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 of the application 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 polyamide-imide insulating layer coated insulating electric wire of the application improves the flexibility of the wire rod, is suitable for closer arrangement of complex groove types, and thus improves 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, and the requirement of light weight is met.

Description

Technical Field

[0001] This invention relates to the field of insulated wire technology, and more specifically, to an insulated wire, coil, and electronic / electrical device. Background Technology

[0002] Polyamide-imide insulated conductors are widely used in drive motors for new energy vehicles, but their flexibility is significantly limited during actual winding. When the conductor is wound on a mandrel with a diameter 1.5 times the conductor's width (wide-side winding) or 1.5 times the conductor's narrow side (narrow-side winding), the polyamide-imide insulation layer is prone to micro-cracks or even cracking, severely affecting insulation integrity and long-term reliability. This defect limits the application of electromagnetic wire in high-density windings, making it difficult to meet the development requirements of drive motors for "higher slot fill factor" and "superior lightweight design." Improving flexibility can not only adapt to the close arrangement of complex slots and increase the slot fill factor, but also reduce the stator core size (such as shortening the core length or reducing the outer diameter) at the same output power, thereby effectively reducing the overall weight of the motor and achieving lightweight design.

[0003] Therefore, how to modify the flexibility of polyamide-imide insulated wires and break through the existing bottleneck in bending performance has become a key issue that urgently needs to be addressed in the field of insulation wire technology. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide an insulated wire, coil, and electronic / electrical device to solve the problems in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] The first aspect of the present invention is to provide an insulating wire having a highly flexible insulating layer after curing and including the insulating layer.

[0007] The insulated wire includes a conductor, an inner insulation layer and an outer insulation layer sequentially disposed around the outer periphery of the conductor, the outer insulation layer including a modified insulation layer, the thickness of the modified insulation layer being 5-95% of the sum of the thicknesses of the inner insulation layer and the outer insulation layer, the modified insulation layer being formed by high-temperature curing of modified polyamide-imide varnish, the modified polyamide-imide varnish being obtained by reacting diisocyanate with mixed acid anhydrides, wherein the mixed acid anhydrides include short-chain acid anhydrides and long-chain acid anhydrides.

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

[0009] Furthermore, the modified polyamide-imide varnish is obtained by an addition reaction of diisocyanate with a mixed acid anhydride, wherein the mixed acid anhydride includes short-chain acid anhydride and long-chain acid anhydride.

[0010] The short-chain anhydride includes at least one of the following: aromatic short-chain anhydride, aliphatic short-chain anhydride, and alicyclic short-chain anhydride. The aromatic short-chain anhydride refers to an aromatic anhydride having a chain of aliphatic substituents with no more than 5 carbon atoms on its aromatic ring, or an unsubstituted aromatic anhydride. The aliphatic short-chain anhydride refers to an aliphatic anhydride whose molecule contains a chain of aliphatic structures with no more than 5 carbon atoms. The alicyclic short-chain anhydride refers to an alicyclic anhydride whose cyclic alicyclic structure has no more than 7 carbon atoms. The molecular structure of the short-chain anhydride should contain at least one anhydride structure and one carboxyl group; or it should have a dianhydride structure.

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

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

[0013] In this invention, the long-chain anhydride includes at least one of alicyclic anhydrides, aromatic anhydrides, and bio-based long-chain anhydrides. The molecular structure of the long-chain anhydride should contain at least one anhydride structure and one carboxyl group. More specifically, the long-chain anhydride is prepared from a long-chain aliphatic diacid or its derivative and a short-chain carboxylic acid or its derivative.

[0014] In this invention, the long-chain aliphatic diacid or its derivative refers to an aliphatic chain structure with not less than 6 carbon atoms or an alicyclic structure with not less than 8 carbon atoms in its molecular structure. The short-chain carboxylic acid or its derivative refers to an aromatic monocarboxylic acid or its derivative with an aliphatic chain structure with not more than 5 carbon atoms in its molecular structure, or an aromatic monocarboxylic acid substituted with aliphatic substituents with not more than 5 carbon atoms.

[0015] It should be noted that the term "not greater than" in this invention includes the case of 0.

[0016] In this invention, the modified polyamide-imide varnish is formed by reacting a mixed anhydride containing long-chain anhydride and short-chain anhydride with a diisocyanate.

[0017] In the mixed anhydrides, the molar ratio of long-chain anhydrides is less than 10%, preferably 3-5%.

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

[0019] (1) Long-chain aliphatic dicarboxylic acids and monocarboxylic acids are fed in a 1:1 molar ratio, and solvent A, activator and catalyst are added to react and react to obtain long-chain acid anhydrides.

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

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

[0022] The obtained modified polyamide-imide varnish was applied to the wire and heated to cure, forming a modified insulation layer.

[0023] In step (1), the activator is DCC (dicyclohexylcarbodiimide), the catalyst is DMAP (4-dimethylaminopyridine), and solvent A includes dichloromethane and ethylbenzene.

[0024] The activator DCC is diluted and added dropwise in a stirred reactor, wherein the concentration of the diluted DCC is not greater than 3 mol / L. During the DCC addition process, the reaction temperature is preferably 0~10℃, more preferably 0~5℃.

[0025] In this invention, preferably, the activator DCC is added in excess, based on the molar amount of the monocarboxylic acid in the mixed carboxylic acids. The molar ratio of DCC to the monocarboxylic acid is 1.05~1.2:1.

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

[0027] In step (2), the feeding ratio of long-chain anhydrides is no more than 10% of the mixed anhydrides, preferably 3-5%. The feeding ratio is based on molar ratio. In step (2), based on the theoretical amount of diisocyanate added to react with the anhydride, the actual added diisocyanate in this invention is added in excess relative to the anhydride molar ratio, wherein the isocyanate group in the diisocyanate is in excess relative to the sum of the carboxyl group and the anhydride group in the corresponding anhydride by 10-20%. That is, for this invention, when the reactant is a diisocyanate reacting with an anhydride or diacid anhydride containing one anhydride and a carboxyl group, the molar ratio of diisocyanate to anhydride is 1.1-1.2:1.

[0028] In one embodiment of the present invention, the modified polyamide-imide varnish is coated onto a conductor containing a conventional insulation layer and further cured to form an insulated wire with a multilayer insulation structure.

[0029] In a more preferred embodiment of the present invention, the modified polyamide-imide varnish of the present invention has a thickness of 5 to 95% of the total thickness of the insulation layer after curing.

[0030] In this invention, the inner insulating layer is a polyamide-imide layer. Specifically, the inner insulating layer can be:

[0031] 1) Polyamide-imide layer, or

[0032] 2) A 5-10% thick high-adhesion polyamide-imide layer + a functional polyamide-imide layer (such as a corona-resistant polyamide-imide layer, an oil- and water-resistant polyamide-imide layer, etc.).

[0033] Among them, conventional polyamide-imide layers, high-adhesion polyamide-imide layers, corona-resistant polyamide-imide layers, and oil- and water-resistant polyamide-imide layers are all obtained by high-temperature curing of commercially available polyamide-imide paints; such as ELANTAS' TONGMID 595 series and RESONAC' HI 406 series. The above are just examples and not limitations. Products with corresponding effects can be used as inner insulation layer materials.

[0034] Another objective of this invention is to provide an electrical or electronic device prepared from the above-described coil.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The polyamide-imide insulation layer of the present invention improves the flexibility of the wire, adapts to more compact arrangement of complex slots, and thus improves the slot fill factor of the motor. This reduces the volume of the stator core at the same power, indirectly reducing the weight of the motor and achieving the requirement of lightweighting. Detailed Implementation

[0037] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0038] Example 1

[0039] 1) In a 500 mL three-necked flask, dodecanoic acid (20.2 g, 0.1 mol), benzoic acid (12.2 g, 0.1 mol), and DMAP (4-dimethylaminopyridine) (1.22 g, 0.01 mol) were added sequentially, followed by 200 mL of anhydrous dichloromethane. The mixture was stirred until the solids were completely dissolved. The three-necked flask was placed in an ice bath (0-5℃), and a dichloromethane solution of DCC (dicyclohexylcarbodiimide) (24.7 g, 0.12 mol of DCC dissolved in 50 mL of anhydrous dichloromethane) was slowly added dropwise, maintaining the temperature ≤10℃ during the addition. After the addition was complete, the ice bath was removed, and the mixture was stirred at room temperature (25-30℃) for 12-16 hours. After the reaction was stopped, the mixture was filtered, and the filtrate was washed with anhydrous petroleum ether and then rotary evaporated under reduced pressure (0.08 MPa) to obtain a pale yellow oily crude product. Further separation was performed by silica gel column chromatography using ethyl acetate / petroleum ether as eluent. After purification and drying, a white solid terminal carboxyl-dodecanoyl-benzoyl anhydride was obtained, with the structure shown in Formula 1 below.

[0040] Formula 1;

[0041] In a flask equipped with a reflux condenser, 5 mmol of terminal carboxyl-dodecanoyl-benzoic anhydride was added, followed by 95 mmol of trimellitic anhydride (TMA), 500 mL of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190 °C for 2 hours. After the reaction was complete, the product was washed with n-hexane, and the solvent was removed under reduced pressure to obtain the modified polyamide-imide intermediate.

[0042] 2) The modified polyamide-imide intermediate obtained in step 1) is dissolved in NMP (N-methylpyrrolidone) to prepare a modified polyamide-imide varnish (30% solid content). This varnish is then applied to an insulated wire that has been coated with a 70 μm polyamide-imide insulation layer. The conductor size of the wire is 2.5 × 3.8 mm. After baking and curing, an insulated wire with a modified insulation layer thickness of approximately 30 μm is obtained. The total insulation layer thickness of the insulated wire is 100 μm.

[0043] The polyamide-imide varnish corresponding to the 70μm polyamide-imide insulating layer in step 2) is a commercially available product.

[0044] Example 2

[0045] Using the same method as in Example 1, octadecanoic acid was used to prepare a carboxyl-terminated octadecanoyl-benzoic anhydride, the structure of which is shown in Formula 2.

[0046] Formula 2;

[0047] In a flask equipped with a reflux condenser, 3 mmol of terminal carboxyl octadecyl-benzoic anhydride was added, followed by 97 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190 °C for 2 hours to prepare a modified polyamide imide intermediate.

[0048] Furthermore, the obtained modified polyamide-imide intermediate was dissolved in NMP to prepare a modified polyamide-imide varnish (30% solid content), which was then coated onto an insulated wire that had already been coated with a 50 μm polyamide-imide insulation layer. The varnish was then baked and cured to obtain a modified insulation layer with a thickness of approximately 50 μm, for a total insulation layer thickness of 100 μm.

[0049] Example 3

[0050] Using the same method as in Example 1, a carboxyl-terminated hexadecanoyl-benzoyl anhydride was prepared from hexadecanoic acid, with the structure shown in Formula 3.

[0051] Formula 3;

[0052] In a flask equipped with a reflux condenser, 10 mmol of terminal carboxyl hexadecanoyl-benzoic anhydride was added, followed by 90 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190 °C for 2 hours to prepare a modified polyamide-imide intermediate.

[0053] Furthermore, the obtained modified polyamide-imide intermediate was dissolved in a mixed solvent composed of NMP and DMF to prepare a modified polyamide-imide varnish (solid content 30%), which was then coated onto an insulated wire that had already been coated with a 95μm polyamide-imide insulation layer. After baking and curing, a modified insulation layer with a thickness of approximately 5μm was obtained, and the total insulation layer thickness was 100μm.

[0054] Example 4

[0055] Using the same method as in Example 1, terminal carboxyl dodecanoyl-benzoyl anhydride was prepared. In a flask equipped with a reflux condenser, 5 mmol of terminal carboxyl dodecanoyl-benzoyl anhydride was added, followed by 95 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190 °C for 2 hours to prepare a modified polyamide imide intermediate.

[0056] Furthermore, 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 (30% solid content). This varnish was then coated onto an insulated wire that had already been coated with a 10μm bottom insulation layer and a 60μm intermediate insulation layer. After baking and curing, a modified insulation layer with a thickness of approximately 30μm was obtained, and the total insulation layer thickness was 100μm. The bottom insulation layer was made of conventional polyamide-imide varnish, and the intermediate insulation layer was made of corona-resistant polyamide-imide varnish.

[0057] Example 5

[0058] Using the same method as in Example 1, terminal carboxyl dodecanoyl-benzoyl anhydride was prepared. In a flask equipped with a reflux condenser, 5 mmol of terminal carboxyl dodecanoyl-benzoyl anhydride was added, followed by 95 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190 °C for 2 hours to prepare a modified polyamide imide intermediate.

[0059] Furthermore, the obtained modified polyamide-imide intermediate was dissolved in DMF to prepare a modified polyamide-imide varnish (30% solid content), which was then coated onto an insulated wire that had already been coated with a 30μm polyamide-imide insulation layer. After baking and curing, a modified insulation layer with a thickness of approximately 70μm was obtained, and the total insulation layer thickness was 100μm.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that the modified polyamide-imide varnish prepared in Example 1 was not coated on the insulated wire coated with a 100 μm polyamide-imide insulation layer; that is, the thickness of the modified insulation layer was 0.

[0062] Comparative Example 2

[0063] Using the same method as in Example 1, terminal carboxyl-dodecanoyl-benzoic anhydride was prepared. In a flask equipped with a reflux condenser, 20 mmol of terminal carboxyl-dodecanoyl-benzoic anhydride was added, followed by 80 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190°C for 2 hours to prepare a modified polyamide-imide intermediate. Further, the obtained modified polyamide-imide intermediate was dissolved in NMP to prepare a modified polyamide-imide varnish (30% solids content). This varnish was coated onto an insulated wire already coated with a 70 μm polyamide-imide insulation layer, and baked to cure, resulting in a modified polyamide-imide-coated wire with a thickness of approximately 30 μm, thus obtaining an insulated wire with a total insulation layer thickness of 100 μm.

[0064] In this comparative example, when preparing the modified polyamide imide intermediate, the amount of long-chain anhydride with a terminal carboxyl group of dodecanoyl-benzoyl anhydride added was 20% of the molar amount of the mixed anhydrides.

[0065] Comparative Example 3

[0066] Using the same method as in Example 1, terminal carboxyl-dodecanoyl-benzoic anhydride was prepared. In a flask equipped with a reflux condenser, 5 mmol of terminal carboxyl-dodecanoyl-benzoic anhydride was added, followed by 95 mmol of TMA, 500 ml of ethylbenzene, and 0.12 mol of MDI. The mixture was refluxed at 190°C for 2 hours to prepare a modified polyamide-imide intermediate. Further, the obtained modified polyamide-imide intermediate was dissolved in NMP to prepare a modified polyamide-imide varnish. This varnish was coated onto an insulated wire already coated with a 98 μm polyamide-imide insulation layer, and baked to cure, resulting in a modified insulation layer with a thickness of approximately 2 μm. This yielded an insulated wire with a total insulation layer thickness of 100 μm.

[0067] In this comparative example, the thickness of the outer insulation layer accounts for 2% of the total insulation layer thickness.

[0068] The insulated wires of Examples 1-5 and Comparative Examples 1-3 were tested as follows:

[0069] 1. Flexibility test at 25℃

[0070] The flexibility test shall be conducted according to the following method. The flexibility test shall be conducted using the flexibility test method provided in IEC 60851-3 2019 Test Method 8, and the specific steps are as follows:

[0071] Take two 500mm long straight insulated wires. Bend each wire 180±2° around a polished test core. One wire is wound horizontally (core diameter = N times wire thickness, where N is 1.0 or 1.5), and the other is wound vertically (core diameter = N times wire width). In this test, after horizontal and vertical winding, a smooth, crack-free surface is recorded as "qualified"; a cracked surface is recorded as "unqualified".

[0072] 2. Thermal shock test at 240℃ for 30 minutes

[0073] The test was conducted using the test method provided in GB / T4074.6-2024 Test Method 9.

[0074] Prepare the specimen according to the provisions of 6.2.2 in GB / T4074.3-2024. Take a 400mm straightening sample wire and bend it 180±2° around a polished test shaft for flat winding (shaft diameter = wire thickness N times).

[0075] Place the sample in a forced-ventilation oven and heat for 30 minutes at a temperature of 240±5℃. Remove the sample from the oven and cool it to room temperature. Then, examine the insulation layer for cracks using a 10x magnifying glass. The presence of cracks indicates a failure, while the absence of cracks indicates a pass.

[0076] 3. Solvent resistance test

[0077] Solvent resistance tests were conducted using the test method provided in GB / T4074.4-2024 / IEC60851-4:2016 Test Method 12.

[0078] A straightening sample approximately 150 mm long is pretreated in a forced-ventilation oven at (130±3)℃ for (10±1) min. Then, the effective length of the sample is immersed in a glass container filled with standard solvent at (60±3)℃ for (30±3) min. The sample is then removed from the solvent. The surface hardness should be tested within 30 seconds of removal.

[0079] The standard solvent for this test method is a mixture in the following proportions (by volume): 60% petroleum solvent with a maximum aromatic content of 18%, 30% xylene, and 10% butanol.

[0080] This experiment used a commercially available NRJ-I solvent resistance tester to test the surface hardness, and the pencil hardness was selected as 6H.

[0081] The test is conducted three times. If the paint film is scraped off and the conductor is exposed, it is considered unqualified; otherwise, it is considered qualified.

[0082] The test results are shown in the table below:

[0083]

[0084] Note: In the table, 1.5x means that the diameter of the core of the insulated wire when it is bent is 1.5 times the wire width or thickness, and 1.0x means that the diameter of the core when it is bent is 1.0 times the wire width or thickness.

[0085] As can be seen from the above tests, when the wires of Examples 1-5 and Comparative Examples 1-3 were repeatedly tested for flexibility, no cracking occurred in the 1.5x winding group, and the pass rate was 100%. However, Comparative Examples 1-3 all cracked when the flexibility of the 1.0x winding group was tested. In comparison, the wires of Examples 1-5 were all 100% qualified. In the thermal shock test, the pass rate of Comparative Examples 1-3 for the 1.0x winding group was significantly reduced, that is, the winding wire underwent undesirable deformation. The wires of Examples 1-5 were all 100% qualified at 1.0x. In addition, in Comparative Example 2, due to the excessive content of long-chain anhydride, its solvent resistance was significantly reduced, and the test result was unqualified.

[0086] This invention prepares a modified polyamide-imide intermediate by adding an appropriate amount of long-chain anhydride and short-chain anhydride, which is then coated on the outer layer of an insulated wire. After baking and curing, the resulting insulated wire has better flexibility and heat resistance, while also ensuring its solvent resistance.

[0087] In summary, the insulated wire provided by this invention improves the flexibility of the wire, adapts to more compact arrangement of complex slots, and thus improves the slot fill factor of the motor. This reduces the volume of the stator core at the same power, indirectly reducing the weight of the motor and achieving the requirement of lightweighting.

Claims

1. An insulated electric wire characterized by comprising: The conductor, an inner insulation layer and an outer insulation layer arranged in sequence outside the conductor, the outer insulation layer comprising a modified insulation layer, the thickness of the modified insulation layer being 5-95% of the total thickness of the inner insulation layer and the outer insulation layer, the modified insulation layer being formed by high-temperature curing of a modified polyamide-imide varnish obtained by reacting a diisocyanate with a mixed anhydride, wherein the mixed anhydride comprises a short-chain anhydride and a long-chain anhydride; The long-chain anhydride is an aromatic anhydride; the aromatic anhydride comprises at least one anhydride structure and one carboxyl group in the molecular structure; 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 not more than 5 carbon atoms in the aliphatic chain structure, or an aromatic monocarboxylic acid with not more than 5 carbon atoms in the chain aliphatic substituent or an unsubstituted aromatic monocarboxylic acid or a derivative thereof; The molar proportion of the long-chain anhydride is not more than 10% of the mixed anhydride.

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 short-chain anhydride comprises at least one anhydride structure and one carboxyl group in the molecular structure, or has a dianhydride structure; The short-chain anhydride is an aromatic short-chain anhydride with not more than 5 carbon atoms in the chain aliphatic structure, an aliphatic short-chain anhydride with not more than 5 carbon atoms in the chain aliphatic structure, or a cycloaliphatic short-chain anhydride with not more than 7 carbon atoms in the cyclic aliphatic substituent.

4. The insulated electric wire according to claim 2, characterized by 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, characterized by 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. The insulated electric wire according to claim 1, characterized by The inner insulation layer is a polyamide-imide layer.

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

9. An electric / electronic equipment, characterized by comprising: The coil according to claim 8.

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