JP3951896B2 - A method for treating a carbonaceous material, a carbon nanotube dispersion, and a solution. - Google Patents

Description

【００３３】
Ａｃ：カーボンナノチューブ１ｇに含まれる酸性官能基のモル数
２πＲａ：カーボンナノチューブ平均外周（nm）
［（Ｒａ−Ｒｂ）／Ｒｋ］＋１：カーボンナノチューブ平均層数
Ｒａ：カーボンナノチューブ平均外半径
Ｒｂ：カーボンナノチューブ平均内半径
Ｒｋ：カーボンナノチューブ層間距離
上式に示す分子のＡｃは、外表面に官能基を有するカーボンナノチューブ１ｇに含まれる酸性官能基のモル数である。純度１００％のカーボンナノチューブを得ることは困難であり、それを同定することも困難であるため、ここで言うカーボンナノチューブとは５万倍の倍率で走査型電子顕微鏡で見たときに繊維状の物質がその電子顕微鏡の視野の中に８０％以上であるカーボン質材料であればカーボンナノチューブと言って差し支えない。従って、厳密に定義すればカーボンナノチューブ外表面だけに酸性官能基を有するのではなく、カーボンナノチューブに付着した炭素、カーボンナノチューブに混在する炭素粒子も含んだ状態で酸量を測定し、すべてカーボンナノチューブの表面に酸性官能基があるとして計算したものである。外表面に官能基を有するカーボンナノチューブとは、図１の模式図に示されるように、カーボンナノチューブ外表面に少なくとも１種類以上の官能基を有するカーボンナノチューブのことである。官能基の種類は特に限定されないが、例えば、水酸基、カルボニル基、カルボキシル基、ニトロ基、スルホン基、エーテル基、などを挙げることができる。外表面に官能基を有するカーボンナノチューブに含まれる酸性官能基のモル数の測定には、水酸化ナトリウム水溶液を用いた中和滴定の測定から計算によって求める。
【００３４】
上式に示す分母は、カーボンナノチューブ１ｇに含まれるカーボンナノチューブ外表面の炭素のモル数である。カーボンナノチューブ平均外周を、カーボンナノチューブ平均層数とカーボンナノチューブ平均円周の乗算結果を用いて除算することで、カーボンナノチューブ全体に対するカーボンナノチューブ外表面の炭素率を求める。これに、カーボンナノチューブ１ｇを炭素原子の原子量（１２ｇ／ｍｏｌ）で除算した結果（つまり、カーボンナノチューブ１ｇ中に含まれる炭素原子のモル数）を乗算することで、カーボンナノチューブ１ｇに含まれるカーボンナノチューブ外表面の炭素のモル数を求める。
【００３５】
カーボンナノチューブ平均外半径Ｒａ、カーボンナノチューブ平均内半径Ｒｂは図１に示すように定義され、例えば、透過型電子顕微鏡（ＴＥＭ）観察結果から、ひとつのカーボンナノチューブを重複して用いないルール適用して、任意に少なくとも１０点以上、好ましくは２０点以上のカーボンナノチューブの外半径、内半径を計測し、それぞれ平均値を計算することで求める。
【００３６】
カーボンナノチューブ層間距離Ｒｋは、公知の値である０．３４ｎｍを用いる。
【００３７】
上記のようにして、カーボンナノチューブ外表面の炭素に対する酸性官能基の含有率を求めるわけであるが、その概略を記すと、走査型電子顕微鏡（または透過型電子顕微鏡）で見たときに、顕微鏡の視野中に繊維状物質（カーボンナノチューブ）を含む（好ましくは繊維状物質を１０％以上、より好ましくは５０％以上、さらに好ましくは８０％以上含む）カーボン質材料を用いて、水酸化ナトリウム水溶液を用いた中和滴定の値と、透過型電子顕微鏡（ＴＥＭ）ＴＥＭ観察結果から求めたカーボンナノチューブ平均外半径、平均内半径の値を前記式に代入し、カーボンナノチューブ外表面の炭素に対する酸性官能基の含有率を求めることになる。後述の実施例２（走査型電子顕微鏡での繊維状物質の確認）、実施例１４（中和滴定）、実施例１５（透過型電子顕微鏡写真からのカーボンナノチューブ直径計算）、実施例１６（酸性官能基含有率の計算）参照。
【００３８】
前記式で示される、カーボンナノチューブ外表面の炭素に対する酸性官能基の含有率は２％以上、好ましくは４％以上、さらに好ましくは８％以上であることが好ましい。２％より小さいと、液中への分散性が悪化する。
【００３９】
また、前記式を満たすカーボンナノチューブの官能基を、化学反応などの手法をもちいてさらに修飾して用いてもかまわない。
【００４０】
前記式で求められるカーボンナノチューブ外表面の炭素に対する酸性官能基含有率が２％以上であるカーボンナノチューブは、親水性溶媒に分散又は溶解し、カーボンナノチューブの分散液、溶液になる。親水性溶媒の中でも、取り扱い上の安全性や、コストの面から、水が最も好ましい。
【００４１】
本発明は、プラズマ処理したカーボンナノチューブを液に分散させた後、分級することを特徴とする精製カーボンナノチューブ溶液の製造方法も含む。プラズマで処理したカーボンナノチューブを液に分散させたものは、カーボンナノチューブの固まりの大きさによって沈降速度が変わってくる。その性質を利用して、カーボンナノチューブを遠心分離、フィルトレーション等で固まりの大きさで分級する事が可能である。また、カーボンナノチューブの製造に触媒を用いた場合、触媒部分を含んでいるカーボンナノチューブと含んでいないカーボンナノチューブの比重の違いを利用して遠心分離で分級することも可能で、触媒を除去する精製も可能である。このように、分級して固まりの大きさを均一にしたカーボンナノチューブは、フィールドエミッションディスプレーの電子源や、各種電極触媒としてコーティングする場合に有用である。
【００４２】
本発明は、上記の方法で得られたカーボンナノチューブ分散液、またはカーボンナノチューブ溶液を濃縮および／または乾燥することを特徴とする高濃度カーボンナノチューブ分散液、溶液および粉末状カーボンナノチューブの製造方法も含む。分散液から分級した分散液や溶液を濃縮することによって高濃度のカーボンナノチューブ分散液や溶液が得られ、乾燥すれば粉末が得られる。このようにして得られた粉末は、カーボンナノチューブの絡まり方や固まり径が制御されているので好ましい。濃縮や乾燥の方法は、通常の加熱による溶媒の除去、真空排気による溶媒除去、凍結乾燥など従来公知のすべての方法が利用できる。
【００４３】
本発明では、好ましくは（１）カーボンナノチューブ合成工程、（２）カーボンナノチューブをプラズマ処理する工程、（３）カーボンナノチューブを液に分散する工程、（４）カーボンナノチューブを分級又は固液分離する工程の４つの工程によりカーボンナノチューブを製造する。従来、カーボンナノチューブの合成方法は数多く提案されている。多くのカーボンナノチューブは絡まり合った固まり状で得られる。しかしながら、実用化を考えた場合、カーボンナノチューブは、分散していた方が良く、不純物と分離されていた方が好ましい。種々の精製方法が提案されているが、通常は強酸やフッ酸を使用するという厳しい条件を使うものである。また、今まで分散したカーボンナノチューブを効率よく連続生産するプロセスは提案されていない。本発明者らは、プラズマ処理によりカーボンナノチューブが液中に良く分散することを見出し、その分散液が分級によって、溶液部分、微分散部分、触媒付着部分に分けることができることを見出した。
【００４４】
本発明において、第一工程のカーボンナノチューブ合成工程とは、どのような方法でも良い。公知のあらゆる技術が利用できる。レーザーアブレーション法、アーク放電法、熱ＣＶＤ法、プラズマＣＶＤ法、燃焼法などが挙げられる。工程をスムーズに進めるためには、気相で連続生産できる熱ＣＶＤ法が好ましい。熱ＣＶＤ法は、６００℃から１２００℃の高温で触媒と炭素源を接触させる方法で触媒を連続的に供給すれば連続的にカーボンナノチューブを回収することができる。
【００４５】
第２工程は、プラズマ処理工程であり、この工程は前述したとおりである。酸素ガスプラズマ処理が好ましい。粉末のカーボンナノチューブを連続的に処理できるプラズマ装置が好ましい。例えば、粉末のカーボンナノチューブを連続的（断続的でもよい）に供給し、さらに、かき混ぜながらプラズマ処理を行うプラズマ処理装置として、外部電極方式を用いることが、装置設計に自由度があり、且つ容易なことから好ましい。
【００４６】
第３工程の分散工程は、プラズマ処理されたカーボンナノチューブを液中に分散させる工程である。分散させる方法は特に限定されないが、例えば、超音波処理は、出力が大きいものほど良く、１０Ｗ以上、好ましくは２０Ｗ以上、さらに好ましくは５０Ｗ以上であることが好ましい。ホモジナイザー（処理圧力は３ＭＰａ以上が好ましい）のような高速攪拌、アトライター（回転数は１００ｒｐｍ以上が好ましい）、ボールミル（ボールの衝撃は１Ｇ以上が好ましい）等の機械的衝撃を加える攪拌でもよい。もちろん、通常の攪拌でもかまわない。
【００４７】
第４の工程は、分散されたカーボンナノチューブ分散液を分級又は固液分離する工程である。その方法は特に限定されないが、例えばフィルトレーションや遠心分離が適用できる。分級や固液分離によって、分離された固体部分は、再度第３の工程に戻して、再分散させて、再度第４の工程で溶液を回収することもできる。また、第４の工程で分級又は固液分離された、分散度の低い部分は、乾燥した後、再度第２の工程に戻してプラズマ処理をすることも行われる。また、第４の工程で回収された最も比重の重い触媒を含有するカーボンナノチューブは、空気中で焼成するなどしてカーボンナノチューブを除去して、触媒を第一の工程に戻すこともできる。
【００４８】
本発明では、次の２つの工程を有することを特徴とする触媒組成物の製造方法によって優れた触媒組成物を製造することができる。（１）カーボンナノチューブをプラズマ処理する工程と、（２）プラズマ処理後のカーボンナノチューブを金属を含有する液と接触する工程である。具体的な製造方法としては、プラズマ処理したカーボンナノチューブを金属を含有する水溶液に加え、この水溶液を撹拌することで触媒組成物を得ることができる。さらに、上記液体状態の触媒組成物は、乾燥させて溶媒を取り除き、固体状態とすることもできる。本発明の触媒組成物についての詳細を以下に記す。
【００４９】
本発明における親水性のカーボンナノチューブは、水に分散するので触媒担体として好ましく使用できる。通常触媒成分である金属は、金属塩の水溶液の形で、担体上に担持するが、従来カーボンナノチューブは疎水性であり、カーボンナノチューブ表面に担持することは困難であった。しかし本発明の親水性のカーボンナノチューブを使用すれば、金属塩の水溶液と馴染みが良く、高分散にカーボンナノチューブ表面に金属触媒を担持することが出来る。特に、カーボンナノチューブ表面にカルボニル基やカルボン酸基が存在するため、金属イオンを、これらの官能基との相互作用により特に良く分散させることが出来る。本発明で言う触媒成分とは、触媒能力があれば特に限定されないが、例えば、Pd,Pt,Ru,Rh,Ag,Au,Re等の貴金属やTi,V,Cr,Mn,Fe,Co,Ni,Cu,Zn等の金属やその酸化物が挙げられ、還元能や酸化能を発現することが出来る。カーボンナノチューブはお互い絡まり合っており、ガスや液の拡散性、濾過性ともに優れており触媒として非常に適している。さらに、１〜５層のカーボンナノチューブは直径が細くその外表面積が大きいので優れている。本発明触媒組成物が優れている点は、カーボンナノチューブが細いチューブ状であるためその曲率が大きく、触媒金属を微粒子化できることである。
【００５０】
触媒金属が、微粒子化できると金属の表面積が高くなり、触媒の活性は非常に高くなることは容易に推定できる。また、金属を微粒子で担持させたカーボンナノチューブは、カーボンナノチューブの製造触媒としても使用できる。例えば、コバルトを担持したカーボンナノチューブを管状炉内に設置された石英管に置き、アルゴン等の不活性ガスを流しながら、管状炉で５００℃〜１２００℃に加熱し、加熱された時点で炭素含有化合物を導入する事によりカーボンナノチューブを製造できる。
【００５１】
また、本発明では次の２つの工程を有することを特徴とする有機化合物含有カーボンナノチューブの製造方法によって、優れた有機化合物含有カーボンナノチューブを製造することができる。（１）カーボンナノチューブをプラズマ処理する工程と、（２）プラズマ処理後のカーボンナノチューブを有機化合物を含有する液と接触する工程である。ここでいう有機化合物の好ましい例として、薬剤を挙げることができる。その理由と、具体的な製造方法を以下に記す。上記のごとき親水性のカーボンナノチューブは、薬剤輸送剤としても優れた性能を示す。本発明の親水性のカーボンナノチューブは、中空部分がオープンになっていれば、中空部分が疎水性、外表面が親水性である。従って、中空部分に疎水性の薬剤を吸着させたカーボンナノチューブを水に分散させたものができる。人間や動物の体は、ほとんどが水で出来ておりこのような物質は薬剤として使用できる。中空部分に薬剤を吸着させたカーボンナノチューブを水に分散させて、カテーテルで患部に挿入しても良く、そのまま飲み薬や、塗り薬、点眼薬などとして使用しても良い。中空部分をオープンにするためには、酸化してやればよい。酸化は、気相酸化でも液相酸化でも良い。勿論酸素プラズマ処理でも良い。薬剤輸送剤として使用する場合、重さ当たりの効果を考えた場合、壁が薄い方が良いので細い方が好ましく、１０層以下、更に好ましくは５層以下、特に好ましくは２層カーボンナノチューブがベストである。体内での移動を考えた場合も、細い方が好ましく２層カーボンナノチューブが最も好ましい。単層カーボンナノチューブは、親水性と疎水性の両立が困難である。このような薬剤の作り方は、特に限定されないが、（１）酸化処理によりナノチューブの先端をオープンにする。（ナノチューブ先端は、反応性の高い炭素５員環を多く含むため選択的に燃えて簡単にオープンに出来る。オープンになったかどうかは７７Ｋで窒素吸着実験をすることによって確認できる）（２）本発明のプラズマ処理を行い、水中で超音波をかけ分散させる。（３）遠心分離により、浮遊物を取り除く。（４）カーボンナノチューブ分散水溶液に、疎水性の薬剤を少量添加すると、疎水性の薬剤は疎水性のカーボンナノチューブ中空部分に選択的に吸着される。このような工程によって作ることが出来る。
【００５２】
さらに本発明では、次の２つの工程を有することを特徴とするコーティング用組成物の製造方法によって、優れたコーティング用組成物を製造することができる。（１）カーボンナノチューブをプラズマ処理する工程と、（２）プラズマ処理後のカーボンナノチューブをコーティング用の主剤と混合する工程である。ここでいうコーティング用の主剤としては、例えば樹脂を挙げることができる。樹脂としては、常温で液状態、または固体状態のものを挙げることができ、さらに、熱可塑性、熱硬化性のものを挙げることができる。中でも、常温で液状態の樹脂を用いることが、プラズマ処理したカーボンナノチューブを樹脂と混合させる工程が常温で行え工程設備が簡素化できることや、常温でコーティングしたい任意形状の対象物に塗布できることからコーティングの工程設備が簡素化できることから好ましい。さらに、硬化性の樹脂を用いることが、例えばコーティング用組成物をコーティングしたい任意形状の対象物表面に塗布した後、コーティング用組成物を硬化させることで、コーティング用組成物を任意形状の対象物表面に強固に固定することができることから好ましい。プラズマ処理後のカーボンナノチューブをコーティング用の主剤と混合する方法としては、超音波やホモジナイザー、アトライター、ボールミル、バンバリーミキサー、ニーダー、ロール、単軸もしくは二軸の押出機を用いることができる。なお、ここでいうコーティング用組成物とは、ペースト状組成物も含む。本発明のコーティング用組成物に関する詳細を以下に記す。
【００５３】
本発明における官能基を付与したカーボンナノチューブは、前述したように、親水化処理されたカーボンナノチューブの場合は親水性溶媒に、疎水化されたカーボンナノチューブは疎水性溶媒に分散、溶解させることが容易である。このため、官能基を付与したカーボンナノチューブと、官能基を付与したカーボンナノチューブを分散可能な溶媒を含有する組成物を作成することで、カーボンナノチューブが高分散した組成物を得ることができる。カーボンナノチューブが高分散した組成物は、カーボンナノチューブの持つ良導電性、高強度特性、電界電子放出特性を十分に引き出すことができる優れた組成物となる。
【００５４】
このため、官能基を付与したカーボンナノチューブを含有し、好ましくは官能基を付与したカーボンナノチューブが分散可能な溶媒も含有し、さらに好ましくは硬化性を有する液状物質をも含有することを特徴とするコーティング用組成物を作成することで、コーティング用組成物を固体表面に塗布して固体表面の導電性を向上することができる。もちろんコーティング用組成物は固体表面上で硬化させてもよい。また、コーティング用組成物を型に流し込み硬化させることで、導電性や強度に優れた任意形状の固体物質を得ることができる。さらに、コーティング用組成物（硬化させた後でも良い）に電極を取り付けることで、優れた電界電子放出特性を示す電子デバイスを得ることができる。
【００５５】
コーティング用組成物を作成する際に用いる原料として、透明性を有する原料を選択し、カーボンナノチューブの添加量を１ｗｔ％以下にすることで、得られるコーティング用組成物は透明性を有することができる。コーティング用組成物を作成する際に用いる原料として、硬化後も透明性を有する原料を選択することで、硬化後も透明性を有するコーティング用組成物を得ることができる。このため、上記特性（良導電性、高強度特性、電界電子放出特性）に加えて、透明性の特性を併せ持つことができる。
【００５６】
コーティング用組成物を硬化させる方法としては、コーティング用組成物に熱硬化や光硬化を起こす原料などの、徐々に反応し固体状態へと移行する原料を含有する方法が挙げられる。例えば、コーティング用組成物に１分子中に２個以上のエポキシ基を有する化合物（エポキシ樹脂）と、エポキシ基と反応する水酸基を有する化合物（硬化剤）、さらに、エポキシ樹脂と硬化剤の反応を促進する硬化促進剤を含有することで、熱硬化により硬化させることができる。
【００５７】
また、常温では固体状態の原料を用いて、コーティング用組成物を高温で溶融させた状態で保持し、硬化が必要なときに冷却する方法、などが挙げられる。具体的には、常温では比較的固体状態に近い、長鎖脂肪酸の金属塩、長鎖脂肪酸のエステル、パラフィンワックス、シリコーン化合物などを用いることができる。
【００５８】
上記コーティング用組成物は、非晶性シリカ、結晶性シリカ、炭酸カルシウム、炭酸マグネシウム、アルミナ、マグネシア、窒化珪素、酸化マグネシウムアルミニウム、ジルコニア、ジルコン、クレー、タルク、マイカ、珪酸カルシウム、酸化チタン、酸化アンチモン、アスベスト、ガラス繊維などの無機材料を含んでいても構わない。
【００５９】
本発明は、粉末状のカーボンナノチューブを効率よくプラズマ処理できる方法を見出したものである。プラズマ処理の結果、表面が特定の官能基化できた新規なカーボンナノチューブを得ることができ、新規なカーボンナノチューブの分散液、溶液が得られるようになった。更には、触媒の担体として、また薬剤輸送材料、コーティング用組成物として非常に使いやすい状態となった。プラズマ処理は、マイルドにカーボンナノチューブ表面を親水化できる処理であり、今まで困難であった層数の少ない１〜５層のカーボンナノチューブをその構造を大きく壊すことなく処理できる点で有利である。また、プラズマ処理のガスの種類、プラズマ処理条件を選べば、ＣＶＤ法でカーボンナノチューブを作った場合に、カーボンナノチューブ表面の熱分解炭素を取り除いたり、残したまま処理することも可能である。通常の酸化処理では、熱分解炭素の被覆物は実質的に取り除かれるケースが多い。
【００６０】
【実施例】
以下に実施例を挙げて本発明を具体的に説明するが、本発明はここに掲げる実施例によって限定されるものではない。
【００６１】
実施例１（カーボンナノチューブの合成）
Ｋ．Ｈｅｒｎａｄｉ、Ａ．Ｆｏｎｓｅｃａらによる報告を参照（Ｚｅｏｌｉｔｅｓ １７：４１６−４２３、１９９６）し、酢酸鉄（２ｇ）、酢酸コバルト（２ｇ）、Ｙ型ゼオライト（東ソー社製ＨＳＺ−３１０ＮＡＡ Ｌｏｔ．Ｎｏ．ＧＺ−１４３−３〜５）（１０ｇ）を秤量し、メタノール（１００ｍｌ）を加えて、振とう器にて１時間攪拌後、メタノール分を乾燥除去し、触媒を得た。次に、図２に示すＣＶＤ反応装置を用いて、反応管内の石英ウール上に触媒１ｇをあらかじめセットし、窒素（３０ｃｃ／分）雰囲気下で６００℃まで昇温後、アセチレン（６ｃｃ／分）、窒素（３０ｃｃ／分）雰囲気下で６００℃×５時間保持しカーボンナノチューブを合成した。その後、窒素（３０ｃｃ／分）雰囲気下で室温まで冷却し、反応物を取り出した。
【００６２】
実施例２（カーボンナノチューブの確認）
実施例１で得られた触媒とカーボンナノチューブの混合物を、フッ化水素酸１０％水溶液中で３時間攪拌後、ろ紙（Ｔｏｙｏ Ｒｏｓｈｉ Ｋａｉｓｈａ、Ｆｉｌｔｅｒ Ｐａｐｅｒ ２号 １２５ｍｍ）を用いてろ過し、ろ紙上の固形物を、イオン交換水、アセトン溶液にて洗浄後、乾燥し、カーボンナノチューブを得た。図３、４に、得られたカーボンナノチューブの透過型電子顕微鏡（ＴＥＭ）観察結果を、図５、６に走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図３〜６から、多層カーボンナノチューブを多く含むことがわかる。図５、図６から、繊維状物質がほとんどであり、粒子状物質がないことがわかる。つまり、カーボンナノチューブを９０％以上含むサンプルであることがわかる。また、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。
【００６３】
実施例３（プラズマ処理）
実施例２で得られたカーボンナノチューブ０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、酸素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行った。図７、８に、得られたプラズマ処理カーボンナノチューブの透過型電子顕微鏡（ＴＥＭ）観察結果を、図９，１０に走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図７〜１０から、多層カーボンナノチューブを多く含み、その大きさは、実施例２で得られたものと同様であることがわかる。そして、カーボンナノチューブ外表面の付着物が減少していることも確認できる。
【００６４】
実施例４（分散液の製造）
実施例３で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、振とう器にて１時間攪拌後、４８時間静置した結果、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図９、１０と同様のカーボンナノチューブが確認できた。
【００６５】
実施例５（プラズマ処理）
実施例２で得られたカーボンナノチューブ０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、酸素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、一度取り出して、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計１５分（計３回）のプラズマ処理を行った。図１１、１２に、得られたプラズマ処理カーボンナノチューブの透過型電子顕微鏡（ＴＥＭ）観察結果を、図１３、１４に走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図７〜１０とよく似た結果であり、多層カーボンナノチューブを多く含み、その大きさは、実施例２と同様であることが確認できた。そして、カーボンナノチューブ外表面の付着物が減少していた。
【００６６】
実施例６（分散液の製造）
実施例５で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、振とう器にて１時間攪拌後、４８時間静置した結果、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図１３、１４と同様のカーボンナノチューブが確認できた。
【００６７】
実施例７ （分散液の製造）
実施例５で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図１３、１４と同様のカーボンナノチューブが確認できた。
【００６８】
実施例８
実施例４、実施例６、実施例７で得られたカーボンナノチューブ分散液２０ｍｌを透明ガラス製サンプル瓶に移して比較した結果、実施例７＞実施例６＞実施例４の順で分散液が濃い結果を得た。プラズマ処理の際にカーボンナノチューブをかき混ぜる、さらに超音波処理を用いることで、より高濃度なカーボンナノチューブ分散液が得られることがわかる。
【００６９】
実施例９
実施例５で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、エタノール５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図１３、１４と同様のカーボンナノチューブが確認できた。
【００７０】
実施例１０
実施例５で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、エチレングリコール５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図１３、１４と同様のカーボンナノチューブが確認できた。
【００７１】
実施例１１
実施例７で得られた、カーボンナノチューブ分散液を、ろ紙（Ｔｏｙｏ Ｒｏｓｈｉ Ｋａｉｓｈａ、Ｆｉｌｔｅｒ Ｐａｐｅｒ ２号 １２５ｍｍ）を用いてろ過したところ、ろ紙を通過したろ液として、透明感のある黒色の溶液を得た。図１５、１６に、得られた溶液を乾燥させた試料の、透過型電子顕微鏡（ＴＥＭ）観察結果を、図１７、１８に得られた溶液を乾燥させた試料の、走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図１５〜１８から、多層カーボンナノチューブを多く含み、その大きさは図１１〜１４と比較して長軸方向に短く、互いに絡まり合っていないことがわかる。
【００７２】
実施例１２
実施例７で得られた、カーボンナノチューブ分散液を、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、溶液に図１７、１８と同様のカーボンナノチューブが確認できた。
【００７３】
実施例１３
実施例５で得られたプラズマ処理後のカーボンナノチューブについて、Ｘ線光電子分光法を用いたカーボンナノチューブの表面組成分析を行った結果、酸素原子が１０％の割合であり、Ｃ１ｓピーク分割から、芳香環又はＣＨｘ（８８％）に対して、カルボキシル基又はエステル（ＣＯＯ、２％）、カルボニル基（Ｃ＝Ｏ、４％）、エーテル基又は水酸基（Ｃ−Ｏ、５％）の官能基を持つ結果を得た。カルボキシル基又はフェノール性水酸基の影響で、分散液や溶液は、酸性を呈すると考えられる。
【００７４】
実施例１４
実施例５で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた分散液のｐＨを、ガラス電極式水素イオン濃度計（東亜電波工業、ＨＭ−３０Ｖ）を用いて測定したところ、ｐＨ＝５．５であった。一般によく知られた中和滴定を、４２．５×１０^-6（ｍｏｌ／ｌ）の水酸化ナトリウム水溶液を用いて、ｐＨ＝７．０を終点として行った結果、水酸化ナトリウム水溶液１４５ｍｌを要した。つまり、０．２５ｍｇの水酸化ナトリウム（ＮａＯＨ、４０ｇ／ｍｏｌ）を要した。この結果から、プラズマ処理後のカーボンナノチューブ１０ｍｇ中の酸性官能基のモル数は６．３×１０^-6（ｍｏｌ）と計算できる。
【００７５】
実施例１５
図３、４に示す透過型電子顕微鏡（ＴＥＭ）を用いて、ひとつのカーボンナノチューブを重複して用いないルールを適用して、任意に２０点のカーボンナノチューブの外半径、内半径を計測し、それぞれ平均値を計算した結果、Ｒａ：カーボンナノチューブ平均外半径１１．５ｎｍ、Ｒｂ：カーボンナノチューブ平均内半径３．３ｎｍの結果を得た。また、Ｒｋ：カーボンナノチューブ層間距離０．３４ｎｍを用いた。
【００７６】
実施例１６
実施例１４、１５の結果から、前記式を用いてカーボンナノチューブ外表面の炭素に対する酸性官能基の含有率（％）を計算した結果、１２％の結果を得た。
【００７７】
実施例１７
実施例１で得られた触媒とカーボンナノチューブの混合物０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、酸素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行った。
【００７８】
実施例１８
実施例１７で得られたプラズマ処理後の触媒とカーボンナノチューブの混合物１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）で観察した結果、分散液に図９、１０と同様のカーボンナノチューブが確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。一方、沈殿物のＥＤＸ測定結果では、Ｙ型ゼオライトの存在が確認された。これにより、分散液を回収する、すなわち分級することによって、実施例２のような強酸を用いなくても、触媒部分を除去でき、カーボンナノチューブの精製が可能であることがわかる。
【００７９】
実施例１９
実施例１で得られた触媒とカーボンナノチューブの混合物０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、酸素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計１５分（計３回）のプラズマ処理を行った。
【００８０】
実施例２０
実施例１９で得られたプラズマ処理後の触媒とカーボンナノチューブの混合物１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。スポイトで分散液部分を回収し、乾燥させた試料を走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、分散液に図１３、１４と同様のカーボンナノチューブが確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。一方、沈殿物のＥＤＸ測定結果では、Ｙ型ゼオライトの存在が確認された。これにより、実施例１８同様、分散液を回収する、すなわち分級することによって、実施例２のような強酸を用いなくても、触媒部分を除去でき、カーボンナノチューブの精製が可能であることがわかる。
【００８１】
実施例２１
実施例２０で得られた、カーボンナノチューブ分散液を、ろ紙（Ｔｏｙｏ Ｒｏｓｈｉ Ｋａｉｓｈａ、Ｆｉｌｔｅｒ Ｐａｐｅｒ ２号 １２５ｍｍ）を用いてろ過したところ、ろ紙を通過したろ液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、乾燥させた試料を透過型電子顕微鏡（ＴＥＭ）、走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、溶液に図１５〜１８と様のカーボンナノチューブが確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。
【００８２】
実施例２２
実施例２０で得られた、カーボンナノチューブ分散液を、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、乾燥させた試料を透過型電子顕微鏡（ＴＥＭ）、走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、溶液に図１５〜１８と同様のカーボンナノチューブが確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。
【００８３】
実施例２３
実施例２１で得られた、ろ紙を通過しなかったろ紙上の固形物を回収し、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液、黒い沈殿物が得られ、ろ紙（Ｔｏｙｏ Ｒｏｓｈｉ Ｋａｉｓｈａ、Ｆｉｌｔｅｒ Ｐａｐｅｒ ２号 １２５ｍｍ）を用いてろ過したところ、ろ紙を通過したろ液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、乾燥させた試料を透過型電子顕微鏡（ＴＥＭ）、走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、溶液に図１５〜１８と同様のカーボンナノチューブの存在が確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。
【００８４】
実施例２４
実施例２２で得られた、沈殿物を回収し、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液、黒い沈殿物が得られ、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、乾燥させた試料を透過型電子顕微鏡（ＴＥＭ）、走査型電子顕微鏡（ＳＥＭ）を用いて観察したところ、溶液に図１５〜１８と同様のカーボンナノチューブが確認できた。さらに、ＳＥＭのＥＤＸを用いて元素分析を行ったところ、Ｙ型ゼオライトの存在率はＥＤＸの測定限界以下（ほぼ０％）である結果を得た。
【００８５】
実施例２５
実施例２２で得られた溶液を、６０℃に保った恒温槽に静置したところ、溶液が濃縮され、さらに、６０℃に保った恒温槽に静置したところ、カーボンナノチューブ粉末が得られた。
【００８６】
比較例１
実施例２で得られたカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、液状の上層部は無色透明で、黒い沈殿物のみが確認できた。
【００８７】
比較例２
実施例２で得られたカーボンナノチューブについて、Ｘ線光電子分光法を用いたカーボンナノチューブの表面組成分析を行った結果、酸素原子が１％の割合であり、Ｃ１ｓピーク分割から、芳香環又はＣＨｘ（９８％）に対して、カルボキシル基又はエステル（ＣＯＯ、０％）、カルボニル基（Ｃ＝Ｏ、１％）、エーテル基又は水酸基（Ｃ−Ｏ、１％）の官能基を持つ結果を得た。
【００８８】
比較例３
実施例２で得られたカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料のｐＨをガラス電極式水素イオン濃度計（東亜電波工業、ＨＭ−３０Ｖ）を用いて測定したところ、ｐＨ＝７．０であった（酸性官能基の含有率０％）。
【００８９】
実施例２６
酢酸第一鉄（アルドリッチ社製）０．０８ｇと酢酸コバルト４水和物（ナカライテスク）社製）０．１１ｇとを水７ｍｌに加え、超音波洗浄機で１０分間懸濁した。実施例５で得られたプラズマ処理したカーボンナノチューブを１．０ｇ加え、超音波洗浄機で１０分間処理し、６０℃の恒温下で水を除去して金属塩が担持した触媒を得た。内径３０ｍｍの石英管の中央部の石英プレート上に、上記で得た金属塩を担持したカーボンナノチューブを０．０５０ｇ取り、窒素を３０ｍｌ／分で供給した。石英管を電気炉中に設置して中心温度を６００℃に加熱した。超高純度アセチレンガス（高圧ガス工業製）を６ｍｌ／分で３０分間供給した後、アセチレンガスの供給をやめ、温度を室温まで冷却した。石英プレート上に堆積した反応物を日本電子データム（株）走査電子顕微鏡ＪＳＭ６３０１ＮＦで観察したところ、ほとんど非晶質のカーボン質の堆積は無かった。ファイバー状物質の形状を透過型電子顕微鏡で測定したところ、外径が２０ｎｍ以下で内径が５ｎｍ程度の細い中空状ナノファイバーが主成分であることがわかった。高分解能透過型電子顕微鏡で中空状ナノファイバーを観察したところナノファイバーの壁はグラファイト層で構成されていた。
【００９０】
実施例２７
実施例２で得られた多層カーボンナノチューブを空気中４００℃で３０分焼成した。焼成後、実施例５の方法でプラズマ処理し実施例７の方法で水に分散させた。イブプロフェンを少量この系に加えた。５時間後１２０００回転の遠心分離で固形分を回収し、液部分のイブプロフェンを定量したところ、イブプロフェンは加えた量の半分以下になっていた。回収した固形分であるカーボンナノチューブは再び水を加え、超音波をかけると分散した。中空部分に薬剤を吸着した多層カーボンナノチューブの分散水がえられた。
【００９１】
実施例２８（窒素プラズマ処理）
実施例２で得られたカーボンナノチューブ０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、窒素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、一度取り出して、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計１５分（計３回）のプラズマ処理を行った。透過型電子顕微鏡（ＴＥＭ）観察と走査型電子顕微鏡（ＳＥＭ）の観察の結果、実施例２と同様のカーボンナノチューブであることが確認できた。高分解能透過型電子顕微鏡で観察したところプラズマ処理前後とも熱分解炭素の被覆が確認できた。
【００９２】
実施例２９
実施例２８で得られたプラズマ処理後のカーボンナノチューブについて、Ｘ線光電子分光法を用いたカーボンナノチューブの表面組成分析を行った結果、酸素原子が１０％の割合であり、Ｃ１ｓピーク分割から、芳香環又はＣＨｘ（８８％）に対して、カルボキシル基又はエステル（ＣＯＯ、２％）、カルボニル基（Ｃ＝Ｏ、３％）、エーテル基又は水酸基（Ｃ−Ｏ、６％）の官能基を持つ結果を得た。カルボキシル基やフェノール性水酸基の影響で、分散液や溶液は、酸性を呈すると考えられる。
【００９３】
実施例３０
実施例２８で得られたプラズマ処理後のカーボンナノチューブ１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた分散液のｐＨを、ガラス電極式水素イオン濃度計（東亜電波工業、ＨＭ−３０Ｖ）を用いて測定したところ、ｐＨ＝５．５であった。一般によく知られた中和滴定を、４２．５×１０^-6（ｍｏｌ／ｌ）の水酸化ナトリウム水溶液を用いて、ｐＨ＝７．０を終点として行った結果、水酸化ナトリウム水溶液１１８ｍｌを要した。つまり、０．２０ｍｇの水酸化ナトリウム（ＮａＯＨ、４０ｇ／ｍｏｌ）を要した。この結果から、プラズマ処理後のカーボンナノチューブ１０ｍｇ中の酸性官能基のモル数は５．０×１０^-6（ｍｏｌ）と計算できる。
【００９４】
実施例３１
図３、４に示す透過型電子顕微鏡（ＴＥＭ）を用いて、ひとつのカーボンナノチューブを重複して用いないルールを適用して、任意に２０点のカーボンナノチューブの外半径、内半径を計測し、それぞれ平均値を計算した結果、Ｒａ：カーボンナノチューブ平均外半径１１．５ｎｍ、Ｒｂ：カーボンナノチューブ平均内半径３．３ｎｍの結果を得た。また、Ｒｋ：カーボンナノチューブ層間距離０．３４ｎｍを用いた。
【００９５】
実施例３２
実施例３０、３１の結果から、前記式を用いてカーボンナノチューブ外表面の炭素に対する酸性官能基の含有率（％）を計算した結果、９．６％の結果を得た。
【００９６】
実施例３３
J.L.Hutchisonらの方法（Carbon 39 (2001) 761-770)に従って、アーク放電法でカーボンナノチューブを生成した。アノードは直径3.2mm長さ140mmの穴に触媒が埋め込まれた直径8.2mmのグラファイトロッド、カソードは直径10mm,長さ25mmのグラファイトロッドとした。触媒は、次のように調製した。粒子径2-5μmのNi,Co,Fe粉末の混合物と硫黄原子を良く粉砕した後、アルゴンガス下で５００℃１時間焼成した。ボールミルでμサイズまで粉砕した後すぐにカーボン粉末と混ぜた。3.2mmの穴をドリルであけたグラファイトロッドにぎっしりつめた。アノードの組成は、カーボンに対して、Ni 2.6at%,Co 0.7at%,Fe 1.45at%,S 0.75at%であった。アルゴン：水素体積比１：１で３５０torrで７５−８０Aのアーク電流でＣＮＴ合成を行った。両電極は2mmの距離で電圧差は２６〜２８Ｖとした。
【００９７】
実施例３４
実施例３３で得られたカーボンナノチューブを含むカーボン０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、窒素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、一度取り出して、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計１０分（計２回）のプラズマ処理を行った。
【００９８】
プラズマ処理後のカーボン材料１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。分散液を、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、高分解能透過型電子顕微鏡で観察した結果、炭素不純物の付着した２〜５層のカーボンナノチューブが多く見られた。５万倍の走査型電子顕微鏡で見たところ、８０％は、繊維状物質で、２０％は粒子状物質であった。
【００９９】
乾燥させて重量を図り、再度水に分散させて、先の実施例と同様に酸量を量り、酸性官能基の含有率を求めたところ、８．５％であった。
実施例３５
実施例３３で得られたカーボンナノチューブを含むカーボン０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、窒素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、一度取り出して、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計２０分（計４回）のプラズマ処理を行った。
【０１００】
プラズマ処理後のカーボン材料１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒い沈殿物が確認できた。分散液を、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒色の溶液を得た。スポイトで溶液部分を回収し、高分解能透過型電子顕微鏡で観察した結果、炭素不純物の付着した２〜５層のカーボンナノチューブが多く見られた。
実施例３６
フロンティアカーボン社より購入した単層カーボンナノチューブ（純度２０％）０．５ｇを、ガラス製シャーレー上にうすく広げて、ＹＡＭＡＴＯ化学製ＰＬＡＳＭＡ ＣＨＡＭＢＥＲ ＭＯＤＥＬ ＰＣ−１０１Ａを用いて、窒素ガス、圧力２０Ｐａ、ＰＯＷＥＲ３００Ｗの条件で、５分間プラズマ処理を行い、一度取り出して、シャーレー上のプラズマ処理カーボンナノチューブを、かき混ぜ（ひっくり返す、転がす等の動作）、シャーレー上にうすく広げ、再び同様のプラズマ処理を行う作業を繰り返し、合計１５分（計３回）のプラズマ処理を行った。
【０１０１】
プラズマ処理後のカーボン材料１０ｍｇに、イオン交換水５０ｍｌを加えて、超音波洗浄機（ＹＡＭＡＴＯ化学製、ＢＲＡＮＳＯＮ３２１０、発信周波数４７ＫＨｚ、出力１３０Ｗ）にて１時間処理後、４８時間静置して得られた試料を観察したところ、カーボンナノチューブ分散液と黒っぽい沈殿物が確認できた。分散液を、遠心分離器（装置：ＫＵＢＯＴＡ ＫＲ−２００００Ｔ、ローター：ＲＡ−３ ５０ｍｌ×８本）を用いて、回転数１２０００ｒｐｍ（約１７０００（×ｇ））×１時間、遠心分離したところ、上澄み液として、透明感のある黒っぽい色の溶液を得た。スポイトで溶液部分を回収し、高分解能透過型電子顕微鏡で観察した結果、単層のカーボンナノチューブが多く見られた。
実施例３７
ビスフェノールＡ型エポキシ樹脂（エポキシ当量１９０）１６０重量部、ジグリシジルエーテル型希釈剤（エポキシ当量１５０）４０重量部、無機充填材であるアエロジル（平均粒子径３０ｎｍ）１０重量部と、カルボン酸無水物であるメチルテトラヒドロ無水フタル酸１６０重量部とトリフェニルホスフィン４重量部を溶解して得た硬化剤液と、実施例３６で得られたプラズマ処理したカーボンナノチューブ１重量部と、エタノール１００重量部を配合して、カーボンナノチューブの高分散したペースト状組成物を得た。ペースト状組成物を直径３ｃｍ、厚さ５ｍｍの型に流し込み、７０℃で１時間、さらに１８０℃で２時間加熱したところ、ペースト状組成物は硬化し、カーボンナノチューブが高分散した固体の円盤が得られた。
【０１０２】
【発明の効果】
本発明によれば、プラズマ処理したカーボンナノチューブ、分散液、溶液および組成物を得ることができる。
【０１０３】
カーボンナノチューブをプラズマ処理（特に酸素ガスプラズマが好ましい）する方法は、カーボンナノチューブの分散性の向上、精製度の改良、外表面への官能基付与が同時に、簡易的に短時間で行うことができる優れた処理方法である。
【０１０４】
層数の少ない、単層や２〜５層のカーボンナノチューブにおいても、プラズマ処理（特に窒素ガスプラズマが好ましい）であれば、その構造を大きく破壊することなく、分散性の向上、精製度の改良、外表面への官能基付与が可能である。
【０１０５】
プラズマ処理の際にカーボンナノチューブをかき混ぜることで、より大きな効果が得られる。
【０１０６】
カーボンナノチューブ分散液、溶液は、プラズマ処理したカーボンナノチューブ（カーボンナノチューブ外表面の炭素に対する酸性官能基の含有率が２％以上のカーボンナノチューブ）を用いることで得られる。
【０１０７】
また、カーボンナノチューブ分散液、溶液を分級することでカーボンナノチューブを精製することができる。さらに、カーボンナノチューブの製造に触媒を用いた場合、カーボンナノチューブ分散液、溶液を分級することで触媒を除去する精製も行うことができる。
【０１０８】
カーボンナノチューブ分散液、溶液、およびこれらから得られるカーボンナノチューブは、塗料や樹脂への添加剤用途、電子部品用途、医療用途など、その用途は広く期待できる。さらに、カーボンナノチューブ分散液、溶液の分級によるカーボンナノチューブの精製方法は、強酸等を用いないことや触媒のリサイクルが可能となり、人体への影響や環境問題の観点から有効である。これらのことにより、本発明による産業上の利用価値は大きい。
【図面の簡単な説明】
【図１】多層カーボンナノチューブの模式図である。
【図２】ＣＶＤ装置の断面図である。
【図３】実施例２で得たカーボンナノチューブのＴＥＭ写真（×４０００００）。
【図４】実施例２で得たカーボンナノチューブのＴＥＭ写真（×１６００００）。
【図５】実施例２で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図６】実施例２で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図７】実施例３で得たカーボンナノチューブのＴＥＭ写真（×４０００００）。
【図８】実施例３で得たカーボンナノチューブのＴＥＭ写真（×１６００００）。
【図９】実施例３で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図１０】実施例３で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図１１】実施例５で得たカーボンナノチューブのＴＥＭ写真（×４０００００）。
【図１２】実施例５で得たカーボンナノチューブのＴＥＭ写真（×１６００００）。
【図１３】実施例５で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図１４】実施例５で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図１５】実施例１１で得たカーボンナノチューブのＴＥＭ写真（×４０００００）。
【図１６】実施例１１で得たカーボンナノチューブのＴＥＭ写真（×１６００００）。
【図１７】実施例１１で得たカーボンナノチューブのＳＥＭ写真（×５００００）。
【図１８】実施例１１で得たカーボンナノチューブのＳＥＭ写真（×５００００）。[0001]
BACKGROUND OF THE INVENTION
A carbonaceous material plasma processing method that can improve the dispersibility of the carbonaceous material and that can be purified, and in particular, a carbon nanotube dispersion obtained by plasma processing a carbonaceous material containing carbon nanotubes, The present invention relates to solutions, purified carbon nanotubes and compositions, and methods for their production.
[0002]
Since carbon nanotubes have high mechanical strength and high conductivity, they are used as anode materials for fuel cells and lithium secondary batteries, high-strength resins made of composite materials with resins and organic semiconductors, conductive resins, and electromagnetic shielding materials. Furthermore, since L / D (ratio of length / diameter) is large and the diameter is several nm, it is expected as a probe for scanning tunneling microscope, field electron emission source, nanotweezers, Moreover, since it has a nano-sized space, it is expected as an adsorbing material, a medical nanocapsule, and an MRI contrast agent.
[0003]
[Prior art]
The carbon nanotube has a shape in which one surface of graphite is wound into a cylindrical shape. A single-walled carbon nanotube is wound in one layer, a double-walled carbon nanotube is wound in two layers, and is wound in multiple layers. This was called multi-walled carbon nanotube.
[0004]
When carbon nanotubes are used as a filler for resin, for example, in order to obtain the addition effect with a minimum addition of carbon nanotubes, the carbon nanotubes must be dispersed or dissolved in the resin without being entangled with each other. preferable. When used as a drug transport material, an aqueous solution in which carbon nanotubes are dissolved is preferable. When used as an electron source for a field emission display, it is preferable that the entangled mass of carbon nanotubes is uniform because the uniformity of the electron source can be controlled. However, carbon nanotubes are usually obtained in the form of tangled with adjacent carbon nanotubes. The size of the mass is usually not uniform, and the size is too large to be dispersed or dissolved in the liquid. In particular, carbon nanotubes were hydrophobic and did not disperse or dissolve in hydrophilic solvents.
[0005]
When carbon nanotubes are used as a composite material, depending on the type of material used as a matrix, it is possible to remove amorphous carbon adhering to the outer surface or to use carbon nanotubes with functional groups added to the outer surface. The interfacial strength can be improved. As a method of removing carbon impurities such as amorphous carbon from the synthesized crude carbon nanotube, for example, a method of reacting with oxygen at a high temperature or a method of refluxing nitric acid or potassium permanganate at a high temperature (see Non-Patent Document 1) Has been proposed. However, these methods have a problem that carbon impurities such as amorphous carbon are removed, and at the same time, the structure of the carbon nanotube is destroyed and the carbon nanotube is consumed. Furthermore, heating and cooling operations are required under high-temperature conditions, and cleaning and drying operations are required in methods using solvents such as nitric acid and potassium permanganate (wet condition treatment), resulting in complicated operations. was there. Moreover, as a method for introducing a functional group into the outer surface of the carbon nanotube, for example, a method of reacting with fluorine gas at a high temperature (see Non-Patent Document 2) has been proposed. However, there is a problem that the reaction takes a long time. In other words, it is difficult to remove amorphous carbon adhering to the outer surface without greatly destroying the structure of the carbon nanotubes, or to impart functional groups to the outer surface in a short time at a low temperature and in dry conditions. Difficulty was high for single-walled carbon nanotubes and carbon nanotubes having 2 to 5 layers. As described above, there has been no processing method that can simultaneously provide functions such as improvement of dispersibility of carbon nanotubes, purification, and introduction of functional groups on the outer surface by simple operations (low temperature and dry condition treatment, short time). It was.
[0006]
[Non-Patent Document 1]
Yahachi Saito, Shunji Bando, Fundamentals of Carbon Nanotubes, Corona Inc., p53
[Non-Patent Document 2]
ETMickelson, Chemical Physics Letters, 296, 188 (1998)
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide plasma-treated carbon nanotubes, dispersions, solutions and compositions, methods for producing them, and the like.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention mainly has the following configuration.
[0009]
That is, Contains carbon nanotubes When processing carbonaceous materials with plasma, Contains carbon nanotubes A method of treating a carbonaceous material, characterized by stirring the carbonaceous material; Contains carbon nanotubes After treating the carbonaceous material with plasma, Contains carbon nanotubes This is a method for treating a carbonaceous material by ultrasonically treating the carbonaceous material in a liquid. Special To The carbon nanotube has 1 to 5 layers.
[0010]
Further, a method of obtaining a carbon nanotube dispersion liquid, wherein the plasma-treated carbon nanotubes are dispersed in a liquid. A method for obtaining a carbon nanotube solution, characterized by solid-liquid separation after being dispersed in a liquid. A method for purifying carbon nanotubes, characterized in that the carbon nanotubes are classified after being dispersed in a liquid. A method for producing a high-concentration carbon nanotube dispersion, solution, and powdered carbon nanotubes, comprising concentrating and drying a carbon nanotube dispersion or a carbon nanotube solution.
[0011]
(1) a carbon nanotube synthesis step, (2) a carbon nanotube plasma treatment step, (3) a step of dispersing the carbon nanotube in a liquid, and (4) a step of classifying or solid-liquid separating the carbon nanotube. A method for producing a carbon nanotube, which is characterized.
[0012]
A method for producing a catalyst composition comprising contacting the carbon nanotube with a liquid containing a metal, and a method for producing an organic compound-containing carbon nanotube comprising contacting the carbon nanotube with a liquid containing an organic compound A method for producing a coating composition comprising the carbon nanotube.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0014]
The present invention is characterized by a method of treating a carbonaceous material with a plasma generated by applying a high voltage in a state where a carbonaceous material and a gas to be treated are supplied into the treatment space.
[0015]
Examples of the carbonaceous material include carbon nanotubes, fullerenes, activated carbon, carbon black, graphite, amorphous carbon, and carbon fibers. Especially, it is preferable for the process of a carbon nanotube, and is especially preferable for the process of a 1-5 layer carbon nanotube.
[0016]
The plasma treatment is not particularly limited, but refers to, for example, a known low-temperature plasma treatment, and the treatment apparatus is not particularly limited, and a known internal electrode method or external electrode method is used. The external electrode method is preferable because there is no problem. Processing conditions such as processing pressure, power supply frequency, processing output and the like are not particularly limited and may be preferably selected according to the purpose. Although it does not specifically limit as plasma generation gas, Organic and inorganic gas are used individually or in mixture according to the objective. For example, oxygen, nitrogen, hydrogen, ammonia, methane, ethylene, carbon tetrafluoride and the like can be mentioned.
[0017]
The dispersibility and purity of the carbonaceous material can be improved by the plasma treatment. The reason for this is not clear at this time, but is presumed as follows. Plasma is a gas containing charged particles, and is processed by breaking carbon-carbon bonds when the charged particles collide with a carbonaceous material. Alternatively, it is treated by depositing hydrocarbons. When the carbon-carbon bond is broken by the plasma treatment, it is considered that a functional group such as a carboxyl group, a carbonyl group, or a hydroxyl group is generated in the portion by contacting with oxygen.
[0018]
In the plasma treatment in the present invention, it is preferable to stir a carbonaceous material during the plasma treatment. When plasma processing is performed on a powdery sample, the plasma may not spread throughout the powder. As a result of intensive studies, it was found that the plasma treatment can be spread over the entire carbonaceous material by mixing the carbonaceous material during the plasma treatment. In the present invention, “stirring” means turning over or stirring, and moving the material to be treated during the treatment in order to perform the plasma treatment uniformly. In the simplest case, after the plasma treatment, the sample is once taken out and stirred, and again subjected to the plasma treatment. Preferably, the plasma treatment is performed while stirring. As a plasma processing apparatus that performs plasma processing while stirring, it is preferable to use an external electrode system because the design for incorporating a stirring operation into the apparatus is flexible and easy.
[0019]
The present invention is characterized in that a carbonaceous material containing carbon nanotubes is plasma-treated. Since carbon nanotubes have high mechanical strength and high conductivity, they are used as anode materials for fuel cells and lithium secondary batteries, high-strength resins made of composite materials with resins and organic semiconductors, conductive resins, and electromagnetic shielding materials. Furthermore, since L / D (ratio of length / diameter) is large and the diameter is several nm, it is expected as a probe for scanning tunneling microscope, field electron emission source, nanotweezers, Moreover, since it has a nano-sized space, it is expected as an adsorbing material, a medical nanocapsule, and an MRI contrast agent.
[0020]
The form of the carbon nanotube can be examined with a high-resolution transmission electron microscope. The graphite layer is preferred so that it can be seen straight and clearly in a transmission electron microscope, but the graphite layer may be disordered. What disturbs the graphite layer may be defined as carbon nanofiber, and such carbon nanofiber is also included in the carbon nanotube in the present invention. The carbon nanotubes can be generally produced by a laser ablation method, an arc discharge method, a thermal CVD method, a plasma CVD method, a combustion method, or the like, but the carbon nanotubes produced by any method may be used. As reported by Shinohara et al., The method of making acetylene as a raw material by a thermal CVD method using zeolite as a catalyst support has a high purity, although there is some carbon coating such as pyrolytic carbon without any particular purification. This is a particularly preferred method in that well graphitized carbon nanotubes can be obtained (Chemical Physics Letters 303 (1999) 117-124). Use of such a carbon nanotube is very preferable because it can be dispersed or purified only by plasma treatment.
[0021]
The reason why the dispersibility of the carbon nanotube is improved by the plasma treatment can be considered as follows. Usually, carbon nanotubes are obtained in the form of a lump that is entangled with another adjacent carbon nanotube. By plasma treatment, functional groups such as carboxyl groups, carbonyl groups, and hydroxyl groups can be added to the outer surface of carbon nanotubes, and they will repel those functional groups that are present on the outer surface of carbon nanotubes that are different from the adjacent ones. The carbon nanotubes that have been entangled so far are considered to be loosened and dispersed in a liquid such as water.
[0022]
In particular, in the present invention, a carboxyl group, a carbonyl group, or a hydroxyl group can be imparted to the outer surface of the carbon nanotube by plasma treatment (see Example 13 and Comparative Example 2). Among them, it is preferable that a hydroxyl group can be imparted. The reason is that the hydroxyl group (phenolic hydroxyl group) can improve the dispersibility of the carbon nanotube in a state where the structural change on the outer surface of the carbon nanotube is minimized as compared with the carboxyl group or the carbonyl group. Furthermore, it is possible to modify the hydroxyl group (phenolic hydroxyl group) on the outer surface of the carbon nanotube to introduce a new functional group or to bind to another polymer compound. In the present invention, the reason why the hydroxyl group can be added to the outer surface of the carbon nanotube is not clearly clarified, but as one factor, the carbon nanotube outer surface is compared as a whole by stirring the carbon nanotube during the plasma treatment. I think that it is because it is processed mildly.
[0023]
There are various types of plasma processing, but oxygen gas plasma processing is particularly preferable. The reason for this is that usually carbon nanotubes have amorphous carbon attached to the surface, and the amorphous carbon can be oxidized and removed to carbon dioxide. This is because it can be purified. The conditions for the oxygen gas plasma treatment vary depending on the apparatus and discharge mode, but in the case of the external electrode system, the pressure is preferably 5 to 100 Pa. Depending on the conditions of the plasma treatment, the pyrolytic carbon coating such as amorphous carbon can be removed or left moderately. It is preferable to leave it in an appropriate state because the entire surface area of the carbon nanotube is increased, and when used in a composite material such as a composite with a resin, the affinity with the resin is increased.
[0024]
The plasma treatment of the present invention is particularly preferable for a carbon nanotube having a small number of layers, and is preferable for a carbon nanotube having 1 to 5 layers. Carbon nanotubes with a small number of layers are not durable, such as oxidation resistance, compared with carbon nanotubes with a large number of layers. For example, carbon nanotubes can be oxidized by oxidizing using an oxidizing agent or firing in the presence of oxygen gas. Means for improving the dispersibility and the degree of purification are known. However, these methods have drawbacks that it is difficult to control oxidation and that all carbon nanotubes having a small number of layers are burned. In contrast, the plasma treatment can mildly treat only the surface layer, so that the dispersibility and the degree of purification can be improved without destroying the structure of the nanotube having a small number of layers. In particular, there are no 1 to 5 carbon nanotubes having surface modifications that directly modify the surface layer of carbon nanotubes, as well as surface treatment for attaching substances to carbon nanotubes, and the present invention is novel as such. Carbon nanotubes are provided. The surface treatment method by adhering to the surface has the disadvantage that the adhering material is peeled off, but the material obtained by directly modifying the surface of the carbon nanotube is a strong surface treatment and is preferable when mixed with a resin or the like.
[0025]
Nitrogen plasma is preferred for processing 1-5 thin carbon nanotubes. Since it can be processed milder than oxygen plasma, the carbon nanotubes themselves will not burn out and disappear. Even in the nitrogen plasma treatment, the bond cut by the nitrogen plasma reacts with oxygen in the air by being exposed to air after the treatment, and becomes a carboxyl group, a carbonyl group, a hydroxyl group, or the like.
[0026]
In the present invention, a carbon nanotube dispersion can be produced by dispersing carbon nanotubes treated with plasma in a liquid. The dispersion in the present invention refers to a state in which carbon nanotubes are dispersed and floated in the liquid and appear to be uniform in appearance. A dispersion in which carbon nanotubes are present up to the upper part of the liquid part even after standing for more than one day is called a dispersion. In the present invention, by selecting the type of solvent, the type of carbon nanotube, and a combination thereof, a dispersion in which a transparent portion does not appear in the upper layer portion can be obtained even after one week. The dispersion liquid may contain a carbon nanotube solution in which carbon nanotubes are dissolved as described later.
[0027]
Since the surfaces of the carbon nanotubes modified by the plasma treatment repel each other, it is considered that the entangled carbon nanotubes are helped to be loosened and dispersed by performing ultrasonic treatment in the liquid. The higher the output of the ultrasonic treatment, the better. 10W or more, preferably 20W or more, more preferably 50W or more. The method of dispersing the carbon nanotubes treated with plasma in the liquid is not necessarily ultrasonic, and may be high-speed stirring such as a homogenizer, stirring applying mechanical impact such as attritor or ball mill. Of course, normal stirring may be used.
[0028]
The liquid once dispersed in the liquid includes a solution in which carbon nanotubes are partially dissolved. A carbon nanotube solution can be obtained by solid-liquid separation of this dispersion. The carbon nanotube solution in the present invention is a liquid having transparency in which carbon nanotubes are dispersed in the liquid, and passes through the filter paper when filtered using a filter paper, and precipitates when centrifuged. There is no liquid substance, generally called a colloidal solution. A colloidal solution is expressed as a state in which colloidal particles are dissolved (dissolved) in the liquid. Therefore, in the present invention, this colloidal solution of carbon nanotubes is referred to as a carbon nanotube solution in which carbon nanotubes are dissolved in the liquid.
[0029]
The solid-liquid separation method is not particularly limited, and for example, a centrifugal separation method or a filtration method can be used. The filter paper used for the filtration preferably has a retained particle diameter of about 5 (μm) in JIS P 3801, and the centrifugal acceleration is 15000 (× g), more preferably 17000 (× g). ), It is preferable to perform the treatment for about 1 hour because a highly concentrated carbon nanotube solution having transparency can be obtained. In the case of the filtration method, the liquid coming out of the filter paper, and in the case of the centrifugal separation method, the supernatant is the carbon nanotube solution.
[0030]
The liquid for dispersing or dissolving the carbon nanotubes in the present invention is not particularly limited, but in the case of carbon nanotubes subjected to a hydrophilic treatment, it is preferable to disperse and dissolve the hydrophobic carbon nanotubes in a hydrophobic solvent. . Examples of hydrophilic solvents include water, monohydric alcohols such as methanol, ethanol, propanol, isopropanol and butanol, dihydric alcohols such as ethylene glycol, propylene glycol and butanediol, trihydric alcohols such as glycerin, ketones such as acetone, Examples thereof include acids such as formic acid, acetic acid and propionic acid, cyclic ethers such as tetrahydrofuran, solvents such as N-methylpyrrolidone and dimethyl sulfoxide (DMSO). These may be a mixture, and other substances that dissolve in the solvent such as various ions such as metal salts, polymers, and surfactants may be dissolved therein. Examples of the hydrophobic solvent include aromatics such as benzene, toluene and xylene, and aliphatic hydrocarbons such as hexane and cyclohexane.
[0031]
In the present invention, it is preferable for the dispersibility improvement of the carbon nanotube that the content of the acidic functional group with respect to the carbon on the outer surface of the carbon nanotube represented by the following formula is 2% or more.
[0032]
[Expression 1]

[0033]
Ac: Number of moles of acidic functional group contained in 1 g of carbon nanotube
2πRa: Average circumference of carbon nanotube (nm)
[(Ra−Rb) / Rk] +1: average number of carbon nanotube layers
Ra: Carbon nanotube average outer radius
Rb: Average inner radius of carbon nanotube
Rk: Carbon nanotube interlayer distance
Ac of the molecule shown in the above formula is the number of moles of acidic functional groups contained in 1 g of carbon nanotubes having functional groups on the outer surface. It is difficult to obtain carbon nanotubes with a purity of 100%, and it is difficult to identify them, so the carbon nanotubes referred to here are fibrous when viewed with a scanning electron microscope at a magnification of 50,000 times. If the material is a carbonaceous material with 80% or more in the field of view of the electron microscope, it can be called a carbon nanotube. Therefore, if strictly defined, the acid amount is measured not only having an acidic functional group only on the outer surface of the carbon nanotube but also including carbon adhering to the carbon nanotube and carbon particles mixed in the carbon nanotube, and all the carbon nanotubes are measured. It is calculated on the assumption that there is an acidic functional group on the surface. The carbon nanotube having a functional group on the outer surface is a carbon nanotube having at least one functional group on the outer surface of the carbon nanotube, as shown in the schematic diagram of FIG. The type of the functional group is not particularly limited, and examples thereof include a hydroxyl group, a carbonyl group, a carboxyl group, a nitro group, a sulfone group, and an ether group. The number of moles of acidic functional groups contained in the carbon nanotubes having functional groups on the outer surface is determined by calculation from neutralization titration measurement using an aqueous sodium hydroxide solution.
[0034]
The denominator shown in the above formula is the number of moles of carbon on the outer surface of the carbon nanotube contained in 1 g of the carbon nanotube. By dividing the average outer circumference of the carbon nanotube by using the multiplication result of the average number of carbon nanotube layers and the average circumference of the carbon nanotube, the carbon ratio of the outer surface of the carbon nanotube relative to the entire carbon nanotube is obtained. Carbon nanotubes contained in 1 g of carbon nanotubes are multiplied by the result obtained by dividing 1 g of carbon nanotubes by the atomic weight of carbon atoms (12 g / mol) (that is, the number of moles of carbon atoms contained in 1 g of carbon nanotubes). Obtain the number of moles of carbon on the outer surface.
[0035]
The carbon nanotube average outer radius Ra and the carbon nanotube average inner radius Rb are defined as shown in FIG. 1. For example, from the observation result of a transmission electron microscope (TEM), a rule that does not use one carbon nanotube repeatedly is applied. The outer and inner radii of the carbon nanotubes are arbitrarily measured at least 10 points, preferably 20 points or more, and the average value is calculated for each.
[0036]
The carbon nanotube interlayer distance Rk uses a known value of 0.34 nm.
[0037]
As described above, the content of the acidic functional group with respect to the carbon on the outer surface of the carbon nanotube is obtained, but when outlined, when viewed with a scanning electron microscope (or transmission electron microscope), a microscope Sodium hydroxide aqueous solution using a carbonaceous material containing a fibrous substance (carbon nanotube) in the field of view (preferably containing a fibrous substance of 10% or more, more preferably 50% or more, and even more preferably 80% or more) The value of the neutralization titration using, the average outer radius of the carbon nanotubes determined from the transmission electron microscope (TEM) TEM observation results, and the value of the average inner radius are substituted into the above formula, and the acid functionality of the carbon nanotube outer surface with respect to carbon is substituted. The content of the group will be determined. Example 2 (confirmation of fibrous substance by scanning electron microscope), Example 14 (neutralization titration), Example 15 (carbon nanotube diameter calculation from transmission electron micrograph), Example 16 (acidic) See Calculation of functional group content.
[0038]
It is preferable that the content rate of the acidic functional group with respect to carbon on the outer surface of the carbon nanotube represented by the above formula is 2% or more, preferably 4% or more, and more preferably 8% or more. If it is less than 2%, the dispersibility in the liquid deteriorates.
[0039]
Further, the functional group of the carbon nanotube that satisfies the above formula may be further modified using a method such as a chemical reaction.
[0040]
The carbon nanotubes having an acidic functional group content of 2% or more with respect to carbon on the outer surface of the carbon nanotubes obtained by the above formula are dispersed or dissolved in a hydrophilic solvent to become a carbon nanotube dispersion or solution. Among the hydrophilic solvents, water is most preferable from the viewpoint of safety in handling and cost.
[0041]
The present invention also includes a method for producing a purified carbon nanotube solution, characterized in that plasma-treated carbon nanotubes are dispersed in a liquid and then classified. In the case where carbon nanotubes treated with plasma are dispersed in a liquid, the sedimentation speed varies depending on the size of the carbon nanotubes. Using this property, it is possible to classify the carbon nanotubes according to the size of the mass by centrifugation, filtration, or the like. In addition, when a catalyst is used in the production of carbon nanotubes, it is possible to classify by centrifugation using the difference in specific gravity between the carbon nanotubes containing the catalyst part and the carbon nanotubes not containing the catalyst part. Is also possible. As described above, the carbon nanotubes classified and made uniform in size are useful for coating as an electron source for a field emission display or various electrode catalysts.
[0042]
The present invention also includes a method for producing a high-concentration carbon nanotube dispersion, a solution, and powdered carbon nanotubes, characterized by concentrating and / or drying the carbon nanotube dispersion obtained by the above method or the carbon nanotube solution. . A highly concentrated carbon nanotube dispersion or solution is obtained by concentrating the dispersion or solution classified from the dispersion, and a powder can be obtained by drying. The powder obtained in this way is preferable because the entanglement and mass diameter of the carbon nanotubes are controlled. As the concentration and drying methods, all conventionally known methods such as solvent removal by normal heating, solvent removal by evacuation, and freeze-drying can be used.
[0043]
In the present invention, preferably, (1) a carbon nanotube synthesis step, (2) a plasma treatment step of the carbon nanotube, (3) a step of dispersing the carbon nanotube in a liquid, and (4) a step of classifying or solid-liquid separating the carbon nanotube. Carbon nanotubes are manufactured by the following four processes. Conventionally, many methods for synthesizing carbon nanotubes have been proposed. Many carbon nanotubes are obtained in entangled masses. However, when practical application is considered, the carbon nanotubes are preferably dispersed and preferably separated from impurities. Various purification methods have been proposed, but usually the strict conditions of using strong acid or hydrofluoric acid are used. In addition, a process for efficiently and continuously producing dispersed carbon nanotubes has not been proposed. The present inventors have found that the carbon nanotubes are well dispersed in the liquid by plasma treatment, and have found that the dispersion can be divided into a solution portion, a fine dispersion portion, and a catalyst adhesion portion by classification.
[0044]
In the present invention, the carbon nanotube synthesis step in the first step may be any method. Any known technique can be used. Examples thereof include laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion. In order to advance the process smoothly, a thermal CVD method capable of continuous production in the gas phase is preferable. In the thermal CVD method, carbon nanotubes can be continuously recovered by continuously supplying the catalyst by a method in which the catalyst and the carbon source are brought into contact at a high temperature of 600 ° C. to 1200 ° C.
[0045]
The second step is a plasma treatment step, and this step is as described above. Oxygen gas plasma treatment is preferred. A plasma apparatus capable of continuously treating powder carbon nanotubes is preferred. For example, the use of an external electrode system as a plasma processing apparatus that continuously supplies powder carbon nanotubes (may be intermittent) and performs plasma processing while stirring is flexible and easy to design. This is preferable.
[0046]
The dispersion step in the third step is a step of dispersing the plasma-treated carbon nanotubes in the liquid. The dispersion method is not particularly limited. For example, the higher the output, the better the ultrasonic treatment is, and it is preferably 10 W or more, preferably 20 W or more, more preferably 50 W or more. High-speed stirring such as a homogenizer (processing pressure is preferably 3 MPa or more), stirring with mechanical impact such as an attritor (preferably the rotational speed is preferably 100 rpm or more), a ball mill (ball impact is preferably 1 G or more) may be used. Of course, normal stirring may be used.
[0047]
The fourth step is a step of classifying or solid-liquid separating the dispersed carbon nanotube dispersion. Although the method is not particularly limited, for example, filtration or centrifugation can be applied. The separated solid portion by classification or solid-liquid separation can be returned to the third step and redispersed, and the solution can be recovered again in the fourth step. In addition, the low-dispersion portion classified or solid-liquid separated in the fourth step is dried and then returned to the second step to perform plasma treatment. In addition, the carbon nanotubes containing the catalyst with the heaviest specific gravity recovered in the fourth step can be removed by calcination in air or the like, and the catalyst can be returned to the first step.
[0048]
In the present invention, an excellent catalyst composition can be produced by a method for producing a catalyst composition characterized by having the following two steps. (1) a step of plasma-treating the carbon nanotube, and (2) a step of bringing the carbon nanotube after the plasma treatment into contact with a liquid containing a metal. As a specific manufacturing method, a catalyst composition can be obtained by adding plasma-treated carbon nanotubes to an aqueous solution containing a metal and stirring the aqueous solution. Furthermore, the catalyst composition in the liquid state can be dried to remove the solvent to be in a solid state. Details of the catalyst composition of the present invention will be described below.
[0049]
The hydrophilic carbon nanotube in the present invention is preferably used as a catalyst carrier because it is dispersed in water. Usually, the metal which is a catalyst component is supported on a support in the form of an aqueous solution of a metal salt, but conventionally carbon nanotubes are hydrophobic and difficult to support on the surface of carbon nanotubes. However, if the hydrophilic carbon nanotube of the present invention is used, the metal catalyst is well-familiar with the aqueous solution of the metal salt, and the metal catalyst can be supported on the surface of the carbon nanotube with high dispersion. In particular, since a carbonyl group or a carboxylic acid group is present on the surface of the carbon nanotube, metal ions can be dispersed particularly well by interaction with these functional groups. The catalyst component referred to in the present invention is not particularly limited as long as it has catalytic ability, but for example, noble metals such as Pd, Pt, Ru, Rh, Ag, Au, Re, Ti, V, Cr, Mn, Fe, Co, Examples thereof include metals such as Ni, Cu and Zn and oxides thereof, and can exhibit reducing ability and oxidizing ability. The carbon nanotubes are entangled with each other, and are excellent in gas and liquid diffusibility and filterability, and are very suitable as a catalyst. Furthermore, the carbon nanotubes having 1 to 5 layers are excellent because they have a small diameter and a large outer surface area. The excellent point of the catalyst composition of the present invention is that the carbon nanotubes are thin and have a large curvature, so that the catalyst metal can be made fine.
[0050]
It can be easily estimated that if the catalyst metal can be made fine particles, the surface area of the metal becomes high and the activity of the catalyst becomes very high. Moreover, the carbon nanotube which carry | supported the metal with the fine particle can be used also as a manufacturing catalyst of a carbon nanotube. For example, a carbon nanotube carrying cobalt is placed in a quartz tube installed in a tubular furnace, and heated to 500 ° C. to 1200 ° C. in a tubular furnace while flowing an inert gas such as argon. Carbon nanotubes can be produced by introducing a compound.
[0051]
In the present invention, an excellent organic compound-containing carbon nanotube can be produced by the method for producing an organic compound-containing carbon nanotube characterized by having the following two steps. (1) a step of plasma-treating the carbon nanotube, and (2) a step of contacting the carbon nanotube after the plasma treatment with a liquid containing an organic compound. A preferable example of the organic compound referred to here is a drug. The reason and a specific manufacturing method will be described below. The hydrophilic carbon nanotubes as described above exhibit excellent performance as a drug transport agent. In the hydrophilic carbon nanotube of the present invention, if the hollow portion is open, the hollow portion is hydrophobic and the outer surface is hydrophilic. Accordingly, carbon nanotubes in which a hydrophobic drug is adsorbed in the hollow portion can be dispersed in water. The human and animal bodies are mostly made of water, and such substances can be used as drugs. The carbon nanotubes with the drug adsorbed in the hollow part may be dispersed in water and inserted into the affected area with a catheter, or may be used as it is as a drinking medicine, paint, eye drop or the like. In order to open the hollow portion, it may be oxidized. The oxidation may be gas phase oxidation or liquid phase oxidation. Of course, oxygen plasma treatment may be used. When used as a drug transporter, considering the effect per weight, the thinner the wall, the better the thin wall is preferable, 10 or less, more preferably 5 or less, and particularly preferably double-walled carbon nanotubes. It is. In consideration of movement in the body, the thinner one is preferable and the double-walled carbon nanotube is most preferable. Single-walled carbon nanotubes are difficult to achieve both hydrophilicity and hydrophobicity. The method for producing such a drug is not particularly limited, but (1) the tips of the nanotubes are opened by oxidation treatment. (The tip of the nanotube contains many highly reactive carbon 5-membered rings, so it can be opened easily by selectively burning. Whether it is open can be confirmed by performing a nitrogen adsorption experiment at 77K) (2) The inventive plasma treatment is performed and dispersed by applying ultrasonic waves in water. (3) Remove suspended matters by centrifugation. (4) When a small amount of a hydrophobic drug is added to the carbon nanotube-dispersed aqueous solution, the hydrophobic drug is selectively adsorbed on the hydrophobic carbon nanotube hollow portion. It can be made by such a process.
[0052]
Furthermore, in the present invention, an excellent coating composition can be produced by a method for producing a coating composition characterized by having the following two steps. (1) a step of plasma-treating the carbon nanotube, and (2) a step of mixing the carbon nanotube after the plasma treatment with a main agent for coating. Examples of the main agent for coating herein include resins. Examples of the resin include those in a liquid state or a solid state at room temperature, and further, those that are thermoplastic and thermosetting. In particular, the use of a resin in a liquid state at room temperature allows the process of mixing the plasma-treated carbon nanotubes with the resin to be performed at room temperature, simplifying the process equipment, and can be applied to an object of any shape desired to be coated at room temperature. This is preferable because the process equipment can be simplified. Furthermore, by using a curable resin, for example, the coating composition is applied to the surface of an object having an arbitrary shape to be coated, and then the coating composition is cured, so that the coating composition has an arbitrary shape. It is preferable because it can be firmly fixed to the surface. As a method for mixing the carbon nanotubes after the plasma treatment with the main agent for coating, an ultrasonic wave, a homogenizer, an attritor, a ball mill, a Banbury mixer, a kneader, a roll, a single screw or a twin screw extruder can be used. In addition, the coating composition here also includes a paste-like composition. Details regarding the coating composition of the present invention are described below.
[0053]
As described above, the carbon nanotubes to which functional groups are added according to the present invention can be easily dispersed and dissolved in a hydrophilic solvent in the case of carbon nanotubes that have been subjected to a hydrophilic treatment, and the hydrophobic carbon nanotubes in a hydrophobic solvent. It is. For this reason, the composition which contains the carbon nanotube which provided the functional group, and the solvent which can disperse | distribute the carbon nanotube which provided the functional group can be obtained, and the composition in which the carbon nanotube was highly dispersed can be obtained. A composition in which carbon nanotubes are highly dispersed is an excellent composition that can sufficiently bring out good conductivity, high strength characteristics, and field electron emission characteristics of carbon nanotubes.
[0054]
For this reason, it contains carbon nanotubes to which functional groups have been added, preferably contains a solvent in which the carbon nanotubes to which functional groups have been added can be dispersed, and more preferably contains a liquid material having curability. By creating a coating composition, the coating composition can be applied to a solid surface to improve the conductivity of the solid surface. Of course, the coating composition may be cured on a solid surface. Moreover, the solid material of arbitrary shapes excellent in electroconductivity and intensity | strength can be obtained by pouring a coating composition into a type | mold and making it harden | cure. Furthermore, an electronic device exhibiting excellent field electron emission characteristics can be obtained by attaching electrodes to the coating composition (even after curing).
[0055]
By selecting a raw material having transparency as a raw material used when preparing the coating composition, and making the addition amount of the carbon nanotube 1 wt% or less, the resulting coating composition can have transparency. . By selecting a raw material having transparency even after curing as a raw material used in preparing the coating composition, a coating composition having transparency even after curing can be obtained. For this reason, in addition to the above characteristics (good conductivity, high strength characteristics, field electron emission characteristics), it can have transparency characteristics.
[0056]
Examples of the method of curing the coating composition include a method of containing a raw material that gradually reacts and shifts to a solid state, such as a raw material that causes thermal curing or photocuring of the coating composition. For example, a compound having two or more epoxy groups in one molecule (epoxy resin), a compound having a hydroxyl group that reacts with an epoxy group (curing agent), and a reaction between the epoxy resin and the curing agent are added to the coating composition. By containing the hardening accelerator to accelerate, it can be hardened by thermosetting.
[0057]
Moreover, the method of hold | maintaining the coating composition in the state fuse | melted at high temperature using the raw material of a solid state at normal temperature, and cooling when hardening is needed is mentioned. Specifically, a metal salt of a long chain fatty acid, an ester of a long chain fatty acid, paraffin wax, a silicone compound and the like that are relatively close to a solid state at room temperature can be used.
[0058]
The coating composition is made of amorphous silica, crystalline silica, calcium carbonate, magnesium carbonate, alumina, magnesia, silicon nitride, magnesium aluminum oxide, zirconia, zircon, clay, talc, mica, calcium silicate, titanium oxide, oxidized It may contain inorganic materials such as antimony, asbestos and glass fiber.
[0059]
The present invention has found a method capable of efficiently plasma-treating powdered carbon nanotubes. As a result of the plasma treatment, it was possible to obtain novel carbon nanotubes whose surface could be made into a specific functional group, and to obtain novel dispersions and solutions of carbon nanotubes. Furthermore, it has become very easy to use as a catalyst carrier, as a drug transport material, and as a coating composition. The plasma treatment is a treatment capable of mildly hydrophilizing the carbon nanotube surface, and is advantageous in that it can treat 1 to 5 carbon nanotubes having a small number of layers, which has been difficult until now, without greatly breaking the structure. If the type of plasma treatment gas and the plasma treatment conditions are selected, when carbon nanotubes are produced by the CVD method, it is possible to remove the pyrolytic carbon from the surface of the carbon nanotubes or to leave the carbon nanotubes as they are. In normal oxidation processes, the pyrolytic carbon coating is often substantially removed.
[0060]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples listed here.
[0061]
Example 1 (Synthesis of carbon nanotubes)
K. Hernadi, A.M. See the report by Fonseca et al. (Zeolites 17: 416-423, 1996), iron acetate (2 g), cobalt acetate (2 g), Y-type zeolite (HSZ-310NAA Lot. No. GZ-143-3 manufactured by Tosoh Corporation) 5) (10 g) was weighed, methanol (100 ml) was added, and after stirring for 1 hour with a shaker, the methanol content was removed by drying to obtain a catalyst. Next, using the CVD reactor shown in FIG. 2, 1 g of catalyst was set in advance on quartz wool in the reaction tube, heated to 600 ° C. in a nitrogen (30 cc / min) atmosphere, and then acetylene (6 cc / min). Then, carbon nanotubes were synthesized by holding at 600 ° C. for 5 hours in a nitrogen (30 cc / min) atmosphere. Then, it cooled to room temperature under nitrogen (30cc / min) atmosphere, and took out the reaction material.
[0062]
Example 2 (Confirmation of carbon nanotube)
The mixture of the catalyst and the carbon nanotube obtained in Example 1 was stirred in a 10% aqueous solution of hydrofluoric acid for 3 hours, and then filtered using a filter paper (Toyo Rossi Kaisha, Filter Paper No. 125 mm). The solid was washed with ion exchange water and an acetone solution and then dried to obtain carbon nanotubes. 3 and 4 show the transmission electron microscope (TEM) observation results of the obtained carbon nanotubes, and FIGS. 5 and 6 show the observation results of the scanning electron microscope (SEM). 3 to 6 that many multi-walled carbon nanotubes are contained. 5 and 6, it can be seen that most of the fibrous material is present and no particulate material is present. That is, it can be seen that the sample contains 90% or more of carbon nanotubes. Further, when elemental analysis was performed using EDX of SEM, the result was that the abundance of the Y-type zeolite was below the EDX measurement limit (approximately 0%).
[0063]
Example 3 (Plasma treatment)
0.5 g of the carbon nanotube obtained in Example 2 was thinly spread on a glass petri dish, and plasma was applied for 5 minutes under the conditions of oxygen gas, pressure 20 Pa, and POWER 300 W using PLASMA CHAMBER MODEL PC-101A manufactured by YAMATO CHEMICAL. Processed. 7 and 8 show the transmission electron microscope (TEM) observation results of the obtained plasma-treated carbon nanotubes, and FIGS. 9 and 10 show the observation results of the scanning electron microscope (SEM). 7 to 10 that many multi-walled carbon nanotubes are included and the size thereof is the same as that obtained in Example 2. And it can also confirm that the deposit | attachment of the carbon nanotube outer surface is reducing.
[0064]
Example 4 (Production of dispersion)
As a result of adding 50 ml of ion exchange water to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 3 and stirring for 1 hour with a shaker, the mixture was allowed to stand for 48 hours. It could be confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), carbon nanotubes similar to those in FIGS. 9 and 10 were confirmed in the dispersion liquid.
[0065]
Example 5 (Plasma treatment)
0.5 g of the carbon nanotube obtained in Example 2 was thinly spread on a glass petri dish, and plasma was applied for 5 minutes under the conditions of oxygen gas, pressure 20 Pa, and POWER 300 W using PLASMA CHAMBER MODEL PC-101A manufactured by YAMATO CHEMICAL. Once the treatment is performed, the plasma-treated carbon nanotubes on the petri dish are agitated (turned over, rolled, etc.), spread on the petri dish and spread again on the petri dish, and the same plasma treatment is repeated again for a total of 15 minutes (total 3 Plasma treatment). 11 and 12 show the transmission electron microscope (TEM) observation results of the obtained plasma-treated carbon nanotubes, and FIGS. 13 and 14 show the observation results of the scanning electron microscope (SEM). The results were very similar to those shown in FIGS. 7 to 10, and many of the multi-walled carbon nanotubes were included, and the size thereof was confirmed to be the same as in Example 2. And the deposit | attachment of the carbon nanotube outer surface decreased.
[0066]
Example 6 (Production of dispersion)
As a result of adding 50 ml of ion-exchanged water to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 5 and stirring for 1 hour with a shaker, the mixture was allowed to stand for 48 hours. It could be confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), the same carbon nanotubes as in FIGS. 13 and 14 were confirmed in the dispersion liquid.
[0067]
Example 7 (Production of dispersion)
50 mg of ion-exchanged water was added to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 5, and after treatment for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), 48 When the sample obtained by allowing to stand for a period of time was observed, a carbon nanotube dispersion and a black precipitate were confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), the same carbon nanotubes as in FIGS. 13 and 14 were confirmed in the dispersion liquid.
[0068]
Example 8
As a result of transferring and comparing 20 ml of the carbon nanotube dispersion liquid obtained in Example 4, Example 6, and Example 7 into a transparent glass sample bottle, the dispersion liquid was in the order of Example 7> Example 6> Example 4. Strong results were obtained. It can be seen that a carbon nanotube dispersion with a higher concentration can be obtained by mixing the carbon nanotubes during the plasma treatment and further using ultrasonic treatment.
[0069]
Example 9
50 mg of ethanol was added to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 5 and treated for 1 hour with an ultrasonic cleaner (Yamato Chemical Co., BRANSON 3210, transmission frequency 47 KHz, output 130 W), and then left for 48 hours. When the sample obtained by placing the sample was observed, a carbon nanotube dispersion and a black precipitate were confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), the same carbon nanotubes as in FIGS. 13 and 14 were confirmed in the dispersion liquid.
[0070]
Example 10
50 mg of ethylene glycol was added to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 5, and after treatment for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), 48 hours. When the sample obtained by standing still was observed, the carbon nanotube dispersion liquid and the black deposit were confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), the same carbon nanotubes as in FIGS. 13 and 14 were confirmed in the dispersion liquid.
[0071]
Example 11
When the carbon nanotube dispersion liquid obtained in Example 7 was filtered using a filter paper (Toyo Roshi Kaisha, Filter Paper No. 125 mm), a transparent black solution was obtained as the filtrate that passed through the filter paper. It was. 15 and 16 show the observation results of the transmission electron microscope (TEM) of the sample obtained by drying the obtained solution, and the scanning electron microscope (SEM) of the sample obtained by drying the solution obtained in FIGS. ) Shows the observation results. 15-18, it contains that many multi-walled carbon nanotubes are included, and the magnitude | size is short in a major axis direction compared with FIGS. 11-14, and it turns out that it is not entangled mutually.
[0072]
Example 12
Using the centrifugal separator (apparatus: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8), the carbon nanotube dispersion obtained in Example 7 was rotated at 12000 rpm (about 17000 (× g)). When centrifuged for 1 hour, a transparent black solution was obtained as the supernatant. When the solution portion was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), carbon nanotubes similar to those in FIGS. 17 and 18 were confirmed in the solution.
[0073]
Example 13
As a result of analyzing the surface composition of the carbon nanotube using X-ray photoelectron spectroscopy, the carbon nanotube after the plasma treatment obtained in Example 5 has a ratio of oxygen atom of 10%. Carboxy group or ester group (COO, 2%), carbonyl group (C = O, 4%), ether group or hydroxyl group (C-O, 5%) functional group with respect to ring or CHx (88%) The result was obtained. Under the influence of a carboxyl group or a phenolic hydroxyl group, the dispersion or solution is considered to be acidic.
[0074]
Example 14
50 mg of ion-exchanged water was added to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 5, and after treatment for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), 48 When the pH of the dispersion obtained by standing for a period of time was measured using a glass electrode type hydrogen ion concentration meter (Toa Denki Kogyo, HM-30V), it was pH = 5.5. A well-known neutralization titration is performed at 42.5 × 10 ^-6 As a result of using (mol / l) aqueous sodium hydroxide solution with pH = 7.0 as the end point, 145 ml of aqueous sodium hydroxide solution was required. That is, 0.25 mg of sodium hydroxide (NaOH, 40 g / mol) was required. From this result, the number of moles of acidic functional groups in 10 mg of the carbon nanotubes after plasma treatment is 6.3 × 10. ^-6 (Mol).
[0075]
Example 15
Using the transmission electron microscope (TEM) shown in FIGS. 3 and 4, applying the rule that does not use one carbon nanotube redundantly, arbitrarily measure the outer radius and inner radius of 20 carbon nanotubes, As a result of calculating the average values, Ra: carbon nanotube average outer radius 11.5 nm and Rb: carbon nanotube average inner radius 3.3 nm were obtained. Further, Rk: a carbon nanotube interlayer distance of 0.34 nm was used.
[0076]
Example 16
From the results of Examples 14 and 15, the content (%) of the acidic functional group with respect to the carbon on the outer surface of the carbon nanotube was calculated using the above formula. As a result, a result of 12% was obtained.
[0077]
Example 17
A mixture of the catalyst and carbon nanotube obtained in Example 1 (0.5 g) was thinly spread on a glass petri dish, and YAMATO Chemical's PLASMA CHAMBER MODEL PC-101A was used under the conditions of oxygen gas, pressure 20 Pa, and POWER 300 W. Plasma treatment was performed for 5 minutes.
[0078]
Example 18
50 ml of ion-exchanged water is added to 10 mg of the plasma-treated catalyst and carbon nanotube mixture obtained in Example 17, and the mixture is used for 1 hour in an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W). When the sample obtained by allowing to stand for 48 hours after the treatment was observed, a carbon nanotube dispersion and a black precipitate were confirmed. The dispersion liquid part was collected with a dropper and the dried sample was observed with a scanning electron microscope (SEM). As a result, carbon nanotubes similar to those shown in FIGS. 9 and 10 were confirmed in the dispersion liquid. Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%). On the other hand, the presence of Y-type zeolite was confirmed in the EDX measurement result of the precipitate. Thus, it can be seen that by collecting the dispersion, that is, classification, the catalyst portion can be removed without using a strong acid as in Example 2, and the carbon nanotubes can be purified.
[0079]
Example 19
A mixture of the catalyst and carbon nanotube obtained in Example 1 (0.5 g) was thinly spread on a glass petri dish, and YAMATO Chemical's PLASMA CHAMBER MODEL PC-101A was used under the conditions of oxygen gas, pressure 20 Pa, and POWER 300 W. Perform plasma treatment for 5 minutes, stir the plasma-treated carbon nanotubes on the petri dish (upside down, roll, etc.), spread it thinly on the petri dish, and repeat the same plasma treatment again for a total of 15 minutes (total 3 Plasma treatment).
[0080]
Example 20
50 ml of ion-exchanged water is added to 10 mg of the plasma-treated catalyst and carbon nanotube mixture obtained in Example 19, and the mixture is used for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W). When the sample obtained by allowing to stand for 48 hours after the treatment was observed, a carbon nanotube dispersion and a black precipitate were confirmed. When the dispersion liquid part was collected with a dropper and the dried sample was observed using a scanning electron microscope (SEM), the same carbon nanotubes as in FIGS. 13 and 14 were confirmed in the dispersion liquid. Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%). On the other hand, the presence of Y-type zeolite was confirmed in the EDX measurement result of the precipitate. Thus, as in Example 18, by collecting the dispersion, that is, by classification, the catalyst portion can be removed without using a strong acid as in Example 2, and the carbon nanotubes can be purified. .
[0081]
Example 21
When the carbon nanotube dispersion obtained in Example 20 was filtered using a filter paper (Toyo Roshi Kaisha, Filter Paper No. 125 mm), a transparent black solution was obtained as the filtrate that passed through the filter paper. It was. The solution portion was collected with a dropper and the dried sample was observed using a transmission electron microscope (TEM) and a scanning electron microscope (SEM), and carbon nanotubes similar to those shown in FIGS. 15 to 18 were confirmed in the solution. . Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%).
[0082]
Example 22
Using the centrifugal separator (apparatus: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8), the carbon nanotube dispersion obtained in Example 20 was rotated at 12000 rpm (about 17000 (× g)). When centrifuged for 1 hour, a transparent black solution was obtained as the supernatant. The solution portion was collected with a dropper and the dried sample was observed using a transmission electron microscope (TEM) and a scanning electron microscope (SEM), and carbon nanotubes similar to those shown in FIGS. 15 to 18 were confirmed in the solution. . Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%).
[0083]
Example 23
The solid matter on the filter paper that did not pass through the filter paper obtained in Example 21 was collected, 50 ml of ion-exchanged water was added, and the mixture was applied to an ultrasonic cleaner (Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W). After observing the sample obtained after standing for 48 hours, a carbon nanotube dispersion liquid and a black precipitate were obtained and filtered using a filter paper (Toyo Roshi Kaisha, Filter Paper No. 125 mm). As a filtrate that passed through the filter paper, a transparent black solution was obtained. The solution portion was collected with a dropper, and the dried sample was observed with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). As a result, the presence of carbon nanotubes similar to those shown in FIGS. did it. Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%).
[0084]
Example 24
The precipitate obtained in Example 22 was collected, 50 ml of ion-exchanged water was added, and the mixture was treated for 1 hour with an ultrasonic washing machine (manufactured by Yamato Chemical Co., BRANSON 3210, transmission frequency 47 KHz, output 130 W), and then left for 48 hours. When the sample obtained by placing was observed, a carbon nanotube dispersion liquid and a black precipitate were obtained and rotated using a centrifuge (device: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8). Centrifugation was performed for several 12,000 rpm (about 17000 (× g)) × 1 hour, and a transparent black solution was obtained as a supernatant. The solution portion was collected with a dropper and the dried sample was observed using a transmission electron microscope (TEM) and a scanning electron microscope (SEM), and carbon nanotubes similar to those shown in FIGS. 15 to 18 were confirmed in the solution. . Furthermore, when elemental analysis was performed using EDX of SEM, the result was that the abundance of Y-type zeolite was below the measurement limit of EDX (approximately 0%).
[0085]
Example 25
When the solution obtained in Example 22 was allowed to stand in a thermostatic bath maintained at 60 ° C., the solution was concentrated, and further, when left in a thermostatic bath maintained at 60 ° C., carbon nanotube powder was obtained. .
[0086]
Comparative Example 1
To 10 mg of the carbon nanotubes obtained in Example 2, 50 ml of ion-exchanged water was added, treated for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), and allowed to stand for 48 hours. When the sample obtained in this way was observed, the liquid upper layer portion was colorless and transparent, and only a black precipitate could be confirmed.
[0087]
Comparative Example 2
The carbon nanotube obtained in Example 2 was subjected to surface composition analysis of the carbon nanotube using X-ray photoelectron spectroscopy. As a result, the oxygen atom was in a ratio of 1%, and from the C1s peak splitting, an aromatic ring or CHx ( 98%) with respect to carboxyl group or ester (COO, 0%), carbonyl group (C = O, 1%), ether group or hydroxyl group (C-O, 1%). .
[0088]
Comparative Example 3
To 10 mg of the carbon nanotubes obtained in Example 2, 50 ml of ion-exchanged water was added, treated for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), and allowed to stand for 48 hours. The pH of the obtained sample was measured using a glass electrode type hydrogen ion concentration meter (Toa Denpa Kogyo, HM-30V) and found to be 7.0 (acid functional group content 0%).
[0089]
Example 26
Ferrous acetate (manufactured by Aldrich) 0.08 g and cobalt acetate tetrahydrate (manufactured by Nacalai Tesque) 0.11 g were added to 7 ml of water and suspended in an ultrasonic cleaner for 10 minutes. 1.0 g of the plasma-treated carbon nanotube obtained in Example 5 was added and treated with an ultrasonic cleaner for 10 minutes, and water was removed at a constant temperature of 60 ° C. to obtain a catalyst carrying a metal salt. 0.050 g of the carbon nanotube carrying the metal salt obtained above was taken on a quartz plate at the center of a quartz tube having an inner diameter of 30 mm, and nitrogen was supplied at 30 ml / min. A quartz tube was placed in an electric furnace and the center temperature was heated to 600 ° C. After supplying ultrapure acetylene gas (manufactured by High Pressure Gas Industry) at 6 ml / min for 30 minutes, the supply of acetylene gas was stopped and the temperature was cooled to room temperature. When the reaction product deposited on the quartz plate was observed with a scanning electron microscope JSM6301NF of JEOL Datum Co., Ltd., almost no amorphous carbon was deposited. When the shape of the fibrous material was measured with a transmission electron microscope, it was found that thin hollow nanofibers having an outer diameter of 20 nm or less and an inner diameter of about 5 nm were the main components. When the hollow nanofibers were observed with a high-resolution transmission electron microscope, the walls of the nanofibers were composed of graphite layers.
[0090]
Example 27
The multi-walled carbon nanotube obtained in Example 2 was fired at 400 ° C. for 30 minutes in the air. After firing, plasma treatment was performed by the method of Example 5 and dispersed in water by the method of Example 7. A small amount of ibuprofen was added to the system. After 5 hours, the solid content was recovered by centrifugation at 12,000 revolutions, and ibuprofen in the liquid portion was quantified. As a result, ibuprofen was less than half of the added amount. The recovered carbon nanotubes, which were solids, were dispersed again by adding water and applying ultrasonic waves. Dispersed water of multi-walled carbon nanotubes with the drug adsorbed in the hollow part was obtained.
[0091]
Example 28 (nitrogen plasma treatment)
0.5 g of the carbon nanotube obtained in Example 2 was thinly spread on a glass petri dish, and plasma was applied for 5 minutes under the conditions of nitrogen gas, pressure 20 Pa, POWER 300 W using PLASMA CHAMBER MODEL PC-101A manufactured by YAMATO CHEMICAL. Once the treatment is performed, the plasma-treated carbon nanotubes on the petri dish are agitated (turned over, rolled, etc.), spread on the petri dish and spread again on the petri dish, and the same plasma treatment is repeated again for a total of 15 minutes (total 3 Plasma treatment). As a result of observation with a transmission electron microscope (TEM) and observation with a scanning electron microscope (SEM), it was confirmed that the carbon nanotube was the same as in Example 2. Observation with a high-resolution transmission electron microscope confirmed that pyrolytic carbon was coated before and after plasma treatment.
[0092]
Example 29
About the carbon nanotube after the plasma treatment obtained in Example 28, the result of surface composition analysis of the carbon nanotube using the X-ray photoelectron spectroscopy showed that the oxygen atom was in a ratio of 10%. Carboxy group or ester group (COO, 2%), carbonyl group (C═O, 3%), ether group or hydroxyl group (C—O, 6%) functional group with respect to ring or CHx (88%) The result was obtained. It is considered that the dispersion and solution are acidic due to the influence of the carboxyl group and the phenolic hydroxyl group.
[0093]
Example 30
50 mg of ion-exchanged water was added to 10 mg of the carbon nanotubes after plasma treatment obtained in Example 28, and after treatment for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), 48 When the pH of the dispersion obtained by standing for a period of time was measured using a glass electrode type hydrogen ion concentration meter (Toa Denki Kogyo, HM-30V), it was pH = 5.5. A well-known neutralization titration is performed at 42.5 × 10 ^-6 As a result of using (mol / l) aqueous sodium hydroxide solution with pH = 7.0 as the end point, 118 ml of aqueous sodium hydroxide solution was required. That is, 0.20 mg of sodium hydroxide (NaOH, 40 g / mol) was required. From this result, the number of moles of acidic functional groups in 10 mg of the carbon nanotubes after the plasma treatment was 5.0 × 10. ^-6 (Mol).
[0094]
Example 31
Using the transmission electron microscope (TEM) shown in FIGS. 3 and 4, applying the rule that does not use one carbon nanotube redundantly, arbitrarily measure the outer radius and inner radius of 20 carbon nanotubes, As a result of calculating the average values, Ra: carbon nanotube average outer radius 11.5 nm and Rb: carbon nanotube average inner radius 3.3 nm were obtained. Further, Rk: a carbon nanotube interlayer distance of 0.34 nm was used.
[0095]
Example 32
From the results of Examples 30 and 31, the content (%) of the acidic functional group with respect to the carbon on the outer surface of the carbon nanotube was calculated using the above formula. As a result, a result of 9.6% was obtained.
[0096]
Example 33
Carbon nanotubes were produced by the arc discharge method according to the method of JLHutchison et al. (Carbon 39 (2001) 761-770). The anode was a graphite rod with a diameter of 3.2 mm and a catalyst embedded in a hole with a diameter of 3.2 mm and a length of 140 mm, and the cathode was a graphite rod with a diameter of 10 mm and a length of 25 mm. The catalyst was prepared as follows. A mixture of Ni, Co, and Fe powder having a particle size of 2-5 μm and sulfur atoms were pulverized well, and then calcined at 500 ° C. for 1 hour under argon gas. Immediately after being pulverized to μ size with a ball mill, it was mixed with carbon powder. It was tightly packed into a graphite rod with a 3.2mm hole drilled. The composition of the anode was 2.6 at% for Ni, 0.7 at% for Co, 1.45 at% for Fe, and 0.75 at% for S. CNT synthesis was performed at an arc current of 75-80 A at 350 torr with an argon: hydrogen volume ratio of 1: 1. Both electrodes were 2 mm in distance and the voltage difference was 26-28V.
[0097]
Example 34
The carbon 0.5g containing the carbon nanotube obtained in Example 33 was thinly spread on a glass petri dish, and YAMATO Chemical's PLASMA CHAMBER MODEL PC-101A was used under the conditions of nitrogen gas, pressure 20Pa, POWER300W, Perform plasma treatment for 5 minutes, take it out once, stir the plasma-treated carbon nanotubes on the petri dish (overturning, rolling, etc.), spread it thinly on the petri dish, and repeat the same plasma treatment again for a total of 10 minutes Plasma treatment was performed twice (total 2 times).
[0098]
It is obtained by adding 50 ml of ion-exchanged water to 10 mg of the carbon material after the plasma treatment, treating it for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), and allowing it to stand for 48 hours. When the sample was observed, a carbon nanotube dispersion and a black precipitate were confirmed. The dispersion was centrifuged at 12000 rpm (about 17000 (× g)) × 1 hour using a centrifuge (apparatus: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8). As a liquid, a transparent black solution was obtained. The solution portion was collected with a dropper and observed with a high-resolution transmission electron microscope. When viewed with a scanning electron microscope of 50,000 times, 80% were fibrous substances and 20% were particulate substances.
[0099]
It was dried, weighed, and dispersed again in water. The amount of acid was measured in the same manner as in the previous example, and the content of acidic functional groups was determined to be 8.5%.
Example 35
The carbon 0.5g containing the carbon nanotube obtained in Example 33 was thinly spread on a glass petri dish, and YAMATO Chemical's PLASMA CHAMBER MODEL PC-101A was used under the conditions of nitrogen gas, pressure 20Pa, POWER300W, Perform plasma treatment for 5 minutes, take it out once, stir the plasma-treated carbon nanotubes on the petri dish (turn over, roll, etc.), spread it thinly on the petri dish, repeat the same plasma treatment again, total 20 minutes Plasma treatment was performed a total of 4 times.
[0100]
It is obtained by adding 50 ml of ion-exchanged water to 10 mg of the carbon material after the plasma treatment, treating it for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), and allowing it to stand for 48 hours. When the sample was observed, a carbon nanotube dispersion and a black precipitate were confirmed. The dispersion was centrifuged at 12000 rpm (about 17000 (× g)) × 1 hour using a centrifuge (apparatus: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8). As a liquid, a transparent black solution was obtained. As a result of collecting the solution portion with a dropper and observing with a high-resolution transmission electron microscope, many carbon nanotubes having 2 to 5 layers with carbon impurities attached were observed.
Example 36
Single-walled carbon nanotubes (purity 20%) 0.5g purchased from Frontier Carbon Co., Ltd. were spread on a glass petri dish, and YAMATO Chemical's PLASMA CHAMBER MODEL PC-101A was used. Perform plasma treatment for 5 minutes under the conditions, take out once, stir the plasma-treated carbon nanotubes on the petri dish (overturning, rolling, etc.), spread it thinly on the petri dish, repeat the same plasma treatment again, Plasma treatment was performed for a total of 15 minutes (3 times in total).
[0101]
It is obtained by adding 50 ml of ion-exchanged water to 10 mg of the carbon material after the plasma treatment, treating it for 1 hour with an ultrasonic cleaning machine (manufactured by Yamato Chemical, BRANSON 3210, transmission frequency 47 KHz, output 130 W), and allowing it to stand for 48 hours. When the sample was observed, a carbon nanotube dispersion and a dark precipitate were confirmed. The dispersion was centrifuged at 12,000 rpm (about 17000 (× g)) × 1 hour using a centrifuge (apparatus: KUBOTA KR-20000T, rotor: RA-3 50 ml × 8). As a liquid, a clear blackish solution was obtained. The solution portion was recovered with a dropper and observed with a high-resolution transmission electron microscope. As a result, many single-walled carbon nanotubes were observed.
Example 37
160 parts by weight of a bisphenol A type epoxy resin (epoxy equivalent 190), 40 parts by weight of a diglycidyl ether type diluent (epoxy equivalent 150), 10 parts by weight of an inorganic filler, aerosil (average particle size 30 nm), and a carboxylic acid anhydride A curing agent solution obtained by dissolving 160 parts by weight of methyltetrahydrophthalic anhydride and 4 parts by weight of triphenylphosphine, 1 part by weight of plasma-treated carbon nanotubes obtained in Example 36, and 100 parts by weight of ethanol. A paste-like composition in which carbon nanotubes were highly dispersed was obtained by blending. When the paste-like composition was poured into a mold having a diameter of 3 cm and a thickness of 5 mm and heated at 70 ° C. for 1 hour and further at 180 ° C. for 2 hours, the paste-like composition was cured and a solid disk with highly dispersed carbon nanotubes was formed. Obtained.
[0102]
【The invention's effect】
According to the present invention, plasma-treated carbon nanotubes, dispersions, solutions and compositions can be obtained.
[0103]
In the method of plasma-treating carbon nanotubes (especially oxygen gas plasma is preferable), the dispersibility of carbon nanotubes, the improvement of the purification degree, and the addition of functional groups to the outer surface can be performed simultaneously in a short time. It is an excellent treatment method.
[0104]
Even in the case of single-walled or 2-5-walled carbon nanotubes with a small number of layers, plasma treatment (especially nitrogen gas plasma is preferred) improves the dispersibility and improves the purity without greatly destroying the structure. Functional group can be imparted to the outer surface.
[0105]
A larger effect can be obtained by mixing the carbon nanotubes during the plasma treatment.
[0106]
The carbon nanotube dispersion liquid and solution can be obtained by using plasma-treated carbon nanotubes (carbon nanotubes having an acidic functional group content of 2% or more with respect to carbon on the outer surface of the carbon nanotubes).
[0107]
Moreover, a carbon nanotube can be refine | purified by classifying a carbon nanotube dispersion liquid and a solution. Furthermore, when a catalyst is used for the production of carbon nanotubes, purification can be performed to remove the catalyst by classifying the carbon nanotube dispersion liquid and solution.
[0108]
Carbon nanotube dispersions, solutions, and carbon nanotubes obtained from these can be widely expected to be used for additives such as paints and resins, electronic parts, and medical applications. Furthermore, the carbon nanotube refining method by classification of the carbon nanotube dispersion and the solution makes it possible not to use a strong acid or the like and to recycle the catalyst, which is effective from the viewpoint of influence on the human body and environmental problems. For these reasons, the industrial utility value according to the present invention is great.
[Brief description of the drawings]
FIG. 1 is a schematic view of a multi-walled carbon nanotube.
FIG. 2 is a sectional view of a CVD apparatus.
3 is a TEM photograph (× 400000) of the carbon nanotube obtained in Example 2. FIG.
4 is a TEM photograph (× 160000) of a carbon nanotube obtained in Example 2. FIG.
5 is an SEM photograph (× 50000) of the carbon nanotube obtained in Example 2. FIG.
6 is an SEM photograph (× 50000) of the carbon nanotube obtained in Example 2. FIG.
7 is a TEM photograph (× 400000) of the carbon nanotube obtained in Example 3. FIG.
8 is a TEM photograph (× 160000) of the carbon nanotube obtained in Example 3. FIG.
9 is an SEM photograph (× 50000) of the carbon nanotube obtained in Example 3. FIG.
10 is an SEM photograph (× 50000) of the carbon nanotube obtained in Example 3. FIG.
11 is a TEM photograph (× 400000) of a carbon nanotube obtained in Example 5. FIG.
12 is a TEM photograph (× 160000) of a carbon nanotube obtained in Example 5. FIG.
13 is a SEM photograph (× 50000) of the carbon nanotube obtained in Example 5. FIG.
14 is an SEM photograph (× 50000) of the carbon nanotube obtained in Example 5. FIG.
15 is a TEM photograph (× 400000) of a carbon nanotube obtained in Example 11. FIG.
16 is a TEM photograph (× 160000) of a carbon nanotube obtained in Example 11. FIG.
17 is a SEM photograph (× 50000) of the carbon nanotube obtained in Example 11. FIG.
18 is a SEM photograph (× 50000) of the carbon nanotube obtained in Example 11. FIG.

Claims (15)

A method for treating a carbonaceous material, characterized in that, when a carbonaceous material containing carbon nanotubes is treated with plasma, the carbonaceous material containing carbon nanotubes is agitated. A method for treating a carbonaceous material, in which a carbonaceous material containing carbon nanotubes is treated with plasma, and then the carbonaceous material containing carbon nanotubes is ultrasonically treated in a liquid. The method for treating a carbonaceous material according to claim 1 or 2 , wherein the carbon nanotube has 1 to 5 layers. A method of treating carbon nanotubes, comprising treating 1 to 5 layers of powdered carbon nanotubes with plasma using oxygen gas or nitrogen gas as a plasma generating gas . The carbon nanotubes plasma treatment according to any one of claims 1 to 4, wherein the dispersing liquid, a method of obtaining a carbon nanotube dispersion liquid. A method of obtaining a carbon nanotube dispersion, comprising: treating a carbonaceous material containing carbon nanotubes with plasma and then dispersing the carbonaceous material in the liquid. The method for obtaining a carbon nanotube dispersion liquid according to claim 6, wherein the carbonaceous material containing carbon nanotubes is subjected to ultrasonic treatment in the liquid. A method for obtaining a carbon nanotube solution, comprising solid-liquid separation of the carbon nanotube dispersion obtained by the method according to claim 5 . A method for obtaining a purified carbon nanotube solution, wherein the carbon nanotube dispersion obtained by the method according to claim 5 is classified. Concentrating the carbon nanotube dispersion obtained by the method according to any one of claims 5 to 7 , the carbon nanotube solution obtained by the method according to claim 8, or the purified carbon nanotube solution obtained by the method according to claim 9. A method for producing a high-concentration carbon nanotube dispersion, a high-concentration carbon nanotube solution, or a high-concentration purified carbon nanotube solution. A carbon nanotube dispersion obtained by the method according to claim 5, the carbon nanotube solution obtained by the method according to claim 8, or the purified carbon nanotube solution obtained by the method according to claim 9 is dried. A method for producing powdered carbon nanotubes. (1) Carbon nanotube synthesis step, (2) Carbon nanotube plasma treatment step, (3) Carbon nanotube dispersion step, (4) Carbon nanotube classification or solid-liquid separation step A method for producing a carbon nanotube, characterized by comprising: The manufacturing method of the catalyst composition characterized by including the following two processes.
(1) allowing the carbon nanotubes to plasma treatment (2) allowing the carbon nanotubes after the plasma treatment into contact with the liquid containing metals It has the following two processes, The manufacturing method of the carbon nanotube containing an organic compound characterized by the above-mentioned.
(1) Step of plasma treating carbon nanotubes (2) Step of contacting carbon nanotubes after plasma treatment with a liquid containing an organic compound The manufacturing method of the composition for coating characterized by having the following two processes.
(1) Step of plasma treating carbon nanotubes (2) Step of mixing carbon nanotubes after plasma treatment with a main agent for coating

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