Insulated wire

Abstract

To provide an insulated wire having high adhesion between layers constituting an insulating film.SOLUTION: The insulated wire includes a conductor and an insulating film covering the conductor. The insulating film contains a polyimide and an inorganic filler. A storage modulus of the insulating film at 370 °C is 0. 9GPa or less. The raw materials of the polyimide further include, for example, one or more of diphenyl-3, 3 ', 4,4 ' - tetracarbonyl anhydride, 1, 3-bis (4-aminophenoxy) benzene, and 4,4 ' - bis (4-aminophenoxy) biphenyl.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to insulated wire. [Background technology]

[0002] An insulated wire is disclosed in Patent Document 1. The insulated wire includes a conductor and an insulating coating. The insulating coating covers the conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2018 / 230706 Summary of the Invention [Problem to be solved by the invention]

[0004] Insulation coatings are made up of multiple layers stacked together. To improve surge resistance, inorganic fillers are sometimes added to the insulation coating. In this case, the amount of polymer component present at the interface between the layers that make up the insulation coating is reduced. When the amount of polymer component present at the interface is reduced, the entanglement of the polymer component molecules between the layers is reduced. As a result, the adhesion between the layers that make up the insulation coating is reduced.

[0005] In one aspect of the present disclosure, it is preferable to provide an insulated wire having high adhesion between layers constituting an insulating coating. [Means for solving the problem]

[0006] One aspect of the present disclosure is an insulated wire including a conductor and an insulating coating covering the conductor, the insulating coating including polyimide and an inorganic filler, and having a storage modulus of the insulating coating at 370°C of 0.9 GPa or less.

[0007] In the insulated wire according to one aspect of the present disclosure, the layers constituting the insulating coating have high adhesion to each other. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a manufacturing device for a rectangular enameled copper wire. [Figure 2] FIG. 2 is a cross-sectional view showing the cross-sectional shape of a rectangular copper wire. [Figure 3] FIG. 2 is a cross-sectional view showing the cross-sectional shape of a drawn rectangular copper wire. [Figure 4] FIG. 2 is a cross-sectional view showing the cross section of a rectangular enameled copper wire. [Figure 5] 1 is a graph showing the change in temperature and storage modulus during measurement of storage modulus in an example. [Figure 6] FIG. 1 is an explanatory diagram showing a method for a cut extension test. DETAILED DESCRIPTION OF THE INVENTION

[0009] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. First Embodiment 1. Manufacturing method of rectangular enameled copper wire 25 A method for manufacturing a rectangular enameled copper wire 25 will be described with reference to Figs. 1 to 4. The rectangular enameled copper wire 25 corresponds to an insulated electric wire. A manufacturing apparatus 1 shown in Fig. 1 is used for the method for manufacturing the rectangular enameled copper wire 25. The manufacturing apparatus 1 includes a dance ring or bobbin 3, a round wire drawing machine 5, a rectangular rolling mill 7, an annealing furnace 9, a rectangular wire drawing machine 11, an annealing furnace 13, a paint applicator 15, a baking furnace 17, and a winder 19.

[0010] A linear conductor 23 is wound around the dance wheel or bobbin 3. The conductor 23 is drawn out from the dance wheel or bobbin 3, travels along a route that passes through a round wire drawing machine 5, a flat rolling mill 7, an annealing furnace 9, a flat wire drawing machine 11, an annealing furnace 13, a coating machine 15, and a baking furnace 17 in this order, and is wound onto a winder 19. However, the processed conductor 23, which is a flat copper drawn wire material 23B described below, passes through the section including the coating machine 15 and the baking furnace 17 multiple times.

[0011] The conductor 23 is made of copper or a copper alloy. The cross-sectional shape of the conductor 23 is circular until it is subjected to flat-rolling, which will be described later. The cross-section of the conductor 23 is a cross section perpendicular to the longitudinal direction of the conductor 23.

[0012] The round wire drawing machine 5 draws the conductor 23, which has a circular cross-sectional shape. The flat rolling machine 7 performs flat rolling on the traveling conductor 23. The conductor 23 that has undergone flat rolling is called a flat copper wire 23A. As shown in FIG. 2, the cross-sectional shape of the flat copper wire 23A is a shape consisting of two parallel sides 24A, 24B and two arc-shaped end faces 26A, 26B. In the cross-section, the sides 24A, 24B are straight. In the cross-section, the length of the sides 24A, 24B is greater than the length of the end faces 26A, 26B. The annealing furnace 9 anneals the flat copper wire 23A.

[0013] The flat wire drawing machine 11 performs flat wire drawing on the running flat copper wire 23A. Flat wire drawing is a process of continuously cold drawing the flat copper wire 23A using a flat wire drawing die. The conductor 23 that has undergone flat wire drawing is referred to as a flat copper wire material 23B.

[0014] The cross-sectional shape of the drawn rectangular copper wire material 23B is a rounded rectangle, as shown in Fig. 3. The long sides of the rounded rectangle are sides 24A and 24B. The short sides 22A and 22B of the rounded rectangle are sides that originate from end faces 26A and 26B of the rectangular copper wire 23A.

[0015] As shown in Figure 1, in the rectangular wire drawing machine 11, the direction in which the conductor 23 travels is referred to as the traveling direction TR. The opposite direction to the traveling direction TR is referred to as the upstream direction US. The annealing furnace 13 anneals the rectangular copper wire material 23B. The paint applicator 15 applies enamel paint to the surface of the rectangular copper wire material 23B, thereby forming an enamel paint film of a predetermined thickness on the surface of the rectangular copper wire material 23B.

[0016] In the baking furnace 17, a coating of enamel paint of a predetermined thickness is formed by the paint applicator 15, and the running rectangular drawn copper wire material 23B is heated and baked to form an insulating coating 28 shown in Figure 4. As shown in Figure 1, the application of enamel paint by the paint applicator 15 and the baking in the baking furnace 17 are repeated. The rectangular enameled copper wire 25 is wound around the winder 19.

[0017] The method for forming the insulating coating 28 is detailed below. An enamel paint is applied to the surface of the drawn rectangular copper wire 23B using a paint applicator 15. The enamel paint is a paint containing a resin, a solvent, and an inorganic filler. The resin contains polyamic acid. The polyamic acid is a compound synthesized from raw materials containing an acid anhydride and a diamine. The acid anhydride contains PMDA (pyromellitic anhydride). The diamine contains ODA (4,4'-diaminodiphenyl ether).

[0018] The polyamic acid raw material further includes one or more of BPDA (diphenyl-3,3',4,4'-tetracarbonyl acid anhydride), TPE-R (1,3-bis(4-aminophenoxy)benzene), and BODA (4,4'-bis(4-aminophenoxy)biphenyl). BPDA is an acid anhydride. TPE-R and ODA are diamines.

[0019] When the raw material for the polyamic acid further contains one or more of BPDA, TPE-R, and BODA, the storage modulus of the insulating coating 28 at 370°C decreases. The greater the content of one or more of BPDA, TPE-R, and BODA, the smaller the storage modulus of the insulating coating 28 at 370°C becomes.

[0020] In the raw material of the polyamic acid, the ratio of the number of moles of PMDA to the total number of moles of acid anhydrides is preferably 40 mol % or more, more preferably 50 mol % or more, and particularly preferably 60 mol % or more.

[0021] The raw material for the polyamic acid may contain BPDA. When the raw material for the polyamic acid contains BPDA, the ratio of the number of moles of BPDA to the total number of moles of acid anhydrides is preferably less than 60 mol%, more preferably less than 50 mol%, and particularly preferably less than 40 mol%.

[0022] In the raw material for polyamic acid, the ratio of the number of moles of ODA to the total number of moles of diamines is preferably 5 mol % or more, more preferably 10 mol % or more, and particularly preferably 15 mol % or more.

[0023] The raw material for the polyamic acid may contain TPE-R. When the raw material for the polyamic acid contains TPE-R, the ratio of the number of moles of TPE-R to the total number of moles of diamines is preferably 3 mol % or more, more preferably 5 mol % or more, and particularly preferably 10 mol % or more.

[0024] The raw material for the polyamic acid may contain BODA. When the raw material for the polyamic acid contains BODA, the ratio of the number of moles of BODA to the total number of moles of diamines is preferably 10 mol% or more, more preferably 60 mol% or more, more preferably 70 mol% or more, and particularly preferably 80 mol% or more.

[0025] It is preferable that all of the monomers contained in the raw material of the polyamic acid are aromatic monomers. In this case, the heat resistance of the insulating coating 28 is high. Examples of solvents contained in the enamel paint include dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP). The mass ratio of the solid content in the enamel paint is, for example, 15 mass% or more and 30 mass% or less.

[0026] Examples of inorganic fillers contained in enamel paint include silica, alumina, and titanium oxide. For example, the surface of the inorganic filler is treated with an organic substance. In this case, the inorganic filler has good dispersibility in polyimide. When the enamel paint is applied and baked, the polyamic acid is converted to polyimide. Therefore, the insulating coating 28 contains polyimide.

[0027] The inclusion of an inorganic filler in the enamel paint causes the insulating coating 28 to contain an inorganic filler. The inclusion of an inorganic filler in the insulating coating 28 improves the surge resistance of the insulating coating 28. The blending amount of the inorganic filler in the enamel paint and the insulating coating 28 is preferably 1 phr to 100 phr, more preferably 5 phr to 80 phr, and particularly preferably 10 phr to 50 phr.

[0028] Next, the solvent in the enamel paint applied to the surface of the drawn rectangular copper wire 23B is evaporated, and the wire is baked in a baking furnace 17. By applying the enamel paint using the paint applicator 15 and baking in the baking furnace 17 once, one layer that constitutes the insulating coating 28 is formed. By repeating the application of the enamel paint using the paint applicator 15 and baking in the baking furnace 17, the insulating coating 28 is formed, with multiple layers stacked. Through the above process, the insulating coating 28 is formed, and the rectangular enameled copper wire 25 is formed. The insulating coating 28 contains polyimide produced from the polyamic acid contained in the enamel paint. Therefore, the insulating coating 28 contains polyimide and an inorganic filler.

[0029] The raw materials for polyamic acid correspond to the raw materials for polyimide, which include PMDA and ODA, and which further include one or more of BPDA, TPE-R, and BODA.

[0030] 2. Composition of rectangular enamelled copper wire 25 The configuration of rectangular enameled copper wire 25 will be described with reference to Fig. 4. Rectangular enameled copper wire 25 includes rectangular drawn copper wire material 23B and insulating coating 28. Rectangular drawn copper wire material 23B corresponds to a conductor. Insulating coating 28 covers rectangular drawn copper wire material 23B. The thickness of insulating coating 28 is, for example, 30 µm or more and 200 µm or less.

[0031] The insulating coating 28 contains polyimide and inorganic filler. The storage modulus of the insulating coating 28 at 370°C is 0.9 GPa or less. It is preferable that the storage modulus of the insulating coating 28 at 370°C is 0.9 GPa or less for all layers of the insulating coating 28. The storage modulus of the insulating coating 28 is measured as follows: An enamel paint having the same components as the insulating coating 28 is applied to a PEEK substrate and baked. A measurement sample is prepared from the insulating coating peeled from the PEEK substrate. The width of the measurement sample is 5 mm. The thickness of the measurement sample is 30 to 40 μm. Dynamic viscoelasticity measurement is performed on the measurement sample under the following conditions. Note that the measurement sample may also be prepared by peeling the insulating coating 28 from a rectangular enameled copper wire 25.

[0032] Distortion: 0.5% Frequency: 10Hz Heating rate: 10°C / min Chuck distance: 20mm

[0033] 3. Benefits of rectangular enamelled copper wire 25 In rectangular enameled copper wire 25, the layers that make up insulating coating 28 have high adhesion. The reason for this is presumed to be as follows: When rectangular enameled copper wire 25 is stretched, if there is high residual stress inside insulating coating 28, the adhesion between the layers that make up insulating coating 28 decreases. In rectangular enameled copper wire 25, the storage modulus of insulating coating 28 at 370°C is low, so the residual stress is small. As a result, the adhesion between the layers that make up insulating coating 28 is high.

[0034] The reason why the storage modulus of the insulating coating 28 at 370° C. is low is that the raw material of the polyimide further contains one or more of BPDA, TPE-R, and BODA.

[0035] One method for improving the adhesion between the layers that make up the insulating coating 28 is to increase the baking temperature during painting and to significantly slow down the running speed of the conductor 23. However, this method is prone to problems such as thermal degradation of the insulating coating 28 and oxidation of the conductor 23. This method also results in low productivity for the rectangular enameled copper wire 25. The rectangular enameled copper wire 25 of the present disclosure can mitigate the above problems that arise from this method.

[0036] <Example> 1. Manufacturing of enamelled copper wire The enameled copper wires of Examples 1 to 8 and Comparative Example 1 were manufactured using the method described in the first embodiment. However, the enameled copper wires were round wires, not rectangular wires. The manufacturing methods of Examples 1 to 8 and Comparative Example 1 were identical except for the raw materials for the polyamic acid contained in the enamel paint and the amount of inorganic filler added.

[0037] The enamel paint contained polyamic acid, an inorganic filler, and a solvent. The inorganic filler was colloidal silica, and the solvent was dimethylacetamide. The mass ratio of the solid content in the enamel paint was 15 to 30 mass%.

[0038] In Examples 1 to 8 and Comparative Example 1, the types and amounts of raw materials for polyamic acid contained in the enamel paints were as shown in Table 1. The units of raw material amounts are mol %. In addition, in Examples 1 to 8 and Comparative Example 1, the amounts of inorganic fillers contained in the enamel paints were as shown in Table 1.

[0039] [Table 1]

[0040] 2. Storage Modulus Measurement For each of Examples 1 to 8 and Comparative Example 1, a measurement sample for measuring the storage modulus was prepared.

[0041] The storage modulus was measured using the measurement sample by the method described above. The change in temperature and storage modulus during the measurement is shown in Figure 5. The measurement results of the storage modulus at 370°C are shown in Table 1. The storage modulus at 370°C was low in Examples 1 to 8 and high in Comparative Example 1.

[0042] 3. Cutting extension test A cut extension test was conducted for each of Examples 1 to 8 and Comparative Example 1. The cut extension test is a test for evaluating the adhesion between layers constituting the insulating coating 28. First, as shown in S1 of FIG. 6, a measurement sample 101 was prepared. The measurement sample 101 was obtained by cutting an enameled copper wire to a length of 200 mm. The cut surface was a cross section of the enameled copper wire.

[0043] Next, as shown in S2 of FIG. 6, the measurement sample 101 was elongated by 40% in its longitudinal direction. Next, as shown in S3 of FIG. 6, a slit 103 was formed in the measurement sample 101. The slit 103 was located in the center of the measurement sample 101 in the longitudinal direction. The slit 103 extended along the circumferential direction of the measurement sample 101, and was formed around the entire circumference. The slit 103 reached from the surface of the insulating coating 28 to the surface of the conductor 23.

[0044] After the notch 103 was formed, a peeled region 105 occurred around the notch 103, as shown in S4 in FIG. 6. The peeled region 105 is a portion where the inner layer 28A of the insulating coating 28 and the outer layer 28B of the insulating coating 28 are peeled off. The peeled region 105 is visible from the outside of the measurement sample 101. The length L of the peeled region 105 was measured. The length L was the length in the longitudinal direction of the measurement sample 101. The measurement results of the length L are shown in Table 1.

[0045] Length L was short in Examples 1 to 8 and long in Comparative Example 1. The shorter length L, the stronger the adhesion between the layers that make up insulating coating 28. Therefore, the adhesion between the layers that make up insulating coating 28 was high in Examples 1 to 8 and low in Comparative Example 1.

[0046] <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0047] (1) The insulated wire may be an insulated wire other than an enameled wire. (2) Of the layers constituting the insulating coating 28, one or more layers on the conductor 23 side can be an adhesion layer containing polyimide but not containing inorganic filler. The adhesion layer is a layer that contacts the conductor 23. The layer on the outer periphery of the adhesion layer is a surge-resistant layer containing polyimide and inorganic filler. In this case, the insulated wire of the present disclosure can improve adhesion between the adhesion layer and the surge-resistant layer. Furthermore, the insulated wire of the present disclosure can improve adhesion between the surge-resistant layers. Note that because the adhesion layer does not contain inorganic filler, adhesion between the conductor 23 and the adhesion layer is high.

[0048] (3) The function of one component in each of the above embodiments may be shared among multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Furthermore, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0049] (4) In addition to the insulated wire described above, the present disclosure can be realized in various forms, such as a product including the insulated wire as a component, a method for manufacturing the insulated wire, and the like. [Explanation of symbols]

[0050] 1... manufacturing equipment, 3... dance ring or bobbin, 5... round wire drawing machine, 7... flat wire rolling machine, 9... annealing furnace, 11... flat wire drawing machine, 13... annealing furnace, 15... paint application machine, 17... baking furnace, 19... winding machine, 22A, 22B... short side, 23... conductor, 23A... flat copper wire, 23B... flat copper wire drawing material, 24A, 24B... side, 25... flat enameled copper wire, 26A, 26B... end surface, 28... insulating coating, 28A... inner layer, 28B... outer layer, 101... measurement sample, 103... notch, 105... peeling area

Claims

1. A conductor; an insulating coating that covers the conductor; Equipped with the insulating coating contains polyimide and an inorganic filler; The storage modulus of the insulating coating at 370°C is 0.9 GPa or less. Insulated wire.

2. The insulated wire according to claim 1, The raw materials of the polyimide include pyromellitic anhydride and 4,4'-diaminodiphenyl ether, the raw material further comprises one or more of diphenyl-3,3',4,4'-tetracarbonyl anhydride, 1,3-bis(4-aminophenoxy)benzene, and 4,4'-bis(4-aminophenoxy)biphenyl; Insulated wire.

3. The insulated wire according to claim 1, Among the layers constituting the insulating coating, the layer in contact with the conductor contains the polyimide but does not contain the inorganic filler. Insulated wire.

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