JP2015067910A - Carbon fiber and manufacturing method thereof - Google Patents

Carbon fiber and manufacturing method thereof Download PDF

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JP2015067910A
JP2015067910A JP2013201186A JP2013201186A JP2015067910A JP 2015067910 A JP2015067910 A JP 2015067910A JP 2013201186 A JP2013201186 A JP 2013201186A JP 2013201186 A JP2013201186 A JP 2013201186A JP 2015067910 A JP2015067910 A JP 2015067910A
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carbon fiber
yarn
tensile
dtex
carbonization
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秀生 沓屋
Hideo Kutsuya
秀生 沓屋
伸吾 阪口
Shingo Sakaguchi
伸吾 阪口
大介 高尾
Daisuke Takao
大介 高尾
康二 中嶋
Koji Nakajima
康二 中嶋
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Toray Industries Inc
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Toray Industries Inc
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Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber which is superior to tensile modulus of elasticity and tensile strength especially, and also superior to compression modulus of elasticity and compressive strength, and to provide a manufacturing method thereof.SOLUTION: A carbon fiber contains more than 1000 carbon fiber single yarn whose surface arithmetic mean roughness Ra measured by an atomic force microscope is not more than 3.0 nm, whose crystal size of a c-axis Lc known from 002 diffraction lines by X-ray diffraction measurement is 17.0-22.4 Angstrom, and whose crystal orientation πis 83.5-85.5%, and as for the carbon fiber bundle, the degree of intermingling A is 10-80, ellipticity B of its bundle cross section is 0.15-0.40, the number of broken single yarn more than 10 mm is not more than 1.5/m, and its tensile modulus of elasticity YM is 313-345 GPa.

Description

本発明は、特に引張弾性率、引張強度に優れ、圧縮弾性率、圧縮強度にも優れた炭素繊維とその製造方法に関するものである。   The present invention relates to a carbon fiber particularly excellent in tensile elastic modulus and tensile strength, and excellent in compressive elastic modulus and compressive strength, and a method for producing the same.

炭素繊維は、他の繊維に比べて優れた強度および弾性率を有するため、複合材料用補強材料として、スポーツ用途・航空宇宙用途だけではなく、自動車や風車、圧力容器などの一般産業用途にも幅広く使用されている。特に環境・コスト面から機体軽量化が強く求められる航空機分野においては、炭素繊維への需要が高く、近年、更なる高性能化が求められている。炭素繊維強化複合材料の中でも、炭素繊維を用いた織物を補強基材としたプリプレグや、一方向材のプリプレグは、複合材料に成形することで、航空機用部材として多量に使用されている。最近では居住性向上などを図った使用部位の大型化に伴い、高い剛性が必要とされ始めており、高い引張強度、引張弾性率だけでなく、高い圧縮弾性率と圧縮強度を有する炭素繊維への需要が高まっている。   Carbon fiber has superior strength and elastic modulus compared to other fibers, so it can be used not only for sports and aerospace applications, but also for general industrial applications such as automobiles, windmills, and pressure vessels as a reinforcing material for composite materials. Widely used. Particularly in the aircraft field, where weight reduction of the aircraft is strongly demanded from the viewpoint of environment and cost, there is a high demand for carbon fiber, and in recent years, further improvement in performance has been demanded. Among carbon fiber reinforced composite materials, a prepreg using a woven fabric using carbon fibers as a reinforcing base and a prepreg made of a unidirectional material are used in a large amount as an aircraft member by molding into a composite material. Recently, along with the increase in the size of the use site aimed at improving habitability, high rigidity has begun to be required, and not only high tensile strength and tensile elastic modulus, but also to carbon fibers having high compressive elastic modulus and compressive strength. Demand is increasing.

一般に、圧縮弾性率は、引張弾性率と比例関係にあり、引張弾性率を高めることで向上させることができる。引張弾性率と圧縮弾性率を向上させるためには、炭化工程の最高温度を高くすればよいが、炭素繊維網面の成長に伴い、得られる炭素繊維の圧縮強度は１２００℃〜１４００℃付近で極大になりそれ以上の温度で低下するという問題がある。すなわち、炭素繊維の炭素繊維網面の成長を表す結晶サイズＬｃの大きさと圧縮強度はトレードオフの関係にある。一般的に、ポリアクリロニトリル系炭素繊維の炭化最高温度は１２００〜２０００℃で処理されるが、温度アップとともに引張弾性率は確かに向上するものの圧縮強度は低下する。また、引張強度も同様にある程度温度が高くなると低下する傾向を示す。つまり、求められる圧縮弾性率、圧縮強度、引張弾性率、引張強度を同時に満足した炭素繊維を得るためには、結晶サイズを小さく維持し引張弾性率を向上させる、すなわち、炭化処理温度を低くして引張弾性率を高めることが求められる。このような炭素繊維を得るために、現在までに、いくつかの提案がなされている。   In general, the compressive elastic modulus is proportional to the tensile elastic modulus, and can be improved by increasing the tensile elastic modulus. In order to improve the tensile elastic modulus and the compressive elastic modulus, the maximum temperature of the carbonization process may be increased. With the growth of the carbon fiber network surface, the compression strength of the obtained carbon fiber is around 1200 ° C to 1400 ° C. There is a problem that it becomes maximum and falls at a higher temperature. That is, the size of the crystal size Lc representing the growth of the carbon fiber network surface of the carbon fiber and the compressive strength are in a trade-off relationship. Generally, the maximum carbonization temperature of the polyacrylonitrile-based carbon fiber is treated at 1200 to 2000 ° C., but the tensile elastic modulus surely improves with increasing temperature, but the compressive strength decreases. Similarly, the tensile strength tends to decrease as the temperature increases to some extent. In other words, in order to obtain carbon fibers that satisfy the required compressive modulus, compressive strength, tensile modulus, and tensile strength at the same time, the crystal size is kept small and the tensile modulus is improved, that is, the carbonization temperature is lowered. Therefore, it is required to increase the tensile elastic modulus. In order to obtain such carbon fibers, several proposals have been made so far.

特許文献１には、ポリアクリロニトリル重合体の分子量を高めることで、炭化温度領域での高延伸を達成せしめ、一定温度において従来公知の引張弾性率を超える引張弾性率を有する炭素繊維を得る方法が示されている。しかし、その高分子量が原因となり製糸の延伸性低下を伴い、炭素繊維の製造という観点では生産性ダウン、すなわちコストアップや品位の低下を招いてしまう問題があった。   Patent Document 1 discloses a method for obtaining a carbon fiber having a tensile elastic modulus exceeding a conventionally known tensile elastic modulus at a constant temperature by achieving high stretching in the carbonization temperature region by increasing the molecular weight of the polyacrylonitrile polymer. It is shown. However, due to the high molecular weight, there is a problem in that the drawability of the yarn is reduced, and in terms of carbon fiber production, the productivity is lowered, that is, the cost is increased and the quality is lowered.

特許文献２には、特定の分子量分布を有するポリアクリロニトリル重合体を使用することで、高延伸を達成し高い引張弾性率を得る方法が示されている。しかし、本発明者らが検討したところ分子量分布を精密にコントロールしなければ効果は得られないことが問題となった。   Patent Document 2 discloses a method of achieving high stretching and obtaining a high tensile elastic modulus by using a polyacrylonitrile polymer having a specific molecular weight distribution. However, as a result of studies by the present inventors, there has been a problem that the effect cannot be obtained unless the molecular weight distribution is precisely controlled.

特許文献３には、高い引張強度と弾性率を有する乾湿式紡糸プリカーサを一定の張力下で耐炎化・炭化することで、湿式紡糸原糸では得られない引張弾性率と引張強度を有する炭素繊維を得る方法が示されている。しかしながら、炭化温度１４５０℃での最も高い引張弾性率は２９５ＧＰａであった。実際に３００ＧＰａを超える炭素繊維を得るためには延伸すればよいが、品位とのバランスが難しく課題となることが分かった。   Patent Document 3 discloses a carbon fiber having a tensile elastic modulus and a tensile strength that cannot be obtained with a wet spinning raw yarn by flameproofing and carbonizing a dry and wet spinning precursor having a high tensile strength and elastic modulus under a certain tension. The way to get it is shown. However, the highest tensile elastic modulus at a carbonization temperature of 1450 ° C. was 295 GPa. In order to obtain a carbon fiber exceeding 300 GPa, it may be drawn, but it has been found that it is difficult to achieve a balance with quality.

特許文献４には、乾湿式紡糸プリカーサに耐炎化遅延元素および微粒子を含む油剤を付与することで耐炎化での焼け斑を抑制し炭化工程での延伸性を向上させることで、引張強度と引張弾性率を高いレベルで有する炭素繊維を得る方法が示されている。しかし、炭化温度１５５０℃領域までにおいて最も高い引張弾性率は３２０ＧＰａまでであり、それ以上炭化温度を上げると、弾性率は向上するが、強度がかえって低下するという問題があり、また、炉内を汚染し長期運転が困難であるという問題が有った。   Patent Document 4 discloses that a wet and wet spinning precursor is provided with an oil agent containing a flame retarding delay element and fine particles to suppress burn spots in the flame resistance and improve stretchability in the carbonization process, thereby improving tensile strength and tensile strength. A method of obtaining carbon fibers having a high level of elastic modulus is shown. However, the highest tensile elastic modulus up to the carbonization temperature of 1550 ° C. is up to 320 GPa. If the carbonization temperature is further increased, the elastic modulus is improved, but there is a problem that the strength is lowered. There was a problem that it was contaminated and long-term operation was difficult.

特許文献５には、エアー処理による開繊かつ加撚により、耐炎化工程を延伸せしめ引張強度を向上させる技術が示されている。かかる技術については、例えば、２５０ＧＰａ以上に引張弾性率を向上させると品位の著しい悪化が起こる問題があった。また、例えば、乾湿式紡糸によって緻密性がより高いプリカーサにこの技術を適用しようとすると、その高い緻密性ゆえに高温炉での糸傷みや断糸が多発する問題があった。   Patent Document 5 discloses a technique for extending the flameproofing process and improving the tensile strength by opening and twisting by air treatment. With respect to such a technique, for example, when the tensile modulus is improved to 250 GPa or more, there is a problem that the quality is significantly deteriorated. Further, for example, when this technique is applied to a precursor having higher density by dry and wet spinning, there is a problem that yarn damage and yarn breakage frequently occur in a high temperature furnace due to the high density.

特許文献６によれば、乾湿式紡糸により得られたプリカーサは表面平滑、かつ、円形断面構造を有し、耐炎化工程で高い緻密性を有する表層部が酸素透過を阻害して、内層での焼け斑を顕著化させる。この点において、耐炎化工程を延伸せしめ、得られる炭素繊維の引張強度を向上させ、集束性を付与する目的で加撚することは、糸条密度が高くなり酸素供給が遮られ、高温炉での糸傷みや断糸する方向に進むという問題があった。   According to Patent Document 6, the precursor obtained by dry-wet spinning has a smooth surface and a circular cross-sectional structure, and the surface layer portion having high density in the flameproofing process inhibits oxygen permeation, so that in the inner layer Make burnt spots noticeable. In this regard, twisting for the purpose of extending the flameproofing process, improving the tensile strength of the resulting carbon fiber, and imparting converging properties increases the yarn density, interrupts the oxygen supply, and in a high-temperature furnace. There is a problem that the yarn goes in the direction of thread damage or thread breakage.

このような表面平滑で円形断面形態である乾湿式紡糸プリカーサの焼成技術課題に対して、これまでに、単糸表面上で硬化する特定のシリコーン油剤をプリカーサに付与することで、単糸内部への酸素透過性を向上せしめ、焼け斑を抑制する技術はあったが（特許文献７、８）、無撚状態での焼成が限界であり、引張強度を向上させ、焼成最高温度１５００℃以下で引張弾性率３００ＧＰａを超えた弾性率を有し、品位が良好であって、織物用途に適した交絡度や扁平率を有する炭素繊維を得る目的での、乾湿式紡糸プリカーサの加撚焼成技術は、極めて困難と考えられ、確立されていないのが現状であった。   In response to the firing technical problem of a dry and wet spinning precursor having such a smooth surface and a circular cross-sectional shape, by adding a specific silicone oil that cures on the surface of the single yarn to the precursor, the inside of the single yarn can be obtained. Although there was a technique for improving oxygen permeability and suppressing burning spots (Patent Documents 7 and 8), firing in a non-twisted state is the limit, improving tensile strength, and firing at a maximum temperature of 1500 ° C. or less. For the purpose of obtaining carbon fibers having an elastic modulus exceeding 300 GPa, good quality, and good entanglement and flatness suitable for textile use, The current situation is that it is considered extremely difficult and has not been established.

特開２００６−３０７４０７号公報JP 2006-307407 A 国際公開第２００９／１２５８３２号International Publication No. 2009/125832 特開昭６２−１１７８１８号公報JP 62-117818 A 特開平１１−２１７７３４号公報JP-A-11-217734 特開昭５８−２１４５３４号公報JP 58-214534 A 特開平１１−１２８５４号公報Japanese Patent Laid-Open No. 11-12854 特開２００１−１７２８８０号公報JP 2001-172880 A 特開２００３−２５３５６７号公報JP 2003-253567 A

本発明は上記問題点を解決し、毛羽品位に優れ、織物適用に適した交絡度を有し、引張弾性率、引張強度、圧縮強度、圧縮弾性率に優れた、特性のバランスが良好な炭素繊維を提供することを目的とする。   The present invention solves the above-mentioned problems, has excellent fluff quality, has entanglement suitable for textile application, has excellent tensile elastic modulus, tensile strength, compressive strength, and compressive elastic modulus, and has a good balance of properties. The object is to provide fibers.

また、表面平滑で円形断面形態であるプリカーサに対して、一定の温度領域下、高張力下においても、毛羽品位を損なわず、特性のバランスが良好な炭素繊維を製造する方法を提供することを目的とする。   Further, it is intended to provide a method for producing a carbon fiber having a good balance of properties without deteriorating the fluff quality even under a certain temperature range and high tension, with respect to a precursor having a smooth surface and a circular cross-sectional shape. Objective.

上記の課題を達成するために、本発明の炭素繊維は、次の構成を有する。   In order to achieve the above object, the carbon fiber of the present invention has the following configuration.

［１］原子間力顕微鏡により測定される表面算術平均粗さＲａが３．０ｎｍ以下、Ｘ線回折測定による００２回折線から求められるｃ軸方向の結晶サイズＬｃが１７．０〜２２．４オングストローム、結晶配向度π００２が８３．５〜８５．５％である炭素繊維単糸を１０００本以上含む炭素繊維であって、交絡度Ａが１０〜８０、束断面の扁平率Ｂが０．１５〜０．４０であり、１０ｍｍ以上の破断単糸個数が１．５個／ｍ以下で、引張弾性率ＹＭが３１３〜３４５ＧＰａの炭素繊維。 [1] Surface arithmetic average roughness Ra measured by an atomic force microscope is 3.0 nm or less, and crystal size Lc in the c-axis direction obtained from 002 diffraction lines by X-ray diffraction measurement is 17.0 to 22.4 angstroms. , A carbon fiber containing 1000 or more carbon fiber single yarns having a crystal orientation degree π 002 of 83.5 to 85.5%, an entanglement degree A of 10 to 80, and a flatness ratio B of a bundle section of 0.15 Carbon fiber having a tensile single modulus YM of 313 to 345 GPa and a breaking single yarn number of 10 mm or more and 1.5 pieces / m or less.

［２］引張強度が５０００ＭＰａ以上である上記の炭素繊維。   [2] The above carbon fiber having a tensile strength of 5000 MPa or more.

また本発明は、原子間力顕微鏡により測定される表面算術平均粗さＲａが４．０ｎｍ以下であり、単糸数が１０００本以上であるプリカーサに１０〜３０ターン／ｍの撚りを加え、７０〜１３０ｍｇ／ｄｔｅｘの張力下で耐炎化し、不活性雰囲気中で最高焼成温度が１２５０〜１５００℃で加熱して炭化するとともに、９００〜１３５０ｍｇ／ｄｔｅｘの張力下で炭化し、その後、撚りを解舒する炭素繊維の製造方法からなる。   Further, the present invention adds a twist of 10 to 30 turns / m to a precursor having a surface arithmetic average roughness Ra measured by an atomic force microscope of 4.0 nm or less and a single yarn number of 1000 or more, and 70 to Flame resistant under a tension of 130 mg / dtex, carbonized by heating at a maximum firing temperature of 1250-1500 ° C. in an inert atmosphere, carbonized under a tension of 900-1350 mg / dtex, and then untwisted. It consists of the manufacturing method of carbon fiber.

本発明の炭素繊維は、引張弾性率、引張強度が高く、かつ、品位が良好である。また、適度の交絡、嵩高性が付与されているため、製織時の炭素繊維パッケージからの解舒性が良好となり、複合材料として補強織物とする場合、特に圧縮強度、圧縮弾性率がともに優れ、かつ、得られる織物の樹脂含浸性が良好となる。   The carbon fiber of the present invention has high tensile elastic modulus and tensile strength and good quality. In addition, since moderate entanglement and bulkiness are imparted, the unraveling from the carbon fiber package during weaving is good, and when it is used as a reinforced fabric as a composite material, both compressive strength and compressive modulus are particularly excellent. And the resin impregnation property of the textile fabric obtained becomes favorable.

本発明の炭素繊維の製造方法は、単糸表面が平滑で円形断面形態を有するプリカーサ単糸からなるプリカーサに対して、加撚数と耐炎化時の張力を制御することで、酸素透過性を遮ることなく耐炎化を施すことができ、従来の湿式紡糸プリカーサでの加撚焼成では発現しなかった炭化延伸性を発現できる。また、従来技術では達成しない、一定結晶サイズで比較した際に高配向で高い引張弾性率と高い引張強度を有する炭素繊維を、良好な毛羽品位、かつ、織物適用に良好な交絡度と嵩高性を付与して製造することができる。   The carbon fiber manufacturing method according to the present invention controls oxygen permeability by controlling the number of twists and the tension at the time of flame resistance of a precursor made of a precursor single yarn having a smooth single yarn surface and a circular cross-sectional shape. It is possible to provide flame resistance without blocking, and it is possible to develop carbonized stretchability that was not exhibited by twisting firing with a conventional wet spinning precursor. In addition, carbon fibers with high orientation, high tensile modulus and high tensile strength when compared with a constant crystal size, which cannot be achieved with conventional technology, have good fluff quality and good entanglement and bulkiness for textile applications. Can be produced.

本発明の炭素繊維は、次の構成を有する。   The carbon fiber of the present invention has the following configuration.

本発明の炭素繊維単糸の表面は、原子間力顕微鏡で測定される表面算術平均粗さＲａが３．０ｎｍ以下であることが必要であり、２．８ｎｍ以下であることが好ましい。Ｒａを３．０ｎｍ以下とすること、つまり、表面平滑性を高くすることで、炭化工程での延伸性が発現し、一定の結晶サイズ中で、所望の結晶配向度、引張弾性率を有する炭素繊維を良好な品位で得ることができる。また、表面平滑性が高い炭素繊維単糸は、表面平滑性が高いプリカーサ単糸、たとえば、特定の条件で製造した乾湿式紡糸プリカーサを焼成することで得られるが、プリカーサ単糸の表面欠陥が減少することで得られる炭素繊維の引張強度も反映して向上する。すなわち、３．０ｎｍ以下とすることで、高い引張強度の炭素繊維が得られる。   The surface of the carbon fiber single yarn of the present invention needs to have a surface arithmetic average roughness Ra measured by an atomic force microscope of 3.0 nm or less, and preferably 2.8 nm or less. By setting Ra to 3.0 nm or less, that is, by increasing the surface smoothness, carbon develops stretchability in the carbonization process, and has a desired crystal orientation and tensile modulus in a certain crystal size. Fibers can be obtained with good quality. A carbon fiber single yarn having a high surface smoothness is obtained by firing a precursor single yarn having a high surface smoothness, for example, a dry and wet spinning precursor manufactured under specific conditions. The tensile strength of the carbon fiber obtained by the reduction is also reflected and improved. That is, by setting the thickness to 3.0 nm or less, a high tensile strength carbon fiber can be obtained.

また、本発明の炭素繊維は、Ｘ線回折測定による００２回折線から求められるｃ軸方向の結晶サイズＬｃ（オングストローム）が１７．０〜２２．４の範囲であることが必要である。Ｌｃが２２．４オングストローム以下であることで、得られる炭素繊維の引張強度、得られるコンポジットの圧縮強度の低下を抑制することができる。また、Ｌｃが１７．０オングストローム以上であることで、所望の引張弾性率を有する炭素繊維を品位良好に得ることができる。望ましくは引張弾性率向上の観点から１８．０オングストローム以上であることが好ましく、引張強度・圧縮強度低下抑制の観点から、２２．０オングストローム以下であることがより好ましい。   Further, the carbon fiber of the present invention needs to have a crystal size Lc (angstrom) in the c-axis direction obtained from 002 diffraction lines by X-ray diffraction measurement in the range of 17.0 to 22.4. When Lc is 22.4 angstroms or less, the fall of the tensile strength of the carbon fiber obtained and the compressive strength of the composite obtained can be suppressed. Further, when Lc is 17.0 angstroms or more, carbon fibers having a desired tensile elastic modulus can be obtained with good quality. Desirably, it is preferably 18.0 angstroms or more from the viewpoint of improving the tensile modulus, and more preferably 22.0 angstroms or less from the viewpoint of suppressing a decrease in tensile strength / compressive strength.

本発明の炭素繊維は、その結晶配向度π００２（％）が８３．５〜８５．５％であることが必要であり、８４．０〜８５．２％であることが好ましい。上記Ｌｃの範囲で、結晶配向度π００２が８３．５％以上であることで、所望の３１３ＧＰａを上回る引張弾性率が発現する。８５．５％以下であることで所望の引張弾性率を有する炭素繊維を良好な品位で得ることができる。 The carbon fiber of the present invention needs to have a degree of crystal orientation π 002 (%) of 83.5 to 85.5%, and preferably 84.0 to 85.2%. When the crystal orientation degree π 002 is 83.5% or more in the range of Lc, a tensile elastic modulus exceeding the desired 313 GPa is exhibited. The carbon fiber which has a desired tensile elasticity modulus by being 85.5% or less can be obtained by favorable quality.

本発明の炭素繊維は、ＪＩＳ Ｌ １０１３（１９９９）記載の方法で測定し、落下距離Ｌ（ｍｍ）を用いて、“１０００／Ｌ”で表した交絡度（以下Ａとする）が、１０〜８０の範囲であることが必要である。１０以上とすることで、織物上で経糸間、あるいは緯糸間の繊維束間に隙間が無く密に詰まった状態となることを防ぐことができ、織物の樹脂含浸性が向上する。また、８０以下とすることで、織物上で炭素繊維の屈曲が大きくなることを抑え、ＦＲＰ成形時の応力集中起因の強度低下を防ぐことができる。樹脂含浸性のさらなる向上、また屈曲抑制の観点からは、より好ましくは、２０〜５５の範囲であることが好ましい。   The carbon fiber of the present invention is measured by the method described in JIS L 1013 (1999), and the entanglement degree (hereinafter referred to as A) represented by “1000 / L” is 10 to 10 using the fall distance L (mm). It must be in the range of 80. By setting it to 10 or more, it is possible to prevent the fiber bundle between the warp yarns or the weft yarns from having a gap between the warp yarns and a tightly packed state, and the resin impregnation property of the fabric is improved. Moreover, by setting it as 80 or less, it can suppress that the bending of a carbon fiber becomes large on a textile fabric, and can prevent the strength fall resulting from the stress concentration at the time of FRP shaping | molding. From the viewpoint of further improving the resin impregnation property and suppressing bending, the range of 20 to 55 is more preferable.

本発明の炭素繊維は、繊維束断面の扁平率Ｂ、すなわち、炭素繊維束の最大高さＸと、幅Ｙの比Ｂ＝Ｘ／Ｙは、０．１５〜０．４０を有することが必要である。Ｂが０．１５以上であることで、繊維束の嵩高性が高く、炭素繊維パッケージからの繊維束の良好な糸離れ性が得られる。すなわち、炭素繊維を織物の緯糸として使用するときは、通常繊維は横取り解舒されるが、その時に良好な解舒性が得られる。一方Ｂが０．４０以下であることで、繊維束の集束性が維持され、製織時の工程ガイドでの擦過を抑えることができる。解舒性向上の観点からは、より好ましくは、０．２０〜０．４０である。   In the carbon fiber of the present invention, the flatness B of the cross section of the fiber bundle, that is, the ratio of the maximum height X and the width Y of the carbon fiber bundle B = X / Y needs to have 0.15 to 0.40. It is. When B is 0.15 or more, the bulkiness of the fiber bundle is high, and a good yarn release property of the fiber bundle from the carbon fiber package can be obtained. In other words, when carbon fiber is used as a weft of a woven fabric, the fiber is usually taken out in a transverse direction, and good unwinding property is obtained at that time. On the other hand, when B is 0.40 or less, the convergence of the fiber bundle is maintained, and rubbing with a process guide during weaving can be suppressed. From the viewpoint of improving the unraveling property, it is more preferably 0.20 to 0.40.

本発明の炭素繊維は、巻き取りパッケージから繊維束を、ボビンの円筒軸と垂直方向に、５０ｍｇ／ｄｔｅｘの張力下、１０ｍ／ｍｉｎの速度で繊維束を引き出した際に、目視で確認される１０ｍｍ以上の破断単糸個数が１．５個／ｍ以下であることが必要である。１．５個／ｍ以下とすることで、織物を製織する際に製織糸道上のガイドへの毛羽溜まりなどから生じる糸切れや、織物製品としての毛羽品位が劣位となることを防ぐことが可能となる。特に、製織生産性の観点から１．０個／ｍ以下であることが好ましい。   The carbon fiber of the present invention is visually confirmed when a fiber bundle is pulled out from the winding package in a direction perpendicular to the cylindrical axis of the bobbin under a tension of 50 mg / dtex at a speed of 10 m / min. It is necessary that the number of broken single yarns of 10 mm or more is 1.5 pieces / m or less. By setting it to 1.5 pieces / m or less, it is possible to prevent yarn breakage caused by fluff accumulation on guides on the weaving yarn path when weaving the fabric, and inferior fluff quality as a fabric product. It becomes. In particular, it is preferably 1.0 piece / m or less from the viewpoint of weaving productivity.

本発明の炭素繊維の引張弾性率は、３１３ＧＰａ〜３４５ＧＰａであることが必要であり、３２０〜３４５ＧＰａであることが好ましい。この範囲とすることで、引張弾性率と圧縮弾性率を高い範囲に保ち、品位良好で圧縮強度が高い炭素繊維が得られる。特に弾性率を３４５ＧＰａ以下とすることで、束の破断単糸個数１．５個／ｍ以下とすることに大きな効果がある。   The tensile elastic modulus of the carbon fiber of the present invention is required to be 313 GPa to 345 GPa, and preferably 320 to 345 GPa. By setting it as this range, the tensile elastic modulus and the compressive elastic modulus can be kept in a high range, and a carbon fiber with good quality and high compressive strength can be obtained. In particular, by setting the elastic modulus to 345 GPa or less, there is a great effect in setting the number of broken single yarns in the bundle to 1.5 or less.

得られる炭素繊維の引張強度は、好ましくは４９００ＭＰａ以上、より好ましくは５０００ＭＰａが望ましい。引張強度を上記の範囲とすることで、織物において応力集中が発生する交錯部で強いせん断力を受けても単糸破壊が発生することなどを防ぐことができる。   The tensile strength of the obtained carbon fiber is preferably 4900 MPa or more, more preferably 5000 MPa. By setting the tensile strength within the above range, it is possible to prevent the occurrence of single yarn breakage even when subjected to a strong shearing force at the intersection where stress concentration occurs in the woven fabric.

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

本発明における炭素繊維は、単糸表面のＲａが３．０ｎｍ以下である必要があり、２．８ｎｍ以下であることが好ましいが、たとえば、以下に例示されるように、アクリロニトリル重合体の紡糸原液を乾湿式紡糸法により紡糸後、凝固・延伸条件を調整し、後述する焼成条件を適用することによって製造することができる。アクリロニトリル系プリカーサを構成する重合体としては、アクリロニトリルが９０質量％以上、アクリロニトリルと共重合可能なモノマーが１０質量％以下の構成のものが好ましく使用される。共重合可能なモノマーとしては、アクリル酸、メタアクリル酸、イタコン酸又はこれらのメチルエステル、プロピルエステル、ブチルエステル、アルカリ金属塩、アンモニウム塩、アリルスルホン酸、メタリルスルホン酸、スチレンスルホン酸、及びこれらのアルカリ金属塩からなる群から選ばれる少なくとも１種を用いることができる。   The carbon fiber in the present invention needs to have a Ra on the surface of a single yarn of 3.0 nm or less, and preferably 2.8 nm or less. For example, as illustrated below, an acrylonitrile polymer spinning dope Can be manufactured by adjusting the coagulation / stretching conditions and applying the firing conditions described later. As the polymer constituting the acrylonitrile-based precursor, those having a constitution of 90% by mass or more of acrylonitrile and 10% by mass or less of a monomer copolymerizable with acrylonitrile are preferably used. Copolymerizable monomers include acrylic acid, methacrylic acid, itaconic acid or their methyl esters, propyl esters, butyl esters, alkali metal salts, ammonium salts, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, and At least one selected from the group consisting of these alkali metal salts can be used.

かかるアクリル系重合体は、乳化重合、塊状重合、溶液重合などの重合法により得られ、この際の重合度の目安として、極限粘度が１．３〜３．０、好ましくは１．５〜２．０が良い。極限粘度３．０以下とすることは紡糸安定性の点から好ましく、１．３以上とすることは、プリカーサの熱安定性や、炭素繊維にしたときの強度を高く保つ上で、好ましい。得られた重合体は、ジメチルアセトアミド、ジメチルスルホキシド、ジメチルホルムアミド、硝酸、ロダンソーダ水溶液、塩化亜鉛水溶液などを溶媒とした紡糸原液に形成し、一旦空気中へ紡出した後に浴中凝固させる乾湿式紡糸法によって紡糸することが好ましい。   Such an acrylic polymer is obtained by a polymerization method such as emulsion polymerization, bulk polymerization, solution polymerization, etc., and the intrinsic viscosity is 1.3 to 3.0, preferably 1.5 to 2 as a measure of the degree of polymerization at this time. .0 is good. An intrinsic viscosity of 3.0 or less is preferred from the viewpoint of spinning stability, and an intrinsic viscosity of 1.3 or more is preferred for keeping the thermal stability of the precursor and the strength of the carbon fiber high. The resulting polymer is formed into a spinning stock solution using dimethylacetamide, dimethylsulfoxide, dimethylformamide, nitric acid, rhodium soda aqueous solution, zinc chloride aqueous solution, etc. as a solvent, once spun into air and then solidified in a bath. Spinning by the method is preferred.

紡糸する口金吐出孔は、孔径Ｄが０．０５〜１．０ｍｍの範囲であることが好ましい。０．０５ｍｍより大きいことで、製糸性が向上し、１．０ｍｍより小さいことで、糸切れが少なくなる。凝固浴温度は−３０〜５０℃であることが好ましく、−５〜３０℃の範囲であることがより好ましい。選択した凝固浴組成、すなわち凝固浴液中の溶媒と非溶媒の割合や、原液中のポリマ温度、凝固浴温度などの組み合わせにより、凝固速度を制御することができ、条件を適宜選択することによって、延伸後、焼成した炭素繊維の単糸表面平均算術粗さＲａが３．０ｎｍ以下である炭素繊維を得ることができる。またこれらの紡糸条件の選択によって円形断面のプリカーサ単糸を得ることが好ましい。   The nozzle discharge hole for spinning preferably has a hole diameter D in the range of 0.05 to 1.0 mm. When it is larger than 0.05 mm, the yarn-forming property is improved, and when it is smaller than 1.0 mm, yarn breakage is reduced. The coagulation bath temperature is preferably −30 to 50 ° C., more preferably −5 to 30 ° C. The coagulation rate can be controlled by the combination of the selected coagulation bath composition, that is, the ratio of the solvent and non-solvent in the coagulation bath liquid, the polymer temperature in the stock solution, the coagulation bath temperature, etc. After stretching, a carbon fiber having a single-fiber surface average arithmetic roughness Ra of 3.0 nm or less can be obtained after firing. It is also preferable to obtain a precursor single yarn having a circular cross section by selecting these spinning conditions.

紡糸後、得られた凝固糸は、２０〜９８℃に温調された単数または複数の水浴中で水洗、延伸するのがよい。延伸倍率と温度は、糸切れや単繊維間の接着が生じない範囲で、適宜設定することができるが、より表面が平滑なポリアクリロニトリル系プリカーサを得るためには、延伸倍率は５倍以下が好ましく、４倍以下がより好ましい。また、得られるポリアクリロニトリル系プリカーサの緻密性を向上させる観点から、延伸浴の最高温度は、５０℃以上とするのが好ましく、７０℃以上がより好ましい。水洗、延伸された後の水膨潤状態の糸条に、後述するシリコーン油剤を付与するのが好ましい。付与方法としては、糸束内部まで均一に付与できることを勘案し、適宜選択して使用すればよいが、具体的には、糸条の油剤浴中への浸漬、走行糸条への噴霧および滴下などの手段が採用される。かかるシリコーン油剤の付着量は、繊維の乾燥質量に対する純分の割合が、０．１〜５質量％が好ましく、０．３〜３質量％がより好ましく、０．５〜２質量％がさらに好ましい。０．１質量％を下回ると、耐炎化炉で単繊維同士の融着が生じ、前炭化での糸痛み・断糸が発生するため好ましくない。   After spinning, the obtained coagulated yarn is preferably washed and drawn in one or more water baths whose temperature is adjusted to 20 to 98 ° C. The draw ratio and temperature can be appropriately set within the range where yarn breakage or adhesion between single fibers does not occur. To obtain a polyacrylonitrile precursor with a smoother surface, the draw ratio should be 5 times or less. Preferably, 4 times or less is more preferable. Moreover, from the viewpoint of improving the denseness of the polyacrylonitrile-based precursor obtained, the maximum temperature of the stretching bath is preferably 50 ° C. or higher, and more preferably 70 ° C. or higher. It is preferable to apply a silicone oil agent, which will be described later, to the water-swollen yarn after being washed and stretched. The application method may be selected as appropriate, considering that it can be applied uniformly to the inside of the yarn bundle. Specifically, the yarn is immersed in an oil bath, sprayed onto the running yarn and dripped. Such means are adopted. As for the adhesion amount of this silicone oil agent, the ratio of the pure part with respect to the dry mass of a fiber is preferable 0.1-5 mass%, 0.3-3 mass% is more preferable, 0.5-2 mass% is further more preferable. . When the amount is less than 0.1% by mass, fusion of single fibers occurs in a flameproofing furnace, and yarn pain and yarn breakage in pre-carbonization occur, which is not preferable.

かかるシリコーン油剤については、その硬化状態が焼成工程での耐炎化における焼け斑に影響を及ぼすので、油剤の硬化状態を表す指標として、後述する方法で測定される振動周期差Ｔが０．１０〜０．３０であることが好ましく、より好ましくは０．１５〜０．２５が好ましい。０．１０以上とすることで、油剤の硬化が適度に進行し、単糸表面が平滑で円形断面を有するプリカーサ単糸を複数本含む繊維束に撚りをかけて耐炎化せしめる際の酸素透過性を保つことができ、焼け斑による炭化工程での糸切れを防ぐことができる。０．３０以下とすることで、硬化性を適度に保ち、単糸表面が平滑で円形断面を有するプリカーサ単糸を複数本含む繊維束に撚りをかけて耐炎化せしめる際の単繊維間の拘束を抑制し炭化工程での糸傷みを防ぐことができる。   About such silicone oil agent, since the hardening state influences the burning spot in the flame resistance in a baking process, the vibration period difference T measured by the method mentioned later as an index showing the hardening state of oil agent is 0.10 to 10. It is preferably 0.30, more preferably 0.15 to 0.25. By setting it to 0.10 or more, the curing of the oil agent proceeds moderately, and the oxygen permeability when making the fiber bundle containing a plurality of precursor single yarns having a smooth single yarn surface and a circular cross section to make them flame resistant Can be maintained, and yarn breakage in the carbonization process due to burnt spots can be prevented. Constraints between single fibers when the fiber bundle containing a plurality of precursor single yarns having a smooth single yarn surface and a circular cross section are twisted to make them flame-resistant by keeping the curability moderately by setting it to 0.30 or less Can be suppressed and yarn damage in the carbonization process can be prevented.

ここでいう振動周期差Ｔとは、剛体振り子の自由減衰振動法により得られるシリコーン油剤の振動周期の加熱前後の差を意味するものである。すなわち、剛体振り子の自由減衰振動法に基づき、株式会社エーアンドディ製剛体振り子型物性試験機（例えば株式会社エーアンドディ製ＲＰＴ−３０００）を用いて振動周期を測定する。具体的には、長さ５ｃｍ、幅２ｃｍ、厚み０．５ｍｍの亜鉛メッキ鋼板製塗布基板（例えば株式会社エーアンドディ社製ＳＴＰ−０１２）の上に、測定に供するシリコーン油剤を、厚みが２０〜３０μｍとなるように基板幅方向全面に塗布する。塗布後速やかに、試験機にセットし測定を開始する。予め３０℃に温調しておき、塗布板および振り子をセットした後、５０℃／分の速度で１８０℃まで昇温し、１８０℃で１０分間ホールドする。その間、７秒間隔で連続的に周期の測定を行う。なお、振り子は下記のものを使用する。   The vibration period difference T here means the difference between before and after heating of the vibration period of the silicone fluid obtained by the free-damping vibration method of the rigid pendulum. That is, based on the free-damping vibration method of the rigid pendulum, the vibration period is measured using a rigid pendulum type physical property tester manufactured by A & D Corporation (for example, RPT-3000 manufactured by A & D Corporation). Specifically, a silicone oil used for measurement is applied on a galvanized steel sheet coated substrate (for example, STP-012 manufactured by A & D Co., Ltd.) having a length of 5 cm, a width of 2 cm, and a thickness of 0.5 mm. It is applied to the entire surface in the substrate width direction so as to be ˜30 μm. Immediately after application, set on a testing machine and start measurement. The temperature is adjusted to 30 ° C. in advance, and after setting the coating plate and pendulum, the temperature is raised to 180 ° C. at a rate of 50 ° C./min and held at 180 ° C. for 10 minutes. Meanwhile, the period is continuously measured at intervals of 7 seconds. The following pendulum is used.

使用エッジ：ナイフ形状エッジ（株式会社エーアンドディ社製ＲＢＥ−１６０）
振り子重量：慣性能率：１５ｇ／６４０ｇ・ｃｍ（株式会社エーアンドディ社製ＦＲＢ−１００）
振動周期差Ｔは、Ｔ＝Ｔ１−Ｔ２
Ｔ１：昇温を開始する直前の３０℃における振動周期（秒）
Ｔ２：１８０℃到達後１０分間ホールドした直後の振動周期（秒）
で定義される。 Edge used: Knife-shaped edge (RBE-160 manufactured by A & D Corporation)
Pendulum weight: inertia ratio: 15 g / 640 g · cm (FRB-100, manufactured by A & D Corporation)
The vibration period difference T is T = T1-T2.
T1: Vibration period (seconds) at 30 ° C. immediately before starting the temperature increase
T2: Vibration period (seconds) immediately after holding for 10 minutes after reaching 180 ° C
Defined by

上記硬化状態を達成するためのシリコーン油剤としては、例えば２５℃における粘度が５００〜１００００ｃＳｔのアミノ変性シリコーンと、２５℃における粘度が１０００〜３００００ｃＳｔのエポキシ変性シリコーンと、２５℃における粘度が２０〜１０００ｃＳｔのアルキレンオキサイド変性シリコーンの３種を含む水エマルジョンであって、かつ、アミノ変性シリコーン１００質量部に対するエポキシ変性シリコーンの割合が１０〜８０質量部であり、全てのシリコーン系化合物１００質量部に対するアルキレンオキサイド変性シリコーンの割合が０．５〜１０質量部から成り立つ油剤によって達成される。   Examples of the silicone oil for achieving the cured state include an amino-modified silicone having a viscosity of 500 to 10000 cSt at 25 ° C., an epoxy-modified silicone having a viscosity of 1000 to 30000 cSt at 25 ° C., and a viscosity of 20 to 1000 cSt at 25 ° C. And a ratio of the epoxy-modified silicone to 100 parts by mass of the amino-modified silicone in an amount of 10 to 80 parts by mass, and the alkylene oxide to 100 parts by mass of all the silicone-based compounds. The proportion of the modified silicone is achieved by an oil agent comprising 0.5 to 10 parts by mass.

該油剤を付与された繊維束は、速やかに乾燥されるのがよい。乾燥の方法は、特に限定されないが、加熱された複数のローラに直接接触させる方法が好ましく用いられる。乾燥温度は、高いほどシリコーン油剤の架橋反応を促進し、また、生産性の観点からも好ましいので、単繊維間の融着が生じない範囲で高く設定できる。具体的には、１５０℃以上が好ましく、１８０℃以上がより好ましい。通常、乾燥温度の上限は２００℃程度である。乾燥時間は、膨潤糸条が乾燥するのに必要十分な時間とするのがよい。また、糸条への加熱状態が均一になるよう、糸条をできるだけ拡幅した状態でローラに接触させるのがよい。   The fiber bundle to which the oil agent is applied is preferably dried quickly. The drying method is not particularly limited, but a method of directly contacting a plurality of heated rollers is preferably used. The higher the drying temperature, the more the crosslinking reaction of the silicone oil agent is promoted, and it is also preferable from the viewpoint of productivity. Therefore, the drying temperature can be set as high as possible without causing fusion between single fibers. Specifically, 150 ° C. or higher is preferable, and 180 ° C. or higher is more preferable. Usually, the upper limit of the drying temperature is about 200 ° C. The drying time is preferably a time necessary and sufficient for the swollen yarn to dry. Further, it is preferable to bring the yarn into contact with the roller in a state where the yarn is widened as much as possible so that the heating state of the yarn becomes uniform.

乾燥された糸条は、さらに加圧スチーム中または乾熱下で後延伸されるのが、得られるポリアクリロニトリル系プリカーサの緻密性や生産性の観点から好ましい。後延伸時のスチーム圧力または温度や後延伸倍率は、糸切れ、毛羽発生のない範囲で適宜選択して使用するのがよいが、プリカーサ単糸表面の表面算術平均粗さＲａが４．０ｎｍ以下とする範囲となるように、先に記載した紡糸条件と組み合わせ、上記延伸、乾燥、後延伸条件を選定することが、炭素繊維単糸表面の表面算術平均粗さＲａを３．０ｎｍ以下とするために好ましい。   The dried yarn is preferably post-drawn in pressurized steam or under dry heat from the viewpoint of the denseness and productivity of the resulting polyacrylonitrile-based precursor. The steam pressure or temperature at the time of post-drawing and the post-draw ratio are preferably selected and used as long as there is no yarn breakage or fluffing. The surface arithmetic average roughness Ra of the precursor single yarn surface is 4.0 nm or less. The surface arithmetic average roughness Ra of the carbon fiber single yarn surface is set to 3.0 nm or less by selecting the drawing, drying, and post-drawing conditions in combination with the spinning conditions described above so that the range becomes Therefore, it is preferable.

また、本発明に用いるポリアクリロニトリル系プリカーサの単糸繊度は、０．１〜１．５ｄｔｅｘであることが好ましく、０．３〜１．２ｄｔｅｘであることがより好ましく、０．５〜１．０ｄｔｅｘがさらに好ましい。該繊度は小さいほど、得られる炭素繊維束の引張強度や引張弾性率の点で有利であるが、生産性は低下するため、性能とコストのバランスを勘案し選択するのがよい。本発明の炭素繊維は、単糸を１０００本以上含むことが必要である。好ましい範囲は１０００〜７００００であり、より好ましい範囲は３０００〜１８０００である。単糸の本数をこの範囲に設定することによって、本発明の特性を有する炭素繊維が生産性良く、品位がよい状態で製造できる。   The single yarn fineness of the polyacrylonitrile precursor used in the present invention is preferably 0.1 to 1.5 dtex, more preferably 0.3 to 1.2 dtex, and 0.5 to 1.0 dtex. Is more preferable. The smaller the fineness, the more advantageous in terms of the tensile strength and tensile modulus of the carbon fiber bundle to be obtained. However, since the productivity is lowered, it is preferable to select in consideration of the balance between performance and cost. The carbon fiber of the present invention needs to contain 1000 or more single yarns. A preferable range is 1000 to 70000, and a more preferable range is 3000 to 18000. By setting the number of single yarns within this range, carbon fibers having the characteristics of the present invention can be produced with good productivity and good quality.

前述したような好ましい方法により製造された該ポリアクリロニトリル系プリカーサ繊維を焼成工程に供給するに際して、１０〜３０ターン／ｍの撚りを加えることが好ましく、さらに好ましくは１０〜１８ターン／ｍの撚りを加えることが引張強度５０００ＭＰａ以上の炭素繊維を得るために望ましい。加撚数が低いと、炭化温度領域での延伸性が発現せず同張力下では品位が劣位になる。一方で、加撚数が高いと、得られる炭素繊維の引張強度が低下する問題が起こる。撚りを加える方法としては、製糸工程で予め加えておくのもよいが、該ポリアクリロニトリル系プリカーサ繊維をボビンから引き出す際に、ボビンを積極的に回転させ、撚り数を制御しながら縦取り解舒することで行うのが、生産上好ましい。   When supplying the polyacrylonitrile-based precursor fiber produced by the preferred method as described above to the firing step, it is preferable to add a twist of 10 to 30 turns / m, and more preferably a twist of 10 to 18 turns / m. It is desirable to add carbon fibers having a tensile strength of 5000 MPa or more. When the number of twists is low, stretchability in the carbonization temperature region does not appear, and the quality becomes inferior under the same tension. On the other hand, when the number of twists is high, there arises a problem that the tensile strength of the obtained carbon fiber is lowered. As a method of adding twisting, it may be added in advance in the yarn making process, but when pulling out the polyacrylonitrile-based precursor fiber from the bobbin, the bobbin is actively rotated, and the longitudinal removal is performed while controlling the number of twists. It is preferable from the viewpoint of production.

次に加燃された該ポリアクリロニトリル系プリカーサ繊維を、２００〜３００℃の温度範囲内で耐炎化する。得られる耐炎化糸の比重が１．３０〜１．４５、好ましくは１．３５〜１．４０ｇ／ｃｍ３となるまで耐炎化を行う。耐炎化比重が１．３０未満では高温炉にて糸傷みや断糸を誘発し、耐炎化比重が１．４５を超えると品位低下および引張強度が低下する。 Next, the fired polyacrylonitrile-based precursor fiber is flame-resistant within a temperature range of 200 to 300 ° C. Flame resistance is performed until the specific gravity of the obtained flame resistant yarn is 1.30 to 1.45, preferably 1.35 to 1.40 g / cm 3 . If the flameproof specific gravity is less than 1.30, yarn damage or yarn breakage is induced in a high temperature furnace, and if the flameproof specific gravity exceeds 1.45, the quality is lowered and the tensile strength is lowered.

耐炎化時の延伸張力としては７０〜１３０ｍｇ／ｄｔｅｘ、好ましくは９０〜１１０ｍｇ／ｄｔｅｘに制御されることが望ましい。７０ｍｇ／ｄｔｅｘ以上とすることで繊維束が弛み糸飛びや擦れによる品位悪化を防ぐことができる。１３０ｍｇ／ｄｔｅｘ以下とすることで、単糸表面が平滑かつ加撚してあるプリカーサ繊維に対して、酸素透過性が悪くなり耐炎糸の焼け斑が発生し前炭化工程で糸切れすることを防ぐことができる。従来の表面平滑で束の扁平率Ｂが０．１５〜０．４０の炭素繊維は１３０〜３００ｍｇ／ｄｔｅｘ張力下で耐炎化することが一般的であるのに対して、本方法は低張力となる７０〜１３０ｍｇ／ｄｔｅｘの範囲で制御を実施する。なお、ここでの張力とは耐炎化工程以前のプリカーサ繊維の断面積を基準にして計算した値である。耐炎化延伸比は０．８〜１．０が良く、好ましくは０．８５〜０．９５で設定することが良く、上記張力を達成するためにこの範囲から選定を行う。延伸比とは駆動ローラ間の速度の比率を言う。また、生産性向上の観点からは、加撚後の該ポリアクリロニトリル系プリカーサ繊維を２〜４本合糸の後、耐炎化しても良い。   It is desirable that the stretching tension at the time of flame resistance is controlled to 70 to 130 mg / dtex, preferably 90 to 110 mg / dtex. By setting it to 70 mg / dtex or more, it is possible to prevent the fiber bundle from deteriorating in quality due to loose yarn jumping or rubbing. By setting it to 130 mg / dtex or less, the precursor fiber having a smooth and twisted single yarn surface is deteriorated in oxygen permeability and prevents burnout spots of the flame resistant yarn and prevents yarn breakage in the pre-carbonization step. be able to. Conventional carbon fibers having a smooth surface and a flatness ratio B of 0.15 to 0.40 are generally flame resistant under a tension of 130 to 300 mg / dtex, whereas the present method has a low tension. Control is performed in the range of 70 to 130 mg / dtex. In addition, tension | tensile_strength here is the value calculated on the basis of the cross-sectional area of the precursor fiber before a flame-proofing process. The flameproof stretch ratio is preferably 0.8 to 1.0, preferably 0.85 to 0.95, and is selected from this range in order to achieve the above tension. The stretch ratio refers to the ratio of speed between drive rollers. Further, from the viewpoint of improving productivity, the polyacrylonitrile-based precursor fiber after twisting may be flame-resistant after 2 to 4 combined yarns.

続く炭化工程では、不活性雰囲気中、３００〜８００℃で予備炭化し、さらに不活性雰囲気中、８００〜１５００℃で炭化する。後者の炭化における最高温度は、１２５０℃以上が良い。すなわち、１２５０℃以上とすることで、所望の結晶サイズ、結晶配向度中で炭素繊維束の毛羽品位を良好にすることができる。また炭化の温度は１５００℃を上限値とするのが良い。この範囲とすることによって繊維内において結晶の成長が顕著となることによる圧縮強度、樹脂との接着性の低下を抑制できる。   In the subsequent carbonization step, preliminary carbonization is performed at 300 to 800 ° C. in an inert atmosphere, and further carbonization is performed at 800 to 1500 ° C. in an inert atmosphere. The maximum temperature in the latter carbonization is preferably 1250 ° C. or higher. That is, by setting the temperature to 1250 ° C. or higher, the fluff quality of the carbon fiber bundle can be improved in the desired crystal size and crystal orientation. The upper limit of the carbonization temperature is preferably 1500 ° C. By setting it within this range, it is possible to suppress a decrease in compressive strength and adhesiveness with the resin due to remarkable crystal growth in the fiber.

予備炭化工程における延伸張力としては、５０〜２００ｍｇ／ｄｔｅｘ、より好ましくは、９０〜１５０ｍｇ／ｄｔｅｘで延伸することが良い。５０ｍｇ／ｄｔｅｘ以上とすることが所望の弾性率を得る上では好ましく、２００ｍｇ／ｄｔｅｘ以下とすることでプロセス性の低下を抑制する上で好ましい。従来の表面平滑で束の扁平率Ｂが０．１５〜０．４０の炭素繊維は５０〜９０ｍｇ／ｄｔｅｘ張力下で予備炭化することが一般的であるのに対して、本方法では高張力条件においても糸切れなどなくプロセス性良好に、かつ、毛羽品位良好に炭素繊維束が得られる。なお、耐炎糸を予備炭化工程に供給すると減量が起こるが、ここでの張力とは予備炭化後の繊維の断面積を基準にして計算した値である。延伸比としては、０．９５〜１．２０が良く、より好ましくは１．０４〜１．１５が良く、この範囲から選定して上記延伸張力を達成する。   The stretching tension in the preliminary carbonization step is preferably 50 to 200 mg / dtex, more preferably 90 to 150 mg / dtex. 50 mg / dtex or more is preferable for obtaining a desired elastic modulus, and 200 mg / dtex or less is preferable for suppressing deterioration in processability. Conventional carbon fibers having a smooth surface and a flatness ratio B of 0.15 to 0.40 are generally pre-carbonized under a tension of 50 to 90 mg / dtex. In addition, a carbon fiber bundle can be obtained with good processability without yarn breakage and good fluff quality. Incidentally, when the flame resistant yarn is supplied to the preliminary carbonization step, the weight loss occurs. The tension here is a value calculated based on the cross-sectional area of the fiber after the preliminary carbonization. The draw ratio is preferably 0.95 to 1.20, more preferably 1.04 to 1.15, and the draw tension is achieved by selecting from this range.

炭化工程における延伸張力としては、９００〜１３５０ｍｇ／ｄｔｅｘが好ましく、より好ましくは１０００〜１３５０ｍｇ／ｄｔｅｘで延伸することが良い。９００ｍｇ／ｄｔｅｘ以上とすることで、配向度が低くなることを防ぎ、所望の引張弾性率を得ることができる。１３５０ｍｇ／ｄｔｅｘ以下とすることで、単糸切れや糸切れの発生により生産性が低下することを防ぐことができる。さらに好ましくは、上限値を１３００ｍｇ／ｄｔｅｘとすることが品位の観点から好ましい。従来の表面平滑で束の扁平率Ｂが０．１５〜０．４０の炭素繊維は２００〜９００ｍｇ／ｄｔｅｘ張力下で炭化することが一般的であるのに対して、本方法では高張力条件下にて、良好な品位で所望の結晶サイズ中で結晶配向度、引張弾性率を得ることができる。なお、ここでの張力とは炭化後の繊維の断面積を基準にして計算した値である。延伸比としては０．９５〜１．０５が良く、好ましくは０．９７〜１．０３が好ましく、この範囲から選定して上記延伸張力を達成する。   The stretching tension in the carbonization step is preferably 900 to 1350 mg / dtex, more preferably 1000 to 1350 mg / dtex. By setting it as 900 mg / dtex or more, it can prevent that an orientation degree becomes low and can obtain a desired tensile elasticity modulus. By setting it as 1350 mg / dtex or less, it can prevent that productivity falls by generation | occurrence | production of single yarn breakage or yarn breakage. More preferably, the upper limit is 1300 mg / dtex from the viewpoint of quality. Conventional carbon fibers having a smooth surface and a flatness ratio B of 0.15 to 0.40 are generally carbonized under a tension of 200 to 900 mg / dtex, whereas in this method, a high tension condition is applied. Thus, it is possible to obtain a crystal orientation degree and a tensile elastic modulus in a desired crystal size with good quality. In addition, tension | tensile_strength here is the value calculated on the basis of the cross-sectional area of the fiber after carbonization. The draw ratio is preferably 0.95 to 1.05, preferably 0.97 to 1.03, and is selected from this range to achieve the draw tension.

このようにして得られた炭素繊維に、さらに表面処理することにより、コンポジット成形した際の樹脂との接着性をより高めることが可能である。   The carbon fiber thus obtained can be further subjected to a surface treatment to further improve the adhesiveness with the resin when the composite is molded.

表面処理方法としては、気相、液相処理、電解処理などを採用できるが、生産性、品質バラツキを考慮すると電解処理が好ましく採用できる。電解処理に用いられる電解液としては、硫酸、硝酸、塩酸などの酸性化合物の水溶液、水酸化ナトリウム、水酸化カリウム、各種アンモニウム化合物などのアルカリ性化合物又はそれらの塩の水溶液が使用できるが、好ましくはアンモニウムイオンを含む水溶液が良い。具体的には、硝酸アンモニウム、硫酸アンモニウム、過硫酸アンモニウム、塩化アンモニウム、臭化アンモニウム、燐酸二水素アンモニウム、燐酸水素二アンモニウム、炭酸水素アンモニウム、炭酸アンモニウム、テトラエチルアンモニウムヒドロキシド、又は、それらの混合物を含む水溶液を用いることができる。アンモニウムイオンを含む水溶液を用いた電解を施すことで、アンモニウムイオンを含まないときに比較して、他の条件が一定の時に炭素繊維表面の官能基量が増え、つまり、Ｘ線光電子分光法（ＥＳＣＡ）により測定される表面酸素濃度や表面窒素濃度が増え、サイジング剤との接着性はもちろんマトリックス樹脂との接着性も高くなり好ましい。電解処理に要する電気量は、適用する炭素繊維により異なり、例えば、炭化度の高い炭素繊維である程、大きな電気量が必要となるので、表面処理量としては、Ｘ線光電子分光法（ＥＳＣＡ）により測定される炭素繊維の表面酸素濃度（原子数比）Ｏ／Ｃおよび表面窒素濃度Ｎ／Ｃ（原子数比）が、それぞれ０．１３〜０．２０、および、０．０５〜０．１０となるように処理するのが好ましい。   As the surface treatment method, a gas phase, a liquid phase treatment, an electrolytic treatment, or the like can be adopted, but an electrolytic treatment can be preferably adopted in consideration of productivity and quality variation. As an electrolytic solution used for the electrolytic treatment, an aqueous solution of an acidic compound such as sulfuric acid, nitric acid, hydrochloric acid, an alkaline compound such as sodium hydroxide, potassium hydroxide, various ammonium compounds, or an aqueous solution of a salt thereof can be used. An aqueous solution containing ammonium ions is preferable. Specifically, an aqueous solution containing ammonium nitrate, ammonium sulfate, ammonium persulfate, ammonium chloride, ammonium bromide, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium hydrogen carbonate, ammonium carbonate, tetraethylammonium hydroxide, or a mixture thereof. Can be used. By performing electrolysis using an aqueous solution containing ammonium ions, the amount of functional groups on the surface of the carbon fiber increases when other conditions are constant compared to when no ammonium ions are contained, that is, X-ray photoelectron spectroscopy ( The surface oxygen concentration and the surface nitrogen concentration measured by ESCA) are increased, and not only the adhesion to the sizing agent but also the adhesion to the matrix resin is enhanced. The amount of electricity required for the electrolytic treatment differs depending on the carbon fiber to be applied. For example, the carbon fiber having a higher degree of carbonization requires a larger amount of electricity. Therefore, the surface treatment amount is X-ray photoelectron spectroscopy (ESCA). The surface oxygen concentration (atomic number ratio) O / C and the surface nitrogen concentration N / C (atomic number ratio) of the carbon fiber measured by the above are 0.13 to 0.20 and 0.05 to 0.10, respectively. It is preferable to process so that it becomes.

これら条件の適用により、コンポジットにおいて炭素繊維とマトリックスとの接着性を適正化できるため、接着が強すぎてコンポジットの繊維方向における引張強度が低下するといった問題や、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るために非繊維方向における機械的特性が発現しないといった問題が解消され、繊維および非繊維方向にバランスのとれたコンポジット特性が発現されるようになる。   By applying these conditions, it is possible to optimize the adhesion between the carbon fiber and the matrix in the composite, so there is a problem that the adhesion is too strong and the tensile strength in the fiber direction of the composite decreases, and the resin that has high tensile strength in the fiber direction The problem that the mechanical properties in the non-fiber direction are not developed due to the poor adhesion to the fibers is solved, and the composite properties balanced in the fiber and non-fiber directions are developed.

さらに必要に応じて炭素繊維束にサイジング処理がなされる。サイジング剤には、マトリックスとの相溶性の良いサイジング剤が良く、マトリックスに応じて適宜選択される。例えば、ビスフェノールＡエポキシ樹脂やその誘導体を含む化合物を乳化させたものなどが挙げられる。   Further, a sizing process is performed on the carbon fiber bundle as necessary. The sizing agent is preferably a sizing agent having good compatibility with the matrix, and is appropriately selected according to the matrix. For example, what emulsified the compound containing a bisphenol A epoxy resin and its derivative (s) etc. are mentioned.

次に乾燥を行い、巻き取りを行う。合糸している場合は、いずれの工程で分繊を行ってもいいが、好ましくは、炭化処理後、表面処理前に行うことが好ましい。   Next, it is dried and wound up. In the case where the yarns are combined, the fiber separation may be performed in any step, but it is preferably performed after the carbonization treatment and before the surface treatment.

そして、得られた炭素繊維束の撚りを実質撚り数が０になるように解撚しながら解舒し本発明の炭素繊維が得られる。一度撚りがかかった状態で巻き取り、その後、ボビンから取り出すときに解撚しながら解舒して解撚糸パッケージとして巻き取っても良い。   Then, the carbon fiber bundle of the present invention is obtained by untwisting the obtained carbon fiber bundle while untwisting so that the substantial number of twists becomes zero. It may be wound up in a twisted state, and then unwound while untwisted when taken out from the bobbin and wound up as an untwisted yarn package.

以下、実施例において本発明をさらに具体的に説明する。   Hereinafter, the present invention will be described in more detail with reference to Examples.

＜プリカーサ単糸表面および炭素繊維単糸表面の算術平均粗さＲａ＞
プリカーサ単糸表面および炭素繊維単糸表面上の形態は、原子間力顕微鏡を用いた算術平均粗さとして求めた。測定方法は、Ｖｅｅｃｏ社Ｄｉｇｉｔａｌ Ｉｎｓｔｒｕｍｅｎｔｓ製 ＮａｎｏＳｃｏｐｅＩＩＩａ ＡＦＭ Ｄｉｍｅｎｎｓｉｏｎ ３０００ ステージシステムを使用し、タッピングモードで測定した。サンプルは、単糸を１．５ｃｍにカットし、銀ペーストでＳｉウェハに固定した。探針にシリコンカンチレバーを用いて、走査範囲２．５μｍ×２．５μｍの範囲を走査速度０．３３Ｈｚで測定を行った。３視野から測定を行った表面粗さを定量的に評価するために、３次元表面粗さ評価を行い、中心線からの偏差の絶対値の平均値を算術平均粗さＲａとして示した。なお、サイジング剤が付着している炭素繊維束サンプルについては、下記の方法で脱サイジングを行い、測定を実施した。 <Arithmetic mean roughness Ra of precursor single yarn surface and carbon fiber single yarn surface>
The morphology on the surface of the precursor single yarn and the surface of the carbon fiber single yarn was determined as an arithmetic average roughness using an atomic force microscope. The measurement was performed in a tapping mode using a NanoScopeIIIa AFM Dimension 3000 stage system manufactured by Veeco Digital Instruments. In the sample, a single yarn was cut to 1.5 cm and fixed to a Si wafer with a silver paste. Using a silicon cantilever as a probe, a scanning range of 2.5 μm × 2.5 μm was measured at a scanning speed of 0.33 Hz. In order to quantitatively evaluate the surface roughness measured from three fields of view, a three-dimensional surface roughness evaluation was performed, and the average value of the absolute values of deviations from the center line was indicated as the arithmetic average roughness Ra. In addition, about the carbon fiber bundle sample to which the sizing agent adheres, it desized by the following method and implemented the measurement.

（脱サイジング方法）十分な量のアセトン中で３０分間超音波洗浄を行い、続いてメタノール中で同様に超音波洗浄を実施し、その後、繊維束を取り出し、一昼夜、自然乾燥を行った。   (Desizing method) Ultrasonic cleaning was carried out in a sufficient amount of acetone for 30 minutes, followed by ultrasonic cleaning in methanol in the same manner. Thereafter, the fiber bundle was taken out and dried naturally all day and night.

＜炭素繊維の引張強度および引張弾性率＞
次の手順によって求めた。ＪＩＳ Ｒ ７６０８（２００４）の樹脂含浸ストランド試験法に準拠し、次の手順に従い求めた。樹脂処方としては、“セロキサイド（登録商標）”２０２１Ｐ（ダイセル化学工業社製）／三フッ化ホウ素モノエチルアミン（東京化成工業（株）製）／アセトン＝１００／３／４（質量部）を用い、硬化条件としては、常圧、温度１２５℃、時間３０分を用いた。ストランド５本を測定し、その平均値を求めた。なお、弾性率測定伸度域は０．４５〜０．８５％にて行った。 <Tensile strength and tensile modulus of carbon fiber>
It was determined by the following procedure. In accordance with the resin impregnated strand test method of JIS R 7608 (2004), it was determined according to the following procedure. As the resin formulation, “Celoxide (registered trademark)” 2021P (manufactured by Daicel Chemical Industries) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) is used. As curing conditions, normal pressure, temperature of 125 ° C., and time of 30 minutes were used. Five strands were measured and the average value was determined. The elastic modulus measurement elongation range was 0.45 to 0.85%.

＜Ｘ線回折測定による００２回折線から求められるｃ軸方向の結晶サイズＬｃ＞
試料として長さ４ｃｍ程度の炭素繊維を用意し、金型とコロジオン・アルコール溶液を用い固め、角柱形状として結晶サイズ測定用試料とした。広角Ｘ線装置（理学電機社製４０３６Ａ２型）を用いて測定を行った。Ｘ線源としてＣｕＫα線を用い、出力４０ｋｖ−２０ｍＡとし、ゴニオメータとしてのスリット幅を２ｍｍφ‐１°×１°とし、検出機としてシンチレーションカウンターを用いた。測定範囲を２θ＝１０〜４０°とし、ステップ単位０．０５°、積算時間２秒としてスキャンステップ走査モードで測定を行った。得られた回折パターンにおいて、２θ＝２５〜２６°付近に現れる（００２）面のピークについて、半価幅を求め、この値から、次のシェラー（Ｓｃｈｅｒｒｅｒ）の式により結晶サイズＬｃを算出した。 <C-axis direction crystal size Lc determined from 002 diffraction line by X-ray diffraction measurement>
A carbon fiber having a length of about 4 cm was prepared as a sample, and was solidified using a mold and a collodion / alcohol solution to obtain a sample for measuring the crystal size as a prismatic shape. Measurement was performed using a wide-angle X-ray apparatus (4036A2 type, manufactured by Rigaku Corporation). A CuKα ray was used as an X-ray source, an output was 40 kv-20 mA, a slit width as a goniometer was 2 mmφ−1 ° × 1 °, and a scintillation counter was used as a detector. Measurement was performed in scan step scanning mode with a measurement range of 2θ = 10 to 40 °, a step unit of 0.05 °, and an integration time of 2 seconds. In the obtained diffraction pattern, the half width was obtained for the peak of the (002) plane appearing in the vicinity of 2θ = 25 to 26 °, and the crystal size Lc was calculated from this value by the following Scherrer equation.

Ｌｃ（００２）＝Ｋλ／β０ｃｏｓθＢ
Ｌｃ（００２）：微結晶（００２）面に垂直な方向の平均の大きさ
Ｋ：１．０、λ：０．１５４０６ｎｍ（Ｘ線波長）
β０：（βＥ ２−βＩ ２）１／２
βＥ：見かけの半価幅（測定値）ｒａｄ、βＩ：装置定数１．０４６×１０−２ｒａｄ
θＢ：Ｂｒａｇｇの回折角。 Lc (002) = Kλ / β 0 cos θ B
Lc (002): average size in the direction perpendicular to the microcrystal (002) plane K: 1.0, λ: 0.15406 nm (X-ray wavelength)
β 0 : (β E 2 -β I 2 ) 1/2
β E : Apparent half width (measured value) rad, β I : Device constant 1.046 × 10 −2 rad
θ B : Bragg diffraction angle.

＜結晶配向度π００２＞
上述した装置を用い、面指数（００２）回折線の結晶ピークを円周方向にスキャンして測定を行った。測定範囲を９０〜２７０°とし、ステップ単位０．５°、積算時間２秒と設定し測定実施し、得られる強度分布の半価幅から次式を用いて計算して求めた。 <Crystal orientation π 002 >
Using the apparatus described above, measurement was performed by scanning the crystal peak of the plane index (002) diffraction line in the circumferential direction. The measurement range was 90 to 270 °, the step unit was set to 0.5 °, and the integration time was 2 seconds. The measurement was carried out, and the value was calculated from the half width of the obtained intensity distribution using the following formula.

π００２（％）＝（１８０−Ｈ）／１８０×１００（％）
Ｈ：見かけの半価幅（ｄｅｇ）。 π 002 (%) = (180−H) / 180 × 100 (%)
H: Apparent half width (deg).

＜炭素繊維の交絡度＞
ＪＩＳ Ｌ １０１３（２０１０）「化学繊維フィラメント糸試験方法」の交絡度測定方法に準じて測定した。炭素繊維単糸からなる繊維束試料（１２５０〜１００００ｄｔｅｘ）の一端を適当な性能を有する垂下装置の上部つかみ部に取り付け、つかみ部より１ｍ下方の繊維束の位置に荷重（１００ｇ）を吊り下げ、該試料を垂直に垂らす。該試料の上部つかみ部より１ｃｍ下部の点に該繊維束を２分割するようにフック（直径１ｍｍの針金状）を挿入する。フックの他端には所定の荷重（３．６ｇ）を取り付け、約２ｃｍ／秒の速度でフックを降下させる。フックが糸の絡みにより停止した点までのフックの降下距離Ｌ［ｍｍ］を測定し、次式により交絡度を求めた。なお、上述の操作を５０回（１回／ｍ×５０）繰り返し、その平均値で表す。 <Degree of entanglement of carbon fiber>
It measured according to the entanglement degree measuring method of JIS L 1013 (2010) “Testing method for chemical fiber filament yarn”. One end of a fiber bundle sample (1250-10000 dtex) made of carbon fiber single yarn is attached to the upper grip part of a hanging device having appropriate performance, and a load (100 g) is suspended at the position of the fiber bundle 1 m below the grip part, The sample is hung vertically. A hook (wire shape with a diameter of 1 mm) is inserted so that the fiber bundle is divided into two at a point 1 cm below the upper grip portion of the sample. A predetermined load (3.6 g) is attached to the other end of the hook, and the hook is lowered at a speed of about 2 cm / second. The hook descending distance L [mm] to the point where the hook stopped due to the yarn entanglement was measured, and the degree of entanglement was determined by the following equation. In addition, the above-mentioned operation is repeated 50 times (1 time / m × 50), and the average value is expressed.

交絡度Ａ＝１０００／Ｌ
Ｌ：フックの降下距離［ｍｍ］。 Entanglement A = 1000 / L
L: Descent distance of hook [mm].

＜炭素繊維の破断単糸個数＞
繊維束巻き取りパッケージから繊維束を、ボビンの円筒軸と垂直方向に、５０ｍｇ／ｄｔｅｘの張力下、１０ｍ／ｍｉｎの速度で引き出した際に、目視で確認される１０ｍｍ以上の破断単糸個数をａ個としてカウントした。計１００ｍ分の評価を行い、下記式
破断単糸個数（個／ｍ）＝ ａ／１００
より求めた。なお、評価にあたっては、繊維束を赤色光で照射し、３０ｃｍ離れた位置から測定を実施した。 <Number of single broken carbon fiber yarns>
When the fiber bundle is pulled out from the fiber bundle winding package in the direction perpendicular to the cylindrical axis of the bobbin at a speed of 10 m / min under a tension of 50 mg / dtex, the number of broken single yarns of 10 mm or more visually confirmed. Counted as a. Evaluation is made for a total of 100 m, and the following formula: Number of broken single yarns (pieces / m) = a / 100
I asked more. In the evaluation, the fiber bundle was irradiated with red light, and measurement was performed from a position 30 cm away.

＜炭素繊維束断面の扁平率＞
表面粗さ測定装置（小坂研究所ＳＥ−３４００）を用いて、繊維束の最大高さＸ、糸幅Ｙを測定し、炭素繊維束断面の扁平率Ｂを、下記式より求めた。 <Flatness of carbon fiber bundle cross section>
Using a surface roughness measuring device (Kosaka Laboratory SE-3400), the maximum height X and the yarn width Y of the fiber bundle were measured, and the flatness B of the carbon fiber bundle cross section was determined from the following formula.

炭素繊維束断面の扁平率Ｂ＝Ｘ／Ｙ
なお、測定サンプルは、繊維束が巻き取られたパッケージから、形状を保ったまま繊維束３ｃｍ分を引き出しカットし、測定台に設置し両端をテープで固定させた。測定方向としては、プローブを繊維束方向に対して垂直に沿わせて行った。測定条件としては、評価長８ｍｍ、送り速度０．５ｍｍ／秒とした。評価開始と終了位置は、サンプルの固定された土台上となるように測定を行った。 Flatness B of carbon fiber bundle cross section B = X / Y
The measurement sample was cut out by pulling out 3 cm of the fiber bundle while keeping its shape from the package in which the fiber bundle was wound, placed on the measurement table, and fixed at both ends with tape. As a measurement direction, the probe was set along a direction perpendicular to the fiber bundle direction. The measurement conditions were an evaluation length of 8 mm and a feed rate of 0.5 mm / second. The measurement was performed so that the evaluation start and end positions were on the base on which the sample was fixed.

［実施例１］
アクリロニトリル９９．５モル％とイタコン酸０．５モル％からなる共重合体をジメチルスルホキシドを溶媒とする溶液重合法により重合し、紡糸原液を得た。得られた紡糸原液を、紡糸口金を用いて、一旦空気中に吐出し、３℃にコントロールした３５％ジメチルスルホキシドの水溶液からなる凝固浴に導入する乾湿式紡糸法により凝固させた。得られた凝固糸を、水洗した後、温水中で浴延伸し、アミノ変性シリコーン、エポキシ変性シリコーン、及びエチレンオキサイド変性シリコーンを含んだシリコーン系油剤浴中を通して、加熱ローラを用いて乾燥緻密化処理を行った。得られた乾燥緻密化処理糸を、さらに、加圧スチーム中で、延伸することにより、製糸全延伸倍率を１２倍とし、単糸繊度０．７ｄｔｅｘ、単糸表面粗さＲａ３．２ｎｍとなるアクリロニトリル系プリカーサを得た。単糸数６０００本のプリカーサとして、１５ターン／ｍの撚りをかけ、耐炎化２４０〜２８０℃の空気中で、張力１００ｍｇ／ｄｔｅｘに設定し通過させ、比重１．３５の耐炎化糸に転換した。得られた耐炎化糸を３００〜８００℃の不活性雰囲気中で１２０ｍｇ／ｄｔｅｘの張力下で予備炭化した後、最高温度１３５０℃の炭化炉を１２５０ｍｇ／ｄｔｅｘの張力下で通過させ炭化糸に転換した。その後、炭酸水素アンモニウム水溶液中で、８０クーロン／ｇ−ＣＦの陽極酸化処理を行い、純水で洗浄を行った。続けて、ビスフェノールＡエポキシ樹脂を主成分とするサイジング剤を炭素繊維に対して１重量％になるように付着させて、乾燥を行い、巻き取りを行った。さらに、巻き取りを行った後、再度撚りを解舒しながら巻き返し実質的に撚り数０ターン／ｍの炭素繊維を得た。得られた炭素繊維の特性は、表面算術平均粗さ２．２ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．８％、引張弾性率３２５ＧＰａ、引張強度５５６１ＭＰａであった。また、交絡度、扁平率は、それぞれ２８、０．２５であった。目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た（表１）。 [Example 1]
A copolymer consisting of 99.5 mol% of acrylonitrile and 0.5 mol% of itaconic acid was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent to obtain a spinning dope. The obtained spinning dope was once discharged into air using a spinneret and coagulated by a dry and wet spinning method introduced into a coagulation bath made of an aqueous solution of 35% dimethyl sulfoxide controlled at 3 ° C. The obtained coagulated yarn is washed with water, then stretched in warm water, passed through a silicone oil bath containing amino-modified silicone, epoxy-modified silicone, and ethylene oxide-modified silicone, and dried and densified using a heating roller. Went. The obtained dried densified yarn is further stretched in pressurized steam, so that the total spinning ratio is 12 times, the single yarn fineness is 0.7 dtex, and the single yarn surface roughness Ra is 3.2 nm. A system precursor was obtained. As a precursor having 6,000 single yarns, a twist of 15 turns / m was applied, and in a flame-resistant air set at a tension of 100 mg / dtex in air at 240 to 280 ° C., the yarn was converted to a flame-resistant yarn having a specific gravity of 1.35. The obtained flame resistant yarn was pre-carbonized in an inert atmosphere of 300 to 800 ° C. under a tension of 120 mg / dtex, and then passed through a carbonization furnace having a maximum temperature of 1350 ° C. under a tension of 1250 mg / dtex to be converted into carbonized yarn. did. Thereafter, an anodizing treatment of 80 coulomb / g-CF was performed in an aqueous ammonium hydrogen carbonate solution, and washing was performed with pure water. Then, the sizing agent which has a bisphenol A epoxy resin as a main component was made to adhere so that it might become 1 weight% with respect to carbon fiber, and it dried and wound up. Furthermore, after winding, the carbon fiber with substantially 0 twists / m was obtained by rewinding while twisting again. The characteristics of the obtained carbon fiber were a surface arithmetic average roughness of 2.2 nm, a crystal size of 18.5 angstroms, a crystal orientation of 84.8%, a tensile elastic modulus of 325 GPa, and a tensile strength of 5561 MPa. Further, the degree of entanglement and the flatness were 28 and 0.25, respectively. Carbon fibers having the desired surface morphology, quality, and degree of entanglement and well-balanced properties were obtained (Table 1).

表１記載の破断単糸個数評価の判断基準を示す。得られた炭素繊維パッケージから、ボビン胴体と垂直方向に繊維束を１０ｍ／ｍｉｎで引き出した際に、目視で確認される１０ｍｍ以上の破断単糸の個数を次の基準で判断した。評価は１００ｍ長さで行い、１ｍあたりの平均値で表した。   The criteria for determining the number of broken single yarns shown in Table 1 are shown. When the fiber bundle was pulled out at 10 m / min in the direction perpendicular to the bobbin body from the obtained carbon fiber package, the number of broken single yarns of 10 mm or more visually confirmed was judged according to the following criteria. The evaluation was performed with a length of 100 m and expressed as an average value per 1 m.

◎：１．０個以下
○：１．０個／ｍ超え、１．５個／ｍ以下
×：１．５個超え。 A: 1.0 or less ○: More than 1.0 / m, 1.5 / m or less ×: More than 1.5

［比較例１］
実施例１で得られた紡糸原液を、紡糸口金を通して、直接温度６０℃、５０％のジメチルスルホキシド水溶液中に吐出させて凝固糸とした以外は実施例１と同様の操作をし、単糸繊度０．７ｄｔｅｘ、単糸表面粗さＲａ２７．０ｎｍとなる単糸数６０００本のポリアクリロニトリル系プリカーサを得た。そして、実施例１と同様の条件で耐炎化を通過させ、比重１．３５の耐炎糸に転換した。続けて、実施例１と同一の条件にて予備炭化、炭化工程を通過せしめようとしたが、単糸切れが多発し、プロセス性が悪く炭化工程以降のローラで巻付きが多発した。炭化糸への転換を実施できた一部繊維について、実施例１同様の処理を行い、次の炭素繊維を得た。表面算術平均粗さ２３．３ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．６％、引張弾性率３２３ＧＰａ、引張強度４８９０ＭＰａ、交絡度４５の炭素繊維を得た。表面形態が粗く、引張強度が実施例１対比低く、毛羽品位については単糸切れが多く破断単糸個数１．５個／ｍを上回り、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 1]
The spinning dope obtained in Example 1 was directly discharged through a spinneret into a 50% dimethyl sulfoxide aqueous solution at a temperature of 60 ° C. to obtain a coagulated yarn. A polyacrylonitrile-based precursor having a single yarn number of 6000 with 0.7 dtex and a single yarn surface roughness Ra of 27.0 nm was obtained. And it made the flame resistance pass on the same conditions as Example 1, and changed to the flame resistant yarn of specific gravity 1.35. Subsequently, an attempt was made to pass the preliminary carbonization and carbonization processes under the same conditions as in Example 1. However, single yarn breakage occurred frequently, the processability was poor, and the winding after the carbonization process occurred frequently. About the one part fiber which could be converted into carbonized yarn, the process similar to Example 1 was performed and the following carbon fiber was obtained. A carbon fiber having a surface arithmetic average roughness of 23.3 nm, a crystal size of 18.5 angstroms, a crystal orientation of 84.6%, a tensile elastic modulus of 323 GPa, a tensile strength of 4890 MPa, and a confounding degree of 45 was obtained. The surface morphology is rough, the tensile strength is low compared to Example 1, and the fluff quality is high in the number of single yarn breaks and exceeds the number of broken single yarns of 1.5 pieces / m, and carbon fibers in which the desired properties are balanced cannot be obtained. It was. Other characteristics are listed in Table 1.

［比較例２］
比較例１で得られた耐炎糸を用い、プロセス性よく炭化工程を通過させるため、予備炭化張力７０ｍｇ／ｄｔｅｘ、炭化張力８５０ｍｇ／ｄｔｅｘと実施例１条件から変更して炭化工程を通過させ炭化糸に転換した。その後、実施例１同一の条件で処理し、次の炭素繊維を得た。表面算術平均粗さ２３．９ｎｍ、結晶サイズ１８．６オングストローム、結晶配向度８２．９％、引張弾性率２８７ＧＰａ、引張強度４８３０ＭＰａ、交絡度１９となり、所望の結晶配向度、引張弾性率が得られず、表面形態が粗く、引張強度も実施例１対比低く、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 2]
In order to pass the carbonization step with good processability using the flame resistant yarn obtained in Comparative Example 1, the carbonization yarn was passed through the carbonization step by changing the preliminary carbonization tension to 70 mg / dtex and the carbonization tension of 850 mg / dtex from the conditions in Example 1. Converted to. Then, it processed on the same conditions as Example 1, and obtained the following carbon fiber. Surface arithmetic average roughness 23.9 nm, crystal size 18.6 angstrom, crystal orientation 82.9%, tensile modulus 287 GPa, tensile strength 4830 MPa, entanglement 19 and desired crystal orientation and tensile modulus were obtained. In addition, the carbon fiber having a rough surface morphology and a low tensile strength compared to Example 1 and having a balance of desired properties could not be obtained. Other characteristics are listed in Table 1.

［比較例３］
比較例２で得られた炭素繊維の引張強度、引張弾性率を改善するため、比較例２から耐炎化の張力を２５０ｍｇ／ｄｔｅｘと変更し、比重１．３５の耐炎化糸に転換し、炭化工程以降は比較例２と同一の条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２２．６ｎｍ、結晶サイズ１８．６オングストローム、結晶配向度８２．９％、引張弾性率２９０ＧＰａ、引張強度５４８８ＭＰａ、交絡度２４となり、引張強度は向上したが、結晶配向度と引張弾性率が低く、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 3]
In order to improve the tensile strength and tensile modulus of the carbon fiber obtained in Comparative Example 2, the tension of flame resistance was changed to 250 mg / dtex from Comparative Example 2 and converted to a flame resistant yarn having a specific gravity of 1.35, and carbonized. After the process, the operation was performed under the same conditions as in Comparative Example 2 to obtain the following carbon fiber. The surface arithmetic average roughness was 22.6 nm, the crystal size was 18.6 angstroms, the crystal orientation was 82.9%, the tensile modulus was 290 GPa, the tensile strength was 5488 MPa, the entanglement was 24, and the tensile strength was improved. A carbon fiber having a low elastic modulus and a balance of desired properties could not be obtained. Other characteristics are listed in Table 1.

［比較例４］
比較例３で得られる炭素繊維の引張弾性率を改善するため、炭化温度を１５００℃へ変更した以外は比較例３と同条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２３．６ｎｍ、結晶サイズ２１．５オングストローム、結晶配向度８２．８％、引張弾性率３０３ＧＰａ、引張強度５４３０ＭＰａ、交絡度３０となり、引張強度が向上したものの所望の結晶配向度と引張弾性率は得られず、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 4]
In order to improve the tensile elastic modulus of the carbon fiber obtained in Comparative Example 3, the following carbon fiber was obtained by operating under the same conditions as in Comparative Example 3 except that the carbonization temperature was changed to 1500 ° C. The surface arithmetic average roughness was 23.6 nm, the crystal size was 21.5 angstroms, the crystal orientation was 82.8%, the tensile modulus was 303 GPa, the tensile strength was 5430 MPa, and the entanglement degree was 30. No tensile elastic modulus was obtained, and carbon fibers with a balance of desired properties could not be obtained. Other characteristics are listed in Table 1.

［比較例５］
比較例４で得られる炭素繊維の引張弾性率が所望の弾性率より低いため、予備炭化張力１２０ｍｇ／ｄｔｅｘ、炭化張力９５０ｍｇ／ｄｔｅｘと変更した以外は比較例４と同一の条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２４．２ｎｍ、結晶サイズ２１．５オングストローム、結晶配向度８３．６％、引張弾性率３１３ＧＰａ、引張強度５６０１ＭＰａ、交絡度３３となり、所望の結晶配向度と引張弾性率は得られたが、毛羽品位については単糸切れが多く破断単糸個数１．５個／ｍを上回り、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 5]
Since the tensile elastic modulus of the carbon fiber obtained in Comparative Example 4 is lower than the desired elastic modulus, the operation was performed under the same conditions as in Comparative Example 4 except that the preliminary carbonization tension was 120 mg / dtex and the carbonization tension was 950 mg / dtex. The following carbon fibers were obtained. Surface arithmetic average roughness 24.2 nm, crystal size 21.5 angstrom, crystal orientation 83.6%, tensile elastic modulus 313 GPa, tensile strength 5601 MPa, entanglement 33, and desired crystal orientation and tensile elastic modulus are obtained. However, with regard to the fluff quality, there was a lot of single yarn breakage, and the number of broken single yarns exceeded 1.5 / m, and carbon fibers in which the desired characteristics were balanced could not be obtained. Other characteristics are listed in Table 1.

［比較例６］
実施例１に対して引張強度の向上を図る目的で耐炎化張力を１５０ｍｇ／ｄｔｅｘに変更し、比重１．３５の耐炎糸に転換後、実施例１と同一の条件で炭化工程に供給したところ、糸切れが発生し安定生産は不可能であった。炭化糸への転換を実施できた一部繊維については、実施例１同様の処理を行い、次の炭素繊維を得た。表面算術平均粗さ２．３ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．７％、引張弾性率３２３ＧＰａ、引張強度５２００ＭＰａ、交絡度４７となり、かえって引張強度が低下し、毛羽品位については単糸切れが多く破断単糸個数１．５個／ｍを上回り、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 6]
For the purpose of improving the tensile strength with respect to Example 1, the flameproofing tension was changed to 150 mg / dtex, converted to a flame resistant yarn having a specific gravity of 1.35, and then supplied to the carbonization process under the same conditions as in Example 1. Thread breakage occurred and stable production was impossible. About the one part fiber which could be converted into carbonized yarn, the process similar to Example 1 was performed and the following carbon fiber was obtained. Surface arithmetic average roughness 2.3 nm, crystal size 18.5 angstroms, crystal orientation 84.7%, tensile modulus 323 GPa, tensile strength 5200 MPa, entanglement degree 47. There were many yarn breaks, and the number of broken single yarns exceeded 1.5 / m, and a carbon fiber with a balance of desired characteristics could not be obtained. Other characteristics are listed in Table 1.

［比較例７］
実施例１に対して耐炎化張力を６０ｍｇ／ｄｔｅｘに変更したところ、繊維束が弛み、耐炎化工程で糸飛びや擦れが発生し、走行糸の品位が悪化し、安定生産が不可能となった。炭化糸への転換を実施できた一部繊維については、実施例１と同一の条件で処理を行い、次の炭素繊維を得た。表面算術平均粗さ２．４ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．８％、引張弾性率３２３ＧＰａ、引張強度５３４５ＭＰａ、交絡度３５となり、所望の表面形態・品質・交絡度は得られたが、毛羽品位については単糸切れが多く破断単糸個数１．５個／ｍを上回り、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 7]
When the flameproof tension was changed to 60 mg / dtex with respect to Example 1, the fiber bundle was loosened, yarn jumping and rubbing occurred in the flameproofing process, the quality of the running yarn deteriorated, and stable production became impossible. It was. Some fibers that could be converted to carbonized yarn were treated under the same conditions as in Example 1 to obtain the following carbon fibers. Surface arithmetic average roughness 2.4 nm, crystal size 18.5 angstrom, crystal orientation 84.8%, tensile modulus 323 GPa, tensile strength 5345 MPa, entanglement 35, and desired surface morphology / quality / entanglement is obtained However, with regard to the fluff quality, there was a lot of single yarn breakage, and the number of broken single yarns exceeded 1.5 / m, and carbon fibers in which the desired characteristics were balanced could not be obtained. Other characteristics are listed in Table 1.

［比較例８］
実施例１の炭化張力を８５０ｍｇ／ｄｔｅｘに変えた以外は同一条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２．４ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８３．０％、引張弾性率３０４ＧＰａ、引張強度５４００ＭＰａ、交絡度２８となり、結晶配向度、引張弾性率が低く、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 8]
The following carbon fiber was obtained by operating under the same conditions except that the carbonization tension of Example 1 was changed to 850 mg / dtex. Surface arithmetic average roughness 2.4 nm, crystal size 18.5 angstrom, crystal orientation 83.0%, tensile modulus 304 GPa, tensile strength 5400 MPa, entanglement 28, low crystal orientation and tensile modulus, Carbon fibers with well-balanced properties could not be obtained. Other characteristics are listed in Table 1.

［比較例９］
耐炎化工程に供給するプリカーサを無撚とした以外は実施例１と同一の条件で焼成を行ったところ、炭化工程で糸切れが多発し、炭素繊維を得ることが出来なかった。 [Comparative Example 9]
When firing was performed under the same conditions as in Example 1 except that the precursor supplied to the flameproofing process was untwisted, yarn breakage occurred frequently in the carbonization process, and carbon fibers could not be obtained.

［比較例１０］
耐炎化工程に供給するプリカーサを無撚とし、炭化張力を８５０ｍｇ／ｄｔｅｘとした以外は実施例１と同一の条件で生産を行い、次の炭素繊維を得た。表面算術平均粗さ２．３ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８３．０％、引張弾性率２９９ＧＰａ、引張強度６８００ＭＰａ、交絡度６となり、引張弾性率が低く交絡度が小さく、破断単糸個数１．５個／ｍを下回ったものの、目的の特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 10]
Production was performed under the same conditions as in Example 1 except that the precursor supplied to the flameproofing process was untwisted and the carbonization tension was 850 mg / dtex, and the following carbon fiber was obtained. Surface arithmetic average roughness 2.3 nm, crystal size 18.5 angstrom, crystal orientation 83.0%, tensile modulus 299 GPa, tensile strength 6800 MPa, entanglement degree 6, low tensile modulus and low entanglement, Although the number of yarns was less than 1.5 yarns / m, a carbon fiber in which the desired properties were balanced was not obtained. Other characteristics are listed in Table 1.

［実施例２］
炭化張力を１３５０ｍｇ／ｄｔｅｘとした以外は実施例１と同一の条件で、各工程を通過させ、次の炭素繊維を得た。表面算術平均粗さ２．８ｎｍ、結晶サイズ１８．６オングストローム、結晶配向度８５．１％、引張弾性率３３２ＧＰａ、引張強度５６５５ＭＰａ、交絡度３０となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 2]
Except for the carbonization tension of 1350 mg / dtex, each step was passed under the same conditions as in Example 1 to obtain the following carbon fiber. Surface arithmetic average roughness 2.8 nm, crystal size 18.6 angstrom, crystal orientation 85.1%, tensile elastic modulus 332 GPa, tensile strength 5655 MPa, entanglement 30 and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［比較例１１］
最高温度を１２３０℃とした以外は実施例２と同一の条件で、各工程を通過させ、次の炭素繊維を得た。表面算術平均粗さ２．２ｎｍ、結晶サイズ１６．４オングストローム、結晶配向度８４．８％、引張弾性率３１０ＧＰａ、引張強度５４５０ＭＰａ、交絡度３１となり、目的とする結晶サイズ、引張弾性率を得られず、特性のバランスのとれた炭素繊維束は得られなかった。他特性は表１に記載した。 [Comparative Example 11]
Each step was passed under the same conditions as in Example 2 except that the maximum temperature was 1230 ° C., and the following carbon fiber was obtained. Surface arithmetic average roughness 2.2 nm, crystal size 16.4 angstrom, crystal orientation 84.8%, tensile elastic modulus 310 GPa, tensile strength 5450 MPa, entanglement 31, and the desired crystal size and tensile elastic modulus can be obtained. Therefore, a carbon fiber bundle having a well-balanced characteristic could not be obtained. Other characteristics are listed in Table 1.

［実施例３］
実施例１と、炭化最高温度を１４３０℃に昇温し、炭化張力を１１００ｍｇ／ｄｔｅｘと変更した以外は同一の条件で、各工程を通過させ、次の炭素繊維を得た。表面算術平均粗さ２．１ｎｍ、結晶サイズ２０．６オングストローム、結晶配向度８４．２％、引張弾性率３３４ＧＰａ、引張強度５３６１ＭＰａ、交絡度４４となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 3]
Each step was passed under the same conditions as in Example 1 except that the carbonization maximum temperature was raised to 1430 ° C. and the carbonization tension was changed to 1100 mg / dtex to obtain the following carbon fiber. Surface arithmetic average roughness 2.1 nm, crystal size 20.6 angstrom, crystal orientation 84.2%, tensile modulus 334 GPa, tensile strength 5361 MPa, entanglement 44, and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［実施例４］
炭化最高温度を１５００℃に昇温し、炭化張力を１１００ｍｇ／ｄｔｅｘと変更した以外は実施例１と同一の条件で、各工程を通過させ、次の炭素繊維を得た。表面算術平均粗さ１．９ｎｍ、結晶サイズ２１．７オングストローム、結晶配向度８４．１％、引張弾性率３３９ＧＰａ、引張強度５１９４ＭＰａ、交絡度３５となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 4]
Each step was passed under the same conditions as in Example 1 except that the maximum carbonization temperature was raised to 1500 ° C. and the carbonization tension was changed to 1100 mg / dtex to obtain the following carbon fiber. Surface arithmetic average roughness 1.9 nm, crystal size 21.7 angstrom, crystal orientation 84.1%, tensile modulus 339 GPa, tensile strength 5194 MPa, entanglement 35, and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［実施例５］
炭化張力を１２５０ｍｇ／ｄｔｅｘと変更した以外は実施例４と同一の条件で、各工程を通過させ、次の炭素繊維を得た。表面算術平均粗さ２．２ｎｍ、結晶サイズ２１．６オングストローム、結晶配向度８４．７％、引張弾性率３４５ＧＰａ、引張強度５３４３ＭＰａ、交絡度２４となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 5]
Each step was passed under the same conditions as in Example 4 except that the carbonization tension was changed to 1250 mg / dtex to obtain the next carbon fiber. Surface arithmetic average roughness 2.2 nm, crystal size 21.6 angstrom, crystal orientation 84.7%, tensile modulus 345 GPa, tensile strength 5343 MPa, entanglement 24, and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［比較例１２］
炭化張力を１５００ｍｇ／ｄｔｅｘと変更した以外は実施例４と同一の条件で、各工程を通過させた。しかし、炭化工程での単糸切れが多く、炭化工程以降のローラで巻付きが多発する結果となり、炭素繊維を得ることは出来なかった。 [Comparative Example 12]
Each step was passed under the same conditions as in Example 4 except that the carbonization tension was changed to 1500 mg / dtex. However, there was a lot of single yarn breakage in the carbonization process, resulting in frequent winding of the rollers after the carbonization process, and carbon fibers could not be obtained.

［比較例１３］
炭化温度を１５５０℃に変更した以外は実施例１と同一条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２．１ｎｍ、結晶サイズ２２．５オングストローム、結晶配向度８４．７％、引張弾性率３４８ＧＰａ、引張強度５２５０ＭＰａ、交絡度３０となり、結晶サイズが大きく、目的とする特性のバランスのとれた炭素繊維は得られなかった。他特性は表１に記載した。 [Comparative Example 13]
The following carbon fiber was obtained by operating under the same conditions as in Example 1 except that the carbonization temperature was changed to 1550 ° C. Surface arithmetic average roughness 2.1 nm, crystal size 22.5 angstrom, crystal orientation 84.7%, tensile elastic modulus 348 GPa, tensile strength 5250 MPa, entanglement degree 30; crystal size is large and balance of desired properties No taken carbon fiber was obtained. Other characteristics are listed in Table 1.

［比較例１４］
プリカーサに９ターン／ｍの撚りを加えた以外は実施例４と同一の条件で、耐炎化工程、炭化工程を通過させた。しかし、撚数が少なく炭化延伸性が発現せず、単糸切れが多発した。得られた炭化糸については、実施例１同様の処理を行い、次の炭素繊維を得た。表面算術平均粗さ２．２ｎｍ、結晶サイズ２１．６オングストローム、結晶配向度８４．２％、引張弾性率３３１ＧＰａ、引張強度５３１４ＭＰａ、交絡度２６となり、所望の表面形態、品質、交絡度は得られたが、毛羽品位については破断単糸個数１．５個／ｍを上回り、目的とする特性のバランスのとれた炭素繊維は得られなかった。 [Comparative Example 14]
The flameproofing step and the carbonization step were passed under the same conditions as in Example 4 except that a twist of 9 turns / m was added to the precursor. However, the number of twists was small, and carbonization stretchability was not exhibited, and single yarn breakage occurred frequently. About the obtained carbonized yarn, the process similar to Example 1 was performed and the following carbon fiber was obtained. Surface arithmetic average roughness 2.2 nm, crystal size 21.6 angstrom, crystal orientation 84.2%, tensile modulus 331 GPa, tensile strength 5314 MPa, entanglement 26, desired surface morphology, quality, entanglement can be obtained However, with respect to the fluff quality, the number of broken single yarns exceeded 1.5 / m, and carbon fibers having a balance of desired properties could not be obtained.

［比較例１５］
単糸切れを１．５個／ｍ以下となるように炭化張力７５０ｍｇ／ｄｔｅｘとした以外は比較例１２と同一の条件で処理を行い、次の炭素繊維を得た。表面算術平均粗さ２．２ｎｍ、結晶サイズ２１．６オングストローム、結晶配向度８２．９％、引張強度５２１０ＭＰａ、交絡度４０、破断単糸個数１．５個／ｍ以下となり、所望の表面形態、交絡度、毛羽品位は得られたが、引張弾性率が３１２ＧＰａと低く、目的とする特性のバランスのとれた炭素繊維は得られなかった。 [Comparative Example 15]
The following carbon fiber was obtained under the same conditions as in Comparative Example 12 except that the carbonization tension was 750 mg / dtex so that the single yarn breakage was 1.5 pieces / m or less. Surface arithmetic average roughness 2.2 nm, crystal size 21.6 angstrom, crystal orientation 82.9%, tensile strength 5210 MPa, entanglement 40, number of broken single yarns 1.5 m / m or less, desired surface morphology, Although the degree of entanglement and the fluff quality were obtained, carbon fibers with a low tensile elastic modulus of 312 GPa and a balance of desired properties could not be obtained.

［実施例６］
加撚数を２０ターン／ｍに変更した以外は実施例１と同一条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２．２ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．８％、引張弾性率３２３ＧＰａ、引張強度４９９０ＭＰａ、交絡度５１となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 6]
The following carbon fiber was obtained under the same conditions as in Example 1 except that the number of twists was changed to 20 turns / m. Surface arithmetic average roughness 2.2 nm, crystal size 18.5 angstrom, crystal orientation 84.8%, tensile modulus 323 GPa, tensile strength 4990 MPa, entanglement 51, and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［実施例７］
加撚数を３０ターン／ｍに変更した以外は実施例１と同一条件で操作を行い、次の炭素繊維を得た。表面算術平均粗さ２．６ｎｍ、結晶サイズ１８．５オングストローム、結晶配向度８４．８％、引張弾性率３２３ＧＰａ、引張強度４９１０ＭＰａ、交絡度５５となり、目的とする表面形態、品質、交絡度を有し毛羽品位良好な特性のバランスのとれた炭素繊維を得た。他特性は表１に記載した。 [Example 7]
The following carbon fiber was obtained by operating under the same conditions as in Example 1 except that the number of twists was changed to 30 turns / m. Surface arithmetic average roughness 2.6 nm, crystal size 18.5 angstrom, crystal orientation 84.8%, tensile modulus 323 GPa, tensile strength 4910 MPa, entanglement 55, and has the desired surface morphology, quality, and entanglement A carbon fiber with a good balance of properties was obtained. Other characteristics are listed in Table 1.

［比較例１６］
加撚数を３５ターン／ｍに変更した以外は実施例１と同一条件で操作を行ったところ、加撚数が多く耐炎化での焼斑部分が予備炭化工程で糸切れの発端となり、炭化でも糸切れが多発し、炭素繊維を得ることが出来なかった。 [Comparative Example 16]
Except for changing the number of twists to 35 turns / m, the operation was carried out under the same conditions as in Example 1. However, thread breakage occurred frequently and carbon fiber could not be obtained.

［比較例１７］
製糸全延伸倍率を１５倍とした以外は実施例１と同一の条件で操作を行い得られた、単糸繊度０．７ｄｔｅｘ、単糸表面粗さＲａ８．３ｎｍのプリカーサを実施例１と同一の条件で焼成を行ったが、炭化工程での単糸切れが多く、炭化工程以降のローラで巻付きが多発する結果となり、炭素繊維を得ることは出来なかった。 [Comparative Example 17]
A precursor having a single yarn fineness of 0.7 dtex and a single yarn surface roughness Ra of 8.3 nm, which was obtained by performing the operation under the same conditions as in Example 1 except that the total yarn production draw ratio was 15 times, was the same as in Example 1. Although firing was performed under the conditions, there was a lot of single yarn breakage in the carbonization step, resulting in frequent winding of the rollers after the carbonization step, and carbon fibers could not be obtained.

Figure 2015067910
Figure 2015067910

Claims (3)

原子間力顕微鏡により測定される表面算術平均粗さＲａが３．０ｎｍ以下、Ｘ線回折測定による００２回折線から求められるｃ軸方向の結晶サイズＬｃが１７．０〜２２．４オングストローム、結晶配向度π００２が８３．５〜８５．５％である炭素繊維単糸を１０００本以上含む炭素繊維であって、交絡度Ａが１０〜８０、束断面の扁平率Ｂが０．１５〜０．４０であり、１０ｍｍ以上の破断単糸個数が１．５個／ｍ以下で、引張弾性率ＹＭが３１３〜３４５ＧＰａの炭素繊維。 Surface arithmetic average roughness Ra measured by an atomic force microscope is 3.0 nm or less, crystal size Lc in the c-axis direction obtained from 002 diffraction line by X-ray diffraction measurement is 17.0 to 22.4 angstrom, crystal orientation A carbon fiber containing 1000 or more carbon fiber single yarns having a degree π 002 of 83.5 to 85.5%, an entanglement degree A of 10 to 80, and a flatness ratio B of a bundle cross section of 0.15 to 0.005. 40, carbon fiber having a number of broken single yarns of 10 mm or more and 1.5 pieces / m or less and a tensile elastic modulus YM of 313 to 345 GPa. 引張強度が５０００ＭＰａ以上である請求項１記載の炭素繊維。 The carbon fiber according to claim 1, which has a tensile strength of 5000 MPa or more. 原子間力顕微鏡により測定される表面算術平均粗さＲａが４．０ｎｍ以下であり、単糸数が１０００本以上であるプリカーサに１０〜３０ターン／ｍの撚りを加え、７０〜１３０ｍｇ／ｄｔｅｘの張力下で耐炎化し、不活性雰囲気中で最高焼成温度が１２５０〜１５００℃で加熱して炭化するとともに、９００〜１３５０ｍｇ／ｄｔｅｘの張力下で炭化し、その後、撚りを解舒する炭素繊維の製造方法。 A precursor having a surface arithmetic average roughness Ra of 4.0 nm or less and a single yarn number of 1000 or more as measured by an atomic force microscope is added with a twist of 10 to 30 turns / m, and a tension of 70 to 130 mg / dtex. A method for producing carbon fiber, which is flame-resistant under heat, carbonized by heating at a maximum firing temperature of 1250 to 1500 ° C. in an inert atmosphere, carbonized under a tension of 900 to 1350 mg / dtex, and then untwisted .
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