JP2006063307A - Carbon nanotube-containing solution, film, and fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solution, a film and a fiber where a carbon nanotube is singly dissolved. <P>SOLUTION: The solution contains annular glucan having 16-5,000 degree of polymerization and a carbon nanotube. The method for obtaining the carbon nanotube-containing solution comprises the steps of providing a mixture which contains the carbon nanotube, annular glucan having 16-5,000 degree of polymerization, and a solvent; and dissolving the carbon nanotube and the annular glucan into the solvent by projecting ultrasonic waves into the mixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less and a carbon nanotube, a method for producing the same, and a molded product such as a film, a fiber and a gel produced using the carbon nanotube solution.

  Carbon nanotubes are theoretically predicted to have excellent chemical, electronic and mechanical properties, and their properties have recently been confirmed by experiments. Utilizing these excellent properties, carbon nanotubes have been studied for use and partially put into practical use in, for example, electron-emitting devices, fuel cells, composite materials, semiconductors, scanning probe microscope probes, electromagnetic wave shielding materials, and the like. Carbon nanotubes include single-walled carbon nanotubes formed by only one graphite layer and multi-walled carbon nanotubes formed by overlapping a plurality of graphite layers in a coaxial cylindrical shape. Among them, single-walled carbon nanotubes are insoluble in many solvents, and their surfaces have strong hydrophobicity, so that they do not dissolve in water at all. This greatly restricts the chemical use of carbon nanotubes, especially single-walled carbon nanotubes, which must be dissolved or dispersed in a solvent, and as a result, limits the field of use of carbon nanotubes It has become one of the.

  Several methods for dispersing carbon nanotubes in a solvent have been disclosed so far. One of them is a method of chemically modifying the carbon nanotube surface (see Non-Patent Document 1). However, the carbon nanotubes obtained in this way are caused by chemical modification, which changes the chemical, electronic and mechanical properties of the carbon nanotubes before chemical modification, limiting the use of the excellent properties inherent in carbon nanotubes Resulting in.

  As a method of dispersing while maintaining the original properties of carbon nanotubes, there is a method of wrapping with a polymer non-covalently (that is, a polymer wrapping method). Dispersion in an organic solvent by this method is disclosed in Non-Patent Documents 2 and 3, etc., and dispersion in water by this method is disclosed in Patent Document 1 and Non-Patent Document 4.

For dispersion in water, a method is also disclosed in which an amphiphilic compound such as a surfactant is adsorbed on the side wall of the carbon nanotube and dispersed. Examples of such amphiphilic compounds include amphiphilic ammonium salt compounds (Non-Patent Document 5), surfactants (Non-Patent Document 6), synthetic peptides (Non-Patent Document 7), cationic lipids and DNA ( Patent Document 2), starch (amylose and amylopectin) (Non-Patent Documents 8, 9, and 10), DNA (Non-Patent Document 11), and cyclodextrin (Non-Patent Document 12) are disclosed.
JP-T-2004-506530 JP 2004-82663 A "Science", vol. 282, P95 (1998) "J. Phys. Chem. B", vol. 104, P10012 (2000) "J.Am.Chem. Soc.", Vol.124, P9034 (2002) “ChemicalPhysics Letters”, vol. 342, P265 (2001) "ChemistryLetters", P638 (2002) "AppliedPhysics A", vol. 69, P269 (1998) "J. Am. Chem. Soc.", Vol. 125, P1770 (2003) "Angew.Chem Int. Ed.", Vol. 41, P2508 (2002) "CarbohydratePolymers", vol. 51, P93 (2003) "CarbohydratePolymers", vol. 51, P311 (2003) “ChemistryLetters”, vol. 32, P456 (2003) "Chem.Commun.", P986 (2003)

  The method of using an organic solvent as a solvent has a large environmental load, and the organic solvent is often harmful to a living body. In consideration of the influence on the environment and compatibility with living bodies, the solvent is preferably water, and the compound used for dissolving the carbon nanotubes is also preferably a natural product or a biodegradable compound.

  Among the techniques disclosed above, those that serve this purpose include carbon (starch (amylose and amylopectin) (Non-patent Documents 8, 9, 10), DNA (Non-patent Document 11) and cyclodextrin (Non-patent Document 12). Nanotube dispersion technology. However, when these techniques are used (especially when used for dissolving high-purity single-walled carbon nanotubes), the amount of dissolved carbon nanotubes is small, the stability of the aqueous solution is poor, and the long-term (for example, 3 days) As described above, it has become clear that, when stored, there are problems such as precipitation of carbon nanotubes over time.

  The present invention is intended to solve these problems, and provides a solution (particularly an aqueous solution) in which carbon nanotubes are stably dissolved for a long period of time at a higher concentration than the prior art, and a method for dissolving carbon nanotubes. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have used a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less, so that a solution in which carbon nanotubes are stably dissolved at a higher concentration and longer than in the prior art. And the present invention was completed based on this.

  The present invention provides a solution in which carbon nanotubes are stably dissolved at a higher concentration and longer than the prior art by first using a solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less.

  Secondly, the present invention adds a powder containing carbon nanotubes to a solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less, projects ultrasonic waves, and removes undissolved solids by filtration and / or centrifugation. A method for producing a carbon nanotube solution is provided.

  Thirdly, the present invention provides a molded article such as a film, a fiber, or a gel produced using a carbon nanotube solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less.

  The solution of the present invention contains cyclic glucan having a polymerization degree of 16 or more and 5000 or less and carbon nanotubes.

  In one embodiment, the carbon nanotube may be a single-walled carbon nanotube.

  In one embodiment, the cyclic glucan may be a cyclic glucan composed only of a structure in which glucose is cyclically bonded with α-1,4 bonds.

  In one embodiment, the solution can be an aqueous solution.

  In one embodiment, the concentration of carbon nanotubes in the solution may be 50 mg / L or more.

The method of the present invention is a method of obtaining a solution of carbon nanotubes,
Providing a mixture comprising a carbon nanotube, a cyclic glucan having a polymerization degree of 16 or more and 5000 or less, and a solvent, and a solution in which the carbon nanotube and the cyclic glucan are dissolved in the solvent by projecting ultrasonic waves onto the mixture. Obtaining step,
Is included.

  In one embodiment, the mixture may be obtained by adding the carbon nanotubes to a solution containing the cyclic glucan and a solvent.

  In one embodiment, the mixture may be obtained by adding the solvent after mixing the cyclic glucan and the carbon nanotube.

  In one embodiment, the carbon nanotube may be a single-walled carbon nanotube.

  In one embodiment, the cyclic glucan may be a cyclic glucan composed only of a structure in which glucose is cyclically bonded with α-1,4 bonds.

  In one embodiment, the solution can be an aqueous solution.

  In one embodiment, the concentration of carbon nanotubes in the solution may be 50 mg / L or more.

  The molded product of the present invention contains a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less and a carbon nanotube.

  In one embodiment, the molding may further include a polymer.

  In one embodiment, the carbon nanotube may be a single-walled carbon nanotube.

  In one embodiment, the cyclic glucan may be a cyclic glucan composed only of a structure in which glucose is cyclically bonded with α-1,4 bonds.

  In one embodiment, the molded product may be molded from a solution using only water as a solvent.

  In one embodiment, the polymer can be amylose.

  In one embodiment, the polymer can be a polymer other than amylose.

  In one embodiment, the shape of the molding may be a film or fiber shape.

  In one embodiment, the molding may be a stretched film.

  In one embodiment, the molding may be in the form of a gel.

  In one embodiment, the molding may be for electromagnetic shielding.

  In one embodiment, the molding can be biodegradable.

  The solubilizer of the present invention is a solubilizer for dissolving carbon nanotubes in a solvent, and includes a cyclic glucan having a polymerization degree of 16 or more and 5000 or less.

  In one embodiment, the cyclic glucan may consist of a cyclic glucan consisting only of a structure in which glucose is cyclically bound by α-1,4 bonds.

  According to the present invention, it is possible to obtain a solution in which carbon nanotubes are dissolved as a single molecule at a higher concentration than in the prior art and for a long period (for example, 3 days or more). Above all, the availability of carbon nanotubes as an aqueous solution is expected to expand applications to fields where carbon nanotubes have not been used so far, such as cosmetics, pharmaceuticals, and foods, where environmental impact and compatibility with living organisms are problematic. it can. In addition, the chemical reaction of carbon nanotubes can be performed in a solution, so that synthesis of novel chemically modified carbon nanotubes and use expansion thereof can be expected.

  Furthermore, in a preferred embodiment, by using this solution, a gel in which carbon nanotubes are dispersed as a single molecule can be obtained, and further, a molded product such as a film or a fiber can be obtained. Molded products such as films and fibers have an electromagnetic shielding effect and conductivity. The film can also be imparted with polarization by stretching. A molded product such as a film, fiber and gel having biodegradability can also be obtained. By the method of the present invention, a coating material in which carbon nanotubes are homogeneously dissolved in a solution can be obtained. In the molded product obtained by the method of the present invention, since the carbon nanotubes are uniformly distributed, the strength is remarkably increased as compared with the conventional molded product having a biased distribution.

  Hereinafter, the present invention will be described in detail. According to the present invention, there are provided a solution and a molded article containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less and a carbon nanotube.

(1. Cyclic glucan)
The cyclic glucan used in the present invention refers to a molecule containing one structure in which 16 or more and 5000 or less glucose are cyclically bonded by α-1,4 bond or α-1,6 bond. “Glucan” refers to a polysaccharide composed of D-glucose. As used herein, the term glucan includes glucan derivatives. The cyclic glucan that can be used in the present invention may be a glucan having only a cyclic structure or a glucan having an acyclic structure in addition to the cyclic structure. An example of a cyclic glucan having an acyclic structure in addition to a cyclic structure includes a linear molecule in which glucose is bonded by an α-1,4 bond or an α-1,6 bond. -1 and 6 linked molecules are included. The cyclic glucan used in the present invention is preferably a molecule (cycloamylose) having only a structure in which 16 or more and 5000 or less glucose units are cyclically linked by α-1,4 bonds (ie, no branching). is there. Here, the glucose unit constituting the cyclic glucan may be chemically modified as long as the problem of the present invention can be solved.

  As the cyclic glucan used in the present invention, a cyclic glucan having any polymerization degree can be used as long as the polymerization degree is 16 or more and 5000 or less. The degree of polymerization of the cyclic glucan is preferably about 17 or more, more preferably about 22 or more. The degree of polymerization of the cyclic glucan is preferably about 3000 or less, more preferably about 2000 or less, even more preferably about 1000 or less, particularly preferably about 500 or less, and particularly preferably about 300 or less. More preferably about 100 or less, most preferably about 80 or less.

  In addition to the cyclic glucan having a polymerization degree of 16 to 5000, a cyclic glucan having a polymerization degree of 15 or less or a cyclic glucan having a polymerization degree of 5001 or more may be used as necessary. However, it is preferable to use only those having a degree of polymerization of 16 to 5000 (or the preferred range described above).

  As the cyclic glucan, those having one degree of polymerization may be used alone, or a mixture of those having various degrees of polymerization may be used. Usually, a cyclic glucan having a polymerization degree of 16 or more and 5000 or less is produced and sold as a mixture of various polymerization degrees. For example, a mixture of cyclic glucan having a polymerization degree of 22 to several hundreds is sold as cycloamylose by Ezaki Glico Co., Ltd. A method for producing a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less is described in Japanese Patent No. 3150266. Any cyclic glucan known in the art and having a polymerization degree of 16 or more and 5000 or less can be used.

  A mixture of polymers is often indicated by a weight average degree of polymerization (or weight average molecular weight). The weight average polymerization degree of the cyclic glucan used in the present invention is preferably about 17 or more, more preferably about 22 or more. The weight average polymerization degree of the cyclic glucan used in the present invention is preferably about 3000 or less, more preferably about 2000 or less, still more preferably about 1000 or less, and particularly preferably about 500 or less. It is particularly preferably about 300 or less, and most preferably about 100 or less.

(2. Carbon nanotube)
A carbon nanotube is an allotrope of carbon and refers to a structure in which a plurality of carbon atoms are combined and arranged in a cylindrical shape. Arbitrary carbon nanotubes can be used as the carbon nanotubes. Examples of carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes, and those in which they are coiled. Single-walled carbon nanotubes are those in which graphite-like carbon atoms are arranged in a single line, and multi-walled carbon nanotubes are those in which two or more layers of graphite-like carbon atoms are concentrically overlapped. The carbon nanotube used in the present invention may be a multi-walled carbon nanotube or a single-walled carbon nanotube, more preferably a single-walled carbon nanotube. A carbon nanohorn having a closed shape on one side of the carbon nanotube, a cup-shaped nanocarbon material having a hole on the head, a carbon nanotube having a hole on both sides, and the like can also be used.

  The carbon nanotubes can be of any diameter. The diameter of the carbon nanotubes is preferably about 0.4 nanometers or more, more preferably about 0.6 nanometers or more, more preferably about 1.0 nanometers or more, and most preferably about 1.2 nanometers. It is more than nanometer. The diameter of the carbon nanotube is preferably about 100 nanometers or less, more preferably about 60 nanometers or less, still more preferably about 30 nanometers or less, still more preferably about 20 nanometers or less, and even more preferably Is about 10 nanometers or less, more preferably 5 nanometers or less, and most preferably about 2 nanometers or less. In this specification, the diameter of a multi-walled nanotube refers to the diameter of the outermost carbon nanotube.

  The carbon nanotubes can be of any length. The length of the carbon nanotubes is preferably about 0.6 micrometers or more, more preferably about 1 micrometers or more, even more preferably about 2 micrometers or more, and most preferably about 3 micrometers or more. is there. The length of the carbon nanotube is preferably about 20 micrometers or less, more preferably about 15 micrometers or less, still more preferably about 10 micrometers or less, and most preferably about 5 micrometers or less.

  The carbon nanotubes used in the present invention may be commercially available or may be produced by any method known in the art. Carbon nanotubes include, for example, Shenzhen Nanotech Port Co., Ltd., CARBON NANOTECHNOLOGIES INC. , Sold by SES RESEARCH.

  Examples of carbon nanotube production methods include carbon dioxide catalytic hydrogen reduction, arc discharge (see, for example, C. Journal et al., Nature (London), 388 (1997), 756), laser evaporation ( For example, see AG Rinzler et al., Appl. Phys. A, 1998, 67, 29), CVD method, vapor phase growth method, carbon monoxide is reacted with an iron catalyst at high temperature and high pressure, and gas phase is obtained. (See, for example, P. Nikolaev et al., Chem. Phys. Lett., 1999, 313, 91).

  The carbon nanotubes may be purified by washing, centrifugation, filtration, oxidation, chromatography, or the like, or may be unpurified. It is preferable that it is purified. The purity of the carbon nanotube used may be arbitrary, but is preferably about 5% or more, more preferably about 10% or more, more preferably about 20% or more, further preferably about 30% or more, and further preferably about 40%. % Or more, more preferably about 50% or more, more preferably about 60% or more, more preferably about 70% or more, more preferably about 80% or more, more preferably about 90% or more, and most preferably about 95% or more. It is. The higher the purity of the carbon nanotube, the more easily the specific function is expressed. In the present specification, the purity of the carbon nanotube refers to the purity of the carbon nanotube as a whole, not the purity of one carbon nanotube having a specific molecular weight. That is, when the carbon nanotube powder is composed of 30% by weight of carbon nanotubes having a specific molecular weight of A and 70% by weight of carbon nanotubes having a specific molecular weight of B, the purity of the powder is 100%. Of course, the carbon nanotubes used may be selected for a specific diameter, a specific length, a specific structure (single-walled or multi-walled), and the like.

  The carbon nanotubes used in the present invention may be those pulverized using a ball-type kneading apparatus such as a ball mill, vibration mill, sand mill, roll mill, etc., or those cut short by chemical treatment or physical treatment. .

(3. Solvent)
As the solvent for the cyclic glucan solution, a solvent capable of dissolving the cyclic glucan is used. The solvent is preferably water and any organic solvent miscible with water, most preferably water. Examples of organic solvents include methanol, ethanol, isopropanol, acetone, acetonitrile, propionitrile, tetrahydrofuran, 1,4-dioxane, methyl isobutyl ketone, methyl ethyl ketone, γ-butyl lactone, propylene carbonate, sulfolane, nitromethane, N, N -Dimethylformamide, N-methylacetamide, dimethylsulfoxide, dimethylsulfone, N-methylpyrrolidone, benzene, toluene, xylene, methylene chloride, chloroform, dichloroethane.

  When water and an organic solvent are mixed, the proportion of water in the total solvent is preferably about 50% by volume or more, preferably about 60% by volume or more, and about 70% by volume or more. Preferably about 80% by volume or more, preferably about 90% by volume or more, and most preferably about 95% by volume or more. The organic solvent mixed with water may be one type or two or more types. In consideration of the influence on the environment and the human body, the solvent is preferably water or mainly composed of water.

(4. Solution containing cyclic glucan and carbon nanotube)
The solution of the present invention contains cyclic glucan having a polymerization degree of 16 or more and 5000 or less and carbon nanotubes.

  The concentration of the cyclic glucan in the solution can be arbitrarily set as long as the cyclic glucan can be dissolved. The concentration of cyclic glucan in the solution is preferably about 1% by weight or more, more preferably about 5% by weight or more, further preferably about 10% by weight or more, and most preferably about 15% by weight or more. is there. The concentration of cyclic glucan in the solution is preferably about 50% by weight or less, more preferably about 40% by weight or less, further preferably about 30% by weight or less, and most preferably about 25% by weight or less. is there. If the concentration of cyclic glucan is too high, the amount of dissolved carbon nanotubes may decrease. If the concentration of cyclic glucan is too low, the amount of dissolved carbon nanotubes may be too small.

  The concentration of the carbon nanotubes in the solution can be arbitrarily set as long as the carbon nanotubes can be dissolved. The concentration of carbon nanotubes in the solution is preferably about 30 mg / L (about 0.003% by weight) or more, more preferably about 50 mg / L (about 0.005% by weight) or more, and further preferably about 100 mg / L (about 0.01% by weight) or more, more preferably about 150 mg / L (about 0.015% by weight) or more, more preferably about 300 mg / L (about 0.03% by weight) or more. More preferably about 400 mg / L (about 0.04% by weight) or more, more preferably about 500 mg / L (about 0.05% by weight) or more, more preferably about 600 mg / L (about 0.6 wt%) or more, more preferably about 700 mg / L (about 0.07 wt%) or more, and most preferably about 800 mg / L (about 0.08 wt%) or more.As long as the carbon nanotubes can be dissolved, there is no upper limit to the concentration of the carbon nanotubes contained in the solution of the present invention, but usually about 10 g / L (about 1% by weight) or less, about 5 g / L (about 0.5% by weight). %) Or less, about 2 g / L (about 0.2% by weight) or less, or about 1 g / L (about 0.1% by weight) or less.

  In this specification, the solubility of a carbon nanotube is the solubility measured at 20 degreeC.

  The solution of the present invention may contain any substance other than cyclic glucan and carbon nanotubes as long as the solubility of the carbon nanotubes is not significantly reduced.

  If necessary, the solution of the present invention can be used as a raw material for a substrate such as a film, a pigment, a plasticizer, a dispersant, a coating surface conditioner, a fluidity conditioner, an ultraviolet absorber, an antioxidant, a storage stabilizer, and an adhesive. It may further contain various known substances such as auxiliaries and thickeners. The raw material of the substrate such as a film can be a polymer. Examples of such polymers include polyvinyl alcohol, pullulan, dextran, starch and starch derivatives, cellulose derivatives (eg, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, etc.), polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, poly Acrylic acid, polystyrene sulfonic acid, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, deoxyribonucleic acid, ribonucleic acid, guar gum, xanthan gum, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, gelatin, etc. Can be mentioned. Another example of a polymer is amylose. The addition amount of these substances can be arbitrarily set by those skilled in the art.

  The solution of the present invention may further contain a conductive substance in order to further improve the conductivity. Examples of conductive materials include carbon-based materials (eg, carbon fiber, conductive carbon black, graphite, etc.), metal oxides (eg, tin oxide, zinc oxide, etc.), metals (eg, silver, nickel, copper, etc.) ). The addition amount of these substances can be arbitrarily set by those skilled in the art.

  Carbon nanotubes are dissolved in the solution of the present invention. “Carbon nanotubes are dissolved” means that the carbon nanotubes are still distributed throughout the liquid after centrifuging the liquid containing carbon nanotubes at 2,200 g for 10 minutes at 20 ° C. This means that no decrease in coloration or precipitation is observed. In the solution, the carbon nanotube is dissolved as almost a single molecule.

  Carbon nanotubes are stably dissolved in the solution of the present invention. “Carbon nanotubes are stably dissolved” means that when the carbon nanotube solution is left at room temperature (preferably about 20 ° C.) for at least 3 days, the coloration of the liquid due to the carbon nanotubes, precipitation, etc. It means not allowed. The solution of the present invention is preferably used for about 1 week, more preferably about 2 weeks, more preferably about 3 weeks, and most preferably about 4 weeks. unacceptable.

  In the present specification, if the carbon nanotube is dissolved in the solution, it is referred to as a solution even if other substances (for example, pigments) are not dissolved. Other materials may be dissolved, precipitated, dispersed or colloidal. Examples of solutions in which other substances are not dissolved include paints, emulsions, dyes, pigments, cements and the like.

(5. Method of dissolving carbon nanotubes in solution)
The method of the present invention is a method of dissolving carbon nanotubes in a solution. The method includes providing a mixture containing carbon nanotubes, a cyclic glucan having a polymerization degree of 16 or more and 5000 or less, and a solvent, and projecting ultrasonic waves onto the mixture to cause the carbon nanotubes and the cyclic glucan to enter the solvent. A step of obtaining a dissolved solution. This method includes, for example, a step of adding a carbon nanotube to a solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less and a solvent, and a step of dissolving the carbon nanotube by projecting an ultrasonic wave onto the mixture Is included. Alternatively, the method includes a step of obtaining a mixture by adding a solvent after mixing the cyclic glucan and the carbon nanotube, and a step of dissolving the carbon nanotube by projecting an ultrasonic wave onto the mixture. The cyclic glucan and carbon nanotube used in the method of the present invention are as described in 1 and 2 above.

  First, an example of a method for producing a solution in which carbon nanotubes are uniformly dissolved will be described.

  A cyclic glucan solution having a polymerization degree of 16 or more and 5000 or less can be added to the solvent to prepare a cyclic glucan solution. The concentration of the cyclic glucan in the cyclic glucan solution can be arbitrarily set as long as the cyclic glucan can be dissolved. The amount of cyclic glucan added is such that the concentration of cyclic glucan in the resulting solution is preferably about 1% by weight or more, more preferably about 5% by weight or more, and further preferably about 10% by weight or more. Most preferably, the amount is about 15% by weight or more. The amount of cyclic glucan added is such that the concentration of cyclic glucan in the resulting solution is preferably about 50% by weight or less, more preferably about 40% by weight or less, and most preferably about 30% by weight or less. It is an amount like this. For example, the amount is preferably in the concentration range of about 1 to 30% by weight. Depending on the type of cyclic glucan, if the concentration of cyclic glucan is too high, the amount of dissolved carbon nanotubes may decrease. If the concentration of cyclic glucan is too low, the amount of dissolved carbon nanotubes may be too low.

  Next, carbon nanotubes are added to a solution containing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less to obtain a mixture. The carbon nanotube to be added is preferably in the form of powder. The amount of carbon nanotubes added may be any amount as long as it exceeds the amount of carbon nanotubes that can be dissolved by the method of the present invention, and can be set arbitrarily. The amount of carbon nanotubes added can be, for example, from about 0.1% to about 1% by weight of the solution.

  Alternatively, a mixture may be obtained by previously mixing a cyclic glucan having a polymerization degree of 16 or more and 5000 or less and carbon nanotubes, and then adding a solvent thereto. In this case, when a mixture of cyclic glucan and carbon nanotubes is put in a mortar or the like and rubbed with a pestle or the like, dissolution of the carbon nanotubes is promoted. Thorough mixing may be achieved by other mechanical means.

Next, the carbon nanotubes are dissolved by projecting ultrasonic waves onto the obtained mixture. As long as the method of projecting ultrasonic waves is a method capable of uniformly dissolving carbon nanotubes in a cyclic glucan solution, the method of projecting ultrasonic waves, conditions such as frequency and time are not particularly limited. The temperature and pressure at the time of projecting the ultrasonic wave may be any conditions as long as the solution containing the cyclic glucan and the carbon nanotube maintains a liquid state. For example, a solution containing cyclic glucan and carbon nanotubes is placed in a glass container, and ultrasonic waves are projected at room temperature using a bath sonicator. For example, the rated output of the ultrasonic oscillator is preferably about 0.1 to about 2.0 watt / cm ² per unit bottom area of the ultrasonic oscillator, more preferably about 0.2 to about 1.0 watt / cm 2. ² , the oscillation frequency is preferably about 10 to about 200 KHz, more preferably about 20 to about 100 KHz. Further, the duration of the ultrasonic irradiation treatment is preferably about 1 minute to about 3 hours, more preferably about 3 minutes to about 30 minutes. A stirring device such as a vortex mixer, a homogenizer, a spiral mixer, a planetary mixer, a disperser, or a hybrid mixer may be used before or after projecting ultrasonic waves. The temperature of the mixture can be any temperature as long as the solvent does not volatilize too much. The temperature of the mixture is, for example, about 5 ° C. or higher, preferably about 10 ° C. or higher, more preferably about 15 ° C. or higher, more preferably about 20 ° C. or higher, and most preferably about 25 ° C. or higher. It is. The temperature of the mixture is, for example, about 100 ° C. or less, preferably about 90 ° C. or less, more preferably about 80 ° C. or less, more preferably about 70 ° C. or less, and most preferably about 60 ° C. or less. It is.

  After the projection of ultrasonic waves, the solid matter containing undissolved carbon nanotubes in the solution is removed by filtration, centrifugation, etc., thereby obtaining a solution in which the carbon nanotubes are homogeneously dissolved. The method for removing undissolved solids from the solution after projecting ultrasonic waves is not particularly limited as long as the dissolved carbon nanotubes and undissolved solids can be separated, such as filtration with a filter and centrifugation. . In the case of filtration with a filter, a filter having a pore size through which dissolved carbon nanotubes pass and undissolved solids do not pass through is used. Preferably, a filter having a pore diameter of about 1 μm to several hundred μm is used. In the case of centrifugation, a condition is selected in which dissolved carbon nanotubes remain in the supernatant and undissolved solids are separated into precipitates. Preferably, the separation is performed by applying a centrifugal force equivalent to 1,000 to 4,000 × g for 5 to 30 minutes. In this way, a solution in which the carbon nanotubes are homogeneously dissolved is obtained.

  The fact that the carbon nanotubes are homogeneously dissolved in the solution is that the carbon nanotubes in the carbon nanotube solution are recovered by centrifugation, washed with a solvent to remove excess cyclic glucan, and then an atomic force microscope. Use to confirm. An example of a more specific method will be described later in Example 1.

  The amount of the carbon nanotube dissolved in the solution can be measured, for example, by centrifuging at 15,000 × g for 30 minutes, collecting the carbon nanotube, and measuring the weight. Alternatively, as described in the document “Chem. Commun.”, P193 (2001), the concentration of carbon nanotubes has a very good correlation with the absorbance at 500 nm, and cyclic glucan has little absorption at this wavelength. Absent. Therefore, the concentration of carbon nanotubes is easily determined by measuring the absorbance of the solution at 500 nm, unless it contains some other material that has an absorption around 500 nm.

(6. Molded product)
In one embodiment, the molded product of the present invention is formed mainly of carbon nanotubes and cyclic glucan. In general, since cyclic glucan has moldability, a molded product can be formed without using a polymer other than carbon nanotubes and cyclic glucan. When the molded product is mainly composed of carbon nanotubes and cyclic glucan and is formed without other polymers, the content of the carbon nanotubes in the molded product is preferably about 0.01% by weight or more, and more Preferably it is about 0.1% by weight or more, more preferably about 0.2% by weight or more, and most preferably about 0.3% by weight or more. The content of carbon nanotubes in the molded product is preferably about 20% by weight or less, more preferably about 10% by weight or less, still more preferably about 5% by weight or less, and most preferably about 2% by weight. It is as follows. When the molded product is composed of only carbon nanotubes and cyclic glucan, the content of cyclic glucan is an amount obtained by subtracting the content of carbon nanotubes from 100% by weight. The molded product may consist of only carbon nanotubes and cyclic glucan, and other substances other than polymers (for example, pigments, plasticizers, dispersants, coating surface conditioners, fluidity conditioners, UV absorbers, antioxidants) Agents, storage stabilizers, adhesion assistants, thickeners, etc.). When such other substances are contained, the cyclic glucan content in the molded carbon nanotube is preferably about 70% by weight or more, more preferably about 80% by weight or more, and further preferably about 90% by weight. % Or more, and most preferably about 95% by weight or more. The cyclic glucan content in the molded product is preferably about 99% by weight or less, more preferably about 98% by weight or less, still more preferably about 97% by weight or less, and most preferably about 95% by weight. It is as follows.

  In another embodiment, the molded product of the present invention is formed mainly of carbon nanotubes, cyclic glucan and polymer. The polymer is a polymer other than carbon nanotubes and cyclic glucan. By including a polymer, strength, gas barrier properties, and the like are imparted to the molded product depending on the properties of the polymer. In this case, the content of the carbon nanotube in the molded product is preferably about 0.001% by weight or more, more preferably about 0.01% by weight or more, and further preferably about 0.05% by weight or more. And most preferably at least about 0.1% by weight. The content of carbon nanotubes in the molded product is preferably about 20% by weight or less, more preferably about 15% by weight or less, and most preferably about 10% by weight or less. The content of cyclic glucan in the molded product is preferably about 10% by weight or more, more preferably about 20% by weight or more, and most preferably about 30% by weight or more. The content of cyclic glucan in the molded product is preferably about 90% by weight or less, more preferably about 80% by weight or less, and most preferably about 70% by weight or less. The content of the polymer in the molded product is preferably about 10% by weight or more, more preferably about 20% by weight or more, and most preferably about 30% by weight or more. The content of the polymer in the molded product is preferably about 90% by weight or less, more preferably about 80% by weight or less, and most preferably about 70% by weight or less.

  For convenience, carbon nanotubes and cyclic glucans are not included in the “polymer” in this specification. That is, the “polymer” in the present specification means a polymer material other than carbon nanotubes and cyclic glucan having a polymerization degree of 16 to 5000.

  Any polymer that can be used as a molding material can be used as the polymer. In certain embodiments, the polymer is preferably amylose, more preferably enzymatically synthesized amylose. Amylose is a kind of glucose polymer contained in natural starch and is a molecule in which glucose is linearly bonded with α-1,4 bonds, but has a slightly branched structure of α-1,6 bonds. May be included. Enzyme-synthesized amylose refers to a molecule in which glucose synthesized by the enzyme glycogen phosphorylase is bound linearly with only α-1,4 bonds using glucose-1-phosphate as a raw material. In particular, since enzyme-synthesized amylose having an average molecular weight of 600,000 or more dissolves in water, a molded product (for example, a film) in which carbon nanotubes are dispersed can be produced using only water as a solvent. Molded products whose polymer is mainly amylose have biodegradability. Biodegradability refers to a substance that is decomposed into low molecules such as water, carbon dioxide, and ammonia by the action of enzymes synthesized by microorganisms or organisms, or a substance that is decomposed and absorbed by microorganisms or plants.

  Other biodegradable polymers that can be used in the molded article of the present invention include pullulan, dextran, starch and derivatives thereof, cellulose derivatives (eg, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose), deoxyribonucleic acid, ribonucleic acid. , Guar gum, xanthan gum, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, gelatin, lactic acid polymer, glycolic acid polymer, and any combination thereof. In certain embodiments, it is preferred to use a polymer other than amylose, more preferably pullulan.

  The polymer that can be used in the molded article of the present invention may not be biodegradable. Examples of non-biodegradable polymers include polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyvinyl pyrrolidone, polyacrylic acid, polystyrene sulfonic acid, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, poly (methyl methacrylate), polystyrene, polypropylene Nylon, polycarbonate, polyolefin, polyethylene, polyester, polyimide, polyamide, epoxy, phenolic resin, etc., and any combination thereof.

  The moldings of the present invention are used in electromagnetic shielding components for mobile phones, laptop computers, radar absorbing materials for stealth aircraft, nanoelectronic materials (such as new generation computer memory), and high strength, lightweight composites Can be used as The molded product of the present invention can also be used as a film, a fiber, an adhesive layer of a laminate, a coating, or the like.

  The molded product of the present invention may also contain pigments, plasticizers, dispersants, coating surface modifiers, fluidity modifiers, ultraviolet absorbers, antioxidants, storage stabilizers, adhesion assistants, thickeners as necessary. It may further contain various known substances such as. The addition amount of these substances can be arbitrarily set by those skilled in the art.

  The molded article of the present invention may further contain a conductive substance in order to further improve its conductivity. Examples of conductive materials include carbon-based materials (eg, carbon fiber, conductive carbon black, graphite, etc.), metal oxides (eg, tin oxide, zinc oxide, etc.), metals (eg, silver, nickel, copper, etc.) ).

(7. Molding material)
The carbon nanotube solution obtained by the present invention is characterized in that the carbon nanotubes are homogeneously dissolved. By using this solution, a molded product in which the carbon nanotubes are uniformly distributed can be obtained. The molded product of the present invention contains a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less and a carbon nanotube. The molded product may be produced by drying the carbon nanotube solution as it is, or may be produced by adding a polymer (polymer material) and drying. The molded product of the present invention may have any shape. The shape of the molded product of the present invention may be, for example, a shape such as a film or a fiber. The molded product of the present invention may be solid like a film or gel. It is also possible to obtain a gel-like molded product by using a material having a property of forming a gel as a polymer. It is also possible to form a gel using a gelling agent that gels the polymer.

(8. Molding method)
The molding material can be molded by any conventionally known molding method. For example, various known methods can be used as a method for molding the polymer material, and specific examples include injection molding, extrusion molding, press molding, casting, and blow molding.

  In the case of a molding method using a material containing a solvent (for example, a casting method), the solution obtained by the present invention may be used as it is, or a part of the solvent may be removed, or the same type. Or you may add and use another solvent. In the case of a molding method (for example, injection molding, extrusion molding, etc.) performed using a material that does not substantially contain a solvent, the solvent in the solution containing the carbon nanotubes, the cyclic glucan, and the polymer is removed for molding. Can be a material.

  A film production method will be described as an example of molding production. The carbon nanotube solution is used as it is or mixed with a polymer, and a film is produced by a solution casting method or a spin coating method. Similar to the carbon nanotube solution, this film is characterized in that the carbon nanotube solution is uniformly distributed. By stretching the film thus obtained, a stretched film can be obtained. When stretching, it is preferable to mix with a polymer that can withstand stretching.

(7. Solubilizer)
The present invention also provides a solubilizer for dissolving carbon nanotubes in a solvent. This solubilizer contains a cyclic glucan having a polymerization degree of 16 or more and 5000 or less.

  The solubilizer of the present invention may contain an excipient, a bulking agent and the like in addition to the cyclic glucan.

(8. Other uses)
When the solution of the present invention contains a polymer capable of forming a thin film, the solution of the present invention can be processed on the surface of a substrate by a method used for general coating to form a thin film. For example, gravure coater, roll coater, curtain flow coater, spin coater, bar coater, reverse coater, kiss coater, phanten coater, rod coater, air doctor coater, knife coater, blade coater, cast coater, screen coater, etc. Spray methods such as spray coating such as air spray and airless spray, immersion methods such as dip, and the like can be used.

  When the solution of the present invention contains a polymer capable of forming a thin film, the base material on which the solution of the present invention is applied to form a thin film may be a polymer compound, plastic, wood, paper material, ceramic fiber, non-woven fabric, carbon fiber , Carbon fiber paper, and films, foams, porous membranes, elastomers or glass plates thereof can be used. For example, polymer compounds, plastics and films include polyethylene, polyvinyl chloride, polypropylene, polystyrene, ABS resin, AS resin, methacrylic resin, polybutadiene, polycarbonate, polyarylate, polyvinylidene fluoride, polyester, polyamide, polyimide, polyaramid, polyphenylene. There are sulfide, polyether ether ketone, polyphenylene ether, polyether nitrile, polyamide imide, polyether sulfone, polysulfone, polyether imide, polybutylene terephthalate, polyurethane, its film, foam and elastomer. Since these polymer films form a thin film on at least one surface thereof, the film surface is preferably subjected to corona surface treatment or plasma treatment for the purpose of improving the adhesion of the thin film.

  The solution and molded product of the present invention can be suitably used for other uses of a solution containing carbon nanotubes and a molded product.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

(Example 1: Preparation of carbon nanotube solution)
About 1 mg of single-walled carbon nanotube powder (SWCNT manufactured by Shenzhen Nanotechport Co., Ltd.) in 1 mL of a 20% by weight aqueous solution of cycloamylose mixture (cycloamylose manufactured by Ezaki Glico Co., Ltd.) having a polymerization degree of 22 to several hundreds (weight average polymerization degree 46). 1) was added and stirred for about 10 seconds with a vortex mixer. Ultrasonic waves were projected onto this mixture with a bath sonicator (Branson 1200) at room temperature (15 to 25 ° C.) for 5 minutes to dissolve and disperse the carbon nanotubes. This solution was centrifuged at 2,200 × g for 10 minutes, and the supernatant was taken out. The supernatant was a black solution. The obtained black solution had an absorbance at 500 nm of 3.11, and contained about 116 μg / mL of carbon nanotubes.

  The obtained black solution was centrifuged at 15,000 × g for 20 minutes, and the carbon nanotubes dissolved in the aqueous solution were collected as a precipitate. To this, 1 mL of water was added, ultrasonic waves were projected for 5 minutes to redissolve, and the operation of centrifuging again at 15,000 × g for 20 minutes was repeated twice to remove excess cycloamylose in the solution. . When the carbon nanotube solution thus obtained was observed with an atomic force microscope, single-walled carbon nanotubes having an outer diameter of 0.4 to 2.3 nm and a length of 0.15 to 1.0 μm were distributed in the solution as single molecules. Was observed (FIG. 1). From this, it was found that each carbon nanotube was homogeneously dissolved as a substantially single molecule in the carbon nanotube solution.

(Example 2 and Comparative Examples 1-4: Comparison with other glucans)
Cycloamylose mixture (cycloamylose manufactured by Ezaki Glico Co., Ltd.) having a polymerization degree of 22 to several hundreds (weight average polymerization degree 46) (Example 2), amylose being a linear glucan (average molecular weight 2,900; Comparative Example 1), Alternatively, by using respective aqueous solutions of cyclodextrins (α-CD (Comparative Example 2), β-CD (Comparative Example 3), and γ-CD (Comparative Example 4)), which are cyclic glucans having a polymerization degree of 6, 7 and 8. In the same manner as in Example 1, carbon nanotube solutions were prepared and compared.

  Since each glucan has different solubility in water, cycloamylose is 0.1 to 20% by weight, amylose is 0.1 to 5% by weight, α- and γ-CD are 0.1 to 10% by weight, β-CD Used an aqueous solution of 0.1 to 1% by weight.

  FIG. 2 shows the result of measuring the amount of carbon nanotubes in the obtained carbon nanotube solution with the absorbance at 500 nm. As a result, it can be seen that in cycloamylose, the amount of carbon nanotubes dispersed increases with increasing concentration. However, in the case of amylose, the amount of dissolved carbon nanotubes increased as the concentration increased up to 3.0% by weight, but the concentration of dissolved carbon nanotubes decreased conversely at concentrations exceeding 3.0% by weight. On the other hand, in the case of cyclodextrin, carbon nanotubes could hardly be dissolved in the concentration range examined. Thus, an aqueous solution of cycloamylose can dissolve a carbon nanotube in a significantly larger amount than other glucans.

(Example 3 and Comparative Example 5: Stability test)
The stability of carbon nanotube solutions prepared as in Example 1 was compared using 5% by weight aqueous solutions of cycloamylose and amylose, respectively. In both cases of using cycloamylose and amylose, immediately after dissolution, the carbon nanotubes were distributed throughout the solution, and the whole appeared uniformly black (A and B immediately after dissolution in FIG. 3). Each prepared carbon nanotube solution was allowed to stand at room temperature for 3 days for observation. As a result, in the amylose solution, the coloration of the supernatant decreased or precipitation occurred after 3 days (refer to A after 3 days in FIG. 3 and separated into a transparent portion and a black portion). On the other hand, no change was observed in the solution containing cycloamylose and carbon nanotubes, and the carbon nanotubes were distributed throughout the solution, and the whole appeared uniformly black (see B after 3 days in FIG. 3). From this, it was found that when carbon amylose is used, the stability of the carbon nanotube solution is higher than when amylose is used. Furthermore, when the carbon nanotubes using cycloamylose were allowed to stand at room temperature for 1 month, almost no precipitation was observed. From this, it was found that the carbon nanotube solution using cycloamylose is extremely stable.

  From the results of Example 2 and Example 3, it can be seen that a larger amount of carbon nanotubes can be dissolved in the aqueous solution for a longer period by using cycloamylose.

(Example 4: Preparation of carbon nanotube-amylose film and measurement of its complex dielectric constant)
The amylose film is a useful biodegradable film that can be polarized by high transparency and a complex with iodine. A carbon nanotube-amylose film was prepared for the purpose of providing the film with an electromagnetic wave shielding effect and absorption effect by using a uniform and stable cycloamylose-carbon nanotube aqueous solution.

  As experimental samples, 0.8 g of enzyme-synthesized amylose (weight average molecular weight 1 million), 40 mg of single-walled carbon nanotubes (SWCNT-1; manufactured by Shenzhen Nanotechport), cycloamylose (degree of polymerization 22 to several hundred (weight average degree of polymerization 46) 1 g of cycloamylose mixture (cycloamylose manufactured by Ezaki Glico Co., Ltd.), 1 mL of distilled water and Kapton film (manufactured by DuPont).

(Example 4.1)
A cycloamylose-carbon nanotube aqueous solution was prepared by the following procedure. First, 4 mg of carbon nanotube powder and 0.1 g of cycloamylose powder were rubbed together in an agate mortar for about 20 minutes, and 1 mL of distilled water (DW) was added thereto to obtain a mixture. The solution concentration of cycloamylose in this mixture is 10%. The mixture was well vortexed and a Bath type sonicator was applied at room temperature (15-25 ° C.) for 5 minutes, and then the swing rotor was centrifuged at 2,200 × g for 10 minutes.

  The supernatant was extracted into an Eppendorf tube and further centrifuged at 16,600 × g for 10 minutes. After centrifugation, the supernatant was extracted and pooled in a brown bottle. Thereby, a cycloamylose-carbon nanotube aqueous solution was obtained. This was repeated 10 times to obtain about 10 mL of a cycloamylose-carbon nanotube aqueous solution.

(Example 4.2: Film production)
80 mL of distilled water was heated to about 80 ° C. with a hot stirrer, and 0.8 g of enzyme-synthesized amylose was gradually added thereto. Stirring was continued with a hot stirrer until it reached about 60 mL, and then filtered with a G2 glass filter. After filtration, stirring was continued with a hot stirrer for a while to partially evaporate the water, and when the volume became 50 mL or less, about 10 mL of the cycloamylose-carbon nanotube aqueous solution prepared in Example 4.1 was gradually added to form a film. A forming solution was obtained.

  The film-forming solution was stirred with a hot stirrer for a while to partially evaporate the water. When the volume became 50 mL or less, the solution was applied to a cast plate (12 cm × 4 cm) with a Kapton film (made by DuPont). Poured and dried overnight in a dryer set at 60 ° C. As a result, a black film having a thickness of 0.2 to 0.3 mm and 12 cm × 4 cm was formed. This film consists of 0.8 g of amylose, 1 g of cycloamylose and 1.16 mg of carbon nanotubes. Therefore, the content of carbon nanotubes in this film was 0.06% by weight, and the content of cyclic glucan was 55.5% by weight.

(Example 4.3: Measurement of complex dielectric constant)
The complex dielectric constant will be briefly described. The dielectric constant ε is a coefficient that gives the relationship between the electric flux density D and the electrolysis E, and is defined by D = εE. If a high-frequency electric field E = E ₀ exp (jωt) having an angular frequency ω is applied to an object having a dielectric constant ε, it can be expressed by an electric flux density D = D ₀ exp (jωt−jφ), ε = D / E = (J ₀ / E ₀ ) exp (−jφ). Here, when D ₀ / E ₀ = ε1, it can be expressed as ε = ε1 exp (−jφ) = ε1 cos φ−jε1 sinφ. When the real part is represented by ε ′ and the imaginary part is represented by ε ″, ε = ε′−jε ″. This is called complex dielectric constant. Here, ε ′ = ε1 cosφ and ε ″ = ε1 sinφ.

  A relationship of D = ε0E + P is established between the electric flux density D and the electric polarization P. Therefore, the real part of the dielectric constant corresponds to the electric polarization P generated in the same phase as the electric field. On the other hand, the imaginary part corresponds to electrical polarization that is 90 degrees out of phase with the electric field.

  When the electric flux changes with time, a displacement current Jp = dD / dt flows. Substituting D = (ε′−jε ″) E into D, it is possible to write Jp = jω (ε′−jε ″) E = ωε ″ E + jωε′E. When this is written as σE, σ ′ = Ωε ″, σ ″ = ωε ′. In σ and ε, the real part and the imaginary part are flipped. The imaginary part of the dielectric constant works the same as the real part of the conductivity, that is, the energy The imaginary part of the dielectric constant is called dielectric loss, and it is this dielectric loss that heats the food in the microwave oven.

In general, electromagnetic wave absorbing materials are used for electromagnetic fields. (1) Conductive loss materials: Use high resistance conductors such as carbon (2) Magnetic loss materials: Use magnetic materials with high permeability such as ferrite ( 3) Dielectric loss material: Classification is made using a material in which the imaginary part of the complex dielectric constant is increased by containing carbon or the like in the foam.

The complex dielectric constant of the black film containing cycloamylose and carbon nanotubes obtained in Example 4.3 was measured using a cavity resonator (Agilent Technologies Japan, Ltd., trade name: A8361E (PNA series). Measurement was performed by a resonator perturbation method using a microwave network analyzer)) at normal temperature (25 ° C.) and normal pressure (1 atm). As a control, a film obtained by the same method as in Example 4.3 was used except that it did not contain carbon nanotubes. The results are shown in Table 1 below.

Compared with the amylose film, the carbon nanotube-containing amylose film has an improved ε ′ value indicating an electromagnetic wave reflection effect and an ε ″ value indicating an electromagnetic wave absorption effect in all the frequency ranges measured. From these results, it was possible to simultaneously improve the reflection and absorption effects of electromagnetic waves by incorporating carbon nanotubes into the amylose film.

(Example 5: Production of carbon nanotube-containing PVA film)
80 mL of distilled water was heated to 80 ° C., and 0.8 g of polyvinyl alcohol (polymerization degree: about 2,000) was gradually added and dissolved. The solution was further heated and stirred and concentrated to a volume of about 50 mL. To 15 mL of this polyvinyl alcohol solution, 1.5 mL of the carbon nanotube solution prepared as in Example 1 was added and heated and stirred for 10 minutes. This solution was poured into a plastic petri dish and dried at 60 ° C. overnight to obtain a carbon nanotube-containing polyvinyl alcohol film. This film consists of 0.24 g of polyvinyl alcohol, 0.15 g of cycloamylose and 0.17 mg of carbon nanotubes. Therefore, the carbon nanotube content in the film was 0.04% by weight, and the cyclic glucan content was 38.5% by weight.

(Example 6: Production of a pullulan film containing carbon nanotubes)
80 mL of distilled water was heated to 80 ° C., and 0.8 g of pullulan (molecular weight of about 200,000) was gradually added and dissolved. The solution was further heated and stirred and concentrated to a volume of about 50 mL. To 15 mL of this pullulan solution, 1.5 mL of the carbon nanotube solution prepared as in Example 1 was added and heated and stirred for 10 minutes. This solution was poured into a plastic petri dish and dried at 60 ° C. overnight to obtain a carbon nanotube-containing pullulan film. This film consists of 0.24 g pullulan, 0.15 g cycloamylose and 0.17 mg carbon nanotubes. Therefore, the carbon nanotube content in the film was 0.04% by weight, and the cyclic glucan content was 38.5% by weight.

(Example 7 and Comparative Examples 6 to 8: Comparison 2 with other glucans)
Cycloamylose mixture (cycloamylose manufactured by Ezaki Glico Co., Ltd.) (Example 7) having a polymerization degree of 22 to several hundreds (weight average polymerization degree 46), amylose which is a linear glucan (average molecular weight 2,900; Comparative Example 1), Or 0.1 g each of cyclodextrins (α-CD (Comparative Example 6), β-CD (Comparative Example 7), γ-CD (Comparative Example 8)), which are cyclic glucans having a degree of polymerization of 6, 7, 8; About 4 mg of single-walled carbon nanotube powder (SWCNT-1 manufactured by Shenzhen Nanotechport Co., Ltd.) was rubbed in an agate mortar for about 20 minutes. Distilled water is added to the mixture containing cycloamylose in an amount of 0.5 to 10 mL (final concentration of glucan of 1 to 20% by weight), and an α-CD and γ-CD mixture of 1 to 10 mL (final concentration of glucan). 1 to 10% by weight), 6.7 to 20 mL (final concentration of glucan 0.5 to 1.5% by weight) was added to the mixture of β-CD and amylose, and the mixture was stirred with a vortex mixer for about 10 seconds. Ultrasonic waves were projected onto this mixture with a bath sonicator (Branson 1200) at room temperature (15 to 25 ° C.) for 5 minutes to dissolve and disperse the carbon nanotubes. This solution was centrifuged at 2,200 × g for 10 minutes, and the amount of carbon nanotubes in the supernatant was measured by absorbance at 500 nm (FIG. 4).

  As a result, when cycloamylose was used, the amount of carbon nanotubes dissolved increased with an increase in the cycloamylose concentration in the solution. The amount of dissolved carbon nanotubes was larger than that of the method of Example 1, and about 6.5 times more carbon nanotubes were dissolved when compared under the condition of a cycloamylose concentration of 20% by weight.

  On the other hand, when α-CD was used, the amount of dissolved carbon nanotubes was higher than that of cycloamylose at 1.0% by weight, but the amount of dissolved carbon nanotubes decreased conversely as the concentration of α-CD increased. . In addition, when β-CD, γ-CD and amylose were used, the amount of dissolved carbon nanotubes was small compared to cycloamylose.

  Thus, also in the method of adding a solvent after mixing glucan and carbon nanotubes, cycloamylose was able to dissolve a significantly larger amount of carbon nanotubes than other glucans. Also, it was found that the method of adding a solvent after previously mixing the cyclic glucan and the carbon nanotubes can dissolve the carbon nanotubes at a higher concentration than the method of adding the carbon nanotubes to the cyclic glucan solution. It was.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  By using the solution of the present invention, a molded product having excellent physical properties can be obtained by uniformly dispersing the carbon nanotubes. Further, it can be used in fields where carbon nanotubes have not been used so far, such as cosmetics, pharmaceuticals, and foods.

FIG. 1 is an atomic force microscope image of a carbon nanotube dissolved in a carbon nanotube solution obtained in the present invention. The white part is the carbon nanotube, and the black part is the surface of the silicon wafer on the sample stage. It can be seen that the carbon nanotubes were uniformly distributed in the solvent. FIG. 2 is a graph showing the glucan concentration dependence of the amount of carbon nanotubes dissolved in various glucan solutions. FIG. 3 is a photograph showing the results of examining the stability of a carbon nanotube solution prepared using a 5% by weight aqueous solution of cycloamylose and amylose. FIG. 4 is a graph showing the dependence of the amount of carbon nanotubes dissolved in various glucan solutions on each glucan concentration.

Claims (26)

  A solution comprising a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less and a carbon nanotube.   The solution according to claim 1, wherein the carbon nanotube is a single-walled carbon nanotube.   The solution according to claim 1, wherein the cyclic glucan is a cyclic glucan having only a structure in which glucose is cyclically bonded with α-1,4 bonds.   The solution according to claim 1, wherein the solution is an aqueous solution.   The solution according to claim 1, wherein the concentration of the carbon nanotube is 50 mg / L or more. A method for obtaining a carbon nanotube solution,
Providing a mixture comprising a carbon nanotube, a cyclic glucan having a polymerization degree of 16 or more and 5000 or less, and a solvent, and a solution in which the carbon nanotube and the cyclic glucan are dissolved in the solvent by projecting ultrasonic waves onto the mixture. Obtaining step,
Including the method.   The method according to claim 6, wherein the mixture is obtained by adding the carbon nanotubes to a solution containing the cyclic glucan and a solvent.   The method according to claim 6, wherein the mixture is obtained by adding the solvent after mixing the cyclic glucan and the carbon nanotube.   The method of claim 6, wherein the carbon nanotube is a single-walled carbon nanotube.   The method according to claim 6, wherein the cyclic glucan is a cyclic glucan consisting only of a structure in which glucose is cyclically bound by α-1,4 bonds.   The method of claim 6, wherein the solution is an aqueous solution.   The method according to claim 6, wherein the concentration of carbon nanotubes in the solution is 50 mg / L or more.   A molded article containing a cyclic glucan having a degree of polymerization of 16 or more and 5000 or less and a carbon nanotube.   The molded article according to claim 13, further comprising a polymer.   The molded product according to claim 13, wherein the carbon nanotube is a single-walled carbon nanotube.   The molded article according to claim 13, wherein the cyclic glucan is a cyclic glucan having only a structure in which glucose is cyclically bonded by α-1,4 bonds.   The molded article according to claim 13, wherein the molded article is molded from a solution containing only water as a solvent.   The molded article according to claim 14, wherein the polymer is amylose.   The molded article according to claim 14, wherein the polymer is a polymer other than amylose.   The molded product according to claim 13, wherein the molded product has a film or fiber shape.   The molded product according to claim 13, wherein the molded product is a stretched film.   The molded article according to claim 13, wherein the molded article is in a gel form.   The molded article according to claim 13, wherein the molded article is for electromagnetic shielding.   The molded product according to claim 13, wherein the molded product is biodegradable.   A solubilizer for dissolving carbon nanotubes in a solvent, comprising a cyclic glucan having a polymerization degree of 16 or more and 5000 or less.   The solubilizer according to claim 25, wherein the cyclic glucan is composed of a cyclic glucan consisting only of a structure in which glucose is cyclically bound by α-1,4 bonds.