KR102377862B1 - High density and high strength carbon nanotube fibers and evaluating method therof - Google Patents

Abstract

A carbon nanotube fiber having high density and high strength in which the product of the porosity inside the carbon nanotube fiber and the tensile strength of the carbon nanotube fiber satisfies the range of Equation 1 below will be described.
[Equation 1]
30 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 125.

Description

Manufacturing method and evaluation method of high-density and high-strength carbon nanotube fibers

The present invention relates to carbon nanotube fibers having high strength and high density and a method for evaluating the same.

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. has been going on The intrinsic properties of these carbon nanotubes originate from the sp ² bond of carbon, and are stronger than iron, lighter than aluminum, and have electrical conductivity comparable to metals. The types of carbon nanotubes largely depend on the number of walls of the nanotubes: Single-Wall Carbon Nanotubes (SWNT), Double-Wall Carbon Nanotubes (DWNT), and Multi-Wall Carbon Nanotubes (Multi-Wall Carbon Nanotubes). Wall Carbon Nanotube, MWNT), and is divided into zigzag, armchair, and chiral structures according to asymmetry/chirality.

Until now, most researches have been conducted in the direction of dispersing powdered carbon nanotubes to use as a reinforcer for composite materials or manufacturing transparent conductive films using dispersion solutions, and commercialization has already been reached in some fields. However, in order to use carbon nanotubes in composite materials and transparent conductive films, dispersion of carbon nanotubes is important. Because of the cohesive force caused by the strong van der Waals force of carbon nanotubes, they are dispersed at a high concentration and dispersibility is maintained. It's not easy to do. In addition, in the case of a composite material in which carbon nanotubes are used as reinforcing materials, there is a disadvantage in that it is difficult to sufficiently express the excellent properties of carbon nanotubes.

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

Methods for fiberizing the carbon nanotube aggregate include 'solution spinning', 'forest spinning' and 'direct spinning'.

The solution spinning method is a method in which a dispersion solution containing carbon nanotubes is formed into fibers by using the property of forming liquid crystals under specific conditions. It is a method of manufacturing fibers made of carbon nanotubes by applying pressure to a solution in which carbon nanotubes are dispersed, pushing it through small holes, and passing a coagulant. Although this method has the advantage of being able to produce carbon nanotube fibers with good orientation, it has a disadvantage in that the liquid crystal formation conditions of the carbon nanotubes are difficult.

The forest spinning method is a method of forming a carbon nanotube film or ribbon from a carbon nanotube array vertically aligned on a substrate, and twisting it into fibers. Although this method has the advantage of producing carbon nanotube fibers with almost no impurities, it has the disadvantage that continuous processing is impossible.

In the direct spinning method, a gaseous or liquid carbon source, catalyst, and co-catalyst precursor 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. It is a method of obtaining fibers by winding up the carbon nanotube aggregate discharged from the furnace outlet inside or outside the heating furnace. This method has the advantage of being able to manufacture a large amount of carbon nanotube fibers compared to other methods, but has a disadvantage that a large amount of impurities may be present.

Although the mechanical strength of carbon nanotubes (CNTs) itself, particularly tensile strength, is very excellent, exceeding 100 GPa, the synthesized carbon nanotubes are short fibers with short lengths, so their applications are limited. In order to solve this problem, a method of making a long-fiber carbon nanotube aggregate by connecting short-fiber carbon nanotubes has been studied a lot recently.

The problem to be solved by the present invention is to provide a carbon nanotube fiber having improved density and strength.

In addition, the present invention provides a standard for evaluating high-density and high-strength carbon nanotube fibers and an evaluation method using the same.

In order to solve the problem of the present invention,

The product of the porosity (%) and tensile strength (N/tex) inside the carbon nanotube fiber satisfies the range of Equation 1 below.

[Equation 1]

30 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 125

In Equation 1, the porosity is

It is a value defined by porosity (%)=(area of pore region/total area)×100.

According to an embodiment, the porosity (%) and tensile strength (N/tex) of the carbon nanotube fibers satisfying the range of Equation 1 may also satisfy the range of Equation 2 below.

[Equation 2]

-14.2X + 60 ≤ Y ≤ -14.2X + 95

In the above formula 2,

X is the tensile strength (N/tex) of the carbon nanotube fiber,

Y is the porosity (%) of the carbon nanotube fiber.

According to one embodiment, the average tensile strength of the carbon nanotube fibers may be 0.5 N/tex or more.

According to an embodiment, the average porosity (%) of the carbon nanotube fibers may be 70% or less.

According to an embodiment, the porosity is calculated through image processing and may be an average value measured for 10 or more scanning electron microscope images.

According to one embodiment, the diameter of the carbon nanotube fibers may be 100nm to 150㎛.

According to one embodiment, the carbon nanotube,

heating a vertical reaction tube equipped with a heating furnace to a temperature of 1,000 to 3,000° C. and then introducing a catalyst precursor, a catalyst activator, a carbon source gas, and a transport gas to the upper end of the reaction tube;

adjusting the temperature gradient inside the reaction tube by adjusting the inlet temperature of the reaction tube to 200 to 300°C and the temperature at the inlet to 700 to 900°C; and

It may be manufactured by a method comprising the step of winding the carbon nanotube fibers discharged to the outlet of the lower end of the reaction tube by a winding means.

At this time, the pressure in the reaction tube is 0.5~1.5 atm.

According to an embodiment, the catalyst activator may be selected from elemental sulfur, sulfur-containing compounds, and combinations thereof.

According to one embodiment, after the winding of the carbon nanotube fiber, the carbon nanotube fiber is passed through a bath containing one or more solvents selected from chlorosulfonic acid and acetone to shrink it. may include more.

According to an embodiment, after the winding of the carbon nanotube fibers, the method may further include heat-treating the carbon nanotube fibers at a temperature of 200 to 400° C. for 15 minutes to 1 hour in an air atmosphere.

In order to solve another problem of the present invention, the strength evaluation method of carbon nanotube fibers based on whether the porosity (%) and tensile strength (N/tex) inside the carbon nanotube fibers satisfy Equation 1 below. to provide.

[Equation 1]

30 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 125

In Equation 1, the porosity is

It is a value defined as porosity (%) = (area of pore area/total area) x 100.

According to one embodiment, the carbon nanotube fibers satisfying the range of Equation 1 may also satisfy the range of Equation 2 below.

[Equation 2]

-14.2X + 60 ≤ Y ≤ -14.2X + 95

In the above formula 2,

X is the tensile strength (N/tex) of the carbon nanotube fiber,

Y is the porosity (%) of the carbon nanotube fiber.

In the carbon nanotube fiber according to the present invention, the tensile strength and the porosity of the carbon nanotube fiber are in inverse proportion, and the product of the porosity inside the carbon nanotube fiber and the tensile strength of the carbon nanotube fiber is expressed in Equation 1 By satisfying the range, it is possible to provide carbon nanotube fibers having characteristics of high density and high strength.

1 is an SEM image of a cross-section of a carbon nanotube fiber for porosity analysis through Image Processing, (a) is a low magnification (b) is a high magnification.
2 is a graph showing the relationship between average tensile strength and average porosity.
3 shows the tensile strength x porosity (A) value of the carbon nanotube fiber according to the embodiment. A on the Y-axis is the tensile strength (N/tex) x porosity (%) value.

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

The present invention relates to a fibrous aggregate of carbon nanotubes manufactured by connecting carbon nanotubes.

As used herein, the term “aggregate” may be used interchangeably with “aggregate” and may be understood to mean a collection of a singular individual.

As used herein, the term “injection” may be used interchangeably with “inflow, input” within this specification, and it can be understood to mean flowing or putting liquid, gas, or heat into a necessary place. .

In the present specification, the term "carbon nanotube fiber" refers to both carbon nanotubes grown and formed in the form of fibers or formed by fusion of a plurality of carbon nanotubes in the form of fibers.

Hereinafter, carbon nanotube fibers according to embodiments of the present invention will be described in more detail.

Variables affecting the strength of carbon nanotube fibers, which are aggregates of carbon nanotubes, include the length and diameter of carbon nanotubes, bonding force between carbon nanotubes, and internal porosity.

According to the research of the present inventors, when the porosity (%) and tensile strength (N/tex) inside the carbon nanotube fiber satisfies the ranges of Equation 1 below, it was found that high-density and high-strength carbon nanotube fibers are provided. has been completed

[Equation 1]

30 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 125

Preferably,

50 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 110

In Equation 1, the porosity% is a value defined by (area/total area of the pore region)×100.

In addition, the present invention provides an evaluation method using Equation 1 as a strength evaluation criterion in the manufacture of carbon nanotube fibers.

The porosity inside the carbon nanotube fiber is in inverse proportion to the tensile strength of the carbon nanotube fiber, for example, the porosity (%) and tensile strength (N/tex) of the carbon nanotube fiber are in the range of Equation 2 below. may be satisfied with

[Equation 2]

-14.2X + 60 ≤ Y ≤ -14.2X + 95

In the above formula 2,

X is the tensile strength (N/tex) of the carbon nanotube fiber,

Y is the porosity (%) of the carbon nanotube fiber.

In the carbon nanotube fiber according to the present invention, the tensile strength and the porosity of the carbon nanotube fiber are in inverse proportion, and the product of the carbon nanotube fiber porosity and the tensile strength of the carbon nanotube fiber satisfies the range of Equation 1, In the present invention, it can be determined whether the carbon nanotube fibers have high density and high strength based on Equations 1 and 2 above.

According to one embodiment, the average tensile strength of the carbon nanotube fibers may be 0.5 N/tex or more, preferably, 1.5 N/tex or more, and more preferably 2.0 N/tex or more, for example For example, it may have a range of 0.5 to 5.0 N/tex.

According to one embodiment, the average porosity of the carbon nanotube fibers may be 70% or less, preferably 60% or less, more preferably 50% or less, for example, having a porosity of 1 to 70%. it could be

The porosity of the carbon nanotube fiber according to the present invention can be measured by taking a scanning electron microscope (SEM) image of the cross section of the fiber and calculating the porosity inside the fiber by image processing the image. , it is preferable to average the number of measured SEM images to 10 or more for higher accuracy.

The image processing proceeds specifically as follows. After importing the cross-sectional SEM image using the ImageJ program (National Institute of Health, USA, ver.1.51j8), the number of pixels is obtained by selecting an area other than the pores by adjusting the brightness. In the same way, the number of pixels is calculated by selecting the pore area. After confirming that the sum of the number of pixels obtained from the non-pore region and the number of pixels from the pore region is equal to the total number of pixels, the area of the pore region is calculated from the number of pixels in the pore region. Calculate the porosity from the total area and the area of the pore area using the formula below. In the same way, the porosity is calculated from 10 or more SEM images, and the average value is calculated.

Porosity (%) = (area of pore area/total area) x 100

According to the present invention, by satisfying the above range, it is possible to provide higher strength and higher density carbon nanotube fibers.

The linear density of the carbon nanotube fibers satisfying the range of the above formula may be 0.01 to 10 tex.

The breaking strength of the carbon nanotube fibers may be 5 cN or more.

According to an embodiment, the carbon nanotube fiber may be a carbon nanotube fiber manufactured by any one of a solution spinning method, a forest spinning method, and a direct spinning method.

The solution spinning method is a method in which a dispersion solution containing carbon nanotubes is formed into fibers by using the property of forming liquid crystals under specific conditions. It is a method of manufacturing fibers made of carbon nanotubes by applying pressure to a solution in which carbon nanotubes are dispersed, pushing it through small holes, and passing a coagulant.

The forest spinning method is a method of forming a carbon nanotube film or ribbon from a carbon nanotube array vertically aligned on a substrate, and twisting it into fibers.

For example, the method for producing carbon nanotube fibers by the forest spinning method,

For example, growing carbon nanotubes on a silicon substrate; and

It may include the step of drawing out carbon nanotube fibers from the substrate on which the carbon nanotubes are grown.

In the step of withdrawing the carbon nanotube fibers from the substrate on which the carbon nanotubes are grown, the carbon nanotubes grown on the substrate may be drawn out in a plane shape by stretching in one direction. It may be in the form of a nanotube ribbon.

For example, the carbon nanotube ribbon may be pulled out in a planar shape while pulling the end of a carbon nanotube array grown perpendicular to a silicon wafer. Through this, carbon nanotubes can be gathered to form a carbon nanotube bundle of tens to hundreds of nanometers, and the bundles can be gathered to form a carbon nanotube ribbon having a very large surface area.

The step of preparing the carbon nanotube fibers in the method may be performed in a temperature range of 600 to 1000 ℃. Specifically, it may be carried out in a temperature range of 630 to 850 °C.

In addition, as a carbon source for producing the carbon nanotube fiber, one or more selected from the group of hydrocarbons having 1 to 20 carbon atoms may be used as the carbon source, and specifically, it may be one or more of acetylene, methane, and ethylene.

In the direct spinning method by chemical vapor deposition, a carrier gas including liquid and gaseous carbon sources and catalyst and promoter precursors are injected together at a constant speed into a high-temperature furnace to inject carbon nanotubes in a heating furnace. It may be a process of synthesizing and continuously manufacturing carbon nanotube fibers made of a carbon nanotube aggregate.

In the above method, the temperature of the reactor may be heated to 1,000 to 3,000 °C, and preferably, the high temperature region of the reactor can maintain a temperature of 1,100 to 2,000 °C, 1,100 to 1,500 °C, or 1,100 to 1,300 °C, more preferably may be 1,200 to 1,300 °C, for example, 1,200 to 1,250 °C. The temperature of the high temperature region of the reactor affects the rate at which carbon is diffused into the catalyst to control the growth rate of carbon nanotubes. In general, the higher the synthesis temperature, the faster the growth rate of carbon nanotubes. Crystallinity and strength may increase accordingly.

At this time, the temperature of the inlet of the reaction tube was 200 to 300 ° C, and the temperature of the inlet of the heating furnace was 700 to 900 ° C, preferably 800 to 850 ° C. was made not to. When the temperature of the reactor inlet is lower than 700°C, preferably 800°C, rotational flow may occur in the reactor and a temperature gradient may occur.

The amount of the transport gas injected into the reaction region can be controlled by changing the concentration of the reactants when synthesizing the carbon nanotubes. The transport gas may be a hydrocarbon-based gas, an inert gas, a reducing gas, or a mixture thereof.

The transport gas injected into the high temperature region may be injected at a gas hourly space velocity (GHSV) of 5 to 50 hr ^-1 , preferably 10 to 40 hr ^-1 or 15 to 35 hr ^-1 or 20 to 30 hr It can be injected with a GHSV of ^-1 . The catalyst and the promoter precursor may be injected in a molar ratio of 1.0x10 ^-6 to 1.0 relative to the transport gas, and the carbon source may be injected in a molar ratio of 1.0 x 10 ^-4 to 1.0 relative to the transport gas.

For example, the carbon source is 0.5 to 5 hr ^-1 , preferably 1 to 3 hr ^-1 of GHSV, and the transport gas is 20 to 30 hr ^-1 , preferably 25 to 30 hr ^-1 GHSV. It can be added by vaporizing the catalyst precursor at a rate of 0.03-0.2 g/hr, preferably 0.05-0.1 g/hr, and the catalyst activator at a rate of 0.01-0.3 g/hr, preferably 0.01-0.2 g/hr. there is.

The GHSV (Gas Hourly Space Velocity) is a value measured in a standard state (0°C, 1 bar), and refers to the ratio of the volume flow rate of the supplied gas to the reactor volume, and refers to a value given a unit time in hours. .

When the transport gas, carbon source, catalyst and promoter precursor are continuously injected, the carbon nanotubes synthesized inside the reaction zone form a continuous aggregate, and the aggregate is collected and drawn out of the high-temperature zone and wound with a winding means to form a fiber. there is.

The winding means may be a spindle, a reel, a drum, a bobbin, or a conveyor, but is not limited thereto, and any means capable of stably winding the discharged carbon nanotube fibers may be used.

After winding the carbon nanotube fibers, the carbon nanotube fibers are passed through a shrink bath containing a solvent to obtain densified and fiberized carbon nanotube fibers. In this case, the solvent may be one or more selected from chlorosulfonic acid, sulfuric acid, hydrochloric acid, nitric acid, aqua regia, trichloroacetic acid, acetone, NMP, and water.

In addition, the wound carbon nanotube fiber may further include an additional heat treatment step, in an air atmosphere at a temperature of 200 to 400 ° C, preferably at a temperature of 250 to 350 ° C. for 15 minutes to 1 hour. may include more. Due to the additional heat treatment process, the density and tensile strength of the carbon nanotube fibers may be significantly improved.

The transport gas may include a liquid and gaseous carbon compound as a carbon source, a catalyst or a catalyst precursor, and may further include a catalyst activator or a catalyst activator precursor. The carbon compound is synthesized into carbon nanotubes by diffusion as a catalyst as a carbon source, and is used in consideration of molecular weight distribution, concentration, viscosity, surface tension, dielectric constant, and the properties of the solvent used.

As the carbon source used for synthesizing the carbon nanotube fibers, one or more selected from the group of hydrocarbons having 1 to 20 carbon atoms may be used, and specifically, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, di It may be one selected from the group consisting of ethyl ether, polyethylene glycol, ethyl formate, mesitylene, tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane.

The catalyst and 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.

In addition, the catalyst activator and the catalyst activator precursor are used as a promoter when synthesizing carbon nanotubes to increase the carbon diffusion rate so that carbon nanotubes are synthesized within a short time. The catalyst activator may be selected from elemental sulfur, sulfur-containing compounds, and combinations thereof, and the sulfur-containing compounds are methylthiol, methylethylsulfide, dimethylthioketone, phenylthiol, diphenylsulfide, pyridine, quinoline, and benzothiol. offenes, thiophenes, and combinations thereof. Preferred examples include thiophene (C ₄ H ₄ S), sulfur, and the like. Thiophene or sulfur reduces the melting point of the catalyst and enables the synthesis of high-purity carbon nanotubes at low temperatures by removing amorphous carbon.

The carbon nanotube fiber used in the present invention has a shape in which carbon nanotubes are aligned in the axial direction, and specifically, a carbon nanotube ribbon, a carbon nanotube having a structure in which carbon nanotubes are aligned in a film shape, is It is defined as a concept encompassing both carbon nanotube fibers, which are structures arranged in the form of fibers, and carbon nanotube yarns, which are twisted structures of carbon nanotube fibers.

The carbon nanotube fibers according to the present invention may have a diameter of 100 nm to 150 μm, for example, 100 nm to 100 μm, or may have a diameter of 1 μm to 100 μm. In addition, carbon nanotubes are continuously aggregated and may be carbon nanotube fibers having a length of several tens of nm to several cm.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

As the vertical reaction tube, the same reaction tube as disclosed in Korean application 10-2017-0119491 of the present applicant was used. The contents of that application are incorporated herein by reference.

<Example 1>

The ferrocene catalyst precursor is vaporized at a rate of 0.06-0.08 g/hr and the sulfur catalyst activator is vaporized at a rate of 0.01-0.03 g/hr, methane as a carbon compound is GHSV of 1-2 hr ^-1 , and the transport gas (hydrogen) is The GHSV of 25-30 hr ^-1 was introduced into the upper part of the vertical cylindrical reaction tube at a temperature of 1,200-1,250°C. The temperature at the inlet of the reaction tube was set at 250 °C, and the temperature at the inlet of the heating furnace was set at 816 °C to control the temperature gradient inside the reactor, so that there was no rotational flow in the upper part of the reaction tube. Then, the carbon nanotube fibers discharged through the outlet at the bottom of the reaction tube were wound with a winding means composed of a bobbin.

<Example 2>

Carbon nanotube fibers were prepared in the same manner as in Example 1, except that the fibers prepared in Example 1 were shrunk with acetone.

<Example 3>

Carbon nanotube fibers were prepared in the same manner as in Example 1, except that the fibers prepared in Example 1 were heat-treated at 300° C. for 30 minutes in an air atmosphere.

<Example 4>

Carbon nanotube fibers were prepared in the same manner as in Example 1, except that the fibers prepared in Example 1 were shrunk using chlorosulfonic acid and then heat-treated at 300° C. for 30 minutes in an air atmosphere.

<Example 5>

Carbon nanotube fibers were prepared in the same manner as in Example 1, except that the amount of catalyst and catalyst activator was three times that of Example 1.

<Comparative Example 1>

In Comparative Example 1, the reaction tube temperature was set to 1175°C. In addition, the temperature of the inlet of the reaction tube was set to 300 ° C, and the temperature of the inlet of the heating furnace was set to be 750 ° C to control the temperature gradient inside the reaction tube, except that rotational flow occurred in the upper part of the reaction tube. Carbon nanotube fibers were prepared in the same manner.

<Experimental example>

The average tensile strength and average porosity of the six prepared carbon nanotube fiber samples were measured by the following method. The measured average tensile strength and average porosity are shown in Table 1 and FIGS. 2 and 3 .

- Measuring method of average tensile strength

Tensile strength was measured using Textechno's FAVIMAT+ equipment, and the load cell range was 210 cN. The gauge length was 2.0 cm, and the experiment was conducted at a speed of 2 mm/min.

- Measuring method of average porosity

After cutting the cross section of the carbon nanotube fiber using a focused ion beam equipment, the cross section was analyzed using a scanning electron microscope (SEM), and the presence of pores inside the carbon nanotube fiber was observed. The cross-sectional analysis results are shown in FIG. 1 . Using the cross-sectional image of the carbon nanotube fiber obtained by the above-described method, the porosity inside the fiber was calculated through image processing.

Image processing was obtained using ImageJ Program (National Institute of Health, USA, ver.1.51j8), and the number of SEM images used to measure porosity was measured to be 10 or more to increase the accuracy of the experiment. Representatively, the image processing data of Example 3 is as follows.

image Number of pixels outside the pores pore area number of pixels Total Area Pixels Porosity (%) #One 1024108 421947 1594368 26.5 #2 1011254 421994 1594368 26.5 #3 1101242 483126 1594368 30.3 #4 1033518 459134 1594368 28.8 #5 1013255 440953 1594368 27.7 #6 1038312 506055 1594368 31.7 #7 1020465 494153 1594368 31.0 #8 1002156 455645 1594368 28.6 #9 1100215 463214 1594368 29.1 #10 1020548 459513 1594368 28.8

The results of measuring the tensile strength and porosity of the samples of Examples and Comparative Examples are as follows.

Experiment# average tensile strength
(N/tex) average porosity
(%) A
(porosity x tensile strength) 1 (Example 1) 1.85 66.5 123.0 2 (Example 2) 2.04 33.7 68.7 3 (Example 3) 2.50 28.9 72.2 4 (Example 4) 2.00 49.8 99.6 5 (Example 5) 3.24 31.9 103.4 6 (comparative example) 0.40 72.3 28.9

As shown from the results of Table 2 and FIG. 2 , it can be seen that the average tensile strength of the carbon nanotube fibers of Examples 1 to 5 is in inverse proportion, and satisfies the ranges of Equations 1 and 2 below.

[Equation 1]

30 ≤ Porosity x Tensile Strength ≤ 125

[Equation 2]

-14.2X + 60 ≤ Y ≤ -14.2X + 95

In the above formula 2,

X is the tensile strength (N/tex) of the carbon nanotube fiber,

Y is the porosity (%) of the carbon nanotube fiber.

On the other hand, it can be seen that the carbon nanotube fiber of Comparative Example has a product of porosity and tensile strength of less than 30 and a tensile strength of only 0.4 N/tex.

Accordingly, the present invention can provide carbon nanotube fibers having improved strength and density by using the conditions of Equations 1 and 2 above.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (12)

The product of the porosity (%) and tensile strength (N/tex) inside the carbon nanotube fiber satisfies the range of Equation 1 below, the average tensile strength of the carbon nanotube fiber is 1.5 N/tex or more, and the average porosity is 50% Carbon nanotube fibers of:
[Equation 1]
30 ≤ Porosity (%) x Tensile strength (N/tex) ≤ 125
In Equation 1, the porosity is
It is a value defined as porosity (%) = (area of pore area/total area) x 100. According to claim 1,
In the carbon nanotube fiber satisfying the range of Formula 1, the porosity (%) and tensile strength (N/tex) of the carbon nanotube fiber both satisfy the range of Formula 2 below:
[Equation 2]
-14.2X + 60 ≤ Y ≤ -14.2X + 95
In the above formula 2,
X is the tensile strength (N/tex) of the carbon nanotube fiber,
Y is the porosity (%) of the carbon nanotube fiber. delete delete The method of claim 1,
The porosity is calculated through image processing using a scanning electron microscope image, and the carbon nanotube fiber is an average value measured for 10 or more scanning electron microscope images. According to claim 1,
A carbon nanotube fiber having a diameter of 100 nm to 150 μm of the carbon nanotube fiber. heating a vertical reaction tube equipped with a heating furnace to a temperature of 1,000 to 3,000° C. and then introducing a catalyst precursor, a catalyst activator, a carbon source gas, and a transport gas to the upper end of the reaction tube;
adjusting the temperature gradient inside the reaction tube by adjusting the inlet temperature of the reaction tube to 200 to 300°C and the temperature at the inlet to 700 to 900°C;
winding the carbon nanotube fibers discharged to the outlet of the lower end of the reaction tube with a winding means; and
The method for producing the carbon nanotube fiber of claim 1, comprising at least one post-treatment step selected from the following steps a) and b) after the step of winding the carbon nanotube fiber:
a) shrinking the wound carbon nanotube fiber by passing it through a bath containing at least one solvent selected from chlorosulfonic acid and acetone;
b) heat-treating the wound carbon nanotube fibers at a temperature of 200 to 400° C. in an air atmosphere for 15 minutes to 1 hour. 8. The method of claim 7,
The method for producing carbon nanotube fibers, wherein the catalyst activator is selected from elemental sulfur, sulfur-containing compounds, and combinations thereof. delete delete delete delete

Images