Insulated electric wire, coil, and electronic / electrical device

Abstract

The application discloses an insulating electric wire, a coil and an electronic / electrical equipment, and relates to the technical field of insulating electric wires.The modified polyamide-imide insulating layer is composed of an insulating material obtained by reacting diisocyanate with mixed anhydride, wherein the mixed anhydride comprises short-chain anhydride and long-chain anhydride.The insulating electric wire coated with the polyamide-imide insulating layer can improve the flexibility of the wire rod, adapt to more closely arranged complex groove types, and thus improve the motor slot filling rate, so that the volume of the stator core is reduced under the same power, the weight of the motor is indirectly reduced, the light weight requirement is achieved, and the insulating electric wire is suitable for an 800V high-voltage platform, has higher heat resistance, and has stronger insulating performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of insulated wires, and more particularly to an insulated wire, a coil and an electronic / electrical device. BACKGROUND

[0002] Polyamide-imide has been widely used in the insulation system of electromagnetic wires for 400V drive motor platform due to its excellent mechanical strength, heat resistance and solvent resistance. However, with the development of new energy vehicles and high-efficiency motors to higher voltage platforms (such as 800V and above), the existing polyamide-imide insulation material faces multiple challenges: first, its relatively high dielectric constant is not conducive to the electric field distribution under high-frequency conditions, which is prone to partial discharge; second, the heat resistance of the single polyamide-imide system is close to the upper limit, making it difficult to meet the long-term reliability requirements in higher temperature environments; in addition, the polyamide-imide molecular chain is rigid, and the paint film has insufficient flexibility, which requires a higher bending radius during winding, and is prone to paint film cracking, however, an excessively large minimum winding diameter will result in an increase in coil volume and a decrease in slot fill rate, making it difficult to meet the development trend of modern drive motors for "high power density, high slot fill rate, and lightweight".

[0003] Therefore, there is an urgent need to develop an insulated wire with high heat resistance, low dielectric constant and excellent flexibility to meet the stringent requirements of the next generation of high-voltage motors for insulation materials. SUMMARY

[0004] Therefore, the purpose of the present application is to provide an insulated wire, a coil and an electronic / electrical device to solve the problems in the prior art. The insulated wire provided by the present application improves the flexibility of the wire, which can avoid the problem of cracking of the insulation layer, and is beneficial to improving the slot fill rate of the motor.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0006] The first aspect of the present application is to provide an insulated wire formed after curing to have a high-flexibility insulation layer and an insulated wire containing the insulation layer.

[0007] The insulated wire includes a conductor, an inner insulation layer and an outer insulation layer arranged in sequence on the outer periphery of the conductor, the outer insulation layer includes a modified insulation layer, the thickness of the modified insulation layer is 10-50% of the total thickness of the inner insulation layer and the outer insulation layer, the modified insulation layer is formed by high-temperature curing of a modified polyamide-imide varnish, the modified polyamide-imide varnish is obtained by reacting a diisocyanate with a mixed anhydride, wherein the mixed anhydride includes a short-chain anhydride and a long-chain anhydride.

[0008] In the present application, the diisocyanate is selected from aromatic diisocyanates, preferably at least one of toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI).

[0009] Further, the modified polyamide-imide varnish is obtained from the addition reaction of a diisocyanate and a mixed anhydride, wherein the mixed anhydride comprises a short-chain anhydride and a long-chain anhydride.

[0010] The short-chain anhydride comprises at least one of an aromatic short-chain anhydride, an aliphatic short-chain anhydride, and a cycloaliphatic short-chain anhydride. The aromatic short-chain anhydride refers to an aromatic anhydride having not more than 5 carbon atoms of chain-like aliphatic substituents on the aromatic ring thereof, or an unsubstituted aromatic anhydride. The aliphatic short-chain anhydride refers to an aliphatic anhydride having not more than 5 carbon atoms of chain-like aliphatic structures in the molecule thereof. The cycloaliphatic short-chain anhydride refers to a cycloaliphatic anhydride having not more than 7 carbon atoms of cyclic aliphatic structures. The short-chain anhydride should comprise at least one anhydride structure and one carboxyl group in the molecular structure thereof, or have a dianhydride structure.

[0011] In a preferred embodiment of the present application, the short-chain anhydride is an aromatic short-chain anhydride.

[0012] In a preferred embodiment of the present application, the aromatic short-chain anhydride comprises one or more combinations of trimellitic anhydride, methyl-substituted trimellitic anhydride, ethyl-substituted trimellitic anhydride, and pyromellitic dianhydride.

[0013] In the present application, the long-chain anhydride comprises at least one of a cycloaliphatic anhydride, an aromatic anhydride, and a bio-based long-chain anhydride. The long-chain anhydride should comprise at least one anhydride structure and one carboxyl group in the molecular structure thereof. More specifically, the long-chain anhydride is prepared from a long-chain aliphatic diacid or a derivative thereof and a short-chain carboxylic acid or a derivative thereof.

[0014] In the present application, the long-chain aliphatic diacid or a derivative thereof refers to an aliphatic chain structure having not less than 6 carbon atoms in the molecular structure thereof, or a cycloaliphatic structure having not less than 8 carbon atoms. The short-chain carboxylic acid or a derivative thereof refers to an aromatic monocarboxylic acid having not more than 5 carbon atoms of chain-like aliphatic structures in the molecular structure thereof, or having not more than 5 carbon atoms of chain-like aliphatic substituents, or an unsubstituted aromatic monocarboxylic acid or a derivative thereof.

[0015] It should be noted that the "not more than" in the present application includes the case of 0.

[0016] In the present application, the modified polyamide-imide varnish is obtained from the addition reaction of a diisocyanate and a mixed anhydride, wherein the mixed anhydride comprises a short-chain anhydride and a long-chain anhydride.

[0017] In the mixed anhydride, the long-chain anhydride accounts for not more than 10% of the molar ratio of the mixed anhydride, preferably 3-5%.

[0018] The modified polyamide-imide varnish of the outer insulating layer is prepared by the following method:

[0019] (1) The long-chain aliphatic dicarboxylic acid and the monocarboxylic acid are mixed at a molar ratio of 1:1, and a solvent A, an activating agent, and a catalyst are added to react to obtain a long-chain anhydride.

[0020] (2) The long-chain anhydride obtained after the reaction is mixed with a short-chain anhydride, and reacted with a diisocyanate to obtain a modified polyamide-imide intermediate.

[0021] (3) The modified polyamide-imide intermediate is dissolved in a solvent B to obtain a modified polyamide-imide varnish; the solvent B is at least one of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), or dimethylacetamide (DMAC).

[0022] The obtained modified polyamide-imide varnish is coated on a wire and heated and cured to form a modified insulating layer.

[0023] In the step (1), the activating agent is DCC (dicyclohexyl carbodiimide), and the catalyst is DMAP (4-dimethylaminopyridine); the solvent A includes dichloromethane and ethylbenzene.

[0024] The dilute DCC is added dropwise in a reactor with stirring, and the concentration of the dilute DCC is not more than 3 mol / L. During the dropwise addition of the DCC, the reaction temperature is preferably 0-10°C, and more preferably 0-5°C.

[0025] In the present application, the activating agent DCC is preferably added in excess based on the molar amount of the monocarboxylic acid in the mixed carboxylic acid; the molar ratio of the DCC to the monocarboxylic acid is 1.05-1.2:1.

[0026] In the step (1), the catalyst DMAP is added in an amount of 10%-20% based on the molar amount of the monocarboxylic acid.

[0027] In the step (2), the feeding ratio of the long-chain anhydride is not more than 10% of the mixed anhydride, and is preferably 3-5%. The feeding ratio is a molar feeding ratio. In the step (2), the diisocyanate is added in excess based on the theoretical diisocyanate addition amount for the reaction with the anhydride; the molar ratio of the isocyanate groups in the diisocyanate to the sum of the carboxyl groups and the anhydride groups in the anhydride to be reacted is 10-20%. That is, in the present application, when the reactants are diisocyanate and an anhydride or a di-anhydride containing one anhydride and a carboxyl group, the molar ratio of the diisocyanate to the anhydride is 1.1-1.2:1.

[0028] In one embodiment of the present application, the modified polyamide-imide varnish is coated on the outside of the conventional insulation layer and further cured to form an insulated wire with a multi-layer insulation layer structure.

[0029] In a more preferred embodiment of the present application, the modified polyamide-imide varnish of the present application has a thickness of 10-50% of the total thickness of the insulation layer after curing.

[0030] In the present application, the inner insulation layer can be:

[0031] 1) a polyimide layer, or

[0032] 2) a polyamide-imide layer and a polyimide layer;

[0033] That is, the inner insulation layer can be entirely a polyimide layer or composed of a polyamide-imide layer and a polyimide layer, wherein the thickness of the polyimide layer is ≥50% of the total thickness (the total thickness is the sum of the inner insulation layer and the outer insulation layer), and the polyimide layer can be a general polyimide layer (such as a conventional general commercially available polyimide varnish cured at high temperature) or a functional polyimide layer, such as a corona-resistant polyimide layer or a low-dielectric polyimide layer.

[0034] That is, the inner insulation layer includes a bottom layer and an intermediate layer, and when it is the first mode, both the bottom layer and the intermediate layer can be polyimide layers; when it is the second mode, the bottom layer can be a polyamide-imide layer and the intermediate layer can be a polyimide layer; or the two can be exchanged.

[0035] It can be understood that polyimide varnish is generally used for 800V platforms because the polyimide varnish has more excellent performance; it has high heat resistance and good insulation performance, and therefore, the inner insulation layer can be preferably a single-layer polyimide layer.

[0036] However, polyimide varnish is more expensive than polyamide-imide varnish; and compared with polyamide-imide varnish, the production process of polyimide varnish is more environmentally friendly, and therefore, for some scenarios with higher environmental requirements, the inner insulation layer can be a combination of a polyamide-imide layer and a polyimide layer, i.e., the second mode can meet the 800V high voltage, reduce the cost, and have better environmental friendliness.

[0037] The conventional polyimide varnish, low dielectric polyimide varnish and corona-resistant polyimide varnish are commercially available polyimide varnishes; the polyamide-imide varnish is also a conventional commercially available product, such as the TONGMID 595 series of ELANTAS Company, the HI 406 series of RESONAC Company and the like; among them, the low dielectric polyimide varnish refers to a polyimide varnish with a dielectric constant less than 3.5, especially a polyimide varnish with a dielectric constant less than 3; the corona-resistant polyimide varnish is a polyimide varnish with anti-ionizing breakdown. For example, the commercially available Kapton® CR series of DuPont, the Xinbang CR series, the HI-406 series manufactured by RESONAC Company and the like. In addition, the TONGTHERM 537 series of ELANTAS Company, which contains ordinary polyimide varnish, corona-resistant polyimide varnish and low dielectric polyimide varnish.

[0038] The present application also aims to provide an electrical or electronic device prepared from the above-mentioned coil.

[0039] Compared with the prior art, the present application has the following advantages:

[0040] The polyamide-imide insulated layer coated insulated wire of the present application improves the flexibility of the wire, adapts to complex slot type and more closely arranged, thereby improving the motor slot fill rate, reducing the volume of the stator core under the same power, indirectly reducing the weight of the motor, and achieving the requirement of light weight;

[0041] And the insulated wire provided by the present application is suitable for 800V high voltage platform, which has higher heat resistance requirement and stronger insulation performance. DETAILED DESCRIPTION

[0042] The features and properties of the present application are further described in detail below in combination with examples.

[0043] Example 1

[0044] 1) In a 500 mL three-necked flask, add dodecanedioic acid (20.2 g, 0.1 mol), benzoic acid (12.2 g, 0.1 mol), DMAP (4-dimethylaminopyridine) (1.22 g, 0.01 mol) in sequence, add 200 mL anhydrous dichloromethane, and stir until the solids are completely dissolved. Place the three-necked flask in an ice bath (0-5°C), and slowly add a dichloromethane solution of DCC (dicyclohexyl carbodiimide) (DCC 24.7 g, 0.12 mol dissolved in 50 mL anhydrous dichloromethane) dropwise, controlling the temperature ≤10°C during the dropwise addition; after the dropwise addition is complete, remove the ice bath, and stir at room temperature (25-30°C) for 12-16 hours. After the reaction is stopped, filter, wash the filtrate with anhydrous petroleum ether, and rotary evaporate under reduced pressure (vacuum degree 0.08 MPa) to obtain a yellowish oil of the crude product. Further column chromatography on silica gel is performed using ethyl acetate / petroleum ether as the eluent, and the white solid carboxylic dodecanoyl-benzoic anhydride is obtained after purification and drying, and the structure is shown in formula 1,

[0045] Formula 1;

[0046] In a flask equipped with a reflux condenser, add 5 mmol of carboxylic dodecanoyl-benzoic anhydride, further add 95 mmol of trimellitic anhydride (hereinafter referred to as TMA), add 500 mL ethylbenzene, and add 0.12 mol of MDI, and reflux at 190°C for 2 hours. After the reaction is complete, wash the reaction product with n-hexane, and remove the solvent under reduced pressure to obtain the modified polyamide-imide intermediate.

[0047] 2) Dissolve the modified polyamide-imide intermediate obtained in step 1) in NMP (N-methyl pyrrolidone) to prepare a modified polyamide-imide varnish (solid content 30%) which is coated on an insulated wire that has been coated with a 12 μm bottom insulating layer and an 83 μm intermediate insulating layer, the wire conductor size being 2.5×3.8 mm, and after baking and curing, an insulated wire with a modified insulating layer thickness of about 25 μm is obtained, and the total insulating layer thickness of the insulated wire is 120 μm.

[0048] The materials of the bottom insulating layer and the intermediate insulating layer are both conventional commercially available polyimide paint.

[0049] Example 2

[0050] The same method as in Example 1 is used to prepare carboxylic octadecanoyl-benzoic anhydride from octadecanedioic acid, and the structure is shown in formula 2.

[0051] Formula 2;

[0052] In a flask equipped with a reflux condenser, 3 mmol of carboxyl-terminated octadecanoyl-benzoyl anhydride was added, further 97 mmol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours to prepare a modified polyamide-imide intermediate.

[0053] Further, the obtained modified polyamide-imide intermediate was dissolved in NMP to prepare a modified polyamide-imide varnish (solid content 30%), which was coated on an insulated wire that had been coated with a 12 μm bottom insulating layer and a 48 μm intermediate insulating layer, and baked and cured to obtain a modified insulating layer with a thickness of about 60 μm, and an overall insulating layer thickness of 120 μm.

[0054] The bottom insulating layer was made of a conventional commercially available polyimide paint, and the intermediate insulating layer was made of a commercially available corona-resistant polyimide paint.

[0055] Example 3

[0056] Using the same method as in Example 1, carboxyl-terminated octadecanoyl-benzoyl anhydride was prepared from octadecanedioic acid, and had the structure shown in Formula 3.

[0057] Formula 3

[0058] In a flask equipped with a reflux condenser, 10 mmol of carboxyl-terminated octadecanoyl-benzoyl anhydride was added, further 90 mmol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours to prepare a modified polyamide-imide intermediate.

[0059] Further, the obtained modified polyamide-imide intermediate was dissolved in a mixed solvent of NMP and DMF to prepare a modified polyamide-imide varnish (solid content 30%), which was coated on an insulated wire that had been coated with a 12 μm bottom insulating layer and a 96 μm intermediate insulating layer, and baked and cured to obtain a modified insulating layer with a thickness of about 12 μm, and an overall insulating layer thickness of 120 μm.

[0060] The bottom insulating layer and the intermediate insulating layer were both made of a conventional commercially available polyimide paint.

[0061] Example 4

[0062] Using the same method as in Example 1, carboxyl-terminated octadecanoyl-benzoyl anhydride was prepared from octadecanedioic acid, and had the structure shown in Formula 3.

[0063] Formula 3

[0064] In a flask equipped with a reflux condenser, 5 mmol of carboxyl-terminated tetradecanoyl-benzoyl anhydride was added, further 95 mmol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours to prepare a modified polyamide-imide intermediate.

[0065] Further, the obtained modified polyamide-imide intermediate was dissolved in a mixed solvent composed of NMP, DMF and DMA to prepare a modified polyamide-imide varnish (solid content 30%), which was coated on an insulated wire that had been coated with a 12 μm bottom insulating layer and an 83 μm intermediate insulating layer, and baked and cured to obtain a modified insulating layer with a thickness of about 25 μm, thereby obtaining an insulated wire with a total insulating layer thickness of 120 μm.

[0066] Among them, the material of the bottom insulating layer is a conventional commercially available polyamide-imide paint, and the material of the intermediate insulating layer is a commercially available low-dielectric polyamide-imide paint.

[0067] Example 5

[0068] The same method as in Example 1 was used to prepare carboxyl-terminated tetradecanoyl-benzoyl anhydride from tetradecanedioic acid, and the structure is shown in Formula 5.

[0069] Formula 5;

[0070] In a flask equipped with a reflux condenser, 5 mmol of carboxyl-terminated tetradecanoyl-benzoyl anhydride was added, further 95 mmol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours to prepare a modified polyamide-imide intermediate.

[0071] Further, the obtained modified polyamide-imide intermediate was dissolved in a mixed solvent composed of NMP, DMF and DMA to prepare a modified polyamide-imide varnish (solid content 30%), which was coated on an insulated wire that had been coated with a 12 μm bottom insulating layer and an 83 μm intermediate insulating layer, and baked and cured to obtain a modified insulating layer with a thickness of about 25 μm, thereby obtaining an insulated wire with a total insulating layer thickness of 120 μm.

[0072] Among them, the material of the bottom insulating layer is a conventional commercially available polyamide-imide paint, and the material of the intermediate insulating layer is a commercially available low-dielectric polyamide-imide paint.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is that in step 1), the amount of dodecanoyl-benzoyl anhydride added is 0, i.e., this comparative example is specifically:

[0075] 1) In a flask equipped with a reflux condenser, 0.1 mol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours. After the reaction was completed, the reaction product was washed with n-hexane, and the solvent was removed under reduced pressure to obtain a modified polyamide-imide intermediate.

[0076] 2) The modified polyamide-imide intermediate obtained in step 1) was further dissolved in NMP to obtain a polyamide-imide varnish (solid content 30%), which was coated on an insulated wire on which a 12 μm bottom insulating layer and an 83 μm intermediate insulating layer had been coated, and was baked and cured to obtain a modified insulating layer having a thickness of about 25 μm, thereby obtaining an insulated wire having a total insulating layer thickness of 120 μm.

[0077] Here, the materials of the bottom insulating layer and the intermediate insulating layer were both conventional commercially available polyimide paint.

[0078] Comparative Example 2

[0079] In this comparative example, the amount of long-chain anhydride carboxylic dodecanoyl-benzoyl anhydride added in the preparation of the polyamide-imide intermediate was 20% of the molar amount of the mixed anhydride.

[0080] The same method as in Example 1 was used to prepare carboxylic dodecanoyl-benzoyl anhydride, and in a flask equipped with a reflux condenser, 20 mmol of carboxylic dodecanoyl-benzoyl anhydride was added, and further 80 mol of TMA was added, 500 ml of ethylbenzene was added, 0.12 mol of MDI was added, and the reaction was carried out at 190°C for 2 hours to obtain a modified polyamide-imide intermediate.

[0081] Further, the modified polyamide-imide intermediate obtained was dissolved in NMP to prepare a modified polyamide-imide varnish, which was coated on an insulated wire on which a 12 μm bottom insulating layer and an 83 μm intermediate insulating layer had been coated, and was baked and cured to obtain a modified insulating layer having a thickness of about 25 μm, thereby obtaining an insulated wire having a total insulating layer thickness of 120 μm.

[0082] Here, the materials of the bottom insulating layer and the intermediate insulating layer were both conventional commercially available polyimide paint.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 1 was only that the coating thickness of the modified polyamide-imide varnish was 5 μm, and the thickness of the intermediate insulating layer was 103 μm.

[0085] In this comparative example, the thickness ratio of the outer insulating layer was 4% of the total insulating layer thickness.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 1 is only that the coating thickness of the modified polyamide-imide varnish is 70 μm, and the thickness of the intermediate layer insulation layer is 38 μm.

[0088] In this comparative example, the thickness of the outer insulation layer accounts for 58% of the total insulation layer thickness.

[0089] Comparative Example 5

[0090] The difference between this comparative example and Example 1 is only that the material of the bottom layer insulation layer is a conventional commercially available polyamide-imide paint, and the thickness is 45 μm; the material of the intermediate layer insulation layer is a conventional commercially available polyamide-imide paint, and the thickness is 50 μm.

[0091] In this comparative example, the bottom layer is a polyamide-imide layer, and at this time, the thickness of the polyamide-imide layer accounts for 42% of the total insulation layer thickness.

[0092] Comparative Example 6

[0093] The difference between this comparative example and Example 1 is only that in Step 1), 500 mL of a three-necked flask is used, and malonic acid (10.4 g, 0.1 mol), benzoic acid (12.2 g, 0.1 mol), and DMAP (4-dimethylaminopyridine) (1.22 g, 0.01 mol) are sequentially added, 200 mL of anhydrous dichloromethane is added, and stirring is performed until the solids are completely dissolved, to prepare benzoxy malonic anhydride (PhCO-O-COCH2COOH). Further, 5 mmol of benzoxy malonic anhydride and 95 mmol of trimellitic anhydride are added to prepare a modified polyamide-imide intermediate.

[0094] The subsequent steps are completely consistent.

[0095] The insulation wires of the examples and comparative examples are respectively tested according to the following methods:

[0096] 1. Flexibility test. The flexibility test is tested by using the flexibility test method provided in IEC60851-3 2019 test method 8, and the specific steps are as follows:

[0097] Two 500 mm straight insulation wires are taken, and the two insulation wires are respectively bent around a polished test core by 180±2°, one is flat wound (core diameter = wire thickness N times, N is 1, 1.5 or 2), and the other is vertical wound (core diameter = wire width N times). In this test, the surface of the product is smooth without cracking, which is recorded as “qualified”; the surface cracking is recorded as “unqualified”.

[0098] 2. 260°C, 30 min thermal shock test

[0099] Test according to test method 9 of GB / T 4074.6-2024.

[0100] Prepare the sample according to 6.2.2 of GB / T 4074.3-2024, take 400mm straight sample line and bend around a polished test mandrel 180±2°, and then wind it flat (mandrel diameter = N times wire thickness).

[0101] Put the sample in a forced air oven and heat for 30min at 260±5℃. Take the sample out of the oven and cool to room temperature, then check the insulation layer for cracking with a 10x magnifying glass. If there is cracking, it is unqualified, if not, it is qualified.

[0102] 3. Softening breakdown test

[0103] Use softening breakdown tester (model HTC600) to test, place the sample line in the instrument, use the temperature rise method to test, record the temperature at the time of breakdown, and evaluate.

[0104] Test conditions:

[0105] Weight of the weight: 1KG, i.e. 9.8N

[0106] Temperature rise rate: 2℃ / min

[0107] Test voltage: 100V

[0108] Target temperature: 600℃

[0109] Evaluation criteria:

[0110] A: 500℃ or above;

[0111] B: 400-500℃

[0112] Test results are shown in the following table:

[0113]

[0114] Note: In the table, 2x means that the mandrel diameter when bending is 2 times the wire width or thickness, 1.5x means that the mandrel diameter when bending is 1.5 times the wire width or thickness, and 1.0x means that the mandrel diameter is 1 times the wire width or thickness.

[0115] From the above test, it can be seen that the insulating wire prepared by the embodiments 1-5 of the present application has no cracking in the 2.0x, 1.5x and 1.0x winding group flexibility test, and the qualified rate is 100%; in the comparative example 1, because all are short-chain anhydride, the flexibility of the prepared insulating wire is insufficient, and the heat shock resistance is also significantly reduced; in the comparative example 2, because the content of long-chain anhydride is too high, the heat resistance is reduced, and the softening breakdown test result is reduced to B, and cracking deformation occurs in different degrees during heat shock; in the comparative example 3, because the coating thickness of the modified polyamide-imide varnish is insufficient, only 4% of the total insulation layer thickness, cracking occurs in the 1.5x and 1.0x winding group flexibility test, and unexpected deformation also occurs during heat shock test, and the overall flexibility is insufficient; in the comparative example 4, because the coating thickness of the modified polyamide-imide varnish is too thick, accounting for 58% of the total insulation layer thickness, which exceeds 50%, the heat resistance is reduced, the softening breakdown test result is reduced to B, and cracking deformation occurs in different degrees during heat shock, the overall heat resistance grade is reduced, and the mechanical property is reduced; in the comparative example 5, when the bottom layer is polyamide-imide, the proportion of polyamide in the total insulation layer thickness is too low, which does not reach 50%, and the heat resistance is reduced. In the comparative example 6, the mixed anhydride is composed of benzoyl malonic anhydride and trimellitic anhydride, that is, it also does not contain long-chain anhydride, and the obtained insulating wire has cracking of many samples in the flexibility test at 25℃ and the heat shock test at 260℃ for 30min.

[0116] The present application adds an appropriate amount of long-chain anhydride and short-chain anhydride to prepare a modified polyamide-imide intermediate, and then coats the outer layer of the insulating wire, and after baking and curing, the obtained insulating wire, and by optimizing the thickness ratio of the polyimide layer in the intermediate layer and the bottom layer insulation layer, the prepared insulating wire has more excellent flexibility and heat resistance.

[0117] In summary, the insulating wire provided by the present application improves the flexibility of the wire, adapts to complex slot type and more closely arranged to improve the slot fill rate of the motor, thereby reducing the volume of the stator core under the same power, indirectly reducing the weight of the motor, and achieving the requirement of light weight.

Claims

1. An insulated electric wire characterized by comprising: The conductor, the inner insulation layer and the outer insulation layer are sequentially arranged outside the conductor, the outer insulation layer comprises a modified insulation layer, the thickness of the modified insulation layer is 10-50% of the sum of the thicknesses of the inner insulation layer and the outer insulation layer, the modified insulation layer is formed by high-temperature curing of a modified polyamide-imide varnish, the modified polyamide-imide varnish is obtained by reacting a diisocyanate with a mixed anhydride, wherein the mixed anhydride comprises a short-chain anhydride and a long-chain anhydride; The molar proportion of the long-chain anhydride is not more than 10% of the mixed anhydride; The inner insulation layer is: 1) a polyimide layer; or 2) a polyamide-imide layer and a polyimide layer; The thickness of the polyimide layer is not less than 50% of the sum of the thicknesses of the inner insulation layer and the outer insulation layer; The long-chain anhydride is an aromatic anhydride, the molecular structure of the aromatic anhydride comprises at least one anhydride structure and one carboxyl group, and the aromatic anhydride is prepared from a long-chain aliphatic diacid or a derivative thereof and a short-chain carboxylic acid or a derivative thereof; wherein the long-chain aliphatic diacid or a derivative thereof refers to a chain aliphatic diacid with not less than 6 carbon atoms; the short-chain carboxylic acid or a derivative thereof refers to a carboxylic acid with a chain aliphatic structure with not more than 5 carbon atoms, or an aromatic monocarboxylic acid with a chain aliphatic substituent with not more than 5 carbon atoms or an unsubstituted aromatic monocarboxylic acid or a derivative thereof.

2. The insulated electric wire according to claim 1, characterized by The short-chain anhydride comprises at least one of an aromatic short-chain anhydride, an aliphatic short-chain anhydride and a cycloaliphatic short-chain anhydride.

3. The insulated electric wire according to claim 2, characterized by The molecular structure of the short-chain anhydride comprises at least one anhydride structure and one carboxyl group, or has a dianhydride structure; The short-chain anhydride is an aromatic short-chain anhydride with a chain aliphatic structure with not more than 5 carbon atoms, an aliphatic short-chain anhydride with a chain aliphatic structure with not more than 5 carbon atoms, or a cycloaliphatic short-chain anhydride with a cyclic aliphatic substituent with not more than 7 carbon atoms.

4. The insulated electric wire according to claim 2, wherein The aromatic short-chain anhydride comprises at least one of trimellitic anhydride, pyromellitic dianhydride, methyl-substituted trimellitic anhydride and ethyl-substituted trimellitic anhydride.

5. The insulated electric wire according to claim 1, wherein The molar proportion of the long-chain anhydride is 3-5% of the mixed anhydride.

6. The insulated electric wire according to claim 1, wherein The molar ratio of the diisocyanate to the mixed anhydride is 1.1-1.2:

1.

7. A coil, characterized by The insulated wire of any one of claims 1-6.

8. An electric / electronic equipment, characterized by comprising: The coil of claim 7.

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