Insulating varnishes, enameled wires and their preparation methods based on nanocomposite materials

Abstract

This invention relates to the field of enameled wire production technology, and more particularly to an insulating varnish and enameled wire based on nanocomposite materials. The insulating varnish comprises the following components by weight percentage: polyester resin: 40-60%, amide-imide resin: 15-25%, xylene: 10-25%, N-methylpyrrolidone: 5-15%, nano-silica: 1.0-5.0%, nano-alumina: 0.5-2.0%, fluorinated surfactant: 0.5-2.5%, epoxy resin tackifier: 0.2-2.0%, antioxidant: 0.2-0.5%, and ultraviolet absorber: 0.1-0.5%. This invention significantly improves the mechanical strength, abrasion resistance, and heat resistance of the varnish layer by introducing nano-silica and nano-alumina; improves the wettability and adhesion of the varnish by adding fluorinated surfactant; and enhances the adhesion and durability of the varnish layer by using epoxy resin tackifier.

Description

Technical Field

[0001] This invention relates to the field of enameled wire production technology, and in particular to an insulating varnish based on nanocomposite materials, an enameled wire, and a method for preparing the same. Background Technology

[0002] Enameled wire, a key material widely used in motors, electrical appliances, transformers, and electronic equipment, directly affects the reliability and lifespan of these devices. The core of enameled wire lies in its insulating varnish layer, which not only needs excellent insulation properties but also high mechanical strength, heat resistance, and adhesion to ensure long-term stable operation under various complex working conditions.

[0003] Traditional enameled wire insulation primarily consists of polymer resins, solvents, and various additives. Commonly used polymer resins include polyester resins, polyurethane resins, and polyamide-imide resins. These resins provide basic mechanical strength and insulation properties. However, with the increasingly harsh operating environments of electronic devices and motors, the performance requirements for enameled wires are constantly increasing, and traditional formulations and processes are no longer sufficient to meet these demands. In particular, maintaining stable insulation and mechanical properties in harsh environments such as high temperature, high humidity, and high frequency has become an urgent problem to be solved.

[0004] In recent years, the introduction of nanomaterials has provided new ideas for improving the performance of enameled wires. Due to their ultra-high specific surface area and unique physicochemical properties, nanomaterials have significant advantages in enhancing material performance. For example, Chinese invention patent application publication number CN115926615A (publication date: April 7, 2023) discloses a high-wear-resistant polyimide enameled wire varnish and its preparation method. The polyimide enameled wire varnish comprises the following components in weight percentages: 40-76 parts of fluorinated polyimide; 10-20 parts of nano-silica; 0.2-0.9 parts of polydimethylsiloxane; 1-6 parts of modified graphene; and 1-6 parts of nano-calcium carbonate. By introducing fluorine atoms into the polyimide, the wear resistance of the polyimide enameled wire varnish is improved. The addition of polydimethylsiloxane along with nano-silica to the polyimide composite material enhances the frictional properties of the polyimide enameled wire varnish through their synergistic effect. Furthermore, the tribological properties of the polyimide composite material are significantly improved by mixing and filling nano-calcium carbonate and graphene due to their synergistic effect. Through the synergistic effect between the components, the final polyimide enameled wire varnish exhibits high wear resistance.

[0005] Meanwhile, the applicant filed a Chinese invention patent application (application number: 2024105462138, application date: 20240506) disclosing a modified polyamide-imide enameled wire topcoat. The topcoat is prepared from raw materials comprising the following components: 1-8 parts graphene, 1-5 parts silica nanoparticles, 1-5 parts fluororubber, 1-5 parts nano-alumina, 70-95 parts modified polyamide-imide, 1-10 parts isopropanol, and 1-10 parts ethyl acetate. The modified polyamide-imide is obtained by reacting polyamide-imide with bisphenol A type epoxy resin. This invention not only improves the basic properties of enameled wire, such as heat resistance and electrical insulation, but also specifically addresses the requirements for wear resistance and a low coefficient of friction, while enhancing resistance to chemical corrosion and mechanical strength, providing a superior material choice for high-performance motors and electrical appliances.

[0006] However, traditional insulating varnishes have weak adhesion to metal wire surfaces, leading to varnish peeling or cracking during use. This not only affects the insulation performance of the enameled wire but may also cause electrical faults and safety hazards. How to significantly improve the adhesion between the varnish layer and the metal wire through formulation and process improvements is a crucial issue that urgently needs to be addressed. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide an insulating varnish based on nanocomposite materials. By introducing nano-silica and nano-alumina, the mechanical strength, abrasion resistance, and heat resistance of the varnish layer are significantly improved; by adding fluorinated surfactants, the wetting and adhesion of the varnish are improved; and by using epoxy resin tackifiers, the adhesion and durability of the varnish layer are enhanced. Furthermore, by optimizing solvent selection and coating curing processes, the uniformity and environmental friendliness of the varnish layer are ensured, thereby preparing an insulating varnish with excellent comprehensive performance to meet the needs of modern high-performance electronic devices and motors.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An insulating varnish based on nanocomposite materials, comprising the following components by weight percentage:

[0010] Polyester resin: 40-60%

[0011] Polyamide-imide resin: 15-25%

[0012] Xylene: 10-25%

[0013] N-Methylpyrrolidone: 5-15%

[0014] Nano-silica: 1.0-5.0%

[0015] Nano-alumina: 0.5-2.0%

[0016] Fluorinated surfactants: 0.5-2.5%

[0017] Epoxy resin tackifier: 0.2-2.0%

[0018] Antioxidant: 0.2-0.5%

[0019] Ultraviolet absorber: 0.1-0.5%.

[0020] Preferably, the insulating varnish consists of the following components by weight percentage:

[0021] Polyester resin: 45-55%

[0022] Polyamide-imide resin: 18-20%

[0023] Xylene: 15-20%

[0024] N-Methylpyrrolidone: 8-12%

[0025] Nano-silica: 1.5-3.0%

[0026] Nano-alumina: 1.0-1.5%

[0027] Fluorinated surfactants: 0.8-1.5%

[0028] Epoxy resin tackifier: 0.5-1.5%

[0029] Antioxidant: 0.2-0.5%

[0030] Ultraviolet absorber: 0.1-0.5%.

[0031] Preferably, the polyester resin is one of the following: DuPont's Rynite FR530, DSM's Arnite T06200, BASF's Ultradur B4300 G6, SABIC's Valox 420SE0, and Eastman's Tritan EX401.

[0032] Preferably, the polyamide-imide resin is selected from one of the following: Solvay's Torlon 4000T, Torlon AI-10, Amodel A-1000, Mitsui Chemicals' Aurum PL450C, and Saint-Gobain's Meldin 7001.

[0033] Preferably, the fluorinated surfactant is one or a mixture of fluorinated alkyl surfactants, fluorinated alkyl phosphates, fluorinated alkyl alcohol polyoxyethylene ethers, fluorinated alkyl polyethers, and fluorinated alkyl alcohols. More preferably, the fluorinated surfactant is one of DuPont's Zonyl FSN-100 and Zonyl FSP, Chemours' Capstone FS-3100 and Capstone FS-63, 3M's Novec 2704 and Novec FC-4432, and Solvay's Forafac 1157.

[0034] Preferably, the epoxy resin tackifier is one or a mixture of bisphenol A type liquid epoxy resin, bisphenol A type solid epoxy resin, and modified amine epoxy resin curing agent. More preferably, the epoxy resin tackifier is one of Dow Chemical DER 331, Huntsman Epon 828, Araldite GY 6010, Westlake Chemical Epikote 1001, and EpikureCuring Agent 3253.

[0035] Preferably, the surface area of ​​the nano-silica is 100-300 m² / g, and the surface is treated with organosilane; the average particle size of the nano-alumina is 10-50 nanometers; even more preferably, the nano-silica is Evonik Aerosil R812S or Cabot Cab-O-Sil TS-720; and the nano-alumina is Nanophase Technologies NanOx or US Research Nanomaterials NanoTek.

[0036] Furthermore, the present invention also discloses a method for preparing the insulating varnish, the method comprising the following steps:

[0037] 1) Weigh out the polyester resin and polyamide-imide resin, prepare xylene and NMP, and add the polyester resin and polyamide-imide resin to a mixing container; add xylene and N-methylpyrrolidone in proportion; use a mechanical stirrer to stir at 300-500 rpm for 20-40 minutes to ensure that the resin is completely dissolved;

[0038] 2) While continuing to stir, slowly add nano-silica; increase the stirring speed to 1000-1500 rpm and stir for 20-40 minutes to ensure uniform dispersion of nano-SiO2; while continuing to stir, slowly add nano-alumina, increase the stirring speed to 1500-2000 rpm, and stir again for 30-40 minutes to ensure uniform dispersion of nano-Al2O3.

[0039] 3) Add the fluorinated surfactant in the specified proportion and continue stirring for 10-15 minutes; add the epoxy resin tackifier and continue stirring for 20-25 minutes; finally, add the antioxidant and UV absorber and continue stirring for 15-20 minutes to ensure uniform dispersion.

[0040] 4) Filtration and degassing: Use a 200-mesh filter to filter the evenly mixed paint to remove impurities and undissolved particles; place the filtered paint in a vacuum degassing device with a vacuum degree of -0.08 MPa for 30 minutes to remove air bubbles from the paint.

[0041] Furthermore, the present invention also discloses an enameled wire, wherein the enamel of the enameled wire is the aforementioned enamel.

[0042] Furthermore, the present invention also discloses a method for preparing the enameled wire, the method comprising the following steps:

[0043] 1. Surface pretreatment

[0044] The metal wires were chemically etched using a 5% sulfuric acid solution for 1.5-3.0 minutes; then rinsed with deionized water and dried; and finally, the metal wires were surface activated using a plasma processor for 1-1.5 minutes at a power of 100-120W.

[0045] 2. Multi-layer coating

[0046] First coating:

[0047] The pretreated metal wire is first coated at a speed of 1-1.5 m / min using a coating device; after coating, it is pre-dried in an oven at 80-85°C for 5-8 minutes.

[0048] First curing:

[0049] The pre-baked metal wire is first cured in a curing oven at 150-160°C for 10-15 minutes.

[0050] Second coating and curing:

[0051] Repeat the first coating and curing steps, performing a total of three coatings and curing processes to ensure the formation of a uniform and dense multi-layer paint film;

[0052] 3. Final curing

[0053] After the final coating, a UV curing device is used for curing, with a UV power of 200-220 mW / cm² and a curing time of 30-40 seconds.

[0054] By employing the above-mentioned technical solution, the formulation of this invention mainly integrates key components such as nanomaterials, high-performance resins, fluorinated surfactants, and epoxy resin tackifiers, achieving the following technical effects:

[0055] 1. Improve the adhesion between the paint layer and the metal wire.

[0056] The addition of a fluorinated surfactant significantly improved the wettability of the paint on the metal wire surface. This surfactant reduces the interfacial tension between the paint and the metal surface, enhancing the adhesion between the paint layer and the substrate. Furthermore, the use of an epoxy resin tackifier, through chemical bonding with the metal surface, further enhanced the adhesion of the paint layer. The combination of these two factors makes the paint layer more difficult to peel off under mechanical or thermal stress, effectively preventing cracking and flaking.

[0057] 2. Enhances the mechanical strength and abrasion resistance of the paint layer.

[0058] By introducing nano-silica and nano-alumina, the mechanical strength and abrasion resistance of the coating are significantly improved. These nanofillers have extremely high specific surface area and excellent mechanical properties, and can form a uniformly distributed reinforcing phase in the coating layer, improving the overall abrasion resistance and impact resistance of the coating layer. This makes the enameled wire more durable during processing and application, reducing damage and failure caused by external forces.

[0059] 3. Improve the high-temperature resistance and environmental stability of the paint layer.

[0060] The addition of polyamide-imide resin effectively improves the high-temperature resistance of the paint layer. This resin maintains good physical and chemical stability under high-temperature conditions, preventing softening or chemical decomposition of the paint layer in high-temperature environments. Simultaneously, the application of ultraviolet absorbers (such as UV-328) and antioxidants (such as BHT) enhances the paint layer's anti-aging ability, effectively resisting the damage from ultraviolet radiation and oxidative environments.

[0061] 4. Improved environmental protection and safety

[0062] By optimizing solvent usage and introducing UV curing technology, the amount of organic solvents used and the emission of volatile organic compounds (VOCs) have been significantly reduced. This not only mitigates the environmental impact of paint production and application but also improves the safety of the operating environment, meeting modern environmental and safety standards for production.

[0063] 5. Improve the controllability of the manufacturing process and product consistency.

[0064] By precisely controlling the proportions of various components in the enamel formula and using advanced coating and curing processes, a high degree of consistency in enamel layer thickness and quality has been achieved. This increased controllability makes the quality of enameled wire products more stable, reduces the scrap rate in the production process, and improves overall manufacturing efficiency. Detailed Implementation

[0065] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0066] Example 1

[0067] Formula composition (by weight):

[0068] Polyester resin: 50%

[0069] Polyamide-imide resin: 18%

[0070] Xylene: 16.5%

[0071] N-Methylpyrrolidone: 10%

[0072] Nano silica (Evonik Aerosil R812S): 2%

[0073] Nanophase Technologies NanOx: 1%

[0074] Fluorinated surfactant (Zonyl FSN-100): 1%

[0075] Epoxy resin tackifier (DER 331): 1%

[0076] Antioxidant (BHT): 0.3%

[0077] Ultraviolet absorber (UV-328): 0.2%;

[0078] The components are as follows: the polyester resin used is BASF's Ultradur B4300 G6; the polyamide-imide resin used is Solvay Torlon series Torlon 4000T; the nano silica (Evonik Aerosil R812S), particle size: 7 nm (average), surface treatment: oleophilic silicone treatment, surface area (approximately 260 m² / g); the nano alumina (Nanophase Technologies NanOx), particle size: 20 nm (average); the fluorinated surfactant (Zonyl FSN-100), manufactured by DuPont, contains fluorinated alkyl surfactants; the epoxy resin tackifier (DER331), Dow Chemical, composition: bisphenol A type liquid epoxy resin; other components were obtained from conventional market channels.

[0079] The preparation method of the above-mentioned insulating varnish is as follows:

[0080] 1. Mixing polymer resins and solvents

[0081] Weigh out the polyester resin and polyamide-imide resin, and prepare xylene and NMP; add the polyester resin and polyamide-imide resin to a mixing container; add xylene and NMP in proportion; use a mechanical stirrer to stir at 300-500 rpm for 30 minutes to ensure that the resin is completely dissolved.

[0082] 2. Dispersed nanofillers

[0083] While continuing to stir, slowly add nano-silica (Evonik Aerosil R812S); increase the stirring speed to 1000-1500 rpm and stir for 30 minutes to ensure uniform dispersion of nano-SiO2; while continuing to stir, slowly add nano-alumina (Nanophase Technologies NanOx); increase the stirring speed to 1500-2000 rpm and stir again for 30 minutes to ensure uniform dispersion of nano-Al2O3.

[0084] 3. Adding additives

[0085] Add Zonyl FSN-100 in the specified proportion and continue stirring for 10 minutes; add DER 331 in the specified proportion and continue stirring for 20 minutes; add BHT and UV-328 in the specified proportions respectively and continue stirring for 15 minutes to ensure uniform dispersion.

[0086] 4. Filtration and degassing

[0087] Use a 200-mesh filter to filter the well-mixed paint to remove impurities and undissolved particles; place the filtered paint in a vacuum degassing device with a vacuum degree of -0.08 MPa for 30 minutes to remove air bubbles from the paint.

[0088] The coating and curing process of the above-mentioned insulating varnish is as follows:

[0089] 1. Surface pretreatment

[0090] The metal wire was chemically etched using a 5% sulfuric acid solution for 2 minutes, then rinsed with deionized water and dried. Next, the metal wire underwent surface activation treatment using a plasma processor for 1 minute at a power of 100 W.

[0091] 2. Multi-layer coating

[0092] The pretreated metal wire is first coated at a speed of 1 m / min using a coating device; after coating, it is pre-baked in an oven at 80°C for 5 minutes.

[0093] First curing:

[0094] The pre-baked metal wire is first cured in a curing oven at 150°C for 10 minutes.

[0095] Second coating and curing:

[0096] Repeat the first coating and curing steps, performing a total of three coatings and curing processes to ensure the formation of a uniform and dense multilayer paint film.

[0097] 3. Final curing

[0098] After the final coating, a UV curing device is used for curing, with a UV power of 200 mW / cm² and a curing time of 30 seconds.

[0099] Example 2

[0100] Formula composition (by weight):

[0101] Polyester resin: 45%

[0102] Polyamide-imide resin: 20%

[0103] Xylene: 20%

[0104] N-Methylpyrrolidone: 8%

[0105] Nano silica (Cabot Cab-O-Sil TS-720): 3%

[0106] Nano-alumina (Nanophase Technologies NanOx): 1.0%

[0107] Fluorinated surfactant (Capstone FS-3100): 1.5%

[0108] Epoxy resin tackifier (Epon 828): 1%

[0109] Antioxidant (BHT): 0.3%

[0110] Ultraviolet absorber (UV-328): 0.2%;

[0111] The preparation method and coating and curing process of the above-mentioned insulating varnish are as described in Example 1.

[0112] Example 3

[0113] Formula composition (by weight):

[0114] Polyester resin: 54%

[0115] Polyamide-imide resin: 18%

[0116] Xylene: 15%

[0117] N-Methylpyrrolidone: 8%

[0118] Nano-silica (Evonik Aerosil R812S): 1.5%

[0119] Nano-alumina (US Research Nanomaterials NanoTek): 1.0%

[0120] Fluorinated surfactant (Novec 2704): 1%

[0121] Epoxy resin tackifier (Araldite GY 6010): 1%

[0122] Antioxidant (BHT): 0.3%

[0123] Ultraviolet absorber (UV-328): 0.2%;

[0124] The preparation method and coating and curing process of the above-mentioned insulating varnish are as described in Example 1.

[0125] Comparative Example 1

[0126] Formula composition (by weight):

[0127] Polyester resin: 60%

[0128] Polyamide-imide resin: 20%

[0129] Xylene: 20%

[0130] The raw materials are sourced as in Example 1, and contain no nanomaterials, no fluorinated surfactants, no epoxy resin tackifiers, no antioxidants, and no UV absorbers.

[0131] Comparative Example 2

[0132] Formula composition (by weight):

[0133] Polyester resin: 50%

[0134] Polyamide-imide resin: 20%

[0135] 2% Nano-silica

[0136] 1% Nano-alumina

[0137] Xylene: 16.5%

[0138] N-Methylpyrrolidone: 10%

[0139] Antioxidant: 0.3%

[0140] Ultraviolet absorber: 0.2%;

[0141] The raw materials and preparation methods are as described in Example 1, with no fluorinated surfactants and no epoxy resin tackifiers.

[0142] Comparative Example 3

[0143] Formula composition (by weight):

[0144] Polyester resin: 50%

[0145] Polyamide-imide resin: 20%

[0146] Xylene: 15.5%

[0147] N-Methylpyrrolidone: 10%

[0148] Nano silica: 2%

[0149] Nano-alumina: 1%

[0150] Epoxy resin tackifier (DER 331): 1%

[0151] Antioxidant: 0.3%

[0152] Ultraviolet absorber: 0.2%;

[0153] The source of raw materials and preparation method are as in Example 1, and the surfactant is fluorinated.

[0154] Comparative Example 4

[0155] Formula composition (by weight):

[0156] Polyester resin: 50%

[0157] Polyamide-imide resin: 20%

[0158] Xylene: 15.5%

[0159] N-Methylpyrrolidone: 10%

[0160] Nano silica: 2%

[0161] Nano-alumina: 1%

[0162] Fluorinated surfactant: 1%

[0163] Antioxidant: 0.3%

[0164] Ultraviolet absorber: 0.2%;

[0165] The raw material source and preparation method are the same as in Example 1, without epoxy resin tackifier.

[0166] 1. Specific testing methods for adhesion

[0167] Adhesion testing typically employs the cross-cut test, which is performed according to standard ISO 2409. The specific test steps are as follows:

[0168] Test steps

[0169] Sample preparation: Prepare the enameled wire sample, ensuring that its surface is flat, dry and free of contamination; apply and cure the paint to be tested on the sample surface, ensuring that the paint layer thickness is uniform.

[0170] Grid marking: Use a grid cutter (6 teeth) to mark a grid of mutually perpendicular parallel lines on the paint film surface; the grid size is 1mm×1mm or 2mm×2mm, depending on the thickness of the paint film and standard requirements.

[0171] Tape application: Use transparent tape (3M 610) and apply it firmly to the grid area, ensuring there are no air bubbles; the width of the tape should cover the entire grid area.

[0172] Tearing off the tape: Quickly and evenly tear off the tape vertically; check and record the extent of paint film peeling within the marked areas.

[0173] Evaluation results:

[0174] Based on the extent of paint film peeling, an evaluation is conducted against standards, typically categorized into grades ranging from 0B (no paint film peeling) to 5B (complete peeling).

[0175] Evaluation criteria for test results

[0176] grade describe 0B The paint film was completely undamaged and there was no peeling. 1B A small amount of paint film has peeled off at the intersection (≤5%). 2B A small amount of paint film has peeled off at the intersection points (5-15%). 3B There is obvious peeling of the paint film at the intersection points (15-35%). 4B Significant paint film peeling occurred at the intersection points (35-65%). 5B The paint film has almost completely peeled off (>65%).

[0177] 2. Mechanical strength test

[0178] Tensile strength: Tested using a universal testing machine according to ASTM D638 standard.

[0179] Elongation at break: The elongation at break of the sample is measured in a tensile test, in accordance with ASTM D638.

[0180] 3. Abrasion resistance test

[0181] The wear resistance test was performed using a Taber abrasion tester according to ASTM D4060. The wear volume was recorded in mm³.

[0182] 4. Heat resistance test

[0183] The sample was placed in a high-temperature environment of 200°C for 24 hours, and the changes in the paint layer were observed and recorded, including discoloration and cracking.

[0184] The following is a table of test data for adhesion, mechanical strength, abrasion resistance, and heat resistance based on examples and comparative examples:

[0185] sample Adhesion (Grade) Tensile strength (MPa) Elongation at break (%) Wear volume (mm³) Heat resistance (200°C) Example 1 0B 125 12 3 No significant changes Example 2 0B 130 13 2.5 No significant changes Example 3 0B 128 12.5 2.8 No significant changes Comparative Example 1 4B 90 7 15 Discoloration and cracking Comparative Example 2 3B 100 8 10 Slight discoloration Comparative Example 3 2B 110 9 8 Slight discoloration Comparative Example 4 2B 110 9 8 Slight discoloration

[0186] Analysis of the adhesion, mechanical strength, abrasion resistance, and heat resistance test results of the examples and comparative examples leads to the following conclusions:

[0187] Adhesion:

[0188] The adhesion of Examples 1-3 all reached Grade 0B, and the paint layer did not peel off in the cross-cut test, demonstrating extremely high adhesion.

[0189] The adhesion of Comparative Example 1 was 4B, and the paint layer showed obvious peeling, indicating that the traditional formula had significant deficiencies in adhesion.

[0190] Comparative Examples 2, 3, and 4 showed adhesion grades of 3B and 2B, respectively, with slight peeling of the paint layer, indicating that the formulation lacking fluorinated surfactants and epoxy resin tackifiers could not provide sufficient adhesion.

[0191] Mechanical strength:

[0192] The tensile strength and elongation at break of Examples 1-3 were significantly higher than those of the comparative examples, indicating that the addition of nanofillers and tackifiers effectively improved the mechanical properties of the coating.

[0193] The lower tensile strength and elongation at break of Comparative Example 1 indicate that the traditional formulation has shortcomings in terms of mechanical properties.

[0194] Abrasion resistance:

[0195] The wear volume of Examples 1-3 was significantly smaller than that of the comparative example, indicating that the introduction of nano-SiO2 and nano-Al2O3 significantly improved the wear resistance of the coating.

[0196] Comparative Example 1 showed the largest wear volume, while the traditional formula performed poorly in terms of wear resistance.

[0197] Heat resistance:

[0198] Examples 1-3 showed no significant changes at 200°C, indicating that the addition of polyamide-imide resin and antioxidants effectively improved the heat resistance of the coating.

[0199] Comparative Example 1 showed discoloration and cracking at high temperatures, indicating that the traditional formula had significant deficiencies in heat resistance.

[0200] Comparative Examples 2, 3, and 4 showed slight discoloration at high temperatures, indicating that although some improved materials were introduced, the heat resistance problem was not completely solved.

[0201] To verify the effects of surface pretreatment and multi-layer coating on the adhesion of insulating varnish, the following experiment was designed. The changes in adhesion were evaluated by comparing samples with different surface treatment methods and coating layers.

[0202] 1. Surface pretreatment methods

[0203] Chemical etching: The metal wire is chemically etched using a 5% sulfuric acid solution for 2 minutes; then rinsed with deionized water and dried.

[0204] Plasma treatment: The metal wire is surface activated using a plasma processor for 1 minute at a power of 100 W.

[0205] 2. Number of coating layers

[0206] Single-layer coating: Only one coating and curing process is performed.

[0207] Multi-layer coating: Three coats and curing processes are performed to ensure the formation of a uniform and dense multi-layer paint film.

[0208] 3. Sample grouping

[0209] Sample number Surface pretreatment methods Number of coating layers Sample A No processing single layer Sample B Chemical etching single layer Sample C Chemical etching + plasma treatment single layer Sample D Chemical etching Multi-story Sample E Plasma treatment Multi-story Sample F Chemical etching + plasma treatment Multi-story

[0210] Test methods

[0211] Use the cross-cut test and operate according to ISO 2409 standard.

[0212] Data Table

[0213] Sample number Surface pretreatment methods Number of coating layers Adhesion (Grade) Sample A No processing single layer 2B Sample B Chemical etching single layer 2B Sample C Chemical etching + plasma treatment single layer 1B Sample D Chemical etching Multi-story 0B Sample E Plasma treatment Multi-story 0B Sample F Chemical etching + plasma treatment Multi-story 0B

[0214] Experimental data show that surface pretreatment (chemical etching or plasma treatment) and multi-layer coating significantly improve the adhesion of insulating varnish:

[0215] Surface pretreatment: Plasma treatment is better than chemical etching in improving adhesion, indicating that plasma treatment can more effectively activate the metal surface and improve the adhesion of the paint.

[0216] Multi-layer coating: Compared with single-layer coating, multi-layer coating can significantly improve the adhesion of the paint layer, forming a uniform and dense multi-layer paint film, making the paint layer more durable.

[0217] Overall effect: The combination of chemical etching or plasma treatment with multi-layer coating can maximize the adhesion of insulating varnish and achieve the best technical effect.

[0218] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A method for producing an enameled wire, characterized by, The preparation method includes the following steps: 1) Surface pretreatment The metal wires were chemically etched using a 5% sulfuric acid solution for 1.5-3.0 minutes; then rinsed with deionized water and dried; and finally, the metal wires were surface activated using a plasma processor for 1-1.5 minutes at a power of 100-120W. 2) Multi-layer coating and curing First coating: The pretreated metal wire is passed through a coating device and coated for the first time at a speed of 1-1.5 m / min; After coating, pre-bake in an oven at 80-85℃ for 5-8 minutes; First curing: The pre-baked metal wire is first cured in a curing oven at 150-160℃ for 10-15 minutes. Repeated coating and curing: Repeat the first coating and curing steps, performing a total of three coatings and curing processes to ensure the formation of a uniform and dense multi-layer paint film; 3) Final curing The curing process is carried out using UV curing equipment with a UV power of 200-220 mW / cm² and a curing time of 30-40 seconds. The insulating varnish used in the three coats consists of the following components by weight percentage: Polyester resin: 40-60% Polyamide-imide resin: 15-25% Xylene: 10-25% N-Methylpyrrolidone: 5-15% Nano-silica: 1.0-5.0% Nano-alumina: 0.5-2.0% Fluorinated surfactants: 0.5-2.5% Epoxy resin tackifier: 0.2-2.0% Antioxidant: 0.2-0.5% Ultraviolet absorber: 0.1-0.5%; The fluorinated surfactant is one of Zonyl FSN-100, Zonyl FSP of DuPont Company, Capstone FS-3100, Capstone FS-63 of Solvay Company, Novec FC-4432 of 3M Company and Forafac 1157 of Solvay Company; the specific surface area of nano-silicon dioxide is 100-300 m 2 / g, and the surface is treated by organosilane; the average particle size of nano-aluminum oxide is 10-50 nanometers.

2. The method of claim 1, wherein, The insulating varnish consists of the following components by weight percentage: Polyester resin: 45-55% Polyamide-imide resin: 18-20% Xylene: 15-20% N-Methylpyrrolidone: 8-12% Nano-silica: 1.5-3.0% Nano-alumina: 1.0-1.5% Fluorinated surfactants: 0.8-1.5% Epoxy resin tackifier: 0.5-1.5% Antioxidant: 0.2-0.5% Ultraviolet absorber: 0.1-0.5%.

3. The method of claim 1, wherein The polyester resin selected is one of the following: DuPont's Rynite FR530, DSM's Arnite T06 200, BASF's Ultradur B4300G6, SABIC's Valox 420SE0, and Eastman's Tritan EX401.

4. The method of claim 1, wherein The polyamide-imide resin selected is either Solvay's Torlon 4000T or Torlon AI-10.

5. The preparation method according to claim 1, characterized in that, The epoxy resin tackifier is a mixture of one or more of bisphenol A type liquid epoxy resin and bisphenol A type solid epoxy resin.

6. The preparation method according to claim 1, characterized in that, The epoxy resin tackifier used is one of Dow Chemical's DER331, Huntsman's Araldite GY 6010, or Westlake Chemical's Epikote 1001.

7. The preparation method according to claim 1, characterized in that, The nano-silica used is Evonik Aerosil R812S.

8. The preparation method according to claim 1, characterized in that, The preparation method of insulating varnish includes the following steps: 1) Weigh out the polyester resin and polyamide-imide resin, prepare xylene and N-methylpyrrolidone, add the polyester resin and polyamide-imide resin to the mixing container; add xylene and N-methylpyrrolidone in proportion; use a mechanical stirrer to stir at 300-500 rpm for 20-40 minutes to ensure that the resin is completely dissolved; 2) While continuing to stir, slowly add nano-silica; increase the stirring speed to 1000-1500 rpm and stir for 20-40 minutes to ensure that the nano-silica is evenly dispersed; while continuing to stir, slowly add nano-alumina, increase the stirring speed to 1500-2000 rpm, and stir again for 30-40 minutes to ensure that the nano-alumina is evenly dispersed. 3) Add the fluorinated surfactant in the specified proportion and continue stirring for 10-15 minutes; add the epoxy resin tackifier and continue stirring for 20-25 minutes; finally, add the antioxidant and UV absorber and continue stirring for 15-20 minutes to ensure uniform dispersion. 4) Filtration and degassing: Use a 200-mesh filter to filter the evenly mixed paint to remove impurities and undissolved particles; place the filtered paint in a vacuum degassing device with a vacuum degree of -0.08 MPa for 30 minutes to remove air bubbles from the paint.

9. An enameled wire, characterized in that, The enameled wire is prepared using the preparation method described in any one of claims 1-8.