Method for manufacturing spun yarn made from carbon nanotubes

Abstract

This invention provides a means for producing high-strength CNT spun yarn. [Solution] One aspect of the present invention is a method for producing spun yarn made of carbon nanotubes, comprising the following steps: a spun yarn precursor preparation step of preparing a spun yarn precursor made of carbon nanotubes; a spun yarn precursor immersion step of immersing the spun yarn precursor in a solution containing graphene oxide or fine graphene particles; and a spun yarn production step of producing spun yarn made of carbon nanotubes by applying tension and heating with an electric current to the spun yarn precursor.

Description

[Technical Field]

[0001] This invention relates to a method for producing spun yarn made of carbon nanotubes. [Background technology]

[0002] Carbon nanotubes (hereinafter also referred to as "CNTs") possess high mechanical strength, thermal conductivity, and electrical conductivity. Furthermore, multiple CNTs can be spun together to produce spun yarn made of CNTs (hereinafter also referred to as "CNT spun yarn"). Because CNT spun yarn also possesses high mechanical strength, thermal conductivity, and electrical conductivity, it is being developed as a material for various products.

[0003] For example, Patent Document 1 describes a twisted yarn made from carbon nanotubes and a crosslinking agent, wherein the carbon nanotubes form a crosslinked structure between molecules by the crosslinking agent. The same document also describes a method for producing the carbon nanotube twisted yarn described in the same document, characterized by irradiating the twisted yarn containing carbon nanotubes and a crosslinking agent with an electron beam.

[0004] Patent Document 2 relates to a method for producing spun yarn made of carbon nanotubes, comprising the following steps: a spun yarn precursor α production step, in which a plurality of carbon nanotubes are drawn from a carbon nanotube forest, and the plurality of carbon nanotubes are spun together while a tension of 6 mN or less per 1 cm width of the carbon nanotube forest is applied to the plurality of carbon nanotubes to produce a spun yarn precursor α made of carbon nanotubes; a spun yarn precursor β production step, in which a higher tension than that in the spun yarn precursor α is applied to the spun yarn precursor α to densify the spun yarn precursor α to produce a spun yarn precursor β; and a spun yarn production step, in which the spun yarn precursor β is heated by applying tension while being electrically heated to produce a spun yarn made of carbon nanotubes. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5429751 [Patent Document 2] Japanese Patent Publication No. 2022-159032 [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, methods for producing CNT spun yarn have been developed. However, conventional methods have several drawbacks. For example, it is known that densification by applying tension and structural change from amorphous carbon to graphene by heating are effective in improving the strength of CNT spun yarn. However, CNT spun yarn obtained by conventional methods has the problem of insufficient density of CNTs and insufficient improvement in strength.

[0007] Therefore, the present invention aims to provide a means for producing high-strength CNT spun yarn. [Means for solving the problem]

[0008] The inventors investigated various means to solve the above-mentioned problems. The inventors found that by immersing the CNT spun yarn in a solution containing graphene material before applying electric heating treatment to the CNT spun yarn, the graphene material is introduced into the bundles of multiple CNTs, and the strength of the resulting CNT spun yarn is improved. Based on the above findings, the inventors completed the present invention.

[0009] In other words, the present invention encompasses the following aspects and embodiments. (Embodiment 1) A method for producing spun yarn made of carbon nanotubes, comprising the following steps: A process for preparing a spinning yarn precursor consisting of carbon nanotubes; A yarn precursor immersion step involves immersing the yarn precursor in a solution containing graphene oxide or fine graphene particles; A process for producing spun yarn by applying tension to a spun yarn precursor while heating it with an electric current; The method, including the method described above. (Embodiment 2) A yarn precursor densification step, in which tension is applied to the yarn precursor obtained in the yarn precursor immersion step to densify the yarn precursor; The method according to Embodiment 1, further comprising: (Embodiment 3) The method according to Embodiment 2, wherein in the densification step of the spun yarn precursor, tension is applied to the spun yarn precursor while it is in contact with ethanol. (Embodiment 4) A graphene solution preparation step, in which graphene oxide or graphene is micronized to prepare a solution containing fine particles of graphene oxide or graphene having a 50% particle size (D50) in the range of 0.1 to 0.6 μm; The method according to any one of the embodiments 1 to 3, further comprising: (Embodiment 5) The method according to any one of Embodiments 1 to 4, wherein electric heating is performed at a temperature of 3200 K or less in the yarn spinning process. [Effects of the Invention]

[0010] The present invention makes it possible to provide a means for producing high-strength CNT spun yarn. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the relationship between the time spent on the micronization process during the graphene solution preparation step and the particle size distribution of graphene oxide. In the figure, A is the particle size distribution of graphene oxide without micronization, B is the particle size distribution of graphene oxide after 1 hour of micronization, C is the particle size distribution of graphene oxide after 2 hours of micronization, and D is the particle size distribution of graphene oxide after 3 hours of micronization. In each panel, the horizontal axis represents the particle size (μm) of graphene oxide (GO), and the vertical axis represents the frequency distribution (percentage). [Figure 2]Regarding the CNT spun yarn obtained by the method of one embodiment of the present invention, the relationship between the time of the refinement treatment in the graphene solution preparation step and the tensile strength and Young's modulus of the resulting CNT spun yarn is shown. In the figure, A is a graph showing the relationship between the time of the refinement treatment and the tensile strength. The horizontal axis is the time of the refinement treatment (h, hour), and the vertical axis is the tensile strength (GPa). B is a graph showing the relationship between the time of the refinement treatment and the Young's modulus. The horizontal axis is the time of the refinement treatment (h, hour), and the vertical axis is the Young's modulus (GPa). In both A and B, the values in the figure represent the average value, as well as the maximum and minimum values. [Figure 3] Regarding the CNT spun yarn obtained by the method of one embodiment of the present invention, the relationship between the tension in the spun yarn precursor densification step and the tensile strength and Young's modulus of the resulting CNT spun yarn is shown. In the figure, A is a graph showing the relationship between the tension of the densification treatment and the tensile strength. The horizontal axis is the tension of the densification treatment (mN), and the vertical axis is the tensile strength (GPa). B is a graph showing the relationship between the tension of the densification treatment and the Young's modulus. The horizontal axis is the tension of the densification treatment (mN), and the vertical axis is the Young's modulus (GPa). In both A and B, the values in the figure represent the average value, as well as the maximum and minimum values. [Figure 4] The Raman spectrum of the CNT spun yarn obtained by the method of one embodiment of the present invention is shown. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm-1), and the vertical axis is the intensity of the Raman scattered light (a.u.). [Figure 5] The relationship between the introduction amount of graphene and the breaking stress in the CNT spun yarn obtained by the method of one embodiment of the present invention is shown. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa).

Mode for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0013] One aspect of the present invention relates to a method for manufacturing a spun yarn made of carbon nanotubes (CNTs).

[0014] In each aspect of the present invention, CNT means a carbon material in which a single layer plane of graphite (graphene) has a cylindrical structure. Usually, CNTs having a single-layer cylindrical structure are classified as single-layer CNTs, and CNTs having a multi-layer cylindrical structure are classified as multi-layer CNTs. The CNTs applied to each aspect of the present invention may be either single-layer CNTs or multi-layer CNTs.

[0015] The method of this aspect includes at least a spun yarn precursor preparation step, a spun yarn precursor immersion step, and a spun yarn production step. The method of this aspect may optionally include a graphene solution preparation step, a spun yarn precursor densification step, and a crosslinking step. Hereinafter, each step will be described in detail.

[0016] [1. Spun yarn precursor preparation step] This step includes preparing a spun yarn precursor made of CNTs (hereinafter, also referred to as "CNT spun yarn precursor" or "spun yarn precursor").

[0017] In this step, the spun yarn precursor can be prepared by various methods known in the art. For example, the spun yarn precursor can be obtained by pulling out a plurality of CNTs from a CNT forest and spinning the plurality of CNTs while applying tension to them. Such a method is known as the "dry spinning method". Alternatively, the spun yarn precursor can also be obtained by discharging a CNT dispersion in which CNTs are dispersed into a solvent through a nozzle to form a plurality of CNTs and spinning the plurality of CNTs while solidifying them in the solvent. Such a method is known as the "wet spinning method".

[0018] In this step, the spun yarn precursor is preferably obtained in the form of a yarn wound around the circumferential surface of a rotating body.

[0019] In each aspect of the present invention, examples of rotating bodies include glass rods, bobbins, and rollers.

[0020] [2. Graphene Solution Preparation Step] This process involves micronizing the graphene material to prepare a solution containing fine particles of the graphene material.

[0021] The graphene material used in this process is preferably graphene oxide (GO) or graphene, and more preferably graphene oxide. By carrying out the method of this embodiment using the graphene material exemplified above, high-strength CNT spun yarn can be obtained.

[0022] When the graphene material used in this process is graphene, the solvent for the solution containing the fine particles of the graphene material can be a strong acid or an aqueous solution thereof. In this case, the solvent is preferably selected from the group consisting of sulfonic acid chloride, hydrochloric acid, sulfuric acid, and mixtures thereof, and more preferably sulfonic acid chloride. The strong acid or aqueous solution thereof exemplified above, particularly sulfonic acid chloride, is used as a solvent when preparing the CNT spun yarn precursor by wet spinning in the spun yarn precursor preparation step, and can widen the spacing between CNTs. Therefore, when using the solvent exemplified above, the fine particles of the graphene material can be easily introduced between the CNTs contained in the spun yarn precursor in the spun yarn precursor immersion step described below, and the spun yarn precursor can be densely densified in the spun yarn precursor densification step. Furthermore, when the graphene material used in this process is graphene oxide, the solvent for the solution containing the fine particles of the graphene material can be water and water-miscible organic solvents, and mixtures thereof. The solvent is preferably selected from the group consisting of water, methanol, ethanol, propanol, and acetone, and mixtures thereof; more preferably selected from the group consisting of water, methanol, ethanol, and propanol, and mixtures thereof; and even more preferably a mixed solvent of water and ethanol (volume ratio of 5:1 to 1:5, preferably 1:1). By carrying out this step using the solvent exemplified above, a solution containing fine particles of graphene material having a desired particle size can be obtained.

[0023] In this process, the means for micronizing the graphene material are not particularly limited. Micronization can be carried out, for example, by irradiating a solution containing the graphene material with ultrasound using an ultrasonic homogenizer. Alternatively, micronization can be carried out by pulverizing the graphene material with a grinding means (for example, a ball mill, hammer mill, or ultrasonic crusher (homogenizer)).

[0024] The fine particles of graphene material contained in the solution prepared in this process typically have a 50% particle size (D50) of 1 μm or less. The D50 of the fine particles of graphene material is preferably 0.8, 0.6, or 0.5 μm or less, more preferably in the range of 0.3 to 0.8 μm, 0.2 to 0.6 μm, or 0.1 to 0.5 μm, and even more preferably in the range of 0.1 to 0.6 μm. By carrying out the method of this embodiment using fine particles of graphene material having the particle sizes exemplified above, high-strength CNT spun yarn can be obtained.

[0025] In each embodiment of the present invention, the particle size of the fine particles of the graphene material can be evaluated, for example, by measuring the particle size distribution of the fine particles of the graphene material using a particle size distribution analyzer and determining D50 from the particle size distribution.

[0026] [3. Immersion process for spinning yarn precursor] This process involves immersing the yarn precursor in a solution containing fine particles of graphene material.

[0027] In this process, the immersion time of the spinning yarn precursor in the solution containing fine particles of graphene material is preferably 24 hours or less, and more preferably in the range of 1 to 24 hours. The temperature at which the spinning yarn precursor is immersed in the solution containing fine particles of graphene material can be room temperature, and is usually in the range of 10 to 40°C. By carrying out this process under the above conditions, fine particles of graphene material can be introduced into the CNT spinning yarn contained in the spinning yarn precursor, and high-strength CNT spinning yarn can be obtained.

[0028] [4. Densification process for spun yarn precursor] This process includes applying tension to the yarn precursor obtained in the yarn precursor immersion process to densify the yarn precursor.

[0029] This process can be carried out, for example, by drawing the yarn precursor from the circumferential surface of the rotating body and applying tension. In this embodiment, the densified yarn precursor is recovered by winding it around the circumferential surface of the rotating body. By winding the yarn precursor around the circumferential surface of the rotating body, a desired tension can be applied to the yarn precursor.

[0030] In this process, the tension applied to the yarn precursor is preferably 0.5 or 1 mN or more and 100 mN or less, more preferably in the range of 0.5 to 100 mN, and even more preferably in the range of 1 to 50 mN. If the tension is below the lower limit, the density of the resulting yarn precursor may be low. If the tension exceeds the upper limit, the yarn precursor may break. By performing this process with tension within the range exemplified above, the yarn precursor can be densified, and the strength of the resulting CNT spun yarn can be improved.

[0031] In this process, tension can be applied to the spun yarn precursor by applying a load using a tensioning rod, slider system, or motor.

[0032] In this process, it is preferable to apply tension to the spun yarn precursor while bringing it into contact with a solvent. The solvent is preferably the same as the solvent used in the graphene solution preparation step exemplified above. In this embodiment, means for bringing the spun yarn precursor into contact with the solvent include, for example, impregnating the spun yarn precursor with the solvent, spraying the solvent onto the spun yarn precursor, dropping the solvent onto the spun yarn precursor, and exposing the spun yarn precursor to the vapor of the solvent. It is preferable to impregnate the spun yarn precursor with the solvent. In this embodiment, it is preferable to dry the spun yarn precursor that has been in contact with the solvent at room temperature or a higher temperature. By bringing the spun yarn precursor into contact with the solvent using the means described above, it is possible to aggregate multiple CNTs using the cohesive force due to the vaporization of the solvent, thereby improving the density of the resulting spun yarn precursor.

[0033] [5. Yarn production process] This process includes applying tension to a yarn precursor while electrically heating it to produce a spun yarn made of carbon nanotubes (CNTs).

[0034] This process can be carried out, for example, by drawing the spun yarn precursor from the circumferential surface of a rotating body and subjecting it to electric heating while applying tension. In this embodiment, the formed CNT spun yarn is recovered by winding it around the circumferential surface of a rotating body. By winding the CNT spun yarn around the circumferential surface of a rotating body, a desired tension can be applied to the spun yarn precursor.

[0035] In this process, the tension applied to the yarn precursor may be the same as or greater than that applied in the yarn precursor densification process. Preferably, the tension applied to the yarn precursor is 0.5 or 1 mN or more and 100 mN or less, more preferably in the range of 0.5 to 100 mN, and even more preferably in the range of 1 to 50 mN. If the tension is below the lower limit, the density of the resulting CNT spun yarn may be low. Also, if the tension exceeds the upper limit, the yarn precursor may break. Therefore, by performing this process while applying tension within the range exemplified above to the yarn precursor, high-strength CNT spun yarn can be obtained.

[0036] In this process, tension can usually be applied by applying a load to the spun yarn precursor drawn from the circumferential surface of the rotating body using a tensioning rod, slider system, or motor.

[0037] In this process, the means for applying electric heating to the yarn precursor are not particularly limited, and various means commonly used in the art can be applied. This process may be carried out, for example, in an inert gas atmosphere (e.g., argon or other gas) using a heater (e.g., a quartz heater, etc.), or in an atmosphere furnace capable of ultra-high temperature heating equipped with a tension application mechanism.

[0038] In this process, the temperature of the electric heating is preferably 3200 K or less, more preferably in the range of above room temperature and 3200 K or less, even more preferably in the range of 1000 to 3200 K, and particularly preferably in the range of 2000 to 3000 K. If the electric heating temperature is below the lower limit, the graphenization of amorphous carbon in the CNTs contained in the spun yarn precursor may not proceed sufficiently. Also, if the electric heating temperature exceeds the upper limit, the spun yarn precursor may break. Therefore, by carrying out this process under the conditions exemplified above, at least a portion of the amorphous carbon in the CNTs contained in the spun yarn precursor can be graphenized to obtain high-strength CNT spun yarn.

[0039] In this process, the time of electrical heating is preferably in the range of greater than 0.1 seconds and less than 10 seconds, more preferably in the range of 0.5 to 10 seconds, and even more preferably in the range of 0.5 to 1 second. If the time of electrical heating is less than the lower limit, the graphenization of amorphous carbon in the CNTs contained in the spun yarn precursor may not proceed sufficiently. Also, if the time of electrical heating exceeds the upper limit, the spun yarn precursor may break. Therefore, by carrying out this process under the above conditions, at least a portion of the amorphous carbon in the CNTs contained in the spun yarn precursor can be graphenized, and a high-strength CNT spun yarn can be obtained.

[0040] By carrying out this process under the above conditions, the spun yarn precursor is densified and / or at least a portion of the amorphous carbon contained in the spun yarn precursor is graphenized to obtain CNT spun yarn with high density and strength.

[0041] [6. Crosslinking process] The method according to this embodiment may further include a crosslinking step in which the spun yarn made of CNTs obtained in the spinning yarn manufacturing step is impregnated with an aqueous solution containing a sulfide salt (hereinafter also referred to as "sulfidant"). When the CNT spun yarn is treated with a sulfidant, the CNTs are crosslinked by disulfide bonds. When tensile force is applied to this crosslinked CNT spun yarn, the disulfide bonds repeatedly recombine, which can improve the strength.

[0042] In this process, the sulfide salt used as a sulfiding agent is preferably a salt of tetrasulfide, trisulfide, or disulfide; more preferably a salt of tetrasulfide or disulfide; even more preferably a salt of tetrasulfide or disulfide with sodium ions, potassium ions, calcium ions, or magnesium ions; and particularly preferably sodium tetrasulfide or sodium disulfide. When the sulfide salt is a salt of tetrasulfide with the counterions exemplified above, particularly sodium tetrasulfide, this process can further improve the strain resistance of the CNT spun yarn. Furthermore, when the sulfide salt is a salt of disulfide with the counterions exemplified above, particularly sodium disulfide, this process can further improve the breaking stress of the CNT spun yarn. Therefore, by performing this process using the sulfide salts exemplified above, the strength of the resulting CNT spun yarn can be further improved.

[0043] The method of this embodiment makes it possible to produce CNT spun yarn with high strength. The CNT spun yarn obtained by the method of this embodiment usually has a Young's modulus of 100 GPa or more, for example, in the range of 100 to 400 GPa. In addition, the CNT spun yarn of this embodiment usually has a tensile strength or breaking stress of 1.5 GPa or more, for example, in the range of 1.5 to 7 GPa. Therefore, the CNT spun yarn of this embodiment can have higher strength than CNT spun yarn obtained by conventional methods.

[0044] In each aspect of the present invention, the strength of the CNT spun yarn precursor and the CNT spun yarn can be evaluated, for example, using the Young's modulus, tensile strength, and breaking stress as indicators. The Young's modulus, tensile strength, and breaking stress of the CNT spun yarn precursor and the CNT spun yarn can be measured, for example, based on ISO 11566:1996 (JIS R 7606:2000) under the conditions of a test speed of 1 mm / min and a gripping tool distance of 25 mm.

[0045] As described in detail above, the CNT spun yarn can be produced by the method of this aspect. The CNT spun yarn produced or producible by the method of this aspect has high strength. Therefore, the CNT spun yarn produced or producible by the method of this aspect can be used as a high-strength carbon material to replace carbon fiber reinforced plastic (CFRP). The CNT spun yarn produced or producible by the method of this aspect can be used, for example, as a material for parts such as automotive parts (e.g., high-pressure tanks or bodies), parts for wind turbines (e.g., blades), or parts for aircraft (e.g., bodies).

Example

[0046] <I: Production of Spun Yarn Composed of CNTs> [I-1: Spun Yarn Precursor Preparation Step] Based on the method described in Patent Document 2, a spun yarn precursor composed of a plurality of CNTs was spun from a CNT forest using a dry spinning method. The spun yarn precursor was wound around the circumferential surface of a rotating body (glass rod) to obtain a yarn of the spun yarn precursor.

[0047] [I-2: Graphene Solution Preparation Step] Graphene oxide (GO) was added to a mixed solvent of water and ethanol (1:1 volume ratio) to obtain a graphene oxide solution. The graphene oxide in the solution was micronized using an ultrasonic homogenizer for a predetermined time (1, 2, or 3 hours). Figure 1 shows the relationship between the micronization time and the particle size distribution of graphene oxide. In the figure, A is the particle size distribution of graphene oxide without micronization, B is the particle size distribution of graphene oxide after 1 hour of micronization, C is the particle size distribution of graphene oxide after 2 hours of micronization, and D is the particle size distribution of graphene oxide after 3 hours of micronization. In each panel, the horizontal axis represents the particle size (μm) of graphene oxide (GO), and the vertical axis represents the frequency distribution (percentage).

[0048] As shown in Figure 1, graphene oxide without micronization treatment had a 50% particle size (D50) in the range of 0.5 to 1.8 μm (Figure 1A). In contrast, the D50 of graphene oxide decreased as the micronization treatment time increased. Graphene oxide treated for 1 hour had a D50 in the range of 0.3 to 0.8 μm, graphene oxide treated for 2 hours had a D50 in the range of 0.2 to 0.6 μm, and graphene oxide treated for 3 hours had a D50 in the range of 0.1 to 0.5 μm.

[0049] [I-3: Spinning Yarn Precursor Immersion Process] The yarn of the yarn precursor obtained in the yarn precursor preparation step was immersed in the graphene oxide solution obtained in the graphene solution preparation step for a predetermined time (1, 12, or 24 hours).

[0050] [I-4: Densification process of the spinning yarn precursor] The yarn precursor was removed from the graphene oxide solution. The yarn precursor was drawn out from the circumferential surface of a rotating body at a constant drawing speed. The yarn precursor was impregnated with ethanol while a predetermined tension (1, 10, or 20 mN) was applied, and then wound around the circumferential surface of another rotating body. The yarn precursor was densified by the above procedure.

[0051] [I-5: Spinning yarn production process] The spinning yarn precursor was drawn from the circumferential surface of the rotating body at a constant drawing speed. Under an argon atmosphere, while applying tension to the spinning yarn precursor, it was electrically heated using a quartz heater under the conditions of a temperature of 3000 K, a time of 1 second, and an electrode distance of 10 mm, and then wound around the circumferential surface of another rotating body. By the above procedure, CNT spinning yarn was produced.

[0052] <II: Property analysis of spinning yarn made of CNTs>[[]END] Based on ISO11566:1996 (JIS R 7606:2000), under the conditions of a test speed of 1 mm / min and a gripping tool distance of 25 mm, the tensile strength, Young's modulus, and breaking stress of the CNT spinning yarn obtained in the procedure of I were measured. The measurement was carried out 4 times, and the average value was calculated.

[0053] In the graphene solution preparation process (I-2), the micronization treatment was carried out for a predetermined time, and then the spinning yarn precursor immersion process (I-3) was carried out under the condition of 1 hour, and the spinning yarn precursor densification process (I-4) was carried out under the condition of a tension of 1 mN. As a control, CNT spinning yarn was produced without carrying out the spinning yarn precursor immersion process (that is, without immersing the spinning yarn precursor in the graphene oxide solution). Regarding the obtained CNT spinning yarn, the relationship between the micronization treatment time in the graphene solution preparation process and the tensile strength and Young's modulus of the resulting CNT spinning yarn is shown in Figure 2. In the figure, A is a graph showing the relationship between the micronization treatment time and the tensile strength. The horizontal axis is the micronization treatment time (h, hour), and the vertical axis is the tensile strength (GPa). B is a graph showing the relationship between the micronization treatment time and the Young's modulus. The horizontal axis is the micronization treatment time (h, hour), and the vertical axis is the Young's modulus (GPa). For both A and B, the values in the figure represent the average value, as well as the maximum value and the minimum value.

[0054] As shown in Figure 2, the CNT spinning yarn obtained by immersing the spinning yarn precursor in the graphene oxide solution subjected to the micronization treatment for 2 hours showed significantly higher tensile strength and Young's modulus compared to the control CNT spinning yarn produced without immersing the spinning yarn precursor in the graphene oxide solution.

[0055] In the graphene solution preparation step (I-2), a micronization treatment was performed for 2 hours, followed by a spinning yarn precursor immersion step (I-3) for 24 hours. Then, a spinning yarn precursor densification step (I-4) was carried out under predetermined tension conditions. Figure 3 shows the relationship between the tension in the spinning yarn precursor densification step and the resulting tensile strength and Young's modulus of the CNT spinning yarn. In the figure, A is a graph showing the relationship between the tension of the densification treatment and the tensile strength. The horizontal axis represents the tension of the densification treatment (mN), and the vertical axis represents the tensile strength (GPa). B is a graph showing the relationship between the tension of the densification treatment and the Young's modulus. The horizontal axis represents the tension of the densification treatment (mN), and the vertical axis represents the Young's modulus (GPa). In both A and B, the values ​​shown are the average, maximum, and minimum values.

[0056] As shown in Figure 3, the CNT spun yarn obtained by densification treatment while applying a tension of 1 mN or more showed higher tensile strength and Young's modulus in a tension-dependent manner.

[0057] In the graphene solution preparation step (I-2), a micronization treatment was performed for 2 hours to obtain 0.005, 0.02, 0.15, and 0.2 mass% graphene oxide solutions. Using these graphene oxide solutions, the spinning yarn precursor immersion step (I-3) was performed for 24 hours, the spinning yarn precursor densification step (I-4) was performed under the same conditions, and the spinning yarn production step (I-5) was performed under the same conditions. As control 1, untreated CNT spun yarn was produced without performing the spinning yarn precursor immersion step (I-3), the spinning yarn precursor densification step (I-4), and the spinning yarn production step (I-5). As control 2, CNT spun yarn was produced by performing only the electrochemical heating treatment in the spinning yarn production step (I-5) under the same conditions, without performing the spinning yarn precursor immersion step (I-3) and the spinning yarn precursor densification step (I-4).

[0058] The obtained CNT spun yarn was subjected to Raman spectroscopy. In the Raman spectrum, crystalline sp was observed. 2 sp, which exhibits G-band peaks, defects, or amorphous properties originating from the structure. 3The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). * The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). G The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). C The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). G The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). C The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 之2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). G The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 之D band peak was separated into a 2D band peak derived from single-layer graphene and a之D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa). -1 The D-band peak derived from the structure, the 2D band peak which is a secondary D-band peak, and the G band peak derived from graphene were observed. The observed 2D band peak was separated into a 2D band peak derived from single-layer graphene and a 2D band peak derived from multi-layer graphene. Also, based on the observed data, a fitting curve was obtained. From the integral values of each separated peak, the ratio (%) of single-layer graphene = 2D / (2D + 2D) was calculated. The ratio of single-layer graphene calculated in the CNT spun yarn corresponds to the amount of graphene introduced in the CNT spun yarn. The Raman spectrum of the obtained CNT spun yarn is shown in FIG. 4. In the figure, A is the Raman spectrum of the CNT spun yarn of Control 2, B is the Raman spectrum of the CNT spun yarn prepared using a 0.02 mass% graphene oxide solution, and C is the Raman spectrum of the CNT spun yarn prepared using a 0.15 mass% graphene oxide solution. In the figure, the horizontal axis is the Raman shift (cm), and the vertical axis is the intensity (a.u.) of the Raman scattered light. Also, the relationship between the amount of graphene introduced in the obtained CNT spun yarn and the breaking stress is shown in FIG. 5. In the figure, the horizontal axis is the ratio (%) of single-layer graphene, and the vertical axis is the breaking stress (GPa).

[0059] As shown in FIG. 4, the peak area of the 2D band derived from single-layer graphene increased with an increase in the graphene oxide concentration of the graphene oxide solution used in the spun yarn precursor immersion process. Also, as shown in FIG. 5, the breaking stress of the CNT spun yarn increased with an increase in the amount of graphene introduced in the CNT spun yarn. G As shown in FIG. 4, the peak area of the 2D band derived from single-layer graphene increased with an increase in the graphene oxide concentration of the graphene oxide solution used in the spun yarn precursor immersion process. Also, as shown in FIG. 5, the breaking stress of the CNT spun yarn increased with an increase in the amount of graphene introduced in the CNT spun yarn.

[0060] From the above results, it became clear that the CNT spun yarn obtained in this example had graphene oxide introduced into the CNT bundle, and its strength was improved.<00002%50>

[0061] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. In addition, it is possible to add, delete, and / or replace some of the configurations in each embodiment with other configurations.

Claims

1. A method for producing spun yarn made of carbon nanotubes, comprising the following steps: A process for preparing a spinning yarn precursor consisting of carbon nanotubes; A yarn precursor immersion step involves immersing the yarn precursor in a solution containing graphene oxide or fine graphene particles; A process for producing spun yarn made of carbon nanotubes by applying tension to a spun yarn precursor while heating it with an electric current; The method, including the method described above.

2. A yarn precursor densification step involves applying tension to the yarn precursor obtained in the yarn precursor immersion step to densify the yarn precursor; The method according to claim 1, further comprising:

3. The method according to claim 2, wherein, in the densification step of the spun yarn precursor, tension is applied to the spun yarn precursor while it is in contact with ethanol.

4. A graphene solution preparation step involves preparing a solution containing fine particles of graphene oxide or graphene having a 50% particle size (D50) in the range of 0.1 to 0.6 μm, obtained by micronizing graphene oxide or graphene; The method according to claim 1, further comprising:

5. The method according to claim 1, wherein electric heating is performed at a temperature of 3200 K or less in the yarn spinning process.

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