Carbon nanotube assembly, carbon nanotube dispersion, conductive material, electrode, secondary battery, planar assembly, filter, electromagnetic wave shield, and extreme-ultraviolet pellicle

Abstract

To provide a carbon nanotube assembly which exhibits excellent dispersibility in the form of a carbon nanotube dispersion and which is capable of producing a carbon nanotube dispersion having an appropriate viscosity, and an application thereof.SOLUTION: A carbon nanotube assembly, a carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic wave shield, and an extreme-ultraviolet pellicle which satisfy the conditions (1) and (2). (1) The peak intensity ratio G1 / D1, which is the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in a Raman spectrum of carbon nanotubes, is 0.70-10.0, and the ratio of the peak area ratio G2 / D2, which is the ratio of the peak area G2 of the G band to the peak area D2 of the D band, to the peak intensity ratio G1 / D1 is 1.20-3.00. (2) The BET specific surface area of carbon nanotubes is 100 m2 / g to 300 m2 / g.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a carbon nanotube aggregate, a carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar aggregate, a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays. [Background technology]

[0002] Carbon nanotubes are substances with a cylindrical structure formed by rolling up graphene sheets in which carbon atoms are arranged in a hexagonal honeycomb pattern. Carbon nanotubes are basically broadly classified into single-walled carbon nanotubes formed from a single layer of graphene sheets and multi-walled carbon nanotubes formed from multiple layers of graphene sheets. Carbon nanotubes have good mechanical and electronic properties and are expected to be used in a variety of applications. In recent years, various attempts have been proposed to further improve the properties of carbon nanotubes.

[0003] For example, Patent Document 1 relates to a method for manufacturing a catalyst support for an anode of a direct methanol fuel cell, and discloses a method for manufacturing N,P-CNTs by mixing nitrogen-doped carbon nanotubes with a P-containing material. The resulting CNTs are said to improve the conductivity and stability of the catalyst support. Patent Document 2 discloses a carbon nanotube dispersion liquid having high dispersibility and elastic modulus, in which the ratio of peak intensity G to peak intensity D in the Raman spectrum of CNTs, G / D ratio, is 5 to 100, a predetermined amount of dispersant is contained, and the BET specific surface area of ​​the CNTs is 550 to 1200 m 2 / g of CNT dispersion is disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Chinese Patent Publication No. 114620712 [Patent Document 2] Japanese Patent Publication No. 2022-63234 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment of the present disclosure is to provide an aggregate of carbon nanotubes that has excellent dispersibility when made into a carbon nanotube dispersion, and from which a carbon nanotube dispersion with an appropriate viscosity can be obtained. The problem to be solved by another embodiment of the present disclosure is to provide a carbon nanotube dispersion liquid that contains the above-mentioned carbon nanotube aggregate, has excellent dispersibility of the carbon nanotube aggregate in a dispersion medium, and has an appropriate viscosity. Another problem to be solved by another embodiment of the present disclosure is to provide a conductive material, an electrode, and a secondary battery that include the carbon nanotube aggregate. The problem to be solved by another embodiment of the present disclosure is the above-mentioned carbon nanotube aggregate, wherein the carbon nanotube aggregate is a planar aggregate including carbon nanotubes having a maximum length of 1000 μm to 30000 μm. Another problem to be solved by another embodiment of the present disclosure is to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays using the above-mentioned planar assembly. [Means for solving the problem]

[0006] <1> An aggregate of carbon nanotubes that satisfies the following conditions (1) and (2): (1) The peak intensity ratio G1 / D1, which is the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum of the carbon nanotube, is 0.70 to 10.0; The ratio of the peak area ratio G2 / D2, which is the ratio of the peak area G2 of the G band to the peak area D2 of the D band, to the peak intensity ratio G1 / D1 is 1.20 to 3.00. (2) The BET specific surface area of ​​carbon nanotubes is 100m 2 / g~300m 2 / g. <2> The ratio of the peak area ratio G2 / D2 to the peak intensity ratio G1 / D1 in the Raman spectrum of the carbon nanotube is 1.20 to 2.50; <1> The carbon nanotube aggregate according to claim 1. <3> BET specific surface area is 100m 2 / g~420m 2 / g, <1> or <2> The carbon nanotube aggregate according to claim 1. <4> <1> ~ <3> 1. A carbon nanotube dispersion liquid comprising the aggregate of carbon nanotubes according to any one of 1 to 8 above and a dispersion medium. <5> <1> ~ <3> A conductive material comprising the aggregate of carbon nanotubes according to any one of the above. <6> an electrode active material; <5> and an electrode comprising the conductive material according to claim 1. <7> <6> A secondary battery comprising the electrode according to claim 1. <8> <1> ~ <3> 2. A planar aggregate comprising the aggregate of carbon nanotubes according to any one of 1 to 10, wherein the aggregate of carbon nanotubes has a maximum length of 1000 μm to 30000 μm. <9> <8> A filter using the planar assembly described in 1. <10> <8> An electromagnetic wave shield using the planar assembly described in 1. <11> <8> A pellicle for extreme ultraviolet radiation using the planar assembly described in . [Effects of the Invention]

[0007] According to an embodiment of the present disclosure, it is possible to provide an aggregate of carbon nanotubes that has excellent dispersibility when made into a carbon nanotube dispersion liquid, and from which a carbon nanotube dispersion liquid with an appropriate viscosity can be obtained. According to another embodiment of the present disclosure, it is possible to provide a carbon nanotube dispersion liquid that contains the aggregate of carbon nanotubes, has excellent dispersibility of the aggregate of carbon nanotubes in a dispersion medium, and has an appropriate viscosity. According to another embodiment of the present disclosure, it is possible to provide a conductive material, an electrode, and a secondary battery, each including the above-described carbon nanotube aggregate. According to another embodiment of the present disclosure, there can be provided the above-mentioned aggregate of carbon nanotubes, wherein the aggregate of carbon nanotubes is a planar aggregate containing carbon nanotubes having a maximum length of 1000 μm to 30000 μm. According to another embodiment of the present disclosure, a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays can be provided using the above-mentioned planar assembly. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a scanning electron microscope photograph showing one embodiment of a specific CNT aggregate. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the carbon nanotube aggregate, the carbon nanotube dispersion, the conductive material, the electrode, and the secondary battery according to the present disclosure will be described in detail. The following description may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances unless otherwise specified. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0011] In the present disclosure, the terms "carbon nanotubes," "single-walled carbon nanotubes," "multi-walled carbon nanotubes," "multi-walled carbon nanotubes having a maximum length of 1000 μm to 30000 μm," "carbon nanotube aggregate," and "carbon nanotube dispersion" may be abbreviated as "CNT," "SWCNT," "MWCNT," "ULMWCNT," "CNT aggregate," and "CNT dispersion," respectively.

[0012] [Carbon nanotube aggregates] One embodiment of the present disclosure is an aggregate of carbon nanotubes that satisfies the following conditions (1) and (2). (1) In the Raman spectrum of carbon nanotubes, the peak intensity ratio G1 / D1, which is the ratio of the G band peak intensity G1 to the D band peak intensity D1, is 0.70 to 10.0, and the ratio of the peak area ratio G2 / D2, which is the ratio of the G band peak area G2 to the D band peak area D2, to the peak intensity ratio G1 / D1 is 1.20 to 3.00. (2) The BET specific surface area of ​​carbon nanotubes is 100m 2 / g~300m 2 / g. Hereinafter, the carbon nanotube aggregate of this embodiment will also be referred to as a "specific CNT aggregate."

[0013] When the specific CNT aggregate is used to prepare a carbon nanotube dispersion, the resulting CNT dispersion has excellent dispersibility in a dispersion medium and an appropriate viscosity. That is, a carbon nanotube dispersion containing a specific CNT aggregate and a dispersion medium that satisfies the above conditions (1) and (2) (hereinafter also referred to as a "specific CNT dispersion") has good dispersibility of the CNT aggregate in the dispersion medium, and the resulting CNT dispersion has an appropriate viscosity.

[0014] The specific CNT dispersion is another embodiment of the present disclosure, and details regarding the specific CNT dispersion other than the specific CNT aggregate will be described later.

[0015] On the other hand, Patent Documents 1 and 2 disclose that, from the viewpoint of suppressing defects in CNTs, the peak intensity ratio G / D, which is the ratio of the peak intensity G of the G band to the peak intensity D of the D band in the Raman spectrum of carbon nanotubes, is within a specific range, but they do not focus on the peak area ratio G2 / D2, which is the ratio of the peak area G2 of the G band to the peak area D2 of the D band, or the relationship between the peak intensity ratio G / D and the peak area ratio G2 / D2.

[0016] The inventors of the present invention have noticed that by using the peak area ratio in addition to the peak intensity ratio, which has conventionally been used as an index for evaluating CNTs, information on the peak shape and peak half-width can be more accurately reflected in the evaluation of CNTs, and therefore more reliable structural analysis information can be obtained for CNT aggregates. In other words, it is estimated that the information obtained by analysis can now more accurately evaluate, for example, crystallinity and defect properties, compared to conventional methods.

[0017] The specific CNT aggregate will be described in detail below. However, the speculations described in the following description are not intended to limit the interpretation of the specific CNT aggregate, but are described as an example.

[0018] <Condition (1)> The specific CNT aggregate has a peak intensity ratio G1 / D1, which is the ratio of the G band peak intensity G1 to the D band peak intensity D1 in the Raman spectrum of the carbon nanotubes, of 0.80 to 10.0, and a peak area ratio G2 / D2, which is the ratio of the G band peak area G2 to the D band peak area D2, relative to the peak intensity ratio G1 / D1, of 1.30 to 3.00.

[0019] The CNTs contained in the specific CNT aggregate of the present disclosure have a peak intensity ratio G1 / D1, which is the ratio of the G band peak intensity G1 to the D band peak intensity D1 in the Raman spectrum, of 0.70 to 10.0. The G band indicates the crystallinity and lattice vibration of graphene contained in carbon nanotube aggregates, and is expressed at 1590 cm -1 The D band is due to structural disorder and defects in the CNT, and a peak intensity G1 appears around 1350 cm -1 A peak intensity D1 appears around this point. When the peak intensity ratio G1 / D1 (hereinafter sometimes abbreviated as "peak intensity ratio G1 / D1"), which is the ratio of the peak intensity G1 of the G band of the CNT to the peak intensity D1 of the D band, is 0.70 or more, the number of defects contained in the specific CNT aggregate is reduced, and the resulting specific CNT dispersion tends to have improved conductivity. When the peak intensity ratio G1 / D1 is 10.0 or less, the uniformity of the shape of the CNT aggregate is partially disrupted, and it is thought that the appropriate non-uniformity in the shape makes it possible to avoid unnecessary aggregation of the CNT aggregates, resulting in good dispersibility in the dispersion medium. From the viewpoint of improving dispersibility, the peak intensity ratio G1 / D1 is preferably from 0.70 to 9.00, more preferably from 0.70 to 8.70, still more preferably from 0.80 to 8.50, and particularly preferably from 0.90 to 8.40.

[0020] In the present disclosure, the peak intensity ratio G1 / D1, which is the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum of MWCNT, is determined by the following method. Using a Raman spectrometer, obtain a Raman spectrum of the MWCNT under the following measurement conditions: From the obtained Raman spectrum, the G band peak intensity G1 and the D band peak intensity D1 are read, and the peak intensity ratio G1 / D1 is calculated. As the Raman spectrometer, for example, a Raman spectrometer, RAMAN-11 (product name) manufactured by Nanophoto Co., Ltd., can be suitably used. However, the Raman spectrometer is not limited to this.

[0021] <Measurement conditions> Excitation laser wavelength: 532 nm Grating: 600 grooves / mm Objective lens: 20x, numerical aperture (NA) 0.45

[0022] In peak analysis, peak fitting can be used to avoid the effects of peak overlapping, improve resolution, and calculate peak intensities more accurately. The Lorentzian function is preferred for fitting, as it provides a high level of fitting. Depending on the peak shape, a Gaussian function may be preferred, as it provides a high level of fitting.

[0023] In the present disclosure, the peak intensity G1 of the G band in the Raman spectrum is 1550 cm -1 ~1600cm -1 In the present disclosure, the peak intensity D1 of the D band in the Raman spectrum refers to the maximum scattering intensity at the Raman shift of 1300 cm -1 ~1400cm -1 This means the maximum scattering intensity at the Raman shift of The half-value width of each peak, which will be described later, can also be measured in the same manner.

[0024] The peak intensity ratio G1 / D1, which is the ratio of the G band peak intensity G1 to the D band peak intensity D1 in the Raman spectrum of MWCNT, can be controlled by the synthesis conditions such as the firing temperature, gas flow rate, and gas introduction method when synthesizing MWCNT. The peak intensity ratio G1 / D1 can be increased by, for example, increasing the firing temperature during synthesis of MWCNT, and can be decreased by decreasing the firing temperature during synthesis of MWCNT.

[0025] The specific CNT aggregate has a peak area ratio G2 / D2 (hereinafter sometimes abbreviated as "area ratio G2 / D2"), which is the ratio of the G band peak area G2 to the D band peak area D2, relative to the peak ratio G1 / D1, of 1.20 to 3.00. As described above, the peak intensity ratio G1 / D1 is calculated from the peak height of the G band and the peak height of the D band. The peak area ratio G2 / D2 is calculated from the peak area G2, calculated by drawing a baseline connecting both ends of the G band peak, and the peak area D2, calculated by drawing a baseline connecting both ends of the D band peak. As with peak intensity calculation, peak area calculation can be performed with peak fitting to obtain more accurate peak area calculations.

[0026] The peak area can be approximately expressed by the following formula using the peak intensity height of each band and the half-width of the peak intensity. G band peak area G2 (G band peak intensity G1 × G band half width G1a × 2) / 2 D band peak area D2 (D band peak G1 × D band half width D1a × 2) / 2

[0027] It is known that the peak intensity of a band in a Raman spectrum indicates the tendency of concentration and orientation, and the half-width indicates the crystallinity and interaction with the surroundings. Therefore, (intensity ratio G1 / D1) / (area ratio G2 / D2) is a parameter that represents the ratio of the crystallinity represented by the G peak intensity to the crystallinity represented by the D peak intensity. Highly crystalline materials tend to have narrower half-width peaks, and it is believed that the presence of defects or impurities can broaden the half-width peaks.

[0028] When the ratio of the intensity ratio G1 / D1 to the area ratio G2 / D2 [(intensity ratio G1 / D1) / (area ratio G2 / D2)] is 1.20 or higher, it means that the crystallinity of the CNTs represented by the G peak is not too high compared to the crystallinity of the CNTs represented by the D peak. When this ratio is 1.20 or higher, excessive aggregation of the CNTs is unlikely to occur, and dispersibility in the dispersion medium tends to be easily ensured. Furthermore, because the CNT aggregates have good dispersibility in the dispersion medium, the viscosity of the resulting specific CNT dispersion liquid does not increase too much, making it suitable. A ratio of the intensity ratio G1 / D1 to the area ratio G2 / D2 of 3.00 or less means that the crystallinity of the carbon nanotubes represented by the G peak is sufficiently high compared to the crystallinity of the carbon nanotubes represented by the D peak. For this reason, dispersions obtained from specific CNT aggregates tend to have good electrical conductivity.

[0029] The ratio of the intensity ratio G1 / D1 to the area ratio G2 / D2 is preferably 1.20 to 2.80, more preferably 1.20 to 2.60, and even more preferably 1.20 to 2.50, from the viewpoint of further improving the balance between the viscosity of the dispersion and the conductivity of the dispersion.

[0030] <Condition (2)> The CNTs contained in the specific CNT aggregate have a BET specific surface area of ​​100 m 2 / g~300m 2 / g.

[0031] If the specific surface area is small, it becomes difficult to secure contact points between CNTs, but it is presumed that the effect of increasing contact points due to load pressure is significant. On the other hand, if the specific surface area is large, it becomes easier to secure contact points between CNTs, but it is presumed that the effect of increasing contact points due to load pressure is small. When the BET specific surface area of ​​the CNTs contained in a specific CNT aggregate is 100 m 2 / g~300m 2 / g, it is presumed that this ensures contact between the CNTs, improves the conductivity of the resulting CNT dispersion, and makes it difficult for the CNT aggregates to aggregate in the dispersion medium, resulting in better dispersibility. The BET specific surface area of ​​the CNTs contained in the specific CNT aggregate is 120m 2 / g~250m 2 / g, and 130m 2 / g~230m 2 / g, more preferably 130m 2 / g~200m 2 / g is more preferred.

[0032] In the present disclosure, the BET specific surface area of ​​CNTs is determined by a gas adsorption method using nitrogen gas in accordance with JIS Z 8830:2013. As the specific surface area measuring device, for example, BELSORP-mini II (product name), which is a specific surface area measuring device manufactured by Microtrack-Bell Co., Ltd., can be suitably used. However, the specific surface area measuring device is not limited to this.

[0033] The BET specific surface area of ​​CNTs can be controlled by adjusting synthesis conditions such as the firing temperature, gas flow rate, and gas introduction method when synthesizing CNTs. The BET specific surface area of ​​CNTs can be increased by, for example, increasing the firing temperature during CNT synthesis, and can be decreased by decreasing the firing temperature during CNT synthesis.

[0034] The specific CNT aggregate is composed of CNTs with a large specific surface area (e.g., 420 m 2 / g~1400m 2 / g) and CNTs with a small specific surface area (e.g., 10 m 2 / g~100m 2 / g) in combination.

[0035] <Preferable properties of specific CNT aggregates> The specific CNT aggregate of the present disclosure satisfies the conditions (1) and (2), so that when it is made into a CNT dispersion, the dispersibility of the CNT aggregate becomes good and a suitable viscosity can be achieved. Preferred guidelines for viscosity and fluidity are shown below.

[0036] 1.Rsp value The specific CNT aggregate preferably has an Rsp value of 300 to 10,000 with respect to the dispersion medium, more preferably 500 to 7,000, even more preferably 1,000 to 5,000, and particularly preferably 3,500 to 4,500. The Rsp value is a measure of the affinity of a specific CNT aggregate for a dispersion medium and can be measured by pulsed nuclear magnetic resonance (pulse NMR) spectroscopy. Pulse NMR spectroscopy allows measurements without diluting the dispersion liquid and does not approximate the shape of the dispersoid to a sphere, making it suitable for measuring the affinity of a dispersion such as a specific CNT aggregate for a dispersion medium. The Rsp value is the relaxation time T 2s and the relaxation time T measured by putting only the dispersion medium in the test tube. 2b By comparing the above, it can be calculated using the following formula. Rsp=(T 2b / T 2s )-1

[0037] 2.Viscosity As mentioned above, the specific CNT aggregate has a high affinity for the dispersion medium, which tends to result in a low viscosity dispersion. When the shear rate of the dispersion is 1 / s, the viscosity is preferably 0.1η / (Pa·s) to 4.8η / (Pa·s), more preferably 0.5η / (Pa·s) to 4.5η / (Pa·s), and even more preferably 1.0η / (Pa·s) to 4.2η / (Pa·s). The viscosity of the dispersion at a shear rate of 100 / s is preferably 0.001η / (Pa·s) to 0.11η / (Pa·s), more preferably 0.005η / (Pa·s) to 0.1η / (Pa·s), and even more preferably 0.01η / (Pa·s) to 0.09η / (Pa·s). The viscosity at each shear rate can be obtained by rheometer measurement. For example, the shear rate dependency of viscosity can be evaluated using a viscoelasticity measuring device (manufactured by Anton Paar, MCR302) under the following measurement conditions. Measuring tool: cone plate Measurement mode: Rotation mode Shear rate: 0.01 s-1 ~1000s -1 Temperature: 25℃ From the data obtained, the viscosity is read at the following shear rates: Shear rate=1 / s(η / (Pa s)) Shear rate=100 / s(η / (Pa s))

[0038] <Bundle structure> The specific CNT aggregate preferably includes a bundle structure from the viewpoint of improving handleability. A bundle structure refers to an aggregate in which multiple CNTs aggregate together due to van der Waals forces or the like, forming a bundle. It is believed that the inclusion of bundle structures of an appropriate size in a specific CNT aggregate improves the handleability of the CNT aggregate and further improves its stability. However, if the bundle structures contained in the specific CNT aggregate become too large, the size of the specific CNT aggregate itself becomes too large, and it becomes difficult to separate and disperse the CNTs contained in the bundle structures, which may reduce dispersibility in a dispersion medium.

[0039] For this reason, from the viewpoint of achieving both ease of handling of the specific CNT aggregate and dispersibility in a solvent, the width of each bundle structure contained in the specific CNT aggregate, i.e., the size in the width direction of the fiber bundle, is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm. The content of the bundle structure in the specific CNT aggregate is preferably 10% by mass to 100% by mass, and more preferably 20% by mass to 90% by mass, relative to the total mass of the specific CNT aggregate. The presence or absence of a bundle structure in a specific CNT aggregate can be confirmed by observing the specific CNT aggregate with an optical microscope, a scanning electron microscope (SEM), etc. The location of the bundle structure in the specific CNT aggregate where the bundle structure exists is identified, and the length is determined by measuring the image of the bundle structure.

[0040] The bundle structure in the specific CNT aggregate can be formed, for example, by controlling the catalyst particle size distribution in production by chemical vapor deposition (CVD) or by controlling the cooling rate in the cooling process.

[0041] <Other matters regarding specific CNT aggregates> In the present disclosure, the CNTs contained in the specific CNT aggregate may be SWCNTs or MWCNTs, but it is preferable that the specific CNT aggregate contain MWCNTs, as these have a wall number distribution and are slightly less uniform, making it easier to improve dispersibility.

[0042] In general, SWCNTs have a lower volume resistivity than MWCNTs, and the lower the volume resistivity, the smaller the change in resistivity due to applied load. The number of walls of CNTs can be controlled by selecting the manufacturing method for CNTs.

[0043] The longer the CNT, the lower its volume resistivity tends to be. The length of the CNT can be controlled by selecting the CNT manufacturing method.

[0044] In one embodiment, the specific CNT aggregate may be an aggregate containing MWCNTs having a maximum length of 500 μm or less as a main component and not containing MWCNTs having a maximum length of 10 μm to 30,000 μm. Here, "main component" means that 90 mass % or more of the CNTs constituting the specific CNT aggregate are MWCNTs having a maximum length of 500 μm or less. The specific CNT aggregate may also contain SWCNTs having a maximum length of 500 μm or less.

[0045] In one embodiment, the specific CNT aggregate preferably includes MWCNTs having a maximum length of 10 μm to 30,000 μm. In one aspect, the MWCNTs preferably include ULMWCNTs.

[0046] ULMWCNT is MWCNT with a maximum length of 1000 μm to 30000 μm, which is longer than general-purpose MWCNT and can take the form of a fiber.

[0047] By taking on a fibrous form, ULMWCNTs have the property of easily entangling with each other. The MWCN contains at least one ULMWCNT, and from the viewpoint that the MWCNTs are more likely to entangle with each other and form a more stable aggregate, it is preferable that the MWCN is an aggregate containing multiple ULMWCNTs. Hereinafter, an aggregate containing ULMWCNT may be abbreviated as "ULMWCNT aggregate."

[0048] Here, the term "fiber" is generally used to refer to a structure in which one dimension is larger than the other two. The fiber may be a thread-like fiber with a circular cross section, a ribbon-like fiber with a rectangular cross section, hollow, or have another shape. From the viewpoint of increasing electrical conductivity, the cross section of the ULMWCNT is preferably circular, and hollow is preferred.

[0049] The aggregate of MWCNTs may be an aggregate having a three-dimensional structure in which the MWCNTs are entangled with one another. Figure 1 is a scanning electron microscope (SEM) photograph showing one embodiment of an aggregate of MWCNTs according to the present disclosure. The SEM photograph shown in Figure 1 reveals that multiple fibrous ULMWCNTs are entangled to form an aggregate. In this way, the entangled state of the ULMWCNTs according to the present disclosure can be confirmed by SEM observation.

[0050] The length of ULMWCNTs can be measured by focusing on a single ULMWCNT and observing multiple SEM images taken at adjacent viewing angles. Here, "ULMWCNT length" refers to the measured length of the ULMWCNT in the longitudinal direction, and the maximum value of the measured lengths is taken as the "maximum length." When observing an SEM photograph, if one MWCNT with a maximum length in the range of 1000 μm to 30000 μm is observed within the viewing angle of the SEM photograph, it can be confirmed that the observed MWCNT includes ULWMCNT.

[0051] It is preferable that multiple ULMWCNTs are present within the viewing angle of the SEM photograph. Focusing on 100 MWCNTs within the viewing angle of the SEM photograph, the maximum length of each is measured, and from the viewpoint of further improving the stability of the MWCNT aggregate due to the entanglement of ULMWCNTs, it is preferable that 10% or more of the observed MWCNTs have a maximum length in the range of 1000 μm to 30,000 μm (i.e., ULMWCNTs), calculated as numbers, be present, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more.

[0052] The diameter of ULMWCNT can be measured by observing SEM or transmission electron microscope (TEM) photographs. Here, the diameter refers to the length in the direction perpendicular to the longitudinal direction of the ULMWCNT. The diameter is measured at 10 different points on one ULMWCNT, and the average value is used as the diameter of that ULMWCNT.

[0053] The length of the ULMWCNT is in the range of 1,000 μm to 30,000 μm, preferably in the range of 1,050 μm to 25,000 μm, more preferably in the range of 1,100 μm to 20,000 μm, even more preferably in the range of 1,200 μm to 18,000 μm, and particularly preferably in the range of 1,300 μm to 15,000 μm. The diameter of the ULMWCNT is preferably 1 nm to 100 nm, more preferably in the range of 2 nm to 80 nm, even more preferably in the range of 3 nm to 50 nm, and particularly preferably in the range of 5 nm to 30 nm.

[0054] The length / diameter ratio of the ULMWCNT, the so-called aspect ratio, is preferably 1,000 or more, more preferably 3,000 or more, further preferably 5,000 or more, and particularly preferably 10,000 or more. The aspect ratio can be calculated from the ratio of the maximum length to the diameter of a single ULMWCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measurements of 20 or more ULMWCNTs.

[0055] Furthermore, from the viewpoint of dispersibility, the specific gravity of the ULMWCNT aggregate is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.4, and even more preferably in the range of 1.8 to 2.2. The specific gravity of the ULMWCNT aggregate can be measured by the method described in JIS Z8807:2012 "Method for measuring density and specific gravity of solids."

[0056] The purity of the ULMWCNT aggregate as MWCNT can be measured by thermogravimetric analysis. For example, a thermal analyzer (Shimadzu Corporation, DTG-60) is used to obtain a thermogravimetric (TG) curve and a differential thermal analysis (DTA) curve of the ULMWCNT aggregate. The largest exothermic peak in the DTA curve, which appears at a peak top near 650°C to 750°C, is considered to be the combustion of MWCNT, and any other exothermic peaks are considered to be the combustion of substances other than MWCNT. The purity of the MWCNT is determined from the weight loss rate of the TG curve. From the viewpoint of the resulting conductivity, the purity of the ULMWCNT aggregate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and particularly preferably 95% by mass or more.

[0057] ULMWCNT may contain 0.01% to 50% by mass of Fe atoms derived from the iron catalyst used during production. ULMWCNT may contain Fe atoms, for example, in a state where they are adsorbed on the surface of the ULMWCNT or in a state where they are incorporated into the fibrous ULMWCNT formed during production.

[0058] The resulting fibrous ULMWCNTs are preferably flexible and strong. In addition, the conductivity of ULMWCNT itself is 5000 ohms. -1 m -1 It is preferable that it is 10,000 ohms or more. -1 m -1 It is more preferable that the conductivity of the ULMWCNT itself is 1,000,000 ohms or more. -1 m -1 The following is the result.

[0059] <Method for Manufacturing CNT> The method for manufacturing CNT in the present disclosure is not particularly limited. For example, as the method for manufacturing MWCNT in the present disclosure, methods such as a conventionally known chemical vapor deposition (CVD) method, a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst, etc. can be applied.

[0060] The CNT in the present disclosure can be manufactured, for example, by referring to the methods described in Japanese Patent Application Laid-Open No. 2016-102047, Japanese Patent Publication No. 2021-527611, etc.

[0061] Hereinafter, the method for manufacturing CNT in the present disclosure will be described with examples. However, the method for manufacturing CNT in the present disclosure is not limited to the following examples.

[0062] =Manufacturing Method X= As an example of the method for manufacturing CNT referred to in the present disclosure, the manufacturing method described in Japanese Patent Application Laid-Open No. 2016-102047 can be cited. That is, a step of passing a gaseous reactant containing one or more carbon sources through a reactor, a step of reacting one or more gaseous reactants in the reaction region of the reactor in the presence of a catalyst to form product particles containing carbon, a step of aggregating the product particles into aggregates, and a step of applying a force to the aggregates to continuously move the aggregates outside the reaction region (hereinafter, also referred to as "Manufacturing Method X").

[0063] According to Manufacturing Method X, MWCNT containing ULMWCNT can be obtained in the form of fibrous aggregates or other aggregate forms that are easy to handle.

[0064] In Manufacturing Method X, the force applied to the product particles may be a mechanical force. When the aggregate is fibrous MWCNT, the mechanical force applied to the product particles can be applied by a rotating spindle around which the aggregate is wound. The fibrous CNT may be collected on the spindle, or after rotating around the spindle one or more times, the spindle may be continuously rewound and accumulated at other locations.

[0065] The spindle is preferably oriented with its axis perpendicular or parallel to the flow direction of the gaseous reactant(s), although other orientations are also possible, for example, a spindle with its axis oriented at a 25° angle to the flow direction of the gaseous reactants may also be suitable for applying mechanical forces to the product particles.

[0066] The spindle can rotate around two axes (e.g., two perpendicular axes). In particular, the spindle can rotate around axes perpendicular and parallel to the flow direction of the gaseous reactants. Such a spindle can pull and twist the fibrous CNT aggregates to control the twist number and length.

[0067] The spindle may be made of metal, ceramic, or resin. The spindle can have different suitable shapes depending on the material properties and the intended use of the MWCNTs. The spindle can be used as a mold for producing carbon products, for example, by a spin-coating process. Preferred spindle shapes are rod-shaped or box-shaped.

[0068] The fibrous MWCNTs are deposited on a spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and conditions, or by the conditions under which an electric or other field is applied to the carbon product. The coating thickness and orientation of the carbon product can be controlled, for example, by gas flow forces.

[0069] The rotation speed of the spindle is preferably 0.01 rpm (revolutions / minute; the same applies hereinafter) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the rotational speed of the spindle) may be adjusted so that the material is collected at a similar rate as it is produced. The rotational speed of the spindle may also control the thickness of the accumulated MWCNT fiber. In a preferred embodiment, as the spindle rotates, the MWCNT fiber is processed in the axial direction of the spindle. This processing ensures that the MWCNT fiber is evenly wrapped along the spindle, rather than being wrapped only at one specific point on the spindle.

[0070] The MWCNT fibers may be collected, for example, on the reactor wall by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide that is used to apply a strong and equal force to the MWCNT fibers as they are collected. Suitable substrate configurations for fiber technology include a substrate consisting of two guides positioned at right angles to each other.

[0071] In production method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow may be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube downstream of the reaction zone. A vacuum may be applied to the product particles.

[0072] Other forces that can be applied to the product particles include electrostatic forces, which are appropriately applied by a charged plate. Electrostatic forces require that the product particles be charged. The use of a charged plate allows the MWCNTs to grow in the form of intertwined sheets on the charged plate.

[0073] Other forces applied to the product particles may also be magnetic forces or photon pressure applied by a light source.

[0074] Instead of a gaseous reactant containing a carbon source, the CNT precursor may be injected in the form of a liquid containing a carbon source. When a liquid is used as the CNT precursor, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0075] Preferably, the gaseous reactant(s) are reacted at a temperature between 500° C. and 1600° C., more preferably between 1000° C. and 1500° C. A temperature gradient is preferably maintained within the reactor, with the reaction zone being maintained at a higher temperature than the product zone of the reactor.

[0076] The gaseous reactants may be mixed with one or more gases that act as diluents. The gaseous reactants may also be mixed with gases that play a supporting but not direct role in the reaction. It is also preferred to use a diluent gas that can react with the amorphous carbon by-product, if any, to keep the reactive sites on the catalyst intact and produce nanotubes.

[0077] Examples of gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, hydrogen is particularly preferred as a gas that can be used as a diluent. The flow rate of the gas used as a diluent is preferably 2000 mL (milliliters) / min or less, and more preferably 400 mL / min to 800 mL / min.

[0078] The gas pressure of the gaseous reactants and any diluents is preferably 0.1 bar to 50 bar, more preferably 0.5 bar to 5 bar, and even more preferably 1 bar to 2 bar. If there is a gas effluent from the furnace, the effluent gas can be recycled with or without cleaning.

[0079] The composition of the product particles can be controlled by monitoring the agglomerates and modifying the reaction conditions based on the information obtained. For example, the agglomerates can be monitored by online Raman spectroscopy, which provides data indicating whether the CNTs are single-walled or multi-walled. It also provides data indicating the diameter and crystallinity of the CNTs. The agglomerates can also be monitored by online conductivity measurements, gas analysis, measuring the opacity of the reaction zone, and / or measuring the winding force.

[0080] When the agglomerate is removed from the reactor, it is preferable to prevent air from entering the reactor. When the diluent gas contains hydrogen, preventing air from entering the reactor is particularly important, for example, from the viewpoint of preventing an explosive mixture of hydrogen and air from forming in the reactor.

[0081] The product particles in production method X contain ULMWCNTs. Depending on the production conditions, SWCNTs may also be contained in addition to MWCNTs.

[0082] The product particles may be produced by chemical vapor deposition, where a gaseous reactant, a carbon source, is reacted in the presence of a catalyst.

[0083] Carbon-containing compounds suitable as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, and hydrocarbons containing mixtures of two or more thereof). The carbon-containing compound is preferably carbon monoxide, methane, ethylene or acetylene.

[0084] Preferably, the carbon source contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other methods, such as by using a diluent gas or a carbon source containing water.

[0085] The gaseous reactant, which is a carbon source, is preferably injected into the reactor at a rate of 0.01 mL / min to 10 mL / min, more preferably 0.08 mL / min to 0.25 mL / min.

[0086] The catalyst is preferably a transition metal, particularly a group VIB transition metal such as chromium (Cr), molybdenum (Mo), or tungsten (W), or a group VIIIB transition metal. Specifically, the catalyst is preferably, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), or manganese (Mn), or a mixture thereof. Metals from the lanthanide and actinide series (e.g., yttrium (Y)) can also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof, such as a mixture of Ni and Co (50 / 50 by mass), a mixture of Fe and Ni, or a mixture of Fe and Mo, are more preferred. Any of these transition metals, either alone or in combination with any of the other transition metals listed, can serve as a catalyst for CNT growth, with it being particularly preferred that the catalyst be a mixture of two or more of the listed metals.

[0087] The catalyst is preferably formed by decomposition of a precursor. The precursor is preferably a thermally, photo-, or plasma-decomposable compound of one or more of the above metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickelocene, and cobaltocene are particularly preferred precursors. Suitably, at least 0.01% by weight of the precursor is contained in the carbon source, and preferably 0.2% to 2.5% by weight of the precursor is contained in the carbon source. In one embodiment, 0.23% to 2.3% by weight of the precursor is contained in the carbon source. The catalyst may be used supported on a carrier, and preferred carriers include silica and magnesium oxide.

[0088] The carbon source is preferably reacted in the presence of a promoter. Suitable promoters are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred promoter. Suitably, up to 10% by weight of the promoter is included in the carbon source. Preferably, 0.2% to 6% by weight of the promoter is included in the carbon source. When high or low concentrations of thiophene are used as the promoter, MWCNTs are formed. For example, MWCNTs are successfully formed using ethanol containing 0 mass % or 1.5 mass % to 4.0 mass % thiophene and 0.5 mass % to 5.0 mass % (particularly 2.3 mass %) ferrocene under conditions of an injection rate of 3.0 mL / hour to 12.0 mL / hour (particularly 7.5 mL / hour), a hydrogen flow rate of 400 mL / min to 800 mL / min, and a synthesis temperature of 1100°C to 1180°C.

[0089] According to production method X, it is possible to obtain fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm. The fibrous CNTs can be in the form of threads or sheets. The length of the fibrous CNT can be controlled, for example, by the winding capacity of the spindle used in producing the fibrous CNT.

[0090] The manufacturing method X preferably includes the steps of reacting a carbon source in a reaction zone of a reactor to produce CNTs, and aggregating the CNTs into aggregates by applying force to the CNTs. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0091] In another embodiment, steps may be taken that include forming MWCNTs containing ULMWCNTs in a reaction zone by the methods described above, followed by condensing to form MWCNTs containing ULMWCNTs, and continuously withdrawing the MWCNTs from near the reaction zone. In another embodiment, the method may include producing MWCNTs containing ULMWCNTs in a reaction zone, continuously electrostatically attracting the MWCNTs containing ULMWCNTs from the reaction zone, and recovering the MWCNTs containing ULMWCNTs.

[0092] =Manufacturing method Y= In the present disclosure, the manufacturing method described in JP-A 2021-527611 can be referred to as an example of a method for manufacturing CNTs. That is, the manufacturing method includes a step (1) of supporting a mixture containing a main catalyst precursor and a co-catalyst precursor on γ-Al2O3 to manufacture an active support, a step (2) of drying the active support by multistage drying including vacuum drying, a step (3) of subjecting the dried active support to a heat treatment to manufacture a supported catalyst, and a step (4) of manufacturing CNTs in the presence of the supported catalyst (hereinafter also referred to as "manufacturing method Y").

[0093] ·Process (1) In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is supported on γ-Al 2 O 3 to produce an active support.

[0094] In order to uniformly support the main catalyst precursor and the co-catalyst precursor on γ-AlO, the mixture may further contain a solvent, and the main catalyst precursor and the co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, and water is preferred.

[0095] Because γ-Al2O3 has a high porosity and a spinel structure, the main catalyst and the promoter can be randomly arranged in γ-Al2O3. The CNTs grown from the randomly arranged main catalyst can be produced in an entangled state.

[0096] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese and chromium, with cobalt being preferred.

[0097] The main catalyst precursor may be one or more selected from the group consisting of nitrates, sulfates, carbonates and acetates of the main catalyst, with nitrates of the main catalyst being preferred.

[0098] The main catalyst precursor may be one or more selected from the group consisting of Co(NO3)2, Co(NO3)2·6H2O, Co2(CO)8, Co2(CO)6[HC=C(C(CH3)3)], Co(CH3CO2)2, Fe(NO3)3, Fe(NO3)2·nH2O, Fe(CH3CO2)2, Ni(NO3)2, Ni(NO3)2·6H2O, Mn(NO3)2, Mn(NO3)2·6H2O, Mn(CH3CO2)2·n(H2O) and Mn(CO)5Br, of which Co(NO3)2·6H2O, Fe(NO3)2·nH2O and Ni(NO3)2·6H2O are preferred.

[0099] The promoter improves the dispersibility of the main catalyst, and may be one or more selected from the group consisting of vanadium and molybdenum.

[0100] The promoter precursors were NH4VO3, NaVO3, V2O5, V(C5H7O2)3, and (NH4)6Mo7O. 24 4H2O, NH4VO3 and (NH4)6Mo7O 24 Preferably, one or more selected from the group consisting of 4H2O.

[0101] When the mixture contains two or more promoter precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and preferably 1:0.5 to 1:0.9. When the above conditions are met, the CNT structure can be stably maintained and CNTs with the desired pore volume can be produced.

[0102] The mixture may contain the main catalyst precursor and the co-catalyst precursor such that the molar ratio of the main catalyst to the co-catalyst is 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, and preferably 1:0.1 to 1:0.25. Satisfying the above molar ratio improves the dispersibility of the main catalyst, enabling the production of CNTs with the desired pore volume.

[0103] The mixture may further include an organic acid which serves to inhibit precipitation of the main catalyst precursor and the co-catalyst precursor.

[0104] The organic acid may be one or more selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid, with citric acid being preferred.

[0105] The mixture may contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. When the above range is satisfied, it is possible to produce a transparent catalyst metal solution during catalyst production, and it is advantageous in that it is possible to produce a catalyst in which fine particles are suppressed during impregnation.

[0106] After step (1), a step of aging may be further included.

[0107] The aging may be carried out for 1 to 60 minutes or 10 to 50 minutes. Preferably, it is carried out for 10 to 50 minutes. When the above conditions are satisfied, the main catalyst precursor and the co-catalyst precursor can be sufficiently supported on the γ-Al2O3. In addition, air bubbles present in the support are removed to the maximum extent possible, and the main catalyst precursor and the co-catalyst precursor can be sufficiently supported even in the fine pores inside the support.

[0108] ·Process (2) The active support is then dried by multi-stage drying, including vacuum drying.

[0109] Multi-stage drying may mean that a drying process including vacuum drying is performed two or more times. Specifically, multi-stage drying may include atmospheric drying and vacuum drying, or may include vacuum drying two or more times.

[0110] The vacuum drying may be carried out at 80° C. to 300° C. or 120° C. to 250° C., preferably at 120° C. to 250° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0111] The vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0112] The vacuum drying can be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0113] On the other hand, when the multi-stage drying includes atmospheric drying and vacuum drying, atmospheric drying can be performed before the above-mentioned vacuum drying, and the atmospheric drying can remove solvent that may be present in the active support.

[0114] Drying at normal pressure may be carried out at 80°C to 160°C or 100°C to 140°C, and is preferably carried out at 100°C to 140°C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0115] Drying at atmospheric pressure may be performed at 900 mbar to 1,100 mbar, preferably 950 mbar to 1,050 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0116] Drying under atmospheric pressure may be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0117] On the other hand, when the multi-stage drying includes two or more vacuum dryings, the multi-stage drying may include two or more vacuum dryings performed at different temperatures, more specifically, a primary vacuum drying performed at a first temperature and a secondary vacuum drying performed at a second temperature higher than the first temperature.

[0118] The primary vacuum drying can remove any solvent that may be present in the active support.

[0119] The first temperature may be 80° C. to 160° C., and preferably 100° C. to 140° C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0120] The primary vacuum drying can be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0121] The primary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, and is preferably performed at 80 mbar to 150 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0122] The secondary vacuum drying is as described above in the description of vacuum drying.

[0123] The second temperature may be 175 to 300° C., and preferably 180 to 280° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0124] The secondary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, and more preferably at 1 mbar to 70 mbar. If the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0125] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0126] ·Process (3) The dried active support is then subjected to a heat treatment to produce a supported catalyst.

[0127] By carrying out the heat treatment, a supported catalyst is produced in which the main catalyst and the promoter are present in a coated state on the surface and in the pores of γ-Al2O3.

[0128] The heat treatment may be carried out at 600 to 800°C or 620 to 750°C, preferably at 620 to 750°C. If the above conditions are met, a supported catalyst can be produced in which the main catalyst and the co-catalyst are uniformly coated on the surface and pores of the γ-Al2O3, and energy consumption can be minimized.

[0129] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, preferably 2 to 8 hours. When the above-mentioned time is satisfied, a supported catalyst can be produced in which the catalyst precursor is uniformly coated on the surface and in the pores of γ-AlO.

[0130] ·Process (4) CNTs are then produced in the presence of a supported catalyst.

[0131] Specifically, CNTs can be produced by contacting a supported catalyst with a carbon-based compound, and specifically, by chemical vapor synthesis.

[0132] To explain the steps for producing CNTs in detail, first, a supported catalyst is loaded into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, the gaseous carbon-based compound or a mixture of the gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen) is injected at a temperature above the thermal decomposition temperature of the gaseous carbon-based compound or below the melting point of the catalyst supported on the supported catalyst. CNTs can be grown by chemical vapor synthesis through the decomposition of the gaseous carbon-based compound.

[0133] The CNTs produced by the above-mentioned chemical vapor synthesis method have a crystal growth direction that is nearly parallel to the tube axis, and the graphite structure has high crystallinity along the tube length. As a result, CNTs with small unit diameters and high conductivity and strength can be produced.

[0134] The chemical vapor synthesis method may be carried out at 600° C. to 800° C. or 650° C. to 750° C., and is preferably carried out at 650° C. to 750° C. If the above temperature is satisfied, CNTs can be produced while minimizing the generation of amorphous carbon.

[0135] The heat source for the reaction may be induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating, or the like.

[0136] Any carbonaceous compound can be used without particular limitations as long as it can supply carbon and can exist in a gaseous state at temperatures of 300° C. or higher.

[0137] The carbon-based compound may be a carbon-based compound having 6 or less carbon atoms, and may be one or more compounds selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0138] After growing CNTs by the above-mentioned reaction, a cooling step may be optionally performed to align the CNTs more regularly. Specifically, the cooling step may be performed by natural cooling by removing the heat source or by using a cooler.

[0139] The above manufacturing methods X and Y are merely examples, and the manufacturing methods for CNTs that can be contained in the specific CNT aggregate are not limited to the above.

[0140] [Carbon nanotube dispersion liquid] The carbon nanotube dispersion liquid (specific CNT dispersion liquid) according to the present disclosure contains a specific CNT aggregate and a dispersion medium. The specific CNT dispersion liquid has good dispersibility of the specific CNT aggregate according to the present disclosure in the dispersion medium, and is also excellent in electrical conductivity. The specific CNT dispersion liquid is preferably used for forming electrodes, forming transparent conductive films, resin additives, conductive inks, coating agents, antistatic agents, paints, and the like.

[0141] <Specific CNT aggregate> The specific CNT aggregate contained in the specific CNT dispersion liquid is the same as the specific CNT aggregate according to the present disclosure described above, and therefore a description thereof will be omitted here.

[0142] <Dispersion medium> The dispersion medium preferably contains water, and more preferably contains water as the main component. "Containing water as a main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, and may be, for example, 100% by mass.

[0143] The water is not particularly limited, but is preferably distilled water, ion-exchanged water, pure water, or the like, which contains fewer impurities.

[0144] The dispersion medium may be a mixture of water and a hydrophilic solvent. Examples of hydrophilic solvents include carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and butylene carbonate; ether compounds such as tetrahydrofuran; ketone compounds such as acetone; lower alcohol compounds such as methanol and ethanol; and solvents such as acetonitrile. When the dispersion medium contains a hydrophilic solvent, the proportion of the hydrophilic solvent in the dispersion medium is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0145] The specific CNT dispersion may further contain other components that can be used in a dispersion, in addition to the specific CNT aggregate and the dispersion medium. Examples of other components include dispersants, antifoaming agents, antistatic agents, conductive assistants other than the conductive assistant according to the present disclosure, etc. Furthermore, the composition may further contain trace amounts of impurity components, so-called inevitable impurities, etc.

[0146] <Dispersant> The carbon nanotube dispersion liquid may contain a dispersant for the purpose of further improving the dispersibility and dispersion stability of the specific CNT aggregates. The dispersant is not particularly limited and may be, for example, various surfactants. The dispersant may also be a polymer compound such as a resin. The dispersant is preferably a surfactant. The surfactant may be an ionic surfactant or a nonionic surfactant, and is not particularly limited. In the specific CNT dispersion, the surfactant may be used alone or in combination of two or more.

[0147] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzenesulfonates (e.g., dodecylbenzenesulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine surfactants and amine oxide surfactants. As the ionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic ionic surfactant) is preferred, and aromatic sulfonic acid surfactants such as alkylbenzene sulfonate and dodecyl phenyl ether sulfonate are more preferred. Aromatic ionic surfactants tend to be excellent in dispersibility, dispersion stabilization, and concentration of multi-walled carbon nanotubes.

[0148] Examples of nonionic surfactants include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers and polyoxyethylene polypropylene glycols; and aromatic nonionic surfactants such as polyoxyalkylene octyl phenyl ether, polyoxyalkylene nonyl phenyl ether, polyoxyalkyl dibutyl phenyl ether, polyoxyalkyl styryl phenyl ether, polyoxyalkyl benzyl phenyl ether, polyoxyalkyl bisphenyl ether, polyoxyalkyl cumyl phenyl ether and polyoxyalkylene phenyl ether. As the nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to be excellent in dispersibility, dispersion stabilization, and concentration of multi-walled carbon nanotubes.

[0149] Other dispersants that are excellent in CNT dispersibility, dispersion stabilization, and concentration enhancement include DEMOL (registered trademark: the same applies hereinafter) N, DEMOL RN, and DEMOL T (manufactured by Kao Corporation), which are sodium salts of β-naphthalenesulfonic acid formalin condensates; Brij S 100 (manufactured by Sigma-Aldrich), which is a polyoxyethylene stearyl ether; polyvinylpyrrolidone K30 (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.); carboxymethylcellulose (CMC) (manufactured by, for example, Daicel Miraize Co., Ltd.); sodium deoxycholate (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.); and SOLSPERSE TM W100, SOLSPERSE TM W150 (manufactured by Lubrizol Japan, Inc.) is particularly preferred from the viewpoint of excellent dispersibility, dispersion stability and high concentration of multi-walled carbon nanotubes.

[0150] When the specific CNT dispersion liquid contains a dispersant, the amount of the dispersant used is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of multi-walled carbon nanotubes, the amount of dispersion medium, and the like.

[0151] [Method for producing specific CNT dispersion liquid] The method for producing the specific CNT dispersion liquid is not particularly limited. The specific CNT dispersion can be produced by dispersing the specific CNT aggregate in a dispersion medium. That is, the specific CNT dispersion can be produced by a method including a step of dispersing the specific CNT aggregate in a dispersion medium (also referred to as a "dispersion step"). The dispersion medium that can be used in the dispersion step is as described above.

[0152] The dispersion method is not particularly limited. Examples of the dispersion method include methods using a dispersion device such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device. Examples of the dispersion method include known pulverization means, such as ball milling (e.g., ball mill, vibration ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, a vertical or horizontal agitator mill, an attritor, a colloid mill, a three-roll mill, a pearl mill, a super mill, an impeller, a disperser, a KD mill, a dynatron, a pressure kneader, and the like. As a dispersion method, a method using a jet mill is preferred, and a method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pumps a mixture in a solvent as a high-speed flow through a nozzle arranged in a sealed pressure-resistant container. In a wet jet mill, multi-walled carbon nanotubes are dispersed in the pressure-resistant container by collisions between countercurrent flows, collisions with the container wall, turbulence caused by the high-speed flow, shear flow, etc. As a wet jet mill, an ultra-high-pressure homogenizer (model numbers: NAGS20, NAGS100, JAGS200, NAGS1000, etc.) manufactured by Joko Co., Ltd. can be suitably used. However, the wet jet mill is not limited to this. When the ultra-high pressure homogenizer is used as the dispersing device, the processing pressure for dispersion is preferably 10 MPa to 250 MPa.

[0153] The method for producing the specific CNT dispersion may include a step of drying the specific CNT aggregate (also referred to as a "drying step") before the dispersion step.

[0154] If water adheres to the CNTs, the CNTs tend to adhere to each other due to the surface tension of the water, which may result in a decrease in dispersibility. Therefore, by performing a drying process on the conductive additive before the dispersion process, the water adhered to the CNTs is removed, preventing the multi-walled carbon nanotubes from adhering to each other due to water adhesion, and further improving the dispersibility of the CNTs in the dispersion medium. The drying method is not particularly limited. Drying methods include, for example, heat drying, vacuum drying, and heat vacuum drying. The drying method is preferably heated vacuum drying. The drying temperature is not particularly limited, and is preferably 40°C to 100°C, for example. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhering to the multi-walled carbon nanotubes in the present disclosure, and the like.

[0155] An example of the production of the specific CNT dispersion liquid will be shown below, but the production of the specific CNT dispersion liquid is not limited to the following.

[0156] <Production Example 1: Example of production of dispersion liquid> 0.040 g of the specific CNT aggregate according to the present disclosure is weighed and placed in a three-neck flask. After the specific CNT aggregate is placed in the flask, a large excess of ion-exchanged water (e.g., 20 mL) is poured into the flask and stirred at room temperature (25°C, the same applies below). At this time, a known dispersant (e.g., carboxymethyl cellulose) may be added as appropriate. Next, a conductive additive is dispersed in the dispersion medium using a known dispersion device (e.g., an ultrasonic irradiation device or a wet jet mill). The obtained dispersion is further stirred with a stirrer at room temperature for a long period of time (e.g., 1 hour to 48 hours). In this way, a specific CNT dispersion is obtained.

[0157] [Conductive materials] The conductive material according to the present disclosure includes a specific CNT aggregate. As described above, the specific CNT aggregate contained in the conductive material according to the present disclosure has excellent conductivity when made into a dispersion, and is therefore suitable as a conductive auxiliary agent. The conductive material according to the present disclosure contains the specific CT aggregate according to the present disclosure, and therefore has excellent conductive efficiency and can effectively impart high conductivity to the object of use.

[0158] The conductive material according to the present disclosure may contain a known conductive additive such as graphite, Ketjen black, etc. Furthermore, the conductive material according to the present disclosure may contain CNTs other than the specific CNT aggregate.

[0159] The conductive material according to the present disclosure can be used as one of electrode materials. An example of an electrode formed using the electrode material is an electrode included in a secondary battery. Hereinafter, an embodiment of the electrode and the secondary battery including the electrode will be described.

[0160] [Electrodes and secondary batteries] The electrode according to the present disclosure includes an electrode active material and a conductive material according to the present disclosure. The secondary battery according to the present disclosure includes the electrode according to the present disclosure. The electrode according to the present disclosure contains the conductive material according to the present disclosure, and therefore has excellent conductive path formation properties within the electrode, and therefore the secondary battery according to the present disclosure has excellent cycle characteristics. An embodiment of an electrode and a secondary battery including the electrode will be described below.

[0161] <Electrode> The electrode can include a specific CNT aggregate. In the electrode, the specific CNT aggregates can function as a conductive additive. The CNT aggregate contained in the electrode described below is synonymous with the specific CNT aggregate, and the preferred embodiments are also the same, so a description of the CNT aggregate will be omitted below.

[0162] The electrode may be at least one of a positive electrode and a negative electrode. The electrode may include an electrode active material layer, or may include a current collector and an electrode active material layer disposed on the current collector.

[0163] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. The current collector may be, for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal such as copper or nickel that has good carbon adsorption properties may be used as the current collector.

[0164] The electrode active material layer can include an electrode active material. The electrode active material is preferably electrode active material particles. When the electrode is a positive electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a positive electrode active material that is commonly used as an electrode material for a positive electrode. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+c1 Mn 2-c1Lithium manganese oxides such as O4 (0 ≦ c1 ≦ 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≦ c2 ≦ 0.66).) Nickel-site type lithium nickel oxide represented by; chemical formula LiMn 2-c3 M c3 O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01 ≦ c3 ≦ 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn).); Examples include LiMn2O4 in which a part of the Li in the chemical formula is substituted with an alkaline earth metal ion.

[0165] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer can contain a negative electrode active material usually used for negative electrode materials. Specifically, the negative electrode active material can contain graphite-based active material particles or silicon-based active material particles. As the graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads may be used. By using artificial graphite as the graphite-based active material particles, the rate characteristics can be improved. As the silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element, a Group 14 element, a rare earth element, and combinations thereof) may be used. By using silicon-based active material particles, the battery can be made to have a higher capacity.

[0166] The electrode active material layer can further contain a binder. The binder is not particularly limited, and the electrode active material layer can contain a binder that is commonly used in electrode materials. Examples of binders include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which the hydrogen atoms of these polymers have been substituted with Li, Na, Ca, or the like.

[0167] <Secondary battery> The secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode is an electrode formed using a conductive material containing the specific CNT aggregate as an electrode material.

[0168] The separator separates the negative electrode from the positive electrode and provides a path for lithium ions to move, and is not particularly limited as long as it is a separator that is typically used as a separator in a secondary battery. The separator preferably has low resistance to ion movement of the electrolyte and is excellent in the ability to retain moisture in the electrolyte solution. A specific example of the separator is a porous polymer film. The porous polymer film may be, for example, a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure in which two or more layers of these films are laminated. The separator may also be a typical porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. The separator may also be coated with a ceramic component or a polymeric substance to ensure heat resistance or mechanical strength. The separator may optionally be of a single layer or multi-layer structure.

[0169] The electrolyte is not particularly limited, and examples thereof include electrolytes such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in producing lithium secondary batteries.

[0170] Specifically, the electrolyte can include a non-aqueous organic solvent and a metal salt. Examples of non-aqueous organic solvents include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0171] Among carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high viscosity and high dielectric constants and dissociate lithium salts well. It is more preferred to use a non-aqueous organic solvent obtained by mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, in order to obtain an electrolyte having high electrical conductivity.

[0172] The metal salt may be a lithium salt. Lithium salts are substances that are easily dissolved in non-aqueous electrolytes. The anion portion of the lithium salt may be, for example, F - , Cl - , I - , NO3 - , N(CN )2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - Examples include:

[0173] In addition to the non-aqueous organic solvent and metal salt, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for the purposes of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0174] The above-described secondary battery can be used to form a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack can be used as a power source for a medium to large device selected from the group consisting of, for example, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage system.

[0175] The planar aggregate of the present disclosure is the aggregate of carbon nanotubes of the present disclosure, and the aggregate of carbon nanotubes includes carbon nanotubes having a maximum length of 1000 μm to 30000 μm. The proportion of carbon nanotubes having a maximum length of 1000 μm to 30000 μm contained in the planar assembly of the present disclosure is usually 1 mass % or more. The planar aggregate of the present disclosure may contain other components such as an aggregate of carbon nanotubes containing carbon nanotubes having a maximum length of less than 1000 μm, that is, an aggregate of carbon nanotubes not containing carbon nanotubes having a maximum length of 1000 μm to 30000 μm. The planar aggregate of the present disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing a carbon nanotube aggregate containing carbon nanotubes with a maximum length of 1000 μm to 30000 μm, or the carbon nanotube aggregate and other components such as a carbon nanotube aggregate containing carbon nanotubes with a maximum length of less than 1000 μm, in water or other fluid and filtering once or twice or more times.

[0176] The planar assembly of the present disclosure may be, for example, a film. The planar assemblies of the present disclosure are useful, for example, in filters, electromagnetic shields, and extreme ultraviolet (EUV) pellicles. [Example]

[0177] The specific CNT aggregate, dispersion containing the specific CNT aggregate, and the like according to the present disclosure will be described in more detail below with reference to examples. The aggregate and dispersion according to the present disclosure are not limited to the following examples as long as they do not deviate from the gist of the disclosure. Unless otherwise specified, "%" means "% by mass".

[0178] Example 1 1. Production of sheet-shaped CNT aggregate 1 Sheet-like CNT aggregate 1 was prepared by the floating catalyst method (CVD method) which directly interacts with the self-assembly of CNT bundles in the gas phase. First, ferrocene as a metal catalyst precursor containing Fe atoms and thiophene as a promoter were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled between 400 and 700°C. A mixture of nitrogen and argon was used as the carrier gas. The flow rate of the carrier gas was 30,000 sccm (standard cubic centimeters per minute). By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor was produced as a particulate metal catalyst. The region where the metal catalyst was produced is referred to as the first temperature zone.

[0179] Next, methane, a carbon source, was released into the carrier gas stream. The metal catalyst and carbon source were fed into a second temperature zone downstream of the first temperature zone, which was controlled at 1400°C. The second temperature zone was maintained at a temperature sufficient to produce carbon nanotube aggregates.

[0180] In the second temperature zone, an electric field was generated within the temperature-controlled flow reactor, which generated CNT aggregates. The aggregates of CNTs were continuously discharged through the outlet of a flow-type reactor whose temperature was controlled at 100°C to 500°C, and a sheet-like CNT aggregate was collected by continuous discharge. The obtained sheet-like CNT aggregate contains MWCNTs. The obtained sheet-like CNT aggregate was washed with pure water for 10 seconds to obtain a sheet-like CNT aggregate 1, which is a specific CNT aggregate.

[0181] 2. Preparation of CNT Dispersion 1 The following materials were mixed and pre-dispersed by processing for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. to obtain pre-dispersion 1. Note that the sheet-like CNT aggregate 1 was cut into small pieces measuring 1 cm x 1 cm with scissors before mixing to prevent the sheet-like CNT aggregate 1 from becoming tangled in the blades of the homogenizer.

[0182] (Dispersion liquid composition) 1.1g of the sheet-like CNT aggregate 1 obtained above ·CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals) 1.65g ·Pure water 547.25g

[0183] The pre-dispersion liquid 1 was subjected to main dispersion using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Joko Corporation as a wet jet mill under the following conditions to obtain CNT dispersion liquid 1, which is a specific CNT dispersion liquid. (dispersion condition) Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of times: 8 Method: Circulation method

[0184] 3. Evaluation 3-1.Raman spectrum The Raman spectrum was measured using a Raman spectrometer (product name "RAMAN-11", manufactured by Nanophoton Inc.). The sheet-shaped CNT aggregate 1 of Example 1 was used as a measurement sample. The sheet-like CNT aggregate 1 was fixed on a sample stage, and the Raman spectrum was measured at 10 points. The excitation laser wavelength was 532 nm, the grating was 600 grooves / mm, the objective lens was ×20 and the numerical aperture (NA) was 0.45, and the wavenumber range was 110–2650 cm -1 It was decided.

[0185] In the obtained Raman spectrum, 1550 cm -1 ~1600cm -1 The peak detected in the Raman shift region of 1325 cm is a peak originating from the G band. -1 ~1360cm -1 The peaks detected in the Raman shift region were determined to be peaks derived from the D band. Peak fitting was performed using a Lorentzian function for each peak derived from the band, and the intensities and areas of the fitted peaks were calculated. Furthermore, the peak intensity ratio G1 / D1, which is the ratio of the peak intensity G1 of the peak derived from the G band to the peak intensity D1 of the peak derived from the D band, and the peak area ratio G2 / D2, which is the ratio of the peak area G2 of the peak derived from the G band to the peak area D2 of the peak derived from the D band, were calculated. The peak intensity ratio G1 / D1 and peak area ratio G1 / D1 were calculated for all 10 measurement points, and their average values ​​were used as the peak intensity ratio G1 / D1 and peak area ratio G2 / D2 of the sheet-like CNT aggregate 1. As a result, the peak intensity ratio G1 / D1 was 8.23, and the peak area ratio G2 / D2 was 4.21. The ratio of the peak area ratio G2 / D2 to the peak intensity ratio G1 / D1 was 1.96.

[0186] 3-2.BET specific surface area The BET specific surface area was measured using a gas adsorption measurement device (product name "BELSORP-miniII", manufactured by Microtrack-Bel). The sheet-shaped CNT aggregate 1 of Example 1 was used as a measurement sample. The BET specific surface area was measured using a pretreatment device (product name "BELPREP-vacII", manufactured by Microtrac-Bel) after the sheet-like CNT aggregate 1 was subjected to vacuum degassing treatment at 300°C for 3 hours. For the sheet-shaped CNT aggregate 1 after the vacuum degassing treatment, the adsorption / desorption isotherm with nitrogen was measured using a constant volume method. The measurement temperature was 77 K, the adsorbate was nitrogen, the saturated vapor pressure was measured, and the adsorbate cross section was 0.162 nm 2 The waiting time after the adsorption equilibrium state was reached was set to 500 seconds. The BET method (BET-Plot) was used for analysis to calculate the BET specific surface area from the obtained adsorption / desorption isotherms. As a result, the BET specific surface area of ​​the sheet-shaped CNT aggregate 1 was 178 m 2 / g.

[0187] 3-3.Rsp value The Rsp value was measured using a pulsed NMR device (product name "the minispec mq20", manufactured by Bruker). The CNT dispersion liquid 1 of Example 1 was used as the measurement sample. The Rsp value was measured by placing CNT dispersion 1 in a sample tube and measuring the relaxation time T 2s and the relaxation time T measured in a test tube containing pure water. 2b was used to calculate using the following formula. As a result, the Rsp value of CNT dispersion 1 was 4,320. Rsp=(T 2b / T 2s )-1

[0188] 3-4.Viscosity The viscosity was measured using a viscoelasticity measuring device (product name "MCR302", manufactured by Anton Paar). The CNT dispersion liquid 1 of Example 1 was used as the measurement sample. The viscosity of CNT dispersion 1 was measured by a rheometer to evaluate the shear rate dependency of the viscosity. The measurement jig is a cone plate, the measurement mode is rotational mode, and the shear rate range is 0.01 to 1000 s -1 The temperature was 25°C. From the obtained data, the viscosity at a shear rate of 1 / s and the viscosity at a shear rate of 100 / s were read. As a result, the viscosity was 4.210 Pa·s at a shear rate of 1 / s and 0.0796 Pa·s at a shear rate of 100 / s.

[0189] 3-5. Confirmation of bundle structure The obtained sheet-like CNT aggregate 1 of Example 1 was observed with an SEM (device name: S-4800, manufactured by Hitachi High-Technologies Corporation), and it was confirmed that it contained a bundle structure. Measurements were taken at 20 points, and the average value was calculated, and the width of the bundle structure was found to be 70 nm.

[0190] The results of the above evaluations are shown in Table 1. In the section on confirmation of bundle structure, if a bundle structure was confirmed, it was recorded as "Yes," and if not, it was recorded as "-."

[0191] Example 2 1. Preparation of Fibrous CNT Aggregates 2 Like the sheet-like CNT aggregate 1, the fibrous CNT aggregate 2 was also produced by the floating catalyst method (CVD method) which directly interacts with the self-assembly of CNT bundles in the gas phase. First, ferrocene as a metal catalyst precursor containing Fe atoms and thiophene as a promoter were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled between 400 and 700°C. A mixture of nitrogen and argon was used as the carrier gas. The flow rate of the carrier gas was 30,000 sccm. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor was produced as a particulate metal catalyst. The region where the metal catalyst was produced is referred to as the first temperature zone.

[0192] Next, methane, a carbon source, was released into the carrier gas stream. The metal catalyst and carbon source were fed into a second temperature zone downstream of the first temperature zone, which was controlled at 1400°C. The second temperature zone was maintained at a temperature sufficient to produce carbon nanotube aggregates.

[0193] In the second temperature zone, an electric field was generated within the temperature-controlled flow reactor, which produced fibrous CNT aggregates. The carbon nanotube aggregates were continuously discharged through the outlet of a flow reactor whose temperature was controlled at 100°C to 500°C, and fibrous CNT aggregates were collected by continuous discharge. The obtained fibrous CNT aggregate contains MWCNTs. The obtained fibrous CNT aggregate was washed with pure water for 10 seconds, and a fibrous CNT aggregate 2 was obtained.

[0194] 2. Preparation of CNT Dispersion 2 Using the obtained fibrous CNT aggregate 2, a CNT dispersion liquid 2 was obtained in the same manner as in Example 1.

[0195] 3. Evaluation The fibrous CNT aggregate 2 and CNT dispersion 2 of Example 2 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0196] Example 3 1. Production of sheet-shaped CNT aggregate 7 A sheet-like CNT aggregate 7 was produced in accordance with Example 1, except that the temperature of the second temperature zone was controlled to 1300°C and the obtained sheet-like CNT aggregate was not washed with pure water.

[0197] 2. Preparation of CNT Dispersion 7 Using the obtained sheet-shaped CNT aggregate 7, a CNT dispersion 7 was obtained in the same manner as in Example 1.

[0198] 3. Evaluation The sheet-shaped CNT aggregate 7 and the CNT dispersion 7 of Example 3 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0199] (Comparative Example 1) 1. Production of sheet-shaped CNT aggregate 3 The sheet-like CNT aggregate obtained in Example 1 was washed with hydrochloric acid (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) for 10 minutes to obtain a sheet-like CNT aggregate 3 of Comparative Example 1.

[0200] 2. Preparation of CNT Dispersion 3 Using the obtained sheet-shaped CNT aggregate 3, a CNT dispersion 3 was obtained in the same manner as in Example 1.

[0201] 3. Evaluation The sheet-shaped CNT aggregate 3 and the CNT dispersion liquid 3 of Comparative Example 1 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0202] (Comparative Example 2) 1. Preparation of Powdered CNT Aggregates 4 As the powdered CNT aggregate 4, "multi-walled carbon nanotubes" (catalog number: FT7000, manufactured by C-nano Co., Ltd.) were prepared.

[0203] 2. Preparation of CNT Dispersion 4 Using the prepared powdered CNT aggregate 4, a CNT dispersion liquid 4 was obtained in the same manner as in Example 1.

[0204] 3. Evaluation The powdered CNT aggregate 4 and the CNT dispersion liquid 4 of Comparative Example 2 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0205] (Comparative Example 3) 1. Preparation of Powdered CNT Aggregates 5 As the powdered CNT aggregate 5, "multi-walled carbon nanotubes" (catalog number: FT6120, manufactured by C-nano Co., Ltd.) were prepared.

[0206] 2. Preparation of CNT Dispersion 5 Using the prepared powdered CNT aggregate 5, a CNT dispersion liquid 5 was obtained in the same manner as in Example 1.

[0207] 3. Evaluation The powdered CNT aggregate 5 and the CNT dispersion liquid 5 of Comparative Example 3 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0208] Comparative Example 4 1. Preparation of Powdered CNT Aggregates 6 As the powdered CNT aggregate 6, "single-walled carbon nanotubes" (catalog number: TUBALL TM (manufactured by OCSiAl) was prepared.

[0209] 2. Preparation of CNT Dispersion 6 Using the prepared powdered CNT aggregate 6, a CNT dispersion liquid 6 was obtained in the same manner as in Example 1.

[0210] 3. Evaluation The powdered CNT aggregate 6 and the CNT dispersion liquid 6 of Comparative Example 4 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0211] [Table 1]

[0212] As shown in Table 1, it can be seen that the CNT dispersion obtained by dispersing the CNT aggregates of the example has good dispersibility and an appropriate viscosity. On the other hand, the CNT aggregates of Comparative Examples 1 and 2, which had too low an intensity ratio / area ratio in the Raman spectrum, had low Rsp values ​​and were found to have poor CNT dispersibility in the CNT dispersion. Therefore, good conductivity cannot be expected. In addition, the viscosity was too high or too low, making them difficult to handle, making them difficult to use as a dispersion. The CNT aggregate of Comparative Example 3, which had too high a BET specific surface area, had a low Rsp value and was found to have poor CNT dispersibility in the CNT dispersion. Therefore, good conductivity cannot be expected. Furthermore, the viscosity was too low, making it difficult to handle, making it difficult to use as a dispersion. The CNT aggregate of Comparative Example 4, which had an excessively large intensity ratio G1 / D1 and an excessively high BET specific surface area, had a low Rsp value and was found to have poor CNT dispersibility in the CNT dispersion. Therefore, good conductivity cannot be expected. In addition, the viscosity was too high, making it difficult to handle, making it difficult to use as a dispersion.

Claims

1. An aggregate of carbon nanotubes that satisfies the following conditions (1) and (2): (1) The peak intensity ratio G1 / D1, which is the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum of the carbon nanotube, is 0.70 to 10.0; The ratio of the peak area ratio G2 / D2, which is the ratio of the peak area G2 of the G band to the peak area D2 of the D band, to the peak intensity ratio G1 / D1 is 1.20 to 3.

00. (2) The BET specific surface area of ​​the carbon nanotube is 100 m ２ / g to 300m ２ / g.

2. 2. The aggregate of carbon nanotubes according to claim 1, wherein a ratio of a peak area ratio G2 / D2 to a peak intensity ratio G1 / D1 in a Raman spectrum of the carbon nanotubes is 1.20 to 2.

50.

3. The carbon nanotube aggregate according to claim 1 , which comprises a bundle structure.

4. A carbon nanotube dispersion liquid comprising the aggregate of carbon nanotubes according to claim 1 or 2 and a dispersion medium.

5. A conductive material comprising the carbon nanotube aggregate according to claim 1 or 2.

6. An electrode comprising an electrode active material and the conductive material according to claim 5 .

7. A secondary battery comprising the electrode according to claim 6.

8. 3. The carbon nanotube aggregate according to claim 1, wherein the carbon nanotube aggregate is a planar aggregate containing carbon nanotubes having a maximum length of 1000 μm to 30000 μm.

9. A filter using the planar assembly according to claim 8.

10. An electromagnetic wave shield using the planar assembly according to claim 8.

11. A pellicle for extreme ultraviolet rays, which uses the planar assembly according to claim 8.

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