CA1118717A - Converting a diaphragm electrolytic cell to a membrane electrolytic cell - Google Patents
Converting a diaphragm electrolytic cell to a membrane electrolytic cellInfo
- Publication number
- CA1118717A CA1118717A CA000278937A CA278937A CA1118717A CA 1118717 A CA1118717 A CA 1118717A CA 000278937 A CA000278937 A CA 000278937A CA 278937 A CA278937 A CA 278937A CA 1118717 A CA1118717 A CA 1118717A
- Authority
- CA
- Canada
- Prior art keywords
- foraminous electrode
- electrode
- matting
- foraminous
- membrane
- 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
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
- C08J5/2218—Synthetic macromolecular compounds
- C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
- C08J5/2237—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds containing fluorine
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/20—Manufacture of shaped structures of ion-exchange resins
- C08J5/22—Films, membranes or diaphragms
- C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
- C08J5/2218—Synthetic macromolecular compounds
- C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Polymers & Plastics (AREA)
- Medicinal Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Inorganic Chemistry (AREA)
- Electrochemistry (AREA)
- Metallurgy (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Cell Separators (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method is disclosed forming a membrane over a standard diaphragm cell foraminous electrode and may comprise the steps of suspending a matting material in a liquid medium, inserting a foraminous electrode into the suspension, vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material, applying to the surface of the foraminous electrode with the matting material thereon; a layer of thermoplastic material which includes particles of perfluorosulfonic acid resin in the sulfonyl fluoride form, baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially permeable to hydraulic flow and hydrolyzing the perfluorosulfonic acid resin to change the sulfonyl fluoride form to the cation exchange sulfonic acid form. The forming of the membrane over a standard diaphragm cell electrode assembly eliminates sub-stantial cathode costs involved currently for converting the diaphragm electrolytic cell to a membrane electrolytic cell.
A method is disclosed forming a membrane over a standard diaphragm cell foraminous electrode and may comprise the steps of suspending a matting material in a liquid medium, inserting a foraminous electrode into the suspension, vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material, applying to the surface of the foraminous electrode with the matting material thereon; a layer of thermoplastic material which includes particles of perfluorosulfonic acid resin in the sulfonyl fluoride form, baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially permeable to hydraulic flow and hydrolyzing the perfluorosulfonic acid resin to change the sulfonyl fluoride form to the cation exchange sulfonic acid form. The forming of the membrane over a standard diaphragm cell electrode assembly eliminates sub-stantial cathode costs involved currently for converting the diaphragm electrolytic cell to a membrane electrolytic cell.
Description
37i~
CONVERTING A DIAPHRAGM ELECTROLYTIC
CELL TO A lvlEMBRANE ELECTROLYTIC CELL
BACKGROUND OF THE INVENTION
The present invention relates generally to the conversion of a standard diaphragm electrolytic cell which is being used for chlorine and caustic (sodium hydroxide) production, to an electrolytic cell having a membrane for the same type of chemical production with the lnherent advantageous characteristics of a membrane electrolytic cell.
More particularly the present invention relates to a method for forming a membrane over a standard diaphragm electrolytic cell cathode by vacuum forming a matting material on the foraminous electrode and subsequently applying a membrane material on top of thematting mate~ial which is fused into a thin and uniform substantially hydraulically impermeable film. Such a method will allow manufacturers having standard diaphragm electrolytic cell equipment in current use to convert that equipment to membraneelectrolytic cells with a smaller capital expenditure to yield a saving in the operational costs associated with the use of membrane electrolytic cells.
l~lectrochemical methods of manufacture are becoming ever increasingly im-por~ant to the chemical industry due to their greater ecological acceptability, potential for energy conservation, and the resultant cost reductions possible. Therefore a great deal of research and development effort is being applied to the electrochemical processes and the hardware for these processes. From this efforthavecome technological advances such as the dimensionally stable anode and various coating compositions therefor which permit ever narrowing gaps between the electrodes, such that the electrolytic cell has become more ef~icient for use in electrochemical processes. Also the hydraulically impermeable membrane has added a great deal to the potential use of electrolytic cells in terms of the selective migration Gf various ions across the membrane surface so as to e~cludecontaminants from the resultant product thereby eliminating some costly purification and concentration steps of processing.
,~, -;
~187~7 One significant commercial possibility for these advances in electrolytic cells would be in chlorine and caustic production. Chlorine and caustic are essential and laroe volume commodities which are oasic chemicals required by all industrial societies. They are produced almost entirely electrolytically from aqueous solutions of alkali metal chlorides, with a major proportion of such production coming from diaphragm-type electrolytic cells.
In the diaphragm cell process, brine (sodium chloride solution~ is fed con~inuously into the anode compartment and flows through the diaphragm usually made of asbestos, backed by the cathode. To minimi~e back migration of the hydroxide ions, the flow is always main-tained in excess of the conversion rate so that the resulting catholyte solution has unused alkali metal chloride present. The hydrogen ions are discharged from the solution at the cathode in the form of molecular hydrogen gas. The cathode solution, containing cau~tic, unreacted sodium chloride, and other impurities, generally has been concentrated and purified later to obtain a marketable sodium hydroxide commodity and a sodium chloride which can be reused in a chlorine and caustic electrolytic cell for further production of sodium hydroxide.
The dimensionally stable anode is today being used by a large number of chlorineand caustic producers but thè extensive commercial use of the hydraulically impermeable membrane has been at least in part militated against by the s~Jbstantial capital cost involved in conver~ing from diaphragm electrolytic cells to membrane electrolytic cells. This is caused by the difficulty encountered in placing a more or less planar membrane onto the cathode assembly which is generally a three dimensional assembly onto which the asbestos diaphragm is placed by vacuum forming from a slurry. The diaphragm has been modified by adding to the slurry from which the diaphragm is deposited onto the cathode assembly, a polymeric material to act as a binding substance so as to improve the chemical resistivity of the diaphragm material. This dimensionally stable polymer modified diaphragm though is not a hydraulically impermeable mem-brane. Another approach has been to form a membrane on the electrode suface itself.
The problem with this approach is that most of the cathode assemblies in curren~
use are foraminous in nature and such porosity makes it very difficu1t to deposite a membrane material to form a film directly onto the cathode assemb1-~.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for forming .~
a membrane over a standard diaphragm cell electrode assemby so as to eliminate the sub-stantial capital costs involved currently for converting a diaphragm electrolytic cell to a membrane electrolytic cell.
It is another object of the present invention to provide a method for forming a membrane over a standard diaphragm cell electrode assembly so that the advantages of a membrane may be realized by using existing diaphragm electrolytic cell equipment.
These and other objects of the present invention, together with the advantages thereof over existing and prior art forms which will become apparent to those skilled in the art from the detailed disclosure of the present invention as set forth hereinbelow, are accomplished by the improvements herein described and claimed.
It has been found that a method for forming a membrane over a standard dia-phragm cell foraminous electrode can comprise the steps of: suspending a matting material in a liquid medium; inserting a foraminous electrode into the suspension; vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon a layer ofthermoplastic material including NAFlON particles in the sulfonyl fluoride form; baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow; and hydrolyzing the NAFION to change the sulfonyl fluoride form to the cation exchange sulfonic acid form.
It has also been found that a membrane separator for a standard diaphragm electrolytic cell can comprise: a standard diaphragm cell foraminous electrode; on the surface of the standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm cell foraminous electrode; and on the surface of the matting material a thin and uniform hy-draulically impermeable cation exchange membrane consisting essentially of a film of co-polymers having the repeating structural units of the formula:
3'717 (1) -CF2-CF-n and (2) -CF2-CXXl- .
Rl wherein R represents the group -CF-CF2-O ~CFY-CF2O~m, in which Rl is fluorine or per-fluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is O or l; X is fluorine, chlorine, or trifluoromethyl; Xl is X or CF3 ~CF2~aO-; a is O or integer from 1 to 5; and the units of the formula (1) being present in an amount to provide a co-polymer having a -S03H equivalent weight in the range of 800 to 1600.
A method for forming a membrane over a standard diaphragm cell :~oraminous electrode may comprise the steps of: suspending a matting material in a liquid medium;
inserting a foraminous electrode into the suspension; vacuum forming a layer of suspended matting ~aterial over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon a layer of thermoplastic material including material containing carboxyl ion exchange groups; and baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow.
A membrane separator for a standard diaphragm electrolytic cell can comprise:
a standard diaphragm cell foraminous electrode; on the surface of the standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm cell foraminous electrode; and on the surface of the matting material a thin and uniform hydraulically impermeable cation exchange membrane consisting essentially of a film of copolymers having the repeating structural units of the formula:
'7 ~ 7 (1) -CF2-CF-(R)n
CONVERTING A DIAPHRAGM ELECTROLYTIC
CELL TO A lvlEMBRANE ELECTROLYTIC CELL
BACKGROUND OF THE INVENTION
The present invention relates generally to the conversion of a standard diaphragm electrolytic cell which is being used for chlorine and caustic (sodium hydroxide) production, to an electrolytic cell having a membrane for the same type of chemical production with the lnherent advantageous characteristics of a membrane electrolytic cell.
More particularly the present invention relates to a method for forming a membrane over a standard diaphragm electrolytic cell cathode by vacuum forming a matting material on the foraminous electrode and subsequently applying a membrane material on top of thematting mate~ial which is fused into a thin and uniform substantially hydraulically impermeable film. Such a method will allow manufacturers having standard diaphragm electrolytic cell equipment in current use to convert that equipment to membraneelectrolytic cells with a smaller capital expenditure to yield a saving in the operational costs associated with the use of membrane electrolytic cells.
l~lectrochemical methods of manufacture are becoming ever increasingly im-por~ant to the chemical industry due to their greater ecological acceptability, potential for energy conservation, and the resultant cost reductions possible. Therefore a great deal of research and development effort is being applied to the electrochemical processes and the hardware for these processes. From this efforthavecome technological advances such as the dimensionally stable anode and various coating compositions therefor which permit ever narrowing gaps between the electrodes, such that the electrolytic cell has become more ef~icient for use in electrochemical processes. Also the hydraulically impermeable membrane has added a great deal to the potential use of electrolytic cells in terms of the selective migration Gf various ions across the membrane surface so as to e~cludecontaminants from the resultant product thereby eliminating some costly purification and concentration steps of processing.
,~, -;
~187~7 One significant commercial possibility for these advances in electrolytic cells would be in chlorine and caustic production. Chlorine and caustic are essential and laroe volume commodities which are oasic chemicals required by all industrial societies. They are produced almost entirely electrolytically from aqueous solutions of alkali metal chlorides, with a major proportion of such production coming from diaphragm-type electrolytic cells.
In the diaphragm cell process, brine (sodium chloride solution~ is fed con~inuously into the anode compartment and flows through the diaphragm usually made of asbestos, backed by the cathode. To minimi~e back migration of the hydroxide ions, the flow is always main-tained in excess of the conversion rate so that the resulting catholyte solution has unused alkali metal chloride present. The hydrogen ions are discharged from the solution at the cathode in the form of molecular hydrogen gas. The cathode solution, containing cau~tic, unreacted sodium chloride, and other impurities, generally has been concentrated and purified later to obtain a marketable sodium hydroxide commodity and a sodium chloride which can be reused in a chlorine and caustic electrolytic cell for further production of sodium hydroxide.
The dimensionally stable anode is today being used by a large number of chlorineand caustic producers but thè extensive commercial use of the hydraulically impermeable membrane has been at least in part militated against by the s~Jbstantial capital cost involved in conver~ing from diaphragm electrolytic cells to membrane electrolytic cells. This is caused by the difficulty encountered in placing a more or less planar membrane onto the cathode assembly which is generally a three dimensional assembly onto which the asbestos diaphragm is placed by vacuum forming from a slurry. The diaphragm has been modified by adding to the slurry from which the diaphragm is deposited onto the cathode assembly, a polymeric material to act as a binding substance so as to improve the chemical resistivity of the diaphragm material. This dimensionally stable polymer modified diaphragm though is not a hydraulically impermeable mem-brane. Another approach has been to form a membrane on the electrode suface itself.
The problem with this approach is that most of the cathode assemblies in curren~
use are foraminous in nature and such porosity makes it very difficu1t to deposite a membrane material to form a film directly onto the cathode assemb1-~.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for forming .~
a membrane over a standard diaphragm cell electrode assemby so as to eliminate the sub-stantial capital costs involved currently for converting a diaphragm electrolytic cell to a membrane electrolytic cell.
It is another object of the present invention to provide a method for forming a membrane over a standard diaphragm cell electrode assembly so that the advantages of a membrane may be realized by using existing diaphragm electrolytic cell equipment.
These and other objects of the present invention, together with the advantages thereof over existing and prior art forms which will become apparent to those skilled in the art from the detailed disclosure of the present invention as set forth hereinbelow, are accomplished by the improvements herein described and claimed.
It has been found that a method for forming a membrane over a standard dia-phragm cell foraminous electrode can comprise the steps of: suspending a matting material in a liquid medium; inserting a foraminous electrode into the suspension; vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon a layer ofthermoplastic material including NAFlON particles in the sulfonyl fluoride form; baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow; and hydrolyzing the NAFION to change the sulfonyl fluoride form to the cation exchange sulfonic acid form.
It has also been found that a membrane separator for a standard diaphragm electrolytic cell can comprise: a standard diaphragm cell foraminous electrode; on the surface of the standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm cell foraminous electrode; and on the surface of the matting material a thin and uniform hy-draulically impermeable cation exchange membrane consisting essentially of a film of co-polymers having the repeating structural units of the formula:
3'717 (1) -CF2-CF-n and (2) -CF2-CXXl- .
Rl wherein R represents the group -CF-CF2-O ~CFY-CF2O~m, in which Rl is fluorine or per-fluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is O or l; X is fluorine, chlorine, or trifluoromethyl; Xl is X or CF3 ~CF2~aO-; a is O or integer from 1 to 5; and the units of the formula (1) being present in an amount to provide a co-polymer having a -S03H equivalent weight in the range of 800 to 1600.
A method for forming a membrane over a standard diaphragm cell :~oraminous electrode may comprise the steps of: suspending a matting material in a liquid medium;
inserting a foraminous electrode into the suspension; vacuum forming a layer of suspended matting ~aterial over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon a layer of thermoplastic material including material containing carboxyl ion exchange groups; and baking the foraminous electrode with the layers in place until the thermoplastic material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow.
A membrane separator for a standard diaphragm electrolytic cell can comprise:
a standard diaphragm cell foraminous electrode; on the surface of the standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm cell foraminous electrode; and on the surface of the matting material a thin and uniform hydraulically impermeable cation exchange membrane consisting essentially of a film of copolymers having the repeating structural units of the formula:
'7 ~ 7 (1) -CF2-CF-(R)n
(2) -CF2-CXX 1_ R
wherein R represents the group -C~:-CF2-0 ~CFY-CF20~m, in which R iS~luorine or per-fluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is O or l; X isf~lorine, chlorine, or trifluoromethyl; Xl is X or CF3 ~CF2~aO-; a is O or integer from 1 to 5; wherein R2 is an ion exchange group selected from ~he group of oxy acids, salts 10 and ester~ of Cl-C3 carbon, or an ion exchange group based on one ~ nitro~en, silicon, phosphorus, sulfur, chlorine, arsenlc, selenium or tellurium.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The membrane separator for a standard diaphragm electrolytic cell electrode assembly and the method for forming such a membrane will overcome many of the 15 disadvantages of the prior art forms Jisted above and yield the benefits of the use of a membrane in an electrolytic cell without the substantial capi~al cost associated heretofore with the conversion of a diaphragm electrolytic cell to a membrane electrolytic cell. Most of these diaphragm electrolytic cells in use today are of two general types. Both consist of an outer steel shell either cylinderical or rectangular which supports a cathode of perforated 20 iron plate or woven iron screen inside of the shell, generally referred to as a foraminous electrode element. This constitutes the cathode assembly. The actual cathode surfaces are generally lined with a layer of asbestos either in the form of paper wrapped around it or vacuum deposited fibers. The type of cathode assembly for which the present invention is especially useful is that known as the Diamond Shamrock Cell wherein the cathode assembly 25 consists of a rectangular steel shell housing with an inner assembly of lateral rows of vertically flattened ~I/ire-screen tubes, upon which the diaphragm has been deposited by suction from a cell liquor suspension of asbestos fibers.
Since thes~e foraminous electrode assemblies generally have a high porosity it is necessary to reduce the porosity by vacuuming some type of matting material onto the 30 foraminous electrode surface before applying a membrane material. The matting material ...... .. ....... . ... . .. . ... . .
may be an asbestos support made from chrysotile asbestos fibers mixed with 5% (by weight) fluorinated ethylene propylene copolymer particles, or any other material which will form a sufficient mat upon the foraminous electrode. Another example would be a cellulosic material. Alternatively, sheets of material such as filter paper could be wrapped around the electrode tube. It is believed that the exact nature of the matting material is not of great significance since it is generally of a temporary nature for the purpose of supporting the polymeric materials to form a film upon the foraminous electrode. It is believed that any depositable fiber will serve as an adequate support structure, inertness to chlorine cell environments not being necessary. Since the thickness of the support structure affects the cell potential it is desirable to obtain the thinnest matting structure consistent with the purpose of substantially reducing the porosity of the foraminous electrode material. One way of building a matting which is often used in industry is to suspend the matting material in a fluid medium and in the case of the asbestos fibers usually the cell liquor. The foraminous electrode material may then be suspended into the slurry of matting material and a vacuum pulled to the inside of the foraminous electrode material such that the fibers of the mattin8 material will be drawn onto the surface of the foraminous electrode. This support structure will then provide a uniform surface on which the slurry of thermoplastic materials 3uch as NAFION can be applied. Once the thermoplastic material has been applied and fused, the support structure is no longer necessary and the film performs lilse a membrane. The matting structure itself must have a low enough porosity as to retain particles in the range of less than one micron on the surface without their being pulled to the interior portions of the mattin~ material.
The NAFION material being used in the present invention is a fluorinated co-polymer having pendent sulfonic acid groups. The fluorinated copolymer is derived from monomers of the formula 2~ (l) CF2=CF ~R~n SO2F
in which the pendent -SO2F groups are converted to -SO3H groups, and monomers of the formula (2) CR2 = CXxl Rl where R represents the group -CF-CF2-O ~CFY-CF2O~m in which Rl is fluorine or 7i7 per fluoroalkyl of 1 thru 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is O or 1; X is fluorine, chlorine or ~rifluoromethyl; and Xl is X or CF3 ~CF2~aO-, wherein a is O or an integer from I to 5.
This results in copolymers having the repeating structural units
wherein R represents the group -C~:-CF2-0 ~CFY-CF20~m, in which R iS~luorine or per-fluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is O or l; X isf~lorine, chlorine, or trifluoromethyl; Xl is X or CF3 ~CF2~aO-; a is O or integer from 1 to 5; wherein R2 is an ion exchange group selected from ~he group of oxy acids, salts 10 and ester~ of Cl-C3 carbon, or an ion exchange group based on one ~ nitro~en, silicon, phosphorus, sulfur, chlorine, arsenlc, selenium or tellurium.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The membrane separator for a standard diaphragm electrolytic cell electrode assembly and the method for forming such a membrane will overcome many of the 15 disadvantages of the prior art forms Jisted above and yield the benefits of the use of a membrane in an electrolytic cell without the substantial capi~al cost associated heretofore with the conversion of a diaphragm electrolytic cell to a membrane electrolytic cell. Most of these diaphragm electrolytic cells in use today are of two general types. Both consist of an outer steel shell either cylinderical or rectangular which supports a cathode of perforated 20 iron plate or woven iron screen inside of the shell, generally referred to as a foraminous electrode element. This constitutes the cathode assembly. The actual cathode surfaces are generally lined with a layer of asbestos either in the form of paper wrapped around it or vacuum deposited fibers. The type of cathode assembly for which the present invention is especially useful is that known as the Diamond Shamrock Cell wherein the cathode assembly 25 consists of a rectangular steel shell housing with an inner assembly of lateral rows of vertically flattened ~I/ire-screen tubes, upon which the diaphragm has been deposited by suction from a cell liquor suspension of asbestos fibers.
Since thes~e foraminous electrode assemblies generally have a high porosity it is necessary to reduce the porosity by vacuuming some type of matting material onto the 30 foraminous electrode surface before applying a membrane material. The matting material ...... .. ....... . ... . .. . ... . .
may be an asbestos support made from chrysotile asbestos fibers mixed with 5% (by weight) fluorinated ethylene propylene copolymer particles, or any other material which will form a sufficient mat upon the foraminous electrode. Another example would be a cellulosic material. Alternatively, sheets of material such as filter paper could be wrapped around the electrode tube. It is believed that the exact nature of the matting material is not of great significance since it is generally of a temporary nature for the purpose of supporting the polymeric materials to form a film upon the foraminous electrode. It is believed that any depositable fiber will serve as an adequate support structure, inertness to chlorine cell environments not being necessary. Since the thickness of the support structure affects the cell potential it is desirable to obtain the thinnest matting structure consistent with the purpose of substantially reducing the porosity of the foraminous electrode material. One way of building a matting which is often used in industry is to suspend the matting material in a fluid medium and in the case of the asbestos fibers usually the cell liquor. The foraminous electrode material may then be suspended into the slurry of matting material and a vacuum pulled to the inside of the foraminous electrode material such that the fibers of the mattin8 material will be drawn onto the surface of the foraminous electrode. This support structure will then provide a uniform surface on which the slurry of thermoplastic materials 3uch as NAFION can be applied. Once the thermoplastic material has been applied and fused, the support structure is no longer necessary and the film performs lilse a membrane. The matting structure itself must have a low enough porosity as to retain particles in the range of less than one micron on the surface without their being pulled to the interior portions of the mattin~ material.
The NAFION material being used in the present invention is a fluorinated co-polymer having pendent sulfonic acid groups. The fluorinated copolymer is derived from monomers of the formula 2~ (l) CF2=CF ~R~n SO2F
in which the pendent -SO2F groups are converted to -SO3H groups, and monomers of the formula (2) CR2 = CXxl Rl where R represents the group -CF-CF2-O ~CFY-CF2O~m in which Rl is fluorine or 7i7 per fluoroalkyl of 1 thru 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is O or 1; X is fluorine, chlorine or ~rifluoromethyl; and Xl is X or CF3 ~CF2~aO-, wherein a is O or an integer from I to 5.
This results in copolymers having the repeating structural units
(3) -CF2 -CF - and (4) -CF2 -CXX 1_.
~R)n In the copolymer there should be sufficient repeating units according to formula(3) above~ to provide an -SO3H equivalent weight of about 800 to 1600. Materials having a water absorption rate of about 25 percent or greater are preferred since higher cell po-tentials-at any given current density are required for materials having less water absorption.
Similarily~ materials having a film thickness (unlaminated) of about 8 mils or more require higher cell potentials resulting in a lower power effidency.
Polymeric materials of this type are further described in the following patents:U.S. Patent Nos. 3~041,317; 3,282,875;
3,560,568; 3,624,033; 3,718,627; and British Patent No. 1,184,321. Polymeric materials as aforedescribed are available from E.I. duPont deNemours ~cCo. under the trademark NAFION.
Polymeric materials according t~ formulas 1 and 2 can also be made wherein the ion exchange group instead of being a sulfonic acid exchange group could be many other types of structures. One pacticular type of s~ructure is a carboxyl group ending in either an acid9 and ester or a salt to form an ion exchange group similiar to that of the sulfonic acid. In such a group instead of SO2F one would find COOR2 wherein R2 may be selected from the group of hydrogen, an alkali metal ion and an organic radicalThese polymeric materials are available presently from F. I. duPont deNemours dc Co. Furthermore it has 2~ been found that a substrate material such as NAFION having any ion exchange group or function group capable of being converted into an ion exchange group or a function group in which an ion exchange group can easily be introduced may include such groups as oxy acids, salts, or esters of Cl-C3 carbon, nitrogen, silicon, phosphor-~-s, sul:Eur, chlorine, arsenic,selenium, or tellurium.
., 37:~7 The NAFION material along with any filler materials used may be applied by any method which will result in a thin uniform film as required above to form an adequate membrane over top of the deposited mating material Among the methods through to be suitable would be: deposition from a slurry, drawiny the material onto the surface of the matting material with a vacuum, pouring the slurry over the matting material, brushing on a solution, or spraying in some fashion such as by a plasma spray. Vacuum form-ing from a slurry may be the most economic method since the equip-ment used for such a method would be the same as that used to apply the asbestos diaphragms.
A typical slurry for deposition upon a foraminous cathode with the mat in place can be made by using NAFION particulate material with a 1208 equivalent weight or 1073 equivalent weight mixed with a suitable solvent such as 1,1,2-trichlorotrifluoro-ethane which is available from E.I. duPont deNemours & Co. under the trademark FREON 113. FREON 113 works well because it softens the NAFION particles thus making it easier to reduce the particle size by shearing to yield a very uniform NAFION dispersion. It is also believed an aqueous slurry of NAFION with an alkylaryl-polyether alcohol available from Diamond Shamrock Corp. under the trademark HYONIC PE260 used as a wetting agent would also perform well. The NAFION particulate material is in the sulfonyl fluoride form in a thermoplastic polymeric layer. A typical method for making such a suspension would be to utilize a stirrer fitted with a jacketed chamber and a reflux condenser into which NAFION
particulate material is added along with FREON 113 solvent. The system is heated wit~ hot water to boil the FREON 113 solvent and cold water is run through the reflux condenser to condense the FREON 113 solvent. Refluxing of the NAFION and FREON 113 mixture for approximately 10 minutes and then shearing for 30 minutes while continuing to reflux the FREON 113 solvent, produces a good _ 9 _ NAFION slurry from which to deposit a film onto the matting material surface. Various thermoplastic materials compatible with NAFION may be used as fillers :in the slurry to reduce the cost while producing a good film. Examples of such fillers would be a fluorinated ethylene propylene copolymer or a perfluoro-alkoxy material.
The NAFION slurry may be applied to the support structure in various ways, the object being to produce a continuous uniform film after fusing. Subsequent to application - 9a -. ~.
'71~7 the FREON 113 is allowed to evaporate and then the particulate material is fused into a film. This is accomplished by baking the entire foraminous electrode assembly in an oven generally at a temperature in the range of 240to 300C. More than one application and subsequent fusion of a thermoplastic material slurry may be necessary in order to produce hole ~ree continuous film.
Once a thin and uniform film is formed on the surface of the mattin8 material which is substantially impermeable to hydraulic flow, the film may then be hydrolyzed into the infusible ion exchange sulfonic acid form. Hydrolyzing or saponifying of the NAFION is a fairly simple procedure for the conversion of a sulfonyl fluoride form to the free acid form. This may be accomplished by soaking the film in a sodium hydroxide solution, sodium hydroxide in dimethyl sulfoxide solution, potassium hydroxide solution, or potassium hydroxide in dimethyl sulfoxide solution. Any of these treatments appear to work equally well although different temperatures and times are required to accomplish the hydrolysis.
Once this has been accomplished, the electrode is then ready for use in a standard diaphragm electrolytic cell. The conditions of the cell should be altered to operate the cell as a membrane electrolytic cell.
Various means of improving these substrate materials have been sought, one of the most effective of which is the surface chemical treatment of the substrate itself.
Generally these treatments consist of reacting the sulfonyl fluoride pendent groups with substances which will yield less polar bonding and thereby absorb fewer water molecules by hydrogen bonding. This has a tendency to narrow the pore openings through which the càtions travel so that less water of hydration is transmitted with the cations through the membrane. An example of this would be to react the ethylene diamine with the pendent groups in the sulfonyl fluoride form to tie two of the pendent groups together by two nitrogen atoms in the ethylene diamine. Generally, in a film thickness of 7 mils, the surface treatment will be donle to a depth of approximately 2 mils on one side of the film by control-ling the time of reaction. This will result in good electrical conductivity and cation trans-mission with less hydroxide ion and associated water reverse migration.
The resultant membrane electrolytic cell will yield a high current density, a lower sodium chloride concentration in the resultant sodium hydroxide solution compared to 71'~
;tandard diaphragm cell, a higher resultant sodium hydroxide concentration, good utiliza-tion of existing cell space, longer lifetimes for the cell and a lower potential. Thus, those skilled in the art will recognize the advantages of the present invention to the chlorine and caustic industry.
In order that those skilled in the ar~ may more readily understand the present invention and certain preferred aspects by which it may be practiced, the following specific examples are afforded.
EXAMP1.E 1 For testing in a laboratory cell, a membrane was formed over an asbestos matting using a auchner funnel as a framework structure over which to form the matting material. The matting material consisted of asbestos plus 5% fluorinated ethylene propylene copolymer as a binder to form a suspension in water. A vacuum was pulled on the Buchner funnel to draw the matting material onto the foraminous surface of the funnel until thP porosity was reduced so as to capture particles in the size range of one micron. A thermoplastic material sl~rry was made from a 1208 equivalent weight NAFION (a Trademark for p~rfluorosulonic acid resin) resin particle material mixed with a solvent known as FREON 113, a Trademark for 1,1,2-trichlorotri~luoroethane. T~e mixture was stirred at 47.8C. to obtaina lO gram slurry The slurry was then filtered thr~ugh the matting material overtop of the Buchner funnel. Fusion of the NAFION resin particles was accom-plished by baking tha matting material with the ~AEION particles on the surface at a temperature of 300C. for 60 minutes. This resulted in a thin and uniform film which was substantially impermeable to hydraulic flow. Thereafter the NAFlON was hydroly~ed in a solution of dimethyl sulfoxide and water plus 1096 sodium hydroxide at a temperature of 70C. for a time period of 70 minutes to convert the sulfonyl fluorideform to the cation exchange sulfonic acid form.
This membrane over the mattin~ material was then inserted into a laboratory test cell with a flow ral:e of .053 cc/min/sq.in. of cathode area, a head of 14 inches of brine, a potential of 4.29 volts and a current of 6.2~ arnperes at 92C~ to achieve a current efficiency of 6496 over a period of 37 days.
'7i'~
An asbestos matting was formed over a Buchner funnel as described in Example 1. A thermoplastic material slurry was made utilizing a 1073 equivalent weight NAFION
resin particle material in FREON 113 solvent ~1,1,2-trichlorotrifluoroethane~ and refluxed at 50C. for 10 minutes. The resultant slurry was then poured over the asbestos mat. After evaporation of the FREON 113, the NAFION resin particles were fused at a temperature of 275C. for 30 minutes into a thin and uniform film. It was then hydrolyzed in 35% sodium hydroxide for one week.
The resultant membrane over the matting material was then inserted into a laboratory test cell under conditions according to Example 1 to achieve a maximum current efficiency of 5096.
An asbestos slurry was formed over a Buchner funnel according to Example 1. A
slurry of thermoplastic material was made of 1073 equivalent weight NAFION resin particle material in FREON 113 solvent and refluxed according to Example 2. The slurry was then drawn onto the matting material with a 26 inch vacuum. The NAFION resin particles were fused at a temperature of 250C. for 30 minutes, a second coat of the slurry was added by eye dropper to close holes in the film and a subsequent fusion was performed. The material was then hydroly~ed in dimethyl sulfoxide and sodium hydroxide at a temperature for 80 for 70 minutes.
The resultant membrane on the matting material was then inserted into a labora-tory test cell under conditions according to Example 1 to achieve a 53~6 current efficiency for a period of 78 days.
A matting material was applied over a Buchner funnel and dried at 150C. for 45 minutes as described in Example 1. A thermoplastic material slurry was made according to Example 1 and applied in a series of four coats the first two of which were brushed over the entire surface, the third and fourth were partial coatings to cover up holes. The film was fused at a temperature of 250C. for thirty minutes and air tested for leaks after fusing each coat. The resultant film was then hydrolyzed in a solution of dimethyl sulfoxide and sodium hydorxide at a temperature of 80C. for a period of 70 minutes.
The resultant membrane was then placed in a laboratory cell for testing under conditions according to E.Yample 1 to achieve a current efficiency of approximately 60% for a time period of 67 days.
Thus it should be apparent from the foregoing description of the preferred embodiments that the method herein described accomplishes the objects of the invention and solves the problems attendant on conversion of diaphragm electrolytic cells to rnembrane electrolytic cells without the substantial capital costs associated with prior methods of conversion.
. . .
~R)n In the copolymer there should be sufficient repeating units according to formula(3) above~ to provide an -SO3H equivalent weight of about 800 to 1600. Materials having a water absorption rate of about 25 percent or greater are preferred since higher cell po-tentials-at any given current density are required for materials having less water absorption.
Similarily~ materials having a film thickness (unlaminated) of about 8 mils or more require higher cell potentials resulting in a lower power effidency.
Polymeric materials of this type are further described in the following patents:U.S. Patent Nos. 3~041,317; 3,282,875;
3,560,568; 3,624,033; 3,718,627; and British Patent No. 1,184,321. Polymeric materials as aforedescribed are available from E.I. duPont deNemours ~cCo. under the trademark NAFION.
Polymeric materials according t~ formulas 1 and 2 can also be made wherein the ion exchange group instead of being a sulfonic acid exchange group could be many other types of structures. One pacticular type of s~ructure is a carboxyl group ending in either an acid9 and ester or a salt to form an ion exchange group similiar to that of the sulfonic acid. In such a group instead of SO2F one would find COOR2 wherein R2 may be selected from the group of hydrogen, an alkali metal ion and an organic radicalThese polymeric materials are available presently from F. I. duPont deNemours dc Co. Furthermore it has 2~ been found that a substrate material such as NAFION having any ion exchange group or function group capable of being converted into an ion exchange group or a function group in which an ion exchange group can easily be introduced may include such groups as oxy acids, salts, or esters of Cl-C3 carbon, nitrogen, silicon, phosphor-~-s, sul:Eur, chlorine, arsenic,selenium, or tellurium.
., 37:~7 The NAFION material along with any filler materials used may be applied by any method which will result in a thin uniform film as required above to form an adequate membrane over top of the deposited mating material Among the methods through to be suitable would be: deposition from a slurry, drawiny the material onto the surface of the matting material with a vacuum, pouring the slurry over the matting material, brushing on a solution, or spraying in some fashion such as by a plasma spray. Vacuum form-ing from a slurry may be the most economic method since the equip-ment used for such a method would be the same as that used to apply the asbestos diaphragms.
A typical slurry for deposition upon a foraminous cathode with the mat in place can be made by using NAFION particulate material with a 1208 equivalent weight or 1073 equivalent weight mixed with a suitable solvent such as 1,1,2-trichlorotrifluoro-ethane which is available from E.I. duPont deNemours & Co. under the trademark FREON 113. FREON 113 works well because it softens the NAFION particles thus making it easier to reduce the particle size by shearing to yield a very uniform NAFION dispersion. It is also believed an aqueous slurry of NAFION with an alkylaryl-polyether alcohol available from Diamond Shamrock Corp. under the trademark HYONIC PE260 used as a wetting agent would also perform well. The NAFION particulate material is in the sulfonyl fluoride form in a thermoplastic polymeric layer. A typical method for making such a suspension would be to utilize a stirrer fitted with a jacketed chamber and a reflux condenser into which NAFION
particulate material is added along with FREON 113 solvent. The system is heated wit~ hot water to boil the FREON 113 solvent and cold water is run through the reflux condenser to condense the FREON 113 solvent. Refluxing of the NAFION and FREON 113 mixture for approximately 10 minutes and then shearing for 30 minutes while continuing to reflux the FREON 113 solvent, produces a good _ 9 _ NAFION slurry from which to deposit a film onto the matting material surface. Various thermoplastic materials compatible with NAFION may be used as fillers :in the slurry to reduce the cost while producing a good film. Examples of such fillers would be a fluorinated ethylene propylene copolymer or a perfluoro-alkoxy material.
The NAFION slurry may be applied to the support structure in various ways, the object being to produce a continuous uniform film after fusing. Subsequent to application - 9a -. ~.
'71~7 the FREON 113 is allowed to evaporate and then the particulate material is fused into a film. This is accomplished by baking the entire foraminous electrode assembly in an oven generally at a temperature in the range of 240to 300C. More than one application and subsequent fusion of a thermoplastic material slurry may be necessary in order to produce hole ~ree continuous film.
Once a thin and uniform film is formed on the surface of the mattin8 material which is substantially impermeable to hydraulic flow, the film may then be hydrolyzed into the infusible ion exchange sulfonic acid form. Hydrolyzing or saponifying of the NAFION is a fairly simple procedure for the conversion of a sulfonyl fluoride form to the free acid form. This may be accomplished by soaking the film in a sodium hydroxide solution, sodium hydroxide in dimethyl sulfoxide solution, potassium hydroxide solution, or potassium hydroxide in dimethyl sulfoxide solution. Any of these treatments appear to work equally well although different temperatures and times are required to accomplish the hydrolysis.
Once this has been accomplished, the electrode is then ready for use in a standard diaphragm electrolytic cell. The conditions of the cell should be altered to operate the cell as a membrane electrolytic cell.
Various means of improving these substrate materials have been sought, one of the most effective of which is the surface chemical treatment of the substrate itself.
Generally these treatments consist of reacting the sulfonyl fluoride pendent groups with substances which will yield less polar bonding and thereby absorb fewer water molecules by hydrogen bonding. This has a tendency to narrow the pore openings through which the càtions travel so that less water of hydration is transmitted with the cations through the membrane. An example of this would be to react the ethylene diamine with the pendent groups in the sulfonyl fluoride form to tie two of the pendent groups together by two nitrogen atoms in the ethylene diamine. Generally, in a film thickness of 7 mils, the surface treatment will be donle to a depth of approximately 2 mils on one side of the film by control-ling the time of reaction. This will result in good electrical conductivity and cation trans-mission with less hydroxide ion and associated water reverse migration.
The resultant membrane electrolytic cell will yield a high current density, a lower sodium chloride concentration in the resultant sodium hydroxide solution compared to 71'~
;tandard diaphragm cell, a higher resultant sodium hydroxide concentration, good utiliza-tion of existing cell space, longer lifetimes for the cell and a lower potential. Thus, those skilled in the art will recognize the advantages of the present invention to the chlorine and caustic industry.
In order that those skilled in the ar~ may more readily understand the present invention and certain preferred aspects by which it may be practiced, the following specific examples are afforded.
EXAMP1.E 1 For testing in a laboratory cell, a membrane was formed over an asbestos matting using a auchner funnel as a framework structure over which to form the matting material. The matting material consisted of asbestos plus 5% fluorinated ethylene propylene copolymer as a binder to form a suspension in water. A vacuum was pulled on the Buchner funnel to draw the matting material onto the foraminous surface of the funnel until thP porosity was reduced so as to capture particles in the size range of one micron. A thermoplastic material sl~rry was made from a 1208 equivalent weight NAFION (a Trademark for p~rfluorosulonic acid resin) resin particle material mixed with a solvent known as FREON 113, a Trademark for 1,1,2-trichlorotri~luoroethane. T~e mixture was stirred at 47.8C. to obtaina lO gram slurry The slurry was then filtered thr~ugh the matting material overtop of the Buchner funnel. Fusion of the NAFION resin particles was accom-plished by baking tha matting material with the ~AEION particles on the surface at a temperature of 300C. for 60 minutes. This resulted in a thin and uniform film which was substantially impermeable to hydraulic flow. Thereafter the NAFlON was hydroly~ed in a solution of dimethyl sulfoxide and water plus 1096 sodium hydroxide at a temperature of 70C. for a time period of 70 minutes to convert the sulfonyl fluorideform to the cation exchange sulfonic acid form.
This membrane over the mattin~ material was then inserted into a laboratory test cell with a flow ral:e of .053 cc/min/sq.in. of cathode area, a head of 14 inches of brine, a potential of 4.29 volts and a current of 6.2~ arnperes at 92C~ to achieve a current efficiency of 6496 over a period of 37 days.
'7i'~
An asbestos matting was formed over a Buchner funnel as described in Example 1. A thermoplastic material slurry was made utilizing a 1073 equivalent weight NAFION
resin particle material in FREON 113 solvent ~1,1,2-trichlorotrifluoroethane~ and refluxed at 50C. for 10 minutes. The resultant slurry was then poured over the asbestos mat. After evaporation of the FREON 113, the NAFION resin particles were fused at a temperature of 275C. for 30 minutes into a thin and uniform film. It was then hydrolyzed in 35% sodium hydroxide for one week.
The resultant membrane over the matting material was then inserted into a laboratory test cell under conditions according to Example 1 to achieve a maximum current efficiency of 5096.
An asbestos slurry was formed over a Buchner funnel according to Example 1. A
slurry of thermoplastic material was made of 1073 equivalent weight NAFION resin particle material in FREON 113 solvent and refluxed according to Example 2. The slurry was then drawn onto the matting material with a 26 inch vacuum. The NAFION resin particles were fused at a temperature of 250C. for 30 minutes, a second coat of the slurry was added by eye dropper to close holes in the film and a subsequent fusion was performed. The material was then hydroly~ed in dimethyl sulfoxide and sodium hydroxide at a temperature for 80 for 70 minutes.
The resultant membrane on the matting material was then inserted into a labora-tory test cell under conditions according to Example 1 to achieve a 53~6 current efficiency for a period of 78 days.
A matting material was applied over a Buchner funnel and dried at 150C. for 45 minutes as described in Example 1. A thermoplastic material slurry was made according to Example 1 and applied in a series of four coats the first two of which were brushed over the entire surface, the third and fourth were partial coatings to cover up holes. The film was fused at a temperature of 250C. for thirty minutes and air tested for leaks after fusing each coat. The resultant film was then hydrolyzed in a solution of dimethyl sulfoxide and sodium hydorxide at a temperature of 80C. for a period of 70 minutes.
The resultant membrane was then placed in a laboratory cell for testing under conditions according to E.Yample 1 to achieve a current efficiency of approximately 60% for a time period of 67 days.
Thus it should be apparent from the foregoing description of the preferred embodiments that the method herein described accomplishes the objects of the invention and solves the problems attendant on conversion of diaphragm electrolytic cells to rnembrane electrolytic cells without the substantial capital costs associated with prior methods of conversion.
. . .
Claims (13)
1. A method for forming a membrane over a standard diaphragm cell foram-inous electrode comprising the steps of: suspending a matting material in a fluid medium; inserting a foraminous electrode into the suspension; vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material;
applying to the surface of the foraminous electrode with the matting material there-on, a layer of thermoplastic polymeric material including a material containing carboxyl ion exchange groups and baking the foraminous electrode with the layers in place until the thermoplastic polymeric material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow.
applying to the surface of the foraminous electrode with the matting material there-on, a layer of thermoplastic polymeric material including a material containing carboxyl ion exchange groups and baking the foraminous electrode with the layers in place until the thermoplastic polymeric material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow.
2. A method according to claim 1 wherein the thermoplastic polymeric material is applied by vacuum forming a slurry of thermoplastic polymeric material from a 1,1,2-trichlorotrifluoroethane solvent.
3. A method according to claim 1 wherein the thermoplastic polymeric material is applied by plasma spray.
4. A method according to claim 1 wherein said baking step is done at a temperature within the range of 240° to 300°C.
5. A method according to claim 1 wherein the matting material is selected from the group of: asbestos and cellulose.
6. A membrane separator for a standard diaphragm electrolytic cell comprising:
a standard diaphragm cell foraminous electrode; on the surface of said standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm foraminous electrode; and on the surface of said matting material, a thin and uniform hydraulically impermeable cation exchange membrane consisting essentially of a film of copolymer having the repeating structure units of the formula:
(1) and (2) wherein R represents the group , in which fluorine or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is 0 or 1; X is fluorine, chlorine or trifluoromethyl; X1 is X or ; a is 0 or integer from 1 to 5; and wherein R2 is an ion exchange group selected from the group of oxy acids, salts and esters of C1-C3 carbon, and an ion exchange group based on one of nitrogen, silicon, phosphorus, sulfur, chlorine, arsenic, selenium or tellurium.
a standard diaphragm cell foraminous electrode; on the surface of said standard diaphragm cell foraminous electrode, a layer of matting material of such thickness as to substantially reduce the porosity of the standard diaphragm foraminous electrode; and on the surface of said matting material, a thin and uniform hydraulically impermeable cation exchange membrane consisting essentially of a film of copolymer having the repeating structure units of the formula:
(1) and (2) wherein R represents the group , in which fluorine or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1,2 or 3; n is 0 or 1; X is fluorine, chlorine or trifluoromethyl; X1 is X or ; a is 0 or integer from 1 to 5; and wherein R2 is an ion exchange group selected from the group of oxy acids, salts and esters of C1-C3 carbon, and an ion exchange group based on one of nitrogen, silicon, phosphorus, sulfur, chlorine, arsenic, selenium or tellurium.
7. A method for forming a membrane over a standard diaphragm cell foraminous electrode comprising the steps of: suspending a matting material in a fluid medium; inserting a foraminous electrode into the suspension;
vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon, a layer of thermoplastic polymeric material including particles of perfluorosulfonic acid resin in the sulfonyl fluoride form;
baking the foraminous electrode with the layers in place until the thermoplastic polymeric material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow; and hydrolyzing perfluorosulfonic acid resin to change the sulfonyl fluoride form to the cation exchange sulfonic acid form.
vacuum forming a layer of the suspended matting material over the surface of the foraminous electrode so as to substantially reduce the porosity of the foraminous electrode material; applying to the surface of the foraminous electrode with the matting material thereon, a layer of thermoplastic polymeric material including particles of perfluorosulfonic acid resin in the sulfonyl fluoride form;
baking the foraminous electrode with the layers in place until the thermoplastic polymeric material is fused into a thin and uniform film on the surface of the matting material which is substantially impermeable to hydraulic flow; and hydrolyzing perfluorosulfonic acid resin to change the sulfonyl fluoride form to the cation exchange sulfonic acid form.
8. A method according to claim 7 wherein the thermoplastic polymeric material is applied by vacuum forming a slurry of thermoplastic polymeric material 1,1,2-trichlorotrifluoroethane solvent.
9. A method according to claim 7 wherein the thermoplastic polymeric material is applied by plasma spray.
10. A method according to claim 7 wherein said baking step is done at a temperature with the range of 240° to 300°C.
11. A method according to claim 7 wherein said hydrolyzing step is done in a solution having active ingredients selected from the group of:
sodium hydroxide, potassium hydroxide, sodium hydroxide in dimethyl sulfoxide, and potassium hydroxide in dimethyl sulfoxide.
sodium hydroxide, potassium hydroxide, sodium hydroxide in dimethyl sulfoxide, and potassium hydroxide in dimethyl sulfoxide.
12. A method according to claim 7 wherein the matting material is selected from the group of: asbestos and cellulose.
13. A membrane separator for a standard diaphragm electrolytic cell comprising: a standard diaphragm cell foraminous electrode; on the surface of said standard diaphragm cell foraminous electrode, a layer of a matting material of such thickness as to substantially reduce the porosity of said standard diaphragm cell foraminous electrode; and on the surface of said matting material, a thin and uniform hydraulically impermeable cation exchange membrane consisting essentially of a film of copolymer having the repeating structural units of the formula:
(1) and (2) wherein R represents the group , in which R1 is fluorine or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is O
or 1; X is fluorine, chlorine, or trifluoromethyl; X1 is X or ; a is O or integer from 1 to 5; and the units of formula (I) being present in an amount to provide a copolymer having an -SO3H equivalent weight in the range of 800 to 1600.
(1) and (2) wherein R represents the group , in which R1 is fluorine or perfluoroalkyl of 1 to 10 carbon atoms; Y is fluorine or trifluoromethyl; m is 1, 2 or 3; n is O
or 1; X is fluorine, chlorine, or trifluoromethyl; X1 is X or ; a is O or integer from 1 to 5; and the units of formula (I) being present in an amount to provide a copolymer having an -SO3H equivalent weight in the range of 800 to 1600.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/688,842 US4036728A (en) | 1976-05-21 | 1976-05-21 | Converting a diaphragm electrolytic cell to a membrane electrolytic cell |
| US688,842 | 1976-05-21 | ||
| US05/790,756 US4112149A (en) | 1976-05-21 | 1977-04-25 | Converting a diaphragm electrolytic cell to a membrane electrolytic cell |
| US790,756 | 1977-04-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118717A true CA1118717A (en) | 1982-02-23 |
Family
ID=27104291
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000278937A Expired CA1118717A (en) | 1976-05-21 | 1977-05-20 | Converting a diaphragm electrolytic cell to a membrane electrolytic cell |
Country Status (17)
| Country | Link |
|---|---|
| JP (1) | JPS52142678A (en) |
| AR (1) | AR218623A1 (en) |
| AU (1) | AU514868B2 (en) |
| BR (1) | BR7703280A (en) |
| CA (1) | CA1118717A (en) |
| DD (1) | DD131188A5 (en) |
| DE (1) | DE2722313A1 (en) |
| FI (1) | FI771620A (en) |
| FR (1) | FR2352073A1 (en) |
| GB (1) | GB1565876A (en) |
| IL (1) | IL52135A (en) |
| MX (1) | MX145160A (en) |
| NL (1) | NL7705600A (en) |
| NO (1) | NO771758L (en) |
| PL (1) | PL117739B1 (en) |
| RO (1) | RO72502A (en) |
| SE (1) | SE7705911L (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4470889A (en) * | 1980-06-11 | 1984-09-11 | The Dow Chemical Company | Electrolytic cell having an improved ion exchange membrane and process for operating |
| US4337137A (en) * | 1980-06-11 | 1982-06-29 | The Dow Chemical Company | Composite ion exchange membranes |
| US4358545A (en) * | 1980-06-11 | 1982-11-09 | The Dow Chemical Company | Sulfonic acid electrolytic cell having flourinated polymer membrane with hydration product less than 22,000 |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE788557A (en) * | 1971-09-09 | 1973-03-08 | Ppg Industries Inc | DIAPHRAGMS FOR ELECTROLYTIC CELLS |
-
1977
- 1977-05-13 MX MX169139A patent/MX145160A/en unknown
- 1977-05-17 DE DE19772722313 patent/DE2722313A1/en not_active Withdrawn
- 1977-05-17 JP JP5698477A patent/JPS52142678A/en active Pending
- 1977-05-18 SE SE7705911A patent/SE7705911L/en not_active Application Discontinuation
- 1977-05-19 PL PL1977198230A patent/PL117739B1/en unknown
- 1977-05-20 NL NL7705600A patent/NL7705600A/en not_active Application Discontinuation
- 1977-05-20 CA CA000278937A patent/CA1118717A/en not_active Expired
- 1977-05-20 DD DD7700199046A patent/DD131188A5/en unknown
- 1977-05-20 FI FI771620A patent/FI771620A/fi not_active Application Discontinuation
- 1977-05-20 IL IL7752135A patent/IL52135A/en unknown
- 1977-05-20 RO RO7790423A patent/RO72502A/en unknown
- 1977-05-20 AU AU25346/77A patent/AU514868B2/en not_active Expired
- 1977-05-20 FR FR7715495A patent/FR2352073A1/en active Granted
- 1977-05-20 NO NO771758A patent/NO771758L/en unknown
- 1977-05-20 GB GB21385/77A patent/GB1565876A/en not_active Expired
- 1977-05-20 AR AR267723A patent/AR218623A1/en active
- 1977-05-20 BR BR7703280A patent/BR7703280A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IL52135A0 (en) | 1977-07-31 |
| PL198230A1 (en) | 1978-02-13 |
| SE7705911L (en) | 1977-11-22 |
| AU514868B2 (en) | 1981-03-05 |
| AU2534677A (en) | 1978-11-23 |
| DE2722313A1 (en) | 1977-12-01 |
| BR7703280A (en) | 1978-03-14 |
| RO72502A (en) | 1982-05-10 |
| MX145160A (en) | 1982-01-12 |
| FI771620A (en) | 1977-11-22 |
| AR218623A1 (en) | 1980-06-30 |
| FR2352073A1 (en) | 1977-12-16 |
| NL7705600A (en) | 1977-11-23 |
| FR2352073B1 (en) | 1982-08-13 |
| JPS52142678A (en) | 1977-11-28 |
| NO771758L (en) | 1977-11-22 |
| PL117739B1 (en) | 1981-08-31 |
| GB1565876A (en) | 1980-04-23 |
| DD131188A5 (en) | 1978-06-07 |
| IL52135A (en) | 1980-05-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4112149A (en) | Converting a diaphragm electrolytic cell to a membrane electrolytic cell | |
| US5094895A (en) | Composite, porous diaphragm | |
| KR850000052B1 (en) | Improved composite ion exchange membranes | |
| US4341605A (en) | Process for cation permeable membrane with reinforcement fabric embedded therein and product thereof | |
| US4680101A (en) | Electrolyte permeable diaphragm including a polymeric metal oxide | |
| DE2713677C3 (en) | Hydraulically impermeable cation exchange membrane | |
| CA1072057A (en) | Electrolytic cell membrane conditioning | |
| US5288384A (en) | Wetting of diaphragms | |
| CA1141705A (en) | Diaphragm having zirconium oxide and a hydrophilic fluorocarbon resin in a hydrophobic matrix | |
| US4181592A (en) | Converting a diaphragm electrolytic cell to a membrane electrolytic cell | |
| US4093533A (en) | Bonded asbestos diaphragms | |
| US4547411A (en) | Process for preparing ion-exchange membranes | |
| US4604323A (en) | Multilayer cation exchange membrane | |
| CA1118717A (en) | Converting a diaphragm electrolytic cell to a membrane electrolytic cell | |
| US4253935A (en) | Method of preparing a diaphragm having a gel of a hydrous oxide or zirconium in a porous matrix | |
| JPS6045711B2 (en) | Electrolysis method and electrochemical cell | |
| US4686120A (en) | Multilayer cation exchange membrane | |
| US4125450A (en) | Previous diaphragms for cells for the electrolysis of aqueous solutions of alkali metal halides | |
| CA1146911A (en) | Oxygen electrode rejuvenation methods | |
| US4020235A (en) | Novel composite diaphragm material | |
| US4356068A (en) | Permionic membrane | |
| US4243504A (en) | Fluorovinyl ether polymers | |
| JPS591690A (en) | Porous diaphragm for electrolytic tank and production thereof | |
| FI68671C (en) | PERMEABEL DIAPHRAGM AV ETT HYDROFOBT ORGANIC POLYMER MATERIAL FOER ELECTROLYSIS AV EQUIPMENT ALKALINE METAL HALOGEN | |
| GB1498733A (en) | Diaphragms for electrolytic cells |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |