JPH0320862B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a carbonaceous member for a fuel cell having a configuration in which a porous carbon electrode plate and a carbon separator plate are integrally joined. [Prior Art] In a fuel cell, a unit cell is constructed by arranging porous electrode plates carrying a platinum catalyst on both sides of an electrolyte layer holding phosphoric acid, and each unit cell is connected in series through a separator. It is formed into a predetermined stack structure. Porous electrode plates and separators can be divided into ribbed or flat plate shapes depending on whether they are provided with gas flow grooves for fuel and oxidizer, but these materials have heat resistance, chemical resistance,
Carbon materials that meet required properties such as electrical conductivity, thermal conductivity, and ease of processing are useful. However, since the carbon material does not have sufficient mechanical strength, it sometimes breaks during handling or assembly and compression. In recent years, as electrodes and separators have become thinner and thinner in order to reduce resistance and stack thickness, the above-mentioned failure phenomenon tends to increase further.
Further, in the conventional method of laminating a porous electrode plate and a separator plate, it is difficult to obtain sufficiently uniform close contact between both surfaces, and therefore there is a limit to the reduction in battery internal resistance. For these reasons, attempts have been made to eliminate the above-mentioned drawbacks by previously integrally forming a porous electrode and a separator in a composite manner. Among these integrally formed methods, the simplest and most practical means are JP-A-60-20471 and JP-A-60-15759.
This is a bonding and firing method in which a carbon-based porous electrode plate and a separator plate, or precursors of these members, as proposed in et al., are bonded via an adhesive and then fired. [Problems to be solved by the invention] In the bonding firing method, the electrode and separator are bonded using a resin with a high carbon retention rate or an organic liquid adhesive such as Pitch, but at this stage the adhesive becomes porous. There is a problem in that it permeates into the electrode skeleton, which is a solid structure, clogging the porous structure of the electrode and significantly impairing adhesiveness. Furthermore, an inconvenient phenomenon often occurs in which the adhesive flows into the gas flow grooves of the electrode or separator and locally blocks the grooves. [Means for Solving the Problems] The present invention provides a method for manufacturing carbonaceous members for fuel cells that solves the above-mentioned problems in the conventional bonding and firing method. It is characterized in that the electrode plate is impregnated with a substance that dissipates in a temperature range of 50 to 600°C, then bonded to a carbon separator plate via a carbonizable adhesive, and then fired at a temperature of 800°C or higher. As the porous carbon electrode plate, a flat plate or a ribbed plate obtained by firing and carbonizing a composite of carbon fibers and a thermosetting resin is used. On the other hand, carbon separator plates can be made by impregnating a graphite substrate with a thermosetting resin liquid such as phenol or furan and then curing it, or by kneading fine carbon powder with phenol resin, furan resin, or tar pitch. An impermeable flat plate or a ribbed plate obtained by a method of molding and then firing, or a method of directly firing a molded plate of a thermosetting resin such as a phenol type or furan type to form a glassy carbon is used. The porous carbon electrode plate and the carbon separator plate are joined as follows. A porous carbon electrode plate is impregnated with a liquid substance that dissipates in a temperature range of 50 to 600°C. The impregnation treatment is performed by appropriate means such as dipping, spraying, or coating until at least the surface layer of the electrode plate structure is filled with the impregnating material. At this time, it is desirable to fill and solidify the impregnating material into the gas flow grooves provided in the porous carbon electrode plate or the carbon separator plate at the same time as the impregnation process. Substances that are used as impregnating materials and disappear in the temperature range of 50 to 600℃ refer to substances that disappear from the electrode structure through phenomena such as thermal decomposition, melting, and vaporization within the above temperature range, but include metals, inorganic It is not preferable to use materials such as salts and thermosetting resins that react with the base carbon during the firing process or generate a large amount of residual carbon. Suitable materials are polystyrene, polymethyl methacrylate, polymethyl acrylate, polyethylene, polypropylene, paraffin, naphthalene or anthracene, selected from among these. After the porous carbon electrode plate is impregnated or simultaneously filled with the impregnating material in the gas flow grooves, the impregnating material is fixed by drying naturally or by heating, and then the impregnating material that adheres to and remains on the joint surface is wiped off as necessary. Then, it is bonded to a carbon separator plate via a carbonizable adhesive. Carbonizable adhesives include initial condensates of thermosetting resins such as phenol resins and furan resins, which have a high carbonization rate and have excellent bonding strength after firing, or the resins contain fine powders such as coke, graphite, and glassy carbon. A mixture of these is used. After joining, the adhesive layer of the bonded member is cured, and then fired in an inert atmosphere at a temperature of 800°C or higher using a conventional method to obtain a carbon member for fuel cells in which a porous carbon electrode plate and a carbon separator plate are integrally formed. . [Function] In the present invention, before joining the porous carbon electrode plate and the carbon separator plate, the electrode plate is
Since the porous structure is impregnated with a substance that dissipates in the temperature range of 600℃, the porous structure is essentially filled with the substance, so the situation where the carbonizable adhesive seeps into the electrode framework during the bonding process is effectively prevented. thwarted. Furthermore, if the impregnating material is filled and solidified into the gas flow grooves of the porous carbon electrode plate or carbon separator plate during the impregnation treatment, the phenomenon of the adhesive flowing into these areas can be prevented. The impregnated substance is thermally decomposed, melted, or vaporized during the subsequent firing process, and is smoothly dissipated from within the tissue framework of the porous carbon electrode or the filled and solidified gas distribution groove, returning to the form before the impregnation/filling treatment. Due to the intervening elimination effect of the substances that are dissipated in the temperature range of 50 to 600° C., the porous structure and gas flow grooves are not blocked by the adhesive, which contributes to improved adhesiveness. [Example] A porous carbon electrode plate (150 mm square on a side, 2.4 mm thick) with a porosity of 53% and an average pore diameter of 55 μm, which has a gas flow groove of 1.5 mm width and 1.0 mm depth on one side, was made of polystyrene. % toluene solution (impregnating material) three times for impregnation treatment, and was air-dried for 24 hours to fix the polystyrene as a resin. At the same time, paraffin (softening point 60℃) is poured into the gas distribution groove.
Filled and solidified. After cleaning the bonding surface (rib part) of the porous carbon electrode plate that has been impregnated and filled, fine graphite powder (particle size
A carbon separator plate (square, 150 mm on a side, 1 mm thick) coated with a thin layer of carbonizable adhesive made of a phenolic resin containing 30 μm or less) was stacked and pressed. The thus bonded members were allowed to stand at room temperature for 12 hours, and then held at 180° C. for 3 hours to completely cure the adhesive. Next, the bonding members were packed in a graphite crucible, surrounded by coke packing, set in an electric furnace, and fired at a temperature of 1300°C. By this method
We manufactured 10 integrated composite type carbonaceous members for fuel cells. For comparison, 10 composite type members were manufactured by using a porous carbon electrode that was not subjected to the above-mentioned impregnation/filling treatment, and bonding and firing with a carbon separator plate under the same conditions. The table below shows a comparison of the properties of the members obtained in the invention example and the comparative example.

〔Effect of the invention〕

According to the present invention, the occurrence of property deterioration such as tissue clogging of porous carbon electrode plates and gas flow groove clogging in porous carbon electrode plates or carbon separator plates due to adhesives, which have been problems with conventional bonding and firing methods, can be avoided. In addition to being effectively prevented, the adhesive performance can be significantly improved. Therefore, it is possible to stably produce a high-performance carbonaceous member for fuel cells in which an electrode and a separator are integrated.

Claims (1)

[Claims] 1. A porous carbon electrode plate is impregnated with a substance that dissipates in a temperature range of 50 to 600°C, then bonded to a carbon separator plate via a carbonizable adhesive, and then fired at a temperature of 800°C or higher. A method for manufacturing a carbonaceous member for a fuel cell, characterized by: 2. The carbonaceous member for a fuel cell according to claim 1, wherein the gas flow grooves provided in the porous carbon electrode plate or the carbon separator plate are filled with a substance that is dispersed in a temperature range of 50 to 600°C during impregnation treatment. manufacturing method. 3 Substances that dissipate in the temperature range of 50 to 600°C include polystyrene, polymethyl methacrylate, polymethyl acrylate, polyethylene, polypropylene,
The method for producing a carbonaceous member for a fuel cell according to claim 1, wherein the carbonaceous member is selected from paraffin, naphthalene, or anthracene.