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EP0069772A1 - Opferverstärkung in kationaustauschmembranen. - Google Patents

Opferverstärkung in kationaustauschmembranen.

Info

Publication number
EP0069772A1
EP0069772A1 EP82900710A EP82900710A EP0069772A1 EP 0069772 A1 EP0069772 A1 EP 0069772A1 EP 82900710 A EP82900710 A EP 82900710A EP 82900710 A EP82900710 A EP 82900710A EP 0069772 A1 EP0069772 A1 EP 0069772A1
Authority
EP
European Patent Office
Prior art keywords
exchange membrane
cation exchange
reinforcing web
fluorinated polymer
anode
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.)
Granted
Application number
EP82900710A
Other languages
English (en)
French (fr)
Other versions
EP0069772B1 (de
EP0069772A4 (de
Inventor
Thomas Charles Bissot
Raimund Heinrich Silva
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Publication of EP0069772A1 publication Critical patent/EP0069772A1/de
Publication of EP0069772A4 publication Critical patent/EP0069772A4/de
Application granted granted Critical
Publication of EP0069772B1 publication Critical patent/EP0069772B1/de
Expired legal-status Critical Current

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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
    • 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
    • C25B13/02—Diaphragms; Spacing elements characterised by shape or form
    • 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

Definitions

  • Fluorinated polymers containing pendant side chains having functional groups are used as ion exchange membranes for electrochemical cells, particularly as membranes in chloralkali electrolytic cells.
  • the side chains on the fluorinated polymers contain sulfonyl or carboxyl groups or both.
  • the desired performance characteristics are obtained using a particularly thin membrane. It is desirable to minimize the thickness of this membrane, to reduce the operating voltage of the electrolytic cell.
  • the thin membranes are difficult to handle without damage or tearing during installation in the electrolytic cells. Accordingly, the thin membranes are frequently reinforced with woven or nonwoven webs. However, such reinforcing webs, in the operation of an electrolytic cell, cause uneven current distribution and increased operating voltage.
  • the instant invention provides an improved reinforced fluorinated polymer membrane which exhibits adequate strength for normal installation procedures without increasing the operating voltage of the cell.
  • the instant invention provides, in a fluorocarbon cation exchange membrane of at least one fluorinated polymer having side chains containing sulfonyl and/or carboxyl groups, the improvement which comprises a reinforcing web embedded in the fluorinated polymer which is degraded by hypochlorite.
  • the fluorocarbon cation exchange membranes which can be used in the instant invention have side chains containing either or both sulfonyl and carboxyl groups.
  • Polymers having sulfonyl functional groups typically contain pendant side chains having
  • R f is F, Cl, or a C, to C 10 perfluoralkyl radical, and preferably F.
  • the functional group in the side chains of the polymer will be present in terminal
  • Fluorinated polymers of this kind and their preparation are disclosed in United States Patents 3,282,875, 3,560,568, 3,718,627 and 3,041,317, hereby incorporated by reference. Perfluorinated polymers are preferred because of their inertness to a wide variety of chemicals. The equivalent weight of these polymers is generally about from 1000 to 1600.
  • the fluorinated polymers having carboxyl functional groups are typically polymers having a fluorinated hydrocarbon backbone chain to which are attached the functional groups or pendant side chains which in turn carry the functional groups. Fluorinated polymers of this kind and their preparation are disclosed in British Patent 1,145,445, United States Patents 3,506,635, 4,116,888 and 3,852,326, all hereby incorporated by reference.
  • Preferred monomers for use in the preparation of such polymers are found in United States Patents 4,121,740 and 3,852,326, also hereby incorporated by reference.
  • perfluorinated polymers are preferred.
  • Polymers are preferred in which the carbon atom adjacent to the carboxyl group bears one, and especially two, fluorine atoms.
  • perfluorinated polymers are also preferred.
  • the equivalent weight of the polymers having carboxyl functional groups is preferably about from 500 to 1500.
  • the membranes used in the instant invention comprise single layers of polymers having sulfonyl or carboxylic functional groups, single layers of polymer containing both types of functional groups, as well as laminar structures containing different polymers or different equivalent weights of similar polymers. Such laminar structures are preferred.
  • the central feature of the present invention is a reinforcing web embedded in the fluorinated polymer which is degraded by hypochlorite.
  • the reinforcing web provides added strength for the membrane during manufacturing operations and the installation of the membrane in an electrolytic cell, but, because of its degradability in hypochlorite, is disintegrated in operation.
  • the oxidation of the reinforcing web to low molecular weight products results in its removal from the membrane.
  • the disintegration of the reinforcing web eliminates the areas in the membrane that typically cause higher operating voltages.
  • reinforcing webs can be used in the present invention. These include woven and knitted fabrics as well as nonwoven felts and papers and randomly dispersed fibrils.
  • the particular composition of the reinforcing web can also vary widely, including most natural and synthetic fibers.
  • Representative of reinforcing fibers that can be used are those of cotton, linen, silk, rayon, acetate, nitrocellulose, nylon, polyester, polyvinyl alcohol, polyacrylonitriles, polyolefins and cellulose.
  • nonwoven materials which can be used in the present invention lightweight tissue paper has been found particularly satisfactory.
  • a low denier rayon is particularly preferred.
  • the reinforcing web be. embedded in the fluorinated polymer. That is, the reinforcing web must not be present throughout the entire thickness of the cation exchange membrane, since this would produce passages through the entire thickness of the membrane after the reinforcing web was degraded and removed.
  • the reinforcing web is completely encapsulated in the fluorinated polymer.
  • the reinforcing web is preferably embedded in the fluorinated polymer having sulfonic acid groups in the pendant side chains.
  • the thickness of the reinforcing web can vary with the total thickness of the fluorocarbon cation exchange membrane. However, in general, the reinforcing web has a thickness of about from 1 to 5 mil (25 to 127 micron) and preferably of about from 2 to 4 mil (50 to 101 micron).
  • the cation exchange membranes of the present invention exhibit increased structural integrity and are resistant to tears often encountered in the installation of such membranes in an electrolytic cell. This structural integrity is achieved without the presence of permanent reinforcing materials such as perfluorinated polymer webs.
  • the reinforcing web is degraded so as to not interfere with the electrical conduction of the membrane.
  • the voids remaining after disintegration of the reinforcing web actually aid in electrical conduction, thereby further reducing the voltage requirements of the operating cell.
  • the period for degradation of the reinforcing web will, of course, vary with the particular material selected, the thickness of the reinforcing web and the operating conditions of the cell. In general, however, the period of degradation will vary from several hours to up to two months.
  • the membranes of this invention can be used in any known membrane electrochemical cell, especially cells for the electrolysis of brine.
  • the membrane can be held in contact with either the anode or the cathode with the aid of a hydraulic head in one cell compartment, or with an open-mesh or grid or woven soacer to urge the membrane against the electrode. It is often advantageous for the membrane to be in contact with both porous anode and porous cathode in narrow-gap cells of this type. Such arrangements minimize the resistance contributed by the anolyte and catholyte, thus providing for operation at low voltage.
  • the membranes of this invention can also be used in a solid polymer electrolyte or composite electrode/membrane arrangement, in which a thin porous anode and/or porous cathode are attached directly to the membrane surface, and rigid current collectors can also be used in contact with these electrodes.
  • either or both of the electrodes can have a catalytically active surface layer of the type known in the art for lowering the overvoltage at an electrode.
  • Such electrocatalyst can be of a type known in the art, such as those described in U.S. Patents 4,224,121 and
  • the membranes described herein can also be modified on either surface or both surfaces thereof so as to have enhanced gas release properties, for example by providing optimum surface roughness or smoothness, or, preferably, by providing thereon a gas- and liquid-permeable porous non-electrode layer.
  • Such non-electrode layer can be in the form of a thin hydrophilic coating or spacer and is ordinarily of an inert electroinactive or non-electrocatalytic substance.
  • Such non-electrode layer should have a porosity of 10 to 99%, preferably 30 to 70%, and an average pore diameter of 0.01 to
  • a non-electrode layer ordinarily comprises an inorganic component and a binder; the inorganic component can be of a type as set forth in published UK Patent
  • Composite structures having non-electrode layers and/or electrocatalyst composition layers thereon can be made by various techniques known in the art, which include preparation of a decal which is then pressed onto the membrane surface, application of a slurry in a liquid composition
  • Such structures can be made by applying the indicated layers onto membranes in melt-fabricable form, and by some of the methods onto membranes in ion-exchange form; the polymeric component of the resulting structures when in melt-fabricable form can be hydrolyzed in known manner to the ion-exchange form.
  • Non-electrode layers and electrocatalyst composition layers can be used in combination in various ways on a membrane.
  • a surface of a membrane can be modified with a non-electrode layer, and an electrocatalyst composition layer disposed over the latter.
  • One preferred type of membrane is that which carries a cathodic electrocatalyst composition on one surface thereof, and a non-electrode layer on the opposite surface thereof.
  • Membranes which carry thereon one or more electrocatalyst layers, or one or more non-electrode layers, or combinations thereof, can be employed in an electrochemical cell in a narrow-gap or zero-gap configuration as described above.
  • the membranes of this invention after degradation of the reinforcing web, have another surprising advantage. They are more resistant to the deleterious effect of Na 2 SO 4 in the brine than corresponding membranes containing carboxylic or carboxylic and sulfonyl ion exchange resins and a perfluorocarbon reinforcing web, but never having contained a degradable reinforcing web.
  • the control membranes suffer deleterious effects when the brine contains 30 g/1 or even as little as 10 g/1.
  • a reinforced cationic ion exchange membrane was prepared by thermally bonding together two polymeric layers.
  • a cathode surface layer was used consisting of 51 microns (2 mils) of a copolymer of tetrafluoroethylene (TFE) and methyl perfluoro (4,7-dioxa-5-methyl-8-noneate) (EVE) and having an equivalent weight of 1080.
  • An anode surface layer was used consisting of 127 microns (5 mils) of a copolymer of TFE and perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) (PSEPVE) and having an equivalent weight of 1100.
  • PSEPVE perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluoride)
  • PSEPVE perfluoro (3,6-dioxa-4-methyl-7-octenesulfonyl fluor
  • the laminate was made in two steps using a heated platen press. In the first step the TFE/PSEPVE copolymer was pressed into the tissue paper at 270°C and 3.23 MPa (469 psig) for 1 min. In the second step the TFE/EVE layer was thermally bonded at 250oC at 1.1 MPa (156 psig) for 1 min. The resulting laminate was hydrolyzed in a bath containing 30% dimethyl sulfoxide (DMSO) and 11% potassium hydroxide (KOH) for 20 minutes at 90°C.
  • DMSO dimethyl sulfoxide
  • KOH potassium hydroxide
  • the resulting construction was leak-free as determined by a vacuum leak checker.
  • the laminate was treated with a hot solution of 5% sodium hypochlorite (NaOCl) where it was found that the paper was leached out after about 1 hour.
  • NaOCl sodium hypochlorite
  • a portion of the laminate so treated was mounted wet in a laboratory cnloralkali cell having an active area of 45 cm 2 between a dimensionally stable anode and a mild steel expanded metal cathode.
  • the cell was operated at 80oC with a current density of 3.1 KA/m 2 .
  • the anolyte salt content was held at 200 gpl. Water was added to the catholyte to maintain the concentration of the caustic produced at 32 ⁇ 1%.
  • a cationic ion exchange membrane containing a temporary reinforcement is prepared by thermally bonding together the following layers in the order specified.
  • a cathode surface layer consisting of a 25 micron (1 mil) film of TFE/EVE having an equivalent weight of 1080.
  • This construction is thermally bonded and hydrolyzed.
  • the resulting laminate shows improved tear resistance over a nonreinforced construction of similar thickness. If tested in a laboratory cell under the conditions of Example 1, except that the cell is operated at 90°C, after 7 days of operation the membrane is expected to perform well at 3.63 volts and 95% current efficiency. After 7 days of operation, removal and examination of the membrane will indicate a substantial total dissolution of the rayon fibers, leaving a pattern of channels where the fabric had been.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
EP82900710A 1981-01-16 1982-01-15 Opferverstärkung in kationaustauschmembranen Expired EP0069772B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US22565181A 1981-01-16 1981-01-16
US225651 1981-01-16

Publications (3)

Publication Number Publication Date
EP0069772A1 true EP0069772A1 (de) 1983-01-19
EP0069772A4 EP0069772A4 (de) 1983-05-16
EP0069772B1 EP0069772B1 (de) 1986-07-16

Family

ID=22845691

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82900710A Expired EP0069772B1 (de) 1981-01-16 1982-01-15 Opferverstärkung in kationaustauschmembranen

Country Status (3)

Country Link
EP (1) EP0069772B1 (de)
DE (1) DE3271961D1 (de)
WO (1) WO1982002564A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4552631A (en) * 1983-03-10 1985-11-12 E. I. Du Pont De Nemours And Company Reinforced membrane, electrochemical cell and electrolysis process
US4539084A (en) * 1983-03-10 1985-09-03 E. I. Du Pont De Nemours And Company Unreinforced membrane, electrochemical cell and electrolysis process
ZA952384B (en) * 1994-04-13 1996-09-23 Nat Power Plc Cation exchange membranes and method for the preparation of such membranes
JP4150867B2 (ja) 1998-05-13 2008-09-17 ダイキン工業株式会社 燃料電池に使用するのに適した固体高分子電解質用材料

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4169023A (en) * 1974-02-04 1979-09-25 Tokuyama Soda Kabushiki Kaisha Electrolytic diaphragms, and method of electrolysis using the same
US4021327A (en) * 1975-04-29 1977-05-03 E. I. Du Pont De Nemours And Company Reinforced cation permeable separator
US4204938A (en) * 1975-06-11 1980-05-27 Rhone-Poulenc Industries Method of making porous plastic diaphragms and the resulting novel diaphragms
FR2355926A1 (fr) * 1975-11-21 1978-01-20 Rhone Poulenc Ind Diaphragme selectif d'electrolyse
JPS52145397A (en) * 1976-03-31 1977-12-03 Asahi Chem Ind Co Ltd Electrolysis
JPS53149881A (en) * 1977-06-03 1978-12-27 Asahi Glass Co Ltd Strengthened cation exchange resin membrane and production thereof
US4191618A (en) * 1977-12-23 1980-03-04 General Electric Company Production of halogens in an electrolysis cell with catalytic electrodes bonded to an ion transporting membrane and an oxygen depolarized cathode
US4209368A (en) * 1978-08-07 1980-06-24 General Electric Company Production of halogens by electrolysis of alkali metal halides in a cell having catalytic electrodes bonded to the surface of a porous membrane/separator
US4311566A (en) * 1980-07-30 1982-01-19 Ppg Industries, Inc. Electrolyte permeable diaphragm

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8202564A1 *

Also Published As

Publication number Publication date
DE3271961D1 (en) 1986-08-21
EP0069772B1 (de) 1986-07-16
EP0069772A4 (de) 1983-05-16
WO1982002564A1 (en) 1982-08-05

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