JP2009197365A - Method for producing precursor fiber of carbon fiber, and method for producing the carbon fiber - Google Patents

Method for producing precursor fiber of carbon fiber, and method for producing the carbon fiber Download PDF

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JP2009197365A
JP2009197365A JP2008041113A JP2008041113A JP2009197365A JP 2009197365 A JP2009197365 A JP 2009197365A JP 2008041113 A JP2008041113 A JP 2008041113A JP 2008041113 A JP2008041113 A JP 2008041113A JP 2009197365 A JP2009197365 A JP 2009197365A
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carbon fiber
carbon
fiber
polyacrylonitrile
producing
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Makoto Endo
真 遠藤
Fumihiko Tanaka
文彦 田中
Masato Yoshikawa
正人 吉川
Kenichi Sato
謙一 佐藤
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Toray Industries Inc
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Toray Industries Inc
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<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber excellent in tensile strength and tensile modulus without impairing its productivity and processability. <P>SOLUTION: A method for producing a precursor fiber of carbon fiber is characterized by comprising the following process: A spinning dope containing a polyacrylonitrile-based polymer and carbon nanofibers is extruded via a spinneret and coagulated, and single filaments are taken up from the spinning dope in a coagulating bath so that the single filaments just after taken up from the coagulating bath be 5-30 μm in average single filament diameter and 75-90% in crystal orientation degree determined by X-ray diffractometry, and then the single filaments are drawn. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、引張強度および引張弾性率に優れた炭素繊維を与える炭素繊維前駆体繊維の製造方法に関する。   The present invention relates to a method for producing a carbon fiber precursor fiber that provides a carbon fiber excellent in tensile strength and tensile modulus.

炭素繊維は、その優れた力学特性および電気特性から、さまざまな用途に利用されている。近年では、従来のゴルフクラブや釣竿などのスポーツ用途や航空機用途に加え、自動車部材、圧縮天然ガス（ＣＮＧ）用タンク、建造物の耐震補強部材および船舶部材などいわゆる一般産業用途への展開が進みつつある。それに伴い、更なる高性能化の要請が高い。
近年炭素繊維の性能を向上させるために炭素繊維の前駆体であるポリアクリロニトリル繊維にカーボンナノファイバーをフィラーとして混合させる技術が開示されている。（非特許文献１，２）
Ｂｙｕｎｇ Ｇ Ｍｉｎ．等 ＣＡＲＢＯＮ，２００５年，ｖｏｌ４３、ｐ５９９〜６０４ Ｈａｎ Ｇｉ Ｃｈａｅ等 Ｐｏｌｙｍｅｒ，２００７年，ｖｏｌ４３、ｐ３７８１〜３７８９ Carbon fibers are used in various applications because of their excellent mechanical and electrical properties. In recent years, in addition to conventional golf clubs, fishing rods and other sports and aircraft applications, the development of so-called general industrial applications such as automobile members, compressed natural gas (CNG) tanks, building seismic reinforcement members and ship members has progressed. It's getting on. Accordingly, there is a high demand for higher performance.
In recent years, in order to improve the performance of carbon fibers, a technique of mixing carbon nanofibers as fillers with polyacrylonitrile fibers that are precursors of carbon fibers has been disclosed. (Non-Patent Documents 1 and 2)
Byung G Min. CARBON, 2005, vol43, p599-604 Han Gi Chae et al., Polymer, 2007, vol43, p3781-3789.

しかしながら、非特許文献１，２に記載の技術により、ポリアクリロニトリル系炭素繊維を製造すると、著しく強度が低下したり、毛羽・糸切れが発生しプロセスの通過性が悪くなり、その結果弾性率が低下する場合があることが判った。本発明の目的は、かかるプロセス性の問題なく、高品質かつ高品位な炭素繊維を得るための方法を提供することにある。   However, when a polyacrylonitrile-based carbon fiber is produced by the techniques described in Non-Patent Documents 1 and 2, the strength is remarkably reduced, and fluff and thread breakage occur, resulting in poor processability. It has been found that there is a case where it decreases. An object of the present invention is to provide a method for obtaining high-quality and high-quality carbon fibers without such problems of processability.

従来法によりポリアクリロニトリル（以降、ＰＡＮと略記することもある）系重合体とカーボンナノファイバーを含んだ紡糸原液から紡糸し、炭素繊維を製造する方法において、ポリアクリロニトリル系重合体が炭素繊維に変換される過程は化学変化と物理変化を伴い変形してゆくが、本発明者らは、かかる炭素繊維製造時のプロセス性の問題や炭素繊維の物性上の問題が生じる原因について、炭素繊維前駆体繊維を製造する工程で、アクリロニトリル系重合体とカーボンナノファイバーの間にボイドが生じ、これに起因して、プロセス性等が悪化するのであろうとの考えの下に、かかるボイドを生じない製糸条件を検討したところ、従来法と比較して格段にプロセス性・物性が良好となる方法を提供できることを見出した。すなわち、本発明の炭素繊維前駆体繊維の製造方法は、ポリアクリロニトリル系重合体５〜２５重量％とカーボンナノファイバーを含む紡糸原液を口金から吐出して凝固せしめ紡糸原液を凝固浴から引き取る工程における単繊維の平均直径を５〜３０μｍ、Ｘ線回折により測定される結晶配向度を７５〜９０％とし、ついで延伸することを特徴とする。   In a method of producing carbon fiber by spinning from a spinning solution containing a polyacrylonitrile (hereinafter sometimes abbreviated as PAN) polymer and carbon nanofibers by a conventional method, the polyacrylonitrile polymer is converted to carbon fiber. However, the present inventors are concerned about the processability problems during the production of carbon fibers and the causes of physical properties of carbon fibers. In the fiber manufacturing process, voids are generated between the acrylonitrile-based polymer and the carbon nanofibers, and it is considered that processability may be deteriorated due to this. As a result, it has been found that a process with significantly improved processability and physical properties can be provided as compared with the conventional method. That is, the method for producing a carbon fiber precursor fiber of the present invention is a process in which a spinning stock solution containing 5 to 25% by weight of a polyacrylonitrile-based polymer and carbon nanofibers is discharged from a base and solidified to take the spinning stock solution from a coagulation bath. The average diameter of the single fibers is 5 to 30 μm, the degree of crystal orientation measured by X-ray diffraction is 75 to 90%, and then the fibers are stretched.

また、本発明の炭素繊維前駆体繊維の製造方法において、前記炭素繊維前駆体繊維の単繊維直径は、７〜１２μｍであることが好ましい。   Moreover, in the manufacturing method of the carbon fiber precursor fiber of this invention, it is preferable that the single fiber diameter of the said carbon fiber precursor fiber is 7-12 micrometers.

本発明において前記紡糸原液を口金から吐出して凝固せしめた後、温水浴中で２〜３倍延伸し、乾燥緻密化した後、さらに１．５〜５倍延伸することが好ましい。   In the present invention, the spinning solution is preferably discharged from a die and solidified, then stretched 2 to 3 times in a warm water bath, dried and densified, and further stretched 1.5 to 5 times.

本発明において、前記カーボンのナノファイバーのポリアクリロニトリル系重合体への配合比率は０．０１〜５重量％であることが好ましい。   In the present invention, the blending ratio of the carbon nanofibers to the polyacrylonitrile-based polymer is preferably 0.01 to 5% by weight.

また、本発明において前記紡糸原液をを紡糸する方法は乾湿式紡糸法であることが好ましい。   In the present invention, the method for spinning the spinning dope is preferably a dry and wet spinning method.

本発明の炭素繊維前駆体繊維の製造方法において前記ポリアクリロニトリル系重合体のゲルパーミエーションクロマトグラフ（ＧＰＣ）法で測定される重量平均分子量Ｍｗは３０万〜５０万が好ましく、Ｚ平均分子量ＭｚとＭｗとの比で示される多分散度Ｍｚ／Ｍｗは２．７〜６．０が好ましい。   In the method for producing a carbon fiber precursor fiber of the present invention, the weight average molecular weight Mw measured by the gel permeation chromatograph (GPC) method of the polyacrylonitrile polymer is preferably 300,000 to 500,000, and the Z average molecular weight Mz The polydispersity Mz / Mw indicated by the ratio with Mw is preferably 2.7 to 6.0.

本発明の炭素繊維の製造方法は、前記炭素繊維前駆体繊維の製造方法により得られた炭素繊維前駆体繊維を、２００〜３００℃の温度の酸化性雰囲気中において耐炎化した後、３００〜８００℃の温度の不活性雰囲気中において予備炭化処理し、次いで１,０００〜３,０００℃の温度の不活性雰囲気中において炭化することを特徴とする。   In the method for producing carbon fiber of the present invention, the carbon fiber precursor fiber obtained by the method for producing carbon fiber precursor fiber is flameproofed in an oxidizing atmosphere at a temperature of 200 to 300 ° C., and then 300 to 800. It is characterized in that it is pre-carbonized in an inert atmosphere at a temperature of ° C and then carbonized in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.

本発明により、炭素繊維製造工程における生産性とプロセス性を損なうことなく、引張強度、引張弾性率、および品位の優れた炭素繊維を製造することができる。   According to the present invention, carbon fibers excellent in tensile strength, tensile elastic modulus, and quality can be produced without impairing productivity and processability in the carbon fiber production process.

本発明の炭素繊維前駆体繊維の製造方法は、ポリアクリロニトリル系重合体５〜２５重量％とカーボンナノファイバーを含む紡糸原液を口金から吐出して凝固せしめ、ついで延伸するに際し、紡糸原液を引き取った直後の単繊維の平均直径を１２〜３０μｍの範囲とすることが必要である。ここで、凝固浴から引き取った直後の単繊維の平均直径は引き取り直後の繊維をサンプリングし、無緊張下に水洗、乾燥した後顕微鏡観察により、２０本の単糸径を平均して求める。凝固浴から引き取った直後の単繊維の平均直径が３０μｍを超えると炭素繊維前駆体繊維として必要な繊維直径７〜１２μｍ程度に細径化する過程において、紡糸原液を凝固浴から引き取った直後の単繊維を大きく変形させる、すなわち大きな延伸比率で延伸することが必要となり、次のような問題が生じる。すなわち、本発明における紡糸原液に含まれ、ポリアクリロニトリル系重合体と共に炭素繊維前駆体繊維を形成するカーボンナノファイバーは、ポリアクリロニトリル系重合体に比較して弾性率が非常に高いため、単繊維が延伸されてもほとんど変形しないことから、カーボンナノファイバー近傍にボイドが生成してしまい、後の焼成工程で修復できない欠陥を形成するものと考えられる。ボイドが生成することにより、炭素繊維の引張強度を大幅に低下させてしまうだけでなく、焼成プロセスにおいても毛羽、糸切れが発生しやすくなり結果として焼成で付加する張力を低く設定せざるを得なくなり、結果として弾性率が低下してしまうこととなる。また、平均単繊維径が、１２μｍに満たない場合、凝固浴において繊維が随伴流の影響を受けて切断するという問題がある。かかる理由から、紡糸原液を凝固浴から引き取った直後の単繊維の平均直径は、１５〜３０μｍが好ましく、１５〜２５μｍであればさらに好ましい。   In the method for producing a carbon fiber precursor fiber of the present invention, a spinning stock solution containing 5 to 25% by weight of a polyacrylonitrile polymer and carbon nanofibers was discharged from a die to be solidified, and then the spinning stock solution was taken out during stretching. It is necessary to make the average diameter of the single fiber immediately after that into the range of 12-30 micrometers. Here, the average diameter of the single fibers immediately after being taken out from the coagulation bath is obtained by sampling the fibers immediately after being taken up, washing with water under no tension and drying, and then averaging the diameters of 20 single yarns by microscopic observation. When the average diameter of the single fiber immediately after being taken out from the coagulation bath exceeds 30 μm, in the process of reducing the fiber diameter to about 7 to 12 μm necessary for the carbon fiber precursor fiber, the single fiber immediately after taking up the spinning dope from the coagulation bath is obtained. It is necessary to greatly deform the fiber, that is, to draw at a large draw ratio, and the following problems arise. That is, the carbon nanofibers that are included in the spinning dope in the present invention and form the carbon fiber precursor fiber together with the polyacrylonitrile-based polymer have a very high elastic modulus compared to the polyacrylonitrile-based polymer. Since it is hardly deformed even if it is stretched, voids are generated in the vicinity of the carbon nanofibers, and it is considered that defects that cannot be repaired in the subsequent firing step are formed. The formation of voids not only significantly reduces the tensile strength of the carbon fiber, but also tends to cause fluff and yarn breakage in the firing process, resulting in a need to set the tension applied by firing low. As a result, the elastic modulus is lowered. Further, when the average single fiber diameter is less than 12 μm, there is a problem that the fiber is cut in the coagulation bath under the influence of the accompanying flow. For this reason, the average diameter of the single fibers immediately after taking the spinning dope from the coagulation bath is preferably 15 to 30 μm, and more preferably 15 to 25 μm.

本発明において、凝固浴から引取った直後のアクリル繊維の結晶配向度は７５〜９０％になることが必要である。結晶配向度は凝固糸の引き取り速度と口金孔内のポリアクリロニトリル系重合体溶液の線速度（吐出線速度）との比、すなわちドラフト倍率を大きくすると高めることができる。吐出線速度とは、単位時間当たりに吐出される紡糸原液の体積を口金孔面積で割った値をいう。したがって、結晶配向度は口金径を小さくするか、引き取り速度を大きくする事によって高めることができる。かかる結晶配向度が７５％に満たないと炭素繊維前駆体繊維として必要な結晶配向度９０％以上を得るためには、延伸工程での延伸比を高く設定する必要があり、前述の通り、焼成工程でボイドが発生する可能性がある。結晶配向度は高ければ高いほど良いが、凝固工程に於いて高い配向度を得ようとするとドラフト倍率を高める必要があり、一般的には９０％が限界である。   In the present invention, the degree of crystal orientation of the acrylic fibers immediately after being taken out from the coagulation bath needs to be 75 to 90%. The degree of crystal orientation can be increased by increasing the ratio between the take-up speed of the coagulated yarn and the linear velocity (discharge linear velocity) of the polyacrylonitrile polymer solution in the die hole, that is, the draft magnification. The discharge linear velocity means a value obtained by dividing the volume of the spinning dope discharged per unit time by the die hole area. Accordingly, the degree of crystal orientation can be increased by reducing the die diameter or increasing the take-up speed. If the degree of crystal orientation is less than 75%, in order to obtain a degree of crystal orientation of 90% or more required as a carbon fiber precursor fiber, it is necessary to set a high stretch ratio in the stretching step. Voids may occur in the process. The higher the degree of crystal orientation, the better. However, in order to obtain a high degree of orientation in the solidification process, it is necessary to increase the draft magnification, and generally 90% is the limit.

また、本発明の炭素繊維前駆体繊維の単繊維直径は７〜１２μｍである。１２μｍより太い径となると、耐炎化時に繊維内部へ酸素が透過しにくくなり、いわゆる二重構造が生成し、酸素が低下しない内層部の弾性率が、低下し全体として弾性率が低下したり、引張応力付加時に外層部へ応力が集中し、強度を低下させる場合がある。一方、単糸径が７μｍより細くなると、焼成工程に於いて糸切れしやすくなる場合がある。かかる理由から、本発明の炭素繊維前駆体繊維の単繊維直径は好ましくは８μｍ〜１０μｍである。     Moreover, the single fiber diameter of the carbon fiber precursor fiber of this invention is 7-12 micrometers. When the diameter is larger than 12 μm, it is difficult for oxygen to permeate into the fiber at the time of flame resistance, a so-called double structure is formed, and the elastic modulus of the inner layer portion where oxygen does not decrease is lowered and the elastic modulus is lowered as a whole, When tensile stress is applied, stress concentrates on the outer layer, which may reduce the strength. On the other hand, if the single yarn diameter is thinner than 7 μm, yarn breakage may easily occur in the firing step. For this reason, the single fiber diameter of the carbon fiber precursor fiber of the present invention is preferably 8 μm to 10 μm.

本発明に於いて、紡糸原液を口金から吐出して凝固せしめた後、温水浴中で２〜３倍延伸する事が好ましい。延伸倍率が３倍より高くなるとポリアクリロニトリル系重合体とカーボンナノファイバーの間にボイドが生成しやすくなる場合がある。一方温水浴中での延伸倍率を２倍より低くすると、炭素繊維前駆体繊維の配向度が高まらず、炭素繊維に変換したときの弾性率が十分に得られない場合がある。さらに、温水浴中で延伸し、乾燥緻密化した後に、行う延伸の倍率は１．５〜５倍が好ましい。乾燥緻密化後の延伸はドラム間で行っても良いし、加圧スチーム中で行っても良い。乾燥緻密化後の延伸を行うことにより炭素繊維前駆体繊維中のポリアクリロニトリル系重合体の結晶配向度が高まりやすいが、乾燥緻密化により該ポリアクリロニトリル系重合体のポリマー構造が緻密になっていることから、延伸倍率が高いとボイドの生成が増加する方向となるため、５倍より倍率が高くなると、ボイドの発生が顕著となる場合があるため好ましくない。一方、延伸倍率が１．５倍より低くなると、炭素繊維前駆体繊維中のポリアクリロニトリル系重合体の結晶配向度が十分向上せず炭素繊維の弾性率が不十分となる場合がある。かかる理由から、乾燥緻密化後に行う延伸の倍率は好ましくは２〜３倍である。   In the present invention, it is preferable that the spinning solution is discharged from the die and solidified, and then stretched 2 to 3 times in a warm water bath. When the draw ratio is higher than 3 times, voids are likely to be generated between the polyacrylonitrile-based polymer and the carbon nanofibers. On the other hand, when the draw ratio in the warm water bath is lower than 2 times, the degree of orientation of the carbon fiber precursor fibers is not increased, and the elasticity modulus when converted into carbon fibers may not be sufficiently obtained. Furthermore, the stretching ratio is preferably 1.5 to 5 times after stretching in a warm water bath and drying and densification. Stretching after drying and densification may be performed between drums or in pressurized steam. By stretching after drying densification, the degree of crystal orientation of the polyacrylonitrile polymer in the carbon fiber precursor fiber tends to increase, but the polymer structure of the polyacrylonitrile polymer becomes dense due to drying densification. Therefore, when the draw ratio is high, void formation increases. Therefore, when the draw ratio is higher than 5 times, voids may be remarkably generated, which is not preferable. On the other hand, when the draw ratio is lower than 1.5, the degree of crystal orientation of the polyacrylonitrile polymer in the carbon fiber precursor fiber may not be sufficiently improved, and the elastic modulus of the carbon fiber may be insufficient. For this reason, the stretching ratio performed after drying and densification is preferably 2 to 3 times.

本発明に於いて凝固直後の単繊維の直径を５〜３０μｍにする手段として、ポリアクリロニトリル重合体の重量平均分子量Ｍｗは３０万〜５０万が好ましく、より好ましくは３５万〜４５万である。またポリアクリロニトリル系重合体のＺ平均分子量ＭｚとＭｗとの比で示される多分散度Ｍｚ／Ｍｗは２．７〜６．０が好ましく、より好ましくは３．０〜６．０、さらに好ましくは３．２〜６．０である。本発明において、各種平均分子量はゲルパーミエーションクロマトグラフ（以下、ＧＰＣと略記する）法で測定され、ポリスチレン換算値として得られるものである。なお、各分子量や、多分散度Ｍｚ／Ｍｗ等の分子量またはその分布に関する指標は、次の意味を有する。すなわち、数平均分子量（以下、Ｍｎと略記する）は、高分子化合物に含まれる低分子量物の寄与を敏感に受ける。これに対して、Ｍｗは、高分子量物の寄与を敏感に受け、Ｍｚは、高分子量物の寄与をさらに敏感に受ける。そのため、分子量分布であるＭｗ／Ｍｎや多分散度であるＭｚ／Ｍｗを用いることにより分子量分布の広がりを評価することができる。Ｍｗ／Ｍｎが１であるとき単分散であり、大きくなるにつれて分子量分布が低分子量側を中心にブロードになることを示すのに対して、Ｍｚ／Ｍｗは大きくなるにつれて、分子量分布が高分子量側を中心にブロードになることを示す。   In the present invention, as a means for setting the diameter of the single fiber immediately after solidification to 5 to 30 μm, the polyacrylonitrile polymer has a weight average molecular weight Mw of preferably 300,000 to 500,000, more preferably 350,000 to 450,000. The polydispersity Mz / Mw indicated by the ratio of the Z average molecular weight Mz and Mw of the polyacrylonitrile polymer is preferably 2.7 to 6.0, more preferably 3.0 to 6.0, and still more preferably. 3.2 to 6.0. In the present invention, various average molecular weights are measured by a gel permeation chromatograph (hereinafter abbreviated as GPC) method and are obtained as polystyrene equivalent values. In addition, each molecular weight, the molecular weight such as polydispersity Mz / Mw, or an index related to the distribution has the following meaning. That is, the number average molecular weight (hereinafter abbreviated as Mn) is sensitively influenced by the low molecular weight substance contained in the polymer compound. On the other hand, Mw is sensitively influenced by the high molecular weight substance, and Mz is more sensitively influenced by the high molecular weight substance. Therefore, the spread of the molecular weight distribution can be evaluated by using Mw / Mn as the molecular weight distribution and Mz / Mw as the polydispersity. It is monodisperse when Mw / Mn is 1, and shows that the molecular weight distribution becomes broader around the low molecular weight side as it becomes larger, whereas the molecular weight distribution becomes higher as Mz / Mw becomes larger. It shows that it becomes broad around.

本発明において前述のポリアクリロニトリル系重合体を用いることにより、凝固工程において、繊維径を細化することが可能になるため、ポリアクリロニトリル系重合体の組成物が凝固した後の延伸倍率を低く設定することができ、その結果としてポリアクリロニトリル系重合体とカーボンナノファイバーの間に伸びの差ができにくくなり、ボイドを少なくすることができる。さらにこのことにより、焼成工程においてもポリアクリロニトリル系重合体由来の炭素結晶とカーボンナノファイバーが炭素繊維内で相互作用しやすくなり、カーボンナノファイバーによる炭素繊維への補強効果を最大限に享受でき、炭素繊維の引張強度、弾性率が著しく向上するのである。前記分子量分布を有するポリアクリロニトリル系重合体が凝固工程で細化できるメカニズムは、必ずしも明確になってはいないが、次のように考えられる。吐出孔直後でＰＡＮ系重合体が伸長変形する際に、超高分子量物と高分子量物が絡み合い、超高分子量物を中心に絡み合い間の分子鎖が緊張することで伸長粘度の急激な増大、すなわち、歪み硬化がおこる。ＰＡＮ系重合体溶液の細化に伴い細化部分の伸長粘度が高くなり、流動安定化するため紡糸速度を高め、かつ、紡糸ドラフト率を高めることができ、ひいては繊維径を細くすることができる。このことによりポリアクリロニトリルの変形自由度がある凝固工程で繊維径を細くできるためカーボンナノファイバーがポリアクリロニトリル系重合体間に侵入できるため、ボイドが少なくなるのである。かかる理由から、Ｍｚ／Ｍｗは大きいほど好ましく、Ｍｚ／Ｍｗが２．７未満では、歪み硬化が弱くＰＡＮ系重合体の吐出安定性向上が不足する場合がある。   In the present invention, by using the above-mentioned polyacrylonitrile polymer, it becomes possible to reduce the fiber diameter in the coagulation step. Therefore, the draw ratio after the polyacrylonitrile polymer composition is coagulated is set low. As a result, a difference in elongation between the polyacrylonitrile-based polymer and the carbon nanofiber is hardly generated, and voids can be reduced. Furthermore, this makes it easier for carbon crystals derived from polyacrylonitrile-based polymers and carbon nanofibers to interact in the carbon fiber even in the firing step, and the carbon fiber can be maximally reinforced by the carbon nanofibers. The tensile strength and elastic modulus of the carbon fiber are remarkably improved. The mechanism by which the polyacrylonitrile polymer having the molecular weight distribution can be thinned in the coagulation step is not necessarily clarified, but is considered as follows. When the PAN-based polymer is stretched and deformed immediately after the discharge hole, the ultrahigh molecular weight substance and the high molecular weight substance are entangled, and the molecular chain between the entanglement is tensioned around the ultrahigh molecular weight substance, resulting in a rapid increase in the extension viscosity. That is, strain hardening occurs. As the PAN-based polymer solution is thinned, the elongational viscosity of the thinned portion increases, and the flow is stabilized to increase the spinning speed and the spinning draft rate, and thus the fiber diameter can be narrowed. . As a result, the fiber diameter can be reduced in the coagulation process with the degree of freedom of deformation of polyacrylonitrile, so that the carbon nanofibers can penetrate between the polyacrylonitrile polymers, resulting in fewer voids. For this reason, Mz / Mw is preferably as large as possible. When Mz / Mw is less than 2.7, strain hardening is weak and the discharge stability of the PAN-based polymer may be insufficiently improved.

本発明において、前述の分子量分布（重量平均分子量Ｍｗが３０万〜５０万、多分散度（Ｍｚ／Ｍｗ）が２．７〜６．０）をもつ重合体を作成する方法としては、重合開始剤の種類と割合や逐次添加など、特殊な条件で重合を行うか、一般的なラジカル重合を用いる場合、２種以上のＰＡＮ系重合体を混合する方法があるが、重合体を混合する方法が簡便である。混合する種類は、少ないほど簡便であり、吐出安定性の観点からも２種で十分なことが多い。   In the present invention, as a method for producing a polymer having the above-described molecular weight distribution (weight average molecular weight Mw is 300,000 to 500,000, polydispersity (Mz / Mw) is 2.7 to 6.0), polymerization is started. When the polymerization is carried out under special conditions such as the type and ratio of the agent and sequential addition or when general radical polymerization is used, there is a method of mixing two or more PAN-based polymers, but a method of mixing the polymers Is simple. The smaller the number of types to be mixed, the easier and the two types are often sufficient from the viewpoint of ejection stability.

混合する重合体のＭｗは、Ｍｗの大きいＰＡＮ系重合体をＡ成分とし、Ｍｗの小さいＰＡＮ系重合体をＢ成分とすると、Ａ成分のＭｗは好ましくは１００万〜１５００万であり、より好ましくは１００万〜５００万であり、Ｂ成分のＭｗは５万〜９０万であることが好ましい。Ａ成分とＢ成分のＭｗの差が大きいほど、混合された重合体のＭｚ／Ｍｗが大きくなる傾向があるため好ましい態様であるが、Ａ成分のＭｗが１５００万より大きいときはＡ成分の生産性は低下する場合があり、Ｂ成分のＭｗが１５万未満のときは前駆体繊維の強度が不足する場合があり、Ｍｚ／Ｍｗは６以下とすることが現実的である。   The Mw of the polymer to be mixed is a PAN-based polymer having a large Mw as the A component, and a PAN-based polymer having a small Mw is the B component. Is 1 million to 5 million, and Mw of the B component is preferably 50,000 to 900,000. The larger the difference between the Mw of the A component and the B component, the greater the Mz / Mw of the mixed polymer tends to increase. This is a preferred embodiment, but when the Mw of the A component is greater than 15 million, production of the A component When the Mw of the B component is less than 150,000, the strength of the precursor fiber may be insufficient, and it is realistic that Mz / Mw is 6 or less.

本発明においてポリアクリロニトリル系重合体には共重合可能な成分が含まれても良い。共重合可能な成分としては耐炎化を促進する成分と繊維の延伸性を向上させる成分が共重合されることが好ましい。耐炎化を促進する成分としては、例えば、カルボキシル基またはアミド基を一つ以上有するものが好ましく用いられる。該成分の共重合量を多くするほど、耐炎化反応が促進され、短時間で耐炎化処理でき、生産性を高める目的から好ましい。しかしながら一方で、該成分の共重合量が多くなるほど、発熱速度が大きくなり、暴走反応の危険が生じることがある。かかる理由から、共重合量は、０．５〜５ｍｏｌ％が好ましく、０．５〜３ｍｏｌ％がより好ましく、１〜３ｍｏｌ％が更に好ましい。耐炎化促進するための共重合可能な成分の具体例としては、アクリル酸、メタクリル酸、イタコン酸、クロトン酸、シトラコン酸、エタクリル酸、マレイン酸、メサコン酸、アクリルアミドおよびメタクリルアミドがある。含有されるアミド基とカルボキシル基の数は、１つよりも２つ以上であることがより好ましく、その観点からは、イタコン酸、マレイン酸およびメサコン酸、シトラコン酸がより好ましく、中でも、イタコン酸が最も好ましい。   In the present invention, the polyacrylonitrile-based polymer may contain a copolymerizable component. As the copolymerizable component, it is preferable that a component that promotes flame resistance and a component that improves the stretchability of the fiber are copolymerized. As a component that promotes flame resistance, for example, those having at least one carboxyl group or amide group are preferably used. Increasing the amount of copolymerization of the component is preferable for the purpose of promoting the flameproofing reaction, enabling flameproofing treatment in a short time, and increasing productivity. On the other hand, however, the greater the amount of copolymerization of the components, the greater the rate of heat generation and the risk of runaway reaction. For this reason, the copolymerization amount is preferably 0.5 to 5 mol%, more preferably 0.5 to 3 mol%, and still more preferably 1 to 3 mol%. Specific examples of the copolymerizable component for promoting flame resistance include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, ethacrylic acid, maleic acid, mesaconic acid, acrylamide and methacrylamide. The number of amide groups and carboxyl groups to be contained is more preferably two or more than one, and from that viewpoint, itaconic acid, maleic acid and mesaconic acid, and citraconic acid are more preferable. Is most preferred.

また、製糸延伸性を向上させるモノマーを共重合成分を導入することも可能である。具体的にはは、アクリレートやメタクリレートなどのエステルが好ましい。   Moreover, it is also possible to introduce a copolymerization component with a monomer that improves the yarn-drawing stretchability. Specifically, esters such as acrylate and methacrylate are preferable.

本発明で用いられるポリアクリロニトリル系重合体を製造する重合方法としては、溶液重合、懸濁重合、および、乳化重合などの重合方法から選択することができるが、共重合成分を均一に重合する目的からは、溶液重合を用いることが好ましい。   The polymerization method for producing the polyacrylonitrile-based polymer used in the present invention can be selected from polymerization methods such as solution polymerization, suspension polymerization, and emulsion polymerization, but the purpose is to uniformly polymerize the copolymer components. Is preferably solution polymerization.

溶液重合で用いられる溶液としては、ジメチルスルホキシド、ジメチルフォルムアミドおよびジメチルアセトアミドなどのポリアクリロニトリルが可溶な溶媒を用いることが好ましい。中でも、生成したポリアクリロニトリル系重合体の溶解性の観点から、ジメチルスルホキシドが好ましく用いられる。   As the solution used in the solution polymerization, it is preferable to use a solvent in which polyacrylonitrile is soluble, such as dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. Among these, dimethyl sulfoxide is preferably used from the viewpoint of solubility of the produced polyacrylonitrile-based polymer.

本発明の炭素繊維前駆体繊維の製造方法には、前記したポリアクリロニトリル系重合体の溶液が用いられる。前記ポリアクリロニトリル系重合体を、ジメチルスルホキシド、ジメチルフォルムアミドおよびジメチルアセトアミドなどのポリアクリロニトリルが可溶な溶媒に溶解し、紡糸原液とする。溶液重合を用いる場合、重合に用いられる溶媒と紡糸原液に用いられる溶媒（紡糸溶媒）とを同じものにしておくと、得られたポリアクリロニトリル系重合体を分離し紡糸溶媒に再溶解する工程が不要となるので好ましい。   In the method for producing the carbon fiber precursor fiber of the present invention, the above-mentioned polyacrylonitrile polymer solution is used. The polyacrylonitrile-based polymer is dissolved in a solvent in which polyacrylonitrile such as dimethyl sulfoxide, dimethylformamide and dimethylacetamide is soluble to obtain a spinning dope. When using solution polymerization, if the solvent used for the polymerization and the solvent used for the spinning dope (spinning solvent) are the same, the step of separating the resulting polyacrylonitrile-based polymer and re-dissolving it in the spinning solvent This is preferable because it is unnecessary.

本発明に於いて紡糸原液は、ポリアクリロニトリル系重合体とカーボンナノファイバーを含むものであり、より具体的には、紡糸溶媒にポリアクリロニトリル系重合体が溶解し、カーボンナノファイバーが分散したものである。   In the present invention, the spinning dope includes a polyacrylonitrile-based polymer and carbon nanofibers, and more specifically, a polyacrylonitrile-based polymer is dissolved in a spinning solvent and carbon nanofibers are dispersed. is there.

また、本発明において、カーボンナノファイバーは、その平均繊維直径が好ましくは１〜３００ｎｍ、より好ましくは１〜１００ｎｍ、さらに好ましくは１〜５０ｎｍの範囲内で、その平均繊維長が好ましくは０．０１〜１００μｍ、より好ましくは０．０３〜５０μｍ、さらに好ましくは０．０５〜２０μｍの範囲内で紡糸原液内に分散することが好ましい。平均繊維長が大きすぎるカーボンナノファイバーはポリアクリロニトリルと均一に分散させることが困難である場合があり、一方、平均繊維直径が大きすぎたり、平均繊維長が小さすぎるカーボンナノファイバーは、特に所望の力学特性付与効果を得ることが出来ない場合がある。なお、ここでいう平均繊維直径は、高分解能透過型電子顕微鏡観察などの方法により求めることができる。具体的には、紡糸原液中に含まれるカーボンナノファイバーの平均繊維直径は、繊維成形後、繊維を薄切片に加工した後、高分解能透過型電子顕微鏡などで観察する方法により求めることができる。炭素繊維の一般的な繊維径は５〜７ミクロンであり、ナノファイバーの直径は炭素繊維直径の１／１０〜１／１０００程度が好ましい。   In the present invention, the carbon nanofibers have an average fiber diameter of preferably 1 to 300 nm, more preferably 1 to 100 nm, and still more preferably 1 to 50 nm, and an average fiber length of preferably 0.01. It is preferable to disperse in the spinning dope within a range of ˜100 μm, more preferably 0.03 to 50 μm, still more preferably 0.05 to 20 μm. Carbon nanofibers with an average fiber length that is too large may be difficult to disperse uniformly with polyacrylonitrile, while carbon nanofibers with an average fiber diameter that is too large or an average fiber length that is too small are particularly desirable. In some cases, the effect of imparting mechanical properties cannot be obtained. The average fiber diameter here can be obtained by a method such as observation with a high-resolution transmission electron microscope. Specifically, the average fiber diameter of the carbon nanofibers contained in the spinning dope can be obtained by a method of observing with a high-resolution transmission electron microscope or the like after processing the fiber into a thin slice. The general fiber diameter of the carbon fiber is 5 to 7 microns, and the diameter of the nanofiber is preferably about 1/10 to 1/1000 of the carbon fiber diameter.

最も好ましいカーボンナノファイバーは、層数の少ない多層カーボンナノチューブである（以降、カーボンナノチューブをＣＮＴと略記することもある）。単層ＣＮＴは直径が細く、添加効果が高いが、その凝集力が強く、強固に束になっており分散させることが困難な場合がある。一方層数が多くなると添加効果が低くなるので好ましくない。２〜５層ＣＮＴは単層と多層のそれぞれの良い特性を有しており好ましい。２−５層ＣＮＴは、強固に束になる凝集力が弱くかつ多層ＣＮＴよりも超音波ホモジナイザーで短く切ることが容易で分散させやすいため好ましい。中でも２層ＣＮＴが最も好ましく用いられる。２層ＣＮＴとしては直径が１〜３ｎｍのものが単層の性質も有しており、かつ分散性も良く更に好ましい。２〜５層ＣＮＴであってかつ分散性に優れたＣＮＴが好ましく用いられる。なお、ＣＮＴは、通常アモルファスカーボンや触媒の残留物が不純物として含まれていることから、厳密には、ＣＮＴ組成物と記される場合も多いが、本明細書では、特に断らない限り、単にＣＮＴと記すこととし、ＣＮＴ配合量等を計算するベースとしては、ＣＮＴ組成物中の純粋なＣＮＴをベースとするのではなく、ＣＮＴ組成物は全てＣＮＴであると見なして計算することとする。アモルファスカーボンの存在は分散性に大きく影響するのでアモルファスカーボンが少ない方が好ましい。単層ＣＮＴが一部含まれていても良いがこの含有量は少ないほうが良い。好ましい組成は、高分解能透過型顕微鏡で観察した時に、無作為に測定した１００本中５０本以上が２〜５層ＣＮＴであることが好ましい。更に好ましくは１００本中６０本以上が２〜５層ＣＮＴであり、最も好ましくは１００本中７０本以上が２〜５層ＣＮＴである。このようなカーボンナノチューブは、市販品を購入しても良いし、公知のいかなる方法を使用して合成しても良い。分散を容易にするためアモルファスカーボンの量を減らすために、カーボンナノチューブをあらかじめ酸化剤が存在する雰囲気下で酸化してアモルファスカーボンを除去することが好ましい。その方法の一例として空気中で３００〜６００℃で焼成する方法が挙げられる。かかるアモルファスカーボンを酸化除去する温度としては、４００〜６００℃が好ましい。   The most preferred carbon nanofiber is a multi-walled carbon nanotube having a small number of layers (hereinafter, the carbon nanotube may be abbreviated as CNT). Single-walled CNTs have a small diameter and a high effect of addition, but their cohesive strength is strong and they are tightly bundled and sometimes difficult to disperse. On the other hand, an increase in the number of layers is not preferable because the effect of addition decreases. Two to five-layer CNTs are preferable because they have good characteristics of single layers and multilayers. 2-5-layer CNTs are preferred because they have a weak cohesive force to form a strong bundle and are easier to disperse and easily disperse with an ultrasonic homogenizer than multilayer CNTs. Of these, 2-layer CNTs are most preferably used. Two-walled CNTs having a diameter of 1 to 3 nm are more preferable because they have a single-layer property and good dispersibility. CNTs that are 2 to 5 layer CNTs and excellent in dispersibility are preferably used. In addition, since CNT usually contains amorphous carbon and catalyst residues as impurities, strictly speaking, it is often described as a CNT composition, but in this specification, unless otherwise specified, The base for calculating the CNT blending amount and the like is not based on pure CNT in the CNT composition, but is calculated assuming that the CNT composition is all CNT. Since the presence of amorphous carbon greatly affects dispersibility, it is preferable that the amount of amorphous carbon is small. A part of the single-walled CNTs may be contained, but the content is preferably small. As for a preferable composition, it is preferable that 50 or more out of 100 randomly measured with a high-resolution transmission microscope are 2 to 5 layer CNTs. More preferably, 60 or more out of 100 are 2 to 5 layer CNTs, and most preferably 70 or more of 100 are 2 to 5 layer CNTs. Such carbon nanotubes may be purchased commercially or synthesized using any known method. In order to reduce the amount of amorphous carbon in order to facilitate dispersion, it is preferable to remove the amorphous carbon by previously oxidizing the carbon nanotubes in an atmosphere containing an oxidizing agent. An example of the method is a method of baking at 300 to 600 ° C. in air. The temperature for removing the amorphous carbon by oxidation is preferably 400 to 600 ° C.

分散性に優れたＣＮＴとは、ＣＮＴ１０ｍｇポリスチレンスルホン酸ナトリウム３０ｍｇ及び水１０ｍＬの混合物を超音波ホモジナイザーで２０分間処理し、続いて２万Ｇにて遠心処理したのち、上清９ｍＬをサンプリングした時、上清中のＣＮＴ含有量が０．３ｍｇ/ｍＬ以上となるＣＮＴである。更に好ましくは、０．５ｍｇ/ｍＬ以上であり、特に好ましくは、０．６ｍｇ/ｍＬ以上である。   CNT excellent in dispersibility is a mixture of CNT 10 mg sodium polystyrene sulfonate 30 mg and water 10 mL treated with an ultrasonic homogenizer for 20 minutes, then centrifuged at 20,000 G, and then sampled 9 mL of supernatant. The CNT content in the supernatant is 0.3 mg / mL or more. More preferably, it is 0.5 mg / mL or more, and particularly preferably 0.6 mg / mL or more.

ＣＮＴとしては、グラファイト化度が高い多層ＣＮＴが最も好ましい。グラファイト化度はラマン分光により測定でき、波長５３２ｎｍのラマン分光分析のＧバンドとＤバンドの比が５より高いことが好ましい。更に好ましくは１０より高く、特に好ましくは２０より高いものである。多層ＣＮＴと単層ＣＮＴは粉末Ｘ線回折で２４°±２°にグラファイト層間に起因するピークの有無で区別できる。即ち粉末Ｘ線回折で２４±２°にグラファイト層間に起因するピークを有し、かつ、波長５３２ｎｍのラマン分光分析のＧバンドとＤバンドの比が５より高いＣＮＴが好ましい。   As the CNT, a multilayer CNT having a high degree of graphitization is most preferable. The degree of graphitization can be measured by Raman spectroscopy, and it is preferable that the ratio of G band to D band in Raman spectroscopy at a wavelength of 532 nm is higher than 5. More preferably, it is higher than 10, particularly preferably higher than 20. Multi-wall CNT and single-wall CNT can be distinguished by the presence or absence of a peak due to the graphite layer at 24 ° ± 2 ° by powder X-ray diffraction. That is, CNT having a peak due to the graphite layer at 24 ± 2 ° in powder X-ray diffraction and having a G-band to D-band ratio higher than 5 in Raman spectroscopic analysis at a wavelength of 532 nm is preferable.

本発明で用いるカーボンナノファイバーは、表面処理を施されたものであることが好ましい。これにより、ポリポリアクリロニトリル系重合体との親和性が高まり、紡糸原液中のカーボンナノファイバーの分散状態が均一化し、繊維内でもカーボンナノファイバーが均一に存在できる。かかる表面処理の方法は特に限定されないが、例えば、カーボンナノファイバー表面にポリビニルピロリドンなどの極性ポリマーやポリ（アリールエチニレン）などの共役ポリマーを非共有結合的に付着させる方法、硝酸、過マンガン酸などの酸化剤と反応させ酸化させる方法、フッ素ガスにより表面をフッ素化する方法、さらに導入された官能基を、アミノ基、カルボキシル基、水酸基、エポキシ基、スルホキシル基等、あるいはそれらから誘導された活性な官能基を有する化合物で処理する方法などが挙げられる。   The carbon nanofibers used in the present invention are preferably subjected to a surface treatment. Thereby, the affinity with the polypolyacrylonitrile-based polymer is increased, the dispersion state of the carbon nanofibers in the spinning dope is made uniform, and the carbon nanofibers can be present evenly in the fibers. The surface treatment method is not particularly limited. For example, a method of attaching a polar polymer such as polyvinylpyrrolidone or a conjugated polymer such as poly (arylethynylene) to the carbon nanofiber surface in a non-covalent manner, nitric acid, permanganic acid A method of oxidizing by reacting with an oxidizing agent such as a method of fluorinating the surface with fluorine gas, and an introduced functional group derived from amino group, carboxyl group, hydroxyl group, epoxy group, sulfoxyl group, etc. Examples include a method of treating with a compound having an active functional group.

また、カーボンナノファイバーの分散性を向上させるため、ポリアクリロニトリル系重合体、カーボンナノファイバー、以外の第３成分として別の化合物を混合しても良い。   Moreover, in order to improve the dispersibility of carbon nanofiber, you may mix another compound as 3rd components other than a polyacrylonitrile-type polymer and carbon nanofiber.

カーボンナノファイバーを繊維中に均一に分散させるためには、紡糸原液溶媒にカーボンナノファイバーを均一分散させてからポリアクリロニトリル系重合体を溶解する方法、重合溶媒にカーボンナノファイバーを分散させてから重合を行う方法、あるいはアクリロニトリル系重合体溶液とカーボンナノファイバー分散液とを混合する方法のいずれを選択してもよい。こうして得られた紡糸原液にさらにホモジナイザーなどの剪断撹拌機またはスタティックミキサー等を用い剪断を加えることでより分散性の向上した紡糸原液を得ることができる。   To uniformly disperse carbon nanofibers in the fiber, a method of uniformly dispersing carbon nanofibers in the spinning dope solvent and then dissolving the polyacrylonitrile-based polymer, dispersing carbon nanofibers in the polymerization solvent and then polymerizing Either a method of performing the above or a method of mixing the acrylonitrile-based polymer solution and the carbon nanofiber dispersion may be selected. A spinning stock solution with improved dispersibility can be obtained by further applying shear to the spinning stock solution thus obtained using a shearing stirrer such as a homogenizer or a static mixer.

カーボンナノファイバーの含有率は、補強効果を得るために、アクリル繊維（１００体積％）中、０．０１重量％以上が好ましく、０．１重量％以上がより好ましい。カーボンナノファイバーの含有率は、アクリル繊維の特性が損なわないために、アクリル繊維（１００体積％）中、５体積％以下が好ましい。   In order to obtain a reinforcing effect, the carbon nanofiber content is preferably 0.01% by weight or more, more preferably 0.1% by weight or more in acrylic fiber (100% by volume). The content of the carbon nanofiber is preferably 5% by volume or less in the acrylic fiber (100% by volume) so that the properties of the acrylic fiber are not impaired.

紡糸原液中のポリアクリロニトリル系重合体の濃度は、５〜２５重量％であることが必要である。ポリアクリロニトリル系重合体の濃度は、８〜２３重量％であることが好ましく、１４〜２１重量％であることがより好ましい。ポリアクリロニトリル系重合体の濃度が５重量％を下回ると、紡糸原液中における分子間のからみ合いが低下し、紡糸して得られる炭素繊維前駆体繊維の半径方向のポリアクリロニトリル系重合体同士のつながりが弱くなり、炭素繊維前駆体繊維の緻密性が著しく低下する。ポリアクリロニトリル系重合体濃度は高いほど、前記したポリアクリロニトリル系重合体同士のつながりが強くなり好ましいが、２５重量％を超えると、紡糸原液のゲル化が顕著となり、安定した紡糸が困難となる。ポリアクリロニトリル系重合体濃度は、ポリアクリロニトリル系重合体に対する、紡糸溶媒の割合により調整することができる。   The concentration of the polyacrylonitrile polymer in the spinning dope needs to be 5 to 25% by weight. The concentration of the polyacrylonitrile-based polymer is preferably 8 to 23% by weight, and more preferably 14 to 21% by weight. If the concentration of the polyacrylonitrile polymer is less than 5% by weight, the entanglement between the molecules in the spinning dope will decrease, and the connection between the polyacrylonitrile polymers in the radial direction of the carbon fiber precursor fiber obtained by spinning will be reduced. Becomes weak, and the denseness of the carbon fiber precursor fiber is significantly lowered. The higher the polyacrylonitrile polymer concentration, the stronger the connection between the polyacrylonitrile polymers described above, which is preferable. However, if the concentration exceeds 25% by weight, gelation of the spinning dope becomes remarkable and stable spinning becomes difficult. The concentration of the polyacrylonitrile polymer can be adjusted by the ratio of the spinning solvent to the polyacrylonitrile polymer.

さらに、カーボンナノファイバーを均一分散させた紡糸原液は、分散不良部または異物を除くために濾過することが好ましい。フィルターの目開きのサイズは０．５〜３０μｍが好ましく、より好ましくは０．５〜１０μｍ、さらに好ましくは１〜３μｍである。   Furthermore, it is preferable to filter the spinning solution in which the carbon nanofibers are uniformly dispersed in order to remove poorly dispersed portions or foreign matters. The size of the aperture of the filter is preferably 0.5 to 30 μm, more preferably 0.5 to 10 μm, and still more preferably 1 to 3 μm.

本発明では前述の紡糸原液を用いて、アクリル繊維を紡糸する。紡糸法としては、湿式紡糸法、乾湿式紡糸法、乾式紡糸法が挙げられ、本発明では特に乾湿式紡糸法が好ましい。   In the present invention, acrylic fiber is spun using the above-described spinning dope. Examples of the spinning method include a wet spinning method, a dry and wet spinning method, and a dry spinning method. In the present invention, the dry and wet spinning method is particularly preferable.

乾湿式紡糸の詳しい説明としては、紡糸工程において用いられる凝固浴には、紡糸原液の溶媒として用いたジメチルスルホキシド、ジメチルホルムアミドおよびジメチルアセトアミドなどの溶媒と、いわゆる凝固促進成分を含ませることが好ましい。凝固促進成分としては、ポリアクリロニトリル系重合体を溶解せず、かつ、紡糸原液に用いる溶媒と相溶性があるものを使用することができる。具体的には、凝固促進成分として水を使用することが好ましい。   As a detailed description of dry-wet spinning, the coagulation bath used in the spinning process preferably contains a solvent such as dimethyl sulfoxide, dimethylformamide, and dimethylacetamide used as a solvent for the spinning dope and a so-called coagulation promoting component. As the coagulation accelerating component, a component that does not dissolve the polyacrylonitrile-based polymer and is compatible with the solvent used for the spinning dope can be used. Specifically, it is preferable to use water as a coagulation promoting component.

乾湿式紡糸では紡糸原液をノズル孔より一旦空気中に吐出しその後直ちに凝固浴にて凝固糸とする。凝固浴は、上記のように細径化した凝固糸を引き取るに十分余裕がある条件に設定することが好ましく、これらの要件を満たすよう凝固浴濃度、温度を設定することが好ましい。凝固浴には、紡糸原液に用いられる溶剤を含む水溶液が好適に使用され、含まれる溶剤の濃度を適宜調節する。また、凝固浴の温度は、凝固糸の緻密性の観点からは温度が低い方が好ましいが、温度を下げすぎると凝固糸の引き取り速度が低下し生産性が低下する点を考慮し、３０℃以下が好ましく、さらに好ましくは０℃以上２０℃以下である。   In dry-wet spinning, the spinning solution is once discharged into the air from the nozzle holes, and then immediately coagulated in a coagulation bath. The coagulation bath is preferably set to a condition that has a sufficient margin for pulling the thinned coagulated yarn as described above, and the coagulation bath concentration and temperature are preferably set to satisfy these requirements. For the coagulation bath, an aqueous solution containing the solvent used in the spinning dope is preferably used, and the concentration of the solvent contained is adjusted as appropriate. Further, the temperature of the coagulation bath is preferably lower from the viewpoint of the density of the coagulated yarn. However, if the temperature is lowered too much, the take-up speed of the coagulated yarn is lowered and the productivity is lowered. The following is preferable, and more preferably 0 ° C. or higher and 20 ° C. or lower.

前記の通り、得られた凝固糸を沸水中で凝固糸に含まれている溶媒を洗浄しながら延伸する湿熱延伸を行う。湿熱延伸における延伸浴温度は、単糸同士が融着しない範囲でできるだけ高温にすることが効果的である。この観点から、延伸浴の温度は７０℃以上の高温とすることが好ましい。湿熱延伸方法として、２段以上の多段延伸方法を用いることも可能である。多段延伸法で行う場合は、最終浴を９０℃以上の高温にすることが好ましい。   As described above, wet heat drawing is performed in which the obtained coagulated yarn is drawn in boiling water while washing the solvent contained in the coagulated yarn. It is effective to set the drawing bath temperature in the wet heat drawing as high as possible within a range where the single yarns are not fused. From this viewpoint, it is preferable that the temperature of the stretching bath is a high temperature of 70 ° C. or higher. As the wet heat stretching method, a multi-stage stretching method having two or more stages can be used. When performing by a multistage stretching method, it is preferable to make the final bath a high temperature of 90 ° C. or higher.

浴中延伸工程の後、単繊維同士の接着を防止する目的から、繊維束にシリコーン等からなる油剤を付与することが好ましい。かかるシリコーン油剤は、変性されたシリコーンを用いることが好ましい。シリコーン油剤として、耐熱性の高いアミノ変性シリコーンを含有する油剤を用いることが好ましい。   For the purpose of preventing adhesion between single fibers after the stretching step in the bath, it is preferable to apply an oil agent made of silicone or the like to the fiber bundle. As such a silicone oil agent, it is preferable to use a modified silicone. As the silicone oil agent, an oil agent containing amino-modified silicone having high heat resistance is preferably used.

乾燥熱処理の温度は、１２０〜２００℃であることが好ましく、１３０〜１９８℃であることがより好ましく、１４０〜１９５℃であることが更に好ましい。乾燥熱処理の温度が１６０℃を下回ると、得られる炭素繊維製造用ポリアクリロニトリル系前駆体繊維の緻密性が不十分となり、本発明の効果が得にくくなる場合がある。また、乾燥熱処理の温度が２００℃を超えると、単繊維間の融着が顕著となり、得られる炭素繊維の引張強度が低下する場合がある。   The temperature of the drying heat treatment is preferably 120 to 200 ° C, more preferably 130 to 198 ° C, and still more preferably 140 to 195 ° C. If the temperature of the drying heat treatment is lower than 160 ° C., the resulting polyacrylonitrile-based precursor fiber for producing carbon fibers is insufficiently dense, and it may be difficult to obtain the effects of the present invention. On the other hand, when the temperature of the drying heat treatment exceeds 200 ° C., the fusion between the single fibers becomes remarkable, and the tensile strength of the obtained carbon fibers may be lowered.

乾燥熱処理は、繊維束を加熱されたローラーに接触させて行っても、加熱された雰囲気中を走行させて行っても良いが、乾燥効率と云う観点からは、加熱されたローラーに接触させ行うのが好ましい。   The drying heat treatment may be performed by bringing the fiber bundle into contact with a heated roller or by running in a heated atmosphere. From the viewpoint of drying efficiency, the drying heat treatment is performed by contacting with a heated roller. Is preferred.

炭素繊維製造用ポリアクリロニトリル系前駆体繊維束を形成するフィラメントの本数は、好ましくは１，０００〜３，０００，０００、より好ましくは３，０００〜３，０００，０００、更に好ましくは６，０００〜４８０，０００、最も好ましくは１２，０００〜２４０，０００である。フィラメントの本数は、生産性の向上の目的からは、１，０００以上で多い方が好ましいが、３，０００，０００を超えると炭素繊維製造用ポリアクリロニトリル系前駆体繊維束の内部まで均一に耐炎化処理できないことがある。   The number of filaments forming the polyacrylonitrile-based precursor fiber bundle for carbon fiber production is preferably 1,000 to 3,000,000, more preferably 3,000 to 3,000,000, and still more preferably 6,000. ˜480,000, most preferably 12,000 to 240,000. The number of filaments is preferably 1,000 or more for the purpose of improving productivity, but when it exceeds 3,000,000, the inside of the polyacrylonitrile-based precursor fiber bundle for producing carbon fibers is uniformly flame resistant. May not be able to be processed.

次に、本発明の炭素繊維の製造方法について説明する。   Next, the manufacturing method of the carbon fiber of this invention is demonstrated.

本発明の炭素繊維製造用ポリアクリロニトリル系前駆体繊維の製造方法で製造された炭素繊維製造用ポリアクリロニトリル系前駆体繊維は、２００〜３００℃の温度の酸化性雰囲気中において耐炎化した後、３００〜８００℃の温度の不活性雰囲気中において予備炭化し、１,０００〜３,０００℃の温度の不活性雰囲気中において炭化することにより、炭素繊維とすることができる。   The polyacrylonitrile precursor fiber for carbon fiber production produced by the method for producing the polyacrylonitrile precursor fiber for carbon fiber production of the present invention is flame-resistant in an oxidizing atmosphere at a temperature of 200 to 300 ° C., and then 300 Carbon fiber can be obtained by preliminary carbonization in an inert atmosphere at a temperature of ˜800 ° C. and carbonization in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.

２００〜３００℃の温度の酸化性雰囲気中において耐炎化する際の延伸比は、０．８０〜１．２０であることが好ましく、０．８５〜１．２０であることがより好ましく、０．９０〜１．１０であることが更に好ましい。延伸比が０．８０を下回ると、得られる耐炎化繊維の配向度が不十分となり、また、得られる炭素繊維のストランド引張弾性率が低下する場合がある。また、延伸比が１．２０を超えると、毛羽発生、糸切れ発生により、プロセス性が低下する場合がある。   The stretch ratio when flameproofing in an oxidizing atmosphere at a temperature of 200 to 300 ° C. is preferably 0.80 to 1.20, more preferably 0.85 to 1.20, and More preferably, it is 90-1.10. When the draw ratio is less than 0.80, the degree of orientation of the obtained flame-resistant fiber becomes insufficient, and the strand tensile modulus of the obtained carbon fiber may be lowered. On the other hand, when the draw ratio exceeds 1.20, processability may be deteriorated due to generation of fluff and yarn breakage.

前記耐炎化の処理時間は、１０〜１００分の範囲で適宜選択することができるが、続く予備炭化のプロセス性、および、得られる炭素繊維の力学物性向上の目的から、得られる耐炎化繊維の比重が１．３〜１．４の範囲となるように設定することが好ましい。   The flameproofing treatment time can be appropriately selected within a range of 10 to 100 minutes, but for the purpose of the subsequent preliminary carbonization process and the improvement of the mechanical properties of the resulting carbon fiber, It is preferable to set the specific gravity within a range of 1.3 to 1.4.

予備炭化、および、炭化は、不活性雰囲気中で行なわれるが、用いられる不活性ガスとしては、例えば、窒素、アルゴン、および、キセノンなどが用いられる。経済的な観点からは、窒素が好ましく用いられる。   Pre-carbonization and carbonization are performed in an inert atmosphere, and as the inert gas used, for example, nitrogen, argon, xenon, or the like is used. Nitrogen is preferably used from an economical viewpoint.

予備炭化工程は炉外温度から予備炭化炉内の最高温度までの温度勾配を有するが、該最高温度は、７００〜８００℃であることが好ましく、本工程における３００℃から５００℃までの温度領域では、被熱処理糸条の昇温速度が、５００℃／分以下に設定されることが好ましい。   The preliminary carbonization step has a temperature gradient from the outside temperature to the maximum temperature in the preliminary carbonization furnace, and the maximum temperature is preferably 700 to 800 ° C., and the temperature range from 300 ° C. to 500 ° C. in this step. Then, it is preferable that the temperature increase rate of the yarn to be heat-treated is set to 500 ° C./min or less.

予備炭化を行う際の延伸比は、１．００〜１．３０であることが好ましく、１．１０〜１．３０であることがより好ましく、１．１０〜１．２０であることが更に好ましい。延伸比が１．００を下回ると、得られる予備炭化繊維の配向度が不十分となり、炭素繊維のストランド引張弾性率が低下する場合がある。また、延伸比が１．３０を超えると、毛羽発生や糸切れ発生により、プロセス性が低下する場合がある。   The draw ratio during the preliminary carbonization is preferably 1.00 to 1.30, more preferably 1.10 to 1.30, and even more preferably 1.10 to 1.20. . When the draw ratio is less than 1.00, the degree of orientation of the obtained preliminary carbonized fiber becomes insufficient, and the strand tensile elastic modulus of the carbon fiber may decrease. On the other hand, if the draw ratio exceeds 1.30, the processability may deteriorate due to the occurrence of fluff or yarn breakage.

炭化の温度は、１,０００〜３,０００℃であることが好ましく、１,２００〜１８００℃であることがより好ましく、１,３００〜１,６００℃であることが更に好ましい。炭化の最高温度が高いほど、ストランド引張弾性率は高まるものの、黒鉛化が進行し、結晶サイズが高まり、その結果、圧縮強度の低下が生じる場合があるので、両者のバランスを勘案して、炭化の温度を設定する。   The carbonization temperature is preferably from 1,000 to 3,000 ° C, more preferably from 1,200 to 1800 ° C, still more preferably from 1,300 to 1,600 ° C. The higher the maximum carbonization temperature, the higher the tensile tensile modulus of the strand, but the graphitization proceeds and the crystal size increases, resulting in a decrease in compressive strength. Set the temperature.

炭化を行う際の延伸比は、０．９６〜１．０５であることが好ましく、０．９７〜１．０５であることがより好ましく、０．９８〜１．０３であることが更に好ましい。延伸比が０．９６を下回ると、得られる炭素繊維の配向度や緻密性が不十分となり、ストランド引張弾性率が低下する場合がある。また、延伸比が１．０５を超えると、毛羽発生や糸切れ発生により、プロセス性が低下する場合がある。   The stretch ratio when carbonizing is preferably 0.96 to 1.05, more preferably 0.97 to 1.05, and still more preferably 0.98 to 1.03. When the draw ratio is less than 0.96, the degree of orientation and denseness of the obtained carbon fiber may be insufficient, and the strand tensile elastic modulus may decrease. On the other hand, when the draw ratio exceeds 1.05, processability may be deteriorated due to generation of fluff or yarn breakage.

得られた炭素繊維は、その表面を改質するために、電解処理されても良い。電解処理に用いられる電解液としては、硫酸、硝酸および塩酸等の酸性溶液や、水酸化ナトリウム、水酸化カリウム、テトラエチルアンモニウムヒドロキシド、炭酸アンモニウムおよび重炭酸アンモニウムのようなアルカリまたはそれらの塩の水溶液を使用することができる。電解処理に要する電気量は、適用する炭素繊維の炭化度に応じて、適宜選択することができる。   The obtained carbon fiber may be subjected to electrolytic treatment in order to modify its surface. Examples of the electrolytic solution used for the electrolytic treatment include acidic solutions such as sulfuric acid, nitric acid and hydrochloric acid, and aqueous solutions of alkalis or salts thereof such as sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, ammonium carbonate and ammonium bicarbonate. Can be used. The amount of electricity required for the electrolytic treatment can be appropriately selected according to the carbonization degree of the applied carbon fiber.

かかる電解処理により、得られる複合材料において、炭素繊維とマトリックス樹脂との接着性が適正化でき、接着が強すぎることによる複合材料のブリトルな破壊や、繊維方向の引張強度が低下する問題や、繊維方向における引張強度は高いものの、樹脂との接着性に劣り、非繊維方向における強度特性が発現しないと云うような問題が解消され、得られる複合材料において、繊維方向と非繊維方向の両方向にバランスのとれた強度特性が発現されるようになる。   By such electrolytic treatment, in the obtained composite material, the adhesion between the carbon fiber and the matrix resin can be optimized, the brittle breakage of the composite material due to too strong adhesion, the problem that the tensile strength in the fiber direction decreases, Although the tensile strength in the fiber direction is high, the problem that the adhesive property with the resin is inferior and the strength property in the non-fiber direction is not solved is solved, and in the resulting composite material, both the fiber direction and the non-fiber direction are solved. A balanced strength characteristic is developed.

かかる電解処理の後、得られた炭素繊維に集束性を付与するため、サイジング処理をすることができる。サイジング剤としては、複合材料に使用されるマトリックス樹脂の種類に応じて、マトリックス樹脂との相溶性の良いサイジング剤を適宜選択することができる。   After the electrolytic treatment, a sizing treatment can be performed in order to give the obtained carbon fiber a focusing property. As the sizing agent, a sizing agent having good compatibility with the matrix resin can be appropriately selected according to the type of the matrix resin used in the composite material.

本発明により得られる炭素繊維は、高い圧縮強度およびストランド引張弾性率を有する。従って、本発明の炭素繊維は、プリプレグを用いたオートクレーブ成形法、織物などのプリフォームを用いたレジントランスファーモールディング成形法、フィラメントワインディング成形法などの種々の成形法に適用可能であり、これらの成形法を用いた、航空機部材、圧力容器部材、自動車部材、釣り竿およびゴルフシャフトなどのスポーツ部材の成形に、好適に用いられる。   The carbon fiber obtained by the present invention has high compressive strength and strand tensile elastic modulus. Therefore, the carbon fiber of the present invention can be applied to various molding methods such as an autoclave molding method using a prepreg, a resin transfer molding method using a preform such as a woven fabric, and a filament winding molding method. The method is suitably used for molding sports members such as aircraft members, pressure vessel members, automobile members, fishing rods, and golf shafts.

本明細書に記載の各種物性値の測定方法は、次の通りであり、特に断らない限りは、実施例においても本測定方法を適用している。   The measurement method of various physical property values described in this specification is as follows. Unless otherwise specified, this measurement method is also applied to the examples.

＜各種分子量：Ｚ平均分子量（Ｍｚ）、重量平均分子量（Ｍｗ）、＞
測定しようとするポリアクリロニトリル系重合体の濃度０．１重量％のジメチルホルムアミド（０．０１Ｎ−臭化リチウム添加）に溶解した検体溶液を調製する。調製した検体溶液について、ＧＰＣ装置を用いて、次の条件で測定したＧＰＣ曲線から分子量分布曲線を求め、Ｍｚ、ＭｗおよびＭｎを算出する。測定は、それぞれｎ＝３で行い、平均を分子量とした。
・カラム ：極性有機溶媒系ＧＰＣ用カラム
・流速 ：０．５ｍｌ／分
・温度 ：７５℃
・試料濾過 ：メンブレンフィルター（０．４５μｍカット）
・注入量 ：２００μl
・検出器 ：示差屈折率検出器
Ｍｗは、分子量が異なる分子量既知の単分散ポリスチレンを少なくとも６種類用いて、溶出時間―分子量の検量線を作成し、その検量線上において、該当する溶出時間に対応するポリスチレン換算の分子量を読み取ることにより求める。 <Various molecular weights: Z average molecular weight (Mz), weight average molecular weight (Mw),>
A sample solution prepared by dissolving 0.1% by weight of a polyacrylonitrile polymer to be measured in dimethylformamide (added with 0.01 N lithium bromide) is prepared. For the prepared specimen solution, a molecular weight distribution curve is obtained from a GPC curve measured under the following conditions using a GPC apparatus, and Mz, Mw and Mn are calculated. Each measurement was performed at n = 3, and the average was defined as molecular weight.
-Column: Column for polar organic solvent GPC-Flow rate: 0.5 ml / min-Temperature: 75 ° C
・ Sample filtration: Membrane filter (0.45μm cut)
・ Injection volume: 200 μl
・ Detector: Differential refractive index detector Mw uses at least six types of monodispersed polystyrenes with different molecular weights and known molecular weights to create an elution time-molecular weight calibration curve, and corresponds to the corresponding elution time on the calibration curve. It is obtained by reading the molecular weight in terms of polystyrene.

実施例においては、ＧＰＣ装置として（株）島津製作所製ＣＬＡＳＳ−ＬＣ２０１０を、カラムとして東ソー（株）製ＴＳＫ−ＧＥＬ−α―Ｍ（×２）＋東ソー（株）製ＴＳＫ−ｇｕａｒｄ Ｃｏｌｕｍｅ αを、ジメチルホルムアミドおよび臭化リチウムとして和光純薬工業（株）製を、メンブレンフィルターとしてミリポアコーポレーション製０．４５μ−ＦＨＬＰ ＦＩＬＴＥＲを、示差屈折率検出器として（株）島津製作所製ＲＩＤ−１０ＡＶを、検量線作成用の単分散ポリスチレンとして、分子量１８４０００、４２７０００、７９１０００および１３０００００、１８１００００、４２１００００のものを、それぞれ用いた。   In the examples, CLASS-LC2010 manufactured by Shimadzu Corporation as a GPC apparatus, TSK-GEL-α-M (× 2) manufactured by Tosoh Corporation as a column, and TSK-guard Volume α manufactured by Tosoh Corporation, Calibration curves were manufactured by Wako Pure Chemical Industries, Ltd. as dimethylformamide and lithium bromide, 0.45 μ-FHLP FILTER manufactured by Millipore Corporation as a membrane filter, and RID-10AV manufactured by Shimadzu Corporation as a differential refractive index detector. Monodispersed polystyrenes for preparation were those having molecular weights of 184000, 427000, 791000 and 1300000, 1810000, and 4210000, respectively.

＜凝固浴から引き取った直後の繊維中の結晶配向度＞
ポリアクリロニトリル系重合体の炭素繊維前駆体繊維の軸方向の配向度は、次のように測定した。凝固浴から引き取った直後の繊維束（以降、凝固糸と記すこともある）を金属製の枠に巻き付け、エタノール溶液に１時間浸した後、新しいエタノール溶液に更に１時間浸すことにより、凝固糸中に含まれるＤＭＳＯとエタノールを置換する。枠に巻き付けたまま、遠心分離器で溶液を除去したのち、繊維束中（及び繊維束中の繊維）に含まれる水分が２％以下になるまで風乾する。かかる繊維束を４０ｍｍ長に切断して、２０ｍｇを精秤して採取し、試料繊維軸が正確に平行になるようにそろえた後、試料調整用治具を用いて幅１ｍｍの厚さが均一な試料繊維束に整えた。薄いコロジオン液を含浸させて形態が崩れないように固定した後、広角Ｘ線回折測定試料台に固定した。Ｘ線源として、Ｎｉフィルターで単色化されたＣｕのＫα線を用い、２θ＝１７°付近に観察される回折の最高強度を含む子午線方向のプロフィールの広がりの半価幅（°）を求めた。半価幅３点の平均Ｈから、次式を用いて結晶配向度（％）を求めた。 <Crystal orientation in the fiber immediately after being taken off from the coagulation bath>
The degree of orientation in the axial direction of the carbon fiber precursor fiber of the polyacrylonitrile-based polymer was measured as follows. A fiber bundle immediately after being taken out from the coagulation bath (hereinafter, sometimes referred to as a coagulated yarn) is wound around a metal frame, immersed in an ethanol solution for 1 hour, and then immersed in a new ethanol solution for another hour to obtain a coagulated yarn. DMSO and ethanol contained therein are replaced. After removing the solution with a centrifuge while being wound around the frame, the solution is air-dried until the moisture contained in the fiber bundle (and the fibers in the fiber bundle) becomes 2% or less. This fiber bundle is cut into a length of 40 mm, and 20 mg is precisely weighed and sampled so that the sample fiber axes are exactly parallel, and then a thickness of 1 mm is uniform using a sample adjustment jig. Sample fiber bundles were arranged. After impregnating with a thin collodion solution and fixing it so as not to lose its shape, it was fixed to a sample table for wide angle X-ray diffraction measurement. The half-width (°) of the spread of the profile in the meridian direction including the highest intensity of diffraction observed near 2θ = 17 ° was obtained using Cu Kα ray monochromated with a Ni filter as the X-ray source. . The degree of crystal orientation (%) was determined from the average H of three half widths using the following formula.

結晶配向度（％）＝［（１８０−Ｈ）／１８０］×１００。         Degree of crystal orientation (%) = [(180−H) / 180] × 100.

＜炭素繊維の品位等級の基準＞
検査項目は、焼成後、表面処理・サイジング処理前に２４０００フィラメントの繊維束を１ｍ／分の速度で９０ｍ走行させながら、毛玉・毛羽の個数を数え、三段階評価した。評価基準は、次のとおりである。
・等級１：繊維３０ｍ中、１個以内
・等級２：繊維３０ｍ中、２〜１５個
・等級３：繊維３０ｍ中、１６個以上。 <Standards for carbon fiber grades>
The inspection items were evaluated in three stages by counting the number of fluff and fluff while running a fiber bundle of 24000 filaments at a speed of 1 m / min for 90 m after firing and before surface treatment and sizing treatment. The evaluation criteria are as follows.
-Grade 1: within 1 fiber in 30m-Grade 2: 2-15 in 30m fiber-Grade 3: 16 or more in 30m fiber

＜炭素繊維束の引張強度および弾性率＞
ＪＩＳ Ｒ７６０１（１９８６）「樹脂含浸ストランド試験法」に従って求める。測定する炭素繊維の樹脂含浸ストランドは、３、４−エポキシシクロヘキシルメチル−３、４−エポキシシクロヘキシル−カルボキシレート（１００重量部）／３フッ化ホウ素モノエチルアミン（３重量部）／アセトン（４重量部）を、炭素繊維または黒鉛化繊維に含浸させ、１３０℃の温度で３０分硬化させて作製する。また、炭素繊維のストランドの測定本数は６本とし、各測定結果の平均値を引張強度とする。本実施例では、３、４−エポキシシクロヘキシルメチル−３、４−エポキシシクロヘキシル−カルボキシレートとして、ユニオンカーバイド（株）製“ベークライト”（登録商標）ＥＲＬ４２２１を用いた。
測定はｎ＝６で行い、その平均値をストランド強度、ストランド弾性率とした。 <Tensile strength and elastic modulus of carbon fiber bundle>
Determined according to JIS R7601 (1986) “Resin-impregnated strand test method”. The carbon fiber resin-impregnated strand to be measured is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl-carboxylate (100 parts by weight) / 3 boron trifluoride monoethylamine (3 parts by weight) / acetone (4 parts by weight). ) Is impregnated into carbon fiber or graphitized fiber and cured at a temperature of 130 ° C. for 30 minutes. The number of carbon fiber strands to be measured is 6, and the average value of each measurement result is the tensile strength. In this example, “Bakelite” (registered trademark) ERL4221 manufactured by Union Carbide Co., Ltd. was used as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl-carboxylate.
The measurement was performed at n = 6, and the average value was defined as the strand strength and the strand elastic modulus.

＜炭素繊維前駆体繊維の単糸径＞
測定する多数本の炭素フィラメントからなる炭素繊維前駆体繊維の繊維束について、単位長さ当たりの重量Ａ（ｇ／ｍ）および比重Ｂ（ｇ／ｃｍ３）を求める。測定する炭素繊維束のフィラメント数をＣとし、炭素繊維の平均単繊維径（μｍ）を、下記式で算出する。 <Single yarn diameter of carbon fiber precursor fiber>
A weight A (g / m) and a specific gravity B (g / cm 3 ) per unit length are determined for a fiber bundle of carbon fiber precursor fibers composed of a large number of carbon filaments to be measured. The number of filaments of the carbon fiber bundle to be measured is C, and the average single fiber diameter (μm) of the carbon fiber is calculated by the following formula.

炭素繊維の平均単繊維径（μｍ）
＝（（Ａ／Ｂ／Ｃ）／π）（１／２）×２×１０３
上記測定を３回行い、その算術平均を、その炭素繊維の平均単繊維径とする。 Average single fiber diameter of carbon fiber (μm)
= ((A / B / C) / π) (1/2) × 2 × 10 3
The said measurement is performed 3 times and let the arithmetic mean be the average single fiber diameter of the carbon fiber.

以下、実施例により本発明をさらに具体的に説明する。   Hereinafter, the present invention will be described more specifically with reference to examples.

＜カーボンナノファイバー＞
次に示す３種を用いた。
（１）ＣＮＦ−１：表面処理多層カーボンナノチューブ（ＭＷＣＮＴ）
［参考例１］により調製したものを用いた。
（２）ＣＮＦ−２：二層カーボンナノチューブ（ＤＷＮＴ）
［参考例２］により調製したものを用いた。
（３）ＣＮＦ−３：単層カーボンナノチューブ（ＳＷＮＴ）
ナノシル社製単層カーボンナノチューブ（バッチＮｏ．ＬＳＷ−Ｐ９０／０４０４０６）を用いた。ラマンＧ／Ｄ比を共鳴ラマン散乱測定法において６３３ｎｍのレーザーを用いて測定し、１５５０〜１６５０ｃｍ−１の範囲内で最大のピーク強度をＧ、１３００〜１４００ｃｍ−１の範囲内で最大のピーク強度をＤとしたときのＧ／Ｄ比を計算したところ３回測定した平均のＧ／Ｄ比は８であった。 <Carbon nanofiber>
The following three types were used.
(1) CNF-1: surface-treated multi-walled carbon nanotube (MWCNT)
What was prepared by [Reference Example 1] was used.
(2) CNF-2: Double-walled carbon nanotube (DWNT)
What was prepared by [Reference Example 2] was used.
(3) CNF-3: single-walled carbon nanotube (SWNT)
Single-wall carbon nanotubes (Batch No. LSW-P90 / 040406) manufactured by Nanosil Corporation were used. Raman G / D ratio was measured using a 633nm laser at resonance Raman scattering measurement method, the maximum peak intensity maximum peak intensity in the range of 1550~1650cm -1 G, within the 1300～1400Cm -1 When the G / D ratio was calculated with D being D, the average G / D ratio measured three times was 8.

［参考例１］ＣＮＦ−１：表面処理多層カーボンナノチューブ（ＭＷＣＮＴ）の調製
・Ｋ．Ｈｅｒｎａｄｉ、Ａ．Ｆｏｎｓｅｃａらによる報告を参照（Ｚｅｏｌｉｔｅｓ １
７：４１６−４２３、１９９６）し、酢酸鉄（２ｇ）、酢酸コバルト（２ｇ）、Ｙ型ゼオライト（１０ｇ）を秤量し、メタノール（１００ｍｌ）を加えて、振とう器にて１時間撹拌後、メタノール分を乾燥除去し、触媒を得た。次に、ＣＶＤ反応装置を用いて、反応管内の石英ウール上に触媒１ｇをあらかじめセットし、窒素（３０ｃｃ／分）雰囲気下で６００℃まで昇温後、アセチレン（６ｃｃ／分）、窒素（３０ｃｃ／分）雰囲気下で６００℃×５時間保持しカーボンナノファイバーを合成した。その後、窒素（３０ｃｃ／分）雰囲気下で室温まで冷却し、反応混合物を取り出した。 [Reference Example 1] CNF-1: Preparation of surface-treated multi-walled carbon nanotube (MWCNT) Hernadi, A.M. See report by Fonseca et al. (Zeolites 1
7: 416-423, 1996), iron acetate (2 g), cobalt acetate (2 g), Y-type zeolite (10 g) were weighed, methanol (100 ml) was added, and the mixture was stirred for 1 hour on a shaker. Methanol was removed by drying to obtain a catalyst. Next, using a CVD reactor, 1 g of catalyst was set in advance on quartz wool in the reaction tube, heated to 600 ° C. in a nitrogen (30 cc / min) atmosphere, acetylene (6 cc / min), nitrogen (30 cc) / Min) Carbon nanofibers were synthesized by holding at 600 ° C. for 5 hours in an atmosphere. Then, it cooled to room temperature under nitrogen (30cc / min) atmosphere, and took out the reaction mixture.

前記の反応混合物を、フッ化水素酸１０％水溶液中で３時間撹拌後、ろ紙（Ｔｏｙｏ Ｒｏｓｈｉ Ｋａｉｓｈａ、Ｆｉｌｔｅｒ Ｐａｐｅｒ ２号 １２５ｍｍ）を用いてろ過し、ろ紙上の固形物を、イオン交換水、アセトン溶液にて洗浄後、乾燥し、ＭＷＣＮＴ（ＣＮＦ−１）を得た。カーボンナノチューブの透過型電子顕微鏡（ＴＥＭ）観察結果から、平均繊維直径が１０ｎｍであることが分かった。
得られたカーボンナノチューブをフラスコに５ｇ測り取り、濃硫酸１５０ｇ、６０％硝酸５０ｇを加え、１００℃で３０分加熱した。反応液を水５００ｍｌで希釈し、メンブレンフィルターで濾別後、水でよく洗浄し、表面処理ＭＷＣＮＴ（ＣＮＦ−１）を得た。 The reaction mixture was stirred in a 10% aqueous solution of hydrofluoric acid for 3 hours, and then filtered using a filter paper (Toyo Roshi Kaisha, Filter Paper No. 125 mm). The solid on the filter paper was subjected to ion exchange water, acetone. After washing with a solution and drying, MWCNT (CNF-1) was obtained. From the observation result of the transmission electron microscope (TEM) of the carbon nanotube, it was found that the average fiber diameter was 10 nm.
5 g of the obtained carbon nanotube was measured in a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 30 minutes. The reaction solution was diluted with 500 ml of water, filtered through a membrane filter, and washed well with water to obtain surface-treated MWCNT (CNF-1).

［参考例２］ＣＮＦ−２：二層カーボンナノチューブ（ＤＷＮＴ）の調製

クエン酸アンモニウム鉄（和光純薬工業社製）２．４６ｇをメタノール（関東化学社製）５００ｍＬに溶解した。この溶液に、軽質マグネシア（岩谷社製）を１００ｇ加え、室温で６０分間攪拌し、４０℃から６０℃で攪拌しながら減圧乾燥してメタノールを除去し、軽質マグネシア粉末に金属塩が担持された触媒を得た。 [Reference Example 2] CNF-2: Preparation of double-walled carbon nanotube (DWNT)

2.46 g of ammonium iron citrate (Wako Pure Chemical Industries, Ltd.) was dissolved in 500 mL of methanol (Kanto Chemical Co., Ltd.). To this solution, 100 g of light magnesia (manufactured by Iwatani Corporation) was added, stirred at room temperature for 60 minutes, dried under reduced pressure while stirring at 40 ° C. to 60 ° C. to remove methanol, and a metal salt was supported on the light magnesia powder. A catalyst was obtained.

カーボンナノチューブの合成には、図１に示した反応器を用いた。反応器１００は内径３２ｍｍ 、長きは１２００ｍｍの石英管で、中央部に石英焼結板１０１を具備し、反応器１００の下方部には、不活性ガスおよび原料ガス（炭素含有ガス）を供給するための原料ガス供給ライン１０４、反応器１００の上部には排出ライン１０５、および、触媒を供給するための触媒供給ライン１０３と、反応器を任意温度に保持できるように、反応器の周囲を取り囲む加熱器１０６を具備する。また加熱器には装置流動状態が確認出来るよう点検口１０７が設けられている 。   The reactor shown in FIG. 1 was used for the synthesis of carbon nanotubes. The reactor 100 is a quartz tube having an inner diameter of 32 mm and a length of 1200 mm, and is provided with a quartz sintered plate 101 at the center, and an inert gas and a raw material gas (carbon-containing gas) are supplied to the lower part of the reactor 100. A raw material gas supply line 104, a discharge line 105 at the top of the reactor 100, a catalyst supply line 103 for supplying a catalyst, and surround the reactor so that the reactor can be maintained at an arbitrary temperature. A heater 106 is provided. The heater is provided with an inspection port 107 so that the flow state of the apparatus can be confirmed.

軽質マグネシア粉末に金属塩が担持された前記触媒１２ｇを、触媒供給ライン１０３を通して、石英焼結板１０１上に触媒をセットした。次いで、原料ガス供給ライン１０４から窒素ガスを１０００ｍＬ／分で供給し、反応器内を窒素ガス雰囲気下とした後、温度を９００℃に加熱した（昇温時間３０分）。９００℃に到達した後、温度を保持し、原料ガス供給ライン１０４の窒素流量を２０００ｍＬ/分に上げ、石英焼結板上の固体触媒を流動化させ、点検口１０７から流動化を確認した後、原料ガス供給ライン１０４にメタンを９５ｍＬ／分を供給開始した（反応器に供給される混合ガス中のメタン濃度４．５ｖｏｌ％）。該混合ガスを３０分供給した後、窒素ガスのみの流通に切り替え、合成を終了させた。加熱を停止させ室温まで放置し、室温になってから反応器から触媒とカーボンナノチューブの集合体を含有する組成物を取り出した。上記操作を繰り返し、得られたカーボンナノチューブの集合体を含有する組成物を以下の工程に供した。   The catalyst was set on the quartz sintered plate 101 through the catalyst supply line 103 with 12 g of the catalyst in which the metal salt was supported on the light magnesia powder. Next, nitrogen gas was supplied from the source gas supply line 104 at 1000 mL / min, and the reactor was placed in a nitrogen gas atmosphere. After reaching 900 ° C., after maintaining the temperature, increasing the nitrogen flow rate of the raw material gas supply line 104 to 2000 mL / min, fluidizing the solid catalyst on the quartz sintered plate, and confirming fluidization from the inspection port 107 Then, supply of 95 mL / min of methane to the raw material gas supply line 104 was started (methane concentration of 4.5 vol% in the mixed gas supplied to the reactor). After supplying the mixed gas for 30 minutes, the flow was switched to a flow of only nitrogen gas, and the synthesis was terminated. The heating was stopped and the mixture was allowed to stand at room temperature. After the temperature reached room temperature, the composition containing the aggregate of the catalyst and the carbon nanotube was taken out from the reactor. The above operation was repeated, and the resulting composition containing an aggregate of carbon nanotubes was subjected to the following steps.

カーボンナノチューブ集合体を含有する組成物３０ｇを磁性皿（１５０φ）に取り、マッフル炉（ヤマト科学社製、ＦＰ４１）にて大気下、４４６℃まで１時間で昇温し、６０分保持した後、自然放冷した。さらに、上記のカーボンナノチューブから触媒を除去するため、次のように精製処理を行った。カーボンナノチューブを６Ｎの塩酸水溶液に添加し、８０℃のウォーターバス内で２時間攪拌した。孔径１μｍのフィルターを用いてろ過して得られた回収物を、さらに６Ｎの塩酸水溶液に添加し、８０℃のウォーターバス内で１時間攪拌した。これを孔径１μｍのフィルターを用いてろ過し、数回水洗した後、ろ過物を１２０℃のオーブンで一晩乾燥することでマグネシアおよび金属を除去でき、カーボンナノチューブの集合体を精製することができた。（以降、かかる精製を経たものをカーボンナノチューブの集合体と記す）
＜参考例２で得たＤＷＮＴの確認＞
このようにして得たカーボンナノチューブの集合体を高分解能透過型電子顕微鏡で観察したところ、カーボンナノチューブはきれいなグラファイト層で構成されており、層数が２層のカーボンナノチューブが観察された。またカーボンナノチューブ１００本中の８８％（８８本）を２層のカーボンナノチューブが占めていた。さらに得られたカーボンナノチューブの集合体を、ラマン分光測定した。その結果、Ｇ／Ｄ比は８４（５３２ｎｍ）、７５（６３３ｎｍ）と、グラファイト化度の高い高品質２層カーボンナノチューブであることがわかった。５０ｍＬの容器に上記カーボンナノチューブの集合体１０ｍｇおよびポリスチレンスルホン酸ナトリウム水溶液（アルドリッチ社製、３０重量％、重量平均分子量２０万）１００ｍｇを量りとり、蒸留水９．９３ｍＬを加えて、超音波ホモジナイザー出力２５Ｗ、２０分間で氷冷下分散処理し、カーボンナノチューブの集合体を分散した液を調製した。調製した液には凝集体は目視では確認できず、カーボンナノチューブの集合体はよく分散していた。得られた液を高速遠心分離機にて２００００Ｇ、１５分遠心処理し、上清９ｍＬをサンプリングした。この時の残存液１ｍＬを孔径１μｍのフィルターを用いてろ過、その後よく洗浄して得られたろ過物を１２０℃乾燥機にて乾燥した。ろ過物の重量を測ったところ、３．９ｍｇであった。よって６．１ｍｇ（０．６８ｍｇ／ｍＬ）のカーボンナノチューブ集合体が上清中に分散していることがわかった。粉末Ｘ線回折装置（理学電機株式会社製 ＲＩＮＴ２１００）に上記で得たカーボンナノチューブを含有する集合体の粉末試料を設置し、１．５°から８０°まで操作し、分析を行った。Ｘ線源はＣｕＫα線である。ステップ幅は０．０１０°、計測時間は１．０秒である。その結果、２θ＝２４．８°にピークが検出された。このピークの半値幅は６．９６°であった。
［実施例１］
アクリロニトリル（ＡＮ）１００重量部、イタコン酸１重量部、およびジメチルスルホキシド１３０重量部を混合し、それを還流管と攪拌翼を備えた反応容器に入れた。反応容器内の空間部を酸素濃度が１０００ｐｐｍまで窒素置換した後、ラジカル開始剤として２，２’−アゾビスイソブチロニトリル（ＡＩＢＮ）０．００２重量部を投入し、撹拌しながら下記の条件（重合条件Ａと呼ぶ。）の熱処理を行った。
重合条件Ａ
（１）７０℃の温度で１．５時間保持
（２）７０℃から３０℃へ降温（降温速度１２０℃／時間）
次に、その反応容器中に、ジメチルスルホキシド２４０重量部、ラジカル開始剤としてＡＩＢＮ ０．４重量部、および連鎖移動剤としてオクチルメルカプタン０．１重量部を計量導入した後、さらに撹拌しながら重合条件Ｂの熱処理を行い、残存する未反応単量体を溶液重合法により重合してＰＡＮ系重合体溶液を得た。
重合条件Ｂ
（１）３０℃から６０℃へ昇温（昇温速度１０℃/時間）
（２）６０℃の温度で４時間保持
（３）６０℃から８０℃へ昇温（昇温速度１０℃/時間）
（４）８０℃の温度で６時間保持
ＰＡＮ系重合体は、Ｍｗが３７万、Ｍｚ／Ｍｗが３．４であった。 30 g of a composition containing a carbon nanotube aggregate was placed in a magnetic dish (150φ), heated in a muffle furnace (FP41, manufactured by Yamato Scientific Co., Ltd.) in the atmosphere to 446 ° C. in 1 hour, and held for 60 minutes. It was allowed to cool naturally. Furthermore, in order to remove the catalyst from the carbon nanotube, a purification treatment was performed as follows. Carbon nanotubes were added to a 6N hydrochloric acid aqueous solution and stirred in an 80 ° C. water bath for 2 hours. The recovered material obtained by filtration using a filter having a pore size of 1 μm was further added to a 6N hydrochloric acid aqueous solution and stirred in an 80 ° C. water bath for 1 hour. This is filtered using a filter with a pore size of 1 μm, washed with water several times, and then the filtrate is dried in an oven at 120 ° C. overnight to remove magnesia and metals, and the aggregate of carbon nanotubes can be purified. It was. (Hereafter, this refined product is referred to as an aggregate of carbon nanotubes.)
<Confirmation of DWNT obtained in Reference Example 2>
When the aggregate of carbon nanotubes thus obtained was observed with a high-resolution transmission electron microscope, the carbon nanotubes were composed of a clean graphite layer, and carbon nanotubes with two layers were observed. Two-layer carbon nanotubes accounted for 88% (88) of 100 carbon nanotubes. Furthermore, the obtained carbon nanotube aggregate was subjected to Raman spectroscopic measurement. As a result, it was found that the G / D ratio was 84 (532 nm) and 75 (633 nm), which are high-quality double-walled carbon nanotubes having a high degree of graphitization. Weigh 10 mg of the carbon nanotube aggregate and 100 mg of polystyrene sulfonate aqueous solution (manufactured by Aldrich, 30 wt%, weight average molecular weight 200,000) in a 50 mL container, add 9.93 mL of distilled water, and output with ultrasonic homogenizer Dispersion treatment was carried out at 25 W for 20 minutes under ice cooling to prepare a liquid in which aggregates of carbon nanotubes were dispersed. Aggregates were not visually confirmed in the prepared liquid, and the aggregates of carbon nanotubes were well dispersed. The obtained liquid was centrifuged at 20000 G for 15 minutes with a high-speed centrifuge, and 9 mL of the supernatant was sampled. 1 mL of the remaining liquid at this time was filtered using a filter having a pore diameter of 1 μm, and then the well-washed filtrate was dried with a 120 ° C. dryer. The weight of the filtrate was measured and found to be 3.9 mg. Therefore, it was found that 6.1 mg (0.68 mg / mL) of carbon nanotube aggregates were dispersed in the supernatant. The powder sample of the aggregate containing the carbon nanotubes obtained above was installed in a powder X-ray diffractometer (RINT2100, manufactured by Rigaku Corporation), and the analysis was performed by operating from 1.5 ° to 80 °. The X-ray source is CuKα ray. The step width is 0.010 ° and the measurement time is 1.0 second. As a result, a peak was detected at 2θ = 24.8 °. The full width at half maximum of this peak was 6.96 °.
[Example 1]
100 parts by weight of acrylonitrile (AN), 1 part by weight of itaconic acid, and 130 parts by weight of dimethyl sulfoxide were mixed and put into a reaction vessel equipped with a reflux tube and a stirring blade. After replacing the space in the reaction vessel with nitrogen to an oxygen concentration of 1000 ppm, as a radical initiator, 0.002 part by weight of 2,2′-azobisisobutyronitrile (AIBN) was added and stirred under the following conditions: The heat treatment (referred to as polymerization condition A) was performed.
Polymerization condition A
(1) Hold for 1.5 hours at a temperature of 70 ° C. (2) Decrease in temperature from 70 ° C. to 30 ° C. (Cooling rate 120 ° C./hour)
Next, 240 parts by weight of dimethyl sulfoxide, 0.4 part by weight of AIBN as a radical initiator, and 0.1 part by weight of octyl mercaptan as a chain transfer agent were weighed and introduced into the reaction vessel, and the polymerization conditions were further stirred. The heat treatment of B was performed, and the remaining unreacted monomer was polymerized by a solution polymerization method to obtain a PAN polymer solution.
Polymerization condition B
(1) Temperature increase from 30 ° C to 60 ° C (temperature increase rate 10 ° C / hour)
(2) Hold for 4 hours at a temperature of 60 ° C. (3) Increase the temperature from 60 ° C. to 80 ° C. (temperature increase rate 10 ° C./hour)
(4) The PAN-based polymer held at 80 ° C. for 6 hours had Mw of 370,000 and Mz / Mw of 3.4.

ポリアクリロニトリル重合体溶液の重合体濃度が２０重量％となるように調製した後、アンモニアガスをｐＨが８．５になるまで吹き込むことにより、イタコン酸を中和しつつ、アンモニウム基を重合体に導入して得られた溶液を金属製の容器に入れ、カーボンナノファイバーＣＮＦ−２（二層カーボンナノチューブ（ＤＷＮＴ））を重量分率で０．５ｗｔ％の比率で混合し、ホモジナイザーで混合したのち、目開き０．５μｍの金属焼結フィルターを通過させた後、紡糸原液の温度を４０℃に維持して、吐出孔数６，０００の紡糸口金から、紡糸原液を温度３℃にコントロールした４０重量％ジメチルスルホキシドの水溶液からなる凝固浴に導入し、凝固した繊維束を製造した。この際、吐出線速度および引き取り速度を制御する事により凝固浴から引き取った直後の繊維径が１８ミクロンで、ポリアクリロニトリル結晶配向度が７６％となった。この繊維をさらに、常法により水洗した後、温水中で２．５倍に延伸し、更に、アミノ変性シリコーン系シリコーン油剤を付与した。得られた延伸繊維束を、温度１４０℃に加熱した１０個のローラーに接触させて走行させ、乾燥熱処理を行った。この際、第１番目のローラーの回転数と最終の回転ロールの回転数の比を２倍に設定することにより２倍の延伸を行い、単糸径８ミクロンの前駆体繊維を得た。   After preparing the polymer concentration of the polyacrylonitrile polymer solution to be 20% by weight, by blowing ammonia gas until the pH becomes 8.5, it neutralizes itaconic acid and converts ammonium groups into the polymer. The solution obtained by introduction is put into a metal container, carbon nanofiber CNF-2 (double-walled carbon nanotube (DWNT)) is mixed at a weight fraction of 0.5 wt%, and then mixed with a homogenizer. After passing through a metal sintered filter having an opening of 0.5 μm, the temperature of the spinning dope was maintained at 40 ° C., and the spinning dope was controlled at a temperature of 3 ° C. from a spinneret having 6,000 discharge holes. The solution was introduced into a coagulation bath made of an aqueous solution of weight% dimethyl sulfoxide to produce a coagulated fiber bundle. At this time, by controlling the discharge linear speed and the take-off speed, the fiber diameter immediately after taking out from the coagulation bath was 18 microns, and the polyacrylonitrile crystal orientation was 76%. This fiber was further washed with water by a conventional method, and then stretched 2.5 times in warm water to give an amino-modified silicone silicone oil. The obtained stretched fiber bundle was run while being brought into contact with 10 rollers heated to a temperature of 140 ° C. and subjected to a drying heat treatment. At this time, the ratio of the number of rotations of the first roller to the number of rotations of the final rotating roll was set to 2 times to perform a 2 times stretching to obtain a precursor fiber having a single yarn diameter of 8 microns.

次に、得られたポリアクリロニトリル系前駆体繊維を２本合糸し、トータルフィラメント数を１２，０００の炭素繊維繊維束を作成した。本炭素繊維前駆体繊維束を、温度２４０〜２６０℃の空気中において、延伸比１．０で延伸しながらで耐炎化処理し、比重１．３５の耐炎化繊維束を得た。得られた耐炎化繊維束を、温度３００〜７００℃の窒素雰囲気中において、延伸比１．０５で延伸しながら予備炭化処理を行い、予備炭化繊維束を得た。   Next, two obtained polyacrylonitrile-based precursor fibers were combined to prepare a carbon fiber fiber bundle having a total filament number of 12,000. This carbon fiber precursor fiber bundle was subjected to a flame resistance treatment in air at a temperature of 240 to 260 ° C. while being stretched at a stretch ratio of 1.0 to obtain a flame resistant fiber bundle having a specific gravity of 1.35. The obtained flame-resistant fiber bundle was subjected to preliminary carbonization treatment while being drawn at a draw ratio of 1.05 in a nitrogen atmosphere at a temperature of 300 to 700 ° C. to obtain a preliminary carbonized fiber bundle.

得られた予備炭化繊維束を、最高温度１,５００℃の窒素雰囲気中において、延伸比を０．９７で炭化した。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例２］
引き取り速度を実施例１の１９０％にしたこと以外は実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が１３μｍで、ポリアクリロニトリル結晶配向度が８０％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を２倍とし、単糸径６μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例３］
口金孔径を実施例１の１．４倍、紡糸原液の吐出量を実施例１の１９０％にしたこと以外は実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が２５μｍで、ポリアクリロニトリル結晶配向度が７５％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を４倍とし、単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例４］
口金孔径を実施例１の１．４倍にしたこと以外は実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が１８μｍで、ポリアクリロニトリル結晶配向度が８０％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を２倍とし、単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例５］
温水中での延伸倍率を４倍にした以外は実施例１と同じにして単糸径６ミクロンの前駆体繊維を作成した。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例６］
温水中での延伸倍率を１．５倍にし、乾燥緻密化後の延伸倍率を５倍にした以外は実施例１と同じにして単糸径７ミクロンの炭素繊維前駆体繊維を作成した。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例７］
温水中での延伸倍率を２倍にし、乾燥緻密化後の延伸倍率を７倍にした以外は実施例１と同じにして単糸径５ミクロンの炭素繊維前駆体繊維を作成した。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例８］
反応容器内の空間部を酸素濃度が１００ｐｐｍまで窒素置換したこと、重合条件Ａにおいて、保持温度を６５℃にし、保持時間を２時間にした以外は、実施例１と同様にして重合してＰＡＮ系重合体溶液を得た。ＰＡＮ系重合体は、Ｍｗが４８万、Ｍｚ／Ｍｗが５．７であった。 The obtained pre-carbonized fiber bundle was carbonized at a draw ratio of 0.97 in a nitrogen atmosphere having a maximum temperature of 1,500 ° C. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 2]
A coagulated yarn was prepared in the same manner as in Example 1 except that the take-up speed was 190% of that in Example 1. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 13 μm, and the degree of crystal orientation of polyacrylonitrile was 80%. The coagulated yarn had a hot water draw ratio of 2.5 times, a draw ratio after drying and densification of 2 times, and a carbon fiber precursor fiber having a single yarn diameter of 6 μm was obtained. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 3]
A coagulated yarn was prepared in the same manner as in Example 1 except that the diameter of the nozzle hole was 1.4 times that of Example 1 and the discharge amount of the spinning dope was 190% of Example 1. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 25 μm, and the degree of crystal orientation of polyacrylonitrile was 75%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 4 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 8 μm. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 4]
A coagulated yarn was prepared in the same manner as in Example 1 except that the diameter of the nozzle hole was 1.4 times that of Example 1. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 18 μm, and the degree of crystal orientation of polyacrylonitrile was 80%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 2 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 8 μm. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 5]
A precursor fiber having a single yarn diameter of 6 microns was prepared in the same manner as in Example 1 except that the draw ratio in warm water was set to 4 times. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 6]
A carbon fiber precursor fiber having a single yarn diameter of 7 microns was prepared in the same manner as in Example 1 except that the draw ratio in warm water was 1.5 times and the draw ratio after drying and densification was 5 times. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 7]
A carbon fiber precursor fiber having a single yarn diameter of 5 microns was prepared in the same manner as in Example 1 except that the draw ratio in warm water was doubled and the stretch ratio after drying and densification was seven times. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 8]
PAN was polymerized in the same manner as in Example 1 except that the space in the reaction vessel was purged with nitrogen to an oxygen concentration of 100 ppm, the polymerization temperature A was maintained at 65 ° C., and the retention time was 2 hours. A system polymer solution was obtained. The PAN-based polymer had Mw of 480,000 and Mz / Mw of 5.7.

このＰＡＮ系重合体を実施例１と同じ方法で炭素繊維前駆体繊維を得、引き続いて耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例９］
ＡＮ１００重量部、イタコン酸１重量部、およびジメチルスルホキシド１３０重量部を混合し、それを還流管と攪拌翼を備えた反応容器に入れた。反応容器内の空間部を酸素濃度が１０００ｐｐｍまで窒素置換した後、重合開始剤としてＡＩＢＮ０．００１重量部を投入し、撹拌しながら下記の条件（重合条件Ｃと呼ぶ。）の熱処理を行った。
（１）７０℃の温度で４時間保持
（２）７０℃から３０℃へ降温（降温速度１２０℃／時間）
次に、その反応容器中に、ジメチルスルホキシド２４０重量部、重合開始剤としてＡＩＢＮ ０．４重量部、および連鎖移動剤としてオクチルメルカプタン０．１重量部を計量導入した後、さらに撹拌しながら前記の重合条件Ｂの熱処理を行い、残存する未反応単量体を溶液重合法により重合してＰＡＮ系重合体溶液を得た。ＧＰＣ法で測定されるＭｗが３５万であり、Ｍｚ／Ｍｗが２．４であった。このＰＡＮ系重合体を実施例１と同じ方法で前駆体繊維を得、引き続いて耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例１０］
カーボンナノファイバーを１ｗｔ％混合させたこと以外は実施例１と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例１１］
カーボンナノファイバーを０．１ｗｔ％混合させたこと以外は実施例１と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表１に示す。
［実施例１２］
ポリアクリロニトリル重合体溶液の重合体濃度が６重量％となるように調製し、紡糸原液の吐出量を２００％とした以外はは実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が１２μｍで、ポリアクリロニトリル結晶配向度が７６％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を２倍とし、単糸径５μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得たが、凝固工程で部分的に断糸が発生しており、品位が低下した。この炭素繊維の引張強度、弾性率、品位を表１に示す。
［実施例１３］
ポリアクリロニトリル重合体溶液の重合体濃度が２３重量％となるように調製した以外はは実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が１９μｍで、ポリアクリロニトリル結晶配向度が７５％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を２倍とし、単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表１に示す。ところが、
、紡糸原液粘度が高く、運転１日で金属焼結フィルターの圧損が上昇により連続運転ができなかった。
［実施例１４］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例１と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例１５］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例２と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表３に示す。
［実施例１６］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例３と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例１７］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例４と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例１８］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例５と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例１９］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例６と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２０］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例７と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２１］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例８と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２２］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例９と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２３］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例１０と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２４］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例１１と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２５］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例１２と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２６］
カーボンナノファイバーをＣＮＦ−３（単層ナノチューブ（ＳＷＮＴ））に変更した以外は実施例１３と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［実施例２７］
カーボンナノファイバーをＣＮＦ−１（表面処理多層カーボンナノチューブ（ＭＷＮＴ））に変更した以外は実施例１と同じ方法で炭素繊維前駆体を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位は表２に示す。
［比較例１］
引き取り速度を実施例１の４２％にしたこと以外は実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が２８μｍで、ポリアクリロニトリル結晶配向度が６９％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を５倍とし、単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表３に示す。
［比較例２］
口金孔径を実施例１の０．６５倍にしたこと以外は実施例１と同じ方法で凝固糸を作成した。この際、凝固浴から引き取った直後の繊維直径が１８μｍで、ポリアクリロニトリル結晶配向度が６９％となった。この凝固糸を、温水延伸倍率を２．５倍、乾燥緻密化後の延伸倍率を２倍とし、単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表３に示す。
［比較例３］
カーボンナノファイバーを混合しない以外は実施例１と同じ方法で単糸径８μｍの炭素繊維前駆体繊維を得た。得られた炭素繊維前駆体繊維を実施例１と同じ条件で耐炎化、炭化を行い炭素繊維を得た。この炭素繊維の引張強度、弾性率、品位を表３に示す。 A carbon fiber precursor fiber was obtained from this PAN-based polymer in the same manner as in Example 1, and subsequently subjected to flame resistance and carbonization to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 9]
100 parts by weight of AN, 1 part by weight of itaconic acid, and 130 parts by weight of dimethyl sulfoxide were mixed and placed in a reaction vessel equipped with a reflux tube and a stirring blade. After replacing the space in the reaction vessel with nitrogen to an oxygen concentration of 1000 ppm, 0.001 part by weight of AIBN was added as a polymerization initiator, and heat treatment was performed under the following conditions (referred to as polymerization conditions C) while stirring.
(1) Hold for 4 hours at a temperature of 70 ° C. (2) Decrease in temperature from 70 ° C. to 30 ° C. (Cooling rate 120 ° C./hour)
Next, 240 parts by weight of dimethyl sulfoxide, 0.4 part by weight of AIBN as a polymerization initiator, and 0.1 part by weight of octyl mercaptan as a chain transfer agent were weighed and introduced into the reaction vessel, and then the above-described stirring was performed. A heat treatment under polymerization condition B was performed, and the remaining unreacted monomer was polymerized by a solution polymerization method to obtain a PAN polymer solution. Mw measured by the GPC method was 350,000, and Mz / Mw was 2.4. Precursor fibers were obtained from this PAN-based polymer in the same manner as in Example 1, and subsequently subjected to flame resistance and carbonization to obtain carbon fibers. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 10]
A carbon fiber precursor was obtained by the same method as in Example 1 except that 1 wt% of carbon nanofibers were mixed. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 11]
A carbon fiber precursor was obtained by the same method as in Example 1 except that 0.1 wt% of carbon nanofibers were mixed. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 12]
A coagulated yarn was prepared in the same manner as in Example 1 except that the polymer concentration of the polyacrylonitrile polymer solution was adjusted to 6% by weight, and the amount of spinning solution discharged was 200%. At this time, the fiber diameter immediately after taking out from the coagulation bath was 12 μm, and the degree of crystal orientation of polyacrylonitrile was 76%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 2 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 5 μm. The obtained carbon fiber precursor fiber was flame-proofed and carbonized under the same conditions as in Example 1 to obtain carbon fiber, but the yarn was partially broken in the coagulation process, and the quality was lowered. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 13]
A coagulated yarn was prepared in the same manner as in Example 1 except that the polymer concentration of the polyacrylonitrile polymer solution was 23% by weight. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 19 μm, and the degree of crystal orientation of polyacrylonitrile was 75%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 2 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 8 μm. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 1 shows the tensile strength, elastic modulus, and quality of this carbon fiber. However,
The spinning dope viscosity was high, and continuous operation could not be performed due to an increase in pressure loss of the sintered metal filter in one day of operation.
[Example 14]
A carbon fiber precursor was obtained in the same manner as in Example 1 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 15]
A carbon fiber precursor was obtained in the same manner as in Example 2 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 3 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 16]
A carbon fiber precursor was obtained in the same manner as in Example 3 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 17]
A carbon fiber precursor was obtained in the same manner as in Example 4 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 18]
A carbon fiber precursor was obtained in the same manner as in Example 5 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 19]
A carbon fiber precursor was obtained in the same manner as in Example 6 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 20]
A carbon fiber precursor was obtained in the same manner as in Example 7 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 21]
A carbon fiber precursor was obtained in the same manner as in Example 8, except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 22]
A carbon fiber precursor was obtained in the same manner as in Example 9 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 23]
A carbon fiber precursor was obtained in the same manner as in Example 10 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 24]
A carbon fiber precursor was obtained in the same manner as in Example 11 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 25]
A carbon fiber precursor was obtained in the same manner as in Example 12 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 26]
A carbon fiber precursor was obtained in the same manner as in Example 13 except that the carbon nanofiber was changed to CNF-3 (single-walled nanotube (SWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Example 27]
A carbon fiber precursor was obtained in the same manner as in Example 1 except that the carbon nanofiber was changed to CNF-1 (surface-treated multi-walled carbon nanotube (MWNT)). The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 2 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Comparative Example 1]
A coagulated yarn was prepared in the same manner as in Example 1, except that the take-up speed was 42% of Example 1. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 28 μm, and the degree of crystal orientation of polyacrylonitrile was 69%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 5 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 8 μm. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 3 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Comparative Example 2]
A coagulated yarn was prepared in the same manner as in Example 1 except that the diameter of the nozzle hole was 0.65 times that in Example 1. At this time, the fiber diameter immediately after being taken out from the coagulation bath was 18 μm, and the degree of crystal orientation of polyacrylonitrile was 69%. The coagulated yarn had a hot water draw ratio of 2.5 times and a draw ratio after drying and densification of 2 times to obtain a carbon fiber precursor fiber having a single yarn diameter of 8 μm. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 3 shows the tensile strength, elastic modulus, and quality of this carbon fiber.
[Comparative Example 3]
A carbon fiber precursor fiber having a single yarn diameter of 8 μm was obtained in the same manner as in Example 1 except that carbon nanofibers were not mixed. The obtained carbon fiber precursor fiber was flameproofed and carbonized under the same conditions as in Example 1 to obtain a carbon fiber. Table 3 shows the tensile strength, elastic modulus, and quality of this carbon fiber.

Figure 2009197365
Figure 2009197365

Figure 2009197365
Figure 2009197365

Figure 2009197365
Figure 2009197365

本発明によれば、ポリアクリロニトリルとカーボンナノファイバーを混合した紡糸原液を用いてプロセス性を損なうことなく、引張強度、引張弾性率および品位の優れた炭素繊維を製造することができる。   According to the present invention, a carbon fiber excellent in tensile strength, tensile elastic modulus and quality can be produced without impairing processability by using a spinning dope mixed with polyacrylonitrile and carbon nanofibers.

本発明により得られる炭素繊維は、高い引張強度および引張弾性率を有する。従って、本発明の炭素繊維は、プリプレグを用いたオートクレーブ成形法、織物などのプリフォームを用いたレジントランスファーモールディング成形法、フィラメントワインディング成形法など種々の成形法に適用可能であり、これらの成形法を用いた、航空機部材、圧力容器部材、自動車部材、釣り竿およびゴルフシャフトなどのスポーツ部材の成形に、好適に用いられる。   The carbon fiber obtained by the present invention has high tensile strength and tensile elastic modulus. Therefore, the carbon fiber of the present invention can be applied to various molding methods such as an autoclave molding method using a prepreg, a resin transfer molding method using a preform such as a woven fabric, and a filament winding molding method. Is suitably used for molding sports members such as aircraft members, pressure vessel members, automobile members, fishing rods, and golf shafts.

図１は、本発明で用いられるカーボンナノチューブ製造用の反応器である。FIG. 1 shows a reactor for producing carbon nanotubes used in the present invention.

符号の説明Explanation of symbols

１００：反応器
１０１：石英焼結板
１０２：密閉型触媒供給機
１０３：触媒供給ライン
１０４：原料ガス供給ライン
１０５：排出ライン
１０６：加熱器
１０７：点検口
１０８：触媒 DESCRIPTION OF SYMBOLS 100: Reactor 101: Quartz sintered plate 102: Sealed catalyst supply machine 103: Catalyst supply line 104: Raw material gas supply line 105: Discharge line 106: Heater 107: Inspection port 108: Catalyst

Claims (7)

ポリアクリロニトリル系重合体５〜２５重量％とカーボンナノファイバーを含む紡糸原液を口金から吐出して凝固せしめ、紡糸原液を凝固浴から引き取った直後の単繊維の平均直径を１２〜３０μｍ、Ｘ線回折により測定される結晶配向度を７５〜９０％とし、ついで延伸することを特徴とする炭素繊維前駆体繊維の製造方法。   A spinning stock solution containing 5 to 25% by weight of a polyacrylonitrile polymer and carbon nanofibers is discharged from a die and solidified, and the average diameter of single fibers immediately after taking the spinning stock solution from the coagulation bath is 12 to 30 μm. X-ray diffraction A method for producing a carbon fiber precursor fiber, characterized in that the degree of crystal orientation measured by the method is 75 to 90% and then drawn. 前記炭素繊維前駆体繊維の単繊維直径が、７〜１２μｍである請求項１に記載の炭素繊維前駆体繊維の製造方法。   The method for producing a carbon fiber precursor fiber according to claim 1, wherein the carbon fiber precursor fiber has a single fiber diameter of 7 to 12 μm. 前記紡糸原液を口金から吐出して凝固せしめた後、温水浴中で２〜３倍延伸し、乾燥緻密化した後、さらに１．５〜５倍延伸する請求項１または２に記載の炭素繊維前駆体繊維の製造方法。   The carbon fiber according to claim 1 or 2, wherein the spinning solution is discharged from a die and solidified, then stretched 2-3 times in a warm water bath, dried and densified, and further stretched 1.5-5 times. A method for producing precursor fibers. 前記ポリアクリロニトリル系重合体のゲルパーミエーションクロマトグラフ（ＧＰＣ）法で測定される重量平均分子量Ｍｗが３０万〜５０万であり、多分散度（Ｍｚ／Ｍｗ）（Ｍｚは、Ｚ平均分子量を表す）が２．７〜６．０である
請求項１〜３のいずれかに記載の炭素繊維前駆体繊維の製造方法 The polyacrylonitrile-based polymer has a weight average molecular weight Mw measured by a gel permeation chromatograph (GPC) method of 300,000 to 500,000, and polydispersity (Mz / Mw) (Mz represents a Z average molecular weight). ) Is 2.7 to 6.0, The method for producing a carbon fiber precursor fiber according to any one of claims 1 to 3 前記カーボンのナノファイバーのポリアクリロニトリル系重合体への配合比率が０．０１〜５重量％である請求項１〜４のいずれかに記載の炭素繊維前駆体繊維の製造方法。   The method for producing a carbon fiber precursor fiber according to any one of claims 1 to 4, wherein a blending ratio of the carbon nanofibers to the polyacrylonitrile-based polymer is 0.01 to 5% by weight. 前記紡糸原液を紡糸する方法が乾湿式紡糸法である請求項１〜５のいずれかに記載の炭素繊維前駆体繊維の製造方法   The method for producing a carbon fiber precursor fiber according to any one of claims 1 to 5, wherein the method for spinning the spinning dope is a dry and wet spinning method. 請求項１〜６のいずれかに記載の製造方法によって得られた炭素繊維前駆体繊維を、２００〜３００℃の温度の酸化性雰囲気中において耐炎化処理した後、３００〜８００℃の温度の不活性雰囲気中において予備炭化処理し、次いで１，０００〜３，０００℃の温度の不活性雰囲気中において炭化処理することを特徴とする炭素繊維の製造方法。   The carbon fiber precursor fiber obtained by the production method according to claim 1 is subjected to flame resistance treatment in an oxidizing atmosphere at a temperature of 200 to 300 ° C, and then the temperature of 300 to 800 ° C is not increased. A method for producing carbon fiber, comprising pre-carbonizing in an active atmosphere and then carbonizing in an inert atmosphere at a temperature of 1,000 to 3,000 ° C.
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