Epoxy resin-based high-voltage-resistant high-resistance powder coating and preparation method thereof
By combining alicyclic epoxy resin and glycidyl ether epoxy resin with flexible insulating polyamide fiber and modified boron nitride nanosheets to form a dense network, the electrical and mechanical damage problems of epoxy resin powder coatings under high temperature and high pressure environments are solved, and the high resistivity and high pressure resistance performance are improved, making it suitable for surface coating of new energy vehicle battery boxes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG SUNRIS ENVIRONMENTAL PROTECTION NEW MATERIAL CO LTD
- Filing Date
- 2026-03-02
- Publication Date
- 2026-05-12
AI Technical Summary
Existing epoxy resin powder coatings suffer severe electrical and mechanical damage under high temperature and high pressure environments, failing to effectively improve the resistivity and high pressure resistance of the coatings.
A compound of alicyclic epoxy resin and glycidyl ether epoxy resin is used, combined with flexible insulating polyamide fiber and modified boron nitride nanosheet filler, to form a dense network through hydrogen bonding, which inhibits charge migration and partial discharge, and improves insulation performance and mechanical strength.
It significantly improves the resistivity and high voltage resistance of powder coatings, suppresses insulation breakdown and partial discharge, and enhances the adhesion and impact resistance of the coating, making it suitable for surface coating of battery boxes in new energy vehicles.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of epoxy resin powder coating manufacturing technology, specifically relating to an epoxy resin-based high-voltage-resistant and high-resistance powder coating and its preparation method. Background Technology
[0002] Powder coatings are solid powders composed of solid resin, curing agents, pigments, fillers, and additives. They adhere to the surface of a workpiece through electrostatic spraying or other methods, and are then baked at high temperatures to melt, level, and cure, forming a strong and dense coating. Epoxy powder coatings differ fundamentally from traditional liquid coatings in morphology, application, and curing principles. They exhibit extremely strong adhesion, high hardness, excellent chemical resistance, and superior electrical insulation, making them a commonly used coating for high-voltage electrical equipment. While my country currently ranks among the world's leading producers of epoxy resin, its production and research have primarily focused on general-purpose epoxy products of common grades. These general-purpose epoxy resins, when used in high-power power electronic devices, cannot withstand the electrical and mechanical damage caused by high temperatures, high pressures, and other multi-field effects. Therefore, it is necessary to add insulating fillers to modify the insulating and mechanical properties of epoxy resins. Thus, developing epoxy resin composite insulating materials with excellent insulating and mechanical properties is of great significance.
[0003] Chinese invention patent CN117384528B discloses a formula and preparation method for a high-temperature and high-voltage resistant insulating coating. The formula comprises the following components in parts by weight: 60-100 parts epoxy resin, 20-80 parts polyesterimide resin, 20-80 parts bismaleimide resin, 20-40 parts curing agent, 40-80 parts color filler, 2-10 parts leveling agent, and 2-20 parts accelerator. The epoxy resin, polyesterimide resin, and bismaleimide resin are mixed as a film-forming substrate. This invention uses epoxy resin as the main film-forming substrate, supplemented by polyesterimide resin and bismaleimide resin, and the three are mixed as a film-forming substrate. After spraying and curing, the insulating coating has a smooth and flat surface, free from scratches, damage, peeling, and other defects. The coating thickness can meet the construction requirements of 100μm-150μm, and it exhibits excellent high-temperature and high-voltage resistance. However, existing technologies have a technical problem: they do not further improve the resistivity and high-voltage resistance of coatings by modifying the composition of insulating powder. Summary of the Invention
[0004] The purpose of this invention is to provide an epoxy resin-based high-voltage and high-resistivity powder coating and its preparation method, which solves the technical problem in the prior art that the resistivity and high-voltage resistance of the coating have not been further improved by modifying the composition of the epoxy resin.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: An epoxy resin-based high-voltage and high-resistance powder coating is prepared from the following raw materials in parts by weight: 40-50 parts alicyclic epoxy resin, 30-40 parts glycidyl ether epoxy resin, 8-10 parts flexible insulating polyamide fiber, 5-8 parts insulating filler, 15-25 parts curing agent, 0.5-2 parts leveling agent, 0.5-2 parts defoamer, and 1-5 parts curing accelerator.
[0006] The alicyclic epoxy resin has an epoxy equivalent of 190-210, and the glycidyl ether epoxy resin is any one of E51, E20, and E44. The curing agent is an acid anhydride curing agent, and the curing accelerator is a tertiary amine accelerator.
[0007] Preferably, the preparation method of the flexible insulating polyamide fiber includes the following steps: S11. 1,4-bis(4-aminophenoxy)benzene and N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere, and isophthaloyl chloride was added dropwise at low temperature. After the reaction was completed, deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. Aromatic polyamide is added to concentrated sulfuric acid and wet-spun to obtain aramid fiber. The aramid fiber is added to a modifying solvent and heated to modify it. The fiber is collected by filtration, washed and vacuum dried to obtain modified aramid fiber. S13. Modified aramid fibers are added to dimethyl sulfoxide and oxalic acid, ball-milled to obtain a dispersion, acetone is added to precipitate, the precipitate is collected by filtration, washed and vacuum dried to obtain flexible insulating polyamide fibers.
[0008] Preferably, the mass ratio of 1,4-bis(4-aminophenoxy)benzene, N,N-dimethylacetamide and isophthaloyl chloride in S11 is 29~31:100~150:20~22, and the reaction is carried out by adding isophthaloyl chloride dropwise at -5~-10℃ for 0.5~1h.
[0009] Preferably, in step S12, the amount of aromatic polyamide added is 15-20% of the mass of concentrated sulfuric acid, the micropore diameter of the spinneret is 0.03-0.04 mm, the spinning is carried out at a spinning speed of 200-300 m / min at room temperature, the fibers are coagulated in deionized water, collected by a drawing roller at 60-120℃, and cut into segments to obtain aramid fibers with an aspect ratio of 5-10:1. The modified solvent is prepared by adding 1.2-1.4 g of tris(hydroxymethyl)aminomethane to 250-300 mL of deionized water, adjusting the pH to 8.5 by adding hydrochloric acid, and dissolving 0.5-0.8 g of dopamine. The mass ratio of aromatic polyamide to modified solvent is 3-5:60-80. The reaction is carried out at 40-50℃ for 12-24 h, and the fibers are washed with deionized water until neutral.
[0010] Preferably, in S13, the mass ratio of modified aramid fiber, dimethyl sulfoxide, and oxalic acid is 1:2.5~3:0.1~0.15, ball milling is performed for 40~60 min, the amount of acetone added is 200~300% of the mass of dimethyl sulfoxide, the mixture is washed with acetone until neutral, and vacuum dried at 40~60℃. The average diameter of the flexible insulating polyamide fiber is 200~300 nm, and the average aspect ratio is 600~800:1.
[0011] Preferably, the method for preparing the insulating filler includes the following steps: S21. Add boron nitride and ethanol to a ball mill and ball mill to obtain a suspension. After centrifugation and filtration of the suspension, take the supernatant and dry it to obtain boron nitride nanosheets. S22. Add tannic acid and deionized water to the reaction vessel and stir to dissolve. Add nano boron nitride sheets to ethanol, disperse ultrasonically, and then add to the reaction vessel. React at room temperature, filter to remove the solid, wash and dry to obtain the insulating filler.
[0012] Preferably, in S21, the mass ratio of boron nitride to ethanol is 1~2:7~10. The mixture is ball-milled at 400~500 rpm for 12~16 h, centrifuged and filtered at 1000~3000 rpm for 20~30 min, and dried at 80~100℃. The average thickness of the boron nitride nanosheets is 7~10 nm, and the average diameter is 5~10 μm.
[0013] Preferably, the mass ratio of tannic acid, deionized water, nano boron nitride sheets and ethanol in S22 is 2~3:50~60:3~5:20~30, the reaction is carried out at room temperature for 20~24h, washed with deionized water, and dried under vacuum at 80~100℃.
[0014] A method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating includes the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Add alicyclic epoxy resin and glycidyl ether epoxy resin to a mixing tank, add leveling agent and defoamer, and stir at 300~500 rpm for 5~10 min. Then add insulating filler and flexible insulating polyamide fiber and stir at 2000~3000 rpm for 3~5 min. Finally, add curing agent and curing accelerator and stir at 500~800 rpm for 2~3 min at 30~40℃. Melt extrusion granulation is performed at 140~150℃, and the mixture is ground through a 300 mesh sieve to obtain an epoxy resin-based high pressure resistance and high resistance powder coating.
[0015] An application of an epoxy resin-based high-voltage and high-resistance powder coating involves spraying the powder coating, heating it to 100-120℃ for 1-2 hours, and then heating it to 130-140℃ for 3-4 hours to obtain an insulating coating.
[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention prepares boron nitride nanosheets by ball milling and mechanically exfoliating boron nitride, and then modifies the surface with tannic acid to prepare an insulating filler. The tannic acid is anchored to the boron atoms on the surface of boron nitride through the reaction of phenolic hydroxyl groups, introducing polar phenolic hydroxyl groups, so that the insulating filler can be uniformly dispersed in epoxy resin, reducing the insulation breakdown phenomenon caused by the accumulation of charge at the interface between epoxy resin and filler due to interfacial polarization.
[0017] 2. This invention obtains aromatic polyamide by reacting 1,4-bis(4-aminophenoxy)benzene and isophthaloyl chloride, then melt-spins it to obtain polyamide fibers. After surface modification with dopamine, flexible insulating polyamide fibers are obtained by wet ball milling. Dopamine modification enhances the chemical activity of the polyamide fiber surface and improves its dispersibility in epoxy resin. It can form a dense network with insulating fillers through hydrogen bonding, inhibiting the accumulation and migration of space charge, significantly improving the mechanical strength and insulation performance of powder coatings. Furthermore, polyamide has excellent thermal stability and can maintain its insulation performance under extreme environments.
[0018] 3. This invention uses alicyclic epoxy resin and glycidyl ether epoxy resin in combination. The rigid alicyclic groups of the alicyclic epoxy resin inhibit charge migration and improve the breakdown field strength, while the glycidyl ether epoxy resin adjusts the toughness of the resin to ensure a strong bond between the coating and the substrate. The flexible insulating polyamide fiber can form a dense network with the insulating filler through hydrogen bonding, effectively suppressing partial discharge and breakdown. The network also shares the impact stress of the powder coating, improving the adhesion and impact resistance of the powder coating. The powder coating prepared by this invention is less prone to sagging and can form a coating of 60~600μm on the workpiece surface. The coating process is simple and can be automated for production lines, making it suitable for the surface of battery boxes in new energy vehicles. Detailed Implementation
[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] The curing agent involved in this invention is phthalic anhydride, the curing accelerator is 2,4,6-tris(dimethylaminomethyl)phenol, the leveling agent is BYK-333, and the defoamer is BYK-A530.
[0021] Example 1: An epoxy resin-based high-voltage and high-resistance powder coating of this example is prepared from the following raw materials: 45g of alicyclic epoxy resin, 30g of glycidyl ether epoxy resin, 10g of flexible insulating polyamide fiber, 5g of insulating filler, 15g of curing agent, 0.5g of leveling agent, 2g of defoamer and 3g of curing accelerator.
[0022] The alicyclic epoxy resin is of type S28, and the glycidyl ether epoxy resin is of type E51. The preparation method of the flexible insulating polyamide fiber in this embodiment includes the following steps: S11. 30g of 1,4-bis(4-aminophenoxy)benzene and 100g of N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere. 20g of isophthaloyl chloride was added dropwise at -5℃ and the reaction was carried out for 0.5h. After the reaction was completed, 300g of deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. Add 20g of aromatic polyamide to 100g of 98% concentrated sulfuric acid. The spinneret has a micropore diameter of 0.03mm. Spin at a spinning speed of 300m / min at room temperature. Add deionized water to solidify. Collect the fibers using a 60℃ drawing roller to obtain aramid fibers. Add 10g of aramid fibers to 200g of modified solvent and react at 40℃ for 24h. The modified solvent is prepared by adding 1.2g of tris(hydroxymethyl)aminomethane to 300mL of deionized water, adjusting the pH to 8.5 with hydrochloric acid, and dissolving with 0.8g of dopamine. Filter to collect the fibers, wash with deionized water until neutral, and vacuum dry at 50℃ to obtain modified aramid fibers. S13. 10g of modified aramid fiber was added to 25g of dimethyl sulfoxide and 1.5g of oxalic acid, and ball-milled for 60min to obtain a dispersion. The dispersion was precipitated in 75g of acetone, filtered and collected, washed with acetone until neutral, and dried under vacuum at 60℃ to obtain flexible insulating polyamide fiber. The average diameter of the flexible insulating polyamide fiber was 240nm and the average aspect ratio was 600:1.
[0023] The method for preparing the insulating filler in this embodiment includes the following steps: S21. Add 10g of boron nitride and 100g of ethanol to a ball mill and mill at 500rpm for 12h to obtain a suspension. Centrifuge and filter the suspension at 1000rpm for 20min. Take the supernatant and dry it at 80℃ to obtain boron nitride nanosheets. The average thickness of the boron nitride nanosheets is 8nm and the average diameter is 5μm. S22. Add 2g of tannic acid and 50g of deionized water to the reaction vessel and stir to dissolve. Add 5g of nano boron nitride sheets to 30g of ethanol and ultrasonically disperse for 30min before adding to the reaction vessel. React at room temperature for 24h. Filter to remove the solid, wash with deionized water, and vacuum dry at 100℃ to obtain the insulating filler.
[0024] This embodiment describes a method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating, comprising the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Alicyclic epoxy resin and glycidyl ether epoxy resin are added to a mixing tank. Leveling agent and defoamer are added and stirred at 300 rpm for 5 min. Then, insulating filler and flexible insulating polyamide fiber are added and stirred at 2000 rpm for 3 min. Finally, curing agent and curing accelerator are added and stirred at 500 rpm for 2 min at 40℃. The mixture is then melt-extruded and granulated at 140℃ and ground through a 300-mesh sieve to obtain an epoxy resin-based high-pressure-resistant and high-resistance powder coating.
[0025] This embodiment describes the application of an epoxy resin-based high-voltage and high-resistance powder coating. After spraying the powder coating, the temperature is raised to 110°C and cured for 1 hour, and then raised to 140°C and cured for 4 hours to obtain an insulating coating.
[0026] Example 2: An epoxy resin-based high-voltage and high-resistance powder coating of this example is prepared from the following raw materials: 40g of alicyclic epoxy resin, 30g of glycidyl ether epoxy resin, 9.5g of flexible insulating polyamide fiber, 6g of insulating filler, 20g of curing agent, 1g of leveling agent, 1g of defoamer and 1g of curing accelerator.
[0027] The alicyclic epoxy resin is of type S28, and the glycidyl ether epoxy resin is of type E20. The preparation method of the flexible insulating polyamide fiber in this embodiment includes the following steps: S11. 29g of 1,4-bis(4-aminophenoxy)benzene and 150g of N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere. 22g of isophthaloyl chloride was added dropwise at -10℃ and the reaction was carried out for 0.5h. After the reaction was completed, 500g of deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. Add 16g of aromatic polyamide to 100g of 98% concentrated sulfuric acid. The spinneret has a micropore diameter of 0.03mm. Spin at a spinning speed of 300m / min at room temperature. Add deionized water to solidify. Collect the fibers with a 100℃ drawing roller to obtain aramid fibers. Add 10g of aramid fibers to 160g of modified solvent and react at 45℃ for 12h. The modified solvent is prepared by adding 1.2g of tris(hydroxymethyl)aminomethane to 300mL of deionized water, adjusting the pH to 8.5 with hydrochloric acid, and dissolving with 0.5g of dopamine. Filter to collect the fibers, wash with deionized water until neutral, and vacuum dry at 40℃ to obtain modified aramid fibers. S13. 10g of modified aramid fiber was added to 26g of dimethyl sulfoxide and 1.5g of oxalic acid, and ball-milled for 45min to obtain a dispersion. The dispersion was precipitated in 60g of acetone, filtered and collected, washed with acetone until neutral, and dried under vacuum at 60℃ to obtain flexible insulating polyamide fiber. The average diameter of the flexible insulating polyamide fiber was 280nm and the average aspect ratio was 750:1.
[0028] The method for preparing the insulating filler in this embodiment includes the following steps: S21. Add 15g of boron nitride and 75g of ethanol to a ball mill and mill at 400rpm for 12h to obtain a suspension. Centrifuge and filter the suspension at 1500rpm for 20min. Take the supernatant and dry it at 100℃ to obtain boron nitride nanosheets. The average thickness of the boron nitride nanosheets is 8nm and the average diameter is 6μm. S22. Add 4g of tannic acid and 100g of deionized water to the reaction vessel and stir to dissolve. Add 6g of nano boron nitride sheets to 40g of ethanol and ultrasonically disperse for 30min before adding to the reaction vessel. React at room temperature for 20h. Filter to remove the solid, wash with deionized water, and vacuum dry at 100℃ to obtain the insulating filler.
[0029] This embodiment describes a method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating, comprising the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Alicyclic epoxy resin and glycidyl ether epoxy resin are added to a mixing tank. Leveling agent and defoamer are added and stirred at 400 rpm for 7 minutes. Then, insulating filler and flexible insulating polyamide fiber are added and stirred at 2400 rpm for 4 minutes. Finally, curing agent and curing accelerator are added and stirred at 800 rpm for 3 minutes at 30°C. The mixture is then melt-extruded and granulated at 145°C and ground through a 300-mesh sieve to obtain an epoxy resin-based high-pressure-resistant and high-resistance powder coating.
[0030] This embodiment describes the application of an epoxy resin-based high-voltage and high-resistance powder coating. After spraying the powder coating, the temperature is raised to 120°C and cured for 2 hours, and then raised to 140°C and cured for 4 hours to obtain an insulating coating.
[0031] Example 3: An epoxy resin-based high-voltage and high-resistance powder coating of this example is prepared from the following raw materials: 50g of alicyclic epoxy resin, 35g of glycidyl ether epoxy resin, 8g of flexible insulating polyamide fiber, 7g of insulating filler, 20g of curing agent, 2g of leveling agent, 0.5g of defoamer and 5g of curing accelerator.
[0032] The alicyclic epoxy resin is model EPR-2081, and the glycidyl ether epoxy resin is E44. The preparation method of the flexible insulating polyamide fiber in this embodiment includes the following steps: S11. 30g of 1,4-bis(4-aminophenoxy)benzene and 130g of N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere. 21g of isophthaloyl chloride was added dropwise at -6℃ and reacted for 1h. After the reaction was completed, 400g of deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. Add 20g of aromatic polyamide to 100g of 98% concentrated sulfuric acid. The spinneret has a micropore diameter of 0.04mm. Spin at a spinning speed of 250m / min at room temperature. Add deionized water to solidify. Collect the fibers using a drawing roller at 80℃ to obtain aramid fibers. Add 10g of aramid fibers to 140g of modified solvent and react at 40℃ for 24h. The modified solvent is prepared by adding 1.4g of tris(hydroxymethyl)aminomethane to 300mL of deionized water, adjusting the pH to 8.5 with hydrochloric acid, and dissolving with 0.8g of dopamine. Filter to collect the fibers, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain modified aramid fibers. S13. 10g of modified aramid fiber was added to 29g of dimethyl sulfoxide and 1g of oxalic acid, and ball-milled for 60min to obtain a dispersion. The dispersion was precipitated in 70g of acetone, filtered and collected, washed with acetone until neutral, and vacuum dried at 50℃ to obtain flexible insulating polyamide fiber. The average diameter of the flexible insulating polyamide fiber was 210nm and the average aspect ratio was 800:1.
[0033] The method for preparing the insulating filler in this embodiment includes the following steps: S21. Add 20g of boron nitride and 80g of ethanol to a ball mill and mill at 500rpm for 16h to obtain a suspension. Centrifuge and filter the suspension at 3000rpm for 30min. Take the supernatant and dry it at 90℃ to obtain boron nitride nanosheets. The average thickness of the boron nitride nanosheets is 10nm and the average diameter is 5μm. S22. Add 5g of tannic acid and 120g of deionized water to the reaction vessel and stir to dissolve. Add 10g of nano boron nitride sheets to 50g of ethanol and ultrasonically disperse for 30min before adding to the reaction vessel. React at room temperature for 24h. Filter to remove the solid, wash with deionized water, and vacuum dry at 80℃ to obtain the insulating filler.
[0034] This embodiment describes a method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating, comprising the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Alicyclic epoxy resin and glycidyl ether epoxy resin are added to a mixing tank. Leveling agent and defoamer are added and stirred at 400 rpm for 8 minutes. Then, insulating filler and flexible insulating polyamide fiber are added and stirred at 2800 rpm for 5 minutes. Finally, curing agent and curing accelerator are added and stirred at 600 rpm for 3 minutes at 30°C. The mixture is then melt-extruded and granulated at 150°C and ground through a 300-mesh sieve to obtain an epoxy resin-based high-pressure-resistant and high-resistance powder coating.
[0035] This embodiment describes the application of an epoxy resin-based high-voltage and high-resistance powder coating. After spraying the powder coating, the temperature is raised to 100°C and cured for 1 hour, and then raised to 130°C and cured for 3 hours to obtain an insulating coating.
[0036] Example 4: An epoxy resin-based high-voltage and high-resistance powder coating of this example is prepared from the following raw materials: 50g of alicyclic epoxy resin, 40g of glycidyl ether epoxy resin, 10g of flexible insulating polyamide fiber, 8g of insulating filler, 25g of curing agent, 2g of leveling agent, 2g of defoamer and 5g of curing accelerator.
[0037] The alicyclic epoxy resin is model EPR-2081, and the glycidyl ether epoxy resin is E51. The preparation method of the flexible insulating polyamide fiber in this embodiment includes the following steps: S11. 31g of 1,4-bis(4-aminophenoxy)benzene and 140g of N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere. 22g of isophthaloyl chloride was added dropwise at -9℃ and reacted for 1h. After the reaction was completed, 400g of deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. 17.5g of aromatic polyamide was added to 100g of 98% concentrated sulfuric acid. The spinneret had a micropore diameter of 0.04mm. Spinning was carried out at a spinning speed of 250m / min at room temperature. The fibers were then coagulated in deionized water and collected using a 120℃ drawing roller to obtain aramid fibers. 10g of aramid fibers were added to 150g of modified solvent and reacted at 40℃ for 18h. The modified solvent was prepared by adding 1.3g of tris(hydroxymethyl)aminomethane to 270mL of deionized water, adjusting the pH to 8.5 with hydrochloric acid, and dissolving it with 0.7g of dopamine. The fibers were collected by filtration, washed with deionized water until neutral, and dried under vacuum at 60℃ to obtain modified aramid fibers. S13. 10g of modified aramid fiber was added to 30g of dimethyl sulfoxide and 1g of oxalic acid, and ball-milled for 55min to obtain a dispersion. The dispersion was precipitated in 90g of acetone, filtered and collected, washed with acetone until neutral, and dried under vacuum at 50℃ to obtain flexible insulating polyamide fiber. The average diameter of the flexible insulating polyamide fiber was 230nm and the average aspect ratio was 650:1.
[0038] The method for preparing the insulating filler in this embodiment includes the following steps: S21. Add 15g of boron nitride and 90g of ethanol to a ball mill and mill at 450rpm for 16h to obtain a suspension. Centrifuge and filter the suspension at 2000rpm for 25min. Take the supernatant and dry it at 90℃ to obtain boron nitride nanosheets. The average thickness of the boron nitride nanosheets is 9nm and the average diameter is 7μm. S22. Add 4g of tannic acid and 100g of deionized water to the reaction vessel and stir to dissolve. Add 10g of nano boron nitride sheets to 60g of ethanol and ultrasonically disperse for 30min before adding to the reaction vessel. React at room temperature for 24h. Filter to remove the solid, wash with deionized water, and vacuum dry at 100℃ to obtain the insulating filler.
[0039] This embodiment describes a method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating, comprising the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Alicyclic epoxy resin and glycidyl ether epoxy resin are added to a mixing tank. Leveling agent and defoamer are added and stirred at 300 rpm for 5 min. Then, insulating filler and flexible insulating polyamide fiber are added and stirred at 2500 rpm for 4 min. Finally, curing agent and curing accelerator are added and stirred at 600 rpm for 2.5 min at 35℃. The mixture is then melt-extruded and granulated at 150℃ and ground through a 300-mesh sieve to obtain an epoxy resin-based high-pressure-resistant and high-resistance powder coating.
[0040] This embodiment describes the application of an epoxy resin-based high-voltage and high-resistance powder coating. After spraying the powder coating, the temperature is raised to 120°C and cured for 1.5 hours, and then raised to 140°C and cured for 3.5 hours to obtain an insulating coating.
[0041] Comparative Example 1 differs from Example 1 in that the flexible insulating polyamide fiber is replaced with nano-polyamide 6 fiber with an average diameter of 250 nm and an average aspect ratio of 800:1.
[0042] Comparative Example 2 differs from Example 1 in that the insulating filler is replaced with nano-silica with an average particle size of 200 nm.
[0043] Comparative Example 3 differs from Example 1 in that it does not contain flexible insulating polyamide fibers.
[0044] Performance testing The powder coatings prepared in each embodiment and comparative example were applied to the surface of an aluminum plate and cured to obtain a coating sample with a thickness of 100 μm.
[0045] The volume resistivity, dielectric constant, and dielectric loss of the coated samples prepared in each embodiment and comparative example were measured using a ohmmeter.
[0046] The breakdown field strength of the coating samples prepared in each example and comparative example was tested according to GB / T 1408.1-2016 "Test methods for electrical strength of insulating materials - Part 1: Test at power frequency".
[0047] The impact resistance of the coating samples prepared in each example and comparative example was tested according to GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film".
[0048] The test results are shown in Table 1 below: Table 1 Test Results As shown in the table above, the volume resistivity of the coating samples obtained in Examples 1-4 is 5.45 × 10⁻⁶. 14 ~5.87×10 14 The breakdown field strength is 45.6~47.8kv / mm in the range of Ω×m, indicating that the powder coating prepared by the present invention has excellent high voltage resistance and high resistivity. The impact strength of the coating samples prepared in Examples 1 to 4 is 60kg×cm, indicating that the powder coating prepared by the present invention has excellent impact resistance.
[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
[0050] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. An epoxy resin-based high-voltage-resistant and high-resistance powder coating, characterized in that, It is prepared from the following raw materials in parts by weight: 40-50 parts alicyclic epoxy resin, 30-40 parts glycidyl ether epoxy resin, 8-10 parts flexible insulating polyamide fiber, 5-8 parts insulating filler, 15-25 parts curing agent, 0.5-2 parts leveling agent, 0.5-2 parts defoamer and 1-5 parts curing accelerator.
2. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 1, characterized in that, The alicyclic epoxy resin has an epoxy equivalent of 190-210, and the glycidyl ether epoxy resin is any one of E51, E20, and E44; the curing agent is an acid anhydride curing agent, and the curing accelerator is a tertiary amine accelerator.
3. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 1, characterized in that, The preparation method of the flexible insulating polyamide fiber includes the following steps: S11. 1,4-bis(4-aminophenoxy)benzene and N,N-dimethylacetamide were added to a reaction vessel under a nitrogen atmosphere, and isophthaloyl chloride was added dropwise at low temperature. After the reaction was completed, deionized water was added to precipitate the solid. Sodium bicarbonate was added to neutralize the solid to neutrality. The solid was collected by filtration, washed and dried to obtain aromatic polyamide. S12. Aromatic polyamide is added to concentrated sulfuric acid and wet-spun to obtain aramid fiber. The aramid fiber is added to a modifying solvent and heated to modify it. The fiber is collected by filtration, washed, and vacuum dried to obtain modified aramid fiber. S13. Modified aramid fibers are added to dimethyl sulfoxide and oxalic acid, ball-milled to obtain a dispersion, acetone is added to precipitate, the precipitate is collected by filtration, washed and vacuum dried to obtain flexible insulating polyamide fibers.
4. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 3, characterized in that, The mass ratio of 1,4-bis(4-aminophenoxy)benzene, N,N-dimethylacetamide and isophthaloyl chloride in S11 is 29~31:100~150:20~22. After adding isophthaloyl chloride dropwise at -5~-10℃, the reaction proceeds for 0.5~1h.
5. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 3, characterized in that, In S12, the amount of aromatic polyamide added is 15-20% of the mass of concentrated sulfuric acid. The spinneret micropore diameter is 0.03-0.04 mm. Spinning is performed at a speed of 200-300 m / min at room temperature. The filaments are then coagulated in deionized water, collected using a drawing roller at 60-120℃, and cut into segments to obtain aramid fibers. The modifying solvent is prepared by adding 1.2-1.4 g of tris(hydroxymethyl)aminomethane to 250-300 mL of deionized water, adjusting the pH to 8.5 with hydrochloric acid, and then dissolving it with 0.5-0.8 g of dopamine. The aromatic polyamide and the modified... The mass ratio of the solvent is 3~5:60~80, the temperature is raised to 40~50℃ and the reaction is carried out for 12~24h, and then washed with deionized water until neutral; the mass ratio of modified aramid fiber, dimethyl sulfoxide and oxalic acid in S13 is 1:2.5~3:0.1~0.15, ball milling is carried out for 40~60min, the amount of acetone added is 200~300% of the mass of dimethyl sulfoxide, the mixture is washed with acetone until neutral, and then vacuum dried at 40~60℃. The average diameter of the flexible insulating polyamide fiber is 200~300nm and the average aspect ratio is 600~800:
1.
6. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 1, characterized in that, The method for preparing the insulating filler includes the following steps: S21. Add boron nitride and ethanol to a ball mill and ball mill to obtain a suspension. After centrifugation and filtration of the suspension, take the supernatant and dry it to obtain boron nitride nanosheets. S22. Add tannic acid and deionized water to the reaction vessel and stir to dissolve. Add nano boron nitride sheets to ethanol, disperse by ultrasonication, and then add to the reaction vessel. React at room temperature, filter to remove the solid, wash, and dry to obtain the insulating filler.
7. The epoxy resin-based high-voltage-resistant and high-resistance powder coating according to claim 6, characterized in that, In S21, the mass ratio of boron nitride to ethanol is 1~2:7~10. The mixture is ball-milled at 400~500 rpm for 12~16 h, centrifuged and filtered at 1000~3000 rpm for 20~30 min, and dried at 80~100℃. The average thickness of the boron nitride nanosheets is 7~10 nm, and the average diameter is 5~10 μm. In S22, the mass ratio of tannic acid, deionized water, boron nitride nanosheets, and ethanol is 2~3:50~60:3~5:20~30. The mixture is reacted at room temperature for 20~24 h, washed with deionized water, and vacuum dried at 80~100℃.
8. A method for preparing an epoxy resin-based high-voltage-resistant and high-resistance powder coating according to any one of claims 1-7, characterized in that, Includes the following steps: S1. After removing water and drying the raw materials, set aside for later use; S2. Add alicyclic epoxy resin and glycidyl ether epoxy resin to a mixing tank, add leveling agent and defoamer, and stir at 300~500 rpm for 5~10 min. Then add insulating filler and flexible insulating polyamide fiber and stir at 2000~3000 rpm for 3~5 min. Finally, add curing agent and curing accelerator and stir at 500~800 rpm for 2~3 min at 30~40℃. Melt extrusion granulation is performed at 140~150℃, and the mixture is ground through a 300 mesh sieve to obtain an epoxy resin-based high pressure resistance and high resistance powder coating.
9. The application of an epoxy resin-based high-voltage, high-resistance powder coating according to any one of claims 1-7, characterized in that, After spraying the powder coating, heat it to 100~120℃ and cure it for 1~2 hours, then heat it to 130~140℃ and cure it for 3~4 hours to obtain an insulating coating.