JP2007002392A - Carbon fiber bundle and method for producing the same - Google Patents
Carbon fiber bundle and method for producing the same Download PDFInfo
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本発明は、層間剪断強度(ILSS)変動が小さいポリアクリロニトリル系炭素繊維束およびその製造方法に関する。 The present invention relates to a polyacrylonitrile-based carbon fiber bundle having a small interlayer shear strength (ILSS) variation and a method for producing the same.
炭素繊維は他の補強用繊維に比べ比強度および比弾性率が大きいという機械的特性によって複合材料(コンポジット)の補強繊維として極めて優れた性能を有する。この炭素繊維を補強繊維とする複合材料は航空、宇宙用途あるいは自動車、船舶等の輸送機械における軽量化もしくは燃費低減の要請から、それらの構造材として広く、大量に使用されるようになってきた。しかしながら、炭素繊維の優れた機械的性能を複合材料に反映させるためには複合材料の母材樹脂と炭素繊維が十分に接着し一体化する必要がある。 Carbon fiber has extremely excellent performance as a reinforcing fiber of a composite material (composite) due to mechanical properties such that the specific strength and specific elastic modulus are larger than those of other reinforcing fibers. This composite material using carbon fiber as a reinforced fiber has been widely used as a structural material for aerospace, space use, or a demand for weight reduction or fuel consumption reduction in transportation equipment such as automobiles and ships. . However, in order to reflect the excellent mechanical performance of the carbon fiber in the composite material, the base material resin of the composite material and the carbon fiber need to be sufficiently bonded and integrated.
一般的に炭素繊維と母材樹脂との接着性評価は、炭素繊維に樹脂を含浸させた層間剪断強度(ILSS)が用いられる。そのために通常炭素繊維には焼成後、電解酸化、薬液酸化、気相酸化といった酸化処理が施され、炭素繊維表面に酸素含有官能基を導入し、母材樹脂との濡れ性を向上させている。このような酸化処理によって得られる炭素繊維の表面
特性について、特許文献1には炭素繊維最表面の官能基を特定することによる母材樹脂との接着強度の向上について、特許文献2には表面処理後、複数のエポキシ基を有する脂肪酸化合物をサイジング剤として付与することによる接着強度の向上について開示されている。
In general, evaluation of adhesion between carbon fiber and base material resin uses interlaminar shear strength (ILSS) in which carbon fiber is impregnated with resin. For this purpose, carbon fibers are usually subjected to oxidation treatment such as electrolytic oxidation, chemical solution oxidation, and gas phase oxidation after firing, and oxygen-containing functional groups are introduced on the surface of carbon fibers to improve wettability with the base resin. . Regarding the surface characteristics of carbon fibers obtained by such an oxidation treatment, Patent Document 1 discloses improvement of adhesive strength with a base resin by specifying a functional group on the outermost surface of carbon fiber, and Patent Document 2 discloses surface treatment. Later, it is disclosed that the adhesion strength is improved by applying a fatty acid compound having a plurality of epoxy groups as a sizing agent.
ところが炭素繊維表面はグラファイト結晶面で覆われているだけではなく多くの不純物が付着存在しており、炭素繊維束と樹脂との間に不純物が介入することによる樹脂接着の低下がひきおこされる。これらの不純物としては、焼成工程で発生するガス成分のうち分子量の大きな金属化合物からなるタールミストがその後の工程で加熱され無機質化した焼結物、プリカーサー油剤として用いられたシリコーン系油剤に起因するシリカ化合物または含硫黄油剤に起因する硫黄化合物等があげられる。 However, the carbon fiber surface is not only covered with the graphite crystal plane, but also has many impurities adhering to it, causing a decrease in resin adhesion due to the intervention of impurities between the carbon fiber bundle and the resin. These impurities are derived from a sintered product in which tar mist composed of a metal compound having a large molecular weight among the gas components generated in the firing process is heated and mineralized in the subsequent process, and a silicone-based oil used as a precursor oil. Examples thereof include a sulfur compound derived from a silica compound or a sulfur-containing oil agent.
不純物の洗浄手段として特許文献3では、表面処理を施された炭素繊維をアルカリ水溶液(PH>8)、続いて酸性水溶液(PH<6)中で洗浄し、中和するまで洗浄した後アルカリ洗浄後酸性化洗浄し中性になるまで水洗洗浄する方法が開示されている。これらの不純物は、耐炎化繊維の熱分解が急激かつ大半進行する400℃〜600℃の温度域で、耐炎化繊維の熱分解と共に排ガスとして排出されるが、排出されずに残った不純物はその後1000℃〜2000℃の熱処理を受けることで炭素繊維と密に接着し、表面処理工程での除去を困難にしていることが検討の結果わかっている。熱分解中に発生するタールミストの汚染、再付着防止方法として、例えば特許文献4、特許文献5では排ガスの抜き出し口を熱分解反応温度域に調整すること、特許文献6では、加熱炉を順次高温となるように設定した複数の加熱域に区画することが開示されている。しかしながら、加熱炉内の温度が常時均一に保たれている場合は問題ないが、耐炎化繊維熱分解により発生するガス、加熱炉内を不活性ガスに保つための供給ガス等が加熱炉内で対流をおこし、設定された複数の加熱域区画における設定温度維持が非常に困難である。かかる加熱炉内の経時的な温度変動が、不純物付着バラツキを引き起こし、最終的に炭素繊維束の樹脂接着バラツキにつながることが今回の検討の結果わかったが、その対策がなされなければ、洗浄を行っても不純物付着のバラツキは十分には解決されず、結果炭素繊維束の長手方向、複数の同一焼成炭素繊維束間のバラツキ解決に至らない。 In Patent Document 3, as a means for cleaning impurities, the surface-treated carbon fiber is washed in an alkaline aqueous solution (PH> 8), then in an acidic aqueous solution (PH <6), washed until neutralized, and then washed with alkali. A method of washing with water until post-acidification washing and neutralization is disclosed. These impurities are discharged as exhaust gas together with the thermal decomposition of the flame resistant fiber in the temperature range of 400 ° C. to 600 ° C. where the thermal decomposition of the flame resistant fiber proceeds rapidly and mostly. As a result of the examination, it is known that the heat treatment at 1000 ° C. to 2000 ° C. causes the carbon fiber to adhere closely to the carbon fiber and makes it difficult to remove it in the surface treatment process. As a method for preventing tar mist contamination and re-adhesion generated during thermal decomposition, for example, in Patent Document 4 and Patent Document 5, the exhaust gas outlet is adjusted to the thermal decomposition reaction temperature range, and in Patent Document 6, the heating furnace is sequentially installed. It is disclosed to partition into a plurality of heating zones set to be high temperature. However, there is no problem if the temperature in the heating furnace is always kept uniform, but the gas generated by the flame-resistant fiber pyrolysis, the supply gas for keeping the heating furnace in an inert gas, etc. It is very difficult to maintain a set temperature in a plurality of heating zone sections set by convection. As a result of this study, it was found that temperature fluctuations in the heating furnace over time cause variations in the adhesion of impurities and ultimately leads to variations in the resin adhesion of the carbon fiber bundles. Even if it is performed, the variation in impurity adhesion is not sufficiently solved, and as a result, the variation in the longitudinal direction of the carbon fiber bundle and between a plurality of the same calcined carbon fiber bundles cannot be solved.
このような現状に鑑み、本発明者らは炭素繊維束における樹脂接着強度の長手方向、機幅方向における変動率改善を図るために、炭素繊維表面不純物を取り除くことを見出し、本発明を完成するに至った。
本発明の目的は、層間剪断強度(ILSS)バラツキすなわち変動率が小さい品質安定性に優れた炭素繊維およびその製造方法を提供することにある。 An object of the present invention is to provide a carbon fiber excellent in quality stability having a small variation in interlaminar shear strength (ILSS), that is, a fluctuation rate, and a method for producing the same.
前記した目的を達成するために、本発明の炭素繊維束は、次のいずれかの構成を有する。すなわち、層間剪断強度(ILSS)の長手方向変動率が2.5%以下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束、または、複数本の炭素繊維用前駆体繊維を同一焼成設備内で並行して焼成することで得られる、層間剪断強度(ILSS)の機幅方向の変動率が2.5%以下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束である。 In order to achieve the above-described object, the carbon fiber bundle of the present invention has one of the following configurations. That is, a polyacrylonitrile-based carbon fiber bundle or a plurality of precursor fibers for carbon fibers are characterized in that the longitudinal shear rate of interlaminar shear strength (ILSS) is 2.5% or less in the same firing facility. The polyacrylonitrile-based carbon fiber bundle is characterized in that the variation rate in the machine width direction of the interlaminar shear strength (ILSS) obtained by firing in parallel is 2.5% or less.
また、前記した目的を達成するために、本発明の炭素繊維束の製造方法は、次のいずれかの構成を有する。すなわち、ポリアクリロニトリル系前駆体糸条を酸化雰囲気中で加熱することによって得られた耐炎化糸条を前炭化処理、炭化処理して炭素繊維束を製造する方法において、前炭化処理の際、不活性雰囲気に保たれた加熱炉における経時的温度変動率、機幅方向の温度変動率を2.5%以下に制御することを特徴とする炭素繊維束の製造方法、または、ポリアクリロニトリル系前駆体糸条を酸化雰囲気中で加熱することによって得られた耐炎化糸条を前炭化処理、炭化処理して炭素繊維束を製造する方法において、不活性雰囲気に保たれた加熱炉中で300〜800℃領域で前炭化処理するに際し、糸条を加熱処理するための不活性ガスを300℃以上に加熱してから加熱炉に供給することを特徴とする炭素繊維束の製造方法である。 In order to achieve the above-described object, the method for producing a carbon fiber bundle of the present invention has one of the following configurations. That is, in a method for producing a carbon fiber bundle by pre-carbonizing and carbonizing a flame resistant yarn obtained by heating a polyacrylonitrile-based precursor yarn in an oxidizing atmosphere, A method for producing a carbon fiber bundle, or a polyacrylonitrile-based precursor, characterized by controlling a temporal temperature fluctuation rate in a heating furnace maintained in an active atmosphere and a temperature fluctuation rate in a machine width direction to 2.5% or less In a method for producing a carbon fiber bundle by pre-carbonizing and carbonizing a flame-resistant yarn obtained by heating a yarn in an oxidizing atmosphere, 300 to 800 in a heating furnace maintained in an inert atmosphere. In the pre-carbonization treatment in the ° C region, an inert gas for heating the yarn is heated to 300 ° C or higher and then supplied to a heating furnace.
本発明によれば、以下に説明するとおり、炭素繊維束の長手方向、機幅方向の層間剪断強度(ILSS)の変動率を小さくしてその品質安定性を向上せしめ、その結果高次加工品の品質安定化を達成することができる。 According to the present invention, as described below, the fluctuation rate of the interlaminar shear strength (ILSS) in the longitudinal direction and the machine width direction of the carbon fiber bundle is reduced to improve its quality stability, and as a result, a high-order processed product. Quality stabilization can be achieved.
本発明の炭素繊維束の繊維糸条形態としては、前駆体繊維に撚りをかけて焼成して得られる有撚糸、その有撚糸の撚りを解いて得られる解撚糸、前駆体繊維に実質的に撚りをかけずに熱処理を行う無撚糸などが使用できるが、高次加工性を考慮すると無撚糸または解撚糸が好ましく、さらに高次加工時の拡がり性の観点から無撚糸が好ましい。
さらに、本発明の炭素繊維束は、炭素繊維束の長手方向層間剪断強度(ILSS)変動率が2.5%以下であることが必要であり、2.0%以下であればより好ましく、1.5%以下であればさらに好ましい。
As the fiber yarn form of the carbon fiber bundle of the present invention, the twisted yarn obtained by twisting and firing the precursor fiber, the untwisted yarn obtained by untwisting the twisted yarn, and the precursor fiber substantially Although untwisted yarns that are heat-treated without twisting can be used, non-twisted yarns or untwisted yarns are preferable in consideration of higher-order processability, and non-twisted yarns are more preferable from the viewpoint of spreadability during higher-order processing.
Furthermore, in the carbon fiber bundle of the present invention, the rate of change in the longitudinal interlaminar shear strength (ILSS) of the carbon fiber bundle needs to be 2.5% or less, more preferably 2.0% or less. More preferably, it is 5% or less.
炭素繊維束の長手方向層間剪断強度(ILSS)変動率が2.5%を超えると、プリプレグ成形、フィラメントワインディング成形などの高次加工において、炭素繊維束と母材樹脂との樹脂接着安定性が低下してくる。そのため成形品の剪断強度低下がおこり、製品収率低下につながる。多糸条を使用するプリプレグにおいては、層間剪断強度の長手方向のバラツキは多少なりとも隣接糸によりカバーされる面があるが、特に数本の炭素繊維束を原料として加工するフィラメントワインディング成形においては、炭素繊維束の層間剪断強度(ILSS)の長手方向の安定性が非常に問われる。数本の糸を使用するため、長手方向のばらつきは、成形品の品質に直接影響を及ぼし、そのまま製品収率につながる。検討の結果、樹脂接着不足による剪断強度低下は、炭素繊維束の層間剪断強度(ILSS)が、2.5%以下であると影響が殆どないことがわかった。 If the variation rate of the longitudinal interlaminar shear strength (ILSS) of the carbon fiber bundle exceeds 2.5%, the resin adhesion stability between the carbon fiber bundle and the base material resin is increased in higher processing such as prepreg molding and filament winding molding. It will decline. For this reason, the shear strength of the molded product is reduced, leading to a reduction in product yield. In prepregs using multiple yarns, the longitudinal variation in interlaminar shear strength is somewhat covered by adjacent yarns, but in particular, filament winding molding that uses several carbon fiber bundles as raw materials. The longitudinal stability of the interlaminar shear strength (ILSS) of the carbon fiber bundle is very important. Since several yarns are used, the variation in the longitudinal direction directly affects the quality of the molded product and directly leads to the product yield. As a result of the study, it was found that the decrease in shear strength due to insufficient resin adhesion had little effect when the interlaminar shear strength (ILSS) of the carbon fiber bundle was 2.5% or less.
ここで、本発明において、炭素繊維束の層間剪断強度(ILSS)、またその長手方向変動率は次の様にして求められる。 Here, in the present invention, the interlaminar shear strength (ILSS) of the carbon fiber bundle and the longitudinal variation rate thereof are obtained as follows.
炭素繊維束に硬化剤として三フッ化ホウ素モノエチルアミンを添加したビスフェノールA型エポキシ樹脂をそれぞれの重量比6:4の比率となるよう含浸し、170℃オーブンで1時間硬化させ試験片を作成する。作成した試験片をASTM−D−2344に基づき3点曲げ方式で測定し層間剪断強度を求める。層間剪断強度は次式で求められる。 A test piece is prepared by impregnating a carbon fiber bundle with bisphenol A type epoxy resin added with boron trifluoride monoethylamine as a curing agent in a weight ratio of 6: 4 and curing in a 170 ° C. oven for 1 hour. . The prepared test piece is measured by a three-point bending method based on ASTM-D-2344 to determine the interlaminar shear strength. Interlaminar shear strength is determined by the following equation.
層間剪断強度(ζ:Pa)=(3×P)/(4×b×t)
ここで、Pは最大荷重(kg)、bは試験片の幅(mm)、tは試験片の厚さ(mm)である。
Interlaminar shear strength (ζ: Pa) = (3 × P) / (4 × b × t)
Here, P is the maximum load (kg), b is the width (mm) of the test piece, and t is the thickness (mm) of the test piece.
測定した炭素繊維束の層間剪断強度について次式に基づいて変動率を求める。 The variation rate is obtained based on the following formula for the measured interlaminar shear strength of the carbon fiber bundle.
長手方向層間剪断強度変動率(%)=(σ1/A1)×100
式で使用するσ1は測定層間剪断強度全データの標準偏差、A1は測定層間剪断強度全データの平均値である。ここで全データとは各ボビンから長手方向に100m毎に採取した10個の炭素繊維束についての層間剪断強度データを指す。
Longitudinal interlayer shear strength fluctuation rate (%) = (σ1 / A1) × 100
Σ1 used in the equation is a standard deviation of all measured interlayer shear strength data, and A1 is an average value of all measured interlayer shear strength data. Here, the total data refers to interlaminar shear strength data for 10 carbon fiber bundles collected every 100 m in the longitudinal direction from each bobbin.
また、炭素繊維束の層間剪断強度(ILSS)バラツキの要因として機幅方向のバラツキも考えられるため、これを低減することが重要である。通常効率的に生産するために、炭素繊維束の前駆体繊維束であるポリアクリロニトリル系などからなる繊維束を複数仕掛けて、平行に走行させて同時に焼成し、複数の炭素繊維束を同時に得ているが、それら同
時に焼成される複数の炭素繊維束間の機幅方向における層間剪断強度(ILSS)変動率は以下のとおりに求める。
Moreover, since the variation in the machine width direction is also considered as a factor of the interlaminar shear strength (ILSS) variation of the carbon fiber bundle, it is important to reduce this. Usually, in order to produce efficiently, multiple fiber bundles made of polyacrylonitrile, etc., which are precursor fiber bundles of carbon fiber bundles, are placed in parallel and fired simultaneously to obtain multiple carbon fiber bundles simultaneously. However, the fluctuation rate of the interlaminar shear strength (ILSS) in the machine width direction between a plurality of carbon fiber bundles fired at the same time is obtained as follows.
機幅方向層間剪断強度変動率(%)=(σ2/A2)×100
式で使用するσ2は測定層間剪断強度全データの標準偏差、A2は測定層間剪断強度全データの平均値である。ここで全データとは、MIL−STD−414(1957)にて規定されるサンプリング方法に従い、同時焼成したロットの中からサンプリングした28ボビンそれぞれのボビン最表層から採取した炭素繊維束試験片についての層間剪断強度デー
タを指す。
Machine width direction interlaminar shear strength fluctuation rate (%) = (σ2 / A2) × 100
Σ2 used in the equation is a standard deviation of all measured interlayer shear strength data, and A2 is an average value of all measured interlayer shear strength data. Here, the total data refers to the carbon fiber bundle specimens taken from the outermost layer of each of the 28 bobbins sampled from the co-fired lots according to the sampling method specified in MIL-STD-414 (1957). Refers to interlaminar shear strength data.
次に、本発明の炭素繊維束の製造方法について説明する。 Next, the manufacturing method of the carbon fiber bundle of this invention is demonstrated.
本発明に関する炭素繊維束は次のようにして製造することができる。まず、炭素繊維の前駆体としてアクリロニトリルが90重量%以上でアクリロニトリルと共重合可能なモノマーが10重量%未満の構成であるポリアクリロニトリル系繊維束を使用する。上述の共重合可能なモノマーとしてはアクリル酸、メタアクリル酸、イタコン酸またはこれらのメチルエステル、プロピルエステル、ブチルエステル、アルカリ金属塩、アンモニウム塩、アリルスルホン酸、メタリルスルホン酸、スチレンスルホン酸およびこれらのアルカリ金属塩からなるグループから選択される少なくとも1種を用いることが可能である。このポリアクリロニトリル系前駆体繊維束を空気などの酸化性雰囲気中にて200℃から300℃の温度範囲で加熱耐炎化することで耐炎化繊維を製造した後に、炭化処理前に窒素などの不活性雰囲気中にて300℃から800℃の温度範囲内で前炭化処理を行う。このように前炭化処理を施した後で窒素などの不活性雰囲気中で最高温度が1000℃から2500℃の温度範囲で炭化することで炭素繊維を製造することができる。炭化処理後に施す表面処理として、炭素繊維表面に官能基を生成して樹脂との接着性を高めることを目的として電解酸化表面処理がある。その方法には、薬液を用いる液相酸化、電解液溶液中で炭素繊維を陽極として処理する電解酸化、および相状態でのプラズマ処理などによる気相酸化等がある。表面処理方法としては、比較的取り扱い性がよく、製造コスト的に有利な電解酸化処理方法が好適に採用される。電解液としては、酸性水溶液またはアルカリ水溶液のいずれも使用可能であるが、酸性水溶液としては強酸性を示す硫酸または硝酸が好ましく、またアルカリ水溶液としては炭酸アンモニウムや炭酸水素アンモニウム等の無機アルカリの水溶液が好ましく用いられる。 The carbon fiber bundle according to the present invention can be produced as follows. First, a polyacrylonitrile fiber bundle having a constitution in which acrylonitrile is 90% by weight or more and a monomer copolymerizable with acrylonitrile is less than 10% by weight is used as a carbon fiber precursor. The above copolymerizable monomers include acrylic acid, methacrylic acid, itaconic acid or their methyl ester, propyl ester, butyl ester, alkali metal salt, ammonium salt, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid and It is possible to use at least one selected from the group consisting of these alkali metal salts. This polyacrylonitrile-based precursor fiber bundle is heated and flame-resistant in an oxidizing atmosphere such as air in a temperature range of 200 ° C. to 300 ° C. to produce flame-resistant fibers, and then inert such as nitrogen before carbonization treatment. A pre-carbonization treatment is performed in a temperature range of 300 ° C. to 800 ° C. in an atmosphere. Thus, carbon fiber can be manufactured by carbonizing in the temperature range whose maximum temperature is 1000 degreeC to 2500 degreeC in inert atmosphere, such as nitrogen, after performing a pre-carbonization process. As a surface treatment to be applied after the carbonization treatment, there is an electrolytic oxidation surface treatment for the purpose of generating a functional group on the surface of the carbon fiber and enhancing the adhesion to the resin. The method includes liquid phase oxidation using a chemical solution, electrolytic oxidation in which carbon fiber is treated as an anode in an electrolytic solution, and vapor phase oxidation by plasma treatment in a phase state. As the surface treatment method, an electrolytic oxidation treatment method that is relatively easy to handle and advantageous in terms of manufacturing cost is preferably employed. As the electrolytic solution, either an acidic aqueous solution or an alkaline aqueous solution can be used. As the acidic aqueous solution, sulfuric acid or nitric acid exhibiting strong acidity is preferable, and as the alkaline aqueous solution, an aqueous solution of an inorganic alkali such as ammonium carbonate or ammonium hydrogen carbonate is preferable. Is preferably used.
上記電解酸化処理を施したあと、炭素繊維束にサイジング剤を付与して成形品に供することができる。ここでいうサイジング剤の種類は特に限定するものではないが、エポキシ樹脂を主成分とするビスフェノールA型エポキシ樹脂や直鎖状構造を有する両端に2個以上のエポキシ基を有する脂肪族化合物が好ましく用いられる。エポキシ基としては、反応
性の高いグリシジル基が好ましい。本発明におけるエポキシ基を有する脂肪族化合物の具体例としては、グリシジルエーテル化合物ではグリセリンポリグリシジルエーテル類、またジグリシジルエーテル化合物ではポリエチレングリコールジグリシジルエーテル類が上げられる。
After the electrolytic oxidation treatment, a sizing agent can be applied to the carbon fiber bundle and used for a molded product. The kind of the sizing agent here is not particularly limited, but a bisphenol A type epoxy resin mainly composed of an epoxy resin or an aliphatic compound having two or more epoxy groups at both ends having a linear structure is preferable. Used. The epoxy group is preferably a highly reactive glycidyl group. Specific examples of the aliphatic compound having an epoxy group in the present invention include glycerin polyglycidyl ethers for glycidyl ether compounds and polyethylene glycol diglycidyl ethers for diglycidyl ether compounds.
本発明者らは鋭意調査した結果、上述した方法で製造される炭素繊維束のコンポジット成形の際、母剤樹脂との接着バラツキを引き起こす炭素繊維束の表面付着不純物が前炭化炉工程における温度分布に起因することを見出した。前炭化炉の構造としては大きく2種類ある。1つは糸条を水平に走行させ熱処理を施す横型炉であり、熱処理時の発生ガス、
供給不活性ガスによる対流が比較的小さく、炉内の温度変動も比較的小さいものの、炭素繊維自重による懸垂を抑制するため、機長を長く取れず、数回にわける熱処理が必要となり、プロセス性に優れない。もう1つは糸条を垂直に走行させ熱処理を施す縦型炉であり、炭素繊維束自重による懸垂がないために、機長を長く取ることができ、プロセス性に優
れるため、主流として用いられている。しかしながら、熱処理時の発生ガス、供給不活性ガスによる対流がおこりやすく、炉内の温度の安定を保ち難いという欠点がある。耐炎化繊維熱分解による発生ガス、供給ガス等による対流により、加熱炉内の設定温度ごとに分けられた区画内の部分的あるいは全体的な実温度が、設定温度に対し上下にばらつくのみ
ならず、経時的にも変動する。この経時的温度変動により、設定温度に対し高い温度領域より低い温度領域に向かってガスの流れがおこるために、ある時間で見た場合、低い温度領域を走行している糸に付着する不純物が高い温度領域を走行している糸に対し多くなる。つまり、前炭化炉の温度変動と糸条に付着する不純物の量は密に関係している。
As a result of earnest investigation, the inventors of the present invention have found that the carbon fiber bundle surface adhering impurities causing adhesion variation with the base resin during the composite molding of the carbon fiber bundle produced by the above-described method is the temperature distribution in the pre-carbonization furnace process. It was found to be due to. There are two main types of pre-carbonization furnace structures. One is a horizontal furnace in which the yarn runs horizontally and heat treatment is performed.
Although the convection due to the supplied inert gas is relatively small and the temperature fluctuation in the furnace is also relatively small, in order to suppress the suspension due to the carbon fiber's own weight, it is not possible to make the machine length long, and several heat treatments are required, which improves the processability. Not good. The other is a vertical furnace where the yarns run vertically and heat treatment is performed, and since there is no suspension due to the weight of the carbon fiber bundle, the length of the machine can be increased and the processability is excellent, so it is used as the mainstream. Yes. However, there is a drawback that convection due to the generated gas during the heat treatment and the supplied inert gas is likely to occur, and it is difficult to keep the temperature in the furnace stable. Due to convection due to gas generated by flameproof fiber pyrolysis, supply gas, etc., not only the partial or total actual temperature in the compartment divided for each set temperature in the heating furnace varies up and down with respect to the set temperature. , Also varies over time. Due to this temperature fluctuation over time, the gas flows toward a lower temperature range than a higher temperature range with respect to the set temperature. Therefore, when viewed at a certain time, impurities attached to the yarn running in the lower temperature range Increased for yarn running in high temperature range. That is, the temperature fluctuation of the pre-carbonization furnace and the amount of impurities adhering to the yarn are closely related.
300℃〜800℃に加熱された炉内に室温のガスを供給した場合、前炭化炉に入るとすぐに供給ガス温度が急激に上昇するためにガス温度のバラツキが局所的に生まれ、この局所的な温度変動は前炭化炉内の温度が高くなるにつれ増幅し、結果対流の原因の一つとなる。その場合、後述する測定方法により前炭化炉内実温度を30分毎に24時間測定し
たとき、炉内温度変動率は3〜10%であり、得られた炭素繊維束の層間剪断強度(ILSS)長手方向変動率・機幅方向変動率はともに2.5%を超える。これは、前記したように、温度の高いところから低いところへ、耐炎化繊維熱分解により発生するガスが流れるため、ある時間で見た場合、低い温度領域を走行している糸に付着する不純物が高い温
度領域を走行している糸に対して大きくなるためである。炭素繊維束に付着した不純物はその後炭化処理工程において1000℃〜2500℃の熱処理を受けることで炭素繊維と密に接着し、表面処理工程での除去を困難にしていることが検討の結果わかっている。特に1000℃〜2000℃の温度領域にて熱処理を受けることによる影響が大きい。しか
しながら、日本工業規格(JIS)−R−7601(1986)「樹脂含浸ストランド試験法」によって求められるストランド強度が5000MPa以上、ストランド弾性率が250GPa以上の炭素繊維束の設計には、1000℃〜2000℃の温度領域での炭化処理は不可欠である。前炭化炉内の温度変動を抑制する手段としては、供給ガスを少なくとも前炭化炉内の低温領域である300℃以上に加熱しておくことが必須である。供給ガスをあらかじめ300℃以上に加熱することで、前出の炉内温度変動率は2.5%以下に抑える事ができ、得られた炭素繊維束の層間剪断強度(ILSS)長手方向・機幅方向変動率もともに2.5%以下になり、高次加工性に優れた炭素繊維束が得られる。この効果は
、特に前出の縦型炉において顕著に見出される。さらに前炭化処理で熱反応が活性化される500℃以上に加熱すると、炉内温度安定化の点でより好ましい。供給ガスの温度上限には特に制限はないが、前炭化炉の高温領域である800℃とすることが好ましいといえる。供給ガスは、炉内のシール性を考慮すると、前炭化炉内の両端つまり、温度の高い区
画と低い区画の両方から供給する方法が好ましい。
When a room temperature gas is supplied into a furnace heated to 300 ° C. to 800 ° C., the supply gas temperature rapidly rises as soon as it enters the pre-carbonization furnace, resulting in local variations in gas temperature. The temperature fluctuation is amplified as the temperature in the pre-carbonization furnace is increased, and this is one of the causes of convection. In that case, when the actual temperature in the previous carbonization furnace was measured every 30 minutes for 24 hours by the measurement method described later, the temperature fluctuation rate in the furnace was 3 to 10%, and the interlaminar shear strength (ILSS) of the obtained carbon fiber bundle Longitudinal direction fluctuation rate and machine width direction fluctuation rate both exceed 2.5%. This is because, as described above, the gas generated by the pyrolysis of the flame-resistant fiber flows from a high temperature to a low temperature, so that impurities attached to the yarn running in the low temperature region when viewed at a certain time. This is because it becomes larger for the yarn traveling in the high temperature region. As a result of the examination, impurities adhering to the carbon fiber bundle are closely adhered to the carbon fiber by being subjected to a heat treatment at 1000 ° C. to 2500 ° C. in the carbonization treatment process, making it difficult to remove in the surface treatment process. Yes. In particular, there is a great influence due to heat treatment in a temperature range of 1000 ° C. to 2000 ° C. However, the design of a carbon fiber bundle having a strand strength of 5000 MPa or more and a strand elastic modulus of 250 GPa or more required by the Japanese Industrial Standard (JIS) -R-7601 (1986) “resin impregnated strand test method” is 1000 ° C. to 2000 ° C. Carbonization in the temperature range of ° C is indispensable. As a means for suppressing temperature fluctuation in the pre-carbonization furnace, it is essential to heat the supply gas to at least 300 ° C., which is a low temperature region in the pre-carbonization furnace. By heating the supply gas to 300 ° C or higher in advance, the temperature fluctuation rate in the furnace can be suppressed to 2.5% or less, and the interlaminar shear strength (ILSS) of the obtained carbon fiber bundle in the longitudinal direction / machine Both the fluctuation rates in the width direction are 2.5% or less, and a carbon fiber bundle excellent in high-order workability is obtained. This effect is particularly noticeable in the above vertical furnace. Further, heating to 500 ° C. or higher at which the thermal reaction is activated by the pre-carbonization treatment is more preferable in terms of stabilizing the furnace temperature. Although there is no restriction | limiting in particular in the temperature upper limit of supply gas, it can be said that it is preferable to set it as 800 degreeC which is the high temperature area | region of a pre-carbonization furnace. In consideration of the sealing property in the furnace, a method of supplying the supply gas from both ends in the pre-carbonization furnace, that is, from both the high temperature section and the low temperature section is preferable.
なお、前炭化炉内の温度変動は以下のようにして求める。機幅方向に対しては、熱処理室内の両端から20cm毎に熱伝対を設置する。高さ方向については、加熱温度領域ごとに区画された部分の中央部に熱伝対を設置する。それぞれについて30分毎に8時間炉内温度を測定し、変動を求める。 The temperature fluctuation in the pre-carbonization furnace is obtained as follows. For the machine width direction, thermocouples are installed every 20 cm from both ends in the heat treatment chamber. About a height direction, a thermocouple is installed in the center part of the part divided for every heating temperature area | region. For each, the furnace temperature is measured every 30 minutes for 8 hours, and the fluctuation is determined.
本発明によれば、長手方向および機幅方向の炭素繊維束の層間剪断強度(ILSS)変動率を小さくしてその品質安定性を向上せしめ、その結果、一方向プリプレグ法やフィラメントワインディング法で製造されるプリプレグなどの高次加工品の品質安定化を達成することができる。 According to the present invention, the rate of fluctuation of the interlaminar shear strength (ILSS) of the carbon fiber bundle in the longitudinal direction and the machine width direction is reduced to improve its quality stability, and as a result, produced by the unidirectional prepreg method or the filament winding method. Stabilization of the quality of high-order processed products such as prepregs can be achieved.
以下本発明を実施例により具体的に説明する。
(実施例1)
アクリロニトリル99モル%とイタコン酸1モル%からなるアクリル系重合体の溶液を重合により調整し、乾湿式紡糸方法により単繊維繊度1dtex、フィラメント数24000本からなるアクリロニトリル系前駆体繊維を得た。これを200〜270℃の温度の空気中にて加熱して耐炎化繊維束とし、次いで窒素雰囲気中300〜800℃の温度領域
で縦型前炭化炉にて前炭化処理を行った。前炭化炉内に供給する窒素は300℃に加熱した。加熱温度領域ごとに区画された前炭化炉内の温度を熱伝対で30分毎に8時間、炉内の機幅方向に20cm毎に測定した結果、2%の温度変動を確認した。続いて1000〜1800℃の温度領域で炭化して炭素繊維束を得た。その後、硫酸水溶液を電解液として
炭素繊維1gあたり10クーロンの電気量で表面処理を行い水洗洗浄した後、ビスフェノールA型エポキシ樹脂を主成分とするサイジング剤を炭素繊維に対して1重量%になるように付着させて、炭素繊維束を得た。
得られた炭素繊維束の日本工業規格(JIS)−R−7601(1986)「樹脂含浸ストランド試験法」により測定したストランド強度は5200MPa、ストランド弾性率は270GPaであった。得られた炭素繊維束に硬化剤を添加したエピコート828エポキシ樹脂をそれぞれの重量比6:4の比率で含浸し、170℃に加熱したオーブンで1時間硬化させ試験片を作成した。作成した試験片についてASTM−D−2344に基づき3点曲げ方式で層間剪断強度(ILSS)を求めた。
Hereinafter, the present invention will be specifically described by way of examples.
Example 1
An acrylic polymer solution composed of 99 mol% acrylonitrile and 1 mol% itaconic acid was prepared by polymerization, and an acrylonitrile precursor fiber having a single fiber fineness of 1 dtex and a filament number of 24,000 was obtained by a dry and wet spinning method. This was heated in air at a temperature of 200 to 270 ° C. to form a flame-resistant fiber bundle, and then pre-carbonized in a vertical pre-carbonization furnace in a temperature range of 300 to 800 ° C. in a nitrogen atmosphere. Nitrogen supplied into the pre-carbonization furnace was heated to 300 ° C. As a result of measuring the temperature in the pre-carbonization furnace divided for each heating temperature region by thermocouple every 30 minutes for 8 hours and every 20 cm in the machine width direction in the furnace, 2% temperature fluctuation was confirmed. Subsequently, carbonization was performed in a temperature range of 1000 to 1800 ° C. to obtain a carbon fiber bundle. Thereafter, the surface treatment is carried out with an aqueous sulfuric acid solution as an electrolytic solution at an electric quantity of 10 coulombs per gram of carbon fiber, followed by washing with water, and then the sizing agent mainly composed of bisphenol A type epoxy resin is 1% by weight with respect to the carbon fiber. Thus, a carbon fiber bundle was obtained.
The obtained carbon fiber bundle had a strand strength of 5200 MPa and a strand elastic modulus of 270 GPa as measured by Japanese Industrial Standard (JIS) -R-7601 (1986) “Resin-impregnated strand test method”. The resulting carbon fiber bundle was impregnated with Epicoat 828 epoxy resin with a curing agent added at a weight ratio of 6: 4, and cured in an oven heated to 170 ° C. for 1 hour to prepare a test piece. The interlaminar shear strength (ILSS) of the prepared test piece was determined by a three-point bending method based on ASTM-D-2344.
その結果、層間剪断強度(ILSS)の長手・機幅方向変動率がともに2.0%である、バラツキの少ない品質に優れた炭素繊維束を得ることができた。
(比較例1)
前炭化炉供給窒素の温度を室温にした以外は実施例1と同じくして、前炭化炉の温度を実施例1と同様に測定したところ、5%の温度変動を確認した。得られた炭素繊維束の層間剪断強度(ILSS)変動率は長手方向・機幅方向ともに、4%と増加し、品質ポテンシャルの低い炭素繊維束ができた。
(実施例2)
アクリルニトリル99モル%とイタコン酸1モル%からなるアクリル系重合体の溶液を重合により調整し、乾湿式紡糸方法により単繊維繊度0.5dtex、フィラメント数24000本からなるアクリルニトリル系前駆体繊維を用いて、前炭化炉供給窒素の温度を500℃にした以外は実施例1と同じくして、前炭化炉の温度を実施例1と同様に測定し
たところ、1%の温度変動を確認した。得られた炭素繊維束の日本工業規格(JIS)−R−7601(1986)「樹脂含浸ストランド試験法」により測定したストランド強度は5700MPa、ストランド弾性率は290GPaであった。得られた炭素繊維束の長手方向層間剪断強度(ILSS)変動率は1.0%、機幅方向変動率は1.5%とバラツキの少ない品質に優れた炭素繊維束を得ることができた。
As a result, it was possible to obtain a carbon fiber bundle excellent in quality with little variation, in which both the longitudinal shear rate and the machine width direction variation rate of ILSS were 2.0%.
(Comparative Example 1)
When the temperature of the pre-carbonization furnace was measured in the same manner as in Example 1 except that the temperature of the nitrogen supplied to the pre-carbonization furnace was changed to room temperature, a temperature fluctuation of 5% was confirmed. The variation rate of the interlaminar shear strength (ILSS) of the obtained carbon fiber bundle increased to 4% in both the longitudinal direction and the machine width direction, and a carbon fiber bundle having a low quality potential was obtained.
(Example 2)
A solution of an acrylic polymer composed of 99 mol% acrylonitrile and 1 mol% itaconic acid was prepared by polymerization, and an acrylic nitrile precursor fiber composed of a single fiber fineness of 0.5 dtex and a filament number of 24,000 was obtained by a dry and wet spinning method. Using this, the temperature of the pre-carbonization furnace was measured in the same manner as in Example 1 except that the temperature of the nitrogen supplied to the pre-carbonization furnace was changed to 500 ° C., and 1% temperature fluctuation was confirmed. The obtained carbon fiber bundle had a strand strength of 5700 MPa and a strand elastic modulus of 290 GPa as measured by Japanese Industrial Standard (JIS) -R-7601 (1986) “Resin-impregnated strand test method”. The obtained carbon fiber bundle had a longitudinal interlaminar shear strength (ILSS) fluctuation rate of 1.0% and a machine width direction fluctuation rate of 1.5%, and a carbon fiber bundle excellent in quality with little variation was obtained. .
本発明の炭素繊維は、その層間剪断強度(ILSS)が小さく高次加工性での品質安定性が期待できることから宇宙用途、自動車用途、スポーツおよび一般産業用途に応用できるが応用範囲がこれらに限られるものではない。本発明の炭素繊維束は、複合材料の補強繊維として工業的に幅広く利用されるものであり、産業上有用である。 The carbon fiber of the present invention has low interlaminar shear strength (ILSS) and can be expected to be stable in quality with high-order processability. Therefore, the carbon fiber of the present invention can be applied to space use, automobile use, sports and general industrial use. Is not something The carbon fiber bundle of the present invention is widely used industrially as a reinforcing fiber for composite materials, and is industrially useful.
Claims (5)
間剪断強度(ILSS)の機幅方向の変動率が2.5%以下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束。 The variation rate in the machine width direction of interlaminar shear strength (ILSS) obtained by firing a plurality of precursor fibers for carbon fiber in parallel in the same firing facility is 2.5% or less. A polyacrylonitrile-based carbon fiber bundle.
請求項1または2に記載の炭素繊維束。 The carbon fiber bundle according to claim 1 or 2, wherein the strand strength is 5000 MPa or more and the strand elastic modulus is 250 GPa or more.
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CN107429477A (en) * | 2015-03-31 | 2017-12-01 | 霓达株式会社 | The manufacture method and composite of composite |
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