JP2004060069A - Polyacrylonitrile-based carbon fiber, and method for producing the same - Google Patents
Polyacrylonitrile-based carbon fiber, and method for producing the same Download PDFInfo
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- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 161
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 161
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- 229920002239 polyacrylonitrile Polymers 0.000 title claims abstract description 30
- 238000004519 manufacturing process Methods 0.000 title claims description 20
- 238000000034 method Methods 0.000 claims abstract description 35
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- 238000009987 spinning Methods 0.000 claims description 19
- 229920001577 copolymer Polymers 0.000 claims description 10
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 8
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- 239000000178 monomer Substances 0.000 claims description 5
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、高強度炭素繊維、及びその製造方法に関する。
【０００２】
【従来の技術】
従来、ポリアクリロニトリル（ＰＡＮ）系繊維を原料として高性能の炭素繊維が製造されることは知られており、航空機を始めとして、スポーツ用品まで幅広い範囲で使用されている。とりわけ、高強度・高弾性の炭素繊維は宇宙航空用途に使用されており、更なる高性能化が求められている。その要求性能の代表的なものが、引張強度向上の要求である。
【０００３】
炭素繊維の繊維軸方向の引張強度を支配する要因の一つには、グラファイト構造の乱れや欠陥が挙げられる。
【０００４】
繊維内部のグラファイト構造を制御し、欠陥を減らすことが炭素繊維の高強度化には求められる。このグラファイト構造の乱れや欠陥を減らすことが出来れば、航空宇宙用途で求められている高性能化を図ること事ができ、航空宇宙分野で使用される炭素繊維材料の飛躍的な向上が期待出来る。
【０００５】
現在、ＰＡＮ系炭素繊維を製造するためには、炭素繊維用前駆体繊維を製造する工程と、その繊維を焼成して炭素繊維を製造する工程の２つの工程が必要となる。これは、ポリマー原液を紡糸して炭素繊維用前駆体繊維を生産する速度と、炭素繊維用前駆体繊維を焼成して炭素繊維を生産する速度が著しく異なることにある。特に、炭素繊維用前駆体繊維を焼成する際の耐炎化処理が最も律速となる。
【０００６】
炭素繊維を製造する上で、この２つの工程（前工程と後工程）が存在することにより、前工程で得られた中間繊維は炭素繊維用前駆体繊維として、一時的に保存する事が一般的である。しかし、この炭素繊維用前駆体繊維は、保存中に乾燥することにより配向緩和が生じやすく、分子配向が緩和した繊維を焼成した場合は、低強度の炭素繊維が得られ、好ましくない。
【０００７】
高強度炭素繊維を得るための製造方法としては、特公昭６１−１４２４８号公報に記載されている様に、ＰＡＮを主成分とする共重合体を紡糸、延伸した後、表面温度１２０〜１８０℃のロールにより乾燥処理して炭素繊維用前駆体繊維を得、得られた前駆体繊維を炭素化することによって炭素繊維を製造する方法が開示されている。
【０００８】
また、特公昭６２−２４５２６号公報に記載されている様に、ＰＡＮを主成分とする共重合体を紡糸、延伸した後、１２０〜１７０℃の熱風中あるいはホットローラー上で熱処理して炭素繊維用前駆体繊維を得、得られた前駆体繊維を炭素化することによって炭素繊維を製造する方法が開示されている。
【０００９】
これらの方法では、乾熱ローラー等を使用して熱処理する事により、一方では炭素繊維用前駆体繊維の配向緩和を抑制する事を可能としている。しかし、他方では熱処理により繊維内の分子の自由度が規制されているため、後の焼成工程における２００〜３００℃での耐炎化工程で、ＰＡＮの分子内環化及び酸化反応や、環化反応後に生ずる分子の高次構造に影響を与えている。その結果その後、高温で焼成して得られる炭素繊維の強度低下を招き、好ましくない面もある。
【００１０】
また、これらの方法では、乾熱ローラーを使用することにより、ローラーとの接触で糸切れが生じ、毛羽が発生して炭素繊維の品位が低下したり、熱処理の工程が追加されることにより、工程が煩雑化するという問題点がある。
【００１１】
【発明が解決しようとする課題】
本発明者等は、上記問題を解決するために種々検討しているうちに、炭素繊維用前駆体繊維を炭素化炉で焼成して炭素化することにより得られる炭素繊維であって、この炭素繊維において固体ＮＭＲ法にて求められた緩和時間（Ｔ１ ｓｈｏｒｔ）と、同炭素繊維の電気抵抗値との間に一定の関係がある炭素繊維は、高強度であることを発見した。この関係を満足する炭素繊維は、炭素繊維用前駆体繊維の熱処理を行わずに、耐炎化工程で、繊維を緊張させながら前駆体繊維の分子内環化及び酸化反応を行い、繊維内部の分子配向性を保持させながら耐炎化処理することにより、工程を煩雑化させることなく製造する事が可能となることを知得し本発明を完成するに至った。
【００１２】
よって、本発明の目的とするところは、上記問題を解決した、グラファイト構造の乱れや欠陥が少ない高強度炭素繊維、及びその製造方法を提供することにある。
【００１３】
【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、以下に記載のものである。
【００１４】
〔１〕 固体ＮＭＲ法にて求められた緩和時間〔Ｔ１ ｓｈｏｒｔ（ｓｅｃ）〕と、Ｘ Ω・ｇ／ｍ２で示した電気抵抗値とが、下式
Ｘ ＞ ２４．３の時、Ｔ１ ≧ −１．３１４Ｘ＋３４．４３
Ｘ ≦ ２４．３の時、Ｔ１ ≧ １．３１４Ｘ−２９．４３
〔但し、２２．４ ≦ Ｘ ≦ ２６．２、Ｔ１ ≧ １〕
を満足する物性を有するポリアクリロニトリル系炭素繊維。
【００１５】
〔２〕 炭素繊維用前駆体繊維が、アクリロニトリルを９４質量％以上含有する単量体を重合した共重合体を含む紡糸溶液を紡糸して得られた前駆体繊維であり、前記紡糸溶液を湿式又は乾湿式紡糸法において紡糸して糸を得、得られた糸を、７０〜１５０℃のドラム式熱風乾燥機で乾燥緻密化した後、飽和水蒸気中、温度１００〜１３０℃、延伸比３．０〜７．０倍の条件で湿熱延伸処理して炭素繊維用前駆体繊維を得、得られた前駆体繊維を、そのまま加熱空気中２２０〜２７０℃、延伸比１．００〜１．１０倍で熱処理して耐炎化繊維を得、得られた耐炎化繊維を、不活性雰囲気中３００〜１０００℃、延伸比１．０〜１．１倍で１段目の炭素化をし、更に不活性雰囲気中３００〜２０００℃で２段目の炭素化をする〔１〕に記載のポリアクリロニトリル系炭素繊維の製造方法。
【００１６】
〔３〕 炭素繊維用前駆体繊維の、比重がアルキメデス法による比重測定で１．１２〜１．１８であり、水分率が１０〜９０質量％である〔２〕に記載のポリアクリロニトリル系炭素繊維の製造方法。
【００１７】
〔４〕 炭素繊維のストランド強度が６００ｋｇｆ／ｍｍ２以上、ストランド伸度が２．０％以上である、〔２〕に記載の炭素繊維の製造方法によって得られるポリアクリロニトリル系炭素繊維。
【００１８】
〔５〕 炭素繊維の単繊維径が３〜８μｍである、〔２〕に記載の炭素繊維の製造方法によって得られるポリアクリロニトリル系炭素繊維。
【００１９】
【発明の実施の形態】
以下、本発明を詳細に説明する。
【００２０】
炭素繊維の繊維軸方向の引張強度を支配する要因には、グラファイト構造の乱れや欠陥が挙げられる。グラファイト構造を制御し、欠陥を減らすことが炭素繊維の高強度化には求められる。グラファイト構造の乱れや欠陥を調べる方法としては、固体ＮＭＲの緩和時間を測定する方法が知られている。
【００２１】
ＮＭＲ測定によって求められる緩和時間〔Ｔ１ ｓｈｏｒｔ成分（後述する方法により１３Ｃ緩和時間Ｔ１として測定される）〕については、グラファイト構造の乱れや欠陥によって生じたラジカルとの常磁性緩和と考えられ、緩和時間Ｔ１が長くなるほどグラファイト構造の乱れが少ないことを表している。即ち、この緩和時間Ｔ１が長いものほど、炭素繊維内部のグラファイト構造の欠陥や乱れが少なく、高強度が得やすい構造であると考えられる。
【００２２】
以上のような緩和時間Ｔ１を用いて表すと、本発明のＰＡＮ系炭素繊維は、固体ＮＭＲ法にて求められた緩和時間〔Ｔ１ ｓｈｏｒｔ（ｓｅｃ）〕と、Ｘ Ω・ｇ／ｍ２で示された電気抵抗値とが、下式を満足することを特徴とする。
Ｘ ＞ ２４．３の時、Ｔ１ ≧ −１．３１４Ｘ＋３４．４３
Ｘ ≦ ２４．３の時、Ｔ１ ≧ １．３１４Ｘ−２９．４３
但し、電気抵抗値Ｘ、緩和時間Ｔ１の範囲は、２２．４ ≦ Ｘ ≦ ２６．２、Ｔ１ ≧ １ である。
【００２３】
また、緩和時間Ｔ１については、電気抵抗値との関係が有り、上記電気抵抗値の範囲で緩和時間Ｔ１が長くなるほど、グラファイト構造の乱れが少ないことから、本発明はＴ１ ≧ １を満足することを特徴とする。
【００２４】
なお、炭素繊維は繊維内部にグラファイト構造を有しているため、電気伝導性を示す。この内部のグラファイト構造が発達するにつれて、電気伝導性が高くなっていく。特に電子は炭素繊維のより表面付近に流れ易いため、炭素繊維表面付近のグラファイト構造の成長を示す指標として、電気抵抗値を用いることができる。この電気抵抗値と焼成温度とは、より高温で焼成された炭素繊維ほど、表面付近のグラファイト構造が成長し、電子が移動しやすいために、電気抵抗値が低い値を示す関係にある。
【００２５】
本発明のＰＡＮ系炭素繊維は、強度の強い炭素繊維である。すなわち、上記の電気抵抗値Ｘと緩和時間Ｔ１との条件を適宜選択することにより、炭素繊維の強度を５５０ｋｇｆ／ｍｍ２（５．４ＧＰａ）以上、より好ましくは５８０ｋｇｆ／ｍｍ２（５．７ＧＰａ）以上、更に好ましくは６００ｋｇｆ／ｍｍ２（５．９ＧＰａ）以上とすることができる。
【００２６】
なお、強度は樹脂含浸ストランド法に従って測定することができる。例えば、炭素繊維束（炭素繊維ストランド）に、エピコート８２８／無水メチルハイミック酸／ベンジルジメチルアミン／アセトン＝１００／９０／１／５０質量部の樹脂含有液を含浸し、得られた樹脂含浸ストランドをプリキュア後、１５０℃で２時間加熱、更に１７０℃で３０分間加熱して硬化させる、ＪＩＳ−Ｒ−７６０１に規定する樹脂含浸ストランド試験法に準拠して測定することができる。
【００２７】
釣竿、ゴルフシャフトなどのエネルギー吸収部材、ＣＮＧタンクや航空宇宙分野の用途では、伸度の高い炭素繊維が要望されている。
【００２８】
本発明のＰＡＮ系炭素繊維は、高強度且つ高伸度の物性を有しているため、これらの用途への展開がより可能となってくる。
【００２９】
従って、炭素繊維の伸度は、２％以上であることが好ましい。伸度の測定については、上記樹脂含浸ストランド試験において求めた強度を弾性率で割ることで計算できる。
【００３０】
得られる炭素繊維について、緩和時間Ｔ１と電気抵抗値Ｘとが上記関係式を満足する、本発明のＰＡＮ系炭素繊維の製造方法を以下に詳しく示す。
【００３１】
即ち本発明のＰＡＮ系炭素繊維の製造方法は、炭素繊維用前駆体繊維が、アクリロニトリルを９４質量％以上、好ましくは９５質量％以上含有する単量体を重合した共重合体を含む紡糸溶液を紡糸して得られた前駆体繊維であり、前記紡糸溶液を湿式又は乾湿式紡糸法において紡糸して糸を得、得られた糸を、７０〜１５０℃、好ましくは８０〜１４０℃のドラム式熱風乾燥機で乾燥緻密化した後、飽和水蒸気中、温度１００〜１３０℃、好ましくは１００〜１２０℃、延伸比３．０〜７．０倍の条件で湿熱延伸処理して炭素繊維用前駆体繊維を得、得られた前駆体繊維を、必要に応じ、純水等で濡れたままの状態（水分率１０〜９０質量％、好ましくは２０〜６０質量％）で収納容器に蓄えた後、熱ローラーで熱処理することなく、そのまま加熱空気中２２０〜２７０℃、延伸比１．００〜１．１０倍、好ましくは１．００〜１．０８倍で熱処理して耐炎化繊維を得、得られた耐炎化繊維を、不活性雰囲気中３００〜１０００℃、好ましくは３００〜９００℃、延伸比１．０〜１．１倍で１段目の炭素化をし、更に不活性雰囲気中３００〜２０００℃、好ましくは３００〜１９００℃で２段目の炭素化をすることを特徴とする。
【００３２】
本発明の炭素繊維の原料であるＰＡＮ系炭素繊維の炭素繊維用前駆体繊維としては、アクリロニトリルと、このアクリロニトリルと共重合可能なオレフィン構造を有するコモノマーとの共重合体を用いることができる。
【００３３】
この共重合体中のアクリロニトリル含有量は９４質量％以上が好ましく、９５質量％以上が更に好ましい。また、共重合体中のコモノマー含有量は６質量％以下が好ましく、５質量％以下が更に好ましい。
【００３４】
コモノマーとしては、アクリル酸、メタクリル酸、イタコン酸等の不飽和カルボン酸及びそれらのアンモニウム塩及びアルキルエステル類、アクリルアミド、メタクリルアミド及びそれらの誘導体等を挙げることができ、それらを２種類以上組み合わせることもできる。
【００３５】
特に低コスト化を進める上で、コモノマーとして不飽和カルボン酸を用いることは、耐炎化反応を促進させる意味で好ましいものである。不飽和カルボン酸の共重合体中の含有量は、０．１〜３質量％であることが好ましく、特に０．５〜２質量％がより好ましい。
【００３６】
不飽和カルボン酸の例としては、アクリル酸、クロトン酸、メタクリル酸、イタコン酸、マレイン酸、フマル酸等をあげることができる。
【００３７】
なお、高強度の炭素繊維を得る為には、炭素繊維用前駆体繊維の分子配向性を高くする必要性がある。そのため、炭素繊維用前駆体繊維製造工程で、高延伸しやすくする為に、炭素繊維用前駆体繊維中の分子自由度を高くする目的で、不飽和カルボン酸エステルを共重合することが好ましい。不飽和カルボン酸エステルの共重合体中の含有量は、０．１〜６質量％が好ましく、２〜５質量％が更に好ましい。
【００３８】
不飽和カルボン酸エステルの例としては、アクリル酸アルキル、メタクリル酸アルキルがある。好ましいアルキル基の長さは、炭素数（Ｃ）が１〜４であり、特に好ましいアルキル基の長さは、Ｃが１〜２である。
【００３９】
上記モノマーとコモノマーとの重合方法としては、溶液重合、懸濁重合、乳化重合等を用いることができるが、そのまま紡糸できることにより溶液重合が最も好ましい。
【００４０】
紡糸する際の液（紡糸原液）は、ジメチルホルムアミド、ジメチルスルホキシド、ジメチルアセトアミド等の有機溶媒や、硝酸、塩化亜鉛水溶液、ロダン塩水溶液等の無機溶媒を溶媒として用い、上記モノマーとコモノマーとを重合させたポリマー溶液を、紡糸原液とすることが好ましい。その中でも、高分子量ポリマーを溶解させるのに優位性がある塩化亜鉛水溶液を溶媒に用いるのがより好ましい。
【００４１】
紡糸は、低温に冷却した凝固液（紡糸する際の溶媒−水混合液）を入れた凝固浴中に直接紡出する湿式紡糸が好ましい。また、空気中にまず吐出させた後、３〜５ｍｍ程度の空間を有して凝固浴に投入し凝固させる乾湿式紡糸法でもよい。
【００４２】
紡出糸は、濃度勾配をかけた凝固浴で徐々に凝固させ、同時に溶媒を除去しながら、水洗して直接浴中延伸する。浴中延伸では、数種の水洗〜熱水浴中で、延伸比２〜６倍に紡出糸を延伸していく。
【００４３】
浴中延伸の条件については、上記凝固浴温度と、水洗温度又は熱水浴温度との温度勾配は最大で９８℃にするのが好ましい。ここで、高強度の炭素繊維を得る為には、より高温側の熱水浴中で延伸することが特に好ましい。
【００４４】
その後、乾燥緻密化に先立って、耐熱性向上や紡糸安定性を目的として、親水基を持つ浸透性油剤とシリコーン系油剤を組み合わせた炭素繊維用前駆体繊維油剤を付与することが、高強度の炭素繊維を品位よく得る点から好ましい。
【００４５】
浸透性油剤は官能基として、スルフィン酸、スルホン酸、燐酸、カルボン酸やそのアルカリ金属塩、アンモニウム塩、その誘導体を有するものが好ましい。これらの浸透性油剤のうちでも、炭素繊維の高強度化の妨げにならず、高熱の環境下でも耐熱酸化性に優れた燐酸のアンモニウム塩若しくはその誘導体を用いるのが特に好ましい。
【００４６】
シリコーン系油剤は、未変性あるいは変性されたもののいずれでもよいが、中でもエポキシ変性シリコーン、エチレンオキサイド変性シリコーン、ポリシロキサン、アミノ変性シリコーンが好ましく、特に好ましくはアミノ変性シリコーンである。
【００４７】
乾燥緻密化においては、温度勾配をかけた幾層にも連なる部屋を有するドラム式熱風乾燥機で乾燥することが好ましい。乾燥温度については、より緻密性が向上するように、７０〜１５０℃で適宜調節して行うことが好ましく、８０〜１４０℃で適宜調節して行うことが更に好ましい。乾燥時間については、１〜１０分間が好ましい。
【００４８】
また、高温での延伸を行うことによって、作製される炭素繊維用前駆体繊維の繊度や分子配向を整えることができる。特に加圧スチーム中での熱延伸は有効である。この熱延伸の条件は、炭素繊維用前駆体繊維の緻密性に大きな影響を与える。高強度の炭素繊維を得る為には、緻密性の高い炭素繊維用前駆体繊維を作製することが好ましい。
【００４９】
緻密性を評価する手段として、アルキメデス法による見かけ比重の評価、Ｌ値の測定等がある。
【００５０】
Ｌ値の測定では、標準白板に対する試料の明度をハンター色差計によって測定し、基準炭素繊維用前駆体繊維に対する明度を算出する。この値は、繊維中のボイドが多い場合に高い値を示し、緻密性が高くなると基準炭素繊維用前駆体繊維の値に近くなる。
【００５１】
炭素繊維用前駆体繊維は約５ｃｍに切断してハンドカードにて綿上に開繊し２ｇをとる。油圧プレス機でプレスしてアニソール中に浸漬し、脱泡して、ハンター色差計にかけＬ値〔Ｌ値＝測定値−標準値（５）〕を測定する。このＬ値が、好ましくは２０以下、より好ましくは１８以下、更に好ましくは１６以下になるように、乾燥緻密化及び熱延伸条件を変更する。
【００５２】
アルキメデス法による比重の測定は、炭素繊維用前駆体繊維を約２ｇ採取し、直径３ｃｍ以内の円状にまとめ、形状が崩れないようにする。測定溶剤には、水、若しくは親水性溶媒が好ましい。なお、炭素繊維用前駆体繊維に付与させた油剤の影響等で脱泡時に泡が取れ難い場合がある。この場合は、エタノール若しくはアセトンを用いるのが最も好ましい。
【００５３】
次に、上記円状のサンプルを溶媒中に浸漬し、減圧下で脱泡する。常温下で、溶媒中の質量を測定し、更にサンプルを加熱乾燥して乾燥質量を求め、炭素繊維用前駆体繊維の見かけ比重を求める。この比重は、ＰＡＮの比重１．１８より低くなるが、好ましくは１．１２〜１．１８、より好ましくは１．１４〜１．１７、更に好ましくは１．１５〜１．１７になるように、Ｌ値と同様に乾燥緻密化及び熱延伸条件を変更する。
【００５４】
本発明において、炭素繊維用前駆体繊維の単繊維繊度は、強度向上の観点から、耐炎化工程での酸化斑（むら）が生じ難いように、細い方が好ましい。具体的には、１．２ｄ以下が好ましく、０．８〜０．５ｄがより好ましく、０．７〜０．５ｄが更に好ましい。
【００５５】
得られた炭素繊維用前駆体繊維は、分子配向の緩和が生じ難いように、糸（前駆体繊維）の乾燥を防ぐ必要がある。そのため、前駆体繊維の水分率は、好ましくは１０〜９０質量％、特に好ましくは２０〜６０質量％に保つ必要がある。炭素繊維用前駆体繊維の水分率が低くなりすぎると、集束性が低下することによって取扱性が悪くなり、また、水分率が高すぎると水の表面張力により、耐炎化工程中のローラーに巻き付きやすくなりトラブルの原因になる。
【００５６】
上記のようにして作製され、適宜調節された水分率を有する炭素繊維用前駆体繊維は、密閉容器中に一時保存することが可能である。保存容器としては、円筒形の容器が好ましく、ビニール袋も好ましい。但し、保存する際は、内部の水分が保持できるものでなければいけない。
【００５７】
なお、本発明で用いられる炭素繊維用前駆体繊維は、乾熱ローラー等の熱処理を施しておらず、湿熱延伸後の糸を用いているため、そのままの状態で保存すると、繊維の配向緩和が生じ、炭素繊維の強度低下を招いてしまう。
【００５８】
この炭素繊維用前駆体繊維の配向緩和を防ぐ方法としては、以下に示す、従来既存の技術が応用できる。
【００５９】
即ち、炭素繊維用前駆体繊維の製造後の後工程（耐炎化工程、炭素化工程）において、繊維内部の分子配向性を向上させるための方法として、湿熱延伸して前駆体繊維の糸を製造した後における、純水等で濡れたままの状態の糸を、収納容器に蓄える方法が利用できる。
【００６０】
この濡れたまま糸を収納容器に蓄える方法によれば、繊維が乾燥することによって生ずる配向緩和や空気による酸化、空気中の異物の付加等が防止でき、高強度の炭素繊維を製造する事ができる。
【００６１】
次いで、上記前工程で製造した炭素繊維用前駆体繊維を、耐炎化工程で耐炎化処理する。この耐炎化処理は、例えば加熱空気中２室以上に分かれた横型炉で、多段ローラー群を介して、２２０〜２７０℃、延伸比１．００〜１．１０倍、好ましくは１．００〜１．０８倍で熱処理して行うことができる。
【００６２】
この耐炎化工程では、前駆体繊維成分ＰＡＮの分子内環化及び酸化反応、及び糸の物理的な収縮が生ずる。この耐炎化工程の初期の段階では、糸の物理的な収縮が生ずるが、上記延伸比の緊張化で行うことにより、分子の配向緩和を抑制することができる。
【００６３】
また、ＰＡＮの分子内環化における分子の再配列化についても、緊張化で行うことにより、再配列化の際の配向性を、高く保持しながら耐炎化を行うことが可能となる。
【００６４】
このように、分子の高次構造を制御することにより、その後の、２段での炭素化炉における高温焼成で得られる炭素繊維のグラファイト構造の乱れを制御することが可能となり、高強度の炭素繊維を得ることが可能となる。
【００６５】
これに対し、耐炎化の延伸比が低いと、分子配向が緩和されてしまう為好ましくない。また、通常耐炎化が進むにつれて繊維が脆弱化するので、延伸比が高すぎると、単糸切れによる毛羽が発生し、後に得られる炭素繊維の品位を著しく低下させるので好ましくない。
【００６６】
従って、耐炎化時の延伸比については、１．００〜１．１０倍で熱処理することが好ましく、１．００〜１．０８倍で熱処理で熱処理することが更に好ましい。
【００６７】
なお、耐炎化の度合いは、耐炎化処理をした糸（耐炎化繊維）の比重を測定することにより評価できる。比重の測定は、炭素繊維用前駆体繊維と同様にアルキメデス法を用いてできる。
【００６８】
耐炎化繊維の比重は、好ましくは１．２０〜１．４０、より好ましくは１．３０〜１．３８、更に好ましくは１．３２〜１．３７がよい。
【００６９】
上記耐炎化繊維は、従来の公知の方法を採用して炭素化することができる。例えば、窒素雰囲気下９００℃以下で３室以上に分けた焼成炉（第一炭素化炉）で徐々に温度勾配をかけ、耐炎化繊維の張力を制御して緊張下で１段目の炭素化（予備炭素化）をする。
【００７０】
この予備炭素化の度合いは、予備炭素化処理後の繊維の比重を測定することにより評価できる。比重の測定は、炭素繊維用前駆体繊維と同様にアルキメデス法を用いてできる。
【００７１】
予備炭素化処理後の繊維の比重は、好ましくは１．４５〜１．６０、より好ましくは１．４８〜１．５５、更に好ましくは１．５０〜１．５３である。
【００７２】
より炭素化を進め且つグラファイト化（炭素の高結晶化）を進める為に、窒素等の不活性ガス雰囲気下で昇温し、２室以上に分けた焼成炉（第二炭素化炉）で徐々に温度勾配をかけ、糸（予備炭素化繊維）の張力を制御して弛緩条件で焼成する。弛緩条件については、好ましくは０．９〜１．０倍の範囲、より好ましくは０．９２〜０．９９倍の範囲、更に好ましくは０．９５〜０．９８倍の範囲がよい。
【００７３】
焼成温度については、第二炭素化炉で温度勾配を徐々にかけていき、最高温度領域で、１５００℃から２０００℃、好ましくは１５００℃から１９００℃、より好ましくは、１５００℃から１８００℃、更に好ましくは、１５００℃から１７００℃がよい。
【００７４】
温度勾配については、好ましくは、２００℃／分以上の昇温、より好ましくは３００〜６００℃／分の昇温、更に好ましくは、４００〜６００℃／分の昇温である。生産性やコスト面から炉長があまり長すぎるのは好ましくなく、また、炉内の高温部での滞留時間が長くなると、グラファイト化が進み過ぎ、脆性化した炭素繊維が得られることになるので好ましくない。
【００７５】
得られた炭素繊維は、酸若しくはアルカリ水溶液を用いた電解層中で電解酸化処理して、表面処理する。炭素繊維を樹脂と複合化させて材料として使用する場合は、炭素繊維とマトリックス樹脂との親和性や接着性を向上させる目的で行う必要がある。
【００７６】
電解処理の電解液としては、酸性若しくはアルカリ性のものが使用できる。酸性のものとして、硝酸、硫酸、塩酸、酢酸、それらのアンモニウム塩、硫酸水素アンモニウム等がある。
【００７７】
これらの電解液のうちでも、好ましくは、弱酸性を示す硫酸アンモニウム、硫酸水素アンモニウム等のアンモニウム塩がよい。
【００７８】
なお、アルカリ性のものは、水酸化カリウム、水酸化ナトリウム、アンモニア等が挙げられるが、アルカリ金属を含む電解液を用いると炭素繊維の耐熱酸化性が低下し、また、樹脂の硬化を妨げる働きがあるため、あまり好ましくない。
【００７９】
電解酸化する際の電気量は、炭素繊維外層部のグラファイト化の度合いに伴い調整する必要がある。樹脂との複合化をすることを踏まえると、親和性を向上する炭素繊維１ｇ当り５ｃ以上が好ましい。なお、電気量が多すぎると炭素繊維表面の小規模欠陥を取り除く以上に表面が酸化され、欠陥を新たに生じさせる場合があり、多くとも４０ｃ以下が好ましい。
【００８０】
また、電解酸化による表面処理を施した後は、電解液やその副生成物等が炭素繊維に付着しているので、よく水洗し、乾燥する必要がある。さらに、炭素繊維の後加工をしやすくし、取扱性を向上させる目的で、サイジング処理する。サイジング方法は、従来の公知の方法で行うことができ、サイジング剤は、用途に即して適宜組成を変更して使用し、均一付着させた後に、乾燥する。付着量は、好ましくは、０．１〜２．０質量％、より好ましくは、０．５〜１．５質量％である。
【００８１】
【実施例】
本発明を以下の実施例及び比較例により具体的に説明する。また、以下の実施例及び比較例の条件により前駆体繊維、耐炎化繊維及び炭素繊維を作製し、得られた耐炎化繊維及び炭素繊維の諸物性値を、前述又は以下の方法により測定した。
【００８２】
緩和時間Ｔ１（１３Ｃ緩和時間Ｔ１）：ＢＲＵＫＥＲ社製ＤＳＸ３００ＷＢを用い、長さ１５ｍｍの繊維状試料を繊維軸方向に揃えてＮＭＲ試料管に充填し、観測周波数７５．５ＭＨｚ、スペクトル幅３０ｋＨｚ、π／２パルス３．０μｓ、インバージョンリカバリー（Ｉｎｖｅｒｓｉｏｎ ｒｅｃｏｖｅｒｙ）法でスタティック（ｓｔａｔｉｃ）の条件で室温にて測定した。
【００８３】
緩和時間解析にはＮＭＲプローブの１３Ｃにおけるバックグランドの影響が少ない約１７０ｐｐｍ付近のスペクトル強度を用い、２成分（Ｔ１ ｓｈｏｒｔ、ｌｏｎｇ）の指数（ｅｘｐｏｎｅｎｔｉａｌ）として解析した。
【００８４】
電気抵抗値の測定に関しては、ＪＩＳ−Ｒ−７６０１に規定する体積抵抗率のストランドの試験Ａ法を参考に行うことができる。ただし、ＪＩＳ−Ｒ−７６０１では、電気抵抗値に、炭素繊維の比重を掛け合わせた体積抵抗率を求めており、電気抵抗値〔Ｘ（Ω・ｇ／ｍ２）〕を求めるには、下式を用いて行った。
Ｘ ＝ Ｒｂ×ｔ／Ｌ
Ｒｂ：試験片長Ｌのときの電気抵抗（Ω）、ｔ：試験片の繊度（ｔｅｘ）、Ｌ：抵抗測定時の試験片長（ｍ）
なお、抵抗測定時の試験片長については、１ｍ程度で測定することが好ましい。
【００８５】
実施例１
塩化亜鉛水溶液を溶媒とする溶液重合法により、アクリロニトリル９５質量％、アクリル酸メチル４質量％、イタコン酸１質量％とからなる重合度が１．６、ポリマー濃度８質量％のポリマー原液を得た。
【００８６】
このポリマー原液を、１２０００フィラメント用の口金を通して、５℃の２５質量％塩化亜鉛水溶液中に吐出して凝固させ、凝固糸を得た。
【００８７】
この凝固糸を水洗し、９０℃で熱延伸し、アミノ変性シリコーン系油剤と燐酸アンモニウム誘導体を有する浸透性油剤を同量で０．１質量％付着させ、ドラム式熱風乾燥機を用いて７０〜１４０℃で乾燥緻密化、１００〜１２０℃で延伸比５．８倍で湿熱延伸し、水分率を４０質量％に調整して、単繊維繊度が０．６ｄの炭素繊維用前駆体繊維を得た。繊維比重は、１．１６、Ｌ値は１６であった。
【００８８】
得られた炭素繊維用前駆体繊維を空気中２３０℃から２６０℃の温度分布を持った雰囲気下で、延伸比１．０６倍で耐炎化させた。耐炎化糸の比重は１．３５であった。
【００８９】
この耐炎化糸を、不活性雰囲気中３００〜５００℃の温度分布を持った第一炭素化炉において、延伸比１．０６倍で炭素化させ、更に、不活性雰囲気中で最高温度が１６００℃になるように設定（雰囲気中の温度分布：３００〜１６００℃）した第二炭素化炉で炭素化させた。
【００９０】
次に、１０質量％硫酸アンモニウム水溶液を電解液として、炭素繊維１ｇ当り１３ｃの電解酸化処理をした後、水洗し、更にサイジング処理してサイジング剤−水エマルジョン溶液を３質量％付着させ、これを１５０℃で乾燥した。サイジング剤の付着量は１質量％であった。このようにして得られた炭素繊維の物性を表１に示す。
【００９１】
実施例２
第二炭素化炉の最高温度領域を１６７０℃に変更（雰囲気中の温度分布：３００〜１６７０℃）した以外は、実施例１と同様に行った。このようにして得られた炭素繊維の物性を表１に示す。
【００９２】
実施例３
第二炭素化炉の最高温度領域を１７２０℃に変更（雰囲気中の温度分布：３００〜１７２０℃）した以外は、実施例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９３】
実施例４
第二炭素化炉の最高温度領域を１７８０℃に変更（雰囲気中の温度分布：３００〜１７８０℃）した以外は、実施例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９４】
実施例５
第二炭素化炉の最高温度領域を１８３０℃に変更（雰囲気中の温度分布：３００〜１８３０℃）した以外は、実施例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９５】
実施例６
第二炭素化炉の最高温度領域を１９００℃に変更（雰囲気中の温度分布：３００〜１９００℃）した以外は、実施例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９６】
比較例１
実施例１で得た炭素繊維用前駆体繊維を、空気中２３０℃から２６０℃の温度分布を持った雰囲気下で、延伸比０．９５倍で耐炎化させた。耐炎化糸の比重は１．３６であった。
【００９７】
この耐炎化糸を、不活性雰囲気中３００〜５００℃の温度、延伸比１．０６倍で炭素化させ、以下、実施例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９８】
比較例２
第二炭素化炉の最高温度領域を１７００℃に変更（雰囲気中の温度分布：３００〜１７００℃）した以外は、比較例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【００９９】
比較例３
第二炭素化炉の最高温度領域を１７８０℃に変更（雰囲気中の温度分布：３００〜１７８０℃）した以外は、比較例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【０１００】
比較例４
第二炭素化炉の最高温度領域を１８５０℃に変更（雰囲気中の温度分布：３００〜１８５０℃）した以外は、比較例１と同様にして炭素繊維を作製した。このようにして得られた炭素繊維の物性を表１に示す。
【０１０１】
比較例５
実施例１で得た湿熱延伸処理後の凝固糸を、定長下１２０℃で乾熱ローラーを用いて熱処理をして、単繊維繊度が０．６ｄの炭素繊維用前駆体繊維を得た。繊維比重は、１．１７、Ｌ値は１５、水分率は３質量％であった。
【０１０２】
得られた炭素繊維用前駆体繊維を空気中２３０℃から２６０℃の温度分布を持った雰囲気下で、延伸比１．０６倍で耐炎化させた。耐炎化糸の比重は１．３５であった。
【０１０３】
この耐炎化糸の焼成処理、その後の電解酸化処理、更にサイジング処理については、実施例１と同様に行い、炭素繊維を得た。このようにして得られた炭素繊維の物性を表１に示す。
【０１０４】
比較例６
乾熱ローラーを用いて熱処理温度を１８０℃に変更した以外は、比較例２と同様に炭素繊維用前駆体繊維を作製した。単繊維繊度は０．６ｄ、比重は１．１８、Ｌ値は１４、水分率は１質量％以下であった。
【０１０５】
得られた炭素繊維用前駆体繊維を空気中２３０℃から２６０℃の温度分布を持った雰囲気下で、延伸比１．０６倍で耐炎化させた。耐炎化糸の比重は１．３６であった。
【０１０６】
この耐炎化糸の焼成処理、その後の電解酸化処理、更にサイジング処理については、実施例１と同様に行い、炭素繊維を得た。このようにして得られた炭素繊維の物性を表１に示す。
【０１０７】
【表１】
実施例１〜６及び比較例１〜６において得られた炭素繊維のＮＭＲ測定における１３Ｃ緩和時間（Ｔ１ ｓｈｏｒｔ）と、電気抵抗値Ｘとをプロットしたグラフを図１に示す。
【０１０９】
図１に示されるように、実施例１〜６におけるプロット○は全て、下式
Ｘ ＞ ２４．３の時、Ｔ１ ≧ −１．３１４Ｘ＋３４．４３
Ｘ ≦ ２４．３の時、Ｔ１ ≧ １．３１４Ｘ−２９．４３
〔但し、２２．４ ≦ Ｘ ≦ ２６．２、Ｔ１ ≧ １〕
で表される折れ線の上方にあり、比較例１〜６におけるプロット×は全て、上式で表される折れ線の下方にあることが解る。
【０１１０】
【発明の効果】
本発明のＰＡＮ系炭素繊維は、固体ＮＭＲ法にて求められた緩和時間（Ｔ１ ｓｈｏｒｔ）と、電気抵抗値との関係について、所定の関係式を満足させることにより、グラファイト構造の乱れや欠陥が少ない高強度且つ高伸度の炭素繊維とすることができる。
【図面の簡単な説明】
【図１】実施例１〜６及び比較例１〜６において得られた炭素繊維のＮＭＲ測定における１３Ｃ緩和時間（Ｔ１ ｓｈｏｒｔ）と、電気抵抗値Ｘとの関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-strength carbon fiber and a method for producing the same.
[0002]
[Prior art]
BACKGROUND ART Conventionally, it has been known that high-performance carbon fibers are produced from polyacrylonitrile (PAN) fibers as raw materials, and are used in a wide range of fields, including aircraft and sporting goods. In particular, high-strength and high-elasticity carbon fibers are used for aerospace applications, and further higher performance is required. Typical of the required performance is a demand for improvement in tensile strength.
[0003]
One of the factors governing the tensile strength of carbon fibers in the fiber axis direction is a disorder or defect in the graphite structure.
[0004]
Controlling the graphite structure inside the fiber and reducing defects are required for increasing the strength of the carbon fiber. If the disorder and defects of the graphite structure can be reduced, the high performance required for aerospace applications can be achieved, and a dramatic improvement in the carbon fiber material used in the aerospace field can be expected. .
[0005]
At present, manufacturing a PAN-based carbon fiber requires two steps, a step of manufacturing a precursor fiber for a carbon fiber and a step of firing the fiber to manufacture a carbon fiber. This is because the speed of producing the precursor fiber for carbon fiber by spinning the polymer stock solution is significantly different from the speed of producing the carbon fiber by firing the precursor fiber for carbon fiber. In particular, the flame-resistant treatment at the time of firing the precursor fiber for carbon fiber is the most rate-determining.
[0006]
In the production of carbon fiber, the presence of these two steps (pre-step and post-step) makes it possible to temporarily store the intermediate fiber obtained in the previous step as a precursor fiber for carbon fiber. It is a target. However, this precursor fiber for carbon fiber tends to relax the orientation by drying during storage, and when the fiber whose molecular orientation is relaxed is fired, a low-strength carbon fiber is obtained, which is not preferable.
[0007]
As a production method for obtaining a high-strength carbon fiber, as described in JP-B-61-14248, after spinning and stretching a copolymer containing PAN as a main component, a surface temperature of 120 to 180 ° C. A method for producing a carbon fiber by subjecting a precursor fiber for a carbon fiber to a drying treatment with a roll of (i) and carbonizing the obtained precursor fiber is disclosed.
[0008]
Further, as described in JP-B-62-24526, a copolymer containing PAN as a main component is spun and drawn, and then heat-treated in hot air at 120 to 170 ° C. or on a hot roller to produce carbon fiber. A method for producing a carbon fiber by obtaining a precursor fiber for use and carbonizing the obtained precursor fiber is disclosed.
[0009]
In these methods, by performing a heat treatment using a dry heat roller or the like, on the other hand, it is possible to suppress the relaxation of the orientation of the precursor fiber for carbon fiber. However, on the other hand, since the degree of freedom of the molecules in the fiber is regulated by the heat treatment, the PAN and cyclization reaction and the intramolecular PAN reaction in the subsequent sintering process at 200 to 300 ° C. It affects the higher order structure of the molecules that occur later. As a result, the strength of the carbon fiber obtained by firing at a high temperature thereafter is reduced, which is not preferable.
[0010]
Also, in these methods, by using a dry heat roller, yarn breakage occurs in contact with the roller, fuzz is generated, the quality of the carbon fiber is reduced, or a heat treatment step is added, There is a problem that the process is complicated.
[0011]
[Problems to be solved by the invention]
The present inventors have made various studies to solve the above problems, and among them, carbon fibers obtained by firing and carbonizing a precursor fiber for carbon fiber in a carbonization furnace, Relaxation time (T 1 (short) and the electrical resistance value of the carbon fiber have been found to have a high strength. Carbon fibers satisfying this relationship are subjected to an intramolecular cyclization and oxidation reaction of the precursor fibers while tensioning the fibers in the flame-proofing step without performing a heat treatment of the precursor fibers for carbon fibers, and thereby producing the molecules inside the fibers. It has been found that by performing the flameproofing treatment while maintaining the orientation, it is possible to manufacture without complicating the process, thereby completing the present invention.
[0012]
Accordingly, it is an object of the present invention to provide a high-strength carbon fiber which solves the above-mentioned problem and has less disorder and defects in a graphite structure, and a method for producing the same.
[0013]
[Means for Solving the Problems]
The present invention that achieves the above object is as described below.
[0014]
[1] Relaxation time [T 1 short (sec)] and X Ω · g / m 2 The electrical resistance value shown by
When X> 24.3, T 1 ≧ -1.314X + 34.43
When X ≦ 24.3, T 1 ≧ 1.314X-29.43
[However, 22.4 ≦ X ≦ 26.2, T 1 ≧ 1]
A polyacrylonitrile-based carbon fiber having physical properties satisfying the following.
[0015]
[2] The precursor fiber for a carbon fiber is a precursor fiber obtained by spinning a spinning solution containing a copolymer obtained by polymerizing a monomer containing 94% by mass or more of acrylonitrile, and the spinning solution is wet-processed. Alternatively, the yarn is spun in a dry-wet spinning method to obtain a yarn, and the obtained yarn is dried and densified by a drum-type hot-air dryer at 70 to 150 ° C, and then stretched in saturated steam at a temperature of 100 to 130 ° C and a draw ratio of 3. The precursor fiber for carbon fiber is obtained by wet heat drawing under the condition of 0 to 7.0 times, and the obtained precursor fiber is directly heated to 220 to 270 ° C in a heated air at a draw ratio of 1.00 to 1.10 times. Heat-treated to obtain an oxidized fiber, and the obtained oxidized fiber is subjected to first-stage carbonization in an inert atmosphere at 300 to 1000 ° C. and a draw ratio of 1.0 to 1.1 times, and is further inerted. The second stage of carbonization at 300 to 2000 ° C in an atmosphere is performed according to [1]. Manufacturing method of the acrylonitrile-based carbon fiber.
[0016]
[3] The polyacrylonitrile-based carbon fiber according to [2], wherein the specific gravity of the precursor fiber for a carbon fiber is 1.12 to 1.18, and the water content is 10 to 90% by mass, as measured by a specific gravity according to the Archimedes method. Manufacturing method.
[0017]
[4] Strand strength of carbon fiber is 600 kgf / mm 2 As described above, polyacrylonitrile-based carbon fibers obtained by the method for producing carbon fibers according to [2], wherein the strand elongation is 2.0% or more.
[0018]
[5] A polyacrylonitrile-based carbon fiber obtained by the method for producing a carbon fiber according to [2], wherein the carbon fiber has a single fiber diameter of 3 to 8 µm.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0020]
Factors governing the tensile strength of carbon fibers in the fiber axis direction include disorder and defects in the graphite structure. Controlling the graphite structure and reducing defects are required to increase the strength of carbon fibers. As a method of examining the disorder or defect of the graphite structure, a method of measuring the relaxation time of solid-state NMR is known.
[0021]
Relaxation time [T 1 short component (by the method described below) 13 C relaxation time T 1 )] Is considered to be paramagnetic relaxation with radicals generated by the disorder or defect of the graphite structure, and the relaxation time T 1 It means that the longer the is, the less the disorder of the graphite structure. That is, the relaxation time T 1 It is considered that the longer the length is, the fewer the defects and disorder of the graphite structure inside the carbon fiber, and the higher the strength of the structure.
[0022]
Relaxation time T as described above 1 The PAN-based carbon fiber of the present invention has a relaxation time [T 1 short (sec)] and X Ω · g / m 2 Is characterized by satisfying the following expression.
When X> 24.3, T 1 ≧ -1.314X + 34.43
When X ≦ 24.3, T 1 ≧ 1.314X-29.43
However, electric resistance value X, relaxation time T 1 Range is 22.4 ≦ X ≦ 26.2, T 1 ≧ 1.
[0023]
The relaxation time T 1 Has a relationship with the electric resistance, and the relaxation time T falls within the range of the electric resistance. 1 The present invention is based on the fact that the longer the 1 Satisfies ≧ 1.
[0024]
In addition, since the carbon fiber has a graphite structure inside the fiber, it shows electric conductivity. As the internal graphite structure develops, the electrical conductivity increases. In particular, since the electrons are more likely to flow near the surface of the carbon fiber, the electric resistance value can be used as an index indicating the growth of the graphite structure near the surface of the carbon fiber. The electrical resistance value and the firing temperature are in a relationship such that the higher the carbon fiber fired at a higher temperature, the lower the electrical resistance value because the graphite structure near the surface grows and electrons move more easily.
[0025]
The PAN-based carbon fiber of the present invention is a strong carbon fiber. That is, the above-mentioned electric resistance value X and relaxation time T 1 By appropriately selecting the conditions described above, the strength of the carbon fiber is set to 550 kgf / mm. 2 (5.4 GPa) or more, more preferably 580 kgf / mm 2 (5.7 GPa) or more, more preferably 600 kgf / mm 2 (5.9 GPa) or more.
[0026]
The strength can be measured according to the resin impregnated strand method. For example, a carbon fiber bundle (carbon fiber strand) is impregnated with a resin-containing liquid of Epicoat 828 / methylhymic anhydride / benzyldimethylamine / acetone = 100/90/1/50 parts by mass, and the obtained resin-impregnated strand is obtained. Is cured at 150 ° C. for 2 hours after curing, and further heated at 170 ° C. for 30 minutes for curing, which can be measured according to a resin-impregnated strand test method specified in JIS-R-7601.
[0027]
Carbon fibers with high elongation are demanded for energy absorbing members such as fishing rods and golf shafts, CNG tanks and aerospace applications.
[0028]
Since the PAN-based carbon fiber of the present invention has high strength and high elongation properties, it can be more developed for these uses.
[0029]
Therefore, the elongation of the carbon fibers is preferably 2% or more. The elongation can be measured by dividing the strength obtained in the above-mentioned resin-impregnated strand test by the elastic modulus.
[0030]
For the obtained carbon fiber, the relaxation time T 1 The method for producing a PAN-based carbon fiber of the present invention, in which the electrical resistance X satisfies the above relational expression, will be described in detail below.
[0031]
That is, in the method for producing a PAN-based carbon fiber of the present invention, a spinning solution containing a copolymer in which a precursor fiber for carbon fiber contains a monomer polymerized with acrylonitrile of 94% by mass or more, preferably 95% by mass or more. A precursor fiber obtained by spinning, wherein the spinning solution is spun in a wet or dry-wet spinning method to obtain a yarn, and the obtained yarn is subjected to a drum-type process at 70 to 150 ° C, preferably 80 to 140 ° C. After being dried and densified by a hot air drier, the precursor for carbon fiber is subjected to wet heat drawing in saturated steam at a temperature of 100 to 130 ° C., preferably 100 to 120 ° C. and a draw ratio of 3.0 to 7.0 times. The fibers are obtained, and the obtained precursor fibers are stored in a storage container, if necessary, in a state of being kept wet with pure water or the like (water content: 10 to 90% by mass, preferably 20 to 60% by mass). Without heat treatment with a heat roller Heat treatment is performed in a heated air at 220 to 270 ° C. and a draw ratio of 1.00 to 1.10 times, preferably 1.00 to 1.08 times to obtain an oxidized fiber, and the obtained oxidized fiber is subjected to an inert atmosphere. The first stage carbonization is performed at a medium temperature of 300 to 1000 ° C, preferably 300 to 900 ° C, and a draw ratio of 1.0 to 1.1 times, and further at 300 to 2000 ° C, preferably 300 to 1900 ° C in an inert atmosphere. The second stage of carbonization is characterized.
[0032]
As the precursor fiber for the carbon fiber of the PAN-based carbon fiber which is a raw material of the carbon fiber of the present invention, a copolymer of acrylonitrile and a comonomer having an olefin structure copolymerizable with the acrylonitrile can be used.
[0033]
The acrylonitrile content in this copolymer is preferably at least 94% by mass, more preferably at least 95% by mass. Further, the comonomer content in the copolymer is preferably 6% by mass or less, more preferably 5% by mass or less.
[0034]
Examples of the comonomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid and their ammonium salts and alkyl esters, acrylamide, methacrylamide, and their derivatives, and a combination of two or more thereof. You can also.
[0035]
In particular, in order to promote cost reduction, it is preferable to use an unsaturated carboxylic acid as a comonomer from the viewpoint of accelerating a flame resistance reaction. The content of the unsaturated carboxylic acid in the copolymer is preferably 0.1 to 3% by mass, more preferably 0.5 to 2% by mass.
[0036]
Examples of unsaturated carboxylic acids include acrylic acid, crotonic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and the like.
[0037]
In order to obtain high-strength carbon fibers, it is necessary to increase the molecular orientation of the precursor fibers for carbon fibers. Therefore, it is preferable to copolymerize an unsaturated carboxylic acid ester for the purpose of increasing the degree of molecular freedom in the precursor fiber for carbon fiber in order to facilitate high drawing in the process for producing the precursor fiber for carbon fiber. The content of the unsaturated carboxylic acid ester in the copolymer is preferably from 0.1 to 6% by mass, more preferably from 2 to 5% by mass.
[0038]
Examples of unsaturated carboxylic esters include alkyl acrylates and alkyl methacrylates. A preferred length of the alkyl group is 1 to 4 carbon atoms (C), and a particularly preferred length of the alkyl group is 1 to 2 carbon atoms.
[0039]
As a polymerization method of the above-mentioned monomer and comonomer, solution polymerization, suspension polymerization, emulsion polymerization and the like can be used, but solution polymerization is most preferable because spinning can be performed as it is.
[0040]
The spinning solution (spinning solution) is prepared by polymerizing the above monomer and comonomer using an organic solvent such as dimethylformamide, dimethylsulfoxide, and dimethylacetamide, or an inorganic solvent such as nitric acid, zinc chloride aqueous solution, and rodane salt aqueous solution. It is preferable that the polymer solution thus obtained is used as a spinning solution. Among them, it is more preferable to use, as a solvent, an aqueous solution of zinc chloride which has an advantage in dissolving a high molecular weight polymer.
[0041]
The spinning is preferably wet spinning which is directly spun into a coagulation bath containing a coagulation liquid cooled at a low temperature (solvent-water mixture during spinning). Alternatively, a dry-wet spinning method in which the material is first discharged into the air and then put into a coagulation bath with a space of about 3 to 5 mm to coagulate may be used.
[0042]
The spun yarn is gradually coagulated in a coagulation bath having a concentration gradient, washed with water and stretched directly in the bath while simultaneously removing the solvent. In the in-bath drawing, the spun yarn is drawn at a draw ratio of 2 to 6 times in several types of washing to hot water baths.
[0043]
Regarding the conditions for stretching in the bath, it is preferable that the temperature gradient between the above-mentioned coagulation bath temperature and the rinsing temperature or hot water bath temperature be 98 ° C. at the maximum. Here, in order to obtain a high-strength carbon fiber, it is particularly preferable to draw in a hot water bath at a higher temperature.
[0044]
After that, prior to drying and densification, for the purpose of improving heat resistance and spinning stability, it is possible to provide a precursor fiber oil agent for carbon fiber combining a permeable oil agent having a hydrophilic group and a silicone oil agent with a high strength. It is preferable because carbon fibers can be obtained with high quality.
[0045]
The permeable oil agent preferably has a sulfinic acid, a sulfonic acid, a phosphoric acid, a carboxylic acid, an alkali metal salt, an ammonium salt, or a derivative thereof as a functional group. Among these permeable oil agents, it is particularly preferable to use an ammonium salt of phosphoric acid or a derivative thereof which does not hinder the strength of the carbon fiber from being hindered and has excellent thermal oxidation resistance even in a high heat environment.
[0046]
The silicone oil may be unmodified or modified, but among them, epoxy-modified silicone, ethylene oxide-modified silicone, polysiloxane, and amino-modified silicone are preferred, and amino-modified silicone is particularly preferred.
[0047]
In the case of drying and densification, it is preferable to dry with a drum type hot air dryer having a room having several layers connected to each other with a temperature gradient. The drying temperature is preferably adjusted appropriately at 70 to 150 ° C, and more preferably adjusted at 80 to 140 ° C, so as to further improve the compactness. The drying time is preferably 1 to 10 minutes.
[0048]
Further, by performing drawing at a high temperature, the fineness and molecular orientation of the produced precursor fiber for carbon fiber can be adjusted. In particular, hot stretching in pressurized steam is effective. The conditions of the hot drawing have a great influence on the denseness of the precursor fiber for carbon fiber. In order to obtain a high-strength carbon fiber, it is preferable to produce a precursor fiber for a carbon fiber having a high density.
[0049]
Means for evaluating denseness include evaluation of apparent specific gravity by the Archimedes method, measurement of L value, and the like.
[0050]
In the measurement of the L value, the brightness of the sample with respect to the standard white plate is measured by a Hunter color difference meter, and the brightness with respect to the reference carbon fiber precursor fiber is calculated. This value shows a high value when the number of voids in the fiber is large, and approaches a value of the reference carbon fiber precursor fiber when the density is high.
[0051]
The precursor fiber for carbon fiber is cut into about 5 cm and spread on cotton with a hand card to obtain 2 g. It is immersed in anisole by pressing with a hydraulic press, defoamed, and subjected to a Hunter colorimeter to measure the L value [L value = measured value−standard value (5)]. The dry densification and hot stretching conditions are changed so that the L value is preferably 20 or less, more preferably 18 or less, and still more preferably 16 or less.
[0052]
In the measurement of the specific gravity by the Archimedes method, about 2 g of a precursor fiber for a carbon fiber is collected and collected into a circle having a diameter of 3 cm or less so that the shape does not collapse. As the measurement solvent, water or a hydrophilic solvent is preferable. In some cases, it is difficult to remove bubbles at the time of defoaming due to the effect of an oil agent applied to the precursor fiber for carbon fibers. In this case, it is most preferable to use ethanol or acetone.
[0053]
Next, the circular sample is immersed in a solvent and defoamed under reduced pressure. At normal temperature, the mass in the solvent is measured, and the sample is further heated and dried to obtain a dry mass, and the apparent specific gravity of the precursor fiber for carbon fiber is obtained. This specific gravity is lower than the specific gravity of PAN of 1.18, but is preferably 1.12 to 1.18, more preferably 1.14 to 1.17, and still more preferably 1.15 to 1.17. , L values are changed as in the case of the dry densification and hot stretching.
[0054]
In the present invention, the fineness of the single fiber of the precursor fiber for carbon fiber is preferably small from the viewpoint of improving strength, so that oxidation spots (unevenness) are less likely to occur in the flame-proofing step. Specifically, 1.2d or less is preferable, 0.8-0.5d is more preferable, and 0.7-0.5d is still more preferable.
[0055]
In the obtained precursor fiber for carbon fiber, it is necessary to prevent the yarn (precursor fiber) from drying so that the molecular orientation is not easily relaxed. Therefore, the moisture content of the precursor fiber must be maintained preferably at 10 to 90% by mass, particularly preferably at 20 to 60% by mass. If the water content of the precursor fiber for carbon fiber is too low, the bunching property is reduced and the handleability becomes poor.If the water content is too high, the surface tension of the water causes it to wrap around the rollers during the flame-proofing process. It becomes easy and causes trouble.
[0056]
The precursor fiber for carbon fiber produced as described above and having an appropriately adjusted moisture content can be temporarily stored in a closed container. As the storage container, a cylindrical container is preferable, and a plastic bag is also preferable. However, when storing, it must be able to retain the internal moisture.
[0057]
In addition, the precursor fiber for carbon fiber used in the present invention is not subjected to a heat treatment such as a dry heat roller, and uses a yarn after wet heat drawing. This causes a reduction in the strength of the carbon fiber.
[0058]
As a method for preventing the relaxation of the orientation of the precursor fiber for carbon fiber, the following existing technology can be applied.
[0059]
That is, in a post-process (flame-proofing process, carbonization process) after the production of the precursor fiber for carbon fiber, as a method for improving the molecular orientation inside the fiber, wet-heat stretching is performed to produce a yarn of the precursor fiber. After that, a method of storing the yarn in a state of being wet with pure water or the like in a storage container can be used.
[0060]
According to the method of storing the yarn in the storage container while being wet, it is possible to prevent orientation relaxation, oxidation by air, addition of foreign matter in the air, and the like caused by drying of the fiber, thereby producing high-strength carbon fiber. it can.
[0061]
Next, the precursor fiber for carbon fiber produced in the preceding step is subjected to a flame-proof treatment in a flame-proof step. This oxidization treatment is carried out, for example, in a horizontal furnace divided into two or more chambers in heated air, at a temperature of 220 to 270 ° C. and a stretching ratio of 1.00 to 1.10, preferably 1.00 to 1 through a multistage roller group. The heat treatment can be performed at a factor of 0.08.
[0062]
In this flame-proofing step, an intramolecular cyclization and oxidation reaction of the precursor fiber component PAN and physical shrinkage of the yarn occur. In the initial stage of the flame-proofing process, physical shrinkage of the yarn occurs, but relaxation of the molecular orientation can be suppressed by increasing the stretching ratio.
[0063]
Also, regarding the rearrangement of the molecules in the intramolecular cyclization of the PAN, the flame resistance can be performed while maintaining the orientation during the rearrangement at a high level by performing the tensioning.
[0064]
Thus, by controlling the higher-order structure of the molecule, it is possible to control the disorder of the graphite structure of the carbon fiber obtained by the subsequent high-temperature sintering in the two-stage carbonization furnace. It is possible to obtain fibers.
[0065]
On the other hand, if the draw ratio for flame resistance is low, the molecular orientation is unfavorably relaxed. Further, since the fibers are usually weakened as the flame resistance advances, if the draw ratio is too high, fluffs due to breakage of single yarns are generated, and the quality of carbon fibers obtained later is notably reduced, which is not preferable.
[0066]
Therefore, the heat treatment is preferably performed at a 1.00 to 1.10 times heat treatment, and more preferably at a 1.00 to 1.08 times heat treatment.
[0067]
The degree of oxidization can be evaluated by measuring the specific gravity of the oxidized yarn (oxidized fiber). The specific gravity can be measured by using the Archimedes method as in the case of the precursor fiber for carbon fiber.
[0068]
The specific gravity of the oxidized fiber is preferably 1.20 to 1.40, more preferably 1.30 to 1.38, and still more preferably 1.32 to 1.37.
[0069]
The oxidized fiber can be carbonized by using a conventionally known method. For example, a temperature gradient is gradually applied in a baking furnace (first carbonization furnace) divided into three or more chambers at 900 ° C. or less under a nitrogen atmosphere, and the tension of the oxidized fiber is controlled to perform the first-stage carbonization under tension. (Preliminary carbonization).
[0070]
The degree of the pre-carbonization can be evaluated by measuring the specific gravity of the fiber after the pre-carbonization treatment. The specific gravity can be measured by using the Archimedes method as in the case of the precursor fiber for carbon fiber.
[0071]
The specific gravity of the fiber after the pre-carbonization treatment is preferably 1.45 to 1.60, more preferably 1.48 to 1.55, and still more preferably 1.50 to 1.53.
[0072]
In order to further promote carbonization and graphitization (high crystallization of carbon), the temperature was raised in an atmosphere of an inert gas such as nitrogen and gradually increased in a firing furnace (second carbonization furnace) divided into two or more chambers. Is subjected to a temperature gradient, and the tension of the yarn (pre-carbonized fiber) is controlled to bake it under a relaxation condition. The relaxation conditions are preferably in the range of 0.9 to 1.0 times, more preferably in the range of 0.92 to 0.99 times, and still more preferably in the range of 0.95 to 0.98 times.
[0073]
Regarding the firing temperature, a temperature gradient is gradually applied in the second carbonization furnace, and in the highest temperature range, from 1500 ° C to 2000 ° C, preferably from 1500 ° C to 1900 ° C, more preferably from 1500 ° C to 1800 ° C, further preferably 1500 ° C to 1700 ° C is good.
[0074]
The temperature gradient is preferably a temperature rise of 200 ° C./min or more, more preferably 300 to 600 ° C./min, and still more preferably 400 to 600 ° C./min. It is not preferable that the furnace length is too long from the viewpoint of productivity and cost.In addition, if the residence time in the high temperature part in the furnace is long, the graphitization will progress too much, and brittle carbon fibers will be obtained. Not preferred.
[0075]
The obtained carbon fiber is subjected to an electrolytic oxidation treatment in an electrolytic layer using an acid or alkali aqueous solution to perform a surface treatment. When carbon fibers are used as a material after being compounded with a resin, it is necessary to improve the affinity and adhesion between the carbon fibers and the matrix resin.
[0076]
As an electrolytic solution for the electrolytic treatment, an acidic or alkaline electrolyte can be used. Examples of acidic substances include nitric acid, sulfuric acid, hydrochloric acid, acetic acid, ammonium salts thereof, and ammonium hydrogen sulfate.
[0077]
Among these electrolytes, ammonium salts such as ammonium sulfate and ammonium hydrogen sulfate showing weak acidity are preferable.
[0078]
In addition, examples of the alkaline substance include potassium hydroxide, sodium hydroxide, and ammonia. However, when an electrolytic solution containing an alkali metal is used, the heat-resistant oxidizing property of the carbon fiber is reduced, and a function of preventing curing of the resin is also provided. Not so desirable.
[0079]
The amount of electricity during electrolytic oxidation needs to be adjusted according to the degree of graphitization of the carbon fiber outer layer. In view of forming a composite with a resin, the carbon content is preferably 5 c or more per 1 g of carbon fiber for improving the affinity. If the amount of electricity is too large, the surface may be oxidized more than the small-scale defects on the carbon fiber surface are removed, and new defects may be generated.
[0080]
After the surface treatment by electrolytic oxidation, since the electrolytic solution and its by-products are attached to the carbon fibers, it is necessary to wash and dry well. Further, sizing treatment is performed for the purpose of facilitating post-processing of the carbon fiber and improving handleability. The sizing method can be performed by a conventionally known method, and the sizing agent is used after changing the composition as appropriate according to the application, and after being uniformly adhered, dried. The adhesion amount is preferably from 0.1 to 2.0% by mass, and more preferably from 0.5 to 1.5% by mass.
[0081]
【Example】
The present invention will be specifically described with reference to the following Examples and Comparative Examples. Further, precursor fibers, oxidized fibers and carbon fibers were produced under the conditions of the following Examples and Comparative Examples, and various physical property values of the obtained oxidized fibers and carbon fibers were measured by the above-described or the following methods.
[0082]
Relaxation time T 1 ( 13 C relaxation time T 1 ): Using DSX300WB manufactured by Bruker, a fibrous sample having a length of 15 mm was aligned in the fiber axis direction and filled in an NMR sample tube, and the observation frequency was 75.5 MHz, the spectrum width was 30 kHz, the π / 2 pulse was 3.0 μs, and the inversion was performed. The measurement was performed at room temperature under static conditions by an inversion recovery method.
[0083]
NMR probe for relaxation time analysis 13 Using a spectral intensity of about 170 ppm where the influence of background on C is small, two components (T 1 analysis was performed as an exponential of short, long).
[0084]
The measurement of the electric resistance value can be carried out with reference to the strand A test method for volume resistivity specified in JIS-R-7601. However, in JIS-R-7601, the volume resistivity obtained by multiplying the electric resistance value by the specific gravity of the carbon fiber is obtained, and the electric resistance value [X (Ω · g / m 2 )] Was obtained using the following equation.
X = Rb × t / L
Rb: electrical resistance (Ω) when the test piece length is L, t: fineness (tex) of the test piece, L: test piece length (m) when measuring the resistance
In addition, it is preferable to measure about 1 m about the test piece length at the time of resistance measurement.
[0085]
Example 1
By a solution polymerization method using a zinc chloride aqueous solution as a solvent, a polymer stock solution having a polymerization degree of 1.6% and a polymer concentration of 8% by mass, comprising 95% by mass of acrylonitrile, 4% by mass of methyl acrylate, and 1% by mass of itaconic acid was obtained. .
[0086]
This polymer stock solution was discharged into a 25% by mass aqueous solution of zinc chloride at 5 ° C. through a die for 12,000 filaments to coagulate, thereby obtaining a coagulated yarn.
[0087]
The coagulated yarn was washed with water, hot stretched at 90 ° C., and an amino-modified silicone-based oil agent and an osmotic oil agent having an ammonium phosphate derivative were adhered in an equal amount of 0.1% by mass. Dry densification at 140 ° C., wet heat stretching at a draw ratio of 5.8 times at 100 to 120 ° C., and adjusting the water content to 40% by mass to obtain a precursor fiber for carbon fiber having a single fiber fineness of 0.6 d. Was. The fiber specific gravity was 1.16 and the L value was 16.
[0088]
The obtained precursor fiber for carbon fiber was made flame-resistant at a draw ratio of 1.06 times in an atmosphere having a temperature distribution of 230 ° C. to 260 ° C. in air. The specific gravity of the flame-resistant yarn was 1.35.
[0089]
This flame-resistant yarn is carbonized at a draw ratio of 1.06 times in a first carbonization furnace having a temperature distribution of 300 to 500 ° C. in an inert atmosphere. (Temperature distribution in the atmosphere: 300 to 1600 ° C.) in a second carbonization furnace.
[0090]
Next, using an aqueous solution of 10% by mass of ammonium sulfate as an electrolytic solution, an electrolytic oxidation treatment of 13 c per 1 g of carbon fiber is performed, followed by washing with water, and further sizing treatment to attach 3% by mass of a sizing agent-water emulsion solution, Dried at ° C. The amount of the sizing agent attached was 1% by mass. Table 1 shows the physical properties of the carbon fibers thus obtained.
[0091]
Example 2
The same operation as in Example 1 was performed, except that the maximum temperature range of the second carbonization furnace was changed to 1670 ° C. (temperature distribution in atmosphere: 300 to 1670 ° C.). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0092]
Example 3
Carbon fibers were produced in the same manner as in Example 1 except that the maximum temperature range of the second carbonization furnace was changed to 1720 ° C (temperature distribution in atmosphere: 300 to 1720 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0093]
Example 4
Carbon fibers were produced in the same manner as in Example 1 except that the maximum temperature range of the second carbonization furnace was changed to 1780 ° C (temperature distribution in atmosphere: 300 to 1780 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0094]
Example 5
Carbon fibers were produced in the same manner as in Example 1 except that the maximum temperature region of the second carbonization furnace was changed to 1830 ° C (temperature distribution in atmosphere: 300 to 1830 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0095]
Example 6
Carbon fibers were produced in the same manner as in Example 1 except that the maximum temperature region of the second carbonization furnace was changed to 1900 ° C (temperature distribution in atmosphere: 300 to 1900 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0096]
Comparative Example 1
The precursor fiber for carbon fiber obtained in Example 1 was made flame-resistant at a draw ratio of 0.95 times in an atmosphere having a temperature distribution of 230 ° C. to 260 ° C. in air. The specific gravity of the oxidized yarn was 1.36.
[0097]
This oxidized yarn was carbonized in an inert atmosphere at a temperature of 300 to 500 ° C. and a draw ratio of 1.06 times, and carbon fibers were produced in the same manner as in Example 1. Table 1 shows the physical properties of the carbon fibers thus obtained.
[0098]
Comparative Example 2
Carbon fibers were produced in the same manner as in Comparative Example 1 except that the maximum temperature range of the second carbonization furnace was changed to 1700 ° C (temperature distribution in atmosphere: 300 to 1700 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0099]
Comparative Example 3
Carbon fibers were produced in the same manner as in Comparative Example 1 except that the maximum temperature range of the second carbonization furnace was changed to 1780 ° C (temperature distribution in atmosphere: 300 to 1780 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0100]
Comparative Example 4
Carbon fibers were produced in the same manner as in Comparative Example 1, except that the maximum temperature range of the second carbonization furnace was changed to 1850 ° C (temperature distribution in atmosphere: 300 to 1850 ° C). Table 1 shows the physical properties of the carbon fibers thus obtained.
[0101]
Comparative Example 5
The coagulated yarn obtained in Example 1 after the wet heat drawing treatment was subjected to a heat treatment at a constant length of 120 ° C. using a dry heat roller to obtain a precursor fiber for carbon fiber having a single fiber fineness of 0.6 d. The fiber specific gravity was 1.17, the L value was 15, and the water content was 3% by mass.
[0102]
The obtained precursor fiber for carbon fiber was made flame-resistant at a draw ratio of 1.06 times in an atmosphere having a temperature distribution of 230 ° C. to 260 ° C. in air. The specific gravity of the flame-resistant yarn was 1.35.
[0103]
The firing treatment of the flame-resistant yarn, the subsequent electrolytic oxidation treatment, and the sizing treatment were performed in the same manner as in Example 1 to obtain carbon fibers. Table 1 shows the physical properties of the carbon fibers thus obtained.
[0104]
Comparative Example 6
A precursor fiber for a carbon fiber was produced in the same manner as in Comparative Example 2, except that the heat treatment temperature was changed to 180 ° C. using a dry heat roller. The single fiber fineness was 0.6 d, the specific gravity was 1.18, the L value was 14, and the water content was 1% by mass or less.
[0105]
The obtained precursor fiber for carbon fiber was made flame-resistant at a draw ratio of 1.06 times in an atmosphere having a temperature distribution of 230 ° C. to 260 ° C. in air. The specific gravity of the oxidized yarn was 1.36.
[0106]
The firing treatment of the flame-resistant yarn, the subsequent electrolytic oxidation treatment, and the sizing treatment were performed in the same manner as in Example 1 to obtain carbon fibers. Table 1 shows the physical properties of the carbon fibers thus obtained.
[0107]
[Table 1]
In the NMR measurement of the carbon fibers obtained in Examples 1 to 6 and Comparative Examples 1 to 6 13 C relaxation time (T 1 FIG. 1 is a graph plotting the electrical resistance value X and the short circuit.
[0109]
As shown in FIG. 1, plots ○ in Examples 1 to 6 are all expressed by the following formulas.
When X> 24.3, T 1 ≧ -1.314X + 34.43
When X ≦ 24.3, T 1 ≧ 1.314X-29.43
[However, 22.4 ≦ X ≦ 26.2, T 1 ≧ 1]
It can be seen that the plots x in Comparative Examples 1 to 6 are all below the polygonal line represented by the above equation.
[0110]
【The invention's effect】
The PAN-based carbon fiber of the present invention has a relaxation time (T 1 By satisfying a predetermined relational expression with respect to the relationship between short (short) and the electrical resistance value, it is possible to obtain a carbon fiber having high strength and high elongation with few disturbances and defects in the graphite structure.
[Brief description of the drawings]
FIG. 1 shows NMR measurements of carbon fibers obtained in Examples 1 to 6 and Comparative Examples 1 to 6. 13 C relaxation time (T 1 9 is a graph showing a relationship between short (short) and an electric resistance value X.
Claims (5)
Ｘ ＞ ２４．３の時、Ｔ１ ≧ −１．３１４Ｘ＋３４．４３
Ｘ ≦ ２４．３の時、Ｔ１ ≧ １．３１４Ｘ−２９．４３
〔但し、２２．４ ≦ Ｘ ≦ ２６．２、Ｔ１ ≧ １〕
を満足する物性を有するポリアクリロニトリル系炭素繊維。When the relaxation time [T 1 short (sec)] obtained by the solid-state NMR method and the electric resistance value represented by XΩ · g / m 2 satisfy the following formula X> 24.3, T 1 ≧ − 1.314X + 34.43
When X ≦ 24.3, T 1 ≧ 1.314X−29.43
[However, 22.4 ≦ X ≦ 26.2, T 1 ≧ 1]
A polyacrylonitrile-based carbon fiber having physical properties satisfying the following.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2004060126A (en) * | 2002-07-31 | 2004-02-26 | Toho Tenax Co Ltd | Carbon fiber and method for producing the same |
| JP2004277972A (en) * | 2003-03-19 | 2004-10-07 | Toho Tenax Co Ltd | High strength carbon fiber and method for producing the same |
| JP2005248368A (en) * | 2004-03-04 | 2005-09-15 | Toho Tenax Co Ltd | Method for producing carbon fiber |
| CN102822400A (en) * | 2010-03-31 | 2012-12-12 | 可隆工业株式会社 | Method for preparing carbon fiber and precursor fiber for carbon fiber |
| CN106702509A (en) * | 2016-12-19 | 2017-05-24 | 哈尔滨天顺化工科技开发有限公司 | M-type solvent drafting device for carbon fiber precursor production |
| CN106757435A (en) * | 2016-12-19 | 2017-05-31 | 哈尔滨天顺化工科技开发有限公司 | A kind of M type hot gas spring devices for carbon fibre precursor production |
| CN111088541A (en) * | 2018-10-23 | 2020-05-01 | 中国石油化工股份有限公司 | Preparation method of polyacrylonitrile fiber |
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2002
- 2002-07-25 JP JP2002216793A patent/JP2004060069A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004060126A (en) * | 2002-07-31 | 2004-02-26 | Toho Tenax Co Ltd | Carbon fiber and method for producing the same |
| JP2004277972A (en) * | 2003-03-19 | 2004-10-07 | Toho Tenax Co Ltd | High strength carbon fiber and method for producing the same |
| JP2005248368A (en) * | 2004-03-04 | 2005-09-15 | Toho Tenax Co Ltd | Method for producing carbon fiber |
| JP4626939B2 (en) * | 2004-03-04 | 2011-02-09 | 東邦テナックス株式会社 | Carbon fiber manufacturing method |
| CN102822400A (en) * | 2010-03-31 | 2012-12-12 | 可隆工业株式会社 | Method for preparing carbon fiber and precursor fiber for carbon fiber |
| JP2013524028A (en) * | 2010-03-31 | 2013-06-17 | コーロン インダストリーズ インク | Carbon fiber manufacturing method and carbon fiber precursor fiber |
| CN106702509A (en) * | 2016-12-19 | 2017-05-24 | 哈尔滨天顺化工科技开发有限公司 | M-type solvent drafting device for carbon fiber precursor production |
| CN106757435A (en) * | 2016-12-19 | 2017-05-31 | 哈尔滨天顺化工科技开发有限公司 | A kind of M type hot gas spring devices for carbon fibre precursor production |
| CN111088541A (en) * | 2018-10-23 | 2020-05-01 | 中国石油化工股份有限公司 | Preparation method of polyacrylonitrile fiber |
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