CA1165678A

CA1165678A - Web supported membrane and process and apparatus therefor

Info

Publication number: CA1165678A
Application number: CA000418561A
Authority: CA
Inventors: Michael S. Withers
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1979-12-27
Filing date: 1982-12-23
Publication date: 1984-04-17

Abstract

TITLE
WEB-SUPPORTED MEMBRANE AND PROCESS
AND APPARATUS THEREFOR
ABSTRACT OF THE DISCLOSURE

A process and apparatus for continuously forming a reinforced membrane of fluorinated polymers containing sulfonyl and/or carboxyl groups in melt-fabricable form and, after hydrolysis, the corresponding membrane in ion exchange form. The membrane thus formed has exceptional uniformity, and this membrane so made, when used as the membrane which separates the compart-ments of a chloralkali cell, offers the advantages of low operating voltage, low power consumption and high current efficiency, and a long useful life without rupture.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for continuously forming a reinforced membrane comprising (1) continuously brining at least two films of melt-fabricable fluorinated polymer which contain side chains containing sulfonyl and/or carboxyl functional groups in melt-fabricable form and a web of reinforcing material into face-to-face contact such that proximate surfaces of two of said films contact opposite planar surfaces of said web, and moving the resulting combina-tion of said films and said web vertically, unsupported except at two opposite edges thereof, (2) removing air from between said films at the two opposite edge portions thereof, (3) applying heat to the two outermost opposite planar film surfaces, first in the center portions thereof and progressively moving toward and including the edge portions thereof, and (4) cooling the resulting reinforced membrane.

2. The process of Claim 1 wherein said reinforcing material is a fabric comprising strands of fluorinated polymer.

3. The process of Claim 2 wherein said heat is radiant heat.

4. The process of Claim 3 wherein said combination of films and web is moved vertically upward as heat is applied.

5. The process of Claim 1 wherein two films of substantially equal thickness are used.

6. The process of Claim 1 wherein two films of different thickness are used.

7. The process of Claim 1 wherein three films are used, the two films on one side of said reinforcing material having substantially the same total thickness as the one film on the other side of said reinforcing material.

8. The process of Claim 1 wherein three films are used, the two films on one side of said reinforcing material having a different total thickness than the one film on the other side of said reinforcing material.

9. The process of Claim 5 or Claim 6 wherein heat is applied equally to the two outermost opposite planar film surfaces.

10. The process of Claim 7 or Claim 8 wherein heat is applied equally to the two outermost opposite planar film surfaces.

11. The process of Claim 5 or Claim 6 wherein heat is applied unequally to the two outermost opposite planar film surfaces.

12. The process of Claim 7 or Claim 8 wherein heat is applied unequally to the two outermost opposite planar film surfaces.

13. Apparatus for making a reinforced membrane, comprising (1) a frame, and mounted on said frame, (2) means for guiding at least two continuous webs of film and a continuous web of reinforcing material into face-to-face contact such that proximate surfaces of two of said webs of film contact opposite sides of said web of reinforcing material, (3) two sets of flexible endless belts which cooperate to engage opposite sides of the resulting assembly of said webs at the edge portions thereof and to transport said assembly, each set consisting of two belts, one belt of each set having a series of perforations along its entire length, each set of belts extending beyond an edge of said assembly and guide means for said belts, (4) vacuum means including two vacuum mani-folds, one manifold adjacent each said perforated belt, for removing air from between said films of said assembly at the edge portions thereof through said perforations, (5) two banks of heaters, one bank adjacent each exposed film surface, each bank consisting of a plurality of heaters disposed for heating first the center portion of said assembly and then progressively toward and including the edges thereof as said assembly is transported therebetween, to fuse said assembly into a reinforced membrane, (6) means for guiding said assembly between said banks of heaters, (7) a wind-up for collecting said reinforced membrane, and (8) means for driving said wind-up.

14. The apparatus of Claim 13 wherein said heaters are radiant heaters.

15. The apparatus of Claim 14 wherein said heaters are arranged in a chevron-shaped array, disposed such that said assembly of webs is first heated in the center portion thereof.

16. The apparatus of Claim 15 wherein said guide means for said belts includes for each said belt one guide which is moveable toward and away from said belt for increasing or decreasing the tension on said belt.