KR20180047307A - Control method of linear density of cnt fiber aggregates - Google Patents

Abstract

The present invention relates to a linear density control method of carbon nanotube fibers. According to an embodiment of the present invention, the linear density control method of carbon nanotube fibers manufactures carbon nanotube fibers by spinning a spinning raw material to carrier gas. According to the present invention, the linear density control method of carbon nanotube fibers can improve manufacturing efficiency.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to carbon nanotube fibers,

The present invention relates to a method for producing carbon nanotube fibers comprising carbon nanotubes.

Carbon nanotubes (CNTs), a kind of carbon isotopes, have a diameter of several to several tens of nanometers and are several hundreds of micrometers to several millimeters in length. Since their report in the journal Nature in 1991 by Dr Iijima in 1991, Due to its physical properties and high aspect ratio, research has been conducted in various fields. The inherent properties of these carbon nanotubes are due to the sp ² bonds of carbon, stronger than iron, lighter than aluminum, and exhibit electrical conductivity similar to that of metals. According to the number of nanotubes, single-wall carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-walled carbon nanotubes (Multi- Wall carbon nanotube (MWNT), and can be divided into zigzag, armchair, and chiral structures depending on the asymmetry / chirality.

To date, most of the studies have focused on dispersing powdered carbon nanotubes as a reinforcing agent for composites, or for producing transparent conductive films using dispersion solutions, and have already been commercialized in some fields. However, in order to use carbon nanotubes in composite materials and transparent conductive films, dispersion of carbon nanotubes is important. Due to the strong van der Waals force of carbon nanotubes, they are dispersed at a high concentration and dispersed It is not easy to do. Also, in the case of a composite material in which carbon nanotubes are used as a reinforcement material, it is difficult to sufficiently manifest the excellent properties of carbon nanotubes.

Recently, carbon nanotube fibrillation researches have been carried out to fabricate carbon nanotube structures that fully manifest the properties of carbon nanotubes in recent years.

Coagulation spinning, liquid-crystalline spinning, and direct spinning are typical examples of methods of forming fibers using a dispersion solution containing carbon nanotubes and a dispersant .

Coagulation spinning is a method in which a dispersing solution containing carbon nanotubes and a dispersing agent is injected into a polymer solution to allow the dispersing agent in the dispersing solution to pass through the polymer solution and the polymer is substituted for the site to act as a binder, .

The liquid crystal spinning method is a method in which a carbon nanotube solution is fibrousized using a property of forming a liquid crystal under a specific condition. This method is advantageous in that it can produce carbon nanotube fibers having good orientation, but has a disadvantage in that the spinning speed is very slow and the liquid crystal forming conditions of carbon nanotubes are difficult.

As shown in FIG. 1, the direct spinning method is a method in which carbon nanotubes are synthesized and transported in a heating furnace by injecting a liquid carbon source and a catalyst together with a carrier gas into an upper injection port by a vertically erected high temperature heating carbon nanotube aggregates that have been brought to the lower end of the heating furnace together with carrier gas are winded up inside the heating furnace (FIG. 1A) or outside (FIG. 1B) to obtain fibers.

Carbon nanotubes (CNTs) can be roughly divided into single-wall CNTs and multi-wall CNTs depending on the number of graphene layers. Among the multi-wall CNTs, two-layered CNTs may be classified and classified into separate application fields. The mechanical strength of the CNT itself, especially the tensile strength, is very high, exceeding 100 GPa. However, since the synthesized CNT is a short fiber having a short length, application is restricted. In order to solve such a problem, a method of making CNT fibers, which are long fibers, by connecting short fibers CNTs has been recently studied.

Variables affecting the strength of CNT fiber include CNT length, diameter, defect, internal void, CNT inter-alignment, and attraction.

The strength of the CNT fiber increases as the linear density of the fiber increases. Therefore, in order to apply the CNT fiber to the actual industrial field, the strength to withstand the fiber till it breaks is important, so a method of adjusting the linear density of the fiber to the desired level is needed.

It is an object of the present invention to provide a method for controlling the linear density of carbon nanotube fibers composed of carbon nanotubes to a desired ratio.

In order to solve the above problems,

The carbon nanotube fiber according to claim 1, wherein the carbon nanotube fiber is prepared by spinning a spinning raw material containing a carbon source in the presence of a carrier gas containing a reducing gas, And a manufacturing method thereof.

[Equation 1]

lambda _m = 0.0032 exp (72.551 x)

In this formula,

x is the original consumption of reducing gas and carbon source [carbon source / reducing gas]

lambda _m is the linear density (tex) of the carbon nanotube fibers.

According to one embodiment, the original consumption of the carrier gas and the carbon source [carbon source / reducing gas] may be selected in the range of 0.01 to 0.05.

According to one embodiment, the linear density of the carbon nanotube fibers may range from 0.001 to 0.5 tex.

The reducing gas may include hydrogen gas, ammonia gas, or a mixed gas thereof.

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

The spinning raw material may be one in which a catalyst precursor and a catalyst activator are dispersed in a liquid or gaseous carbon compound.

The liquid or gaseous carbon compound may be at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, vinylacetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, diethyl ether, polyethylene glycol, And one or more selected from the group consisting of tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane.

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

The catalyst activator may include at least one member selected from the group consisting of a sulfur element, a sulfur-containing compound, and a combination thereof. Specific examples thereof include methylthiol, methylethylsulfide, dimethylthioketone, phenylthiol, phenylthiol, di Phenyl sulfide, pyridine, quinoline, benzothiophene, thiophene, and combinations thereof.

According to a preferred embodiment, carbon nanotubes may be formed from the spinning raw material and fused continuously to spin the carbon nanotube fibers directly.

The supply amount of the spinning raw material may be selected in the range of 10 to 500 ml / min, and the supply flow rate of the carrier gas may be selected in the range of 1 to 5 l / min.

Other details of the embodiments of the present invention are included in the following detailed description.

The present invention can improve the production efficiency of carbon nanotube fibers composed of single-wall carbon nanotubes by a simple process of controlling the molar ratio or the flow ratio of the reducing gas among the carbon source and the carrier gas injected in the production of the carbon nanotube fiber aggregate. The carbon nanotube fibers produced by the method according to the present invention are useful as reinforcements for multifunctional composites, strain and damage detectors using stable and repeated piezoresistive effects, transmission lines using high conductivity, high specific surface area, excellent mechanical properties and electrical conductivity It is expected to be applicable to various fields such as electrochemical devices used, for example, microelectrode materials for sensing biomaterials, supercapacitors and actuators.

1 schematically shows a method for producing carbon nanotube fibers by direct spinning.
2 is a graph showing the relationship between the carbon source / reducing gas source consumption and linear density used in the production of carbon nanotube fibers.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

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

The term "injection" as used herein may be described interchangeably with "inlet and outlet" herein, and may be understood to mean the flow of liquid, gas or heat, etc. into the required place .

The term "carbon nanotube fibers" in the present specification refers to both carbon nanotubes grown in a fiber form or formed by fusing a plurality of carbon nanotubes in a fiber form.

As used herein, the term " raw consumption "refers to the ratio of the carbon element of the carbon source to the element of the reducing gas. According to a preferred embodiment, when the reducing gas is used as the hydrogen gas, the original consumption of the carbon source and the carrier gas may be C / H ratio.

Hereinafter, a method for fabricating carbon nanotube fibers according to embodiments of the present invention will be described in detail.

Techniques for producing carbon nanotube fibers include solution spinning, array spinning, aerogel spinning, film twisting / rolling methods, and the like. The present invention follows a process of directly spinning carbon nanotube fibers or ribbons from a carbon nanotube aerogel formed immediately after the introduction of a raw material in a reactor by chemical vapor deposition (CD).

In the direct spinning, carbon nanotubes are injected into a vertical furnace at a constant rate together with a carrier gas to synthesize carbon nanotubes in a furnace and fuse them together Is a process for continuously producing carbon nanotube fibers composed of only purely carbon nanotubes.

The spinning raw material containing a carbon source is carbonized and graphitized while flowing from the upper end to the lower end or from the lower end to the upper end of the heating furnace, thereby forming carbon nanotube fibers composed of continuous aggregates of carbon nanotubes (sock or aggregates).

The present invention can induce carbon nanotube fibers composed of single-walled carbon nanotubes to be formed by controlling the molar ratio of hydrogen gas in the carbon source and the carrier gas in the spinning raw material injected to produce carbon nanotube fibers.

The spinning raw material may include a carbon compound, a catalyst, or a catalyst precursor, and each is dispersed and introduced into the gas phase. When an excess catalyst or a catalyst precursor is used in comparison with the carbon source, the catalyst acts as an impurity, which makes it difficult to obtain high-purity carbon nanotube fibers. Rather, it may hinder thermal, electrical, and physical properties of carbon nanotube fibers .

The catalyst precursor is a substance that is not contained in the catalyst cycle but is changed into an active catalyst (or produces an active catalyst) in the system of the catalytic reaction, and the CNT is synthesized after the catalyst precursor forms a catalyst.

In the present invention, the catalyst or the 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. The catalyst may also be in the form of nanoparticles and may be in metallocene form, such as ferrocene, preferably a compound containing iron, nickel, cobalt, and the like.

In the present invention, the spinning raw material may further comprise a catalytic activator. Generally, carbon nanotubes are synthesized by diffusion of carbon into the catalyst in the molten state of the catalyst, followed by precipitation of the carbon nanotubes. The catalyst activator is used as a promoter in the synthesis of carbon nanotubes to increase the carbon diffusion rate, Thereby synthesizing carbon nanotubes.

As the catalytic activator, for example, a sulfur element and a sulfur-containing compound can be used. Specific examples thereof include sulfur-containing aliphatic compounds such as methylthiol, methylethylsulfide, dimethylthioketone and the like; Sulfur-containing aromatic compounds such as phenylthiol, diphenylsulfide and the like; Sulfur-containing heterocyclic compounds such as pyridine, quinoline, benzothiophene, thiophene and the like; It can be sulfur as an element. Preferably sulfur or thiophene, and more preferably sulfur. Sulfur reduces the melting point of the catalyst and removes the amorphous carbon, allowing synthesis of high purity carbon nanotubes at low temperatures.

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 vapor in the vapor carbon compound. Therefore, the liquid carbon compound can be injected by dissolving the catalyst precursor or the catalytic activator, and vaporized into the gas-phase carbon compound to be injected into the gas form

In the present invention, the carbon compound may be in a liquid or gas phase, and it may be synthesized into carbon nanotubes by diffusing as a carbon source as a catalyst. The carbon nanotubes may be synthesized in consideration of molecular weight distribution, concentration, viscosity, surface tension, dielectric constant, .

The liquid or gaseous carbon compound may be at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, vinylacetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, diethyl ether, polyethylene glycol, And may include at least one member selected from the group consisting of tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane.

Specifically, the liquid carbon compound may be at least one selected from the group consisting of ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetate, diethyl ether, polyethylene glycol, ethyl formate, mesitylene, tetrahydrofuran (THF) DMF), dichloromethane, hexane, benzene, carbon tetrachloride, and pentane. (CH 2 CH 2 O) 9], 1-propanol (CH 3 CH 2 CH 2 OH), acetone (CH 3 OCH 3), and the like, May include at least one selected from the group consisting of ethyl formate (CH3CH2COOH), benzene (C6H6), hexane (C6H14), and mesitylene [C6H3 (CH3) 3].

The gas-phase carbon compound may include at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, and vinyl acetylene.

The carbon nanotube fiber according to claim 1, wherein the carbon nanotube fiber is prepared by spinning a spinning raw material containing a carbon source in the presence of a carrier gas containing a reducing gas, And a manufacturing method thereof.

[Equation 1]

lambda _m = 0.0032 exp (72.551 x)

In this formula,

x is the original consumption of the carbon source and the reducing gas [carbon source / reducing gas]

lambda _m is the linear density (tex) of the carbon nanotube fibers.

According to one embodiment, the original consumption of the reducing gas in the carbon source and the carrier gas may be selected in the range of 0.01 to 0.05.

The inventors of the present invention have confirmed from the above range that the raw consumption of the source and the linear density of the carbon nanotube fibers have a linear proportional relationship according to the relational expression.

According to one embodiment, the linear density of the carbon nanotube fibers may range from 0.001 to 0.5 tex, preferably from 0.01 to 0.2 tex.

According to one embodiment, the reducing gas may be a hydrogen gas, an ammonia gas, or a combination thereof.

Further, the carrier gas may further include an inert gas. The inert gas may include a gas containing nitrogen, helium, neon, argon, krypton, xenon, radon or a mixture thereof. Such an inert gas is chemically very stable, Therefore, the carbon nanotube can flow and move due to the inflow of gas without reacting with the carbon nanotube (CNT).

In the present invention, the feed flow rate of the raw material supplied to the reaction zone may be 10 to 500 ml / min, preferably 50 to 200 ml / min or 70 to 160 ml / min.

The flow rate of the carrier gas injected into the reaction region can be determined in a range satisfying the condition of the above-mentioned formula (1). For example, in the case of hydrogen gas, it can be appropriately selected in the range of 1 to 5 L / min or 1.5 to 3 L / min.

According to another embodiment, the carrier gas may be injected at a linear velocity of 1 to 5 cm / sec, preferably at a linear velocity of 1.5 to 3 cm / sec or 1.8 to 2.5 cm / sec. The carrier injection linear velocity may vary depending on the kind of the carrier gas, the reactor size, the catalyst type, and the like.

According to a preferred embodiment, the carbon nanotube fibers can be produced by direct spinning, in which the carbon nanotube fibers or ribbon are radiated directly from the carbon nanotube aerogels formed by chemical vapor deposition. The direct spinning is carried out by adding a catalyst to a carbon source and injecting the carbon nanotube into a vertical furnace in a vertical furnace together with a carrier gas to synthesize carbon nanotubes in a heating furnace, Is a process for continuously producing carbon nanotube fibers composed of only carbon nanotubes.

The reaction zone of the high-temperature furnace is a region in which the carbon source forms carbon nanotubes by the graphenization catalyst and simultaneously forms a continuous aggregate. When the spinning raw material is reacted in the reaction zone, carbon nanotubes are synthesized, and the synthesized carbon nanotubes are grown or fused to form a continuous carbon nanotube fiber. Then, the formed carbon nanotube fibers are wound using a winding means.

The temperature of the reaction zone may be 1,000 to 3,000 占 폚. Preferably 1,000 to 2,000 ° C, 1,000 to 1,500 ° C or 1,000 to 1,300 ° C, and more preferably 1,150 to 1,250 ° C. If it is less than 1000 ° C, carbon nanotube fibers may not be formed. If the temperature is higher than 3000 ° C, carbon nanotubes may be vaporized. Therefore, the above range is preferable.

The resulting carbon nanotube fibers can be wound and collected. The winding speed influences the orientation of the carbon nanotubes in the fiber in the fiber axis direction, thereby determining the thermal, electrical, and physical properties of the carbon nanotube fibers. Preferably, it can be wound in the range of 5 to 100 rpm.

According to the present invention, carbon nanotube fibers composed of single-walled carbon nanotubes can be easily provided, and fibers made of single-walled carbon nanotubes can minimize the diameter of carbon nanotubes. As a result, The strength can be improved.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Manufacturing Example: Carbon Nanotube Fiber Synthesis

(Hydrogen) is fed at a rate of 70 to 152.5 ml / min as a carbon compound, and the carrier gas (hydrogen) is fed to the reaction vessel at a rate of 0.05 to 0.2 g / And introduced at the top of a cylindrical reactor at a temperature of 1200 ° C at a rate of 1.8 to 2.2 L / min. Then, the carbon nanotube fibers discharged to the discharge port at the bottom of the reactor were wound by a winding means composed of a bobbin. The molar ratios of methane and hydrogen gas were adjusted as shown in Table 1 below.

division Consumption of C / H Linear density (tex) Example 1 0.032252 0.034291 Example 2 0.037866 0.058614 Example 3 0.027910 0.024258 Example 4 0.036259 0.050088 Example 5 0.049618 0.120073

Test Example 1: Strength of Carbon Nanotube Fibers

The linear density of carbon nanotube fibers prepared according to the examples was measured by FAVIMAT and is shown in FIG. The principle of linear density measurement is the vibroscopic testing principle, ISO 1973; ASTM D 1577; BISFA 1985/1989 chapter F and so on. It is possible to obtain the linear density by measuring the resonance frequency by applying a tensile force to the end of a single fiber and applying a tension to the whole fiber, applying vibration to the fiber, and using the following equation.

Tt = FV / (4 · f ² · L ² )

Tt = linear density

FV = pre-tensioning force

f = resonance frequency

L = test section length

The measurement gauge length was 20.0 mm and the test speed was 2.0 mm / min.

Fig. 2 is a graph showing the relationship between the linear density? _M (tex) of the CNT fibers to the C / H raw consumption (x), and it is confirmed that the following formula (1) is satisfied.

[Equation 1]

lambda _m = 0.0032 exp (72.551 x)

In this formula,

x is the original consumption of the carbon source and the reducing gas [carbon source / reducing gas]

lambda _m is the linear density (tex) of the carbon nanotube fibers.

In FIG. 2, the x-axis represents the raw consumption of the reducing gas and the carbon source [the carbon source / the reducing gas], and the y-axis represents the logarithmic value of the linear density of the carbon nanotube fiber.

From the above results, it can be seen that the linear density and the strength of the carbon nanotube fibers can be easily controlled by controlling the supply ratio of the carbon source and the carrier gas.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (12)

The carbon nanotube fiber according to claim 1, wherein the carbon nanotube fiber is prepared by spinning a spinning raw material containing a carbon source in the presence of a carrier gas containing a reducing gas, Manufacturing method:
[Equation 1]
lambda _m = 0.0032 exp (72.551 x)
In this formula,
x is the original consumption of the carbon source and the reducing gas [carbon source / reducing gas]
lambda _m is the linear density (tex) of the carbon nanotube fibers. The method according to claim 1,
Wherein the carbon source and the reduced gas have an original consumption (carbon source / reducing gas) of 0.01 to 0.05. The method according to claim 1,
Wherein the linear density of the carbon nanotube fibers is in the range of 0.001 to 0.5 tex. The method according to claim 1,
Wherein the reducing gas comprises hydrogen gas, ammonia gas, or a mixed gas thereof. The method according to claim 1,
Wherein the carrier gas further comprises an inert gas. The method according to claim 1,
Wherein the spinning raw material is a catalyst precursor, a catalytic activator, or a combination thereof dispersed in a liquid or gaseous carbon compound. The method according to claim 6,
The liquid or gaseous carbon compound may be at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, vinyl acetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, diethyl ether, polyethylene glycol, Wherein the carbon nanotube fiber comprises at least one selected from the group consisting of tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane. The method of claim 6, wherein the catalyst precursor comprises at least one selected from the group consisting of iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium and oxides thereof. 9. The method of claim 8,
Wherein the catalyst precursor is in a metallocene form. The method according to claim 6,
Wherein the catalyst activator comprises at least one selected from the group consisting of a sulfur element, a sulfur-containing compound, and a combination thereof. The method according to claim 6,
Wherein the catalyst activator is at least one compound selected from the group consisting of methylthiol, methyl ethyl sulfide, dimethylthioketone, phenylthiol, phenylthiol, diphenylsulfide, pyridine, quinoline, benzothiophene, thiophene, Carbon nanotube fibers. The method according to claim 1,
Wherein the carbon nanotube fibers are directly spinned by forming carbon nanotubes from the spinning raw materials and fusing them continuously.

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