Method for producing conductive composition

Abstract

To provide a method for producing a conductive composition by which conductive coating having excellent conductivity can be formed.SOLUTION: A method for producing a conductive composition includes the following steps (i) to (iii): (i) a step of mixing carbon nano-tubes, dispersant and aqueous diluent to obtain preliminary dispersion liquid; (ii) a step of dispersing the preliminary dispersion liquid to obtain dispersion liquid; and (iii) a step of adding one or more selected from a group consisting of basic compound, aqueous diluent and aqueous binder to the dispersion liquid, in this order, and also includes the following step (iv): (iv) a step of maturing the dispersion liquid for 50 to 10000 hours at 1 to 40°C, between at least step (ii) and step (iii) or after step (iii).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a conductive composition. [Background technology]

[0002] Carbon nanotubes are a material with excellent conductivity and durability, and are expected to be used in a variety of applications requiring conductivity. Conductive coating compositions containing carbon nanotubes have been investigated to form conductive thin films. For example, Patent Document 1 describes a coating composition containing (a) a carbon nanomaterial, (b) a binder resin, (c) a leveling agent, and (d) an organic solvent. However, for example, when a conductive coating composition contains a binder, the conductivity of the conductive composition may become insufficient. For these reasons, there is a demand for improving the conductivity of conductive coating compositions containing carbon nanotubes.

[0003] In addition to carbon nanotubes, conductive polymers are known as materials that can impart conductivity to thin films. Patent Documents 2 and 3 describe methods for producing conductive compositions, which include a step of aging a dispersion containing a conductive polymer that is a complex of poly(3,4-disubstituted thiophene) and a polyanion. However, Patent Documents 2 and 3 do not describe conductive compositions containing carbon nanotubes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-189857 [Patent Document 2] Patent Publication No. 2021-116370 [Patent Document 3] Patent Publication No. 2021-014113 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing a conductive composition that can form a conductive coating film with excellent conductivity. [Means for solving the problem]

[0006] The present inventors have discovered that a conductive composition capable of forming a conductive coating film with excellent conductivity can be obtained by aging a dispersion containing carbon nanotubes and a dispersant at 1 to 40°C for 50 to 10,000 hours, and have completed the present invention.

[0007] That is, the present invention provides the following steps (i) to (iii): (i) mixing carbon nanotubes, a dispersant, and an aqueous diluent to obtain a pre-dispersion; (ii) dispersing the preliminary dispersion to obtain a dispersion; and (iii) adding one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder to the dispersion; in this order, At least between step (ii) and step (iii) or after step (iii), The following step (iv): (iv) Aging the dispersion at 1 to 40°C for 50 to 10,000 hours The present invention relates to a method for producing a conductive composition, comprising:

[0008] In the above production method, the aqueous diluent in step (i) or (iii) is preferably a mixed solvent of water and a water-soluble organic solvent.

[0009] In the above-described production method, the dispersant is preferably an anionic dispersant or a nonionic dispersant.

[0010] In the above production method, it is preferable to carry out step (iv) between step (ii) and step (iii).

[0011] In the above production method, it is preferable that an aqueous diluent is added to the dispersion in step (iii), and step (iv) is carried out after step (iii).

[0012] The present invention also provides a method for producing a conductive composition, comprising: applying a conductive composition onto a substrate; and A step of drying the applied conductive composition to form a conductive coating film. Including, The present invention relates to a method for producing a conductive laminate. [Effects of the Invention]

[0013] According to the method for producing a conductive composition of the present invention, a conductive composition capable of forming a conductive coating film having excellent conductivity can be produced. DETAILED DESCRIPTION OF THE INVENTION

[0014] <<Method of manufacturing conductive composition>> The method for producing the conductive composition of the present invention includes the following steps (i) to (iii): (i) mixing carbon nanotubes, a dispersant, and an aqueous diluent to obtain a pre-dispersion; (ii) dispersing the preliminary dispersion to obtain a dispersion; and (iii) adding one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder to the dispersion; in this order, At least between step (ii) and step (iii) or after step (iii), The following step (iv): (iv) Aging the dispersion at 1 to 40°C for 50 to 10,000 hours Includes:

[0015] <Step (i) of Obtaining Preliminary Dispersion> In step (i), the carbon nanotubes, the dispersant, and the aqueous diluent are mixed to obtain a preliminary dispersion. The order in which the carbon nanotubes, the dispersant, and the aqueous diluent are mixed is not particularly limited.

[0016] <Carbon nanotubes> The type of carbon nanotube is not particularly limited, and any of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures containing these in any ratio can be used. Carbon nanotubes produced by known methods such as arc discharge, laser evaporation, and chemical vapor deposition (CVD) can be selected and used. Among these, single-walled carbon nanotubes are preferred because of their excellent conductivity.

[0017] The length of the carbon nanotubes is preferably 0.1 to 2000 μm, more preferably 0.5 to 1000 μm, and even more preferably 0.5 to 600 μm. If the length exceeds 2000 μm, the carbon nanotubes tend to aggregate, break, or be destroyed. If the length is less than 0.1 μm, the formation of conductive paths tends to be insufficient.

[0018] The diameter of the carbon nanotubes is preferably 0.1 to 50 nm, more preferably 0.3 to 20 nm, even more preferably 0.5 to 10 nm, and particularly preferably 0.5 to 5 nm. If the diameter exceeds 50 nm, the conductivity tends to decrease. Carbon nanotubes of less than 0.1 nm are difficult to produce. Within the range of 0.5 to 5 nm, it is easy to increase the conductivity while maintaining dispersibility.

[0019] The content of carbon nanotubes in the preliminary dispersion is preferably 0.1 to 60 wt %, more preferably 1 to 40 wt %, and even more preferably 5 to 20 wt %, based on the total solid content. The content of carbon nanotubes in the final conductive composition is preferably 0.01 to 30 wt %, more preferably 0.05 to 25 wt %, and even more preferably 0.1 to 20 wt % based on the total solid content. When the conductive composition contains an aqueous binder, the content of carbon nanotubes in the conductive composition is preferably 0.1 to 5 wt %, more preferably 0.1 to 3 wt %, and even more preferably 0.1 to 1 wt % based on the total solid content. When the conductive composition does not contain an aqueous binder, the content of carbon nanotubes in the conductive composition is preferably 1 to 30 wt %, more preferably 5 to 30 wt %, and even more preferably 10 to 30 wt % based on the total solid content. By setting the content within the above range, aggregation of carbon nanotubes can be suppressed.

[0020] <Dispersant> The dispersant has the function of suppressing aggregation of carbon nanotubes in the conductive composition and stably dispersing them. The dispersant may be any of cationic dispersants, anionic dispersants, amphoteric dispersants, nonionic dispersants, and polymeric dispersants, as long as it can suppress aggregation of carbon nanotubes. These may be used alone or in combination of two or more. Furthermore, the dispersant preferably has an HLB value of 7 or more, more preferably 9 or more. The HLB value can be calculated using the following formula: Griffin method: HLB value = [(molecular weight of hydrophilic portion) ÷ (total molecular weight)] × 20

[0021] Examples of cationic dispersants include alkylamine salts having an alkyl group with 8 to 22 carbon atoms, such as stearylamine acetate, and quaternary ammonium salts, such as lauryltrimethylammonium chloride and hexadecyltrimethylammonium bromide.

[0022] Examples of the anionic dispersant include sodium alkyl sulfates having 8 to 18 carbon atoms, such as sodium lauryl sulfate; polyoxyethylene alkyl ether sulfates having 8 to 18 carbon atoms, such as sodium polyoxyethylene lauryl ether sulfate; alkylbenzenesulfonates having an alkyl group having 8 to 18 carbon atoms, such as sodium deoxycholate and sodium dodecylbenzenesulfonate; fatty acid salts; and naphthalenesulfonate-formalin condensates, such as the sodium salt of β-naphthalenesulfonate-formalin condensate.

[0023] Examples of amphoteric dispersants include alkylbetaines having an alkyl group with 8 to 22 carbon atoms, and alkylamine oxides having an alkyl group with 8 to 18 carbon atoms.

[0024] Examples of nonionic dispersants include polyoxyethylene alkyl ethers having an alkyl group with 1 to 20 carbon atoms, block copolymers composed of ethylene oxide and propylene oxide, alkylphenol polyethylene glycol ethers having an alkyl group with 1 to 20 carbon atoms, polyoxyalkylene derivatives such as polycarboxylate ethers having an alkylene group with 2 to 4 carbon atoms, and sorbitan fatty acid esters such as sorbitan tristearate.

[0025] Examples of polymeric dispersants include polyvinylpyrrolidone, polyvinyl alcohol, hydroxycellulose, hydroxyalkylcellulose having an alkyl group with 1 to 8 carbon atoms, cellulose derivatives such as carboxymethylcellulose and carboxypropylcellulose, starch, gelatin, acrylic copolymers, sulfonic acid group-containing polymers, and carboxylic acid group-containing polymers.

[0026] Among polymeric dispersants, sulfonic acid group-containing polymers are polymeric compounds having sulfonic acid in the side chain of the main skeleton, such as fluorine-based polymers having sulfonic acid and hydrocarbon-based polymers having sulfonic acid. Fluorine-based polymers having sulfonic acid include perfluorosulfonic acid polymers and partially fluorinated sulfonic acid polymers. Hydrocarbon-based polymers having sulfonic acid include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyisoprene sulfonic acid, sulfoethylated corn starch, polyester sulfonic acid, polyimide sulfonic acid, polyvinylidene fluoride sulfonic acid, polyether sulfonic acid, polyphenylene sulfide sulfonic acid, polyphenylene oxide sulfonic acid, polyethylene naphthalate sulfonic acid, polypyrrole sulfonic acid, aromatic sulfonic acid polymers, and bisphenol fluorene sulfonic acid. Among these, perfluorosulfonic acid polymers and polystyrene sulfonic acid are preferred, with Nafion (NAFION (registered trademark, manufactured by DuPont), Aquivion (registered trademark, manufactured by Solvay Specialty Polymers), and polystyrene sulfonic acid being more preferred. The weight-average molecular weight of the polymeric sulfonic acid is preferably 1,000 to 200,000, and more preferably 75,000 to 100,000.

[0027] From the viewpoint of dispersion stability of carbon nanotubes, the dispersant is preferably an anionic dispersant or a nonionic dispersant, more preferably an alkylbenzene sulfonate having an alkyl group with 8 to 18 carbon atoms or a polyoxyalkylene derivative, and even more preferably sodium dodecylbenzene sulfonate, or a polyoxyethylene alkyl ether having an alkyl group with 1 to 20 carbon atoms, a block copolymer composed of ethylene oxide and propylene oxide, an alkylphenol polyethylene glycol ether having an alkyl group with 1 to 20 carbon atoms, or a polycarboxylate ether having an alkylene group with 2 to 4 carbon atoms.

[0028] The content of the dispersant is preferably 10 to 10,000 parts by weight, more preferably 100 to 4,000 parts by weight, and even more preferably 400 to 2,000 parts by weight, per 100 parts by weight of the solid content of the carbon nanotubes. Within this range, the coating film tends to have excellent conductivity.

[0029] <Aqueous diluent> The aqueous diluent is added to the preliminary dispersion and the dispersion for adjusting the solid content, stabilizing the dispersion of the conductive composition, and improving the efficiency of step (iv). Examples of the aqueous diluent include water and water-soluble organic solvents.

[0030] Examples of water-soluble organic solvents include alcohols, ethylene glycols, and amide compounds. Examples of alcohols include ethanol, methanol, 2-propanol, and 1-propanol. Examples of ethylene glycols include ethylene glycol, diethylene glycol, trimethylene glycol, triethylene glycol, and tetraethylene glycol. Examples of amide compounds include acetonitrile, N-methylformamide, N,N-dimethylformamide, γ-butyrolactone, and N-methylpyrrolidone. A mixed solvent of water and a water-soluble organic solvent may be used as the aqueous diluent. When a mixed solvent is used, the concentration of the water-soluble organic solvent is preferably 0.5 to 70% by weight, more preferably 1 to 60% by weight, and even more preferably 1 to 50% by weight.

[0031] The aqueous diluent is preferably a mixed solvent of water and alcohol, more preferably a mixed solvent of water and ethanol.

[0032] When the aqueous diluent contains a water-soluble organic solvent, the amount of the water-soluble organic solvent added is preferably 1 wt % or more, more preferably 2 wt % or more, and even more preferably 5 wt % or more of the total conductive composition. If the amount is less than 1 wt %, the surface resistivity of the coating film tends to be too high, the rate of change in surface resistivity tends to be large, and the coatability during film formation tends to be poor.

[0033] The solid content of the preliminary dispersion can be adjusted by adjusting the amount of aqueous diluent added in step (i). The solid content of the preliminary dispersion is preferably 0.1 to 30 wt %, more preferably 0.2 to 10 wt %, and even more preferably 0.5 to 1 wt %. When the solid content is within the above range, dispersion in step (ii) can be carried out efficiently, and aggregation of carbon nanotubes can be suppressed.

[0034] <Step (ii) of Obtaining Dispersion Liquid> In step (ii), the preliminary dispersion obtained in step (i) is dispersed to obtain a dispersion. In step (ii), the preliminary dispersion obtained in step (i) is preferably subjected to a disperser to obtain a dispersion.

[0035] The preliminary dispersion can be dispersed using, for example, a vibration mill, a planetary mill, a ball mill, a bead mill, a sand mill, a jet mill, a roll mill, a homogenizer, an ultrasonic homogenizer, a high-pressure homogenizer, an ultrasonic device, etc. In order to obtain a conductive composition that can exhibit high conductivity, it is preferable to use at least one of an ultrasonic homogenizer or a high-pressure homogenizer.

[0036] The pH condition during dispersion of the preliminary dispersion is preferably 0.5 to 6.0, more preferably 1.0 to 3.0, and even more preferably 1.5 to 2.5. The temperature condition is preferably 0 to 40°C, more preferably 5 to 30°C. The dispersion time is preferably 0.02 to 2 hours, and more preferably 0.2 to 1 hour. After dispersion of the carbon nanotubes, aggregates remaining in the dispersion may be removed by centrifugation or filtration, if necessary.

[0037] After step (i) of obtaining a preliminary dispersion and before step (ii) of obtaining a dispersion, a pre-dispersion step may be performed as a pretreatment step, in which a mixture of carbon nanotubes and a dispersant is subjected to high-speed stirring. The high-speed stirring in the pre-dispersion step is preferably performed under milder conditions than in a dispersion step using an ultrasonic homogenizer or the like. By performing the pre-dispersion step, the aggregation of carbon nanotubes can be loosened, thereby improving the dispersion efficiency of the carbon nanotubes in the subsequent dispersion step. The time for high-speed stirring in the pre-dispersion step can be appropriately set depending on the amount of the mixture to be treated. For example, in the case of 500 to 1000 mL, it is preferably within 1 hour, more preferably within 30 minutes, even more preferably within 10 minutes, and particularly preferably within 5 minutes.

[0038] <Step (iii) of adding one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder> In step (iii), one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder is added to the dispersion obtained in step (ii).

[0039] <Basic compounds> A basic compound may be blended into the dispersion. This is because, if an aqueous binder is added directly to an acidic dispersion, aggregation may occur depending on the type of aqueous binder, and aggregation is particularly pronounced at high concentrations during drying after film formation. The pH of the dispersion is preferably adjusted to 4 to 10 by blending a basic compound, more preferably 5 to 9, and even more preferably 6 to 9. The type of basic compound is not particularly limited, but examples include bases containing alkali metals or alkaline earth metals, NH3, nitrogen-based aliphatic compounds, and nitrogen-based aromatic compounds. It is not necessary to add a basic compound when using an aqueous binder that can crosslink under acidic conditions or when sufficient corrosion protection measures are in place for the film-forming equipment.

[0040] Examples of bases containing alkali metals or alkaline earth metals include sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, sodium bicarbonate, and potassium bicarbonate. Examples of nitrogen-based aliphatic compounds include triethanolamine, ethanolamine, diethanolamine, dimethylamine, diethylamine, dipropylamine, trimethylamine, triethylamine, and tripropylamine. Examples of nitrogen-based aromatic compounds include imidazole, 2-methylimidazole, 2-propylimidazole, 1-(2-hydroxyethyl)imidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-aminobenzimidazole, pyridine, aniline, and toluidine. The basic compounds may be used alone or in combination of two or more. Among these, a base containing an alkali metal or an alkaline earth metal is preferred, a base containing an alkali metal is more preferred, and sodium hydroxide is even more preferred. The amount of the basic compound added is not particularly limited as long as it achieves a predetermined pH in the final conductive composition.

[0041] <Aqueous diluent> The aqueous diluent used in step (iii) can be the same as the aqueous diluent used in step (i). Alternatively, the aqueous diluent used in step (iii) may be a mixed solvent containing the same types of water and water-soluble organic solvent as the aqueous diluent used in step (i), but with a different blending ratio. For example, the aqueous diluent used in step (iii) may have a higher or lower ratio of water-soluble organic solvent than the aqueous diluent used in step (i). The aqueous diluent used in step (iii) may be different from the aqueous diluent used in step (i).

[0042] The aqueous diluent used in step (iii) is preferably a mixed solvent of water and alcohol, more preferably a mixed solvent of water and ethanol.

[0043] The solid content of the dispersion can be adjusted by adjusting the amount of aqueous diluent added in step (iii). The solid content of the dispersion is preferably 0.001 to 10%, more preferably 0.01 to 5%. When the solid content is within the above range, aggregation of the carbon nanotubes can be suppressed.

[0044] <Water-based binder> The addition of an aqueous binder can improve the film-forming properties and strength of the coating film formed from the conductive composition. Examples of aqueous binders include acrylic resins, polyether resins, polyester resins, polyurethane resins, polyolefin resins, siloxanes, and melamine resins. The aqueous binder is preferably soluble or dispersible in water to facilitate blending with carbon nanotubes. The aqueous binder may be a resin that has been solubilized or dispersed as a result of being imparted with a hydrophilic functional group, or a resin that has been forcibly solubilized or dispersed using an emulsifier. These may be used alone or in combination of two or more.

[0045] Examples of acrylic resins include (meth)acrylic resins and vinyl ester resins. These acrylic resins may be polymers containing, as constituent monomers, polymerizable monomers having an acid group such as a carboxyl group, an acid anhydride group, a sulfonic acid group, or a phosphoric acid group, and a fluoro group such as a perfluoroalkyl group or a perfluoroalkenyl group. Examples of such polymers include homopolymers or copolymers of polymerizable monomers having an acid group, and copolymers of polymerizable monomers having an acid group and copolymerizable monomers.

[0046] The (meth)acrylic resin may be polymerized with a copolymerizable monomer as long as it contains a (meth)acrylic monomer as the main constituent monomer (for example, 50 mol % or more). At least one of the (meth)acrylic monomer and the copolymerizable monomer preferably has an acid group.

[0047] Examples of the (meth)acrylic resin include (meth)acrylic monomers having an acid group [(meth)acrylic acid, sulfoalkyl (meth)acrylate, sulfonic acid group-containing (meth)acrylamide, etc.] or copolymers thereof, copolymers of (meth)acrylic monomers which may have an acid group with other polymerizable monomers having an acid group [other polymerizable carboxylic acids, polymerizable polycarboxylic acids or anhydrides, vinyl aromatic sulfonic acids, etc.] and / or copolymerizable monomers [for example, (meth)acrylic acid alkyl esters, glycidyl (meth)acrylate, (meth)acrylonitrile, aromatic vinyl monomers, etc.] ... with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with other polymerizable monomers having an acid group with and copolymers of other polymer monomers having an acid group with (meth)acrylic copolymerizable monomers [for example, (meth)acrylic acid alkyl esters, hydroxyalkyl (meth)acrylates, glycidyl (meth)acrylates, (meth)acrylonitrile, etc.], (meth)acrylic monomers not having an acid group [alkyl (meth)acrylates, aryl (meth)acrylates, fluorene-based (meth)acrylates, etc.] or copolymers thereof, rosin-modified urethane acrylate, specially modified acrylic resins, urethane acrylate, epoxy acrylate, urethane acrylate emulsion, etc.

[0048] Among these (meth)acrylic resins, (meth)acrylic acid-(meth)acrylic acid ester polymers (acrylic acid-methyl methacrylate copolymers, etc.), (meth)acrylic acid-(meth)acrylic acid ester-styrene copolymers (acrylic acid-methyl methacrylate-styrene copolymers, etc.), etc. are preferred.

[0049] Examples of polyether resins include polyalkylene glycols, polyvinyl alcohols, polyether polyols, polyglycerin, pullulan, and derivatives thereof. These polyether resins may have an acid group such as a carboxyl group, an acid anhydride group, a sulfonic acid group, or a phosphoric acid group, a fluoro group such as a perfluoroalkyl group or a perfluoroalkenyl group, and an alkyl group or an alkenyl group.

[0050] The polyester resin is not particularly limited as long as it is a polymeric compound obtained by a method of polycondensing a compound having two or more carboxyl groups in the molecule with a compound having two or more hydroxyl groups, a method of direct dehydration polycondensation of a hydroxycarboxylic acid, or a method of ring-opening polymerization of a cyclic ester of a hydroxycarboxylic acid. For example, compounds having two or more hydroxyl groups (diol components) include aliphatic diols, alicyclic diols, aromatic diols, (poly)carbonate diols, polyether diols, and polyester diols. Compounds having two or more carboxyl groups in the molecule (dicarboxylic acid components) include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and alicyclic dicarboxylic acids. Cyclic esters of hydroxycarboxylic acids include lactide, glycolide, and ε-caprolactone. General names for the resulting polymeric compounds include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. These polyester resins may have an acid group such as a carboxyl group, an acid anhydride group, a sulfonic acid group or a phosphoric acid group, a fluoro group such as a perfluoroalkyl group or a perfluoroalkenyl group, an alkyl group or an alkenyl group.

[0051] The polyurethane resin is not particularly limited as long as it is a polymeric compound obtained by copolymerizing a compound having an isocyanate group and a compound having a hydroxyl group, and examples thereof include ester-ether polyurethane resins, ether polyurethane resins, polyester polyurethane resins, carbonate polyurethane resins, and acrylic polyurethane resins. These polyurethane resins may contain nonionic, anionic, or cationic hydrophilic polar groups. Sources for introducing the hydrophilic polar groups include linear nonionic hydrophilic polar groups such as poly(oxyethylene) polyols, anionic hydrophilic polar groups such as -COOM and -SO3M (where M represents an alkali metal, ammonium group, or organic amine), and cationic hydrophilic polar groups such as quaternary ammonium salts.

[0052] Examples of polyolefin resins include polyethylene, polypropylene, poly-4-methyl-1-pentene, poly-1-butene, chlorinated polypropylene, maleic anhydride-modified polypropylene, maleic anhydride-modified chlorinated polypropylene, etc. These polyolefin resins may be copolymers with α-olefin comonomers such as butene-1, pentene-1, hexene-1, heptene-1, octene-1, cyclopentene, cyclohexene, and norbornene, or comonomers such as vinyl acetate, acrylic esters, and methacrylic esters, and may have hydrophilic polar groups introduced therein, such as a carboxylic acid group (—COOH), a sulfo group (—SOH), a sulfino group (—SOH), a phosphono group (—POH), a vinyl alcohol chain, a vinylpyrrolidone chain, or an ether chain.

[0053] Examples of siloxanes include alkoxysilane monomers represented by the following formula (II), and alkoxysilanes that have been previously polymerized by condensation of these monomers and have one or more siloxane bonds (Si-O-Si) in each molecule. SiR4(II) (In the formula, R represents hydrogen, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group which may have a substituent, or a phenyl group which may have a substituent, provided that at least one of the four Rs is an alkoxy group having 1 to 4 carbon atoms or a hydroxyl group.) When an alkoxysilane monomer is used, it may be added to the conductive composition and then polymerized in the conductive composition.

[0054] The structure of the siloxane is not particularly limited and may be linear or branched. Furthermore, the siloxane may be a compound represented by formula (II) used alone or in combination of two or more. These siloxanes may be modified with a polyether group, a polyalkyl group, a polyester group, or a polyol group. The modification may be linear or branched. The weight-average molecular weight of the siloxane is not particularly limited, but is preferably greater than 4,000 and not greater than 500,000, and more preferably 5,000 to 200,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC).

[0055] Examples of melamine resins include benzoguanamine-melamine-formaldehyde condensation products and melamine-formaldehyde condensation products. Commercially available melamine resins include Eposter manufactured by Nippon Shokubai Co., Ltd. and Bekkamin M-3 manufactured by DIC Corporation.

[0056] The content of the aqueous binder in the conductive composition is not particularly limited, but is preferably 100 to 200,000 parts by weight, more preferably 100 to 100,000 parts by weight, and even more preferably 500 to 50,000 parts by weight, relative to 100 parts by weight of the total amount of carbon nanotubes and dispersant, calculated as solid content. Within this range, sufficient conductivity can be ensured in the coating film formed from the conductive composition.

[0057] <Optional ingredients> In the present invention, optional components may be further added in any step, such as a leveling agent, a conductive polymer, a crosslinking agent, a catalyst, a water-soluble antioxidant, an antifoaming agent, a rheology control agent, a neutralizing agent, and a thickener.

[0058] Examples of the leveling agent include a silicone-based leveling agent, a fluorine-based leveling agent, a polyether-based leveling agent, a polyester-based leveling agent, and an acrylic-based leveling agent. Adding a leveling agent to the conductive composition can increase the affinity for the substrate and can suppress the occurrence of repelling or unevenness when forming a conductive coating film.

[0059] Examples of silicone leveling agents include polysiloxanes; reactive polysiloxanes into which reactive groups such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups have been introduced; and non-reactive polysiloxanes into which non-reactive groups such as alkyl groups, ester groups, aralkyl groups, phenyl groups, and polyether groups have been introduced.

[0060] Examples of fluorine-based leveling agents include perfluoropolyether-modified polydimethylsiloxane, perfluoropolyester-modified polydimethylsiloxane, perfluorobutanesulfonic acid, oligomers containing fluorine-containing groups, hydrophilic groups, and lipophilic groups, carboxylates containing perfluoroalkyl groups, and phosphate esters containing perfluoroalkyl groups and phosphate groups.

[0061] Examples of polyether-based leveling agents include cellulose ether; pullulan; polyethylene glycol; silicone-modified polyethers such as polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, and polyether-modified acrylic group-containing polydimethylsiloxane; polyglycerin; polyether polyol, polyoxyethylene-polyoxypropylene condensate, polyoxyethylene alkylphenyl ether, alkyl ether derivatives such as lauryl alcohol alkoxylate, and alkyl ether sulfates.

[0062] Examples of polyester-based leveling agents include polyester-modified acrylic group-containing polydimethylsiloxane, polyester-modified polydimethylsiloxane, and polyester polyol.

[0063] Examples of the acrylic leveling agent include acrylic copolymers made of silicone and acrylic.

[0064] The content of the leveling agent is preferably 0.1 to 20 wt % of the total solid content of the conductive composition, and more preferably 1 to 10 wt %. Within this range, the coating properties on the substrate, the dispersion stability of the blended components, and the film strength when formed into a conductive coating film are good.

[0065] Examples of conductive polymers include polythiophene, polypyrrole, polyaniline, polyacetylene, polyphenylene vinylene, polynaphthalene, and derivatives thereof. Among these, conductive polymers containing at least one thiophene ring in the molecule are preferred because the inclusion of a thiophene ring in the molecule makes it easier to form molecules with high conductivity. The conductive polymer may form a complex with a dopant such as a polyanion. As a complex of a conductive polymer and a polyanion, a complex of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid is preferred because it has particularly excellent conductivity. When a conductive polymer is added, the amount added is preferably 1 to 10,000 parts by weight, more preferably 1 to 100 parts by weight, per 100 parts by weight of carbon nanotubes.

[0066] The crosslinking agent is not particularly limited, but examples thereof include melamine-based, carbodiimide-based, oxazoline-based, epoxy-based, isocyanate-based, and acrylate-based crosslinking agents. The content of the crosslinking agent in the conductive composition is preferably 30% by weight or less, and more preferably 20% by weight or less. When the conductive composition contains a thermosetting binder and a crosslinking agent, the catalyst for crosslinking the thermosetting binder is not particularly limited, and examples thereof include an acid catalyst, a base catalyst, a photopolymerization initiator, and a thermal polymerization initiator.

[0067] <Aging process (iv)> In step (iv), at least between step (ii) and step (iii) or after step (iii), the dispersion is aged for 50 to 10,000 hours at 1 to 40° C. In the present invention, it is believed that the step of aging the dispersion at 1 to 40° C. for 50 to 10,000 hours allows the dispersant to be adsorbed to or blended with the carbon nanotubes, thereby improving the conductivity of the conductive composition and the conductive coating film, but the present invention is not limited to this mechanism.

[0068] The aging temperature is 1 to 40° C., preferably 5 to 40° C., and more preferably 15 to 35° C. If the temperature is below 1° C., the dispersion will freeze, and if the temperature exceeds 40° C., the carbon nanotubes will aggregate, which will tend to impair the coatability, conductivity, and transparency.

[0069] The aging time is 50 to 10,000 hours, preferably 100 to 5,000 hours, more preferably 200 to 3,000 hours, and even more preferably 300 to 1,000 hours. If the aging time is less than 50 hours, the conductivity of the conductive composition and the conductive coating film tends to be poor. If the aging time exceeds 10,000 hours, the carbon nanotubes tend to aggregate, resulting in poor conductivity of the conductive composition and the conductive coating film. The aging is preferably carried out by placing the dispersion in a container and leaving it in a shaded location or by applying weak friction as appropriate. Examples of the container include glass containers, stainless steel containers, and plastic containers made of polyethylene terephthalate, polyarylate, polyethylene naphthalate, polycarbonate, polyethylene, polytetrafluoroethylene, polypropylene, polybutylene terephthalate, polyimide, polymethylpentene, polystyrene, copolymers of monomers constituting these, and combinations of two or more of these materials. Plastic containers are preferred. Stirring is preferably avoided because it inhibits the dispersant from adsorbing or blending with the carbon nanotubes, reducing aging efficiency.

[0070] Step (iv) may be performed both between step (ii) and step (iii) and after step (iii), or only between step (ii) and step (iii), or only after step (iii). When aging is performed for 50 to 10,000 hours between step (ii) and step (iii), the aging time after step (iii) may be less than 50 hours. When aging is performed for 50 to 10,000 hours after step (iii), the aging time between step (ii) and step (iii) may be less than 50 hours. It is preferable that the aging time in step (iv) between step (ii) and step (iii) and in step (iv) after step (iii) does not exceed 10,000 hours.

[0071] When an aqueous binder is added to the dispersion in step (iii), it is preferable to carry out step (iv) at least between steps (ii) and (iii). By carrying out step (iv) between steps (ii) and (iii) and allowing the dispersant to be adsorbed and intimately mixed with the carbon nanotubes, it is possible to prevent the addition of the aqueous binder from decreasing the conductivity of the conductive composition and the conductive coating film.

[0072] When an aqueous diluent is added to the dispersion in step (iii), step (iv) may be performed after step (iii). In particular, when an aqueous diluent is added to the dispersion without adding an aqueous binder in step (iii), it is preferable to perform step (iv) at least after step (iii). For example, when only an aqueous diluent is added to the dispersion in step (iii), it is preferable to perform step (iv) at least after step (iii). This can prevent the conductivity of the conductive composition and the conductive coating film from decreasing.

[0073] The solids concentration of the finally obtained conductive composition is preferably 0.001 to 10%, more preferably 0.01 to 8%, and the pH of the conductive composition is preferably 2 to 11, more preferably 6 to 11. Strong acidic conditions of less than pH 2 may cause metal corrosion in the production line, or the surface resistivity may increase if the coating film formed from the conductive composition is thin.

[0074] <<Method of manufacturing conductive laminate>> The method for producing a conductive laminate of the present invention includes the steps of obtaining a conductive composition by the above-mentioned method, applying the conductive composition to a substrate, and drying the applied conductive composition to form a conductive coating film. Because the conductive composition obtained by the above-mentioned method is used, the produced conductive coating film has high conductivity.

[0075] In the step of applying the conductive composition to a substrate, examples of the application method that can be used include roll coating, bar coating, dip coating, spin coating, casting, die coating, blade coating, bar coating, gravure coating, curtain coating, spray coating, doctor coating, slit coating, relief (letterpress) printing, stencil (screen) printing, lithographic (offset) printing, intaglio (gravure) printing, spray printing, inkjet printing, and pad printing. Before applying the conductive composition to the substrate, the surface of the substrate may be subjected to a surface treatment, if necessary. Examples of surface treatments include corona treatment, plasma treatment, itro treatment, and flame treatment. Alternatively, a primer layer or the like may be formed on the substrate, and then the conductive composition may be applied to the primer layer or the like.

[0076] Examples of materials for the substrate include glass, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, and modified polyester, polyolefin resins such as polyethylene (PE) resin, polypropylene (PP) resin, polystyrene resin, and cyclic olefin resin, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic (PMMA) resin, triacetyl cellulose (TAC) resin, and metals such as copper and aluminum.

[0077] The shape of the substrate is not particularly limited, but is preferably a film. The thickness of the film is preferably 10 to 10,000 μm, more preferably 25 to 5,000 μm. The total light transmittance of the substrate film is preferably 70% or more, more preferably 80% or more.

[0078] In the step of drying the applied conductive composition to form a conductive coating film, the solvent contained in the conductive composition is removed. The conductive composition is preferably dried by heating using a blast oven, infrared oven, vacuum oven, or the like. The temperature condition during heating is preferably 60 to 200°C, more preferably 80 to 180°C. The treatment time for the heat treatment is not particularly limited, but is preferably 0.1 to 20 minutes, more preferably 1 to 5 minutes.

[0079] In the produced conductive laminate, when the conductive composition contains an aqueous binder, the thickness of the conductive coating film is preferably 1 to 20,000 nm, more preferably 2 to 5,000 nm, and even more preferably 5 to 1,500 nm. When the conductive composition does not contain an aqueous binder, the thickness of the conductive coating film is preferably 0.1 to 100 nm, more preferably 0.5 to 50 nm, and even more preferably 1 to 20 nm. The thickness of the conductive coating film is calculated from the total solid content of the conductive composition and the amount applied to the substrate.

[0080] In the produced conductive laminate, the content of (A) carbon nanotubes in the conductive coating film is 0.2 to 50 mg / m 2 is preferred, and 2 to 5 mg / m 2 Within the above range, sufficient conductivity and strength can be imparted to the conductive coating film.

[0081] The produced conductive laminate has excellent conductivity and durability, and can therefore be suitably used in applications where these properties are required, such as electromagnetic wave shielding, solar power generation, transparent electrodes, antistatic properties, and batteries. [Example]

[0082] The present invention will be described below with reference to examples, but is not limited to the following examples. Hereinafter, "parts" and "%" mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

[0083] (Major materials used) 1. Carbon nanotubes Carbon nanotube dispersion (SW-CNT, Zeon Nano Technology Co., Ltd., ZEONANO SG101, length 300 μm, diameter 4 nm) 2. Dispersants Anionic dispersant (sodium dodecylbenzenesulfonate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Non-ionic dispersant (Genapol PF 80, a block copolymer of ethylene oxide and propylene oxide, manufactured by BASF, HLB value 19) 3. Basic compounds 10% NaOH (sodium hydroxide) solution 4. Aqueous diluents 30% ethanol solution 50% ethanol solution 5. Water-based binder Polyester resin (Toagosei, Aronmelt PES-2405A30, solid content 30%) Melamine resin (DIC Corporation, Beckamin M-3, solid content 77%) Acrylic resin (Toagosei, Jurimer FC-80, solid content 30%) 6. Base material Polyethylene terephthalate resin (Toray, Lumirror T60:PET) PMMA (acrylic resin film, (prepared in Manufacturing Example 1))

[0084] (Production Example 1) Production of PMMA (acrylic resin film) Pellets of a mixture (Tg 127°C) of 90 parts by weight of a (meth)acrylic resin having a lactone ring structure (comonomer weight ratio = methyl methacrylate / methyl 2-(hydroxymethyl)acrylate = 8 / 2, lactone cyclization rate approximately 100%, lactone ring structure content 19.4%, weight average molecular weight 133,000, melt flow rate 6.5 g / 10 min (240°C, 10 kgf), Tg 131°C) and 10 parts by weight of an acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) were fed into a twin-screw extruder and melt-extruded into a sheet at approximately 280°C to obtain a (meth)acrylic resin sheet having a lactone ring structure with a thickness of 110 μm. This unstretched sheet was stretched 2.0 times longitudinally and 2.4 times laterally at a temperature of 160° C. to obtain a PMMA substrate (thickness: 40 μm, in-plane retardation Δnd: 0.8 nm, thickness direction retardation Rth: 1.5 nm).

[0085] (1) Production of Conductive Compositions (Examples 1 to 12, Comparative Examples 1 to 4) (i) Preparation of the pre-dispersion The carbon nanotubes, dispersant, and aqueous diluent were mixed in the weight ratios shown in Table 1.

[0086] (ii) Dispersion of the preliminary dispersion The preliminary dispersion was pre-dispersed by stirring at 500 rpm for 5 minutes using a stirrer. Following pre-dispersion, the main dispersion was carried out. The main dispersion was carried out using a high-pressure homogenizer (Starburst Mini manufactured by Sugino Machine Co., Ltd.) at 80 MPa, followed by immediate cooling to 20°C using a cooling tube. This dispersion and cooling process was repeated 50 times to obtain a dispersion.

[0087] (iii) Addition of a basic compound, an aqueous diluent, and an aqueous binder to the dispersion To the dispersion, a basic compound, an aqueous diluent, and an aqueous binder were added in the weight ratios shown in Table 1. In Table 1, the weight of the aqueous binder is the weight part including the solvent.

[0088] (iv) Aging Between the steps (ii) and (iii) and after the step (iii), the dispersion was aged under the temperature and time conditions shown in Table 1.

[0089] (2) Formation of conductive coating film The conductive composition was applied to a resin substrate using a wire bar to form a conductive coating film on the resin substrate under the coating and drying conditions shown in Table 1. In Table 1, "Wet film thickness" means the film thickness before drying, and "Dry film thickness" means the film thickness after drying.

[0090] (3) Surface resistivity of conductive coating film The surface resistivity of the dried conductive coating film was measured in accordance with JIS K7194 using a Mitsubishi Chemical Corporation Hiresta UP (MCP-HT-450, product name) probe UA at an applied voltage of 10 V to 500 V. The results are shown in Table 1. In Table 1, "over" in Comparative Examples 1 to 4 means OVER RANGE, and indicates that the surface resistivity is 14th power or higher.

[0091] [Table 1]

[0092] In Comparative Examples 1, 2, and 4, the aging times between step (ii) and step (iii) and after step (iii) were all less than 50 hours, so the coating films formed from the obtained conductive compositions had high surface resistivity and poor conductivity. In Comparative Example 3, the aging time between step (ii) and step (iii) exceeded 10,000 hours, and the aging time after step (iii) was less than 50 hours, so the coating films formed from the obtained conductive compositions had high surface resistivity and poor conductivity.

[0093] In Examples 1 to 12, aging was carried out at an appropriate temperature for 50 to 10,000 hours at least between steps (ii) and (iii) or after step (iii), and therefore the coating films formed from the obtained conductive compositions had low surface resistivity and excellent conductivity.

[0094] The present invention may include, for example, the following aspects. <1> The method includes the following steps (i) to (iii), in this order: (i) a step of mixing carbon nanotubes, a dispersant, and an aqueous diluent to obtain a preliminary dispersion; (ii) a step of dispersing the preliminary dispersion to obtain a dispersion; and (iii) a step of adding one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder to the dispersion, and at least between steps (ii) and (iii) or after step (iii), A method for producing a conductive composition, comprising the following step (iv): (iv) aging the dispersion at 1 to 40°C for 50 to 10,000 hours.

[0095] <2> Item 2. The method for producing a conductive composition according to Item 1, wherein the aqueous diluent in step (i) or (iii) is a mixed solvent of water and a water-soluble organic solvent.

[0096] <3> Item 3. The method for producing a conductive composition according to Item 1 or 2, wherein the dispersant is an anionic dispersant or a nonionic dispersant.

[0097] <4> 4. The method for producing a conductive composition according to any one of items 1 to 3, wherein step (iv) is carried out between step (ii) and step (iii).

[0098] <5> 5. The method for producing a conductive composition according to any one of items 1 to 4, wherein an aqueous diluent is added to the dispersion in step (iii), and step (iv) is carried out after step (iii).

[0099] <6> Item 6. A method for producing a conductive laminate, comprising the steps of obtaining a conductive composition by the production method according to any one of Items 1 to 5, applying the conductive composition to a substrate, and drying the applied conductive composition to form a conductive coating film.

Claims

1. The following steps (i) to (iii): (i) mixing carbon nanotubes, a dispersant, and an aqueous diluent to obtain a pre-dispersion; (ii) dispersing the pre-dispersion to obtain a dispersion; and (iii) adding one or more selected from the group consisting of a basic compound, an aqueous diluent, and an aqueous binder to the dispersion; in this order, At least between step (ii) and step (iii) or after step (iii), The following step (iv): (iv) Aging the dispersion at 1 to 40°C for 50 to 10,000 hours A method for producing a conductive composition, comprising:

2. The method for producing a conductive composition according to claim 1 , wherein the aqueous diluent in step (i) or (iii) is a mixed solvent of water and a water-soluble organic solvent.

3. The method for producing a conductive composition according to claim 1 or 2, wherein the dispersant is an anionic dispersant or a nonionic dispersant.

4. The method for producing a conductive composition according to claim 1 or 2, wherein step (iv) is carried out between step (ii) and step (iii).

5. In step (iii), an aqueous diluent is added to the dispersion; The method for producing a conductive composition according to claim 1 or 2, wherein step (iv) is carried out after step (iii).

6. A step of obtaining a conductive composition by the manufacturing method according to claim 1 or 2; applying a conductive composition onto a substrate; and A step of drying the applied conductive composition to form a conductive coating film. Including, A method for manufacturing a conductive laminate.

Images