US4098672A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Porous diaphragms
Assignee: Imperial Chemical Industries Ltd
•
Filing: 1976-02-12
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Granted: 1978-07-04
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Expires: 1996-02-12
Abstract
Abstract A process for the manufacture of a porous diaphragm of a synthetic material, especially polytetrafluoroethylene, which comprises forming a sheet of the synthetic material in admixture with a solid particulate additive (eg starch) to be removed therefrom, introducing said sheet into an electrolytic cell, filling the cell with the working electrolyte and removing the solid particulate in situ in the cell by electrolysing the said electrolyte. The porous diaphragms are especially suitable for use in diaphragm cells for the production of chlorine wherein the working electrolyte is sodium chloride brine.
Inventors
- 👤 David Stephen Riley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:45
CPC Classifications
C; C25; C25B; C25B13/00; C25B13/04; C25B13/08; H; H01; H01J; H01J31/00; H01J31/08; H01J31/26; H01J31/28; H01J31/34; H01J31/36
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
91 words
A process for the manufacture of a porous diaphragm of a synthetic material for use in an electrolytic cell which comprises forming a sheet of the synthetic organic polymeric material selected from the group consisting essentially of polytetrafluoroethylene and polyvinylidene fluoride in admixture with a solid particulate additive to be removed therefrom, assembling said sheet into an electrolytic cell, filling the cell with the working electrolyte and removing solid particulate additive from the sheet in situ in the cell by electrolysing the said electrolyte, said additive being insoluble in said electrolyte.
Claim 2
Dependent Claim
91 words
A process for the manufacture of a porous diaphragm of a synthetic material for use in an electrolytic cell which comprises forming a sheet of the synthetic organic polymeric material selected from the group consisting essentially of polytetrafluoroethylene and polyvinylidene fluoride in admixture with a solid particulate additive to be removed therefrom, assembling said sheet into an electrolytic cell, filling the cell with the working electrolyte and removing solid particulate additive from the sheet in situ in the cell by electrolysing the said electrolyte, said additive being insoluble in said electrolyte.
Claim 3
Dependent Claim
17 words
A process as claimed in claim 1 comprising electrolysing at the normal operating voltage of the cell.
Claim 4
Dependent Claim
17 words
A process as claimed in claim 1 comprising electrolysing at the normal current density of the cell.
Claim 5
Dependent Claim
41 words
A process as claimed in claim 1 comprising electrolysing at a reduced rate of feed of electrolyte as compared with the normal electrolyte flow in the cell whilst maintaining a constant head of liquor in the anolyte side of the cell.
Claim 6
Dependent Claim
20 words
A process as claimed in claim 4 wherein the electrolytic flow is 10% to 30% of the full design rate.
Claim 7
Dependent Claim
18 words
A process as claimed in claim 5 wherein the electrolyte flow is 20% of the full design rate.
Claim 8
Dependent Claim
21 words
A process as claimed in claim 1 wherein the electrolyte is preheated in the cell before applying current to the cell.
Claim 9
Dependent Claim
18 words
A process as claimed in claim 7 wherein the electrolyte is preheated to 50° C. to 60° C.
Claim 10
Dependent Claim
86 words
A process as claimed in claim 1 wherein the sheet of the synthetic material is formed in admixture with the solid particulate additive by preparing an aqueous slurry or dispersion comprising the synthetic material and the solid particulate additive, thickening said aqueous slurry or dispersion to effect agglomeration of the solid particles therein, forming from the thickened slurry or dispersion a dough-like material containing sufficient water to serve as lubricant in a subsequent sheet forming operation, and forming a sheet of desired thickness from said dough.
Claim 11
Dependent Claim
83 words
A process as claimed in claim 1 wherein the sheet of the synthetic material is formed in admixture with the solid particulate additive by preparing an aqueous slurry or dispersion comprising the synthetic material and the solid particulate additive, adding an organic coagulating agent to said dispersion, drying the coagulated dispersion, adding an organic lubricant to the dried coagulated material to serve as a lubricant in a subsequent sheet forming operation, and forming a sheet of the desired thickness from the coagulated material.
Claim 12
Dependent Claim
29 words
A process as claimed in claim 10 wherein the particle size of the polytetrafluoroethylene in the aqueous slurry or dispersion is in the range of 0.05 to 1 micron.
Claim 13
Dependent Claim
22 words
A process as claimed in claim 11 wherein the particle size of the polytetrafluoroethylene is in the range 0.1 to 0.2 micron.
Claim 14
Dependent Claim
24 words
A process as claimed in claim 10 wherein the solid particulate additive has a particle size substantially within the range 5 to 100 microns.
Claim 15
Dependent Claim
20 words
A process as claimed in claim 10 wherein the ratio of solid particulate additive to polytetrafluoroethylene is 10:1 to 1:10.
Claim 16
Dependent Claim
20 words
A process as claimed in claim 14 wherein the ratio of solid particulate additive to polytetrafluoroethylene is 5:1 to 1:1.
Claim 17
Dependent Claim
33 words
A process as claimed in claim 10 wherein the aqueous slurry or dispersion comprises other components which are not removed when the sheet is subjected to the treatment to remove the particulate additive.
Claim 18
Dependent Claim
15 words
A process as claimed in claim 16 wherein said other component is an inorganic filler.
Claim 19
Dependent Claim
20 words
A process as claimed in claim 17 wherein the inorganic filler is titanium dioxide, barium sulphate, asbestos, graphite or alumina.
Claim 20
Dependent Claim
19 words
A process as claimed in claim 16 wherein said other component has a particle size less than 10 microns.
Claim 21
Dependent Claim
19 words
A process as claimed in claim 19 wherein said other component has a particle size less than 1 micron.
Claim 22
Dependent Claim
21 words
A process as claimed in claim 16 wherein the weight ratio of said other component to polytetrafluoroethylene is 10:1 to 1:10.
Claim 23
Dependent Claim
15 words
A process as claimed in claim 21 wherein said weight ratio is 2:1 to 1:2.
Claim 24
Dependent Claim
16 words
A process as claimed in claim 10 wherein the diaphragm is provided with a strengthening support.
Claim 25
Dependent Claim
16 words
A process as claimed in claim 23 wherein the support is a sheet of polymer gauze.
Claim 26
Dependent Claim
14 words
A process as claimed in claim 24 wherein the support is a polypropylene gauze.
Claim 27
Dependent Claim
17 words
A process as claimed in claim 1 wherein the working electrolyte is an alkali metal chloride brine.
Claim 28
Dependent Claim
15 words
A process as claimed in claim 26 wherein the working electrolyte is sodium chloride brine.
Claim 29
Dependent Claim
20 words
The process of claim 1, wherein said additive has a particle size within the range between 5 to 100 microns.
Claim 30
Dependent Claim
20 words
A process as claimed in claim 1, wherein the solid particulate additive is starch, cellulose or cellulose or cellulose acetate.
Claim 31
Dependent Claim
19 words
A process as claimed in claim 1, wherein the solid particulate additive is a water-insoluble inorganic base or carbonate.
Claim 32
Dependent Claim
15 words
A process as claimed in claim 30, wherein the solid particulate additive is calcium carbonate.
References Cited (Backward Citations)
US2592686A
Cited
US508084A
Cited
US2293928A
Cited
US2542527A
Cited
US2967806A
Cited
US2860096A
Cited
DE1174973B
Cited
DE1144357B
Cited
US3556161A
Cited
GB1124362A
Cited
FR1491033A
Cited
US3718561A
Cited
DE2139646B2
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-07-03 | 1982-01-02 | 1982-07-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-07-03 | 1986-01-02 | 1986-07-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-07-03 | 1990-01-02 | 1990-07-04 | $7700.00 | Window Closed / Lapsed |