JP2010229572A - Polyacrylonitrile-based carbon fiber and method for producing the same - Google Patents
Polyacrylonitrile-based carbon fiber and method for producing the same Download PDFInfo
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- 229920002239 polyacrylonitrile Polymers 0.000 title claims description 16
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 125000000524 functional group Chemical group 0.000 claims abstract description 21
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims abstract description 20
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- 239000000835 fiber Substances 0.000 claims description 26
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- 239000007864 aqueous solution Substances 0.000 claims description 22
- 238000004381 surface treatment Methods 0.000 claims description 13
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 12
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- 238000006386 neutralization reaction Methods 0.000 claims description 6
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- RBDWCSWYBOZGGD-UHFFFAOYSA-N [C].C(C=C)#N Chemical compound [C].C(C=C)#N RBDWCSWYBOZGGD-UHFFFAOYSA-N 0.000 claims 1
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- 238000007254 oxidation reaction Methods 0.000 abstract description 24
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- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 8
- 238000011156 evaluation Methods 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 238000009987 spinning Methods 0.000 description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000002243 precursor Substances 0.000 description 6
- 239000003822 epoxy resin Substances 0.000 description 5
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
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- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 4
- 235000017557 sodium bicarbonate Nutrition 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229920002430 Fibre-reinforced plastic Polymers 0.000 description 3
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 3
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- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 3
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- 229910052743 krypton Inorganic materials 0.000 description 3
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 3
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- 238000010301 surface-oxidation reaction Methods 0.000 description 3
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 235000011130 ammonium sulphate Nutrition 0.000 description 2
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- 229910052757 nitrogen Inorganic materials 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
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- 238000005406 washing Methods 0.000 description 2
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- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 description 1
- 229920002972 Acrylic fiber Polymers 0.000 description 1
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
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- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 229910001853 inorganic hydroxide Inorganic materials 0.000 description 1
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
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Abstract
Description
本発明は、優れた機械的物性を有し、且つ、マトリックス樹脂との界面接着性等に優れたポリアクリロニトリル系炭素繊維（以下、単に炭素繊維ともいう。）及びこれの製造方法に関する。 The present invention relates to a polyacrylonitrile-based carbon fiber (hereinafter, also simply referred to as carbon fiber) having excellent mechanical properties and excellent interfacial adhesion with a matrix resin, and a method for producing the same.
近年、炭素繊維を用いる複合材料は、軽く、高強度等の優れた機械的特性を有するので、航空機、自動車等の部材として多く用いられている。これらの複合材料は、例えば、炭素繊維にマトリックス樹脂が含浸されたものが挙げられる。 In recent years, composite materials using carbon fibers are light and have excellent mechanical properties such as high strength, and thus are often used as members for aircraft, automobiles, and the like. Examples of these composite materials include carbon fibers impregnated with a matrix resin.
炭素繊維とマトリックス樹脂との複合化において、高性能化を追求するためには、炭素繊維そのもの自体の強度や弾性率等の機械的物性の他、マトリックス樹脂との接着性に関与する炭素繊維の表面特性を向上させることが必要不可欠である。つまり、炭素繊維表面とマトリックス樹脂との接着性が高いもの同士を複合化し、マトリックス樹脂と炭素繊維をより均一に分散することで、より高性能のコンポジット特性(高強度、高弾性、高耐衝撃性等)を有する複合材料を得ることができると期待される。 In order to pursue high performance in the composite of carbon fiber and matrix resin, in addition to the mechanical properties such as strength and elastic modulus of the carbon fiber itself, the carbon fiber involved in the adhesion to the matrix resin It is essential to improve surface properties. In other words, by combining materials with high adhesion between the carbon fiber surface and the matrix resin, and dispersing the matrix resin and the carbon fiber more uniformly, higher performance composite properties (high strength, high elasticity, high impact resistance) It is expected that a composite material having properties such as properties) can be obtained.
炭素繊維の表面状態と複合材料の強度との関係は、一般的に表面が平坦な炭素繊維ではマトリクス樹脂との接着性が低いため、複合材料としての強度が十分に発現されず、また表面の凹凸が大きな炭素繊維ではマトリックス樹脂との接着性は高いが、大きすぎる表面の凹凸が繊維欠陥となり、複合材料の強度低下につながるといわれている。従って、炭素繊維表層部に、表面処理によって適度な凹凸を適当な量、形成させることが重要であると考えられている。 The relationship between the surface condition of carbon fiber and the strength of the composite material is that the carbon fiber with a flat surface generally has low adhesion to the matrix resin, so that the strength as a composite material is not fully expressed, and the surface Carbon fibers with large irregularities have high adhesion to the matrix resin, but it is said that irregularities on the surface that are too large become fiber defects, leading to a decrease in strength of the composite material. Accordingly, it is considered important to form an appropriate amount of appropriate irregularities on the surface of the carbon fiber by surface treatment.
表面処理の方法・手段としては、強酸などの酸化薬液を用いる薬液酸化、電解質溶液中で炭素繊維を陽極として処理する電解酸化、及び気相状態でのプラズマ処理などによる気相酸化等がある。その中でも、工業的に効率性の高い電解酸化処理法が好適に採用される。電解酸化による表面処理によって、炭素繊維の形成過程で生じた表面の脆弱層が除去され、繊維の強度等の機械的物性が向上する。また、炭素繊維表層部のカルボキシル基、カルボニル基、水酸基等の官能基量が増加され、マトリックス樹脂との接着性を高めるのに寄与する。 Examples of surface treatment methods and means include chemical oxidation using an oxidizing chemical solution such as a strong acid, electrolytic oxidation in which carbon fiber is treated as an anode in an electrolyte solution, and vapor phase oxidation by plasma treatment in a gas phase. Among these, an industrially highly efficient electrolytic oxidation treatment method is preferably employed. By the surface treatment by electrolytic oxidation, the fragile layer on the surface generated in the process of forming the carbon fiber is removed, and mechanical properties such as fiber strength are improved. Further, the amount of functional groups such as carboxyl group, carbonyl group, hydroxyl group and the like in the surface portion of the carbon fiber is increased, which contributes to enhancing adhesiveness with the matrix resin.
本発明者らは、炭素繊維の表面を電解処理する方法において、先ず、陽極槽と陰極槽の組合せからなる電解処理浴が複数連続して設置される多段電解処理浴を用いて、各段の電気量が２０〜３００Ｃ／ｇの範囲で、且つ総電気量が１５０〜５００Ｃ／ｇの範囲で電解処理を行い、その後、陰極槽と陽極槽の組合せからなる電解処理浴を用いて電位を逆転させて、逆転した電位での電気量が２０〜６０Ｃ／ｇの範囲で電解処理を行うことを特徴とする炭素繊維の表面電解処理方法を開発し、先に特許出願を行った（特許文献１）。 In the method of electrolytically treating the surface of carbon fiber, the present inventors firstly used a multistage electrolytic treatment bath in which a plurality of electrolytic treatment baths composed of a combination of an anode tank and a cathode tank are continuously installed, Electrolytic treatment is performed in the range of 20 to 300 C / g and the total amount of electricity in the range of 150 to 500 C / g, and then the potential is reversed using an electrolytic bath composed of a combination of a cathode cell and an anode cell. And developed a carbon fiber surface electrolytic treatment method characterized by performing an electrolytic treatment in the range of 20 to 60 C / g of electricity at a reversed potential, and filed a patent application first (Patent Document 1). ).
該発明によると、炭素繊維表層部の官能基量が増加され、炭素繊維の表面が改質される。また、得られる炭素繊維は、マトリックス樹脂との接着性が向上され、高いコンポジット特性を有する複合材料が製造される。該発明は炭素繊維表面の官能基の量を増加させることは出来る。しかし、該発明は炭素繊維表層部の各官能基の存在比率を制御するものではない。 According to this invention, the functional group amount of the carbon fiber surface layer is increased, and the surface of the carbon fiber is modified. Further, the obtained carbon fiber has improved adhesion to the matrix resin, and a composite material having high composite characteristics is produced. The invention can increase the amount of functional groups on the carbon fiber surface. However, this invention does not control the abundance ratio of each functional group in the surface portion of the carbon fiber.
また、特許文献２には、炭素繊維の製造方法について記載されている。この方法においては、まず、凝固糸条を乾燥緻密化前に、空中で延伸倍率１〜３倍に、温水中で１〜３倍にそれぞれ延伸させる湿式紡糸法により得られるアクリル繊維を耐炎化後、最高温度１７００℃以下の不活性雰囲気中で炭素化させて炭素繊維とする。次いで、この炭素繊維を電解質濃度０．１〜２０質量％、電気量０．１〜２００Ｃ／ｇで電解酸化する。その後、引き続き、水中で周波数０．０１〜２００ｋＨｚ、処理時間０．１秒〜６０分で超音波洗浄を行った後、５００℃以下の温度で乾燥させる。この方法によっても、炭素繊維表層部の官能基の量は増加される。しかし、この方法は、炭素繊維表層部の各官能基の存在比率を制御するものではない。
炭素繊維表層部における各官能基の存在比率を制御することが出来れば、様々なコンポジット特性を有する複合材料が得られる可能性がある。以上のような状況のもと、多様なコンポジット特性を有する複合材料を製造するために、炭素繊維の表面特性の、より高度な制御が求められている。 If the abundance ratio of each functional group in the carbon fiber surface layer part can be controlled, composite materials having various composite characteristics may be obtained. Under the circumstances as described above, in order to manufacture a composite material having various composite characteristics, higher-level control of the surface characteristics of the carbon fiber is required.
本発明の課題は、電解処理により表面改質される炭素繊維の表層部における各官能基の存在比率を制御し、マトリックス樹脂と複合材料とした際に優れたコンポジット特性を示す炭素繊維を提供することにある。 An object of the present invention is to provide a carbon fiber exhibiting excellent composite characteristics when a matrix resin and a composite material are formed by controlling the abundance ratio of each functional group in the surface layer portion of the carbon fiber surface-modified by electrolytic treatment. There is.
本発明者は、炭素繊維を電解処理して表面改質される炭素繊維を調製する過程において、炭素繊維の電解酸化処理後にアルカリ性水溶液に接触させることにより、炭素繊維表層部のカルボキシル基とヒドロキシル基との存在比率を制御することが出来ることを見出した。そして、炭素繊維表層部のカルボキシル基とヒドロキシル基との存在比率が所定の範囲内にある炭素繊維を用いてマトリックス樹脂との複合材料を調製すると、該複合材料が高い衝撃後圧縮強度（以下、ＣＡＩとも表記する）を有する、並びに層間剥離亀裂進展抵抗を改善させることを見出し、本発明を完成するに至った。 In the process of preparing carbon fibers to be surface-modified by electrolytic treatment of carbon fibers, the present inventor made contact with an alkaline aqueous solution after electrolytic oxidation treatment of the carbon fibers, so that the carboxyl groups and hydroxyl groups of the carbon fiber surface layer portion were obtained. It was found that the abundance ratio can be controlled. Then, when a composite material with a matrix resin is prepared using carbon fibers in which the abundance ratio between the carboxyl group and the hydroxyl group in the surface portion of the carbon fiber is within a predetermined range, the composite material has a high post-impact compressive strength (hereinafter, It was also found to improve the delamination crack propagation resistance, and the present invention was completed.
上記目的を達成する本発明は、以下に記載するものである。 The present invention for achieving the above object is described below.
〔１〕Ｘ線光電子分光器により測定される表面酸素濃度が８〜２５％であるポリアクリロニトリル系炭素繊維であって、且つ、中和滴定法により測定される単位質量当りのヒドロキシル基量（Ａ）（単位はｅｑ／ｇ）と、単位質量当りのカルボキシル基量（Ｂ）（単位はｅｑ／ｇ）とから算出されるＡ／Ｂの値が２．０〜５．０であることを特徴とするポリアクリロニトリル系炭素繊維。 [1] Polyacrylonitrile-based carbon fiber having a surface oxygen concentration of 8 to 25% measured by an X-ray photoelectron spectrometer, and the amount of hydroxyl groups per unit mass (A ) (Unit: eq / g) and carboxyl group amount per unit mass (B) (unit: eq / g), A / B value is 2.0 to 5.0 Polyacrylonitrile-based carbon fiber.
〔２〕ポリアクリロニトリル系炭素繊維に表面処理を施してポリアクリロニトリル系炭素繊維を製造する方法であって、
電解処理を施して炭素繊維表層部の官能基量を増加させたポリアクリロニトリル系炭素繊維にｐＨ８〜１３のアルカリ性水溶液を接触させることにより、
Ｘ線光電子分光器により測定される表面酸素濃度を８〜２５％、中和滴定法により測定される単位質量当りのヒドロキシル基量（Ａ）（単位はｅｑ／ｇ）と、単位質量当りのカルボキシル基量（Ｂ）（単位はｅｑ／ｇ）とから算出されるＡ／Ｂの値を２．０〜５．０に変化させる工程を有することを特徴とする〔１〕記載のポリアクリロニトリル系炭素繊維の製造方法。
[2] A method for producing polyacrylonitrile-based carbon fiber by subjecting polyacrylonitrile-based carbon fiber to surface treatment,
By contacting an alkaline aqueous solution having a pH of 8 to 13 with polyacrylonitrile-based carbon fiber that has been subjected to electrolytic treatment to increase the amount of functional groups on the surface portion of the carbon fiber,
Surface oxygen concentration measured by X-ray photoelectron spectrometer is 8 to 25%, hydroxyl group amount per unit mass (A) (unit is eq / g) measured by neutralization titration method, and carboxyl per unit mass The polyacrylonitrile-based carbon according to [1], comprising a step of changing the value of A / B calculated from the base amount (B) (unit: eq / g) to 2.0 to 5.0 A method for producing fibers.
〔３〕アルカリ性水溶液が、炭酸ナトリウム水溶液である〔２〕記載のポリアクリロニトリル系炭素繊維の製造方法。 [3] The method for producing polyacrylonitrile-based carbon fiber according to [2], wherein the alkaline aqueous solution is an aqueous sodium carbonate solution.
本発明によると、炭素繊維の表面状態が改質され、マトリックス樹脂との接着性が向上する。従って、本発明の炭素繊維を用いると、従来のものよりも高性能(高強度、高弾性)な複合材料を得ることができる。 According to the present invention, the surface state of the carbon fiber is modified and the adhesion with the matrix resin is improved. Therefore, when the carbon fiber of the present invention is used, a composite material having higher performance (higher strength and higher elasticity) than the conventional one can be obtained.
以下、本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail.
炭素繊維は、通常、前駆体繊維の耐炎化処理、炭素化処理を経て得られる。その後、マトリックス樹脂との接着性を高めることを目的として、炭素繊維に表面処理が施される。表面処理は電解処理による酸化処理（以下、電解酸化処理ともいう。）が広く行われている。電解酸化処理により、炭素繊維表層部の各官能基（ヒドロキシル基やカルボキシル基、カルボニル基等）の量は通常、数倍に増加する。これにより、炭素繊維表層部とマトリックス樹脂との接着性は向上する。しかし、通常、表面処理電気量が高いと、複合材料の脆弱性の原因となりうるカルボキシル基の存在比率が増加され、また、表面処理電気量が低いと、接着性を低下させる原因となる。 The carbon fiber is usually obtained through a flameproofing treatment and a carbonization treatment of the precursor fiber. Thereafter, the carbon fiber is subjected to a surface treatment for the purpose of enhancing the adhesion with the matrix resin. As the surface treatment, oxidation treatment by electrolytic treatment (hereinafter also referred to as electrolytic oxidation treatment) is widely performed. By the electrolytic oxidation treatment, the amount of each functional group (hydroxyl group, carboxyl group, carbonyl group, etc.) in the carbon fiber surface layer usually increases several times. Thereby, the adhesiveness of a carbon fiber surface layer part and matrix resin improves. However, usually, when the amount of electricity for surface treatment is high, the abundance ratio of carboxyl groups that can cause fragility of the composite material is increased, and when the amount of electricity for surface treatment is low, the adhesiveness is lowered.
本発明の炭素繊維は電解酸化処理がなされた後、アルカリ性水溶液に接触させる（以下、アルカリ処理ともいう。）。このアルカリ処理によって、炭素繊維表層部の各官能基のうち、複合材料の脆弱性の原因となりうるカルボキシル基の存在比率を選択的に低下させることが出来る。その後は、必要に応じてサイジング処理等がなされる。このようにして得られる炭素繊維はマトリックス樹脂との接着性が高く、複合材料とすると高い衝撃後圧縮強度（以下、ＣＡＩとも表記する。）を有する。また、面内剪断応力（ＩＰＳＳ）の荷重―伸び線図により求める層間剥離亀裂進展抵抗が改善される。 The carbon fiber of the present invention is subjected to an electrolytic oxidation treatment and then contacted with an alkaline aqueous solution (hereinafter also referred to as alkali treatment). By this alkali treatment, it is possible to selectively reduce the abundance ratio of carboxyl groups that can cause the brittleness of the composite material among the functional groups of the carbon fiber surface layer portion. Thereafter, a sizing process or the like is performed as necessary. The carbon fiber thus obtained has high adhesion to the matrix resin, and has a high post-impact compressive strength (hereinafter also referred to as CAI) when a composite material is used. Further, the delamination crack propagation resistance obtained from the load-elongation diagram of in-plane shear stress (IPSS) is improved.
図１及び図２は本発明の炭素繊維を用いる複合材料の層間剥離亀裂進展抵抗と、従来の炭素繊維を用いる複合材料の層間剥離亀裂進展抵抗を比較したグラフである。本発明及び従来の炭素繊維を用いる複合材料の層間剪断強度はほぼ同一である。しかし、従来の炭素繊維を用いる複合材料はストローク７ｍｍ近傍から荷重の低下が見られる。即ち、従来の炭素繊維を用いる複合材料の面内剪断応力（ＩＰＳＳ）の下降伏点荷重は上降伏点荷重よりも低い値を示している。一方、本発明の炭素繊維を用いる複合材料は係る低下は見られず、面内剪断応力（ＩＰＳＳ）の荷重―伸び線図により求める層間剥離亀裂進展抵抗において性能向上が見られる。図３は炭素繊維を用いて製造する複合材料の面内剪断応力（ＩＰＳＳ）の上降伏点荷重、下降伏点荷重、最大点荷重を表す説明図である。図３中、１は上降伏点荷重、２は下降伏点荷重、３は最大点荷重を表す。 1 and 2 are graphs comparing the delamination crack growth resistance of a composite material using the carbon fiber of the present invention and the delamination crack growth resistance of a composite material using a conventional carbon fiber. The interlayer shear strength of the composite material using the present invention and the conventional carbon fiber is almost the same. However, in the composite material using the conventional carbon fiber, the load is reduced from around the stroke of 7 mm. That is, the lower yield point load of the in-plane shear stress (IPSS) of the composite material using the conventional carbon fiber is lower than the upper yield point load. On the other hand, the composite material using the carbon fiber of the present invention does not show such a decrease, and shows an improvement in delamination crack growth resistance obtained from a load-elongation diagram of in-plane shear stress (IPSS). FIG. 3 is an explanatory diagram showing the upper yield point load, the lower yield point load, and the maximum point load of the in-plane shear stress (IPSS) of the composite material manufactured using carbon fibers. In FIG. 3, 1 represents the upper yield point load, 2 represents the lower yield point load, and 3 represents the maximum point load.
<炭素繊維>
前駆体繊維の耐炎化処理、炭素化処理は従来公知の方法で行うことが出来る。例えば、次のように行うことが出来る。まず、ＰＡＮ系前駆体繊維を空気中において、２００〜３００℃で加熱して耐炎化処理することにより、耐炎化繊維が得られる。この耐炎化繊維を窒素雰囲気下、温度１０００〜１５００℃で加熱して炭素化処理することにより、炭素繊維が得られる。
<Carbon fiber>
Flameproofing treatment and carbonization treatment of the precursor fiber can be performed by a conventionally known method. For example, it can be performed as follows. First, a flame-resistant fiber is obtained by heating the PAN-based precursor fiber at 200 to 300 ° C. in the air for flame resistance treatment. Carbon fiber is obtained by heating this flame-resistant fiber at a temperature of 1000 to 1500 ° C. in a nitrogen atmosphere to perform carbonization treatment.
〈電解処理〉
得られた炭素繊維の表面酸化処理は電解処理により行う。電解処理に用いられる電解液としては、硫酸や硝酸、塩酸等の無機酸、水酸化ナトリウムや水酸化カリウム等の無機水酸化物、硫酸アンモニウムや炭酸ナトリウム、炭酸水素ナトリウム等の無機塩類が挙げられる。電解酸化処理は、電解処理浴を用いて、電解電気量が５〜２５０Ｃ／ｇの範囲で行うことが好ましい。５Ｃ／ｇ未満である場合は、電解酸化処理の効果が低く、炭素繊維表面とマトリックス樹脂との接着性が改善されにくいため好ましくない。２５０Ｃ／ｇを超える場合は、繊維表面が強く削られて粗さが増大し、削れ過ぎた部分が新たな欠陥となり、繊維強度の低下を招くため好ましくない。
<Electrolytic treatment>
The surface oxidation treatment of the obtained carbon fiber is performed by electrolytic treatment. Examples of the electrolytic solution used for the electrolytic treatment include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, inorganic hydroxides such as sodium hydroxide and potassium hydroxide, and inorganic salts such as ammonium sulfate, sodium carbonate, and sodium hydrogen carbonate. The electrolytic oxidation treatment is preferably performed using an electrolytic treatment bath in the range of electrolytic electricity of 5 to 250 C / g. If it is less than 5 C / g, the effect of the electrolytic oxidation treatment is low, and the adhesion between the carbon fiber surface and the matrix resin is hardly improved, which is not preferable. When it exceeds 250 C / g, the fiber surface is sharply cut to increase the roughness, and the excessively cut portion becomes a new defect, which leads to a decrease in fiber strength.
かかる電解酸化処理により、炭素繊維の焼成過程で生じる脆弱層が除去されると共に、酸化反応により、炭素繊維表層部のカルボキシル基やカルボニル基、ヒドロキシル基等の官能基が増加する。官能基の増加量は、Ｘ線光電子分光器により測定される表面酸素濃度が８〜２５％となる程度である。 Such an electrolytic oxidation treatment removes a fragile layer generated during the firing process of carbon fiber, and an oxidation reaction increases functional groups such as a carboxyl group, a carbonyl group, and a hydroxyl group in the surface portion of the carbon fiber. The increase amount of the functional group is such that the surface oxygen concentration measured by an X-ray photoelectron spectrometer is 8 to 25%.
本発明において電解処理は、特許文献１に記載されている様に、陽極酸化による表面電解処理と陰極還元による表面電解処理が交互に連続して行われることが好ましい。例えば、陽極槽と陰極槽とからなる一対の処理槽が連続して設置されている電解表面処理装置を用いて、炭素繊維のトウに対して、電解質溶液を介して間接給電して、陽極酸化による電解表面処理と陰極還元による電解表面処理が行われる。本発明において、電解処理浴とは、陽極と陰極が別々の槽に設置された陽極槽と陰極槽とからなる処理槽を意味し、かかる電解処理浴が連続して設置されているものが多段電解処理浴と定義される。本発明においては、前記一対の処理槽からなる電解処理浴、即ち、電解酸化と電解還元が行われる一対の陽極槽と陰極槽を、１ユニットと称するものとする。電位を逆転させる場合には、陰極槽と陽極槽の順序に配列されたものが１ユニットの電解処理浴と定義される。 In the present invention, as described in Patent Document 1, it is preferable that the electrolytic treatment is carried out alternately and continuously by surface electrolytic treatment by anodic oxidation and surface electrolytic treatment by cathodic reduction. For example, using an electrolytic surface treatment apparatus in which a pair of treatment tanks consisting of an anode tank and a cathode tank are continuously installed, an anodization is performed by indirectly feeding carbon fiber tow through an electrolyte solution. Electrolytic surface treatment by electrolysis and electrolytic surface treatment by cathodic reduction are performed. In the present invention, the electrolytic treatment bath means a treatment tank composed of an anode tank and a cathode tank in which an anode and a cathode are installed in separate tanks, and a plurality of such electrolytic treatment baths are continuously installed. Defined as electrolytic bath. In the present invention, an electrolytic treatment bath comprising the pair of treatment tanks, that is, a pair of anode tank and cathode tank in which electrolytic oxidation and electrolytic reduction are performed is referred to as one unit. In the case of reversing the electric potential, a unit arranged in the order of a cathode tank and an anode tank is defined as one unit of electrolytic treatment bath.
本発明において電解処理浴は、２ユニット以上設置されていることが好ましい。１ユニットで電解酸化処理した炭素繊維は、束の外側に位置する繊維の酸化状態に比較して内側に位置する繊維の酸化状態が不十分となり、表面の酸化状態にばらつきがある。２ユニット以上での電解酸化処理の場合は、炭素繊維の酸化処理がユニットごとで緩やかに行われ、炭素繊維の表面が均一に酸化処理されるためである。本発明においては、炭素繊維の表面を電解処理するに際し、先ず、陽極槽と陰極槽の組合せからなる電解処理浴が複数連続して設置された多段電解処理浴を用いて電解処理を行い、電解処理の最終の段階で、陰極槽と陽極槽の組合せを逆にした電解処理浴を用いて、電位を逆転させて電解処理を行う方法を採用することが好ましい。 In the present invention, it is preferable that two or more units of the electrolytic treatment bath are installed. The carbon fiber subjected to the electrolytic oxidation treatment in one unit has an insufficient oxidation state of the fiber located inside compared to the oxidation state of the fiber located outside the bundle, and the surface oxidation state varies. This is because in the case of electrolytic oxidation treatment with two or more units, the oxidation treatment of the carbon fibers is performed gently for each unit, and the surface of the carbon fibers is uniformly oxidized. In the present invention, when electrolytically treating the surface of the carbon fiber, first, electrolytic treatment is performed using a multi-stage electrolytic treatment bath in which a plurality of electrolytic treatment baths composed of a combination of an anode tank and a cathode tank are continuously installed, and electrolysis is performed. In the final stage of the treatment, it is preferable to employ a method in which the electrolytic treatment is performed by reversing the potential using an electrolytic treatment bath in which the combination of the cathode and anode vessels is reversed.
〈官能基の比率制御〉
炭素繊維表層部における各官能基の存在比率の制御は、アルカリ処理により行う。アルカリ性水溶液としては、水酸化ナトリウムや水酸化カリウム、炭酸ナトリウム、炭酸カリウム、炭酸水素ナトリウム、炭酸アンモニウム等の各水溶液が挙げられ、その中でも安全性が高く、ｐＨをコントロールしやすい炭酸ナトリウムが好ましい。アルカリ性水溶液はｐＨが８以上であることが必要で、８〜１３が好ましい。８未満の場合は、炭素繊維表層部の各種官能基の存在比率を変えることが殆ど出来ない。１３を超える場合は、カルボキシル基以外の官能基にも大きく作用をおよぼし、表面状態を制御することが困難である。アルカリ処理は、例えば、アルカリ性水溶液を貯留する槽に炭素繊維を通過させることにより行うことが出来る。アルカリ性水溶液の温度は、特に制限されないが、通常は１０〜４０℃が好ましく、２０〜３０℃がより好ましい。炭素繊維とアルカリ性水溶液とを接触させる時間は、用いるアルカリ水溶液の温度やｐＨによっても異なるため特に制限されないが、通常は１〜６０秒が好ましく、５〜２０秒がより好ましい。
<Functional group ratio control>
Control of the abundance ratio of each functional group in the carbon fiber surface layer is performed by alkali treatment. Examples of the alkaline aqueous solution include aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, ammonium carbonate, and the like. Among them, sodium carbonate is preferable because it is highly safe and the pH can be easily controlled. The alkaline aqueous solution needs to have a pH of 8 or higher, and preferably 8-13. If it is less than 8, the abundance ratio of various functional groups in the carbon fiber surface layer can hardly be changed. When it exceeds 13, it acts on a functional group other than the carboxyl group, and it is difficult to control the surface state. The alkali treatment can be performed, for example, by allowing the carbon fiber to pass through a tank that stores an alkaline aqueous solution. The temperature of the alkaline aqueous solution is not particularly limited, but is usually preferably 10 to 40 ° C and more preferably 20 to 30 ° C. The time for contacting the carbon fiber and the alkaline aqueous solution is not particularly limited because it varies depending on the temperature and pH of the alkaline aqueous solution to be used, but is usually preferably 1 to 60 seconds, and more preferably 5 to 20 seconds.
上記表面酸化処理後の繊維束には、必要に応じ、サイジング処理を施す。サイジング方法は、従来の公知の方法で行うことができる。サイジング剤は、複合化するマトリックス樹脂に合わせ、適宜組成を変更して使用することが好ましい。例えば、エポキシ樹脂やポリエステル樹脂、フェノール樹脂、ポリアミド樹脂等が挙げられる。 The fiber bundle after the surface oxidation treatment is subjected to sizing treatment as necessary. The sizing method can be performed by a conventionally known method. It is preferable to use the sizing agent by appropriately changing the composition in accordance with the matrix resin to be combined. For example, an epoxy resin, a polyester resin, a phenol resin, a polyamide resin, etc. are mentioned.
本発明の炭素繊維は、Ｘ線光電子分光器により測定される表面酸素濃度が８〜２５％であり、１１〜２０％が好ましい。８％未満の場合は、炭素繊維表層部とマトリックス樹脂との接着性が劣り、得られる複合材料の物性低下の原因になる。２５％を超える場合は、炭素繊維表層部とマトリクス樹脂との接着性が強すぎるため、かえって応力集中が生じ、耐衝撃性などのコンポジット特性が低下するため好ましくない。表面酸素濃度（以下、Ｏ／Ｃとも表記する。）とは、Ｘ線光電子分光器により測定される炭素繊維表面の炭素原子に対する酸素原子の存在比率を意味する。Ｏ／Ｃの値は電解処理の条件によってコントロールできる。一般には、電解処理の処理電気量や処理液濃度や処理時間を増すとＯ／Ｃの値は上昇する。 The carbon fiber of the present invention has a surface oxygen concentration measured by an X-ray photoelectron spectrometer of 8 to 25%, preferably 11 to 20%. If it is less than 8%, the adhesion between the carbon fiber surface layer and the matrix resin is inferior, causing a decrease in the physical properties of the resulting composite material. If it exceeds 25%, the adhesion between the carbon fiber surface layer portion and the matrix resin is too strong, so stress concentration occurs on the contrary, and composite properties such as impact resistance deteriorate, which is not preferable. The surface oxygen concentration (hereinafter also referred to as O / C) means the abundance ratio of oxygen atoms to carbon atoms on the carbon fiber surface measured by an X-ray photoelectron spectrometer. The value of O / C can be controlled by the conditions of electrolytic treatment. In general, the value of O / C increases as the amount of electricity for treatment, the concentration of treatment solution, and the treatment time increase.
本発明の炭素繊維は、中和滴定法により測定される単位質量当りのヒドロキシル基量（Ａ）（単位はｅｑ／ｇ）と、単位質量当りのカルボキシル基量（Ｂ）（単位はｅｑ／ｇ）とから算出されるＡ／Ｂの値が２．０〜５．０であり、２．５〜４．０が好ましい。２．０未満の場合は、炭素繊維表層部のカルボキシル基の存在比率が多く、得られる複合材料の脆弱性の原因となる。５．０を超える場合は、炭素繊維表層部の官能基が少ない場合か、または、過剰に処理された状態であり、炭素繊維表層部とマトリックス樹脂との接着性が劣る。そのため、得られる複合材料の物性低下の原因になる。Ａ／Ｂの値は電解処理の条件、アルカリ処理の条件によりコントロールできる。一般には、アルカリ処理の処理液濃度、処理時間を増すとＡ／Ｂの値は増加する。 The carbon fiber of the present invention has a hydroxyl group amount (A) (unit: eq / g) per unit mass and a carboxyl group amount (B) (unit: eq / g) per unit mass measured by a neutralization titration method. The A / B value calculated from the above is 2.0 to 5.0, preferably 2.5 to 4.0. When the ratio is less than 2.0, the carbon fiber surface layer portion has a large proportion of carboxyl groups, which causes brittleness of the resulting composite material. When it exceeds 5.0, the functional group of the carbon fiber surface layer part is small, or the carbon fiber surface layer part is in an excessively treated state, and the adhesion between the carbon fiber surface layer part and the matrix resin is poor. Therefore, it causes a decrease in physical properties of the obtained composite material. The value of A / B can be controlled by electrolytic treatment conditions and alkali treatment conditions. In general, the value of A / B increases as the concentration of the treatment liquid and the treatment time for alkali treatment are increased.
本発明の炭素繊維は公知の方法によりマトリックス樹脂と複合化することが出来る。例えば、炭素繊維束を一方向に引きそろえて並べ、得られる炭素繊維シートにエポキシ樹脂を含浸させた後、８０〜１００℃に加熱、０．３〜０．５ＭＰaに加圧してエポキシ樹脂を予備含浸させ、一方向プリプレグを得た。得られたプリプレグを用いて、ＣＦＲＰ（繊維強化プラスチック板材）を製造することが出来る。 The carbon fiber of the present invention can be combined with a matrix resin by a known method. For example, carbon fiber bundles are aligned in one direction, and the resulting carbon fiber sheet is impregnated with an epoxy resin, then heated to 80 to 100 ° C. and pressurized to 0.3 to 0.5 MPa to preliminarily prepare the epoxy resin. Impregnation was performed to obtain a unidirectional prepreg. A CFRP (fiber reinforced plastic plate material) can be produced using the obtained prepreg.
以下、本発明を実施例及び比較例により更に具体的に説明する。また、各評価は以下の方法により実施した。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Moreover, each evaluation was implemented with the following method.
〔炭素繊維１ｇ当たりのクーロン数（Ｃ／ｇ）〕
下記式で計算される値である。
Ｃ／ｇ＝０．３６×Ａ／（Ｅ×Ｓ×Ｙ×Ｆ）
ここで、Ａ(電流値：A)、Ｅ（炭素繊維のストランド数）、Ｓ（速度：ｍ／ｈｒ）、Ｙ（繊度：ｄtex）、Ｆ(フィラメント数)である。
[Number of coulombs per gram of carbon fiber (C / g)]
It is a value calculated by the following formula.
C / g = 0.36 × A / (E × S × Y × F)
Here, A (current value: A), E (number of carbon fiber strands), S (speed: m / hr), Y (fineness: dtex), and F (number of filaments).
〔比表面積〕
ＢＥＴ理論に従ってＢＥＴプロットの約０．１〜０．２５の相対圧域を解析し算出した。ガス吸着に際しては、ユアサアイオニクス（株）社製全自動ガス吸着装置「ＡＵＴＯＳＯＲＢ ― １」を使用し、下記条件により行った。
吸着ガス：Ｋｒ（クリプトン）
死容積：Ｈｅ（ヘリウム）
吸着温度：７７Ｋ（液体窒素温度）
測定範囲：相対圧（Ｐ／Ｐ０）＝ ０．０５−０．３
Ｐ：測定圧
Ｐ０：Ｋｒ（クリプトン）の飽和蒸気圧
Ｋｒ（クリプトン）吸着によるＢＥＴ法での比表面積値とは、吸着占有面積の判明しているガス分子をサンプルに吸着させ、その際の単分子層吸着量の値を用い、次の式によって算出される。
Ｓ＝（［Ｖｍ×Ｎ×Ａｃｓ］Ｍ）／ｗ
Ｓ：比表面積
Ｖｍ：単分子層吸着量
Ｎ：アボガドロ定数
Ａｃｓ：吸着断面積
Ｍ：分子量
ｗ：サンプル重量
〔Specific surface area〕
According to the BET theory, a relative pressure range of about 0.1 to 0.25 in the BET plot was analyzed and calculated. The gas adsorption was performed using a fully automatic gas adsorption device “AUTOSORB-1” manufactured by Yuasa Ionics Co., Ltd. under the following conditions.
Adsorbed gas: Kr (krypton)
Dead volume: He (Helium)
Adsorption temperature: 77K (liquid nitrogen temperature)
Measuring range: relative pressure (P / P 0 ) = 0.05−0.3
P: Measurement pressure P 0 : Saturated vapor pressure of Kr (krypton) The specific surface area value by the BET method by Kr (krypton) adsorption is the adsorption of gas molecules whose adsorption occupation area is known to the sample Using the value of the monomolecular layer adsorption amount, it is calculated by the following formula.
S = ([Vm × N × Acs] M) / w
S: Specific surface area Vm: Monolayer adsorption amount N: Avogadro constant Acs: Adsorption cross section M: Molecular weight w: Sample weight
〔繊維の樹脂含浸ストランド強度及び弾性率〕
ＪＩＳ Ｒ ７６０８に規定された方法により測定した、エポキシ樹脂含浸ストランド物性である。
[Strength and elastic modulus of resin-impregnated strand of fiber]
It is an epoxy resin-impregnated strand physical property measured by a method defined in JIS R 7608.
〔炭素繊維の表面酸素濃度（Ｏ／Ｃ）〕
次の手順に従って、Ｘ線光電子分光器（ＸＰＳ、化学分析用電子分光法(ＥＳＣＡ)ともいう）によって求める。炭素繊維をカットしてステンレス製の試料支持台上に拡げて並べた後、光電子脱出角度を９０度に設定し、Ｘ線源としてＭｇＫαを用い、試料チャンバー内を１×１０−６Ｐａの真空度に保つ。測定時の帯電に伴うピークの補正として、まずＣ１ｓの主ピークの結合エネルギー値Ｂ．Ｅ．を２８４．６ｅＶに合わせる。Ｏ１ｓピーク面積は、５２８〜５４０ｅＶの範囲で直線のベースラインを引くことにより求め、Ｃ１ｓピーク面積は、２８２〜２９２ｅＶの範囲で直線のベースラインを引くことにより求める。炭素繊維表面の表面酸素濃度Ｏ／Ｃは、上記Ｏ１ｓピーク面積とＣ１ｓピーク面積の比で計算して求められる。
[Surface oxygen concentration of carbon fiber (O / C)]
According to the following procedure, it is determined by an X-ray photoelectron spectrometer (XPS, also referred to as electron spectroscopy for chemical analysis (ESCA)). After cutting the carbon fibers and spreading them on a stainless steel sample support table, the photoelectron escape angle was set to 90 degrees, MgKα was used as the X-ray source, and the inside of the sample chamber was vacuumed at 1 × 10 −6 Pa. Keep it up. As correction of the peak accompanying charging during measurement, first, the binding energy value B. of the main peak of C1s. E. Is adjusted to 284.6 eV. The O1s peak area is obtained by drawing a straight base line in the range of 528 to 540 eV, and the C1s peak area is obtained by drawing a straight base line in the range of 282 to 292 eV. The surface oxygen concentration O / C on the surface of the carbon fiber is determined by calculating the ratio of the O1s peak area to the C1s peak area.
〔面内剪断応力（ＩＰＳＳ）の荷重―伸び線図により求める層間剥離亀裂進展抵抗〕
面内剪断応力の測定には、サイジングを行った後の炭素繊維及び東邦テナックス社製エポキシ樹脂を使用し、炭素繊維目付け１９０ｇ／ｍ２、樹脂含有率３３％の一方向性プリプレグを作製し、次いで、得られた一方向プリプレグ８枚を繊維の方向が順に［＋４５°／―４５°］ 2Sとなるように積層し、オートクレーブ中で温度１８０℃、圧力０．６ＭＰａで２時間加熱硬化し、ＣＦＲＰ（繊維強化プラスチック板材）試験片を得た。得られた試験片を用いて、ＪＩＳ Ｋ ７０７９に記載の±４５°方向引張法に従って、面内剪断応力（ＩＰＳＳ）を測定し、荷重―伸び線図を求め、図３に示すような、上降伏点荷重、下降伏点荷重、最大点荷重を求めた。
[In-plane shear stress (IPSS) load-delamination crack growth resistance obtained from elongation diagram]
For the measurement of in-plane shear stress, carbon fiber after sizing and epoxy resin manufactured by Toho Tenax Co., Ltd. are used to produce a unidirectional prepreg with a carbon fiber basis weight of 190 g / m 2 and a resin content of 33%. Next, the obtained eight unidirectional prepregs were laminated so that the fiber direction was [+ 45 ° / −45 °] 2S in order, and heat-cured at a temperature of 180 ° C. and a pressure of 0.6 MPa for 2 hours in an autoclave. A CFRP (fiber reinforced plastic sheet) test piece was obtained. Using the obtained test piece, in-plane shear stress (IPSS) was measured according to the ± 45 ° direction tensile method described in JIS K 7079, and a load-elongation diagram was obtained. As shown in FIG. Yield point load, descending point load, and maximum point load were determined.
〔衝撃後圧縮強度（ＣＡＩ）〕
ＣＡＩの測定には、サイジングを行った後の炭素繊維及び東邦テナックス社製エポキシ樹脂を使用し、炭素繊維目付け１９０ｇ／ｍ２、樹脂含有率３３％の一方向性プリプレグを作製し、［＋４５°／０°／―４５°／９０°］ 3Sの擬似等法に積層した。オートクレーブ中で温度１８０℃、圧力０．６ＭＰａで２時間加熱硬化し、ＣＦＲＰ（繊維強化プラスチック板材）を得た。
[Compressive strength after impact (CAI)]
For the measurement of CAI, a carbon fiber after sizing and an epoxy resin manufactured by Toho Tenax Co., Ltd. were used to prepare a unidirectional prepreg with a carbon fiber basis weight of 190 g / m 2 and a resin content of 33%, [+ 45 ° / 0 ° / −45 ° / 90 °] Laminated in a 3S pseudo-equal method. Heat curing was performed for 2 hours at a temperature of 180 ° C. and a pressure of 0.6 MPa in an autoclave to obtain CFRP (fiber reinforced plastic plate material).
このＣＦＲＰについて、ＪＩＳ Ｋ７０８９（１９９６）に従い、０度方向が１５２．４ｍｍ、９０度方向が１０１．６ｍｍの長方形に切り出し、この中央に落錘衝撃（３０．５Ｊの衝撃エネルギー）を与えた。衝撃試験は落錘型衝撃試験機（Ｄｙｎａｔｕｐ社製ＧＲＣ―８２５０）を用いて、衝撃後、供試体の損傷面積は、超音波探傷試験機（キャノン社製Ｍ６１０）にて測定した。衝撃後、供試体の強度試験は、供試体の上から２５．４ｍｍでサイドから２５．４ｍｍの位置に、歪みゲージを左右各１本ずつ貼付し、同様に表裏に合計４本／体の歪みゲージを貼付た後、試験機（島津製作所製オートグラフＡＧ−１００ＴＢ型）のクロスヘッド速度を１．３ｍｍ／ｍｉｎ．とし、供試体の破断まで荷重を負荷した。 This CFRP was cut into a rectangle of 152.4 mm in the 0 degree direction and 101.6 mm in the 90 degree direction according to JIS K7089 (1996), and a falling weight impact (impact energy of 30.5 J) was applied to the center. For the impact test, a falling weight impact tester (GRC-8250 made by Dynapup) was used, and after the impact, the damaged area of the specimen was measured by an ultrasonic flaw detector (M610 made by Canon). After the impact, the strength test of the specimen was performed by applying one strain gauge to each of the left and right sides of the specimen at 25.4 mm from the top and 25.4 mm from the side. After affixing the gauge, the crosshead speed of the testing machine (Autograph AG-100TB type, manufactured by Shimadzu Corporation) was adjusted to 1.3 mm / min. The load was applied until the specimen was broken.
〔単位質量当りのカルボキシル基量〕
中和滴定法により測定される単位質量当りのカルボキシル基量（Ｂ）（単位は〔ｅｑ／ｇ〕）は以下の通り測定した。
濃度Ｎ〔ｅｑ／ｍＬ〕の炭酸水素ナトリウムの溶液Ｙ〔ｍＬ〕を塩酸（ファクター：ｆ）により滴定を行い、ブランク滴定量Ｋ〔ｍＬ〕を求めた。次いで、濃度Ｎ〔ｅｑ／ｍＬ〕の炭酸水素ナトリウム水溶液Ｘ〔ｍＬ〕に炭素繊維Ｍ〔ｇ〕を浸漬した後、上澄み液をＹ〔ｍＬ〕採取し、塩酸（ファクター：ｆ）により、逆滴定を行い、滴定量Ｌ〔ｍＬ〕を求めた。測定結果から、下記式
カルボキシル基量〔ｅｑ／ｇ〕＝（（Ｋ-Ｌ）×Ｎ×f×Ｘ／Ｙ）／Ｍ
で求めた。
[Amount of carboxyl groups per unit mass]
The carboxyl group amount (B) (unit: [eq / g]) per unit mass measured by the neutralization titration method was measured as follows.
A sodium bicarbonate solution Y [mL] having a concentration of N [eq / mL] was titrated with hydrochloric acid (factor: f) to obtain a blank titer K [mL]. Next, after immersing the carbon fiber M [g] in a sodium hydrogen carbonate aqueous solution X [mL] having a concentration of N [eq / mL], the supernatant was collected from Y [mL] and back titrated with hydrochloric acid (factor: f). And titrated amount L [mL] was determined. From the measurement results, the following formula carboxyl group amount [eq / g] = ((KL) × N × f × X / Y) / M
I asked for it.
〔単位質量当りのヒドロキシル基量〕
中和滴定法により測定される単位質量当りのヒドロキシル基量（Ａ）（単位は〔ｅｑ／ｇ〕）は以下の通り測定した。
濃度Ｎ〔ｅｑ／ｍＬ〕の水酸化ナトリウムの溶液Ｙ〔ｍＬ〕を塩酸（ファクター：ｆ）により滴定を行い、ブランク滴定量Ｋ〔ｍＬ〕を求めた。次いで、濃度Ｎ〔ｅｑ／ｍＬ〕の水酸化ナトリウム水溶液Ｘ〔ｍＬ〕に炭素繊維Ｍ〔ｇ〕を浸漬した後、上澄み液をＹ〔ｍＬ〕採取し、塩酸（ファクター：ｆ）により、逆滴定を行い、滴定量Ｌ〔ｍＬ〕を求めた。
濃度ｎ〔ｅｑ／ｍＬ〕の炭酸ナトリウムの溶液ｙ〔ｍＬ〕を塩酸（ファクター：ｆ）により滴定を行い、ブランク滴定量ｋ〔ｍＬ〕を求めた。次いで、濃度ｎ〔ｅｑ／ｍＬ〕の炭酸ナトリウム水溶液ｘ〔ｍＬ〕に炭素繊維ｍ〔ｇ〕を浸漬した後、上澄み液をｙ〔ｍＬ〕採取し、塩酸（ファクター：ｆ）により、逆滴定を行い、滴定量ｌ〔ｍＬ〕を求めた。測定結果から、下記式
ヒドロキシル基量〔ｅｑ／ｇ〕＝（（Ｋ-Ｌ）×Ｎ×f×Ｘ／Ｙ）／Ｍ ― （（ｋ-ｌ）×ｎ×f×x／y）／ｍ
で求めた。
[Amount of hydroxyl groups per unit mass]
The hydroxyl group amount (A) (unit: [eq / g]) per unit mass measured by the neutralization titration method was measured as follows.
A sodium hydroxide solution Y [mL] having a concentration of N [eq / mL] was titrated with hydrochloric acid (factor: f) to obtain a blank titer K [mL]. Next, after immersing the carbon fiber M [g] in a sodium hydroxide aqueous solution X [mL] having a concentration of N [eq / mL], the supernatant was collected from Y [mL] and back titrated with hydrochloric acid (factor: f). And titrated amount L [mL] was determined.
A sodium carbonate solution y [mL] having a concentration of n [eq / mL] was titrated with hydrochloric acid (factor: f) to obtain a blank titer k [mL]. Next, after immersing the carbon fiber m [g] in a sodium carbonate aqueous solution x [mL] having a concentration of n [eq / mL], y [mL] of the supernatant was collected and back titrated with hydrochloric acid (factor: f). The titer l [mL] was determined. From the measurement results, the following formula hydroxyl group amount [eq / g] = ((KL) × N × f × X / Y) / M − ((k−l) × n × f × x / y) / m
I asked for it.
（実施例１）
アクリロニトリル９５質量％／アクリル酸メチル４質量％／イタコン酸１質量％よりなる共重合体紡糸原液を湿式紡糸し、水洗、乾燥、延伸、オイリングして繊度１．２８ｄｔｅｘ、フィラメント数 １２０００の前駆体繊維を得た。この前駆体繊維（プレカーサー）を２２０〜２６０℃の熱風循環型の耐炎化炉を６０分間かけて通過せしめて耐炎化処理するに際して６％の伸長操作を施した。次に得られた耐炎化繊維を純粋な窒素気流中３００〜６００℃の温度勾配を有する第一炭素化炉を通過せしめるに際して２〜８％の伸長を加え、更に同雰囲気中１１００〜１２００℃の最高温度を有する第二炭素化炉中において炭素化処理して炭素繊維を得た。引き続いて、３ユニットからなる多段表面処理浴を用いて、非接触電解処理を行った。電解質溶液として硫酸アンモニウム８質量％水溶液を使用し、走行中の炭素繊維を陽極として、被処理炭素繊維１ｇ当り３０クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて電位を逆転させ、還元処理を施した。次いで炭酸ナトリウム８質量％水溶液（ｐＨ＝１２．１）で１０秒及び温水９０℃で１分間洗浄した後乾燥、サイジング処理し、炭素繊維を得た。その結果、表１に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は３．９１であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
Example 1
Precursor fiber having a fineness of 1.28 dtex and a filament number of 12000 is obtained by wet spinning a copolymer spinning stock solution of 95% by mass of acrylonitrile / 4% by mass of methyl acrylate / 1% by mass of itaconic acid, washing with water, drying, stretching and oiling. Got. This precursor fiber (precursor) was passed through a hot air circulation type flameproofing furnace at 220 to 260 ° C. over 60 minutes to perform a flameproofing treatment, and an extension operation of 6% was performed. Next, when the obtained flame-resistant fiber is passed through a first carbonization furnace having a temperature gradient of 300 to 600 ° C. in a pure nitrogen stream, elongation of 2 to 8% is added, and further 1100 to 1200 ° C. in the same atmosphere. Carbon fiber was obtained by carbonization in a second carbonization furnace having the highest temperature. Subsequently, non-contact electrolytic treatment was performed using a multi-stage surface treatment bath composed of 3 units. Using an 8% by weight aqueous solution of ammonium sulfate as the electrolyte solution, using the running carbon fiber as the anode, conducting an energization treatment with the counter electrode so that the amount of electricity is 30 coulomb per 1 g of the carbon fiber to be treated. The potential was reversed and reduction treatment was performed. Next, it was washed with an 8% by mass aqueous solution of sodium carbonate (pH = 12.1) for 10 seconds and warm water at 90 ° C. for 1 minute, followed by drying and sizing treatment to obtain carbon fibers. As a result, carbon fibers having various physical properties shown in Table 1 with a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa were obtained. The A / B value was 3.91. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（実施例２）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り１５クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて電位を逆転させ、還元処理を施して得られた炭素繊維を、炭酸ナトリウム８質量％水溶液で１０秒及び温水９０℃で１分間洗浄した後乾燥、サイジング処理し、炭素繊維を得た。その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は２．６３であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Example 2)
Spinning, flameproofing, and carbonization were carried out in the same manner as in Example 1, and the energization treatment was performed with the counter electrode so that the amount of electricity was 15 coulomb per 1 g of carbon fiber to be treated, and the potential was reversed in the final unit. The carbon fiber obtained by the reduction treatment was washed with an 8% by mass aqueous solution of sodium carbonate for 10 seconds and at 90 ° C. for 1 minute, and then dried and sizing to obtain carbon fibers. As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 2.63. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（比較例１）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り３０クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて電位を逆転させ、還元処理を施して得られた炭素繊維を、水洗水のみで洗浄後、乾燥、サイジング処理し、炭素繊維を得た。その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は１．５５であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Comparative Example 1)
Spinning, flameproofing, and carbonization were carried out in the same manner as in Example 1, and the energization treatment was performed with the counter electrode so that the amount of electricity was 30 coulomb per gram of carbon fiber to be treated, and the potential was reversed in the final unit. The carbon fiber obtained by performing the reduction treatment was washed with water only and then dried and sizing to obtain carbon fiber. As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 1.55. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（比較例２）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り３０クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて酸化処理を施して得られた炭素繊維を、炭酸ナトリウム８質量％水溶液で１０秒及び温水９０℃で１分間洗浄した後乾燥、サイジング処理し、炭素繊維を得た。その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は５．４２であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Comparative Example 2)
Spinning, flameproofing, and carbonization were carried out in the same manner as in Example 1, and an electric current treatment was conducted with the counter electrode so that the amount of electricity was 30 coulomb per gram of carbon fiber to be treated, and an oxidation treatment was carried out in the final unit. The carbon fiber obtained was washed with an 8% by weight aqueous solution of sodium carbonate for 10 seconds and warm water at 90 ° C. for 1 minute, then dried and sizing to obtain carbon fibers. As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 5.42. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（比較例３）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り５クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて電位を逆転させ、還元処理を施して得られた炭素繊維を、炭酸ナトリウム８質量％水溶液で１０秒及び温水９０℃で１分間洗浄した後乾燥、サイジング処理し、炭素繊維を得た。その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は２．５７であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Comparative Example 3)
Spinning, flameproofing, and carbonization were performed in the same manner as in Example 1, and an energization treatment was performed with the counter electrode so that the amount of electricity was 5 coulomb per 1 g of carbon fiber to be treated, and the potential was reversed in the final unit. The carbon fiber obtained by the reduction treatment was washed with an 8% by mass aqueous solution of sodium carbonate for 10 seconds and at 90 ° C. for 1 minute, and then dried and sizing to obtain carbon fibers. As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 2.57. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（比較例４）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り３０クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて酸化処理を施して得られた炭素繊維を、水洗水のみで洗浄後、乾燥、サイジング処理し、炭素繊維を得た。
その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は２．６４であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Comparative Example 4)
Spinning, flameproofing, and carbonization were carried out in the same manner as in Example 1, and an electric current treatment was conducted with the counter electrode so that the amount of electricity was 30 coulomb per gram of carbon fiber to be treated, and an oxidation treatment was carried out in the final unit. The carbon fiber obtained in this way was washed with only washing water, dried and sizing to obtain carbon fiber.
As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 2.64. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
（比較例５）
実施例１と同様にて紡糸、耐炎化、炭素化を行い、被処理炭素繊維１ｇ当り３０クーロンの電気量となる様に対極との間で通電処理を行い、最終ユニットにて電位を逆転させ、還元処理を施して得られた炭素繊維を、水酸化ナトリウム４質量％水溶液（ｐＨ＝１４）で１０秒及び温水９０℃で１分間洗浄した後乾燥、サイジング処理し、炭素繊維を得た。その結果、表1に示す諸物性の繊維直径７μｍ、ストランド引張弾性率２４０ＧＰａの炭素繊維を得た。Ａ／Ｂ値は１６．０であった。また、本炭素繊維を用いて調製する複合材料のコンポジット評価結果を表２に、上降伏点荷重、下降伏点荷重、最大点荷重の測定結果を表３に示す。
(Comparative Example 5)
Spinning, flameproofing, and carbonization were carried out in the same manner as in Example 1, and the energization treatment was performed with the counter electrode so that the amount of electricity was 30 coulomb per gram of carbon fiber to be treated, and the potential was reversed in the final unit. The carbon fiber obtained by the reduction treatment was washed with a 4% by weight aqueous solution of sodium hydroxide (pH = 14) for 10 seconds and warm water at 90 ° C. for 1 minute, and then dried and sizing to obtain carbon fibers. As a result, carbon fibers having a fiber diameter of 7 μm and a strand tensile modulus of 240 GPa having various physical properties shown in Table 1 were obtained. The A / B value was 16.0. Table 2 shows composite evaluation results of composite materials prepared using the present carbon fiber, and Table 3 shows measurement results of upper yield point load, lower yield point load, and maximum point load.
実施例１、２の炭素繊維は、アルカリ処理によっても強度や弾性率の低下は認められなかった。この炭素繊維を用いた複合材料は、本発明の範囲外の炭素繊維を用いた複合材料（比較例１〜５）と比較してＣＡＩ強度が高かった。また、実施例１、２の炭素繊維を用いて製造した複合材料の層間剥離亀裂進展抵抗は、比較例１、２、４、５の炭素繊維を用いて製造した複合材料のように、荷重が下がる部分は認められず、高い層間強度を有していた。 In the carbon fibers of Examples 1 and 2, no decrease in strength or elastic modulus was observed even by alkali treatment. The composite material using the carbon fiber had a higher CAI strength than the composite material using the carbon fiber outside the scope of the present invention (Comparative Examples 1 to 5). Moreover, the delamination crack growth resistance of the composite material manufactured using the carbon fibers of Examples 1 and 2 is the same as that of the composite material manufactured using the carbon fibers of Comparative Examples 1, 2, 4, and 5. No lowering part was observed, and the interlayer strength was high.
比較例１の炭素繊維は、アルカリ処理を行っていないため、Ａ／Ｂ値が本発明の範囲外となった。そのため、この炭素繊維を原料とする複合材料は、アルカリ処理を行った炭素繊維を原料とする複合材料（実施例１）と比較してＣＡＩ強度が低かった。また、層間剥離亀裂進展抵抗において荷重が下がる部分が認められた。 Since the carbon fiber of Comparative Example 1 was not subjected to alkali treatment, the A / B value was out of the scope of the present invention. Therefore, the composite material using carbon fiber as a raw material had lower CAI strength than the composite material using carbon fiber subjected to alkali treatment as a raw material (Example 1). Moreover, the part where a load falls was recognized in the delamination crack propagation resistance.
比較例２の炭素繊維は、通電処理の最終ユニットにおいて還元処理を行わなかったため、Ａ／Ｂ値が本発明の範囲外となった。そのため、この炭素繊維を原料とする複合材料は、アルカリ処理を行った炭素繊維を原料とする複合材料（実施例１）と比較してＣＡＩ強度が低かった。 Since the carbon fiber of Comparative Example 2 was not subjected to the reduction treatment in the final unit of the energization treatment, the A / B value was out of the scope of the present invention. Therefore, the composite material using carbon fiber as a raw material had lower CAI strength than the composite material using carbon fiber subjected to alkali treatment as a raw material (Example 1).
比較例３の炭素繊維は、通電処理の電気量が低かったため、Ｏ／Ｃ値が本発明の範囲外となった。そのため、この炭素繊維を原料とする複合材料は、本発明の炭素繊維を原料とする複合材料（実施例１）と比較してＣＡＩ強度が低かった。 The carbon fiber of Comparative Example 3 had an O / C value outside the scope of the present invention because the amount of electricity in the energization treatment was low. Therefore, the composite material using carbon fiber as a raw material had lower CAI strength than the composite material using carbon fiber of the present invention (Example 1).
比較例４の炭素繊維は、通電処理の最終ユニットにおいて還元処理を行わず、さらにアルカリ処理も行わなかったため、Ｏ／Ｃ値が本発明の範囲外となった。そのため、この炭素繊維を原料とする複合材料は、通電処理の最終ユニットにおいて還元処理を行い、アルカリ処理を行った炭素繊維を原料とする複合材料（実施例１）と比較してＣＡＩ強度が低かった。 The carbon fiber of Comparative Example 4 was not subjected to the reduction treatment in the final unit of the energization treatment, and further was not subjected to the alkali treatment, so the O / C value was out of the scope of the present invention. Therefore, the composite material using carbon fiber as a raw material is reduced in CAI strength compared to the composite material (Example 1) in which the reduction treatment is performed in the final unit of the energization treatment and the carbon fiber subjected to alkali treatment is used as a raw material. It was.
比較例５の炭素繊維は、水酸化ナトリウムを用いてアルカリ処理を行い、カルボキシル基の量を減らした。しかし、ｐＨが本発明の範囲外であったため、官能基比率の制御が十分に行えず、Ａ／Ｂ値が本発明の範囲外となった。そのため、この炭素繊維を原料とする複合材料は、炭酸ナトリウムを用いてアルカリ処理を行った炭素繊維を原料とする複合材料（実施例１）と比較してＣＡＩ強度が低かった。 The carbon fiber of Comparative Example 5 was subjected to an alkali treatment using sodium hydroxide to reduce the amount of carboxyl groups. However, since the pH was outside the range of the present invention, the functional group ratio could not be sufficiently controlled, and the A / B value was outside the range of the present invention. Therefore, the composite material using carbon fiber as a raw material had a lower CAI strength than the composite material using carbon fiber as a raw material (Example 1) subjected to alkali treatment using sodium carbonate.
１・・・上降伏点
２・・・下降伏点
３・・・最大点
1 ... Up-
Claims (3)
電解処理を施して炭素繊維表層部の官能基量を増加させたポリアクリロニトリル系炭素繊維にｐＨ８〜１３のアルカリ性水溶液を接触させることにより、
Ｘ線光電子分光器により測定される表面酸素濃度を８〜２５％、中和滴定法により測定される単位質量当りのヒドロキシル基量（Ａ）（単位はｅｑ／ｇ）と、単位質量当りのカルボキシル基量（Ｂ）（単位はｅｑ／ｇ）とから算出されるＡ／Ｂの値を２．０〜５．０に変化させる工程を有することを特徴とする請求項１記載のポリアクリロニトリル系炭素繊維の製造方法。 A method for producing polyacrylonitrile-based carbon fiber by subjecting polyacrylonitrile-based carbon fiber to surface treatment,
By contacting an alkaline aqueous solution having a pH of 8 to 13 with polyacrylonitrile-based carbon fiber that has been subjected to electrolytic treatment to increase the amount of functional groups on the surface portion of the carbon fiber,
Surface oxygen concentration measured by X-ray photoelectron spectrometer is 8 to 25%, hydroxyl group amount per unit mass (A) (unit is eq / g) measured by neutralization titration method, and carboxyl per unit mass The polyacrylonitrile-based carbon according to claim 1, further comprising a step of changing the value of A / B calculated from the base amount (B) (unit: eq / g) to 2.0 to 5.0. A method for producing fibers.
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| JP2012102439A (en) * | 2010-11-12 | 2012-05-31 | Toho Tenax Co Ltd | Surface treatment method of carbon fiber |
| CN108442122A (en) * | 2018-04-26 | 2018-08-24 | 湖南师范大学 | Sizing agent for preparing quartz fiber/nitrile resin composite material |
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| JP2012102439A (en) * | 2010-11-12 | 2012-05-31 | Toho Tenax Co Ltd | Surface treatment method of carbon fiber |
| CN108442122A (en) * | 2018-04-26 | 2018-08-24 | 湖南师范大学 | Sizing agent for preparing quartz fiber/nitrile resin composite material |
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