Process for producing microporous films and products

• US 3,876,738 A
• Filed: 07/18/1973
• Issued: 04/08/1975
• Est. Priority Date: 07/18/1973
• Status: Expired due to Term

• Current Assignee: Cuno Incorporated (3M Company)
• Original Assignee: Paul J. Marinaccio, Rodney A. Knight
• Inventors: Knight, Rodney A., Marinaccio, Paul J.
• Primary Examiner(s): Jacobs, Lewis T.
• Application Number:
  US05/380,403
• Time in Patent Office: 629 Days
• Field of Search: 264/41,DIG.62 260/2.5N
• US Class Current: 264/41
• CPC Class Codes: B01D 2323/12 Specific ratios of components used
• CPC Class Codes: B01D 2325/02834 more than 0.1 and up to 1 µm
• CPC Class Codes: B01D 67/0009 by phase separation, sol-gel transition, evaporation or solvent quenching
• CPC Class Codes: B01D 67/0011 Casting solutions therefor
• CPC Class Codes: B01D 69/06 Flat membranes
• CPC Class Codes: B01D 71/56 Polyamides, e.g. polyester-amides
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: Y10S 264/62 Processes of molding porous films

Abstract

Microporous films are produced by a process of quenching a polymer solution cast in a quench bath containing a non-solvent system for the polymer to form micropores in the resulting polymer film.

Claims

1. A PROCESS FOR PREPARING A MICROPOROUS MEMBRANE WHICH COMPRISES PERPARING A DOPE SOLUTION OF A FILM-FORMING POLYMER IN A SOLVENT SYSTEM AND DIRECTLY CASTING SAID SOLUTION UNDER THE SURFACE OF A QUENCHING MEDIUM COMPRISING A NONSOLVENT SYSTEM FOR SAID POLYMER FOR A TIME SUFFICIENT TO FORM MICROPORES IN SAID FILM.

2. A process according to claim 1 wherein the film-forming polymer is a nylon.

3. A process according to claim 2 wherein the nylon is alcohol-soluble.

4. A process according to claim 2 wherein the solvent is formic acid.

5. A process according to claim 1 wherein the solvent system is a mixture of at least one solvent and one non-solvent for the polymer, the amount of non-solvent being insufficient to cause precipitation of the polymer.

6. A process according to claim 5 wherein the polymer is a nylon and the solvent system comprises formic acid and methanol.

7. A process according to claim 5 wherein the polymer is a nylon and the solvent system comprises formic acid, methyl formate and water.

8. A process according to claim 1 wherein the polymer is a nylon, and the solvent system comprises a mixture of formic acid and glycerol.

9. The process according to claim 5, wherein the quenching medium also comprises a solvent for said polymer, wherein the ratio of solvent to non-solvent is lower in the quenching medium than in the polymer solution.

10. A process according to claim 1, wherein the polymer is a nylon, and the quench bath non-solvent system is a mixture of methanol and water.

11. A process for preparing a microporous membrane comprising preparing a dope solution of a nylon polymer in a solvent system comprising a mixture of at least one solvent and one non-solvent for the polymer, the amount of non-solvent being insufficient to cause precipitation of the polymer, said solvent being formic acid and said non-solvent being selected from the group consisting of methanol, methyl formate/water, and glycerol, directly casting said solution under the surface of a quenching bath comprising a non-solvent system for said polymer for a time sufficient to form micropores in said film, said non-solvent system being a mixture of methanol and water.

12. The process of claim 11, wherein the mixture of methanol and water forming the non-solvent system ranges in proportion from 30/70 to 50/50.