of the type described herein can be used in a variety of applications including macromolecular blotting and filtration.

Claims

1. A hydrophobic substrate comprising a hydrophobic, microporous membrane coated with a cross-linked, cationic charge-modifying polymer such that the ion-exchange capacity of the coated substrate is provided by fixed formal positive charge groups associated with the polymer, thereby providing a coated substrate having both ionic and hydrophobic surface effects.

2. A hydrophobic microporous membrane as in claim 1 which comprises polyvinylidene fluoride, polypropylene, polyethylene, polysulphone or polytetrafluoroethylene.

3. A membrane as in claim 1 wherein the fixed formal positive charge groups are provided by a water soluble, organic polymer having a molecular weight greater than about 1000, the polymer having a polymer chain having fixed formal positive charge groups as well as halohydrin groups.

4. A membrane as in claim 3 wherein the halohydrin groups comprise epichlorohydrin groups.

5. A membrane as in claim 3 wherein the fixed formal positive charge groups are selected from the group consisting of quaternary ammonium, quaternary phosphonium and quaternary sulfonium.

6. A membrane as in claim 3 wherein the fixed formal positive charge is provided by a polyamino epichlorohydrin surface coating.

7. A membrane as in claim 1 additionally comprising a surfactant or wetting agent incorporated into the material.

8. A method for producing a microporous membrane having both ionic and hydrophobic surface effects comprising:

a. contacting a hydrophobic microporous membrane with a solution of (i) an organic polymer having a molecular weight of greater than about 100 daltons, wherein the polymer contains fixed formal positive charge groups and halohydrin groups; and

(ii) an alkaline, aqueous organic solvent; and

b. curing the coated microporous membrane.

9. A method as in claim 8 wherein the hydrophobic microporous membrane comprises a material selected from the group consisting of polyvinylidene fluoride, polypropylene, polyethylene, polysulphone and polytetrafluoroethylene.

10. A method as in claim 8 wherein the charge-modifying solution is maintained at a pH of between about 9.0 and about 12.0.

11. A method as in claim 8 wherein the curing comprises drying the coated hydrophobic substrate using heat.

12. A method as in claim 8 wherein the fixed formal positive charge groups are selected from the group consisting of quaternary ammonium, quaternary phosphonium and quaternary sulfonium.

13. A method as in claim 8 wherein the halohydrin groups comprise epichlorohydrin groups.

14. A method as in claim 8 comprising the additional step of contacting the coated hydrophobic substrate with an aqueous wetting agent or surfactant solution subsequent to the curing step.

15. A filtration material which comprises a hydrophobic, microporous membrane coated with a cross-linked, cationic polymer such that the ion exchange capacity of the coated membrane is provided by fixed, formal positive charge groups associated with the polymer, thereby providing a filtration material having both ionic and hydrophobic surface effects.

16. A method for producing a microporous membrane having both ionic and hydrophobic surface effects comprising:

a. immersing a hydrophobic microporous membrane in an aqueous organic solvent containing a polyamine epichlorohydrin resin, for a time period sufficient to allow the resin to coat the membrane;

b. removing the coated membrane from the aqueous organic solution; and

c. curing the coated membrane.

17. The method according to claim 16 wherein the aqueous organic solution comprises alcohol in water.

18. The method according to claim 16 wherein the aqueous organic solution comprises about 25% isopropyl alcohol by volume in water and about 0.5% to 5.0% solids by weight of a polyamine epichlorohydrin resin.