A low dielectric loss coating composition and its preparation method, and a film-coated stranded wire.

Abstract

This application belongs to the field of film-coated stranded wire, specifically providing a low dielectric loss coating film composition and its preparation method, and a film-coated stranded wire. The preparation method for the low dielectric loss coating film composition includes the following steps: S01. Ferrocene carboxylic acid, octaphenylaminopropyl cage-like polysilsesquioxane, and diethylene glycol are mixed and dispersed using N,N-dimethylformamide. The mixture is stirred at room temperature to obtain a precursor liquid. Then, octaphenylaminopropyl cage-like polysilsesquioxane is added, and the reaction continues. Next, N,N-dimethylformamide is added, and the mixture is redispersed. This is designated as solution A for later use. S02. Diol and diisocyanate are mixed and reacted at elevated temperature. Then, N,N-dimethylformamide is added for dispersion. Further processing yields a polyurethane prepolymer dispersion, designated as solution B for later use. S03. Solution A and solution B are mixed, and then concentrated to obtain the coating film composition. The coating film composition obtained by this application has the advantages of low dielectric loss and good mechanical properties.

Description

Technical Field

[0001] This application belongs to the field of film-coated stranded wire technology, and in particular relates to a low dielectric loss coating composition and its preparation method, and film-coated stranded wire. Background Technology

[0002] Membrane-wrapped stranded wire is a high-performance electromagnetic wire widely used in high-frequency transformers, micro motors, drive motors for new energy vehicles, and aerospace electronic equipment. Its main advantage lies in its special structural design, which combines multiple thin-diameter conductors into a single composite conductor, effectively reducing skin effect and proximity effect losses at high frequencies, while simultaneously improving the reliability of electrical connections and space utilization.

[0003] Structurally, the membrane-wrapped stranded wire is made of multiple copper conductor cores twisted together. Each conductor core is pre-coated with a thin and dense insulating varnish film after baking treatment to achieve electrical isolation between individual conductors. One or more layers of insulating film (such as polyester film) are tightly wrapped around the outside of the stranded conductor cores to fix the wire bundle, enhance the overall insulation strength and environmental resistance.

[0004] The enamel coating on the surface of copper conductors is crucial for ensuring electrical insulation. Depending on the raw materials, enamel coatings are mainly classified as polyurethane, polyester, and polyesterimide. Among them, polyurethane enamel coatings are particularly advantageous in precision electronic coils and high-frequency transformers due to their direct solderability, excellent flexibility, and low dielectric constant at high frequencies. However, polyurethane enamel coatings still suffer from dielectric loss. Under alternating electric fields, the dipole reorientation of polyurethane molecules leads to energy loss, especially in extreme high or low temperature environments where molecular motion changes, significantly increasing dielectric loss. This not only reduces equipment energy efficiency but may also affect system stability and safety due to localized overheating or insulation degradation, thus limiting the application potential of film-wrapped stranded wires in wider temperature ranges and high-frequency, high-field-strength scenarios. Therefore, it is necessary to find a low-dielectric-loss enamel coating composition that reduces the dielectric loss of polyurethane film-wrapped stranded wires while meeting the performance requirements of the enamel coating. Summary of the Invention

[0005] To address the aforementioned issues and further reduce the dielectric loss of polyurethane-based film-wrapped stranded wires while improving the mechanical properties of the coating film, this application provides a low dielectric loss coating film composition, its preparation method, and the film-wrapped stranded wire.

[0006] In a first aspect, this application provides a method for preparing a low dielectric loss coating film composition, the preparation steps of which include the following: S01. Take ferrocene carboxylic acid, octaphenylaminopropyl cage-like polysilsesquioxane, and diethylene glycol, mix them, disperse them with N,N-dimethylformamide, stir the reaction at room temperature to obtain a precursor liquid, then add octaphenylaminopropyl cage-like polysilsesquioxane, continue the reaction, then add N,N-dimethylformamide, redisperse, and record it as solution A for later use. S02. Mix diol and diisocyanate, heat and react, then add N,N-dimethylformamide to disperse, and continue treatment to obtain polyurethane prepolymer dispersion, which is designated as solution B for later use; S03. Mix liquid A and liquid B, then concentrate to obtain a paint film composition; In step S01, the mass-to-volume ratio of ferroceneic acid, octaphenylaminopropyl cage-like polysilsesquioxane, diethylene glycol, and N,N-dimethylformamide used in the precursor fluid is (3.5-5.5) g:(2-2.3) g:(1.3-2.1) g:(20-30) mL; the amount of octaphenylaminopropyl cage-like polysilsesquioxane added is 2-2.5 times the initial amount.

[0007] By employing the above technical solution, the carboxylic acid groups on ferrocene react with the amine groups on octaphenylaminopropyl cage-like polysilsesquioxane and the terminal hydroxyl groups of diethylene glycol to form a grafted composite structure. When subsequently blended with polyurethane prepolymer to form a film, this composite structure acts as a "microcapacitor," effectively suppressing dielectric losses caused by current in the coating film. Simultaneously, the octaphenylaminopropyl cage-like polysilsesquioxane in this grafted structure possesses a nanoscale cage-like structure, which can act as a physical barrier to isolate adjacent "microcapacitors," preventing the formation of interconnected conductive pathways and avoiding any impact on the insulation performance of the polyurethane coating film.

[0008] Furthermore, in step S01, the amount of N,N-dimethylformamide added is 3-4 times the amount added initially.

[0009] Furthermore, in step S01, the stirring speed is 50-150 r / min.

[0010] Furthermore, in step S02, the molar ratio of the diol to the diisocyanate is 1:(1.1-1.4).

[0011] Furthermore, in step S02, the diisocyanate is one or more of toluene-2,4-diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.

[0012] Furthermore, in step S02, the temperature of the heating reaction is set to 75-80℃, and the reaction time is 2-3 hours.

[0013] Furthermore, the solid content of the polyurethane prepolymer dispersion is 19.3%-21.2%.

[0014] Furthermore, in step S03, the volume ratio of liquid A to liquid B is 1:(50-100).

[0015] Secondly, this application provides a low dielectric loss coating composition, which is prepared by the above-described preparation method.

[0016] This application also provides a film-coated stranded wire, comprising a copper conductor and a surface coating composition thereof, the preparation steps of which include the following: Copper wires are taken, baked with enamel, and then inspected, stranded, and coated to obtain the final product. The enamel used in the baking process is a enamel film composition prepared by the above method. The baking process is set with an inlet temperature of 280-300℃, an outlet temperature of 375-405℃, and a traction speed of 38-40m / min.

[0017] Compared with the prior art, this application has the following beneficial effects: 1. In this application, ferrocene carboxylic acid, octaphenylaminopropyl cage-like polysilsesquioxane, diethylene glycol, etc. are mixed to prepare a ferrocene derivative dispersion. When the dispersion is blended with a polyurethane prepolymer dispersion and baked into a film, the trace amount of ferrocene derivative forms a dispersed "microcapacitor" in the polyurethane, thereby suppressing the dielectric loss of the film. The addition of octaphenylaminopropyl cage-like polysilsesquioxane, through its cage structure, spatially hinders the π-π stacking between ferrocene derivative molecules, so that the ferrocene derivative presents an "isolated island" state in the polyurethane matrix, avoiding the interaction of microcapacitors to form a long-range conductive network, which would affect the insulation performance of the insulating film.

[0018] 2. The unreacted octaphenylaminopropyl cage-like polysilsesquioxane and diethylene glycol molecules in the ferrocene derivative dispersion of this application can react with the residual isocyanate groups in the polyurethane prepolymer during the film-forming stage, thereby reinforcing and strengthening the paint film and improving its performance. Attached Figure Description

[0019] Figure 1 The dielectric loss factor-temperature change curves are for Example 1 and Control Groups 1-2 of this application.

[0020] Figure 2 The dielectric loss factor versus temperature (85-130℃) curves for Examples 1-3 and Control Groups 1-2 of this application are shown.

[0021] Figure 3 This is a schematic diagram of the membrane-covered stranded wire structure of this application.

[0022] Figure 4 This is a flow chart of the manufacturing process of the membrane-covered stranded wire in this application. Detailed Implementation

[0023] To make the inventive purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description of this application is provided in conjunction with embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0025] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0026] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0027] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0028] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0029] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0030] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0031] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0032] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0033] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0034] The schematic diagram of the membrane-covered stranded wire structure and the manufacturing process flow chart of this application are shown below. Figure 3 and Figure 4 As shown.

[0035] Example 1 S01. Add 3.5g of ferrocene carboxylic acid to a three-necked flask, mix with 2g of octaphenylaminopropyl cage-like polysilsesquioxane, 1.3g of diethylene glycol, 0.2g of 4-dimethylaminopyridine, and 1.1g of N,N'-dicyclohexylcarbodiimide, then add 20ml of DMF, adjust the stirring speed to 50r / min, and react for 2h. Then add 4g of octaphenylaminopropyl cage-like polysilsesquioxane to the system and continue to treat for 1h. Then add 3 times the volume of DMF, maintain the stirring speed and continue to treat for 5min to obtain homogeneous liquid A for later use.

[0036] S02. Add 35g of polytetrahydrofuran ether diol (Mn = 1000) to a three-necked flask, then place the three-necked flask in a 75°C water bath and stir. Add 6.7g of toluene-2,4-diisocyanate, purge with nitrogen, and react for 2 hours. Then add DMF and continue treatment for 1 hour. After cooling to room temperature, a polyurethane prepolymer dispersion with a solid content of 19.3% is obtained, which is denoted as solution B. S03. Mix liquid A and liquid B at a volume ratio (v / v) of 1:50, and then concentrate to a solid content of 34.2% to obtain a paint film composition.

[0037] In this embodiment, the preparation steps of the film-wrapped stranded wire are as follows: 1) Paint preparation: Stir the above-prepared paint film composition at high speed for 30 minutes and set aside; 2) Preparatory work before starting the machine: First, use a cotton cloth and brush to wipe all the guide wheels, the sand guide grooves in front and behind the guide wheels and the nylon strip clamps, all the heads of the machine head, the furnace inlet and outlet, the paint tank, the nylon strip shelf and nylon strip pressing block above the paint tank and the paint roller, etc. Then wipe them again with a small amount of acetone until they are clean and smooth; install one finished bobbin and one waste wire bobbin on each set of heads, replace the nylon strips on time, then check and record the bobbin markings on the wire record sheet, place the bobbin under the wire laying positioning steel ring, align it with the positioning steel ring vertically, and cover it with a brush; 3) Start-up: Connect the power supply, set the furnace inlet temperature to 280℃ and the furnace outlet temperature to 375℃. After the temperature reaches the set temperature, turn on the exhaust gas switch, turn the exhaust fan speed to 200r / min, set the traction speed to 38m / min, turn on the waxing device power supply, so that the wax enters the nylon strip of the waxing box and the entire nylon strip is soaked in wax; transport the wire spool to the wire feeding area, thread the wire through the felt pressure plate, wire groove, and guide wheel, and then to the annealing furnace mouth. Use steel wire to guide the wire into the thin tube of the annealing furnace. After the wire passes out of the annealing furnace, it passes through the wire hook and guide wheel into the oven mouth, and is split back and forth, and brought out of the oven mouth in 8 sections; 4) Coating: Pass the 0.2mm copper wire through the white nylon strip, thread it onto the guide wheel, and wind it onto the waste wire spool of the take-up spool. Turn on the spool power and slowly open it. After all the wire ends are wound onto the take-up spool, turn on the paint pump power to fill the paint tank with paint. Arrange the dry nylon strips and painted nylon strips neatly and evenly on the nylon strip shelf, and press them down with the nylon pressing plate that conforms to the wire gauge. Open all the take-up spools and slowly increase the speed to 60m / min. Open the paint tank to coat the copper wire. Slowly increase the speed to 120m / min and use a laser diameter gauge to measure the diameter. Record the outer diameter of each spool as 0.27±0.01mm.

[0038] 5) Twisting: Twisting the enameled copper wire monofilaments from the previous step, setting the maximum number of twisting times to 4, the maximum number of strands to 7200, the maximum finished outer diameter to 8mm, and the minimum twist pitch to 2.2mm.

[0039] 6) Coating: The stranded wires can be coated with polyester film (UL rating 155) or polyimide film (UL rating 220).

[0040] Example 2 S01. Add 4.2 g of ferrocene carboxylic acid to a three-necked flask, mix it with 2.1 g of octaphenylaminopropyl cage-like polysilsesquioxane, 1.5 g of diethylene glycol, 0.2 g of 4-dimethylaminopyridine, and 1.3 g of N,N'-dicyclohexylcarbodiimide, then add 25 mL of DMF, adjust the stirring speed to 50 r / min, and react for 2.5 h. Then add 4.2 g of octaphenylaminopropyl cage-like polysilsesquioxane to the system and continue to treat for 1 h. After that, add 3.3 times the volume of DMF, maintain the stirring speed and continue to treat for 10 min to obtain homogeneous liquid A for later use.

[0041] S02. Add 35g of polytetrahydrofuran ether diol (Mn = 1000) to a three-necked flask, then place the three-necked flask in an 80°C water bath and stir. Add 7.6g of hexamethylene diisocyanate, purge with nitrogen, and react for 3 hours. Then add DMF and continue treatment for 1 hour. After cooling to room temperature, a polyurethane prepolymer dispersion with a solid content of 20.8% is obtained, which is denoted as solution B. S03. Mix liquid A and liquid B at a volume ratio (v / v) of 1:75, and then concentrate to a solid content of 33% to obtain a paint film composition.

[0042] In this embodiment, the preparation steps of the film-wrapped stranded wire are as follows: 1) Paint preparation: Stir the above-prepared paint film composition at high speed for 30 minutes and set aside; 2) Preparatory work before starting the machine: First, use a cotton cloth and brush to wipe all the guide wheels, the sand guide grooves in front and behind the guide wheels and the nylon strip clamps, all the heads of the machine head, the furnace inlet and outlet, the paint tank, the nylon strip shelf and nylon strip pressing block above the paint tank and the paint roller, etc. Then wipe them again with a small amount of acetone until they are clean and smooth; install one finished bobbin and one waste wire bobbin on each set of heads, replace the nylon strips on time, then check and record the bobbin markings on the wire record sheet, place the bobbin under the wire laying positioning steel ring, align it with the positioning steel ring vertically, and cover it with a brush; 3) Start-up: Connect the power supply, set the furnace inlet temperature to 300℃ and the furnace outlet temperature to 405℃. After the temperature reaches the set temperature, turn on the exhaust gas switch, turn the exhaust fan speed to 200r / min, set the traction speed to 40m / min, turn on the waxing device power supply, and let the white wax enter the nylon strip of the waxing box, so that the entire nylon strip is soaked in white wax; transport the wire spool to the wire feeding area, thread the wire through the felt pressure plate, wire groove, and guide wheel, and then to the annealing furnace mouth. Use steel wire to guide the wire into the thin tube of the annealing furnace. After the wire passes out of the annealing furnace, it passes through the wire hook and guide wheel into the oven mouth, performs back and forth wire splitting, and brings it out of the oven mouth in 8 segments; 4) Coating: Pass the 0.2mm copper wire through the white nylon strip, thread it onto the guide wheel, and wind it onto the waste wire spool of the take-up spool. Turn on the spool power and slowly open it. After all the wire ends are wound onto the take-up spool, turn on the paint pump power to fill the paint tank with paint. Arrange the dry nylon strips and painted nylon strips neatly and evenly on the nylon strip shelf, and press them down with the nylon pressing plate that conforms to the wire gauge. Open all the take-up spools and slowly increase the speed to 60m / min. Open the paint tank to coat the copper wire. Slowly increase the speed to 120m / min and use a laser diameter gauge to measure the diameter. Record the outer diameter of each spool as 0.27±0.01mm.

[0043] 5) Twisting: Twisting the enameled copper wire monofilaments from the previous step, setting the maximum number of twisting times to 4, the maximum number of strands to 7200, the maximum finished outer diameter to 8mm, and the minimum twist pitch to 2.2mm.

[0044] 6) Coating: The stranded wires can be coated with polyester film (UL rating 155) or polyimide film (UL rating 220).

[0045] Example 3 S01. Add 5.5g of ferrocene carboxylic acid to a three-necked flask, mix it with 2.3g of octaphenylaminopropyl cage-like polysilsesquioxane, 2.1g of diethylene glycol, 0.3g of 4-dimethylaminopyridine, and 1.5g of N,N'-dicyclohexylcarbodiimide, then add 30ml of DMF, adjust the stirring speed to 150r / min, and react for 3h. Then add 5.8g of octaphenylaminopropyl cage-like polysilsesquioxane to the system and continue to treat for 2h. After that, add 4 times the volume of DMF, maintain the stirring speed and continue to treat for 20min to obtain homogeneous liquid A for later use.

[0046] S02. Add 35g of polytetrahydrofuran ether diol (Mn = 1000) to a three-necked flask, then place the three-necked flask in an 80°C water bath and stir. Add 12.3g of diphenylmethane diisocyanate, purge with nitrogen, and react for 3 hours. Then add DMF and continue treatment for 2 hours. After cooling to room temperature, a polyurethane prepolymer dispersion with a solid content of 21.2% is obtained, which is denoted as solution B. S03. Mix liquid A and liquid B at a volume ratio (v / v) of 1:100, and then concentrate to a solid content of 35% to obtain a paint film composition.

[0047] The preparation steps of the membrane-wrapped stranded wire in this embodiment are the same as those in Example 1.

[0048] Control group 1 The difference between this control group and Example 1 is that an equal amount of polydimethylsiloxane was used instead of octaphenylaminopropyl cage-like polysilsesquioxane.

[0049] The remaining steps are the same as in Example 1.

[0050] Among them, polydimethylsiloxane (model: DM5) was supplied by Huangshan Qiangli Chemical Co., Ltd.

[0051] Control group 2 The difference between this control group and Example 1 is that the polyurethane prepolymer dispersion was directly concentrated to a solid content of 32.7% to obtain the coating composition.

[0052] The remaining steps are the same as in Example 1.

[0053] Performance testing Preparation of enameled wire coating for testing The paint film compositions of Examples 1-3 and Control Groups 1-2 were laid flat on a polytetrafluoroethylene plate and allowed to dry naturally at room temperature for 24 hours. Then, they were placed in a forced-air drying oven and dried at 65°C for 6 hours, followed by drying in a vacuum drying oven at 65°C for 6 hours. The resulting samples were cut into dumbbell-shaped standard strips with a length of 40 mm and a width of 10 mm for later use. The paint film thickness was measured to be 0.3 ± 0.1 mm.

[0054] Thermal aging treatment: Take the cut standard samples of Examples 1-3 and Control Groups 1-2 and place them in a muffle furnace. Heat them to 180°C and keep them at that temperature for 12 hours before storing them for subsequent appearance performance testing.

[0055] Table 1. Apparent performance test results of Examples 1-3 and Control Groups 1-2 Surface quality, visual inspection; number of pinholes, visual inspection; breakdown voltage, GB / T1408.1-2016; tensile strength and elongation at break, the tensile strength and elongation at break of the standard specimens were measured using a benchtop electronic precision universal testing machine, and tensile tests were conducted using a 500N sensor at a tensile rate of 100 mm / min. The average value of three tensile specimens was taken as the test result; thermal shock properties, GB / T 4074.6-2024 (200℃ / 1d, 230℃ / 1d).

[0056] Combining Examples 1-3, Control Groups 1-2, and Table 1, it can be seen that the paint film prepared using the example scheme has good surface quality after heat aging treatment, and has high tensile strength and elongation at break. After being treated at 200℃ and 230℃ for 1 day, the paint film did not crack and maintained good integrity. In contrast, the tensile strength and elongation at break of the polyurethane paint film in Control Group 2 decreased, which was not as good as the example scheme. Moreover, the paint film cracked under the thermal shock condition of 230℃ / 1 day, indicating poor thermal shock performance. Control Group 1 used polydimethylsiloxane instead of octaphenylaminopropyl cage-like polysilsesquioxane. Due to the lack of interaction between the introduced polydimethylsiloxane and the polyurethane matrix, the phase separation of the paint film was aggravated, the apparent performance of the paint film was significantly reduced, and the quality of the paint film was poor. Furthermore, the paint film in Control Group 1 after the replacement had insulation problems, resulting in a significant decrease in its breakdown voltage compared to the other groups.

[0057] Dielectric loss factor test The dielectric loss tester (model: TD7S) was used in accordance with the national standard GB / T4074.5-2024. During the test, film-coated stranded wire samples from Examples 1-3 and Control Groups 1-2 were used. Test conditions were: sample length 150mm, test frequency 1kHz, AC voltage 1.0V, and dielectric loss factor test range of 0-0.1. The dielectric loss factor-temperature change curves for Examples 1 and Control Groups 1-2 during the test are shown below. Figure 1 As shown; the dielectric loss factor-temperature variation curves of Examples 1-3 and Control Groups 1-2 under temperature conditions of 85-130℃ are as follows. Figure 2 As shown.

[0058] Combining Examples 1-3, Control Groups 1-2, and Figures 1-2It can be seen that the dielectric loss factor of both Example 1 and Control Groups 1-2 showed a trend of first slowly increasing and then suddenly increasing with temperature. The peak inflection point of the dielectric loss factor with temperature change was concentrated between 159.2-164.9℃, which coincides with the glass transition temperature of the polyurethane coating. Due to the relaxation of the orientation polarization of the polyurethane dipoles caused by the glass transition, the dielectric loss of the coating increased sharply. Moreover, before reaching the glass transition temperature, the dielectric loss factor of the coating films in Control Groups 1-2 was greater than that in Example 1. Further combined with Figure 2 Data shows that under extreme operating temperatures of the coating film, the dielectric loss factor of the control group 1-2 increases approximately exponentially with increasing temperature, while the embodiment scheme can still maintain a low dielectric loss factor under the test environment. The dielectric loss of the coating film is lower than that of the control group, which can meet the industrial requirements of low-loss transmission.

[0059] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a low dielectric loss coating film composition, characterized in that, The preparation steps include the following: S01. Take ferrocene carboxylic acid, octaphenylaminopropyl cage-like polysilsesquioxane, and diethylene glycol, mix them, disperse them with N,N-dimethylformamide, stir the reaction at room temperature to obtain a precursor liquid, then add octaphenylaminopropyl cage-like polysilsesquioxane, continue the reaction, then add N,N-dimethylformamide, redisperse, and record it as solution A for later use. S02. Mix diol and diisocyanate, heat and react, then add N,N-dimethylformamide to disperse, and continue treatment to obtain polyurethane prepolymer dispersion, which is designated as solution B for later use; S03. Mix liquid A and liquid B, and then concentrate to obtain a paint film composition.

2. The method for preparing a low dielectric loss coating composition according to claim 1, characterized in that, In step S01, the mass-to-volume ratio of ferroceneic acid, octaphenylaminopropyl cage-like polysilsesquioxane, diethylene glycol, and N,N-dimethylformamide used in the precursor fluid is (3.5-5.5) g:(2-2.3) g:(1.3-2.1) g:(20-30) mL; the amount of octaphenylaminopropyl cage-like polysilsesquioxane added is 2-2.5 times the initial amount.

3. The method for preparing a low dielectric loss coating composition according to claim 1, characterized in that, In step S01, the amount of N,N-dimethylformamide added is 3-4 times the amount added initially.

4. The method for preparing a low dielectric loss coating composition according to claim 1, characterized in that, In step S01, the stirring speed is 50-150 r / min.

5. The method for preparing a low dielectric loss coating film composition according to claim 1, characterized in that, In step S02, the molar ratio of diol to diisocyanate used is 1:(1.1-1.4).

6. The method for preparing a low dielectric loss coating composition according to claim 1, characterized in that, In step S02, the diisocyanate is one or more of toluene-2,4-diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate.

7. The method for preparing a low dielectric loss coating film composition according to claim 1, characterized in that, In step S02, the temperature for the heating reaction is set at 75-80℃, and the reaction is carried out for 2-3 hours; the solid content of the polyurethane prepolymer dispersion is 19.3%-21.2%.

8. The method for preparing a low dielectric loss coating composition according to claim 1, characterized in that, In step S03, the volume ratio of liquid A to liquid B is 1:(50-100).

9. A low dielectric loss coating composition, characterized in that, It is prepared by any one of the preparation methods described in claims 1-8.

10. A film-wrapped stranded wire, characterized in that, The composition includes a copper conductor and its surface coating, and the preparation steps include the following: Copper wires are taken, baked with enamel, and then inspected, stranded, and coated to obtain the final product. The enamel used in the baking process is the low dielectric loss enamel film composition as described in claim 9. The baking process is set with an inlet temperature of 280-300℃, an outlet temperature of 375-405℃, and a traction speed of 38-40m / min.

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