JP2008078143A - Coating material for fuel cell separator - Google Patents
Coating material for fuel cell separator Download PDFInfo
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- JP2008078143A JP2008078143A JP2007261623A JP2007261623A JP2008078143A JP 2008078143 A JP2008078143 A JP 2008078143A JP 2007261623 A JP2007261623 A JP 2007261623A JP 2007261623 A JP2007261623 A JP 2007261623A JP 2008078143 A JP2008078143 A JP 2008078143A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
Description
本発明は、燃料電池の金属製またはカーボン製セパレーターの表面に塗布して導電性塗膜を形成する導電塗料に関する。 The present invention relates to a conductive paint that is applied to the surface of a metal or carbon separator of a fuel cell to form a conductive coating film.
燃料電池は、水素と酸素の結合反応の際に発生するエネルギーを利用するため、省エネルギーと環境対策の両面から、その導入および普及が期待されている次世代の発電システムである。中でも固体高分子型燃料電池（ＰＥＦＣ：Ｐｏｌｙｍｅｒ Ｅｌｅｃｔｒｏｌｙｔｅ Ｆｕｅｌ Ｃｅｌｌ）は、出力密度が高く小型化が可能であり、また他のタイプの燃料電池より低温で作動し、起動停止が容易であることから、電気自動車や家庭用の小型コジェネレーションへの利用が期待されており、近年、特に注目を集めている。 A fuel cell is a next-generation power generation system that is expected to be introduced and spread from both the viewpoint of energy saving and environmental measures because it uses the energy generated during the hydrogen-oxygen bonding reaction. Among them, the polymer electrolyte fuel cell (PEFC) has a high output density and can be downsized, operates at a lower temperature than other types of fuel cells, and is easy to start and stop. It is expected to be used for electric vehicles and small cogeneration for home use, and has attracted particular attention in recent years.
この燃料電池に用いられるセパレーターの基材材料としては、大きく分けて金属系材料とカーボン系材料とがある。ＳＵＳ、炭素鋼などの金属系材料は、プレス加工等の方法によりセパレーターを製造し、一方、カーボン系材料は、黒鉛基板にフェノール系、フラン系などの熱硬化性樹脂を含浸硬化して焼成する方法、炭素粉末をフェノール樹脂、フラン樹脂またはタールピッチなどと混練し、板状にプレス成形または成形板に射出成形して焼成し、ガラス状カーボンにする方法などによりセパレーターを製造する。 The base material of the separator used in this fuel cell is roughly divided into a metal material and a carbon material. For metal materials such as SUS and carbon steel, separators are manufactured by a method such as press working. On the other hand, for carbon materials, a graphite substrate is impregnated with a thermosetting resin such as phenol or furan and cured. The separator is manufactured by a method, such as a method in which carbon powder is kneaded with phenol resin, furan resin, tar pitch or the like, press-molded into a plate shape, or injection molded into a molded plate and baked to form glassy carbon.
ところが、金属系材料は、金属特有の加工性に優れ、セパレーターの厚みを薄くすることができ、セパレーターの軽量化が図れるなどの利点を有するが、腐食による金属イオンの溶出や金属表面の酸化により電気伝導性が低下する懸念があり、一方、カーボン系材料は軽量なセパレーターが得られる利点があるが、ガス透過性を有するといった問題や、機械的強度が低いといった問題があった。 However, metal-based materials have advantages such as excellent workability peculiar to metals, the thickness of the separator can be reduced, and the weight of the separator can be reduced, but due to elution of metal ions due to corrosion and oxidation of the metal surface. There is a concern that the electrical conductivity is lowered. On the other hand, the carbon-based material has an advantage that a lightweight separator can be obtained, but has a problem that it has gas permeability and a low mechanical strength.
このような問題を解決する方法としては、セパレーター基材の表面に導電性塗膜を形成する方法が考えられ、これによれば、金属系材料においては、腐食の懸念を払拭することができ、また、カーボン系材料においては、ガス透過性および機械的強度の問題を改善することができる。このようなセパレーター基材に塗膜を被覆させる方法としては、酸洗したステンレス鋼基材の表面に黒鉛とカーボンブラックとの混合粉末からなる導電材を３〜２０μｍの厚さで被覆する方法が特開平１１−３４５６１８号公報に開示されている。 As a method for solving such a problem, a method of forming a conductive coating film on the surface of the separator substrate is considered, and according to this, in a metal-based material, the concern of corrosion can be wiped out, Further, in the carbon-based material, problems of gas permeability and mechanical strength can be improved. As a method of coating such a separator substrate with a coating film, there is a method of coating a surface of a pickled stainless steel substrate with a conductive material made of a mixed powder of graphite and carbon black in a thickness of 3 to 20 μm. It is disclosed in JP-A-11-345618.
しかしながら、このような導電性塗膜は、例えばプレッシャークッカー試験（ＰＣＴ）における環境下では、導電性塗膜がセパレーター基材から剥離してしまうといった、導電塗料から得られる塗膜とセパレーター基材との密着性に問題を有していた。
よって、本発明は、優れた耐食性を有するとともに、良好な導電性と密着性とを併せ持つ導電性塗膜を形成することができる燃料電池セパレーター用塗料を提供することを目的としている。 Accordingly, an object of the present invention is to provide a coating material for a fuel cell separator that has excellent corrosion resistance and can form a conductive coating film having both good conductivity and adhesion.
本発明の燃料電池セパレーター用塗料は、導電材として黒鉛を使用し、燃料電池用の金属製またはカーボン製セパレーターの表面に塗布して導電性塗膜を形成する燃料電池セパレーター用塗料において、該塗料の結着材としてスチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコーン共重合体のエマルションのうちいずれか１つ以上を５重量％以上含有し、媒体として上記結着材と相溶性のある溶媒を用い、上記導電材と結着材の配合比率が重量比で２０：８０〜９５：５であり、塗料中に占める固形分が１０〜６０重量％であることを特徴としている。 The fuel cell separator paint of the present invention is a fuel cell separator paint that uses graphite as a conductive material and is applied to the surface of a metal or carbon separator for fuel cells to form a conductive coating film. 5% by weight or more of any one of styrene-butadiene copolymer, acrylic-styrene copolymer, and acrylic-silicone copolymer emulsion as a binder, and a phase as a medium with the binder. Using a soluble solvent, the blending ratio of the conductive material and the binder is 20:80 to 95: 5 by weight, and the solid content in the paint is 10 to 60% by weight. .
この塗料においては、塗料中に占める固形分を１０〜６０重量％にすることにより、好適な厚さを有する均一な導電性塗膜が形成されてセパレーター基材の耐食性が改善され、さらに、このようにして形成された導電性塗膜は、好適な導電材の配合比率により良好な導電性を有し、また、スチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコーン共重合体のエマルションのうちいずれか１つ以上を５重量％以上含有することによりセパレーター基材に対する密着性が優れる。 In this coating material, by setting the solid content in the coating material to 10 to 60% by weight, a uniform conductive coating film having a suitable thickness is formed, and the corrosion resistance of the separator substrate is improved. The conductive coating film thus formed has good conductivity due to a suitable blending ratio of conductive materials, and also has a styrene-butadiene copolymer, an acrylic-styrene copolymer, and an acrylic-silicone copolymer. The adhesiveness with respect to a separator base material is excellent by containing 5 weight% or more of any one or more of these emulsions.
さらに、本発明の燃料電池セパレーター用塗料においては、導電材が黒鉛にさらにカーボンブラックを配合した炭素系混合物であり、黒鉛とカーボンブラックの配合比率が重量比で３０：７０〜９０：１０であることが好ましい形態である。 Furthermore, in the coating for a fuel cell separator of the present invention, the conductive material is a carbon-based mixture obtained by further mixing carbon black with graphite, and the mixing ratio of graphite and carbon black is 30:70 to 90:10 by weight ratio. Is a preferred form.
加えて、本発明の燃料電池セパレーター用塗料においては、導電材の黒鉛の平均粒子径（Ｄ５０）が３０μｍ以下であることが好ましい形態である。 In addition, in the coating material for a fuel cell separator of the present invention, it is preferable that the average particle diameter (D50) of graphite as a conductive material is 30 μm or less.
また、本発明の燃料電池セパレーター用塗料においては、２５℃における粘度が５０〜１００,０００ｍＰａ・ｓの範囲内であることが好ましい形態である。 In the fuel cell separator paint of the present invention, the viscosity at 25 ° C. is preferably in the range of 50 to 100,000 mPa · s.
本発明の燃料電池セパレーター用塗料は、結着材としてスチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコーン共重合体のエマルションのいずれか１つ以上を用いたことを特徴としているが、この塗料の実施形態について以下に詳細に述べる。 The coating material for a fuel cell separator according to the present invention is characterized in that any one or more of styrene-butadiene copolymer, acrylic-styrene copolymer, and acrylic-silicone copolymer emulsion is used as a binder. However, embodiments of this paint are described in detail below.
結着材であるスチレン−ブタジエン共重合体としては、スチレン−ブタジエンのランダム共重合体、スチレン−ブタジエン−スチレンブロック共重合体、カルボキシル基で変成した上記共重合体などが挙げられる。スチレン−ブタジエン共重合体は金属との密着性、塗膜の柔軟性の点で優れている。一方、アクリル−スチレン共重合体、アクリル−シリコーン共重合体は金属への密着性、防食性の点で優れている。また、これらの結着材はエマルションであり、溶媒としては有機溶剤を用いる必要がなく、水とすることができるため環境面でも負荷が少なく、取り扱いが容易でコスト面でも利点がある。 Examples of the styrene-butadiene copolymer that is a binder include a styrene-butadiene random copolymer, a styrene-butadiene-styrene block copolymer, and the above copolymer modified with a carboxyl group. The styrene-butadiene copolymer is excellent in terms of adhesion to metal and flexibility of the coating film. On the other hand, acrylic-styrene copolymers and acrylic-silicone copolymers are excellent in terms of adhesion to metals and corrosion resistance. Further, these binders are emulsions, and it is not necessary to use an organic solvent as a solvent, and since it can be made of water, there is little load in terms of environment, handling is easy, and there are advantages in terms of cost.
本発明の燃料電池セパレーター用塗料では、導電材と結着材の配合比率は重量比で２０：８０〜９５：５、好ましくは２５：７５〜９０：１０、さらに好ましくは３０：７０〜８５：１５が好適である。本発明の導電塗料からなる導電性塗膜としては、前述のとおり電気抵抗値ができる限り低く、かつ耐腐食性および基材に対する密着性が高いことが望まれる。電気抵抗値を低くするためには導電材の配合量をできるだけ多くすることが望ましく、耐腐食性および密着性を向上させるためには、結着材の配合量を多くすることが望ましい。これらの相反する要求を満たすために、導電材と結着材の配合としては前記の範囲が適切である。 In the fuel cell separator coating material of the present invention, the blend ratio of the conductive material and the binder is 20:80 to 95: 5, preferably 25:75 to 90:10, more preferably 30:70 to 85: by weight. 15 is preferred. As described above, the conductive coating film made of the conductive paint of the present invention is desired to have as low an electrical resistance value as possible, and to have high corrosion resistance and high adhesion to a substrate. In order to reduce the electrical resistance value, it is desirable to increase the blending amount of the conductive material as much as possible, and in order to improve corrosion resistance and adhesion, it is desirable to increase the blending amount of the binder. In order to satisfy these conflicting requirements, the above range is appropriate for the blending of the conductive material and the binder.
次に、本発明の燃料電池セパレーター用塗料中の有機溶剤配合量は、多くなれば塗料の粘度は低くなり、得られる塗膜の厚みは薄くなる。逆に、有機溶剤配合量が少ないと塗料粘度は高くなり、得られる塗膜の厚みも厚くなる。緻密でピンホールなどの欠陥が無い均一な塗膜を形成するためには、粘度がある程度低い方が有利であり、例えば、塗膜厚さ２０μｍ程度の薄い塗膜では基材に対する密着性は向上する。一方、このような薄い塗膜では、塗膜を厚くすることができなくなり、耐腐食性が低下してしまう。また、粘度が低すぎる場合、金属セパレーターへの塗布時に塗料のハジケが生じたり、膜厚が薄く、耐食性に問題が生じる。逆に、粘度が高い場合は、泡の巻き込みやピンホールによる塗膜欠陥、膜厚の不均一などの問題を生じ、耐腐食性および基材に対する密着性が低下する。 Next, if the blending amount of the organic solvent in the fuel cell separator paint of the present invention is increased, the viscosity of the paint is lowered, and the thickness of the obtained coating film is reduced. On the other hand, when the amount of the organic solvent is small, the viscosity of the paint increases and the thickness of the resulting coating film also increases. In order to form a uniform coating film that is dense and free from defects such as pinholes, it is advantageous that the viscosity is low to some extent. For example, a thin coating film with a thickness of about 20 μm improves adhesion to the substrate. To do. On the other hand, with such a thin coating film, the coating film cannot be made thick and the corrosion resistance is lowered. On the other hand, if the viscosity is too low, the paint may be repelled at the time of application to the metal separator, or the film thickness may be thin, resulting in a problem with corrosion resistance. Conversely, when the viscosity is high, problems such as bubble entrainment, coating film defects due to pinholes, non-uniform film thickness, etc. occur, resulting in a decrease in corrosion resistance and adhesion to the substrate.
したがって、本発明においては、固形分量が１０〜６０重量％であることが好ましく、また、２５℃における粘度が５０〜１００,０００ｍＰａ・ｓの範囲であることが好ましい。本発明のエマルション系結着材を用いた場合は、塗料中の固形分を変えることで低粘度から高粘度まで塗料粘度を任意に調整することが容易であり、２５℃における粘度が５０〜１００,０００ｍＰａ・ｓの範囲内で均一な塗布が可能となる。これらの粘度は、ＩＳＯ ３２１９（ＪＩＳ Ｚ８８０３）に規定される方法により測定された値である。また、塗膜作製のための塗料の塗布方法としては、ディッピング、スプレー、ブレードコーター、スクリーン印刷など種々の方法が挙げられる。 Therefore, in the present invention, the solid content is preferably 10 to 60% by weight, and the viscosity at 25 ° C. is preferably in the range of 50 to 100,000 mPa · s. When the emulsion binder of the present invention is used, it is easy to arbitrarily adjust the paint viscosity from low viscosity to high viscosity by changing the solid content in the paint, and the viscosity at 25 ° C. is 50-100. Uniform application is possible within a range of 1,000 mPa · s. These viscosities are values measured by the method defined in ISO 3219 (JIS Z8803). Examples of the coating method for coating film preparation include various methods such as dipping, spraying, blade coater, and screen printing.
本発明の燃料電池セパレーター用塗料においては、導電塗料の結着材として、スチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコーン共重合体のエマルションのいずれか１つ以上を５重量％以上含有することが好ましい。この結果、本発明の塗料から形成された塗膜は、優れた耐食性と基材に対する密着性とを併せ持つことができる。なお、本発明の燃料電池セパレーター用塗料においては、塗料の特性改善のために、他の樹脂材料を結着材として適宜配合してもよい。 In the fuel cell separator paint of the present invention, 5 wt.% Of any one or more of a styrene-butadiene copolymer, an acrylic-styrene copolymer, and an acrylic-silicone copolymer emulsion is used as a binder for the conductive paint. % Or more is preferable. As a result, the coating film formed from the coating material of the present invention can have both excellent corrosion resistance and adhesion to the substrate. In the fuel cell separator paint of the present invention, another resin material may be appropriately blended as a binder for improving the properties of the paint.
また、本発明の塗料においては、導電材として黒鉛にさらにカーボンブラックを配合することが好ましい。導電材を黒鉛のみとした場合では、粒子配列の配向性により基材との密着性向上が期待できるが、黒鉛は抵抗値異方性を有するため、導電ネットワーク間に電気的接点が不足するので、電気抵抗値の低減には必然的に限界がある。そこで、炭素系混合物としてカーボンブラックを併用することにより、黒鉛粒子の間隙をカーボンブラックが埋めるように充填され、塗膜全体としての電気抵抗値の低減を可能としている。なお、本発明に係る導電塗料の炭素系混合物における黒鉛とカーボンブラックの配合比率は、重量比で３０：７０〜９０：１０であり、好ましくは３５：６５〜８５：１５、さらに好ましくは４０：６０〜８０：２０が好適である。 Moreover, in the coating material of this invention, it is preferable to mix | blend carbon black further with graphite as a electrically conductive material. When the conductive material is only graphite, the improvement in adhesion to the substrate can be expected due to the orientation of the particle arrangement, but because graphite has resistance anisotropy, there are insufficient electrical contacts between the conductive networks. Inevitably, there is a limit to the reduction of the electric resistance value. Therefore, by using carbon black as a carbon-based mixture, the gap between the graphite particles is filled so as to be filled with carbon black, and the electric resistance value of the entire coating film can be reduced. In addition, the compounding ratio of graphite and carbon black in the carbon-based mixture of the conductive paint according to the present invention is 30:70 to 90:10, preferably 35:65 to 85:15, more preferably 40: 60-80: 20 is preferred.
さらに、本発明の燃料電池セパレーター用塗料において、黒鉛は導電材の役割の他に、耐食性を向上させる役割も有している。リン状またはリン片状に代表されるフレーク状の黒鉛粒子は、塗装面に平行に配向し水等を遮蔽し、耐食性を向上させる。なお、黒鉛の平均粒子径（Ｄ５０）が大きいほどこの遮蔽効果は大きくなる傾向がある。しかしながら、黒鉛のＤ５０が大きくなるほど配向しやすくなり、また黒鉛は抵抗値異方性を有するため、配向するほど電気抵抗値は高くなってしまう。したがって黒鉛のＤ５０を大きくすることには必然的に限界があり、本発明者らの検討によれば、黒鉛の平均粒子径（Ｄ５０）は３０μｍ以下であることが好ましいことが分かった。 Furthermore, in the fuel cell separator paint of the present invention, graphite has a role of improving corrosion resistance in addition to the role of a conductive material. Flakes-like graphite particles represented by phosphorus or flakes are oriented parallel to the painted surface to shield water and the like and improve corrosion resistance. In addition, there exists a tendency for this shielding effect to become large, so that the average particle diameter (D50) of graphite is large. However, the larger the D50 of graphite, the easier it is to align, and the graphite has resistance anisotropy, so that the electrical resistance value increases as it is aligned. Therefore, there is inevitably a limit to increasing D50 of graphite, and according to the study by the present inventors, it was found that the average particle diameter (D50) of graphite is preferably 30 μm or less.
以下、実施例により本発明を説明するが、本発明はこれらの実施例のみに限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited only to these Examples.
１．導電材と結着材の配合比率の検討
（塗料および試料の作製）
結着材であるスチレン−ブタジエン共重合体として、スチレン−ブタジエンのランダム共重合体のエマルション（固形分４０重量％）を用い、表１に示す配合で、平均粒子径４μｍの天然黒鉛粉末（黒鉛）とファーネスブラック（カーボンブラック）を８：２で投入し、分散処理を行い、試料番号１１〜１５の燃料電池セパレーター用の導電塗料を作製した。
1. Examination of mixing ratio of conductive material and binder (preparation of paint and sample)
As a binder styrene-butadiene copolymer, an emulsion of styrene-butadiene random copolymer (solid content 40% by weight) was used, and a natural graphite powder (graphite with an average particle size of 4 μm) was blended as shown in Table 1. ) And furnace black (carbon black) were added at 8: 2, and dispersion treatment was performed to prepare conductive paints for fuel cell separators of sample numbers 11 to 15.
作製した導電塗料の粘度は、レオメーター粘度計（ＨＡＫＫＥ社製のレオメーターＲＶ２０）を用い、コーン型回転子の回転数が１００ｒｐｍおよび１,５００ｒｐｍにおける粘度を測定した。回転子の回転数を２種とした理由は、この種の導電塗料の塗布方法が種々考えられるためであり、例えば、ディッピングにより塗布する場合では塗料にはそれほどの外力がかからないので低回転で評価した結果が対応することとなり、スクリーン印刷法、ブレードコーターなどで塗布する場合には塗料にある程度の外力がかかることとなるので高回転数で評価した結果が対応することとなるからである。 The viscosity of the produced conductive paint was measured using a rheometer viscometer (Rheometer RV20 manufactured by HAKKE) at a rotation speed of a cone type rotor of 100 rpm and 1,500 rpm. The reason why the number of rotations of the rotor is two is that there are various methods of applying this type of conductive paint. For example, when applying by dipping, the paint does not take much external force, so it is evaluated at low rotation. This is because the results of the evaluation correspond to each other, and when coating is performed by a screen printing method, a blade coater, or the like, a certain amount of external force is applied to the paint, and the result of evaluation at a high rotational speed corresponds.
次に、８０ｍｍ×１５０ｍｍ×１ｍｍのガラス板、１０ｍｍ×１５ｍｍ×４ｍｍのステンレス鋼（ＳＵＳ３０４）板、３０ｍｍ×８０ｍｍ×１ｍｍのステンレス鋼（ＳＵＳ３０４）板および炭素鋼（ＳＳ４００）板に、それぞれの導電塗料をドクターブレードにて塗布し、１５０℃で１５分間加熱乾燥して、評価用試料とした。また、塗布性評価としてステンレス鋼（ＳＵＳ３０４）板にドクターブレードにて塗布した後の塗膜状態を観察し、全面均一に塗布できた場合を◎、ほぼ均一に塗布できた場合を○、ピンホールやハジケ等が発生した場合を×とした。 Next, each conductive paint is applied to a glass plate of 80 mm × 150 mm × 1 mm, a stainless steel (SUS304) plate of 10 mm × 15 mm × 4 mm, a stainless steel (SUS304) plate of 30 mm × 80 mm × 1 mm, and a carbon steel (SS400) plate. Was applied with a doctor blade and dried by heating at 150 ° C. for 15 minutes to obtain a sample for evaluation. In addition, as a coating evaluation, the state of the coating film was observed after being applied to a stainless steel (SUS304) plate with a doctor blade. And x where the haze and the like occur.
（塗膜の評価）
上記の評価用試料の塗膜について、体積抵抗、面抵抗および密着性を次に示す方法により評価した。体積抵抗は、ガラス板上に塗料を塗布した試験片の塗膜に測定端子を押し付け、４探針４端子法（ダイアインスツルメンツ社製のロレスターＡＰ）により塗膜面方向の体積抵抗を測定した。面抵抗は、炭素鋼板上に塗料を塗布した試験片を銀板により挟み込み、４端子法（ＨＩＯＫＩ社製の３５６０ｍΩＨｉＴＥＳＴＥＲ）を用いて、炭素鋼込みの塗膜面に垂直な方向の面抵抗を測定した。
(Evaluation of coating film)
About the coating film of said evaluation sample, volume resistance, surface resistance, and adhesiveness were evaluated by the method shown next. The volume resistance was measured by pressing a measurement terminal against a coating film of a test piece coated with a paint on a glass plate, and measuring the volume resistance in the coating film surface direction by a four-probe four-terminal method (Lorestar AP manufactured by Dia Instruments). The sheet resistance is measured by sandwiching a test piece coated with a paint on a carbon steel plate with a silver plate and measuring the sheet resistance in a direction perpendicular to the coating surface of the carbon steel using a four-terminal method (HIROKI 3560 mΩ HiTESTER). did.
また、密着性は、ＪＩＳ Ｋ５４００に準拠した方法として、ステンレス鋼板、炭素鋼板上に塗料を塗布した試験片の塗膜に１ｍｍ幅で各々直角に交わる１１本のカットをカッターで入れ、１８ｍｍ幅のメンディングテープを指圧で塗膜に圧着させた後、テープを１８０°方向に引き剥がし、引き剥がした後のテープに付着した塗膜を観察し密着性を評価した。さらに、各試験片について、プレッシャークッカー試験（１２１℃、２気圧の環境下で２４時間：ＰＣＴ）を行った後、その塗膜についても同様の密着性の評価を行い、耐食性の評価とした。これらの評価結果は表１に示した。 In addition, as a method in conformity with JIS K5400, 11 cuts that intersect at right angles each with a width of 1 mm are put into a coating film of a test piece obtained by applying a paint on a stainless steel plate or a carbon steel plate with a cutter, After the mending tape was pressure-bonded to the coating film with finger pressure, the tape was peeled off in the 180 ° direction, and the coating film adhered to the tape after peeling was observed to evaluate the adhesion. Further, each test piece was subjected to a pressure cooker test (121 ° C., 24 hours under an atmosphere of 2 atm: PCT), and then the same adhesion was evaluated for the coating film to evaluate corrosion resistance. These evaluation results are shown in Table 1.
導電材と結着材の配合比率が２０：８０〜９５：５の範囲内である試料番号１１〜１３は、電気抵抗値および密着性はいずれも使用可能な範囲にあることが分かった。これに対し、導電材と結着材の配合比率が１０：９０である試料番号１４は、密着性は高く良好であるが、面抵抗が７２０ｍΩｃｍ２と高く、電気伝導性が劣っていた。また、導電材と結着材の配合比率が９８：２である試料番号１５は、面抵抗が０.５ｍΩｃｍ２と良好であるが、ＰＣＴ後に塗膜の剥離が見られた。 It was found that Sample Nos. 11 to 13 in which the blending ratio of the conductive material and the binder was in the range of 20:80 to 95: 5 were both in the usable range. On the other hand, Sample No. 14 in which the blending ratio of the conductive material and the binder was 10:90 had good adhesion and good, but the sheet resistance was as high as 720 mΩcm 2 and the electrical conductivity was inferior. Sample No. 15 in which the blending ratio of the conductive material and the binder was 98: 2 was good at a sheet resistance of 0.5 mΩcm 2 , but peeling of the coating film was observed after PCT.
つまり、本発明の燃料電池セパレーター用塗料においては、結着材の配合量が多いものほど密着性が向上する傾向にあるが、結着材は不導体のため電気抵抗値が上昇してしまう。一方、結着材が少なすぎると、良好な密着性が得られない。したがって、本発明における導電材と結着材の配合比率は、重量比で２０：８０〜９５：５の範囲が好適であることが分かった。 That is, in the coating for a fuel cell separator of the present invention, as the amount of the binder is increased, the adhesion tends to be improved. However, since the binder is a non-conductor, the electrical resistance value is increased. On the other hand, when there are too few binders, favorable adhesiveness cannot be obtained. Therefore, it was found that the blending ratio of the conductive material and the binder in the present invention is preferably in the range of 20:80 to 95: 5 by weight ratio.
２．エマルションの検討
結着材であるスチレン−ブタジエン共重合体として、スチレン−ブタジエンのランダム共重合体、スチレン−ブタジエン−スチレンブロック共重合体のエマルションを用い、アクリル系エマルションとしてアクリル−スチレン共重合体、およびアクリル酸エステルとアルコキシシランとの共重合体からなるアクリル−シリコーン共重合体を用い、さらに比較例として、ポリ酢酸ビニルエマルションを表２に示す配合とし、上記の導電材と結着材の配合比率の検討における塗料および試料の作製に記載の方法と同様に試料番号２１〜２５の燃料電池セパレーター用の導電塗料を作製し、同様の評価を行って樹脂の種類の影響について検討した。塗料組成および得られた塗膜の評価結果は表２に示した。
2. Examination of emulsion As the styrene-butadiene copolymer as a binder, a random copolymer of styrene-butadiene, an emulsion of styrene-butadiene-styrene block copolymer, an acrylic-styrene copolymer as an acrylic emulsion, In addition, an acrylic-silicone copolymer made of a copolymer of acrylic acid ester and alkoxysilane is used, and as a comparative example, a polyvinyl acetate emulsion is blended as shown in Table 2, and the above-described conductive material and binder are blended. Conductive paints for fuel cell separators of sample numbers 21 to 25 were produced in the same manner as described in the preparation of paints and samples in the examination of the ratio, and the same evaluation was performed to examine the influence of the type of resin. The coating composition and the evaluation results of the obtained coating film are shown in Table 2.
スチレン−ブタジエン共重合体として、スチレン−ブタジエンのランダム共重合体、スチレン−ブタジエン−スチレンブロック共重合体のエマルションを用いた場合（試料番号２１、２２）では、良好な電気抵抗値と密着性を示した。また、スチレン−ブタジエン−スチレンブロック共重合体を用いたものが、塗布時のハジケが無く、最も良好な塗布性を示した。また、アクリル−スチレン共重合体、アクリル−シリコーン共重合（試料番号２３、２４）も電気抵抗、密着性ともに良好であった。しかしポリ酢酸エマルジョン（試料番号２５）では、導電材の分散が悪く、電気抵抗が高く、またＰＣＴ後に塗膜の剥離があった。 When a random copolymer of styrene-butadiene or an emulsion of styrene-butadiene-styrene block copolymer is used as the styrene-butadiene copolymer (Sample Nos. 21 and 22), good electrical resistance and adhesion are obtained. Indicated. Moreover, the thing using a styrene-butadiene-styrene block copolymer did not have a rash at the time of application | coating, and showed the best application | coating property. The acrylic-styrene copolymer and acrylic-silicone copolymer (Sample Nos. 23 and 24) also had good electrical resistance and adhesion. However, in the polyacetic acid emulsion (Sample No. 25), the dispersion of the conductive material was poor, the electric resistance was high, and the coating film was peeled off after PCT.
したがって、本発明の燃料電池セパレーター用塗料では、エマルション系結着材としてスチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコーン共重合体のいずれかを５重量％以上含有されることにより、優れた特性が得られることが分かった。 Therefore, the paint for a fuel cell separator of the present invention contains at least 5% by weight of any one of a styrene-butadiene copolymer, an acrylic-styrene copolymer, and an acrylic-silicone copolymer as an emulsion binder. Thus, it was found that excellent characteristics can be obtained.
３．固形分および粘度の検討
次に、表３に示す配合は、固形分量を変更した以外は、上記の導電材と結着材の配合比率の検討における塗料および試料の作製に記載の方法と同様として、試料番号３１〜３４の燃料電池セパレーター用の導電塗料を作製し、同様の評価を行って塗料の固形分および粘度が及ぼす影響について検討を行った。塗料組成および得られた塗膜の評価結果は表３に示した。
3. Examination of solid content and viscosity Next, the formulation shown in Table 3 is the same as the method described in the preparation of paint and sample in the examination of the blending ratio of the conductive material and the binder, except that the solid content was changed. Then, conductive paints for fuel cell separators of sample numbers 31 to 34 were prepared, and the same evaluation was performed to examine the influence of the solid content and viscosity of the paint. The coating composition and the evaluation results of the obtained coating film are shown in Table 3.
塗料中の固形分が１０重量％〜６０重量％（試料番号３１、３２）で良好な塗布性を示した。しかしながら、固形分量が少ない場合（試料番号３３）では、塗料粘度も低く、塗料のハジケが生じ、塗料を厚く塗布することができなかった。一方、固形分量が多い場合（試料番号３４）では、塗料粘度も高く、印刷性が悪くなり、得られた塗膜にはピンホールが発生した。さらに、ＰＣＴ後に塗膜剥離が発生し、実用に供し得ないことが分かった。 The solid content in the paint was 10 wt% to 60 wt% (Sample Nos. 31 and 32), and good coating properties were exhibited. However, when the solid content was small (Sample No. 33), the viscosity of the paint was low and the paint was crushed, and the paint could not be applied thickly. On the other hand, when the amount of solid content was large (sample number 34), the paint viscosity was high, the printability was poor, and pinholes were generated in the obtained coating film. Furthermore, it was found that the coating film peeled after PCT and could not be put to practical use.
したがって、本発明の燃料電池セパレーター用塗料においては、塗料の粘度および塗布状態を最適にするために、塗料中の固形分が１０〜６０重量％の範囲内であることが好ましいことが分かった。 Therefore, in the fuel cell separator paint of the present invention, it was found that the solid content in the paint is preferably in the range of 10 to 60% by weight in order to optimize the viscosity and application state of the paint.
４．カーボンブラックの添加量の検討
次に、導電材の黒鉛に添加するカーボンブラックの添加量を、表４に示す配合に変更した以外は、上記の導電材と結着材の配合比率の検討における塗料および試料の作製に記載の方法と同様に、試料番号４１〜４５の燃料電池セパレーター用の導電塗料を作製し、同様の評価を行ってカーボンブラックの添加量の及ぼす影響について検討を行った。塗料組成および得られた塗膜の評価結果は表４に示した。
4). Examination of addition amount of carbon black Next, the coating material in the examination of the blending ratio of the conductive material and the binder described above except that the addition amount of carbon black added to the graphite of the conductive material was changed to the formulation shown in Table 4 Similarly to the method described in the preparation of the sample, conductive paints for the fuel cell separators of sample numbers 41 to 45 were prepared, and the same evaluation was performed to examine the influence of the added amount of carbon black. The coating composition and the evaluation results of the obtained coating film are shown in Table 4.
黒鉛のみの試料番号４４に比べ、カーボンブラックを添加した試料番号４１〜４３では、その添加量の増加に伴い抵抗値が小さくなり、密着性も良好であった。しかしながら、黒鉛とカーボンブラックの配合比率が重量比で２５：７５である試料番号４５では、抵抗値が高くなってしまった。 Compared to graphite-only sample number 44, sample numbers 41 to 43 to which carbon black was added had a smaller resistance value and better adhesion as the addition amount increased. However, in sample number 45 in which the mixing ratio of graphite and carbon black was 25:75 by weight, the resistance value was high.
したがって、本発明の燃料電池セパレーター用塗料においては、導電材が黒鉛にさらにカーボンブラックを配合した炭素系混合物であり、黒鉛とカーボンブラックの配合比率が重量比で３０：７０〜９０：１０であることが好ましいことが分かった。 Accordingly, in the fuel cell separator paint of the present invention, the conductive material is a carbon-based mixture obtained by further mixing carbon black with graphite, and the mixing ratio of graphite and carbon black is 30:70 to 90:10 by weight. It turned out to be preferable.
以上説明したように、本発明は、導電材として黒鉛を使用し、燃料電池用の金属製またはカーボン製セパレーターの表面に塗布して導電性塗膜を形成する燃料電池セパレーター用塗料において、塗料の結着材としてスチレン−ブタジエン共重合体、アクリル−スチレン共重合体、アクリル−シリコン共重合体のエマルションのいずれか１つ以上を用い、結着材量として５重量％以上含有し、導電材と結着材の配合比率を重量比で２０：８０〜９５：５とし、塗料中の固形分を１０〜６０重量％とすることにより、その塗膜は、優れた耐食性を有するとともに、良好な導電性と密着性とを併せ持つことができまた、環境上、コスト的にも優れた塗料を得ることができる。 As described above, the present invention uses a graphite as a conductive material and is applied to the surface of a metal separator or a carbon separator for a fuel cell to form a conductive coating film. Using any one or more of a styrene-butadiene copolymer, an acrylic-styrene copolymer, and an acrylic-silicon copolymer emulsion as a binder, and containing 5% by weight or more as a binder, By setting the blending ratio of the binder to 20:80 to 95: 5 by weight and the solid content in the coating to 10 to 60% by weight, the coating film has excellent corrosion resistance and good conductivity. In addition, it is possible to obtain a coating material that is excellent in terms of cost and environment.
耐食性、導電性および密着性を兼ね備えた導電性塗量を、環境に対して軽負荷で、かつ低コストで提供することができる。 It is possible to provide a conductive coating amount having both corrosion resistance, conductivity and adhesion with a light load on the environment and at a low cost.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010128676A1 (en) * | 2009-05-08 | 2010-11-11 | 日本軽金属株式会社 | Fuel cell separator and method for producing same |
| KR101011014B1 (en) | 2008-06-13 | 2011-01-26 | 한국타이어 주식회사 | Process for preparing separator material for a fuel cell having high electrical conductivity, separator for a fuel cell and feul cell |
| JP2011057942A (en) * | 2009-09-14 | 2011-03-24 | Kikusui Chemical Industries Co Ltd | Water-based rustproof coating |
| WO2013125611A1 (en) * | 2012-02-23 | 2013-08-29 | 日本ゼオン株式会社 | Aqueous conductive paste for fuel cell separator |
| JP2015220162A (en) * | 2014-05-20 | 2015-12-07 | 日本ゼオン株式会社 | Method for manufacturing aqueous conductive paste for fuel battery separators |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000058083A (en) * | 1998-06-05 | 2000-02-25 | Nisshinbo Ind Inc | Separator for fuel cell and its manufacture |
| WO2003044888A1 (en) * | 2001-11-21 | 2003-05-30 | Hitachi Powdered Metals Co.,Ltd. | Coating material for fuel cell separator |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000058083A (en) * | 1998-06-05 | 2000-02-25 | Nisshinbo Ind Inc | Separator for fuel cell and its manufacture |
| WO2003044888A1 (en) * | 2001-11-21 | 2003-05-30 | Hitachi Powdered Metals Co.,Ltd. | Coating material for fuel cell separator |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101011014B1 (en) | 2008-06-13 | 2011-01-26 | 한국타이어 주식회사 | Process for preparing separator material for a fuel cell having high electrical conductivity, separator for a fuel cell and feul cell |
| WO2010128676A1 (en) * | 2009-05-08 | 2010-11-11 | 日本軽金属株式会社 | Fuel cell separator and method for producing same |
| JP2011057942A (en) * | 2009-09-14 | 2011-03-24 | Kikusui Chemical Industries Co Ltd | Water-based rustproof coating |
| WO2013125611A1 (en) * | 2012-02-23 | 2013-08-29 | 日本ゼオン株式会社 | Aqueous conductive paste for fuel cell separator |
| JPWO2013125611A1 (en) * | 2012-02-23 | 2015-07-30 | 日本ゼオン株式会社 | Water-based conductive paste for fuel cell separator |
| JP2015220162A (en) * | 2014-05-20 | 2015-12-07 | 日本ゼオン株式会社 | Method for manufacturing aqueous conductive paste for fuel battery separators |
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