JP2006004858A5

JP2006004858A5 -

Info

Publication number: JP2006004858A5
Application number: JP2004182407A
Authority: JP
Filing date: 2004-06-21
Publication date: 2007-06-21

Description

Porous electrode substrate and method for producing the same

本発明は、多孔質電極基材およびその製造方法に関する。 The present invention relates to a porous electrode substrate and a method for producing the same.

多孔質電極基材は、固体高分子型燃料電池中で、セパレーターと触媒層の間に位置する部材で、セパレーターと触媒層間の電気伝達体としての機能だけでなく、セパレーターから供給される水素や酸素などの反応ガスを触媒層に分配する機能と触媒層で発生する水を吸収して外部に排出する機能を併せ持つことを求められ、現在のところ一般的に炭素質が有効とされている。 The porous electrode base material is a member located between the separator and the catalyst layer in the polymer electrolyte fuel cell, and not only functions as an electric conductor between the separator and the catalyst layer but also hydrogen supplied from the separator. It is required to have a function of distributing a reaction gas such as oxygen to the catalyst layer and a function of absorbing water generated in the catalyst layer and discharging it to the outside, and at present, carbon is generally effective.

特許文献１には、安価な多孔質電極基材の製造方法が記載されている。この多孔質電極基材中でウェブが厚み方向にも配向しているため、厚み方向の導電性やガス透過性は優れているが、機械強度が弱く、繊維が厚み方向に配向した繊維が電解質膜と接合する際膜を突き破ってしまうなど取り扱いの面で課題があった。 Patent Document 1 describes an inexpensive method for producing a porous electrode substrate. Since the web is oriented in the thickness direction in this porous electrode substrate, the electrical conductivity and gas permeability in the thickness direction are excellent, but the mechanical strength is weak, and the fibers oriented in the thickness direction are electrolytes. There was a problem in terms of handling such as breaking through the film when joining with the film.

WO０１／００４９８０号公報WO01 / 004980 Publication

本発明は、上記のような問題点を克服し、安価でありながら、ガス透過性、曲げ強度に優れた多孔質電極基材およびこの多孔質電極基材の製造方法を提供することを目的とする。 An object of the present invention is to overcome the above-mentioned problems and to provide a porous electrode substrate excellent in gas permeability and bending strength while being inexpensive, and a method for producing the porous electrode substrate. To do.

本発明の第1の要旨は、実質的に二次元平面内においてランダムな方向に分散した炭素短繊維が樹脂炭化物によって互いに結着してなる多孔質電極基材であって、指標Kが、１．１×１０⁵（ＭＰａ・ｍ／ｓｅｃ／ＭＰａ）以上である多孔質電極基材にある。
指標K＝曲げ強度×ガス透過度 The first gist of the present invention is a porous electrode substrate in which carbon short fibers dispersed in a random direction in a substantially two-dimensional plane are bound to each other by a resin carbide, and the index K is 1 It is in the porous electrode base material which is 1 × 10 ⁵ (MPa · m / sec / MPa) or more.
Index K = bending strength x gas permeability

また、本発明の第２の要旨は、炭素繊維、合成繊維および有機高分子化合物からなる炭
素繊維紙に炭素繊維１質量部に対し、３〜８質量部の炭素前駆体樹脂を付着し、炭素前駆体樹脂を硬化し、次いで炭素化する孔質炭素電極基材の製造方法にある。 Moreover, the second gist of the present invention is that carbon precursor paper of 3 to 8 parts by mass is attached to carbon fiber paper made of carbon fiber, synthetic fiber and organic polymer compound with respect to 1 part by mass of carbon fiber, and carbon There exists a manufacturing method of the porous carbon electrode base material which hardens precursor resin and then carbonizes.

本発明によれば、安価でありながら、ガス透過性、曲げ強度に優れた多孔質電極基材を得ることができる。また、本発明の多孔質電極基材の製造方法によれば、前記多孔質電極基材を低コストで生産することができる。 According to the present invention, it is possible to obtain a porous electrode base material that is inexpensive and excellent in gas permeability and bending strength. Moreover, according to the manufacturing method of the porous electrode base material of this invention, the said porous electrode base material can be produced at low cost.

＜炭素短繊維＞
本発明で用いる炭素短繊維の原料である炭素繊維は、ポリアクリロニトリル系炭素繊維、ピッチ系炭素繊維、レーヨン系炭素繊維などいずれであって良いが、ポリアクリロニトリル系炭素繊維が好ましく、特に用いる炭素繊維がポリアクリロニトリル系炭素繊維のみからなることが多孔質炭素電極基材の機械的強度が比較的高くすることができるので好ましい。
炭素短繊維の繊維長は、後述のバインダーとの結着性や分散性の点から、２〜１２ｍｍが好ましい。 <Short carbon fiber>
The carbon fiber that is a raw material of the short carbon fiber used in the present invention may be any of polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, etc., but polyacrylonitrile-based carbon fiber is preferable, and carbon fiber used in particular Is preferably composed only of polyacrylonitrile-based carbon fibers because the mechanical strength of the porous carbon electrode substrate can be made relatively high.
The fiber length of the short carbon fiber is preferably 2 to 12 mm from the viewpoint of binding properties and dispersibility with the binder described below.

＜分散＞
本発明において、「実質的に二次元平面内においてランダムな方向に分散（する）」とは、炭素短繊維がおおむね一つの面を形成するように横たわっているという意味である。これにより炭素短繊維による短絡や炭素短繊維の折損を防止することができる。 <Dispersion>
In the present invention, “dispersing in a random direction in a substantially two-dimensional plane” means that the carbon short fibers lie so as to form a single plane. Thereby, the short circuit by carbon short fiber and the breakage of carbon short fiber can be prevented.

＜樹脂炭化物＞
本発明において、樹脂炭化物は、炭素前駆体樹脂を炭化してできた、炭素短繊維同士を結着する物質である。炭素前駆体樹脂としては、フェノール樹脂など炭素繊維との結着力が強く、炭化時の残存質量が大きいものが好ましいが特に限定はされない。
この樹脂炭化物は、炭素前駆体樹脂の種類や炭素繊維紙への含浸量により、最終的に多孔質炭素電極基材に炭化物として残る割合が異なる。多孔質電極基材を１００質量％とした時に、その中の樹脂炭化物が５０〜９０質量％であることが好ましく、更に好ましい下限及び上限は、それぞれ６０質量％及び８０質量％である。 <Resin carbide>
In the present invention, the resin carbide is a substance that binds short carbon fibers, which is obtained by carbonizing a carbon precursor resin. As the carbon precursor resin, those having strong binding force with carbon fibers such as phenol resin and a large residual mass upon carbonization are preferable, but are not particularly limited.
Depending on the type of carbon precursor resin and the amount of carbon fiber paper impregnated with this resin carbide, the proportion of the carbon carbide finally remaining as a carbide on the porous carbon electrode substrate varies. When the porous electrode substrate is taken as 100% by mass, the resin carbide is preferably 50 to 90% by mass, and more preferable lower and upper limits are 60% by mass and 80% by mass, respectively.

樹脂炭化物が５０質量％未満の場合は、原料コスト及び機械強度、ガス透過性の両立が困難であるという観点から好ましくない。逆に９０質量％を超える場合は、炭化の際の収縮に耐えられず、形状を保持するのが困難であることから好ましくない。 When the resin carbide is less than 50% by mass, it is not preferable from the viewpoint that it is difficult to satisfy both raw material cost, mechanical strength, and gas permeability. Conversely, if it exceeds 90% by mass, it is not preferable because it cannot withstand the shrinkage during carbonization and it is difficult to maintain the shape.

＜曲げ強度＞
本発明における曲げ強度とは、ＪＩＳ規格Ｋ−６９１１に準拠した方法よって求められる値で、曲げに対する強さを表す。本発明の多孔質電極基材の好ましい曲げ強度は、歪み速度１０ｍｍ／ｍｉｎ、支点間距離２ｃｍ、試験片幅１ｃｍの条件下で、１０ＭＰａ以上、さらに好ましくは４０ＭＰａ以上である。１０ＭＰａ未満であると、取り扱いが困難になり、多孔質電極基材をロール上に巻き取る際に割れやすい。
また、曲げ強度を１０ＭＰａ以上とすることにより、電極基材の曲げの際に亀裂が生じないものとすることができる。曲げ強度を強くする方法としては、密度を高くする、炭素繊維の目付を増やすなどの方法が挙げられるが、あまり増やしすぎるとガスがとおりにくくなり、セルに組んだときの性能が低下するため好ましくない。 <Bending strength>
The bending strength in the present invention is a value obtained by a method based on JIS standard K-6911 and represents the strength against bending. The preferred bending strength of the porous electrode substrate of the present invention is 10 MPa or more, more preferably 40 MPa or more, under the conditions of a strain rate of 10 mm / min, a fulcrum distance of 2 cm, and a test piece width of 1 cm. When it is less than 10 MPa, handling becomes difficult, and the porous electrode base material is easily cracked when wound on a roll.
Further, by setting the bending strength to 10 MPa or more, it is possible to prevent cracks from being generated when the electrode base material is bent. As a method of increasing the bending strength, there are methods such as increasing the density and increasing the basis weight of the carbon fiber. However, if the amount is increased too much, it is difficult to pass the gas, and the performance when assembled in the cell is reduced. Absent.

＜ガス透過度＞
本発明におけるガス透過度とは、ＪＩＳ規格Ｐ−８１１７に準拠した方法によって求められる値で、多孔質電極基材のガスの抜けやすさを表す。多孔質電極基材の試験片を３ｍｍφの孔を有するセルに挟み、孔から１．２９ｋＰａの圧力で２００ｍｌのガスを流し、ガスが透過するのにかかった時間を測定することで算出できる。
本発明の多孔質電極基材の好ましいガス透過度は、１４００ｍ／ｓｅｃ／ＭＰａ以上で、さらに好ましくは、２０００ｍ／ｓｅｃ／ＭＰａ以上である。ガス透過度が１４００ｍ／ｓｅｃ／ＭＰａ以上の場合は、セルの使用条件によるが、特に高密度電流にて発電しようとすると発生した水がセル外部に排出できなくなり、発電能力が著しく低下するフラッディングと呼ばれる現象が起こりにくく好ましい。ガス透過度を大きくする方法としては、曲げ強度を強くするのと逆で、密度を低くする、炭素繊維の目付を減らすなどの方法が挙げられるが、この場合もあまり減らしすぎると機械強度が低下するため好ましくない。 <Gas permeability>
The gas permeability in this invention is a value calculated | required by the method based on JIS specification P-8117, and represents the ease of degassing of a porous electrode base material. It can be calculated by sandwiching a test piece of a porous electrode substrate between cells having 3 mmφ holes, flowing 200 ml of gas from the holes at a pressure of 1.29 kPa, and measuring the time taken for the gas to permeate.
The gas permeability of the porous electrode substrate of the present invention is preferably 1400 m / sec / MPa or more, and more preferably 2000 m / sec / MPa or more. When the gas permeability is 1400 m / sec / MPa or more, depending on the use conditions of the cell, the generated water cannot be discharged to the outside of the cell especially when trying to generate power at a high-density current, and the power generation capacity is significantly reduced. It is preferable that the phenomenon called is difficult to occur. As a method of increasing gas permeability, there are methods such as decreasing the density and reducing the basis weight of carbon fiber in reverse to increasing the bending strength, but in this case too much mechanical strength decreases. Therefore, it is not preferable.

＜指標Ｋ＞
本発明における指標Ｋとは、多孔質電極基材の曲げ強度、ガス透過性を合わせた性能の総合的に評価するための指標である。一般的に、多孔質電極基材の機械強度を横軸に、ガス透過度を縦軸に取り、同じ組成の多孔質電極基材の厚み、目付、嵩密度等の物性をかえたものの曲げ強度に代表される機械強度とガス透過性の評価結果をグラフにプロットすると、図１のような反比例直線に近い挙動を示す。指標Ｋは、同じ組成であればほぼ一定となる。
本発明においては、指標Ｋが１．１×１０⁵（ＭＰａ・ｍ／ｓｅｃ／ＭＰａ）以上であることが必要である。
これは、多孔質電極基材のロール上への巻き取りやプレスなどの工程に耐えうる機械強度を持ち、燃料電池セルに組み込み高電流密度で発電したとき、フラッディングを起こさない、十分なガス透過性をもつための必須条件である。指標Ｋが1.1×１０^５（ＭＰａ・ｍ／ｓｅｃ／ＭＰａ）未満の場合は、機械強度、ガス透過性の両方を満足するものは得られない。 <Indicator K>
The index K in the present invention is an index for comprehensively evaluating the performance combining the bending strength and gas permeability of the porous electrode base material. Generally, the bending strength of the porous electrode substrate with the mechanical strength of the porous electrode substrate taken on the horizontal axis and the gas permeability on the vertical axis, and the physical properties such as the thickness, basis weight, and bulk density of the porous electrode substrate of the same composition were changed. When the mechanical strength and gas permeability evaluation results typified by are plotted on a graph, a behavior close to an inversely proportional line as shown in FIG. 1 is shown. The index K is almost constant if the composition is the same.
In the present invention, the index K needs to be 1.1 × 10 ⁵ (MPa · m / sec / MPa) or more.
It has sufficient mechanical strength to withstand the process of winding the porous electrode substrate onto a roll and pressing, and does not cause flooding when it is built into a fuel cell and generated at a high current density. It is an indispensable condition for having sex. When the index K is less than 1.1 × 10 ⁵ (MPa · m / sec / MPa), a material satisfying both mechanical strength and gas permeability cannot be obtained.

＜細孔分布＞
本発明では、水銀圧入法で測定したとき、細孔径が１０μｍ以下の細孔と細孔径が５０μｍ以上の細孔をともに有することが好ましい。
多孔質電極基材には、反応ガスを反応部（触媒層）に効率よく送り届ける機能だけでなく、反応ガスに含まれている水分や発電により発生する水分を効率よく排出する機能が求められる。反応ガスを効率よく反応部（触媒層）に送り届けるためには、５０μｍ以上の細孔を有することが好ましく、効率よく水を排出するためには、大量に水分が発生した時に水分を一時的に取り込むための孔として１０μｍ以下の細孔を有することが好ましい。
前記のような細孔を有する多孔質電極基材の製造方法としては、炭素繊維紙を抄紙する段階で直径５μｍ以下の炭素短繊維と直径７μｍ以上の炭素短繊維を混合する方法や炭素繊維と繊維径の異なる合成繊維を混合する方法などが挙げられる。多孔質電極基材に含まれる樹脂炭化物の比率が高いほど細孔径が１０μｍ以下の細孔と細孔径が５０μｍ以上の細孔の、それぞれの数が増える傾向にある。 <Pore distribution>
In the present invention, it is preferable to have both pores having a pore diameter of 10 μm or less and pores having a pore diameter of 50 μm or more when measured by mercury porosimetry.
The porous electrode base material is required to have not only the function of efficiently delivering the reaction gas to the reaction part (catalyst layer) but also the function of efficiently discharging the water contained in the reaction gas and the water generated by power generation. In order to efficiently deliver the reaction gas to the reaction part (catalyst layer), it is preferable to have pores of 50 μm or more. In order to efficiently discharge water, the water is temporarily removed when a large amount of water is generated. It is preferable to have pores of 10 μm or less as pores for incorporation.
As a method for producing a porous electrode substrate having pores as described above, a method of mixing carbon short fibers having a diameter of 5 μm or less and carbon short fibers having a diameter of 7 μm or more at the stage of making carbon fiber paper, Examples include a method of mixing synthetic fibers having different fiber diameters. As the ratio of the resin carbide contained in the porous electrode substrate is higher, the number of pores having a pore diameter of 10 μm or less and pores having a pore diameter of 50 μm or more tend to increase.

＜ネット状構造＞
本発明の多孔質電極基材においては、曲げ強度とガス透過性を両立させるという観点から、樹脂炭化物が炭素繊維と結着していない部分でネット状構造が形成されていることが好ましい。樹脂炭化物が炭素繊維と結着していない部分でネット状構造が形成されている様子を図２に示す。樹脂炭化物が炭素繊維と炭素繊維を結着させることによってその強度を維持しているが、図２のように接触していない炭素繊維間に樹脂炭化物がネット状構造を張ることにより、一層強度を向上させることができる。この場合、樹脂炭化物のネットが炭素繊維と同様な役目を果たすため、多孔質電極基材に含まれる炭素繊維の比率を減らすことができ、低コストで多孔質電極基材を提供することができる。ガス透過性を維持したまま曲げ強度を向上する方法としては、繊維長を長くする方法も挙げられるが、均一分散性が問題となる可能性がある。 <Net-like structure>
In the porous electrode substrate of the present invention, it is preferable that a net-like structure is formed at a portion where the resin carbide is not bound to the carbon fiber from the viewpoint of achieving both bending strength and gas permeability. FIG. 2 shows a state in which the net-like structure is formed at the portion where the resin carbide is not bound to the carbon fiber. Resin carbide maintains its strength by binding carbon fibers and carbon fibers, but the resin carbide stretches a net-like structure between carbon fibers that are not in contact as shown in FIG. Can be improved. In this case, since the resin carbide net plays the same role as the carbon fiber, the ratio of the carbon fiber contained in the porous electrode substrate can be reduced, and the porous electrode substrate can be provided at low cost. . Examples of a method for improving the bending strength while maintaining gas permeability include a method of increasing the fiber length, but uniform dispersibility may be a problem.

＜製造方法＞
本発明における多孔質電極基材の製造方法は、炭素繊維、合成繊維および有機高分子化合物からなる炭素繊維紙に、炭素繊維１質量部に対し、３〜８質量部の炭素前駆体樹脂を付着し、次いで炭素前駆体樹脂を炭素化する多孔質炭素電極基材の製造方法である。製造コストの低下ができるという点から全工程にわたり多孔質電極基材の製造が連続的に行なわれることが好ましい。 <Manufacturing method>
In the method for producing a porous electrode substrate according to the present invention, 3 to 8 parts by mass of carbon precursor resin is attached to 1 part by mass of carbon fiber on carbon fiber paper made of carbon fiber, synthetic fiber, and organic polymer compound. And then a method for producing a porous carbon electrode substrate in which the carbon precursor resin is carbonized. It is preferable that the production of the porous electrode substrate is continuously performed over the entire process from the viewpoint that the production cost can be reduced.

＜合成繊維＞
本発明で用いる合成繊維は、炭素化により分解してなくなるが、合成繊維の周りに付着した炭素前駆体樹脂の形状はそのまま残り、樹脂炭化物がネット構造を形成する。
そのため、ガス透過性を維持したまま、曲げ強度の高い多孔質電極基材を製造する上で合成繊維は必須である。
合成繊維の種類は、特に限定されないが、樹脂炭化物の前駆体である炭素前駆体樹脂との親和性が高く、その炭素前駆体樹脂との接触により分解、劣化しないものが好ましい。
また、炭素繊維や合成繊維などを抄紙して炭素繊維紙にする場合は、分散媒である液体に不要であることが好ましい。
合成繊維の繊度は、特に限定されないが、０．０５〜１．５ｄｔｅｘのものが好ましい。繊度が０．０５ｄｔｅｘ未満の場合は、合成繊維一本あたりの炭素前駆体樹脂の付着が十分でなく、焼成後、多孔質電極基材から樹脂炭化物が剥離してしまう場合がある。逆に、繊度が１．５ｄｔｅｘより大きい場合は、多孔質電極基材表面が粗くなり、多孔質電極基材と周辺部材との接触があまりよくない場合がある。合成繊維の長さも特に限定されないが、同時に用いる炭素短繊維と同程度のものが好ましい。バインダーとの結着性や分散性の点から、２〜１２ｍｍが好ましい。
合成繊維は、炭素繊維と一緒に分散することで、炭素繊維の再収束を防止する役割も果たす。そのため、水との親和性にも優れているものが好ましい。本発明に公的に用いられる合成繊維としてはビニロン繊維、ポリエステル繊維、ポリエチレン繊維、ポリプロピレン繊維、アクリル繊維、アラミド繊維、ナイロン繊維、ポリアセタール繊維、ポリウレタン繊維、ノボロイド繊維などが挙げられる。
炭素繊維紙中の合成繊維の質量比率は、１０〜８０質量％であることが好ましい。
合成繊維が１０質量％未満の場合は、合成繊維により形成されるネット構造が疎で、曲げ強度とガス透過性の両立の効果が分かりにくい。
一方、合成繊維が８０質量％を超える場合は、炭素繊維に付着する炭素前駆体樹脂の量が少なくなるため、多孔質電極基材の形態を保つのが困難となる場合がある。
合成繊維の形態としては、短繊維状が好ましい。また、短繊維とは繊維糸または繊維のトウを所定の長さにカットして得られるものである。 <Synthetic fiber>
The synthetic fiber used in the present invention is not decomposed by carbonization, but the shape of the carbon precursor resin attached around the synthetic fiber remains as it is, and the resin carbide forms a net structure.
For this reason, synthetic fibers are essential for producing a porous electrode substrate having high bending strength while maintaining gas permeability.
The type of the synthetic fiber is not particularly limited, but it is preferable to have a high affinity with a carbon precursor resin that is a precursor of a resin carbide and that does not decompose or deteriorate due to contact with the carbon precursor resin.
In addition, when carbon fiber or synthetic fiber is made into carbon fiber paper, it is preferably unnecessary for the liquid as the dispersion medium.
The fineness of the synthetic fiber is not particularly limited, but 0.05 to 1.5 dtex is preferable. When the fineness is less than 0.05 dtex, the carbon precursor resin per synthetic fiber is not sufficiently adhered, and the resin carbide may be peeled off from the porous electrode substrate after firing. On the contrary, when the fineness is larger than 1.5 dtex, the surface of the porous electrode substrate becomes rough, and the contact between the porous electrode substrate and the peripheral member may not be so good. The length of the synthetic fiber is not particularly limited, but is preferably about the same as the short carbon fiber used at the same time. From the viewpoint of binding properties and dispersibility with the binder, 2 to 12 mm is preferable.
Synthetic fibers also serve to prevent re-convergence of carbon fibers by dispersing together with carbon fibers. Therefore, what is excellent also in the affinity with water is preferable. Examples of synthetic fibers that are publicly used in the present invention include vinylon fibers, polyester fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, aramid fibers, nylon fibers, polyacetal fibers, polyurethane fibers, and novoloid fibers.
The mass ratio of the synthetic fiber in the carbon fiber paper is preferably 10 to 80% by mass.
When the synthetic fiber is less than 10% by mass, the net structure formed by the synthetic fiber is sparse, and it is difficult to understand the effect of both bending strength and gas permeability.
On the other hand, when the synthetic fiber exceeds 80% by mass, the amount of the carbon precursor resin adhering to the carbon fiber decreases, and it may be difficult to maintain the form of the porous electrode substrate.
The form of the synthetic fiber is preferably a short fiber. The short fibers are obtained by cutting fiber yarns or fiber tows into a predetermined length.

＜有機高分子化合物＞
有機高分子化合物は、炭素繊維紙中で各成分をつなぎとめるバインダーとしてはたらく。有機高分子化合物としては、ポリビニルアルコール（ＰＶＡ）、ポリ酢酸ビニル、などを用いることができる。その中でも、ポリビニルアルコール、ポリアクリロニトリル、セルロース、ポリ酢酸ビニル等が好ましく用いられる。特にポリビニルアルコールは抄紙工程での結着力に優れるため、炭素短繊維の脱落が少なくバインダーとして好ましい。本発明では、有機高分子化合物を繊維状として用いることも可能である。 <Organic polymer compound>
The organic polymer compound serves as a binder that holds the components together in the carbon fiber paper. As the organic polymer compound, polyvinyl alcohol (PVA), polyvinyl acetate, or the like can be used. Among these, polyvinyl alcohol, polyacrylonitrile, cellulose, polyvinyl acetate and the like are preferably used. In particular, polyvinyl alcohol is preferable as a binder because it has excellent binding power in the paper making process, and the short carbon fibers are not dropped off. In the present invention, it is also possible to use an organic polymer compound as a fiber.

＜炭素繊維紙の抄紙＞
炭素繊維紙の抄紙方法としては、液体の媒体中に炭素繊維を分散させて抄造する湿式法や、空気中に炭素繊維を分散させて降り積もらせる乾式法が適用できるが、中でも湿式法が好ましい。また、前述したように炭素繊維同士の開繊、再収束を防止する役割を果たす合成繊維を適当量、および炭素繊維同士を結着させるバインダーとして適当量の有機高分子物質を混ぜることが好ましい。 <Carbon fiber paper making>
As a paper making method for carbon fiber paper, a wet method in which carbon fiber is dispersed in a liquid medium for paper making and a dry method in which carbon fiber is dispersed in air to be deposited can be applied. Among these, a wet method is preferable. . Further, as described above, it is preferable to mix an appropriate amount of a synthetic fiber that serves to prevent the opening and re-convergence of carbon fibers, and an appropriate amount of an organic polymer substance as a binder for binding the carbon fibers together.

これらの合成繊維および有機高分子化合物を炭素繊維に混入する方法としては、炭素繊維とともに水中で攪拌分散させる方法と、直接混ぜ込む方法があるが、均一に分散させるためには水中で拡散分散させる方法が好ましい。このように有機高分子化合物を混ぜることにより、炭素繊維紙の強度を保持し、その製造途中で炭素繊維紙から炭素繊維が剥離したり、炭素繊維の配向が変化したりするのを防止することができる。また、抄紙は連続で行なう方法やバッチ式で行なう方法があるが、本発明において行なう抄紙は、特に目付のコントロールが容易であるという点と生産性および機械的強度の観点から連続抄紙が好ましい。 As a method of mixing these synthetic fibers and organic polymer compounds into carbon fibers, there are a method of stirring and dispersing in water together with carbon fibers, and a method of mixing directly, but in order to disperse uniformly, it is diffused and dispersed in water. The method is preferred. By mixing the organic polymer compound in this way, the strength of the carbon fiber paper is maintained, and it is possible to prevent the carbon fiber from peeling off from the carbon fiber paper or changing the orientation of the carbon fiber during its production. Can do. Further, there are a continuous paper making method and a batch paper making method. However, the paper making performed in the present invention is preferably continuous paper making from the viewpoint of easy control of the basis weight and productivity and mechanical strength.

＜炭素前駆体樹脂＞
本発明で炭素前駆体樹脂として用いる樹脂は、常温において粘着性、あるいは流動性を示す物でかつ炭素化後も導電性物質として残存する物質が好ましく、フェノール樹脂、フラン樹脂、エポキシ樹脂、メラミン樹脂、イミド樹脂、ウレタン樹脂、アラミド樹脂、ピッチ等を単体もしくは混合物として用いることができる。前記フェノール樹脂としては、アルカリ触媒存在下においてフェノール類とアルデヒド類の反応によって得られるレゾールタイプフェノール樹脂を用いることができる。 <Carbon precursor resin>
The resin used as the carbon precursor resin in the present invention is preferably a substance that is sticky or fluid at room temperature and remains as a conductive substance even after carbonization, such as a phenol resin, a furan resin, an epoxy resin, or a melamine resin. An imide resin, a urethane resin, an aramid resin, pitch, or the like can be used alone or as a mixture. As the phenol resin, a resol type phenol resin obtained by reaction of phenols and aldehydes in the presence of an alkali catalyst can be used.

又、レゾールタイプのフェノール樹脂に公知の方法によって酸性触媒下においてフェノール類とアルデヒド類の反応によって生成する、固体の熱融着性を示すノボラックタイプのフェノール樹脂を溶解混入させることもできるが、この場合は硬化剤、例えばヘキサメチレンジアミンを含有した、自己架橋タイプのものが好ましい。 In addition, it is possible to dissolve and mix a novolac type phenolic resin, which is produced by the reaction of phenols and aldehydes in the presence of an acidic catalyst, by a known method, and exhibits a solid heat-fusible property. In this case, a self-crosslinking type containing a curing agent such as hexamethylenediamine is preferred.

フェノール類としては、例えば、フェノール、レゾルシン、クレゾール、キシロール等が用いられる。アルデヒド類としては、例えばホルマリン、パラホルムアルデヒド、フルフラール等が用いられる。また、これらを混合物として用いることができる。これらはフェノール樹脂として市販品を利用することも可能である。 As phenols, for example, phenol, resorcin, cresol, xylol and the like are used. As aldehydes, for example, formalin, paraformaldehyde, furfural and the like are used. Moreover, these can be used as a mixture. These can also use a commercial item as a phenol resin.

＜樹脂量＞
炭素繊維紙に付着する炭素前駆体樹脂の樹脂量は、炭素繊維１質量部に対し、３〜８質量部の炭素前駆体樹脂を付着させる。前述した、曲げ強度、ガス透過性に優れた電極基材を製造するには、樹脂炭化物の比率が５０〜９０質量％になるように炭素前駆体樹脂を付着しておく必要があるため、少なくとも３質量部付着させる必要がある。一方８質量部を超えて多く炭素前駆体樹脂を付着させるためには、高濃度で高粘度の樹脂溶液が必要となり、この場合は、炭素前駆体樹脂を均一に塗布するのが困難となるため樹脂量は８質量部以下とする。 <Resin amount>
The resin amount of the carbon precursor resin attached to the carbon fiber paper is such that 3 to 8 parts by mass of the carbon precursor resin is attached to 1 part by mass of the carbon fiber. In order to produce the electrode base material excellent in bending strength and gas permeability as described above, it is necessary to attach the carbon precursor resin so that the ratio of the resin carbide is 50 to 90% by mass. It is necessary to attach 3 parts by mass . On the other hand, in order to deposit more carbon precursor resin in excess of 8 parts by mass , a high-concentration and high-viscosity resin solution is required. In this case, it is difficult to uniformly apply the carbon precursor resin. The amount of resin is 8 parts by mass or less.

＜炭素前駆体樹脂付着方法＞
炭素繊維紙に炭素前駆体樹脂を含浸する方法としては、炭素繊維紙に炭素前駆体樹脂を含浸させることができればよく、本発明による特段の制限はないが、コーターを用いて炭素繊維紙表面に炭素前駆体樹脂を均一にコートする方法、絞り装置を用いるｄｉｐ−ｎｉｐ方法、もしくは炭素繊維紙と炭素前駆体樹脂フィルムを重ねて、炭素前駆体樹脂を炭素繊維紙に転写する方法が、連続的に行なうことができ、生産性および長尺ものも製造できるという点で好ましい。 < Carbon precursor resin adhesion method>
The carbon fiber paper may be impregnated with the carbon precursor resin as long as the carbon fiber paper can be impregnated with the carbon precursor resin, and there is no particular limitation according to the present invention. The method of uniformly coating the carbon precursor resin , the dip-nip method using a drawing device, or the method of transferring the carbon precursor resin to the carbon fiber paper by stacking the carbon fiber paper and the carbon precursor resin film is continuous. It is preferable in that it can be carried out and productivity and a long product can be manufactured.

＜硬化、炭素化＞
硬化工程は、樹脂炭化物の炭素化時の気化を抑制し、多孔質電極基材の強度向上のために不可欠な工程であり、電極基材に均等に加熱できる技術であれば、いかなる技術も適用できる。その例としては、上下両面から剛板にて加熱する方法や上下両面から熱風を吹き付ける方法、また連続ベルト装置や連続熱風炉を用いる方法が挙げられる。また、本発明においては、炭素前駆体樹脂を炭化し、多孔質電極基材の導電性を高めるために、不活性ガス中で炭素化することが必要である。炭素化は、炭素繊維紙の全長にわたって連続で行なうことが好ましい。電極基材が長尺であれば、電極基材の生産性が高くなるだけでなく、その後工程のＭｅｍｂｒａｎｅＥｌｅｃｔｒｏｄｅＡｓｓｅｍｂｌｙ（ＭＥＡ）製造も連続で行なうことができ、燃料電池のコスト低減化に大きく寄与することができる。 <Curing and carbonization>
The curing process is an indispensable process for suppressing the vaporization of carbonized resin carbide during carbonization and improving the strength of the porous electrode substrate. Any technology can be applied as long as the electrode substrate can be heated evenly. it can. Examples thereof include a method of heating with rigid plates from both upper and lower surfaces, a method of blowing hot air from both upper and lower surfaces, and a method using a continuous belt device and a continuous hot air furnace. Moreover, in this invention, in order to carbonize carbon precursor resin and to improve the electroconductivity of a porous electrode base material, it is necessary to carbonize in inert gas. Carbonization is preferably performed continuously over the entire length of the carbon fiber paper. If the electrode base material is long, not only the productivity of the electrode base material is increased, but also the subsequent process of manufacturing the membrane electrode assembly (MEA) can be performed continuously, which greatly contributes to the cost reduction of the fuel cell. can do.

炭素化は、不活性処理雰囲気下にて１０００〜３０００℃の温度範囲で、炭素繊維紙の全長にわたって連続して焼成処理することが好ましい。本発明の炭素化においては、不活性雰囲気下にて１０００〜３０００℃の温度範囲で焼成する炭素化処理の前に行われる、３００〜８００℃の程度の不活性雰囲気での焼成による前処理を行っても良い。 Carbonization is preferably performed by continuous firing over the entire length of the carbon fiber paper in a temperature range of 1000 to 3000 ° C. in an inert treatment atmosphere. In the carbonization of the present invention, a pretreatment by firing in an inert atmosphere of about 300 to 800 ° C., which is performed before a carbonization treatment in a temperature range of 1000 to 3000 ° C. in an inert atmosphere, is performed. You can go.

多孔質電極基材が炭素前駆体樹脂を炭素化炉で完全硬化することは、製造コストを下げられるという観点で好ましい。多孔質電極基材を炭素化炉に入れる前に硬化させる場合も高温で長時間硬化させる必要があり、多大な電力を消費する。炭素化炉に入る前に炭素前駆体樹脂の硬化が完全に進行していない場合でも性能の低下が見られないため、炭素化炉に炭素繊維紙を導入する前には、熱による炭素前駆体樹脂の移動が起こらない程度に固まっていれば良い。あまり硬化が進行していない場合は、炭素化炉内で発生する排ガス量が増えるので、あらかじめ炉材を強化する、不活性ガスの流量を増やすなどの処置が必要となる。 It is preferable that the porous electrode base material completely cures the carbon precursor resin in the carbonization furnace from the viewpoint of reducing the manufacturing cost. Even when the porous electrode base material is cured before being put into the carbonization furnace, it is necessary to cure at a high temperature for a long time, which consumes a large amount of power. Even if the curing of the carbon precursor resin has not progressed completely before entering the carbonization furnace, no deterioration in performance is seen, so before introducing the carbon fiber paper into the carbonization furnace, the carbon precursor by heat It only needs to be hardened to such an extent that the resin does not move. If the curing has not progressed so much, the amount of exhaust gas generated in the carbonization furnace increases, so that measures such as strengthening the furnace material in advance and increasing the flow rate of the inert gas are required.

炭素繊維紙に炭素前駆体樹脂を付着したのち、加熱により、炭素繊維紙表面を平滑にする工程を含んでいることが好ましい。炭素繊維表面を平滑する方法としては、特に限定されないが、上下両面から平滑な剛板にて熱プレスする方法や連続ベルトプレス装置を用いて行なう方法がある。中でも連続ベルトプレス装置を用いて行なう方法が、長尺の電極基材ができるという点で好ましい。電極基材が長尺であれば、電極基材の生産性が高くなるだけでなく、その後工程のＭＥＭＢＲＡＮＥＥＬＥＣＴＲＯＤＥＡＳＳＥＭＢＬＹ（ＭＥＡ）製造も連続で行なうことができ、燃料電池のコスト低減化に大きく寄与することができる。表面を平滑にする工程がない場合も電極基材としても強度、ガス透過性ともに良好なものが得られるが、基材に起伏があるため、セルを組むときの周辺基材との接触性があまり良くない。 It is preferable to include a step of smoothing the carbon fiber paper surface by heating after adhering the carbon precursor resin to the carbon fiber paper. The method of smoothing the carbon fiber surface is not particularly limited, and there are a method of performing hot pressing with smooth rigid plates from both the upper and lower surfaces and a method of using a continuous belt press apparatus. Among these, the method performed using a continuous belt press is preferable in that a long electrode substrate can be formed. If the electrode base material is long, not only the productivity of the electrode base material is increased, but also the subsequent MEMBRANE ELECTRODE ASSEMBLY (MEA) manufacturing can be continuously performed, which greatly contributes to the cost reduction of the fuel cell. can do. Even if there is no step to smooth the surface, the electrode substrate can have good strength and gas permeability, but the substrate has undulations, so the contact with the surrounding substrate when assembling the cell is not really good.

連続ベルト装置におけるプレス方法としては、ロールプレスによりベルトに線圧で圧力を加える方法と液圧ヘッドプレスにより面圧でプレスする方法があるが、後者の方がより平滑なサンプルが得られるという点で好ましい。効果的に表面を平滑にするためには、樹脂が最も軟化する温度にてプレスし、その後加熱または冷却により樹脂を固定する方法が最も良い。本発明における電極基材に含まれる樹脂の比率が多いため、プレス圧が低くても平滑になる。逆にプレス圧が高すぎると緻密になりすぎる、激しく変形するなどの問題が生じるのであまり好ましくない。プレス圧が高く緻密になりすぎた場合は、焼成時に発生するガスが排出されず基材を壊してしまうこともある。本工程を実施する時は、あらかじめ剛板やベルトに樹脂が付着しないように剥離剤を塗っておくか、間に離型紙を挟んで行なうことが好ましい。 As a pressing method in a continuous belt apparatus, there are a method of applying pressure to a belt by a roll press with a linear pressure and a method of pressing with a surface pressure by a hydraulic head press, but the latter can obtain a smoother sample. Is preferable. In order to effectively smooth the surface, the best method is to press at a temperature at which the resin is most softened, and then fix the resin by heating or cooling. Since the ratio of the resin contained in the electrode base material in the present invention is large, it becomes smooth even if the press pressure is low. On the other hand, if the press pressure is too high, problems such as becoming too dense and severe deformation occur. If the press pressure is too high and dense, the gas generated during firing may not be discharged and the substrate may be destroyed. When carrying out this step, it is preferable to apply a release agent in advance so that the resin does not adhere to the rigid plate or belt, or sandwich release paper between them.

（実施例）
以下、本発明を実施例により、さらに具体的に説明する。
実施例中の各物性値等は以下の方法で測定した。 (Example)
Hereinafter, the present invention will be described more specifically with reference to examples.
Each physical property value in the examples was measured by the following method.

１）電極基材の曲げ強度
電極基材のＭＤが試験片の長辺になるように、８０×１０ｍｍのサイズに１０枚切り取る。曲げ強度試験装置を用いて、支点間距離は２ｃｍにし、歪み速度１０ｍｍ／ｍｉｎで荷重をかけていき、荷重がかかり始めた点から試験片が破断したときの加圧くさびの破断荷重を１０枚の試験片に対し、測定し次式より求めた。
曲げ強度（ＭＰａ）＝３ＰＬ／２Ｗｈ^２
ここで、Ｐ：破断荷重（Ｎ）、Ｌ：支点間距離（ｍｍ）、Ｗ：試験片の幅（ｍｍ）、ｈ：試験片の厚み（ｍｍ）である。 1) Bending strength of electrode substrate Ten sheets are cut into a size of 80 × 10 mm so that the MD of the electrode substrate becomes the long side of the test piece. Using a bending strength test device, the distance between the fulcrums is 2 cm, a load is applied at a strain rate of 10 mm / min, and the breaking load of the pressure wedge when the test piece breaks from the point at which the load starts to be applied is 10 sheets. It measured and calculated | required from the following formula.
Bending strength (MPa) = 3PL / 2Wh ²
Here, P: breaking load (N), L: distance between supporting points (mm), W: width of test piece (mm), h: thickness of test piece (mm).

２）ガス透過度
先述したとおり、ＪＩＳ規格Ｐ−８１１７に準拠した方法によって求められる。多孔質電極基材の試験片を３ｍｍφの孔を有するセルに挟み、孔から１.２９ｋＰａの圧力で２００ｍｌのガスを流し、ガスが透過するのにかかった時間を測定することで以下の式より算出できる。
ガス透過度（ｍ／ｓｅｃ／ＭＰａ）
＝気体透過量（ｍ^３）／気体透過孔面積（ｍ^２）／透過時間（ｓｅｃ）／透過圧（ＭＰａ
） 2) Gas permeability As described above, the gas permeability is determined by a method based on JIS standard P-8117. By sandwiching a test piece of porous electrode base material in a cell having a hole of 3 mmφ, flowing 200 ml of gas from the hole at a pressure of 1.29 kPa, and measuring the time taken for the gas to permeate, It can be calculated.
Gas permeability (m / sec / MPa)
= Gas permeation amount (m ³ ) / gas permeation hole area (m ² ) / permeation time (sec) / permeation pressure (MPa
)

３）電極基材の平均細孔径
公知の水銀圧入法により、細孔容積と細孔半径の細孔分布を求め、その５０％の細孔容積を示す時の半径を電極基材の平均細孔径とした。なお、水銀ポロシメーターはＱｕａｎｔａｃｈｒｏｍｅ社製ＰｏｒｅＭａｓｔｅｒ−６０を用いた。 3) Average pore diameter of electrode substrate The pore distribution of pore volume and pore radius was determined by a known mercury intrusion method, and the radius when showing 50% of the pore volume was the average pore diameter of the electrode substrate. It was. As the mercury porosimeter, Pore Master-60 manufactured by Quantachrome was used.

４）厚み、嵩密度
厚み測定装置ダイヤルシックネスゲージ７３２１（ミツトヨ製）を使用し、測定した。
なお、このときの測定子の大きさは、直径１０ｍｍで測定圧力は１．５ｋＰａで行った。
実測した厚みを用いて、以下の式により算出した。
嵩密度（ｇ／ｃｍ^３）＝坪量（ｇ／ｍ^２）／厚み（ｍｍ）／１０００ 4) Thickness and bulk density The thickness was measured using a dial thickness gauge 7321 (Mitutoyo).
Note that the size of the probe at this time was 10 mm in diameter and the measurement pressure was 1.5 kPa.
Using the measured thickness, the following formula was used.
Bulk density (g / cm ³ ) = basis weight (g / m ² ) / thickness (mm) / 1000

５）面抵抗
電極基材のＭＤが試験片の長辺になるように、１００×２０ｍｍのサイズに切り取る。電極基材の片面に２ｃｍの間隔をあけて銅線をのせ、１０ｍＡ／ｃｍ^２の電流密度で電流を流した時の抵抗を測定した。 5) Surface resistance Cut to a size of 100 × 20 mm so that the MD of the electrode base material is the long side of the test piece. A copper wire was placed on one side of the electrode substrate with an interval of 2 cm, and the resistance when a current was passed at a current density of 10 mA / cm ² was measured.

６）貫通抵抗の測定
電極基材の厚さ方向の貫通抵抗は試料を銅板にはさみ、銅板の上下から１ＭＰａで加圧し、１０ｍＡ／ｃｍ²の電流密度で電流を流したときの抵抗値を測定し、次式より求めた。
貫通抵抗（Ω・cm²）＝測定抵抗値（Ω）×試料面積（cm²） 6) Measurement of penetration resistance The penetration resistance in the thickness direction of the electrode substrate was measured by holding the sample between copper plates, pressurizing at 1 MPa from the top and bottom of the copper plate, and passing a current at a current density of 10 mA / cm ^2. And obtained from the following equation.
Penetration resistance (Ω · cm ² ) = Measurement resistance value (Ω) × Sample area (cm ² )

炭素短繊維として、平均繊維径が７μｍ、平均繊維長が３ｍｍのポリアクリロニトリル（ＰＡＮ）系炭素繊維を用意した。
有機高分子化合物として、ポリビニルアルコール（ＰＶＡ）の短繊維（クラレ株式会社製ＶＢＰ１０５−１カット長３ｍｍ）を用意した。さらに合成繊維として、ビニロン短繊維（１．１ｄｔｅｘ、カット長５ｍｍ）を用意した。
炭素短繊維を湿式短網連続抄紙装置のスラリータンクで水中に均一に分散解繊し、十分に分散したところにＰＶＡ短繊維およびビニロン短繊維を炭素短繊維１００質量部に対して、それぞれ１８質量部、３２質量部となるように均一に分散し、送り出した。
送り出されたウェブを短網板に通し、ドライヤー乾燥後、坪量３３ｇ/ｍ^２、長さ１００ｍの炭素繊維紙Ａを得た（各組成の坪量は表1に記載、以下同じ）。分散状態は良好であった。
次に炭素繊維紙Ａをフェノール樹脂（フェノライトＪ−３２５・大日本インキ化学株式会社製）の４０質量％メタノール溶液が付着したローラーに炭素繊維紙を均一に片面ずつ接触させた後、連続的に熱風を吹きかけ乾燥した。坪量１１３ｇ/ｍ^２の樹脂付着炭素繊維紙Ｂを得た。このとき炭素繊維紙１００質量部に対し、フェノール樹脂を２４０質量部付着した。（炭素繊維１００質量部に対しは、フェノール樹脂量は３６０質量部となる。）
次に、この樹脂付着炭素繊維紙Ｂを図３に示した一対のエンドレスベルトを備えた連続式加熱プレス装置（ダブルベルトプレス装置：ＤＢＰ）にて連続的に加熱し、表面が平滑化されたシートＣを得た。（シート厚み：２７０μｍ）このときの予熱ゾーンでの予熱温度は１５０℃、予熱時間は５分であり、加熱加圧ゾーンでの温度は予熱ゾーンと同じ１５０℃、プレス方式は液圧プレス方式でプレス圧力は面圧２．０ＭＰａであった。なお、シートＣがベルトに貼り付かないように２枚の離型紙の間に挟んで通した。
その後、３０ｃｍ幅で１００ｍ得られたこのシートＣを、窒素ガス雰囲気中にて５００℃の連続焼成炉にて５分間フェノール樹脂の硬化処理および前炭素化したのち、窒素ガス雰囲気中にて２０００℃の連続焼成炉において５分間加熱し、炭素化することで長さ１００ｍの電極基材を連続的に得て、外径３０ｃｍの円筒型紙管に巻き取った。炭素繊維の分散は取り扱いやすく、曲げ強度およびガス透過性に優れた電極基材であった。評価結果を表に示した。 As short carbon fibers, polyacrylonitrile (PAN) carbon fibers having an average fiber diameter of 7 μm and an average fiber length of 3 mm were prepared.
As an organic polymer compound, polyvinyl alcohol (PVA) short fibers (VBP 105-1 manufactured by Kuraray Co., Ltd., cut length: 3 mm) were prepared. Further, vinylon short fibers (1.1 dtex, cut length 5 mm) were prepared as synthetic fibers.
Carbon short fibers were uniformly dispersed and defibrated in water in a slurry tank of a wet short net continuous paper making machine, and when sufficiently dispersed, PVA short fibers and vinylon short fibers were each 18 masses per 100 mass parts of carbon short fibers. Part and 32 parts by mass were uniformly dispersed and sent out.
The fed web was passed through a short mesh plate, and after drying with a dryer, carbon fiber paper A having a basis weight of 33 g / m ² and a length of 100 m was obtained (the basis weight of each composition is described in Table 1, the same applies hereinafter). The dispersion state was good.
Next, the carbon fiber paper A was contacted uniformly with each side of the carbon fiber paper on a roller to which a 40 mass% methanol solution of phenol resin (Phenolite J-325, manufactured by Dainippon Ink and Chemicals, Inc.) was adhered, and then continuously. The product was dried by blowing hot air over it. A resin-attached carbon fiber paper B having a basis weight of 113 g / m ² was obtained. At this time, 240 parts by mass of phenol resin was attached to 100 parts by mass of carbon fiber paper. (For 100 parts by mass of carbon fiber, the amount of phenol resin is 360 parts by mass.)
Next, the resin-attached carbon fiber paper B was continuously heated by a continuous heating press device (double belt press device: DBP) provided with a pair of endless belts shown in FIG. 3 to smooth the surface. Sheet C was obtained. (Sheet thickness: 270 μm) At this time, the preheating temperature in the preheating zone is 150 ° C., the preheating time is 5 minutes, the temperature in the heating and pressing zone is 150 ° C., and the press method is a hydraulic press method. The pressing pressure was a surface pressure of 2.0 MPa. The sheet C was sandwiched between two release sheets so that the sheet C did not stick to the belt.
Thereafter, the sheet C obtained 100 m in a width of 30 cm was subjected to phenol resin curing treatment and pre-carbonization for 5 minutes in a continuous baking furnace at 500 ° C. in a nitrogen gas atmosphere, and then 2000 ° C. in a nitrogen gas atmosphere. An electrode base material having a length of 100 m was continuously obtained by heating in a continuous baking furnace for 5 minutes and carbonizing, and wound around a cylindrical paper tube having an outer diameter of 30 cm. The dispersion of carbon fiber was easy to handle and was an electrode substrate excellent in bending strength and gas permeability. The evaluation results are shown in the table.

実施例２
炭素短繊維として、平均繊維径が４μｍ、平均繊維長が３ｍｍのポリアクリロニトリル（ＰＡＮ）系炭素繊維を使用した以外は実施例１と同様の方法で電極基材を得た。表面が平滑な電極基材であった。評価結果を表に示した。 Example 2
An electrode base material was obtained in the same manner as in Example 1 except that polyacrylonitrile (PAN) carbon fiber having an average fiber diameter of 4 μm and an average fiber length of 3 mm was used as the short carbon fiber. The electrode base material had a smooth surface. The evaluation results are shown in the table.

実施例３
実施例１で得た樹脂付着炭素繊維紙Ｂを一対のエンドレスベルトを備えた連続式加熱プレス装置（ダブルベルトプレス装置：ＤＢＰ）にて連続的に加熱加圧し、樹脂硬化炭素繊維紙を得た。（シート厚み：１４０μｍ）このときの予熱ゾーンでの予熱温度は１５０℃、予熱時間は５分であり、加熱加圧ゾーンでの温度は２５０℃、プレス圧力は線圧１．０×１０４Ｎ／ｍであった。なお、樹脂付着炭素繊維紙がベルトに張り付かないように２枚の離型紙の間に挟んで通した。
その後、３０ｃｍ幅で１００ｍ得られたこの樹脂硬化炭素繊維紙Ｅを、窒素ガス雰囲気中にて２０００℃の連続焼成炉において１０分間加熱し、炭素化することで長さ１００ｍの炭素電極基材を連続的に得て、外径３０ｃｍの円筒型紙管に巻き取った。取り扱いやすく、曲げ強度およびガス透過性に優れた電極基材であった。評価結果を表に示した。 Example 3
The resin-attached carbon fiber paper B obtained in Example 1 was continuously heated and pressurized with a continuous heating press device (double belt press device: DBP) equipped with a pair of endless belts to obtain a resin-cured carbon fiber paper. . (Sheet thickness: 140 μm) At this time, the preheating temperature in the preheating zone is 150 ° C., the preheating time is 5 minutes, the temperature in the heating and pressing zone is 250 ° C., and the press pressure is a linear pressure of 1.0 × 104 N / m. Met. The resin-attached carbon fiber paper was sandwiched between two release papers so as not to stick to the belt.
Thereafter, the resin-cured carbon fiber paper E obtained 100 m with a width of 30 cm is heated for 10 minutes in a continuous firing furnace at 2000 ° C. in a nitrogen gas atmosphere, and carbonized to form a carbon electrode substrate having a length of 100 m. It was continuously obtained and wound up on a cylindrical paper tube having an outer diameter of 30 cm. The electrode substrate was easy to handle and excellent in bending strength and gas permeability. The evaluation results are shown in the table.

実施例４
実施例２と同じ炭素繊維を使用し、実施例３と同じ方法で加熱プレスおよび炭素化をした。ガス透過性が少し悪くなった分、曲げ強度が強くなった。評価結果を表に示した。 Example 4
The same carbon fiber as in Example 2 was used, and hot pressing and carbonization were performed in the same manner as in Example 3 . The bending strength increased as gas permeability deteriorated a little. The evaluation results are shown in the table.

実施例５
実施例２で得た樹脂付着炭素繊維紙を連続式加熱プレス装置を使用せず、直接窒素ガス雰囲気中にて５００℃の連続焼成炉にて５分間フェノール樹脂の硬化処理および前炭素化した。その後、窒素ガス雰囲気中にて２０００℃の連続焼成炉において５分間加熱し、炭素化した。得られた電極基材は、実施例２よりガス透過性に優れたものが得られた。 Example 5
The resin-attached carbon fiber paper obtained in Example 2 was subjected to phenol resin curing treatment and pre-carbonization for 5 minutes in a continuous baking furnace at 500 ° C. directly in a nitrogen gas atmosphere without using a continuous heating press. Then, it heated for 5 minutes in a 2000 degreeC continuous baking furnace in nitrogen gas atmosphere, and carbonized. The obtained electrode base material was superior in gas permeability to that of Example 2.

実施例６
実施例１で、ビニロン繊維の添加量を炭素短繊維１００質量部に対して７７質量部としたほかは、実施例１と同様にして、坪量４３ｇ/ｍ^２、長さ１００ｍの炭素繊維紙Eを得た。分散状態は良好であった。次に、実施例１と同様にして樹脂付着炭素繊維紙Gを得た。このとき炭素繊維紙１００質量部に対し、フェノール樹脂を１８５質量部付着した。（炭素繊維１００質量部に対しは、フェノール樹脂量は３６０質量部）これ以降は、実施例１と同様の方法にて電極基材を得た。 Example 6
Carbon fiber paper having a basis weight of 43 g / m ² and a length of 100 m in the same manner as in Example 1 except that the amount of vinylon fiber added was 77 parts by mass with respect to 100 parts by mass of carbon short fibers in Example 1. E got. The dispersion state was good. Next, a resin-attached carbon fiber paper G was obtained in the same manner as in Example 1. At this time, 185 parts by mass of phenol resin was attached to 100 parts by mass of carbon fiber paper. (The amount of phenol resin is 360 parts by mass with respect to 100 parts by mass of carbon fiber) Thereafter, an electrode substrate was obtained by the same method as in Example 1.

比較例１
実施例１において、ビニロン繊維の添加量を０とするほかは、実施例１と同様にして、坪量２６ｇ/ｍ^２、長さ１００ｍの炭素繊維紙Ｈを得た。分散状態は良好であった。次に、実施例１と同様にして樹脂付着炭素繊維紙Ｉを得た。このとき炭素繊維紙１００質量部に対し、フェノール樹脂を１５０質量部付着した。これ以降は、実施例１と同様の方法にて電極基材を得た。ガス透過性には優れているが、脆く、繊維の脱落が見られた。 Comparative Example 1
In Example 1, a carbon fiber paper H having a basis weight of 26 g / m ² and a length of 100 m was obtained in the same manner as in Example 1 except that the addition amount of vinylon fiber was set to 0. The dispersion state was good. Next, resin-attached carbon fiber paper I was obtained in the same manner as in Example 1. At this time, 150 parts by mass of phenol resin was attached to 100 parts by mass of carbon fiber paper. Thereafter, an electrode substrate was obtained in the same manner as in Example 1. The gas permeability was excellent, but it was brittle and the fibers were detached.

比較例２
比較例１と同じ樹脂付着炭素繊維シートＩを実施例５と同様連続式加熱装置を使用せずに焼成し、電極基材を得た。比較例１よりもさらに脆いものとなった。 Comparative Example 2
The same resin-attached carbon fiber sheet I as in Comparative Example 1 was baked without using a continuous heating apparatus as in Example 5 to obtain an electrode substrate. It was more brittle than Comparative Example 1.

多孔質電極基材およびこの多孔質電極基材の製造方法を提供することにより従来技術の問題点を克服し、安価でありながら、ガス透過性、曲げ強度に優れた多孔質電極基材を提供することができる。 Porous electrode substrate and overcome the problems of the porous prior art by providing a method of manufacturing the electrode substrate, yet inexpensive, providing a gas permeable, excellent flexural strength porous electrode substrate can do.

ガス透過度と曲げ強度の関係を示したグラフである。It is the graph which showed the relationship between gas permeability and bending strength. 本発明の多孔質電極基材表面の電子顕微鏡写真である。It is an electron micrograph of the porous electrode base material surface of this invention. 連続ベルト方式の液圧ヘッドプレスの一例を示した概念図である。It is the conceptual diagram which showed an example of the hydraulic head press of a continuous belt system.

Explanation of symbols

１炭素前駆体樹脂を付着した炭素繊維紙
２離型剤をコーティングした基材
３ａ，３ｂ連続ベルト装置
４加熱装置
５液圧ヘッドプレス装置 DESCRIPTION OF SYMBOLS 1 Carbon fiber paper to which carbon precursor resin was adhered 2 Base material coated with release agent 3a, 3b Continuous belt device 4 Heating device 5 Hydraulic head press device

Claims

A porous electrode base material in which carbon short fibers dispersed substantially in a random direction in a two-dimensional plane are bound to each other by a resin carbide, and an index K is 1.1 × 10 ⁵ (MPa · m / Sec / MPa) or more.
Index K = bending strength x gas permeability

The porous carbon electrode base material according to claim 1, wherein the resin carbide is contained in an amount of 50 to 90 mass% of the total mass .

The porous carbon electrode substrate according to claim 1 or 2, which has both pores having a pore diameter of 10 µm or less and pores having a pore diameter of 50 µm or more when measured by a mercury intrusion method.

The porous carbon electrode substrate according to any one of claims 1 to 3, wherein the resin carbide forms a net-like structure at a portion not bound to the carbon fiber.

3 to 8 parts by mass of carbon precursor resin is attached to 1 part by mass of carbon fiber on carbon fiber paper made of carbon fiber, synthetic fiber and organic polymer compound, and the carbon precursor resin is cured and then carbonized. A method for producing a porous carbon electrode substrate.

The method for producing a porous carbon electrode substrate according to claim 5 , wherein all steps are continuously carried out.

The method for producing a porous carbon electrode substrate according to claim 5 or 6, wherein the carbon precursor resin is completely cured in a carbonization furnace.

The manufacturing method of the porous carbon electrode base material as described in any one of Claims 5-7 including the process of making a carbon fiber paper surface smooth by heating, after attaching carbon precursor resin to carbon fiber paper.

The manufacturing method of the porous carbon electrode base material as described in any one of Claims 5-8 which performs the process of smoothing the carbon fiber paper surface using a continuous belt press apparatus.