JP6051427B2 - Method for preparing highly dispersible nanomaterials - Google Patents
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Description
本発明は、高分散性ナノマテリアルの調製方法に関する。詳しくは、液相分散性のみならず気相分散性にも優れたナノマテリアルを簡便かつ高収率に得る方法に関するものである。 The present invention relates to a method for preparing a highly dispersible nanomaterial. Specifically, the present invention relates to a method for obtaining a nanomaterial excellent not only in liquid phase dispersibility but also in gas phase dispersibility in a simple and high yield.
ナノマテリアルはナノメートル（ｎｍ、１ｎｍ＝１０-9ｍ）領域の材料であり、例えば、カーボンナノチューブ（ＣＮＴ）、フラーレン等がある。ナノマテリアルは、導電性や機械的特性、化学的安定性等に優れており、既に触媒や液晶等の基盤材料として利用されているとともに、近年では医療や化粧品等の分野への応用も期待されている。 The nanomaterial is a material in a nanometer (nm, 1 nm = 10 −9 m) region, and examples thereof include carbon nanotubes (CNT) and fullerene. Nanomaterials are excellent in electrical conductivity, mechanical properties, chemical stability, etc., and have already been used as base materials for catalysts and liquid crystals. In recent years, nanomaterials are also expected to be applied to fields such as medicine and cosmetics. ing.
しかし、ナノマテリアルを構成する原子は全てが表面原子であるか表面原子である割合が高いことから、隣接するナノマテリアルとの間で強いファンデアワールス力やπ−π相互作用が働くので、極めて凝集し易く、水にも有機溶媒にも分散し難いという共通の欠点を有している。 However, since all the atoms constituting the nanomaterial are surface atoms or the ratio of being surface atoms is high, strong van der Waals force and π-π interaction work between adjacent nanomaterials. It has the common drawback of being easy to aggregate and difficult to disperse in water and organic solvents.
そこで、従来、例えばＣＮＴを液相分散させる方法として、ＣＮＴ表面をプリスタン、ポリアミノベンゼン、ポリエチレングリコール等で化学修飾して親媒性を与え、ジクロロベンゼンやクロロホルム等に分散させる方法（例えば、非特許文献１参照）、ＳＤＳやＳＤＢＳ等の界面活性剤をＣＮＴの表面に吸着させて親水性を高め水に分散させる方法（例えば、非特許文献２及び３参照）、ピレン誘導体、ピレンポリマー、ポリイミド、ＤＮＡ等を分散剤として用いて水に分散させる方法（非特許文献４〜８参照）等が提案されてきた。 Therefore, conventionally, for example, as a method of dispersing CNT in the liquid phase, a method of chemically modifying the CNT surface with pristane, polyaminobenzene, polyethylene glycol, etc. to impart lyophilicity and dispersing it in dichlorobenzene, chloroform, etc. (for example, non-patented) Reference 1), a method in which a surfactant such as SDS or SDBS is adsorbed on the surface of CNTs to increase hydrophilicity and disperse in water (for example, see Non-Patent Documents 2 and 3), pyrene derivatives, pyrene polymers, polyimides, A method of dispersing DNA or the like in water using a dispersant or the like (see Non-Patent Documents 4 to 8) has been proposed.
しかしながら、これらの液相分散方法は、ＣＮＴ表面に親媒性分子や分散剤を導入するものであるので、ＣＮＴ本来の物性に何らかの影響を与えてしまうことが懸念されるとともに、製造コストの面でも不利であり、分散剤等を用いずに安価にＣＮＴを液相に高分散させる方法が求められていた。 However, since these liquid phase dispersion methods are those in which a lyophilic molecule or a dispersant is introduced to the CNT surface, there is a concern that it may have some influence on the original physical properties of the CNT, and in terms of manufacturing cost. However, it is disadvantageous, and there has been a demand for a method for highly dispersing CNT in a liquid phase at low cost without using a dispersant or the like.
一方、ナノマテリアルは、工業的利用における便益性が期待されている一方で、生体への影響が懸念されている。特にＣＮＴは安定性が高く、その形状がアスベストと類似しており、実験動物の腹腔内投与により中皮腫発がん性が示されている。ナノマテリアルの有害性は暴露経路により大きく変わることが示されており、人においては、全身暴露による吸入毒性が最も重要である。 On the other hand, nanomaterials are expected to have benefits in industrial use, but there are concerns about the impact on living bodies. In particular, CNT has high stability, and its shape is similar to asbestos, and mesothelioma carcinogenicity has been shown by intraperitoneal administration of experimental animals. The hazards of nanomaterials have been shown to vary greatly depending on the route of exposure, and in humans, inhalation toxicity from systemic exposure is most important.
しかしながら、上記のとおりナノマテリアルは凝集体を作り易く、液相だけでなく気相においても同様に分散性を確保することが困難であり、気相に分散させて実験動物に吸入させようとしても分散性が低いため、人において問題となる気相で分散したナノマテリアルの独立体（凝集体を形成せずにナノマテリアル単独で存在する粒子）の吸入毒性を模倣することができない。つまり、ナノマテリアルの独立体と凝集体とでは吸入毒性試験における挙動が異なるため、気相分散性の低い検体では凝集体の試験結果への影響を排除できず、ナノマテリアルの独立体の吸入毒性を正しく評価できないという問題があった。 However, as described above, nanomaterials easily form aggregates, and it is difficult to ensure dispersibility not only in the liquid phase but also in the gas phase. Due to the low dispersibility, the inhalation toxicity of independent nanomaterials dispersed in the gas phase, which is a problem in humans (particles that exist in the nanomaterial alone without forming aggregates), cannot be mimicked. In other words, because the behavior of inhalation toxicity tests differs between independent nanomaterials and aggregates, it is not possible to eliminate the influence of aggregates on the test results for samples with low gas phase dispersibility. There was a problem that could not be evaluated correctly.
また、上記従来の液相分散技術によっても、ＣＮＴ表面の親媒性分子や分散剤と溶媒との相互作用によって分散性を確保するものであるため、溶媒が存在しない状態では分散性が確保できず、気相分散性に優れたナノマテリアルを得ることができなかった。 In addition, the above conventional liquid phase dispersion technology ensures dispersibility by the interaction between the solvent and the amphiphilic molecule or dispersant on the CNT surface, so that dispersibility can be ensured in the absence of a solvent. Therefore, a nanomaterial excellent in gas phase dispersibility could not be obtained.
本発明は上記従来技術の有する問題点に鑑みなされたものであり、その目的とするところは、液相分散性のみならず気相分散性にも優れたナノマテリアルを得る方法を提供することにある。 The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide a method for obtaining a nanomaterial that is excellent not only in liquid phase dispersibility but also in gas phase dispersibility. is there.
本発明の他の目的は、ナノマテリアル本来の物性を変化させることなく、簡便かつ高収率で安価に、分散性に優れたナノマテリアルを得る方法を提供することにある。 Another object of the present invention is to provide a method for obtaining a nanomaterial excellent in dispersibility simply, at a high yield and at low cost without changing the original physical properties of the nanomaterial.
本発明の上記目的は、下記の手段によって達成される。 The above object of the present invention is achieved by the following means.
（１）即ち、本発明は、原末を常温常圧で固体であり、かつ真空状態において昇華する溶媒に混合し懸濁する懸濁工程と、前記懸濁工程で得られた懸濁液を濾過する濾過工程と、前記濾過工程で得られた濾液を直ちにかつ急速に凍結固化する凍結工程と、前記凍結工程で得られた凍結固化物から真空乾燥により前記溶媒を昇華除去する真空乾燥工程と、を有し、前記懸濁工程は、前記原末を前記溶媒に添加して撹拌しながら前記溶媒の融点以下の温度まで冷却しシャーベット状態で更に混合させることを特徴とする、高分散性ナノマテリアルの調製方法である。
(1) That is, the present invention comprises a suspension step of mixing and suspending the bulk powder in a solvent that is solid at ordinary temperature and pressure and sublimates in a vacuum state, and the suspension obtained in the suspension step. A filtration step for filtration, a freezing step for immediately and rapidly freezing and solidifying the filtrate obtained in the filtration step, and a vacuum drying step for subliming and removing the solvent from the freeze-solidified product obtained in the freezing step by vacuum drying. And the suspension step comprises adding the bulk powder to the solvent and stirring the mixture to cool to a temperature below the melting point of the solvent and further mixing in a sherbet state. This is a method for preparing a material.
（２）本発明はまた、前記溶媒は、ターシャリーブチルアルコール、１，４−ジオキサン、ｐ−キシレン、ジフェニルメタン、シクロヘキサノール、フェノキシエタノール、ジフェニルエーテル、アセトフェノン、プロピオフェノン、安息香酸ベンジル、ｐ−クロロトルエン又は１，２，４−トリクロロベンゼンである、（１）に記載の高分散性ナノマテリアルの調製方法である。
( 2 ) In the present invention, the solvent is tertiary butyl alcohol, 1,4-dioxane, p-xylene, diphenylmethane, cyclohexanol, phenoxyethanol , diphenyl ether, acetophenone, propiophenone, benzyl benzoate, p-chlorotoluene. Or it is a preparation method of the highly dispersible nanomaterial as described in ( 1 ) which is 1,2,4-trichlorobenzene.
（３）本発明はまた、前記懸濁工程と前記濾過工程の間に、前記懸濁工程で得られた懸濁液を凍結した後再融解する凍結再融解工程を更に有する、（１）又は（２）に記載の高分散性ナノマテリアルの調製方法である。
( 3 ) The present invention further includes a freeze-thaw step for freezing and re-thawing the suspension obtained in the suspension step between the suspension step and the filtration step, (1) or ( 2 ) A method for preparing a highly dispersible nanomaterial according to ( 2 ).
（４）本発明はまた、前記濾過工程は、フィルターを振動させながら前記懸濁液を濾過することを特徴とする、（１）〜（３）のいずれか１つに記載の高分散性ナノマテリアルの調製方法である。
( 4 ) The high-dispersibility nanometer according to any one of (1) to ( 3 ), wherein in the filtration step, the suspension is filtered while vibrating the filter. This is a method for preparing a material.
（５）本発明はまた、前記ナノマテリアルは、カーボンナノチューブ、フラーレン、カーボンブラック、シリカ、酸化チタン、酸化亜鉛、銀、鉄、アルミナ、酸化セリウム、白金ナノコロイド、量子ドット又はニッケルである、（１）〜（４）のいずれか１つに記載の高分散性ナノマテリアルの調製方法である。
( 5 ) In the present invention, the nanomaterial is carbon nanotube, fullerene, carbon black, silica, titanium oxide, zinc oxide, silver, iron, alumina, cerium oxide, platinum nanocolloid, quantum dot or nickel. It is a preparation method of the highly dispersible nanomaterial as described in any one of 1)-( 4 ).
本発明の高分散性ナノマテリアルの調製方法によれば、原末を溶媒に混合して懸濁し、得られた懸濁液を濾過することにより、懸濁液中のナノマテリアルの凝集体を除去して独立体のみを取り出すことができ、また、得られた濾液を直ちにかつ急速に凍結固化することにより、ナノマテリアルの再凝集化を防止して、高分散状態を維持したまま凍結固化物とすることができる。更に、得られた凍結固化物から真空乾燥により溶媒を昇華除去することにより、溶媒を固相から液相を介さずに気化して除去するので、表面張力の影響を受けることがなく、ナノマテリアルを高分散状態のまま独立体として取得することができる。 According to the method for preparing a highly dispersible nanomaterial of the present invention, the bulk powder is mixed with a solvent and suspended, and the resulting suspension is filtered to remove nanomaterial aggregates in the suspension. It is possible to remove only the independent body, and the obtained filtrate is immediately and rapidly frozen and solidified to prevent re-aggregation of the nanomaterial and to maintain the highly dispersed state. can do. Furthermore, by removing the solvent from the frozen solid by sublimation by vacuum drying, the solvent is removed by vaporization from the solid phase without going through the liquid phase. Can be obtained as an independent body in a highly dispersed state.
特に、常温常圧で固体の溶媒を用いることにより、凍結及び昇華除去が容易となるので、製造コストを抑えて目的の高分散性ナノマテリアルを得ることができる。
In particular, by using a solvent of the solid body at room temperature and atmospheric pressure, since it is easy to freeze and removed by sublimation, it is possible to obtain a high dispersibility nanomaterials object while suppressing the manufacturing cost.
また、懸濁工程において、溶媒の融点以下の温度においてシャーベット状態で混合させることにより、混練効果によって液相で混合するよりも懸濁液の分散性が向上するので、得られる高分散性ナノマテリアルの収率を向上させることができる。 Also, in the suspension step, mixing in the sherbet state at a temperature below the melting point of the solvent improves the dispersibility of the suspension rather than mixing in the liquid phase due to the kneading effect, so the resulting highly dispersible nanomaterial The yield of can be improved.
更に、濾過工程の前に、懸濁工程で得られた懸濁液を一旦凍結した後再融解することにより、液体より固体の体積の方が大きい溶媒では、液体の状態でナノマテリアルの凝集体の中に浸透した溶媒が凍結により膨張し、凝集体を分散させるので、高分散性ナノマテリアルの収率を向上させることができる。
Furthermore, before the filtration step, by once remelted After freezing suspension obtained in the suspension step, the solvent is larger volume of solid from liquid material, coagulation of nanomaterials in liquid Since the solvent that has penetrated into the aggregate expands due to freezing and disperses the aggregates, the yield of the highly dispersible nanomaterial can be improved.
また、濾過工程において、フィルターを振動させながら懸濁液を濾過することにより、高分散性ナノマテリアルの収率を更に向上させることができる。 In the filtration step, the yield of the highly dispersible nanomaterial can be further improved by filtering the suspension while vibrating the filter.
更に、凍結及び真空乾燥工程に替えて、濾過工程で得られた濾液から直ちにかつ急速に臨界点乾燥により前記溶媒を除去することによっても、同様の効果を達成することができる。 Further, the same effect can be achieved by removing the solvent immediately and rapidly from the filtrate obtained in the filtration step by critical point drying instead of the freezing and vacuum drying steps.
本発明の高分散性ナノマテリアルの調製方法によれば、ナノマテリアル本来の物性を変化させることなく、液相及び気相の何れにおいても極めて高い分散性を有する高分散性ナノマテリアルを得ることができる。即ち、本発明により得られる高分散性ナノマテリアルは、適当な溶媒に再懸濁させ、或いは適当な方法で気相に分散させると、いずれも速やかに高分散し、その後も高分散状態を長く保持することができるものである。 According to the method for preparing a highly dispersible nanomaterial of the present invention, it is possible to obtain a highly dispersible nanomaterial having extremely high dispersibility in both a liquid phase and a gas phase without changing the original physical properties of the nanomaterial. it can. That is, when the highly dispersible nanomaterial obtained by the present invention is resuspended in an appropriate solvent or dispersed in a gas phase by an appropriate method, both of them are rapidly dispersed, and the highly dispersed state is prolonged thereafter. It can be held.
以下に、本発明の実施の形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.
本発明の高分散性ナノマテリアルの調製方法は、原末を溶媒に混合し懸濁する懸濁工程と、前記懸濁工程で得られた懸濁液を濾過する濾過工程と、前記濾過工程で得られた濾液を直ちに凍結固化する凍結工程と、前記凍結工程で得られた凍結固化物から真空乾燥により前記溶媒を昇華除去する真空乾燥工程と、を有することを特徴とするものである。 The method for preparing a highly dispersible nanomaterial according to the present invention comprises a suspension step of mixing and suspending the bulk powder in a solvent, a filtration step of filtering the suspension obtained in the suspension step, and the filtration step. The method includes a freezing step in which the obtained filtrate is immediately frozen and solidified, and a vacuum drying step in which the solvent is sublimated and removed by vacuum drying from the frozen solidified product obtained in the freezing step.
本発明の調製方法を利用可能なナノマテリアルとしては、単層又は多層のカーボンナノチューブ（ＣＮＴ）、Ｃ60フラーレン、Ｃ70フラーレン等のフラーレン、カーボンブラック、シリカ、酸化チタン、酸化亜鉛、銀、鉄、アルミナ、酸化セリウム、白金ナノコロイド、量子ドット、ニッケル等が挙げられ、これらの中では、特にＣＮＴに好適に利用することができる。これらのナノマテリアルは、いずれも構成する原子が表面原子ばかりであること等から極めて凝集し易く、分散性に乏しいという欠点を有するが、本発明の方法によれば、液相及び気相のいずれにおいても分散性に優れたナノマテリアルとすることができる。 The nanomaterials available a preparation method of the present invention, a single-layer or multi-layer carbon nanotubes (CNT), C 60 fullerene, fullerene such as C 70 fullerene, carbon black, silica, titanium oxide, zinc oxide, silver, iron , Alumina, cerium oxide, platinum nanocolloid, quantum dots, nickel and the like. Among these, it can be suitably used particularly for CNT. All of these nanomaterials have the disadvantage that they are very easily aggregated and have poor dispersibility because the atoms constituting them are only surface atoms, but according to the method of the present invention, either the liquid phase or the gas phase can be used. Can be made into a nanomaterial having excellent dispersibility.
本発明で利用される溶媒としては、ナノマテリアル原末を懸濁させて濾過に供することができ、濾液から凍結乾燥により除去可能なものであれば特に限定されるものではないが、凍結のし易さ及び真空乾燥による昇華除去のし易さの観点から、常温・常圧で固体の高融点溶媒、すなわち融点が常温（５〜１５℃）以上の溶媒が好ましい。具体的には、ターシャリーブチルアルコール（ＴＢＡ）、１，４−ジオキサン、ｐ−キシレン、ジフェニルメタン、シクロヘキサノール、フェノキシエタノール、ジフェニルエーテル、アセトフェノン、プロピオフェノン、安息香酸ベンジル、ｐ−クロロトルエン、１，２，４−トリクロロベンゼン等が挙げられ、これらの中ではＴＢＡが特に好適に利用される。
The solvent used in the present invention is not particularly limited as long as the nanomaterial bulk powder can be suspended and used for filtration, and can be removed from the filtrate by lyophilization. from the standpoint of ease and vacuum drying by sublimation removal easiness, high melting point solvent of the solid body at normal temperature and normal pressure, i.e. melting point is room temperature (5 to 15 ° C.) or more solvents preferred. Specifically, tertiary butyl alcohol (TBA), 1,4-dioxane, p-xylene, diphenylmethane, cyclohexanol, phenoxyethanol , diphenyl ether, acetophenone, propiophenone, benzyl benzoate, p-chlorotoluene, 1,2 , 4-trichlorobenzene and the like, among which TBA is particularly preferably used.
本発明の高分散性ナノマテリアルの調製方法では、まず、懸濁工程において、上記ナノマテリアルの原末を上記溶媒に混合して懸濁する。原末と溶媒との混合は、溶媒の融点以上の温度において液相で行ってもよいが、好ましくは、溶媒の融点以上の温度下で原末を溶媒に添加して、撹拌しながら溶媒の融点以下の温度まで冷却し、半固相のシャーベット（スラリー）状態で更に混合するのがよい。原末と溶媒を半固相で混合することにより、混練効果によって液相で混合するよりも懸濁液の分散性が向上し、結果として得られる目的物の収率が上がるからである。 In the method for preparing a highly dispersible nanomaterial according to the present invention, first, in the suspension step, the raw material of the nanomaterial is mixed and suspended in the solvent. The bulk powder and the solvent may be mixed in a liquid phase at a temperature equal to or higher than the melting point of the solvent. Preferably, the bulk powder is added to the solvent at a temperature equal to or higher than the melting point of the solvent, and the solvent is stirred. It is preferable to cool to a temperature below the melting point and further mix in a semi-solid sherbet (slurry) state. This is because mixing the bulk powder and the solvent in a semi-solid phase improves the dispersibility of the suspension rather than mixing in the liquid phase due to the kneading effect, resulting in a higher yield of the desired product.
また、上記懸濁工程で得られた懸濁液は、そのまま濾過工程に供してもよいが、利用する溶媒によっては、懸濁液を一旦凍結した後再融解してから濾過工程に供することが好ましい。即ち、液体より固体の体積の方が大きい溶媒では、液体の状態でナノマテリアルの凝集体の中に浸透した溶媒が凍結により膨張し、凝集体を分散させるので、結果として得られる目的物の収率が向上するからである。
In addition, the suspension obtained in the suspension step may be subjected to the filtration step as it is, but depending on the solvent used, the suspension may be frozen once and then re-thawed before being subjected to the filtration step. preferable. That is, in the solvent is greater of the volume of the solid from the liquid body, the solvent has penetrated into aggregates of nanomaterials in liquid expands by freezing, because the dispersing aggregates, the desired product obtained as a result of This is because the yield is improved.
次に、濾過工程において、上記懸濁工程で得られた懸濁液を濾過する。これにより、懸濁液中のナノマテリアルの凝集体を除去して独立体のみを取り出すことができる。懸濁液の濾過方法は特に限定されるものではなく、自然濾過、減圧濾過、加圧濾過、遠心濾過等を用いることができるが、好ましくは自然濾過であり、更に目詰まりを抑制し濾過効率を向上させる観点から、振動モーター等を取り付けたフィルター等を利用してフィルターを振動させながら懸濁液を濾過することが好ましい。利用するフィルターの種類は特に限定されるものではなく、例えば、金属フィルター、セルロース（濾紙）、ガラス繊維フィルター、メンブレンフィルター等を利用することができるが、強い相互作用により結合している凝集体からナノマテリアルの独立体を強力に乖離させる観点から、好ましくは金属フィルターがよく、ナノマテリアルの凝集体が補足され独立体は通過する程度の目開き（例えばＣＮＴの場合１〜５０μｍ）のものが利用される。 Next, in the filtration step, the suspension obtained in the suspension step is filtered. Thereby, the aggregate of the nanomaterial in suspension can be removed and only an independent body can be taken out. The filtration method of the suspension is not particularly limited, and natural filtration, vacuum filtration, pressure filtration, centrifugal filtration, and the like can be used, but natural filtration is preferable, and filtration efficiency is further suppressed by clogging. From the viewpoint of improving the efficiency, it is preferable to filter the suspension while vibrating the filter using a filter or the like equipped with a vibration motor or the like. The type of filter to be used is not particularly limited. For example, a metal filter, cellulose (filter paper), a glass fiber filter, a membrane filter, or the like can be used. From the viewpoint of strongly separating the independent nanomaterials, a metal filter is preferable, and an opening having a degree of opening (for example, 1 to 50 μm in the case of CNT) is used so that the aggregates of the nanomaterial are captured and the independent material passes. Is done.
次いで、凍結工程において、上記濾過工程で得られた濾液を直ちにかつ急速に凍結固化する。濾液を直ちに濾過することにより、ナノマテリアルの再凝集化を防止して、高分散状態を維持したまま凍結・乾燥することができるので、結果として得られる目的物の収率を向上させることができる。また、濾液を急速に凍結することにより、溶媒が非晶質の状態で固化するため、真空乾燥により溶媒が昇華し易く乾燥時間を短縮させることができる。濾液の凍結方法は特に限定されるものではなく、例えば、濾液に液体窒素等の冷媒を直接投下する方法、濾液を噴霧して急速冷却する方法等が挙げられる。 Next, in the freezing step, the filtrate obtained in the filtration step is immediately and rapidly frozen and solidified. By filtering the filtrate immediately, it is possible to prevent re-aggregation of the nanomaterial and to freeze and dry while maintaining a highly dispersed state, so that the yield of the target product obtained can be improved. . Moreover, since the solvent is solidified in an amorphous state by rapidly freezing the filtrate, the solvent is easily sublimated by vacuum drying, and the drying time can be shortened. The method for freezing the filtrate is not particularly limited, and examples thereof include a method in which a refrigerant such as liquid nitrogen is directly dropped into the filtrate, a method in which the filtrate is sprayed and rapidly cooled.
そして、最後に、真空乾燥工程において、上記凍結工程で得られた凍結固化物から真空乾燥により溶媒を昇華除去する。これにより、溶媒を固相から液相を介さずに気化して除去するので、表面張力の影響を受けることがなく、ナノマテリアルを高分散状態のまま独立体として取得することができる。真空乾燥の方法は特に限定されるものではなく、例えば溶媒回収型真空ポンプ等を利用して行うことができる。 Finally, in the vacuum drying step, the solvent is sublimated and removed from the freeze-solidified product obtained in the freezing step by vacuum drying. As a result, the solvent is vaporized and removed from the solid phase without going through the liquid phase, so that the nanomaterial can be obtained as an independent body in a highly dispersed state without being affected by the surface tension. The method of vacuum drying is not particularly limited, and can be performed using, for example, a solvent recovery type vacuum pump.
なお、本発明の高分散性ナノマテリアルの調製方法では、上記凍結工程及び上記真空乾燥工程の替わりに臨界点乾燥工程を設け、上記濾過工程で得られた濾液から直ちにかつ急速に臨界点乾燥により溶媒を除去するようにしてもよい。即ち、溶媒の臨界点以上に温度を上げて超臨界状態で濾液から溶媒を除去するので、上記凍結・乾燥の場合と同様に、表面張力を掛けることがなく、ナノマテリアルの高分散状態を維持したまま目的物を得ることができる。臨界点乾燥を利用する場合の溶媒としては、臨界温度が室温付近で臨界圧力が数十気圧程度のものであれば特に限定されるものではなく、二酸化炭素、エタン、プロパン、エチレン、プロピレン等が挙げられるが、これらの中では、特に二酸化炭素が好適に利用される。 In the method for preparing the highly dispersible nanomaterial of the present invention, a critical point drying step is provided instead of the freezing step and the vacuum drying step, and the critical point drying is performed immediately and rapidly from the filtrate obtained in the filtration step. The solvent may be removed. In other words, since the solvent is removed from the filtrate in a supercritical state by raising the temperature above the critical point of the solvent, the surface tension is not applied and the highly dispersed state of the nanomaterial is maintained as in the case of freezing and drying. The desired product can be obtained as it is. The solvent for using critical point drying is not particularly limited as long as the critical temperature is around room temperature and the critical pressure is about several tens of atmospheres, such as carbon dioxide, ethane, propane, ethylene, propylene, and the like. Among these, carbon dioxide is particularly preferably used.
本発明の方法で得られた高分散性ナノマテリアルは、ナノマテリアル本来の諸物性を維持しつつ、液相及び気相の何れにおいても極めて高い分散性を発揮するものであり、適当な溶媒に再懸濁させ、或いは適当な方法で気相に分散させると、いずれも速やかに高分散し、その後も高分散状態を長く保持することができる。 The highly dispersible nanomaterial obtained by the method of the present invention exhibits extremely high dispersibility in both the liquid phase and the gas phase while maintaining the original properties of the nanomaterial. When they are resuspended or dispersed in the gas phase by an appropriate method, all of them are rapidly highly dispersed, and the highly dispersed state can be maintained for a long time thereafter.
次に、本発明の高分散性ナノマテリアルの調製方法を、実施例によりさらに詳細に説明するが、本発明はこれに限定されるものではない。 Next, the preparation method of the highly dispersible nanomaterial of the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
高分散性多層カーボンナノチューブ（ＭＷＣＮＴ）の調製Preparation of highly dispersible multi-walled carbon nanotubes (MWCNT)
本発明の方法により、ＭＷＣＮＴ原末からＴＢＡを用いて高分散性ＭＷＣＮＴを調製した。
The method of the present invention were manufactured by adjusting the highly dispersed MWCNT with TBA in the late MWCNT original.
マントルヒーター（柴田科学社製）でＴＢＡ（（ＣＨ3）3ＣＯＨ、関東化学株式会社製、特級、分子量７４．１２、融点２５．５５℃、密度０．７８７）５００ｍＬ（３９０ｇ）を６０℃に加温して溶解した。５００ｍＬボトルにＭＷＣＮＴ原末（保土ヶ谷化学社製「ＭＷＮＴ−７」、繊維径４０〜９０ｎｍ、平均一次粒径：直径６０ｎｍ、長さ１０μｍ、製品粒径３０〜１００ｎｍ（ＳＥＭ）、密度０．００５〜０．０１ｇ／ｍ3（沈降嵩密度法）、比表面積２５〜３０ｍ2／ｇ（窒素吸着法）、炭素純度９９．５％以上）を０．２ｇ投入し、上記により得られた約２００ｍＬのＴＢＡを加えてＭＷＣＮＴを分散させた後、ＴＢＡを撹拌しながら氷冷してシャーベット状にした。更に、スパーテルでＴＢＡを練るように混和し、ＴＢＡとＭＷＣＮＴを肉眼的に均一になるまで混和した（図１参照）。次いで、ボトルを−２５℃で凍結して一晩放置した後（図２参照）、約６０℃に加温し、ＴＢＡを添加して全量を５００ｍＬとした。
TBA ((CH 3 ) 3 COH, manufactured by Kanto Chemical Co., Ltd., special grade, molecular weight 74.12, melting point 25.55 ° C., density 0.787) 500 mL (390 g) to 60 ° C. with a mantle heater (manufactured by Shibata Kagaku) Warmed to dissolve. In a 500 mL bottle, MWCNT bulk powder (“MWNT-7” manufactured by Hodogaya Chemical Co., Ltd., fiber diameter 40 to 90 nm, average primary particle diameter: diameter 60 nm, length 10 μm , product particle diameter 30 to 100 nm (SEM), density 0. 0.25 to 0.01 g / m 3 (sedimentation bulk density method), specific surface area 25 to 30 m 2 / g (nitrogen adsorption method, carbon purity 99.5% or more) were charged, and about After 200 mL of TBA was added to disperse the MWCNT, the TBA was cooled with ice to form a sherbet. Further, TBA was mixed so as to knead with a spatula, and TBA and MWCNT were mixed until they became macroscopically uniform (see FIG. 1). The bottle was then frozen at −25 ° C. and allowed to stand overnight (see FIG. 2), then warmed to about 60 ° C. and TBA was added to a total volume of 500 mL.
図３（ａ）は、得られた懸濁液のボトルを転倒混和により混合し、３０分間放置したものであり、図３（ｂ）は、凍結再融解処理を施さなかった以外は上記と同様に処理したものである。これより、懸濁液の凍結再融解により、ＭＷＣＮＴの分散性が向上することが確認された。 FIG. 3 (a) shows the suspension bottle obtained by mixing by inversion and left for 30 minutes. FIG. 3 (b) is the same as above except that the freeze-thaw treatment was not performed. Is processed. From this, it was confirmed that the dispersibility of MWCNT is improved by freeze-thawing of the suspension.
次に、ボトルを激しく振盪させてＭＷＣＮＴを分散させ（図４参照）、ボトルを約６０℃に加温した。振動モーター（ＤＣモーター、Ｔ．Ｐ．Ｃ．社製「ＦＭ３４Ｆ」、標準電圧３．０Ｖ（使用範囲；２．５〜３．５Ｖ）、標準電流１００ｍＡ以下、標準回転数１３，０００ｒｐｍ、振動量１７．６ｍ／ｓ2（１．８Ｇ））を４個装着したフィルター（金属製シーブ、セイシン企業社製、メッシュサイズ２５μｍ）を用いて（図５参照）、ＭＷＣＮＴ懸濁液をフィルターを振動させながら濾過した（所要時間５〜１０分、図６参照）。
The bottle was then shaken vigorously to disperse the MWCNT (see FIG. 4) and the bottle was warmed to about 60 ° C. Vibration motor (DC motor, “FM34F” manufactured by TPC Corporation, standard voltage 3.0 V (use range: 2.5 to 3.5 V), standard current 100 mA or less, standard rotation speed 13,000 rpm, vibration amount Using a filter (metal sheave, Seishin Enterprise Co., Ltd., mesh size 25 μm ) equipped with four 17.6 m / s 2 (1.8 G)) (see FIG. 5 ), the MWCNT suspension was filtered. Filtered while vibrating (required time 5-10 minutes, see FIG. 6).
そして、ろ液を回収したボトルに液体窒素を投入して凍結し、溶媒回収型真空ポンプ（バキューブランド社製「ＭＤ４Ｃ ＮＴ＋ＡＫ＋ＥＫ」、排出速度５７Ｌ／ｍｉｎ，真空到達度１．５ｈＰａ（１．１Ｔｏｒｒ））で吸引してＴＢＡを昇華除去し（図７参照）、目的の高分散性ＭＷＣＮＴ（処理体１）を得た（図８参照）。 Then, liquid nitrogen is poured into the bottle from which the filtrate has been collected to freeze it, and a solvent recovery type vacuum pump (“MD4C NT + AK + EK” manufactured by Vacuum Brand, discharge rate 57 L / min, vacuum reach 1.5 hPa (1.1 Torr) ) To sublimate and remove TBA (see FIG. 7) to obtain the desired highly dispersible MWCNT (processed body 1) (see FIG. 8).
外観性の評価（１）Appearance evaluation (1)
図９（ａ）はＭＷＣＮＴ原末、図９（ｂ）は本実施例で得られた処理体１（何れも１ｍｇ）である。図９から明らかなとおり、本発明の処理体１は原末よりも嵩高い外観を有していた。 FIG. 9 (a) shows the MWCNT bulk powder, and FIG. 9 (b) shows the treated body 1 (1 mg each) obtained in this example. As is apparent from FIG. 9, the treated body 1 of the present invention had a bulky appearance as compared with the bulk powder.
外観性の評価（２）Appearance evaluation (2)
図１０（ａ）はＭＷＣＮＴ原末、図１０（ｂ）は本実施例で得られた処理体１の走査型電子顕微鏡写真（ＫＥＹＥＮＳＥ社製「ＶＥ−９８００」、ＴＢＡに再懸濁しメンブレンフィルターに展開して観察）である。図１０から明らかなとおり、原末ではＭＷＣＮＴがまゆ状に凝集した凝集体が多数観察されたのに対し、本発明の処理体１では係る凝集体は全く見られず、殆どが単繊維として観察された。
FIG. 10 (a) is the MWCNT bulk powder, FIG. 10 (b) is a scanning electron micrograph of the treated body 1 obtained in this example (“VE-9800” manufactured by KEYENSE), resuspended in TBA and used as a membrane filter. Expand and observe). As apparent from FIG. 10, whereas the bulk powder were observed many aggregates aggregated MWCNT Gamayu shape, aggregates of the process 1 of the invention was not observed at all, as mostly single textiles Observed.
液相分散性の評価Evaluation of liquid phase dispersibility
ＭＷＣＮＴ原末と本実施例で得られた処理体１のそれぞれ１ｍｇをＴＢＡ５ｍＬに再懸濁させたところ、原末は分散性が悪く（図１１（ａ）参照）、その後も直ぐに再凝集してしまうのに対し、本発明の処理体１は速やかに高分散し（図１１（ｂ））、その後も長く高分散状態が保持されることがわかった。 When 1 mg each of the MWCNT bulk powder and the treated body 1 obtained in this example was resuspended in 5 mL of TBA, the bulk powder was poorly dispersible (see FIG. 11 (a)), and then immediately re-aggregated. On the other hand, it was found that the treated body 1 of the present invention rapidly highly dispersed (FIG. 11 (b)) and maintained a highly dispersed state for a long time thereafter.
気相分散性の評価Evaluation of gas phase dispersibility
ＭＷＣＮＴ原末と本実施例で得られた処理体１のそれぞれ３０ｍｇを吸入曝露実験で使用するダスト発生装置（柴田科学社製「ＤＦ−７」）で気相に分散させて、パーティクルカウンター（柴田科学社製「ＯＰＣ−１１０ＧＴ」、最小検出径０．３μｍ）で相対濃度（ＣＰＭ）を測定した（図１２及び図１３参照）。図１２及び図１３の結果から明らかなとおり、本発明の処理体１は、ＭＷＣＮＴ原末と比較して相対濃度が有意に低く、そのため、相対濃度から質量濃度に換算するＫ値（質量濃度／相対濃度）は大きな値を示した。従って、本発明の処理体１は、気相において最小検出径以下の微細な粒子の状態で分散していることが分かった。 30 mg each of the MWCNT bulk powder and the treated body 1 obtained in this example were dispersed in the gas phase by a dust generator ("DF-7" manufactured by Shibata Kagakusha) used in an inhalation exposure experiment, and a particle counter (Shibata) Relative concentration (CPM) was measured with “OPC-110GT” (minimum detection diameter 0.3 μm) manufactured by Kagakusha (see FIGS. 12 and 13). As is apparent from the results of FIGS. 12 and 13, the treated body 1 of the present invention has a significantly lower relative concentration compared to the MWCNT bulk powder. Therefore, the K value (mass concentration / The relative concentration was large. Therefore, it turned out that the processing object 1 of this invention is disperse | distributing in the state of the fine particle below the minimum detection diameter in a gaseous phase.
物性変化の評価Evaluation of changes in physical properties
ＭＷＣＮＴ原末と本実施例で得られた処理体１の長さの分布を測定した（図１４参照）。具体的には、ＭＷＣＮＴ原末と本実施例で得られた処理検体を１％ドデシルベンゼンスルホン酸ナトリウム水溶液に５０μｇ／ｍＬの濃度で懸濁液を調製し、５μＬをメンブレンフィルター（０．０２５μｍＶＳＷＰ、φ１２ｍｍ、ミリポア）に展開後、オスミウムコーター（ＨＰＣ−１ＳＷ型、真空デバイス）により５秒間オスミウムコートを行いＳＥＭ（ＫＥＹＥＮＳＥ社製「ＶＥ−９８００」）で２０００倍、加速電圧２ｋＶの条件で観察した。ＭＷＣＮＴの計測には、ＩｍａｇｅＪ（http://rsbweb.nih.gov/ij/）を使用し、ＭＷＣＮＴの繊維長を、計測可能な繊維約３００本について計測した。 The length distribution of the MWCNT bulk powder and the treated body 1 obtained in this example was measured (see FIG. 14). Specifically, a suspension of the MWCNT bulk powder and the treated specimen obtained in this example in a 1% sodium dodecylbenzenesulfonate aqueous solution at a concentration of 50 μg / mL, 5 μL of a membrane filter (0.025 μm VSWP, After deployment to φ12 mm, Millipore), osmium coating was performed with an osmium coater (HPC-1SW type, vacuum device) for 5 seconds, and observation was performed with SEM (“VE-9800” manufactured by KEYENSE) at 2000 times and acceleration voltage of 2 kV. For measurement of MWCNT, ImageJ (http://rsbweb.nih.gov/ij/) was used, and the fiber length of MWCNT was measured for about 300 measurable fibers.
図１４の結果から明らかなとおり、本発明の処理体１（図１４（ｂ））は、ＭＷＣＮＴ原末（図１４（ａ））とほぼ同等の長さ分布を有しており、本発明の方法によってＭＷＣＮＴ本来の物性が変化していないことが確認された。 As is clear from the results of FIG. 14, the treated body 1 (FIG. 14 (b)) of the present invention has a length distribution substantially equivalent to that of the MWCNT bulk powder (FIG. 14 (a)). It was confirmed that the original physical properties of MWCNT were not changed by the method.
上述したように、本発明の高分散性ナノマテリアルの調製方法により得られる高分散性ナノマテリアルは、液相のみならず気相においても極めて高い分散性を有するので、全身暴露による吸入毒性試験用の検体として利用した場合極めて有用である。また、粉末材料に均等に分散混和することができるので、機械強度を向上させたり、人工ビロードに類似した繊維の配向を容易に実現すること等ができ、各種工業製品に利用した場合も極めて有用である。
As described above, the highly dispersible nanomaterial obtained by the method for preparing the highly dispersible nanomaterial of the present invention has extremely high dispersibility not only in the liquid phase but also in the gas phase. It is extremely useful when used as a specimen. Further, it is possible to balance miscible in the powder material, or improve the machinery strength, the orientation of textiles similar to artificial velvet can such be easily achieved, even when using a variety of industrial products Very useful.
Claims (5)
前記懸濁工程で得られた懸濁液を濾過する濾過工程と、
前記濾過工程で得られた濾液を直ちにかつ急速に凍結固化する凍結工程と、
前記凍結工程で得られた凍結固化物から真空乾燥により前記溶媒を昇華除去する真空乾燥工程と、を有し、
前記懸濁工程は、前記原末を前記溶媒に添加して撹拌しながら前記溶媒の融点以下の温度まで冷却しシャーベット状態で更に混合させる
ことを特徴とする、高分散性ナノマテリアルの調製方法。 A suspension step of mixing and suspending the bulk powder in a solvent that is solid at normal temperature and pressure and sublimates in a vacuum state;
A filtration step of filtering the suspension obtained in the suspension step;
A freezing step of immediately and rapidly freezing and solidifying the filtrate obtained in the filtration step;
A vacuum drying step for sublimation removal of the solvent by vacuum drying from the frozen solidified product obtained in the freezing step ,
The highly-dispersible nanomaterial characterized in that the suspension step comprises adding the bulk powder to the solvent, cooling to a temperature below the melting point of the solvent with stirring, and further mixing in a sherbet state Preparation method.
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