Insulated electric wire, method for manufacturing the same, coil, and electronic / electrical device

Abstract

The application discloses an insulating electric wire, a preparation method thereof, a coil and an electronic / electrical equipment. The insulating electric wire comprises a conductor and a corona-resistant insulating layer covering the outer periphery of the conductor. The corona-resistant insulating layer is obtained by melt extrusion of a corona-resistant resin. The corona-resistant resin comprises a base resin and corona-resistant inorganic particles, wherein the outer surface of the corona-resistant inorganic particles is partially or totally wrapped with a compatible resin. The application effectively improves the dispersibility and interfacial bonding force of the corona-resistant inorganic particles in the base resin by wrapping the compatible resin on the surface of the corona-resistant inorganic particles, thereby ensuring that the insulating layer has excellent corona-resistant performance while maintaining good flexibility and processability, and realizing efficient and stable production through a melt extrusion process.

Description

Technical Field

[0001] This invention relates to the field of wire and cable manufacturing technology, specifically to an insulated wire and its preparation method, a coil, and electronic / electrical equipment. Background Technology

[0002] During operation, when the local electric field strength on the surface of an insulated wire's insulation layer exceeds the breakdown field strength of air, it causes local ionization of the surrounding air, producing a visible blue fluorescent discharge—a phenomenon known as corona discharge. The accompanying thermal effects and bombardment by reactive particles from corona discharge lead to a localized increase in the temperature of the insulation material, triggering thermal degradation, oxidation, and even carbonization of the polymer chains. Over time, this causes aging and performance deterioration of the insulation layer, potentially leading to electrical short circuits and severely impacting the reliability and lifespan of electronic and electrical equipment.

[0003] To improve the corona resistance of insulated wires, existing technologies mainly employ the following methods: First, increasing the overall thickness of the insulation layer and reducing the working field strength by increasing the insulation distance, making it lower than the corona initiation field strength; Second, adding a functional corona-resistant layer to the insulation structure, for example, in the manufacturing of enameled wire, dispersing nano-sized inorganic fillers (such as alumina, silica, etc.) in the insulating varnish, and then curing it through multiple coatings and high-temperature baking to form a varnish film with corona-resistant properties; Third, melt-blending corona-resistant fillers with thermoplastic resin to prepare a corona-resistant thermoplastic composite material, and then coating it onto the conductor surface through an extrusion process to form an insulation layer.

[0004] Although the above methods improve the corona resistance of insulated wires to some extent, the following technical bottlenecks still exist in practical applications: (1) The challenge of balancing the proportion of corona-resistant fillers: When adding corona-resistant fillers to a thermoplastic resin matrix, there is a performance balance that is difficult to achieve. If the amount added is too high, a large amount of inorganic filler will destroy the continuous phase of the resin matrix, resulting in a significant increase in the hardness of the composite material and a decrease in its flexibility and ductility. This makes the insulated wires produced in the end prone to cracking or breakage during bending, winding and other processing. Conversely, if the amount added is insufficient, an effective barrier network to inhibit the generation and development of corona cannot be formed in the insulation layer. Especially under the pursuit of thin-layer and miniaturized insulation designs, the improvement in corona resistance is minimal and cannot meet the requirements of stringent operating conditions such as high frequency and high voltage.

[0005] (2) Issues related to filler dispersion uniformity and interfacial bonding: Uniform dispersion of corona-resistant fillers (especially nanofillers) in the resin matrix is ​​crucial for ensuring consistent performance. Due to their small particle size, large specific surface area, and tendency to agglomerate, it is difficult to achieve nanoscale uniform dispersion in the resin through conventional mechanical mixing. Agglomerates not only become local stress concentration points, affecting mechanical properties, but may also become initiation points for partial discharge due to their interfacial defects, thus accelerating insulation degradation. At the same time, poor interfacial compatibility between the filler and the resin matrix leads to weak interfacial bonding, affecting the overall dielectric properties and long-term stability of the composite material.

[0006] (3) Challenges in synergistic optimization of comprehensive performance: Existing technical solutions often focus on improving a single corona resistance index, while neglecting the multi-functional synergy required for insulating materials. For example, corona-resistant enameled wires made by multiple coating and curing often have insufficient thermal shock resistance (i.e., the ability to resist cracking under rapid temperature changes) due to the bonding strength between the enamel film and the conductor, and between the enamel film layers, as well as the insulation layer made of thermoplastic composite materials. Under conditions of frequent equipment start-up and shutdown or drastic fluctuations in ambient temperature, the insulation layer is prone to microcracks due to the mismatch between the expansion coefficients of the insulation layer and the conductor. These cracks will become new corona discharge points and moisture intrusion channels, accelerating insulation failure.

[0007] To address the above problems, existing technologies have adopted corresponding solutions, but these solutions themselves have limitations: For enameled wire technology, performance is improved through precise control of the enamel formulation and process. However, this technology relies on a complex process of multiple coatings and high-temperature baking, resulting in long production cycles, high energy consumption, and low efficiency. Furthermore, controlling the uniformity of coating for thicker wire diameters or irregularly shaped conductors is challenging. The resulting enamel film is essentially a thermosetting material; once cured, it cannot be further processed, thus limiting its flexibility.

[0008] For extruded thermoplastic corona-resistant insulated wires, efficient continuous production is attempted through melt blending and extrusion molding. However, the core contradiction of this approach remains unresolved: physical blending methods struggle to overcome the inherent contradiction between the effects of filler dispersibility and dosage on the intrinsic properties of the matrix (especially flexibility). Simple mechanical blending and screw extrusion processes have limited ability to depolymerize nanofiller agglomerates, and to ensure processing flowability, it is often necessary to sacrifice the filler dosage or plasticize the resin matrix, which may compromise its heat resistance or electrical properties. Therefore, existing extruded insulated wires often struggle to achieve an ideal balance between "corona resistance," "processing flexibility," and "long-term environmental reliability (such as resistance to thermal shock)." Summary of the Invention

[0009] This application aims to overcome the shortcomings of existing corona-resistant insulated wires in terms of filler addition ratio, dispersion uniformity, and synergistic material performance. It provides an insulated wire, its preparation method, coil, and electronic / electrical equipment that possess excellent corona resistance, good processing flexibility, and reliable environmental stability. The core of this application lies in the innovative structural design of the corona-resistant functional layer and the control of the filler-matrix interface. This ensures that a high proportion of corona-resistant filler achieves nanoscale uniform and stable dispersion while maintaining the intrinsic flexibility and interfacial bonding strength of the composite material. This simultaneously solves the problem of synergistic optimization of corona resistance, flexibility, and thermal shock resistance, providing a crucial foundational material guarantee for the long-term reliable operation of electronic and electrical equipment under harsh conditions such as high frequency and high voltage.

[0010] To address the aforementioned problems, a first aspect of the present invention provides an insulated wire comprising a conductor and a corona-resistant insulating layer covering the outer periphery of the conductor; the corona-resistant insulating layer is obtained by melt extrusion of a corona-resistant resin; the corona-resistant resin comprises a matrix resin and corona-resistant inorganic particles, wherein the outer surface of the corona-resistant inorganic particles is partially or completely coated with a compatible resin.

[0011] This application provides an insulated wire, the core of which lies in the specific structure and material composition of the conductor and the corona-resistant insulation layer covering it. The corona-resistant insulation layer is formed in one step by a melt extrusion process from corona-resistant resin; the corona-resistant resin comprises a matrix resin and corona-resistant inorganic particles, wherein the outer surface of the corona-resistant inorganic particles is at least partially or completely coated with a compatible resin. Through the transition and bridging formed by the compatible resin between the corona-resistant inorganic particles and the matrix resin, the dispersion uniformity and interfacial bonding force of the corona-resistant inorganic particles in the matrix resin are significantly improved, thereby ensuring excellent corona resistance of the insulation layer while maintaining good flexibility and processability of the material.

[0012] Further, the matrix resin comprises polyether ether ketone resin (PEEK) and polyether resin, wherein the polyether resin is selected from at least one of polyether diphenyl ether ketone, polyether o-ether ketone, polyether ketone, polyether ketone ketone, polyether ether ketone-polyether diphenyl ether ketone, polyether ether ketone-polyether o-ether ketone, and polyether diphenyl ether ketone-polyether o-ether ketone.

[0013] Furthermore, the corona-resistant inorganic particles account for 5 wt% to 35 wt% of the corona-resistant resin, and the matrix resin accounts for 65 wt% to 95 wt%.

[0014] Further, the mass ratio of the polyether ether ketone resin to the at least one polyether resin is 99-90:1-10.

[0015] Furthermore, the compatibility resin is phenolphthalein polyaryletherketone (PEK-C); and the compatibility resin accounts for 0.5 wt% to 5 wt% of the total weight of the corona-resistant inorganic particles encapsulated therein.

[0016] Furthermore, the corona-resistant inorganic particles include a first particle and a second particle; the first particle is talc, and the second particle is selected from at least one of barium sulfate, calcium sulfate, chromium oxide, glass fiber, iron oxide, magnesium carbonate, magnesium oxide, mica, silicon dioxide, silicon carbide, silicon nitride, sodium silicate, titanium dioxide, zinc oxide, zirconium oxide, boron nitride, and wollastonite.

[0017] Furthermore, the first particle accounts for less than 5 wt% of the total mass of the corona-resistant resin; the second particle accounts for 5 wt% to 30 wt% of the total mass of the corona-resistant resin.

[0018] Furthermore, the particle size of the corona-resistant inorganic particles satisfies the following conditions: D90 is less than 1 μm, and D60 is in the range of 5 nm to 500 nm.

[0019] Furthermore, the thickness of the corona-resistant insulating layer is from 1 μm to 300 μm.

[0020] According to another aspect of the present invention, a method for preparing a corona-resistant insulated wire is provided, the method comprising the following steps: Step S1, dissolving a compatible resin in an organic solvent, adding a first particle and a second particle and mixing them evenly to obtain corona-resistant inorganic particles whose surface is partially or completely coated with the compatible resin; Step S2, mixing the corona-resistant inorganic particles obtained in Step S1 with a matrix resin to obtain a corona-resistant resin; Step S3, melting and extruding the corona-resistant resin and coating it onto the surface of a conductor to form a corona-resistant insulating layer, thereby obtaining a corona-resistant insulated wire.

[0021] According to another aspect of the invention, a coil is provided that comprises the insulated wire described above.

[0022] According to another aspect of the present invention, an electronic / electrical device is provided, the electronic / electrical device comprising the coil described above.

[0023] The above-described technical solution of the present invention has the following beneficial technical effects: 1. Significantly improves the synergy between corona resistance and flexibility, and fundamentally solves the dispersion problem. By coating the outer surface of corona-resistant inorganic particles with a specific resin (such as PEK-C) that has good compatibility with the matrix resin, this resin forms an effective transition and bridge between the corona-resistant inorganic particles and the matrix resin. This greatly improves the dispersion uniformity of the corona-resistant inorganic particles in the matrix, fundamentally preventing particle agglomeration and ensuring that the functional particles are stably and uniformly dispersed at the nano / submicron scale. Specifically, although the solubility of PEK-C in solvents is known, its use in improving the dispersibility of corona-resistant inorganic particles in the matrix resin and preventing agglomeration is not common knowledge in the art and has not been described in the prior art. This invention adopts a process path of "pre-dispersing corona-resistant inorganic particles in PEK-C solution → drying and coating → melt blending with matrix resin", which solves the technical problem of easy agglomeration and uneven dispersion of corona-resistant inorganic particles in traditional mechanical blending. Furthermore, by introducing talc as a lubricating phase, this invention further optimizes extrusion processing performance, forming a complete technical solution with multi-particle synergy and process compatibility. Based on the aforementioned distinguishing features, this invention achieves unexpected technical effects in terms of corona resistance, flexibility, and resistance to thermal shock. This allows for optimization of the amount of corona-resistant inorganic particles added while ensuring excellent corona resistance, thereby achieving a high corona resistance level while avoiding material hardening and embrittlement caused by excessive filler or agglomeration, significantly maintaining the good bending flexibility and processability of insulated wires.

[0024] 2. Imparts excellent resistance to thermal shock to the insulation layer. The corona-resistant inorganic particles, uniformly dispersed in the matrix resin, effectively reduce the coefficient of thermal expansion (CTE) of the composite material. A better-matched CTE reduces the difference in thermal expansion and contraction between the insulation layer and the metal conductor during rapid temperature changes, thus greatly mitigating the risk of interface debonding or insulation layer cracking caused by accumulated thermal stress. This directly translates into superior long-term environmental reliability and service life of the wire under harsh temperature cycling conditions.

[0025] 3. Achieving efficient, stable, and high-quality processing and manufacturing. Based on the aforementioned excellent dispersibility and interfacial state, the corona-resistant resin can be smoothly formed into an insulating layer in one step through a "melt extrusion" process. This process is not only simple, efficient, and energy-saving, but also ensures a dense insulating layer structure, uniform performance, and stable and reliable product quality, making it suitable for large-scale continuous production.

[0026] In summary, the technical solution of this application, through the core design of "particle surface coating with a compatibility layer", logically achieves a dual technical effect chain of "improved dispersion → optimized addition → synergistic improvement of electromechanical performance" and "reduced CTE → enhanced thermal stability", simultaneously overcoming the industry problem of difficulty in balancing corona resistance, flexibility and environmental reliability. Attached Figure Description

[0027] Figure 1 This is a cross-sectional structural diagram of an insulated wire according to an embodiment of the present invention; Figure label: 1: Corona-resistant insulating layer; 2: Conductor. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] To address the problems of uneven filler dispersion, difficulty in achieving synergistic overall performance, and complex manufacturing processes in existing corona-resistant insulated wires, this invention proposes a corona-resistant insulated wire. By introducing corona-resistant inorganic particles with a surface coated with a compatible resin into its corona-resistant insulation layer, highly uniform dispersion of the filler within the matrix resin and interfacial reinforcement are achieved. The insulation layer is formed in one step using corona-resistant resin through melt extrusion. The compatibility between the corona-resistant inorganic particles and the matrix resin is improved by coating the surface of the inorganic particles with a compatible resin (such as PEK-C), ensuring uniform dispersion and preventing agglomeration. This effectively enhances the material's corona resistance while maintaining good flexibility. Furthermore, the addition of corona-resistant inorganic particles reduces the linear expansion coefficient of the composite material, significantly improving the wire's resistance to thermal shock. This solution avoids performance defects caused by filler agglomeration by adopting an interface design of "particle surface coating with a compatible layer" and a process of "melt extrusion one-time molding". It solves the problem of difficulty in balancing corona resistance and flexibility, and finally achieves synergistic optimization of corona resistance, processing flexibility and long-term environmental stability. It provides a reliable and efficient insulated wire for electronic and electrical equipment under harsh conditions such as high frequency and high voltage.

[0030] The following is combined with Figure 1 The insulated wires, their preparation methods, coils, and electronic / electrical devices provided by this invention are described.

[0031] Figure 1 This is a cross-sectional structural diagram of an insulated wire according to an embodiment of the present invention.

[0032] like Figure 1 As shown, this embodiment provides an insulated wire, which includes a conductor 2 located at the center and a corona-resistant insulation layer 1 covering the outer periphery of the conductor 2.

[0033] The corona-resistant insulating layer 1 is formed in one step from corona-resistant resin through a melt extrusion process. This corona-resistant resin consists of a matrix resin and corona-resistant inorganic particles (such as those composed of talc and silica). To improve interfacial compatibility and dispersion uniformity, the outer surface of the corona-resistant inorganic particles is pre-coated with a compatible resin (e.g., PEK-C coated on the surface of the corona-resistant inorganic particles) that has good compatibility with both the corona-resistant inorganic particles and the matrix resin. During production, the corona-resistant inorganic particles are first surface-treated to coat their outer surface with the compatible resin, forming corona-resistant inorganic particles whose surface is partially or completely coated with the compatible resin. Subsequently, the corona-resistant inorganic particles whose surface is partially or completely coated with the compatible resin are mixed uniformly with the matrix resin in a predetermined ratio, and then granulated using a twin-screw extruder to obtain corona-resistant resin granules. Next, corona-resistant resin particles are melt-extruded and coated onto the surface of conductor 2 using a melt extruder. After cooling and shaping, a continuous, dense corona-resistant insulating layer 1 is formed that is tightly bonded to the conductor.

[0034] This structural design allows the corona-resistant inorganic particles to be highly uniformly dispersed in the matrix resin at the nanometer or submicron scale, effectively suppressing partial discharge and significantly improving the corona resistance of the wire. Simultaneously, excellent interfacial bonding and optimized filler content ensure good flexibility of the insulation layer, facilitating subsequent bending and installation of the wire. Furthermore, the uniformly dispersed corona-resistant inorganic particles reduce the linear expansion coefficient of the composite material, making the thermal expansion behavior of the insulation layer and conductor more compatible, thus endowing the wire with excellent resistance to thermal shock. Through the above methods, the insulated wire of this embodiment achieves a synergistic improvement in corona resistance, processing flexibility, and long-term environmental reliability in a single extrusion molding process.

[0035] Optionally, the matrix resin comprises polyetheretherketone (PEEK) resin and a polyether resin, wherein the polyether resin is selected from at least one of polyether diphenyl etherketone, polyether o-etherketone, polyetherketone, polyetherketoneketone, polyetheretherketone-polyether diphenyl etherketone, polyetheretherketone-polyether o-etherketone, and polyether diphenyl etherketone-polyether o-etherketone. By introducing at least one polyether resin with a structure similar to PEEK but slightly different in flexibility, solubility parameters, or processing window, the overall properties of the matrix resin are fine-tuned, such as improving melt flowability, optimizing interfacial interactions with the compatibility layer, or adjusting the crystallization behavior of the composite material, thereby providing a more refined performance control space for the material system without significantly impairing heat resistance.

[0036] Optionally, the corona-resistant inorganic particles account for 5 wt% to 35 wt% of the corona-resistant resin mass, and the matrix resin accounts for 65 wt% to 95 wt%.

[0037] Optionally, the mass ratio of PEEK resin to at least one polyether resin is 99–90:1–10. By controlling the amount of at least one polyether resin added within this low range, the aforementioned fine-tuning effect can be introduced while ensuring that the matrix resin remains dominated by high-performance PEEK. This ensures that the core characteristics of the composite insulation layer, such as high strength, high heat resistance, and excellent inherent electrical insulation properties, are not fundamentally affected, achieving a balance between stable main properties and optimized auxiliary properties.

[0038] Preferably, the mass ratio of PEEK resin to at least one polyether resin is 95:5. This specific ratio is an optimal balance point obtained based on extensive experiments. It can typically significantly improve processability or specific interfacial properties while ensuring the main properties of PEEK, resulting in a better overall performance of the composite material. Moreover, the ratio is easy to precisely control and achieve in industrial production.

[0039] Preferably, the compatible resin is PEK-C; and the mass percentage of the compatible resin in the corona-resistant inorganic particles coated with the compatible resin layer is 0.5 wt% to 5 wt%. Compared to standard PEEK, the molecular chain structure of PEK-C exhibits higher flexibility and better solubility, allowing for uniform dispersion of the corona-resistant inorganic particles in organic solvents without significant agglomeration. This is mainly due to the phenolphthalein side bonds of PEK-C, which endow it with solvent solubility; simultaneously, the ether and ketone bonds on PEK-C have similar molecular structures to those on PEEK, thus exhibiting good compatibility. In other words, PEK-C demonstrates good compatibility with both the matrix resin and the corona-resistant inorganic particles. Taking advantage of the solvent-soluble nature of PEK-C, it is dissolved and mixed with corona-resistant inorganic particles. Due to the low viscosity of the solution, the corona-resistant inorganic particles can achieve nanoscale uniform dispersion in the PEK-C solution without easily agglomerating. However, if the corona-resistant inorganic particles are directly mechanically mixed with solvent-insoluble PEEK resin through a twin-screw extruder, the particles are prone to agglomeration under the strong shear force of the screw, making uniform dispersion difficult to achieve. Therefore, this invention adopts a process path of "solution pre-dispersion - drying and coating - melt blending". First, the corona-resistant inorganic particles are uniformly dispersed at the nanoscale using a PEK-C solution. Then, after drying, corona-resistant inorganic particles coated with PEK-C are obtained. Finally, these particles are melt-blended with the matrix resin through a twin-screw extruder, thereby achieving uniform dispersion of the corona-resistant inorganic particles in the matrix resin. This characteristic allows it to effectively coat the surface of the corona-resistant inorganic particles and form a good compatibility interface with the matrix resin through the interaction between molecular chains. By controlling the mass percentage of this compatibility layer within the range of 0.5wt% to 5wt%, it is possible to ensure the formation of a continuous and complete coating layer on the particle surface, thereby achieving effective dispersion and interface modification of corona-resistant inorganic particles, while avoiding the formation of a low-modulus transition zone at the interface due to excessive coating thickness or adverse effects on the overall heat resistance and mechanical strength of the composite material.

[0040] Optionally, the corona-resistant inorganic particles include a first particle and a second particle; the first particle is talc, and the second particle is selected from at least one of barium sulfate, calcium sulfate, chromium oxide, glass fiber, iron oxide, magnesium carbonate, magnesium oxide, mica, silicon dioxide, silicon carbide, silicon nitride, sodium silicate, titanium dioxide, zinc oxide, zirconium oxide, boron nitride, and wollastonite. Talc primarily serves a lubricating function, which helps improve processing fluidity during melt extrusion; the second particle primarily provides corona resistance. The two types of particles are not fundamentally different in their addition process; they are uniformly mixed together in the finished product and coated by the PEK-C solution, working synergistically. This composite filler system, through the synergistic effect of the first and second particles, can achieve multi-dimensional enhancement of the composite material's properties. Talc can effectively improve the dimensional stability and heat resistance of the material and form a physical barrier effect in the insulation system; the selected functional particles in the second particle can specifically improve the corona resistance, thermal conductivity, mechanical strength, or optimize the dielectric properties of the composite material. The two complement each other in function and structure, jointly constructing a more stable insulation system, thereby achieving synergistic optimization of overall performance.

[0041] Preferably, the proportion of the first particle in the total mass of the corona-resistant resin is less than 5 wt%; the proportion of the second particle in the total mass of the corona-resistant resin is 5 wt% to 30 wt%. Controlling the talc content at a low level (<5 wt%) can prevent a sharp increase in melt viscosity, processing difficulties, and excessive material anisotropy caused by excessive filler. Setting the total amount of functional filler (second part) in a wider range of 5 wt% to 30 wt% provides flexible formulation design space to meet the differentiated requirements of corona resistance performance for different voltage levels, frequencies, and operating environments, ensuring that significant functional improvements are achieved without seriously impairing the flexibility and processability of the matrix resin.

[0042] Preferably, the corona-resistant inorganic particles have the following particle size requirements: D90 < 1 μm, and D60 within the range of 5 nm to 500 nm. This limitation on the particle size distribution of the filler is crucial. D90 is a parameter of particle size distribution; D90 < 1 μm indicates that 90% of the particles are smaller than 1 μm, ensuring that the vast majority of particles are at the submicron scale, effectively avoiding local electric field distortion and mechanical weaknesses caused by the presence of large particles. Similarly, D60 within the range of 5 nm to 500 nm means that the main particles are at the nanometer to submicron scale, possessing extremely high specific surface area, enabling them to more effectively perform their functions (such as trapping effect and discharge suppression), while also facilitating uniform dispersion through surface treatment, which is key to achieving thin-layer, high-performance insulation.

[0043] Preferably, the thickness of the corona-resistant insulating layer is from 1 μm to 300 μm. This thickness range covers a wide range of applications, from ultrafine wires for precision electronic components to electromagnetic wires for small and medium-sized motors and electrical appliances. Thinner insulating layers (e.g., 1-50 μm) are beneficial for device miniaturization and high thermal conductivity requirements; thicker insulating layers (e.g., 50-300 μm) are suitable for higher operating voltages. Due to its excellent dispersibility and interfacial properties, the material system of this invention enables the preparation of uniform, dense, and defect-free insulating layers throughout this entire thickness range, thereby ensuring the reliable realization of its designed functions.

[0044] This embodiment also provides a method for preparing a corona-resistant insulated wire, which includes the following steps: Step S1: Dissolve the compatible resin in an organic solvent, add the first and second particles and mix them evenly to obtain corona-resistant inorganic particles whose surface is partially or completely coated with the compatible resin.

[0045] In some embodiments, step S1 is mainly used for surface coating pretreatment, and its specific operation is as follows: (1) PEK-C is added to an organic solvent for dissolution. The organic solvent is selected from DMAc or DMF to obtain a primary mixture. (2) Add the first and second particles to the primary mixture and disperse them evenly to obtain the secondary mixture; (3) The secondary mixture is made into particles by spray drying, specifically including: after adjusting the secondary mixture to a suitable concentration for atomization, atomizing it into tiny droplets through a nozzle, and contacting the droplets with hot air to quickly remove organic solvents, thereby obtaining dry, corona-resistant inorganic particles coated with PEK-C resin layer.

[0046] Step S2: The corona-resistant inorganic particles obtained in step S1 are mixed with the matrix resin and then granulated by a twin-screw extruder to obtain corona-resistant resin particles.

[0047] Unlike the traditional process of directly feeding corona-resistant inorganic particles and matrix resin into a twin-screw extruder for mechanical blending, this step utilizes the property of the compatibility resin (PEK-C) being soluble in organic solvents to achieve nanoscale uniform dispersion of corona-resistant inorganic particles in solution. This effectively avoids particle agglomeration caused by the strong shear force of the screw during subsequent melt blending, which is a key process feature to ensure the uniformity of filler dispersion and interfacial bonding.

[0048] In some embodiments, step S2 is mainly used for premixing, and its specific operation is as follows: (1) PEEK resin particles, at least one polyether resin particles, and corona-resistant inorganic particles coated with PEK-C resin layer obtained in step S1 are physically premixed in a predetermined mass ratio to obtain a mixture. (2) The mixture is added to a twin-screw extruder for extrusion granulation to obtain corona-resistant resin granules.

[0049] In step S3, the corona-resistant resin particles obtained in S2 are melt-extruded through an extruder and coated onto the conductor surface to form a corona-resistant insulating layer, thereby obtaining an insulated wire.

[0050] In some embodiments, step S3 is mainly used for extrusion molding, and its specific operation is as follows: (1) The conductor is preheated to reach the preset preheating temperature; (2) The corona-resistant resin particles obtained in step S2 are added to an extruder and heated, melted and plasticized to form a uniform melt; (3) The melt is extruded through an extrusion die, and during the travel of the preheated conductor, the melt is continuously and uniformly coated and wrapped on the surface of the conductor; (4) After cooling and shaping, a continuous and dense corona-resistant insulation layer is formed, and finally a corona-resistant insulated wire is obtained.

[0051] The present invention also provides a coil comprising the insulated wire described above.

[0052] The present invention also provides an electronic / electrical device comprising the coil described above.

[0053] For details regarding the principle, implementation, and beneficial effects of this insulated wire, as well as the process flow and advantages of its preparation method, please refer to the preceding text. Figure 1 The descriptions of corona-resistant insulated wires and their preparation methods shown are not repeated here.

[0054] The corona-resistant insulated wire provided in this application will be further described below with reference to specific embodiments and performance test data. Unless otherwise specified, all raw materials used are commercially available. In the embodiments and comparative examples, the conductor size is a 1.4mm × 3.0mm rectangular copper wire, and the target insulation layer thickness is 110μm ± 20μm. The following embodiments specifically involve corona resistance time testing, thermal shock resistance and insulation strength testing, and flexibility testing.

[0055] The following are the specific formulations and performance test results of Examples 1 to 3 and Comparative Examples 1 to 4. The material ratios of each experimental group were calculated based on the total mass of the corona-resistant resin. In each example and comparative example, the proportion of talc in the total mass of the corona-resistant resin was 4 wt%. The PEK-C proportion refers to its mass percentage in the final corona-resistant inorganic particle powder coated with a PEK-C resin layer. Specific data are detailed in Table 1.

[0056]

[0057] The specific test methods and evaluation criteria involved in the above embodiments in Table 1 are as follows: (1) Corona resistance time test method: The test method of GB / T4074.21 is adopted, and the specific steps are as follows: Place the insulated wire in the high-frequency pulse voltage test instrument, apply a high-frequency pulse voltage between the two conductors of the sample under the following specified conditions, test and record the test value.

[0058] Test conditions: pulse frequency 20kHz, pulse duty cycle 50%, pulse square wave, bipolar pulse, test voltage 1.5kV, temperature 155℃, rise time 100ns.

[0059] The evaluation criteria are as follows: A: Corona resistance time ≥200h; B: Corona resistance time ≥50h and <200h; C: Corona resistance time < 50h.

[0060] In this case, A represents qualified, and the others represent unqualified.

[0061] (2) Thermal shock test: The test method is: high temperature 200℃ / 60min-low temperature-40℃ / 60min, switching time <2min, switching from high temperature to low temperature and then back to high temperature is one cycle, and 100 cycles are performed.

[0062] Then, the insulation breakdown voltage (BDV) test is performed: the test method for breakdown voltage provided in IEC 60851-5-2019 Test Method 13 is adopted, and the specific steps are as follows: Remove the outer layer from one end of the insulated wire from Examples 1-3 and Comparative Examples 1-4. Bend the wire along the wider side of a φ25mm diameter round rod and place it into a container of metal beads at least 5mm thick. Ensure the insulated wire end extends sufficiently to prevent flashover. Apply a test voltage between the conductor and the metal beads. Increase the voltage at a rate of 500V / second and a leakage current of 5mA. Record the breakdown voltage (kV) and classify it according to the following method: A+: BDV ≥ 12kV; A: BDV ≥ 10kV and < 12kV; B: BDV ≥ 8kV and < 10kV; C: BDV < 8kV; A+ and A are considered qualified, while the others are considered unqualified.

[0063] (3) Flexibility test The insulated wires of the embodiments and comparative examples were subjected to flexibility tests according to the following methods.

[0064] The flexibility test was conducted using the flexibility test method provided in IEC 60851-3-2019 Test Method 8. The specific steps are as follows: Take two 500mm long straight insulated wires and bend each wire 180±2° around a polished test core. One wire is wound horizontally (core diameter = wire thickness twice), and the other is wound vertically (core diameter = wire width twice). In this test, after horizontal and vertical winding, the product with a smooth surface without cracks is recorded as "qualified"; the product with cracks is recorded as "unqualified".

[0065] Based on the data in Table 1, the analysis is as follows: Effectiveness of the technical solution in this application (Examples 1 to 3): All embodiments exhibit excellent comprehensive performance, and all tests for corona resistance time, insulation strength after thermal shock, and flexibility are qualified. This demonstrates that the technical solution of "coating the surface of corona-resistant inorganic particles with a PEK-C layer" and "controlling the particle size and amount of filler" has successfully achieved a synergistic improvement in corona resistance, environmental reliability, and processing flexibility.

[0066] The necessity of corona-resistant inorganic particles (Comparative Example 1): Comparative Example 1, which did not contain any corona-resistant inorganic particles, had seriously substandard corona resistance performance (Grade C), proving that functional corona-resistant inorganic particles are the key component that imparts corona resistance to materials.

[0067] Effects of excessive filler content (Comparative Example 2): When the amount of corona-resistant inorganic particles added is as high as 50wt%, although the corona resistance time (Grade B) is improved, the excessive filler causes the composite to become brittle and the flexibility is unqualified. Furthermore, after thermal shock, the insulation layer is damaged due to excessive internal stress, and the breakdown voltage (Grade C) drops significantly.

[0068] The key role of the PEK-C coating layer (Comparative Example 3): Comparative Example 3, which did not use PEK-C to coat the particles, had a better corona resistance time (Grade B) than Comparative Example 1 without PEK-C, but it was significantly lower than Example 1 (Grade A) with the same amount of PEK-C. This indicates that without a compatibility layer, the particle dispersibility and interfacial bonding are poor, and its corona resistance performance cannot be fully utilized.

[0069] The Importance of Particle Size Control (Comparative Example 4): Comparative Example 4, using micron-sized large particles (D90 3-5μm), showed a comprehensive deterioration in all performance aspects (corona resistance C grade, BDV C grade, and unacceptable flexibility). Large particles are inherently prone to becoming defects and are difficult to effectively encapsulate and disperse, resulting in numerous weak points in the insulation layer. This demonstrates that controlling the particle size to the submicron level (D90 < 1μm) is a necessary condition for ensuring uniform and reliable thin-layer insulation performance.

[0070] Therefore, the technical solution provided in this application, by controlling the surface coating (PEK-C layer), addition ratio (5-35wt%) and particle size (D90<1μm) of corona-resistant inorganic particles, can prepare insulated wires that simultaneously meet the requirements of high corona resistance, excellent thermal shock resistance and good flexibility, thus solving the performance contradiction that is difficult to achieve in traditional technologies.

[0071] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An insulated wire, characterized in that, include: The conductor, and the corona-resistant insulating layer covering the outer periphery of the conductor; The corona-resistant insulating layer is obtained by melt extrusion of corona-resistant resin; the corona-resistant resin comprises a matrix resin and corona-resistant inorganic particles, and the outer surface of the corona-resistant inorganic particles is partially or completely coated with a compatible resin. The corona-resistant inorganic particles account for 5 wt% to 35 wt% of the corona-resistant resin, and the matrix resin accounts for 65 wt% to 95 wt% of the corona-resistant resin. The compatibility resin is phenolphthalein polyaryletherketone, and the compatibility resin accounts for 0.5-5 wt% of the total weight of the corona-resistant inorganic particles encapsulated therein. The particle size of the corona-resistant inorganic particles meets the following requirements: D90 is less than 1 μm, and D60 is in the range of 5 nm to 500 nm.

2. The insulated wire according to claim 1, characterized in that, The matrix resin includes polyether ether ketone resin and polyether resin, wherein the polyether resin is selected from at least one of polyether diphenyl ether ketone, polyether o-ether ketone, polyether ketone, polyether ketone ketone, polyether ether ketone-polyether diphenyl ether ketone, polyether ether ketone-polyether o-ether ketone, and polyether diphenyl ether ketone-polyether o-ether ketone.

3. The insulated wire according to claim 2, characterized in that, The mass ratio of the polyether ether ketone resin to the at least one polyether resin is 99-90:1-10.

4. The insulated wire according to any one of claims 1-3, characterized in that, The corona-resistant inorganic particles include a first particle and a second particle; the first particle is talc, and the second particle is selected from at least one of barium sulfate, calcium sulfate, chromium oxide, glass fiber, iron oxide, magnesium carbonate, magnesium oxide, mica, silicon dioxide, silicon carbide, silicon nitride, sodium silicate, titanium dioxide, zinc oxide, zirconium oxide, boron nitride, and wollastonite.

5. The insulated wire according to claim 4, characterized in that, The first particle accounts for less than 5 wt% of the total mass of the corona-resistant resin; the second particle accounts for 5 wt% to 30 wt% of the total mass of the corona-resistant resin.

6. The insulated wire according to any one of claims 1-3 and 5, characterized in that, The thickness of the corona-resistant insulating layer is from 1 μm to 300 μm.

7. A method for preparing an insulated wire, used to prepare the insulated wire according to claim 4 or 5, characterized in that, Includes the following steps: Step S1: Dissolve the compatibility resin in an organic solvent, add the first particle and the second particle and mix them evenly to obtain corona-resistant inorganic particles whose surface is partially or completely coated with the compatibility resin. Step S2: The corona-resistant inorganic particles obtained in step S1 are mixed with the matrix resin and then granulated by a twin-screw extruder to obtain corona-resistant resin particles. In step S3, the corona-resistant resin particles obtained in S2 are melt-extruded through an extruder and coated onto the conductor surface to form a corona-resistant insulating layer, thereby obtaining an insulated wire.

8. A coil, characterized in that, It comprises an insulated wire made by any one of claims 1-6 or an insulated wire made by the method for making an insulated wire as described in claim 7.

9. An electronic / electrical device, characterized in that, It includes the coil as described in claim 8.

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