JP2004214072A - Carbon fiber sheet and its manufacturing method - Google Patents
Carbon fiber sheet and its manufacturing method Download PDFInfo
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- JP2004214072A JP2004214072A JP2003000855A JP2003000855A JP2004214072A JP 2004214072 A JP2004214072 A JP 2004214072A JP 2003000855 A JP2003000855 A JP 2003000855A JP 2003000855 A JP2003000855 A JP 2003000855A JP 2004214072 A JP2004214072 A JP 2004214072A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 166
- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 157
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 145
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 239000000835 fiber Substances 0.000 claims abstract description 79
- 239000005518 polymer electrolyte Substances 0.000 claims abstract description 24
- 239000000446 fuel Substances 0.000 claims abstract description 21
- 239000011230 binding agent Substances 0.000 claims abstract description 20
- 239000011261 inert gas Substances 0.000 claims abstract description 7
- 239000007772 electrode material Substances 0.000 claims description 15
- 238000010000 carbonizing Methods 0.000 claims description 5
- 239000003575 carbonaceous material Substances 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 26
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 5
- 239000001257 hydrogen Substances 0.000 abstract description 5
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 5
- 239000001301 oxygen Substances 0.000 abstract description 5
- 229910052760 oxygen Inorganic materials 0.000 abstract description 5
- 230000006866 deterioration Effects 0.000 abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 3
- 229920000867 polyelectrolyte Polymers 0.000 abstract 1
- 238000007906 compression Methods 0.000 description 27
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 26
- 230000006835 compression Effects 0.000 description 26
- 230000000704 physical effect Effects 0.000 description 20
- 229920002239 polyacrylonitrile Polymers 0.000 description 20
- 239000002994 raw material Substances 0.000 description 18
- 229910052757 nitrogen Inorganic materials 0.000 description 13
- 238000010304 firing Methods 0.000 description 9
- 239000012528 membrane Substances 0.000 description 9
- 238000013329 compounding Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 6
- 239000004372 Polyvinyl alcohol Substances 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 229920000728 polyester Polymers 0.000 description 6
- 229920002451 polyvinyl alcohol Polymers 0.000 description 6
- 206010016807 Fluid retention Diseases 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000003672 processing method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000001307 helium Substances 0.000 description 2
- 229910052734 helium Inorganic materials 0.000 description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
- 239000004745 nonwoven fabric Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229920003043 Cellulose fiber Polymers 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- -1 PAN-based Chemical class 0.000 description 1
- 229910002848 Pt–Ru Inorganic materials 0.000 description 1
- 229920006231 aramid fiber Polymers 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
Classifications
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、固体高分子電解質型燃料電池（高分子型燃料電池）のガス拡散電極用の炭素繊維シート及びその製造方法に関する。
【０００２】
【従来の技術】
炭素繊維にはポリアクロニトリル（ＰＡＮ）系、ピッチ系、フェノール系などがある。これら炭素繊維は、電気導電性を示し薄層のシート状の素材の作製が可能なことより、近年実用化が進められている高分子電解質型燃料電池用の電極材として期待され応用研究が行われている。
【０００３】
一方、活性炭素繊維には、炭素繊維と同様のＰＡＮ系、ピッチ系、フェノール系のものがある。これらは、比表面積が約５００〜２５００ｍ２／ｇであり、触媒特性に優れているが、炭素繊維に比べ電気伝導性がやや劣る。
【０００４】
特許文献１に、特定の細孔容積、細孔直径の活性炭素繊維を電極材に用いる記載はあるが、比表面積の記載はなく、燃料電池への応用に関しては、触れられていない。
【０００５】
特許文献２に、レドックスフロー型２次電池用に比表面積１５〜６０ｍ２／ｇ、塩素含有量が１０ｐｐｍ以上のＰＡＮ系炭素繊維を用いる記載はあるが、高分子電解質型燃料電池への応用に関する記載は無い。
【０００６】
高分子電解質型燃料電池は、燃料源として水素と酸素を反応させ、そのエネルギーを電気エネルギーに変換させる電池であり、高分子電解質膜と電極材が一体化され使用される。高分子電解質型燃料電池用電極材としては、下記の物性に優れることが必須となる。
【０００７】
・電気伝導性
・触媒特性（水素を酸素との反応を促進させる特性）
・保水性（高分子電解質膜の乾燥による劣化防止）
高分子電解質膜は厚さが約２０〜５０μｍと非常に薄く、乾燥すると脆くなり破損し易いため、長期間電池を作動しない場合などには電池性能の低下を生ずることがある。
【０００８】
【特許文献１】
特開昭６２−１５４４６１号公報 （特許請求の範囲）
【特許文献２】
特開昭６３−２２６１号公報 （特許請求の範囲）
【０００９】
【発明が解決しようとする課題】
本発明者は、上記問題について種々検討しているうちに、炭素繊維と活性炭素繊維（吸湿性と触媒特性を有する）をバインダー（繊維）と共にシート状に圧縮成型してシート状にして得られる炭素繊維シートを、又はこのシートを焼成（炭素化）して得られる炭素繊維シートを、高分子電解質型燃料電池用電極として用いることによって、水素と酸素の反応効率を向上させると共に高分子電解質膜の保水性を持たせ、電解質膜の劣化を防止させ、電池の性能を改善をすることができることを知得し、本発明を完成するに到った。
【００１０】
従って、本発明の目的とするところは、上記問題を解決した炭素繊維シート及びその製造方法を提供することにある。
【００１１】
【課題を解決するための手段】
上記目的を達成する本発明は、以下に記載するものである。
【００１２】
〔１〕 炭素繊維と活性炭素繊維とを含み、比表面積１５〜３５０ｍ２／ｇ、厚さ０．１〜０．７ｍｍ、厚さ方向の電気抵抗値６ｍΩ以下、嵩密度０．１６〜０．４０ｇ／ｃｍ３の高分子電解質型燃料電池電極材用の炭素繊維シート。
【００１３】
〔２〕 炭素繊維と活性炭素繊維とが互いにバインダー繊維で結合された〔１〕に記載の炭素繊維シート。
【００１４】
〔３〕 炭素繊維と活性炭素繊維とが互いにこれらの交絡部において炭素材により結合された〔１〕に記載の炭素繊維シート。
【００１５】
〔４〕 炭素繊維と比表面積５００〜２５００ｍ２／ｇの活性炭素繊維と炭素化可能なバインダーとを混合されてなる炭素繊維シートを９５０〜１５５０℃の温度下で不活性ガス雰囲気中で炭素化する、比表面積１５〜３５０ｍ２／ｇ、厚さ０．１〜０．７ｍｍ、厚さ方向の電気抵抗値６ｍΩ以下、嵩密度０．１６〜０．４０ｇ／ｃｍ３の高分子電解質型燃料電池電極材用の炭素繊維シートの製造方法。
【００１６】
〔５〕 酸化繊維と比表面積５００〜２５００ｍ２／ｇの活性炭素繊維と炭素化可能なバインダーとを混合されてなる炭素繊維シートを９５０〜１５５０℃の温度下で不活性ガス雰囲気中で炭素化する、比表面積１５〜３５０ｍ２／ｇ、厚さ０．１〜０．７ｍｍ、厚さ方向の電気抵抗値６ｍΩ以下、嵩密度０．１６〜０．４０ｇ／ｃｍ３の高分子電解質型燃料電池電極材用の炭素繊維シートの製造方法。
【００１７】
【発明の実施の形態】
以下、本発明を詳細に説明する。
【００１８】
本発明の高分子電解質型燃料電池電極材用の炭素繊維シートは、炭素繊維と活性炭素繊維とを混合してなる炭素繊維シートである。
【００１９】
この炭素繊維シートの比表面積は１５〜３５０ｍ２／ｇである。炭素繊維シートの比表面積が１５ｍ２／ｇ未満の場合は、電極材の保水性が低下し、電池性能が低下するので好ましくない。炭素繊維シートの比表面積が３５０ｍ２／ｇを超える場合は、電極材の電気抵抗値が増加し、電池性能が低下するので好ましくない。
【００２０】
炭素繊維シートの厚さは０．１〜０．７ｍｍである。炭素繊維シートの厚さが０．１ｍｍ未満の場合は、シート強度が低下するので好ましくない。炭素繊維シートの厚さが０．７ｍｍを超える場合は、このシートを高分子電解質型燃料電池用電極として用いた電池が嵩高くなり、コンパクト化が困難となるので好ましくない。
【００２１】
炭素繊維シートの嵩密度は０．１６〜０．４０ｇ／ｃｍ３である。炭素繊維シートの嵩密度が０．１６ｇ／ｃｍ３未満の場合は、炭素繊維シートの電気抵抗値が増加し、このシートを用いた電池の性能が低下するので好ましくない。炭素繊維シートの嵩密度が０．４０ｇ／ｃｍ３を超える場合は、このシートを高分子電解質型燃料電池用電極として用いた電池における高電流密度（１．６Ａ／ｃｍ２）側での電池性能が低下するので好ましくない。
【００２２】
炭素繊維シートの厚さ方向の電気抵抗値は６ｍΩ以下である。このシートを高分子電解質型燃料電池用電極材として用いる場合、電気抵抗値が低い程、電池性能が良い。この電気抵抗値が６ｍΩを超えると起電力が下がり、電池性能が悪くなるので好ましくない。
【００２３】
なお、炭素繊維シートにおける厚さ方向の電気比抵抗値は、後述する測定方法により測定して得られる。
【００２４】
本発明炭素繊維シートの第１の例としては、炭素繊維と活性炭素繊維とが互いに繊維同士がバインダー繊維で結合されてシート化された形態がある。
【００２５】
本発明炭素繊維シートの第２の例としては、炭素繊維と活性炭素繊維とが混合され、繊維同士の交絡部において炭素材により互いの繊維同士が結合された形態があるが、これらに限定されない。
【００２６】
活性炭素繊維は、比表面積が５００〜２５００ｍ２／ｇのものが好ましく、８００〜２５００ｍ２／ｇのものが更に好ましい。バインダー繊維は、炭素化可能なものが好ましい。
【００２７】
炭素繊維と活性炭素繊維との混合割合は、活性炭素繊維の比表面積により異なるが、炭素繊維シートの全成分１００質量部に対し、炭素繊維は５０〜８０質量部、活性炭素繊維は５〜４０質量部が好ましい。バインダー繊維の混合割合は、炭素繊維シートの全成分１００質量部に対し、３〜１５質量部が好ましい。
【００２８】
炭素繊維シートの製造方法としては、特に限定されるものではないが、例えば以下の製造方法により製造することができる。
【００２９】
混合シートα
炭素繊維カットファイバー（成分Ａ）と、活性炭素繊維カットファイバー（成分Ｂ）とを混合し、シート加工した後、圧縮処理する。
【００３０】
混合シートβ
炭素繊維カットファイバー（成分Ａ）と、活性炭素繊維カットファイバー（成分Ｂ）と、バインダーカットファイバー（成分Ｃ）とを混合し、シート加工した後、圧縮処理する。
【００３１】
焼成後の炭素繊維シートγ
炭素繊維カットファイバー（成分Ａ）と、活性炭素繊維カットファイバー（成分Ｂ）と、バインダーカットファイバー（成分Ｃ）とを混合し、シート加工した後、圧縮処理する。更に焼成炭素化する（９５０〜１５５０℃、窒素中）。
【００３２】
焼成後の炭素繊維シートδ
酸化繊維カットファイバー（成分Ａ）と、活性炭素繊維カットファイバー（成分Ｂ）と、バインダーカットファイバー（成分Ｃ）とを混合し、シート加工した後、圧縮処理する。更に焼成炭素化する（９５０〜１５５０℃、窒素中）。
【００３３】
次に、本例の炭素繊維シートの製造方法における個々の原料、工程について詳細に説明する。
【００３４】
〔炭素繊維カットファイバー（成分Ａ）〕
炭素繊維シート原料の成分Ａの炭素繊維としては、ＰＡＮ系、ピッチ系、フェノ−ル系等の炭素繊維を用いることができるが、強度の面から特にＰＡＮ系が好ましい。
【００３５】
炭素繊維カットファイバーのカット長さは、３〜１００ｍｍが好ましい。カット長さが３ｍｍ未満の場合は、得られる炭素繊維シートの強度が低下するので好ましくない。カット長さが１００ｍｍを超える場合は、繊維の分散性が低下するので好ましくない。
【００３６】
炭素繊維カットファイバーの繊維直径は、特に限定されないが、３〜２０μｍが好ましい。
【００３７】
炭素繊維カットファイバーの配合比は、成分Ａの配合比として炭素繊維シート原料の全成分１００質量部に対して３０〜８０質量部が好ましい。
【００３８】
〔酸化繊維カットファイバー（成分Ａ）〕
炭素繊維シート原料の成分Ａの酸化繊維としては、ＰＡＮ系、ピッチ系、フェノ−ル系等の酸化繊維の種類にこだわらないが、ＰＡＮ系酸化繊維が強度面、加工性に優れており好ましい。
【００３９】
酸化繊維カットファイバーのカット長さは、３〜１００ｍｍが好ましい。カット長さが３ｍｍ未満の場合は、得られる炭素繊維シートの強度が低下するので好ましくない。カット長さが１００ｍｍを超える場合は、繊維の分散性が低下するので好ましくない。
【００４０】
酸化繊維カットファイバーの繊維直径は、特に限定されないが、３〜３０μｍが好ましい。
【００４１】
酸化繊維カットファイバーの配合比は、成分Ａの配合比として炭素繊維シート原料の全成分１００質量部に対して３０〜８０質量部が好ましい。
【００４２】
〔活性炭素繊維カットファイバー（成分Ｂ）〕
炭素繊維シート原料の成分Ｂの活性炭素繊維としては、ＰＡＮ系、ピッチ系、フェノ−ル系等の活性炭素繊維の種類にこだわらないが、ＰＡＮ系活性炭素繊維が強度面、加工性に優れており好ましい。
【００４３】
活性炭素繊維カットファイバーのカット長さは、３〜１００ｍｍが好ましい。カット長さが３ｍｍ未満の場合は、得られる炭素繊維シートの強度が低下するので好ましくない。カット長さが１００ｍｍを超える場合は、繊維の分散性が低下するので好ましくない。
【００４４】
活性炭素繊維カットファイバーの繊維直径は、特に限定されないが、３〜２５μｍが好ましい。
【００４５】
活性炭素繊維カットファイバーの比表面積は、５００〜２５００ｍ２／ｇが好ましく、８００〜２５００ｍ２／ｇが更に好ましい。比表面積が５００ｍ２／ｇ未満の場合は、保水性低下、触媒特性低下等の不具合を生ずるので好ましくない。比表面積が２５００ｍ２／ｇを超える場合は、繊維強度が低く、シート加工性低下、微粉末発生等の不具合を生ずるので好ましくない。
【００４６】
活性炭素繊維カットファイバーの配合比は、成分Ｂの配合比として炭素繊維シート原料の全成分１００質量部に対して１５〜５０質量部が好ましい。
【００４７】
〔バインダーカットファイバー（成分Ｃ）〕
炭素繊維シート原料の成分Ｃのバインダーとしては、ポリビニルアルコ−ル（ＰＶＡ）繊維、ポリエステル（ＰＥＴ）繊維、アラミド繊維、セルロ−ズ繊維等が用いられる。
【００４８】
バインダーカットファイバーの繊維直径は、特に限定されないが、３〜２５μｍが好ましい。
【００４９】
バインダーカットファイバーの配合比は、成分Ｃの配合比として炭素繊維シート原料の全成分１００質量部に対して３〜３０質量部が好ましい。
【００５０】
〔シート加工〕
シート加工方法については特に限定はされないが、湿式の抄紙法や、乾式のウエッブよりウォータージェット方式による不織布加工方法等が用いられる。
【００５１】
このシート加工により、目付が４０〜２００ｇ／ｍ２、厚さが０．２０〜１．００ｍｍ、嵩密度が０．１０〜０．３５ｇ／ｃｍ３のシート加工後のシート（混合シート）を得ることができる。
【００５２】
上記範囲外の物性の混合シートは、これを圧縮処理して炭素繊維シートとして用いる場合（例えば前述の混合シートα若しくはβ）、目標の物性の炭素繊維シートが得られないので好ましくない。また、上記範囲外の物性の混合シートを圧縮処理後、焼成した場合（例えば前述の焼成後の炭素繊維シートγ若しくはδ）、目標の物性の炭素繊維シートが得られないので好ましくない。
【００５３】
〔圧縮処理〕
上記シート加工により得られた混合シートは、圧縮処理される。この圧縮処理において、圧縮処理温度は１００〜３００℃であり、圧縮処理圧力は０．５〜３０ＭＰａである。
【００５４】
この圧縮処理により、目付が４０〜２００ｇ／ｍ２、厚さが０．１０〜０．８０ｍｍ、嵩密度が０．１３〜０．６０ｇ／ｃｍ３の圧縮処理後のシートを得ることができる。
【００５５】
上記範囲外の物性の圧縮処理後シートは、これを炭素繊維シートとして用いる場合（例えば前述の混合シートα若しくはβ）、目標の物性の炭素繊維シートではないので好ましくない。また、上記範囲外の物性の圧縮処理後シートを焼成した場合（例えば前述の焼成後の炭素繊維シートγ若しくはδ）、目標の物性の炭素繊維シートが得られないので好ましくない。
【００５６】
〔炭素化〕
圧縮処理後のシートは、必要に応じ（例えば前述の混合シートα若しくはβの場合）、バッチ又は連続的に、不活性ガス雰囲気下、９５０〜１５５０℃の温度にて焼成し炭素化する。不活性ガスとしては、窒素、アルゴン、ヘリウム等が用いられる。この中でもコスト面で窒素が最も好ましい。
【００５７】
焼成温度が９５０℃未満の場合は、得られる炭素繊維シートの電気抵抗値が増加するので好ましくない。焼成温度が１５５０℃を超える場合は、得られる炭素繊維シートにおける前述した成分Ｂの活性炭素繊維の比表面積が低下又は消失するので好ましくない。
【００５８】
【実施例】
本発明を以下の実施例及び比較例により詳述する。
【００５９】
以下の実施例及び比較例の条件により炭素繊維シートを作製した。原料繊維、抄紙バインダー、混合シート、圧縮処理後のシート及び焼成後の炭素繊維シートの諸物性値を、以下の方法により測定した。
【００６０】
厚さ：直径３０ｍｍの円形圧板で２００ｇｆの荷重（２．８ｋＰａ）時の厚さを測定した。
【００６１】
目付：シートの寸法及び１２０℃での乾燥質量より、単位面積当たりの質量を算出した。
【００６２】
嵩密度：上記条件により測定した厚さ及び目付から算出した。
【００６３】
比表面積：ＢＥＴ吸着法により、相対圧（窒素／ヘリウム）０．３０での窒素吸着量より単位質量当たりの表面積を算出した。
【００６４】
電気抵抗値：２枚の５０ｍｍ角（厚さ１０ｍｍ）の金メッキした電極に炭素繊維シ−トを両面の圧力１ＭＰａで挟み、両電極間の電気抵抗値（ｍΩ）を測定した。
【００６５】
電池性能評価法：炭素繊維シートを５０ｍｍ角にカットし、これに触媒（Ｐｔ−Ｒｕ）を０．２ｍｇ／ｃｍ２担持させて、高分子電解質膜（デュポン社製：ナフィオン膜１１７）の両側に、上記５０ｍｍ角にカットした電極材を接合してセルを構成し、温度８０℃、電流密度１．６Ａ／ｃｍ２においてセル電圧を測定した。
【００６６】
実施例１
表１に示すように、炭素繊維シート原料の成分ＡとしてＰＡＮ系炭素繊維（繊維直径１１μｍ、カット長５ｍｍ）７５質量部と、成分ＢとしてＰＡＮ系活性炭素繊維（比表面積９００ｍ２／ｇ、繊維直径１１μｍ、カット長５ｍｍ）２０質量部と、成分Ｃとしてポリエステル（ＰＥＴ）繊維（繊維直径１５μｍ、カット長５ｍｍ）５質量部を均一に混合した後、湿式抄紙し、目付１００ｇ／ｍ２、厚さ０．３５ｍｍ、嵩密度０．２８ｇ／ｃｍ３の炭素繊維シート（混合シート）を得た。
【００６７】
更に、この混合シートを温度１５０℃、圧力１０ＭＰａにて圧縮処理し、厚さを０．３０ｍｍに調整した。
【００６８】
得られた圧縮処理後の炭素繊維シートは、目付が１００ｇ／ｍ２、厚さが０．３０ｍｍ、嵩密度が０．３３ｇ／ｃｍ３、比表面積が１５０ｍ２／ｇ、厚さ方向の電気抵抗値が４ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．７３Ｖｏｌｔであり、良好な物性の炭素繊維シートであった。
【００６９】
実施例２
表１に示すように、炭素繊維シート原料の成分ＡとしてＰＡＮ系酸化繊維（繊維直径１４μｍ、カット長５ｍｍ）６０質量部と、成分ＢとしてＰＡＮ系活性炭素繊維（比表面積１２００ｍ２／ｇ、繊維直径９μｍ、カット長５ｍｍ）３０質量部と、成分Ｃとしてポリビニルアルコール（ＰＶＡ）繊維（繊維直径２０μｍ、カット長５ｍｍ）１０質量部を均一に混合した後、湿式抄紙し、目付１４０ｇ／ｍ２、厚さ０．４５ｍｍ、嵩密度が０．３１ｇ／ｃｍ３のシート（混合シート）を得た。
【００７０】
更に、この混合シートを温度１５０℃、１０ＭＰａにて圧縮処理し、厚さを０．４０ｍｍに調整した後、窒素中で１２５０℃、２分間焼成した結果、目付９０ｇ／ｍ２、厚さ０．４０ｍｍの炭素繊維シートを得た。
【００７１】
この焼成後の炭素繊維シートは、嵩密度が０．２３ｇ／ｃｍ３、比表面積が１１５ｍ２／ｇ、厚さ方向の電気抵抗値が３ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．８２Ｖｏｌｔであり、良好な物性の炭素繊維シートであった。
【００７２】
実施例３
表１に示すように、炭素繊維シート原料の成分Ｂとしてフェノール系活性炭素繊維（比表面積２５００ｍ２／ｇ、繊維直径１５μｍ、カット長５ｍｍ）を用いた以外は実施例２と同様の条件で混合シートを作製した。
【００７３】
更に、この混合シートを温度１８０℃、圧力１０ＭＰａにて圧縮処理し、厚さを０．３７ｍｍに調整した後、窒素中で１２５０℃、２分間焼成した結果、目付９５ｇ／ｍ２、厚さ０．３７ｍｍの炭素繊維シートを得た。
【００７４】
この焼成後の炭素繊維シートは、嵩密度が０．２６ｇ／ｃｍ３、比表面積が３００ｍ２／ｇ、厚さ方向の電気抵抗値が４ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．８１Ｖｏｌｔであり、良好な物性の炭素繊維シートであった。
【００７５】
【表１】
実施例４
表２に示すように、炭素繊維シート原料の成分ＡとしてＰＡＮ系酸化繊維（繊維直径１４μｍ、カット長５１ｍｍ）６０質量部と、成分ＢとしてＰＡＮ系活性炭素繊維（比表面積１２００ｍ２／ｇ、繊維直径１１μｍ、カット長５１ｍｍ）３０質量部と、成分Ｃとしてポリビニルアルコール（ＰＶＡ）繊維（繊維直径１５μｍ、カット長５１ｍｍ）１０質量部を均一に混合した後、ウォータージェット方式による不織布加工方法でシート作製を行い、目付１４０ｇ／ｍ２、厚さ０．７０ｍｍ、嵩密度が０．２０ｇ／ｃｍ３のシート（混合シート）を得た。
【００７７】
更に、この混合シートを温度１８０℃、１５ＭＰａにて圧縮処理し、厚さを０．４０ｍｍに調整した後、窒素中で１２５０℃、２分間焼成した結果、目付９２ｇ／ｍ２、厚さ０．４５ｍｍ、嵩密度が０．２０ｇ／ｃｍ３の炭素繊維シートを得た。
【００７８】
この焼成後の炭素繊維シートは、比表面積が１２０ｍ２／ｇ、厚さ方向の電気抵抗値が４ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．７８Ｖｏｌｔであり、良好な物性の炭素繊維シートであった。
【００７９】
実施例５
表２に示すように、炭素繊維シート原料の成分ＢとしてＰＡＮ系活性炭素繊維（比表面積１２００ｍ２／ｇ、繊維直径１１μｍ、カット長５ｍｍ）を用いた以外は実施例１と同様の条件で、圧縮処理後の炭素繊維シートを作製した。
【００８０】
更に、この圧縮処理後の炭素繊維シートを、窒素中で１２５０℃、２分間焼成した結果、目付９１ｇ／ｍ２、厚さ０．３２ｍｍの炭素繊維シートを得た。
【００８１】
この焼成後の炭素繊維シートは、嵩密度が０．３１ｇ／ｃｍ３、比表面積が１３ｍ２／ｇ、厚さ方向の電気抵抗値が３ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．８４Ｖｏｌｔであり、良好な物性の炭素繊維シートであった。
【００８２】
比較例１
表２に示すように、炭素繊維シート原料の成分ＢとしてＰＡＮ系活性炭素繊維（比表面積５００ｍ２／ｇ、繊維直径１１μｍ、カット長５ｍｍ）を用いた以外は実施例１と同様の条件で、圧縮処理後の炭素繊維シートを作製した。
【００８３】
更に、この圧縮処理後の炭素繊維シートを、窒素中で１２５０℃、２分間焼成した結果、目付９５ｇ／ｍ２、厚さ０．３１ｍｍの炭素繊維シートを得た。
【００８４】
この焼成後の炭素繊維シートは、嵩密度が０．２８ｇ／ｃｍ３、比表面積が１３ｍ２／ｇ、厚さ方向の電気抵抗値が４ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．６７Ｖｏｌｔであり、良好な物性の炭素繊維シートではなかった。表２中×で示す箇所が本発明の構成から逸脱している。
【００８５】
【表２】
比較例２
表３に示すように、炭素繊維シート原料の成分ＡとしてＰＡＮ系炭素繊維（繊維直径１１μｍ、カット長５ｍｍ）２５質量部と、成分ＢとしてＰＡＮ系活性炭素繊維（比表面積９００ｍ２／ｇ、繊維直径１１μｍ、カット長５ｍｍ）７０質量部と、成分Ｃとしてポリエステル（ＰＥＴ）繊維（繊維直径１５μｍ、カット長５ｍｍ）５質量部を均一に混合した後、湿式抄紙し、目付１００ｇ／ｍ２、厚さ０．８０ｍｍ、嵩密度０．１５ｇ／ｃｍ３の炭素繊維シート（混合シート）を得た。
【００８７】
更に、この混合シートを温度１５０℃、１０ＭＰａにて圧縮処理し、厚さを０．７０ｍｍに調整した後、窒素中で１２５０℃、２分間焼成した結果、目付９２ｇ／ｍ２、厚さ０．６５ｍｍの炭素繊維シートを得た。
【００８８】
この焼成後の炭素繊維シートは、嵩密度が０．１４ｇ／ｃｍ３、比表面積が１３０ｍ２／ｇ、厚さ方向の電気抵抗値が２５ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．５５Ｖｏｌｔであり、良好な物性の炭素繊維シートではなかった。表３中×で示す箇所が本発明の構成から逸脱している。
【００８９】
比較例３
比較例２で得られた圧縮処理後で焼成前の炭素繊維シートについて、その物性測定を行ったところ、この炭素繊維シートは表３に示すように、嵩密度が０．１４ｇ／ｃｍ３、比表面積が４００ｍ２／ｇ、厚さ方向の電気抵抗値が３４ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．４１Ｖｏｌｔであり、良好な物性の炭素繊維シートではなかった。表３中×で示す箇所が本発明の構成から逸脱している。
【００９０】
比較例４
実施例１で得られた混合シートを温度２００℃、２０ＭＰａにて圧縮処理し、厚さを０．２１ｍｍに調整した後、窒素中で１２５０℃、２分間焼成した結果、目付９２ｇ／ｍ２、厚さ０．６５ｍｍの炭素繊維シートを得た。
【００９１】
この焼成後の炭素繊維シートは、嵩密度が０．４３ｇ／ｃｍ３、比表面積が１３０ｍ２／ｇ、厚さ方向の電気抵抗値が３ｍΩ、電流密度１．６ｍＡ／ｃｍ２時の起電圧（電池性能）が０．５７Ｖｏｌｔであり、良好な物性の炭素繊維シートではなかった。表３中×で示す箇所が本発明の構成から逸脱している。
【００９２】
【表３】
【発明の効果】
本発明の炭素繊維シートは、所定の原料を混合されてなる混合シート又は前記混合シートを所定条件下で焼成されてなるシートであり、比表面積、厚さ、厚さ方向の電気抵抗値、嵩密度などの諸物性が所定範囲にあるので、この炭素繊維シートを高分子電解質型燃料電池用電極として用いることによって、水素と酸素の反応効率を向上させると共に高分子電解質膜の保水性を持たせ、電解質膜の劣化を防止させ、電池の性能を改善をすることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a carbon fiber sheet for a gas diffusion electrode of a solid polymer electrolyte fuel cell (polymer fuel cell) and a method for producing the same.
[0002]
[Prior art]
Carbon fibers include polyacrylonitrile (PAN) type, pitch type, and phenol type. Since these carbon fibers have electrical conductivity and can be made into a thin layer of sheet-like material, they are expected to be used as electrode materials for polymer electrolyte fuel cells that have been put into practical use in recent years, and applied research will be conducted. Has been done.
[0003]
On the other hand, activated carbon fibers include PAN-based, pitch-based, and phenol-based activated carbon fibers. These have a specific surface area of about 500 to 2500 m 2 / g and are excellent in catalytic properties, but are slightly inferior in electric conductivity as compared with carbon fibers.
[0004]
Patent Literature 1 describes using an activated carbon fiber having a specific pore volume and a specific pore diameter as an electrode material, but does not describe a specific surface area and does not mention application to a fuel cell.
[0005]
Patent Document 2 discloses that a PAN-based carbon fiber having a specific surface area of 15 to 60 m 2 / g and a chlorine content of 10 ppm or more is used for a redox flow type secondary battery, but it relates to application to a polymer electrolyte fuel cell. There is no description.
[0006]
A polymer electrolyte fuel cell is a battery that reacts hydrogen and oxygen as a fuel source and converts the energy into electric energy, and is used by integrating a polymer electrolyte membrane and an electrode material. It is essential that the electrode material for a polymer electrolyte fuel cell has the following excellent properties.
[0007]
・ Electric conductivity ・ Catalyst properties (Properties that promote the reaction of hydrogen with oxygen)
・ Water retention (prevention of deterioration due to drying of polymer electrolyte membrane)
The polymer electrolyte membrane has a very small thickness of about 20 to 50 μm, and becomes brittle and easily broken when dried. Therefore, when the battery is not operated for a long time, the battery performance may be deteriorated.
[0008]
[Patent Document 1]
JP-A-62-154461 (Claims)
[Patent Document 2]
JP-A-63-2261 (Claims)
[0009]
[Problems to be solved by the invention]
The present inventor has obtained carbon fibers and activated carbon fibers (having hygroscopicity and catalytic properties) together with a binder (fiber) into a sheet by compression-molding the sheet while examining the above problems in various ways. By using a carbon fiber sheet or a carbon fiber sheet obtained by firing (carbonizing) this sheet as an electrode for a polymer electrolyte fuel cell, the reaction efficiency between hydrogen and oxygen is improved, and the polymer electrolyte membrane is improved. It has been found that it is possible to improve the performance of the battery by giving the water retention of the electrolyte and to prevent the deterioration of the electrolyte membrane, thereby completing the present invention.
[0010]
Accordingly, it is an object of the present invention to provide a carbon fiber sheet that solves the above-mentioned problems and a method for producing the same.
[0011]
[Means for Solving the Problems]
The present invention that achieves the above object is as described below.
[0012]
[1] It contains carbon fiber and activated carbon fiber, has a specific surface area of 15 to 350 m 2 / g, a thickness of 0.1 to 0.7 mm, an electric resistance value of 6 mΩ or less in a thickness direction, and a bulk density of 0.16 to 0. 40 g / cm 3 of a carbon fiber sheet for a polymer electrolyte fuel cell electrode material.
[0013]
[2] The carbon fiber sheet according to [1], wherein the carbon fiber and the activated carbon fiber are bonded to each other with a binder fiber.
[0014]
[3] The carbon fiber sheet according to [1], wherein the carbon fiber and the activated carbon fiber are bonded to each other by a carbon material at their entangled portions.
[0015]
[4] Carbonizing a carbon fiber sheet comprising a mixture of carbon fiber, activated carbon fiber having a specific surface area of 500 to 2500 m 2 / g, and a carbonizable binder in an inert gas atmosphere at a temperature of 950 to 1550 ° C. Polymer electrolyte fuel cell having a specific surface area of 15 to 350 m 2 / g, a thickness of 0.1 to 0.7 mm, an electric resistance in the thickness direction of 6 mΩ or less, and a bulk density of 0.16 to 0.40 g / cm 3 A method for producing a carbon fiber sheet for an electrode material.
[0016]
[5] Carbonizing a carbon fiber sheet comprising a mixture of oxidized fiber, activated carbon fiber having a specific surface area of 500 to 2500 m 2 / g, and a carbonizable binder in an inert gas atmosphere at a temperature of 950 to 1550 ° C. Polymer electrolyte fuel cell having a specific surface area of 15 to 350 m 2 / g, a thickness of 0.1 to 0.7 mm, an electric resistance in the thickness direction of 6 mΩ or less, and a bulk density of 0.16 to 0.40 g / cm 3 A method for producing a carbon fiber sheet for an electrode material.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0018]
The carbon fiber sheet for a polymer electrolyte fuel cell electrode material of the present invention is a carbon fiber sheet formed by mixing carbon fibers and activated carbon fibers.
[0019]
The specific surface area of this carbon fiber sheet is 15 to 350 m 2 / g. If the specific surface area of the carbon fiber sheet is less than 15 m 2 / g, the water retention of the electrode material is reduced, and the battery performance is undesirably reduced. If the specific surface area of the carbon fiber sheet exceeds 350 m 2 / g, the electric resistance of the electrode material increases, and the battery performance decreases, which is not preferable.
[0020]
The thickness of the carbon fiber sheet is 0.1 to 0.7 mm. If the thickness of the carbon fiber sheet is less than 0.1 mm, the sheet strength is undesirably reduced. If the thickness of the carbon fiber sheet exceeds 0.7 mm, a battery using this sheet as an electrode for a polymer electrolyte fuel cell becomes bulky, and it is difficult to make the battery compact, which is not preferable.
[0021]
The bulk density of the carbon fiber sheet is 0.16~0.40g / cm 3. If the bulk density of the carbon fiber sheet is less than 0.16 g / cm 3 , the electric resistance value of the carbon fiber sheet increases, and the performance of a battery using this sheet is undesirably reduced. When the bulk density of the carbon fiber sheet exceeds 0.40 g / cm 3 , the battery performance on the high current density (1.6 A / cm 2 ) side in a battery using this sheet as an electrode for a polymer electrolyte fuel cell Is undesirably reduced.
[0022]
The electrical resistance in the thickness direction of the carbon fiber sheet is 6 mΩ or less. When this sheet is used as an electrode material for a polymer electrolyte fuel cell, the lower the electrical resistance value, the better the cell performance. If the electric resistance exceeds 6 mΩ, the electromotive force decreases, and the battery performance deteriorates.
[0023]
The electrical resistivity in the thickness direction of the carbon fiber sheet is obtained by measuring by a measuring method described later.
[0024]
As a first example of the carbon fiber sheet of the present invention, there is a form in which carbon fibers and activated carbon fibers are sheeted by mutually binding fibers with binder fibers.
[0025]
As a second example of the carbon fiber sheet of the present invention, there is a form in which carbon fibers and activated carbon fibers are mixed, and the fibers are bonded to each other by a carbon material in a entangled portion of the fibers, but is not limited thereto. .
[0026]
The activated carbon fibers preferably have a specific surface area of 500 to 2500 m 2 / g, more preferably 800 to 2500 m 2 / g. The binder fibers are preferably carbonizable.
[0027]
The mixing ratio of the carbon fiber and the activated carbon fiber varies depending on the specific surface area of the activated carbon fiber. For 100 parts by mass of all components of the carbon fiber sheet, the carbon fiber is 50 to 80 parts by mass, and the activated carbon fiber is 5 to 40 parts by mass. Parts by weight are preferred. The mixing ratio of the binder fiber is preferably 3 to 15 parts by mass with respect to 100 parts by mass of all components of the carbon fiber sheet.
[0028]
The method for producing the carbon fiber sheet is not particularly limited, but for example, it can be produced by the following production method.
[0029]
Mixed sheet α
The carbon fiber cut fiber (component A) and the activated carbon fiber cut fiber (component B) are mixed, processed into a sheet, and then compressed.
[0030]
Mixed sheet β
The carbon fiber cut fiber (component A), the activated carbon fiber cut fiber (component B), and the binder cut fiber (component C) are mixed, processed into a sheet, and then subjected to a compression treatment.
[0031]
Carbon fiber sheet γ after firing
The carbon fiber cut fiber (component A), the activated carbon fiber cut fiber (component B), and the binder cut fiber (component C) are mixed, processed into a sheet, and then subjected to a compression treatment. Further, it is calcined (950-1550 ° C., in nitrogen).
[0032]
Carbon fiber sheet δ after firing
The oxidized fiber cut fiber (component A), the activated carbon fiber cut fiber (component B), and the binder cut fiber (component C) are mixed, processed into a sheet, and then subjected to a compression treatment. Further, it is calcined (950-1550 ° C., in nitrogen).
[0033]
Next, individual raw materials and steps in the method for producing a carbon fiber sheet of the present example will be described in detail.
[0034]
[Carbon fiber cut fiber (component A)]
As the carbon fiber of the component A of the carbon fiber sheet raw material, a PAN-based, pitch-based, phenol-based carbon fiber, or the like can be used, but a PAN-based carbon fiber is particularly preferable in terms of strength.
[0035]
The cut length of the carbon fiber cut fiber is preferably 3 to 100 mm. If the cut length is less than 3 mm, the strength of the obtained carbon fiber sheet is undesirably reduced. If the cut length exceeds 100 mm, the dispersibility of the fibers is undesirably reduced.
[0036]
Although the fiber diameter of the carbon fiber cut fiber is not particularly limited, it is preferably 3 to 20 μm.
[0037]
The compounding ratio of the carbon fiber cut fibers is preferably 30 to 80 parts by mass, based on 100 parts by mass of all the components of the carbon fiber sheet raw material, as the compounding ratio of the component A.
[0038]
[Oxidized fiber cut fiber (component A)]
The oxidized fiber of the component A of the carbon fiber sheet raw material is not limited to the type of oxidized fiber such as PAN-based, pitch-based, and phenol-based, but PAN-based oxidized fiber is preferable because it has excellent strength and workability.
[0039]
The cut length of the oxidized fiber cut fiber is preferably 3 to 100 mm. If the cut length is less than 3 mm, the strength of the obtained carbon fiber sheet is undesirably reduced. If the cut length exceeds 100 mm, the dispersibility of the fibers is undesirably reduced.
[0040]
The fiber diameter of the oxidized fiber cut fiber is not particularly limited, but is preferably 3 to 30 μm.
[0041]
The compounding ratio of the oxidized fiber cut fiber is preferably 30 to 80 parts by mass based on 100 parts by mass of all components of the carbon fiber sheet raw material as the compounding ratio of component A.
[0042]
[Activated carbon fiber cut fiber (component B)]
The activated carbon fiber of the component B of the carbon fiber sheet raw material is not limited to the type of activated carbon fiber such as PAN-based, pitch-based and phenol-based. However, PAN-based activated carbon fiber has excellent strength and workability. And preferred.
[0043]
The cut length of the activated carbon fiber cut fiber is preferably 3 to 100 mm. If the cut length is less than 3 mm, the strength of the obtained carbon fiber sheet is undesirably reduced. If the cut length exceeds 100 mm, the dispersibility of the fibers is undesirably reduced.
[0044]
The fiber diameter of the activated carbon fiber cut fiber is not particularly limited, but is preferably 3 to 25 μm.
[0045]
The specific surface area of the activated carbon fibers cut fibers is preferably 500~2500m 2 / g, more preferably 800~2500m 2 / g. When the specific surface area is less than 500 m 2 / g, disadvantages such as a decrease in water retention and a decrease in catalyst characteristics occur, which is not preferable. When the specific surface area is more than 2500 m 2 / g, the fiber strength is low, and disadvantages such as deterioration of sheet processability and generation of fine powder occur, which is not preferable.
[0046]
The compounding ratio of the activated carbon fiber-cut fibers is preferably 15 to 50 parts by mass based on 100 parts by mass of all components of the carbon fiber sheet raw material as the compounding ratio of the component B.
[0047]
[Binder cut fiber (component C)]
As the binder for the component C of the carbon fiber sheet raw material, polyvinyl alcohol (PVA) fiber, polyester (PET) fiber, aramid fiber, cellulose fiber, and the like are used.
[0048]
The fiber diameter of the binder cut fiber is not particularly limited, but is preferably 3 to 25 μm.
[0049]
The compounding ratio of the binder cut fiber is preferably from 3 to 30 parts by mass based on 100 parts by mass of all the components of the carbon fiber sheet raw material as the compounding ratio of the component C.
[0050]
[Sheet processing]
The sheet processing method is not particularly limited, and a wet papermaking method, a nonwoven fabric processing method using a water jet method from a dry web, or the like is used.
[0051]
By this sheet processing, a sheet (mixed sheet) having a basis weight of 40 to 200 g / m 2 , a thickness of 0.20 to 1.00 mm, and a bulk density of 0.10 to 0.35 g / cm 3 is obtained. be able to.
[0052]
When a mixed sheet having physical properties outside the above range is subjected to a compression treatment and used as a carbon fiber sheet (for example, the above-described mixed sheet α or β), a carbon fiber sheet having desired physical properties is not obtained, which is not preferable. In addition, when the mixed sheet having physical properties outside the above range is subjected to the compression treatment and then fired (for example, the above-described fired carbon fiber sheet γ or δ), the carbon fiber sheet having the desired physical properties cannot be obtained, which is not preferable.
[0053]
[Compression processing]
The mixed sheet obtained by the sheet processing is subjected to a compression process. In this compression processing, the compression processing temperature is 100 to 300 ° C., and the compression processing pressure is 0.5 to 30 MPa.
[0054]
By this compression treatment, a sheet after the compression treatment having a basis weight of 40 to 200 g / m 2 , a thickness of 0.10 to 0.80 mm, and a bulk density of 0.13 to 0.60 g / cm 3 can be obtained.
[0055]
If the sheet after the compression treatment having physical properties outside the above range is used as a carbon fiber sheet (for example, the above-mentioned mixed sheet α or β), it is not preferable because the carbon fiber sheet is not the target physical property. Further, when the sheet after the compression treatment having physical properties outside the above range is fired (for example, the above-described fired carbon fiber sheet γ or δ), the carbon fiber sheet having the target physical properties is not obtained, which is not preferable.
[0056]
(Carbonization)
The sheet after the compression treatment is fired and carbonized at 950 to 1550 ° C. in an inert gas atmosphere, if necessary (for example, in the case of the aforementioned mixed sheet α or β), in a batch or continuous manner. As the inert gas, nitrogen, argon, helium or the like is used. Of these, nitrogen is most preferable in terms of cost.
[0057]
If the firing temperature is lower than 950 ° C., the resulting carbon fiber sheet has an undesirably increased electric resistance. When the firing temperature exceeds 1550 ° C., the specific surface area of the activated carbon fiber of the component B in the obtained carbon fiber sheet is undesirably reduced or disappeared.
[0058]
【Example】
The present invention will be described in detail by the following Examples and Comparative Examples.
[0059]
Carbon fiber sheets were produced under the conditions of the following Examples and Comparative Examples. Various physical property values of the raw material fiber, the papermaking binder, the mixed sheet, the sheet after the compression treatment, and the carbon fiber sheet after the firing were measured by the following methods.
[0060]
Thickness: The thickness was measured with a circular pressure plate having a diameter of 30 mm under a load of 200 gf (2.8 kPa).
[0061]
Basis weight: The mass per unit area was calculated from the dimensions of the sheet and the dry mass at 120 ° C.
[0062]
Bulk density: Calculated from the thickness and basis weight measured under the above conditions.
[0063]
Specific surface area: The surface area per unit mass was calculated from the amount of nitrogen adsorbed at a relative pressure (nitrogen / helium) of 0.30 by the BET adsorption method.
[0064]
Electric resistance value: A carbon fiber sheet was sandwiched between two 50 mm square (10 mm thick) gold-plated electrodes at a pressure of 1 MPa on both sides, and the electric resistance value (mΩ) between both electrodes was measured.
[0065]
Battery performance evaluation method: A carbon fiber sheet was cut into a 50 mm square, and 0.2 mg / cm 2 of a catalyst (Pt-Ru) was supported on the carbon fiber sheet. Both sides of a polymer electrolyte membrane (manufactured by DuPont: Nafion membrane 117) were placed on both sides. A cell was formed by joining the electrode materials cut into the above-mentioned 50 mm square, and the cell voltage was measured at a temperature of 80 ° C. and a current density of 1.6 A / cm 2 .
[0066]
Example 1
As shown in Table 1, 75 parts by mass of PAN-based carbon fiber (fiber diameter 11 μm, cut length 5 mm) as component A of the carbon fiber sheet raw material, and PAN-based activated carbon fiber (specific surface area 900 m 2 / g, fiber After uniformly mixing 20 parts by mass of 11 μm in diameter and a cut length of 5 mm) and 5 parts by mass of polyester (PET) fiber (fiber diameter of 15 μm and a cut length of 5 mm) as a component C, wet papermaking is performed, and the basis weight is 100 g / m 2 , A carbon fiber sheet (mixed sheet) having a thickness of 0.35 mm and a bulk density of 0.28 g / cm 3 was obtained.
[0067]
Further, this mixed sheet was subjected to a compression treatment at a temperature of 150 ° C. and a pressure of 10 MPa to adjust the thickness to 0.30 mm.
[0068]
The obtained carbon fiber sheet after compression treatment has a basis weight of 100 g / m 2 , a thickness of 0.30 mm, a bulk density of 0.33 g / cm 3 , a specific surface area of 150 m 2 / g, and an electrical resistance in the thickness direction. The electromotive voltage (battery performance) at a value of 4 mΩ and a current density of 1.6 mA / cm 2 was 0.73 Volt, and the carbon fiber sheet had good physical properties.
[0069]
Example 2
As shown in Table 1, 60 parts by mass of PAN-based oxidized fiber (fiber diameter 14 μm, cut length 5 mm) as component A of the carbon fiber sheet raw material, and PAN-based activated carbon fiber (specific surface area 1200 m 2 / g, fiber After uniformly mixing 30 parts by mass of 9 μm in diameter and 5 mm in cut length) and 10 parts by mass of polyvinyl alcohol (PVA) fiber (fiber diameter 20 μm and 5 mm in cut length) as Component C, wet papermaking is performed, and the basis weight is 140 g / m 2 . A sheet (mixed sheet) having a thickness of 0.45 mm and a bulk density of 0.31 g / cm 3 was obtained.
[0070]
Further, the mixture sheet temperature 0.99 ° C., and compressed at 10 MPa, after adjusting the thickness 0.40 mm, 1250 ° C. in nitrogen fired result for 2 minutes, basis weight 90 g / m 2, a thickness of 0. A 40 mm carbon fiber sheet was obtained.
[0071]
The fired carbon fiber sheet has an electromotive voltage at a bulk density of 0.23 g / cm 3 , a specific surface area of 115 m 2 / g, an electrical resistance value in the thickness direction of 3 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.82 Volt, and the carbon fiber sheet had good physical properties.
[0072]
Example 3
As shown in Table 1, mixing was carried out under the same conditions as in Example 2 except that phenolic activated carbon fibers (specific surface area 2500 m 2 / g, fiber diameter 15 μm, cut length 5 mm) were used as Component B of the carbon fiber sheet raw material. A sheet was prepared.
[0073]
Further, the mixed sheet was subjected to a compression treatment at a temperature of 180 ° C. and a pressure of 10 MPa to adjust the thickness to 0.37 mm, and then calcined in nitrogen at 1250 ° C. for 2 minutes. As a result, the basis weight was 95 g / m 2 and the thickness was 0 A 37 mm carbon fiber sheet was obtained.
[0074]
The fired carbon fiber sheet has an electromotive force at a bulk density of 0.26 g / cm 3 , a specific surface area of 300 m 2 / g, an electric resistance in the thickness direction of 4 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.81 Volt, and the carbon fiber sheet had good physical properties.
[0075]
[Table 1]
Example 4
As shown in Table 2, 60 parts by mass of PAN-based oxidized fiber (fiber diameter 14 μm, cut length 51 mm) as component A of the carbon fiber sheet raw material and PAN-based activated carbon fiber (specific surface area 1200 m 2 / g, fiber After uniformly mixing 30 parts by mass of 11 μm in diameter and cut length of 51 mm) and 10 parts by mass of polyvinyl alcohol (PVA) fiber (fiber diameter of 15 μm and cut length of 51 mm) as the component C, a sheet is produced by a non-woven fabric processing method by a water jet method. To obtain a sheet (mixed sheet) having a basis weight of 140 g / m 2 , a thickness of 0.70 mm, and a bulk density of 0.20 g / cm 3 .
[0077]
Further, the mixed sheet was subjected to a compression treatment at a temperature of 180 ° C. and 15 MPa to adjust the thickness to 0.40 mm, and then baked in nitrogen at 1250 ° C. for 2 minutes. As a result, the basis weight was 92 g / m 2 and the thickness was 0.1 mm. A carbon fiber sheet having a diameter of 45 mm and a bulk density of 0.20 g / cm 3 was obtained.
[0078]
The fired carbon fiber sheet has a specific surface area of 120 m 2 / g, an electric resistance value in the thickness direction of 4 mΩ, and an electromotive voltage (battery performance) at a current density of 1.6 mA / cm 2 of 0.78 Volt. The carbon fiber sheet had good physical properties.
[0079]
Example 5
As shown in Table 2, under the same conditions as in Example 1 except that PAN-based activated carbon fiber (specific surface area: 1200 m 2 / g, fiber diameter: 11 μm, cut length: 5 mm) was used as Component B of the carbon fiber sheet raw material, A carbon fiber sheet after the compression treatment was produced.
[0080]
Further, the carbon fiber sheet after the compression treatment was baked in nitrogen at 1250 ° C. for 2 minutes to obtain a carbon fiber sheet having a basis weight of 91 g / m 2 and a thickness of 0.32 mm.
[0081]
After firing, the carbon fiber sheet has an electromotive force at a bulk density of 0.31 g / cm 3 , a specific surface area of 13 m 2 / g, an electric resistance in the thickness direction of 3 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.84 Volt, and the carbon fiber sheet had good physical properties.
[0082]
Comparative Example 1
As shown in Table 2, under the same conditions as in Example 1, except that PAN-based activated carbon fiber (specific surface area: 500 m 2 / g, fiber diameter: 11 μm, cut length: 5 mm) was used as Component B of the carbon fiber sheet raw material. A carbon fiber sheet after the compression treatment was produced.
[0083]
Further, the carbon fiber sheet after the compression treatment was calcined in nitrogen at 1250 ° C. for 2 minutes to obtain a carbon fiber sheet having a basis weight of 95 g / m 2 and a thickness of 0.31 mm.
[0084]
The fired carbon fiber sheet has an electromotive force at a bulk density of 0.28 g / cm 3 , a specific surface area of 13 m 2 / g, an electric resistance value in the thickness direction of 4 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.67 Volt, which was not a carbon fiber sheet having good physical properties. The portions indicated by x in Table 2 deviate from the configuration of the present invention.
[0085]
[Table 2]
Comparative Example 2
As shown in Table 3, 25 parts by mass of PAN-based carbon fiber (fiber diameter 11 μm, cut length 5 mm) as component A of the carbon fiber sheet raw material, and PAN-based activated carbon fiber (specific surface area 900 m 2 / g, fiber After uniformly mixing 70 parts by mass of a diameter 11 μm, cut length 5 mm) and 5 parts by mass of polyester (PET) fiber (fiber diameter 15 μm, cut length 5 mm) as the component C, wet papermaking is performed, and the basis weight is 100 g / m 2 , thickness. A carbon fiber sheet (mixed sheet) having a thickness of 0.80 mm and a bulk density of 0.15 g / cm 3 was obtained.
[0087]
Further, the mixed sheet was subjected to a compression treatment at a temperature of 150 ° C. and 10 MPa to adjust the thickness to 0.70 mm, and then baked in nitrogen at 1250 ° C. for 2 minutes. As a result, the basis weight was 92 g / m 2 and the thickness was 0.1 mm. A 65 mm carbon fiber sheet was obtained.
[0088]
The fired carbon fiber sheet has an electromotive force at a bulk density of 0.14 g / cm 3 , a specific surface area of 130 m 2 / g, an electric resistance value in the thickness direction of 25 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.55 Volt, which was not a carbon fiber sheet having good physical properties. The portions indicated by x in Table 3 deviate from the configuration of the present invention.
[0089]
Comparative Example 3
Physical properties of the carbon fiber sheet obtained after the compression treatment obtained in Comparative Example 2 and before firing were measured. As shown in Table 3, the carbon fiber sheet had a bulk density of 0.14 g / cm 3 and a ratio of The surface area was 400 m 2 / g, the electrical resistance in the thickness direction was 34 mΩ, the electromotive voltage (battery performance) at a current density of 1.6 mA / cm 2 was 0.41 Volt, and the carbon fiber sheet was not a good physical property. . The portions indicated by x in Table 3 deviate from the configuration of the present invention.
[0090]
Comparative Example 4
The mixed sheet obtained in Example 1 was subjected to a compression treatment at a temperature of 200 ° C. and 20 MPa to adjust the thickness to 0.21 mm, and then calcined in nitrogen at 1250 ° C. for 2 minutes. As a result, the basis weight was 92 g / m 2 , A carbon fiber sheet having a thickness of 0.65 mm was obtained.
[0091]
The fired carbon fiber sheet has an electromotive force at a bulk density of 0.43 g / cm 3 , a specific surface area of 130 m 2 / g, an electrical resistance in the thickness direction of 3 mΩ, and a current density of 1.6 mA / cm 2 ( Battery performance) was 0.57 Volt, which was not a carbon fiber sheet having good physical properties. The portions indicated by x in Table 3 deviate from the configuration of the present invention.
[0092]
[Table 3]
【The invention's effect】
The carbon fiber sheet of the present invention is a mixed sheet obtained by mixing predetermined raw materials or a sheet obtained by firing the mixed sheet under predetermined conditions, and has a specific surface area, a thickness, an electric resistance value in a thickness direction, and a bulk. Since various physical properties such as density are within a predetermined range, by using this carbon fiber sheet as an electrode for a polymer electrolyte fuel cell, the reaction efficiency of hydrogen and oxygen is improved and the water retention of the polymer electrolyte membrane is provided. In addition, it is possible to prevent the electrolyte membrane from deteriorating and improve the performance of the battery.
Claims (5)
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| CN102422469A (en) * | 2009-05-01 | 2012-04-18 | 日产自动车株式会社 | Gas diffusion layer for fuel cell |
| JP4819981B2 (en) * | 2009-05-01 | 2011-11-24 | 日産自動車株式会社 | Gas diffusion layer for fuel cells |
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| WO2010126063A1 (en) * | 2009-05-01 | 2010-11-04 | 日産自動車株式会社 | Gas diffusion layer for fuel cell |
| EP2426762A4 (en) * | 2009-05-01 | 2012-10-17 | Nissan Motor | Gas diffusion layer for fuel cell |
| JP2013157314A (en) * | 2012-01-06 | 2013-08-15 | Mitsubishi Rayon Co Ltd | Gas diffusion layer for polymer electrolyte fuel cell |
| KR101856887B1 (en) * | 2013-09-06 | 2018-05-10 | 에스지엘 카본 에스이 | Electrode substrate made of carbon fibers |
| EP3041989B1 (en) * | 2013-09-06 | 2019-10-02 | SGL Carbon SE | Electrode substrate made of carbon fibers |
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| WO2018016626A1 (en) * | 2016-07-22 | 2018-01-25 | 三菱ケミカル株式会社 | Porous base material, porous electrode, carbon fiber paper, method for manufacturing carbon fiber paper, and method for manufacturing porous base material |
| JPWO2018016626A1 (en) * | 2016-07-22 | 2018-07-19 | 三菱ケミカル株式会社 | Porous substrate, porous electrode, carbon fiber paper, method for producing carbon fiber paper, method for producing porous substrate |
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