WO2019132265A1 - Entangled type carbon nanotubes and manufacturing method therefor - Google Patents

Abstract

The present invention relates to an entangled type carbon nanotubes having a bulk density of 31-85 ㎏/㎥ and a ratio of tap density to bulk density of 1.37-2.05,and to a manufacturing method therefor.

Description

Entangled carbon nanotubes and a method for manufacturing the same

[Mutual quotation with related application]

The present invention claims the benefit of priority based on Korean Patent Application No. 10-2017-0179768 filed on December 27, 2017, and Korean Patent Application No. 10-2018-0146925 filed on November 21, 2016, The disclosure of which is incorporated herein by reference in its entirety.

[TECHNICAL FIELD]

The present invention relates to an entangled carbon nanotube and a method for manufacturing the same, and more particularly, to an entangled carbon nanotube having improved dispersibility and conductivity by controlling a ratio of a tap density to a bulk density, and a method for manufacturing the same .

Carbon nanotubes, which are one kind of fine carbon fibers, are tubular carbon having an average diameter of 1 μm or less. It is expected to be applied to various fields due to its high conductivity, tensile strength and heat resistance due to its specific structure. However, despite the availability of such carbon nanotubes, the use of carbon nanotubes is limited due to their low solubility and dispersibility. The carbon nanotubes were linearly dispersed in a dispersion medium, and a conductive material dispersion was prepared and used. However, carbon nanotubes are not stable in dispersion medium due to strong Van der Waals attraction between them, and coagulation phenomenon occurs.

Various attempts have been made to solve these problems. Specifically, a method of dispersing carbon nanotubes in a dispersion medium through a mechanical dispersion treatment such as an ultrasonic treatment has been proposed. However, this method has excellent dispersibility during the irradiation of ultrasonic waves, but there is a problem that aggregation of carbon nanotubes starts when the ultrasonic irradiation is finished. In addition, a method of dispersing and stabilizing carbon nanotubes by using various dispersants has been proposed. However, these methods also have a problem in that when the carbon nanotubes are dispersed in the dispersion medium at a high concentration, the handling becomes difficult due to an increase in viscosity.

Accordingly, development of carbon nanotubes with improved dispersibility without deterioration of conductivity is required.

An object of the present invention is to provide an entangled carbon nanotube excellent in dispersibility and conductivity and a method for producing the same.

In order to solve the above problems, the present invention provides an entangled carbon nanotube having a bulk density of 31 to 85 kg / m 3 and satisfying the following formula 1:

<Formula 1>

1.37? X / Y? 2.05

In Equation (1)

X is the tap density (unit: kg / m &lt; 3 &gt;) of the entangled carbon nanotube,

Y is the bulk density (unit: kg / m3) of the entangled carbon nanotube.

The present invention also relates to a process for preparing a mixture comprising mixing an organic acid and a vanadium precursor in a molar ratio of 1: 0.0463 to 1: 0.0875 to prepare a mixture; Mixing the mixture with a cobalt precursor to produce a catalyst precursor; Subjecting the aluminum hydroxide to a first heat treatment to produce a support; Supporting a catalyst precursor on the support, and then performing a second heat treatment to produce a supported catalyst; And reacting the supported catalyst with the carbon-based compound. The present invention also provides a method for manufacturing the entangled carbon nanotube.

The entangled carbon nanotube according to the present invention is excellent in conductivity and dispersibility and can be contained in a high concentration in the carbon nanotube dispersion.

1 is a scanning electron microscope image of a surface of an Entangled carbon nanotube of Example 3 magnified 400 times.

2 is an image of a scanning electron microscope obtained by enlarging the surface of the entangled carbon nanotube of Example 3 1,000 times.

3 is a scanning electron microscope image of the surface of the Entangled carbon nanotube of Example 4 magnified 400 times.

4 is an image of a scanning electron microscope obtained by enlarging the surface of the entangled carbon nanotube of Example 4 1,000 times.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

In the present invention, a carbon nanotube refers to a pristine carbon nanotube that has not been subjected to any further processing.

In the present invention, the entangled carbon nanotubes refer to a secondary structure in which a plurality of carbon nanotubes are entangled without a uniform shape such as a bundle or a rope.

In the present invention, the bundle-type carbon nanotubes are formed by arranging a plurality of carbon nanotubes in a bundle or rope-like secondary structure in which axes in the longitudinal direction of the unit are aligned in substantially the same orientation, Shape.

In the present invention, the unit of carbon nanotubes is a graphite sheet having a nano-sized diameter cylinder shape and has an sp ² bonding structure. At this time, depending on the angle and structure of the graphite surface, the characteristics of the conductor or semiconductor may be exhibited. The unit of the carbon nanotube may be a single-walled carbon nanotube (SWCNT), a double-walled carbon nanotube (DWCNT), or a multi-walled carbon nanotube (DWCNT) according to the number of walls MWCNT, and multi-walled carbon nanotubes. The thinner the wall thickness, the lower the resistance.

In the present invention, the bulk density of the carbon nanotubes can be measured according to ASTM B329, specifically, according to ASTM B329-06. The bulk density can be measured using a Scott volumeter (Version USP 616).

In the present invention, the bulk density of the carbon nanotubes can be measured in accordance with the laboratory conditions, and substantially the same result as the result based on the above rule can be obtained.

When measuring in the laboratory, place 5 ml cylinder (manufacturer: DURAN, material: glass) on the balance and set the zero point, put 5 ml of carbon nano tube in the cylinder, adjust the height of carbon nanotube and eye level, , The volume is measured, the weight is measured on the scale, and then the bulk density can be calculated by the following formula.

Bulk density (kg / m 3) = Weight of carbon nanotube (kg) / Volume of carbon nanotube (m 3)

In the present invention, the Tapped Bulk Density (TD) of carbon nanotubes is measured in accordance with ASTM B527-06, and specifically, can be measured using TAP-2S manufactured by LOGAN.

In the present invention, the tap density of the carbon nanotubes can be measured in accordance with the laboratory conditions, and even when the measurement is performed in accordance with the laboratory scale, substantially the same results as those based on the above rule can be obtained.

When measuring in a laboratory, put a 5 mL cylinder (manufacturer: DURAN, material: glass) on the balance, align the zero point, put the carbon nano tube in the cylinder, read the scale by adjusting the height of the carbon nanotube and eye level, The weight can be measured by placing it on the balance. After tapping the cylinder lightly against the floor about 100 times, read the scale of the cylinder, measure the volume, and calculate the tap density by the following formula.

Tap density (kg / m 3) = (weight of carbon nanotube (kg)) / (volume of carbon nanotube after tapping 100 times (m 3))

In the present invention, the specific surface area of the carbon nanotube is measured by the BET method and can be calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77 K) using, for example, BEL Japan's BELSORP-mino II .

In the present invention, the average diameter and length of the carbon nanotube unit can be measured using an electric field-type scanning electron microscope.

One. Entangled  Carbon nanotube

The entangled carbon nanotube according to an embodiment of the present invention has a bulk density of 31 to 85 kg / m 3 and satisfies the following formula 1:

<Formula 1>

1.37? X / Y? 2.05

In Equation (1)

X is the tap density (unit: kg / m &lt; 3 &gt;) of the entangled carbon nanotube,

Y is the bulk density (unit: kg / m3) of the entangled carbon nanotube.

If the bulk density of the entangled carbon nanotubes is less than the above-mentioned range, the properties of the entangled carbon nanotubes can not be realized. Therefore, the carbon nanotubes can not be dispersed in the dispersion medium at a high concentration in the production of the carbon nanotube dispersion. When the bulk density of the entangled carbon nanotubes exceeds the above range, the carbon nanotube units constituting the entangled carbon nanotubes are too close to each other and are not easily released in the solvent. As a result, there is a high possibility that the carbon nanotube unit is broken during the dispersion process of the ingot-type carbon nanotubes, and as a result, the conductivity may be deteriorated.

The bulk density of the entangled carbon nanotubes may be preferably 32 to 80 kg / m &lt; 3 &gt;, more preferably 32 to 68 kg / m &lt; 3 &gt;. When the above-mentioned range is satisfied, the carbon nanotube dispersion can be sufficiently dispersed and dispersed at a high concentration in the production of the carbon nanotube dispersion.

The formula 1 is an index showing the morphology of the entangled carbon nanotube. The value of the formula 1 may be 1.37 to 2.05, preferably 1.4 to 2.0, and more preferably 1.49 to 2.0. When the value of the formula 1 is less than the above-mentioned range, it means that the carbon nanotube units are entangled carbon nanotubes which are closely intertwined with each other. Therefore, it is difficult for the carbon nanotube units to be easily dispersed in the production of the carbon nanotube dispersion. When the value of the formula 1 exceeds the above range, it means that the distance between the carbon nanotube units is wide due to the interaction between the carbon nanotube units, so that it is difficult to disperse the carbon nanotube dispersion at a high concentration in the production of the carbon nanotube dispersion.

Entangled carbon nanotubes satisfying the above-described bulk density and Equation 1 have sufficient particle properties as conventional Entangled carbon nanotubes, and have a loose structure between carbon nanotubes like bundled carbon nanotubes Lt; / RTI &gt; That is, the shape may be an entangled shape, or may have some characteristics of a bundled carbon nanotube. Accordingly, the entangled carbon nanotubes can be dispersed at a high concentration because the dispersion of the carbon nanotubes may occur slowly during the production of the carbon nanotube dispersion. Also, since the carbon nanotube units are loose, the carbon nanotube units can be more easily released than the conventional entangled carbon nanotube unit when dispersed in the dispersion medium. As a result, the breakage of the carbon nanotube unit during the dispersion process is reduced, and as a result, the carbon nanotube unit having a relatively long length in the dispersion medium can be present. Accordingly, the conductivity of the carbon nanotube dispersion can be further improved.

The tap density of the entangled carbon nanotubes may be preferably 63 to 116 kg / m 3, and more preferably 65 to 102 kg / m 3. When the above-mentioned range is satisfied, the carbon nanotube unit is loosened between the carbon nanotube unit and the carbon nanotube unit in the dispersion medium, As a result, a relatively long carbon nanotube unit can be present in the dispersion medium. Accordingly, the conductivity of the carbon nanotube dispersion can be further improved.

The BET specific surface area of the entangled carbon nanotube may be 100 to 300 m 2 / g, preferably 150 to 280 m 2 / g, and more preferably 170 to 250 m 2 / g. When the above-mentioned range is satisfied, powder resistance is excellent, and it is advantageous for high-concentration dispersion.

The entangled carbon nanotubes may have a powder resistance value of 0.0171? · Cm or less, a maximum dispersion concentration of 3.3% by weight or more, preferably a powder resistance value of 0.0170? · Cm or less and a maximum dispersion concentration of 3.4% More preferably, the powder resistance value may be 0.0168? 占 ㎝ m or less, and the maximum dispersion concentration may be 3.5% by weight or more. When the above-mentioned conditions are satisfied, the entangled carbon nanotubes having excellent conductivity can be contained in the carbon nanotube dispersion liquid at a high concentration, so that they may be more suitable than the conductive carbon nanotubes.

Herein, the maximum dispersion concentration of the entangled carbon nanotubes is determined by preparing a carbon nanotube dispersion by gradually injecting carbon nanotubes into N-methylpyrrolidone, and thereafter dispersing the maximum amount of carbon nanotubes dispersible in the carbon nanotube dispersion . &Lt; / RTI &gt; The powder resistance value of the ingot-type carbon nanotubes was measured by filling the insulating mold with the ingot-type carbon nanotubes at 1 g / cc, pressing the mixture, and then using Loresta-GX (trade name: MITSUBISHI CHEMICAL ANALYTECH) The surface current and voltage can be measured and calculated with four probes.

The average diameter of the unit bodies of the entangled carbon nanotubes may be preferably 30 nm or less, more preferably 10 to 30 nm. When the above-mentioned range is satisfied, the dispersibility and the conductivity can be improved.

The average length of the unit pieces of the entangled carbon nanotubes may be preferably 0.5 μm to 200 μm, more preferably 10 to 60 μm. When the above-mentioned range is satisfied, it is excellent in electrical conductivity and strength, and stable at room temperature and high temperature.

The entangled carbon nanotube unit preferably has an aspect ratio defined by the ratio of the length of the carbon nanotube unit (the length of the long axis passing through the center of the unit) to the diameter of the carbon nanotube unit (passing the center of the unit and the length of the minor axis perpendicular to the long axis) May be from 5 to 50,000, and more preferably from 10 to 20,000.

The average diameter and length of the carbon nanotube unit can be measured using an electric field scanning electron microscope.

The carbon nanotube layer surface per unit interval is a carbon crystal obtained by X-ray diffraction method (d ₀₀₂₎ and to the O.335 O.342 nm, layer surface spacing _{(d 002) <O.3448-0.0028 (logφ} ) ( wherein , and? is the average diameter of the carbon nanotube unit), and the thickness Lc of the crystal in the C axis direction may be 40 nm or less. The interplanar spacing (d ₀₀₂ ) may preferably be less than 0.3444-0.0028 (1og φ), and more preferably less than 0.3441-0.0028 (log φ). When the above range is satisfied, the crystallinity of the carbon nanotube unit is improved, so that the conductivity of the entangled carbon nanotube including the same can be further improved.

2. Entangled  Method for manufacturing carbon nanotubes

The entangled carbon nanotube according to an embodiment of the present invention comprises: 1) mixing an organic acid and a vanadium precursor in a molar ratio of 1: 0.0463 to 1: 0.0875 to prepare a mixture; 2) preparing a catalyst precursor by mixing the mixture with a cobalt precursor; 3) subjecting the aluminum hydroxide to a first heat treatment to produce a support; 4) supporting a catalyst precursor on the support, and then performing a second heat treatment to produce a supported catalyst; 5) and reacting the supported catalyst with the carbon-based compound.

Hereinafter, each step of the method for manufacturing the entangled carbon nanotube according to one embodiment of the present invention will be described in more detail.

1) Step of preparing the mixture

First, an organic acid and a vanadium precursor are mixed in a molar ratio of 1: 0.0463 to 1: 0.0875 to prepare a mixture.

The organic acid and the vanadium precursor can be mixed preferably in a molar ratio of 1: 0.047 to 1: 0.086, more preferably in a molar ratio of 1: 0.0475 to 1: 0.077. When the above-mentioned range is satisfied, it is possible to produce an entangled carbon nanotube having a low bulk density and a low tap density that can be dispersed at high concentration in a conductive material dispersion.

If the molar ratio of the organic acid to the vanadium precursor is less than the above-mentioned range, the particle size distribution of the catalyst particles becomes small. When the molar ratio of the organic acid to the vanadium precursor exceeds the above-mentioned range, bundle-type carbon nanotubes are produced in addition to the entangled carbon nanotubes.

The organic acid may be at least one member selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid, of which citric acid is preferable.

The vanadium precursor may be a salt of a vanadium compound, preferably at least one selected from the group consisting of NH ₄ VO ₃ , NaVO ₃ , V ₂ O ₅ and V (C ₅ H ₇ O ₂ ) ₃ , NH ₄ VO ₃ is more preferable.

2) Step of preparing catalyst precursor

The mixture and the cobalt precursor are then mixed to produce a catalyst precursor.

The mixture and the cobalt precursor may be mixed so that the molar ratio of vanadium and cobalt is 1: 1 to 1: 100, preferably 1: 5 to 1:20. When the above-mentioned range is satisfied, there is an advantage that the yield is increased.

The cobalt precursor may be a salt of the cobalt compound, preferably _{Co (NO 3) 2 · 6H} 2 O, CoCl 2 · 6H 2 O, Co 2 (CO) 8, [Co 2 (CO) 6 (t-BuC = CH)] may be at least one selected from the group consisting, of which more preferably _{Co (NO 3) 2 · 6H} 2 O (a)

The mixture and the cobalt precursor, that is, the organic acid, the vanadium precursor, and the cobalt precursor can be used in the form of a solution dissolved in a solvent, and the solvent can be at least one kind selected from the group consisting of water, methanol and ethanol, desirable.

The concentration of the citric acid, vanadium precursor and cobalt precursor in the solution may be preferably 0.1 to 3 g / ml, more preferably 0.5 to 2 g / ml, even more preferably 0.7 to 1.5 g / ml .

3) Step of preparing the support

Then, aluminum hydroxide (Al (OH) ₃ ) is subjected to a first heat treatment to produce a support.

The aluminum hydroxide may be pretreated before performing the first heat treatment.

The pretreatment may be carried out at 50 to 150 ° C for 1 to 24 hours. By performing the pretreatment, the residual solvent or impurities that may be present on the surface of the aluminum hydroxide can be removed.

The aluminum hydroxide may have an average particle diameter of 20 to 200 占 퐉, a porosity of 0.1 to 1.0 cm3 / g, and a specific surface area of less than 1 m2 / g.

The first heat treatment may be performed at 250 to 500 ° C, preferably 400 to 500 ° C. Also, the first heat treatment may be performed in an air atmosphere.

Aluminum (OH) ₃ is contained in an amount of 30 wt% or more, Al (OH) ₃ is 70 wt% or less, specifically, AlO (OH) ₃ is contained in an amount of 60% by weight or less, but does not contain Al ₂ O ₃ .

The support may further include a metal oxide such as ZrO ₂ , MgO, and SiO ₂ .

The shape of the support is not particularly limited, but may be spherical or potato-shaped. In addition, the support may have a porous structure, a molecular sieve structure, a honeycomb structure, or the like so as to have a relatively high surface area per unit mass or unit volume.

4) Step of preparing supported catalyst

Subsequently, a catalyst precursor is supported on the support and then subjected to a second heat treatment to produce a supported catalyst.

The support may be such that the support and the catalyst precursor are uniformly mixed and aged for a predetermined time. The mixing can be carried out specifically by rotating or stirring at a temperature of 45 to 80 占 폚. The aging can be carried out for 3 to 60 minutes.

The catalyst precursor may be supported on the support and then dried.

The drying may be carried out at 60 to 200 ° C for 4 to 16 hours.

The second heat treatment may be performed in an air atmosphere for 1 to 6 hours. The second heat treatment may preferably be performed at 700 to 800 ° C. When the above-mentioned conditions are satisfied, a supported catalyst in which the catalyst precursor is present in a state coated on the surface and the pores of the support is produced. In addition, the final product, entangled carbon nanotubes manufactured using the supported catalyst, satisfies the above-described bulk density and Equation (1).

5) Reaction step of supported catalyst with carbon-based compound

Then, the supported catalyst is reacted with the carbon-based compound.

The reaction of the supported catalyst with the carbon-based compound can be carried out by a chemical vapor synthesis method.

Specifically, the supported catalyst is fed into a horizontal fixed bed reactor or a fluidized bed reactor, and the temperature of the catalyst is maintained at a temperature not lower than the pyrolysis temperature of the carbon-based compound in the gaseous state (hereinafter referred to as' The gas-phase carbon compound or a gas mixture of the gas-phase carbon compound and a reducing gas (for example, hydrogen) and a carrier gas (for example, nitrogen) is injected to decompose the gas- And then growing the carbon nanotubes. The carbon nanotubes produced by the chemical vapor synthesis method as described above have a crystal growth direction nearly parallel to the tube axis and a high crystallinity of the graphite structure in the tube length direction. As a result, the diameter of the unit is small, and the electrical conductivity and strength are high.

The production of the entangled carbon nanotubes may be performed at a temperature of 500 to 800 ° C, more specifically 550 to 750 ° C. In the reaction temperature range, the weight of the carbon nanotubes is maintained while maintaining the bulk size of the carbon nanotubes while minimizing the generation of amorphous carbon, so that the dispersibility according to the reduction of the bulk density can be further improved. As the heat source for the heat treatment, induction heating, radiation heat, laser, IR, microwave, plasma, surface plasmon heating and the like can be used.

The carbon-based compound can supply carbon, and can be used without limitation, as long as it can exist in a vapor state at a temperature of 300 ° C or higher.

The carbon-based compound may be a carbon-based compound having a carbon number of 6 or less. More specifically, the carbon-based compound may be carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, Cyclohexane, benzene, and toluene.

In the manufacturing method of the present invention, a removal step for removing metal impurities from the metal catalyst remaining in the entangled carbon nanotube can be selectively performed. At this time, the metal impurity removing step may be performed according to a conventional method such as washing and acid treatment.

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.

< Entangled  Production of Carbon Nanotubes>

Example  One

Aluminum hydroxide (Al (OH) ₃ ) as an aluminum-based support precursor was first heat-treated at 450 DEG C for 4 hours in an air atmosphere to prepare an aluminum-based support containing AlO (OH) in an amount of 40 wt% or more.

Separately, NH ₄ VO ₃ aqueous solution was prepared by adding citric acid and NH ₄ VO ₃ in water at a molar ratio of 1: 0.0475 and dissolving them. Co: V molar ratio of 10: Co so that the _{1 (NO 3) 2 · 6H} 2 O and NH ₄ VO ₃ Aqueous solution to prepare a clear aqueous solution of catalyst precursor aqueous solution.

The support and the catalyst precursor aqueous solution were mixed such that the amount of Co and the amount of V in the catalyst precursor aqueous solution were 23 moles and 2.3 moles, respectively, based on 100 moles of Al in the support.

The catalyst precursor aqueous solution was supported on the support in a thermostatic chamber at 60 DEG C for 5 minutes and then dried in an air atmosphere at 120 DEG C for 12 hours. Subsequently, the supported catalyst was subjected to a second heat treatment at 720 占 폚 for 4 hours in an air atmosphere to prepare a supported catalyst.

0.1 g of the supported catalyst was placed in the center of a quartz tube having an inside diameter of 55 mm in diameter located in the fixed bed reactor. The inside of the fixed bed reactor was heated to 650 ° C in a nitrogen atmosphere and maintained. The mixture was stirred for 60 minutes while flowing nitrogen gas, ethylene gas, and hydrogen gas at a ratio of 1: 1: 1 at 0.3 l / min to prepare an entangled carbon nanotube &Lt; / RTI &gt;

Example  2

Citrate and NH ₄ VO ₃ 1: a molar ratio of 0.05 was put into water and NH ₄ VO ₃ was dissolved Except that an aqueous solution was prepared in the same manner as in Example 1, except that an aqueous solution was prepared.

Example  3

Citrate and NH ₄ VO ₃ 1: a molar ratio of 0.072 was added to the water and dissolved NH ₄ VO ₃ Except that an aqueous solution was prepared in the same manner as in Example 1, except that an aqueous solution was prepared.

Example  4

Citrate and NH ₄ VO ₃ 1: a molar ratio of 0.082 was added to the water and dissolved NH ₄ VO ₃ Except that an aqueous solution was prepared in the same manner as in Example 1, except that an aqueous solution was prepared.

Example  5

Citrate and NH ₄ VO ₃ 1: a molar ratio of 0.085 was added to the water and dissolved NH ₄ VO ₃ Except that an aqueous solution was prepared in the same manner as in Example 1, except that an aqueous solution was prepared.

Comparative Example  One

Entangled carbon nanotubes were prepared in the same manner as in Example 1, except that NH ₄ VO ₃ aqueous solution was prepared by adding citric acid and NH ₄ VO ₃ to water at a molar ratio of 1: 0.045 and dissolving them to prepare an NH ₄ VO ₃ aqueous solution.

Comparative Example  2

Entangled carbon nanotubes were prepared in the same manner as in Example 1, except that NH ₄ VO ₃ aqueous solution was prepared by adding citric acid and NH ₄ VO ₃ at a molar ratio of 1: 0.09 to water and dissolving them to prepare an NH ₄ VO ₃ aqueous solution.

Comparative Example  3

Citrate and NH ₄ VO ₃ 1: a molar ratio of 5.8 was added to water and dissolved NH ₄ VO ₃ The carbon nanotubes were prepared in the same manner as in Example 1 except that an aqueous solution was prepared, but the shape of the carbon nanotubes produced was of the bundle type.

Comparative Example  4

Entangled carbon nanotubes (manufacturer: bayer, trade name: C150P) were used.

Comparative Example  5

Entangled carbon nanotubes (manufacturer: LG Chem) were used.

Experimental Example  One

Entangled carbon nanotubes of Examples 3 and 4 were photographed by a scanning electron microscope (SEM), the results of Example 3 are shown in Figs. 1 and 2, and the results of Example 4 are shown in Figs. 3 and 4 .

Here, FIGS. 1 and 3 are SEM images obtained by enlarging the surface of the Entangled carbon nanotube 400 times, and FIGS. 2 and 4 are SEM images showing the surface of the Entangled carbon nanotube enlarged 1,000 times.

Referring to FIGS. 1 to 4, it was confirmed that the carbon nanotubes of Example 3 and Example 4 were Entangled.

Experimental Example  2

The properties of the carbon nanotubes of Examples and Comparative Examples were measured by the following methods, and the results are shown in Tables 1 and 2 below.

(1) Production yield: {(total weight of the produced carbon nanotubes) - (total weight of the used supported catalyst)} / (total weight of the used supported catalyst)

(2) Bulk density: A carbon nanotube was charged into a 5 ml cylinder (manufacturer: DURAN, material: glass) having a known weight, and the bulk density was calculated according to the following equation.

Bulk density (kg / m 3) = weight of carbon nanotube (kg) / volume of carbon nanotube (m 3)

(3) Tap density: Measured using TAP-2S manufactured by LOGAN, in accordance with ASTM B527-06.

(4) Specific surface area (m 2 / g): It can be calculated from the adsorption amount of nitrogen gas under liquid nitrogen temperature (77K) using BEL Japan's BELSORP-mino II.

(5) Secondary structure: confirmed by photographing with a scanning electron microscope (SEM).

(6) Powder resistance value (ohm-cm @ 1 g / cc): An insulating mold was filled with carbon nanotubes at 1 g / cc and pressed. Using Loresta-GX (trade name: MITSUBISHI CHEMICAL ANALYTECH) The surface current and voltage were measured with four probes and the powder resistance was calculated.

(7) Maximum Dispersion Concentration (wt%): A carbon nanotube dispersion was prepared while slightly injecting carbon nanotubes into N-methylpyrrolidone. Then, the maximum dispersion concentration of carbon nanotubes that can be dispersed in the carbon nanotube dispersion was measured.

division	Example 1	Example 2	Example 3	Example 4	Example 5
The molar ratio of citric acid and NH 4 VO 3	1: 0.0475	1: 0.05	1: 0.072	1: 0.082	1: 0.085
Secondary structural feature	Entangled	Entangled	Entangled	Entangled	Entangled
Manufacturing yield	11	11	18.5	21.8	22.7
Bulk density (kg / m3)	32	36	61	76	80
Tap density (kg / m3)	64	65	93	111	112
Tap Density / Bulk Density	2.0	1.8	1.52	1.46	1.41
Powder resistance value (ohm · cm @ 1 g / cc)	0.0162	0.0161	0.0166	0.0170	0.0171
Maximum dispersion concentration (% by weight)	3.5	3.5	3.5	3.5	3.5

division	Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4	Comparative Example 5
The molar ratio of citric acid and NH 4 VO 3	1: 0.045	1: 0.09	1: 5.8	-	-
Secondary structural feature	Entangled	Entangled	Bundled	Entangled	Entangled
Manufacturing yield	10	24	19.2	20	44
Bulk density (kg / m3)	29	90	45	150	172
Tap density (kg / m3)	61	120	75	172	208
Tap Density / Bulk Density	2.1	1.33	1.66	1.17	1.21
Powder resistance value (ohm · cm @ 1 g / cc)	0.0171	0.0181	0.0088	0.0180	0.0179
Maximum dispersion concentration (% by weight)	2.0	3.0	1.25	3.5	3.5

Referring to Tables 1 and 2, the entangled carbon nanotubes of Examples 1 to 5 prepared by adding citric acid and NH ₄ VO ₃ at a molar ratio of 1: 0.0475 to 1: 0.085 had a bulk density of 32 to 80 Kg / m &lt; 3 &gt; In addition, since the entangled carbon nanotubes of Examples 1 to 5 have low powder resistance and a high maximum dispersion concentration, they are not only excellent in conductivity but can be contained in the dispersion at a high concentration. Therefore, It could be predicted that it was appropriate.

On the other hand, it was confirmed that the bulk density of the Entangled carbon nanotubes of Comparative Example 1, which was prepared by adding citric acid and NH ₄ VO ₃ at a molar ratio of 1: 0.045, was lower than the bulk density of the present invention and did not satisfy Formula 1 . Further, even though the entangled carbon nanotubes of Comparative Example 1 had a low powder resistance value, they could not be contained at a high concentration in the dispersion, and therefore, it was predicted that they were not suitable for use as a conductive material dispersion.

It was also confirmed that the bulk density of the Entangled carbon nanotubes of Comparative Example 2 prepared by adding citric acid and NH ₄ VO ₃ at a molar ratio of 1: 0.09 was higher than the bulk density of the present invention and did not satisfy Formula 1 . It was predicted that the Entangled carbon nanotubes of Comparative Example 2 were not suitable for use as a conductive material dispersion because they had a high powder resistance value and could not be contained at a high concentration in the dispersion.

In addition, the carbon nanotubes of Comparative Example 3 were prepared by mixing citric acid and NH ₄ VO ₃ 1: 5.8, it was confirmed to be a bundle type and did not satisfy the formula (1). Further, even though the bundle-type carbon nanotubes of Comparative Example 3 are low in the powder resistance value, they can not be contained in the dispersion at a high concentration, and therefore, it is predicted that they are not suitable for use as a conductive material dispersion.

It was confirmed that the entangled carbon nanotubes of Comparative Example 4 and Comparative Example 5, which are commercially available carbon nanotubes, are not only excessively high in bulk density, but also do not satisfy Equation 1. Further, since the powder resistance value is low, it can be predicted that it is not suitable for use as a conductive material dispersion.

Claims (10)

1. A bulk density of 31 to 85 kg / m &lt; 3 &

   Entangled carbon nanotubes satisfying the following formula 1:

   <Formula 1>

   1.37? X / Y? 2.05

   In Equation (1)

   X is the tap density (unit: kg / m &lt; 3 &gt;) of the entangled carbon nanotube,

   Y is the bulk density (unit: kg / m3) of the entangled carbon nanotube.
2. The method according to claim 1,

   Wherein the value of the formula 1 is 1.4 to 2.0.
3. The method according to claim 1,

   And the bulk density of the entangled carbon nanotube is 32 to 80 kg / m &lt; 3 &gt;.
4. The method according to claim 1,

   Wherein the entangled carbon nanotubes have a tap density of 63 to 116 kg / m &lt; 3 &gt;.
5. The method according to claim 1,

   Wherein the entangled carbon nanotube comprises a carbon nanotube unit having an average diameter of 10 to 30 nm.
6. The method of claim 5,

   The carbon nanotube unit preferably has a layer plane spacing (d ₀₀₂ ) of carbon crystals obtained by X-ray diffractometry of from 0.355 to 0.332 nm,

   Layer plane interval (d ₀₀₂ ) &lt; O.3448 - 0.0028 (log?) (Wherein? Is an average diameter of the carbon nanotube unit)

   An entangled carbon nanotube having a thickness (Lc) in the C-axis direction of the crystal of 40 nm or less.
7. Mixing the organic acid and the vanadium precursor in a molar ratio of 1: 0.0463 to 1: 0.0875 to prepare a mixture;

   Mixing the mixture with a cobalt precursor to produce a catalyst precursor;

   Subjecting the aluminum hydroxide to a first heat treatment to produce a support;

   Supporting a catalyst precursor on the support, and then performing a second heat treatment to produce a supported catalyst; And

   And reacting the supported catalyst with the carbon-based compound.
8. The method of claim 7,

   Wherein the step of preparing the mixture is a step of mixing the organic acid and the vanadium precursor at a molar ratio of 1: 0.047 to 1: 0.086 to prepare a mixture.
9. The method of claim 7,

   Wherein the step of preparing the catalyst precursor comprises preparing a catalyst precursor by mixing the mixture with a cobalt precursor such that a molar ratio of vanadium and cobalt is 1: 1 to 1: 100.
10. The method of claim 7,

    Wherein the organic acid is at least one selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid.

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