Carbon nanotube aggregate, carbon nanotube dispersion, conductive material, electrode, secondary battery, planar aggregate, filter, electromagnetic wave shield, and extreme ultraviolet protection film

Abstract

Provided is a carbon nanotube aggregate having excellent electrical conductivity when a carbon nanotube dispersion liquid is produced, and an application thereof. A carbon nanotube aggregate and an application thereof that satisfy the following (1) and (2), (1) the ratio of the pore volume to the BET specific surface area is 0.0100 μm to 0.0200 μm; (2) the ratio of the volume resistivity under 20 kN pressure to the volume resistivity under 1 kN pressure is 0.18 or greater and 0.30 or less.

Description

Technical Field

[0001] This disclosure relates to carbon nanotube aggregates, carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar aggregates, filters, electromagnetic wave shields, and protective films for extreme ultraviolet radiation. Background Technology

[0002] Carbon nanotubes are materials with a cylindrical structure formed by rolling graphene sheets with carbon atoms arranged in a hexagonal honeycomb pattern into a tube. Carbon nanotubes are broadly classified into single-walled carbon nanotubes formed from a single layer of graphene sheets and multi-walled carbon nanotubes formed from multiple layers of graphene sheets. Carbon nanotubes possess excellent mechanical and electronic properties, making them promising for various applications. In recent years, various attempts have been made to further improve the properties of carbon nanotubes.

[0003] For example, Patent Document 1 describes a pore volume of 0.94 cm³. 3 Carbon nanotubes of entangled structure with a density of 6g or more, their manufacturing method, and positive electrode for primary batteries.

[0004] Patent document 2 describes a carbon nanotube, a carbon nanotube dispersion, a carbon nanotube resin composition, and a non-aqueous electrolyte secondary battery. In this case, when the pore size of the peak in the pore size distribution of carbon nanotubes with a diameter of 2 nm or more and less than 200 nm calculated by the BJH method is set as Z (nm), it satisfies 3≦Z≦80, and the pore volume in the pore size distribution satisfies the specified condition (A) or (B).

[0005] [Existing Technical Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2021-527611

[0008] [Patent Document 2] Japanese Patent Application Publication No. 2023-98706 Summary of the Invention

[0009] [The problem the invention aims to solve]

[0010] One embodiment of this disclosure aims to solve the problem of providing a carbon nanotube aggregate with excellent conductivity when prepared as a carbon nanotube dispersion.

[0011] Another problem to be solved by this disclosure is to provide a carbon nanotube dispersion containing the above-described carbon nanotube aggregate and having excellent electrical conductivity.

[0012] Another problem to be solved by this disclosure is to provide a conductive material, an electrode, and a secondary battery comprising the above-described carbon nanotube aggregate.

[0013] Another problem to be solved by this disclosure is to provide a planar aggregate comprising the above-described carbon nanotube aggregate.

[0014] Another problem to be solved by this disclosure is to provide a filter, an electromagnetic wave shield, and an extreme ultraviolet protective film using the above-described planar assembly.

[0015] [Methods used to solve problems]

[0016] <1> A carbon nanotube aggregate that satisfies the following conditions (1) and (2),

[0017] (1) The ratio of pore volume to BET specific surface area is 0.010 μm to 0.020 μm;

[0018] (2) The ratio of the volume resistivity under 20kN pressure to the volume resistivity under 1kN pressure is above 0.18 and below 0.30.

[0019] <2> according to <1> The carbon nanotube assembly includes a bundle structure.

[0020] <3> according to <1> or <2> The carbon nanotube assembly, wherein the BET specific surface area is 100 m². 2 / g~420m 2 / g.

[0021] <4> according to <1> or <2> The carbon nanotube aggregate described herein has a pore volume of 0.60 cm³. 3 / g~5.00cm 3 / g.

[0022] <5> A carbon nanotube dispersion comprising <1> ~ <4> The carbon nanotube aggregate and dispersion medium described in any one of the following.

[0023] <6> A conductive material comprising <1> ~ <5> The carbon nanotube assembly described in any one of the following statements.

[0024] <7> An electrode comprising an electrode active material and <6> The aforementioned conductive material.

[0025] <8> A secondary battery, which has <7> The aforementioned electrode.

[0026] <9> A planar aggregate containing <1> ~ <3> The carbon nanotube assembly according to any one of the following methods, wherein the carbon nanotube assembly comprises carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

[0027] <10> A filter that is used <9> The aforementioned planar aggregate.

[0028] <11> An electromagnetic wave shield, which is used <9> The aforementioned planar aggregate.

[0029] <12> A protective film for extreme ultraviolet radiation, its use <9> The aforementioned planar aggregate.

[0030] <13> A composition comprising <1> ~ <4> The carbon nanotube assembly described in any one of the following, and at least one selected from the group consisting of resin, ceramics, and concrete.

[0031] [Invention Effects]

[0032] According to one embodiment of the present disclosure, a carbon nanotube aggregate with excellent conductivity when prepared as a carbon nanotube dispersion can be provided.

[0033] According to another embodiment of this disclosure, a carbon nanotube dispersion containing the above-described carbon nanotube aggregate and exhibiting excellent electrical conductivity can be provided.

[0034] According to another embodiment of this disclosure, a conductive material, an electrode, and a secondary battery comprising the above-described carbon nanotube aggregate can be provided.

[0035] According to another embodiment of this disclosure, a planar aggregate comprising the above-described carbon nanotube aggregate can be provided.

[0036] According to another embodiment of this disclosure, a filter, an electromagnetic wave shield, and an extreme ultraviolet protective film using the above-described planar assembly can be provided. Attached Figure Description

[0037]

【 Figure 1 [A scanning electron microscope image showing one manner of a specific CNT assembly] Detailed Implementation

[0038] The following provides a detailed description of carbon nanotube assemblies, carbon nanotube dispersions, conductive materials, electrodes, secondary batteries, planar assemblies, filters, electromagnetic wave shields, and protective films for extreme ultraviolet radiation related to this disclosure. The following description is sometimes based on representative embodiments of this disclosure, but this disclosure is not limited to such embodiments, and appropriate modifications can be made to implement it within the scope of the purposes of this disclosure.

[0039] In this disclosure, the numerical range indicated by “~” means that the numerical values ​​recorded before and after “~” are included as the minimum and maximum values, respectively.

[0040] In the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different segments. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the value shown in the embodiments.

[0041] In this disclosure, a combination of two or more preferred methods is a more preferred method.

[0042] In this disclosure, where there are multiple substances that conform to each component, unless otherwise stated, the amount of each component refers to the total amount of the multiple substances.

[0043] In this specification, the term "process" includes not only independent processes, but also processes that can not be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved.

[0044] In this disclosure, the terms “carbon nanotube”, “single-walled carbon nanotube”, “multi-walled carbon nanotube”, “multi-walled carbon nanotube with a maximum length of 1000 μm to 30000 μm”, “carbon nanotube aggregate”, and “carbon nanotube dispersion” are sometimes abbreviated as “CNT”, “SWCNT”, “MWCNT”, “ULMWCNT”, “CNT aggregate”, and “CNT dispersion”, respectively.

[0045] [Carbon nanotube assembly]

[0046] One embodiment of this disclosure is a carbon nanotube assembly that satisfies the following conditions (1) and (2).

[0047] (1) The ratio of pore volume to BET specific surface area is 0.010 μm to 0.020 μm;

[0048] (2) The ratio of the volume resistivity under 20kN pressure to the volume resistivity under 1kN pressure is above 0.18 and below 0.30.

[0049] Hereinafter, the carbon nanotube assembly of this embodiment will also be referred to as a "specific CNT assembly".

[0050] The carbon nanotube dispersion exhibits excellent conductivity when prepared according to a specific CNT aggregate. That is, the carbon nanotube dispersion (hereinafter also referred to as "specific CNT dispersion") containing a specific CNT aggregate and a dispersion medium that satisfy the conditions of (1) and (2) above has excellent conductivity.

[0051] The specific CNT dispersion is another embodiment of this disclosure, and details regarding the specific CNT dispersion, other than the specific CNT aggregate, will be described later.

[0052] On the other hand, neither Patent Document 1 nor Patent Document 2 takes into account obtaining a carbon nanotube dispersion with excellent conductivity, nor do they focus on specifying the pore volume of the CNT aggregate and the ratio of the volume resistivity under 20 kN pressure to the volume resistivity under 1 kN pressure as conditions.

[0053] The following is a detailed description of a specific set of CNTs. However, the speculations described below are not intended to limit the interpretation of the specific set of CNTs, but are provided as examples.

[0054] <Condition (1)>

[0055] In a specific CNT aggregate, the ratio of pore volume to BET specific surface area (pore volume / BET specific surface area) is 0.0100 μm to 0.0200 μm, preferably 0.0100 μm to 0.0180 μm.

[0056] In a specific CNT aggregate, the ratio of pore volume to BET specific surface area is related to the depth and diameter of the pores of the CNTs constituting the aggregate. It is hypothesized that by maintaining a pore volume-to-BET specific surface area ratio of 0.0100 μm to 0.0200 μm, the friction between the CNT aggregates is kept within an appropriate range, making it easier to stably form conductive pathways in the form of a dispersion, thus improving the conductivity of the dispersion.

[0057] In contrast, it is speculated that for CNT aggregates with a pore volume to BET specific surface area ratio of less than 0.0100 μm, the CNT aggregates have less surface roughness, resulting in less friction between them and making it difficult to maintain a stable contact state, thus making the conductive path unstable.

[0058] In addition, it is speculated that for CNT aggregates with a pore volume to BET specific surface area ratio greater than 0.0200 μm, the dispersion in the dispersion liquid becomes insufficient due to the increased friction between the CNT aggregates, which is not conducive to the formation of conductive pathways.

[0059] Furthermore, when the ratio of pore volume to BET specific surface area is greater than 0.0200 μm, the cavities in the CNT aggregate become deeper, which may reduce the physical strength of the CNT aggregate. Due to the reduced physical strength of the CNT aggregate, it may not withstand shear forces applied to the CNT aggregate, such as in processes that apply shear force (e.g., the possibility of partial pore blockage or partial destruction of the CNT aggregate), and is therefore not preferred. Additionally, when the ratio of pore volume to BET specific surface area is too large, the cavities in the CNT aggregate become deeper, and the conductive pathways in the CNT aggregate may become excessively long, leading to increased resistance, which is also not preferred.

[0060] In this disclosure, the BET specific surface area of ​​the CNT aggregate is determined by gas adsorption using nitrogen in accordance with JIS Z 8830:2013.

[0061] As a specific surface area measuring device, the BELSORP-mini II (trade name) specific surface area measuring device manufactured by MicrotracBEL Co., Ltd. can be used, for example. However, the specific surface area measuring device is not limited to this.

[0062] The BET specific surface area of ​​a particular CNT aggregate can be controlled by synthesis conditions such as sintering temperature, gas flow rate, and gas introduction method during CNT synthesis.

[0063] The BET specific surface area of ​​a particular CNT aggregate can be increased, for example, by increasing the sintering temperature during CNT synthesis, or decreased by decreasing the sintering temperature during CNT synthesis.

[0064] The preferred BET specific surface area for a specific CNT aggregate is 100m². 2 / g~420m 2 / g.

[0065] It is speculated that if the specific surface area is small, it is difficult to ensure the contact points between CNTs, but the effect of increasing the contact points due to load pressure will be significant. On the other hand, it is speculated that if the specific surface area is large, it is easy to ensure the contact points between CNTs, but the effect of increasing the contact points due to load pressure will be smaller. It is speculated that by making the BET specific surface area of ​​the CNTs contained in a specific CNT assembly 100m²... 2 / g~420m 2 / g, thereby ensuring the contact points between CNTs, and the effect of increased contact points caused by load pressure also becomes good.

[0066] Certain CNT assemblies can also contain CNTs with a large specific surface area (e.g., 420m²). 2 / g~1400m 2 / g) and CNTs with smaller specific surface areas (e.g., 10m²) 2 / g~100m 2 The / g) combination is included.

[0067] In this disclosure, the pore volume of the CNT aggregate is determined using a constant volume method. A specific surface area / pore distribution measuring device can be used as the measuring apparatus.

[0068] Pore ​​volume of CNT aggregates (cm³) 3 / g), specifically, is determined by the steps shown below.

[0069] First, the CNT aggregates to be measured were subjected to vacuum degassing at 300°C for 3 hours to prepare samples for measurement.

[0070] For the prepared samples, nitrogen-based adsorption-desorption isotherms were determined using the constant volume method. The BJH method was used for the analysis to calculate the pore volume.

[0071] Measuring Apparatus: Specific Surface Area / Pore Distribution Measuring Apparatus (Product Name "BEL SORP-miniII", manufactured by MicrotracBEL)

[0072] Measurement temperature: 77K

[0073] Adsorbate: Nitrogen

[0074] Saturated vapor pressure: Measured value

[0075] Adsorbate cross-sectional area: 0.162 nm 2

[0076] Waiting time after adsorption equilibrium is reached: 500 seconds

[0077] The preferred pore volume of a specific CNT aggregate is 0.60 cm³. 3 / g~5.00cm 3 / g, more preferably 0.60cm 3 / g~3.20cm 3 / g.

[0078] It is speculated that for a specific CNT aggregate, when the pore volume is 0.60 cm³, 3 / g~5.00cm 3 When the friction between specific CNT aggregates is within an appropriate range, and when a dispersion is prepared, a conductive path can be easily and stably formed, further improving the conductivity of the dispersion.

[0079] In contrast, it is speculated that for pore volumes below 0.60 cm³... 3 / g of CNT aggregates, due to the lack of surface irregularities on the CNT aggregates, the friction between the CNT aggregates is small, making it difficult to maintain a stable contact state, and thus the conductive path tends to become unstable.

[0080] Additionally, it is speculated that for pore volumes greater than 5.00 cm³... 3 / g of CNT aggregates, due to the increased friction between the CNT aggregates, tend to be insufficiently dispersed in the dispersion liquid, which is not conducive to the formation of conductive pathways.

[0081] Furthermore, the pore volume is greater than 5.00 cm³. 3 At a density of / g, the number of voids in CNT aggregates increases, thus reducing the physical strength of the CNT aggregates. Due to this reduced physical strength, the CNT aggregates may not withstand shear forces applied during processes such as those involving the formation of CNT dispersions (e.g., partial pore blockage, partial destruction of the CNT aggregates). Furthermore, when the pore volume is too large, the increased voids in the CNT aggregates may lead to excessively long conductive pathways, potentially increasing resistance.

[0082] In this disclosure, the pore volume of a CNT aggregate is defined as the pore volume (cm³) of a CNT aggregate per unit mass (g). 3 The morphology of CNT aggregates, which are the objects of pore volume measurement, is not limited and can be any form of powder, fiber, sheet, etc.

[0083] <Condition (2)>

[0084] The ratio of the volume resistivity of a specific CNT assembly under 20kN pressure to its volume resistivity under 1kN pressure (hereinafter also referred to as the "resistivity ratio") is 0.18 or higher and 0.30 or lower.

[0085] Because the resistivity ratio of certain CNT aggregates is above 0.18, their aggregation in powder form is not very high, resulting in good dispersibility in the dispersion medium and allowing for wide micro-dispersion in the dispersion. Therefore, it is speculated that the conductive pathways formed between CNTs in the dispersion can easily reach an appropriate length, thus resulting in a dispersion with excellent conductivity. Furthermore, it is speculated that because the resistivity ratio of certain CNT aggregates is below 0.30, the contact between CNTs is moderately enhanced, and conductive pathways can be easily and stably formed, thus enabling a dispersion with excellent conductivity.

[0086] In one embodiment, the resistivity ratio of the specific CNT aggregate is preferably 0.21 or higher and 0.24 or lower. When the resistivity ratio is 0.21 or higher and 0.24 or lower, the aggregation of the specific CNT aggregate in the powder state is not very high, making it easy to ensure dispersibility in the dispersion medium. Therefore, it is possible to ensure the connectivity between the micro-dispersed CNTs in the dispersion, and it is speculated that the conductivity of the dispersion is improved.

[0087] In another embodiment, the resistivity ratio of the specific CNT aggregate is preferably 0.25 or higher and 0.29 or lower. It is speculated that when the resistivity ratio is 0.25 or higher and 0.29 or lower, the aggregation in the powder state will not be too high, and the conductivity of the specific CNT dispersion can be more easily and stably ensured.

[0088] In this disclosure, the volume resistivity of the CNT assembly is measured using a resistivity meter at 25°C via a four-probe method. A Loresta apparatus can be used as the resistivity meter.

[0089] Specifically, using the Loresta apparatus (product name: MCP-PD51 powder resistance measurement system, Loresta-GP low resistivity meter, MCP-PD511 low resistance probe for powder (constant current application method 4-probe method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the sample to be measured is introduced into the resistivity measurement probe unit, and the accompanying hydraulic pump is used to apply pressure at 1kN or 20kN. After reaching the target load, the volume resistivity (Ω·cm) is measured.

[0090] As a sample for measuring volume resistivity, powder of CNT aggregates is used.

[0091] When the CNT aggregates are in a form other than powder (e.g., fibers or sheets), they can be pulverized to become powder. There are no particular limitations on the pulverization process; any pulverization method capable of breaking the CNT aggregates into small pieces can be used. For example, a cryogenic pulverization process can be used.

[0092] In this disclosure, the resistivity ratio is calculated by dividing the measured volume resistivity under 20 kN pressure by the volume resistivity under 1 kN pressure, and rounding off the third decimal place.

[0093] The resistivity ratio of CNT assemblies can be adjusted using conventional methods.

[0094] Methods for adjusting the resistivity ratio of CNT assemblies include, for example, controlling the content of impurities in CNTs, controlling structural defects in CNTs, controlling the ratio of SWCNTs to MWCNTs, controlling the length of CNTs, and controlling the specific surface area of ​​CNTs.

[0095] Regarding impurities contained in CNTs, it can be considered that at low load pressures, impurities trapped between CNTs significantly obstruct the conductive path, leading to an increase in resistivity. Conversely, as the load pressure increases, the number of contact points between CNTs increases, reducing the impact of impurity-induced resistance increases and decreasing resistivity. Therefore, by controlling the content of key impurities—namely, Fe and / or Co atoms derived from the catalyst—the resistivity ratio can be controlled.

[0096] The structural defects of CNTs can be quantified by the G / D intensity ratio in Raman spectroscopy. A high G / D intensity ratio indicates fewer structural defects, thus the resistivity tends to decrease. The G / D intensity ratio can be controlled by selecting the conditions of the CNT manufacturing method described later. The resistivity ratio can be controlled by adjusting the mixing ratio of CNTs with high G / D intensity ratios to those with lower G / D intensity ratios as needed.

[0097] Typically, SWCNTs have lower resistivity than MWCNTs, and with lower resistivity, the resistivity change caused by applied load tends to be smaller. The number of CNT layers can be controlled by selecting the conditions of the CNT manufacturing method described later.

[0098] As the length of a CNT increases, its resistivity tends to decrease. Taking this into account, methods for incorporating ULMWCNTs are also cited as one control method. ULMWCNTs can be obtained, for example, by controlling the manufacturing method of the CNT.

[0099] The resistivity ratio of a specific CNT assembly can also be controlled by the specific surface area of ​​the CNTs. It is speculated that if the specific surface area is small, it is difficult to ensure contact points between CNTs, but the increase in contact points due to applied load will be significant. Conversely, it is speculated that if the specific surface area is large, it is easier to ensure contact points between CNTs, but the increase in contact points due to applied load will be smaller. The specific surface area of ​​CNTs can be controlled by adjusting the conditions in the CNT manufacturing method described later. The mixing ratio of CNTs with large and small specific surface areas can be controlled as needed, and the two can be used after being uniformly mixed.

[0100] <Bundle Structure>

[0101] From the perspective of improved operability, a particular CNT assembly preferably includes a bundle structure.

[0102] A bundle structure refers to a collection of multiple CNTs that are aggregated together by van der Waals forces, forming a bundle-like or handle-like structure. It is speculated that a particular CNT assembly, by containing a bundle structure of a suitable size, exhibits improved operability and stability. However, on the other hand, if the bundle structure within a particular CNT assembly is too large, the CNT assembly itself may become excessively large, making it difficult to separate and disperse the CNTs within the bundle structure, thus reducing its dispersibility in the dispersion medium.

[0103] Therefore, from the viewpoint of balancing the operability of CNT assemblies and their dispersibility with solvents, the width of each bundle structure contained in a specific CNT assembly, i.e., the width dimension of the fiber bundle, is preferably 5 nm to 500 nm, and more preferably 10 nm to 300 nm.

[0104] The presence or absence of bundle structures within a specific CNT assembly can be confirmed by observing the assembly using optical microscopy or scanning electron microscopy (SEM). The width of the bundle structure is determined by identifying the locations within the assembly where bundle structures are present and measuring their length using images captured from the bundle structures.

[0105] Bundle structures, for example, can be formed in manufacturing processes using chemical vapor deposition (CVD) by controlling catalyst particle size distribution and cooling rate during the cooling process.

[0106] <Other matters concerning specific CNT collections>

[0107] In this disclosure, the CNTs contained in a particular CNT collection may be SWCNTs or MWCNTs, but from the viewpoint that they have a layered distribution and slightly lower uniformity, thus making it easier to improve dispersion, MWCNTs are preferred.

[0108] Generally, SWCNTs have lower volume resistivity than MWCNTs, and lower volume resistivity means a smaller resistivity change caused by applied load. Therefore, in a specific CNT assembly, SWCNTs and MWCNTs can be used in combination as needed. The number of CNT layers can be controlled by selecting the CNT manufacturing method.

[0109] As the length of a CNT increases, its volume resistivity tends to decrease. The length of a CNT can be controlled by selecting the manufacturing method.

[0110] In one embodiment, a specific CNT assembly may comprise MWCNTs with a maximum length of 500 μm or less as the principal component, and may not comprise an assembly of MWCNTs with a length of 500 μm to 30000 μm. Here, the principal component refers to MWCNTs with a maximum length of 500 μm or less comprising at least 90% by mass of the CNTs constituting the specific CNT assembly. The specific CNT assembly may also comprise SWCNTs with a maximum length of 500 μm or less.

[0111] In one embodiment, a particular CNT assembly preferably comprises MWCNTs with a maximum length of 10 μm to 30,000 μm. In another embodiment, the MWCNTs preferably comprise ULMWCNTs.

[0112] ULMWCNTs are MWCNTs with a maximum length of 1000μm to 30000μm. Compared with general MWCNTs, they are longer and can be designed in fiber shape.

[0113] By being shaped like fibers, ULMWCNTs have the property of easily entangled with each other. MWCN contains at least one type of ULMWCNT, and from the viewpoint that MWCNTs can easily form a more stable aggregate by entanglement, an aggregate containing multiple ULMWCNTs is preferred. Hereinafter, an aggregate containing ULMWCNTs will sometimes be simply referred to as an "ULMWCNT aggregate".

[0114] Here, the term "fiber" is generally used to refer to a structure whose preferred dimension is larger than the other two dimensions. The fiber can be a filamentous fiber with a circular cross-section, a strip-shaped fiber with a rectangular cross-section, a hollow fiber, or other shapes. From the viewpoint of improving conductivity, it is preferred that the ULMWCNT has a circular cross-section, and preferably a hollow one.

[0115] An assembly of MWCNTs can also be an assembly of intertwined three-dimensional structures.

[0116] Figure 1 This is a scanning electron microscope (SEM) image showing one manner of assembling MWCNTs in this disclosure. From Figure 1 The SEM images shown reveal that multiple fibrous ULMWCNTs are intertwined and form aggregates. This SEM observation confirms the entangled state of the ULMWCNTs in this disclosure.

[0117] The length of a ULMWCNT can be determined by observing multiple SEM images of adjacent field-of-view angles focusing on a single ULMWCNT. Here, "length of ULMWCNT" refers to the measured length along the long side of the ULMWCNT, and the maximum value among the measured lengths is taken as the "maximum length".

[0118] When a MWCNT with a maximum length ranging from 1000 μm to 30000 μm is observed within the field of view of a SEM image, it can be confirmed that the observed MWCNT contains a ULWMCNT.

[0119] It is preferable that multiple ULMWCNTs are present in the field of view of the SEM image. Considering 100 MWCNTs contained in the field of view of the SEM image, the maximum length of each MWCNT is measured. From the viewpoint of further improving the stability of the MWCNT aggregate caused by the entanglement of ULMWCNTs, it is preferable that 10% or more of the MWCNTs (i.e., ULMWCNTs) with a maximum length in the range of 1000 μm to 30000 μm are present, more preferably more than 20%, more preferably more than 30%, and particularly preferably more than 50%.

[0120] The diameter of a ULMWCNT can be determined by observing SEM or transmission electron microscopy (TEM) images. Here, the diameter refers to the length of a direction orthogonal to the long side of the ULMWCNT. The diameter is measured at 10 different locations for a single ULMWCNT, and the average value is taken as the diameter of that ULMWCNT.

[0121] The length of the ULMWCNT is in the range of 1000 μm to 30000 μm, preferably in the range of 1050 μm to 25000 μm, more preferably in the range of 1100 μm to 20000 μm, even more preferably in the range of 1200 μm to 18000 μm, and particularly preferably in the range of 1300 μm to 15000 μm. The diameter of the ULMWCNT 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.

[0122] The length-to-diameter ratio of the ULMWCNT, also known as the aspect ratio, is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more.

[0123] The length-to-diameter ratio can be calculated from the ratio of the maximum length to the diameter of a single ULMWCNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of measurements from 20 or more ULMWCNTs.

[0124] Furthermore, from the viewpoint of dispersion, the specific gravity of the ULMWCNT aggregate is preferably in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.4, and even more preferably in the range of 1.8 to 2.2.

[0125] The specific gravity of the ULMWCNT aggregate can be measured by the method described in JIS Z8807:2012 "Methods for Measuring the Density and Specific Gravity of Solids".

[0126] The purity of MWCNTs in the ULMWCNT aggregate can be measured by thermogravimetric analysis. For example, using a thermal analyzer (manufactured by Shimadzu Corporation, DTG-60), the thermogravimetric (TG) curve and differential thermal analysis (DTA) curve of the ULMWCNT aggregate are obtained. The maximum exothermic peak with a peak top near 650°C to 750°C in the DTA curve is regarded as the combustion of MWCNTs, and exothermic peaks appearing elsewhere are regarded as the combustion of substances other than MWCNTs. The purity of MWCNTs is determined from the weight reduction rate of the TG curve. From the viewpoint of the obtained electrical conductivity, the purity of the ULMWCNT aggregate is preferably 50 mass% or more, more preferably 65 mass% or more, further preferably 80 mass% or more, and particularly preferably 95 mass% or more.

[0127] ULMWCNTs may contain 0.01 mass% to 50 mass% of Fe atoms derived from iron, which is the catalyst used during production. When ULMWCNTs contain Fe atoms, for example, the Fe atoms may be present in a state of being adsorbed on the surface of ULMWCNTs or a state of being encapsulated inside the fibrous ULMWCNTs formed during production.

[0128] The obtained fibrous ULMWCNTs preferably have flexibility and high strength.

[0129] In addition, the electrical conductivity of ULMWCNTs themselves is preferably 5000 ohm -1 ·m -1 or more, more preferably 10000 ohm -1 ·m -1 or more. Furthermore, the electrical conductivity of ULMWCNTs themselves is usually 1000000 ohm -1 ·m -1 or less.

[0130] <Method for Producing CNTs>

[0131] The method for producing CNTs in the present disclosure is not particularly limited. For example, as the method for producing MWCNTs in the present disclosure, conventionally known methods such as the chemical vapor deposition (CVD) method, a method of reacting a gaseous reaction substance containing a carbon source in the presence of a catalyst, and the like can be applied.

[0132] The CNTs in the present disclosure can be produced, for example, by referring to the methods described in Japanese Patent Application Laid-Open No. 2016-102047, Japanese Patent Application National Publication No. 2021-527611, and the like.

[0133] The following describes the manufacturing method of CNTs according to this disclosure by way of example. However, the manufacturing method of CNTs according to this disclosure is not limited to the following example.

[0134] =Manufacturing Method X=

[0135] As an example of a CNT manufacturing method referenced in this disclosure, the manufacturing method described in Japanese Patent Application Publication No. 2016-102047 can be cited. That is, a manufacturing method (hereinafter also referred to as "manufacturing method X") comprising the following steps: passing a gaseous reactant containing one or more carbon sources 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 a force to the aggregates to cause the aggregates to move continuously out of the reaction zone.

[0136] According to manufacturing method X, MWCNTs containing ULMWCNTs can be obtained in the form of easily manipulated fibrous aggregates or other aggregates.

[0137] In manufacturing method X, the force applied to the product particles can also be a mechanical force.

[0138] When the aggregates are fibrous MWCNTs, the mechanical force applied to the product particles can be applied by a rotating mandrel that winds around the aggregates. The fibrous CNTs can be recycled onto the mandrel, or they can be accumulated in other locations by continuously unwinding the mandrel after rotating around it once or more.

[0139] The mandrel is preferably configured perpendicularly or parallel to the flow direction of one or more gaseous reactants, but it can also be configured in other orientations. For example, a mandrel configured at a 25° angle to the flow direction of the gaseous reactants can also be suitably used to apply mechanical force to product particles.

[0140] The mandrel can rotate about two axes (e.g., two perpendicular axes). In particular, the mandrel can rotate about axes perpendicular and parallel to the flow direction of the gaseous reactants, respectively. With such a mandrel, the aggregates of fibrous CNTs can be drawn and twisted to control the twist count and length.

[0141] The mandrel can be made of metal, ceramic or resin.

[0142] Depending on the material properties and the intended use of MWCNTs, the mandrel can take on different suitable shapes. The mandrel can be produced by spin coating, for example, as a mold for manufacturing carbon products. Preferred mandrel shapes are rod-shaped or box-shaped.

[0143] Fibrous MWCNTs accumulate on the mandrel or other sites. 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 the orientation of the carbon products can be controlled, for example, by the dynamics of the gas flow.

[0144] The rotational speed of the mandrel is preferably 0.01 rpm to 10,000 rpm, more preferably 0.1 rpm to 100 rpm.

[0145] The spinning speed (i.e., the rotation speed of the mandrel) can be adjusted to be the same speed as the generated material. The thickness of the accumulated fibrous MWCNTs can be controlled by the rotation speed of the mandrel. In a preferred embodiment, the fibrous CNTs are processed along the axial direction of the mandrel as the mandrel rotates. In the above processing, the fibrous MWCNTs are not wound only at a specific location on the mandrel, but are wound uniformly along the mandrel.

[0146] Fibrous MWCNTs can be recovered, for example, from the reactor wall using a matrix placed within the reactor. The matrix can be a stationary matrix, or, in the case of recovering fibrous MWCNTs, a rotating guide component for applying a strong and uniform force to the fibrous MWCNTs. As a suitable matrix configuration for fiber technology, a matrix consisting of two guide components positioned orthogonally to each other can be cited as an example.

[0147] In manufacturing method X, the mechanical force applied to the product particles can be a force applied by accelerating a gas flow. Accelerating the 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.

[0148] Other forces applied to the product particles include electrostatic forces applied appropriately via charged electrode plates. When using electrostatic forces, the product particles need to be charged. By using charged electrode plates, MWCNTs can be generated on the charged electrode plates in the form of intertwined sheets.

[0149] Alternatively, other forces applied to the product particles could be magnetic force or photon pressure applied by a light source.

[0150] The raw material for CNTs can replace the gaseous reactants containing a carbon source, and can be injected in liquid form containing a carbon source. When using liquid as the raw material for CNTs, injection can be performed through a single injection port or multiple injection ports, for example, injection can be performed using a spray head configuration.

[0151] One or more gaseous reactants are preferably reacted at 500°C to 1600°C, more preferably at 1000°C to 1500°C. It is preferable to maintain a temperature gradient within the reactor and keep the reaction zone at a higher temperature than the product zone of the reactor.

[0152] The gaseous reactant can be mixed with one or more gases that act as a diluent. The gaseous reactant can also be mixed with a gas that does not play a direct role in the reaction but plays an auxiliary role. In the case of generating amorphous carbon as a byproduct, it is preferable to use a gas that can properly maintain the reaction sites on the catalyst and generate nanotubes by reacting with amorphous carbon as a diluent.

[0153] Examples of gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, hydrogen is particularly preferred as a diluent. 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.

[0154] The pressure of the gaseous reactants and optional diluents is preferably 0.1 bar to 50 bar, more preferably 0.5 bar to 5 bar, and even more preferably 1 bar to 2 bar. In the presence of gas outflow from the furnace, the outflowing gas can be recycled with or without purging.

[0155] 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 the CNTs are single-walled or multi-walled. Additionally, 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 winding force measurements.

[0156] When removing the aggregates from the reactor, it is preferable to prevent air from entering the reactor. This is especially important when the gas used as a diluent contains hydrogen, for example, from the viewpoint of suppressing the formation of an explosive mixture of hydrogen and air in the reactor.

[0157] The product particles produced in manufacturing method X contain ULMWCNTs. Additionally, depending on the manufacturing conditions, SWCNTs may sometimes be present in addition to MWCNTs.

[0158] Product particles can also be generated via chemical vapor deposition. In the case of product particles generated via chemical vapor deposition, the carbon source, which is a gaseous reactant, reacts in the presence of a catalyst.

[0159] Suitable carbon-containing compounds as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, and mixtures of two or more of these).

[0160] As a carbon-containing compound, carbon monoxide, methane, ethylene, or acetylene are preferred.

[0161] The carbon source preferably contains oxygen. Ethanol is a particularly preferred carbon source.

[0162] Oxygen can be introduced into the reactor by other methods, such as by using a carbon source containing diluent gas or water.

[0163] The gaseous reactant, which serves as a carbon source, is 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.

[0164] As catalysts, transition metals, particularly Group VIB chromium (Cr), molybdenum (Mo), tungsten (W), or Group 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. Fe, Ni, Co, Mo, and mixtures thereof are more preferred, such as mixtures of Ni and Co (mass ratio: 50 / 50), mixtures of Fe and Ni, or mixtures of Fe and Mo.

[0165] Any of these transition metals can be used alone or in combination with any of the other listed transition metals to function as a catalyst for CNT growth. The catalyst is particularly preferably a mixture of two or more of the listed metals.

[0166] The catalyst is preferably formed by the decomposition of a precursor. The precursor is preferably a thermally decomposable, photodecomposable, 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 as precursors. The carbon source preferably 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.

[0167] The catalyst can be supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0168] 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. The carbon source preferably contains up to 10% by mass of the promoter. Preferably, the carbon source contains 0.2% to 6% by mass of the promoter. When high or low concentrations of thiophene are used as the promoter, MWCNTs will form.

[0169] For example, MWCNTs can be well formed using ethanol containing 0% or 1.5% to 4.0% by mass of thiophene and 0.5% to 5.0% by mass (especially 2.3% by mass) of ferrocene, at an injection rate of 3.0 mL / h to 12.0 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.

[0170] According to manufacturing method X, fibrous CNTs with a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can take the form of filaments or sheets.

[0171] The length of fibrous CNTs can be controlled, for example, by the winding capability of the mandrel used in manufacturing fibrous CNTs.

[0172] Manufacturing method X preferably includes: a step of reacting a carbon source in the reaction zone of a reactor to generate CNTs; and a step of applying force to the CNTs to cause them to aggregate into aggregates. According to this manufacturing method, fibrous CNTs can be easily manufactured.

[0173] Alternatively, the following methods can be used: after generating MWCNTs containing ULMWCNTs in the reaction zone using the above method, condense them to form MWCNTs containing ULMWCNTs; and continuously extract MWCNTs from the vicinity of the reaction zone.

[0174] Alternatively, the following methods may be employed: generating MWCNTs containing ULMWCNTs in the reaction zone; continuously electrostatically attracting MWCNTs containing ULMWCNTs from the reaction zone; and recovering MWCNTs containing ULMWCNTs.

[0175] =Manufacturing Method Y=

[0176] In this disclosure, as an example of a method for manufacturing CNTs, reference can be made to the manufacturing method described in Japanese Patent Application Publication No. 2021-527611. That is, a manufacturing method (hereinafter also referred to as "manufacturing method Y") including the following steps: Step (1), a step (1) of supporting an active support on γ-Al2O3 by supporting a mixture of a main catalyst precursor and a co-catalyst precursor, a step (2) of drying the active support by multi-stage drying including vacuum drying, a step (3) of heat treating the dried active support to manufacture a supported catalyst, and a step (4) of manufacturing CNTs in the presence of the supported catalyst.

[0177] Process (1)

[0178] In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is supported on γ-Al2O3 to produce an active support.

[0179] To ensure that the main catalyst precursor and the co-catalyst precursor are uniformly supported on γ-Al₂O₃, the mixture may further contain a solvent, wherein the main catalyst precursor and the co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, preferably water.

[0180] Due to the high porosity and spinel structure of γ-Al₂O₃, the main catalyst and co-catalyst can be irregularly arranged on γ-Al₂O₃. CNTs grown from the irregularly arranged main catalyst can be fabricated in an entangled manner.

[0181] The main catalyst may be selected from one or more of the group consisting of cobalt, iron, nickel, manganese and chromium, with cobalt being preferred.

[0182] The precursor of the main catalyst can be one or more selected from the group consisting of nitrates, sulfates, carbonates and acetates of the main catalyst, preferably nitrates of the main catalyst.

[0183] The main catalyst precursor can be one or more selected from the group consisting of Co(NO3)2, Co(NO3)2·6H2O, Co2(CO)8, Co2(CO)6[HC=C(C(CH3)3)], Co(CH3CO2)2, Fe(NO3)3, Fe(NO3)2·nH2O, Fe(CH3CO2)2, Ni(NO3)2, Ni(NO3)2·6H2O, Mn(NO3)2, Mn(NO3)2·6H2O, Mn(CH3CO2)2·n(H2O) and Mn(CO)5Br, among which Co(NO3)2·6H2O, Fe(NO3)2·nH2O and Ni(NO3)2·6H2O are preferred.

[0184] A co-catalyst is a substance that improves the dispersibility of the main catalyst and can be one or more selected from the group consisting of vanadium and molybdenum.

[0185] The catalyst precursor can be selected from NH4VO3, NaVO3, V2O5, V(C5H7O2)3, and (NH4)6Mo7O 24 One or more of the group consisting of 4H2O, preferably free from NH4VO3 and (NH4)6Mo7O. 24 One or more of the groups consisting of ·4H2O.

[0186] When the mixture contains two or more co-catalyst precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, it can be contained in such a way that the total molar ratio of vanadium and molybdenum to vanadium is 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, preferably in a way that is 1:0.5 to 1:0.9. When the above conditions are met, the structure of CNTs can be stably maintained, and CNTs with the target pore volume can be manufactured.

[0187] The mixture can contain the main catalyst to the co-catalyst in a molar ratio of 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, preferably in a molar ratio of 1:0.1 to 1:0.25. Satisfying the above molar ratio improves the dispersibility of the main catalyst and enables the production of CNTs with the target pore volume.

[0188] The mixture may further contain organic acids that inhibit the precipitation of the main catalyst precursor and the co-catalyst precursor.

[0189] The organic acid may be one or more selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid, with citric acid being preferred.

[0190] The mixture may contain organic acids and co-catalyst precursors in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. Meeting these ranges provides the advantage that a transparent catalyst metal solution can be produced during catalyst manufacturing, and that a catalyst with suppressed microparticles can be produced during impregnation.

[0191] After step (1), a maturation step may be further included.

[0192] The maturation process can be carried out for 1 to 60 minutes or 10 to 50 minutes. Preferably, it is carried out for 10 to 50 minutes. When the above conditions are met, the main catalyst precursor and the co-catalyst precursor can be adequately supported on γ-Al₂O₃. Furthermore, bubbles present within the support are removed to the maximum extent, and the main catalyst precursor and the co-catalyst precursor can be adequately supported within the micropores of the support.

[0193] Process (2)

[0194] Next, the active support is dried through a multi-stage drying process, including vacuum drying.

[0195] Multi-stage drying can refer to drying processes that include vacuum drying, performed more than twice. Specifically, multi-stage drying can include both atmospheric pressure drying and vacuum drying, or it can consist of only two or more vacuum drying processes.

[0196] Vacuum drying can be carried out at 80℃~300℃ or 120℃~250℃, preferably at 120℃~250℃. When the above conditions are met, the main catalyst precursor, i.e., the coordination complex of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0197] Vacuum drying can be carried out at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably at 30 mbar to 150 mbar. Under these conditions, the main catalyst precursor, i.e., the coordination compound of the main catalyst, is rapidly decomposed and expelled, thus facilitating the formation of the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0198] Vacuum drying can be carried out for 10 minutes to 3 hours or 10 minutes to 2 hours, with 10 minutes to 2 hours being preferred. When the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0199] On the other hand, in the case of multi-stage drying including atmospheric pressure drying and vacuum drying, atmospheric pressure drying can be carried out before the aforementioned vacuum drying, and solvents that may be present in the active support can be removed by atmospheric pressure drying.

[0200] Drying under normal pressure can be carried out at 80℃~160℃ or 100℃~140℃, preferably at 100℃~140℃. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0201] Drying at atmospheric pressure can be carried out at 900 mbar to 1,100 mbar, preferably at 950 mbar to 1,050 mbar. Meeting these conditions ensures thorough removal of the solvent present in the active support while minimizing energy consumption.

[0202] Drying under normal pressure can be carried out over 1 to 12 hours, preferably 3 to 9 hours. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0203] On the other hand, in the case where multi-stage drying only includes two or more vacuum drying processes, it can include two or more vacuum drying processes performed at different temperatures. More specifically, it can include one vacuum drying process performed at a first temperature and a second vacuum drying process performed at a second temperature higher than the first temperature.

[0204] Solvents that may be present in the active support can be removed by a single vacuum drying process.

[0205] The first temperature can be 80℃ to 160℃, preferably 100℃ to 140℃. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0206] A single vacuum drying process can last from 1 hour to 12 hours, preferably from 3 hours to 9 hours. When the above conditions are met, the solvent present in the active support can be completely removed, and energy consumption can be minimized.

[0207] A single vacuum drying operation can be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, preferably at 80 mbar to 150 mbar. Meeting these conditions ensures thorough removal of the solvent from the active support and minimizes energy consumption.

[0208] The explanation of secondary vacuum drying is as described in the above explanation of vacuum drying.

[0209] The second temperature can be 175–300°C, preferably 180–280°C. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0210] Secondary vacuum drying can be carried out at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, more preferably at 1 mbar to 70 mbar. When the above conditions are met, the main catalyst precursor, i.e., the coordination compound of the main catalyst, will be rapidly decomposed and discharged, thus making it easier to form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0211] Secondary vacuum drying can be carried out for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. When the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0212] Process (3)

[0213] Next, the dried active support is heat-treated to produce a supported catalyst.

[0214] If heat treatment is performed, a supported catalyst is produced in which the main catalyst and co-catalyst are coated on the surface and pores of γ-Al2O3.

[0215] The heat treatment can be carried out at 600℃~800℃ or 620℃~750℃, preferably at 620℃~750℃. When the above conditions are met, the supported catalyst can be manufactured with the main catalyst and the co-catalyst uniformly coated on the surface and pores of γ-Al2O3, and energy consumption can be minimized.

[0216] The heat treatment can be carried out for 1 hour to 12 hours or 2 hours to 8 hours, preferably 2 hours to 8 hours. When the above time is met, a supported catalyst can be produced in which the catalyst precursor is uniformly coated on the surface and pores of γ-Al2O3.

[0217] Process (4)

[0218] Next, CNTs are manufactured in the presence of a supported catalyst.

[0219] Specifically, CNTs can be manufactured by contacting a supported catalyst with a carbonaceous compound. More specifically, substances synthesized using a chemical vapor phase method can also be used.

[0220] The steps for manufacturing CNTs are described in detail. First, a supported catalyst can be added to a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, at a temperature above the thermal decomposition temperature of the gaseous carbonaceous compound or below the melting point of the catalyst supported on the catalyst, a gaseous carbonaceous compound, or a mixture of a gaseous carbonaceous compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen), is injected. Through the decomposition of the gaseous carbonaceous compound, CNTs can be grown using a chemical vapor phase synthesis method.

[0221] CNTs manufactured using the chemical vapor deposition method described above exhibit crystal growth directions that are approximately parallel to the tube axis, and sometimes show higher crystallinity of the graphite structure along the tube length. As a result, it is possible to produce CNTs with small unit diameters, high conductivity, and high strength.

[0222] Chemical vapor phase synthesis can be carried out at 600℃~800℃ or 650℃~750℃, preferably at 650℃~750℃. Meeting these temperatures allows for the fabrication of CNTs while minimizing the generation of amorphous carbon.

[0223] As a heat source for the reaction, induction heating, radiant heat, laser, IR, microwave, plasma, surface plasma heating, etc. can be used.

[0224] In addition, carbon-based compounds can be used without particular restrictions as long as they can supply carbon and exist in a gaseous state at temperatures above 300°C.

[0225] Carbon-based compounds can be carbon-based compounds with 6 or fewer carbon atoms, or they can be one or more compounds selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0226] After CNTs are grown through the above-described reaction, a selective cooling process can be performed to further refine the arrangement of the CNTs. Specifically, the cooling process can be carried out through natural cooling accompanied by the removal of the heat source, or by using a cooler.

[0227] The manufacturing methods X and Y described above are just examples; the manufacturing methods of CNTs that can be included in a specific CNT collection are not limited to the methods described above.

[0228] [Carbon nanotube dispersion]

[0229] The carbon nanotube dispersions (specific CNT dispersions) disclosed herein comprise specific CNT aggregates and a dispersion medium.

[0230] In a specific CNT dispersion, the specific CNT aggregates involved in this disclosure exhibit good dispersibility to the dispersion medium and excellent conductivity.

[0231] Certain CNT dispersions are preferred for use in forming electrodes, forming transparent conductive films, resin additives, conductive inks, coating agents, antistatic agents, paints, etc.

[0232] <Specific CNT Collection>

[0233] The specific CNT aggregate contained in a particular CNT dispersion is the same as the specific CNT aggregate involved in this disclosure, and therefore description is omitted here.

[0234] <Dispersion Medium>

[0235] The dispersion medium preferably contains water, and more preferably contains water as the main component.

[0236] "Contains water as a main component" means that water accounts for more than 50% by mass of the dispersion medium. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. For example, it can also be 100% by mass.

[0237] There are no particular limitations on the water, but distilled water, ion-exchanged water, or pure water are preferred in terms of having fewer impurities.

[0238] The dispersion medium can be a mixture of water and a hydrophilic solvent.

[0239] 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.

[0240] 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.

[0241] In addition to specific CNT aggregates and dispersion media, a particular CNT dispersion may further contain other components that can be used in the dispersion.

[0242] Other components may include dispersants, defoamers, antistatic agents, and conductive additives other than those disclosed herein. Additionally, it may contain trace amounts of impurities, i.e., so-called unavoidable impurities.

[0243] <Dispersant>

[0244] To further improve the dispersibility and dispersion stability of specific CNT aggregates, carbon nanotube dispersions may contain dispersants.

[0245] There are no particular limitations on the dispersant; for example, various surfactants can be cited. Additionally, polymers such as resins can also be cited as dispersants.

[0246] Surfactants are preferred as dispersants.

[0247] Surfactants can be either ionic or nonionic, without any particular limitation.

[0248] In a specific CNT dispersion, a single surfactant may be used alone, or two or more surfactants may be used in combination.

[0249] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0250] 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.

[0251] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts.

[0252] Examples of amphoteric surfactants include alkyl betaine surfactants and amine oxide surfactants.

[0253] As ionic surfactants, ionic surfactants having aromatic rings (so-called aromatic ionic surfactants) are preferred, and aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecyl phenyl ether sulfonates are more preferred.

[0254] Aromatic ionic surfactants tend to excel in dispersing ability, dispersion stability, and high concentration of multi-walled carbon nanotubes.

[0255] Examples of nonionic surfactants include sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid esters such as polyoxyethylene resin esters and polyoxyethylene diethyl fatty acid esters; ethers 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.

[0256] 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.

[0257] Aromatic nonionic surfactants tend to excel in dispersing ability, dispersion stability, and high concentration of multi-walled carbon nanotubes.

[0258] Other dispersants that excel in dispersing ability, dispersion stability, and high concentration of CNTs include Demol N, Demol RN, and Demol T (manufactured by Kao Corporation) of sodium β-naphthalenesulfonic acid formaldehyde condensate; Brij S 100 (manufactured by Sigma-Aldrich) of polyoxyethylene stearyl ether; polyvinylpyrrolidone K30 (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd., for example); carboxymethyl cellulose (CMC) (manufactured by Daicel Miraizu Co., Ltd., for example); sodium deoxycholate (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd., for example); and SOLSPERSE. TM W100, SOLSPERSE TM W150 (manufactured by Lubrizol Corporation, Japan), etc. From the viewpoint of its superior dispersion ability, dispersion stability and high concentration of multi-walled carbon nanotubes, CMC is particularly preferred.

[0259] When a specific CNT dispersion contains a dispersant, there is no particular limitation on the amount of dispersant used. It can be appropriately set according to the type of dispersant, the amount of multi-walled carbon nanotubes, the amount of dispersion medium, etc.

[0260] [Method for manufacturing specific CNT dispersions]

[0261] There are no particular limitations on the manufacturing method of a specific CNT dispersion.

[0262] A specific CNT dispersion can be manufactured by dispersing a specific CNT aggregate in a dispersion medium. That is, a specific CNT dispersion can be manufactured by a method that includes a step of dispersing the specific CNT aggregate in a dispersion medium (also known as a "dispersion step").

[0263] The dispersion media that can be used in the dispersion process are as described above.

[0264] There are no particular restrictions on the method of dispersion.

[0265] Examples of dispersion methods include those using dispersion devices such as agitators, homogenizers, colloid mills, jet mixers, dissolving machines, paint conditioners, paint emulsifying devices, jet mills, and ultrasonic devices.

[0266] In addition, as a dispersion method, examples include the use of well-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 agitator mills, grinding mills, colloid mills, three-roll mills, pearl mills, super mills, impeller mills, dispersers, KD mills, Dynatron, pressure kneaders, and other dispersing machines.

[0267] As a dispersion method, jet milling is preferred, and wet jet milling is more preferred.

[0268] A wet jet mill is a dispersion device that uses a mixture in a solvent as a high-speed flow, pressurized through nozzles arranged in a sealed pressure vessel. In a wet jet mill, multi-walled carbon nanotubes are dispersed due to 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, JAGS200, NAGS1000, etc.) can be suitable as wet jet mills. However, wet jet mills are not limited to these models.

[0269] When the above-mentioned ultra-high pressure homogenizer is used as a dispersion device, the dispersion processing pressure is preferably 10MPa to 250MPa.

[0270] The method for manufacturing a specific CNT dispersion may include a step of drying the specific CNT aggregate (also known as a "drying step") prior to the dispersion step described above.

[0271] When moisture adheres to CNTs, the surface tension of water causes the CNTs to easily adhere to each other, which may reduce dispersibility. Therefore, by performing a drying process of the conductive additive before the dispersion process, the moisture adhering to the CNTs is removed, and the adhesion of multi-walled carbon nanotubes caused by moisture is suppressed, which can further improve the dispersibility of CNTs in the dispersion medium.

[0272] There are no particular restrictions on the drying method.

[0273] Examples of drying methods include heating drying, vacuum drying, and heated vacuum drying.

[0274] As a drying method, heating and vacuum drying is preferred.

[0275] There is no particular limitation on the drying temperature, but it is preferably 40°C to 100°C.

[0276] There is no particular limitation on the drying time, which can be appropriately set according to the drying temperature, the degree of moisture adhesion of the multi-walled carbon nanotubes in this disclosure, etc.

[0277] The following shows a specific example of the manufacture of a CNT dispersion, but the manufacture of a specific CNT dispersion is not limited to the following.

[0278] <Manufacturing Example 1: Manufacturing Example of Dispersion>

[0279] 0.040 g of the specific CNT aggregate disclosed herein is measured and added to a three-necked flask. A large excess of ion-exchanged water (e.g., 20 mL) as the dispersion medium is added to the flask, and the mixture is stirred at room temperature (25°C). At this time, a known dispersant (e.g., carboxymethyl cellulose) may be added as appropriate. Next, the conductive additive is dispersed in the dispersion medium using a known dispersion apparatus (e.g., an ultrasonic irradiation device or a wet jet mill). The resulting dispersion is further stirred at room temperature using a magnetic stirrer for an extended period (e.g., 1 hour to 48 hours). Thus, a specific CNT dispersion is obtained.

[0280] [Conductive Materials]

[0281] The conductive materials disclosed herein comprise specific CNT aggregates.

[0282] The specific CNT aggregates contained in the conductive materials disclosed herein, as previously described, are suitable as conductive additives due to their excellent conductivity when formed into dispersions.

[0283] Since the conductive material disclosed herein contains the specific CNT aggregates disclosed herein, it has excellent conductivity and can effectively impart high conductivity to the object to be used.

[0284] The conductive materials disclosed herein may contain known conductive additives such as graphite and Ketjen black. Furthermore, the conductive materials disclosed herein may contain CNTs other than specific CNT aggregates.

[0285] The conductive material disclosed herein 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.

[0286] [Electrodes and secondary batteries]

[0287] The electrodes disclosed herein comprise electrode active materials and conductive materials as described herein. The secondary batteries disclosed herein possess the electrodes described herein.

[0288] Because the electrodes disclosed herein contain the conductive materials disclosed herein, the formation of conductive pathways within the electrodes is excellent. Therefore, the secondary batteries disclosed herein exhibit excellent cycle characteristics.

[0289] The following describes one embodiment of the electrode and the secondary battery having the electrode.

[0290] <Electrode>

[0291] Electrodes may contain specific CNT aggregates.

[0292] In electrodes, specific CNT aggregates can function as conductive aids.

[0293] The CNT aggregates contained in the electrodes described below are synonymous with specific CNT aggregates and have the same preferred method, so the description of CNT aggregates is omitted below.

[0294] The electrode can be either a positive electrode or a negative electrode.

[0295] 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.

[0296] There are no particular restrictions on the current collector as long as it does not induce chemical changes in the battery and has electrical conductivity.

[0297] As a current collector, it can be, for example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or a material whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals such as copper and nickel, which have good adsorption properties for carbon, can also be used as current collectors.

[0298] The electrode active material layer may contain electrode active materials.

[0299] The electrode active material is preferably electrode active material particles.

[0300] When the electrode is a positive electrode, there are no particular limitations on the electrode active material, and the electrode active material layer may contain the positive electrode active material commonly used in positive electrode materials.

[0301] Specifically, examples of positive electrode active materials include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), compounds replaced by one or more transition metals; lithium iron oxide (LiFe3O4); and compounds with the chemical formula Li1 + 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 c2O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≦c2≦0.66.) represented Ni-site type lithium nickel oxide; the chemical formula LiMn 2-c3 M c3 O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦c3≦0.1.), or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn.) represented lithium-manganese composite oxide; LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions, and the like.

[0302] 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.

[0303] Specifically, the negative electrode active material may contain graphite-based active material particles or silicon-based active material particles.

[0304] As the graphite-based active material particles, at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fibers and graphitized mesophase carbon microbeads can be used. By using artificial graphite as the graphite-based active material particles, rate characteristics can be improved.

[0305] As the silicon-based active material particles, at least one selected from the group consisting of Si, SiOx (0<x<2), Si-C composites and Si-Y alloys (herein, Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, Group 13 elements, Group 14 elements, rare earth elements, and combinations thereof.) can be used. By using the silicon-based active material particles, the battery can achieve high capacity.

[0306] The electrode active material layer may further contain a binder.

[0307] The binder is not particularly limited, and the electrode active material layer may contain a binder commonly used in electrode materials.

[0308] Examples of adhesives include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which hydrogen atoms of these polymers are replaced by Li, Na, Ca, etc.

[0309] Secondary batteries

[0310] A secondary battery can be constructed by comprising 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 a conductive material containing specific CNT aggregates as the electrode material.

[0311] The separator separates the negative electrode from the positive electrode and provides a pathway for lithium ions to move. Generally, there are no particular limitations on the material used as a separator in a secondary battery. Preferably, the separator has low resistance to ion movement in the electrolyte and excellent electrolyte impregnation capacity.

[0312] As a diaphragm, a specific example is a porous polymer film.

[0313] Porous polymer films can be porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or they can be laminated structures formed by stacking two or more of these films.

[0314] Alternatively, the diaphragm can be a typical porous nonwoven fabric, such as a nonwoven fabric composed of high-melting-point glass fiber or polyethylene terephthalate fiber. Furthermore, to ensure heat resistance or mechanical strength, the diaphragm can also be a material coated with ceramic components or polymers.

[0315] The diaphragm can be optionally designed as a single-layer or multi-layer structure.

[0316] There are no particular limitations on electrolytes. Examples of electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes.

[0317] Specifically, electrolytes can contain non-aqueous organic solvents and metal salts.

[0318] 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, tetrahydroxyfuran, 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-imidazolium ketone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0319] 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 effectively dissociate lithium salts. Furthermore, for the purpose of obtaining an electrolyte with high conductivity, it is even more preferable to use a mixture of low-viscosity, low-dielectric-constant linear carbonates such as dimethyl carbonate and diethyl carbonate in appropriate proportions as a non-aqueous organic solvent.

[0320] The metal salt can be a lithium salt.

[0321] Lithium salts are substances that are readily soluble in non-aqueous solutions.

[0322] For example, F can be used as the anion portion of lithium salts. - 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 - .

[0323] In addition to non-aqueous organic solvents and metal salts, the electrolyte may further contain one or more additives such as halogenated alkylene carbonate compounds such as ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether (glyme), triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidinyl ethers, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for purposes such as improving battery life characteristics, suppressing battery capacity reduction, and increasing battery discharge capacity.

[0324] The aforementioned secondary batteries can be used to construct battery modules that include secondary batteries as unit cells, and battery packs that include battery modules.

[0325] Battery modules and battery packs can be used as power sources for medium to large-sized devices selected from groups consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems.

[0326] [Planar aggregate]

[0327] The planar aggregates disclosed herein include specific CNT aggregates, which contain CNTs with a maximum length of 1000 μm to 30000 μm. The proportion of CNTs with a maximum length of 1000 μm to 30000 μm in the planar aggregates disclosed herein is typically 1% by mass or more. The planar aggregates disclosed herein may also include other components such as aggregates containing carbon nanotubes with a maximum length less than 1000 μm, or CNT aggregates that do not contain carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

[0328] [Methods for constructing planar aggregates]

[0329] The method for fabricating the planar aggregate disclosed herein is not particularly limited.

[0330] The planar aggregate disclosed herein can be manufactured, for example, as a nonwoven fabric-like planar aggregate by dispersing CNT aggregates with a maximum length of 1000 μm to 30000 μm, or CNT aggregates with a maximum length of 1000 μm to 30000 μm and carbon nanotube aggregates with a maximum length of less than 1000 μm, in water or other fluids and filtering them once or twice or more.

[0331] [Composition]

[0332] The compositions disclosed herein are compositions comprising the CNT aggregates disclosed herein and at least one selected from the group consisting of resins, ceramics and concrete.

[0333] 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.

[0334] As ceramics, examples include crystalline ceramics and amorphous ceramics.

[0335] As for concrete, Portland cement concrete is an example.

[0336] The compositions disclosed herein may further include other components such as water and organic solvents.

[0337] In the compositions disclosed herein, when the content of the CNT aggregate is set to 100 parts by mass, the content of at least one selected from the group consisting of 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. In addition, 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.

[0338] In the compositions disclosed herein, the CNT aggregate, resin, ceramic, concrete, and other components may each contain one or more of the following:

[0339] <Method for manufacturing the composition>

[0340] The compositions disclosed herein can be manufactured, for example, by incorporating the CNT aggregates of this disclosure into a resin, ceramic, or pre-hardened concrete. The resin may be in the form of a powder, granules, solution, or dispersion. The ceramic may be in the form of a powder, precursor solution, or dispersion.

[0341] The compositions disclosed herein can also be manufactured, for example, by dispersing the CNT dispersion disclosed herein in a solution of resin, a ceramic precursor or dispersion, or in concrete before hardening and then molding it.

[0342] <Uses of the Composition>

[0343] The compositions disclosed herein are useful, for example, as structural materials, conductive materials, thermal management materials, and antistatic materials, when they contain resin or ceramics.

[0344] The compositions disclosed herein are useful as lightweight, durable building materials, or as energy storage devices (impregnated with electrolytes, if necessary), when they contain concrete.

[0345] A planar assembly as an example of this disclosure is a thin film.

[0346] The planar assemblies disclosed herein can be used, for example, in filters, electromagnetic wave shields, and protective films for extreme ultraviolet (EUV) radiation.

[0347]

Example

[0348] The following examples illustrate specific CNT aggregates and dispersions containing such CNT aggregates as described in this disclosure. Without departing from its spirit, the aggregates and dispersions of this disclosure are not limited to the following examples.

[0349] In addition, unless otherwise stated, “%” means “quality%”.

[0350] (Example 1)

[0351] 1. Manufacturing of sheet-like CNT aggregate 1

[0352] The sheet-like CNT aggregate 1 was fabricated by a suspension catalyst method (CVD) that directly interacts with the self-assembly of CNT bundles in the gas phase.

[0353] First, ferrocene, as a metal catalyst precursor containing Fe atoms, and thiophene, as 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 (standard cubic centimeters per minute).

[0354] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a particulate metal catalyst. The region where the metal catalyst is generated is referred to as the first temperature zone.

[0355] Next, methane, serving as a carbon source, is released in the carrier gas flow. The metal catalyst and carbon source are then supplied to a second temperature zone downstream of the first temperature zone, where the temperature is controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0356] In the second temperature zone, an electric field is generated within the temperature-controlled flow reactor, thereby generating aggregates of CNTs.

[0357] The aggregates of CNTs are discharged continuously through the outlet of a flow-through reactor with the temperature controlled between 100°C and 500°C, and the sheet-like CNT aggregates are collected by continuous discharge.

[0358] The resulting sheet-like CNT aggregate contains MWCNTs.

[0359] The obtained sheet-like CNT aggregate was washed with pure water for 10 seconds to obtain sheet-like CNT aggregate 1 as a specific CNT aggregate.

[0360] 2. Preparation of CNT Dispersion 1

[0361] The following materials were mixed and pre-dispersed by processing them for 1 hour using an Ace homogenizer manufactured by Nippon Seiki Co., Ltd., to obtain a pre-dispersion liquid 1. In order to prevent the sheet-like CNT aggregate 1 from tangling on the blades of the homogenizer, the sheet-like CNT aggregate 1 was cut into small fragments of 1cm × 1cm with scissors before mixing.

[0362] (Dispersion composition)

[0363] • The above-obtained sheet-like CNT aggregate 1 1.1g

[0364] ·CARBOXYMETHYL CELLULOSE SODIUM SALT HIGH VISCOSITY (manufactured by MP Biomedicals) 1.65g

[0365] ·Pure water 547.25g

[0366] Using a high-pressure homogenizer (model: NAGS100) manufactured by Tokimitsu Corporation as a wet jet mill, the pre-dispersion liquid 1 was subjected to primary dispersion under the following conditions to obtain CNT dispersion 1 as a specific CNT dispersion.

[0367] (Dispersion conditions)

[0368] Nozzle diameter: 0.22mm

[0369] Pressure: 85MPa

[0370] Number of times: 8

[0371] Method: Looping

[0372] 3. Evaluation

[0373] 3-1. Pore volume and BET specific surface area

[0374] Pore ​​volume and BET surface area were measured using a gas adsorption capacity measuring device (product name "BELSORP-miniII", manufactured by MicrotracBEL).

[0375] The sheet-like CNT aggregate 1 obtained in Example 1 was used as the sample for measurement.

[0376] The pore volume was determined after the sheet-like CNT aggregate 1 was vacuum degassed at 300°C for 3 hours using a pretreatment device (product name "BELPREP-vacII", manufactured by MicrotracBEL).

[0377] For the sheet-like CNT aggregate 1 after vacuum degassing, nitrogen-based adsorption-desorption isotherms were determined using the constant volume method.

[0378] The measurement temperature was set to 77 K, the adsorbate to nitrogen, the saturated vapor pressure to the measured value, and the adsorbate cross-sectional area to 0.162 nm. 2 The waiting time after reaching adsorption equilibrium is set to 500 seconds.

[0379] The BJH method was used to calculate the pore volume based on the obtained adsorption-desorption isotherms.

[0380] As a result, the pore volume of the sheet-like CNT aggregate 1 was 2.06 cm³. 3 / g.

[0381] The BET specific surface area was calculated analytically using the BET method (BET-Plot) from the obtained adsorption-desorption isotherms.

[0382] As a result, the BET specific surface area of ​​the sheet-like CNT aggregate 1 is 178 m². 2 / g.

[0383] Divide the value of pore volume by the value of BET specific surface area, and round the fifth decimal place to calculate the ratio of pore volume to BET specific surface area.

[0384] The ratio of pore volume to BET specific surface area is 0.0116 μm.

[0385] 3-2. Volume resistivity

[0386] The sheet-like CNT aggregate 1 from Example 1 was pulverized using a cryogenic pulverization method. Using a Loresta apparatus (product name: Powder Resistance Measurement System MCP-PD51, Low Resistivity Meter Loresta-GP, Powder Low Resistance Probe MCP-PD511 (Constant Current Application Method 4 Probe Method), all manufactured by Nitto Seiko Analytical Technology Co., Ltd.), the pulverized sheet-like CNT aggregate 1 was introduced into the powder resistivity measurement probe unit. Using the attached hydraulic pump, pressure was applied at 1 kN and 20 kN. After reaching the target load, the volume resistivity (Ω·cm) was measured.

[0387] As a result, the volume resistivity is 1.7 × 10⁻⁶ at 1 kN. -2 Ω·cm, which is 5.0 × 10⁻⁶ at 20 kN. -3 Ω·cm. The ratio of the volume resistivity at 20 kN to that at 1 kN (referred to as "resistivity ratio" in Table 1) is 0.29.

[0388] 3-3. Confirmation of the bundle structure

[0389] The sheet-like CNT assembly 1 of Example 1 was observed using SEM (device name: S-4800, manufactured by Hitachi High Technology Co., Ltd.), and the result confirmed that it contained a bundle structure. The length was measured at 20 locations and the average value was calculated. The width of the bundle structure was 70 nm.

[0390] 3-4. Electrical conductivity of the dispersion

[0391] One drop of CNT dispersion was added to a glass substrate (10cm × 10cm), and a film was formed using a stainless steel applicator with a gap size of 150μm. The film was then dried on a hot plate at 110°C for 10 minutes.

[0392] The surface resistivity of the membrane was measured using a Loresta GXII sensor manufactured by Nitto Seiko Analytical Technology Co., Ltd. Measurements were taken at five locations on the membrane, and the average of the five values ​​was used as the surface resistivity.

[0393] As a result, the surface resistivity is 164.42 Ω / □.

[0394] The evaluation results are shown in Table 1.

[0395] (Example 2)

[0396] 1. Manufacturing of fibrous CNT aggregates 2

[0397] The fibrous CNT aggregate 2, like the sheet-like CNT aggregate 1, was also prepared by a suspension catalyst method (CVD) in which the CNT bundles directly interact with each other in the gas phase through self-assembly.

[0398] First, ferrocene, as a precursor for a metal catalyst containing Fe atoms, and thiophene, as a promoter, are introduced into a continuous flow of carrier gas within a cross-flow reactor where the temperature is controlled between 400℃ and 700℃. A mixture of nitrogen and argon is used as the carrier gas. The carrier gas flow rate is set to 30,000 sccm.

[0399] By maintaining the temperature within the transverse reactor within the aforementioned range, the metal catalyst precursor is generated as a particulate metal catalyst. The region where the metal catalyst is generated is referred to as the first temperature zone.

[0400] Next, methane, serving as a carbon source, is released in the carrier gas flow. The metal catalyst and carbon source are then supplied to a second temperature zone downstream of the first temperature zone, where the temperature is controlled at 1400°C. The second temperature zone is maintained at a temperature sufficient to generate carbon nanotube aggregates.

[0401] In the second temperature zone, an electric field is generated within the temperature-controlled flow reactor, thereby generating aggregates of fibrous CNTs.

[0402] The carbon nanotube aggregates are discharged continuously through the outlet of a flow-through reactor with the temperature controlled between 100°C and 500°C, and the fibrous CNT aggregates are collected by continuous discharge.

[0403] The resulting fibrous CNT aggregates contain MWCNTs.

[0404] The obtained fibrous CNT aggregates were washed with pure water for 10 seconds to obtain fibrous CNT aggregate 2.

[0405] 2. Preparation of CNT Dispersion 2

[0406] Using the obtained fibrous CNT aggregate 2, a CNT dispersion 2 was obtained in the same manner as in Example 1.

[0407] 3. Evaluation

[0408] The fibrous CNT aggregate 2 and CNT dispersion 2 of Example 2 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0409] (Example 3)

[0410] 1. Manufacturing of sheet-like CNT aggregate 3

[0411] Except for the sheet-like CNT aggregates obtained without washing with pure water, sheet-like CNT aggregates 3 were prepared according to Example 1.

[0412] 2. Preparation of CNT Dispersion 3

[0413] Using the obtained sheet-like CNT aggregate 3, a CNT dispersion 3 was obtained in the same manner as in Example 1.

[0414] 3. Evaluation

[0415] The sheet-like CNT aggregate 3 and CNT dispersion 3 of Example 3 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0416] (Comparative Example 1)

[0417] 1. Preparation of powdered CNT aggregate 4

[0418] As a powdered CNT assembly 4, “multi-walled carbon nanotubes” (catalog number: 901019, 50-90nm diameter, >95% carbon basis, manufactured by Sigma-Aldrich) were prepared.

[0419] 2. Preparation of CNT Dispersion 4

[0420] Using the prepared powdered CNT aggregate 4, a CNT dispersion 4 was obtained in the same manner as in Example 1.

[0421] 3. Evaluation

[0422] The powdered CNT aggregate 4 and CNT dispersion 4 of Comparative Example 1 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0423] (Comparative Example 2)

[0424] 1. Preparation of powdered CNT aggregate 5

[0425] As a powdered CNT assembly 5, "multi-walled carbon nanotubes" (catalog number: FT7000, manufactured by C-nano Corporation) were prepared.

[0426] 2. Preparation of CNT Dispersion 4

[0427] Using the prepared powdered CNT aggregate 5, a CNT dispersion 5 was obtained in the same manner as in Example 1.

[0428] 3. Evaluation

[0429] The powdered CNT aggregate 4 and CNT dispersion 4 of Comparative Example 2 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0430] Table 1

[0431]

[0432] In Table 1, a "-" in the column for bundle structure indicates that no bundle structure was identified.

[0433] As shown in Table 1, the CNT dispersion obtained by dispersing the CNT aggregates of the examples has good conductivity.

[0434] On the other hand, the CNT aggregates of Comparative Example 1 and Comparative Example 2, whose pore volume to BET specific surface area ratio is less than 0.0100 μm, have problems with the conductivity of the CNT dispersions obtained by preparing them into dispersions. It can be seen that the CNT aggregate of Comparative Example 1 is a poor conductive material.

[0435] Furthermore, the CNT aggregate of Comparative Example 2, which has a pore volume to BET specific surface area ratio of less than 0.0100 μm and a volume resistivity ratio of less than 0.18 at 20 kN to 1 kN, has problems with the conductivity of the CNT dispersion obtained by preparing it into a dispersion. It can be seen that the CNT aggregate of Comparative Example 2 is a poor conductive material.

Claims

1. A carbon nanotube aggregate that satisfies the following conditions (1) and (2), (1) The ratio of pore volume to BET specific surface area is 0.0100μm~0.0200μm; (2) The ratio of the volume resistivity under 20kN pressure to the volume resistivity under 1kN pressure is above 0.18 and below 0.

30.

2. The carbon nanotube assembly according to claim 1, comprising a bundle structure.

3. The carbon nanotube assembly according to claim 1 or claim 2, wherein, The specific surface area of ​​the BET is 100 m². 2 / g~420m 2 / g.

4. The carbon nanotube assembly according to claim 1 or claim 2, wherein, The pore volume is 0.60 cm³. 3 / g~5.00cm 3 / g.

5. A carbon nanotube dispersion comprising the carbon nanotube aggregate and dispersion medium as described in claim 1 or claim 2.

6. A conductive material comprising the carbon nanotube assembly of claim 1 or claim 2.

7. An electrode comprising an electrode active material and the conductive material of claim 6.

8. A secondary battery comprising the electrode as described in claim 7.

9. A planar aggregate comprising the carbon nanotube aggregate of claim 1 or claim 2, wherein the carbon nanotube aggregate comprises carbon nanotubes with a maximum length of 1000 μm to 30000 μm.

10. A filter that uses the planar assembly of claim 9.

11. An electromagnetic wave shielding body that uses the planar assembly as described in claim 9.

12. A protective film for extreme ultraviolet radiation, which uses the planar assembly as described in claim 9.

13. A composition comprising a carbon nanotube aggregate as described in any one of claims 1 to 4, and at least one selected from the group consisting of resin, ceramics, and concrete.

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