Insulated wire, coil, motor, and method for manufacturing insulated wire

Abstract

Provided is an insulated wire comprising a rectangular conductor (A) and an insulating coating (B) that is formed on the outer periphery of the rectangular conductor (A), wherein: the insulating coating (B) is formed of a resin composition that contains a fluorine-containing copolymer (I) and amorphous silica particles (II); the fluorine-containing copolymer (I) contains a tetrafluoroethylene unit and a unit that is based on at least one monomer selected from the group consisting of hexafluoropropylene and fluoroalkyl vinyl ethers; and the yield point strength of the insulating coating (B) is 12.0 MPa or more.

Description

Insulated wires, coils, motors, and methods for manufacturing insulated wires

[0001] This disclosure relates to insulated wires, coils, motors, and methods for manufacturing insulated wires.

[0002] Patent Document 1 contains repeating units (A) based on tetrafluoroethylene and repeating units (B) based on perfluoro(propyl vinyl ether), with a molar ratio of (A) / (B) of 97.5 / 2.5 to 85 / 15, and a volumetric flow rate of 0.1 to 20 mm at 380°C. ３ The invention describes a heat-resistant electric wire in which a conductor is covered with a coating material containing a fluorine-containing copolymer and an insulating filler, which has a bending life of 3 million cycles or more and a bending life of 3 million cycles per second.

[0003] Japanese Patent Publication No. 2006-066329

[0004] This disclosure aims to provide an insulated wire comprising a rectangular conductor and an insulating coating, in which the insulating coating of the bent portion does not easily become thinner even when a bent portion is formed.

[0005] According to this disclosure, an insulated electric wire is provided, comprising a rectangular conductor (A) and an insulating coating (B) formed on the outer circumference of the rectangular conductor (A), wherein the insulating coating (B) is formed from a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II), the fluorine-containing copolymer (I) contains units based on tetrafluoroethylene units and at least one monomer selected from the group consisting of hexafluoropropylene and fluoroalkyl vinyl ethers, and the yield strength of the insulating coating (B) is 12.0 MPa or higher.

[0006] According to this disclosure, it is possible to provide an insulated wire that comprises a rectangular conductor and an insulating coating, and even when a bent portion is formed, the insulating coating of the bent portion does not easily become thinner.

[0007] Figure 1 is a schematic cross-sectional view showing the shape of the bent portion formed on the insulated wire in the examples and comparative examples.

[0008] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0009] As described in Patent Document 1, insulated wires are known that have an insulating coating formed from a fluorine-containing copolymer containing tetrafluoroethylene units and perfluoro(propyl vinyl ether) units. Since the conductor of such conventional insulated wires usually has a circular cross-section, even when the insulated wire is bent, the insulating coating easily follows the shape of the conductor after bending, and problems such as a decrease in insulating performance are unlikely to occur.

[0010] On the other hand, it has been found that when a rectangular conductor is used as the conductor of an insulated wire, the insulating coating becomes thinner around the bent part when the insulated wire is bent, resulting in a decrease in the insulating performance of the coating. Insulated wires equipped with rectangular conductors are suitable for use as motor coils because they can achieve a high packing ratio. Since a decrease in the insulating performance of the coating directly leads to a decrease in motor performance, a solution to this problem is desirable.

[0011] In light of this situation, this disclosure provides an insulated wire comprising a rectangular conductor and an insulating coating, wherein the insulating coating does not easily become thinner even when a bent portion is formed.

[0012] This disclosure relates to an insulated wire comprising a rectangular conductor (A) and an insulating coating (B) formed on the outer circumference of the rectangular conductor (A), wherein the insulating coating (B) is formed from a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II). The configuration of the insulated wire of this disclosure will be described in detail below.

[0013] 1. Flat rectangular conductor (A) The insulated wire of this disclosure comprises a flat rectangular conductor.

[0014] The rectangular conductor is not particularly limited as long as it is made of a conductive material. Examples of materials that form the rectangular conductor include metals such as copper, copper alloys, aluminum, aluminum alloys, iron, silver, and nickel. Rectangular conductors made of copper, copper alloys, aluminum, or aluminum alloys are preferred. Conductors that have been plated with silver plating, nickel plating, etc., can also be used.

[0015] The shape of a rectangular conductor is not particularly limited, as long as its cross-section is that of a rectangular wire with a roughly rectangular shape. The corners of the rectangular conductor's cross-section may be right angles, or they may be rounded. Furthermore, the rectangular conductor may be a single wire, a bundled wire, a stranded wire, etc., as long as the overall cross-section of the conductor is roughly rectangular, but a single wire is preferred.

[0016] The cross-sectional width of the rectangular conductor may be 1 to 75 mm, and the cross-sectional thickness of the rectangular conductor may be 0.1 to 10 mm. The outer diameter of the rectangular conductor may be 6.5 mm or more and 200 mm or less. The ratio of width to thickness may be greater than 1 and 30 or less.

[0017] 2. Insulating Coating (B) The insulating coating (B) is formed from a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II). Since the insulating wire of this disclosure has an insulating coating formed from the resin composition around the rectangular conductor, the insulating coating does not easily become thin even when a bent portion is formed. Therefore, even when the insulating wire of this disclosure has a bent portion, the insulating coating has high insulating performance. The bent portion may be a portion formed by bending the insulating wire in the edgewise direction, or a portion formed by bending the insulating wire in the flatwise direction. Even when the insulating wire of this disclosure has a bent portion bent in the edgewise direction, the insulating coating does not easily become thin and exhibits high insulating performance.

[0018] In one embodiment, the yield strength of the insulating coating (B) is 12.0 MPa or higher. It has been found that by setting the yield strength to 12.0 MPa or higher, the insulating coating does not easily become thinner even when a bent portion is formed. The yield strength of the insulating coating (B) is preferably 12.3 MPa or higher, more preferably 12.5 MPa or higher, even more preferably 12.8 MPa or higher, still more preferably 13.0 MPa or higher, particularly preferably 13.3 MPa or higher, and there is no particular upper limit, but it is 30.0 MPa or lower or 24.0 MPa or lower.

[0019] The yield strength of the insulating coating (B) can be adjusted by adjusting the surface area of ​​the amorphous silica particles, the average primary particle diameter of the amorphous silica particles, and the mass ratio of the fluorine-containing copolymer to the amorphous silica particles in the resin composition.

[0020] The yield strength of the insulating coating (B) can be measured by preparing a test specimen of a predetermined shape by cutting the insulating coating (B) from an insulated wire, and then performing a tensile test by pulling the test specimen in the direction corresponding to the longitudinal direction of the insulated wire. A test specimen that breaks in the elastic region during the tensile test and cannot be pulled sufficiently to measure the yield strength can be considered to not have a yield strength within the range described above. Details of the tensile test will be described later.

[0021] The yield strength of the insulating coating (B) can be measured by the method described later.

[0022] (Fluorine-containing copolymer (I)) Fluorine-containing copolymer (I) contains tetrafluoroethylene (TFE) units and units based on at least one monomer selected from the group consisting of hexafluoropropylene (HFP) and fluoroalkyl vinyl ether (FAVE).

[0023] The fluorine-containing copolymer (I) used in this disclosure is typically a melt-processable fluororesin. In this disclosure, melt-processability means that the polymer can be melted and processed using conventional processing equipment such as extruders and injection molding machines. Therefore, melt-processable fluororesins typically have a melt flow rate of 0.01 to 500 g / 10 min, as measured by the measurement method described later.

[0024] Examples of fluorine-containing copolymers (I) include fluorine-containing copolymers containing at least TFE units and HFP units (sometimes referred to as "TFE / HFP copolymer" in this disclosure) and fluorine-containing copolymers containing at least TFE units and FAVE units (sometimes referred to as "TFE / FAVE copolymer" in this disclosure). TFE / FAVE copolymers are preferred as fluorine-containing copolymers (I).

[0025] The TFE / FAVE copolymer contains at least TFE units and FAVE units.

[0026] As the FAVE constituting the FAVE unit, a monomer represented by the general formula (1): CF ２ =CFO(CF ２ CFY １ O) ｐ -(CF ２ CF ２ CF ２ O) ｑ -Rf (1) (where Y １ represents F or CF ３ , Rf represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents an integer of 0 to 5), and a monomer represented by the general formula (2): CFX = CXOCF ２ OR １ (2) (where X is the same or different and represents H, F or CF ３ , and R １ represents a fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I, which may be linear or branched, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I). At least one selected from the group consisting of the monomers represented by the above can be mentioned.

[0027] As the FAVE, among others, the monomer represented by the general formula (1) is preferable, at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) (PEVE) and perfluoro(propyl vinyl ether) (PPVE) is more preferable, at least one selected from the group consisting of PEVE and PPVE is still more preferable, and PPVE is particularly preferable.

[0028] The content of FAVE units in the TFE / FAVE copolymer is preferably 1.0 to 10.0% by mass, more preferably 3.0% by mass or more, even more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, more preferably 8.0% by mass or less, and even more preferably 7.5% by mass or less, based on the total monomer units.

[0029] The TFE unit content in the TFE / FAVE copolymer is preferably 99.0 to 90.0% by mass, more preferably 97.0% by mass or less, even more preferably 96.5% by mass or less, particularly preferably 96.0% by mass or less, more preferably 92.0% by mass or more, and even more preferably 92.5% by mass or more, relative to the total monomer units.

[0030] In this disclosure, the content of each monomer unit in the copolymer is: １９ Measurement is performed using the F-NMR method.

[0031] The TFE / FAVE copolymer may also contain monomer units derived from monomers copolymerizable with TFE and FAVE. In this case, the content of monomers copolymerizable with TFE and FAVE is preferably 0 to 9.0% by mass, and more preferably 0.1 to 2.0% by mass, relative to the total monomer units of the copolymer.

[0032] Monomers copolymerizable with TFE and FAVE include HFP and CZ. １ Z ２ = CZ ３ (CF ２ ) ｎ Z ４ (In the formula, Z １ Z ２ and Z ３ These represent H or F, and Z, either identical or different. ４ ) represents a vinyl monomer, and CF ２ = CF - OCH ２ -Rf １ (wherein, Rf １∫ represents a perfluoroalkyl group having 1 to 5 carbon atoms. Examples include alkyl perfluorovinyl ether derivatives represented by ∫. Among these, HFP is preferred.

[0033] The TFE / FAVE copolymer is preferably at least one selected from the group consisting of a copolymer consisting only of TFE units and FAVE units, and the TFE / HFP / FAVE copolymer described above, and more preferably a copolymer consisting only of TFE units and FAVE units.

[0034] The melting point of the TFE / FAVE copolymer is preferably 280 to 322°C, more preferably 290°C or higher, and more preferably 315°C or lower.

[0035] In this disclosure, the melting point can be measured using a differential scanning calorimetry (DSC).

[0036] The TFE / HFP copolymer contains at least TFE units and HFP units.

[0037] The HFP unit content in the TFE / HFP copolymer is preferably 1.0% to 30.0% by mass, more preferably 2.0% or more by mass, and more preferably 15.0% or less by mass, relative to the total monomer units.

[0038] The TFE unit content in the TFE / HFP copolymer is preferably 70.0 to 99.0% by mass, more preferably 85.0% by mass or more, and more preferably 98.0% by mass or less, relative to the total monomer units.

[0039] The above TFE / HFP copolymer preferably has a mass ratio (TFE / HFP) of 70 to 99 / 1 to 30 (mass%) of TFE units to HFP units. More preferably, the above mass ratio (TFE / HFP) is 85 to 95 / 5 to 15 (mass%).

[0040] The TFE / HFP copolymer may further contain FAVE units. Examples of FAVE units contained in the TFE / HFP copolymer include those similar to the FAVE units described above.

[0041] When the TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and FAVE units (hereinafter also referred to as "TFE / HFP / FAVE copolymer"), it is preferable that the mass ratio (TFE / HFP / FAVE) is 70.0 to 99.0 / 0.1 to 25.0 / 0.1 to 25.0 (mass%). It is more preferable that the above mass ratio (TFE / HFP / FAVE) is 75.0 to 98.0 / 1.0 to 15.0 / 1.0 to 10.0 (mass%). It is preferable that the TFE / HFP / FAVE copolymer contains 1% by mass or more in total HFP units and FAVE units.

[0042] The TFE / HFP copolymer may further contain other ethylenically active monomer (α) units other than TFE units, HFP units, and FAVE units. These other ethylenically active monomer (α) units are not particularly limited as long as they are copolymerizable with TFE, HFP, and FAVE, and include, for example, fluorinated ethylenically active monomers such as vinyl fluoride (VF), vinylidene fluoride (VdF), and chlorotrifluoroethylene (CTFE); and non-fluorinated ethylenically active monomers such as ethylene, propylene, and alkyl vinyl ethers. The content of these other ethylenically active monomer (α) units is preferably 0 to 25.0% by mass, and more preferably 0.1 to 25.0% by mass.

[0043] When the above copolymer is a TFE / HFP / FAVE / other ethylenically active monomer (α) copolymer, the mass ratio (TFE / HFP / FAVE / other ethylenically active monomer (α)) is preferably 70.0 to 98 / 0.1 to 25.0 / 0.1 to 25.0 / 0.1 to 25.0 (mass%). The above TFE / HFP / FAVE / other ethylenically active monomer (α) copolymer preferably contains a total of 1% by mass or more of monomer units other than TFE units.

[0044] The melting point of the TFE / HFP copolymer is preferably 200 to 322°C, more preferably 220°C or higher, more preferably 300°C or lower, and even more preferably 280°C or lower.

[0045] The melt flow rate of the fluorine-containing copolymer (I) is preferably 0.1 to 120 g / 10 min, more preferably 1.0 g / 10 min or more, even more preferably 10 g / 10 min or more, more preferably 90 g / 10 min or less, and even more preferably 80 g / 10 min or less. Furthermore, the melt flow rate of the fluorine-containing copolymer (I) is even more preferably 25 g / 10 min or more, and particularly preferably 30 g / 10 min or more, since it facilitates mixing with amorphous silica particles with a large surface area or amorphous silica particles with a small average primary particle diameter. If the melt flow rate of the fluorine-containing copolymer (I) is too low, for example, when attempting to knead the fluorine-containing copolymer and amorphous silica particles in the cylinder of an extruder, the amorphous silica particles are so small that they retain a large amount of air, and the air is discharged to the raw material supply section during kneading, making it difficult to push the raw materials into the cylinder, which may make it difficult to produce the resin composition. If the melt flow rate of the fluorine-containing copolymer (I) is too high, problems may arise, such as the fluorine-containing copolymer overflowing from the vent holes of the cylinder when attempting to knead the fluorine-containing copolymer and amorphous silica particles in the cylinder of an extruder.

[0046] In this disclosure, the melt flow rate is a value obtained in accordance with ASTM D1238, using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) as the mass of polymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes at 372°C and a load of 5 kg (g / 10 min).

[0047] Fluorine-containing copolymer (I) is -CF=CF ２ , -CF ２ H, -COF, -COOH, -COOCH ３ , -CONH ２ ien-CH ２ The fluorine-containing copolymer (I) may have functional groups such as OH. The presence of functional groups in the fluorine-containing copolymer (I) can improve the adhesion between the rectangular conductor (A) and the insulating coating (B).

[0048] -CF=CF of fluorine-containing copolymer (I) ２ , -CF ２H, -COF, -COOH, -COOCH ３ , -CONH ２ and -CH ２ The total number of OH groups is 10 carbon atoms. ６ The number of functional groups per atom is preferably 5 to 2000. The total number of functional groups is 10 carbon atoms. ６ More preferably, there are 100 or more functional groups per unit, even more preferably 200 or more, still more preferably 250 or more, particularly preferably 300 or more, more preferably 1500 or less, still more preferably 1000 or less, still more preferably 800 or less, and particularly preferably 600 or less. By having the total number of functional groups of the fluorine-containing copolymer (I) within the above range, the adhesion between the rectangular conductor (A) and the insulating coating (B) can be further improved.

[0049] -CH of fluorine-containing copolymer (I) ２ The number of OH groups is 10 carbon atoms. ６ Preferably, there are 100 to 2000 functional groups per atom. ６ More preferably, there are 200 or more per unit, even more preferably 250 or more, even more preferably 300 or more, more preferably 1500 or less, even more preferably 900 or less, even more preferably 800 or less, particularly preferably 600 or less, and most preferably 500 or less. Fluorine-containing copolymer (I) -CH ２ By keeping the number of OH groups within the above range, the adhesion between the rectangular conductor (A) and the insulating coating (B) can be further improved, and foaming during molding of the resin composition to form the insulating coating can be suppressed. Unintended foaming during molding can cause pinholes in the insulating coating or sparks. By suppressing foaming, a highly insulating coating layer can be formed.

[0050] Infrared spectroscopy can be used to identify the types of functional groups and measure their number.

[0051] The number of functional groups is specifically measured by the following method. First, the copolymer is melted at 330-340°C for 30 minutes and then compressed to produce a film with a thickness of 0.20-0.25 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the copolymer and the difference spectrum from the base spectrum, which is completely fluorinated and lacks functional groups. From the absorption peaks of specific functional groups appearing in this difference spectrum, the number of carbon atoms in the copolymer (1 × 10) is calculated according to the following formula (A). ６ Calculate the number of functional groups N per individual. N = I × K / t (A) I: absorbance K: correction factor t: film thickness (mm)

[0052] For reference, Table 1 shows the absorption frequency, molar extinction coefficient, and correction factor for the functional groups in this disclosure. The molar extinction coefficient was determined from FT-IR measurement data of a small molecule model compound.

[0053]

[0054] Note that -CH ２ CF ２ H, -CH ２ COF, -CH ２ COOH, -CH ２ COOCH ３ ien-CH ２ CONH ２ The absorption frequencies are shown in the table below, -CF ２ H, -COF, -COOH free and -COOH bonded, -COOCH ３ , -CONH ２ From the absorption frequency to several tens of kaiser (cm) －１ ) becomes lower. Therefore, for example, the number of functional groups in -COF is -CF ２ The absorption frequency due to COF is 1883 cm⁻¹. －１ The number of functional groups determined from the absorption peak, and -CH ２ The absorption frequency due to COF is 1840 cm⁻¹. －１ This is the sum of the number of functional groups determined from the absorption peaks.

[0055] The above-mentioned functional groups are introduced into the fluorine-containing copolymer, for example, by chain transfer agents or polymerization initiators used in the production of the fluorine-containing copolymer. For example, alcohols may be used as chain transfer agents, or -CH may be used as polymerization initiators. ２ When using peroxides with an OH structure, -CH is added to the main chain end of the fluorine-containing copolymer. ２ An OH group is introduced. Furthermore, by polymerizing monomers having functional groups, the functional groups are introduced to the side chain ends of the fluorine-containing copolymer. The fluorine-containing copolymer may also contain units derived from monomers having functional groups.

[0056] (Amorphous Silica Particles (II)) The resin composition that forms the insulating coating contains amorphous silica particles (II). By using a resin composition containing amorphous silica particles (II), it is possible to form an insulating coating that does not easily become thin even when a bent portion is formed.

[0057] Amorphous silica particles (II) are amorphous (non-crystalline) silica particles that do not have crystallinity. The amorphous silica particles (II) are preferably at least one selected from the group consisting of fumed silica and colloidal silica, with fumed silica being more preferred.

[0058] The average primary particle diameter of amorphous silica particles (II) is preferably 5 to 70 nm, more preferably 7 nm or more, even more preferably 9 nm or more, more preferably 60 nm or less, even more preferably 50 nm or less, still more preferably 45 nm or less, and particularly preferably 40 nm or less. The smaller the average primary particle diameter of amorphous silica particles (II), the easier it is to increase the yield strength of the insulating coating even with a small amount of amorphous silica particles (II), and as a result, it becomes easier to obtain an insulated wire in which the insulating coating does not become thin even when a bent portion is formed. On the other hand, if the average primary particle diameter of amorphous silica particles (II) is too small, it may become difficult to knead the fluorine-containing copolymer and amorphous silica particles. If the average primary particle diameter of amorphous silica particles (II) is too large, it may become difficult to increase the yield strength of the insulating coating.

[0059] The average primary particle size of amorphous silica particles (II) can be measured by analyzing images of amorphous silica particles taken with a scanning electron microscope.

[0060] The surface area of ​​amorphous silica particles (II) contained in the resin composition per 100 g of the resin composition is preferably 250 to 3000 m². ２ / 100g, more preferably 350m ２ / 100g or more, more preferably 400m ２ / 100g or more, and more preferably 500m ２ / 100g or more, and particularly preferably 600m ２ / 100g or more, more preferably 2500m ２ / 100g or less, more preferably 2000m ２ / 100g or less. By adjusting the surface area of ​​amorphous silica particles (II) contained in the resin composition to within the above range, the moldability of the resin composition is improved, and it becomes easier to obtain an insulated wire in which the insulating coating does not become thin even when a bent portion is formed.

[0061] The surface area of ​​amorphous silica particles (II) contained in 100 g of the resin composition can be calculated using the following formula: Surface area (m²) ２ ( / 100g) = (Specific surface area of ​​amorphous silica particles (m²) ２ (g) × (Content of amorphous silica particles in the resin composition (g / 100g))

[0062] In one embodiment, it is preferable that the amorphous silica particles (II) are amorphous silica particles surface-treated with a silane coupling agent. By using amorphous silica particles surface-treated with a silane coupling agent, foaming can be suppressed when molding the resin composition to form an insulating coating, and a highly insulating coating layer can be formed.

[0063] In one embodiment, it is preferable that amorphous silica particles (II) have a hydrophobic surface. By using amorphous silica particles having a hydrophobic surface, foaming can be suppressed when molding the resin composition to form an insulating coating, and a highly insulating coating layer can be formed.

[0064] Alkylchlorosilanes are examples of silane coupling agents. By using amorphous silica particles surface-treated with alkylchlorosilane, foaming during the molding of the resin composition to form an insulating coating can be suppressed, and a highly insulating coating layer can be formed. Furthermore, the affinity between the fluorine-containing copolymer and the amorphous silica particles is improved, and the amorphous silica particles can be sufficiently dispersed in the resin composition, making it easier to obtain insulated wires in which the insulating coating does not become thinner even when a bent section is formed.

[0065] As a silane coupling agent, at least one selected from the group consisting of monomethyltrichlorosilane and dimethyldichlorosilane is preferred because it can further suppress foaming and further improve the affinity between the fluorine-containing copolymer and amorphous silica particles.

[0066] Surface area of ​​amorphous silica particles (II) 1 nm ２ The number of silanol groups per layer is preferably 10 or less, more preferably 6.0 or less, even more preferably 3.0 or less, and still more preferably 2.0 or less. The lower limit is not particularly limited, but may be 0.1 or more or 1.0 or more. By having the number of silanol groups within the above range, foaming can be suppressed when molding the resin composition to form an insulating coating, and a highly insulating coating layer can be formed.

[0067] The number of silanol groups in amorphous silica particles (II) can be measured by the Karl Fischer method.

[0068] The metal oxide content of amorphous silica particles (II) is preferably 500 ppm or less, more preferably 450 ppm by mass or less, and the lower limit is not particularly limited and may be 0 ppm by mass or more, greater than 0 ppm by mass, or 10 ppm by mass or more.

[0069] In one embodiment, the metal oxide is an oxide of a metal with a specific gravity of 4.0 or higher. Examples of metal oxides include iron(II) oxide, aluminum oxide, sodium oxide, calcium oxide, and magnesium oxide.

[0070] In one embodiment, the total content of iron(II) oxide, aluminum oxide, sodium oxide, calcium oxide, and magnesium oxide in amorphous silica particles (II) is preferably 500 ppm or less, more preferably 450 ppm by mass or less, and the lower limit is not particularly limited and may be 0 ppm by mass or more, greater than 0 ppm by mass, or 10 ppm by mass or more.

[0071] Using amorphous silica particles (II) with a low iron(II) oxide content is also a preferred embodiment. In one embodiment, the iron(II) oxide content of the amorphous silica particles (II) is preferably 500 ppm or less, more preferably 450 ppm by mass or less, and the lower limit is not particularly limited and may be 0 ppm by mass or more, greater than 0 ppm by mass, or 10 ppm by mass or more.

[0072] Due to its manufacturing process, fumed silica tends to have a lower metal oxide content than colloidal silica. By using fumed silica as amorphous silica particles (II), the metal oxide content of amorphous silica particles (II) can be adjusted to within the above-mentioned range.

[0073] The metal oxide content of amorphous silica particles (II) can be measured by atomic absorption spectrophotometry.

[0074] (Resin Composition) Next, a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II) will be described in more detail.

[0075] In one embodiment, 100 seconds at 380°C －１The shear viscosity of the resin composition, measured at a shear rate, is 100 to 2000 Pa·s, preferably 300 Pa·s or more, more preferably 500 Pa·s or more, preferably 1700 Pa·s or less, and more preferably 1400 Pa·s or less. If the shear viscosity is too low, the thickness of the insulating coating after bending may be too thin. If the shear viscosity is too high, the moldability of the resin composition may decrease, or molding defects such as melt fractures may occur more easily.

[0076] The shear viscosity of the resin composition can be adjusted within the above-mentioned range by selecting the type of amorphous silica particles or adjusting the content of amorphous silica particles.

[0077] The shear viscosity of a resin composition can be measured using a capillary rheometer.

[0078] In the resin composition, the mass ratio ((I) / (II)) of the fluorine-containing copolymer (I) to amorphous silica particles (II) is preferably 99.0 / 1.0 to 85.0 / 15.0, more preferably 98.0 / 2.0 or less, more preferably 87.0 / 13.0 or more, even more preferably 89.0 / 11.0 or more, and still more preferably 90.0 / 10.0 or more, as this makes it easier to maintain the thickness of the insulating coating after bending and improves the moldability of the resin composition. By appropriately adjusting the mass ratio ((I) / (II)), it becomes easy to adjust the yield strength of the insulating coating (B) within the above range. If the mass ratio ((I) / (II)) is too high, the thickness of the insulating coating after bending may become too thin. If the mass ratio ((I) / (II)) is too low, the moldability of the resin composition may decrease, molding defects such as melt fractures may occur more easily, and cracks may form in the bent parts.

[0079] The weight loss rate when the resin composition is heated at 360°C for 1 hour is preferably less than 5000 ppm by mass, more preferably 4500 ppm by mass or less, and the lower limit is not particularly limited but may be 10 ppm by mass or more, 50 ppm by mass or more, or 100 ppm by mass or more. By adjusting the weight loss rate within the above range, it becomes easier to increase the yield strength of the insulating coating, and as a result, it becomes easier to obtain an insulated wire in which the insulating coating does not become thin even when a bent portion is formed. In addition, foaming when molding the resin composition to form the insulating coating can be suppressed, and a coating layer with high insulating properties can be formed.

[0080] The weight loss rate of the resin composition can be adjusted within the above-mentioned range by using amorphous silica particles that have been surface-treated with a silane coupling agent, or by adjusting the content of amorphous silica particles.

[0081] The weight loss rate of the resin composition can be measured using a thermogravimetric differential thermal analyzer (TG-DTA).

[0082] The resin composition may contain other components as needed. Examples of other components include additives such as crosslinking agents, antistatic agents, heat stabilizers, foaming agents, foaming nucleating agents, antioxidants, surfactants, photopolymerization initiators, anti-abrasion agents, surface modifiers, and pigments. The content of other components in the resin composition is preferably less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit, although it may be 0% by mass or more. In other words, the resin composition does not have to contain other components.

[0083] 3. Insulated wire The insulated wire of this disclosure comprises a rectangular conductor (A) and an insulating coating (B) formed on the outer circumference of the rectangular conductor (A).

[0084] In the insulated wire of this disclosure, it is preferable that the rectangular conductor and the insulating coating are in contact. The insulated wire of this disclosure exhibits excellent insulating properties, as the insulating coating is less likely to lift from the rectangular conductor even without forming a primer layer. The formation of a primer layer is undesirable because it increases the dielectric constant. The insulated wire of this disclosure may further include other layers formed on the outer circumference of the insulating coating, or it may not include other layers formed on the outer circumference of the insulating coating.

[0085] The thickness of the insulating coating is not particularly limited, but from the viewpoint of insulating properties, it is preferably 10 to 300 μm. Furthermore, even when a bent portion is formed, an insulated wire can be obtained in which the insulating coating does not become thinner. Therefore, the thickness of the insulating coating is more preferably 30 μm or more, even more preferably 60 μm or more, and still more preferably 90 μm or more. The thickness of the insulating coating may be 200 μm or less or 150 μm or less. Compared with conventional insulated wires having an insulating coating made of polyamide-imide or the like, the insulated wire of this disclosure can exhibit sufficient insulating properties even with a thinner insulating coating. Moreover, even when a bent portion is formed, the insulating coating of the bent portion does not become thinner, so the thickness of the insulating coating can be reduced. Therefore, by using the insulated wire of this disclosure in coils and motors, motors can be miniaturized.

[0086] The insulated wires of this disclosure have a low tendency for the insulating coating to thin at the bent portion, so the thickness of the thinnest part of the insulating coating at the bent portion does not differ significantly from the thickness of the insulating coating before bending. In one embodiment, the insulating coating of the insulated wire has a film thickness retention rate of 70.0% or more, 80.0% or more, or 90.0% or more. The film thickness retention rate can be calculated by the method described later.

[0087] The insulated wire of this disclosure can be manufactured, for example, by a manufacturing method in which the above-described resin composition is extruded onto the outer circumference of a rectangular conductor to form an insulating coating.

[0088] The resin composition can be extruded using an extruder equipped with a cylinder and a die. The fluorine-containing copolymer in the resin composition is melted in the cylinder of the extruder. The temperature of the molten resin composition is usually above the melting point of the fluorine-containing copolymer, preferably at least 15°C higher than the melting point of the fluorine-containing copolymer, more preferably at least 20°C higher than the melting point of the fluorine-containing copolymer, and even more preferably at least 25°C higher than the melting point of the fluorine-containing copolymer. There is no upper limit to the temperature of the molten fluorine-containing copolymer, but for example, it should be below the thermal decomposition temperature of the fluorine-containing copolymer.

[0089] The insulated wire of this disclosure can be used as a coil. Even when the insulated wire of this disclosure is bent to form a bent portion, the insulation coating of the bent portion does not easily become thinner. Therefore, the insulated wire of this disclosure can be suitably used as a coil having a bent portion.

[0090] The insulated wires and coils of this disclosure can be suitably used in electrical equipment or electronic devices such as motors, generators, and inductors. Furthermore, the insulated wires and coils of this disclosure can be suitably used in automotive electrical equipment or automotive electronic devices such as automotive motors, automotive generators, and automotive inductors.

[0091] The insulated wires of this disclosure also have the characteristic of having a long energized life because the insulating coating is formed from a resin composition containing a fluorine-containing copolymer and amorphous silica particles. In one embodiment, the energized life (2.5 kV-10 kHz) of the insulated wire is 2.0 hours or more, 3.0 hours or more, or 3.5 hours or more. Such an energized life is several times longer than that of conventional insulated wires having an insulating coating formed from a fluorine-containing copolymer that does not contain amorphous silica. The energized life of the insulated wire can be measured by the method described later.

[0092] The motor may include, for example, a stator provided with slots and the aforementioned insulated wires housed in the slots. The insulated wires housed in the slots may have bent portions. Even when bent portions are formed in the insulated wires of this disclosure, the insulating coating of the bent portions does not easily become thinner. Therefore, by forming bent portions in the insulated wires and then housing the insulated wires in the slots, a motor can be obtained in which insulated wires with insulating coatings exhibiting high insulating performance are housed at a very high space factor.

[0093] In one embodiment, the space ratio of the insulated wires relative to the opening area of ​​the stator slots can be set to 60% or more. By using the insulated wires of this disclosure, dielectric breakdown can be suppressed even when the insulated wires are housed at such a high space ratio.

[0094] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0095] <1> According to a first aspect of this disclosure, an insulated wire is provided, comprising a rectangular conductor (A) and an insulating coating (B) formed on the outer circumference of the rectangular conductor (A), wherein the insulating coating (B) is formed from a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II), the fluorine-containing copolymer (I) contains units based on tetrafluoroethylene units and at least one monomer selected from the group consisting of hexafluoropropylene and fluoroalkyl vinyl ethers, and the yield strength of the insulating coating (B) is 12.0 MPa or higher. <2> According to a second aspect of this disclosure, an insulated wire according to the first aspect is provided, wherein the amorphous silica particles (II) are amorphous silica particles surface-treated with a silane coupling agent. <3> According to a third aspect of this disclosure, an insulated wire according to the first or second aspect is provided, wherein the amorphous silica particles (II) are amorphous silica particles surface-treated with alkylchlorosilane. <4> According to a fourth aspect of this disclosure, an insulated wire according to any of the first to third aspects is provided, wherein the average primary particle size of amorphous silica particles (II) is 5 to 70 nm, and the amorphous silica particles (II) are fumed silica. <5> According to a fifth aspect of this disclosure, an insulated wire according to any of the first to fourth aspects is provided, wherein the melt flow rate of the fluorine-containing copolymer (I), measured under conditions of 372°C and a 5 kg load, is 25 to 120 g / min. <6> According to a sixth aspect of this disclosure, －１An insulated wire according to any of the first to fifth aspects is provided, wherein the shear viscosity of the resin composition, measured at a shear rate of , is 300 to 1700 Pa·s. <7> According to the seventh aspect of this disclosure, an insulated wire according to any of the first to sixth aspects is provided, wherein the mass ratio ((I) / (II)) of the fluorine-containing copolymer (I) to amorphous silica particles (II) in the resin composition is 99.0 / 1.0 to 85.0 / 15.0. <8> According to the eighth aspect of this disclosure, an insulated wire according to any of the first to seventh aspects is provided, wherein the weight loss rate when the resin composition is heated at 360°C for 1 hour is less than 5000 ppm by mass. <9> According to the ninth aspect of this disclosure, an insulated wire according to any of the first to eighth aspects is provided, wherein the thickness of the insulating coating (B) is 30 μm or more and 300 μm or less. <10> According to the tenth aspect of this disclosure, a coil is provided which is made of an insulated wire according to any of the first to ninth aspects. <11> According to the eleventh aspect of this disclosure, a motor is provided which comprises a coil made of an insulated wire according to any of the first to ninth aspects. <12> According to the twelfth aspect of this disclosure, a method for manufacturing an insulated wire according to any of the first to ninth aspects is provided, wherein the resin composition is extruded onto the outer circumference of a rectangular conductor (A) to form an insulating coating (B).

[0096] Next, embodiments of the present disclosure will be described with reference to examples, but the present disclosure is not limited to such embodiments.

[0097] The physical properties of the materials used in the examples and comparative examples were measured by the following methods.

[0098] (Melt flow rate of fluorine-containing copolymer) In accordance with ASTM D1238, the mass (g / 10 min) of copolymer flowing out of a nozzle with an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes was determined using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) at 372°C and under a 5 kg load.

[0099] (Number of functional groups in fluorine-containing copolymers) The fluorine-containing copolymer was melted at 330-340°C for 30 minutes and compressed to produce a film with a thickness of 0.20-0.25 mm. This film was scanned 40 times using a Fourier transform infrared spectrometer [FT-IR (product name: 1760X, manufactured by PerkinElmer)] and analyzed to obtain an infrared absorption spectrum. A difference spectrum was obtained from the base spectrum, which is completely fluorinated and does not contain any functional groups. From the absorption peaks of specific functional groups appearing in this difference spectrum, the number of carbon atoms in the fluorine-containing copolymer was determined according to the following formula (A). ６ The number of functional units N per individual was calculated.

[0100] N = I × K / t (A) I: Absorbance K: Correction factor t: Film thickness (mm)

[0101] For reference, Table 2 shows the absorption frequency, molar extinction coefficient, and correction factor for the functional groups in this disclosure. The molar extinction coefficient was determined from FT-IR measurement data of a small molecule model compound.

[0102]

[0103] (Primary average particle diameter of amorphous silica particles) This was determined by analyzing images of amorphous silica particles taken with a scanning electron microscope. Specifically, 50 images were taken with a scanning electron microscope at a magnification of 100,000x, with different fields of view, and the primary average particle diameter of 2,500 amorphous silica particles was analyzed using image analysis, and the average by number of particles was calculated.

[0104] (Specific surface area of ​​amorphous silica particles) The specific surface area of ​​amorphous silica was measured using a nitrogen adsorption apparatus as described in the silica gel test method of JIS-K1150:1994. Amorphous silica particles were vacuum dried at 120°C for 6 hours, and the amount of nitrogen adsorption and desorption at liquid nitrogen temperature was measured. The actual surface area was calculated from the BET plot using the nitrogen adsorption BET method. The specific surface area was calculated by dividing the measured actual surface area using the nitrogen adsorption BET method by the apparent surface area. However, the specific surface area is the specific surface area measured by the BET method for amorphous silica particles with a hydrophilic surface before surface treatment.

[0105] (Metal Oxide Content of Amorphous Silica Particles) The content of metal oxides in the amorphous silica particles was quantified by atomic absorption spectrometry targeting iron (II) oxide, aluminum oxide, sodium oxide, calcium oxide, and magnesium oxide, as described in the silica gel test method of JIS-K1150:1994.

[0106] (Silanol Group Number of Amorphous Silica Particles) The silanol group number of the amorphous silica particles was measured by the Karl Fischer method. The amorphous silica particles were dispersed in a methanol solvent, and the water content was titrated using a Karl Fischer moisture meter. Hydranal - Composite 5K (manufactured by Honeywell - Fluka) was used as the titration reagent. The amount of surface silanol groups was calculated from the water content measured by the above method using the following formula. Surface silanol groups (per nm ２ ) = 668.9 × H ２ O (mass%) / specific surface area (m ２ / g)

[0107] In the examples and comparative examples, the following materials were used. Fluorine - containing copolymer (1): Tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, MFR = 70 g / 10 min, functional group number (per 10 carbon atoms ６ ) = 535 (-CH ２ OH group number (per 10 carbon atoms ６ ) = 411) Fluorine - containing copolymer (2): Tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, MFR = 40 g / 10 min, functional group number (per 10 carbon atoms ６ ) = 344 (-CH ２ OH group number (per 10 carbon atoms ６ ) = 325) Fluorine - containing copolymer (3): Tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer, MFR = 30 g / 10 min, functional group number (per 10 carbon atoms ６ ) = 321 (-CH ２ OH group number (per 10 carbon atoms ６ ) = 244)

[0108] Silica particles (1): Fumed silica, average primary particle diameter = 14 nm, particles surface-treated with monomethyltrichlorosilane (MMTCSi), metal oxide content = 420 ppm by mass, number of silanol groups (1 nm on the surface) ２ (per particle) = 1.5 silica particles (2): Fumed silica, average primary particle diameter = 40 nm, particles surface-treated with monomethyltrichlorosilane (MMTCSi), metal oxide content = 420 ppm by mass, number of silanol groups (surface 1 nm) ２ (per particle) = 1.7 silica particles (3): Fumed silica, average primary particle diameter = 12 nm, particles surface-treated with dimethyldichlorosilane (DMDCSi), metal oxide content = 360 ppm by mass, number of silanol groups (surface 1 nm) ２ (per unit) = 1.2 silica particles (4): Colloidal silica, average primary particle diameter = 50 nm, particles surface-treated with dimethyldichlorosilane (DMDCSi), metal oxide content = 3200 ppm by mass, number of silanol groups (surface 1 nm) ２ (per unit) = 1.1 pieces

[0109] Examples 1 to 10 and Comparative Examples 1 to 3: Resin compositions and insulated wires were prepared using the materials listed in Table 3 by the following methods. The results are shown in Table 3.

[0110] <Preparation of Resin Composition> A fluorine-containing copolymer and silica particles were mixed in the proportions (mass%) shown in Table 3. The resulting mixture was supplied to a twin-screw extruder (φ25 mm, L / D = 41) and melt-kneaded under conditions of a cylinder temperature of 360°C and a screw rotation speed of 200 rpm to produce a resin composition (pellets). Various physical properties were evaluated using the obtained resin composition.

[0111] (Surface area of ​​silica particles in 100g of resin composition) The surface area of ​​amorphous silica particles contained in 100g of resin composition was calculated using the following formula: Surface area (m²) ２ ( / 100g) = (Specific surface area of ​​amorphous silica particles (m²) ２ (g) × (Content of amorphous silica particles in the resin composition (g / 100g))

[0112] (Shear Viscosity of Resin Composition) Using a capillary rheometer, it was measured at a shear rate of 100 s at 380 °C. The pellet preheating time was 5 minutes. －１ It was measured at a shear rate of. The pellet preheating time was 5 minutes.

[0113] (Weight Loss Rate of Resin Composition) Using a thermogravimetric differential thermal analyzer (TG-DTA) (STA7200 manufactured by Hitachi High-Technologies Science), the resin composition was heated from 25 °C to 360 °C at a heating rate of 10 °C / min in air, and then heated at 360 °C for 60 minutes. The weight loss rate (mass ppm) of the resin composition was calculated from the mass of the resin composition before and after heating.

[0114] <Wire Molding > Using an extrusion molding machine, the obtained resin composition (pellets) was extruded onto a flat conductor (thickness: 2.00 mm, width: 3.40 mm) at a shear rate of 30 s at 360 °C to obtain an insulated wire having an insulating coating with the thickness (thickness (A)) described in Table 3. The obtained insulated wire was evaluated by the following method. The results are shown in Table 3. －１ It was extruded onto a flat conductor (thickness: 2.00 mm, width: 3.40 mm) at a shear rate of, to obtain an insulated wire having an insulating coating with the thickness (thickness (A)) described in Table 3. The obtained insulated wire was evaluated by the following method. The results are shown in Table 3.

[0115] (Melt Fracture) The surface of the insulating coating was visually observed and evaluated according to the following criteria. Good: No melt fracture is observed. Poor: Melt fracture is observed.

[0116] (Foaming) The cross section of the insulating coating was visually observed and evaluated according to the following criteria. Good: No foaming is observed. Poor: Foaming is observed.

[0117] (Yield Point Strength of Insulating Coating) A cut was made in the insulating coating of the insulated wire to prepare a test piece having a length of 50 mm, a width of 2.5 mm, and the thickness (thickness A) described in Table 3. Using the obtained test piece, a tensile test was performed under the following conditions to measure the yield point strength. (Tensile Test Conditions) Chuck distance: 22 mm Tensile speed: 10 mm / min Measurement temperature: 25 °C Tensile direction: Longitudinal direction of the insulated wire

[0118] (Thickness and film thickness retention rate of insulated wire) Using a press die, the insulated wire obtained above was pressed at a pressure of 0.2 MPa to form a bent section that was bent in a crank shape in the edgewise direction, as shown in Figure 1. The thickness of the insulated wire (A) of the straight section (part other than the bent section) and the thickness of the insulated wire in the bent section were measured. The thickness of the thinnest part of the insulated wire in the bent section was defined as thickness (B). The film thickness retention rate was calculated according to the following formula: Film thickness retention rate [%] = Thickness (B) / Thickness (A) × 100 The thickness of the insulated wire (A) is the same as the thickness of the insulated wire before bending in the bent section. The film thickness retention rate is the ratio of the thickness of the insulating coating in the bent section (B) to the thickness of the insulating coating before bending (A). Insulated wires with a high film thickness retention rate can exhibit excellent electrical properties because the insulating coating in the bent section sufficiently maintains the thickness of the insulating coating before bending.

[0119] (Electrified Lifetime) Arrow pair samples were prepared from insulated wires, and voltages of 2500V (10kHz) and 2500V (10kHz) were applied between the two wires of the arrow pair sample in a constant temperature bath set to 40°C. The time until dielectric breakdown was defined as the energized lifetime.

[0120]

[0121] 1. Insulated wire 11. Bent section 2. Flat rectangular conductor 3. Insulation coating

Claims

An insulated electric wire comprising a rectangular conductor (A) and an insulating coating (B) formed on the outer circumference of the rectangular conductor (A), The insulating coating (B) is formed from a resin composition containing a fluorine-containing copolymer (I) and amorphous silica particles (II). The fluorine-containing copolymer (I) contains tetrafluoroethylene units and units based on at least one monomer selected from the group consisting of hexafluoropropylene and fluoroalkyl vinyl ethers. The yield strength of the insulating coating (B) is 12.0 MPa or higher. Insulated wire. 　 The insulated wire according to claim 1, wherein the amorphous silica particles (II) are amorphous silica particles surface-treated with a silane coupling agent. 　 The insulated wire according to claim 1 or 2, wherein the amorphous silica particles (II) are amorphous silica particles surface-treated with alkylchlorosilane. 　 An insulated wire according to any one of claims 1 to 3, wherein the average primary particle diameter of amorphous silica particles (II) is 5 to 70 nm, and the amorphous silica particles (II) are fumed silica. 　 An insulated wire according to any one of claims 1 to 4, wherein the melt flow rate of the fluorine-containing copolymer (I), measured under the conditions of 372°C and a 5 kg load, is 25 to 120 g / min. 380°C for 100 seconds －１ An insulated electric wire according to any one of claims 1 to 5, wherein the shear viscosity of the resin composition, as measured at a shear rate, is 300 to 1700 Pa·s. 　 An insulated electric wire according to any one of claims 1 to 6, wherein the mass ratio ((I) / (II)) of the fluorine-containing copolymer (I) to amorphous silica particles (II) in the resin composition is 99.0 / 1.0 to 85.0 / 15.

0. The insulated wire according to any one of claims 1 to 7, wherein the weight loss rate when the resin composition is heated at 360°C for 1 hour is less than 5,000 ppm by mass. 　 An insulated electric wire according to any one of claims 1 to 8, wherein the thickness of the insulating coating (B) is 30 μm or more and 300 μm or less. 　 A coil made of an insulated wire according to any one of claims 1 to 9. 　 A motor comprising a coil made of an insulated wire as described in any one of claims 1 to 9. 　 A method for manufacturing an insulated wire according to any one of claims 1 to 9, A manufacturing method for forming an insulating coating (B) by extruding the resin composition onto the outer circumference of a rectangular conductor (A).

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