Thin film sintering line and preparation method thereof

Abstract

The invention belongs to the technical field of sintering lines, and particularly relates to a thin film sintering line and a preparation method thereof. The preparation method comprises the following steps: reacting 4, 4-diaminodiphenyl ether, norbornene dianhydride and pyromellitic dianhydride to prepare a polyamic acid precursor, adding a nano insulating aid prepared from a silicon dioxide coated nano hexagonal boron nitride in-situ growth copper metal organic framework, compounding with a polyimide film, and carrying out imidization to prepare a modified polyimide film. The norbornene dianhydride reduces the internal stress generated in the formation process of the modified polyimide film, and the nano insulation auxiliary agent can present the stacking tendency in the substrate direction in the film drying and curing process, so that the corona resistance and the mechanical property of the modified polyimide film are improved. According to the invention, the conductor is wrapped by the modified polyimide film, then the fluorine rubber outer sheath is coated, and finally the film sintered wire prepared by sintering has excellent corona resistance and mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of sintering wires, and in particular relates to a thin film sintering wire and a preparation method thereof. Background Art

[0002] Sintered wire is a composite film formed by coating a synthetic resin film with an adhesive, wrapping it around a conductor, and sintering it to bond the films together and to form a single piece. Sintered film wire is pinhole-free, has a smooth, uniform surface, and offers enhanced mechanical strength and electrical performance, capable of withstanding high shock loads. It is therefore commonly used in the manufacture of electrical equipment such as transformers. Polyimide film is one of the most heat-resistant organic insulating materials, but it is also susceptible to corona aging under variable frequency conditions. Simultaneously improving the corona resistance and mechanical properties of polyimide film has long been a key research area for polyimide corona-resistant films.

[0003] Chinese invention patent publication number CN116543984B discloses a winding wire and its production process, comprising: a copper conductor coated with a thin film layer; the thin film layer is made of polyimide-doped nanosilica; and an insulating layer coated on the outside of the thin film layer. The incorporation of nanosilica into the polyimide improves the mechanical properties of the thin film layer, effectively reducing its thickness and thereby increasing the heat dissipation performance of the copper conductor. The thin film layer also improves heat resistance, further reducing the risk of burning out the winding wire. In the production process, a shaping mechanism performs initial shaping using a non-rigid contact method with the insulating layer to prevent adhesion to the contact surface. After initial shaping, when the fluidity of the insulating layer is low, its thickness is corrected to achieve a more uniform thickness, resulting in a more uniform diameter of the winding wire. This results in a tighter coil, improved heat conduction, and effectively enhanced heat dissipation uniformity. However, the prior art lacks a technical problem in improving the structure and composition of the polyimide film filler to enhance the corona resistance and mechanical properties of the thin film sintered wire. Summary of the Invention

[0004] The object of the present invention is to provide a thin film sintering wire and a preparation method thereof, so as to solve the technical problem in the prior art that the structure and components of the polyimide film filler have not been improved to improve the insulation and mechanical properties of the thin film sintering wire.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A thin film sintered wire comprises, from the inside to the outside, a conductor, a modified polyimide film layer and an outer sheath; The conductor is a copper wire; The modified polyimide film layer is prepared by coating a modified polyamic acid precursor solution on a polyimide film, drawing the modified polyimide film, and heating the modified polyimide film to obtain an imidization product, and then wrapping the modified polyimide film around the conductor. The thickness of the modified polyimide film is 0.03-0.04 mm, and the modified polyimide film is wrapped at a wrapping angle of 40-60 degrees, with a wrapping overlap ratio of 45-65%. The modified polyamic acid precursor solution is prepared from the following components in parts by mass: 3-5 parts of 4,4-diaminodiphenyl ether, 0.5-0.8 parts of a nano-insulation additive, 0.5-1.1 parts of nadic anhydride, 3-5 parts of pyromellitic anhydride, 40-50 parts of N,N-dimethylacetamide solvent, and 0.5-2 parts of triphenyl phosphite release agent; The molar ratio of 4,4-diaminodiphenyl ether to pyromellitic anhydride is 1:(0.8-1.1), the nano-insulating agent is prepared by coating nano-hexagonal boron nitride with silicon dioxide, grafting 3-aminopropyltriethoxysilane to obtain modified nano-hexagonal boron nitride, and then adding copper nitrate and pyromellitic acid to in-situ grow a copper metal organic framework, and the amounts of modified nano-hexagonal boron nitride, copper nitrate and pyromellitic acid are 1-2 parts, 2-3 parts and 1-2 parts respectively by weight; The outer sheath has a thickness of 2-4 mm and is made of the following components by weight: 50-60 parts of fluororubber raw rubber, 10-20 parts of polytetrafluoroethylene, 0.5-1.5 parts of antioxidant 224, 0.5-2 parts of sulfur, 2-4 parts of stearic acid, 0.5-1 part of zinc oxide, 0.5-2 parts of vulcanization accelerator MBT, and 10-15 parts of filler; The filler is prepared by mixing silicon micropowder, carbon black and magnesium silicate fiber in a mass ratio of 1: (4-5): (2-3).

[0006] Preferably, the method for preparing the modified polyimide film comprises the following steps: S11, adding nano hexagonal boron nitride to anhydrous ethanol, adding an ethanol solution of ethyl silicate, adding ammonia water dropwise and stirring to react, filtering and drying, adding to anhydrous ethanol, adding 3-aminopropyltriethoxysilane dropwise and stirring to react, vacuum drying to obtain modified nano hexagonal boron nitride, adding the modified nano hexagonal boron nitride and polyvinyl pyrrolidone to deionized water, ultrasonically stirring, adding copper nitrate, adding an ethanol solution of trimesic acid to react, filtering and vacuum drying to obtain a nano insulating agent; S12, dissolving 4,4-diaminodiphenyl ether and a nano-insulating additive in N,N-dimethylacetamide solvent, ultrasonically stirring, then adding pyromellitic anhydride, nadic anhydride and triphenyl phosphite release agent, passing nitrogen into an ice bath for reaction, and then heating to room temperature for reaction to obtain a modified polyamic acid precursor solution; S13, vacuum degassing the polyamic acid precursor solution, applying the polyamic acid precursor solution to the surface of the F46 polyimide film not containing the polyperfluoroethylene propylene resin, drawing it flat through a mold, heating to remove the solvent, and heating in a nitrogen atmosphere for imidization to obtain a modified polyimide film.

[0007] Preferably, in S11, the amounts of nano hexagonal boron nitride, ethyl silicate, ammonia water and 3-aminopropyltriethoxysilane are 4 to 5 parts, 5 to 8 parts, 5 to 10 parts and 5 to 7 parts by mass, ammonia water is added dropwise at 40 to 50°C, and the reaction is stirred for 4 to 6 hours. The volume ratio of polyvinyl pyrrolidone and deionized water is 1:100, and ultrasonic stirring is carried out at a power of 300 to 500 W for 10 to 12 hours. After adding 3-aminopropyltriethoxysilane dropwise, the temperature is raised to 60 to 70°C in a nitrogen atmosphere and stirred for 3 to 4 hours. After adding an ethanol solution of trimesic acid, the reaction is carried out at 160 to 180°C for 10 to 12 hours.

[0008] Preferably, in S12, ultrasonic stirring is performed at a power of 300-500 W for 4-6 hours, nitrogen is introduced into an ice bath for reaction for 4-6 hours, and then the temperature is raised to room temperature for reaction for 6-8 hours.

[0009] Preferably, in S13, the temperature is raised to 140-160° C. to remove the solvent, and then the mixture is heated in a nitrogen atmosphere in a gradient manner, reacting at 80-100° C. for 1-2 h, then raised to 200-300° C. for 1-2 h, and then reacted at 300-350° C. for 1-2 h.

[0010] Preferably, the method for preparing the outer sheath comprises the following steps: S21, adding fluororubber raw rubber to an open mill and mixing, adding polytetrafluoroethylene, antioxidant 224, stearic acid, zinc oxide and filler in sequence, and finally adding sulfur and vulcanization accelerator MBT, mixing evenly and then thinning, and standing at room temperature for 12 to 24 hours to obtain a rubber mixture; S22. Place the mixed rubber in a vulcanizer for vulcanization to obtain an outer sheath.

[0011] Preferably, in S21, mixing is performed at 50-60° C. for 5-15 minutes, and thin-passing is performed 4-6 times.

[0012] Preferably, the S22 is vulcanized at 130-140° C. for 1-2 hours.

[0013] A method for preparing a thin film sintering line comprises the following steps: S1. Film wrapping: The modified polyimide film is processed and cut into a strip, and wrapped around the conductor by a traction machine to obtain a modified polyimide film layer; S2. Outer sheath coating: The outer sheath material is evenly coated around the modified polyimide film layer by an extruder, and air-cooled and shaped to obtain the outer sheath; S3. Sintering and wire taking-up: Sintering is done by heater, cooling and wire taking-up, and the quality of the sintered wire is checked to obtain a thin film sintered wire.

[0014] Preferably, the extrusion temperature of the extruder in S2 is 70-90°C.

[0015] Preferably, in S3, the material is heated to 300-400° C. and sintered for 5-10 minutes, then cooled to 250-270° C. and kept warm for 1-2 hours.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention improves the dispersibility of nano-hexagonal boron nitride by coating it with silicon dioxide, then grafts 3-aminopropyltriethoxysilane to provide reaction sites, and finally reacts with copper nitrate and trimesic acid to in situ grow a copper metal organic framework to prepare a nano-insulating agent. The nano-insulating agent forms hydrogen bonds with the carboxyl groups of the polyamic acid precursor through the amino groups, thereby improving the dispersibility of the nano-insulating agent in the modified polyimide film and avoiding the agglomeration of nanoparticles.

[0017] 2. The present invention introduces nadic anhydride during the preparation of a polyamic acid precursor by reacting 4,4-diaminodiphenyl ether and pyromellitic anhydride, thereby controlling the molecular weight of the reaction crosslinking to reduce crosslinking defects, reducing the internal stress generated during the formation of the modified polyimide film, and improving the wrapping adaptability. The nano-insulating additive can be precipitated during the corona discharge process of the polyimide film, hindering the application of a strong electric field, thereby improving the corona resistance of the modified polyimide film. Moreover, the nano-insulating additive has a two-dimensional structure and can show a stacking tendency in the direction of the substrate during the drying and curing process of the film, forming a continuous load transfer network, thereby improving the mechanical properties of the modified polyimide film.

[0018] 3. The present invention wraps a conductor with a modified polyimide film, then covers it with a fluororubber outer sheath, and finally sinters the resulting film sintered wire, which has excellent corona resistance and mechanical properties. A polyamic acid precursor is prepared by reacting 4,4-diaminodiphenyl ether, nadic anhydride, and pyromellitic anhydride, and a nano-insulating agent is added to the F46 polyimide film to react with silica-coated nano-hexagonal boron nitride, copper nitrate, and pyromellitic acid to in situ grow a copper metal organic framework. The nano-insulating agent is compounded with the F46 polyimide film and imidized to obtain a modified polyimide film. Nadic anhydride reduces cross-linking defects by controlling the molecular weight of the reaction crosslinking, thereby reducing the internal stress generated during the formation of the modified polyimide film. The nano-insulating agent forms hydrogen bonds with the carboxyl groups of the polyamic acid precursor through amino groups, thereby improving the dispersibility of the nano-insulating agent in the modified polyimide film, forming a load continuous transfer network, and improving the corona resistance and mechanical properties of the modified polyimide film. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a cross-sectional schematic diagram of a thin film sintering line of the present invention; Reference numerals: 1. conductor; 2. modified polyimide film layer; 3. outer sheath. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] The copper wire involved in the present invention is made by drawing and annealing T1 pure copper as specified in GB / T 5231-2022 "Processing Copper and Copper Alloy Grades and Chemical Composition", with a wire gauge of 3.35 mm × 9 mm; the fluororubber raw rubber is of model F2603, the average diameter of nano hexagonal boron nitride is 500 nm, the purity is 99.9%, and the polyimide film is 0.02 mm thick and of model F46.

[0023] Example 1, see Figure 1 As shown, a thin film sintered wire of this embodiment includes, from the inside to the outside, a conductor 1, a modified polyimide film layer 2 and an outer sheath 3; The conductor is a copper wire; The modified polyimide film layer is prepared by coating a modified polyamic acid precursor solution on a polyimide film, and then wrapping the modified polyimide film around the conductor after drawing and heating imidization. The modified polyamic acid precursor solution is prepared from the following components in parts by weight: 3g of 4,4-diaminodiphenyl ether, 0.7g of a nano-insulating additive, 0.5g of nadic anhydride, 3.27g of pyromellitic anhydride, 50g of N,N-dimethylacetamide solvent, and 1g of triphenyl phosphite release agent; The modified polyimide film has a thickness of 0.04 mm, and the modified polyimide film is wrapped at a wrapping angle of 50°, with a wrapping overlap rate of 45%; The molar ratio of 4,4-diaminodiphenyl ether and pyromellitic anhydride is 1:1. The nano-insulating agent is prepared by coating nano-hexagonal boron nitride with silicon dioxide to prepare modified nano-hexagonal boron nitride, followed by adding copper nitrate and in-situ grown copper metal organic framework. The amounts of modified nano-hexagonal boron nitride, copper nitrate and pyromellitic acid are 1g, 2.3g and 1.3g respectively. The outer sheath has a thickness of 2 mm and is made of the following components: 50 g of fluororubber, 10 g of polytetrafluoroethylene, 1 g of antioxidant 224, 2 g of sulfur, 2 g of stearic acid, 0.5 g of zinc oxide, 1 g of vulcanization accelerator MBT, and 15 g of filler. The filler is prepared by mixing silicon micropowder, carbon black and magnesium silicate fiber in a mass ratio of 1:4:2.

[0024] The method for preparing the modified polyimide film of this embodiment includes the following steps: S11, 5g of nano hexagonal boron nitride was added to 50mL of anhydrous ethanol, 6mL of ethyl silicate was added to 25mL of ethanol and then added to the reaction system, 7mL of ammonia water was added dropwise at 50°C and stirred for 4h, filtered and dried, added to 50mL of anhydrous ethanol, 6mL of 3-aminopropyltriethoxysilane was added dropwise, the temperature was raised to 60°C in a nitrogen atmosphere, stirred for 4h, and vacuum dried to obtain modified nano hexagonal boron nitride, 1g of modified nano hexagonal boron nitride and 0.5mL of polyvinyl pyrrolidone were added to 50mL of deionized water, ultrasonically stirred at a power of 500W for 12h, and then 2.3g of copper nitrate was added, and 1.3g of ethanol solution of trimesic acid was added and reacted at 180°C for 12h, filtered and vacuum dried to obtain a nano insulating additive; S12, 3g of 4,4-diaminodiphenyl ether and 0.7g of nano-insulation additive were dissolved in 50g of N,N-dimethylacetamide solvent, and ultrasonically stirred. Then, 3.27g of pyromellitic anhydride, 0.5g of nadic anhydride and 1g of triphenyl phosphite release agent were added, and nitrogen was passed through an ice bath to react for 4h, and then the temperature was raised to room temperature and reacted for 8h to obtain a modified polyamic acid precursor solution; S13. Vacuum degassing the polyamic acid precursor solution, applying the polyamic acid precursor solution to the surface of the F46 polyimide film that does not contain polyperfluoroethylene propylene resin, flattening it through a mold, heating it to 160°C to remove the solvent, gradient heating it in a nitrogen atmosphere, reacting it at 80°C for 2h, then heating it to 200°C for 1h, and then reacting it at 350°C for 2h, and imidization to obtain a modified polyimide film.

[0025] The method for preparing the outer sheath of this embodiment includes the following steps: S21. Silica powder, carbon black and magnesium silicate fiber are mixed in a mass ratio of 1:4:2 to prepare a filler, 50 g of fluororubber raw rubber is added to an open mill for mixing, 10 g of polytetrafluoroethylene, 1 g of antioxidant 224, 2 g of stearic acid, 0.5 g of zinc oxide and 15 g of filler are added in sequence, and finally 2 g of sulfur and 1 g of vulcanization accelerator MBT are added, and the mixture is mixed at 60°C for 10 min. After mixing evenly, the mixture is thinned 5 times and allowed to stand at room temperature for 12 h to prepare a rubber compound; S22. Place the rubber mixture in a vulcanizer and vulcanize it at 130° C. for 2 hours to obtain an outer sheath.

[0026] A method for preparing a thin film sintering line according to this embodiment includes the following steps: S1. Film wrapping: The modified polyimide film is processed and cut into a strip, and wrapped around the conductor by a traction machine to obtain a modified polyimide film layer; S2. Outer sheath coating: The outer sheath material is evenly coated around the modified polyimide film layer through an extruder at an extrusion temperature of 80°C and air-cooled to obtain the outer sheath; S3. Sintering and winding: heating to 300°C by a heater and sintering for 10 minutes, cooling to 250°C and keeping warm for 2 hours, cooling and winding, checking the quality of the sintered wire, and obtaining a thin film sintered wire.

[0027] Example 2: A thin film sintered wire of this embodiment comprises, from the inside to the outside, a conductor, a modified polyimide film layer, and an outer sheath; The conductor is a copper wire; The thickness of the modified polyimide film layer is 0.037 mm, the modified polyimide film layer is wrapped at a wrapping angle of 40°, and the wrapping overlap rate is between 45%; The modified polyimide film layer is prepared by coating a modified polyamic acid precursor solution on a polyimide film, and then wrapping the modified polyimide film around the conductor after drawing and heating for imidization. The modified polyamic acid precursor solution is prepared from the following components in parts by weight: 4g of 4,4-diaminodiphenyl ether, 0.5g of a nano-insulating additive, 0.9g of nadic anhydride, 3.9g of pyromellitic anhydride, 40g of N,N-dimethylacetamide solvent, and 0.5g of triphenyl phosphite release agent; The molar ratio of 4,4-diaminodiphenyl ether to pyromellitic anhydride is 1:0.9. The nano-insulating agent is prepared by coating nano-hexagonal boron nitride with silicon dioxide, grafting 3-aminopropyltriethoxysilane to obtain modified nano-hexagonal boron nitride, and then adding copper nitrate and pyromellitic acid to in-situ grow a copper metal organic framework. The amounts of modified nano-hexagonal boron nitride, copper nitrate and pyromellitic acid are 2g, 2.6g and 1.5g respectively. The outer sheath has a thickness of 2.5 mm and is made of the following components: 55 g of fluororubber, 15 g of polytetrafluoroethylene, 1.2 g of antioxidant 224, 1.3 g of sulfur, 3 g of stearic acid, 0.75 g of zinc oxide, 2 g of vulcanization accelerator MBT, and 10 g of filler. The filler is prepared by mixing silicon micropowder, carbon black and magnesium silicate fiber in a mass ratio of 1:4.5:2.5.

[0028] The method for preparing the modified polyimide film of this embodiment includes the following steps: S11, adding 4g of nano hexagonal boron nitride to 50mL of anhydrous ethanol, adding 5mL of ethyl silicate to 25mL of ethanol and then adding the reaction system, adding 5mL of ammonia water dropwise at 50°C and stirring for 4h, filtering and drying, adding to 50mL of anhydrous ethanol, adding 5mL of 3-aminopropyltriethoxysilane dropwise, heating to 60°C in a nitrogen atmosphere and stirring for 3h, vacuum drying to obtain modified nano hexagonal boron nitride, adding 2g of modified nano hexagonal boron nitride and 0.5mL of polyvinyl pyrrolidone to 50mL of deionized water, ultrasonically stirring at 300W for 10h, then adding 2.6g of copper nitrate, adding 1.5g of ethanol solution of trimesic acid and reacting at 160°C for 10h, filtering and vacuum drying to obtain a nano insulating agent; S12, 4g of 4,4-diaminodiphenyl ether and 0.5g of nano-insulation additive were dissolved in 40g of N,N-dimethylacetamide solvent, and ultrasonically stirred. Then, 3.9g of pyromellitic anhydride, 0.9g of nadic anhydride and 1g of triphenyl phosphite release agent were added, and nitrogen was passed through an ice bath to react for 6h, and then the temperature was raised to room temperature and reacted for 6h to obtain a modified polyamic acid precursor solution; S13. Vacuum degassing the polyamic acid precursor solution, applying the polyamic acid precursor solution to the surface of the F46 polyimide film that does not contain polyperfluoroethylene propylene resin, flattening it through a mold, heating it to 140°C to remove the solvent, gradient heating it in a nitrogen atmosphere, reacting it at 80°C for 1 hour, then heating it to 200°C for 1 hour, and then reacting it at 300°C for 1.5 hours, and imidization to obtain a modified polyimide film.

[0029] The method for preparing the outer sheath of this embodiment includes the following steps: S21. Silica powder, carbon black and magnesium silicate fiber were mixed in a mass ratio of 1:4.5:2.5 to prepare a filler, 55 g of fluororubber raw rubber was added to an open mill for mixing, 15 g of polytetrafluoroethylene, 1.2 g of antioxidant 224, 3 g of stearic acid, 0.75 g of zinc oxide and 10 g of filler were added in sequence, and finally 1.3 g of sulfur and 2 g of vulcanization accelerator MBT were added, and the mixture was mixed at 60°C for 5 min. After mixing evenly, the mixture was thinned 4 times and allowed to stand at room temperature for 24 h to prepare a rubber compound; S22. Place the rubber mixture in a vulcanizer and vulcanize it at 140° C. for 1 hour to obtain an outer sheath.

[0030] A method for preparing a thin film sintering line according to this embodiment includes the following steps: S1. Film wrapping: The modified polyimide film is processed and cut into a strip, and wrapped around the conductor by a traction machine to obtain a modified polyimide film layer; S2. Outer sheath coating: The outer sheath material is evenly coated around the modified polyimide film layer through an extruder at an extrusion temperature of 70°C and air-cooled to form the outer sheath; S3. Sintering and winding: heating to 350°C by a heater and sintering for 5 minutes, cooling to 270°C and keeping warm for 1.5 hours, cooling and winding, checking the quality of the sintered wire, and obtaining a thin film sintered wire.

[0031] Example 3, a thin film sintered wire of this embodiment comprises, from the inside to the outside, a conductor, a modified polyimide film layer and an outer sheath; The conductor is a copper wire; The thickness of the modified polyimide film layer is 0.035 mm, the modified polyimide film layer is wrapped at a wrapping angle of 55°, and the wrapping overlap rate is between 60%; The modified polyimide film layer is prepared by coating a modified polyamic acid precursor solution on a polyimide film, and then wrapping the modified polyimide film around the conductor after drawing and heating for imidization. The modified polyamic acid precursor solution is prepared from the following components in parts by weight: 4g of 4,4-diaminodiphenyl ether, 0.8g of a nano-insulating additive, 0.52g of nadic anhydride, 4.8g of pyromellitic anhydride, 45g of N,N-dimethylacetamide solvent, and 1.5g of triphenyl phosphite release agent; The molar ratio of 4,4-diaminodiphenyl ether to pyromellitic anhydride is 1:1.1. The nano-insulating agent is prepared by coating nano-hexagonal boron nitride with silicon dioxide, grafting 3-aminopropyltriethoxysilane to obtain modified nano-hexagonal boron nitride, and then adding copper nitrate and pyromellitic acid to in-situ grow a copper metal organic framework. The amounts of modified nano-hexagonal boron nitride, copper nitrate and pyromellitic acid are 1.5g, 2.9g and 1.6g respectively. The outer sheath has a thickness of 4 mm and is made of the following components: 60 g of fluororubber, 20 g of polytetrafluoroethylene, 1.5 g of antioxidant 224, 2 g of sulfur, 4 g of stearic acid, 1 g of zinc oxide, 0.5 g of vulcanization accelerator MBT, and 15 g of filler. The filler is prepared by mixing silicon micropowder, carbon black and magnesium silicate fiber in a mass ratio of 1:5:3.

[0032] The method for preparing the modified polyimide film of this embodiment includes the following steps: S11, adding 4.5g of nano hexagonal boron nitride to 50mL of anhydrous ethanol, adding 8mL of ethyl silicate to 25mL of ethanol and then adding the reaction system, adding 10mL of ammonia water dropwise at 40°C and stirring for 6h, filtering and drying, adding to 50mL of anhydrous ethanol, adding 7mL of 3-aminopropyltriethoxysilane dropwise, heating to 70°C in a nitrogen atmosphere and stirring for 4h, vacuum drying to obtain modified nano hexagonal boron nitride, adding 1.5g of modified nano hexagonal boron nitride and 0.5mL of polyvinyl pyrrolidone to 50mL of deionized water, ultrasonically stirring at 300W for 12h, then adding 2.9g of copper nitrate, adding 1.6g of ethanol solution of trimesic acid and reacting at 180°C for 10h, filtering and vacuum drying to obtain a nano insulating agent; S12, 4g of 4,4-diaminodiphenyl ether and 0.8g of nano-insulation additive were dissolved in 45g of N,N-dimethylacetamide solvent, and ultrasonically stirred. Then, 4.8g of pyromellitic anhydride, 0.52g of nadic anhydride and 1.5g of triphenyl phosphite release agent were added, and nitrogen was passed through an ice bath to react for 4h, and then the temperature was raised to room temperature and reacted for 6h to obtain a modified polyamic acid precursor solution; S13. The polyamic acid precursor solution is vacuum degassed, and the polyamic acid precursor solution is applied to the surface of 200g of F46 polyimide film that does not contain polyperfluoroethylene propylene resin. The film is flattened by drawing through a mold, and the temperature is raised to 150°C to remove the solvent. The film is gradient heated in a nitrogen atmosphere, reacted at 100°C for 2h, then heated to 300°C for 1h, and then reacted at 350°C for 2h, and imidization is performed to obtain a modified polyimide film.

[0033] The method for preparing the outer sheath of this embodiment includes the following steps: S21. Silica powder, carbon black and magnesium silicate fiber are mixed in a mass ratio of 1:5:3 to prepare a filler, 60 g of fluororubber raw rubber is added to an open mill for mixing, 20 g of polytetrafluoroethylene, 1.5 g of antioxidant 224, 4 g of stearic acid, 1 g of zinc oxide and 15 g of filler are added in sequence, and finally 2 g of sulfur and 0.5 g of vulcanization accelerator MBT are added, and the mixture is mixed at 50°C for 10 min. After mixing evenly, the mixture is thinned 4 times and allowed to stand at room temperature for 18 h to prepare a rubber mixture; S22. Place the rubber mixture in a vulcanizer and vulcanize it at 135° C. for 1.5 hours to obtain an outer sheath.

[0034] A method for preparing a thin film sintering line according to this embodiment includes the following steps: S1. Film wrapping: The modified polyimide film is processed and cut into a strip, and wrapped around the conductor by a traction machine to obtain a modified polyimide film layer; S2. Outer sheath coating: The outer sheath material is evenly coated around the modified polyimide film layer through an extruder at an extrusion temperature of 90°C and air-cooled to form the outer sheath; S3. Sintering and winding: heating to 400°C by a heater and sintering for 5 minutes, cooling to 250°C and keeping warm for 1 hour, cooling and winding, checking the quality of the sintered wire, and obtaining a thin film sintered wire.

[0035] Comparative Example 1: This comparative example differs from Example 1 in that no nano-insulating additive is added.

[0036] Comparative Example 2: The difference between this comparative example and Example 1 is that the nano-insulating auxiliary agent is replaced by silicon dioxide with an average particle size of 500 nm.

[0037] Comparative Example 3: The difference between this comparative example and Example 1 is that nadic anhydride is not added to the modified polyimide film.

[0038] Performance Testing According to the standard GB / T 23310-2009 "240 Grade Aromatic Polyimide Film Wrapped Rectangular Copper Wire", the thin film sintered wires prepared in each embodiment and comparative example were subjected to mechanical property tests of tensile strength and elongation using a tensile testing machine and other equipment in accordance with GB / T4074.3-2024. The thin film sintered wires prepared in each embodiment and comparative example were subjected to a breakdown voltage performance test using a high-voltage test transformer in accordance with GB / T 4074.5-2024. The thin film sintered wires prepared in each embodiment and comparative example were subjected to a corona resistance test in accordance with GB / T 22566-2017. The thin film sintered wires prepared in each embodiment and comparative example were subjected to a thermal property test in accordance with GB / T 4074.6-2024.

[0039] The test results are shown in Table 1 below: Table 1 Performance test results It can be seen from the above data that the thin film sintered wire prepared in Examples 1 to 3 has a tensile strength of 25.0 to 25.2 MPa, an elongation of 90.1 to 90.4%, and no cracks, indicating that the thin film sintered wire prepared in the present invention has excellent mechanical properties and thermal stability; the thin film sintered wire prepared in Examples 1 to 3 has a breakdown voltage of 8.32 to 8.37 kV and a corona resistance life of 95 to 97 min, indicating that the thin film sintered wire prepared in the present invention has excellent insulation and corona resistance. Comparative Example 1 does not add nano-insulating additives, and due to the lack of corona hindering effect of nano-insulating additives during corona discharge, its breakdown voltage is 7.26 kV and its corona resistance life is 42 min.

[0040] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0041] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A thin film sintering line, characterized in that: From the inside to the outside, it includes a conductor, a modified polyimide film layer and an outer sheath; The modified polyimide film layer is prepared by coating a modified polyamic acid precursor solution on a polyimide film, and then wrapping the modified polyimide film around the conductor through drawing and heating imidization. The modified polyamic acid precursor solution is prepared from the following components in parts by weight: 3-5 parts of 4,4-diaminodiphenyl ether, 0.5-0.8 parts of a nano-insulating additive, 0.5-1.1 parts of nadic anhydride, 3-5 parts of pyromellitic anhydride, 40-50 parts of N,N-dimethylacetamide solvent, and 0.5-2 parts of triphenyl phosphite release agent. The molar ratio of 4,4-diaminodiphenyl ether to pyromellitic anhydride is 1:(0.8-1.1); the nano-insulating additive is prepared by coating nano-hexagonal boron nitride with silicon dioxide, grafting 3-aminopropyltriethoxysilane to obtain modified nano-hexagonal boron nitride, and then adding copper nitrate and pyromellitic acid to in-situ grow a copper metal organic framework; in terms of mass, the amounts of modified nano-hexagonal boron nitride, copper nitrate and pyromellitic acid are 1-2 parts, 2-3 parts and 1-2 parts respectively.

2. A thin film sintering line according to claim 1, characterized in that: The conductor is a copper wire; the modified polyimide film has a thickness of 0.03-0.04 mm, is wrapped at a wrapping angle of 40-60 degrees, and has a wrapping overlap rate of 45-65%; the outer sheath has a thickness of 2-4 mm, and is made of the following components by weight: 50-60 parts of fluororubber raw rubber, 10-20 parts of polytetrafluoroethylene, 0.5-1.5 parts of antioxidant 224, 0.5-2 parts of sulfur, 2-4 parts of stearic acid, 0.5-1 part of zinc oxide, 0.5-2 parts of vulcanization accelerator MBT, and 10-15 parts of filler; The filler is prepared by mixing silicon micropowder, carbon black and magnesium silicate fiber in a mass ratio of 1: (4-5): (2-3).

3. The thin film sintering line according to claim 1, characterized in that: The method for preparing the modified polyimide film comprises the following steps: S11, adding nano hexagonal boron nitride to anhydrous ethanol, adding an ethanol solution of ethyl silicate, adding ammonia water dropwise and stirring to react, filtering and drying, adding to anhydrous ethanol, adding 3-aminopropyltriethoxysilane dropwise and stirring to react, vacuum drying to obtain modified nano hexagonal boron nitride, adding the modified nano hexagonal boron nitride and polyvinyl pyrrolidone to deionized water, ultrasonically stirring, adding copper nitrate, adding an ethanol solution of trimesic acid to react, filtering and vacuum drying to obtain a nano insulating agent; S12, dissolving 4,4-diaminodiphenyl ether and a nano-insulating additive in N,N-dimethylacetamide solvent, stirring with ultrasound, adding pyromellitic anhydride and triphenyl phosphite release agent, passing nitrogen into an ice bath for reaction, and then heating to room temperature for reaction to obtain a modified polyamic acid precursor solution; S13, vacuum degassing the polyamic acid precursor solution, applying the polyamic acid precursor solution to the surface of the polyimide film not containing the polyperfluoroethylene propylene resin, drawing it flat through a mold, heating to remove the solvent, and heating in a nitrogen atmosphere for imidization to obtain a modified polyimide film.

4. A thin film sintering line according to claim 3, characterized in that: In terms of mass, the amounts of nano hexagonal boron nitride, ethyl silicate, ammonia water and 3-aminopropyltriethoxysilane in the S11 are 4-5 parts, 5-8 parts, 5-10 parts and 5-7 parts, and ammonia water is added dropwise at 40-50°C and stirred for reaction for 4-6 hours. The volume ratio of polyvinyl pyrrolidone and deionized water is 1:

100. After adding 3-aminopropyltriethoxysilane, the temperature is raised to 60-70°C in a nitrogen atmosphere and stirred for reaction for 3-4 hours. Ultrasonic stirring is carried out at a power of 300-500W for 10-12 hours. After adding an ethanol solution of trimesic acid, the reaction is carried out at 160-180°C for 10-12 hours.

5. The thin film sintering line according to claim 3, characterized in that: In the S12, ultrasonic stirring is performed at a power of 300-500 W for 4-6 hours, nitrogen is introduced into an ice bath for reaction for 4-6 hours, and then the temperature is raised to room temperature for reaction for 6-8 hours; in the S13, the temperature is raised to 140-160° C. to remove the solvent, and then gradient heating is performed in a nitrogen atmosphere, reacting at 80-100° C. for reaction for 1-2 hours, then the temperature is raised to 200-300° C. for reaction for 1-2 hours, and then at 300-350° C. for reaction for 1-2 hours.

6. The thin film sintering line according to claim 1, characterized in that: The method for preparing the outer sheath comprises the following steps: S21, adding fluororubber raw rubber to an open mill and mixing, adding polytetrafluoroethylene, antioxidant 224, stearic acid, zinc oxide and filler in sequence, and finally adding sulfur and vulcanization accelerator MBT, mixing evenly and then thinning, and standing at room temperature for 12 to 24 hours to obtain a rubber mixture; S22. Place the mixed rubber in a vulcanizer for vulcanization to obtain an outer sheath.

7. The thin film sintering line according to claim 6, characterized in that: In the S21, the mixture is mixed at 50-60° C. for 5-15 minutes and thin-passed 4-6 times; and in the S22, the mixture is vulcanized at 130-140° C. for 1-2 hours.

8. The method for preparing a thin film sintering line according to any one of claims 1 to 7, characterized in that: The steps include: S1. Film wrapping: The polyimide film is processed and cut into a strip, and wrapped around the conductor by a traction machine to obtain a modified polyimide film layer; S2. Outer sheath coating: The outer sheath material is evenly coated around the polyimide film through an extruder, and air-cooled and shaped to obtain the outer sheath; S3. Sintering and wire taking-up: Sintering is done by heater, cooling and wire taking-up, and the quality of the sintered wire is checked to obtain a thin film sintered wire.

9. The method for preparing a thin film sintering line according to claim 8, characterized in that: The extrusion temperature of the extruder in S2 is 70-90° C.; in S3, the material is heated to 300-400° C. and sintered for 5-10 minutes, then cooled to 250-270° C. and kept warm for 1-2 hours.

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