# US 4,399,183 A · Web-supported membrane

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- Number: US 4,399,183 A
- Document ID: US4399183A
- Status: Granted
- Kind: A
- Application number: 06/304,105
- Filed: 1981-09-21
- Granted: 1983-08-16
- Earliest claimed: 1979-12-27
- Assignees: E. I. Du Pont de Nemours and Company
- Inventors: Michael S. Withers
- Web page: https://patentgrep.com/patent/US4399183A

## CPC

- B32B 27/12: next to a fibrous or filamentary layer
- B01D 69/1071: {Woven, non-woven or net mesh}
- B01D 69/108: {Inorganic support material}
- B32B 37/04: characterised by the partial melting of at least one layer
- B32B 37/06: characterised by the heating method
- B32B 37/10: characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
- B32B 37/1018: {using only vacuum}
- B32B 37/1027: {Pressing using at least one press band}
- B32B 38/1858: {using vacuum}
- C08J 5/2206: {based on organic and/or inorganic macromolecular compounds}
- C08J 5/2237: {containing fluorine}
- C25B 13/00: Diaphragms; Spacing elements
- B29C 70/687: {the inserts being oriented, e.g. nets or meshes}
- B32B 2262/106: Carbon fibres, e.g. graphite fibres
- B32B 2315/085: Glass fiber cloth or fabric
- B32B 2323/04: Polyethylene
- B32B 2323/10: Polypropylene
- B32B 2327/18: PTFE, i.e. polytetrafluoroethylene
- C08J 2327/18: Homopolymers or copolymers of tetrafluoroethylene
- Y10T 428/30: Self-sustaining carbon mass or layer with impregnant or other layer
- Y10T 428/3154: Of fluorinated addition polymer from unsaturated monomers
- Y10T 428/31544: Addition polymer is perhalogenated
- Y10T 442/167: Fluorinated polyolefin film or sheet
- Y10T 442/176: Three or more layers
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B)
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

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 compartments 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

### Claim 1

A reinforced membrane which consists essentially of at least two layers of melt fabricable fluorinated polymer which contains side chains containing sulfonyl and/or carboxyl groups in melt fabricable form, and a woven reinforcing fabric comprising warp and fill strands, there being at least one layer of a said fluorinated polymer on each side of said reinforcing fabric, the warp and fill strands of said reinforcing fabric defining windows between said strands, each layer of fluorinated polymer in at least 70% of the area in each of at least 90% of said windows being of uniform thickness within plus or minus 10%.

### Claim 2 (depends on 1)

The membrane of claim 1 wherein the average total thickness of said fluorinated polymer which covers both sides of said strands is at least 80% of the average total thickness of said polymer in that portion of said windows which is uniform within plus or minus 10%.

### Claim 3 (depends on 2)

The membrane of claim 2 wherein said reinforcing fabric comprises strands of fluorinated polymer.

### Claim 4 (depends on 3)

The membrane of claim 3 wherein each said strand of said fabric is a monofilament.

### Claim 5 (depends on 3)

The membrane of claim 3 wherein each said strand of said fabric consists of a plurality of filaments.

### Claim 6 (depends on 1)

The membrane of claim 1 wherein there are two layers of melt fabricable fluorinated polymer which contains side chains containing sulfonyl groups in melt fabricable form.

### Claim 7 (depends on 1)

The membrane of claim 1 wherein there are two layers of melt fabricable fluorinated polymer which contains side chains containing carboxyl groups in melt fabricable form.

### Claim 8 (depends on 1)

The membrane of claim 1 wherein there is a layer of melt fabricable fluorinated polymer which contains side chains containing sulfonyl groups in melt fabricable form on a first side of said reinforcing fabric, and a layer of melt fabricable fluorinated polymer which contains side chains containing carboxyl groups in melt fabricable form on a second side of said reinforcing fabric.

### Claim 9 (depends on 1)

The membrane of claim 1 wherein there is a layer of melt fabricable fluorinated polymer which contains side chains containing sulfonyl groups in melt fabricable form on each side of and in contact with said reinforcing fabric, and a layer of melt fabricable fluorinated polymer which contains side chains. containing carboxyl groups in melt fabricable form in contact with one of said layers of fluorinated polymer having sulfonyl groups at its side facing away from said reinforcing fabric.

### Claim 10 (depends on 8, 9)

The membrane of claim 8 or 9 wherein a first exposed surface of the membrane is smoother than a second exposed surface of the membrane.

### Claim 11 (depends on 10)

The membrane of claim 10 wherein the exposed surface of the membrane which is the fluorinated polymer having carboxyl groups is smoother than the exposed surface of the membrane which is the polymer having sulfonyl groups.

### Claim 12 (depends on 1)

The membrane of claim 1 wherein the total thickness of said layers of melt fabricable fluorinated polymer is in the range of 0.025 to 0.25 mm.

### Claim 13 (depends on 6, 7, 8, 9)

The membrane of claim 6, 7, 8, 9, or 12 wherein each layer of fluorinated polymer in at least 70% of the area in each of at least 95% of said windows is of uniform thickness within plus or minus 10%.

### Claim 14

A reinforced ion exchange membrane which consists essentially of at least two layers of fluorinated polymer which contains side chains containing sulfonyl groups in ion exchange form and/or carboxylic acid groups in ion exchange form and a woven reinforcing fabric comprising warp and fill strands, there being at least one layer of a said fluorinated polymer on each side of said reinforcing fabric, the warp and fill strands of said fabric defining windows between said strands, each layer of fluorinated polymer in at least 70% of the area in each of at least 90% of said windows being of uniform thickness within plus or minus 10%.

### Claim 15 (depends on 14)

The membrane of claim 14 wherein the total thickness of said fluorinated polymer which covers both sides of said strands is at least 80% of the average total thickness of said polymer in that portion of said windows which is uniform within plus or minus 10%.

### Claim 16 (depends on 15)

The membrane of claim 15 wherein said reinforcing fabric comprises stands of fluorinated polymer.

### Claim 17 (depends on 16)

The membrane of claim 16 wherein each said strand of said fabric is a monofilament.

### Claim 18 (depends on 16)

The membrane of claim 16 wherein each said strand of said fabric consists of a plurality of filaments.

### Claim 19 (depends on 14)

The membrane of claim 14 wherein there are two layers of fluorinated polymer which contains side chains containing sulfonyl groups in ion exchange form.

### Claim 20 (depends on 14)

The membrane of claim 14 wherein there are two layers of fluorinated polymer which contains side chains containing carboxylic acid groups in ion exchange form.

### Claim 21 (depends on 14)

The membrane of claim 14 wherein there is a layer of fluorinated polymer which contains side chains containing sulfonyl groups in ion exchange form on a first side of said reinforcing fabric, and a layer of fluorinated polymer which contains side chains containing carboxylic acid groups in ion exchange form on a second side of said reinforcing fabric.

### Claim 22 (depends on 14)

The membrane of claim 14 wherein there is a layer of fluorinated polymer which contains side chains containing sulfonyl groups in ion exchange form on each side of and in contact with said reinforcing fabric, and a layer of melt fabricable fluorinated polymer which contains side chains containing carboxylic acid groups in ion exchange form in contact with one of said layers of fluorinated polymer having sulfonyl groups at its side facing away from said reinforcing fabric.

### Claim 23 (depends on 21, 22)

The membrane of claim 21 or 22 wherein a first exposed surface of the membrane is smoother than a second exposed surface of the membrane.

### Claim 24 (depends on 23)

The membrane of claim 23 wherein the exposed surface of the membrane which is the fluorinated polymer having carboxylic acid groups is smoother than the exposed surface of the membrane which is the polymer having sulfonyl groups.

### Claim 25 (depends on 14)

The membrane of claim 14 wherein the total thickness of said layers of fluorinated polymer is in the range of 0.025 to 0.25 mm.

### Claim 26 (depends on 19, 20, 21, 22, 25)

The membrane of claim 19, 20, 21, 22 or 25 wherein each layer of fluorinated polymer in at least 70% of the area in each of at least 95% of said windows is of uniform thickness within plus or minus 10%.