Dispersant for carbon nanotubes, carbon nanotube dispersion, and method for producing the carbon nanotube dispersant.

Abstract

The present invention provides a dispersant for carbon nanotubes that can effectively disperse carbon nanotubes in a solvent. [Solution] The dispersant for carbon nanotubes contains polysaccharides and betaines.

Description

Technical Field

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[0001] The present invention relates to a dispersant for carbon nanotubes, a carbon nanotube dispersion, and a method for producing a dispersant for carbon nanotubes.

Background Art

[0002] Since carbon nanotubes have excellent electrical conductivity, their application to members of non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries has been studied. Carbon nanotubes have strong aggregation due to van der Waals forces and are difficult to disperse in a solvent. In order to improve the dispersibility of carbon nanotubes in a solvent, it is known to use a dispersant.

[0003] For example, Patent Document 1 discloses a carbon nanotube aqueous dispersion using one or more of a group A of specific anionic surfactants and a group B of specific polysaccharides as a dispersant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, since carbon nanotubes form a high-density bundle due to van der Waals forces, it is difficult to dissociate the bundle and uniformly disperse it in a solvent, and improvement in dispersibility is desired.

[0006] The main object of the present disclosure is to provide a dispersant for carbon nanotubes that can disperse carbon nanotubes well in a solvent.

Means for Solving the Problems

[0007] The aspects of this disclosure that solve the above problems are as follows:

[0008] [1] A dispersant for carbon nanotubes containing polysaccharides and betaines. [2] The carbon nanotube dispersant according to [1], wherein the polysaccharide is glucuronoxylan. [3] The carbon nanotube dispersant according to [2], wherein the weight-average molecular weight of the glucuronoxylan is 1000 to 1,000,000. [4] A dispersant for carbon nanotubes according to any one of [1] to [3], wherein the weight ratio of the betaine content to the polysaccharide (betaine / polysaccharide) is 0.0040 to 0.35. [5] The carbon nanotube dispersant according to any one of [1] to [4], wherein the betaines are at least one selected from the group consisting of alkylbetaines and alkylamidopropylbetaines. [6] A carbon nanotube dispersion containing polysaccharides, betaines, carbon nanotubes, and water. [7] The carbon nanotube dispersion according to [6], wherein the betaine content is 0.008% to 0.5% by weight. [8] The weight ratio of the polysaccharide content to the carbon nanotube (polysaccharide / carbon nanotube) is 0.10 to 2.5, A carbon nanotube dispersion according to [6] or [7], wherein the weight ratio of the betaine content to the carbon nanotube (betaine / carbon nanotube) is 0.0014 to 0.15. [9] A method for producing a carbon nanotube dispersant, comprising the step of mixing polysaccharides and betaines.

[10] A step of preparing an aqueous solution by mixing polysaccharides, betaines, and a solvent, A method for producing a dispersant for carbon nanotubes, comprising the step of removing water from the aqueous solution to obtain a powder containing polysaccharides and betaines. [Effects of the Invention]

[0009] According to this disclosure, a dispersant for carbon nanotubes that can effectively disperse carbon nanotubes in a solvent can be provided. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure are described in detail below. However, the present disclosure is not limited to these embodiments. The elements listed below can be combined in any way, and the scope of the present invention is intended to include all modifications within the claims and scopes equivalent to the claims. The upper and lower limits in each numerical range of the embodiments of the present disclosure can be combined in any way to form any numerical range.

[0011] (Dispersant for carbon nanotubes) The carbon nanotube (hereinafter also referred to as CNT) dispersant of this embodiment contains polysaccharides and betaines. The CNT dispersant of this embodiment, containing polysaccharides and betaines, can disperse CNTs well in a solvent, particularly an aqueous solvent. Excellent dispersibility can be achieved even when dispersing CNTs at high concentrations, such as 5% by weight.

[0012] Although the detailed reasons for the effects of this invention are unclear, it is presumed to be due to the following mechanism. Carbon nanotubes (CNTs) are prone to aggregation due to van der Waals forces between adjacent CNTs, forming strong bundle structures consisting of multiple CNTs. To uniformly disperse CNTs in a solvent, it is necessary to dissociate these bundles. The CNT dispersant of this embodiment is thought to prevent aggregation due to intermolecular interactions between CNTs by having hydrophilic polysaccharides act on the CNT surface, and to be able to stably disperse CNTs, especially in aqueous solvents. Furthermore, by incorporating amphoteric molecules such as betaines, one CNT forming a bundle structure and an adjacent CNT forming a bundle structure are electrostatically bonded via the betaines. It is thought that this bonding via betaines strengthens the planar interactions between bundle structures, stabilizing the structure and strengthening the hydrophobic interactions between the upper and lower hydrophobic groups, thereby maintaining the dispersed state of the CNTs and further improving dispersibility.

[0013] According to the CNT dispersant of this embodiment, the synergistic effect of polysaccharides and betaines improves dispersibility, allowing for a higher concentration of CNTs in the dispersion when CNTs are dispersed in a solvent using the CNT dispersant. This higher concentration of CNTs reduces the transportation costs of the dispersion and also reduces the drying load and environmental impact during coating using the dispersion.

[0014] In the case of dispersants using polysaccharides, adding a large amount of the dispersant to improve dispersibility may increase the viscosity or cause gelation in the resulting dispersion, making coating work with the dispersion difficult and potentially reducing its handling properties. The CNT dispersant of this embodiment exhibits remarkable dispersibility even in small amounts, thus suppressing the increase in viscosity of the dispersion and improving its fluidity.

[0015] Since the polysaccharides and betaines contained in the CNT dispersant of this embodiment are all naturally derived substances, the burden on the environment and living organisms can be reduced.

[0016] Examples of the polysaccharides used as the dispersant for CNTs in the embodiments include glucuronoxylan, carboxymethyl cellulose, xanthan gums, guar gums, and gellan gums, etc. Glucuronoxylan and carboxymethyl cellulose are preferred, and glucuronoxylan is more preferred. The polysaccharides may be used alone or in combination of two or more.

[0017] Glucuronoxylan is a molecule containing six or more xylose residues linked by β-1,4 bonds, and refers to a molecule in which 4-O-methylglucuronic acid residues and acetyl groups are bonded to a molecule composed only of xylose residues (xylose polymer). It is known that the main component of hemicellulose contained in hardwood is glucuronoxylan. Glucuronoxylan contained in hardwood often has a composition ratio of 10 xylose residues: 1 4-O-methylglucuronic acid: 6 acetyl groups. There are also those in which arabinose residues and 4-O-methylglucuronic acid are bonded to the xylose polymer. These are generally called arabinoglucuronoxylan or glucuronoarabinoxylan. In this specification, these are collectively referred to as glucuronoxylan. That is, the glucuronoxylan of the polysaccharide used as the dispersant for CNTs includes arabinoglucuronoxylan, glucuronoarabinoxylan, and arabinoxylan, etc.

[0018] Glucuronoxylan is preferably derived from hardwood. Natural-derived glucuronoxylan may be used in a state containing impurities as long as its effects can be exerted, may be used as a population having a wide molecular weight distribution, or may be purified to a higher purity so as to become a population having a narrower molecular weight distribution before use.

[0019] From the viewpoint of water solubility, the average degree of polymerization of the main chain in glucuronoxylan, that is, the longest chain linked by β-1,4-bonds, is preferably 6 to 1000, more preferably 8 to 100, and even more preferably 10 to 50.

[0020] The weight average molecular weight of glucuronoxylan is preferably from 1,000 to 1,000,000, more preferably from 2,000 to 30,000, and even more preferably from 5,000 to 25,000. When the weight average molecular weight is 1,000 or more, the dispersion degree of CNT is further improved. When the weight average molecular weight is 1,000,000 or less, the viscosity of the CNT dispersion can be kept low, and it has excellent fluidity.

[0021] Glucuronoxylan is purified from, for example, wood according to a known method. Examples of the purification method of glucuronoxylan include, for example, a method of extracting lignin-removed wood with a potassium hydroxide solution of about 10%. Commercially available products can also be used as glucuronoxylan.

[0022] The dispersant for CNT of the embodiment contains betaines. Betaines refer to compounds having non-adjacent positive and negative charges in the same molecule and having no charge as a whole molecule.

[0023] Examples of betaines include at least one selected from the group consisting of alkyl betaines, alkylamidopropyl betaines, sulfobetaines, and amidosulfobetaines. As betaines, alkyl betaines and alkylamidopropyl betaines are preferable. Betaines may be used alone or in combination of two or more.

[0024] Examples of alkyl betaines include trimethylglycine, lauryl betaine, myristyl betaine, palmitoyl betaine, stearyl betaine, oleyl betaine, and coco betaine. Among them, from the viewpoint of improving the synergistic effect with polysaccharides, trimethylglycine and lauryl betaine are preferable, and trimethylglycine is more preferable.

[0025] Examples of alkylamidopropyl betaines include cocoamidopropyl betaine, lauramidopropyl betaine, myristylamidopropyl betaine, and oleylamidopropyl betaine. Among them, from the viewpoint of improving the synergistic effect with polysaccharides, cocoamidopropyl betaine is preferable.

[0026] The number of carbon atoms constituting the betaine is preferably 4 to 20, more preferably 4 to 18, even more preferably 4 to 12, and even more preferably 4 to 6. When the number of carbon atoms in the betaine is within the above range, the dispersibility of CNTs in aqueous solvents is further improved. Commercially available betaines can also be used.

[0027] The dispersant for CNTs in the embodiment preferably contains glucuronoxylan and at least one selected from the group consisting of alkylbetaine and alkylamidopropylbetaine.

[0028] From the viewpoint of dispersibility and fluidity when used as a CNT dispersion, the polysaccharide content is preferably 80% to 99.8% by weight, more preferably 90% to 99.7% by weight, and even more preferably 96.5% to 99.5% by weight, based on the total amount of the CNT dispersant. When two or more types are used in combination, the content refers to the total amount.

[0029] From the viewpoint of dispersibility, the betaine content is preferably 0.40% to 20% by weight, more preferably 0.45% to 8% by weight, and even more preferably 0.50% to 3.5% by weight, based on the total amount of the dispersant for CNTs. When two or more types are used in combination, the content refers to the total amount.

[0030] In dispersants for CNTs, from the viewpoint of dispersibility and fluidity, the weight ratio of betaine content to polysaccharide content (betaine / polysaccharide) is preferably 0.0040 to 0.35, more preferably 0.0045 to 0.10, even more preferably 0.0050 to 0.035, and still more preferably 0.0050 to 0.026.

[0031] (Method for manufacturing dispersant for CNTs) The method for producing the dispersant for CNTs according to this embodiment includes a mixing step of mixing polysaccharides and betaines. The method of mixing the polysaccharides and betaines is not particularly limited and may be done, for example, using a powder mixer or by manual stirring.

[0032] Another method for producing a dispersant for CNTs provided in this embodiment includes a first step of preparing an aqueous solution by mixing polysaccharides, betaines, and a solvent, and a second step of obtaining a powder containing polysaccharides and betaines by removing water from the aqueous solution.

[0033] The first step is an example of a mixing step. In the first step, an aqueous solution is prepared by dissolving polysaccharides and betaines in a solvent. The first step is carried out, for example, by mixing the above components. The mixing method is not particularly limited, but known methods such as stirring can be used. The order in which the components are added is not particularly limited. As the solvent, an aqueous solvent is preferred, water or mainly water is more preferred, and water is even more preferred.

[0034] Methods for removing water in the second step include, for example, drying. Specifically, these methods include removing water by letting the aqueous solution prepared in the first step stand under heating, removing water while stirring and flowing the aqueous solution under heating, and spraying and dispersing the aqueous solution in a hot air stream, such as with a spray dryer. The water removal process may also be carried out under reduced pressure. By removing the water, a powder containing polysaccharides and betaines is obtained. The drying temperature, pressure, and drying time of the aqueous solution should be sufficient to evaporate and remove the water from the aqueous solution, and can be set appropriately according to the composition and amount of the aqueous solution. For example, when using a spray dryer, the drying temperature is, for example, 80°C to 160°C, and the drying time is, for example, 1 second or more.

[0035] In the manufacturing method of this embodiment, the polysaccharides and betaines are dissolved in water, and then the water is removed to obtain a powder. This improves the miscibility between the polysaccharides and betaines, and makes it possible to produce a powder in which the polysaccharides and betaines are well integrated.

[0036] The CNT dispersant of this embodiment can effectively disperse CNTs in a solvent, and therefore can be suitably used as a dispersant for dispersing CNTs in a solvent. A water-based solvent is preferred as the solvent, water or a solvent mainly composed of water is more preferred, and water is even more preferred.

[0037] CNTs are allotropes of carbon, consisting of multiple carbon atoms bonded together in a cylindrical shape. Examples of CNTs include single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and coiled versions of these. The CNTs to which the dispersant for CNTs of this embodiment is applied are not particularly limited and may be single-walled or multi-walled carbon nanotubes. CNTs may also be carbon nanohorns with one end closed, cup-shaped nanocarbon materials with a hole at the top, or carbon nanotubes with holes on both ends. CNTs may be used alone or in combination of two or more types.

[0038] The average diameter of the CNTs is not particularly limited and may be, for example, 0.4 nm to 100 nm, preferably 0.5 nm to 50 nm, more preferably 1 nm to 30 nm, and more preferably 2 nm to 15 nm. The diameter of the CNTs corresponds to the outer diameter of the CNTs, and in the case of multi-walled carbon nanotubes, it means the diameter of the outermost carbon nanotube. The average length of the CNTs is not particularly limited and may be, for example, 0.5 μm to 1000 μm, preferably 0.8 μm to 800 μm, and more preferably 1 μm to 700 μm.

[0039] The aspect ratio of the CNTs (i.e., the ratio of the average length to the average diameter) is not particularly limited and may be, for example, 10 to 150,000, with 100 to 130,000 being more preferred. When the aspect ratio of the CNTs is within the above range, the dispersibility when dispersed with a CNT dispersant can be further improved.

[0040] (CNT dispersion) The CNT dispersion of the embodiment contains the above-mentioned CNT dispersant, CNTs, and water as a solvent.

[0041] Examples of CNTs used in the CNT dispersion of the embodiment include CNTs similar to those to which the CNT dispersant described above is applied. CNTs may be used alone or in combination of two or more types.

[0042] The method for producing carbon nanotubes (CNTs) is not particularly limited and can be obtained by known methods such as catalytic hydrogen reduction of carbon dioxide, arc discharge, CVD, vapor phase growth, and the HiPco method, in which carbon monoxide is reacted with an iron catalyst at high temperature and pressure to grow in the gas phase. Commercially available CNTs can also be used.

[0043] The water used in the CNT dispersion of the embodiment may be tap water, industrial water, deionized water, distilled water, or any other type.

[0044] The CNT content is preferably 0.1% to 8% by weight, more preferably 3% to 7% by weight, and even more preferably 4% to 6% by weight, based on the total amount of the CNT dispersion. Within the above ranges of CNT content, the properties of the CNTs can be maximized, and the dispersibility of the CNTs can be further improved. When two or more types are used in combination, the content refers to the total amount.

[0045] From the viewpoint of dispersibility and fluidity, the content of the dispersant for CNTs is preferably 0.5% to 3.0% by weight, more preferably 1.5% to 2.5% by weight, and even more preferably 1.8% to 2.0% by weight, based on the total amount of the CNT dispersion. The content of the dispersant for CNTs is the sum of the content of polysaccharides and the content of betaines.

[0046] From the viewpoint of dispersibility, the betaine content is preferably 0.008% to 0.5% by weight, more preferably 0.009% to 0.2% by weight, and even more preferably 0.01% to 0.06% by weight, based on the total amount of the CNT dispersion. When two or more types are used in combination, the content refers to the total amount.

[0047] From the viewpoint of dispersibility and fluidity, the water content is preferably 88% to 99% by weight, more preferably 89% to 95% by weight, and even more preferably 90% to 93% by weight, based on the total amount of the CNT dispersion. When two or more types are used in combination, the content refers to the total amount.

[0048] In dispersants for CNTs, from the viewpoint of dispersibility and fluidity, the weight ratio of polysaccharide content to CNT content (polysaccharide / CNT) is preferably 0.10 to 2.5, more preferably 0.20 to 1.0, and even more preferably 0.30 to 0.50.

[0049] In dispersants for CNTs, from the viewpoint of dispersibility, the weight ratio of betaine content to CNT content (betaine / CNT) is preferably 0.0014 to 0.15, more preferably 0.0015 to 0.10, even more preferably 0.0016 to 0.030, and still more preferably 0.0016 to 0.010.

[0050] In dispersants for CNTs, from the viewpoint of dispersibility and fluidity, the weight ratio of the total content of polysaccharides and betaines to the CNT content [(polysaccharides + betaines) / CNT] is preferably 0.20 to 2.5, more preferably 0.25 to 1.0, and even more preferably 0.30 to 0.50.

[0051] The viscosity of the CNT dispersant at 25°C is preferably 10 mPa·s to 500 mPa·s, more preferably 50 mPa·s to 200 mPa·s. The viscosity of the CNT dispersant at 25°C can be measured using a tuning fork vibrating viscometer.

[0052] In addition to the components described above, the CNT dispersion of the embodiment may contain, as necessary, solvents, substrates, additives, etc., to the extent that it does not impede the effects of the present invention.

[0053] Examples of solvents include organic solvents, specifically 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, dimethyl sulfoxide, dimethyl sulfone, N-methylpyrrolidone, benzene, toluene, xylene, methylene chloride, chloroform, and dichloroethane.

[0054] Examples of additives include pigments, plasticizers, solubilizers, coating modifiers, fluidity modifiers, UV absorbers, antioxidants, preservatives, adhesive aids, thickeners, and release agents.

[0055] The CNT dispersant is obtained by mixing the above components and dispersing CNTs in a water-containing solvent. As a dispersion method, from the viewpoint of ensuring good dispersion of CNTs, a method of uniform dispersion by ultrasonic treatment using ultrasonic equipment such as an ultrasonic container, ultrasonic cleaner, or ultrasonic homogenizer is preferred. Various conditions such as the voltage and treatment time during ultrasonic treatment can be appropriately set according to the type of CNT dispersant and the CNT content. The order of addition of each component is not particularly limited.

[0056] The CNT dispersion of this embodiment exhibits excellent dispersibility of CNTs, and the uniformly dispersed CNTs allow for good expression of CNT properties, including conductivity. Therefore, it can be used in molded products and coatings such as containers, films, sheets, blisters, pipes, hoses, tubes, beads, fibers, automotive parts, electrical equipment parts, stationery, toys, furniture, and daily necessities. Because the CNT dispersion can exhibit excellent conductivity, it is particularly suitable for conductive coatings, electromagnetic shielding materials, field emission materials, and battery electrode materials. [Examples]

[0057] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not intended to be limited to those examples. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0058] [Example 1] First, a dispersant for CNTs was obtained by mixing powdered glucuronoxylan and trimethylglycine, weighed so that the weight ratio of glucuronoxylan to trimethylglycine (trimethylglycine / glucuronoxylan) was 0.2, with powdered trimethylglycine. Next, the CNT dispersion was obtained by mixing the CNT dispersant in the following proportions: 2.28 parts (1.9 parts glucuronoxylan, 0.38 parts trimethylglycine), 5 parts CNT-1, and water in an amount that made up 100 parts of the total CNT dispersion (remaining amount). Specifically, CNT-1 and the CNT dispersant were added to water and dispersed using an ultrasonic homogenizer at an output of 600W to obtain the CNT dispersion.

[0059] [Examples 2-10 and Comparative Examples 1-4] The formulations of the CNT dispersant and CNT dispersion were changed as shown in Tables 1 to 3, and the CNT dispersant and CNT dispersion were obtained in the same manner as in Example 1. In Comparative Examples 1 to 4, the preparation of the CNT dispersant was not carried out, and in the preparation of the CNT dispersion, glucuronoxylan or glucuronoxylan and sodium dodecyl sulfate were weighed according to the formulation.

[0060] In Tables 1 and 2, the values ​​in parentheses for polysaccharides (B) and betaines (C) represent the ratio (%) of the content of each component to the total amount of polysaccharides and betaines, i.e., the total amount of dispersant for CNTs. "C / B" is the weight ratio of the betaine content to the polysaccharide content. "(B+C) / A" is the weight ratio of the total content of polysaccharides and betaines to the CNT content. "B / A" is the weight ratio of the polysaccharide content to the CNT content. "C / A" is the weight ratio of the betaine content to the CNT content.

[0061] The details of each component shown in Tables 1-3 are as follows. (A) Carbon nanotubes CNT-1:MWCNT, average diameter 9.5nm, average length 1.5μm CNT-2: SWCNT, average diameter 3nm~5nm, average length 100μm~600μm CNT-3: SWCNT, average diameter 2nm~3nm, average length several 10μm CNT-4: MWCNT, average diameter approximately 10nm, average length 100μm~400μm (B) Polysaccharide Glucuronoxylan: Weight-average molecular weight approximately 20,000, viscosity of 40.4 mPa·s in a 5% aqueous solution at 25°C. CMC: Carboxymethylcellulose, viscosity 70.0 mPa·s at 2% aqueous solution at 25°C

[0062] The dispersibility and viscosity of the CNT dispersions of Examples 1-10 and Comparative Examples 1-4 were measured and evaluated. The measurement and evaluation methods are as follows. The results are shown in Tables 1-3. In the tables, "-" in the evaluation column for Examples means that measurement was not performed, and "-" in the evaluation column for Comparative Examples means that measurement was not possible.

[0063] [Assessment of variance] Each prepared CNT dispersion was allowed to stand for 10 minutes. The appearance of the CNT dispersion after standing was visually inspected, and its dispersibility was evaluated according to the following criteria. ○ or △ was considered acceptable. ○: It was fluid and glossy. △: Lack of fluidity, but gloss was observed. ×: Lacked fluidity and lacked shine.

[0064] [Measurement of variance] Each CNT dispersion was centrifuged using a centrifuge (CT18R, Eppendorf Hi-Mac Technologies) at 10,000 G and 25°C for 1 hour, and the supernatant was collected. The absorbance of this supernatant at a wavelength of 500 nm was measured using a UV-Vis spectrophotometer (UV-1900, Shimadzu Corporation), and the dispersion degree was calculated based on the obtained absorbance. A higher dispersion degree value indicates that the CNTs are uniformly dispersed in the water, resulting in superior dispersibility.

[0065] [Viscosity measurement] The viscosity of each CNT dispersion was measured using a tuning fork vibratory viscometer (SV-1A, A&D Corporation). The measurement conditions were 25°C.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] As shown in Tables 1-3, Examples 1-10, which contained polysaccharides and betaines, were confirmed to have excellent dispersibility. Furthermore, it was confirmed that the degree of dispersion was high and the CNTs were uniformly dispersed. In addition, the viscosity values ​​were low, and it was confirmed that viscosity increase could be effectively suppressed. Comparative Examples 1-4, which did not contain betaines, exhibited poor dispersibility.

[0070] Examples 2-6 and Comparative Examples 1-2 showed that the combined use of polysaccharides and betaines allowed for good dispersion of even high concentrations of CNTs, such as 6%, in water, effectively suppressing viscosity increase. Similarly, Examples 7 and Comparative Example 3, and Examples 8 and Comparative Example 4 also showed that the addition of betaines improved dispersibility. Examples 9-10 confirmed that excellent dispersibility was also achieved when carboxymethylcellulose was used. Although not shown in the figures, CNT dispersants and CNT dispersions with the same CNT and glucuronoxylan content but lower betaine content than in Example 2 were prepared and their dispersibility evaluated. The results showed that dispersibility decreased when the betaine content in the CNT dispersion fell below 0.008% by weight. Therefore, the preferred range for the betaine content in the CNT dispersion is 0.008% by weight to 0.5% by weight. Furthermore, in dispersants for CNTs, the preferred weight ratio of betaines to polysaccharides (betaines / polysaccharides) is 0.0040 to 0.35.

[0071] Based on the above, it has been confirmed that the CNT dispersant of this disclosure can effectively disperse carbon nanotubes in a solvent.

Claims

1. A dispersant for carbon nanotubes containing polysaccharides and betaines.

2. The carbon nanotube dispersant according to claim 1, wherein the polysaccharide is glucuronoxylan.

3. The carbon nanotube dispersant according to claim 2, wherein the weight-average molecular weight of the glucuronoxylan is 1,000 to 1,000,000.

4. The carbon nanotube dispersant according to claim 1 or claim 2, wherein the weight ratio of the betaine content to the polysaccharide (betaine / polysaccharide) is 0.0040 to 0.

35.

5. The carbon nanotube dispersant according to claim 1 or claim 2, wherein the betaines are at least one selected from the group consisting of alkylbetaines and alkylamidopropylbetaines.

6. A carbon nanotube dispersion containing polysaccharides, betaines, carbon nanotubes, and water.

7. The carbon nanotube dispersion according to claim 6, wherein the betaine content is 0.008% to 0.5% by weight.

8. The weight ratio of the polysaccharide content to the carbon nanotube (polysaccharide / carbon nanotube) is 0.10 to 2.

5. The carbon nanotube dispersion according to claim 6 or claim 7, wherein the weight ratio of the betaine content to the carbon nanotube (betaine / carbon nanotube) is 0.0014 to 0.

15.

9. A method for producing a dispersant for carbon nanotubes, comprising the step of mixing polysaccharides and betaines.

10. A step of preparing an aqueous solution by mixing polysaccharides, betaines, and a solvent, A method for producing a dispersant for carbon nanotubes, comprising the step of removing water from the aqueous solution to obtain a powder containing polysaccharides and betaines.

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