KR101264147B1 - Preparation of Concentrated CNT Dispersion Solution Using the Treated CNT - Google Patents

Abstract

The present invention relates to a high concentration carbon nanotube dispersion in which dispersion stability is increased by dispersing carbon nanotubes in an organic solvent as well as water using surface treated carbon nanotubes with improved dispersibility. The surface-treated carbon nanotubes, including the dispersion medium, are characterized by including a functional group including oxygen, nitrogen and sulfur or a mixture thereof with respect to the total weight of the surface-treated carbon nanotubes. The carbon nanotube dispersion according to the present invention not only improves dispersibility compared to the prior art but also specifically secures uniform distribution of CNTs, excellent long-term dispersion stability, expansion of applications, and minimizing damage of CNTs generated during CNT surface treatment. Electrical conductivity, thermal conductivity, mechanical properties, etc. are very improved.

Description

Preparation of Concentrated Carbon Nanotube Dispersions Using Surface-treated Carbon Nanotubes {Preparation of Concentrated CNT Dispersion Solution Using the Treated CNT}

The present invention relates to a high concentration carbon nanotube dispersion using the surface-treated carbon nanotubes.

Carbon nanotubes (CNT) were first discovered in 1991, and research on synthesis, physical properties, and applications has been actively conducted. In addition, it was confirmed that CNTs are produced by adding transition metals such as Fe, Ni, Co, etc. during electric discharge, and full-scale studies began in 1996 by producing a considerable amount of samples by laser evaporation. Such CNTs are in the form of hollow tubes in which graphite surfaces are rounded to a nano-sized diameter, and the electrical properties thereof are conductors or semiconductors according to angles and structures in which the graphite surfaces are dried. In addition, CNTs are single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and thin multi-walled carbons, depending on the number of graphite walls. nanotubes), multi-walled carbon nanotubes (MWCNT), and rolled carbon nanotubes (Roped carbon nanotubes).

In particular, CNTs have excellent mechanical strength and elasticity, are chemically stable, environmentally friendly, electrically conductive and semiconducting, and have diameters ranging from 1 nm to tens of nm and lengths of several to tens of μm. It is larger than any conventional material with an aspect ratio of about 1,000. In addition, the specific surface area is very large, and is being spotlighted as an advanced new material that will lead the 21st century in the fields of next-generation information electronic materials, high efficiency energy materials, high functional composite materials, and eco-friendly materials.

However, in spite of the various advantages of CNTs, the cohesion phenomenon is large, and the surface hydrophobic property is large, so that the mixing properties with other media are very poor, and there is no solubility in water and organic solvents. Therefore, in order to utilize the advantages of CNT and to expand the range of applications for various purposes, a method for improving the dispersion efficiency by increasing the compatibility with various media is needed.

 In order to solve the above problems, an object of the present invention is to provide a carbon nanotube dispersion having high dispersion stability by dispersing carbon nanotubes in not only water but also an organic solvent by using surface-treated carbon nanotubes having improved dispersibility. There is this.

The present invention includes a surface-treated carbon nanotubes, a dispersant and a dispersion medium, but the surface-treated carbon nanotubes contain 0.1 to 10% by weight of at least one element of oxygen, nitrogen, and sulfur based on the total weight of the surface-treated carbon nanotubes. It relates to a carbon nanotube dispersion, characterized in that.

Carbon nanotubes of the present invention may be any type selected from the group consisting of single-walled, double-walled, multi-walled, bundled, and mixtures thereof.

The dispersion medium is at least one solvent selected from the group consisting of water, alcohols, ketones, amines, esters, amides, alkyl halogens, ethers, and furans, and more preferably water is used.

The present invention is characterized in that the surface-treated carbon nanotubes are surface-treated to include 0.1 to 10% by weight of oxygen formed by the surface treatment.

The surface-treated carbon nanotubes are surface treated with carbon nanotubes in subcritical or supercritical conditions of 50 to 400 atm using an oxidant selected from oxygen, air, ozone, hydrogen peroxide, nitric acid, nitro compounds, and mixtures thereof. Can be generated.

The surface-treated carbon nanotubes are subcritical or supercritical conditions at a pressure of 50 to 400 atm and a temperature of 100 to 600 ° C. using an oxidant selected from oxygen, air, ozone, hydrogen peroxide, nitric acid, nitro compounds, and mixtures thereof. Oxidation of the carbon nanotube surface, followed by carboxylic acid, carboxyl salt, amine, amine salt, tetravalent-amine, phosphate, sulfate, alcohol, thiol, ester, amide, epoxide, aldehyde, ketone and their A functional compound having at least one functional group selected from the group consisting of a mixture may be obtained by surface treatment by injecting the functional compound into a surface treatment reactor at a pressure of 50 to 400 atm and a temperature of 100 to 600 ° C.

The reaction temperature, residence time, and oxidizing agent should be optimized to minimize CNT damage during CNT surface treatment. The oxidation degree of the surface-treated CNTs is confirmed by the oxygen content generated on the surface of the CNTs. The reaction temperature is 150 ~ 250 ℃, residence time is 5 ~ 15 minutes, the amount of oxidizing agent is preferably injected 0.1 to 3.0 equivalents to the carbon equivalent of CNT.

In another example, the surface-treated carbon nanotubes may be obtained by adding carboxylic acid, nitric acid, phosphoric acid or sulfuric acid to the carbon nanotubes by oxidation of the surface of the carbon nanotubes. Oxidation may be provided. More specifically, the surface-treated carbon nanotubes are obtained by oxidizing carbon nanotube surfaces by mixing carbon nanotubes with carboxylic acid, nitric acid, phosphoric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, hydrogen peroxide or a mixture thereof. do.

In the present invention, the dispersant is more specifically polyacetal, acrylic acid, methyl methacrylate, alkyl (C1-C10) acrylate, 2-ethylhexyl acrylate, polycarbonate, styrene, alpha methyl styrene, vinyl acrylate, poly Esters, polyphenylene ether resins, polyolefins, acrylonitrile-butadiene-styrene copolymers, polyarylates, polyamides, polyamideimides, polyarylsulfones, polyetherimides, polyethersulfones, polyphenylene sulfides, polyimides Mead, polyetherketone, polybenzoxazole, polyoxadiazole, polybenzothiazole, polybenzimidazole, polypyridine, polytriazole, polypyrrolidine, polydibenzofuran, polysulfone, polyurea, polyurethane, poly At least one selected from the group of phosphazenes, and copolymers thereof.

As a more preferable example of a dispersing agent, the styrene / acrylic water-soluble resin which superposed | polymerized the styrene-type monomer and the acryl-type monomer is mentioned. It can be prepared by the method described in Korean Patent Application Nos. 10-2001-0088773, 10-2001-0084640, 10-2000-040715, etc., which the applicant has previously filed with respect to the method for producing a styrene / acrylic water-soluble resin.

 The dispersing agent according to the present invention is a styrene monomer and an acrylic monomer selected from a mixture of styrene, styrene and alphamethyl styrene, under a mixed solvent of diethylene glycol monoethyl ether or dipropylene glycol methyl ether and water. Polymers subjected to continuous bulk polymerization at a reaction temperature of 占 폚 may be used. In this case, the styrene monomer and the acrylic monomer are mixed by a weight ratio of 60 to 80:20 to 40, and the styrene monomer includes styrene and alpha methyl styrene monomer alone or in a mixing weight ratio of 50 to 90:10 to 50. In addition, the acrylic monomer may include acrylic acid alone or an acrylic acid and an alkyl acrylate monomer having a mixed weight ratio of 80 to 90:10 to 20.

In the presence of a mixed solvent in which dipropylene glycol methyl ether and water are mixed, the dispersing agent polymerizes 25 to 45 wt% of styrene and 25 to 35 wt% of acrylic acid with 25 to 45 wt% of acrylic acid based on the total weight of the polymer. The polymer is prepared by using the polymer having a weight average molecular weight of 1,000 ~ 100,000.

In the present invention, the surface-treated carbon nanotubes are preferably contained in 0.0001 to 10% by weight based on the total weight of the carbon nanotube dispersion, more preferably 0.01 to 6% by weight.

The dispersant may include 10 to 500 parts by weight based on 100 parts by weight of the surface treated carbon nanotubes.

Although it is possible to reduce the surface resistance by reducing the content of the dispersant, it may be difficult to manufacture the dispersion simply by reducing the content of the dispersant because the excessive amount of carbon nanotubes that do not disperse may be present if the content is significantly below the content. In addition, the carbon nanotube dispersion in the present invention is characterized in that it further comprises a dispersion stabilizer.

The dispersion stabilizer may be one or more selected from the group consisting of additives such as anionic, cationic, nonionic surfactants, wetting agents, wetting enhancers, and more preferably nonionic fluorine-based additives. The dispersion stabilizer is 5 to 15 parts by weight based on 100 parts by weight of the surface-treated carbon nanotubes is excellent in dispersibility and dispersion stability.

The present invention may further include 1 to 150 parts by weight of an amine compound or an aqueous inorganic alkali solution based on 100 parts by weight of carbon nanotubes.

The amine compound is selected from monoethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine and tripropanolamine, and the inorganic alkaline solution is KOH, NaOH, LiOH, K ₂ CO ₃ , Na It is preferable to use selected from ₂ CO ₃ and LiCO ₃ .

The carbon nanotube dispersion according to the present invention is an antistatic material, electrostatic dispersion material, conductive material, electromagnetic shielding material, electromagnetic wave absorber, RF (Radio Frequency) absorber, solar cell material, dye-sensitized solar cell (DSSC) electrode material, Electric device materials, electronic device materials, semiconductor device materials, optoelectronic device materials, notebook parts materials, computer parts materials, mobile phone parts materials, PDA parts materials, PSP parts materials, game machine parts materials, housing materials, transparent electrode materials, opaque electrodes Materials, field emission display (FED) materials, back light unit (BLU) materials, liquid crystal display (LCD) materials, plasma display panel (PDP) materials, light emitting diodes (LEDs) ; Light emitting diode materials, touch panel materials, billboard materials, billboard materials, display materials, heating elements, radiators, plating materials, catalysts, promoters, oxidizing agents, reducing agents, automotive parts materials , Ship parts materials, aircraft parts materials, protective tape materials, adhesive materials, tray materials, clean room materials, transportation equipment parts materials, flame retardant materials, antibacterial materials, metal composite materials, nonferrous metal composite materials, medical equipment materials, construction Material, flooring material, wallpaper material, light source component material, lamp material, optical device component material, textile manufacturing material, clothing manufacturing material, electric product material, electronic product manufacturing material, secondary battery positive electrode active material, secondary battery negative electrode active material, secondary battery It is used for one or more materials selected from the group consisting of materials, fuel cell materials, solar cell materials, memory elements and capacitor materials.

Carbon nanotube dispersion according to the present invention not only improves the dispersibility compared to the prior art, but also specifically can ensure a uniform particle size distribution of the CNT and excellent long-term dispersion stability. The CNTs used in the dispersion may be surface treated to improve dispersibility, and various applications using CNT dispersions having highly improved electrical conductivity, thermal conductivity, and mechanical properties by minimizing damage of CNTs generated during the surface treatment of CNTs are possible. It is possible.

Figure 1 shows the particle size analysis results of Example 1, Example 2 and Comparative Example 2.
Figure 2 shows a figure showing the coating film surface of Comparative Example 1 and Example 1.

The present invention will be described in more detail with reference to the following examples.

[Production Example 1]

15 g of carbon nanotubes (CNT) were mixed with 985 g of distilled water and a circulation pump to prepare a CNT solution in a pretreatment tank. Before the CNT solution is introduced into the preheater at a flow rate of 11 g / min through a high pressure injection pump, oxygen in the gaseous state compressed at 245 atm to 252 atm is mixed with the CNT solution at a flow rate of 0.4 g / min at the front end of the heat exchanger. The mixed solution was added to a preheater preheated to 150 to 200 ° C. through a heat exchanger. The preheated mixed solution is injected into a surface treatment reactor in a subcritical water state of 210 ° C. and 230 atm to 250 atm, and the surface is treated. After cooling to a temperature of 14.3g of carbon nanotubes were continuously obtained. At this time, the oxygen content present on the surface of the carbon nanotubes is 2.2wt%.

[Production Example 2]

Except for using the air 2g / min instead of oxygen as the oxidizing agent was prepared in the same manner as in Preparation Example 1.

[Production Example 3]

The preparation was carried out in the same manner as in Preparation Example 1, except that 0.27 g / min ozone was used instead of oxygen as the oxidizing agent.

[Production Example 4]

The preparation was carried out in the same manner as in Preparation Example 1, except that 3.4 g of 50% aqueous hydrogen peroxide solution was added instead of oxygen as the oxidizing agent.

[Production Example 5]

In order to modify the surface of CNTs, one or more organic or inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, and hydrogen peroxide are mixed and boiled for at least 12 hours. Washing gave surface modified CNTs.

Preparation Example 6 Preparation of Dispersant

A styrene / acrylic water-soluble resin was prepared using a styrene monomer (35% styrene and 32% alphamethylstyrene) and an acrylic monomer (33% acrylic acid), and a dipropylene glycol methyl ether / water mixture was used as a solvent to 100 parts by weight Prepared using 15 parts by weight.

[Example 1]

30 g of the surface-treated CNT prepared in Preparation Example 1, 30 g of the dispersant prepared in Preparation Example 6, 935.5 g of distilled water, and 4.5 g of monoethanolamine were mixed and completely dispersed using a dispersing equipment.

[Example 2]

In the same manner as in Example 1, but as a dispersion stabilizer, a nonionic fluorine-based additive 2,5,8,11-tetramethyl-6-dodecine-5,8-diol itosylate (2,5,8, 11-Tetramethyl-6-dodecyn-5,8-Diol Ethoxylate) 4g was added and the rest was the same as in Example 1.

[Example 3]

Example 2 was carried out in the same manner as in Example 2 except that CNT having an oxygen content of 6.0 wt% bonded to the surface of CNT was used, and the rest was performed in the same manner as in Example 1.

[Comparative Example 1]

There was a difference between using CNTs that were not surface treated, and the rest was performed in the same manner as in Example 1.

[Comparative Example 2]

The surface-treated CNTs prepared in Preparation Example 1 were mixed with 30 g of distilled water and 970 g of distilled water, and dispersed using a dispersion equipment to prepare a dispersion. Particle size analyzer, viscometer, and the like were measured.

[Test Example]

The physical properties of the dispersions prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were respectively measured, and the results are shown in Table 1 below.

1. Grain size analysis

Particle Size Analyzer was measured using Malvern's Model 2000.

The particle size analysis results of Example 1, Example 2 and Comparative Example 2 are shown in Figure 1 below. Referring to FIG. 1, one peak (Mono-Modal) is shown when complete dispersion is made in the particle size analysis, and when the complete dispersion is not achieved, the particle size distribution is shown in large particles (10 μm or more). It could not be seen that.

2. Viscosity Measurement

Viscometer was measured by Brookfield's model Viscometer DV-II PRO and the conditions were measured under conditions of Spindle 18/100 rpm / 25 ℃.

3. Measurement of oxygen content on CNT surface

It was measured using an elemental analyzer and X-ray photoelectron spectroscopy.

4. Surface resistance measurement

1) Coating film manufacturing

The dispersions prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were each coated with a thickness of 10 μm on the surface of the substrate. The base material used for coating could be implemented using glass. The coated surface was prepared by removing the surface medium and solidifying or curing the surface by irradiating hot air or ultraviolet rays.

Figures showing the coating film surface of Comparative Example 1 and Example 1 are shown in Figure 2 below. According to FIG. 2, Comparative Example 1 was observed that the coating was poor because the dispersion was not performed smoothly even though the dispersant was used.

2) Using Mitsubishi's Loresta GP (MCP-T600) to measure the surface resistance of the coating film prepared in accordance with JISK 7194 / ASTM D991.

Table 1

×: poor coating quality, ◎: excellent coating quality

(Reference) In the particle size analysis, one peak (Mono-Modal) is shown when complete dispersion occurs, and when the complete dispersion is not achieved, the particle size distribution is shown in large particles (10 μm or more).

Claims (17)

Surface-treated carbon nanotubes, including surface-treated carbon nanotubes, dispersants, dispersion media, dispersion stabilizers and amine-based compounds or inorganic alkali aqueous solutions, the surface-treated carbon nanotubes are one or more of oxygen, nitrogen and sulfur based on the total weight of the surface-treated carbon nanotubes 0.1 to 10% by weight of the element, the surface-treated carbon nanotubes are contained from 0.0001 to 10% by weight based on the total weight of the carbon nanotube dispersion, the dispersant is 10 ~ 10 parts by weight based on 100 parts by weight of the surface-treated carbon nanotubes 500 parts by weight is included, and the dispersion stabilizer is included in an amount of 5 to 15 parts by weight based on 100 parts by weight of the surface-treated carbon nanotubes, and the amine-based compound or the inorganic alkali aqueous solution is included in about 1 part by weight of 100 parts by weight of the surface-treated carbon nanotubes. Carbon nanotube dispersion characterized in that it comprises ~ 150 parts by weight. The method of claim 1,

The surface-treated carbon nanotubes are carbon nanotube dispersions, characterized in that the surface treatment to include 0.1 to 10% by weight of oxygen formed by the surface treatment. The method of claim 1,

The carbon nanotubes are selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, multiple carbon nanotubes, and mixtures thereof. The method of claim 1,
The surface-treated carbon nanotubes are produced by surface-treating carbon nanotubes in subcritical or supercritical conditions of 50 to 400 atm using an oxidant selected from oxygen, air, ozone, hydrogen peroxide, nitro compounds, and mixtures thereof. Carbon nanotube dispersion, characterized in that. 5. The method of claim 4,
The surface-treated carbon nanotubes are carbon in subcritical or supercritical conditions at a pressure of 50 to 400 atm and a temperature of 100 to 600 ° C. using an oxidant selected from oxygen, air, ozone, hydrogen peroxide, nitro compounds and mixtures thereof. The nanotube surface is oxidized, followed by carboxylic acid, carboxyl salt, amine, amine salt, tetravalent-amine, phosphate, sulfate, alcohol, thiol, ester, amide, epoxide, aldehyde, ketone and mixtures thereof. Carbon nanotube dispersion obtained by injecting a functional compound having at least one functional group selected from the group consisting of a surface treatment reaction tank at a pressure of 50 to 400 atm and a temperature of 100 to 600 ℃. The method of claim 1,
The surface-treated carbon nanotubes are carbon nanotubes obtained by oxidizing the surface of carbon nanotubes by mixing carbon nanotubes with carboxylic acid, nitric acid, phosphoric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, hydrogen peroxide or a mixture thereof. Dispersion. The method of claim 1,
The dispersant may be polyacetal, methyl methacrylate, alkyl (C1-C10) acrylate, 2-ethylhexyl acrylate, polycarbonate, styrene, alpha methyl styrene, vinyl acrylate, polyester, polyphenylene ether resin, Polyolefin, acrylonitrile-butadiene-styrene copolymer, polyarylate, polyamide, polyamideimide, polyarylsulfone, polyetherimide, polyethersulfone, polyphenylene sulfide, polyimide, polyetherketone, polybenzoxazole , Polyoxadiazole, polybenzothiazole, polybenzimidazole, polypyridine, polytriazole, polypyrrolidine, polydibenzofuran, polysulfone, polyurea, polyurethane, polyphosphazene and copolymers thereof Carbon nanotube dispersion, characterized in that at least one selected. The method of claim 1,
The dispersing agent is a mixture of styrene, styrene and alphamethyl styrene under a mixed solvent of diethylene glycol monoethyl ether or dipropylene glycol methyl ether and water, and a styrene monomer and an acrylic monomer selected from 100 to 200 ° C. Carbon nanotube dispersion using a polymer subjected to continuous bulk polymerization at a temperature. The method of claim 1,
In the presence of a mixed solvent in which dipropylene glycol methyl ether and water are mixed, the dispersing agent polymerizes 25 to 45% by weight of styrene and 25 to 35% by weight of 25% to 45% by weight of acrylic acid based on the total weight of the polymer. The prepared polymer is a carbon nanotube dispersion having a weight average molecular weight of 1,000 ~ 100,000. delete delete delete The method of claim 1,

The dispersion stabilizer is a carbon nanotube dispersion, characterized in that at least one selected from the group consisting of anionic cationic nonionic surfactant, wetting agent, wettability enhancer. delete The method of claim 1,
The amine compound is selected from monoethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine and tripropanolamine, and the inorganic alkaline solution is KOH, NaOH, LiOH, K ₂ CO ₃ , Na Carbon nanotube dispersion, characterized in that selected from ₂ CO ₃ and LiCO ₃ used. The method of claim 1,
The dispersion medium is carbon nanotube dispersion, characterized in that at least one solvent selected from the group consisting of water, alcohol, ketone, amine, ester, amide, alkyl halogen, ether, and furan. The method according to any one of claims 1 to 9, 13, 15 and 16, wherein the carbon nanotube dispersion is an antistatic material, an electrostatic dispersion material, a conductive material, an electromagnetic shielding material, an electromagnetic wave absorber, RF ( Radio Frequency) Absorber, Solar Cell Material, Electrode Material for Dye-Sensitized Solar Cell (DSSC), Electric Device Material, Electronic Device Material, Semiconductor Device Material, Optoelectronic Device Material, Notebook Component Material, Computer Component Material, Mobile Phone Component Material, PDA Component Materials, PSP parts materials, game machine parts materials, housing materials, transparent electrode materials, opaque electrode materials, field emission display (FED) materials, back light unit (BLU) materials, liquid crystal displays (LCD) display materials, plasma display panel (PDP) materials, light emitting diode (LED) materials, touch panel materials, electronic signboard materials, billboard materials, display materials, heating elements, radiators, plating materials Materials, catalysts, promoters, oxidizing agents, reducing agents, automotive parts materials, ship parts materials, aircraft parts materials, protective tape materials, adhesive materials, tray materials, clean room materials, transportation equipment parts materials, flame retardant materials, antibacterial materials, metals Composite materials, non-ferrous metal composite materials, medical device materials, building materials, flooring materials, wallpaper materials, light source parts materials, lamp materials, optical device parts materials, textile manufacturing materials, clothing manufacturing materials, electrical products materials, electronic products manufacturing Carbon nanotube dispersion, characterized in that used in at least one material selected from the group consisting of a material, a cathode active material for a secondary battery, a cathode active material for a secondary battery, a secondary battery material, a fuel cell material, a solar cell material, a memory device and a capacitor material.

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