Insulating powder coating and preparation method thereof

Abstract

The invention relates to the technical field of powder coatings, and provides an insulating powder coating and a preparation method thereof. The insulating powder coating comprises the following raw materials in parts by weight: 82-96 parts of epoxy resin, 5-8 parts of phenolic resin, 12-18 parts of silica powder, 10-15 parts of modified nano aluminum oxide, 3-9 parts of a flame retardant and 0.5-1 part of a flatting agent. Wherein the modified nano aluminum oxide and the silica powder can remarkably improve the breakdown voltage, the arc resistance and the insulativity of the coating; the flame retardant can improve the flame retardance and chemical resistance of the coating, is a halogen-free flame-retardant system, avoids the toxicity problem of the traditional brominated flame retardant, and improves the environmental protection property; in conclusion, the flame-retardant insulating powder coating overcomes the defects of the traditional insulating powder coating in flame retardance, chemical resistance and environmental protection, and has important application value in high-end power electronic equipment.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, specifically to an insulating powder coating and its preparation method. Background Technology

[0002] Insulating powder coatings, as an important functional coating, are widely used in power equipment, electronic components, household appliances, and industrial machinery. Their core function is to provide excellent electrical insulation and mechanical protection for the substrate. However, with the increasing demands of modern industry for miniaturized, efficient, and environmentally friendly equipment, the limitations of traditional insulating coatings in terms of performance, processing, and environmental adaptability are becoming increasingly apparent.

[0003] In the traditional field of insulating coatings, solvent-based insulating varnishes once dominated. However, solvent-based insulating coatings contain volatile organic compounds (VOCs), which easily release harmful gases during application and curing, endangering not only the health of operators but also facing increasingly stringent environmental regulations. In contrast, powder coatings have significant environmental advantages. Because they do not contain chemical solvents, they produce almost no VOC emissions during production and use, greatly reducing environmental pollution and aligning with the current global advocacy for green and environmentally friendly practices.

[0004] Despite the numerous advantages of insulating powder coatings, some problems still need to be addressed in their practical applications. For example, most current insulating powder coatings use epoxy resin as a matrix, which, while possessing certain insulating properties, exhibits poor chemical resistance and flame retardancy. Therefore, it is urgent to solve these problems to meet the higher demands of the powder coating technology field. Summary of the Invention

[0005] This invention proposes an insulating powder coating and its preparation method, which solves the problems of poor chemical resistance and flame retardant properties of epoxy resin powder coatings in related technologies.

[0006] The technical solution of the present invention is as follows: This invention proposes an insulating powder coating comprising the following raw materials in parts by weight: 82-96 parts epoxy resin, 5-8 parts phenolic resin, 12-18 parts silica powder, 10-15 parts modified nano alumina, 3-9 parts flame retardant and 0.5-1 part leveling agent.

[0007] In the above raw materials, phenolic resin acts as a curing agent to cross-link and cure with epoxy resin, thereby improving the chemical stability of the coating; nano-alumina can enhance dielectric strength and improve arc resistance; and silica powder can improve the insulation performance of the coating.

[0008] As a further technical solution, the particle size of the silicon micropowder is 5-10 μm.

[0009] As a further technical solution, the leveling agent is an acrylate leveling agent.

[0010] As a further technical solution, the modified nano-alumina is prepared through the following steps: Nano-alumina and a silane coupling agent were added to an ethanol aqueous solution, ultrasonically dispersed at 60-70℃, filtered, and dried to obtain modified nano-alumina.

[0011] As a further technical solution, the weight parts of the nano-alumina and silane coupling agent are: 10-15 parts nano-alumina and 0.5-1 parts silane coupling agent.

[0012] As a further technical solution, the silane coupling agent is one of KH-550, KH-560 and KH-570.

[0013] As a further technical solution, the ultrasonic dispersion time is 30-60 minutes.

[0014] As a further technical solution, the drying temperature is 80-100℃ and the time is 2-3 hours.

[0015] As a further technical solution, the flame retardant is prepared through the following steps: Step A1: In a three-necked flask, tris(hydroxymethyl)aminomethane hydrochloride, triethylamine, and N,N-dimethylformamide are mixed. The system is placed in an ice bath at 0-5°C. Phosphorus oxychloride is slowly added dropwise using a constant pressure dropping funnel, and the system temperature is controlled to not exceed 25°C during the addition process. After the addition is complete, the mixture is heated to 50-55°C and stirred for 2-3 hours. Then, the temperature is slowly increased until it reaches 105-110°C. The mixture is refluxed for 7-8 hours under stirring. After the reaction is completed, the product is post-processed to obtain the initial product. Step A2: In a three-necked flask, mix the primary product, terephthalaldehyde, p-toluenesulfonic acid and N,N-dimethylformamide, and heat until the temperature reaches 70-80℃. Under stirring, keep the reaction at this temperature for 6-8 hours. After the reaction is complete, perform post-processing to obtain the intermediate product. Step A3: In a three-necked flask, o-phenylenediamine and N,N-dimethylformamide are mixed and stirred until dissolved. Sodium metabisulfite and magnesium sulfate are added at room temperature and stirred until homogeneous. The intermediate product is then added and heated to 120-130°C. The reaction is maintained at this temperature for 6-7 hours. After the reaction is complete, post-treatment is performed to obtain the flame retardant.

[0016] In the preparation of the flame retardant in this invention, tris(hydroxymethyl)aminomethane hydrochloride is first reacted with phosphorus oxychloride to obtain a phosphate ester structure containing an amino group. Then, it is condensed with terephthalaldehyde to obtain an intermediate product. Finally, the aldehyde group of the intermediate product is condensed with o-phenylenediamine to obtain the flame retardant. It should be noted that triethylamine needs to be in excess in step A1 to improve the reaction efficiency. In step A2, the molar ratio of the initial product to terephthalaldehyde is controlled at 1:1, and terephthalaldehyde is in excess to reduce side reactions.

[0017] As a further technical solution, the ratio of the amounts of tris(hydroxymethyl)aminomethane hydrochloride, triethylamine, N,N-dimethylformamide, and phosphorus oxychloride in step A1 is 15.9g:31.2-35.7g:100mL:15.1g.

[0018] As a further technical solution, the ratio of the initial product, terephthalaldehyde, p-toluenesulfonic acid, and N,N-dimethylformamide in step A2 is 16.5g:14.1-15.3g:0.3g:100mL.

[0019] As a further technical solution, the ratio of o-phenylenediamine, N,N-dimethylformamide, sodium metabisulfite, magnesium sulfate, and intermediate product in step A3 is 10.8g:150mL:18.9g:11.9g:28.1g.

[0020] The overall reaction formula for preparing the flame retardant in this invention is as follows:

[0021] As can be seen from the reaction formula, the flame retardant prepared by this invention contains phosphate ester, Schiff base and benzimidazole structure. The phosphate ester and Schiff base can play a synergistic role to significantly improve the flame retardancy of epoxy resin, while benzimidazole can participate in the curing of epoxy resin while having certain flame retardant properties, thus improving the chemical resistance of the matrix.

[0022] This invention also provides a method for preparing an insulating powder coating, comprising the following steps: B1. First, the silica powder and modified nano alumina are dried to remove moisture and prevent clumping during processing, resulting in a dry filler. B2. Add the dried filler, epoxy resin, phenolic resin, flame retardant and leveling agent to a high-speed mixer and stir to ensure uniform dispersion to obtain a mixture; B3. Add the mixture to a twin-screw extruder, melt and extrude, cool and press into sheets, break into small pieces, pulverize using a grinding mill, and sieve to obtain an insulating powder coating.

[0023] As a further technical solution, the drying temperature in step B1 is 80-100℃, and the drying time is 4-6 hours.

[0024] As a further technical solution, in step B2, the speed of the high-speed mixer is 1000-1500 r / min, and the time is 5-10 min.

[0025] As a further technical solution, in step B3, the temperature of the twin-screw extruder is set to 80-90℃ in zone I, 100-110℃ in zone II, and 110-120℃ in zone III, and the rotation speed is 300-400 r / min.

[0026] As a further technical solution, the mesh size of the sieve in step B3 is 200-300 mesh.

[0027] The working principle and beneficial effects of the present invention are: Advantage 1: The coating prepared by this invention has a low VOC content, which conforms to the concept of green environmental protection and effectively avoids the harm to the environment and the health of operators caused by traditional solvent-based insulating paint; Advantage 2: The addition of modified nano-alumina and silicon micro powder to the raw materials of this invention significantly improves the breakdown voltage, arc resistance and insulation of the coating, making it suitable for high-voltage electrical equipment; Advantage 3: The flame retardant made in this invention can improve the flame retardancy and chemical resistance of coatings, and it is a halogen-free flame retardant system, avoiding the toxicity problem of traditional bromine-based flame retardants and improving environmental friendliness. In summary, this invention addresses the shortcomings of traditional insulating powder coatings in terms of flame retardancy, chemical resistance, and environmental friendliness, and has significant application value in high-end power electronic equipment. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 Preparation of flame retardants: Step A1: In a three-necked flask, mix 15.9 g of tris(hydroxymethyl)aminomethane hydrochloride, 31.2 g of triethylamine and 100 mL of N,N-dimethylformamide. Place the system in an ice bath at 0-5°C. Slowly add 15.1 g of phosphorus oxychloride using a constant pressure dropping funnel, controlling the system temperature to not exceed 25°C during the addition. After the addition is complete, heat to 50°C and stir for 2 hours. Then slowly raise the temperature until it reaches 105°C. Reflux the reaction for 7 hours under stirring. After the reaction is complete, cool to room temperature, distill under reduced pressure, add water to precipitate the solid, filter, and dry to obtain the initial product. Step A2: In a three-necked flask, mix 16.5g of the initial product, 14.1g of terephthalaldehyde, 0.3g of p-toluenesulfonic acid and 100mL of N,N-dimethylformamide, and heat until the temperature reaches 70℃. Under stirring, keep the reaction at this temperature for 6 hours. After the reaction is complete, slowly pour the reaction solution into n-hexane, stir to precipitate the solid, filter and collect the precipitate, wash with n-hexane, and dry to obtain the intermediate product. Step A3: In a three-necked flask, mix 10.8 g of o-phenylenediamine and 150 mL of N,N-dimethylformamide, stir to dissolve, add 18.9 g of sodium metabisulfite and 11.9 g of magnesium sulfate at room temperature, stir evenly, add 28.1 g of intermediate product and heat to 120 °C, keep the temperature for 6 h. After the reaction is complete, filter and extract the filtrate with dichloromethane / water, remove the solvent by rotary evaporation, and dry under vacuum to obtain the flame retardant; Preparation of modified nano-alumina: 10g of nano-alumina and 0.5g of silane coupling agent KH-550 were added to 100mL of ethanol aqueous solution, ultrasonically dispersed at 60℃ for 30min, filtered, and dried at 80℃ for 2h to obtain modified nano-alumina. A method for preparing an insulating powder coating includes the following steps: B1. First, dry 12g of silicon micro powder (5-10μm) and 10g of modified nano alumina at 80℃ for 4h to remove moisture and prevent clumping during processing, thus obtaining a dry filler. B2. Add the dried filler, 82g of epoxy resin E12, 5g of phenolic resin, 3g of flame retardant and 0.5g of acrylate leveling agent BYK-361N to a high-speed mixer with a speed of 1000r / min and stir for 5min to ensure uniform dispersion and obtain the mixture. B3. Add the mixture to a twin-screw extruder (temperature set to 80℃ in zone I, 100℃ in zone II, and 110℃ in zone III, speed 300r / min), melt extrude, cool and press into sheets, crush into small pieces, pulverize using a grinding mill, and sieve through a 200-mesh sieve to obtain an insulating powder coating.

[0030] Example 2 Preparation of flame retardants: Step A1: In a three-necked flask, mix 15.9 g of tris(hydroxymethyl)aminomethane hydrochloride, 35.7 g of triethylamine and 100 mL of N,N-dimethylformamide. Place the system in an ice bath at ℃. Slowly add 15.1 g of phosphorus oxychloride using a constant pressure dropping funnel, controlling the system temperature to not exceed 25℃ during the addition. After the addition is complete, heat to 55℃ and stir for 3 h. Then slowly raise the temperature until it reaches 110℃. Reflux the reaction for 8 h under stirring. After the reaction is complete, cool to room temperature, distill under reduced pressure, add water to precipitate the solid, filter, and dry to obtain the initial product. Step A2: In a three-necked flask, mix 16.5g of the initial product, 15.3g of terephthalaldehyde, 0.3g of p-toluenesulfonic acid and 100mL of N,N-dimethylformamide, and heat until the temperature reaches 80℃. Keep the mixture at this temperature for 8 hours with stirring. After the reaction is complete, slowly pour the reaction solution into n-hexane, stir to precipitate the solid, filter and collect the precipitate, wash with n-hexane, and dry to obtain the intermediate product. Step A3: In a three-necked flask, mix 10.8 g of o-phenylenediamine and 150 mL of N,N-dimethylformamide, stir to dissolve, add 18.9 g of sodium metabisulfite and 11.9 g of magnesium sulfate at room temperature, stir evenly, add 28.1 g of intermediate product and heat to 130 °C, keep the temperature for 7 h. After the reaction is complete, filter and extract the filtrate with dichloromethane / water, remove the solvent by rotary evaporation, and dry under vacuum to obtain the flame retardant; Preparation of modified nano-alumina: 15g of nano-alumina and 1g of silane coupling agent KH-560 were added to 100mL of ethanol aqueous solution, ultrasonically dispersed at 70℃ for 60min, filtered, and dried at 100℃ for 3h to obtain modified nano-alumina. A method for preparing an insulating powder coating includes the following steps: B1. First, dry 16g of silica micro powder (5-10μm) and 12.5g of modified nano alumina at 100℃ for 6h to remove moisture and prevent clumping during processing, thus obtaining a dry filler. B2. Add the dried filler, 89g of epoxy resin E12, 7g of phenolic resin, 6g of flame retardant and 0.8g of acrylate leveling agent BYK-361N to a high-speed mixer with a speed of 1500r / min and stir for 10min to ensure uniform dispersion and obtain the mixture. B3. Add the mixture to a twin-screw extruder (temperature set to 80℃ in zone I, 110℃ in zone II, and 20℃ in zone III, speed 400r / min), melt extrude, cool and press into sheets, crush into small pieces, pulverize using a grinding mill, and sieve through a 300-mesh sieve to obtain an insulating powder coating.

[0031] Example 3 This embodiment differs from Embodiment 2 in that it provides a method for preparing an insulating powder coating, comprising the following steps: B1. First, dry 18g of silica micro powder (5-10μm) and 15g of modified nano alumina at 100℃ for 6h to remove moisture and prevent clumping during processing, thus obtaining a dry filler. B2. Add the dried filler, 96g of epoxy resin E12, 8g of phenolic resin, 9g of flame retardant and 1g of acrylate leveling agent BYK-361N to a high-speed mixer with a speed of 1500r / min and stir for 10min to ensure uniform dispersion and obtain the mixture. B3. Add the mixture to a twin-screw extruder (temperature set to 80℃ in zone I, 110℃ in zone II, and 20℃ in zone III, speed 400r / min), melt extrude, cool and press into sheets, crush into small pieces, pulverize using a grinding mill, and sieve through a 300-mesh sieve to obtain an insulating powder coating.

[0032] Comparative Example 1 The only difference between this comparative example and Example 2 is that in this comparative example, 6g of triphenyl phosphate was used to replace the flame retardant in Example 2 to prepare the coating.

[0033] Comparative Example 2 The only difference between this comparative example and Example 2 is that no silica powder is added in this comparative example to obtain the coating.

[0034] The following performance tests were performed on Examples 1, 2, and 3 and Comparative Examples 1 and 2: The breakdown voltage was determined according to GB / T 1408.1-2016 standard. Flame retardant performance was determined according to GB / T 2408-2021 standard; The acid and alkali resistance was determined according to GB / T 1763-2022 standard. The VOC content was determined according to the GB / T 23986-2021 standard. The measurement results are shown in the table below:

[0035] As can be seen from the table above, the coating prepared in Example 2 of the present invention has higher flame retardancy and chemical resistance than that in Comparative Example 1, and also has excellent insulation and environmental protection performance. Therefore, the present invention has important application value in high-end power electronic equipment.

[0036] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An insulating powder coating, characterized in that, It includes the following raw materials in parts by weight: 82-96 parts epoxy resin, 5-8 parts phenolic resin, 12-18 parts silica powder, 10-15 parts modified nano alumina, 3-9 parts flame retardant and 0.5-1 parts leveling agent.

2. The insulating powder coating according to claim 1, characterized in that, The flame retardant is prepared by the following steps: Step A1: Mix tris(hydroxymethyl)aminomethane hydrochloride, triethylamine and N,N-dimethylformamide, place the system in an ice bath at 0-5℃, add phosphorus oxychloride dropwise, stir at 50-55℃ for 2-3 hours after the addition is complete, and then reflux at 105-110℃ with stirring for 7-8 hours. After the reaction is complete, the initial product is obtained. Step A2: Mix the primary product, terephthalaldehyde, p-toluenesulfonic acid and N,N-dimethylformamide, and react at 70-80℃ with stirring for 6-8 hours. After the reaction is complete, the intermediate product is obtained. Step A3: Mix o-phenylenediamine and N,N-dimethylformamide, stir to dissolve, add sodium metabisulfite and magnesium sulfate, stir evenly, add intermediate product and react at 120-130℃ for 6-7 hours. After the reaction is completed, the flame retardant is obtained.

3. An insulating powder coating according to claim 2, characterized in that, In step A1, the ratio of the amounts of tris(hydroxymethyl)aminomethane hydrochloride, triethylamine, N,N-dimethylformamide, and phosphorus oxychloride is 15.9g:31.2-35.7g:100mL:15.1g.

4. An insulating powder coating according to claim 2, characterized in that, The ratio of the initial product, terephthalaldehyde, p-toluenesulfonic acid, and N,N-dimethylformamide used in step A2 is 16.5g:14.1-15.3g:0.3g:100mL.

5. An insulating powder coating according to claim 2, characterized in that, In step A3, the ratio of o-phenylenediamine, N,N-dimethylformamide, sodium metabisulfite, magnesium sulfate, and the intermediate product is 10.8 g: 150 mL: 18.9 g: 11.9 g: 28.1 g.

6. An insulating powder coating according to claim 1, characterized in that, The particle size of the silicon micropowder is 5-10 μm.

7. An insulating powder coating according to claim 1, characterized in that, The leveling agent is an acrylate leveling agent.

8. An insulating powder coating according to claim 1, characterized in that, The modified nano-alumina is prepared by the following steps: Nano-alumina and a silane coupling agent were added to an ethanol aqueous solution, ultrasonically dispersed at 60-70℃, filtered, and dried to obtain modified nano-alumina.

9. A method for preparing an insulating powder coating, used to prepare an insulating powder coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: First, the silica powder and modified nano-alumina are dried and then added to a high-speed mixer with epoxy resin, phenolic resin, flame retardant and leveling agent to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion, cooled and pressed into sheets, broken into small pieces, pulverized by a grinding mill, and sieved to obtain an insulating powder coating.

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