JPS6059660A - Manufacture of porous electrode plate for fuel cell - Google Patents

Abstract

PURPOSE:To provide by easy operation a porous electrode plate having good gas diffusion capability and mechanical strength by filtering the mixture of carbon fibers and binder and applying carbonization treatment. CONSTITUTION:Carbon fibers are mixed in carboxymethylcellulose solution and stirred to make slurry. Flake-shaped phenol resin powder is mixed in the slurry and stirred. The lurry is filtered through a metal mesh of 100-200 mesh to form a mixed mat of carbon fiber and phenol resin on the metal mesh. The mat is dried by heating to obtain a dried mat. Phenol resin in the mat is cured in a heat press process to obtain a carbon plate having a specified thickness and good mechanical strength. Then cured phenol resin is carbonized by heating in an atmosphere of nitrogen at 500 deg.C or more.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a method for manufacturing a porous electrode plate for a fuel cell, and in particular to a method for manufacturing a porous electrode plate for a fuel cell, in particular a porous electrode plate made of carbon fiber as a main material, and a flat plate portion and a piece thereof containing gas 3i.
This invention relates to a method for manufacturing a porous electrode plate for a fuel cell, which is formed by integrally molding a plurality of protrusions forming u*k'Ia.

[Background of the invention]

Conventionally, as shown in Fig. 1, porous electrode plates for fuel cells have a carbon material such as carbon fiber, carbon powder, or carbon particles as the main material 1, and a binder such as phenol resin 2 mixed therein.
The binder 2 is hardened and bonded using a heat press or the like, and a flat plate part 3 and a plurality of protrusions 5 forming gas passages 4 on one side thereof are integrally molded, and then this is carbonized and fired at a high temperature. Manufactured. In this case, if carbon powder, carbon grains, etc. are used as the main material 1, the strength of the main material itself is low;
Since the overall strength of the porous electrode plate is low and it becomes brittle, there are many problems in use such as breakage. Therefore, carbon fiber material is often used as the main material in order to improve the strength and rebound.

How to manufacture conventional electrode plates using carbon fiber? This will be explained with reference to FIGS. 2 and 3. In FIG. 2, a dispersion bath liquid 6 in which carbon fibers are appropriately dispersed is filtered through a filter 7, and a mat 8 (+-) of carbon fibers is formed on the filter 7.

Next, the mat 8 formed on the filter 7 is heated to remove moisture. Evaporate to form a dry mat. After this dry matting is uniformly immersed in a solution of phenol resin dissolved in a solvent as a binder, the inder is hardened by applying pressure and heating with a heat press, and the k-th cutting is performed to form the gas flow path. This is done during the work, and then heated at a high temperature in an inert gas or vacuum to form a sufficiently carbonized heel porous electrode plate. These steps are carried out as shown in FIG.

However, with this conventional manufacturing method, is it possible to make a tsubinder?
Since an organic solvent is used for dissolution, in addition to problems in the working environment due to the volatilization of the organic solvent, the binder 3 solution is filled in the gap 9 between the carbon fibers with a capillary plate as shown in Figure 40. Therefore, gas diffusivity as an electrode plate is reduced. On the other hand, decrease in gas diffusivity? prevent f
If the binder bath ri and wo are reduced in c, the strength necessary for the electrode plate cannot be obtained.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a porous electrode plate for a fuel cell that is easy to manufacture and has good gas diffusivity and mechanical strength.

[Summary of the invention]

This purpose? In order to achieve this, the present invention pre-intermixes a powdery binder with carbon fiber, which is the main material, filters and molds the mixture containing at least the binder and the main material, and evenly distributes the binder in the form of powdery particles to form an electrode plate. It is characterized by good gas diffusivity and mechanical strength.

[Embodiments of the invention]

FIG. 5 is a process diagram showing an example of the manufacturing method of the present invention,
Before the filtration process, there is a material dispersion process.

In this material dispersion step, for example, the length is 0.5 to 10 cm.
, carbon fiber with thickness lO~30μ? zCMC (carboxymethyl cellulose) dispersant 1 in an aqueous solution of 0.1 to 5
~3% is mixed and stirred to form a slurry. 'To this slurry, a total of 5 to 50 pieces of phenol resin powder in the form of 7 lakes at room temperature is mixed and further stirred. Next, in the filtration step, the mixture is filtered through a wire mesh having 100 to 200 meshes to form a mixed mat of carbon fiber and phenolic resin on the wire mesh. This pine) (1
1- In the drying step, heat at 100C to 130C,
Evaporate the remaining water and obtain dry pine thorns.

In the heat press process, a pressure of 5 to 20 Kf/ctA is applied at a temperature of 150 to 200 C and left for 1 to 3 hours to heat cure the phenolic resin in the mat, improve its strength, and form a carbon plate of a predetermined thickness. obtain.

After that, the carbon plate was machined to form a gas flow path of the electrode plate, and then the carbon plate was cut for 50 minutes in N2 gas.
The hardened phenol resin is carbonized by heating at a temperature of 0C or higher.

In the manufacturing method shown in Figure 5, if the mixing damage of the phenolic resin powder in the slurry to be filtered is less than 5% by weight, the strength of the electrode plate obtained will be low, and if the weight is more than 50% by weight, the electrode plate will be weak. If they are too dense, gas diffusion will be poor.

When the wire mesh for the filter becomes less than 100 meshes, powdered phenol resin flows out through the mesh, and
If the mesh is 0 or more, the mesh resistance will be too high and it will take a long time to form a mat.

In the main embodiment, the particulate binder is uniformly dispersed in the slurry in the material dispersion step, and a mat is formed in this state. Therefore, as shown in FIG. 6, since the binder 2 is mainly bound to the vicinity of the fork points of the carbon fibers 1, the strength is high. Sufficient gaps 9 are formed between the carbon fibers while maintaining the carbon fibers, so there is no obstruction to scum diffusion.In addition, the inder treatment process (which is carried out after filtration) can be completely omitted, reducing the number of processes. do.

FIG. 7 shows another implementation f of the manufacturing method of the present invention! As shown in l',
In the banime treatment process, a novolatile phenolic resin is mixed and bonded to carbon fibers. Next, the carbon fibers bound with resin are dispersed in an aqueous solution. Next, a filtration process, a drying process, a heat press process and a carbonization process 1
After eight steps, a predetermined front electrode plate is formed.

In this embodiment, in the filtration step, it is sufficient to allow only the aqueous solution for dispersing carbon fibers to pass through and to prevent the carbon fibers from passing through.

Therefore, the mesh of the filter can be made coarser, and the filtration speed can be increased, so that the manufacturing time of the electrode plate can be shortened. Further, since the binder such as a resin is bound to the carbon fibers and can be used without being dissolved or dispersed in the aqueous solution, only the amount of binder required for the carbon fibers can be used efficiently.

Example 1 Carbon fibers with a fiber length of 2 m and a thickness of 11 μm were used and mixed with a CMC technology dispersion solution to form a slurry with a carbon fiber content of 2% by weight. Next, 40% by weight of slurry trap novolac phenolic resin butt was added, filtered and molded using a 200 mesh wire mesh, heat pressed under the conditions of 20 (1°10 K-q/cM), and then carbonized at 800C. The variation in gas diffusion of the electrode plate was 5% or less.

〔Effect of the invention〕

According to the present invention, since the binder is evenly distributed, the strength is improved and an electrode plate with good gas diffusion can be obtained by a simple method.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a porous electrode plate, Figure 2 is an explanatory diagram showing the principle of the filtration molding method, Figure 3 is a process diagram showing the conventional porous X electrode substrate manufacturing process, and Figure 4 is a diagram of the conventional porous electrode plate. FIG. 5, an enlarged view showing a part of the internal structure of the electrode substrate, is an example of the electrode substrate manufacturing process according to the present invention. 6 is an enlarged view showing a part of the internal structure of the electrode substrate manufactured by the method according to the present invention,
FIG. 7 is a process diagram showing another example of the electrode plate manufacturing process according to the present invention. O 1... Carbon fiber, 2... Binder, 3... Flat plate part, 4... Gas flow path, 5... Projection part, 6... Dispersion water bath liquid, 7... Filter , 8...Matt, 9...
・Gap between fibers. Tsumugi 4 Tier Katsugeki High School 7 Figure

Claims (1)

[Claims] A method for producing a porous electrode plate for a fuel cell, which comprises carbonizing carbon fibers and a binder to form a flat plate portion and a plurality of protrusions on one side of the flat plate portion for forming gas flow paths. A method for producing a porous electrode plate for a fuel cell, which comprises carbonizing a mixture containing at least carbon fibers and a binder after filtration and molding. 2. The method of manufacturing a porous electrode plate for a fuel cell according to claim 1, wherein the mixture is a slurry of carbon fibers, a dispersant, and resin powder. 3. In claim 1, the mixture binds the entire resin mixture to the carbon fibers, and this? A method for producing a porous electrode plate for a fuel cell, characterized in that the porous electrode plate is dispersed in water. 4. A method for producing a porous electrode plate for a fuel cell according to any one of claims 1 to 3, wherein the resin is a novolak phenolic resin.