Insulating paint and insulated wire

Abstract

To provide an insulating paint capable of forming an insulating coating composed of a polyimide resin with reduced dielectric constant without a reduction in adhesiveness, and an insulated wire with an insulating coating formed from the insulating paint.SOLUTION: A insulating paint A comprises a diamine B and an acid dianhydride C. In the diamine B, the proportion of diamine with a side chain containing a benzene ring is 50 mol% or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an insulated wire having an insulating coating made of a polyamic acid coating and an insulating coating made of a polyimide resin. [Background technology]

[0002] Conventionally, a winding wire having an insulating coating made of polyimide is known (see Patent Document 1). In general, a winding wire having an insulating coating made of polyimide has excellent heat resistance.

[0003] The winding of Patent Document 1 uses a polyimide having a fluorine group as the material for the insulating coating, thereby reducing the dielectric constant of the insulating coating. According to Patent Document 1, the winding described in Patent Document 1 has a smaller dielectric constant of the insulating coating than ordinary windings, and therefore exhibits excellent resistance to deterioration when high-frequency voltage is applied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-44827 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the winding of Patent Document 1 has a problem in that the insulating coating easily peels off from the conductor. This is because the fluorine-substituted monomer contained in the polyimide, which is the material of the insulating coating of Patent Document 1, reduces the adhesion of the polyimide.

[0006] An object of the present invention is to provide an insulating varnish capable of forming an insulating coating made of a polyimide resin having a reduced dielectric constant without reducing adhesion, and an insulated wire provided with an insulating coating formed from the insulating varnish. [Means for solving the problem]

[0007] The present invention aims to solve the above-mentioned problems by providing an insulating coating material comprising a diamine and an acid dianhydride, in which the proportion of diamines having a side chain containing a benzene ring in the diamine is 50 mol % or more.

[0008] Furthermore, in order to solve the above-mentioned problems, the present invention provides an insulated wire comprising an insulating coating made of a polyimide resin containing a diamine and an acid dianhydride, in which the diamine contains a diamine having a side chain containing a benzene ring in a proportion of 50 mol % or more. Effect of the Invention

[0009] According to the present invention, it is possible to provide an insulating varnish capable of forming an insulating coating made of a polyimide resin having a reduced dielectric constant without reducing adhesion, and an insulated wire provided with an insulating coating formed from the insulating varnish. [Brief description of the drawings]

[0010] [Figure 1] 1(a) and (b) are examples of the structural formulas of polyimide molecular chains containing diamine and acid dianhydride, respectively. [Diagram 2] Figures 2(a), (b), and (c) are schematic diagrams showing the state of multiple polyimide molecular chains contained in a polyimide resin formed using a polyamic acid paint containing a diamine and an acid dianhydride, such as insulating paint A, as a precursor. [Diagram 3] 3(a) and 3(b) are cross-sectional views in a radial direction of an insulated wire which is an example of an insulated wire according to a second embodiment of the present invention. [Figure 4] Fig. 4(a) is a perspective view of a motor device including a motor winding made of an insulated wire according to a second embodiment of the present invention, and Fig. 4(b) is a side view of the motor device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First Embodiment The insulating paint according to the first embodiment of the present invention is a polyamic acid paint containing a diamine and an acid dianhydride, in which the ratio of the diamine having a side chain containing a benzene ring in the diamine is 50 mol % or more. Hereinafter, the insulating paint according to the first embodiment of the present invention will be referred to as insulating paint A, and the diamine and acid dianhydride contained in insulating paint A will be referred to as diamine B and acid dianhydride C, respectively.

[0012] Insulating paint A is obtained by dissolving diamine B and acid dianhydride C in a solvent such as NMP (N-methyl-2-pyrrolidone), DMAc (N,N-dimethylacetamide), DMF (N,N-dimethylformamide), cyclohexanone, or a mixture thereof. Insulating paint A can be used as a precursor for the insulating coating of an insulated electric wire such as an enameled wire.

[0013] Insulating coating material A, diamine B and acid dianhydride C are contained in equimolar amounts (molar ratio of 100:100). Alternatively, in order to adjust the molecular weight, the content of either diamine B or acid dianhydride C may be increased or decreased by about several mol %. In addition, insulating coating material A may contain additives such as foaming agents, defoamers, leveling agents, antioxidants, fillers, polymer powders, and microparticles including hollow microparticles, in addition to diamine B and acid dianhydride C, to the extent that the properties of the polyimide are not impaired.

[0014] As described above, diamine B is composed of a diamine having a side chain containing 50 mol % or more of a benzene ring and the other diamine having no side chain containing a benzene ring. The diamine having a side chain containing a benzene ring contained in diamine B is, for example, PDPE (2-phenyl-4,4'-diaminophenyl diphenyl ether).

[0015] Diamine B may contain a diamine having a side chain containing a plurality of kinds of benzene rings. That is, the diamine having a side chain containing a benzene ring contained in diamine B contains, for example, at least PDPE.

[0016] Examples of diamines that do not have a side chain containing a benzene ring, which are included in diamine B, include ODA (4,4'-diaminodiphenyl ether), BAPP (2,2-bis[4-(4-aminophenoxy)phenyl]propane), BAPE (bis[4-(4-aminophenoxy)phenyl]ether), and BAPB (4,4'-bis(4-aminophenoxy)biphenyl).

[0017] Diamine B may contain multiple types of diamines that do not have a side chain containing a benzene ring. That is, the diamines that do not have a side chain containing a benzene ring contained in diamine B include, for example, at least one of ODA, BAPP, BAPE, and BAPB.

[0018] The acid dianhydride C is, for example, PMDA (pyromellitic dianhydride) or BPDA (3,3'4,4'-biphenyltetracarboxylic dianhydride).

[0019] Acid dianhydride C may contain a plurality of types of acid dianhydrides, i.e., acid dianhydride C contains at least one of PMDA and BPDA, for example.

[0020] Figures 1(a) and (b) are examples of the structural formulas of polyimide molecular chains containing diamines and acid dianhydrides, respectively. The polyimide molecular chain shown in Figure 1(a) contains ODA, which does not have a side chain containing a benzene ring, as the diamine component, and PMDA as the acid dianhydride component. The polyimide molecular chain shown in Figure 1(b) contains PDPE, which has a side chain containing a benzene ring, as the diamine component, and PMDA as the acid dianhydride component.

[0021] That is, the polyimide molecular chain shown in Fig. 1(b) is an example of a polyimide molecular chain contained in insulating varnish A according to an embodiment of the present invention, and the polyimide molecular chain shown in Fig. 1(a) is an example of a polyimide molecular chain as a comparative example in which a side chain containing a benzene ring is not contained in the diamine component. The part surrounded by the dotted line in the polyimide molecular chain shown in Fig. 1(b) is the side chain containing a benzene ring.

[0022] 2(a), (b), and (c) are schematic diagrams showing the state of multiple polyimide molecular chains 30 contained in a polyimide resin formed using a polyamic acid coating material containing a diamine and an acid dianhydride as a precursor. In each polyimide molecular chain 30, a diamine component 31 (31a or 31b) and an acid dianhydride component 32 are arranged alternately.

[0023] The diamine component 31 in the polyimide molecular chain 30 shown in Fig. 2(a) is a diamine component 31a that does not include a side chain containing a benzene ring, and the diamine component 31 in the polyimide molecular chain 30 shown in Fig. 2(b) is a diamine component 31b that includes a side chain 310 containing a benzene ring.

[0024] 2(b), the side chain 310 containing a benzene ring contained in the diamine component 31b expands the distance d between adjacent polyimide molecular chains 30. This increases the space between adjacent polyimide molecular chains 30, i.e., increases the free volume of the polyimide molecular chains 30, and reduces the relative dielectric constant of the polyimide resin formed using insulating paint A as a precursor.

[0025] 2(c) includes both diamine component 31a that does not include a side chain containing a benzene ring and diamine component 31b that includes side chain 310 containing a benzene ring as diamine component 31. As shown in FIG. 2(c), even when a part of diamine component 31 is diamine component 31b that includes side chain 310 containing a benzene ring, the distance d between adjacent polyimide molecular chains 30 can be increased.

[0026] When the ratio of the diamine component 31b to the entire diamine component 31 of the plurality of polyimide molecular chains 30 contained in the polyimide resin is 50 mol % or more, the relative dielectric constant of the polyimide resin is effectively reduced.

[0027] In addition, when the proportion of diamine B having a side chain containing a benzene ring in the diamine B contained in the insulating paint A is 50 mol % or more, the polyimide resin formed using the insulating paint A as a precursor will have a proportion of diamine B having a side chain containing a benzene ring in the diamine B contained therein of 50 mol % or more.

[0028] Table 1 below shows the measured values ​​of the structures of diamine B and dianhydride C and the relative dielectric constant of eight types of polyimide resins (samples I to VIII) that have different structures of diamine B and dianhydride C. In Table 1, "PDPE" and "ODA" respectively indicate the proportions (mol%) of PDPE and ODA in diamine B, and "BPDA" and "PMDA" respectively indicate the proportions (mol%) of BPDA and PMDA in dianhydride C.

[0029] [Table 1]

[0030] Table 1 shows that the dielectric constant is relatively small in samples I, II, III, V, VI, VII, and VIII, in which the ratio of PDPE in diamine B is 50% or more. This is believed to be due to the fact that the free volume of the polyimide molecular chain is increased by the side chains containing the benzene rings contained in the PDPE.

[0031] Furthermore, comparing samples I, II, and III, it can be seen that the relative dielectric constant of the polyimide resin is particularly small when only PMDA is used as acid dianhydride C. For this reason, in terms of the relative dielectric constant, it is preferable to use only PMDA as acid dianhydride C, but the ratio of the materials that make up acid dianhydride C may be adjusted taking into account the mechanical properties, etc.

[0032] (Effects of the First Embodiment) According to the first embodiment of the present invention, since the ratio of diamines having a side chain containing a benzene ring in diamine B is 50 mol % or more, it is possible to provide insulating coating material A that can be used as a precursor of a polyimide resin having a low dielectric constant.

[0033] In addition, since the insulating coating material A does not contain a fluorine-substituted monomer, it does not reduce the adhesion of the polyimide resin as in the above-mentioned Patent Document 1, and for example, it is possible to suppress peeling of the insulating coating made of the polyimide resin contained in the insulated wire from the conductor, etc. In addition, since the insulating coating material A does not contain an aliphatic group-containing monomer and is capable of lowering the dielectric constant, it does not reduce the heat resistance of the polyimide resin, and for example, it is possible to suppress embrittlement of the insulating coating made of the polyimide resin contained in the insulated wire at the operating temperature.

[0034] Second Embodiment The second embodiment of the present invention relates to an insulated wire provided with an insulating coating made of polyimide resin formed using the insulating varnish A according to the first embodiment.

[0035] 3(a) and 3(b) are radial cross-sectional views of insulated electric wires 1 and 2, which are examples of the insulated electric wire according to the second embodiment of the present invention. The insulated electric wire 1 shown in Fig. 3(a) is an insulated electric wire having a rectangular cross-sectional shape in which an insulating coating 11 is formed around a rectangular wire-shaped conductor 10 made of copper or the like. The insulated electric wire 2 shown in Fig. 3(b) is an insulated electric wire having a circular cross-sectional shape in which an insulating coating 21 is formed around a round wire-shaped conductor 20 made of copper or the like.

[0036] The insulating coating 11 of the insulated wire 1 and the insulating coating 21 of the insulated wire 2 are both insulating coatings formed using the insulating varnish A according to the first embodiment of the present invention as a precursor, and are formed by applying the insulating varnish A to the surfaces of the conductors 10 and 20, respectively. Specifically, for example, the insulating coatings 11 and 21 made of polyimide resin can be obtained by repeating a process multiple times in which the insulating varnish A is applied to the surfaces of the conductors 10 and 20 and then baked and cured in a drying oven.

[0037] The insulating coatings 11, 12 formed using insulating paint A as a precursor are made of a polyimide resin containing diamine B and acid dianhydride C contained in insulating paint A, with the proportion of diamines in diamine B having a side chain containing a benzene ring being 50 mol % or more. Therefore, the free volume of the polyimide molecular chains contained in the insulating coatings 11, 12 is large, and the insulating coatings 11, 12 have a low dielectric constant. And because the insulating coatings 11, 12 have a low dielectric constant, the insulated wires 1, 2 have a high partial discharge inception voltage.

[0038] The diamine B and acid dianhydride C contained in the polyimide resin constituting the insulating coatings 11, 12 are the same as the diamine B and acid dianhydride C contained in the above-mentioned insulating coating A. That is, the diamine B contained in the polyimide resin constituting the insulating coatings 11, 12 includes, as a diamine having a side chain containing a benzene ring, for example, PDPE, and includes, as a diamine not having a side chain containing a benzene ring, for example, at least one of ODA, BAPP, BAPE, and BAPB.

[0039] Furthermore, the acid dianhydride C contained in the polyimide resin constituting insulating coatings 11, 12 includes, for example, at least one of PMDA and BPDA. In order to further reduce the relative dielectric constant of insulating coatings 11, 12, it is preferable to use only PMDA as the acid dianhydride C contained in the polyimide resin constituting insulating coatings 11, 12; however, the ratio of materials constituting acid dianhydride C may be adjusted in consideration of mechanical properties, etc.

[0040] In order to further reduce the dielectric constant, the insulating coatings 11, 12 may include pores dispersed therein. When providing pores in the insulating coatings 11, 12, for example, a foaming agent such as tetraglyme, thermally expandable microcapsules, hollow fillers, or the like is added to the insulating coating A, and the insulating coatings 11, 12 are formed using the insulating coating A as a precursor.

[0041] As described above, the insulated wires 1 and 2 are each an example of an insulated wire according to the second embodiment of the present invention, and the insulated wire according to the second embodiment of the present invention may include a conductor and an insulating coating made of the same polyimide resin as the insulating coatings 11 and 12 provided around the conductor. Here, the insulating coating may be provided directly on the surface of the conductor, or may be provided via another film. An adhesive layer may be provided between the conductor and the insulating coating A to improve adhesion with the conductor, and a slipping layer may be provided on the top layer to improve the slipperiness of the insulated wire.

[0042] Insulated electric wires such as the insulated electric wires 1 and 2 according to the second embodiment of the present invention, which have a high partial discharge inception voltage, can be suitably used as motor windings of electric motors built into, for example, xEVs (electric vehicles), railways, and various industrial equipment. Hereinafter, a specific description will be given of a case where the insulated electric wires 1 and 2 are used as motor windings of a motor device as an example of use of the insulated electric wires 1 and 2.

[0043] Fig. 4(a) is a perspective view of a motor device 51 including a motor winding 53 made of an insulated wire 1. Fig. 4(b) is a side view of the motor device 51. Fig. 4(b) shows a cross section of the inside of the motor main body inside the fractured area surrounded by the fractured line.

[0044] This motor device 51 is configured to include a motor 52 and a plurality of connection members 55 that connect between a motor winding 53 of the motor 52 and a terminal block 54. As shown in Fig. 4(b), the motor 52 has a cylindrical motor case 60 with a bottom, an annular stator core 61 housed in the motor case 60, a rotor 62 arranged inside the stator core 61, a motor shaft 63 that penetrates the center of the rotor 62 and is supported so as to be rotatable integrally with the rotor 62, and a cover member 64 made of molded resin that covers the opening of the motor case 60.

[0045] The motor device 51 is used, for example, as a drive source for driving a vehicle, and is supported by a support portion of a vehicle body (not shown). A wire harness (not shown) having one end connected to an inverter is connected to the terminal block 54, and the other end of the wire harness is electrically connected to a connection member 55 at the terminal block 54. A motor current output from the inverter is supplied to the motor 52 via the wire harness and the connection member 55. The terminal block 54 is fixed to a terminal block fixing portion of the vehicle body (not shown).

[0046] The stator core 61 is made of a magnetic material such as steel. The stator core 61 is provided with a plurality of teeth 611 that protrude inward toward the rotor 62, and the motor winding 53 is wound around each of the plurality of teeth 611. In the example shown in Figures 4(a) and (b), the motor winding 53 uses an insulated electric wire 1 having a rectangular cross-sectional shape, but an insulated electric wire 2 having a circular cross-sectional shape may also be used. A part of the motor winding 53 is exposed to the outside of the motor case 60 from the cover member 64 and is molded into the cover member 64.

[0047] The rotor 62 has a cylindrical rotor core 621 with a through hole for inserting the motor shaft 63 therethrough, and a magnet 622 arranged on the outer periphery of the rotor core 621. The magnet 622 is provided with a plurality of magnetic poles such that S poles and N poles are positioned alternately. The motor shaft 63 is rotatably supported by the motor case 60 via a bearing (not shown).

[0048] 4(a) and (b), motor 52 is a three-phase AC motor, and motor winding 53 is made up of a U-phase winding, a V-phase winding, and a W-phase winding. The U-phase winding, the V-phase winding, and the W-phase winding are each connected to a neutral point at their center. Ends of the U-phase winding, the V-phase winding, and the W-phase winding are exposed from cover member 64, and are each connected to connecting member 55 by welding.

[0049] (Advantages of the second embodiment) The insulating coating of the insulated wires such as the insulated wires 1 and 2 according to the second embodiment of the present invention is made of polyimide resin formed using the insulating varnish A according to the first embodiment, and therefore has a low dielectric constant. Therefore, the insulated wire according to the second embodiment of the present invention has a high partial discharge inception voltage and can be suitably used in electric motors and the like.

[0050] (Summary of the embodiment) Next, the technical ideas understood from the above-described embodiment will be described by using the reference numerals and the like in the embodiment. However, the following description does not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0051] [1] An insulating coating material (A) comprising a diamine (B) and an acid dianhydride (C), wherein the proportion of diamines having a side chain containing a benzene ring in the diamine (B) is 50 mol % or more.

[0052] [2] The insulating coating material (A) according to the above [1], wherein the diamine having a side chain containing a benzene ring includes PDPE (2-phenyl-4,4'-diaminophenyl diphenyl ether).

[0053] [3] An insulated wire (1, 2) comprising an insulating coating (11, 21) made of a polyimide resin containing a diamine (B) and an acid dianhydride (C), wherein the proportion of diamines having a side chain containing a benzene ring in the diamine (B) is 50 mol % or more.

[0054] [4] The insulated wire (1, 2) according to the above [3], wherein the diamine having a side chain containing a benzene ring includes PDPE (2-phenyl-4,4'-diaminophenyl diphenyl ether).

[0055] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. Furthermore, the above-described embodiment does not limit the invention according to the claims. Furthermore, it should be noted that not all of the combinations of features described in the embodiment are essential to the means for solving the problems of the invention. [Explanation of symbols]

[0056] 1, 2 Insulated wire 11, 21 Insulation coating

Claims

1. Contains a diamine and an acid dianhydride, The ratio of diamines having a side chain containing a benzene ring in the diamine is 50 mol % or more. Insulating paint.

2. The diamine having a side chain containing a benzene ring includes PDPE (2-phenyl-4,4'-diaminophenyl diphenyl ether). The insulating paint according to claim 1.

3. The insulating coating is made of a polyimide resin containing a diamine and an acid dianhydride, The ratio of diamines having a side chain containing a benzene ring in the diamine is 50 mol % or more. Insulated wire.

4. The diamine having a side chain containing a benzene ring includes PDPE (2-phenyl-4,4'-diaminophenyl diphenyl ether). The insulated wire according to claim 3.

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