Multi-walled carbon nanotube aggregate, multi-walled carbon nanotube dispersion, conductive material, electrode, secondary battery, planar aggregate, filter, electromagnetic shield, and protective film for extreme ultraviolet

Abstract

The present invention provides a multi-walled carbon nanotube assembly having high conductivity, a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film. The present invention relates to a multi-walled carbon nanotube assembly comprising multi-walled carbon nanotubes, a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film, and more particularly, to a multi-walled carbon nanotube assembly comprising multi-walled carbon nanotubes, a multi-walled carbon nanotube dispersion, a conductive material, an electrode, a secondary battery, a planar assembly, a filter, an electromagnetic shield, and an extreme ultraviolet protective film. The median diameter of the volume-based particle size distribution obtained by a centrifugal sedimentation method is 80 nm or more, and the rate of change in transmittance measured by the centrifugal sedimentation method when made into an aqueous dispersion having a concentration of 0.2 mass% is 0.3% / hour or less.

Description

Technical Field

[0001] This invention relates to multi-walled carbon nanotube assemblies, multi-walled carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar assemblies, filters, electromagnetic shields, and protective films for extreme ultraviolet radiation. Background Technology

[0002] Carbon nanotubes (also known as "CNTs") are materials with a cylindrical structure consisting of graphene sheets arranged in a hexagonal honeycomb pattern of carbon atoms rolled up. Due to their excellent electrical conductivity, thermal conductivity, and heat resistance, CNTs are expected to be used in various electronic materials, such as electrode materials for energy storage devices.

[0003] Carbon nanotubes (CNTs) are broadly classified into single-walled carbon nanotubes (SWCNTs) formed from a single layer of graphene sheets and multi-walled carbon nanotubes (MWCNTs) formed from multiple layers of graphene sheets. MWCNTs have superior thermal and chemical stability compared to SWCNTs, and in recent years, efforts have been made to improve the properties of MWCNTs more effectively.

[0004] For example, Patent Document 1 discloses a MWCNT comprising two or more layers of coaxial carbon atoms arranged in a hexagonal honeycomb pattern as graphene sheets. Based on transmission electron microscopy, the diameter of its outermost layer is 3 nm to 15 nm, and based on scanning electron microscopy, its length is 1.0 mm or more. It is claimed that the MWCNT described in Patent Document 1 can improve the applicability to materials requiring high electrical and thermal conductivity.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-180028 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In recent years, there has been increasing attention paid to the usefulness of MWCNTs as electronic materials. For example, if MWCNTs are used as electrode materials such as conductive additives, they can impart high conductivity to the electrodes, thus potentially improving the performance of energy storage devices.

[0010] However, existing MWCNTs, including the MWCNT described in Patent Document 1, still have room for improvement in terms of improving conductivity when used as electrode materials.

[0011] The present invention was made in view of the above circumstances.

[0012] One embodiment of the present invention aims to solve the problem of providing a multi-walled carbon nanotube assembly with high conductivity.

[0013] Another problem to be solved by an embodiment of the present invention is to provide a multi-walled carbon nanotube dispersion comprising the above-mentioned multi-walled carbon nanotube aggregate, a conductive material, an electrode, a secondary battery, and a planar aggregate.

[0014] Furthermore, another problem to be solved by an embodiment of the present invention is to provide a filter, an electromagnetic shield, and an extreme ultraviolet protective film using the above-described planar assembly.

[0015] Methods for solving problems

[0016] The specific means used to solve the above problems include the following methods.

[0017] [1] A multi-walled carbon nanotube aggregate containing multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following conditions: when prepared as an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation is greater than 80 nm, and when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is less than 0.3% / hour.

[0018] [2] An aggregate of multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following condition: when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering profile obtained by small-angle X-ray scattering is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90.

[0019] [3] An aggregate of multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following condition: when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.02nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0020] [4] An aggregate of multi-walled carbon nanotubes comprising multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following conditions: when prepared as an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volumetric particle size distribution obtained by centrifugal sedimentation is greater than 80 nm; when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is less than 0.3% / hour; and when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the magnitude of the scattering vector q in the scattering curve obtained by small-angle X-ray scattering is 0.2 nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90.

[0021] [5] An aggregate of multi-walled carbon nanotubes comprising multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following conditions: when prepared as an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation is greater than 80 nm; when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is less than 0.3% / hour; and when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the magnitude of the scattering vector q in the scattering curve obtained by small-angle X-ray scattering is 0.02 nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0022] [6] An aggregate of multi-walled carbon nanotubes, wherein the multi-walled carbon nanotubes satisfy the following condition: when prepared as an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90, and the magnitude of the scattering vector in the above scattering curve is q = 0.02 nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0023] [7] The multi-walled carbon nanotube assembly as described in any one of [1] to [6], wherein the maximum length of the multi-walled carbon nanotube is 1000 μm to 30000 μm.

[0024] [8] The multi-walled carbon nanotube assembly as described in any one of [1] to [7] is a conductive additive.

[0025] [9] A multi-walled carbon nanotube dispersion comprising an aggregate of multi-walled carbon nanotubes as described in any one of [1] to [7], and a dispersion medium.

[0026]

[10] A conductive material comprising an aggregate of multi-walled carbon nanotubes as described in any one of [1] to [7].

[0027]

[11] An electrode comprising an electrode active material and the conductive material described in

[10] .

[0028]

[12] A secondary battery having the electrodes described in

[11] .

[0029]

[13] A composition comprising a multi-walled carbon nanotube aggregate as described in any one of [1] to [7], and at least one selected from resin, ceramic and concrete.

[0030]

[14] A planar aggregate comprising any one of the multi-walled carbon nanotubes described in [1] to [7].

[0031]

[15] A filter that uses the planar assembly described in

[14] .

[0032]

[16] An electromagnetic shielding body that uses the planar assembly described in

[14] .

[0033]

[17] An extreme ultraviolet protective film, which uses the planar aggregate described in

[14] .

[0034] Invention Effects

[0035] According to one embodiment of the present invention, a multi-walled carbon nanotube assembly with high conductivity is provided.

[0036] According to another embodiment of the present invention, a multi-walled carbon nanotube dispersion comprising the above-described multi-walled carbon nanotube aggregate, an electrode, a secondary battery, a conductive material, and a planar aggregate are provided.

[0037] Furthermore, according to another embodiment of the present invention, a filter, an electromagnetic shield, and an extreme ultraviolet protective film using the above-described planar assembly are provided. Attached Figure Description

[0038] 【 Figure 1A [Image 1] is a scanning electron microscope (SEM) image of the dispersion containing MWCNT aggregates in Example 1.

[0039] 【 Figure 1B [Image 1] is a scanning electron microscope (SEM) image of the dispersion containing SWCNT aggregates of Comparative Example 1.

[0040] 【 Figure 1C [Image 1] is a scanning electron microscope (SEM) image of the dispersion containing MWCNT aggregates of Comparative Example 2.

[0041] 【 Figure 2 [Image shows] scattering curves obtained by small-angle X-ray scattering of the MWCNT assembly of Example 1, the SWCNT assembly of Comparative Example 1, and the MWCNT assembly of Comparative Example 2. Detailed Implementation

[0042] The following describes in detail the multi-walled carbon nanotube aggregates, multi-walled carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic shields, and extreme ultraviolet protective films of the present invention. The following descriptions are based on representative embodiments of the present invention, but the present invention is not limited to these embodiments; appropriate modifications can be made to implement the invention within the scope of its objectives.

[0043] In this invention, the numerical range represented by “~” refers to the range in which the values ​​recorded before and after “~” are respectively used as the lower limit and the upper limit.

[0044] In the numerical ranges described in this invention, the upper or lower limit of a certain numerical range can be replaced with the upper or lower limit of other numerical ranges described in different segments. Furthermore, in the numerical ranges described in this invention, the upper or lower limit of a certain numerical range can also be replaced with the values ​​shown in the embodiments.

[0045] In this invention, a combination of two or more preferred methods is a more preferred method.

[0046] In this invention, the term "process" not only refers to an independent process, but also includes it as long as the intended purpose of the process can be achieved, even if it cannot be clearly distinguished from other processes.

[0047] In this invention, the term "fiber" refers to a structure in which one dimension is larger than the other two dimensions. A fiber can be a thread-like fiber with a circular cross-section, or a ribbon-like fiber with a rectangular cross-section; it can be hollow, or it can have other shapes.

[0048] From the perspective of improving the conductivity of the assembly of the present invention, the cross-section of MWCNT is preferably circular, and more preferably hollow.

[0049] In this invention, "carbon nanotubes" are also called "CNTs", "single-walled carbon nanotubes" are also called "SWCNTs", "multi-walled carbon nanotubes" are also called "MWCNTs", "multi-walled carbon nanotube aggregates" are also called "MWCNT aggregates", and "multi-walled carbon nanotube dispersions" are also called "MWCNT dispersions".

[0050] [Multi-walled carbon nanotube assemblies]

[0051] One embodiment of the multi-walled carbon nanotube assembly of the present invention is a multi-walled carbon nanotube assembly containing multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are made into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, and when the multi-walled carbon nanotubes are made into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is less than 0.3% / hour.

[0052] In this invention, the multi-walled carbon nanotube assembly of this embodiment is also referred to as "MWCNT assembly (A)".

[0053] The MWCNT assembly (A) of the present invention has high conductivity.

[0054] The reason why the MWCNT assembly (A) of the present invention has high conductivity is not yet clear, but the inventors speculate as follows. However, the following speculation is not intended to limit the interpretation of the MWCNT assembly (A) of the present invention, but is provided as an example.

[0055] The inventors have discovered a correlation between the median particle size of the volumetric particle size distribution obtained by centrifugation sedimentation when MWCNTs are prepared into an aqueous dispersion of a specific concentration and the structure formed by the entanglement of MWCNTs. Specifically, a larger median particle size indicates a larger size of the entangled MWCNT structure. Furthermore, the inventors have also discovered a correlation between the rate of change of transmittance measured by centrifugation sedimentation when MWCNTs are prepared into an aqueous dispersion of a specific concentration and the stability of the entangled MWCNT structure in the aqueous dispersion. Specifically, a slower rate of change of transmittance indicates that the entangled MWCNT structure can stably exist in the aqueous dispersion.

[0056] It can be considered that the MWCNT assembly (A) of the present invention forms a large network structure that can exist stably in an aqueous dispersion by the MWCNTs intertwining with each other. It is speculated that because the MWCNTs form a network structure, the contact between the MWCNTs occurs at multiple points, forming a large conductive path, thereby improving conductivity.

[0057] Another embodiment of the multi-walled carbon nanotube assembly of the present invention is a multi-walled carbon nanotube assembly containing multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are prepared into an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering (SAXS) is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90.

[0058] In this invention, the multi-walled carbon nanotube assembly of this embodiment is also referred to as "MWCNT assembly (B)".

[0059] The MWCNT assembly (B) of the present invention has high conductivity.

[0060] The reason why the MWCNT assembly (B) of the present invention has high conductivity is not yet clear, but the inventors speculate as follows. However, the following speculation is not intended to limit the interpretation of the MWCNT assembly (B) of the present invention, but is provided as an example.

[0061] The inventors discovered that when MWCNT is prepared into an aqueous dispersion of a specific concentration, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of scattering intensity S1 to S2 at a given point is correlated with the size of the primary aggregates of MWCNTs. Specifically, a larger scattering intensity ratio S1 / S2 indicates a smaller diameter deviation of the MWCNTs. When the diameter deviation of the MWCNTs is small, the interaction force between the MWCNTs increases, making them more likely to entangle and form a network structure.

[0062] It can be assumed that the MWCNTs in the MWCNT assembly (B) of the present invention have small diameter deviations, forming a network structure in which the MWCNTs are intertwined. It is speculated that because the MWCNTs form a network structure, the contact between the MWCNTs occurs at multiple points, forming a large conductive path, thereby improving conductivity.

[0063] Another embodiment of the multi-walled carbon nanotube assembly of the present invention is a multi-walled carbon nanotube assembly containing multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are prepared into an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.02nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0064] In this invention, the multi-walled carbon nanotube assembly of this embodiment is also referred to as "MWCNT assembly (C)".

[0065] The MWCNT assembly (C) of the present invention has high conductivity.

[0066] The reason why the MWCNT assembly (C) of the present invention has high conductivity is not yet clear, but the inventors speculate as follows. However, the following speculation is not intended to limit the interpretation of the MWCNT assembly (C) of the present invention, but is provided as an example.

[0067] The inventors discovered that when MWCNT is prepared into an aqueous dispersion of a specific concentration, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.02nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of scattering intensity S3 to S4 at a given location is correlated with the entanglement of MWCNTs. Specifically, if the scattering intensity ratio S3 / S4 is smaller, it indicates that the size of the primary aggregates of MWCNTs is smaller. When the size of the primary aggregates of MWCNTs is smaller, the surface area of ​​MWCNTs increases, making it easier for MWCNTs to entangle with each other and form a network structure.

[0068] It can be considered that the MWCNT aggregate (C) of the present invention has a small size of primary aggregates of MWCNTs, forming a network structure in which MWCNTs are intertwined. It is speculated that because the MWCNTs form a network structure, the contact between the MWCNTs occurs at multiple points, forming a large conductive path, thereby improving conductivity.

[0069] In the MWCNT assembly of the present invention, the MWCNTs being in a wound state can be confirmed by SEM observation.

[0070] The MWCNT aggregates of the present invention exhibit high conductivity, making them suitable, for example, as conductive additives. Furthermore, because the MWCNTs in the aggregates are in an intertwined state, they are less prone to swelling even when in contact with organic solvents. Therefore, if the MWCNTs of the present invention are used as conductive additives, for example, in forming electrodes for secondary batteries such as lithium-ion batteries, their structure is less likely to change during battery operation, thus improving battery durability.

[0071] Hereinafter, after describing the MWCNT assembly (A), the MWCNT assembly (B), and the MWCNT assembly (C) of the present invention, other possible embodiments of the MWCNT assembly of the present invention will be described.

[0072] [MWCNT collection (A)]

[0073] The MWCNT aggregate (A) of the present invention comprises MWCNTs, wherein when the MWCNTs are prepared into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation is 80 nm or more, and when the MWCNTs are prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is 0.3% / hour or less.

[0074] The MWCNTs included in the MWCNT assembly (A) of the present invention preferably have a fiber shape from the perspective of easily forming a network structure based on the MWCNTs intertwining with each other.

[0075] The maximum length of the MWCNTs included in the MWCNT assembly (A) of the present invention is not particularly limited, but is preferably 500 μm to 30000 μm, more preferably 1000 μm to 25000 μm, even more preferably 1100 μm to 20000 μm, particularly preferably 1200 μm to 18000 μm, and especially preferably 1300 μm to 15000 μm.

[0076] When the maximum length of the MWCNTs contained in the MWCNT assembly (A) of the present invention is 500 μm or more, there is a tendency to further improve the conductivity of the MWCNT assembly (A). The reason for this is believed to be that the MWCNTs contained in the MWCNT assembly (A) are more likely to contact each other and more likely to form conductive pathways.

[0077] The MWCNTs contained in the MWCNT assembly (A) of the present invention tend to be easy to manufacture when the maximum length is less than 30,000 μm.

[0078] In this invention, the length of the MWCNT can be determined by taking multiple SEM images of adjacent fields of view for one MWCNT. Here, "length of MWCNT" refers to the measured value of the longitudinal length of the MWCNT, and the maximum value among the length measurements is taken as the "maximum length".

[0079] For example, if more than one MWCNT with a maximum length in the range of 500 μm to 30000 μm is observed within the field of view of the SEM image of a MWCNT ensemble, it can be determined that the observed MWCNT ensemble contains MWCNTs with a maximum length in the range of 500 μm to 30000 μm.

[0080] The length of fibrous MWCNTs can be controlled, for example, by the winding capability of the spindle used in manufacturing fibrous MWCNTs.

[0081] The MWCNT assembly (A) of the present invention preferably includes one or more MWCNTs with a maximum length of 500 μm to 30000 μm, and more preferably includes multiple MWCNTs.

[0082] In this invention, "MWCNTs with a maximum length of 500μm to 30000μm" are also referred to as "SLMWCNTs".

[0083] The proportion of SLMWCNTs in the MWCNT assembly (A) of the present invention, for example, based on the number of units, is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 50% or more.

[0084] When the proportion of SLMWCNTs in the MWCNT aggregate (A) of the present invention is 10% or more based on the number of MWCNTs, the stability of the MWCNT aggregate (A) in the aqueous dispersion due to the entanglement of MWCNTs tends to be further improved.

[0085] In this invention, the proportion of SLMWCNTs in the MWCNT aggregate is determined by taking multiple SEM images of adjacent field of view, measuring the maximum length of each of the 100 MWCNTs contained in the field of view of the SEM images, and confirming the MWCNTs (i.e., SLMWCNTs) whose maximum length is in the range of 500μm to 30000μm among the observed MWCNTs.

[0086] The same applies to the proportion of ULMWCNT in the MWCNT set and the proportion of a specific ULMWCNT in the MWCNT set, as described later.

[0087] The diameter of the MWCNTs included in the MWCNT assembly (A) of the present invention is not particularly limited. For example, it is 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.

[0088] In this invention, the diameter of the MWCNT can be determined by taking SEM or transmission electron microscopy (TEM) images. Here, the diameter refers to the length in a direction orthogonal to the longitudinal direction of the MWCNT. The diameter is measured at 10 different points on a single MWCNT, and the average value is taken as the diameter of the MWCNT.

[0089] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNTs included in the MWCNT assembly (A) of the present invention is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0090] In this invention, the aspect ratio of the MWCNT can be calculated based on the ratio of the maximum length to the diameter of a single MWCNT. From the perspective of measurement accuracy, it is preferable to use the average value of measurements from 20 or more MWCNTs.

[0091] The specific gravity of the MWCNT aggregate (A) of the present invention is not particularly limited. For example, from the perspective of dispersibility when preparing an aqueous dispersion, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0092] In this invention, the specific gravity of the MWCNT aggregate (A) can be determined using the method described in JIS Z8807:2012, "Methods for Determination of Density and Specific Gravity of Solids".

[0093] The MWCNT aggregate (A) of the present invention comprises MWCNTs, which, when prepared as an aqueous dispersion with a concentration of 0.004% by mass, have a median particle size of 80 nm or more in the volume-based particle size distribution obtained by centrifugation sedimentation.

[0094] When the median particle size of the MWCNTs contained in the MWCNT aggregate (A) of the present invention is 80 nm or more, the conductivity of the MWCNT aggregate (A) can be improved.

[0095] The median particle size of the MWCNTs included in the MWCNT aggregate (A) of the present invention is preferably 90 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more.

[0096] The upper limit of the median particle size of the MWCNTs contained in the MWCNT aggregate (A) of the present invention is not particularly limited. For example, from the perspective of dispersibility when making an aqueous dispersion, it is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 500 nm or less.

[0097] In this invention, when MWCNT is prepared into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volumetric particle size distribution obtained by centrifugal sedimentation is determined by the following method. Furthermore, in this invention, "the median particle size of the volumetric particle size distribution obtained by centrifugal sedimentation" refers to the particle size with a cumulative frequency of 50% in the volumetric particle size distribution obtained by centrifugal sedimentation (so-called d50).

[0098] MWCNT and a dispersant were added to ion-exchanged water and dispersed to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added was set to achieve a concentration of 0.004% by mass when preparing the aqueous dispersion. The obtained aqueous dispersion was used as the test sample, and the volumetric particle size distribution of MWCNT was determined using a centrifugal sedimentation particle size analyzer under the following test conditions. The particle size at the 50% cumulative frequency in the determined volumetric particle size distribution was recorded as the median particle size.

[0099] As a centrifugal sedimentation particle size distribution measuring device, the LUM GmbH LUMSizer 611 centrifugal sedimentation dispersion stability particle size distribution measuring device (trade name) can be used, for example. However, centrifugal sedimentation particle size distribution measuring devices are not limited to this.

[0100] <Measurement Conditions>

[0101] Sample cell for measurement: Polycarbonate sample cell (optical path length: 2 mm)

[0102] Speed: 4000rpm

[0103] Centrifugal acceleration: 2300 × g

[0104] Measurement interval: 30 seconds

[0105] Number of measurements: 1000

[0106] Measurement temperature: 25℃

[0107] The aforementioned median particle size can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0108] The aforementioned median particle size can be increased, for example, by increasing the calcination temperature during the synthesis of MWCNT, and decreased by decreasing the calcination temperature during the synthesis of MWCNT.

[0109] The MWCNT aggregate (A) of the present invention comprises MWCNTs, wherein when the MWCNTs are prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugation sedimentation is less than 0.3% / hour.

[0110] When the rate of change of the transmittance of the MWCNTs contained in the MWCNT aggregate (A) of the present invention is less than 0.3% / hour, the stability of the MWCNT aggregate (A) in the aqueous dispersion is improved, and the conductivity is improved.

[0111] The rate of change of the transmittance of the MWCNTs included in the MWCNT assembly (A) of the present invention is preferably 0.25% / hour or less, more preferably 0.2% / hour or less, and even more preferably 0.15% / hour or less.

[0112] The lower limit of the rate of change of the transmittance of the MWCNTs included in the MWCNT assembly (A) of the present invention is not particularly limited. For example, from the point of view of ease of manufacture, it is preferably 0.01% / hour or more, and more preferably 0.03% / hour or more.

[0113] In this invention, when MWCNT is prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation is determined by the following method.

[0114] MWCNT and a dispersant were added to ion-exchanged water and dispersed to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added was set to achieve a concentration of 0.2% by mass when preparing the aqueous dispersion. The obtained aqueous dispersion was used as a test sample, and a sedimentation profile was obtained using a centrifugal sedimentation particle size distribution analyzer under the following measurement and analysis conditions. From the obtained sedimentation profile, the rate of change of overall transmittance was analyzed to determine the rate of change of transmittance.

[0115] As a centrifugal sedimentation particle size distribution measuring device, the LUM GmbH LUMSizer 611 centrifugal sedimentation dispersion stability particle size distribution measuring device (trade name) can be used, for example. However, centrifugal sedimentation particle size distribution measuring devices are not limited to this.

[0116] <Measurement and Analysis Conditions>

[0117] Sample cell for measurement: Polycarbonate sample cell (optical path length: 2 mm)

[0118] Speed: 4000rpm

[0119] Centrifugal acceleration: 2300 × g

[0120] Measurement interval: 30 seconds

[0121] Number of measurements: 1000

[0122] Viscosity of the dispersion medium: 0.8946 mPa·s

[0123] Density of the dispersion medium: 997.3 kg / m³ 3

[0124] Density of the dispersed phase: 1350 kg / m³ 3

[0125] Refractive index (real part) of the dispersion medium: 1.326

[0126] Refractive index (real part) of the dispersed phase: 1.630

[0127] Refractive index (imaginary part) of the dispersion medium: 0.5153

[0128] In the above analytical conditions, the dispersion medium is water and the dispersed phase is MWCNT.

[0129] The viscosity, density, and refractive index values ​​mentioned above are all values ​​at 25°C.

[0130] The rate of change in the aforementioned transmittance can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0131] The rate of change in transmittance can be accelerated, for example, by increasing the gas flow rate during MWCNT synthesis, and slowed down by decreasing the gas flow rate during MWCNT synthesis.

[0132] [MWCNT collection (B)]

[0133] The MWCNT aggregate (B) of the present invention comprises MWCNTs, wherein the scattering vector magnitude of the scattering curve obtained by small-angle X-ray scattering method when the MWCNTs are prepared into a 0.2% by mass aqueous dispersion is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90.

[0134] The MWCNTs included in the MWCNT assembly (B) of the present invention preferably have a fiber shape from the perspective of easily forming a network structure based on the MWCNTs intertwining with each other.

[0135] The maximum length of the MWCNTs included in the MWCNT assembly (B) of the present invention is not particularly limited. For example, it is preferably 500 μm to 30000 μm, more preferably 1000 μm to 25000 μm, even more preferably 1100 μm to 20000 μm, particularly preferably 1200 μm to 18000 μm, and especially preferably 1300 μm to 15000 μm.

[0136] When the maximum length of the MWCNTs contained in the MWCNT assembly (B) of the present invention is 500 μm or more, there is a tendency to further improve the conductivity of the MWCNT assembly (B). The reason for this is believed to be that the MWCNTs contained in the MWCNT assembly (B) are more likely to contact each other and more likely to form conductive pathways.

[0137] The MWCNTs contained in the MWCNT assembly (B) of the present invention tend to be easy to manufacture when the maximum length is less than 30,000 μm.

[0138] The MWCNT assembly (B) of the present invention preferably includes one or more MWCNTs (i.e., SLMWCNTs) with a maximum length of 500 μm to 30000 μm, and more preferably includes multiple MWCNTs.

[0139] The proportion of SLMWCNTs in the MWCNT assembly (B) of the present invention, for example, based on the number of units, is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 50% or more.

[0140] When the proportion of SLMWCNTs in the MWCNT aggregate (B) of the present invention is 10% or more based on the number of MWCNTs, the stability of the MWCNT aggregate (B) in the aqueous dispersion due to the entanglement of MWCNTs tends to be further improved.

[0141] The diameter of the MWCNTs included in the MWCNT assembly (B) of the present invention is not particularly limited. For example, it is 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.

[0142] The ratio of the length to the diameter (so-called aspect ratio) of the MWCNTs included in the MWCNT assembly (B) of the present invention is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0143] The specific gravity of the MWCNT aggregate (B) of the present invention is not particularly limited. For example, from the perspective of dispersibility when preparing an aqueous dispersion, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0144] The MWCNT aggregate (B) of the present invention comprises MWCNTs, which, when prepared as an aqueous dispersion with a concentration of 0.2% by mass, have a scattering intensity ratio S1 / S2 of 90 or higher in a scattering curve obtained by small-angle X-ray scattering.

[0145] When the scattering intensity ratio S1 / S2 of the MWCNTs contained in the MWCNT assembly (B) of the present invention is 90 or more, the conductivity of the MWCNT assembly (B) can be improved.

[0146] The scattering intensity ratio S1 / S2 of the MWCNTs included in the MWCNT aggregate (B) of the present invention is preferably 95 or more, more preferably 98 or more, even more preferably 100 or more, and particularly preferably 110 or more.

[0147] The upper limit of the scattering intensity ratio S1 / S2 of the MWCNTs included in the MWCNT assembly (B) of the present invention is not particularly limited. For example, from the point of view of ease of manufacture, it is preferably 250 or less, and more preferably 200 or less.

[0148] The aforementioned scattering intensity ratio S1 / S2 can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0149] The aforementioned scattering intensity ratio S1 / S2 can be increased, for example, by increasing the calcination temperature during the synthesis of MWCNT, and decreased by decreasing the calcination temperature during the synthesis of MWCNT.

[0150] [MWCNT collection (C)]

[0151] The MWCNT aggregate (C) of the present invention comprises MWCNTs, wherein the scattering vector magnitude of the scattering curve obtained by small-angle X-ray scattering method when the MWCNTs are prepared into a 0.2% by mass aqueous dispersion is q=0.02nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0152] The MWCNTs included in the MWCNT assembly (C) of the present invention preferably have a fiber shape from the perspective of easily forming a network structure based on the MWCNTs intertwining with each other.

[0153] The maximum length of the MWCNTs included in the MWCNT assembly (C) of the present invention is not particularly limited. For example, it is preferably 500 μm to 30000 μm, more preferably 1000 μm to 25000 μm, even more preferably 1100 μm to 20000 μm, particularly preferably 1200 μm to 18000 μm, and especially preferably 1300 μm to 15000 μm.

[0154] When the maximum length of the MWCNTs contained in the MWCNT assembly (C) of the present invention is 500 μm or more, there is a tendency to further improve the conductivity of the MWCNT assembly (C). The reason for this is believed to be that the MWCNTs contained in the MWCNT assembly (C) are more likely to contact each other and more likely to form conductive pathways.

[0155] The MWCNTs contained in the MWCNT assembly (C) of the present invention tend to be easy to manufacture when the maximum length is less than 30,000 μm.

[0156] The MWCNT assembly (C) of the present invention preferably includes one or more MWCNTs (i.e., SLMWCNTs) with a maximum length of 500 μm to 30000 μm, and more preferably includes multiple MWCNTs.

[0157] The proportion of SLMWCNTs in the MWCNT assembly (C) of the present invention, for example, based on the number of units, is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 50% or more.

[0158] When the proportion of SLMWCNTs in the MWCNT aggregate (C) of the present invention is 10% or more based on the number of MWCNTs, the stability of the MWCNT aggregate (C) in the aqueous dispersion due to the entanglement of MWCNTs tends to be further improved.

[0159] The diameter of the MWCNTs included in the MWCNT assembly (C) of the present invention is not particularly limited. For example, it is 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.

[0160] The aspect ratio (so-called longitudinal-to-transverse ratio) of the MWCNTs included in the MWCNT assembly (C) of the present invention is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0161] The specific gravity of the MWCNT aggregate (C) of the present invention is not particularly limited. For example, from the perspective of dispersibility when preparing an aqueous dispersion, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0162] The MWCNT aggregate (C) of the present invention comprises MWCNTs, wherein when the MWCNTs are prepared into an aqueous dispersion with a concentration of 0.2% by mass, the scattering intensity ratio S3 / S4 in the scattering curve obtained by small-angle X-ray scattering is 10 or less.

[0163] When the scattering intensity ratio S3 / S4 of the MWCNTs contained in the MWCNT assembly (C) of the present invention is less than 10, the conductivity of the MWCNT assembly (C) can be improved.

[0164] The scattering intensity ratio S3 / S4 of the MWCNTs included in the MWCNT aggregate (C) of the present invention is preferably 9.5 or less, more preferably 9 or less, and even more preferably 8.5 or less.

[0165] The lower limit of the scattering intensity ratio S3 / S4 of the MWCNTs included in the MWCNT assembly (C) of the present invention is not particularly limited. For example, from the perspective of ease of manufacture, it is preferably 1 or more, and more preferably 4 or more.

[0166] The aforementioned scattering intensity ratio S3 / S4 can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0167] The aforementioned scattering intensity ratio S3 / S4 can be increased, for example, by increasing the gas flow rate during MWCNT synthesis and decreased by decreasing the gas flow rate during MWCNT synthesis.

[0168] In this invention, when MWCNT is prepared into an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is the scattering intensity ratio, and the magnitude of the scattering vector q = 0.02 nm in the scattering curve obtained by small-angle X-ray scattering is also considered. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4, i.e., the scattering intensity ratio S3 / S4, is obtained by the following method.

[0169] MWCNT and a dispersant were added to ion-exchanged water and dispersed to obtain an aqueous dispersion of MWCNT. The amount of MWCNT added was set to achieve a MWCNT concentration of 0.2% by mass when preparing the aqueous dispersion. The obtained aqueous dispersion was used as the test sample.

[0170] The sample to be measured was 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 not to introduce air bubbles. Then, the scattering curve of MWCNT was obtained using a small-angle X-ray scattering device.

[0171] The small-angle X-ray scattering measurements were performed according to the record in "Structural Science of Crystalline Polymers", Kohji Tashiro, Springer, 2022.

[0172] More specifically, X-rays were incident near the axial center of the NMR tube in a direction perpendicular to its length. Ten measurements were taken, with an exposure time of 1 second, changing the irradiation position every 100 μm along the length, to obtain the total two-dimensional scattering image Ms. Furthermore, simultaneously with capturing the two-dimensional scattering image, the transmitted light intensity fs was measured in the ionization chamber downstream of the NMR tube. Under the same conditions as described above, except that ion-exchanged water was used instead of an aqueous dispersion to fill the NMR tube, the background two-dimensional scattering image Mb and the transmitted light intensity fb were measured.

[0173] According to the following formula (1), the background-corrected two-dimensional scattering image M is obtained. At this time, the range of X-rays that are blocked by beam blockers (set to prevent direct beams from entering the detector) is removed from the two-dimensional scattering image M.

[0174] M = Ms / fs - Mb / fb (1)

[0175] A radial one-dimensional curve is obtained from the two-dimensional scattering image M through circular integration. Additionally, the magnitude of the scattering vector q is corrected for the horizontal axis using the standard substance collagen.

[0176] From the obtained one-dimensional curve, the scattering vector size q = 0.2 nm is read. -1 The scattering intensity S1 and the scattering vector magnitude q = 0.8 nm at that location. -1 The scattering intensity S2 and the scattering vector magnitude q = 0.02 nm at that point. -1 The scattering intensity S3 and the scattering vector magnitude q = 0.08 nm at the location. -1 Given the scattering intensity S4 at point S4, calculate the scattering intensity ratios S1 / S2 and S3 / S4.

[0177] As a small-angle X-ray scattering experimental apparatus, the beamline BL03XU of the large synchrotron radiation facility SPring-8 can be appropriately used, for example. However, small-angle X-ray scattering experimental apparatus is not limited to this. Alternatively, a large synchrotron radiation facility can be used, for example, the NANOPIX small-angle X-ray scattering device manufactured by Rigaku Corporation (trade name).

[0178] 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, measurements can be taken with a scattering vector size of q = 0.2 nm. -1 And the scattering vector size q = 0.8 nm -1 The camera length (e.g., 700mm–8000mm) was determined, along with the scattering vector size q = 0.02nm. -1 And the scattering vector size q = 0.08 nm-1 Measurement of camera length (e.g., 8000mm to 20000mm).

[0179] As a detector, for example, the Pilatus1M (trade name) manufactured by Dectris can be appropriately used. However, the detector is not limited to this.

[0180] As preferred embodiments of the multi-walled carbon nanotube assemblies of the present invention, embodiments 1, 2, and 3 are listed below. The details of each element in embodiments 1, 2, and 3 are the same as the details of each element in the embodiments of MWCNT assemblies (A), (B), and (C).

[0181] A preferred embodiment 1 of the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are prepared into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volumetric particle size distribution obtained by centrifugation sedimentation is 80 nm or more. When prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugation sedimentation is 0.3% / hour or less. Furthermore, when prepared into an aqueous dispersion with a concentration of 0.2% by mass, the magnitude of the scattering vector q in the scattering curve obtained by small-angle X-ray scattering is 0.2 nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90.

[0182] Method 1 is a combination of the MWCNT assembly (A) of the present invention and the MWCNT assembly (B) of the present invention.

[0183] A preferred embodiment 2 of the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are prepared into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volumetric particle size distribution obtained by centrifugation sedimentation is 80 nm or more. When prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugation sedimentation is 0.3% / hour or less. Furthermore, when prepared into an aqueous dispersion with a concentration of 0.2% by mass, the magnitude of the scattering vector q in the scattering curve obtained by small-angle X-ray scattering is 0.02 nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0184] Method 2 is a combination of the MWCNT collection (A) of the present invention and the MWCNT collection (C) of the present invention.

[0185] A preferred embodiment 3 of the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes. When the multi-walled carbon nanotubes are prepared as an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering is q = 0.2 nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2 at point S1 is greater than 90, and the magnitude of the scattering vector in the above scattering curve is q = 0.02 nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0186] Method 3 is a combination of the MWCNT assembly (B) of the present invention and the MWCNT assembly (C) of the present invention.

[0187] [MWCNT collection (D)]

[0188] In one embodiment, the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes with a maximum length of 1000 μm to 30000 μm, wherein 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, i.e., the peak intensity ratio G1 / D1, is greater than 0.9 and less than 15, and the BET specific surface area of ​​the multi-walled carbon nanotubes is 50 m². 2 / g~400m 2 / g.

[0189] In this invention, the multi-walled carbon nanotube assembly of this type is also referred to as "MWCNT assembly (D)". In addition, in this invention, "MWCNTs with a maximum length of 1000 μm to 30000 μm" are also referred to as "ULMWCNTs".

[0190] The MWCNT assembly (D) of the present invention has high conductivity.

[0191] The reason why the MWCNT assembly (D) of the present invention has high conductivity is not yet clear, but the inventors speculate as follows. However, the following speculation is not intended to limit the interpretation of the MWCNT assembly (D) of the present invention, but is provided as an example.

[0192] The MWCNT assembly (D) of the present invention comprises MWCNTs with a maximum length of 1000 μm to 30000 μm (i.e., ULMWCNTs), thus MWCNTs are considered to be easily contactable with each other. Easy contact between MWCNTs facilitates the formation of conductive pathways, thereby improving conductivity. Furthermore, the MWCNTs contained in the MWCNT assembly (D) of the present invention have a peak intensity ratio G1 / D1 in their Raman spectra, which is a specific value or higher, indicating fewer defects in the MWCNTs. Fewer defects in the MWCNTs further improve conductivity. Additionally, the MWCNTs contained in the MWCNT assembly (D) of the present invention have a peak intensity ratio G1 / D1 below the aforementioned specific value, indicating a relatively non-uniform shape, thus a tendency for MWCNTs to easily entangle with each other. The more entanglement occurs between MWCNTs, the higher the conductivity. Furthermore, the MWCNTs contained in the MWCNT assembly (D) of the present invention have a moderately large BET specific surface area, thus it is believed that the MWCNTs are in close contact with each other. With the MWCNTs in close contact with each other, the volume resistivity of the MWCNTs decreases, thereby improving conductivity.

[0193] In summary, it is speculated that the MWCNT assembly (D) of the present invention has high conductivity.

[0194] The ULMWCNTs included in the MWCNT assembly (D) of the present invention can be in a fibrous shape. Because of their fibrous shape, ULMWCNTs have the property of easily entangled with each other. Therefore, in the MWCNT assembly (D) of the present invention, a network structure based on the entanglement of MWCNTs can be easily formed.

[0195] The MWCNT assembly (D) of the present invention comprises MWCNTs (i.e., ULMWCNTs) with a maximum length of 1000 μm to 30000 μm. ULMWCNTs are longer than conventional MWCNTs.

[0196] The MWCNT assembly (D) of the present invention tends to improve conductivity by including MWCNTs with a maximum length of 1000 μm or more. This can be attributed to the fact that the MWCNTs contained in the MWCNT assembly (D) can easily contact each other, thus readily forming conductive pathways.

[0197] The MWCNTs contained in the MWCNT assembly (D) of the present invention tend to be easy to manufacture when the maximum length is less than 30,000 μm.

[0198] The MWCNT assembly (D) of the present invention preferably includes MWCNTs with a maximum length of 1050 μm to 25000 μm, more preferably includes MWCNTs with a maximum length of 1100 μm to 20000 μm, even more preferably includes MWCNTs with a maximum length of 1200 μm to 18000 μm, and particularly preferably includes MWCNTs with a maximum length of 1300 μm to 15000 μm.

[0199] The MWCNT assembly (D) of the present invention comprises one or more MWCNTs (i.e., ULMWCNTs) with a maximum length of 1000μm to 30000μm, and preferably comprises multiple MWCNTs.

[0200] The proportion of ULMWCNTs in the MWCNT assembly (D) of the present invention, for example, based on the number of units, is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 50% or more.

[0201] When the proportion of ULMWCNTs in the MWCNT aggregate (D) of the present invention is 10% or more based on the number of units, the stability of the MWCNT aggregate (D) in the aqueous dispersion due to the entanglement of MWCNTs tends to be further improved.

[0202] The diameter of the MWCNTs included in the MWCNT assembly (D) of the present invention is not particularly limited. For example, it is 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.

[0203] The aspect ratio (so-called longitudinal-to-transverse ratio) of the MWCNTs included in the MWCNT assembly (D) of the present invention is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0204] The specific gravity of the MWCNT aggregate (D) of the present invention is not particularly limited. For example, from the perspective of dispersibility when preparing an aqueous dispersion, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0205] The MWCNTs included in the MWCNT aggregate (D) of the present invention have a peak intensity ratio G1 / D1 in their Raman spectra where the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band is greater than 0.9 and less than 15, preferably more than 1.0 and less than 14, more preferably more than 1.2 and less than 13, even more preferably more than 1.3 and less than 12, and particularly preferably more than 1.5 and less than 12.

[0206] When the peak intensity ratio of the MWCNTs contained in the MWCNT assembly (D) of the present invention exceeds 0.9, the defects present in the MWCNTs are reduced, and there is a tendency to improve conductivity.

[0207] When the peak intensity ratio G1 / D1 of the MWCNTs contained in the MWCNT assembly (D) of the present invention is less than 15, the MWCNTs tend to easily become entangled with each other because the uniformity of the shape is disrupted.

[0208] In this invention, the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum of MWCNT, i.e., the peak intensity ratio G1 / D1, is determined by the following method.

[0209] Raman spectra of MWCNTs were obtained using a Raman spectroscopy apparatus under the following measurement conditions. The peak intensity G1 of the G band and the peak intensity D1 of the D band were read from the obtained Raman spectra, and the peak intensity ratio G1 / D1 was calculated.

[0210] As a Raman spectroscopy device, the RAMAN-11 Raman spectroscopy device manufactured by Nanophoton Corporation (trade name) can be used, for example. However, Raman spectroscopy devices are not limited to this.

[0211] <Measurement Conditions>

[0212] Excitation laser wavelength: 532 nm

[0213] Raster: 600 Grooves / mm

[0214] Objective lens: 20x, numerical aperture (NA) 0.45

[0215] In this invention, the peak intensity G1 of the G band in the Raman spectrum refers to 1550 cm⁻¹. -1 ~1600cm -1 The maximum scattering intensity within the Raman shift range. Furthermore, in this invention, the peak intensity D1 of the D band in the Raman spectrum refers to 1300 cm⁻¹. -1 ~1400cm -1 The maximum value of scattering intensity within the range of Raman shifts.

[0216] The ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum of MWCNT, i.e., the peak intensity ratio G1 / D1, can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0217] The aforementioned peak intensity ratio G1 / D1 can be increased, for example, by increasing the calcination temperature during the synthesis of MWCNT, and decreased by decreasing the calcination temperature during the synthesis of MWCNT.

[0218] The MWCNTs contained in the MWCNT assembly (D) of this invention have a BET specific surface area of ​​50 m². 2 / g~400m 2 / g, preferably 60m 2 / g~350m 2 / g, more preferably 70m 2 / g~300m 2 / g, further preferably 80m 2 / g~280m 2 / g, preferably 100m 2 / g~250m 2 / g.

[0219] The MWCNTs contained in the MWCNT assembly (D) of this invention have a BET specific surface area of ​​50 m². 2 When the volume resistivity of MWCNT aggregates (D) exceeds a certain value, there is a tendency to increase the conductivity of the MWCNTs. This is believed to be because the contact between MWCNTs becomes tighter, thereby reducing the volume resistivity of the MWCNTs.

[0220] The MWCNTs contained in the MWCNT assembly (D) of this invention have a BET specific surface area of ​​400 m². 2 When the concentration is below a certain level, MWCNTs are less likely to aggregate in aqueous dispersions, and the dispersibility of MWCNTs tends to improve.

[0221] In this invention, the BET specific surface area of ​​MWCNTs is determined by a gas adsorption method using nitrogen based on JIS Z 8830:2013. Specifically, MWCNTs are loaded into sample tubes and pretreated by vacuum degassing at 300°C for 3 hours using a pretreatment device. The pretreated MWCNTs are then used as test samples, and the amount of nitrogen adsorbed by the MWCNTs is measured using a specific surface area measuring device under the following conditions to obtain adsorption-desorption isotherms. From the obtained adsorption-desorption isotherms, the BET specific surface area is determined according to the following analytical conditions.

[0222] As specific surface area measuring devices and pretreatment devices, for example, the BELSORP-mini II specific surface area measuring device (trade name) and the BELPREP-vac II pretreatment device (trade name) manufactured by MicrotracBEL can be appropriately used. However, specific surface area measuring devices and pretreatment devices are not limited to these.

[0223] <Measurement and Analysis Conditions>

[0224] Determination method: Static volumetric method

[0225] Adsorption temperature: 77K

[0226] Adsorbate: Nitrogen

[0227] Saturated vapor pressure: measured

[0228] Balance wait time: 500 seconds

[0229] Specific surface area: BET method (BET-Plot)

[0230] The BET specific surface area of ​​MWCNT can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0231] The BET specific surface area of ​​MWCNT can be increased, for example, by increasing the calcination temperature during the synthesis of MWCNT, and decreased by decreasing the calcination temperature during the synthesis of MWCNT.

[0232] The MWCNT assembly (D) of the present invention may include MWCNTs other than ULMWCNTs without impairing its effectiveness. MWCNTs other than ULMWCNTs may be MWCNTs with a maximum length of less than 1000 μm or MWCNTs with a maximum length of more than 30000 μm.

[0233] Furthermore, the MWCNT assembly (D) of the present invention may include MWCNTs with a peak intensity ratio G1 / D1 of less than 0.9 in the ratio of peak intensity G1 of the G band to peak intensity D1 of the D band in the Raman spectrum, or may include MWCNTs with more than 15, without compromising its effectiveness.

[0234] Furthermore, the MWCNT assembly (D) of the present invention may contain components with a BET specific surface area of ​​less than 50 m² without impairing its effectiveness. 2 / g of MWCNT can also contain more than 400m 2 / g of MWCNT.

[0235] [MWCNT collection (E)]

[0236] In one embodiment, the multi-walled carbon nanotube assembly of the present invention comprises multi-walled carbon nanotubes with a maximum length exceeding 1600 μm and less than 30000 μm, wherein 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, i.e., the peak intensity ratio G1 / D1, is less than 10, and the BET specific surface area of ​​the multi-walled carbon nanotubes is 200 m². 2 / g~300m 2 / g.

[0237] In this invention, the multi-walled carbon nanotube assembly of this method is also referred to as "MWCNT assembly (E)". In addition, in this invention, "MWCNTs with a maximum length of 1600 μm to 30000 μm" are also referred to as "specific ULMWCNTs".

[0238] The MWCNT assembly (E) of the present invention has high conductivity.

[0239] The reason why the MWCNT assembly (E) of the present invention has high conductivity is not yet clear, but the inventors speculate as follows. However, the following speculation is not intended to limit the interpretation of the MWCNT assembly (E) of the present invention, but is provided as an example.

[0240] The MWCNT assembly (E) of the present invention comprises MWCNTs with a maximum length of 1600 μm to 30000 μm (i.e., specific ULMWCNTs), thus it is considered that the MWCNTs are likely to make contact with each other. Easy contact between MWCNTs facilitates the formation of conductive pathways, thereby improving conductivity. Furthermore, the MWCNTs contained in the MWCNT assembly (E) of the present invention have a peak intensity ratio (G1 / D1) in their Raman spectra where the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band is below a specific value, and their shapes are relatively non-uniform, thus there is a tendency for the MWCNTs to easily entangle with each other. The more entanglement occurs between MWCNTs, the better the conductivity. Moreover, the MWCNTs contained in the MWCNT assembly (E) of the present invention have a moderately large BET specific surface area, thus it is considered that the contact between the MWCNTs is tighter. Tight contact between MWCNTs reduces the surface resistivity of the MWCNTs, thereby improving conductivity.

[0241] In summary, it is presumed that the MWCNT assembly (E) of the present invention has high conductivity.

[0242] The specific ULMWCNTs included in the MWCNT assembly (E) of the present invention can be in a fibrous shape. Because of their fibrous shape, the specific ULMWCNTs have the property of easily entangled with each other. Therefore, in the MWCNT assembly (E) of the present invention, a network structure based on the entanglement of MWCNTs can be easily formed.

[0243] The MWCNT assembly (E) of the present invention comprises MWCNTs with a maximum length of 1600 μm to 30000 μm (i.e., specific ULMWCNTs). Specific ULMWCNTs are much longer than general MWCNTs.

[0244] The MWCNT assembly (E) of the present invention tends to improve conductivity by including MWCNTs with a maximum length of 1600 μm or more. The reason for this is believed to be that the MWCNTs included in the MWCNT assembly (E) can easily contact each other and form conductive paths.

[0245] The MWCNTs included in the MWCNT assembly (E) of the present invention tend to be easy to manufacture when the maximum length is less than 30,000 μm.

[0246] The MWCNT assembly (E) of the present invention preferably includes MWCNTs with a maximum length of 1700 μm to 25000 μm, more preferably includes MWCNTs with a maximum length of 1800 μm to 20000 μm, even more preferably includes MWCNTs with a maximum length of 1900 μm to 18000 μm, and particularly preferably includes MWCNTs with a maximum length of 2000 μm to 15000 μm.

[0247] The MWCNT assembly (E) of the present invention comprises one or more MWCNTs (i.e. specific ULMWCNTs) with a maximum length of 1600μm to 30000μm, preferably comprising multiple MWCNTs.

[0248] The proportion of a specific ULMWCNT in the MWCNT assembly (E) of the present invention, for example, based on the number of units, is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 50% or more.

[0249] When the proportion of a specific ULMWCNT in the MWCNT aggregate (E) of the present invention is 10% or more based on the number of units, the stability of the MWCNT aggregate (E) in the aqueous dispersion due to the entanglement of MWCNTs tends to be further improved.

[0250] The diameter of the MWCNTs included in the MWCNT assembly (E) of the present invention is not particularly limited. For example, it is 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.

[0251] The aspect ratio (the ratio of the length to the diameter of the MWCNTs included in the MWCNT assembly (E) of the present invention is preferably 1000 or more, more preferably 3000 or more, even more preferably 5000 or more, and particularly preferably 10000 or more.

[0252] The specific gravity of the MWCNT aggregate (E) of the present invention is not particularly limited. For example, from the perspective of dispersibility when preparing an aqueous dispersion, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0253] The MWCNTs included in the MWCNT assembly (E) of the present invention have a peak intensity ratio G1 / D1 of 10 or less, preferably 9 or less, and more preferably 8 or less in the Raman spectrum of the G band peak intensity G1 to the D band peak intensity D1.

[0254] When the peak intensity ratio G1 / D1 of the MWCNTs included in the MWCNT assembly (E) of the present invention is less than 10, the MWCNTs tend to easily become entangled with each other because the uniformity of their shapes is disrupted.

[0255] The lower limit of the peak intensity ratio G1 / D1 of the MWCNTs included in the MWCNT assembly (E) of the present invention is not particularly limited. For example, from the perspective of improving conductivity due to the reduction of defects present in MWCNTs, it is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more.

[0256] The peak intensity ratio G1 / D1 of the MWCNTs included in the MWCNT assembly (E) of the present invention can be, for example, 1 to 10, 1.5 to 9, or 2 to 8.

[0257] The MWCNTs contained in the MWCNT assembly (E) of this invention have a BET specific surface area of ​​200 m². 2 / g~300m 2 / g, preferably 205m 2 / g~290m 2 / g, more preferably 210m 2 / g~280m 2 / g, further preferably 220m 2 / g~275m 2 / g.

[0258] The MWCNTs contained in the MWCNT assembly (E) of this invention have a BET specific surface area of ​​200 m². 2 When the concentration of MWCNTs exceeds a certain value (g), there is a tendency to increase the conductivity of the MWCNT aggregate (E). The reason for this is believed to be that the contact between MWCNTs becomes tighter, thereby reducing the surface resistivity of the MWCNTs.

[0259] The MWCNT aggregate (E) of this invention contains MWCNTs with a BET specific surface area of ​​300 m². 2 When the concentration is below a certain level, MWCNTs do not easily aggregate in aqueous dispersions, and there is a tendency to improve the dispersibility of MWCNTs.

[0260] The BET specific surface area of ​​MWCNT can be controlled by synthesis conditions such as calcination temperature, gas flow rate, and gas introduction method during the synthesis of MWCNT.

[0261] The BET specific surface area of ​​MWCNT can be increased, for example, by increasing the calcination temperature during the synthesis of MWCNT, and decreased by decreasing the calcination temperature.

[0262] The MWCNT assembly (E) of the present invention may include MWCNTs other than a specific ULMWCNT without impairing its effectiveness. The MWCNTs other than the specific ULMWCNT may be MWCNTs with a maximum length of less than 1600 μm or MWCNTs with a maximum length of more than 30000 μm.

[0263] Furthermore, the MWCNT assembly (E) of the present invention may include MWCNTs whose peak intensity ratio G1 / D1 in the Raman spectrum exceeds 10 without compromising its effectiveness.

[0264] Furthermore, the MWCNT assembly (E) of the present invention may contain components with a BET specific surface area of ​​less than 200 m² without impairing its effectiveness. 2 / g of MWCNT can also contain more than 300m 2 / g of MWCNT.

[0265] Applications of Multi-walled Carbon Nanotube Assemblies

[0266] The uses of the MWCNT assembly of the present invention are not particularly limited.

[0267] The MWCNT assembly of the present invention has high conductivity and can therefore be suitably used, for example, as a conductive aid (particularly a conductive aid for negative electrodes).

[0268] Because MWCNTs in the present invention easily intertwine with each other and form conductive pathways, the conductivity of conductive materials can be further improved, for example, by coexisting with conductive materials such as positive electrode active materials and negative electrode active materials in electrodes.

[0269] The MWCNT assembly of the present invention can be used, for example, with known conductive additives such as graphite and Ketjen black.

[0270] The MWCNT aggregate of the present invention can be used as a conductive material, for example. Examples of conductive materials using the MWCNT aggregate of the present invention include electrode materials in secondary batteries (e.g., lithium-ion batteries), specifically negative electrode materials and positive electrode materials.

[0271] [Manufacturing methods for multi-walled carbon nanotubes]

[0272] The manufacturing method of the MWCNTs (so-called MWCNTs in this invention) included in the MWCNT assembly of this invention is not particularly limited.

[0273] As a method for manufacturing MWCNTs in this invention, conventional methods such as chemical vapor deposition (CVD) and methods for reacting gaseous reactants containing a carbon source in the presence of a catalyst can be applied.

[0274] The MWCNT in this invention can be manufactured, for example, by referring to the manufacturing method described in Japanese Patent Application Publication No. 2016-102047.

[0275] The following is an example illustrating the manufacturing method of the MWCNT in this invention. However, the manufacturing method of the MWCNT in this invention is not limited to the following example.

[0276] As an example of the manufacturing method of MWCNT in this invention, the manufacturing method disclosed in Japanese Patent Application Publication No. 2016-102047 can be cited, namely, a manufacturing method (also called "manufacturing method X") comprising the following steps: passing one or more gaseous reactants containing a carbon source through a reactor; reacting one or more gaseous reactants in the reaction zone of the reactor in the presence of a catalyst to form carbon-containing product particles; aggregating the product particles into aggregates; and applying force to the aggregates to continuously move the aggregates outside the reaction zone.

[0277] According to manufacturing method X, the MWCNT of the present invention can be obtained in the form of easily handled fibrous aggregates or other aggregates.

[0278] In manufacturing method X, the force applied to the product particles can be a mechanical force.

[0279] When the aggregates are fibrous MWCNTs, the mechanical force applied to the product particles can be applied by a rotating spindle around the aggregates. Fibrous MWCNTs can be recycled onto the spindle, or accumulated at other locations by continuous unwinding from the spindle after one or more rotations around it.

[0280] The spindle is preferably configured such that its axis is perpendicular or parallel to the flow direction of one or more gaseous reactants, but it can also be configured in other orientations. For example, a spindle with its axis configured at a 25° angle to the flow direction of the gaseous reactants can also be suitably used to impart mechanical force to the product particles.

[0281] The spindle can rotate about two axes (e.g., two perpendicular axes). In particular, the spindle can rotate about axes that are perpendicular and parallel to the flow direction of the gaseous reactants, respectively. Using such a spindle, the twist and length can be controlled by drawing or twisting the aggregate of fibrous MWCNTs.

[0282] The spindle can be made of metal, ceramic or resin.

[0283] Depending on the material properties and the intended use of the MWCNT, the spindle can be adopted in different suitable shapes. For example, the spindle can be used as a mold for manufacturing carbon products via spin coating. Preferred spindle shapes are rod-shaped or box-shaped.

[0284] Fibrous MWCNTs accumulate on spindles or other locations. The coating thickness and orientation can be controlled by adjusting the reaction time and conditions, or by applying an electric field or other field to the carbon products. The coating thickness and orientation can also be controlled, for example, by the dynamics of the gas flow.

[0285] The rotational speed of the spindle is preferably 0.01 rpm (revolutions per minute; the same applies below) to 10,000 rpm, more preferably 0.1 rpm to 100 rpm.

[0286] The spinning speed (i.e., the rotational speed of the spindle) can be adjusted to recover at the same rate as the material generation rate. The thickness of the accumulated fibrous MWCNTs can be controlled by the rotational speed of the spindle. In a preferred embodiment, the fibrous MWCNTs are processed along the axial direction of the spindle as the spindle rotates. In the above processing, the fibrous MWCNTs are not wound only at a specific point on the spindle, but are wound uniformly along the spindle.

[0287] Fibrous MWCNTs can be recovered onto the reactor wall, for example, by a matrix placed in the reactor. The matrix can be a fixed matrix or a rotating guide used to apply a strong and uniform force to the fibrous MWCNTs during recovery. As a suitable matrix configuration for fiber technology, a matrix consisting of two guides positioned orthogonally to each other can be cited as an example.

[0288] In manufacturing method X, the mechanical force applied to the product particles can be a force applied by an accelerating gas flow. The accelerating gas flow can be generated by passing the product particles through a reactor with a narrow diameter, or through a capillary located downstream of the reaction zone. A vacuum can also be applied to the product particles.

[0289] Other forces applied to product particles include electrostatic forces appropriately applied by charged plates. When using electrostatic forces, the product particles need to be charged. By using charged plates, MWCNTs can be generated in an intertwined, felt-like manner on the charged plates.

[0290] In addition, other forces applied to the product particles can be magnetic force or light pressure applied by a light source.

[0291] The raw material for CNTs can be injected in liquid form containing a carbon source instead of gaseous reactants containing a carbon source. When using liquid as the raw material for CNTs, it can be injected through a single injection port or multiple injection ports, for example, through a spray nozzle.

[0292] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, more preferably at 1000°C to 1500°C or 1600°C (especially 1000°C to 1500°C). It is preferable to maintain a temperature gradient within the reactor, with the reaction zone maintained at a higher temperature than the product zone of the reactor.

[0293] Gaseous reactants can be mixed with one or more gases that act as diluents. Gaseous reactants can also be mixed with gases that do not play a direct role in the reaction but play an auxiliary role. When amorphous carbon is generated as a byproduct, it is also preferable to use a gas that reacts with amorphous carbon to maintain normal reaction sites on the catalyst, thereby generating nanotubes, as a diluent.

[0294] 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. The flow rate of the gas used as a diluent is preferably 2000 mL / min or less, more preferably 400 mL / min to 800 mL / min.

[0295] The gas pressure of the gaseous reactants and any diluent is preferably 0.1 bar to 50 bar, more preferably 0.5 bar to 5 bar, and even more preferably 1 bar to 2 bar. When gas flows out of the reactor, the outflowing gas can be recycled, either cleaned or not.

[0296] The composition of the product particles can be controlled by monitoring the aggregates and adjusting the reaction conditions based on the obtained information. For example, the aggregates can be monitored using online Raman spectroscopy. Online Raman spectroscopy can provide data indicating whether they are single-walled or multi-walled CNTs. Furthermore, data indicating the diameter and crystallinity of the CNTs can also be obtained. The aggregates can also be monitored using online conductivity measurements, gas analysis, opacity measurements of the reaction zone, and / or encapsulation force measurements.

[0297] When removing the aggregate from the reactor, it is preferable to prevent air from entering the reactor. When the gas used as a diluent contains hydrogen, preventing air inflow is particularly important, for example, to suppress the formation of an explosive mixture of hydrogen and air in the reactor.

[0298] The product particles in manufacturing method X include MWCNTs as described in this invention. Furthermore, depending on the manufacturing conditions, in addition to MWCNTs as described in this invention, MWCNTs other than those described in this invention and / or SWCNTs may be included.

[0299] Product particles can be generated via chemical vapor deposition. When product particles are generated via chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0300] Suitable carbon-containing compounds as carbon sources include, for example, 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 two or more of these).

[0301] As a carbon-containing compound, carbon monoxide, methane, ethylene, or acetylene are preferred.

[0302] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source.

[0303] Oxygen can be introduced into the reactor by other methods, such as by using a carbon source containing diluent gas or water.

[0304] The gaseous reactants used as carbon sources are preferably injected into the reactor at a rate of 0.01 mL / min to 10 mL / min, and more preferably at a rate of 0.08 mL / min to 0.25 mL / min.

[0305] As catalysts, transition metals, particularly Group VIB chromium (Cr), molybdenum (Mo), tungsten (W), or VIIIB transition metals, are preferred. Specifically, as catalysts, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) or manganese (Mn), or mixtures thereof, are preferred. Metals from the lanthanides and actinides (e.g., yttrium (Y)) can also be used as catalysts. More preferred are Fe, Ni, Co, Mo, and mixtures thereof, such as mixtures of Ni and Co (mass ratio: 50 / 50), mixtures of Fe and Ni, or mixtures of Fe and Mo.

[0306] Any of these transition metals can be used alone or in combination with any of the other listed transition metals to function as a CNT growth catalyst. A mixture of two or more of the listed metals is particularly preferred as the catalyst.

[0307] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermal, photochemical, or plasma-decomposable compound of one or more of the aforementioned metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickel dicene, and cobalt dicene are particularly preferred precursors. Suitably, the carbon source contains at least 0.01% by mass of the precursor, preferably 0.2% to 2.5% by mass. In one embodiment, the carbon source contains 0.23% to 2.3% by mass of the precursor.

[0308] The catalyst can be used supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0309] The carbon source preferably reacts in the presence of a promoter. Suitable promoters are one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is also a preferred promoter. Suitably, the carbon source contains up to 10% by mass (less than 10% by mass) of promoter. Preferably, the carbon source contains 0.2% to 6% by mass of promoter. When high or low concentrations of thiophene are used as promoters, MWCNTs can be formed.

[0310] For example, MWCNTs can be well formed using ethanol containing 0% or 1.5% to 4.0% by mass of thiophene and 1.0% to 10.0% by mass (especially 2.3% by mass) of ferrocene, at an injection rate of 5.0 mL / h to 30.0 mL / h (especially 7.5 mL / h), a hydrogen flow rate of 400 mL / min to 800 mL / min, and a synthesis temperature of 1100°C to 1180°C.

[0311] According to manufacturing method X, fibrous CNTs with a length of at least 500 μm, for example, at least 1 mm, can be obtained.

[0312] Fibrous CNTs can take the form of threads (so-called fibrous), sheets, etc.

[0313] The length of fibrous CNTs can be controlled, for example, by the winding capability of the spindle used in manufacturing fibrous CNTs.

[0314] Manufacturing method X preferably includes: a step of reacting a carbon source to generate CNTs within the reaction zone of a reactor; and a step of agglomerating the CNTs into aggregates by applying force to the CNTs. According to this manufacturing method, fibrous CNTs can be easily manufactured.

[0315] Alternatively, the following steps can be taken: generating MWCNTs in the reaction zone using the method described above, aggregating MWCNTs to form MWCNT aggregates, and continuously extracting MWCNTs from the vicinity of the reaction zone.

[0316] In addition, as another approach, means including the following steps can be adopted: generating MWCNTs in the reaction region, continuously electrostatically attracting MWCNTs from the reaction region, and recovering MWCNTs.

[0317] [Multi-walled carbon nanotube dispersion]

[0318] The MWCNT dispersion of the present invention comprises the MWCNT aggregate of the present invention described above and a dispersion medium.

[0319] The MWCNT aggregate of the present invention has excellent dispersibility in dispersion media such as water, and therefore can be used appropriately in the form of a dispersion.

[0320] <Multi-walled carbon nanotube assemblies>

[0321] The MWCNT dispersion of the present invention comprises the MWCNT aggregate of the present invention.

[0322] The details of the MWCNT assembly of the present invention are as described above, and therefore are omitted here.

[0323] The content of the MWCNT aggregate of the present invention in the MWCNT dispersion of the present invention is not particularly limited, and can be appropriately set according to the purpose.

[0324] The content of the MWCNT aggregate of the present invention in the MWCNT dispersion of the present invention, for example from the perspective of conductivity, is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more, relative to the total mass of the MWCNT dispersion.

[0325] Furthermore, the content of the MWCNT aggregate of the present invention in the MWCNT dispersion of the present invention, for example from the perspective of dispersibility, is preferably 20% by mass or less relative to the total mass of the MWCNT dispersion, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

[0326] In one embodiment, the content of the MWCNT aggregate of the present invention in the MWCNT dispersion of the present invention, relative to the total mass of the MWCNT dispersion, may be 0.01% to 20% by mass, 0.05% to 15% by mass, 0.1% to 10% by mass, or 0.2% to 5% by mass.

[0327] <Dispersion Medium>

[0328] The MWCNT dispersion of the present invention contains a dispersion medium.

[0329] The dispersion medium preferably contains water, and more preferably contains water as the main component.

[0330] "Containing water as a main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and for example, it can also be 100% by mass.

[0331] There are no particular limitations on the water, but distilled water, ion-exchange water, or pure water are preferred in terms of having fewer impurities.

[0332] The dispersion medium can be a mixture of water and a hydrophilic solvent.

[0333] Examples of hydrophilic solvents include carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and butenyl carbonate; ether compounds such as tetrahydrofuran; ketone compounds such as acetone; lower alcohol compounds such as methanol and ethanol; and solvents such as acetonitrile.

[0334] 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.

[0335] <Dispersant>

[0336] The MWCNT dispersion of the present invention may contain a dispersant.

[0337] When the MWCNT dispersion of the present invention contains a dispersant, it can improve the dispersibility and dispersion stability of the MWCNT aggregate of the present invention.

[0338] There are no particular limitations on what can be considered a dispersant; for example, various surfactants can be listed. Furthermore, polymers such as resins can also be listed as dispersants.

[0339] Surfactants are preferred as dispersants.

[0340] Surfactants can be either ionic or nonionic, without any particular limitation.

[0341] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0342] Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzene sulfonic acid) and dodecylphenyl ether sulfonates; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants.

[0343] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts.

[0344] Examples of amphoteric surfactants include alkyl betaine surfactants and amine oxide surfactants.

[0345] As ionic surfactants, ionic surfactants having aromatic rings are preferred (so-called aromatic ionic surfactants), and aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecyl phenyl ether sulfonates are more preferred.

[0346] Aromatic ionic surfactants tend to have excellent dispersion ability, dispersion stability and high concentration of MWCNT aggregates.

[0347] Examples of nonionic surfactants include glycol ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin esters and polyoxyethylene diethyl fatty acid esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene / polypropylene glycol; and aromatic nonionic surfactants such as polyoxyalkylene octylphenyl ether, polyoxyalkylene nonylphenyl ether, polyoxyalkylene dibutylphenyl ether, polyoxyalkylene styrene phenyl ether, polyoxyalkylene benzylphenyl ether, polyoxyalkylene diphenyl ether, polyoxyalkylene cumylphenyl ether, and polyoxyalkylene phenyl ether.

[0348] As a nonionic surfactant, an ionic surfactant having an aromatic ring (so-called aromatic nonionic surfactant) is preferred, polyoxyalkylene phenyl ether is more preferred, and polyoxyethylene phenyl ether is even more preferred.

[0349] Aromatic nonionic surfactants tend to have excellent dispersion ability, dispersion stability and high concentration of MWCNT aggregates.

[0350] Other dispersants that enhance the dispersion, dispersion stability, and high concentration of MWCNT aggregates include β-naphthalenesulfonic acid formaldehyde condensate sodium salts Demol N, Demol RN, Demol T (manufactured by Kao Corporation), polyoxyethylene stearyl ether Brij S 100 (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (e.g., manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.), carboxymethyl cellulose (CMC) (e.g., manufactured by Caillou Meco Co., Ltd.), sodium deoxycholate (e.g., manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.), and SOLSPERSE. TM W100, SOLSPERSE TM W150 (manufactured by Lubrizol Corporation, Japan), etc. From the perspective of superior dispersion ability, dispersion stability, and high concentration of MWCNT aggregates, CMC is particularly preferred.

[0351] When the MWCNT dispersion of the present invention contains a dispersant, it may contain only one type of dispersant or two or more types of dispersants.

[0352] When the MWCNT dispersion of the present invention contains a dispersant, the content of the dispersant in the MWCNT dispersion is not particularly limited, and can be appropriately set according to the type of dispersant, the amount of MWCNT aggregate, the amount of dispersion medium, etc.

[0353] As an example of the content of dispersant in the MWCNT dispersion of the present invention, a content of 0.01% to 20% by mass relative to the total mass of the MWCNT dispersion can be cited.

[0354] <Other Ingredients>

[0355] The MWCNT dispersion of the present invention may contain components other than the MWCNT aggregate and dispersion medium of the present invention (so-called other components), to a extent that does not impair its effectiveness. Examples of other components include various additives such as defoamers and antistatic agents. Furthermore, examples of other components include CNTs other than MWCNTs of the present invention, carbon materials other than CNTs, etc. In addition, the MWCNT dispersion of the present invention may contain trace amounts of impurity components (e.g., unavoidable impurities), provided that it does not impair its effectiveness.

[0356] <<Applications of Multi-walled Carbon Nanotube Dispersions>>

[0357] The uses of the MWCNT dispersion of the present invention are not particularly limited.

[0358] The MWCNT dispersion of the present invention 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 patterning, transparent electrode materials, and water-soluble polymer fillers.

[0359] The MWCNT dispersion of the present invention can be used, for example, as a conductive ink for forming electrodes (especially negative electrodes) of various secondary batteries such as lithium-ion batteries, and can be used appropriately.

[0360] By using the MWCNT dispersion of the present invention as a conductive ink, electrodes with high conductivity can be easily manufactured.

[0361] [Preparation method of multi-walled carbon nanotube dispersion]

[0362] The method for manufacturing the MWCNT dispersion of the present invention is not particularly limited.

[0363] The MWCNT dispersion of the present invention can be manufactured by dispersing the MWCNT aggregate of the present invention in a dispersion medium. That is, the MWCNT dispersion of the present invention can be manufactured by a method including a step of dispersing the MWCNT aggregate of the present invention in a dispersion medium (also referred to as a "dispersion step").

[0364] <Distributed Processes>

[0365] The dispersion process is the process of dispersing the MWCNT aggregate of the present invention in a dispersion medium. In the dispersion process, a dispersant can be used to improve the dispersibility and dispersion stability of the MWCNT aggregate of the present invention.

[0366] Details of the MWCNT aggregate, dispersion medium, and dispersant of the present invention are as described above, and therefore are omitted here.

[0367] There are no particular restrictions on the method of dispersion.

[0368] Examples of dispersion methods include those using agitators, homogenizers, colloid mills, flow jet mixers, dissolvers, paint conditioners, Manton emulsifiers, jet mills, and ultrasonic devices (e.g., ultrasonic dispersers).

[0369] In addition, dispersion methods also include, for example, the use of known pulverizing means, such as ball mills (e.g., ball mills, vibratory ball mills, planetary ball mills, bead mills, etc.), sand mills, colloid mills, jet mills, roller mills, vertical or horizontal stirred mills, grinders, colloid mills, three-roll mills, pearl mills, super mills, impeller mixers, dispersers, KD mills, Dyno mills, pressure kneaders, and other dispersing machines.

[0370] As a dispersion method, jet milling is preferred, and wet jet milling is more preferred.

[0371] A wet jet mill is a dispersion device that uses a mixture in a solvent as a high-speed flow, pressurized and conveyed through a sealed nozzle located within a pressure vessel. In a wet jet mill, multi-walled carbon nanotube aggregates are dispersed through collisions between opposing flows within the pressure vessel, collisions with the vessel walls, turbulence generated by the high-speed flow, and shear flow. Ultra-high pressure homogenizers manufactured by Tsunemitsu Corporation (models: NAGS20, NAGS100, NAGS200, NAGS1000, etc.) can be appropriately used as wet jet mills. However, wet jet mills are not limited to these.

[0372] When using the above-mentioned ultra-high pressure homogenizer as a dispersion device, the dispersion processing pressure is preferably 10MPa to 250MPa.

[0373] <Drying Process>

[0374] The method for manufacturing the MWCNT dispersion of the present invention may include a step of drying the MWCNT aggregate of the present invention (also referred to as the "drying step") before the above-described dispersion step.

[0375] If MWCNTs are covered with moisture, they tend to adhere to each other due to the surface tension of water. If a drying process is performed before the dispersion process, the moisture attached to the MWCNTs is removed, inhibiting the adhesion of MWCNTs to each other caused by moisture, thus further improving the dispersibility of the MWCNT aggregate.

[0376] There are no particular restrictions on the drying method.

[0377] Examples of drying methods include heating drying, vacuum drying, and heated vacuum drying.

[0378] As a drying method, heating and vacuum drying is preferred.

[0379] There is no particular limitation on the drying temperature, but it is preferably 40°C to 100°C.

[0380] There is no particular limit to the drying time; it can be set appropriately based on factors such as the drying temperature and the degree of moisture adhesion on the MWCNT.

[0381] The MWCNT dispersion of the present invention can be suitably manufactured, for example, by the method described in the examples described later.

[0382] [Conductive Materials]

[0383] The conductive material of the present invention comprises the MWCNT assembly of the present invention.

[0384] The conductive material of the present invention contains the MWCNT aggregate of the present invention, which, as described above, exhibits high conductivity and excellent dispersibility when formulated into a dispersion, thus making it suitable as a conductive additive. Because the conductive material of the present invention contains the MWCNT aggregate of the present invention, it possesses excellent conductivity and can effectively impart high conductivity to the object being used.

[0385] The conductive material of the present invention may contain known conductive additives such as graphite and Ketjen black. Furthermore, the conductive material of the present invention may contain CNTs other than the MWCNT aggregate of the present invention.

[0386] The conductive material of the present invention can be used as one of the electrode materials. As an example of an electrode formed using this electrode material, the electrode of a secondary battery can be cited. Hereinafter, an embodiment of the electrode and a secondary battery having the electrode will be described.

[0387] <Electrode>

[0388] The electrode may comprise the MWCNT assembly described above.

[0389] In the electrode, the MWCNT aggregate of the present invention can function as a conductive aid.

[0390] The MWCNT assembly included in the electrodes described below is synonymous with the MWCNT assembly of the present invention, and the preferred embodiment is also the same; therefore, the description of the MWCNT assembly is omitted below.

[0391] The electrode can be at least one of the positive and negative electrodes.

[0392] An electrode may include an electrode active material layer, or it may include a current collector and an electrode active material layer disposed on the current collector.

[0393] There are no special restrictions on the current collector, as long as it does not induce chemical changes in the battery and has electrical conductivity.

[0394] The current collector can be made of materials such as copper, stainless steel, aluminum, nickel, titanium, calcined coke, or materials whose surfaces have been treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals with good carbon adsorption properties, such as copper and nickel, can be used as current collectors.

[0395] The electrode active material layer may contain electrode active materials.

[0396] The electrode active material is preferably electrode active material particles.

[0397] When the electrode is a positive electrode, there are no particular limitations on the electrode active material. The electrode active material layer can contain the positive electrode active material commonly used in positive electrode materials.

[0398] Specifically, as positive electrode active materials, examples include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), compounds substituted with one or more transition metals; lithium iron oxides such as LiFe3O4; and compounds with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and those with the chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.66) represents a Ni-substituted lithium nickel oxide; LiMn 2-c3 M c3A lithium manganese composite oxide represented by O2 (where M is at least one selected from Co, Ni, Fe, Cr, Zn, and Ta, and 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from Fe, Co, Ni, Cu, and Zn); LiMn2O4 in which a part of Li in the chemical formula is substituted with an alkaline earth metal ion, etc.

[0399] When the electrode is a negative electrode, the electrode active material is not particularly limited, and the electrode active material layer may contain a negative electrode active material commonly used in negative electrode materials for electrodes.

[0400] Specifically, the negative electrode active material may contain graphite-based active material particles or silicon-based active material particles.

[0401] As the graphite-based active material particles, at least one selected from artificial graphite, natural graphite, graphitized carbon fiber, and graphitized mesophase carbon microspheres can be used. By using artificial graphite as the graphite-based active material particles, the rate performance can be improved.

[0402] As the silicon-based active material particles, at least one selected from Si, SiOx (0 < x < 2), Si-C composite, and Si-Y alloy (where Y is an element selected from alkali metals, alkaline earth metals, transition metals, group 13 elements, group 14 elements, rare earth elements, and combinations thereof) can be used. By using the silicon-based active material particles, the battery can be made to have a high capacity.

[0403] The electrode active material layer may further contain a binder. <000095​​​​​​​​​A secondary battery may comprise a negative electrode, a positive electrode, a separator between the positive and negative electrodes, and an electrolyte. At least one of the positive and negative electrodes is an electrode formed using an electrode material comprising the MWCNT assembly of the present invention.

[0408] The separator is used to separate the negative and positive electrodes and provide a migration channel for lithium ions. Generally, any separator used in a secondary battery is acceptable, without particular limitations. Preferably, the separator has low resistance to ion migration in the electrolyte and excellent electrolyte wetting ability.

[0409] As a diaphragm, porous polymer membranes can be specifically cited.

[0410] Porous polymer membranes can be, for example, porous polymer membranes made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures formed by stacking two or more of these membranes.

[0411] In addition, the diaphragm can also be a typical porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. Furthermore, the diaphragm can also be a diaphragm coated with ceramic components or polymeric substances to ensure heat resistance or mechanical strength.

[0412] The diaphragm can be optionally designed as a single-layer or multi-layer structure.

[0413] As an electrolyte, there are no particular limitations. For example, 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 the manufacture of lithium secondary batteries can be listed.

[0414] Specifically, electrolytes can include non-aqueous organic solvents and metal salts.

[0415] Examples of non-aqueous organic solvents include N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butenyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate, among other non-protic organic solvents.

[0416] Among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, being cyclic carbonates, are preferred as non-aqueous organic solvents due to their high dielectric constant and ability to readily dissociate lithium salts. Solvents made by mixing low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions are even more preferable as non-aqueous organic solvents, as they can produce electrolytes with high conductivity.

[0417] The metal salt can be a lithium salt.

[0418] Lithium salts are substances that are readily soluble in non-aqueous electrolytes.

[0419] As the anionic moiety of lithium salts, F can be cited as an example. - Cl - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - .

[0420] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives to improve battery life characteristics, suppress battery capacity reduction, and increase battery discharge capacity. These additives include: halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, dimethyl ethylene glycol ether (glyme), triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolines, dialkyl ethylene glycol ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc.

[0421] The aforementioned secondary batteries can be used to construct battery modules containing secondary batteries as individual battery cells, and battery packs containing battery modules.

[0422] Battery modules and battery packs can be used as power sources for medium to large-sized devices selected from electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0423] [Composition]

[0424] <Resins, ceramics, and concrete, etc.>

[0425] The composition of the present invention is a composition comprising the MWCNT aggregates (A) to (E) of the present invention, and at least one selected from resin, ceramic and concrete.

[0426] Examples of resins include thermoplastic resins and thermosetting resins, with preferred resins being olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, thermoplastic polyurethane resins, polysulfone-based resins, and silicone resins.

[0427] As ceramics, examples include crystalline ceramics and amorphous ceramics.

[0428] As for concrete, silicate cement concrete can be cited as an example.

[0429] The compositions of the present invention may further contain other components such as water and organic solvents.

[0430] In the composition of the present invention, when the content of the MWCNT aggregate (A) to (E) of the present invention is 100 parts by mass, the content of at least one selected from resin, ceramic and concrete is generally 10 to 1,000,000 parts by mass, preferably 100 to 100,000 parts by mass, more preferably 1,000 to 40,000 parts by mass. Furthermore, when other components are included, the content is preferably 1 to 10,000 parts by mass, more preferably 10 to 1,000 parts by mass.

[0431] In the composition of the present invention, the MWCNT aggregate (A) to (E), resin, ceramic, concrete, and other components may each contain one or more of the following:

[0432] <Method for manufacturing the composition>

[0433] The compositions of the present invention can be manufactured, for example, by mixing the MWCNT aggregates (A) to (E) of the present invention with resin, ceramics, or pre-hardened concrete. The resin may be in the form of powder, granules, solution, or dispersion. The ceramic may be in the form of powder, precursor solution, or dispersion.

[0434] The compositions of the present invention can also be manufactured, for example, by dispersing the MWCNT aggregates (A) to (E) of the present invention in a solution of resin, a ceramic precursor or dispersion, or in concrete before hardening and then molding them.

[0435] <Uses of the Composition>

[0436] When the compositions of the present invention contain resin or ceramic, they are useful, for example, as structural materials, conductive materials, thermal management materials, or antistatic materials.

[0437] When the composition of the present invention contains concrete, it is useful as a lightweight, durable building material, or (if necessary) an energy storage device impregnated with electrolyte.

[0438] [Planar aggregate]

[0439] The planar assembly of the present invention includes the MWCNT assembly of the present invention.

[0440] The proportion of the MWCNT assembly of the present invention included in the planar assembly of the present invention is typically 1% by mass or more relative to the total mass of the planar assembly.

[0441] The planar aggregate of the present invention may include other components such as CNT aggregates (especially MWCNT aggregates) with a maximum length of less than 1000 μm.

[0442] [Methods for constructing planar aggregates]

[0443] The method for manufacturing the planar assembly of the present invention is not particularly limited.

[0444] The planar aggregate of the present invention can be made into a non-woven fabric-like planar aggregate by dispersing the MWCNT aggregate of the present invention, or the MWCNT aggregate of the present invention and other components such as CNT aggregates with a maximum length of less than 1000 μm (especially MWCNT aggregates), in water or other fluids and filtering it once or twice or more.

[0445] Thin films can be cited as examples of planar aggregates in this invention.

[0446] The planar assembly of the present invention is useful, for example, as a filter, an electromagnetic shield, and a protective film for extreme ultraviolet (EUV) radiation.

[0447] Example

[0448] The following examples illustrate the MWCNT collection of the present invention in more detail. The MWCNT collection of the present invention is not limited to the following examples as long as it does not depart from its spirit.

[0449] [The creation of MWCNT aggregates or the preparation of SWCNT aggregates]

[0450] <Example 1>

[0451] The MWCNT assembly 1 of Example 1 was prepared by a floating catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0452] First, ferrocene, a precursor for a metal catalyst containing Fe atoms, and thiophene, a promoter, are introduced into a continuous flow of carrier gas in a cross-flow reactor where the temperature is controlled between 400°C and 700°C. A mixture of nitrogen and argon is used as the carrier gas, and the flow rate is set to 30,000 sccm (standard cubic centimeters per minute).

[0453] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a granular metal catalyst. The region where the metal catalyst is generated is called the first temperature zone.

[0454] Next, methane, serving as a carbon source, is released into the carrier gas stream. The metal catalyst and carbon source are then supplied to a second temperature zone, located downstream of the first temperature zone and controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0455] In the second temperature zone, an electric field is generated in the temperature-controlled continuous flow reactor, thereby generating MWCNT aggregates.

[0456] The generated aggregates are continuously discharged through the outlet of a continuous flow reactor with the temperature controlled between 100℃ and 500℃, and are collected as sheet-like MWCNT aggregates through continuous discharge.

[0457] The collected flake-like MWCNT aggregates were immersed in a PTFE tray containing hydrochloric acid (manufactured by Fujifilm and Koichi Chemical Co., Ltd., premium grade reagent) for 24 hours. Afterward, the MWCNT aggregates were removed from the tray and rinsed with deionized water until the pH of the rinsing water reached 7.

[0458] In the manner described above, the MWCNT assembly 1 of Example 1 was obtained.

[0459] <Example 2>

[0460] The MWCNT aggregate 2 of Example 2 was obtained in accordance with Example 1, except that the cleaning of the sheet-like MWCNT aggregate collected in Example 1 was changed to cleaning with deionized water for 10 seconds.

[0461] <Example 3>

[0462] The MWCNT aggregate 3 of Example 3, like the sheet-like MWCNT aggregate collected in Example 1, was prepared by a floating catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0463] First, ferrocene, a precursor for a metal catalyst containing Fe atoms, and thiophene, a promoter, are introduced into a continuous flow of carrier gas within a cross-flow reactor at a temperature controlled between 400°C and 700°C. A mixture of nitrogen and argon is used as the carrier gas. The carrier gas flow rate is set to 30,000 sccm.

[0464] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a granular metal catalyst. The region where the metal catalyst is generated is called the first temperature zone.

[0465] Next, methane, serving as a carbon source, is released into the carrier gas stream. The metal catalyst and carbon source are then supplied to a second temperature zone, located downstream of the first temperature zone and controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0466] In the second temperature zone, an electric field is generated in the temperature-controlled continuous flow reactor, thereby generating MWCNT aggregates.

[0467] The generated aggregates are continuously discharged through the outlet of a continuous flow reactor with the temperature controlled between 100°C and 500°C, and are collected as fibrous MWCNT aggregates through continuous discharge.

[0468] The collected fibrous MWCNT aggregates were washed with deionized water for 10 seconds.

[0469] In the manner described above, the MWCNT assembly 3 of Example 3 was obtained.

[0470] <Comparative Example 1>

[0471] Use SWCNT aggregate 1 [trade name: TUBALL TM [Single-walled carbon nanotube powder, manufactured by OCSiAl Corporation] was used as Comparative Example 1.

[0472] <Comparative Example 2>

[0473] MWCNT assembly 4 [product number: 901019, multi-walled carbon nanotube powder, manufactured by Sigma-Aldrich] was used as Comparative Example 2.

[0474] <Comparative Example 3>

[0475] MWCNT assembly 5 [product number: FT7000, multi-walled carbon nanotube powder, manufactured by C-nano Corporation] was used as Comparative Example 3.

[0476] [evaluate]

[0477] The following evaluations were conducted on the MWCNT collection 1 of Example 1, the MWCNT collection 2 of Example 2, the MWCNT collection 3 of Example 3, the SWCNT collection 1 of Comparative Example 1, the MWCNT collection 4 of Comparative Example 2, and the MWCNT collection 5 of Comparative Example 3. Hereinafter, for convenience, the MWCNT collection 1 of Example 1, the MWCNT collection 2 of Example 2, the MWCNT collection 3 of Example 3, the SWCNT collection 1 of Comparative Example 1, the MWCNT collection 4 of Comparative Example 2, and the MWCNT collection 5 of Comparative Example 3 will be collectively referred to as the "CNT collection".

[0478] 1. Observation of SEM images

[0479] (1) Preparation of CNT dispersion for SEM imaging

[0480] (1-1) MWCNT assembly 1 of Example 1

[0481] 1.1 g of MWCNT aggregate 1 from Example 1, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MPBiomedicals) as a dispersant, and 547.25 g of deionized water were mixed. The resulting mixture was pre-dispersed for 1 hour using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain dispersion A. In addition, to prevent MWCNT aggregate 1 from tangling on the blades of the homogenizer, MWCNT aggregate 1 was cut into small fragments of about 1 cm square with scissors before mixing.

[0482] Next, the dispersion A obtained above was subjected to formal dispersion treatment under the following conditions using an ultra-high pressure homogenizer (model: NAGS100) manufactured by Toshoku Corporation, a wet jet mill, to obtain CNT dispersion A for SEM photography.

[0483] -condition-

[0484] Nozzle diameter: 0.22mm

[0485] Pressure: 85MPa

[0486] Number of times: 8

[0487] Method: Looping

[0488] (1-2) MWCNT assembly 2 of Example 2

[0489] 1.1 g of MWCNT aggregate 2 from 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 deionized water were mixed. The resulting mixture was pre-dispersed for 1 hour using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain dispersion B. In addition, to prevent MWCNT aggregate 2 from tangling on the blades of the homogenizer, MWCNT aggregate 2 was cut into small fragments of about 1 cm square with scissors before mixing.

[0490] Next, the dispersion B obtained above was subjected to a formal dispersion treatment under the same conditions as the formal dispersion treatment in "(1-1) Example 1 MWCNT assembly 1" using a wet jet mill manufactured by Tokimitsu Corporation (model: NAGS100) to obtain CNT dispersion B for SEM photography.

[0491] (1-3) MWCNT assembly 3 of Example 3

[0492] 1.1g of MWCNT aggregate 3 from Example 3, 1.65g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MPBiomedicals) as a dispersant, and 547.25g of deionized water were mixed. The resulting mixture was pre-dispersed for 1 hour using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain dispersion C. In addition, to prevent MWCNT aggregate 3 from tangling on the blades of the homogenizer, the MWCNT aggregate 3 was cut into lengths of about 1cm with scissors before mixing.

[0493] Next, the dispersion C obtained above was subjected to a formal dispersion treatment under the same conditions as the formal dispersion treatment in "(1-1) Example 1 MWCNT assembly 1" using a wet jet mill manufactured by Tokimitsu Corporation (model: NAGS100) to obtain CNT dispersion C for SEM photography.

[0494] (1-4) Comparative Example 1: SWCNT collection 1

[0495] As a comparative example 1, the dispersion of SWCNT aggregate 1 was photographed using SEM image-taking CNT dispersion D (trade name: TUBALL). TM BATT H2O, an aqueous solution of single-walled carbon nanotubes (CNTs), manufactured by OCSiAl. The concentration of CNTs was adjusted to 0.2% by mass.

[0496] (1-5) Comparative Example 2 MWCNT assembly 4

[0497] 1.1 g of MWCNT aggregate 4 from Comparative Example 2, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MPBiomedicals) as a dispersant, and 547.25 g of deionized water were mixed. The resulting mixture was subjected to a pre-dispersion treatment for 1 hour using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain dispersion E.

[0498] Next, the dispersion E obtained above was subjected to a formal dispersion treatment under the same conditions as the formal dispersion treatment in “(1-1) Example 1 MWCNT assembly 1” using a wet jet mill manufactured by Tokimitsu Corporation (model: NAGS100) to obtain CNT dispersion E for SEM photography.

[0499] (1-6) Comparative Example 3 MWCNT assembly 5

[0500] 1.1 g of MWCNT aggregate 5 from Comparative Example 3, 1.65 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MPBiomedicals) as a dispersant, and 547.25 g of deionized water were mixed. The resulting mixture was subjected to a pre-dispersion treatment for 1 hour using an ACE homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain dispersion F.

[0501] Next, the dispersion F obtained above was subjected to a formal dispersion treatment under the same conditions as the formal dispersion treatment in “(1-1) Example 1 MWCNT assembly 1” using a wet jet mill manufactured by Tokimitsu Corporation (model: NAGS100) to obtain CNT dispersion F for SEM photography.

[0502] (2) SEM photo taking

[0503] (2-1) MWCNT assembly 1 of Example 1

[0504] An SEM image (magnification: 5000x) of the MWCNT assembly 1 of Example 1 was taken, confirming that multiple MWCNTs with a maximum length ranging from 500μm to 30000μm existed within the field of view of the SEM image.

[0505] In addition, multiple SEM images (magnification: 5000x) of adjacent field-of-view areas of the MWCNT assembly 1 of Example 1 were taken. For the 100 MWCNTs contained in the field of view of the SEM images, their maximum lengths were measured. The results showed that the proportion of MWCNTs with a maximum length in the range of 500μm to 30000μm (i.e., SLMWCNTs) was 90%, and the maximum length of the 100 MWCNTs observed was 3500μm.

[0506] (2-2) MWCNT assembly 2 of Example 2

[0507] SEM images (magnification: 5000x) of the MWCNT assembly 2 in Example 2 were taken, confirming that multiple MWCNTs with a maximum length ranging from 500μm to 30000μm existed within the field of view of the SEM images.

[0508] In addition, multiple SEM images (magnification: 5000x) of adjacent field-of-view areas of the MWCNT assembly 2 of Example 2 were taken. For the 100 MWCNTs contained in the field of view of the SEM images, their maximum lengths were measured. The results showed that 90% of the observed MWCNTs had a maximum length in the range of 500μm to 30000μm (i.e., SLMWCNTs), and the maximum length of the 100 observed MWCNTs was 3500μm.

[0509] (2-3) MWCNT assembly 3 of Example 3

[0510] SEM images (magnification: 5000x) of the MWCNT assembly 3 of Example 3 were taken, confirming that multiple MWCNTs with a maximum length ranging from 500μm to 30000μm existed within the field of view of the SEM images.

[0511] In addition, multiple SEM images (magnification: 5000x) of adjacent field-of-view areas of the MWCNT assembly 3 of Example 3 were taken. For the 100 MWCNTs contained in the field of view of the SEM images, their maximum lengths were measured. The results showed that 90% of the observed MWCNTs had a maximum length in the range of 500μm to 30000μm (i.e., SLMWCNTs), and the maximum length of the 100 observed MWCNTs was 4000μm.

[0512] (2-4) CNT dispersion A, CNT dispersion D and CNT dispersion E

[0513] Using a scanning electron microscope, SEM images of the CNT dispersions A, D, and E prepared above were taken at a magnification of 500x.

[0514] The results are as follows Figure 1A , Figure 1B and Figure 1C As shown.

[0515] Figure 1A This is an SEM image of the CNT dispersion A used to take SEM images of the MWCNT aggregate 1 containing Example 1. Figure 1B This is a SEM image of the SWCNT aggregate 1 containing Comparative Example 1, taken using CNT dispersion D. Figure 1C The image shows an SEM image of the MWCNT aggregate 4 containing Comparative Example 2, taken using CNT dispersion E.

[0516] like Figure 1AAs shown, in the CNT dispersion A used for SEM imaging of the MWCNT aggregate 1 from Example 1, multiple fibrous MWCNTs were found to be intertwined to form an aggregate. On the other hand, as... Figure 1B and Figure 1C As shown, in the CNT dispersion D for SEM imaging containing the SWCNT aggregate 1 of Comparative Example 1 and the CNT dispersion E for SEM imaging containing the MWCNT aggregate 4 of Comparative Example 2, almost no CNT entanglement was observed.

[0517] 2. Median particle size

[0518] The median particle size of CNTs contained in the CNT aggregate was determined.

[0519] The CNT dispersions A to F obtained in “(1) Preparation of CNT dispersion for SEM photography” in “1. Observation of SEM photographs” were diluted with ion-exchanged water to obtain aqueous dispersions A to F with a CNT concentration of 0.004% by mass.

[0520] The obtained aqueous dispersions A to F were used as test samples. A LUM GmbH LUM Sizer 611 centrifugal sedimentation dispersion stability particle size distribution analyzer was used as the testing apparatus. The volumetric particle size distribution of CNTs was determined under the following test conditions. The particle size at which the cumulative frequency reaches 50% was recorded in the determined volumetric particle size distribution and taken as the median particle size.

[0521] The results are shown in Table 1.

[0522] <Measurement Conditions>

[0523] Sample cell for measurement: Polycarbonate sample cell (optical path length: 2 mm)

[0524] Speed: 4000rpm

[0525] Centrifugal acceleration: 2300 × g

[0526] Measurement interval: 30 seconds

[0527] Number of measurements: 1000

[0528] Measurement temperature: 25℃

[0529] 3. Rate of change of transmittance

[0530] The rate of change of the transmittance of CNTs contained in a CNT aggregate was measured.

[0531] The CNT dispersions A to F (CNT concentration: 0.2% by mass) obtained in "(1) Preparation of CNT dispersion for SEM photography" of "1. Observation of SEM images" above were used as test samples. A LUM GmbH centrifugal sedimentation dispersion stability particle size distribution device (LUMiSizer 611) was used as the test device. Sedimentation curves were obtained according to the following test and analysis conditions. The rate of change of overall transmittance was determined from the obtained sedimentation curves by analyzing the rate of change of overall transmittance.

[0532] The results are shown in Table 1.

[0533] <Determination and Analysis Conditions>

[0534] Sample cell for measurement: Polycarbonate sample cell (optical path length: 2 mm)

[0535] Speed: 4000rpm

[0536] Centrifugal acceleration: 2300 × g

[0537] Measurement interval: 30 seconds

[0538] Number of measurements: 1000

[0539] Viscosity of the dispersion medium: 0.8946 mPa·s

[0540] Density of the dispersion medium: 997.3 kg / m³ 3

[0541] Density of the dispersed phase: 1350 kg / m³ 3

[0542] Refractive index (real part) of the dispersion medium: 1.326

[0543] Refractive index (real part) of the dispersed phase: 1.630

[0544] Refractive index (imaginary part) of the dispersion medium: 0.5153

[0545] In the above analytical conditions, the dispersion medium is water and the dispersed phase is CNT.

[0546] The viscosity, density, and refractive index values ​​mentioned above are all values ​​at 25°C.

[0547] 4. Scattering intensity ratio S1 / S2 and scattering intensity ratio S3 / S4

[0548] The scattering intensity ratios S1 / S2 and S3 / S4 of the CNTs contained in the CNT aggregate were measured.

[0549] The CNT dispersions A to F (CNT concentration: 0.2% by mass) obtained in “(1) Preparation of CNT dispersion for SEM photography” in “1. Observation of SEM photographs” above were used as the test samples.

[0550] The sample was 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 not to introduce air bubbles. Then, the scattering curve of CNT was obtained using the beamline BL03XU of the large synchrotron radiation facility SPring-8 as a small-angle X-ray scattering experimental device.

[0551] The small-angle X-ray scattering (SAXS) measurements were performed according to the description in "Structural Science of Crystalline Polymers," Kohji Tashiro, Springer, 2022. More specifically, measurements were conducted using a Dectris Pilatus 1M detector at an ambient temperature of 25°C, with an X-ray wavelength of 0.1 nm, a beam diameter of 100 μm, and a camera length of 8000 mm. No attenuator was used; X-rays were incident near the axis center of the NMR tube in a direction perpendicular to the length direction. Ten measurements were performed with an exposure time of 1 second, changing the irradiation position every 100 μm along the length direction, to obtain the total two-dimensional scattering image Ms. Simultaneously, the transmitted light intensity fs was measured in the ionization chamber downstream of the NMR tube while capturing the two-dimensional scattering image. The background two-dimensional scattering image Mb and the transmitted light intensity fb were measured under the same conditions as described above, except that ion-exchanged water was used instead of an aqueous dispersion to fill the NMR tube.

[0552] According to the following formula (1), the background-corrected two-dimensional scattering image M is obtained. At this time, the range of X-rays that are blocked by beam blockers (set to prevent direct beams from entering the detector) is removed from the two-dimensional scattering image M.

[0553] M = Ms / fs - Mb / fb (1)

[0554] A radial one-dimensional curve is obtained from the two-dimensional scattering image M through circular integration. Additionally, the magnitude of the scattering vector q is corrected for the horizontal axis using the standard substance collagen.

[0555] From the obtained one-dimensional curve, the scattering vector size q = 0.2 nm is read. -1 The scattering intensity S1 and the scattering vector magnitude q = 0.8 nm at that location. -1 The scattering intensity S2 and the scattering vector magnitude q = 0.02 nm at that point. -1The scattering intensity S3 and the scattering vector magnitude q = 0.08 nm at the location. -1 Given the scattering intensity S4 at point S4, calculate the scattering intensity ratios S1 / S2 and S3 / S4.

[0556] The results are shown in Table 2. Furthermore, the scattering curves of each CNT assembly obtained by small-angle X-ray scattering are shown in... Figure 2 .

[0557] 5. Electrical conductivity

[0558] The CNT dispersions A to F (CNT concentration: 0.2% by mass) obtained in "(1) Preparation of CNT dispersion for SEM photography" of "1. Observation of SEM images" above were dropped onto glass substrates cut to 10cm × 10cm size, and a stainless steel coater with a gap size of 150μm was used to form a film. Then, the glass substrate was heated on a hot plate at 110°C for 10 minutes to dry the film, and CNT aggregate films A to F were obtained. The surface resistivity of the obtained CNT aggregate films A to F was measured using a resistivity meter Loresta GX II (trade name) manufactured by Nitto Seiko Analytical Technology Co., Ltd. The surface resistivity of the CNT aggregate films A to F was measured at 5 different locations of the CNT aggregate film, and the average value was taken as the surface resistivity of the CNT aggregate. In addition, the conductivity of the CNT aggregate was evaluated according to the following evaluation criteria based on the surface resistivity of the CNT aggregate.

[0559] The results are shown in Tables 1 and 2. An evaluation result of "A" or "B" indicates excellent conductivity. The optimal evaluation result is "A".

[0560] -Evaluation Criteria-

[0561] A: The surface resistivity of the CNT assembly is less than 1.00 × 10⁻⁶. 2 Ω / sq.

[0562] B: The surface resistivity of the CNT assembly is 1.00 × 10⁻⁶. 2 Ω / sq or higher and less than 3.00 × 10 2 Within the range of Ω / sq.

[0563] C: The surface resistivity of the CNT assembly is 3.00 × 10⁻⁶. 2 Ω / sq or higher and less than 1.00 × 10 5 Within the range of Ω / sq.

[0564] D: The surface resistivity of the CNT assembly is 1.00 × 10⁻⁶. 5 Ω / sq or higher.

[0565] 6. Peak intensity ratio G1 / D1 in Raman spectra

[0566] The Raman spectra of CNTs contained in CNT aggregates were determined.

[0567] The CNT assembly was fixed on the sample stage, and Raman spectra were obtained using a RAMAN-11 Raman spectrometer (trade name) manufactured by Nanophoton under the following measurement conditions.

[0568] <Measurement Conditions>

[0569] Excitation laser wavelength: 532 nm

[0570] Grating: 600 grooves / mm

[0571] Objective lens: 20x, numerical aperture (NA) 0.45

[0572] Wavenumber range: 110cm -1 ~2650cm -1

[0573] 1550cm -1 ~1600cm -1 The maximum scattering intensity within the Raman shift range is taken as the peak intensity G1 of the G band in the Raman spectrum, with 1300 cm⁻¹ as the value. -1 ~1400cm -1 The maximum value of the scattering intensity in the Raman shift within the range is taken as the peak intensity D1 of the D band in the Raman spectrum. The ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band in the Raman spectrum, i.e., the peak intensity ratio G1 / D1, is calculated from their respective values.

[0574] The results are shown in Table 3.

[0575] 7. BET specific surface area

[0576] The BET specific surface area of ​​CNTs contained in a CNT aggregate was determined.

[0577] The BET specific surface area of ​​CNTs was determined by gas adsorption using nitrogen, based on JIS Z 8830:2013. Specifically, it was determined by the following method.

[0578] First, the CNT aggregates were loaded into the sample tube and pretreated by vacuum degassing the sample tube at 300°C for 3 hours using the BELPREP-vac II (trade name) pretreatment device manufactured by MicrotracBEL.

[0579] Pretreated CNT aggregates were used as test samples. Using a MicrotracBEL BELSORP-mini II surface area analyzer, the nitrogen adsorption capacity of the CNT aggregates was measured under the following conditions, and adsorption-desorption isotherms were obtained. The BET surface area was then calculated from the obtained adsorption-desorption isotherms according to the following analytical conditions.

[0580] The results are shown in Table 3.

[0581] <Determination and Analysis Conditions>

[0582] Determination method: Static volumetric method

[0583] Adsorption temperature: 77K

[0584] Adsorbate: Nitrogen

[0585] Saturated vapor pressure: measured

[0586] Balance wait time: 500 seconds

[0587] Specific surface area: BET method (BET-Plot)

[0588] Table 1

[0589]

[0590] As shown in Table 1, the MWCNT assembly 1 of Example 1, the MWCNT assembly 2 of Example 2, and the MWCNT assembly 3 of Example 3, which contain the following MWCNTs, were confirmed to have excellent conductivity. When the MWCNTs were prepared into an aqueous dispersion with a concentration of 0.004% by mass, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation was 80 nm or more, and when the MWCNTs were prepared into an aqueous dispersion with a concentration of 0.2% by mass, the rate of change of transmittance measured by centrifugal sedimentation was 0.3% / hour or less.

[0591] On the other hand, it was confirmed that the SWCNT assembly 1 of Comparative Example 1, the MWCNT assembly 4 of Comparative Example 2, and the MWCNT assembly 5 of Comparative Example 3, which contain CNTs that do not satisfy at least one of the above-mentioned median particle size of 80 nm or more and the above-mentioned rate of change of transmittance of 0.3% / hour or less, have poorer conductivity compared with the examples.

[0592] Table 2

[0593]

[0594] As shown in Table 2, the MWCNT assembly 1 of Example 1, the MWCNT assembly 2 of Example 2, and the MWCNT assembly 3 of Example 3, which contain the following MWCNTs, were confirmed to have excellent conductivity. When the MWCNTs were prepared as an aqueous dispersion with a concentration of 0.2% by mass, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering was q=0.2nm. -1 The scattering intensity S1 at point q = 0.8 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S1 to S2, i.e., the scattering intensity ratio S1 / S2, is 90 or higher. Furthermore, the excellent conductivity of MWCNT assembly 1 (Example 1), MWCNT assembly 2 (Example 2), and MWCNT assembly 3 (Example 3), which contain the following MWCNTs, was confirmed. When prepared as a 0.2% by mass aqueous dispersion, the scattering vector magnitude in the scattering curve obtained by small-angle X-ray scattering was q = 0.02 nm. -1 The scattering intensity S3 at point q = 0.08 nm is related to the scattering vector magnitude. -1 The ratio of the scattering intensity S3 to S4 at point S4 is less than 10.

[0595] On the other hand, it was confirmed that the SWCNT assembly 1 of Comparative Example 1, the MWCNT assembly 4 of Comparative Example 2, and the MWCNT assembly 5 of Comparative Example 3, which contain CNTs that do not satisfy the above-mentioned scattering intensity ratio S1 / S2 of 90 or more, have poorer conductivity compared to the embodiments. Furthermore, it was confirmed that the SWCNT assembly 1 of Comparative Example 1, the MWCNT assembly 4 of Comparative Example 2, and the MWCNT assembly 5 of Comparative Example 3, which contain CNTs that do not satisfy the above-mentioned scattering intensity ratio S3 / S4 of 10 or less, have poorer conductivity compared to the embodiments.

[0596] Table 3

[0597]

[0598] Based on the results of SEM image determination of the maximum length of MWCNTs, the conductivity evaluation results shown in Tables 1 and 2, and the results shown in Table 3, it can be seen that for MWCNTs with a maximum length of 1000 μm to 30000 μm (so-called ULMWCNTs), 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 MWCNTs, i.e., the peak intensity ratio G1 / D1, exceeds 0.9 and is less than 15. The BET specific surface area of ​​MWCNTs is 50 m². 2 / g~400m 2 / g of MWCNT aggregates exhibit excellent electrical conductivity.

[0599] Furthermore, it is known that MWCNTs (so-called specific ULMWCNTs) include those with a maximum length exceeding 1600 μm but less than 30000 μm. In the Raman spectrum of MWCNTs, the ratio of the peak intensity G1 of the G band to the peak intensity D1 of the D band, i.e., the peak intensity ratio G1 / D1, is less than 10. The BET specific surface area of ​​MWCNTs is 200 m². 2 / g~300m 2 The MWCNT aggregate of / g also exhibits excellent conductivity.

Claims

1. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following conditions: when a water dispersion liquid of 0.004 mass% concentration is prepared, the median particle size of the volume-based particle size distribution obtained by centrifugal sedimentation method is 80 nm or more, and when a water dispersion liquid of 0.2 mass% concentration is prepared, the rate of change of transmittance determined by centrifugal sedimentation method is 0.3% / hour or less.

2. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following condition: when a water dispersion liquid of 0.2 mass% concentration is prepared, the ratio of the scattering intensity SI at a scattering vector magnitude q = 0.2 nm"1 in the scattering curve obtained by small-angle X-ray scattering method to the scattering intensity S2 at a scattering vector magnitude q = 0.8 nm"1, that is, the scattering intensity ratio SI / S2 is 90 or greater. -1 -1 the scattering intensity ratio SI / S2 is 90 or greater.​ 3. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following condition: when a water dispersion liquid of 0.2 mass% concentration is prepared, the ratio of the scattering intensity S3 at a scattering vector magnitude q = 0.02 nm"1 in a scattering curve obtained by a small-angle X-ray scattering method to the scattering intensity S4 at a scattering vector magnitude q = 0.08 nm"1, that is, the scattering intensity ratio S3 / S4 is 10 or less. -1 -1 -1 ​ 4. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following conditions: when a water dispersion liquid is prepared at a concentration of 0.004 mass%, the median particle size of a volume-based particle size distribution obtained by a centrifugal sedimentation method is 80 nm or more, when a water dispersion liquid is prepared at a concentration of 0.2 mass%, the rate of change of transmittance determined by a centrifugal sedimentation method is 0.3% / hour or less, and when a water dispersion liquid is prepared at a concentration of 0.2 mass%, the ratio of the scattering intensity SI at a scattering vector magnitude q = 0.2 nm -1 in a scattering curve obtained by a small-angle X-ray scattering method to the scattering intensity S2 at a scattering vector magnitude q = 0.8 nm -1 in the scattering curve is 90 or more.

5. The multi-walled carbon nanotube aggregate according to any one of claims 1 to 4, wherein the multi-walled carbon nanotubes satisfy the following condition: when a water dispersion liquid is prepared at a concentration of 0.2 mass%, the rate of change of transmittance determined by a centrifugal sedimentation method is 0.2% / hour or less.

5. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following conditions: when a water dispersion liquid is prepared at a concentration of 0.004 mass%, the median particle size of a volume-based particle size distribution obtained by a centrifugal sedimentation method is 80 nm or more, when a water dispersion liquid is prepared at a concentration of 0.2 mass%, the rate of change of transmittance determined by a centrifugal sedimentation method is 0.3% / hour or less, and when a water dispersion liquid is prepared at a concentration of 0.2 mass%, the ratio of the scattering intensity S3 at a scattering vector magnitude q = 0.02 nm -1 to the scattering intensity S4 at a scattering vector magnitude q = 0.08 nm -1 in a scattering curve obtained by a small-angle X-ray scattering method, that is, the scattering intensity ratio S3 / S4 is 10 or less.

6. A multi-walled carbon nanotube aggregate comprising multi-walled carbon nanotubes satisfying the following conditions: when a water dispersion liquid of 0.2 mass% concentration is prepared, the ratio of the scattering intensity SI at a scattering vector magnitude q = 0.2 nm"1 in a scattering curve obtained by a small-angle X-ray scattering method to the scattering intensity S2 at a scattering vector magnitude q = 0.8 nm"1, that is, the scattering intensity ratio SI / S2 is 90 or greater, and the ratio of the scattering intensity S3 at a scattering vector magnitude q = 0.02 nm"1 in the scattering curve to the scattering intensity S4 at a scattering vector magnitude q = 0.08 nm"1, that is, the scattering intensity ratio S3 / S4 is 10 or less. -1 -1 -1 -1 SI / S2, S3 / S4​​​ 7. The multi-walled carbon nanotube assembly of any one of claims 1-6, wherein, The maximum length of the multi-walled carbon nanotubes is 1000 μm to 30000 μm.

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

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

10. An electrically 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 electrically conductive material according to claim 10.

12. A secondary battery provided with the electrode according to claim 11.

13. A composition comprising the multi-walled carbon nanotube aggregate according to any one of claims 1 to 6, and at least one selected from the group consisting of a resin, a ceramic, and a 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 aggregate according to claim 14.

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

17. A protective film for extreme ultraviolet light using the planar aggregate according to claim 14.

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