Dispersion containing poly(amic acid) / carbon nanotubes

Abstract

Provided is a dispersion containing poly(amic acid) / carbon nanotubes which comprises an organic solvent, a poly(amic acid), and carbon nanotubes, the poly(amic acid) having an alicyclic structure. When having a carbon nanotube concentration of 0.001 mass%, the dispersion containing poly(amic acid) / carbon nanotubes has an optical density at 500-nm wavelength exceeding 0.40.

Description

Polyamic acid / carbon nanotube-containing dispersion

[0001] The present invention relates to a polyamic acid / carbon nanotube-containing dispersion in which carbon nanotubes are highly dispersed.

[0002] Carbon materials such as carbon blacks, fullerenes, graphene, and carbon nanotubes are used in a wide range of fields, including electronics and energy, due to their electrical properties and thermal conductivity. In particular, carbon nanotubes are tubular carbons with a diameter of 1 μm or less, and are expected to be used in a variety of applications due to their high electrical conductivity, tensile strength, heat resistance, and other properties based on their unique structure.

[0003] On the other hand, carbon nanotubes are obtained as entangled aggregates (also called bundles), and because the mutual cohesive forces (van der Waals forces) cause them to form bundles or ropes, and because their atomically smooth surfaces reduce their affinity for solvents, they are difficult to disperse in both polar and nonpolar solvents. For this reason, attempts have been made to disperse carbon nanotubes well in order to apply them to various applications.

[0004] For example, Patent Document 1 discloses a fine carbon dispersion composition containing a dispersant for fine carbon, which contains a polyimide precursor and a basic compound having a pKa of 7.5 or more and 0.7 times or more equivalent to the carboxyl group of the polyimide precursor, fine carbon such as carbon nanotubes, and a polar solvent.

[0005] International Publication No. 2013 / 147087

[0006] However, although conventional methods have been able to disperse fine carbon such as carbon nanotubes in polar solvents, the dispersibility of the fine carbon such as carbon nanotubes in the resulting dispersion composition has not always been sufficient. The present invention has been made in view of the conventional problems, and an object of the present invention is to provide a polyamic acid / carbon nanotube-containing dispersion in which carbon nanotubes are highly dispersed.

[0007] In order to solve the above-mentioned problems, the present inventors have conducted extensive research and have found that the above-mentioned problems can be solved by controlling the optical density at a wavelength of 500 nm to a predetermined value in a polyamic acid / carbon nanotube-containing dispersion liquid containing an organic solvent, polyamic acid, and carbon nanotubes, in which the polyamic acid contains an alicyclic structure and the carbon nanotube concentration is 0.001% by mass.

[0008] That is, the present invention provides the following [1] to

[12] : [1] A polyamic acid / carbon nanotube-containing dispersion liquid comprising an organic solvent, a polyamic acid, and carbon nanotubes, wherein the polyamic acid contains an alicyclic structure, and the polyamic acid / carbon nanotube-containing dispersion liquid has an optical density of more than 0.40 at a wavelength of 500 nm when the carbon nanotube concentration is 0.001% by mass.

[0009] [2] The polyamic acid / carbon nanotube-containing dispersion according to [1], further containing a proton-accepting nitrogen-containing compound.

[0010] [3] The polyamic acid / carbon nanotube-containing dispersion according to [1] or [2], wherein the carbon nanotubes are single-walled carbon nanotubes.

[0011] [4] The polyamic acid / carbon nanotube-containing dispersion according to any one of [1] to [3], wherein the content of the carbon nanotubes in the dispersion is 0.1 mass % or more.

[0012] [5] The polyamic acid / carbon nanotube-containing dispersion according to any one of [1] to [4], wherein the organic solvent contains N-methyl-2-pyrrolidone.

[0013] [6] A binder composition for an electrical storage device, comprising the polyamic acid / carbon nanotube-containing dispersion liquid according to any one of [1] to [5].

[0014] [7] A slurry for an electrode containing the binder composition for a storage battery device according to [6] and an active material.

[0015] [8] An electrode for an electricity storage device, obtained by using the electrode slurry according to [7].

[0016] [9] An electric storage device for an electric storage device, comprising the electrode according to [8].

[0017]

[10] An electromagnetic wave shielding composition comprising the polyamic acid / carbon nanotube-containing dispersion liquid according to any one of [1] to [5].

[0018]

[11] An electromagnetic wave shielding coating film obtained by using the electromagnetic wave shielding composition according to

[10] .

[0019]

[12] An electromagnetic wave shielding laminate comprising the electromagnetic wave shielding coating film according to

[11] and a substrate.

[0020] According to the present invention, it is possible to provide a polyamic acid / carbon nanotube-containing dispersion in which carbon nanotubes are highly dispersed. Furthermore, according to the present invention, it is possible to provide a binder composition for an electricity storage device, an electrode slurry, and electrodes and electricity storage devices obtained using the same, which are obtainable using the polyamic acid / carbon nanotube-containing dispersion and are capable of providing electrodes and electricity storage devices with excellent capacity retention. Furthermore, according to the present invention, it is also possible to provide an electromagnetic wave shielding composition, an electromagnetic wave shielding coating film, and an electromagnetic wave shielding laminate, which are obtainable using the polyamic acid / carbon nanotube-containing dispersion and are suitable for use in electromagnetic wave shielding.

[0021] <Polyamic Acid / Carbon Nanotube-Containing Dispersion> The polyamic acid / carbon nanotube-containing dispersion of the present invention is a polyamic acid / carbon nanotube-containing dispersion comprising an organic solvent, polyamic acid, and carbon nanotubes, wherein the polyamic acid contains an alicyclic structure, and the polyamic acid / carbon nanotube-containing dispersion has an optical density of more than 0.40 at a wavelength of 500 nm when the carbon nanotube concentration is 0.001% by mass.

[0022] The organic solvent is not particularly limited, but from the viewpoint of affinity with polyamic acid, a polar solvent is preferred, and among the polar solvents, either a protic polar solvent or an aprotic polar organic solvent may be used.

[0023] Examples of the protic polar solvent include aliphatic alcohols such as methanol, ethanol, and propanol, and phenols such as phenol, m-cresol, and 4-chlorophenol.

[0024] Examples of aprotic polar organic solvents include amide-based solvents such as N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylisobutyramide (DMIB), 3-methoxy-N,N-dimethylpropanamide (for example, Equamide (registered trademark) M100, KJCMPA (registered trademark)-100), and N-methylcaprolactam. Examples of suitable organic solvents include 1,3-dimethyl-2-imidazolidinone, hexamethylphosphorotriamide, 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, tetrahydrofuran, bis[2-(2-methoxyethoxy)ethyl]ether, 1,4-dioxane, dimethyl sulfoxide, diphenyl ether, sulfolane, diphenyl sulfone, tetramethylurea, anisole, and γ-butyrolactone. The protic polar solvents and aprotic polar organic solvents can be used alone or in combination of two or more.

[0025] In the present invention, from the viewpoint of dissolving the polyamic acid well and further enhancing the dispersibility of the carbon nanotubes in the polyamic acid / carbon nanotube-containing dispersion liquid of the present invention (hereinafter referred to as "polyamic acid / CNT dispersion liquid" as appropriate), an amide-based solvent is preferred, N-methyl-2-pyrrolidone (NMP) or N-ethyl-2-pyrrolidone (NEP) is more preferred, and N-methyl-2-pyrrolidone (NMP) is even more preferred.

[0026] Examples of carbon nanotubes (CNTs) include vapor-grown carbon fibers, single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs). Among these, single-walled carbon nanotubes (SWCNTs) are preferred because, when the polyamic acid / CNT dispersion of the present invention is used as a binder composition for an electricity storage device, higher conductivity can be imparted to the resulting electrode.

[0027] The method for producing carbon nanotubes is not particularly limited, and any conventionally known production method can be used, such as a thermal decomposition method using a catalyst, an arc discharge method, a laser evaporation method, and a CVD method such as a HiPco method or a CoMoCAT method. In addition, commercially available single-walled carbon nanotubes and multi-walled carbon nanotubes can also be used.

[0028] The carbon nanotube content in the polyamic acid / CNT dispersion of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more. The upper limit is not particularly limited, but is preferably 1.2% by mass or less, more preferably 1.0% by mass or less, even more preferably 0.8% by mass or less, and particularly preferably 0.6% by mass or less. According to the polyamic acid / CNT dispersion of the present invention, even when the carbon nanotube content is set to such a relatively high level, the carbon nanotubes can be highly dispersed. In particular, while it has been difficult to disperse carbon nanotubes when the carbon nanotube content is set to such a relatively high level in the past, the present invention makes it possible to highly disperse carbon nanotubes.

[0029] The polyamic acid used in the present invention is obtained by reacting a tetracarboxylic acid component with a diamine component to form an amide bond (-CONH-). Therefore, the polyamic acid used in the present invention has units derived from the tetracarboxylic acid component and units derived from the diamine component. The polyamic acid preferably contains a repeating unit represented by the following formula (1), and the content of the repeating unit represented by the following formula (1) is preferably 50 mol % or more, more preferably 75 mol % or more, and even more preferably 90 mol % or more. In the above formula (1), A is one or more tetravalent groups selected from tetracarboxylic acid components by removing a carboxyl group, and B is one or more divalent groups selected from diamine components by removing an amino group.

[0030] The polyamic acid used in the present invention has an alicyclic structure. According to the present invention, by using a polyamic acid having an alicyclic structure and setting the optical density at a wavelength of 500 nm in a specific range when the carbon nanotube concentration is 0.001% by mass, as described below, the polyamic acid / CNT dispersion of the present invention can be one in which carbon nanotubes are highly dispersed. Note that the polyamic acid used in the present invention may contain an alicyclic structure in either the unit derived from the tetracarboxylic acid component or the unit derived from the diamine component, or may contain the alicyclic structure in both, but it is preferable that the alicyclic structure be contained at least in the unit derived from the tetracarboxylic acid component (i.e., it is preferable to use a tetracarboxylic acid component having an alicyclic structure as the tetracarboxylic acid component).

[0031] The alicyclic structure may be a non-aromatic ring structure that does not contain a heteroatom in the ring structure, and is usually a non-aromatic ring structure in which the ring structure (skeleton of the ring structure) is formed only from carbon atoms, and may be any of a three-membered ring structure, a four-membered ring structure, a five-membered ring structure, a six-membered ring structure, a seven-membered ring structure, an eight-membered ring structure, etc., and may contain a carbon-carbon double bond, form a polycyclic structure, or have a bridged ring structure. Another example of an alicyclic structure may be one in which a heteroatom is directly bonded to a carbon atom forming the ring structure, and in this case, the heteroatom is not introduced into the ring structure, but may be directly bonded to the carbon atom forming the ring structure toward the outside of the ring, for example.

[0032] The polyamic acid used in the present invention may be any polyamic acid as long as it contains an alicyclic structure. From the viewpoint of further enhancing the dispersibility of carbon nanotubes, the content of units derived from components having an alicyclic structure, based on the total molar amount of units derived from components constituting the polyamic acid, is preferably 25 mol % or more, more preferably 30 mol % or more, even more preferably 40 mol %, and still more preferably 50 to 100 mol %.

[0033] Examples of the tetracarboxylic acid component include aromatic tetracarboxylic acid dianhydrides and aliphatic tetracarboxylic acid dianhydrides.

[0034] As the aromatic tetracarboxylic dianhydride, a tetracarboxylic dianhydride having an aromatic ring can be suitably used. Specific examples of the aromatic tetracarboxylic dianhydride include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), pyromellitic dianhydride (PMDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride (ODPA), diphenylsulfone-3,4,3',4'-tetracarboxylic dianhydride, and bis(3,4-dicarboxyphenyl)sulfonyl ether. dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (also known as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride), 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4 1,4-bis(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, p-phenylenebis(trimellitic acid monoester acid anhydride), p-biphenylenebis(trimellitic acid monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride. These may be used alone or in combination of two or more.

[0035] As the aliphatic tetracarboxylic acid dianhydride, an alicyclic tetracarboxylic acid dianhydride (a tetracarboxylic acid dianhydride having an alicyclic structure and no aromatic ring) can be suitably used. Specific examples of the alicyclic tetracarboxylic acid dianhydride include (1R,2S,4S,5R)-cyclohexanetetracarboxylic acid dianhydride (H″-PMDA), (1S,2R,4S,5R)-cyclohexanetetracarboxylic acid dianhydride, (1S,2S,4R,5R)-cyclohexanetetracarboxylic acid dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic acid anhydride, Tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo-3,3',4,4'-tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, pentacyclo[8.2.1.1] ４，７ .0 ２，９ .0 ３，８ ]tetradecane-5,6,11,12-tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, cyclohex-1-ene-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride, etc. These may be used alone or in combination of two or more.

[0036] In the present invention, from the viewpoint of further improving the dispersibility of carbon nanotubes, it is preferable to use at least an alicyclic tetracarboxylic acid dianhydride as the tetracarboxylic acid component. Among alicyclic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides having a monocyclic alicyclic structure are preferred, and alicyclic tetracarboxylic acid dianhydrides having a monocyclic four-membered alicyclic structure, alicyclic tetracarboxylic acid dianhydrides having a monocyclic five-membered alicyclic structure, and alicyclic tetracarboxylic acid dianhydrides having a monocyclic six-membered alicyclic structure are more preferred, and 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,4-dimethyl- 1,2,3,4-Cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are more preferred, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are even more preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) is particularly preferred.

[0037] When the polyamic acid used in the present invention contains units derived from a tetracarboxylic acid component having an alicyclic structure such as an alicyclic tetracarboxylic dianhydride, the content of the units derived from the tetracarboxylic acid component having an alicyclic structure such as an alicyclic tetracarboxylic dianhydride, based on the total molar amount of the units derived from the tetracarboxylic acid component, is preferably 50 mol % or more, more preferably 70 to 100 mol %, and even more preferably 90 to 100 mol %. It is particularly preferred that the polyamic acid contains only units derived from a tetracarboxylic acid component having an alicyclic structure such as an alicyclic tetracarboxylic dianhydride as the units derived from the tetracarboxylic acid component (it is particularly preferred that the units derived from the tetracarboxylic acid component having an alicyclic structure such as an alicyclic tetracarboxylic dianhydride account for 100 mol %).

[0038] Examples of the diamine component include aromatic diamines having an aromatic group and aliphatic diamines having no aromatic ring.

[0039] Examples of aromatic diamines include 4,4'-diaminodiphenyl ether (ODA), 2,2'-dimethylbenzidine, 4,4'-diaminodiphenylmethane, 4,4'-diamino-1,2-diphenylethane, p-phenylenediamine (PPD), m-phenylenediamine, 2,4-diaminotoluene, 3,5-diaminobenzoic acid (3,5-DABA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)] Examples of suitable bis(4-aminophenoxy)phenyl propane (BAPP), m-xylylenediamine, p-xylylenediamine, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-methylenebis(2,6-xylidine), α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, 2,2'-dimethyl-4,4'-aminobiphenyl, 3,3'-dimethyl-4,4'-aminobiphenyl, 2,2'-ethylenedianiline, and 4,4'-diaminobenzanilide are listed below. These may be used alone or in combination of two or more.

[0040] Examples of the aliphatic diamine include linear and branched aliphatic diamines not containing an alicyclic structure, such as diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminononane, diaminodecane, diaminoundecane, and diaminododecane; 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, and 1,2-diaminocyclohexane. alicyclic diamines having an alicyclic structure such as cyclohexane, 1,3-diaminocyclobutane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, diaminobicycloheptane, diaminomethylbicycloheptane, diaminooxybicycloheptane, diaminomethyloxybicycloheptane, isophoronediamine, diaminotricyclodecane, diaminomethyltricyclodecane, bis(aminocyclohexyl)methane, bis(aminocyclohexyl)isopropylidene, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, and 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane. These can be used alone or in combination of two or more.

[0041] When an alicyclic tetracarboxylic dianhydride is used as the tetracarboxylic acid component, an alicyclic structure is introduced into the polyamic acid by the use of the alicyclic tetracarboxylic dianhydride, so it is not necessarily necessary to use an alicyclic diamine as the diamine component, but even in this case, an alicyclic diamine may be used as the diamine component. Furthermore, when an alicyclic tetracarboxylic dianhydride is not used as the tetracarboxylic acid component, it is desirable to use an alicyclic diamine as the diamine component in order to introduce an alicyclic structure into the polyamic acid.

[0042] Among the alicyclic diamines, 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, and 1,3-diaminocyclobutane are preferred.

[0043] When the polyamic acid used in the present invention contains units derived from a diamine component having an alicyclic structure such as an alicyclic diamine, the content of the units derived from a diamine component having an alicyclic structure such as an alicyclic diamine based on the total molar amount of the units derived from the diamine component is preferably 50 mol % or more, more preferably 70 to 100 mol %, and even more preferably 90 to 100 mol %.

[0044] Furthermore, when a diamine component other than an alicyclic diamine is used as the diamine component, it is preferable to use 4,4'-diaminodiphenyl ether (ODA), 3,5-diaminobenzoic acid (3,5-DABA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), or the like as the aromatic diamine, and it is preferable to use diaminodecanes such as 1,10-diaminodecane (DMD) as the linear or branched aliphatic diamine not containing an alicyclic structure. When a diamine component other than an alicyclic diamine is used, it is more preferable to use at least 3,5-diaminobenzoic acid (3,5-DABA) and 1,3-bis(4-aminophenoxy)benzene (TPE-R), and the total content of units derived from 3,5-diaminobenzoic acid (3,5-DABA) and units derived from 1,3-bis(4-aminophenoxy)benzene (TPE-R) based on the total molar amount of units derived from the diamine component is preferably 5 to 50 mol %, more preferably 10 to 50 mol %, even more preferably 15 to 40 mol %, 15 to 35 mol %, and still more preferably 20 to 35 mol %.

[0045] The polyamic acid used in the present invention can be obtained by reacting the above-mentioned tetracarboxylic acid component and diamine component in approximately equimolar amounts in a solvent, optionally with heating, until the desired viscosity (or molecular weight) is achieved. In the present invention, "approximately equimolar" means that the molar ratio of the tetracarboxylic acid component to the diamine component is about 0.90 to 1.10, preferably about 0.95 to 1.05.

[0046] The solvent used in the synthesis of polyamic acid is not particularly limited, and any known solvent used in the synthesis of polyamic acid can be selected and used. For example, from the viewpoint of the solubility of the tetracarboxylic acid component, the diamine component, and the polyamic acid, it is preferable to include at least one nitrogen-containing solvent. Examples of such solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylisobutyramide (DMIB), 3-methoxy-N,N-dimethylpropanamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidinone, and N,N-dimethylpropionamide.

[0047] The polyamic acid can be produced by adding a tetracarboxylic acid component, a diamine component, and a solvent to a reaction vessel equipped with a stirrer and stirring the mixture. The order of addition of these raw materials is not particularly limited. For example, a predetermined amount of the diamine component may be dissolved in the solvent and then the tetracarboxylic acid component may be added, or the tetracarboxylic acid component may be dissolved in the solvent and then the diamine component may be added, or the tetracarboxylic acid component and the diamine component may be added alternately to the solvent. If necessary, additives such as known reaction catalysts may be added at any time.

[0048] The reaction temperature is not particularly limited, but is preferably 0° C. or higher and 100° C. or lower, more preferably 10° C. or higher, and even more preferably 20° C. or higher. The reaction temperature is more preferably 90° C. or lower, and even more preferably 70° C. or lower. The polyamic acid may be partially imidized.

[0049] The content ratio of polyamic acid in the polyamic acid / CNT dispersion of the present invention is preferably 1.5 times or more, more preferably 3 times or more, and even more preferably 5 times or more, by mass relative to the mass of carbon nanotubes, and although there is no particular upper limit, it is preferably 10 times or less, and more preferably 7 times or less. By setting the mass equivalent of polyamic acid within the above range, it is possible to further increase the dispersibility of carbon nanotubes while maintaining the viscosity of the polyamic acid / CNT dispersion relatively low.

[0050] The polyamic acid / CNT dispersion of the present invention preferably further contains a proton-accepting nitrogen-containing compound. By further containing a proton-accepting nitrogen-containing compound, the dispersibility of carbon nanotubes can be further improved, and as a result, when the polyamic acid / CNT dispersion of the present invention is used, for example, in the production of an electrode for an electricity storage device, the dispersion state in the electrode can be improved, and as a result, the resulting electrode and electricity storage device can have better capacity retention characteristics.

[0051] The proton-accepting nitrogen-containing compound may be any compound having a proton-accepting nitrogen atom, but nitrogen-containing heterocyclic compounds are preferred from the viewpoint of being able to further enhance the effect of improving the dispersibility of carbon nanotubes. Examples of the nitrogen-containing heterocyclic compounds include imidazole, 1-methylimidazole, 1-ethylimidazole, 1,2-dimethylimidazole (1,2-DMZ), 1,4-dimethylimidazole, 1,5-dimethylimidazole, 1,2,4-trimethylimidazole, 1-ethyl-2-methylimidazole, 1,4-dimethyl-2-ethylimidazole, 1-methoxyethylimidazole, 1-methyl-2-methoxyimidazole, 1-methyl-2-ethoxyimidazole, 1-methyl-4-methoxyimidazole, 1-ethoxymethyl-2-methylimidazole, 1-methyl-4-nitroimidazole, 1,2-dimethyl-5-nitroimidazole, 1,2-dimethyl-5-aminoimidazole, 1-methyl- Five-membered nitrogen-containing heterocyclic compounds such as 4-(2-aminoethyl)imidazole, 2-phenylimidazole, 1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-undecylimidazoline, 1-methyl-2-heptadecylimidazoline, 1-methyl-2-ethoxymethylimidazoline, 1-ethoxymethyl-2-methylimidazoline, pyrrole, methylpyrrole, thiazole, oxazole, pyrazole, and isoxazole; and six-membered nitrogen-containing heterocyclic compounds such as pyridine, pyrazine, pyrimidine, pyridazine, triazine, and 2,6-lutidine. These may be used alone or in combination of two or more.

[0052] As the proton-accepting nitrogen-containing compound, a compound having an imidazole ring is preferred, and 1,5-dimethylimidazole (1,2-DMZ) is more preferred.

[0053] The content ratio of the proton-accepting nitrogen-containing compound in the polyamic acid / CNT dispersion of the present invention is 0.3 to 1 times, more preferably 0.4 to 1 times, even more preferably 0.5 to 1 times, and still more preferably 0.5 to 0.8 times, by mass relative to the mass of the polyamic acid.

[0054] The polyamic acid / CNT dispersion of the present invention may contain components other than the organic solvent, polyamic acid, carbon nanotubes, and the proton-accepting nitrogen-containing compound used as needed. Examples of such components include carbon black (e.g., furnace black, acetylene black, channel black, thermal black), fullerene, graphene, pH adjuster, negative electrode active material particles (e.g., Si, SiO), and positive electrode active material (e.g., LCO, LFP). Since the polyamic acid / CNT dispersion of the present invention can highly disperse carbon nanotubes without using known dispersants such as carboxymethyl cellulose, it is preferable that the dispersion is substantially free of dispersants such as carboxymethyl cellulose. In particular, since carboxymethyl cellulose has insufficient heat resistance, it is preferable that the dispersion is substantially free of carboxymethyl cellulose (e.g., preferably less than 1 ppm by mass).

[0055] The method for preparing the polyamic acid / CNT dispersion of the present invention is not particularly limited, and can be prepared by mixing an organic solvent, polyamic acid, carbon nanotubes, and optionally a proton-accepting nitrogen-containing compound and other components. The method for mixing these is also not particularly limited, but from the viewpoint of further enhancing the dispersibility of carbon nanotubes, a preferred method is to disperse or dissolve the polyamic acid and optionally a proton-accepting nitrogen-containing compound in an organic solvent to prepare a polyamic acid-containing solution, and then disperse the carbon nanotubes in the polyamic acid-containing solution. In this case, if an organic solvent or a proton-accepting nitrogen-containing compound is used in synthesizing the polyamic acid, the polyamic acid-containing solution obtained by synthesis can be used as is, and the solids concentration can be adjusted as necessary before dispersing the carbon nanotubes.

[0056] The method for dispersing or dissolving the polyamic acid and the proton-accepting nitrogen-containing compound used as needed in the organic solvent is not particularly limited, and examples thereof include a method in which the polyamic acid and the proton-accepting nitrogen-containing compound used as needed are added to the organic solvent and stirred and mixed using a stirring device or a mixing device. In this case, when the polyamic acid and the proton-accepting nitrogen-containing compound used as needed are added to the organic solvent, they may be added all at once, or they may be added continuously or in portions.

[0057] Furthermore, the method for dispersing carbon nanotubes in a polyamic acid-containing solution is not particularly limited, but examples include a method in which carbon nanotubes are added to a polyamic acid-containing solution and then subjected to ultrasonic treatment or a stirring / dispersion treatment. For ultrasonic treatment, a bath-type or probe-type sonicator can be used. For stirring / dispersion treatment, a high-speed stirring device such as a homomixer or homogenizer, a media-type wet dispersion device such as an attritor, a bead mill, a sand mill, or a planetary mill, or a high-pressure dispersion treatment device such as a wet jet mill can be used. The treatment time for ultrasonic treatment or stirring / dispersion treatment is not particularly limited, but is preferably 10 minutes to 50 hours, more preferably 20 minutes to 10 hours, and even more preferably 30 minutes to 3 hours.

[0058] The polyamic acid / CNT dispersion of the present invention has an optical density of greater than 0.40 at a wavelength of 500 nm when the carbon nanotube concentration is 0.001% by mass. According to the present invention, by using a polyamic acid having an alicyclic structure and adjusting the optical density at a wavelength of 500 nm to greater than 0.40 when the carbon nanotube concentration is 0.001% by mass, the polyamic acid / CNT dispersion of the present invention can have carbon nanotubes highly dispersed. As a result, when the polyamic acid / CNT dispersion of the present invention is used, for example, in the manufacture of electrodes for electricity storage devices, the dispersion state in the electrodes can be improved, resulting in the resulting electrodes and electricity storage devices with excellent capacity retention. The optical density of the polyamic acid / CNT dispersion can be measured with reference to the measurement method for evaluating dispersion stability disclosed in Japanese Patent No. 7194860.

[0059] The optical density at a wavelength of 500 nm when the carbon nanotube concentration is 0.001% by mass is an index showing the dispersibility of carbon nanotubes in the polyamic acid / CNT dispersion, and the higher this value, the higher the dispersibility of the carbon nanotubes can be determined to be. When the carbon nanotube concentration is 0.001% by mass, the optical density at a wavelength of 500 nm is preferably 0.4 or more, more preferably 0.45 or more, and even more preferably 0.5 or more. There is no particular upper limit to the optical density, but it is preferably 1.0 or less.

[0060] The optical density at 500 nm when the carbon nanotube concentration is 0.001% by mass is determined by adding an organic solvent to the polyamic acid / CNT dispersion to dilute it to a carbon nanotube concentration of 0.001% by mass, and then performing UV / visible spectrum measurement on the resulting measurement sample at 25°C to measure the absorbance at 500 nm. The obtained absorbance value at 500 nm can be used as the optical density at 500 nm. The organic solvent used to adjust the carbon nanotube concentration to 0.001% by mass is the same organic solvent as contained in the polyamic acid / CNT dispersion. In this case, if the polyamic acid / CNT dispersion contains two or more organic solvents, the two or more organic solvents are used in the content ratios contained in the polyamic acid / CNT dispersion. Furthermore, if the polyamic acid / CNT dispersion contains water or other organic solvents in addition to the organic solvents, the water or other organic solvents are added in accordance with the content ratios contained in the polyamic acid / CNT dispersion.

[0061] <Binder composition for electricity storage device, electrode slurry> The polyamic acid / CNT dispersion of the present invention can be used as a binder composition for electricity storage device. Furthermore, an electrode slurry of the present invention contains the polyamic acid / CNT dispersion of the present invention as a binder composition for electricity storage device and an active material. In this case, the polyamic acid acts as a binder for binding the active material, and as described below, the polyamic acid may be allowed to undergo an imidization reaction to form a polyimide, thereby acting as a binder.

[0062] The active material may be either a negative electrode active material or a positive electrode active material, that is, the electrode slurry of the present invention may be a slurry for a negative electrode or a slurry for a positive electrode.

[0063] When the electrode slurry of the present invention is a slurry for a negative electrode, examples of the negative electrode active material, particularly as a negative electrode active material for a lithium secondary battery, include lithium metal, lithium alloys, carbon materials capable of absorbing and releasing lithium (e.g., easily graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less), tin (simple substance), tin compounds, silicon (simple substance), silicon compounds, Li ４ Ti ５ O １２ Examples of the lithium titanate compounds include lithium titanate compounds such as silicon (single element) and silicon compounds. These compounds can be used alone or in combination of two or more. Because the use of the polyamic acid / CNT dispersion of the present invention significantly improves performance, silicon-containing negative electrode active materials, such as silicon (single element) or silicon compounds, are preferred as negative electrode active materials. While silicon-containing negative electrode active materials, such as silicon (single element) or silicon compounds, have significantly higher theoretical capacities than graphite, they suffer from the problem of a relatively large volume expansion rate of the negative electrode active material itself during charging. However, the polyamic acid / CNT dispersion of the present invention, in which carbon nanotubes are highly dispersed, can appropriately mitigate such volume expansion, thereby more appropriately improving the capacity retention characteristics of electrodes and power storage devices.

[0064] The silicon-containing negative electrode active material is not particularly limited, but examples thereof include silicon (element), silicon compounds, partial substitution products of silicon, partial substitution products of silicon compounds, solid solutions of silicon compounds, etc. Specific examples of silicon compounds include SiO ｘ Silicon oxide represented by (0.05<x<1.95), SiC ｙ Silicon carbide represented by (0<y<1), SiN ｚ (0<z<4 / 3), and silicon alloys which are alloys of silicon and a different element M. In silicon alloys, the different element M is preferably at least one element selected from the group consisting of Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti.

[0065] Furthermore, the silicon partial substitution product is a compound in which a portion of the silicon contained in silicon (simple substance) and a silicon compound is substituted with a different element M. Specific examples of the different element M include B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn. Among these silicon-containing negative electrode active materials, silicon (simple substance), silicon oxide, or silicon alloy is preferred, and silicon (simple substance) or silicon oxide is more preferred.

[0066] Furthermore, when the electrode slurry of the present invention is a slurry for a negative electrode, it may contain, in addition to the negative electrode active material, a conductive material other than carbon nanotubes. The conductive material is not particularly limited as long as it is an electron-conductive material that does not undergo chemical change, and examples thereof include metal powders such as copper, nickel, titanium, and aluminum, and carbon materials other than carbon nanotubes.

[0067] When the electrode slurry of the present invention is a slurry for a positive electrode, the positive electrode active material is, in particular, a composite metal oxide containing lithium and at least one selected from cobalt, manganese, and nickel, which is used as a positive electrode active material for a lithium secondary battery. Examples of such lithium composite metal oxides include LiCoO ２ , LiMn ２ O ４ , LiNiO ２, LiCo １－ｘ Ni ｘ O ２ (0.01<x<1), LiCo １／３ Ni １／３ Mn １／３ O ２ , LiNi １／２ Mn ３／２ O ４ , LiCo ０．９８ Mg ０．０２ O ２ In addition, LiCoO ２ and LiMn ２ O ４ , LiCoO ２ and LiNiO ２ , LiMn ２ O ４ and LiNiO ２ They may be used in combination as follows.

[0068] When the electrode slurry of the present invention is a slurry for a positive electrode, it may contain, in addition to the positive electrode active material, a conductive material other than carbon nanotubes. The conductive material is not particularly limited as long as it is an electron-conductive material that does not undergo chemical change, and examples thereof include carbon materials other than carbon nanotubes.

[0069] The electrode slurry of the present invention can be produced by mixing the polyamic acid / CNT dispersion of the present invention described above, a negative electrode active material or a positive electrode active material, and an optional conductive material other than carbon nanotubes. In this case, an organic solvent may be further mixed, if necessary, to adjust the solid content concentration.

[0070] <Electrode for Electricity Storage Device> The electrode for an electricity storage device of the present invention is formed using the above-described electrode slurry of the present invention.

[0071] The electrode for an electricity storage device of the present invention can be produced, for example, by forming the above-described electrode slurry of the present invention into a sheet or the like.

[0072] The electrode for an electricity storage device of the present invention can be formed into a sheet by, for example, casting or applying the above-described electrode slurry of the present invention onto a conductive current collector such as aluminum foil or copper foil, heating the slurry to remove the organic solvent, and optionally applying pressure to form an active material layer on the current collector. In this case, the heating during the formation of the active material layer on the current collector may promote an imidization reaction of the polyamic acid contained in the electrode slurry, converting the polyamic acid as a polyimide precursor into a polyimide.

[0073] In this case, the polyimide preferably contains, as the main component (50 mol % or more), more preferably 75 mol % or more, and even more preferably 90 mol % or more, a polyimide containing a repeating unit represented by the following formula (2): That is, the polyimide may be a partially imidized polyimide in which a portion of the amic acid structures contained in the polyamic acid as the polyimide precursor are imidized, or a fully imidized polyimide in which all of the amic acid structures contained in the polyamic acid as the polyimide precursor are imidized, or a mixture of these. In the above formula (2), X １ represents one or more tetravalent groups obtained by removing a carboxyl group from a tetracarboxylic acid component, and Y １ represents one or more divalent groups obtained by removing an amino group from a diamine component.

[0074] The method for imidizing the polyamic acid as a polyimide precursor is not particularly limited, but examples include chemical imidization and / or thermal imidization by heat treatment of the polyamic acid. Taking thermal imidization as an example, the maximum heating temperature in the heat treatment is typically 150°C or higher, preferably 200°C or higher, more preferably 250°C or higher, and even more preferably 350°C or higher. The upper limit of the heat treatment temperature is any temperature that does not deteriorate the properties, and is preferably 450°C or lower, more preferably 430°C or lower, and even more preferably 400°C or lower. While the heat treatment can be carried out in an air atmosphere, it is preferably carried out in an inert gas atmosphere, more preferably a nitrogen gas atmosphere. Chemical imidization can be carried out under milder heat treatment conditions than thermal imidization, depending on the type of additive, such as a chemical imidization catalyst. For example, the heat treatment may be carried out at a temperature range of usually 100°C or higher, preferably 120°C or higher, more preferably 150°C or higher, and even more preferably 200°C or higher, and usually 360°C or lower, preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 220°C or lower.

[0075] The heat treatment for chemical imidization and / or thermal imidization may be carried out in stages. For example, a first heat treatment is preferably carried out at a relatively low temperature of 100°C or higher and 170°C or lower for 0.5 minutes to 30 minutes, followed by a second heat treatment at a temperature above 170°C and 220°C or lower for 0.5 minutes to 30 minutes, followed by a third heat treatment at a high temperature above 220°C and lower than 350°C for 0.5 minutes to 30 minutes, and then a fourth high-temperature heat treatment from 350°C or higher to the maximum heating temperature. The heat treatment is preferably carried out continuously. For example, the heat treatment is preferably carried out from a relatively low temperature of 100°C or higher and 170°C or lower to the maximum heating temperature. The temperature rise rate is not particularly limited, but is preferably 1°C / min to 30°C / min, and particularly preferably 2°C / min to 20°C / min. The above range is preferable because it can suppress foaming due to a sudden rise in temperature.

[0076] The thickness of the active material layer in the electrode for an electricity storage device of the present invention may be appropriately determined depending on the application and the desired capacity. It is not limited, but is preferably in the range of 0.1 μm or more and 500 μm or less. It is more preferably 1 μm or more, even more preferably 10 μm or more, even more preferably 20 μm or more, and more preferably 300 μm or less, even more preferably 100 μm or less, and even more preferably 50 μm or less.

[0077] <Electricity storage device> The electricity storage device of the present invention includes the electrode for the electricity storage device of the present invention described above. The electricity storage device includes electricity storage devices such as lithium batteries, electric double layer capacitors, and lithium ion capacitors. Among these, lithium batteries using a lithium salt as the electrolyte salt are preferred, and lithium secondary batteries are suitable.

[0078] The lithium secondary battery includes a positive electrode, a negative electrode, a non-aqueous electrolyte, a separator, and other components, and can employ any known configuration required for a lithium secondary battery. In the present invention, the above-described electrode for the power storage device of the present invention is used as the positive electrode and / or the negative electrode. The lithium secondary battery may be a lithium polymer battery using a gel electrolyte as the electrolyte, or an all-solid-state battery using an inorganic solid electrolyte such as an oxide or sulfide.

[0079] The non-aqueous electrolyte is a non-aqueous solvent in which an electrolyte salt is dissolved. There are no particular limitations on the non-aqueous electrolyte, and various types can be used.

[0080] The electrolyte salt used is one that dissolves in a non-aqueous electrolyte, such as LiPF ６ , LiBF ４ , LiPO ２ F ２ , LiN(SO ２ F) ２ , LiClO ４ Inorganic lithium salts such as LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ )２ , LiCF ３ SO ３ , LiC(SO ２ CF ３ ) ３ , LiPF ４ (CF ３ ) ２ , LiPF ３ (C ２ F ５ ) ３ , LiPF ３ (CF ３ ) ３ , LiPF ３ (iso-C ３ F ７ ) ３ , LiPF ５ (iso-C ３ F ７ ) and lithium salts containing chain-like fluorinated alkyl groups such as (CF ２ ) ２ (SO ２ ) ２ NLi, (CF ２ ) ３ (SO ２ ) ２ Examples include lithium salts containing a cyclic fluorinated alkylene chain such as NLi, and lithium salts having an oxalate complex as the anion such as lithium bis[oxalate-O,O']borate and lithium difluoro[oxalate-O,O']borate.

[0081] The concentration of all of these electrolyte salts dissolved in the non-aqueous solvent is preferably 0.3 M or more, more preferably 0.5 M or more, and even more preferably 0.7 M or more. The upper limit is preferably 2.5 M or less, more preferably 2.0 M or less, and even more preferably 1.5 M or less.

[0082] Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, chain esters, ethers, amides, phosphate esters, sulfones, lactones, nitriles, and S═O bond-containing compounds, and the non-aqueous solvent preferably contains a cyclic carbonate. Note that the term "chain ester" is used as a concept that includes chain carbonates and chain carboxylic acid esters.

[0083] Examples of cyclic carbonates include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans- or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter collectively referred to as "DFEC"), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1,3-dioxolan-2-one (EEC). The proportion of cyclic carbonates having alkylene chains in all cyclic carbonates is preferably 55% to 100% by volume, more preferably 60% by volume or more, and even more preferably 90% by volume or less.

[0084] In addition, non-aqueous solvents are preferably used in combination to achieve appropriate physical properties. Examples of such combinations include a combination of a cyclic carbonate and a chain ester. Suitable examples of the chain ester include one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate; one or more symmetric chain carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate; pivalic acid esters such as methyl pivalate, ethyl pivalate, and propyl pivalate; and one or more chain carboxylic acid esters selected from methyl propionate, ethyl propionate, propyl propionate, methyl acetate, and ethyl acetate (EA).

[0085] <Electromagnetic Wave Shielding Composition> The polyamic acid / CNT dispersion of the present invention can be used as an electromagnetic wave shielding composition for forming an electromagnetic wave shielding paint, an electromagnetic wave shielding film, or the like.

[0086] The electromagnetic wave shielding composition of the present invention may contain, as optional components, a leveling agent, a dispersing agent, a crosslinking agent, a catalyst, a water-soluble antioxidant, an antifoaming agent, a rheology control agent, a neutralizing agent, a thickener, an inorganic filler, etc.

[0087] Examples of the leveling agent include a silicone-based leveling agent, a fluorine-based leveling agent, a polyether-based leveling agent, a polyester-based leveling agent, and an acrylic-based leveling agent.

[0088] Examples of dispersants include cationic dispersants, anionic dispersants, amphoteric dispersants, nonionic dispersants, and polymeric dispersants.

[0089] Examples of inorganic fillers include silica such as colloidal silica, hollow silica, and fumed silica; metal oxides such as titania and zirconia; and organic-inorganic composites such as a core-shell type acrylic-silica composite in which a thermoplastic or thermosetting acrylic resin is coated with silica, a core-shell type melamine-silica composite in which a melamine resin is coated with silica, a core-shell type acrylic-silica composite in which silica is coated with a thermoplastic or thermosetting acrylic resin, a core-shell type melamine-silica composite in which silica is coated with a melamine resin, and an acrylic-silica composite in which small silica particles are supported by a thermoplastic or thermosetting acrylic resin.

[0090] When the electromagnetic wave shielding composition of the present invention contains the above-mentioned optional components in addition to the above-mentioned polyamic acid / CNT dispersion of the present invention, it can be produced by mixing the above-mentioned polyamic acid / CNT dispersion of the present invention with the above-mentioned optional components. At this time, an organic solvent may be further mixed, if necessary, to adjust the solid content concentration.

[0091] <Electromagnetic Wave Shielding Coating Film> The electromagnetic wave shielding coating film of the present invention is a coating film formed using the electromagnetic wave shielding composition of the present invention.

[0092] The electromagnetic wave shielding coating film of the present invention can be formed, for example, by casting or applying the electromagnetic wave shielding composition of the present invention onto at least one surface of a substrate, followed by heat treatment to remove the organic solvent. In this case, as in the case of the electrode for the electricity storage device described above, the imidization reaction of the polyamic acid contained in the electromagnetic wave shielding composition may be promoted by heating, and the polyamic acid as a polyimide precursor may be converted into a polyimide.

[0093] The electromagnetic wave shielding coating film may be formed by directly casting or applying the electromagnetic wave shielding composition onto a substrate, or may be formed by first providing another layer such as a primer layer on a substrate and then casting or applying the composition onto the other layer.

[0094] <Electromagnetic wave shielding laminate> The electromagnetic wave shielding laminate of the present invention comprises the electromagnetic wave shielding coating film of the present invention and a substrate. The electromagnetic wave shielding laminate may further comprise a dielectric layer, an adhesive layer, a protective layer, a decorative layer, etc.

[0095] The dielectric layer is preferably present on the surface of the electromagnetic wave shielding coating film opposite to the surface that contacts the substrate. The dielectric layer is not particularly limited in composition as long as it can generate dielectric loss and absorb electromagnetic waves, but is preferably formed from a composition containing: a synthetic resin such as polyurethane, acrylic resin, ethylene-vinyl acetate copolymer, or polyvinyl chloride; a rubber material such as polyisoprene rubber, polystyrene-butadiene rubber, polybutadiene rubber, chloroprene rubber, or acrylonitrile-butadiene rubber; a carbon material such as carbon nanotubes, graphene, fullerene, or carbon nanofibers; titanium oxide, polyvinylidene fluoride, polyester resin, glass, or silicone rubber.

[0096] The adhesive layer is a layer containing an adhesive composition, and is preferably formed on the surface of the substrate opposite to the surface on which the electromagnetic wave shielding coating film is present.

[0097] The protective layer is a layer that prevents the electromagnetic wave shielding properties from being reduced due to mechanical impact or humidity in the air, and examples of materials for the protective layer include polyethylene terephthalate (PET) and polyethylene (PE).

[0098] The decorative layer is a layer formed to improve the appearance of the electromagnetic wave shielding laminate and to conceal the internal structure, such as electronic circuits, and examples of materials for the decorative layer include resins such as polyethylene terephthalate (PET) and polyethylene (PE), and metals such as aluminum, gold, platinum, copper, silver, and zinc.

[0099] The electromagnetic wave shielding laminate of the present invention can be used as an electromagnetic wave shield, for example, in semiconductor packages, conductive gaskets, shielding films, shielding cases, communication devices, sensors, clothing, and the interior and exterior decoration of buildings.

[0100] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0101] The abbreviations for the compounds used in the following examples are as follows: CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride H''-PMDA: (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane 3,5-DABA: 3,5-diaminobenzoic acid TPE-R: 1,3-bis(4-aminophenoxy)benzene ODA: 4,4'-diaminodiphenyl ether DMD: 1,10-diaminodecane PPD: p-phenylenediamine 1,2-DMZ: 1,2-dimethylimidazole

[0102] Example 1 600 g of N-methyl-2-pyrrolidone (NMP), 69.3785 g of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 31.0288 g of 1,3-bis(4-aminophenoxy)benzene (TPE-R), and 49.5927 g of 4,4'-diaminodiphenyl ether (ODA) were added to a stirring vessel equipped with a stirrer and a nitrogen inlet tube, and the mixture was stirred at 50°C for 7 hours under a nitrogen atmosphere to react, yielding 750 g of an NMP solution of polyamic acid. The molar ratio of CBDA:TPE-R:ODA was 100:30:70.

[0103] Next, a portion of the resulting polyamic acid NMP solution was removed and diluted by adding N-methyl-2-pyrrolidone (NMP), after which 0.4 g of single-walled carbon nanotubes (SWCMT: manufactured by OCSiAl Corporation, product name "TUBALL (registered trademark) 01RW03", hereinafter simply referred to as SWCNT) were added and dispersed to obtain 100 g of a polyamic acid / CNT dispersion. The resulting polyamic acid / CNT dispersion contained 2.19 mass% polyamic acid and 0.4 mass% single-walled carbon nanotubes (SWCMT).

[0104] [Optical Density at 500 nm Wavelength in the Case of a Carbon Nanotube Concentration of 0.001% by Mass] The resulting polyamic acid / CNT dispersion was diluted with N-methyl-2-pyrrolidone (NMP) until the single-walled carbon nanotube (SWCMT) concentration reached 0.001% by mass, to prepare a measurement sample. The resulting measurement sample was then subjected to ultraviolet / visible spectrum measurement using an absorption spectrometer at a temperature of 25°C to measure the absorbance at a wavelength of 500 nm. The resulting absorbance value at a wavelength of 500 nm was used as the optical density at a wavelength of 500 nm. The optical density of the polyamic acid / CNT dispersion was measured with reference to the measurement method for evaluating dispersion stability disclosed in Japanese Patent No. 7194860. The results are shown in Table 1.

[0105] [Preparation of negative electrode sheet] The polyamic acid / CNT dispersion obtained above and silicon element (Si) were mixed so that the silicon element (Si): polyamic acid (polyimide equivalent mass): acetylene black: single-walled carbon nanotube (SWCMT) = 88: 7: 4.8: 0.2 (mass ratio) to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was applied to one side of a nickel-plated steel foil (current collector), dried at 110 ° C. for 1 minute, then pressurized, heated from room temperature to 360 ° C. at a constant rate over 1.5 hours, heated at 360 ° C. for 1.5 hours, and then allowed to cool to remove the solvent and imidize. By punching to a predetermined size, a negative electrode sheet with a thickness of about 25 μm was prepared with a current collector of 10 μm.

[0106] [Preparation of Evaluation Battery] The negative electrode sheet obtained above and metallic lithium were placed opposite each other via a glass filter (GA-100 manufactured by ADVANTEC), and a non-aqueous electrolyte solution was added and sealed to prepare a 2032-type coin battery. The non-aqueous electrolyte solution was a non-aqueous solvent containing ethylene carbonate (EC):diethyl carbonate (DEC) in a volume ratio of 1:1, with 1% by mass of vinylene carbonate added, and LiPF as an electrolyte salt. ６ was dissolved to a concentration of 1M and used.

[0107] [Battery Capacity Retention Rate] A cycle test was performed on the coin-type battery prepared above in a 30°C thermostatic chamber. The battery was charged at a constant current of 0.1 C to 0.001 V, with charging in the direction in which Li was absorbed into the negative electrode sheet, and then discharged at a constant current of 0.1 C to 1.5 V. This cycle test was repeated. The results of the cycle test were calculated as a ratio to the initial discharge capacity [mAh], and this was defined as the battery capacity retention rate (battery capacity retention rate [%] = discharge capacity after cycle test [mAh] / initial discharge capacity [mAh] × 100), and the results were evaluated according to the following criteria. The results are shown in Table 1. The "C" in 0.1 C refers to the current value during charging and discharging. For example, 1 C refers to the current value at which the theoretical capacity can be fully discharged (or fully charged) in 1 / 1 hour, and 0.1 C refers to the current value at which the theoretical capacity can be fully discharged (or fully charged) in 1 / 0.1 hour. The measurement results were evaluated based on the following criteria: the improvement in battery capacity retention relative to the capacity retention of an electrode without SWCNTs, which clearly shows a deterioration in cycle capacity retention, was calculated, and the results were evaluated based on the following criteria: For example, the following evaluation of "◎" means that the battery capacity retention (unit: %) is 30% or more higher than the capacity retention (unit: %) of the electrode without SWCNTs. ◎: The battery capacity retention rate after 30 cycles was improved by 30% or more compared to the capacity retention rate of the SWCNT-free electrode. ◯: The battery capacity retention rate after 30 cycles was improved by 15% or more but less than 30% compared to the capacity retention rate of the SWCNT-free electrode. △: The battery capacity retention rate after 30 cycles was improved by 5% or more but less than 15% compared to the capacity retention rate of the SWCNT-free electrode. ×: The battery capacity retention rate after 30 cycles was improved by less than 5% compared to the capacity retention rate of the SWCNT-free electrode, or was lower than the capacity retention rate of the SWCNT-free electrode.

[0108] Example 2 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that when obtaining the polyamic acid, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 3,5-diaminobenzoic acid (3,5-DABA) were used as the diamine components in the proportions shown in Table 1, and the content of the polyamic acid was set to the proportion shown in Table 1. The results are shown in Tables 1 and 2.

[0109] Example 3 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 2, except that 1,2-dimethylimidazole (1,2-DMZ) was added during polymerization of the polyamic acid, and the content ratio of the polyamic acid and the content ratio of 1,2-dimethylimidazole (1,2-DMZ) were changed to those shown in Table 1. The results are shown in Tables 1 and 2.

[0110] Example 4 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that, when obtaining the polyamic acid, 3,3,4,4-biphenyltetracarboxylic dianhydride (s-BPDA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) were used as the tetracarboxylic acid components in the proportions shown in Table 1, 3,5-diaminobenzoic acid (3,5-DABA) and 1,10-diaminodecane (DMD) were used as the diamine components in the proportions shown in Table 1, 1,2-dimethylimidazole (1,2-DMZ) was added during the polymerization of the polyamic acid, and the polyamic acid content and the 1,2-dimethylimidazole (1,2-DMZ) content were changed to those shown in Table 1. The results are shown in Table 1.

[0111] Example 5 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 2, except that when obtaining the polyamic acid, (1R,2S,4S,5R)-cyclohexanetetracarboxylic dianhydride (H″-PMDA) was used as the tetracarboxylic acid component in the proportion shown in Table 1, and the content of the polyamic acid was changed to the proportion shown in Table 1. The results are shown in Table 1.

[0112] Example 6 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 5, except that 1,2-dimethylimidazole (1,2-DMZ) was added during polymerization of the polyamic acid, and the content ratio of the polyamic acid and the content ratio of 1,2-dimethylimidazole (1,2-DMZ) were changed to those shown in Table 1. The results are shown in Table 1.

[0113] Example 7 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that, when obtaining the polyamic acid, 3,3,4,4-biphenyltetracarboxylic dianhydride (s-BPDA) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) were used as the tetracarboxylic acid components in the proportions shown in Table 1, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 3,5-diaminobenzoic acid (3,5-DABA) were used as the diamine components in the proportions shown in Table 1, 1,2-dimethylimidazole (1,2-DMZ) was added to the NMP solution of polyamic acid before adding single-walled carbon nanotubes (SWCMT), and the polyamic acid content and the 1,2-dimethylimidazole (1,2-DMZ) content were changed to those shown in Table 1. The results are shown in Table 1.

[0114] Example 8 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that, when obtaining the polyamic acid, 3,3,4,4-biphenyltetracarboxylic dianhydride (s-BPDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and 4,4'-oxydiphthalic dianhydride (ODPA) were used as the tetracarboxylic acid components in the proportions shown in Table 1, 3,5-diaminobenzoic acid (3,5-DABA) and 1,10-diaminodecane (DMD) were used as the diamine components in the proportions shown in Table 1, 1,2-dimethylimidazole (1,2-DMZ) was added during the polymerization of the polyamic acid, and the polyamic acid content and the 1,2-dimethylimidazole (1,2-DMZ) content were changed to those shown in Table 1. The results are shown in Table 1.

[0115] Comparative Examples 1 and 2 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that when obtaining the polyamic acid, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) and 4,4'-oxydiphthalic dianhydride (ODPA) were used as the tetracarboxylic acid components in the proportions shown in Table 1, and 4,4'-diaminodiphenyl ether (ODA) and p-phenylenediamine (PPD) were used as the diamine components in the proportions shown in Table 1. The results are shown in Tables 1 and 2.

[0116] Comparative Examples 3 to 6 Polyamic acid / CNT dispersions were obtained and evaluated in the same manner as in Comparative Example 1, except that 1,2-dimethylimidazole (1,2-DMZ) was added during polymerization of the polyamic acid and the content ratio of the polyamic acid and the content ratio of 1,2-dimethylimidazole (1,2-DMZ) were changed to those shown in Table 1. The results are shown in Table 1.

[0117] Comparative Example 7 A polyamic acid / CNT dispersion was obtained and evaluated in the same manner as in Example 1, except that when obtaining the polyamic acid, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) was used as the tetracarboxylic acid component in the proportions shown in Table 1, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 3,5-diaminobenzoic acid (3,5-DABA) were used as diamine components in the proportions shown in Table 1, 1,2-dimethylimidazole (1,2-DMZ) was added during the polymerization of the polyamic acid, and the polyamic acid content and the 1,2-dimethylimidazole (1,2-DMZ) content were changed to those shown in Table 1. The results are shown in Table 1.

[0118]

[0119] As shown in Table 1, the polyamic acid / CNT dispersions of Examples 1 to 8, which contained polyamic acid having an alicyclic structure and had an optical density of more than 0.40 at a wavelength of 500 nm when the carbon nanotube concentration was 0.001% by mass, had high optical density and highly dispersed carbon nanotubes, thereby enabling the capacity retention of the resulting electrodes and batteries to be increased (see Table 2 below). Considering the results of Examples 2 and 3, it is believed that similar results can be obtained in other Examples. This effect was particularly pronounced when the dispersion contained 1,2-dimethylimidazole (1,2-DMZ), a proton-accepting nitrogen-containing compound.

[0120] On the other hand, when the polyamic acid having an alicyclic structure was not contained, the optical density at a wavelength of 500 nm was 0.40 or less when the carbon nanotube concentration was 0.001% by mass, resulting in low dispersibility of the carbon nanotubes and low capacity retention of the resulting electrode and battery. This tendency was also observed when the proton-accepting nitrogen-containing compound 1,2-dimethylimidazole (1,2-DMZ) was contained.

[0121]

[0122] The polyamic acid / CNT dispersion of the present invention is suitable for use, for example, in the production of electrodes for electricity storage devices. Furthermore, by forming an electromagnetic wave shielding composition containing the polyamic acid / CNT dispersion of the present invention into a coating film, it is possible to obtain, for example, an electromagnetic wave shielding coating film that is suitable as an electromagnetic wave shielding film having excellent heat resistance and durability.

Claims

1. A polyamic acid / carbon nanotube-containing dispersion comprising an organic solvent, a polyamic acid, and carbon nanotubes, wherein the polyamic acid contains an alicyclic structure, and the polyamic acid / carbon nanotube-containing dispersion has an optical density of more than 0.40 at a wavelength of 500 nm when the carbon nanotube concentration is 0.001% by mass.

2. The polyamic acid / carbon nanotube-containing dispersion according to claim 1, further comprising a proton-accepting nitrogen-containing compound.

3. The polyamic acid / carbon nanotube-containing dispersion according to claim 1 or 2, wherein the carbon nanotubes are single-walled carbon nanotubes.

4. The polyamic acid / carbon nanotube-containing dispersion according to claim 1 or 2, wherein the content of the carbon nanotubes in the dispersion is 0.1 mass % or more.

5. The polyamic acid / carbon nanotube-containing dispersion according to claim 1 or 2, wherein the organic solvent contains N-methyl-2-pyrrolidone.

6. A binder composition for an electrical storage device, comprising the polyamic acid / carbon nanotube-containing dispersion liquid according to claim 1 or 2.

7. A slurry for an electrode comprising the binder composition for an electrical storage device according to claim 6 and an active material.

8. An electrode for an electricity storage device, which is made using the electrode slurry according to claim 7.

9. An electricity storage device comprising the electrode for an electricity storage device according to claim 8.

10. An electromagnetic wave shielding composition comprising the polyamic acid / carbon nanotube-containing dispersion liquid according to claim 1 or 2.

11. An electromagnetic wave shielding coating film obtained by using the electromagnetic wave shielding composition according to claim 10.

12. An electromagnetic wave shielding laminate comprising the electromagnetic wave shielding coating film according to claim 11 and a substrate.

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