JPH05205750A - Carbonaceous preformed body and manufacture of electrode base for fuel cell - Google Patents

Abstract

PURPOSE:To provide an electrode base for a fuel cell, which is superior in its gas permeability, electric conductivity and mechanical strength, and in which pores and distribution of the pores are well controlled, by performing compression molding of a homogeneous carbonaceous preformed body, and after that, firing it. CONSTITUTION:A preformed body having paper making structure is made by using 20-50 weight percent of fiber which can be carbonized or short carbon fiber, 15-50 weight percent of a bonding agent whose carbonization yield is 40-75 weight percent, and 30-60 weight percent of an organic granular material whose carbonization yield is not more than 30 weight percent. After that, a homogeneous formed body having no segregation of the organic granular substance is provided through hot and pressure forming of the preformed body. An electrode base for a fuel cell is formed by carbonizing or graphitizing this formed body. Especially, in the case of using a thermosetting resin hardened body which is not softened by heat, as an organic granular material, an electrode base having higher performance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous preform and a fuel cell electrode substrate useful for preparing an electrode plate for a phosphoric acid fuel cell or the like.

[0002]

2. Description of the Related Art Fuel cells, unlike other power generators,
It is characterized by extremely low emissions of pollutants such as Ox, NOx and dust, and low noise sources. Among such fuel cells, the phosphoric acid fuel cell has a structure in which a porous cathode and an anode are provided on both sides of an electrolytic solution to form a unit cell, and each unit cell is laminated via a separator. The cathode and the anode are required to have a controlled pore distribution and high gas permeability in order to increase the efficiency of conversion into electric energy. Furthermore, electrical conductivity, thermal conductivity, mechanical strength and resistance to phosphoric acid at operating temperature are required.

Conventionally, as a method for manufacturing a fuel cell electrode plate,
A method of dry-mixing a binder such as a phenolic resin, carbon fiber, and a granular thermoplastic resin in a specific ratio, press-molding the mixture into a sheet with a hot roll or hot press, and carbonizing or graphitizing the mixture. Has been adopted (Tokuhei 1-36
670).

[0004]

However, in this method, since the carbon fiber and the thermoplastic resin as the pore-forming agent are in a fibrous form and powdery granules having poor miscibility, the carbon fiber and the thermoplastic resin are mixed during dry mixing. It tends to segregate and it is difficult to obtain a homogeneous mixture. In addition, when the powder mixture is pressure-molded, the segregated thermoplastic resin is aggregated, and the molded product is likely to become more inhomogeneous. Therefore, it is difficult to control the pore size distribution. Especially when obtaining a thin electrode plate, it is difficult to form uniform pores.

More specifically, in the above method, when the thickness is 1 mm or more, the size is 1000 mm ×
Even if the thickness is about 1000 mm, the pores of the electrode plate are relatively homogeneous, but if the thickness is less than 1 mm, the homogeneous pores are not formed. Furthermore, since it is in the form of powder obtained by dry-mixing short fibers of carbon fiber, a binder, and a granular organic material, it is difficult to uniformly fill the mold during pressure molding, and the workability is extremely poor.

Further, in the above method, when the mixture is heated and pressure-molded into a sheet by a hot roll or a hot press, the segregated thermoplastic resin is softened, and the molded plate is apt to warp or swell. Occurrence is sometimes remarkable. Furthermore, when the molded plate is carbonized or graphitized by firing, the thermoplastic resin is softened and decomposed again, so that the fired plate is apt to warp and swell, and the uniformity and dimensional stability are deteriorated. The yield of high quality electrode plates is poor. Moreover, in the above method, since the particle size of the thermoplastic resin as the pore-forming agent is directly related to the pore size distribution, the thermoplastic resin is softened twice at the time of heating and pressurizing and firing, and Coupled with the segregation of the curable resin, the pore size changes greatly, and the pore size and its distribution are likely to be non-uniform. As a result, the pore size and its distribution cannot be controlled arbitrarily and accurately, and an electrode plate excellent in gas permeability, electrical conductivity and mechanical strength cannot be obtained.

[0007]

Therefore, an object of the present invention is to produce a homogeneous fuel cell electrode substrate which is capable of controlling the pore size and its distribution and is excellent in gas permeability, electrical conductivity and mechanical strength. Another object of the present invention is to provide a useful carbonaceous preform.

Another object of the present invention is to provide a carbonaceous preform capable of controlling the pore size and the distribution of the pores of the fuel cell electrode substrate arbitrarily and accurately.

Still another object of the present invention is to provide a homogeneous fuel cell electrode substrate having the above-mentioned excellent properties.

[0010]

In order to achieve the above object, the inventors of the present invention have, as a result of extensive studies, compression-molded and carbonized a carbonaceous preform having a papermaking structure containing carbon fibers, a binder and an organic particulate matter. In the case of graphitization, it was found that segregation of organic particulate matter can be prevented and a homogeneous carbonaceous substrate can be obtained, and the present invention was completed.

That is, according to the present invention, carbon fiber-forming fibers or carbon fiber short fibers 20 to 50% by weight, carbonization yield 4
Provided is a carbonaceous preform having a papermaking structure, which comprises 0 to 75% by weight of a binder of 15 to 50% by weight, and a carbonization yield of 30 to 60% by weight of an organic particulate matter.

In the preform, the organic particulate matter is preferably a thermosetting resin cured product, and the particle size of the organic particulate matter is preferably 50 to 300 μm.

The present invention also provides a fuel cell electrode substrate in which the above-mentioned preform is compression-molded and carbonized or graphitized.

In the present specification, carbonization means that a carbonizable component is calcined at a temperature of, for example, about 450 to 1500 ° C. Graphitization means, for example, 1
It means firing at a temperature of about 500 to 3000 ° C.,
It is included in the concept of graphitization even when it does not have the crystal structure of graphite. In addition, the carbonization yield refers to the residual carbon rate when carbonizable components are carbonized or graphitized.

Carbon fiber refers to carbonized or graphitized fiber. The flameproofing treatment is a treatment of heating fibers other than pitch-based fibers at a temperature of about 200 to 450 ° C. in the presence of oxygen to form a heat-resistant layer on the surface and preventing melting during firing. The infusibilizing treatment, for example, pitch-based fiber,
In the presence of oxygen, it is a treatment of heating at a temperature of about 200 to 450 ° C. to form a heat resistant layer on the surface and preventing melting during firing.

In the present invention, the carbon fiber-forming fibers are various fibers which can be used as a raw material for carbon fibers, for example, polyacrylonitrile fiber, phenol resin fiber,
Examples include rayon, cellulosic fibers, pitch fibers and the like. The carbon fiber-formable fiber may be subjected to a flameproofing treatment or an infusibilization treatment. Examples of the carbon fibers include fibers obtained by carbonizing or graphitizing the above-mentioned carbon fiber-forming fibers. One kind or two or more kinds of carbon fiber and carbon fiber can be used.

In the present invention, carbon fiber-forming fibers or carbon fiber short fibers are used. The fiber length of the short fibers is, for example, 0.05 mm to 10 mm, preferably 0.5 mm to 3
It is about mm. The fiber length of the carbon fiber greatly contributes to the bending strength, electric conductivity and thermal conductivity of the electrode substrate. If the fiber length exceeds 10 mm, the pore size and its distribution are likely to be non-uniform, and if it is less than 0.05 mm, the strength and the like are likely to decrease.

The proportion of fibers or carbon fibers that can be made into carbon fibers is about 20 to 50% by weight, preferably about 22.5 to 40% by weight. When it is less than 20% by weight, the electric conductivity, thermal conductivity and bending strength of the electrode substrate are lowered, and when it exceeds 50% by weight, the porosity tends to be small.

As the binder, for example, a thermosetting resin such as phenol resin or furan resin; a thermoplastic resin such as polyacrylonitrile; coal or petroleum pitch can be used. Of these binders, thermosetting resins, especially phenolic resins, are preferred. The carbonization yield of the binder is about 40 to 75% by weight, preferably about 50 to 75% by weight in order to prevent the mechanical strength of the electrode substrate from decreasing and to adjust the porosity. The carbonization yield of the phenolic resin is usually as large as about 65 to 75% by weight. At least one of these binders can be used.

The proportion of the binder is 15 to 50% by weight, preferably about 15 to 40% by weight. If it is less than 15% by weight, the mechanical strength tends to be low, and if it exceeds 50% by weight, the porosity tends to be small and the pore size and its distribution are likely to be non-uniform.

As the organic particulate matter in the present invention, an organic particulate matter having a carbonization yield of 30% by weight or less is used. If the carbonization yield exceeds 30%, it is difficult to form fine and uniform pores and adjust the porosity.

Examples of such organic particulate matter include powdery particles of thermosetting resin such as phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, diallyl phthalate resin, urea resin and polyurethane, and the like. Granules composed of a cured product of a curable resin; polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl chloride, acrylic polymer,
Styrene-based polymers such as polyester, nylon, polystyrene, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-acrylic copolymer, synthetic resins such as polycarbonate and polyacetal, natural products such as rosin and their derivatives And the like, and the like, and the like, such as thermoplastic resin powders and the like.

Of the thermosetting resins, the phenol resin is different from the binder in the carbonization yield of 30%.
The following are used: These organic particulate materials may be used alone or in combination of two or more.

These organic particulate materials function as a pore-forming agent that creates pores in the carbon material. Among the organic particulate materials, a powder or granular material made of a cured product of a thermosetting resin is preferable. In particular, powder particles of a cured product such as an epoxy resin and an unsaturated polyester resin are preferable. By using a powder or granular material made of a cured product of a thermosetting resin, the porosity and the pore size can be controlled with high accuracy. That is, since the powder or granular material made of the cured product of the thermosetting resin is not softened by heating, pores having pore diameters corresponding to the particle size and amount of the cured product are formed. Therefore, an electrode plate in which the pore diameter and its distribution are arbitrarily controlled can be obtained. Further, for the same reason, it is possible to obtain a homogeneous electrode plate having excellent gas permeability, electrical conductivity and mechanical strength.

Furthermore, since the powder or granular material made of the above-mentioned cured product does not soften during heat and pressure molding, the thickness is as thin as 1 mm or less, and even if it has a large area of about 1000 mm × 1000 mm, it warps and swells at the time of demolding. It is possible to obtain an electrode substrate having excellent uniformity and dimensional stability. Moreover, since the pore-forming agent is not re-softened during the carbonization or graphitization treatment, the electrode plate does not warp, swell, or crack, and the yield in the manufacturing process is very high.

The particle size of the above-mentioned granular material can be selected according to the desired pore size, etc., but is usually 10 to 500 μm, preferably 50 to 300 μm, more preferably 100 to
It is about 250 μm. If the particle size is less than 10 μm, the gas permeability is significantly reduced, and if it exceeds 500 μm, the gas permeability is improved but the bending strength is reduced. The "particle diameter" here mainly means the average particle diameter, and the powdery and granular cured product may contain fine particles and coarse particles that are inevitably mixed. By appropriately selecting the particle size of the organic particulate matter, the porosity and the pore size can be adjusted.

The proportion of the above organic particulate matter is 30 to 60% by weight, preferably 30 to 55% by weight. If it deviates from this range, either one of the porosity and bending strength of the electrode plate deteriorates.

The carbonaceous preform of the present invention comprises carbon fiber,
It has a papermaking structure containing a binder and organic particulate matter. The papermaking structure means a structure in which fibers are randomly oriented, like Japanese paper. Such a preform can be obtained by, for example, a suction molding method. Examples of the suction molding method include (1) a method of sucking a slurry containing the components with a suction molding die having a large number of suction holes, and depositing the components on the surface of the suction molding die, (2) suction A method of injecting the slurry into the molding die and sucking the slurry can be adopted. The density of the suction molded body obtained by the suction molding method can be easily controlled by the suction pressure.

When preparing the slurry, the carbon fibers may be beaten to form the short fibers. The solid content concentration of the slurry can be selected within a range that does not impair the suction moldability, and is, for example, about 0.1 to 2% by weight. In addition, in order to uniformly disperse the carbon fibers, the binder and the organic particulate matter in the slurry, a dispersant, a stabilizer, a viscosity modifier, an anti-settling agent, etc. may be added. Various additives such as a strengthening agent and a surfactant having an aggregating action, particularly a polymer aggregating agent and a yield improving agent may be added.

The carbonaceous preform removed from the suction mold is usually heated and dried. The carbonaceous preform in a wet state can be dried by heating at atmospheric pressure or reduced pressure at a temperature of about 50 to 200 ° C.

According to the suction molding method as described above, even if a fibrous substance and a granular material which are difficult to uniformly mix by the conventional dry mixing method are used, the fibrous substance and the granular material are not segregated. Thus, a homogeneous carbonaceous preform can be obtained. Even if the carbonaceous preform is compression-molded, the homogeneity of the compact is maintained. Therefore, even if a thermoplastic resin that is softened by heat is used as the organic particulate matter, the warpage or swelling of the molded body or the electrode plate, which occurs during the heating and pressure molding and firing due to the segregation of the plastic resin, can be significantly suppressed, The uniformity of the body and electrode plate can be improved.

When the carbonaceous preform is compression-molded, a compact having a uniform composition, density and thickness can be obtained even if the thickness is less than 1 mm. In particular, when a thermosetting resin is used as the binder, the carbonaceous preform functions as a prepreg and is cured and integrated by heat and pressure molding. Therefore, even if the thickness is less than 1 mm, a homogeneous and uniform molded body can be obtained.

Further, since a complicated dry mixing step is unnecessary, the preform can be easily manufactured by suction molding. Furthermore, when compression molding the preform, it is not necessary to uniformly load the powder-granular mixture into the mold, and it is sufficient to load the sheet-form preform into the mold, which facilitates the loading operation. In addition, the molding cycle can be shortened, and the molding efficiency and hence the production efficiency of the electrode substrate can be improved.

The fuel cell electrode substrate of the present invention can be produced by subjecting the above-mentioned carbonaceous preform to compression molding, preferably heat and pressure molding, and then subjecting it to a firing step of carbonization or graphitization. The compression molding can further improve the homogeneity of the molded body.

The compression molding of the suction molded article can be carried out by a conventional method such as a die press or a roller press. The compression molding is preferably performed under heating in order to improve the uniformity of the molded product. The heating temperature can be appropriately selected, but is usually about 100 to 250 ° C. The molding pressure can be selected according to the desired density and thickness of the electrode plate, and is, for example, about 30 to 750 kgf / cm ² , preferably about 50 to 500 kgf / cm ² .

The carbonaceous preform, after being compression molded,
It is subjected to a firing step of carbonizing or graphitizing. The firing temperature is 800 ° C. or higher, preferably about 1000 to 3000 ° C. Firing is performed under vacuum or in an inert gas atmosphere. Nitrogen, helium, argon or the like can be used as the inert gas.

The carbonaceous electrode substrate thus obtained has a uniform preform, so that even if the thickness is less than 1 mm, the pore size is uniform, the mechanical strength is large, and it is excellent. Has gas permeability and conductivity.

[0038]

EFFECTS OF THE INVENTION The carbonaceous preform of the present invention has a papermaking structure containing carbon fibers, a binder and an organic particulate matter, so that there is no segregation of the organic particulate matter and it is homogeneous and has pores and Controllable distribution, gas permeability, electrical conductivity,
It is useful for obtaining a carbonaceous electrode substrate having excellent mechanical strength and uniformity.

In particular, when a cured product of a thermosetting resin is used as the organic particulate material, the pore size and its distribution of the electrode substrate can be accurately controlled, and the uniform pore size and its distribution can be obtained, and the warp, swelling, It is possible to obtain a uniform electrode substrate without cracks and the like.

Furthermore, the fuel cell electrode substrate of the present invention comprises:
Homogeneous, the pore size and its distribution can be controlled arbitrarily.
Excellent gas permeability, electrical conductivity, mechanical strength and uniformity.

[0041]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 100 parts by weight of phenolic resin [Gunei Chemical Industry Co., Ltd., trade name REGITOP PS-4101, carbonization yield 60% by weight], carbon fiber having an average fiber length of 0.7 mm [(Ltd.) 100 parts by weight of Donac, trade name Dona Carbo S-244] and a powder of epoxy resin cured product [Yukaka Shell Co., Ltd., trade name Epicoat 815, carbonization yield 10% by weight] (particle size 20 to
250 parts by weight (80 μm) was dispersed in water to prepare a uniform slurry.

Then, the above-mentioned slurry was poured into a suction mold (600 mm × 600 mm) having a large number of small holes for suction formed on the bottom face while being sucked, and deposited on the bottom face of the mold. The wet plate thus formed was removed from the mold and dried at 100 ° C. for 4 hours. The thus obtained preform having a papermaking structure has a thickness of 10 mm × 600 m.
m × 600 mm and its density was 0.2 g / cm ³ .

Then, this preform is 600 mm ×
The mixture was placed in a flat plate mold of 600 mm, heated and pressed at a pressing temperature of 165 ° C. and a molding pressure of 150 kgf / cm ² for 20 minutes to be cured, and a molded body having a thickness of 1 mm and a density of 1.3 g / cm ³ was obtained. This molded body is left for 4 hours at a temperature of 220 ° C. to be post-cured, then sandwiched between graphite plates, heated up to 2000 ° C. at a heating rate of 30 ° C./hour, and graphitized at the same temperature for 3 hours. By processing, a carbonaceous electrode substrate was obtained.

Example 2 A preform having a papermaking structure obtained in the same manner as in Example 1 was pressure-molded in the same manner as in Example 1 except that the molding pressure was changed, and the thickness was 1.3 mm and the density was 1. A molded body of 0 g / cm ³ was obtained. This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Example 3 Phenolic resin [Kanebo Co., Ltd., trade name Bell Pearl S-
899, carbonization yield 65% by weight] 60 parts by weight, carbon fiber having an average fiber length of 0.7 mm [DONAC Co., Ltd., product name Donacarb S-244] 100 parts by weight and unsaturated polyester resin cured product [Takeda Yakuhin Kogyo ( Co., Ltd., trade name Polymer 9802, carbonization yield 10 wt%] powder (particle size 100-
100 parts by weight (250 μm) was dispersed in water to prepare a uniform slurry.

Then, a preformed body was prepared in the same manner as in Example 1 and then molded, and a spacer was used to obtain a molded body having a thickness of 2 mm and a density of 1.0 g / cm ³ . This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Example 4 When a preform having a papermaking structure obtained in the same manner as in Example 3 was molded, pressure molding was carried out in the same manner as in Example 3 except that the molding pressure was changed, and the thickness was 2.5 mm and the density was 2.5 mm. A molded body of 0.8 g / cm ³ was obtained. This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Comparative Example 1 100 parts by weight of the phenol resin used in Example 1, 100 parts by weight of carbon fiber having an average fiber length of 0.7 mm, and polyvinyl alcohol [manufactured by Kuraray Co., Ltd., particle size 20-80 μm] 2
50 parts by weight were dry mixed.

This mixture was placed in a flat plate mold of 600 mm × 600 mm, the press temperature was 165 ° C., the molding pressure was 150 k.
It was heated and pressed at gf / cm ² for 20 minutes to obtain a cured plate having a thickness of 1 mm. This cured plate was left at 220 ° C. for 4 hours for post-curing, then sandwiched between graphite plates, heated to 2000 ° C. at a heating rate of 30 ° C./hour, and graphitized at the same temperature for 3 hours. By processing, a carbonaceous electrode substrate was obtained.

Comparative Example 2 60 parts by weight of the phenol resin used in Example 1, 100 parts by weight of carbon fiber having an average fiber length of 0.7 mm and polyvinyl alcohol [manufactured by Kuraray Co., Ltd., particle size 100 to 250 μm]
100 parts by weight were dry mixed. Using this mixture, a carbonaceous electrode substrate was obtained in the same manner as in Comparative Example 1.

When the porosity, bending strength, gas permeability and volume resistivity of the electrode substrates obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were measured, the results shown in Table 1 were obtained.

[0053]

[Table 1] From Table 1, the electrode substrates obtained in Examples 1 to 4 have an appropriate porosity, and, as compared with Comparative Examples 1 and 2, the bending strength and the conductivity are very large, and the excellent gas permeability is obtained. Indicated.

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[Procedure amendment]

[Submission date] June 8, 1992

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Manufacturing method of carbonaceous preform and electrode substrate for fuel cell

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous preform useful for producing an electrode plate for a phosphoric acid fuel cell and a method for producing a fuel cell electrode substrate.

[0002]

2. Description of the Related Art Fuel cells, unlike other power generators,
It is characterized by extremely low emission of pollutants such as Ox, NOx and dust, and low noise generation source. Among such fuel cells, the phosphoric acid fuel cell has a structure in which a porous cathode and an anode are provided on both sides of an electrolytic solution to form a unit cell, and each unit cell is laminated via a separator. The cathode and the anode are required to have a controlled pore distribution and high gas permeability in order to increase the efficiency of conversion into electric energy. Furthermore, electrical conductivity, thermal conductivity, mechanical strength and resistance to phosphoric acid at operating temperature are required.

Conventionally, as a method for manufacturing a fuel cell electrode plate,
A method of dry-mixing a binder such as a phenolic resin, carbon fiber, and a granular thermoplastic resin in a specific ratio, press-molding the mixture into a sheet with a hot roll or hot press, and carbonizing or graphitizing the mixture. Has been adopted (Tokuhei 1-36
670).

However, in this method, since the carbon fiber and the thermoplastic resin as the pore-forming agent are in a fibrous form and powdery granules having poor miscibility, the carbon fiber and the thermoplastic resin are mixed during dry mixing. It tends to segregate and it is difficult to obtain a homogeneous mixture. In addition, when the powder mixture is pressure-molded, the segregated thermoplastic resin is aggregated, and the molded product is likely to become more inhomogeneous. Therefore, it is difficult to control the pore size distribution. Especially when obtaining a thin electrode plate, it is difficult to form uniform pores.

More specifically, in the above method, when the thickness is 1 mm or more, the size is 1000 mm ×
Even if the thickness is about 1000 mm, the pores of the electrode plate are relatively homogeneous, but if the thickness is less than 1 mm, the homogeneous pores are not formed. Furthermore, since it is in the form of powder obtained by dry-mixing short fibers of carbon fiber, a binder, and a granular organic material, it is difficult to uniformly fill the mold during pressure molding, and the workability is extremely poor.

Further, in the above method, when the mixture is heated and pressure-molded into a sheet by a hot roll or a hot press, the segregated thermoplastic resin is softened, and the molded plate is apt to warp or swell. Occurrence is sometimes remarkable. Furthermore, when the molded plate is carbonized or graphitized by firing, the thermoplastic resin is softened and decomposed again, so that the fired plate is apt to warp and swell, and the uniformity and dimensional stability are deteriorated. The yield of high quality electrode plates is poor. Moreover, in the above method, since the particle size of the thermoplastic resin as the pore-forming agent is directly related to the pore size distribution, the thermoplastic resin is softened twice at the time of heating and pressurizing and firing, and Coupled with the segregation of the curable resin, the pore size changes greatly, and the pore size and its distribution are likely to be non-uniform. As a result, the pore size and its distribution cannot be controlled arbitrarily and accurately, and an electrode plate excellent in gas permeability, electrical conductivity and mechanical strength cannot be obtained.

[0007]

Therefore, an object of the present invention is to produce a homogeneous fuel cell electrode substrate which is capable of controlling the pore size and its distribution and is excellent in gas permeability, electrical conductivity and mechanical strength. Another object of the present invention is to provide a useful carbonaceous preform.

Another object of the present invention is to provide a carbonaceous preform capable of controlling the pore size and the distribution of the pores of the fuel cell electrode substrate arbitrarily and accurately.

Still another object of the present invention is to provide a method for producing a homogeneous fuel cell electrode substrate having the above-mentioned excellent properties.

[0010]

In order to achieve the above object, the inventors of the present invention have, as a result of extensive studies, compression-molded and carbonized a carbonaceous preform having a papermaking structure containing carbon fibers, a binder and an organic particulate matter. In the case of graphitization, it was found that segregation of organic particulate matter can be prevented and a homogeneous carbonaceous substrate can be obtained, and the present invention was completed.

That is, according to the present invention, carbon fiber-forming fibers or carbon fiber short fibers 20 to 50% by weight, carbonization yield 4
Provided is a carbonaceous preform having a papermaking structure, which comprises 0 to 75% by weight of a binder of 15 to 50% by weight, and a carbonization yield of 30 to 60% by weight of an organic particulate matter.

In the preform, the organic particulate matter is preferably a thermosetting resin cured product, and the particle size of the organic particulate matter is preferably 50 to 300 μm.

Further, the present invention is compression molded the preform, and manufacturing of the electrode substrate for a fuel cell to carbonization or graphitization
A manufacturing method is provided.

In the present specification, carbonization means that a carbonizable component is calcined at a temperature of, for example, about 450 to 1500 ° C. Graphitization means, for example, 1
It means firing at a temperature of about 500 to 3000 ° C.,
It is included in the concept of graphitization even when it does not have the crystal structure of graphite. In addition, the carbonization yield refers to the residual carbon rate when carbonizable components are carbonized or graphitized.

Carbon fiber refers to carbonized or graphitized fiber. The flameproofing treatment is a treatment of heating fibers other than pitch-based fibers at a temperature of about 200 to 450 ° C. in the presence of oxygen to form a heat-resistant layer on the surface and preventing melting during firing. The infusibilizing treatment, for example, pitch-based fiber,
In the presence of oxygen, it is a treatment of heating at a temperature of about 200 to 450 ° C. to form a heat resistant layer on the surface and preventing melting during firing.

In the present invention, the carbon fiber-forming fibers are various fibers which can be used as a raw material for carbon fibers, for example, polyacrylonitrile fiber, phenol resin fiber,
Examples include rayon, cellulosic fibers, pitch fibers and the like. The carbon fiber-formable fiber may be subjected to a flameproofing treatment or an infusibilization treatment. Examples of the carbon fibers include fibers obtained by carbonizing or graphitizing the above-mentioned carbon fiber-forming fibers. One kind or two or more kinds of carbon fiber and carbon fiber can be used.

In the present invention, carbon fiber-forming fibers or carbon fiber short fibers are used. The fiber length of the short fibers is, for example, 0.05 mm to 10 mm, preferably 0.5 mm to 3
It is about mm. The fiber length of the carbon fiber greatly contributes to the bending strength, electric conductivity and thermal conductivity of the electrode substrate. If the fiber length exceeds 10 mm, the pore size and its distribution are likely to be non-uniform, and if it is less than 0.05 mm, the strength and the like are likely to decrease.

The proportion of fibers or carbon fibers that can be made into carbon fibers is about 20 to 50% by weight, preferably about 22.5 to 40% by weight. When it is less than 20% by weight, the electric conductivity, thermal conductivity and bending strength of the electrode substrate are lowered, and when it exceeds 50% by weight, the porosity tends to be small.

As the binder, for example, a thermosetting resin such as phenol resin or furan resin; a thermoplastic resin such as polyacrylonitrile; coal or petroleum pitch can be used. Of these binders, thermosetting resins, especially phenolic resins, are preferred. The carbonization yield of the binder is about 40 to 75% by weight, preferably about 50 to 75% by weight in order to prevent the mechanical strength of the electrode substrate from decreasing and to adjust the porosity. The carbonization yield of the phenolic resin is usually as large as about 65 to 75% by weight. At least one of these binders can be used.

The proportion of the binder is 15 to 50% by weight, preferably about 15 to 40% by weight. If it is less than 15% by weight, the mechanical strength tends to be low, and if it exceeds 50% by weight, the porosity tends to be small and the pore size and its distribution are likely to be non-uniform.

As the organic particulate matter in the present invention, an organic particulate matter having a carbonization yield of 30% by weight or less is used. If the carbonization yield exceeds 30%, it is difficult to form fine and uniform pores and adjust the porosity.

Examples of such organic particulate matter include powdery particles of thermosetting resin such as phenol resin, epoxy resin, unsaturated polyester resin, melamine resin, diallyl phthalate resin, urea resin and polyurethane, and the like. Granules composed of a cured product of a curable resin; polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl chloride, acrylic polymer,
Styrene-based polymers such as polyester, nylon, polystyrene, styrene-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-acrylic copolymer, synthetic resins such as polycarbonate and polyacetal, natural products such as rosin and their derivatives And the like, and the like, and the like, such as thermoplastic resin powders and the like.

Of the thermosetting resins, the phenol resin is different from the binder in the carbonization yield of 30%.
The following are used: These organic particulate materials may be used alone or in combination of two or more.

These organic particulate materials function as a pore-forming agent that creates pores in the carbon material. Among the organic particulate materials, a powder or granular material made of a cured product of a thermosetting resin is preferable. In particular, powder particles of a cured product such as an epoxy resin and an unsaturated polyester resin are preferable. By using a powder or granular material made of a cured product of a thermosetting resin, the porosity and the pore size can be controlled with high accuracy. That is, since the powder or granular material made of the cured product of the thermosetting resin is not softened by heating, pores having pore diameters corresponding to the particle size and amount of the cured product are formed. Therefore, an electrode plate in which the pore diameter and its distribution are arbitrarily controlled can be obtained. Further, for the same reason, it is possible to obtain a homogeneous electrode plate having excellent gas permeability, electrical conductivity and mechanical strength.

Furthermore, since the powder or granular material made of the above-mentioned cured product does not soften during heat and pressure molding, the thickness is as thin as 1 mm or less, and even if it has a large area of about 1000 mm × 1000 mm, it warps and swells at the time of demolding. It is possible to obtain an electrode substrate having excellent uniformity and dimensional stability. Moreover, since the pore-forming agent is not re-softened during the carbonization or graphitization treatment, the electrode plate does not warp, swell, or crack, and the yield in the manufacturing process is very high.

The particle size of the above-mentioned granular material can be selected according to the desired pore size, etc., but is usually 10 to 500 μm, preferably 50 to 300 μm, more preferably 100 to
It is about 250 μm. If the particle size is less than 10 μm, the gas permeability is significantly reduced, and if it exceeds 500 μm, the gas permeability is improved but the bending strength is reduced. The "particle diameter" here mainly means the average particle diameter, and the powdery and granular cured product may contain fine particles and coarse particles that are inevitably mixed. By appropriately selecting the particle size of the organic particulate matter, the porosity and the pore size can be adjusted.

The proportion of the above organic particulate matter is 30 to 60% by weight, preferably 30 to 55% by weight. If it deviates from this range, either one of the porosity and bending strength of the electrode plate deteriorates.

The carbonaceous preform of the present invention comprises carbon fiber,
It has a papermaking structure containing a binder and organic particulate matter. The papermaking structure means a structure in which fibers are randomly oriented, like Japanese paper. Such a preform can be obtained by, for example, a suction molding method. Examples of the suction molding method include (1) a method of sucking a slurry containing the components with a suction molding die having a large number of suction holes, and depositing the components on the surface of the suction molding die, (2) suction A method of injecting the slurry into the molding die and sucking the slurry can be adopted. The density of the suction molded body obtained by the suction molding method can be easily controlled by the suction pressure.

When preparing the slurry, the carbon fibers may be beaten to form the short fibers. The solid content concentration of the slurry can be selected within a range that does not impair the suction moldability, and is, for example, about 0.1 to 2% by weight. In addition, in order to uniformly disperse the carbon fibers, the binder and the organic particulate matter in the slurry, a dispersant, a stabilizer, a viscosity modifier, an anti-settling agent, etc. may be added. Various additives such as a strengthening agent and a surfactant having an aggregating action, particularly a polymer aggregating agent and a yield improving agent may be added.

The carbonaceous preform removed from the suction mold is usually heated and dried. The carbonaceous preform in a wet state can be dried by heating at atmospheric pressure or reduced pressure at a temperature of about 50 to 200 ° C.

According to the suction molding method as described above, even if a fibrous substance and a granular material which are difficult to uniformly mix by the conventional dry mixing method are used, the fibrous substance and the granular material are not segregated. Thus, a homogeneous carbonaceous preform can be obtained. Even if the carbonaceous preform is compression-molded, the homogeneity of the compact is maintained. Therefore, even if a thermoplastic resin that is softened by heat is used as the organic particulate matter, the warpage or swelling of the molded body or the electrode plate, which occurs during the heating and pressure molding and firing due to the segregation of the plastic resin, can be significantly suppressed, The uniformity of the body and electrode plate can be improved.

When the carbonaceous preform is compression-molded, a compact having a uniform composition, density and thickness can be obtained even if the thickness is less than 1 mm. In particular, when a thermosetting resin is used as the binder, the carbonaceous preform functions as a prepreg and is cured and integrated by heat and pressure molding. Therefore, even if the thickness is less than 1 mm, a homogeneous and uniform molded body can be obtained.

Further, since a complicated dry mixing step is unnecessary, the preform can be easily manufactured by suction molding. Furthermore, when compression molding the preform, it is not necessary to uniformly load the powder-granular mixture into the mold, and it is sufficient to load the sheet-form preform into the mold, which facilitates the loading operation. In addition, the molding cycle can be shortened, and the molding efficiency and hence the production efficiency of the electrode substrate can be improved.

The fuel cell electrode substrate of the present invention can be produced by subjecting the carbonaceous preform to compression molding, preferably heat and pressure molding, and then subjecting it to a firing step of carbonization or graphitization. The compression molding can further improve the homogeneity of the molded body.

The compression molding of the suction molded body can be carried out by a conventional method such as a die press or a roller press. The compression molding is preferably performed under heating in order to improve the uniformity of the molded product. The heating temperature can be appropriately selected, but is usually about 100 to 250 ° C. The molding pressure can be selected according to the desired density and thickness of the electrode plate, and is, for example, about 30 to 750 kgf / cm ² , preferably about 50 to 500 kgf / cm ² .

The carbonaceous preform, after being compression molded,
It is subjected to a firing step of carbonizing or graphitizing. The firing temperature is 800 ° C. or higher, preferably about 1000 to 3000 ° C. The firing is performed under vacuum or in an inert gas atmosphere. Nitrogen, helium, argon or the like can be used as the inert gas.

The carbonaceous electrode substrate thus obtained has a uniform preform, so that even if the thickness is less than 1 mm, the pore size is uniform, the mechanical strength is large, and it is excellent. Has gas permeability and conductivity.

[0038]

Since the carbonaceous preform of the present invention has a papermaking structure containing carbon fibers, a binder and an organic particulate matter, it is homogeneous without segregation of the organic particulate matter and has pores and Controllable distribution, gas permeability, electrical conductivity,
It is useful for obtaining a carbonaceous electrode substrate having excellent mechanical strength and uniformity.

In particular, when a cured product of a thermosetting resin is used as the organic particulate material, the pore size and its distribution of the electrode substrate can be accurately controlled, and the uniform pore size and its distribution can be obtained, and the warp, swelling, It is possible to obtain a uniform electrode substrate without cracks and the like.

Further, the fuel cell electrode substrate of the present invention is manufactured.
According to the manufacturing method, it is possible to obtain a fuel cell electrode substrate that is homogeneous and has a pore size and its distribution arbitrarily controlled , and that is excellent in gas permeability, electrical conductivity, mechanical strength and uniformity. Can
It

[0041]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 100 parts by weight of phenolic resin [Gunei Chemical Industry Co., Ltd., trade name REGITOP PS-4101, carbonization yield 60% by weight], carbon fiber having an average fiber length of 0.7 mm [(Ltd.) 100 parts by weight of Donac, trade name Dona Carbo S-244] and a powder of epoxy resin cured product [Yukaka Shell Co., Ltd., trade name Epicoat 815, carbonization yield 10% by weight] (particle size 20 to
250 parts by weight (80 μm) was dispersed in water to prepare a uniform slurry.

Then, the above-mentioned slurry was poured into a suction mold (600 mm × 600 mm) having a large number of small holes for suction formed on the bottom face while being sucked, and deposited on the bottom face of the mold. The wet plate thus formed was removed from the mold and dried at 100 ° C. for 4 hours. The thus obtained preform having a papermaking structure has a thickness of 10 mm × 600 m.
m × 600 mm, and its density was 0.2 g / cm ³ .

Then, this preform is 600 mm ×
It was put in a 600 mm flat plate mold, heated and pressed at a pressing temperature of 165 ° C. and a molding pressure of 150 kgf / cm ² for 20 minutes to be cured, and a molded body having a thickness of 1 mm and a density of 1.3 g / cm ³ was obtained. This molded body is left for 4 hours at a temperature of 220 ° C. to be post-cured, then sandwiched between graphite plates, heated up to 2000 ° C. at a heating rate of 30 ° C./hour, and graphitized at the same temperature for 3 hours. By processing, a carbonaceous electrode substrate was obtained.

Example 2 A preform having a papermaking structure obtained in the same manner as in Example 1 was pressure-molded in the same manner as in Example 1 except that the molding pressure was changed, and the thickness was 1.3 mm and the density was 1. A molded body of 0 g / cm ³ was obtained. This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Example 3 Phenolic resin [Kanebo Co., Ltd., trade name Bell Pearl S-
899, carbonization yield 65% by weight] 60 parts by weight, carbon fiber having an average fiber length of 0.7 mm [DONAC Co., Ltd., product name Donacarb S-244] 100 parts by weight and unsaturated polyester resin cured product [Takeda Yakuhin Kogyo ( Co., Ltd., trade name Polymer 9802, carbonization yield 10 wt%] powder (particle size 100-
100 parts by weight (250 μm) was dispersed in water to prepare a uniform slurry.

Then, a preform was prepared in the same manner as in Example 1 and then formed, and a spacer was used to obtain a form having a thickness of 2 mm and a density of 1.0 g / cm ³ . This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Example 4 When a preform having a papermaking structure obtained in the same manner as in Example 3 was molded, pressure molding was carried out in the same manner as in Example 3 except that the molding pressure was changed, and the thickness was 2.5 mm and the density was 2.5 mm. A molded body of 0.8 g / cm ³ was obtained. This molded body was treated in the same manner as in Example 1 to obtain a carbonaceous electrode substrate.

Comparative Example 1 100 parts by weight of the phenol resin used in Example 1, 100 parts by weight of carbon fiber having an average fiber length of 0.7 mm, and polyvinyl alcohol [manufactured by Kuraray Co., Ltd., particle size 20-80 μm] 2
50 parts by weight were dry mixed.

This mixture was placed in a flat plate mold of 600 mm × 600 mm, the press temperature was 165 ° C., the molding pressure was 150 k.
It was heated and pressed at gf / cm ² for 20 minutes to obtain a cured plate having a thickness of 1 mm. This cured plate was left at 220 ° C. for 4 hours for post-curing, then sandwiched between graphite plates, heated to 2000 ° C. at a heating rate of 30 ° C./hour, and graphitized at the same temperature for 3 hours. By processing, a carbonaceous electrode substrate was obtained.

Comparative Example 2 60 parts by weight of the phenol resin used in Example 1, 100 parts by weight of carbon fiber having an average fiber length of 0.7 mm and polyvinyl alcohol [manufactured by Kuraray Co., Ltd., particle size 100 to 250 μm]
100 parts by weight were dry mixed. Using this mixture, a carbonaceous electrode substrate was obtained in the same manner as in Comparative Example 1.

When the porosity, bending strength, gas permeability and volume resistivity of the electrode substrates obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were measured, the results shown in Table 1 were obtained.

[0053]

[Table 1] From Table 1, the electrode substrates obtained in Examples 1 to 4 have an appropriate porosity, and, as compared with Comparative Examples 1 and 2, the bending strength and the conductivity are very large, and the excellent gas permeability is obtained. Indicated.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Okamoto 4-1-2, Hirano-cho, Chuo-ku, Osaka City Osaka Gas Co., Ltd.

Claims (4)

[Claims] 1. A carbon fiber-forming fiber or carbon fiber short fiber 20 to 50% by weight, carbonization yield 40 to 75% by weight binder 15 to 50% by weight, and carbonization yield 30% by weight or less. A carbonaceous preform having a papermaking structure containing 30 to 60% by weight of a granular material. 2. The carbonaceous preform according to claim 1, wherein the organic particulate material is a thermosetting resin cured product. 3. The particle size of the organic particulate matter is 10 to 500 μm.
The carbonaceous preform according to claim 1, which is m. 4. A fuel cell electrode substrate in which the preform according to claim 1 is compression-molded and carbonized or graphitized.