JP3240062B2 - Method for manufacturing fuel cell separator with end seal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a separator with an end seal constituting a composite member for a phosphoric acid type fuel cell in which a carbonaceous porous electrode plate and a dense separator are integrated.

[0002]

2. Description of the Related Art Materials such as an electrode plate and a separator plate forming a phosphoric acid type fuel cell are made of materials having heat resistance, chemical resistance, and the like.
Carbonaceous materials satisfying required characteristics such as good electrical conductivity and easy workability have been used. However, since the carbonaceous material has essentially low mechanical strength, it may be damaged during handling or cell assembly. Recently, in order to reduce the internal resistance of the battery and the thickness of the stack, the electrode plate and the separator plate have been increasingly thinned, and the degree of breakage has been increasing.

In order to solve such a problem, a porous electrode substrate previously formed of a carbon material and a separator substrate or a precursor thereof (a material before carbonization) are bonded via an adhesive. A bonding firing method for firing carbonization has been developed (JP-A-60-20471, JP-A-60-16759).
. However, in the case of using the bonding firing method, although an excellent effect is exhibited in terms of lowering the internal resistance of the battery, a step of bonding the front surface of the carbon member and further performing a firing treatment is required, so that the manufacturing cost is reduced. There is the disadvantage that it is significantly higher.

[0004] For this reason, an end sealing material is joined to both end portions of the separator with a heat-resistant and corrosion-resistant fluorine resin or the like.
A seal joining method in which a porous electrode base material is inserted into the formed concave portion (Japanese Patent Application Laid-Open No. 62-296368) has been proposed.

[0005]

According to the above-mentioned seal joining method, it is possible to greatly simplify the manufacturing process, but the bonding strength of the end seal is not sufficient, and the post-processing (finishing) is difficult. There is a problem that a peeling phenomenon of a member is easily caused. In addition, there is a complication that requires a hot press step at the time of joining.

SUMMARY OF THE INVENTION The present invention has been developed to solve the above-mentioned problems of the prior art. The purpose of the present invention is to provide an end seal material having sufficient airtightness, heat cycle resistance and corrosion resistance when a seal joining method is employed. It is an object of the present invention to provide a method of manufacturing a fuel cell separator with an end seal, which can efficiently join while holding the fuel cell.

[0007]

According to the present invention, there is provided a method of manufacturing a fuel cell separator with an end seal, which comprises the steps of: Roughness of 10μm Rz or more
A 300 μm thin joining portion is provided, and an end sealing material of the same material as the separator is provided at the joining portion with 100 parts by weight of carbon powder having an average particle size of 70 μm or less, and an aromatic polyimide precursor 1
00 to 200 parts by weight and phenol resin precondensate 20 to 50
It is characterized in that it is joined by using an adhesive having a composition consisting of parts by weight, and is heat-pressed and cured.

As the carbonaceous material constituting the separator, glassy carbon such as glassy carbon having heat resistance, corrosion resistance, high strength and excellent gas impermeability or a composite carbon material based on the same is used. Applies. Therefore, for example, a resin such as a phenolic resin, a furan resin, a polyimide resin, or a mixture of carbon powder, graphite powder, carbon fiber chop, and the like is molded into a plate shape, and then calcined and carbonized. Applicable materials.

The above-mentioned glassy carbon-based separator has a surface roughness of 10 μm Rz or more at each end (joining portion of the end sealing material) of the front surface and the back surface orthogonal to each other, and is 5 to 300 times higher than the other separator portions. μm Form a thin junction. The surface roughness Rz refers to the surface roughness standard defined in JIS B0601 (1982). By adjusting this surface roughness to 10 μm Rz or more, the adhesion wettability of the bonding surface is improved, and at the same time the bonding area is increased. As a result, the adhesive strength is effectively improved. The purpose of forming a thinned joint surface is to improve the airtightness based on the uneven structure. However, if the thickness is less than 5 μm, the effect of improving the airtightness cannot be obtained. Is easily damaged. The junction is
After the thickness is reduced to the above range by machining such as milling, it can be formed by a method of paper finishing or a surface roughening method such as a shot blast method or a sand blast method so as to have a surface roughness of 10 μm Rz or more. . At this time, the thinning is performed at the green stage of the separator (before carbonization).
Alternatively, the thinning and the roughening can be simultaneously performed by the above-described roughening.

[0010] The end sealing material is made of a glassy carbon-based material of the same material as the above-mentioned separator. This member functions to prevent gas leakage from the side of the fuel cell. If the airtightness is incomplete, the power generation efficiency is reduced, and hydrogen and oxygen are mixed to cause an explosion. If the material of the end sealing material is different from that of the separator, peeling, cracking, and the like are generated at the joining interface due to the difference in thermal expansion, and the above-mentioned phenomenon is easily caused. The size of the end sealing material varies depending on the size of the separator, but is generally 20 to 50 mm in width and 0.1 mm in thickness.
It is about 8 to 2.0 mm. In addition, if the joining surface of the end sealing material is roughened in the same manner as the separator joining portion, the joining strength can be further increased.

The composition of the adhesive is 100 parts by weight of carbon powder, 100 to 200 parts by weight of an aromatic polyimide precursor, and 20 to 50 parts by weight of a phenol resin precondensate. Coke powder having an average particle size of 70 μm or less, natural or artificial graphite powder, or the like is used as the carbon powder. A varnish-like polyamic acid is effectively used as the aromatic polyimide precursor. Further, the phenol resin precondensate is preferably a resol-based resin having fluidity at room temperature. These three components are uniformly kneaded with a kneader or the like to form an adhesive.

The bonding is performed by uniformly applying the above-mentioned adhesive to the bonding portion of the vitreous carbon-based separator using an appropriate means such as a brush coating method, a spraying method, a doctor blade method, and then placing an end seal material. This is performed by a method of curing the adhesive layer while applying heat and pressure. At this time, the thickness of the adhesive layer is 50 ~
Preferably it is in the range of 200 μm. It is desirable to use a press equipped with a heating plate for the hot-press operation, and to apply the conditions of a temperature of 100 to 250 ° C. and a pressure of 0.5 to ² kg / cm ² .

After bonding, a dispersion of polytetrafluoroethylene, for example, is applied and cured to a bonding portion which is particularly likely to come into contact with phosphoric acid to form a fluororesin coating layer, thereby further improving the stability of the bonding portion. The joining member thus formed is finally processed into a predetermined width, length and thickness to obtain a fuel cell separator with an end seal.

[0014]

According to the present invention, first, the bonding portion of the vitreous carbon-based separator is roughened to 10 μm Rz or more to enhance the adhesiveness, and further, the portion is formed thin in the range of 5 to 300 μm. Improve airtightness based on uneven joining. Second, by forming the separator and the end seal material from the same vitreous carbon-based material, it is possible to prevent the members from peeling or cracking due to a difference in thermal expansion of the material in a practical stage.

Third, the component composition of the adhesive is specified to improve the strength, heat resistance and corrosion resistance of the bonding layer. In other words, the function of each component is that the compounding of carbon powder with an average particle size of 70 μm or less imparts toughness to the bonding layer due to the combined effect, and the aromatic polyimide precursor has excellent bonding strength without applying high temperature and pressure unlike fluororesin. And a polyimide resin having heat and corrosion resistance, and the phenol resin precondensate contributes to increase interfacial adhesion.

By synergistically acting together, an end sealing material is firmly and airtightly joined to both ends of the separator which are orthogonal to each other, so that a fuel cell separator with an end seal that is stable for a long period of time even in a practical use stage. It is possible to obtain.

[0017]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Examples 1 to 7 and Comparative Examples 1 to 9 Fine powder of graphite having an average particle size of 7 μm was added to a phenol resin, kneaded, roll-formed, calcined at a temperature of 1300 ° C., and carbonized at a temperature of 1300 ° C. and a thickness of 0.6 mm. Was prepared. Then, the 45 mm-wide end portions of the front surface and the back surface of the separator, which are orthogonal to each other, were shot blasted to simultaneously perform the surface roughening and the thinning so as to obtain the surface roughness and the thinness shown in Table 1.

As the adhesive, a kneaded material having the component composition shown in Table 1 (mixed parts by weight per 100 parts by weight of graphite fine powder) was used. The aromatic polyimide precursor is pyromellitic anhydride [Kanto Chemical Co., Ltd., special grade reagent] and 4,4 'diaminodiphenyl ether [Tokyo Kasei Co., Ltd., special grade reagent]
Was polymerized in N, N dimethylacetamide [Kanto Chemical Co., Ltd., special grade reagent], and a resin content of 20% was used.
As the phenol resin precondensate, a commercially available product [PR940, manufactured by Sumitomo Durez Co., Ltd.] was used.

[0019]

[Table 1] <Table notes> (1) Polyimide precursor (2) Phenolic resin precondensate

After the adhesive having the composition shown in the same column was uniformly applied to the joints shown in Table 1 by brushing, an end seal material was overlaid on the joints, and the pressure was 1 kg / cm ² and the temperature was 200 ° C.
Heat-pressed and cured under the following conditions. The composite member integrally joined in this way was machined and finished to a dimension of a square having a variable length of 700 mm and a thickness of the end sealing material of 2.4 mm. In Example 7, of each example, a polytetrafluoroethylene dispersion [AD-1 manufactured by Asahi Glass Co., Ltd.] was applied to the joint, dried at 100 ° C., and then dried.
Curing was performed at a temperature of 0 ° C.

With respect to each of the obtained fuel cell separators with end seals, the gas permeability (airtightness) of the joints, the processing yield, the heat cycle test, the phosphoric acid (200 ° C.) immersion test, and the like were measured. Are shown in Table 2. The gas permeability was measured at room temperature with 1 kg / cm ² of nitrogen gas. In the heat cycle test, the operation of putting the joining member in a thermostat kept at 250 ° C., taking it out, and returning it to room temperature was performed once.

From the results shown in Table 2, defects are observed in any of the airtightness, processing yield, heat cycle resistance, and corrosion resistance in the comparative example. However, in the examples satisfying the requirements of the present invention, defects were observed in all characteristics. It turns out to be excellent.

[0023]

[Table 2]

[0024] Using the end seal member made of carbon material of Comparative Example 10 the thermal expansion coefficient of 1 × consists of glassy carbon of 10 ^-6 ° C. ^-1 separator and thermal expansion coefficient of 2 × 10 ^-6 ℃ ^-1, performed A composite member was produced by joining under the same conditions and process as in Example 1. When the various performances of the fuel cell separator with the end seal bonded to the different materials were measured, the gas permeability was 10 ⁻⁶ cc / cm ² min and the processing yield was 90%, which was a good result. In the test, a peeling phenomenon was observed five times.

COMPARATIVE EXAMPLE 11 The same separator and end seal material as in Example 1 were used to obtain a thickness of about 0.1 without any processing at the junction of the separator.
Bonding was performed under a hot and pressure condition of a temperature of 340 ° C. and a pressure of 10 kg / cm ^{2 with} a 05 mm polytetrafluoroethylene sheet (manufactured by Nichias Corporation) interposed. When various performances of the fuel cell separator with the end seal were measured, the gas permeability was 10%.
^It showed good airtightness of ^-6 cc / cm ² min, but the processing yield was
At a heat cycle test of 40%, the peeling phenomenon occurred 38 times.

[0026]

As described above, according to the present invention, a fuel cell separator with an end seal excellent in airtightness, heat cycle resistance and corrosion resistance can be manufactured by a simple means with good processing yield. Therefore, it is possible to efficiently produce and supply high-performance cells that can withstand long-term operation, and it is also effective in reducing manufacturing costs.

Claims (1)

(57) [Claims] 1. A joining portion having a surface roughness of not less than 10 μm Rz and a thickness of 5 to 300 μm is provided at an end portion of a front surface and a back surface of a glassy carbon-based separator which are orthogonal to each other. 70μm average particle size
The following carbon powder 100 parts by weight, aromatic polyimide precursor 100 to 200 parts by weight and phenol resin precondensate 20
A method for producing a fuel cell separator with end seals, comprising joining with an adhesive having a composition of 50 to 50 parts by weight, followed by heat-pressure and curing.