WO2023229108A1 - Method for pretreatment of carbon nanotubes with improved process stability and carbon nanotubes pretreated thereby - Google Patents

Method for pretreatment of carbon nanotubes with improved process stability and carbon nanotubes pretreated thereby Download PDF

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WO2023229108A1
WO2023229108A1 PCT/KR2022/013662 KR2022013662W WO2023229108A1 WO 2023229108 A1 WO2023229108 A1 WO 2023229108A1 KR 2022013662 W KR2022013662 W KR 2022013662W WO 2023229108 A1 WO2023229108 A1 WO 2023229108A1
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carbon nanotubes
sulfate
phosphate
potassium
debundled
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PCT/KR2022/013662
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French (fr)
Korean (ko)
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한중탁
김정훈
박종환
이도근
조준영
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한국전기연구원
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/02—Single-walled nanotubes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/06—Multi-walled nanotubes

Definitions

  • the present invention relates to a pretreatment method for carbon nanotubes with improved process stability, and to carbon nanotubes pretreated thereby.
  • Carbon nanotubes are fine molecules made of carbon connected in hexagonal rings forming a long tube shape. They have excellent electrical properties such as conductivity and reflectivity, as well as physical properties such as adhesion, durability, wear resistance, and flexibility, making them useful in flat display devices and highly integrated memory devices. It is widely used as a component material for electrochemical devices such as secondary batteries, ultra-high capacity capacitors, hydrogen storage materials, electrochemical sensors, electromagnetic wave shielding, and cables.
  • carbon nanotubes can be applied through the process of preparing a carbon nanotube dispersion in which carbon nanotubes are uniformly dispersed in a solvent or polymer, and applying or spraying this to parts of an electrochemical device to form a carbon nanotube layer.
  • composition for carbon nanotube nanocomposite conductive fiber and its manufacturing method (Publication number: 10-2019-0108734)
  • carbon is treated with acid by mixing acid and nitrate to prevent carbon nanotubes from being oxidized or carbon bonds on the surface to be broken.
  • a technology was proposed to debundle nanotubes and disperse them within the polymer. However, this only prevents fiber breakage during the stretching process by increasing the polymer content compared to carbon nanotubes, but also improves the dispersion stability of carbon nanotubes. There is a limit to this.
  • nitrate which is used to debundle carbon nanotubes
  • nitrate nitrogen which is a substance that is decomposed and mineralized as nitrogen compounds among organic substances are oxidized.
  • Nitrate when used indiscriminately and in excessive amounts, causes green algae, causes harmful pollution to water quality, and has been pointed out as a major cause of groundwater pollution for decades. In the end, nitrate causes oxygen depletion and eutrophication, harming the ecosystem.
  • nitrate when nitrate enters the human body (especially the stomach of an infant) through drinking water, it is reduced to nitrite by reducing bacteria, and the nitrite reacts with hemoglobin in the blood to produce methemoglobin, a hemoglobin without oxygen transport function, causing cyanosis. It is threatening human health.
  • the present invention was invented to solve the above problems, and its technical problem is to provide a pretreatment method for carbon nanotubes that improves process stability without using nitrates, and carbon nanotubes pretreated thereby.
  • the present invention mixes a composite powder in which bundle-shaped carbon nanotubes are mixed with one or more of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent while applying shear stress, producing debundled carbon nanotubes by co-intercalating one or more of sulfate and phosphate between adjacent layers of the carbon nanotubes; Heating the debundled carbon nanotubes at 30 to 50° C.
  • the sulfate is sodium sulfate (Na 2 SO 4 ), potassium sulfate (K 2 SO 4 ), sodium hydrogen sulfate (NaHSO 4 ), potassium hydrogen sulfate (KHSO 4 ), potassium peroxymonosulfate (KHSO 5 ), and At least one selected from the group consisting of ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), and the phosphate is selected from the group consisting of dipotassium phosphate (K 2 HPO 4 ) and potassium phosphate (KH 2 PO 4 ). It is characterized in that there is at least one type selected.
  • the alkali metal-containing oxidizing agent is potassium permanganate (KMnO 4 ), sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ) , potassium chlorate (KClO 3 ), and potassium perchlorate. (KClO 4 ) and potassium peroxymonosulfate (Potassium Peroxymonosulfate, KHSO 5 ).
  • the carbon nanotubes include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multiwalled carbon nanotubes (multiwalled carbon nanotubes). It is characterized by one or more of MWCNT).
  • the step of manufacturing the debundled carbon nanotubes is characterized by applying the shear stress using one or more of an impeller, a paste mixer, a blade mixer, and a Couette-Taylor reactor.
  • the present invention provides carbon nanotubes, characterized in that they have been pretreated by the above method.
  • sulfate or phosphate cointercalates between adjacent layers of carbon nanotubes, and the pretreated carbon nanotubes form a liquid crystalline phase with a self-assembled structure, thereby introducing oxygen-containing functional groups, thereby promoting the debundling effect of carbon nanotubes. It can be maximized.
  • carbon nanotubes pretreated by the method of the present invention are used not only as a conductive additive for secondary batteries and a conductive primer for secondary battery current collectors, but also as transparent electrodes, antistatic, and electromagnetic wave shielding, as well as conductive fibers, sensors, and conductive polymer composite materials. It has effects that can be applied to various fields such as:
  • FIG. 1 is a flowchart showing a method for pretreating carbon nanotubes according to the present invention.
  • Figure 2 is a schematic diagram showing rotation and revolution according to the present invention.
  • Figure 3 is a polarizing microscope image showing carbon nanotubes pretreated according to Example 1.
  • Figure 4 is an SEM photograph showing carbon nanotubes that were not pretreated according to Comparative Example 1.
  • Figure 5 is a graph showing the results of XPS analysis according to Example 1.
  • the present invention relates to a pretreatment method for carbon nanotubes with improved process stability.
  • Figure 1 shows a flow chart of a method for pre-treating carbon nanotubes according to the present invention.
  • the method of pretreating carbon nanotubes with improved process stability of the present invention includes a composite powder mixed with one or more of sulfate and phosphate in bundle-shaped carbon nanotubes, an acid solution, and an oxidizing agent containing an alkali metal.
  • the pretreatment described in this specification causes one or more of sulfate and phosphate to cointercalate between adjacent layers of carbon nanotubes through shear stress, and introduces oxygen-containing functional groups into the carbon nanotubes through heat treatment. It means process.
  • a composite powder of bundle-shaped carbon nanotubes mixed with one or more of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent are mixed while applying shear stress to form a mixture of sulfate and phosphate.
  • At least one carbon nanotube is co-intercalated between adjacent layers to produce debundled carbon nanotubes (S10).
  • Carbon nanotubes that can be pretreated in the present invention include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multiwalled carbon nanotubes (multiwalled carbon nanotubes).
  • MWCNT may be used.
  • single-walled carbon nanotubes have a diameter of only 1 nm, so they cannot exist alone and have the characteristic of being aggregated into a bundle shape by van der Waals attraction.
  • Multi-walled carbon nanotubes have a large diameter, so agglomeration may occur, but they exhibit characteristics similar to the tangle phenomenon of polymer chains.
  • some with small diameters have characteristics similar to single-walled carbon nanotubes, and some with large diameters have characteristics similar to multi-walled carbon nanotubes.
  • carbon nanotubes having the above characteristics are in the spotlight as conductive materials due to their unique electrical, thermal, and physicochemical properties, they have the disadvantage of agglomerating into bundle shapes due to entanglement, making it difficult to secure dispersion stability. In particular, the agglomeration phenomenon of carbon nanotubes has been difficult to physically treat.
  • a method of pre-treating the carbon nanotubes is needed to disperse the carbon nanotubes in a stable state by preventing them from bundling, agglomerating, or precipitating in the solvent.
  • the carbon nanotubes are mixed with one or more of sulfate and phosphate in a solid state.
  • a composite powder is prepared by mixing, and then the composite powder, an acid solution, and an alkali metal-containing oxidizing agent are mixed while applying shear stress to prepare debundled carbon nanotubes.
  • Sulfates include sodium sulfate (Na 2 SO 4 ), potassium sulfate (K 2 SO 4 ), sodium hydrogen sulfate (NaHSO 4 ), potassium hydrogen sulfate (KHSO 4 ), potassium peroxymonosulfate (KHSO 5 ), and ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), and the phosphate may be at least one selected from the group consisting of dipotassium phosphate (K 2 HPO 4 ) and potassium phosphate (KH 2 PO 4 ). .
  • nitrate like sulfate or phosphate, it can be used as a cointercalant that can be inserted between carbon nanotube layers, but due to the environmental problems caused by the use of nitrate, it is advantageous in terms of process cost to exclude it, and unlike sulfate or phosphate, nitrate Since oxidation of carbon nanotubes occurs only when heated above 70°C, oxygen-containing functional groups caused by nitrate cannot be introduced into carbon nanotubes at room temperatures close to at least 30°C.
  • the acid solution may be at least one selected from the group consisting of sulfuric acid (H 2 SO 4 ), nitric acid (HNO 3 ), phosphoric acid (H 3 PO 4 ), hydrogen peroxide (H 2 O 2 ), and hydrochloric acid (HCl).
  • the acid solution is not limited to the above-mentioned types, and various substances that can be included in the liquid acid solution can be used.
  • oxidation efficiency of carbon nanotubes may be somewhat low, so it is desirable to use an oxidizing agent containing an alkali metal together.
  • alkali metal-containing oxidizing agents potassium permanganate (KMnO 4 ), sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ), potassium chlorate (KClO 3 ), potassium perchlorate (KClO 4 ), and potassium perchlorate (NaClO 4 ).
  • a general oxidizing agent for example, sulfuric acid or nitric acid
  • oxidation must proceed at a high temperature of approximately 70°C or higher.
  • carbon nanotubes and one or more of sulfate and phosphate are first mixed in a powder state using a mixer before adding the acid solution that functions as a solvent and an oxidizing agent is to prevent sulfate and phosphate between adjacent layers of the carbon nanotubes. This is to increase functionalization efficiency by creating a co-intercalation structure by facilitating the penetration of one or more of the phosphates.
  • sulfate or phosphate it is desirable to minimize the amount of sulfate or phosphate in the composite powder so that the debundled carbon nanotubes form a liquid crystalline phase.
  • nitrate rather than sulfate or phosphate
  • more than 10 times the amount of carbon nanotubes is used. Since shear stress is used in this step, at least one of sulfate and phosphate is mixed at a weight ratio of 0.1 to 10 based on 1 weight of carbon nanotubes. Just being is enough.
  • sulfate and phosphate are mixed in a weight ratio of less than 0.1, it is difficult to functionalize the interior, surface, or end of the carbon nanotube with an oxygen-containing functional group such as a carboxyl group or a hydroxy group. Because of this, it is difficult to functionalize the carbon nanotubes with oxygen-containing functional groups, so the weight ratio must be at least 0.1. If at least one of sulfate and phosphate is less than 0.1 weight ratio, the number of oxygen-containing functional groups introduced into the carbon nanotubes decreases, and eventually the carbon nanotubes cannot self-assemble and are forced to disperse in a disordered direction.
  • At least one of sulfate and phosphate be at a weight ratio of at least 0.1 relative to 1 weight ratio of carbon nanotubes.
  • one or more of sulfate and phosphate exceeds a weight ratio of 10, the content of metal ions cannot be minimized.
  • the liquid crystal phase composed of debundled carbon nanotubes forms a structure in which at least one of sulfate and phosphate is cointercalated between adjacent layers of carbon nanotubes through shear stress. That is, when shear stress is applied to the composite powder and acid solution, at least one of sulfate and phosphate is cointercalated between adjacent layers in the carbon nanotube, and at least one of sulfate and phosphate is solvated by the liquid acid solution. In this state, it can be placed between adjacent layers of carbon nanotubes.
  • the debundled carbon nanotubes which are co-intercalated and debundled so that one or more of sulfate and phosphate are positioned between the layers of the carbon nanotubes, may be self-assembled in a liquid crystalline form.
  • the shear stress is applied according to the rpm control, which is the stirring speed. It is preferable to apply the shear stress while stirring at a rotation speed of 100 to 2,000 rpm. The faster the stirring speed, the more evenly the oxidizing agent is dispersed, which helps form a liquid crystalline phase and further increases the oxidizing power, so the stirring speed should be at least 100 rpm.
  • the rotation speed is less than 100 rpm, it is not enough to create a cointercalation structure in which sulfate or phosphate is placed between adjacent layers of the carbon nanotubes, so even if heat treatment is performed later, the bundle size of the carbon nanotubes is minimized or the carbon nanotubes are It is difficult to sufficiently create oxygen-containing functional groups such as carboxyl groups and hydroxy groups on the inside, surface, or ends of nanotubes. If the carbon nanotubes are rotated at a speed exceeding 2,000 rpm, this may cause shape deformation of the carbon nanotubes and cause re-agglomeration, which is not desirable.
  • the shear stress is applied within the range of 10 minutes to 3 hours. It is recommended to maintain stirring for at least 10 minutes to allow the sulfate, phosphate, and oxidizing agent to be evenly distributed and to reduce the bundle size. If the shear stress is applied for less than 10 minutes, there is not enough time for sulfate or phosphate to be located between the layers of the carbon nanotubes in the liquid crystalline crystal, and the sulfate or phosphate that is not located between the layers of the carbon nanotubes becomes disordered in the liquid crystalline crystal. It remains and is not effective.
  • shear stress is applied for more than 3 hours, the process is inefficient because it does not provide a more excellent intercalation effect compared to the case where the shear stress is applied for less than that time.
  • shear stress is applied for 10 to 30 minutes.
  • one or more of an impeller, blade mixer, Couette-Taylor reactor, and paste mixer capable of rotation and revolution can be used.
  • stirring can be performed by double rotation of rotation and revolution using a paste mixer, which can be seen in Figure 2, which schematically shows rotation and revolution according to the present invention.
  • a paste mixer which can be seen in Figure 2, which schematically shows rotation and revolution according to the present invention.
  • FIG. 2 after adding a composite powder in which carbon nanotubes and one or more of sulfate and phosphate are mixed in powder form and an acid solution into at least one container 100, the container is rotated around the rotation axis R1.
  • R2 a preset angle of inclination and simultaneously revolving around the axis of revolution
  • centrifugal force and shear stress are generated, and sulfate or phosphate forms a co-intercalated structure between adjacent layers of the carbon nanotube.
  • a bundled carbon nanotube liquid crystalline phase may be formed.
  • the revolution of the plurality of containers 100 radially connected to the revolution axis R2 around the revolution axis R2, which can be the central rotation axis, and the rotation by the rotation axis R1 at the center of each container 100 are simultaneously performed.
  • the stirring power is improved, making it possible to produce a carbon nanotube liquid crystalline phase in which sulfate or phosphate has a cointercalation structure between adjacent layers of carbon nanotubes.
  • the rotation speed of the container 100 by the rotation axis (R1) and the rotation speed by the revolution axis (R2), which is the central rotation axis, may be in a ratio of 0.1 to 10:1. If the rotation speed is less than 0.1, the rotation speed is too slow compared to the revolution speed, so centrifugal force and shear stress sufficient to form a cointercalation structure in the liquid crystal phase are not generated, and the carbon nanotubes do not have a self-assembled structure. If the rotation speed exceeds a ratio of 10, the rotation speed is too fast than the revolution speed, and sulfate or phosphate cannot be stably positioned between the carbon nanotube layers, so this is also not suitable for forming a co-intercalation structure in the liquid crystalline phase.
  • the rotation axis (R1) can be rotated in the same direction as the revolution axis (R2) based on the rotational temperature of the revolution axis (R2), but in order to form a cointercalation structure in the liquid crystalline crystal, the rotation axis (R1) and the revolution axis (R2) are separated. ) can also be rotated in opposite directions.
  • the rotation axis (R1) and the revolution axis (R2) rotate in opposite directions, there is an advantage in that the power can be divided by rotating the rotation axis (R1) and the revolution axis (R2) at the same speed.
  • a composite powder containing sulfate or phosphate mixed with carbon nanotubes and an acid solution are immediately heated without applying shear stress to first form debundled carbon nanotubes in the form of a liquid crystalline phase, the sulfate or phosphate will form carbon nanotubes. If they are not located between adjacent layers of nanotubes, they may be transformed into oxygen-containing functional groups. Accordingly, before heating the debundled carbon nanotubes, shear stress is first applied to the composite powder in which sulfate or phosphate is mixed with the carbon nanotubes in a solid state, an acid solution, and an alkali metal-containing oxidizing agent to form a liquid crystalline form. This can be said to be an important process.
  • the bundled carbon nanotubes are heated at 30 to 50° C. to prepare carbon nanotubes into which an oxygen-containing functional group is introduced using an acid solution and at least one of sulfate and phosphate (S20).
  • At least one of sulfate and phosphate that is solvated by the acid solution between adjacent layers of the carbon nanotube is removed from the inside, surface or end of the carbon nanotube by the acid solution.
  • Oxygen-containing functional groups such as carboxyl groups and hydroxy groups may be introduced.
  • Heat treatment may be performed at 30 to 50°C, which is close to room temperature, and preferably may be in the range of 30 to 45°C.
  • the heat treatment may be performed for 30 minutes to 24 hours, and is preferably performed for 1 to 10 hours.
  • the heating temperature can be lowered to at least 30 °C, which has the advantage of enabling stable heat treatment without raising the temperature to close to 100 °C. If the debundled carbon nanotubes in the liquid crystalline form are heated below 30°C or for less than 1 hour, it takes a lot of time for oxygen-containing functional groups to be formed in the carbon nanotubes, so it is preferable that the temperature be at least 30°C. If the temperature exceeds 50°C or exceeds 24 hours, there is a disadvantage that electrical conductivity may be reduced due to the formation of defect structures due to excessive introduction of oxygen-containing functional groups into the carbon nanotubes.
  • This step is a process in which the pretreatment of the carbon nanotubes is completed, and only pure carbon nanotube powder can be obtained by neutralizing and washing to remove acids, sulfates, or phosphates used in the heat treatment process.
  • the carbon nanotubes into which oxygen-containing functional groups have been introduced are washed by adding an excessive amount of distilled water, and then filtered through a process such as centrifugation to remove acids, sulfates, and phosphates, thereby obtaining purified carbon nanotubes.
  • the carbon nanotube powder pretreated in this way has dispersibility due to the introduction of oxygen-containing functional groups from the debundled liquid crystalline phase of the carbon nanotube.
  • the carbon nanotubes that are pretreated in this way and have dispersibility can be dispersed in one or more solvents among water (H 2 O), alcohol, dimethylformamide (DMF), and N-methylformamide (NMP). It can be used as a conductive paste to form a conductive film.
  • solvents among water (H 2 O), alcohol, dimethylformamide (DMF), and N-methylformamide (NMP). It can be used as a conductive paste to form a conductive film.
  • carbon nanotubes are made using sulfate or phosphate instead of nitrate, which causes environmental problems in carbon nanotubes (especially single-walled carbon nanotubes) that are aggregated through the bundle phenomenon. It can be debundled.
  • oxygen-containing functional groups can be introduced into carbon nanotubes simply by applying heat to a minimum of 30 °C, which is close to room temperature, rather than a high temperature close to 100 °C, there is an advantage of improving process stability by not having to create a high temperature environment. there is.
  • a composite powder was prepared by mixing 5 g of bundle-shaped single-walled carbon nanotubes and 5 g of sodium sulfate (Na 2 SO 4 ) in a powder state.
  • the prepared composite powder was added to 1,000 ml of sulfuric acid solution, 1 g of potassium peroxymonosulfate was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to form a debundled carbon nanotube liquid crystalline phase.
  • Manufactured This was heated at 45°C for 20 hours to introduce hydroxyl and carboxyl groups into the carbon nanotubes.
  • pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
  • a composite powder was prepared by mixing 5 g of bundle-shaped multi-walled carbon nanotubes and 5 g of sodium sulfate (Na 2 SO 4 ) in a powder state.
  • the prepared composite powder was added to 1,000 ml of sulfuric acid solution, 1 g of potassium peroxymonosulfate was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to form a debundled carbon nanotube liquid crystalline phase.
  • Manufactured This was heated at 50°C for 10 hours to introduce hydroxyl and carboxyl groups into the carbon nanotubes.
  • pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
  • a composite powder was prepared by mixing 5 g of bundle-shaped single-walled carbon nanotubes and 5 g of potassium phosphate (KH 2 PO 4 ) in a powder state.
  • the prepared composite powder was added to 1,000 ml of sulfuric acid solution, 2 g of potassium permanganate (KMnO 4 ) was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to obtain debundled carbon nano.
  • a tube liquid crystal phase was prepared. This was heated at 30°C for 20 hours to introduce a carboxyl group into the carbon nanotube. Afterwards, pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
  • a composite powder was prepared by mixing 5 g of single-walled carbon nanotubes and 5 g of sodium nitrate (NaNO 3 ), which is a nitrate rather than sulfate, in a powder state. Unlike Examples 1 and 2, 1,000 ml of the prepared composite powder and sulfuric acid solution were stirred for 40 minutes using a general stirring method using a magnetic bar. Then, it was heated at 80°C for 20 hours, washed with excess distilled water, centrifuged, and filtered to obtain carbon nanotubes.
  • NaNO 3 sodium nitrate
  • Figure 3 shows a polarizing microscope image of carbon nanotubes pretreated according to Example 1.
  • the carbon nanotubes pretreated as in Example 1 are cointercalated between adjacent layers of the carbon nanotubes by simply applying shear stress for 10 minutes, so the bundle size is reduced, thereby reducing the carbon nanotubes. It was confirmed that the nanotubes were formed in a self-assembled structure in the form of a liquid crystalline phase and exhibited orientation.
  • Figure 4 shows an SEM photograph of carbon nanotubes that were not pretreated according to Comparative Example 1.
  • Figure 4(a) is an SEM photograph showing carbon nanotubes pretreated according to Comparative Example 1 using sodium nitrate, a nitrate, measured at 10.0 kV and magnified at a million times magnification
  • Figure 4(b) is a pretreated carbon nanotube according to Comparative Example 1.
  • This is an SEM photo of carbon nanotubes measured at 15.0 kV and magnified at 1 million times.
  • the carbon nanotubes unlike in Example 1, if the carbon nanotubes are not pretreated, the carbon nanotubes exist in large bundles of 100 nm or more. In contrast, when treated according to Example 1, the bundle size of the carbon nanotubes is 50 nm. It can be controlled below.
  • FIG. 5 graphically shows the results of XPS (X-ray photoelectron spectroscopy) analysis according to Example 1.
  • XPS X-ray photoelectron spectroscopy
  • the present invention is a pretreatment method for carbon nanotubes with improved process stability, which involves debundling carbon nanotubes using one or more of sulfate and phosphate, rather than nitrate, which causes environmental problems in bundle-shaped carbon nanotubes. It has the characteristic of increasing dispersibility by introducing an oxygen-containing functional group.
  • This feature is achieved by applying shear stress to a composite powder mixed with carbon nanotubes and at least one of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent, so that at least one of sulfate and phosphate is deposited between adjacent layers of carbon nanotubes.
  • After manufacturing the co-intercalated and debundled carbon nanotubes in a liquid crystalline form they are heated in the range from 30 °C to 50 °C, which is close to room temperature, and carbon nanotubes into which oxygen-containing functional groups are introduced by sulfate, phosphate and acid solutions are produced.
  • improved process stability can be achieved by introducing an oxygen-containing functional group from the debundled carbon nanotube liquid crystalline phase of the pretreated carbon nanotubes.
  • sulfate or nitrate can very easily penetrate between the layers of carbon nanotubes, and thus functionalization efficiency can be maximized through the acid solution, which is an acid treatment medium.
  • oxygen-containing functional groups are introduced from debundled carbon nanotubes using a small amount of acid solution and sulfate or phosphate rather than nitrate, which has a negative effect on the environment and the human body, in a short period of time. Since functionalization is possible, it is meaningful that carbon nanotubes can be dispersed in a solvent without using a dispersant.

Abstract

The present invention relates to a method for pretreatment of carbon nanotubes with improved process stability and carbon nanotubes pretreated thereby, the method comprising the steps of: mixing composite powder in which at least one of a sulfate and a phosphate is mixed with bundled carbon nanotubes, an acid solution, and an alkali metal-containing oxidizer while applying shear stress thereto, to thereby produce carbon nanotubes debundled through co-intercalation of the at least one of a sulfate and a phosphate into adjacent layers between the carbon nanotubes; heating the debundled carbon nanotubes at 30-50 °C to thereby produce carbon nanotubes in which an oxygen-containing functional group is introduced by the at least one of a sulfate and a phosphate and the acid solution; and washing and filtering the carbon nanotubes in which an oxygen-containing functional group is introduced, to thereby produce pretreated carbon nanotubes.

Description

공정 안정성이 개선된 탄소나노튜브의 전처리 방법, 이에 의해 전처리된 탄소나노튜브Pretreatment method for carbon nanotubes with improved process stability, carbon nanotubes pretreated thereby
본 발명은 공정 안정성이 개선된 탄소나노튜브의 전처리 방법, 이에 의해 전처리된 탄소나노튜브에 관한 것이다.The present invention relates to a pretreatment method for carbon nanotubes with improved process stability, and to carbon nanotubes pretreated thereby.
탄소나노튜브는 6각형 고리로 연결된 탄소들이 긴 대롱 모양을 이루는 미세한 분자로, 전도성, 반사율 등의 전기적 특성과 접착력, 내구성, 내마모성 및 굴곡성 등의 물리적 특성이 우수함에 따라 평면표시소자, 고집적 메모리소자, 이차전지, 초고용량 커패시터, 수소저장 소재, 전기화학 센서, 전자파 차폐 및 케이블 등 전기화학 장치의 부품재료로 널리 이용되고 있다.Carbon nanotubes are fine molecules made of carbon connected in hexagonal rings forming a long tube shape. They have excellent electrical properties such as conductivity and reflectivity, as well as physical properties such as adhesion, durability, wear resistance, and flexibility, making them useful in flat display devices and highly integrated memory devices. It is widely used as a component material for electrochemical devices such as secondary batteries, ultra-high capacity capacitors, hydrogen storage materials, electrochemical sensors, electromagnetic wave shielding, and cables.
보통 탄소나노튜브는, 탄소나노튜브가 용매 또는 고분자 내에 균일하게 분산된 탄소나노튜브 분산액을 제조하고, 이를 전기화학 장치의 부품에 도포 또는 분사하여 탄소나노튜브층을 형성하는 과정으로 적용될 수 있다.Usually, carbon nanotubes can be applied through the process of preparing a carbon nanotube dispersion in which carbon nanotubes are uniformly dispersed in a solvent or polymer, and applying or spraying this to parts of an electrochemical device to form a carbon nanotube layer.
하지만 탄소나노튜브는 원자가 수십 개의 탄소 원자로 이루어진 반면, 길이는 수 ㎛에 달해 종횡비(aspect ratio)가 매우 크며, 탄소나노튜브 사이의 인력으로 인해 응집되는 현상이 발생되어 분산 안정성이 낮기 때문에, 탄소나노튜브가 용매 또는 고분자 내에 균일하게 분산된 탄소나노튜브 분산액의 제조가 어려울 뿐만 아니라, 탄소나노튜브가 균일하게 분산된 탄소나노튜브층을 형성할 수 없어 전기화학 특성이 충분히 향상되지 못하는 문제점이 있다.However, while carbon nanotubes are made up of dozens of carbon atoms, their length is several ㎛, so their aspect ratio is very large, and agglomeration occurs due to the attractive force between carbon nanotubes, resulting in low dispersion stability. Not only is it difficult to manufacture a carbon nanotube dispersion in which the tubes are uniformly dispersed in a solvent or polymer, but there is a problem in that the electrochemical properties are not sufficiently improved because a carbon nanotube layer in which the carbon nanotubes are uniformly dispersed cannot be formed.
상기 문제점을 해결해 보기 위한 예로서 "고농도 고분산 탄소나노튜브 분산액의 제조방법(등록번호: 10-1365456)"에서는 수퍼 로프(Super-rope) 탄소나노튜브 번들을 건식 분쇄하고, 이를 습식 분쇄한 후 용매와 혼합하여 고농도 및 고분산 특성을 갖는 탄소나노튜브 분산액을 제조하는 기술을 제시하였다. 그러나 탄소나노튜브 번들을 건식 분쇄 및 습식 분쇄하기 위한 별도의 장치가 요구되고, 탄소나노튜브 번들의 분쇄가 완전하지 않아 분산 안정성 향상 효과가 미미하며, 건식방법으로 물리적 응력을 가할 경우 탄소나노튜브 길이가 짧아짐에 따른 전기전도성 저하의 문제점이 있다.As an example to solve the above problem, in "Method for producing a highly concentrated and highly dispersed carbon nanotube dispersion (registration number: 10-1365456)", super-rope carbon nanotube bundles are dry-ground, and then wet-ground. A technology for producing a carbon nanotube dispersion with high concentration and high dispersion characteristics by mixing with a solvent was presented. However, separate devices are required for dry grinding and wet grinding of the carbon nanotube bundles, and the grinding of the carbon nanotube bundles is not complete, so the effect of improving dispersion stability is minimal, and when physical stress is applied using the dry method, the length of the carbon nanotubes is reduced. There is a problem of decreased electrical conductivity as is shortened.
"탄소나노튜브 나노복합 전도성 섬유용 조성물 및 그 제조방법(공개번호: 10-2019-0108734)'에서는 탄소나노튜브가 산화되거나 표면에 카본결합이 끊어지지 않도록 산과 질산염을 혼합하여 산처리를 통해 탄소나노튜브를 디번들링하여 고분자 내에 분산되게 하는 기술을 제시하였다. 그러나 탄소나노튜브에 비해 고분자의 함량을 높게 하여 연신 과정에서 섬유의 끊어짐이 발생하지 않도록 하는 것일 뿐, 탄소나노튜브의 분산 안정성을 높이는 데에는 한계점이 있다.In "Composition for carbon nanotube nanocomposite conductive fiber and its manufacturing method (Publication number: 10-2019-0108734)", carbon is treated with acid by mixing acid and nitrate to prevent carbon nanotubes from being oxidized or carbon bonds on the surface to be broken. A technology was proposed to debundle nanotubes and disperse them within the polymer. However, this only prevents fiber breakage during the stretching process by increasing the polymer content compared to carbon nanotubes, but also improves the dispersion stability of carbon nanotubes. There is a limit to this.
특히 탄소나노튜브의 디번들링시키는데 활용되는 질산염은 질산성 질소로서, 유기물 중 질소 화합물이 산화되면서 분해돼 무기화한 물질이다. 질산염은 무분별하게 과량 사용하게 되면 녹조의 원인이 되고, 수질에 유해한 오염을 일으켜 수십 년 동안 지하수 오염의 주요 원인으로 지적받고 있으며, 결국 질산염에 의해 산소 고갈과 부영양화를 초래하여 생태계에 해로움을 끼친다. 또한 질산염은 식수를 통해 인체 내(특히, 유아의 위)에 들어오면 환원균에 의해 아질산염으로 환원되고, 상기 아질산염이 혈액 중의 헤모글로빈과 반응하여 산소 운반 기능이 없는 혈색소인 메트헤모글로빈을 생성함으로서 청색증을 유발하는 등 인간의 건강을 위협하고 있다.In particular, nitrate, which is used to debundle carbon nanotubes, is nitrate nitrogen, which is a substance that is decomposed and mineralized as nitrogen compounds among organic substances are oxidized. Nitrate, when used indiscriminately and in excessive amounts, causes green algae, causes harmful pollution to water quality, and has been pointed out as a major cause of groundwater pollution for decades. In the end, nitrate causes oxygen depletion and eutrophication, harming the ecosystem. In addition, when nitrate enters the human body (especially the stomach of an infant) through drinking water, it is reduced to nitrite by reducing bacteria, and the nitrite reacts with hemoglobin in the blood to produce methemoglobin, a hemoglobin without oxygen transport function, causing cyanosis. It is threatening human health.
이에, 질산염의 회귀 공정을 위해 수질 정화와 같은 경제적 처리 방법을 필요로 하고 있으나, 질산염의 사용으로 증대되는 문제점들의 심각성에 비하여 수질 정화 등 관련 처리 기술의 발전은 아직 미비한 상황이다. 따라서 번들 상태로 응집되어 있는 탄소나노튜브에 질산염을 사용하지 않고 디번들링시켜 분산성을 높일 수 있으면서 공정 안정성을 개선할 수 있는 전처리 방법에 대한 기술개발이 요구되고 있는 실정이다.Accordingly, economical treatment methods such as water purification are needed for the nitrate regression process, but compared to the severity of problems that increase due to the use of nitrates, the development of related treatment technologies such as water purification is still insufficient. Therefore, there is a need to develop technology for a pretreatment method that can increase dispersibility and improve process stability by debundling carbon nanotubes aggregated in a bundle state without using nitrate.
본 발명은 상기한 문제점을 해소하기 위하여 발명된 것으로, 질산염을 사용하지 않고 공정 안정성을 개선할 수 있도록 하는 탄소나노튜브의 전처리 방법, 이에 의해 전처리된 탄소나노튜브을 제공하는 것을 기술적 해결과제로 한다.The present invention was invented to solve the above problems, and its technical problem is to provide a pretreatment method for carbon nanotubes that improves process stability without using nitrates, and carbon nanotubes pretreated thereby.
상기의 기술적 과제를 해결하기 위하여 본 발명은, 번들 형상의 탄소나노튜브에 황산염 및 인산염 중 하나 이상을 혼합한 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하면서 혼합하여, 상기 황산염 및 인산염 중 하나 이상이 상기 탄소나노튜브의 상호 인접하는 층간에 코인터칼레이션(co-intercalation)되어 디번들링된 탄소나노튜브를 제조하는 단계; 상기 디번들링된 탄소나노튜브를 30 내지 50 ℃에서 가열하여, 상기 황산염 및 인산염 중 하나 이상과 상기 산 용액에 의해 산소 함유 관능기가 도입된 탄소나노튜브를 제조하는 단계; 및 상기 산소 함유 관능기가 도입된 탄소나노튜브를 세척 및 여과하여, 전처리된 탄소나노튜브를 제조하는 단계;를 포함하여, 상기 황산염 및 인산염 중 하나 이상을 이용하여 디번들링된 탄소나노튜브를 제조하고 산소 함유 관능기를 도입하는 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법을 제공한다.In order to solve the above technical problem, the present invention mixes a composite powder in which bundle-shaped carbon nanotubes are mixed with one or more of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent while applying shear stress, producing debundled carbon nanotubes by co-intercalating one or more of sulfate and phosphate between adjacent layers of the carbon nanotubes; Heating the debundled carbon nanotubes at 30 to 50° C. to produce carbon nanotubes into which an oxygen-containing functional group is introduced by at least one of the sulfate and phosphate and the acid solution; And washing and filtering the carbon nanotubes into which the oxygen-containing functional group has been introduced to prepare pretreated carbon nanotubes; including, preparing debundled carbon nanotubes using one or more of the sulfate and phosphate salts, and A pretreatment method for carbon nanotubes with improved process stability, characterized by introducing an oxygen-containing functional group, is provided.
본 발명에 있어서, 상기 황산염은 황산나트륨(Na2SO4), 황산칼륨(K2SO4), 황산수소나트륨(NaHSO4), 황산수소칼륨(KHSO4), 과산화일황산칼륨(KHSO5) 및 과황산암모늄((NH4)2S2O8)으로 이루어진 군으로부터 선택되는 1종 이상이고, 상기 인산염은 디포타슘포스페이트(K2HPO4) 및 인산칼륨(KH2PO4)으로 이루어진 군으로부터 선택되는 1종 이상인 것을 특징으로 한다.In the present invention, the sulfate is sodium sulfate (Na 2 SO 4 ), potassium sulfate (K 2 SO 4 ), sodium hydrogen sulfate (NaHSO 4 ), potassium hydrogen sulfate (KHSO 4 ), potassium peroxymonosulfate (KHSO 5 ), and At least one selected from the group consisting of ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), and the phosphate is selected from the group consisting of dipotassium phosphate (K 2 HPO 4 ) and potassium phosphate (KH 2 PO 4 ). It is characterized in that there is at least one type selected.
본 발명에 있어서, 상기 알칼리금속 함유 산화제는, 과망간산 칼륨(Potassium manganate, KMnO4), 소듐 클로레이트(Sodium chlorate, NaClO3), 소듐 퍼클로레이트(NaClO4), 포타슘 클로레이트(KClO3), 포타슘 퍼클로레이트(KClO4) 및 포타슘 퍼옥시모노설페이트(Potassium Peroxymonosulfate, KHSO5) 중 하나 이상인 것을 특징으로 한다.In the present invention, the alkali metal-containing oxidizing agent is potassium permanganate (KMnO 4 ), sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ) , potassium chlorate (KClO 3 ), and potassium perchlorate. (KClO 4 ) and potassium peroxymonosulfate (Potassium Peroxymonosulfate, KHSO 5 ).
본 발명에 있어서, 상기 탄소나노튜브는, 단일벽 탄소나노튜브(single-walled carbon nanotube, SWCNT), 이중벽 탄소나노튜브(double-walled carbon nanotube, DWCNT) 및 다중벽 탄소나노튜브(multiwalled carbon nanotube, MWCNT) 중 하나 이상인 것을 특징으로 한다.In the present invention, the carbon nanotubes include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multiwalled carbon nanotubes (multiwalled carbon nanotubes). It is characterized by one or more of MWCNT).
본 발명에 있어서, 상기 디번들링된 탄소나노튜브를 제조하는 단계는, 임펠러, 페이스트 믹서, 블레이드 믹서 및 쿠에트-테일러 반응기 중 하나 이상을 이용하여 상기 전단응력을 가하는 것을 특징으로 한다.In the present invention, the step of manufacturing the debundled carbon nanotubes is characterized by applying the shear stress using one or more of an impeller, a paste mixer, a blade mixer, and a Couette-Taylor reactor.
상기의 다른 기술적 과제를 해결하기 위하여 본 발명은, 상기 방법으로 전처리된 것을 특징으로 하는, 탄소나노튜브를 제공한다.In order to solve the above-mentioned other technical problems, the present invention provides carbon nanotubes, characterized in that they have been pretreated by the above method.
상기 과제의 해결 수단에 의한 본 발명에 따르면, 번들 현상으로 응집되어 있는 탄소나노튜브에 환경 문제를 야기하는 질산염 대신 황산염이나 인산염을 사용하여 탄소나노튜브를 디번들링시킬 수 있으며, 100 ℃에 가까운 고온이 아닌 상온에 가까운 최소 30 ℃로 열을 가하는 것만으로 탄소나노튜브에 산소 함유 관능기를 도입할 수 있으므로, 고온 환경을 조성하지 않아도 되어 공정 안정성을 개선할 수 있는 효과가 있다.According to the present invention as a means of solving the above problem, it is possible to debundle carbon nanotubes using sulfate or phosphate instead of nitrate, which causes environmental problems in carbon nanotubes that are aggregated due to the bundling phenomenon, and at a high temperature close to 100 ° C. Rather than this, oxygen-containing functional groups can be introduced into carbon nanotubes simply by applying heat to at least 30°C, which is close to room temperature, so there is no need to create a high temperature environment, which has the effect of improving process stability.
또한 황산염 또는 인산염이 탄소나노튜브의 상호 인접하는 층간 사이에서 코인터칼레이션되어, 전처리된 탄소나노튜브가 자기조립 구조로 액정상을 형성하여 산소 함유 관능기가 도입되므로 탄소나노튜브의 디번들링 효과를 극대화시킬 수 있다.In addition, sulfate or phosphate cointercalates between adjacent layers of carbon nanotubes, and the pretreated carbon nanotubes form a liquid crystalline phase with a self-assembled structure, thereby introducing oxygen-containing functional groups, thereby promoting the debundling effect of carbon nanotubes. It can be maximized.
또한 본 발명의 방법으로 전처리된 탄소나노튜브는 이차전지용 도전성 첨가제, 이차전지 집전장치(current collector)용 도전성 프라이머 뿐만 아니라, 투명전극, 대전방지, 전자파 차폐 용도 외에 전도성 섬유, 센서, 전도성 고분자복합소재 등 다양한 분야에 응용할 수 있는 효과가 있다.In addition, carbon nanotubes pretreated by the method of the present invention are used not only as a conductive additive for secondary batteries and a conductive primer for secondary battery current collectors, but also as transparent electrodes, antistatic, and electromagnetic wave shielding, as well as conductive fibers, sensors, and conductive polymer composite materials. It has effects that can be applied to various fields such as:
도 1은 본 발명에 따라 탄소나노튜브를 전처리하는 방법을 나타낸 순서도.1 is a flowchart showing a method for pretreating carbon nanotubes according to the present invention.
도 2는 본 발명에 따른 자전과 공전을 나타낸 모식도.Figure 2 is a schematic diagram showing rotation and revolution according to the present invention.
도 3은 실시예 1에 따라 전처리된 탄소나노튜브를 나타낸 편광현미경 이미지.Figure 3 is a polarizing microscope image showing carbon nanotubes pretreated according to Example 1.
도 4는 비교예 1에 따라 전처리되지 않은 탄소나노튜브를 나타낸 SEM 사진.Figure 4 is an SEM photograph showing carbon nanotubes that were not pretreated according to Comparative Example 1.
도 5는 실시예 1에 따른 XPS 분석 결과를 나타낸 그래프.Figure 5 is a graph showing the results of XPS analysis according to Example 1.
이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.
본 발명은 공정 안정성이 개선된 탄소나노튜브의 전처리 방법에 관한 것이다. 관련하여 도 1은 본 발명에 따라 탄소나노튜브를 전처리하는 방법을 순서도로 나타낸 것이다. 본 발명의 공정 안정성이 개선된 탄소나노튜브를 전처리하는 방법은 도 1에서와 같이, 번들 형상의 탄소나노튜브에 황산염 및 인산염 중 하나 이상을 혼합한 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하면서 혼합하여, 황산염 및 인산염 중 하나 이상이 탄소나노튜브의 상호 인접하는 층간에 코인터칼레이션(co-intercalation)되어 디번들링된 탄소나노튜브를 제조하는 단계(S10), 디번들링된 탄소나노튜브를 30 내지 50 ℃에서 가열하여, 황산염 및 인산염 중 하나 이상과 산 용액에 의해 산소 함유 관능기가 도입된 탄소나노튜브를 제조하는 단계(S20), 산소 함유 관능기가 도입된 탄소나노튜브를 세척 및 여과하여, 전처리된 탄소나노튜브를 제조하는 단계(S30)를 포함하여 이루어진다.The present invention relates to a pretreatment method for carbon nanotubes with improved process stability. In relation to this, Figure 1 shows a flow chart of a method for pre-treating carbon nanotubes according to the present invention. As shown in FIG. 1, the method of pretreating carbon nanotubes with improved process stability of the present invention includes a composite powder mixed with one or more of sulfate and phosphate in bundle-shaped carbon nanotubes, an acid solution, and an oxidizing agent containing an alkali metal. Step (S10) of mixing while applying shear stress to produce debundled carbon nanotubes in which at least one of sulfate and phosphate co-intercalates between adjacent layers of the carbon nanotubes, Heating the bundled carbon nanotubes at 30 to 50°C to produce carbon nanotubes into which an oxygen-containing functional group is introduced by an acid solution with at least one of sulfate and phosphate (S20), carbon nanotubes into which an oxygen-containing functional group is introduced It includes a step (S30) of washing and filtering the tube to produce pretreated carbon nanotubes.
단, 본 명세서에서 기재된 전처리는 전단응력을 통하여 탄소나노튜브의 상호 인접하는 층간 사이에 황산염 및 인산염 중 하나 이상이 코인터칼레이션되도록 하고, 열처리를 통하여 탄소나노튜브에 산소 함유 관능기가 도입되도록 하는 과정을 의미한다.However, the pretreatment described in this specification causes one or more of sulfate and phosphate to cointercalate between adjacent layers of carbon nanotubes through shear stress, and introduces oxygen-containing functional groups into the carbon nanotubes through heat treatment. It means process.
탄소나노튜브를 전처리하기 위하여 먼저, 번들 형상의 탄소나노튜브에 황산염 및 인산염 중 하나 이상을 혼합한 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하면서 혼합하여, 황산염 및 인산염 중 하나 이상이 탄소나노튜브의 상호 인접하는 층간에 코인터칼레이션(co-intercalation)되어 디번들링된 탄소나노튜브를 제조한다(S10).In order to pre-treat carbon nanotubes, first, a composite powder of bundle-shaped carbon nanotubes mixed with one or more of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent are mixed while applying shear stress to form a mixture of sulfate and phosphate. At least one carbon nanotube is co-intercalated between adjacent layers to produce debundled carbon nanotubes (S10).
본 발명에서 전처리될 수 있는 탄소나노튜브는 단일벽 탄소나노튜브(single-walled carbon nanotube, SWCNT), 이중벽 탄소나노튜브(double-walled carbon nanotube, DWCNT) 및 다중벽 탄소나노튜브(multiwalled carbon nanotube, MWCNT) 중 하나 이상이 사용될 수 있다. 이중에서 단일벽 탄소나노튜브는 직경이 1 nm 수준에 불과하여 단독으로 존재하지 못하고 van der Waals 인력에 의해 번들 형상으로 응집되는 특성을 갖는다. 다중벽 탄소나노튜브는 직경이 커서 응집현상이 일어나기도 하나, 이보다는 고분자 사슬의 엉킴 현상와 유사한 특성을 나타낸다. 이중벽 탄소나노튜브의 경우 직경이 작은 일부는 단일벽 탄소나노튜브와 유사한 특성을 갖기도 하며, 직경이 큰 일부는 다중벽 탄소나노튜브와 유사한 특성을 갖는다.Carbon nanotubes that can be pretreated in the present invention include single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multiwalled carbon nanotubes (multiwalled carbon nanotubes). MWCNT) may be used. Among them, single-walled carbon nanotubes have a diameter of only 1 nm, so they cannot exist alone and have the characteristic of being aggregated into a bundle shape by van der Waals attraction. Multi-walled carbon nanotubes have a large diameter, so agglomeration may occur, but they exhibit characteristics similar to the tangle phenomenon of polymer chains. In the case of double-walled carbon nanotubes, some with small diameters have characteristics similar to single-walled carbon nanotubes, and some with large diameters have characteristics similar to multi-walled carbon nanotubes.
상기 특성을 갖는 탄소나노튜브는 고유한 전기적, 열적 및 물리화학적 특성에 의해 전도성 소재로 각광받고 있음에도 불구하고 엉킴 현상에 의한 번들 형상으로의 응집이 되어 분산 안정성을 확보하기 어려운 단점이 있다. 특히 탄소나노튜브의 응집 현상은 물리적으로 처리하는데 어려움이 있어왔다.Although carbon nanotubes having the above characteristics are in the spotlight as conductive materials due to their unique electrical, thermal, and physicochemical properties, they have the disadvantage of agglomerating into bundle shapes due to entanglement, making it difficult to secure dispersion stability. In particular, the agglomeration phenomenon of carbon nanotubes has been difficult to physically treat.
이에 탄소나노튜브를 용매 내에서 번들링 또는 응집되거나 침전되지 않도록 하여 안정된 상태로 분산시키기 위해서 탄소나노튜브를 전처리하는 방법이 필요하기에, 본 단계에서는 탄소나노튜브를 황산염 및 인산염 중 하나 이상을 고체 상태로 혼합하여 복합분말을 제조하고, 이후 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하면서 혼합하여 디번들링된 탄소나노튜브를 제조한다.Accordingly, a method of pre-treating the carbon nanotubes is needed to disperse the carbon nanotubes in a stable state by preventing them from bundling, agglomerating, or precipitating in the solvent. In this step, the carbon nanotubes are mixed with one or more of sulfate and phosphate in a solid state. A composite powder is prepared by mixing, and then the composite powder, an acid solution, and an alkali metal-containing oxidizing agent are mixed while applying shear stress to prepare debundled carbon nanotubes.
황산염은 황산나트륨(Na2SO4), 황산칼륨(K2SO4), 황산수소나트륨(NaHSO4), 황산수소칼륨(KHSO4), 과산화일황산칼륨(KHSO5) 및 과황산암모늄((NH4)2S2O8)으로 이루어진 군으로부터 선택되는 1종 이상이고, 인산염은 디포타슘포스페이트(K2HPO4) 및 인산칼륨(KH2PO4)으로 이루어진 군으로부터 선택되는 1종 이상일 수 있다.Sulfates include sodium sulfate (Na 2 SO 4 ), potassium sulfate (K 2 SO 4 ), sodium hydrogen sulfate (NaHSO 4 ), potassium hydrogen sulfate (KHSO 4 ), potassium peroxymonosulfate (KHSO 5 ), and ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), and the phosphate may be at least one selected from the group consisting of dipotassium phosphate (K 2 HPO 4 ) and potassium phosphate (KH 2 PO 4 ). .
질산염의 경우 황산염이나 인산염처럼 탄소나노튜브 층간 사이에 삽입 가능한 코인터켈런트로 사용이 가능하긴 하지만 질산염 사용에 따른 환경 문제 야기로 인해 배제하는 것이 공정단가 측면에서 유리하며, 황산염이나 인산염과 달리 질산염 자체로는 70 ℃ 이상으로 가열해야만 탄소나노튜브의 산화가 이루어지기 때문에 최소 30 ℃에 가까운 상온에서는 탄소나노튜브에 질산염에 의한 산소 함유 관능기가 도입될 수 없다.In the case of nitrate, like sulfate or phosphate, it can be used as a cointercalant that can be inserted between carbon nanotube layers, but due to the environmental problems caused by the use of nitrate, it is advantageous in terms of process cost to exclude it, and unlike sulfate or phosphate, nitrate Since oxidation of carbon nanotubes occurs only when heated above 70°C, oxygen-containing functional groups caused by nitrate cannot be introduced into carbon nanotubes at room temperatures close to at least 30°C.
산 용액은 황산(H2SO4), 질산(HNO3), 인산(H3PO4), 과산화수소(H2O2) 및 염산(HCl)으로 이루어진 군으로부터 1종 이상이 선택될 수 있다. 다만 산 용액은 상술한 종류에 한정되는 것은 아니고 액상의 산 용액에 포함될 수 있는 물질이라면 다양하게 사용될 수 있다.The acid solution may be at least one selected from the group consisting of sulfuric acid (H 2 SO 4 ), nitric acid (HNO 3 ), phosphoric acid (H 3 PO 4 ), hydrogen peroxide (H 2 O 2 ), and hydrochloric acid (HCl). However, the acid solution is not limited to the above-mentioned types, and various substances that can be included in the liquid acid solution can be used.
황산염이나 인산염만을 사용하게 되면 탄소나노튜브의 산화 효율이 다소 낮을 수 있어 알칼리금속 함유 산화제를 함께 사용하는 것이 바람직하다. 알칼리금속 함유 산화제의 경우 과망간산 칼륨(Potassium manganate, KMnO4), 소듐 클로레이트(Sodium chlorate, NaClO3), 소듐 퍼클로레이트(NaClO4), 포타슘 클로레이트(KClO3), 포타슘 퍼클로레이트(KClO4) 및 포타슘 퍼옥시모노설페이트(Potassium Peroxymonosulfate, KHSO5) 중 하나 이상일 사용할 수 있다. 알칼리금속 함유 산화제 대신 일반적인 산화제(예를 들어, 황산이나 질산)를 사용하게 되면 대략 70 ℃ 이상의 고온으로 승온시켜야 산화가 진행되는 단점이 있다.If only sulfate or phosphate is used, the oxidation efficiency of carbon nanotubes may be somewhat low, so it is desirable to use an oxidizing agent containing an alkali metal together. For alkali metal-containing oxidizing agents, potassium permanganate (KMnO 4 ), sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ), potassium chlorate (KClO 3 ), potassium perchlorate (KClO 4 ), and potassium perchlorate (NaClO 4 ). One or more of peroxymonosulfate (Potassium Peroxymonosulfate, KHSO 5 ) can be used. If a general oxidizing agent (for example, sulfuric acid or nitric acid) is used instead of an alkali metal-containing oxidizing agent, there is a disadvantage that oxidation must proceed at a high temperature of approximately 70°C or higher.
용매 기능과 산화제 기능을 하는 산 용액을 투입하기 전에 탄소나노튜브와, 황산염 및 인산염 중 하나 이상을 믹서 등을 이용하여 파우더 상태로 먼저 혼합하는 이유는 탄소나노튜브의 상호 인접하는 층간 사이에 황산염 및 인산염 중 하나 이상의 침투가 용이하도록 하여 코인터칼레이션 구조를 만들어 기능화 효율을 높이기 위함이다.The reason that carbon nanotubes and one or more of sulfate and phosphate are first mixed in a powder state using a mixer before adding the acid solution that functions as a solvent and an oxidizing agent is to prevent sulfate and phosphate between adjacent layers of the carbon nanotubes. This is to increase functionalization efficiency by creating a co-intercalation structure by facilitating the penetration of one or more of the phosphates.
복합분말 내에서의 황산염이나 인산염 양을 최소화하여 디번들링된 탄소나노튜브가 액정상을 형성하는 것이 바람직하다. 보통 황산염이나 인산염이 아닌 질산염을 이용하는 경우 탄소나노튜브 양의 10 배 초과하여 사용하는데, 본 단계에서는 전단응력을 이용하기 때문에 탄소나노튜브 1 중량 대비 황산염 및 인산염 중 하나 이상이 0.1 내지 10 중량비로 혼합되는 것만으로 충분하다.It is desirable to minimize the amount of sulfate or phosphate in the composite powder so that the debundled carbon nanotubes form a liquid crystalline phase. Usually, when using nitrate rather than sulfate or phosphate, more than 10 times the amount of carbon nanotubes is used. Since shear stress is used in this step, at least one of sulfate and phosphate is mixed at a weight ratio of 0.1 to 10 based on 1 weight of carbon nanotubes. Just being is enough.
황산염 및 인산염 중 하나 이상이 0.1 중량비 미만으로 혼합되면 탄소나노튜브의 내부, 표면 또는 말단을 카르복실기나 하이드록시기인 산소 함유 관능기로 기능화해주기 어렵다. 이로 인해 탄소나노튜브에 도입되는 산소 함유 관능기로 기능화해주기 어렵기 때문에 최소 0.1 중량비 이상은 되어야 한다. 황산염 및 인산염 중 하나 이상이 0.1 중량비 미만인 경우 탄소나노튜브에 도입되는 산소 함유 관능기도 적어져 결국 탄소나노튜브가 자기조립되지 못하고 무질서한 방향으로 분산될 수 밖에 없다. 전단응력을 가하여 탄소나노튜브에 산소 함유 관능기를 도입하여 탄소나노튜브의 자기조립화를 형성하기 위해 황산염 및 인산염 중 하나 이상은 탄소나노튜브 1 중량비 대비 최소 0.1 중량비가 되게 하는 것이 바람직하다. 반면 황산염 및 인산염 중 하나 이상이 10 중량비를 초과하면 금속이온의 함량을 최소화할 수 없게 된다.If one or more of sulfate and phosphate are mixed in a weight ratio of less than 0.1, it is difficult to functionalize the interior, surface, or end of the carbon nanotube with an oxygen-containing functional group such as a carboxyl group or a hydroxy group. Because of this, it is difficult to functionalize the carbon nanotubes with oxygen-containing functional groups, so the weight ratio must be at least 0.1. If at least one of sulfate and phosphate is less than 0.1 weight ratio, the number of oxygen-containing functional groups introduced into the carbon nanotubes decreases, and eventually the carbon nanotubes cannot self-assemble and are forced to disperse in a disordered direction. In order to form self-assembly of carbon nanotubes by introducing oxygen-containing functional groups into carbon nanotubes by applying shear stress, it is preferable that at least one of sulfate and phosphate be at a weight ratio of at least 0.1 relative to 1 weight ratio of carbon nanotubes. On the other hand, if one or more of sulfate and phosphate exceeds a weight ratio of 10, the content of metal ions cannot be minimized.
디번들링된 탄소나노튜브로 이루어진 액정상은 전단응력을 통하여 황산염 및 인산염 중 하나 이상이 탄소나노튜브의 상호 인접하는 층간 사이에서 코인터칼레이션된 구조를 이루게 된다. 즉 복합분말 및 산 용액에 전단응력이 가해지면 황산염 및 인산염 중 하나 이상이 탄소나노튜브 내 인접하는 층 사이에 코인터칼레이션되되, 황산염 및 인산염 중 하나 이상이 액상의 산 용액에 의해 용매화된 상태로 탄소나노튜브의 상호 인접하는 층간 사이에 배치될 수 있게 된다. 이렇게 탄소나노튜브의 층간 사이에 황산염 및 인산염 중 하나 이상이 위치되도록 코인터칼레이션되어 디번들링된 탄소나노튜브는 액정상 형태로 자기조립이 된 상태가 될 수 있다.The liquid crystal phase composed of debundled carbon nanotubes forms a structure in which at least one of sulfate and phosphate is cointercalated between adjacent layers of carbon nanotubes through shear stress. That is, when shear stress is applied to the composite powder and acid solution, at least one of sulfate and phosphate is cointercalated between adjacent layers in the carbon nanotube, and at least one of sulfate and phosphate is solvated by the liquid acid solution. In this state, it can be placed between adjacent layers of carbon nanotubes. The debundled carbon nanotubes, which are co-intercalated and debundled so that one or more of sulfate and phosphate are positioned between the layers of the carbon nanotubes, may be self-assembled in a liquid crystalline form.
전단응력은 교반 속도인 rpm 조절에 따라 인가되는데, 100 내지 2,000 rpm의 회전속도로 교반하면서 전단응력을 가하는 것이 바람직하다. 교반 속도가 빠를수록 산화제가 더 고르게 분산되어 액정상 형성에 도움이 되고 산화력을 더 높여줄 수 있으므로 교반 속도가 최소 100 rpm은 되어야 한다. 만약 회전속도가 100 rpm 미만이면 탄소나노튜브의 상호 인접하는 층간 사이에 황산염 또는 인산염이 배치되는 코인터칼레이션 구조를 만들어 주기에 부족하여 추후 열처리를 하게 되더라도 탄소나노튜브의 번들 크기를 최소화하거나 탄소나노튜브의 내부나, 표면 또는 말단에 카르복실기와 하이드록시기와 같은 산소 함유 관능기를 충분히 만들어주기 어렵다. 2,000 rpm를 초과하는 속도로 회전되면 오히려 탄소나노튜브의 형상 변형을 초래하여 다시 응집되는 현상이 발생할 수 있어 바람직하지 않다.The shear stress is applied according to the rpm control, which is the stirring speed. It is preferable to apply the shear stress while stirring at a rotation speed of 100 to 2,000 rpm. The faster the stirring speed, the more evenly the oxidizing agent is dispersed, which helps form a liquid crystalline phase and further increases the oxidizing power, so the stirring speed should be at least 100 rpm. If the rotation speed is less than 100 rpm, it is not enough to create a cointercalation structure in which sulfate or phosphate is placed between adjacent layers of the carbon nanotubes, so even if heat treatment is performed later, the bundle size of the carbon nanotubes is minimized or the carbon nanotubes are It is difficult to sufficiently create oxygen-containing functional groups such as carboxyl groups and hydroxy groups on the inside, surface, or ends of nanotubes. If the carbon nanotubes are rotated at a speed exceeding 2,000 rpm, this may cause shape deformation of the carbon nanotubes and cause re-agglomeration, which is not desirable.
또한 전단응력은 10 분 내지 3 시간 범위 내로 가해지는 것이 바람직하다. 황산염이나 인산염, 산화제가 고르게 분산될 수 있도록 하면서 번들 크기가 줄어들도록 최소 10 분 이상을 교반을 유지하는 것이 좋다. 만약 10 분 미만으로 전단응력을 가하면 액정상 내에 탄소나노튜브의 층간 사이에 황산염 또는 인산염이 위치될 수 있는 시간이 부족해지고, 탄소나노튜브 층간 사이에 위치하지 못한 황산염 또는 인산염이 액정상 내에 무질서하게 잔류하여 효율적이지 못하다. 3 시간을 초과하여 전단응력을 가하게 되면 그 이하의 시간으로 실시한 경우와 비교하여 더 탁월한 인터칼레이션 작용을 나타내지 못하여 공정 측면에서 비효율적이다. 바람직하게는 10 내지 30 분 동안 전단응력을 가하는 것이 바람직하다.Additionally, it is preferable that the shear stress is applied within the range of 10 minutes to 3 hours. It is recommended to maintain stirring for at least 10 minutes to allow the sulfate, phosphate, and oxidizing agent to be evenly distributed and to reduce the bundle size. If the shear stress is applied for less than 10 minutes, there is not enough time for sulfate or phosphate to be located between the layers of the carbon nanotubes in the liquid crystalline crystal, and the sulfate or phosphate that is not located between the layers of the carbon nanotubes becomes disordered in the liquid crystalline crystal. It remains and is not effective. If the shear stress is applied for more than 3 hours, the process is inefficient because it does not provide a more excellent intercalation effect compared to the case where the shear stress is applied for less than that time. Preferably, shear stress is applied for 10 to 30 minutes.
전단응력을 가하는 방법으로는 임펠러, 블레이드 믹서, 쿠에트-테일러 반응기 및 자전(rotation)과 공전(revolution)이 가능한 페이스트 믹서 중 어느 하나 이상을 이용할 수 있으며, 전단응력이 강할수록 액정상을 형성하는 시간을 단축시킬 수 있게 된다.As a method of applying shear stress, one or more of an impeller, blade mixer, Couette-Taylor reactor, and paste mixer capable of rotation and revolution can be used. The stronger the shear stress, the more likely it is to form a liquid crystalline phase. Time can be shortened.
예를 들면 페이스트 믹서를 이용하여 자전과 공전의 2중 회전에 의해 교반을 수행할 수 있으며, 이는 본 발명에 따른 자전과 공전을 모식도로 나타낸 도 2에서 알 수 있다. 도 2를 참조하면, 적어도 하나 이상의 용기(100)에 탄소나노튜브와 황산염 및 인산염 중 하나 이상이 분말 상태로 혼합된 복합분말과, 산 용액을 투입한 후, 용기를 자전축(R1)을 중심으로 기 설정된 각도의 기울기로 자전시킴과 동시에 공전축(R2)을 중심으로 공전시켜 원심력과 전단응력이 생성되면서 황산염 또는 인산염이 탄소나노튜브의 상호 인접하는 층간 사이에서 코인터칼레이션된 구조를 이루어 디번들링된 탄소나노튜브 액정상이 형성될 수 있다.For example, stirring can be performed by double rotation of rotation and revolution using a paste mixer, which can be seen in Figure 2, which schematically shows rotation and revolution according to the present invention. Referring to FIG. 2, after adding a composite powder in which carbon nanotubes and one or more of sulfate and phosphate are mixed in powder form and an acid solution into at least one container 100, the container is rotated around the rotation axis R1. By rotating at a preset angle of inclination and simultaneously revolving around the axis of revolution (R2), centrifugal force and shear stress are generated, and sulfate or phosphate forms a co-intercalated structure between adjacent layers of the carbon nanotube. A bundled carbon nanotube liquid crystalline phase may be formed.
즉 중심회전축이 될 수 있는 공전축(R2)을 중심으로 공전축(R2)에 방사상으로 연결된 다수 용기(100)의 공전과, 각각의 용기(100) 중심의 자전축(R1)에 의한 자전이 동시에 진행됨으로서 교반력을 향상시켜 황산염 또는 인산염이 탄소나노튜브의 상호 인접하는 층간 사이에 코인터칼레이션 구조의 탄소나노튜브 액정상을 제조할 수 있게 되는 것이다.That is, the revolution of the plurality of containers 100 radially connected to the revolution axis R2 around the revolution axis R2, which can be the central rotation axis, and the rotation by the rotation axis R1 at the center of each container 100 are simultaneously performed. As the process progresses, the stirring power is improved, making it possible to produce a carbon nanotube liquid crystalline phase in which sulfate or phosphate has a cointercalation structure between adjacent layers of carbon nanotubes.
용기(100)의 자전축(R1)에 의한 자전속도와 중심회전축인 공전축(R2)에 의한 공전속도는 0.1 내지 10 : 1 비율일 수 있다. 자전속도가 0.1 비율 미만이면 공전속도에 비해 자전속도가 너무 느려 액정상에 코인터칼레이션 구조가 형성될 만큼의 원심력과 전단응력이 생성되지 않아 탄소나노튜브가 자기조립 구조를 갖지 못하게 된다. 자전속도가 10 비율을 초과하면 자전속도가 공전속도보다 너무 빨라 탄소나노튜브 층간 사이에 황산염 또는 인산염이 안정적으로 위치되지 못하기 때문에, 이 역시 액정상 내의 코인터칼레이션 구조 형성에 적절하지 못하다.The rotation speed of the container 100 by the rotation axis (R1) and the rotation speed by the revolution axis (R2), which is the central rotation axis, may be in a ratio of 0.1 to 10:1. If the rotation speed is less than 0.1, the rotation speed is too slow compared to the revolution speed, so centrifugal force and shear stress sufficient to form a cointercalation structure in the liquid crystal phase are not generated, and the carbon nanotubes do not have a self-assembled structure. If the rotation speed exceeds a ratio of 10, the rotation speed is too fast than the revolution speed, and sulfate or phosphate cannot be stably positioned between the carbon nanotube layers, so this is also not suitable for forming a co-intercalation structure in the liquid crystalline phase.
자전축(R1)은 공전축(R2)의 회전온동에 기반하여 공전축(R2)과 동일방향으로 회전될 수 있으나, 액정상 내 코인터칼레이션 구조 형성을 위해 자전축(R1)과 공전축(R2)이 서로 반대방향으로 회전될 수 있도록 할 수도 있다. 자전축(R1)과 공전축(R2)이 서로 반대방향으로 회전되면 자전축(R1)과 공전축(R2)을 동일한 속도로 회전되도록 하여 동력을 분할할 수 있는 장점이 있다.The rotation axis (R1) can be rotated in the same direction as the revolution axis (R2) based on the rotational temperature of the revolution axis (R2), but in order to form a cointercalation structure in the liquid crystalline crystal, the rotation axis (R1) and the revolution axis (R2) are separated. ) can also be rotated in opposite directions. When the rotation axis (R1) and the revolution axis (R2) rotate in opposite directions, there is an advantage in that the power can be divided by rotating the rotation axis (R1) and the revolution axis (R2) at the same speed.
전단응력을 가하여 액정상 형태의 디번들링된 탄소나노튜브를 먼저 형성하지 않고, 탄소나노튜브에 황산염 또는 인산염이 혼합된 복합분말과 산 용액을 혼합한 상태에서 바로 가열을 하게 되면 황산염이나 인산염이 탄소나노튜브의 상호 인접하는 층간 사이에 위치되지 못한 상태에서 산소 함유 관능기로 변해버릴 수 있다. 이에, 디번들링된 탄소나노튜브를 가열하기 전에 탄소나노튜브에 황산염 또는 인산염이 고체 상태로 혼합된 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 먼저 전단응력을 인가하여 액정상 형태로 형성하는 것은 중요한 과정이라 할 수 있다.If a composite powder containing sulfate or phosphate mixed with carbon nanotubes and an acid solution are immediately heated without applying shear stress to first form debundled carbon nanotubes in the form of a liquid crystalline phase, the sulfate or phosphate will form carbon nanotubes. If they are not located between adjacent layers of nanotubes, they may be transformed into oxygen-containing functional groups. Accordingly, before heating the debundled carbon nanotubes, shear stress is first applied to the composite powder in which sulfate or phosphate is mixed with the carbon nanotubes in a solid state, an acid solution, and an alkali metal-containing oxidizing agent to form a liquid crystalline form. This can be said to be an important process.
다음으로, 번들링된 탄소나노튜브를 30 내지 50 ℃에서 가열하여 황산염 및 인산염 중 하나 이상과 산 용액에 의해 산소 함유 관능기가 도입된 탄소나노튜브를 제조한다(S20).Next, the bundled carbon nanotubes are heated at 30 to 50° C. to prepare carbon nanotubes into which an oxygen-containing functional group is introduced using an acid solution and at least one of sulfate and phosphate (S20).
본 단계에서 열처리를 하게 되면 탄소나노튜브의 인접하는 층간 사이에 산 용액에 의해 용매화된 상태로 위치되어 있던 황산염 및 인산염 중 하나 이상과, 산 용액에 의하여 탄소나노튜브의 내부와, 표면이나 말단에 카르복실기와 하이드록시기와 같은 산소 함유 관능기가 도입될 수 있다.When heat treatment is performed in this step, at least one of sulfate and phosphate that is solvated by the acid solution between adjacent layers of the carbon nanotube is removed from the inside, surface or end of the carbon nanotube by the acid solution. Oxygen-containing functional groups such as carboxyl groups and hydroxy groups may be introduced.
열처리는 상온에 가까운 30 내지 50 ℃에서 실시될 수 있으며, 바람직하게는 30 내지 45 ℃ 범위일 수 있다. 상기 열처리는 30 분 내지 24 시간 동안 이루어질 수 있으며, 바람직하게는 1 내지 10 시간 동안 실시될 수 있다.Heat treatment may be performed at 30 to 50°C, which is close to room temperature, and preferably may be in the range of 30 to 45°C. The heat treatment may be performed for 30 minutes to 24 hours, and is preferably performed for 1 to 10 hours.
황산염이나 인산염의 사용으로 가열 온도를 최소 30 ℃까지 낮출 수 있으며, 이에 따라 100 ℃ 가까이 온도를 높이지 않아도 안정적인 열처리가 가능한 장점이 있다. 30 ℃ 미만이거나 1 시간 미만으로 액정상 형태의 디번들링된 탄소나노튜브를 가열하면 탄소나노튜브에 산소 함유 관능기가 형성되는데 까지 많은 시간이 소모되므로 최소 30 ℃ 이상이 되는 것이 바람직하다. 50 ℃를 초과하거나 24 시간을 초과하는 경우 탄소나노튜브에 산소 함유 관능기가 과도하게 도입됨에 따른 결함 구조가 형성됨으로 인해 전기전도도가 감소될 수 있는 단점이 있다.By using sulfate or phosphate, the heating temperature can be lowered to at least 30 ℃, which has the advantage of enabling stable heat treatment without raising the temperature to close to 100 ℃. If the debundled carbon nanotubes in the liquid crystalline form are heated below 30°C or for less than 1 hour, it takes a lot of time for oxygen-containing functional groups to be formed in the carbon nanotubes, so it is preferable that the temperature be at least 30°C. If the temperature exceeds 50°C or exceeds 24 hours, there is a disadvantage that electrical conductivity may be reduced due to the formation of defect structures due to excessive introduction of oxygen-containing functional groups into the carbon nanotubes.
마지막으로, 산소 함유 관능기가 도입된 탄소나노튜브를 세척 및 여과하여, 전처리된 탄소나노튜브를 제조한다(S30).Finally, the carbon nanotubes into which the oxygen-containing functional group has been introduced are washed and filtered to prepare pretreated carbon nanotubes (S30).
본 단계는 탄소나노튜브의 전처리가 완료되는 과정으로, 열처리 과정에서 사용을 다 한 산과, 황산염 또는 인산염을 제거하는 중화 및 세척하여 순수 탄소나노튜브 분말만을 얻을 수 있게 된다. 이를 위해 산소 함유 관능기가 도입된 탄소나노튜브에 과량의 증류수를 첨가하여 세정하고, 원심분리 등의 과정을 거쳐 필터링하여 산과, 황산염이나 인산염이 제거되어 정제된 탄소나노튜브를 수득할 수 있게 되며, 이렇게 전처리된 탄소나노튜브 분말은 디번들링된 탄소나노튜브 액정상으로부터 산소 함유 관능기가 도입되어 분산성을 갖게 된다.This step is a process in which the pretreatment of the carbon nanotubes is completed, and only pure carbon nanotube powder can be obtained by neutralizing and washing to remove acids, sulfates, or phosphates used in the heat treatment process. To this end, the carbon nanotubes into which oxygen-containing functional groups have been introduced are washed by adding an excessive amount of distilled water, and then filtered through a process such as centrifugation to remove acids, sulfates, and phosphates, thereby obtaining purified carbon nanotubes. The carbon nanotube powder pretreated in this way has dispersibility due to the introduction of oxygen-containing functional groups from the debundled liquid crystalline phase of the carbon nanotube.
이렇게 전처리되어 분산성을 갖는 탄소나노튜브를 물(H2O), 알코올, 디메틸포름아마이드(dimethylformamide, DMF) 및 N-메틸포름아마이드(N-methylformamide, NMP) 중 어느 하나 이상의 용매에 분산시킬 수 있으며, 이를 전도성 페이스트로 활용하여 전도성 필름으로 형성할 수 있다.The carbon nanotubes that are pretreated in this way and have dispersibility can be dispersed in one or more solvents among water (H 2 O), alcohol, dimethylformamide (DMF), and N-methylformamide (NMP). It can be used as a conductive paste to form a conductive film.
상술한 과정에 따른 탄소나노튜브의 전처리 방법에 따르면, 번들 현상으로 응집되어 있는 탄소나노튜브(특히, 단일벽 탄소나노튜브)에 환경 문제를 야기하는 질산염 대신 황산염이나 인산염을 사용하여 탄소나노튜브를 디번들링시킬 수 있다. 특히 100 ℃에 가까운 고온이 아닌, 상온에 가까운 최소 30 ℃로 열을 가하는 것만으로 탄소나노튜브에 산소 함유 관능기를 도입할 수 있으므로, 고온 환경을 조성하지 않아도 되어 공정 안정성을 개선할 수 있는 장점이 있다.According to the pretreatment method of carbon nanotubes according to the above-described process, carbon nanotubes are made using sulfate or phosphate instead of nitrate, which causes environmental problems in carbon nanotubes (especially single-walled carbon nanotubes) that are aggregated through the bundle phenomenon. It can be debundled. In particular, since oxygen-containing functional groups can be introduced into carbon nanotubes simply by applying heat to a minimum of 30 ℃, which is close to room temperature, rather than a high temperature close to 100 ℃, there is an advantage of improving process stability by not having to create a high temperature environment. there is.
이하, 본 발명의 실시예를 더욱 상세하게 설명하면 다음과 같다. 단, 이하의 실시예는 본 발명의 이해를 돕기 위하여 예시하는 것일 뿐, 이에 의하여 본 발명의 범위가 한정되는 것은 아니다.Hereinafter, embodiments of the present invention will be described in more detail as follows. However, the following examples are merely illustrative to aid understanding of the present invention and are not intended to limit the scope of the present invention.
<실시예 1><Example 1>
번들 형상의 단일벽 탄소나노튜브 5 g과 황산나트륨(Na2SO4) 5 g을 파우더 상태에서 혼합하여 복합분말을 제조하였다. 제조된 복합분말을 황산 용액 1,000 ㎖에 투입하고 포타슘 퍼옥시모노설페이트 1 g을 첨가하여 자전과 공전이 가능한 페이스트 믹서를 이용해 1,000 rpm으로 10 분 동안 교반하면서 혼합하여 디번들링된 탄소나노튜브 액정상을 제조하였다. 이를 45 ℃에서 20 시간 동안 가열하여 탄소나노튜브에 하이드록실기와 카르복실기를 도입하였다. 이후 과량의 증류수를 첨가하고 반복적으로 원심분리와 필터링을 통해 세정하고 수분을 제거함으로서 전처리된 탄소나노튜브를 수득하였다.A composite powder was prepared by mixing 5 g of bundle-shaped single-walled carbon nanotubes and 5 g of sodium sulfate (Na 2 SO 4 ) in a powder state. The prepared composite powder was added to 1,000 ml of sulfuric acid solution, 1 g of potassium peroxymonosulfate was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to form a debundled carbon nanotube liquid crystalline phase. Manufactured. This was heated at 45°C for 20 hours to introduce hydroxyl and carboxyl groups into the carbon nanotubes. Afterwards, pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
<실시예 2><Example 2>
번들 형상의 다중벽 탄소나노튜브 5 g과 황산나트륨(Na2SO4) 5 g을 파우더 상태에서 혼합하여 복합분말을 제조하였다. 제조된 복합분말을 황산 용액 1,000 ㎖에 투입하고 포타슘 퍼옥시모노설페이트 1 g을 첨가하여 자전과 공전이 가능한 페이스트 믹서를 이용해 1,000 rpm으로 10 분 동안 교반하면서 혼합하여 디번들링된 탄소나노튜브 액정상을 제조하였다. 이를 50 ℃에서 10 시간 동안 가열하여 탄소나노튜브에 하이드록실기와 카르복실기를 도입하였다. 이후 과량의 증류수를 첨가하고 반복적으로 원심분리와 필터링을 통해 세정하고 수분을 제거함으로서 전처리된 탄소나노튜브를 수득하였다.A composite powder was prepared by mixing 5 g of bundle-shaped multi-walled carbon nanotubes and 5 g of sodium sulfate (Na 2 SO 4 ) in a powder state. The prepared composite powder was added to 1,000 ml of sulfuric acid solution, 1 g of potassium peroxymonosulfate was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to form a debundled carbon nanotube liquid crystalline phase. Manufactured. This was heated at 50°C for 10 hours to introduce hydroxyl and carboxyl groups into the carbon nanotubes. Afterwards, pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
<실시예 3><Example 3>
번들 형상의 단일벽 탄소나노튜브 5 g과 인산칼륨(KH2PO4) 5 g을 파우더 상태에서 혼합하여 복합분말을 제조하였다. 제조된 복합분말을 황산 용액 1,000 ㎖에 투입하고 과망간산 칼륨(Potassium manganate, KMnO4) 2 g을 첨가하여 자전과 공전이 가능한 페이스트 믹서를 이용해 1,000 rpm으로 10 분 동안 교반하면서 혼합하여 디번들링된 탄소나노튜브 액정상을 제조하였다. 이를 30 ℃에서 20 시간 동안 가열하여 탄소나노튜브에 카르복실기를 도입하였다. 이후 과량의 증류수를 첨가하고 반복적으로 원심분리와 필터링을 통해 세정하고 수분을 제거함으로서 전처리된 탄소나노튜브를 수득하였다.A composite powder was prepared by mixing 5 g of bundle-shaped single-walled carbon nanotubes and 5 g of potassium phosphate (KH 2 PO 4 ) in a powder state. The prepared composite powder was added to 1,000 ml of sulfuric acid solution, 2 g of potassium permanganate (KMnO 4 ) was added, and mixed while stirring at 1,000 rpm for 10 minutes using a paste mixer capable of rotation and revolution to obtain debundled carbon nano. A tube liquid crystal phase was prepared. This was heated at 30°C for 20 hours to introduce a carboxyl group into the carbon nanotube. Afterwards, pretreated carbon nanotubes were obtained by adding an excess amount of distilled water, repeatedly washing through centrifugation and filtering, and removing moisture.
<비교예 1><Comparative Example 1>
단일벽 탄소나노튜브 5 g과, 황산염이 아닌 질산염인 질산나트륨(NaNO3) 5 g을 파우더 상태에서 혼합하여 복합분말을 준비하였다. 준비된 복합분말과 황산 용액 1,000 ㎖를 실시예 1 및 2와 달리, 마그네틱 바를 이용한 일반적인 교반 방법으로 40 분 동안 교반하였다. 이어서 80 ℃에서 20 시간 동안 가열하고, 과량의 증류수로 세정하고 원심분리하여 필터링을 통해 탄소나노튜브를 얻었다.A composite powder was prepared by mixing 5 g of single-walled carbon nanotubes and 5 g of sodium nitrate (NaNO 3 ), which is a nitrate rather than sulfate, in a powder state. Unlike Examples 1 and 2, 1,000 ml of the prepared composite powder and sulfuric acid solution were stirred for 40 minutes using a general stirring method using a magnetic bar. Then, it was heated at 80°C for 20 hours, washed with excess distilled water, centrifuged, and filtered to obtain carbon nanotubes.
상기 실시예 1 및 비교예 1의 방법으로 전처리된 탄소나노튜브의 자기조립 구조가 형성되었는지의 유무를 확인해 보기 위하여 SEM 사진을 측정해 보았다.SEM photographs were measured to confirm whether a self-assembled structure was formed in the carbon nanotubes pretreated by the method of Example 1 and Comparative Example 1.
관련해서 우선, 도 3은 실시예 1에 따라 전처리된 탄소나노튜브를 편광현미경 이미지로 나타낸 것이다. 도 3을 참조하면 실시예 1에서와 같이 전처리된 탄소나노튜브는 10 분 동안 전단응력을 가하는 것만으로 황산염이 탄소나노튜브의 상호 인접하는 층간 사이에서 코인터칼레이션되기 때문에 번들 크기가 감소하여 탄소나노튜브가 액정상 형태로 자기조립된 구조로 형성되어 방향성을 나타냄이 확인된다.First of all, Figure 3 shows a polarizing microscope image of carbon nanotubes pretreated according to Example 1. Referring to FIG. 3, the carbon nanotubes pretreated as in Example 1 are cointercalated between adjacent layers of the carbon nanotubes by simply applying shear stress for 10 minutes, so the bundle size is reduced, thereby reducing the carbon nanotubes. It was confirmed that the nanotubes were formed in a self-assembled structure in the form of a liquid crystalline phase and exhibited orientation.
도 4는 비교예 1에 따라 전처리되지 않은 탄소나노튜브를 SEM 사진으로 나타낸 것이다. 도 4(a)는 질산염인 질산나트륨을 사용한 비교예 1에 따라 전처리된 탄소나노튜브를 10.0 kV에서 측정하여 백만배율로 확대하여 나타낸 SEM 사진이고, 도 4(b)는 비교예 1에 따라 전처리된 탄소나노튜브를 15.0 kV에서 측정하여 백만배율로 확대하여 나타낸 SEM 사진이다. 도 4를 참조하면 실시예 1에서와 달리 탄소나노튜브를 전처리하지 않으면 탄소나노튜브가 100 nm 이상의 큰 번들로 존재하고, 이에 반해 실시예 1에 따라 처리할 경우 탄소나노튜브의 번들 크기가 50 nm 이하로 제어될 수 있다.Figure 4 shows an SEM photograph of carbon nanotubes that were not pretreated according to Comparative Example 1. Figure 4(a) is an SEM photograph showing carbon nanotubes pretreated according to Comparative Example 1 using sodium nitrate, a nitrate, measured at 10.0 kV and magnified at a million times magnification, and Figure 4(b) is a pretreated carbon nanotube according to Comparative Example 1. This is an SEM photo of carbon nanotubes measured at 15.0 kV and magnified at 1 million times. Referring to Figure 4, unlike in Example 1, if the carbon nanotubes are not pretreated, the carbon nanotubes exist in large bundles of 100 nm or more. In contrast, when treated according to Example 1, the bundle size of the carbon nanotubes is 50 nm. It can be controlled below.
도 5는 실시예 1에 따른 XPS(X-ray photoelectron spectroscopy) 분석 결과를 그래프로 나타낸 것이다. 도 5를 참조하면, 285±1 eV의 결합에너지에서 C=C bond, C-C bond와 함께, 289±1 eV의 결합에너지에서 COOH bond 그리고 286±1 eV의 결합에너지에서 C-O band의 4가지 관능기가 나타남을 확인할 수 있다. 이를 통하여 실시예 1에 따라 제조되는 탄소나노튜브가 그 구조를 유지하는 것이 확인되며, 이와 함께 카르복실기가 존재하는 것은 탄소나노튜브의 상호 인접하는 층간 사이에 황산염이 코인터칼레이션되어 결국 탄소나토튜브가 액정상 형태로 전처리가 진행되어 탄소나노튜브의 번들 크기가 제어된 상태로 산소 함유 관능기가 도입된 것을 알 수 있다.Figure 5 graphically shows the results of XPS (X-ray photoelectron spectroscopy) analysis according to Example 1. Referring to Figure 5, there are four functional groups in the C=C bond and C-C bond at a binding energy of 285±1 eV, a COOH bond at a binding energy of 289±1 eV, and a C-O band at a binding energy of 286±1 eV. You can confirm that it appears. Through this, it was confirmed that the carbon nanotubes manufactured according to Example 1 maintained their structure, and the presence of a carboxyl group resulted in cointercalation of sulfate between adjacent layers of the carbon nanotubes, ultimately forming carbon nanotubes. It can be seen that the oxygen-containing functional group was introduced with the bundle size of the carbon nanotubes controlled by pretreatment in the liquid crystalline form.
정리하면, 본 발명은 공정 안정성이 개선된 탄소나노튜브의 전처리 방법으로, 번들 형상의 탄소나노튜브에 환경 문제를 야기하는 질산염이 아닌, 황산염 및 인산염 중 하나 이상을 이용하여 탄소나노튜브를 디번들링시키고 산소 함유 관능기를 도입함으로서 분산성을 높일 수 있는 특징이 있다.In summary, the present invention is a pretreatment method for carbon nanotubes with improved process stability, which involves debundling carbon nanotubes using one or more of sulfate and phosphate, rather than nitrate, which causes environmental problems in bundle-shaped carbon nanotubes. It has the characteristic of increasing dispersibility by introducing an oxygen-containing functional group.
이러한 특징은 탄소나노튜브에 황산염 및 인산염 중 하나 이상을 혼합한 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하여, 황산염 및 인산염 중 하나 이상이 탄소나노튜브의 상호 인접하는 층간 사이에 코인터칼레이션되어 디번들링된 탄소나노튜브를 액정상 형태로 제조한 후, 상온에 가까운 30 ℃에서부터 50 ℃까지의 범위에서 가열하여 황산염, 인산염과 산 용액에 의해 산소 함유 관능기가 도입된 탄소나노튜브를 세척 및 여과하는 과정으로 전처리함으로서, 공정 안정성이 개선된 방법으로 전처리된 탄소나노튜브가 디번들링된 탄소나노튜브 액정상으로부터 산소 함유 관능기가 도입되는 것으로 달성될 수 있다.This feature is achieved by applying shear stress to a composite powder mixed with carbon nanotubes and at least one of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent, so that at least one of sulfate and phosphate is deposited between adjacent layers of carbon nanotubes. After manufacturing the co-intercalated and debundled carbon nanotubes in a liquid crystalline form, they are heated in the range from 30 ℃ to 50 ℃, which is close to room temperature, and carbon nanotubes into which oxygen-containing functional groups are introduced by sulfate, phosphate and acid solutions are produced. By pretreating the nanotubes through a washing and filtering process, improved process stability can be achieved by introducing an oxygen-containing functional group from the debundled carbon nanotube liquid crystalline phase of the pretreated carbon nanotubes.
또한 황산염 또는 질산염과 탄소나노튜브를 먼저 파우더 상태로 혼합함으로서 황산염이나 질산염이 탄소나노튜브의 층간 사이로 매우 용이하게 침투하고, 이에 산처리 매개체인 산 용액을 통하여 기능화 효율을 극대화시킬 수 있다.In addition, by first mixing sulfate or nitrate and carbon nanotubes in a powder state, sulfate or nitrate can very easily penetrate between the layers of carbon nanotubes, and thus functionalization efficiency can be maximized through the acid solution, which is an acid treatment medium.
상기와 같은 본 발명에 의하면, 탄소나노튜브를 소량의 산 용액과, 환경 및 인체에 악영향을 미치는 질산염이 아닌 황산염이나 인산염을 사용하여, 디번들링된 탄소나노튜브로부터 산소 함유 관능기가 도입되면서 단시간에 기능화가 가능하므로, 분산제를 사용하지 않고도 용매에 탄소나노튜브를 분산시킬 수 있다는 점에 의미가 있다.According to the present invention as described above, oxygen-containing functional groups are introduced from debundled carbon nanotubes using a small amount of acid solution and sulfate or phosphate rather than nitrate, which has a negative effect on the environment and the human body, in a short period of time. Since functionalization is possible, it is meaningful that carbon nanotubes can be dispersed in a solvent without using a dispersant.
이상의 설명은 본 발명의 기술 사상을 예시적으로 설명한 것에 불과한 것으로, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자라면 본 발명의 본질적인 특성에서 벗어나지 않는 범위에서 다양한 수정 및 변형이 가능할 것이다. 따라서 본 발명에 개시된 실시예는 본 발명의 기술 사상을 한정하기 위한 것이 아니라, 설명하기 위한 것이고, 이러한 실시예에 의하여 본 발명의 기술 사상의 범위가 한정되는 것도 아니다. 본 발명의 보호 범위는 특허청구범위에 의하여 해석되어야 하며, 그와 동등한 범위 내에 있는 모든 기술사상은 본 발명의 권리범위에 포함되는 것으로 해석되어야 할 것이다.The above description is merely an illustrative explanation of the technical idea of the present invention, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but are for explanation, and the scope of the technical idea of the present invention is not limited by these examples. The scope of protection of the present invention should be interpreted in accordance with the scope of the patent claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Claims (6)

  1. 번들 형상의 탄소나노튜브에 황산염 및 인산염 중 하나 이상을 혼합한 복합분말과, 산 용액과, 알칼리금속 함유 산화제에 전단응력을 가하면서 혼합하여, 상기 황산염 및 인산염 중 하나 이상이 상기 탄소나노튜브의 상호 인접하는 층간에 코인터칼레이션(co-intercalation)되어 디번들링된 탄소나노튜브를 제조하는 단계;A composite powder obtained by mixing bundle-shaped carbon nanotubes with at least one of sulfate and phosphate, an acid solution, and an alkali metal-containing oxidizing agent are mixed while applying shear stress, so that at least one of the sulfate and phosphate is added to the carbon nanotube. Manufacturing debundled carbon nanotubes by co-intercalating between adjacent layers;
    상기 디번들링된 탄소나노튜브를 30 내지 50 ℃에서 가열하여, 상기 황산염 및 인산염 중 하나 이상과 상기 산 용액에 의해 산소 함유 관능기가 도입된 탄소나노튜브를 제조하는 단계; 및Heating the debundled carbon nanotubes at 30 to 50° C. to produce carbon nanotubes into which an oxygen-containing functional group is introduced by at least one of the sulfate and phosphate and the acid solution; and
    상기 산소 함유 관능기가 도입된 탄소나노튜브를 세척 및 여과하여, 전처리된 탄소나노튜브를 제조하는 단계;를 포함하여,Including the step of washing and filtering the carbon nanotubes into which the oxygen-containing functional group has been introduced, thereby producing pretreated carbon nanotubes,
    상기 황산염 및 인산염 중 하나 이상을 이용하여 디번들링된 탄소나노튜브를 제조하고 산소 함유 관능기를 도입하는 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법.A pretreatment method for carbon nanotubes with improved process stability, characterized by manufacturing debundled carbon nanotubes using one or more of the sulfate and phosphate and introducing an oxygen-containing functional group.
  2. 제1 항에 있어서,According to claim 1,
    상기 황산염은 황산나트륨(Na2SO4), 황산칼륨(K2SO4), 황산수소나트륨(NaHSO4), 황산수소칼륨(KHSO4), 과산화일황산칼륨(KHSO5) 및 과황산암모늄((NH4)2S2O8)으로 이루어진 군으로부터 선택되는 1종 이상이고,The sulfate is sodium sulfate (Na 2 SO 4 ), potassium sulfate (K 2 SO 4 ), sodium hydrogen sulfate (NaHSO 4 ), potassium hydrogen sulfate (KHSO 4 ), potassium peroxymonosulfate (KHSO 5 ), and ammonium persulfate (( NH 4 ) 2 S 2 O 8 ) at least one selected from the group consisting of,
    상기 인산염은 디포타슘포스페이트(K2HPO4) 및 인산칼륨(KH2PO4)으로 이루어진 군으로부터 선택되는 1종 이상인 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법.A pretreatment method for carbon nanotubes with improved process stability, wherein the phosphate is at least one selected from the group consisting of dipotassium phosphate (K 2 HPO 4 ) and potassium phosphate (KH 2 PO 4 ).
  3. 제1 항에 있어서,According to claim 1,
    상기 알칼리금속 함유 산화제는,The alkali metal-containing oxidizing agent,
    과망간산 칼륨(Potassium manganate, KMnO4), 소듐 클로레이트(Sodium chlorate, NaClO3), 소듐 퍼클로레이트(NaClO4), 포타슘 클로레이트(KClO3), 포타슘 퍼클로레이트(KClO4) 및 포타슘 퍼옥시모노설페이트(Potassium Peroxymonosulfate, KHSO5) 중 하나 이상인 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법.Potassium manganate (KMnO 4 ), sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ), potassium chlorate (KClO 3 ), potassium perchlorate (KClO 4 ), and potassium peroxymonosulfate (Potassium ) . Peroxymonosulfate, KHSO 5 ) A pretreatment method for carbon nanotubes with improved process stability, characterized in that one or more of the following.
  4. 제1 항에 있어서,According to claim 1,
    상기 탄소나노튜브는,The carbon nanotubes are,
    단일벽 탄소나노튜브(single-walled carbon nanotube, SWCNT), 이중벽 탄소나노튜브(double-walled carbon nanotube, DWCNT) 및 다중벽 탄소나노튜브(multiwalled carbon nanotube, MWCNT) 중 하나 이상인 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법.A process characterized by one or more of single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), and multiwalled carbon nanotubes (MWCNT). Pretreatment method for carbon nanotubes with improved stability.
  5. 제1 항에 있어서,According to claim 1,
    상기 디번들링된 탄소나노튜브를 제조하는 단계는,The step of manufacturing the debundled carbon nanotubes is,
    임펠러, 페이스트 믹서, 블레이드 믹서 및 쿠에트-테일러 반응기 중 하나 이상을 이용하여 상기 전단응력을 가하는 것을 특징으로 하는, 공정 안정성이 개선된 탄소나노튜브의 전처리 방법.A pretreatment method for carbon nanotubes with improved process stability, characterized in that the shear stress is applied using one or more of an impeller, paste mixer, blade mixer, and Couette-Taylor reactor.
  6. 제1 항 내지 제5 항 중 어느 한 항의 방법으로 전처리된 것을 특징으로 하는, 탄소나노튜브.A carbon nanotube, characterized in that it has been pretreated by the method of any one of claims 1 to 5.
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