US3583891A - Gas-tight diaphragms for electrochemical cells - Google Patents
Gas-tight diaphragms for electrochemical cells Download PDFInfo
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- US3583891A US3583891A US731324A US3583891DA US3583891A US 3583891 A US3583891 A US 3583891A US 731324 A US731324 A US 731324A US 3583891D A US3583891D A US 3583891DA US 3583891 A US3583891 A US 3583891A
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- binder
- weight
- diaphragms
- styrene
- gas
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- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 abstract description 33
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 abstract description 32
- 239000011230 binding agent Substances 0.000 abstract description 24
- 229920001577 copolymer Polymers 0.000 abstract description 20
- 239000002657 fibrous material Substances 0.000 abstract description 12
- 239000000463 material Substances 0.000 abstract description 11
- 238000007127 saponification reaction Methods 0.000 abstract description 6
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 abstract description 4
- 239000002243 precursor Substances 0.000 abstract description 3
- 150000002825 nitriles Chemical group 0.000 abstract 1
- 239000000835 fiber Substances 0.000 description 23
- 239000010425 asbestos Substances 0.000 description 19
- 229910052895 riebeckite Inorganic materials 0.000 description 19
- 239000006185 dispersion Substances 0.000 description 18
- 239000003792 electrolyte Substances 0.000 description 15
- 239000000126 substance Substances 0.000 description 14
- 239000002002 slurry Substances 0.000 description 9
- 239000000446 fuel Substances 0.000 description 7
- 125000002560 nitrile group Chemical group 0.000 description 7
- -1 polyethylene Polymers 0.000 description 7
- 229920000642 polymer Polymers 0.000 description 7
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 6
- 238000013019 agitation Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229920002126 Acrylic acid copolymer Polymers 0.000 description 4
- 239000012528 membrane Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 229920006395 saturated elastomer Polymers 0.000 description 4
- AGBXYHCHUYARJY-UHFFFAOYSA-N 2-phenylethenesulfonic acid Chemical compound OS(=O)(=O)C=CC1=CC=CC=C1 AGBXYHCHUYARJY-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229920000049 Carbon (fiber) Polymers 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000007792 addition Methods 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000004917 carbon fiber Substances 0.000 description 3
- 150000002148 esters Chemical class 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- NZIDBRBFGPQCRY-UHFFFAOYSA-N octyl 2-methylprop-2-enoate Chemical compound CCCCCCCCOC(=O)C(C)=C NZIDBRBFGPQCRY-UHFFFAOYSA-N 0.000 description 3
- 229920002994 synthetic fiber Polymers 0.000 description 3
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 2
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- 125000005397 methacrylic acid ester group Chemical group 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229920002818 (Hydroxyethyl)methacrylate Polymers 0.000 description 1
- NARVIWMVBMUEOG-UHFFFAOYSA-N 2-Hydroxy-propylene Natural products CC(O)=C NARVIWMVBMUEOG-UHFFFAOYSA-N 0.000 description 1
- UWRZIZXBOLBCON-UHFFFAOYSA-N 2-phenylethenamine Chemical compound NC=CC1=CC=CC=C1 UWRZIZXBOLBCON-UHFFFAOYSA-N 0.000 description 1
- KGIGUEBEKRSTEW-UHFFFAOYSA-N 2-vinylpyridine Chemical compound C=CC1=CC=CC=N1 KGIGUEBEKRSTEW-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- WOBHKFSMXKNTIM-UHFFFAOYSA-N Hydroxyethyl methacrylate Chemical compound CC(=C)C(=O)OCCO WOBHKFSMXKNTIM-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000012876 carrier material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 239000007857 degradation product Substances 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 125000001165 hydrophobic group Chemical group 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 125000005395 methacrylic acid group Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920000193 polymethacrylate Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 229940117958 vinyl acetate Drugs 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/14—Dynamic membranes
- B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
- B01D69/148—Organic/inorganic mixed matrix membranes
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/42—Acrylic resins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/44—Fibrous material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- a gas-tight diaphragm material of high mechanical stability comprised of fibrous material and a synthetic binder.
- the material is characterized by the fact that the binder therefor consists of a copolymer produced by the saponification of the nitrile groups of a butadiene/ styrene/acrylonitrile precursor and that the content of the binder is from 6 to by weight and particularly 8 to 12% relative to the weight of the fiber material.
- asbestos diaphragms in electrochemical cells, particularly in fuel cells.
- asbestos diaphragms are inserted between a supporting structure containing the electrolyte and the electrodes which border both sides, in order to reduce the danger of penetration of the reaction gas into the electrolyte.
- a number of synthetic dispersions have become known which possess the required chemical stability with respect to electrolytes. Adequate chemical stability is offered by dispersions of polychloroprene, polyethylene, polytrifiuorochloroethylene, polytetrafluoroethylene, polystyrene, polymethacrylate and butadiene/styrene copolymer.
- the disadvantage of these synthetic materials as a binder is that they are hydrophobic and therefore can be used only in amounts up to 6% by weight of the asbestos fiber. As a result, the mechanical stability of the diaphragms is unsatisfactory in many instances. By increasing the amount of the binder added to above 6% by weight, it is possible to obtain diaphragms of high stability, however, simultaneously worsening the electric conductivity and reducing the gas tightness.
- a binder for the fiber material which is comprised of a copolymer constituting hydratable groups, particularly carboxyl, hydroxy, sulfo or amino groups, with the amount of the binder used constituting 6 to 15 by weight, and particularly 8 to 12% by weight, of the weight of the fiber material.
- the production of the asbestos diaphragms is effected in a known manner by drawing the polymer on a fiber material from aqueous polymer dispersions.
- the dispersions used therefor may be those whose polymers already contain the hydratable groups, required by the present invention, as well as those polymers wherein hydratable groups are formed through a chemical aftertreatment of the finished diaphragm.
- Suitable binders are dispersions of copolymers based on styrene/styrene sulfonic acid, butadiene/styrene/styrene sulfonic acid, styrene/aminostyrene, butadiene/styrene/vinylpyridine, ethylene/vinylacetate and chlorosulfonated or carboxylated polyethylene.
- esters for methacrylic acids one may use esters of aliphatic alcohols with 1 to 10 C-atoms, as well as alicyclic alcohols.
- binders for the diaphragms of the present invention such polymers whose hydratable groups are freed only in the finished diaphragms through a chemical aftertreament.
- ester or nitrile groups of polymers may be subsequently saponified.
- Particularly preferred for this purpose are the butadiene/styrene/acrylonitrile copolymers.
- one will proceed in such a manner that the finished diaphragms will be brought into contact, at room or higher temperature, with the electrolytes to be used later, for example 2 N or 6 N KOH.
- the freeing of the hydratable groups may be effected independently of the electrolyte.
- the polymers employed in accordance with the present invention contain hydrophilic as well as hydrophobic groups.
- the installation of the hydrophilic groups into the binder results in the increasibility of the mechanical stability of the diaphragm by increasing the share of the binder, without at the same time impairing their wettability and thereby their gas-tightness, as well as electric conductivity.
- the diaphragms of the present invention are gas-tight up to above 2 atm. g. (atmospheres gauge) and operate completely undisturbed in fuel cells at approximately 70 C., in 6 N KOH, even for very long periods. In diaphragms of 0.25 to 0.6 mm. thickness, the electrical resistance is below 0259 -cm.
- the mechanical stability, especially the wet break strength as well as the chemical resistance of the diaphragms may be further increased by cross-linking the copolymers employed.
- butadiene containing copolymers may be polymerized peroxidically.
- the peroxides are added, for this purpose, to the binder prior to their application onto the fiber material, whereby the desired polymerization is brought about at the finished diaphragm through a thermal aftertreatment. Due to the relatively low binder content, this does not significantly affect the swellability of the diaphragms.
- the following may be used to advantage in lieu of the asbestos fibers as a carrier material: fibers, fleece, felts, tissues or paper of carbon, low alkali glass or fibers of synthetic material, for example polypropylene fibers.
- EXAMPLE 1 For a diaphragm of 300 cm. (36 mgr/cm. weight/ area) and approximately 0.5 mm. thickness, 12 g. dry, clean asbestos fibers are first dispersed to a slurry in 750 ml. Water. Subsequently, to this dispersion are added, by being dripped in under strong agitation, 2.4 g. of an aqueous dispersion, 40% by weight of dry substance, of a butadiene/styrene/acrylic acid copolymer (acrylic acid content -8% in copolymers). To effect complete precipitation onto the fiber, the mixture is admixed also with 25 ml. of cold saturated NH Al(SO solution.
- the mixture may be immediately processed into a diaphragm on a sheet former or a similar device. If dispersions are used with self-polymerizing additions, a thermal aftertreatment is necessary, depending on the addition, up to 140 C. for 20 to 30 minutes.
- EXAMPLE 2 To the fiber slurry indicated in Example 1, one adds, under strong agitation, 3.1 g. of an aqueous dispersion (30% by weight of dry substance) of a butadiene/styrene/acrylonitrile copolymer to content of acrylonitrile in the copolymer). For complete precipitation, ml. of a cold saturated NH Al(SO solution are also added. For saponification of most of the free nitrile groups of the binders to carboxyl groups (hydrophilation), the finished diaphragm is processed with 2 N KOH, at room temperature for minutes. Diaphragms thus produced are very well wetted by aqueous electrolytes and have a gas tightness up to above 2 atmospheres gauge.
- EXAMPLE 3 A felt of carbon fibers (thickness of felt 1 mm., area weight 18 mg./cm. is saturated with a dispersion (10% by weight of solid substance) of butadiene/styrene/ acrylic acid copolymer.
- the carbon felt is placed in a coagulating bath comprised of a cold saturated NH.,A1(SO.,) solution. After a single washing with distilled water it is pressed between two heatable, planar parallel plates, at 130 C. and 5-10 kp./cm. pressure, for 20 minutes.
- the diaphragm thus obtained has a thickness of 0.5 to 0.7 mm.
- the diaphragm When using a binder containing nitrile groups, in accordance with Example 2, the diaphragm must be aftertreated with 2 N KOH,'whereby the saponification of the nitrile groups takes place.
- EXAMPLE 4 To produce a diaphragm, 2,6 g. of an aqueous dispersion by weight of dry substance) of a butadiene/ styrene/styrene sulfonic acid copolymer (5% styrene sulfonic acid content in copolymer) are added to the fiber slurry which is produced from 12 g. of highly pure asbestos fibers in 750 ml. water. ml. 2 N H 80 are additionally admixed for a complete precipitation of the binder onto the fiber. Further processing is carried out as in Example 1.
- EXAMPLE 5 To a slurry dispersion of 12 g. blue asbestos fibers in 750 ml. water, 2.9 g. of an aqueous dispersion (30% by weight of dry substance) of a methylrnethacrylate/ octylmethacrylate-dimethylaminoethylmethacrylate copolymer are added, under strong agitation. After a completed precipitation and further treatment on the sheet former, diaphragms are obtained, which are particularly well suited for electrochemical cells with acid electrolytes.
- EXAMPLE 6 3.1 g. of an aqueous dispersion (2 8% by weight of dry substance) of a methylmethacrylate/dimethylaminoethy1- methacrylate copolymer are dripped into the fiber slurry of Example 5, under strong agitation. The production of these diaphragms, which are also particularly suitable for acid electrolytes, is effected analogously to Example 1.
- EXAMPLE 7 2.95 g. of an aqueous dispersion (30% by weight of dry substance) of a methylmethacrylate/octylmethacrylate hydroxyethylmethacrylate copolymer are added by dripping to the fiber slurry described in Examples 1 or 5, under strong agitation. After standing for 2 hours, the mixtures are processed into diaphragms on a sheet former or another suitable device and may be employed, according to the type of asbestos fiber used, either in acid or in alkaline electrolytes.
- EXAMPLE 8 3.2 g. of an aqueous dispersion (26% by weight of dry substance) of a methylmethacrylateloctylmethacrylate/2-hydroxypropylene methacrylate copolymer are added by dripping into a fiber slurry in accordance with Examples 1 and 5, under strong agitation. After standing for 3 hours, these mixtures also produce diaphragms, on the sheet former, which will be gas-tight up to above 2 atmospheres gauge.
- a gas-tight diaphragm material of high mechanical stability comprised of fibrous material selected from asbestos fibers and carbon fibers, and a synthetic hinder
- the improvement which comprises using a binder consisting of a copolymer which contains hydrated groups, said binder being a butadiene/styrene/acrylic acid copolymer produced by saponification of the nitrile groups of a butadiene/styrene/acrylonitrile precursor, said saponification being in the presence of said fibers, said binder being in an amount of from 6 to 15% by weight of the fibrous material.
- the membrane material of claim 1 wherein the binder consists of a cross-linkable butadiene/styrene/ acrylic acid copolymer.
- the method of forming a membrane material for a gas-tight diaphragm which comprises forming a slurry of a material selected from the group consisting of asbestos and carbon, which comprises adding from 6 to 15% by weight of a butadiene/styrene/acrylonitrile copolymer, containing hydratable groups, based upon the solids content to a dispersion of fibrous material selected from asbestos, and carbon fibers to form said slurry thereafter drawing the water from said sluury to form the membrane material and saponifying the nitrile group in the said copolymer.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Metallurgy (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Dispersion Chemistry (AREA)
- Organic Chemistry (AREA)
- Fuel Cell (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Paper (AREA)
- Inert Electrodes (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
Abstract
DESCRIBED IS A GAS-TIGHT DIAPHRAGM MATERIAL OF HIGH MECHANICAL STABILITY COMPRISED OF FIBROUS MATERIAL AND A SYNTHETIC BINDER. THE MATERIAL IS CHARACTERIZED BY THE FACT THAT THE BINDER THEREFOR CONSISTS OF A COPOLYMER PRODUCED BY THE SAPONIFICATION OF THE NITRILE GROUPS OF A BUTADIENE/ STYRENE/ACRYLONITRILE PRECURSOR AND THAT THE CONTENT OF THE BINDER IS FROM 6 TO 15% BY WEIGHT AND PARTICULARLY 8 TO 12% RELATIVE TO THE WEIGHT OF THE FIBER MATERIAL.
Description
United States Patent Ofice Patented June 8, 1971 US. Cl. 162-155 5 Claims ABSTRACT OF THE DISCLOSURE Described is a gas-tight diaphragm material of high mechanical stability comprised of fibrous material and a synthetic binder. The material is characterized by the fact that the binder therefor consists of a copolymer produced by the saponification of the nitrile groups of a butadiene/ styrene/acrylonitrile precursor and that the content of the binder is from 6 to by weight and particularly 8 to 12% relative to the weight of the fiber material.
It is known to use asbestos diaphragms in electrochemical cells, particularly in fuel cells. For example in fuel cells described in the French patent of addition No. 87,850, asbestos diaphragms are inserted between a supporting structure containing the electrolyte and the electrodes which border both sides, in order to reduce the danger of penetration of the reaction gas into the electrolyte.
It is also known that conventional asbestos diaphragms can only under specific operational conditions meet the demands placed upon fuel elements, The asbestos fibers or the asbestos papers swell strongly under the influence of an alkaline electrolyte, forming a fleece of unbound fibers which may cause considerable disturbance during the operation of the fuel element. Bound, commercially available, asbestos papers possess a low chemical stability of the binding means with respect to the electrolytes. Re-
action or degradation products from reactions between the binder and the electrolyte may lead to other significant disturbances with respect to the electrolyte.
It has been proposed, therefore, to produce gas-tight or hermetic diaphragms for fuel element from highly pure asbestos fibers whose binder is comprised of a synthetic material, stable to the electrolytes and used in amounts of from 0.5 to 6% by weight, and particularly from 1.5 to 3% by weight, relative to the weight of the asbestos fibers. According to this proposal, aqueous synthetic latices are used for the production of diaphragms drawn on asbestos fibers dispersed in water. Suitable synthetic latices are those which are not attacked by the aqueous electrolyte and which show good stability with respect to air or oxygen.
A number of synthetic dispersions have become known which possess the required chemical stability with respect to electrolytes. Adequate chemical stability is offered by dispersions of polychloroprene, polyethylene, polytrifiuorochloroethylene, polytetrafluoroethylene, polystyrene, polymethacrylate and butadiene/styrene copolymer. The disadvantage of these synthetic materials as a binder is that they are hydrophobic and therefore can be used only in amounts up to 6% by weight of the asbestos fiber. As a result, the mechanical stability of the diaphragms is unsatisfactory in many instances. By increasing the amount of the binder added to above 6% by weight, it is possible to obtain diaphragms of high stability, however, simultaneously worsening the electric conductivity and reducing the gas tightness.
We have now found that the properties of gas-tight diaphragms for electromechanical cells, particularly for fuel elements, can be considerably improved by using a binder for the fiber material, which is comprised of a copolymer constituting hydratable groups, particularly carboxyl, hydroxy, sulfo or amino groups, with the amount of the binder used constituting 6 to 15 by weight, and particularly 8 to 12% by weight, of the weight of the fiber material.
The production of the asbestos diaphragms is effected in a known manner by drawing the polymer on a fiber material from aqueous polymer dispersions. The dispersions used therefor may be those whose polymers already contain the hydratable groups, required by the present invention, as well as those polymers wherein hydratable groups are formed through a chemical aftertreatment of the finished diaphragm.
Suitable binders are dispersions of copolymers based on styrene/styrene sulfonic acid, butadiene/styrene/styrene sulfonic acid, styrene/aminostyrene, butadiene/styrene/vinylpyridine, ethylene/vinylacetate and chlorosulfonated or carboxylated polyethylene. To build up the hermetic diaphragms it is preferable to employ dispersions of copolymers of butadiene/styrene/acrylic acid, methacrylic acid/methacrylic acid ester, methacrylic acid/ methacrylic acid aminoalkylester, methacrylic acid ester/ methacrylic acid hydroxyalkylester, for example methacrylic acid octylester/methacrylic acid Z-hydroxypropylester and methacrylic acid octylester/methacrylic acid hydroxyethylester. As esters for methacrylic acids one may use esters of aliphatic alcohols with 1 to 10 C-atoms, as well as alicyclic alcohols.
As previously mentioned, it is also possible to use as binders for the diaphragms of the present invention, such polymers whose hydratable groups are freed only in the finished diaphragms through a chemical aftertreament. Thus, ester or nitrile groups of polymers may be subsequently saponified. Particularly preferred for this purpose are the butadiene/styrene/acrylonitrile copolymers. Preferably, one will proceed in such a manner that the finished diaphragms will be brought into contact, at room or higher temperature, with the electrolytes to be used later, for example 2 N or 6 N KOH. Naturally, the freeing of the hydratable groups may be effected independently of the electrolyte.
The polymers employed in accordance with the present invention contain hydrophilic as well as hydrophobic groups. The installation of the hydrophilic groups into the binder results in the increasibility of the mechanical stability of the diaphragm by increasing the share of the binder, without at the same time impairing their wettability and thereby their gas-tightness, as well as electric conductivity. The diaphragms of the present invention are gas-tight up to above 2 atm. g. (atmospheres gauge) and operate completely undisturbed in fuel cells at approximately 70 C., in 6 N KOH, even for very long periods. In diaphragms of 0.25 to 0.6 mm. thickness, the electrical resistance is below 0259 -cm.
The mechanical stability, especially the wet break strength as well as the chemical resistance of the diaphragms may be further increased by cross-linking the copolymers employed. Thus, for example, butadiene containing copolymers may be polymerized peroxidically. The peroxides are added, for this purpose, to the binder prior to their application onto the fiber material, whereby the desired polymerization is brought about at the finished diaphragm through a thermal aftertreatment. Due to the relatively low binder content, this does not significantly affect the swellability of the diaphragms.
According to a further embodiment of the invention the following may be used to advantage in lieu of the asbestos fibers as a carrier material: fibers, fleece, felts, tissues or paper of carbon, low alkali glass or fibers of synthetic material, for example polypropylene fibers.
The object of the present invention Will be disclosed in still greater details by means of the following examples.
EXAMPLE 1 For a diaphragm of 300 cm. (36 mgr/cm. weight/ area) and approximately 0.5 mm. thickness, 12 g. dry, clean asbestos fibers are first dispersed to a slurry in 750 ml. Water. Subsequently, to this dispersion are added, by being dripped in under strong agitation, 2.4 g. of an aqueous dispersion, 40% by weight of dry substance, of a butadiene/styrene/acrylic acid copolymer (acrylic acid content -8% in copolymers). To effect complete precipitation onto the fiber, the mixture is admixed also with 25 ml. of cold saturated NH Al(SO solution.
The mixture may be immediately processed into a diaphragm on a sheet former or a similar device. If dispersions are used with self-polymerizing additions, a thermal aftertreatment is necessary, depending on the addition, up to 140 C. for 20 to 30 minutes.
EXAMPLE 2 To the fiber slurry indicated in Example 1, one adds, under strong agitation, 3.1 g. of an aqueous dispersion (30% by weight of dry substance) of a butadiene/styrene/acrylonitrile copolymer to content of acrylonitrile in the copolymer). For complete precipitation, ml. of a cold saturated NH Al(SO solution are also added. For saponification of most of the free nitrile groups of the binders to carboxyl groups (hydrophilation), the finished diaphragm is processed with 2 N KOH, at room temperature for minutes. Diaphragms thus produced are very well wetted by aqueous electrolytes and have a gas tightness up to above 2 atmospheres gauge.
EXAMPLE 3 A felt of carbon fibers (thickness of felt 1 mm., area weight 18 mg./cm. is saturated with a dispersion (10% by weight of solid substance) of butadiene/styrene/ acrylic acid copolymer.
Subsequently, the carbon felt is placed in a coagulating bath comprised of a cold saturated NH.,A1(SO.,) solution. After a single washing with distilled water it is pressed between two heatable, planar parallel plates, at 130 C. and 5-10 kp./cm. pressure, for 20 minutes. The diaphragm thus obtained has a thickness of 0.5 to 0.7 mm.
When using a binder containing nitrile groups, in accordance with Example 2, the diaphragm must be aftertreated with 2 N KOH,'whereby the saponification of the nitrile groups takes place.
EXAMPLE 4 To produce a diaphragm, 2,6 g. of an aqueous dispersion by weight of dry substance) of a butadiene/ styrene/styrene sulfonic acid copolymer (5% styrene sulfonic acid content in copolymer) are added to the fiber slurry which is produced from 12 g. of highly pure asbestos fibers in 750 ml. water. ml. 2 N H 80 are additionally admixed for a complete precipitation of the binder onto the fiber. Further processing is carried out as in Example 1.
EXAMPLE 5 To a slurry dispersion of 12 g. blue asbestos fibers in 750 ml. water, 2.9 g. of an aqueous dispersion (30% by weight of dry substance) of a methylrnethacrylate/ octylmethacrylate-dimethylaminoethylmethacrylate copolymer are added, under strong agitation. After a completed precipitation and further treatment on the sheet former, diaphragms are obtained, which are particularly well suited for electrochemical cells with acid electrolytes.
EXAMPLE 6 3.1 g. of an aqueous dispersion (2 8% by weight of dry substance) of a methylmethacrylate/dimethylaminoethy1- methacrylate copolymer are dripped into the fiber slurry of Example 5, under strong agitation. The production of these diaphragms, which are also particularly suitable for acid electrolytes, is effected analogously to Example 1.
EXAMPLE 7 2.95 g. of an aqueous dispersion (30% by weight of dry substance) of a methylmethacrylate/octylmethacrylate hydroxyethylmethacrylate copolymer are added by dripping to the fiber slurry described in Examples 1 or 5, under strong agitation. After standing for 2 hours, the mixtures are processed into diaphragms on a sheet former or another suitable device and may be employed, according to the type of asbestos fiber used, either in acid or in alkaline electrolytes.
EXAMPLE 8 3.2 g. of an aqueous dispersion (26% by weight of dry substance) of a methylmethacrylateloctylmethacrylate/2-hydroxypropylene methacrylate copolymer are added by dripping into a fiber slurry in accordance with Examples 1 and 5, under strong agitation. After standing for 3 hours, these mixtures also produce diaphragms, on the sheet former, which will be gas-tight up to above 2 atmospheres gauge.
We claim:
1. In a gas-tight diaphragm material of high mechanical stability comprised of fibrous material selected from asbestos fibers and carbon fibers, and a synthetic hinder, the improvement which comprises using a binder consisting of a copolymer which contains hydrated groups, said binder being a butadiene/styrene/acrylic acid copolymer produced by saponification of the nitrile groups of a butadiene/styrene/acrylonitrile precursor, said saponification being in the presence of said fibers, said binder being in an amount of from 6 to 15% by weight of the fibrous material.
2. The material of claim 1, wherein the binder is 8 to 12% by weight.
3. The membrane material of claim 1 wherein the binder consists of a cross-linkable butadiene/styrene/ acrylic acid copolymer.
4. The membrane material of claim 1, wherein the fibrous material forms an interfelted web.
5. The method of forming a membrane material for a gas-tight diaphragm, which comprises forming a slurry of a material selected from the group consisting of asbestos and carbon, which comprises adding from 6 to 15% by weight of a butadiene/styrene/acrylonitrile copolymer, containing hydratable groups, based upon the solids content to a dispersion of fibrous material selected from asbestos, and carbon fibers to form said slurry thereafter drawing the water from said sluury to form the membrane material and saponifying the nitrile group in the said copolymer.
References Cited UNITED STATES PATENTS 2,789,903 4/1957 Lukman et al. 162-468 2,901,390 8/1959 Conklin et al. 162-152 3,014,835 12/1961 Feigley et al. 162156X 3,057,794 10/1962 Carlin 204-296X 3,066,066 11/1962 Keim et al 162-155X 3,093,609 6/ 1963 Feigley et al. 162155X 3,144,379 8/1964 Gelbert 162-155 3,153,610 10/1964 Heiser et al 162-155 3,269,889 8/1966 Hutchins 162-155 3,275,575 9/1966 Fogle 204-296X S. LEON BASHORE, Primary Examiner F. FREI, Assistant Examiner U.S. Cl. X.R.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DES0107252 | 1966-12-03 | ||
DES0111724 | 1967-09-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3583891A true US3583891A (en) | 1971-06-08 |
Family
ID=25998691
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US731324A Expired - Lifetime US3583891A (en) | 1966-12-03 | 1968-05-22 | Gas-tight diaphragms for electrochemical cells |
Country Status (6)
Country | Link |
---|---|
US (1) | US3583891A (en) |
CA (1) | CA845032A (en) |
CH (1) | CH510333A (en) |
DE (2) | DE1596241B1 (en) |
GB (1) | GB1213472A (en) |
SE (1) | SE335190B (en) |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3945910A (en) * | 1973-06-15 | 1976-03-23 | Solvay & Cie | Diaphragm for an electrolysis cell |
US3989615A (en) * | 1971-07-06 | 1976-11-02 | Nippon Soda Company Limited | Diaphragm process electrolytic cell |
US4125450A (en) * | 1976-04-26 | 1978-11-14 | Solvay & Cie | Previous diaphragms for cells for the electrolysis of aqueous solutions of alkali metal halides |
US4210515A (en) * | 1975-02-10 | 1980-07-01 | Basf Wyandotte Corporation | Thermoplastic fibers as separator or diaphragm in electrochemical cells |
US4216072A (en) * | 1977-11-10 | 1980-08-05 | Olin Corporation | Diaphragms for use in the electrolysis of alkali metal chlorides |
US4221642A (en) * | 1978-03-01 | 1980-09-09 | Oronzio Denora Impianti Elettrochimici S.P.A. | Anionic membranes |
US4326914A (en) * | 1979-09-20 | 1982-04-27 | Siemens Aktiengesellschaft | Diaphragms for electrochemical cells and the manufacture thereof |
US4367270A (en) * | 1979-09-20 | 1983-01-04 | Siemens Aktiengesellschaft | Asbestos diaphragms for electrochemical cells and the manufacture thereof |
US4410411A (en) * | 1973-01-17 | 1983-10-18 | Diamond Shamrock Corporation | Dimensionally stable asbestos diaphragms |
US4489025A (en) * | 1973-01-17 | 1984-12-18 | Diamond Shamrock Chemicals Company | Preparation of dimensionally stable asbestos diaphragms |
US4701250A (en) * | 1973-01-17 | 1987-10-20 | Eltech Systems Corporation | Dimensionally stable asbestos diaphragm coated foraminous cathode |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2032549A1 (en) * | 1970-07-01 | 1972-01-05 | Siemens Ag | Electrode for electrochemical cells and process for their manufacture |
DE2902957C2 (en) * | 1979-01-26 | 1983-11-24 | Deutsche Automobilgesellschaft Mbh, 3000 Hannover | Process for the production of separators for galvanic cells |
ATE24550T1 (en) * | 1980-01-29 | 1987-01-15 | Atochem | DIAPHRAGM FOR ELECTROLYSIS AND PROCESS FOR ITS MANUFACTURE. |
FR2505879B1 (en) * | 1981-05-15 | 1985-09-27 | Chloe Chemie | DIAPHRAGM, ITS PREPARATION METHOD AND THE ELECTROLYSIS METHOD USING THE SAME |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3342642A (en) * | 1964-12-10 | 1967-09-19 | American Cyanamid Co | Fuel cell electrolyte matrix |
-
0
- CA CA845032A patent/CA845032A/en not_active Expired
-
1966
- 1966-12-03 DE DE19661596241 patent/DE1596241B1/en active Pending
-
1967
- 1967-09-08 DE DE1671902A patent/DE1671902C3/en not_active Expired
- 1967-10-16 CH CH1449267A patent/CH510333A/en not_active IP Right Cessation
- 1967-11-10 SE SE15438/67A patent/SE335190B/xx unknown
- 1967-11-13 GB GB51623/67A patent/GB1213472A/en not_active Expired
-
1968
- 1968-05-22 US US731324A patent/US3583891A/en not_active Expired - Lifetime
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3989615A (en) * | 1971-07-06 | 1976-11-02 | Nippon Soda Company Limited | Diaphragm process electrolytic cell |
US4410411A (en) * | 1973-01-17 | 1983-10-18 | Diamond Shamrock Corporation | Dimensionally stable asbestos diaphragms |
US4489025A (en) * | 1973-01-17 | 1984-12-18 | Diamond Shamrock Chemicals Company | Preparation of dimensionally stable asbestos diaphragms |
US4701250A (en) * | 1973-01-17 | 1987-10-20 | Eltech Systems Corporation | Dimensionally stable asbestos diaphragm coated foraminous cathode |
US3945910A (en) * | 1973-06-15 | 1976-03-23 | Solvay & Cie | Diaphragm for an electrolysis cell |
US4210515A (en) * | 1975-02-10 | 1980-07-01 | Basf Wyandotte Corporation | Thermoplastic fibers as separator or diaphragm in electrochemical cells |
US4125450A (en) * | 1976-04-26 | 1978-11-14 | Solvay & Cie | Previous diaphragms for cells for the electrolysis of aqueous solutions of alkali metal halides |
US4216072A (en) * | 1977-11-10 | 1980-08-05 | Olin Corporation | Diaphragms for use in the electrolysis of alkali metal chlorides |
US4221642A (en) * | 1978-03-01 | 1980-09-09 | Oronzio Denora Impianti Elettrochimici S.P.A. | Anionic membranes |
US4326914A (en) * | 1979-09-20 | 1982-04-27 | Siemens Aktiengesellschaft | Diaphragms for electrochemical cells and the manufacture thereof |
US4367270A (en) * | 1979-09-20 | 1983-01-04 | Siemens Aktiengesellschaft | Asbestos diaphragms for electrochemical cells and the manufacture thereof |
Also Published As
Publication number | Publication date |
---|---|
DE1671902A1 (en) | 1971-10-21 |
GB1213472A (en) | 1970-11-25 |
CH510333A (en) | 1971-07-15 |
DE1671902B2 (en) | 1974-11-14 |
DE1671902C3 (en) | 1975-06-26 |
DE1596241B1 (en) | 1971-07-01 |
CA845032A (en) | 1970-06-23 |
SE335190B (en) | 1971-05-17 |
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