Carbon nanotube aggregate, carbon nanotube dispersion, conductivity aid, electrode, secondary battery, planar aggregate, filter, electromagnetic shield, pellicle for extreme ultraviolet radiation, and composition

Abstract

The present invention provides: a carbon nanotube aggregate that has excellent dispersibility in a dispersion medium when in the form of a carbon nanotube dispersion, and that has excellent transport efficiency; and applications thereof.　Provided are: a carbon nanotube aggregate that satisfies the following conditions (1), (2), and (3); and applications thereof.　(1) The cumulative 50% particle diameter D50 in a number-based particle diameter distribution is 0.5-2.0 mm.　(2) The ratio (D75 / D25) of the cumulative 75% particle diameter D75 to the cumulative 25% particle diameter D25 from the small-diameter side in a number-based particle diameter distribution is 1.50-2.70.　(3) The tap density is 0.06-0.25 g / cm3 <sp / >.

Description

Carbon nanotube aggregates, carbon nanotube dispersions, conductive additives, electrodes, secondary batteries, planar aggregates, filters, electromagnetic wave shields, pellicles for extreme ultraviolet rays, and compositions

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

[0002] Carbon nanotubes have excellent mechanical and electronic properties and are expected to be used in a variety of applications. For example, Patent Document 1 describes a carbon nanotube aggregate containing one or more elements selected from the group consisting of aluminum, magnesium, and silicon, and one or more metals selected from the group consisting of cobalt, nickel, iron, manganese, and molybdenum, and having a volume density of 0.15 g / ml to 0.4 g / ml and an average particle size of 0.6 mm to 10 mm. Patent Document 2 describes a carbon nanotube-sulfur composite containing a carbon nanotube aggregate and sulfur or a sulfur compound located on the outer surface and inside of the carbon nanotube aggregate, the carbon nanotube aggregate having a tap density of 0.01 g / ml to 1 g / ml and a diameter of 500 μm or less. Patent Document 3 describes a carbon nanotube pellet having a diameter of 3 mm to 20 mm and a length of 10 mm to 200 mm.

[0003] Korean Patent Application Publication No. 10-2015-0027675 Special Publication No. 2016-535716 Special Publication No. 2018-514491

[0004] If carbon nanotubes could be used as a dispersion, the range of applications for carbon nanotubes could be expanded. Therefore, carbon nanotubes are required to have excellent dispersibility in the dispersion medium when they are used as a dispersion. In addition, when using carbon nanotubes, excellent transport efficiency is generally required.

[0005] The present disclosure has been made in consideration of the above circumstances. A problem to be solved by one embodiment of the present disclosure is to provide a carbon nanotube aggregate that has excellent dispersibility in a dispersion medium when made into a carbon nanotube dispersion and has excellent transport efficiency. A problem to be solved by another embodiment of the present disclosure is to provide a carbon nanotube dispersion that has excellent dispersibility of carbon nanotube aggregates in a dispersion medium. A problem to be solved by another embodiment of the present disclosure is to provide a conductive additive, an electrode, a secondary battery, a planar aggregate, and a composition that include the carbon nanotube aggregate. A problem to be solved by another embodiment of the present disclosure is to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays that use the planar aggregate.

[0006] Specific means for solving the above problems include the following aspects. <1> An aggregate of carbon nanotubes that satisfies the following conditions (1), (2), and (3): (1) A cumulative 50% particle diameter D50 in a particle size distribution based on number is 0.5 mm to 2.0 mm. (2) A ratio (D75 / D25) of a cumulative 75% particle diameter D75 to a cumulative 25% particle diameter D25 from the small diameter side in a particle size distribution based on number is 1.50 to 2.70. (3) A tap density is 0.06 g / cm ３ ~0.25g / cm ３ <2> The cumulative 50% area A50 in the area distribution based on the number of particles is 0.10 mm ２ ~2.00mm ２<3> The carbon nanotube aggregate according to <1>, comprising carbon nanotubes having a maximum length of 500 μm to 10,000 μm. <4> A carbon nanotube dispersion comprising the carbon nanotube aggregate according to any one of <1> to <3> and a dispersion medium. <5> A conductive additive comprising the carbon nanotube aggregate according to any one of <1> to <3>. <6> An electrode comprising an electrode active material and the carbon nanotube aggregate according to any one of <1> to <3>. <7> A secondary battery comprising the electrode according to <6>. <8> A planar aggregate comprising the carbon nanotube aggregate according to any one of <1> to <3>. <9> A filter using the planar aggregate according to <8>. <10> An electromagnetic wave shield using the planar aggregate according to <8>. <11> A pellicle for extreme ultraviolet rays using the planar aggregate according to <8>. <12> A composition comprising the aggregate of carbon nanotubes according to any one of <1> to <3> and at least one selected from the group consisting of resin, ceramics, and concrete.

[0007] According to one embodiment of the present disclosure, it is possible to provide a carbon nanotube aggregate that has excellent dispersibility in a dispersion medium when made into a carbon nanotube dispersion and excellent transport efficiency. According to another embodiment of the present disclosure, it is possible to provide a carbon nanotube dispersion that has excellent dispersibility of the carbon nanotube aggregate in a dispersion medium. According to another embodiment of the present disclosure, it is possible to provide a conductive additive, an electrode, a secondary battery, a planar aggregate, and a composition that include the carbon nanotube aggregate. According to another embodiment of the present disclosure, it is possible to provide a filter, an electromagnetic wave shield, and a pellicle for extreme ultraviolet rays that use the planar aggregate.

[0008] 1 is a scanning electron microscope photograph showing one embodiment of a CNT aggregate according to the present disclosure.

[0009] Hereinafter, the carbon nanotube aggregate, carbon nanotube dispersion, conductive additive, electrode, secondary battery, planar aggregate, filter, electromagnetic wave shield, pellicle for extreme ultraviolet rays, and composition according to the present disclosure will be described in detail. The explanation of the requirements described below may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

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

[0011] In the present disclosure, the terms "carbon nanotube," "single-walled carbon nanotube," "multi-walled carbon nanotube," "carbon nanotube aggregate," and "carbon nanotube dispersion" may be abbreviated as "CNT," "SWCNT," "MWCNT," "CNT aggregate," and "CNT dispersion," respectively.

[0012] In the present disclosure, the terms "cumulative 50% particle size D50," "cumulative 75% particle size D75," "cumulative 25% particle size D25," and "cumulative 50% area A50" in the number-based particle size distribution may be abbreviated as "D50," "D75," "D25," and "A50," respectively.

[0013] [CNT aggregate] The carbon nanotube aggregate (CNT aggregate) according to the present disclosure satisfies the following conditions (1), (2), and (3).

[0014] (1) The cumulative 50% particle diameter D50 in the particle size distribution based on the number is 0.5 mm to 2.0 mm. (2) The ratio (D75 / D25) of the cumulative 75% particle diameter D75 from the small diameter side to the cumulative 25% particle diameter D25 in the particle size distribution based on the number is 1.50 to 2.70. (3) The tap density is 0.06 g / cm. ３ ~0.25g / cm ３ is.

[0015] A CNT aggregate satisfying conditions (1), (2), and (3), i.e., a CNT aggregate according to the present disclosure, has excellent dispersibility in a dispersion medium when made into a CNT dispersion, and also has excellent transport efficiency. Meanwhile, Patent Document 1 (Korean Patent Application Publication No. 10-2015-0027675) and Patent Document 2 (Japanese Translation of PCT International Publication No. 2016-535716) do not mention conditions (1) and (2). Furthermore, Patent Document 3 (Japanese Translation of PCT International Publication No. 2018-514491) does not mention conditions (1), (2), and (3).

[0016] The CNT aggregate according to the present disclosure has excellent dispersibility in a dispersion medium when made into a CNT dispersion. In the present disclosure, "excellent dispersibility in a dispersion medium when made into a CNT dispersion" means that when the CNT aggregate is dispersed in a dispersion medium, the CNT aggregate is well dispersed in the dispersion medium with high particle size uniformity. If the CNT aggregate has excellent dispersibility in a dispersion medium when made into a CNT dispersion, the CNT aggregate can exhibit excellent electrical properties in the dispersion medium, thereby increasing the usefulness of the CNT dispersion and widening the range of applications for the CNT aggregate. Furthermore, if the CNT aggregate has excellent dispersibility in a dispersion medium when made into a CNT dispersion, the rate at which the CNT aggregate diffuses into the dispersion medium increases when transferred from a container such as a paper bag or a gallon bottle to the dispersion medium, thereby suppressing CNT scattering and expected to improve the working environment. Furthermore, if the CNT aggregate has excellent dispersibility in the dispersion medium when made into a CNT dispersion, it becomes possible to disperse the CNT aggregate in the dispersion medium with less shear force, thereby reducing physical damage to the CNT aggregate due to dispersion. As a result, the electrical properties, thermal properties, and mechanical properties of the CNT can be maximized, and improved performance as a conductive additive for the CNT dispersion can be expected, for example.

[0017] The CNT aggregate according to the present disclosure has excellent transport efficiency. When the tap density of the CNT aggregate is low, the dispersibility of the CNT aggregate in a dispersion medium when made into a CNT dispersion increases, but the volume per unit mass increases. Therefore, the lower the tap density of the CNT aggregate, the larger the capacity of the container filling the CNT aggregate. In contrast, the CNT aggregate according to the present disclosure has a moderately high tap density and a relatively small volume per unit mass, so the volume of the container filling the CNT aggregate can be made smaller, and the labor involved in transportation can be reduced. Furthermore, because the tap density of the CNT aggregate according to the present disclosure is not excessively high, the dispersibility in a dispersion medium when made into a CNT dispersion is less likely to be impaired.

[0018] The CNT aggregate according to the present disclosure satisfies the condition (1) that the cumulative 50% particle size D50 in the number-based particle size distribution is 0.5 mm to 2.0 mm. The D50 of the CNT aggregate according to the present disclosure is preferably 0.6 mm to 1.8 mm, and more preferably 0.7 mm to 1.6 mm.

[0019] The CNT aggregate according to the present disclosure has a D50 of 0.5 mm or more from the viewpoint of manufacturability. When the D50 of the CNT aggregate is 0.5 mm or more, for example, when the CNT aggregate is manufactured by pulverizing a CNT agglomerate (for example, fibers and sheets), the workload of pulverization, etc. tends to be reduced. Furthermore, when the D50 of the CNT aggregate is 0.5 mm or more, the tap density of the CNT aggregate increases and tends to be equal to or greater than the lower limit of the tap density of condition (3). When the D50 of the CNT aggregate is 2.0 mm or less, the CNT aggregate tends to have excellent dispersibility in a dispersion medium when made into a CNT dispersion.

[0020] The CNT aggregate according to the present disclosure satisfies the condition (2) that the ratio (D75 / D25) of the cumulative 75% particle diameter D75 to the cumulative 25% particle diameter D25 from the small diameter side in the number-based particle size distribution is 1.50 to 2.70. The D75 / D25 of the CNT aggregate according to the present disclosure is preferably 1.60 to 2.68, and more preferably 1.80 to 2.64.

[0021] D75 / D25 is an index of the uniformity of particle size distribution exhibited by the CNT aggregate according to the present disclosure. From the viewpoint of manufacturability, the CNT aggregate according to the present disclosure has a D75 / D25 of 1.50 or more. When the D75 / D25 of the CNT aggregate is 1.50 or more, the workload of crushing, particle size sorting, etc. when manufacturing the CNT aggregate tends to be reduced. When the D75 / D25 of the CNT aggregate is 2.70 or less, the uniformity of dispersion of the CNT aggregate in a dispersion medium tends to be increased when a CNT dispersion liquid is prepared.

[0022] The D25 of the CNT aggregate related to the present disclosure is preferably 0.3 mm to 1.0 mm, and more preferably 0.4 mm to 0.9 mm, from the viewpoint of dispersibility in a dispersion medium when the CNT aggregate is made into a CNT dispersion and manufacturing suitability, for example. The D75 of the CNT aggregate related to the present disclosure is preferably 1.2 mm to 2.0 mm, and more preferably 1.3 mm to 1.8 mm, from the viewpoint of dispersibility in a dispersion medium when the CNT aggregate is made into a CNT dispersion and manufacturing suitability, for example.

[0023] In the present disclosure, the D25, D50, and D75 in the number-based particle size distribution of a CNT aggregate are determined by the following method. A CNT aggregate is placed on a 76 mm x 26 mm glass slide, and the position of the CNT aggregate is adjusted using tweezers so that the CNT aggregates do not overlap each other and so that 80 or more CNT aggregates can be observed. The magnifications of the objective lens and eyepiece are set so that the shape of the CNT aggregate can be clearly observed (for example, the objective lens magnification is set to 5x and the eyepiece magnification is set to 10x), and the shape of the CNT aggregate is observed using an optical microscope and photographed with a digital camera. The photographed image is imported into a computer and image processing is performed using image analysis software (for example, Image J). After converting the image to 8-bit, it is binarized using a predetermined threshold so that the area of ​​the CNT aggregate becomes black, and a binarized image is obtained. The black area that is the area of ​​the CNT aggregate is approximated as an ellipse, and the length of the long side of the ellipse is calculated. The CNT aggregates are arranged in order from the shortest calculated long side length, and the long side lengths of the CNT aggregates that account for 25%, 50%, and 75% of the total number from the shortest are defined as D25 (unit: mm), D50 (unit: mm), and D75 (unit: mm), respectively.

[0024] The D50 of the CNT aggregate can be controlled by the pulverization time, the hole diameter of the screen attached to the pulverization device, etc. The D50 of the CNT aggregate can be increased by, for example, lengthening the pulverization time or increasing the hole diameter of the screen attached to the pulverization device, and can be decreased by shortening the pulverization time or decreasing the hole diameter of the screen attached to the pulverization device.

[0025] The D25 of the CNT aggregate can be controlled by the grinding time, the hole diameter of the screen attached to the grinding device, etc. The D25 of the CNT aggregate can be increased, for example, by shortening the grinding time or increasing the hole diameter of the screen attached to the grinding device, and can be decreased by increasing the grinding time or decreasing the hole diameter of the screen attached to the grinding device. The D75 of the CNT aggregate can be controlled by the grinding time, the hole diameter of the screen attached to the grinding device, etc. The D75 of the CNT aggregate can be increased, for example, by shortening the grinding time or increasing the hole diameter of the screen attached to the grinding device, and can be decreased by increasing the grinding time or decreasing the hole diameter of the screen attached to the grinding device.

[0026] The CNT aggregate according to the present disclosure has a tap density of 0.06 g / cm ３ ~0.25g / cm ３ The tap density of the CNT aggregate according to the present disclosure is 0.07 g / cm ３ ~0.23 g / cm ３ It is preferable that the density is 0.08 g / cm ３ ~0.20 g / cm ３ It is more preferable that:

[0027] Tap density is 0.06 g / cm ３Since a CNT aggregate having a volume per unit mass of 0.25 g / cm or more has a relatively small volume, the capacity of a container for filling the CNT aggregate can be reduced. If the capacity of a container for filling the CNT aggregate is small, the transport efficiency of the CNT aggregate can be improved. In addition, the storage efficiency of the CNT aggregate can also be improved. If the tap density of the CNT aggregate is 0.25 g / cm or more, the capacity of the container for filling the CNT aggregate can be reduced. ３ When the tap density is 0.25 g / cm or less, the dispersibility of the CNT aggregate in a dispersion medium when the CNT aggregate is prepared as a CNT dispersion tends to be improved. ３ The following CNT aggregates are considered to have relatively low aggregation between CNTs: ３ If the particle size is less than this, it is thought that there will be an appropriate amount of voids between the CNT aggregates, and the dispersion medium will easily penetrate between the CNT aggregates. Therefore, it is presumed that the CNTs will be easily dispersed in the dispersion medium.

[0028] In the present disclosure, the tap density of a CNT aggregate is calculated by introducing a CNT aggregate into a measuring cylinder, tapping it, and measuring the volume and mass at the point when there is no longer any visible change in volume.

[0029] The tap density of a CNT aggregate can be controlled by the particle shape, particle size, particle size distribution, etc., and can therefore be controlled by the crushing device, crushing method, crushing conditions, etc. The tap density of a CNT aggregate can be increased, for example, by making the particle shape spherical, and decreased by making the shape uneven. The particle shape can be adjusted by the crushing method, sieving, etc. The tap density of a CNT aggregate can be increased, for example, by extending the crushing time or reducing the hole diameter of the screen attached to the crushing device, as this reduces the particle size of the CNT aggregate. The tap density of a CNT aggregate can be decreased, for example, by shortening the crushing time or increasing the hole diameter of the screen attached to the crushing device, as this increases the particle size of the CNT aggregate. The tap density of a CNT aggregate can be increased, for example, by selecting a crushing method that easily applies pressure to the CNT aggregate, as this crushes the voids between the CNT aggregates. The tap density of a CNT aggregate can be decreased, for example, by selecting a crushing method that easily applies pressure to the CNT aggregate, as this crushes the voids between the CNT aggregates.

[0030] The CNT aggregate according to the present disclosure has a cumulative 50% area A50 in the number-based area distribution of 0.10 mm ２ ~2.00mm ２ Preferably, it is 0.20 mm ２ ~1.50mm ２ It is more preferable that the A50 of the CNT aggregate is 0.10 mm ２ If the A50 of the CNT aggregate is 0.10 mm or more, for example, when the CNT aggregate is produced by pulverizing an agglomerate of CNTs (for example, fibers and sheets), the workload of pulverization tends to be reduced. ２ If A50 of the CNT aggregate is 2.00 mm or more, the tap density of the CNT aggregate becomes high and tends to be equal to or higher than the lower limit of the tap density of the condition (3). ２ If it is below this, there is a tendency that the dispersibility of the CNT aggregate in the dispersion medium when it is made into a CNT dispersion liquid is more excellent.

[0031] In the present disclosure, A50 in the number-based area distribution of CNT aggregates is determined by the following method. A CNT aggregate is placed on a slide glass measuring 76 mm x 26 mm, and the position of the CNT aggregate is adjusted using tweezers so that the CNT aggregates do not overlap each other and so that 80 or more CNT aggregates can be observed. The magnifications of the objective lens and eyepiece are set so that the shape of the CNT aggregate can be clearly observed (for example, the objective lens magnification is set to 5x and the eyepiece magnification is set to 10x), and the shape of the CNT aggregate is observed using an optical microscope and photographed with a digital camera. The photographed image is imported into a computer and image processing is performed using image analysis software (for example, Image J). After converting the image to 8-bit, it is binarized using a predetermined threshold so that the areas of the CNT aggregate are black, and a binarized image is obtained. The black areas that are the areas of the CNT aggregate are approximated by an ellipse, and the area of ​​the ellipse is calculated. The CNT aggregates were arranged in order from the smallest calculated area, and the area of ​​the CNT aggregate that was 50% of the total number was designated as A50 (unit: mm ２ )

[0032] The A50 of the CNT aggregate can be controlled by the pulverization time, the hole diameter of the screen attached to the pulverization device, etc. The A50 of the CNT aggregate can be increased by, for example, shortening the pulverization time or increasing the hole diameter of the screen attached to the pulverization device, and can be decreased by increasing the pulverization time or decreasing the hole diameter of the screen attached to the pulverization device.

[0033] The CNTs contained in the CNT aggregate according to the present disclosure may be SWCNTs, MWCNTs, or both SWCNTs and MWCNTs. The CNT aggregate according to the present disclosure preferably contains MWCNTs, for example, from the viewpoint of having a wall number distribution, slightly lower uniformity, and easily increasing dispersibility in a dispersion medium when made into a CNT dispersion. The number of walls of the CNT can be controlled by selecting the manufacturing method for the CNT.

[0034] The maximum length of the CNTs contained in the CNT aggregate according to the present disclosure is not particularly limited. The CNT aggregate according to the present disclosure preferably contains CNTs having a maximum length of 500 μm to 10,000 μm, more preferably contains CNTs having a maximum length of 1,000 μm to 9,000 μm, and even more preferably contains CNTs having a maximum length of 1,200 μm to 8,000 μm. When the maximum length of the CNTs contained in the CNT aggregate according to the present disclosure is 500 μm or more, the entanglement between the CNTs becomes appropriately strong, and the CNTs tend to form a network structure more easily. When a CNT network structure is well formed, for example, the tap density of the CNT aggregate increases, and tends to be more likely to be equal to or greater than the lower limit of the tap density of condition (3). When the maximum length of the CNTs contained in the CNT aggregate according to the present disclosure is 10,000 μm or less, the entanglement between the CNTs does not become excessively strong, and the dispersion of the CNTs in the dispersion medium tends not to be impaired. When the dispersion of the CNTs in the dispersion medium is good, the CNT aggregate can be used as a dispersion liquid, and can be added to an electrode as a conductive additive, for example.

[0035] In the present disclosure, the length of a CNT can be measured by focusing on a single CNT and taking multiple scanning electron microscope (SEM) photographs at adjacent viewing angles. Here, "CNT length" refers to the measured length of the CNT in the longitudinal direction, and the maximum value of the measured lengths is referred to as the "maximum length." For example, when an SEM photograph of a CNT aggregate is taken, if one or more CNTs with a maximum length in the range of 500 μm to 10,000 μm are observed within the viewing angle of the SEM photograph, it can be determined that the observed CNT aggregate contains a CNT with a maximum length of 500 μm to 10,000 μm (also referred to as a "specific CNT"). The length of the CNT can be controlled by selecting the CNT manufacturing method.

[0036] The proportion of the specific CNTs in the CNT aggregate according to the present disclosure is not particularly limited, but for example, on a number basis, it is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, particularly preferably 50% or more, and may be 100%. When the proportion of the specific CNTs in the CNT aggregate according to the present disclosure is 10% or more on a number basis, there is a tendency for the stability of the CNT aggregate in the dispersion medium due to entanglement of the CNTs with each other to be further improved.

[0037] In the present disclosure, the proportion of specific CNTs in a CNT aggregate is determined by taking multiple SEM photographs at adjacent viewing angles, focusing on 100 CNTs included in the viewing angles of the SEM photographs, measuring the maximum length of each, and identifying, among the observed CNTs, CNTs with a maximum length in the range of 500 μm to 10,000 μm (i.e., specific CNTs).

[0038] The diameter of the CNTs contained in the CNT aggregate related to the present disclosure 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.

[0039] The diameter of the CNTs contained in the CNT aggregate according to the present disclosure can be measured by observing an SEM photograph or a transmission electron microscope (TEM) photograph. Here, "CNT diameter" refers to the length in a direction perpendicular to the longitudinal direction of the CNT, and the diameter is measured at 10 different locations on one CNT, and the average value is taken as the diameter of that CNT.

[0040] The ratio of the length to the diameter of a CNT (length / diameter; so-called aspect ratio) is preferably 1000 or more, more preferably 3000 or more, and even more preferably 5000 or more. The aspect ratio can be calculated from the ratio of the maximum length to the diameter of a single CNT. From the viewpoint of measurement accuracy, it is preferable to use the average value of the measured values ​​of 20 or more CNTs as the aspect ratio.

[0041] The CNTs contained in the CNT aggregate according to the present disclosure may have a fiber shape. In the present disclosure, the term "fiber" is used to refer to a structure in which one dimension is larger than the other two dimensions. The fibers may be thread-like fibers with a circular cross section, ribbon-like fibers with a rectangular cross section, hollow, or may have any other shape. From the viewpoint of electrical conductivity, the cross section of the CNTs contained in the CNT aggregate according to the present disclosure is preferably circular, and more preferably hollow.

[0042] The CNT aggregate according to the present disclosure may be an aggregate with a three-dimensional structure in which CNTs are entangled with one another. Figure 1 is a scanning electron microscope (SEM) photograph showing one embodiment of a CNT aggregate according to the present disclosure. From the SEM photograph shown in Figure 1, it can be seen that a plurality of fibrous CNTs are entangled to form an aggregate. From SEM observation, it can be confirmed that the CNTs are in an entangled state.

[0043] The shape of the CNT aggregate according to the present disclosure is not particularly limited. Examples of the shape of the CNT aggregate according to the present disclosure include a sphere, a string, a rod, a needle, a scale, a plate, a block, and a cube. From the viewpoint of having a large surface area and easily ensuring a contact area with the dispersion medium, the shape of the CNT aggregate according to the present disclosure is preferably a string, a rod, a needle, a plate, or a scale.

[0044] The specific gravity of the CNT aggregate according to the present disclosure is not particularly limited, but, for example, from the viewpoint of dispersibility in a dispersion medium when the CNT aggregate is made into a CNT dispersion liquid, it is preferably 1.5 to 2.5, more preferably 1.7 to 2.4, and even more preferably 1.8 to 2.2.

[0045] In the present disclosure, the specific gravity of the CNT aggregate can be measured by the method described in JIS Z8807:2012 "Method for measuring density and specific gravity of solids."

[0046] <<Uses of CNT aggregate>> The uses of the CNT aggregate according to the present disclosure are not particularly limited. The CNT aggregate according to the present disclosure has conductivity and excellent dispersibility in a dispersion medium when made into a CNT dispersion, and therefore, when made into a dispersion, can be suitably used, for example, as a conductive additive (particularly, a conductive additive for a negative electrode). For example, by coexisting the CNT aggregate according to the present disclosure with a conductive material such as a conductive polymer in an electrode, the conductivity of the conductive material can be further improved. The CNT aggregate according to the present disclosure can be used, for example, together with known conductive additives such as graphite and ketjen black.

[0047] The CNT aggregate according to the present disclosure can be used, for example, as a conductive material. The conductive material to which the CNT aggregate according to the present disclosure is applied can be used, for example, as an electrode material for a secondary battery (for example, a lithium ion battery), specifically, as one of the negative electrode material and positive electrode material.

[0048] [Method for Producing CNT] The method for producing the CNTs contained in the CNT aggregate according to the present disclosure is not particularly limited. For example, the method for producing CNTs according to the present disclosure can be a conventionally known chemical vapor deposition (CVD) method, a method for reacting a gaseous reactant containing a carbon source in the presence of a catalyst, or the like.

[0049] The CNTs in the present disclosure can be obtained by, for example, producing CNT agglomerates with reference to the methods described in JP 2016-102047 A, JP 2021-527611 A, etc., and then subjecting the produced CNT agglomerates to a pulverization process or the like. The CNT production method in the present disclosure will be described below with examples. However, the CNT production method in the present disclosure is not limited to the following examples.

[0050] =Manufacturing Method X= An example of a method for manufacturing a CNT agglomerate referred to in the present disclosure is the manufacturing method described in JP 2016-102047 A. That is, an example of a manufacturing method (also referred to as "Manufacturing Method X") includes the steps of passing gaseous reactants containing one or more carbon sources through a reactor, reacting the one or more gaseous reactants in the presence of a catalyst within a reaction zone of the reactor to form product particles containing carbon, agglomerating the product particles into agglomerates, and applying force to the agglomerates to continuously move the agglomerates out of the reaction zone.

[0051] According to production method X, CNTs can be obtained in the form of fibrous aggregates or other aggregate forms that are easy to handle.

[0052] In production method X, the force applied to the product particles may be a mechanical force. When the agglomerates are fibrous CNTs, the mechanical force applied to the product particles may be applied by a rotating spindle around which the agglomerates are wound. The fibrous CNTs may be collected on the spindle, or may be accumulated elsewhere by rotating around the spindle one or more times and then successively unwinding the spindle.

[0053] The spindle is preferably oriented with its axis perpendicular or parallel to the flow direction of the gaseous reactant(s), although other orientations are also possible, for example, a spindle with its axis oriented at an angle of 25° to the flow direction of the gaseous reactants may also be suitable for applying mechanical forces to the product particles.

[0054] The spindle can rotate about two axes (e.g., two perpendicular axes). In particular, the spindle can rotate about axes perpendicular and parallel to the flow direction of the gaseous reactants. Such a spindle can pull and twist the CNT fiber aggregates to control the twist number and length.

[0055] The spindle material may be made of metal, ceramic, or resin. The spindle can have different suitable shapes depending on the properties of the material and the intended use of the CNTs. The spindle can be used as a mold for producing carbon products, for example, by a spin coating process. The preferred shape of the spindle is a rod or box.

[0056] Fibrous CNTs are deposited on a spindle or elsewhere, and the coating thickness and orientation can be controlled by controlling the reaction time and conditions, or by the application of electric or other fields to the carbon product. Coating thickness and orientation can be controlled, for example, by gas flow forces.

[0057] The rotational speed of the spindle is preferably 0.01 rpm (revolutions per minute; hereinafter the same) to 10,000 rpm, and more preferably 0.1 rpm to 100 rpm. The spinning speed (i.e., the rotational speed of the spindle) may be adjusted so that the material is collected at a similar rate to that at which it is produced. The rotational speed of the spindle may also control the thickness of the accumulated CNT fiber. In a preferred embodiment, as the spindle rotates, the CNT fiber is processed in the axial direction of the spindle. In this processing, the CNT fiber is evenly wrapped along the spindle, rather than being wrapped only at one specific point on the spindle.

[0058] The CNT fibers may be collected, for example, on the reactor wall by a substrate placed in the reactor. The substrate may be a fixed substrate or a rotating guide used to apply a strong and equal force to the CNT fibers as they are collected. Suitable substrate configurations for fiber technology include a substrate consisting of two guides positioned at right angles to each other.

[0059] In manufacturing method X, the mechanical force applied to the product particles may be a force applied by an accelerating gas flow. The accelerating gas flow may be generated by passing the product particles through a reactor having a narrow diameter or through a capillary tube downstream of the reaction zone. A vacuum may be applied to the product particles.

[0060] Other forces that can be applied to the product particles include electrostatic forces, suitably applied by a charged plate. Electrostatic forces require that the product particles be charged. The use of a charged plate allows the CNTs to grow in an entangled mat on the charged plate.

[0061] Other forces applied to the product particles may also be magnetic forces or photon pressure applied by a light source.

[0062] Instead of a gaseous reactant containing a carbon source, the CNT source may be injected in the form of a liquid containing a carbon source. When a liquid is used as the CNT source, it can be injected through a single inlet or multiple inlets, for example, in a showerhead configuration.

[0063] Preferably, the gaseous reactant or reactants are reacted at a temperature between 500° C. and 1600° C., more preferably between 1000° C. and 1500° C. or 1600° C. (especially between 1000° C. and 1500° C.). A temperature gradient is preferably maintained within the reactor, with the reaction zone being maintained at a higher temperature than the product zone of the reactor.

[0064] The gaseous reactants may be mixed with one or more gases that act as diluents. The gaseous reactants may also be mixed with gases that play a supporting but not direct role in the reaction. It is also preferred to use a diluent gas that can react with the amorphous carbon by-product, if any, to maintain active sites on the catalyst for nanotube production.

[0065] Examples of gases that can be used as diluents include argon or other inert gases, hydrogen, nitrogen, ammonia, carbon dioxide, and helium. Among these, a mixed gas of nitrogen and argon, or hydrogen, is particularly preferred as a gas that can be used as a diluent. The flow rate of the gas used as a diluent is preferably 2000 mL (milliliters) / min or less, and more preferably 400 mL / min to 800 mL / min.

[0066] The gas pressure of the gaseous reactants and any diluents is preferably between 0.1 bar and 50 bar, more preferably between 0.5 bar and 5 bar, and even more preferably between 1 bar and 2 bar. If there is a gas effluent from the furnace, the effluent gas can be recycled with or without cleaning.

[0067] The composition of the product particles can be controlled by monitoring the agglomerates and modifying the reaction conditions based on the information obtained. For example, the agglomerates can be monitored by online Raman spectroscopy, which provides data indicating whether the CNTs are single-walled (i.e., SWCNTs) or multi-walled (i.e., MWCNTs). It also provides data indicating the diameter and crystallinity of the CNTs. The agglomerates can also be monitored by online conductivity measurements, gas analysis, measuring the opacity of the reaction zone, and / or measuring the winding force.

[0068] When the agglomerate is removed from the reactor, it is preferable to prevent air from entering the reactor. When the diluent gas contains hydrogen, preventing air from entering the reactor is particularly desirable, for example, from the viewpoint of preventing an explosive mixture of hydrogen and air from forming in the reactor.

[0069] The product particles in Production Method X contain MWCNT. Depending on the production conditions, the product particles may contain SWCNT in addition to MWCNT.

[0070] The product particles may be produced by chemical vapor deposition, where a gaseous reactant, a carbon source, is reacted in the presence of a catalyst.

[0071] Examples of carbon-containing compounds suitable as carbon sources include carbon monoxide, carbon dioxide, aromatic hydrocarbons (e.g., benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, or mesitylene), non-aromatic hydrocarbons (e.g., methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, or acetylene), and oxygen-containing hydrocarbons (e.g., formaldehyde, acetaldehyde, acetone, methanol, ethanol, diethyl ether, polyethylene glycol, 1-propanol, ethyl formate, or hydrocarbons containing a mixture of two or more thereof). Preferred carbon-containing compounds are carbon monoxide, methane, ethylene, or acetylene.

[0072] Preferably, the carbon source contains oxygen. Ethanol is a particularly preferred carbon source. Oxygen can be introduced into the reactor by other methods, such as by using a diluent gas or a carbon source containing water.

[0073] The gaseous reactant, which is a carbon source, is preferably injected into the reactor at a rate of 0.01 mL / min to 10 mL / min, more preferably 0.08 mL / min to 0.25 mL / min.

[0074] The catalyst is preferably a transition metal, particularly a Group VIB transition metal such as chromium (Cr), molybdenum (Mo), tungsten (W), or a Group VIIIB transition metal. Specifically, the catalyst may be, for example, iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), or manganese (Mn), or a mixture thereof. Metals from the lanthanide and actinide series, such as yttrium (Y), may also be used as catalysts. Fe, Ni, Co, Mo, and mixtures thereof, such as a 50 / 50 mixture of Ni and Co, a mixture of Fe and Ni, or a mixture of Fe and Mo, are more preferred. Any of these transition metals, alone or in combination with any of the other transition metals listed, may serve as a catalyst for CNT growth. It is particularly preferred that the catalyst is a mixture of two or more of the metals listed.

[0075] The catalyst is preferably formed by decomposition of a precursor. The precursor is preferably a thermally, photo-, or plasma-decomposable compound of one or more of the above metals, such as a carbonyl or cyclopentadienyl organometallic compound. Ferrocene, iron pentacarbonyl, nickelocene, and cobaltocene are particularly preferred precursors. Suitably, at least 0.01% by weight of the precursor is contained in the carbon source, and preferably 0.2% to 2.5% by weight of the precursor is contained in the carbon source. In one embodiment, 0.23% to 2.3% by weight of the precursor is contained in the carbon source. The catalyst may be supported on a carrier. Preferred carriers include silica and magnesium oxide.

[0076] The carbon source is preferably reacted in the presence of a promoter. Suitable promoters include one or more of sulfur, phosphorus, molybdenum, and organic compounds of these elements. Thiophene is one preferred promoter. Suitably, up to 10% by weight (10% by weight or less) of the promoter is contained in the carbon source. Preferably, 0.2% to 6% by weight of the promoter is contained in the carbon source. When a high or low concentration of thiophene is used as the promoter, MWCNTs are formed. For example, MWCNTs are successfully formed using ethanol containing 0% by weight or 1.5% to 4.0% by weight of thiophene and 1.0% to 10.0% by weight (particularly 2.3% by weight) of ferrocene, with an injection rate of 5.0 mL / hour to 30.0 mL / hour (particularly 7.5 mL / hour), a hydrogen flow rate of 400 mL / min to 800 mL / min, and a synthesis temperature of 1100°C to 1180°C.

[0077] According to production method X, fibrous CNTs having a length of at least 500 μm, for example, at least 1 mm, can be obtained. The fibrous CNTs can be in the form of threads (so-called fibers), sheets, etc. The length of the fibrous CNTs can be controlled, for example, by the winding capacity of the spindle used to produce the fibrous CNTs.

[0078] The manufacturing method X preferably includes the steps of reacting a carbon source in a reaction zone of a reactor to produce CNTs, and aggregating the CNTs into aggregates by applying force to the CNTs. This manufacturing method makes it possible to easily produce fibrous CNTs.

[0079] Another embodiment may include producing CNTs in a reaction zone by the above method, followed by condensation to form CNT agglomerates, and continuously withdrawing the CNT agglomerates from near the reaction zone. Another embodiment may include producing CNTs in a reaction zone, continuously electrostatically withdrawing the CNTs from the reaction zone, and recovering the CNTs.

[0080] =Production Method Y= As an example of a method for producing a CNT aggregate referred to in the present disclosure, the production method described in JP-A No. 2021-527611 can be mentioned. That is, a mixture containing a main catalyst precursor and a co-catalyst precursor is mixed with γ-Al ２ O ３ a production method (also referred to as "production method Y") that includes a step (1) of supporting a carbon nanotube on a support to produce an active support; a step (2) of drying the active support by multistage drying including vacuum drying; a step (3) of subjecting the dried active support to a heat treatment to produce a supported catalyst; and a step (4) of producing CNTs in the presence of the supported catalyst.

[0081] <<Step (1)>> In step (1), a mixture containing a main catalyst precursor and a co-catalyst precursor is added to a γ-Al ２ O ３ to produce an active support.

[0082] The mixture contained a main catalyst precursor and a co-catalyst precursor in a γ-Al ２ O ３ In order to uniformly support the catalyst precursor and the co-catalyst precursor on the catalyst support, a solvent may be further contained, and the main catalyst precursor and the co-catalyst precursor may be dissolved in the solvent. The solvent may be one or more selected from the group consisting of water, methanol, and ethanol, and is preferably water.

[0083] γ-Al ２ O ３ has high porosity and a spinel structure, and therefore the main catalyst and co-catalyst are γ-Al. ２ O ３ The CNTs grown from the randomly arranged primary catalyst can be produced in an entangled state.

[0084] The main catalyst may be one or more selected from the group consisting of cobalt, iron, nickel, manganese and chromium, and is preferably cobalt.

[0085] The main catalyst precursor may be one or more selected from the group consisting of nitrates, sulfates, carbonates and acetates of the main catalyst, and is preferably a nitrate of the main catalyst.

[0086] The main catalyst precursor is Co(NO ３ )２ , Co(NO ３ ) ２ ・6H ２ O, Co ２ (CO) ８ , Co ２ (CO) ６ [HC=C(C(CH ３ ) ３ )], Co(CH ３ CO ２ ) ２ , Fe(NO ３ ) ３ , Fe(NO ３ ) ２ ・nH ２ O, Fe(CH ３ CO ２ ) ２ , Ni(NO ３ ) ２ , Ni(NO ３ ) ２ ・6H ２ O, Mn(NO ３ ) ２ , Mn(NO ３ ) ２ ・6H ２ O, Mn(CH ３ CO ２ ) ２ ・n (H ２ O), and Mn(CO)5Br, ３ ) ２ ・6H ２ O and / or Fe(NO ３ ) ２ ・nH ２ O, Ni(NO ３ ) ２ ・6H ２ It is preferably O.

[0087] The promoter improves the dispersibility of the main catalyst, and may be one or more members selected from the group consisting of vanadium and molybdenum.

[0088] The cocatalyst precursor is NH ４ VO ３ , NaVO ３ , V ２ O ５ , V(C ５ H７ O ２ ) ３ , and (NH ４ ) 6Mo ７ O ２４ ・4H ２ O, and NH ４ VO ３ and (NH ４ ) 6Mo ７ O ２４ ・4H ２ Preferably, it is one or more selected from O.

[0089] When the mixture contains two or more promoter precursors, i.e., when it contains both a vanadium precursor and a molybdenum precursor, the molar ratio of the sum of vanadium and molybdenum to vanadium can be 1:0.45 to 1:0.95 or 1:0.5 to 1:0.9, and preferably 1:0.5 to 1:0.9. When the above conditions are satisfied, the structure of the CNT tends to be maintained stably.

[0090] The mixture may contain the main catalyst precursor and the co-catalyst precursor such that the molar ratio of the main catalyst to the co-catalyst is 1:0.01 to 1:0.5, 1:0.1 to 1:0.4, or 1:0.1 to 1:0.25, and preferably 1:0.1 to 1:0.25. Satisfying the above molar ratios can improve the dispersibility of the main catalyst.

[0091] The mixture may further include an organic acid which serves to inhibit precipitation of the main catalyst precursor and the co-catalyst precursor.

[0092] 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, and is preferably citric acid.

[0093] The mixture may contain the organic acid and the co-catalyst precursor in a molar ratio of 1:1 to 1:20, 1:2 to 1:10, or 1:3 to 1:6, preferably 1:3 to 1:6. When the above molar ratio is satisfied, it is possible to produce a transparent catalyst metal solution when producing a catalyst, and there are advantages in that it is possible to produce a catalyst in which fine powder is suppressed during impregnation.

[0094] After step (1), a step of aging may be further included.

[0095] The aging may be carried out for 1 minute to 60 minutes or 10 minutes to 50 minutes, and is preferably carried out for 10 minutes to 50 minutes. ２ O ３ The main catalyst precursor and the co-catalyst precursor can be sufficiently supported on the support. In addition, bubbles present in the support can be removed to the maximum extent, and the main catalyst precursor and the co-catalyst precursor can be sufficiently supported even in the fine pores inside the support.

[0096] <<Step (2)>> Next, the active support is dried by multi-stage drying including vacuum drying.

[0097] Multi-stage drying may mean that a drying step including vacuum drying is performed two or more times. Specifically, multi-stage drying may include both atmospheric drying and vacuum drying, or may include vacuum drying only two or more times.

[0098] The vacuum drying may be carried out at a temperature of 80° C. to 300° C. or 120° C. to 250° C., and is preferably carried out at a temperature of 120° C. to 250° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0099] The vacuum drying may be performed at 1 mbar to 200 mbar or 30 mbar to 150 mbar, preferably 30 mbar to 150 mbar. When the above conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it possible to more easily form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0100] The vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, and is preferably performed for 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0101] On the other hand, when the multi-stage drying includes both atmospheric drying and vacuum drying, atmospheric drying can be performed before the above-mentioned vacuum drying. By atmospheric drying, the solvent that may be present in the active support can be removed.

[0102] Drying at atmospheric pressure may be carried out at 80° C. to 160° C. or 100° C. to 140° C., and is preferably carried out at 100° C. to 140° C. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0103] Drying under atmospheric pressure may be carried out at 900 mbar to 1,100 mbar, preferably 950 mbar to 1,050 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0104] Drying at atmospheric pressure may be carried out for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0105] On the other hand, when the multi-stage drying includes two or more vacuum dryings, the multi-stage drying may include two or more vacuum dryings performed at different temperatures, more specifically, a primary vacuum drying performed at a first temperature and a secondary vacuum drying performed at a second temperature higher than the first temperature.

[0106] In the primary vacuum drying, the solvent that may be present in the active support can be removed.

[0107] The first temperature may be 80° C. to 160° C., and preferably 100° C. to 140° C. If the above conditions are met, the solvent present in the active support can be sufficiently removed, and energy consumption can be minimized.

[0108] The primary vacuum drying may be performed for 1 to 12 hours, preferably 3 to 9 hours. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0109] The primary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 80 mbar to 150 mbar, and is preferably performed at 80 mbar to 150 mbar. If the above conditions are met, the solvent present in the active support can be sufficiently removed and energy consumption can be minimized.

[0110] The secondary vacuum drying is as described above in the description of the vacuum drying.

[0111] The second temperature may be 175 to 300° C., and preferably 180 to 280° C. If the above conditions are met, the main catalyst precursor, i.e., the coordinate bond of the main catalyst, can be easily decomposed to form the main catalyst oxide, and energy consumption can be minimized.

[0112] The secondary vacuum drying may be performed at 1 mbar to 200 mbar, 1 mbar to 150 mbar, or 1 mbar to 70 mbar, preferably 1 mbar to 70 mbar. When these conditions are met, the main catalyst precursor, i.e., the main catalyst coordinated compound, is rapidly decomposed and discharged, making it possible to more easily form the main catalyst oxide under vacuum conditions and minimizing energy consumption.

[0113] The secondary vacuum drying may be performed for 10 minutes to 3 hours or 10 minutes to 2 hours, preferably 10 minutes to 2 hours. If the above conditions are met, the main catalyst precursor can be easily decomposed and converted into the main catalyst oxide, and energy consumption can be minimized.

[0114] <<Step (3)>> Next, the dried active support is subjected to a heat treatment to produce a supported catalyst.

[0115] When the dried active support is subjected to heat treatment, the main catalyst and the co-catalyst are converted to γ-Al. ２ O ３ A supported catalyst is produced which is present coated on the surface and in the pores of the catalyst.

[0116] The heat treatment may be carried out at 600°C to 800°C or 620°C to 750°C, and is preferably carried out at 620°C to 750°C. When the above conditions are satisfied, the main catalyst and the co-catalyst are γ-Al ２ O ３ In this way, a supported catalyst can be produced with the surface and pores of the catalyst uniformly coated, and energy consumption can be minimized.

[0117] The heat treatment may be carried out for 1 to 12 hours or 2 to 8 hours, and is preferably carried out for 2 to 8 hours. When the above conditions are satisfied, the catalyst precursor is γ-Al ２ O ３ A supported catalyst can be produced in which the catalyst is present in a uniform coating on the surface and in the pores of the catalyst.

[0118] <<Step (4)>> Next, CNTs are produced in the presence of a supported catalyst.

[0119] Specifically, the CNTs are produced by contacting a supported catalyst with a carbon-based compound. The CNTs may be produced by chemical vapor synthesis.

[0120] The steps for producing CNTs will be described in detail. First, a supported catalyst is loaded into a horizontal fixed-bed reactor or a fluidized-bed reactor. Next, a gaseous carbon-based compound or a mixture of a gaseous carbon-based compound, a reducing gas (e.g., hydrogen), and a carrier gas (e.g., nitrogen) is injected at a temperature equal to or higher than the thermal decomposition temperature of the gaseous carbon-based compound or lower than the melting point of the catalyst supported on the supported catalyst, thereby decomposing the gaseous carbon-based compound and growing CNTs by chemical vapor synthesis.

[0121] The CNTs produced by the above-mentioned chemical vapor synthesis method have a crystal growth direction that is nearly parallel to the tube axis, and the graphite structure has high crystallinity along the tube length. As a result, CNTs with small unit diameters and high electrical conductivity and strength can be produced.

[0122] The chemical vapor synthesis method may be carried out at a temperature of 600° C. to 800° C. or 650° C. to 750° C., and is preferably carried out at a temperature of 650° C. to 750° C. If the above conditions are met, CNTs can be produced while minimizing the generation of amorphous carbon.

[0123] As a heat source for the reaction, induction heating, radiant heat, laser, IR, microwave, plasma, surface plasmon heating, etc. can be used.

[0124] Any carbonaceous compound can be used without particular limitation as long as it can supply carbon and can exist in a gaseous state at a temperature of 300° C. or higher.

[0125] The carbon-based compound may be a carbon-based compound having 6 or less carbon atoms, and may be one or more compounds selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene, and toluene.

[0126] After growing CNTs by the above reaction, a cooling step may be optionally performed to arrange the CNTs more regularly. Specifically, the cooling step may be performed by natural cooling by removing the heat source or by using a cooler.

[0127] The above-described manufacturing methods X and Y are examples of manufacturing methods of CNT agglomerates, and the manufacturing methods of CNT agglomerates are not limited to the above.

[0128] The CNT aggregate according to the present disclosure can be obtained by pulverizing the CNT agglomerates produced by the above-mentioned production method X and production method Y. The pulverization method is not particularly limited as long as it can cut the CNT agglomerates to the desired size. Examples of the pulverization method include methods using a cutter mill, a hammer mill, a ball mill, etc. Among these, a cutter mill is preferred because it is difficult to apply pressure to the CNT agglomerates, which makes it easier for voids to remain between the CNT aggregates, and therefore it is possible to reduce the tap density of the obtained CNT aggregate.

[0129] After the pulverization treatment, classification treatment using a sieving method, an air classification method, or the like may be carried out from the viewpoint of adjusting the D50, D75 / D25, tap density, A50, and the like of the CNT aggregate to desired values.

[0130] [CNT Dispersion] The CNT dispersion according to the present disclosure includes the CNT aggregate according to the present disclosure and a dispersion medium. The CNT dispersion according to the present disclosure is excellent in dispersibility of the CNT aggregate in the dispersion medium. That is, in the CNT dispersion according to the present disclosure, the CNT aggregate is well dispersed in the dispersion medium with high particle size uniformity.

[0131] <CNT aggregate> Details of the CNT aggregate according to the present disclosure are as described above. The content of the CNT aggregate according to the present disclosure in the CNT dispersion according to the present disclosure is not particularly limited and can be set appropriately depending on the purpose. For example, from the viewpoint of conductivity, the content of the CNT aggregate according to the present disclosure in the CNT dispersion according to the present disclosure is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and particularly preferably 0.2 mass% or more, relative to the total mass of the CNT dispersion. Furthermore, for example, from the viewpoint of dispersibility of the CNT aggregate in a dispersion medium, the content of the CNT aggregate according to the present disclosure in the CNT dispersion according to the present disclosure is preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 10 mass% or less, and particularly preferably 5 mass% or less, relative to the total mass of the CNT dispersion. In an embodiment, the content of the CNT aggregate according to the present disclosure in the CNT dispersion according to the present disclosure may be 0.01 mass % to 20 mass %, 0.05 mass % to 15 mass %, 0.1 mass % to 10 mass %, or 0.2 mass % to 5 mass %, relative to the total mass of the CNT dispersion.

[0132] <Dispersion medium> The dispersion medium preferably contains water, more preferably contains water as the main component, and even more preferably is water. "Contains water as the main component" means that the proportion of water in the dispersion medium is more than 50% by mass. The proportion of water in the dispersion medium is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, and may be, for example, 100% by mass. The water is not particularly limited, but is preferably distilled water, ion-exchanged water, pure water, etc., in terms of having few impurities.

[0133] The dispersion medium may be a mixture of water and a hydrophilic solvent. Examples of the hydrophilic solvent include carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and butylene carbonate; ether compounds such as tetrahydrofuran; ketone compounds such as acetone; lower alcohol compounds such as methanol and ethanol; and solvents such as acetonitrile. When the dispersion medium contains a hydrophilic solvent, the proportion of the hydrophilic solvent in the dispersion medium is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0134] <Other Components> The CNT dispersion according to the present disclosure may contain, in addition to the CNT aggregate and dispersion medium according to the present disclosure, other components that can be used in the dispersion. Examples of other components include dispersants, antifoaming agents, antistatic agents, carbon materials other than CNT, etc. Furthermore, the CNT dispersion according to the present disclosure may further contain trace amounts of impurity components, so-called inevitable impurities.

[0135] -Dispersant- The CNT dispersion according to the present disclosure may contain a dispersant. When the CNT dispersion according to the present disclosure contains a dispersant, the dispersibility and dispersion stability of the CNT aggregate according to the present disclosure in the dispersion medium may be improved. The dispersant is not particularly limited, and examples thereof include various surfactants. Further examples of the dispersant include polymer compounds such as resins. As the dispersant, a surfactant is preferred. The surfactant may be an ionic surfactant or a nonionic surfactant, and is not particularly limited.

[0136] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of anionic surfactants include aromatic sulfonic acid surfactants such as alkylbenzene sulfonates (e.g., dodecylbenzene sulfonate) and dodecylphenyl ether sulfonate; ether sulfate surfactants; phosphate surfactants; and carboxylic acid surfactants. Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Examples of amphoteric surfactants include alkylbetaine surfactants and amine oxide surfactants. Examples of ionic surfactants include ionic surfactants having an aromatic ring (so-called aromatic ionic surfactants), and more preferably aromatic sulfonic acid surfactants such as alkylbenzene sulfonates and dodecylphenyl ether sulfonates. Aromatic ionic surfactants tend to have excellent dispersibility, dispersion stability, and high concentration of CNT aggregates.

[0137] Examples of nonionic surfactants include sugar ester surfactants such as sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters; fatty acid ester surfactants such as polyoxyethylene resin acid esters and polyoxyethylene fatty acid diethyl esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene-polypropylene glycols; and aromatic nonionic surfactants such as polyoxyalkylene octyl phenyl ether, polyoxyalkylene nonyl phenyl ether, polyoxyalkyl dibutyl phenyl ether, polyoxyalkyl styryl phenyl ether, polyoxyalkyl benzyl phenyl ether, polyoxyalkyl bisphenyl ether, polyoxyalkyl cumyl phenyl ether, and polyoxyalkylene phenyl ether. As nonionic surfactants, ionic surfactants having an aromatic ring (so-called aromatic nonionic surfactants) are preferred, polyoxyalkylene phenyl ethers are more preferred, and polyoxyethylene phenyl ether is even more preferred. Aromatic nonionic surfactants tend to be excellent in dispersibility, dispersion stability, and concentration of CNT aggregates.

[0138] Other dispersants include Demol N, Demol RN, and Demol T, which are sodium salts of β-naphthalenesulfonic acid formalin condensates (all manufactured by Kao Corporation), Brij S 100, which is a polyoxyethylene stearyl ether (manufactured by Sigma-Aldrich), polyvinylpyrrolidone K30 (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), carboxymethylcellulose (CMC) (manufactured by, for example, Daicel Miraize Co., Ltd.), sodium deoxycholate (manufactured by, for example, Fujifilm Wako Pure Chemical Industries, Ltd.), and SOLSPERSE ＴＭ W100 and SOLSPERSE ＴＭ Examples of the dispersant include W150 (manufactured by Lubrizol Japan, Inc.). Another preferred dispersant is CMC. CMC tends to be excellent in dispersibility, dispersion stabilization, and concentration enhancement of CNT aggregates.

[0139] When the CNT dispersion according to the present disclosure contains a dispersant, it may contain one type of dispersant alone or two or more types of dispersants.

[0140] When the CNT dispersion according to the present disclosure contains a dispersant, the content of the dispersant in the CNT dispersion is not particularly limited and can be set appropriately depending on the amount of CNT aggregates, the type of dispersant, the amount of dispersion medium, etc. An example of the content of the dispersant in the CNT dispersion according to the present disclosure is 0.01% by mass to 20% by mass with respect to the total mass of the CNT dispersion.

[0141] <<Dispersibility of CNT aggregate in dispersion medium when formed into a CNT dispersion>> The CNT dispersion according to the present disclosure preferably has a median diameter of 100 nm to 1000 nm and a peak half width of 250 nm to 750 nm in the volumetric particle size distribution when formed into a CNT dispersion of the CNT aggregate, and more preferably has a median diameter of 300 nm to 900 nm and a peak half width of 350 nm to 700 nm. In the present disclosure, the median diameter and peak half width in the volumetric particle size distribution when formed into a CNT dispersion of the CNT aggregate are indicators of the dispersibility of the CNT aggregate in a dispersion medium when formed into a CNT dispersion, and a smaller median diameter and a smaller peak half width in the particle size distribution indicate that the CNT aggregate is well dispersed in the dispersion medium with high particle size uniformity. Here, the "median diameter in the volume-based particle size distribution" means the particle size at which the cumulative frequency is 50% in the volume-based particle size distribution (so-called D50).

[0142] In the present disclosure, the median diameter and peak half-width in the volumetric particle size distribution when a CNT aggregate is prepared as a CNT dispersion are determined by the following method. A CNT aqueous dispersion with a CNT aggregate concentration of 0.01% by mass is used as a measurement sample, and the volumetric particle size distribution when the CNT aggregate is prepared as a CNT dispersion is measured using a laser diffraction / scattering particle size distribution measurement method. In the measured volumetric particle size distribution, the particle size at which the cumulative frequency is 50% is read and taken as the median diameter (unit: nm). The peak half-width (unit: nm) is calculated from the peak width at a position half the height of the peak top in the peak detected in the particle size distribution measurement. For example, a laser diffraction / scattering particle size distribution analyzer LA-960 (model number) manufactured by Horiba, Ltd. can be suitably used as the laser diffraction / scattering particle size distribution analyzer. However, the particle size distribution measurement device is not limited to this.

[0143] <<Uses of CNT Dispersion>> The uses of the CNT dispersion according to the present disclosure are not particularly limited. The CNT dispersion according to the present disclosure exhibits excellent dispersibility of the CNT aggregate according to the present disclosure in a dispersion medium and excellent conductivity. Because the CNT dispersion according to the present disclosure has high conductivity, it is preferably used for forming electrodes, forming transparent conductive films, resin additives, coating agents, antistatic agents, paints, and the like. Furthermore, the CNT dispersion according to the present disclosure can be suitably used, for example, as a conductive ink for forming electrodes (particularly negative electrodes) of various secondary batteries such as lithium-ion batteries. By using the CNT dispersion according to the present disclosure as a conductive ink, highly conductive electrodes can be easily manufactured.

[0144] [Method for producing CNT dispersion] The method for producing the CNT dispersion according to the present disclosure is not particularly limited. The CNT dispersion according to the present disclosure can be produced by dispersing the CNT aggregate according to the present disclosure in a dispersion medium. That is, the CNT dispersion according to the present disclosure can be produced by a method including a step of dispersing the CNT aggregate according to the present disclosure in a dispersion medium (also referred to as a "dispersion step").

[0145] <Dispersion step> The dispersion step is a step of dispersing the CNT aggregate according to the present disclosure in a dispersion medium. In the dispersion step, a dispersant may be used from the viewpoint of improving the dispersibility and dispersion stability of the CNT aggregate according to the present disclosure in the dispersion medium. Details of the CNT aggregate, dispersion medium, and dispersant according to the present disclosure are as described above.

[0146] The dispersion method is not particularly limited. Examples of dispersion methods include methods using dispersion devices such as a stirrer, homogenizer, colloid mill, flow jet mixer, dissolver, paint conditioner, Manton emulsifier, jet mill, and ultrasonic device (e.g., ultrasonic disperser). Examples of dispersion methods include methods using known pulverization means, such as ball milling (e.g., ball mill, vibration ball mill, planetary ball mill, bead mill, etc.), sand milling, colloid milling, jet milling, roller milling, vertical or horizontal agitator mill, attritor, colloid mill, three-roll mill, pearl mill, super mill, impeller, disperser, KD mill, dynatron, and pressure kneader. As a dispersion method, a method using a jet mill is preferred, and a method using a wet jet mill is more preferred. A wet jet mill is a dispersion device that pressure-feeds a mixture in a solvent as a high-speed flow from a nozzle arranged in a sealed pressure-resistant container. In a wet jet mill, aggregates of multi-walled carbon nanotubes are dispersed by collisions between countercurrent flows in a pressure-resistant container, collisions with the container wall, turbulence caused by high-speed flow, shear flow, etc. As the wet jet mill, an ultra-high pressure homogenizer (model number: NAGS20, NAGS100, NAGS200, NAGS1000, etc.) manufactured by Joko Co., Ltd. can be suitably used. However, the wet jet mill is not limited to this. When the ultra-high pressure homogenizer is used as the dispersing device, the processing pressure for dispersion is preferably 10 MPa to 250 MPa.

[0147] <Drying Step> The method for producing a CNT dispersion according to the present disclosure may include a step of drying the CNT aggregate according to the present disclosure (also referred to as a "drying step") before the dispersion step. If moisture adheres to the CNTs, the CNTs tend to adhere to each other due to the surface tension of the water, which may result in a decrease in dispersibility in the dispersion medium. If a drying step is performed before the dispersion step, moisture adhered to the CNTs is removed and adhesion between CNTs due to moisture adhesion is suppressed, thereby further improving the dispersibility of the CNT aggregate in the dispersion medium. The drying method is not particularly limited. Examples of drying methods include heat drying, vacuum drying, and heat vacuum drying. Heat vacuum drying is preferred as the drying method. The drying temperature is not particularly limited and is preferably, for example, 40°C to 100°C. The drying time is not particularly limited and can be set appropriately depending on the drying temperature, the degree of moisture adhesion to the CNTs, etc.

[0148] The CNT dispersion according to the present disclosure can be suitably produced, for example, by the method described in the examples below.

[0149] [Conductive Aid] The conductive aid according to the present disclosure includes the CNT aggregate according to the present disclosure. Details of the CNT aggregate according to the present disclosure are as described above. The CNT aggregate according to the present disclosure has high conductivity and excellent dispersibility in a dispersion medium when made into a CNT dispersion, and is therefore suitable as a conductive aid. Since the conductive aid according to the present disclosure includes the CNT aggregate according to the present disclosure, it has excellent conductivity and can effectively impart high conductivity to an object to which it is used.

[0150] The conductive additive according to the present disclosure may contain, in addition to the CNT aggregate according to the present disclosure, known components having electrical conductivity such as graphite, ketjen black, etc.

[0151] [Electrode] The electrode according to the present disclosure includes an electrode active material and a CNT aggregate according to the present disclosure. In the electrode according to the present disclosure, the CNT aggregate according to the present disclosure can function as a conductive assistant. Details of the CNT aggregate according to the present disclosure are as described above. The electrode according to the present disclosure may be a positive electrode, a negative electrode, or both a positive electrode and a negative electrode.

[0152] The electrode active material is preferably an electrode active material particle. When the electrode is a positive electrode, the electrode active material is not particularly limited, and examples thereof include positive electrode active materials that are commonly used as electrode materials for positive electrodes. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), compounds substituted with one or more transition metals; LiFe ３ O ４ Lithium iron oxides such as those with the chemical formula Li １＋ｃ１ Mn ２－ｃ１ O ４ (0≦c1≦0.33), LiMnO ３ , LiMn ２ O ３ , LiMnO ２ Lithium manganese oxides such as lithium copper oxide (Li ２ CuO ２ ); LiV ３ O ８ , V ２ O ５ , Cu ２ V ２ O ７ Vanadium oxides such as LiNi １－ｃ２ M ｃ２ O ２ (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦c2≦0.66 is satisfied); Ni-site type lithium nickel oxide represented by the chemical formula LiMn ２－ｃ３ M ｃ３ O ２ (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≦c3≦0.1), or the chemical formula Li ２ Mn ３ MO ８ (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn ２ O ４ Examples include:

[0153] When the electrode is a negative electrode, the electrode active material is not particularly limited and may be, for example, a negative electrode active material typically used for a negative electrode. Specific examples of the negative electrode active material include graphite-based active materials and silicon-based active materials. The graphite-based active material may be at least one selected from the group consisting of artificial graphite particles, natural graphite particles, graphitized carbon fibers, and graphitized mesocarbon microbeads. For example, using artificial graphite particles as the negative electrode active material can improve rate characteristics. The silicon-based active material may be at least one particle selected from the group consisting of Si, SiOx (0<x<2), Si-C composites, and Si-Y alloys (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, transition metals, Group 13 elements, Group 14 elements, rare earth elements, and combinations thereof). For example, using particles of silicon-based active material as the negative electrode active material can increase the capacity of the battery.

[0154] The electrode according to the present disclosure preferably comprises an electrode active material layer containing an electrode active material, and may comprise a current collector and an electrode active material layer disposed on the current collector. The electrode active material layer may contain a binder in addition to the electrode active material. The binder is not particularly limited, and examples thereof include binders commonly used in electrode materials. Examples of the binder include at least one polymer selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and polyacrylic acid, as well as polymers in which the hydrogen atoms of these polymers have been substituted with Li, Na, Ca, or the like.

[0155] The current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. Examples of current collectors include copper, stainless steel, aluminum, nickel, titanium, and calcined carbon. The current collector may be made of aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like. Transition metals that have good carbon adsorption properties are suitable as current collectors.

[0156] [Secondary Battery] A secondary battery according to the present disclosure includes an electrode according to the present disclosure. The secondary battery according to the present disclosure may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Here, at least one of the positive electrode and the negative electrode is an electrode according to the present disclosure.

[0157] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. It is not particularly limited as long as it is typically used as a separator in a secondary battery. The separator preferably has low resistance to ion migration of the electrolyte and excellent electrolyte humidification capacity. Specific examples of the separator include porous polymer films. The porous polymer film may be, for example, a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure comprising two or more layers of these films. The separator may also be a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fiber or polyethylene terephthalate fiber. The separator may also be coated with a ceramic component or a polymeric substance to ensure heat resistance or mechanical strength. The separator may be selectively formed into a single-layer or multi-layer structure.

[0158] The electrolyte is not particularly limited, and examples thereof include electrolytes such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in producing lithium secondary batteries.

[0159] Specifically, the electrolyte may contain a non-aqueous organic solvent and a metal salt. Examples of the non-aqueous organic solvent include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0160] Among carbonate organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate are preferred as non-aqueous organic solvents because they have high viscosity, high dielectric constants, and effectively dissociate lithium salts. It is more preferred to use a non-aqueous organic solvent obtained by mixing such cyclic carbonates with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, in order to obtain an electrolyte having high electrical conductivity.

[0161] The metal salt may be a lithium salt. The lithium salt is a substance that is easily dissolved in a non-aqueous electrolyte solution. The anion portion of the lithium salt may be, for example, F － , Cl － , I － , NO ３ － , N (CN) ２ － , B.F. ４ － , ClO ４ － , P.F. ６ － , (CF ３ ) ２ PF ４ － , (CF３ ) ３ PF ３ － , (CF ３ ) ４ PF ２ － , (CF ３ ) ５ PF － , (CF ３ ) ６ P － , CF ３ SO ３ － , CF ３ CF ２ SO[[ID=A35]] ３ － , (CF ３ SO ２ ) ２ N － , (FSO ２ ) ２ N － , CF ３ CF ２ , (CF ３ ) ２ CO － , (CF ３ SO[[ID=A64]] ２ ) ２ CH － , (SF ５ ) ３ C － , (CF ３ SO<A79>) ３ C － , CF ３ , (CF ２ ) ７ SO ３ － , CF ３ CO ２ － , CH ３ CO ２ － , SCN － , and (CF ３ CF ２ SO ２ ) ２ N<0000A2{17}> are included.

[0162] In addition to the non-aqueous organic solvent and metal salt, the electrolyte may further contain one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for the purposes of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0163] The secondary battery according to the present disclosure can be used to form a battery module including the secondary battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0164] [Planar aggregate] The planar aggregate according to the present disclosure includes the CNT aggregate according to the present disclosure. The ratio of the CNT aggregate according to the present disclosure contained in the planar aggregate according to the present disclosure is usually 1 mass % or more relative to the total mass of the planar aggregate. The planar aggregate according to the present disclosure may include components other than the CNT aggregate according to the present disclosure.

[0165] An example of the planar aggregate according to the present disclosure is a film including the CNT aggregate according to the present disclosure.

[0166] Planar assemblies according to the present disclosure are useful, for example, in filters, electromagnetic wave shields, and extreme ultraviolet (EUV) pellicles.

[0167] [Method for producing a planar aggregate] There are no particular limitations on the method for producing a planar aggregate according to the present disclosure. The planar aggregate according to the present disclosure can be produced, for example, as a nonwoven fabric-like planar aggregate by dispersing the CNT aggregate according to the present disclosure in water or other fluid and filtering once or twice or more times.

[0168] [Composition] The composition according to the present disclosure is a composition comprising the CNT aggregate according to the present disclosure and at least one selected from the group consisting of resin, ceramic, and concrete. Examples of resins include thermoplastic resins and thermosetting resins, and preferably olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, thermoplastic polyurethane resins, polysulfone-based resins, and silicone resins. Examples of ceramics include crystalline ceramics and amorphous ceramics. Examples of concrete include Portland cement concrete. The composition according to the present disclosure may further contain other components such as water and organic solvents. In the composition according to the present disclosure, when the content of the CNT aggregate is taken as 100 parts by mass, the content of at least one selected from the group consisting of resin, ceramic, and concrete is usually 10 parts by mass to 1,000,000 parts by mass, preferably 100 parts by mass to 100,000 parts by mass, and more preferably 1,000 parts by mass to 40,000 parts by mass, and when other components are included, it is preferably 1 part by mass to 10,000 parts by mass, and more preferably 10 parts by mass to 1,000 parts by mass. In the composition according to the present disclosure, the CNT aggregate, resin, ceramic, concrete, and other components may each be included as a single type, or two or more types may be included.

[0169] [Method for producing the composition] The composition according to the present disclosure can be produced, for example, by mixing the CNT aggregate according to the present disclosure with a resin, ceramics, or pre-hardened concrete. The resin may be in the form of a powder, pellets, solution, or dispersion. The ceramics may be in the form of a powder, precursor solution, or dispersion. The composition according to the present disclosure can also be produced, for example, by dispersing the CNT dispersion according to the present disclosure in a resin solution, a ceramic precursor or dispersion, or pre-hardened concrete, and then molding the resultant.

[0170] <<Uses of the Composition>> When the composition according to the present disclosure contains a resin or ceramic, it is useful as, for example, a structural material, a conductive material, a heat management material, or an antistatic material. When the composition according to the present disclosure contains concrete, it is useful as a lightweight, durable building material, or an electricity storage device (impregnated with an electrolyte as needed).

[0171] The CNT aggregate and CNT dispersion according to the present disclosure will be explained in more detail below with reference to examples. The CNT aggregate and CNT dispersion according to the present disclosure are not limited to the following examples as long as they do not deviate from the gist of the disclosure.

[0172] [Production of CNT Aggregate] Example 1 The CNT aggregate of Example 1 was obtained by collecting CNT aggregates produced by a floating catalyst method (CVD method), which directly interacts with the self-assembly of CNT bundles in the gas phase, as a sheet-like CNT aggregate, and then cutting the sheet-like CNT aggregate. First, ferrocene as a metal catalyst precursor containing Fe atoms and thiophene as a promoter were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled to 400°C to 700°C. A mixture of nitrogen and argon was used as the carrier gas, and the flow rate of the carrier gas was 30,000 sccm (standard cubic centimeter per minute; the same applies hereinafter). By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor was produced as a particulate metal catalyst. The region where the metal catalyst was produced is referred to as the first temperature zone.

[0173] Next, methane, a carbon source, was released into the carrier gas flow. The metal catalyst and carbon source were supplied to a second temperature zone downstream of the first temperature zone, which was temperature-controlled at 1400°C. The second temperature zone was maintained at a temperature sufficient to produce CNT aggregates. In the second temperature zone, an electric field was generated within a temperature-controlled flow reactor, thereby producing CNT aggregates. The CNT aggregates were continuously discharged through an outlet of the flow reactor, which was temperature-controlled at 100°C to 500°C, and collected as a sheet-like CNT aggregate by continuous discharge. The obtained sheet-like CNT aggregate was washed with deionized water for 10 seconds and then cut using a rotary cutter (product name: RC250 type crusher, manufactured by Yoshiko Co., Ltd.) equipped with a crushing particle size screen with a hole diameter of 1.5 mm, thereby obtaining CNT aggregate 1 of Example 1.

[0174] Example 2 The CNT aggregate in Example 2 was obtained by collecting CNT aggregates produced by a floating catalyst method (CVD method), which directly interacts with the self-assembly of CNT bundles in the gas phase, as fibrous CNT aggregates, and then cutting the fibrous CNT aggregates. First, ferrocene as a metal catalyst precursor containing Fe atoms and thiophene as a promoter were introduced into a continuous flow of carrier gas in a once-through reactor whose temperature was controlled at 400°C to 700°C. A mixture of nitrogen and argon was used as the carrier gas, and the flow rate of the carrier gas was set to 30,000 sccm. By maintaining the temperature in the once-through reactor within the above range, the metal catalyst precursor was produced as a particulate metal catalyst. The region where the metal catalyst was produced is referred to as the first temperature zone.

[0175] Next, methane, a carbon source, was released into the carrier gas flow. The metal catalyst and carbon source were supplied to a second temperature zone downstream of the first temperature zone, which was temperature-controlled at 1400°C. The second temperature zone was maintained at a temperature sufficient to produce CNT aggregates. In the second temperature zone, an electric field was generated within a temperature-controlled flow reactor, thereby producing CNT aggregates. The CNT aggregates were continuously discharged through an outlet of the flow reactor, which was temperature-controlled at 100°C to 500°C, and collected as fibrous CNT aggregates by continuous discharge. The obtained fibrous CNT aggregate was washed with deionized water for 10 seconds and then cut using a rotary cutter (product name: RC250 type crusher, manufactured by Yoshiko Co., Ltd.) equipped with a crushing particle size screen with a hole diameter of 1.5 mm, thereby obtaining CNT aggregate 2 of Example 2.

[0176] <Comparative Example 1> A sheet-like CNT aggregate was obtained in the same manner as in Example 1. The obtained sheet-like CNT aggregate was washed with deionized water for 10 seconds, and then cut into pieces of about 2 cm x 2 cm using scissors, to obtain CNT aggregate 3 of Comparative Example 1.

[0177] <Comparative Example 2> A fibrous CNT aggregate was obtained in the same manner as in Example 2. The obtained fibrous CNT aggregate was washed with deionized water for 10 seconds, and then cut into pieces with scissors to a length of about 5 cm, thereby obtaining CNT aggregate 4 of Comparative Example 2.

[0178] <Comparative Example 3> A sheet-like CNT aggregate was obtained in the same manner as in Example 1. The obtained sheet-like CNT aggregate was pulverized under the following conditions using a freezing pulverizer [model number: JFC-2000, manufactured by Japan Analytical Industry Co., Ltd.] to obtain CNT aggregate 5 of Comparative Example 3. More specifically, 5 g of the sheet-like CNT aggregate was placed in a 75 mL sample container, and one steel ball made of tungsten carbide was further placed in the sample container, and then the sample container was attached to a pulverizing rod. The entire sample container was immersed in liquid nitrogen to cool the sheet-like CNT aggregate and the steel ball, and then the pulverizing rod was moved up and down to move the steel ball inside the sample container and pulverize the sheet-like CNT aggregate.

[0179] <Conditions> Freezing time: 5 minutes Crushing time: 2 minutes

[0180] <Comparative Example 4> As the CNT aggregate 6 of Comparative Example 4, MWCNT powder (product number: FT7000) manufactured by C-nano Corporation was prepared.

[0181] <Comparative Example 5> As a CNT aggregate 7 of Comparative Example 5, MWCNT powder (product number: 901019) manufactured by Sigma-Aldrich was prepared.

[0182] <Measurement of maximum length of CNT> A plurality of SEM photographs (magnification: 5000x) of adjacent CNT aggregates were taken, and the maximum length of each was measured, focusing on 100 CNTs included in the viewing angle of the SEM photograph. As a result, it was confirmed that a plurality of CNTs (specific CNTs) with a maximum length in the range of 500 μm to 10000 μm were present in the CNT aggregate 1 of Example 1 and the CNT aggregate 2 of Example 2. In the CNT aggregate 1 of Example 1, of the observed CNTs, the proportion of CNTs (specific CNTs) with a maximum length in the range of 500 μm to 10000 μm was 75%, and the maximum value of the maximum length of the 100 observed CNTs was 3500 μm. In the CNT aggregate 2 of Example 2, of the observed CNTs, the proportion of CNTs (specific CNTs) having a maximum length in the range of 500 μm to 10,000 μm was 75%, and the maximum value of the maximum length out of 100 observed CNTs was 4,000 μm. The maximum values ​​of the maximum lengths of the CNTs measured above and contained in the CNT aggregate 1 of Example 1, CNT aggregate 2 of Example 2, CNT aggregate 3 of Comparative Example 1, CNT aggregate 4 of Comparative Example 2, CNT aggregate 5 of Comparative Example 3, CNT aggregate 6 of Comparative Example 4, and CNT aggregate 7 of Comparative Example 5 are shown in Table 1.

[0183] <Measurement of particle size distribution of CNT aggregate> A CNT aggregate was placed on a slide glass measuring 76 mm x 26 mm, and the position of the CNT aggregate was adjusted using tweezers so that the CNT aggregates did not overlap each other and so that 80 or more CNT aggregates could be observed. The shape of the CNT aggregate was observed using an optical microscope with the objective lens set to 5x magnification and the eyepiece lens set to 10x magnification, and photographed with a digital camera. The photographed image was imported into a computer and image processing was performed using Image J, an image analysis software. After converting the image to 8-bit, it was binarized at a predetermined threshold so that the area of ​​the CNT aggregate would be black, and a binarized image was obtained. The black area, which was the area of ​​the CNT aggregate, was approximated as an ellipse, and the length of the long side of the ellipse was calculated. The CNT aggregates were arranged in order from the shortest calculated long side length, and the long side lengths of the CNT aggregates that accounted for 25%, 50%, and 75% of the total number were designated D25 (unit: mm), D50 (unit: mm), and D75 (unit: mm), respectively. The black area that was the region of the CNT aggregate was approximated as an ellipse, and the area of ​​the ellipse was calculated. The CNT aggregates were arranged in order from the smallest calculated area, and the area of ​​the CNT aggregate that accounted for 50% of the total number was designated A50 (unit: mm ２ ) The D25, D50, D75, D75 / D25, and A50 of CNT aggregate 1 of example 1, CNT aggregate 2 of example 2, CNT aggregate 5 of comparative example 3, CNT aggregate 6 of comparative example 4, and CNT aggregate 7 of comparative example 5 are shown in Table 1. Note that CNT aggregate 3 of comparative example 1 was in the form of fragments with a size of about 2 cm x 2 cm, and CNT aggregate 4 of comparative example 2 was in the form of fibers with a length of about 5 cm, and both were large in size, so it was not possible to measure the particle size distribution of the CNT aggregates using an optical microscope.

[0184] <Measurement of Tap Density of CNT Assembly> The tap density of the CNT assembly (unit: g / cm ３) was calculated by introducing a CNT aggregate into a measuring cylinder, tapping it, and measuring the volume and weight at the point when there was no more visual change in volume. Table 1 shows the tap densities of CNT aggregate 1 of Example 1, CNT aggregate 2 of Example 2, CNT aggregate 5 of Comparative Example 3, CNT aggregate 6 of Comparative Example 4, and CNT aggregate 7 of Comparative Example 5. Note that CNT aggregate 3 of Comparative Example 1 was in the form of fragments measuring about 2 cm x 2 cm, and CNT aggregate 4 of Comparative Example 2 was in the form of fibers measuring about 5 cm, and both were large in size, so it was not possible to measure the tap density of the CNT aggregate using a measuring cylinder.

[0185] <Evaluation of dispersibility in dispersion medium when CNT aggregate is prepared as CNT dispersion> (1) Preparation of CNT dispersion 0.55 g of CNT aggregate, 0.825 g of carboxymethyl cellulose (trade name: Carboxymethyl Cellulose Sodium Salt High Viscosity, manufactured by MP Biomedicals) as a dispersant, and 273.625 g of ion-exchanged water were mixed. The obtained mixture was subjected to a dispersion treatment at 10,000 rpm for 1 hour using an Ace Homogenizer (trade name) manufactured by Nippon Seiki Seisakusho Co., Ltd., to obtain a CNT dispersion.

[0186] (2) Measurement of Particle Size Distribution The CNT dispersion obtained above was diluted with ion-exchanged water so that the concentration of CNT aggregates was 0.01% by mass. The CNT dispersion (CNT aggregate concentration: 0.01% by mass) was used as the measurement sample, and particle size distribution measurement was performed using a laser diffraction particle size distribution analyzer (model number: LA-960, manufactured by Horiba, Ltd.). The refractive index of carbon was set to 1.920-0.522i, and the refractive index of water was set to 1.333, and the volume-based particle size distribution of a CNT dispersion of CNT aggregates was measured. In the measured volume-based particle size distribution, the particle size at which the cumulative frequency was 50% was read and used as the median diameter (unit: nm). Furthermore, for the peaks detected in the particle size distribution measurement, the peak half-width (unit: nm) was calculated from the peak width at half the height of the peak top. The results are shown in Table 1.

[0187] In the evaluation of dispersibility, it was determined that the smaller the median diameter in the volume-based particle size distribution when the CNT aggregate was made into a CNT dispersion liquid and the smaller the peak half width of the particle size distribution, the better the CNT aggregate was dispersed in the dispersion medium with high particle size uniformity, that is, the better the dispersibility of the CNT aggregate in the dispersion medium when made into a CNT dispersion liquid.

[0188]

[0189] As shown in Table 1, it was confirmed that CNT aggregate 1 of Example 1 and CNT aggregate 2 of Example 2 have excellent dispersibility in a dispersion medium when made into a CNT dispersion. CNT aggregate 1 of Example 1 and CNT aggregate 2 of Example 2 have a moderately high tap density and a relatively small volume per unit mass, so the capacity of the filling container can be reduced and it can be said that they have excellent transport efficiency. On the other hand, it was confirmed that CNT aggregate 3 of Comparative Example 1, CNT aggregate 4 of Comparative Example 2, and CNT aggregate 5 of Comparative Example 3 have inferior dispersibility in a dispersion medium when made into a CNT dispersion compared to the CNT aggregates of the Examples. It was confirmed that CNT aggregate 6 of Comparative Example 4 and CNT aggregate 7 of Comparative Example 5 have excellent dispersibility in a dispersion medium when made into a CNT dispersion. However, the CNT aggregate 6 of Comparative Example 4 and the CNT aggregate 7 of Comparative Example 5 have low tap density and large volume per unit mass, so the capacity of the filling container becomes large and it can be said that the transportation efficiency is poor.

Claims

1. An aggregate of carbon nanotubes that satisfies the following conditions (1), (2), and (3): (1) The cumulative 50% particle diameter D50 in the particle size distribution based on the number is 0.5 mm to 2.0 mm. (2) The ratio of the cumulative 75% particle diameter D75 from the small diameter side to the cumulative 25% particle diameter D25 in the particle size distribution based on the number is 1.50 to 2.

70. (3) The tap density is 0.06 g / cm. ３ ~0.25g / cm ３ is.

2. The cumulative 50% area A50 in the area distribution based on the number of particles is 0.10 mm ２ ~2.00mm ２ The carbon nanotube aggregate according to claim 1, wherein 3. The carbon nanotube aggregate according to claim 1, comprising carbon nanotubes having a maximum length of 500 μm to 10,000 μm.

4. A carbon nanotube dispersion liquid comprising the carbon nanotube aggregate according to any one of claims 1 to 3 and a dispersion medium.

5. A conductive assistant comprising the aggregate of carbon nanotubes according to any one of claims 1 to 3.

6. An electrode comprising an electrode active material and the carbon nanotube aggregate according to any one of claims 1 to 3.

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

8. A planar aggregate comprising the carbon nanotube aggregate according to any one of claims 1 to 3.

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

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

11. A pellicle for extreme ultraviolet rays using the planar assembly according to claim 8.

12. A composition comprising the aggregate of carbon nanotubes according to any one of claims 1 to 3 and at least one material selected from the group consisting of resin, ceramics and concrete.

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