CA1287599C - Membrane unit for electrolytic cell - Google Patents
Membrane unit for electrolytic cellInfo
- Publication number
- CA1287599C CA1287599C CA000494496A CA494496A CA1287599C CA 1287599 C CA1287599 C CA 1287599C CA 000494496 A CA000494496 A CA 000494496A CA 494496 A CA494496 A CA 494496A CA 1287599 C CA1287599 C CA 1287599C
- Authority
- CA
- Canada
- Prior art keywords
- membrane
- gasket
- reinforcing material
- unit
- cell
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/70—Assemblies comprising two or more cells
- C25B9/73—Assemblies comprising two or more cells of the filter-press type
- C25B9/75—Assemblies comprising two or more cells of the filter-press type having bipolar electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
- C25B13/04—Diaphragms; Spacing elements characterised by the material
- C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/70—Assemblies comprising two or more cells
- C25B9/73—Assemblies comprising two or more cells of the filter-press type
- C25B9/77—Assemblies comprising two or more cells of the filter-press type having diaphragms
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
ABSTRACT
A membrane unit for use in an electrolytic cell comprising a combination of a membrane material and a reinforcing material around only the gasket--bearing surface of the membrane material. Damage to the gasket bearing surface of the membrane structure is minimized when the membrane unit is employed in, for example, electrolytic cells of the filter press-type.
A membrane unit for use in an electrolytic cell comprising a combination of a membrane material and a reinforcing material around only the gasket--bearing surface of the membrane material. Damage to the gasket bearing surface of the membrane structure is minimized when the membrane unit is employed in, for example, electrolytic cells of the filter press-type.
Description
7~9 MEMBRANE UNIT FOR ELECTROLYTIC CELL
This invention relates to membranes for use in electrolytic cells and, more particularly, to a membrane unit which will resist tearing upon appli-cation of a compressive force to a gasket bearing surface of the membrane.
There are many well-known membranes for use in electrolytic cells. For example, typical membranes include the perfluorinated carboxylic or sulfonic cation exchange membranes such as the Nafion~ membranes manufactured by E. I. duPont de Nemours and Company or the Flemion~ membranes manu~actured by Asahi Glass Company, Ltd. These membranes are typically available in sheet form and employed in filter press-type or flat plate-type electrolytic cells having monopolar or bipolar electrodes. Examples of bipolar, filter press-type cells are described in U.S. Patent Nos.
4,111,779 and 4,103,742. These cells are used, for example, to carry out electrolysis of an a~ueous alkali metal halide to produce a halogen, for example chlorine, and an alkali me-tal hydroxide such as sodium hydroxide.
Generally, the bipolar, filter press-type electrolytic cell is composed of several bipolar unit cells aFranged ..
~, 31,365-F
ô'S~39 in series. One bipolar unit cell has an anode and cathode compartment separated by a partition wall.
Typically, the anode and cathode are attached to opposite sides of the parti-tion wall. The membrane is usually interposed between two adjacent unit cells to separate the anode compartment from the cathode com-~ partment. A~plurality of anode and cathode frames areinstalled in a parallel fashion and a longitudinal compressive clamping means is applied to the anode and cathole frames with the membrane interposed between the frames to form-the electrolytic cell in toto.
It is common practice to interpose a gasket between the membrane and the anode or cathode frame to provide the electrolytic cell with fluid-tight, i.e., a liquid- and gas-tight seal to prevent leakage o~ elec-trolyte between anode and cathode compartments or to the atmosphere. It is important to have a complete liguid- and gas-tight seal in electrolytic cells because these cells typically operate under corrosive environments. Generally, one side of the gasket is in contact with the lateral face of an electrode frame and the other side of the gasket is in contact with one side of the membrane's peripheral surface.
Typical gasket materials include resilient material such as rubber or an elastomer. Commercial bipolar membrane electrolyzers generally use ethylene-propylene (EPM) or ethylene-propylene-diene (EPDM) as gasket material between the membrane and electrode frames. These materials tend to deform and expand outwardly as pressure is applied to the frames via the frame members. As the gaskets deform outwardly, cer-tain membranes which are in contact with the gaskets 31,365-F -2-.
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~8~5~9 tend to stretch when they are pulled under the pressure of the outwardly deforming gaskets. This stretching of the membrane beneath the gaskets employed on adjacent electrode frames can cause the membranes to break or tear when attempting to compress the frames into a fluid-tight cell. In addition, resilient yaskets require a high compressive force to effect a seal which increases the risk of breaking or tearing the membrane.
Any tears or breaks in the membranes may reduce current efficiency during operation~ yreatly increasing electrical current usage while reducing the electro-lytic operating efficiency and/or electrolytic operating efficiency can require costly shutdown of the entire cell while the damaged membrane or membranes are replaced.
The invention resides in an ion exchange membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening.
The invention also resides in an electrolytic cell comprising an ion exchange membrane unit separating - 30 at least two electrode compartments, said membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket-bearing peripheral surface of the membrane, wherein said membrane has at least one ope~ing 31,365-F -3-,, , ::, . .
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and the reinEorcing material is heat sealed to the membrane through the opening.
The invention further resides in a method of sealing an electrolytic cell comprising the steps of (a) interposing at least one gasket between at least one electrode frame and an ion exchange membrane in an electrolytic cell, securing at least one layer of a reinforcing material to at least one side of the membrane around a gasket bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening, and (b) applying a compressive force to the cell.
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Although alternative embodiments of the present invention are shown in the following Figures, the same reference numbers are used in the drawings to describe identical elements.
Figure 1 is a perspective view of the membrane unit of the present invention showing a membrane sheet haviny a reinforcement material along the periphery of the sheet.
Figure 2 is a perspective view of another embodiment of the present invention showing a membrane having a plurality of openings and a reinforcing material along the periphery of the sheet.
Figure 3 is a cross-sectional view taken along line 3-3 of Figure 1.
Figure 4 is a cross-sectional view of an alternate embodiment of the present invention showing a membrane having a reinforcement material on one planar peripheral surface of the membrane sheet.
Figure 5 is a cross-sectional view taken along line 5-5 of Figure 2.
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75~9 Figure 6 is a sectional view showing a por tion of an electrolytic cell series assembly including the membrane unit of Figure 1.
With reference to Figure 1, a rectangular sheet ll made of a membrane material is shown with a layer of a reinf-orcing material 12 attached, bonded or otherwise adhered to a peripheral portion of the mem-` brane on opposite planar surfac`es thereof.~ Figure 3 more clearly illustrates the reinforcing material 12 as a strip secured to both sides of the membrane 11 andonly along a gasket-bearing surface of the membrane.
Figure 4 shows the reinforcing material 12 applied to only one planar sur~ace of the membrane and only along the peripheral, gasket-bearing surface of the membrane.
"Gasket-bearing surface" is defined as that portion of the periphery of the membrane sheet which is subject to compression forces in order to effect a seal at the periphery of an electrode frame of an electrolyzer. In Figure 1, the reinforcing material 12 has a picture-frame shape. It is to be understood, however, that the membrane unit or structure of this invention is not limited to a rectangular sheet but can be circular or of some other desired shape.
The membrane 11 is made of a material having ion exchange properties. Such membrane is substantially impervious to the hydrodynamic flow of the electrolyte and the passage of gas products produced during el~c-trolysis. Suitable are cation exchange membranes such as those composed of fluorocarbon polymers having a plurality of pendant sulfonic acid groups or carboxylic acid groups or mixtures of sulfonic and carboxylic-acid gr~ups. The terms "sulfonic acid groups" and "car-boxylic acld groups" are meant to include salts of 31,365-F -5-..
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. . . .
.
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sulfonic acid or salts of carboxylic acid which are suitably converted to or from the acid group by pro-cesses such as hydrolysis. An example of a carboxylic acid type cation exchange membrane is commercially available from Asahi Glass Company under the trademark Flemion~. Another example of a suitable membrane having cation exchange properties is a perfluoro-sulfonic acid membrane sold commercially by E. I.
duPont de Nemours and Company under the trademark Nafion~.
The reinforcing material 12 can be made of any material suitable for strengthening the gasket bearing surface area of the membrane 11. The rein-forcing material 12 can be of the same or different material as the membrane. Preferably the reinforcing material 12 should have a heavier scrim than that of the membrane material. Both the membrane and the reinforcing material should be made of a corrosion-resistant, non-contaminating material which is stable upon contact with electrolyte media present in an electrolytic cell. Suitable ma~erials which can be employed in accordance with this in~ention include, but are not limited ~o, the following: fluorine~containing polymers such as polytetrafluoroethylene (PTFE), fluo-rinated ethylene propylene copolymer (FEP) and per-fluoroalkoxy resin (PFA); polysulfide polymers, poly-vinyl chloride, fluoroelastomers such as Viton~, a trademark of E. I. duPont de Nemours and Company, and chlorosulfonated polyethylenes such as Hypalon~, a trademark of E. I. duPont de Nemours and Company.
The reinforcing material 12 can be attached or otherwise secured to the membrane 11 by any well known method in the art, for example, bonding with an 31,365-F -6~
~:
.
.
~Z~3'75j9~1 adhesive, heat sealing, or ultrasonic sealing. It is preferred to heat seal the reinforcing material to the membrane.
In Figures 2 and 5, the membrane 11 contains perforations or openings 13 along its periphery or gasket-bearing surface. The reinforcing material 1~ is secured to the gasket bearing surface and covers the openings 13 on both sides o~ the membrane 11. The membrane having such openings 13 allows the reinforcing ma~erial 12 on one side of the membrane to form a bond through the membrane to the reinforcing material 12 on the opposite side through the openings 13. This is particularly useful when bonding a reinforcing material which is di~ficult to attach to the membrane material.
Generally, when the reinforcing material and the mem-brane material are made of dissimilar materials, open-ing~13 should be provided in the peripheral surface of the membrane to provide additional securement of the reinforcing material to the membrane.
Referring to Figure 6, an electrolysis cell assembly is shown wherein a membrane unit generally designated by reference number lO, comprising a mem-brane 11 and a reinforcing material 12 attached to both sides of the membrane 11, is interposed between two electrode frame units 14. A gasket 18 may be inter-posed between the membrane unit lO and an electrode frame 14. It- is also within the scope of the invention to interpose a gasket 18 on both sides of the membrane unit 10 and two adjacent electrode frames 14. Any gasket used in an electrolytic cell of the filter press type may be used. The gasket should be made of a corrosion resistant material, shduld have a high volume .
31,365-F -7-. .
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resistivity and ~ood sealability after it has been compressed. Suitable materials for the gasket 14 may be, for example, EPDM, a chlorinated polyethylene (CPE), a polytetrafluoroethylene such as Teflon~, manufactured by E. I. duPont de Nemours and Company, and reinforced asbestos. An anode 15 and a cathode 16 are electrically connected with connectors 17 through the electrode frame 14. The electrolysis assembly abovè is typical of bipolar electrolytic cells of the - ~ -filter press type such as described in U.S. Patent Nos.
4,111,779 and 4,108,742. Any cell of the filter pr~ss type may be used in the present invention.
In order to effect sealing of the periphery of the electrode frame 14, the membrane unit 10 and a gasket 18 are interposed between two adjacent electrode frames 14 and a compressive force is app~ied to the cell assembly. The compressive force may be applied by any means known to those skilled in the art, for example, by clamping the frames together or by using a hydraulic ram. Preferably a hydraulic ram is used to squeeze the electrode frames, gaskets and membranes together. The actual compressive force applied will be dictated by the type of material used for the gasket.
The invention will be illustrated further in ~5 the examples which follow.
Example 1 A 10 cm by 10 cm test sample o Nafion~ 901 membrane, obtained from the duPont Company of Wilmington, Delaware, was reinforced by heat sealing strips of PFA
fluoroplastic film around the edges on both sides of the - membrane. Any heat-sealing technique known in the art .
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may be used. In this instance, the heat sealing was performed by the EGC Corporation of Houston, Texas, under contract to The Dow Chemical Company. The film thickness used on the ca-thode side of the mer~rane was 15 mils thick while the film -thickness used on the anode side of the membrane was 5 mils thick. The actual design used is the design shown in Figures l and 3.
A laboratory electrolytic cell was used for testing the test samples. The cell consisted of an anode compartment frame and a cathode compartment frame. The anode compartment frame was made of titanium having the titanium surfac~e located under the gasket area coated with a ruthenium dioxide coating to avoid possible crevice corrosion problems.
The cathode compartment frame of the cell was made of an acrylic polymer. The anode of the cell was made of titanium with a ruthenium dioxide coating and -the cathode was a nickel cathode.
The gasket usedj was a 6.35 mm thick gasket made of EPDM rubber purchased from the Prince Rubber &
Plastics Co., Inc. of Buffalo, New York. The gaskets were cut from single EPDM rubber sheets to form a picture-frame shape with dimensions of 9.5 cm outside--to-outside and 7.62 cm inside-to-inside. Thus, the width of the gasket surface was 9.5 mm. The total gasket area was 32.65 cm2. The gasket was used on both ~ -sides of the membrane and contact loading was distri-buted over the reinforced surface.
Ten 9.5 mm diameter bolts were torqued to 12 ft-lbs (16.3 Joules) force to press together the anode 31,365-F -9-:'. , ,. ,, ' .' : ' , , ~
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and cathode compartments, the mernbrane and gaskPts resulting in a total force of 8,626 kg from the bolt loading. The force exerted on the membrane under the gaskets was equivalent to 25,856 kPa. The force used on this test sample was ten times greater than the force used on the test sample described in the Comparative Example A, below.
~ The cell of this e~ample was operated to produce 32 weight percent caustic while contro'ling the anolyte salt at 200 grams per liter sodium chloride concentration. The cell temperature was maintained at 90C with ampere loading controlled at 0.31 amp/cm2 of projected anode area current density. The test was conducted for 210 days and during this period the caustic current efficiency averaged 95 percent with an average cell voltage of 3.5. The cell operated without leaks and performed without complications.
Visual inspection of the membrane after dismantling the cell showed the membrane to be in excellent condition with no tears or breaks in the gasket contact and loading area. Thus, the reinforcing concept of the invention protected the membrane from damage and showed a successful improvement over the membrane used in the Comparative E~ample A, below.
Comparative Example A
A 249 cm by 127 cm test sample of Nafion~ 324 membrane, obtained from the duPont Company of Wilmington, Delaware was used in this test. The gaskek surfaces of the membrane were not reinforced.
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~ 64693-3700 The electrolytic cell used in this test is of a type well known in the industry as a bipolar flat plate-type cell having a nominal size of 1.22 met. by 3.05 met. The cell contained an anode of titanium with a ruthenium oxide coating and a cathode of steel.
The gasket used was a 4.76 mm thick gasket made of EPDM rubber purchased from the Prince Rubber and Plastics Co., Inc., of Bu~falo, New York.
Speci~ications for the EPDM include "EPDM ~or Chlor-Alkali Service, Prince #6962." The gaskets were cut from single EPDM rubber sheets to form a picture-frame shape with dimensions of 2.47 meter outside-to-outside and 2.37 meter inside-to-inside in the long direction and 1.25 meter outside-to-outside and 1.15 meter inside-to-inside in the short direction. Thus, the width of the gasket surface was 5.1 cm. The total gasket area was 3,676 cm2. The gasket was used on both sides of the membrane and contact loading was distributed over the reinforoed surface.
A hydraulic cylinder in a filter press arrangement was used to press together the cell units.
The total force resulting from the action o~ the hydraulic press was 78,152 kg. The force exerted on the membrane was equivalent to 2,080 kPa.
The cells were operated to produce from 12 to 16 weight percent caustic while controlling the anolyte salt at 200 gram~ per liter sodium chloride concentration. The cell temperature was maintained at 90-C with D~C. current controlled at 10.0 kiloamperes.
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Thus, the ampere loading was 0.31 amperes per square cm of projected anode area current density. The test was conducted for 199 days and during this period, the caustic current efficiency averaged 82-84 percent which was 4 percent below the expected caus-tic current efficiency for Nafion~ 324.
Visual inspection of the membrane after dis-~ mantling the cell showed the me~brane to have severe damage in the areas beneath the gaskets and in the area next to the gaskets. The gasket loading forces had stretched and cracked the membrane so severely to render the overall cell performance unsatisfactory.
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This invention relates to membranes for use in electrolytic cells and, more particularly, to a membrane unit which will resist tearing upon appli-cation of a compressive force to a gasket bearing surface of the membrane.
There are many well-known membranes for use in electrolytic cells. For example, typical membranes include the perfluorinated carboxylic or sulfonic cation exchange membranes such as the Nafion~ membranes manufactured by E. I. duPont de Nemours and Company or the Flemion~ membranes manu~actured by Asahi Glass Company, Ltd. These membranes are typically available in sheet form and employed in filter press-type or flat plate-type electrolytic cells having monopolar or bipolar electrodes. Examples of bipolar, filter press-type cells are described in U.S. Patent Nos.
4,111,779 and 4,103,742. These cells are used, for example, to carry out electrolysis of an a~ueous alkali metal halide to produce a halogen, for example chlorine, and an alkali me-tal hydroxide such as sodium hydroxide.
Generally, the bipolar, filter press-type electrolytic cell is composed of several bipolar unit cells aFranged ..
~, 31,365-F
ô'S~39 in series. One bipolar unit cell has an anode and cathode compartment separated by a partition wall.
Typically, the anode and cathode are attached to opposite sides of the parti-tion wall. The membrane is usually interposed between two adjacent unit cells to separate the anode compartment from the cathode com-~ partment. A~plurality of anode and cathode frames areinstalled in a parallel fashion and a longitudinal compressive clamping means is applied to the anode and cathole frames with the membrane interposed between the frames to form-the electrolytic cell in toto.
It is common practice to interpose a gasket between the membrane and the anode or cathode frame to provide the electrolytic cell with fluid-tight, i.e., a liquid- and gas-tight seal to prevent leakage o~ elec-trolyte between anode and cathode compartments or to the atmosphere. It is important to have a complete liguid- and gas-tight seal in electrolytic cells because these cells typically operate under corrosive environments. Generally, one side of the gasket is in contact with the lateral face of an electrode frame and the other side of the gasket is in contact with one side of the membrane's peripheral surface.
Typical gasket materials include resilient material such as rubber or an elastomer. Commercial bipolar membrane electrolyzers generally use ethylene-propylene (EPM) or ethylene-propylene-diene (EPDM) as gasket material between the membrane and electrode frames. These materials tend to deform and expand outwardly as pressure is applied to the frames via the frame members. As the gaskets deform outwardly, cer-tain membranes which are in contact with the gaskets 31,365-F -2-.
- . ~
:
' ' ' .
.
~8~5~9 tend to stretch when they are pulled under the pressure of the outwardly deforming gaskets. This stretching of the membrane beneath the gaskets employed on adjacent electrode frames can cause the membranes to break or tear when attempting to compress the frames into a fluid-tight cell. In addition, resilient yaskets require a high compressive force to effect a seal which increases the risk of breaking or tearing the membrane.
Any tears or breaks in the membranes may reduce current efficiency during operation~ yreatly increasing electrical current usage while reducing the electro-lytic operating efficiency and/or electrolytic operating efficiency can require costly shutdown of the entire cell while the damaged membrane or membranes are replaced.
The invention resides in an ion exchange membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening.
The invention also resides in an electrolytic cell comprising an ion exchange membrane unit separating - 30 at least two electrode compartments, said membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket-bearing peripheral surface of the membrane, wherein said membrane has at least one ope~ing 31,365-F -3-,, , ::, . .
, 59~
and the reinEorcing material is heat sealed to the membrane through the opening.
The invention further resides in a method of sealing an electrolytic cell comprising the steps of (a) interposing at least one gasket between at least one electrode frame and an ion exchange membrane in an electrolytic cell, securing at least one layer of a reinforcing material to at least one side of the membrane around a gasket bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening, and (b) applying a compressive force to the cell.
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31,365-F -4-', . . .
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Although alternative embodiments of the present invention are shown in the following Figures, the same reference numbers are used in the drawings to describe identical elements.
Figure 1 is a perspective view of the membrane unit of the present invention showing a membrane sheet haviny a reinforcement material along the periphery of the sheet.
Figure 2 is a perspective view of another embodiment of the present invention showing a membrane having a plurality of openings and a reinforcing material along the periphery of the sheet.
Figure 3 is a cross-sectional view taken along line 3-3 of Figure 1.
Figure 4 is a cross-sectional view of an alternate embodiment of the present invention showing a membrane having a reinforcement material on one planar peripheral surface of the membrane sheet.
Figure 5 is a cross-sectional view taken along line 5-5 of Figure 2.
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75~9 Figure 6 is a sectional view showing a por tion of an electrolytic cell series assembly including the membrane unit of Figure 1.
With reference to Figure 1, a rectangular sheet ll made of a membrane material is shown with a layer of a reinf-orcing material 12 attached, bonded or otherwise adhered to a peripheral portion of the mem-` brane on opposite planar surfac`es thereof.~ Figure 3 more clearly illustrates the reinforcing material 12 as a strip secured to both sides of the membrane 11 andonly along a gasket-bearing surface of the membrane.
Figure 4 shows the reinforcing material 12 applied to only one planar sur~ace of the membrane and only along the peripheral, gasket-bearing surface of the membrane.
"Gasket-bearing surface" is defined as that portion of the periphery of the membrane sheet which is subject to compression forces in order to effect a seal at the periphery of an electrode frame of an electrolyzer. In Figure 1, the reinforcing material 12 has a picture-frame shape. It is to be understood, however, that the membrane unit or structure of this invention is not limited to a rectangular sheet but can be circular or of some other desired shape.
The membrane 11 is made of a material having ion exchange properties. Such membrane is substantially impervious to the hydrodynamic flow of the electrolyte and the passage of gas products produced during el~c-trolysis. Suitable are cation exchange membranes such as those composed of fluorocarbon polymers having a plurality of pendant sulfonic acid groups or carboxylic acid groups or mixtures of sulfonic and carboxylic-acid gr~ups. The terms "sulfonic acid groups" and "car-boxylic acld groups" are meant to include salts of 31,365-F -5-..
. .
. . . .
.
.~2~
sulfonic acid or salts of carboxylic acid which are suitably converted to or from the acid group by pro-cesses such as hydrolysis. An example of a carboxylic acid type cation exchange membrane is commercially available from Asahi Glass Company under the trademark Flemion~. Another example of a suitable membrane having cation exchange properties is a perfluoro-sulfonic acid membrane sold commercially by E. I.
duPont de Nemours and Company under the trademark Nafion~.
The reinforcing material 12 can be made of any material suitable for strengthening the gasket bearing surface area of the membrane 11. The rein-forcing material 12 can be of the same or different material as the membrane. Preferably the reinforcing material 12 should have a heavier scrim than that of the membrane material. Both the membrane and the reinforcing material should be made of a corrosion-resistant, non-contaminating material which is stable upon contact with electrolyte media present in an electrolytic cell. Suitable ma~erials which can be employed in accordance with this in~ention include, but are not limited ~o, the following: fluorine~containing polymers such as polytetrafluoroethylene (PTFE), fluo-rinated ethylene propylene copolymer (FEP) and per-fluoroalkoxy resin (PFA); polysulfide polymers, poly-vinyl chloride, fluoroelastomers such as Viton~, a trademark of E. I. duPont de Nemours and Company, and chlorosulfonated polyethylenes such as Hypalon~, a trademark of E. I. duPont de Nemours and Company.
The reinforcing material 12 can be attached or otherwise secured to the membrane 11 by any well known method in the art, for example, bonding with an 31,365-F -6~
~:
.
.
~Z~3'75j9~1 adhesive, heat sealing, or ultrasonic sealing. It is preferred to heat seal the reinforcing material to the membrane.
In Figures 2 and 5, the membrane 11 contains perforations or openings 13 along its periphery or gasket-bearing surface. The reinforcing material 1~ is secured to the gasket bearing surface and covers the openings 13 on both sides o~ the membrane 11. The membrane having such openings 13 allows the reinforcing ma~erial 12 on one side of the membrane to form a bond through the membrane to the reinforcing material 12 on the opposite side through the openings 13. This is particularly useful when bonding a reinforcing material which is di~ficult to attach to the membrane material.
Generally, when the reinforcing material and the mem-brane material are made of dissimilar materials, open-ing~13 should be provided in the peripheral surface of the membrane to provide additional securement of the reinforcing material to the membrane.
Referring to Figure 6, an electrolysis cell assembly is shown wherein a membrane unit generally designated by reference number lO, comprising a mem-brane 11 and a reinforcing material 12 attached to both sides of the membrane 11, is interposed between two electrode frame units 14. A gasket 18 may be inter-posed between the membrane unit lO and an electrode frame 14. It- is also within the scope of the invention to interpose a gasket 18 on both sides of the membrane unit 10 and two adjacent electrode frames 14. Any gasket used in an electrolytic cell of the filter press type may be used. The gasket should be made of a corrosion resistant material, shduld have a high volume .
31,365-F -7-. .
~2~
resistivity and ~ood sealability after it has been compressed. Suitable materials for the gasket 14 may be, for example, EPDM, a chlorinated polyethylene (CPE), a polytetrafluoroethylene such as Teflon~, manufactured by E. I. duPont de Nemours and Company, and reinforced asbestos. An anode 15 and a cathode 16 are electrically connected with connectors 17 through the electrode frame 14. The electrolysis assembly abovè is typical of bipolar electrolytic cells of the - ~ -filter press type such as described in U.S. Patent Nos.
4,111,779 and 4,108,742. Any cell of the filter pr~ss type may be used in the present invention.
In order to effect sealing of the periphery of the electrode frame 14, the membrane unit 10 and a gasket 18 are interposed between two adjacent electrode frames 14 and a compressive force is app~ied to the cell assembly. The compressive force may be applied by any means known to those skilled in the art, for example, by clamping the frames together or by using a hydraulic ram. Preferably a hydraulic ram is used to squeeze the electrode frames, gaskets and membranes together. The actual compressive force applied will be dictated by the type of material used for the gasket.
The invention will be illustrated further in ~5 the examples which follow.
Example 1 A 10 cm by 10 cm test sample o Nafion~ 901 membrane, obtained from the duPont Company of Wilmington, Delaware, was reinforced by heat sealing strips of PFA
fluoroplastic film around the edges on both sides of the - membrane. Any heat-sealing technique known in the art .
31,365-F -8-, . .
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.
. - . : : .
- . '.: : ~ ' .
may be used. In this instance, the heat sealing was performed by the EGC Corporation of Houston, Texas, under contract to The Dow Chemical Company. The film thickness used on the ca-thode side of the mer~rane was 15 mils thick while the film -thickness used on the anode side of the membrane was 5 mils thick. The actual design used is the design shown in Figures l and 3.
A laboratory electrolytic cell was used for testing the test samples. The cell consisted of an anode compartment frame and a cathode compartment frame. The anode compartment frame was made of titanium having the titanium surfac~e located under the gasket area coated with a ruthenium dioxide coating to avoid possible crevice corrosion problems.
The cathode compartment frame of the cell was made of an acrylic polymer. The anode of the cell was made of titanium with a ruthenium dioxide coating and -the cathode was a nickel cathode.
The gasket usedj was a 6.35 mm thick gasket made of EPDM rubber purchased from the Prince Rubber &
Plastics Co., Inc. of Buffalo, New York. The gaskets were cut from single EPDM rubber sheets to form a picture-frame shape with dimensions of 9.5 cm outside--to-outside and 7.62 cm inside-to-inside. Thus, the width of the gasket surface was 9.5 mm. The total gasket area was 32.65 cm2. The gasket was used on both ~ -sides of the membrane and contact loading was distri-buted over the reinforced surface.
Ten 9.5 mm diameter bolts were torqued to 12 ft-lbs (16.3 Joules) force to press together the anode 31,365-F -9-:'. , ,. ,, ' .' : ' , , ~
.- " :: , :. , ' . . .
- : :
and cathode compartments, the mernbrane and gaskPts resulting in a total force of 8,626 kg from the bolt loading. The force exerted on the membrane under the gaskets was equivalent to 25,856 kPa. The force used on this test sample was ten times greater than the force used on the test sample described in the Comparative Example A, below.
~ The cell of this e~ample was operated to produce 32 weight percent caustic while contro'ling the anolyte salt at 200 grams per liter sodium chloride concentration. The cell temperature was maintained at 90C with ampere loading controlled at 0.31 amp/cm2 of projected anode area current density. The test was conducted for 210 days and during this period the caustic current efficiency averaged 95 percent with an average cell voltage of 3.5. The cell operated without leaks and performed without complications.
Visual inspection of the membrane after dismantling the cell showed the membrane to be in excellent condition with no tears or breaks in the gasket contact and loading area. Thus, the reinforcing concept of the invention protected the membrane from damage and showed a successful improvement over the membrane used in the Comparative E~ample A, below.
Comparative Example A
A 249 cm by 127 cm test sample of Nafion~ 324 membrane, obtained from the duPont Company of Wilmington, Delaware was used in this test. The gaskek surfaces of the membrane were not reinforced.
31,365 F -10-.
`.`'"' ' ` '' ... ~. ". `' ;,`'.`- ' :
-, ' ~ .' ~ . .
~z~
~ 64693-3700 The electrolytic cell used in this test is of a type well known in the industry as a bipolar flat plate-type cell having a nominal size of 1.22 met. by 3.05 met. The cell contained an anode of titanium with a ruthenium oxide coating and a cathode of steel.
The gasket used was a 4.76 mm thick gasket made of EPDM rubber purchased from the Prince Rubber and Plastics Co., Inc., of Bu~falo, New York.
Speci~ications for the EPDM include "EPDM ~or Chlor-Alkali Service, Prince #6962." The gaskets were cut from single EPDM rubber sheets to form a picture-frame shape with dimensions of 2.47 meter outside-to-outside and 2.37 meter inside-to-inside in the long direction and 1.25 meter outside-to-outside and 1.15 meter inside-to-inside in the short direction. Thus, the width of the gasket surface was 5.1 cm. The total gasket area was 3,676 cm2. The gasket was used on both sides of the membrane and contact loading was distributed over the reinforoed surface.
A hydraulic cylinder in a filter press arrangement was used to press together the cell units.
The total force resulting from the action o~ the hydraulic press was 78,152 kg. The force exerted on the membrane was equivalent to 2,080 kPa.
The cells were operated to produce from 12 to 16 weight percent caustic while controlling the anolyte salt at 200 gram~ per liter sodium chloride concentration. The cell temperature was maintained at 90-C with D~C. current controlled at 10.0 kiloamperes.
31,365-F
.
., ' ., , . ': ', .' :, ; ;
', .'',' . ., ~.'" '. , . , . ~,' .
., . , , : . .. . ..
. : : . ~ . " ~
.~2~5~3~
Thus, the ampere loading was 0.31 amperes per square cm of projected anode area current density. The test was conducted for 199 days and during this period, the caustic current efficiency averaged 82-84 percent which was 4 percent below the expected caus-tic current efficiency for Nafion~ 324.
Visual inspection of the membrane after dis-~ mantling the cell showed the me~brane to have severe damage in the areas beneath the gaskets and in the area next to the gaskets. The gasket loading forces had stretched and cracked the membrane so severely to render the overall cell performance unsatisfactory.
31,365-F -12-,, ~. .
Claims (7)
1. An ion exchange membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket-bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening.
2. The membrane unit of Claim 1, wherein the reinforcing material is of the same material as the membrane.
3. The membrane unit of Claim 1 or 2, wherein the reinforcing material has a thickness of from 0.076 to 0.51 mm.
4. The membrane unit of Claim 1 or 2, wherein the reinforcing material has a heavier scrim than that of the membrane material.
5. The membrane unit of Claim 1 or 2, wherein the membrane is composed of a fluorocarbon polymer having a plurality of pendant groups selected from sulfonic acid groups, carboxylic acid groups or mixtures of sulfonic and carboxylic acid groups.
31,365-F -13-
31,365-F -13-
6. An electrolytic cell comprising an ion exchange membrane unit separating at least two electrode compartments, said membrane unit comprising at least one layer of a ion exchange membrane and at least one layer of a membrane reinforcing material secured to at least one side of the membrane around a gasket-bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening.
7. A method of sealing an electrolytic cell comprising the steps of (a) interposing at least one gasket between at least one electrode frame and an ion exchange membrane in an electrolytic cell, securing at least one layer of a reinforcing material to at least one side of the membrane around a gasket bearing peripheral surface of the membrane, wherein said membrane has at least one opening and the reinforcing material is heat sealed to the membrane through the opening, and (b) applying a compressive force to the cell.
xx,xxx-F -14-
xx,xxx-F -14-
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66804384A | 1984-11-05 | 1984-11-05 | |
| US668,043 | 1984-11-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1287599C true CA1287599C (en) | 1991-08-13 |
Family
ID=24680765
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000494496A Expired - Fee Related CA1287599C (en) | 1984-11-05 | 1985-11-04 | Membrane unit for electrolytic cell |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0183096B1 (en) |
| JP (1) | JPS61117294A (en) |
| CN (1) | CN85108122A (en) |
| AU (1) | AU562125B2 (en) |
| BR (1) | BR8505502A (en) |
| CA (1) | CA1287599C (en) |
| DE (1) | DE3581896D1 (en) |
| DK (1) | DK501585A (en) |
| ES (1) | ES296350Y (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4770757A (en) * | 1987-03-03 | 1988-09-13 | E. I. Du Pont De Nemours And Company | Edge reinforcement of membranes for chlor-alkali cells |
| EP0339114A1 (en) * | 1988-04-28 | 1989-11-02 | E.I. Du Pont De Nemours And Company | Edge reinforcement of membranes for chlor-alkali cells |
| US5175795A (en) * | 1988-07-29 | 1992-12-29 | Hitachi, Ltd. | Hybridized frame inference and fuzzy reasoning system and method |
| DE3928934C2 (en) * | 1989-08-31 | 1999-04-29 | Sartorius Gmbh | Textile reinforced microporous membrane filter, process for its preparation and its use |
| JP3480988B2 (en) * | 1994-07-01 | 2003-12-22 | ジャパンゴアテックス株式会社 | Sealing and reinforcing membrane material for fluoropolymer solid electrolyte membrane, fluoropolymer solid electrolyte membrane using the same, and plating method thereof |
| US5945192A (en) * | 1995-06-29 | 1999-08-31 | Japan Gore-Tex, Inc. | Sealing assembly for a solid polymer ion exchange membrane |
| JP4500083B2 (en) * | 2004-03-29 | 2010-07-14 | 有限会社ルミネ | Image composition apparatus and program |
| AT502170B1 (en) * | 2005-12-23 | 2007-02-15 | Semperit Ag Holding | Molding for use in filter presses (especially as a support for the membrane) comprises a first polymer at least partly covered by a layer of ultra-high molecular polyethylene |
| CN106830213A (en) * | 2017-03-27 | 2017-06-13 | 长春云卫科技有限公司 | Acidic oxidized electric potential water electrolytic cell |
| EP4194588A1 (en) * | 2021-12-08 | 2023-06-14 | thyssenkrupp nucera AG & Co. KGaA | Method for sealing an electrolysis cell and sealed electrolysis cell |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1540964A (en) * | 1966-06-21 | 1968-10-04 | Monsanto Co | Electrolytic cell and composite membrane |
| FR2146602A5 (en) * | 1971-07-20 | 1973-03-02 | Alsthom | Zinc/air cell - with plastics grid as spacer between anode and microporous membrane |
| JPS53146272A (en) * | 1977-05-27 | 1978-12-20 | Tokuyama Soda Co Ltd | Holder for ion exchange membrane |
| GB2013242B (en) * | 1977-12-26 | 1982-06-16 | Kanegafuchi Chemical Ind | Method and apparatus of installation of membrane to electrolytic cell |
| DE2821983A1 (en) * | 1978-05-19 | 1979-11-22 | Hooker Chemicals Plastics Corp | SEALING ELEMENT FOR MEMBRANES, ESPECIALLY FOR ELECTROLYSIS CELLS ARRANGED IN A FILTER PRESS |
| JPS5933195B2 (en) * | 1979-09-04 | 1984-08-14 | 東ソー株式会社 | How to install an ion exchange membrane |
| US4441977A (en) * | 1980-11-05 | 1984-04-10 | Olin Corporation | Electrolytic cell with sealing means |
| CA1174729A (en) * | 1981-06-01 | 1984-09-18 | Patrick G. Grimes | Electrochemical construction |
| JPS584926U (en) * | 1981-07-02 | 1983-01-13 | ミサワホ−ム株式会社 | ventilation system |
-
1985
- 1985-10-31 DK DK501585A patent/DK501585A/en not_active Application Discontinuation
- 1985-11-01 AU AU49293/85A patent/AU562125B2/en not_active Ceased
- 1985-11-01 JP JP60244235A patent/JPS61117294A/en active Granted
- 1985-11-04 BR BR8505502A patent/BR8505502A/en unknown
- 1985-11-04 CA CA000494496A patent/CA1287599C/en not_active Expired - Fee Related
- 1985-11-04 CN CN198585108122A patent/CN85108122A/en active Pending
- 1985-11-04 ES ES1985296350U patent/ES296350Y/en not_active Expired
- 1985-11-05 EP EP85114059A patent/EP0183096B1/en not_active Expired - Lifetime
- 1985-11-05 DE DE8585114059T patent/DE3581896D1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DK501585A (en) | 1986-05-06 |
| JPS61117294A (en) | 1986-06-04 |
| DE3581896D1 (en) | 1991-04-04 |
| CN85108122A (en) | 1986-07-16 |
| ES296350U (en) | 1987-10-16 |
| JPH0364598B2 (en) | 1991-10-07 |
| EP0183096B1 (en) | 1991-02-27 |
| BR8505502A (en) | 1986-08-05 |
| AU562125B2 (en) | 1987-05-28 |
| DK501585D0 (en) | 1985-10-31 |
| ES296350Y (en) | 1988-04-16 |
| EP0183096A1 (en) | 1986-06-04 |
| AU4929385A (en) | 1986-05-15 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |