An insulating layer of an enameled wire and a preparation method thereof

Abstract

The present invention discloses an insulating layer of an enameled wire and a preparation method thereof, comprising an inner layer providing basic electrical insulation and thermal stability, an intermediate layer enhancing mechanical strength and thermal stability and providing self-healing ability, and an outer layer maintaining the flexibility and wear resistance of the enameled wire at low temperatures; the outermost surface of the insulating layer is provided with a plurality of insulating protrusions arranged at a spiral pitch along its length direction; the insulating protrusions are circular or elliptical protrusions. The present invention not only realizes a high-performance insulating layer of an enameled wire, but also ensures reliability and durability in a variety of extreme environments, meeting the requirements of modern electrical equipment for high-standard insulating materials.

Description

Technical Field

[0001] The invention relates to the technical field of enameled wire processing, and more specifically to an insulating layer of an enameled wire and a preparation method thereof. Background Art

[0002] In the electrical industry, enameled wire is widely used in motors, transformers, electromagnetic coils and other equipment as a key component of the winding. Traditional enameled wire usually consists of a metal conductor, most commonly copper or aluminum, and an outer insulation layer. The basic function of this insulation layer is to prevent current leakage, ensure that the current flows only within the intended path, and provide physical protection to prevent mechanical damage.

[0003] Traditional insulation materials usually include various types of resins, such as polyester, polyimide, etc. Although these materials have good electrical insulation properties and certain mechanical strength, their performance may be limited under specific application conditions, such as high temperature, low temperature or high radiation environment. For example, some insulation materials may become hard, brittle or lose flexibility after being exposed to high temperature or low temperature environment for a long time, which limits their application range. In addition, once the insulation layer of traditional enameled wire is damaged, it is difficult to repair, and the entire coil usually needs to be replaced, which is time-consuming and increases maintenance costs; although the existing enameled wire has good high-voltage insulation effect, it still has some shortcomings: 1. The enameled wire mainly relies on a single polyurethane insulation paint layer and a simple anti-corrosion layer and heat insulation layer structure, lacks a multi-layer structure design, and does not optimize the materials of different layers; a single material is difficult to provide high electrical insulation, mechanical strength, thermal stability and low-temperature flexibility at the same time, and the comprehensive performance is poor. 2. There is no design that introduces a self-healing function. When the enameled wire is slightly damaged, it cannot be automatically repaired; the service life and reliability are poor, and long-term use in a high-voltage environment may lead to more maintenance needs. 3. It is not specially designed for low temperature environments. Polyurethane and nylon may become brittle at low temperatures. In extreme low temperature environments, the enameled wire has insufficient flexibility and durability, which may affect normal use. 4. The preparation process is relatively simple, lacking the application of sophisticated processes such as synchronous extrusion and UV curing of multi-layer structures. The material layers are not tightly bonded, and there may be gaps between the layers, affecting the insulation performance and overall stability. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention proposes an insulating layer of an enameled wire and a preparation process. The present invention not only realizes a high-performance enameled wire insulation layer, but also ensures reliability and durability in a variety of extreme environments, meeting the needs of modern electrical equipment for high-standard insulating materials.

[0005] To solve the above problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides an insulating layer of an enameled wire, comprising an inner layer for electrical insulation and thermal stability, an intermediate layer for enhancing mechanical strength and thermal stability and having self-healing ability, and an outer layer for maintaining flexibility and wear resistance of the enameled wire at low temperatures;

[0007] Wherein, the inner layer comprises, by mass percentage:

[0008] Main material: 90%-95% polyimide;

[0009] Crosslinking agent: 5%-10% trimellitic anhydride;

[0010] The intermediate layer comprises, by mass percentage:

[0011] Main material: 75%-85% polyimide:

[0012] Reinforcement material: 10%-15% zinc oxide nanoparticles;

[0013] Microcapsules: 3%-5%;

[0014] Crosslinking agent: 2%-5% trimellitic anhydride;

[0015] The outer layer comprises, by mass percentage:

[0016] Main material: 80%-90% polyimide;

[0017] Low temperature plastic enhancer: 5%-10% polyacrylate;

[0018] Crosslinking agent: 5%-10% trimellitic anhydride.

[0019] Preferably, the microcapsules, measured by mass percentage, include:

[0020] Monomer: Methyl methacrylate as a repair agent, which accounts for 70%-89% of the mass of the microcapsules;

[0021] Wall material: polyurethane or polymethyl methacrylate used to form the microcapsule shell, which accounts for 10%-25% of the microcapsule mass;

[0022] Initiator: ammonium persulfate or potassium persulfate used to initiate polymerization under UV light, accounting for 1%-5% of the mass of the microcapsule.

[0023] Preferably, the microcapsules are prepared according to the following steps:

[0024] Step 1: Solution preparation

[0025] Mixing monomers and initiators: Mix the monomers and initiators evenly to ensure that the initiator is fully dissolved;

[0026] Step 2: Preparation of wall material solution

[0027] Dissolving the wall material: dissolving the wall material in chloroform or toluene to form a uniform wall material solution;

[0028] Step 3: Emulsification process

[0029] Emulsification: slowly add the mixed solution obtained in step 1 to the wall material solution obtained in step 2, and stir using a high shear stirrer to form an O / W type emulsion. The stirring speed is set at 1000 to 5000 rpm for 30 minutes to 1 hour to form a stable emulsion.

[0030] Step 4: Microencapsulation

[0031] Polymerization: The emulsion is transferred to a reactor and the polymerization reaction is carried out at a temperature of 60°C to 80°C and under stirring conditions for 2 to 4 hours. After the polymerization is completed, it is cooled to room temperature, centrifuged or filtered, and then washed and dried to obtain microcapsule powder.

[0032] In a second aspect, the present invention provides a method for preparing an insulating layer of the enameled wire according to the first aspect, comprising the following steps:

[0033] Step 1: Mixing Materials

[0034] Weigh the raw materials for the inner layer, middle layer and outer layer respectively and mix them evenly;

[0035] Step 2: Multi-layer extrusion

[0036] Use a multi-hopper extruder, with each hopper responsible for a mixture, to extrude three layers of material through a die and cover them on the outer circumference of the copper core in the order of inner layer, middle layer and outer layer, ensuring that each layer of material is correctly covered on the previous layer;

[0037] Step 3: UV Curing

[0038] The extruded three-layer enameled wire is passed through a UV light source to cure the polyimide matrix in each layer and activate the polymerization reaction in the microcapsules;

[0039] Step 4: Low temperature treatment

[0040] The cured enameled wire is subjected to low-temperature treatment to activate the low-temperature plasticity enhancer to ensure that the outer layer remains flexible in an extremely low-temperature environment, while promoting the cross-linking agent in all layers to complete the cross-linking reaction and enhance the stability of the overall structure.

[0041] Preferably, in step 1, when the inner layer materials are mixed, the temperature is maintained at 80°C to 100°C, and the mixing time is 1 hour to start the pre-crosslinking reaction; when the middle layer materials are mixed, the mixing temperature is maintained at 80°C, and the mixing time is 1.5 hours to ensure uniform dispersion of the materials and the start of the crosslinking reaction; when the outer layer materials are mixed, the mixing temperature is maintained at 80°C, and the mixing time is 1.5 hours to ensure uniform dispersion of the reinforcing agent in the resin and the crosslinking effect.

[0042] Preferably, in step 2, the multilayer extrusion molding comprises the following steps:

[0043] Preheat the copper core: First, preheat the copper core to 50℃ to 70℃ to improve the adhesion of the material;

[0044] Loading materials: Load the pre-mixed inner layer, middle layer and outer layer materials into the corresponding hoppers respectively; the output temperature of each hopper is: the inner layer is set at 220℃, the middle layer is 230℃, and the outer layer is 210℃ to ensure that the materials are completely melted;

[0045] Synchronous extrusion: The material gathers at the extruder head, passes through a multi-layer die, and is synchronously extruded onto the moving copper core in a set order and thickness; the extrusion speed is 5 to 15 meters / minute, ensuring that each layer of material evenly covers the copper core and there is no air inclusion between the layers;

[0046] Cooling: The extruded composite material is cooled and shaped through a cold water tank or air cooling system.

[0047] Preferably, in step 3, UV curing includes:

[0048] Before UV curing, it passes through a preheating stage, and the preheating temperature is set at 50℃ to 70℃ to pre-soften the polyimide matrix, making the subsequent UV curing more effective;

[0049] The extruded three-layer enameled wire is then cured by a UV light source, wherein the wavelength of light emitted by the UV light source is 320 to 400 nanometers; the UV light intensity is 100 to 200 mW / cm 2 ; The speed of the enameled wire passing through the UV light source area is controlled to be 1 to 5 meters per minute to ensure that each layer of material receives appropriate UV irradiation time, promote the cross-linking reaction of the polyimide matrix and activate the polymerization reaction in the microcapsules; the cross-linking agent trimellitic anhydride reacts with the polyimide under the influence of UV light to form a cross-linking network, thereby enhancing the mechanical stability and temperature resistance of the insulating layer; the repair agent methyl methacrylate in the microcapsules polymerizes under the action of UV light to form polymethyl methacrylate, which is used to automatically repair minor damage in the insulating layer;

[0050] After UV curing, cooling treatment is carried out, and the cooling temperature is controlled between room temperature and 30°C to stabilize the structure of the cured material and reduce internal stress.

[0051] Preferably, in step 4, the low temperature treatment comprises:

[0052] The cured enameled wire is placed in a low-temperature treatment chamber; the temperature of the treatment chamber is set at -40°C to -60°C; the treatment time under this temperature condition is maintained for 12 to 24 hours to activate the low-temperature plastic enhancer in the outer layer and promote the cross-linking agent in all layers to complete the cross-linking reaction; and the step of returning the enameled wire to room temperature after the low-temperature treatment is also included to stabilize the structure of the material and reduce the internal stress introduced by the treatment.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The insulating layer design of the enameled wire of the present invention realizes a complex insulating layer structure by carefully selecting and optimizing the material composition and by highly controlled multi-layer extrusion technology. Each layer has a specific function, and these layers work together to provide a series of beneficial effects:

[0055] Inner layer: basic electrical insulation and thermal stability

[0056] Polyimide is the main material for the inner layer, chosen for its excellent electrical insulation properties and ability to withstand high temperatures. In high temperature environments such as motors and transformers, polyimide ensures long-term stable operation of the enameled wire and prevents electrical failures.

[0057] As a cross-linking agent, trimellitic anhydride forms a more stable three-dimensional network structure through chemical reaction with polyimide, which not only enhances the thermal stability of the material, but also improves the mechanical strength and chemical resistance, making the insulating layer more difficult to be destroyed.

[0058] Intermediate layer: Enhances mechanical strength, thermal stability and provides self-healing ability

[0059] Zinc oxide nanoparticles are added to improve UV resistance and enhance overall mechanical strength. The nanoparticles are dispersed in the polyimide matrix, enhancing the wear resistance and hardness of the middle layer while also providing additional protection against external environmental factors.

[0060] The repair agent contained in the microcapsule can react quickly and repair tiny cracks or damage in the insulating layer when the material is damaged. The microcapsule ruptures at the damaged point, releasing the repair agent, which quickly polymerizes to fill the damage.

[0061] Outer layer: flexibility and abrasion resistance at low temperatures

[0062] Low temperature plasticity enhancers maintain the flexibility of materials in extremely low temperature environments and prevent brittle cracking of materials due to low temperatures. This is achieved by enhancing the ductility and elasticity of materials at low temperatures.

[0063] The use of cross-linking agents also extends to the outer layer, ensuring that the outer layer of the enameled wire maintains sufficient mechanical strength and structural integrity even under low temperature conditions.

[0064] The preparation process of the insulating layer of the present invention ensures perfect bonding between the layers:

[0065] The multi-hopper extruder allows each layer of material to be heated and extruded independently, and the three layers of material are extruded synchronously through a precisely controlled die system, ensuring that each layer is evenly and tightly covered on the copper core, avoiding inter-layer gaps and material confusion.

[0066] The UV curing process not only cures each layer quickly, but also enhances the consistency and durability of the entire insulation layer by activating the polymerization reaction in the microcapsules and promoting the cross-linking of the cross-linking agent.

[0067] Low temperature treatment activates the low temperature plasticity enhancer in the outer layer and completes the cross-linking process, enhancing structural stability while maintaining low temperature flexibility.

[0068] Through the organic combination of the above-mentioned processes and materials, the present invention not only realizes a high-performance enameled wire insulation layer, but also ensures reliability and durability in a variety of extreme environments, meeting the needs of modern electrical equipment for high-standard insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a process schematic diagram of the present invention;

[0070] Figure 2 is a schematic diagram of the distribution of insulating bumps of the present invention;

[0071] Figure 3 It is a cross-sectional schematic diagram of the injection molding gun of the present invention facing downward normally;

[0072] Figure 4 for Figure 3 Enlarged view of the middle circle A;

[0073] Figure 5 It is a cross-sectional schematic diagram of the injection molding gun of the present invention when extruding material;

[0074] Figure 6 for Figure 5 Enlarged view of the middle circle B;

[0075] Figure 7 It is a plan view of the closed petal-shaped elastic diaphragm.

[0076] In the figure: 1. insulating protrusion; 2. injection molding gun; 21. gun body; 22. discharge port; 23. pushing piston; 24. electromagnet; 25. permanent magnet; 26. guide rod; 27. return spring; 28. petal-shaped elastic diaphragm; 29. ​​injection molding feeding tube. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] The present invention provides an insulating layer of an enameled wire, comprising an inner layer for electrical insulation and thermal stability, an intermediate layer for enhancing mechanical strength and thermal stability and having self-healing ability, and an outer layer for maintaining the flexibility and wear resistance of the enameled wire at low temperatures. In particular, the outer surface of the outermost layer of the insulating layer is provided with a plurality of insulating protrusions arranged at a spiral pitch along its length direction; the insulating protrusions are circular or elliptical protrusions, and are made of silicone rubber, polytetrafluoroethylene or epoxy resin.

[0079] The insulating projection is molded by mold injection; the insulating projection uses an injection molding gun that can rotate around the outer circumference of the enameled wire while the enameled wire is fed along its length direction; the injection molding gun includes a tubular gun body; the front end of the gun body is reduced in diameter and provided with a discharge port, and the rear inner sealing sliding sleeve is provided with a pushing piston; an electromagnet is fixedly provided in the gun body behind the pushing piston; a permanent magnet is fixed to the rear of the pushing piston; the electromagnet is opposite to the permanent magnet, and the electromagnet and the opposite surfaces of the permanent magnet can be controlled to repel or attract each other by controlling the power on and off of the electromagnet and the direction of the magnetic poles through the circuit; one end of a guide rod is fixed to the pushing piston, and the other end slides through the electromagnet; a return spring is sleeved on the guide rod; the two ends of the return spring are fixedly connected to the pushing piston and the electromagnet respectively; a petal-shaped elastic diaphragm is provided at the discharge port, which is closed under normal conditions and is squeezed open to expose the discharge port when the thrust exceeds a threshold; an injection molding feeding pipe is connected between the pushing piston and the discharge port on the side wall of the gun body.

[0080] The spirally arranged insulating protrusions provided in the present invention have the following effects:

[0081] Uniform electric field distribution: The spirally arranged protrusions can form a uniform electric field distribution on the cable surface, reduce the concentration of electric field strength, reduce the risk of corona discharge, and thus improve the insulation performance of the cable.

[0082] Enhanced heat dissipation: The spirally arranged protrusions increase the contact area of ​​the cable surface, which helps to dissipate heat. The air flows more smoothly in the spiral structure, promoting convection and heat dissipation, thereby reducing the operating temperature of the cable and improving its durability.

[0083] Reduce cable vibration: The spirally arranged protrusions can disperse the transmission path of external vibration and reduce the impact of vibration on the internal structure of the cable. This structure helps to protect the stability and reliability of the cable in a vibrating environment.

[0084] Improved mechanical strength: The spirally arranged protrusions enhance the overall mechanical strength of the cable, especially its tensile and torsional properties, by providing multi-directional support. This helps maintain the structural integrity of the cable when subjected to external forces.

[0085] Enhanced flexibility: The spirally arranged protrusions allow the cable to have more buffer areas when it is bent, dispersing stress and reducing stress concentration, thereby improving the flexibility of the cable and adapting to more complex wiring environments.

[0086] Reduce static electricity accumulation: The spirally arranged protrusions can increase the charge release path on the cable surface, reduce static electricity accumulation, and thus reduce the risk of cable damage caused by electrostatic discharge.

[0087] Improve UV resistance: The spiral convex structure can disperse and reflect ultraviolet rays, reduce the direct exposure of ultraviolet rays to the cable surface, reduce the aging speed of cable materials, and improve the durability of the cable.

[0088] Self-cleaning function: The spirally arranged convex design can utilize the principle of aerodynamics to allow wind and rain to more effectively wash the cable surface, reduce the accumulation of dust and dirt, and keep the cable clean.

[0089] Improved thermal expansion buffer: The spiral protrusion structure can provide buffering when the cable expands due to heat, reduce thermal stress concentration, and prevent cracking of the insulation layer.

[0090] Example:

[0091] See also Figure 1 , an insulating layer of an enameled wire, comprising an inner layer providing basic electrical insulation and thermal stability, an intermediate layer enhancing mechanical strength and thermal stability and providing self-healing ability, and an outer layer maintaining flexibility and wear resistance of the enameled wire at low temperatures;

[0092] The components of the inner layer include:

[0093] Main material: 90%-95% polyimide by mass;

[0094] Cross-linking agent: 5%-10% by mass of trimellitic anhydride;

[0095] The components of the intermediate layer include:

[0096] Main material: 75%-85% polyimide by mass:

[0097] Reinforcement material: 10%-15% by mass of zinc oxide nanoparticles;

[0098] Microcapsules: 3%-5% by mass;

[0099] Cross-linking agent: 2%-5% by mass of trimellitic anhydride;

[0100] The composition of the outer layer includes:

[0101] Main material: 80%-90% polyimide by mass;

[0102] Low temperature plasticity enhancer: 5%-10% by mass of polyacrylate;

[0103] Cross-linking agent: 5%-10% by mass of trimellitic anhydride.

[0104] Furthermore, the preparation process of the insulation layer of the enameled wire is:

[0105] Step 1: Mixing Materials

[0106] Inner layer mixing: polyimide and cross-linking agent are mixed to form the basic insulation layer;

[0107] Middle layer mixing: polyimide, zinc oxide nanoparticles, microcapsules and part of the cross-linking agent;

[0108] Outer layer mixing: polyimide, low temperature plastic reinforcing agent and cross-linking agent are mixed;

[0109] Step 2: Multi-layer extrusion

[0110] Use a multi-hopper extruder, with each hopper responsible for a mixture, to simultaneously extrude three layers of material onto the outer circumference of the copper core through a special die, ensuring that each layer of material correctly covers the previous layer;

[0111] Step 3: UV Curing

[0112] The extruded three-layer enameled wire is passed through a UV light source to cure the polyimide matrix in each layer and activate the polymerization reaction in the microcapsules;

[0113] Step 4: Low temperature treatment

[0114] The cured enameled wire is subjected to low-temperature treatment to activate the low-temperature plastic enhancer to ensure that the outer layer remains flexible in an extremely low-temperature environment, while promoting the cross-linking agent in all layers to complete the cross-linking reaction and enhance the stability of the overall structure;

[0115] Step 5: Post-processing and testing

[0116] After the enameled wire is wound, it undergoes performance tests, including electrical tests, mechanical strength tests, and low-temperature performance tests.

[0117] The cooled enameled wire is rolled up, and a constant tension is maintained during the rolling process; the electrical test includes an insulation resistance test and a withstand voltage test. In the withstand voltage test, a voltage 150% higher than its nominal working voltage is applied to the enameled wire for a duration of not less than 1 minute; the mechanical strength test includes a tensile test and a bending test. In the tensile test, the maximum tensile force and elongation of the enameled wire are measured. In the bending test, the enameled wire is bent to four times its diameter and the performance changes are observed; the low-temperature performance test includes a low-temperature bending test and an impact test conducted at -40°C to -60°C to evaluate the flexibility and breakage resistance of the enameled wire under extreme low temperature conditions.

[0118] Specifically, the specific contents of material mixing in step 1 include:

[0119] Inner layer mixing

[0120] Materials: polyimide resin, cross-linking agent (trimellitic anhydride, TMA);

[0121] Ratio: polyimide resin: 95% (by mass ratio); cross-linking agent: 5% (by mass ratio);

[0122] Mixing process: Mix the polyimide and the crosslinking agent in a high-speed mixer; maintain the mixing temperature at 80°C to 100°C to promote uniform distribution of the crosslinking agent and start the pre-crosslinking reaction;

[0123] Reaction formula: polyimide + TMA → cross-linked polyimide;

[0124] Processing Time: Stirring and heating lasts approximately 1 hour to ensure complete mixing and homogeneity.

[0125] Inner layer: basic electrical insulation and thermal stability

[0126] Polyimide is the main material for the inner layer, chosen for its excellent electrical insulation properties and ability to withstand high temperatures. In high temperature environments such as motors and transformers, polyimide ensures long-term stable operation of the enameled wire and prevents electrical failures.

[0127] As a cross-linking agent, trimellitic anhydride forms a more stable three-dimensional network structure through chemical reaction with polyimide, which not only enhances the thermal stability of the material, but also improves the mechanical strength and chemical resistance, making the insulating layer more difficult to be destroyed.

[0128] Middle layer mixing

[0129] Materials: polyimide resin, zinc oxide nanoparticles, microcapsules (containing repairing agent), cross-linking agent (trimellitic anhydride);

[0130] Ratio: polyimide resin: 80% (by mass ratio), zinc oxide nanoparticles: 10% (by mass ratio), microcapsules: 5% (by mass ratio), crosslinking agent: 5% (by mass ratio);

[0131] Mixing process: First, mix the polyimide resin and the crosslinking agent evenly, and then gradually add the zinc oxide nanoparticles and microcapsules. Under high-speed stirring, maintain the mixing temperature at 80°C to ensure uniform dispersion of the materials and the initiation of the crosslinking reaction;

[0132] Processing Time: Total mixing time is about 1.5 hours, ensuring all ingredients are fully incorporated.

[0133] Intermediate layer: Enhances mechanical strength, thermal stability and provides self-healing ability

[0134] Zinc oxide nanoparticles are added to improve UV resistance and enhance overall mechanical strength. The nanoparticles are dispersed in the polyimide matrix, enhancing the wear resistance and hardness of the middle layer while also providing additional protection against external environmental factors.

[0135] The repair agent contained in the microcapsule can react quickly and repair tiny cracks or damage in the insulating layer when the material is damaged. The microcapsule ruptures at the damaged point, releasing the repair agent, which quickly polymerizes to fill the damage.

[0136] Outer layer mixing

[0137] Materials: polyimide resin, low temperature plasticity enhancer (polyacrylate), cross-linking agent (trimellitic anhydride);

[0138] Ratio: polyimide resin: 85% (by mass ratio), low temperature plasticity enhancer: 10% (by mass ratio), cross-linking agent: 5% (by mass ratio);

[0139] Mixing process: first mix the polyimide and crosslinking agent evenly, then add the low-temperature plastic enhancer. Keep the temperature at about 80°C during high-speed stirring to ensure that the enhancer can be evenly dispersed in the resin and promote crosslinking;

[0140] Processing time: Total mixing time is about 1.5 hours to complete the thorough incorporation of all ingredients.

[0141] Outer layer: flexibility and abrasion resistance at low temperatures

[0142] Low temperature plasticity enhancers maintain the flexibility of materials in extremely low temperature environments and prevent brittle cracking of materials due to low temperatures. This is achieved by enhancing the ductility and elasticity of materials at low temperatures.

[0143] The use of cross-linking agents also extends to the outer layer, ensuring that the outer layer of the enameled wire maintains sufficient mechanical strength and structural integrity even under low temperature conditions.

[0144] Through the special ratio and mixing process of the above layers, it can be ensured that each layer of the enameled wire has its specific functional properties, including basic electrical insulation, self-healing ability and low-temperature flexibility. This multi-layer mixing and preparation process not only improves the performance of the final product, but also increases its application range in harsh environments.

[0145] Specifically, the process of multi-layer extrusion molding in step 2 is:

[0146] Multi-hopper extruder: has at least three independent hoppers and feeding systems, each hopper is equipped with a temperature and speed control system.

[0147] Special mold: designed for simultaneous extrusion of three layers of material to ensure the correct alignment and bonding of each layer of material; to ensure that the three layers of material can accurately overlap and dock during extrusion to form a tight multi-layer structure; the mold outlet design must ensure that the materials will not mix during the flow process, each layer of material remains independent, and at the same time form a good physical bond at the interface.

[0148] Mixed Materials:

[0149] Inner layer mixture: mainly composed of polyimide and a small amount of cross-linking agent;

[0150] Intermediate layer mixture: comprising polyimide, zinc oxide nanoparticles, microcapsules and a crosslinking agent;

[0151] Outer layer mixture: composed of polyimide, low temperature plastic reinforcing agent and cross-linking agent;

[0152] Temperature settings:

[0153] Inner layer: 220℃ to ensure full melting of polyimide and activity of cross-linking agent.

[0154] Middle layer: 230℃, suitable for melting and dispersion of zinc oxide nanoparticles and microcapsules.

[0155] Outer layer: 210℃, to adapt to the processing temperature of low-temperature plastic reinforcing agent and prevent excessive melting.

[0156] Extrusion speed:

[0157] The speed is uniformly set to 5-10 m / min, depending on the material fluidity and mold design, to ensure good bonding between layers.

[0158] Extrusion process:

[0159] Hopper loading: Load the corresponding mixture into the three hoppers of the extruder respectively;

[0160] Synchronous extrusion: Start the extruder, and the three layers of materials converge in the die through their respective channels to form a composite structure according to the predetermined thickness and sequence;

[0161] Cooling and shaping: The extruded composite material passes through a cold water tank or air cooling system to quickly cool and solidify to maintain shape and dimensional stability.

[0162] Quality Control:

[0163] Layer Thickness Detection: Use online thickness measurement equipment to monitor and adjust the thickness of each layer to ensure that the product meets the design specifications.

[0164] Interface quality monitoring: Check the bonding quality between layers through visual inspection and regular sampling to ensure there is no layer separation.

[0165] Through the above process, high-quality multi-layer structure enameled wire production can be achieved, and the function of each layer of material can be fully utilized, thereby enhancing the performance and durability of the final product.

[0166] Specifically, the UV curing in step 3 aims to improve the mechanical strength and repair ability of the insulating layer by curing the polyimide matrix in each layer using a UV light source and activating the polymerization reaction in the microcapsules. The following is the process of this step:

[0167] UV light source: usually a high-intensity UV lamp is used, which can emit light of a specific wavelength suitable for the curing of polyimide and polymers in microcapsules.

[0168] Conveying system: used to steadily pass the extruded enameled wire through the UV curing area.

[0169] Process flow:

[0170] Light source selection: Use UV lamps with wavelengths in the range of 320 to 400 nanometers to most effectively activate the cross-linking reaction of the polyimide and the polymerization reaction in the microcapsules.

[0171] Light intensity and exposure time:

[0172] Light intensity: set between 100 and 200 mW / cm 2 , ensuring sufficient energy to promote the polymerization reaction.

[0173] Exposure time: Adjust the speed of the enameled wire passing through the UV light source area, set it to a conveying speed of 1 to 5 meters / minute, and ensure that each layer of material receives appropriate UV exposure time.

[0174] Curing process:

[0175] Under the action of UV light, the crosslinking agent (trimellitic anhydride) helps polyimide form a more stable network structure.

[0176] Reaction formula: polyimide-NH,

[0177] Polymerization activation of microcapsules:

[0178] The monomer (methyl methacrylate) in the microcapsules polymerizes under the influence of UV light to form polymethyl methacrylate, which is used to repair minor damage.

[0179] Reaction formula:

[0180] Quality Control

[0181] UV curing effect detection: Use online UV intensity monitoring equipment to ensure the uniformity of the curing process.

[0182] The mechanical and electrical properties of the cured materials are inspected through sampling tests to ensure that each batch of products meets the quality standards.

[0183] Through the above process flow, UV curing not only enhances the mechanical and electrical properties of the enameled wire, but also gives it self-healing ability, making the product suitable for more demanding application environments.

[0184] Specifically, the low temperature treatment in step 4 activates the low temperature plastic enhancer under low temperature conditions and promotes further cross-linking of the cross-linking agent, thereby enhancing the performance of the enameled wire in an extreme low temperature environment:

[0185] Low temperature treatment chamber: Special equipment capable of maintaining a certain low temperature range, equipped with a temperature control system.

[0186] Low temperature plasticity enhancer: polyacrylate, premixed in the outer layer material.

[0187] Crosslinking agent: trimellitic anhydride (TMA), premixed in each layer material.

[0188] Process

[0189] Temperature and time:

[0190] Temperature range: -40℃ to -60℃, set according to the characteristics of the specific material and the required processing effect.

[0191] Processing time: 12 to 24 hours, long enough to ensure sufficient reaction of the crosslinking agent at low temperature and activation of the low temperature plastic enhancer.

[0192] Reaction process

[0193] Activation of low-temperature plastic enhancers: Under low-temperature conditions, the reinforcing agent polyacrylate can maintain or increase its flexibility and prevent the material from becoming brittle.

[0194] The cross-linking reaction of the cross-linking agent is accelerated:

[0195] Low temperatures facilitate certain types of chemical crosslinking, especially in the presence of low-temperature plasticizers, which can help form a more stable network structure.

[0196]

[0197] Through the above process flow, low temperature treatment not only enhances the structural stability of the enameled wire, but also ensures its flexibility and functionality in extreme low temperature environments, making the product suitable for more demanding application environments.

[0198] Specifically, the post-processing process in step 5 specifically includes:

[0199] Cooling and winding

[0200] After the enameled wire comes out of the low temperature treatment chamber, it is immediately cooled by a cooling system (air or water cooling system) to quickly reduce the wire temperature to room temperature.

[0201] Control the cooling speed and method to prevent the material from generating internal stress or deformation due to rapid temperature changes.

[0202] The cooled enameled wire is neatly wound by an automatic winder.

[0203] Maintain constant tension during winding to avoid introducing excessive mechanical stress.

[0204] Test items include:

[0205] Electrical test: Insulation resistance test: ensure that the insulation performance of each batch of enameled wires meets the standards.

[0206] Withstand voltage test: Apply a voltage higher than the normal operating voltage to the enameled wire to check for breakdown or leakage.

[0207] Tensile test: Measures the tensile strength and elongation of the enameled wire to ensure that the mechanical strength of the material meets the requirements.

[0208] Bending test: Check the performance of enameled wire after repeated bending to ensure its reliability in practical applications.

[0209] Low temperature bending test: Test the flexibility and breaking resistance of the enameled wire at the lowest operating temperature that may be encountered in actual applications.

[0210] Impact test: The enameled wire is impact tested under low temperature conditions to verify its impact resistance.

[0211] Through the above post-processing and testing processes, it can be ensured that the quality and performance of the enameled wire products meet the requirements of various demanding applications, thereby providing high reliability and long-term stability products to end users.

[0212] Specifically, the formula and preparation process of the microcapsules are:

[0213] Microcapsule formulation

[0214] Monomer: Methyl methacrylate (MMA) - the main repair agent, accounting for 70%-89% of the microcapsule content.

[0215] Wall material: polyurethane or polymethyl methacrylate - used to form the shell of microcapsules, accounting for 10%-25%.

[0216] Initiator: Ammonium persulfate or potassium persulfate - used to initiate polymerization under UV light, accounting for 1%-5%.

[0217] Preparation process

[0218] Step 1: Solution preparation

[0219] Mixing monomers and initiator: Mix methyl methacrylate and an appropriate amount of initiator in a container, making sure the initiator is fully dissolved.

[0220] Step 2: Preparation of wall material solution

[0221] Dissolving the wall material: In another container, dissolve the wall material (polyurethane) in an appropriate solvent (chloroform or toluene) to form a uniform wall material solution.

[0222] Step 3: Emulsification process

[0223] Emulsification: Slowly add the mixture of monomer and initiator to the wall material solution, and stir with a high shear stirrer to form an O / W (oil-in-water) emulsion. The stirring speed is usually set at 1000 to 5000 rpm, and the duration is 30 minutes to 1 hour to form a stable emulsion.

[0224] Step 4: Microencapsulation

[0225] Polymerization: The emulsion is transferred to a reactor and the polymerization reaction is carried out under controlled temperature (60°C to 80°C) and stirring conditions for about 2 to 4 hours. In this step, methyl methacrylate polymerizes in the wall material capsule to form a strong microcapsule wall.

[0226] Cooling and curing: After the polymerization is completed, the emulsion is cooled to room temperature to solidify the microcapsule structure.

[0227] Step 5: Recovery and cleaning of microcapsules

[0228] Separation: The microcapsules are separated from the emulsion using centrifugation or filtration techniques.

[0229] Cleaning: Wash the microcapsules several times with an appropriate solvent (water or ethanol) to remove unreacted monomers and by-products.

[0230] Step 6: Drying

[0231] Drying: The washed microcapsules are dried under reduced pressure or using a freeze dryer to remove all solvents to obtain dry microcapsule powder.

[0232] Through this preparation process, high-quality microcapsules can be obtained, which can play a self-healing role in the enameled wire and repair tiny damage caused by mechanical or thermal stress.

[0233] The following are the test results of the insulating layer and preparation process of the enameled wire of the present invention, which are summarized in Table 1 below:

[0234] Table 1

[0235]

[0236] Test Description

[0237] 1. Electrical test-voltage test

[0238] Measure the maximum withstand voltage of enameled wire to evaluate its electrical insulation performance.

[0239] Voltage application method: gradually increase the voltage until the insulation fails.

[0240] The test voltage starts at 0 kV and increases at a rate of 1 kV / s.

[0241] Test termination condition: record the voltage value when electrical breakdown occurs in the enameled wire.

[0242] Environmental conditions: room temperature 25°C, relative humidity 50%.

[0243] 2. Mechanical strength test-tensile test

[0244] Determine the tensile strength of magnet wire to evaluate its load-bearing capacity and structural integrity.

[0245] Equipment: Use a standard tensile testing machine.

[0246] Speed: The stretching rate is 5 mm / min.

[0247] Sample length: Each sample is 200 mm long.

[0248] Environmental conditions: room temperature 25℃.

[0249] 3. Low temperature performance test-low temperature bending test

[0250] Evaluate the flexibility and wear resistance of magnet wire in low temperature environments.

[0251] Temperature: Set to -40℃ to -60℃.

[0252] Test cycle: Bend the enameled wire 180 degrees for 10 times at the specified temperature.

[0253] Sample size: Each sample is 100 mm long.

[0254] Environmental conditions: The test environment temperature is kept constant at the test set temperature.

[0255] Results Analysis and Conclusion

[0256] Electrical test (withstand voltage):

[0257] The enameled wire of the present invention has a minimum withstand voltage of 18 kV and a maximum withstand voltage of 20 kV, showing a relatively high electrical insulation performance, which exceeds the withstand voltage values ​​of existing products, wherein product A is 16 kV and product B is 17 kV. This indicates that the present invention can effectively improve the electrical insulation strength of the enameled wire by adding a cross-linking agent and other reinforcing materials.

[0258] Mechanical strength test (tensile):

[0259] The enameled wire of the present invention has a tensile strength between 275 MPa and 300 MPa, which also exceeds the existing products, and its maximum tensile strength is 260 MPa. This shows that the optimized ratio of polyimide and the addition of zinc oxide nanoparticles and microcapsules in the present invention significantly enhance the mechanical properties of the material, especially the ability to resist tensile stress.

[0260] Low temperature performance test (bending test):

[0261] The enameled wire of the present invention does not break under extreme low temperature conditions and shows excellent flexibility, while existing products break or crack under the same conditions. The low temperature plasticity enhancer added in the present invention significantly improves the performance of the enameled wire under low temperature conditions and prevents the material from breaking due to embrittlement.

[0262] in conclusion

[0263] Electrical performance: The present invention significantly improves the voltage resistance of the enameled wire by increasing the proportion of the cross-linking agent and optimizing the use of polyimide, which makes the enameled wire more suitable for high voltage applications and provides better safety protection.

[0264] Mechanical properties: Through reasonable material design, especially the addition of zinc oxide nanoparticles and microcapsules in the middle layer, the present invention significantly improves the mechanical strength of the enameled wire, making it more wear-resistant and tensile-resistant, and suitable for environments with greater mechanical stress.

[0265] Low temperature adaptability: The enameled wire of the present invention exhibits excellent flexibility and durability in low temperature environments, which is significantly better than existing products on the market. This makes the enameled wire of the present invention very suitable for use in cold areas or refrigeration equipment, greatly reducing performance degradation and failure rates caused by low temperatures.

[0266] In summary, the enameled wire of the present invention has excellent performance in electrical insulation, mechanical strength and low-temperature adaptability through innovative material combination and preparation process, surpassing existing mainstream products, and has significant market competitive advantages and broad application prospects.

[0267] In addition, see Figures 2 to 7 Furthermore, the outermost surface of the insulating layer is provided with a plurality of insulating bumps 1 arranged at a spiral pitch along its length direction; the insulating bumps 1 are circular or elliptical protrusions, and are made of silicone rubber, polytetrafluoroethylene or epoxy resin.

[0268] The insulating protrusion 1 is molded by injection molding; the insulating protrusion 1 uses an injection molding gun 2 that can rotate around the outer circumference of the enameled wire while feeding the enameled wire along its length direction; the injection molding gun 2 includes a tubular gun body 21; the front end of the gun body 21 is reduced in diameter and provided with a discharge port 22, and the rear inner sealing sliding sleeve is provided with a pushing piston 23; an electromagnet 24 is fixedly provided in the gun body 21 behind the pushing piston 23; a permanent magnet 25 is fixed to the rear of the pushing piston 23; the electromagnet 24 is opposite to the permanent magnet 25, and the on and off of the electromagnet 24 is controlled by a circuit The electricity and magnetic pole direction can control the electromagnet 24 and the permanent magnet 25 to repel or attract each other; one end of a guide rod 26 is fixed to the pushing piston 23, and the other end slides through the electromagnet 24; a return spring 27 is sleeved on the guide rod 26; the two ends of the return spring 27 are respectively fixedly connected to the pushing piston 23 and the electromagnet 24; a petal-shaped elastic diaphragm 28 is provided at the discharge port 22, which is closed under normal conditions and is squeezed open to expose the discharge port when the thrust exceeds a threshold; an injection molding feeding pipe 29 is connected between the pushing piston 23 and the discharge port 22 on the side wall of the gun body 21.

[0269] When the molded insulating layer is fed along its length, the injection gun 2 revolves around the outer circumference of the insulating layer. During the revolution, the discharge port 22 of the gun body 21 approaches the insulating layer, and the electromagnet 25 is energized at intervals of a short period of time through the circuit control, so that the electromagnet 24 and the permanent magnet 25 repel each other, thereby pushing the permanent magnet 25 and the pushing piston 23 to move toward the discharge port 22, pushing the material in the gun body 21, squeezing the petal-shaped elastic diaphragm 28, so that the material is spherical and adheres to the surface of the insulating layer; then the electromagnet 24 is immediately disconnected. By energizing or reversing the direction of the magnetic pole of the electromagnet 24, the permanent magnet 25 and the pushing piston 23 move back under the magnetic attraction and the restoring force of the return spring 27, so that the extrusion force at the discharge port 22 is lost or reduced, and the petal-shaped elastic diaphragm 28 is restored to a closed state under the action of the restoring force, and in the process, the material at the discharge port 22 is cut off, so that the extruded material is disconnected; in this way, the insulating protrusions 1 with spiral distribution can be formed on the surface of the insulating layer. In this process, the material is automatically replenished into the gun body 21 through the injection molding feeding tube 29 by means of pressure maintenance. The insulating protrusions 1 can be completely solidified later.

[0270] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and improved concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. An insulating layer of an enameled wire, characterized in that: It includes an inner layer for electrical insulation and thermal stability, an intermediate layer for enhancing mechanical strength and thermal stability and having self-healing ability, and an outer layer that maintains the flexibility and wear resistance of the enameled wire at low temperatures of -40°C to -60°C; Wherein, the inner layer comprises, by mass percentage: Main material: 90% - 95% polyimide; Crosslinking agent: 5% - 10% trimellitic anhydride; The intermediate layer comprises, by mass percentage: Main material: 75% - 85% polyimide: Reinforcement material: 10% - 15% zinc oxide nanoparticles; Microcapsules: 3% - 5%; Crosslinking agent: 2% - 5% trimellitic anhydride; The outer layer comprises, by mass percentage: Main material: 80% - 90% polyimide; Low temperature plasticity enhancer: 5% - 10% polyacrylate; Crosslinker: 5% - 10% trimellitic anhydride.

2. The insulating layer of the enameled wire according to claim 1, characterized in that: Microcapsules, by mass percentage, include: Monomer: Methyl methacrylate as a repair agent, which accounts for 70%-89% of the mass of the microcapsules; Wall material: polyurethane or polymethyl methacrylate used to form the microcapsule shell, which accounts for 10%-25% of the microcapsule mass; Initiator: ammonium persulfate or potassium persulfate used to initiate polymerization under UV light, accounting for 1%-5% of the mass of the microcapsule.

3. The insulating layer of the enameled wire according to claim 1 or 2, characterized in that: Microcapsules were prepared according to the following steps: Step 1: Solution preparation Mixing monomers and initiators: Mix the monomers and initiators evenly to ensure that the initiator is fully dissolved; Step 2: Preparation of wall material solution Dissolving the wall material: dissolving the wall material in chloroform or toluene to form a uniform wall material solution; Step 3: Emulsification process Emulsification: slowly add the mixed solution obtained in step 1 to the wall material solution obtained in step 2, and stir using a high shear stirrer to form an O / W type emulsion. The stirring speed is set at 1000 to 5000 rpm for 30 minutes to 1 hour to form a stable emulsion; Step 4: Microencapsulation Polymerization: The emulsion is transferred to a reactor and the polymerization reaction is carried out at a temperature of 60°C to 80°C and under stirring conditions for 2 to 4 hours. After the polymerization is completed, it is cooled to room temperature, centrifuged or filtered, and then washed and dried to obtain microcapsule powder.

4. The insulating layer of the enameled wire according to claim 1, characterized in that: The outermost outer surface of the insulating layer is provided with a plurality of insulating protrusions (1) arranged at a spiral pitch along its length direction; the insulating protrusions (1) are circular or elliptical protrusions, and are made of silicone rubber, polytetrafluoroethylene or epoxy resin.

5. The insulating layer of the enameled wire according to claim 4, characterized in that: The insulating protrusion (1) is molded by injection molding; the insulating protrusion (1) uses an injection molding gun (2) that can rotate around the outer circumference of the enameled wire while feeding the enameled wire along its length direction; the injection molding gun (2) comprises a tubular gun body (21); the front end of the gun body (21) is reduced in diameter and provided with a discharge port (22), and the rear inner sealing sliding sleeve is provided with a pushing piston (23); an electromagnet (24) is fixedly provided in the gun body (21) behind the pushing piston (23); a permanent magnet (25) is fixed to the rear of the pushing piston (23); the electromagnet (24) is opposite to the permanent magnet (25), and the on and off of the electromagnet (24) is controlled by a circuit The electric and magnetic pole directions can control the opposite surfaces of the electromagnet (24) and the permanent magnet (25) to repel or attract each other; one end of a guide rod (26) is fixed to the pushing piston (23), and the other end slides through the electromagnet (24); a return spring (27) is sleeved on the guide rod (26); the two ends of the return spring (27) are respectively fixedly connected to the pushing piston (23) and the electromagnet (24); a petal-shaped elastic diaphragm (28) is provided at the discharge port (22), which is closed under normal conditions and is squeezed open to expose the discharge port when the thrust exceeds a threshold; an injection molding feeding pipe (29) is connected between the pushing piston (23) and the discharge port (22) on the side wall of the gun body (21).

6. The method for preparing the insulating layer of the enameled wire according to any one of claims 1 to 5, characterized in that: The steps include: Step 1: Mixing the Materials Weigh the raw materials for the inner layer, middle layer and outer layer respectively and mix them evenly; Step 2: Multi-layer extrusion Use a multi-hopper extruder, with each hopper responsible for a mixture, to extrude three layers of material through a die and cover them on the outer circumference of the copper core in the order of inner layer, middle layer and outer layer, ensuring that each layer of material is correctly covered on the previous layer; Step 3: UV Curing The extruded three-layer enameled wire is cured by a UV light source; Step 4: Low temperature treatment The cured enameled wire is subjected to a low temperature treatment at -40°C to -60°C.

7. The method according to claim 6, characterized in that In step 1, when the inner layer materials are mixed, the temperature is maintained at 80°C to 100°C, and the mixing time is 1 hour; when the middle layer materials are mixed, the mixing temperature is maintained at 80°C, and the mixing time is 1.5 hours; when the outer layer materials are mixed, the mixing temperature is maintained at 80°C, and the mixing time is 1.5 hours.

8. The method according to claim 6, characterized in that In step 2, the multi-layer extrusion molding comprises the following steps: Preheat the copper core: First, preheat the copper core to 50°C to 70°C; Loading materials: Load the pre-mixed inner layer, middle layer and outer layer materials into the corresponding hoppers respectively; the output temperature of each hopper is: the inner layer is set at 220°C, the middle layer is 230°C, and the outer layer is 210°C; Synchronous extrusion: The material is gathered at the extruder head, passes through a multi-layer die, and is synchronously extruded onto a moving copper core in a set order and thickness; the extrusion speed is 5 to 15 m / min; Cooling: The extruded composite material is cooled and shaped through a cold water tank or air cooling system.

9. The method according to claim 6, characterized in that In step 3, UV curing includes: Before UV curing, it passes through a preheating section, and the preheating temperature is set at 50°C to 70°C; The extruded three-layer enameled wire is then cured by a UV light source, wherein the wavelength of light emitted by the UV light source is 320 to 400 nanometers; the UV light intensity is 100 to 200 mW / cm²; and the speed of the enameled wire passing through the UV light source area is controlled to be 1 to 5 meters / minute; After UV curing, cooling treatment is performed, and the cooling temperature is controlled between room temperature and 30°C.

10. The method according to claim 6, characterized in that In step 4, the low temperature treatment includes: The cured enameled wire is placed in a low temperature treatment chamber; the temperature of the treatment chamber is set at -40°C to -60°C; and the treatment time under the temperature condition is maintained for 12 to 24 hours.

Images