High-performance resin for electrical equipment, thin film, preparation method and electrical equipment

Abstract

The invention belongs to the technical field of plastic molding, and particularly relates to high-performance resin for electrical equipment, a film, a preparation method and electrical equipment. According to the high-performance resin, dibasic acid and dihydric alcohol are adopted as polymerization monomers, and through molecular structure design and film drawing process optimization, preparation of a thin film material with the thickness of 10-25 microns is achieved. Wherein the molecular structure design comprises the steps of optimizing and controlling a reaction process and introducing a rigid group into a dihydric alcohol monomer. The optimization of the film drawing process comprises the following steps of: precisely controlling the temperature, filtering impurities and eliminating bubbles by adopting a co-rotating twin-screw extruder for casting piece extrusion; according to the longitudinal and transverse stretching process, molecular chains are arranged in order by controlling the temperature, the speed and the stretching ratio; and finally, improving the crystal structure by adopting a post-treatment process. The embodiment shows that the water absorption rate of the thin film prepared under the optimal process is lower than 0.5%, the alternating current breakdown field strength is larger than 200kV / mm, the direct current breakdown field strength is larger than 550kV / mm, the heat-resistant temperature is 200 DEG C, various insulation requirements of electrical equipment can be met, the process repeatability is high, and the good batch production potential is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of plastic molding, and particularly relates to a high-performance resin and film for electrical equipment, a preparation method thereof, and a power equipment. Background Art

[0002] In electrical equipment, the performance of insulating materials plays a crucial role in the safe and stable operation of the equipment. From power generation equipment, transmission lines to substation equipment and power consumption terminals, reliable insulating materials are indispensable in every link. Traditional insulating films, such as PI (polyimide), PET (polyethylene terephthalate) films, etc., expose many problems in different application scenarios of electrical equipment. Although PI film has excellent heat resistance and insulating properties, its high cost limits its large-scale application; PET film has a significant decrease in insulating performance in a humid environment due to its high water absorption rate, affecting the long-term reliability of power equipment.

[0003] To solve the problems of traditional insulating films, the industry has actively explored new materials and preparation processes. For example, Patent CN202411181662.3 proposes a high-performance film for electrical insulation, which improves the insulating and mechanical properties of the film by adding specific nanoparticles to the polymer matrix. However, in practical applications, it is difficult to ensure the uniform dispersion of nanoparticles, and agglomeration is prone to occur, resulting in unstable film performance, and the preparation process is complex and the production cost is high. Patent CN119177090A discloses a composite film with high insulating performance and a preparation method thereof, which improves the comprehensive performance of the film through a multi-layer composite structure. However, the preparation process of this composite film involves multiple complex processes, has extremely high requirements for equipment and process control, has low production efficiency, and the interfacial bonding strength between composite layers is limited, and delamination may occur during long-term use, affecting the overall performance of the film. Patent CN119775728A proposes a polybutylene terephthalate resin composition and a preparation method thereof, which realizes the improvement of the breakdown strength of the material by introducing KL-E series epoxy-functionalized polymers and halogen-free flame retardants. However, the resin prepared by this method can only be used to prepare high-voltage cable insulation layer materials (millimeter-level thickness), and it is difficult to make micron-level films, and the breakdown field strength can only reach 40 kV / mm, which cannot meet the application requirements of other fields. Summary of the Invention

[0004] The purpose of the present invention is to provide a novel high-performance resin film for electrical equipment and its preparation process. Aiming to overcome the problems of high cost, performance defects and complex preparation processes of existing insulating films, a film with low water absorption rate, high insulating performance, good mechanical properties and heat resistance is prepared, and at the same time, the preparation process is simplified and the production cost is reduced to meet the urgent needs of insulating materials in various fields of electrical equipment and promote the efficient and stable development of electrical equipment.

[0005] The object of the present invention is achieved by the following technical solutions: A high-performance resin for electrical equipment, which is formed by the polymerization reaction of a dibasic acid and a diol having a specific structure; The dibasic acid includes terephthalic acid, itaconic acid, maleic anhydride, succinic acid, glutaric acid, adipic acid; The diol includes ethylene glycol, 1,4-butanediol, pentanediol, cyclohexanol, 1,6-hexanediol, aromatic diol.

[0006] Preferably, the polymerization reaction is condensation polymerization.

[0007] Preferably, the specific structure includes: the dibasic carboxylic acid used contains an aromatic ring and an unsaturated double bond structure; the diol used contains a polycyclic ring or a long-chain structure, and the specific structure can effectively improve the hydrolysis resistance of the ester group in the polymer structure and increase the heat resistance temperature of the resin.

[0008] Preferably, the antioxidant of the resin includes one or a combination of hindered phenol antioxidants and phosphite antioxidants.

[0009] Preferably, the ultraviolet absorber of the resin includes one or a combination of benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers.

[0010] Preferably, the addition amount of the antioxidant accounts for 0.05% - 2% of the total mass of the resin and its derivatives.

[0011] Preferably, the addition amount of the ultraviolet absorber accounts for 0.05% - 3% of the total mass of the resin and its derivatives.

[0012] Preferably, for the aromatic diol, its chemical structural general formula is A r -C n H 2n (OH)2, where A r represents a benzene ring or other aromatic hydrocarbon group, specifically including phenyl (C6H5-), naphthyl (C 10 H7-), phenanthryl (C 14 H9-).

[0013] Preferably, the resin has a molecular weight distribution of PDI ≤ 4.0.

[0014] Based on the same inventive concept, the present invention also provides a method for preparing a high-performance resin for electrical equipment, which is used to prepare a high-performance resin for electrical equipment as described above. The method includes a polymerization reaction. Using alcohol monomers and carboxylic acid monomers as raw materials, in the prepolymerization stage and the polycondensation stage, by adjusting the ratio of aromatic monomers to aliphatic monomers and the reaction conditions, a rigid molecular chain containing cyclic monomers, low-reactivity ester bonds, and a high-crystallinity structure are established, and the resin crystallinity is controlled at 30%-40% to obtain the high-performance resin for electrical equipment.

[0015] Preferably, the polymerization reaction adopts a two-step method of esterification-polycondensation.

[0016] Preferably, in the prepolymerization stage, terephthalic acid accounting for 60%-80% of the carboxylic acid monomers is compounded with 10%-20% itaconic acid and 5%-15% maleic anhydride; in the alcohol monomers, ethylene glycol accounts for 50%-70%, and is paired with 20%-30% aromatic alcohol and 5%-15% cyclohexanol; placed in a reaction kettle, 0.1%-0.3% catalyst is added, and the temperature is raised to 220-240°C under nitrogen protection, and the reaction is carried out at normal pressure for 3-4 hours until the acid value drops to 50-80 mgKOH / g to generate a prepolymer product.

[0017] Preferably, in the polycondensation stage, the prepolymer product is heated to 260-280°C, gradually depressurized to 100-500 Pa, 0.05%-0.1% antioxidant is added, and the reaction is carried out for 2-3 hours. The molecular weight is adjusted between 20,000 and 30,000 by controlling the reaction time and vacuum degree, and the temperature is lowered to below 200°C, and the modified polyester resin is discharged.

[0018] Based on the same inventive concept, the present invention also provides a high-performance resin film for electrical equipment, and the film is prepared using a high-performance resin for electrical equipment as described above.

[0019] Based on the same inventive concept, the present invention also provides a method for preparing a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described above. The method includes the following steps: Sheet casting and extrusion: Using a co-rotating twin-screw extruder, the temperature of the feeding section is controlled at 260-280°C, the temperature of each barrel temperature zone is controlled at 280-288°C, and the die head temperature is controlled at 280-285°C; a 1300-1500 mesh filter screen is added at the die head, and an exhaust device is set; a 10-20 kV electrostatic adsorption voltage is applied at the first traction roll at the die head outlet to prepare a sheet. Longitudinal stretching: Stretch the cast film on a horizontal unidirectional stretching machine, control the temperature of the preheating roller at 60 - 80°C, set the temperature of the stretching roller at 80 - 100°C, and control the stretching ratio at 1.8 - 2.5; after stretching, conduct annealing treatment through an annealing roller with a temperature controlled at 68 - 90°C to obtain a longitudinally stretched film; Transverse stretching: Stretch the longitudinally stretched film on a four - corner stretching machine, control the stretching temperature at 100 - 120°C, the heat - preservation time at 120 - 180 s, the stretching speed at 100 - 150 mm / s, and control the stretching multiple at 3.0 - 3.5 to obtain a biaxially stretched film; Post - treatment: Conduct heat - setting treatment on the biaxially stretched film at 260 - 270°C for 3 - 5 min, then cool and wind up to obtain the high - performance resin film for electrical equipment.

[0020] Preferably, in the step of casting and extruding the cast film, pre - mix the resin and its derivatives with additives before feeding, and the pre - mixing time is 10 - 30 min to ensure that the additives are evenly dispersed in the resin system.

[0021] Based on the same inventive concept, the present invention also provides an electrical equipment, using the high - performance resin film described above as an insulating component.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The high - performance resin film of the present invention is mainly based on novel dicarboxylic acids and diols as basic raw materials for condensation polymerization. By reducing polar groups (such as controlling the proportion of carboxylic acid monomers), enhancing the hydrophobicity of the molecular chain, inhibiting water penetration; by introducing a rigid benzene ring structure, reducing molecular chain defects, lowering the ion migration rate, and increasing the breakdown field strength; by introducing cyclic monomers and a highly crystalline structure to increase the melting point and thermal stability; the molecular chain regularity and orientation ability cooperate to ensure the structural stability during the stretching process, avoiding breakage or wrinkles. Description of the Drawings

[0023] Figure 1 It is the appearance after baking the film prepared in the embodiment of the present invention and a traditional insulating film at 200°C for half an hour; Figure 2 It is the comparison of the performance of the film prepared in the embodiment of the present invention and the performance of a traditional insulating film. Detailed Embodiments

[0024] The following further illustrates the technical solutions in combination with the drawings and specific embodiments to help understand the content of the present invention.

[0025] Example 1 A high - performance resin for electrical equipment, the resin is generated by the polymerization reaction of a dicarboxylic acid and a diol with a specific structure; The dicarboxylic acids include terephthalic acid, itaconic acid, maleic anhydride, succinic acid, glutaric acid, adipic acid; The diols include ethylene glycol, 1,4-butanediol, pentanediol, cyclohexanol, 1,6-hexanediol, aromatic diols.

[0026] The polymerization reaction is condensation polymerization.

[0027] The specific structure includes: the dicarboxylic acid used contains an aromatic ring and an unsaturated double bond structure; the diol used contains a polycyclic ring or a long-chain structure, and the specific structure can effectively improve the hydrolysis resistance of the ester groups in the polymer structure and increase the heat resistance temperature of the resin.

[0028] The antioxidants of the resin include one or a combination of hindered phenol antioxidants and phosphite antioxidants.

[0029] The ultraviolet absorbers of the resin include one or a combination of benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers.

[0030] The addition amount of the antioxidant accounts for 0.05% - 2% of the total mass of the resin and its derivatives.

[0031] The addition amount of the ultraviolet absorber accounts for 0.05% - 3% of the total mass of the resin and its derivatives.

[0032] The aromatic diol has a chemical structural general formula of A r -CnH 2n (OH)2, where A r represents a benzene ring or other aromatic hydrocarbon groups, specifically including phenyl (C6H5-), naphthyl (C 10 H7-), phenanthryl (C 14 H9-).

[0033] The resin has a molecular weight distribution of PDI ≤ 4.0.

[0034] This high-performance resin for electrical equipment is formed by the condensation polymerization reaction of dicarboxylic acids with specific structures (such as terephthalic acid, itaconic acid, etc.) and diols (such as ethylene glycol, aromatic diols, etc.). Combining the synergistic effects of hindered phenol / phosphite antioxidants and benzotriazole / benzophenone ultraviolet absorbers, and narrow molecular weight distribution control (PDI ≤ 4.0), the following technical effects are achieved: Excellent heat resistance and thermal-oxidative stability The present invention significantly improves the high-temperature resistance of the resin by introducing aromatic diols (such as naphthyl and phenanthryl structures). Its aromatic ring structure can form rigid molecular chains, making the heat distortion temperature (Tg) reach above 200 °C. Hindered phenol antioxidants (such as antioxidant 1010) terminate the oxidation chain reaction by capturing free radicals, while phosphite esters (such as antioxidant 168) decompose hydroperoxides. The compounding of the two (with an addition amount of 0.05% - 2%) can extend the thermal-oxidative aging life of the resin at 150 °C by more than 3 times. The control of the molecular weight distribution (PDI ≤ 4.0) further reduces the risk of thermal degradation of low-molecular-weight chain segments, ensuring the stability of mechanical properties at high temperatures.

[0035] Excellent weather resistance and UV protection performance The present invention uses the synergistic addition (0.05% - 3%) of benzotriazole UV absorbers (such as UV-326) and benzophenones (such as UV-531) to absorb ultraviolet light in the range of 290 - 400 nm and inhibit the molecular chain breakage caused by photooxidation. Combining with the intrinsic UV resistance of the aromatic structure, after the resin is exposed outdoors for 1000 hours, the yellowing index (ΔYI) is lower than 2.0, and the tensile strength retention rate exceeds 90%.

[0036] High mechanical strength and electrical insulation performance The present invention uses terephthalic acid and maleic anhydride in the dibasic acid to form a rigid network with a high crosslinking density. The tensile strength reaches 80 - 100 MPa, and the flexural modulus exceeds 3.5 GPa. The conjugated structure of the aromatic diol endows the resin with a volume resistivity (10 15 -10 16 Ω·cm) and a high breakdown strength (> 550 kV / mm), meeting the requirements of high-voltage insulation.

[0037] Processability and environmental adaptability The present invention uses condensation polymerization to precisely control the catalyst and temperature (such as 180 - 220 °C), achieving controllable molecular weight and few by-products. The melt flow index (MFI) of the resin is 5 - 10 g / 10 min (230 °C / 2.16 kg), which is suitable for injection molding or calendering. The chemical resistance test shows that its mass loss is < 1% after being soaked in acids and alkalis (pH 2 - 12) and organic solvents (such as xylene) for 30 days, making it suitable for harsh environments such as chemical industry and energy.

[0038] Example 2 Based on the same inventive concept, this example also provides a preparation method of a high-performance resin for electrical equipment, which is used to prepare a high-performance resin for electrical equipment as described in Example 1. The method includes a polymerization reaction, using an esterification-condensation two-step method, with alcohol monomers and carboxylic acid monomers as raw materials, and adjusting the monomer ratio and reaction conditions through a prepolymerization stage and a condensation stage to prepare a modified polyester resin with a specific structure; By adjusting the ratio of aromatic monomers to aliphatic monomers, the resin crystallinity is controlled to be 30%-40%.

[0039] In the prepolymerization stage, terephthalic acid accounting for 60%-80% of the carboxylic acid monomers is compounded with 10%-20% itaconic acid and 5%-15% maleic anhydride; among the alcohol monomers, ethylene glycol accounts for 50%-70%, and is combined with 20%-30% aromatic alcohol and 5%-15% cyclohexanol; placed in a reaction kettle, 0.1%-0.3% catalyst is added, and the temperature is raised to 220-240°C under nitrogen protection, and the reaction is carried out at normal pressure for 3-4 hours until the acid value drops to 50-80 mgKOH / g to produce a prepolymer product.

[0040] In the polycondensation stage, the prepolymer product is heated to 260-280°C, gradually depressurized to 100-500 Pa, 0.05%-0.1% antioxidant is added, and the reaction is carried out for 2-3 hours. The molecular weight is adjusted to be between 20,000 and 30,000 by controlling the reaction time and vacuum degree, and the temperature is lowered to below 200°C, and the modified polyester resin is discharged.

[0041] The present invention combines the precise compounding of monomers and the coordinated regulation of process parameters to achieve a breakthrough optimization of the molecular structure, crystallization behavior and comprehensive performance of high-performance resins for electrical equipment. Its creativity is mainly reflected in the following aspects: 1. Precise regulation of monomer combination and crystallinity Through the compounding of terephthalic acid (60%-80%) with itaconic acid (10%-20%) and maleic anhydride (5%-15%), a molecular chain structure with both rigidity and flexibility is constructed. The α,β-unsaturated double bond of itaconic acid can introduce crosslinking sites, while the cyclic structure of maleic anhydride enhances the thermal stability. The combination of ethylene glycol (50%-70%) with aromatic alcohol (20%-30%) and cyclohexanol (5%-15%) among the alcohol monomers precisely controls the crystallinity in the golden range of 30%-40% through the rigidity of the aromatic ring (such as phenyl, naphthyl) and the steric hindrance effect of the alicyclic structure, avoiding both the brittleness caused by high crystallinity and the insufficient heat resistance caused by low crystallinity.

[0042] 2. Optimization of the reaction kinetics in stages Prepolymerization stage: React at 220-240°C under normal pressure for 3-4 hours, and monitor the esterification degree in real time through the acid value (50-80 mgKOH / g) to ensure the uniformity of the prepolymer molecular weight distribution (PDI≤4.0), laying a foundation for subsequent polycondensation. Nitrogen protection effectively inhibits side oxidation reactions.

[0043] Polycondensation stage: Heat up to 260 - 280 °C and gradually reduce the pressure to 100 - 500 Pa. Adjust the molecular weight to 20,000 - 30,000 through the coupling control of vacuum degree - time to avoid branching or gelation caused by excessive polycondensation. The timely addition of antioxidants (0.05% - 0.1%) blocks the high - temperature degradation chain reaction.

[0044] 3. Performance Synergy Enhancement Mechanism Electrical insulation: The conjugated structure of aromatic monomers (such as naphthyl) can capture free electrons, increasing the volume resistivity to 10 15 -10 16 Ω·cm. Meanwhile, the narrow molecular weight distribution (PDI ≤ 4.0) reduces the risk of local breakdown caused by weak - bond defects.

[0045] Weather resistance: The synergistic effect of antioxidants (hindered phenols / phosphites) and ultraviolet absorbers (benzotriazoles) enables the resin to have a yellowing index ΔYI < 2.0 and a tensile strength retention rate > 90% after 1000 hours of UV irradiation.

[0046] 4. Process Economy and Environmental Protection Compared with the complex processes (such as nano - doping or flame retardant addition) that traditional epoxy resins need for multi - step modification, this solution realizes performance integration through in - situ functionalization of monomers, reducing energy consumption by more than 20% and releasing no harmful substances such as halogens, meeting the trend of green manufacturing.

[0047] In summary, through the full - chain innovation of molecular design - process regulation - performance optimization, the present invention provides a resin solution for high - voltage electrical equipment with high insulation, heat resistance, weather resistance, and processability.

[0048] Example 3 Based on the same inventive concept, this example also provides a high - performance resin film for electrical equipment, and the film is prepared from a high - performance resin for electrical equipment as described in Example 1.

[0049] Example 4 Based on the same inventive concept, this example also provides a preparation method for a high - performance resin film for electrical equipment, which is used to prepare a high - performance resin film for electrical equipment as described in Example 3. The method includes the following steps: Sheet Extrusion: A co-rotating twin-screw extruder is selected and equipped with a high-precision temperature control system. The temperature of the feeding section is set between 260 - 280°C to promote the initial melting of the resin; the temperature of each barrel zone is precisely controlled within the range of 280 - 288°C to ensure sufficient melting and plasticization of the resin; the die head temperature is stabilized at 280 - 285°C. A 1300 - 1500 mesh filter screen is installed at the die head to effectively filter impurities, and an exhaust device is set to eliminate air bubbles in the melt. An electrostatic adsorption voltage of 10 - 20 kV is applied at the first traction roller at the die head outlet to enhance the adhesion effect between the extruded sheet and the casting roller, thereby producing a high-quality sheet with a thickness of 50 μm and a width of about 100 mm.

[0050] Longitudinal Stretching: The sheet is placed on a horizontal unidirectional stretching machine for longitudinal stretching. Before stretching, the sheet is preheated using a preheating roller, and the temperature of the preheating roller is controlled at 60 - 80°C; the temperature of the stretching roller is set at 80 - 100°C. According to the target thickness and performance requirements of the film, the stretching speed is reasonably adjusted, and the stretching ratio is controlled between 1.8 - 2.5. With the help of large-diameter stretching rollers and a long preheating distance, it is ensured that the film is uniformly heated and stretched, reducing internal stress concentration. After stretching, annealing treatment is carried out through an annealing roller, and the temperature of the annealing roller is maintained at 68 - 90°C to effectively eliminate internal stress in the film and stabilize the film structure.

[0051] Transverse Stretching: The longitudinally stretched film is transferred to a four-corner stretching machine for transverse stretching. The stretching temperature is controlled at 100 - 120°C, the holding time is set at 120 - 180 s, the stretching speed is 100 - 150 mm / s, and the stretching multiple is controlled between 3.0 - 3.5. Through transverse stretching, the molecular chains of the film are arranged orderly both horizontally and longitudinally, forming a stable biaxially stretched structure, significantly improving the mechanical properties, heat resistance, and dimensional stability of the film.

[0052] Post-treatment: The biaxially stretched film is subjected to heat setting treatment, with the temperature controlled at 260 - 270°C and the time being 3 - 5 min, to further improve the crystallization structure of the film and reduce the thermal shrinkage rate of the film. Subsequently, it is cooled and wound up to obtain the final high-performance resin film.

[0053] In the sheet extrusion step, the resin and its derivatives are premixed with additives before feeding, and the premixing time is 10 - 30 min to ensure uniform dispersion of the additives in the resin system.

[0054] Through precise process design and coordinated regulation of multiple parameters, the present invention has achieved a breakthrough optimization in the molecular orientation, crystallization structure, and comprehensive performance of the high-performance resin film for electrical equipment. Its creativity is mainly reflected in the following aspects: 1. High-precision Melting Extrusion and Impurity Control The present invention uses a co-rotating twin-screw extruder with zone temperature control at 280 - 288 °C to ensure sufficient plasticization of the resin (such as polyethylene terephthalate) and avoid thermal degradation. A 1300 - 1500 mesh filter at the die head can intercept impurities with a particle size > 5 μm (such as ash or unmelted particles), and combined with an exhaust device to eliminate air bubbles, reducing the defect rate of the cast sheet to < 0.1%. The 10 - 20 kV electrostatic adsorption technology enhances the adhesion between the melt and the casting roll through Coulomb force, solving the thickness fluctuation problem caused by the traditional air knife method (±1 μm → ±0.3 μm), and finally obtaining a cast sheet with a thickness of 50 μm and a width of 100 mm with high uniformity.

[0055] 2. Staged stretching and optimization of molecular chain orientation Longitudinal stretching: The gradient temperature rise design of the preheating roll (60 - 80 °C) and the stretching roll (80 - 100 °C), combined with a stretching ratio of 1.8 - 2.5, enables the molecular chains to be arranged orderly in the longitudinal direction, and the tensile strength is increased to more than 200 MPa (3 times that of the unstretched film). The large-diameter stretching roll (such as Φ500 mm) and the long preheating distance (> 1 m) ensure uniform heat conduction, and the internal stress concentration coefficient (σmax / σavg ) is reduced from 2.5 to 1.3.

[0056] Transverse stretching: The four-corner stretching machine realizes a stretching ratio of 3.0 - 3.5 at 100 - 120 °C, and the molecular chains are oriented bidirectionally to form a network structure, so that the transverse tensile modulus of the film reaches 4.5 GPa, and the thermal shrinkage rate (150 °C / 30 min) < 1.5%. Synchronously control the holding time (120 - 180 s) and speed (100 - 150 mm / s) to avoid brittleness caused by excessive crystallization.

[0057] 3. Strengthening of crystal structure and performance stability Heat setting treatment at 260 - 270 °C for 3 - 5 minutes promotes the transformation of metastable crystals, and the crystallinity is increased from 25% to 30% - 40%, and the dielectric strength is increased to more than 550 kV / mm (ASTM D149). The annealing process (68 - 90 °C) eliminates residual stress through chain segment relaxation, so that the dimensional change rate of the film in the range of - 60 °C to 180 °C < 0.05%.

[0058] 4. Auxiliary agent dispersion and function integration Pre-mixing for 10 - 30 minutes ensures the uniform dispersion of antioxidants (such as hindered phenol 1010) and ultraviolet absorbers (such as benzotriazole UV - 326) (dispersion phase size < 100 nm), and synergistically improves heat aging resistance (strength retention rate > 90% at 150 °C / 1000 h) and ultraviolet resistance (QUV test ΔYI < 2).

[0059] 5. Process economy and industrial adaptability Compared with the solution casting method of traditional PI films (which requires solvent recovery), this solution adopts a solvent-free melt extrusion - biaxial stretching process, reducing energy consumption by 30%. Moreover, the narrow-width design with a width of 100 mm is suitable for the small-batch customization requirements of special electrical equipment (such as the insulation layer of high-frequency transformers), filling the gap in domestic high-end films in the precision field.

[0060] In summary, through the full-chain innovation of molecular orientation - crystallization regulation - defect suppression, the present invention provides a film solution for high-voltage electrical equipment that combines high insulation, heat resistance, dimensional stability, and processability, breaking through the application bottleneck of the biaxial stretching process in the field of narrow-width high-performance films.

[0061] Example 5 Based on the same inventive concept, this example also provides a method for preparing a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described in Example 3. The method includes the following steps: Resin synthesis: Among the carboxylic acid monomers, terephthalic acid accounts for 70%, itaconic acid accounts for 15%, and maleic anhydride accounts for 15%; among the alcohol monomers, ethylene glycol accounts for 60%, aromatic alcohol (phenyl diol, with the chemical structural formula C6H5-C2H4(OH)2) accounts for 25%, and cyclohexanol accounts for 15%. The catalyst tetrabutyl titanate accounts for 0.2% of the total mass, and the antioxidant triphenyl phosphite accounts for 0.08%. Under nitrogen protection, the above monomers are put into a reaction kettle, heated to 230 °C, and reacted at normal pressure for 3.5 hours until the acid value drops to 65 mgKOH / g to form oligomers; then it enters the polycondensation stage. The prepolymer is heated to 270 °C, gradually depressurized to 300 Pa, and reacted for 2.5 hours. The weight-average molecular weight reaches 25,000, the crystallinity is 35%, the PDI is 3.5, and it is cooled below 200 °C and discharged to obtain a modified polyester resin.

[0062] Sheet casting and extrusion: The new polyester resin and its derivatives are mixed evenly with 0.5% hindered phenol antioxidant and 0.8% benzotriazole ultraviolet absorber for 10 minutes. Then they are put into a co-rotating twin-screw extruder. The feeding section temperature is set at 260 °C to preliminarily melt the resin; the temperatures of the 1st - 7th zones of the barrel are 280 °C, 282 °C, 284 °C, 285 °C, 283 °C, 286 °C, and 280 °C in sequence to fully melt and plasticize the resin; the die head temperature is controlled at 280 °C. A 1300-mesh filter screen is installed at the die head to filter impurities, and at the same time, an exhaust device is set to eliminate bubbles. A 10 kV electrostatic adsorption voltage is applied at the first traction roll at the die head outlet to ensure good adhesion between the cast sheet and the casting roll, and a cast sheet with a thickness of 50 μm and a width of 100 mm is extruded.

[0063] Longitudinal stretching: Put the cast film into a horizontal unidirectional stretching machine. Set the temperature of the preheating roller at 60°C to evenly heat the cast film; the temperature of the stretching roller is 80°C, and the stretching ratio is adjusted to 1.8 to preliminarily orient and arrange the molecular chains of the film. After stretching, anneal the film on an annealing roller at 68°C to eliminate internal stress and stabilize the film structure.

[0064] Transverse stretching: Place the longitudinally stretched film in a transverse stretching machine. Control the stretching temperature at 100°C and the holding time at 120 s to fully stretch the film at this temperature; the stretching speed is 100 mm / s and the stretching multiple is 3.0 to make the molecular chains of the film achieve an orderly arrangement both horizontally and vertically, forming a stable biaxially stretched structure.

[0065] Post-treatment: Heat-set the film at 260°C for 3 min to further improve the crystalline structure and reduce the thermal shrinkage rate. After cooling, wind up the film to obtain a high-performance resin film. After testing, the water absorption rate of this film is 0.48%, the DC breakdown field strength is 552 kV / mm, the AC breakdown field strength is 231 kV / mm, the tensile strength is 181 MPa, the elongation at break is 42%, and there is no obvious change after baking at 200°C for half an hour.

[0066] Example 6 Based on the same inventive concept, this example also provides a preparation method of a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described in Example 3. The method includes the following steps: Resin synthesis: Among the carboxylic acid monomers, terephthalic acid accounts for 60%, itaconic acid accounts for 20%, and maleic anhydride accounts for 5%; among the alcohol monomers, ethylene glycol accounts for 50%, aromatic alcohol (naphthalene diol, chemical structural formula C 10 H7-C2H4-(OH)2) accounts for 30%, and cyclohexanol accounts for 5%. Tetrabutyl titanate as the catalyst accounts for 0.1% of the total mass, and triphenyl phosphite as the antioxidant accounts for 0.05%. Under nitrogen protection, put the monomers into the reaction kettle, heat up to 220°C, and react at normal pressure for 4 hours until the acid value drops to 50 mgKOH / g; in the polycondensation stage, heat up to 260°C, gradually reduce the pressure to 500 Pa, and react for 3 hours. The weight-average molecular weight is 20,000, the crystallinity is 30%, and the PDI is 4.0. Cool down and discharge to obtain the modified polyester resin.

[0067] Sheet Extrusion: The novel polyester resin and its derivatives are premixed with 0.8% phosphite antioxidant and 1.2% benzophenone ultraviolet absorber for 30 minutes. After thorough mixing, they are added to a co-rotating twin-screw extruder. The temperature of the feeding section is raised to 270°C; the temperatures of each barrel zone are set at 282°C, 285°C, 287°C, 286.5°C, 285.2°C, 288°C, and 283°C respectively; the die head temperature is 282°C. A 1400-mesh filter screen is used, and a 15-kV electrostatic adsorption voltage is applied at the first pulling roller at the die head outlet to extrude a sheet with a thickness of 50 μm and a width of 100 mm.

[0068] Longitudinal Stretching: The sheet is placed into a horizontal unidirectional stretching machine. The temperature of the preheating roller is 70°C, the temperature of the stretching roller is 90°C, and the stretching ratio is 2.0. After stretching, it is annealed on an annealing roller at 75°C to relieve stress.

[0069] Transverse Stretching: The longitudinally stretched film is placed into a transverse stretching machine. The stretching temperature is 110°C, the holding time is 150 s, the stretching speed is 120 mm / s, and the stretching multiple is 3.2.

[0070] Post-treatment: The heat setting temperature is 265°C and the time is 4 minutes. The test results show that the water absorption rate of the film is 0.45%, the DC breakdown field strength is 558 kV / mm, the AC breakdown field strength is 234 kV / mm, the tensile strength is 184 MPa, the elongation at break is 48%, and there is no obvious change after baking at 200°C for half an hour.

[0071] Example 7 Based on the same inventive concept, this example also provides a method for preparing a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described in Example 3. The method includes the following steps: Resin Synthesis: Among the carboxylic acid monomers, terephthalic acid accounts for 80%, itaconic acid accounts for 10%, and maleic anhydride accounts for 10%; among the alcohol monomers, ethylene glycol accounts for 70%, aromatic alcohol (phenanthrene glycol, with the chemical structural formula C 14 H9-C2H4(OH)2) accounts for 20%, and cyclohexanol accounts for 10%. The catalyst tetrabutyl titanate accounts for 0.3% of the total mass, and the antioxidant triphenyl phosphite accounts for 0.1%. Under nitrogen protection, the monomers are put into a reaction kettle, heated to 240°C, and reacted at normal pressure for 3 hours until the acid value drops to 80 mgKOH / g; in the polycondensation stage, the temperature is raised to 280°C, gradually reduced to 100 Pa, and reacted for 2 hours. The weight average molecular weight is 30,000, the crystallinity is 40%, the PDI is 3.2, and after cooling, a modified polyester resin is obtained.

[0072] Casting sheet extrusion: Add 1.2% of hindered phenol antioxidant and phosphite antioxidant compound (mass ratio 1:1) and 1.5% of benzotriazole and benzophenone UV absorber compound (mass ratio 2:1) to the new polyester resin and its derivatives, pre-mix for 15 minutes and put into the co-rotating twin-screw extruder. The feeding section temperature is 275℃, the temperature of each temperature zone of the barrel is 284℃, 286℃, 288℃, 287℃, 286℃, 288.6℃, 285℃, and the die temperature is 284℃. Install a 1500 mesh filter, apply 18kV electrostatic adsorption voltage, and prepare casting sheets.

[0073] Longitudinal stretching: preheating roller temperature 75°C, stretching roller temperature 95°C, stretching ratio 2.2, annealing roller temperature 85°C.

[0074] Transverse stretching: stretching temperature 115°C, holding time 160s, stretching speed 130mm / s, stretching multiple 3.3.

[0075] Post-treatment: heat setting temperature 268℃, time 4.5min. After testing, the film water absorption rate is 0.42%, DC breakdown field strength is 562kV / mm, AC breakdown field strength is 236kV / mm, tensile strength is 187MPa, elongation at break is 52%, and there is no obvious change after baking at 200℃ for half an hour.

[0076] Example 8 Based on the same inventive concept, this embodiment also provides a method for preparing a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described in Example 3, and the method comprises the following steps: Resin synthesis: Among carboxylic acid monomers, terephthalic acid accounts for 65%, itaconic acid accounts for 18%, and maleic anhydride accounts for 12%; among alcohol monomers, ethylene glycol accounts for 55%, aromatic alcohol (phenyl glycol) accounts for 28%, and cyclohexanol accounts for 11%. The catalyst tetrabutyl titanate accounts for 0.15% of the total mass, and the antioxidant triphenyl phosphite accounts for 0.07%. Reaction process: Under nitrogen protection, the monomer is put into the reactor and the temperature is raised to 225°C, and the reaction is carried out at normal pressure for 3.8 hours, and the acid value drops to 60mgKOH / g; in the polycondensation stage, the temperature is raised to 265°C, and the pressure is gradually reduced to 400Pa, and the reaction is carried out for 2.8 hours. The weight average molecular weight is 23,000, the crystallinity is 33%, and the PDI is 3.6. The material is cooled and discharged to obtain a modified polyester resin.

[0077] Casting sheet extrusion: The new polyester resin and its derivatives were fully premixed with 1.5% phosphite antioxidant and 2% benzotriazole ultraviolet absorber for 20 minutes, and then added to the co-rotating twin-screw extruder. The feeding section temperature was 280°C, the temperature of each temperature zone of the barrel was fine-tuned, and the die head temperature was 285°C. A 1500 mesh filter was used and a 20kV electrostatic adsorption voltage was applied to prepare the casting sheet.

[0078] Longitudinal stretching: The temperature of the preheating roller is 80°C, the temperature of the stretching roller is 100°C, the stretching ratio is 2.5, and the temperature of the annealing roller is 90°C.

[0079] Transverse stretching: The stretching temperature is 120°C, the heat preservation time is 180 s, the stretching speed is 150 mm / s, and the stretching multiple is 3.5.

[0080] Post-treatment: The heat setting temperature is 270°C and the time is 5 min. The test data shows that the water absorption rate of the film is 0.40%, the DC breakdown field strength is 565 kV / mm, the AC breakdown field strength is 238 kV / mm, the tensile strength is 189 MPa, the elongation at break is 55%, and there is no obvious change after baking at 200°C for half an hour.

[0081] Example 9 Based on the same inventive concept, this example also provides a preparation method of a high-performance resin film for electrical equipment, which is used to prepare a high-performance resin film for electrical equipment as described in Example 3. The method includes the following steps: Resin synthesis: Among the carboxylic acid monomers, terephthalic acid accounts for 75%, itaconic acid accounts for 12%, and maleic anhydride accounts for 13%; among the alcohol monomers, ethylene glycol accounts for 65%, aromatic alcohol (naphthalene diol) accounts for 22%, and cyclohexanol accounts for 13%. The catalyst tetrabutyl titanate accounts for 0.25% of the total mass, and the antioxidant triphenyl phosphite accounts for 0.09%. Under nitrogen protection, the monomers are put into the reaction kettle, heated to 235°C, and reacted at atmospheric pressure for 3.2 hours until the acid value drops to 70 mgKOH / g; in the polycondensation stage, the temperature is raised to 275°C, gradually reduced to 200 Pa, and reacted for 2.2 hours. The weight-average molecular weight is 27000, the crystallinity is 37%, the PDI is 3.4, and the modified polyester resin is obtained after cooling.

[0082] Sheet casting extrusion: Add 0.6% of hindered phenol antioxidant and 1% of benzophenone ultraviolet absorber to the new polyester resin and its derivatives, fully premix for 25 min, and then put it into a co-rotating twin-screw extruder. The temperature of the feeding section is 265°C, the temperature of each barrel zone is adjusted between 280 - 288°C, and the die head temperature is 281°C. Install a 1400-mesh filter screen, apply a 12 kV electrostatic adsorption voltage, and prepare a sheet.

[0083] Longitudinal stretching: The temperature of the preheating roller is 65°C, the temperature of the stretching roller is 85°C, the stretching ratio is 1.9, and the temperature of the annealing roller is 72°C.

[0084] Transverse stretching: The stretching temperature is 105°C, the heat preservation time is 130 s, the stretching speed is 110 mm / s, and the stretching multiple is 3.1.

[0085] Post-treatment: Heat setting temperature is 262°C and time is 3.5 min. After testing, the water absorption rate of the film is 0.46%, the DC breakdown field strength is 555 kV / mm, the AC breakdown field strength is 233 kV / mm, the tensile strength is 183 MPa, the elongation at break is 45%, and there is no obvious change after baking at 200°C for half an hour.

[0086] Figure 1 This is a comparison photo of the appearance of the film prepared in the embodiment of the present invention and the traditional insulating film after baking at 200°C for half an hour. Figure 2 This is a comparison of the performance of the film prepared in the embodiment of the present invention and the performance of the traditional insulating film. The films prepared in the five embodiments of the present invention have excellent performance in all aspects and are significantly better than the film products prepared by the prior art.

[0087] The maximum water absorption rate of the film prepared in the embodiment of the present invention is 0.46% and the minimum is 0.40%. Compared with the existing polyimide film, it is reduced by at least (1.14 - 0.46) / 1.14 ≈ 59.65%, and compared with the traditional PET film, it is reduced by at least (0.87 - 0.46) / 0.87 ≈ 47.13%. A 59.65% reduction in water absorption rate directly reduces the impact of moisture on the dielectric properties of the material. Moisture will ionize to generate conductive ions, resulting in a decrease in volume resistivity (the resistivity of the traditional PI film drops from 1×10 16 Ω·cm to 1×10 14 Ω·cm after water absorption). The low water absorption rate (<0.5%) of the present invention can keep the resistivity stable above 1×10 18 Ω·cm, which is especially suitable for high-voltage equipment (such as transformers, cables) and high-humidity environments. The water absorption expansion coefficient is reduced by 47% - 60%, suppressing the deformation problem in microelectronic packaging. For example, the linear expansion rate of the traditional PI film can reach 0.3% after water absorption, increasing the risk of delamination of the flexible printed circuit board (FPC) by 30%, while the expansion rate of the modified film is <0.1%, which is suitable for high-density integrated circuit packaging. Moisture will increase the dielectric constant (ε) and loss tangent (tanδ). The dielectric constant of the film of the present invention is stable at 2.8 at 1 GHz (the traditional PI film rises from 3.2 to 3.8 after water absorption), and the signal transmission loss is reduced by 15%, meeting the requirements of 5G base stations and millimeter-wave communications. The life L of the insulating material is exponentially related to the humidity stress (L∝e-k·RH, where k is the attenuation coefficient). A 59.6% reduction in water absorption rate can extend the life of the motor insulation system from 10 years to more than 15 years, reducing the replacement cost (taking a wind turbine as an example, the single maintenance cost can save hundreds of thousands). The low-water-absorption film can replace imported products (such as DuPont Kapton HN, with a unit price of 200 / square meter), and the cost is greatly reduced after localization. The present invention solves the bottleneck of film hygroscopicity through molecular design and process innovation, provides key material support for high-end electrical equipment, and at the same time brings significant economic benefits.

[0088] In the embodiments of the present invention, the DC breakdown field strength of the prepared thin film is up to 565 kV / mm and the lowest is 552 kV / mm.

[0089] In the embodiments of the present invention, the AC breakdown field strength of the prepared thin film is up to 238 kV / mm and the lowest is 231 kV / mm; compared with the existing polyimide thin film, it is increased by at least (231 - 212) / 212 ≈ 8.96%, and compared with the traditional PET thin film, it is increased by at least (231 - 217) / 217 ≈ 6.45%. A higher breakdown field strength allows the thin film to work under higher voltages or more severe electric field environments, such as high-voltage cables, transformer insulation, or power electronics device packaging. The lifespan (L) of an insulating material is exponentially inversely proportional to the applied electric field strength (E) (L ∝ E -n, where n is the material coefficient). An 8.96% increase in the AC breakdown field strength means that at the same operating voltage, the aging rate of the material decreases and the lifespan is significantly extended. The insulation lifespan of a transformer can be extended from 15 years to over 20 years, resulting in significant economic benefits. The extended insulation lifespan directly reduces the frequency of equipment replacement and downtime maintenance. Taking a power transformer as an example, insulation failures account for 30% of its total failures, and the increased breakdown field strength can significantly reduce such failure rates. The increase in the AC breakdown field strength provides key technical support for the high-efficiency, miniaturization, and long-term operation of electrical equipment by enhancing insulation performance and lifespan, and can achieve significant economic benefits.

[0090] In the embodiments of the present invention, the tensile strength of the prepared thin film is up to 189 MPa and the lowest is 181 MPa; compared with the existing polyimide thin film, it is increased by at least (181 - 176) / 176 ≈ 2.84%, and compared with the traditional PET thin film, it is increased by at least (181 - 168) / 168 ≈ 7.74%. The tensile strength is increased from 176 MPa to 181 - 189 MPa (an increase of 2.84% - 7.74%), significantly enhancing the anti-fracture ability of the thin film under stress. For example, in the application of flexible printed circuit boards (FPCs), a higher tensile strength can reduce microcracks caused by bending or assembly stress, increasing the fatigue lifespan of the FPC by approximately 20%. According to the Arrhenius model, the lifespan L of an insulating material is positively correlated with its mechanical strength σ (L ∝ σn, where n is the material coefficient). A 7.74% increase in tensile strength can extend the lifespan of the transformer insulation system from 15 years to 18 years, significantly reducing the single-unit maintenance cost. The increased strength allows the thickness of the thin film to be reduced by 10% - 15% (e.g., from 50 μm to 45 μm), saving approximately 8% in material costs in the field of cable insulation. Calculated based on a thin film production line with an annual output of 1000 tons, the annual cost savings reach $2.4 million.

[0091] In the embodiments of the present invention, the elongation at break of the prepared thin film is up to 55% and the lowest is 42%.

[0092] The thin films prepared in the embodiments of the present invention can all withstand baking at 200 °C for half an hour without obvious changes.

[0093] Example 10 Based on the same inventive concept, the present invention also provides a power device that uses the high-performance resin film described in Example 3 as an insulating component.

[0094] The above are only examples of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included within the scope of the claims of the present invention.

Claims

1. A high-performance resin for electrical equipment, characterized in that, The resin is formed by the polymerization reaction of a dibasic acid and a diol; The dibasic acid includes terephthalic acid, itaconic acid, maleic anhydride, succinic acid, glutaric acid, adipic acid; The diol includes ethylene glycol, 1,4-butanediol, pentanediol, cyclohexanol, 1,6-hexanediol, aromatic diol; The dibasic carboxylic acid used contains an aromatic ring and an unsaturated double bond structure; The diol used contains a polycyclic ring or a long-chain structure.

2. The high-performance resin for electrical equipment according to claim 1, wherein The polymerization reaction is condensation polymerization.

3. The high-performance resin for electrical equipment according to claim 1, characterized in that, The antioxidant of the resin includes one or a combination of hindered phenol antioxidants and phosphite antioxidants.

4. The high-performance resin for electrical equipment according to claim 1, characterized in that, The ultraviolet absorber of the resin includes one or a combination of benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers.

5. The high-performance resin for electrical equipment according to claim 3, characterized in that, The addition amount of the antioxidant accounts for 0.05% - 2% of the total mass of the resin and its derivatives.

6. The high-performance resin for electrical equipment according to claim 4, wherein, The addition amount of the ultraviolet absorber accounts for 0.05% - 3% of the total mass of the resin and its derivatives.

7. The high-performance resin for electrical equipment according to claim 1, characterized in that, The aromatic diol has a general chemical structure formula of A r -C n H 2n (OH)2, where Ar represents a benzene ring or other aromatic hydrocarbon groups, specifically including phenyl (C6H5-), naphthyl (C 10 H7-), phenanthryl (C 14 H9-).

8. The high-performance resin for electrical equipment according to claim 1, wherein The molecular weight distribution of the resin is PDI ≤ 4.

0.

9. A preparation method of a high-performance resin for electrical equipment, characterized in that, For preparing a high-performance resin for electrical equipment as described in any one of claims 1-8, the method includes a polymerization reaction. Using alcohol monomers and carboxylic acid monomers as raw materials, in the prepolymerization stage and the polycondensation stage, by adjusting the ratio of aromatic monomers to aliphatic monomers and the reaction conditions to establish a rigid molecular chain containing cyclic monomers, low-reactivity ester bonds, and a high-crystallinity structure, controlling the resin crystallinity at 30% - 40% to obtain the high-performance resin for electrical equipment.

10. The preparation method of a high-performance resin for electrical equipment according to claim 9, characterized in that, The polymerization reaction adopts a two-step method of esterification-polycondensation.

11. The preparation method of a high-performance resin for electrical equipment according to claim 9, characterized in that, In the prepolymerization stage, use terephthalic acid accounting for 60% - 80% of the carboxylic acid monomers, compounded with 10% - 20% itaconic acid and 5% - 15% maleic anhydride; in the alcohol monomers, ethylene glycol accounts for 50% - 70%, combined with 20% - 30% aromatic alcohol and 5% - 15% cyclohexanol; place them in a reaction kettle, add 0.1% - 0.3% catalyst, heat up to 220 - 240°C under nitrogen protection, and react at atmospheric pressure for 3 - 4 hours until the acid value drops to 50 - 80 mgKOH / g to produce a prepolymer.

12. The preparation method of a high-performance resin for electrical equipment according to claim 11, characterized in that, In the polycondensation stage, heat the prepolymer to 260 - 280°C, gradually reduce the pressure to 100 - 500 Pa, add 0.05% - 0.1% antioxidant, react for 2 - 3 hours, adjust the molecular weight between 20,000 - 30,000 by controlling the reaction time and vacuum degree, cool down to below 200°C, and discharge to obtain a modified polyester resin.

13. A high-performance resin film for electrical equipment, characterized in that, The film is prepared using a high-performance resin for electrical equipment as described in any one of claims 1-8.

14. A preparation method of a high-performance resin film for electrical equipment, characterized in that, For preparing a high-performance resin film for electrical equipment as described in claim 13, the method includes the following steps: Sheet casting extrusion: Use a co-rotating twin-screw extruder, control the feeding section temperature at 260 - 280°C, control the temperature of each barrel zone at 280 - 288°C, and control the die head temperature at 280 - 285°C; add a 1300 - 1500 mesh filter screen at the die head and set an exhaust device; apply a 10 - 20 kV electrostatic adsorption voltage at the first traction roll at the die head outlet to prepare a sheet; Longitudinal stretching: Stretch the cast sheet on a horizontal unidirectional stretching machine, control the temperature of the preheating roller at 60 - 80°C, set the temperature of the stretching roller at 80 - 100°C, and control the stretching ratio at 1.8 - 2.5; after stretching, conduct annealing treatment through an annealing roller with a temperature controlled at 68 - 90°C to obtain a longitudinally stretched film; Transverse stretching: Stretch the longitudinally stretched film on a four - corner stretching machine, control the stretching temperature at 100 - 120°C, the heat preservation time at 120 - 180 s, the stretching speed at 100 - 150 mm / s, and control the stretching multiple at 3.0 - 3.5 to obtain a biaxially stretched film; Post - treatment: Conduct heat setting treatment on the biaxially stretched film at 260 - 270°C for 3 - 5 min, then cool and wind up to obtain the high - performance resin film for electrical equipment.

15. The preparation method of a high-performance resin film for electrical equipment according to claim 14, characterized in that, In the cast sheet extrusion step, premix the resin and its derivatives with additives before feeding, and the premixing time is 10 - 30 min.

16. A power device, characterized in that Use the high - performance resin film as described in claim 13 as an insulating component.

Images