JP2024082443A - Fiber-reinforced resin molding substrate and fiber-reinforced resin molding - Google Patents
Fiber-reinforced resin molding substrate and fiber-reinforced resin molding Download PDFInfo
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- XMTQQYYKAHVGBJ-UHFFFAOYSA-N 3-(3,4-DICHLOROPHENYL)-1,1-DIMETHYLUREA Chemical compound CN(C)C(=O)NC1=CC=C(Cl)C(Cl)=C1 XMTQQYYKAHVGBJ-UHFFFAOYSA-N 0.000 description 1
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- UHESRSKEBRADOO-UHFFFAOYSA-N ethyl carbamate;prop-2-enoic acid Chemical compound OC(=O)C=C.CCOC(N)=O UHESRSKEBRADOO-UHFFFAOYSA-N 0.000 description 1
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Abstract
【課題】高いレベルで機械特性と工程通過性を両立することが可能な繊維強化樹脂成形用基材、及びそれを成形してなる耐疲労特性に優れた繊維強化樹脂成形体を提供する。【解決手段】アラミド繊維からなる補強用布帛（Ａ）と半硬化状態の熱硬化性樹脂（Ｂ）とからなる繊維強化樹脂成形用基材であって、前記アラミド繊維は、繊維表面に未硬化の硬化性エポキシ化合物を有しており、前記繊維強化樹脂成形用基材を用いて成形・硬化させた繊維強化樹脂成形体は、ボイド率が５．０％以下、かつ、ＪＩＳ Ｋ７０１７に準じた３点曲げ試験条件における曲げ歪み１．０％時の曲げ荷重から算出される強力保持率が９６．０％以上であることを特徴とする繊維強化樹脂成形用基材、並びに、それを成形してなる繊維強化樹脂成形体。【選択図】図２[Problem] To provide a substrate for fiber-reinforced resin molding capable of achieving both high levels of mechanical properties and processability, and a fiber-reinforced resin molded body having excellent fatigue resistance properties obtained by molding the same. [Solution] A substrate for fiber-reinforced resin molding comprising a reinforcing cloth (A) made of aramid fibers and a thermosetting resin (B) in a semi-cured state, the aramid fibers having an uncured curable epoxy compound on the fiber surface, and a fiber-reinforced resin molded body molded and cured using the substrate for fiber-reinforced resin molding, characterized in that the void ratio is 5.0% or less and the strength retention calculated from the bending load at a bending strain of 1.0% in a three-point bending test condition according to JIS K7017 is 96.0% or more. [Selected Figure] Figure 2
Description
本発明は、アラミド繊維からなる補強用布帛（Ａ）と半硬化状態の熱硬化性樹脂（Ｂ）とからなる繊維強化樹脂成形用基材、及び、前記繊維強化樹脂成形用基材を成形してなる繊維強化樹脂成形体に関する。 The present invention relates to a fiber-reinforced resin molding substrate comprising a reinforcing fabric (A) made of aramid fibers and a semi-cured thermosetting resin (B), and a fiber-reinforced resin molded body obtained by molding the fiber-reinforced resin molding substrate.
強化繊維からなる布帛（以下、補強用布帛）と熱硬化性樹脂からなる繊維強化樹脂成形体は、軽量で優れた機械特性を有することから、航空機材、車両部品、電子部品、家電製品の各種ハウジング等幅広い分野に使用され、軽量、かつ高剛性、高強度、耐摩耗性等の特性が要求される分野において有効に用いられている。 Fiber-reinforced resin molded products made of fabrics made of reinforcing fibers (hereafter referred to as reinforcing fabrics) and thermosetting resins are lightweight and have excellent mechanical properties, and are therefore used in a wide range of fields, including aircraft materials, vehicle parts, electronic parts, and various housings for home appliances, and are effectively used in fields that require lightweight properties as well as high rigidity, high strength, and abrasion resistance.
繊維強化樹脂成形体は、例えば、炭素繊維、アラミド繊維、ガラス繊維等の強化繊維からなる布帛に、熱硬化性樹脂を含浸させ、半硬化状態としたシート状等の基材（プリプレグ）を用いて製造されている。また、繊維強化樹脂複合体を得る方法の多くは、その取扱い性及び賦形性から、半硬化状態としたシート状の基材（プリプレグ）を複数積層し、オートクレーブ等で加熱加圧することにより硬化させる方法である。 Fiber-reinforced resin molded bodies are manufactured by impregnating a fabric made of reinforcing fibers such as carbon fiber, aramid fiber, or glass fiber with a thermosetting resin and using a sheet-like substrate (prepreg) in a semi-cured state. In addition, in many methods for obtaining fiber-reinforced resin composites, due to their ease of handling and shaping, multiple sheets of semi-cured substrates (prepregs) are stacked together and cured by heating and pressurizing in an autoclave or the like.
繊維強化樹脂成形体の機械的特性等を向上させるためには、強化繊維と熱硬化性樹脂との界面の接着性を高めることが求められる。しかしながら、アラミド繊維は他の実用強化繊維である炭素繊維やガラス繊維に比して、熱硬化性樹脂との密着性が劣る傾向がある。これはアラミド繊維が不活性繊維であり、繊維表面に存在する官能基と熱硬化性樹脂との間に相互作用が生じ難いためである。 To improve the mechanical properties of fiber-reinforced resin moldings, it is necessary to increase the adhesion at the interface between the reinforcing fibers and the thermosetting resin. However, aramid fibers tend to have poorer adhesion to thermosetting resins than other practical reinforcing fibers such as carbon fiber and glass fiber. This is because aramid fibers are inactive fibers, and interactions are unlikely to occur between the functional groups present on the fiber surface and the thermosetting resin.
特許文献１では、プラズマを用いた化学的気相成長（プラズマＣＶＤ）法により強化繊維とマトリックス樹脂との界面接着性を向上させている。しかし、強化繊維表面上に化学蒸着工程を施す必要があり、また熱可塑性樹脂に限定された手法である。 In Patent Document 1, the interfacial adhesion between reinforcing fibers and matrix resin is improved by a plasma-based chemical vapor deposition (plasma CVD) method. However, this method requires a chemical vapor deposition process to be performed on the reinforcing fiber surface, and is limited to thermoplastic resins.
特許文献２では、マトリックス樹脂との界面接着性改良のために、フェノール性水酸基含有ポリアミド樹脂とアルコール成分を含む溶剤から成る表面処理剤をアラミド繊維に含浸させる製造方法が記載されている。しかし、特殊な表面処理手法が必要であり、得られるフェノール性水酸基含有アラミド繊維は、取り扱い性が悪く、毒性が高く作業環境が悪いといった問題点がある。 Patent Document 2 describes a manufacturing method in which aramid fibers are impregnated with a surface treatment agent consisting of a phenolic hydroxyl group-containing polyamide resin and a solvent containing an alcohol component in order to improve the interfacial adhesion with the matrix resin. However, a special surface treatment method is required, and the resulting phenolic hydroxyl group-containing aramid fibers have problems such as poor handling, high toxicity, and a poor working environment.
特許文献３では、ウレタンアクリレート（接着剤）により界面接着性に優れたアラミド樹脂成形材料が提示されている。しかし、マトリックス樹脂側からの改質手法であり、反応を促進するためにラジカル重合性単量体を添加する必要がある。 Patent Document 3 presents an aramid resin molding material with excellent interfacial adhesion due to the use of urethane acrylate (adhesive). However, this is a method of modifying the matrix resin, and it is necessary to add a radical polymerizable monomer to promote the reaction.
本発明は、上記事情に鑑みてなされたものであり、特殊な表面処理手法を施すことなく高いレベルで耐疲労特性と工程通過性を両立できる繊維強化樹脂成形用基材を提供することを目的とする。 The present invention was made in consideration of the above circumstances, and aims to provide a substrate for fiber-reinforced resin molding that can achieve high levels of both fatigue resistance and processability without the need for special surface treatment techniques.
本発明者等は上記目的を達成すべく誠意検討した。その結果、アラミド繊維表面に存在する硬化性エポキシ化合物の未硬化物（遊離エポキシ）量を制御し、さらに補強用布帛の織縮率を低減させて成形体のボイド率を抑えることで、耐疲労特性、工程通過性にも優れた繊維強化樹脂成形用基材を提供できることを見出し、本発明に至った。 The present inventors have conducted thorough research to achieve the above object. As a result, they have discovered that by controlling the amount of uncured (free epoxy) curable epoxy compound present on the surface of aramid fibers and further reducing the shrinkage rate of the reinforcing fabric to suppress the void rate of the molded product, it is possible to provide a substrate for fiber-reinforced resin molding that is excellent in fatigue resistance and processability, and have arrived at the present invention.
すなわち、本発明は、アラミド繊維からなる補強用布帛（Ａ）と半硬化状態の熱硬化性樹脂（Ｂ）とからなる繊維強化樹脂成形用基材であって、
前記アラミド繊維は、繊維表面に未硬化の硬化性エポキシ化合物を有しており、
前記繊維強化樹脂成形用基材を用いて成形・硬化させた繊維強化樹脂成形体は、
（１）ボイド率が５．０％以下であり、かつ、
（２）ＪＩＳ Ｋ７０１７に準じた３点曲げ試験条件における曲げ歪み１．０％時の曲げ荷重から算出される強力保持率が９６．０％以上である
ことを特徴とする繊維強化樹脂成形用基材を提供する。
That is, the present invention provides a fiber-reinforced resin molding substrate comprising a reinforcing fabric (A) made of aramid fibers and a semi-cured thermosetting resin (B),
The aramid fiber has an uncured curable epoxy compound on a fiber surface,
A fiber-reinforced resin molded body molded and cured using the fiber-reinforced resin molding substrate is
(1) The void ratio is 5.0% or less, and
(2) Provided is a substrate for fiber-reinforced resin molding, characterized in that the strength retention calculated from the bending load at a bending strain of 1.0% in a three-point bending test condition in accordance with JIS K7017 is 96.0% or more.
本発明によれば、特殊な表面処理手法を施すことなく、高いレベルで耐疲労特性と基材製造時における工程通過性を両立できる繊維強化樹脂成形用基材を提供することができる。 The present invention provides a substrate for fiber-reinforced resin molding that can achieve high levels of fatigue resistance and processability during substrate manufacturing without the need for special surface treatment methods.
以下、本発明の実施形態について詳細に説明する。
本発明に係る繊維強化樹脂成形用基材は、アラミド繊維からなる補強用布帛（Ａ）と半硬化状態の熱硬化性樹脂（Ｂ）とからなる繊維強化樹脂成形用基材であって、前記アラミド繊維は、繊維表面に未硬化の硬化性エポキシ化合物を有しており、前記繊維強化樹脂成形用基材を用いて成形・硬化させた繊維強化樹脂成形体は、（１）ボイド率が５．０％以下、かつ（２）ＪＩＳ Ｋ７０１７に準じた３点曲げ試験条件における曲げ歪み１．０％時の曲げ荷重から算出される強力保持率が９６．０％以上である、ことを特徴とする。
Hereinafter, an embodiment of the present invention will be described in detail.
The substrate for fiber-reinforced resin molding according to the present invention is a substrate for fiber-reinforced resin molding comprising a reinforcing cloth (A) made of aramid fibers and a semi-cured thermosetting resin (B), in which the aramid fibers have an uncured curable epoxy compound on the fiber surface, and a fiber-reinforced resin molding molded and cured using the substrate for fiber-reinforced resin molding is characterized in that (1) it has a void ratio of 5.0% or less, and (2) it has a strength retention of 96.0% or more calculated from a bending load at a bending strain of 1.0% in a three-point bending test condition in accordance with JIS K7017.
＜アラミド繊維＞
アラミド繊維は、繊維を形成するポリマーの繰り返し単位中に、通常置換されていても良い二価の芳香族基を少なくとも一個有する繊維であって、アミド結合を少なくとも一個有する繊維であれば特に限定はなく、全芳香族ポリアミド繊維、又はアラミド繊維と称されるものであって良い。「置換されていても良い二価の芳香族基」とは、同一又は異なる１以上の置換基を有していても良い二価の芳香族基を意味する。
アラミド繊維としては、パラ系アラミド繊維、メタ系アラミド繊維等を挙げることができるが、機械的特性に優れているパラ系アラミド繊維が好ましい。このようなアラミド繊維は市販品として入手でき、その具体例としては、パラ系アラミド繊維として、例えば、ポリパラフェニレンテレフタルアミド繊維（米国デュポン社、東レ・デュポン（株）製、商品名「Ｋｅｖｌａｒ」（登録商標））、コポリパラフェニレン－３，４´－オキシジフェニレンテレフタルアミド繊維（帝人（株）製、商品名「テクノーラ」（登録商標））等を挙げることができる。これらのパラ系アラミド繊維の中でも、機械的特性に優れる点より、ポリパラフェニレンテレフタルアミド繊維が特に好ましい。
<Aramid fiber>
The aramid fiber is a fiber having at least one divalent aromatic group, which may be substituted, in the repeating unit of the polymer forming the fiber, and is not particularly limited as long as it has at least one amide bond, and may be a fiber called a wholly aromatic polyamide fiber or an aramid fiber. The "divalent aromatic group, which may be substituted" means a divalent aromatic group, which may have one or more identical or different substituents.
Examples of the aramid fiber include para-aramid fiber and meta-aramid fiber, but para-aramid fiber having excellent mechanical properties is preferred. Such aramid fiber is commercially available, and specific examples of the para-aramid fiber include polyparaphenylene terephthalamide fiber (manufactured by DuPont USA, Toray DuPont Co., Ltd., trade name "Kevlar" (registered trademark)) and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide fiber (manufactured by Teijin Limited, trade name "Technora" (registered trademark)). Among these para-aramid fibers, polyparaphenylene terephthalamide fiber is particularly preferred because of its excellent mechanical properties.
その中でも、ＪＩＳ Ｌ１０１３：２０２１「化学繊維フィラメント糸試験方法」に記載の方法により測定される引張強度が１７ｃＮ／ｄｔｅｘ以上で、かつ同法により測定される引張弾性率が４００ｃＮ／ｄｔｅｘ以上である、ポリパラフェニレンテレフタルアミド繊維が望ましい。前記特性を有するポリパラフェニレンテレフタルアミド繊維を用いることにより、繊維強化樹脂成形体に十分な引張強度及び弾性率を発揮させることが可能となる。ポリパラフェニレンテレフタルアミド繊維の引張強度は、好ましくは２０ｃＮ／ｄｔｅｘ以上、より好ましくは２３ｃＮ／ｄｔｅｘ以上である。ポリパラフェニレンテレフタルアミド繊維の引張弾性率は、好ましくは４２０ｃＮ／ｄｔｅｘ以上、より好ましくは４５０ｃＮ／ｄｔｅｘ以上である。 Among them, polyparaphenylene terephthalamide fibers having a tensile strength of 17 cN/dtex or more and a tensile modulus of elasticity of 400 cN/dtex or more measured by the method described in JIS L1013:2021 "Testing Method for Chemical Fiber Filament Yarn" are desirable. By using polyparaphenylene terephthalamide fibers having the above characteristics, it is possible to provide a fiber-reinforced resin molding with sufficient tensile strength and modulus of elasticity. The tensile strength of polyparaphenylene terephthalamide fibers is preferably 20 cN/dtex or more, more preferably 23 cN/dtex or more. The tensile modulus of elasticity of polyparaphenylene terephthalamide fibers is preferably 420 cN/dtex or more, more preferably 450 cN/dtex or more.
本発明において、補強用布帛（Ａ）を構成するアラミド繊維は、繊維表面に未硬化の硬化性エポキシ化合物を有している。このようなアラミド繊維は、アラミド繊維の製造工程で、硬化性エポキシ化合物を付与する方法で得ることができる。あるいは、既存のアラミド繊維に硬化性エポキシ化合物を付与する方法でも得ることもできる。 In the present invention, the aramid fibers constituting the reinforcing fabric (A) have an uncured curable epoxy compound on the fiber surface. Such aramid fibers can be obtained by a method of adding a curable epoxy compound during the aramid fiber manufacturing process. Alternatively, they can also be obtained by a method of adding a curable epoxy compound to existing aramid fibers.
アラミド繊維の製造工程で繊維表面に未硬化の硬化性エポキシ化合物を付与する方法としては、油剤付与工程で付与する方法、その後の仕上げ工程で付与する方法等が挙げられるが、アラミド繊維の表面に未硬化の硬化性エポキシ化合物を多く付着させることができる点で、油剤付与工程で付与する方法が好ましい。 Methods for applying uncured curable epoxy compounds to the fiber surface during the aramid fiber manufacturing process include applying them during the oil application process and applying them during the subsequent finishing process. However, the method of applying them during the oil application process is preferred because it allows a large amount of uncured curable epoxy compounds to adhere to the surface of the aramid fibers.
油剤付与工程では、油剤として、硬化性エポキシ化合物を含む油剤を用いることが好ましい。詳細には、（ａ）未硬化の硬化性エポキシ化合物と（ｂ）該硬化性エポキシ化合物を溶解する相溶剤とから構成され、アミン等のエポキシ硬化剤を含まない油剤であることが好ましい。前記の（ａ）成分及び（ｂ）成分は、混合物として付与されても良いし、別々に２工程で付与されていても良い。２工程で付与される場合、付与順序は問わない。生産時の取り扱い性の面からは、（ａ）成分と（ｂ）成分が混合物として付与されることが、より好ましい。 In the oil application step, it is preferable to use an oil containing a curable epoxy compound as the oil. In detail, it is preferable that the oil is composed of (a) an uncured curable epoxy compound and (b) a compatible solvent that dissolves the curable epoxy compound, and does not contain an epoxy curing agent such as an amine. The above-mentioned components (a) and (b) may be applied as a mixture, or may be applied separately in two steps. When applied in two steps, the order of application is not important. From the viewpoint of handleability during production, it is more preferable that components (a) and (b) are applied as a mixture.
油剤を構成する（ａ）硬化性エポキシ化合物／（ｂ）相溶剤の比率（質量比）としては、８０／２０～３０／７０が好ましく、より好ましくは７５／２５～３５／６５、さらに好ましくは７０／３０～４０／６０である。前記（ｂ）成分の比率が、７０を超えると、エポキシ化合物が減少することにより熱硬化性樹脂との界面接着性が阻害され、反対に、２０を下回ると、アラミド繊維の収束性が低下し工程通過性が悪化する恐れがある。また、油剤中に（ｂ）成分が過剰に存在すると、アラミド繊維の熱硬化性樹脂に対する接着性が阻害される傾向がある。 The ratio (mass ratio) of (a) curable epoxy compound/(b) compatible solvent constituting the oil agent is preferably 80/20 to 30/70, more preferably 75/25 to 35/65, and even more preferably 70/30 to 40/60. If the ratio of the (b) component exceeds 70, the epoxy compound is reduced, inhibiting interfacial adhesion with the thermosetting resin. Conversely, if it is below 20, the convergence of the aramid fiber is reduced, which may deteriorate processability. In addition, if the (b) component is present in excess in the oil agent, the adhesion of the aramid fiber to the thermosetting resin tends to be inhibited.
本発明では、アラミド繊維表面に付与する硬化性エポキシ化合物が、前記アラミド繊維を半硬化状態の熱硬化性樹脂に作用させる時点で、全て硬化していないこと（すなわち、未硬化の遊離エポキシ化合物がアラミド繊維表面に存在すること）が肝要である。但し、アラミド繊維表面には、硬化したエポキシ化合物と、未硬化（遊離）の硬化性エポキシ化合物が併存していても良い。 In the present invention, it is essential that the curable epoxy compound applied to the aramid fiber surface is not completely cured (i.e., uncured free epoxy compound is present on the aramid fiber surface) when the aramid fiber is exposed to a semi-cured thermosetting resin. However, the aramid fiber surface may contain both a cured epoxy compound and an uncured (free) curable epoxy compound.
アラミド繊維表面における未硬化の硬化性エポキシ化合物は、アラミド繊維１ｋｇ当たり２０．０ｍｍｏｌ以上であることが好ましく、より好ましくは４０．０ｍｍｏｌ以上であり、特に好ましくは５０．０ｍｍｏｌ以上である。 The amount of uncured curable epoxy compound on the surface of the aramid fiber is preferably 20.0 mmol or more per kg of aramid fiber, more preferably 40.0 mmol or more, and particularly preferably 50.0 mmol or more.
本発明においては、アラミド繊維表面に一定量以上の遊離エポキシ化合物が存在することで、エポキシ基を介してアラミド繊維と熱硬化性樹脂との界面接着性が良好になり、繊維強化樹脂成形体のボイド率が低減し、惹いては機械的特性が向上するのではないかと推察される。また、油剤に遊離エポキシ化合物が含まれていると、繊維表面に付着した遊離エポキシ化合物によって、アラミド繊維束（繊維束－繊維束間）への熱硬化性樹脂の含浸性が良好になる。同時に繊維と樹脂間の界面接着性が良好となるため、耐疲労特性に優れた繊維強化樹脂成形体を得ることができる。 In the present invention, it is presumed that the presence of a certain amount or more of free epoxy compound on the aramid fiber surface improves the interfacial adhesion between the aramid fiber and the thermosetting resin via the epoxy groups, reduces the void ratio of the fiber-reinforced resin molding, and improves the mechanical properties. In addition, if the oil contains free epoxy compound, the free epoxy compound attached to the fiber surface improves the impregnation of the thermosetting resin into the aramid fiber bundles (between the fiber bundles). At the same time, the interfacial adhesion between the fiber and the resin is improved, so that a fiber-reinforced resin molding with excellent fatigue resistance can be obtained.
一方、油剤にアミン等の硬化剤が含まれていると、硬化性エポキシ化合物が早期に硬化してしまい、油剤中の遊離エポキシ化合物量が低下したり、また油剤粘度も高くなるため、繊維束への熱硬化性樹脂の含浸性が低下する恐れがあり、繊維と樹脂間の界面接着性に影響を及ぼす恐れがある。 On the other hand, if the oil contains a hardener such as an amine, the curable epoxy compound will harden prematurely, reducing the amount of free epoxy compound in the oil and increasing the viscosity of the oil, which may reduce the impregnation of the thermosetting resin into the fiber bundle and affect the interfacial adhesion between the fiber and the resin.
なお、未硬化（遊離）の硬化性エポキシ化合物の量は、油剤を付与する際のアラミド繊維の水分率及び／又は油剤の種類、もしくは組成を変更することにより調整できる。 The amount of uncured (free) curable epoxy compound can be adjusted by changing the moisture content of the aramid fiber when applying the oil and/or the type or composition of the oil.
上記の（ｂ）成分である硬化性エポキシ化合物を溶解する相溶剤としては、繊維用油剤を用いることが好ましい。これにより、アラミド繊維の工程通過性が良好となることで生産効率が向上するだけでなく、熱硬化性樹脂含浸後の繊維強化樹脂成形体におけるアラミド繊維と熱硬化性樹脂との界面接着性を高めることができる。 As a compatible solvent for dissolving the curable epoxy compound, which is the above-mentioned component (b), it is preferable to use a fiber oil. This not only improves the processability of the aramid fiber, thereby improving production efficiency, but also increases the interfacial adhesion between the aramid fiber and the thermosetting resin in the fiber-reinforced resin molding after impregnation with the thermosetting resin.
なお、油剤には、本発明による効果を阻害しない範囲で、公知の平滑剤、非イオン活性剤、アニオン活性剤、カチオン活性剤、両性活性剤等の界面活性剤、制電剤等が配合されていても良い。 The oil may contain known smoothing agents, surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, and antistatic agents, as long as they do not impair the effects of the present invention.
上記の油剤を付与するアラミド繊維としては、紡糸、中和、洗浄後の繊維を、乾燥し、水分率３～１５質量％に調整したアラミド繊維が好ましく、より好ましくは水分率３．５～１０質量％であり、特に好ましくは水分率３．５～８質量％である。水分率が３質量％以上であると、繊維表面上の残留水で適度に硬化性エポキシ化合物が硬化され、繊維表面に硬化膜が形成されるため、工程通過時の擦過による毛羽の発生が抑制される。また、水分率１５質量％以下であると、繊維内部に油剤が取り込まれることなく、繊維表面上に一定量以上の遊離エポキシ化合物が保持されることで熱硬化性樹脂との濡れ性が向上し、繊維束への熱硬化性樹脂の含浸性が高まると共に、繊維束表面と熱硬化性樹脂との界面接着性が良好となる。さらに水分率１５質量％以下であると、製糸工程でのロールへの巻付き頻度が低減し、経済性が高くなる。一方、水分率１５質量％を超えると、繊維内のボイドと呼ばれる水分が保持されている隙間が大きくなることで、繊維内部に油剤が吸着し、繊維表面上の遊離エポキシ化合物の含有量が少なくなるため、アラミド繊維の熱硬化性樹脂に対する接着性が阻害される恐れがある。 As the aramid fiber to which the oil agent is applied, it is preferable to use aramid fiber which has been dried after spinning, neutralization and washing to adjust the moisture content to 3 to 15% by mass, more preferably 3.5 to 10% by mass, and particularly preferably 3.5 to 8% by mass. If the moisture content is 3% by mass or more, the curable epoxy compound is moderately cured by the residual water on the fiber surface, and a cured film is formed on the fiber surface, so that the generation of fluff due to rubbing during the process is suppressed. Furthermore, if the moisture content is 15% by mass or less, the oil agent is not taken into the fiber, and a certain amount or more of free epoxy compound is retained on the fiber surface, improving the wettability with the thermosetting resin, increasing the impregnation of the thermosetting resin into the fiber bundle, and improving the interfacial adhesion between the fiber bundle surface and the thermosetting resin. Furthermore, if the moisture content is 15% by mass or less, the frequency of winding around the roll in the spinning process is reduced, which increases the economy. On the other hand, if the moisture content exceeds 15% by mass, the gaps in the fibers where moisture is held, called voids, become larger, causing the oil agent to be adsorbed inside the fibers and reducing the amount of free epoxy compound on the fiber surface, which may impair the adhesion of the aramid fibers to the thermosetting resin.
上記の中和、洗浄後、乾燥した状態のアラミド繊維表面の付着水は、中和処理で用いたアルカリ由来のアルカリイオンを含むため、アラミド繊維の水分率が高くなるほど、アラミド繊維周辺のアルカリイオン量が増加する。そのため、アラミド繊維の水分率が高くなるほど、アルカリイオンの触媒作用により硬化性エポキシ化合物が硬化し、硬化膜が形成され易くなることで、遊離エポキシ化合物が減少する傾向になる。一方、アラミド繊維の水分率が低くなるほど、アラミド繊維周辺のアルカリイオン量が減少するため、アラミド繊維表面にエポキシ化合物の硬化膜が形成され難くなる。 After the above neutralization and washing, the water adhering to the surface of the dried aramid fiber contains alkali ions derived from the alkali used in the neutralization treatment, so the higher the moisture content of the aramid fiber, the greater the amount of alkali ions around the aramid fiber. Therefore, the higher the moisture content of the aramid fiber, the more the curable epoxy compound hardens due to the catalytic action of the alkali ions, making it easier to form a cured film, and the amount of free epoxy compound tends to decrease. On the other hand, the lower the moisture content of the aramid fiber, the less the amount of alkali ions around the aramid fiber, making it more difficult to form a cured film of the epoxy compound on the surface of the aramid fiber.
本発明のアラミド繊維は、水分率３～１５質量％に乾燥したアラミド繊維に、油剤を付与した後、続いて巻き取り工程でボビンに巻き取り、巻き上げたアラミド繊維の水分率を３～１５質量％に保持したアラミド繊維であって、硬化性エポキシ化合物が１００％硬化していない（すなわち、少なくとも遊離エポキシ化合物がアラミド繊維表面に付着している）状態にあるものが好ましい。また油剤を付与した後の乾燥工程は、遊離エポキシ化合物が減少するため、不要であることが好ましい。 The aramid fiber of the present invention is an aramid fiber obtained by applying an oil agent to aramid fiber dried to a moisture content of 3 to 15% by mass, and then winding the aramid fiber around a bobbin in a winding process, so that the moisture content of the wound aramid fiber is maintained at 3 to 15% by mass. It is preferable that the curable epoxy compound is not 100% cured (i.e., at least free epoxy compound is attached to the surface of the aramid fiber). In addition, it is preferable that the drying process after applying the oil agent is unnecessary because the amount of free epoxy compound is reduced.
アラミド繊維への硬化性エポキシ化合物を含む油剤の付着量は、アラミド繊維質量（乾燥基準）に対してエポキシ成分（未硬化及び硬化エポキシの合計量）が０．５～３．０質量％であることが好ましく、より好ましくは０．７～２．５質量％、特に好ましくは１．０～２．０質量％である。油剤の付着量がこの範囲にあると、水分率の影響により繊維内部に多少油剤が取り込まれても、繊維表面に遊離エポキシ化合物が存在し、熱硬化性樹脂との反応点に大きく寄与する。また紡糸工程におけるスカム発生の抑制にも繋がるため、工程通過性にも大きく関与する。 The amount of oil containing a curable epoxy compound attached to the aramid fiber is preferably 0.5 to 3.0 mass% of the epoxy component (total amount of uncured and cured epoxy) relative to the mass of the aramid fiber (on a dry basis), more preferably 0.7 to 2.5 mass%, and particularly preferably 1.0 to 2.0 mass%. If the amount of oil attached is within this range, even if some oil is taken into the fiber due to the moisture content, free epoxy compound will be present on the fiber surface, which will greatly contribute to reaction points with the thermosetting resin. It also helps to suppress the generation of scum in the spinning process, and therefore plays a major role in process passability.
油剤を構成する（ａ）硬化性エポキシ化合物は、脂肪族エポキシ化合物及び芳香環を有するエポキシ化合物から選ばれる１種、又は２種以上が用いられ、例えば、グリセロールジグリシジルエーテル、グリセロールトリグリシジルエーテル、ポリグリセロールポリグリシジルエーテル、ソルビトールポリグリシジルエーテル、トリメチロールプロパンポリグリシジルエーテル、ペンタエリスリトールポリグリシジルエーテル等が挙げられる。なかでも、グリシジル基を２個又は３個有する多官能性エポキシ化合物が好ましい。 The (a) curable epoxy compound constituting the oil agent is one or more selected from aliphatic epoxy compounds and epoxy compounds having an aromatic ring, such as glycerol diglycidyl ether, glycerol triglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, etc. Among these, polyfunctional epoxy compounds having two or three glycidyl groups are preferred.
これらのエポキシ化合物の中でも、工程通過性を向上させるために、２５℃における粘度が５００ｍＰａ・ｓ以下であることが好ましく、より好ましくは３００ｍＰａ・ｓ以下、特に好ましくは２００ｍＰａ・ｓ以下である。具体的には、脂肪族エポキシ化合物が好ましく、グリセロールジグリシジルエーテル、グリセロールトリグリシジルエーテル等の、グリセロール系エポキシ化合物が特に好ましい。ここで、粘度とは、動的粘弾性測定装置（レオメーターＲＤＡ２：レオメトリックス社製、又は、レオメーターＡＲＥＳ：ＴＡインスツルメント社製）を用い、直径４０ｍｍのパラレルプレートを用い、周波数０．５Ｈｚ、Ｇａｐ１ｍｍで測定を行った複素粘性率η＊のことを指す。 Among these epoxy compounds, in order to improve processability, it is preferable that the viscosity at 25°C is 500 mPa·s or less, more preferably 300 mPa·s or less, and particularly preferably 200 mPa·s or less. Specifically, aliphatic epoxy compounds are preferable, and glycerol-based epoxy compounds such as glycerol diglycidyl ether and glycerol triglycidyl ether are particularly preferable. Here, viscosity refers to the complex viscosity η* measured using a dynamic viscoelasticity measuring device (Rheometer RDA2: manufactured by Rheometrics, Inc., or Rheometer ARES: manufactured by TA Instruments, Inc.) with a parallel plate having a diameter of 40 mm, at a frequency of 0.5 Hz and a gap of 1 mm.
油剤を構成する（ｂ）成分；硬化性エポキシ化合物を溶解する相溶剤は、特に限定されないが、繊維用油剤の中でも、上記エポキシ化合物との溶解度パラメータ（Ｆｅｄｏｒｓ法によるＳＰ値）差が２．０ｃａｌ／ｃｍ３以下、かつ、紡糸又はプリプレグ製造工程におけるロールとの擦過が少ないものが好ましい。特に、ポリアルキレングリコールと脂肪酸のエステル化物、又は、ポリエチレングリコールとポリプロピレングリコールの共重合体が好ましい。 The (b) component constituting the oil agent, i.e., a compatible solvent that dissolves the curable epoxy compound, is not particularly limited, but among oil agents for fibers, those having a difference in solubility parameter (SP value by Fedors method) with the above-mentioned epoxy compound of 2.0 cal/ cm3 or less and causing little abrasion with the roll in the spinning or prepreg production process are preferred. In particular, esters of polyalkylene glycol and fatty acid, or copolymers of polyethylene glycol and polypropylene glycol are preferred.
アラミド繊維の総繊度は特に限定されないが、通常、５０～１０，０００ｄｔｅｘ、好ましくは１００～５，０００ｄｔｅｘ、より好ましくは２００～２，５００ｄｔｅｘのものが用いられる。布帛に対する熱硬化性樹脂の含浸が容易で、それにより布帛の布目曲りが防止される点より、比較的薄い布帛が望ましく、そのためには総繊度の小さいアラミド繊維束を用いることが望ましい。アラミド繊維の総繊度は、さらに好ましくは２００～２，０００ｄｔｅｘである。また、本発明による効果を阻害しない範囲で、アラミド繊維にタスラン加工やインターレース加工等を施したエアー交絡糸；加撚－熱固定－解撚糸（捲縮糸）；仮撚加工糸；押込加工糸等の長繊維束も用いることができる。 The total fineness of the aramid fibers is not particularly limited, but is usually 50 to 10,000 dtex, preferably 100 to 5,000 dtex, and more preferably 200 to 2,500 dtex. A relatively thin fabric is desirable because it is easy to impregnate the fabric with a thermosetting resin and thus prevents the fabric from twisting, and therefore it is desirable to use an aramid fiber bundle with a small total fineness. The total fineness of the aramid fibers is more preferably 200 to 2,000 dtex. In addition, long fiber bundles such as air-entangled yarns obtained by subjecting aramid fibers to taslan processing or interlacing processing, twisted-heat-set-untwisted yarns (shrunk yarns), false twisted yarns, and push-processed yarns can also be used within the range that does not impair the effects of the present invention.
＜アラミド繊維からなる補強用布帛（Ａ）＞
補強用布帛の形態としては、織布、編布及びＮＣＦ（ノンクリンプファブリック）からなる群から少なくとも１つの形態から選択することができる。ノンクリンプファブリックは、複数本の連続繊維が互いを交錯させない状態で経編組織を形成する補助繊維糸により一体化されたシート状の基材であり、公知の態様を採用できる。例えば、複数本の連続繊維が一方向の層状に並列した層を１層又は２層以上有する形態が挙げられる。補助繊維糸としては、特に限定されず、例えば、ポリエステル繊維糸、ポリアミド繊維糸、ポリエチレン繊維糸、全芳香族ポリアミド（アラミド）繊維糸等が挙げられる。
<Reinforcing fabric (A) made of aramid fibers>
The form of the reinforcing fabric can be selected from at least one form from the group consisting of woven fabric, knitted fabric, and NCF (non-crimp fabric). The non-crimp fabric is a sheet-like substrate integrated with auxiliary fiber yarns that form a warp knitted structure without intersecting multiple continuous fibers, and a known form can be adopted. For example, there can be mentioned a form having one or more layers in which multiple continuous fibers are arranged in parallel in one direction. The auxiliary fiber yarn is not particularly limited, and examples thereof include polyester fiber yarn, polyamide fiber yarn, polyethylene fiber yarn, fully aromatic polyamide (aramid) fiber yarn, etc.
補強用布帛は、樹脂が含浸し得る程度の隙間（孔）を有するものであれば特に限定されない。補強用布帛は、例えば、織布と織布、織布と編み布、織布とＮＣＦ、編布とＮＣＦなど積層した布帛としてもよい。 The reinforcing fabric is not particularly limited as long as it has gaps (holes) large enough to allow the resin to be impregnated. The reinforcing fabric may be a laminated fabric, such as a woven fabric and a woven fabric, a woven fabric and a knitted fabric, a woven fabric and an NCF, or a knitted fabric and an NCF.
織物としては、アラミド繊維束を一方向に配列させたトウシートや、アラミド繊維糸条を一方向又は二方向に配列させた一方向性織物、や二方向性織物、三方向に配列させた三軸織物等が挙げられる。編物としては、丸編機等のよこ編機、トリコット編機、ラッセル編機、ミラニーズ編機等のたて編機で製編したものが挙げられる。 Examples of woven fabrics include tow sheets in which aramid fiber bundles are aligned in one direction, unidirectional fabrics in which aramid fiber yarns are aligned in one or two directions, bidirectional fabrics, and triaxial fabrics in which aramid fiber yarns are aligned in three directions. Examples of knitted fabrics include those knitted with a weft knitting machine such as a circular knitting machine, or a warp knitting machine such as a tricot knitting machine, a raschel knitting machine, or a Milanese knitting machine.
補強用布帛の目付（単位面積当りの重量）は、２０～１，０００ｇ／ｍ２が好ましく、より好ましくは５０～６００ｇ／ｍ２の範囲内である。シート状基材の目付が小さすぎると任意の製品厚みを得るための積層数が多くなり作業性が悪化し、目付が大きすぎると樹脂の種類によっては樹脂との接着性に劣ることがあり、アラミド繊維がフィブリル化して成形後の外観を損ない、成形品の重量化に繋がったりする。 The basis weight (weight per unit area) of the reinforcing fabric is preferably 20 to 1,000 g/m 2 , and more preferably within the range of 50 to 600 g/m 2. If the basis weight of the sheet-like substrate is too small, the number of layers to obtain a desired product thickness increases, resulting in poor workability, whereas if the basis weight is too large, the adhesion to the resin may be poor depending on the type of resin, the aramid fibers may fibrillate, impairing the appearance after molding, and leading to an increase in the weight of the molded product.
補強用布帛は、下記式（Ｉ）で示す織縮み率が２．０％以下であることが好ましく、より好ましくは１．５％以下、特に好ましくは１．０％以下である。織縮み率が２．０％以下であれば、布帛の構造伸びを小さく抑えることができ、結果として、繊維強化樹脂成形体の剛性を均一に保ち、曲げ荷重にかかる応力集中を軽減させることができるため、耐疲労特性に優れた繊維強化樹脂成形体を得ることができる。
織縮み率＝［（糸長－織物長）／織物長］×１００ ・・・ （Ｉ）
The reinforcing fabric preferably has a weave shrinkage ratio of 2.0% or less, more preferably 1.5% or less, and particularly preferably 1.0% or less, as shown in the following formula (I). If the weave shrinkage ratio is 2.0% or less, the structural elongation of the fabric can be kept small, and as a result, the rigidity of the fiber-reinforced resin molded body can be kept uniform and the stress concentration applied to the bending load can be reduced, so that a fiber-reinforced resin molded body with excellent fatigue resistance can be obtained.
Weaving shrinkage rate = [(yarn length - woven fabric length) / woven fabric length] x 100 (I)
＜半硬化状態の熱硬化性樹脂（Ｂ）＞
本発明で用いられる、半硬化状態の熱硬化性樹脂は特に限定されないが、一例として、エポキシ樹脂、シアネート系樹脂、ビスマレイミド系樹脂、ベンゾオキサジン系樹脂が挙げられ、耐熱性、力学特性及びアラミド繊維との接着性のバランスに優れていることから、エポキシ樹脂を用いることが好ましい。熱硬化性樹脂は、繊維表面の遊離エポキシ化合物と反応し得るために半硬化状態であることが必要である。半硬化状態とは、硬化反応の中間段階の状態であり、ワニス状態であるＡステージと硬化した状態のＣステージの間の段階である。半硬化状態の熱硬化性樹脂は、粘着性及び体積の経時変化が小さいため、成形時の取り扱いに適切なタック性を有する効果が得られる。
<Semi-cured thermosetting resin (B)>
The semi-cured thermosetting resin used in the present invention is not particularly limited, but examples include epoxy resins, cyanate resins, bismaleimide resins, and benzoxazine resins. It is preferable to use epoxy resins because they have an excellent balance of heat resistance, mechanical properties, and adhesion to aramid fibers. The thermosetting resin needs to be in a semi-cured state so that it can react with the free epoxy compound on the fiber surface. The semi-cured state is an intermediate stage of the curing reaction, and is a stage between the A stage, which is a varnish state, and the C stage, which is a cured state. The semi-cured thermosetting resin has small changes in adhesion and volume over time, so it has the effect of having tackiness suitable for handling during molding.
エポキシ樹脂としては、特に限定されるものではなく、ビスフェノール型エポキシ樹脂、アミン型エポキシ樹脂、フェノールノボラック型エポキシ樹脂、クレゾールノボラック型エポキシ樹脂、レゾルシノール型エポキシ樹脂、フェノールアラルキル型エポキシ樹脂、ナフトールアラルキル型エポキシ樹脂、ジシクロペンタジエン型エポキシ樹脂、ビフェニル骨格を有するエポキシ樹脂、イソシアネート変性エポキシ樹脂、テトラフェニルエタン型エポキシ樹脂、トリフェニルメタン型エポキシ樹脂、ジグリシジルアニリン誘導体などの中から１種以上を選択して用いることができる。 The epoxy resin is not particularly limited, and one or more types can be selected from bisphenol type epoxy resins, amine type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, resorcinol type epoxy resins, phenol aralkyl type epoxy resins, naphthol aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, epoxy resins having a biphenyl skeleton, isocyanate modified epoxy resins, tetraphenylethane type epoxy resins, triphenylmethane type epoxy resins, diglycidyl aniline derivatives, etc.
＜繊維強化樹脂成形用基材＞
本発明の繊維強化樹脂成形用基材は、上記のアラミド繊維からなる補強用布帛に半硬化状態の熱硬化性樹脂を含浸してなるものであるが、含浸させる手段は特に限定されるものではなく、公知の製造方法を用いて製造することができる。
例えば、熱硬化性樹脂組成物をメチルエチルケトン、メタノール等の溶媒に溶解して低粘度化し、含浸させるウェット法、及び、加熱により低粘度化し、含浸させるホットメルト法（ドライ法）等を挙げることができる。ウェット法は、強化繊維を熱硬化性樹脂組成物の溶液に浸漬した後、引き上げ、オーブン等を用いて溶媒を蒸発させる方法である。ホットメルト法は、加熱により低粘度化した熱硬化性樹脂組成物を直接、強化繊維からなる繊維基材に含浸させる方法であり、熱硬化性樹脂組成物を加熱加圧することにより前記強化繊維からなる繊維基材に樹脂を含浸させる方法である。ホットメルト法によれば、プリプレグ中に残留する溶媒が実質上皆無となるため好ましい。
<Substrate for fiber reinforced resin molding>
The fiber-reinforced resin molding substrate of the present invention is obtained by impregnating the reinforcing fabric made of the above-mentioned aramid fiber with a semi-cured thermosetting resin. The means for impregnation is not particularly limited, and the substrate can be produced using a known production method.
For example, the wet method in which the thermosetting resin composition is dissolved in a solvent such as methyl ethyl ketone or methanol to reduce the viscosity and impregnate the composition, and the hot melt method (dry method) in which the thermosetting resin composition is heated to reduce the viscosity and impregnated, can be mentioned. The wet method is a method in which the reinforcing fiber is immersed in a solution of the thermosetting resin composition, then pulled up, and the solvent is evaporated using an oven or the like. The hot melt method is a method in which the thermosetting resin composition, the viscosity of which has been reduced by heating, is directly impregnated into a fiber substrate made of reinforcing fibers, and the thermosetting resin composition is heated and pressurized to impregnate the fiber substrate made of the reinforcing fibers with the resin. The hot melt method is preferable because substantially no solvent remains in the prepreg.
本発明の繊維強化樹脂成形用基材における樹脂の占める割合（ＲＣ）は、繊維強化樹脂成形用基材全体を１００とした場合で１０～９０質量％、好ましくは２０～８０質量％、より好ましくは３０～７０質量％である。全体に占める割合が１０質量％未満であると、成形時に十分に繊維内で含浸していない恐れがあり、９０質量％を超えると繊維による補強効果が十分に得られない恐れがある。 The resin ratio (RC) in the fiber-reinforced resin molding substrate of the present invention is 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass, assuming the entire fiber-reinforced resin molding substrate to be 100. If the ratio is less than 10% by mass, there is a risk that the resin will not be sufficiently impregnated into the fibers during molding, and if it exceeds 90% by mass, there is a risk that the reinforcing effect of the fibers will not be fully obtained.
＜繊維樹脂成形体＞
本発明の繊維強化樹脂成形用基材を用いて成形した繊維強化樹脂成形体において、アラミド繊維の占める割合（Ｖｆ）は、繊維強化樹脂成形体全体を１００とした場合で１０～９０体積％であり、好ましくは２０～８０体積％、より好ましくは３０～７０体積％である。全体に占める割合が１０体積％未満であると、製品中にボイド（空隙）が生じ製品特性が悪化する恐れがあり、９０％を超えると繊維による補強効果が十分に得られない恐れがある。
<Fiber resin molding>
In the fiber-reinforced resin molded product molded using the fiber-reinforced resin molding substrate of the present invention, the proportion of aramid fibers (V f ) is 10 to 90 volume %, preferably 20 to 80 volume %, and more preferably 30 to 70 volume %, when the entire fiber-reinforced resin molded product is taken as 100. If the proportion of the entire product is less than 10 volume %, voids (gaps) may occur in the product, deteriorating the product characteristics, and if it exceeds 90%, the reinforcing effect of the fibers may not be sufficiently obtained.
本発明によれば、ボイド率が５．０％以下の繊維強化樹脂成形体が得られる。前記ボイド率は、より好ましくは２．０％以下、さらに好ましくは１．０％以下である。ボイド率がこの範囲にあると、曲げ荷重にかかる応力集中を避けることができ、耐疲労特性に優れた繊維強化樹脂成形体を得ることができる。
また、本発明の繊維強化樹脂成形体における、ＪＩＳ Ｋ７０１７に準じた３点曲げ試験条件における曲げ歪み１．０％時の曲げ荷重から算出される強力保持率は、９６．０％以上である。従って、ボイド率が５．０％以下の繊維強化樹脂成形体でありながら、成形体の強力保持率が高い。
According to the present invention, a fiber-reinforced resin molding having a void ratio of 5.0% or less can be obtained. The void ratio is more preferably 2.0% or less, and even more preferably 1.0% or less. When the void ratio is in this range, stress concentration due to bending load can be avoided, and a fiber-reinforced resin molding having excellent fatigue resistance can be obtained.
In addition, the fiber reinforced resin molding of the present invention has a strength retention of 96.0% or more, calculated from a bending load at a bending strain of 1.0% in a three-point bending test according to JIS K 7017. Therefore, even though the fiber reinforced resin molding has a void ratio of 5.0% or less, the molding has a high strength retention.
本発明の繊維強化樹脂成形体を成形する方法に特に規定はなく、任意の成形方法（フィラメントワインディング、オートクレーブ、シートワインディング、プレス成形等）を取ることができる。しかし、ボイド発生を抑制するためには、真空状態で加温することが可能なオートクレーブでの成形方法がより好ましい。 There are no particular restrictions on the method for molding the fiber-reinforced resin molding of the present invention, and any molding method (filament winding, autoclave, sheet winding, press molding, etc.) can be used. However, in order to suppress the generation of voids, a molding method using an autoclave, which allows heating in a vacuum state, is more preferable.
以下に実施例を挙げて本発明をさらに具体的に説明するが、本発明はそれらに限定されるものではない。また、以下の実施例等において、特に言及する場合を除き、「重量部」は「部」と略記する。なお、実施例中に記載した評価方法は以下の通りである。 The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the following examples, "parts by weight" will be abbreviated to "parts" unless otherwise specified. The evaluation methods described in the examples are as follows.
（１）繊維の水分率（質量％）
試料約５ｇの質量を測定し、１０５℃×４時間処理を行い、２４℃、５５％ＲＨで５分間放置した後、再度質量を測定し、下記式にてドライベース水分率を求めた。
水分率＝（［乾燥前質量－乾燥後質量］／［乾燥後質量］）×１００
(1) Moisture content of fiber (mass%)
The mass of about 5 g of the sample was measured, treated at 105° C. for 4 hours, and then allowed to stand at 24° C. and 55% RH for 5 minutes. The mass was then measured again and the dry base moisture content was calculated using the following formula.
Moisture content = ([mass before drying - mass after drying] / [mass after drying]) x 100
（２）繊維表面に用いる硬化性エポキシ樹脂の粘度（ｍＰａ・ｓ）
ＪＩＳ Ｋ７２４４「プラスチック－動的機械特性の試験方法－第１０部：平行平板振動レオメーターによる複素せん断粘度」に記載される方法に従った。
(2) Viscosity of the curable epoxy resin used on the fiber surface (mPa·s)
The method described in JIS K7244 "Plastics-Test methods for dynamic mechanical properties-Part 10: Complex shear viscosity by parallel plate oscillatory rheometer" was followed.
（３）繊維表面の遊離エポキシ化合物量（ｍｍｏｌ／ｋｇ）
アラミド繊維約１０ｇ（実重量Ａｇ）をビーカーに入れ、アセトンで試料表面に付着した遊離エポキシ化合物を抽出した後、アセトンを除去して、抽出物重量を測定する。前記抽出物に、塩酸／１，４－ジオキサン混合溶液（１５／１０００（容量比））２０ｍＬとエタノール３０ｍＬを添加した後、０．５ｍｏｌ／ＬのＮａＯＨ溶液で中和滴定（滴定量：ＣｍＬ）を行う。抽出物を含まない前記の塩酸／１，４－ジオキサン混合溶液についてブランク滴定（滴定量：ＤｍＬを行い、アラミド繊維１ｋｇ当りに存在する遊離エポキシ基のミリモル数を算出する。
［遊離エポキシ化合物量（ｍｍｏｌ／ｋｇ）］＝０．５×１０００×（Ｄ－Ｃ）／Ａ
(3) Amount of free epoxy compound on fiber surface (mmol/kg)
Approximately 10 g (actual weight Ag) of aramid fiber is placed in a beaker, and the free epoxy compounds attached to the sample surface are extracted with acetone, and then the acetone is removed and the weight of the extract is measured. 20 mL of a hydrochloric acid/1,4-dioxane mixed solution (15/1000 (volume ratio)) and 30 mL of ethanol are added to the extract, and neutralization titration (titration amount: C mL) is performed with a 0.5 mol/L NaOH solution. A blank titration (titration amount: D mL) is performed on the hydrochloric acid/1,4-dioxane mixed solution not containing the extract, and the number of millimoles of free epoxy groups present per kg of aramid fiber is calculated.
[Amount of free epoxy compound (mmol/kg)]=0.5×1000×(D−C)/A
（４）補強用布帛の目付（ｇ／ｍ２）
ＪＩＳ Ｌ１０９６：２０２０「織物および編物の生地試験方法」に記載される方法に従った。
(4) Weight of reinforcing fabric (g/m 2 )
The method described in JIS L1096:2020 "Testing methods for woven and knitted fabrics" was followed.
（５）補強用布帛を構成するポリパラフェニレンテレフタルアミド繊維の織縮み率
ＪＩＳ Ｌ１０９６：２０２０「織物および編物の生地試験方法」に記載される方法に従い、下記式にて織縮み率を求めた。
織縮み率＝［（糸長－織物長）／織物長］×１００
(5) Weave shrinkage rate of polyparaphenylene terephthalamide fiber constituting reinforcing fabric The weave shrinkage rate was calculated using the following formula according to the method described in JIS L1096:2020 “Fabric test method for woven and knitted fabrics”.
Weaving shrinkage rate = [(yarn length - woven fabric length) / woven fabric length] x 100
（６）繊維強化樹脂成形体の繊維体積含有率
成形品のサイズ、並びに積層数から強化繊維樹脂成形体中の有機長繊維の重量（Ｗ）を算出し、下記式にて繊維体積含有率（Ｖｆ）を求める。
Ｗｆ ＝ Ｗ ／ ＷＦ × １００
Ｖｆ ＝ Ｗｆ × ρc ／ ρｆ
Ｗｆ ： 繊維質量含有率（％）
Ｗ ： 繊維強化樹脂成形体中の有機長繊維重量（ｇ）
ＷＦ ： 繊維強化樹脂成形体の重量（ｇ）
Ｖｆ ： 繊維体積含有率（％）
ρｃ ： 繊維強化樹脂成形体の密度（ｇ／ｃｍ３）
ρｆ ： 有機長繊維の密度（ｇ／ｃｍ３）
(6) Fiber Volume Content of Fiber-Reinforced Resin Molded Product The weight (W) of the organic long fibers in the fiber-reinforced resin molded product is calculated from the size of the molded product and the number of layers, and the fiber volume content (V f ) is calculated using the following formula.
Wf = W / WF x 100
Vf = Wf × ρc / ρf
Wf : Fiber mass content (%)
W: Weight of organic long fibers in the fiber-reinforced resin molding (g)
WF : Weight of fiber-reinforced resin molding (g)
Vf : fiber volume content (%)
ρ c : Density of fiber reinforced resin molding (g/cm 3 )
ρ f : Density of organic long fiber (g/cm 3 )
（７）繊維強化樹脂成形体のボイド率
成形品のサイズ、ならびに重量、比重から強化繊維樹脂成形体中のボイド（空隙）体積（Ｖｖ）を算出し、下記式にてボイド率（Ｒ）を求める。
Ｖｖ ＝ Ｖ － ＷＦ ／ ρｃ
Ｒ ＝ Ｖｖ ／ Ｖ
Ｖｖ ： 繊維強化樹脂成形体中のボイド（空隙）体積（ｃｍ３）
Ｖ ： 成形品サイズから求めた繊維強化樹脂成形体の体積（ｃｍ３）
ＷＦ ： 繊維強化樹脂成形体の重量（ｇ）
ρｃ ： 繊維強化樹脂成形体の比重（ｇ／ｃｍ３）
Ｒ ： ボイド率（％）
(7) Void Fraction in Fiber-Reinforced Resin Molded Product The void (air space) volume (V v ) in a fiber-reinforced resin molded product is calculated from the size, weight, and specific gravity of the molded product, and the void fraction (R) is calculated using the following formula.
Vv = V - WF / ρc
R = Vv /V
V v : void (air gap) volume in the fiber reinforced resin molding (cm 3 )
V: Volume of the fiber reinforced resin molding calculated from the molded product size (cm 3 )
WF : Weight of fiber-reinforced resin molding (g)
ρ c : Specific gravity of fiber reinforced resin molding (g/cm 3 )
R: Void ratio (%)
（８）繊維強化樹脂成形体の曲げ強度及び曲げ弾性率
ＪＩＳ Ｋ７０７４に記載される方法（３点曲げ試験）に従った。
(8) Flexural strength and flexural modulus of fiber-reinforced resin molding The method described in JIS K7074 (three-point bending test) was followed.
（９）繊維強化樹脂成形体の曲げ疲労特性（強力保持率）
ＪＩＳ Ｋ７０７４に記載される方法（３点曲げ試験）に従い、支点間距離を４０ｍｍで固定、下記式の試験速度における曲げ歪み１．０％で１００回繰り返し測定し、曲げ歪み１．０％時の曲げ荷重から強力保持率を算出する。
Ｖ ＝ Ｓｒ × Ｌ２ ／ （６ × Ｈ）
Ｖ ： 試験速度（ｍｍ／ｍｉｎ）
Ｓｒ ： ひずみ速度（ｍｉｎ－１）, Ｓｒ ＝ ０．０１
Ｌ ： 支点間距離（ｍｍ）, Ｌ ＝ ４０
Ｈ ： 試験片の厚み（ｍｍ）
(9) Bending fatigue properties (strength retention rate) of fiber-reinforced resin molded body
According to the method described in JIS K7074 (three-point bending test), the distance between the supports is fixed at 40 mm, and measurements are repeated 100 times at a bending strain of 1.0% at a test speed according to the following formula, and the strength retention is calculated from the bending load at the bending strain of 1.0%.
V = Sr × L2 / (6 × H)
V: Test speed (mm/min)
Sr : Strain rate (min -1 ), Sr = 0.01
L: Distance between supports (mm), L = 40
H: Thickness of test piece (mm)
（１０）繊維強化樹脂成形用基材の工程通過性
工程通過性は繊維強化樹脂成形用基材のホットメルト法（ドライ法）製造工程における毛羽やスカム発生を基に以下通り評価した。
〇：毛羽やスカム発生なし
×：毛羽やスカム発生あり
(10) Processability of Fiber-Reinforced Plastic Molding Substrate The processability was evaluated as follows based on the generation of fluff and scum in the hot melt method (dry method) manufacturing process of the fiber-reinforced plastic molding substrate.
◯: No fluff or scum generated. ×: Fuzz or scum generated.
実施例で用いたアラミド繊維布帛（Ａ－１）～（Ａ－７）の詳細を表１に示す。 Details of the aramid fiber fabrics (A-1) to (A-7) used in the examples are shown in Table 1.
実施例で用いた熱硬化性樹脂（Ｂ）は、三菱ケミカル社製ｊＥＲ８２８（ビスフェノールＡグリシジルエーテル；エポキシ等量１８９ｇ／ｅｑ）５０部及び三菱ケミカル社製ｊＥＲ１００１（ビスフェノールＡグリシジルエーテル；エポキシ当量４７５ｇ／ｅｑ）５０部とからなる主剤１００部に対し、ジシアンジアミド５部、及び３－（３、４－ジクロロフェニル）－１、１－ジメチル尿素５部を硬化剤として加えた後に均一に混合し、一液硬化エポキシ樹脂組成物を用いた。 The thermosetting resin (B) used in the examples was a one-part curing epoxy resin composition prepared by adding 5 parts of dicyandiamide and 5 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea as hardeners to 100 parts of a base material consisting of 50 parts of Mitsubishi Chemical Corporation's jER828 (bisphenol A glycidyl ether; epoxy equivalent 189 g/eq) and 50 parts of Mitsubishi Chemical Corporation's jER1001 (bisphenol A glycidyl ether; epoxy equivalent 475 g/eq), and then mixing them uniformly.
［実施例１～３、比較例１～５］
表１のアラミド繊維布帛に、事前に調製したエポキシ樹脂を、ホットメルト法（ドライ法）にて含浸させ、繊維強化樹脂成形用基材を得た。得られた繊維強化樹脂複合体成形用基材を指定枚数、指定構成に積層した。
[Examples 1 to 3, Comparative Examples 1 to 5]
The aramid fiber fabric in Table 1 was impregnated with the epoxy resin prepared in advance by a hot melt method (dry method) to obtain a substrate for fiber reinforced resin molding. The obtained substrate for fiber reinforced resin composite molding was laminated in the specified number and configuration.
実施例１～３、比較例１～３、比較例５に関しては、オートクレーブにて加圧・加熱（１３５℃×０．５ＭＰａ×２時間）、比較例４に関しては、手動熱プレス装置（東洋精機社製「ミニテストプレス」）にて加圧・加熱（１２０℃×１０ＭＰａ×２時間）を行い、繊維強化樹脂成形体を得た。各水準について、前記した測定方法で各種評価を行った結果を表２に示す。 For Examples 1 to 3, Comparative Examples 1 to 3, and Comparative Example 5, pressurization and heating were performed in an autoclave (135°C x 0.5 MPa x 2 hours), and for Comparative Example 4, pressurization and heating (120°C x 10 MPa x 2 hours) were performed in a manual heat press device (Toyo Seiki Co., Ltd.'s "Mini Test Press") to obtain fiber-reinforced resin molded bodies. The results of various evaluations performed for each level using the measurement methods described above are shown in Table 2.
表２に記載した通り、アラミド繊維表面に、未硬化の硬化性エポキシ化合物（遊離エポキシ含有量）を有しない、もしくは繊維１ｋｇ当たり２０．０ｍｍｏｌ未満の未硬化の硬化性エポキシ化合物（遊離エポキシ含有量）を有する繊維強化樹脂成形用基材を成形してなる繊維強化樹脂成形体は、ボイド率が５．０％以下であったが、曲げ歪を繰り返した後の強力保持率が低く、耐疲労性向上効果を発揮できない（比較例１、２）ことが分かる。 As shown in Table 2, fiber-reinforced resin moldings obtained by molding a fiber-reinforced resin molding substrate that does not have uncured curable epoxy compounds (free epoxy content) on the aramid fiber surface or has uncured curable epoxy compounds (free epoxy content) of less than 20.0 mmol per kg of fiber had a void ratio of 5.0% or less, but had low strength retention after repeated bending strain, and could not demonstrate the effect of improving fatigue resistance (Comparative Examples 1 and 2).
一方、アラミド繊維表面に、繊維１ｋｇ当たり２０．０ｍｍｏｌ以上の未硬化の硬化性エポキシ化合物（遊離エポキシ含有量）を有する繊維強化樹脂成形用基材であっても、補強用布帛の織縮み率が２．０％を超える、あるいは、ボイド率が５．０％を超える繊維強化樹脂成形体は、耐疲労性向上効果を充分発揮できない（比較例３、４）ことが分かる。 On the other hand, even if the fiber-reinforced resin molding substrate has 20.0 mmol or more of uncured curable epoxy compound (free epoxy content) per 1 kg of fiber on the aramid fiber surface, the fiber-reinforced resin molding cannot fully exhibit the fatigue resistance improvement effect when the reinforcing fabric has a shrinkage rate of more than 2.0% or a void rate of more than 5.0% (Comparative Examples 3 and 4).
また該硬化性エポキシ化合物の２５℃における粘度が５００ｍＰａ・ｓを超える繊維強化樹脂成形用基材は毛羽・スカムが発生するため工程通過性が悪く、その繊維強化樹脂成形体は強力発現率が悪いため、耐疲労特性を充分発揮できない（比較例５）ことが分かる。 Furthermore, it can be seen that a fiber-reinforced resin molding substrate in which the viscosity of the curable epoxy compound at 25°C exceeds 500 mPa·s generates fluff and scum, leading to poor processability, and the fiber-reinforced resin molding has a poor strength expression rate and is therefore unable to fully demonstrate fatigue resistance (Comparative Example 5).
これに対して、本発明の繊維強化樹脂成形用基材は、低粘度の硬化性エポキシ化合物で処理されたアラミド繊維を用い、かつ、アラミド繊維表面に付着した硬化性エポキシ化合物の未硬化物（遊離エポキシ）の含有量を制御し、さらに補強用布帛の織縮率を低減させることにより、成形体のボイド率を非常に低く抑えることが可能であることが分かる。 また、該繊維強化樹脂成形用基材を成形してなる本発明の繊維強化樹脂成形体は、耐疲労特性、工程通過性にも優れることが分かる。よって本発明は有用であることが示された。 In contrast, the fiber-reinforced resin molding substrate of the present invention uses aramid fibers treated with a low-viscosity curable epoxy compound, controls the content of uncured curable epoxy compound (free epoxy) attached to the aramid fiber surface, and further reduces the shrinkage rate of the reinforcing fabric, making it possible to keep the void rate of the molded product extremely low. In addition, the fiber-reinforced resin molding of the present invention, which is molded from the fiber-reinforced resin molding substrate, is also excellent in fatigue resistance and processability. This demonstrates that the present invention is useful.
本発明の繊維強化樹脂成形用基材ならびに繊維強化樹脂成形体は、従来のアラミド繊維補強複合材料よりも優れた耐疲労特性を有することから、航空機、宇宙用各種部品、圧力容器、産業機器部品、プリント基板、スポーツ用品など幅広く利用できる。 The fiber-reinforced resin molding substrate and fiber-reinforced resin molding of the present invention have superior fatigue resistance properties compared to conventional aramid fiber-reinforced composite materials, and can therefore be used in a wide range of applications, including aircraft and space parts, pressure vessels, industrial equipment parts, printed circuit boards, and sporting goods.
１０ 繊維強化樹脂成形用基材
２０ 繊維強化樹脂成形体
10 Fiber-reinforced resin molding substrate 20 Fiber-reinforced resin molding
Claims (5)
前記アラミド繊維は、繊維表面に未硬化の硬化性エポキシ化合物を有しており、
前記繊維強化樹脂成形用基材を用いて成形・硬化させた繊維強化樹脂成形体は、
（１）ボイド率が５．０％以下であり、かつ
（２）ＪＩＳ Ｋ７０１７に準じた３点曲げ試験条件における曲げ歪み１．０％時の曲げ荷重から算出される強力保持率が９６．０％以上である
ことを特徴とする繊維強化樹脂成形用基材。 A fiber-reinforced resin molding substrate comprising a reinforcing fabric (A) made of aramid fibers and a semi-cured thermosetting resin (B),
The aramid fiber has an uncured curable epoxy compound on a fiber surface,
A fiber-reinforced resin molded body molded and cured using the fiber-reinforced resin molding substrate is
(1) A substrate for fiber-reinforced resin molding, characterized in that the void ratio is 5.0% or less, and (2) the strength retention calculated from the bending load at a bending strain of 1.0% in a three-point bending test condition in accordance with JIS K7017 is 96.0% or more.
請求項１に記載の繊維強化樹脂成形用基材。 the curable epoxy compound is a tri- or higher functional curable epoxy compound, and the viscosity of the epoxy compound at 25° C. is 500 mPa·s or less;
The fiber-reinforced resin molding substrate according to claim 1 .
請求項１に記載の繊維強化樹脂成形用基材。 The aramid fiber surface has 20.0 mmol or more of an uncured curable epoxy compound (free epoxy content) per 1 kg of fiber.
The fiber-reinforced resin molding substrate according to claim 1 .
請求項１に記載の繊維強化樹脂成形用基材。
織縮み率（％）＝［（糸長－織物長）／織物長］×１００ ・・・ （Ｉ）
The reinforcing fabric (A) made of the aramid fibers has a yarn shrinkage rate of 2.0% or less, as defined by the following formula (I), measured by the method described in JIS L1096:
The fiber-reinforced resin molding substrate according to claim 1 .
Weaving shrinkage rate (%) = [(yarn length - woven fabric length) / woven fabric length] x 100 (I)
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