A method for preparing paper-insulated enameled copper flat wire

Abstract

This invention discloses a method for preparing paper-insulated enameled copper flat wire, relating to the field of paper-insulated conductor technology. The method includes the following steps: forming a copper conductor into a copper flat wire; coating the copper flat wire with insulating varnish and baking to cure, thus obtaining an enameled copper flat wire; covering the enameled copper flat wire with a gap wrapping layer to form a composite wire A, the gap wrapping layer being formed by spirally winding insulating paper along the length of the enameled copper flat wire, with two layers; taking one composite wire A or multiple composite wires bundled together as composite wire B, and spirally wrapping and overlapping the composite wire A or composite wire B to form a self-locking wrapping layer. This invention, by employing a composite wrapping method of inner gap wrapping (two layers) and outer self-locking wrapping, combined with the spiral winding design of the insulating paper, ensures that the paper layers are tightly bonded under bending or mechanical stress, avoiding loosening and gaps, thereby significantly improving the mechanical stability and electrical insulation reliability of the insulation layer.

Description

Technical Field

[0001] This invention relates to the field of paper-insulated conductor technology, and more particularly to a method for preparing paper-insulated enameled copper flat wire. Background Technology

[0002] Paper-insulated enameled copper flat wire is widely used in power equipment such as transformers and motors, requiring excellent electrical insulation performance, mechanical strength, and long-term stability under extreme environments such as high temperature (e.g., 160℃), low temperature (e.g., -50℃), and high humidity. In existing technologies, the fabrication of paper-insulated enameled copper flat wire typically employs a single wrapping method, which makes it difficult to simultaneously meet the requirements of high insulation and resistance to mechanical stress. When the copper flat wire is bent or subjected to vibration, the insulating paper layers are prone to loosening, leading to gaps between the layers. The presence of these gaps may reduce electrical insulation performance and increase the risk of partial discharge or breakdown. Summary of the Invention

[0003] To solve the above-mentioned technical problems, the present invention provides a method for preparing paper-insulated enameled copper flat wire, the specific technical solution of which is as follows:

[0004] A method for preparing paper-insulated enameled copper flat wire includes the following steps:

[0005] S1. Copper conductors are drawn and annealed to obtain copper flat wires;

[0006] S2. Apply insulating varnish to the copper flat wire and bake it to cure, thereby obtaining enameled copper flat wire;

[0007] S3. A gap wrapping layer is wrapped around the enameled copper flat wire to form a composite wire A. The gap wrapping layer is formed by spirally wrapping insulating paper around the gap along the length of the enameled copper flat wire. The number of gap wrapping layers is two.

[0008] S4. Take one composite wire A or multiple composite wires bundled together as composite wire B, and spirally wrap and overlap the composite wire A or composite wire B to form a self-locking wrapping layer.

[0009] Preferably, step S1 specifically includes the following sub-steps:

[0010] a1. Process the cathode copper plate into a copper rod;

[0011] a2. The copper rod is drawn in multiple passes to obtain copper flat wire of the required specifications;

[0012] a3. The copper flat wire is annealed once at a temperature of 290~310℃;

[0013] a4. Perform ultrasonic cleaning on the copper flat wire to remove surface impurities;

[0014] a5. The cleaned copper flat wire is subjected to a second annealing at a temperature of 290~310℃.

[0015] Preferably, step S2 specifically includes the following sub-steps:

[0016] b1. An insulating varnish is prepared using polyesterimide varnish and a thinner, the insulating varnish comprising a primer, an intermediate coat, and a topcoat, wherein the mass ratio of polyesterimide varnish to thinner in the primer, intermediate coat, and topcoat is 22:3, 22:3, and 4:1, respectively;

[0017] b2. Apply primer, bake and cure to form a primer layer. Baking temperature: 200~250℃, curing temperature: 410~450℃;

[0018] b3. Apply intermediate paint, bake and cure to form intermediate paint layer. Baking temperature: 250~310℃, curing temperature: 410~450℃;

[0019] b4. Apply topcoat, bake and cure to form topcoat layer. Baking temperature: 300~340℃, curing temperature: 410~450℃.

[0020] Preferably, the gap width of the gap wrapping layer does not exceed 1 mm; and / or the gap stagger width between two layers of the gap wrapping layer is 25% to 40% of the width of the insulating paper; and / or the overlap width of the insulating paper of the self-locking wrapping layer is 45% to 55% of the width of the insulating paper; and / or the width between the overlap seam of the self-locking wrapping layer and the gap of the adjacent gap wrapping layer is 15% to 35% of the width of the insulating paper.

[0021] Preferably, the insulating paper is selected from Nomex paper or modified aromatic polyamide paper.

[0022] Preferably, the modified aromatic polyamide paper is made of the following components by weight: 40-50 parts aromatic polyamide fiber, 35-45 parts thermally activated binder, 8-12 parts curing agent, and 3-7 parts toughening agent.

[0023] Preferably, the thermally activated adhesive is selected from epoxy resin microcapsules; the curing agent is selected from amine curing agents; and the toughening agent is selected from nano-silica.

[0024] Preferably, the modified aromatic polyamide paper is prepared by the following steps:

[0025] Aromatic polyamide fibers are dispersed in deionized water to form a fiber suspension;

[0026] The thermally activated binder, curing agent and toughening agent were added to deionized water, and after adding a dispersant, the mixture was ultrasonically dispersed to obtain a component dispersion.

[0027] The component dispersion is mixed with the fiber suspension to form a mixed slurry;

[0028] Insulating paper with a thickness of 0.04~0.06 mm is prepared by wet papermaking process, and the moisture is squeezed out and dried at 40~50℃.

[0029] Preferably, the epoxy resin microcapsules are silane coupling agent modified epoxy resin microcapsules, and the modification process specifically includes the following steps:

[0030] Bisphenol A type epoxy resin is mixed with an emulsifier to form a water-in-oil emulsion;

[0031] The silane coupling agent is hydrolyzed and added to the emulsion, and the mixture is stirred to bond the silane groups to the surface of the epoxy resin.

[0032] Add urea-formaldehyde prepolymer, adjust pH to 3-4, and heat to 50-60℃ for microencapsulation;

[0033] The modified epoxy resin microcapsules were obtained by filtration, washing, and drying.

[0034] Preferably, the amine curing agent is a polyetheramine-modified alicyclic amine curing agent, and its modification process specifically includes the following steps:

[0035] Isophorone diamine was dissolved in anhydrous ethanol and stirred until homogeneous under nitrogen protection.

[0036] Slowly add polyetheramine, add triethylamine as a catalyst, and heat to 50-60℃ to react for 4-8 hours;

[0037] Ethanol was removed by vacuum distillation, followed by washing and drying to obtain a polyetheramine-modified alicyclic amine curing agent.

[0038] The paper-insulated enameled copper flat wire prepared by the method of this invention has the following beneficial effects:

[0039] 1. A composite wrapping method is adopted, which combines inner layer gap wrapping (two layers) and outer layer self-locking wrapping. Combined with the spiral winding design of the insulating paper, it ensures that the paper layers are tightly bonded under bending or mechanical stress, avoiding loosening and gaps, thereby significantly improving the mechanical stability and electrical insulation reliability of the insulation layer.

[0040] 2. By optimizing the production process through wire drawing, annealing, coating and composite wrapping, the complexity of the process is reduced, and the production efficiency and product quality stability are improved, making it suitable for the large-scale production of copper flat wire. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a side cross-sectional view of the paper-insulated enameled copper flat wire provided in an embodiment of the present invention.

[0043] Reference numerals: 1-Enameled copper flat wire; 2-Gap wrapping layer; 3-Self-locking wrapping layer. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0045] It should be noted that similar labels in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0046] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0047] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] Please see Figure 1 This embodiment provides a method for preparing paper-insulated enameled copper flat wire, including the following steps:

[0050] S1. Copper conductors are drawn and annealed to obtain copper flat wires.

[0051] S2. Apply insulating varnish to copper flat wire and bake to cure, to obtain enameled copper flat wire 1.

[0052] S3. A gap wrapping layer 2 is wrapped around the enameled copper flat wire 1 to form a composite wire A. The gap wrapping layer 2 is formed by spirally wrapping the gap with insulating paper along the length of the enameled copper flat wire 1. The number of gap wrapping layers 2 is two.

[0053] S4. Take one composite line A or multiple composite lines bundled together as composite line B, and spirally wrap and overlap the composite line A or composite line B to form a self-locking wrapping layer 3.

[0054] Among them, the gap wrapping layer 2, as the name suggests, has a gap between the insulating paper in the same layer of the wrapping layer. The gap does not exceed 1mm. The wrapping layer is set in two layers to ensure that the insulation layer has excellent flexibility and heat dissipation while ensuring electrical insulation performance. The gaps of the two gap wrapping layers 2 can be staggered, and the staggered width can be 25% to 40% of the width of the insulating paper. This can effectively disperse mechanical stress and avoid the paper layer from being subjected to concentrated force during bending or vibration, which would lead to cracks or loosening. This improves the mechanical stability and long-term reliability of the insulation layer.

[0055] When the self-locking wrapping layer 3 is wrapped, the adjacent insulating paper overlaps with each other, with an overlap width of 45% to 55% of the width of the insulating paper. It is also staggered from the gap of the adjacent wrapping layer 2 by 15% to 35%, forming a tight locking structure. This design significantly enhances the overall bonding force of the paper layer, prevents the paper layer from sliding or separating under bending or external force, and completely solves the loosening and gap problems that are easy to occur in the traditional single wrapping method, ensuring the stability of electrical insulation performance. The self-locking wrapping layer 3 supports self-locking wrapping of single composite wires or multiple bundled composite wires, adapting to different winding design requirements and enhancing the application flexibility of the product.

[0056] It is important to note that the insulating paper must be smooth, without pores or cracks, to provide excellent dielectric strength.

[0057] The paper-insulated enameled copper flat wire prepared by the method of this embodiment has the following beneficial effects:

[0058] The composite wrapping method, which uses inner layer gap wrapping (two layers) and outer layer self-locking wrapping, combined with the spiral winding design of the insulating paper, ensures that the paper layers are tightly bonded under bending or mechanical stress, avoiding loosening and gaps, thereby significantly improving the mechanical stability and electrical insulation reliability of the insulation layer.

[0059] By employing wire drawing, annealing, coating, and composite wrapping processes, the production flow has been optimized, process complexity has been reduced, and production efficiency and product quality stability have been improved, making it suitable for large-scale production of copper flat wires.

[0060] Furthermore, step S1 specifically includes the following sub-steps:

[0061] a1. Process the cathode copper plate into a copper rod.

[0062] a2. The copper rod is drawn in multiple passes to produce copper flat wire of the required specifications.

[0063] a3. Perform a first annealing on the copper flat wire at a temperature of 290~310℃.

[0064] a4. Perform ultrasonic cleaning on the copper flat wire to remove surface impurities.

[0065] a5. Perform a second annealing on the cleaned copper flat wire at a temperature of 290~310℃.

[0066] Beneficially, through multiple drawing stages and two annealing processes, the specifications and dimensions of the copper flat wire can be precisely controlled, ensuring that the conductor has high yield strength and excellent elongation, which can improve the mechanical toughness and processing adaptability of the copper flat wire. Ultrasonic cleaning can effectively remove impurities such as oxides and oil stains from the surface of the copper flat wire, enhance the adhesion of the insulating varnish, provide a high-quality substrate for subsequent coating processes, and reduce the risk of varnish peeling or unevenness. The step-by-step drawing and annealing processes optimize the crystal structure of the copper conductor and reduce internal stress. Combined with ultrasonic cleaning, this ensures the stability and consistency of the enameled copper flat wire production process, making it suitable for large-scale production.

[0067] Furthermore, step S2 specifically includes the following sub-steps:

[0068] b1. An insulating varnish is prepared using polyesterimide varnish and thinner. The insulating varnish includes a primer, intermediate varnish, and topcoat. The mass ratio of polyesterimide varnish to thinner in the primer, intermediate varnish, and topcoat is 22:3, 22:3, and 4:1, respectively.

[0069] b2. Apply primer, bake and cure to form a primer layer. Baking temperature: 200~250℃, curing temperature: 410~450℃.

[0070] b3. Apply intermediate paint, bake and cure to form intermediate paint layer. Baking temperature: 250~310℃, curing temperature: 410~450℃.

[0071] b4. Apply topcoat, bake and cure to form topcoat layer. Baking temperature: 300~340℃, curing temperature: 410~450℃.

[0072] Advantageously, by using layered coating of polyesterimide varnish, combined with increasing baking and curing temperatures, a uniform and strongly adherent varnish film can be formed, which can significantly improve electrical insulation performance. Layered coating and precise temperature control ensure the hardness, scratch resistance, and solvent resistance of the varnish film, which can improve the long-term stability of enameled copper flat wire in extreme environments. By layered coating and optimizing temperature parameters, it is possible to adapt to different production equipment and process conditions, thereby improving production efficiency and the stability of varnish film quality.

[0073] Furthermore, the gap width of the gap wrapping layer 2 does not exceed 1 mm; and / or the gap stagger width of the two gap wrapping layers 2 is 25% to 40% of the width of the insulating paper; and / or the overlap width of the insulating paper of the self-locking wrapping layer 3 is 45% to 55% of the width of the insulating paper; and / or the width between the overlap seam of the self-locking wrapping layer 3 and the gap of the adjacent gap wrapping layer 2 is 15% to 35% of the width of the insulating paper.

[0074] Among them, the gap width of the gap wrapping layer 2 is ≤1 mm and the staggered spacing is 25%~40%, which ensures the flexibility and heat dissipation of the insulation layer, while avoiding paper layer cracks caused by concentrated stress; the overlap of the self-locking wrapping layer 3 is 45%~55% and the interlayer stagger is 15%~35%, forming a tight locking structure to prevent the paper layer from loosening or separating when bending or vibrating; the precise wrapping parameters ensure that the insulating paper layer is smooth, without holes or cracks, reducing the risk of partial discharge. Combined with the high dielectric strength of the varnish film, it significantly improves the overall insulation performance; the parameterized wrapping design (gap, overlap, staggered spacing) facilitates process control, reduces quality deviations in production, and improves the reliability of paper-insulated enameled copper flat wire.

[0075] Furthermore, the insulating paper is selected from Nomex paper or modified aromatic polyamide paper.

[0076] Nomex paper possesses excellent heat resistance and dielectric strength, ensuring the stability of the paper insulation layer under high and low temperature conditions; modified aromatic polyamide paper enhances the adaptability and performance improvement potential of the insulation paper; Nomex paper and modified aromatic polyamide paper are highly compatible with transformer oil, exhibit excellent solvent resistance and moisture resistance, and are suitable for demanding power equipment applications.

[0077] Further, by weight, the modified aromatic polyamide paper is made of the following components: 40-50 parts aromatic polyamide fiber, 35-45 parts thermally activated binder, 8-12 parts curing agent, and 3-7 parts toughening agent.

[0078] The introduction of thermally activated adhesives and curing agents enables the insulating paper to be activated to form interlayer bonding or chemical bonds when heated (50~80℃), which can significantly enhance the bonding force of the paper layers. When paper-insulated enameled copper flat wires are put into use, their interlayer bonding force can be activated by heating equipment such as hot air guns after bending, thereby bonding the insulating paper layers and completely solving the loosening and gap problems of traditional wrapping methods when bending.

[0079] Furthermore, the thermally activated binder is selected from epoxy resin microcapsules; the curing agent is selected from amine curing agents; and the toughening agent is selected from nano-silica.

[0080] Among them, epoxy resin microcapsules are activated at low temperatures of 50~80℃, reacting with amine curing agents to form a tough cross-linked network, ensuring interlayer bonding strength and effectively preventing paper layers from loosening.

[0081] Furthermore, the modified aromatic polyamide paper is prepared through the following steps:

[0082] Aromatic polyamide fibers are dispersed in deionized water to form a fiber suspension.

[0083] The thermally activated binder, curing agent, and toughening agent were added to deionized water, and then a dispersant was added and ultrasonically dispersed to obtain a component dispersion.

[0084] The component dispersion is mixed with the fiber suspension to form a mixed slurry.

[0085] Insulating paper with a thickness of 0.04~0.06 mm is prepared by wet papermaking process, and the moisture is squeezed out and dried at 40~50℃.

[0086] Furthermore, the epoxy resin microcapsules are silane coupling agent modified epoxy resin microcapsules, and the modification process specifically includes the following steps:

[0087] Bisphenol A type epoxy resin is mixed with an emulsifier to form a water-in-oil emulsion.

[0088] After hydrolyzing the silane coupling agent, it is added to the emulsion and stirred to allow the silane groups to bond with the epoxy resin surface.

[0089] Add urea-formaldehyde prepolymer, adjust the pH to 3-4, and heat to 50-60℃ for microencapsulation.

[0090] The modified epoxy resin microcapsules were obtained by filtration, washing, and drying.

[0091] Among them, silane coupling agent modification significantly improves the interfacial adhesion between epoxy resin microcapsules and aromatic polyamide fibers, thereby improving the structural integrity and interlayer bonding strength of insulating paper; silane groups reduce the water absorption rate of insulating paper, enhance electrical insulation performance in high humidity environments, and broaden the application range.

[0092] Furthermore, the amine curing agent is a polyether amine-modified alicyclic amine curing agent, and its modification process specifically includes the following steps:

[0093] Isophorone diamine was dissolved in anhydrous ethanol and stirred until homogeneous under nitrogen protection.

[0094] Slowly add polyetheramine, add triethylamine as a catalyst, and heat to 50-60℃ to react for 4-8 hours.

[0095] Ethanol was removed by vacuum distillation, followed by washing and drying to obtain a polyetheramine-modified alicyclic amine curing agent.

[0096] Among them, the polyetheramine modification introduces flexible polyether segments, which makes the cured adhesive layer have both high strength and toughness, preventing brittleness under low temperature or mechanical stress and improving the durability of the insulating paper; the modified curing agent can react rapidly at 50~60℃, and works synergistically with epoxy resin microcapsules to form a stable chemical bond network, simplifying the activation process and improving production efficiency.

[0097] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0098] Example 1

[0099] Take 5 kg of cathode copper plate and process it into copper rods with a diameter of 8 mm using a continuous extrusion press (extrusion speed 10 m / min). Use a multi-head wire drawing machine (12 passes) to draw the copper rods into copper flat wires with a specification of 2.26 × 3.35 mm at a drawing speed of 15 m / min and a water-based emulsion (concentration 5%) as the coolant. Place the copper flat wires in a tubular annealing furnace (nitrogen protection, flow rate 2 L / min) at 300℃ for 20 minutes, and then cool to room temperature. Use an ultrasonic cleaner (500 W power, 40 kHz frequency) with 500 L of deionized water as the medium to clean the copper flat wires for 10 minutes to remove surface impurities. Place them again in the tubular annealing furnace at 305℃ for 15 minutes, and then cool to room temperature to obtain copper flat wires.

[0100] Prepare the paint solution using polyesterimide paint and thinner. Primer: 1100 g polyesterimide paint, 150 g thinner; Intermediate coat: 1100 g polyesterimide paint, 150 g thinner; Topcoat: 800 g polyesterimide paint, 200 g thinner. Mix for 10 minutes using a high-speed mixer (1000 rpm) to form a homogeneous paint solution.

[0101] Apply the coating using an enameled wire coating machine, in passes. Primer: 2 passes, film thickness approximately 0.015 mm; Intermediate coat: 8 passes, film thickness approximately 0.010 mm; Topcoat: 4 passes, film thickness approximately 0.008 mm.

[0102] Baking and curing are performed using a vertical baking oven. Primer baking: lower layer temperature 205℃, curing temperature 415℃, linear speed 8m / min; intermediate paint baking: lower layer temperature 255℃, curing temperature 420℃, linear speed 7.5 m / min; topcoat baking: lower layer temperature 305℃, curing temperature 425℃, linear speed 7 m / min.

[0103] Each time the coating is applied, the wire is passed through a baking oven, with a single baking time of about 30 seconds, to obtain enameled copper flat wire.

[0104] Using Nomex T410 insulating paper (0.05 mm thick, 8 mm wide), spirally wind it along the length of the enameled copper flat wire on an automatic wrapping machine (wrapping angle 30°) to form two layers with gaps. The gap width of each layer is controlled at 0.8 mm, and the stagger width between layers is 2.2 mm. The wrapping speed is 5 m / min, and the tension is controlled at 10 N.

[0105] Take a single strand of the composite wire after gap wrapping, and continue to wrap it with a self-locking wrapping layer on an automatic wrapping machine. The overlap width is 4.2 mm, the overlap seam is staggered from the gap of the adjacent gap wrapping layer by 1.6 mm, the wrapping speed is 4.5 m / min, and the tension is controlled at 12 N to obtain a paper-insulated enameled copper flat wire.

[0106] The prepared paper-insulated enameled copper flat wire was cut into 1-m long samples, and its performance was tested and the data was recorded.

[0107] The resistivity of the conductor was measured using a four-probe resistivity meter at 20°C, and the average value of 5 points was taken.

[0108] Immerse the sample in transformer oil for 72 hours and observe whether swelling or decomposition occurs, and record the results.

[0109] Peel off 200-300 mm of the sample, rub it with a nylon stocking to check for surface burrs, and record the results.

[0110] The breakdown voltage of the paint film was measured using a withstand voltage tester (test voltage rise rate 500 V / s), and the average value of 5 measurements was taken.

[0111] Using a springback tester, the sample is wound around a cylinder with a diameter of 10 mm, and the springback angle is measured. The average value of three measurements is taken.

[0112] Wrap the sample around a cylinder with a diameter of 10 mm, bend it 90°, repeat 3 times, and use a magnifying glass (10x) to observe whether the paper layer becomes loose or separate, and record the results.

[0113] The breakdown voltage was measured on the bent sample using a withstand voltage tester (test voltage rise rate 500 V / s), and the average value of 5 measurements was taken.

[0114] The test data is shown in the table below:

[0115]

[0116] Example 2

[0117] Take 5 kg of cathode copper plate and process it into copper rods with a diameter of 8 mm using a continuous extrusion press (extrusion speed 10 m / min). Use a multi-head wire drawing machine (12 passes) to draw the copper rods into copper flat wires with a specification of 2.26 × 3.35 mm at a drawing speed of 15 m / min and a water-based emulsion (concentration 5%) as the coolant. Place the copper flat wires in a tubular annealing furnace (nitrogen protection, flow rate 2 L / min) at 300℃ for 20 minutes, and then cool to room temperature. Use an ultrasonic cleaner (500 W power, 40 kHz frequency) with 500 L of deionized water as the medium to clean the copper flat wires for 10 minutes to remove surface impurities. Place them again in the tubular annealing furnace at 305℃ for 15 minutes, and then cool to room temperature to obtain copper flat wires.

[0118] Prepare the paint solution using polyesterimide paint and thinner. Primer: 1100 g polyesterimide paint, 150 g thinner; Intermediate coat: 1100 g polyesterimide paint, 150 g thinner; Topcoat: 800 g polyesterimide paint, 200 g thinner. Mix for 10 minutes using a high-speed mixer (1000 rpm) to form a homogeneous paint solution.

[0119] Apply the coating using an enameled wire coating machine, in passes. Primer: 2 passes, film thickness approximately 0.015 mm; Intermediate coat: 8 passes, film thickness approximately 0.010 mm; Topcoat: 4 passes, film thickness approximately 0.008 mm.

[0120] Baking and curing are performed using a vertical baking oven. Primer baking: lower layer temperature 205℃, curing temperature 415℃, linear speed 8m / min; intermediate paint baking: lower layer temperature 255℃, curing temperature 420℃, linear speed 7.5 m / min; topcoat baking: lower layer temperature 305℃, curing temperature 425℃, linear speed 7 m / min.

[0121] Each time the coating is applied, the wire is passed through a baking oven, with a single baking time of about 30 seconds, to obtain enameled copper flat wire.

[0122] Take 45 g of aromatic polyamide fiber and add it to 10 L of deionized water. Disperse the fiber using a high-speed disperser (2000 rpm) for 15 minutes to form a fiber suspension. Take 40 g of epoxy resin microcapsules (bisphenol A type), 10 g of amine curing agent (isophorone diamine), and 5 g of nano-silica (30 nm particle size) and add them to 2 L of deionized water. Add 0.5 g of polyvinyl alcohol as a dispersant and disperse the mixture using an ultrasonic disperser (400 W power, 20 kHz frequency) for 20 minutes to obtain a component dispersion. Mix the component dispersion with the fiber suspension and stir using a mixer (500 rpm) for 10 minutes to form a homogeneous slurry.

[0123] Using a paper machine (0.5 m / min), the mixed pulp was formed into insulating paper with a thickness of 0.05 mm. Excess moisture was removed by pressing with a press (pressure 2 MPa), and the paper was dried in an oven (temperature 45°C) for 30 minutes to obtain modified aromatic polyamide paper (width 8 mm).

[0124] Modified aromatic polyamide paper (0.05 mm thick, 8 mm wide) is spirally wound along the length of the enameled copper flat wire on an automatic wrapping machine (wrapping angle 30°) to form two layers with gaps. The gap width of each layer is controlled at 0.8 mm, and the stagger width between layers is 2.2 mm. The wrapping speed is 5 m / min, and the tension is controlled at 10 N.

[0125] Take a single strand of the composite wire after gap wrapping, and continue to wrap it with a self-locking wrapping layer on an automatic wrapping machine. The overlap width is 4.2 mm, the overlap seam is staggered from the gap of the adjacent gap wrapping layer by 1.6 mm, the wrapping speed is 4.5 m / min, and the tension is controlled at 12 N to obtain a paper-insulated enameled copper flat wire.

[0126] The prepared paper-insulated enameled copper flat wire was cut into 1-m long samples, and its performance was tested and the data was recorded.

[0127] The resistivity of the conductor was measured using a four-probe resistivity meter at 20°C, and the average value of 5 points was taken.

[0128] Immerse the sample in transformer oil for 72 hours and observe whether swelling or decomposition occurs, and record the results.

[0129] Peel off 200-300 mm of the sample, rub it with a nylon stocking to check for surface burrs, and record the results.

[0130] The breakdown voltage of the paint film was measured using a withstand voltage tester (test voltage rise rate 500 V / s), and the average value of 5 measurements was taken.

[0131] Using a springback tester, the sample is wound around a cylinder with a diameter of 10 mm, and the springback angle is measured. The average value of three measurements is taken.

[0132] Wrap the sample around a 10 mm diameter cylinder, bend it 90°, repeat 3 times, then heat it for 5 minutes with a hot air gun (temperature 60℃, air speed 500 L / min). Use a magnifying glass (10x) to observe whether the paper layer is loose or separated, and record the results.

[0133] The breakdown voltage was measured on the sample after bending and heating with a hot air gun using a withstand voltage tester (test voltage rise rate 500 V / s), and the average value of 5 measurements was taken.

[0134] The test data is shown in the table below:

[0135]

[0136] Comparative Example

[0137] Take 5 kg of cathode copper plate and process it into a copper rod with a diameter of 8 mm using a continuous extrusion press (extrusion speed 10 m / min). Use a multi-head wire drawing machine (12 passes) to draw the copper rod into a copper flat wire with a specification of 2.26 × 3.35 mm, at a drawing speed of 15 m / min, using a water-based emulsion (concentration 5%) as the coolant. Place the copper flat wire in a tubular annealing furnace (nitrogen protection, flow rate 2 L / min), anneal at 300℃ for 20 minutes, and then cool to room temperature. Use an ultrasonic cleaner (power 500 W, frequency 40 kHz) with deionized water (500 L) as the medium to clean the copper flat wire for 10 minutes to remove surface impurities.

[0138] Prepare the paint solution using polyesterimide paint and thinner. Primer: 1100 g polyesterimide paint, 150 g thinner; Intermediate coat: 1100 g polyesterimide paint, 150 g thinner; Topcoat: 800 g polyesterimide paint, 200 g thinner. Mix for 10 minutes using a high-speed mixer (1000 rpm) to form a homogeneous paint solution.

[0139] Apply the coating using an enameled wire coating machine, in passes. Primer: 2 passes, film thickness approximately 0.015 mm; Intermediate coat: 8 passes, film thickness approximately 0.010 mm; Topcoat: 4 passes, film thickness approximately 0.008 mm.

[0140] Baking and curing are performed using a vertical baking oven. Primer baking: lower layer temperature 205℃, curing temperature 415℃, linear speed 8m / min; intermediate paint baking: lower layer temperature 255℃, curing temperature 420℃, linear speed 7.5 m / min; topcoat baking: lower layer temperature 305℃, curing temperature 425℃, linear speed 7 m / min.

[0141] Each time the coating is applied, the wire is passed through a baking oven, with a single baking time of about 30 seconds, to obtain enameled copper flat wire.

[0142] Using Nomex T410 insulating paper (0.05 mm thick, 8 mm wide), spirally wound along the length of the enameled copper flat wire on an automatic wrapping machine (wrapping angle 30°) to form an overlapping wrapping layer. The overlap width is 4.0 mm, the wrapping speed is 5 m / min, and the tension is controlled at 10 N to obtain paper-insulated enameled copper flat wire.

[0143] The prepared paper-insulated enameled copper flat wire was cut into 1-m long samples, and its performance was tested and the data was recorded.

[0144] The test items and methods are the same as in Example 1, and the test data are shown in the table below:

[0145]

[0146] The data above shows that Example 1 demonstrates the advantages of the gap + self-locking composite wrapping. The breakdown voltage before bending is 8.7 kV and after bending is 8.4 kV. There is no loosening of the paper layer and the resilience is 4.1°, which is better than the comparative example (8.3 kV, 7.6 kV, slight loosening, 4.3°).

[0147] Example 2 further optimized the performance, with a breakdown voltage of 9.3 kV before bending and 9.1 kV after bending, no paper layer loosening, and a resilience of 3.8°, all of which are superior to Example 1 and the comparative example. Heating the modified insulating paper with a hot air gun enhanced interlayer adhesion, significantly improving the insulation performance after bending (decreasing by only 2.2%) and mechanical toughness (resilient improvement of 7.3%). Compared with Example 1, Example 2 showed improvements in both breakdown voltage and resilience, verifying the synergistic effect of the modified insulating paper.

[0148] The gap wrapping disperses mechanical stress, and the self-locking wrapping forms a mechanical lock, solving the problems of easy loosening and gaps in single wrapping in the prior art, and significantly improving insulation performance and interlayer stability.

[0149] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0150] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other occasions without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A method of making paper-insulated enameled flat copper wire, characterized by, It comprises the following steps: S1. The copper conductor is drawn into a copper flat wire after annealing; S2. Insulating paint is coated on the copper flat wire and baked and cured to obtain an enameled copper flat wire (1); S3. A gap covering layer (2) is wrapped around the enameled copper flat wire (1) to form a composite wire A, the gap covering layer (2) is formed by spirally wrapping the insulating paper along the length direction of the enameled copper flat wire (1), the number of the gap covering layer (2) is two, and the gap width of the gap covering layer (2) is not more than 1mm; S4. Take one of the composite wires A or multiple as a bundle as a composite wire B, and spirally wrap the composite wire A or the composite wire B to form a self-locking wrapping layer (3); Wherein, The insulating paper is selected from modified aromatic polyamide paper, and the modified aromatic polyamide paper is made of the following components by weight: 40-50 parts of aromatic polyamide fiber, 35-45 parts of heat-activated adhesive, 8-12 parts of curing agent, and 3-7 parts of toughening agent; the heat-activated adhesive is selected from epoxy resin microcapsules, and the curing agent is selected from amine curing agent; The gap width of the two layers of the gap covering layer (2) is 25%-40% of the width of the insulating paper; The overlapping width of the self-locking wrapping layer (3) is 45%-55% of the width of the insulating paper; The width between the overlapping seam of the self-locking wrapping layer (3) and the gap of the adjacent gap covering layer (2) is 15%-35% of the width of the insulating paper.

2. The paper-insulated enameled flat copper wire production method according to claim 1, characterized by, Step S1 specifically comprises the following sub-steps: a1. Process the cathode copper plate into a copper rod; a2. Draw the copper rod in multiple passes to obtain copper flat wires of required specifications; a3. Anneal the copper flat wires once, and the annealing temperature is 290-310℃; a4. Ultrasonic clean the copper flat wires to remove surface impurities; a5. Anneal the cleaned copper flat wires twice, and the annealing temperature is 290-310℃.

3. The paper-insulated enameled flat copper wire preparation method according to claim 1, characterized by, Step S2 specifically comprises the following sub-steps: b1. Prepare the insulating paint by using polyester imine paint and diluent, the insulating paint comprises primer, midcoat and topcoat, and the mass ratio of polyester imine paint to diluent in the primer, midcoat and topcoat is 22:3, 22:3 and 4:1 respectively; b2. Apply the primer, and form a primer layer after baking and curing, the baking temperature is 200-250℃, and the curing temperature is 410-450℃; b3. Apply the midcoat, and form a midcoat layer after baking and curing, the baking temperature is 250-310℃, and the curing temperature is 410-450℃; b4. Apply the topcoat, and form a topcoat layer after baking and curing, the baking temperature is 300-340℃, and the curing temperature is 410-450℃.

4. The paper-insulated enameled flat copper wire production method according to claim 1, characterized by, The toughening agent is selected from nano silicon dioxide.

5. The paper-insulated enameled flat copper wire manufacturing method according to claim 1 or 4, characterized by, The modified aromatic polyamide paper is prepared by the following steps: Disperse the aromatic polyamide fiber in deionized water to form a fiber suspension; Add the heat-activated adhesive, curing agent and toughening agent to the deionized water, and ultrasonically disperse after adding the dispersant to obtain a component dispersion; Mix the component dispersion and the fiber suspension to form a mixed slurry; An insulating paper with a thickness of 0.04-0.06 mm is prepared by a wet papermaking process, is pressed to remove water and is dried at 40-50 DEG C.

6. The method for preparing paper-insulated enameled copper flat wire according to claim 4, characterized in that, The epoxy resin microcapsule is a silane coupling agent modified epoxy resin microcapsule, and the modification process specifically comprises the following steps: The bisphenol A type epoxy resin is mixed with an emulsifier to form a water-in-oil emulsion; The silane coupling agent is hydrolyzed and then added to the emulsion, and the silane groups are bonded to the surface of the epoxy resin by stirring; A urea-formaldehyde prepolymer is added, the pH is adjusted to 3-4, and microencapsulation is performed by heating to 50-60 DEG C; After filtration, washing and drying, the modified epoxy resin microcapsule is obtained.

7. The method for preparing paper-insulated enameled copper flat wire according to claim 4, characterized in that, The amine curing agent is a polyether amine modified alicyclic amine curing agent, and the modification process specifically comprises the following steps: Isophorone diamine is dissolved in anhydrous ethanol, and stirring is performed under nitrogen protection until uniform; Polyether amine is slowly added dropwise, a catalyst triethylamine is added, and reaction is performed at 50-60 DEG C for 4-8 hours; Anhydrous ethanol is removed by reduced pressure distillation, and the polyether amine modified alicyclic amine curing agent is obtained after washing and drying.

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