Carbon nanotube structure

Abstract

The present invention relates to a carbon nanotube structure in which the average compressive strength and the average bulk density satisfy a predetermined correlation relationship.

Description

carbon nanotube structure

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0126566 filed September 19, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a carbon nanotube structure having excellent dispersibility and excellent handling properties in terms of transport and packaging.

[0005] Carbon nanotubes (CNTs) are materials in which three adjacent carbon atoms are bonded in a hexagonal honeycomb structure to form a carbon plane, which is then rolled into a cylindrical shape to form a tube. Depending on their structure, carbon nanotubes can act as conductors or semiconductors, and they are receiving attention as novel materials because they can be widely applied in various technological fields. For example, carbon nanotubes can be applied as electrodes for electrochemical storage devices such as secondary batteries, fuel cells, or supercapacitors, as well as for electromagnetic shielding, field emission displays, or gas sensors.

[0006] Meanwhile, most mass-produced carbon nanotubes are manufactured by growing them from powdered catalyst particles; in particular, carbon nanotubes are synthesized by dispersing catalyst particles using equipment such as fluidized bed reactors. Carbon nanotubes produced in such conventional reactors are in powder form, similar to catalysts, and present problems such as difficulty in handling and unsuitability for packaging due to their extremely low density. Specifically, these low-density powdered carbon nanotubes can scatter during handling, potentially degrading the environment, and may result in losses during packaging and transportation. Therefore, methods to form structures by compressing or molding carbon nanotubes are being studied to facilitate the packaging and transportation of such low-density carbon nanotubes; however, these carbon nanotube structures generally have poor dispersibility, which limits their utility when used in actual industrial applications, such as in dispersions. Accordingly, there is a need for research on new carbon nanotube structures that offer excellent handling during packaging and transportation while maintaining satisfactory dispersibility when applied in dispersions.

[0007] The present invention relates to a carbon nanotube structure manufactured by compressing carbon nanotube particles. The present invention aims to provide a carbon nanotube structure that is simultaneously excellent in terms of dispersibility and handling properties by satisfying a certain correlation between the compressive strength and bulk density of the carbon nanotubes.

[0008] The present invention provides a carbon nanotube structure.

[0009] More specifically, (1) the present invention provides a carbon nanotube structure characterized by satisfying the following formula 1:

[0010] [Equation 1]

[0011] 60.844 * ln(x) + 5 ≤ y ≤ 60.844 * ln(x) + 12

[0012] In the above Equation 1, x is the average compressive strength (N) of the carbon nanotube structure, and

[0013] y is the average bulk density (kg / m³) of the carbon nanotube structure 3 )am.

[0014] (2) The present invention provides a carbon nanotube structure in which x is 4 to 9 N, in accordance with (1).

[0015] (3) In the present invention according to (1) or (2), the y is 95 to 140 kg / m² 3 Provides a carbon nanotube structure.

[0016] (4) The present invention provides a carbon nanotube structure in which, in any one of (1) to (3), the carbon nanotube structure is formed by aggregating a plurality of carbon nanotube particles.

[0017] (5) In any one of (1) to (4) above, the present invention is such that the average bulk density of the carbon nanotube particles is 15 to 80 kg / m³ 3 Provides a carbon nanotube structure.

[0018] (6) The present invention provides a carbon nanotube structure in which, in any one of (1) to (5), the carbon nanotube particles are multi-walled carbon nanotubes.

[0019] (7) The present invention provides a carbon nanotube structure in which, in any one of (1) to (6), the carbon nanotube structure has a granular structure.

[0020] The carbon nanotube structure of the present invention is easy to package and transport, and has excellent dispersibility when applied to a dispersion.

[0021] FIG. 1 is a front view illustrating an exemplary apparatus for manufacturing a carbon nanotube structure that can be used to manufacture a carbon nanotube structure according to the present invention.

[0022] FIG. 2 is a perspective view showing a compressor in a carbon nanotube structure manufacturing apparatus that can be used to manufacture a carbon nanotube structure of the present invention.

[0023] FIG. 3 is a front view illustrating an exemplary embodiment in which a compression device that can be used to manufacture a carbon nanotube structure of the present invention is applied.

[0024] The objects, specific advantages, and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings. It should be noted that in assigning reference numerals to the components of each drawing in this specification, the same components are assigned the same number whenever possible, even if they are shown in different drawings. Furthermore, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Also, in describing the present invention, detailed descriptions of related known technologies that could unnecessarily obscure the essence of the invention are omitted.

[0025]

[0026] carbon nanotube structure

[0027] Most mass-produced carbon nanotubes are manufactured in powder form, which causes the problem of scattering during transport. When carbon nanotubes scatter, not only is the loss of the nanotubes themselves occurring, but the scattered particles can also degrade the environment and the health of workers. Therefore, before packaging and transporting synthesized carbon nanotubes, they are manufactured into a structured form and then undergo the packaging and transport process. However, the carbon nanotube structures manufactured during this process cause another problem: the particles are strongly bonded together, resulting in clumped particles that do not easily disperse during actual use. Therefore, it is necessary to provide carbon nanotube structures that have excellent dispersibility and handling properties by optimizing various variables in the manufacturing process of carbon nanotube structures.

[0028] In this regard, the present invention provides a carbon nanotube structure satisfying Formula 1 below:

[0029] [Equation 1]

[0030] 60.844 * ln(x) + 5 ≤ y ≤ 60.844 * ln(x) + 12

[0031] In the above Equation 1, x is the average compressive strength (N) of the carbon nanotube structure, and

[0032] y is the average bulk density (kg / m³) of the carbon nanotube structure 3 )am.

[0033]

[0034] The carbon nanotube structure of the present invention has the characteristic that, as various process variables in the manufacturing process are optimized, it can simultaneously have excellent dispersibility and handling properties, and at the same time satisfies Equation 1.

[0035]

[0036] In the above Equation 1, x is the average compressive strength of the carbon nanotube structure, and its unit is N. The average compressive strength refers to the average of compressive strength values ​​measured one or more times for the carbon nanotube structure, and more specifically, the average compressive strength may be the average of compressive strength values ​​measured one to five times, preferably one to three times, for the carbon nanotube structure.

[0037] Meanwhile, the above compressive strength can be measured according to the "Push-Pull Gauge Machine" measurement procedure. More specifically, a carbon nanotube structure sample to be measured is placed on the bottom surface of a compression jig, and a compression test is performed according to the "Push-Pull Gauge Machine" measurement procedure to measure the strength value at which the sample breaks.

[0038] The above x may be 4 to 9N, preferably 4N or more, 4.2N or more, 4.4N or more, 4.5N or more, 4.7N or more, or 4.75N or more, and may be 9N or less, 8.8N or less, 8.6N or less, 8.4N or less, 8.3N or less, 8.2N or less, or 8.1N or less.

[0039] In addition, the above y is 95 to 140 kg / m² 3 It may be, preferably 95 kg / m² 3 Above, 97 kg / m² 3 100kg / m² or more 3 Above, and 140 kg / m² 3 Below, 138 kg / m² 3 Below, 136 kg / m² 3 135 kg / m³ or less 3 It may be less than.

[0040]

[0041] In the above Equation 1, y is the average bulk density of the carbon nanotube structure, and its unit is kg / m³. The average bulk density refers to the average of bulk density values ​​measured one or more times for the carbon nanotube structure, and more specifically, the average bulk density may be the average of bulk density values ​​measured one to five times, preferably one to three times, for the carbon nanotube structure.

[0042] Meanwhile, the above bulk density can be calculated by filling a 25ml cup with carbon nanotube structures and dividing the mass of the filled carbon nanotube structures by the volume of the cup.

[0043]

[0044] In the above Equation 1, if the value of y is less than 60.844 * ln(x) + 5 or greater than 60.844 * ln(x) + 12, one or more of the dispersibility and handling properties may exhibit inferior effects.

[0045]

[0046] Meanwhile, the carbon nanotube structure provided by the present invention may be formed by aggregating a plurality of carbon nanotube particles. By forming a structure by aggregating a plurality of carbon nanotube particles in this manner, scattering of carbon nanotube particles during packaging and transportation processes can be minimized.

[0047] The average bulk density of carbon nanotube particles constituting the carbon nanotube structure provided by the present invention is 10 to 80 kg / m³ 3 It may be, preferably 10 kg / m² 3 Above, 15kg / m² 3 Above, 17kg / m² 3 19 kg / m² or more 3 While being above, 80kg / m 3 Below, 75 kg / m² 3 Below, 70 kg / m² 3 Below, 65 kg / m² 3 Below, 60 kg / m² 3 Below, 55 kg / m²3 50 kg / m² or less 3 Below, 48 kg / m² 3 Below, 46 kg / m² 3 45 kg / m² or less 3 It may be less than or equal to the above range. When the average bulk density of carbon nanotube particles is within the range described above, the dispersibility and handling properties of the carbon nanotube structure formed therefrom may be excellent.

[0048] Meanwhile, the carbon nanotube particles mentioned above may be multi-walled carbon nanotubes.

[0049]

[0050] The shape of the carbon nanotube structure provided by the present invention may vary depending on the manufacturing process, but specifically, it may have a granular structure. The granular structure has the advantage of being easy to manufacture and having excellent handling properties in terms of packaging and transport.

[0051]

[0052] Apparatus and method for manufacturing carbon nanotube structures

[0053] The carbon nanotube structure provided by the present invention may be manufactured using a specific carbon nanotube structure manufacturing apparatus. Below, the manufacturing apparatus used for manufacturing the carbon nanotube structure of the present invention will be described in detail.

[0054]

[0055] FIG. 1 is a front view exemplarily showing a manufacturing apparatus for a carbon nanotube structure according to an embodiment of the present invention.

[0056] Referring to FIG. 1, a manufacturing apparatus (100) for a carbon nanotube structure according to an embodiment of the present invention includes a screw feeder (110) into which carbon nanotube particles are introduced, a compressor (120) for compressing carbon nanotubes to a predetermined size, an oscillator (140) for crushing carbon nanotubes compressed to a predetermined size to a certain size, and a hopper (150) for recovering the final product.

[0057] In addition, the manufacturing apparatus (100) for a carbon nanotube structure according to an embodiment of the present invention may further include a receiving tank (130) in which a receiving portion (131) for receiving a compressor (120) is formed, and a magnetic separator (180) for removing iron from the carbon nanotube.

[0058]

[0059] More specifically, carbon nanotubes (CNT) in powder form are fed into the screw feeder (110). The carbon nanotube particles can be compressed primarily as they pass through the screw feeder, and the extent to which the carbon nanotube powder is primarily compressed can be determined by adjusting the rotational speed of the screw feeder. More specifically, if the rotational speed of the screw feeder is increased, the bulk density of the primary compressed carbon nanotubes formed after passing through the screw feeder can be increased.

[0060] Additionally, the screw feeder (110) may be mounted on the upper part of the receiving tank (130) to be connected to the receiving portion (131) of the receiving tank (130), and may be positioned in the upper direction of the compressor (120) received in the receiving tank (130).

[0061]

[0062] FIG. 2 is a perspective view showing a compressor (120) in a manufacturing apparatus for a carbon nanotube structure according to an embodiment of the present invention.

[0063] Referring to FIGS. 1 and 2, the compressor (120) can secondarily compress the carbon nanotube (T) that has been primarily compressed while passing through the screw feeder (110) to form a carbon nanotube structure.

[0064] The compressor (120) includes a pair of rollers (121, 122) having a predetermined shape formed on their outer surface, and can compress a carbon nanotube (T) that has been compressed once by passing it between the pair of rollers (121, 122) to form a compressed mass of a certain size.

[0065] A pair of rollers (121, 122) each have a plurality of protrusions (121a, 122a) and / or grooves (121b, 122b) formed along their outer surfaces, and a carbon nanotube (T) that has been compressed once can be further compressed into a certain shape through the grooves (121b, 122b) of the pair of rollers (121, 122). In the present invention, the carbon nanotube formed by the secondary compression is referred to as a carbon nanotube structure. The carbon nanotube structure may refer to a carbon nanotube assembly in the form of a single mass formed by the aggregation of a plurality of carbon nanotube particles.

[0066] A pair of rollers (121, 122) can be rotated such that the protrusions (121a, 122a) and / or grooves (121b, 122b) formed on each of the pair of rollers (121, 122) correspond to each other. Depending on the rotational speed of the rollers, the bulk density of the carbon nanotube structure formed may vary. More specifically, when the rotational speed of the rollers is high and rotates quickly, the carbon nanotubes that are initially compressed pass through the rollers quickly, which means that the time for an external force to be applied for additional compression is shortened, and thus may result in a lower bulk density of the carbon nanotube structure formed at the end.

[0067]

[0068] The receiving tank (130) is formed with a receiving section (131) that accommodates the compressor (120) inside. Additionally, the receiving tank (130) may be equipped with a screw feeder (110) at the top and an oscillator (140) at the bottom.

[0069] At this time, the receiving tank (130) can be formed in a cylindrical shape, for example, and specifically, in a rectangular cylindrical shape.

[0070] The above oscillator (140) performs the role of crushing the compressed carbon nanotubes back into a predetermined size.

[0071]

[0072] FIG. 3 is a front view exemplarily showing an embodiment in which a manufacturing apparatus for a carbon nanotube structure according to an embodiment of the present invention is applied.

[0073] Referring to FIGS. 1 to 3, a permanent magnet (160) for removing magnetic foreign matter within carbon nanotubes crushed to a certain size may be provided between the oscillator and the hopper. The permanent magnet can further increase the purity of the final product by removing magnetic foreign matter remaining within the carbon nanotube structure corresponding to the final product.

[0074] Meanwhile, the magnetic separator (180) can remove carbon nanotube particles fed into the screw feeder (110).

[0075] Additionally, the magnetic separator (180) may include a permanent magnet or an electromagnet. Accordingly, it can prevent iron foreign matter contained in the carbon nanotube from entering the screw feeder (110) by adsorbing it through magnetic force.

[0076] In addition, one or more magnetic separators (180) may be provided.

[0077] For reference, the magnetic separator (180) is shown as one in FIG. 1 and as multiple in FIG. 3, but the present invention is not limited thereto and can be provided in various numbers.

[0078]

[0079] Meanwhile, referring to FIG. 3, a device for manufacturing carbon nanotubes may include a reactor (10) having a receiving space, a heater (30) for heating the reactor (10), a supply unit (20) for supplying reaction gas to the reactor (10), a cooler (40) for recovering and cooling the reaction, and a storage tank (50) for storing the cooled reaction product.

[0080] And, carbon nanotube particles stored in the storage tank (50) can be introduced into the carbon nanotube structure manufacturing device (100) according to an embodiment of the present invention and compressed.

[0081] The reactor (10) can be manufactured by supplying reaction gas and catalyst to the internal receiving space (11), generating flow, and growing carbon nanotubes as reactants.

[0082] The reaction gas may include hydrocarbon-based raw materials, specifically, at least one of nitrogen (N2), ethylene (C2H4), acetylene, methane, or carbon monoxide.

[0083] A heater (30) is provided on the outside of the reactor (10) and can heat the reactor (10) to a high temperature.

[0084]

[0085] The carbon nanotube structure of the present invention can be manufactured using the carbon nanotube structure manufacturing apparatus, and in particular, can be manufactured by appropriately controlling the rotational speed of the screw feeder and roller of the manufacturing apparatus.

[0086] In order to manufacture the carbon nanotube structure of the present invention using the above-described carbon nanotube structure manufacturing apparatus, the rotational speed of the screw feeder may be 15 rpm or more and 300 rpm or less, and preferably 15 rpm or more, 30 rpm or more, 40 rpm or more, or 50 rpm or more, and 300 rpm or less, 280 rpm or less, 250 rpm or less, 220 rpm or less, or 200 rpm or less. In addition, in order to manufacture the carbon nanotube structure of the present invention, the rotational speed of the roller may be 0.5 rpm or more and 10 rpm or less, and preferably 0.5 rpm or more, 1 rpm or more, or 2 rpm or more, and 10 rpm or less, 8 rpm or less, or 7 rpm or less. In addition, to manufacture the carbon nanotube structure of the present invention, the ratio between the rotational speed of the screw feeder and the rotational speed of the roller (screw feeder rotational speed / roller rotational speed) may be 5 or more and 60 or less, preferably 5 or more, 8 or more, or 10 or more, and 60 or less, 50 or less, or 45 or less.

[0087]

[0088] Examples and Comparative Examples

[0089] Using the manufacturing apparatus shown in FIG. 1, a bulk density of 15 to 50 kg / m³ 3 Carbon nanotube structures were prepared from carbon nanotube particles. Carbon nanotube structures of the examples and comparative examples were prepared by controlling the rotational speeds of the screw feeder and the roller. The rotational speed of the screw feeder and the roller, as well as the average bulk density and particle strength of the carbon nanotube structures prepared in each case, are shown in Table 1 below. Meanwhile, the compressive strength and bulk density were measured using the following method.

[0090] 1) Compressive strength: A carbon nanotube structure sample to be measured was placed on the bottom surface of a compression jig, and a compression test was performed according to the "Push-Pull Gauge Machine" measurement procedure, and the strength value was measured at the point when the sample fractured.

[0091] 2) Bulk density: After filling a 25ml cup with carbon nanotube structures, the mass of the filled carbon nanotube structures was calculated by dividing it by the volume of the cup.

[0092] Screw feeder rotation speed (Hz) Roller rotation speed (Hz) Average bulk density (kg / m³) 3 Average Compressive Strength (N) Satisfaction of Formula 1 Example 1 2540 100 4.75O Example 2 2530 112 5.2O Example 3 2520 120 6.12O Example 4 6025 134 8.02O Comparative Example 1 2550 83 1.97X Comparative Example 2 2560 75 1.22X

[0093]

[0094] As can be seen from Table 1 above, even when carbon nanotube particles of the same material are used, if the rotational speed of the screw feeder or the rotational speed of the roller in the manufacturing device is not appropriate, it can be seen that a structure is formed that does not satisfy Equation 1 of the present invention. Meanwhile, the rotational speed of the screw feeder and the rotational speed of the roller listed in Table 1 above are based on the rotational speed of the motor, and 60 Hz of the screw feeder is approximately 178 rpm, and 60 Hz of the roller is approximately 9.86 rpm.

[0095]

[0096] Experimental Example 1. Comparison of the Dispersibility of Carbon Nanotube Structures

[0097] The dispersibility of the carbon nanotube structures of Examples 1 to 4 and Comparative Examples 1 and 2 was compared. Specifically, the carbon nanotube structure samples prepared in the examples and comparative examples were pretreated in an oven, mixed with NMP (a solvent) and a dispersant in a constant weight ratio, and then homogenized using a high-pressure homogenizer. The viscosity of the dispersion prepared through the above process was measured using a spindle viscometer at 30°C, and the results are summarized in Table 2 below.

[0098] Whether Formula 1 is satisfied Viscosity (cP) Example 1: 4,650 Example 2: 4,610 Example 3: 4,500 Example 4: 4,550 Comparative Example 1: 5,000 Comparative Example 2: 5,050

[0099] As can be seen from the results in Table 2 above, the carbon nanotube structure satisfying Formula 1 of the present invention exhibited excellent dispersibility, whereas the carbon nanotube structure of the comparative example that did not satisfy Formula 1 exhibited inferior dispersibility.

[0100]

[0101] Explanation of the symbols

[0102] 10: Reactor

[0103] 11: Accommodation space

[0104] 20: Supply unit

[0105] 30: Heater

[0106] 40: Cooler

[0107] 50: Storage tank

[0108] 100: Manufacturing apparatus for carbon nanotube structures

[0109] 110: Screw feeder

[0110] 120: Compressor

[0111] 121,122: Roller

[0112] 121a,122a: protrusions

[0113] 121b,122b: Home

[0114] 130: Storage tank

[0115] 131: Reception Department

[0116] 140: Oscillator

[0117] 150: Hopper

[0118] 160: Permanent magnet

[0119] 180: Magnetic separator

[0120] 190: Discharge line

Claims

1. A carbon nanotube structure characterized by satisfying the following Equation 1: [Equation 1] 60.844 * ln(x) + 5 ≤ y ≤ 60.844 * ln(x) + 12 In the above Equation 1, x is the average compressive strength (N) of the carbon nanotube structure, and y is the average bulk density (kg / m³) of the carbon nanotube structure 3 )am.

2. In Paragraph 1, The above x is a carbon nanotube structure having a n of 4 to 9 N.

3. In Paragraph 1, The above y is 95 to 140 kg / m² 3 Phosphorus carbon nanotube structure.

4. In Paragraph 1, The above carbon nanotube structure is a carbon nanotube structure formed by the aggregation of a plurality of carbon nanotube particles.

5. In Paragraph 4, The average bulk density of the above carbon nanotube particles is 10 to 80 kg / m³ 3 Phosphorus carbon nanotube structure.

6. In Paragraph 4, The above carbon nanotube particles are carbon nanotube structures that are multi-walled carbon nanotubes.

7. In Paragraph 1, The carbon nanotube structure above is a carbon nanotube structure having a granular structure.

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