WO2023153182A1 - Nanotube de carbone oxydé et sa méthode de production, et liquide de dispersion de nanotubes de carbone oxydés - Google Patents

Nanotube de carbone oxydé et sa méthode de production, et liquide de dispersion de nanotubes de carbone oxydés Download PDF

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WO2023153182A1
WO2023153182A1 PCT/JP2023/001783 JP2023001783W WO2023153182A1 WO 2023153182 A1 WO2023153182 A1 WO 2023153182A1 JP 2023001783 W JP2023001783 W JP 2023001783W WO 2023153182 A1 WO2023153182 A1 WO 2023153182A1
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oxidized
carbon nanotubes
oxidized carbon
carbon nanotube
cnt
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Japanese (ja)
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広和 高井
宏晃 周
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日本ゼオン株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • C01B32/16—Preparation
    • 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

Definitions

  • the present invention relates to oxidized carbon nanotubes, methods for producing the same, and oxidized carbon nanotube dispersions.
  • Carbon nanotubes have attracted attention as a material with various excellent properties due to their unique structure.
  • CNTs are excellent in various properties such as mechanical strength, optical properties, electrical properties, thermal properties, ion storage capacity, and ion adsorption capacity. Development as a material is expected.
  • CNTs when using CNTs, it is necessary to disperse them uniformly in a solvent in order to fully demonstrate their properties.
  • CNTs tend to aggregate and become entangled with each other, and it is very difficult to disperse them uniformly.
  • Patent Document 1 discloses that a fibrous carbon nanostructure containing CNT and having at least one absorption peak in the wavenumber region of 500 cm ⁇ 1 or more and 600 cm ⁇ 1 or less in the spectroscopic absorption spectrum has excellent dispersibility.
  • Patent Document 2 discloses that CNTs satisfying predetermined conditions for a peak based on plasmon resonance, the maximum peak in differential pore volume distribution, or a peak in the two-dimensional spatial frequency spectrum of an electron microscope image are excellent in dispersibility. It is
  • an object of the present invention is to provide oxidized carbon nanotubes with excellent dispersibility, a method for producing the same, and an oxidized carbon nanotube dispersion in which oxidized carbon nanotubes are well dispersed.
  • the present inventors have conducted intensive studies with the aim of solving the above problems.
  • the inventors of the present invention have newly discovered that oxidized carbon nanotubes satisfying predetermined conditions, which are obtained by oxidation treatment of carbon nanotubes satisfying predetermined conditions, can have excellent dispersibility, and have completed the present invention. let me
  • an object of the present invention is to advantageously solve the above problems, and the present invention is [1] an oxidized carbon nanotube that satisfies the following conditions (1) to (3).
  • the ratio of the number of oxidized single-walled carbon nanotubes to the total number of the oxidized carbon nanotubes is 51% or more.
  • the oxygen atomic ratio is 13 atomic % or more.
  • Oxidized carbon nanotubes that satisfy all of the above conditions (1) to (3) can have excellent dispersibility.
  • the "peak based on plasmon resonance" in the spectrum obtained by Fourier transform infrared spectroscopy can be detected by the method described in Examples.
  • the "proportion of the number of oxidized single-walled carbon nanotubes to the total number of oxidized carbon nanotubes" and the “oxygen atomic ratio” can be measured by the methods described in Examples.
  • the oxidized carbon nanotube of [1] above preferably has an average diameter of 3.5 nm or more and 5 nm or less. Oxidized carbon nanotubes having an average diameter within the above range may have better dispersibility.
  • the "average diameter of oxidized carbon nanotubes" can be measured by the method described in Examples.
  • the oxidized carbon nanotubes of [1] or [2] above preferably have an average length of 30 nm or more and 200 nm or less. Oxidized carbon nanotubes having an average length within the above range can have even better dispersibility.
  • the "average length of oxidized carbon nanotubes" can be measured by the method described in Examples.
  • Another object of the present invention is to advantageously solve the above problems. and a step of oxidizing carbon nanotubes including single-walled carbon nanotubes that satisfy at least one of the following conditions (1) and (2).
  • the carbon nanotube dispersion At least one peak based on the plasmon resonance of the body exists in the wave number range of 500 cm ⁇ 1 to 900 cm ⁇ 1 .
  • the tap bulk density is 0.02 g/cm 3 or more and 0.04 g/cm 3 or less.
  • oxidized carbon nanotubes including single-walled carbon nanotubes, that satisfy at least one of the above conditions (1) and (2), oxidized carbon nanotubes that can have excellent dispersibility can be obtained.
  • the "tap bulk density" can be measured by the method described in Examples.
  • the present invention is intended to advantageously solve the above problems, and the present invention provides [5] an oxidized carbon nanotube according to any one of [1] to [3] above, and a solvent. It is an oxidized carbon nanotube dispersion. Any one of the oxidized carbon nanotubes described above is unlikely to aggregate in a dispersion, and a dispersion containing such oxidized carbon nanotubes has excellent dispersibility of the oxidized carbon nanotubes.
  • oxidized carbon nanotubes with excellent dispersibility, a method for producing the same, and an oxidized carbon nanotube dispersion in which oxidized carbon nanotubes are well dispersed.
  • the oxidized carbon nanotubes of the present invention are not particularly limited, and can be suitably produced by the method for producing oxidized carbon nanotubes of the present invention.
  • the method for producing an oxidized carbon nanotube of the present invention can be suitably used, for example, when producing an oxidized carbon nanotube of the present invention.
  • the oxidized carbon nanotube dispersion of the present invention can be produced using the oxidized carbon nanotubes of the present invention.
  • the oxidized carbon nanotubes of the present invention are aggregates (oxidized carbon nanotube aggregates) in which a plurality of oxidized carbon nanotubes are aggregated.
  • the oxidized carbon nanotubes of the present invention must satisfy the following conditions (1) to (3).
  • (1) The ratio of the number of oxidized single-walled carbon nanotubes to the total number of oxidized carbon nanotubes is 51% or more.
  • the oxygen atomic ratio is 13 atomic % or more.
  • the oxidized carbon nanotubes of the present invention that satisfy these conditions can have excellent dispersibility in dispersion liquids. Each condition will be described below.
  • Condition (1) is that ⁇ the ratio of the number of oxidized single-walled carbon nanotubes to the total number of oxidized carbon nanotubes (hereinafter, simply referred to as the ⁇ proportion of oxidized single-walled carbon nanotubes'') is 51% or more. stipulate. If the proportion of oxidized single-walled carbon nanotubes is less than 51%, the dispersibility of the oxidized carbon nanotubes is poor. From the viewpoint of further improving the dispersibility of oxidized carbon nanotubes, the proportion of oxidized single-walled carbon nanotubes is preferably 60% or more, more preferably 65% or more, and even more preferably 70% or more. .
  • the oxidized carbon nanotubes of the present invention can include oxidized multi-walled carbon nanotubes in addition to oxidized single-walled carbon nanotubes.
  • Condition (2) is that "in the spectrum obtained by Fourier transform infrared spectroscopic analysis of the oxidized carbon nanotube, the peak based on the plasmon resonance of the oxidized carbon nanotube is at least 1 in the wavenumber range of more than 700 cm -1 and 1000 cm -1 or less. “the existence of one”.
  • a strong absorption characteristic in the far-infrared region has been widely known as an optical characteristic of CNTs. Such strong absorption properties in the far-infrared region are believed to be due to the diameter and length of CNTs.
  • the absorption characteristics in the far-infrared region more specifically, the relationship between the peak based on the plasmon resonance of CNTs and the length of CNTs is described in non-patent literature (T.Morimoto et al., “Length-Dependent Plasmon Resonance in Single-Walled Carbon Nanotubes”, pp 9897-9904, Vol.8, No.10, ACS NANO, 2014).
  • the inventors of the present invention based on the study described in the non-patent literature and their own knowledge, detected peaks based on the plasmon resonance of CNTs in the spectrum obtained by Fourier transform infrared spectrophotometry.
  • Oxidized CNT satisfying the above conditions has a peak based on plasmon resonance in a spectrum obtained by Fourier transform infrared spectroscopy at a position with a large wave number. It is inferred that it has a structure. Oxidized CNTs having such a structure are hard to agglomerate and are presumed to have excellent dispersibility in a dispersion liquid.
  • the oxidized carbon nanotubes of the present invention preferably have only one peak based on plasmon resonance.
  • the oxidized carbon nanotube of the present invention has a plurality of peaks based on plasmon resonance, it is preferable that at least the peak based on the strongest plasmon resonance has a wavenumber in the range of more than 700 cm ⁇ 1 and 1000 cm ⁇ 1 or less.
  • the oxidized carbon nanotube of the present invention preferably does not have a peak due to plasmon resonance in the wavenumber range of 700 cm -1 or less or in the wavenumber range of more than 1000 cm -1 .
  • the oxidized carbon nanotube of the present invention has a peak based on plasmon resonance within the range of 800 cm ⁇ 1 or more and 950 cm ⁇ 1 or less in wavenumber, preferably 850 cm ⁇ 1 or more and 950 cm ⁇ 1 or less in wavenumber. It is preferable to have at least one peak within the range, and the peak based on plasmon resonance is in the range of 800 cm -1 to 950 cm -1 , preferably in the wavenumber range of 850 cm -1 to 950 cm -1 . preferable.
  • Condition (3) defines that "the oxygen atomic ratio of the oxidized carbon nanotubes is 13 at % or more". If the oxygen atomic ratio is less than 13 at %, the dispersibility of the oxidized carbon nanotubes cannot be ensured.
  • the “oxygen atomic ratio” is a value represented by the ratio of the total atomic weight on the carbon nanotube surface and the abundance of oxygen atoms (O) determined by X-ray photoelectron spectroscopy. More specifically, the “oxygen atomic ratio” is a value obtained by calculating the ratio of the abundance of oxygen atoms (O), assuming that the total atomic weight constituting the carbon nanotube surface is 100 at %.
  • the "oxygen atomic ratio” can be calculated based on X-ray photoelectron spectroscopy.
  • the oxygen atomic ratio of the oxidized carbon nanotubes is preferably 14 at% or more, more preferably 15 at% or more.
  • the oxygen atomic ratio is preferably 20 atomic % or less, and 18 atomic % or less. is more preferred.
  • the oxygen atomic ratio of the oxidized carbon nanotubes is determined, for example, in the oxidation treatment step in the method for producing the oxidized carbon nanotubes of the present invention, which will be described later, according to various conditions for oxidation treatment of carbon nanotubes as a material (for example, when an acidic solution is used, an acidic solution
  • various conditions for oxidation treatment of carbon nanotubes as a material for example, when an acidic solution is used, an acidic solution
  • the type of acid in the acid solution, the acid concentration of the acid solution, the stirring time of the mixed solution of the carbon nanotubes as the material and the acid solution, the reflux temperature/reflux time of the mixed solution, etc. can be adjusted as appropriate. .
  • the oxidized carbon nanotubes of the present invention preferably further have, for example, the following properties.
  • the oxidized carbon nanotubes of the present invention preferably have an average diameter of 3.5 nm or more, more preferably 3.7 nm or more, still more preferably 4.0 nm or more, and 5 nm or less. is preferred, and 4.8 nm or less is more preferred. If the average diameter of the oxidized carbon nanotubes is within the above range, the dispersibility can be further enhanced.
  • the oxidized carbon nanotubes of the present invention preferably have an average length of 30 nm or more, more preferably 50 nm or more, even more preferably 155 nm or more, and preferably 200 nm or less, and 180 nm or less. is more preferable. If the average length of the oxidized carbon nanotubes is within the above range, the dispersibility can be further enhanced.
  • the oxidized carbon nanotubes of the present invention preferably have a total specific surface area measured by the BET method of 100 m 2 /g or less, more preferably 70 m 2 /g or less. If the total specific surface area by the BET method is equal to or less than the above upper limit, the dispersibility and dispersion stability of the oxidized CNTs in water will be even more excellent.
  • the total specific surface area of the oxidized carbon nanotubes by the BET method can be measured using, for example, a BET specific surface area measuring device conforming to JIS Z8830.
  • the G/D ratio of the oxidized carbon nanotubes of the present invention is preferably 0.6 or more and 2.0 or less. If the G/D ratio is within the above range, the dispersibility of the oxidized CNTs in water will be even more excellent.
  • the G/D ratio is an index commonly used to evaluate the quality of CNTs. Vibrational modes called G band (near 1600 cm ⁇ 1 ) and D band (near 1350 cm ⁇ 1 ) are observed in the Raman spectrum of CNTs measured by a Raman spectrometer.
  • the G band is a vibrational mode derived from the hexagonal lattice structure of graphite, which is the cylindrical surface of CNT
  • the D band is a vibrational mode derived from amorphous sites. Therefore, a CNT with a higher peak intensity ratio (G/D ratio) between the G band and the D band can be evaluated as having higher crystallinity (linearity).
  • Various attributes of the oxidized carbon nanotubes as described above can be obtained by performing a general dispersion treatment such as ultrasonic dispersion treatment when preparing an oxidized carbon nanotube dispersion as described later using the oxidized carbon nanotubes. does not change significantly. That is, the values of various attributes measured for the oxidized carbon nanotubes before the dispersion treatment usually apply as they are to the oxidized carbon nanotubes in the oxidized carbon nanotube dispersion. Moreover, the reverse is similarly established.
  • a method for producing an oxidized carbon nanotube of the present invention is a method for producing an oxidized carbon nanotube of the present invention described above, and is a single-walled carbon nanotube that satisfies at least one of the following conditions (1) and (2): It is characterized by oxidizing a carbon nanotube (hereinafter also simply referred to as “material CNT”) containing (1) A carbon nanotube dispersion obtained by dispersing carbon nanotubes including single-walled carbon nanotubes so that the bundle length is 10 ⁇ m or more.
  • the carbon nanotube dispersion At least one peak based on the plasmon resonance of the body exists in the wave number range of 500 cm ⁇ 1 to 900 cm ⁇ 1 .
  • the tap bulk density is 0.02 g/cm 3 or more and 0.04 g/cm 3 or less.
  • the method for producing oxidized carbon nanotubes of the present invention preferably oxidizes carbon nanotubes that satisfy both the above conditions (1) and (2). Each condition will be described below.
  • Condition (1) is "a spectrum obtained by Fourier transform infrared spectroscopic analysis of a carbon nanotube dispersion obtained by dispersing carbon nanotubes containing single-walled carbon nanotubes so that the bundle length is 10 ⁇ m or more, At least one peak based on plasmon resonance of the carbon nanotube dispersion exists in the wavenumber range of 500 cm ⁇ 1 or more and 900 cm ⁇ 1 or less.”
  • the oxidized carbon nanotubes of the present invention can be suitably obtained by oxidizing the material CNT that satisfies these conditions.
  • the position of the peak based on plasmon resonance in the spectrum obtained by Fourier transform infrared spectroscopy can be changed, for example, by changing the feed rate of the raw material gas in the CNT growth step of "Method for synthesizing CNT material" described later. can be controlled.
  • the CNT material preferably has only one peak based on plasmon resonance within the wave number range of 500 cm ⁇ 1 or more and 900 cm ⁇ 1 or less.
  • the material CNT has a plurality of peaks based on plasmon resonance, it is preferable that at least the peak based on the strongest plasmon resonance has a wavenumber within the range of 500 cm ⁇ 1 to 900 cm ⁇ 1 .
  • the material CNT preferably does not have a peak due to plasmon resonance in the wavenumber range of less than 500 cm ⁇ 1 or in the wavenumber range of more than 900 cm ⁇ 1 .
  • the material CNT preferably has at least one peak based on plasmon resonance within a range of wavenumbers of 600 cm -1 or more and 850 cm -1 or less. It is more preferable to have all peaks within the wavenumber range of 600 cm ⁇ 1 or more and 850 cm ⁇ 1 or less.
  • the material CNT can include multi-walled carbon nanotubes in addition to single-walled carbon nanotubes.
  • condition (1) in obtaining a spectrum by Fourier transform infrared spectrophotometry, carbon nanotubes including single-walled carbon nanotubes are dispersed so that the bundle length is 10 ⁇ m or more, so that carbon nanotubes are dispersed.
  • a body for example, carbon nanotubes including single-walled carbon nanotubes, water, and a surfactant (for example, sodium dodecylbenzenesulfonate) are blended in an appropriate ratio and stirred for a predetermined period of time using ultrasonic waves or the like.
  • a dispersion liquid in which a carbon nanotube dispersion having a bundle length of 10 ⁇ m or more is dispersed in water can be obtained.
  • the bundle length of the carbon nanotube dispersion can be obtained by analyzing it with a wet image analysis type particle size measuring device. Such a measurement device calculates the area of each dispersion from the image obtained by photographing the carbon nanotube dispersion, and the diameter of the circle having the calculated area (hereinafter also referred to as ISO area diameter) can be obtained).
  • ISO area diameter the diameter of the circle having the calculated area
  • the bundle length of each dispersion is defined as the value of the ISO circle diameter thus obtained.
  • Condition (2) defines that "the tapped bulk density of CNT material is 0.02 g/cm 3 or more and 0.04 g/cm 3 or less". If material CNTs having a tapped bulk density within the above range are used, the material CNTs can be sufficiently oxidized to suitably obtain the oxidized carbon nanotubes of the present invention. From the viewpoint of further enhancing the dispersibility of the resulting oxidized carbon nanotubes, the tapped bulk density of the CNT material is preferably 0.025 g/cm 3 or more, and preferably 0.035 g/cm 3 or less. Note that the tap bulk density of the CNT material can be controlled, for example, by changing the feed rate of the raw material gas in the CNT growth step of the "method for synthesizing CNT material" described later.
  • the CNT material preferably has an average diameter of 3.5 nm or more, more preferably 3.7 nm or more, and preferably 5 nm or less, more preferably 4.8 nm or less. If the average diameter of the material CNTs is within the above range, the dispersibility of the resulting oxidized CNTs can be further enhanced.
  • the CNT material preferably has a total specific surface area of 600 m 2 /g or more, more preferably 800 m 2 /g or more, and preferably 2600 m 2 / g or less, more preferably 1400 m 2 /g or less, according to the BET method. be.
  • the material CNT preferably has a G/D ratio of 1 or more and 50 or less.
  • Carbon nanotubes with a G/D ratio of less than 1 are considered to have low crystallinity of single-walled CNTs, a large amount of dirt such as amorphous carbon, and a large content of multi-walled CNTs. Conversely, CNTs with a G/D ratio exceeding 50 have high linearity, tend to form bundles with few gaps, and may have a reduced specific surface area.
  • the material CNT is not particularly limited, and can be synthesized by a known CNT synthesis method such as chemical vapor deposition (CVD) method.
  • the CNT material is prepared by supplying a raw material compound and a carrier gas onto a base material having a catalyst layer for CNT production on its surface, and synthesizing CNT by a CVD method.
  • Activating substance the catalytic activity of the catalyst layer is dramatically improved (super-growth method; see International Publication No. 2006/011655).
  • a method for synthesizing the material CNT includes a catalyst carrier forming step of forming a catalyst carrier, a CNT synthesis step of synthesizing CNT using the catalyst carrier obtained in the catalyst carrier forming step, and and a recovery step of recovering the CNTs synthesized in the CNT synthesis step.
  • the catalyst support formation step can be carried out according to known wet or dry catalyst support methods.
  • the base material, the catalyst, the method of forming the catalyst, and the like used in producing the supported catalyst are not particularly limited, and for example, those described in International Publication No. 2017/170579 can be used.
  • CNT synthesis step In the CNT synthesis step, a raw material gas that serves as a carbon source is supplied to the catalyst carrier, and CNTs are grown on the catalyst layer by the CVD method (CNT growth step). A large number of CNTs are formed on the catalyst layer in a state of being arranged (orientated) in a predetermined direction.
  • the raw material gas serving as a carbon source is not particularly limited, and hydrocarbon gases such as methane, ethane, ethylene, propane, butane, pentane, hexane, heptane, propylene and acetylene; Gases of lower alcohols; as well as mixtures thereof can also be used.
  • this raw material gas may be diluted with an inert gas such as helium gas, argon gas, nitrogen gas, or a mixed gas thereof.
  • an inert gas such as helium gas, argon gas, nitrogen gas, or a mixed gas thereof.
  • the growth rate of CNTs is preferably 10 ⁇ m/min or more. Note that the temperature can be adjusted, for example, in the range of 400° C. or higher and 1100° C. or lower.
  • the raw material gas serving as a carbon source contain ethylene.
  • ethylene By heating ethylene in a predetermined temperature range (700° C. or higher and 900° C. or lower), the decomposition reaction of ethylene is promoted, and when the decomposition gas comes into contact with the catalyst, CNTs can grow at high speed.
  • the thermal decomposition time is too long, the decomposition reaction of ethylene proceeds too much, causing deactivation of the catalyst and adhesion of carbon impurities to the CNTs.
  • the thermal decomposition time is preferably in the range of 0.5 seconds to 10 seconds with respect to the ethylene concentration in the range of 0.1 volume % to 40 volume %.
  • Thermal decomposition time (heating channel volume)/ ⁇ (source gas flow rate) x (273.15+T)/273.15 ⁇
  • the heated channel volume is the volume of the channel heated to a predetermined temperature T° C. through which the raw material gas passes before coming into contact with the catalyst, and the raw material gas flow rate is the flow rate at 0° C. and 1 atm.
  • the catalyst activating material supplied during CNT growth is not particularly limited, and oxygen-containing compounds with a low carbon number such as water, oxygen, ozone, acid gases, nitrogen oxides, carbon monoxide and carbon dioxide; alcohols such as ethanol and methanol. ethers such as tetrahydrofuran; ketones such as acetone; aldehydes; esters; and mixtures thereof. Among these, it is preferable to use water. Substances containing both carbon and oxygen, such as carbon monoxide and alcohols, may function as both a raw material gas and a catalyst activating substance.
  • carbon monoxide acts as a catalyst activating substance when combined with a more reactive raw material gas such as ethylene, and acts as a raw material gas when combined with a catalyst activating substance that exhibits a large catalytic activation effect even in a small amount such as water.
  • the concentration of the catalyst activation substance in the growth atmosphere of the CNT aggregates is preferably 0.01% by volume or more.
  • the concentration of the catalyst activation material in the growth atmosphere of the CNT aggregate is usually 1.0% by volume or less.
  • the catalyst activation material concentration can be controlled by appropriately adjusting the feed rate of the catalyst activation material supplied during CNT growth.
  • a "formation step” can be performed to reduce the catalyst supported on the catalyst support.
  • the atmosphere containing the catalyst carrier is used as a reducing gas atmosphere, and at least one of the reducing gas atmosphere and the catalyst carrier is heated to reduce and atomize the catalyst supported on the catalyst carrier. do.
  • the temperature of the catalyst carrier or reducing gas atmosphere in the formation step is preferably 400° C. or higher and 1100° C. or lower.
  • the execution time of a formation process can be 3 minutes or more and 120 minutes or less.
  • the reducing gas for example, hydrogen gas, ammonia gas, water vapor, or a mixed gas thereof can be used.
  • the reducing gas may be a mixed gas in which these gases are mixed with an inert gas such as helium gas, argon gas, or nitrogen gas.
  • the recovery step is not particularly limited, and can be performed, for example, by using a spatula with a sharp edge to peel the CNTs from the substrate.
  • the recovery may be performed using a known separation and recovery device such as a classifier.
  • the method of oxidizing the CNT material is not particularly limited, and the oxidizing treatment can be performed, for example, by adding the CNT material to an acidic solution and mixing.
  • a mixing method is not particularly limited, and stirring operation can be performed by any method.
  • the mixing time is not particularly limited, but is preferably 0.1 hour or more and 10 hours or less.
  • the acidic solution include solutions containing acids such as nitric acid, hydrochloric acid, and sulfuric acid. From the viewpoint of sufficiently oxidizing the material CNT, it is preferable to use a solution containing nitric acid.
  • the solvent of the acidic solution can be a solvent that can be contained in the oxidized carbon nanotube dispersion of the present invention, which will be described later, but it is preferable to use water. That is, the acidic solution is preferably an acidic aqueous solution.
  • the pH of the acidic solution can be, for example, 2 or less.
  • the oxidation treatment is preferably performed by refluxing the mixed solution of the CNT material and the acid solution under a predetermined temperature condition.
  • the temperature condition for refluxing the mixture is preferably 100° C. or higher and 150° C. or lower, and the reflux time is preferably 3 hours or longer and 20 hours or shorter.
  • the oxidized carbon nanotubes of the present invention can be obtained by filtering the oxidized carbon nanotubes in the mixed liquid that has undergone the oxidation treatment step and optionally drying them by a known method.
  • the mixed liquid can be used for the production of the oxidized carbon nanotube dispersion of the present invention, which will be described later.
  • the oxidized carbon nanotube dispersion of the present invention contains the oxidized carbon nanotubes of the present invention described above and a solvent. As described above, since the oxidized carbon nanotubes of the present invention are excellent in dispersibility, the oxidized carbon nanotubes are highly dispersed in the oxidized carbon nanotube dispersion of the present invention.
  • the oxidized carbon nanotubes are those described in the above item "the oxidized carbon nanotubes of the present invention".
  • the oxidized carbon nanotube preferably satisfies various suitable attributes as described in the section "Oxidized carbon nanotube of the present invention” above.
  • the oxidized carbon nanotubes can be produced by the above-described method for producing oxidized carbon nanotubes of the present invention.
  • solvent contained in the oxidized carbon nanotube dispersion of the present invention include non-halogen solvents and non-aqueous solvents.
  • water methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, amyl alcohol, methoxy Alcohols such as propanol, propylene glycol and ethylene glycol; Ketones such as acetone, methyl ethyl ketone and cyclohexanone; Esters such as ethyl acetate, butyl acetate, ethyl lactate, ⁇ -hydroxycarboxylic acid esters and benzyl benzoate (benzyl benzoate) Ethers such as diethyl ether, dioxane, tetrahydrofuran, and monomethyl ether; Amide-based polar organic solvents such as N,N-dimethylformamide and N-
  • the oxidized carbon nanotube dispersion of the present invention preferably does not substantially contain a dispersant.
  • the term “substantially free” means that it is not actively blended except when it is unavoidably mixed.
  • the content in the oxidized carbon nanotube dispersion is It is preferably less than 0.05% by mass, more preferably less than 0.01% by mass, and even more preferably less than 0.001% by mass in terms of solid content.
  • surfactant, a synthetic polymer, a natural polymer, etc. are mentioned as said dispersing agent.
  • the viscosity of the oxidized carbon nanotube dispersion of the present invention is preferably 0.5 mPa s or more, more preferably 1 mPa s or more, preferably 100 mPa s or less, and 10 mPa s or less. It is more preferable to have When the viscosity of the oxidized carbon nanotube dispersion liquid is 0.5 mPa ⁇ s or more and 100 mPa ⁇ s or less, the oxidized carbon nanotubes are excellent in dispersibility.
  • the "viscosity of the oxidized carbon nanotube dispersion” is at least one shear rate within the range of 10 s -1 or more and 1000 s -1 or less (for example, 152 s -1 ) in accordance with JIS Z8803. It can be measured at a temperature of 25°C.
  • the absorbance of the oxidized carbon nanotube dispersion of the present invention measured using a spectrophotometer is preferably 0.1 or more, preferably 0.2, at an optical path length of 1 mm and a wavelength of 550 nm, from the viewpoint of dispersibility. It is more preferably 10 or less, preferably 10 or less, and more preferably 5 or less. If the absorbance of the oxidized carbon nanotube dispersion is 0.1 or more, a sufficient amount of oxidized carbon nanotubes in the oxidized carbon nanotube dispersion can be ensured. Further, when the absorbance of the oxidized carbon nanotube dispersion is 10 or less, the proportion of highly dispersible oxidized carbon nanotubes contained in the oxidized carbon nanotube dispersion can be increased.
  • the absorbance ratio of the oxidized carbon nanotube dispersion liquid of the present invention is preferably 0.5 or more, preferably 0.7 or more, from the viewpoint of high purity with few aggregates and excellent dispersibility of oxidized carbon nanotubes. It is more preferably 0 or less.
  • the "absorbance ratio" is defined for the oxidized carbon nanotube dispersion and the purified dispersion obtained by filtering and purifying the oxidized carbon nanotube dispersion, respectively, using a spectrophotometer with an optical path length of 1 mm.
  • the oxidized carbon nanotube dispersion of the present invention is not particularly limited, and can be obtained by subjecting a mixture (coarse dispersion) containing the oxidized carbon nanotubes of the present invention and a solvent to dispersion treatment.
  • a coarse dispersion can be obtained, for example, by adding oxidized carbon nanotubes to the solvent described above and optionally mixing them under normal pressure using a mixer or the like.
  • the acidic solution containing oxidized CNT obtained in the oxidation treatment step in the method for producing oxidized carbon nanotubes of the present invention described above may be used as it is as the coarse dispersion.
  • the coarse dispersion may also optionally contain additives such as the dispersing agents described above.
  • the obtained dispersion is centrifuged to precipitate a part of the oxidized carbon nanotubes (centrifugation treatment), and the supernatant is separated from the centrifuged dispersion.
  • the supernatant may be obtained as an oxidized carbon nanotube dispersion liquid by performing a treatment for collecting (fractionation treatment).
  • the dispersion treatment is not particularly limited, and can be performed using a known dispersion treatment method used for dispersing a liquid containing carbon nanotubes, such as ultrasonic dispersion treatment.
  • the dispersion treatment time is not particularly limited, but is preferably from 1 hour to 30 hours.
  • Any neutralizing agent may be added in order to adjust the pH of the crude dispersion to neutrality (approximately pH 6 to pH 8) during the dispersion treatment.
  • the neutralizing agent include, but are not particularly limited to, alkaline solutions having a pH of 9 or more and 14 or less, more specifically sodium hydroxide aqueous solution, ammonia aqueous solution, and the like.
  • the solvent described above may be added to the acidic solution as necessary during the dispersion treatment.
  • Such solvent may be the same as or different from the solvent of the acidic solution, but is preferably the same solvent.
  • Centrifugation of the liquid (dispersion mixed liquid) that has undergone the dispersion treatment is not particularly limited, and can be performed using a known centrifuge. Among them, from the viewpoint of obtaining an oxidized carbon nanotube dispersion liquid having excellent dispersibility of oxidized carbon nanotubes by leaving an appropriate amount of oxidized carbon nanotubes having excellent dispersibility in the supernatant liquid obtained, centrifugation when centrifuging the dispersed mixed liquid
  • the acceleration is preferably 2000G or more, more preferably 5000G or more, preferably 20000G or less, and more preferably 15000G or less.
  • centrifugation during centrifugation of the dispersion mixture The separation time is preferably 20 minutes or longer, more preferably 30 minutes or longer, preferably 120 minutes or shorter, and more preferably 90 minutes or shorter.
  • the supernatant liquid from the centrifuged dispersion can be collected by, for example, decantation, pipetting, or the like, leaving a sediment layer and recovering the supernatant liquid.
  • the supernatant liquid present in a portion from the liquid surface of the dispersed mixed liquid after centrifugation to a depth of 5/6 may be recovered.
  • the supernatant liquid separated from the dispersed mixture after centrifugation contains oxidized carbon nanotubes that were not precipitated by centrifugation. Therefore, the supernatant liquid is an oxidized carbon nanotube dispersion in which the oxidized carbon nanotubes are more highly dispersed.
  • FT-IR ⁇ Fourier transform infrared spectroscopy
  • CNT bundle length measurement 100 g of water containing sodium dodecylbenzenesulfonate as a surfactant at a concentration of 1% by mass was added to 10 mg of CNT material prepared in each example and comparative example and 10 mg of oxidized CNT prepared in Comparative Example 2, An ultrasonic bath was used to stir at 45 Hz for 1 minute to obtain 100 ml of each CNT dispersion.
  • a CNT dispersion or oxidized CNT dispersion present in the dispersion was analyzed using a flow-type particle image analyzer (manufactured by Jusco International Co., Ltd., a circulation type image analysis particle size distribution meter "CF-3000").
  • the ISO circle diameter average value was measured, and the obtained value was defined as the CNT bundle length.
  • the analysis conditions were as follows.
  • the plasmon peak top position (FIR resonance peak) was obtained from an approximated curve by polynomial fitting using drawing software.
  • ⁇ Average diameter of material CNT and oxidized CNT> Using a transmission electron microscope, the diameters (outer diameters) of 100 randomly selected material CNTs and 100 oxidized CNTs were measured, and the arithmetic average value was taken as the average diameter of the material CNTs and oxidized CNTs.
  • ⁇ Tap bulk density> The tapped bulk density (g/cm 3 ) of the CNT materials prepared in Examples and Comparative Examples was measured according to the method specified in JIS R 1628 "Method for measuring bulk density of fine ceramic powder".
  • ⁇ Average length of oxidized CNT> The oxidized CNTs prepared in each example and comparative example were observed with a scanning electron microscope (SEM), and the lengths of 50 oxidized CNTs were measured from the obtained SEM images. Then, the arithmetic average value of the measured lengths of the oxidized CNTs was taken as the average length of the oxidized CNTs. In Comparative Example 2 in which the average length of oxidized CNTs exceeded 1.0 ⁇ m, the above ⁇ CNT bundle length> was used as the average length of oxidized CNTs.
  • ⁇ Absorbance ratio> The oxidized carbon nanotube dispersion liquid prepared in each example and comparative example was filtered and purified using a 0.2 ⁇ m syringe filter (manufactured by Pall Corporation, product name “Acrodisc Syringe Filter”) to obtain a purified dispersion liquid.
  • a spectrophotometer manufactured by JASCO Corporation, Absorbance at an optical path length of 1 mm and a wavelength of 550 nm was measured using a product name "V670").
  • the absorbance ratio was determined by the following formula.
  • Absorbance ratio (absorbance of purified dispersion)/(absorbance of unpurified dispersion) ⁇ Dispersion stability of oxidized CNT>
  • the oxidized CNT dispersions prepared in Examples and Comparative Examples were stored at room temperature in a dark place for one month. The absorbance ratio is determined for the oxidized CNT dispersion after storage. If the decrease in the absorbance ratio before and after storage is less than 0.1, the dispersion stability is “good”, and if it is 0.1 or more, the dispersion stability is “poor”. ” he decided.
  • Example 1 [Synthesis of material CNT]
  • a coating solution A was prepared by dissolving aluminum tri-sec-butoxide as an aluminum compound in 2-propanol. Further, a coating liquid B was prepared by dissolving iron acetate as an iron compound in 2-propanol.
  • the above-described coating liquid A was applied to the surface of an Fe--Cr alloy SUS430 substrate as a substrate by dip coating under an environment of room temperature of 25° C. and relative humidity of 50%. Specifically, after the substrate was immersed in the coating liquid A, the substrate was held for 20 seconds and pulled up at a pulling speed of 10 mm/sec. Then, it was air-dried for 5 minutes, heated in an air environment at 300° C.
  • the above-described coating liquid B was applied by dip coating on the alumina thin film provided on the substrate under an environment of room temperature of 25° C. and relative humidity of 50%. Specifically, after the substrate provided with the alumina thin film was immersed in the coating liquid B, the substrate was held for 20 seconds, and the substrate provided with the alumina thin film was pulled up at a lifting speed of 3 mm/second.
  • the catalyst for CNT synthesis (iron) is reduced to promote the formation of fine particles of iron, and a state suitable for the growth of single-walled CNTs (a state in which a large number of nanometer-sized catalyst fine particles are formed on the underlayer).
  • the density of the fine catalyst particles at this time was adjusted to 1 ⁇ 10 12 to 1 ⁇ 10 14 particles/cm 2 .
  • a reaction chamber maintained at a furnace temperature of 750° C. and a furnace pressure of 1.02 ⁇ 10 5 Pa, He: 850 sccm, C 2 H 4 : 150 sccm, and H 2 O: 300 ppm. was fed for 5 minutes.
  • CNT growth step single-walled CNTs were grown from each fine catalyst particle.
  • He: 1000 sccm was supplied into the reaction chamber, and the remaining raw material gas and catalyst activator were eliminated.
  • a substrate with CNTs formed on the surface was obtained.
  • the CNTs grown on the substrate were peeled off from the surface of the obtained substrate.
  • a plastic spatula with a sharp edge was used to separate the CNTs (recovery step).
  • the sharp part of the spatula was brought into contact with the boundary between the CNTs and the base material, and the sharp part was moved along the surface of the base material so as to scrape off the CNTs from the base material.
  • the CNTs were stripped from the substrate to obtain the material CNTs.
  • the wavenumber of the FIR resonance peak, the tapped bulk density, and the average diameter were obtained for the obtained material CNT. Table 1 shows the results.
  • oxidized CNT dispersion Using the obtained oxidized CNT dispersion, FT-IR measurement, absorbance ratio measurement, and dispersion stability evaluation were performed. Table 1 shows the results. Also, the oxidized CNTs in the oxidized CNT dispersion were collected by filtration and dried. Then, the ratio of oxidized single-walled carbon nanotubes, the ratio of oxygen atoms, the average diameter, and the average length of the dried oxidized CNTs were determined. Table 1 shows the results.
  • Example 2 A CNT material was synthesized in the same manner as in Example 1 except that He: 800 sccm and C 2 H 4 : 200 sccm in the CNT growth step in synthesizing the material CNT, and an oxidized CNT and an oxidized CNT dispersion were obtained. Then, various measurements and evaluations were performed. Table 1 shows the results.
  • Example 1 A CNT material was synthesized in the same manner as in Example 1, except that He: 900 sccm and C 2 H 4 : 100 sccm in the CNT growth step in the synthesis of the material CNT, to obtain oxidized CNT and an oxidized CNT dispersion. Then, various measurements and evaluations were performed. Table 1 shows the results.
  • Example 2 An oxidized CNT and an oxidized CNT dispersion were prepared in the same manner as in Example 1, except that the material CNT was synthesized according to the method described in Example 1 of WO2021/172078. Then, various measurements and evaluations were performed. Table 1 shows the results.
  • oxidized carbon nanotubes with excellent dispersibility, a method for producing the same, and an oxidized carbon nanotube dispersion in which oxidized carbon nanotubes are well dispersed.

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Abstract

Le but de la présente invention est de fournir : des nanotubes de carbone oxydés ayant une excellente dispersibilité et une méthode de production de ceux-ci ; et un liquide de dispersion de nanotubes de carbone oxydés dans lequel des nanotubes de carbone oxydés sont de préférence dispersés. Les nanotubes de carbone oxydés selon la présente invention sont caractérisés en ce qu'ils satisfont les conditions (1) à (3) : (1) Le rapport du nombre de nanotubes de carbone monocouche oxydés par rapport au nombre total des nanotubes de carbone oxydés est supérieur ou égal à 51 %. (2) Dans un spectre obtenu par réalisation d'une analyse spectroscopique infrarouge à transformée de Fourier sur les nanotubes de carbone oxydés, au moins un pic basé sur une résonance plasmonique des nanotubes de carbone oxydés existe dans une plage de nombre d'ondes supérieure à 700 cm-1 mais inférieure ou égale à 1000 cm-1. (3) Le rapport d'atomes d'oxygène est supérieur ou égal à 13 %at.
PCT/JP2023/001783 2022-02-14 2023-01-20 Nanotube de carbone oxydé et sa méthode de production, et liquide de dispersion de nanotubes de carbone oxydés WO2023153182A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011207758A (ja) * 2008-12-30 2011-10-20 National Institute Of Advanced Industrial Science & Technology 単層カーボンナノチューブ配向集合体、バルク状単層カーボンナノチューブ配向集合体、粉体状単層カーボンナノチューブ配向集合体
JP2018131348A (ja) * 2017-02-14 2018-08-23 東洋インキＳｃホールディングス株式会社 酸化カーボンナノチューブおよびその分散液
WO2018168346A1 (fr) * 2017-03-16 2018-09-20 日本ゼオン株式会社 Méthode de production d'une nanostructure de carbone traitée en surface

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011207758A (ja) * 2008-12-30 2011-10-20 National Institute Of Advanced Industrial Science & Technology 単層カーボンナノチューブ配向集合体、バルク状単層カーボンナノチューブ配向集合体、粉体状単層カーボンナノチューブ配向集合体
JP2018131348A (ja) * 2017-02-14 2018-08-23 東洋インキＳｃホールディングス株式会社 酸化カーボンナノチューブおよびその分散液
WO2018168346A1 (fr) * 2017-03-16 2018-09-20 日本ゼオン株式会社 Méthode de production d'une nanostructure de carbone traitée en surface

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CHEN ZHEYI, ET AL: "Soluble ultra-short single-walled carbon nanotubes", JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMERICAN CHEMICAL SOCIETY, vol. 128, no. 32, 16 August 2006 (2006-08-16), pages 10568 - 10571, XP002479239, ISSN: 0002-7863, DOI: 10.1021/ja063283p *

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