JP7286987B2 - Carbon fiber bundle and its manufacturing method - Google Patents
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本発明は、単繊維あたりの耐荷重が高く耐擦過性および工程通過性に優れ、生産性の高い炭素繊維束とその製造方法に関する。 TECHNICAL FIELD The present invention relates to a carbon fiber bundle having high load resistance per single fiber, excellent scratch resistance and process passability, and high productivity, and a method for producing the same.
炭素繊維を用いた複合材料は航空・宇宙用途をはじめとし、自転車やゴルフクラブなどのスポーツ用途などに利用されており、最近では自動車用部材や圧力容器などの産業用途にも展開が進んでいる。このように炭素繊維を用いた複合材料の需要は高まってきており、炭素繊維の生産性を向上することが求められている。 Composite materials using carbon fiber are used not only for aerospace applications, but also for sports applications such as bicycles and golf clubs.Recently, they are also being used in industrial applications such as automotive parts and pressure vessels. . Demand for composite materials using carbon fibers is increasing in this way, and it is required to improve the productivity of carbon fibers.
炭素繊維は、共重合成分を含むポリアクリロニトリルなどの前駆体繊維を２００－３００℃の空気中で酸化する耐炎化工程、５００－１２００℃の不活性雰囲気中で加熱する予備炭素化工程、１２００－３０００℃の不活性雰囲気中で加熱する炭素化工程を経ることで製造される。炭素繊維の生産性を高めるためには、単繊維あたりの質量、すなわち単繊維繊度を大きくすることで生産性の向上が可能であるが、そのためには炭素繊維前駆体繊維の単繊維繊度を大きくすることが最も有効である。しかし、単繊維繊度の大きい繊維束を得る上で、耐炎化工程における構造斑（焼け斑) が生じることが障害となっている。 For carbon fibers, a flameproofing step of oxidizing precursor fibers such as polyacrylonitrile containing copolymer components in air at 200-300 ° C., a preliminary carbonization step of heating in an inert atmosphere at 500-1200 ° C., 1200- It is produced through a carbonization process of heating in an inert atmosphere at 3000°C. In order to increase the productivity of carbon fibers, it is possible to increase the mass per single fiber, that is, the single fiber fineness. It is most effective to However, in obtaining a fiber bundle having a large single fiber fineness, the occurrence of structural unevenness (burning unevenness) in the flameproofing process is an obstacle.
特許文献１では、かさ高く、酸素透過性のある不飽和カルボン酸アルキルエステルをポリアクリロニトリルに共重合したポリマーを炭素繊維前駆体繊維束に適用することで、耐炎化工程で繊維内部の酸素濃度分布が均一になり、耐炎化時間の短縮および炭素繊維の高物性化が可能になる技術を提案している。特許文献２では、酸素透過性のあるビニル系モノマーと耐炎化遅延効果のあるホウ素化合物を用いることで耐炎化時に生成する繊維断面の断面二重構造を抑制し、引張特性に優れた炭素繊維とその製法を示している。特許文献３では、ビニル系のモノマーを共重合したポリアクリロニトリルを用いることで前駆体繊維束の酸素透過性と延伸性を高め、炭素繊維の生産性と強度を改善する技術が提案されている。特許文献４および５は、かさ高く、酸素透過性があり、さらに耐炎化促進効果をもつヒドロキシアルキル基をもつビニル化合物をポリアクリロニトリルに共重合したポリマーを炭素繊維前駆体繊維束に適用することで、単繊維繊度の大きい炭素繊維を効率よく製造する方法を提案している。特許文献６では、さらに単繊維繊度が大きくても耐炎化できる技術と、樹脂含浸性に優れる炭素繊維の製法を示している。 In Patent Document 1, by applying a polymer obtained by copolymerizing a bulky and oxygen-permeable unsaturated carboxylic acid alkyl ester with polyacrylonitrile to a carbon fiber precursor fiber bundle, the oxygen concentration distribution inside the fiber is improved in the flameproofing process. We are proposing a technology that makes it possible to reduce the flame resistance time and improve the physical properties of the carbon fiber. In Patent Document 2, by using a vinyl-based monomer with oxygen permeability and a boron compound with an effect of retarding flame resistance, the cross-sectional double structure of the fiber cross section generated during flame resistance is suppressed, resulting in a carbon fiber with excellent tensile properties. It shows the manufacturing method. Patent Document 3 proposes a technique for improving the productivity and strength of carbon fibers by using polyacrylonitrile obtained by copolymerizing a vinyl-based monomer to increase the oxygen permeability and drawability of precursor fiber bundles. Patent Documents 4 and 5 disclose that a polymer obtained by copolymerizing polyacrylonitrile with a vinyl compound having a hydroxyalkyl group, which is bulky, oxygen-permeable, and has an effect of promoting flame resistance, is applied to a carbon fiber precursor fiber bundle. proposed a method for efficiently producing carbon fibers having a large single fiber fineness. Patent Literature 6 discloses a technique for making flame resistant even with a large single fiber fineness and a method for producing carbon fibers with excellent resin impregnability.
特許文献１では、炭素繊維前駆体繊維の共重合成分として酸素透過性に優れる成分を用いているが、炭素繊維の単繊維繊度が十分に大きくはなく、単繊維の耐荷重が不十分であり、操業性の悪化が懸念される問題があった。特許文献２では、また、ホウ素により表面の耐炎化進行を抑制する手法であるため、繊維径が大きくなると繊維断面方向の耐炎化ムラが悪化する懸念から単繊維繊度を大きくできない問題があった。特許文献３では、炭素繊維前駆体繊維束に酸素透過性に優れる共重合成分が少なく、さらに単繊維繊度も小さいため、生産量の低下と操業性の悪化により炭素繊維束の生産効率を向上できない問題があった。特許文献４では、外層比率が低く、さらに繊維表面が粗いため、耐擦過性の低下と単繊維耐荷重の低下による毛羽発生による品位の低下が懸念される。特許文献５では、酸素透過性にやや劣る（メタ）アクリル酸ヒドロキシアルキルを含むポリアクリロニトリル系共重合体を用いており、外層比率が低いために品位が劣り、得られる炭素繊維の表面が平滑でないために繊維束の耐擦過性が悪く、操業性の悪化が懸念される。特許文献６では、炭素繊維前駆体繊維束の単繊維繊度は大きいものの、共重合成分の酸素透過性が劣る上、共重合量も不十分であるため、外層比率が低くなっており、操業性向上に十分な単繊維耐荷重が得られない問題があった。 In Patent Document 1, a component having excellent oxygen permeability is used as a copolymer component of the carbon fiber precursor fiber, but the single fiber fineness of the carbon fiber is not sufficiently large and the load resistance of the single fiber is insufficient. , there was a problem of concern about deterioration of operability. In Patent Document 2, since boron is used to suppress the progress of surface flame resistance, there is a problem that the single fiber fineness cannot be increased due to the concern that the flame resistance unevenness in the cross-sectional direction of the fiber will worsen as the fiber diameter increases. In Patent Document 3, since the carbon fiber precursor fiber bundle has a small amount of a copolymer component that has excellent oxygen permeability and the single fiber fineness is also small, the production efficiency of the carbon fiber bundle cannot be improved due to a decrease in production volume and deterioration of workability. I had a problem. In Patent Document 4, since the ratio of the outer layer is low and the fiber surface is rough, there is concern about deterioration in quality due to fluff generation due to deterioration in abrasion resistance and reduction in load resistance of single fibers. In Patent Document 5, a polyacrylonitrile-based copolymer containing hydroxyalkyl (meth)acrylate, which is slightly inferior in oxygen permeability, is used, and the quality is inferior due to the low outer layer ratio, and the surface of the resulting carbon fiber is not smooth. Therefore, the abrasion resistance of the fiber bundle is poor, and there is concern about deterioration of workability. In Patent Document 6, although the single fiber fineness of the carbon fiber precursor fiber bundle is large, the oxygen permeability of the copolymerization component is poor and the amount of copolymerization is insufficient, so the outer layer ratio is low, resulting in poor operability. There was a problem that a single fiber withstand load sufficient for improvement could not be obtained.
本発明では、単繊維あたりの耐荷重が必要とされる炭素繊維強化複合材料に適しており、耐擦過性および工程通過性に優れ、生産性の良い炭素繊維束とその製造方法を提供することを目的とする。 An object of the present invention is to provide a carbon fiber bundle that is suitable for carbon fiber reinforced composite materials that require a load bearing capacity per single fiber, is excellent in abrasion resistance and process passability, and has good productivity, and a method for producing the same. With the goal.
かかる目的を達成するために、本発明は次の構成を有する。 In order to achieve this object, the present invention has the following configurations.
すなわち、本発明の炭素繊維束は、単繊維繊度Ｆｃが１．５～４．０ｄｔｅｘであり、単繊維の繊維軸に垂直な方向の断面の形状が真円度０．９１～１．００であり、単繊維断面の中心側と円周側に観察される断面二重構造のうち、円周側の面積の単繊維断面積に占める割合である外層比率Ａｃ（％）と単繊維繊度Ｆｃ（ｄｔｅｘ）が次の条件（Ａ）と条件（Ｂ）を満たす炭素繊維束である。
（Ａ） Ａｃ≧１２１－１７Ｆｃ／ｄｔｅｘ
（Ｂ） Ａｃ≧９０。
That is, the carbon fiber bundle of the present invention has a single fiber fineness Fc of 1.5 to 4.0 dtex and a circularity of 0.91 to 1.00 in the cross-sectional shape of the single fiber in the direction perpendicular to the fiber axis. Outer layer ratio Ac (%) and single fiber fineness Fc ( dtex) is a carbon fiber bundle that satisfies the following conditions (A) and (B).
(A) Ac≧121-17Fc/dtex
(B) Ac≧90.
また、本発明の炭素繊維束の製造方法は、アクリロニトリル単位９０．０～９７．０質量％と構造式ＣＨ２＝ＣＨＣＯＯＣｎＨ２ｎ＋１（構造式中、ｎ＝２～４であり、アルキル鎖は直鎖である。）で表されるアクリレート系モノマー（Ｘ）単位３．０～１０．０質量％を含むポリアクリロニトリル系重合体を用いて、単繊維繊度が２．３～６．０ｄｔｅｘであり、単繊維の繊維軸に垂直な方向の断面の形状が真円度０．９１～１．００である炭素繊維前駆体繊維束を得た後に、該炭素繊維前駆体繊維束を次の条件（ａ）から条件（ｃ）を満たしながら酸化性雰囲気中で処理する耐炎化工程と、該耐炎化工程で得られた耐炎化繊維束を最高温度５００～１２００℃の不活性雰囲気中において予備炭素化する予備炭素化工程と、該予備炭素化工程で得られた予備炭素化繊維束を１２００～３０００℃の不活性雰囲気中において炭素化する炭素化工程を含む炭素繊維束の製造方法である。
（ａ） 耐炎化繊維束の単繊維断面の中心側と円周側に観察される断面二重構造のうち、円周側の面積の単繊維断面積に占める割合である外層比率Ａｓ（％）がＡｓ≧９０を満たす。
（ｂ）耐炎化初期温度Ｔｉ（℃）とアクリレート系モノマー（Ｘ）単位の質量組成比Ｚａ（％）が、Ｔｉ×Ｚａ≧１０００の関係を満たす。
（ｃ）耐炎化温度が２００～３００℃の範囲内である。
In addition, the method for producing a carbon fiber bundle of the present invention includes 90.0 to 97.0% by mass of acrylonitrile units and a structural formula CH 2 ═CHCOOC n H 2n+1 (where n is 2 to 4, and the alkyl chain is A polyacrylonitrile-based polymer containing 3.0 to 10.0% by mass of acrylate-based monomer (X) units represented by ) is used, and the single fiber fineness is 2.3 to 6.0 dtex. , After obtaining a carbon fiber precursor fiber bundle having a circularity of 0.91 to 1.00 in the shape of the cross section in the direction perpendicular to the fiber axis of the single fiber, the carbon fiber precursor fiber bundle is subjected to the following conditions ( A flameproofing step of treating in an oxidizing atmosphere while satisfying conditions a) to (c), and pre-carbonizing the flameproofed fiber bundle obtained in the flameproofing step in an inert atmosphere at a maximum temperature of 500 to 1200 ° C. and a carbonization step of carbonizing the pre-carbonized fiber bundle obtained in the preliminary carbonization step in an inert atmosphere at 1200 to 3000°C.
(a) Outer layer ratio As (%), which is the ratio of the area of the circumference side to the cross-sectional area of the single fiber in the cross-sectional double structure observed on the center side and the circumference side of the single fiber cross section of the flameproof fiber bundle satisfies As≧90.
(b) The initial flame-proofing temperature Ti (° C.) and the mass composition ratio Za (%) of the acrylate-based monomer (X) unit satisfy the relationship of Ti×Za≧1000.
(c) The flameproofing temperature is in the range of 200-300°C.
本発明によれば、単繊維あたりの耐荷重が高く、耐擦過性および工程通過性に優れた生産性のよい炭素繊維束が得られる。 EFFECTS OF THE INVENTION According to the present invention, a carbon fiber bundle having high load resistance per single fiber, excellent abrasion resistance and process passability, and good productivity can be obtained.
単繊維あたりの耐荷重を増やすためには炭素繊維束の単繊維断面の外層比率と単繊維繊度のバランスが重要であり、耐擦過性および工程通過性を高めるためには断面形状が円形であることを明確にして発明に到達した。 In order to increase the load resistance per single fiber, it is important to balance the outer layer ratio of the single fiber cross section of the carbon fiber bundle and the single fiber fineness. The inventor arrived at the invention by clarifying the above.
本発明の炭素繊維束は、単繊維繊度が１．５～４．０ｄｔｅｘであり、好ましくは１．８～３．８ｄｔｅｘであり、より好ましくは２．２～３．６ｄｔｅｘである。単繊維繊度とは、単繊維の単位長さあたりの質量であり、１ｄｔｅｘは単繊維１０，０００ｍあたりの質量が１ｇとなるような繊維であることから、単繊維直径に関連する。単繊維繊度が大きいと単繊維あたりでは耐荷重が大きくなるために擦過などの炭素繊維束のハンドリング中に荷重の大きくなる外力に対して単繊維破断（毛羽生成）しにくくなる。炭素繊維束の単繊維繊度が１．５ ｄｔｅｘ以上あれば単繊維断面積が大きく、想定されるハンドリング中の荷重に十分な単繊維が得られ、工程中で毛羽が発生しにくく耐炎化工程・予備炭素化工程・炭素化工程の工程通過性が良くなる。単繊維繊度が４．０ｄｔｅｘ以下であると断面二重構造の外層比率が小さく抑えることができ、毛羽が発生しにくくなる。単繊維繊度は炭素繊維束の目付とフィラメント数から算出することができる。かかる単繊維繊度を制御するためには、炭素繊維前駆体繊維束の製糸工程における紡糸溶液の吐出量・延伸倍率および耐炎化から炭素化工程での炭素化収率を制御することが重要であり、主には紡糸溶液の吐出量を制御することで達成される。 The carbon fiber bundle of the present invention has a single fiber fineness of 1.5 to 4.0 dtex, preferably 1.8 to 3.8 dtex, more preferably 2.2 to 3.6 dtex. The single fiber fineness is the mass per unit length of a single fiber, and since 1 dtex is a fiber having a mass of 1 g per 10,000 m of single fiber, it is related to the single fiber diameter. When the single fiber fineness is high, the load resistance per single fiber increases, so that single fiber breakage (fluffing) is less likely to occur due to an external force that increases the load during handling of the carbon fiber bundle, such as rubbing. If the single fiber fineness of the carbon fiber bundle is 1.5 dtex or more, the cross-sectional area of the single fiber is large, and the single fiber sufficient for the load during handling can be obtained. The process passability of the preliminary carbonization step and the carbonization step is improved. When the single fiber fineness is 4.0 dtex or less, the outer layer ratio of the cross-sectional double structure can be kept small, and fluff is less likely to occur. The single fiber fineness can be calculated from the basis weight of the carbon fiber bundle and the number of filaments. In order to control the single fiber fineness, it is important to control the carbonization yield in the carbonization step from the discharge amount and draw ratio of the spinning solution in the spinning step of the carbon fiber precursor fiber bundle and flame resistance. , is achieved mainly by controlling the ejection rate of the spinning solution.
本発明の炭素繊維束は、単繊維の繊維軸に垂直な断面の形状が真円度０．９１～１．００であり、好ましくは０．９３～１．００であり、より好ましくは０．９５～１．００である。真円度は下記式（１）によって求められる値であり、Ｓ、Ｌはそれぞれ単繊維の繊維軸に垂直な断面の断面積と周長である。真円度は真円では１．００であり、楕円やその他の形状では１．００よりも小さくなる。 The carbon fiber bundle of the present invention has a circularity of 0.91 to 1.00, preferably 0.93 to 1.00, more preferably 0.93 to 1.00, more preferably 0.91 to 1.00, more preferably 0.93 to 1.00. 95 to 1.00. The roundness is a value obtained by the following formula (1), and S and L are the cross-sectional area and the perimeter of the cross section perpendicular to the fiber axis of the single fiber, respectively. The circularity is 1.00 for a perfect circle and less than 1.00 for ellipses and other shapes.
（真円度）＝ ４πＳ／Ｌ２ （１）
真円度が０．９１以上であれば耐擦過性が良くなるため、単繊維破断が起きにくく毛羽が発生しにくくなり、結果的に炭素化工程の工程通過性に優れる。真円度は高いほど好ましい。真円度は、繊維束を樹脂包埋し、繊維軸に垂直な面を湿式研磨することで露出した断面を光学顕微鏡で観察し、画像解析から繊維断面積および周長を算出することで求められる。かかる繊維の真円度を制御するためには、炭素繊維束の形状は炭素繊維前駆体繊維束の凝固条件と延伸条件によって決定されるため、凝固浴の組成および温度、さらに延伸浴の温度と延伸倍率を制御することで達成できる。
(Roundness) = 4πS/L 2 (1)
If the roundness is 0.91 or more, the abrasion resistance is improved, so that single fiber breakage is less likely to occur and fluff is less likely to occur, resulting in excellent process passability in the carbonization step. The higher the circularity, the better. The roundness is obtained by embedding the fiber bundle in resin, observing the cross section exposed by wet polishing the surface perpendicular to the fiber axis with an optical microscope, and calculating the fiber cross-sectional area and circumference from image analysis. be done. In order to control the roundness of such fibers, since the shape of the carbon fiber bundle is determined by the coagulation and drawing conditions of the carbon fiber precursor fiber bundle, the composition and temperature of the coagulation bath, and also the temperature and temperature of the drawing bath. It can be achieved by controlling the draw ratio.
本発明の炭素繊維束は、単繊維断面の円周側と中心側に生じる構造差（断面二重構造と呼ぶ）のうち、円周側の面積の単繊維の断面積に対して占める割合として定義する炭素繊維の外層比率Ａｃ（％）（以下単に外層比率とする）が炭素繊維の単繊維繊度Ｆｃ（ｄｔｅｘ）に対して、
（Ａ） Ａｃ≧１２１－１７Ｆｃ／ｄｔｅｘ
を満たし、好ましくは上式における切片が１２３、さらに好ましくは切片が１２５である。上式を満たしていれば、太繊度かつ断面二重構造が抑制されており、単繊維の耐荷重およびプロセス性に優れる。上式は耐炎化工程における断面二重構造を抑制することで制御され、主に耐炎化温度やポリアクリロニトリル系共重合体の酸素透過成分の共重合量などにより制御される。
In the carbon fiber bundle of the present invention, the ratio of the area on the circumference side to the cross-sectional area of the single fiber is The outer layer ratio Ac (%) of the defined carbon fiber (hereinafter simply referred to as the outer layer ratio) is the single fiber fineness Fc (dtex) of the carbon fiber,
(A) Ac≧121-17Fc/dtex
and preferably the intercept is 123, more preferably 125 in the above equation. If the above formula is satisfied, the large fineness and cross-sectional double structure are suppressed, and the load capacity and processability of the single fiber are excellent. The above formula is controlled by suppressing the cross-sectional double structure in the flameproofing process, and is mainly controlled by the flameproofing temperature and the copolymerization amount of the oxygen-permeable component of the polyacrylonitrile-based copolymer.
本発明の炭素繊維束は、断面二重構造の外層比率が、
（Ｂ） Ａｃ≧９０％
を満たし、好ましくは９３％以上であり、より好ましくは９５～９８％である。断面二重構造の外層比率が９０％以上であれば、単繊維の耐荷重が増すことで破断しにくくなり工程通過性に優れ、外層比率が高いほど望ましい。ただし、外層比率が９８％以下の場合は単繊維強度の低下が起こらず、耐荷重を高くすることができる。断面二重構造の外層比率は炭素繊維束を樹脂包埋し、繊維軸に垂直な面を湿式研磨することで露出した断面を光学顕微鏡で観察し、画像解析から繊維断面積および断面二重構造のうち円周側の構造の面積を算出することで求められる。かかる断面二重構造の外層比率を制御するためには、耐炎化工程の処理時間と処理温度、もしくはポリアクリロニトリル系重合体の共重合成分を変更することで制御できる。
In the carbon fiber bundle of the present invention, the outer layer ratio of the cross-sectional double structure is
(B) Ac≧90%
, preferably 93% or more, more preferably 95 to 98%. If the outer layer ratio of the cross-sectional double structure is 90% or more, the load resistance of the single fiber is increased, making it difficult to break and excellent in process passability. However, when the outer layer ratio is 98% or less, the single fiber strength does not decrease and the load resistance can be increased. The outer layer ratio of the cross-sectional double structure is obtained by embedding the carbon fiber bundle in resin and wet-polishing the surface perpendicular to the fiber axis. It is obtained by calculating the area of the structure on the circumference side. In order to control the outer layer ratio of such a cross-sectional double structure, it can be controlled by changing the processing time and processing temperature of the flameproofing step or the copolymerization component of the polyacrylonitrile-based polymer.
本発明の炭素繊維束は、断面二重構造の円周側の構造の厚み（以下外層厚みとする）が４．０～６．７μｍであることが好ましく、より好ましくは４．２～６．５μｍであり、さらに好ましくは４．５～６．３μｍ以上である。外層厚みが４．０μｍ以上であれば、断面二重構造が十分小さく、単繊維の耐荷重が高くなるため、品位が向上する。外層厚みが６．７μｍ以下であれば、断面二重構造の抑制に対して十分な効果が得られる。断面二重構造の外層厚みは炭素繊維束を樹脂包埋し、繊維軸に垂直な面を湿式研磨することで露出した断面を光学顕微鏡で観察し、画像解析から断面二重構造のうち円周側の構造の厚みを算出することで求められる。かかる断面二重構造の外層厚みを制御するためには、耐炎化工程の処理時間と処理温度、もしくはポリアクリロニトリル系重合体の共重合成分を変更することで制御できる。 In the carbon fiber bundle of the present invention, the thickness of the structure on the circumferential side of the cross-sectional double structure (hereinafter referred to as the outer layer thickness) is preferably 4.0 to 6.7 μm, more preferably 4.2 to 6.0 μm. It is 5 μm, more preferably 4.5 to 6.3 μm or more. When the thickness of the outer layer is 4.0 μm or more, the cross-sectional double structure is sufficiently small, and the load resistance of the single fiber is increased, so that the quality is improved. If the thickness of the outer layer is 6.7 μm or less, a sufficient effect can be obtained for suppressing the cross-sectional double structure. The thickness of the outer layer of the cross-sectional double structure is determined by embedding the carbon fiber bundle in resin and wet-polishing the surface perpendicular to the fiber axis. It is obtained by calculating the thickness of the structure on the side. In order to control the outer layer thickness of such a cross-sectional double structure, it can be controlled by changing the treatment time and treatment temperature in the flameproofing step or the copolymerization component of the polyacrylonitrile-based polymer.
次に、本発明の炭素繊維束を得ることに好ましい炭素繊維束の製造方法について述べる。 Next, a preferred method for producing a carbon fiber bundle for obtaining the carbon fiber bundle of the present invention will be described.
本発明の炭素繊維の製造方法によると、炭素繊維前駆体繊維束の製造に供する原料の組成について、アクリロニトリル単位が９０．０～９７．０質量％とアクリレート系モノマー（Ｘ）単位が３．０～１０．０質量％であり、好ましくはアクリロニトリル単位が９０．０～９６．０質量％とアクリレート系モノマー（Ｘ）単位が４．０～１０．０質量％、より好ましくはアクリロニトリル単位が９０．０～９５．０質量％とアクリレート系モノマー（Ｘ）単位が５．０～１０．０質量％であるポリアクリロニトリル系重合体を用いる。アクリレート系モノマー（Ｘ）とは、構造式ＣＨ２＝ＣＨＣＯＯＣｎＨ２ｎ＋１で表され、ｎ＝２～４であり、アルキル基が直鎖であるアクリル酸エステル系モノマーである。アクリレート系モノマー単位が３．０質量％以上であれば、炭素繊維前駆体繊維束の耐炎化工程における外層比率が高くなり、１０．０質量％以下であれば得られる炭素繊維単繊維の強度および耐荷重が増加することにより、工程通過性に優れる。ポリアクリロニトリル系共重合体のアクリロニトリル単位とアクリレート系モノマー（Ｘ）単位の比率は、重合時のそれぞれの単量体の組成比を調整することで制御できる。アクリレート系モノマー（Ｘ）としては、アクリル酸エチル、アクリル酸プロピル、アクリル酸ノルマルブチルが例示され、延伸性向上による品位向上と酸素透過性の両立の観点から、アクリル酸エチルが特に好ましい。その他の共重合成分としては、耐炎化反応の促進を目的としてメタクリル酸、アクリル酸、イタコン酸、アクリルアミドなどを用いることができる。 According to the carbon fiber production method of the present invention, the composition of the raw material used for the production of the carbon fiber precursor fiber bundle contains 90.0 to 97.0% by mass of acrylonitrile units and 3.0% of acrylate monomer (X) units. to 10.0% by mass, preferably 90.0 to 96.0% by mass of acrylonitrile units and 4.0 to 10.0% by mass of acrylate monomer (X) units, more preferably 90.0% by mass of acrylonitrile units. A polyacrylonitrile polymer containing 0 to 95.0% by mass and 5.0 to 10.0% by mass of acrylate monomer (X) units is used. The acrylate-based monomer (X) is an acrylic acid ester-based monomer represented by the structural formula CH 2 ═CHCOOC n H 2n+1 , n=2 to 4, and a linear alkyl group. When the acrylate-based monomer unit is 3.0% by mass or more, the outer layer ratio in the flameproofing step of the carbon fiber precursor fiber bundle is high, and when it is 10.0% by mass or less, the strength and strength of the carbon fiber single fiber obtained is increased. By increasing the withstand load, it is excellent in process passability. The ratio of acrylonitrile units and acrylate monomer (X) units in the polyacrylonitrile copolymer can be controlled by adjusting the composition ratio of each monomer during polymerization. Examples of the acrylate-based monomer (X) include ethyl acrylate, propyl acrylate, and normal-butyl acrylate. Ethyl acrylate is particularly preferred from the viewpoint of achieving both improved stretchability and oxygen permeability. As other copolymerization components, methacrylic acid, acrylic acid, itaconic acid, acrylamide, etc. can be used for the purpose of promoting the flame-resistant reaction.
炭素繊維前駆体繊維束を製造するにあたり、乾湿式紡糸法および湿式紡糸法のいずれかを用いて製糸する。製糸工程は一般に、紡糸口金から凝固浴に紡糸溶液を吐出させて紡糸する凝固工程と、該凝固工程で得られた繊維を水浴中で洗浄する水洗工程と、該水洗工程で得られた繊維を水浴中で延伸する水浴延伸工程と、該水浴延伸工程で得られた繊維に工程油剤を塗布する油剤工程と、該油剤工程で得られた繊維を乾燥熱処理する乾燥熱処理工程からなり、必要に応じて、該乾燥熱処理工程で得られた繊維をスチーム延伸するスチーム延伸工程を含む。なお、各工程の順序を適宜入れ替えることも可能である。紡糸溶液とは、前記したポリアクリロニトリル共重合体を、ジメチルスルホキシド・ジメチルホルムアミド・ジメチルアセトアミドなどの有機溶媒や、硝酸・塩化亜鉛・ロダンソーダなどの水溶液といったポリアクリロニトリル共重合体が可溶な溶媒に溶解したものである。 In producing the carbon fiber precursor fiber bundle, either a dry-wet spinning method or a wet spinning method is used. The spinning process generally includes a coagulation process in which a spinning solution is discharged from a spinneret into a coagulation bath for spinning, a water washing process in which the fibers obtained in the coagulation process are washed in a water bath, and the fibers obtained in the water washing process are washed. It consists of a water bath drawing step of drawing in a water bath, an oil step of applying a processing oil to the fibers obtained in the water bath drawing step, and a dry heat treatment step of drying and heat treating the fibers obtained in the oil step. and a steam drawing step of steam drawing the fibers obtained in the dry heat treatment step. In addition, it is also possible to change the order of each step as appropriate. The spinning solution is a solution in which the polyacrylonitrile copolymer is dissolved in a solvent in which the polyacrylonitrile copolymer is soluble, such as an organic solvent such as dimethylsulfoxide, dimethylformamide, or dimethylacetamide, or an aqueous solution such as nitric acid, zinc chloride, or rhodan soda. It is what I did.
前記凝固浴には、紡糸溶液の溶媒として用いたジメチルスルホキシド、ジメチルホルムアミドおよびジメチルアセトアミドなどの溶媒と、凝固促進成分を含ませることが好ましい。凝固促進成分としては、前記ポリアクリロニトリル共重合体を溶解せず、かつ紡糸溶液に用いる溶媒と相溶性があるものを使用することができる。具体的には、凝固促進成分として水を使用することが好ましい。単繊維の横断面が真円状で、かつ繊維側面が平滑となる範囲で有機溶剤の濃度を高くし、凝固浴の温度を低く設定することが好ましい。例えば、溶剤にジメチルスルホキシドを用いた場合には、ジメチルスルホキシド水溶液の濃度を５～３０質量％、あるいは７０～８０質量％とし、凝固浴温度を－１０～３０℃とすることが望ましい。 The coagulation bath preferably contains a solvent such as dimethylsulfoxide, dimethylformamide and dimethylacetamide used as the solvent for the spinning solution, and a coagulation accelerating component. As the coagulation promoting component, a component that does not dissolve the polyacrylonitrile copolymer and is compatible with the solvent used for the spinning solution can be used. Specifically, it is preferable to use water as the coagulation promoting component. It is preferable to increase the concentration of the organic solvent and set the temperature of the coagulation bath low within the range in which the cross section of the single fiber is perfectly circular and the side surface of the fiber is smooth. For example, when dimethyl sulfoxide is used as the solvent, it is desirable to set the concentration of the dimethyl sulfoxide aqueous solution to 5 to 30% by mass, or 70 to 80% by mass, and the coagulation bath temperature to -10 to 30°C.
前記水洗工程における水洗浴としては、温度が３０～９８℃の複数段からなる水洗浴を用いることが好ましい。また、水浴延伸工程における延伸倍率は、高い真円度の断面形状を維持する観点から、１～６倍であることが好ましい。 As the water washing bath in the water washing step, it is preferable to use a water washing bath having a temperature of 30 to 98° C. and comprising a plurality of stages. Further, the draw ratio in the water bath drawing step is preferably 1 to 6 times from the viewpoint of maintaining a cross-sectional shape with high roundness.
水浴延伸工程の後、単繊維同士の融着を防止する目的から、繊維束にシリコーン等からなる油剤を付与することが好ましい。かかるシリコーン油剤は、変性されたシリコーンを用いることが好ましく、耐熱性の高いアミノ変性シリコーンを含有するものを用いることが好ましい。 After the water-bath stretching step, it is preferable to apply an oil such as silicone to the fiber bundle for the purpose of preventing fusion between single fibers. It is preferable to use a modified silicone as such a silicone fluid, and it is preferable to use one containing an amino-modified silicone having high heat resistance.
乾燥熱処理工程は、公知の方法を利用することができる。例えば、乾燥温度は１００～２００℃が例示される。 A known method can be used for the dry heat treatment step. For example, the drying temperature is 100-200°C.
前記した水洗工程、水浴延伸工程、油剤付与工程、乾燥熱処理工程の後、必要に応じ、スチーム延伸を行うことにより、本発明の炭素繊維束を得るのに好適な炭素繊維前駆体繊維束が得られる。スチーム延伸は、加圧スチーム中において、延伸倍率は２～６倍であることが好ましい。 After the water washing step, the water bath drawing step, the oil application step, and the drying heat treatment step, if necessary, steam drawing is performed to obtain a carbon fiber precursor fiber bundle suitable for obtaining the carbon fiber bundle of the present invention. be done. Steam drawing is preferably performed at a draw ratio of 2 to 6 times in pressurized steam.
本発明の炭素繊維の製造方法によると、炭素繊維前駆体繊維束の単繊維繊度は２．３～６．０ｄｔｅｘであり、好ましくは２．５～５．５ｄｔｅｘ、より好ましくは２．８～４．４ｄｔｅｘである。単繊維繊度が２．３ｄｔｅｘ以上あれば耐荷重の高い単繊維が得られ、毛羽が発生しにくく工程通過性が良くなる。単繊維繊度が６．０ｄｔｅｘを超えると、耐炎化および予備炭素化、炭素化における耐擦過性が低下し、工程通過性が悪化する。単繊維繊度は炭素繊維前駆体繊維束の単位長さあたりの質量とフィラメント数から算出する。かかる単繊維繊度を制御するためには、炭素繊維前駆体繊維束の紡糸工程における紡糸溶液の吐出量・延伸倍率および焼成工程での炭素化収率を制御することが重要であり、主には紡糸溶液の吐出量を制御することで達成される。 According to the carbon fiber manufacturing method of the present invention, the single fiber fineness of the carbon fiber precursor fiber bundle is 2.3 to 6.0 dtex, preferably 2.5 to 5.5 dtex, more preferably 2.8 to 4. .4 dtex. If the single fiber fineness is 2.3 dtex or more, a single fiber having a high load resistance can be obtained, fluff is less likely to occur, and processability is improved. If the single fiber fineness exceeds 6.0 dtex, the flame resistance, pre-carbonization, and abrasion resistance in carbonization are lowered, and the processability is deteriorated. The single fiber fineness is calculated from the mass per unit length of the carbon fiber precursor fiber bundle and the number of filaments. In order to control the single fiber fineness, it is important to control the discharge amount and draw ratio of the spinning solution in the carbon fiber precursor fiber bundle spinning process and the carbonization yield in the baking process. This is achieved by controlling the amount of spinning solution discharged.
本発明の炭素繊維束の製造方法によると、炭素繊維前駆体繊維束の単繊維の繊維軸に垂直な断面の形状が真円度０．９１～１．００であり、好ましくは０．９３～１．００であり、より好ましくは０．９５～１．００である。真円度は上述の式（１）によって求められる値である。真円度は真円では１．００であり、楕円やその他の形状では１．００よりも小さくなる。真円度が０．９１以上であれば耐擦過性が良くなるため、単繊維破断が起きにくく毛羽が発生しにくくなり、結果的に耐炎化工程・予備炭素化工程・炭素化工程の工程通過性に優れる。真円度は高いほど好ましい。真円度は、繊維束を樹脂包埋し、繊維軸に垂直な面を湿式研磨することで露出した断面を光学顕微鏡で観察し、画像解析から繊維断面積および周長を算出することで求められる。かかる繊維の真円度を制御するためには、炭素繊維前駆体繊維束の凝固条件と延伸条件によって決定されるため、凝固浴の組成および温度、さらに延伸浴の温度と延伸倍率を制御することで達成できる。 According to the method for producing a carbon fiber bundle of the present invention, the circularity of the shape of the cross section perpendicular to the fiber axis of the single fiber of the carbon fiber precursor fiber bundle is 0.91 to 1.00, preferably 0.93 to 0.93. 1.00, more preferably 0.95 to 1.00. The circularity is a value determined by the above formula (1). The circularity is 1.00 for a perfect circle and less than 1.00 for ellipses and other shapes. If the roundness is 0.91 or more, the abrasion resistance is improved, so that single fiber breakage is less likely to occur and fluff is less likely to occur, and as a result, the process passes through the flameproofing process, preliminary carbonization process, and carbonization process. Excellent in nature. The higher the circularity, the better. The roundness is obtained by embedding the fiber bundle in resin, observing the cross section exposed by wet polishing the surface perpendicular to the fiber axis with an optical microscope, and calculating the fiber cross-sectional area and circumference from image analysis. be done. In order to control the roundness of such fibers, since it is determined by the coagulation conditions and drawing conditions of the carbon fiber precursor fiber bundle, it is necessary to control the composition and temperature of the coagulation bath, as well as the temperature and drawing ratio of the drawing bath. can be achieved with
本発明の炭素繊維束の製造方法によると、耐炎化繊維束の外層比率Ａｓ（％）はＡｓ≧９０％であり、好ましくは９３％以上、さらに好ましくは９５～９８％である。外層比率が大きいほど断面二重構造が小さくなるため、該耐炎化繊維束を炭素化した後の炭素繊維束の単繊維の強度が優れ、工程における毛羽の発生を抑えることができる。耐炎化繊維束の外層比率は、耐炎化繊維束を樹脂包埋したのち、表面を研磨することで現れる繊維軸に垂直な断面を光学顕微鏡により観察し、繊維断面の色調が異なる領域のうち、外側の領域の断面積全体に占める面積を算出することで得られる。外層比率を９０％以上とするためには、耐炎化工程で耐炎化繊維束をサンプリングして外層比率を確認し、耐炎化温度を調整することや、炭素繊維前駆体繊維の原料として酸素透過性に優れる共重合成分を使用することで達成できる。 According to the carbon fiber bundle manufacturing method of the present invention, the outer layer ratio As (%) of the flameproof fiber bundle is As≧90%, preferably 93% or more, more preferably 95 to 98%. Since the cross-sectional double structure becomes smaller as the outer layer ratio increases, the strength of the single fiber of the carbon fiber bundle after carbonizing the flameproof fiber bundle is excellent, and the generation of fluff in the process can be suppressed. The outer layer ratio of the flame-resistant fiber bundle was determined by embedding the flame-resistant fiber bundle in resin and then polishing the surface. It is obtained by calculating the area occupied by the entire cross-sectional area of the outer region. In order to make the outer layer ratio 90% or more, the flameproofing fiber bundle is sampled in the flameproofing process to confirm the outer layer ratio, and the flameproofing temperature is adjusted. can be achieved by using a copolymer component that is excellent in
また、本発明の炭素繊維束の製造方法によると、耐炎化処理の条件について、耐炎化初期温度Ｔｉ（℃）とポリアクリロニトリル系共重合体のアクリレート系モノマー（Ｘ）単位の質量組成比Ｚａ（％）が以下の関係を満たし、好ましくは右辺が１１００、さらに好ましくは右辺が１２００である。式を満たす場合、炭素繊維前駆体繊維束の酸素透過性に応じて高温かつ短時間で効率よく耐炎化処理できるため、生産性に優れる。酸素透過性に優れる共重合成分を炭素繊維前駆体繊維束の原料として適量使用することで達成できる。
Ｔｉ×Ｚａ≧１０００。
Further, according to the method for producing a carbon fiber bundle of the present invention, the conditions for the flameproofing treatment are the initial flameproofing temperature Ti (°C) and the mass composition ratio Za (X) of the acrylate monomer (X) unit of the polyacrylonitrile copolymer. %) satisfies the following relationship, preferably 1100 on the right side, more preferably 1200 on the right side. When the formula is satisfied, the flameproofing treatment can be efficiently performed at a high temperature in a short period of time depending on the oxygen permeability of the carbon fiber precursor fiber bundle, resulting in excellent productivity. It can be achieved by using an appropriate amount of a copolymer component having excellent oxygen permeability as a raw material for the carbon fiber precursor fiber bundle.
Ti x Za≧1000.
また、本発明の炭素繊維束の製造方法によると、耐炎化工程の熱処理温度が２００～３００℃であり、好ましくは２２０～２８０℃であり、より好ましくは２３０℃～２７０℃である。耐炎化工程の熱処理温度が２００℃以上であれば予備炭素化工程および炭素化工程の通過性が良好であり、３００℃以下であれば炭素繊維前駆体繊維束の熱暴走が抑制され、操業性に優れる。 Further, according to the carbon fiber bundle manufacturing method of the present invention, the heat treatment temperature in the flameproofing step is 200 to 300°C, preferably 220 to 280°C, more preferably 230 to 270°C. If the heat treatment temperature in the flameproofing step is 200°C or higher, the passageability of the preliminary carbonization step and the carbonization step is good. Excellent for
本発明の炭素繊維束の製造方法によると、耐炎化繊維束の断面二重構造の円周側の構造の厚み（以下外層厚みとする）が５．３～８．９μｍであることが好ましく、より好ましくは５．６～８．６μｍであり、さらに好ましくは６．１～８．３μｍである。外層厚みが５．３μｍ以上であれば、断面二重構造が十分小さく、炭素化工程での糸切れが起こりにくくなり、品位が向上する。外層厚みが８．６μｍであれば、断面二重構造の抑制に対して十分な効果が得られる。断面二重構造の外層厚みは耐炎化繊維束を樹脂包埋し、繊維軸に垂直な面を湿式研磨することで露出した断面を光学顕微鏡で観察し、画像解析から断面二重構造のうち円周側の構造の厚みを算出することで求められる。かかる断面二重構造の外層厚みを制御するためには、耐炎化工程の処理時間と処理温度、もしくはポリアクリロニトリル系重合体の共重合成分を変更することで制御できる。 According to the carbon fiber bundle manufacturing method of the present invention, the thickness of the structure on the circumferential side of the cross-sectional double structure of the flameproof fiber bundle (hereinafter referred to as the outer layer thickness) is preferably 5.3 to 8.9 μm, It is more preferably 5.6 to 8.6 μm, still more preferably 6.1 to 8.3 μm. When the thickness of the outer layer is 5.3 μm or more, the cross-sectional double structure is sufficiently small, so that thread breakage is less likely to occur in the carbonization step, and the quality is improved. If the thickness of the outer layer is 8.6 μm, a sufficient effect can be obtained for suppressing the cross-sectional double structure. The thickness of the outer layer of the cross-sectional double structure was determined by embedding the flameproof fiber bundle in resin and wet-polishing the surface perpendicular to the fiber axis, and observing the exposed cross-section with an optical microscope. It is obtained by calculating the thickness of the structure on the peripheral side. In order to control the outer layer thickness of such a cross-sectional double structure, it can be controlled by changing the treatment time and treatment temperature in the flameproofing step or the copolymerization component of the polyacrylonitrile-based polymer.
該耐炎化工程で得られた繊維束を予備炭素化する予備炭素化工程においては、得られた耐炎化繊維束を、不活性雰囲気中、最高温度５００～１２００℃において、比重が１．５～１．８になるまで熱処理する。 In the preliminary carbonization step of pre-carbonizing the fiber bundle obtained in the flameproofing step, the obtained flameproofed fiber bundle is treated in an inert atmosphere at a maximum temperature of 500 to 1200 ° C. to a specific gravity of 1.5 to 1.5. Heat to 1.8.
予備炭素化された該予備炭素化繊維束を不活性雰囲気中、最高温度１２００～３０００℃において炭素化する。 The pre-carbonized pre-carbonized fiber bundle is carbonized at a maximum temperature of 1200 to 3000° C. in an inert atmosphere.
以上のようにして得られた炭素繊維束は、酸化処理が施されることが好ましく、酸素含有官能基が導入される。本発明の電解表面処理については、気相酸化、液相酸化および液相電解酸化が用いられるが、生産性が高く、均一処理ができるという観点から、液相電解酸化が好ましく用いられる。本発明において、液相電解酸化の方法については特に制約はなく、公知の方法で行えばよい。 The carbon fiber bundle obtained as described above is preferably subjected to an oxidation treatment to introduce an oxygen-containing functional group. As for the electrolytic surface treatment of the present invention, vapor phase oxidation, liquid phase oxidation and liquid phase electrolytic oxidation are used. Liquid phase electrolytic oxidation is preferably used from the viewpoint of high productivity and uniform treatment. In the present invention, the liquid-phase electrolytic oxidation method is not particularly limited, and a known method may be used.
かかる電解処理の後、得られた炭素繊維束に集束性を付与するため、サイジング処理をすることもできる。サイジング剤には、複合材料に使用されるマトリックス樹脂の種類に応じて、マトリックス樹脂との相溶性の良いサイジング剤を適宜選択することができる。 After such an electrolytic treatment, a sizing treatment may be applied to impart bundling properties to the obtained carbon fiber bundles. As the sizing agent, a sizing agent having good compatibility with the matrix resin can be appropriately selected according to the type of the matrix resin used in the composite material.
以下、実施例により本発明をさらに具体的に説明する。ただし、本発明はこれらに限定されるものではない。本実施例における各測定方法は以下の通りである。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to these. Each measuring method in this example is as follows.
＜耐炎化繊維、炭素繊維の外層厚み、外層比率の測定＞
長さ２ｃｍに切断した耐炎化繊維もしくは炭素繊維をエポキシ樹脂（主剤：ＢＵＥＨＬＥＲ社製ＥＰＯ－ＫＷＩＣＫ ＲＥＳＩＮ、硬化剤：ＥＰＯ－ＫＷＩＣＫ ＨＡＲＤＥＮＥＲ）に包埋し、繊維軸に垂直な断面を湿式研磨処理した後、顕微鏡（ライカマイクロシステムズ社製工業用正立顕微鏡ＤＭ２７００Ｍ）を用いて観察して写真を撮影した。撮影した写真は画像処理ソフトウェア（ＩｍａｇｅＪ）を用いて解析した。条件によっては外層と内層が一定の範囲にグラデーションを形成したり、外層と内層の境界に中間的な層が形成されリング状に観察されたりする場合があるが、これらの境界部分と外層とが形成するグラデーションの外側端を二重構造の境界と定めた。単繊維３０本について画像解析を行った。外層厚みは周から断面の中心方向に計測した周から外層と内層の境界までの距離として算出した。外層比率は耐炎化繊維や炭素繊維の平均断面積ａ０と内層部分の平均面積ａ１を求めた後、下記式にしたがって算出した。
外層比率（％）＝（１－ａ１）÷ａ０×１００
＜真円度の算出方法＞
長さ２ｃｍに切断した炭素繊維前駆体繊維束をエポキシ樹脂（主剤：ＢＵＥＨＬＥＲ社製ＥＰＯ－ＫＷＩＣＫ ＲＥＳＩＮ、硬化剤：ＥＰＯ－ＫＷＩＣＫ ＨＡＲＤＥＮＥＲ）に包埋し、繊維軸に垂直な断面を湿式研磨処理した後、顕微鏡（ライカマイクロシステムズ社製工業用正立顕微鏡ＤＭ２７００Ｍ）を用いて観察して写真を撮影した。撮影した写真は画像処理ソフトウェア（ＩｍａｇｅＪ）を用いて解析した。繊維断面の面積と周長を計測し、以下の式から真円度を算出した。
<Measurement of outer layer thickness and outer layer ratio of flame-resistant fiber and carbon fiber>
A flame-resistant fiber or carbon fiber cut to a length of 2 cm was embedded in an epoxy resin (main agent: EPO-KWICK RESIN manufactured by BUEHLER, curing agent: EPO-KWICK HARDENER), and a cross section perpendicular to the fiber axis was wet-polished. After that, it was observed and photographed using a microscope (industrial upright microscope DM2700M manufactured by Leica Microsystems). Photographs taken were analyzed using image processing software (ImageJ). Depending on the conditions, the outer layer and the inner layer may form a gradation in a certain range, or an intermediate layer may be formed at the boundary between the outer layer and the inner layer and observed in a ring shape. The outer edge of the forming gradation was defined as the boundary of the double structure. Image analysis was performed on 30 single fibers. The outer layer thickness was calculated as the distance from the circumference to the boundary between the outer layer and the inner layer measured from the circumference toward the center of the cross section. The outer layer ratio was calculated according to the following formula after determining the average cross-sectional area a0 of the flame-resistant fiber and carbon fiber and the average area a1 of the inner layer portion.
Outer layer ratio (%) = (1-a 1 )/a 0 × 100
<Method for calculating roundness>
A carbon fiber precursor fiber bundle cut to a length of 2 cm was embedded in an epoxy resin (main agent: EPO-KWICK RESIN manufactured by BUEHLER, curing agent: EPO-KWICK HARDENER), and a cross section perpendicular to the fiber axis was wet-polished. After that, it was observed and photographed using a microscope (industrial upright microscope DM2700M manufactured by Leica Microsystems). Photographs taken were analyzed using image processing software (ImageJ). The area and circumference of the fiber cross section were measured, and the roundness was calculated from the following formula.
（真円度）＝（４πＳ）／Ｌ２
Ｓ：繊維断面積
Ｌ：繊維断面の周長。
(Roundness) = (4πS)/L 2
S: fiber cross-sectional area L: perimeter of the fiber cross-section.
＜品位の評価方法＞
フィラメント数３０００の炭素繊維束に、炭素繊維単繊維あたりの平均荷重が７ｇｆ（６９ｍＮ）となるように重りをとりつけ、その後、炭素繊維束の毛羽を目視で観察し、品位を評価した。品位は良好なものを○、プロセス上許容できる範囲であるものを△、劣るものを×とした。
<Method for evaluating quality>
A weight was attached to the carbon fiber bundle having filaments of 3000 so that the average load per carbon fiber single fiber was 7 gf (69 mN). The quality was evaluated as ◯ when the quality was good, Δ when the quality was within an allowable range in terms of the process, and x when the quality was poor.
（実施例１）
アクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルを９３．５：１．０：５．５の質量比で混合した単量体混合物を、ジメチルスルホキシド（ＤＭＳＯ）を溶媒とした溶液重合法により重合し、ポリアクリロニトリル系共重合体溶液を得、紡糸溶液とした。得られた紡糸溶液を孔数３０００の口金を用いて一旦空気中に吐出し、空間を通過させた後、ＤＭＳＯの水溶液からなる凝固浴に導く乾湿式紡糸法により凝固させ、凝固糸とした。得られた凝固糸を水洗した後、温水浴中で２倍に延伸し、シリコーン系油剤を付与し、表面温度が１８０℃のホットドラムで加熱処理を行った。その後、加圧水蒸気中で５倍に延伸して単繊維繊度３．３ｄｔｅｘの炭素繊維前駆体繊維束を得た。この炭素繊維前駆体繊維束を、熱風循環式オーブンを用いて２５０℃の空気中で熱処理し、耐炎化繊維束を得た。得られた耐炎化繊維束をエポキシ樹脂に樹脂包埋し、耐炎化繊維束の繊維軸方向に垂直な面を湿式研磨し、断面を光学顕微鏡で観察し、外層比率を算出した。得られた耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化することで炭素繊維束を得た。炭素繊維束の毛羽数を数え、品位を評価した。
(Example 1)
A monomer mixture of acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer in a mass ratio of 93.5:1.0:5.5 is polymerized by a solution polymerization method using dimethyl sulfoxide (DMSO) as a solvent. Then, a polyacrylonitrile-based copolymer solution was obtained and used as a spinning solution. The obtained spinning solution was once discharged into the air using a spinneret with 3000 holes, passed through a space, and then coagulated by a dry-wet spinning method leading to a coagulation bath consisting of an aqueous solution of DMSO to form a coagulated yarn. After the obtained coagulated yarn was washed with water, it was stretched twice in a hot water bath, applied with a silicone-based oil agent, and heat-treated with a hot drum having a surface temperature of 180°C. After that, it was drawn 5 times in pressurized steam to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 3.3 dtex. This carbon fiber precursor fiber bundle was heat-treated in air at 250° C. using a hot air circulating oven to obtain a flameproof fiber bundle. The resulting flame-resistant fiber bundle was embedded in an epoxy resin, the surface of the flame-resistant fiber bundle perpendicular to the fiber axis direction was wet-polished, the cross section was observed with an optical microscope, and the outer layer ratio was calculated. The obtained flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800° C., and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300° C. to obtain a carbon fiber bundle. The number of fluffs on the carbon fiber bundle was counted to evaluate the quality.
（実施例２）
実施例１で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 2)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1, except that the carbon fiber precursor fiber bundle obtained in Example 1 was heat-treated in air at 230°C.
（実施例３）
実施例１の紡糸溶液の吐出量を変更して単繊維繊度４．４ｄｔｅｘの炭素繊維前駆体繊維束を得、２３０℃の空気中で熱処理した以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 3)
A carbon fiber precursor fiber bundle having a single fiber fineness of 4.4 dtex was obtained by changing the discharge amount of the spinning solution in Example 1, and the flameproof fiber bundle was prepared in the same manner as in Example 1 except that the fiber bundle was heat-treated in the air at 230°C. and carbon fiber bundles were obtained.
（実施例４）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルの質量比が９０．０：１．０：９．０である単量体組成物とした以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 4)
Except for using a monomer composition in which the mass ratio of acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer is 90.0:1.0:9.0 as the raw material of the polyacrylonitrile-based copolymer in Example 1. was carried out in the same manner as in Example 1 to obtain a flameproof fiber bundle and a carbon fiber bundle.
（実施例５）
実施例４で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は実施例４と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 5)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 4, except that the carbon fiber precursor fiber bundle obtained in Example 4 was heat-treated in air at 230°C.
（実施例６）
実施例４の紡糸溶液の吐出量を変更して単繊維繊度４．４ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は実施例４と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 6)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 4, except that the discharge rate of the spinning solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 4.4 dtex.
（実施例７）
実施例６で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は実施例６と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 7)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 6, except that the carbon fiber precursor fiber bundle obtained in Example 6 was heat-treated in air at 230°C.
（実施例８）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸ノルマルブチルの質量比が９２．０：１．０：７．０である単量体組成物とした以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Example 8)
In Example 1, the raw materials of the polyacrylonitrile-based copolymer were acrylonitrile, itaconic acid, and a monomer composition having a mass ratio of 92.0:1.0:7.0 of n-butyl acrylate as an acrylate-based monomer. A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1 except for the above.
（比較例１）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルの質量比が９７．１：１．０：１．９である単量体組成物とし、紡糸溶液の吐出量を変更して単繊維繊度２．２ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative example 1)
In Example 1, a monomer composition having a mass ratio of 97.1:1.0:1.9 of acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer was used as the starting material for the polyacrylonitrile-based copolymer. A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1, except that the discharge amount of the solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 2.2 dtex.
（比較例２）
比較例１で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は比較例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative example 2)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Comparative Example 1, except that the carbon fiber precursor fiber bundle obtained in Comparative Example 1 was heat-treated in air at 230°C.
（比較例３）
比較例１の紡糸溶液の吐出量を変更して単繊維繊度３．３ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は比較例３と同様にし、耐炎化繊維束を得た。耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化を行ったところ、繊維束が切れ、炭素繊維束は得られなかった。
(Comparative Example 3)
A flameproof fiber bundle was obtained in the same manner as in Comparative Example 3, except that the discharge amount of the spinning solution in Comparative Example 1 was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 3.3 dtex. When the flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800°C and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300°C, the fiber bundle was cut and no carbon fiber bundle was obtained. .
（比較例４）
比較例３で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は比較例３と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 4)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Comparative Example 3, except that the carbon fiber precursor fiber bundle obtained in Comparative Example 3 was heat-treated in air at 230°C.
（比較例５）
比較例１の紡糸溶液の吐出量を変更して単繊維繊度４．４ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は比較例１と同様にし、耐炎化繊維束を得た。耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化を行ったところ、繊維束が切れ、炭素繊維束は得られなかった。
(Comparative Example 5)
A flameproof fiber bundle was obtained in the same manner as in Comparative Example 1, except that the discharge rate of the spinning solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 4.4 dtex. When the flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800°C and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300°C, the fiber bundle was cut and no carbon fiber bundle was obtained. .
（比較例６）
比較例５で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は比較例５と同様にし、耐炎化繊維束を得た。耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化を行ったところ、繊維束が切れ、炭素繊維束は得られなかった。
(Comparative Example 6)
A flameproof fiber bundle was obtained in the same manner as in Comparative Example 5, except that the carbon fiber precursor fiber bundle obtained in Comparative Example 5 was heat-treated in air at 230°C. When the flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800°C and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300°C, the fiber bundle was cut and no carbon fiber bundle was obtained. .
（比較例７）
実施例１の紡糸溶液の吐出量を変更して単繊維繊度２．２ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 7)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1, except that the discharge rate of the spinning solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 2.2 dtex.
（比較例８）
比較例７で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は比較例７と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 8)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Comparative Example 7, except that the carbon fiber precursor fiber bundle obtained in Comparative Example 7 was heat-treated in air at 230°C.
（比較例９）
実施例１の紡糸溶液の吐出量を変更して単繊維繊度４．４ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 9)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1, except that the discharge rate of the spinning solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 4.4 dtex.
（比較例１０）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルの質量比が９０．０：１．０：９．０である単量体組成物とし、紡糸溶液の吐出量を変更して単繊維繊度２．２ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 10)
In Example 1, a monomer composition having a mass ratio of 90.0: 1.0: 9.0 of acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer was used as the raw material for the polyacrylonitrile-based copolymer, and spinning was performed. A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Example 1, except that the discharge amount of the solution was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 2.2 dtex.
（比較例１１）
比較例１０で得た炭素繊維前駆体繊維束を２３０℃の空気中で熱処理した以外は比較例１０と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 11)
A flameproof fiber bundle and a carbon fiber bundle were obtained in the same manner as in Comparative Example 10, except that the carbon fiber precursor fiber bundle obtained in Comparative Example 10 was heat-treated in air at 230°C.
（比較例１２）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸ノルマルブチルの質量比が９６．６：１．０：２．４である単量体組成物とし、紡糸溶液の吐出量を変更して単繊維繊度２．２ｄｔｅｘの炭素繊維前駆体繊維束を得、２２０℃の空気中で熱処理を行った以外は実施例１と同様にし、耐炎化繊維束および炭素繊維束を得た。
(Comparative Example 12)
In Example 1, the raw materials of the polyacrylonitrile-based copolymer were acrylonitrile, itaconic acid, and a monomer composition having a mass ratio of n-butyl acrylate as an acrylate-based monomer at a mass ratio of 96.6: 1.0: 2.4, A carbon fiber precursor fiber bundle having a single fiber fineness of 2.2 dtex was obtained by changing the discharge rate of the spinning solution, and a flameproof fiber bundle and carbon A fiber bundle was obtained.
（比較例１３）
比較例１２の紡糸溶液の吐出量を変更して単繊維繊度４．４ｄｔｅｘの炭素繊維前駆体繊維束を得た以外は比較例１２と同様にし、耐炎化繊維束を得た。耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化を行ったところ、繊維束が切れ、炭素繊維束は得られなかった。
(Comparative Example 13)
A flameproof fiber bundle was obtained in the same manner as in Comparative Example 12, except that the discharge rate of the spinning solution in Comparative Example 12 was changed to obtain a carbon fiber precursor fiber bundle having a single fiber fineness of 4.4 dtex. When the flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800°C and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300°C, the fiber bundle was cut and no carbon fiber bundle was obtained. .
（比較例１４）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸の質量比が９９．０：１．０である単量体組成物とし、紡糸溶液の吐出量を変更して単繊維繊度２．２ｄｔｅｘの炭素繊維前駆体繊維束を得、２３０℃の空気中で熱処理を行った以外は実施例１と同様にし、耐炎化繊維束を得た。耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化を行ったところ、繊維束が切れ、炭素繊維束は得られなかった。
(Comparative Example 14)
In Example 1, a monomer composition having a mass ratio of acrylonitrile and itaconic acid of 99.0:1.0 was used as the raw material for the polyacrylonitrile-based copolymer, and the single fiber fineness was adjusted to 2 by changing the discharge amount of the spinning solution. A flameproof fiber bundle was obtained in the same manner as in Example 1, except that a carbon fiber precursor fiber bundle of .2 dtex was obtained and heat-treated in air at 230°C. When the flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800°C and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300°C, the fiber bundle was cut and no carbon fiber bundle was obtained. .
（比較例１５）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルの質量比が９３．５：１．０：５．５である単量体組成物として得られた紡糸溶液を孔数３０００の口金を用いてＤＭＳＯの水溶液からなる凝固浴中に吐出する湿式紡糸法により凝固させ、凝固糸とした以外は実施例１と同様にし、耐炎化繊維束を得た。得られた耐炎化繊維束を温度３００～８００℃の窒素雰囲気中において予備炭素化し、その後、最高温度１３００℃の窒素雰囲気中で炭素化することで炭素繊維束を得た。炭素繊維束の毛羽数を数え、品位を評価した。
(Comparative Example 15)
In Example 1, the starting materials for the polyacrylonitrile-based copolymer were acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer. A flame-resistant fiber bundle was obtained in the same manner as in Example 1 except that the resulting spinning solution was coagulated by a wet spinning method in which it was discharged into a coagulation bath consisting of an aqueous solution of DMSO using a spinneret with 3000 holes to form a coagulated yarn. . The obtained flameproof fiber bundle was pre-carbonized in a nitrogen atmosphere at a temperature of 300 to 800° C., and then carbonized in a nitrogen atmosphere at a maximum temperature of 1300° C. to obtain a carbon fiber bundle. The number of fluffs on the carbon fiber bundle was counted to evaluate the quality.
（比較例１６）
実施例１でポリアクリロニトリル系共重合体の原料をアクリロニトリル、イタコン酸、アクリレート系モノマーとしてアクリル酸エチルの質量比が９３．５：１．０：５．５である単量体組成物とした以外は実施例１と同様にし、炭素繊維前駆体繊維束を得た。得られた炭素繊維前駆体繊維束を３１０℃の空気中で熱処理を行ったところ、繊維束が断糸し、耐炎化繊維束は得られなかった。
(Comparative Example 16)
Except for using a monomer composition having a mass ratio of 93.5:1.0:5.5 of acrylonitrile, itaconic acid, and ethyl acrylate as an acrylate-based monomer as raw materials for the polyacrylonitrile-based copolymer in Example 1. was carried out in the same manner as in Example 1 to obtain a carbon fiber precursor fiber bundle. When the obtained carbon fiber precursor fiber bundle was heat-treated in the air at 310° C., the fiber bundle was broken and no flame-resistant fiber bundle was obtained.
以上の実施例および比較例の条件、結果について、実施例１～８は表１に、比較例１～８は表２に、比較例９～１６は表３にそれぞれまとめた。 The conditions and results of the above examples and comparative examples are summarized in Table 1 for Examples 1 to 8, Table 2 for Comparative Examples 1 to 8, and Table 3 for Comparative Examples 9 to 16.
Claims (4)
（Ａ） Ａｃ≧１２１－１７Ｆｃ／ｄｔｅｘ
（Ｂ） Ａｃ≧９０ The single fiber fineness Fc is 1.5 to 2.4 dtex, the shape of the cross section perpendicular to the fiber axis of the single fiber has a circularity of 0.91 to 1.00, and the center side of the single fiber cross section and the Among the cross-sectional double structures observed on the circumferential side, the outer layer ratio Ac (%), which is the ratio of the area on the circumferential side to the single fiber cross-sectional area, and the single fiber fineness Fc (dtex) are the following conditions (A). and a carbon fiber bundle that satisfies the condition (B).
(A) Ac≧121-17Fc/dtex
(B) Ac≧90
（ａ） 耐炎化繊維束の単繊維断面の中心側と円周側に観察される断面二重構造のうち、円周側の面積の単繊維断面積に占める割合である外層比率Ａｓ（％）がＡｓ≧９０を満たす。
（ｂ） 耐炎化初期温度Ｔｉ（℃）とアクリレート系モノマー（Ｘ）単位の質量組成比Ｚａ（％）が、Ｔｉ×Ｚａ≧１０００の関係を満たす。
（ｃ） 耐炎化温度が２００～３００℃の範囲内である。 90.0 to 97.0% by mass of acrylonitrile units and an acrylate-based monomer represented by the structural formula CH 2 =CHCOOC n H 2n+1 (where n = 2 to 4 and the alkyl chain is linear). (X) Using a polyacrylonitrile-based polymer containing 3.0 to 10.0% by mass of units, having a single fiber fineness of 2.3 to 6.0 dtex, and having a cross section in the direction perpendicular to the fiber axis of the single fiber After obtaining a carbon fiber precursor fiber bundle having a shape with a circularity of 0.91 to 1.00, the carbon fiber precursor fiber bundle is exposed to an oxidizing atmosphere while satisfying the following conditions (a) to (c). a flameproofing step of treating in a flameproofing step, a preliminary carbonization step of precarbonizing the flameproofed fiber bundle obtained in the flameproofing step in an inert atmosphere at a maximum temperature of 500 to 1200 ° C., and the preliminary carbonization step A method for producing a carbon fiber bundle including a carbonization step of carbonizing the obtained pre-carbonized fiber bundle in an inert atmosphere at 1200 to 3000°C.
(a) Outer layer ratio As (%), which is the ratio of the area of the circumference side to the cross-sectional area of the single fiber in the cross-sectional double structure observed on the center side and the circumference side of the single fiber cross section of the flameproof fiber bundle satisfies As≧90.
(b) The initial flame-proofing temperature Ti (°C) and the mass composition ratio Za (%) of the acrylate-based monomer (X) unit satisfy the relationship Ti x Za≧1000.
(c) The flameproofing temperature is in the range of 200-300°C.
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