JP2004225191A

JP2004225191A - Polyacrylonitrile-based carbon fiber sheet and method for producing the same

Info

Publication number: JP2004225191A
Application number: JP2003014264A
Authority: JP
Inventors: Kenji Shimazaki; 賢司島崎
Original assignee: Toho Tenax Co Ltd
Current assignee: Teijin Ltd
Priority date: 2003-01-23
Filing date: 2003-01-23
Publication date: 2004-08-12
Anticipated expiration: 2023-01-23
Also published as: JP4138510B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin polyacrylonitrile (PAN)-based carbon fiber sheet including the fiber dispersed well, and having little unevenness in thickness, good post processability and high strength. <P>SOLUTION: The PAN-based carbon fiber sheet comprises homogeneously dispersed carbon fiber A having 8.0-15.0 μm fiber diameter C<SB>A</SB>and carbon fiber B having a fiber diameter C<SB>B</SB>satisfying the formula 1: 0.40<C<SB>B</SB>/C<SB>A</SB><0.80. The content of the carbon fiber B is 4-25 mass%, and the content of the total of the carbon fiber A and the carbon fiber B is ≥95 mass%. The carbon fiber sheet has 0.1-0.5 mm thickness and ≥7 N/cm tensile strength. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ポリアクリロニトリル系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】
ポリアクリロニトリル（ＰＡＮ）系酸化繊維は、不融性があり、難燃性に優れ、一般の有機繊維と同様の引張り伸度を示す。また不活性ガス中で炭素化することにより高強度の炭素繊維が得られることが知られている。
【０００３】
ＰＡＮ系酸化繊維は短綿化され、単独又は他のバインダーと分散混合され、湿式の抄紙により紙状のシートや、乾式の不織布製造方式（ニードルパンチによるフェルトも含む）により不織布状のシートに加工される。更に、これらのシートを不活性ガス中にて炭素化することにより紙状や不織布状の炭素化シートを得ることができる。
【０００４】
不織布状の炭素化シートに関しては、特許文献１、２に記載されたものがある。
【０００５】
特許文献１には、耐炎繊維（酸化繊維）をフェルト加工した後、１８００℃以上で炭素化する記載、電池伝導材用の記載、並びに、ＰＡＮ系酸化繊維フェルト（厚さ２０ｍｍ、目付３５００ｇ／ｍ^２）を窒素雰囲気下、炭素化する記載などがある。
【０００６】
しかし、いずれの記載も、厚さの薄い素材の対象ではなく、強度については、ふれられていない。
【０００７】
フェルト作製についてはニードルパンチ方式で一般には行われる。しかし、本発明のシートのように薄いシートで且つ用いる酸化繊維の綿長が短い場合は、特許文献１に記載の方法でフェルト（酸化繊維シート）作製を行うと、そのシートはパンチングにより強度低下を招く。
【０００８】
なお、特許文献１には、副成分繊維（原料酸化繊維Ｂ）を含有させる記述や、樹脂処理、圧縮処理等の記載はない。
【０００９】
特許文献２には、ＰＡＮ系酸化繊維をウォータージェット方式により不織布を作製する記載、並びに、酸化繊維不織布の厚さ、強度の記載がある。しかし、副成分としてより細い繊維含有する記載や、炭素化に関する記述はない。
【００１０】
なお、特許文献２には不織布の原料繊維として綿長５１ｍｍの耐炎化繊維（酸化繊維）を用いることが記載されている。しかし、この繊維長の酸化繊維を用いて得られる不織布は、強度は高いが、繊維の分散性については綿長の短い湿式抄紙法により得られるシートに劣る。
【００１１】
一般に不織布加工に用いられる酸化繊維は綿長２５〜７５ｍｍの長繊維である。これを用いて得られる乾式の不織布タイプのシートは、綿長の短い（１５ｍｍ以下）酸化繊維を用いて得られる湿式の紙（抄紙）タイプのシートに比べ、シート強度がより高いが、シート内の繊維の分散性に劣る。一方、湿式抄紙による場合は、酸化繊維の分散性が良く、厚さのバラツキが少ないシートが作り易い。
【００１２】
しかし、湿式抄紙により薄型（低目付）のシートを得ようとした場合、強度が低いシートしか得られない。しかも、この低強度シートは、種々の用途に応用できる為、その様な用途に応用するように連続的に後加工を必要とする場合が多く、この場合は後加工時に裂けや切断を生じ易いなど加工性トラブルを生じ易い。
【００１３】
湿式抄紙による酸化繊維シートの高強度化のためには、より細い繊維を用いる方が良い。しかし、抄紙に用いる繊維は細くなるほど、その分散性が低下し、繊維同士の絡みが生じ易くなる。この細い酸化繊維を用いた湿式抄紙工程では、繊維の水への分散時に、繊維同士の収束繊維、繊維塊が生じ、得られた酸化繊維シートの炭素化時におけるシートの強度低下や、炭素化後における炭素繊維シートの強度低下を招く。
【００１４】
【特許文献１】
特開平２−１３９４６４号公報（特許請求の範囲、実施例１）
【特許文献２】
特開平９−１１９０５２号公報（段落番号［００１３］）
【００１５】
【発明が解決しようとする課題】
本発明者は、繊維の分散性が良く、厚さのバラツキが少なく、後加工性の良い高強度の薄型の炭素繊維シートを得るために種々検討しているうちに、ＰＡＮ系酸化繊維シート中の副成分繊維（原料酸化繊維Ｂ）として、主成分繊維（原料酸化繊維Ａ）より細い酸化繊維を、所定の範囲に混合組み合わせてシート加工することにより、繊維の分散性が改善された酸化繊維シートを得、得られた酸化繊維シートを樹脂処理し、更に圧縮処理後、出来るだけ張力をかけずに不活性ガス中で焼成・炭素化することにより、上記物性のＰＡＮ系炭素繊維シートを得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。
【００１６】
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ＰＡＮ系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。
【００１７】
【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。
【００１８】
〔１〕繊維直径Ｃ_Ａが８．０〜１５．０μｍの炭素繊維Ａと、繊維直径Ｃ_Ｂが式１
０．４０＜Ｃ_Ｂ／Ｃ_Ａ＜０．８０式１
を満たす炭素繊維Ｂとが、均一に分散含有されたポリアクリロニトリル系炭素繊維シートであって、炭素繊維Ｂの炭素繊維含有率が４〜２５質量％、炭素繊維Ａと炭素繊維Ｂとの合計含有率が９５質量％以上、厚さが０．１〜０．５ｍｍ、引っ張り強度が７Ｎ／ｃｍ以上のポリアクリロニトリル系炭素繊維シート。
【００１９】
〔２〕繊維直径Ｏ_Ａが１１．０〜２５．０μｍ、繊維長が３〜１５ｍｍの酸化繊維Ａと、繊維直径Ｏ_Ｂが式２
０．４０＜Ｏ_Ｂ／Ｏ_Ａ＜０．８０式２
を満たし、繊維長が３〜１５ｍｍの酸化繊維Ｂとが、均一に分散含有されてなり、酸化繊維Ｂの繊維含有率が４〜２５質量％である酸化繊維シートを、樹脂処理後、更に圧縮処理し、厚さを０．１〜１．０ｍｍにした後、不活性ガス中で０．５Ｎ／ｃｍ以下の張力下、１１００〜１７００℃の温度で連続的に焼成・炭素化する、繊維直径Ｃ_Ａが８．０〜１５．０μｍの炭素繊維Ａと、繊維直径Ｃ_Ｂが式１
０．４０＜Ｃ_Ｂ／Ｃ_Ａ＜０．８０式１
を満たす炭素繊維Ｂとが、均一に分散含有されたポリアクリロニトリル系炭素繊維シートであって、炭素繊維Ｂの炭素繊維含有率が４〜２５質量％、炭素繊維Ａと炭素繊維Ｂとの合計含有率が９５質量％以上、厚さが０．１〜０．５ｍｍ、引っ張り強度が７Ｎ／ｃｍ以上のポリアクリロニトリル系炭素繊維シートの製造方法。
【００２０】
【発明の実施の形態】
以下、本発明を詳細に説明する。
【００２１】
本発明のＰＡＮ系炭素繊維シートは、繊維直径Ｃ_Ａが８．０〜１５．０μｍの炭素繊維Ａと、繊維直径Ｃ_Ｂが式１
０．４０＜Ｃ_Ｂ／Ｃ_Ａ＜０．８０式１
を満たす炭素繊維Ｂとが、均一に分散含有されたポリアクリロニトリル系炭素繊維シートであって、炭素繊維Ｂの炭素繊維含有率が４〜２５質量％、炭素繊維Ａと炭素繊維Ｂとの合計含有率が９５質量％以上、厚さが０．１〜０．５ｍｍ、引っ張り強度が７Ｎ／ｃｍ以上の炭素繊維シートである。
【００２２】
本発明のＰＡＮ系炭素繊維シートは、その物性が上記範囲内にあれば、そ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。
【００２３】
〔酸化繊維Ａ、Ｂ〕
炭素繊維シート原料の酸化繊維Ａ（主成分）、酸化繊維Ｂ（副成分）は何れも、ＰＡＮ系酸化繊維であり、例えば市販のＰＡＮ系繊維を空気中、高温で処理することにより環化反応を生じさせ、酸素結合量を増加させて不融化、難燃化させる耐炎化処理によって得られるものを用いることができる。
【００２４】
なお、炭素繊維シートの原料として考えられる酸化繊維ついては、ＰＡＮ系酸化繊維以外に、ピッチ系、フェノール系、レーヨン系等の酸化繊維があるが、ＰＡＮ系酸化繊維が最も高強度の炭素繊維シートが得られる。
【００２５】
酸化繊維Ａの繊維直径Ｏ_Ａは１１．０〜２５．０μｍである。酸化繊維Ａの繊維直径Ｏ_Ａが１１．０μｍ未満の場合は、得られる酸化繊維シート及び炭素繊維シートの強度が低下するので好ましくない。酸化繊維Ａの繊維直径Ｏ_Ａが２５．０μｍを超える場合は、得られる酸化繊維シート及び炭素繊維シートの強度が低下し、所期のシート厚さの薄いものが得られ難いので好ましくない。
【００２６】
酸化繊維Ｂについては、酸化繊維シート中の酸化繊維Ｂ含有率が４〜２５質量％であり、酸化繊維Ａとの直径比Ｏ_Ｂ／Ｏ_Ａが０．４０〜０．８０である。この範囲以外の場合は、所期物性の炭素繊維シートが得られない。
【００２７】
酸化繊維Ａ、酸化繊維Ｂの何れも、その繊維長（カット長）は３〜１５ｍｍである。繊維長が３ｍｍ未満の場合は、得られる酸化繊維シート及び炭素繊維シートの強度が低下するので好ましくない。繊維長が１５ｍｍを超える場合は、得られる酸化繊維シートにおける繊維の分散性が低下し、更にこの酸化繊維シートが炭素化されてなる炭素繊維シートの強度が低下するので好ましくない。
【００２８】
酸化繊維Ａ、酸化繊維Ｂの何れも、その比重は、特に限定されないが、１．３５〜１．４５が好ましい。
【００２９】
酸化繊維Ａ、酸化繊維Ｂの何れも、その乾強度は１５ｋｇｆ／ｍｍ^２（１４７Ｎ／ｍｍ^２）以上が好ましい。乾強度が１５ｋｇｆ／ｍｍ^２（１４７Ｎ／ｍｍ^２）未満の場合は、これら酸化繊維Ａ、Ｂをシート化して得られる酸化繊維シートの強度低下、更にこの酸化繊維シートが炭素化されてなる炭素繊維シートの強度低下による微粉末発生が増加するので好ましくない。
【００３０】
なお、酸化繊維Ａ、酸化繊維Ｂにおける乾強度は、ＪＩＳＬ１０１５により測定される物性値である。
【００３１】
〔バインダー繊維〕
炭素繊維シート原料としては必要に応じ、レーヨン繊維、セルローズ繊維、ポリエステル繊維、フェノール繊維、ポリビニール繊維、ポリアミド繊維等のバインダー繊維を、酸化繊維シート中に混合して用いてもよい。
【００３２】
酸化繊維シート中のバインダー繊維の含有率は３０質量％以下が好ましい。バインダー繊維含有率が３０質量％を超える場合は、この酸化繊維シートを炭素化して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。
【００３３】
〔酸化繊維シート〕
上述した酸化繊維Ａ、酸化繊維Ｂなどの原料酸化繊維は、必要に応じバインダー繊維を加え、シート加工して原料酸化繊維等が均一に分散含有されてなる酸化繊維シートにする。
【００３４】
シート加工方法については特に限定はされないが、原料酸化繊維等を湿式抄紙して紙状にする湿式抄紙法、原料酸化繊維等を乾式方式によりウエッブを作製した後ウォータージェット方式により不織布を作製する不織布加工方法等を用いることができる。
【００３５】
上記シート加工方法の中でも、繊維長３〜１５ｍｍの短繊維の原料酸化繊維についてはシート加工が容易なことから、湿式抄紙法が特に好ましい。
【００３６】
酸化繊維シートの厚さは０．２０〜０．８０ｍｍが好ましい。
【００３７】
酸化繊維シートの嵩密度は１．０ｇ／ｃｍ^３以下が後工程での圧縮処理による厚さコントロールがし易いので好ましい。酸化繊維シートの嵩密度が１．０ｇ／ｃｍ^３を超えると厚さ低減化に対するコントロールが難しい。
【００３８】
〔樹脂処理〕
上述した酸化繊維シートには、圧縮処理する前に、強度向上効果及び厚さ低減効果をより発揮させることを目的として、樹脂処理を行う。樹脂処理により、炭素化時の厚さ復元を抑制し、厚さの薄い素材を得易くなる。
【００３９】
樹脂の種類は熱可塑性、熱硬化性樹脂のいずれでもよいが、後工程で高温（１００〜３５０℃）圧縮処理される際に軟化し、繊維間で融着し、かつ焼成炭素化時に僅かでも炭素化し残留する樹脂を用いることが好ましい。例えば、ポリビニルアルーコール（ＰＶＡ）、カルボキシメチルセルローズ（ＣＭＣ）、エポキシ、フェノールノボラック、アラミド、ポリイミド等の樹脂が好ましい。なお、水分散性又は水に溶解性の高いものが取扱性の点でより好ましい。
【００４０】
樹脂の付着量は、樹脂の種類や、炭素化後の織物の目標とする硬さにより最適量は異なるが、通常０．２〜１０質量％の範囲が好ましい。樹脂の付着量が１０質量％を超える場合、焼成炭素化して得られる炭素繊維シートは、柔軟性がなくなり、脆くなるので好ましくない。
【００４１】
樹脂処理の方法は浸漬法が好ましい。この方法によれば最も均一に樹脂添着が可能である。樹脂処理時の温度は常温（２５℃）〜９０℃の範囲が好ましい。
【００４２】
〔圧縮処理〕
上述した酸化繊維シートを、樹脂処理後又は処理せずに、１００〜３５０℃の温度下、圧力０．５〜２０ＭＰａにて圧縮処理し、圧縮処理後の酸化繊維シートの厚さを０．１〜１．０ｍｍにする。
【００４３】
圧縮処理後の酸化繊維シートの厚さが０．１ｍｍ未満の場合は、酸化繊維シートの強度が低く炭素化が難しい。圧縮処理後の酸化繊維シートの厚さが１．０ｍｍを超える場合は、所期の薄型炭素繊維シートが得られない。
【００４４】
圧縮処理時の温度が１００℃未満の場合は、圧縮処理による酸化繊維シートの強度向上効果がない。圧縮処理時の温度が３５０℃を超える場合は、繊維軟化損傷のためシート強度が低下する。
【００４５】
圧縮処理時の圧力が０．５ＭＰａ℃未満の場合は、酸化繊維シートの強度向上効果や、厚さの低減効果がない。圧縮処理時の圧力が２０ＭＰａを超える場合は、繊維損傷のためシート強度が低下する。
【００４６】
この圧縮処理時の温度及び圧力は、樹脂処理時の樹脂の種類及び目標とする炭素繊維シートの厚さにより適宜調整する。
【００４７】
〔焼成・炭素化〕
圧縮処理後、酸化繊維シートを、窒素ガス中などの不活性ガス中で０．５Ｎ／ｃｍ以下の張力下、１１００〜１７００℃の温度で連続的に焼成・炭素化する。１１００〜１７００℃の温度での焼成時間は０．５〜２０分間が好ましい。
【００４８】
焼成時の温度が１１００℃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。焼成時の温度が１７００℃を超える場合は、炭素繊維シートの強度が低下し、微粉末が発生するので好ましくない。
【００４９】
以上の本発明製造方法の一例により、前述の本発明のＰＡＮ系炭素繊維シートを製造することができる。以下、本発明のＰＡＮ系炭素繊維シートについて詳細に説明する。
【００５０】
本発明のＰＡＮ系炭素繊維シートは、炭素繊維Ａ（主成分）と炭素繊維Ｂ（副成分）とが均一に分散含有されてなる炭素繊維シートである。
【００５１】
炭素繊維Ａの繊維直径Ｃ_Ａは８．０〜１５．０μｍである。炭素繊維Ａの繊維直径Ｃ_Ａが８．０μｍ未満の場合は、炭素繊維シートの強度が低下するので好ましくない。炭素繊維Ａの繊維直径Ｃ_Ａが１５．０μｍを超える場合は、薄層の炭素繊維シートが得られ難いので好ましくない。
【００５２】
炭素繊維Ｂと炭素繊維Ａとの直径比Ｃ_Ｂ／Ｃ_Ａは０．４０〜０．８０である。繊維直径比Ｃ_Ｂ／Ｃ_Ａが０．４０未満の場合、繊維直径比Ｃ_Ｂ／Ｃ_Ａが０．８０を超える場合の何れの場合も、炭素繊維シートの強度が低下するので好ましくない。
【００５３】
炭素繊維Ｂの炭素繊維含有率は４〜２５質量％である。炭素繊維Ｂの炭素繊維含有率が４質量％未満の場合は、炭素繊維Ｂによる強度向上効果がなく、炭素繊維シートの強度が低下するので好ましくない。炭素繊維Ｂの炭素繊維含有率が２５質量％を超える場合は、繊維の分散性低下に伴い炭素繊維シートの強度が低下するので好ましくない。
【００５４】
炭素繊維Ａと炭素繊維Ｂとの合計含有率は９５質量％以上である。
【００５５】
本発明のＰＡＮ系炭素繊維シートの厚さは０．１〜０．５ｍｍである。シートの厚さが０．１ｍｍ未満の場合は、炭素繊維シートの原料となる酸化繊維シートの強度が低く炭素化が難しい。シートの厚さが０．５ｍｍを超える場合は、所期の薄型炭素繊維シートではない。
【００５６】
本発明のＰＡＮ系炭素繊維シートの引っ張り強度は７Ｎ／ｃｍ以上である。引っ張り強度が７Ｎ／ｃｍ未満の場合は、炭素化前の酸化繊維シートの引っ張り強度も低く、この酸化繊維シートの炭素化時に伸びや切断を生じ易い。炭素繊維シートの後加工（樹脂処理、セラミック塗布処理、カーボンブラック処理など）時に過度な張力がかかると伸びや切断を生じ易い。
【００５７】
なお、本発明のＰＡＮ系炭素繊維シートの形状は、上記物性を満たすものであれば湿式の抄紙加工による炭素繊維紙、及び乾式の不織布加工による炭素繊維不織布等の何れの形状でもよい。
【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。原料酸化繊維Ａ、原料酸化繊維Ｂ、バインダー繊維、酸化繊維シート及び炭素繊維シートの諸物性値を、前述又は以下の方法により測定した。
【００６０】
繊維比重：アルキメデス法（溶媒アセトン）により測定した。
【００６１】
厚さ：直径３０ｍｍの円形圧板で２００ｇｆを負荷したとき（２．８ｋＰａ）の厚さを測定した。
【００６２】
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。
【００６３】
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。
【００６４】
炭素繊維シート中の炭素繊維Ａ（主成分）及び炭素繊維Ｂ（副成分）の繊維直径、並びに、炭素繊維含有率：
測定対象シートを５０ｍｍ角にカットし、この５０ｍｍ角のシートを更に３ｍｍ間隔に短冊状にカットした。次いで各短冊の単繊維をピンセットでほぐした後、２００ｍｌビーカーに入れ、１ｖｏｌ％のエタノール水溶液を１５０ｍｌビーカーに入れ、攪拌分散させる。この分散液をスポイトで採取し、繊維をプレパラートの上に載せ、倍率２００倍で顕微鏡で顕微鏡写真撮影を行う。この顕微鏡写真より検体数ｎ＝１００について繊維直径を測定した。繊維直径についてはμｍ単位で小数１桁まで求めた。
【００６５】
この繊維直径について、横軸を繊維直径、縦軸を繊維の個数としてヒストグラムにまとめると、太い繊維（炭素繊維Ａ）のピークと細い繊維（炭素繊維Ｂ）のピークとが出現した。
【００６６】
このピークの±１０％の繊維直径における繊維の個数より、各繊維直径の平均値を算出し、測定対象が炭素繊維の場合はそれぞれ、Ｃ_Ａμｍ及びＣ_Ｂμｍとした。
【００６７】
炭素繊維Ｂと炭素繊維Ａの質量比は、
（炭素繊維Ｂの個数×Ｃ_Ｂの自乗×原料酸化繊維Ｂの繊維長）／（炭素繊維Ａの個数×Ｃ_Ａの自乗×原料酸化繊維Ａの繊維長）
の式を用いて算出した。
【００６８】
炭素繊維Ａの繊維含有率、炭素繊維Ｂの繊維含有率、及び炭素繊維Ａと炭素繊維Ｂとの合計含有率は、以下の方法で求めた。
【００６９】
測定対象シート１００ｍｍ角を１２０℃、２ｈｒｓ乾燥、精秤後、熱濃硫酸（８０℃）３００ｍｌ中で３０分処理した。次いで、この酸処理シートを放冷した後、Ｈ_２Ｏ_２５質量％水溶液を１００ｍｌ加え、１ｈｒｓ放置した。この放置後のシートを磁性フィルターで濾過し純水で洗浄した。この洗浄後のシートの乾燥質量より炭素繊維Ａと炭素繊維Ｂとの合計含有率を求めた。
【００７０】
この炭素繊維Ａと炭素繊維Ｂとの合計含有率と、上記炭素繊維Ｂと炭素繊維Ａの質量比とから、それぞれ炭素繊維Ｂ及び炭素繊維Ａの繊維含有率を算出した。
【００７１】
シートの引張強度；幅２０ｍｍ，長さ２００ｍｍの試験片をつかみ間隔１００ｍｍ、引張速度１００ｍｍ／ｍｉｎにて測定した。
【００７２】
Ｘ線結晶サイズ：広角Ｘ線回折測定での２θのピークの半値幅と下記のシェラーの式
Ｘ線結晶サイズ（ｎｍ）＝（ｋ×λ）／β×ｃｏｓθ
ｋ：装置定数０．９０
λ：Ｘ線波長０．１５４ｎｍ
β：２θ＝２６．０°付近の最大ピークの半値幅
より求めた。
【００７３】
実施例１
表１に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．１μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度２１．０ｋｇｆ／ｍｍ^２（２０６Ｎ／ｍｍ^２）〕を繊維含有率で９５．０質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．１μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２２．５ｋｇｆ／ｍｍ^２（２２１Ｎ／ｍｍ^２）〕を繊維含有率で５．０質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６０、厚さ０．６ｍｍ、目付１２０ｇ／ｃｍ^２、嵩密度０．２０ｇ／ｃｍ^３〕を作製した。
【００７４】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．８質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．３０ｍｍまで圧縮処理し、目付１２２ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００７５】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００７６】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１１．１μｍの炭素繊維Ａの含有率が９４．５質量％、炭素繊維直径（Ｃ_Ｂ）６．５ μｍの炭素繊維Ｂの含有率が５．０質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５９、炭素繊維含有率〔表１中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．５質量％、厚さが０．３１ｍｍ、目付が７４ｇ／ｍ^２、嵩密度が０．２４ｇ／ｃｍ^３、引っ張り強度が８Ｎ／ｃｍ、Ｘ線結晶サイズが２．２ｎｍであり、良好な物性の炭素繊維シートであった。
【００７７】
実施例２
表１に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１４．９μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度２２．４ｋｇｆ／ｍｍ^２（２２０Ｎ／ｍｍ^２）〕を繊維含有率で８５．０質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．１μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２５．３ｋｇｆ／ｍｍ^２（２４８Ｎ／ｍｍ^２）〕を繊維含有率で１５．０質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６１、厚さ０．５５ｍｍ、目付１１９ｇ／ｃｍ^２、嵩密度０．２２ｇ／ｃｍ^３〕を作製した。
【００７８】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．５質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．２８ｍｍまで圧縮処理し、目付１２１ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００７９】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００８０】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１１．０μｍの炭素繊維Ａの含有率が８５．０質量％、炭素繊維直径（Ｃ_Ｂ）６．３μｍの炭素繊維Ｂの含有率が１４．９質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５７、炭素繊維含有率〔表１中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．９質量％、厚さが０．２８ｍｍ、目付が７３ｇ／ｍ^２、嵩密度が０．２６ｇ／ｃｍ^３、引っ張り強度が１５．５Ｎ／ｃｍ、Ｘ線結晶サイズが２．２５ｎｍであり、良好な物性の炭素繊維シートであった。
物であった。
【００８１】
実施例３
表１に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．０μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度２０．５ｋｇｆ／ｍｍ^２（２０１Ｎ／ｍｍ^２）〕を繊維含有率で７８．５質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．０μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２６．０ｋｇｆ／ｍｍ^２（２５５Ｎ／ｍｍ^２）〕を繊維含有率で２１．５質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６０、厚さ０．５３ｍｍ、目付１１５ｇ／ｃｍ^２、嵩密度０．２２ｇ／ｃｍ^３〕を作製した。
【００８２】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．５質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．２７ｍｍまで圧縮処理し、目付１１７ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００８３】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００８４】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１０．９μｍの炭素繊維Ａの含有率が７８．５質量％、炭素繊維直径（Ｃ_Ｂ）６．４μｍの炭素繊維Ｂの含有率が２１．３質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５９、炭素繊維含有率〔表１中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．８質量％、厚さが０．２６ｍｍ、目付が７０ｇ／ｍ^２、嵩密度が０．２７ｇ／ｃｍ^３、引っ張り強度が１３．５Ｎ／ｃｍ、Ｘ線結晶サイズが２．２７ｎｍであり、良好な物性の炭素繊維シートであった。
【００８５】
実施例４
表１に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１３．１μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度２４．３ｋｇｆ／ｍｍ^２（２３８Ｎ／ｍｍ^２）〕を繊維含有率で８４．９質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）８．９μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２７．４ｋｇｆ／ｍｍ^２（２６９Ｎ／ｍｍ^２）〕を繊維含有率で１５．１質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６８、厚さ０．５７ｍｍ、目付１２０ｇ／ｃｍ^２、嵩密度０．２１ｇ／ｃｍ^３〕を作製した。
【００８６】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、２．０質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．２９ｍｍまで圧縮処理し、目付１２２ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００８７】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００８８】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）９．５μｍの炭素繊維Ａの含有率が８５．０質量％、炭素繊維直径（Ｃ_Ｂ）６．４μｍの炭素繊維Ｂの含有率が１４．８質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．６７、炭素繊維含有率〔表１中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．８質量％、厚さが０．２９ｍｍ、目付が７３ｇ／ｍ^２、嵩密度が０．２５ｇ／ｃｍ^３、引っ張り強度が１２．５Ｎ／ｃｍ、Ｘ線結晶サイズが２．２４ｎｍであり、良好な物性の炭素繊維シートであった。
【００８９】
比較例１
表１に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．２μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度１９．３ｋｇｆ／ｍｍ^２（１８９Ｎ／ｍｍ^２）〕を繊維含有率で９６．８質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．２μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２５．４ｋｇｆ／ｍｍ^２（２４９Ｎ／ｍｍ^２）〕を繊維含有率で３．２質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６１、厚さ０．７２ｍｍ、目付１２０ｇ／ｃｍ^２、嵩密度０．１７ｇ／ｃｍ^３〕を作製した。
【００９０】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．５質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．３５ｍｍまで圧縮処理し、目付１２２ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００９１】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００９２】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１１．２μｍの炭素繊維Ａの含有率が９７．０質量％、炭素繊維直径（Ｃ_Ｂ）６．５μｍの炭素繊維Ｂの含有率が２．８質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５８、炭素繊維含有率〔表１中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．８質量％、厚さが０．３８ｍｍ、目付が７３ｇ／ｍ^２、嵩密度が０．１９ｇ／ｃｍ^３、引っ張り強度が５．２Ｎ／ｃｍ、Ｘ線結晶サイズが２．２４ｎｍであり、良好な物性の炭素繊維シートではなかった。表１中×で示す箇所が本発明の構成から逸脱している。
【００９３】
【表１】

【００９４】
比較例２
表２に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．１μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長７ｍｍ、乾強度２１．０ｋｇｆ／ｍｍ^２（２０６Ｎ／ｍｍ^２）〕を繊維含有率で７１．５質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．０μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２２．５ｋｇｆ／ｍｍ^２（２２１Ｎ／ｍｍ^２）〕を繊維含有率で２８．５質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６０、厚さ０．５５ｍｍ、目付１１４ｇ／ｃｍ^２、嵩密度０．２１ｇ／ｃｍ^３〕を作製した。
【００９５】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．６質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．３０ｍｍまで圧縮処理し、目付１２２ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【００９６】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【００９７】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１０．９μｍの炭素繊維Ａの含有率が７２．７質量％、炭素繊維直径（Ｃ_Ｂ）６．３μｍの炭素繊維Ｂの含有率が２７．０質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５８、炭素繊維含有率〔表２中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．７質量％、厚さが０．３２ｍｍ、目付が７３ｇ／ｍ^２、嵩密度が０．２３ｇ／ｃｍ^３、引っ張り強度が３．２Ｎ／ｃｍ、Ｘ線結晶サイズが２．２０ｎｍ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。
【００９８】
比較例３
表２に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．１μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長５１ｍｍ、乾強度２１．０ｋｇｆ／ｍｍ^２（２０６Ｎ／ｍｍ^２）〕を繊維含有率で８５．０質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）５．５μｍのＰＡＮ系酸化繊維〔比重１．３８、カット長３１ｍｍ、乾強度２９．３ｋｇｆ／ｍｍ^２（２８７Ｎ／ｍｍ^２）〕を繊維含有率で１５．０質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．３６、厚さ０．６２ｍｍ、目付１２０ｇ／ｃｍ^２、嵩密度０．１９ｇ／ｃｍ^３〕を作製した。
【００９９】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．６質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．３５ｍｍまで圧縮処理し、目付１２２ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【０１００】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【０１０１】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１１．３μｍの炭素繊維Ａの含有率が８５．０質量％、炭素繊維直径（Ｃ_Ｂ）３．９μｍの炭素繊維Ｂの含有率が１４．６質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．３５、炭素繊維含有率〔表２中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．６質量％、厚さが０．３８ｍｍ、目付が７４ｇ／ｍ^２、嵩密度が０．１９ｇ／ｃｍ^３、引っ張り強度が４．２Ｎ／ｃｍ、Ｘ線結晶サイズが２．２２ｎｍ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。
【０１０２】
比較例４
表２に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１５．２μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長５１ｍｍ、乾強度１９．３ｋｇｆ／ｍｍ^２（１８９Ｎ／ｍｍ^２）〕を繊維含有率で８５．０質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）１２．５μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５１ｍｍ、乾強度２４．８ｋｇｆ／ｍｍ^２（２４３Ｎ／ｍｍ^２）〕を繊維含有率で１５．０質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．８２、厚さ０．５９ｍｍ、目付１２１ｇ／ｃｍ^２、嵩密度０．２１ｇ／ｃｍ^３〕を作製した。
【０１０３】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、１．７質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．３１ｍｍまで圧縮処理し、目付１２３ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【０１０４】
この酸化繊維シートを窒素雰囲気下、張力０．２Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【０１０５】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１０．９μｍの炭素繊維Ａの含有率が８５．０質量％、炭素繊維直径（Ｃ_Ｂ）９．３μｍの炭素繊維Ｂの含有率が１４．７質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．８５、炭素繊維含有率〔表２中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．７質量％、厚さが０．３２ｍｍ、目付が７４ｇ／ｍ^２、嵩密度が０．２３ｇ／ｃｍ^３、引っ張り強度が３．５Ｎ／ｃｍ、Ｘ線結晶サイズが２．１５ｎｍ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。
【０１０６】
実施例５
表２に示すように、原料酸化繊維Ａとして繊維直径（Ｏ_Ａ）１４．９μｍのＰＡＮ系酸化繊維〔比重１．３９、カット長５ｍｍ、乾強度２０．０ｋｇｆ／ｍｍ^２（１９６Ｎ／ｍｍ^２）〕を繊維含有率で９２．０質量％と、原料酸化繊維Ｂとして繊維直径（Ｏ_Ｂ）９．０μｍのＰＡＮ系酸化繊維〔比重１．３７、カット長５ｍｍ、乾強度２６．０ｋｇｆ／ｍｍ^２（２５５Ｎ／ｍｍ^２）〕を繊維含有率で５．０質量％と、バインダー繊維として繊維直径１２．０μｍのレーヨン繊維（比重１．２２）を繊維含有率で３．０質量％とを、水中にて分散させ均一に混綿後、連続的に抄紙し、酸化繊維シート〔原料酸化繊維Ａと原料酸化繊維Ｂとの繊維直径比（Ｏ_Ｂ／Ｏ_Ａ）０．６０、厚さ０．２８ｍｍ、目付１１５ｇ／ｃｍ^２、嵩密度０．４１ｇ／ｃｍ^３〕を作製した。
【０１０７】
さらに、得られた酸化繊維シートをＰＶＡ水溶液（濃度１．０質量％）にて浸漬処理し、２．０質量％添着せしめた後、温度１５０℃、圧力１５ＭＰａにて厚さ０．２４ｍｍまで圧縮処理し、目付１１７ｇ／ｍ^２の樹脂・圧縮処理後の酸化繊維シートを得た。
【０１０８】
この酸化繊維シートを窒素雰囲気下、張力０．１Ｎ／ｃｍ、１５００℃、２分間連続的に焼成・炭素化することによって炭素繊維シートを得た。
【０１０９】
得られた炭素繊維シートは、炭素繊維直径（Ｃ_Ａ）１１．２μｍの炭素繊維Ａの含有率が９４．８質量％、炭素繊維直径（Ｃ_Ｂ）６．４μｍの炭素繊維Ｂの含有率が５．１質量％、炭素繊維Ａと炭素繊維Ｂとの繊維直径比（Ｃ_Ｂ／Ｃ_Ａ）が０．５７、炭素繊維含有率〔表２中の炭素繊維（Ａ＋Ｂ）含有率〕が９９．９質量％、厚さが０．２５ｍｍ、目付が７１／ｍ^２、嵩密度が０．２８ｇ／ｃｍ^３、引っ張り強度が１１．０Ｎ／ｃｍ、Ｘ線結晶サイズが２．００ｎｍであり、良好な物性の炭素繊維シートであった。
【０１１０】
【表２】

【０１１１】
【発明の効果】
本発明のＰＡＮ系炭素繊維シートは、主成分炭素繊維（炭素繊維Ａ）と副成分炭素繊維（炭素繊維Ｂ）とが均一に分散含有されたＰＡＮ系炭素繊維シートであって、炭素繊維Ａの繊維直径Ｃ_Ａ、炭素繊維Ｂと炭素繊維Ａとの繊維直径比Ｃ_Ｂ／Ｃ_Ａ、炭素繊維Ｂの炭素繊維含有率、炭素繊維Ａと炭素繊維Ｂとの合計含有率、厚さ、引っ張り強度などの諸物性が所定範囲にあるので、繊維の分散性が良く、厚さのバラツキが少なく、後加工性の良い高強度の薄型のＰＡＮ系炭素繊維シートである。
【０１１２】
このＰＡＮ系炭素繊維シートを製造するに当たっては、本発明の製造方法：ＰＡＮ系酸化繊維シート中の副成分繊維（原料酸化繊維Ｂ）として、主成分繊維（原料酸化繊維Ａ）より細い酸化繊維を、所定の範囲に混合組み合わせてシート加工することにより、繊維の分散性が改善された酸化繊維シートを得、得られた酸化繊維シートを樹脂処理し、更に圧縮処理後、出来るだけ張力をかけずに不活性ガス中で焼成・炭素化することを特徴とする製造方法により、加工時の裂けや切断を生じ易いなど加工性トラブルを生ずることなく、繊維の分散時に、繊維同士の収束繊維、繊維塊が生じ、得られた酸化繊維シートの炭素化時におけるシートの強度低下や、炭素化後における炭素繊維シートの強度低下を招くなど製造時トラブルを生ずることなく、上記ＰＡＮ系炭素繊維シートを安定して得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyacrylonitrile-based carbon fiber sheet and a method for producing the same.
[0002]
[Prior art]
Polyacrylonitrile (PAN) -based oxidized fibers are infusible, have excellent flame retardancy, and exhibit the same tensile elongation as ordinary organic fibers. It is known that carbonization in an inert gas can provide high-strength carbon fibers.
[0003]
The PAN-based oxidized fiber is shortened, singly or dispersed and mixed with another binder, and processed into a paper-like sheet by wet papermaking or a nonwoven-like sheet by a dry nonwoven fabric manufacturing method (including felt by needle punch). Is done. Further, by carbonizing these sheets in an inert gas, a paper-like or nonwoven-like carbonized sheet can be obtained.
[0004]
Patent Documents 1 and 2 disclose non-woven carbonized sheets.
[0005]
Patent Document 1 describes that a flame-resistant fiber (oxidized fiber) is subjected to felt processing and then carbonized at 1800 ° C. or more, a description for a battery conductive material, and a PAN-based oxidized fiber felt (thickness: 20 mm, basis weight: 3500 g / m 2). ² ) In a nitrogen atmosphere.
[0006]
However, none of the descriptions is directed to a material having a small thickness, and the strength is not described.
[0007]
The felt is generally produced by a needle punch method. However, when a thin sheet such as the sheet of the present invention is used and the cotton length of the oxidized fiber to be used is short, if the felt (oxidized fiber sheet) is produced by the method described in Patent Document 1, the strength of the sheet decreases due to punching. Invite.
[0008]
Note that Patent Document 1 does not include a description of including a subcomponent fiber (raw material oxidized fiber B), a resin treatment, a compression treatment, and the like.
[0009]
Patent Literature 2 includes a description of preparing a nonwoven fabric of a PAN-based oxidized fiber by a water jet method, and a description of the thickness and strength of the oxidized fiber nonwoven fabric. However, there is no description containing finer fibers as an accessory component, nor is there any description about carbonization.
[0010]
In addition, Patent Document 2 discloses that as a raw material fiber of the nonwoven fabric, an oxidized fiber having a cotton length of 51 mm (oxidized fiber) is used. However, the nonwoven fabric obtained by using the oxidized fiber having this fiber length has a high strength, but the dispersibility of the fiber is inferior to a sheet obtained by a wet papermaking method having a short cotton length.
[0011]
Generally, the oxidized fiber used for the nonwoven fabric processing is a long fiber having a cotton length of 25 to 75 mm. The dry-type nonwoven fabric sheet obtained by using this has higher sheet strength than the wet paper (papermaking) type sheet obtained by using oxidized fiber having a short cotton length (15 mm or less), Poor fiber dispersibility. On the other hand, in the case of using wet papermaking, a sheet having a good dispersibility of the oxidized fiber and a small variation in thickness is easily produced.
[0012]
However, when trying to obtain a thin (low-weight) sheet by wet papermaking, only a sheet having low strength can be obtained. Moreover, since this low-strength sheet can be applied to various uses, it is often necessary to continuously perform post-processing so as to apply to such uses, and in this case, tearing or cutting is likely to occur during post-processing. Such as workability troubles are likely to occur.
[0013]
In order to increase the strength of the oxidized fiber sheet by wet papermaking, it is better to use finer fibers. However, the thinner the fibers used for papermaking, the lower the dispersibility and the more likely the fibers are entangled. In the wet papermaking process using this thin oxidized fiber, when the fibers are dispersed in water, converging fibers and fiber clumps are generated between the fibers, and the resulting oxidized fiber sheet has a reduced strength at the time of carbonization, This causes a reduction in the strength of the carbon fiber sheet later.
[0014]
[Patent Document 1]
JP-A-2-139464 (Claims, Example 1)
[Patent Document 2]
JP-A-9-119052 (paragraph number [0013])
[0015]
[Problems to be solved by the invention]
The present inventor has studied various methods to obtain a high-strength thin carbon fiber sheet having a good fiber dispersibility, a small thickness variation and a good post-processability. Oxidized fiber with improved dispersibility of fibers by mixing and combining oxidized fibers finer than the main component fiber (raw oxidized fiber A) in a predetermined range as a subcomponent fiber (raw oxidized fiber B) A PAN-based carbon fiber sheet having the above physical properties is obtained by obtaining a sheet, subjecting the obtained oxidized fiber sheet to a resin treatment, further compressing, and calcining and carbonizing in an inert gas without applying tension as much as possible. Knowing that it is possible, they have completed the present invention.
[0016]
Accordingly, it is an object of the present invention to provide a PAN-based carbon fiber sheet which solves the above problems and a method for producing the same.
[0017]
[Means for Solving the Problems]
The present invention that achieves the above object is as described below.
[0018]
[1] Fiber diameter C _A Is 8.0-15.0 μm carbon fiber A and fiber diameter C _B Is Equation 1
0.40 <C _B / C _A <0.80 Equation 1
Is a polyacrylonitrile-based carbon fiber sheet uniformly dispersed and contained, wherein the carbon fiber content of carbon fiber B is 4 to 25% by mass, and the total content of carbon fiber A and carbon fiber B A polyacrylonitrile-based carbon fiber sheet having a ratio of 95% by mass or more, a thickness of 0.1 to 0.5 mm, and a tensile strength of 7 N / cm or more.
[0019]
[2] Fiber diameter O _A Is oxidized fiber A having a fiber length of 3 to 15 mm and a fiber diameter O of 11.0 to 25.0 μm. _B Is Equation 2
0.40 <O _B / O _A <0.80 Equation 2
Oxidized fiber B having a fiber length of 3 to 15 mm is uniformly dispersed and contained, and the fiber content of the oxidized fiber B is 4 to 25% by mass. After processing to a thickness of 0.1 to 1.0 mm, the fiber diameter is continuously fired and carbonized at a temperature of 1100 to 1700 ° C. under a tension of 0.5 N / cm or less in an inert gas. C _A Is 8.0-15.0 μm carbon fiber A and fiber diameter C _B Is Equation 1
0.40 <C _B / C _A <0.80 Equation 1
Is a polyacrylonitrile-based carbon fiber sheet uniformly dispersed and contained, wherein the carbon fiber content of carbon fiber B is 4 to 25% by mass, and the total content of carbon fiber A and carbon fiber B A method for producing a polyacrylonitrile-based carbon fiber sheet having a ratio of 95% by mass or more, a thickness of 0.1 to 0.5 mm, and a tensile strength of 7 N / cm or more.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0021]
The PAN-based carbon fiber sheet of the present invention has a fiber diameter C _A Is 8.0-15.0 μm carbon fiber A and fiber diameter C _B Is Equation 1
0.40 <C _B / C _A <0.80 Equation 1
Is a polyacrylonitrile-based carbon fiber sheet uniformly dispersed and contained, wherein the carbon fiber content of carbon fiber B is 4 to 25% by mass, and the total content of carbon fiber A and carbon fiber B The carbon fiber sheet has a ratio of 95% by mass or more, a thickness of 0.1 to 0.5 mm, and a tensile strength of 7 N / cm or more.
[0022]
The production method of the PAN-based carbon fiber sheet of the present invention is not particularly limited as long as its physical properties are within the above range, but can be produced by, for example, the following production method.
[0023]
[Oxidized fibers A and B]
Both the oxidized fiber A (main component) and the oxidized fiber B (subcomponent) as carbon fiber sheet raw materials are PAN-based oxidized fibers. For example, a cyclization reaction is performed by treating a commercially available PAN-based fiber at a high temperature in the air. Which is obtained by a flame-proofing treatment for increasing the amount of oxygen bond to make it infusible and flame-retardant.
[0024]
In addition, as for the oxidized fiber considered as a raw material of the carbon fiber sheet, in addition to the PAN-based oxidized fiber, there are pitch-based, phenol-based, rayon-based and other oxidized fibers, and the PAN-based oxidized fiber has the highest strength carbon fiber sheet. can get.
[0025]
Fiber diameter O of oxidized fiber A _A Is 11.0 to 25.0 μm. Fiber diameter O of oxidized fiber A _A Is less than 11.0 μm, the strength of the resulting oxidized fiber sheet and carbon fiber sheet is undesirably reduced. Fiber diameter O of oxidized fiber A _A Is more than 25.0 μm, the strength of the resulting oxidized fiber sheet and carbon fiber sheet decreases, and it is difficult to obtain a desired sheet thickness, which is not preferable.
[0026]
As for the oxidized fiber B, the oxidized fiber B content in the oxidized fiber sheet is 4 to 25% by mass, and the diameter ratio O to the oxidized fiber A is O. _B / O _A Is 0.40 to 0.80. If the ratio is out of this range, a carbon fiber sheet having desired physical properties cannot be obtained.
[0027]
The fiber length (cut length) of each of the oxidized fiber A and the oxidized fiber B is 3 to 15 mm. When the fiber length is less than 3 mm, the strengths of the obtained oxidized fiber sheet and carbon fiber sheet are undesirably reduced. When the fiber length exceeds 15 mm, the dispersibility of the fibers in the obtained oxidized fiber sheet is reduced, and the strength of the carbon fiber sheet obtained by carbonizing the oxidized fiber sheet is not preferable.
[0028]
The specific gravity of each of the oxidized fiber A and the oxidized fiber B is not particularly limited, but is preferably 1.35 to 1.45.
[0029]
The dry strength of each of the oxidized fibers A and B is 15 kgf / mm. ² (147 N / mm ² Is preferred. Dry strength is 15kgf / mm ² (147 N / mm ² In the case of less than), the strength of the oxidized fiber sheet obtained by forming the oxidized fibers A and B into a sheet is reduced, and the generation of fine powder due to the reduced strength of the carbon fiber sheet obtained by carbonizing the oxidized fiber sheet is increased. Not preferred.
[0030]
In addition, the dry strength of the oxidized fiber A and the oxidized fiber B is a property value measured according to JIS L1015.
[0031]
(Binder fiber)
As the carbon fiber sheet raw material, if necessary, a binder fiber such as rayon fiber, cellulose fiber, polyester fiber, phenol fiber, polyvinyl fiber, polyamide fiber or the like may be mixed in the oxidized fiber sheet and used.
[0032]
The content of the binder fiber in the oxidized fiber sheet is preferably 30% by mass or less. If the binder fiber content exceeds 30% by mass, the strength of the carbon fiber sheet obtained by carbonizing this oxidized fiber sheet is undesirably reduced.
[0033]
(Oxidized fiber sheet)
The raw material oxidized fibers such as the oxidized fiber A and the oxidized fiber B described above are added with a binder fiber as necessary, and processed into a sheet to obtain an oxidized fiber sheet in which the raw material oxidized fiber and the like are uniformly dispersed and contained.
[0034]
The sheet processing method is not particularly limited, but a wet papermaking method in which the raw material oxidized fibers and the like are made into a paper by wet papermaking, a nonwoven fabric in which the raw material oxidized fibers and the like are made into a web by a dry method and then a water jet method is used to form a nonwoven fabric A processing method or the like can be used.
[0035]
Among the above sheet processing methods, wet papermaking is particularly preferable for raw material oxidized fibers of short fibers having a fiber length of 3 to 15 mm, since sheet processing is easy.
[0036]
The thickness of the oxidized fiber sheet is preferably from 0.20 to 0.80 mm.
[0037]
The bulk density of the oxidized fiber sheet is 1.0 g / cm ³ The following is preferred because the thickness can be easily controlled by a compression treatment in a later step. The bulk density of the oxidized fiber sheet is 1.0 g / cm ³ When it exceeds, it is difficult to control the thickness reduction.
[0038]
(Resin treatment)
The above-mentioned oxidized fiber sheet is subjected to a resin treatment before the compression treatment for the purpose of exhibiting a strength improving effect and a thickness reducing effect more. Resin treatment suppresses thickness restoration during carbonization and facilitates obtaining a thin material.
[0039]
The type of the resin may be either a thermoplastic resin or a thermosetting resin. However, the resin softens when subjected to a high-temperature (100 to 350 ° C.) compression treatment in a later step, fuses between the fibers, and even a little during firing carbonization. It is preferable to use a resin that is carbonized and remains. For example, resins such as polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), epoxy, phenol novolak, aramid, and polyimide are preferable. In addition, the thing with high water dispersibility or water solubility is more preferable at the point of handleability.
[0040]
The optimum amount of the resin adhered varies depending on the type of the resin and the target hardness of the woven fabric after carbonization, but is usually preferably in the range of 0.2 to 10% by mass. If the amount of the applied resin exceeds 10% by mass, the carbon fiber sheet obtained by firing and carbonizing loses flexibility and becomes brittle, which is not preferable.
[0041]
The resin treatment method is preferably an immersion method. According to this method, the resin can be most uniformly applied. The temperature at the time of the resin treatment is preferably in the range of normal temperature (25 ° C) to 90 ° C.
[0042]
[Compression processing]
The above-mentioned oxidized fiber sheet is subjected to a compression treatment at a temperature of 100 to 350 ° C. and a pressure of 0.5 to 20 MPa after or without resin treatment, and the thickness of the oxidized fiber sheet after the compression treatment is set to 0.1. To 1.0 mm.
[0043]
When the thickness of the oxidized fiber sheet after the compression treatment is less than 0.1 mm, the strength of the oxidized fiber sheet is low and carbonization is difficult. If the thickness of the oxidized fiber sheet after the compression treatment exceeds 1.0 mm, a desired thin carbon fiber sheet cannot be obtained.
[0044]
If the temperature during the compression treatment is lower than 100 ° C., there is no effect of improving the strength of the oxidized fiber sheet by the compression treatment. If the temperature at the time of the compression treatment exceeds 350 ° C., the sheet strength decreases due to fiber softening damage.
[0045]
If the pressure during the compression treatment is less than 0.5 MPa ° C., there is no effect of improving the strength of the oxidized fiber sheet or reducing the thickness. If the pressure during the compression treatment exceeds 20 MPa, the sheet strength decreases due to fiber damage.
[0046]
The temperature and pressure during the compression treatment are appropriately adjusted according to the type of the resin during the resin treatment and the target thickness of the carbon fiber sheet.
[0047]
[Firing and carbonization]
After the compression treatment, the oxidized fiber sheet is continuously fired and carbonized at a temperature of 1100 to 1700 ° C. in an inert gas such as a nitrogen gas under a tension of 0.5 N / cm or less. The firing time at a temperature of 1100 to 1700 ° C is preferably 0.5 to 20 minutes.
[0048]
If the temperature at the time of firing is lower than 1100 ° C., the strength of the obtained carbon fiber sheet is undesirably reduced. If the temperature during firing exceeds 1700 ° C., the strength of the carbon fiber sheet decreases, and fine powder is generated, which is not preferable.
[0049]
The above-described PAN-based carbon fiber sheet of the present invention can be manufactured by one example of the manufacturing method of the present invention. Hereinafter, the PAN-based carbon fiber sheet of the present invention will be described in detail.
[0050]
The PAN-based carbon fiber sheet of the present invention is a carbon fiber sheet in which carbon fiber A (main component) and carbon fiber B (subcomponent) are uniformly dispersed and contained.
[0051]
Fiber diameter C of carbon fiber A _A Is 8.0 to 15.0 μm. Fiber diameter C of carbon fiber A _A Is less than 8.0 μm, the strength of the carbon fiber sheet is undesirably reduced. Fiber diameter C of carbon fiber A _A Is more than 15.0 μm, it is not preferable because it is difficult to obtain a thin carbon fiber sheet.
[0052]
Diameter ratio C between carbon fiber B and carbon fiber A _B / C _A Is 0.40 to 0.80. Fiber diameter ratio C _B / C _A Is less than 0.40, the fiber diameter ratio C _B / C _A Is more than 0.80, it is not preferable because the strength of the carbon fiber sheet is reduced.
[0053]
The carbon fiber content of the carbon fiber B is 4 to 25% by mass. If the carbon fiber content of the carbon fiber B is less than 4% by mass, the strength improvement effect of the carbon fiber B is not obtained, and the strength of the carbon fiber sheet is undesirably reduced. If the carbon fiber content of the carbon fiber B exceeds 25% by mass, the strength of the carbon fiber sheet decreases with a decrease in the dispersibility of the fiber, which is not preferable.
[0054]
The total content of carbon fiber A and carbon fiber B is 95% by mass or more.
[0055]
The thickness of the PAN-based carbon fiber sheet of the present invention is 0.1 to 0.5 mm. When the thickness of the sheet is less than 0.1 mm, the strength of the oxidized fiber sheet as a raw material of the carbon fiber sheet is low, and it is difficult to carbonize. If the thickness of the sheet exceeds 0.5 mm, it is not the expected thin carbon fiber sheet.
[0056]
The tensile strength of the PAN-based carbon fiber sheet of the present invention is 7 N / cm or more. When the tensile strength is less than 7 N / cm, the tensile strength of the oxidized fiber sheet before carbonization is low, and the oxidized fiber sheet is likely to be stretched or cut during carbonization. If excessive tension is applied during post-processing of the carbon fiber sheet (resin treatment, ceramic coating treatment, carbon black treatment, etc.), elongation and cutting are likely to occur.
[0057]
The shape of the PAN-based carbon fiber sheet of the present invention may be any shape such as a carbon fiber paper formed by wet papermaking and a carbon fiber nonwoven fabric formed by dry nonwoven fabric as long as the above physical properties are satisfied.
[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 oxidized fiber A, the raw material oxidized fiber B, the binder fiber, the oxidized fiber sheet, and the carbon fiber sheet were measured by the methods described above or the following methods.
[0060]
Fiber specific gravity: Measured by Archimedes method (solvent acetone).
[0061]
Thickness: The thickness at a load of 200 gf (2.8 kPa) measured by a circular pressure plate having a diameter of 30 mm was measured.
[0062]
Basis weight: The mass per unit area was calculated from the dimensions of the sheet and the dry mass at 120 ° C.
[0063]
Bulk density: Calculated from the thickness and basis weight measured under the above conditions.
[0064]
Fiber diameter of carbon fiber A (main component) and carbon fiber B (subcomponent) in carbon fiber sheet, and carbon fiber content:
The sheet to be measured was cut into a 50 mm square, and the 50 mm square sheet was further cut into strips at 3 mm intervals. Next, the individual fibers of each strip are loosened with tweezers, put into a 200 ml beaker, put a 1 vol% aqueous ethanol solution into a 150 ml beaker, and stir and disperse. The dispersion is collected with a dropper, the fiber is placed on a preparation, and a micrograph is taken with a microscope at a magnification of 200 times. From this micrograph, the fiber diameter was measured for n = 100 samples. The fiber diameter was determined to one decimal place in μm units.
[0065]
When the horizontal axis represents the fiber diameter and the vertical axis represents the number of fibers in the histogram, the peak of the thick fiber (carbon fiber A) and the peak of the thin fiber (carbon fiber B) appeared.
[0066]
From the number of fibers at a fiber diameter of ± 10% of this peak, the average value of each fiber diameter is calculated. _A μm and C _B μm.
[0067]
The mass ratio of carbon fiber B to carbon fiber A is
(Number of carbon fibers B x C _B Square x fiber length of raw material oxidized fiber B) / (number of carbon fibers A x C _A Square x fiber length of raw material oxidized fiber A)
It calculated using the formula of.
[0068]
The fiber content of carbon fiber A, the fiber content of carbon fiber B, and the total content of carbon fiber A and carbon fiber B were determined by the following methods.
[0069]
A 100 mm square sheet to be measured was dried at 120 ° C. for 2 hours, precisely weighed, and then treated in 300 ml of hot concentrated sulfuric acid (80 ° C.) for 30 minutes. Then, after allowing the acid-treated sheet to cool, ₂ O ₂ 100 ml of a 5% by mass aqueous solution was added and left for 1 hr. The sheet after standing was filtered with a magnetic filter and washed with pure water. The total content of carbon fiber A and carbon fiber B was determined from the dry mass of the washed sheet.
[0070]
The fiber content of carbon fiber B and carbon fiber A was calculated from the total content of carbon fiber A and carbon fiber B and the mass ratio of carbon fiber B and carbon fiber A, respectively.
[0071]
Tensile strength of the sheet: A test piece having a width of 20 mm and a length of 200 mm was measured at a grip interval of 100 mm and a tensile speed of 100 mm / min.
[0072]
X-ray crystal size: The half-value width of the 2θ peak in wide-angle X-ray diffraction measurement and the following Scherrer's formula
X-ray crystal size (nm) = (k × λ) / β × cos θ
k: equipment constant 0.90
λ: X-ray wavelength 0.154 nm
β: half value width of the maximum peak near 2θ = 26.0 °
I asked more.
[0073]
Example 1
As shown in Table 1, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.1 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 21.0 kgf / mm ² (206N / mm ² )] Is 95.0% by mass in terms of fiber content, and the fiber diameter (O _B ) 9.1 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 22.5 kgf / mm ² (221 N / mm ² )] At a fiber content of 5.0% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and oxidized fiber sheet [fiber diameter ratio of raw material oxidized fiber A and raw material oxidized fiber B ( O _B / O _A ) 0.60, thickness 0.6 mm, basis weight 120 g / cm ² , Bulk density 0.20g / cm ³ ] Was produced.
[0074]
Further, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.8% by mass, and then compressed to a thickness of 0.30 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 122 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0075]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0076]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 11.1 μm carbon fiber A was 94.5% by mass, and the carbon fiber diameter (C _B ) The content of 6.5 μm carbon fiber B is 5.0% by mass, and the fiber diameter ratio of carbon fiber A to carbon fiber B (C _B / C _A ) Was 0.59, the carbon fiber content [carbon fiber (A + B) content in Table 1] was 99.5% by mass, the thickness was 0.31 mm, and the basis weight was 74 g / m. ² , Bulk density is 0.24g / cm ³ , The tensile strength was 8 N / cm, the X-ray crystal size was 2.2 nm, and the carbon fiber sheet had good physical properties.
[0077]
Example 2
As shown in Table 1, as the raw material oxidized fiber A, the fiber diameter (O _A ) 14.9 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 22.4 kgf / mm ² (220 N / mm ² )] At a fiber content of 85.0% by mass, and a fiber diameter (O _B ) 9.1 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 25.3 kgf / mm ² (248 N / mm ² )] At a fiber content of 15.0% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B ( O _B / O _A ) 0.61, thickness 0.55 mm, basis weight 119 g / cm ² , Bulk density 0.22g / cm ³ ] Was produced.
[0078]
Further, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.5% by mass, and then compressed to a thickness of 0.28 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 121 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0079]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0080]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 11.0 μm carbon fiber A was 85.0% by mass, and the carbon fiber diameter (C _B ) The content of 6.3 μm carbon fiber B is 14.9% by mass, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Was 0.57, the carbon fiber content [carbon fiber (A + B) content in Table 1] was 99.9% by mass, the thickness was 0.28 mm, and the basis weight was 73 g / m. ² , Bulk density 0.26g / cm ³ , Tensile strength was 15.5 N / cm, X-ray crystal size was 2.25 nm, and it was a carbon fiber sheet having good physical properties.
It was a thing.
[0081]
Example 3
As shown in Table 1, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.0 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 20.5 kgf / mm ² (201 N / mm ² )] At a fiber content of 78.5% by mass, and a fiber diameter (O _B ) 9.0 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 26.0 kgf / mm ² (255 N / mm ² )] In a fiber content of 21.5% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and oxidized fiber sheet [fiber diameter ratio of raw material oxidized fiber A and raw material oxidized fiber B ( O _B / O _A ) 0.60, thickness 0.53 mm, basis weight 115 g / cm ² , Bulk density 0.22g / cm ³ ] Was produced.
[0082]
Furthermore, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.5% by mass, and then compressed to a thickness of 0.27 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 117 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0083]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0084]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 10.9 μm carbon fiber A was 78.5% by mass, and the carbon fiber diameter (C _B ) The content of 6.4 μm carbon fiber B is 21.3 mass%, and the fiber diameter ratio of carbon fiber A to carbon fiber B (C _B / C _A ) Was 0.59, the carbon fiber content [carbon fiber (A + B) content in Table 1] was 99.8% by mass, the thickness was 0.26 mm, and the basis weight was 70 g / m. ² , Bulk density is 0.27 g / cm ³ , The tensile strength was 13.5 N / cm, the X-ray crystal size was 2.27 nm, and the carbon fiber sheet had good physical properties.
[0085]
Example 4
As shown in Table 1, as the raw material oxidized fiber A, the fiber diameter (O _A ) 13.1 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 24.3 kgf / mm ² (238 N / mm ² )] At a fiber content of 84.9% by mass, and a fiber diameter (O _B ) 8.9 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 27.4 kgf / mm ² (269 N / mm ² )] At a fiber content of 15.1% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw material oxidized fiber A and raw material oxidized fiber B ( O _B / O _A ) 0.68, thickness 0.57 mm, basis weight 120 g / cm ² , Bulk density 0.21 g / cm ³ ] Was produced.
[0086]
Furthermore, the obtained oxidized fiber sheet was immersed in an aqueous PVA solution (concentration: 1.0% by mass), impregnated with 2.0% by mass, and then compressed to a thickness of 0.29 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 122 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0087]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0088]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 9.5 μm carbon fiber A is 85.0% by mass, and the carbon fiber diameter (C _B ) The content of 6.4 μm carbon fiber B is 14.8 mass%, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Is 0.67, the carbon fiber content [carbon fiber (A + B) content in Table 1] is 99.8 mass%, the thickness is 0.29 mm, and the basis weight is 73 g / m. ² , Bulk density is 0.25g / cm ³ , The tensile strength was 12.5 N / cm, the X-ray crystal size was 2.24 nm, and the carbon fiber sheet had good physical properties.
[0089]
Comparative Example 1
As shown in Table 1, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.2 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 19.3 kgf / mm ² (189 N / mm ² )] At a fiber content of 96.8% by mass, and a fiber diameter (O _B ) 9.2 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 25.4 kgf / mm ² (249 N / mm ² )] At a fiber content of 3.2% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B ( O _B / O _A ) 0.61, thickness 0.72 mm, basis weight 120 g / cm ² , Bulk density 0.17g / cm ³ ] Was produced.
[0090]
Furthermore, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.5% by mass, and then compressed to a thickness of 0.35 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 122 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0091]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0092]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 11.2 μm carbon fiber A is 97.0 mass%, and the carbon fiber diameter (C _B ) The content of 6.5 μm carbon fiber B is 2.8 mass%, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Was 0.58, the carbon fiber content [carbon fiber (A + B) content in Table 1] was 99.8% by mass, the thickness was 0.38 mm, and the basis weight was 73 g / m. ² , Bulk density is 0.19 g / cm ³ , The tensile strength was 5.2 N / cm, the X-ray crystal size was 2.24 nm, and it was not a carbon fiber sheet having good physical properties. The portions indicated by x in Table 1 deviate from the configuration of the present invention.
[0093]
[Table 1]

[0094]
Comparative Example 2
As shown in Table 2, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.1 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 7 mm, dry strength 21.0 kgf / mm ² (206N / mm ² )] At a fiber content of 71.5% by mass, and a fiber diameter (O _B ) 9.0 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 22.5 kgf / mm ² (221 N / mm ² )] At a fiber content of 28.5% by mass, dispersed in water, uniformly mixed, and then continuously made into paper. Then, an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B ( O _B / O _A ) 0.60, thickness 0.55 mm, basis weight 114 g / cm ² , Bulk density 0.21 g / cm ³ ] Was produced.
[0095]
Furthermore, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.6% by mass, and then compressed to a thickness of 0.30 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 122 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0096]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0097]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 10.9 μm carbon fiber A was 72.7% by mass, and the carbon fiber diameter (C _B ) The content of 6.3 μm carbon fiber B is 27.0% by mass, and the fiber diameter ratio of carbon fiber A to carbon fiber B (C _B / C _A ) Was 0.58, the carbon fiber content [carbon fiber (A + B) content in Table 2] was 99.7% by mass, the thickness was 0.32 mm, and the basis weight was 73 g / m. ² , Bulk density is 0.23g / cm ³ , The tensile strength was 3.2 N / cm, the X-ray crystal size was 2.20 nm, and it 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.
[0098]
Comparative Example 3
As shown in Table 2, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.1 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 51 mm, dry strength 21.0 kgf / mm ² (206N / mm ² )] At a fiber content of 85.0% by mass, and a fiber diameter (O _B ) 5.5 μm PAN-based oxidized fiber [specific gravity 1.38, cut length 31 mm, dry strength 29.3 kgf / mm ² (287 N / mm ² )] At a fiber content of 15.0% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B ( O _B / O _A ) 0.36, thickness 0.62 mm, basis weight 120 g / cm ² , Bulk density 0.19g / cm ³ ] Was produced.
[0099]
Furthermore, the obtained oxidized fiber sheet was immersed in a PVA aqueous solution (concentration: 1.0% by mass), impregnated with 1.6% by mass, and then compressed to a thickness of 0.35 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 122 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0100]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0101]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 11.3 μm carbon fiber A was 85.0% by mass, and the carbon fiber diameter (C _B ) The content of 3.9 μm carbon fiber B is 14.6 mass%, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Was 0.35, the carbon fiber content [carbon fiber (A + B) content in Table 2] was 99.6% by mass, the thickness was 0.38 mm, and the basis weight was 74 g / m. ² , Bulk density is 0.19 g / cm ³ , The tensile strength was 4.2 N / cm, the X-ray crystal size was 2.22 nm, and it 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.
[0102]
Comparative Example 4
As shown in Table 2, as the raw material oxidized fiber A, the fiber diameter (O _A ) 15.2 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 51 mm, dry strength 19.3 kgf / mm ² (189 N / mm ² )] At a fiber content of 85.0% by mass, and a fiber diameter (O _B ) 12.5 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 51 mm, dry strength 24.8 kgf / mm ² (243N / mm ² )] At a fiber content of 15.0% by mass, dispersed in water, uniformly mixed, then continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B ( O _B / O _A ) 0.82, thickness 0.59 mm, basis weight 121 g / cm ² , Bulk density 0.21 g / cm ³ ] Was produced.
[0103]
Further, the obtained oxidized fiber sheet was immersed in an aqueous PVA solution (concentration: 1.0% by mass), and impregnated with 1.7% by mass, and then compressed to a thickness of 0.31 mm at a temperature of 150 ° C and a pressure of 15 MPa. Treated, basis weight 123 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0104]
This oxidized fiber sheet was continuously fired and carbonized for 2 minutes at a tension of 0.2 N / cm at 1500 ° C. in a nitrogen atmosphere to obtain a carbon fiber sheet.
[0105]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 10.9 μm carbon fiber A was 85.0% by mass, and the carbon fiber diameter (C _B ) The content of 9.3 μm carbon fiber B is 14.7 mass%, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Is 0.85, the carbon fiber content [carbon fiber (A + B) content in Table 2] is 99.7% by mass, the thickness is 0.32 mm, and the basis weight is 74 g / m. ² , Bulk density is 0.23 g / cm ³ , The tensile strength was 3.5 N / cm, the X-ray crystal size was 2.15 nm, and it 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.
[0106]
Example 5
As shown in Table 2, as the raw material oxidized fiber A, the fiber diameter (O _A ) 14.9 μm PAN-based oxidized fiber [specific gravity 1.39, cut length 5 mm, dry strength 20.0 kgf / mm ² (196 N / mm ² )] With a fiber content of 92.0% by mass, and a fiber diameter (O _B ) 9.0 μm PAN-based oxidized fiber [specific gravity 1.37, cut length 5 mm, dry strength 26.0 kgf / mm ² (255 N / mm ² )] Was dispersed in water, and 5.0% by mass of a fiber content and 3.0% by mass of a rayon fiber having a fiber diameter of 12.0 μm (specific gravity 1.22) as a binder fiber were 3.0% by mass in water. , And continuously paper-made, and an oxidized fiber sheet [fiber diameter ratio of raw oxidized fiber A and raw oxidized fiber B (O _B / O _A ) 0.60, thickness 0.28 mm, basis weight 115 g / cm ² , Bulk density 0.41 g / cm ³ ] Was produced.
[0107]
Furthermore, the obtained oxidized fiber sheet was immersed in an aqueous PVA solution (concentration: 1.0% by mass), impregnated with 2.0% by mass, and then compressed to a thickness of 0.24 mm at a temperature of 150 ° C. and a pressure of 15 MPa. Treated, basis weight 117 g / m ² The resin-compressed oxidized fiber sheet was obtained.
[0108]
The carbon fiber sheet was obtained by continuously firing and carbonizing the oxidized fiber sheet under a nitrogen atmosphere at a tension of 0.1 N / cm at 1500 ° C. for 2 minutes.
[0109]
The obtained carbon fiber sheet has a carbon fiber diameter (C _A ) The content of 11.2 μm carbon fiber A was 94.8% by mass, and the carbon fiber diameter (C _B ) The content of 6.4 μm carbon fiber B is 5.1% by mass, and the fiber diameter ratio of carbon fiber A and carbon fiber B (C _B / C _A ) Was 0.57, the carbon fiber content [carbon fiber (A + B) content in Table 2] was 99.9% by mass, the thickness was 0.25 mm, and the basis weight was 71 / m. ² , Bulk density 0.28g / cm ³ , The tensile strength was 11.0 N / cm, the X-ray crystal size was 2.00 nm, and the carbon fiber sheet had good physical properties.
[0110]
[Table 2]

[0111]
【The invention's effect】
The PAN-based carbon fiber sheet of the present invention is a PAN-based carbon fiber sheet in which a main component carbon fiber (carbon fiber A) and an auxiliary component carbon fiber (carbon fiber B) are uniformly dispersed and contained. Fiber diameter C _A , Fiber diameter ratio C between carbon fiber B and carbon fiber A _B / C _A Since various properties such as carbon fiber content of carbon fiber B, total content of carbon fiber A and carbon fiber B, thickness, and tensile strength are within predetermined ranges, fiber dispersibility is good and thickness variation. This is a high-strength and thin PAN-based carbon fiber sheet with little post-processing and good post-processing properties.
[0112]
In producing this PAN-based carbon fiber sheet, an oxidized fiber thinner than the main fiber (raw oxidized fiber A) is used as a subcomponent fiber (raw oxidized fiber B) in the production method of the present invention: PAN-based oxidized fiber sheet. By mixing and processing a sheet in a predetermined range, an oxidized fiber sheet having improved fiber dispersibility is obtained, and the obtained oxidized fiber sheet is subjected to resin treatment. In the production method characterized by firing and carbonizing in an inert gas, without causing workability troubles such as tearing or cutting during processing, converging fibers between fibers, Agglomeration does not occur and causes no trouble at the time of production, such as lowering the strength of the obtained oxidized fiber sheet during carbonization, or lowering the strength of the carbon fiber sheet after carbonization. It can be obtained by the PAN-based carbon fiber sheet stably.

Claims

Carbon fibers A fiber diameter _{C A} is 8.0～15.0Myuemu, fiber diameter _{C B} has the formula 1
_{_{0.40 <C B / C A <}} 0.80 Equation 1
Is a polyacrylonitrile-based carbon fiber sheet uniformly dispersed and contained, wherein the carbon fiber content of carbon fiber B is 4 to 25% by mass, and the total content of carbon fiber A and carbon fiber B A polyacrylonitrile-based carbon fiber sheet having a ratio of 95% by mass or more, a thickness of 0.1 to 0.5 mm, and a tensile strength of 7 N / cm or more.

Fiber diameter _{O A} is 11.0～25.0Myuemu, oxide fibers A fiber length is 3 to 15 mm, fiber diameter _{O B} has the formula 2
_{_{0.40 <O B / O A <}} 0.80 Equation 2
Oxidized fiber B having a fiber length of 3 to 15 mm is uniformly dispersed and contained, and the fiber content of the oxidized fiber B is 4 to 25% by mass. After processing to a thickness of 0.1 to 1.0 mm, the fiber diameter is continuously fired and carbonized at a temperature of 1100 to 1700 ° C. under a tension of 0.5 N / cm or less in an inert gas. and C _a carbon fiber a of 8.0～15.0Myuemu, fiber diameter _{C B} has the formula 1
_{_{0.40 <C B / C A <}} 0.80 Equation 1
Is a polyacrylonitrile-based carbon fiber sheet uniformly dispersed and contained, wherein the carbon fiber content of carbon fiber B is 4 to 25% by mass, and the total content of carbon fiber A and carbon fiber B A method for producing a polyacrylonitrile-based carbon fiber sheet having a ratio of 95% by mass or more, a thickness of 0.1 to 0.5 mm, and a tensile strength of 7 N / cm or more.