KR20210015232A - Method for manufacturing cnt fiber having improved tensile strength - Google Patents

Abstract

The present invention relates to a manufacturing method of carbon nanotube fibers, which are a continuous aggregate of carbon nanotubes. By adjusting the difference between the surface temperature and the internal temperature of a reaction tube to 53°C or less between a reaction tube inlet and a heating furnace inlet in a region inside the heating furnace inlet and the reaction tube to keep the Richardson number (Ri) defined by equation 1 below 42, the rotational flow in the reaction tube can be minimized and the tensile strength of the carbon nanotube fibers produced as a result can be improved.

Description

Manufacturing method of carbon nanotube fiber with improved tensile strength {METHOD FOR MANUFACTURING CNT FIBER HAVING IMPROVED TENSILE STRENGTH}

The present invention relates to a method of manufacturing a carbon nanotube fiber, and more particularly, to a method of manufacturing a carbon nanotube fiber capable of improving the tensile strength of a carbon nanotube fiber made of a continuous aggregate of carbon nanotubes.

Carbon Nanotube (CNT), a type of carbon allotrope, is a material with a diameter of several to tens of nm and a length of several hundred μm to several mm, and is researched in various fields due to its excellent thermal, electrical and physical properties and high aspect ratio. Has been going on. These unique properties of carbon nanotubes are due to the sp ² bond of carbon, are stronger than iron, lighter than aluminum, and exhibit electrical conductivity comparable to metal. The types of carbon nanotubes are largely dependent on the number of walls of the nanotubes: Single-Wall Carbon Nanotube (SWNT), Double-Wall Carbon Nanotube (DWNT), and Multi-Wall Carbon Nanotube (Multi-Wall Carbon Nanotube). Wall Carbon Nanotube, MWNT), and is divided into zigzag, armchair, and chiral structures according to asymmetry/chirality.

Until now, most of the research has been conducted in the direction of dispersing carbon nanotubes in powder form and using them as reinforcing agents of composite materials or manufacturing transparent conductive films using dispersion solutions, and some fields have already reached commercialization. However, in order to use carbon nanotubes in composite materials and transparent conductive films, dispersion of carbon nanotubes is important. Due to the cohesive force of the carbon nanotubes, the strong van der Waals force disperses them in high concentration and dispersibility. Maintaining is not easy. In addition, in the case of a composite material in which carbon nanotubes are used as reinforcing materials, it is difficult to sufficiently express the excellent properties of carbon nanotubes.

Accordingly, in recent years, many studies have been conducted on carbon nanotube fiber formation for the production of carbon nanotube structures that sufficiently express the properties of carbon nanotubes.

As a method of fiberizing using a dispersion solution containing carbon nanotubes and a dispersant, representatively,'coagulation spinning','liquid-crystalline spinning','array spinning' and ' There is'direct spinning'.

The coagulation spinning method is a carbon nanotube by injecting a dispersion solution containing carbon nanotubes and a dispersant into a polymer solution, allowing the dispersant in the dispersion solution to escape into the polymer solution, and replacing the place with the polymer to act as a binder. It is a method of fiberizing.

The liquid crystal spinning method is a method in which a carbon nanotube solution is made into fibers using the property of forming a liquid crystal under specific conditions. Although this method has the advantage of being able to make carbon nanotube fibers with good orientation, it has the disadvantage that the spinning speed is very slow and the liquid crystal formation conditions of the carbon nanotubes are difficult.

The array spinning method is a method of forming a carbon nanotube film from an array of carbon nanotubes vertically aligned on a substrate, twisting it to form fibers. This method has the advantage of being able to make carbon nanotube fibers with almost no impurities, but it has a disadvantage that a continuous process is impossible.

As shown in FIG. 1, as shown in FIG. 1, a liquid carbon source and a catalyst are injected together with a carrier gas to synthesize carbon nanotubes in a heating furnace, and a carrier gas and This is a method of obtaining fibers by winding up the carbon nanotube aggregates discharged to the outlet of the heating furnace together inside the furnace (FIG. 1A) or outside (FIG. 1B). This method has the advantage of being able to produce a large amount of carbon nanotube fibers compared to other methods with a spinning speed of up to 20 to 30 m/min, but due to the characteristics of the fibrous particles, the carbon nanotube fiber particles may be twisted or aggregated again, Since it can be easily attached to the wall of the heating furnace, it is very difficult to discharge the carbon nanotube fibers smoothly.

The mechanical strength of the carbon nanotube (CNT) itself, especially the tensile strength, is so excellent that it exceeds 100 GPa, but the synthesized CNT is a short fiber with a short length, so its application is limited. In order to solve this problem, a method of making a long fiber CNT aggregate by connecting short fiber CNTs has been studied recently.

Variables that affect the strength of the fiber, which is an aggregate of CNTs, include the length and diameter of CNTs, and the bonding force between CNTs. In order to improve the tensile strength of the CNT aggregate, the bonding force between the CNTs forming the CNT fibers must be increased, and for this, the length of the CNTs must be lengthened [Gary G. Tibbetts, Carbon 30, 399, (1992)].

However, in the vertical reaction tube as shown in FIG. 1, the flow of air is formed from the top to the bottom of the reaction tube, and the gas injected into the high temperature reaction tube is affected by buoyancy, so that a stable gas flow cannot be formed and rotates. There is a problem of generating flow [Ya-Li Li et al. Science 304, 276 (2004)]. The rotational flow promotes the growth of catalyst particles inside the reaction tube and makes it difficult to form long CNTs. On the other hand, a similar rotational flow is formed in the horizontal reaction tube, which may cause this problem.

Therefore, in order to improve the tensile strength of the CNT aggregate fiber, it is necessary to remove or suppress the rotational flow formed inside the reaction tube.

An object of the present invention is to provide a method for producing CNT fibers that can efficiently improve the tensile strength of CNT fibers, which is a continuous aggregate of CNTs.

In order to solve the above problems, the present invention

In the method of producing a carbon nanotube fiber, which is a continuous aggregate of carbon nanotubes, by injecting a reaction gas containing a carbon source into a reaction tube equipped with a heating furnace together with a catalyst or a catalyst precursor and a transfer gas,

The difference between the surface temperature and the internal temperature of the reaction tube between the inlet of the reaction tube and the inlet of the heating furnace, in the area of the inlet of the heating furnace and the inside of the reaction tube, is adjusted to 53°C or less, and the Richardson number defined by the following equation (1) It provides a method for producing a carbon nanotube fiber, characterized in that the rotational flow is suppressed by maintaining Ri ) below 42:

[Equation 1]

Ri = Gr/Re ²

In the above formula,

Gr is the Grashof number calculated from (d ³ gβΔθ)/(ν ² )

Re is the Reynolds number calculated from wd/ν,

Where d is the inner diameter of the reaction tube, g is the gravitational acceleration, β is the thermal expansion coefficient of the reaction gas containing a carbon source, Δθ is the difference between the surface temperature and the internal temperature of the reaction tube, ν is the kinematic viscosity coefficient, and w is the carbon source. It is the flow rate of the contained reaction gas.

According to one aspect, the difference (Δθ) between the surface temperature and the internal temperature of the reaction tube is adjusted in the range of -3°C to 53°C, so that the Richardson number ( Ri ) defined by Equation 1 is 0 to It can be kept below 42.

The reaction zone of the reaction tube may be heated to 1,000 ℃ to 3,000 ℃.

According to one aspect, the reaction tube is a vertical reaction tube, and the reaction gas, catalyst or catalyst precursor and the transfer gas are injected into the upper part of the reaction tube, and the generated carbon nanotubes are discharged to the lower part of the reaction tube to form a continuous assembly. I can.

According to one aspect, the transfer gas may be a reducing gas including hydrogen gas, ammonia gas, or a mixture gas thereof.

In addition, the transfer gas may further include an inert gas.

The carbon source is methane, ethylene, acetylene, methylacetylene, vinylacetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethylacetic acid, diethyl ether, polyethylene glycol, ethylformate, mesitylene, tetrahydrofuran (THF ), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride, and pentane.

The catalyst or catalyst precursor may include at least one selected from the group consisting of iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium, and oxides thereof.

According to an aspect, a catalyst activator selected from elemental sulfur, a sulfur-containing compound, and combinations thereof may be further injected together with the catalyst or catalyst precursor.

The catalytic activator may include a compound selected from methylthiol, methylethylsulfide, dimethylthioketone, phenylthiol, diphenylsulfide, pyridine, quinoline, benzothiophene, thiophene, and combinations thereof.

Preferably, the catalyst or catalyst precursor may be in the form of a metallocene.

In addition, the gas hourly space velocity (GHSV) of the reaction gas may be selected in the range of 0.12 to 6.0 hr ^-1 , and the GHSV of the transfer gas may be selected in the range of 1.2 to 300 hr ^-1 . The GHSV (Gas Hourly Space Velocity) is a value measured in a standard state (0℃, 1 bar) and means the ratio of the volume flow rate of the supplied gas and the volume of the reaction tube, and the unit time is a value given in hours. Say.

According to another embodiment of the present invention, a carbon nanotube fiber manufactured according to the above method is provided.

Other specifics of the embodiments of the present invention are included in the detailed description below.

According to the method for manufacturing a carbon nanotube fiber assembly according to the present invention, the tensile strength of the resulting CNT fibrous assembly can be improved by minimizing the rotational flow formed inside the reaction tube to stably form the gas flow. Therefore, the carbon nanotube fiber assembly manufactured by the method according to the present invention is a reinforcement material of a multifunctional composite material, a deformation and damage detector using a stable and repetitive piezo resistance effect, a transmission line using a high conductivity, a high specific surface area, excellent mechanical properties and electricity. It is expected that it can be applied to various fields such as electrochemical devices using conductivity, for example, microelectrode materials for detecting biomaterials, supercapacitors, and actuators.

1 schematically shows a method of manufacturing carbon nanotube fibers by direct spinning.
FIG. 2 shows a schematic structure of a reaction tube for manufacturing CNT aggregate fibers according to an embodiment of the present invention, and results of simulations of computational fluid dynamics (CFD) for airflow directions according to Examples and Comparative Examples.
3 shows whether or not rotational flow occurs due to the difference between the surface temperature and the internal temperature of the reaction tube in Examples and Comparative Examples of the present invention.

Since the present invention can apply various transformations and have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all conversions, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

The term "aggregate" as used herein may be described interchangeably with "aggregate", and may be understood to mean a collection of singular individuals.

The term "injection" used in the present specification may be used interchangeably with "inflow, infusion" in the present specification, and may be understood as meaning to flow in or inject liquid, gas, or heat into a required place. .

In the present specification, the term "carbon nanotube fiber" refers to both formed by growing carbon nanotubes in a fiber form or by fusing a plurality of carbon nanotubes into a fiber form.

Hereinafter, a method of manufacturing a carbon nanotube fiber according to an embodiment of the present invention will be described in more detail.

As a technology for producing carbon nanotube fibers, there are coagulation spinning, liquid crystal spinning, array spinning, and direct spinning. The present invention follows a process of directly spinning carbon nanotube fibers among them.

In the direct spinning method, a gaseous or liquid carbon source and a catalyst are injected together with a carrier gas into the inlet of a high-temperature furnace to synthesize carbon nanotubes in the furnace and heated together with the carrier gas. This is a method of obtaining fibers by winding up the carbon nanotube aggregate discharged to the outlet of the furnace inside or outside the furnace.

The rotational flow refers to a vortex flow generated by a gas flowing in the opposite direction to the flow of a reaction gas containing a carbon source, and this means that the gas injected into the reaction tube is affected by buoyancy to form a stable gas flow. This may be caused by failure to do so, and consequently adversely affects the tensile strength of the finally produced carbon nanotube fiber.

Accordingly, in the present invention, in a method for producing a carbon nanotube fiber, a continuous aggregate of carbon nanotubes, by injecting a reaction gas containing a carbon source into a reaction tube together with a catalyst or a catalyst precursor and a transfer gas,

The difference between the surface temperature and the internal temperature of the reaction tube between the inlet of the reaction tube and the inlet of the heating furnace, in the area of the inlet of the heating furnace and the inside of the reaction tube, is adjusted to 53°C or less, and the Richardson number defined by the following equation (1) It is characterized in that the rotational flow is suppressed by keeping Ri ) below 42.

[Equation 1]

Ri = Gr/Re ²

In the above formula,

Gr is the Grashof number calculated from (d ³ gβΔθ)/(ν ² )

Re is the Reynolds number calculated from wd/ν,

Where d is the inner diameter of the reaction tube, g is the gravitational acceleration, β is the thermal expansion coefficient of the reaction gas containing a carbon source, Δθ is the difference between the surface temperature and the internal temperature of the reaction tube, ν is the kinematic viscosity coefficient, and w is the carbon source. It is the flow rate of the contained reaction gas.

Here, the Richardson number ( Ri ) represents a hydrodynamic scale of buoyancy.

More specifically, according to the research of the present inventors, in the structure in which the furnace surrounds the reaction tube, among various variables defined by Equation 1, the difference between the surface temperature and the internal temperature of the reaction tube (Δθ) When the Richardson number ( Ri ) is maintained at 0 to less than 42 by adjusting the range of -3°C to 53°C, the rotational flow in the reaction tube can be suppressed as shown in FIG. 2. As a result, the tensile strength of the finally produced carbon nanotube fiber can be improved, for example, 2 to 3 times.

In particular, the area at the entrance of the heating furnace is the area where the reaction temperature (about 600℃ or higher) to generate carbon nanotube fibers starts, and it is important to form a stable downward flow for smooth discharge of the fibers initially generated in this area. . Therefore, it is necessary to control the rotational flow by controlling the surface temperature, the internal temperature and the Richardson number of the reaction tube in the inlet region of the heating furnace under the above conditions.

In addition, in order to satisfy the Richardson number ( Ri ) of Equation 1 below 42, in addition to the temperature gradient of the reaction tube, the gas flow rate and the inner diameter of the reaction tube may be adjusted.

According to one embodiment, the catalyst or catalyst precursor may be injected in an amount of 0.5 to 10% by weight, or 1 to 5% by weight, or 1.5 to 4% by weight based on the carbon source. In the case of using an excess catalyst or catalyst precursor than the carbon source, the catalyst acts as an impurity, making it difficult to obtain high-purity carbon nanotube fibers, but rather can be a factor that hinders the thermal, electrical, and physical properties of the carbon nanotube fibers. .

The catalyst precursor is a material that is not included in the catalyst cycle itself, but changes into an active catalyst or generates an active catalyst, and synthesizes carbon nanotubes after the catalyst precursor forms a catalyst. .

The catalyst or catalyst precursor may include at least one selected from the group consisting of iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium, and oxides thereof, but is not limited thereto. In addition, the catalyst may be in the form of nanoparticles, preferably in the form of a metallocene such as ferrocene, which is a compound containing iron, nickel, cobalt, and the like. According to a preferred embodiment, the ferrocene catalyst precursor may be injected at a rate of 0.05-0.2 g/hr or 0.05-0.1 g/hr.

In the present invention, when the catalyst or the catalyst precursor is injected, a catalyst activator may be injected together. In general, the synthesis of carbon nanotubes proceeds as carbon diffuses into the catalyst and then precipitates while the catalyst is molten. The catalytic activator increases the carbon diffusion rate when synthesizing carbon nanotubes, so that the carbon nanotubes are rapidly Let the tube synthesize. In addition, the catalytic activator reduces the melting point of the catalyst and removes amorphous carbon so that high-purity carbon nanotubes can be synthesized at a low temperature.

As the catalyst activator, for example, elemental sulfur, a sulfur-containing compound, and combinations thereof may be used. Specific examples include sulfur-containing aliphatic compounds such as methylthiol, methylethylsulfide, dimethylthioketone, and the like; Sulfur-containing aromatic compounds such as phenylthiol and diphenylsulfide; Sulfur-containing heterocyclic compounds such as pyridine, quinoline, benzothiophene, and thiophene; It may be sulfur as an element, preferably sulfur or thiophene, and more preferably sulfur. According to a preferred embodiment, the catalyst activator may be injected at a rate of 0.01-0.3 g/hr, or 0.01-0.2 g/hr or 0.01-0.1 g/hr.

According to a preferred embodiment of the present invention, the catalyst precursor and the catalytic activator may be liquid in the liquid carbon compound, and may be gaseous in the gaseous carbon compound. Accordingly, a catalyst precursor or a catalyst activator can be dissolved and injected into a liquid carbon compound, and a gaseous carbon compound can be vaporized and injected in the form of a gas.

In the present invention, the carbon source may be liquid or gaseous, and the carbon source is synthesized into carbon nanotubes by diffusion into the catalyst, and is used in consideration of molecular weight distribution, concentration, viscosity, surface tension, dielectric constant, and properties of the solvent used. .

The liquid or gaseous carbon source is methane, ethylene, acetylene, methylacetylene, vinylacetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethylacetic acid, diethyl ether, polyethylene glycol, ethyl formate, mesitylene, tetra Hydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride, and may include at least one selected from the group consisting of pentane.

Specifically, the liquid carbon source is ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, diethyl ether, polyethylene glycol, ethyl formate, mesitylene, tetrahydrofuran (THF), dimethylformamide (DMF). ), dichloromethane, hexane, benzene, carbon tetrachloride, and may include one or more selected from the group consisting of pentane. Preferably ethanol (C ₂ H ₅ OH), xylene (C ₈ H ₁₀ ), diethyl ether [(C ₂ H ₅ ) ₂ O], polyethylene glycol [-(CH ₂ CH ₂ O) ₉ ], 1 -Propanol (CH ₃ CH ₂ CH ₂ OH), acetone (CH ₃ OCH ₃ ), ethyl formate (CH ₃ CH ₂ COOH), benzene (C ₆ H ₆ ), hexane (C ₆ H ₁₄ ) and mesitylene [ It may include any one or more selected from the group consisting of C ₆ H ₃ (CH ₃ ) ₃ ].

The gaseous carbon source may include at least one selected from the group consisting of methane, ethylene, acetylene, methylacetylene, and vinylacetylene.

In the present invention, the GHSV of the reaction gas supplied to the reaction zone may be 0.12 to 6.0 hr ^-1 , preferably 0.6 to 3.6 hr ^-1 , or 0.84 to 2 hr ^-1 , or 1 to 2 hr ^-1 Can be

In addition, the GHSV of the transport gas injected into the reaction zone can be appropriately selected in the range of 1.2 to 60 hr ^-1 , 6 to 30 hr ^-1 , or 12 to 30 hr ^-1 in the case of hydrogen gas, for example.

According to another embodiment, the transport gas may be injected at a linear speed of 0.5 to 50 cm/min, and preferably 0.5 to 40 cm/min or 0.5 to 30 cm/min or 0.5 to 20 cm/min or 1 to It can be injected at a linear speed of 10 cm/min. The transfer gas injection linear speed may vary depending on the type of the transfer gas, the size of the reaction tube, and the type of catalyst.

According to one embodiment, the transfer gas (carrier gas) may be an inert gas, a reducing gas, or a combination thereof, and preferably may include a reducing gas containing a hydrogen atom. The reducing gas may include hydrogen, ammonia, or a gas containing a mixture thereof.

As an inert gas, nitrogen, helium, neon, argon, krypton, xenon, radon, or a gas containing a mixture thereof may be included, and these inert gases are chemically very stable and have a property not to send or receive electrons or share them. Therefore, it can play a role of allowing the carbon nanotubes to flow and move due to the inflow of gas without reacting with the carbon nanotubes (CNT).

According to a preferred embodiment, the carbon nanotube fiber aggregate may be produced by a direct spinning method in which carbon nanotube fibers are directly spun by a chemical vapor deposition method. In the direct spinning method, a gaseous or liquid carbon source and a catalyst are injected together with a carrier gas into the inlet of a high-temperature furnace to synthesize carbon nanotubes in the furnace and heated together with the carrier gas. This is a method of obtaining fibers by winding up the carbon nanotube aggregate discharged to the outlet of the furnace inside or outside the furnace.

The temperature of the reaction zone may be 1,000°C to 3,000°C. Preferably, a temperature of 1,000°C to 2,000°C or 1,000°C to 1,500°C or 1,000°C to 1,300°C may be maintained, and more preferably 1,150°C to 1,300°C. If it is less than 1000 ℃, there may be a problem that the carbon nanotube fibers are not formed. In addition, the above range is preferable since there may be a problem in that carbon nanotubes are vaporized when it exceeds 3000°C.

On the other hand, the difference (Δθ) between the surface temperature and the internal temperature of the reaction tube is 53°C or less, such as -3°C to 53°C, particularly, Δθ at the entrance region of the furnace is 25°C to 53°C, such as 30°C to 45°C. When adjusted to the degree of, the occurrence of rotational flow in the reaction tube can be minimized.

The produced carbon nanotube fibers may be wound and collected. The winding speed affects the orientation of the carbon nanotubes in the fiber in the fiber axis direction, and determines the thermal, electrical, and physical properties of the carbon nanotube fibers. Preferably, it can be wound in the range of 1 to 100 m/min.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Example 1: Synthesis of carbon nanotube fibers

The ferrocene catalyst precursor was vaporized at a rate of 0.06-0.08 g/hr and a sulfur catalyst activator was added at a rate of 0.01-0.03 g/hr, and methane as a carbon compound was added to a GHSV of 1 to 2 hr ^-1 , and the transport gas (hydrogen) was It was introduced into the top of a vertical cylindrical reaction tube (inner diameter: 0.065m) with a GHSV of 25-30 hr ^-1 . At this time, as shown in Table 1 below, by adjusting the surface temperature and the internal temperature of the reaction tube between the inlet of the reaction tube and the inlet of the heating furnace, in both the inlet of the heating furnace and the area inside the reaction tube, the difference (Δθ) is 53°C By so as to be, while maintaining the Richardson number (Richardson number, Ri ) defined by the following Equation 1 to less than 0 to 42, the reaction was performed.

Subsequently, the carbon nanotube fibers discharged to the outlet at the bottom of the reaction tube were wound with a winding means composed of a bobbin.

[Equation 1]

Ri = Gr/Re ²

In the above formula,

Gr is the Grashof number calculated from (d ³ gβΔθ)/(ν ² )

Re is the Reynolds number calculated from wd/ν,

Where d is the inner diameter of the reaction tube, g is the gravitational acceleration, β is the thermal expansion coefficient of the reaction gas containing a carbon source, Δθ is the difference between the surface temperature and the internal temperature of the reaction tube, ν is the kinematic viscosity coefficient, and w is the carbon source. It is the flow rate of the contained reaction gas.

Comparative Example 1: Synthesis of carbon nanotube fibers

As shown in Table 1 below, except for controlling variables including the surface temperature and the internal temperature of the reaction tube in all regions between the inlet of the reaction tube and the inlet of the heating furnace, the inlet of the heating furnace, and the interior of the reaction tube, Carbon nanotube fibers were synthesized in the same process.

Table 1 below shows the variables used to obtain the Richardson number ( Ri ) of Equation 1 in the production of carbon nanotube fibers according to Examples and Comparative Examples and their results.

[Table 1a]

[Table 1b]

In addition, Figure 3 shows whether or not rotational flow occurs due to the difference between the surface temperature and the internal temperature of the reaction tube in Examples and Comparative Examples.

As can be seen in Table 1 and Figure 3, the embodiment is the difference between the surface temperature and the internal temperature of the reaction tube between the inlet of the reaction tube and the inlet of the heating furnace, the inlet of the heating furnace and the inside of the reaction tube, especially at the inlet of the heating furnace ) Was adjusted to 53° C. or less to maintain the Richardson number ( Ri #) defined by Equation 1 below to be less than 42, and as a result, rotational flow was not formed, whereas in the comparative example, the temperature difference (Δθ ) Exceeded 53° C., the rotational flow was generated as the Grashof number (Gr#) and thus the Richardson number ( Ri #) increased.

This result proves that the greater the temperature difference (Δθ) in the situation where the inner diameter of the reaction tube is the same, the greater the buoyancy effect increases, thereby increasing the possibility of the occurrence of rotational flow in the reaction zone.

On the other hand, Table 2 below shows the Richardson number ( Ri ) according to Examples and Comparative Examples and the tensile strength of carbon nanotube fibers manufactured under the conditions. Tensile strength was measured using Textechno's FAVIMAT+ equipment, the load cell range was 210cN, the gauge length was 2.0cm, and the speed was 2mm/min.

[Table 2]

As can be seen from Table 2, in the case of Example 1 in which rotational flow did not occur by maintaining the Richardson number Ri below 42, the average tensile strength was improved by about 2.8 times compared to the Comparative Example. This is because the rotational flow in the reaction tube was suppressed in the range of the Richardson number, so that airflow formation became stable.

As described above, specific parts of the present invention have been described in detail, and for those of ordinary skill in the art, it is obvious that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Therefore, it will be said that the practical scope of the present invention is defined by the appended claims and their equivalents.

Claims (11)

In the method of producing a carbon nanotube fiber, which is a continuous aggregate of carbon nanotubes, by injecting a reaction gas containing a carbon source into a reaction tube equipped with a heating furnace together with a catalyst or a catalyst precursor and a transfer gas,
The difference between the surface temperature and the internal temperature of the reaction tube between the inlet of the reaction tube and the inlet of the heating furnace, in the area of the inlet of the heating furnace and the inside of the reaction tube, is adjusted to 53°C or less, and the Richardson number defined by the following equation (1) Ri ) a method for producing a carbon nanotube fiber, characterized in that the rotational flow is suppressed by maintaining below 42:
[Equation 1]
Ri = Gr/Re ²
In the above formula,
Gr is the Grashof number calculated from (d ³ gβΔθ)/(ν ² )
Re is the Reynolds number calculated from wd/ν,
Where d is the inner diameter of the reaction tube, g is the gravitational acceleration, β is the thermal expansion coefficient of the reaction gas containing a carbon source, Δθ is the difference between the surface temperature and the internal temperature of the reaction tube, ν is the kinematic viscosity coefficient, and w is the carbon source. It is the flow rate of the contained reaction gas. The method of claim 1,
By the difference (Δθ) of the surface temperature and internal temperature of the reaction tube adjusted in the range of -3 ℃ to 53 ℃, for holding the Richardson number (Richardson number, Ri), which is defined by the equation (1) in a range from 0 to 42 Method for producing a carbon nanotube fiber The method of claim 1,
The reaction zone of the reaction tube is a method of producing a carbon nanotube fiber heated to 1,000 ℃ to 3,000 ℃. The method of claim 1,
The method of manufacturing a carbon nanotube fiber, wherein the transfer gas includes a reducing gas including hydrogen gas, ammonia gas, or a mixture gas thereof. The method of claim 1,
The method of manufacturing a carbon nanotube fiber wherein the transfer gas further includes an inert gas. The method of claim 1,
The carbon source is methane, ethylene, acetylene, methylacetylene, vinylacetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethylacetic acid, diethyl ether, polyethylene glycol, ethylformate, mesitylene, tetrahydrofuran (THF ), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride, and a method for producing a carbon nanotube fiber comprising at least one selected from the group consisting of pentane. The method of claim 1,
The method for producing a carbon nanotube fiber wherein the catalyst or catalyst precursor comprises at least one selected from the group consisting of iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium, and oxides thereof. The method of claim 1,
A method for producing a carbon nanotube fiber to further inject a catalyst activator selected from elemental sulfur, a sulfur-containing compound, and combinations thereof together with the catalyst or catalyst precursor. The method of claim 8,
The catalytic activator is a carbon nanotube comprising a compound selected from methylthiol, methylethylsulfide, dimethylthioketone, phenylthiol, diphenylsulfide, pyridine, quinoline, benzothiophene, thiophene, and combinations thereof Methods of making fibers. The method of claim 1,
The method for producing carbon nanotube fibers in which the catalyst or catalyst precursor is in the form of metallocene. The method of claim 1,
The method for producing a carbon nanotube fiber, wherein the reaction gas has a GHSV (Gas Hourly Space Velocity) of 0.12 to 6.0 hr ^-1 , and the transfer gas GHSV of 1.2 to 60 hr ^-1 .

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