JP4056928B2 - Method for forming sealing material for fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a sealing material for a fuel cell, particularly a polymer electrolyte fuel cell.
[0002]
[Prior art]
A polymer electrolyte fuel cell uses a membrane such as an ion exchange resin having ionic conductivity as a polymer electrolyte membrane, and a cathode electrode (positive electrode) and an anode electrode (negative electrode) on both sides of the polymer electrolyte membrane. By arranging both electrodes, for example, by supplying a fuel gas such as hydrogen gas on the negative electrode side and an oxidizing gas such as oxygen gas or air on the positive electrode side to cause an electrochemical reaction, the chemical energy of the fuel gas is obtained. Is converted into an amount of electricity to generate electricity.
[0003]
Such a polymer electrolyte fuel cell is configured by laminating a plurality of single cells. Between adjacent single cells, a fuel gas channel and an oxidizing gas channel are formed between the cells and the fuel gas. And a separator for partitioning the oxidizing gas. The gap between the electrode and the separator must be gas-tightly sealed so that fuel gas and oxidizing gas do not leak from the peripheral edge of the polymer electrolyte membrane, and usually formed by compression molding, injection molding, sheet punching, or the like. An operation is performed in which the thin rubber packing is interposed when the fuel cell is assembled.
[0004]
[Problems to be solved by the invention]
The above rubber packing is a gas seal against fuel gas and oxidizing gas, and the seal must be held strictly for a long period of time. The rubber packing includes compression set, heat resistance, electrical insulation, etc. Those with excellent physical properties are required. The above rubber packing is a very thin film-like thin film body, and when it is molded by compression molding, injection molding, etc., there is a variation in thickness and high accuracy cannot be obtained. The work of assembling the packing at a predetermined position between the electrode and the separator is difficult, and there is a problem that a reliable sealing performance cannot be ensured due to deformation or positional deviation during assembly.
[0005]
The present invention solves the above-described problems, and does not require the work of incorporating a rubber packing. The rubber packing is securely disposed at a predetermined position to ensure complete sealing, and the rubber packing component is a fuel cell. The purpose is not to impede the performance of the.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is based on the basic means that the rubber seal material is previously crosslinked and molded and integrated directly into the separator before assembling the single cell. A method for forming a sealing material comprising a rubber packing interposed between a separator and a fuel cell main body comprising an electrolyte membrane, a cathode electrode and an anode electrode, wherein a rubber solution is applied to a surface of a predetermined position of the separator to form an uncrosslinked A process of forming a rubber thin film, a process of molding and integrating a non-crosslinked rubber thin film into a separator, and a single cell by assembling a separator with a crosslinked rubber thin film molded and integrated into contact with a cathode electrode and an anode electrode , the step of sealing the peripheral portion of the polymer electrolyte membrane comprises a, in the rubber thin film formation process, the separator The method of forming a fuel cell sealing member to form a rubber film of the rubber solution was applied by screen printing on the periphery surface of uncrosslinked it is an gist.
[0007]
That is, the invention according to claim 1 is characterized in that a mask having a through hole that matches the planar shape of the rubber thin film to be formed is coated on the surface of the separator, and for example, a rubber solution obtained by dissolving a rubber compound with a solvent is used as the mask. It is applied a plurality of times from above, and a rubber thin film having a predetermined thickness is formed through the through holes. Therefore, in the present invention, it is not necessary to incorporate a rubber packing when a fuel cell is configured by stacking a large number of separators that are required to be smaller.
[0008]
The invention according to claim 2 uses silicone rubber as the rubber base material of the rubber packing according to claim 1, and the invention according to claim 3 uses ethylene as the rubber base material of the rubber packing according to claim 1. Propylene rubber or ethylene propylene diene rubber is used, the invention according to claim 4 uses fluororubber as the rubber base material of the rubber packing according to claim 1, and the invention according to claim 5 uses the rubber according to claim 1. The gist is that any rubber of natural rubber , acrylonitrile butadiene rubber , chloroprene rubber and acrylic rubber is used as the rubber base material of the packing .
[0009]
When the rubber thin film is molded by radiation crosslinking without blending a crosslinking agent, a cationic impurity (for example, oxidation) that inhibits the performance of the fuel cell is formed because the rubber molecular chains are directly C—C bonded during crosslinking. Metal oxides such as zinc and magnesium oxide) are not eluted. The radiation crosslinking is preferably crosslinking with a high energy active ray such as electron beam or γ ray. Furthermore, since the rubber thin film is crosslinked and molded without heating and pressing, the quality of the separator formed of carbon graphite or the like is not deteriorated without any damage.
[0010]
Furthermore, in the present invention, thermal black can be blended in the rubber thin film as carbon black for reinforcing rubber packing. This thermal black is a thermal (pyrolysis) method, that is, natural gas is introduced into a furnace heated to a temperature equal to or higher than the pyrolysis temperature by burning fuel, and carbon black is produced by pyrolysis of natural gas. Compared to oil furnace black, acetylene black, etc., this carbon black has a large particle size and low structure and a very small specific surface area. It has excellent electrical insulation performance and contains impurities such as ash and sulfur due to its complete combustion method. the amount has an extremely small features, the nitrogen adsorption specific surface area 9.0~9.5m / g, DBP oil absorption 34~40cm ³ / 100g, average particle size than those in the range of 240~310nm is there. Therefore, the rubber packing containing this thermal black contains almost no impurities that adversely affect the power generation of the fuel cell, and can be suitably used as a rubber packing for a fuel cell.
[0011]
As the base rubber of the rubber packing is formed integrally with the separator, a natural rubber (NR), silicone rubber (Q), ethylene-flop Ropirengomu (EPM), ethylene propylene diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR ), chloroprene rubber (CR), acrylic rubber (ACM), are formed by any rubber or mixture thereof, such as full Tsu-containing rubber (FKM), preferably it is selected EPM or EPDM having excellent cushioning The The rubber base material may be added with a plasticizer and other general compounding agents as required, but it is preferable to select one containing a component that does not adversely affect the power generation of the fuel cell.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of a single cell 1 constituting a solid polymer fuel cell, and a normal fuel cell is configured as a laminated body (not shown) in which a plurality of single cells 1 are stacked. In FIG. 1, a single cell 1 includes a fuel cell body comprising a polymer electrolyte membrane 2 and a cathode electrode 3 and an anode electrode 4 disposed on both sides of the polymer electrolyte membrane 2, and a cathode electrode 3 and an anode. The separators 5 and 6 are provided so as to be in contact with the electrodes 4 respectively.
Further, an oxidizing gas supply groove 7 is provided on the electrode 3 side of the cathode electrode side separator 5, and a fuel gas supply groove 8 is provided on the electrode 4 side of the anode electrode side separator 6. The groove 8 communicates with a fuel gas supply pipe (not shown). The single cell 1 includes a fuel cell body made up of a polymer electrolyte membrane 2, a cathode electrode 3, and an anode electrode 4, and prevents leakage of fuel gas and oxidizing gas around the cathode electrode side separator 5 and anode electrode side. Frame-shaped rubber packings 9 and 10 that secure insulation with the separator 6 are interposed between the separators 5 and 6.
[0013]
In the present invention, the rubber packings 9 and 10 are formed directly on the peripheral surface of the separators 5 and 6 in advance and integrated in the crosslinking step. That is, as shown in FIGS. 2 and 3, the rubber packings 9 and 10 are loaded with a mask 11 having a frame-shaped through-hole 12 on the surface of the separator 5 (6), and the rubber compound is removed from the mask over the solvent. Screen printing for applying the rubber solution dissolved by the above is performed a predetermined number of times, an uncrosslinked rubber thin film 13 matching the shape is formed through the through holes 12, dried and the solvent is volatilized, and then the rubber thin film 13 is formed. This is a state in which a cross-linking treatment is performed by electron beam irradiation without heating and pressurizing, and a frame-like rubber thin film 13 (rubber packing 9) is cross-linked and integrally formed on the peripheral portion of the separator 5. In this way, the single cell is configured using a separator in which rubber packing is molded and integrated in advance, and a solid polymer fuel cell that is easy to assemble is configured. In addition, when using liquid rubber like liquid silicone rubber as a rubber solution, it can apply | coat, without melt | dissolving with a solvent.
[0014]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. 40 parts by weight of thermal black (MT Carbon N990 Ultrapure, manufactured by Cancarb Co., Ltd.) as a reinforcing agent is added to and blended with 100 parts by weight of commercially available EPDM 100 parts as raw rubber, and about 1 cm of unvulcanized rubber kneaded with a mixing roll. Finely cut into corners, and the obtained fine pieces together with toluene are put into a stirrer equipped with a vacuum defoaming device, stirred for 10 hours under atmospheric pressure and dissolved, and then the vacuum defoaming device is driven to further vacuum for 15 minutes. Stirred and degassed. Next, the dissolved and defoamed EPDM rubber solution was applied to a predetermined surface of a carbon graphite separator by screen printing, and then dried in a hot air dryer (80 ° C.) for 5 minutes to volatilize the solvent. This coating and drying process was repeated seven times to form an uncrosslinked rubber thin film having a thickness of 300 μm on the peripheral surface of the separator. Thereafter, the rubber thin film on the separator is introduced into an electron beam irradiation device and crosslinked by irradiating with an electron beam with an irradiation dose of 15 to 80 Mrad in a nitrogen atmosphere, so that the rubber packing is directly molded and bonded and integrated. A separator was obtained.
[0015]
In addition, considering the heat resistance and strength properties of rubber packing, the irradiation method and irradiation conditions can be optimized, and not only complete rubber crosslinking, but also pre-crosslinking, heat treatment and micro Wave post-crosslinking can be performed.
[0016]
Moreover, in the said Example, although the polymer electrolyte fuel cell was used as a fuel cell provided with a separator, if it can endure a use environment, it can be applied also to another kind of fuel cell.
[0017]
【The invention's effect】
According to the sealing material forming method of the present invention, the sealing material interposed between the fuel cell main body and the separator is configured by the rubber packing that is molded and integrated in advance on the surface of the separator at a predetermined position. No work is required, and the gas seal between the fuel cell body and the separator can be easily and reliably performed without causing deformation or displacement of the rubber packing. In the inventions according to claims 2 to 5 , the rubber packing can be formed of any rubber. In particular, if EPM or EPDM is selected, an excellent cushioning rubber packing can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a single cell constituting a solid polymer fuel cell.
FIG. 2 is a diagram showing a part of a rubber packing molding process.
FIG. 3 is a view showing a state in which a rubber packing is integrally formed with a separator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Single cell 2 Polymer electrolyte membrane 3 Cathode electrode 4 Anode electrode 5 Cathode electrode side separator 6 Anode electrode side separator 7, 8 Groove 9, 10 Rubber packing 11 Mask 12 Through-hole 13 Rubber thin film

Claims (5)

A method for forming a sealing material made of rubber packing , which is interposed between a separator and a fuel cell main body made of a polymer electrolyte membrane, a cathode electrode and an anode electrode,
Forming a non-crosslinked rubber thin film by applying a rubber solution to a predetermined surface of the separator;
A step of molding and integrating with the separator by crosslinking an uncrosslinked rubber thin film;
A step of sealing the periphery of the polymer electrolyte membrane by assembling a single cell by contacting a separator in which a crosslinked rubber thin film is molded and integrated with a cathode electrode and an anode electrode;
Equipped with a,
A method for forming a sealing material for a fuel cell, wherein in the rubber thin film forming step, an uncrosslinked rubber thin film is formed by applying a rubber solution to the peripheral surface of the separator by screen printing . The method for forming a sealing material for a fuel cell according to claim 1, wherein silicone rubber is used as a rubber base material of the rubber packing . The method for forming a sealing material for a fuel cell according to claim 1 , wherein ethylene-propylene rubber or ethylene-propylene-diene rubber is used as the rubber base material of the rubber packing . 2. The method for forming a sealing material for a fuel cell according to claim 1 , wherein fluororubber is used as the rubber base material of the rubber packing . Natural rubber as a rubber base material for rubber packing , Acrylonitrile butadiene rubber , The method for forming a sealing material for a fuel cell according to claim 1, wherein any one of chloroprene rubber and acrylic rubber is used.

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