Thermoplastic polyimide and insulated wires

Abstract

A thermoplastic polyimide is provided that can be used to form an insulating film with excellent film thickness accuracy and heat resistance. [Solution] The thermoplastic polyimide of this disclosure has a repetitive structural unit containing an imide bond. The repetitive structural unit satisfies all of the following (a) to (c). (a) The main chain contains 6 to 10 aromatic rings. (b) Six to ten of the aforementioned aromatic rings include at least one substituted aromatic ring in which at least one hydrogen atom is substituted with an alkyl group, The total number of carbon atoms in the alkyl groups of all the substituted aromatic rings is between 2 and 6. (c) The six to ten aforementioned aromatic rings include divalent aromatic rings linked by ortho-coordination or meta-coordination.

Description

[Technical Field]

[0001] This disclosure relates to thermoplastic polyimide and insulated wires. [Background technology]

[0002] Polyimide possesses excellent mechanical properties and heat resistance. Therefore, it is widely used as an insulating material in various components (e.g., industrial materials, automobiles, electrical and electronic equipment, etc.).

[0003] Patent Document 1 discloses a molded article. This molded article contains a specific polyimide-based thermoplastic resin P and a specific fluoropolymer-based thermoplastic resin F in specific proportions. The fluoropolymer-based thermoplastic resin F is dispersed in the polyimide-based thermoplastic resin P in a state where the average dispersed particle size is less than 10 μm. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2024 / 048726 [Overview of the project] [Problems that the invention aims to solve]

[0005] The molded product disclosed in Patent Document 1 uses two types of thermoplastic resins. As a result, the heat resistance of the resin interface is poor. Consequently, cracks may occur at the resin interface at high temperatures. In other words, the heat resistance of the molded product disclosed in Patent Document 1 may not be sufficient.

[0006] The embodiments of this disclosure have been made in view of the above, and aim to provide a thermoplastic polyimide and an insulated wire that can be used to make an insulating coating with excellent film thickness accuracy and heat resistance. [Means for solving the problem]

[0007] The following embodiments are included as means for solving the above problems. <1> It has a repeating structural unit containing an imide bond, The aforementioned repeating structural unit satisfies all of the following conditions (a) to (c): a thermoplastic polyimide. (a) The main chain contains 6 to 10 aromatic rings. (b) Six to ten of the aforementioned aromatic rings include at least one substituted aromatic ring in which at least one hydrogen atom is substituted with an alkyl group, The total number of carbon atoms in the alkyl groups of all the substituted aromatic rings is between 2 and 6. (c) The six to ten aforementioned aromatic rings include divalent aromatic rings linked by ortho-coordination or meta-coordination. <2> The aforementioned repeating unit has a repeating unit represented by the following formula (I), <1> The thermoplastic polyimide described above.

[0008] [ka]

[0009] In formula (I), A 1 , A 2 , A 3 and A 4 Each of these independently represents a single bond, an ether group, a carbonyl group, a sulfonyl group, or an isopropylidene group. 1 and R 2 Each independently represents an alkyl group. n and m independently represent integers from 1 to 4. 1 The number of carbon atoms in the alkyl group and m R 2 The total number of carbon atoms in the alkyl group is between 2 and 6. In equation (I), X represents a group represented by the following equations (X-1), (X-2), (X-3), or (X-4).

[0010] [ka]

[0011] In Formula (X-1) to Formula (X-4), * indicates the bonding position. In Formula (I), Y represents a group represented by the following Formula (Y-1), Formula (Y-2), Formula (Y-3), Formula (Y-4), Formula (Y-5), Formula (Y-6), Formula (Y-7), or Formula (Y-8).

[0012]

Chemical formula

[0013] In Formula (Y-1) to Formula (Y-8), * indicates the bonding position. At least one of the substituted or unsubstituted phenylene group and naphthylene group constituting the main chain of Formula (I) is linked in a meta coordination or ortho coordination. <3> The thermoplastic polyimide according to <2> above, wherein the constitutional repeating unit represented by Formula (I) contains a constitutional repeating unit represented by the following Formula (I-1).

[0014]

Chemical formula

[0015] <4> The thermoplastic polyimide according to <3> above, wherein in Formula (I-1), Y is a group represented by Formula (Y-1) or Formula (Y-2). <5> The thermoplastic polyimide according to <4> above, wherein in Formula (I-1), Y is a group represented by Formula (Y-1). <6> The thermoplastic polyimide according to <2> above, wherein the constitutional repeating unit represented by Formula (I) contains a constitutional repeating unit represented by the following Formula (I-2).

[0016]

Chemical formula

[0017] <7> The thermoplastic polyimide according to <6> above, wherein in Formula (I-2), Y is a group represented by Formula (Y-1). <8> The glass transition temperature Tg is 230 °C or higher, and The melt flow rate measured at 400°C and a load of 1.05 kg in accordance with JIS K7210-1:2014 is 20 g / 10 min or more. <1> ~ <7> A thermoplastic polyimide as described in any one of the following. <9> It comprises a conductor and an insulating film covering the conductor, The insulating film, <1> ~ <8> The thermoplastic polyimide described in any one of the above, <1> Insulated wire as described above. <10> The ratio of the variation in the thickness of the insulating film to the average thickness of the insulating film is 7% or less. <9> Insulated wire as described above. <11> The insulating film is made of one type of thermoplastic polyimide, <9> or <10> Insulated wire as described above. [Effects of the Invention]

[0018] According to embodiments of this disclosure, thermoplastic polyimide and insulated wires are provided that can be used to form an insulating coating with excellent film thickness accuracy and heat resistance. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a cross-sectional view of an example of an insulated wire according to this disclosure. [Figure 2] Figure 2 is a schematic diagram of the insulated wire manufacturing apparatus of the embodiment. [Modes for carrying out the invention]

[0020] In this disclosure, the "~" symbol indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. In this disclosure, the term "process" includes not only independent processes but also any process that cannot be clearly distinguished from other processes, as long as its intended purpose is achieved. In this disclosure, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, it means the total amount of all substances present in the composition unless otherwise specified.

[0021] (1) Thermoplastic polyimide The thermoplastic polyimide of this disclosure (hereinafter also simply referred to as "thermoplastic polyimide") has a recurring unit comprising an imide bond. The recurring unit satisfies all of the following (a) to (c). (a) The main chain contains 6 to 10 aromatic rings. (b) Six to ten of the aforementioned aromatic rings include at least one substituted aromatic ring in which at least one hydrogen atom is substituted with an alkyl group, The total number of carbon atoms in the alkyl groups of all the substituted aromatic rings (hereinafter also referred to as the "total number of carbon atoms in the alkyl groups") is between 2 and 6. (c) The six to ten aforementioned aromatic rings include a divalent aromatic ring (hereinafter also referred to as a "non-para-coordinate aromatic ring") linked by ortho-coordination or meta-coordination.

[0022] In this disclosure, "thermoplastic polyimide" refers to a polyimide having thermoplastic properties. More specifically, "thermoplastic polyimide" refers to a polyimide whose main chain has divalent flexible linking groups (for example, an ether group (-O-), a carbonyl group (-CO-), a sulfonyl group (-SO2-), an isopropylidene group (-C(CH3)2-), a methylene group (-CH2-), a perfluoroisopropylidene group (-C(CF3)2-), etc.).

[0023] Because the thermoplastic polyimide of this disclosure has the above-described structure, it can be used to make an insulating film with excellent film thickness accuracy and heat resistance. This effect is presumed to be due to, but is not limited to, the following reasons. In this disclosure, the repetitive structural unit satisfies (a). When the repetitive structural unit satisfies (a), the thermoplastic polyimide of this disclosure can improve the heat resistance of the insulating film. In this disclosure, the repetitive structural unit satisfies (b) and (c). When the repetitive structural unit satisfies (b) and (c), the intermolecular forces are relatively weak, and the fluidity of the molten thermoplastic polyimide is improved. As a result, the thermoplastic polyimide of this disclosure can improve the film thickness accuracy of the insulating film. From the above, it is presumed that the thermoplastic polyimide of this disclosure can be used to make an insulating film with excellent film thickness accuracy and heat resistance.

[0024] The melt flow rate (hereinafter also referred to as "MFR") of thermoplastic polyimide is not particularly limited. From the viewpoint of improving the accuracy of the insulating film thickness, the MFR of thermoplastic polyimide is preferably 20 g / 10 min or more, more preferably 27 g / 10 min or more, and even more preferably 32 g / 10 min or more. The MFR of thermoplastic polyimide may be 40 g / 10 min or less. If the MFR of thermoplastic polyimide is 40 g / 10 min or less, sagging may occur in the molten insulating film coated on the conductor during the manufacture of the current collector, and the accuracy of the insulating film thickness may not be stable. The MFR of thermoplastic polyimide may be between 20 g / 10 min and 40 g / 10 min. MFR is measured at 400°C and under a load of 1.05 kg, in accordance with JIS K7210-1:2014.

[0025] The glass transition temperature (hereinafter also referred to as "Tg") of thermoplastic polyimide is not particularly limited. From the viewpoint of improving the heat resistance of the insulating film, the Tg of thermoplastic polyimide is preferably 230°C or higher, more preferably 235°C or higher, and even more preferably 240°C or higher. The Tg of thermoplastic polyimide may be 260°C or lower, 245°C or lower, or 235°C or lower. The Tg of thermoplastic polyimide may be between 230°C and 260°C. The method for measuring Tg is the same as that described in the examples.

[0026] It is preferable that the glass transition temperature (Tg) is 230°C or higher, and the melt flow rate, measured at 400°C and a load of 1.05 kg in accordance with JIS K7210-1:2014, is 20 g / 10 min or higher. This improves the film thickness accuracy and heat resistance of the insulating coating.

[0027] (1.1) Constituent repeating units The constituent repeating units of thermoplastic polyimide satisfy all of the following conditions (a) to (c). (a) The main chain contains 6 to 10 aromatic rings. (b) Six to ten of the aforementioned aromatic rings include at least one substituted aromatic ring in which at least one hydrogen atom is substituted with an alkyl group, The total number of carbon atoms in the alkyl groups of all the substituted aromatic rings (i.e., the total number of carbon atoms in the alkyl groups) is between 2 and 6. (c) Six to ten of the aforementioned aromatic rings include divalent aromatic rings (i.e., non-para-coordinate aromatic rings) linked by ortho-coordination or meta-coordination.

[0028] The number of aromatic rings in the main chain of the constituent repeating unit is between 6 and 10. If the number of aromatic rings is less than 6, the heat resistance of the insulating film may be insufficient. If the number of aromatic rings is more than 10, the synthesis of thermoplastic polyimide may become difficult. The number of aromatic rings may be between 6 and 8, or between 6 and 7. Examples of aromatic rings include phenylene groups, naphthylene groups, anthracenylene groups, and biphenylylene groups.

[0029] The number of substituted aromatic rings in the main chain of the constituent repeating unit is 1 or more, may be between 1 and 6, or may be 2. The number of alkyl groups in one substituted aromatic ring is 1 or more, and may be between 1 and 6, or 2. The total number of carbon atoms in all the alkyl groups of the substituted aromatic rings included in the main chain of the constituent repeating unit (i.e., the total number of carbon atoms in the alkyl groups) is between 2 and 6. If the total number of carbon atoms in the alkyl groups is 1, the heat resistance of the insulating film may be insufficient. If the total number of carbon atoms in the alkyl groups is greater than 6, the synthesis of thermoplastic polyimide may become difficult. The total number of carbon atoms in the alkyl groups may be between 2 and 4, may be 4, or may be 2. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl groups.

[0030] The number of divalent aromatic rings (i.e., non-para-coordinate aromatic rings) linked by ortho-coordination or meta-coordination in the main chain of the constituent repeating unit is 1 or more, may be 1 to 10, 1 to 4, 1 to 2, 2, or 1. The divalent aromatic rings linked by ortho-coordination or meta-coordination may or may not contain substituted aromatic rings. Divalent aromatic rings that are not non-para-coordinated may be linked by para coordination.

[0031] The repeating units of thermoplastic polyimides typically contain divalent linking groups that connect aromatic rings. These divalent linking groups are usually divalent flexible linking groups (e.g., ether groups, carbonyl groups, sulfonyl groups, isopropylidene groups, methylene groups, and perfluoroisopropylidene groups) and may have single bonds.

[0032] (1.1.1) Equation (I) The aforementioned repeating unit preferably has a repeating unit represented by the following formula (I). This allows the thermoplastic polyimide to be an insulating film with superior film thickness accuracy and heat resistance.

[0033] [ka]

[0034] In formula (I), A 1 , A 2 , A 3 and A 4 each independently represents a single bond, an ether group, a carbonyl group, a sulfonyl group, or an isopropylidene group. R 1 and R 2 each independently represents an alkyl group. n and m each independently represent an integer from 1 to 4. The total number of carbon atoms in the alkyl groups of n R 1 and the total number of carbon atoms in the alkyl groups of m R 2 (i.e., the total number of carbon atoms in the alkyl groups) is from 2 to 6. In formula (I), X represents a group represented by the following formula (X-1), formula (X-2), formula (X-3), or formula (X-4).

[0035]

Chemical formula

[0036] In formula (X-1) to formula (X-4), * indicates the bonding position. In formula (I), Y represents a group represented by the following formula (Y-1), formula (Y-2), formula (Y-3), formula (Y-4), formula (Y-5), formula (Y-6), formula (Y-7), or formula (Y-8).

[0037]

Chemical formula

[0038] In formula (Y-1) to formula (Y-8), * indicates the bonding position. At least one of the substituted or unsubstituted phenylene group and naphthylene group (i.e., the non-para-coordinated aromatic ring) constituting the main chain of formula (I) is linked in a meta coordination or ortho coordination.

[0039] The "substituted phenylene group" means that at least one hydrogen atom of the phenylene group is R 1 or R 2This indicates a phenylene group that is substituted with R. An "unsubstituted phenylene group" is one in which all hydrogen atoms of the phenylene group are R. 1 or R 2 This shows an unsubstituted phenylene group.

[0040] R 1 and R 2 Examples of alkyl groups represented by include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl groups. n and m each independently represent integers between 1 and 4. n and m can be between 1 and 2, or they can be 1. n and m may or may not be the same. n R 1 The number of carbon atoms in the alkyl group and m R 2 The total number of carbon atoms, including the alkyl group, is between 2 and 6. The total number of carbon atoms may be between 2 and 4, 4, or 2. Substituted or unsubstituted phenylene and naphthylene groups that are not para-coordinated aromatic rings may be linked by para coordination. The number of non-para-coordinate aromatic rings is 1 or more, and may be 1 to 10, 1 to 4, 1 to 2, 2, or 1. The non-para-coordinate aromatic ring may or may not contain a substituted phenylene group.

[0041] (1.1.1.1) Equation (I-1) It is preferable that the repetitive structural unit represented by formula (I) includes the repetitive structural unit represented by formula (I-1) below. This allows the thermoplastic polyimide to be an insulating film with superior film thickness accuracy.

[0042] [ka]

[0043] The constructive repeating unit represented by equation (I) may consist of constructive repeating units represented by equation (I-1).

[0044] In formula (I-1), Y is preferably a group represented by formula (Y-1) or formula (Y-2). This allows the thermoplastic polyimide to be an insulating film with superior film thickness accuracy and heat resistance.

[0045] In formula (I-1), Y is preferably the group represented by formula (Y-1). This allows the thermoplastic polyimide to be an insulating film with even better film thickness accuracy.

[0046] Specifically, examples of constructive repeating units represented by formula (I-1) include the constructive repeating unit represented by formula (I-1A) below, and the constructive repeating unit represented by formula (I-1B) below.

[0047] [ka]

[0048] (1.1.1.2) Equation (I-2) It is preferable that the repeating structural unit represented by formula (I) includes the repeating structural unit represented by formula (I-2) below. This allows the thermoplastic polyimide to be an insulating film with superior film thickness accuracy and heat resistance.

[0049] [ka]

[0050] The constructive repeating unit represented by equation (I) may consist of constructive repeating units represented by equation (I-2).

[0051] In formula (I-2), Y is preferably the group represented by formula (Y-1). This allows the thermoplastic polyimide to be an insulating film with superior heat resistance.

[0052] Specifically, examples of constructive repeating units represented by formula (I-2) include the constructive repeating unit represented by formula (I-2A) below.

[0053] [ka]

[0054] (1.2) Raw materials The thermoplastic polyimide resins of this disclosure can be obtained, for example, by polycondensation of a diamine (a) and an acid dianhydride (b). The reaction between the diamine (a) and the acid dianhydride (b) may be carried out in or without an organic solvent. Examples of reaction methods for the diamine (a) and the acid dianhydride (b) include a two-step synthesis method via a precursor polyamic acid and a one-step synthesis method of direct imidation. The reaction conditions may be known conditions. At least one of the diamine (a) and the acid dioxide (b) may be a biomass-derived compound.

[0055] Examples of diamine(a) include the diamine represented by formula (a-1), formula (a-2), formula (a-3), formula (a-4), formula (a-5), formula (a-6), formula (a-7), formula (a-8), and formula (a-9). Diamine(a) may be used alone or in combination of two or more types.

[0056] Diamine (a) has two amino groups in its molecule, and preferably has 3 to 9 divalent aromatic rings in the molecular chain between the two amino groups, more preferably 4 to 8 divalent aromatic rings, and even more preferably 5 to 7 divalent aromatic rings. Diamine (a) preferably contains divalent aromatic rings (non-para-coordinated aromatic rings) linked by ortho-coordination or meta-coordination.

[0057] The thermoplastic polyimide resin of this disclosure preferably contains structural units derived from diamine (a) and structural units derived from acid dianhydride (b). The thermoplastic polyimide resin of this disclosure preferably has 3 to 9 divalent aromatic rings in the structural units derived from diamine (a), more preferably 4 to 8 divalent aromatic rings, and even more preferably 5 to 7 divalent aromatic rings. Furthermore, the thermoplastic polyimide resin of this disclosure preferably contains divalent aromatic rings (non-para-coordinate aromatic rings) linked in ortho-coordinate or meta-coordinate within the structural units derived from diamine (a).

[0058] [ka]

[0059] Examples of dianhydride(b) include the dianhydride represented by formula (b-1), formula (b-2), formula (b-3), formula (b-4), formula (b-5), formula (b-6), formula (b-7), and formula (b-8). Dianhydride(b) may be used individually or in combination of two or more types.

[0060] [ka]

[0061] The repeating structural unit represented by formula (I-1A) is obtained by polycondensation of the diamine represented by formula (a-1) and the acid dianhydride represented by formula (b-1b). The repeating structural unit represented by formula (I-1B) is obtained by polycondensation of the diamine represented by formula (a-1) and the acid dianhydride represented by formula (b-2). The repeating structural unit represented by formula (I-2B) is obtained by polycondensation of the diamine represented by formula (a-2) and the acid dianhydride represented by formula (b-1).

[0062] (2) Insulated wires The insulated wire of this disclosure comprises a conductor and an insulating coating covering the conductor. The insulating coating includes the thermoplastic polyimide of this disclosure.

[0063] Because the insulated wire of this disclosure has the above configuration, it has excellent accuracy in the thickness of the insulating coating and excellent heat resistance.

[0064] Figure 1 shows a cross-sectional view of an example of an insulated wire. As shown in Figure 1, the insulated wire 10 comprises a conductor 11 and an insulating coating 12. The insulating coating 12 directly covers the conductor 11.

[0065] (2.1) Conductors A conductor has the function of carrying electric current.

[0066] The shape of the conductor is not particularly limited. The cross-sectional shape of the conductor when cut by a plane perpendicular to the axial direction of the insulated wire (hereinafter also simply referred to as "cross-sectional shape") is not particularly limited and can be rectangular (e.g., square, rectangle, etc.), polygonal (except for rectangles), circular, elliptical, etc. Among these, a rectangular cross-sectional shape of the conductor is preferred. Hereinafter, a conductor having a rectangular cross-sectional shape will also be referred to as a "rectangular conductor".

[0067] From the viewpoint of suppressing the occurrence of partial discharge, the cross-sectional shape of the rectangular conductor is preferably such that chamfers (radius of curvature) are provided at all four corners of the rectangular conductor, as shown in Figure 1. The radius of curvature is not particularly limited and is appropriately selected according to the application of the insulated wire, and is preferably 0.6 mm or less, more preferably 0.2 mm to 0.4 mm.

[0068] The size of the conductor is not particularly limited. In the cross-section of a rectangular conductor when cut in a plane perpendicular to the axial direction of an insulated wire, the lengths of the long side and short side of the rectangular conductor are not particularly limited and are appropriately selected according to the application of the insulated wire, and are preferably within the following ranges. The length of the long side of the rectangular conductor is preferably 1.0 mm to 5.0 mm, more preferably 1.4 mm to 4.0 mm. The length of the short side of the rectangular conductor is preferably 0.4 mm to 3.0 mm, more preferably 0.5 mm to 2.5 mm. The ratio of the length of the long side of the rectangular conductor to the length of the short side of the rectangular conductor (length of the long side of the rectangular conductor / length of the short side of the rectangular conductor) is preferably 1 to 4. When the cross-sectional shape of the conductor is circular, the diameter of the conductor is preferably 0.3 mm to 3.0 mm, more preferably 0.4 mm to 2.7 mm.

[0069] The material of the conductor may be a metal. The metal is not particularly limited and includes, for example, copper, iron, nickel, gold, silver, platinum, cobalt, zinc, lead, tin, titanium, chromium, aluminum, magnesium, manganese, and alloys thereof (e.g., stainless steel, brass, and phosphor bronze). The copper may be low-oxygen copper or oxygen-free copper. The oxygen content of low-oxygen copper is 30 ppm or less, preferably 20 ppm or less.

[0070] (2.2) Insulating coating The insulating coating has the function of covering the conductor and providing electrical insulation to the insulated wire.

[0071] The thickness of the insulating coating is not particularly limited and may be appropriately selected depending on the application of the insulated wire, and may be 30 μm to 300 μm, 40 μm to 250 μm, or 80 μm to 150 μm.

[0072] The ratio of the variation in the thickness of the insulating coating to the average thickness of the insulating coating (hereinafter also referred to as the "thickness variation ratio") is preferably 7% or less. This ensures that the insulation properties of the insulated wire are reliably maintained even when the insulating coating is thin (for example, 100 μm). Consequently, the quality of the insulated wire is improved. The lower the film thickness variation rate, the better. Preferably, the film thickness variation rate is 5% or less, more preferably 3% or less. The film thickness variation rate may be 0%, or 1% or more. The method for measuring the variation in the thickness of the insulating film is the same as that described in the examples. One method for adjusting the film thickness variation rate to 7% or less is to adjust the MFR of the thermoplastic polyimide to 27 g / 10 min or more.

[0073] The insulating film includes the thermoplastic polyimide of the Disclosure. The insulating film may consist of the thermoplastic polyimide of the Disclosure.

[0074] The insulating film may further contain additives in addition to the thermoplastic polyimide of this disclosure.

[0075] Examples of additives include carbon fibers, glass fibers, potassium titanate fibers, aluminum borate fibers, metal fibers, ceramic fibers, boron fibers, silicon carbide fibers, asbestos fibers, rock wool fibers, and aramid fibers.

[0076] Examples of additives include fillers, lubricants, release agents, stabilizers, colorants, and nucleating agents. Examples of fillers include mica, synthetic mica, wollastonite, talc, silicone oil, fluorinated oil, glass beads, molybdenum disulfide, clay, silica, alumina, diatoms, soil, hydrated alumina, shirasu balloons, carbon nanotubes, calcium carbonate, hydrotalcite, fluorine, and graphite (e.g., artificial graphite, natural graphite (e.g., flake graphite, scaly graphite, and earthy graphite)).

[0077] Examples of additives include various liquid crystal polymers, thermoplastic resins (e.g., fluororesins, polyetherimides, polyethernitriles, polyetherketones, polyetheretherketones, polyetherketoneketones, polyetherketones, polyamideimides, polyethersulfones, polysulfones, polyarylates, and polyphenylene sulfides), and thermosetting resins (e.g., epoxy resins, polybenzimidazole resins, and polyimide resins).

[0078] The insulating coating is preferably made of one type of thermoplastic polyimide of this disclosure. If the insulating coating is not made of multiple types of thermoplastic polyimide, interfaces are likely to form between different types of resins constituting the insulating coating, which may result in insufficient heat resistance of the insulating coating. By making the insulating coating of one type of thermoplastic polyimide, no interfaces are formed between the resins constituting the insulating coating. As a result, the heat resistance of the insulating coating of the insulated wire is improved.

[0079] (2.3) Other layers Depending on the intended use of the insulated wire, other layers different from the insulating coating may be provided on the outer periphery of the insulating coating. Examples of these other layers include an electrical insulating layer and an adhesive layer.

[0080] (2.4) Application The applications of insulated wires are not particularly limited, and include windings in electrical equipment (e.g., electric motors and transformers). In particular, insulated wires are preferably used as windings in electric motors.

[0081] (2.5) Method for manufacturing insulated wires The method for manufacturing an insulated wire according to this disclosure includes a preparation step and a coating step. The preparation step and the coating step are carried out in this order.

[0082] (2.5.1) Preparation process In the preparation step, a composition containing thermoplastic polyimide and the conductor are prepared.

[0083] The method for preparing the composition containing thermoplastic polyimide and the conductor may be a known method. The composition may consist solely of thermoplastic polyimide.

[0084] (2.5.2) Coating process In the coating process, a molten material of the composition is applied to a conductor flowing at a specific line speed. This yields the insulated wire of the present disclosure.

[0085] For example, a known extruder and a known winding machine may be used in the coating process. The extruder extrudes the molten composition. The winding machine conveys the insulated wire at a specific line speed.

[0086] An example of an insulated wire manufacturing apparatus is shown in Figure 2. In Figure 2, "90" indicates the insulated wire manufacturing apparatus. "91" indicates the feeder. "92" indicates the preheating device. "93" indicates the extruder. "94" indicates the cooling device. "95" indicates the winding machine. "D" indicates the winding direction of the insulated conductor. "11" indicates the conductor. "10" indicates the insulated wire.

[0087] The line speed may be 10 m / min to 25 m / min, 20 m / min to 30 m / min, or 10 m / min to 20 m / min, from the viewpoint of improving the productivity of insulated wires. The line speed is appropriately selected according to the MFR of the thermoplastic polyimide, etc.

[0088] The method for coating the molten composition onto the conductor is not particularly limited and may be a known method. [Examples]

[0089] The present disclosure will be described in further detail below based on examples. However, the present disclosure is not limited to these examples.

[0090] [1] Examples of diamine synthesis The diamine was synthesized as shown below.

[0091] [1.1] Synthesis Example 1 (Diamine (a-1)) 37.9 g (0.20 mol) of 1-chloro-3-methyl-4-nitro-5-methylbenzene and 138.6 g (0.40 mol) of 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene were dissolved in 150 g of dimethylformamide. Then, 13.8 g (0.10 mol) of potassium carbonate was added, and the reaction was carried out at 120°C. After 26 hours, it was confirmed that the starting material 1-chloro-3-methyl-4-nitro-5-methylbenzene had disappeared, and the mixture was cooled. 300 g of distilled water and 500 g of toluene were added to the reaction mixture, and extraction and liquid-liquid separation were performed. The resulting organic phase was concentrated, and the resulting residue was dissolved in ethanol. After that, distilled water was added, reprecipitation occurred, the mixture was filtered, and dried. This yielded 52.2 g of crystals of the intermediate dinitro compound. The yield was 81.0%.

[0092] 20.0 g (0.031 mol) of crystals of the intermediate dinitro compound were dissolved in 120 g of ethanol. Catalytic hydrogenation reduction was then carried out in the presence of a 5% Pd / C catalyst. After the reaction was complete, the catalyst was filtered off, and distilled water was added to the resulting solution for reprecipitation. The solution was then filtered and dried. This yielded 14.9 g of crystals of diamine(a-1). The yield was 82.0%.

[0093] The reaction scheme for Synthesis Example 1 was as follows:

[0094] [ka]

[0095] [1.2] Synthesis Example 2 (Diamine (a-2)) 266 g (1.5 mol) of 1-chloro-4-nitro-5-methylbenzene and 217 g (1.57 mol) of m-hydroxybenzoic acid were dissolved in 2 L of sulfolane. Then, 436 g (3.16 mol) of potassium carbonate was added, and the reaction was carried out at 180°C. After 4 hours, it was confirmed that the starting material p-nitrochlorobenzene had disappeared, and the mixture was cooled. 300 g of distilled water and 50 g of toluene were added to the reaction mixture, and reprecipitation occurred. The mixture was filtered and dried. Furthermore, recrystallization was performed with 1850 g of isopropanol / distilled water (8:2) mixed solvent, filtered, and dried. This yielded 357.5 g of carboxylic acid intermediate crystals. The yield was 87.0%.

[0096] 312 g (1.09 mol) of the carboxylic acid intermediate was dissolved in 850 g of dichloromethane. Then, 168 g (1.42 mol) of thionyl chloride was added, and the reaction was carried out at 70°C. After 4 hours, it was confirmed that the starting carboxylic acid intermediate had disappeared, and the mixture was cooled. The mixture was filtered and dried. This yielded 338 g of the intermediate chloride. The yield was 98.8%.

[0097] 320 g (1.11 mol) of intermediate chloride and 85.5 g (0.50 mol) of 1,1'-oxydibenzene were dissolved in 1000 g of dichloromethane. Then, 198 g (1.49 mol) of aluminum chloride was added, and the temperature was raised to 60°C to carry out the reaction. After 11 hours, it was confirmed that the starting intermediate chloride had disappeared, and the mixture was cooled. 2000 g of ice water was added to the reaction mixture, and extraction and liquid-liquid separation were performed. The obtained organic phase was washed with 5% aqueous sodium hydroxide solution. The residue obtained by concentration was then concentrated and dried. This yielded 331 g of dinitro intermediate. The yield was 96.0%.

[0098] 37.76 g (0.12 mol) of the dinitro intermediate was dissolved in 233 g of 2-methoxyethanol. Catalytic hydrogenation reduction was then carried out in the presence of a 5% Pd / C catalyst. After the reaction was complete, the catalyst was filtered off, and distilled water was added to the resulting solution for reprecipitation. The solution was then filtered and dried. This yielded 12.5 g of diamine(a-2) crystals. The yield was 77.0%.

[0099] The reaction scheme for Synthesis Example 2 was as follows:

[0100] [ka]

[0101] [1.3] Synthesis Example 3 (Diamine(a)) 35.5 g (0.20 mol) of 1-chloro-4-nitro-5-methylbenzene and 44.04 g (0.40 mol) of hydroquinone were dissolved in 150 g of dimethylformamide. Then, 13.8 g (0.10 mol) of potassium carbonate was added, and the reaction was carried out at 120°C. After 13 hours, it was confirmed that the starting material 1-chloro-3-methyl-4-nitro-5-methylbenzene had disappeared, and the mixture was cooled. 400 g of distilled water and 600 g of toluene were added to the reaction mixture, and extraction and liquid-liquid separation were performed. The resulting organic phase was concentrated, and the resulting residue was dissolved in ethanol. Then, distilled water was added to reprecipitation, the mixture was filtered, and dried. This yielded 41.8 g of nitro intermediate crystals. The yield was 83.2%.

[0102] 20.0 g (0.080 mol) of nitro intermediate crystals were dissolved in 120 g of ethanol. Catalytic hydrogenation reduction was then carried out in the presence of a 5% Pd / C catalyst. After the reaction was complete, the catalyst was filtered off, and distilled water was added to the resulting solution for reprecipitation. The solution was then filtered and dried. This yielded 15.0 g of amine intermediate crystals. The yield was 85.0%.

[0103] 1.8 g (0.008 mol) of the amine intermediate was reacted with 1.15 g (0.0038 mol) of 4,4-dichlorophenylsulfone in 12 mL of dry NMP (N-methyl-2-pyrrolidone) and 10 mL of dry toluene, and the mixture was placed in a two-neck flask. The two-neck flask was equipped with a magnetic stirrer, condenser, Dean-Stark trap, and nitrogen inlet tube. Next, 1.7 g (0.32 mol) of K2CO3 was added to the mixture. The reaction mixture was then heated to 140°C with continued stirring. The water produced was removed from the reaction by azeotropic distillation. The reaction temperature was raised to 160°C and continued for 20 hours to remove residual water and toluene. The resulting reaction mixture was cooled and poured into 200 mL of water, then 20 mL of 5% NaOH was added to the mixture and it was filtered. The mixture was repeatedly washed with 5% NaOH solution and water. The resulting diamine was dried in a vacuum oven at 70°C for 24 hours. This yielded 2.02 g of diamine (Ai). The yield was 82.0%.

[0104] The reaction scheme for Synthesis Example 3 was as follows:

[0105] [ka]

[0106] [1.4] Synthesis Example 4 (Diamine (a-ii)) 237 g (1.5 mol) of p-nitrochlorobenzene and 217 g (1.57 mol) of m-hydroxybenzoic acid were dissolved in 2 L of sulfolane. Then, 436 g (3.16 mol) of potassium carbonate was added, and the reaction was carried out at 180°C. After 4 hours, it was confirmed that the starting material p-nitrochlorobenzene had disappeared, and the mixture was cooled. 300 g of distilled water and 50 g of toluene were added to the reaction mixture, and reprecipitation occurred. The mixture was filtered and dried. Furthermore, it was recrystallized in a mixed solvent of isopropanol / distilled water (8:2) in 1850 g, filtered, and dried. This yielded 314.5 g of carboxylic acid intermediate crystals. The yield was 85.0%.

[0107] 282 g (1.09 mol) of the carboxylic acid intermediate was dissolved in 850 g of dichloromethane. Then, 168 g (1.42 mol) of thionyl chloride was added, and the reaction was carried out at 70°C. After 4 hours, it was confirmed that the carboxylic acid intermediate had disappeared, and the mixture was cooled. The mixture was filtered and dried. This yielded 293 g of the intermediate chloride. The yield was 96.8%.

[0108] 309 g (1.11 mol) of intermediate chloride and 85.5 g (0.50 mol) of 1,1'-oxydibenzene were dissolved in 1000 g of dichloromethane. Then, 198 g (1.49 mol) of aluminum chloride was added, and the temperature was raised to 60°C to carry out the reaction. After 11 hours, it was confirmed that the starting intermediate chloride had disappeared, and the mixture was cooled. 2000 g of ice water was added to the reaction mixture, and extraction and liquid-liquid separation were performed. The obtained organic phase was washed with 5% aqueous sodium hydroxide solution. The residue obtained by concentration was then concentrated and dried. This yielded 312 g of dinitro intermediate. The yield was 95.0%.

[0109] 34.76 g (0.12 mol) of the dinitro intermediate was dissolved in 233 g of 2-methoxyethanol, and catalytic hydrogenation reduction was carried out in the presence of a 5% Pd / C catalyst. After the reaction was complete, the catalyst was filtered off, and distilled water was added to the resulting solution to reprecipitation. The solution was then filtered and dried. This yielded 11.7 g of diamine (a-ii) crystals. The yield was 78.5%.

[0110] The reaction scheme for Synthesis Example 4 was as follows:

[0111] [ka]

[0112] [1.5] Synthesis Example 5 (Diamine (a-iii)) 36.7 g (0.20 mol) of 1-chloro-3-nitro-5-ethylbenzene and 74.5 g (0.40 mol) of 4,4'-dihydroxybiphenyl were dissolved in 150 g of dimethylformamide. Then, 13.8 g (0.10 mol) of potassium carbonate was added, and the reaction was carried out at 120°C. After 13 hours, it was confirmed that the starting material 1-chloro-3-nitro-5-ethylbenzene had disappeared, and the mixture was cooled. 300 g of distilled water and 500 g of toluene were added to the reaction mixture, and extraction and liquid-liquid separation were performed. The resulting organic phase was concentrated, and the resulting residue was dissolved in ethanol. Then, distilled water was added to reprecipitation, the mixture was filtered, and dried. This yielded 39.2 g of crystals of the intermediate dinitro compound. The yield was 81.0%.

[0113] 20.0 g (0.041 mol) of the crystal was dissolved in 120 g of ethanol, and catalytic hydrogenation reduction was carried out in the presence of a 5% Pd / C catalyst. After the reaction was complete, the catalyst was filtered off, and distilled water was added to the resulting solution to reprecipitation. The solution was then filtered and dried. This yielded 15.1 g of diamine (a-iii) crystals. The yield was 86.0%.

[0114] The reaction scheme for Synthesis Example 5 was as follows:

[0115] [ka]

[0116] [2] Examples and Comparative Examples [2.1] Example 1 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 4.559 kg (7.8 mol) of diamine (a-1), 1.570 kg (7.25 mol) of pyromellitic dianhydride (acid dianhydride (b-1)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. This polyimide powder was washed with toluene and dried at 180°C for 24 hours to obtain 8.72 kg (yield 99.0%) of polyimide powder (thermoplastic polyimide 1 powder). Using a Takayasu-type 25mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (1). Thermoplastic polyimide 1 had the constituent repeating units of formula (I-1A).

[0117] [ka]

[0118] [2.2] Example 2 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 4.559 kg (7.8 mol) of diamine (a-1), 2.133 kg (7.25 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (acid dianhydride (b-2)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. After washing this polyimide powder with toluene, it was dried at 180°C for 24 hours to obtain 10.59 kg (yield 97.8%) of polyimide powder (thermoplastic polyimide 2 powder). Using a Takayasu 25 mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (2). Thermoplastic polyimide 2 had the constituent repeating units of formula (I-1B).

[0119] [ka]

[0120] [2.3] Example 3 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 4.841 kg (7.8 mol) of diamine (a-2), 1.570 kg (7.25 mol) of pyromellitic dianhydride (acid dianhydride (b-1)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. This polyimide powder was washed with toluene and dried at 180°C for 24 hours to obtain 9.18 kg (yield 98.3%) of polyimide powder (thermoplastic polyimide 3 powder). Using a Takayasu-type 25mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (3). Thermoplastic polyimide 3 had the following repeating unit structure (I-2A).

[0121] [ka]

[0122] [2.4] Comparative Example 1 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 5.054 kg (7.8 mol) of diamine (Ai), 1.570 kg (7.25 mol) of pyromellitic dianhydride (acid dianhydride (B-1)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. This polyimide powder was washed with toluene and dried at 180°C for 24 hours to obtain 9.59 kg (yield 98.3%) of polyimide powder (thermoplastic polyimide 4 powder). Using a Takayasu 25mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (4). Thermoplastic polyimide 4 had the following repeating unit structure:

[0123] [ka]

[0124] [2.5] Comparative Example 2 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 4.623 kg (7.8 mol) of diamine (a-ii), 1.570 kg (7.25 mol) of pyromellitic dianhydride (acid dianhydride (b-1)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. This polyimide powder was washed with toluene and dried at 180°C for 24 hours to obtain 8.73 kg (yield 97.8%) of polyimide powder (thermoplastic polyimide 5 powder). Using a Takayasu 25mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (5). Thermoplastic polyimide 5 had the following repeating units of formula (I-ii).

[0125] [ka]

[0126] [2.6] Comparative Example 3 A container equipped with a stirrer, reflux condenser, water separator, and nitrogen inlet tube was prepared. 3.310 kg (7.8 mol) of diamine (a-iii), 1.570 kg (7.25 mol) of pyromellitic dianhydride (acid dianhydride (b-1)), 0.148 kg (1.0 mol) of phthalic anhydride, and 21.53 kg of m-cresol were added to this container. The mixture was then heated to 200°C while stirring under a nitrogen atmosphere. During this time, approximately 350 ml of water was observed to distillate. The reaction was continued at 200°C for 6 hours. Afterward, the mixture was cooled to room temperature, and 10.8 kg of toluene was added. The mixture was then filtered to obtain a yellow polyimide powder. This polyimide powder was washed with toluene and dried at 180°C for 24 hours to obtain 6.33 kg (yield 99.1%) of polyimide powder (thermoplastic polyimide 6 powder). Using a Takayasu-type 25mmΦ extruder, this polyimide powder was extruded at 400°C to obtain pellets (6). Thermoplastic polyimide 6 had the following repeating units of formula (I-iii).

[0127] [ka]

[0128] [3]Measurement method

[0129] [3.1] Melt flow rate (MFR) A melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd., model number: A-371401705) was used to measure the MFR. Measurement was performed in accordance with JIS K7210-1:2014, with the cylinder temperature set to 400°C and a load of 1.05 kg.

[0130] [3.2] Glass transition temperature The glass transition temperature was measured using a differential scanning calorimeter (DSC220C model, Seiko Instruments Inc.). Specifically, approximately 5 mg of the material was sealed in a measuring aluminum pan and placed in the differential scanning calorimeter. It was then heated from room temperature to 450°C at a rate of 10°C / min. To completely melt the resin, it was held at 450°C for 5 minutes, and then cooled to 30°C at a rate of 10°C / min. After being left at 30°C for 5 minutes, it was heated a second time to 450°C at a rate of 10°C / min. The displacement point corresponding to the glass transition was defined as the glass transition temperature (Tg).

[0131] [3.3] Film thickness and thickness variation Insulated wires for evaluation (20 m / min) were prepared using the pellets from Examples 1-3 and Comparative Examples 1-3 as described below, and the film thickness and thickness variation were measured. The measurement results are shown in Table 1.

[0132] [3.3.1] Insulated wire for evaluation (20m / min) As a conductor, a rectangular copper wire (material: copper with an oxygen content of 15 ppm) was prepared. The length of the long side of the rectangular cross-section of the rectangular copper wire was 2.99 mm. The length of the short side of the rectangular cross-section of the rectangular copper wire was 1.54 mm. The radius of curvature of the chamfers at the four corners of the rectangular cross-section of the rectangular copper wire was 6 mm.

[0133] An extruder equipped with dies (screw: 20mm diameter full flight, L / D=24, compression ratio: 3.0) was prepared. The heating temperature in the cylinder section of the extruder was controlled by dividing it into three zones, C1, C2, and C3, starting from the material input side. The heating temperatures were set to 380°C for zone C1, 410°C for zones C2 and C3, and 420°C for the head section at the rear of the extruder cylinder and the die at the front of the head section. The shape of the die holes was similar to the cross-sectional shape of the flat copper wire described above.

[0134] A conductor was passed through the die of an extruder, and an insulating film was formed on the conductor by extrusion coating while the conductor was fed out at a constant speed. Pellets (1) to (6) were fed into the extruder. The molten pellets (1) to (6) were directly coated onto the outer circumference of a conductor preheated to 260°C at a line speed of 20 m / min, and then allowed to cool. This yielded an evaluation insulated wire (20 m / min). The evaluation insulated wire (20 m / min) comprises a conductor and an insulating film directly covering the conductor. The insulating film consists of thermoplastic polyimides 1 to 6. The cross-sectional shape of the evaluation insulated wire (20 m / min) was similar to the shape of the conductor.

[0135] [3.3.2] Film thickness of insulating coating A 5m length of evaluation-grade insulated wire (20m / min) was taken, and the thickness of the insulating coating on the long side of the cross-section perpendicular to the axial direction of the evaluation-grade insulated wire (20m / min) was measured every 100mm. The average thickness obtained by arithmetic mean of multiple measurements was defined as the "insulating coating thickness."

[0136] [3.3.3] Variation in the thickness of the insulating film A 5m length of evaluation-grade insulated wire (20m / min) was taken, and the thickness of the insulating coating on the long side of the cross-section perpendicular to the axial direction of the evaluation-grade insulated wire (20m / min) was measured every 100mm. The unbiased standard deviation of multiple measurement values ​​was defined as the "variation in insulating coating thickness." The acceptable variation in insulating film thickness is 9 μm or less.

[0137] [3.3.4] Insulated wire for evaluation (25m / min) Using the pellets from Example 1 or Example 2, an evaluation insulated wire (25 m / min) was prepared in the same manner as the evaluation insulated wire (20 m / min), except that the line speed was changed to 25 m / min. The variation in the thickness of the insulating coating of the evaluation insulated wire (25 m / min) was measured in the same manner as the variation in the thickness of the insulating coating of the evaluation insulated wire (20 m / min).

[0138] [3.4] Heat resistance Three straight test specimens, each 400 mm long, were obtained by cutting an insulated wire (20 m / min) for evaluation. The straight test specimens were bent 180° (U-shaped) along a round bar (diameter: 8 mm) with the center of the specimen as the axis. These bent test specimens were heated for 30 minutes in a forced-circulation constant temperature bath maintained at 220°C. After being removed from the bath and allowing the specimens to return to room temperature, the presence or absence of cracks in the insulating coating was checked visually or at a magnification of 6x or less. The heat resistance of the insulated wire was evaluated according to the following evaluation criteria. An acceptable rating for the heat resistance of an insulated wire is "A".

[0139] [3.4.1] Evaluation Criteria A: No cracks were found in any of the three test specimens. B: Cracks were found in at least one of the rods.

[0140] [Table 1]

[0141] In Table 1, "PI" indicates thermoplastic polyimide. "CRU" indicates the constituent repeating unit. "Thickness variation (20 m / min)" indicates the thickness variation of the insulating coating of the evaluation insulated wire (20 m / min). "Thickness variation (25 m / min)" indicates the thickness variation of the insulating coating of the evaluation insulated wire (25 m / min). "Non-para-coordinate aromatic ring" refers to phenylene groups that are not linked by para coordination among the substituted or unsubstituted phenylene groups constituting the main chain.

[0142] The repeating unit of the composition of Comparative Example 1 did not satisfy (c). The repeating unit of the composition of Comparative Example 2 did not satisfy (b). Therefore, the thickness variation of the insulating film in Comparative Example 1 and Comparative Example 2 was not 8 μm or less. The repeating unit of the composition of Comparative Example 3 did not satisfy (a). Therefore, the heat resistance evaluation of Comparative Example 3 was "B". From these results, it was found that thermoplastic polyimides 4 to 6 of Comparative Examples 1 to 3 are not "thermoplastic polyimides that can be used to make insulating films with excellent film thickness accuracy and heat resistance".

[0143] The repeating units of the configuration in Examples 1 to 3 satisfied all of (a) to (c). Therefore, the thickness variation of the insulating film in Examples 1 to 3 was 8 μm or less. The heat resistance evaluation for Examples 1 to 3 was "A". From these results, it was found that thermoplastic polyimides 1 to 3 in Examples 1 to 3 are "thermoplastic polyimides that can be used to make insulating films with excellent film thickness accuracy and heat resistance". [Explanation of symbols]

[0144] 10: Insulated wire, 11: Conductor, 12: Insulating coating

Claims

1. It has a repeating structural unit containing an imide bond, The aforementioned repeating structural unit satisfies all of the following conditions (a) to (c), and is a thermoplastic polyimide. (a) The main chain contains 6 to 10 aromatic rings. (b) Six to ten of the aforementioned aromatic rings include at least one substituted aromatic ring in which at least one hydrogen atom is substituted with an alkyl group, The total number of carbon atoms in the alkyl groups of all the substituted aromatic rings is between 2 and 6. (c) The six to ten aforementioned aromatic rings include divalent aromatic rings linked by ortho-coordination or meta-coordination.

2. The thermoplastic polyimide according to claim 1, wherein the recurring unit has a recurring unit represented by the following formula (I). 【Chemistry 1】 In formula (I), A １ A ２ A ３ and A ４ Each of these independently represents a single bond, an ether group, a carbonyl group, a sulfonyl group, or an isopropylidene group. １ and R ２ Each independently represents an alkyl group. n and m each independently represent an integer from 1 to 4. n R １ The number of carbon atoms in the alkyl group and m R ２ The total number of carbon atoms in the alkyl group is between two and six. In equation (I), X represents a base represented by the following equations (X-1), (X-2), (X-3), or (X-4). 【Chemistry 2】 In equations (X-1) to (X-4), * indicates the bond position. In formula (I), Y represents a base represented by the following formulas: (Y-1), (Y-2), (Y-3), (Y-4), (Y-5), (Y-6), (Y-7), or (Y-8). 【Transformation 3】 In equations (Y-1) to (Y-8), * indicates the bonding position. At least one of the substituted or unsubstituted phenylene group and naphthylene group constituting the main chain of formula (I) is linked by meta-coordination or ortho-coordination.

3. The thermoplastic polyimide according to claim 2, wherein the repeating unit of structure represented by formula (I) includes the repeating unit of structure represented by the following formula (I-1). 【Chemistry 4】

4. The thermoplastic polyimide according to claim 3, wherein Y is a group represented by formula (Y-1) or formula (Y-2) in formula (I-1).

5. The thermoplastic polyimide according to claim 4, wherein Y is a group represented by formula (Y-1) in formula (I-1).

6. The thermoplastic polyimide according to claim 2, wherein the repeating unit of structure represented by formula (I) includes the repeating unit of structure represented by the following formula (I-2). 【Transformation 5】

7. The thermoplastic polyimide according to claim 6, wherein Y is a group represented by formula (Y-1) in formula (I-2).

8. The glass transition temperature Tg is 230°C or higher, and The thermoplastic polyimide according to claim 1, wherein the melt flow rate measured at 400°C and a load of 1.05 kg in accordance with JIS K7210-1:2014 is 20 g / 10 min or more.

9. It comprises a conductor and an insulating film covering the conductor, The insulated wire according to claim 1, wherein the insulating coating comprises a thermoplastic polyimide according to any one of claims 1 to 8.

10. The insulated wire according to claim 9, wherein the ratio of the amount of variation in the thickness of the insulating coating to the average thickness of the insulating coating is 7% or less.

11. The insulated wire according to claim 9, wherein the insulating coating is made of one type of thermoplastic polyimide.

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