Multilayer carbon nanotube assembly, multilayer carbon nanotube dispersion liquid, conductive material, electrode, secondary battery, planar assembly, filter, electromagnetic wave shield, and pellicle for extreme ultraviolet rays

Abstract

Provided are: a multilayer carbon nanotube assembly having high conductivity; a multilayer carbon nanotube dispersion liquid; a conductive material; an electrode; a secondary battery; a planar assembly; a filter; an electromagnetic wave shield; and a pellicle for extreme ultraviolet rays.　Provided are: a multilayer carbon nanotube assembly including a multilayer carbon nanotube that has a median diameter of 80 nm or more in a volume-based particle size distribution obtained by a centrifugal sedimentation method when measured as an aqueous dispersion liquid at a concentration of 0.004% by mass, and has a rate of change in transmittance measured by a centrifugal sedimentation method of 0.3% or less per hour when measured as an aqueous dispersion liquid at a concentration of 0.2% by mass; a multilayer carbon nanotube dispersion liquid; a conductive material; an electrode; a secondary battery; a planar assembly; a filter; an electromagnetic wave shield; and a pellicle for extreme ultraviolet rays.

Description

Multi-walled carbon nanotube aggregates, multi-walled carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic wave shields, and pellicles for extreme ultraviolet rays

[0001] The present disclosure relates to a multi-walled carbon nanotube aggregate, a multi-walled 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.

[0002] Carbon nanotubes (also referred to as "CNTs") are substances with a cylindrical structure formed by rolling up graphene sheets in which carbon atoms are arranged in a hexagonal honeycomb pattern. CNTs have excellent properties such as electrical conductivity, thermal conductivity, and heat resistance, and are therefore expected to be applied to various electronic materials, including electrode materials for energy storage devices. CNTs are basically broadly classified into single-walled carbon nanotubes (also referred to as "SWCNTs") formed from a single layer of graphene sheets and multi-walled carbon nanotubes (also referred to as "MWCNTs") formed from multiple layers of graphene sheets. MWCNTs have the advantage of being superior in thermal stability and chemical stability compared to SWCNTs, and in recent years, attempts have been made to more effectively enhance the properties of MWCNTs.

[0003] For example, Patent Document 1 discloses MWCNTs that are CNTs having two or more coaxial layers of graphene sheet cylinders in which carbon atoms are arranged in a hexagonal honeycomb pattern, with the diameter of the outermost layer being 3 nm to 15 nm based on observation of an image with a transmission electron microscope, and the length being 1.0 mm or more based on observation of an image with a scanning electron microscope. The MWCNTs described in Patent Document 1 are said to have increased applicability to materials that require high electrical conductivity, high thermal conductivity, etc.

[0004] Japanese Patent Application Laid-Open No. 2020-180028

[0005] In recent years, interest in the usefulness of MWCNTs as electronic materials has been growing. For example, when MWCNTs are used as electrode materials such as conductive additives, high conductivity can be imparted to electrodes, which is expected to improve the performance of electricity storage devices. However, conventional MWCNTs, including the MWCNTs described in Patent Document 1, still have room for improvement in terms of the effect of improving conductivity when used as electrode materials.

[0006] The present disclosure has been made in view of the above circumstances. An object of one embodiment of the present disclosure is to provide a multi-walled carbon nanotube aggregate having high electrical conductivity. An object of another embodiment of the present disclosure is to provide a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, and a planar aggregate, each containing the multi-walled carbon nanotube aggregate. Another object of another embodiment of the present disclosure is to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet radiation, each using the planar aggregate.

[0007] Specific means for solving the above problems include the following aspects: [1] An aggregate of multi-walled carbon nanotubes, comprising multi-walled carbon nanotubes, which when dispersed in water at a concentration of 0.004% by mass have a median diameter of 80 nm or more in a volume-based particle size distribution obtained by centrifugal sedimentation, and when dispersed in water at a concentration of 0.2% by mass, have a rate of change in transmittance measured by centrifugal sedimentation of 0.3% / hour or less. [2] When dispersed in water at a concentration of 0.2% by mass, the magnitude q of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ [3] When the multi-walled carbon nanotube aggregate is dispersed in water at a concentration of 0.2 mass %, the scattering vector of the scattering profile obtained by small-angle X-ray scattering has a magnitude q of 0.02 nm. －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１[4] An aggregate of multi-walled carbon nanotubes, comprising multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4 of 10 or less, which is the ratio of the scattering intensity S3 to the scattering intensity S4 at 0.004 mass% in an aqueous dispersion. [5] When the aggregate is made into an aqueous dispersion of 0.004 mass%, the median diameter in a volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, when the aggregate is made into an aqueous dispersion of 0.2 mass%, the rate of change in transmittance measured by centrifugal sedimentation is 0.3% / hour or less, and when the aggregate is made into an aqueous dispersion of 0.2 mass%, the magnitude q of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is 0.2 nm －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ [5] An aggregate of multi-walled carbon nanotubes, comprising multi-walled carbon nanotubes having a scattering intensity ratio S1 / S2 of 90 or more, which is the ratio of the scattering intensity S1 / S2 at a concentration of 0.004% by mass to the scattering intensity S2 at a concentration of 0.2% by mass, wherein the median diameter in a volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more when the aggregate is made into an aqueous dispersion at a concentration of 0.004% by mass, the rate of change in transmittance measured by centrifugal sedimentation is 0.3% / hour or less when the aggregate is made into an aqueous dispersion at a concentration of 0.2% by mass, and the magnitude q of the scattering vector in a scattering profile obtained by small-angle X-ray scattering is 0.02 nm when the aggregate is made into an aqueous dispersion at a concentration of 0.2% by mass. －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ [6] An aggregate of multi-walled carbon nanotubes, comprising multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4 of 10 or less, which is the ratio of the scattering intensity S3 to the scattering intensity S4 at a concentration of 0.2 mass % in an aqueous dispersion. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ The scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 to the scattering intensity S2 at －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１[7] The aggregate of multi-walled carbon nanotubes according to any one of [1] to [6], wherein the multi-walled carbon nanotubes have a maximum length of 1000 μm to 30000 μm. [8] The aggregate of multi-walled carbon nanotubes according to any one of [1] to [7], which is a conductive assistant. [9] A multi-walled carbon nanotube dispersion comprising the aggregate of multi-walled carbon nanotubes according to any one of [1] to [7] and a dispersion medium.

[10] A conductive material comprising the aggregate of multi-walled carbon nanotubes according to any one of [1] to [7].

[11] An electrode comprising an electrode active material and the conductive material according to

[10] .

[12] A secondary battery comprising the electrode according to

[11] .

[13] A composition comprising the aggregate of multi-walled carbon nanotubes according to any one of [1] to [7], and at least one selected from the group consisting of resin, ceramics, and concrete.

[14] A planar assembly comprising the multi-walled carbon nanotube aggregate according to any one of [1] to [7].

[15] A filter using the planar assembly according to

[14] .

[16] An electromagnetic wave shield using the planar assembly according to

[14] .

[17] A pellicle for extreme ultraviolet rays using the planar assembly according to

[14] .

[0008] According to one embodiment of the present disclosure, a multi-walled carbon nanotube aggregate having high conductivity is provided. According to another embodiment of the present disclosure, a multi-walled carbon nanotube dispersion, an electrode, a secondary battery, a conductive material, and a planar aggregate containing the multi-walled carbon nanotube aggregate are provided. Furthermore, according to another embodiment of the present disclosure, a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays using the planar aggregate are provided.

[0009] 1 is a scanning electron microscope (SEM) photograph of a dispersion containing a MWCNT aggregate of Example 1. FIG. 2 is a scanning electron microscope (SEM) photograph of a dispersion containing a SWCNT aggregate of Comparative Example 1. FIG. 3 is a scanning electron microscope (SEM) photograph of a dispersion containing a MWCNT aggregate of Comparative Example 2. FIG. 4 is a graph of scattering profiles obtained by small-angle X-ray scattering for the MWCNT aggregate of Example 1, the SWCNT aggregate of Comparative Example 1, and the MWCNT aggregate of Comparative Example 2.

[0010] Hereinafter, the multi-walled carbon nanotube aggregate, multi-walled carbon nanotube dispersion, conductive material, electrode, secondary battery, planar aggregate, filter, electromagnetic wave shield, and pellicle for extreme ultraviolet radiation according to the present disclosure will be described in detail. The explanation of the requirements described below 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 purpose of the present disclosure.

[0011] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.

[0012] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0013] In the present disclosure, 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.

[0014] In this disclosure, the term "fiber" is used to refer to a structure having one dimension greater than the other two dimensions. The fiber may be a thread-like fiber having a circular cross section, a ribbon-like fiber having a rectangular cross section, a hollow fiber, or any other shape. From the viewpoint of increasing the electrical conductivity of the aggregate of the present disclosure, the cross section of the MWCNT is preferably circular, and more preferably hollow.

[0015] In the present disclosure, "carbon nanotubes" are also referred to as "CNTs," "single-walled carbon nanotubes" are also referred to as "SWCNTs," "multi-walled carbon nanotubes" are also referred to as "MWCNTs," "multi-walled carbon nanotube aggregates" are also referred to as "MWCNT aggregates," and "multi-walled carbon nanotube dispersions" are also referred to as "MWCNT dispersions."

[0016] [Multi-walled carbon nanotube aggregate] One embodiment of the multi-walled carbon nanotube aggregate according to the present disclosure is an aggregate of multi-walled carbon nanotubes, which contains multi-walled carbon nanotubes having a median diameter of 80 nm or more in a volume-based particle size distribution obtained by centrifugal sedimentation when made into an aqueous dispersion of 0.004 mass%, and a rate of change in transmittance measured by centrifugal sedimentation when made into an aqueous dispersion of 0.2 mass%. In the present disclosure, the multi-walled carbon nanotube aggregate according to this embodiment is also referred to as "MWCNT aggregate (A)".

[0017] The MWCNT aggregate (A) according to the present disclosure has high electrical conductivity. The reason why the MWCNT aggregate (A) according to the present disclosure has high electrical conductivity is not clear, but the present inventors speculate as follows. However, the following speculation is not intended to limit the MWCNT aggregate (A) according to the present disclosure, but is described as an example.

[0018] The present inventors have discovered a relationship between the median diameter in the volumetric particle size distribution obtained by centrifugal sedimentation when MWCNTs are dispersed in water at a specific concentration and the structure formed by entanglement of MWCNTs. Specifically, they found that a larger median diameter suggests a larger size of the structure formed by entanglement of MWCNTs. The present inventors have also discovered a relationship between the rate of change in transmittance measured by centrifugal sedimentation when MWCNTs are dispersed in water at a specific concentration and the stability of the structure formed by entanglement of MWCNTs in the water dispersion. Specifically, they found that a slow rate of change in transmittance suggests that the structure formed by entanglement of MWCNTs can stably exist in the water dispersion. It is believed that the MWCNTs in the MWCNT aggregate (A) according to the present disclosure are entangled with each other to form a giant network structure that can exist stably in the water dispersion. It is speculated that the formation of a network structure by MWCNTs results in multiple contacts between MWCNTs, forming huge conductive paths and thereby increasing conductivity.

[0019] In another embodiment of the multi-walled carbon nanotube aggregate according to the present disclosure, when the aggregate is made into an aqueous dispersion of 0.2 mass %, the magnitude of the scattering vector of the scattering profile obtained by a small angle X-ray scattering (SAXS) method is q=0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 to the scattering intensity S2 in a multi-walled carbon nanotube array, of 90 or more. In the present disclosure, the multi-walled carbon nanotube aggregate according to this embodiment is also referred to as a "MWCNT aggregate (B)".

[0020] The MWCNT aggregate (B) according to the present disclosure has high electrical conductivity. The reason why the MWCNT aggregate (B) according to the present disclosure has high electrical conductivity is not clear, but the present inventors speculate as follows. However, the following speculation is not intended to limit the MWCNT aggregate (B) according to the present disclosure, but is described as an example.

[0021] The present inventors have found that when MWCNT is dispersed in water at a specific concentration, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ The present disclosure has obtained findings regarding the relationship between the scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 to the scattering intensity S2 at the time of measurement, and the size of the MWCNT primary aggregates. In particular, it has been found that a large scattering intensity ratio S1 / S2 suggests a small variation in the diameter of the MWCNT, and that a small variation in the diameter of the MWCNT increases the interaction force between the MWCNTs, making it easier for the MWCNTs to entangle with each other and form a network structure. The MWCNT aggregate (B) according to the present disclosure is thought to have a small variation in the diameter of the MWCNTs, forming a network structure in which the MWCNTs are entangled with each other. It is presumed that the formation of a network structure by the MWCNTs causes contact between the MWCNTs at multiple points, forming huge conductive paths, and thereby increasing the conductivity.

[0022] In another embodiment of the aggregate of multi-walled carbon nanotubes according to the present disclosure, when the aggregate is made into an aqueous dispersion of 0.2 mass %, the magnitude of the scattering vector of the scattering profile obtained by small-angle X-ray scattering method is q=0.02 nm －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S3 to the scattering intensity S4 in the multi-walled carbon nanotube array, of 10 or less. In the present disclosure, the multi-walled carbon nanotube aggregate according to this embodiment is also referred to as a "MWCNT aggregate (C)".

[0023] The MWCNT aggregate (C) according to the present disclosure has high electrical conductivity. The reason why the MWCNT aggregate (C) according to the present disclosure has high electrical conductivity is not clear, but the present inventors speculate as follows. However, the following speculation is not intended to limit the MWCNT aggregate (C) according to the present disclosure, but is described as an example.

[0024] The present inventors have found that when MWCNT is dispersed in water at a specific concentration, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.02 nm. －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ The present disclosure has obtained findings regarding the relationship between the scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S3 to the scattering intensity S4 at 1000 kJ / s, and the entanglement of MWCNT. In particular, it has been found that a small scattering intensity ratio S3 / S4 suggests that the size of the primary aggregates of MWCNT is small, and that when the size of the primary aggregates of MWCNT is small, the surface area of ​​the MWCNT increases, the MWCNTs are more likely to entangle with each other, and a network structure is more likely to be formed. The MWCNT aggregate (C) according to the present disclosure is thought to have small primary aggregates of MWCNT, forming a network structure in which the MWCNTs are entangled with each other. It is presumed that the formation of a network structure by the MWCNTs causes contact between the MWCNTs at multiple points, forming huge conductive paths, and thereby increasing the conductivity.

[0025] In the MWCNT aggregate according to the present disclosure, it can be confirmed by SEM observation that the MWCNTs are in an entangled state.

[0026] The MWCNT aggregate according to the present disclosure has high conductivity and is suitable, for example, as a conductive additive. Furthermore, since the MWCNTs in the MWCNT aggregate according to the present disclosure are in a state in which they are entangled with one another, they tend to be less susceptible to swelling even when they come into contact with an organic solvent. Therefore, when the MWCNT according to the present disclosure is used as a conductive additive when forming an electrode for a secondary battery such as a lithium-ion battery, the structure is less likely to change even when the battery is operated, and the durability of the battery can be improved.

[0027] Hereinafter, the MWCNT aggregate (A) according to the present disclosure, the MWCNT aggregate (B) according to the present disclosure, and the MWCNT aggregate (C) according to the present disclosure will be explained, and then other possible aspects of the MWCNT aggregate according to the present disclosure will be explained.

[0028] [MWCNT aggregate (A)] The MWCNT aggregate (A) according to the present disclosure contains MWCNTs which, when made into an aqueous dispersion at a concentration of 0.004 mass%, have a median diameter of 80 nm or more in a volume-based particle size distribution obtained by centrifugal sedimentation, and when made into an aqueous dispersion at a concentration of 0.2 mass%, have a rate of change in transmittance measured by centrifugal sedimentation of 0.3% / hour or less.

[0029] The MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure preferably have a fibrous shape, from the viewpoint that a network structure is easily formed by entanglement of the MWCNTs with each other.

[0030] The maximum length of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is not particularly limited, but is, for example, preferably 500 μm to 30,000 μm, more preferably 1,000 μm to 25,000 μm, even more preferably 1,100 μm to 20,000 μm, particularly preferably 1,200 μm to 18,000 μm, and particularly preferably 1,300 μm to 15,000 μm. When the maximum length of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is 500 μm or more, the conductivity of the MWCNT aggregate (A) tends to be higher. This is thought to be because the MWCNTs contained in the MWCNT aggregate (A) are more likely to come into contact with each other, making it easier to form conductive paths. When the MWCNTs contained in the MWCNT aggregate (A) have a maximum length of 30,000 μm or less, they tend to be easier to produce.

[0031] In the present disclosure, the length of a MWCNT can be measured by focusing on a single MWCNT and taking multiple SEM photographs at adjacent viewing angles. Here, "MWCNT length" refers to the measured length of the MWCNT in the longitudinal direction, and the maximum value of the measured lengths is defined as the "maximum length." For example, when an SEM photograph of a MWCNT aggregate is taken, if one or more MWCNTs with a maximum length in the range of 500 μm to 30,000 μm are observed within the viewing angle of the SEM photograph, it is determined that the observed MWCNT aggregate contains MWCNTs with a maximum length of 500 μm to 30,000 μm.

[0032] The length of the fibrous MWCNT can be controlled, for example, by the winding capacity of the spindle used in producing the fibrous MWCNT.

[0033] The MWCNT aggregate (A) according to the present disclosure preferably contains one or more MWCNTs having a maximum length of 500 μm to 30,000 μm, and more preferably contains a plurality of MWCNTs. In the present disclosure, "MWCNTs having a maximum length of 500 μm to 30,000 μm" is also referred to as "SLMWCNTs."

[0034] The ratio of SLMWCNTs in the MWCNT aggregate (A) according to the present disclosure is, for example, preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more, on a number basis. When the ratio of SLMWCNTs in the MWCNT aggregate (A) according to the present disclosure is 10% or more, on a number basis, there is a tendency for the stability of the MWCNT aggregate (A) in an aqueous dispersion due to entanglement of the MWCNTs to be further improved.

[0035] In the present disclosure, the proportion of SLMWCNTs in a MWCNT aggregate is determined by taking multiple SEM photographs at adjacent viewing angles, focusing on 100 MWCNTs included in the viewing angles of the SEM photographs, measuring the maximum length of each, and identifying MWCNTs (i.e., SLMWCNTs) among the observed MWCNTs whose maximum length is in the range of 500 μm to 30,000 μm. The same applies to the proportion of ULMWCNTs in a MWCNT aggregate and the proportion of specific ULMWCNTs in a MWCNT aggregate, which will be described later.

[0036] The diameter of the MWCNT contained in the MWCNT aggregate (A) according to the present disclosure is not particularly limited, but is, for example, preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0037] In the present disclosure, the diameter of MWCNT can be measured by taking SEM or transmission electron microscope (TEM) photographs. Here, the diameter refers to the length in the direction perpendicular to the longitudinal direction of the MWCNT, and the diameter is measured at 10 different points on one MWCNT, and the average value is taken as the diameter of that MWCNT.

[0038] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNT contained in the MWCNT aggregate (A) according to the present disclosure is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0039] In the present disclosure, the aspect ratio of a MWCNT can be calculated from the ratio of the maximum length to the diameter of a single MWCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measurements of 20 or more MWCNTs.

[0040] The specific gravity of the MWCNT aggregate (A) according to the present disclosure is not particularly limited, but from the viewpoint of dispersibility when made into an aqueous dispersion, for example, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0041] In the present disclosure, the specific gravity of the MWCNT aggregate (A) can be measured by the method described in JIS Z8807:2012 "Method for measuring density and specific gravity of solids."

[0042] The MWCNT aggregate (A) according to the present disclosure contains MWCNTs having a median diameter of 80 nm or more in a volume-based particle size distribution obtained by centrifugal sedimentation when made into an aqueous dispersion at a concentration of 0.004 mass%. When the median diameter of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is 80 nm or more, the conductivity of the MWCNT aggregate (A) can be improved. The median diameter of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is preferably 90 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more. The upper limit of the median diameter of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is not particularly limited, but is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less, from the viewpoint of dispersibility when made into an aqueous dispersion, for example.

[0043] In the present disclosure, the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation when MWCNT is dispersed in an aqueous solution at a concentration of 0.004 mass% is determined by the following method. In the present disclosure, the "median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation" refers to the particle diameter at which the cumulative frequency is 50% (so-called d50) in the volume-based particle size distribution obtained by centrifugal sedimentation. MWCNT and a dispersant are added to ion-exchanged water, followed by a dispersion treatment to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added is such that the MWCNT concentration in the aqueous dispersion becomes 0.004 mass%. Using the obtained aqueous dispersion as a measurement sample, the volume-based particle size distribution of MWCNT is measured using a centrifugal sedimentation particle size distribution analyzer under the following measurement conditions. The particle diameter at which the cumulative frequency is 50% in the measured volume-based particle size distribution is read and used as the median diameter. As the centrifugal sedimentation particle size distribution analyzer, for example, LUMiSizer 611 (trade name), which is a centrifugal sedimentation dispersion stability particle size analyzer manufactured by LUM GmbH, can be suitably used. However, the centrifugal sedimentation particle size distribution analyzer is not limited to this.

[0044] <Measurement conditions> Measurement cell: Polycarbonate cell (optical path length: 2 mm) Rotation speed: 4000 rpm Centrifugal acceleration: 2300×g Measurement interval: 30 seconds Number of measurements: 1000 Measurement temperature: 25°C

[0045] The median diameter can be controlled by the synthesis conditions during MWCNT synthesis, such as the calcination temperature, gas flow rate, gas introduction method, etc. The median diameter can be increased by increasing the calcination temperature during MWCNT synthesis, and can be decreased by decreasing the calcination temperature during MWCNT synthesis, for example.

[0046] The MWCNT aggregate (A) according to the present disclosure contains MWCNTs having a rate of change in transmittance measured by centrifugal sedimentation of 0.3% / hour or less when made into an aqueous dispersion at a concentration of 0.2% by mass. When the rate of change in transmittance of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is 0.3% / hour or less, the stability of the MWCNT aggregate (A) in an aqueous dispersion can be improved, and the conductivity can be improved. The rate of change in transmittance of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is preferably 0.25% / hour or less, more preferably 0.2% / hour or less, and even more preferably 0.15% / hour or less. The lower limit of the rate of change in transmittance of the MWCNTs contained in the MWCNT aggregate (A) according to the present disclosure is not particularly limited, but, for example, from the viewpoint of ease of production, it is preferably 0.01% / hour or more, and more preferably 0.03% / hour or more.

[0047] In the present disclosure, the rate of change in transmittance measured by centrifugal sedimentation when an aqueous dispersion of MWCNT is prepared at a concentration of 0.2 mass% is determined by the following method. MWCNT and a dispersant are added to ion-exchanged water, followed by a dispersion treatment to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added is such that the MWCNT concentration in the aqueous dispersion becomes 0.2 mass%. Using the obtained aqueous dispersion as a measurement sample, a centrifugal sedimentation particle size analyzer is used to obtain a sedimentation profile under the following measurement and analysis conditions. The rate of change in transmittance as a whole is analyzed from the obtained sedimentation profile to determine the rate of change in transmittance. As a centrifugal sedimentation particle size analyzer, for example, the LUMiSizer 611 (trade name), a centrifugal sedimentation dispersion stability particle size analyzer manufactured by LUM GmbH, can be suitably used. However, the centrifugal sedimentation particle size analyzer is not limited to these.

[0048] <Measurement and analysis conditions> Measurement cell: Polycarbonate cell (optical path length: 2 mm) Rotation speed: 4000 rpm Centrifugal acceleration: 2300 × g Measurement interval: 30 seconds Number of measurements: 1000 Viscosity of dispersion medium: 0.8946 mPa·s Density of dispersion medium: 997.3 kg / m ３ Dispersoid density: 1350 kg / m３ Refractive index (real part) of dispersion medium: 1.326 Refractive index (real part) of dispersoid: 1.630 Refractive index (imaginary part) of dispersion medium: 0.5153 Under the above analysis conditions, the dispersion medium is water and the dispersoid is MWCNT. The above viscosity, density, and refractive index values ​​are all values ​​at 25°C.

[0049] The rate of change in the transmittance can be controlled by the synthesis conditions during MWCNT synthesis, such as the firing temperature, gas flow rate, gas introduction method, etc. The rate of change in the transmittance can be increased by, for example, increasing the gas flow rate during MWCNT synthesis, and can be decreased by decreasing the gas flow rate during MWCNT synthesis.

[0050] [MWCNT aggregate (B)] When the MWCNT aggregate (B) according to the present disclosure is made into an aqueous dispersion with a concentration of 0.2 mass %, the magnitude of the scattering vector of the scattering profile obtained by small-angle X-ray scattering method is q=0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ The MWCNTs have a scattering intensity ratio S1 / S2 of 90 or more, which is the ratio of the scattering intensity S1 to the scattering intensity S2 in the measured value.

[0051] The MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure preferably have a fibrous shape, from the viewpoint that a network structure is easily formed by entanglement of the MWCNTs with each other.

[0052] The maximum length of the MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure is not particularly limited, but is, for example, preferably 500 μm to 30,000 μm, more preferably 1,000 μm to 25,000 μm, even more preferably 1,100 μm to 20,000 μm, particularly preferably 1,200 μm to 18,000 μm, and particularly preferably 1,300 μm to 15,000 μm. When the maximum length of the MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure is 500 μm or more, the conductivity of the MWCNT aggregate (B) tends to be higher. This is thought to be because the MWCNTs contained in the MWCNT aggregate (B) are more likely to come into contact with each other, making it easier to form conductive paths. When the MWCNTs contained in the MWCNT aggregate (B) have a maximum length of 30,000 μm or less, they tend to be easier to produce.

[0053] The MWCNT aggregate (B) according to the present disclosure preferably contains one or more MWCNTs having a maximum length of 500 μm to 30,000 μm (that is, SLMWCNTs), and more preferably contains a plurality of MWCNTs.

[0054] The ratio of SLMWCNTs in the MWCNT aggregate (B) according to the present disclosure is, for example, preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more, on a number basis. When the ratio of SLMWCNTs in the MWCNT aggregate (B) according to the present disclosure is 10% or more, on a number basis, there is a tendency for the stability of the MWCNT aggregate (B) in an aqueous dispersion due to entanglement between the MWCNTs to be further improved.

[0055] The diameter of the MWCNT contained in the MWCNT aggregate (B) according to the present disclosure is not particularly limited, but is, for example, preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0056] The ratio of the length to the diameter of the MWCNT contained in the MWCNT aggregate (B) according to the present disclosure (so-called aspect ratio) is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0057] The specific gravity of the MWCNT aggregate (B) according to the present disclosure is not particularly limited, but from the viewpoint of dispersibility when made into an aqueous dispersion, for example, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0058] The MWCNT aggregate (B) according to the present disclosure contains MWCNTs in which the scattering intensity ratio S1 / S2 of the scattering profile obtained by small-angle X-ray scattering is 90 or more when the MWCNTs are made into an aqueous dispersion at a concentration of 0.2 mass%. When the scattering intensity ratio S1 / S2 of the MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure is 90 or more, the conductivity of the MWCNT aggregate (B) can be improved. The scattering intensity ratio S1 / S2 of the MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure is preferably 95 or more, more preferably 98 or more, even more preferably 100 or more, and particularly preferably 110 or more. The upper limit of the scattering intensity ratio S1 / S2 of the MWCNTs contained in the MWCNT aggregate (B) according to the present disclosure is not particularly limited, but is preferably 250 or less, more preferably 200 or less, from the viewpoint of ease of production, for example.

[0059] The scattering intensity ratio S1 / S2 can be controlled by the synthesis conditions during MWCNT synthesis, such as the calcination temperature, gas flow rate, gas introduction method, etc. The scattering intensity ratio S1 / S2 can be increased by, for example, increasing the calcination temperature during MWCNT synthesis, and can be decreased by decreasing the calcination temperature during MWCNT synthesis.

[0060] [MWCNT aggregate (C)] When the MWCNT aggregate (C) according to the present disclosure is made into an aqueous dispersion with a concentration of 0.2 mass %, the magnitude of the scattering vector of the scattering profile obtained by small-angle X-ray scattering method is q = 0.02 nm. －１Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ The MWCNTs have a scattering intensity ratio S3 / S4 of 10 or less, which is the ratio of the scattering intensity S3 to the scattering intensity S4 in the measured value.

[0061] The MWCNT contained in the MWCNT aggregate (C) according to the present disclosure preferably has a fibrous shape, from the viewpoint that a network structure is easily formed by entanglement of the MWCNTs with each other.

[0062] The maximum length of the MWCNTs contained in the MWCNT aggregate (C) according to the present disclosure is not particularly limited, but is, for example, preferably 500 μm to 30,000 μm, more preferably 1,000 μm to 25,000 μm, even more preferably 1,100 μm to 20,000 μm, particularly preferably 1,200 μm to 18,000 μm, and particularly preferably 1,300 μm to 15,000 μm. When the maximum length of the MWCNTs contained in the MWCNT aggregate (C) according to the present disclosure is 500 μm or more, the conductivity of the MWCNT aggregate (C) tends to be higher. This is thought to be because the MWCNTs contained in the MWCNT aggregate (C) are more likely to come into contact with each other, making it easier to form conductive paths. When the MWCNTs contained in the MWCNT aggregate (C) have a maximum length of 30,000 μm or less, they tend to be easier to produce.

[0063] The MWCNT aggregate (C) according to the present disclosure preferably contains one or more MWCNTs having a maximum length of 500 μm to 30,000 μm (that is, SLMWCNTs), and more preferably contains a plurality of MWCNTs.

[0064] The ratio of SLMWCNTs in the MWCNT aggregate (C) according to the present disclosure is, for example, preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more, on a number basis. When the ratio of SLMWCNTs in the MWCNT aggregate (C) according to the present disclosure is 10% or more, on a number basis, there is a tendency for the stability of the MWCNT aggregate (C) in an aqueous dispersion due to entanglement between the MWCNTs to be further improved.

[0065] The diameter of the MWCNT contained in the MWCNT aggregate (C) according to the present disclosure is not particularly limited, but is, for example, preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0066] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNT contained in the MWCNT aggregate (C) according to the present disclosure is preferably 1000 or more, more preferably 3000 or more, further preferably 5000 or more, and particularly preferably 10000 or more.

[0067] The specific gravity of the MWCNT aggregate (C) according to the present disclosure is not particularly limited, but from the viewpoint of dispersibility when made into an aqueous dispersion, for example, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0068] The MWCNT aggregate (C) according to the present disclosure contains MWCNTs in which the scattering intensity ratio S3 / S4 of the scattering profile obtained by small-angle X-ray scattering is 10 or less when the MWCNTs are made into an aqueous dispersion at a concentration of 0.2 mass%. When the scattering intensity ratio S3 / S4 of the MWCNTs contained in the MWCNT aggregate (C) according to the present disclosure is 10 or less, the conductivity of the MWCNT aggregate (C) can be improved. The scattering intensity ratio S3 / S4 of the MWCNTs contained in the MWCNT aggregate (C) according to the present disclosure is preferably 9.5 or less, more preferably 9 or less, and even more preferably 8.5 or less. The lower limit of the scattering intensity ratio S3 / S4 of the MWCNTs contained in the MWCNT aggregate (C) according to the present disclosure is not particularly limited, but is preferably 1 or more, more preferably 4 or more, from the viewpoint of ease of production, for example.

[0069] The scattering intensity ratio S3 / S4 can be controlled by the synthesis conditions during MWCNT synthesis, such as the firing temperature, gas flow rate, gas introduction method, etc. The scattering intensity ratio S3 / S4 can be increased by, for example, increasing the gas flow rate during MWCNT synthesis, and can be decreased by decreasing the gas flow rate during MWCNT synthesis.

[0070] In the present disclosure, when MWCNT is dispersed in water at a concentration of 0.2 mass%, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ the scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S2 at 0.02 nm to the scattering intensity S1 at 0.02 nm, and the magnitude q of the scattering vector of the scattering profile obtained by small-angle X-ray scattering －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１The scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S4 at 1000 kJ / s to the scattering intensity S3 at 1000 kJ / s, is determined by the following method. MWCNT and a dispersant are added to ion-exchanged water, and then a dispersion treatment is carried out to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added is an amount such that the MWCNT concentration in the aqueous dispersion becomes 0.2 mass%. The obtained aqueous dispersion is used as the measurement sample. The measurement sample is filled into an NMR tube (trade name: S-3-HT-7, manufactured by NORELL) with an outer diameter of 2.99±0.03 mm and an inner diameter of 2.41±0.03 mm, taking care to prevent bubbles from entering, and then a small-angle X-ray scattering device is used to obtain the scattering profile of the MWCNT. Measurements using small-angle X-ray scattering are performed in accordance with the description in "Structural Science of Crystalline Polymers, Kohji Tashiro, Springer, 2022." More specifically, X-rays are incident near the axial center of the NMR tube in a direction perpendicular to the longitudinal direction. Ten measurements are performed with an exposure time of 1 second, changing the irradiation position in the longitudinal direction by 100 μm increments, to obtain a total two-dimensional scattering image Ms. Simultaneously with capturing the two-dimensional scattering image, the transmitted light intensity fs is measured in the ion chamber downstream of the NMR tube. The background two-dimensional scattering image Mb and transmitted light intensity fb are measured under the same conditions as above, except that the NMR tube is filled with ion-exchanged water instead of the aqueous dispersion. The background-corrected two-dimensional scattering image M is obtained using the following formula (1): At this time, the area where the scattered X-rays are blocked by a beam stopper or the like that is installed to prevent the direct beam from entering the detector is excluded from the two-dimensional scattered image M. M = Ms / fs - Mb / fb (1) A one-dimensional profile in the radial direction is obtained from the two-dimensional scattered image M by circular averaging. The horizontal axis is calibrated to the magnitude q of the scattering vector using the standard substance collagen. From the obtained one-dimensional profile, the magnitude q of the scattering vector is determined to be 0.2 nm. －１ Scattering intensity S1, scattering vector magnitude q = 0.8 nm －１ Scattering intensity S2 at q = 0.02 nm －１ Scattering intensity S3 at q = 0.08 nm and the magnitude of the scattering vector q －１The scattering intensity S4 at this point is read, and the scattering intensity ratios S1 / S2 and S3 / S4 are calculated. For example, beamline BL03XU at SPring-8, a large-scale synchrotron radiation facility, can be suitably used as the small-angle X-ray scattering experimental equipment. However, the small-angle X-ray scattering experimental equipment is not limited to this. Instead of a large-scale synchrotron radiation facility, for example, a small-angle X-ray scattering device, NANOPIX (trade name) manufactured by Rigaku Corporation, can also be used. The wavelength of the X-rays is preferably 0.03 nm to 0.13 nm. The beam diameter is preferably 1 μm to 100 μm. The measurement temperature is preferably 20°C to 30°C. The camera length is preferably 8000 mm. However, the magnitude of the scattering vector q = 0.2 nm. －１ and the magnitude of the scattering vector q = 0.8 nm －１ and a camera length of, for example, 700 mm to 8000 mm, and a scattering vector magnitude q=0.02 nm. －１ and the magnitude of the scattering vector q = 0.08 nm －１ Measurements of camera lengths including the above, for example, 8000 mm to 20000 mm, may be performed separately. As a detector, for example, Pilatus 1M (trade name) manufactured by Dectris can be suitably used. However, the detector is not limited to this.

[0071] Preferred aspects of the multi-walled carbon nanotube aggregate according to the present disclosure include the following aspects 1, 2, and 3. Details of the requirements in aspects 1, 2, and 3 are the same as the details of the requirements in the aspects of the MWCNT aggregate (A), the MWCNT aggregate (B), and the MWCNT aggregate (C).

[0072] A preferred aspect 1 of the aggregate of multi-walled carbon nanotubes according to the present disclosure is such that, when it is made into an aqueous dispersion of 0.004 mass %, the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, when it is made into an aqueous dispersion of 0.2 mass %, the rate of change of transmittance measured by centrifugal sedimentation is 0.3% / hour or less, and when it is made into an aqueous dispersion of 0.2 mass %, the magnitude q of the scattering vector of the scattering profile obtained by small-angle X-ray scattering is 0.2 nm －１Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ Aspect 1 is an aspect in which the multi-walled carbon nanotube has a scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 in the sample to the scattering intensity S2 in the sample, of 90 or more. Aspect 1 is an aspect in which the aspect of the MWCNT aggregate (A) according to the present disclosure and the aspect of the MWCNT aggregate (B) according to the present disclosure are combined.

[0073] A preferred aspect 2 of the aggregate of multi-walled carbon nanotubes according to the present disclosure is such that, when the aggregate is made into an aqueous dispersion of 0.004 mass%, the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, when the aggregate is made into an aqueous dispersion of 0.2 mass%, the rate of change in transmittance measured by centrifugal sedimentation is 0.3% / hour or less, and when the aggregate is made into an aqueous dispersion of 0.2 mass%, the magnitude q of the scattering vector of the scattering profile obtained by small-angle X-ray scattering is 0.02 nm －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ Aspect 2 is an aspect in which the multi-walled carbon nanotube has a scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S3 in a sample to the scattering intensity S4 in a sample, of 10 or less. Aspect 2 is an aspect in which the aspect of the MWCNT aggregate (A) according to the present disclosure and the aspect of the MWCNT aggregate (C) according to the present disclosure are combined.

[0074] In a preferred embodiment 3 of the aggregate of multi-walled carbon nanotubes according to the present disclosure, when the aggregate is made into an aqueous dispersion of 0.2 mass %, the magnitude of the scattering vector of the scattering profile obtained by small-angle X-ray scattering method is q=0.2 nm －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ The scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 to the scattering intensity S2 at －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１ Aspect 3 is an aspect in which the multi-walled carbon nanotube has a scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S3 in a sample to the scattering intensity S4 in a sample, of 10 or less. Aspect 3 is an aspect in which the aspect of the MWCNT aggregate (B) according to the present disclosure and the aspect of the MWCNT aggregate (C) according to the present disclosure are combined.

[0075] [MWCNT aggregate (D)] In an embodiment, the multi-walled carbon nanotube aggregate according to the present disclosure comprises multi-walled carbon nanotubes having a maximum length of 1000 μm to 30000 μm, and 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 multi-walled carbon nanotubes, is more than 0.9 and 15 or less, and the BET specific surface area of ​​the multi-walled carbon nanotubes is 50 m ２ / g~400m ２ / g. In the present disclosure, the multi-walled carbon nanotube aggregate according to this embodiment is also referred to as "MWCNT aggregate (D)". In addition, in the present disclosure, "MWCNT having a maximum length of 1000 μm to 30000 μm" is also referred to as "ULMWCNT".

[0076] The MWCNT aggregate (D) according to the present disclosure has high electrical conductivity. The reason why the MWCNT aggregate (D) according to the present disclosure has high electrical conductivity is not clear, but the present inventors speculate as follows. However, the following speculation is not intended to limit the MWCNT aggregate (D) according to the present disclosure, but is described as an example.

[0077] The MWCNT aggregate (D) according to the present disclosure contains MWCNTs with a maximum length of 1,000 μm to 30,000 μm (i.e., ULMWCNTs), and therefore it is believed that the MWCNTs are likely to come into contact with each other. When the MWCNTs are more likely to come into contact with each other, conductive paths are more likely to be formed, and conductivity can be improved. Furthermore, the MWCNTs contained in the MWCNT aggregate (D) according to 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 a Raman spectrum, of a specific value or more, and have relatively few defects present in the MWCNT. The fewer defects present in the MWCNT, the more conductivity can be improved. Furthermore, the MWCNTs contained in the MWCNT aggregate (D) according to the present disclosure have a peak intensity ratio G1 / D1 of a specific value or less and are relatively non-uniform in shape, and therefore tend to easily become entangled with each other. The more entanglement between MWCNTs occurs, the more the electrical conductivity can be improved. Furthermore, since the MWCNTs contained in the MWCNT aggregate (D) according to the present disclosure have a moderately large BET specific surface area, it is thought that the MWCNTs are in close contact with each other. When the MWCNTs are in close contact with each other, the volume resistivity of the MWCNTs decreases, and the electrical conductivity can be improved. From the above, it is presumed that the MWCNT aggregate (D) according to the present disclosure has high electrical conductivity.

[0078] The ULMWCNT contained in the MWCNT aggregate (D) according to the present disclosure can have a fibrous shape. When the ULMWCNTs have a fibrous shape, they have the property of easily becoming entangled with each other. Therefore, in the MWCNT aggregate (D) according to the present disclosure, a network structure is easily formed by the entanglement of the MWCNTs.

[0079] The MWCNT aggregate (D) according to the present disclosure contains MWCNTs having a maximum length of 1000 μm to 30000 μm (i.e., ULMWCNTs). ULMWCNTs are longer than general-purpose MWCNTs. The MWCNT aggregate (D) according to the present disclosure tends to have higher conductivity by containing MWCNTs having a maximum length of 1000 μm or more. This is thought to be because the MWCNTs contained in the MWCNT aggregate (D) are more likely to come into contact with each other, making it easier to form conductive paths. The MWCNTs contained in the MWCNT aggregate (D) according to the present disclosure tend to be easier to produce when they have a maximum length of 30000 μm or less. The MWCNT aggregate (D) according to the present disclosure preferably contains MWCNTs having a maximum length of 1050 μm to 25000 μm, more preferably contains MWCNTs having a maximum length of 1100 μm to 20000 μm, further preferably contains MWCNTs having a maximum length of 1200 μm to 18000 μm, and particularly preferably contains MWCNTs having a maximum length of 1300 μm to 15000 μm.

[0080] The MWCNT aggregate (D) according to the present disclosure preferably contains one or more MWCNTs having a maximum length of 1000 μm to 30000 μm (i.e., ULMWCNTs). The ratio of ULMWCNTs in the MWCNT aggregate (D) according to the present disclosure is, for example, preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more, on a number basis. When the ratio of ULMWCNTs in the MWCNT aggregate (D) according to the present disclosure is 10% or more, on a number basis, there is a tendency for the stability of the MWCNT aggregate (D) in an aqueous dispersion due to entanglement of the MWCNTs to be further improved.

[0081] The diameter of the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure is not particularly limited, but is, for example, preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0082] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNTs contained in the MWCNT aggregate (D) according to the present disclosure is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0083] The specific gravity of the MWCNT aggregate (D) according to the present disclosure is not particularly limited, but from the viewpoint of dispersibility when made into an aqueous dispersion, for example, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0084] The MWCNT contained in the MWCNT aggregate (D) according to the present disclosure has a 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 more than 0.9 and 15 or less, preferably 1.0 to 14, more preferably 1.2 to 13, even more preferably 1.3 to 12, and particularly preferably 1.5 to 12. When the peak intensity ratio G1 / D1 of the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure exceeds 0.9, the number of defects present in the MWCNT decreases, and the conductivity tends to improve. When the peak intensity ratio G1 / D1 of the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure is 15 or less, the uniformity of the shape is disrupted, and the MWCNTs tend to become entangled with each other.

[0085] In the present disclosure, 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, is determined by the following method. A Raman spectrum of MWCNT is obtained using a Raman spectrometer under the following measurement conditions. The G band peak intensity G1 and the D band peak intensity D1 are read from the obtained Raman spectrum, and the peak intensity ratio G1 / D1 is determined. As the Raman spectrometer, for example, a RAMAN-11 (product name) Raman spectrometer manufactured by Nanophoton Co., Ltd. can be suitably used. However, the Raman spectrometer is not limited to this.

[0086] <Measurement conditions> Excitation laser wavelength: 532 nm Grating: 600 grooves / mm Objective lens: 20x, numerical aperture (N.A.) 0.45

[0087] 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 1000 nm.

[0088] 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 calcination temperature, gas flow rate, gas introduction method, etc. The peak intensity ratio G1 / D1 can be increased by, for example, increasing the calcination temperature when synthesizing MWCNT, and can be decreased by decreasing the calcination temperature when synthesizing MWCNT.

[0089] The BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure is 50 m ２ / g~400m ２ / g, and 60m ２ / g~350m ２ / g, and 70m ２ / g to 300m ２ / g, more preferably 80m ２ / g~280m ２ / g, and more preferably 100m ２ / g~250m ２ It is particularly preferable that the BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure is 50 m ２ / g or more, the conductivity of the MWCNT aggregate (D) tends to increase. The reason for this is thought to be that the contact between the MWCNTs becomes denser, which reduces the volume resistivity of the MWCNT. When the BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (D) according to the present disclosure is 400 m ２ When the molecular weight is 1 / g or less, the MWCNTs are less likely to aggregate in the aqueous dispersion, and the dispersibility of the MWCNTs tends to increase.

[0090] In the present disclosure, the BET specific surface area of ​​MWCNT is determined by a gas adsorption method using nitrogen gas in accordance with JIS Z 8830:2013. Specifically, the MWCNT is pretreated by packing the MWCNT into a sample tube and vacuum-degassing the sample tube using a pretreatment device at 300°C for 3 hours. The pretreated MWCNT is used as a measurement sample, and the amount of nitrogen adsorption of the MWCNT is measured using a specific surface area measurement device under the measurement conditions below to obtain an adsorption / desorption isotherm. The BET specific surface area is determined from the obtained adsorption / desorption isotherm under the analysis conditions below. Examples of suitable specific surface area measurement devices and pretreatment devices include the BELSORP-mini II (product name), a specific surface area measurement device manufactured by Microtrac-Bell Corporation, and the BELPREP-vac II (product name), a pretreatment device manufactured by Microtrac-Bell Corporation. However, the specific surface area measurement device and pretreatment device are not limited to these.

[0091] <Measurement and analysis conditions> Measurement method: constant volume method Adsorption temperature: 77 K Adsorbate: nitrogen Saturated vapor pressure: actual measurement Equilibrium waiting time: 500 sec Specific surface area: BET method (BET-Plot)

[0092] The BET specific surface area of ​​MWCNT can be controlled by the synthesis conditions during MWCNT synthesis, such as the calcination temperature, gas flow rate, gas introduction method, etc. The BET specific surface area of ​​MWCNT can be increased by, for example, increasing the calcination temperature during MWCNT synthesis, and can be decreased by decreasing the calcination temperature during MWCNT synthesis.

[0093] The MWCNT aggregate (D) according to the present disclosure may contain MWCNTs other than ULMWCNTs, as long as the effect of the MWCNT aggregate (D) is not impaired. The MWCNTs other than ULMWCNTs may be MWCNTs having a maximum length of less than 1000 μm or MWCNTs having a maximum length of more than 30000 μm.

[0094] Furthermore, the MWCNT aggregate (D) according to the present disclosure may contain MWCNTs having a 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 0.9 or less, within a range that does not impair the effects thereof, and may contain more than 15 MWCNTs.

[0095] In addition, the MWCNT aggregate (D) according to the present disclosure has a BET specific surface area of ​​50 m within a range that does not impair its effects. ２ / g, and may contain less than 400 m ２ / g of MWCNTs.

[0096] [MWCNT aggregate (E)] In an embodiment, the multi-walled carbon nanotube aggregate according to the present disclosure comprises multi-walled carbon nanotubes having a maximum length of more than 1600 μm and not more than 30000 μm, and the multi-walled carbon nanotubes have a peak intensity ratio G1 / D1 of 10 or less, which is a 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 multi-walled carbon nanotubes, and the multi-walled carbon nanotubes have a BET specific surface area of ​​200 m ２ / g to 300m ２ / g. In the present disclosure, the multi-walled carbon nanotube aggregate according to this embodiment is also referred to as "MWCNT aggregate (E)". In addition, in the present disclosure, "MWCNT having a maximum length of 1600 μm to 30000 μm" is also referred to as "specific ULMWCNT".

[0097] The MWCNT aggregate (E) according to the present disclosure has high electrical conductivity. The reason why the MWCNT aggregate (E) according to the present disclosure has high electrical conductivity is not clear, but the present inventors speculate as follows. However, the following speculation is not intended to limit the MWCNT aggregate (E) according to the present disclosure, but is described as an example.

[0098] The MWCNT aggregate (E) according to the present disclosure contains MWCNTs with a maximum length of 1,600 μm to 30,000 μm (i.e., specific ULMWCNTs), and therefore it is believed that the MWCNTs are more likely to come into contact with each other. When the MWCNTs are more likely to come into contact with each other, conductive paths are more likely to be formed, and conductivity can be improved. Furthermore, the MWCNTs contained in the MWCNT aggregate (E) according to 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 a Raman spectrum, that is a specific value or less, and have a relatively non-uniform shape, so that entanglement between the MWCNTs tends to occur easily. The more entanglement between the MWCNTs occurs, the more the conductivity can be improved. Furthermore, it is believed that the MWCNTs contained in the MWCNT aggregate (E) according to the present disclosure have a moderately large BET specific surface area, which results in close contact between the MWCNTs. When the MWCNTs are in close contact with each other, the surface resistivity of the MWCNTs decreases and the conductivity can be improved. From the above, it is presumed that the MWCNT aggregate (E) according to the present disclosure has high conductivity.

[0099] The specific ULMWCNT contained in the MWCNT aggregate (E) according to the present disclosure can have a fibrous shape. The specific ULMWCNT has the property of easily entangling with each other when it has a fibrous shape. Therefore, in the MWCNT aggregate (E) according to the present disclosure, a network structure is easily formed by the entanglement of the MWCNTs.

[0100] The MWCNT aggregate (E) according to the present disclosure contains MWCNTs having a maximum length of 1600 μm to 30,000 μm (i.e., specific ULMWCNTs). The specific ULMWCNTs are much longer than general-purpose MWCNTs. The MWCNT aggregate (E) according to the present disclosure tends to have higher conductivity by containing MWCNTs having a maximum length of 1600 μm or more. This is thought to be because the MWCNTs contained in the MWCNT aggregate (E) are more likely to come into contact with each other, making it easier to form conductive paths. The MWCNTs contained in the MWCNT aggregate (E) according to the present disclosure tend to be easier to produce when they have a maximum length of 30,000 μm or less. The MWCNT aggregate (E) according to the present disclosure preferably contains MWCNTs having a maximum length of 1700 μm to 25000 μm, more preferably contains MWCNTs having a maximum length of 1800 μm to 20000 μm, further preferably contains MWCNTs having a maximum length of 1900 μm to 18000 μm, and particularly preferably contains MWCNTs having a maximum length of 2000 μm to 15000 μm.

[0101] The MWCNT aggregate (E) according to the present disclosure preferably contains one or more MWCNTs having a maximum length of 1600 μm to 30000 μm (i.e., specific ULMWCNTs). The ratio of the specific ULMWCNTs in the MWCNT aggregate (E) according to the present disclosure is, for example, preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 50% or more, on a number basis. When the ratio of the specific ULMWCNTs in the MWCNT aggregate (E) according to the present disclosure is 10% or more, on a number basis, there is a tendency for the stability of the MWCNT aggregate (E) in an aqueous dispersion due to entanglement of the MWCNTs to be further improved.

[0102] The diameter of the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is not particularly limited, but is, for example, preferably 1 nm to 100 nm, more preferably 2 nm to 80 nm, even more preferably 3 nm to 50 nm, and particularly preferably 5 nm to 30 nm.

[0103] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNTs contained in the MWCNT aggregate (E) according to the present disclosure is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0104] The specific gravity of the MWCNT aggregate (E) according to the present disclosure is not particularly limited, but from the viewpoint of dispersibility when made into an aqueous dispersion, for example, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0105] The MWCNT contained in the MWCNT aggregate (E) according to the present disclosure has a 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 10 or less, preferably 9 or less, and more preferably 8 or less. When the peak intensity ratio G1 / D1 of the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is 10 or less, the uniformity of the shape is disrupted, and the MWCNTs tend to become entangled with each other. The lower limit of the peak intensity ratio G1 / D1 of the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is not particularly limited, but, for example, from the viewpoint of improving conductivity by reducing defects present in the MWCNT, it is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more. The peak intensity ratio G1 / D1 of the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure may be, for example, 1 to 10, 1.5 to 9, or 2 to 8.

[0106] The BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is 200 m ２ / g to 300m ２ / g, and 205m ２ / g~290m ２ / g, and 210m ２ / g~280m ２ / g, and more preferably 220m ２ / g~275m ２ / g. It is more preferable that the BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is 200 m ２ / g or more, the conductivity of the MWCNT aggregate (E) tends to increase. The reason for this is thought to be that the contact between the MWCNTs becomes denser, resulting in a decrease in the surface resistivity of the MWCNT. When the BET specific surface area of ​​the MWCNT contained in the MWCNT aggregate (E) according to the present disclosure is 300 m ２ When the molecular weight is 1 / g or less, the MWCNTs are less likely to aggregate in the aqueous dispersion, and the dispersibility of the MWCNTs tends to increase.

[0107] The BET specific surface area of ​​MWCNT can be controlled by the synthesis conditions during MWCNT synthesis, such as the calcination temperature, gas flow rate, gas introduction method, etc. The BET specific surface area of ​​MWCNT can be increased by, for example, increasing the calcination temperature during MWCNT synthesis, and can be decreased by decreasing the calcination temperature.

[0108] The MWCNT aggregate (E) according to the present disclosure may contain MWCNTs other than the specific ULMWCNTs, as long as the effect of the MWCNT aggregate (E) is not impaired. The MWCNTs other than the specific ULMWCNTs may be MWCNTs having a maximum length of less than 1600 μm or MWCNTs having a maximum length of more than 30000 μm.

[0109] Furthermore, the MWCNT aggregate (E) according to the present disclosure may contain MWCNTs having a 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 more than 10, within a range that does not impair the effects thereof.

[0110] In addition, the MWCNT aggregate (E) according to the present disclosure has a BET specific surface area of ​​200 m within a range that does not impair its effects. ２ / g, and may contain less than 300 m ２ / g of MWCNTs.

[0111] <<Uses of Multi-Walled Carbon Nanotube Aggregates>> The uses of the MWCNT aggregate according to the present disclosure are not particularly limited. The MWCNT aggregate according to the present disclosure has high conductivity and can therefore be suitably used, for example, as a conductive additive (particularly, a conductive additive for a negative electrode). The MWCNTs in the MWCNT aggregate according to the present disclosure are easily entangled with each other to form conductive paths, and therefore, for example, by coexisting with a conductive material such as a positive electrode active material or a negative electrode active material in an electrode, the conductivity of the conductive material can be further improved. The MWCNT aggregate according to the present disclosure can be used, for example, together with known conductive additives such as graphite and ketjen black.

[0112] The MWCNT aggregate according to the present disclosure can be used, for example, as a conductive material. Examples of conductive materials to which the MWCNT aggregate according to the present disclosure is applied include electrode materials in secondary batteries (e.g., lithium ion batteries), specifically, negative electrode materials and positive electrode materials.

[0113] [Method for Producing Multi-Walled Carbon Nanotubes] There are no particular limitations on the method for producing MWCNTs contained in the MWCNT aggregate according to the present disclosure (so-called MWCNTs in the present disclosure).

[0114] As a method for producing MWCNT in the present disclosure, a conventionally known method such as a chemical vapor deposition (CVD) method or a method of reacting a gaseous reactant containing a carbon source in the presence of a catalyst can be applied.

[0115] The MWCNTs of the present disclosure can be produced, for example, by referring to the production method described in JP 2016-102047 A. An example of the production method for MWCNTs of the present disclosure will be described below. However, the production method for MWCNTs of the present disclosure is not limited to the following example.

[0116] An example of a method for producing MWCNTs in the present disclosure is the method described in JP 2016-102047 A, i.e., a production method (also referred to as "Production Method X") comprising the steps of passing gaseous reactants containing one or more carbon sources through a reactor, reacting the one or more gaseous reactants in a reaction zone of the reactor in the presence of a catalyst to form product particles containing carbon, aggregating the product particles into agglomerates, and applying force to the agglomerates to continuously move the agglomerates out of the reaction zone. Production Method X makes it possible to obtain MWCNTs in the present disclosure in the form of fibrous agglomerates or other agglomerate forms that are easy to handle.

[0117] In production method X, the force applied to the product particles may be a mechanical force. When the agglomerates are fibrous MWCNTs, the mechanical force applied to the product particles may be applied by a rotating spindle around which the agglomerates are wound. The fibrous MWCNTs may be collected on the spindle, or may be accumulated elsewhere by rotating around the spindle one or more times and then successively unwinding the spindle.

[0118] 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 an angle of 25° to the flow direction of the gaseous reactants may also be suitable for applying mechanical forces to the product particles.

[0119] The spindle can rotate about two axes (e.g., two perpendicular axes). In particular, the spindle can rotate about axes perpendicular and parallel to the flow direction of the gaseous reactants. Such a spindle can pull and twist the fibrous MWCNT agglomerates to control the twist number and length.

[0120] The spindle material may be made of metal, ceramic, or resin. The spindle can have different suitable shapes depending on the properties of the material 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.

[0121] 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 application of electric or other fields to the carbon product. Coating thickness and orientation can be controlled, for example, by gas flow forces.

[0122] The rotational speed of the spindle is preferably 0.01 rpm (revolutions per minute; hereinafter the same) 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 to that at which it is produced. The rotational speed of the spindle may also control the thickness of the accumulated fibrous MWCNT. In a preferred embodiment, as the spindle rotates, the fibrous MWCNT is processed in the axial direction of the spindle. In this processing, the fibrous MWCNT is evenly wrapped along the spindle, rather than being wrapped only at one specific point on the spindle.

[0123] 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 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.

[0124] In manufacturing 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.

[0125] Other forces that can be applied to the product particles include electrostatic forces, suitably applied by a charged plate. Electrostatic forces require that the product particles be charged. The use of a charged plate allows the MWCNTs to form an entangled mat on the charged plate.

[0126] Other forces applied to the product particles may also be magnetic forces or photon pressure applied by a light source.

[0127] Instead of a gaseous reactant containing a carbon source, the CNT source may be injected in the form of a liquid containing a carbon source. When a liquid is used as the CNT source, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0128] Preferably, the gaseous reactant or reactants are reacted at a temperature between 500° C. and 1600° C., more preferably between 1000° C. and 1500° C. or 1600° C. (especially 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.

[0129] 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 maintain active sites on the catalyst for nanotube production.

[0130] 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.

[0131] The gas pressure of the gaseous reactants and any diluents is preferably between 0.1 bar and 50 bar, more preferably between 0.5 bar and 5 bar, and even more preferably between 1 bar and 2 bar. If there is a gas effluent from the furnace, the effluent gas can be recycled with or without cleaning.

[0132] 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.

[0133] 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.

[0134] The product particles in Production Method X contain the MWCNTs defined in the present disclosure. Depending on the production conditions, in addition to the MWCNTs defined in the present disclosure, MWCNTs and / or SWCNTs other than the MWCNTs defined in the present disclosure may also be contained.

[0135] 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.

[0136] Examples of 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). Preferred carbon-containing compounds are carbon monoxide, methane, ethylene, or acetylene.

[0137] 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.

[0138] 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.

[0139] The catalyst is preferably a transition metal, particularly a Group VIB transition metal such as chromium (Cr), molybdenum (Mo), tungsten (W), or a Group VIIIB transition metal. Specifically, the catalyst may be, 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, such as yttrium (Y), may also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof, such as a 50 / 50 mixture of Ni and Co, a mixture of Fe and Ni, or a mixture of Fe and Mo, are more preferred. Any of these transition metals, alone or in combination with any of the other transition metals listed, may serve as a catalyst for CNT growth. It is particularly preferred that the catalyst is a mixture of two or more of the metals listed.

[0140] 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 supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0141] The carbon source is preferably reacted in the presence of a promoter. Suitable promoters include one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is one preferred promoter. Suitably, up to 10% by weight (10% by weight or less) of the promoter is contained in the carbon source. Preferably, 0.2% to 6% by weight of the promoter is contained in the carbon source. When a high or low concentration of thiophene is used as the promoter, MWCNTs are formed. For example, MWCNTs are successfully formed using ethanol containing 0% by weight or 1.5% to 4.0% by weight of thiophene and 1.0% to 10.0% by weight (particularly 2.3% by weight) of ferrocene, with an injection rate of 5.0 mL / hour to 30.0 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.

[0142] According to production method X, fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can be in the form of threads (so-called fibers), sheets, etc. The length of the fibrous CNTs can be controlled, for example, by the winding capacity of the spindle used to produce the fibrous CNTs.

[0143] 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.

[0144] Another embodiment may involve producing MWCNTs in a reaction zone by the above method, followed by condensation to form agglomerates of MWCNTs, and continuously withdrawing the MWCNTs from near the reaction zone. Another embodiment may involve producing MWCNTs in a reaction zone, continuously electrostatically withdrawing the MWCNTs from the reaction zone, and recovering the MWCNTs.

[0145] [Multi-walled carbon nanotube dispersion] The MWCNT dispersion according to the present disclosure contains the MWCNT aggregate according to the present disclosure described above and a dispersion medium. The MWCNT aggregate according to the present disclosure has excellent dispersibility in a dispersion medium such as water, and therefore can be suitably used in the state of a dispersion.

[0146] <Multi-walled carbon nanotube aggregate> The MWCNT dispersion according to the present disclosure contains the MWCNT aggregate according to the present disclosure. Details of the MWCNT aggregate according to the present disclosure are as described above, and therefore description thereof will be omitted here.

[0147] The content of the MWCNT aggregate according to the present disclosure in the MWCNT dispersion according to the present disclosure is not particularly limited and can be set appropriately depending on the purpose. For example, from the viewpoint of conductive effect, the content of the MWCNT aggregate according to the present disclosure in the MWCNT dispersion according to the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and particularly preferably 0.2 mass% or more, relative to the total mass of the MWCNT dispersion. Furthermore, for example, from the viewpoint of dispersibility, the content of the MWCNT aggregate according to the present disclosure in the MWCNT dispersion according to the present disclosure is preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 10 mass% or less, and particularly preferably 5 mass% or less, relative to the total mass of the MWCNT dispersion. In an embodiment, the content of the MWCNT aggregate according to the present disclosure in the MWCNT dispersion according to the present disclosure may be 0.01 mass % to 20 mass %, 0.05 mass % to 15 mass %, 0.1 mass % to 10 mass %, or 0.2 mass % to 5 mass %, relative to the total mass of the MWCNT dispersion.

[0148] <Dispersion Medium> The MWCNT dispersion according to the present disclosure contains a dispersion medium. The dispersion medium preferably contains water, and more preferably contains water as the main component. "Containing water as the main component" means that the proportion of water in the dispersion medium is more than 50 mass%. The proportion of water in the dispersion medium is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 99 mass% or more, and may be, for example, 100 mass%. The water is not particularly limited, but is preferably distilled water, ion-exchanged water, pure water, or the like, in terms of having few impurities.

[0149] The dispersion medium may be a mixture of water and a hydrophilic solvent. Examples of the hydrophilic solvent 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.

[0150] <Dispersant> The MWCNT dispersion according to the present disclosure may contain a dispersant. When the MWCNT dispersion according to the present disclosure contains a dispersant, the dispersibility and dispersion stability of the MWCNT aggregate according to the present disclosure may be improved. The dispersant is not particularly limited, and examples thereof include various surfactants. Further examples of the dispersant include polymer compounds such as resins. As the dispersant, a surfactant is preferred. The surfactant may be an ionic surfactant or a nonionic surfactant, and is not particularly limited.

[0151] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzene sulfonate) and dodecylphenyl ether sulfonate; 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. Examples of ionic surfactants include ionic surfactants having an aromatic ring (so-called aromatic ionic surfactants), and more preferably aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecylphenyl ether sulfonates. Aromatic ionic surfactants tend to be excellent in dispersibility, dispersion stability, and concentration of MWCNT aggregates.

[0152] 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 nonionic surfactants, ionic surfactants having an aromatic ring (so-called aromatic nonionic surfactants) are preferred, polyoxyalkylene phenyl ethers are more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to be excellent in dispersibility, dispersion stability, and concentration of MWCNT aggregates.

[0153] Other dispersants that are excellent in dispersibility, dispersion stabilization, and concentration enhancement of MWCNT aggregates include β-naphthalenesulfonic acid formalin condensate sodium salts, such as Demol N, Demol RN, and Demol T (manufactured by Kao Corporation), polyoxyethylene stearyl ether Brij S 100 (manufactured by Sigma-Aldrich), 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 Co., Ltd.) is an example. CMC is particularly preferred from the viewpoint of excellent dispersibility, dispersion stabilization ability, and high concentration of MWCNT aggregates.

[0154] When the MWCNT dispersion according to the present disclosure contains a dispersant, it may contain only one type of dispersant, or may contain two or more types of dispersants.

[0155] When the MWCNT dispersion according to the present disclosure contains a dispersant, the content of the dispersant in the MWCNT dispersion is not particularly limited and can be set appropriately depending on the type of dispersant, the amount of MWCNT aggregates, the amount of dispersion medium, etc. An example of the content of the dispersant in the MWCNT dispersion according to the present disclosure is 0.01% by mass to 20% by mass with respect to the total mass of the MWCNT dispersion.

[0156] <Other Components> The MWCNT dispersion according to the present disclosure may contain components (so-called other components) other than the MWCNT aggregate and dispersion medium according to the present disclosure, as long as the effects of the dispersion are not impaired. Examples of other components include various additives such as antifoaming agents and antistatic agents. Examples of other components include CNTs other than the MWCNTs of the present disclosure, carbon materials other than CNTs, and the like. The MWCNT dispersion according to the present disclosure may also contain trace amounts of impurity components (for example, unavoidable impurities) as long as the effects of the dispersion are not impaired.

[0157] <<Uses of Multi-Walled Carbon Nanotube Dispersion>> The uses of the MWCNT dispersion according to the present disclosure are not particularly limited. The MWCNT dispersion according to the present disclosure has excellent dispersibility of MWCNT aggregates and high conductivity, and therefore can be applied to conductive materials such as conductive inks, antistatic agents, conductive materials for circuit pattern formation, transparent electrode materials, and water-soluble polymer fillers. The MWCNT dispersion according to the present disclosure can be suitably used, for example, as a conductive ink for forming electrodes (particularly negative electrodes) of various secondary batteries such as lithium-ion batteries. By using the MWCNT dispersion according to the present disclosure as a conductive ink, highly conductive electrodes can be easily produced.

[0158] [Method for producing multi-walled carbon nanotube dispersion] The method for producing the MWCNT dispersion according to the present disclosure is not particularly limited. The MWCNT dispersion according to the present disclosure can be produced by dispersing the MWCNT aggregate according to the present disclosure in a dispersion medium. That is, the MWCNT dispersion according to the present disclosure can be produced by a method including a step of dispersing the MWCNT aggregate according to the present disclosure in a dispersion medium (also referred to as a "dispersion step").

[0159] <Dispersion step> The dispersion step is a step of dispersing the MWCNT aggregate according to the present disclosure in a dispersion medium. In the dispersion step, a dispersant may be used from the viewpoint of improving the dispersibility and dispersion stability of the MWCNT aggregate according to the present disclosure. Details of the MWCNT aggregate, dispersion medium, and dispersant according to the present disclosure are as described above, and therefore will not be described here.

[0160] The dispersion method is not particularly limited. Examples of dispersion methods include methods using dispersion devices such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device (e.g., ultrasonic disperser). Examples of dispersion methods include methods using 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, vertical or horizontal agitator mill, attritor, colloid mill, three-roll mill, pearl mill, super mill, impeller, disperser, KD mill, dynatron, and pressure kneader. 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 pressure-feeds a mixture in a solvent as a high-speed flow from a nozzle arranged in a sealed pressure-resistant container. In a wet jet mill, aggregates of multi-walled carbon nanotubes are dispersed by collisions between countercurrent flows in a pressure-resistant container, collisions with the container wall, turbulence caused by high-speed flow, shear flow, etc. As the wet jet mill, an ultra-high pressure homogenizer (model number: NAGS20, NAGS100, NAGS200, 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.

[0161] <Drying Step> The method for producing a MWCNT dispersion according to the present disclosure may include a step of drying the MWCNT aggregate according to the present disclosure (also referred to as a "drying step") before the dispersion step. When moisture adheres to the MWCNT, the MWCNTs tend to stick together due to the surface tension of the water. If a drying step is performed before the dispersion step, moisture adhered to the MWCNT is removed and the adhesion of the MWCNTs to each other due to moisture adhesion is suppressed, thereby further improving the dispersibility of the MWCNT aggregate. The drying method is not particularly limited. Examples of drying methods include heat drying, vacuum drying, and heat vacuum drying. Heat vacuum drying is preferred as the drying method. The drying temperature is not particularly limited and is preferably, for example, 40°C to 100°C. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhesion to the MWCNT, etc.

[0162] The MWCNT dispersion according to the present disclosure can be suitably produced, for example, by the method described in the examples below.

[0163] [Conductive Material] The conductive material according to the present disclosure includes the MWCNT aggregate according to the present disclosure. As described above, the MWCNT aggregate according to the present disclosure contained in the conductive material according to the present disclosure has high conductivity and excellent dispersibility when made into a dispersion, and is therefore suitable as a conductive auxiliary agent. Since the conductive material according to the present disclosure includes the MWCNT aggregate according to the present disclosure, it has excellent conductive efficiency and can effectively impart high conductivity to an object of use.

[0164] 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 MWCNT aggregate according to the present disclosure.

[0165] 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.

[0166] <Electrode> The electrode may contain the MWCNT aggregate according to the present disclosure described above. In the electrode, the MWCNT aggregate according to the present disclosure may function as a conductive additive. The MWCNT aggregate contained in the electrode described below is synonymous with the MWCNT aggregate according to the present disclosure, and preferred embodiments are also the same, so description of the MWCNT aggregate will be omitted below.

[0167] 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.

[0168] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of the current collector include copper, stainless steel, aluminum, nickel, titanium, baked carbon, and aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like. Specifically, transition metals such as copper and nickel that have good carbon adsorption properties may be used as the current collector.

[0169] The electrode active material layer may contain 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 may 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 lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), compounds substituted with one or more transition metals; LiFe ３ O ４ Lithium iron oxides such as those with the chemical formula Li １＋ｃ１ Mn ２－ｃ１ O ４ (0≦c1≦0.33), LiMnO ３ , LiMn ２ O ３ , LiMnO ２ Lithium manganese oxides such as lithium copper oxide (Li ２ CuO ２ ); LiV ３ O ８ , V２ O ５ , Cu ２ V ２ O ７ Vanadium oxides such as LiNi １－ｃ２ M ｃ２ O ２ (wherein 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); Ni-site type lithium nickel oxide represented by the chemical formula LiMn ２－ｃ３ M ｃ３ O ２ (wherein 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 Li ２ Mn ３ MO ８ (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn ２ O ４ Examples include:

[0170] 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 commonly used for negative electrode materials. Specifically, the negative electrode active material can contain graphite-based active material particles or silicon-based active material particles. The graphite-based active material particles may be at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesocarbon microbeads. Using artificial graphite as the graphite-based active material particles can improve rate characteristics. The silicon-based active material particles may be at least one selected from the group consisting of Si, SiOx (0<x<2), Si-C composites, and Si-Y alloys (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, Group 13 elements, Group 14 elements, rare earth elements, and combinations thereof). The use of silicon-based active material particles can increase the capacity of the battery.

[0171] The electrode active material layer may further contain a binder. The binder is not particularly limited, and the electrode active material layer may contain a binder that is commonly used in electrode materials. Examples of the binder include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, 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.

[0172] <Secondary Battery> The secondary battery may be configured to 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 an electrode material including the MWCNT aggregate according to the present disclosure.

[0173] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. It is not particularly limited as long as it is typically used as a separator in a secondary battery. The separator preferably has low resistance to ion migration of the electrolyte and excellent electrolyte humidification capacity. Specific examples of the separator include porous polymer films. 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 comprising two or more layers of these films. The separator may also be a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fiber or polyethylene terephthalate fiber. The separator may also be coated with a ceramic component or a polymeric substance to ensure heat resistance or mechanical strength. The separator may be selectively formed into a single-layer or multi-layer structure.

[0174] 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.

[0175] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt. Examples of the non-aqueous organic solvent 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.

[0176] Among carbonate 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.

[0177] The metal salt may be a lithium salt. The lithium salt is a substance that is easily dissolved in a non-aqueous electrolyte. The anion portion of the lithium salt may be, for example, F － , Cl － , I － , NO ３ － , N (CN) ２ － , B.F. ４ － , ClO ４ － , P.F. ６ － , (CF ３ ) ２ PF ４ － , (CF３ ) ３ PF ３ － , (CF ３ ) ４ PF ２ － , (CF ３ ) ５ PF － , (CF ３ ) ６ P － , CF ３ SO ３ － , CF ３ CF ２ SO ３ － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) ２ N － , CF ３ CF ２ , (CF ３ ) ２ CO － , (CF ３ SO ２ ) ２ CH － , (SF ５ ) ３ C － , (CF ３ SO ２ ) ３ C － , CF ３ , (CF ２ ) ７ SO ３ － , CF ３ CO ２ － , CH ３ CO ２ － , SCN － , and, (CF ３ CF ２ SO ２ ) ２ N － are included.

[0178] 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 life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0179] 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 medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0180] [Composition] <Resin, ceramics, concrete, etc.> The composition according to the present disclosure is a composition containing the MWCNT aggregates (A) to (E) according to the present disclosure and at least one selected from the group consisting of resin, ceramic, and concrete. Examples of the resin include thermoplastic resins and thermosetting resins, and preferred are olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, thermoplastic polyurethane resins, polysulfone-based resins, and silicone resins. Examples of the ceramic include crystalline ceramics and amorphous ceramics. Examples of the concrete include Portland cement concrete. The composition according to the present disclosure may further contain other components such as water and an organic solvent. In the composition according to the present disclosure, when the content of the MWCNT aggregates (A) to (E) according to the present disclosure is taken as 100 parts by mass, the content of at least one selected from the group consisting of resin, ceramic, and concrete is usually 10 to 1,000,000 parts by mass, preferably 100 to 100,000 parts by mass, and more preferably 1,000 to 40,000 parts by mass, and in cases where other components are included, the content is preferably 1 to 10,000 parts by mass, and more preferably 10 to 1,000 parts by mass. In the composition according to the present disclosure, the MWCNT aggregates (A) to (E), resin, ceramic, concrete, and other components may each be included singly, or two or more types may be included.

[0181] <Method for producing composition> The composition according to the present disclosure can be produced, for example, by mixing the MWCNT aggregates (A) to (E) according to the present disclosure with resin, ceramics, or pre-hardened concrete. The resin may be in the form of powder, pellets, solution, or dispersion. The ceramics may be in the form of powder, precursor solution, or dispersion. The composition according to the present disclosure can also be produced, for example, by dispersing the MWCNT aggregates (A) to (E) according to the present disclosure in a resin solution, ceramic precursor or dispersion, or pre-hardened concrete, and then molding the resultant.

[0182] <Uses of the Composition> When the composition according to the present disclosure contains a resin or ceramic, it is useful as, for example, a structural material, a conductive material, a heat management material, or an antistatic material. When the composition according to the present disclosure contains concrete, it is useful as a lightweight, durable building material, or an electricity storage device (impregnated with an electrolyte as needed).

[0183] [Planar aggregate] The planar aggregate according to the present disclosure includes the MWCNT aggregate according to the present disclosure. The ratio of the MWCNT aggregate according to the present disclosure contained in the planar aggregate according to the present disclosure is usually 1 mass% or more with respect to the total mass of the planar aggregate. The planar aggregate according to the present disclosure may include other components such as a CNT aggregate (particularly a MWCNT aggregate) having a maximum length of less than 1000 μm.

[0184] [Method for producing planar aggregate] There are no particular limitations on the method for producing the planar aggregate according to the present disclosure. The planar aggregate according to the present disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing the MWCNT aggregate according to the present disclosure, or the MWCNT aggregate according to the present disclosure and other components such as a CNT aggregate (particularly a MWCNT aggregate) having a maximum length of less than 1000 μm, in water or other fluid, and filtering once or twice or more times.

[0185] An example of the planar assembly according to the present disclosure is a film.

[0186] Planar assemblies according to the present disclosure are useful, for example, in filters, electromagnetic wave shields, and extreme ultraviolet (EUV) pellicles.

[0187] The MWCNT aggregate according to the present disclosure will be described in more detail below with reference to examples. The MWCNT aggregate according to the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0188] [Manufacturing MWCNT Aggregates or Preparation of SWCNT Aggregates] Example 1 The MWCNT aggregate 1 in Example 1 was produced by a floating catalyst method (CVD method) that 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 at 400°C to 700°C. A mixture of nitrogen and argon was used as the carrier gas, and 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. Next, methane, a carbon source, was released into the carrier gas flow. A metal catalyst and a carbon source were supplied to 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. In the second temperature zone, an electric field was generated in a temperature-controlled flow reactor, thereby producing MWCNT aggregates. The produced aggregates were continuously discharged through an outlet of the flow reactor, which was controlled at a temperature of 100°C to 500°C, and collected as sheet-like MWCNT aggregates by continuous discharge. The collected sheet-like MWCNT aggregate was immersed in a PTFE tray containing hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) for 24 hours. Thereafter, the MWCNT aggregate was removed from the tray and washed with deionized water until the pH of the wash water reached 7. In this manner, MWCNT aggregate 1 of Example 1 was obtained.

[0189] Example 2 MWCNT aggregate 2 of Example 2 was obtained in accordance with Example 1, except that the sheet-like MWCNT aggregate collected in Example 1 was washed with deionized water for 10 seconds.

[0190] Example 3 Similar to the sheet-like MWCNT aggregate collected in Example 1, MWCNT aggregate 3 in Example 3 was produced by a floating catalyst method (CVD method) that 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°C and 700°C. A mixture of nitrogen and argon was used as the carrier gas. The carrier gas flow rate 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. Next, methane, a carbon source, was released into the carrier gas flow. The metal catalyst and carbon source were supplied to a second temperature zone downstream of the first temperature zone, whose temperature was controlled at 1,400°C. The second temperature zone is maintained at a temperature sufficient to produce carbon nanotube aggregates. In the second temperature zone, an electric field is generated in a temperature-controlled flow-type reactor, thereby producing MWCNT aggregates. The produced aggregates are continuously discharged through an outlet of the flow-type reactor, the temperature of which is controlled at 100°C to 500°C, and collected as fibrous MWCNT aggregates by continuous discharge. The collected fibrous MWCNT aggregates are washed with deionized water for 10 seconds. In this manner, MWCNT aggregate 3 of Example 3 is obtained.

[0191] <Comparative Example 1> SWCNT aggregate 1 [product name: TUBALL ＴＭ , single-walled carbon nanotube powder, manufactured by OCSiAl Co., Ltd.] was used as Comparative Example 1.

[0192] Comparative Example 2 MWCNT aggregate 4 (product number: 901019, multi-walled carbon nanotube powder, manufactured by Sigma-Aldrich) was used as Comparative Example 2.

[0193] Comparative Example 3 MWCNT aggregate 5 (product number: FT7000, multi-walled carbon nanotube powder, manufactured by C-nano Corporation) was used as Comparative Example 3.

[0194] [Evaluation] The following evaluations were performed on the MWCNT aggregate 1 of Example 1, the MWCNT aggregate 2 of Example 2, the MWCNT aggregate 3 of Example 3, the SWCNT aggregate 1 of Comparative Example 1, the MWCNT aggregate 4 of Comparative Example 2, and the MWCNT aggregate 5 of Comparative Example 3. Hereinafter, for convenience, "the MWCNT aggregate 1 of Example 1, the MWCNT aggregate 2 of Example 2, the MWCNT aggregate 3 of Example 3, the SWCNT aggregate 1 of Comparative Example 1, the MWCNT aggregate 4 of Comparative Example 2, and the MWCNT aggregate 5 of Comparative Example 3" may be collectively referred to as "CNT aggregate".

[0195] 1. Observation of SEM Photos (1) Preparation of CNT Dispersion for SEM Photography (1-1) MWCNT Aggregate 1 of Example 1 1.1 g of the MWCNT aggregate 1 of Example 1, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 547.25 g of ion-exchanged water were mixed. The resulting mixture was subjected to a dispersion treatment for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. as a pre-dispersion before the main dispersion, to obtain a dispersion A. Note that the MWCNT aggregate 1 was cut into small pieces of about 1 cm square using scissors before mixing so that the MWCNT aggregate 1 would not get tangled in the blades of the homogenizer. Next, the dispersion liquid A obtained above was subjected to a main dispersion treatment under the following conditions using an ultra-high pressure homogenizer (model number: NAGS100) manufactured by Joko Corporation, which is a wet jet mill, to obtain CNT dispersion liquid A for SEM photography.

[0196] -Conditions- Nozzle diameter: 0.22 mm Pressure: 85 MPa Number of times: 8 Method: Circulation method

[0197] (1-2) MWCNT aggregate 2 of Example 2 1.1 g of the MWCNT aggregate 2 of Example 2, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 547.25 g of ion-exchanged water were mixed. The obtained mixture was subjected to a dispersion treatment for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. as a pre-dispersion before the main dispersion, to obtain a dispersion B. Note that the MWCNT aggregate 2 was cut into small pieces of about 1 cm square using scissors before mixing so that the MWCNT aggregate 2 would not get tangled in the blades of the homogenizer. Next, the dispersion liquid B obtained above was subjected to main dispersion treatment under the same conditions as the main dispersion treatment in "(1-1) MWCNT aggregate 1 of Example 1" above, using an ultra-high pressure homogenizer [model number: NAGS100], which is a wet jet mill, manufactured by Joko Corporation, to obtain a CNT dispersion liquid B for SEM photography.

[0198] (1-3) MWCNT aggregate 3 of Example 3 1.1 g of the MWCNT aggregate 3 of Example 3, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 547.25 g of ion-exchanged water were mixed. The resulting mixture was subjected to a dispersion treatment for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. as a pre-dispersion before the main dispersion, to obtain a dispersion C. Note that the MWCNT aggregate 3 was cut to a length of about 1 cm using scissors before mixing so that the MWCNT aggregate 3 would not get tangled in the blades of the homogenizer. Next, the dispersion liquid C obtained above was subjected to main dispersion treatment under the same conditions as the main dispersion treatment in "(1-1) MWCNT aggregate 1 of Example 1" above, using an ultra-high pressure homogenizer [model number: NAGS100], which is a wet jet mill, manufactured by Joko Corporation, to obtain a CNT dispersion liquid C for SEM photography.

[0199] (1-4) SWCNT aggregate 1 of Comparative Example 1 As a dispersion of SWCNT aggregate 1 of Comparative Example 1, CNT dispersion D for SEM photography (trade name: TUBALL ＴＭ BATT H ２ The CNT concentration was adjusted to 0.2 mass %.

[0200] (1-5) MWCNT aggregate 4 of Comparative Example 2 1.1 g of MWCNT aggregate 4 of Comparative Example 2, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 547.25 g of ion-exchanged water were mixed. The obtained mixture was subjected to a dispersion treatment for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. as a pre-dispersion before the main dispersion, to obtain a dispersion E. Next, the dispersion liquid E obtained above was subjected to main dispersion treatment under the same conditions as the main dispersion treatment in "(1-1) MWCNT aggregate 1 of Example 1" using an ultra-high pressure homogenizer [model number: NAGS100] manufactured by Joko Corporation, which is a wet jet mill, to obtain a CNT dispersion liquid E for SEM photography.

[0201] (1-6) MWCNT aggregate 5 of Comparative Example 3 1.1 g of the MWCNT aggregate 5 of Comparative Example 3, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 547.25 g of ion-exchanged water were mixed. The obtained mixture was subjected to a dispersion treatment for 1 hour using an Ace Homogenizer manufactured by Nippon Seiki Co., Ltd. as a pre-dispersion before the main dispersion, to obtain a dispersion F. Next, the dispersion liquid F obtained above was subjected to main dispersion treatment under the same conditions as the main dispersion treatment in "(1-1) MWCNT aggregate 1 of Example 1" using an ultra-high pressure homogenizer [model number: NAGS100] manufactured by Joko Corporation, which is a wet jet mill, to obtain a CNT dispersion liquid F for SEM photography.

[0202] (2) Taking SEM Photographs (2-1) MWCNT Aggregate 1 of Example 1 When an SEM photograph (magnification: 5000x) of the MWCNT aggregate 1 of Example 1 was taken, it was confirmed that a plurality of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm were present within the viewing angle of the SEM photograph. Furthermore, a plurality of SEM photographs (magnification: 5000x) of adjacent viewing angles of the MWCNT aggregate 1 of Example 1 were taken, and focusing on 100 MWCNTs included in the viewing angle of the SEM photograph, the maximum length of each was measured. Of the observed MWCNTs, the proportion of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm (i.e., SLMWCNTs) was 90%, and the maximum value of the maximum length of the 100 observed MWCNTs was 3,500 μm.

[0203] (2-2) MWCNT aggregate 2 of Example 2 When an SEM photograph (magnification: 5000x) of the MWCNT aggregate 2 of Example 2 was taken, it was confirmed that a plurality of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm were present within the viewing angle of the SEM photograph. Furthermore, a plurality of SEM photographs (magnification: 5000x) of adjacent viewing angles of the MWCNT aggregate 2 of Example 2 were taken, and focusing on 100 MWCNTs included in the viewing angle of the SEM photograph, the maximum length of each was measured. Of the observed MWCNTs, the proportion of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm (i.e., SLMWCNTs) was 90%, and the maximum value of the maximum length of the 100 observed MWCNTs was 3,500 μm.

[0204] (2-3) MWCNT aggregate 3 of Example 3 When an SEM photograph (magnification: 5000x) of the MWCNT aggregate 3 of Example 3 was taken, it was confirmed that a plurality of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm were present within the viewing angle of the SEM photograph. Furthermore, a plurality of SEM photographs (magnification: 5000x) of the MWCNT aggregate 3 of Example 3 at adjacent viewing angles were taken, and focusing on 100 MWCNTs included in the viewing angle of the SEM photograph, the maximum length of each was measured. Of the observed MWCNTs, the proportion of MWCNTs with a maximum length in the range of 500 μm to 30,000 μm (i.e., SLMWCNTs) was 90%, and the maximum value of the maximum length of the 100 observed MWCNTs was 4,000 μm.

[0205] (2-4) CNT Dispersion A, CNT Dispersion D, and CNT Dispersion E SEM photographs of the CNT Dispersion A, CNT Dispersion D, and CNT Dispersion E for SEM photography prepared above were taken using a scanning electron microscope at a magnification of 500. The results are shown in Figures 1A, 1B, and 1C.

[0206] Fig. 1A is an SEM photograph of CNT dispersion A for SEM photography containing MWCNT aggregate 1 of Example 1, Fig. 1B is an SEM photograph of CNT dispersion D for SEM photography containing SWCNT aggregate 1 of Comparative Example 1, and Fig. 1C is an SEM photograph of CNT dispersion E for SEM photography containing MWCNT aggregate 4 of Comparative Example 2. As shown in Fig. 1A, it was confirmed that in the CNT dispersion A for SEM photography containing MWCNT aggregate 1 of Example 1, a plurality of fibrous MWCNTs were entangled to form aggregates. On the other hand, as shown in Figs. 1B and 1C, almost no entanglement of CNTs was confirmed in the CNT dispersion D for SEM photography containing SWCNT aggregate 1 of Comparative Example 1 and the CNT dispersion E for SEM photography containing MWCNT aggregate 4 of Comparative Example 2.

[0207] 2. Median Diameter The median diameter of the CNTs contained in the CNT aggregate was measured. The CNT dispersions A to F for SEM photography obtained in "(1) Preparation of CNT dispersions for SEM photography" in "1. Observation of SEM photographs" above were diluted with ion-exchanged water to obtain aqueous dispersions A to F with CNT concentrations of 0.004 mass%. The obtained aqueous dispersions A to F were used as measurement samples, and the volume-based particle size distribution of the CNTs was measured using a LUMiSizer 611 (trade name), a centrifugal sedimentation-type dispersion stability particle size distribution analyzer manufactured by LUM GmbH, under the following measurement conditions. In the measured volume-based particle size distribution, the particle diameter at which the cumulative frequency was 50% was read and taken as the median diameter. The results are shown in Table 1.

[0208] <Measurement conditions> Measurement cell: Polycarbonate cell (optical path length: 2 mm) Rotation speed: 4000 rpm Centrifugal acceleration: 2300×g Measurement interval: 30 seconds Number of measurements: 1000 Measurement temperature: 25°C

[0209] 3. Rate of Change in Transmittance The rate of change in transmittance of the CNT contained in the CNT aggregate was measured. CNT dispersions A to F for SEM photography (CNT concentration: 0.2 mass%) obtained in "(1) Preparation of CNT dispersion for SEM photography" in "1. Observation of SEM photographs" above were used as measurement samples, and a LUMiSizer 611 (trade name), a centrifugal sedimentation-type dispersion stability particle size distribution analyzer manufactured by LUM GmbH, was used as the measurement device to obtain a sedimentation profile under the following measurement and analysis conditions. The rate of change in transmittance was determined by analyzing the rate of change in the overall transmittance from the obtained sedimentation profile. The results are shown in Table 1.

[0210] <Measurement and analysis conditions> Measurement cell: Polycarbonate cell (optical path length: 2 mm) Rotation speed: 4000 rpm Centrifugal acceleration: 2300 × g Measurement interval: 30 seconds Number of measurements: 1000 Viscosity of dispersion medium: 0.8946 mPa·s Density of dispersion medium: 997.3 kg / m ３ Dispersoid density: 1350 kg / m ３Refractive index (real part) of dispersion medium: 1.326 Refractive index (real part) of dispersoid: 1.630 Refractive index (imaginary part) of dispersion medium: 0.5153 Under the above analysis conditions, the dispersion medium is water and the dispersoid is CNT. The above viscosity, density, and refractive index values ​​are all values ​​at 25°C.

[0211] 4. Scattering Intensity Ratio S1 / S2 and Scattering Intensity Ratio S3 / S4 The scattering intensity ratio S1 / S2 and scattering intensity ratio S3 / S4 of the CNTs contained in the CNT aggregate were measured. The CNT dispersions A to F (CNT concentration: 0.2% by mass) for SEM photography obtained in "(1) Preparation of CNT dispersion for SEM photography" in "1. Observation of SEM photographs" above were used as measurement samples. The measurement sample was filled into an NMR tube (product name: S-3-HT-7, manufactured by NORELL) with an outer diameter of 2.99±0.03 mm and an inner diameter of 2.41±0.03 mm, taking care to avoid bubbles, and then the beamline BL03XU of SPring-8, a large-scale synchrotron radiation facility, was used as small-angle X-ray scattering experimental equipment to obtain a CNT scattering profile. Measurements using small-angle X-ray scattering were performed in accordance with the description in "Structural Science of Crystalline Polymers, Kohji Tashiro, Springer, 2022." More specifically, measurements were performed under conditions of an X-ray wavelength of 0.1 nm, a beam diameter of 100 μm, and a camera length of 8000 mm, using a Pilatus 1M detector manufactured by Dectris, and in an environment with an ambient temperature of 25 ° C. During the measurement, no attenuator was used, and X-rays were incident on the NMR tube in a direction perpendicular to the longitudinal direction near the axial center. Measurements were performed 10 times with an exposure time of 1 second, changing the irradiation position in the longitudinal direction by 100 μm each time, to obtain a total two-dimensional scattering image Ms. In addition, simultaneously with the capture of the two-dimensional scattering image, the transmitted light intensity fs was measured in the ion chamber downstream of the NMR tube. The background two-dimensional scattering image Mb and transmitted light intensity fb were measured under the same conditions as above, except that the NMR tube was filled with ion-exchanged water instead of the aqueous dispersion. A two-dimensional scattering image M after background correction was obtained using the following formula (1). At this time, the area where the scattered X-rays were blocked by a beam stopper or the like installed to prevent the direct beam from entering the detector was excluded from the two-dimensional scattering image M. M = Ms / fs - Mb / fb (1) A one-dimensional profile in the radial direction was obtained from the two-dimensional scattering image M by circular averaging. The horizontal axis was calibrated to the magnitude q of the scattering vector using the standard substance collagen. From the obtained one-dimensional profile, the magnitude q of the scattering vector was determined to be 0.2 nm. －１ Scattering intensity S1, scattering vector magnitude q = 0.8 nm－１ Scattering intensity S2 at q = 0.02 nm －１ Scattering intensity S3 at q = 0.08 nm and the magnitude of the scattering vector q －１ The scattering intensity S4 at this point was read, and the scattering intensity ratio S1 / S2 and the scattering intensity ratio S3 / S4 were calculated. The results are shown in Table 2. The scattering profile of each CNT aggregate obtained by small-angle X-ray scattering is shown in Figure 2.

[0212] 5. Conductivity CNT dispersions A to F for SEM photography (CNT concentration: 0.2% by mass) obtained in "(1) Preparation of CNT dispersion for SEM photography" in "1. Observation of SEM photographs" above were dropped onto a glass substrate cut to a size of 10 cm x 10 cm, and a film was formed using a stainless steel applicator with a gap size of 150 μm. The glass substrate was then heated on a hot plate at 110°C for 10 minutes, the film was dried, and CNT aggregate films A to F were obtained. The surface resistivities of the CNT aggregate films A to F obtained in this manner were measured using a Loresta GXII (trade name) resistivity meter manufactured by Nitto Seiko Analytech Co., Ltd. The surface resistivities were measured at five different points on the CNT aggregate film, and the average value was taken as the surface resistivity of the CNT aggregate. Furthermore, based on the surface resistivity of the CNT aggregate, the conductivity of the CNT aggregate was evaluated according to the following evaluation criteria. The results are shown in Tables 1 and 2. If the evaluation result was "A" or "B", it was determined that the electrical conductivity was excellent. An evaluation result of "A" is most preferable.

[0213] -Evaluation criteria- A: The surface resistivity of the CNT aggregate is 1.00 × 10 ２ B: The surface resistivity of the CNT aggregate is less than 1.00 × 10 ２ Ω / sq or more 3.00×10 ２ C: The surface resistivity of the CNT aggregate is in the range of less than 3.00 × 10 ２ Ω / sq or more 1.00×10 ５ D: The surface resistivity of the CNT aggregate is in the range of less than 1.00 × 10 ５ It is Ω / sq or more.

[0214] 6. Peak intensity ratio G1 / D1 in Raman spectrum The Raman spectrum of the CNT contained in the CNT aggregate was measured. The CNT aggregate was fixed to a sample stage, and a Raman spectrum was obtained under the following measurement conditions using a Raman spectrometer RAMAN-11 (trade name) manufactured by Nanophoton Co., Ltd.

[0215] <Measurement conditions> Excitation laser wavelength: 532 nm Grating: 600 grooves / mm Objective lens: 20x, numerical aperture (N.A.) 0.45 Wavenumber range: 110 cm －１ ~2650cm －１

[0216] 1550 cm －１ ~1600cm －１ The maximum scattering intensity at the Raman shift of 1300 cm is taken as the peak intensity G1 of the G band in the Raman spectrum. －１ ~1400cm －１ The maximum scattering intensity at the Raman shift of 1000 nm was taken as the peak intensity D1 of the D band in the Raman spectrum, and 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, was calculated from these values. The results are shown in Table 3.

[0217] 7. BET Specific Surface Area The BET specific surface area of ​​the CNT contained in the CNT aggregate was measured. The BET specific surface area of ​​the CNT was determined by a gas adsorption method using nitrogen gas in accordance with JIS Z 8830:2013. Specifically, it was determined by the following method. First, the CNT aggregate was packed into a sample tube, and the sample tube was vacuum-degassed at 300°C for 3 hours using a BELPREP-vacII (trade name) pretreatment device manufactured by Microtrac-Bell Corporation, thereby pretreating the CNT aggregate. The pretreated CNT aggregate was used as a measurement sample, and the nitrogen adsorption amount of the CNT aggregate was measured under the following measurement conditions using a BELSORP-mini II (trade name) specific surface area measurement device manufactured by Microtrac-Bell Corporation, to obtain an adsorption / desorption isotherm. The BET specific surface area was determined from the obtained adsorption / desorption isotherm under the following analysis conditions. The results are shown in Table 3.

[0218] <Measurement and analysis conditions> Measurement method: constant volume method Adsorption temperature: 77 K Adsorbate: nitrogen Saturated vapor pressure: actual measurement Equilibrium waiting time: 500 sec Specific surface area: BET method (BET-Plot)

[0219]

[0220] As shown in Table 1, it was confirmed that MWCNT aggregate 1 of Example 1, MWCNT aggregate 2 of Example 2, and MWCNT aggregate 3 of Example 3, which contain MWCNTs having a median diameter of 80 nm or more in the volume-based particle size distribution obtained by centrifugal sedimentation when made into a 0.004 mass% aqueous dispersion and a rate of change in transmittance measured by centrifugal sedimentation of 0.3% / hour or less when made into a 0.2 mass% aqueous dispersion, are excellent in conductivity. On the other hand, it was confirmed that SWCNT aggregate 1 of Comparative Example 1, MWCNT aggregate 4 of Comparative Example 2, and MWCNT aggregate 5 of Comparative Example 3, which contain CNTs that do not satisfy at least one of the median diameter being 80 nm or more and the rate of change in transmittance being 0.3% / hour or less, are inferior in conductivity compared to the Examples.

[0221]

[0222] As shown in Table 2, when the aqueous dispersion was prepared at a concentration of 0.2 mass %, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering was q = 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q = 0.8 nm －１ It was confirmed that the MWCNT aggregate 1 of Example 1, the MWCNT aggregate 2 of Example 2, and the MWCNT aggregate 3 of Example 3, which contain MWCNTs having a scattering intensity ratio S1 / S2 of 90 or more, which is the ratio of the scattering intensity S1 to the scattering intensity S2 at 0.2 mass %, are excellent in conductivity. －１ Scattering intensity S3 and scattering vector magnitude q = 0.08 nm －１It was confirmed that the MWCNT aggregate 1 of Example 1, the MWCNT aggregate 2 of Example 2, and the MWCNT aggregate 3 of Example 3, which contain MWCNTs having a scattering intensity ratio S3 / S4, which is the ratio of the scattering intensity S1 / S2 to the scattering intensity S4 at 10 or less, are excellent in conductivity. On the other hand, it was confirmed that the SWCNT aggregate 1 of Comparative Example 1, the MWCNT aggregate 4 of Comparative Example 2, and the MWCNT aggregate 5 of Comparative Example 3, which contain CNTs that do not satisfy the requirement that the scattering intensity ratio S1 / S2 be 90 or more, are inferior in conductivity compared to the Examples. It was also confirmed that the SWCNT aggregate 1 of Comparative Example 1, the MWCNT aggregate 4 of Comparative Example 2, and the MWCNT aggregate 5 of Comparative Example 3, which contain CNTs that do not satisfy the requirement that the scattering intensity ratio S3 / S4 be 10 or less, are inferior in conductivity compared to the Examples.

[0223] From the results of measuring the maximum length of the MWCNT by taking SEM photographs, the results of evaluating the electrical conductivity shown in Tables 1 and 2, and the results shown in Table 3, it was found that the MWCNT contained MWCNT with a maximum length of 1,000 μm to 30,000 μm (so-called ULMWCNT), and that 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 the MWCNT, was greater than 0.9 and 15 or less, and the BET specific surface area of ​​the MWCNT was 50 m ２ / g~400m ２ It has been revealed that the MWCNT aggregate having a maximum length of more than 1600 μm and not more than 30000 μm (so-called specific ULMWCNT), 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 the MWCNT, is 10 or less, and the BET specific surface area of ​​the MWCNT is 200 m ２ / g to 300m ２ It was also revealed that the MWCNT aggregate with a .beta. / g also had excellent electrical conductivity.

Claims

1. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes, which when dispersed in water at a concentration of 0.004 mass%, have a median diameter of 80 nm or more in a volume-based particle size distribution obtained by centrifugal sedimentation, and when dispersed in water at a concentration of 0.2 mass%, have a rate of change in transmittance measured by centrifugal sedimentation of 0.3% / hour or less.

2. When the sample is dispersed in water at a concentration of 0.2% by mass, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q at 0.8 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S1 / S2 of 90 or more, the ratio being a scattering intensity S1 / S2 in the multi-walled carbon nanotube array and a scattering intensity S2 in the multi-walled carbon nanotube array.

3. When the sample is dispersed in water at a concentration of 0.2% by mass, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.02 nm. －１ Scattering intensity S3 and the magnitude of the scattering vector q at q = 0.08 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4 of 10 or less, the ratio being a scattering intensity S3 / S4 in the multi-walled carbon nanotube array and a scattering intensity S4 in the multi-walled carbon nanotube array.

4. When the powder is dispersed in water at a concentration of 0.004% by mass, the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, when the powder is dispersed in water at a concentration of 0.2% by mass, the rate of change in transmittance measured by centrifugal sedimentation is 0.3% / hour or less, and when the powder is dispersed in water at a concentration of 0.2% by mass, the magnitude q of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q at 0.8 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S1 / S2 of 90 or more, the ratio being a scattering intensity S1 / S2 in the multi-walled carbon nanotube array and a scattering intensity S2 in the multi-walled carbon nanotube array.

5. When the powder is dispersed in water at a concentration of 0.004% by mass, the median diameter in the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, when the powder is dispersed in water at a concentration of 0.2% by mass, the rate of change in transmittance measured by centrifugal sedimentation is 0.3% / hour or less, and when the powder is dispersed in water at a concentration of 0.2% by mass, the magnitude q of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is 0.02 nm. －１ Scattering intensity S3 and the magnitude of the scattering vector q at q = 0.08 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4 of 10 or less, the ratio being a scattering intensity S3 / S4 in the multi-walled carbon nanotube array and a scattering intensity S4 in the multi-walled carbon nanotube array.

6. When the sample is dispersed in water at a concentration of 0.2% by mass, the magnitude of the scattering vector in the scattering profile obtained by small-angle X-ray scattering is q = 0.2 nm. －１ Scattering intensity S1 and scattering vector magnitude q at 0.8 nm －１ the scattering intensity ratio S1 / S2, which is the ratio of the scattering intensity S1 to the scattering intensity S2 at the scattering profile, is 90 or more, and the magnitude q of the scattering vector of the scattering profile is 0.02 nm －１ Scattering intensity S3 and the magnitude of the scattering vector q at q = 0.08 nm －１ The multi-walled carbon nanotube aggregate includes multi-walled carbon nanotubes having a scattering intensity ratio S3 / S4 of 10 or less, the ratio being a scattering intensity S3 / S4 in the multi-walled carbon nanotube array and a scattering intensity S4 in the multi-walled carbon nanotube array.

7. The aggregate of multi-walled carbon nanotubes according to any one of claims 1 to 6, wherein the multi-walled carbon nanotubes have a maximum length of 1,000 μm to 30,000 μm.

8. The aggregate of multi-walled carbon nanotubes according to any one of claims 1 to 6, which is a conductive assistant.

9. A multi-walled carbon nanotube dispersion liquid comprising the aggregate of multi-walled carbon nanotubes according to any one of claims 1 to 6 and a dispersion medium.

10. A conductive material comprising the multi-walled carbon nanotube aggregate according to any one of claims 1 to 6.

11. An electrode comprising an electrode active material and the conductive material of claim 10.

12. A secondary battery comprising the electrode according to claim 11.

13. A composition comprising the aggregate of multi-walled carbon nanotubes according to any one of claims 1 to 6 and at least one material selected from the group consisting of resin, ceramics and concrete.

14. A planar aggregate comprising the multi-walled carbon nanotube aggregate according to any one of claims 1 to 6.

15. A filter using the planar assembly according to claim 14.

16. An electromagnetic wave shield using the planar assembly according to claim 14.

17. A pellicle for extreme ultraviolet rays using the planar assembly according to claim 14.

Images