JP3653906B2 - Epoxy resin composition, prepreg and fiber reinforced composite material - Google Patents

Description

式中、Ｒ₁〜Ｒ₂は、無置換またはハロゲン、水酸基、シアノ基より選ばれる置換基を１個または複数個有するアルキル基、アリール基、アラルキル基を表し、Ｒ₃〜Ｒ₄は、無置換またはハロゲン、水酸基、シアノ基より選ばれる置換基を１個または複数個有するアルキル基、アリール基、アラルキル基または水素原子を表す。ここでアルキル基とは、飽和炭化水素より誘導される置換基を意味し、直鎖でも、分岐を有しても、環状構造を有してもよい。アリール基とは、芳香族炭化水素により誘導される置換基で、自由原子価が芳香環上にあるものを意味し、フェニル基のように芳香環のみからなるものでも、トリル基のような芳香族炭化水素構造を部分構造として有するものでもよい。アラルキル基とは、アリール基を無置換またはハロゲン、水酸基、シアノ基より選ばれる置換基を１個または複数個有するアルキル基、アリール基、アラルキル基を置換基として有するアルキル基を意味する。
【００２４】
上式（１）に示すイミダゾール誘導体の具体例としては、１-ベンジル-２-メチルイミダゾール、１-ベンジル-２-エチルイミダゾール、１-ベンジル-２-フェニルイミダゾール、１-ベンジル-２-エチル-４-メチルイミダゾール、１-ベンジル-２-エチル-４-メチルイミダゾール、１-ベンジル-２-エチル-５-メチルイミダゾール、１-（２-シアノエチル）-２-メチルイミダゾール、１-（２-シアノエチル）-２-エチルイミダゾール、１-（２-シアノエチル）-２-イソプロピルイミダゾール、１-（２-シアノエチル）-２-ウンデシルイミダゾール、１-（２-シアノエチル）-２-ヘプタデシルイミダゾール、１-（２-シアノエチル）-２-フェニルイミダゾール、１-（２-シアノエチル）-２-エチル-４-メチルイミダゾール、１-（２-シアノエチル）-２-エチル-５-メチルイミダゾールなどを挙げることができる。
【００２５】
１-位に置換基を有するイミダゾール誘導体としては、次式（２）に示す１-位に置換基をもたないイミダゾール誘導体とエポキシ化合物の反応により得られる付加物が特に好ましい。
【００２６】
【化２】

式中、Ｒ₅は無置換またはハロゲン、水酸基、シアノ基より選ばれる置換基を１個または複数個有するアルキル基、アリール基、アラルキル基を表し、Ｒ₆〜Ｒ₇は、無置換またはハロゲン、水酸基、シアノ基より選ばれる置換基を１個または複数個有するアルキル基、アリール基、アラルキル基または水素原子を表す。
【００２７】
本発明の複合材料用エポキシ樹脂組成物中の成分［Ｃ］として、１-位に置換基をもたないイミダゾール誘導体とエポキシ化合物の反応により得られる付加物を用いると、１３５℃、２時間の加熱で９０％以上の高い硬化反応率を示し、且つ沸騰水に２０時間浸漬後でも０.８ＧＰａ以上の高い剛性率を有するエポキシ樹脂組成物が得られる。一般にイミダゾール系化合物はその高い反応性のために、保存安定性が低いことがしばしば問題となる。しかし、このイミダゾール誘導体とエポキシ化合物の反応により得られる付加物とホウ酸エステル化合物を併用した場合、優れた保存安定性が得られる。また、このイミダゾール誘導体とエポキシ化合物の付加物による硬化物は、吸水率が低いという好ましい性質を有する。
【００２８】
上記の付加物からなる粒子を、成分［Ｃ］として用いる場合、上記の付加物の配合量は、成分［Ａ］と成分［Ｂ］のエポキシ樹脂の総重量の１/１０〜３/１０の範囲内であることが好ましい。１/１０未満であれば、加熱後の硬化反応率が不十分になることがあり、３/１０を越えると、付加物が硬化過程で析出し、硬化反応率が不均一になるいう問題を生じる場合がある。
上記の付加物の合成に用いるイミダゾール誘導体の具体例としては、2-メチルイミダゾール、2-エチルイミダゾール、2-イソプロピルイミダゾール、2-ウンデシルイミダゾール、2-ヘプタデシルイミダゾール、2-フェニルイミダゾール、2-エチル-4-メチルイミダゾール、4、5-ビスヒドロキシメチル-2-フェニルイミダゾール、5-ヒドロキシメチル-4-メチル-2-フェニルイミダゾール、4-ベンジル-5-ヒドロキシメチル-2-フェニルイミダゾール、4、5-ビスヒドロキシメチル-2-フェニルイミダゾールなどを挙げることができる。また、上記の付加物の合成に用いるエポキシ化合物の具体例としては、フェニルグリシジルエーテル、ブチルグリシジルエーテルなどのモノエポキシ化合物、ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂などのジエポキシ化合物が挙げられる。
【００２９】
２-エチル-４-メチルイミダゾールとビスフェノールＡ型エポキシ樹脂をあらかじめ反応させた付加物を粒子としたものが、四国化成工業（株）より商品名「キュアダクトP-０５０５」として市販されている。キュアダクトP-０５０５の平均粒径は２μｍであり、粒径２０μｍ以上の粒子が占める割合は１重量％未満である。本発明において、成分［Ｃ］としてこのような市販品を使用することもできる。
【００３０】
本発明において、成分［Ｄ］はホウ酸エステル化合物である。ホウ酸エステル化合物としては、下記の一般式で表される化合物を用いることができる。
【００３１】
【化３】

（式中、R₈〜R₁₀はアルキル基、アラルキル基、またはアリール基を表す。）
ホウ酸エステル化合物は、上述したアミン系化合物からなる粒子の表面で、そのアミン系化合物と反応し錯体を形成し、アミン系化合物の活性を低めるため、樹脂組成物及びこれを用いたプリプレグの保存安定性を大幅に向上できる。
【００３２】
ホウ酸エステル化合物の代表的なものとしては、ホウ酸トリメチルエステルホウ酸トリエチルエステル、ホウ酸トリプロピルエステル、ホウ酸トリイソプロピルエステル、ホウ酸トリブチルエステル、ホウ酸トリイソブチルエステル、ホウ酸トリペンチルエステル、ホウ酸トリヘキシルエステル、ホウ酸トリオクチルエステル、ホウ酸トリヘキサデシルエステル、ホウ酸トリオクタデシルエステル、ホウ酸トリクレジルエステル、ホウ酸トリヘキサデシルエステル、ホウ酸トリシクロヘキシルエステル、ホウ酸トリフェニルエステル、ホウ酸トリトリルエステル、ホウ酸トリベンジルエステル、ホウ酸ジメチルエステル、ホウ酸ジエチルエステル、及びホウ酸モノメチルエステル等がある。これらのホウ酸エステル化合物は毒性、金属腐食性に問題がないので本発明において好適に用いられる。
【００３３】
成分［Ｄ］としては、ホウ酸エステル化合物を単独で用いてもよく、またシランカップリング剤、チタネートカップリング剤、アルミネートカップリング剤、及びジルコアルミネートカップリング剤等をホウ酸エステル化合物と併用しても差し支えない。また、アミン系化合物の付加反応の制御または酸化防止のため、成分［Ｄ］には、フェノール系化合物などの添加剤が含まれていてもよい。添加するフェノール系化合物としてはピロガロール、フェノール樹脂などの化合物、及びヒンダードフェノール系酸化防止剤、トコフェロール系酸化防止剤などが用いられる。
【００３４】
上記成分［Ｄ］は、エポキシ樹脂への混練前に、上記成分［Ｃ］に予め付与し、成分［Ｃ］の表面を被覆、すなわち表面処理しておいてもよい。本発明において、エポキシ樹脂及び必要に応じて他の原料と混練する前に、［Ｃ］成分を［Ｄ］成分で予め表面処理する場合には、その表面処理の方法としては、ミキサー中で撹拌する方法、あるいは、特開平６-７３１５６号公報に記載されるように、気流型粉砕機または気流型分級機中で接触させる方法が用いられる。
【００３５】
また、本発明のエポキシ樹脂組成物は、［Ｃ］成分及び［Ｄ］成分を個別にエポキシ樹脂及び必要に応じて他の原料に加えた後、撹拌混練することによっても得られる。この製造方法の場合、ホウ酸エステル化合物はエポキシ樹脂と反応性がないので、エポキシ樹脂中で［Ｃ］成分の表面がホウ酸エステル化合物により処理される。また、混練時にアミン系化合物からなる粒子の表面処理が破壊されても、修復が可能であることを示唆するものである。
【００３６】
ホウ酸エステル化合物とエポキシ樹脂、フェノール樹脂を予め配合したものが、四国化成工業（株）より商品名「キュアダクトL０１-B」として市販されている。キュアダクトL０１-Bは、ホウ酸トリブチルエステル５重量％とフェノールノボラック樹脂５重量％とビスフェノールＡ型エポキシ樹脂９０重量％の混合物である。本発明には、このような市販品を使用することもできる。
【００３７】
本発明のエポキシ樹脂組成物は、上記成分［Ａ］、［Ｂ］、［Ｃ］および［Ｄ］に加えて、上記成分［Ｃ］以外の硬化剤、熱可塑性樹脂、エラストマー、熱可塑性エラストマー等を配合することもできる。
【００３８】
成分［Ｃ］以外の硬化剤を配合する場合は、前述のイミダゾールおよび／またはその誘導体により硬化反応が促進作用または触媒作用を受けるものが好ましい。
【００３９】
熱可塑性樹脂、エラストマー、熱可塑性エラストマーは、エポキシ樹脂の粘度調整、プリプレグのタック調整、硬化過程におけるフロー制御、硬化物の靭性向上、強化繊維との接着性向上の目的で添加される。
【００４０】
熱可塑性樹脂としては、エポキシ樹脂に溶解が容易なものが好ましく用いられる。またエポキシ樹脂に不溶の熱可塑性樹脂であっても、微粒子化したものであれば、配合することができる。具体的には、アクリル樹脂、フェノキシ樹脂、ポリビニルアセタール、ポリエステル、ポリカーボネート、ポリスルホン、ポリアリーレンオキシド、ポリアミド、ポリイミドが用いられる。ポリビニルアセタールはポリビニルアルコールをホルムアルデヒドやアセトアルデヒドなどのカルボニル化合物でアセタール化した樹脂で、ポリビニルホルマール、ポリビニルアセタールが挙げられる。フェノキシ樹脂はビスフェノールＡとエポクロロヒドリンを縮合させて得られる樹脂である。ポリエステルは、主鎖にカルボン酸エステル結合有するポリマーである。ポリカーボネートは、主鎖に炭酸エステル結合を有するポリマーで、ビスフェノールＡカーボネートが代表的である。ポリアリーレンオキシドは、芳香族二価基と酸素原子が交互に配列した主鎖構造を有する樹脂である。ポリスルホンは主鎖にスルホニル基を有する樹脂である。他にエーテル結合などを主鎖に有するものでもよい。ポリアミドは、主鎖にカルボン酸アミドを有する樹脂である。ポリイミドは、主鎖にジカルボン酸イミド構造を有する樹脂である。他にエーテル結合やアミド結合を有する場合もある。アクリル樹脂はアクリル酸エステルまたはメタクリル酸エステルの重合体で、代表的なものは、ポリメタクリル酸メチルである。
【００４１】
これらのうちポリスルホン、ポリアリーレンオキシド、ポリイミドは耐熱性の要求される用途に適する。ポリビニルホルマールは樹脂のフロー制御及びプリプレグのタックの向上に効果がある。ポリスルホン、ポリビニルホルマールは炭素繊維との接着性の向上及び層間剪断強度、圧縮強度の向上に効果がある。
【００４２】
エラストマーとしては、アクリロニトリルとブタジエンを原料とする共重合体が、エポキシ樹脂に対する溶解性に優れるため好ましく用いられる。特に、カルボキシル基、アミノ基、エポキシ基などのエポキシ樹脂またはその硬化剤と反応しうる官能基を有するものを用いると、硬化物の靭性向上効果が大きいため好ましい。
【００４３】
また、エポキシ樹脂不溶のエラストマー相を含有する粒子も好ましく用いることができる。架橋したエラストマー粒子そのものを用いることもできるが、エポキシ樹脂不溶のエラストマー粒子の表面を非エラストマー成分で被覆したコアシェル型エラストマー粒子を特に好ましく用いることができる。この場合被覆する成分はポリメタクリル酸メチルのようにエポキシ樹脂に溶解、あるいは膨潤するものでもよく、むしろ粒子のエポキシ樹脂中への分散が良好になるため好ましい。エポキシ樹脂不溶のエラストマー相を含有する粒子を用いた場合は、樹脂硬化物の耐熱性が通常のエラストマーより優れる。
【００４４】
これらのエラストマーの添加には、靭性の向上効果及びプリプレグのタック性の向上効果がある。特に粒径が０.１〜０.３μｍ程度の微細なコアシェル型エラストマー粒子を配合した場合は、靭性の向上効果が著しい。
【００４５】
熱可塑性エラストマーとしては、エポキシ樹脂に溶解が容易なものが好ましく用いられる。具体的には、ソフトセグメントとしてポリエーテル構造、ハードセグメントとして、芳香族ポリエステルまたは脂肪族ポリアミド構造をもつブロック共重合体が好ましい。これらの熱可塑性エラストマーの添加は、硬化物の靭性向上、またプリプレグのマトリックス樹脂として用いた場合のタック向上などの効果がある。また通常のエラストマーを添加した場合より、硬化物の耐熱性が優れる。
【００４６】
本発明のエポキシ樹脂組成物には、さらにシリカ、アルミナ、酸化チタン、ジルコニア、粘土鉱物、タルク、雲母、フェライトなどの無機粒子を配合することもできる。これらを添加することにより、樹脂組成物の粘度を高め、樹脂フローを小さくする粘度調整効果、樹脂硬化物の弾性率、耐熱性を向上させる効果、耐摩耗性を向上させる効果がある。
【００４７】
本発明のエポキシ樹脂を強化繊維に含浸させ、加熱することにより、ＦＲＰを得ることができる。強化繊維としては、ガラス繊維、炭素繊維、アラミド繊維、ボロン繊維、アルミナ繊維、炭化ケイ素繊維等が用いられる。この中では、強度、弾性率とも優れ、比重の小さい炭素繊維が、比強度、比弾性率に優れるＦＲＰが得られるため特に好ましい。
【００４８】
エポキシ樹脂組成物と強化繊維から直接ＦＲＰを得る方法としては、強化繊維の織物やマットなどにエポキシ樹脂組成物を塗布し、ローラーなどで加圧含浸させた後、加熱硬化するウェットレイアップ法、強化繊維束にエポキシ樹脂組成物を含浸させてマンドレルと称する型に巻き付け、加熱硬化して成形するフィラメントワインディング法、強化繊維をエポキシ樹脂組成物に含浸させながら所定の形状を有する加熱ダイに供給し、連続的に引き取ることにより賦形と加熱硬化を行って製品を得るプルトルージョン法、連続あるいは所定寸法に切断した強化繊維とともにエポキシ樹脂組成物をシート成形機に供給して加圧含浸し、シート状材料を得るシート・モールディング・コンパウンド法、強化繊維の織物やマットを製品の形状に賦形したプリフォームを金型内に配置し、エポキシ樹脂組成物を金型に注入して硬化するレジン・トランスファー・モールディング法等の方法を用いることができる。これらの方法においては従来は二液型のエポキシ樹脂組成物を用いることが多く、二液混合後の可使時間が短いため、プロセス上の制限が多かったが、本発明のエポキシ樹脂組成物は一液で使用することが可能であり、可使時間の制限も実用上ないためプロセス上の自由が大きく有利である。
【００４９】
また、強化繊維に未硬化のエポキシ樹脂組成物を含浸させて、シート、テープ、あるいは紐状にしたプリプレグという中間体を用いてＦＲＰを得ることができる。プリプレグは一液型のエポキシ樹脂を使用するため、従来のものは、保存安定性が悪く、冷凍保管が必要であった。本発明のエポキシ樹脂組成物は保存安定性に優れるため、冷蔵保管あるいは室温保管が可能になり、従来品と比較してはるかに使いやすい。プリプレグにおける強化繊維の形状は、特に限定されるものではなく、例えば一方向に引き揃えられた長繊維、トウ織物、マット、ニット、組み紐等がある。プリプレグの製造には、例えば、エポキシ樹脂組成物をリバースロールコーターなどを用いて離型紙の上に塗布して樹脂フィルムを作製し、強化繊維の片面または両面から樹脂フィルムを重ね、加熱加圧して強化繊維に含浸させる方法などを用いることができる。
【００５０】
本発明において、エポキシ樹脂組成物の硬化反応率は、赤外線吸収測定により求める。具体的には、エポキシ基の吸収ピーク（９２０cm^-1）強度とフェニレン基の吸収ピーク（８７０cm^-1）強度の相対比の変化から硬化反応率を求める。測定試料は、未硬化樹脂あるいは硬化樹脂を臭化カリウムと混合した後、これを錠剤としたものを用いる。
【００５１】
また、本発明において、樹脂硬化物の吸水率は、１２０℃、２０時間の加熱乾燥した試料の重量と１００℃の沸騰水に２０時間浸漬後の吸水した試料の重量の差から求める。試料の寸法は、厚さ２mm、幅１０mm、長さ５cmである。
【００５２】
さらに、本発明において、樹脂硬化物の剛性率は、動的粘弾性測定により求める。具体的な測定条件は、周波数３.１４rad／s、昇温速度５℃／min、歪０.１％、測定開始温度３０℃である。試料の寸法は、吸水率測定と同様で、厚さ２mm、幅１０mm、長さ５cmである。乾燥状態の剛性率は、乾燥試料として、１２０℃、２０時間の加熱処理したものを用いる。吸水状態の剛性率は、吸水試料として、１００℃の沸騰水に２０時間浸漬したものを用い、試料を沸騰水から取り出した後、直ちに測定を行う。吸水状態の剛性率を測定するとき試料の温度は、通常８２゜程度である。
【００５３】
【実施例】
以下、実施例により本発明をさらに具体的に説明する。
【００５４】
（実施例１〜９、比較例１〜４）
以下に列挙した材料から選ばれた成分を混合し、表１〜３に示す組成のエポキシ樹脂組成物を得た。
【００５５】
これらエポキシ樹脂組成物のそれぞれを１３５℃、２時間加熱して硬化させ硬化物とした。それぞれの硬化物の硬化反応率、吸水率、剛性率を表１〜３に併せて示す。
【００５６】
＜２官能のエポキシ樹脂＞
次の構造式のビスフェノールＡ型エポキシ樹脂 ＹＤ-１２８（東都化成（株）製）
【化４】

次の構造式で示されるビスフェノールＦ型エポキシ樹脂 エピコート８０６（油化シェルエポキシ（株）製）
【化５】

次の構造式で示されるビスフェノールＳ型エポキシ樹脂 ＥＰＢＳ-３００（日本化薬（株）製）
【化６】

次の構造式で示されるナフタレン型エポキシ樹脂 ＨＰ-４０３２（大日本インキ化学工業（株）製）
【化７】

次の構造式で示されるレソルシノール型エポキシ樹脂 ＥＸ-２０１（ナガセ化成（株）製）
【化８】

＜４官能のエポキシ樹脂＞
次の構造式で示されるテトラグリシジルアミン型エポキシ樹脂 ＥＬＭ４３４（住友化学（株）製）
【化９】

次の構造式で示されるテトラグリシジルアミン型エポキシ樹脂 ＴＥＴＲＡ−Ｘ（三菱ガス化学（株）製）
【化１０】

次の構造式で示されるテトラグリシジルエーテル型エポキシ樹脂 ＭＴ-０１６３（日本チバガイギー（株）製）
【化１１】

ここで、式（４）〜（11）において、Ｇはグリシジル基を表わす。
【００５７】
＜アミン系化合物＞
キュアダクトP-０５０５（四国化成工業（株）製）
ジシアンジアミド（以下、ＤＩＣＹと略記）
1,1-ジメチル-3-（3,4-ジクロロフェニル）ウレア（以下、ＤＣＭＵと略記）
＜ホウ酸エステル化合物を含む組成物＞
キュアダクトL-０１B（四国化成工業（株）製）
＜改質剤＞
ポリエーテルスルホン グレード５００３P（三井東圧化学（株）製）
ポリビニルホルマール ビニレックK（チッソ（株）製）
シリカ微粒子 アエロジル３８０（日本アエロジル（株）製）
【表１】

【表２】

【表３】

（実施例１０〜１２、比較例５〜６）
実施例７〜９、比較例３〜４における樹脂組成物をフィルムコーターを用いて、離型紙上に塗布し、それぞれ樹脂フィルムを作製した。樹脂フィルムの目付は５２ｇ／ｍ²とした。この樹脂フィルムを一方向に引き揃えた炭素繊維 "トレカ"Ｔ８００Ｈ（東レ）の両面から加熱加圧含浸し、プリプレグを得た。炭素繊維の目付は１９０ｇ／ｍ²とした。
【００５８】
上記のプリプレグを（＋４５゜／０゜／−４５゜／９０゜）_2Sの１６層の構成及び一方向に６層の構成の２通りで積層した。積層板をオートクレーブ中で温度１３５℃、圧力０.２９４MPaの条件で２時間硬化した。
【００５９】
（＋４５゜／０゜／−４５゜／９０゜）_2Sの構成の硬化板を０゜方向が３０４.８mm、９０度方向が３８.１mmの長方形に切り出し、中央部に直径６.３５mmの円形の孔を穿孔し有孔板に加工し、室温乾燥圧縮強度（１２０℃のオーブン中で２４時間乾燥後、２５℃で測定）および高温高湿圧縮強度（７０℃の温水に２週間浸漬後８２℃で測定）を求めた。
【００６０】
また、一方向に６層積層した硬化板から試験片を切り出し、室温での０゜圧縮強度及び０゜引張強度を測定した。なお、０゜圧縮強度の測定はJIS K７０７６のＡ法、０゜引張強度はJIS K７０７３に従った。以上の測定結果を表３にまとめた。
【００６１】
【表４】

【００６２】
【発明の効果】
本発明のＦＲＰ用エポキシ樹脂組成物およびこれをマトリックスとした繊維強化複合材料は、１３５℃の加熱で硬化反応率が十分高く、かつ硬化後に吸水させても優れた剛性率を有しており、しかも保存安定性に優れる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition and a prepreg used for a fiber-reinforced composite material.
[0002]
[Prior art]
Fiber reinforced composite materials (hereinafter abbreviated as FRP) composed of carbon fiber, glass fiber, aramid fiber, and other reinforcing fibers and matrix resins are used in structural materials such as aircraft, vehicles, ships, buildings, and sports equipment. ing.
[0003]
At present, epoxy resins are mainly used as matrix resins for composite materials used in aircraft and the like because of their excellent properties such as mechanical properties and thermal properties. As a curing agent for epoxy resin for aircraft use, diaminodiphenyl sulfone is widely used because of its high rigidity and high glass transition temperature. When an epoxy resin composition is prepared using diaminodiphenyl sulfone as a curing agent, it is necessary to cure it by heating it to about 180 ° C.
[0004]
However, at present, in order to promote energy saving at the time of molding and reduce the molding cost, the appearance of a matrix resin for a composite material that can be cured at a lower temperature is strongly desired. A combination of dicyandiamide and 1,1-dimethyl-3- (3,4-dichlorophenyl) urea is widely known as an epoxy resin curing agent system that can be cured at a lower temperature. When this curing agent system is used, curing is possible by heating at about 135 ° C. However, there is a problem that the obtained epoxy resin cured product has a high water absorption rate and the rigidity in the water absorption state is not sufficient. For this reason, it is necessary to improve the matrix resin in the aircraft field and the like that require high compressive strength in the water absorption state.
[0005]
[Problems to be solved by the invention]
The present invention shows a high curing reaction rate even when heated at a relatively low temperature of, for example, 135 ° C. for about 2 hours, and has a high cured product even in a state of high water absorption such as after being immersed in boiling water at 100 ° C. for 20 hours. It is an object of the present invention to provide an epoxy resin composition suitable for FRP and a prepreg obtained therefrom, in which a fiber-reinforced composite material having a rigidity and a matrix resin has excellent strength at a high water absorption state. .
[0006]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention has one of the following configurations. That is,
Consists of the following components [A], [B], [C] and [D]An epoxy resin composition in which the weight ratio of the component [A] to the component [B] is 1 to 10, and the cured resin obtained by heating the epoxy resin composition at 135 ° C. for 2 hours is 100. The rigidity at 82 ° C. determined by dynamic viscoelasticity measurement after being immersed in boiling water at 20 ° C. for 20 hours is 0.8 GPa or more.An epoxy resin composition for fiber-reinforced composite materials.
[A]: Bifunctional epoxy resin
[B]:N, N, N'N'- Tetraglycidyldiaminodiphenylmethane, N, N, N'N'- Tetraglycidyl -m- Xylenediamine, and 1,1,2,2,-( Tetraglycidyl oxyfel )- One or more tetrafunctional groups selected from ethaneEpoxy resin
[C]: The average particle size is 10 μm or less.Contains imidazole and / or its derivativesparticle
[D]: borate ester compound
  Or it is a prepreg characterized by consisting of said epoxy resin composition and a reinforced fiber.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
[0008]
In the present invention, the component [A] is a bifunctional epoxy resin. As a bifunctional epoxy resin, it is preferable to use a diglycidyl ether type epoxy resin because a sufficient curing reaction rate can be obtained. Examples of such diglycidyl ether type epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins, and resorcinol type epoxy resins. Among them, a bisphenol A type epoxy resin is particularly preferably used because a high curing reaction rate can be obtained by heating at 135 ° C. for 2 hours. A naphthalene type epoxy resin is also preferred because the cured product has low water absorption. The epoxy equivalent of these diglycidyl ether type epoxy resins is preferably less than 250. If the epoxy equivalent is 250 or more, even if the curing reaction rate is sufficient, the heat resistance of the cured product in a water-absorbing state is not preferable.
[0009]
  In the present invention, the component [B] isThe boilingTetraglycidylamine type epoxy resin and tetraglycidyl ether type epoxy resin because the cured product has high rigidity even after being immersed in rising water for 20 hours.ForI can. These tetrafunctional epoxy resins include N, N, N'N'-tetraglycidyldiaminodiphenylmethane, N, N, N'N'-tetraglycidyl-m-xylenediamine., 11,2,2,-(tetraglycidyloxyfel) -ethane and the like.
[0010]
  The weight ratio [A] / [B] of the component [A] to the component [B] is in the range of 1 to 10, preferably 1.5 to 5. When [A] / [B] exceeds 10, the rigidity tends to be low, and when [A] / [B] is less than 1, the curing reaction rate tends to be low. Within this range, for example, an epoxy resin composition having a sufficiently high curing reaction rate by heating at 135 ° C. for 2 hours and a cured product having low water absorption and high rigidity even after being immersed in boiling water for 20 hours can be obtained. . In the present invention,As component [C] to be described laterIn the case of using an adduct resulting from the reaction of an imidazole derivative and an epoxy compound, if [A] / [B] is within the above range, the adduct is precipitated during the curing process and the curing reaction rate becomes uneven. There is also an advantage that does not occur.
[0011]
In the present invention, the total weight of the component [A] and the component [B] is preferably in the range of 7/10 to 9/10 of the total amount of the epoxy resin composition. If it is less than 7/10, the rigidity of the cured product tends to be low, and if it is 9/10 or more, the curing reaction rate tends to be low.
[0012]
In the present invention, if the viscosity of the epoxy resin composition is too low, when the FRP is molded by heating a prepreg using the epoxy resin composition, the resin may flow out too much and it may be difficult to obtain an FRP having a desired resin content. On the other hand, if the viscosity is too high, the resin does not sufficiently impregnate the reinforcing fibers when producing the prepreg. From this viewpoint, the viscosity at 100 ° C. of the mixture of the components [A] and [B] is preferably in the range of 0.01 to 100 Pa · S. If it is less than 0.01 Pa · S, a large amount of a thickener such as a thermoplastic resin must be added, and as a result, the compressive strength of the FRP may decrease. On the other hand, if it exceeds 100 Pa · S, impregnation failure may occur during the preparation of the prepreg even if no thickener such as a thermoplastic resin is added.
[0013]
  In the present invention, the component [C] has an average particle size of 10 μm or less.Contains imidazole and / or its derivativesParticles. ParticlesImidazole and / or its derivativesAloneImidazole and / or its derivativesAlthough it may contain other components, it may be solid and substantially insoluble in the epoxy resin at room temperature. And make up particlesImidazole and / or its derivativesBecomes a complex on the particle surface with the boric acid ester compound [D] coexisting in the epoxy resin composition, and loses its activity as a curing agent or a curing catalyst. Thereby, the storage composition of the resin composition and the prepreg using the resin composition can be greatly improved.
[0014]
  Contains imidazole and / or its derivativesIf the average particle diameter of the particles is 10 μm or less, preferably 0.1 to 5 μm, the matrix resin in FRP exhibits a uniform and high curing reaction rate, and the cured composite material has low water absorption and high rigidity. Become.Contains imidazole and / or its derivativesIf the average particle size of the particles is too large, when an FRP is produced using the epoxy resin composition as a matrix resin, the particles having a large particle size do not enter the reinforcing fiber bundle, so the amount of the curing agent in the reinforcing fiber bundle is small. A phenomenon occurs that the curing reaction rate is partially insufficient. Such a phenomenon is not preferable because it causes an increase in the water absorption rate of FRP after curing and a decrease in the compression property after water absorption. Also,Contains imidazole and / or its derivativesWhen the average particle diameter of the particles is too small, when the particles are coated with the component [D], the amount of the component [D] added may be excessive if the particles are to be coated uniformly. In addition, if the proportion of particles having a particle diameter of 20 μm or more in the component [C] is 10% by weight or less, the curing reaction rate of the cured product is higher, for example, higher than 90% by heating at 135 ° C. for 2 hours. A curing reaction rate can be given, which is preferable.
[0015]
  Imidazole and / or its derivativesIs solid at room temperature and is substantially insoluble in epoxy resin, it can be used as is, but if not,Imidazole and / or its derivativesAnd other components such as a thermoplastic resin and a thermosetting resin may be combined by mixing to form particles satisfying the above conditions.
[0016]
  Imidazole and / or its derivativesIt is preferable to use a thermoplastic resin as a resin to be combined with the resin because it has the effect of improving the toughness of the cured resin.Imidazole and / or its derivativesWhen a thermoplastic resin and a thermoplastic resin are combined, a resin that softens or dissolves in the epoxy resin at the curing temperature of the epoxy resin composition is preferably used. In particular, although the softening point of the resin itself is high, it is most preferable to use a resin that dissolves in the epoxy resin at the curing temperature because the heat resistance of the epoxy resin is not impaired. As such a resin, for example, polyethersulfone can be used.
[0017]
  It is also possible to use the component [C] of the present invention in combination with an inorganic substance. For example,Imidazole and / or its derivativesA method of pulverizing a mixture of inorganic fine particles,Imidazole and / or its derivativesMethod of adsorbing and coating inorganic fine particles on the surface of inorganic hollow particlesImidazole and / or its derivativesBetween the pores of porous minerals such as zeolite or layered minerals such as montmorilloniteImidazole and / or its derivativesThere is a method of adsorbing.
[0018]
  Imidazole and / or its derivativesAnd other components in combination as component [C],Imidazole and / or its derivativesIf the content of is too small, the curing reaction rate becomes insufficient and the water absorption rate tends to increase.Imidazole and / or its derivativesThe content of is preferably 5% by weight or more, more preferably 20% by weight or more.
[0020]
  1From the viewpoint that the curing reaction rate is sufficiently high by heating at 35 ° C. and the water absorption of the cured product is further reduced,As mentioned above,ImidazoleAnd / or its derivativesI can.
[0021]
  Ingredient [C]In addition to acting as a curing agent alone, it may act as a curing accelerator or curing catalyst for other epoxy resin curing agents. When acting as a curing accelerator or curing catalyst,Ingredient [C]Preferably has no active hydrogen on the nitrogen atom.Imidazole and / or its derivativesExamples of epoxy resin curing agents that can be promoted or catalyzed by: dicyandiamide, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl hymic anhydride Acid, acid anhydride curing agent such as glycerol trimellitic anhydride, hydrazide curing agent such as adipic acid dihydrazide, naphthalenedicarboxylic acid dihydrazide, novolac resin, trishydroxyphenylmethane, 1,1,1-trishydroxyphenylethane, Mercaps such as phenolic curing agents such as 1,1,2,2-tetrakishydroxyphenylethane, 1,1,2,2-tetrakishydroxyphenylethane, mercaptopropionic acid esters and thioglycolic acid esters Emissions-based curing agent and the like, which alone or in a plurality of mixing, can be incorporated in the epoxy resin composition of the present invention.
[0022]
  Applicable for use as a curing agent alone or as a curing catalyst for other curing agentsIngredient [C]Examples thereof include imidazole derivatives having a substituent at the 1-position shown in the following formula (1). Since the imidazole derivative having a substituent at the 1-position has high reactivity and storage stability is impaired, it is rarely used in a one-pack type epoxy resin composition for composite materials. However, in the present invention, when an imidazole derivative having a substituent at the 1-position is used as the amine compound of component [C], a composition exhibiting extremely excellent storage stability can be obtained.
[0023]
[Chemical 1]

Where R₁~ R₂Represents an unsubstituted, alkyl, aryl, or aralkyl group having one or more substituents selected from halogen, hydroxyl group, and cyano group;_Three~ R_FourRepresents an unsubstituted, alkyl group, aryl group, aralkyl group or hydrogen atom having one or more substituents selected from halogen, hydroxyl group and cyano group. Here, the alkyl group means a substituent derived from a saturated hydrocarbon, and may be linear, branched or cyclic. An aryl group is a substituent derived from an aromatic hydrocarbon, meaning that the free valence is on the aromatic ring. Even if the aryl group is composed of only an aromatic ring such as a phenyl group, an aromatic group such as a tolyl group is used. It may have a group hydrocarbon structure as a partial structure. The aralkyl group means an alkyl group having an aryl group which is unsubstituted or has one or more substituents selected from halogen, hydroxyl group and cyano group, an aryl group and an aralkyl group as a substituent.
[0024]
Specific examples of the imidazole derivative represented by the above formula (1) include 1-benzyl-2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-ethyl- 4-methylimidazole, 1-benzyl-2-ethyl-4-methylimidazole, 1-benzyl-2-ethyl-5-methylimidazole, 1- (2-cyanoethyl) -2-methylimidazole, 1- (2-cyanoethyl) ) -2-ethylimidazole, 1- (2-cyanoethyl) -2-isopropylimidazole, 1- (2-cyanoethyl) -2-undecylimidazole, 1- (2-cyanoethyl) -2-heptadecylimidazole, 1- (2-cyanoethyl) -2-phenylimidazole, 1- (2-cyanoethyl) -2-ethyl-4-methylimidazole, 1- (2-cyanoethyl) -2-ethyl-5-methyl Or the like can be mentioned imidazole.
[0025]
As the imidazole derivative having a substituent at the 1-position, an adduct obtained by the reaction of an imidazole derivative having no substituent at the 1-position shown in the following formula (2) with an epoxy compound is particularly preferable.
[0026]
[Chemical 2]

Where R_FiveRepresents an unsubstituted, alkyl, aryl, or aralkyl group having one or more substituents selected from halogen, hydroxyl group, and cyano group;₆~ R₇Represents an unsubstituted, alkyl group, aryl group, aralkyl group or hydrogen atom having one or more substituents selected from halogen, hydroxyl group and cyano group.
[0027]
  Component [C] in the epoxy resin composition for composite materials of the present invention]WhenWhen an adduct obtained by reacting an imidazole derivative having no substituent at the 1-position with an epoxy compound is used, a high curing reaction rate of 90% or more is exhibited by heating at 135 ° C. for 2 hours and boiling Even after being immersed in water for 20 hours, an epoxy resin composition having a high rigidity of 0.8 GPa or more is obtained. In general, due to its high reactivity, imidazole compounds often have a problem of low storage stability. However, when an adduct obtained by the reaction of this imidazole derivative and an epoxy compound and a borate ester compound are used in combination, excellent storage stability can be obtained. Moreover, the hardened | cured material by the addition product of this imidazole derivative and an epoxy compound has the preferable property that a water absorption is low.
[0028]
When the particles comprising the above adduct are used as the component [C], the amount of the above adduct is 1/10 to 3/10 of the total weight of the epoxy resins of the components [A] and [B]. It is preferable to be within the range. If it is less than 1/10, the curing reaction rate after heating may be insufficient. If it exceeds 3/10, the adduct is precipitated during the curing process, resulting in a non-uniform curing reaction rate. May occur.
Specific examples of imidazole derivatives used in the synthesis of the above adduct include 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2- Ethyl-4-methylimidazole, 4,5-bishydroxymethyl-2-phenylimidazole, 5-hydroxymethyl-4-methyl-2-phenylimidazole, 4-benzyl-5-hydroxymethyl-2-phenylimidazole, 4, And 5-bishydroxymethyl-2-phenylimidazole. Specific examples of the epoxy compound used for the synthesis of the above adduct include monoepoxy compounds such as phenyl glycidyl ether and butyl glycidyl ether, and diepoxy compounds such as bisphenol A type epoxy resin and bisphenol F type epoxy resin.
[0029]
A product obtained by reacting 2-ethyl-4-methylimidazole with a bisphenol A type epoxy resin in advance as particles is commercially available from Shikoku Kasei Kogyo Co., Ltd. under the trade name “Cure Duct P-0505”. Cure duct P-0505 has an average particle size of 2 μm, and the proportion of particles having a particle size of 20 μm or more is less than 1% by weight. In this invention, such a commercial item can also be used as component [C].
[0030]
In the present invention, component [D] is a borate compound. As the borate ester compound, a compound represented by the following general formula can be used.
[0031]
[Chemical 3]

(Where R₈~ R_TenRepresents an alkyl group, an aralkyl group, or an aryl group. )
The boric acid ester compound reacts with the amine compound on the surface of the particle composed of the above-described amine compound to form a complex, and the activity of the amine compound is reduced, so that the resin composition and the prepreg using the same are stored. Stability can be greatly improved.
[0032]
Representative examples of boric acid ester compounds include boric acid trimethyl ester boric acid triethyl ester, boric acid tripropyl ester, boric acid triisopropyl ester, boric acid tributyl ester, boric acid triisobutyl ester, boric acid tripentyl ester, Boric acid trihexyl ester, boric acid trioctyl ester, boric acid trihexadecyl ester, boric acid trioctadecyl ester, boric acid tricresyl ester, boric acid trihexadecyl ester, boric acid tricyclohexyl ester, boric acid triphenyl ester, Examples include boric acid tolyl ester, boric acid tribenzyl ester, boric acid dimethyl ester, boric acid diethyl ester, and boric acid monomethyl ester. These boric acid ester compounds are preferably used in the present invention because there is no problem in toxicity and metal corrosivity.
[0033]
As the component [D], a borate ester compound may be used alone, and a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zircoaluminate coupling agent and the like may be combined with the borate ester compound. They can be used together. In addition, in order to control the addition reaction of the amine compound or prevent oxidation, the component [D] may contain an additive such as a phenol compound. As the phenolic compound to be added, compounds such as pyrogallol and phenolic resin, hindered phenolic antioxidants, tocopherolic antioxidants and the like are used.
[0034]
The component [D] may be applied in advance to the component [C] before kneading into the epoxy resin, and the surface of the component [C] may be coated, that is, surface-treated. In the present invention, when the [C] component is surface-treated with the [D] component in advance before kneading with the epoxy resin and other raw materials as necessary, the surface treatment may be carried out in a mixer. Alternatively, as described in JP-A-6-73156, a method of contacting in an airflow type pulverizer or an airflow type classifier is used.
[0035]
The epoxy resin composition of the present invention can also be obtained by adding the [C] component and the [D] component individually to the epoxy resin and other raw materials as necessary, followed by stirring and kneading. In the case of this production method, since the borate ester compound is not reactive with the epoxy resin, the surface of the [C] component is treated with the borate ester compound in the epoxy resin. Further, it suggests that the repair is possible even if the surface treatment of the particles composed of the amine compound is destroyed during the kneading.
[0036]
A boric acid ester compound, an epoxy resin, and a phenol resin previously blended are commercially available from Shikoku Kasei Kogyo Co., Ltd. under the trade name “Cure Duct L01-B”. Cure duct L01-B is a mixture of 5% by weight of boric acid tributyl ester, 5% by weight of phenol novolac resin, and 90% by weight of bisphenol A type epoxy resin. Such a commercial product can also be used in the present invention.
[0037]
In addition to the components [A], [B], [C], and [D], the epoxy resin composition of the present invention includes a curing agent other than the component [C], a thermoplastic resin, an elastomer, a thermoplastic elastomer, and the like. Can also be blended.
[0038]
  When blending a curing agent other than component [C],Imidazole and / or its derivativesIt is preferable that the curing reaction is accelerated or catalyzed.
[0039]
The thermoplastic resin, elastomer, and thermoplastic elastomer are added for the purpose of adjusting the viscosity of the epoxy resin, adjusting the tack of the prepreg, controlling the flow in the curing process, improving the toughness of the cured product, and improving the adhesion to the reinforcing fiber.
[0040]
As the thermoplastic resin, those that are easily dissolved in an epoxy resin are preferably used. Moreover, even if it is a thermoplastic resin insoluble in an epoxy resin, as long as it is micronized, it can be mix | blended. Specifically, acrylic resin, phenoxy resin, polyvinyl acetal, polyester, polycarbonate, polysulfone, polyarylene oxide, polyamide, and polyimide are used. Polyvinyl acetal is a resin obtained by acetalizing polyvinyl alcohol with a carbonyl compound such as formaldehyde or acetaldehyde, and examples thereof include polyvinyl formal and polyvinyl acetal. The phenoxy resin is a resin obtained by condensing bisphenol A and epochlorohydrin. Polyester is a polymer having a carboxylic ester bond in the main chain. Polycarbonate is a polymer having a carbonate ester bond in the main chain, and bisphenol A carbonate is typical. Polyarylene oxide is a resin having a main chain structure in which aromatic divalent groups and oxygen atoms are alternately arranged. Polysulfone is a resin having a sulfonyl group in the main chain. In addition, it may have an ether bond or the like in the main chain. Polyamide is a resin having a carboxylic acid amide in the main chain. Polyimide is a resin having a dicarboxylic imide structure in the main chain. In addition, there may be an ether bond or an amide bond. The acrylic resin is a polymer of acrylic acid ester or methacrylic acid ester, and a typical one is polymethyl methacrylate.
[0041]
Of these, polysulfone, polyarylene oxide, and polyimide are suitable for applications requiring heat resistance. Polyvinyl formal is effective in controlling the flow of the resin and improving the tack of the prepreg. Polysulfone and polyvinyl formal are effective in improving adhesiveness with carbon fibers and improving interlaminar shear strength and compressive strength.
[0042]
As the elastomer, a copolymer using acrylonitrile and butadiene as raw materials is preferably used because of its excellent solubility in an epoxy resin. In particular, it is preferable to use an epoxy resin such as a carboxyl group, an amino group, or an epoxy group or one having a functional group capable of reacting with a curing agent thereof because the effect of improving the toughness of the cured product is large.
[0043]
Moreover, the particle | grains containing the elastomer phase insoluble in an epoxy resin can also be used preferably. Although crosslinked elastomer particles themselves can be used, core-shell type elastomer particles in which the surface of the epoxy resin-insoluble elastomer particles is coated with a non-elastomeric component can be particularly preferably used. In this case, the component to be coated may be one that dissolves or swells in an epoxy resin, such as polymethyl methacrylate, and is preferable because the dispersion of the particles in the epoxy resin is improved. When particles containing an epoxy resin-insoluble elastomer phase are used, the heat resistance of the cured resin is superior to that of a normal elastomer.
[0044]
The addition of these elastomers has an effect of improving toughness and an effect of improving the tackiness of the prepreg. In particular, when fine core-shell type elastomer particles having a particle size of about 0.1 to 0.3 μm are blended, the effect of improving toughness is remarkable.
[0045]
As the thermoplastic elastomer, those which are easily dissolved in an epoxy resin are preferably used. Specifically, a block copolymer having a polyether structure as a soft segment and an aromatic polyester or aliphatic polyamide structure as a hard segment is preferable. The addition of these thermoplastic elastomers has the effect of improving the toughness of the cured product and improving the tack when used as a matrix resin for a prepreg. Further, the heat resistance of the cured product is superior to the case where a normal elastomer is added.
[0046]
The epoxy resin composition of the present invention can further contain inorganic particles such as silica, alumina, titanium oxide, zirconia, clay mineral, talc, mica, and ferrite. By adding these, there is an effect of increasing the viscosity of the resin composition and reducing the resin flow, an effect of improving the elastic modulus and heat resistance of the cured resin, and an effect of improving wear resistance.
[0047]
FRP can be obtained by impregnating a reinforcing fiber with the epoxy resin of the present invention and heating. As the reinforcing fiber, glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber or the like is used. Among these, carbon fibers having excellent strength and elastic modulus and low specific gravity are particularly preferable because FRP having excellent specific strength and specific elastic modulus can be obtained.
[0048]
As a method for obtaining FRP directly from an epoxy resin composition and reinforcing fibers, a wet layup method in which an epoxy resin composition is applied to a woven fabric or mat of reinforcing fibers, and is impregnated with a roller or the like, followed by heat curing, A filament winding method in which a reinforcing fiber bundle is impregnated with an epoxy resin composition and wound around a mold called a mandrel, and cured by heating, and the reinforcing fiber is impregnated into the epoxy resin composition and supplied to a heating die having a predetermined shape. A pultrusion method in which a product is obtained by forming and heat-curing continuously by pulling, supplying an epoxy resin composition to a sheet molding machine together with continuous or cut reinforcing fibers, and impregnating the sheet with pressure Sheet-molding-compound method to obtain a glass-like material, reinforcing fiber fabric and mat are shaped into the shape of the product The preform is placed in a mold, the epoxy resin composition can be used a method of resin transfer molding method or the like for curing is injected into the mold. Conventionally, in these methods, a two-pack type epoxy resin composition is often used, and since the pot life after the two-pack mixing is short, there are many limitations on the process, but the epoxy resin composition of the present invention is Since it can be used in one liquid and there is no practical limit on the usable time, the freedom of the process is greatly advantageous.
[0049]
Further, FRP can be obtained by using an intermediate called a prepreg formed by impregnating a reinforcing fiber with an uncured epoxy resin composition and forming a sheet, tape, or string. Since the prepreg uses a one-pack type epoxy resin, the conventional prepreg has poor storage stability and has to be stored frozen. Since the epoxy resin composition of the present invention is excellent in storage stability, it can be refrigerated or stored at room temperature, and is much easier to use than conventional products. The shape of the reinforcing fiber in the prepreg is not particularly limited, and examples thereof include long fibers aligned in one direction, tow fabric, mat, knit, braided string, and the like. In the production of the prepreg, for example, an epoxy resin composition is applied on a release paper using a reverse roll coater or the like to produce a resin film, and the resin film is laminated from one side or both sides of the reinforcing fiber and heated and pressed. A method of impregnating reinforcing fibers can be used.
[0050]
In the present invention, the curing reaction rate of the epoxy resin composition is determined by infrared absorption measurement. Specifically, the absorption peak of an epoxy group (920 cm^-1) Strength and absorption peak of phenylene group (870cm^-1) The curing reaction rate is determined from the change in the relative strength ratio. As the measurement sample, an uncured resin or a cured resin mixed with potassium bromide and then used as a tablet is used.
[0051]
In the present invention, the water absorption rate of the cured resin is determined from the difference between the weight of the heat-dried sample at 120 ° C. for 20 hours and the weight of the water-absorbed sample after immersion in boiling water at 100 ° C. for 20 hours. The sample dimensions are 2 mm thick, 10 mm wide, and 5 cm long.
[0052]
Furthermore, in the present invention, the rigidity of the cured resin is determined by dynamic viscoelasticity measurement. Specific measurement conditions are a frequency of 3.14 rad / s, a heating rate of 5 ° C./min, a strain of 0.1%, and a measurement start temperature of 30 ° C. The dimensions of the sample are the same as in the water absorption measurement, and are 2 mm thick, 10 mm wide, and 5 cm long. For the rigidity in the dry state, a dry sample subjected to heat treatment at 120 ° C. for 20 hours is used. The rigidity in the water absorption state is measured immediately after the sample is taken out from boiling water using a water absorption sample immersed in boiling water at 100 ° C. for 20 hours. When measuring the rigidity in the water absorption state, the temperature of the sample is usually about 82 °.
[0053]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0054]
(Examples 1-9, Comparative Examples 1-4)
Components selected from the materials listed below were mixed to obtain epoxy resin compositions having compositions shown in Tables 1 to 3.
[0055]
Each of these epoxy resin compositions was cured by heating at 135 ° C. for 2 hours to obtain a cured product. Tables 1 to 3 show the curing reaction rate, water absorption rate, and rigidity rate of each cured product.
[0056]
<Bifunctional epoxy resin>
Bisphenol A type epoxy resin of the following structural formula YD-128 (manufactured by Toto Kasei Co., Ltd.)
[Formula 4]

Bisphenol F-type epoxy resin represented by the following structural formula Epicoat 806 (manufactured by Yuka Shell Epoxy Co., Ltd.)
[Chemical formula 5]

Bisphenol S-type epoxy resin represented by the following structural formula EPBS-300 (manufactured by Nippon Kayaku Co., Ltd.)
[Chemical 6]

Naphthalene type epoxy resin HP-4032 represented by the following structural formula (Dainippon Ink & Chemicals, Inc.)
[Chemical 7]

Resorcinol type epoxy resin EX-201 represented by the following structural formula (manufactured by Nagase Kasei Co., Ltd.)
[Chemical 8]

<Four sensualityEpoxy resin>
Tetraglycidylamine type epoxy resin ELM434 represented by the following structural formula (manufactured by Sumitomo Chemical Co., Ltd.)
[Chemical 9]

Tetraglycidylamine type epoxy resin TETRA-X (Mitsubishi Gas Chemical Co., Ltd.) represented by the following structural formula
[Chemical Formula 10]

Tetraglycidyl ether type epoxy resin MT-0163 represented by the following structural formula (manufactured by Ciba Geigy Japan)
Embedded image

  Here, in formulas (4) to (11), G represents a glycidyl group.
[0057]
<Amine compound>
Cure duct P-0505 (manufactured by Shikoku Chemicals Co., Ltd.)
Dicyandiamide (hereinafter abbreviated as DICY)
1,1-dimethyl-3- (3,4-dichlorophenyl) urea (hereinafter abbreviated as DCMU)
<Composition containing borate compound>
Cure Duct L-01B (Shikoku Kasei Kogyo Co., Ltd.)
<Modifier>
Polyethersulfone Grade 5003P (Mitsui Toatsu Chemical Co., Ltd.)
Polyvinyl Formal Vinylec K (manufactured by Chisso Corporation)
Silica fine particles Aerosil 380 (Nippon Aerosil Co., Ltd.)
[Table 1]

[Table 2]

[Table 3]

(Examples 10-12, Comparative Examples 5-6)
The resin compositions in Examples 7 to 9 and Comparative Examples 3 to 4 were applied onto release paper using a film coater to prepare resin films, respectively. The basis weight of the resin film is 52 g / m²It was. This resin film was impregnated by heating and pressure from both sides of carbon fiber “Torayca” T800H (Toray) aligned in one direction to obtain a prepreg. Carbon fiber weight is 190g / m²It was.
[0058]
The above prepreg (+ 45 ° / 0 ° / -45 ° / 90 °)_2SThese were laminated in two ways: a 16-layer structure and a 6-layer structure in one direction. The laminate was cured in an autoclave at a temperature of 135 ° C. and a pressure of 0.294 MPa for 2 hours.
[0059]
(+ 45 ° / 0 ° / -45 ° / 90 °)_2SThe hardened plate with the structure of 0 is cut into a rectangle of 304.8mm in the 0 ° direction and 38.1mm in the 90 ° direction, and a 6.35mm diameter circular hole is drilled in the center, and processed into a perforated plate. The strength (measured at 25 ° C. after being dried in an oven at 120 ° C. for 24 hours) and the high temperature and high humidity compressive strength (measured at 82 ° C. after being immersed in warm water at 70 ° C. for 2 weeks) were determined.
[0060]
Further, a test piece was cut out from a cured plate in which six layers were laminated in one direction, and 0 ° compressive strength and 0 ° tensile strength at room temperature were measured. The 0 ° compressive strength was measured according to JIS K7076 method A, and the 0 ° tensile strength was measured according to JIS K7073. The above measurement results are summarized in Table 3.
[0061]
[Table 4]

[0062]
【The invention's effect】
The epoxy resin composition for FRP of the present invention and the fiber reinforced composite material using this as a matrix have a sufficiently high curing reaction rate by heating at 135 ° C., and have an excellent rigidity even when water is absorbed after curing. Moreover, it has excellent storage stability.

Claims (9)

The following components [A], [B], a [C] and [D] Tona is, the epoxy resin composition the weight ratio of the components [A] and the component [B] is 1 to 10, wherein The cured resin obtained by heating the epoxy resin composition at 135 ° C. for 2 hours is immersed in 100 ° C. boiling water for 20 hours, and then the rigidity at 82 ° C. obtained by dynamic viscoelasticity measurement is 0.8 GPa or more. , fiber-reinforced composite material epoxy resin composition.
[A]: Bifunctional epoxy resin [B]: N, N, N′N′- tetraglycidyldiaminodiphenylmethane, N, N, N′N′- tetraglycidyl -m- xylenediamine, and 1,1,2 , 2,-( tetraglycidyloxyfel ) -ethane, one or more tetrafunctional epoxy resins [C]: particles containing imidazole and / or derivatives thereof having an average particle size of 10 μm or less [D]: Acid ester compounds   2. The epoxy resin composition according to claim 1, wherein after being heated at 135 ° C. for 2 hours, the curing reaction rate of the resin determined by infrared absorption measurement is 90% or more. 20 hours immersed during water absorption of the resin cured product obtained by heating 2 hours in boiling water of 100 ° C. at 135 ° C. is an epoxy resin composition according to claim 1 or 2 is 3 wt% or less. Component [A] is an epoxy resin composition according to any one of the diglycidyl ether type epoxy resin der Ru請 Motomeko 1-3. The epoxy resin composition according to any one of claims 1 to 4, wherein the proportion of particles having a particle diameter of 20 µm or more in the component [C] is 10 wt% or less. The epoxy resin composition according to any one of claims 1 to 5, wherein the component [C] contains 5% by weight or more of imidazole and / or a derivative thereof. The epoxy resin composition according to any one of claims 1 to 6 , wherein the component [C] contains a thermoplastic resin. The epoxy resin composition according to any one of claims 1 to 7, wherein the imidazole derivative has no substituent at the 1-position and an epoxy compound is added thereto. A prepreg comprising the epoxy resin composition according to any one of claims 1 to 8 and reinforcing fibers.