CA1162604A - Asbestos diaphragms for electrochemical cells and the manufacture thereof - Google Patents

Asbestos diaphragms for electrochemical cells and the manufacture thereof

Info

Publication number
CA1162604A
CA1162604A CA000360618A CA360618A CA1162604A CA 1162604 A CA1162604 A CA 1162604A CA 000360618 A CA000360618 A CA 000360618A CA 360618 A CA360618 A CA 360618A CA 1162604 A CA1162604 A CA 1162604A
Authority
CA
Canada
Prior art keywords
asbestos
diaphragms
plastic
electrochemical cells
manufacture
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
Application number
CA000360618A
Other languages
French (fr)
Inventor
Karl Hohne
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.)
Siemens AG
Original Assignee
Siemens AG
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 Siemens AG filed Critical Siemens AG
Application granted granted Critical
Publication of CA1162604A publication Critical patent/CA1162604A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/44Fibrous material
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25BELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00Diaphragms; Spacing elements
    • C25B13/04Diaphragms; Spacing elements characterised by the material
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00Electrolytes
    • H01M2300/0002Aqueous electrolytes
    • H01M2300/0014Alkaline electrolytes
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31652Of asbestos

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Fuel Cell (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

ABSTRACT OF THE DISCLOSURE
The invention relates to a method for the manufacture of diaphragms for electrochemical cells by impregnating asbestos paper with an organic plastic, and has as its principal object the development of such a method in a manner such that asbestos diaphragms which have high mechanical strength and are also cost-effective can be manufactured in efficient production.
According to the invention, it is provided for this purpose to treat asbestos paper made by extrusion with a solution of polyvinylchloride or polysulfone in an organic solvent. The diaphragms prepared by the method according to the invention are particularly suitable as cover layers in in fuel cells with an alkaline electrolytc.

Description

~16;2~)4 Tl~e present invention rclates to a method for the manufacture of diaphragms ~or electrochemical cells by impregnating asbestos paper with an organic plastic, and to as6estos diaphragms prepared by such a method.
In addition to suf$icient porosity and high chemical resistance to the media used, diaphragms for electrochemical cells must, in particular, also exhibit high mechanical strength. Accordingly, it is known to use in fuel cells asbestos diaphragms which contain, for example, high-purity asbestos fibers and plastics, in which the plastic is a binder of methacrylic acid ester, polysulfones, chlorosulfonated polyethylene or chloroprene in amounts o$ 0.5 to 6% by weight, in particular, 1.5 to 3% by weight, referred to the weight of the as~estos fibers (British Patent 1,213,472). In the preparation o~ the as~estos diaphragms, the plastic is added to the asbestos fibers in the $orm of an aqueous dispersion.
United ~tates ~atent 3,583,8~1 describes, $or use iD. electrochemical cells, particularly fuel cells, a gas-tight mem6rane of high mechanical strength o$ as~estos or carbon material in iber form and a plastic binder in which, in the fabrication of the membrane from the fiber material, a butadiene-styrene-acrylonitrile copolymerizate is added to the former (copolymerizate content of 6 to 15% by weight, referred to the fiber material) and wherein the nitrile groups of t~e copolymerizate are saponified to carboxyl groups after the membrane has been formed.
The methods mentioned are not well suited for the efficient manufac-ture of asbestos diaphragms for electrochemical cells, however, since they are relatively expensive. In general, the manufacture of diaphragms with an asbestos fiaer base also is known, where asbestos paper is impregnated with a plastic material and is subsequently heated to remove the solvent or dis-persing agent for the plastic material.

~16~ 4 It is an ob~ect of the present invention to develop a method of the above-mentioned type in such a manner that, starting wi.th asbestos paper, asbestos diaphragms which have high mechanical strength and are cost-effective can be manufactured in efficient production.
According to the present invention, this and other objects are achi0ved by treating asbes*os paper made by extrusion with a solution of poly-vinylchloride or polysulfone in an organic solvent.
Thus, in accordance with one broad aspect of the invention, there ~, gG~s - f ~'9/~f is provided a method for the manufacture of/diaphragms for electrochemical lQ cells by impregnating as-bestos paper with an organic plastic, comprising treat-ing asbestos paper made by extrusion wi~h a solution of a plastic member select-ed from polyvinylchloride and polysulfone in an organic solvent.
In accordance with another broad aspect of the invention there is provided a gas-tight diaphragm for electrochemical cells consisting essentially of asbestos paper made by extrusion and containing from about 5 to about 15%
by weight thsreof of a plastic selected from polyvinylchloride and polysulfone.
Essentially, two types of commercial asbestos paper are available which differ as to their method of manufacture. The one type is produced by a casting process, while the other type is produced by an extrusion process.
2Q The as~estos paper made by the casting process has the disadvantage that it is relatively expensive. Asbestos papers made by the extrusion process are con-siderably-cheaper ~their cost is only about 5% of the papers made by the cast-ing process~. However, in these latter asbestos papers so strong a tendency for gas leaks occurs, evidently due to anisotropic strength behavior, that they cannot be utilized in electrochemical cells for safety reasons.
It now has been found surprisingly that the strength behavior of asbestos paper made by the extrusion process can be increased by impregnating it with a polyvinylchloride or polysulfone solution to such a degree that it can be used in electrochemical cells.
In the method according to the present invention, a plastic solution having a concentration of about 2 to 8% by weight is advantageously employed.
Although tetrahydrofuran preferably serves as the solvent, trichloroethylene, dichloromethane or acetone, for example, may also be used. The asbestos diaphragms preferably are made in such a manner that the asbestos paper is immersed in the plastic solution for about 5 to 15 minutes.
Asbestos diaphragms made according to the method of the present in-vention contain, in general, about 5 to 15% by weight plastic, i.e., polyvinyl-chloride or polysulfone, referred to the total weight of the diaphragm. With a plastic content larger than 15% by weight, the electric resistance of the diaphragms increases , and with a content less than 5% by weight, the mechanicalproperties become poorer.
Asbestos diaphragms according to the present invention are found to be gas-tight if used, for example, in and H2/O2 fuel cell with an alkaline electrolyte at the high operating temperature of 93°C, even after far more than 500 hours. These diaphragms also show no appreciable degradation of their electochemical properties.
The invention is explained in greated detail with the aid of the following, non-limiting examples.
EXAMPLE I
Preparation of Diaphragms For the preparation of asbestos diphragms, commerically available asbestos paper made by extrusion is immersed for 10 minutes in a 4.3% solution of polyvinylchloride (PVC) or polysulfone in tetrahydrofuran. Subsequently, the asbestos paper is freed of excess drops of solution by shaking and is 116~6 ~4 dried in air at room temperature. Thls is followod by post-drying in a photo press at about 80~C for about 3a minutes. The asbestos diaphragms obtained in this manner have a plastic content of about 10% by weight.
EXAMPLE II
Determination o~ the So-Called "Bubble Point"
For determining the gas-tightness of diaphragms, a hollow body is employed which is provided with an opening and a gas feeding tube, the opening of which is closed off ~y an asbestos diaphragm. The asbestos diaphragm is supported on the outside ~y a nickel screen and a perforated plate ollowing thereon. The en*ire arrangement is immersed in a ~eaker filled with water, and after a dwelling time of about 15 minutes, hydrogen is fed to the hollow body through the gas-feeding tube with increasing pressure until the first gas bubbles are observed at the diaphragm, i.e., when gas passes through the diaphragm.
EXA~PLE III
Determination of the So-Called "Bursting P~int"
To determine the mechanical strength behavior of the diaphragms, the above-described arrangement is used, with the exception that the asbestos diaphragm is not supported (i.e., neither by a support screen nor by a pe~fo-2Q rated plate). The hydrogen pressure is then increased until the diaphragmbursts ~y the sudden formation of cracks, i.e., becomes leaky.
EXAMPLE IV
Determination of the Permeability Th~e arrangement described also serves for determining permeability of the diaphragms to electrolytic liquid or water. In this case, water under pressure is fed to the hollow body through the gas feeding tube. The pres-sure is generated by a water column of 88.7 cm in a burette. The permeability 116~6~4 is determined by the amount of water passing through the diaphragm (area:
12.6 c~
The results o~ the a~ove tests are summarlzed in the ollowing Table wherein the values given are average values and the pressures are dif-ference pres-sures.
"Bursting Point" "Bubble Point" Permeability [bar] [bar][cm3/cm2-h-bar Asbestos diaphragm, 0.39 ~ 4.0 65 untreated Asbestos diaphragm, Q.68 > 4.0 57 with 10% PYC
As~estos diaphrag~, 0.75 ~ 4.Q 50 w~th 10% polysulfone As can be seen from the table, cracks form ~bursting point) in the asbestos diaphragms according to the invention only at higher pressures. If these pressures are taken as a measure of the mechanical strength, the latter is higher in the diaphrag~s according to the present invention by about 75 to 95%, i.e., almos* doubled, as compared to untreated diaphragms. With other asbestos papers it was possible to achieve, using polysulfone, improvements 2Q of up to nearly 400%.
The "b~Ele point" is above 4 bar in the untreated asbestos dia~
phragms as well as in the diaphragms according to the present invention.
The flow resistance in the pores of asbestos diaphragms should be as small as possi~le so that, for example, the water formed at the anode in H2/02 fuel cells can be transferred into the electrolyte space with a pressure drop as small as possible. Too high a pressure drop would lead to flooding of the electrode. ~ith a current of, for example, 1 A/cm2, 0.6 ml water are tiO4 for~ed per hour and c~2 electrode area in the oxidation of hydrogen. In order to discharge this a~unt of water with a pressure drop of 0.1 bar, the per-meability of the diaphragms must be at least 6 cm3/cm2-h-bar.
As can be seen from the table, the permeability of asbestos dia-phragms is substant~ally above the above-mentioned value, so that the slight lowering caused by the impregnation is not noticeable as a disadvantage. In addition, further investigations have shown that the impregnation also changes the electric resistance only slightly, i.e., increases it slightly.
EXAMPLE V
1~ Electrochemical Properties To determine the electrochemical properties of the asbestos dia-phragms according to the present invention, PVC-containing diaphragms are tested in a 3-ce~l H2/O2 fuel cell battery with supported electrodes and free electrolyte. Raney nickel-titanium electrodes serve as anodes and sedimented doped silver electr~des serve as cathodes. The active sur~ace cf the elec-trodes is 34~ cm . 8 m KOH serves as the electrolyte, and the operating pres-sures Cof H2 and 2~ are 2 bar.
The cell voltage/current density characteristics recorded during the operation of the battery show no difference from those of batteries with 2a untreated asbestos diaphragms, i.e., the electrical properties are not changed by the impregnation. At an operating temperature of 83C, the following elec-tric resistances are measured, for example, at the individual cells of the battery: ~.74, 0.70 and 0.72 mohm. These values also correspond to those of fuel cells ~ith untreated asbestos diaphragms.
The above-described fuel cell battery is otherwise also found to be gas-tight. No gas leaks occurred even at an operating temperature of 93C and after 53Q hours of operation.

6~4 The asbestos diaphragms according to the present invention find application particularly in fuel cells with alkaline electrolytes. In addi-tion, however, they may also be used, for example, in electrolysis apparatus.
If used in fuel cells or fuel cell batteries, these asbestos diaphragms can be used not only as cover layers for the electrodes but also as membranes in so-called gap evaporators, in which the water formed in the electrochemical re-action is removed from the electrolyte liquid.

; - 7 -,

Claims (5)

  1. THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
    PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

    l. A method for the manufacture of gas-tight diaphragms for electrochemical cells by impregnating asbestos paper with an organic plastic, comprising treating asbestos paper made by extrusion with a solution of a plastic member selected from polyvinylchloride and polysulfone in an organic solvent.
  2. 2. The method according to claim 1 wherein the concentration of said plastic in said organic solvent is from about 2 to 8% by weight.
  3. 3. The method according to claim l wherein the organic solvent is tetrahydrofuran.
  4. 4. The method according to claim 1 wherein said treating comprises im-mersing the asbestos paper in the plastic solution for about 5 to 15 minutes.
  5. 5. A gas-tight diaphragm for electrochemical cells consisting essential-ly of asbestos paper made by extrusion and containing from about 5 to about 15% by weight thereof of a plastic selected from polyvinylchloride and poly-sulfone.
CA000360618A 1979-09-20 1980-09-19 Asbestos diaphragms for electrochemical cells and the manufacture thereof Expired CA1162604A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19792938069 DE2938069A1 (en) 1979-09-20 1979-09-20 ASBEST DIAPHRAGMS FOR ELECTROCHEMICAL CELLS AND THEIR PRODUCTION
DEP2938069.6 1979-09-20

Publications (1)

Publication Number Publication Date
CA1162604A true CA1162604A (en) 1984-02-21

Family

ID=6081382

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000360618A Expired CA1162604A (en) 1979-09-20 1980-09-19 Asbestos diaphragms for electrochemical cells and the manufacture thereof

Country Status (5)

Country Link
US (1) US4367270A (en)
EP (1) EP0026362B1 (en)
JP (1) JPS601954B2 (en)
CA (1) CA1162604A (en)
DE (2) DE2938069A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2521174B1 (en) * 1982-02-08 1986-10-17 Electricite De France METHOD FOR REINFORCING AN ELECTROLYTIC CELL DIAPHRAGM
FR2521173B1 (en) * 1982-02-08 1986-04-18 Electricite De France METHOD OF ASSEMBLING ELEMENTS ON AN ASBESTOS FABRIC PLAYING THE DIAPHRAGM ROLE FOR ELECTROLYTIC CELLS
IT1173446B (en) * 1984-03-16 1987-06-24 Milano Politecnico COMPOSITE DIAPHRAGMS FOR ALKALINE ELECTROLYSIS OF WATER
DE19650316A1 (en) * 1996-12-04 1998-06-10 Basf Ag Process for modifying the flow resistance of diaphragms

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU143848A1 (en) 1961-05-31 1961-11-30 Е.С. Ихельзон Paper for alkaline battery separators
CA845032A (en) * 1966-12-03 1970-06-23 Hacker Heinz Gas-tight diaphragms for electrochemical cells
DE1294941B (en) * 1967-08-02 1969-05-14 Siemens Ag Process for the production of diaphragms, in particular diaphragms for fuel elements
FR1568410A (en) * 1968-04-12 1969-05-23
US3625770A (en) * 1969-06-02 1971-12-07 Mc Donnell Douglas Corp Flexible matrix and battery separator embodying same
JPS4911259B1 (en) * 1970-06-04 1974-03-15
ZA74315B (en) * 1973-01-17 1975-03-26 Diamond Shamrock Corp Dimensionally stable asbestos diaphragms
BE800949A (en) * 1973-06-15 1973-10-01 Solvay DIAPHRAGM FOR AN ELECTROLYSIS CELL
IT1033473B (en) * 1975-03-06 1979-07-10 Oronzio De Nora Impianti COMPOSITE MATERIAL FOR DIAPHRAGM AND PROCEDURE FOR OBTAINING IT
US4007059A (en) * 1975-08-20 1977-02-08 General Motors Corporation Electrochemical cell electrode separator and method of making it and fuel cell containing same
JPS5266929A (en) * 1975-12-01 1977-06-02 Yuasa Battery Co Ltd Method of producing lead battery separator
US4065534A (en) * 1976-04-20 1977-12-27 Ppg Industries, Inc. Method of providing a resin reinforced asbestos diaphragm
LU74835A1 (en) * 1976-04-26 1977-12-02
US4233347A (en) * 1978-10-02 1980-11-11 Hughes Aircraft Company Process for reinforcing structurally fragile inorganic fabrics

Also Published As

Publication number Publication date
US4367270A (en) 1983-01-04
JPS601954B2 (en) 1985-01-18
EP0026362A3 (en) 1981-05-13
EP0026362A2 (en) 1981-04-08
EP0026362B1 (en) 1983-10-19
JPS5655585A (en) 1981-05-16
DE3065375D1 (en) 1983-11-24
DE2938069A1 (en) 1981-04-02

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