JPS5946102A - Composite membrane selectively permeable for gaseous oxygen - Google Patents

Abstract

PURPOSE:To prepare composite membrane selectively permeable for gaseous oxygen but prohibiting steam or carbon dioxide in air to permeate into the main body of an electrode, by integrally adhering a thin layer comprising hydrous or hydratable metal oxide on one side of a porous membrane. CONSTITUTION:As a porous membrane, for example, a porous fluorine resin film, a porous polycarbonate membrane or a porous cellulose ester membrane can be represented. As hydrous or hydratable metal oxide is defined by one having superior adsorptivity for water wherein adsorbed water can be a surface hydroxyl group, chemically or physiclally adsorbed water. Specific examples are stannic dioxide, zinc oxide or aluminum oxide alone or a composite in an arbitrary combination comprising two kinds or more of them. In the case of the composite membrane with a two-layered structure, a thin layer of hydrous or hydratable metal oxide is directly adhered to one surface of the porous membrane by a vapor deposition method or a sputtering method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an oxygen gas selectively permeable composite material useful for manufacturing air body electrodes for hydrogen/oxygen fuel cells, metal/air cells, and oxygen sensors. Regarding No. 11a-, more specifically, the present invention relates to an oxygen gas permselective composite material for nitrogen electrodes which is capable of performing heavy load discharge for a long period of 7 hours even if it is thin and has excellent storage performance.

[Technical background of the invention and its problems]

Conventionally, all gas electrodes such as various fuel cells, air/air metal batteries including 1 1/2 lead-acid batteries, and galvanic type oxygen sensors have the following characteristics: Gas diffusion electrodes have been used. Initially, a floating porous electrode with a uniform pore size distribution was used as this gas diffusion electrode, but recently it has been developed to have an electrochemical reduction ability (to ionize oxygen) for oxygen gas. Two-layer electrodes are often used, consisting of a porous electrode body that also functions as a current collector, and a thin film-like water-repellent layer that is integrally attached to the gas side surface of the electrode body. There is.

In this case, the electrode body is mainly made of ``nickel tungstic acid with low oxygen gas reduction overvoltage;
Powder made by supporting conductive powder such as activated carbon powder with tungsten carbide coated with cobalt; nickel: silver; platinum; palladium, etc.
After adding a binder such as
Carbon porous body.

A non-woven fabric made of carden fiber is used.

1. The water-repellent layer attached to the gas side surface of the electrode body is mainly polytetrafluoroethylene.

Polytetrafluoroethylene hekiza 70 is a membrane composed of resins such as polytetrafluoroethylene copolymer, polyethylene-tetraloroethylene copolymer, or polypropylene, and has a particle size of, for example, 0.2~40
μm17) A sintered body of these resin powders; a paper-like thing made by heat-treating these resinous fibers and making it into a non-woven fabric; also a fiber cloth-like thing: a part of these resin powders replaced with laminated graphite : A film-like film made by rolling these fine powders together with a pore-forming agent, lubricant, oil, etc. and then heat-treated, or a film-like film that is not heat-treated after roll-pressing. It is a thin film of sex.

However, in the air electrode of the conventional structure described above,
The water-repellent layer attached to the gas-side surface of the electrode body is impermeable to the electrolyte, but not to water vapor in the empty package or air.

Therefore, for example, water vapor in the empty package may pass through the water-repellent layer and enter the electrode body, thereby diluting the electrolyte, or conversely, water in the electrolyte may escape from the water-repellent layer as water-steam. May dissipate and concentrate the sweet electrolyte. As a result, the concentration of the electrolyte fluctuates, resulting in a situation where stable discharge cannot be maintained for a long period of time.

When carbon dioxide gas in the air passes through the water-repellent layer and enters the electrode body and is absorbed into the active layer, the electrochemical reduction ability for oxygen gas in that area decreases and heavy load discharge is inhibited. Ru. Furthermore, when the electrolyte is an alkaline electrolyte, phenomena such as deterioration of the electrolyte and a decrease in concentration, or when the cathode is zinc, the zinc cathode becomes passivated. Furthermore, in the active layer (the porous part of the electrode), carbonate is generated to block the pores and reduce the area where electrochemical reduction takes place; .

In such cases (when storing the manufactured ljE battery for a long period of time or using it for a long period of time), the battery
Prevent the situation where the performance deteriorates from the NQR standard.

For this reason, in addition to the gas ll111'' (empty bag) in the water-repellent layer of the air electrode, a moisture absorbent such as calcium chloride is added to a carbon dioxide absorbent such as hydroxide of alkaline earth metal. A battery having a structure in which F?j is provided has been proposed.

This can prevent the above-mentioned inconveniences to some extent, but after a certain period of time, if these absorbents reach a saturated state and lose their absorption capacity, the effect disappears, so there is nothing essential about it. I hope this is a viable solution.

Furthermore, attempts have been made to integrally laminate a thin film having oxygen permeability of a polyoloxane film on top of the above-described water-repellent layer. However, to date, a sufficiently effective acid Xζ gas selective permeability j1q has not been developed.

[Purpose of the invention]

The present invention has excellent selective permeability for oxygen gas, and therefore,
Manufacture of a thin air electrode that, when applied to an air electrode, does not allow water vapor or carbon dioxide in the air to enter the electrode body, and is therefore capable of long-term heavy load discharge and has excellent storage performance. The purpose of the present invention is to provide an oxygen gas permselective bonding membrane suitable for use in the present invention.

[Summary of the invention]

The composite membrane of the present invention has a first aspect in which a thin layer of a water-containing or hydratable metal oxide is integrally attached to one side of a porous membrane having micropores with a pore size of 0.1 μm or less. It is a composite membrane with a two-layer structure, and the second aspect is a three-layer structure in which a water-repellent layer is interposed between the porous membrane and the thin layer of the metal oxide, and the whole is integrated. It is a compound j-mo.

In the composite membrane of the present invention, the porous membrane has a pore diameter of 0.
The material may be any winter material as long as it has micropores of 1 μm or less, but it is preferable to use a material with high flexibility in consideration of attachment to the electrode body. In addition, it is preferable that the porous membrane has the above-mentioned fine pores uniformly distributed, and the pore volume of the fine pores is o, i~90 with respect to the total membrane volume.
Preferably, those within the above range are suitable.

Such porous materials include porous fluororesin membranes (trade name: Fluoro JHere; Sumitomo's Jf Engineering).
Co., Ltd.), porous polycarbonate membrane (part name, Nyukuipore; manufactured by Nuclepore Co., Ltd.), -Porous cellulose ester jitJ (trade name, Millipore membrane filter-; manufactured by Millipore Corporation),
Porous polypropylene membrane (trade name, Celguard; Celanese Plastics Co., Ltd. IJσ) can be mentioned.

At these porosity of 1''%, the pore diameter is 0°1/1
If it exceeds m, when a thin metal oxide layer or a water-repellent layer (described later) is formed on the porous membrane, pinholes will occur frequently in the thin layer or the aqueous layer, and water vapor or return light will be generated. In addition to losing its gas intrusion prevention effect, it also causes a decrease in its mechanical strength and becomes easily damaged.

Next, the water-containing or hydratable metal oxides according to the present invention have an excellent ability to absorb water, and the adsorbed water can be absorbed into surface hydroxyl groups, chemically adsorbed water, and physical, g & It refers to substances that have the property of existing as water, specifically, tin dioxide (Sn02), zinc oxide (ZnO), aluminum oxide (At203) + magnesium oxide (M
, FO), calcium 112ide (Cab), strontium oxide (SrO), barium oxide (Ba
d), titanium dioxide (TiO2), silicon dioxide (S
tO,) may be used alone or in combination of two or more of them.

The composite power module of the present invention can be manufactured as follows. First, in the case of a two-layer composite membrane, a thin layer of a hydrous or hydratable metal oxide is directly attached to one side of the porous membrane as described above.

Suitable methods for attachment include vapor deposition and sputtering, which are often used as thin film forming methods.

At this time, the thickness of the thin layer is preferably 0.01 to 1.0 μm, and if the thickness is less than 0.1 μm, pinholes will occur frequently in the formed thin layer and the water vapor will vaporize. Alternatively, the effect of preventing the intrusion of carbon dioxide gas is reduced, and at the same time, the mechanical strength of the thin layer is reduced, making it easy to break. On the other hand, if the length exceeds 111 m 2 , the amount of permeation of oxygen gas decreases, which deteriorates the heavy load discharge characteristics of the prepared electrode.

Tsukiyoko, 3J = m construction, after gold j, J7', C, first, a water repellent layer is formed on one side of the porous membrane, and then 2
r8'24? As with conventional composite films, a thin layer of a water-containing metal oxide is formed on the water-repellent layer by applying a vapor deposition method, a sputtering method, or the like.

Here, the particles constituting the aqueous layer include water repellent,
Any material may be used as long as it has electrolyte resistance, and in practical use, for example, polytetrafluoroethylene (PTFE), 70-ethyleneglopylene (FEP), HIJ phenylene oxide (PPO), polyphenylene sulfide (PPS), etc.
), polyethylene (PE), polypropylene (pp)
and copolymers thereof or mixtures thereof.

At this time, the material of the water repellent layer is polyfluoroethylene propylene (FEP), polyethylene (PE),
If a heat-sealable material such as ethylene-tetrafluoroethylene copolymer is used, it is possible to increase the mechanical strength of the composite membrane by performing appropriate heat treatment.

The water-repellent layer according to the present invention may further include various organic compounds, such as fluorinated organic compounds such as pencitrifluoride, m-chloropencitrifluoride, hexafluorobenzene, penta-70 lobenzene, and interfluorostyrene; mixture; for example, Cl=C12
Hydrocarbon compounds such as saturated hydrocarbon compounds of 01 to C12, unsaturated hydrocarbon compounds of 01 to C12, alkylbenzene compounds of C8 to CI4, styrene, α-methylstyrene, and mixtures thereof, etc. Examples include thin layers formed on membranes. None of these thin layers have a single hole and have excellent selective permeability to oxygen gas. In particular, the above-mentioned fluorinated organic compounds A thin layer formed by plasma polymerizing the single molecule is useful because it has an excellent effect of preventing water vapor or carbon dioxide from entering.

The thickness of the thin film to be formed is practically o, o i ~ 1.0 μm
If the thickness is less than 0.01 μm, the formed thin layer becomes island-like and cannot uniformly cover the surface of the porous membrane, and carbon dioxide gas Or the prevention effect against the intrusion of water vapor is reduced. Moreover, the mechanical strength of the entire thin layer is also reduced.

On the other hand, if the thickness exceeds 1.0 μm, the amount of oxygen gas supplied to the electrode body will be insufficient when the electrode is assembled, and the discharge characteristics of the electrode will deteriorate (heavy load discharge becomes difficult and a: +C).

Further, although the thin layer 11 described above may be formed as a single layer, a polymer thin film made of another type of organic compound may be further formed on this layer.

A thin layer of water-containing or water-friendly metal oxide is further laminated on the water-repellent layer thus formed. The thickness is 0.01 to 1 for the same reason as the water repellent layer.
．． Preferably, it is 0 μm.

In both the two-layer structure and the three-layer structure, when forming a thin layer of water-containing or water-friendly metal oxide, the deposition source or sz! These metal oxides themselves can be used as the ivy source, but it is also possible to use various elemental metals that react with acids to produce these metal oxides as a vapor deposition source or sputtering source, and to maintain the atmosphere. In an oxygen atmosphere, the rate of thin layer formation of the metal oxide increases, and
This is preferable because it facilitates the operation of forming a thin layer.

[Embodiments of the invention]

Examples 1 to 0 A porous polycarbonate membrane (trade name, Nuclepore; Nuclesia Corporation, thickness 5μ
Sn r Zn r AL +M on one side of m)? , C
Using a*Sr*BasTl*St as a sputtering source, a mixed gas of argon and oxygen (Ar 90vot%, 0210
vot%), S A? under the condition of high frequency power 100W? An ivy treatment was applied to form a thin layer of various hydrous or hydrophilic metal oxides. Thickness: 0.2 μm.

Examples 10 to 18 Argon gas pressure of 1 x 10 Torr was applied to one side of a porous polycarbonate membrane having the same specifications as those used in Examples 1 to 9.
Furo-tetraethylene propylene (FE; P) was splattered under conditions of a high-frequency output of 200 W to form a layer with a thickness of 0.2 μtn per corner. Then, on top of this, Examples 1 to 9
In the same manner as above, various water-containing (<U) or thin layers (thickness 0.2 μn+) of water-containing metal oxides were formed.

Examples 19 to 27 A porous polycarbonate membrane having the same specifications as those used in Examples 1 to 9 was placed in a glazma reaction tank, and 13.
Applying high frequency power of 56 ME (z), introducing 6001 nl of iC7 into the tank and introducing pentafluorostyrene monomer gas 600+++f!/-, RF'
Output 0.4 W/at! Glazma polymerization reaction is carried out under the conditions of
A thin layer of 2/Lm pentafluorostyrene polymer was formed.

Then, a thin layer (0.2 μm) of various water-containing or water-friendly metal oxides was formed thereon in the same manner as in Examples 1 to 9.

For the composite membrane of the above 27 glazes, the oxygen permeation rate (JO2: CC/5ec・d・cm H) of the composite membrane was measured by an isobaric method using a gas chromatograph as a detection means, and
Water vapor transmission rate (JH20: CC/5ec-d-cr
n) (S') to JIS Z0208 (cup method)'
;'', I:, was determined by the same method, and the ratio of the two (JOx/J+-r2o) was calculated as the gas permeation ratio.

For comparison, the polysiloxane I in J corner 5011m (Comparative Example 1) is 20 μm thick medium density polyethylene IIIΣ (Comparative Example 2), and the 2011 m thick biaxially oriented polypropylene film (Comparative Example 3) , a polytetrafluoroethylene film with a thickness of 20 jam (Comparative Example 4), a commercially available FEP IIN with a thickness of 20 μm (Comparative Example 5), and a film with a thickness of 0.2 μm formed by the sputtering method of Examples 10 to 18.
Similarly, for FEP 1 (comparative example 6) of m
21JH,o was measured and JO,/Jl-120 was calculated.

The above results are summarized in the table.

〔Effect of the invention〕

As is clear from the above explanation, although the composite membrane of the present invention is extremely thin, it does not allow the permeation of water vapor in the air and has a high ability to selectively permeate oxygen gas. The combined air electrode can be made thinner as a whole,
Moreover, it is possible to discharge 9 heavy loads over a long period of time, and
Its storage performance is also improved. In addition, leakage resistance is also improved.

Therefore, the industrial value of the composite membrane of the present invention is extremely large.

Claims (1)

[Claims] 1. Oxygen gas selection characterized in that a thin layer of water-containing or water-friendly metal oxide is integrally attached to one side of a porous membrane having micropores with a pore diameter of 0.1 μm or less. Permeable composite membrane. 2. The metal oxide is at least one hydrous or water-containing metal oxide selected from the group of tin dioxide, zinc oxide, aluminum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, titanium dioxide, and silicon dioxide. The oxygen gas selectively permeable composite membrane according to claim 1, which is a product. 3. The oxygen gas selectively permeable composite membrane according to claim 1, wherein the thin layer has a thickness of 0.01 to 1.0 μm. 4. A water repellent layer and a thin layer of water-containing or water-friendly metal oxide are integrally laminated in this order on one side of a porous membrane having micropores with a pore diameter of 0.1 μm or less. Oxygen gas selective permeability composite membrane. 5. A patent in which the metal oxide is at least one metal oxide selected from the group of tin dioxide, zinc oxide, aluminum oxide, iron oxide, calcium oxide, strontium oxide, barium oxide, titanium dioxide, and silicon dioxide. Oxygen gas selectively permeable composite 11 according to claim 4; 6. The oxygen gas permselective composite membrane according to claim 4, wherein the water-repellent layer is a thin layer of a monomolecular plasma polymer of a fluorinated organic compound. 7. Claim 4, wherein the water repellent layer and the metal oxide thin layer each have a thickness of 0.01 to 1.0 μm.
- The oxygen gas selectively permeable composite membrane according to any one of Items 6 to 6.