JP7501115B2 - Conductive material dispersion and its use - Google Patents

Description

The present invention relates to a conductive material dispersion, and a composition for secondary battery electrodes, an electrode film, a secondary battery, a conductive paint, and a conductive coating film that use the conductive material dispersion.

In recent years, there has been active development of conductive materials that can be used to impart functions such as antistatic properties, electrical conductivity, thermal conductivity, and electromagnetic shielding properties to various materials. Carbon-based conductive materials are widely used as conductive materials because they are highly heat-resistant, light-resistant, and corrosion-resistant, lightweight, relatively inexpensive, and highly conductive. Although there are methods for imparting such functions, such as kneading them into substrates such as plastics and glass, the method of coating a conductive material dispersion or a wet mixture of a conductive material dispersion and various materials is becoming mainstream due to its high processability. In addition, in order to avoid degrading other application characteristics such as optical properties, design properties, and electrical properties, it is necessary to demonstrate performance with a small amount of conductive material, so it is effective to use nanocarbons with a large specific surface area, especially carbon black (hereinafter referred to as CB) and carbon nanotubes (hereinafter referred to as CNT). However, there is a problem that nanocarbons with a large specific surface area have a strong cohesive force and are difficult to disperse well.

Against this background, various dispersants for conductive materials are being considered. For example, in dispersing CB or CNT, Patent Documents 1 and 2 propose a method of producing a dispersion using a polymer such as polyvinyl alcohol (hereinafter PVA) or polyvinylpyrrolidone (hereinafter PVP) as a dispersant, while Patent Document 3 proposes a conductive material dispersion using a copolymer containing units derived from (meth)acrylonitrile and units containing an active hydrogen group-containing monomer as a dispersant.

An example of an application using a conductive material dispersion is a transparent antistatic paint. Carbon-based and other conductive materials are often colored, and the more the conductive material is added, the better the conductivity, but the more the transparency is lost, so it is very difficult to achieve both transparency and conductivity at a high level. Therefore, among conductive materials, expectations are particularly high for CNTs. CNTs include single-walled nanotubes made of one graphene layer and multi-walled nanotubes made of multiple graphene layers, and due to their structural characteristics of large aspect ratios and small diameters, when dispersed at an extremely high level (ideally monodispersed), a network-like conductive path can be efficiently formed with a small amount. For example, Patent Document 4 reports an example in which transparency and conductivity are achieved by using CNTs with a specific average outer diameter and specific surface area and a CNT dispersion liquid with a specific particle size distribution obtained by dispersing and mixing a water-soluble dispersion resin and water.

There have also been many reports of using conductive material dispersions in secondary batteries. The capacity of a lithium-ion secondary battery depends heavily on the main materials, the positive electrode active material and the negative electrode active material, and various materials have been actively researched, but the charge capacity of all active materials in practical use has reached close to the theoretical value, and improvement is close to the limit. Therefore, since the capacity can be simply increased by increasing the amount of active material filled in the battery, attempts have been made to reduce the amount of conductive material and binder added, which do not directly contribute to the capacity. Of these, the conductive material plays a role in forming a conductive path inside the battery and preventing the conductive path from being cut off due to the expansion and contraction of the active material by connecting the active material particles, and in order to maintain performance with a small amount of addition, it is effective to form an efficient conductive network using a conductive material dispersion. For example, Patent Document 1, Patent Document 5, and Patent Document 6 propose using a polymer such as PVP or PVA as a dispersant to disperse the conductive material in advance to improve the initial characteristics and cycle life of the battery.

Meanwhile, Patent Document 7 discloses an electrode binder composition that contains a water-soluble polymer that contains a monomer containing a nitrile group and an ethylenically unsaturated carboxylic acid monomer unit and has a weight-average molecular weight of 1,000 to 50,000. According to Patent Document 7, by blending a water-soluble binder composition with a small weight-average molecular weight, it is possible to improve the dispersion ability of solids mainly composed of active materials while also improving the flexibility and voltage resistance characteristics of the electrode.

JP 2014-193986 A JP 2003-157846 A Patent No. 6638846 JP 2020-019924 A JP 2005-162877 A JP 2011-70908 A WO2018-235722

For example, in Patent Documents 1 and 2, a polymer such as PVP or PVA is used as a dispersant to disperse a conductive material in a dispersion medium. However, since PVP or PVA is generally highly hydrophilic and soluble in water, when the conductive material dispersion is made into a coating film, problems such as a decrease in the water resistance of the coating film occur. For example, when used as a transparent antistatic paint, deterioration is likely to be accelerated due to the influence of wind and rain when used outdoors, and due to moisture absorption when used indoors. When used as a conductive material dispersion for secondary batteries, problems such as a decrease in battery performance due to moisture absorption occur.

When transparent antistatic coating applications require high designability and strict optical properties, it is necessary to achieve extremely high transparency (for example, total light transmittance of 80% or more) while maintaining a certain level of antistatic properties, which was difficult to achieve even with the inventions of Patent Documents 1 to 4.

Furthermore, the conductive material dispersions of Patent Documents 1, 2 and 6 are insufficient in dispersibility, particularly for dispersing CNTs with a large specific surface area, and the inventions described in Patent Documents 1 to 6 are capable of producing conductive material dispersions in a well-dispersed state, but the problem is that the conductivity deteriorates when an antistatic film or electrode film is formed. Furthermore, the binder composition of Patent Document 7 improves the dispersibility of solids mainly composed of active materials that have a small specific surface area and are easier to disperse than nanocarbon, but the dispersibility is still insufficient for dispersing nanocarbons with a large specific surface area.

The present inventors have intensively studied a method for dispersing nanocarbons, which have a particularly large specific surface area, well and maintaining a good conductive network with a small amount of additive even when the nanocarbons are mixed into a paint composition, or a coating film is formed, or an electrode film is formed. As a result, it was found that while the methods proposed in the above-mentioned Patent Documents 1 to 7 can certainly produce a conductive material dispersion in a well-dispersed state, poor dispersion occurs at the stage of mixing with a binder or hardener for forming a coating film, or in the process of drying the coating film, or in the stage of forming a slurry for an electrode film. This is thought to prevent a good conductive network from being formed, resulting in poor characteristics. In order to form a good conductive network in a transparent antistatic film or secondary battery and improve the application characteristics even with a small amount of conductive material added, it is necessary to achieve both good "dispersibility" at the stage of dispersing the conductive material in the conductive material dispersion and "stability" that allows the conductive material to maintain a dispersed state even when processed for the application. Note that the "stability" referred to here is different from the storage stability when the conductive material dispersion is stored for a long period of time.

Therefore, an object of an embodiment of the present invention is to provide a conductive material dispersion that can achieve both good dispersibility and stability during processing. Another object of an embodiment of the present invention is to provide a conductive paint and a composition for secondary battery electrodes that can achieve both good dispersibility and stability during processing. Another object of an embodiment of the present invention is to provide a conductive coating film and an electrode film that have good dispersibility. Furthermore, an object of an embodiment of the present invention is to provide a transparent antistatic film that has high transparency and antistatic properties. Another object of an embodiment of the present invention is to provide an electrode film that can improve the output and cycle life of a secondary battery, and a secondary battery that has high output and good cycle life.

After extensive research, the inventors have found that by combining a conductive material having a specific amount of acidic groups with a dispersant that is a copolymer having specific structural units and a specific amount of acidic groups, and water, it is possible to disperse the conductive material well in water, and to maintain a good conductive network with a small amount of additive even when the conductive material is incorporated into a paint composition, a coating film is formed, or an electrode film is formed. This makes it possible to improve the transparency of the antistatic film, or to improve the rate characteristics and cycle life of a secondary battery, even with a small amount of conductive material added.

That is, the present invention includes the following embodiments. The embodiments of the present invention are not limited to the following.

The present invention relates to a conductive material, a dispersant, and water.
The conductive material is a carbon nanotube having an acidic group amount of 0.1 to 1.0 μmol/ ^m2 and 60 to 300 μmol/g,
The conductive material dispersion relates to a copolymer in which the dispersant is a copolymer containing units derived from (meth)acrylonitrile and carboxyl group-containing monomer units, the copolymer contains 40 to 99 mass% of units derived from (meth)acrylonitrile in all monomer units constituting the copolymer, and has an acid value of 30 to 400 mgKOH/g.

The present invention also relates to the conductive material dispersion, in which the carbon nanotubes have an average outer diameter of 7 nm or less.

The present invention also relates to the conductive material dispersion, in which the carboxyl group-containing monomer units account for 3 to 40 mass% of all the monomer units constituting the copolymer.

The present invention also relates to the conductive material dispersion, in which the dispersant is a copolymer further comprising one or more monomer units selected from the group consisting of active hydrogen group-containing monomers (excluding carboxyl group-containing monomers), basic monomers, and (meth)acrylic acid alkyl esters.

The present invention also relates to the conductive material dispersion described above, which further contains an antifoaming agent.

The present invention also relates to a composition for secondary battery electrodes comprising the conductive material dispersion.

The present invention also relates to an electrode film that is a coating film of the secondary battery electrode composition.

The present invention also relates to a secondary battery that includes the electrode film.

The present invention also relates to a conductive paint containing the conductive material dispersion.

The present invention also relates to a conductive coating film that is a coating film of the conductive paint.

The present invention also relates to a method for producing a conductive material dispersion according to any one of claims 1 to 4, comprising step 1 of dispersing the conductive material composition by applying shear stress until the dispersed particle size is 250 μm or less, and step 2 of dispersing the conductive material composition using a high-pressure homogenizer at a pressure of 60 to 150 MPa until the median diameter is 100 μm or less, following step 1.

The present invention also relates to a method for producing the conductive material dispersion, further comprising step 3 of reducing the content of metals consisting of iron, nickel, and chromium contained in the conductive material dispersion to 100 ppm or less.

According to an embodiment of the present invention, it is possible to provide a conductive material dispersion that can achieve both good dispersibility and stability during processing. Also, according to an embodiment of the present invention, it is possible to provide a conductive paint and a composition for secondary battery electrodes that can achieve both good dispersibility and stability during processing. Also, according to an embodiment of the present invention, it is possible to provide a conductive coating film and an electrode film that have good dispersibility. Furthermore, according to an embodiment of the present invention, it is possible to provide a transparent antistatic film that has high transparency and antistatic properties. Also, according to an embodiment of the present invention, it is possible to provide an electrode film that can improve the output and cycle life of a secondary battery, and a secondary battery that has high output and good cycle life.

The following describes in detail the conductive material, dispersant, conductive material dispersion, conductive coating film, secondary battery electrode composition, electrode film, and secondary battery, which are embodiments of the present invention. The present invention is not limited to the following embodiments, and includes embodiments that are implemented within the scope of the present invention.

In this specification, the dispersant of the present invention may be referred to as a "copolymer." A monomer unit refers to a monomer that is contained in a polymer as a result of polymerization of the monomer. "Antistatic property" may be referred to as "conductivity."

<Conductive material>
The conductive material of the present invention includes at least carbon nanotubes, and may optionally include other conductive materials. Examples of other conductive materials include metal powders such as gold, silver, copper, silver-plated copper powder, silver-copper composite powder, silver-copper alloy, amorphous copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molbutene, and platinum, inorganic powders coated with these metals, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, and ruthenium oxide, inorganic powders coated with these metal oxides, and carbon materials such as carbon black and graphite. The other conductive materials may be used alone or in combination of two or more. When using other conductive materials, carbon black is preferred from the viewpoint of the adsorption performance of the dispersant.

Examples of carbon black include acetylene black, furnace black, hollow carbon black, channel black, thermal black, and ketjen black. Carbon black may be neutral, acidic, or basic, and oxidation-treated carbon black or graphitized carbon black may be used.

Carbon nanotubes (CNTs) include planar graphite rolled into a cylindrical shape, single-walled carbon nanotubes, and multi-walled carbon nanotubes, and these may be mixed. Single-walled carbon nanotubes have a structure in which one layer of graphite is rolled. Multi-walled carbon nanotubes have a structure in which two or more layers of graphite are rolled. In addition, the sidewalls of carbon nanotubes do not have to have a graphite structure. For example, carbon nanotubes with sidewalls having an amorphous structure are also considered to be carbon nanotubes in this specification.

The shape of the carbon nanotubes is not limited. Examples of such shapes include needle-like, cylindrical tube-like, fishbone-like (fishbone or cup stack type), trump-like (platelet) and coil-like. In this embodiment, the shape of the carbon nanotubes is preferably needle-like or cylindrical tube-like. The carbon nanotubes may be of a single shape or a combination of two or more shapes.

Examples of the form of carbon nanotubes include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. Carbon nanotubes may have any one of these forms or a combination of two or more of them.

The amount of acidic groups in the carbon nanotubes can be determined by back titration from the amount of adsorption of hexylamine. The amount of acidic groups in the carbon nanotubes determined from the amount of adsorption of hexylamine is preferably 0.1 μmol/m ² or more, more preferably 0.2 μmol/m ² or more, based on the surface area of the carbon nanotubes calculated by the BET method. Also, it is preferably 1 μmol/m ² or less, and more preferably 0.7 μmol/m ² or less. Based on the mass of the carbon nanotubes, it is preferably 60 μmol/g or more, more preferably 100 μmol/g or more, and even more preferably 120 μmol/g. Also, it is preferably 300 μmol/g or less, more preferably 250 μmol/g or less, and even more preferably 220 μmol/g or less. By setting the amount of acidic groups in the carbon nanotubes to the above range, it is possible to efficiently obtain a good conductive material dispersion by increasing the affinity with the dispersion medium and the dispersant. If it exceeds the above range, there is a concern that the light resistance and oxidation resistance of the coating film will decrease.

The specific surface area of the carbon nanotubes calculated by the BET method is preferably 100 m ² /g or more, more preferably 150 m ² /g or more. Also, it is preferably 1200 m ² /g or less, more preferably 800 m ² /g or less. When the conductive material dispersion of the present invention is used in a transparent antistatic paint, in order to realize high transparency with a smaller amount of conductive material added, the specific surface area is preferably 200 m ² /g or more, more preferably 350 m ² /g or more, and even more preferably 450 m ² /g or more. Also, when the conductive material dispersion of the present invention is used in a transparent antistatic paint, single-walled carbon nanotubes are particularly preferred. The average outer diameter of the carbon nanotubes is preferably 1 nm or more. Also, it is preferably 30 nm or less, more preferably 20 nm or less, even more preferably 10 nm or less, and especially preferably 7 nm or less. By setting the average outer diameter in the above range, an efficient conductive network can be formed. The average outer diameter is first observed and photographed by a transmission electron microscope. Next, 300 carbon nanotubes are randomly selected from the observation photograph, and the outer diameter of each is measured. The average outer diameter (nm) of the carbon nanotubes is calculated as the number average of the outer diameters.

The carbon purity of the carbon nanotubes can be determined by a general CHN elemental analysis and is expressed as the content (mass%) of carbon atoms in the conductive material. The carbon purity is preferably 80 mass% relative to 100 mass% of the conductive material, and more preferably 90 mass% or more. In particular, when the conductive material dispersion of the present invention is used in a secondary battery, the carbon purity is preferably 90 mass% or more relative to 100 mass% of the conductive material, more preferably 95 mass% or more, and even more preferably 98 mass% or more. By setting the carbon purity within the above range, for example, when used in a transparent antistatic paint, defects such as a decrease in light resistance due to impurities can be prevented. Also, when used in a secondary battery, defects such as the formation of dendrites due to impurities and short circuits can be prevented.

The content of the conductive material is preferably 0.1 to 15% by mass, more preferably 0.3 to 10% by mass, of the non-volatile content of the dispersion. By setting the content within the above range, the conductive material can be maintained in a good and stable state without causing sedimentation or gelation. In addition, it is preferable to appropriately adjust the content of the conductive material so that a conductive material dispersion with appropriate fluidity or viscosity is obtained, depending on the specific surface area of the conductive material, its affinity for the dispersion medium, etc.

<Dispersant>
The dispersant of the present invention contains a copolymer containing a monomer unit derived from (meth)acrylonitrile and a carboxyl group-containing monomer unit. The content of the monomer unit derived from (meth)acrylonitrile is 40% by mass or more and 99% by mass or less based on the mass of all monomer units constituting the copolymer. The dispersant of the present invention contains a high concentration of units derived from (meth)acrylonitrile. The strong polarization of the non-hydrogen-bonding cyano group and the carbon chain of the dispersion resin main chain increase the adsorption to the conductive material and the affinity to the dispersion medium, allowing the conductive material to exist stably in the dispersion medium.

Examples of monomer units derived from (meth)acrylonitrile include acrylonitrile and methacrylonitrile. One type can be used alone, or two or more types can be used in combination, and acrylonitrile is preferable. If the monomer unit derived from (meth)acrylonitrile is acrylonitrile, the copolymer is less bent, and adjacent cyano groups are oriented to form a partial structure with strong polarization, so that the intermolecular force between the dispersant and the dispersed material and/or the dispersant and water is high. From the viewpoint of increasing the intermolecular force, the content of the monomer unit derived from (meth)acrylonitrile is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on the mass of all monomer units constituting the copolymer. Based on the mass of all monomer units constituting the copolymer, it is preferably 99% by mass or less, more preferably 92% by mass or less, and even more preferably 87% by mass or less. By setting the content of the monomer unit derived from (meth)acrylonitrile within the above range, the dispersed material can be stably present in the dispersion medium. In addition, when used in secondary batteries, it is possible to prevent problems such as the dispersant dissolving in the electrolyte inside the battery and increasing the resistance of the electrolyte.

Examples of the carboxyl group-containing monomer unit include unsaturated fatty acids such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, ethylene oxide-modified succinic acid (meth)acrylate, and carboxyl group-containing (meth)acrylate such as β-carboxyethyl (meth)acrylate. In addition, examples of the carboxyl group-containing monomer unit include acid anhydride group-containing monomers such as maleic anhydride, itaconic anhydride, and citraconic anhydride, which are polymers of the above carboxyl group-containing monomers, and monofunctional alcohol adducts thereof. A group having a structure in which two carboxyl groups are dehydrated and condensed, "-C(=O)-O-C(=O)-" (herein referred to as an "acid anhydride group"), also forms a carboxyl group by hydrolysis, and is therefore included in the carboxyl group in this specification. The carboxyl group-containing monomer is preferably an unsaturated fatty acid, more preferably (meth)acrylic acid, and even more preferably acrylic acid. From the viewpoint of providing an appropriate affinity with water, which is the dispersion medium, the content of the carboxyl group-containing monomer unit is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on the mass of all monomer units constituting the copolymer. Based on the mass of all monomer units constituting the copolymer, it is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

The dispersant may contain one or more monomer units selected from the group consisting of active hydrogen group-containing monomers (excluding carboxyl groups), basic monomers, and (meth)acrylic acid alkyl esters. The conductive material dispersion of the present invention can be applied to various applications by selecting and containing the above monomers according to the characteristics such as hydrophilicity, hydrophobicity, acidity, and basicity of the substrate to which the conductive material dispersion of the present invention is applied or the material to be mixed. The content of one or more monomer units selected from the group consisting of active hydrogen group-containing monomers (excluding carboxyl groups), basic monomers, and (meth)acrylic acid alkyl esters is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the mass of all monomer units constituting the copolymer.
When contained within the above range, suitability for various applications can be imparted while maintaining high intermolecular forces.
Among the one or more monomer units selected from the group consisting of active hydrogen group-containing monomers (excluding carboxyl groups), basic monomers, and (meth)acrylic acid alkyl esters used in the synthesis of the dispersant, the active hydrogen group-containing monomer is a monomer having, for example, a hydroxyl group, a primary amino group, a secondary amino group, a mercapto group, etc., as an active hydrogen group. Here, the term "primary amino group" refers to -NH ₂ (amino group), and the term "secondary amino group" refers to a group in which one hydrogen atom on a primary amino group is substituted with an organic residue such as an alkyl group. However, in this specification, the primary amino group and the secondary amino group in the acid amide are not included in the active hydrogen group.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 2-hydroxy-3-phenoxypropyl acrylate, and caprolactone adducts of these monomers (number of moles added: 1 to 5). Among the active hydrogen group-containing monomers, hydroxyl group-containing monomers are preferred from the viewpoints of availability of raw materials, ease of handling, affinity with the dispersion medium described below, and the like. As the hydroxyl group-containing monomer, hydroxyalkyl (meth)acrylate is preferred, hydroxyethyl (meth)acrylate is more preferred, and hydroxyethyl acrylate is even more preferred.

Examples of primary amino group-containing monomers include aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, allylamine hydrochloride, dihydrogen allylamine phosphate, 2-isopropenylaniline, 3-vinylaniline, and 4-vinylaniline.

Examples of secondary amino group-containing monomers include t-butylaminoethyl (meth)acrylate.

Examples of mercapto group-containing monomers include 2-(mercaptoacetoxy)ethyl acrylate and allyl mercaptan.

The active hydrogen group-containing monomers can be used alone or in combination of two or more.

A basic monomer is a monomer having a basic group. Examples of basic groups include a tertiary amino group, an amide group, a pyridine ring, and a maleimide group. Note that a monomer having a primary amino group and a monomer having a secondary amino group can also be included in basic monomers, but in the present invention, they are treated as the active hydrogen group-containing monomer and are not included in basic monomers.

Examples of the basic monomer include dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate and dimethylaminopropyl (meth)acrylate;
N-substituted (meth)acrylamides such as (meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and acryloylmorpholine;
Heterocyclic aromatic amine-containing vinyl monomers such as 1-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, etc.;
N-(alkylaminoalkyl)(meth)acrylamides such as N-(dimethylaminoethyl)(meth)acrylamide and N-(dimethylaminopropyl)acrylamide;
Examples of the alkyl(meth)acrylamides include N,N-alkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide.

The basic monomers may be used alone or in combination of two or more. Among the basic monomers, dimethylaminoethyl (meth)acrylate or dimethylaminopropyl (meth)acrylate is preferred from the viewpoints of availability of raw materials, ease of handling, and affinity with the dispersion medium described below, with dimethylaminoethyl acrylate being more preferred.

An alkyl (meth)acrylate is a monomer having a structure represented by (R ¹ ) ₂ C═C—CO—O—R ² (wherein R ¹ is a hydrogen atom or a methyl group, at least one of which is a hydrogen atom, and R ² is an alkyl group which may have a substituent).
Incidentally, those containing the active hydrogen group or the basic group as a substituent of the alkyl group are treated as the active hydrogen group-containing monomer or the basic monomer, and are not included in the (meth)acrylic acid alkyl ester.
Examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid esters containing a chain alkyl group, such as methyl (meth)acrylate and ethyl (meth)acrylate;
(meth)acrylic acid esters containing a branched alkyl group, such as 2-ethylhexyl (meth)acrylate and isostearyl (meth)acrylate;
(meth)acrylic acid esters containing a cyclic alkyl group, such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate;
(Meth)acrylic acid alkyl esters containing an aromatic ring-substituted alkyl group, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate;
Fluoro-substituted (meth)acrylic acid alkyl esters, such as trifluoroethyl (meth)acrylate and tetrafluoropropyl (meth)acrylate;
Epoxy group-containing (meth)acrylic acid alkyl esters such as glycidyl (meth)acrylate and (3-ethyloxetan-3-yl)methyl (meth)acrylate;
silyl ether group-containing (meth)acrylic acid alkyl esters such as 3-methacryloxypropylmethyldimethoxysilane;
Alkyloxy group-containing (meth)acrylic acid alkyl esters such as 2-methoxyethyl (meth)acrylate and polyethylene glycol monomethyl ether (meth)acrylate;
Examples of the monomer include cyclopolymerizable monomers such as methyl 2-(allyloxymethyl)acrylate.

The (meth)acrylic acid alkyl esters can be used alone or in combination of two or more.
Among the (meth)acrylic acid alkyl esters, from the viewpoints of availability of raw materials, ease of handling, and affinity with the dispersion medium described below, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate are preferred, and 2-ethylhexyl acrylate and lauryl acrylate are more preferred.

The dispersant of the present invention may further have other monomer units. Examples of the monomers constituting the other monomer units include styrenes such as styrene and α-methylstyrene;
Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, and isobutyl vinyl ether;
vinyl acetate, vinyl propionate, and other vinyl fatty acids;
N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide;
heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate or 3-methyloxetanyl (meth)acrylate; and the like.

The method for producing the dispersant is not particularly limited, and examples thereof include solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and precipitation polymerization, with solution polymerization or precipitation polymerization being preferred. The polymerization reaction system may include addition polymerization such as ionic polymerization, free radical polymerization, and living radical polymerization, with free radical polymerization or living radical polymerization being preferred. Examples of the radical polymerization initiator include peroxides and azo initiators. When polymerizing the dispersant, a molecular weight regulator such as a chain transfer agent can be used.

Examples of chain transfer agents include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, and 3-mercapto-1,2-propanediol, thioglycolic acid esters such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, and β-pinene. In particular, 3-mercapto-1,2-propanediol, thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, and β-pinene are preferred in that the resulting polymer has a low odor.

The amount of the chain transfer agent used is preferably 0.01 to 4 mass% relative to 100 mass parts of all monomer units, and more preferably 0.1 to 2 mass%. By setting the amount of the chain transfer agent within the above range, the molecular weight of the dispersant of the present invention can be adjusted to a suitable molecular weight range.

The weight average molecular weight of the dispersant is preferably 5,000 or more, more preferably 6,000 or more, and even more preferably 7,000 or more, in terms of polystyrene. It is also preferably 400,000 or less, more preferably 200,000 or less, even more preferably 100,000 or less, and particularly preferably 60,000 or less. Having an appropriate weight average molecular weight improves the adsorption to the dispersed material, and further improves the stability of the dispersion.

The dispersant of the present invention has excellent dispersibility and storage stability even in the copolymer as described above, but these properties are further improved when the unit derived from acrylonitrile has a cyclic structure. When the copolymer is treated with an alkali, the unit derived from acrylonitrile changes to a cyclic structure such as a hydrogenated naphthyridine ring. In this specification, the presence of the cyclic structure further improves dispersibility. The alkali treatment may be performed at any time from the synthesis of the copolymer until the production of the dispersion is completed. In addition, it is easily changed by heating. In order for the unit derived from acrylonitrile to form a cyclic structure, the unit derived from acrylonitrile must have at least two or more consecutive partial structures, and it is preferable that the unit has three or more consecutive partial structures. For example, when a random polymer is polymerized by addition polymerization such as free radical polymerization, a polymer having two or more consecutive partial structures is easily obtained when the unit derived from acrylonitrile is contained in 50% by mass or more, and is even more easily obtained when the unit derived from acrylonitrile is contained in 70% by mass or more. In addition, it can also be obtained by polymerizing a block polymer by addition polymerization such as ionic polymerization or living radical polymerization.

Furthermore, when the dispersant of the present invention has a unit derived from (meth)acrylic acid, the (meth)acrylic acid unit may form a cyclic structure.
When the dispersant has a (meth)acrylic acid unit, a glutarimide ring may be formed as a cyclic structure together with a unit derived from acrylonitrile by alkali treatment, so that a ring structure such as a hydrogenated naphthyridine ring and a glutarimide ring coexist. This further improves the dispersion stability. When the dispersant is a polymer having a (meth)acrylic acid unit forming a cyclic structure, the (meth)acrylic acid unit is preferably 1 to 25 mass% of the total monomer units of the copolymer, more preferably 10 to 25 mass%. In addition, the unit derived from acrylonitrile is preferably 40 to 99 mass%, more preferably 55 to 99 mass%, and even more preferably 75 to 99 mass% of the total monomer units of the copolymer. In order to form the glutarimide ring, it is necessary to have a partial structure in which at least a unit derived from acrylonitrile and an acrylic acid unit are adjacent to each other.

The acid value of the dispersant can be determined by neutralization titration with KOH. The acid value of the dispersant is preferably 30 mgKOH/g or more, more preferably 55 mgKOH/g or more, and even more preferably 70 mgKOH/g or more. Also, it is preferably 400 mgKOH/g or less, more preferably 300 mgKOH/g or less, and even more preferably 200 mgKOH/g or less. By setting the acid value of the dispersant within the above range, the affinity between the dispersant and the dispersion medium can be appropriately controlled, and the dispersant can maintain a good dispersion state while acting effectively on the dispersed material. If the oxidation of the dispersant exceeds the above range, the affinity to the dispersion medium becomes too high (i.e., the solubility in water becomes too high), and if it falls below the above range, the affinity to the dispersion medium becomes too low (i.e., the solubility in water becomes too low), and in either case, the action as a dispersant may be reduced. Furthermore, by setting the amount of acidic groups in the conductive material and the acid value of the dispersant within the above ranges, the affinity balance between the dispersant, the dispersion medium, and the dispersed material is further improved, improving dispersibility.

It is preferable to experimentally determine the amount of dispersant added in order to achieve the dispersion degree, fluidity, and storage stability required for the conductive material dispersion. Adding an excess amount beyond the required amount may result in problems such as poor storage stability or increased resistance when used in a secondary battery. The amount of dispersant required is influenced by various factors such as the specific surface area, shape, crystallinity, carbon purity, wettability, dispersion medium, and other additives of the conductive material, so it is preferable to determine the amount of dispersant appropriately depending on the type of conductive material. For example, the higher the specific surface area and the poorer the wettability of the conductive material, the more dispersant is required.

The content of the dispersant is preferably 10% by mass or more, and more preferably 20% by mass or more, based on the mass of the conductive material. When used in a transparent antistatic coating, the content is preferably 1000% by mass or less, more preferably 500% by mass or less, and particularly preferably 300% by mass or less. When used in a secondary battery, the content is preferably 100% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less. By keeping the content within the above range, the conductive material can be present well and stably without impairing the application characteristics.

<Antifoaming agent>
The conductive material dispersion of the present invention preferably contains a defoaming agent. Any defoaming agent having a defoaming effect, such as a commercially available defoaming agent, a wetting agent, or a water-soluble organic solvent, can be used as the defoaming agent. One type of defoaming agent or a combination of two or more types of defoaming agents can be used.
For example, alcohols: ethanol, propanol, isopropanol, butanol, octyl alcohol, hexadecyl alcohol, acetylene alcohol, ethylene glycol monobutyl ether, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, acetylene glycol, polyoxyalkylene glycol, propylene glycol, and other glycols;
Fatty acid esters: diethylene glycol laurate, glycerin monoricinoleate, alkenylsuccinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, polyoxyethylene monolaurate, polyoxyethylene sorbitol monolaurate, natural waxes, etc.
Amide-based: polyoxyalkylene amide, acrylate polyamine, etc.
Phosphate esters: tributyl phosphate, sodium octyl phosphate, etc.
Metal soaps: aluminum stearate, calcium oleate, etc.
Oils and fats: animal and vegetable oils, sesame oil, castor oil, etc.
Mineral oils: kerosene, paraffin, etc.
Silicone-based: dimethyl silicone oil, silicone paste, silicone emulsion, organic modified polysiloxane, fluorosilicone oil, etc.
Alternatively, examples of water-soluble organic solvents other than alcohols include N-methyl-2-pyrrolidone.
Among them, acetylene glycol-based is preferred. The use of such an antifoaming agent can reduce the surface tension of the conductive material dispersion. From the viewpoint of the energy efficiency and coatability of the dispersing machine, the surface tension of the conductive material dispersion is preferably 73 mN/m or less, more preferably 70 mN/m or less, and even more preferably 65 mN/m or less. The antifoaming agent can be added at any timing from the start to the end of the dispersion process including the charging, but from the viewpoint of the charging property and the dispersion efficiency, it is preferable to add the antifoaming agent before mixing the dispersed material and the dispersion medium. In addition, the antifoaming agent may be added at once or in multiple portions.

<Dispersion medium>
The dispersion medium of the present invention is water and may optionally contain other solvents.

<Conductive material dispersion>
The conductive material dispersion of the present invention preferably contains a conductive material, a dispersant, and water.The conductive material dispersion is used, for example, in a power storage device, an antistatic material, electronic parts, a transparent electrode (ITO film) replacement, an electromagnetic wave shield, etc.The power storage device is, for example, an electrode for a secondary battery, an electrode for an electric double layer capacitor, an electrode for a non-aqueous electrolyte capacitor, etc.In this case, the conductive material is preferably a carbon material.The antistatic material is, for example, an IC tray of a plastic or rubber product, or a molded body of an electronic component material.

The conductive material dispersion of the present invention can contain an inorganic base, an inorganic metal salt, or an organic base. This further improves the dispersion stability over time of the dispersed material. As the inorganic base and inorganic metal salt, a compound having at least one of an alkali metal and an alkaline earth metal is preferable. As the inorganic base and inorganic metal salt, chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, borates, etc. of alkali metals and alkaline earth metals can be mentioned. Among these, chlorides, hydroxides, and carbonates of alkali metals and alkaline earth metals are preferable in terms of being able to easily supply cations. Examples of the hydroxides of alkali metals include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of the hydroxides of alkaline earth metals include calcium hydroxide, magnesium hydroxide, etc.
Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, and potassium hydrogen carbonate.
Examples of the carbonate salt of an alkaline earth metal include calcium carbonate and magnesium carbonate. Among these, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate are more preferable. The metal contained in the inorganic base and inorganic metal salt of the present invention may be a transition metal.

Examples of organic bases include primary, secondary, and tertiary alkylamines having an optionally substituted alkyl group having 1 to 40 carbon atoms, or compounds containing the basic nitrogen atom.

Examples of primary alkylamines having an optionally substituted alkyl group having 1 to 40 carbon atoms include propylamine, butylamine, isobutylamine, octylamine, 2-ethylhexylamine, laurylamine, stearylamine, oleylamine, 2-aminoethanol, 3-aminopropanol, 3-ethoxypropylamine, and 3-lauryloxypropylamine.

Examples of secondary alkylamines having an optionally substituted alkyl group having 1 to 40 carbon atoms include dibutylamine, diisobutylamine, N-methylhexylamine, dioctylamine, distearylamine, and 2-methylaminoethanol.

Tertiary alkylamines having an optionally substituted alkyl group having 1 to 40 carbon atoms include, for example, triethylamine, tributylamine, N,N-dimethylbutylamine, N,N-diisopropylethylamine, dimethyloctylamine, tri-n-butylamine, dimethylbenzylamine, trioctylamine, dimethyldecylamine, dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, dilaurylmonomethylamine, triethanolamine, and 2-(dimethylamino)ethanol.

Among these, primary, secondary or tertiary alkylamines having an alkyl group having 1 to 30 carbon atoms which may be substituted are preferred, and primary, secondary or tertiary alkylamines having an alkyl group having 1 to 20 carbon atoms which may be substituted are more preferred.
The term "optionally substituted alkyl group" means that a hydrogen atom may be substituted, and examples of the substituent include a hydroxy group.

Other compounds containing basic nitrogen atoms include, for example, 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), imidazole, and 1-methylimidazole.

The total amount of inorganic base, inorganic metal salt, and organic base is preferably 1 to 100 parts by mass, and more preferably 1 to 50 parts by mass, per 100 parts by mass of dispersant. Adding the appropriate amounts further improves dispersibility.

The pH of the conductive material dispersion is preferably 7.0 or more and 11.0 or less, and more preferably 9.0 or more and 10.5 or less. If the pH is below the above range, the conductive material dispersion is likely to gel. If the pH is above the above range, problems such as corrosion of various raw materials and exterior materials in the battery, or gelation of the binder are likely to occur. The pH can be measured with a general pH meter.

The dispersibility of the conductive material in the conductive material dispersion can also be evaluated by the median diameter (μm) determined by a laser diffraction/scattering type particle size distribution analyzer. With the median diameter (μm) determined by a laser diffraction/scattering type particle size distribution analyzer, the particle size of the CNT aggregated particles can be estimated by the scattered light intensity distribution by the particles. The median diameter (μm) is preferably 0.5 to 5.0, more preferably 0.5 to 2.0. By setting it within the above range, a conductive material dispersion in an appropriate dispersion state can be obtained. If it is below the above range, the conductive material will be in an aggregated state, and if it is above the above range, a large number of finely cut conductive materials will be generated, making it difficult to form an efficient conductive network. The median diameter can be measured by the method described in the examples.

The dispersion of the present invention may contain other additives, such as wetting and penetrating agents, antioxidants, preservatives, antifungal agents, and leveling agents, as necessary, within the scope of not impairing the object of the present invention. These additives may be added at any time, such as before, during, or after the preparation of the dispersion. In this specification, the conductive material dispersion may be simply referred to as "dispersion."

<Dispersion method>
The conductive material dispersion of the present invention is preferably produced, for example, by dispersing a conductive material composition containing a conductive material, a dispersant, and water using a dispersing device to finely disperse the conductive material composition. The dispersion treatment can be a multi-stage treatment of two or more steps by arbitrarily adjusting the timing of addition of the materials to be used.

Examples of dispersion devices include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, annular bead mills, attritors, high shear mixers, dispersers, and high-pressure homogenizers. When using a high-pressure homogenizer, the pressure is preferably 60 to 150 MPa, and more preferably 60 to 120 MPa.

Dispersion methods using a dispersion device include batch dispersion, pass dispersion, and circulation dispersion, and any of these methods may be used, or two or more methods may be combined. Batch dispersion is a method in which dispersion is performed using only the dispersion device body without using piping or the like. It is easy to handle, so it is preferable for small-scale production. Pass dispersion is a dispersion method in which the dispersion device body is equipped with a tank that supplies the dispersion liquid through piping and a tank that receives the dispersion liquid, and the liquid passes through the dispersion device body. In circulation dispersion, the liquid that has passed through the dispersion device body is returned to the tank that supplies the dispersion liquid, and dispersion is performed while circulating. In both cases, the longer the processing time, the more the dispersion progresses, so it is sufficient to repeat the pass or circulation until the desired dispersion state is achieved, and the processing amount can be increased by changing the size of the tank or the processing time. Pass dispersion is preferable in that it is easier to homogenize the dispersion state than circulation dispersion. Circulation dispersion is preferable in that the work and manufacturing equipment are simpler than pass dispersion. In the dispersion process, the disintegration of aggregated particles, the loosening, wetting, and stabilization of the conductive material proceed sequentially or simultaneously, and the final dispersion state differs depending on how the steps proceed. Therefore, it is preferable to control the dispersion state in each dispersion process by using various evaluation methods. For example, it can be controlled by the method described in the examples.

In addition, a preferred method is to apply shear stress to the conductive material composition to perform preliminary dispersion until the dispersed particle size is 250 μm or less as judged by a grind gauge (based on JIS K5600-2-5), and then perform main dispersion using a high-pressure homogenizer or the like at a pressure of 60 to 150 MPa until the median diameter is 100 μm or less, thereby producing a conductive material dispersion. In this case, adding a base to adjust the pH of the dispersion medium to 7.0 or more and 13.5 or less can improve the wettability of the conductive material and enhance the effect of the dispersant.

Dispersion methods that apply shear stress include methods using dispersion devices such as a three-roll mill, planetary mixer, high shear mixer, and disperser. Among these, it is preferable to use a high shear mixer, which can disperse at a viscosity equivalent to that suitable for a high-pressure homogenizer.

Moreover, it is preferable to further include a step of removing metallic foreign matter contained in the conductive material dispersion. Metallic foreign matter refers to iron, nickel, chromium, etc. that exists in the conductive material dispersion in particulate form, and does not include those that exist in a dissolved state of metal ions. In the metallic foreign matter removal step, the method of removing particulate metallic foreign matter from the conductive material dispersion is not particularly limited, and examples thereof include a method of removing by filtration using a filter, a method of removing by a vibrating sieve, a method of removing by centrifugation, and a method of removing by magnetic force. Among these, since metallic foreign matter such as iron, nickel, and chromium has magnetism, a method of removing by magnetic force is preferred, and a method of combining a step of removing by magnetic force and a step of removing by filtration using a filter is more preferred.

The method of removing the metal foreign matter by magnetic force is not particularly limited as long as it can remove the metal foreign matter. However, taking into consideration productivity and removal efficiency, a method of removing the metal foreign matter by passing the conductive material composition through a magnetic filter disposed in a production line for the conductive material dispersion is preferred.
The step of removing metallic foreign matter from a conductive material dispersion using a magnetic filter is preferably carried out by passing the conductive material through a magnetic filter that forms a magnetic field with a magnetic flux density of 1,000 gauss or more. Since a low magnetic flux density reduces the efficiency of removing metallic components, the magnetic flux density is preferably 5,000 gauss or more, more preferably 10,000 gauss or more in consideration of removing stainless steel, which has a weak magnetic property, and most preferably 12,000 gauss or more.
When a magnetic filter is disposed in a production line, it is preferable to include a process for removing coarse foreign matter or metal particles using a filter such as a cartridge filter upstream of the magnetic filter. This is because coarse metal particles may pass through the magnetic filter depending on the flow rate of the filtration. Although the magnetic filter is effective even if it is used for filtering only once, it is more preferable that the magnetic filter is of a circulating type. This is because the efficiency of removing metal particles is improved by using a circulating type.
When a magnetic filter is disposed in a production line for a conductive material dispersion, the location of the magnetic filter is not particularly limited, but it is preferable to dispose the magnetic filter immediately before filling a container with the conductive material dispersion, and in the case where a filtration process using a filtration filter is performed before filling the container, it is preferable to dispose the magnetic filter before the filtration filter, in order to prevent metal components from being mixed into the product when they are desorbed from the magnetic filter.

The metal content, or the amount of metal foreign matter in the conductive material dispersion, can be determined by drying the conductive material dispersion and then performing ICP analysis. The metal content of iron, nickel, and chromium detected by ICP analysis includes metal foreign matter that exists in particulate form and that exists in dissolved metal ion form. In other words, the amount of metal foreign matter in the conductive material dispersion that has undergone the metal foreign matter removal process includes metal foreign matter that was not completely removed and that exists in dissolved metal ion form.

The metal content of the conductive material dispersion of the present invention is preferably 100 ppm or less, more preferably 50 ppm or less, in total, of iron, nickel, and chromium. By keeping the metal content within the above range, the storage stability of the conductive material dispersion and paint can be improved, and deterioration when used in coating films and batteries can be suppressed. The amount of metal can be measured by the method described in the examples.

<Composition for secondary battery electrode>
The composition for secondary battery electrodes of the present invention preferably contains the conductive material dispersion and a binder resin. The composition for secondary battery electrodes can be produced by mixing the conductive material dispersion and the binder resin. Any component may be further mixed together with the conductive material dispersion and the binder resin. The composition for secondary battery electrodes contains water, and may optionally contain the water-soluble solvent exemplified as the dispersion medium for the conductive material.

<Binder resin used in secondary battery electrode composition>
The binder resin used in the secondary battery electrode composition is not particularly limited as long as it is normally used as a binder resin for paints, and can be appropriately selected according to the purpose. In addition, the binder resin used in the secondary battery electrode composition is a resin that can bond between substances such as active materials and conductive materials, and is different from the dispersant of the present invention in this specification. Examples of the binder resin used in the secondary battery electrode composition include polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, and fluororesins; cellulose resins (e.g., carboxymethylcellulose (CMC)); elastomers such as styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene. In addition, modified bodies, mixtures, and copolymers of these resins may be used. Among these, when used as a binder resin for a positive electrode, polymers or copolymers having fluorine atoms in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene, are preferred from the viewpoint of durability. In addition, when used as a binder resin for a negative electrode, carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, and the like, which have good adhesion, are preferred.

The content of the binder resin used in the secondary battery electrode composition is preferably 0.5 to 30 mass % of the non-volatile content of the resin composition, and more preferably 0.5 to 25 mass %.

The secondary battery electrode composition may contain a positive electrode active material or a negative electrode active material. In this specification, the positive electrode active material and the negative electrode active material may be simply referred to as "active material". An active material is a material that is the basis of a battery reaction. Active materials are divided into positive electrode active material and negative electrode active material based on electromotive force. In this specification, a secondary battery electrode composition containing a positive electrode active material or a negative electrode active material may be referred to as a "positive electrode composite composition", a "negative electrode composite composition", or simply a "composite composition". The composite composition is preferably in a slurry form to improve uniformity and processability. The composite composition contains at least the conductive material dispersion and an active material, or contains at least the conductive material dispersion, a binder resin, and an active material. In this specification, the composite composition may be referred to as a "composite slurry".

<Positive electrode active material>
The positive electrode active material is not particularly limited. For example, for secondary battery applications, metal compounds such as metal oxides and metal sulfides capable of reversibly doping or intercalating lithium ions can be used. For example, lithium and transition metal composite oxide powders such as lithium manganese composite oxides (e.g., Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxides (e.g., Li _x NiO ₂ ), lithium cobalt composite oxides (Li _x CoO ₂ ), lithium nickel cobalt composite oxides (e.g., Li _x Ni _1-y Co _y O ₂ ), lithium manganese cobalt composite oxides (e.g., Li _x Mn _y Co _1-y O ₂ ), lithium nickel manganese cobalt composite oxides (e.g., Li _x Ni _y Co _z Mn _1-y-z O ₂ ), and spinel-type lithium manganese nickel composite oxides (e.g., Li _x Mn _2-y Ni _y O ₄ ), lithium phosphate powders having an olivine structure (e.g., Li _x FePO ₄ , Li _x Fe Examples of the _positive electrode _{active material include} transition metal oxide powders such as _manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxide (e.g., V ₂ O ₅ , V ₆ O ₁₃ ), titanium oxide, and transition metal sulfide powders such as iron sulfate (Fe ₂ (SO ₄ ) ₃ ), TiS ₂ , and FeS. Here, x, y, and z are numbers, and 0<x<1, 0<y<1, 0<z<1, and 0<y+z<1. These positive electrode active materials can be used alone or in combination.

<Negative Electrode Active Material>
The negative electrode active material is not particularly limited, but may be, for example, a metal Li capable of reversibly doping or intercalating lithium ions, or an alloy thereof, a tin alloy, a silicon alloy negative electrode, a metal oxide system such as Li _x TiO ₂ , Li _x Fe ₂ O ₃ , Li _x Fe ₃ O ₄ , or Li _x WO ₂ , a conductive polymer such as polyacetylene or poly-p-phenylene, an artificial graphite such as a highly graphitized carbon material, or a carbonaceous powder such as natural graphite, or a resin-baked carbon material. However, x is a number, and 0<x<1. These negative electrode active materials may be used alone or in combination.

The content of the conductive material in the composite composition is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, based on the mass of the active material (the mass of the active material being 100% by mass). It is also preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

The content of the dispersant in the composite composition is preferably 0.01% by mass or more, and more preferably 0.02% by mass or more, based on the mass of the active material (the mass of the active material being 100% by mass). Also, it is preferably 10% by mass or less, and more preferably 5% by mass or less.

When the composite composition contains a binder resin, the content of the binder resin in the composite composition is preferably 0.5% by mass or more, and more preferably 0.5% by mass or more, based on the mass of the active material (the mass of the active material being 100% by mass). Also, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

The solid content in the composite composition is preferably 30% by mass or more, and more preferably 40% by mass or more, based on the mass of the composite composition (the mass of the composite composition being 100% by mass). Also, it is preferably 90% by mass or less, and more preferably 80% by mass or less.

The composite composition can be prepared by various methods known in the art. For example, a method of preparing the composite composition by adding an active material to a conductive material dispersion; a method of preparing the composite composition by adding an active material to a conductive material dispersion and then adding a binder resin; a method of preparing the composite composition by adding a binder resin to a conductive material dispersion and then adding an active material, etc. are listed. As a method of preparing the composite composition, a method of adding a binder resin to a conductive material dispersion and then further adding and dispersing an active material is preferable. The dispersing device used for dispersion is not particularly limited. The composite composition can be obtained by using the dispersing means mentioned in the description of the conductive material dispersion. Therefore, as a method of preparing the composite composition, a process of adding and dispersing an active material without adding a binder resin to a conductive material dispersion may be performed.

<Electrode film>
The electrode film includes at least one selected from the group consisting of a film formed using the conductive material dispersion and a film formed using the secondary battery electrode composition. The electrode film may further include a current collector. The electrode film can be obtained, for example, by applying a secondary battery electrode composition onto a current collector and drying it, and includes a current collector and a film. The electrode film formed using the positive electrode mixture composition can be used as a positive electrode. The electrode film formed using the negative electrode mixture composition can be used as a negative electrode. In this specification, the film formed using a secondary battery electrode composition containing an active material may be referred to as an "electrode mixture layer".

The material and shape of the current collector used to form the electrode film are not particularly limited, and can be appropriately selected from those suitable for various secondary batteries. Examples of materials for the current collector include conductive metals or alloys such as aluminum, copper, nickel, titanium, or stainless steel. In addition, the shape of the current collector is generally a flat foil, but a current collector with a roughened surface, a perforated foil current collector, or a mesh current collector can also be used. The thickness of the current collector is preferably about 0.5 to 30 μm.

The method for applying the conductive material dispersion or the secondary battery electrode composition onto the current collector is not particularly limited, and any known method can be used. Specific examples include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic painting. Drying methods include, but are not limited to, leaving to dry, or drying using a blower dryer, hot air dryer, infrared heater, far-infrared heater, etc.

After coating, a rolling process may be performed using a lithographic press, a calendar roll, or the like. The thickness of the formed film is, for example, 1 μm or more and 500 μm or less, and preferably 10 μm or more and 300 μm or less.

A film formed using a conductive material dispersion or a composition for secondary battery electrodes can also be used as an underlayer for an electrode mixture layer to improve adhesion between the electrode mixture layer and the current collector, or to improve the conductivity of the electrode film.

<Secondary battery>
The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and at least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode film.

As the electrolyte, various conventionally known electrolytes capable of moving ions can be used. For example, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₃ C, LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, or LiBPh ₄ (wherein Ph is a phenyl group) containing lithium salts can be used, but are not limited thereto. It is preferable to dissolve the electrolyte in a non-aqueous solvent and use it as an electrolytic solution.

Non-aqueous solvents include, but are not limited to, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. These solvents may be used alone or in combination of two or more.

The non-aqueous electrolyte secondary battery preferably includes a separator. Examples of separators include, but are not limited to, polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and nonwoven fabrics that have been subjected to a hydrophilic treatment.

The structure of the nonaqueous electrolyte secondary battery of this embodiment is not particularly limited, but typically includes a positive electrode, a negative electrode, and a separator that is provided as necessary, and can be in various shapes depending on the purpose of use, such as a paper type, a cylindrical type, a button type, or a laminated type.

<Conductive paint>
The conductive paint of the present invention contains at least the conductive material dispersion and a binder resin. The conductive paint can be produced by mixing the conductive material dispersion and the binder resin. Any optional components may be further mixed together with the conductive material dispersion and the binder resin.

<Binder resin for conductive paint>
The binder resin for conductive paint is not particularly limited as long as it is normally used as a binder resin for paint, and can be appropriately selected according to the purpose. In addition, the binder resin for conductive paint has a film-forming function, and is different from the dispersant of the present invention in this specification. Examples of the binder resin for conductive paint include condensation synthetic resins, addition synthetic resins, and natural polymer compounds. Examples of the condensation synthetic resins include polyester resins, polyurethane resins, polyepoxy resins, polyamide resins, polyether resins, and silicon resins. Examples of the addition synthetic resins include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, and unsaturated carboxylic acid resins. Examples of the natural polymer compounds include celluloses, rosins, and natural rubber. The water-dispersible resin may be used as a homopolymer, or may be used as a copolymer to be used as a composite resin, and any of single-phase structure type, core-shell type, and power feed type emulsions can be used.

As binder resins for conductive paints, those that have hydrophilic groups and are self-dispersible, and those that do not have dispersibility but have been given dispersibility by using a surfactant or a resin with hydrophilic groups can be used. Among these, ionomers of polyester resins or polyurethane resins, and emulsions of resin particles obtained by emulsifying and suspension polymerizing unsaturated monomers are suitable. In the case of emulsion polymerization of unsaturated monomers, a resin emulsion is obtained by reacting with water to which the unsaturated monomer, polymerization initiator, surfactant, chain transfer agent, chelating agent, pH adjuster, etc. have been added, so that a water-dispersible resin can be easily obtained, and the resin composition can be easily changed to create the desired properties.

The unsaturated monomer may be, for example, unsaturated carboxylic acids, (meth)acrylic acid ester monomers, (meth)acrylic acid amide monomers, aromatic vinyl monomers, vinyl cyano compound monomers, vinyl monomers, allyl compound monomers, olefin monomers, diene monomers, oligomers having unsaturated carbons, etc., which may be used alone or in combination. By combining these monomers, it is possible to flexibly modify the properties, and the properties of the resin can also be modified by performing a polymerization reaction or a graft reaction using an oligomer-type polymerization initiator.

Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid.
Examples of the monofunctional (meth)acrylic acid esters include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, methacryloxyethyl trimethyl methacrylate, and dimethylaminoethyl methacrylate. Examples of the acrylates include acrylates of 3-methyl-1,3-dimethyl ...

Examples of the polyfunctional (meth)acrylic acid esters include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, 2,2′-bis(4-methacryloxydiethoxyphenyl)
Propane, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2'-bis(4-acryloxypropyloxyphenyl)propane, 2,2'-bis(4-acryloxydiethoxyphenyl)propane trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate, ditrimethylol tetraacrylate, tetramethylolmethane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and the like.

Examples of the (meth)acrylic acid amide monomers include acrylamide, methacrylamide, N,N-dimethylacrylamide, methylenebisacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.
Examples of the aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, and divinylbenzene.

Examples of the vinyl cyano compound monomers include acrylonitrile and methacrylonitrile.
Examples of the allyl compound monomers include allylsulfonic acid or a salt thereof, allylamine, allyl chloride, diallylamine, and diallyldimethylammonium salt.
Examples of the olefin monomers include ethylene and propylene.
Examples of the diene monomers include butadiene and chloroprene.
Examples of the vinyl monomers include vinyl acetate, vinylidene chloride, vinyl chloride, vinyl ether, vinyl ketone, vinylpyrrolidone, vinylsulfonic acid or a salt thereof, vinyltrimethoxysilane, and vinyltriethoxysilane.

Examples of oligomers having unsaturated carbon include styrene oligomers having a methacryloyl group, styrene-acrylonitrile oligomers having a methacryloyl group, methyl methacrylate oligomers having a methacryloyl group, dimethylsiloxane oligomers having a methacryloyl group, and polyester oligomers having an acryloyl group.

A melamine resin, urea resin, polyisocyanate compound, blocked polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, alkoxysilane group-containing compound or resin, etc., which act as a crosslinking agent capable of reacting with the functional group of the base resin, can be used. It is desirable to use a resin containing a crosslinkable functional group in combination with a resin which acts as a crosslinking agent, and among these, it is preferable to use one selected from acrylic resin, polyester resin, alkyd resin, melamine resin, epoxy resin, and urea resin, it is more preferable to use one selected from acrylic resin, polyester resin, alkyd resin, and melamine resin, and it is more preferable to use a combination of acrylic resin and melamine resin.

Melamine resins are particularly preferred because they are thermosetting and act as a curing agent. The acrylic resin is preferably one obtained by polymerizing a monomer having a polymerizable unsaturated double bond by a conventional method, which is well known to those skilled in the art. Examples of the monomer having a polymerizable unsaturated double bond include carboxylic acid group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ε-caprolactone-modified acrylic monomers, methyl (meth)acrylate, ethyl (meth)acrylate, and (meth) Examples of the monomers include (meth)acrylic acid ester monomers such as propyl acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; and styrene monomers such as styrene, α-methylstyrene, α-methylstyrene dimer, vinyltoluene, and divinylbenzene. In addition, it is preferable to use a radical polymerization initiator well known to those skilled in the art for the polymerization.

Specific examples of melamine resins include methyl etherified melamine resins such as Cymel 300, 303, 325, 327, 350, and 370 (manufactured by Mitsui Cytec), Nikalac MS15, MS17, MX430, and MX650 (manufactured by Sanwa Chemical), Sumimal M-55 (manufactured by Sumitomo Chemical), and Resimin 740 and 741 (manufactured by Monsanto); and methyl ether/butyl ether mixed etherified melamine resins such as Cymel 202, 235, 238, 254, 272, and 1130 (manufactured by Mitsui Cytec), Nikalac MX485 and MX487 (manufactured by Sanwa Chemical), and Resimin 755 (manufactured by Monsanto). These melamine resins can be used alone or as a mixture of two or more types.

<Conductive coating film>
The conductive coating film of the present invention is obtained by applying the conductive paint to a substrate and drying it. The substrate is not particularly limited and various types can be selected. For example, metal substrates such as iron, stainless steel, aluminum, copper, etc. and surface-treated substrates thereof; cement-based substrates such as cements, limes, gypsums, etc.; plastic substrates such as polyvinyl chlorides, polyesters, polycarbonates, acrylics, etc. can be mentioned. In addition, various coated objects in the field of construction and building materials, such as building materials, buildings, structures, etc., made of these various substrates can be mentioned.

The method of applying the conductive paint is not particularly limited, and examples include brush coating, roller coating, spray coating, etc. After coating, a coating film can usually be obtained by drying at room temperature or by heating. The amount of coating; the order of coating (undercoat, middle coat, top coat, etc.); coating film thickness; drying time, etc. can be set as desired depending on the type of carbon nanotube paint and the substrate to which it is applied.

The content of the conductive material in the conductive coating is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and more preferably 0.02% by mass or more, based on the mass of the total solid content of the paint. Also, it is preferably 3.0% by mass or less, and more preferably 1.0% by mass or less.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, so long as it does not depart from the gist of the invention. In addition, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

(Method of measuring the acid value of a dispersant)
The acid value of the dispersant was calculated from the titration of the dispersant/NMP solution. 1 g of the dispersant was collected in a beaker (100 ml), 30 ml of NMP was added, and the mixture was stirred with a stirrer to dissolve. The mixture was further diluted with 20 ml of ion-exchanged water to obtain a titration solution. The titration solution was separately titrated with a 0.1 mol/l KOH/ethanol solution using an automatic potentiometric titrator (AT-710S, manufactured by Kyoto Electronics Manufacturing Co., Ltd.), and the acid value (mg KOH/g) of the dispersant was calculated from the titration amount at the isoelectric point.

(Method of measuring weight average molecular weight (Mw))
The weight average molecular weight (Mw) of the synthesized dispersant was measured by gel permeation chromatography (GPC) equipped with an RI detector.
The apparatus used was an HLC-8320GPC (manufactured by Tosoh Corporation), with three separation columns connected in series, and the packing materials used were Tosoh Corporation's "TSK-GELSUPERAW-4000", "AW-3000", and "AW-2500", respectively. The oven temperature was 40°C, and an N,N-dimethylformamide solution of 30 mM triethylamine and 10 mM LiBr was used as the eluent, with the measurement being performed at a flow rate of 0.6 ml/min. The sample was prepared in a solvent consisting of the above eluent at a concentration of 1 wt%, and 20 microliters were injected. The molecular weight is a polystyrene equivalent value.

(Method for measuring the amount of acidic groups in a conductive material)
The amount of acidic groups in the conductive material was calculated by determining the amount of hexylamine adsorbed by back titration as follows. 0.2 g of the conductive material was collected in a glass bottle (M-70, manufactured by Kashiwa Glass Co., Ltd.), and 30 ml of a hexylamine/NMP solution (0.02 mol/l) was added. The glass bottle was irradiated with ultrasonic waves (frequency 28 Hz) for 1 hour, and coarse particles were removed using a nylon mesh with a mesh size of 25 μm. Further, the mixture was centrifuged at 10,000 rpm for 10 minutes using a centrifuge (mini centrifuge MCF-1350 (manufactured by LMS)), the supernatant was collected, and the filtrate was filtered using a membrane filter (filter pore size 0.22 μm) to recover the filtrate. 10 ml of the obtained filtrate was collected and diluted with 40 ml of ion-exchanged water to obtain a titration liquid. In addition, 10 ml of a hexylamine/NMP solution (0.02 mol/l) that was not subjected to ultrasonic treatment together with the conductive material was diluted with 40 ml of ion-exchanged water to obtain a standard titration liquid. The test solution and the standard test solution were each titrated with a 0.1 mol/l HCl/ethanol solution using a separate automatic potentiometric titrator (AT-710S, manufactured by Kyoto Electronics Manufacturing Co., Ltd.), and the amount of hexylamine adsorbed to the conductive material ([hexylamine adsorption amount] (μmol)) was calculated from the difference in the titration amount at the isoelectric point.
The test solution was 30 ml of hexylamine/NMP solution, of which 10 ml was sampled. The amount of conductive material was 0.2 g, so multiplying the [hexylamine adsorption amount] by 3 and dividing the result by 0.2 gave the [hexylamine adsorption amount] (μmol/g) per unit weight of conductive material, and further dividing this by the specific surface area of the conductive material gave the [hexylamine adsorption amount] per surface area of the conductive material (μmol/ ^m2 ).

(Method for measuring the specific surface area of conductive materials)
The conductive material was weighed out in an amount of 0.03 g using an electronic balance (MSA225S100DI, manufactured by Sartorius), and then dried while degassing for 15 minutes at 110° C. Thereafter, the specific surface area (m ² /g) of the conductive material was measured using a fully automatic specific surface area measuring device (HM-model 1208, manufactured by MOUNTECH).

(Method of measuring the dispersed particle size of conductive material dispersion)
The dispersed particle size was determined by a method conforming to JIS K5600-2-5 using a grind gauge with a maximum groove depth of 300 μm.

(Method of measuring the median particle size of conductive material dispersion)
The median diameter was measured using a particle size distribution analyzer (Partial LA-960V2, manufactured by HORIBA). The circulation/ultrasonic operation conditions were: circulation speed: 3, ultrasonic intensity: 7, ultrasonic time: 1 minute, stirring speed: 1, stirring mode: continuous. During air removal, ultrasonic operation was performed with ultrasonic intensity 7 and ultrasonic time 5 seconds. The refractive index of water was 1.333, and the refractive index of the carbon material was 1.92. The measurement was performed after diluting the measurement sample so that the transmittance of the red laser diode was 60 to 80%, and the particle size standard was volume.

(Method of measuring metal content)
The metal content of the conductive material dispersion was measured by the following method. The conductive material dispersion was added to a glass bottle (M-140, manufactured by Kashiwa Glass Co., Ltd.) and dried in an electric oven at 120°C ± 5°C to obtain a dried conductive material dispersion. The dried conductive material dispersion was powdered using a mortar and subjected to acid decomposition using a microwave sample pretreatment device (manufactured by Milestone General Co., Ltd., ETHOS1) to extract the metals contained in the CNT. Then, analysis was performed using a multi-type ICP emission spectrometer (manufactured by Agilent Co., Ltd., 720-ES) to calculate the metal content of iron, nickel, and chromium contained in the conductive material dispersion.
The metal content in the conductive material dispersion was calculated as follows.
Metal content (ppm) of conductive material dispersion = (iron content in the dried conductive material + nickel content in the dried conductive material + chromium content in the dried conductive material dispersion) x (CNT concentration (%) in the CNT dispersion)

<Synthesis of Dispersant>
(Synthesis Example 1)
(Synthesis of Dispersant 1)
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 100 parts of methyl ethyl ketone, 90.0 parts of acrylonitrile, 10.0 parts of acrylic acid, and 0.5 parts of 3-mercapto-1,2-propanediol, and replaced with nitrogen gas. The reaction vessel was heated to 70°C, and a mixture consisting of 10 parts of methyl ethyl ketone and 0.4 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.: V-65) was dropped into the reaction vessel over 6 hours to carry out a polymerization reaction. After the dropwise addition, the reaction was carried out at 70°C for 1 hour, and then 0.1 parts of V-65 was added, and the reaction was continued at 70°C for another 1 hour to obtain the target product as a precipitate. Thereafter, it was confirmed that the conversion rate exceeded 98% by measuring the nonvolatile content. The product was filtered off by vacuum filtration, washed with 100 parts of ethyl acetate, and the solvent was completely removed by vacuum drying to obtain a polymer (A-1). The weight average molecular weight (Mw) of the dispersant (A-1) was 52,000, and the acid value was 78 mgKOH/g.

(Synthesis Examples 2 to 22)
(Synthesis of Dispersants 2 to 22)
Dispersants 2 to 22 were produced in the same manner as in Synthesis Example 1, except that the monomers and chain transfer agents used were changed according to Table 1. The weight average molecular weight (Mw) and acid value of each dispersant were as shown in Table 1. In the synthesis of the dispersants, the Mw was adjusted by adding the chain transfer agent, adjusting the amount of the polymerization initiator, and appropriately changing the reaction conditions, etc.

AA: acrylic acid IA: itaconic acid SAMA: 2-methacryloyloxyethyl succinate β-CEA: β-carboxyethyl acrylate a-1: isopropyl alcohol adduct of maleic anhydride (following formula (1))
a-2: 2-acryloyloxyethyl succinate a-3: octenylsuccinic anhydride adduct of hydroxyethyl acrylate (following formula (2))
DMAEA: Dimethylaminoethyl acrylate BA: Butyl acrylate 2EHA: 2-Ethylhexyl acrylate

<Example α: Application to secondary batteries>

(Preparation of Conductive Material Dispersion)
(Example 1α-1)
According to the composition shown in Table 2, ion-exchanged water, dispersant, additive, and antifoaming agent (Surfynol 104E, manufactured by Shin-Etsu Industries, Japan) were added to a stainless steel container, and the mixture was stirred with a disperser until it was uniform. Thereafter, the conductive material was added while stirring with a disperser, and a square-hole high shear screen was attached to a high shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,600 rpm until the entire mixture became uniform and the dispersion particle size was 250 μm or less using a grind gauge. At this time, the dispersion particle size confirmed by the grind gauge was 180 μm. Next, the liquid to be dispersed was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) through a pipe, and 20 passes of dispersion processing were performed until the median diameter was 100 μm or less. The dispersion processing was performed using a single nozzle chamber, with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. Furthermore, after passing through a nylon mesh with an opening of 48 μm three times, the mixture was filtered through a magnetic filter (manufactured by Tok Engineering) at room temperature and a magnetic flux density of 12,000 Gauss to obtain a conductive material dispersion (dispersion 1α). After filtration, the magnetic filter showed adhesion of magnetic granular metal pieces. As shown in Table 2, dispersion 1α had low viscosity and good storage stability, and the metal content of iron, nickel, and chromium was 30 ppm.

(Examples 1α-2 to 1α-33, Comparative Examples 1α-1 to 1α-6)
According to the composition shown in Table 2, each dispersion (Dispersion 2α to 33α, Comparative Dispersion 1α to 6α) was obtained in the same manner as in Example 1α-1. However, when the median diameter was 100 μm or more, an additional two-pass dispersion treatment was performed, and the measurement was repeated until the median diameter was 100 μm or less. As shown in Table 2, all of the conductive material dispersions of the present invention (Dispersion 2α to 33α) had low viscosity and good storage stability. In addition, the metal contents of iron, nickel, and chromium were as shown in Table 2.

(Method of measuring viscosity of conductive material dispersion)
The viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., "BL") at a dispersion temperature of 25°C. After the dispersion was thoroughly stirred with a spatula, the viscosity was immediately measured at a rotation speed of the B-type viscometer rotor of 60 rpm. The rotors used in the measurement were No. 1 when the viscosity was less than 100 mPa·s, No. 2 when the viscosity was 100 or more and less than 500 mPa·s, No. 3 when the viscosity was 500 or more and less than 2,000 mPa·s, and No. 4 when the viscosity was 2,000 or more and less than 10,000 mPa·s. The lower the viscosity, the better the dispersibility, and the higher the viscosity, the worse the dispersibility. The dispersion obtained was judged to have poor dispersibility when it was clearly separated or precipitated.
Judgment criteria: Less than 500 mPa·s (excellent)
○: 500 mPa·s or more and less than 2,000 mPa·s (good)
△: 2,000 mPa·s or more and less than 10,000 mPa·s (poor)
×: 10,000 mPa·s or more, settling or separation (very poor)

(Method for Evaluating Stability of Conductive Material Dispersion)
The storage stability was evaluated by measuring the viscosity of the dispersion after storing it at 50° C. for 7 days in the same manner as for the initial viscosity.
Judgment criteria ◎: Same as initial condition (excellent)
○: Viscosity changed slightly (good)
△: Viscosity has increased but gelation has not occurred (bad)
×: Gelled (very poor)

6A: JENOTUBE6A (manufactured by JEIO, multi-walled CNT, average outer diameter 6 nm, specific surface area 700 m ² /g, acidic group amount 0.27 μmol/m ² , 190 μmol/g)
10B: JENOTUBE10B (manufactured by JEIO, multi-walled CNT, average outer diameter 10 nm, specific surface area 230 m ² /g, acidic group amount 0.67 μmol/m ² , 154 μmol/g)
TUBALL1: Single-wall carbon nanotube (OCSiAl, average outer diameter 1.7 nm, purity 80%, specific surface area 490 m ² /g, acidic group amount 0.38 μmol/m ² , 186 μmol/g)
TUBALL2: Single-wall carbon nanotube (OCSiAl, average outer diameter 1.6 nm, purity 93%, specific surface area 975 m ² /g, acidic group amount 0.21 μmol/m ² , 205 μmol/g)
100T: K-Nanos 100T (Kumho Petrochemical, multi-walled CNT, average outer diameter 13 nm, specific surface area 240 m ² /g, acidic group amount 0.23 μmol/m ² , 54 μmol/g)
EC-300J: Ketjen Black (manufactured by Lion Specialty Chemicals, average primary particle size 40 nm, specific surface area 800 m ² /g, acidic group amount 0.27 μmol/m ² , 219 μmol/g)
HS-100: Denka Black HS-100 (manufactured by Denka, acetylene black, average primary particle size 48 nm, specific surface area 39 m ² /g, specific surface area 975 m ² /g, acidic group amount 0.21 μmol/m ² , 205 μmol/g)
PVP: Polyvinylpyrrolidone K-30 (manufactured by Nippon Shokubai, non-volatile content 100%, acid value 0 mgKOH/g)
F01MC: Sodium carboxymethylcellulose salt, Sunrose F F01MC (manufactured by Nippon Paper Industries Co., Ltd., non-volatile content 100%, acid value: insoluble in NMP, cannot be measured)

(Preparation of negative electrode mixture composition and negative electrode)
(Example 2α-1)
After adding the conductive material dispersion (dispersion 1α), CMC, and water to a plastic container with a capacity of 150 cm ³ , the mixture was stirred at 2,000 rpm for 30 seconds using a rotation/revolution mixer (Thinky's Awatori Rentaro, ARE-310). Then, artificial graphite and silicon were added as negative electrode active materials, and the mixture was stirred at 2,000 rpm for 150 seconds using the rotation/revolution mixer. Then, SBR was added, and the mixture was stirred at 2,000 rpm for 30 seconds using the rotation/revolution mixer to obtain a negative electrode mixture composition. The non-volatile content of the negative electrode mixture composition was 48% by mass. Of the non-volatile content of the negative electrode mixture composition, the non-volatile content ratio of artificial graphite:silicon:conductive material:CMC:SBR was 87:10:0.5:1:1.5.

The obtained negative electrode composite composition was applied to a copper foil having a thickness of 20 μm using an applicator, and then the coating was dried in an electric oven at 120° C.±5° C. for 25 minutes to prepare an electrode film. The electrode film was then rolled using a roll press (3t hydraulic roll press, manufactured by Sun Metals) to obtain a negative electrode (negative electrode 1). The weight per unit of the composite layer was 10 mg/cm ² , and the density of the composite layer after the rolling process was 1.6 g/cc.

・Artificial graphite: CGB-20 (manufactured by Nippon Graphite Industry Co., Ltd.), 100% non-volatile content
Silicon: silicon monoxide (manufactured by Osaka Titanium Technology, SILICON MONOXIDE SiO 1.3C 5 μm), non-volatile content 100%
CMC: Carboxymethylcellulose #1190 (manufactured by Daicel Finechem), non-volatile content 100%
SBR: Styrene butadiene rubber TRD2001 (manufactured by JSR), non-volatile content 48%

(Examples 2α-2 to 2α-33, Comparative Examples 2α-1 to 2α-6)
Negative electrodes 2 to 33 and comparative negative electrodes 1 to 6 were obtained in the same manner as in Example 2α-1, except that the conductive material dispersion was changed to each dispersion (dispersion 2α to 33α) shown in Table 3.

(Method of Evaluating Negative Electrode Conductivity)
The surface resistivity (Ω/□) of the composite layer of the obtained negative electrode was measured using Mitsubishi Chemical Analytec's Loresta GP, MCP-T610. After the measurement, the thickness of the composite layer was multiplied to obtain the volume resistivity (Ω cm) of the negative electrode. The thickness of the composite layer was measured at three points in the electrode using a thickness meter (NIKON, DIGIMICROMH-15M) and the average value was subtracted from the thickness of the copper foil to obtain the volume resistivity (Ω cm) of the negative electrode.
Judgment criteria: Less than 0.3 Ω cm (excellent)
○: 0.3 Ω cm or more and less than 0.5 Ω cm (good)
×: 0.5 Ω cm or more (defective)

(Method of Evaluating Adhesion of Negative Electrode)
The obtained negative electrode was cut into two rectangles of 90 mm x 20 mm with the coating direction as the long axis. A bench-top tensile tester (Strograph E3, manufactured by Toyo Seiki Seisakusho) was used to measure the peel strength, and it was evaluated by a 180-degree peel test method. Specifically, a double-sided tape (No. 5000NS, manufactured by Nitto) of 100 mm x 30 mm size was attached to a stainless steel plate, and the composite layer side of the prepared negative electrode was attached to the other side of the double-sided tape to prepare a test sample. Next, the test sample was fixed vertically so that the short sides of the rectangle were at the top and bottom, and the end of the copper foil was peeled off while pulling it from the bottom to the top at a constant speed (50 mm / min), and the average value of the stress at this time was taken as the peel strength.
Judgment criteria: 0.5 N/cm or more (excellent)
○: 0.1 N/cm or more and less than 0.5 N/cm (good)
×: Less than 0.1 N/cm (defective)

(Preparation of Positive Electrode Mixture Composition and Positive Electrode)
(Example 3α-1)
After adding the conductive material dispersion (dispersion 1α), CMC, and water to a plastic container with a capacity of 150 cm ³ , the mixture was stirred for 30 seconds at 2,000 rpm using a rotation and revolution mixer (Thinky's Awatori Rentaro, ARE-310), and then LFP was added as a positive electrode active material, and the mixture was stirred for 150 seconds at 2,000 rpm using a rotation and revolution mixer (Thinky's Awatori Rentaro, ARE-310). Further, PTFE was added, and the mixture was stirred for 30 seconds at 2,000 rpm using a rotation and revolution mixer (Thinky's Awatori Rentaro, ARE-310) to obtain a positive electrode mixture composition. The non-volatile content of the positive electrode mixture composition was 75% by mass. In the nonvolatile content of the positive electrode mixture composition, the nonvolatile content ratio of LFP:conductive material:PTFE:CMC was 97:0.5:1:1.5.

The positive electrode composite composition was applied onto an aluminum foil having a thickness of 20 μm using an applicator, and then dried in an electric oven at 120° C.±5° C. for 25 minutes to prepare an electrode film. The electrode film was then rolled using a roll press (3t hydraulic roll press, manufactured by Sunk Metals) to obtain a positive electrode (positive electrode 1). The weight per unit of the composite layer was 20 mg/cm ² , and the density of the composite layer after the rolling process was 2.1 g/cc.

LFP: Lithium iron phosphate HED (trademark) LFP-400 (manufactured by BASF, 100% non-volatile content)
PTFE: Polytetrafluoroethylene Polyflon PTFE D-210C (manufactured by Daikin, non-volatile content 60%)
CMC: Carboxymethylcellulose #1190 (manufactured by Daicel FineChem, non-volatile content 100%)

(Examples 3α-2 to 3α-33, Comparative Examples 3α-1 to 3α-6)
Positive electrodes 2 to 33 and comparative positive electrodes 1 to 6 were obtained in the same manner as in Example 3α-1, except that the conductive material dispersion was changed to each dispersion (dispersion 2α to 33α) shown in Table 4.

(Method for Evaluating Conductivity of Positive Electrode)
The conductivity of the obtained positive electrode was evaluated in the same manner as for the negative electrode, except that aluminum foil was used instead of the copper foil.
Judgment criteria: Less than 10 Ω cm (excellent)
○: 10 Ω cm or more and less than 20 Ω cm (good)
×: 20 Ω cm or more (defective)

(Method of Evaluating Adhesion of Positive Electrode)
The adhesion of the obtained positive electrode was evaluated in the same manner as for the negative electrode, except that aluminum foil was used instead of the copper foil.
Judgment criteria: 1 N/cm or more (excellent)
○: 0.5 N/cm or more and less than 1 N/cm (good)
×: Less than 0.5 N/cm (bad)

(Preparation of standard positive electrode)
As the positive electrode active material, 92 parts by mass of LFP (HED (trademark) LFP-400, manufactured by BASF, non-volatile content 100%), 4 parts by mass of acetylene black (Denka Black (registered trademark) HS-100, manufactured by Denka, non-volatile content 100%), and 1.6 parts by mass of CMC (#1190, manufactured by Daicel FineChem, non-volatile content 100%) were added to a plastic container with a capacity of 150 ml, and then mixed with a spatula until the powder was uniform. Thereafter, 20.5 parts by mass of water was added, and the mixture was stirred at 2,000 rpm for 30 seconds using a rotation and revolution mixer (Thinky Awatori Rentaro, ARE-310). Thereafter, the mixture in the plastic container was mixed with a spatula until it was uniform, and 4 parts by mass of PTFE (manufactured by Daikin, non-volatile content 60% by mass) was added using the rotation and revolution mixer, and the mixture was stirred at 2,000 rpm for 30 seconds. Thereafter, 11.2 parts by mass of water was added, and the mixture was stirred for 30 seconds at 2,000 rpm using the centrifugal mixer.Finally, the mixture was stirred for 10 minutes at 3,000 rpm using a high-speed stirrer to obtain a standard positive electrode composite material composition.

The standard positive electrode composite composition was applied to a 20 μm thick aluminum foil current collector using an applicator, and then dried in an electric oven at 120° C.±5° C. for 25 minutes to adjust the weight per unit area of the electrode to 20 mg/cm ^2. Further, rolling was performed using a roll press (3 t hydraulic roll press, manufactured by Sun Metals) to produce a standard positive electrode with a composite layer density of 2.1 g/cm ³ .

(Preparation of standard negative electrode)
0.5 parts by mass of acetylene black (Denka Black (registered trademark) HS-100, manufactured by Denka), 1 part by mass of CMC (#1190, manufactured by Daicel FineChem, non-volatile content 100%), and 98.4 parts by mass of water were added to a plastic container having a capacity of 150 ml, and the mixture was stirred at 2,000 rpm for 30 seconds using a centrifugal mixer (Thinky's Awatori Rentaro, ARE-310). Further, 87 parts by mass of artificial graphite (CGB-20, manufactured by Nippon Graphite Industry Co., Ltd., non-volatile content 100%) and 10 parts by mass of silicon (silicon monoxide, manufactured by Osaka Titanium Technology Co., Ltd., SILICON MONOOXIDE SiO 1.3C 5 μm, non-volatile content 100%) were added as active materials, and the mixture was stirred at 2,000 rpm for 150 seconds using a rotation/revolution mixer (Thinky's Awatori Rentaro, ARE-310). Subsequently, 3.1 parts by mass of SBR (TRD2001, manufactured by JSR) was added, and the mixture was stirred at 2,000 rpm for 30 seconds using a rotation/revolution mixer (Thinky's Awatori Rentaro, ARE-310) to obtain a standard negative electrode composite composition. The non-volatile content of the standard negative electrode composite composition was 50% by mass.

The standard negative electrode composite composition was applied to a copper foil having a thickness of 20 μm as a current collector using an applicator, and then dried in an electric oven at 80° C.±5° C. for 25 minutes to adjust the weight per unit area of the electrode to 10 mg/cm ^2. Further, a rolling process was performed using a roll press (3 t hydraulic roll press, manufactured by Sun Metals) to prepare a standard negative electrode with a composite layer density of 1.6 g/cm ³ .

(Examples 4α-1 to 4α-33, Comparative Examples 4-1 to 4-6)
(Examples 5α-1 to 5α-33, Comparative Examples 5-1 to 5-6)
(Preparation of secondary battery)
Using the negative electrode and positive electrode described in Tables 5 and 6, each was punched out to 50 mm x 45 mm and 45 mm x 40 mm, and the separator (porous polypropylene film) inserted between them was inserted into an aluminum laminate bag and dried in an electric oven at 70 ° C. for 1 hour. Then, in a glove box filled with argon gas, an electrolyte (a mixed solvent in which ethylene carbonate, dimethyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 was prepared, and 1 part by mass of vinylene carbonate was added to 100 parts by mass as an additive, and then LiPF ₆ was dissolved at a concentration of 1 M to form a non-aqueous electrolyte) was injected, and the aluminum laminate was sealed to prepare negative electrode evaluation batteries 1 to 33, negative electrode evaluation comparative batteries 1 to 6, positive electrode evaluation batteries 1 to 33, and positive electrode evaluation comparative batteries 1 to 6, respectively.

(Method of Evaluating Rate Characteristics of Secondary Batteries)
The obtained negative electrode evaluation secondary battery and positive electrode evaluation secondary battery were placed in a thermostatic chamber at 25 ° C., and charge and discharge measurements were performed using a charge and discharge device (Hokuto Denko, SM-8). After performing constant current constant voltage charging (cut-off current 1 mA (0.02 C)) at a charge end voltage of 4.3 V at a charge current of 10 mA (0.2 C), constant current discharge was performed at a discharge end voltage of 3 V at a discharge current of 10 mA (0.2 C). After repeating this operation three times, constant current constant voltage charging (cut-off current (1 mA 0.02 C)) was performed at a charge end voltage of 4.3 V at a charge current of 10 mA (0.2 C), and constant current discharge was performed at discharge currents of 0.2 C and 3 C until the discharge end voltage reached 3.0 V, and the discharge capacity was determined. The rate characteristic can be expressed by the ratio of the 0.2 C discharge capacity to the 3 C discharge capacity, as shown in the following formula 1.

(Formula 1) Rate characteristic = 3C discharge capacity / third 0.2C discharge capacity × 100 (%)

Judgment criteria: ◎: 80% or more (excellent)
○: 60% or more but less than 80% (good)
×: Less than 60% (defective)

(Method of Evaluating Cycle Characteristics of Secondary Battery)
The obtained negative electrode evaluation secondary battery and positive electrode evaluation secondary battery were placed in a thermostatic chamber at 25 ° C., and charge/discharge measurements were performed using a charge/discharge device (SM-8, manufactured by Hokuto Denko). After constant current/constant voltage charging (cutoff current 2.5 mA (0.05 C)) at a charge current of 25 mA (0.5 C) and a charge end voltage of 4.3 V, constant current discharging was performed at a discharge current of 25 mA (0.5 C) and a discharge end voltage of 3 V. This operation was repeated 200 times. The cycle characteristics can be expressed by the ratio of the third 0.5 C discharge capacity at 25 ° C. to the 200th 0.5 C discharge capacity, as shown in the following formula 2.

(Formula 2) Cycle characteristic = 3rd 0.5C discharge capacity / 200th 0.5C discharge capacity × 100 (%)

Judgment criteria: 85% or more (excellent)
○: 80% or more but less than 85% (good)
×: Less than 80% (defective)

In the above examples using the conductive material dispersion of the present invention, a good dispersion state was maintained even in the electrode state, which is believed to have resulted in the formation of a developed conductive network, and an electrode with superior conductivity and adhesion compared to the comparative example was obtained. Furthermore, as a result, a nonaqueous electrolyte secondary battery with excellent rate characteristics and cycle characteristics was obtained. It is believed that by combining a conductive material having a specific amount of acidic groups with a dispersant having a specific structure and a specific acid value, a nonaqueous electrolyte secondary battery with superior characteristics compared to the comparative example was obtained. Therefore, it has become clear that the present invention can provide a nonaqueous electrolyte secondary battery with excellent characteristics that are difficult to achieve with conventional conductive material dispersions.

<Example β: Application to conductive paint>

(Preparation of Conductive Material Dispersion)
(Example 1β-1)
According to the composition shown in Table 7, ion-exchanged water, dispersant, additive, and antifoaming agent (Surfynol 104E, manufactured by Shin-Etsu Industries, Japan) were added to a stainless steel container, and the mixture was stirred with a disperser until it was uniform. Thereafter, the conductive material was added while stirring with a disperser, and a square-hole high shear screen was attached to a high shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,600 rpm until the entire mixture became uniform and the dispersion particle size was 250 μm or less using a grind gauge. At this time, the dispersion particle size confirmed by the grind gauge was 170 μm. Next, the liquid to be dispersed was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) through a pipe, and 20 passes of dispersion processing were performed until the median diameter was 100 μm or less. The dispersion processing was performed using a single nozzle chamber, with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. Furthermore, after passing through a nylon mesh with an opening of 48 μm three times, the mixture was filtered through a magnetic filter (manufactured by Tok Engineering) at room temperature and a magnetic flux density of 12,000 Gauss to obtain a conductive material dispersion (dispersion 1β). After filtration, the magnetic filter showed adhesion of magnetic granular metal pieces. As shown in Table 7, dispersion 1β had low viscosity and good storage stability. The metal content of iron, nickel, and chromium was 31 ppm.

(Examples 1β-2 to 1β-32, Comparative Examples 1β-1 to 1β-4)
According to the composition shown in Table 7, each dispersion (Dispersion 2β to 32β, Comparative Dispersion 1β to 4β) was obtained in the same manner as in Example 1β-1. However, when the median diameter was 100 μm or more, an additional two-pass dispersion treatment was performed, and the measurement was repeated until the median diameter was 100 μm or less. As shown in Table 2, all of the conductive material dispersions of the present invention (Dispersion 2β to 32β) had low viscosity and good storage stability. In addition, the metal contents of iron, nickel, and chromium were as shown in Table 7.

(Method of measuring viscosity of conductive material dispersion)
The viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., "BL") at a dispersion temperature of 25°C. After the dispersion was thoroughly stirred with a spatula, the viscosity was immediately measured at a rotation speed of the B-type viscometer rotor of 60 rpm. The rotors used in the measurement were No. 1 when the viscosity was less than 100 mPa·s, No. 2 when the viscosity was 100 or more and less than 500 mPa·s, No. 3 when the viscosity was 500 or more and less than 2,000 mPa·s, and No. 4 when the viscosity was 2,000 or more and less than 10,000 mPa·s. The lower the viscosity, the better the dispersibility, and the higher the viscosity, the worse the dispersibility. The dispersion obtained was judged to have poor dispersibility when it was clearly separated or precipitated.
Judgment criteria: Less than 500 mPa·s (excellent)
○: 500 mPa·s or more and less than 2,000 mPa·s (good)
△: 2,000 mPa·s or more and less than 10,000 mPa·s (poor)
×: 10,000 mPa·s or more, settling or separation (very poor)

(Method for Evaluating Stability of Conductive Material Dispersion)
The storage stability was evaluated by measuring the viscosity of the dispersion after storing it at 50° C. for 7 days in the same manner as for the initial viscosity.
Judgment criteria ◎: Same as initial condition (excellent)
○: Viscosity changed slightly (good)
△: Viscosity has increased but gelation has not occurred (bad)
×: Gelled (very poor)

(Method of measuring metal content)
The metal content was measured in the same manner as in Example 2α-1.

(Preparation of conductive paint and conductive coating film)
(Example 2β-1)
According to the composition shown in Table 8, a conductive material dispersion, a paint binder, and water were added to a container and stirred with a disperser until homogenous, thereby obtaining paint 1.

(Examples 2β-2 to 35, Comparative Examples 2β-1 to 4)
Except for changing the dispersion shown in Table 7, the same procedure as in Example 2β-1 was followed to obtain each paint (paints 2 to 35, comparative paints 1 to 4).

(Paint evaluation)
The resulting paints were then coated on corona discharge treated PET films with a bar coater to a film thickness of 1 μm, and after setting for 30 minutes, the films were dried at 60° C. for 30 minutes and then baked at 140° C. for 20 minutes to prepare test coatings for each paint. The paints and the coatings were evaluated as follows. The results are shown in Table 3.
(Compatibility)
The obtained paint was checked for particle density according to JIS K56002-5 to judge the compatibility of the conductive material dispersion and the paint binder. Evaluation was performed according to the following criteria. Evaluation was performed on a two-level scale of ◯ (good) and × (bad).
Criteria: ○: Dense less than 20 μm ×: Dense 20 μm or more (transparency)
Regarding transparency, the total light transmittance of the test coating film applied to the PET film was measured using a haze meter (300A) manufactured by Nippon Denshoku Industries Co., Ltd. Evaluation was performed according to the following criteria. The evaluation was made on a four-level scale: ◎ (very good), ○ (good), △ (average), × (bad).
Criteria: ◎: 80% or more, 〇: 60% or more and less than 80%, △: 40% or more and less than 60%, ×: Less than 40% (surface resistivity)
Regarding electrical conductivity, the surface resistivity (Ω/□) of the test coating film applied to the PET film was measured using Mitsubishi Chemical's Loresta GP (CP-T610). Evaluation was performed according to the following criteria. Evaluation was performed on a four-level scale: ◎ (very good), ○ (good), △ (average), × (bad).
Judgment criteria: ◎: Less than 1.0 x 10 ⁸ ; ○: 1.0 x 10 ⁸ or more but less than 1.0 x 10 ¹⁰ ; △: 1.0 x 10 ¹⁰ or more but less than 1.0 x 10 ¹⁴ ; ×: 1.0 x 10 ¹⁴ or more (not measurable)

The abbreviations shown in Table 8 have the following meanings.
Urethane: Evaphanol HA-107C (manufactured by Nicca Chemical Co., Ltd., water-based urethane resin, solid content 40%)
Olefin: Superchron E-415 (manufactured by Nippon Paper Industries Co., Ltd., water-based olefin resin, solid content 30%)

The results shown in Tables 7 and 8 indicate that the conductive material dispersion of the present invention is excellent in storage stability, compatibility with paint binders, transparency and surface resistivity.

Claims (12)

The conductive material includes a dispersant and water.
The conductive material is a carbon nanotube having an acidic group amount of 0.1 to 1.0 μmol/ ^m2 and 60 to 300 μmol/g,
The conductive material dispersion, wherein the dispersant is a copolymer containing units derived from (meth)acrylonitrile and carboxyl group-containing monomer units, the copolymer contains 40 to 99 mass% of units derived from (meth)acrylonitrile in all monomer units constituting the copolymer, and has an acid value of 30 to 400 mgKOH/g. The conductive material dispersion according to claim 1, wherein the carbon nanotubes have an average outer diameter of 7 nm or less. The conductive material dispersion according to claim 1 or 2, wherein the carboxyl group-containing monomer units account for 3 to 40 mass% of all monomer units constituting the copolymer. The conductive material dispersion according to any one of claims 1 to 3, wherein the dispersant is a copolymer further comprising one or more monomer units selected from the group consisting of active hydrogen group-containing monomers (excluding carboxyl group-containing monomers), basic monomers, and (meth)acrylic acid alkyl esters. The conductive material dispersion according to any one of claims 1 to 4 further comprises an antifoaming agent. A composition for secondary battery electrodes comprising the conductive material dispersion according to any one of claims 1 to 5. An electrode film that is a coating film of the secondary battery electrode composition according to claim 6. A secondary battery comprising the electrode film according to claim 7. A conductive paint comprising the conductive material dispersion according to any one of claims 1 to 5. A conductive coating film that is a coating film of the conductive paint according to claim 9. The method for producing a conductive material dispersion according to any one of claims 1 to 5, comprising step 1 of dispersing the conductive material composition by applying shear stress until the dispersed particle size is 250 μm or less, and step 2 of dispersing the conductive material composition using a high-pressure homogenizer at a pressure of 60 to 150 MPa until the median diameter is 100 μm or less, following step 1. The method for producing a conductive material dispersion according to claim 11, further comprising a step 3 of reducing the content of metals consisting of iron, nickel and chromium contained in the conductive material dispersion to 100 ppm or less.