Layered body of conductor and insulative coating, coil, rotating electrical machine, insulating resin composition, insulating coating material, and insulating film

Abstract

Provided is a layered body having excellent insulating performance, and excellent resistance to partial discharge even under high humidity environments.　This layered body comprises at least a conductor and an insulating coating. The insulating coating is formed from a nanocomposite composed of a resin composition obtained by dispersing a metal hydroxide hydrate in a resin. The metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP).

Description

Laminate of conductor and insulating coating, coil, rotating electric machine, insulating resin composition, insulating paint, and insulating film

[0001] In one aspect, the present invention relates to a laminate of a conductor and an insulating coating, a coil, a rotating electric machine, an insulating resin composition, an insulating coating, and an insulating film.

[0002] Insulated wires used in electric devices such as motors include insulated wires in which an insulating layer is formed by applying an insulating coating made by dissolving a resin such as polyimide or polyamideimide or a resin precursor in an organic solvent to the surface of a conductor and baking the coating; and insulated wires in which an insulating layer is formed by wrapping an insulating film such as a polyimide film or mica tape around a conductor (so-called tape wrapping).

[0003] In electrical equipment with high operating voltages, such as motors operated at high voltages, high voltages are applied to the insulated wires that make up the coils. If there are minute gaps between adjacent insulated wires or in the insulating coating, an electric field may concentrate in those areas, causing partial discharges. Such partial discharges can cause deterioration of the insulating coating, leading to early breakdown of the coil and damage to the electrical equipment.

[0004] In recent years, in systems that drive motors and other devices using inverters for energy conservation or variable speed, even in devices classified as low-voltage drives, sudden overvoltages (so-called inverter surges) have repeatedly occurred in the drive voltage over a very short period of time, resulting in an increasing number of cases of dielectric breakdown. This dielectric breakdown is caused by partial discharges triggered by the repeated overvoltages caused by inverter surges.

[0005] As a method for improving resistance to partial discharge (partial discharge resistance characteristics), a laminate has been disclosed in which an insulating coating is formed from a resin composition containing nano-sized metal oxide hydrates such as boehmite (see, for example, Patent Document 1).

[0006] Patent No. 6567797

[0007] Many motors are used in harsh environments, such as high humidity environments. In general, high humidity environments decrease the partial discharge inception voltage, making partial discharges more likely to occur, so motors must maintain their performance even in high humidity environments. Generally, when an insulating layer absorbs moisture, the breakdown voltage also decreases. Furthermore, when inorganic substances such as metal oxide hydrates are mixed into the insulating layer to improve partial discharge resistance, flexibility also decreases.

[0008] In one aspect, the present invention aims to provide a laminate that has excellent partial discharge resistance and insulating properties even in a high-humidity environment. Another object of the present invention is to provide a coil and a rotating electric machine that have excellent partial discharge resistance and insulating properties even in a high-humidity environment, as well as an insulating resin composition, an insulating paint, and an insulating film for forming the laminate.

[0009] The present inventors conducted extensive research to solve the above-mentioned problems. As a result, they unexpectedly discovered that a laminate including at least a conductor and an insulating coating, wherein the insulating coating is made of a nanocomposite made of a resin composition in which a metal oxide hydrate is dispersed in a resin, and the metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP), can provide excellent partial discharge resistance in high-humidity environments and excellent insulating properties. The present invention was completed based on this discovery and through further research.

[0010] In one aspect, the present invention provides the following laminate, coil, rotating electric machine, insulating resin composition, insulating coating, and insulating film. Item 1. A laminate including at least a conductor and an insulating coating, wherein the insulating coating is made of a nanocomposite made of a resin composition in which a metal oxide hydrate is dispersed in a resin, and the metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP). Item 2. The laminate according to Item 1, wherein the metal oxide hydrate includes alumina hydrate. Item 3. The laminate according to Item 1 or 2, wherein the nanocomposite is one in which the metal oxide hydrate is dispersed in a sol state. Item 4. The laminate according to any one of Items 1 to 3, wherein the resin contained in the nanocomposite is at least one selected from the group consisting of formal resin, polyurethane, epoxy resin, polyester, polyesterimide, polyetherimide, polyamideimide, polyimide, and precursors thereof. Item 5. Item 6. The laminate according to any one of Items 1 to 4, wherein the resin contained in the nanocomposite is at least one selected from the group consisting of polyimide and polyimide precursors. Item 7. The laminate according to any one of Items 1 to 5, in the form of an insulated wire. Item 8. A rotating electric machine comprising the laminate according to Item 6. Item 9. An insulating resin composition for forming the insulating coating of the laminate according to any one of Items 1 to 5. Item 10. An insulating paint for forming the insulating coating of the laminate according to any one of Items 1 to 5. Item 11. An insulating film formed from the nanocomposite according to any one of Items 1 to 5.

[0011] According to one aspect of the present invention, it is possible to provide a laminate including at least a conductor and an insulating coating, which laminate has excellent partial discharge resistance and excellent insulating properties even in a high-humidity environment. Also, according to another aspect of the present invention, it is possible to provide a coil and a rotating electric machine having excellent partial discharge resistance and excellent insulating properties even in a high-humidity environment, as well as an insulating resin composition, an insulating paint, and an insulating film for forming the laminate.

[0012] Fig. 1 is a schematic cross-sectional view showing an example of a laminate according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing an example of an insulated wire according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention. Fig. 5 is a schematic cross-sectional view showing another example of an insulated wire according to an embodiment of the present invention.

[0013] Hereinafter, several embodiments of the laminate, coil, rotating electrical machine, insulating resin composition, insulating coating, and insulating film according to one aspect of the present invention will be described in detail. In this specification, a numerical value connected with "to" means a numerical range including the numerical values ​​before and after "to" as the lower and upper limits. When multiple lower limit values ​​and multiple upper limit values ​​are listed separately, any lower limit value and any upper limit value can be selected and connected with "to".

[0014] The laminate of the present invention is a laminate comprising at least a conductor and an insulating coating formed on the conductor. In the laminate according to an embodiment of the present invention, the insulating coating is composed of a nanocomposite (i.e., a composite material in which nano-sized metal oxide hydrates are dispersed in a resin) made of a resin composition in which a metal oxide hydrate is dispersed in a resin, and the metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP). By having such a configuration, the laminate according to an embodiment of the present invention has excellent partial discharge resistance and insulating properties even in a high-humidity environment. The laminate according to an embodiment of the present invention will be described in detail below with reference to FIGS. 1 to 5.

[0015] In this invention, "inverter surge" refers to a steep overvoltage that occurs due to inverter switching and is superimposed on the drive voltage. Since the switching frequency of an inverter ranges from a relatively slow 1 kHz to a high 100 kHz, the frequency of inverter surges also ranges from about 1 kHz to 100 kHz, which is extremely high. The voltage ranges from about 1000 V when superimposed on the 400 V drive voltage of an industrial inverter motor to about 3 kV when superimposed on the operating voltage of a high-voltage inverter motor.

[0016] The laminate structure of the laminate 10 according to an embodiment of the present invention is a laminate including at least a conductor 1 and an insulating coating 2, as shown in FIGS. 1 to 5 . Specifically, the laminate 10 according to the present invention may be in the form of a film having at least a conductor 1 and an insulating coating 2 laminated on the conductor 1, as shown in FIG. 1 . The laminate 10 according to an embodiment of the present invention may also be in the form of an insulated wire having a conductor 1 in the center and an insulating coating 2 formed around the periphery of the conductor 1, as shown in FIGS. 2 to 5 . When the laminate 10 according to the present invention is in the form of an insulated wire, the cross-sectional shape may be circular, elliptical, polygonal (it may be rectangular or irregular), or the like. FIGS. 2 to 4 show an insulated wire having a circular cross-section. FIG. 5 shows an insulated wire having 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.

[0017] The laminate structure of the laminate 10 according to an embodiment of the present invention is sufficient to include at least the conductor 1 and the insulating coating 2, and may include other layers. Examples of such other layers include insulating layers 3 and 4. For example, FIG. 3 shows a laminate 10 (insulated wire) including a conductor 1, an insulating coating 2 formed on the upper surface thereof, and an insulating layer 3 formed on the upper surface thereof. Also, FIGS. 4 and 5 show a laminate 10 (insulated wire) including a conductor 1, an insulating layer 4 formed on the upper surface thereof, an insulating coating 2 formed on the upper surface of the insulating layer 4, and an insulating layer 3 formed on the upper surface of the insulating coating 2. Examples of materials constituting the insulating layers 3 and 4 include heat-resistant resins (heat-resistant resins) as described below.

[0018] The insulating layers 3 and 4 may each be made of the same material as the insulating coating 2, or may each be made of a different material. The insulating layers 3 and 4 may each be made of the same material as the insulating coating 2, or may each be made of a different material. The insulating layers 3 and 4 may each be provided below the insulating coating 2 (i.e., on the conductor 1 side) or above the insulating coating 2 (i.e., on the opposite side from the conductor 1 side).

[0019] Other layers include a plating layer made of a metal different from that of the conductor, which is formed between the conductor surface and the insulating layer.

[0020] The material constituting the conductor 1 may be any conductive material, such as copper (low-oxygen copper, oxygen-free copper, copper alloy, etc.), aluminum, silver, nickel, iron, etc. The material constituting the conductor 1 can be appropriately selected depending on the application of the present invention.

[0021] As described above, the insulating coating 2 is made of a nanocomposite made of a resin composition in which a metal oxide hydrate is dispersed in a resin. From the viewpoint of optimally exerting the effects of the present invention, the metal oxide hydrate is preferably an alumina hydrate such as boehmite or gibbsite. The metal oxide hydrate contained in the insulating coating 2 is preferably boehmite. Furthermore, the metal oxide hydrate may be one type or two or more types.

[0022] Furthermore, the shape of the metal oxide hydrate is preferably a flat particle with a large aspect ratio (long side (one side) / thickness) because this provides better partial discharge resistance. The shape of the metal oxide hydrate is preferably plate-like, rod-like, needle-like, or the like. Furthermore, the shape of the metal oxide hydrate when viewed in plan from the main surface (usually a surface perpendicular to the thickness direction) is preferably substantially rectangular (a substantially quadrangular shape such as a substantially square or rectangular). The aspect ratio (long side (one side) / thickness) of the metal oxide hydrate is preferably 4 or more, more preferably 10 or more, and even more preferably 15 or more, and is preferably 200 or less, more preferably 100 or less, and even more preferably 50 or less. Note that the aspect ratio in this specification refers to the ratio observed at a magnification of 5000 times using a scanning electron microscope.

[0023] The metal oxide hydrate is preferably in the form of particles, and the average particle size 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 size of the metal oxide hydrate particles is, for example, 5 nm or more, preferably 10 nm or more. Preferred ranges for the average particle size 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 particles are flat fine particles with a large aspect ratio (long side (one side) / thickness) as described above, the average particle size is determined by the average of the long side and the short side as determined by observation with a scanning electron microscope.

[0024] In the present invention, the metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP). By utilizing a nanocomposite containing the metal oxide hydrate with a negative zeta potential as an insulating coating, the laminate according to the embodiment of the present invention can exhibit excellent partial discharge resistance and excellent insulating properties in high-humidity environments. The mechanism by which these properties are exhibited can be considered, for example, as follows. Specifically, resins typically contain functional groups such as carboxyl groups, aldehyde groups, ether groups, ester groups, amino groups, amide groups, and hydroxyl groups. The surface of the resin is thought to have a negative surface charge due to the generation of hydroxyl groups, amino groups, and the like resulting from polarization of these functional groups and local hydrolysis. Dispersing the metal oxide hydrate of the present invention in these resins is thought to cause repulsion between the resin and the metal oxide hydrate. It is speculated that this repulsion further suppresses molecular vibration of the resin chain, resulting in the exhibiting of these properties.

[0025] The zeta potential of the metal oxide hydrate may be any value as long as it is a negative value, and from the viewpoint of more suitably exhibiting the effects of the present invention, the absolute value of the zeta potential of the metal oxide hydrate is preferably 1 to 100 mV, more preferably 2 to 50 mV, even more preferably 3 to 30 mV, still more preferably 5 to 25 mV, and even more preferably 5 to 10 mV.

[0026] The zeta potential of a metal oxide hydrate is measured by the following method. First, the metal oxide hydrate is diluted in a sol state with N-methyl-2-pyrrolidone (NMP) to prepare a sample with a concentration of 0.1% by mass. Next, the sample is placed in a thermostatic bath at 5°C and kept warm for 1 hour. After that, approximately 1 g of the sample is filled into a zeta dip cell for measurement, and measurement is performed. A Zeta Nanosizer ZS manufactured by Malvern Instruments is used as the measurement device. Specific measurements are performed according to the methods described in the Examples.

[0027] From the viewpoint of more suitably exhibiting the effects of the present invention, it is preferable that the metal oxide hydrate is surface-treated. Examples of the surface treatment method include a method using a surface treatment agent, specifically a method of treating with a silane coupling agent (epoxy-based silane coupling agent, methacrylic-based silane coupling agent, etc.), a method of treating with a titanate coupling agent, a method of treating with an aluminate-based surface treatment agent, a method of treating with a phosphoric acid-based surface treatment agent, and a method of treating with a carboxylic acid 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-based surface treatment agent are preferred, and metal oxide hydrates surface-treated with a phosphoric acid-based surface treatment agent are more preferred. Examples of phosphoric acid surface treatment agents include phosphonic acid derivative surface treatment agents such as 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, and 11-aminoundecylphosphonic acid. Among the phosphoric acid surface treatment agents, metal oxide hydrates surface-treated with the phosphonic acid derivative surface treatment agents can have a suitably negative zeta potential and are particularly suitable as metal oxide hydrates that exhibit the effects of the present invention.

[0028] The surface treatment method is not particularly limited, and when the metal oxide hydrate is a powder, a method in which a solution prepared by dissolving a surface treatment agent in a solvent is sprayed onto the powder using a spray or the like, followed by drying at 20 to 60° C., or when a metal oxide hydrate sol is used, a method in which the surface treatment agent is added and dissolved, followed by stirring for 1 to 24 hours at 20 to 60° C., may be used. When treating the metal oxide hydrate with a surface treatment agent, the amount of the surface treatment agent used is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and 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, relative to 100 parts by mass of the metal oxide hydrate.

[0029] The resin contained in the resin composition (nanocomposite) constituting the insulating coating 2 is preferably a heat-resistant resin. That is, since the insulating coating 2 is formed by applying and baking an insulating coating (a resin composition containing a metal oxide hydrate) used to form the insulating coating 2, excellent heat resistance is required. The heat-resistant resin may be any resin with excellent heat resistance, and resins used in known insulated wires may be used. Examples of heat-resistant resins include formal resins, polyurethanes, epoxy resins, polyesters, polyamides, polyesterimides, polyetherimides, polyamideimides, polyimides, and precursors thereof. Among these, polyesterimides, polyamideimides, polyimides, and precursors thereof are preferred from the viewpoint of further improving heat resistance, and polyimides and polyimide precursors are more preferred. The insulating coating 2 may contain one type of resin or two or more types of resins.

[0030] Furthermore, in the resin composition constituting the insulating coating 2, the lower limit of the resin content is preferably 50% by mass or more, more preferably 60% by mass or more, 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.

[0031] Furthermore, in the resin composition constituting the insulating coating 2, the lower limit of the content of metal oxide hydrate is preferably 3 mass% or more, more preferably 10 mass% or more, and even more preferably 12 mass% or more, and the upper limit is preferably 50 mass% or less, and more preferably 40 mass% or less.

[0032] Furthermore, in the resin composition constituting the insulating coating 2, the ratio (mass ratio) of the resin to the metal oxide hydrate is preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, even more preferably 3 to 25 parts by mass, and still more preferably 15 to 25 parts by mass of the metal oxide hydrate per 100 parts by mass of the total of the resin and the metal oxide hydrate.

[0033] To more effectively exert the effects of the present invention, the thickness of the insulating coating 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 coating 2 is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0034] When preparing the insulating coating material described below that forms the insulating coating 2, the resin and metal oxide hydrate may each be used in a form dissolved or dispersed in a solvent (such as a resin varnish).

[0035] When preparing the insulating coating 2 described below, it is preferable to prepare an insulating coating in which a resin is dissolved or dispersed and a metal oxide hydrate is dispersed in a solvent, and then apply and bake the insulating coating 2. Suitable solvents for dissolving or dispersing the resin and dispersing the metal oxide hydrate include 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, among others. Examples of manufacturing methods for preparing the insulating coating include methods using commonly known mixing means such as a kneader, pressure kneader, kneading roll, Banbury mixer, twin-screw extruder, planetary mixer, and homomixer. The mixing temperature is typically 5 to 30°C.

[0036] The insulating paint may contain an acid or alkali component to stabilize dispersion. Similarly, it may contain water, low-boiling alcohol, or a low-viscosity solvent that contributes to reducing the viscosity of the insulating paint. If necessary, other metal oxide hydrates or metal oxides may be mixed into the insulating paint, and additives may be added to impart hydrophobicity or improve dispersibility. Suitable additives include fluorine-based and silicon-based additives, citric acid, ethylenediaminetetraacetic acid, and 8-quinolinol.

[0037] As described above, the laminate 10 according to an embodiment of the present invention may be composed of only the conductor 1 and the insulating coating 2, or may further include other layers such as insulating layer 3 and insulating layer 4. Examples of such other layers include an organic insulating layer. The organic insulating layer is preferably composed of the heat-resistant resin described above. Specifically, specific examples of heat-resistant resins used in the organic insulating layer include formal resins, polyurethanes, epoxy resins, polyesters, polyamides, polyesterimides, polyetherimides, polyamideimides, polyimides, and precursors thereof. Among these, polyesterimides, polyamideimides, polyimides, and precursors thereof are preferred for enhanced heat resistance. The heat-resistant resin contained in the organic insulating layer may be one type or two or more types. A metal layer, such as a plating layer, may be formed on the conductor 1.

[0038] The total thickness of the insulating layers of the laminate 10 according to the embodiment of the present invention 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 suitably exhibiting the effects of the present invention. The upper limit of the thickness of the organic insulating layer is preferably 200 μm or less.

[0039] When a laminate according to an embodiment of the present invention is exposed to partial discharge caused by an inverter surge, an inorganic insulating layer is formed in part of the insulating coating 2. Patent Document 1 also discloses that a thin inorganic insulating layer having a thickness of 100 nm to 5 μm is formed by partial discharge, which contributes to the extension of the voltage-applied life. In the present invention, an inorganic insulating layer is formed even when moisture is absorbed in a high-humidity environment. This is thought to contribute to the extension of the voltage-applied life even when moisture is absorbed. This inorganic insulating layer is formed, for example, when the frequency is 1 kHz to 100 kHz and the voltage is 600 V to 3 kV.

[0040] The laminate 10 according to the embodiment of the present invention can be manufactured by laminating layers constituting the insulating coating 2 on the conductor 1. For example, it can be manufactured by applying a resin composition that forms the insulating coating 2 onto the conductor 1 and baking it. Alternatively, an insulated wire can be manufactured by wrapping an insulating film formed from the resin composition that forms the insulating coating 2 around the conductor 1. The insulating film can be formed, for example, by molding and baking the resin composition (insulating paint) that forms the insulating coating 2 using a film coater or the like. The difference between these methods of manufacturing an insulated wire is whether the insulating coating 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 an insulating coating 2 in the form of a film.

[0041] The insulating coating can be applied by any method, including but not limited to, coating with a coater, applying and drying repeatedly using a dip coater or die to obtain a coating of a predetermined thickness, or spraying. Baking can be performed, for example, by heating at a high temperature (e.g., 300°C or higher) for a predetermined period of time. The insulating coating 2 can also be formed by repeating a series of application and heating steps multiple times until the insulating coating 2 reaches a predetermined thickness. The baking temperature and time for forming the insulating coating 2 are set depending on the type of metal oxide hydrate, so that the metal oxide hydrate is not transformed into another metal oxide hydrate or metal oxide due to heat.

[0042] For example, when the laminate 10 according to the embodiment of the present invention is in the form of an insulated wire, the insulated wire can be manufactured by applying and baking an insulating varnish to the surface of the wire-shaped conductor 1. The insulating coating 2 can be formed by applying the insulating varnish to the conductor 1 to a predetermined thickness and then heating it at a high temperature (e.g., 300 to 500°C) for a predetermined time (e.g., 1 to 2 minutes), repeating this series of operations (application and heating) multiple times (e.g., 10 to 20 times) until the insulating coating 2 reaches the predetermined thickness.

[0043] The coil according to the embodiment of the present invention can be formed by winding the insulated wire around a core. Furthermore, the rotating electric machine according to the embodiment of the present invention is a motor or the like that uses the coil according to the embodiment of the present invention. That is, the rotating electric machine according to the embodiment of the present invention may be a rotating electric machine that uses the insulated electric wire according to the embodiment of the present invention, or may be a rotating electric machine that is formed using the conductor 1 and then an insulating coating 2 is formed on the surface of the conductor 1 to form the insulated electric wire.

[0044] Examples of rotating electrical machines include motors and generators.

[0045] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0046] The resins (polyimide coating materials) used in the examples and comparative examples are as follows:

[0047] [Resin (Polyimide Paint)] Pyre-ML RC5019 manufactured by IST Corporation was used.

[0048] [Insulating paint containing metal oxide hydrate] Insulating paints having the compositions shown in Table 1 were prepared according to the procedures shown in the following Production Examples 1-4.

[0049] <Production Example 1> NMP-dispersed phosphoric acid-based surface-treated boehmite sol [product name: Alumina Sol A2M7 (containing 7 mass% of boehmite), average particle size: 15 to 50 nm, aspect ratio (long side / thickness): 10 to 50, manufactured by Kawaken Fine Chemicals Co., Ltd.] was uniformly dispersed in a polyimide paint with 85 mass parts of the resin content by stirring at room temperature for 5 minutes using a homomixer so that the boehmite was 15 mass parts in terms of alumina, thereby obtaining insulating paint 1.

[0050] <Production Example 2> Insulating coating material 2 was obtained in the same manner as in Production Example 1, except that the resin content was 87 parts by mass and the boehmite was used in an amount equivalent to 13 parts by mass in terms of alumina.

[0051] <Production Example 3> Insulating coating material 3 was obtained in the same manner as in Production Example 1, except that in Production Example 1, a boehmite sol surface-treated with an NMP dispersion methacrylic silane coupling agent [product name: Alumina Sol 5SK-5-10 (containing 10 mass% of boehmite), average particle size: 20 nm, aspect ratio (long side / thickness): 4 to 20, manufactured by Kawaken Fine Chemicals Co., Ltd.] was used in place of alumina sol A2M7, so that the amount of boehmite was 5 parts by mass in terms of alumina.

[0052] Production Example 4 To an NMP-dispersed boehmite sol [product name: Alumina Sol A1-10 (containing 10% by mass of boehmite), average particle size: 15 to 50 nm, aspect ratio (long side / thickness): 10 to 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 to 47.0%, diester content 53.0 to 67.0%)] relative to 100 parts by mass (equivalent to alumina) of boehmite and 24 parts by mass of 8-quinolinol (manufactured by Tokyo Chemical Industry Co., Ltd.) relative to 100 parts by mass (equivalent to alumina) of boehmite were added, 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, the phosphate ethyl ester surface-treated boehmite sol was uniformly mixed and dispersed at room temperature using an in-line homomixer into the polyimide paint so that the boehmite content was 15 parts by mass, calculated as alumina, per 85 parts by mass of the resin content, thereby obtaining insulating paint 4.

[0053] Production Example 5 Insulating coating material 5 was obtained in the same manner as in Production Example 4, except that 6 parts by mass of ethyl phosphate was replaced with 10 parts by mass of phenylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0054] Production Example 6 Insulating paint 6 was obtained in the same manner as in Production Example 5, except that the amount of phenylphosphonic acid was changed from 10 parts by mass to 30 parts by mass.

[0055] Production Example 7 Insulating paint 7 was obtained in the same manner as in Production Example 5, except that the amount of phenylphosphonic acid was changed from 10 parts by mass to 40 parts by mass.

[0056] [Measurement of Zeta Potential of Metal Oxide Hydrate] The zeta potential of the surface-treated boehmite used to prepare the insulating coatings obtained in Production Examples 1 to 7 was measured using the following method. The surface-treated boehmite was dispersed in NMP as a sol and diluted with N-methyl-2-pyrrolidone to a concentration of 0.1% by mass. When the boehmite was in powder form, the powder was added to N-methyl-2-pyrrolidone and dispersed using a Starburst wet jet mill manufactured by Sugino Machine Co., Ltd. to form a sol, and the concentration was adjusted to 0.1% by mass. The prepared sample was then placed in a thermostatic bath at 5°C and kept warm for 1 hour. Approximately 1 g of the sample was then filled into a zeta dip cell for measurement, and measurements were performed. A Zeta Nanosizer ZS manufactured by Malvern Instruments was used as the measurement device. The measurement conditions are shown below. The zeta potential of each boehmite is shown in Table 1. Sample: boehmite, refractive index 1.65, absorptivity 0.008 Dispersion medium: N-methyl-2-pyrrolidone, viscosity 1.89, refractive index 1.470, dielectric constant 32.0 Equilibration time: 120 seconds F (Ka): 1.5

[0057] [Preparation of Insulating Film] (Example 1) The insulating coating material 1 prepared in Preparation Example 1 was applied to a rectangular, 100 μm-thick PET film using a blade coater with a 600 μm-deep groove. The PET film was held horizontally and dried in a forced-air oven under the following temperature conditions: 70°C for 15 minutes, 90°C for 45 minutes, and 130°C for 10 minutes, forming a film on the PET film. After peeling the 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, yielding an insulating film. The resulting insulating film had a thickness of 55 μm.

[0058] Example 2 An insulating film was obtained in the same manner as in Example 1, except that the insulating paint 1 was replaced with the insulating paint 2. The thickness of the obtained insulating film was 56 μm.

[0059] (Example 3) An insulating film was obtained in the same manner as in Example 1, except that the insulating paint 1 was replaced with the insulating paint 3 and the groove depth was changed to 300 μm. The thickness of the obtained insulating film was 26 μm.

[0060] Comparative Example 1 An insulating film was obtained in the same manner as in Example 1, except that the insulating paint 1 was replaced with the insulating paint 4. The thickness of the obtained insulating film was 49 μm.

[0061] [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 2.

[0062] <Measurement of Breakdown Voltage in Dry State and Breakdown Voltage in Moisture Absorbed State> (Measurement of Breakdown Voltage in Dry State) The insulating films produced in Examples 1 to 3 and Comparative Example 1 were each cut into a rectangular shape of 18 cm x 26 cm, dried in a thermostatic chamber at 120°C for 60 minutes, and then placed in a breakdown voltage measuring device, where a voltage was applied to measure the breakdown voltage. The measuring device used was a breakdown voltage tester (No. 175, manufactured by Yasuda Seiki Seisakusho), and a voltage was applied while increasing at 0.5 V / s, and the voltage at which breakdown occurred was taken as the breakdown voltage. This test was performed five times, and the average of the five measurements was taken as the test result.

[0063] (Evaluation of Breakdown Voltage Upon Moisture Absorption) The insulating films prepared in Examples 1 to 3 and Comparative Example 1 were each cut into a rectangular shape measuring 18 cm x 26 cm and stored in a thermostatic chamber at 30°C and a relative humidity of >95% for 3 days to allow moisture absorption. The samples after moisture absorption were then removed and placed in a breakdown voltage measuring device, where a voltage was applied to measure the breakdown voltage. A breakdown voltage tester (No. 175, manufactured by Yasuda Seiki Seisakusho) was used as the measuring device, and a voltage was applied while increasing at a rate of 0.5 V / s. The voltage at which breakdown occurred was taken as the breakdown voltage. This test was performed five times, and the average of the five measurements was used as the test result. Measurement was started within three minutes of removing the sample from the thermostatic chamber to prevent it from drying out.

[0064] [Production of Insulated Wires] Insulated wires (laminates) were produced according to the procedures shown in the following Examples 4 to 8 and Comparative Example 2. The insulating coatings (paints used) used for each insulated wire are shown in Table 3.

[0065] (Example 4) Insulating varnish 1 was applied to a copper conductor (a copper wire with a diameter of approximately 1 mm (the conductor diameter is shown in Table 3)) and baked for approximately 1 minute while the temperature was continuously raised from 350°C at the inlet to 430°C at the outlet. This process was repeated 20 times to form an insulating layer with a thickness of 40 μm on the surface of the copper conductor, thereby producing an insulated wire using insulating varnish 1 containing boehmite. The thickness of the insulating layer was 40 μm.

[0066] Example 5 An insulated wire was produced in the same manner as in Example 4, except that the insulating varnish 1 was replaced with the insulating varnish 2. The thickness of the insulating layer was 39 μm.

[0067] Example 6 An insulated wire was produced in the same manner as in Example 4, except that the insulating paint 1 was replaced with the insulating paint 5. The thickness of the insulating layer was 37 μm.

[0068] Example 7 An insulated wire was produced in the same manner as in Example 4, except that the insulating paint 1 was replaced with the insulating paint 6. The thickness of the insulating layer was 37 μm.

[0069] Example 8 An insulated wire was produced in the same manner as in Example 4, except that the insulating paint 1 was replaced with the insulating paint 7. The thickness of the insulating layer was 38 μm.

[0070] Comparative Example 2 An insulated wire was produced in the same manner as in Example 4, except that the insulating varnish 1 was replaced with the insulating varnish 4. The thickness of the insulating layer was 38 μm.

[0071] [Evaluation of Insulated Wire Properties] The insulated wires obtained in the examples and comparative examples were evaluated for the following properties. The results are shown in Table 3.

[0072] <Flexibility Evaluation> The flexibility of the insulated wire was tested in accordance with the JIS C3216-5-1 winding test.

[0073] <Measurement of V-t characteristic test> The manufactured insulated wires were subjected to a V-t characteristic test by the following method. The measurement results are shown in Table 3.

[0074] (Dry Vt Characteristics Test) A twisted pair sample was prepared using each insulated wire in accordance with JIS C 3216, and a voltage was applied between the two wires. The measurement environment was controlled at a temperature of 40°C, with dry air introduced into the sample measurement thermostatic chamber and a relative humidity of 30% or less. The measurement was performed using an inverter pulse generator PG-W03KP-A manufactured by Nissin Pulse Electronics Co., Ltd., and the time until the twisted pair sample experienced dielectric breakdown was measured under the following conditions: Measurement conditions: Bipolar square wave with a voltage of 2.5 kVp, a pulse width of 5 μs, and a frequency of 10 kHz.

[0075] (High humidity (50% RH) V-t characteristic test) A twisted pair sample was prepared using each insulated wire in accordance with JIS C 3216, and a voltage was applied between the two wires. The measurement environment was a temperature of 25°C, and air with a relative humidity controlled to 50% was introduced into the sample measurement chamber, so that the relative humidity in the chamber was always controlled at 50%. The measurement was performed using an inverter pulse generator PG-W03KP-A manufactured by Nissin Pulse Electronics Co., Ltd., and the time until the twisted pair sample experienced dielectric breakdown was measured under the following conditions. Measurement conditions: Bipolar square wave with a voltage of 2.5 kVp, a pulse width of 5 μs, and a frequency of 10 kHz.

[0076] (High humidity (70% RH) V-t characteristic test) A twisted pair sample was prepared using each insulated wire in accordance with JIS C 3216, and a voltage was applied between the two wires. The measurement environment was a temperature of 25°C, and air with a relative humidity of 70% was introduced into the sample measurement chamber, so that the relative humidity in the chamber was always controlled at 70%. The measurement was performed using an inverter pulse generator PG-W03KP-A manufactured by Nissin Pulse Electronics Co., Ltd., and the time until the twisted pair sample experienced dielectric breakdown was measured under the following conditions. Measurement conditions: Bipolar square wave with a voltage of 2.5 kVp, a pulse width of 5 μs, and a frequency of 10 kHz.

[0077] (High-Temperature Vt Characteristics Test) A twisted pair sample was prepared using each insulated wire in accordance with JIS C 3216, and a voltage was applied between the two wires. The measurement was performed in a temperature-controlled environment at 240°C. The measurement was performed using an inverter pulse generator PG-W03KP-A manufactured by Nissin Pulse Electronics Co., Ltd., and the time until the twisted pair sample experienced dielectric breakdown was measured under the following conditions: Measurement conditions: Bipolar square wave with a voltage of 1.5 kVp, a pulse width of 5 μs, and a frequency of 10 kHz.

[0078] <Measurement of Breakdown Voltage in Dry State and Breakdown Voltage in Moisture Absorbed State> The breakdown voltage in dry state and breakdown voltage in moisture absorbed state of the manufactured insulated wires were measured by the following method. The measurement results are shown in Table 3.

[0079] (Measurement of Breakdown Voltage After Drying) Twisted pair samples were prepared using each insulated wire in accordance with JIS C 3216 and dried in a thermostatic chamber at 125°C for 30 minutes. Two wires of the twisted pair were then connected to a measuring device, and a voltage was applied between the two wires to measure the breakdown voltage. A breakdown voltage tester (No. 175, manufactured by Yasuda Seiki Seisakusho) was used as the measuring device. A voltage was applied between the two wires while increasing at 0.5 v / s, and the voltage at which breakdown occurred was recorded as the breakdown voltage. This test was performed five times, and the average of the five measurements was recorded as the test result.

[0080] (Evaluation of Breakdown Voltage Upon Moisture Absorption) Twisted pair samples were prepared using each insulated wire according to JIS C 3216 and stored in a thermostatic chamber at 40°C and 95% relative humidity for three days to absorb moisture. Next, the sample after moisture absorption was removed, and two wires of the twisted pair were connected to a measuring device. A voltage was applied between the two wires to measure the breakdown voltage. A breakdown voltage tester (No. 175, manufactured by Yasuda Seiki Seisakusho) was used as the measuring device. A voltage was applied between the two wires while increasing at a rate of 0.5 V / s, and the voltage at which the sample broke down was recorded as the breakdown voltage. Measurement was started within three minutes of removing the sample from the thermostatic chamber to prevent it from drying out. This test was performed five times, and the average of the five measurements was recorded as the test result.

[0081]

[0082]

[0083]

[0084] 10 laminate 1 conductor 2 insulating coating 3 insulating layer 4 insulating layer

Claims

1. A laminate comprising at least a conductor and an insulating coating, wherein the insulating coating is made of a nanocomposite made of a resin composition in which a metal oxide hydrate is dispersed in a resin, and wherein the metal oxide hydrate has a negative zeta potential when dispersed in N-methyl-2-pyrrolidone (NMP).

2. The laminate according to claim 1, wherein the metal oxide hydrate comprises alumina hydrate.

3. The laminate according to claim 1 or 2, wherein the nanocomposite is one in which the metal oxide hydrate is dispersed in a sol state.

4. The laminate according to claim 1 or 2, wherein the resin contained in the nanocomposite is at least one selected from the group consisting of formal resins, polyurethanes, epoxy resins, polyesters, polyesterimides, polyetherimides, polyamideimides, polyimides, and precursors thereof.

5. The laminate according to claim 1 or 2, wherein the resin contained in the nanocomposite is at least one selected from the group consisting of polyimides and polyimide precursors.

6. The laminate according to claim 1 or 2, which is in the form of an insulated wire.

7. A coil comprising the laminate of claim 6.

8. A rotating electric machine comprising the laminate according to claim 6.

9. An insulating resin composition for forming the insulating coating of the laminate according to claim 1 or 2.

10. An insulating paint for forming the insulating coating of the laminate according to claim 1 or 2.

11. An insulating film formed from the nanocomposite of claim 1 or 2.