JP2021002459A - Rectangular magnet wire and coil - Google Patents

Abstract

To provide a rectangular magnet wire with a rectangular conductor and a coating layer strongly adhered, which is less likely to swell or crack in the coating layer coating any of a flexure peripheral part and a flexure inner circumferential part even if bent in an edgewise direction.SOLUTION: A rectangular magnet wire includes a rectangular conductor and a coating layer formed on an outer periphery of the rectangular conductor. The coating layer includes a copolymer containing a tetrafluoroethylene unit and a fluoroalkylvinyl ether unit, and is heat-treated at a temperature equal to or higher than a melting point of the copolymer.SELECTED DRAWING: None

Description

The present disclosure relates to flat magnet wires and coils.

In order to form a coating on a coil wire, an electric wire, a cable or the like, a method of coating and molding a fluororesin on a core wire by a coating molding method such as a melt extrusion molding method is known.

For example, Patent Document 1 is based on tetrafluoroethylene having a carboxyl group at the end of the main chain on a core wire made of metal, a melt flow rate of 20 g / 10 minutes or more, and a melting point of 295 ° C. or less. It comprises a step of coating and molding a copolymer containing a polymerization unit and a polymerization unit based on perfluoro (alkyl vinyl ether), and the metal is selected from the group consisting of copper, stainless steel, aluminum, iron, and alloys thereof. It is described that a laminate such as a coil wire or a cable can be produced by a method for producing a laminate characterized by being at least one type.

Japanese Unexamined Patent Publication No. 2013-78947

In the present disclosure, the flat conductor and the coating layer are firmly adhered to each other, and even when bent in the edgewise direction, the coating layer covering either the bending outer peripheral portion or the bending inner peripheral portion is swelled and swelled. An object of the present invention is to provide a flat magnet wire that is less likely to crack.

According to the present disclosure, a flat conductor and a coating layer formed on the outer periphery of the flat conductor are provided, and the coating layer contains a copolymer containing a tetrafluoroethylene unit and a fluoroalkyl vinyl ether unit. , A flat magnet wire which is a coating layer heat-treated at a temperature equal to or higher than the melting point of the copolymer is provided.

The melt flow rate of the copolymer is preferably 0.1 to 70 g / 10 minutes, and more preferably less than 10 g / 10 minutes.
The content of the fluoroalkyl vinyl ether unit in the copolymer is preferably 3.0 to 8.0% by mass with respect to all the monomer units.
The copolymer has a functional group, the functional groups of the copolymer is preferably a 5 to 1,300 pieces 10 ⁶ per carbon atom.
The thickness of the coating layer is preferably 30 to 100 μm.

Further, according to the present disclosure, a coil including the above-mentioned flat magnet wire is provided.

According to the present disclosure, the flat conductor and the coating layer are firmly adhered to each other, and even when bent in the edgewise direction, the coating layer covering either the bending outer peripheral portion or the bending inner peripheral portion can be used. It is possible to provide a flat magnet wire that is less likely to swell and crack.

FIG. 1 is a cross-sectional view showing an example of a flat magnet wire. FIG. 2 is a schematic view of a bending jig used for an edgewise bending test.

Hereinafter, specific embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

The flat magnet wire of the present disclosure is an electric wire used for passing an electric current when an electric device converts electric energy and magnetic energy with each other. The flat magnet wire of the present disclosure can increase the space factor of the coil as compared with the round wire.

FIG. 1 is a cross-sectional view showing an example of a flat magnet wire. As shown in FIG. 1, the flat magnet wire 1 of the present disclosure includes a flat conductor 10 and a coating layer 11 formed on the outer periphery of the flat conductor 10.

The flat conductor 10 is not particularly limited as long as it is made of a conductive material, but can be made of a material such as copper, copper alloy, aluminum, aluminum alloy, iron, silver, nickel, and copper or copper alloy. It is preferable that it is composed of. Further, a conductor plated with silver plating, nickel plating or the like can also be used.

The shape of the flat conductor is not particularly limited as long as the cross section is a substantially rectangular flat wire shape. The corners of the cross section of the flat conductor may be right-angled, or the corners of the cross section of the flat conductor may be rounded. The flat conductor may be a single wire, an aggregated wire, a stranded wire, or the like as long as the cross section of the entire conductor is substantially rectangular, but it is preferably a single wire.

The width of the cross section of the flat conductor may be 1 to 75 mm, and the thickness of the cross section of the flat conductor may be 0.1 to 10 mm. The outer peripheral diameter of the flat conductor may be 6.5 mm or more, and may be 200 mm or less. Further, the ratio of the width to the thickness may be more than 1 and 30 or less. The flat magnet wire of the present disclosure can be bent even when the flat conductor has such a shape, the flat conductor and the coating layer are firmly adhered to each other, and the flat conductor is bent in the edgewise direction. The coating layer that covers both the outer peripheral portion and the bent inner peripheral portion is less likely to swell and crack.

The coating layer 11 formed on the outer periphery of the flat conductor 10 contains a copolymer containing a tetrafluoroethylene unit and a fluoroalkyl vinyl ether unit, and is heat-treated at a temperature equal to or higher than the melting point of the copolymer.

In the fields of electrical equipment and electronic equipment, higher performance, lighter, thinner, shorter and smaller equipment, and power saving are progressing. Along with this, there is a demand for miniaturization and high performance of coils, inductors, various motors and the like. In particular, inductors and motors for automobiles are being miniaturized by winding a flat magnet wire compactly. However, in motors used in electric vehicles, the working voltage tends to increase from about 400 V to about 1000 V for the purpose of miniaturization and high performance. Therefore, when a conventional flat magnet wire such as an enamel wire is used, partial discharge may occur between the windings, which may lead to dielectric breakdown. Since the coating layer of the flat magnet wire of the present disclosure is formed of the above-mentioned copolymer, partial discharge is unlikely to occur even when the working voltage of the motor is high.

Further, the edgewise coil is formed by bending a flat magnet wire in the edgewise direction (width direction of the flat magnet wire) and winding it vertically. Since the edgewise coil has a high space factor of the conductor, it leads to miniaturization and high efficiency of electric equipment. However, when the flat magnet wire is bent in the edgewise direction, the coating layer covering the bending outer peripheral portion is stretched more than the coating layer covering the bending inner peripheral portion, and is peeled off from the flat conductor to cause swelling. Or cracks are likely to occur. Bulging or cracking reduces insulation properties. For example, in an enamel wire obtained by baking a polyimide resin on a conductor, cracks or swelling may occur at the bending outer peripheral portion. In the flat magnet wire of the present disclosure, since the coating layer is formed of the above copolymer and the coating layer is heat-treated, the outer peripheral portion of the bending is covered even when the coating layer is bent in the edgewise direction. The coating layer is less likely to swell and crack.

Further, when the flat magnet wire is bent in the edgewise direction, the coating layer covering the bending inner peripheral portion shrinks more than the coating layer covering the bending outer peripheral portion, and is peeled off from the flat conductor and swells (wrinkles). Or cracks may occur due to wrinkles. For example, in an extruded coated electric wire in which a thermoplastic resin is extruded onto a flat conductor to form a coating layer by melt extrusion molding, swelling (wrinkles) may occur in the bent inner peripheral portion. In the flat magnet wire of the present disclosure, since the coating layer is formed of the above-mentioned copolymer and the coating layer is heat-treated, even when the coating layer is bent in the edgewise direction, the bent inner peripheral portion is formed. The coating layer to be coated is less likely to swell and crack.

The melt flow rate of the copolymer is preferably 0.1 to 70 g / 10 minutes, more preferably 60 g / 10 minutes or less, still more preferably 50 g / 10 minutes or less, and particularly preferably 40 g / 10 minutes. Minutes or less, most preferably 30 g / 10 minutes or less. When the melt flow rate of the copolymer is within the above range, a flat magnet wire having a coating layer having a uniform thickness can be obtained, and a coating layer having excellent stress crack resistance and less swelling and cracking can be obtained. A flat magnet wire can be obtained.

Further, the melt flow rate of the copolymer may be less than 10 g / 10 minutes. The coating layer of the flat magnet wire of the present disclosure is formed, for example, by coating a copolymer on a flat conductor and then heat-treating it at a temperature equal to or higher than the melting point of the copolymer. Therefore, even when the melt flow rate of the copolymer is relatively small, a flat magnet wire having a coating layer having a uniform thickness can be obtained by the action of heat treatment, and also has excellent stress crack resistance, swelling and swelling. It is possible to obtain a flat magnet wire having a coating layer in which cracks are unlikely to occur. In particular, when the melt flow rate of the copolymer is relatively small and the copolymer has a functional group such as -COF at the end of the main chain, the above effect is remarkably exhibited.

In the present disclosure, the melt flow rate flows out per 10 minutes from a nozzle having an inner diameter of 2.1 mm and a length of 8 mm under a load of 372 ° C. and 5 kg using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) according to ASTM D1238. It is a value obtained as the mass (g / 10 minutes) of the polymer to be used.

The content of the fluoroalkyl vinyl ether (FAVE) unit of the copolymer is preferably 1.0 to 10.0% by mass, more preferably 3.0% by mass or more, and further, based on all the monomer units. It is preferably 3.4% by mass or more, still more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, most preferably 5.0% by mass or more, and more preferably. Is 8.0% by mass or less, more preferably 7.0% by mass or less, still more preferably 6.5% by mass or less, particularly preferably 6.0% by mass or less, and most preferably. It is less than 5.4% by mass. When the content of the FAVE unit of the copolymer is within the above range, a flat magnet wire having a coating layer having a uniform thickness can be obtained, and the coating has excellent stress crack resistance and is less likely to swell and crack. A flat magnet wire having a layer can be obtained. In particular, when the copolymer has a functional group such as -COF at the end of the main chain, if the content of the FAVE unit of the copolymer is within the above range, the heat treatment results in high adhesion and swelling and cracking occur. The effect of suppressing is remarkably exhibited.

The content of the tetrafluoroethylene (TFE) unit of the copolymer is preferably 99.0 to 90.0% by mass, more preferably 97.0% by mass or less, and further, based on the total monomer units. It is preferably 96.6% by mass or less, still more preferably 96.5% by mass or less, particularly preferably 96.0% by mass or less, most preferably 95.0% by mass or less, and more preferably. Is 92.0% by mass or more, more preferably 93.0% by mass or more, still more preferably 93.5% by mass or more, particularly preferably 94.0% by mass or more, and most preferably. It is more than 94.6% by mass. When the content of the TFE unit of the copolymer is within the above range, a flat magnet wire having a coating layer having a uniform thickness can be obtained, and the coating has excellent stress crack resistance and is less likely to swell and crack. A flat magnet wire having a layer can be obtained.

In the present disclosure, the content of each monomer unit in the copolymer is measured by the ¹⁹ F-NMR method.

The copolymer forming the coating layer is a melt-processable fluororesin. Melt processability means that a polymer can be melted and processed using conventional processing equipment such as an extruder and an injection molding machine.

As the FAVE constituting the FAVE unit, the general formula (1):
CF ₂ = CFO (CF ₂ CFY ¹ O) _p − (CF ₂ CF ₂ CF ₂ O) _q −Rf (1)
(In the formula, 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.) The monomer represented by and the general formula (2):
CFX = CXOCF ₂ OR ¹ (2)
(In the formula, X represents the same or different, H, F or CF ₃ , and R ¹ represents at least one atom selected from the group consisting of linear or branched H, Cl, Br and I. It may contain 1 to 2 fluoroalkyl groups having 1 to 6 carbon atoms, or 1 to 2 atoms of at least one selected from the group consisting of H, Cl, Br and I. It can be mentioned at least one selected from the group consisting of monomers represented by (representing a cyclic fluoroalkyl group having 5 or 6 carbon atoms).

Among them, as the FAVE, the monomer represented by the general formula (1) is preferable, and from perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether) (PEVE) and perfluoro (propyl vinyl ether) (PPVE). At least one selected from the group consisting of PEVE and PPVE is more preferable, and at least one selected from the group consisting of PEVE and PPVE is further preferable, and PPVE is particularly preferable.

The copolymer can also contain monomeric units derived from monomers copolymerizable with TFE and FAVE. In this case, the content of the monomer copolymerizable with TFE and FAVE is preferably 0 to 10% by mass, more preferably 0.1 to 1.8, based on the total monomer units of the copolymer. It is mass%.

As monomers copolymerizable with TFE and FAVE, HFP, CZ ¹ Z ² = CZ ³ (CF ₂ ) _n Z ⁴ (in the formula, Z ¹ , Z ² and Z ³ are the same or different, H Or F, Z ⁴ represents H, F or Cl, n represents an integer of 2 to 10), and CF ₂ = CF-OCH _2- Rf ¹ ( In the formula, Rf ¹ represents a perfluoroalkyl group having 1 to 5 carbon atoms), and an alkyl perfluorovinyl ether derivative represented by) can be mentioned. Of these, HFP is preferable.

As the copolymer, at least one selected from the copolymer consisting of only TFE units and FAVE units and the above-mentioned group consisting of TFE / HFP / FAVE copolymers is preferable, and the copolymer consists of only TFE units and FAVE units. Copolymers are more preferred.

From the viewpoint of heat resistance and stress crack resistance, the melting point of the copolymer is preferably 280 to 322 ° C, more preferably 285 ° C or higher, further preferably more than 295 ° C, and particularly preferably 300 ° C. The above is more preferably 315 ° C. or lower, and even more preferably 310 ° C. or lower. The higher the melting point of the copolymer, the higher the heat resistance. In particular, a copolymer having a melting point within the above range, in which a coating layer is formed using a copolymer having a functional group such as -COF at the end of the main chain, and the coating layer is set at a temperature equal to or higher than the melting point of the copolymer. It is presumed that the heat treatment makes it easier for the functional group at the end of the main chain to come into close contact with the flat conductor at the atomic level, and a coating layer that adheres more firmly to the flat conductor can be formed. The melting point can be measured using a differential scanning calorimeter [DSC].

The glass transition temperature (Tg) of the copolymer is preferably 70 to 110 ° C., more preferably 80 ° C. or higher, and more preferably 100 ° C. or lower. The glass transition temperature can be measured by dynamic viscoelasticity measurement.

From the viewpoint of partial discharge resistance, the relative permittivity of the copolymer is preferably 2.40 or less, more preferably 2.10 or less, and the lower limit is not particularly limited, but is preferably 1.80 or more. is there. The relative permittivity is a value obtained by measuring changes in resonance frequency and electric field strength at a temperature of 20 to 25 ° C. using a network analyzer HP8510C (manufactured by Hewlett-Packard Co., Ltd.) and a cavity resonator.

The copolymer used in the present disclosure can form a coating layer that adheres more firmly to a flat conductor, and even when bent in the edgewise direction, the coating layer that covers either the bending outer peripheral portion or the bending inner peripheral portion. Further, since it is possible to form a coating layer in which swelling and cracking are less likely to occur, -COOH (carboxyl group) may be provided at the end of the main chain. The number of -COOH the copolymer having a main chain terminus, carbon atoms 10 ⁶ per, preferably 1 to 100, more preferably 4 or more, and still more preferably 8 or more, more The number is preferably 85 or less, and more preferably 70 or less. The number of -COOH the copolymer having a main chain terminus, carbon atoms 10 ⁶ per, may be less than 50. Even if the number of −COOH is less than 50, if the copolymer has −COF at the end of the main chain, a coating layer that adheres more firmly to the flat conductor can be formed. Even if the number of -COOH is less than 50, if the copolymer has a functional group other than -COOH at the end of the main chain or the end of the side chain, it adheres more firmly to the flat conductor. A coating layer can be formed.

The copolymer used in the present disclosure can form a coating layer that adheres more firmly to a flat conductor, and even when bent in the edgewise direction, the coating layer that covers either the bending outer peripheral portion or the bending inner peripheral portion. Also, since it is possible to form a coating layer in which swelling and cracking are less likely to occur, -COF may be provided at the end of the main chain. The number of -COF the copolymer having a main chain terminus, carbon atoms 10 ⁶ per, preferably 20 to 100, more preferably 25 or more, further preferably 29 or more, more The number is preferably 85 or less, and more preferably 70 or less.

The copolymer used in the present disclosure can form a coating layer that adheres more firmly to a flat conductor, and even when bent in the edgewise direction, the coating layer that covers either the bending outer peripheral portion or the bending inner peripheral portion. Also, since it is possible to form a coating layer in which swelling and cracking are less likely to occur, -COOH (carboxyl group) and -COF may be provided at the end of the main chain. The total number of -COOH and -COF copolymer having a main chain terminus, carbon atoms 10 ⁶ per, preferably 21 to 200, more preferably not more 29 or more, more preferably 37 The above is more preferably 170 or less, further preferably 140 or less, and particularly preferably less than 120.

The copolymer used in the present disclosure can form a coating layer that adheres more firmly to a flat conductor, and even when bent in the edgewise direction, the coating layer that covers either the bending outer peripheral portion or the bending inner peripheral portion. also, blistering and since the cracks can form more hardly causes the coating layer has a functional group, the functional groups of the copolymer is preferably a 5 to 1,300 pieces 10 ⁶ per carbon atom. The number of functional groups, the carbon atoms 10 ⁶ per, more preferably 50 or more, still more preferably at least 100, particularly preferably 200 or more, more preferably 1000 or less, further The number is preferably 800 or less, particularly preferably 700 or less, and most preferably 500 or less.

The functional group is a functional group existing at the main chain end or the side chain end of the copolymer, and a functional group existing in the main chain or the side chain, and preferably exists at the main chain end. Examples of the functional group include -CF = CF ₂ , -CF ₂ H, -COF, -COOH, -COOCH ₃ , -CONH ₂ , -CH ₂ OH, and the like, -CF ₂ H, -COF, and -COOH. , -COOCH ₃ and -CH ₂ OH, at least one selected from the group is preferred.

Infrared spectroscopy can be used to identify the type of functional group and measure the number of functional groups.

Specifically, the number of functional groups is measured by the following method. First, the copolymer is melted at 330 to 340 ° C. for 30 minutes and compression molded to prepare a film having a thickness of 0.25 to 0.25 mm. This film is analyzed by Fourier transform infrared spectroscopic analysis to obtain an infrared absorption spectrum of the copolymer, and a difference spectrum from a base spectrum which is completely fluorinated and has no functional group. From the absorption peak of a specific functional group appearing in this difference spectrum, the number N of functional groups per 1 × 10 ⁶ carbon atoms in the copolymer is calculated according to the following formula (A).
N = I × K / t (A)
I: Absorbance K: Correction coefficient t: Film thickness (mm)

For reference, Table 1 shows the absorption frequency, molar absorption coefficient, and correction coefficient for the functional groups in the present disclosure. The molar extinction coefficient was determined from the FT-IR measurement data of the low molecular weight model compound.

The absorption frequencies of -CH ₂ CF ₂ H, -CH ₂ COF, -CH ₂ COOH, -CH ₂ COOCH ₃ , and -CH ₂ CONH ₂ are shown in the table, respectively, -CF ₂ H, -COF, and-. It is several tens of Kaiser (cm ^-1 ) lower than the absorption frequencies of COOH free and -COOH bounded, -COOCH ₃ , and -CONH ₂ .
Therefore, for example, the number of functional groups of -COF is determined from the number of functional groups obtained from the absorption peak of absorption frequency 1883 cm ^-1 due to -CF ₂ COF and the absorption peak of absorption frequency 1840 cm ^-1 due to -CH ₂ COF. It is the total with the obtained number of functional groups.

The number of functional groups may be the total number of -CF = CF ₂ , -CF ₂ H, -COF, -COOH, -COOCH ₃ , -CONH ₂ and -CH ₂ OH, and may be the total number of -CF ₂ H, -COF, It may be the total number of -COOH, -COOCH ₃ and -CH ₂ OH.

The functional group is introduced into the copolymer by, for example, a chain transfer agent or a polymerization initiator used in producing the copolymer. For example, when alcohol is used as a chain transfer agent or a peroxide having a structure of -CH ₂ OH is used as a polymerization initiator, -CH ₂ OH is introduced at the end of the main chain of the copolymer. .. Further, by polymerizing a monomer having a functional group, the functional group is introduced into the side chain terminal of the copolymer.

The copolymer can be produced, for example, by a conventionally known method such as emulsion polymerization or suspension polymerization by appropriately mixing a monomer as a constituent unit thereof or an additive such as a polymerization initiator.

The coating layer 11 formed on the outer periphery of the flat conductor 10 is heat-treated at a temperature equal to or higher than the melting point of the copolymer. According to the study by the present inventors, after coating the copolymer around the flat conductor 10, the copolymer layer before the heat treatment for coating the flat conductor 10 is heat-treated at a temperature equal to or higher than the melting point of the copolymer. It has been found that by forming the coating layer 11, a flat magnet wire 1 in which the flat conductor 10 and the coating layer 11 are firmly adhered to each other can be obtained. That is, since the flat magnet wire 1 includes the coating layer 11 heat-treated at a temperature equal to or higher than the melting point of the copolymer, the flat conductor 10 and the coating layer 11 formed on the outer periphery of the flat conductor 10 are firmly adhered to each other. Therefore, even when the coating layer 11 is bent in the edgewise direction, swelling and cracking are unlikely to occur in the coating layer 11 that covers either the bending outer peripheral portion or the bending inner peripheral portion.

The thickness of the coating layer is not particularly limited, but is preferably 30 to 150 μm, and more preferably 50 to 100 μm from the viewpoint of insulating properties. In the flat magnet wire of the present disclosure, even if the coating layer is relatively thin, swelling and cracking are unlikely to occur in the coating layer covering the bent outer peripheral portion. Further, since the coating layer contains the above-mentioned copolymer, even if the coating layer is relatively thin, it exhibits sufficient insulating properties.

The coating layer may contain other components if necessary. Other components include cross-linking agents, antistatic agents, heat-stabilizing agents, foaming agents, foaming nucleating agents, antioxidants, surfactants, photopolymerization initiators, abrasion inhibitors, surface modifiers, pigments, etc. Agents and the like can be mentioned. The content of other components in the coating layer is preferably less than 1% by mass, more preferably 0.5% by mass or less, still more preferably 0.1% by mass, based on the mass of the above-mentioned copolymer. It is not more than mass%, and the lower limit is not particularly limited, but it may be 0% by mass or more. That is, the coating layer does not have to contain other components.

The content of the copolymer in the coating layer in the present disclosure is preferably more than 99% by mass, more preferably 99, with respect to the total content of the polymer in the coating layer from the viewpoint of partial discharge resistance. It is 5.5% by mass or more, more preferably 99.9% by mass or more, and the upper limit is not particularly limited, but may be 100% by mass or less. That is, the coating layer may contain only the above-mentioned copolymer as the polymer material, and the content of the copolymer in this case is 100% by mass with respect to the total content of the polymer in the coating layer. ..

Further, the coating layer may contain a fluoropolymer other than the above-mentioned copolymer, if necessary. However, from the viewpoint of heat resistance, stress crack resistance, partial discharge resistance, etc., it is preferable to contain as little fluoropolymer as possible other than the above copolymer. The content of the fluoropolymer other than the copolymer in the coating layer is preferably less than 1% by mass, more preferably 0.5% by mass or less, and further preferably 0.5% by mass or less, based on the mass of the copolymer. It is preferably 0.1% by mass or less, and the lower limit is not particularly limited, but may be 0% by mass or more. That is, the coating layer does not have to contain a fluoropolymer other than the above-mentioned copolymer.

In the flat magnet wire of the present disclosure, it is preferable that the flat conductor and the coating layer are in contact with each other. The flat magnet wire of the present disclosure exhibits excellent insulating properties because the coating layer does not easily float from the flat conductor even if a primer layer is not formed. The formation of the primer layer is not preferable because the dielectric constant becomes high. Further, the flat magnet wire of the present disclosure may further include another layer formed on the outer periphery of the coating layer. Examples of the other layer include a layer containing a thermoplastic resin having a melting point lower than that of the above-mentioned copolymer contained in the coating layer. In particular, by providing a layer containing a thermoplastic resin having a relatively low melting point as the outermost layer, the flat magnet wire of the present disclosure can be used as a self-bonding flat magnet wire.

The flat magnet wire of the present disclosure is, for example, a step of coating the periphery of a flat conductor with the above-mentioned copolymer to obtain a flat-angle conductor coated with the above-mentioned copolymer, and a common weight before heat treatment for coating the flat-angle conductor. The coalesced layer can be suitably produced by a production method including a step of heat-treating at a temperature equal to or higher than the melting point of the copolymer.

Examples of the method of coating the periphery of the flat conductor with the copolymer include a method of extruding the copolymer onto the flat conductor by melt extrusion (extrusion molding method), and a wrapping tape containing the copolymer. Examples thereof include a method of winding around a flat conductor (wrapping method), but an extrusion molding method is preferable because the flat conductor and the coating layer are firmly adhered to each other. When the copolymer is coated by the extrusion molding method, an extrusion coating layer having a history of being heated twice or more above the melting point of the copolymer is finally formed as a coating layer.

The temperature at which the flat conductor is coated with the copolymer is preferably 340 to 410 ° C, more preferably 380 to 400 ° C, from the viewpoint of adhesion between the flat conductor and the coating layer.

After coating the flat conductor with the copolymer, preferably, the flat conductor coated with the copolymer is once cooled and subjected to heat treatment.

The heat treatment can be performed by heating the flat conductor coated with the above-mentioned copolymer in a batch type or a continuous type by using a hot air circulation furnace or a heating furnace using high-frequency induction heating. It can also be carried out by the salt bath method. In the salt bath method, a flat conductor coated with the above-mentioned copolymer is passed through a molten salt and heated. Examples of the molten salt include a mixture of potassium nitrate and sodium nitrate.

The heating temperature during the heat treatment is a temperature equal to or higher than the melting point of the copolymer, preferably 15 ° C. or higher than the melting point of the copolymer, and more preferably 30 ° C. higher than the melting point of the copolymer. It is above the temperature, preferably 360 ° C. or lower, and more preferably 350 ° C. or lower.

The heat treatment time is preferably 0.1 to 5 minutes, more preferably 0.5 minutes or more, and more preferably 3 minutes or less.

The time for heat-treating the coating layer when bending a flat magnet wire is not particularly limited, and it is before bending the flat magnet wire, after bending the flat magnet wire, or for the flat magnet wire. The heat treatment can be performed both before and after the bending process. For example, by heat-treating the coating layer before bending the flat magnet wire, even if the flat magnet wire is bent in the edgewise direction after the heat treatment, the bending outer peripheral portion and the bending inner circumference are performed. The swelling and cracking of the coating layer covering the portion can be further suppressed.

The flat magnet wire of the present disclosure can be wound and used as a coil. The coil of the present disclosure may be a coil in which a flat magnet wire is wound, and even if the flat magnet wire is bent and wound in the edgewise direction (width direction), the flat magnet wire is wound in the flatwise direction (flatwise direction). It may be bent in the thickness direction) and wound. Even when the flat magnet wire of the present disclosure is bent in the edgewise direction, swelling and cracking are unlikely to occur in the coating layer covering both the outer peripheral portion and the inner peripheral portion of the bending. Therefore, the coil of the present disclosure is preferably an edgewise coil formed by bending and winding a flat magnet wire in the edgewise direction.

The flat magnet wires and coils of the present disclosure can be suitably used for electric or electronic devices such as motors, generators and inductors. Further, the flat magnet wire and coil of the present disclosure can be suitably used for an in-vehicle electric device such as an in-vehicle motor, an in-vehicle generator, and an in-vehicle inductor, or an in-vehicle electronic device.

Although the embodiments have been described above, it will be understood that various modifications of the embodiments and details are possible without departing from the purpose and scope of the claims.

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

Each numerical value of the example was measured by the following method.

<Melt flow rate (MFR)>
According to ASTM D1238, the mass of the copolymer (g) flowing out from a nozzle having an inner diameter of 2.1 mm and a length of 8 mm per 10 minutes under a load of 372 ° C. and 5 kg using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). / 10 minutes) was requested.

<Composition of copolymer>
The contents of tetrafluoroethylene (TFE) units and perfluoro (propyl vinyl ether) (PPVE) units in the copolymer were measured by the ¹⁹ F-NMR method.

<Melting point>
It was determined as the temperature corresponding to the maximum value in the heat of fusion curve when the temperature was raised at a rate of 10 ° C./min using a differential scanning calorimeter [DSC].

<Number of functional groups>
The copolymer was melted at 330 to 340 ° C. for 30 minutes and compression molded to prepare a film having a thickness of 0.25 to 0.25 mm. This film was scanned 40 times with a Fourier transform infrared spectrophotometer [FT-IR (trade name: 1760X type, manufactured by PerkinElmer), analyzed to obtain an infrared absorption spectrum, and completely fluorinated to perform functional groups. A difference spectrum from the base spectrum in which is absent was obtained. From the absorption peak of a specific functional group appearing in the difference spectrum, in accordance with the following formula (A), it was calculated functionality N carbon atoms 10 per ⁶ in the copolymer.

N = I × K / t (A)
I: Absorbance K: Correction coefficient t: Film thickness (mm)

For reference, Table 2 shows the absorption frequency, molar absorption coefficient, and correction coefficient for the functional groups in the present disclosure. The molar extinction coefficient was determined from the FT-IR measurement data of the low molecular weight model compound.

<Voltage band>
A dielectric breakdown test was conducted and used as a guideline for voltage band. The dielectric breakdown test conforms to JIS C 3216-5, and the dielectric breakdown tester No. 1 manufactured by Yasuda Seiki Seisakusho Co., Ltd. It was measured using 204. A copper foil tape having a width of 1 cm and a length of 2 cm was wrapped around a portion 7.5 cm from the end of a flat magnet wire cut to a length of 20 cm, and the coating layer having a width of 1 cm was peeled off to expose the conductor, which was used as a sample. One of the electrodes of the testing machine was connected to the copper foil tape part, and the other was connected to the exposed conductor part at the end. The measurement was carried out in an atmosphere of room temperature of 25 ° C. and relative humidity of 50% at a step-up speed of 500 V / sec. The results are shown in Table 3.

<Partial discharge start voltage>
Using a partial discharge measuring device (DAC-PD-7 manufactured by Soken Denki Co., Ltd.), the surfaces including the long sides of the cross-sectional shape of the two flat magnet wires are overlapped over a length of 150 mm so that there is no gap. A combined test piece was prepared, and measurement was performed by applying a 50 Hz sine wave AC voltage between the two conductors. The step-up speed was 50 V / sec, the step-down speed was 50 V / sec, the voltage holding time was 0 sec, and the voltage at the time when a discharge of 10 pC or more occurred was defined as the partial discharge start voltage. The results are shown in Table 3.

<Core wire adhesion strength>
The tensile force when the coating layer 76 mm was pulled out from the flat magnet wire at 12.7 mm / min was measured by a method based on MIL C-17, and the core wire adhesion strength (kg / 3 inch) was determined.
In Table 3, when the coating layer was easily pulled out from the flat magnet wire and the tensile force could not be measured, it was described as “0”. Further, when the flat copper wire and the coating layer are strongly adhered to each other and the coating layer is broken during the measurement and the tensile force cannot be measured, it is described as "material failure".

<Edgewise bending test>
As shown in FIG. 2, the flat magnet wire 1 produced in Examples and Comparative Examples was placed on the V block 21 so that the short side of the cross-sectional shape of the flat magnet wire 1 was in contact with the V block 21. A push metal fitting 22 is applied to the central portion of the flat magnet wire 1 on the V block 21 and a load is applied in the edgewise direction (width direction) so that the bending radius (inner diameter) becomes 3.50 mm (single diameter). , 90 degrees bent and edgewise bent.
The bent outer peripheral portion and inner peripheral portion of the bent flat magnet wire were visually observed and evaluated according to the following criteria.
(Swelling)
X: A bulge was observed on the outer peripheral portion or the inner peripheral portion.
〇: No swelling was observed on the outer and inner circumferences.
(crack)
X: A crack was observed in the outer peripheral portion or the inner peripheral portion.
〇: No cracks were observed on the outer and inner circumferences.

Comparative Example 1
A tetrafluoroethylene (TFE) / perfluoro (propyl vinyl ether) (PPVE) copolymer having the characteristics shown in Table 3 is extruded into a flat copper wire (thickness: 1.95 mm, width: 3.36 mm). ), A die temperature of 390 ° C. and a take-up speed of 2 m / min were extruded to prepare a flat magnet wire provided with a coating layer. The thickness of the coating layer was 75 μm. The obtained flat magnet wire was evaluated by the above method. The results are shown in Table 3.
In the edgewise bending test of the obtained flat magnet wire, swelling was observed in the bending inner peripheral portion.

Comparative Examples 2-4
A flat magnet wire was produced in the same manner as in Comparative Example 1 except that the copolymer was changed to a copolymer having the characteristics shown in Table 3. The obtained flat magnet wire was evaluated by the above method. The results are shown in Table 3.
In the edgewise bending processing test of the obtained flat magnet wire, swelling was observed in the bending inner peripheral portion in all the comparative examples.

Example 1
A tetrafluoroethylene (TFE) / perfluoro (propyl vinyl ether) (PPVE) copolymer having the characteristics shown in Table 3 is extruded into a flat copper wire (thickness: 1.95 mm, width: 3.36 mm). ), Extruded at a die temperature of 390 ° C. and a take-up rate of 2 m / min to prepare a flat copper wire coated with a coating layer containing a copolymer.

Next, the flat copper wire coated with the coating layer is cooled to room temperature and then heat-treated by passing it through a hot air circulation furnace under the conditions shown in Table 3, and a flat magnet provided with the heat-treated coating layer. A wire was made. The obtained flat magnet wire was evaluated by the above method. The results are shown in Table 3.

Examples 2-7
A flat magnet wire was produced in the same manner as in Example 1 except that the copolymer was changed to a copolymer having the characteristics shown in Table 3 and the heat treatment conditions were changed as shown in Table 3. The obtained flat magnet wire was evaluated by the above method. The results are shown in Table 3.

In Table 3, the description "COOH + COF (pieces / C100 thousands)" are to carbon atoms 10 ⁶ copolymer, represents the sum of -COOH and the number of -COF of main chain terminal of the copolymer. Further, _{"COOH + COF + CH 2 OH +} CF 2 H + CO 2 CH 3 ( pieces / C100 thousands)" and the description of, for 10 ⁶ carbon atoms in the copolymer, the main chain terminal of the copolymer -COOH, -COF, - It represents the total number of CH ₂ OH, -CF ₂ H and -COOCH ₃ .

1 Flat magnet wire 10 Flat conductor 11 Coating layer 21 V block 22 Push bracket

Claims (7)

A flat conductor and a coating layer formed on the outer periphery of the flat conductor are provided, and the coating layer contains a copolymer containing a tetrafluoroethylene unit and a fluoroalkyl vinyl ether unit, and is composed of the copolymer. A flat magnet wire that is a coating layer that has been heat-treated above its melting point. The flat magnet wire according to claim 1, wherein the melt flow rate of the copolymer is 0.1 to 70 g / 10 minutes. The flat magnet wire according to claim 1 or 2, wherein the melt flow rate of the copolymer is less than 10 g / 10 minutes. The flat magnet wire according to any one of claims 1 to 3, wherein the content of the fluoroalkyl vinyl ether unit in the copolymer is 3.0 to 8.0% by mass with respect to all the monomer units. The flat magnet wire according to any one of claims 1 to 4, wherein the copolymer has a functional group, and the number of functional groups of the copolymer is ⁵ to 1300 per 106 carbon atoms. The flat magnet wire according to any one of claims 1 to 5, wherein the coating layer has a thickness of 30 to 100 μm. A coil comprising the flat magnet wire according to any one of claims 1 to 6.

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