Carbon nanotube dispersant, and carbon nanotube dispersion liquid

Abstract

To provide a dispersant and dispersion liquid that solve the conventional problem of not being able to disperse carbon nanotubes at high concentrations using only glucurono xylan by developing a dispersant containing N-methylpyrrolidone in addition to glucurono xylan.SOLUTION: A carbon nanotube dispersant of the present invention comprises glucurono xylan and N-methylpyrrolidone. The mixing ratio of N-methylpyrrolidone should be smaller than that of glucurono xylan. Carbon nanotubes may be at least one of single-walled carbon nanotubes (SWCNT's) and multi-walled carbon nanotubes (MWCNT's). Furthermore, the carbon nanotube dispersion liquid of the present invention comprises a dispersion solution composed of water, carbon nanotubes, and a dispersing agent, wherein the dispersing agent is the above-mentioned dispersing agent.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a dispersant and a dispersion liquid for dispersing carbon nanotubes in water at a high concentration and stably.

Background Art

[0002] Carbon nanotubes (hereinafter referred to as "CNT") are substances in the form of cylindrical (tube) shapes with a nanometer-sized diameter composed only of carbon, and have a structure in which benzene rings with carbon atoms arranged in a hexagonal shape are arranged adjacent to each other on a plane and rolled into a cylindrical shape. A single layer of this tube is called a single-walled carbon nanotube (hereinafter referred to as "SWCNT"), and a structure in which a plurality of tubes with different diameters are stacked in layers is called a multi-walled carbon nanotube (hereinafter referred to as "MWCNT").

[0003] CNT has high conductivity and great mechanical strength, and applications to conductive paints, conductive resins, electromagnetic shielding sheets, heater members, and the semiconductor field are being studied by taking advantage of its characteristics. When applying to these, it is important to develop a dispersant that can uniformly disperse CNT in a dispersion solvent such as water at a high concentration. In the solid state, CNT forms a bundle (bundle) structure due to strong π-π interaction and van der Waals force, so it is difficult to disperse in many solvents.

[0004] Therefore, in order to make CNT dispersible in a solvent and enable various applications, an excellent dispersant that helps is required. For this reason, various dispersants have been developed.

[0005] For example, in a CNT-containing composition containing a conductive polymer, a dopant, CNT, water, and a dispersant, a CNT-containing composition in which the dispersant contains at least water-soluble xylan is disclosed (see, for example, Patent Document 1).

[0006] Furthermore, it has been found that by using water-soluble xylan, the affinity of a solvent for the surface of a poorly soluble or insoluble substance can be improved, and there is disclosed a solution containing water-soluble xylan, a substance, and a solvent, wherein the substance is poorly soluble or insoluble in the solvent in the absence of the water-soluble xylan (see, for example, Patent Document 2).

[0007] Also disclosed is a method for producing a CNT film on a substrate surface, the method including: preparing a solution containing CNT, a water-soluble solubilizer for solubilizing CNT, and an aqueous solvent, the solution having CNT dissolved therein; supplying this solution to the substrate surface; depositing CNT in the solution by evaporation of the solvent of the supplied solution to attach CNT to the substrate surface; and washing the substrate surface to which CNT has been attached with water, wherein the water-soluble solubilizer is water-soluble xylan having a property that when the concentration of the solubilizer is increased in a solution in which the water-soluble solubilizer is dissolved in the aqueous solvent, the solubility of CNT decreases beyond a certain concentration. And it has been shown that the water-soluble xylan is glucuronoxylan (see, for example, Patent Document 3).

[0008] Also, as a result of researchers including the present inventors discovering that 4-O-methylglucuronoxylan, which is a hemicellulose, has a function of dispersing hydrophobic substances in water and elucidating the dispersion mechanism of CNT, it is disclosed that a dispersion solution that is most suitable for dispersion in water and is stable for a long time has been developed (see, for example, Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0010]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] The invention described in Patent Document 1 uses water-soluble xylan as a dispersant, but it contains not only CNTs but also conductive polymers and dopants. Furthermore, it is stated that by including alcohol as a dispersant, more CNTs can be stably dispersed. However, the use of N-methylpyrrolidone as a dispersant is not disclosed.

[0012] The invention described in Patent Document 2 discloses a solution in which CNTs are dispersed in water using water-soluble xylan as a dispersant. And in the specification, an example of using glucuronoxylan as water-soluble xylan is disclosed. It is described that for water-soluble xylan, at a concentration of 0.2 mg / mL, the absorbance at a wavelength of 500 nm shows a maximum value, and the absorbance did not change even when the concentration of water-soluble xylan was increased thereafter. That is, when using water-soluble xylan, there is a problem that the dispersion concentration of CNTs in the dispersion liquid cannot be increased. Also, as the dispersion solvent, not only water but also a mixture of water and an organic solvent may be used, and NMP is described as an organic solvent, but there is no disclosure or suggestion about specific examples, nor is there any disclosure or suggestion about using it as a dispersant.

[0013] The invention described in Patent Document 3 is a method of forming a CNT film by using a solution in which CNTs are dissolved in an aqueous solvent with glucuronoxylan, which is a water-soluble xylan, applying this solution to the surface of a substrate, and then evaporating the water in the solution to increase the concentration of the water-soluble xylan. In this invention, it is disclosed that when the concentration of the water-soluble xylan is about 0.1%, the absorbance shows the maximum value, and when the concentration of the water-soluble xylan is increased beyond that, the absorbance decreases. That is, even if the concentration of the water-soluble xylan is simply increased with respect to the aqueous solvent, the result is that CNTs cannot be dispersed at a high concentration, and high-concentration dispersion is a problem.

[0014] In the invention described in Non-Patent Document 1, an example is shown in which, as an application to an electronic material, a dispersion liquid in which SWCNTs are dispersed using a natural product, water-soluble xylan, as a dispersant is prepared and used as a paint. However, in this disclosed example, there is no disclosure or suggestion regarding the use of a dispersant other than water-soluble xylan or a dispersion solvent other than water. In order to utilize CNTs in various applications, a dispersant and a dispersion liquid that can disperse CNTs at a high concentration in an aqueous dispersion liquid and can maintain a dispersed state stably for a long period of time are desired.

[0015] The present invention aims to provide a dispersant and a dispersion liquid that solve the conventional problem that CNTs cannot be dispersed at a high concentration with only glucuronoxylan by developing a dispersant in which N-methylpyrrolidone is further added to glucuronoxylan, which is one of the xylans.

Means for Solving the Problem

[0016] In order to solve the above conventional problems, the CNT dispersant of the present invention is characterized by comprising glucuronoxylan (hereinafter referred to as "GX") and N-methylpyrrolidone (hereinafter referred to as "NMP"). Commercially available products can be used for GX and NMP, and cases where a part of impurities is contained can also be tolerated.

[0017] The inventors investigated the influence of the concentration of GX in order to disperse CNTs at a high concentration. As a result, it was found that in order to disperse CNTs at a high concentration, it is necessary to increase the concentration of GX as well, but even if only GX is at a high concentration, CNTs cannot be dispersed at a high concentration. Therefore, next, various other dispersants were added to GX to examine the dispersibility of CNTs. As a result, it was found that by adding NMP, CNTs can be dispersed at a significantly higher concentration than before, and the present invention was completed.

[0018] In the above configuration, it is preferable that the mixing ratio of NMP is smaller than that of GX. Since GX is also used in food, it is an environmentally friendly material. On the other hand, NMP can also be mixed with water in any ratio, is chemically and thermally stable and non-corrosive, but since its boiling point is 202 °C, problems are likely to occur when making products using the dispersion liquid if a large amount is mixed. Also, NMP does not dissolve GX. For this reason, it is preferable to make it smaller than the mixing ratio of GX.

[0019] In the above configuration, GX may be contained in wood. For example, it is known that the main component of hemicellulose contained in hardwood is GX. GX is a xylose polymer to which 4-O-methylglucuronic acid residues and acetyl groups are bonded, and it may be extracted from wood or the like, or may be chemically synthesized.

[0020] In the above configuration, the CNT may be at least one of SWCNT and MWCNT. Although it is difficult to disperse SWCNT, a dispersion liquid uniformly dispersed at a sufficient concentration can be obtained by using the dispersant of the present invention. Also, when synthesizing CNTs, SWCNT, MWCNT, etc. are produced mixed, and they are purified as necessary. In the present invention, purified SWCNT or MWCNT is used, but even if trace amounts of different CNTs remain in them, they can be used. Also, depending on the application, CNTs actively mixed with SWCNT and MWCNT can also be used. Next, the CNT dispersion of the present invention comprises a dispersion solution composed of water, CNTs, and a dispersant, and is characterized in that the dispersant used is the CNT dispersant having the above configuration.

[0021] As the dispersion medium for CNTs, it is preferable to use water from the environmental aspect. However, if the dispersant of the present invention is used, it is environmentally friendly, and film formation using techniques such as coating is also easy.

[0022] In the above configuration, the CNT may be at least one of SWCNT and MWCNT. Although it is difficult to disperse SWCNT, a dispersion in which it is uniformly dispersed at a sufficient concentration can be obtained by using the dispersant of the present invention. When synthesizing CNTs, SWCNT and MWCNT are produced mixed, and they are purified as necessary. In the present invention, purified SWCNT or MWCNT is used, but even if trace amounts of different CNTs remain in them, they can be used. Also, depending on the application, CNTs obtained by positively mixing SWCNT and MWCNT may be used.

Advantages of the Invention

[0023] The CNT dispersant of the present invention and the CNT dispersion using the same have a great effect in a wide range of fields such as noise prevention in electronic devices, application to secondary batteries, and application to the semiconductor field.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0025] (Embodiment) Hereinafter, the CNT dispersant and the CNT dispersion of the embodiment of the present invention will be described in detail.

[0026] The inventors of the present invention examined various materials in order to obtain an aqueous dispersion in which CNTs are highly dispersed mainly with GX. As disclosed in Patent Document 2 and Patent Document 3, the addition concentration of CNTs varies depending on the concentration of water-soluble xylan, and the CNT concentration shows a maximum value when the water-soluble xylan concentration is about 0.2, and its relative absorbance is shown to be a small concentration of about 10 to 14.

[0027] The inventors of the present invention investigated the influence of the concentration of GX in order to disperse CNTs at a high concentration. As a result, in the case of an aqueous dispersion using GX, it was found that the amount of GX required varies depending on the CNTs used. For example, it was found that in order to disperse MWCNT at a concentration of 4 wt%, about 2 wt% of GX is required, and in order to disperse SWCNT at a concentration of 0.4 wt%, about 0.8 wt% of GX is required.

[0028] It was found that the specific surface area of SWCNT is larger than that of MWCNT, and the concentration of GX required is also affected by the surface state of CNTs. However, if the concentration of GX is simply increased in order to disperse CNTs at a high concentration, a phenomenon occurs in which GX itself takes water, which is a dispersion solution. For this reason, it was found that there is a limit to increasing the dispersion concentration of CNTs, and as a result, there is a limit to dispersing CNTs at a high concentration with a dispersant of only GX.

[0029] Therefore, an attempt was made to disperse CNTs at a high concentration by adding another dispersant to GX. As a result, the present invention was completed by finding that by adding NMP to GX, CNTs can be dispersed at a significantly higher concentration than before.

[0030] That is, the CNT dispersant of the present invention is characterized by comprising GX and NMP. And NMP is characterized in that its mixing ratio is smaller than that of GX. Further, the CNT is characterized by being at least one of SWCNT and MWCNT.

[0031] Next, the CNT dispersion of the present invention comprises a dispersion solution composed of water, carbon nanotubes, and a dispersant, and is characterized in that the dispersant is the above-mentioned one. In the above dispersion, further, the CNT is characterized by being at least one of SWCNT and MWCNT.

[0032] The GX used in the present invention is not a pure xylose polymer, but a molecule in which at least some of the hydroxyl groups in the xylose polymer are replaced by other substituents (for example, acetyl group, glucuronic acid residue, or arabinose residue, etc.).

[0033] What has a 4-O-methylglucuronic acid residue and an acetyl group bonded to the xylose polymer is generally called GX. It is known that the main component of hemicellulose contained in hardwood is GX, and it often has a composition ratio of 10 xylose residues: 1 4-O-methylglucuronic acid: 6 acetyl groups. GX is suitable because of its excellent characteristics as a dispersant. Note that GX extracted from natural sources and containing some different ones may be used, or highly purified GX may be used.

[0034] In the present invention, not only the above-mentioned glucuronoxylan but also arabinoglucuronoxylan, glucuronoarabinoxylan, and arabinoxylan can be used.

[0035] The NMP used in the present invention can be a commercially available one. NMP is a water-soluble, colorless and transparent liquid. It is a five-membered ring compound containing nitrogen, with a high polarity. It can be completely mixed with most organic solvents and has a high solubility in organic and inorganic substances. It can also be mixed with water in any ratio. It is chemically and thermally stable, but since its boiling point is as high as 202 °C, NMP may remain if the processing conditions are not properly selected when manufacturing products using a CNT dispersion. Therefore, considering manufacturing products using a CNT dispersion, it is desirable that the addition amount of NMP be less than that of GX. (Example 1)

[0036] In this Example 1, the CNT dispersant and CNT dispersion for dispersing SWCNT will be described. As the SWCNT, ZEONANO SG101 of Nippon Zeon Co., Ltd. (hereinafter referred to as "SWCNT1") and MEIJO eDIPS EC2.0P of Meijo Nano Carbon Co., Ltd. (hereinafter referred to as "SWCNT2") were used. SWCNT1 has a specific surface area of 800 m 2 / g or more, an average diameter of 3 to 5 nm, and a carbon purity of 99% or more. SWCNT2 has a central diameter of 2 to 3 nm and a carbon purity of 98% or more. Figure 1 shows the results of dispersing SWCNT1 by changing the weight percentage (wt%) with only GX as the dispersant. The horizontal axis represents the GX concentration, and the vertical axis represents the degree of dispersion.

[0037] The dispersibility test in Figure 1 was conducted as follows. SWCNT1 was added to 50 mL of an aqueous solution to which a predetermined amount of the dispersant GX was added, and dispersed using a 600 W ultrasonic homogenizer. That is, GX was added to the dispersion solution water in the addition amounts shown in Figure 1. SWCNT1 was added to this solution at (A) 0.1 wt%, (B) 0.2 wt%, (C) 0.4 wt% and (D) 0.6 wt%, and dispersed using a 600 W ultrasonic homogenizer. Then, it was separated using a centrifuge (himac CT18R) at 10000 G for 1 hour, and the supernatant was used as the sample. Using this supernatant, the absorbance at a wavelength of 500 nm was measured with an ultraviolet-visible spectrophotometer UV-1900 (manufactured by Shimadzu Corporation), and the value obtained using the measured absorbance was defined as the degree of dispersion.

[0038] When the GX concentration was low, the dispersion degree of SWCNT1 was low, and as the GX concentration increased, the dispersion degree increased. However, the dispersion degree of SWCNT1 tended to saturate when the GX concentration was increased. For example, it was found that even when 0.4 wt% of SWCNT1 was added, the dispersion degree saturated at about 250, indicating that not all of the added SWCNT1 was sufficiently dispersed. Also, when 0.6 wt% of SWCNT1 was added, the dispersion degree was larger than when 0.4 wt% was added, but it was found to saturate at about 320. That is, when only GX was used as the dispersant, it was found that the dispersion degree of SWCNT1 could not be increased even by increasing the GX concentration. Note that the concentrations of GX, NMP, and SWCNT1 are shown as weight percentages when the CNT dispersion liquid is set to 100. The same applies hereinafter.

[0039] Figure 2 shows the results of measuring the dispersion degree by changing the GX concentration to 1.2 wt%, 1.6 wt%, and 2.4 wt% with respect to water as the dispersion solution, adding 0.5 wt% of NMP, and then adding 0.6 wt%, 0.8 wt%, and 1.0 wt% of SWCNT1 respectively, and performing the same operations as in the case of Figure 1.

[0040] As can be seen from Figure 2, it was found that if 0.5 wt% of NMP was added, the dispersion degree of SWCNT1 was greatly improved even when the GX concentration was increased. In Figure 2, (E) is the case where 0.6 wt% of SWCNT1 was added to a dispersion liquid with a GX concentration of 1.2 wt% and 0.5 wt% of NMP added, and the dispersion degree was 420. (F) is the case where 0.8 wt% of SWCNT1 was added to a dispersion liquid with a GX concentration of 1.6 wt% and 0.5 wt% of NMP added, and the dispersion degree was 515. (G) is the case where 1.0 wt% of SWCNT1 was added to a dispersion liquid with a GX concentration of 2.4 wt% and 0.5 wt% of NMP added, and the dispersion degree was 670.

[0041] As a result, it was found that for the liquid with 2.4 wt% of GX added and 0.5 wt% of NMP added, even when 1.0 wt% of SWCNT1 was added, good dispersibility was shown.

[0042] Table 1 shows the results of measuring the dispersibility and viscosity depending on the presence or absence of NMP addition when using SWCNT1. The viscosity was measured using an SV-type viscometer SV-1A (manufactured by A&D Company, Limited). This viscometer is of the tuning fork vibration type, which resonates the vibrator in the liquid and obtains the viscosity from the exciting force required to move the vibrator at a constant amplitude.

[0043] Based on the results of the viscosity measurement, the evaluation of dispersibility was as follows: when the measured viscosity was less than 1000 mPa·s and the CNT dispersion liquid was easily deformable, it was marked as ○; when the viscosity was 1000 mPa·s or more or the CNT dispersion liquid did not deform and appeared to be in a solid state visually, it was marked as ×.

[0044]

Table 1

[0045] As can be seen from Table 1, when only GX was used as the dispersant, the viscosity exceeded 1000 mPa·s under all conditions, and the dispersibility evaluation was also ×. On the other hand, when NMP was added, the dispersibility evaluation was ○ under all conditions.

[0046] When 1.2 wt% of GX, 0.3 wt% of NMP, and 0.6 wt% of SWCNT1 were used as the dispersants, the viscosity was 20 mPa·s. When GX was 1.2 wt% and NMP was 0.5 wt%, even when SWCNT1 was 0.6 wt%, the viscosity was 18 mPa·s, resulting in a slightly lower value.

[0047] When SWCNT1 was 0.8 wt%, GX was 1.6 wt%, and the addition amounts of NMP were 0.4 wt% and 0.5 wt% respectively, the viscosities were 40 mPa·s and 38 mPa·s respectively. Also, when SWCNT1 was 1.0 wt%, GX was 2.0 wt%, and the addition amount of NMP was 0.5 wt%, the viscosity became 130 mPa·s.

[0048] From these results, it was found that by adding NMP, the viscosity could be significantly reduced and the dispersibility could be improved. Incidentally, when SWCNT1 was 1.0 wt%, GX was 2.0 wt%, and NMP was 0.5 wt%, the viscosity was 130 mPa·s, but this was a sufficient viscosity for manufacturing the product.

[0049] Table 2 is a table showing the viscosity and dispersibility evaluation results when using SWCNT2. Since the methods for measuring viscosity and evaluating dispersibility are the same as those for SWCNT1, the explanation is omitted.

[0050]

Table 2

[0051] In Table 2, a comparative evaluation was conducted with the total weight percentage of GX and NMP as the dispersant being the same. That is, when SWCNT2 was 0.6 wt%, when no NMP was added, GX was 1.7 wt%, when 0.3 wt% of NMP was added, GX was 1.4 wt%, and when 0.5 wt% of NMP was added, 1.2 wt% of GX was added. As a result, when no NMP was added, the viscosity was 1000 mPa·s or more, and the dispersibility evaluation was also ×. However, when 0.3 wt% of NMP was added, the viscosity was 210 mPa·s, and the dispersibility evaluation was ○. Furthermore, when 0.5 wt% of NMP was added, the viscosity was 150 mPa·s, and the dispersibility evaluation was ○. Also, similar to Table 1, the result that the viscosity decreased as the addition amount of NMP increased was obtained.

[0052] When SWCNT2 was 1.0 wt%, GX was 2.5 wt%, and NMP was 1.0 wt%, the viscosity was 680 mPa s and the dispersibility was evaluated as good. When GX was 2.0 wt% and NMP was 1.5 wt%, the viscosity was 420 mPa s and the dispersibility was evaluated as good.

[0053] These results indicate that when the concentration of GX is increased, by also increasing the concentration of NMP, SWCNT2 can be dispersed at a high concentration and the dispersion can have a viscosity sufficient for use. As described above, it was confirmed that in order to disperse SWCNTs at a high concentration, not only GX but also a dispersant containing NMP was highly effective.

[0054] The preferred range of GX concentration is 0.01 to 10 wt%, and the preferred range of NMP concentration within this range is at least lower than the concentration of GX, and is preferably 0.01 to 5 wt%. The reason is that if the concentration exceeds 5 wt%, NMP acts as a solvent and its function as a dispersant decreases. Also, since GX does not dissolve in NMP, it is difficult to improve dispersibility even if an excess of NMP is added.

[0055] Furthermore, adding only GX at a high concentration causes gelation, making it impossible to prepare a high-concentration dispersion with good fluidity. Adding NMP improves this. As mentioned above, adding NMP can significantly improve dispersibility. In the case of a dispersant containing only GX, the interaction between water and GX-CNT is large, which causes gelation. In contrast, adding NMP weakens this interaction, suppressing gelation and improving the degree of dispersion.

[0056] Furthermore, when dispersing CNTs using a conventional dispersant, it was necessary to repeat mechanical dispersion, and many breakages of CNTs occurred. However, in this example, although an ultrasonic homogenizer is used, sufficient dispersibility can be obtained under softer dispersion conditions than in the past. As a result, it became possible to disperse the CNTs without destruction while maintaining the initial length. This has been confirmed by observing the dispersed CNTs with an SEM (scanning electron microscope). The addition of NMP makes the dispersing power of the CNTs by the dispersant stronger, and sufficient dispersion can be achieved with a weaker force than in the past when dispersing using a machine. Therefore, breakage of the CNTs can be suppressed, and they can be dispersed while maintaining the initial length. (Example 2)

[0057] In this Example 2, the dispersant and the dispersion liquid when dispersing MWCNTs will be described. In this example, as the MWCNT, NC7000 of Nanocyl (hereinafter referred to as "MWCNT1") was used. MWCNT1 has an average diameter of 9.5 nm, an average length of 1.5 μm, a specific surface area of 250 - 300 m 2 / g, and a purity of 90%. Compared with SWCNT1 and SWCNT2, it has a larger average diameter and a lower purity. Table 3 shows the results of evaluating the dispersibility of CNT dispersions prepared by changing the concentration of GX and varying the concentration of MWCNT1.

[0058]

Table 3

[0059] Each dispersion liquid was prepared as follows. An aqueous solution with the GX concentration shown in Table 3 was added to water, which is the dispersion solution, to prepare an aqueous solution. MWCNT1 was added to these aqueous solutions and dispersed using a 600 W ultrasonic homogenizer. Since the method for measuring the viscosity of the dispersion liquid and the method for evaluating the dispersibility were the same as those in Example 1, the description will be omitted.

[0060] As can be seen from Table 3, in the dispersibility evaluation of MWCNT1, there is an optimum value for the concentration of GX. MWCNT1 can be dispersed at 3.8 wt% when the concentration of GX is near 1.9 wt%, but the dispersibility evaluation becomes "×" when it is more than that. From this result, it was found that with only GX as the dispersant, MWCNT1 can only be dispersed to about 3.8 wt%. Table 4 is a table showing the effect of adding NMP.

[0061]

Table 4

[0062] Table 4 evaluated the viscosity and dispersibility of MWCNT1 using GX and NMP as dispersants while keeping the total addition amount the same. For example, when MWCNT1 was 8 wt% and only GX was 4.2 wt%, when GX was 3.7 wt% and NMP was 0.5 wt%, and when GX was 3.2 wt% and NMP was 1.0 wt%, the viscosity and dispersibility were evaluated for each case. As a result, when only GX was used, the viscosity was 1000 mPa·s or higher, but when 0.5 wt% of NMP was added, the viscosity was 340 mPa·s, and when 1.0 wt% of NMP was further added, the viscosity became 240 mPa·s. The dispersibility evaluation was "×" when only GX was used, but "〇" for the others.

[0063] Furthermore, when MWCNT1 was 10 wt% and only GX was 6.0 wt%, when GX was 5.0 wt% and NMP was 1.0 wt%, and when GX was 4.0 wt% and NMP was 2.0 wt%, the viscosity and dispersibility were evaluated for each case. As a result, when only GX was used, the viscosity was 1000 mPa·s or higher, but when 1.0 wt% of NMP was added, the viscosity was 760 mPa·s, and when 2.0 wt% of NMP was further added, the viscosity became 370 mPa·s. Note that the dispersibility evaluation was "×" when only GX was used, but "〇" for the others.

[0064] The viscosity increases as the addition amount of MWCNT1 increases. However, even when 10 wt% of MWCNT1 is added, a viscosity of 760 mPa·s can be obtained, and various products can be manufactured with this viscosity. Furthermore, although the viscosity increases as the addition amount of MWCNT1 increases, it was found that the addition of NMP can suppress the increase in viscosity. As described above, it was found that in addition to GX, adding NMP to MWCNT1 enables high-concentration dispersion.

[0065] In Examples 1 and 2, the cases of using SWCNT and MWCNT were described, but the present invention is not limited thereto. For example, even CNTs in which SWCNT and MWCNT are mixed can be dispersed at a high concentration.

[0066] Furthermore, the dispersion liquid using the dispersant of the present invention can have a lower resistance than conventional ones in transparent conductive films, antistatic agents, etc., and thus can be widely used in the field of electronic materials.

Industrial Applicability

[0067] The CNT dispersant and CNT dispersion liquid of the present invention have a great effect in a wide range of fields such as noise prevention of electronic devices, application to secondary batteries, and application to the semiconductor field.

Claims

1. A carbon nanotube dispersant characterized by comprising glucuronoxylan and N-methylpyrrolidone.

2. The carbon nanotube dispersant according to Claim 1, wherein the mixing ratio of the N-methylpyrrolidone is smaller than that of the glucuronoxylan.

3. The carbon nanotube dispersant according to Claim 1, wherein the carbon nanotubes are at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

4. A carbon nanotube dispersion liquid comprising a dispersion solution composed of water, carbon nanotubes, and a dispersant, wherein the dispersant is the carbon nanotube dispersant according to any one of Claims 1 to 3.

5. The carbon nanotube dispersion liquid according to Claim 4, wherein the carbon nanotubes are at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

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