JP2003013330A - Method for producing carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber excellent in adhesiveness between the carbon fiber and a resin. SOLUTION: This method for producing carbon fiber comprises baking treatment of a precursor fiber of the carbon fiber, wherein the method is characterized by performing 1st baking treatment of the precursor fiber for the carbon fiber to obtain a fiber having >=65 wt.% but <85 wt.% carbon content, performing oxidation treatment of the surface of the obtained fiber and performing 2nd baking treatment to obtain a carbon fiber having >=85 wt.% carbon content.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、炭素繊維を強化材
とする複合材料において、該炭素繊維と樹脂との接着性
を高めた炭素繊維の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon fiber, which is a composite material having carbon fiber as a reinforcing material, in which the adhesion between the carbon fiber and a resin is enhanced.

【０００２】[0002]

【従来の技術】従来、炭素繊維はその力学的、化学的、
電気的諸特性および軽量性などにより、各種の用途、例
えば航空機やロケットなどの航空・宇宙用航空材料、テ
ニスラケット、ゴルフシャフト、釣竿などのスポーツ用
品に広く使用され、さらに船舶、自動車などの運輸機械
用途分野などにも使用されようとしている。2. Description of the Related Art Conventionally, carbon fibers are mechanical, chemical,
Due to its various electrical characteristics and light weight, it is widely used in various applications such as aerospace materials such as aircraft and rockets, sports equipment such as tennis rackets, golf shafts, fishing rods, etc. It is about to be used in machine applications.

【０００３】これらの用途において、炭素繊維は一般に
該炭素繊維と各種樹脂とからなる複合材料（コンポジッ
ト）の補強材料として用いられているが、炭素繊維の特
性、特にその力学的性質を複合材料に反映させるために
は、複合材料の母材（マトリックス）と炭素繊維との接
着性、一体化が重要であり、炭素繊維は予め何らかの表
面処理を行わないとマトリックスからの”すぬけ”が生
じ易く、補強効果を充分に発揮することができない。In these applications, carbon fibers are generally used as a reinforcing material for composite materials (composites) composed of the carbon fibers and various resins. In order to reflect it, the adhesiveness and integration of the base material (matrix) of the composite material and the carbon fiber are important, and if the carbon fiber is not subjected to any surface treatment in advance, "snack" from the matrix is likely to occur. , The reinforcing effect cannot be fully exerted.

【０００４】そこで、炭素繊維の表面処理方法として、
焼成後かあるいは複合材を製造する前に、酸化剤による
湿式酸化処理、ヒートクリーニング、気相酸化、ウイス
カライジングおよび電解処理などの各種表面処理法が知
られている。これらのなかでも湿式酸化処理や電解酸化
処理、特に電解酸化処理法はその操業性が比較的容易な
ことなどから広く採用され、例えば、特開昭５５−１２
８３４号公報には特定の表面処理エネルギーを用い炭素
繊維を電解表面処理する方法、また特開昭５６−１２８
３６２号公報には電流密度などを特定した条件下で、炭
素繊維を硫酸塩水溶液により電解表面処理する方法が開
示されている。これらの方法は、いずれも炭素繊維の表
面に官能基を生成させ、マトリックス樹脂に対する接着
性を向上させるが、電解処理条件を強化すると、かえっ
て炭素繊維の強度が低下することが知られていた。Therefore, as a surface treatment method for carbon fibers,
Various surface treatment methods such as wet oxidation treatment with an oxidizing agent, heat cleaning, gas phase oxidation, whiskerizing, and electrolytic treatment are known after firing or before producing a composite material. Among them, the wet oxidation treatment or the electrolytic oxidation treatment, especially the electrolytic oxidation treatment method is widely adopted because of its relatively easy operability. For example, JP-A-55-12.
No. 834, a method for electrolytically surface-treating carbon fibers by using a specific surface treatment energy, and JP-A-56-128
Japanese Unexamined Patent Publication No. 362 discloses a method of electrolytically surface-treating carbon fibers with an aqueous solution of sulfate under a condition where the current density and the like are specified. All of these methods generate a functional group on the surface of the carbon fiber to improve the adhesiveness to the matrix resin, but it has been known that strengthening the electrolytic treatment conditions rather reduces the strength of the carbon fiber.

【０００５】特公昭５５−１０７５１３号公報には不活
性雰囲気下の８００℃以上の炭化処理時に繊維に通電す
ることによって、従来の表面処理と同等以上の接着性を
付与でき、かつ引張強度の優れた炭素繊維の製造方法が
提供されているが、この方法では、１７００℃以上の高
温領域において通電させると炭素繊維の切断が起こると
いう問題が知られている。また、特公昭６０−２７１１
号公報には炭化（１２００℃）と黒鉛化（２４３０℃）
の間に水酸化ナトリウムによる電解酸化、或いは空気酸
化を行うことにより黒鉛化糸の引張強度を向上させてい
るが、この方法では接着性の向上が望めないという問題
が知られている。In Japanese Patent Publication No. 55-107513, by applying electricity to the fiber during carbonization treatment at 800 ° C. or higher in an inert atmosphere, it is possible to impart adhesiveness equal to or higher than conventional surface treatment, and excellent tensile strength. Although a method for producing carbon fiber is provided, this method is known to cause a problem that the carbon fiber is cut when a current is applied in a high temperature region of 1700 ° C. or higher. In addition, Japanese Patent Publication 60-2711
In the gazette, carbonization (1200 ℃) and graphitization (2430 ℃)
Although the tensile strength of the graphitized yarn is improved by performing electrolytic oxidation with sodium hydroxide or air oxidation during this, it is known that this method cannot improve the adhesiveness.

【０００６】[0006]

【発明が解決しようとする課題】本発明は、かかる従来
技術の背景に鑑み、炭素繊維と樹脂との接着性に優れた
炭素繊維の製造方法を提供せんとするものである。In view of such background of the prior art, the present invention is to provide a method for producing a carbon fiber having excellent adhesiveness between the carbon fiber and the resin.

【０００７】[0007]

【課題を解決するための手段】本発明は、かかる課題を
解決するために、次のような手段を採用するものであ
る。すなわち、本発明の炭素繊維の製造方法は、炭素繊
維前駆体繊維を焼成処理してなる炭素繊維の製造方法に
おいて、該炭素繊維前駆体繊維に第１の焼成処理を施し
て、炭素含有率が６５重量％以上８５重量％未満の繊維
とした後に、この繊維の表面に酸化処理を施し、次い
で、さらに第２の焼成処理をして、炭素含有率が８５重
量％以上の炭素繊維にすることを特徴とするものであ
る。The present invention employs the following means in order to solve the above problems. That is, the method for producing a carbon fiber of the present invention is a method for producing a carbon fiber obtained by subjecting a carbon fiber precursor fiber to a firing treatment, wherein the carbon fiber precursor fiber is subjected to a first firing treatment so that the carbon content is After making fibers of 65% by weight or more and less than 85% by weight, the surface of the fibers is subjected to an oxidation treatment, and then a second firing treatment is performed to obtain carbon fibers having a carbon content of 85% by weight or more. It is characterized by.

【０００８】[0008]

【発明の実施の形態】本発明は、前記課題、つまり炭素
繊維と樹脂との接着性に優れた炭素繊維の製造方法につ
いて、鋭意検討し、炭素繊維前駆体繊維に第１の焼成処
理をして、炭素含有率が６５重量％以上８５重量％未満
の繊維とした後に、この繊維の表面に酸化処理を施し、
次いで、さらに第２の焼成処理をして、炭素含有率が８
５重量％以上の炭素繊維にしてみたところ、かかる課題
を、一挙に解決することを究明したものである。BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the above-mentioned problems, that is, a method for producing a carbon fiber having excellent adhesiveness between a carbon fiber and a resin, has been earnestly studied, and a carbon fiber precursor fiber is subjected to a first firing treatment. Then, after making the fiber having a carbon content of 65% by weight or more and less than 85% by weight, the surface of this fiber is subjected to an oxidation treatment,
Then, a second baking treatment is further performed to obtain a carbon content of 8
When using 5% by weight or more of carbon fiber, it was clarified that these problems can be solved all at once.

【０００９】本発明の炭素繊維前駆体としては、例え
ば、ポリアクリロニトリル系繊維、レーヨン系繊維、ピ
ッチ系繊維、あるいはポリビニルアルコール系繊維等を
使用することができる。中でも、アクリルニトリル重合
体あるいはその共重合体から得られる繊維、すなわち、
ポリアクリロニトリル系繊維から製造される炭素繊維
は、特に樹脂との接着強度に優れ、かつ、高い引張強度
を発現する炭素繊維と成り得るので好ましく用いること
ができる。As the carbon fiber precursor of the present invention, for example, polyacrylonitrile fiber, rayon fiber, pitch fiber, polyvinyl alcohol fiber or the like can be used. Among them, fibers obtained from an acrylonitrile polymer or a copolymer thereof, that is,
A carbon fiber produced from a polyacrylonitrile fiber can be preferably used because it can be a carbon fiber which is particularly excellent in adhesive strength with a resin and exhibits high tensile strength.

【００１０】本発明の炭素繊維の製造方法は、まず、上
記した該炭素繊維前駆体繊維に第１の焼成処理を施し
て、その炭素含有率を６５重量％以上８５重量％未満に
制御する。この炭素含有率は、好ましくは６５重量％以
上７５重量％未満の範囲内に制御するのが、接着性に優
れた炭素繊維を提供する上で好ましい。また、この際に
窒素含有率が１５重量％以上２５重量％未満となること
が好ましく、さらには２０重量％以上２５重量％未満の
範囲内に制御するのが、接着性に優れた炭素繊維を提供
する上で好ましい。本発明の第１の焼成処理は前記した
炭素含有率に制御する方法であれば特に制限されること
はないが、例えば、２００℃以上４００℃以下の空気や
酸化窒素などの酸化性雰囲気中で加熱焼成して酸化繊維
に転換して後、窒素、アルゴン、ヘリウム等の不活性雰
囲気や真空中でさらに加熱する方法が好ましく用いられ
る。In the method for producing carbon fiber of the present invention, first, the above-mentioned carbon fiber precursor fiber is subjected to the first calcination treatment to control the carbon content thereof to 65% by weight or more and less than 85% by weight. It is preferable to control the carbon content in the range of 65% by weight or more and less than 75% by weight in order to provide carbon fibers having excellent adhesiveness. At this time, the nitrogen content is preferably 15% by weight or more and less than 25% by weight, and it is more preferable to control the nitrogen content within the range of 20% by weight or more and less than 25% by weight in order to obtain a carbon fiber having excellent adhesiveness. It is preferable in providing. The first calcination treatment of the present invention is not particularly limited as long as it is a method for controlling the carbon content described above, but for example, in an oxidizing atmosphere such as air or nitric oxide at 200 ° C. or higher and 400 ° C. or lower. A method is preferably used in which after heating and firing to convert into oxidized fiber, further heating in an inert atmosphere of nitrogen, argon, helium or the like or in vacuum.

【００１１】本発明の炭素繊維前駆体繊維に第１の焼成
処理を施して、炭素含有率が６５重量％以上８５重量％
未満の繊維とした後の表面酸化処理法としては、例え
ば、オゾン等の酸化性ガス雰囲気下での気相酸化、酸素
を含む雰囲気中での加熱酸化、硝酸、硫酸等の酸化剤を
含む溶液中での薬液酸化、酸素を含む雰囲気中でのプラ
ズマ酸化、電子線を照射する電子線照射酸化、レーザー
を照射するレーザー酸化、イオン注入によるイオンエッ
チング酸化、酸性水溶液やアルカリ水溶液や中性塩を含
む水溶液中での電解液相酸化等が使用される。The carbon fiber precursor fiber of the present invention is subjected to the first firing treatment so that the carbon content is 65% by weight or more and 85% by weight or more.
As the surface oxidation treatment method after forming the fibers of less than, for example, gas phase oxidation in an oxidizing gas atmosphere such as ozone, heating oxidation in an atmosphere containing oxygen, a solution containing an oxidizing agent such as nitric acid, sulfuric acid, etc. Chemical solution oxidation, plasma oxidation in an atmosphere containing oxygen, electron beam irradiation oxidation for electron beam irradiation, laser oxidation for laser irradiation, ion etching oxidation by ion implantation, acidic aqueous solution, alkaline aqueous solution and neutral salt. For example, electrolytic solution phase oxidation in an aqueous solution containing is used.

【００１２】オゾン気相酸化法による場合は、オゾン濃
度としては０．１重量％以上５重量％以下、処理温度は
５０℃以上３００℃以下が好ましい。When the ozone gas phase oxidation method is used, the ozone concentration is preferably 0.1% by weight or more and 5% by weight or less, and the treatment temperature is preferably 50 ° C. or more and 300 ° C. or less.

【００１３】空気気相酸化法による場合は、通常、４０
０℃以上８００℃以下の加熱空気中で実施する。必要な
らば適当量の窒素を混入せしめ、酸素濃度を調製しても
よい。When using the air-gas phase oxidation method, it is usually 40
It is carried out in heated air at 0 ° C or higher and 800 ° C or lower. If necessary, an appropriate amount of nitrogen may be mixed in to adjust the oxygen concentration.

【００１４】電解液相酸化法による場合は、繊維を陽極
とし、これと電解液中に設けた陰極板とに電圧を印加せ
しめることにより行う。電解液としては、特に制限はな
く、例えば、硫酸、硝酸、塩酸、リン酸等の酸性水溶
液、水酸化ナトリウム、炭酸アンモニウム、炭酸水素ア
ンモニウム、水酸化テトラメチルアンモニウム、水酸化
テトラエチルアンモニウム、コリン等のアルカリ水溶液
や、塩化リチウム、硫酸ナトリウム等の中性塩を含む水
溶液等を使用することができる。かかる酸、アルカリお
よび中性塩などは、重量％で、好ましくは数％から数十
％の範囲で使用される。また、電解液の温度も特に制限
されるものではないが、好ましくは室温ないし８０℃く
らいの範囲で行われる。In the case of the electrolytic solution-phase oxidation method, the fiber is used as an anode, and a voltage is applied to the fiber and a cathode plate provided in the electrolytic solution. The electrolytic solution is not particularly limited, and examples thereof include acidic aqueous solutions of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, choline, and the like. An alkaline aqueous solution or an aqueous solution containing a neutral salt such as lithium chloride or sodium sulfate can be used. Such acids, alkalis, neutral salts and the like are used in weight%, preferably in the range of several% to several tens%. The temperature of the electrolytic solution is not particularly limited, but is preferably room temperature to about 80 ° C.

【００１５】かかる表面酸化処理法の中でも、酸化剤液
相酸化法が、特別な装置を必要とせず、浸漬のみで優れ
た酸化効果を有するという利点の上から、好ましく使用
される。かかる酸化剤液相酸化法の場合は、硝酸、次亜
塩素酸、クロム酸塩、重クロム酸塩、無水クロム酸、マ
ンガン酸塩、過マンガン酸塩等の酸化剤を水、又は有機
溶媒に溶解して行うが、好ましくは酸化効果の高い硝酸
の水溶液が使用される。Among the surface oxidation treatment methods, the oxidant liquid phase oxidation method is preferably used because it does not require a special apparatus and has an excellent oxidation effect only by immersion. In the case of such an oxidizer liquid phase oxidation method, nitric acid, hypochlorous acid, chromate, dichromate, chromic anhydride, manganate, permanganate or the like is added to water or an organic solvent. It is dissolved, but an aqueous solution of nitric acid having a high oxidizing effect is preferably used.

【００１６】上記酸化剤を、水または溶媒に溶存させる
ときの濃度は、好ましくは１重量％以上８０重量％以
下、より好ましくは３０重量％以上８０重量％以下の範
囲とするのがよい。１重量％未満だと、酸化剤の酸化能
力が低く、酸化に時間が要し、また、８０重量％を越え
ると、過剰な酸化によって、該炭素繊維前駆体繊維の切
断が起こることがある。前記水溶液または有機溶媒溶液
の温度は、室温でも若干の接着性向上効果は得られる
が、大きな接着性向上効果を得るためには、３０℃以上
に保つことが好ましい。該水溶液または溶液の温度の上
限は、特に限定されるものではなく、それらの沸点以下
で用いることができるが、プロセス性、安全性等から３
０℃以上１００℃以下の範囲が好ましい。処理時間につ
いても、特に限定されるものではないが、好ましくは
０．０５分間以上１００分間以下、より好ましくは０．
１分間以上６０分間以下がよい。処理時間が０．０５分
間より小さくなると、処理が不十分となり、一方処理時
間が１００分間よりも大きくなると、処理が強すぎて、
かえって炭素繊維の強度や接着性が低下し好ましくな
い。The concentration of the above-mentioned oxidizing agent when dissolved in water or a solvent is preferably 1% by weight or more and 80% by weight or less, more preferably 30% by weight or more and 80% by weight or less. If it is less than 1% by weight, the oxidizing ability of the oxidizing agent is low, and it takes a long time to oxidize. If it exceeds 80% by weight, the carbon fiber precursor fiber may be cut due to excessive oxidation. Although the temperature of the aqueous solution or the organic solvent solution can obtain a slight effect of improving the adhesiveness even at room temperature, it is preferably kept at 30 ° C. or higher in order to obtain a large effect of improving the adhesiveness. The upper limit of the temperature of the aqueous solution or the solution is not particularly limited, and it can be used at a temperature not higher than the boiling point thereof, but it is 3 from the viewpoint of processability and safety.
The range of 0 ° C or higher and 100 ° C or lower is preferable. The treatment time is also not particularly limited, but preferably 0.05 minutes or more and 100 minutes or less, more preferably 0.
It is preferably 1 minute or more and 60 minutes or less. If the treatment time is less than 0.05 minutes, the treatment becomes insufficient, while if the treatment time is more than 100 minutes, the treatment is too strong.
On the contrary, the strength and adhesiveness of the carbon fiber are reduced, which is not preferable.

【００１７】本発明の表面酸化処理を施した後に行う第
２の焼成処理は、該焼成処理の炭素含有率が８５％以上
になる方法であれば特に制限されることはないが、例え
ば、窒素、アルゴン、ヘリウム等の不活性雰囲気中、好
ましくは窒素雰囲気中で１０００℃以上２０００℃以下
の範囲で焼成する方法が好ましい。The second calcination treatment carried out after the surface oxidization treatment of the present invention is not particularly limited as long as the carbon content of the calcination treatment is 85% or more. The firing method is preferably in the range of 1000 ° C. to 2000 ° C. in an inert atmosphere of argon, helium or the like, preferably in a nitrogen atmosphere.

【００１８】上記１０００℃以上の不活性雰囲気中での
焼成後、さらに第２段の酸化処理を施せば、さらなる接
着性の向上が図ることができるので好ましい。After the firing in the inert atmosphere at 1000 ° C. or higher, the second stage oxidation treatment is further performed, which is preferable because the adhesiveness can be further improved.

【００１９】本発明の第２段の表面酸化処理法は、前記
した第１段の表面酸化処理法を用いることができる。ま
た、この際に炭素繊維の表面酸素濃度（Ｏ/Ｃ）が０．
０１以上０．０６以下の範囲内に制御するのが、接着性
に優れた炭素繊維を提供する上で好ましい。As the second-stage surface oxidation treatment method of the present invention, the above-mentioned first-stage surface oxidation treatment method can be used. Further, at this time, the surface oxygen concentration (O / C) of the carbon fiber was 0.
It is preferable to control it within the range of 01 or more and 0.06 or less in order to provide a carbon fiber having excellent adhesiveness.

【００２０】かくして第２段の表面酸化処理された炭素
繊維は、いずれの場合も充分に洗浄した後、適宜乾燥す
ることが好ましい。Thus, in any case, it is preferable that the carbon fiber subjected to the second stage surface oxidation treatment is thoroughly washed and then appropriately dried.

【００２１】以下に、本発明で用いた特性の測定方法に
ついて説明する。 ＜炭素繊維の炭素含有率・窒素含有率の測定＞炭素繊維
の炭素含有率・窒素含有率は、元素分析により求めた。
先ず、試料を真空中４０℃で５時間乾燥処理した後、柳
本分析工業社製、全自動元素分析装置ｖａｒｉｏＥＬを
使用し、試料分解炉温度９５０℃、還元炉温度５００℃
の条件で炭素量、窒素量を測定した。 ＜炭素繊維の表面酸素濃度（Ｏ/Ｃ）＞表面酸素濃度Ｏ/
Ｃは、次の手順に従ってＸ線光電子分光法により求め
た。先ず、炭素繊維束をカットしてステンレス製の試料
支持台上に拡げて並べた後、光電子脱出角度を９０゜と
し、Ｘ線源としてＭｇＫα１,２を用い、試料チャンバ
ー内を１×１０^-8Ｔｏｒｒの真空度に保つ。測定時の帯
電に伴うピークの補正として、まずＣ_1Sの主ピークの結
合エネルギー値を２８４．６ｅＶに合わせる。Ｃ _1Sピー
ク面積は、２８２〜２９６ｅＶの範囲で直線のベースラ
インを引くことにより求め、Ｏ_1Sピーク面積は、５２８
〜５４０ｅＶの範囲で直線のベースラインを引くことに
より求めた。表面酸素濃度Ｏ/Ｃは、上記Ｏ_1Sピーク面
積の比を、装置固有の感度補正値で割ることにより算出
した原子数比で表した。なお、本実施例では島津製作所
（株）製ＥＳＣＡ−７５０を用い、上記装置固有の感度
補正値は２．８５であった。The method for measuring the characteristics used in the present invention is described below.
explain about. <Measurement of carbon content and nitrogen content of carbon fiber> Carbon fiber
The carbon content rate and nitrogen content rate of were determined by elemental analysis.
First, after drying the sample in vacuum at 40 ° C for 5 hours,
Fully automatic elemental analysis device varioEL manufactured by this analysis industry company
Used, sample decomposition furnace temperature 950 ℃, reduction furnace temperature 500 ℃
The amount of carbon and the amount of nitrogen were measured under the conditions. <Surface oxygen concentration (O / C) of carbon fiber> Surface oxygen concentration O /
C is obtained by X-ray photoelectron spectroscopy according to the following procedure.
It was First, cut the carbon fiber bundle and make a stainless steel sample.
After spreading and arranging them on the support stand, set the photoelectron escape angle to 90 °.
Then, using MgKα1,2 as the X-ray source,
ー 1 × 10^-8Maintain a vacuum of Torr. Band when measuring
To correct the peak associated with power, first C_1SOf the main peak of
The combined energy value is adjusted to 284.6 eV. C _1SPee
The area is 282-296 eV, and
Obtained by pulling in, O_1SThe peak area is 528
To draw a straight baseline in the range of ~ 540 eV
I asked more. The surface oxygen concentration O / C is O above._1SPeak plane
Calculated by dividing the product ratio by the device-specific sensitivity correction value
It is expressed by the ratio of the number of atoms. In this example, Shimadzu Corporation
Using ESCA-750 manufactured by Co., Ltd., the sensitivity peculiar to the above device
The corrected value was 2.85.

【００２２】[0022]

【実施例】以下、実施例により本発明を、具体的に説明
するが制限されるものではない。EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

【００２３】実施例中の単糸接着強度は次のようにして
求めたものである。The single yarn adhesive strength in the examples is obtained as follows.

【００２４】ビスフェノールＡ型エポキシ樹脂化合物”
エピコート”８２８（油化シェルエポキシ（株）製）/
ヒマ脂油変性ヘロキシ５０５（油化シェルエポキシ
（株）製）/n-アミノエチルピペラジン＝１５部：１５
部：４．９部をよく混合し、この混合液を炭素繊維単糸
に含浸し、得られた単糸包埋樹脂を室温で約１２時間、
前硬化した後、１００℃で１２０分間加熱、後硬化させ
た。Bisphenol A type epoxy resin compound "
Epicoat "828 (Okaka Shell Epoxy Co., Ltd.) /
Castor fat oil modified herooxy 505 (produced by Yuka Shell Epoxy Co., Ltd.) / N-aminoethylpiperazine = 15 parts: 15
Parts: 4.9 parts were mixed well, the carbon fiber single yarn was impregnated with this mixed solution, and the obtained single yarn-embedded resin was allowed to stand at room temperature for about 12 hours.
After pre-curing, it was heated at 100 ° C. for 120 minutes to be post-cured.

【００２５】次に、厚さ２ｍｍ、巾１０ｍｍ、長さ１５
０ｍｍのテフロン（登録商標）製枠の長手方向に炭素繊
維単糸を３本平行に張り、上記混合液を枠中に含浸し、
室温で約１２時間、前硬化した後、１００℃で１２０分
間加熱、後硬化して単糸包埋樹脂試験片を作製した。Next, the thickness is 2 mm, the width is 10 mm, and the length is 15.
Three carbon fiber single yarns are stretched in parallel in the longitudinal direction of a 0 mm Teflon (registered trademark) frame, and the above mixed solution is impregnated into the frame,
After pre-curing at room temperature for about 12 hours, heating at 100 ° C. for 120 minutes and post-curing, a single-thread-embedded resin test piece was prepared.

【００２６】上記単糸包埋樹脂試験片に繊維軸方向に引
張力を与え、歪みを１０％生じさせた後、光学顕微鏡に
より試験片中心部２０ｍｍの範囲における繊維破断数を
測定した。Tensile force was applied to the single-thread-embedded resin test piece in the fiber axis direction to generate a strain of 10%, and the number of fiber breakages was measured in an area of 20 mm at the center of the test piece by an optical microscope.

【００２７】次に、繊維破断数を平均破断繊維長ｌに換
算し、下記算式により、臨界繊維長ｌｃを計算した。Next, the number of broken fibers was converted into an average broken fiber length l, and the critical fiber length lc was calculated by the following formula.

【００２８】[0028]

【数１】 [Equation 1]

【００２９】繊維・樹脂界面の接着強度τを下記式によ
り計算した。The adhesive strength τ at the fiber / resin interface was calculated by the following formula.

【００３０】[0030]

【数２】 [Equation 2]

【００３１】ただし、σは臨界繊維長での単糸強度、ｄ
は繊維の直径である。Where σ is the single yarn strength at the critical fiber length, d
Is the diameter of the fiber.

【００３２】（実施例１〜２）ポリアクリロニトリル繊
維を３００℃の空気中で加熱焼成した後、窒素中でさら
に６５０℃に加熱焼成して炭素含有率が６８重量％、窒
素含有率が２１重量％の炭素繊維前駆体繊維を得た。(Examples 1 and 2) Polyacrylonitrile fibers were heated and calcined in air at 300 ° C., and then further calcined at 650 ° C. in nitrogen to have a carbon content of 68% by weight and a nitrogen content of 21% by weight. % Carbon fiber precursor fiber was obtained.

【００３３】上記炭素繊維前駆体繊維を濃度３０％、温
度７０℃の硝酸水溶液に、５および１０分接触させた
後、窒素中で、さらに１４５０℃で焼成して、炭素含有
率が９８％の炭素繊維を得た。The above carbon fiber precursor fiber was brought into contact with an aqueous nitric acid solution having a concentration of 30% and a temperature of 70 ° C. for 5 and 10 minutes, and then calcined in nitrogen at 1450 ° C. to obtain a carbon content of 98%. Carbon fiber was obtained.

【００３４】上記炭素繊維を前記した方法に従い試験片
を作製し、接着強度を測定した。得られた炭素繊維の接
着強度を第１表にまとめた。A test piece was prepared from the above carbon fiber according to the method described above, and the adhesive strength was measured. The adhesive strength of the obtained carbon fibers is summarized in Table 1.

【００３５】（実施例３〜４）実施例１〜２で得られた
炭素繊維を、電解酸化処理として、温度２０℃、濃度１
％の重炭酸アンモニウム水溶液を満たした電解処理槽
中、糸速２．４ｍ/分で連続的に走行させるとともに、
該処理槽の直前に配置した金属製ガイドローラーを介し
て、該炭素繊維に陽電圧を印加し、処理液中に配置した
白金製の陰極との間に炭素繊維１ｇ当たりの電気量で２
クーロンになるように電流を流した。(Examples 3 to 4) The carbon fibers obtained in Examples 1 and 2 were subjected to electrolytic oxidation treatment at a temperature of 20 ° C and a concentration of 1
% In an electrolytic treatment tank filled with ammonium bicarbonate aqueous solution, while continuously running at a yarn speed of 2.4 m / min,
A positive voltage is applied to the carbon fiber through a metal guide roller arranged immediately before the treatment tank, and the amount of electricity per 1 g of carbon fiber is 2 between the carbon fiber and a cathode made of platinum arranged in the treatment liquid.
An electric current was passed so that it would be a coulomb.

【００３６】次に、電解処理を施した炭素繊維を充分に
水洗して、約１００℃の加熱空気中で乾燥した。Next, the electrolytically treated carbon fibers were thoroughly washed with water and dried in heated air at about 100 ° C.

【００３７】上記炭素繊維を前記した方法に従い試験片
を作製し、接着強度を測定した。得られた炭素繊維の接
着強度を第１表にまとめた。A test piece was prepared from the above carbon fiber according to the method described above, and the adhesive strength was measured. The adhesive strength of the obtained carbon fibers is summarized in Table 1.

【００３８】（比較例１）炭素繊維前駆体繊維を、濃度
３０％、温度７０℃の硝酸水溶液に接触させない以外は
実施例１〜２と同様にして炭素繊維を得た。また、実施
例１〜２と同様にして、接着強度を測定した。得られた
炭素繊維の接着強度を第１表にまとめた。(Comparative Example 1) A carbon fiber was obtained in the same manner as in Examples 1 and 2 except that the carbon fiber precursor fiber was not brought into contact with an aqueous nitric acid solution having a concentration of 30% and a temperature of 70 ° C. Further, the adhesive strength was measured in the same manner as in Examples 1 and 2. The adhesive strength of the obtained carbon fibers is summarized in Table 1.

【００３９】[0039]

【表１】 [Table 1]

【００４０】表１から明らかなように、実施例１〜４の
ものは、比較例１のものに比して、樹脂との接着性が著
しく優れていることがわかる。As is apparent from Table 1, it is understood that Examples 1 to 4 have remarkably excellent adhesiveness to the resin as compared with Comparative Example 1.

【００４１】[0041]

【発明の効果】本発明によれば、樹脂との接着性に優れ
た、炭素繊維を安定して製造することができる。EFFECTS OF THE INVENTION According to the present invention, it is possible to stably produce a carbon fiber having excellent adhesiveness with a resin.

───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 4L031 AA27 AB04 BA12 BA14 CA02 CB10 DA21 4L037 AT02 CS03 PA53 PC02 PC05 PS02 PS03 UA12    ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4L031 AA27 AB04 BA12 BA14 CA02                       CB10 DA21                 4L037 AT02 CS03 PA53 PC02 PC05                       PS02 PS03 UA12

Claims (5)

【特許請求の範囲】[Claims] 【請求項１】炭素繊維前駆体繊維を焼成処理してなる炭
素繊維の製造方法において、該炭素繊維前駆体繊維に第
１の焼成処理を施して、炭素含有率が６５重量％以上８
５重量％未満の繊維とした後に、この繊維の表面に酸化
処理を施し、次いで、さらに第２の焼成処理をして、炭
素含有率が８５重量％以上の炭素繊維にすることを特徴
とする炭素繊維の製造方法。1. A method for producing a carbon fiber obtained by subjecting a carbon fiber precursor fiber to a firing treatment, wherein the carbon fiber precursor fiber is subjected to a first firing treatment so that the carbon content is at least 65% by weight.
A carbon fiber having a carbon content of 85% by weight or more is obtained by subjecting the surface of this fiber to an oxidation treatment after the fiber of less than 5% by weight and then subjecting the fiber to a second firing treatment. Carbon fiber manufacturing method. 【請求項２】該炭素繊維前駆体繊維が、ポリアクリルニ
トリル系繊維であることを特徴とする請求項１記載の炭
素繊維の製造方法。2. The method for producing a carbon fiber according to claim 1, wherein the carbon fiber precursor fiber is a polyacrylonitrile fiber. 【請求項３】該第２の焼成処理の温度が、１０００℃以
上２０００℃以下の範囲であることを特徴とする請求項
１または２に記載の炭素繊維の製造方法。3. The method for producing carbon fiber according to claim 1, wherein the temperature of the second firing treatment is in the range of 1000 ° C. or higher and 2000 ° C. or lower. 【請求項４】請求項１〜３の方法で得られた炭素繊維
に、さらに第２段の表面酸化処理することを特徴とする
炭素繊維の製造方法。4. A method for producing a carbon fiber, which comprises subjecting the carbon fiber obtained by the method according to any one of claims 1 to 3 to a second stage surface oxidation treatment. 【請求項５】該第２段の酸化処理が、炭素繊維表面酸素
濃度（Ｏ/Ｃ）を０．０１以上０．０６以下の範囲に制
御するものであることを特徴とする請求項４記載の炭素
繊維の製造方法。5. The carbon fiber surface oxygen concentration (O / C) is controlled within the range of 0.01 or more and 0.06 or less in the second-stage oxidation treatment. Of manufacturing carbon fiber of.