Carbon nanotube dispersion and method for producing the same

Abstract

To provide a carbon nanotube dispersion having carbon nanotubes having relatively large average diameter and length even in a dispersed state.SOLUTION: In the carbon nanotube dispersion, the carbon nanotubes in a dispersed state have a mean particle size larger than that of the 30nm portion and a mean length of 1 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a carbon nanotube dispersion and a method for producing the same. [Background technology]

[0002] Carbon nanotubes (hereinafter also referred to as "CNTs") are excellent in thermal conductivity, electrical conductivity, mechanical strength, and the like, and are therefore expected to be used in a variety of applications in a wide range of fields.

[0003] CNT synthesis processes include arc discharge, laser evaporation, and chemical vapor deposition (hereinafter also referred to as "CVD"), among which CVD is mainly used industrially from the viewpoint of mass production.

[0004] In this regard, the CNTs produced are in a bundle state consisting of multiple CNTs due to van der Waals forces, and even if single CNTs are mixed into resin, etc., the dispersion will be uneven, making it difficult to impart the properties of CNTs to the material. Therefore, one method is to dissolve the CNTs in a solution using a dispersant, and then mix the CNT dispersion, in which the CNTs are uniformly dispersed in the solvent, with a base material (material) such as resin, thereby dispersing the CNTs uniformly throughout the material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-175699 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, the inventors of the present application have newly discovered the following point. According to conventional technical common knowledge, the average diameter and average length of carbon nanotubes are generally only around 10 nm and a few μm or less, respectively. In contrast, if the average diameter and length of carbon nanotubes before dispersion are relatively large (i.e., if the carbon nanotubes are thick and long), depending on the carbon nanotube dispersion method, the carbon nanotubes are likely to break, and in the dispersed state, i.e., in the dispersed state, the length is likely to be significantly shorter than before dispersion. As a result, there is a risk that high conductivity, etc., cannot be imparted.

[0007] Therefore, an object of the present disclosure is to provide a carbon nanotube dispersion containing carbon nanotubes with relatively large average diameters and lengths even in a dispersed state, and a method for producing the same. [Means for solving the problem]

[0008] In order to achieve the above object, the present disclosure provides: carbon nanotubes, a solvent, and a dispersant; A carbon nanotube dispersion is provided, wherein the carbon nanotubes in the dispersed state have an average diameter greater than 30 nm and an average length greater than or equal to 1 μm.

[0009] In order to achieve the above object, the present disclosure provides: A first step of preparing a solution containing a dispersant, a solvent, and carbon nanotubes; a second step of supplying the solution to a dispersing device and dispersing the carbon nanotubes in the solution; A method for producing a carbon nanotube dispersion is provided, comprising: [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a carbon nanotube dispersion having carbon nanotubes with a relatively large average diameter and length even in a dispersed state. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a carbon nanotube dispersion according to the present disclosure. [Figure 2] 1 is a schematic diagram of a carbon nanotube dispersion having carbon nanotubes with low dispersibility. [Figure 3] This is a schematic diagram of thick and long carbon nanotubes dispersed in a base material. [Figure 4] This is a schematic diagram of thin and short carbon nanotubes dispersed in a base material. [Figure 5] FIG. 2 is a schematic diagram showing the flow of a method for producing a carbon nanotube dispersion. DETAILED DESCRIPTION OF THE INVENTION

[0012] The carbon nanotube dispersion and its manufacturing method according to the present disclosure will be described below with reference to the drawings. The various elements in the drawings are merely shown as schematic and illustrative examples for the purpose of explaining the present disclosure, and the appearances and dimensional ratios may differ from those of the actual objects.

[0013] Fig. 1 is a schematic diagram of a carbon nanotube dispersion according to the present disclosure. As shown in Fig. 1, a carbon nanotube dispersion 10 according to the present disclosure contains carbon nanotubes 1, a solvent, and a dispersant. The carbon nanotubes 1 are dispersed in a solution 2 containing the dispersant and the solvent.

[0014] Furthermore, in the present disclosure, the carbon nanotubes 1 in a dispersed state have an average diameter greater than 30 nm and an average length of 1 μm or more. According to conventional common technical knowledge, the average diameter and average length of carbon nanotubes are generally only around 10 nm and a few μm or less, respectively. Therefore, in the conventional carbon nanotube dispersion 10′, thin and short carbon nanotubes 1′ may be entangled with each other in the solution 2′ (see FIG. 2).

[0015] In this regard, in the present disclosure, even in a dispersed state, the carbon nanotubes can have a relatively large average diameter and average length that exceed the above-mentioned common sense, i.e., even in a dispersed state, thick and long carbon nanotubes can be obtained.

[0016] In order for carbon nanotubes to impart conductivity to a base material 50 such as a resin, multiple carbon nanotubes must be overlapped and continuous. In this regard, when a carbon nanotube dispersion is mixed into the base material 50, if thick and long carbon nanotubes 1 are dispersed in the base material 50 (see FIG. 3), the number of overlapping points is reduced compared to when relatively thin and short carbon nanotubes 1' overlap each other (see FIG. 4), thereby reducing contact resistance. This makes it possible to ensure desired properties such as conductivity.

[0017] In other words, it is possible to ensure desired properties such as electrical conductivity while reducing the number of carbon nanotubes in the carbon nanotube dispersion, which means that it is possible to improve the consumption efficiency of carbon nanotubes while also providing desired properties such as electrical conductivity.

[0018] In the present disclosure, the average length of the carbon nanotubes 1 in a dispersed state is greater than 5 μm. Furthermore, the longest length of the carbon nanotubes 1 in a dispersed state is 30 μm or more. In this case, the average length of the carbon nanotubes 1 in a dispersed state is greater than 10 μm. The carbon nanotube dispersion 10 of the present disclosure contains 10 parts by mass or more and 200 parts by mass or less of a dispersant per 100 parts by mass of carbon nanotubes. Furthermore, in the present disclosure, the carbon nanotube concentration can be 0.1 wt% or more and 15 wt% or less.

[0019] A method for producing the carbon nanotube dispersion 10 of the present disclosure will now be described (see FIG. 5). Specifically, the manufacturing method of the present disclosure includes: a first step of preparing a solution containing a dispersant, a solvent, and carbon nanotubes; a second step of supplying the solution to a dispersing device and dispersing the carbon nanotubes in the solution; Includes.

[0020] That is, before dispersing the carbon nanotubes in the solution in the dispersing device, a solution containing a dispersant, a solvent, and the carbon nanotubes is prepared.

[0021] In particular, the first step is Providing a first solution having a dispersant and a solvent; mixing the first solution with the carbon nanotubes to form a second solution; It is characterized in that it includes:

[0022] As the dispersing device, an ultrasonic homogenizer, a high-pressure homogenizer, a bead mill, a jet mill, or the like can be used.

[0023] By undergoing the above process, it is possible to prevent the carbon nanotubes from breaking and becoming significantly shorter than their pre-dispersion length when dispersed in a dispersing device. As a result, the carbon nanotubes can have relatively large average diameters and lengths that exceed the above-mentioned common sense when dispersed in a dispersing device. In other words, thick and long carbon nanotubes can be obtained even in a dispersed state.

[0024] This makes it possible to reduce the number of overlapping points while ensuring desired properties such as conductivity, compared to when relatively thin and short carbon nanotubes overlap each other in a base material such as a resin into which a carbon nanotube dispersion is mixed. [Example]

[0025] Hereinafter, examples of the present disclosure will be described.

[0026] Example 1 First, a water-soluble polymer dispersant was placed in a solvent (water) in a container (a glass bottle with a lid) and stirred to prepare a dispersant-containing solution (corresponding to the first solution described above). Note that a solution in which the dispersant is already dissolved may also be used as the first solution. A mixer, stirrer, disperser, etc. may be used for the stirring.

[0027] Thereafter, the first solution and the carbon nanotubes were mixed using a mixer or the like to prepare a second solution, which was prepared so that 100 parts by mass of the carbon nanotubes contained 25 to 200 parts by mass of the dispersant, and 99.9 parts by mass of the solution contained 0.1 part by mass of the carbon nanotubes.

[0028] The second solution was then fed into a dispersing device, and the carbon nanotubes were dispersed in the second solution using the dispersing device. The solution was then allowed to stand. Examples of dispersing devices that can be used include an ultrasonic homogenizer, a high-pressure homogenizer, a bead mill, and a jet mill. As a result, a carbon nanotube dispersion (CNT concentration 0.1 wt%) of Example 1 was obtained (see FIG. 5).

[0029] Resistance measurement The carbon nanotube dispersion was then mixed with a resin material to prepare a carbon nanotube-containing resin composition. Specifically, the carbon nanotube dispersion was mixed with an aqueous acrylic resin emulsion (manufactured by Covestro, product number: Neo Cryl XK-190) so that the carbon nanotube content concentration after drying was 0.5 wt %, thereby preparing a carbon nanotube-containing resin composition. The prepared resin composition was then applied to a resin film and dried for a predetermined time to prepare a laminated film with the carbon nanotube-containing resin composition applied to its surface.

[0030] The resistance [Ω] of the carbon nanotube-containing resin composition of this laminated film was measured using a four-terminal four-probe method. Alternatively, a resistivity meter using a constant current application method could also be used. The film thickness was measured using a micrometer.

[0031] Carbon nanotube length measurement First, an aluminum substrate was immersed in the obtained carbon nanotube dispersion, and then the immersed aluminum substrate was dried. After drying, the longitudinal lengths of multiple (20) carbon nanotubes located on the surface of the aluminum substrate were measured using a microscope to calculate the longest length and average length.

[0032] Carbon nanotube diameter measurement The average diameter of the carbon nanotubes used was measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The average diameter of the carbon nanotubes was obtained by measuring the diameters of multiple (20) carbon nanotubes located on the surface of the dried aluminum substrate using a microscope and calculating the average value.

[0033] Example 2 Example 2 is an example carried out in the same procedure as Example 1. In the same procedure as Example 1, the resistance, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured.

[0034] Example 3 Example 3 differs from Examples 1 and 2 in that a carbon nanotube dispersion (CNT concentration 1.0 wt % / dispersant concentration 1.0 wt %) was obtained.

[0035] Specifically, a water-soluble polymer-based dispersant was placed in a solvent (water) in a container (a glass bottle with a lid) and stirred to prepare a dispersant-containing solution (corresponding to the first solution described above).

[0036] Thereafter, the first solution and the carbon nanotubes were mixed using a mixer or the like to prepare a second solution, which was prepared so that 100 parts by mass of the carbon nanotubes contained 100 parts by mass of the dispersant, and 99 parts by mass of the solution contained 1 part by mass of the carbon nanotubes.

[0037] Thereafter, the second solution was supplied into the dispersing device, and the carbon nanotubes were dispersed in the second solution using the dispersing device, as in Example 1. The mixture was then allowed to stand. As a result, a carbon nanotube dispersion (CNT concentration 1.0 wt% / dispersant concentration 1.0 wt%) of Example 3 was obtained.

[0038] Thereafter, in the same manner as in Example 1, the resistance, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured.

[0039] Example 4 Example 4 is an example carried out in the same procedure as Example 3. In the same procedure as Example 1, the resistance, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured.

[0040] Example 5 Example 5 differs from Examples 1 to 4 in that an organic solvent was used instead of water as the solvent to obtain a carbon nanotube dispersion (CNT concentration 0.5 wt % / dispersant concentration 0.125 wt %).

[0041] Specifically, a non-polar polymer dispersant was placed in an organic solvent (methyl ethyl ketone solution) in a container (a glass bottle with a lid) and stirred to prepare a dispersant-containing solution (corresponding to the first solution described above).

[0042] Thereafter, the first solution and the carbon nanotubes were mixed using a mixer or the like to prepare a second solution, which was prepared so that the second solution contained 99.5 parts by mass of the dispersant-containing solution and 0.5 parts by mass of the carbon nanotubes.

[0043] The second solution was then fed into a dispersing device, and the carbon nanotubes were dispersed in the second solution using the dispersing device. The solution was then allowed to stand. Examples of dispersing devices that can be used include an ultrasonic homogenizer, a high-pressure homogenizer, a bead mill, and a jet mill. As a result, the carbon nanotube dispersion of Example 1 (CNT concentration: 0.5 wt%) was obtained.

[0044] Thereafter, the resistance, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured in the same manner as in Example 1. In Example 5, when measuring the resistance, the obtained carbon nanotube dispersion was mixed with an acrylic resin (manufactured by DIC Corporation, product number: Acrydic A-166) so that the carbon nanotube content concentration after drying was 5 wt %, thereby preparing a carbon nanotube-containing resin composition.

[0045] Example 6 Example 6 differs from Example 5 in that a carbon nanotube dispersion (CNT concentration 1.0 wt %) was obtained on the premise that the same organic solvent as in Example 6 was used as the solvent.

[0046] Specifically, a non-polar polymer dispersant was placed in an organic solvent (methyl ethyl ketone solution) in a container (a glass bottle with a lid) and stirred to prepare a dispersant-containing solution (corresponding to the first solution described above).

[0047] Thereafter, the first solution and the carbon nanotubes were mixed using a mixer or the like to prepare a second solution, which was prepared so that 100 parts by mass of carbon nanotubes contained 25 parts by mass of the dispersant, and 99 parts by mass of the solution contained 1 part by mass of carbon nanotubes.

[0048] Thereafter, the second solution was supplied into the dispersing device, and the carbon nanotubes were dispersed in the second solution using the dispersing device, as in Example 1. The mixture was then allowed to stand. As a result, a carbon nanotube dispersion of Example 6 (CNT concentration 1 wt% / dispersant concentration 0.25 wt%) was obtained.

[0049] Thereafter, in the same manner as in Example 5, the volume resistivity, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured.

[0050] Example 7 Example 7 differs from Example 6 in that a carbon nanotube dispersion (CNT concentration 2.0 wt% / dispersant concentration 0.5 wt%) was obtained on the premise that the same organic solvent as in Example 6 was used as the solvent.

[0051] Specifically, the non-polar polymer dispersant was placed in an organic solvent (methyl ethyl ketone solution) in a container (a glass bottle with a lid) and stirred to prepare a dispersant-containing solution (corresponding to the first solution).

[0052] Thereafter, the first solution and the carbon nanotubes were mixed using a mixer or the like to prepare a second solution, which was prepared so that 100 parts by mass of carbon nanotubes contained 25 parts by mass of the dispersant, and 98 parts by mass of the solution contained 2 parts by mass of carbon nanotubes.

[0053] Thereafter, the second solution was supplied into the dispersing device, and the carbon nanotubes were dispersed in the second solution using the dispersing device, as in Example 1. The mixture was then allowed to stand. As a result, a carbon nanotube dispersion of Example 7 (CNT concentration 2.0 wt% / dispersant concentration 0.5 wt%) was obtained.

[0054] Thereafter, in the same manner as in Example 6, the volume resistivity, the length of the carbon nanotubes, and the average diameter of the carbon nanotubes were measured.

[0055] The measurement results of Examples 1 to 7 are shown in Table 1. [Table 1]

[0056] One of the purposes of mixing CNTs into materials is to prevent static electricity. According to "JIS C 2170:2004 Test method for resistance and resistivity of solid planar materials that prevent static charge accumulation," a resistance of 10 4 ~10 12 The value of Ω is shown. Therefore, the resistance is 10 12 If the resistance is below Ω, it is understood that conductivity is exhibited.

[0057] In this regard, the measurement results in Table 1 above show that when the dispersed carbon nanotubes have an average diameter greater than 30 nm and an average length of 1 μm or more, that is, when they are thick and long, the resistance can be increased by 10 times compared to conventional carbon nanotubes whose average diameter and average length are 30 nm or less and a few μm or less, respectively. 12 It was found that it was possible to keep it below Ω.

[0058] Furthermore, the reduction of the volume resistivity to a predetermined value or less means that thick and long carbon nanotubes have been uniformly dispersed. According to the common technical knowledge of those skilled in the art, thick and long carbon nanotubes are known to be difficult to disperse in a solution due to their size. Therefore, it is generally understood that when thick and long carbon nanotubes are used, there is a large amount of overlap between the carbon nanotubes in the carbon nanotube dispersion.

[0059] In this regard, it is believed that the uniform dispersion of thick and long carbon nanotubes in this study has reduced the overlap of carbon nanotubes in the carbon nanotube dispersion, which has contributed to the reduction of the volume resistivity to a predetermined value or less, even when thick and long carbon nanotubes are used, as described above.

[0060] It was found that such a reduction in volume resistivity makes it possible to improve the conductivity, etc., imparted to the base material by a plurality of thick and long carbon nanotubes. It was also found that, compared to the case where relatively thin and short carbon nanotubes are used, the desired conductivity can be imparted even if the number of carbon nanotubes in the carbon nanotube dispersion is reduced. From the above, it was found that it is possible to achieve both improved carbon nanotube consumption efficiency and the provision of desired properties such as conductivity.

[0061] The above describes the carbon nanotube dispersion and its manufacturing method of the present disclosure, but the present disclosure is not limited to this, and various modifications based on the knowledge of those skilled in the art are possible as long as they do not deviate from the spirit of the claims.

[0062] The present disclosure may include the following aspects. <1> carbon nanotubes, a solvent, and a dispersant; A carbon nanotube dispersion, wherein the carbon nanotubes in a dispersed state have an average diameter greater than 30 nm and an average length of 1 μm or more. <2> The average length of the carbon nanotubes in a dispersed state is greater than 5 μm. <1> The carbon nanotube dispersion according to claim 1. <3> The average length of the carbon nanotubes in a dispersed state is greater than 10 μm. <1> The carbon nanotube dispersion according to claim 1. <4> The maximum length of the carbon nanotubes in a dispersed state is 30 μm or more. <3> The carbon nanotube dispersion according to claim 1. <5> The dispersant is present in an amount of 10 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the carbon nanotubes. <1> ~ <4> 1. The carbon nanotube dispersion according to any one of the preceding items. <6> The carbon nanotube concentration is 0.1 wt% or more and 15 wt% or less. <1> ~ <5> 1. The carbon nanotube dispersion according to any one of the preceding items. <7> A first step of preparing a solution containing a dispersant, a solvent, and carbon nanotubes; a second step of supplying the solution to a dispersing device and dispersing the carbon nanotubes in the solution; A method for producing a carbon nanotube dispersion, comprising: <8> The first step providing a first solution having the dispersant and the solvent; mixing the first solution with carbon nanotubes to prepare a second solution; Including, <7> The manufacturing method described in <9> preparing the solution containing the dispersant, the solvent, and the carbon nanotubes before dispersing the carbon nanotubes in the solution in the dispersing device; <7> or <8> The manufacturing method described in [Industrial Applicability]

[0063] The carbon nanotube dispersion of the present disclosure can be used to impart electrical conductivity and the like. [Explanation of symbols]

[0064] 50, 50' Base material (resin, etc.) 10,10' carbon nanotube dispersion 2, 2' solution 1,1' carbon nanotubes

Claims

1. carbon nanotubes, a solvent, and a dispersant; A carbon nanotube dispersion, wherein the carbon nanotubes in a dispersed state have an average diameter greater than 30 nm and an average length of 1 μm or more.

2. 2. The carbon nanotube dispersion according to claim 1, wherein the average length of the carbon nanotubes in a dispersed state is greater than 5 μm.

3. 2. The carbon nanotube dispersion according to claim 1, wherein the average length of the carbon nanotubes in a dispersed state is greater than 10 μm.

4. 4. The carbon nanotube dispersion according to claim 3, wherein the carbon nanotubes in a dispersed state have a maximum length of 30 μm or more.

5. The carbon nanotube dispersion according to claim 1 , comprising 10 parts by mass or more and 200 parts by mass or less of the dispersant relative to 100 parts by mass of the carbon nanotubes.

6. 2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotube concentration is 0.1 wt % or more and 15 wt % or less.

7. A first step of preparing a solution containing a dispersant, a solvent, and carbon nanotubes; a second step of supplying the solution to a dispersing device and dispersing the carbon nanotubes in the solution; A method for producing a carbon nanotube dispersion, comprising:

8. The first step providing a first solution having the dispersant and the solvent; mixing the first solution with carbon nanotubes to form a second solution; The method of claim 7, comprising:

9. The manufacturing method according to claim 7 , further comprising preparing the solution containing the dispersant, the solvent, and the carbon nanotubes before dispersing the carbon nanotubes in the solution in the dispersing device.

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