Method for manufacturing carbon material dispersion liquid

Abstract

Provided is a method for producing a carbon material dispersion liquid that can simply produce a dispersion liquid with excellent viscosity stability in which a carbon material containing carbon nanotubes is well dispersed and substantially no coarse aggregates are generated. A method for producing a carbon material dispersion liquid includes the following steps: Step (1), stirring a raw material containing a carbon material containing carbon nanotubes, a dispersant, and a liquid medium to obtain a wet mixture; and Step (2), using a high-pressure homogenizer to perform a dispersion treatment on the wet mixture. The high-pressure homogenizer is at least any one of a high-pressure homogenizer (A1) in which the pressurized and ejected wet mixtures collide with each other to be finely granulated, and a high-pressure homogenizer (A2) in which the pressurized wet mixture is introduced into a collision chamber to be finely granulated, and a two-stage dispersion treatment in which the inner diameter of the discharge nozzle and the treatment pressure are changed is carried out.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a carbon material dispersion, a carbon material dispersion, and an article. Background Art

[0002] Carbon materials (nanocarbon materials) such as carbon black, carbon fiber, carbon nanotube, graphite, and graphene have a six-membered ring graphite structure formed by covalent bonds of carbon atoms, and are materials that exhibit various properties such as electrical conductivity and heat conductivity. Methods for making their properties function in various fields are being studied. For example, paying attention to the electrical properties, thermal properties, and properties as fillers of carbon materials, applications to antistatic agents, conductive materials, plastic reinforcing materials, semiconductors, fuel cell electrodes, and cathode wires of transducers are being studied.

[0003] Among these applications, a carbon material dispersion in which the carbon material has good dispersibility and maintains the dispersibility for a long time is necessary. However, the surface energy of nanosized carbon materials is high, and strong van der Waals forces are exhibited, so they tend to aggregate. Therefore, even when dispersed in a liquid medium, direct aggregation often occurs.

[0004] As a method for manufacturing a dispersion in which carbon materials are stably dispersed in a liquid medium, the following method has been proposed: in the presence of a dispersant such as a surfactant or a polymer dispersant, using a bead mill, an ultrasonic disperser, a high-speed mixer, etc., to mix and disperse each component (Patent Documents 1 and 2).

[0005] In addition, a scheme has been proposed to change the pressure conditions for each dispersion treatment and disperse carbon nanotubes under different pressure conditions (Patent Document 3).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-174084

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-537570

[0010] Patent Document 3: Japanese Patent No. 6652049 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, in the case of simply dispersing carbon materials such as carbon nanotubes in the presence of a dispersant, it can be said that the dispersibility of the obtained dispersion is not necessarily sufficient, and sometimes the viscosity increases or coarse aggregates are formed over time.

[0013] It should be noted that Patent Document 3 discloses that by performing multiple dispersions under different pressure conditions, it is possible to suppress damage while effectively and highly dispersing carbon nanotubes. However, the dispersibility of the carbon nanotubes in the dispersion liquid was only evaluated visually, and regarding the physical properties, only the conductivity was measured. Therefore, it is not necessarily possible to fully evaluate the dispersibility of the carbon nanotubes in the obtained dispersion liquid.

[0014] The present invention has been made in view of the problems of such prior art, and its object is to provide: a method for manufacturing a carbon material dispersion liquid that can easily manufacture a dispersion liquid having excellent viscosity stability in which a carbon material containing carbon nanotubes is well dispersed and substantially no coarse aggregates are generated. Another object of the present invention is to provide a carbon material dispersion liquid that is manufactured by this manufacturing method, in which a carbon material containing carbon nanotubes is well dispersed and substantially no coarse aggregates are generated, and has excellent viscosity stability, and an article using the same.

[0015] Means for Solving the Problems

[0016] That is, according to the present invention, there is provided a method for manufacturing a carbon material dispersion liquid as shown below.

[0017] [1] A method for manufacturing a carbon material dispersion liquid, comprising the following steps: Step (1), stirring a raw material containing a carbon material containing carbon nanotubes, a dispersant, and a liquid medium to obtain a wet mixture; and Step (2), using a high-pressure homogenizer, dispersing the wet mixture, wherein the high-pressure homogenizer is at least any one of a high-pressure homogenizer (A1) in which the wet mixture subjected to pressure injection collides with each other to be granulated into fine particles, and a high-pressure homogenizer (A2) in which the wet mixture subjected to pressure is introduced into a collision chamber to be granulated into fine particles, and dispersing the wet mixture in such a manner as to satisfy the following dispersion conditions.

[0018] [Dispersion Conditions]

[0019] After performing the following first treatment X times, perform the following second treatment Y times,

[0020] The first treatment is as follows: using any one of the high-pressure homogenizer (A1) and the high-pressure homogenizer (A2), granulating the wet mixture by applying a treatment pressure of 1 to 100 MPa, and discharging from a discharge nozzle having a nozzle inner diameter D1,

[0021] The second treatment is as follows: using any one of the high-pressure homogenizer (A1) and the high-pressure homogenizer (A2), granulating the wet mixture by applying a treatment pressure of 120 to 250 MPa, and discharging from a discharge nozzle having a nozzle inner diameter D2 (where D1 > D2, X ≥ 2, 2 ≤ Y ≤ 30).

[0022] [2] The method for manufacturing the carbon material dispersion liquid according to [1] above, wherein the inner diameter D1 of the nozzle is 0.15 to 2.0 mm, and the inner diameter D2 of the nozzle is 0.1 to 1.0 mm.

[0023] [3] The method for manufacturing the carbon material dispersion liquid according to [1] or [2] above, wherein the liquid medium is water or a mixed solvent of water and a water-soluble organic solvent, the dispersant is a cellulose derivative or a polymer dispersant, the viscosity of a 1 mass% aqueous solution of the cellulose derivative is 20 to 500 mPa·s and the degree of etherification is 0.5 to 0.9, and the polymer dispersant is a polymer comprising: structural unit (1) derived from at least one monomer 1 selected from the group consisting of 2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, and their quaternary ammonium salts: 5 to 40 mass%; structural unit (2) derived from monomer 2 represented by the following general formula (1): 50 to 80 mass%; and structural unit (3) derived from monomer 3 copolymerizable with the aforementioned monomer 1 and monomer 2: 0.5 to 40 mass%, monomer 3 includes α-methylstyrene and (meth)acrylic acid, the content of the structural unit derived from the aforementioned α-methylstyrene is 0.5 to 5 mass%, the content of the structural unit derived from the aforementioned (meth)acrylic acid is 0.5 to 30 mass%, and the number average molecular weight of the polymer is 5000 to 20000.

[0024]

[0025] (In the aforementioned general formula (1), R1 represents a hydrogen atom or a methyl group, A represents O or NH, X represents an ethylene group or a propylene group, Y represents O, NHCOO, or NHCONH, R2 independently represents a hydrogen atom or a methyl group, n represents the average number of repeating units of 20 to 100, and R3 represents a hydrogen atom or a methyl group. Among them, the number of repeating units n where R2 is a hydrogen atom H is more than 1 / 2 of the total number of repeating units n T of the whole)

[0026] [4] The method for manufacturing the carbon material dispersion liquid according to [1] or [2] above, wherein the liquid medium is a water-soluble organic solvent substantially free of water, and the dispersant is a polymer comprising: structural unit (A) derived from monomer A represented by the following general formula (A): 3 to 55 mass%; structural unit (B) derived from monomer B represented by the following general formula (B): 30 mass% or less; structural unit (C) derived from monomer C represented by the following general formula (C): 45 to 90 mass%; and structural unit (D) derived from monomer D copolymerizable with these monomers: 0.5 to 20 mass%, and the amine value of the polymer is 100 mgKOH / g or less and the number average molecular weight is 5000 to 20000.

[0027]

[0028] (In the aforementioned general formula (A), R represents a hydrogen atom or a methyl group, A represents O or NH, B represents an ethylene group or a propylene group, R1 and R2 independently of each other represent a methyl group or an ethyl group, Ar represents a phenyl group, a naphthyl group, an anthracenyl group, or a pyrenyl group, and X represents a chlorine atom, a bromine atom, bis(trifluoromethyl)sulfonimide, or bis(nonafluorobutanesulfonyl)imide)

[0029]

[0030] (In the aforementioned general formula (B), R represents a hydrogen atom or a methyl group, A represents O or NH, B represents an ethylene group or a propylene group, and R1 and R2 independently of each other represent a methyl group or an ethyl group)

[0031]

[0032] (In the aforementioned general formula (C), R represents a hydrogen atom or a methyl group, A represents O or NH, Q represents an ethylene group or a methylethylene group, Y represents O, NHCOO, or NHCONH, m and n independently of each other represent an average number of repeating units of 0 or more, and m + n = 20 to 100, and R3 represents an alkyl group, an aryl group, or an alkylaryl group having 1 to 18 carbon atoms)

[0033] [5] According to the method for producing a carbon material dispersion liquid described in any one of the foregoing [1] to [4], wherein, in the aforementioned raw materials, the content of the aforementioned dispersant is 10 to 500 parts by mass with respect to 100 parts by mass of the aforementioned carbon material; in the aforementioned raw materials, the content of the aforementioned carbon material is 10% by mass or less; and in the aforementioned raw materials, the content of the aforementioned dispersant is 30% by mass or less.

[0034] In addition, according to the present invention, there is provided a carbon material dispersion liquid as shown below.

[0035] [6] A carbon material dispersion liquid produced by the production method described in any one of the foregoing [1] to [5].[[]END]]

[0036] [7] According to the carbon material dispersion liquid described in the foregoing [6], wherein, for any wavelength W within the range of 350 to 550 nm L and any wavelength W within the range of 650 to 850 nm H of the central value wavelength W M such that the absorbance becomes 1.2 to 2.2, the absorbance A L of the dilute dispersion liquid obtained by diluting with a blank liquid having the same composition as the aforementioned carbon material dispersion liquid except for not containing the aforementioned carbon material with respect to the aforementioned wavelength W L with respect to the aforementioned wavelength WH Absorbance A H The ratio (A L / A H ) is 1.40 or more.

[0037] Furthermore, according to the present invention, there is provided an article as shown below.

[0038] [8] Any article of a coating, ink, coating agent, resin molding material, conductive material, heat conductive material, and antistatic material, which contains the carbon material dispersion liquid described in the foregoing [6] or [7].

[0039] [9] An article of any one of a battery material and a mechanical component, which has a coating film formed from the carbon material dispersion liquid described in the foregoing [6] or [7].

[0040] Effects of the Invention

[0041] According to the present invention, it is possible to provide a method for manufacturing a carbon material dispersion liquid that can easily manufacture a dispersion liquid with excellent viscosity stability in which a carbon material containing carbon nanotubes is well dispersed and substantially no coarse aggregates are generated. In addition, according to the present invention, it is possible to provide a carbon material dispersion liquid that is manufactured by this manufacturing method, in which a carbon material containing carbon nanotubes is well dispersed and substantially no coarse aggregates are generated, and an article using the same. Detailed Embodiments

[0042] <Manufacturing Method of Carbon Material Dispersion Liquid>

[0043] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The manufacturing method of the carbon material dispersion liquid of the present invention (hereinafter, also simply referred to as the “(present invention's) manufacturing method”) includes the following steps: Step (1), stirring a raw material containing a carbon material containing carbon nanotubes, a dispersant, and a liquid medium to obtain a wet mixture; and Step (2), using a high-pressure homogenizer to perform a dispersion treatment on the wet mixture. The high-pressure homogenizer used in Step (2) is at least any one of a high-pressure homogenizer (A1) in which the wet mixture that has been pressurized and sprayed collides with each other to be granulated, and a high-pressure homogenizer (A2) in which the pressurized wet mixture is introduced into a collision chamber to be granulated. Moreover, in Step (2), the wet mixture is subjected to a dispersion treatment in a manner that satisfies the following dispersion conditions to prepare a carbon material dispersion liquid. Hereinafter, the details of the manufacturing method of the carbon material dispersion liquid of the present invention will be described. Hereinafter, the carbon material dispersion liquid will also be simply referred to as “dispersion liquid”.

[0044] [Dispersion Conditions]

[0045] After performing the first treatment as described below X times, perform the second treatment as described below Y times.

[0046] The first treatment is as follows: Using either the high-pressure homogenizer (A1) or the high-pressure homogenizer (A2), apply a treatment pressure of 1 to 100 MPa to the wet mixture to make it into fine particles, and discharge it from a discharge nozzle with a nozzle inner diameter D1.

[0047] The second treatment is as follows: Using either the high-pressure homogenizer (A1) or the high-pressure homogenizer (A2), apply a treatment pressure of 120 to 250 MPa to the wet mixture to make it into fine particles, and discharge it from a discharge nozzle with a nozzle inner diameter D2 (where D1 > D2, X ≥ 2, 2 ≤ Y ≤ 30).

[0048] (Process (1))

[0049] Process (1) is a process for obtaining a wet mixture. The wet mixture is obtained by subjecting a raw material containing a carbon material containing carbon nanotubes, a dispersant, and a liquid medium to a stirring treatment. The wet mixture can also be prepared using relatively mild stirring devices such as a magnetic stirrer, a dissolver, and a homogenizer, for example.

[0050] [Carbon material]

[0051] The carbon material contains carbon nanotubes. As the carbon nanotubes, multi-walled carbon nanotubes with multiple layers and single-walled carbon nanotubes with a single layer can be used. There are no particular limitations on the diameter, length, shape, and manufacturing method, etc., and any carbon nanotubes can be used. The carbon nanotubes can be doped with metals and metal salts such as platinum and palladium. In addition, the carbon nanotubes can be surface-modified by oxidation treatment, plasma treatment, radiation treatment, corona treatment, and coupling treatment, etc.

[0052] As carbon materials other than carbon nanotubes, carbon black, carbon fiber, graphite, and graphene, etc. can be used. As the carbon black, acetylene black, furnace black, thermal cracking carbon black, Ketjen black, etc. can be cited. There are no particular limitations on physical property values such as the structure, oil absorption amount, and specific surface area of the carbon black, and the presence or absence of surface modification such as oxidation, and conventionally known carbon black can be used.

[0053] As the carbon fiber, PAN-based carbon fiber using polyacrylonitrile as a raw material, pitch-based carbon fiber using pitch-based materials as a raw material, and their recycled products, etc. can be cited. Among them, carbon nanofibers with a fiber diameter in the nanometer size and a shape in which a six-membered ring graphite structure is rolled into a tube shape are preferred. There are no particular limitations on the particle size, fiber diameter, fiber length, shape, and manufacturing method, etc. of the carbon materials other than carbon nanotubes. The carbon materials can be doped with metals and metal salts such as platinum and palladium. The carbon materials can be surface-modified by performing oxidation treatment, plasma treatment, radiation treatment, corona treatment, and coupling treatment, etc.

[0054] [Dispersant]

[0055] A dispersant is a component used to disperse carbon materials in a liquid medium. As the dispersant, anionic, cationic, nonionic, and amphoteric surfactants; polymeric dispersants can be used. Among them, it is preferable to use a polymer (resin) as the dispersant. When the liquid medium is an aqueous medium containing water, the dispersant is preferably a cellulose derivative or a polymeric dispersant.

[0056] Examples of the cellulose derivative used as the dispersant when the liquid medium is water or a mixed solvent of water and a water-soluble organic solvent (aqueous medium) include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and their metal salts. Among them, carboxymethyl cellulose and sodium carboxymethyl cellulose are preferable. Further, the cellulose derivative preferably has a viscosity of 20 to 500 mPa·s for a 1 mass% aqueous solution and an etherification degree of 0.5 to 0.9. By using such a cellulose derivative, carbon nanotubes can be dispersed better and the storage stability can be improved.

[0057] When the liquid medium is an aqueous medium containing water, the polymeric dispersant used as the dispersant is preferably a polymer comprising: a structural unit (1) of 5 to 40 mass% derived from at least one monomer 1 selected from the group consisting of 2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, and their quaternary ammonium salts; a structural unit (2) of 50 to 80 mass% derived from monomer 2 represented by the following general formula (1); and a structural unit (3) of 0.5 to 40 mass% derived from monomer 3 copolymerizable with monomer 1 and monomer 2, and the number-average molecular weight of the polymer is 5000 to 20000.

[0058]

[0059] (In the foregoing general formula (1), R1 represents a hydrogen atom or a methyl group, A represents O or NH, X represents an ethylene group or a propylene group, Y represents O, NHCOO, or NHCONH, R2 independently represents a hydrogen atom or a methyl group, n represents an average repeating unit number of 20 to 100, and R3 represents a hydrogen atom or a methyl group. Among them, the number of repeating units n where R2 is a hydrogen atom H is more than 1 / 2 of the total number of repeating units n T .)

[0060] As common basic monomers, there are also dimethylaminoethyl (meth)acrylate and the like. However, by using any one of 2-vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole, the dispersion stability of the carbon material dispersion can be further improved, and the viscosity of the carbon material dispersion can be reduced. 2-Vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole are all monomers having an aromatic ring, and this aromatic ring has a structure similar to the 6-membered ring structure of the carbon material. Therefore, it is considered that by adopting the structural unit (1) derived from these monomers, the adsorption force to the carbon material based on van der Waals force and π-π stacking can be increased. Furthermore, there are cases where the surface of the carbon material is oxidized and carboxyl groups and phenolic hydroxyl groups are present. It is considered that by ionically bonding the carboxyl groups and phenolic hydroxyl groups to the basic groups in the structural unit (1), the polymer dispersant is more easily adsorbed by the carbon material, and the dispersibility is further improved. It should be noted that monomer 1 is particularly preferably 4-vinylpyridine.

[0061] As monomer 1, by using the quaternary ammonium salts of 2-vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole, the dispersibility can be further improved. By quaternizing the structural units derived from 2-vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole, the structural unit (1) derived from the quaternary ammonium salt can be prepared. As the material for quaternization (quaternizing agent), for example, halides and sulfates can be used. As halides, chloromethane, benzyl chloride, etc. can be cited. As sulfates, dimethyl sulfate, diethyl sulfate, etc. can be cited. As the quaternary ammonium salt, an arylmethyl halide is preferred. As the arylmethyl, benzyl, naphthylmethyl, anthrylmethyl, pyrenylmethyl, etc. can be cited. Among them, naphthylmethyl is preferred.

[0062] Monomer 2 is a macromonomer having a polyalkylene glycol chain represented by the following general formula (1). By introducing the structural unit (2) derived from monomer 2, a polymer having a structure in which a polyalkylene glycol chain is grafted can be prepared. The polyalkylene glycol chain is soluble in water as a liquid dispersion medium. Then, the structural unit (1) adsorbed on the carbon material is repelled due to the steric hindrance between particles by the dissolution of the polyalkylene glycol chain, so that the carbon material can be stably dispersed in a good state in the liquid dispersion medium for a long time.

[0063]

[0064] (In the above general formula (1), R1 represents a hydrogen atom or a methyl group, A represents O or NH, X represents an ethylene group or a propylene group, Y represents O, NHCOO, or NHCONH, R2 independently represents a hydrogen atom or a methyl group, n represents an average repeating unit number of 20 to 100, and R3 represents a hydrogen atom or a methyl group. Among them, the number of repeating units n in which R2 is a hydrogen atom H is the total number of repeating units n Tmore than 1 / 2 thereof

[0065] The molecular weight of monomer 2 represented by the general formula (1) is about 880 to 5800. In the general formula (1), the number of repeating units n in which R2 is a hydrogen atom H is the total number of repeating units n T is more than 1 / 2 thereof, whereby the polyalkylene glycol chain can be made water-soluble. Among them, the number of repeating units n in which R2 is a hydrogen atom H is preferably more than 3 / 5 of the total number of repeating units n T of the total number of repeating units n

[0066] Monomer 3 is a monomer that can copolymerize with monomer 1 and monomer 2. As monomer 3, (meth)acrylic acid-based monomers are preferably used. Specific examples of monomer 3 include (meth)acrylic acid; monofunctional (meth)acrylates having substituents such as methyl, ethyl, propyl, butyl, pentyl, 2-ethylhexyl, isooctyl, nonyl, dodecyl, hexadecyl, octadecyl, isostearyl, behenyl, cyclohexyl, trimethylcyclohexyl, tert-butylcyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, isobornyl, dicyclopentyl, dicyclopentenyl, dicyclopentenoxyethyl, 2-hydroxyethyl, 2-hydroxypropyl, 4-hydroxybutyl, etc.; poly(n≥2)alkylene (carbon number 2 to 4) glycol mono(meth)acrylate, poly(n≥2)alkylene (carbon number 2 to 4) glycol monoalkyl (carbon number 1 to 22) mono(meth)acrylate, poly(n≥2)hydroxyalkanoic acid (carbon number 5 to 18) mono(meth)acrylate, etc. as polymer-type (meth)acrylates of macromonomers. In addition, vinyl monomers such as styrene, vinyltoluene, vinylnaphthalene, vinylcaprolactone, α-methylstyrene, and vinyl acetate can also be used as monomer 3

[0067] By using α-methylstyrene as monomer 3, the molecular weight can be easily controlled, so it is preferred. Specifically, monomer 3 contains α-methylstyrene. In the polymer, the content of the structural unit derived from α-methylstyrene is preferably 0.5 to 5% by mass, more preferably 1 to 3% by mass. When the content of the structural unit derived from α-methylstyrene is less than 0.5% by mass, polymerization may proceed slightly unevenly, and there may be a case where monomer 2 remains or gelation occurs. On the other hand, when the content of the structural unit derived from α-methylstyrene is greater than 5% by mass, there may be a case where α-methylstyrene with slightly poor polymerizability remains, or the molecular weight is overly controlled and the polymerization rate is slightly reduced

[0068] In addition, as the monomer 3, (meth)acrylic acid is preferably used. By including a structural unit derived from (meth)acrylic acid as an acid component, the water solubility of the polymer is improved. When a quaternary ammonium salt group is also present in the polymer, the polymer exhibits amphoteric ionicity, so it can be easily adsorbed ionically onto the carbon material, further improving the dispersibility. In addition, by exhibiting amphoteric ionicity, the polymer forms ionic bonds intramolecularly / intermolecularly and easily forms a crosslinked structure, which can further inhibit detachment from the carbon material.

[0069] In the polymer, the content of the structural unit derived from (meth)acrylic acid is preferably 0.5 to 30% by mass, more preferably 1 to 10% by mass. When the content of the structural unit derived from (meth)acrylic acid is less than 0.5% by mass, there is a tendency that the effect as an acid component is insufficient. On the other hand, when the content of the structural unit derived from (meth)acrylic acid is greater than 30% by mass, the water solubility becomes too high and the water resistance of the formed coating film, etc., is slightly reduced.

[0070] In the polymer dispersant (polymer), the content of the structural unit (1) is 5 to 40% by mass, preferably 10 to 20% by mass, the content of the structural unit (2) is 50 to 80% by mass, preferably 55 to 75% by mass, and the content of the structural unit (3) is 0.5 to 40% by mass, preferably 1 to 31% by mass. It should be noted that the total of the structural unit (1), the structural unit (2), and the structural unit (3) is set to 100% by mass.

[0071] When the content of the structural unit (1) is less than 5% by mass, it cannot be sufficiently adsorbed onto the carbon material. On the other hand, when the content of the structural unit (1) is greater than 40% by mass, there is a case of coloring or generating an odor, and there is a case of being easily adsorbed onto the carbon material together or acting as a flocculant.

[0072] Among the structural units contained in the polymer, the proportion of the structural unit (2) is the largest. Therefore, the polyalkylene glycol chains densely present in the polymer become steric hindrances, which can inhibit the approach between the dispersed carbon materials and stably disperse them. When the content of the structural unit (2) is less than 50% by mass, there is a case where the steric hindrance is insufficient and it is difficult to dissolve in water. On the other hand, when the content of the structural unit (2) is greater than 80% by mass, the monomer 2 with slightly lower reactivity does not polymerize and is likely to remain. It should be noted that when the content of the structural unit (3) is greater than 40% by mass, the proportion of other structural units will relatively decrease, so the function as a dispersant will be reduced.

[0073] The number average molecular weight of the polymer used as the polymer dispersant is 5,000 to 20,000, preferably 10,000 to 15,000. When the number average molecular weight of the polymer is less than 5,000, the amount of the structural unit (2) derived from monomer 2 as a macromonomer decreases, so the dispersion stability becomes insufficient. On the other hand, when the number average molecular weight of the polymer is greater than 20,000, the viscosity of the obtained carbon material dispersion may become too high, and the amount of the necessary polymer dispersant may become too large. In this specification, the number average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography.

[0074] The above polymer that can be used as a polymer dispersant can be produced by a conventionally well-known radical polymerization method or a living radical polymerization method. Among them, production by a living radical polymerization method is preferred because it can control the molecular weight of the main chain and can produce an AB block copolymer according to the monomer addition method.

[0075] As the living radical polymerization method, there are a polymerization method using a chain transfer agent such as a thiol to adjust the molecular weight, an atom transfer radical polymerization method (ATRP method), a reversible addition-fragmentation chain transfer polymerization method (RAFT method), a nitroxide method (NMP method), an organotellurium method (TERP method), an iodine transfer polymerization method (ITP method), a reversible transfer catalyst polymerization method (RTCP method), a reversible catalyst medium polymerization method (RCMP method), etc.

[0076] There are no particular limitations on the polymerization conditions, etc. An azo-based radical generator, a peroxide-based radical generator, a photosensitizer, etc. can be added to the reaction system. The polymerization form can be solvent-free, solution polymerization, emulsion polymerization, etc. Among them, solution polymerization is preferred, and further preferably solution polymerization is carried out in the above-mentioned water-soluble organic solvent that can be miscible with the carbon material dispersion. By carrying out solution polymerization in a water-soluble organic solvent, the obtained polymer solution can be directly mixed with the carbon material dispersion.

[0077] By polymerizing monomer 1, monomer 2, and monomer 3 by solution polymerization or the like, a desired polymer can be obtained. In addition, after polymerizing monomer 1, monomer 2, and monomer 3, a halogenated alkyl such as chlorobenzyl methane, chloromethyl naphthalene, chloromethyl anthracene, chloromethyl pyrene, chloromethyl naphthalene, etc. can be added to the reaction system to quaternize the amino group derived from monomer 1. Furthermore, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(heptafluorobutylsulfonyl)imide, etc. can be added to carry out ion exchange on the quaternary ammonium salt to form a sulfonylimide salt. The dispersant used in the present invention can be used without particular limitation within the range that can stably disperse carbon nanotubes. The dispersant can mainly use surfactants classified into anionic, cationic, nonionic, and amphoteric types, and polymer-type dispersants.

[0078] On the other hand, when the liquid medium is a water-soluble organic solvent substantially free of water, the dispersant is preferably a polymer dispersant. Moreover, the dispersant is preferably a polymer comprising 3 to 55% by mass of a structural unit (A) derived from a monomer A represented by the following general formula (A), 45 to 90% by mass of a structural unit (C) derived from a monomer C represented by the following general formula (C), and 0.5 to 20% by mass of a structural unit (D) derived from a monomer D copolymerizable with these monomers.

[0079]

[0080] (In the above general formula (A), R represents a hydrogen atom or a methyl group, A represents O or NH, B represents an ethylene group or a propylene group, R1 and R2 independently represent a methyl group or an ethyl group, Ar represents a phenyl group, a naphthyl group, an anthracenyl group, or a pyrenyl group, and X represents a chlorine atom, a bromine atom, bis(trifluoromethyl)sulfonylimide, or bis(nonafluorobutanesulfonyl)imide)

[0081]

[0082] (In the above general formula (C), R represents a hydrogen atom or a methyl group, A represents O or NH, Q represents an ethylene group or a methylethylene group, Y represents O, NHCOO, or NHCONH, m and n independently represent an average repeating unit number of 0 or more and m + n = 20 to 100, and R3 represents an alkyl group, an aryl group, or an alkylaryl group having 1 to 18 carbon atoms)

[0083] The structural unit (A) is a structural unit having a quaternary ammonium salt group derived from the monomer A. It is considered that the quaternary ammonium salt group in the structural unit (A) adsorbs to the carbon material, thereby contributing to the improvement of the dispersibility of the carbon material in the liquid medium containing the organic solvent. It is also considered that one of the substituents bonded to the nitrogen atom of the quaternary ammonium salt group is an arylmethyl group (-CH2-Ar). The aromatic ring of the arylmethyl group is affinity with the carbon material, and the dispersibility of the carbon material is improved. If the carbon numbers of R1 and R2 in the general formula (A) are too large, the arylmethyl group will be destabilized due to steric hindrance and it will be difficult to form a quaternary ammonium salt group. Therefore, R1 and R2 in the general formula (A) must independently be a methyl group or an ethyl group.

[0084] Since the quaternary ammonium salt group is an ionic functional group, it is expected that a polymer (polymer dispersant) having the structural unit (A) with the quaternary ammonium salt group will exhibit conductivity through water adsorption and ion conduction. That is, by using a polymer having the structural unit (A) as a polymer dispersant, it is expected to prepare a carbon material dispersion liquid capable of forming a coating film in which the reduction of conductivity is suppressed.

[0085] The monomer A is preferably a monomer represented by the following general formula (A-1).

[0086]

[0087] (In the above general formula (A-1), R1 and R2 independently represent methyl or ethyl, Ar represents phenyl, naphthyl, anthryl, or pyrenyl, and X represents a chlorine atom, a bromine atom, bis(trifluoromethyl)sulfonylimide, or bis(nonafluorobutanesulfonyl)imide)

[0088] Examples of the monomer represented by the general formula (A-1) include dimethylnaphthylmethyl ethylammonium chloride methacrylate, dimethylnaphthylmethyl ethylammonium bromide methacrylate, dimethylnaphthylmethyl ethylammonium bis(trifluoromethyl)sulfonylimide methacrylate, dimethylnaphthylmethyl ethylammonium bis(nonafluorobutanesulfonyl)imide methacrylate, diethylnaphthylmethyl ethylammonium chloride methacrylate, diethylnaphthylmethyl ethylammonium bromide methacrylate, diethylnaphthylmethyl ethylammonium bis(trifluoromethyl)sulfonylimide methacrylate, diethylnaphthylmethyl ethylammonium bis(nonafluorobutanesulfonyl)imide methacrylate, anthrylmethyldimethyl ethylammonium chloride methacrylate, anthrylmethyldimethyl ethylammonium bromide methacrylate, anthryldimethyl ethylammonium bis(trifluoromethyl)sulfonylimide methacrylate, anthryldimethyl naphthyl ethylammonium bis(nonafluorobutanesulfonyl)imide methacrylate, diethylpyrenylmethyl ethylammonium chloride methacrylate, diethylpyrenylmethyl ethylammonium bromide methacrylate, diethylpyrenylmethyl ethylammonium bis(trifluoromethyl)sulfonylimide methacrylate, and diethylpyrenylmethyl ethylammonium bis(nonafluorobutanesulfonyl)imide methacrylate, etc.

[0089] The polymer dispersant is preferably a polymer further having a structural unit (B) derived from a monomer B represented by the following general formula (B). By using a polymer further having the structural unit (B) as the polymer dispersant, the dispersibility of the carbon material can be further improved. It should be noted that by quaternizing the amino group in the structural unit (B), a quaternary ammonium salt group in the structural unit (A) can be formed.

[0090]

[0091] (In the above general formula (B), R represents a hydrogen atom or methyl, A represents O or NH, B represents ethylene or propylene, and R1 and R2 independently represent methyl or ethyl)

[0092] The structural unit (B) has an amino group belonging to a basic group. Therefore, it is considered that the carboxyl group and phenolic hydroxyl group formed on the surface of the carbon material by oxidation or the like form an ionic bond with the amino group in the structural unit (B), so that the polymer dispersant is easily adsorbed on the carbon material, and the dispersibility of the carbon material is further improved. Furthermore, it is considered that the dispersibility of the carbon material is further improved according to the synergistic effect of the adsorption of the quaternary ammonium salt group in the structural unit (A) and the polycyclic aromatic group constituting the quaternary ammonium salt group on the carbon material.

[0093] Monomer B is preferably a monomer represented by the following general formula (B-1).

[0094]

[0095] (In the above general formula (B-1), R1 and R2 independently represent methyl or ethyl)

[0096] Examples of the monomer represented by the general formula (B-1) include dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.

[0097] The structural unit (C) is a structural unit having a polyalkylene glycol chain and derived from a monomer C belonging to a so-called macromonomer. The polymer dispersant having this structural unit (C) is a polymer having a structure in which a polyalkylene glycol chain is grafted. Further, the polyalkylene glycol chain is a molecular chain soluble in an organic solvent as a dispersion medium. In the general formula (C), the urethane bond (NHCOO) and urea bond (NHCONH) represented by Y are hydrogen-bonded to a hydrogen atom such as a hydroxyl group formed on the surface of the carbon material by modification. Therefore, the polymer dispersant is as follows: the polyalkylene glycol chain belonging to the graft chain is soluble in an organic solvent as a dispersion medium, and the urethane bond (NHCOO) and urea bond (NHCONH) in the structural unit (C) and the main chain containing the structural unit (A) are adsorbed on the carbon material. Further, the dissolved polyalkylene glycol chain creates steric hindrance and repulsion between the particulate carbon materials, and the carbon materials can be stably dispersed in a liquid medium well over a long period of time.

[0098] In the general formula (C), m is the average number of repeating units of propyleneoxy group (-CH(CH3)CH2O-), and n is the average number of repeating units of ethyleneoxy group (-CH2CH2O-). Further, m and n are independently values of 0 or more, and m + n = 20 to 100, preferably m + n = 35 to 100. That is, the molecular weight of the polyalkylene glycol chain is preferably 880 to 5800, more preferably 1540 to 5800. It should be noted that in the general formula (C), the alkyl group having 1 to 18 carbon atoms represented by R3 is preferably methyl, ethyl, propyl, butyl, dodecyl, stearyl, phenyl, naphthyl, or nonylphenyl.

[0099] Monomer C is preferably represented by the following general formula (C-1).

[0100]

[0101] (In the above general formula (C-1), Y represents NHCOO or NHCONH, m and n independently represent the average number of repeating units of 0 or more and m + n = 20 to 100, and R3 represents an alkyl group, aryl group, or alkylaryl group having 1 to 18 carbon atoms)

[0102] Examples of the monomer represented by the general formula (C-1) include a macromonomer in which isocyanatomethacryloyloxyethyl ester is reacted with a glycol monoalkyl ether such as polyethylene glycol monomethyl ether, polyethylene glycol polypropylene glycol monobutyl ether, polypropylene glycol monomethyl ether, or polyethylene glycol monolauryl ether, and Y is a urethane bond (NHCOO); a macromonomer in which isocyanatomethacryloyloxyethyl ester is reacted with a monoether monoamine such as polyethylene glycol polypropylene glycol monoamine, and Y is a urea bond (NHCONH); and the like.

[0103] In the general formulas (C) and (C-1), Y is preferably a urea bond (NHCONH) that does not require a catalyst when an isocyanate reacts with an amine. In addition, the polyalkylene glycol chain in the general formulas (C) and (C-1) is preferably a random copolymer of propylene oxide and ethylene oxide. Further, in the general formulas (C) and (C-1), R3 is preferably methyl. It should be noted that the molecular weight of the polyalkylene glycol chain is preferably 2000 to 4000, and preferably m + n = 36 to 90.

[0104] The structural unit (D) is a structural unit derived from monomer D that can react with the above monomer. Examples of monomer D include (meth)acrylic acid-based monomers such as (meth)acrylic acid and (meth)acrylic esters; vinyl monomers such as styrene, vinyltoluene, vinylpyridine, vinylcaprolactone, vinylimidazole, α-methylstyrene, and vinyl acetate; and the like. Among them, α-methylstyrene is preferably used as monomer D from the viewpoint of facilitating the control of the molecular weight.

[0105] In the polymer dispersant (polymer), the content of the structural unit (A) is 3 to 55% by mass, preferably 5 to 50% by mass. If the content of the structural unit (A) is less than 3% by mass, the adsorption to the carbon material becomes insufficient. On the other hand, if the content of the structural unit (A) exceeds 55% by mass, the solubility in the organic solvent becomes insufficient.

[0106] In the polymer, the content of the structural unit (B) is preferably 30% by mass or less, more preferably 2 to 25% by mass. It should be noted that the amine value of the polymer is 100 mgKOH / g or less, preferably 3 to 90 mgKOH / g. If the content of the structural unit (B) exceeds 30% by mass, the polymer may be colored.

[0107] In the polymer, the content of structural unit (C) is 45 to 90% by mass, preferably 50 to 85% by mass. That is, structural unit (C) is a structural unit that is contained in the polymer in a relatively large amount. By containing a relatively large amount of structural unit (C), the polyalkylene glycol chains are arranged densely. Therefore, when the polymer as a polymer dispersant adsorbs to the carbon material, the densely arranged polyalkylene glycol chains become steric hindrance, preventing the carbon materials from approaching each other, and the carbon materials can be stably dispersed.

[0108] If the content of structural unit (C) in the polymer is less than 45% by mass, sufficient steric hindrance cannot be formed, and it becomes difficult to improve the dispersibility. On the other hand, if the content of structural unit (C) exceeds 90% by mass, the reactivity of monomer C belonging to the macromonomer is slightly lacking, and therefore, it may remain unreacted and not polymerize.

[0109] In the polymer, the content of structural unit (D) is 0.5 to 20% by mass, preferably 0.6 to 16% by mass. If the content of structural unit (D) exceeds 0.5% by mass, the content of other structural units relatively decreases, and thus the function as a dispersant is reduced.

[0110] Monomer A, monomer B, and monomer C are represented by general formula (A-1), general formula (B-1), and general formula (C-1), respectively. When monomer D contains α-methylstyrene, even when the carbon material is at a high concentration, it is less likely to aggregate again, and a carbon material dispersion liquid that is more stably dispersed can be formed, which is preferred.

[0111] The number average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of the polymer used as a polymer dispersant is 5000 to 20000, preferably 10000 to 15000. If the number average molecular weight of the polymer is less than 5000, the introduction amount of structural unit (C) derived from monomer C belonging to the macromonomer is small, and sufficient dispersion stability cannot be obtained. On the other hand, if the number average molecular weight of the polymer exceeds 20000, the amount of the polymer dispersant required to disperse the carbon material becomes excessively large, and the viscosity of the obtained carbon material dispersion liquid becomes excessively high.

[0112] Polymers belonging to the polymer dispersant can be synthesized by methods known in the past. For example, they can be synthesized by free radical polymerization methods known in the past; polymerization methods using chain transfer agents such as mercaptans to adjust the molecular weight, atom transfer radical polymerization (ATRP method), reversible addition-fragmentation chain transfer polymerization (RAFT method), nitroxide method (NMP method), organotellurium method (TERP method), iodine transfer polymerization (ITP method), reversible transfer catalyst polymerization (RTCP method), reversible catalyst medium polymerization (RCMP method), and other living radical polymerization methods. Among them, from the aspect of enabling the molecular weight of the main chain to be more uniformly arranged and forming an A-B block copolymer according to the addition method, living radical polymerization methods are preferred.

[0113] The polymerization can be either thermal polymerization or photopolymerization, and an azo-based radical initiator, peroxide-based radical initiator, photosensitizer, etc. can be added to the polymerization reaction system. The polymerization form can be any of solvent-free, solution polymerization, and emulsion polymerization, and solution polymerization is preferred. By using the same organic solvent as that used in the carbon material dispersion for solution polymerization, the polymer after the polymerization reaction can be directly used for the carbon material dispersion, so it is preferred.

[0114] For example, by subjecting the aforementioned monomers to solution polymerization, the target polymer (polymer dispersant) can be obtained. It should be noted that by adding an alkyl halide such as benzyl chloride, naphthylmethyl chloride, ethynylmethyl chloride, pyrenylmethyl chloride, naphthylmethyl bromide, etc. to the reaction solution obtained by polymerizing monomers B to D, the amino group in structural unit (B) can be quaternized, and structural unit (B) can be converted into structural unit (A). Furthermore, by adding lithium bis(trifluoromethylsulfonyl)imide, lithium bis(heptafluorobutanesulfonyl)imide, etc., the anion (Cl - , Br - ) constituting the quaternary ammonium salt can be ion-exchanged.

[0115] In the dispersion obtained by neutralizing the raw materials, the content of the dispersant in terms of solid content is preferably 10 to 500 parts by mass, more preferably 30 to 500 parts by mass, per 100 parts by mass of the carbon material. The dispersant can be added in the total amount at the initial compounding stage, or can be added in batches during the middle of step (1). In the dispersion obtained by neutralizing the raw materials, the content of the carbon material is preferably 10% by mass or less, more preferably 5% by mass or less. In addition, in the dispersion obtained by neutralizing the raw materials, the content of the dispersant is preferably 30% by mass or less, more preferably 15% by mass or less. By setting the contents of the carbon material and the dispersant within the above ranges, a carbon material dispersion in which the carbon material is more stably dispersed can be obtained. When the amount of the dispersant is too small relative to the carbon material, the dispersant cannot sufficiently cover the surface of the carbon material, and the dispersibility may sometimes become insufficient. On the other hand, when the amount of the dispersant becomes too large relative to the carbon material, the carbon material dispersion tends to thicken, and the ratio of the carbon material in the solid content may sometimes become relatively low. In addition, when the dispersion is used as an ink or a coating material, the physical properties such as the strength and conductivity of the formed coating film may sometimes be slightly reduced.

[0116] [Liquid medium]

[0117] As the liquid medium, an aqueous medium or an organic solvent can be used. When the liquid medium is an aqueous medium, the carbon material dispersion is an aqueous dispersion. In addition, when the liquid medium is an organic solvent, the carbon material dispersion is a solvent-based (oil-based) dispersion.

[0118] As the aqueous medium, water or a mixed solvent of water and a water-soluble organic solvent can be used. The aqueous dispersion using the aqueous medium as the liquid medium is a more environmentally friendly dispersion. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, and isopropanol; polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and glycerol; ethers such as tetrahydrofuran; glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether; glycol ether esters such as diethylene glycol monomethyl ether acetate; amides such as pyrrolidone, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, 3-methoxy-N,N-dimethylpropanamide, and 3-butoxy-N,N-dimethylpropanamide; urea-based solvents such as tetramethylurea and dimethyl 1,3-imidazolidinone; sulfur-containing solvents such as dimethyl sulfoxide and sulfolane; ionic liquids such as 1-ethyl-3-methylimidazolium chloride; etc. The content of the water-soluble organic solvent in the dispersion is preferably set to 20% by mass or less, more preferably 10% by mass or less. If the content of the water-soluble organic solvent in the dispersion exceeds 20% by mass, the function of the dispersant may sometimes become easily reduced.

[0119] As the water-soluble organic solvent, isopropyl alcohol (IPA), ethanol are preferably used. When these water-soluble organic solvents are used, when the dispersion liquid is used as ink or a coating material, the wettability to the substrate and the drying property of the coating film can be improved.

[0120] [Additives, etc.]

[0121] The wetting mixture and the obtained dispersion liquid may further contain additives, resins, etc. As the additives, water-soluble dyes, pigments, ultraviolet absorbers, light stabilizers, antioxidants, leveling agents, defoaming agents, preservatives, mildew-proof agents, photoinitiators, and other pigment dispersants, etc. can be cited. As the resins, polyolefin resins, polyhalogenated olefin resins, polyester resins, polyamide resins, polyimide resins, polyether resins, polyvinyl resins, polystyrene resins, polyvinyl alcohol resins, polymethacrylate resins, polyurethane resins, polyepoxy resins, polyphenolic resins, polyureas, polyethersulfone resins, etc. can be cited.

[0122] In the wetting mixture and the dispersion liquid, according to the devices used in steps (1) and (2), a defoaming agent is preferably contained as an additive. If a defoaming agent is contained, foaming during the dispersion treatment can be suppressed. Therefore, the shearing force, collision force, etc. imparted during the dispersion treatment can effectively act, and a dispersion liquid with more excellent dispersibility can be formed.

[0123] [Wetting mixing treatment]

[0124] In step (1), for example, using a stirring device such as a magnetic stirrer, the raw materials are stirred and mixed to obtain a wetting mixture in which each component such as a carbon material is wetted. As the stirring device, a magnetic stirrer, a dissolver, a sand mill, a homogenizer, an ultrasonic homogenizer, a grinder, a bead mill, etc. can be cited. For the simplicity of the process, it is preferred to stir and wet with a magnetic stirrer, a dissolver, and a homogenizer, and it is preferred to combine with a high-pressure homogenizer for dispersion. For example, it is preferred to disperse using a bead mill using small-diameter beads. In addition, considering the damage to carbon materials such as carbon nanotubes, a method combining wetting stirring and high dispersion can be combined.

[0125] [Carbon material dispersion liquid]

[0126] The absorbance of the dispersion liquid of the carbon material containing carbon nanotubes depicts a gentle curve in the wavelength range of 300 nm to 1000 nm. Among them, this curve (absorbance curve) varies greatly according to the dispersion state of the carbon nanotubes. For example, when the amount of micro-dispersed carbon nanotubes is large, the absorbance on the short-wavelength side shows a large value. On the other hand, when the amount of aggregates of carbon nanotubes is large, the absorbance on the long-wavelength side shows a large value. Therefore, the absorbance ratio (A L ) obtained by dividing the absorbance on the short-wavelength side (A H ) by the absorbance on the long-wavelength side (A L / A H )It can well reflect the dispersion state of carbon materials in a liquid medium. That is, the thinner and more uniformly the carbon nanotubes are dispersed, the larger the absorbance ratio is. When the carbon nanotubes aggregate, the absorbance ratio is small.

[0127] Wavelength W as a reference M Set as the wavelength W on the short wavelength side L And the wavelength W on the long wavelength side H The median value (W M =(W L +W H ) / 2). In the wavelength region near the median value, it is basically not affected by the dispersion state of carbon materials. Therefore, it is suitable as a reference for evaluating the dispersibility of carbon materials.

[0128] The wavelength W on the short wavelength side L Is arbitrarily selected from the range of 350 - 550 nm, preferably from the range of 350 - 450 nm, and more preferably from the range of 350 - 400 nm. The change in absorbance at wavelengths within the above range is clear, and there are few noises and specific peak changes, so the measurement can be carried out stably. If it is less than 350 nm, the absorption and scattering of light by fine particles irregularly have an impact, and as the dispersion progresses, the peak will change significantly, making it difficult to form an accurate index. On the other hand, if it exceeds 550 nm, the change in absorbance becomes unclear.

[0129] The wavelength W on the long wavelength side H Is arbitrarily selected from the range of 650 - 850 nm, preferably from the range of 700 - 850 nm, and more preferably from the range of 700 - 800 nm. If it is a wavelength within the above range, the absorbance of particles with a small proportion of absorption components and a large proportion of scattering components can be confirmed. In addition, there are few noises and specific peak changes, so the measurement can be carried out stably. If it exceeds 850 nm, noise will be mixed in the peak, making it difficult to measure an accurate value. On the other hand, less than 650 nm is an unsuitable range as an index.

[0130] Wavelength W L The difference from wavelength W H Is preferably 100 nm or more, and more preferably 200 nm or more. By making the difference between wavelength W L and wavelength W H 100 nm or more, the dispersibility of carbon materials can be read more accurately. If the difference between wavelength W L and wavelength W H is too small, it may be difficult to evaluate the dispersion state of carbon materials with good precision.

[0131] The absorbance of the dispersion varies according to the content (concentration) of the carbon material. Therefore, the absorbance of the diluted dispersion prepared by diluting the dispersion is measured. As the diluent for diluting the dispersion, a blank solution having the same composition as the carbon material dispersion to be measured except that it does not contain the carbon material is preferably used. By using such a blank solution, the influence of diffusion, re-aggregation of fine particles, and the environment on the absorbance can be suppressed, and it is not easily affected by the polymer dispersant sometimes used as a dispersant, and the absorbance can be measured more accurately.

[0132] In order to accurately measure the absorbance, it is generally preferable that the content of the carbon material in the sample solution (diluted dispersion) is in the range of 0.001 to 0.01% by mass. If it exceeds 0.01% by mass, the amount of laser scattered light transmitted during measurement is small, and it may be difficult to accurately perform the measurement. On the other hand, if it is less than 0.001% by mass, the value of the absorbance becomes excessively small, and accurate evaluation and comparison may sometimes become difficult.

[0133] The wavelength W of the diluted dispersion obtained by diluting with a diluent containing a liquid medium M has an absorbance of 1.2 to 2.2, preferably 1.5 to 2.0. If the absorbance of the wavelength W of the diluted dispersion M is less than 1.2, it becomes difficult to judge the dispersion state. On the other hand, it is difficult to accurately measure the absorbance exceeding 2.2.

[0134] The absorbance A of the wavelength W of the diluted dispersion L with respect to the wavelength W L of the absorbance A H ratio (A H / A L / A H ) value varies according to the wavelength W H and W L For example, when the value of “A L / A H ” at the wavelength W L = 380 nm and the wavelength W H = 780 nm is “1.60”, the value of “A L / A H ” at the wavelength W L = 400 nm and the wavelength W H = 700 nm is “1.44”, and the value of “A L / A H ” at the wavelength W L = 350 nm and the wavelength W H = 800 nm is “1.78”. In addition, when the wavelength W L = 380 nm and the wavelength W H = 780 nm, the “A L / AH When the value of " is "1.65", the wavelength W L = 400 nm and the wavelength W H = 700 nm, the "A L / A H " value is "1.48", and the wavelength W L = 350 nm and the wavelength W H = 800 nm, the "A L / A H " value is "1.85".

[0135] The absorbance of the dispersion liquid at the wavelength W L is a physical property value that is an index of the dispersion state of the carbon material. On the other hand, the absorbance of the dispersion liquid at the wavelength W H is a physical property value that is an index of the aggregation state of the carbon material. Taking the wavelength W L and W H as the reference, and making the absorbance at this wavelength W M become 1.2 to 2.2, the ratio (A M / A L ) of the absorbance A L at the wavelength W H to the absorbance A H at the wavelength W L / A H ) of the diluted dispersion liquid obtained by diluting with a diluent containing a liquid medium is obtained, and thus the dispersion state of the carbon material in the dispersion liquid can be accurately evaluated.

[0136] For the dispersion liquid, when the wavelength W L is 380 nm, the wavelength W H is 780 nm, and the wavelength W M is 580 nm, and the absorbance at the wavelength W M is 1.5 to 2.0 (preferably 1.8 ± 0.02), the ratio (A L / A H ) of the absorbance A 380 to the absorbance A 780 ) is preferably 1.60 or more, and more preferably 1.65 or more. By making the value of the absorbance ratio (A 380 / A 780 ) within the above range, even if the types and addition amounts of the carbon material and the dispersant change, a dispersion liquid with more excellent viscosity stability can be formed and substantially no coarse aggregates are contained.

[0137] The absorbance ratio (A 380 / A 780) If the value is excessively small, the carbon nanotubes are not in a state of being thin and uniformly dispersed. Therefore, the viscosity stability of the dispersion liquid is low, and there are many thick aggregates. The absorbance ratio (A 380 / A 780 ) The dispersion liquid of the present invention with a value of 1.40 or more contains a carbon material including carbon nanotubes in a state of being thin and uniformly dispersed, has good viscosity stability, and substantially does not contain thick aggregates, and even if it contains fine aggregates, the amount is extremely small.

[0138] When the carbon material is dispersed in the liquid medium by dispersion treatment, in the initial stage of the dispersion treatment, there are many aggregates of the carbon material in the liquid medium, so the absorbance ratio is small. Then, as the dispersion treatment progresses, the dispersant adsorbs onto the carbon nanotubes, and the aggregates are slowly loosened, and the absorbance ratio increases. If the size of the short side of the aggregate becomes less than 100 μm, the absorbance ratio (A 380 / A 780 ) becomes 1.60 or more. When the dispersion treatment is further carried out, the carbon nanotubes are in a state of being more uniformly dispersed in the liquid medium, and the absorbance ratio (A 380 / A 780 ) becomes 1.65 or more. However, when the dispersion treatment is carried out excessively, the carbon nanotubes with their structures damaged will aggregate again, and the absorbance ratio (A 380 / A 780 ) decreases to less than 1.40.

[0139] The viscosity of the dispersion liquid of the present invention is not likely to change even after a long time, and the viscosity stability (storage stability) is excellent. Specifically, taking the viscosity (mPa·s) at 25 °C of the dispersion liquid just prepared (dispersed) as a reference, the change rate of the viscosity (mPa·s) at 25 °C of the dispersion liquid after 10 days at room temperature (25 °C) is usually 15% or less, preferably 10% or less, and more preferably 5% or less.

[0140] When aggregates with a short side of 100 μm or more are present in the dispersion, when the dispersion is used for various purposes, it becomes difficult to exhibit the original properties of the carbon nanotubes, such as electrical conductivity and thermal conductivity, and the growth and sedimentation of aggregates occur, and the viscosity stability and storage stability tend to be easily reduced. For example, when a dispersion containing aggregates with a short side of 100 μm or more is used as a coating material, it tends to be difficult to achieve uniform coating. In contrast, the dispersion of the present invention substantially does not contain coarse aggregates formed from a carbon material containing carbon nanotubes. Specifically, when observing the dispersion just prepared (dispersed) 5 times at a magnification of 200 times and the dispersion after 10 days at room temperature (25 °C) using an optical microscope, usually not even 1 aggregate with a short side of 100 μm or more can be confirmed. Preferably, the number (average value) of aggregates with a short side of 20 μm or more is 10 or more in each observation. More preferably, the number (average value) of aggregates with a short side of 20 μm or more is 1 or more and less than 10 in each observation, and particularly preferably, not even 1 aggregate with a short side of 20 μm or more can be confirmed after observing 5 times.

[0141] (Step (2))

[0142] Step (2) is a step of dispersing the wet mixture obtained in step (1) using a high-pressure homogenizer. By dispersing the wet mixture, the target carbon material dispersion can be obtained.

[0143] [High-pressure homogenizer]

[0144] As the high-pressure homogenizer, at least any one of high-pressure homogenizer (A1) and high-pressure homogenizer (A2) is used. High-pressure homogenizer (A1) is a dispersion device that granulates fine particles by causing the wet mixture (liquid sample) that has been pressurized and sprayed to collide with each other. In addition, high-pressure homogenizer (A2) is a dispersion device that introduces the pressurized wet mixture (liquid sample) into a collision chamber for granulation. As the collision chamber of high-pressure homogenizer (A2), for example, there are: a collision chamber in which the pressurized liquid sample collides with the wall, a ball collision chamber equipped with a ball for colliding the pressurized liquid sample, etc. Any high-pressure homogenizer is a dispersion device that collides with the liquid sample to which a treatment pressure is applied, granulates it, and then discharges it from the discharge nozzle. By using these high-pressure homogenizers to disperse the wet mixture, a dispersion with few aggregates and excellent viscosity stability can be manufactured.

[0145] Examples of commercially available homogenizers include the "NAGS" series of high-pressure homogenizers manufactured by JOKOH CO., LTD.; the "Microfluidizer" series of high-pressure homogenizers manufactured by Powrex Corporation; the "Star Burst" series of high-pressure homogenizers manufactured by SUGINO MACHINE LIMITED; the high-pressure homogenizers manufactured by Yoshida Machinery Co., Ltd.; the homogenizers manufactured by SMT CO., LTD.; the "OMEGA (registered trademark)" series of high-pressure homogenizers manufactured by Ashizawa Finetech Ltd., etc.

[0146] Moreover, the dispersion treatment is carried out in such a way as to satisfy the following dispersion conditions.

[0147] [Dispersion conditions]

[0148] After performing the X-th first treatment, the following second treatment is performed Y times.

[0149] The first treatment is as follows: Using either the high-pressure homogenizer (A1) or the high-pressure homogenizer (A2), the wet mixture is granulated by applying a treatment pressure of 1 to 100 MPa and discharged from a discharge nozzle with a nozzle inner diameter D1.

[0150] The second treatment is as follows: Using either the high-pressure homogenizer (A1) or the high-pressure homogenizer (A2), the wet mixture is granulated by applying a treatment pressure of 120 to 250 MPa and discharged from a discharge nozzle with a nozzle inner diameter D2 (where D1 > D2, X ≥ 2, 2 ≤ Y ≤ 30).

[0151] In the dispersion treatment, the following first treatment is performed X times: First, using an arbitrary high-pressure homogenizer, the wet mixture is granulated by applying a treatment pressure and discharged from a discharge nozzle with a nozzle inner diameter D1. The treatment pressure applied to the wet mixture during the first treatment is 1 to 100 MPa, preferably 2 to 70 MPa. By setting the treatment pressure within the above range, a dispersion liquid with few aggregates and excellent viscosity stability can be obtained. Then, the granulated wet mixture is discharged from the discharge nozzle with a nozzle inner diameter D1. The nozzle inner diameter D1 is preferably 0.15 to 2.0 mm, more preferably 0.15 to 0.8 mm, and particularly preferably 0.2 to 0.5 mm. In addition, the number of times (X: number of passes) of the first treatment is 2 or more. There is no particular limitation on the upper limit of the number of times (X) of the first treatment, as long as it is 50 or less.

[0152] In the dispersion treatment, following the first treatment, the following second treatment is carried out Y times: using an arbitrary high-pressure homogenizer, a treatment pressure is applied to the wet mixture to make it into fine particles, and it is discharged from a discharge nozzle with a nozzle inner diameter D2. The treatment pressure applied to the wet mixture during the second treatment is 120 to 250 MPa, preferably 120 to 170 MPa. If the treatment pressure is too small, the resulting dispersion contains a lot of aggregates and it is difficult to improve the viscosity stability of the dispersion. Then, the wet mixture that has been made into fine particles is discharged from the discharge nozzle with a nozzle inner diameter D2. The nozzle inner diameter D2 is preferably 0.1 to 1.0 mm, more preferably 0.1 to 0.4 mm, and still more preferably 0.1 to 0.3 mm. In addition, the number of times (Y: number of passes) of the second treatment is 2 or more and 30 or less, preferably 3 or more and 25 or less. If the number of times (Y) of the second treatment is too large, the resulting dispersion becomes an over-dispersed state, contains a lot of aggregates, and the viscosity stability cannot be improved.

[0153] The nozzle inner diameter D1 of the discharge nozzle of the high-pressure homogenizer used in the first treatment and the nozzle inner diameter D2 of the discharge nozzle of the high-pressure homogenizer used in the second treatment satisfy the relationship D1 > D2. That is, the nozzle inner diameter D1 of the discharge nozzle of the high-pressure homogenizer used in the first treatment is larger than the nozzle inner diameter D2 of the discharge nozzle of the high-pressure homogenizer used in the second treatment. In this way, by using high-pressure homogenizers with discharge nozzles having different nozzle inner diameters to carry out the first treatment and the second treatment respectively, a dispersion with few aggregates and excellent viscosity stability can be obtained. Regarding the difference between the nozzle diameters D1 and D2, it is preferably 0.1 mm or more, and still more preferably 0.15 mm or more. If the difference in nozzle diameters is small, the dispersion effect may be slightly insufficient.

[0154] When adjusting the concentration of the carbon material, it is preferable to set the number of passes of the dispersion treatment according to the type of carbon material and dispersant to be used. For example, it is preferable to further add a carbon material to the dispersion obtained in step (2) and stir it. After the carbon material is compatible with the dispersion, steps (1) and (2) are carried out again. In this case, a state where a proper amount of dispersant is pre-added with respect to the total amount of the carbon material in the finally obtained dispersion can be formed, or a state where a proper amount of dispersant is added when further adding the carbon material can be formed. Steps (1) and (2) can be carried out 1 or more times each. By carrying out repeated treatment as needed, the number of passes can be effectively reduced, and a high-concentration carbon material dispersion can be manufactured.

[0155] <Product>

[0156] The carbon material of the present invention described above, which contains carbon nanotubes, substantially does not produce large aggregates and is well dispersed in the dispersion liquid, and has excellent viscosity stability. Therefore, by exerting this property, the following products can be provided. That is, any product (first product) of a coating, ink, coating agent, resin molding material, conductive material, heat conductive material, and antistatic material containing the aforementioned carbon material dispersion liquid can be provided. In addition, any product (second product) of a battery material and a mechanical component having a coating film formed from the aforementioned carbon material dispersion liquid can be provided.

[0157] As a method for preparing a coating or ink, for example, there are the following methods: a method of adding a solvent, resin, and various additives, etc. to the dispersion liquid so as to form a coating composition or ink composition; a method of adding the dispersion liquid to a commercially available coating or ink; etc. As a method for manufacturing a resin molding in which a carbon material containing carbon nanotubes is dispersed, for example, there are the following methods: a method of mixing a molten resin material with the dispersion liquid and then removing the liquid medium; a method of adding the dispersion liquid to a resin material in a fine powder state and then removing the liquid medium or precipitating the carbon material; etc.

[0158] Examples

[0159] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. It should be noted that "parts" and "%" in the examples and comparative examples are based on mass unless otherwise specified.

[0160] <Preparation of materials>

[0161] Prepare the following carbon nanotubes (CNT), dispersant, and defoaming agent.

[0162] (Carbon nanotubes (CNT))

[0163] · CNT-A: Multi-walled CNT, average diameter 6 - 9 nm, average length 100 - 200 μm, trade name "JENOTUBE8c", manufactured by JEIO Co., Ltd.

[0164] · CNT-B: Multi-walled CNT, average diameter 5 - 7 nm, average length 50 - 150 μm, trade name "JENOTUBE 6A", manufactured by JEIO Co., Ltd.

[0165] · CNT-C: Multi-walled CNT, average diameter 30 - 50 nm, average length 5 - 12 μm, trade name "s40", manufactured by SUSN Corporation

[0166] · CNT-D: Multi-walled CNT, average diameter 9.5 nm, average length 1.5 μm, trade name "NC7000", manufactured by Nanocyl SA

[0167] · CNT-E: Multi-walled CNT, average diameter 14 - 16 nm, average length 90 - 100 μm, trade name "K-nanos400T", manufactured by Kumho Petrochemical Co., Ltd.

[0168] · CNT-F: Single-walled CNT, average diameter 3 - 5 nm, average length 100 - 600 μm, trade name "SG-101", manufactured by Zeon Corporation

[0169] (Dispersant)

[0170] · Dispersant a: Trade name "DYSPERBYK-2012", manufactured by BYK-Chemie GmbH, solid content 40%

[0171] · Dispersant b: Trade name "FLOWREN GW-1500", manufactured by Kyoeisha Chemical Co., Ltd., solid content 100%

[0172] · Dispersant c: Trade name "Dispex Ultra PA4550", manufactured by BASF Corporation, solid content 50%

[0173] · Dispersant d: Trade name "SUNROSE F01MC", manufactured by Nippon Paper Industries Co., Ltd., sodium carboxymethyl cellulose, viscosity of 1 mass% aqueous solution 7 - 13 mPa·s, degree of etherification 0.65 - 0.75

[0174] · Dispersant e: Trade name "DYSPERBYK-9077", manufactured by BYK-Chemie GmbH, solid content 100%

[0175] (Defoamer)

[0176] · Trade name "BYK-028", manufactured by BYK-Chemie GmbH

[0177] <Manufacture of Dispersant>

[0178] Manufacture dispersants A1, A2, dispersant B1 and dispersant C1 according to the steps shown below.

[0179] (Dispersant A1)

[0180] (a) Synthesis of macromonomer

[0181] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel, 142.5 parts (0.067 mol) of a mono-terminal amino polypropylene glycol polyethylene glycol monomethyl ether copolymer (M41) (trade name “Genami M41 / 2000”, manufactured by Clariant, measured amine value 26.4 mgKOH / g) was added and stirred. 10.4 parts (0.067 mol) of 2-isocyanatoethyl methacrylate (MOI) (trade name “Karenz MOI”, manufactured by Showa Denko K.K.) was added to the dropping funnel and added dropwise to the reaction apparatus cooled with a water bath over 30 minutes. A part of the reaction solution was sampled and subjected to IR measurement, and disappearance of the absorption of the isocyanate group derived from MOI and formation of a urea bond were confirmed. In addition, the amine value of the product was 0.2 mgKOH / g, and it was confirmed that the reaction between the amino group and the isocyanate group was substantially completed. Note that the amine value was measured using an automatic potentiometric titrator with a 0.1 mol / L 2-propanolic hydrochloric acid solution. From the above, it was confirmed that a polypropylene glycol polyethylene glycol copolymer (MC-1) having a methacryloyl group bonded to its mono-terminal was formed. The number-average molecular weight (Mn) of MC-1 in terms of polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the developing solvent was 2,800, and the molecular weight distribution (PDI = weight-average molecular weight (Mw) / number-average molecular weight (Mn)) was 1.09. MC-1 is a macromonomer corresponding to monomer 2 represented by the general formula (1), and the number of repeating units n H is more than 1 / 2 of the total number of repeating units n T .

[0182] (b) Synthesis of dispersant

[0183] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 95 parts of diethylene glycol monobutyl ether (BDG), 70 parts of MC-1, 2.5 parts of α-methylstyrene (αMS), 10.5 parts of styrene (St), and 17 parts of 4-vinylpyridine (4VP) were added, and the mixture was heated to 75 °C while bubbling nitrogen. At the moment when the temperature reached 70 °C, 5 parts of 2,2'-azobis(isobutyric acid) dimethyl ester (V-601) (trade name “V-601”, Wako Chemicals Corporation) was added, and polymerization was carried out at 75 °C for 4 hours. Further, 2.5 parts of V-601 was added, and polymerization was carried out at 75 °C for 4 hours to obtain a liquid containing a polymer. The Mn of the polymer was 9,600, the PDI was 1.83, the peak top molecular weight (PT) was 22,700, and substantially no peak derived from MC-1 used as a raw material was observed. In addition, the amine value (in terms of pure resin component) of the polymer was 86.2 mgKOH / g. The solid content of the liquid containing the polymer measured using a moisture meter was 50.4%.

[0184] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel, 100 parts of the aforementioned polymer was added. After adding 30 parts of BDG and diluting, it was stirred at room temperature for 10 minutes for homogenization to obtain a solution. In the obtained solution, 0.081 mol of amino groups derived from 4VP was present. At room temperature, a solution containing 10.25 g of BDG and 10.25 g (0.081 mol) of benzyl chloride (BzCl) was added dropwise from the dropping funnel over 30 minutes. After the dropwise addition, it was heated to 80 °C and maintained for 5 hours to obtain a liquid containing a polymer (dispersant A1). The solid content of the liquid containing the obtained dispersant A1 was 40.2%. In addition, it was found that the amine value of dispersant A1 was basically 0 mgKOH / g, and the reaction proceeded quantitatively, and all the amino groups derived from 4VP were quaternized.

[0185] (Dispersant A2)

[0186] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 95.0 parts of BDG, 70 parts of MC-1, 2.5 parts of αMS, 10.4 parts of St, 7.7 parts of methacrylic acid (MAA), and 9.4 parts of 4VP were added, and it was heated to 75 °C while bubbling nitrogen. At the moment when the temperature reached 70 °C, 5 parts of V-601 was added, and polymerization was carried out at 75 °C for 4 hours. Further, 2.5 parts of V-601 was added, and polymerization was carried out at 75 °C for 4 hours to obtain a liquid containing a polymer (dispersant A2). The Mn of dispersant A2 (polymer) was 11,900, the PDI was 1.88, the PT was 25,900, and basically no peak derived from MC-1 used as a raw material was confirmed. In addition, the amine value (in terms of pure resin component) of dispersant A2 was 50.0 mgKOH / g, and the acid value (in terms of pure resin component) was 50.0 mgKOH / g. This polymer is an amphoteric polymer dispersant having amino groups and carboxyl groups in its structure. The solid content of the liquid containing dispersant A2 was 50.9%.

[0187] (Dispersant B1)

[0188] (a) Synthesis of macromonomer

[0189] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a dropping funnel, 400 parts (0.2 mol) of a mono-terminally aminated polypropylene glycol polyethylene glycol monomethyl ether copolymer (trade name “JEFFAMINE M2005”, manufactured by Huntsuman Corporation, amine value (measured): 28.05 mgKOH / g) (M2005) and 256.32 parts of propylene glycol monomethyl ether acetate (PGMAc) were added, and stirred at room temperature for 10 minutes for homogenization. In another container, 31.04 parts (0.2 mol) of 2-isocyanatoethyl methacrylate (trade name “Karenz MOI”, manufactured by Showa Denko K.K.) (MOI) and 31.04 parts of PGMAc were added to prepare a mixed solution. The prepared mixed solution was added dropwise to the reaction apparatus through the dropping funnel over 30 minutes. A gentle exotherm was observed just after the start of the dropwise addition. Samples were taken and IR measurement was performed to confirm the disappearance of the absorption of the isocyanate group derived from MOI and the formation of a urethane bond, and the formation of a macromonomer (A) having an α,β-unsaturated bond was confirmed. Heating was carried out at 140 °C with a dryer until a constant weight was reached, and the solid content measured and calculated was 60.0%. Hereinafter, the solid content was measured and calculated by this method. The obtained macromonomer (A) was designated as “MAC-1”. The number average molecular weight (Mn 1) of MAC-1 in terms of polystyrene measured by GPC (eluent: tetrahydrofuran) was 3500. Hereinafter, the molecular weights of various polymers were measured under this condition.

[0190] (b) Synthesis of polymer dispersant

[0191] In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 30.8 parts of PGMAc, 179.6 parts of MAC-1, 3.0 parts of α-methylstyrene (αMS), 25.2 parts of styrene (St), and 18.0 parts of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) were added, and heated to 70 °C while bubbling nitrogen. 3.0 parts of 2,2'-azobis(isobutyric acid) dimethyl ester (trade name “V-601”, Wako Chemicals Corporation) (V-601) was added, and polymerization was carried out at 70 °C for 4 hours. Further, 0.5 part of V-601 was added, and polymerization was carried out at 70 °C for 4 hours to obtain a solution of a polymer (dispersant B1). The number average molecular weight (Mn) of dispersant B1 (polymer) was 6400, the molecular weight distribution (dispersion degree (PDI)) was 2.2, and substantially no peak derived from MAC-1 used as a raw material was observed. In addition, the solid content of the solution containing dispersant B1 was 60.8%. Further, using a potentiometric automatic titrator, the amine value of the polymer measured with a 0.1N hydrochloric acid / isopropanol solution as a titrant was 41.9 mgKOH / g.

[0192] (Dispersant C1)

[0193] Sodium carboxymethyl cellulose was manufactured using a known method. Specifically, 400 g of isopropyl alcohol (IPA) and 60 g of water were placed into a 1-L stainless-steel container equipped with a stirrer. While cooling the stainless-steel container in a water bath, 10 g of sodium hydroxide (purity 98%) was added. After cooling the solution to 25°C or lower, 20 g of shredded pulp was added while stirring. Subsequently, stirring and mixing (mercerization) were continued at 15–25°C for 60 minutes to prepare alkaline cellulose. Next, 30 g of a mixed solution of monochloroacetic acid / isopropyl alcohol = 1:2 was stirred and cooled in the stainless-steel container, and while maintaining the temperature at 15–25°C, it was added and stirred and mixed for 15 minutes. Next, while heating the stainless-steel container in a hot water bath and stirring for approximately 30 minutes, the temperature of the solution was raised to 70°C. After raising the temperature, stirring was continued while maintaining the temperature at 65–75°C for 120 minutes to conduct an etherification reaction. After completion of the reaction, unreacted sodium hydroxide was neutralized with acetic acid. After separating the product, it was washed with a 70% methanol aqueous solution to remove by-products. The product was dried and pulverized to obtain sodium carboxymethyl cellulose (C1). The viscosity of a 1% by mass aqueous solution of the obtained sodium carboxymethyl cellulose was 31 mPa·s, and the degree of etherification (DS) was 0.84.

[0194] The degree of etherification was measured with reference to the test method for synthetic detergent JIS-related substances described in Oil Chemistry 38(11), 962–967, 1989. Specifically, approximately 1 g of sodium carboxymethyl cellulose was precisely weighed and placed into a porcelain crucible, and then heated and ashed at a temperature not exceeding 600°C (around 550–590°C) for 1 hour. After cooling to room temperature, it was transferred to a 500-mL beaker together with the crucible, and 250 mL of water was added. 50 mL of a 0.05 mol / L sulfuric acid aqueous solution was added and boiled for 30 minutes. After cooling to room temperature, the unreacted acid was titrated with 0.1 mol / L sodium hydroxide. Phenolphthalein was used as the indicator. The amount of 0.1 mol / L sodium hydroxide used in the titration was denoted as “X” mL, and the degree of etherification (DS) was calculated using the following formula.

[0195] Degree of etherification (DS) = 162X / (10000 - 80X)

[0196] <Humidifying device and dispersing device>

[0197] The following humidifying device and dispersing device were prepared.

[0198] · Humidifying device α1: 1 / 4G sand mill, manufactured by Aimex Co., Ltd.

[0199] · Humidifying device α2: homogenizer, manufactured by SMT CO., LTD.

[0200] ·Dispersion device A1: A high-pressure homogenizer manufactured by JOKOH CO., LTD., which causes the liquid samples that have been pressure-injected to collide with each other to be finely granulated

[0201] ·Dispersion device A2: A high-pressure homogenizer manufactured by SUGINO MACHINE LIMITED, which is a high-pressure homogenizer that introduces the pressurized liquid sample into a collision chamber to be finely granulated

[0202] <Measurement and evaluation methods>

[0203] (Measurement of absorbance and calculation of absorbance ratio)

[0204] Prepare a blank solution having the same composition as the dispersion except for not containing a carbon material. Measure the baseline with the prepared blank solution, and on this basis, measure the absorbance of the sample solution. The absorbance of the sample solution is measured using a spectrophotometer (trade name "Hitachi Spectrophotometer U-3310 type", manufactured by Hitachi High-Tech Corporation) equipped with a quartz cuvette having an optical path length of 10 mm. For dilution based on the blank solution, a standard curve of the absorbance at a wavelength of 580 nm that plots the change based on the dilution ratio is prepared, and the dilution ratio at which the absorbance becomes 1.8 ± 0.02 is calculated, thereby preparing a dispersion diluted to the target concentration. In addition, it is also possible to adjust the target carbon component concentration in the pre-dispersion stage and adjust the carbon component concentration to satisfy the aforementioned absorbance in the initial compounding stage and then perform dispersion. The specific method for preparing the sample solution is as follows: First, collect the dispersion in a plastic bottle (a polyethylene bottle), and based on the dilution ratio obtained from the standard curve, add an appropriate amount of the blank solution. Stir for 30 seconds using a vortex mixer (manufactured by Scientific Industries, Inc.) to obtain a sample solution having an absorbance A at a wavelength of 580 nm 580 of 1.8 ± 0.02. Measure the absorbance A of the obtained sample solution at a wavelength of 380 nm 380 and the absorbance A at a wavelength of 780 nm 780 , and calculate the absorbance ratio (A 380 / A 780 ). It should be noted that for a dispersion prepared with a highly volatile organic solvent, cover the quartz cuvette with a lid to measure the absorbance

[0205] (Evaluation of the dispersion)

[0206] [Measurement of viscosity and evaluation of viscosity stability]

[0207] Using an E-type viscometer with a rotor of 1°34’×R24, measure the viscosities of the dispersion just after dispersion and the dispersion after 10 days (after standing at room temperature for 10 days) under the conditions of a temperature of 25°C and a rotor speed of 100 rpm. It should be noted that for dispersions with a viscosity less than 25 mPa·s, measure the viscosity using the product name "VISCOMETERTVE-25L" (manufactured by Toki Sangyo Co., Ltd.). In addition, for dispersions with a viscosity of 25 mPa·s or more, measure the viscosity using the product name "VISCOMETERTVE-25H" (manufactured by Toki Sangyo Co., Ltd.). Then, evaluate the viscosity stability of the dispersion according to the evaluation criteria shown below.

[0208] ◎: The change rate of the viscosity after 10 days based on the viscosity just after dispersion is less than 5%.

[0209] ○: The change rate of the viscosity after 10 days based on the viscosity just after dispersion is 5% or more and less than 10%.

[0210] △: The change rate of the viscosity after 10 days based on the viscosity just after dispersion is 10% or more and less than 15%.

[0211] ×: The change rate of the viscosity after 10 days based on the viscosity just after dispersion is 15% or more.

[0212] [Observation of aggregates]

[0213] Collect the dispersion in a plastic bottle (a polyethylene bottle), and add a blank solution and dilute it so that the concentration of the carbon material becomes 0.1 mass%. Stir for 30 seconds using a vortex mixer (manufactured by Scientific Industries, Inc.) to obtain a diluted solution. Drop 30 μL of the obtained diluted solution on a glass slide, place a glass cover slip, and then use an optical microscope to observe the presence or absence of aggregates (200 times magnification). For the dispersion just after dispersion and the dispersion after 10 days (after standing at room temperature for 10 days), prepare samples by dropping on the glass slide 5 times and observe. Evaluate the presence or absence of aggregates according to the evaluation criteria shown below.

[0214] ◎: In 5 observations, no aggregate with a short side of 20 μm or more is confirmed.

[0215] ○: The number (average value) of aggregates with a short side of 20 μm or more is 1 or more and less than 10 in each observation, and in 5 observations, no aggregate with a short side of 100 μm or more is confirmed.

[0216] △: The number (average value) of aggregates with a short side of 20 μm or more is 10 or more in each observation, and in 5 observations, no aggregate with a short side of 100 μm or more is confirmed.

[0217] ×: Aggregates with a short side of 100 μm or more were confirmed in 1 or more of the 5 observations.

[0218] <Preparation and Evaluation of Dispersion Liquid (1)>

[0219] (Examples 1 to 30, Comparative Examples 1 to 26)

[0220] Add each component (excluding CNT) of the types and amounts shown in Tables 1-1 and 1-2 to a plastic cup (polyethylene cup) with a capacity of 500 mL. After stirring until homogeneous, add CNT of the types and amounts shown in Tables 1-1 and 1-2 and stir further. Place a magnetic stir bar in the plastic cup and stir with a magnetic stirrer (denoted as "stirrer" in the table) for 12 hours to obtain a wet mixture. For the obtained wet mixture, perform the first treatment under the conditions shown in Tables 2-1 and 2-2 using the dispersion devices of the types shown in Tables 2-1 and 2-2. Then, perform the second treatment under the conditions shown in Tables 2-1 and 2-2 using the dispersion devices of the types shown in Tables 2-1 and 2-2 to obtain a dispersion liquid. The measurement results of the viscosity of the obtained dispersion liquid, the evaluation results of viscosity stability, and the results of aggregate observation are shown in Tables 3-1 and 3-2.

[0221] Table 1

[0222]

[0223] Table 1-2

[0224]

[0225] Table 2-1

[0226]

[0227] Table 2-2

[0228]

[0229] Table 3

[0230]

[0231] Table 3-2

[0232]

[0233] <Preparation and Evaluation of Dispersion Liquid (2)> (Comparative Example 27)

[0234] In the container of a 1 / 4G sand mill (manufactured by Aimex Co., Ltd.), add each component (except CNT) of the type and amount shown in Table 4. After stirring with a dissolver until it becomes uniform, add the CNT of the type and amount shown in Table 4 and stir further. Add 1000 parts of zirconia beads with an average diameter of 2.0 mm, and while stirring at a speed of 900 rpm, use the sand mill to perform a wetting process for the time shown in Table 5. After that, separate and remove the zirconia beads to obtain a wet mixed liquid. The measurement results of the viscosity, the evaluation results of the viscosity stability, and the results of the aggregate observation of the obtained wet mixed liquid are shown in Table 6.

[0235] (Example 31)

[0236] In the container of a 1 / 4G sand mill (manufactured by Aimex Co., Ltd.), add each component (except CNT) of the type and amount shown in Table 4. After stirring with a dissolver until it becomes uniform, add the CNT of the type and amount shown in Table 4 and stir further. Add 1000 parts of zirconia beads with an average diameter of 2.0 mm, and while stirring at a speed of 900 rpm, use the sand mill to perform a wetting process for the time shown in Table 5. After that, separate and remove the zirconia beads to obtain a wet mixed liquid. For the obtained wet mixed liquid, use the dispersing device of the type shown in Table 5 and perform the first treatment under the conditions shown in Table 5. After that, use the dispersing device of the type shown in Table 5 and perform the second treatment under the conditions shown in Table 5 to obtain a dispersion. The measurement results of the viscosity, the evaluation results of the viscosity stability, and the results of the aggregate observation of the obtained dispersion are shown in Table 6.

[0237] (Example 32)

[0238] In a plastic cup with a capacity of 500 mL (a polyethylene cup), add each component (except CNT) of the type and amount shown in Table 4. After stirring until it becomes uniform, add the CNT of the type and amount shown in Table 4 and stir further. Place a stir bar in the plastic cup and stir with a magnetic stirrer for 1 hour, and then perform 2 treatments with a homogenizer (manufactured by SMT CO., LTD.) to obtain a wet mixed liquid. For the obtained wet mixed liquid, use the dispersing device of the type shown in Table 5 and perform the first treatment under the conditions shown in Table 5. After that, use the dispersing device of the type shown in Table 5 and perform the second treatment under the conditions shown in Table 5 to obtain a dispersion. The measurement results of the viscosity, the evaluation results of the viscosity stability, and the results of the aggregate observation of the obtained dispersion are shown in Table 6.

[0239] (Examples 33 and 34)

[0240] In a plastic cup (made of polyethylene) with a capacity of 500 mL, add each component (except CNT) of the types and amounts shown in Table 4. After stirring until it becomes uniform, add CNT of the types and amounts shown in Table 4 and stir further. Place a magnetic stir bar in the plastic cup and stir with a magnetic stirrer for 12 hours to obtain a wet mixture. For the obtained wet mixture, use the dispersion device of the type shown in Table 5 and perform the first treatment under the conditions shown in Table 5. After that, use the dispersion device of the type shown in Table 5 and perform the second treatment under the conditions shown in Table 5 to obtain a dispersion. The measurement results of the viscosity of the obtained dispersion, the evaluation results of viscosity stability, and the results of aggregate observation are shown in Table 6.

[0241] Table 4

[0242]

[0243] Table dispersion

[0244]

[0245] Table 6

[0246]

[0247] (Example 35)

[0248] In a plastic cup (made of polyethylene) with a capacity of 500 mL, add each component (except CNT) of the types and amounts shown in Table 7. After stirring until it becomes uniform, add CNT of the types and amounts shown in Table 7 and stir further. Place a magnetic stir bar in the plastic cup and stir with a magnetic stirrer for 12 hours to obtain a wet mixture. For the obtained wet mixture, use dispersion device A1 and perform the first treatment (i) 2 passes under the conditions of nozzle inner diameter D1 0.3 mm and treatment pressure 2 - 50 MPa. After that, use dispersion device A2 and perform the second treatment (i) 2 passes under the conditions of nozzle inner diameter D2 0.1 mm and treatment pressure 150 MPa to obtain a dispersion. For the obtained dispersion, add the additional CNT of the types and amounts shown in Table 7 and stir further. Place a magnetic stir bar in the plastic cup and stir with a magnetic stirrer for 12 hours to obtain a wet mixture. For the obtained wet mixture solution, use dispersion device A1 and perform the first treatment (ii) 2 passes under the conditions of nozzle inner diameter D1 0.3 mm and treatment pressure 2 - 50 MPa. After that, use dispersion device A2 and perform the second treatment (ii) 4 passes under the conditions of nozzle inner diameter D2 0.1 mm and treatment pressure 150 MPa to obtain a dispersion. The measurement results of the viscosity of the obtained dispersion, the evaluation results of viscosity stability, and the results of aggregate observation are shown in Table 8.

[0249] Table 7

[0250]

[0251] Table 8

[0252]

[0253] (Reference Example)

[0254] When considering taking Example 35 as a reference, the following methods can be cited: a method of separately adding a dispersant before the wetting step (ii) instead of adding the total amount in the initial compounding; a method of performing treatment under conditions of a device different from that of the first dispersion step in the second dispersion step; etc. (for example, only using dispersion device A1 or A2 in the first treatment (ii) and the second treatment (ii), only using dispersion device A1 or A2 in all dispersion steps, making the nozzle diameter D1 0.44 mm, and the nozzle diameter D2 0.15 mm, etc.). When preparing a carbon dispersion liquid by any method, a dispersion liquid with physical property values within the scope of the examples can be obtained. Furthermore, by performing this operation multiple times, the carbon material concentration can also be increased.

[0255] The absorbance of a part of the dispersion liquids produced in the examples and comparative examples was measured, and the absorbance ratio (A 380 / A 780 ) was calculated. The results are shown in Table 9. As shown in Table 9, the higher the value of the absorbance ratio, the better the viscosity stability, and the less tendency of aggregates to be confirmed. Therefore, the higher the value of the absorbance ratio, the better the dispersibility.

[0256] Table 9

[0257]

[0258] <Preparation and Evaluation of Dispersion Liquid (3)>

[0259] (Examples 36 - 41, Comparative Examples 28 - 31)

[0260] Using NMP as an aqueous liquid medium, the components (other than CNT) of the types and amounts shown in Table 10 were added to a plastic cup (polyethylene cup) with a capacity of 500 mL. After stirring until uniform, CNT of the types and amounts shown in Table 10 was added and further stirred. A magnetic stirrer was placed in the plastic cup and stirred for 12 hours to obtain a wet mixture. For the obtained wet mixture, the first treatment was carried out using the dispersion device of the type shown in Table 11 under the conditions shown in Table 11. After that, the second treatment was carried out using the dispersion device of the type shown in Table 11 under the conditions shown in Table 11 to obtain a dispersion liquid. The absorbance ratio (A 380 / A 780) The measurement results of viscosity, the evaluation results of viscosity stability, and the results of aggregate observation are shown in Table 12.

[0261] (Example 42)

[0262] Using NMP as the aqueous liquid medium, add each component (except CNT) of the type and amount shown in Table 10 to a plastic cup (polyethylene cup) with a capacity of 500 mL. After stirring until uniform, add CNT of the type and amount shown in Table 10 and stir further. Place a magnetic stir bar in the plastic cup and stir with a magnetic stirrer for 1 hour, then perform 2 treatments with a homogenizer (manufactured by SMT CO., LTD.) to obtain a wet mixture. For the obtained wet mixture, perform the first treatment under the conditions shown in Table 11 using the type of dispersion device shown in Table 11. After that, perform the second treatment under the conditions shown in Table 11 using the type of dispersion device shown in Table 11 to obtain a dispersion. The absorbance ratio (A 380 / A 780 ) The measurement results of viscosity, the evaluation results of viscosity stability, and the results of aggregate observation are shown in Table 12.

[0263] Table 10

[0264]

[0265] Table 11

[0266]

[0267] Table 12

[0268]

[0269] As described above, perform the dispersion treatment so that the absorbance ratio (A 380 / A 780 ) becomes 1.60 or more. Thus, even if the composition and dispersion process are different, the original performance of the carbon material containing carbon nanotubes can be fully exerted, and a dispersion with excellent viscosity stability and substantially no observable aggregates can be obtained.

[0270] (Application Example 1-1: Manufacturing method at scale-up)

[0271] Add 1000 parts of dispersant a and 8800 parts of water to a 20 L stainless steel container. Stir with a dissolver until it becomes uniform, and while keeping the stirring unchanged, add 200 parts of CNT-E little by little, and further stir. Use a homogenizer (manufactured by SMT Co., Ltd.) to perform 4 passes of treatment in a circulation form and mix well. Then, use a high-pressure homogenizer (manufactured by Changguang Co., Ltd.) equipped with a nozzle with an inner diameter of 0.44 mm, and perform a time treatment equivalent to 10 passes under the condition of a treatment pressure of 2 to 50 MPa in a circulation form. After that, use a high-pressure homogenizer (manufactured by SUGINO MACHINE LIMITED) equipped with a nozzle with an inner diameter of 0.1 mm, and perform a time treatment equivalent to 5 passes in a circulation form for the high-pressure treatment. The absorbance ratio (A 380 / A 780 ) of the obtained dispersion becomes 1.811. In addition, the viscosity of the obtained dispersion is 9.1 mPa·s, and the viscosity after 10 days is 8.8 mPa·s. The evaluation results of viscosity stability and the results of aggregate observation are both "◎".

[0272] (Application Example 2-1: Battery Material (Negative Electrode))

[0273] When manufacturing the negative electrode of a lithium-ion battery, use the following materials.

[0274] [Negative Electrode Activator]

[0275] · Graphene (FUJIFILM Wako Chemicals Corporation)

[0276] · Silicon monoxide (FUJIFILM Wako Chemicals Corporation)

[0277] [Binder]

[0278] · 10% aqueous polyacrylic acid solution (trade name "CLPA-C07", FUJIFILM Wako ChemicalsCorporation)

[0279] · Carboxymethyl cellulose (trade name "CMC DAICEL 2200", manufactured by DAICEL MIRAIZU LTD.)

[0280] Use a planetary mixer to mix 15 parts of silicon monoxide, 85 parts of graphene, 3 parts of the dispersion liquid manufactured in Example 7, 30 parts of 10% aqueous polyacrylic acid solution, and 2 parts of carboxymethyl cellulose to obtain a negative electrode material. The unit area weight after drying becomes 15 mg / cm 2In the following manner, a negative electrode material was coated on a copper foil with a thickness of 20 μm using an applicator. After being placed in an oven set at 120 °C for 30 minutes to dry, it was rolled using a rolling press to obtain a negative electrode. The volume resistivity of the obtained negative electrode was 0.2 Ω·cm.

[0281] (Application Example 2-2: Battery Material (Negative Electrode))

[0282] Using the dispersion liquid produced in Comparative Example 2, a negative electrode was produced in the same manner as in Application Example 2-1 described above. The volume resistivity of the produced negative electrode was 0.6 Ω·cm. From the above, it can be seen that by using a dispersion liquid with good dispersion evaluation, a negative electrode with a smaller volume resistivity value can be produced.

[0283] (Application Example 3-1: Antistatic Coating Agent)

[0284] 100 g of the dispersion liquid produced in Example 7, 100 g of a polymer binder (trade name “NeoPacR-9699”, manufactured by Kusumoto Chemical Co., Ltd., acrylic urethane resin), and 800 g of pure water were added to a plastic cup and stirred using a dissolver to obtain an antistatic coating agent. Using a bar coater, the obtained antistatic coating agent was coated on the surface of a polyethylene terephthalate film (manufactured by Toray) with a thickness of 38 μm such that the dried coating film became 0.5 μm. It was placed in an oven set at 80 °C for 10 minutes to dry, obtaining an antistatic coated film. The surface resistivity of the obtained film was 7×10 7 Ω / cm 2 .

[0285] (Application Example 3-2: Antistatic Coating Agent)

[0286] Using the dispersion liquid produced in Comparative Example 2, an antistatic coated film was produced in the same manner as in Application Example 3-1 described above. The surface resistivity of the produced film was 9×10 8 Ω / cm 2 . From the above, it can be seen that by using a dispersion liquid with good dispersion evaluation, an antistatic coated film with a smaller surface resistivity value can be produced.

[0287] Industrial Applicability

[0288] According to the manufacturing method of the present invention, it is useful as a constituent material for coatings, inks, resin molded products, etc. that exhibit characteristics such as high conductivity and high thermal conductivity, and a carbon material dispersion liquid suitable for various uses such as battery materials, electronic component trays, covers for IC chips, electromagnetic wave shields, automotive components, and robot components can be produced.

Claims

1. A method for manufacturing a carbon material dispersion liquid, comprising the following steps: Step (1), stirring a raw material containing a carbon material including carbon nanotubes, a dispersant, and a liquid medium to obtain a wet mixture; and Step (2), using a high-pressure homogenizer to disperse the wet mixture, The high-pressure homogenizer is at least any one of a high-pressure homogenizer (A1) in a manner that causes the wet mixture that has been pressurized and ejected to collide with each other to be granulated into fine particles, and a high-pressure homogenizer (A2) in a manner that introduces the pressurized wet mixture into a collision chamber to be granulated into fine particles, Disperse the wet mixture in a manner that satisfies the following dispersion conditions, [Dispersion conditions] After performing the following first treatment X times, perform the following second treatment Y times, The first treatment is as follows: Using any one of the high-pressure homogenizer (A1) and the high-pressure homogenizer (A2), apply a treatment pressure of 1 to 100 MPa to the wet mixture to granulate it into fine particles, and discharge it from a discharge nozzle with a nozzle inner diameter D1, The second treatment is as follows: Using any one of the high-pressure homogenizers (A1) and the high-pressure homogenizer (A2), the wet mixture is granulated into fine particles by applying a treatment pressure of 120 to 250 MPa, and discharged from a discharge nozzle having a nozzle inner diameter D2, wherein, D1 > D2, X ≥ 2, 2 ≤ Y ≤ 30, Wherein, the liquid medium is a water-soluble organic solvent that substantially does not contain water, The dispersant is the following polymer, The polymer contains: structural unit (A) derived from monomer A represented by the following general formula (A) 3 to 55% by mass; structural unit (B) derived from monomer B represented by the following general formula (B) 30% by mass or less; structural unit (C) derived from monomer C represented by the following general formula (C) 45 to 90% by mass; and structural unit (D) derived from monomer D copolymerizable with these monomers 0.5 to 20% by mass, The amine value of the polymer is 100 mgKOH / g or less, and the number average molecular weight is 5000 to 20000, In the general formula (A), R represents a hydrogen atom or a methyl group, A represents O or NH, B represents an ethylene group or a propylene group, R1 and R2 independently represent a methyl group or an ethyl group, Ar represents a phenyl group, a naphthyl group, an anthracenyl group, or a pyrenyl group, X represents a chlorine atom, a bromine atom, bis(trifluoromethyl)sulfonimide, or bis(nonafluorobutanesulfonyl)imide, In the general formula (B), R represents a hydrogen atom or a methyl group, A represents O or NH, B represents an ethylene group or a propylene group, R1 and R2 independently represent a methyl group or an ethyl group, In the general formula (C), R represents a hydrogen atom or a methyl group, A represents O or NH, Q represents an ethylene group or a methylethylene group, Y represents O, NHCOO, or NHCONH, m and n independently represent the average number of repeating units of 0 or more and m + n = 20 to 100, R3 represents an alkyl group, an aryl group, or an alkylaryl group having 1 to 18 carbon atoms.

2. The method for manufacturing the carbon material dispersion according to claim 1, wherein, The nozzle inner diameter D1 is 0.15 to 2.0 mm, and the nozzle inner diameter D2 is 0.1 to 1.0 mm.

3. The method for manufacturing a carbon material dispersion liquid according to claim 1 or 2, wherein, In the raw material, relative to 100 parts by mass of the carbon material, the content of the dispersant is 10 to 500 parts by mass, In the raw material, the content of the carbon material is 10% by mass or less, In the raw materials, the content of the dispersant is 30% by mass or less.

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