Insulating coating material and laminate

Abstract

Provided is an insulating coating material comprising (A) an imide-based resin and / or a precursor thereof, and (B) a metal oxide hydrate. Said (A) satisfies the following (a) and (b): (a) including a molecular chain having an amino group as a terminal group; and (b) having a number average molecular weight of 4.0x10000 or more. As a result, it is possible to provide an insulating coating material from which it is possible to produce an insulating coating that exhibits high flexibility and elongation while containing inorganic particles.

Description

Insulating coatings and laminates

[0001] The present invention relates to an insulating paint and a laminate including an insulating film formed from the insulating paint.

[0002] Insulated wires used in electrical equipment such as motors are laminates having an insulating coating on a conductor. The insulating coating is formed by applying an insulating paint containing a resin such as polyimide or polyamide-imide, or a precursor thereof, to the surface of the conductor and baking it.

[0003] To improve the performance of insulated wires, it is known that inorganic particles such as metal oxide hydrates are incorporated into the insulating coating. For example, the insulating coating of insulated wires used in coils may contain inorganic particles to improve resistance to partial discharge due to inverter surges or to improve the heat resistance of the coil.

[0004] Patent No. 6567797

[0005] However, insulating films containing inorganic particles sometimes lack sufficient elongation and flexibility, and there is a need for insulating films that contain inorganic particles while possessing high elongation and flexibility.

[0006] The present invention aims to provide an insulating coating that can produce an insulating film having high elongation and flexibility while containing inorganic particles.

[0007] This disclosure includes the following aspects: [Item 1] An insulating paint containing (A) an imide resin and / or its precursor and (B) a metal oxide hydrate, wherein the (A) satisfies the following (a) and (b): An insulating paint: (a) includes a molecular chain having an amino group as a terminal group; (b) has a number average molecular weight of 40,000 or more. [Item 2] The insulating paint according to Item 1, wherein the (A) is a reaction product of a diamine and a carboxylic acid or its anhydride having 4 or more carboxy groups, and satisfies the following (c1) or (c2): (c1) The terminal is not sealed by a terminal sealing agent; (c2) The terminal is sealed by a terminal sealing agent, and the amount of the terminal sealing agent in the raw material is 〈0000001〉1 mole part or less with respect to 100 mole parts of the diamine. [Item 3] The molar amount M〈0000001〉 of the diamine ａ and the molar amount M〈0000002〉 of the carboxylic acid or its anhydride having 4 or more carboxy groups ｃ and the molar amount M〈0000003〉 of the terminal sealing agent ｔ have the following relationship: the following formula: M〈0000004〉 ｃ + M〈0000005〉 ｔ × 2 < M〈0000006〉 ａ ; and (M〈0000007〉 ｃ + M〈0000008〉 ｔ ) / M〈0000009〉 ａAn insulating paint according to claim 2, represented by ≥0.980. [Clause 4] An insulating paint according to claim 2 or claim 3, wherein the diamine is an aromatic diamine, the carboxylic acid or anhydride having four or more carboxyl groups is an aromatic tetracarboxylic dianhydride, and the end sealant is an aromatic carboxylic monoanhydride. [Clause 5] An insulating paint according to any one of claims 2 to 4, wherein (A) satisfies the following (c2'): (c2') The end is sealed with an end sealant, and the amount of the end sealant in the raw material is 0.5 moles or less per 100 moles of the diamine. [Clause 6] An insulating paint according to any one of claims 2 to 4, wherein (A) is not sealed with an end sealant. [Clause 7] An insulating paint according to any one of claims 1 to 6, wherein (B) metal oxide hydrate contains alumina hydrate. [Clause 8] An insulating paint according to any one of claims 1 to 7, which is a sol containing the metal oxide hydrate having an average particle size of 5 to 100 nm as a dispersed phase. [Claim 9] A laminate comprising an insulating film formed from an insulating paint according to any one of claims 1 to 8. [Claim 10] The laminate according to claim 9 in the form of an insulated wire. [Claim 11] The laminate according to claim 9 in the form of an insulating film. [Claim 12] A coil comprising the laminate according to any one of claims 9 to 11. [Claim 13] A rotating electric machine comprising the laminate according to any one of claims 9 to 11. [Claim 14] A method for producing an insulating paint comprising (A) an imide resin and / or its precursor and (B) a metal oxide hydrate, comprising reacting a diamine with a carboxylic acid having four or more carboxyl groups or its anhydride, wherein in the reaction, no end sealant is used, or an end sealant is used in an amount of 1 mole or less per 100 moles of the diamine, and the number average molecular weight of (A) is 40,000 or more.

[0008] According to the present invention, it becomes possible to manufacture an insulating film that contains metal oxide hydrates while having high elongation and flexibility.

[0009] It is a schematic cross-sectional view showing an example of a laminate according to an embodiment of the present invention. It is a schematic cross-sectional view showing an example of an insulated wire according to an embodiment of the present invention. It is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention. It is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention. It is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention.

[0010] Hereinafter, the insulating paint and the laminate of the present invention will be described in detail.

[0011] In this specification, numerical values connected by "~" mean a numerical range including the numerical values before and after "~" as the lower limit value and the upper limit value. When a plurality of lower limit values and a plurality of upper limit values are separately described, any lower limit value and upper limit value can be selected and connected by "~".

[0012] The insulating paint according to an embodiment of the present invention is an insulating paint containing (A) an imide resin and / or its precursor and (B) a metal oxide hydrate, and the (A) satisfies the following (a) and (b): (a) It contains a molecular chain having an amino group as a terminal group; (b) The number average molecular weight is 40,000 or more.

[0013] The (A) imide resin and / or its precursor used in the present invention will be described in more detail. Examples of the imide resin include polyesterimide resin, polyetherimide resin, polyamideimide resin, and polyimide resin. The precursor of the imide resin means a resin in which an imide bond is formed by an intramolecular reaction through heating, over time, or the like, and an imide resin is obtained. The intramolecular reaction may be an intramolecular cyclization reaction, an intramolecular dehydration reaction, or an intramolecular dehydration cyclization reaction. Examples of the precursor of the imide resin include polyamic acid resin and the like. From the viewpoint of enhancing heat resistance, polyesterimide resin, polyamideimide resin, polyimide resin, and / or polyamic acid resin are preferably used as the imide resin and / or its precursor. Particularly, polyimide resin and / or polyamic acid resin are more preferably used as the imide resin and / or its precursor used in the present invention.

[0014] Preferred polyesterimide resins are those having ester and imide bonds within their molecules. Examples of polyesterimide resins include resins obtained by subjecting acid anhydrides, diamines, and dialcohols to imidization, esterification, and / or transesterification reactions.

[0015] A preferred polyetherimide resin is a resin having both ether and imide bonds in its molecule. Examples of polyetherimide resins include those obtained by subjecting acid anhydrides and diamines having ether bonds in their molecules to dehydration condensation polymerization and intramolecular dehydration cyclization (imidization) reactions. For example, a polyetherimide resin may be a dehydration condensation polymer of phenylenediamine and 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.

[0016] A preferred polyimide resin is a compound having the repeating structure of formula (1) below. More preferably, the polyamic acid resin is a resin that becomes a polyimide resin having the repeating structure of formula (1) below through intramolecular dehydration condensation reactions between amino groups and carboxyl groups in each of its repeating structures. The repeating unit in the repeating structure of formula (1) below may be one type or two or more types.

[0017] [In the formula: n is the number of repeating units, and is a positive integer, R １ Each of these is independently a tetravalent organic group having one or two benzene rings, R ２ These are, independently, divalent groups derived from aromatic hydrocarbons.

[0018] In formula (1) above, n is the number of repeating units and is a positive integer. n is preferably 50 or more, more preferably 100 or more, even more preferably 120 or more, and even more preferably 150 or more. n may be 500 or less, and more preferably 400 or less.

[0019] In the above formula (1), R １ Each of these is an independent tetravalent organic group having one or two benzene rings.１ It is preferable that R in each repeating unit in formula (1) above be at least one of the structures exemplified in formula (2) below. １ They may be the same or they may be different.

[0020]

[0021] In the above formula (1), R １ It is more preferable that this is at least one of the structures exemplified in formula (3) below.

[0022]

[0023] In the above formula (1), R ２ Each of these independently represents a divalent group derived from an aromatic hydrocarbon. Here, R ２ If it contains two or more aromatic groups, these aromatic groups are -O-, -SO ２ -, -CO-, -CH ２ They may be linked via at least one bonding group selected from the group consisting of - and -S-.

[0024] R ２ For example, at least one of the structures exemplified in formula (4) below is preferred.

[0025]

[0026] R ２ At least one of the structures exemplified by formula (5) below is more preferable.

[0027]

[0028] In addition to the polyimide resins described above, polyimide resins with excellent heat resistance and insulation properties can be used. Specifically, for example, the polyimide resin described in Japanese Patent No. 5281568 or the polyimide resin described in Japanese Patent No. 5523456 can be used.

[0029] A preferred polyamide-imide resin is a resin having a repeating structure of the following formula (6). The polyamide-imide resin may be a resin produced by, for example, the isocyanate method, the amine method (acid chloride method, low-temperature solution polymerization method, room-temperature solution polymerization method, etc.). The polyamide-imide resin used in the present invention is preferably a resin produced by the isocyanate method. The repeating unit in the repeating structure of the following formula (6) may be one type or two or more types.

[0030] [In the formula: m is the number of repeating units, and is a positive integer, R ３ Each of these is independently a trivalent organic group having one or two benzene rings, R ４ These are each independently divalent groups.

[0031] m is the number of repeating units and is a positive integer. m is preferably 50 or more, more preferably 100 or more, even more preferably 120 or more, and even more preferably 150 or more. m may be 500 or less, and more preferably 400 or less.

[0032] In the above formula (6), R ３ Each of these is independently a trivalent organic group having one or two benzene rings. ３ It is preferable that R in each repeating unit in formula (6) above is at least one of the structures exemplified in formula (7) below. ３ They may be the same or they may be different.

[0033]

[0034] R ３ A structure illustrated in formula (8) below is even more preferable.

[0035]

[0036] In the above formula (6), R ４ Each of these is independently a divalent group, preferably a divalent group derived from an aromatic hydrocarbon. ４ At least one of the structures exemplified by formula (9) below is preferred.

[0037] R in each repeating unit of the above formula (6) ４ They may be the same or they may be different.

[0038]

[0039] R ４ At least one of the structures exemplified by formula (10) below is more preferable.

[0040]

[0041] The insulating coating of the present invention may contain only one type of these resins, or it may contain two or more types.

[0042] The (A) imide resin and / or precursor according to the present invention is preferably a reaction product of a diamine and a carboxylic acid or an anhydride having four or more carboxyl groups.

[0043] Examples of diamines include aromatic diamines, aliphatic diamines, and polyether diamines, but aromatic diamines are preferred from the viewpoint of stability, etc. Examples of aromatic diamines include 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, paraphenylenediamine, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-diaminodiphenylmethane, benzidine, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diamino-3,3'-dimethoxybiphenyl, Examples include 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,3-diaminobenzene, and 1,2-diaminobenzene.

[0044] Examples of carboxylic acids having four or more carboxyl groups include benzene-1,2,4,5-tetracarboxylic acid, 4,4'-biphenyltetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, benzenehexacarboxylic acid, 3,4,9,10-perylenetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-oxydiphthalic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, and 2,2',3,3'-biphenyl Examples include tetracarboxylic acids, 3,4,9,10-perylenetetracarboxylic acid, 9,9-bis(3,4-dicarboxyphenyl)fluorene, 1,1-bis(2,3-dicarboxyphenyl)ethane, 1,1-bis(3,4-dicarboxyphenyl)ethane, ethylene glycol bistrimellitic acid, ethylene bis(trimellitic acid monoester), bis(2,3-dicarboxyphenyl)methane, bis(3,4-dicarboxyphenyl)methane, and bis(3,4-dicarboxyphenyl)sulfone. Among carboxylic acids having four or more carboxyl groups, tetracarboxylic acids are preferred, aromatic tetracarboxylic acids or aliphatic tetracarboxylic acids are more preferred, and aromatic tetracarboxylic acids are particularly preferred from the viewpoint of stability.

[0045] As an anhydride of a carboxylic acid having four or more carboxyl groups, it may be an anhydride formed by intramolecular dehydration condensation of some of the four or more carboxyl groups (for example, tetracarboxylic monoanhydride), but it is preferable that it is an anhydride formed by intramolecular dehydration condensation of all four or more carboxyl groups, and more preferably that it is a tetracarboxylic dianhydride formed by intramolecular dehydration condensation of all four carboxyl groups. Examples of tetracarboxylic dianhydrides include aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides, but aromatic tetracarboxylic dianhydrides are preferred from the viewpoint of stability and other factors. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic anhydride, 4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, and 1,1-(3,4-dicarboxyphenyl)ethane dianhydride. Examples include 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylenebis(trimellitic acid monoesteric acid dianhydride), ethylenebis(trimellitic acid monoesteric acid dianhydride), bisphenol Abis(trimellitic acid monoesteric acid dianhydride), and the like.

[0046] In a preferred embodiment, the imide resin and / or precursor according to the present invention may be produced from raw materials comprising a diamine and a carboxylic acid dianhydride. The diamine is preferably an aromatic diamine, more preferably 4,4'-diaminodiphenyl ether. The carboxylic acid dianhydride is preferably an aromatic carboxylic acid dianhydride, more preferably an aromatic tetracarboxylic acid dianhydride, and even more preferably pyromellitic anhydride or 2,2',3,3'-biphenyltetracarboxylic acid dianhydride.

[0047] In the production of an imide resin and / or its precursor according to a preferred embodiment of the present invention, the above-mentioned diamine and a carboxylic acid or anhydride having four or more carboxyl groups may be used individually or in combination of two or more types.

[0048] The content of (A) imide resin and / or its precursor in the insulating coating of the present invention is not particularly limited, but is preferably 3 to 40% by mass, more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass, based on the total mass of the insulating coating. If the content is not low, the amount of organic solvent to be removed can be reduced, which is economically advantageous, and if the content is not high, the viscosity of the solution can be kept relatively low, improving workability such as measuring and transfer.

[0049] The number-average molecular weight of the (A) imide resin and / or its precursor according to the present invention is 40,000 or more. As a result, the insulating film formed from the insulating paint of the present invention can exhibit high physical properties. The number-average molecular weight is more preferably 50,000 or more. Furthermore, the number-average molecular weight of the imide resin and / or its precursor may be 200,000 or less, preferably 150,000 or less, and more preferably 100,000 or less. If the number-average molecular weight is not too high, the increase in viscosity of the imide resin and / or its precursor is suppressed, which is advantageous for stirring and transfer during manufacturing, and improves productivity. Previously, this improvement in productivity was addressed by lowering the concentration of the imide resin in the insulating paint, which was undesirable because it reduced economic efficiency (cost benefit).

[0050] The number-average molecular weight of imide resins and / or their precursors may be measured using known methods, such as gel permeation chromatography (GPC). The GPC measurement conditions may be as follows, for example: Apparatus: Shimadzu GPC system Eluent: NMP containing DMAc, DMF, THF, 30 mmol / L lithium bromide, 30 mmol / L phosphoric acid, etc. Flow rate: Approximately 0.1 to 1.0 mL / min Column: Shodex GPC LF-804, Shim-pack GPC 804, etc. Column oven: Approximately 40°C to 50°C Standard: Polystyrene Sample: Diluted with eluent to approximately 0.5% by mass

[0051] The (A) imide resin and / or precursor according to the present invention contains molecular chains having amino groups as terminal groups. Such molecular chains may have one or two amino groups as terminal groups. All or part of the molecular chains contained in the (A) imide resin and / or precursor according to the present invention may be molecular chains having amino groups as terminal groups. The imide resin and / or precursor is a polymer of a diamine and a monomer other than a diamine. Examples of monomers other than diamine include dicarboxylic acids, dicarboxylic acid anhydrides, tricarboxylic acids, tricarboxylic acid anhydrides, tetracarboxylic acids, tetracarboxylic dianhydrides, and dialcohols. In addition to these monomers, the raw materials for the polymerization reaction may also include end-sealing agents. It is preferable that (A), which contains molecular chains having amino groups as terminal groups, is a polymer of a raw material containing diamine in an amount equal to or greater than the stoichiometric ratio.

[0052] In preferred embodiments of the present invention, the imide resin and / or its precursor are preferably end-sealed by using a small amount of end-sealing agent to stop the polymerization reaction during or after the polymerization reaction between the diamine and a carboxylic acid or anhydride having four or more carboxyl groups, or more preferably the ends are not sealed by not using an end-sealing agent. Specifically, in the raw material for synthesizing the imide resin and / or its precursor, the content of the end-sealing agent in the raw material is preferably 1 mole or less, more preferably 0.5 moles or less, even more preferably 0.4 moles or less, and most preferably 0 moles (i.e., no end-sealing agent) per 100 moles of diamine in the raw material. If the content of the end-sealing agent in the raw material is within the above range, the insulating film formed from the insulating coating of the present invention can exhibit high physical properties.

[0053] When the raw material contains an end-cap encapsulant, examples of such encapsulants include carboxylic acid monoanhydrides, monoamines, and monoisocyanates. Carboxylic acid monoanhydrides are preferred, dicarboxylic acid monoanhydrides are more preferred, and aromatic dicarboxylic acid monoanhydrides are even more preferred. An example of an aromatic carboxylic acid monoanhydride is phthalic anhydride. In the production of the imide resin of the present invention, any of the above-mentioned end-cap encapsulants may be used alone, or two or more may be used.

[0054] An imide resin and / or precursor according to a preferred embodiment of the present invention is produced by dehydration condensation of a diamine, such as those listed above, with a carboxylic acid or an anhydride having four or more carboxyl groups. In a typical method for producing an imide resin and / or precursor, the molar ratio of the carboxylic acid or anhydride having four or more carboxyl groups to the diamine in the raw materials is set to a predetermined ratio (e.g., 0.970 to 0.990), and the reaction is carried out using an excess amount of diamine. In this case, both terminal groups of the resulting polymer may be amino groups. Alternatively, a terminal encapsulant (e.g., an aromatic carboxylic acid monoanhydride) can be used in a predetermined molar ratio (e.g., 0.02 to 0.06) with the diamine to react with the terminal amino groups and encapsulate them.

[0055] In the production of such imide resins and / or precursors, when all terminal amino groups are completely sealed with a terminal encapsulant, the molar relationship of each component in the raw materials is "carboxylic acid or anhydride having 4 or more carboxyl groups + terminal encapsulant × 2 = diamine". When imide resins and / or precursors are produced under conditions that satisfy this molar relationship, the number average molecular weight is often around 20,000. However, in a preferred embodiment of the present invention, the molar amount M of diamine in the imide resin and / or precursor is ａ and the molar amount M of a carboxylic acid or anhydride having four or more carboxyl groups ｃ And the molar amount M of the end-captive agent ｔ The relationship with M ｃ +M ｔ ×2 < M ａ ; and, (M ｃ +M ｔ ) / M ａ It is synthesized from raw materials having a molecular weight of ≥0.980. In this case, unsealed amino groups may remain at the ends of the resulting polymer. When the imide resin and / or precursor of this preferred embodiment is a polyamic acid resin, the resin has a number average molecular weight of 40,000 or more and may contain unsealed terminal amino groups. An insulating film formed from the insulating paint of the present invention containing this resin may more preferably have high elongation and flexibility. Although the principle is not entirely clear, it is thought that the molecular weight of the resin in the insulating film is related. That is, the higher the molecular weight of the polyamic acid resin in the insulating paint, the higher the molecular weight of the polyimide resin in the insulating film, and it is thought that the decrease in molecular weight when the polyamic acid resin is converted to polyimide resin is suppressed by leaving unsealed terminal amino groups.

[0056] The type of solvent used in the polymerization reaction described above is not particularly limited, but it is preferably a solvent in which the imide resin and / or its precursor dissolves or disperses. For example, mainly high-boiling point solvents such as cresol-based phenols, aromatic alcohols, NMP (N-methyl-2-pyrrolidone), DMAC (N,N-dimethylacetamide), DMF (N,N-dimethylformamide), DMI (1,3-dimethyl-2-imidazolidinone), carbonate solvents, lactone solvents, and glycol ethers are preferably used. When synthesizing the imide resin and / or its precursor, generally known mixing methods such as kneaders, pressure kneaders, kneading rolls, Banbury mixers, twin-screw extruders, rotary-orbit mixers, and homomixers can be used in addition to conventional stirrers. The mixing temperature is usually 40 to 60°C.

[0057] The amount of end-capturing agent in the raw materials for the imide resin and / or its precursor according to the present invention can be calculated by hydrolyzing the imide resin and / or its precursor back into monomers (diamines, carboxylic acids having four or more carboxyl groups or their anhydrides, end-capturing agents, etc.) and quantifying the content of each monomer by chromatographic analysis or the like. Also, the molar amount M of the diamine ａ , molar amount M of a carboxylic acid or anhydride having four or more carboxyl groups ｃ , and the molar amount M of the end-capsule ｔ This can also be calculated using a similar method.

[0058] Hydrolysis and chromatographic analysis of imide resins and / or their precursors can be performed, for example, by the following procedure: An article solidified by reprecipitation or film formation of insulating paint, or a laminate containing an insulating film formed from insulating paint, is physically crushed into small pieces using a mill or crusher. These are added to alkaline water with a pH of approximately 9 to 13, and reflux treatment is carried out at approximately 100°C to 125°C under atmospheric pressure with stirring for 24 hours. Subsequently, the water in the resulting treatment solution is removed under reduced pressure, the residue is dissolved in a solvent suitable for chromatographic analysis, and the resulting solution is subjected to chromatographic analysis. Common alkaline components such as sodium hydroxide and ammonia can be used for the alkaline water. Examples of chromatographic analysis include high-performance liquid chromatography (HCM) and gas chromatography. When performing HCM, the column may be either normal-phase or reversed-phase. For a normal-phase column, for example, the stationary phase may be silica gel, and the solvent may be known substances such as n-hexane, methanol, acetone, ethyl acetate, dichloromethane, or chloroform. For a reversed-phase column, for example, the stationary phase may be silica, and the solvent may be known substances such as water or methanol. When performing gas chromatography, the column may be polyethylene glycol or dimethyl silicon, and the solvent may be any known solvent such as acetone, n-hexane, isooctane, methanol, ethyl acetate, dichloromethane, or chloroform. The type of detector used to detect the compounds separated by chromatography is not particularly limited, and for example, mass spectrometry may be used. For quantitative analysis in chromatographic analysis, known methods such as the absolute calibration curve method or the internal standard method may be used.

[0059] The insulating coating of the present invention contains (B) a metal oxide hydrate.

[0060] Preferred types of metal oxide hydrates include alumina hydrate, rhodium oxide hydrate, tantalum oxide hydrate, and zirconium oxide hydrate, with alumina hydrate being more preferred. While not particularly limited, examples of alumina hydrates include gibbsite, bayerite, norstrandite, boehmite, diaspore, and todite. From the viewpoint of improving the insulating properties and heat resistance of the insulating film formed from the insulating coating of the present invention, boehmite is particularly preferred as the metal oxide hydrate. The metal oxide hydrate may be used alone or in combination of two or more types.

[0061] The metal oxide hydrate is preferably in the form of particles. The average particle diameter of the metal oxide hydrate particles is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less. The lower limit of the average particle diameter of the metal oxide hydrate particles is, for example, 5 nm or more, preferably 10 nm or more. Preferred ranges for the average particle diameter of the metal oxide hydrate particles include 5 to 100 nm, 5 to 80 nm, 5 to 50 nm, 10 to 100 nm, 10 to 80 nm, and 10 to 50 nm. When the metal oxide hydrate is in the form of particles, its aspect ratio (long side / thickness) may be 1 to 200, preferably 3 to 150, and more preferably 5 to 100.

[0062] In a preferred embodiment, the insulating coating of the present invention is a sol containing metal oxide hydrates with a fine particle size (e.g., the average particle size described above) as a dispersed phase. As a result, the insulating film formed using the insulating coating of the present invention has a more uniform distribution of metal oxide hydrates, which can improve the electrical properties of the insulating film.

[0063] In the insulating coating of the present invention, the content of the metal oxide hydrate (B) when the total amount of the imide resin and / or precursor (A) and the metal oxide hydrate (B) is 100% by mass is 1.0 to 30% by mass, preferably 5.0 to 25% by mass, and more preferably 7.5 to 20% by mass.

[0064] The metal oxide hydrate (B) used in the present invention is preferably surface-treated. Examples of surface treatment methods include treatment with a surface treatment agent, specifically treatment with a silane coupling agent (epoxy silane coupling agent, methacrylic silane coupling agent, etc.), treatment with a titanate coupling agent, treatment with an aluminate surface treatment agent, treatment with a phosphoric acid surface treatment agent, and treatment with a carboxylic anhydride such as phthalic anhydride. Among these, metal oxide hydrates surface-treated with a silane coupling agent and metal oxide hydrates surface-treated with a phosphoric acid surface treatment agent are preferred, and metal oxide hydrates surface-treated with a phosphoric acid surface treatment agent are more preferred. Examples of phosphoric acid-based surface treatment agents include phenylphosphonic acid, octadecylphosphonic acid, 11-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}undecylphosphonic acid, 1H,1H,2H,2H-perfluoro-n-decylphosphonic acid, 1H,1H,2H,2H-perfluoro-n-hexylphosphonic acid, 11-hydroxyundecylphosphonic acid, 10-carboxydecylphosphonic acid, 11-aminoundecylphosphonic acid, and other phosphonic acid derivative surface treatment agents, as well as triphenyl phosphate, phenyl phosphate, and ethyl phosphate (either monoester or diester).

[0065] The method for treating metal oxide hydrates with a surface treatment agent is not particularly limited. If the metal oxide hydrate is in powder form, a method can be used in which a solution of the surface treatment agent dissolved in a solvent is sprayed onto the powder by a sprayer or the like, and then dried at 20 to 60°C. If the metal oxide hydrate is used in the form of a sol in which the metal oxide hydrate is dispersed, a method can be used in which the surface treatment agent is added to and dissolved in the sol, and then stirred at 20 to 60°C for 1 to 24 hours.

[0066] When treating metal oxide hydrates with a surface treatment agent, the amount of surface treatment agent per 100 parts by mass of metal oxide hydrate is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less.

[0067] Next, a laminate including an insulating film formed from the insulating paint of the present invention will be described with reference to the drawings. The laminated structure of the laminate 10 according to an embodiment of the present invention is a structure comprising at least a conductor 1 and an insulating film 2, as shown in Figures 1 to 5. Specifically, the laminate 10 of the present invention may be in the form of a film having at least a conductor 1 and an insulating film 2 laminated on the conductor 1, as shown in Figure 1, for example. Alternatively, the laminate 10 according to an embodiment of the present invention may be in the form of an insulated wire having a conductor 1 in the central part and an insulating film 2 formed on the outer circumference of the conductor 1, as shown in Figures 2 to 5, for example. When the laminate 10 of the present invention is in the form of an insulated wire, the cross-sectional shape may be circular, elliptical, polygonal (it may be a rectangular shape or an irregular shape), etc. Figures 2 to 4 show an insulated wire with a circular cross-section. Figure 5 shows an insulated wire with a substantially rectangular cross-section. When the cross-sectional shape of the conductor 1 is circular, the diameter is, for example, about 0.03 to 4.0 mm.

[0068] The laminated structure of the laminated body 10 of the present invention, which is an insulated electric wire, only needs to have at least a conductor 1 and an insulating film 2, and may have other layers. Examples of other layers include insulating layers 3 and / or 4. For example, Figure 3 shows a laminated body 10 (i.e., an insulated electric wire) comprising a conductor 1, an insulating film 2 formed on its upper surface, and an insulating layer 3 further formed on its upper surface. Figures 4 and 5 also show a laminated body 10 (i.e., an insulated electric wire) comprising a conductor 1, an insulating layer 4 formed on its upper surface, an insulating film 2 formed on the upper surface of the insulating layer 4, and an insulating layer 3 further formed on the upper surface of the insulating film 2. Examples of materials constituting the insulating layers 3 and 4 include heat-resistant resins (hereinafter also referred to as heat-resistant resins) as described later.

[0069] The insulating layers 3 and 4 may each be made of the same material as the insulating film 2, or they may each be made of a different material. Furthermore, the insulating layers 3 and 4 may each be made of the same material, or they may each be made of a different material. In addition, the insulating layers 3 and 4 may each be provided below the insulating film 2 (i.e., on the conductor 1 side) or above the insulating film 2 (i.e., on the side opposite to the conductor 1 side).

[0070] Other layers may include metal layers, such as a plating layer made of a metal different from that of conductor 1. The metal layer may be formed between the conductor surface and the insulating layer.

[0071] The material constituting the conductor 1 can be any conductive material, such as copper (low-oxygen copper, oxygen-free copper, copper alloys, etc.), aluminum, silver, nickel, or iron. The material constituting the conductor 1 can be appropriately selected depending on the application of the present invention.

[0072] In the insulating film 2, metal oxide hydrates having an average particle size of 5 to 100 nm may be dispersed in the resin (i.e., in a nanocomposite state). From the viewpoint of suitably exhibiting the effects of the present invention, alumina hydrates such as boehmite and gibbsite are preferred as the metal oxide hydrate, and boehmite is more preferred. Furthermore, there may be one type of metal oxide hydrate or two or more types.

[0073] The resin contained in the insulating film 2 is preferably polyesterimide resin, polyamideimide resin, or polyimide resin, with polyimide resin being more preferred. The resin contained in the insulating film 2 may be one type or two or more types.

[0074] In the insulating film 2, the lower limit of the imide resin content is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 75% by mass or more, and particularly preferably 80% by mass or more, relative to the entire insulating film, and the upper limit is preferably 97% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0075] In the insulating film 2, the lower limit of the metal oxide hydrate content is preferably 3% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, and particularly preferably 15% by mass or more, relative to the entire insulating film, and the upper limit is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 25% by mass or less, and particularly preferably 20% by mass or less.

[0076] In the insulating film 2, the amount of metal oxide hydrate is preferably 10 to 25 parts by mass, more preferably 15 to 20 parts by mass, based on 100 parts by mass of the total of the imide resin and the metal oxide hydrate.

[0077] From the viewpoint of more favorably exhibiting the effects of the present invention, the thickness of the insulating film 2 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The upper limit of the thickness of the insulating film 2 is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0078] When preparing insulating coatings for forming insulating film 2, imide resins and / or their precursors, as well as metal oxide hydrates, are typically used in a form dissolved or dispersed in a solvent (such as a resin varnish).

[0079] The insulating coating for forming the insulating film 2 is prepared such that an imide resin and / or its precursor is dissolved or dispersed in a solvent, and a metal oxide hydrate is dispersed. It is preferable to form the insulating film 2 by applying and baking this insulating coating. Suitable solvents for dissolving or dispersing the imide resin and / or its precursor while appropriately dispersing the metal oxide hydrate include high-boiling point solvents such as cresol-based phenols, aromatic alcohols, NMP (N-methyl-2-pyrrolidone), DMAC (N,N-dimethylacetamide), DMF (N,N-dimethylformamide), DMI (1,3-dimethyl-2-imidazolidinone), carbonate solvents, lactone solvents, and glycol ether solvents. Methods for preparing the insulating coating include, for example, manufacturing using generally known mixing means such as a kneader, pressure kneader, kneading roll, Banbury mixer, twin-screw extruder, orbital mixer, and homomixer. The mixing temperature is usually 5 to 30°C.

[0080] The insulating coating described above may contain acidic or alkaline components for dispersion stabilization. Similarly, it may contain water, low-boiling alcohol, or a low-viscosity solvent that contributes to reducing the viscosity of the insulating coating. The insulating coating may also contain metal oxides as needed, or additives may be added for hydrophobicity or to improve dispersibility. Suitable additives include fluorine-based and silicon-based additives, citric acid, ethylenediaminetetraacetic acid, and 8-quinolinol.

[0081] As described above, the laminate 10 according to the embodiment of the present invention may consist only of a conductor 1 and an insulating film 2, or it may further have other insulating layers such as an insulating layer 3 and an insulating layer 4.

[0082] Examples of other insulating layers include organic insulating layers. The organic insulating layer is preferably composed of a heat-resistant resin. Specific examples of heat-resistant resins constituting the organic insulating layer include formal resin, polyurethane, epoxy resin, polyester, polyamide, polyesterimide, polyetherimide, polyamideimide, polyimide, and their precursors. Among these, polyesterimide, polyamideimide, polyimide, and / or their precursors are preferred from the viewpoint of further enhancing heat resistance. The heat-resistant resin contained in the organic insulating layer may be one type or two or more types.

[0083] In the laminate 10 according to the embodiment of the present invention, the total thickness of the insulating film 2 and the other insulating layers is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, from the viewpoint of more favorably exhibiting the effects of the present invention. The upper limit of the total thickness of the insulating film 2 and the other insulating layers is preferably 200 μm or less.

[0084] The laminate 10 according to an embodiment of the present invention can be manufactured, for example, by laminating layers constituting an insulating film 2 on a conductor 1. For example, it can be manufactured by applying and baking an insulating paint that forms the insulating film 2 onto the conductor 1. Alternatively, an insulated wire can be manufactured by wrapping an insulating film formed from the insulating paint around the conductor 1. The insulating film can be formed, for example, by molding and baking the insulating paint that forms the insulating film 2 using a film coater or the like. The difference between these methods for manufacturing insulated wires is whether the insulating film 2 is formed on the conductor or whether an insulating film is formed separately and then wrapped around the conductor 1. The insulating film is the insulating film 2 in film form.

[0085] The method of applying the insulating coating is not particularly limited and includes methods such as applying with a coater, applying with a dip coater and repeating the application and drying process to obtain a film of a predetermined thickness, and applying with a spray. Furthermore, baking can be performed, for example, by heating at a high temperature (e.g., 300°C or higher) for a predetermined time. In addition, the formation of the insulating film 2 can also be performed by repeating a series of operations of application and heating multiple times until the insulating film 2 reaches a predetermined thickness. When forming the insulating film 2, the baking temperature and time should be set according to the type of metal oxide hydrate so that the metal oxide hydrate does not change into another metal oxide hydrate or metal oxide due to the heat.

[0086] For example, if the laminate 10 according to an embodiment of the present invention is in the form of an insulated wire, an insulated wire can be manufactured by applying and baking an insulating coating onto the surface of a wire-shaped conductor 1. The insulating film 2 can be formed by repeating a series of operations (application and heating) multiple times (for example, 10 to 20 times) until the insulating film 2 reaches a predetermined thickness, in which the insulating coating is applied to the conductor 1 to a predetermined thickness and heated at a high temperature (for example, 300 to 500°C) for a predetermined time (for example, 1 to 2 minutes).

[0087] A coil can be manufactured by winding the above-mentioned insulated wire around a core. Furthermore, the above-mentioned coil can be used in a rotating electric machine. That is, the above-mentioned rotating electric machine may be a rotating electric machine made using the insulated wire according to the embodiment of the present invention, or an insulated wire may be formed by forming a rotating electric machine using a conductor 1 and then forming an insulating film 2 on the surface of the conductor 1.

[0088] Examples of rotating electrical machines include motors and generators.

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these examples.

[0090] The resins (imide-based resins or their precursors) used in the examples and comparative examples are as follows:

[0091] [Resin (Imide-based resin or its precursor)] Resin 1. Pyre-M. L. RC5019 from IST Co., Ltd. (A 16% polyamic acid resin solution with NMP as the solvent. The number-average molecular weight is 42,000, the amount of end-capturing agent in the raw materials is zero, and the relationship of the molar amounts of the raw materials is M) ｃ +M ｔ ×2 < M ａ That is. Also, (M ｃ +M ｔ ) / M ａ (= 0.982.)

[0092] Resin 2. Nagoya Chemical Industry's Mayrejicoat 26 (a 20% polyamic acid resin solution with NMP as the solvent. The number-average molecular weight is 27,000, the amount of end-capturing agent in the raw materials is zero, and the relationship of the molar amounts of the raw materials is M ｃ +M ｔ ×2 < M ａ That is. Also, (M ｃ +M ｔ ) / M ａ (= 0.974.)

[0093] Resin 3. Nagoya Chemical Industry's Mayrejicoat 36 (a 20% polyamic acid resin solution with NMP as the solvent. The number-average molecular weight is 55,000, the carboxylic acid monoanhydride used as the end-cap encapsulant is 0.04 molars / diaminodiphenyl ether, and the relationship between the molar amounts of the raw materials is M ｃ +M ｔ ×2 = M ａ (That is the case.)

[0094] Resin 4. Nagoya Chemical Industry's Meirejicoat 46 (a 20% polyamic acid resin solution with NMP as the solvent. The number-average molecular weight is 55,000, the amount of end-capturing agent in the raw materials is zero, and the relationship of the molar amounts of the raw materials is M) ｃ +M ｔ ×2 < M ａ That is. Also, (M ｃ +M ｔ ) / M ａ (= 0.991.)

[0095] Resin 5. A 5 L four-necked flask equipped with a stirrer and thermometer contained a polyamic acid resin synthesized by the method described below. 400.48 g (2.00 mol) of 4,4'-diaminodiphenyl ether and 4109 g of NMP were charged into the flask and heated to 50°C while stirring to dissolve. Next, 220.73 g (1.01 mol) of pyromellitic anhydride and 279.49 g (0.95 mol) of biphenyltetracarboxylic dianhydride were gradually added to the solution. After the addition was complete, the mixture was stirred for 1 hour, then 0.8887 g (0.006 mol) of phthalic anhydride was added, and the mixture was stirred for another 1 hour to obtain 5010.6 g of a solution in which the aromatic polyamic acid resin represented by formula (I) was dissolved at a concentration of 18.0% by mass (number average molecular weight: 55,000, phthalic anhydride used as a terminal encapsulant: 0.003 molar times / diaminodiphenyl ether). The relationship of the molar amounts of the raw materials is M ｃ +M ｔ ×2 < M ａ (M ｃ +M ｔ ) / M ａ = 0.983. [In equation (I), n is an integer greater than or equal to 2.]

[0096] [Insulating paint containing metal oxide hydrates]

[0097] <Manufacturing Example 1> To an NMP-dispersed boehmite sol [product name: Alumina Sol A1-10 (containing 10% by mass of boehmite), average particle size: 15-50 nm, aspect ratio (long side / thickness): 10-50, manufactured by Kawaken Fine Chemicals Co., Ltd.], 6 parts by mass of ethyl phosphate (ethyl acid phosphate [Ethyl Phosphate (Mono- and Di-Ester mixture), manufactured by Tokyo Chemical Industry Co., Ltd., monoester content 35.0-47.0%, diester content 53.0-67.0%)] was added per 100 parts by mass of boehmite (alumina equivalent), and 24 parts by mass of 8-quinolinol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added per 100 parts by mass of boehmite (alumina equivalent), and the mixture was stirred at room temperature for 1 hour to obtain an NMP-dispersed boehmite sol containing ethyl phosphate surface-treated boehmite. Next, using an in-line homomixer, an ethyl phosphate surface-treated boehmite sol was uniformly mixed and dispersed in the above-mentioned resin 1 (Pyre-M.L.RC5019) at room temperature, such that the amount of boehmite was 15 parts by mass (in terms of alumina) per 85 parts by mass of the resin, to obtain insulating paint 1.

[0098] <Manufacturing Example 2> An insulating coating 2 was obtained in the same manner as in Manufacturing Example 1, except that resin 1 was replaced with resin 2 (Meirezicoat 26).

[0099] <Manufacturing Example 3> An insulating coating 3 was obtained in the same manner as in Manufacturing Example 1, except that resin 1 was replaced with resin 3 (Meirezicoat 36) and the amount of ethyl phosphate (6 parts by mass) was replaced with 14 parts by mass.

[0100] <Manufacturing Example 4> An insulating coating 4 was obtained in the same manner as in Manufacturing Example 1, except that resin 1 was replaced with resin 4 (Meirezicoat 46) and the amount of ethyl phosphate (6 parts by mass) was replaced with 14 parts by mass.

[0101] <Manufacturing Example 5> An insulating coating 5 was obtained in the same manner as in Manufacturing Example 1, except that resin 1 was replaced with resin 5.

[0102] <Manufacturing Example 6> An insulating coating 6 was obtained in the same manner as in Manufacturing Example 1, except that 35 parts by mass of phenylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were used instead of 6 parts by mass of ethyl phosphate.

[0103] <Manufacturing Example 7> An insulating coating 7 was obtained in the same manner as in Manufacturing Example 3, except that 35 parts by mass of phenylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were used instead of 14 parts by mass of ethyl phosphate.

[0104] <Production Example 8> An insulating coating 8 was obtained in the same manner as in Production Example 4, except that 35 parts by mass of phenylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were used instead of 14 parts by mass of ethyl phosphate.

[0105] <Production Example 9> An insulating coating 9 was obtained in the same manner as in Production Example 5, except that 35 parts by mass of phenylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were used instead of 6 parts by mass of ethyl phosphate.

[0106] [Preparation of insulating film] Insulating films were prepared according to the procedures shown in Examples 1 to 6 and Comparative Examples 1 to 3 below.

[0107] (Example 1) An insulating coating 1 prepared in Manufacturing Example 1 was applied to a rectangular PET film with a thickness of 100 μm using a blade coater with a groove depth of 600 μm. With the PET film kept horizontal, it was dried in a forced-air oven at the following temperatures in sequence: 70°C for 15 minutes, 90°C for 45 minutes, and 130°C for 10 minutes to form an intermediate film on the PET film. After peeling this intermediate film from the PET film, it was heat-treated at 150°C for 10 minutes, 200°C for 10 minutes, 250°C for 10 minutes, and 300°C for 60 minutes to obtain an insulating film. The thickness of the obtained insulating film was 25 μm.

[0108] (Examples 2-6) Insulating films were obtained in the same manner as in Example 1, except that insulating paint 1 was replaced with insulating paints 4, 5, 6, 8, and 9, respectively. The thicknesses of the obtained insulating films were 36, 33, 25, 25, and 40 μm, respectively.

[0109] (Comparative Examples 1-3) Insulating films were obtained in the same manner as in Example 1, except that insulating paint 1 was replaced with insulating paints 2, 3, and 7, respectively. The thicknesses of the obtained insulating films were 27, 49, and 31 μm, respectively.

[0110] [Evaluation of insulating film properties] The insulating films obtained in the examples and comparative examples were evaluated for the following properties. The results are shown in Table 1.

[0111] <Measurement of Film Elongation> Tensile tests were performed on the insulating films prepared in Examples 1-6 and Comparative Examples 1-3 in accordance with JIS-C-2151. Using a tensile testing machine, the insulating film was pulled at a speed of 200 mm / min, and the elongation at which the insulating film broke (ruptured) was determined. The elongation was calculated using the following formula: Tensile elongation (%) = 100 × (L - L0) / L0 L0: Sample length before testing L: Sample length at rupture

[0112] <Measurement of Film Flexibility> The insulating films prepared in Example 2 and Comparative Example 1 were each subjected to a flexibility test (cylindrical mandrel method) in accordance with JIS-K5600-5-1. The test method involved using mandrels with diameters of 1 to 5 mm, testing each test specimen sequentially from the largest diameter mandrel to the smallest, and defining the mandrel diameter at which cracking or fissure first occurred in the insulating film as the flexibility value. Films that did not crack even with a 1 mm mandrel were defined as <1 mm.

[0113] [Manufacturing of Insulated Wires] Insulated wires (i.e., laminates of the present invention) were manufactured according to the procedures shown in Examples 7 to 12 and Comparative Examples 4 to 6 below.

[0114] (Example 7) An insulating coating 1 was applied to a copper conductor (a copper wire with a diameter of approximately 1 mm), and the process of baking (coating to baking) was repeated 20 times by passing it through a furnace approximately 10 m long for approximately 1 minute, thereby forming an insulating film on the surface of the copper conductor and producing an insulated wire using insulating coating 1 containing boehmite. The furnace described above was one in which the temperature was continuously increased from an inlet temperature of 350°C to an outlet temperature of 430°C. The thickness of the obtained insulating film was 40 μm.

[0115] (Examples 8-12) Insulated wires were prepared in the same manner as in Example 7, except that insulating paint 1 was replaced with insulating paints 4, 5, 6, 8, and 9, respectively. The thickness of the insulating coating was 37, 38, 37, 37, and 39 μm, respectively.

[0116] (Comparative Examples 4-6) Insulated wires were prepared in the same manner as in Example 7, except that insulating paint 1 was replaced with insulating paints 2, 3, and 7, respectively. The thickness of the insulating coating was 38, 41, and 39 μm, respectively.

[0117] [Characteristic Evaluation of Insulated Wires] The insulated wires obtained in the examples and comparative examples were evaluated for the following characteristics. The results are shown in Table 2.

[0118] <Flexibility Evaluation> The flexibility of the insulated wire was tested in accordance with the JIS C3216-3-5-1 winding test.

[0119] (Example 13) When a rectangular enameled wire is manufactured using the manufacturing apparatus 1 described in the first or second embodiment of Japanese Patent Application Publication No. 2021-44197, and using any of the above insulating paints 1, 4-6, and 8-9 as the enamel paint E, it is possible to form an insulating coating with a uniform thickness on the outer circumference of the rectangular conductor wire while suppressing a decrease in productivity, and an electric wire can be obtained that has an insulating coating with high elongation and flexibility while containing metal oxide hydrates.

[0120] 10 Laminate 1 Conductor 2 Insulating film 3 Insulating layer 4 Insulating layer

Claims

1. An insulating coating comprising (A) an imide resin and / or its precursor, and (B) a metal oxide hydrate, wherein (A) satisfies the following (a) and (b): (a) contains molecular chains having amino groups as terminal groups; (b) has a number average molecular weight of 40,000 or more.

2. The insulating paint according to claim 1, wherein (A) is a reaction product of a diamine and a carboxylic acid or an anhydride having four or more carboxyl groups, and satisfies either (c1) or (c2) below: (c1) The ends are not sealed with an end sealant; (c2) The ends are sealed with an end sealant, and the amount of the end sealant in the raw material is 1 mole or less per 100 moles of the diamine.

3. The molar amount M of the diamine ａ and the molar amount M of the carboxylic acid or its anhydride having 4 or more carboxy groups ｃ and the molar amount M of the end-capping agent ｔ are related by the following formula: M ｃ + M ｔ × 2 < M ａ ; and (M ｃ + M ｔ ) / M ａ ≧ 0.

980. The insulating paint according to claim 2 4. The insulating paint according to claim 2, wherein the diamine is an aromatic diamine, the carboxylic acid or anhydride having four or more carboxyl groups is an aromatic tetracarboxylic dianhydride, and the end sealant is an aromatic carboxylic acid monoanhydride.

5. The insulating paint according to claim 2, wherein (A) satisfies the following (c2'): (c2') The end is sealed with an end sealant, and the amount of the end sealant in the raw material is 0.5 moles or less per 100 moles of the diamine.

6. The insulating paint according to claim 2, wherein the end of (A) is not sealed with an end sealant.

7. The insulating paint according to claim 1, wherein the (B) metal oxide hydrate includes alumina hydrate.

8. The insulating paint according to claim 1, wherein the sol contains the metal oxide hydrate having an average particle size of 5 to 100 nm as a dispersed phase.

9. A laminate comprising an insulating film formed from an insulating paint according to any one of claims 1 to 8.

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