Carbon nanotube dispersion

Abstract

To provide a CNT dispersion with excellent dispersibility and resistance to aggregation. [Solution] A carbon nanotube dispersion comprising a plurality of carbon nanotubes, a non-aqueous solvent, and one or more dispersants, wherein the plurality of carbon nanotubes include single-walled carbon nanotubes, and the specific surface area of ​​the plurality of carbon nanotubes is 800 m². 2 A carbon nanotube dispersion liquid having a concentration of 1 / g or more, with a harmonic mean diameter of multiple carbon nanotubes between 1000 nm and 10000 nm, and containing hydrogenated nitrile rubber as one or more dispersants.

Description

[Technical Field]

[0001] This invention relates to a carbon nanotube dispersion. [Background technology]

[0002] Conventionally, carbon nanotubes (hereinafter sometimes abbreviated as "CNT") have attracted attention as a material with excellent properties such as electrical conductivity, thermal conductivity, and strength. While individual carbon nanotubes (CNTs) possess excellent properties, their small outer diameter makes them prone to bundling (forming bundles) due to van der Waals forces. Therefore, conventional methods involve dispersing CNTs in a solvent to prepare a carbon nanotube dispersion (CNT dispersion).

[0003] In recent years, attempts have been made to improve the dispersibility of CNT dispersions. For example, Patent Document 1 discloses a conductive material dispersion containing a conductive material including CNTs and / or acetylene black, a polymer containing specific structural units in a certain proportion, and a dispersion medium, and describes that the Mooney viscosity of the polymer and the product of the complex modulus X and phase angle Y of the conductive material dispersion are both within a certain range. Furthermore, Patent Document 2 discloses a conductive material dispersion containing a conductive material including single-layer and multi-layer CNTs, a polymer containing specific structural units in a certain proportion, and a dispersion medium, and describes that the Mooney viscosity of the polymer and the product of the complex modulus X and phase angle Y of the conductive material dispersion are both within a certain range. Furthermore, according to the inventions described in Patent Documents 1 and 2 above, it is possible to control the dispersion state of the conductive material and obtain a conductive material dispersion liquid with high fluidity. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-165106 [Patent Document 2] Japanese Patent Publication No. 2024-003640 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the conventional conductive material dispersions described above had room for improvement in terms of further enhancing the dispersibility of CNTs. Therefore, the present invention aims to provide a CNT dispersion that is highly dispersible and less prone to aggregation. [Means for solving the problem]

[0006] The inventors diligently conducted research with the aim of solving the above problems. As a result, the inventors discovered that the dispersibility of a CNT dispersion containing multiple CNTs, including single-walled carbon nanotubes (WNTs), a non-aqueous solvent, and a dispersant can be improved by setting the specific surface area of ​​the CNTs to a certain value or higher, the harmonic mean diameter of the CNTs to a certain range, and the dispersant to contain hydrogenated nitrile rubber, thereby completing the present invention.

[0007] In other words, the present invention aims to advantageously solve the above problems, and the present invention is a CNT dispersion comprising [1] a plurality of CNTs, a non-aqueous solvent, and one or more dispersants, wherein the plurality of CNTs include single-walled CNTs, and the specific surface area of ​​the plurality of CNTs is 800 m 2 The CNT dispersion is such that the concentration is 1 / g or more, the harmonic mean diameter of the plurality of CNTs is 1000 nm or more and 10000 nm or less, and the one or more dispersants include hydrogenated nitrile rubber. The above CNT dispersion has excellent dispersibility and is resistant to aggregation. The specific surface area and harmonic mean diameter of the CNTs can be measured by the method described in the embodiment of this application.

[0008] [2] Here, it is preferable that the CNT dispersion in [1] above has a storage modulus of 1.5 Pa or more at 100% strain. If the storage modulus of the CNT dispersion is above the lower limit mentioned above, the dispersibility of the CNT dispersion can be further improved. The storage modulus of the CNT dispersion can be measured by the method described in the embodiment of this application.

[0009] [3] In the CNT dispersion of [1] or [2] above, it is preferable that the one or more dispersants further contain polyvinylidene fluoride. If the dispersant further contains polyvinylidene fluoride, the dispersibility of the CNT dispersion can be further improved, as well as the stability of the dispersion state over time. [Effects of the Invention]

[0010] According to the present invention, a CNT dispersion liquid with excellent dispersibility and low aggregation can be provided. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below.

[0012] (CNT dispersion) The CNT dispersion of the present invention is a CNT dispersion comprising a plurality of CNTs, a non-aqueous solvent, and one or more dispersants, wherein the plurality of CNTs include single-walled CNTs, and the one or more dispersants include hydrogenated nitrile rubber. Furthermore, in the CNT dispersion of the present invention, the specific surface area of ​​the plurality of CNTs is 800 m². 2 It is characterized by having a value of 1 / g or more and a harmonic mean diameter of 1000 nm or more and 10000 nm or less. The CNT dispersion of the present invention exhibits excellent dispersibility and is resistant to aggregation.

[0013] <cnt> The CNT used in the CNT dispersion of the present invention is not particularly limited as long as it contains single-walled CNTs. As the CNT, only single-walled CNTs may be used, or single-walled CNTs and multi-walled CNTs may be used in combination.

[0014] <<Properties of CNT>> [Specific surface area] The CNT needs to have a specific surface area of 800 m 2 / g or more, preferably 900 m 2 / g or more, more preferably 1000 m 2 / g or more. The upper limit of the specific surface area of the CNT is not particularly limited, but generally it is preferably 2000 m 2 / g or less, more preferably 1500 m 2 / g or less. If the specific surface area of the CNT is above the above lower limit value, the dilution stability of the CNT dispersion and the temporal stability of the dispersed state can be further enhanced. In the present invention, the "specific surface area" means the nitrogen adsorption specific surface area (BET specific surface area) measured using the BET method.

[0015] [Harmonic mean diameter] The harmonic mean diameter of the CNT needs to be 1000 nm or more, preferably 1500 nm or more, more preferably 1900 nm or more, and needs to be 10000 nm or less, preferably 7800 nm or less, more preferably 6600 nm or less. If the harmonic mean diameter of the CNT is above the above lower limit value, a CNT dispersion with excellent dispersibility and low aggregation can be obtained. Also, if the harmonic mean diameter of the CNT is below the above upper limit value, the dispersibility of the CNT dispersion can be enhanced, and the conductivity of the molded body obtained using the CNT dispersion can be increased. The harmonic mean diameter of CNTs can be adjusted, for example, by changing the length and diameter of the raw CNTs, the type and amount of dispersant, and the conditions of the dispersion process. Specifically, in the dispersion step of the CNT dispersion manufacturing method described later, increasing the pressure applied to the mixture will decrease the harmonic mean diameter of the CNTs, while decreasing it will increase the harmonic mean diameter. In addition, increasing the number of passes in the dispersion process using a wet jet mill will decrease the harmonic mean diameter of the CNTs, while decreasing it will increase the harmonic mean diameter.

[0016] [G / D ratio] The ratio of the G-band peak intensity to the D-band peak intensity in the Raman spectrum (G / D ratio) of the CNTs is preferably 1.0 or higher, more preferably 3.0 or higher, preferably 120 or lower, more preferably 20 or lower, and even more preferably 10 or lower. If the G / D ratio of the CNTs is within the above range, the dilution stability of the CNT dispersion can be further enhanced. Furthermore, if the G / D ratio of the CNTs is below the above upper limit, the CNTs are sufficiently defibrated, which further enhances the time-dependent stability of the dispersion state of the CNT dispersion. The G / D ratio of CNTs can be measured by the method described in the embodiment of this application.

[0017] [Average bundle diameter] In the CNT dispersion of the present invention, multiple CNTs may aggregate to form bundles (hereinafter sometimes referred to as "CNT bundles"). The average bundle diameter of the CNTs (i.e., the average value of the diameter of the CNT bundles) is preferably 500 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. If the average bundle diameter of the CNTs is below the above upper limit, the CNTs will be sufficiently defibrated in the CNT dispersion, and the dispersibility of the CNT dispersion can be further improved. The lower limit of the average diameter of the CNT bundles is not particularly limited and can be, for example, 5 nm or more, or 10 nm or more. The average bundle diameter of CNTs in the CNT dispersion can be adjusted, for example, by changing the diameter of the raw material CNTs, the type and amount of the dispersant, and the conditions of the dispersion treatment. Specifically, in the method for producing a CNT dispersion described below, increasing the pressure of the dispersion treatment by a wet jet mill (the pressure applied to the mixed liquid) decreases the average bundle diameter of the CNTs, and decreasing the pressure increases the average bundle diameter. Also, increasing the number of passes of the dispersion treatment by a wet jet mill decreases the average bundle diameter of the CNTs in the CNT dispersion, and decreasing the number of passes increases the average bundle diameter.

[0018] <<Content ratio of CNT>> The content ratio of CNTs in the CNT dispersion is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, still more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and still more preferably 0.5% by mass or less, with the total amount of the CNT dispersion being 100% by mass. If the ratio of CNTs in the CNT dispersion is at least the above lower limit value, the conductivity of the molded body produced using the CNT dispersion can be increased. Also, if the ratio of CNTs is at most the above upper limit value, the dispersibility of the CNT dispersion can be further enhanced.

[0019] <Non-aqueous solvent> The non-aqueous solvent contained in the CNT dispersion of the present invention may consist of one type of non-aqueous solvent or may contain two or more types of non-aqueous solvents. The non-aqueous solvent is preferably an organic solvent, and there is no particular limitation on the organic solvent. Examples include N-methylpyrrolidone (NMP), acetonitrile, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, ethylenediamine, acetone, toluene, methanol, ethanol, butyl acetate, pentyl acetate, octyl acetate, etc. From the viewpoint of improving the dispersibility of the CNT dispersion, N-methylpyrrolidone (NMP) is particularly preferred.

[0020] <Dispersant> The dispersant contained in the CNT dispersion of the present invention is not particularly limited as long as it contains hydrogenated nitrile rubber and can assist in the dispersion of CNTs. The dispersant may contain only hydrogenated nitrile rubber, or it may contain hydrogenated nitrile rubber and one or more other dispersants.

[0021] <<Hydrogenated Nitrile Rubber>> Hydrogenated nitrile rubber can be obtained by hydrogenating a polymer obtained by polymerizing a monomer composition containing a conjugated diene monomer and a nitrile group-containing monomer. Hydrogenation can be carried out by a general method using a catalyst (see, for example, International Publication No. 2012165120).

[0022] [Nitrile group-containing monomer] Examples of nitrile group-containing monomers include α,β-ethylenically unsaturated nitrile monomers. The α,β-ethylenically unsaturated nitrile monomers are not particularly limited as long as they are α,β-ethylenically unsaturated compounds having a nitrile group, but examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, from the viewpoint of improving the dispersibility of the CNT dispersion, acrylonitrile and methacrylonitrile are preferred as nitrile group-containing monomers, with acrylonitrile being more preferred. These can be used individually or in combination of two or more types.

[0023] Furthermore, the proportion of nitrile group-containing monomer units in the above-mentioned hydrogenated nitrile rubber is preferably 10% by mass or more, more preferably 15% by mass or more, particularly preferably 20% by mass or more, preferably 50% by mass or less, more preferably 45% by mass or less, and particularly preferably 40% by mass or less, when the total monomer units in the hydrogenated nitrile rubber are considered to be 100% by mass. Note that the proportion of monomer units corresponds to the ratio of the blending amounts of each monomer when manufacturing the hydrogenated nitrile rubber. By keeping the amount of nitrile group-containing monomer units in the hydrogenated nitrile rubber within this range, sufficient solubility in the non-aqueous solvent (e.g., N-methyl-2-pyrrolidone) contained in the CNT dispersion can be ensured. Therefore, the dispersibility of CNTs in the CNT dispersion can be further improved.

[0024] [Conjugated diene monomers] Examples of conjugated diene monomers include conjugated diene compounds having four or more carbon atoms, such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, and 1,3-pentadiene. Among these, 1,3-butadiene is preferred. These conjugated diene monomers may be used individually or in combination of two or more in any ratio.

[0025] Specifically, as the hydrogenated nitrile rubber, it is preferable to use hydrogenated acrylonitrile butadiene rubber (HNBR) obtained by hydrogenating nitrile rubber (NBR) obtained by polymerizing a monomer composition containing 1,3-butadiene and acrylonitrile. Furthermore, the iodine value of the hydrogenated nitrile rubber is preferably 60 mg / 100 mg or less, more preferably 30 mg / 100 mg or less, and particularly preferably 20 mg / 100 mg or less. The lower limit is preferably 3 mg / 100 mg or more, and more preferably 8 mg / 100 mg or more.

[0026] The weight-average molecular weight (Mw) of hydrogenated nitrile rubber is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 50,000 or more, preferably 300,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less, in order to balance the resin viscosity and dispersibility.

[0027] [Other monomers] Hydrogenated nitrile rubber may contain other monomer units besides those described above, as long as the effects of the present invention are not impaired. Examples of monomers that provide such monomer units include monomers having acidic groups (acidic group-containing monomers), crosslinkable monomers, aromatic vinyl monomers, ethylenically unsaturated carboxylic acid amide monomers, and fluorine-containing monomers.

[0028] Here, the monomer having an acidic group is not particularly limited, and monomers having a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group can be used. Examples of compounds having a carboxylic acid group include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethyl acrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, fluoromaleic acid, and maleic acid esters such as methyl allyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of dicarboxylic acid acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, as compounds having a carboxylic acid group, acid anhydrides that generate a carboxyl group by hydrolysis can also be used. Other examples include monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate.

[0029] Examples of compounds having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-alyloxy-2-hydroxypropanesulfonic acid. In this invention, "(meth)allyl" means allyl and / or metallyl.

[0030] Examples of compounds containing a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0031] Furthermore, examples of crosslinkable monomers include monomers containing epoxy groups, monomers containing carbon-carbon double bonds and epoxy groups, monomers containing halogen atoms and epoxy groups, monomers containing N-methylolamide groups, monomers containing oxetanyl groups, monomers containing oxazoline groups, and polyfunctional monomers having two or more olefinic double bonds.

[0032] Furthermore, examples of aromatic vinyl monomers include styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, and chlorostyrene.

[0033] Furthermore, examples of ethylenically unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, and N,N-dimethylacrylamide.

[0034] Furthermore, as the fluorine-containing monomer, fluorine-containing monomers that can form fluorine-based resins, as described later, can be used, such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride, vinyl fluoride, perfluoroalkyl vinyl ether, etc.

[0035] Furthermore, there are no particular restrictions on the polymerization method used to polymerize the above-mentioned monomers to form hydrogenated nitrile rubber; any of the following methods can be used: solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Known emulsifiers and polymerization initiators can be used in each polymerization method as needed.

[0036] <<Other dispersants>> The dispersant contained in the CNT dispersion of the present invention may include dispersants other than hydrogenated nitrile rubber (other dispersants). Examples of other dispersants include surfactants, resin-type dispersants, and polymers having carboxylic acid groups.

[0037] [Surfactants] Here, examples of surfactants include ionic (cationic, anionic) surfactants and nonionic surfactants. Examples of cationic surfactants include alkylamine salts, quaternary ammonium salts, and quaternary phosphonium salts. Specifically, these include stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide and dodecylbenzyltriethylammonium chloride, dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide, distearyldimethylammonium chloride; tetrabutylphosphonium chloride, tetrapentylphosphonium chloride, trioctylmethylphosphonium chloride, pentyltriphenylphosphonium chloride, etc. Examples of amphoteric surfactants include aminocarboxylic acid salts. Examples of anionic surfactants include, but are not limited to, fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfons, alkylnaphthalene sulfons, dialkyl sulfons, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfons, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters. More specifically, examples include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate, sodium salt of β-naphthalene sulfonic acid formalin condensate, sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfate, and sodium dodecyldiphenyloxidedisulfonate. Examples of nonionic surfactants include, but are not limited to, ether ester-type nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkyl allyl ethers, glycerin esters, polyethylene glycol fatty acid esters, and glycerin esters. Specifically, examples include polyoxyethylene lauryl ether, sorbitan fatty acid ester, and polyoxyethylene octylphenyl ether.

[0038] The above-mentioned surfactants may be used individually or in combination of two or more surfactants. For example, a combination of an anionic surfactant and a nonionic surfactant, or a combination of a cationic surfactant and a nonionic surfactant can be used. In such cases, the amount used should preferably be an amount suitable for each surfactant component. Among the surfactants mentioned above, anionic surfactants are preferred from the viewpoint of further enhancing the conductivity of the molded article, and sodium cholate and sodium dodecylbenzene sulfate are more preferred.

[0039] [Resin-type dispersant] Specific examples of resin-type dispersants include fluororesins, cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylonitrile polymers. Fluorine resins, methylcellulose, ethylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylonitrile polymers are particularly preferred. The molecular weight of the resin-type dispersant is preferably between 20,000 and 5,000,000.

[0040] Fluorine-based resins may have a structure in which hydrogen atoms in polyethylene are replaced with fluorine or trifluoromethyl atoms. Examples of fluorine-based resins include homopolymers such as polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), and polychlorotrifluoroethylene (PCTFE); and copolymers such as perfluoroalkoxyalkanes (PFA), perfluoroethylenepropene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and tetrafluoroethylene-perfluorodioxysol copolymer (TPE / PDD). These may be used individually or in combination of two or more. Among fluorine-based resins, polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), resins having these structural units, modified versions thereof, or combinations thereof are preferred in terms of resistance. Among these, polyvinylidene fluoride resins are preferred, for example, polyvinylidene fluoride homopolymers; copolymers of polyvinylidene fluoride with hexafluoropropylene, tetrafluoroethylene, etc. The polyvinylidene fluoride resin may be modified, for example, by introducing acidic groups such as carboxyl groups. The fluorine resin may be used alone or in combination of two or more types.

[0041] The weight-average molecular weight (Mw) of the fluororesin is preferably 200,000 or more, more preferably 600,000 or more, even more preferably 1,000,000 or more, preferably 5,000,000 or less, more preferably 3,000,000 or less, and even more preferably 1,500,000 or less, in order to balance the viscosity and dispersibility of the resin.

[0042] Examples of commercially available polyvinylidene fluoride and its modified forms include the KF Polymer series from Kureha Corporation, such as "W#7300, W#7200, W#1700, W#1300, W#1100, W#9700, W#9300, W#9100, L#7305, L#7208, L#1710, L#1320, L#1120," and the Solvay Solef series, such as "6008, 6010, 6012, 1015, 6020, 5130, 9007, 460, 41308, 11010, 21510, 31508, 60512" (all are product names).

[0043] From the viewpoint of oxidation resistance of the dispersant, polyacrylonitrile polymers and fluororesins are preferred.

[0044] Among these, dispersants other than hydrogenated nitrile rubber are preferably fluorine-based resins, and particularly preferably polyvinylidene fluoride (PVDF), in terms of balancing adsorption capacity to CNTs with affinity to solvents, from the viewpoint of uniformly dispersing and stably maintaining multiple CNTs having different particle size distributions. Furthermore, the mass ratio of fluororesin to CNTs is preferably 0.1 or more, more preferably 0.5 or more, preferably 1 or more, preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. By being within the above range, the dispersibility of the CNT dispersion can be further improved, and the stability of the dispersion state over time can be improved.

[0045] [Polymers containing carboxylic acid groups] Examples of polymers having carboxylic acid groups include carboxymethylcellulose and its salts, and copolymers containing carboxylic acid group-containing monomer units. However, as used herein, "polymers having carboxylic acid groups" do not include nitrile group-containing monomer units. In this invention, the statement that a polymer "contains monomer units" means that "the polymer obtained using those monomers contains repeating units derived from the monomers."

[0046] A copolymer containing carboxylic acid group-containing monomer units is a copolymer containing carboxylic acid group-containing monomer units and other repeating units. Furthermore, the carboxylic acid group in the monomer unit containing the carboxylic acid group may form a salt with alkali metals, ammonia, etc.

[0047] Examples of carboxylic acid group-containing monomers that can form carboxylic acid group-containing monomer units include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, fluoromaleic acid, and maleic acid monoesters such as butyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of dicarboxylic acid acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, and citraconic anhydride. Furthermore, acid anhydrides that generate carboxylic acid groups through hydrolysis can also be used as monomers containing carboxylic acid groups. Furthermore, as monomers containing carboxylic acid groups, ethylenically unsaturated polycarboxylic acids such as butentricarboxylic acid, and partial esters of ethylenically unsaturated polycarboxylic acids such as monobutyl fumarate and mono-2-hydroxypropyl maleate can also be used. The carboxylic acid group-containing monomers described above may be used individually or in combination of two or more types.

[0048] Furthermore, the other repeating units contained in the copolymer are not particularly limited and include conjugated diene monomer units such as 1,3-butadiene and isoprene (2-methyl-1,3-butadiene); nitrile group-containing monomer units such as acrylonitrile units and methacrylonitrile units; and (meth)acrylic acid ester monomer units such as alkyl acrylate units and alkyl methacrylate units. The copolymer may contain one or more of these other repeating units. In the present invention, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0049] Furthermore, it is preferable to add amine compounds or inorganic bases in addition to the dispersant. Primary amines, secondary amines, and tertiary amines can be used as amine compounds, but ammonia and quaternary ammonium compounds are not included. In addition to monoamines, amine compounds such as diamines, triamines, and tetramines, which have multiple amino groups in their molecules, can also be used. Specifically, examples include, but are not limited to, primary aliphatic amines such as methylamine, ethylamine, butylamine, and octylamine; secondary aliphatic amines such as dimethylamine, diethylamine, and dibutylamine; tertiary aliphatic amines such as trimethylamine, triethylamine, and dimethyloctylamine; amino acids such as alanine, methionine, proline, serine, asparagine, glutamine, lysine, arginine, histidine, aspartic acid, glutamic acid, and cysteine; alkanolamines such as dimethylaminoethanol, monoethanolamine, diethanolamine, methylethanolamine, and triethanolamine; and alicyclic nitrogen-containing heterocyclic compounds such as hexamethylenetetramine, morpholine, and piperidine. Examples of inorganic bases include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal phosphates, and alkaline earth metal phosphates.

[0050] <<Dispersant content ratio>> The proportion of the dispersant contained in the CNT dispersion is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.5% by mass or more, preferably 10.0% by mass or less, more preferably 5.0% by mass or less, and still more preferably 3.0% by mass or less, with the total amount of the CNT dispersion being 100% by mass. If the proportion of the dispersant in the CNT dispersion is within the above-mentioned range, the dispersibility of the CNT dispersion can be further enhanced.

[0051] The proportion of the hydrogenated nitrile rubber contained in the CNT dispersion is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, preferably 1.0% by mass or less, and more preferably 0.5% by mass or less, with the total amount of the CNT dispersion being 100% by mass. If the proportion of the hydrogenated nitrile rubber in the CNT dispersion is within the above-mentioned range, the dispersibility of the CNT dispersion can be further enhanced.

[0052] <Other components> Examples of other components that the CNT dispersion may optionally contain include conductive materials other than CNTs, polymer components other than the above-mentioned dispersants, antioxidants, resins, molecular weight regulators, viscosity regulators, and the like. Note that the CNT dispersion may contain only one type of other component or two or more types of other components.

[0053] The proportion of other components contained in the CNT dispersion is preferably 5.0% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0% by mass (that is, the CNT dispersion of the present invention does not contain other components), with the total amount of the CNT dispersion being 100% by mass.

[0054] <Properties of the CNT dispersion> <<Storage elastic modulus>> The CNT dispersion of the present invention preferably has a storage modulus of 1.5 Pa or more at 100% strain, more preferably 15.0 Pa or more, even more preferably 20.0 Pa or more, even more preferably 23.0 Pa or more, and particularly preferably 25.0 Pa or more. The upper limit of the storage modulus of the CNT dispersion at 100% strain is not particularly limited, but is generally preferably 2000 Pa or less, and more preferably 1000 Pa or less. If the storage modulus of the CNT dispersion at 100% strain is above the lower limit, the dispersibility of the CNT dispersion can be further improved. Furthermore, if the storage modulus of the CNT dispersion at 100% strain is below the upper limit, the adhesion between the molded body made using the CNT dispersion and the current collector can be improved when used in secondary batteries, etc.

[0055] The storage modulus of the CNT dispersion can be adjusted by changing the type and amount of dispersant, the type and amount of CNTs, and the conditions of the dispersion treatment.

[0056] <<Viscosity>> The CNT dispersion of the present invention preferably has a viscosity of 3,000 mPa·s or more, more preferably 20,000 mPa·s or more, even more preferably 35,000 mPa·s or more, particularly preferably 40,000 mPa·s or more, preferably 100,000 mPa·s or less, more preferably 90,000 mPa·s or less, and even more preferably 80,000 mPa·s or less under conditions of a shear rate of 1 (1 / s). If the viscosity under a shear rate of 1 (1 / s) is above the lower limit, the conductivity of the molded article obtained from the CNT dispersion, as well as the dilution stability and temporal stability of the dispersion state of the CNT dispersion, can be further improved. Furthermore, if the viscosity under a shear rate of 1 (1 / s) is below the upper limit, the dispersibility of the CNT dispersion can be further improved.

[0057] The viscosity of the CNT dispersion can be adjusted by changing the type and amount of dispersant, adding viscosity modifiers, and modifying the dispersion treatment conditions.

[0058] <<Complex modulus of elasticity and phase angle>> The dispersibility of CNTs in a CNT dispersion can be evaluated by the complex modulus and phase angle measured by dynamic viscoelasticity. In this specification, the complex modulus and phase angle of the CNT dispersion are measured at 25°C and a frequency of 1 Hz. For details, these can be measured by the method described in the examples. The complex modulus of a CNT dispersion indicates its hardness. When the CNT fiber length is broken and shortened, the complex modulus tends to be smaller as the dispersibility of the CNTs improves and as the viscosity of the CNT dispersion decreases. However, when the CNT fiber length is large, even if the CNTs are uniformly and stably unraveled in the medium, the complex modulus may be high due to the structural viscosity of the CNTs themselves. Furthermore, the complex modulus changes not only due to the dispersion state of the CNTs, but also due to the entanglement of CNTs, dispersants, and other resin components, or the intermolecular forces between them. Therefore, it is not sufficient for the CNT dispersion to simply have low viscosity and good (apparent) dispersibility; it is particularly effective to judge the dispersion state by combining the complex modulus and phase angle with conventional indicators such as viscosity. From this perspective, as will be described later, it is effective to adjust the product of the complex modulus X (Pa) and the phase angle Y (°) (X × Y) to a specific range.

[0059] [Complex modulus of elasticity] The complex modulus of elasticity of the CNT dispersion of the present invention, as determined by dynamic viscoelasticity measurement, is preferably 10 Pa or more, more preferably 100 Pa or more, even more preferably 400 Pa or more, preferably 2,000 Pa or less, more preferably 1,000 Pa or less, and even more preferably 900 Pa or less. When the complex modulus of elasticity is within the above range, it becomes easy to obtain (X × Y) values ​​within a predetermined range described later, and a uniform and well-dispersed state can be obtained while maintaining the length of the CNTs. The complex modulus of the CNT dispersion can be measured by the method described in the examples of this specification.

[0060] [Phase angle] The phase angle refers to the phase shift of the stress wave when the strain applied to the CNT dispersion is considered a sine wave. For a purely elastic material, the stress wave is in phase with the applied strain, resulting in a phase angle of 0°. On the other hand, for a purely viscous material, the stress wave is 90° ahead. For typical viscoelasticity measurement samples, the phase angle is greater than 0° and less than 90°, resulting in a sine wave. If the CNT fiber length is broken and shortened, and the CNT dispersion is good, the phase angle approaches 90°, which is the case for a purely viscous material. However, similar to the complex modulus, if the CNTs themselves have structural viscosity in the CNT dispersion, the phase angle may be low even if the CNTs are uniformly and stably dissolved in the dispersion medium. Also, similar to the complex modulus, the phase angle changes not only due to the dispersion state of the CNTs, but also due to the entanglement of CNTs, dispersants, and other resin components, or the influence of their intermolecular forces.

[0061] The phase angle of the CNT dispersion of the present invention, as measured by dynamic viscoelasticity measurement, is preferably 1° or more, more preferably 3° or more, even more preferably 5° or more, particularly preferably 7° or more, preferably 30° or less, preferably 20° or less, more preferably 15° or less, and even more preferably 11° or less. When the phase angle is within the above range, it becomes easy to obtain (X×Y) values ​​within the desired range described later, and a uniform and well-dispersed state can be obtained while maintaining the length of the CNTs.

[0062] [Product of complex modulus of elasticity and phase angle] In the CNT dispersion of the present invention, the product (X × Y) of the complex modulus X (Pa) and the phase angle Y (°) is preferably 200 or more, more preferably 1,000 or more, even more preferably greater than 3,000, preferably 10,000 or less, more preferably 9,000 or less, and even more preferably 8,000 or less. If the above product is within the above range in the CNT dispersion, the CNT dispersion has high fluidity, and the conductivity of the molded article produced using the CNT dispersion can be further increased. Furthermore, it is preferable that the CNT dispersion satisfies the above-mentioned preferred range for the product of the complex modulus X (Pa) and the phase angle Y (°), and that the complex modulus and phase angle measured by dynamic viscoelasticity measurement each satisfy the above-mentioned preferred range.

[0063] (Method for producing CNT dispersion) The method for producing the CNT dispersion of the present invention described above may include, for example, a step of subjecting a mixed solution containing a plurality of CNTs, a non-aqueous solvent, and one or more dispersants to a dispersion treatment using a wet jet mill (dispersion step). The method for producing the CNT dispersion may also include steps other than the dispersion step described above (other steps).

[0064] Furthermore, according to the above-described method for producing a CNT dispersion, a CNT dispersion with excellent dispersibility and resistance to aggregation can be obtained.

[0065] <Dispersion process> In the dispersion process, a mixture containing multiple CNTs, a non-aqueous solvent, and one or more dispersants is subjected to dispersion treatment using a wet jet mill. The CNTs, non-aqueous solvent, and dispersants can be those described above in the "CNT dispersion" section of the present invention.

[0066] <<Wet Jet Mill>> Examples of wet jet mills that can be used for dispersion processing in the dispersion process include "NanoVeta®" (manufactured by Yoshida Machinery Industry Co., Ltd.), "BERYU SYSTEM PRO" (manufactured by Biryu Co., Ltd.), ultra-high pressure wet atomization device (manufactured by Yoshida Industry Co., Ltd.), "Nanomizer®" (manufactured by Nanomizer Co., Ltd.), and "Starburst®" (manufactured by Sugino Machine Co., Ltd.).

[0067] Examples of nozzles used in a wet jet mill include straight nozzles and cross nozzles. A straight nozzle has an I-shaped cross-section and relatively low processing energy. On the other hand, a cross nozzle has an X-shaped cross-section and higher processing energy than a straight nozzle. From the viewpoint of further improving the dispersibility of the CNT dispersion, it is preferable to use a straight nozzle as the nozzle used in a wet jet mill.

[0068] [pressure] Here, the pressure applied during the dispersion treatment of the mixed liquid by the wet jet mill is preferably 30 MPa or higher, more preferably 45 MPa or higher, even more preferably 60 MPa or higher, preferably 200 MPa or lower, more preferably 150 MPa or lower, and even more preferably 120 MPa or lower. If the pressure applied to the mixed liquid is above the lower limit, the dispersibility of the CNT dispersion can be improved, as well as the dilution stability and the time-dependent stability of the dispersion state of the CNT dispersion. Furthermore, if the pressure applied to the mixed liquid is below the upper limit, the cleavage of CNTs due to the dispersion treatment can be suppressed, thereby further enhancing the conductivity of the molded article obtained using the CNT dispersion.

[0069] [Number of passes] Furthermore, the number of passes in the dispersion process using a wet jet mill is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, even more preferably 20 or more, preferably 50 or less, more preferably 45 or less, and even more preferably 35 or less. If the number of passes in the dispersion process using a wet jet mill is equal to or greater than the above lower limit, the dispersibility of the CNT dispersion can be improved, as well as the conductivity of the molded article obtained using the CNT dispersion, the dilution stability of the CNT dispersion, and the time-dependent stability of the dispersion state can be improved. Furthermore, if the number of passes in the dispersion process using a wet jet mill is equal to or less than the above upper limit, the manufacturing efficiency of the CNT dispersion can be sufficiently ensured.

[0070] <Other processes> Other steps include a mixing step (a step in which multiple CNTs, a non-aqueous solvent, and one or more dispersants are mixed together to obtain a mixture) before the dispersion step described above. [Examples]

[0071] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing quantities refer to mass unless otherwise specified. In addition, in a polymer produced by copolymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is usually equal to the ratio of that certain monomer to the total monomers used in the polymerization of the polymer (starting ratio), unless otherwise specified. In the examples and comparative examples, various measurements and evaluations were performed using the following methods.

[0072] (Physical property measurement) <Storage modulus> The storage modulus of the CNT dispersions (CNT concentration: 0.4% by mass) prepared in the examples and comparative examples was measured using a dynamic viscoelasticity measuring apparatus (manufactured by Anton Paar, product name "MCR102", a cone plate with a diameter of 25 mm) under the conditions of a temperature of 20°C, a frequency of 1 Hz, and a strain of 0.01 to 1000%, and the storage modulus (Pa) at a strain of 100% was determined.

[0073] <Harmonic mean diameter> The CNT dispersions prepared in the examples and comparative examples were diluted with an NMP solvent so that the concentration of single-walled CNTs became 10 ppm by mass. The obtained diluted solution was measured using a Zetasizer Nano (manufactured by Malvern, product name "Nano ZS") under the conditions of a temperature of 25°C, a scanning number of 3 times, and a scanning time of 60 seconds, and the harmonic mean diameter (z-average diameter) was determined.

[0074] <Viscosity> Regarding the CNT dispersions prepared in the examples and comparative examples, the viscosity was measured at a temperature of 20°C using a rheometer (manufactured by Antonpaar, product name "MCR-102"). Specifically, a cone plate was used as a measurement jig, the range of a shear rate of 0.01 to 1000 (1 / s) was measured, and the viscosity (mPa·s) at a shear rate of 1 (1 / s) was determined.

[0075] <Complex elastic modulus and phase angle> The storage modulus of the CNT dispersions (CNT concentration: 0.4% by mass) prepared in the examples and comparative examples was measured using a dynamic viscoelasticity measuring apparatus (manufactured by Anton Paar, product name "MCR-Force 102", a cone plate with a diameter of 25 mm) under the conditions of a temperature of 20°C, a frequency of 1 Hz, and a strain of 0.01 to 1000%, and the complex elastic modulus X and the phase angle Y were determined. Furthermore, the product (X×Y) of the obtained complex elastic modulus X (Pa) and the phase angle Y (°) was calculated. For the complex elastic modulus X, the phase angle Y, and the product (X×Y) of X and Y, the minimum value to the maximum value were obtained over the range of the above strain rate, and each average value was used as a representative value.

[0076] <G / D ratio> Using a microscopic laser Raman spectrophotometer (manufactured by Thermo Fisher Scientific, product name "Nicolet Almega XR"), the Raman spectra of the CNTs used in the examples and comparative examples were measured. Then, regarding the obtained Raman spectra, the intensity of the G-band peak observed around 1590 cm -1 and the intensity of the D-band peak observed around 1340 cm -1 were determined, and the G / D ratio was calculated.

[0077] <Specific surface area> The BET specific surface area of the CNT was measured using Belsorp-mini (manufactured by Microtrac·BEL, conforming to ASTM D3037-81).

[0078] <Weight-average molecular weight of HNBR-1> The weight-average molecular weight (Mw) of HNBR-1 was measured by gel permeation chromatography (GPC) under the following measurement conditions using a 10 mM LiBr-dimethylformamide (DMF) solution. ·Separation column: Shodex KD-806M (manufactured by Showa Denko KK) ·Detector: Differential refractive index detector RID-10A (manufactured by Shimadzu Corporation) ·Flow rate of eluent: 0.3 mL / min ·Column temperature: 40 °C ·Standard polymer: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0079] (Evaluation) [[ID= 32]]<Aggregate> The CNT dispersions obtained in the examples and comparative examples were transferred to sample bottles and evaluated based on the following criteria when diluted four times with the solvents of each example and comparative example. A: No particles were visually confirmed. B: Particles were visually confirmed.

[0080] <Volume conductivity of the molded body> The volume conductivity (S / cm) of the carbon films (molded articles) prepared in the examples and comparative examples was measured using a low resistivity meter (Mitsubishi Chemical Analytec Co., Ltd., product name "Lorestar GX") in accordance with JIS K 7194 and evaluated according to the following criteria. The higher the value of this volume conductivity, the better the conductivity of the carbon film (molded article). A: Volume conductivity value exceeds 100 S / cm B: Volume conductivity value is between 50 S / cm and 100 S / cm. C: Volume conductivity value is less than 50 S / cm

[0081] <Dilution Stability> The CNT dispersions obtained in the examples and comparative examples were diluted 400-fold with NMP and evaluated after 10 days based on the following criteria. A: No aggregates or precipitates were observed. B: Suspension of aggregates is observed, but no layer of sediment is seen. C: The precipitate forms a layer, and the supernatant is clear.

[0082] <Viscosity change rate> The viscosity of the CNT dispersions obtained in the examples and comparative examples was measured immediately after preparation and 10 days after preparation. Each viscosity was measured at 20°C using a rheometer (Antonpaar, product name "MCR-102"). Specifically, a cone plate was used as the measuring fixture, and measurements were taken in the range of shear rates from 0.01 to 1000 (1 / s), and the viscosity (mPa·s) at a shear rate of 1 (1 / s) was determined. The viscosity immediately after preparation was set to η0 (mPa·s), and the viscosity 10 days after preparation was set to η1 (mPa·s). The viscosity change rate (%) was calculated using the formula: viscosity change rate (%) = [(η1-η0) / η0] × 100, and evaluated according to the following criteria. A smaller viscosity change rate indicates that the CNT dispersion is less likely to thicken over time, i.e., that it has excellent temporal stability of the dispersion state. A: Viscosity change rate is less than 20% B: Viscosity change rate is between 20% and 50% C: Viscosity change rate exceeds 50%

[0083] (Example 1) <Preparation of dispersant (HNBR-1)> In a reactor with an internal volume of 10 liters, 100 parts of deionized water, 35 parts of acrylonitrile and 65 parts of 1,3-butadiene were charged. 2 parts of potassium oleate were added as an emulsifier, 0.1 parts of potassium phosphate as a stabilizer, and 0.7 parts of tert-dodecyl mercaptan (TDM) as a molecular weight modifier. Emulsion polymerization was carried out at 30°C in the presence of 0.35 parts of potassium persulfate as a polymerization initiator, copolymerizing 1,3-butadiene and acrylonitrile. When the polymerization conversion rate reached 90%, polymerization was stopped by adding 0.2 parts of hydroxylamine sulfate per 100 parts of monomer. Subsequently, the mixture was heated and steam distilled under reduced pressure at approximately 70°C to recover the residual monomer. Then, 2 parts of alkylated phenol were added as an antioxidant to obtain an aqueous dispersion of the polymer. Next, 400 mL of the resulting aqueous dispersion of the polymer (total solids: 48 g) was placed in a 1-liter autoclave equipped with a stirrer, and dissolved oxygen was removed from the aqueous dispersion by flowing nitrogen gas through it for 10 minutes. Then, 50 mg of palladium acetate was dissolved in 180 mL of water to which 4 molar equivalents of nitric acid relative to the palladium was added as a hydrogenation catalyst. After purging the system twice with hydrogen gas, the contents of the autoclave were heated to 50°C under pressure of 3 MPa (gauge pressure) with hydrogen gas, and the hydrogenation reaction was carried out for 6 hours. Subsequently, the contents were allowed to return to room temperature, the system was subjected to a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration reached 40% to obtain an aqueous dispersion of hydrogenated nitrile rubber (HNBR-1). 100 parts of this aqueous dispersion were mixed with 200 parts of NMP. Under reduced pressure, all water and residual monomers were evaporated, and then the NMP was evaporated to obtain an NMP solution of HNBR-1 (solid content concentration: 8%). The weight-average molecular weight of the obtained HNBR-1 was measured to be 130,000.

[0084] <Preparation of the mixed solution> The obtained NMP solution was diluted with NMP to produce PVDF (Solef 5130, manufactured by Solvay, weight-average molecular weight 1,100,000) and single-walled carbon nanotubes (SWCNTs) such as SG101 (manufactured by Zeon Corporation, product name "ZEONANO(registered trademark) SG101", G / D ratio: 4.8, specific surface area 1350 m²). 2 Add ( / g) and adjust to NMP:SG101:PVDF:HNBR = 97.3wt%:0.4wt%:2.0wt%:0.3wt% to obtain a mixed solution.

[0085] <Dispersion process> This mixture was stirred (3000 rpm, 60 minutes) using a homodisperser (Labo-Solution Primix), and then dispersed using a wet jet mill (Yoshida Machinery Industry Co., Ltd., model number "NVL-ES008A-D10", product name "NanoVeta®") at a pressure of 100 MPa and with 5 passes. Specifically, CNTs were dispersed by applying back pressure and shear force to the mixture to obtain a CNT dispersion. The obtained CNT dispersion was subjected to various measurements and evaluations using the method described above. The results are shown in Table 1.

[0086] <Fabrication of carbon film (molded body)> The CNT dispersion prepared as described above was filtered under 0.09 MPa using a vacuum filtration apparatus equipped with a membrane filter. After filtration, the carbon film formed on the membrane filter was washed by passing isopropyl alcohol and water, respectively, through the vacuum filtration apparatus, and then air was passed through for 15 minutes. Next, the carbon film / membrane filter was immersed in ethanol, and the carbon film was peeled off the membrane filter to obtain a molded carbon film. The obtained carbon film was of the same size as the membrane filter, had excellent film-forming properties, and maintained its film state even after peeling from the filter, exhibiting excellent self-supporting properties. The volume conductivity of this carbon film was measured using the method described above. The results are shown in Table 1.

[0087] (Examples 2-32 and Comparative Examples 1-14) Except for changing the type and amount of dispersant, the type of CNT, and the dispersion conditions as shown in Tables 1 to 4, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 1 to 4.

[0088] The properties of PVDF and CNT shown in Tables 1-4 are as follows. PVDF (Solef 6020): Manufactured by Solvay, weight-average molecular weight 685,000 PVDF (Solef6008): Manufactured by Solvay, weight-average molecular weight 255,000 CNT (Tuball): Single-walled carbon nanotube, manufactured by OCSiAl, product name "Tuball", G / D ratio: 113, specific surface area 940 m² 2 / g CNT (CNT-1): A mixture of single-layer and multi-layer carbon nanotubes, G / D ratio: 1.4, specific surface area 854 m² 2 / g The above CNT-1 was manufactured according to the method disclosed in Example 4 of International Publication No. 2022 / 114237.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] Tables 1-3 show a CNT dispersion containing multiple CNTs, including single-walled carbon nanotubes (WYNTs), a non-aqueous solvent, and a dispersant containing hydrogenated nitrile rubber, wherein the specific surface area of ​​the CNTs is 800 m². 2 The CNT dispersions of Examples 1-32, which have a concentration of 1 / g or more and a harmonic mean diameter of 1000 nm to 10000 nm, exhibit excellent dispersibility and show no aggregates. On the other hand, Table 4 shows that the CNT dispersions of Comparative Examples 1-13, where the harmonic mean diameter of the CNTs exceeds 10,000 nm, and Comparative Example 14, where the harmonic mean diameter of the CNTs is less than 1,000 nm, exhibit poor dispersibility. [Industrial applicability]

[0094] According to the present invention, a CNT dispersion liquid with excellent dispersibility and low aggregation can be provided.< / cnt>

Claims

1. A carbon nanotube dispersion comprising multiple carbon nanotubes, a non-aqueous solvent, and one or more dispersants, The aforementioned plurality of carbon nanotubes include single-walled carbon nanotubes. The specific surface area of ​​the aforementioned multiple carbon nanotubes is 800 m². ２ / g or more, The harmonic mean diameter of the plurality of carbon nanotubes is between 1,000 nm and 10,000 nm. The aforementioned one or more dispersants include hydrogenated nitrile rubber. Carbon nanotube dispersion.

2. A carbon nanotube dispersion according to claim 1, wherein the storage modulus at 100% strain is 1.5 Pa or more.

3. A carbon nanotube dispersion according to claim 1, wherein the one or more dispersants further comprises polyvinylidene fluoride.

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