An insulating and weather-resistant powder coating and its preparation method

Abstract

The present invention relates to an insulating and weather-resistant powder coating and a preparation method thereof, belonging to the technical field of coatings. The powder coating includes a composite modified resin, a dual curing agent, a functional filler, a polyacrylate leveling agent, fumed silica, a benzotriazole ultraviolet absorber, a polytetrafluoroethylene wax powder, etc. The present invention designs a core-shell structure of the composite modified resin, maintains high insulation through the epoxy core layer modified by silane, provides a weather-resistant barrier through the acrylic shell layer, and solves the phase separation problem through interfacial chemical bonding; designs a dual curing mechanism, while the anhydride cures the epoxy core layer, the isocyanate reacts with the acrylic hydroxyl group to form an interpenetrating network; designs a filler synergistic effect, the silane coupling agent modifies nano boron nitride to form a three-dimensional heat-conducting and insulating network, and the silica-coated rutile titanium dioxide resists ultraviolet aging. Each component synergizes with each other, enabling the coating to simultaneously possess excellent properties such as insulation, weather resistance, and adhesion.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to an insulating and weather-resistant powder coating and a preparation method thereof. Background Art

[0002] From the development process of coatings, polyethylene powder emerged in the 1940s, opening the chapter of powder coatings. In the 1950s, thermosetting epoxy powder coatings were developed, and since then, the types of powder coatings have been continuously enriched. In the late 1990s, to meet new safety or weather resistance requirements, powder coating varieties with special properties such as low molecular weight epoxy compound-cured polyester and thermosetting fluororesin powder were developed. Entering the new century, powder technology has advanced by leaps and bounds, the market scale has been continuously expanding and becoming more refined, and the growth rate of weather-resistant powder coatings has been particularly significant.

[0003] In many application fields, insulating and weather-resistant powder coatings play an indispensable role. In the power industry, equipment such as high-voltage switchgear, transformers, and magnet wires are in a complex electrical environment for a long time. They not only need to have good insulation performance to ensure the safe and stable power transmission, but also need to resist harsh climate conditions such as sunlight exposure, acid rain erosion, and temperature changes outdoors to prevent equipment failures caused by coating damage. The new energy vehicle industry also has an urgent need for it. Key components such as the battery pack and motor of new energy vehicles generate a large amount of heat and electric fields during operation, requiring the coating to have properties such as insulation, heat resistance, and chemical corrosion resistance. At the same time, the vehicle travels outdoors and faces various climate challenges. Therefore, insulating and weather-resistant powder coatings become an important material to ensure the safety and service life of new energy vehicles. In addition, for some outdoor electronic devices, communication base stations, etc., coatings with both insulation and weather resistance are also needed to protect the equipment and ensure its stable operation.

[0004] However, traditional powder coatings are difficult to simultaneously meet the high standards of insulation and weather resistance. For example, although common epoxy powder coatings have excellent insulation performance, adhesion to metals, corrosion resistance, as well as hardness, flexibility, and impact strength, their weather resistance is poor. They are prone to powdering and discoloration in outdoor environments, and have a short service life, which limits their wide application in outdoor insulation fields. Acrylic resin powder coatings have good weather resistance and insulation performance, but there is still room for improvement in some insulation performance indicators, and there are few reports on their application in the insulation field.

[0005] Although in order to balance various indicators, some curing agents, fillers, and additives are blended, it is still not ideal. At present, the components of coatings on the market are diverse and the performance is uneven. There is still a common problem that it is difficult to comprehensively improve insulation, weather resistance, and adhesion. Summary of the Invention

[0006] Aiming at the problem that it is difficult to comprehensively improve the insulation, weather resistance and adhesion of existing powder coatings, the present invention provides an insulating and weather-resistant powder coating and its preparation method. The core-shell structure of the composite modified resin is designed. The epoxy core layer modified by silane maintains high insulation, and the acrylic shell layer provides a weather-resistant barrier. The interfacial chemical bonding solves the phase separation problem. A dual curing mechanism is designed. While the acid anhydride cures the epoxy core layer, the isocyanate reacts with the acrylic hydroxyl group to form an interpenetrating network. A filler synergistic effect is designed. The silane coupling agent-modified nano-boron nitride forms a three-dimensional thermal conductive and insulating network, and the silica-coated rutile titanium dioxide resists ultraviolet aging. Cooperating with other components, the coating simultaneously has excellent properties such as insulation, weather resistance and adhesion, and solves the problem that it is difficult to comprehensively improve these properties in traditional powder coatings. The specific technical solutions are as follows:

[0007] An insulating and weather-resistant powder coating, the powder coating comprising the following raw materials in parts by mass: 60 parts to 70 parts of composite modified resin, 5 parts to 10 parts of dual curing agent, 20 parts to 30 parts of functional filler, 0.5 part to 1 part of polyacrylate leveling agent, 0.5 part to 1 part of fumed silica, 0.5 part to 1 part of benzotriazole ultraviolet absorber, 0.2 part to 0.5 part of polytetrafluoroethylene wax powder, 1 part to 5 parts of pigment and 0.1 part to 0.5 part of antioxidant 1010;

[0008] The core layer of the composite modified resin is a bisphenol A epoxy resin modified by 3-glycidoxypropyltrimethoxysilane to form a siloxane cross-linked network; the shell layer of the composite modified resin is a hydroxyl acrylic resin and the core layer are chemically bonded through graft polymerization;

[0009] The main curing agent of the dual curing agent is a compound of methyl nadic anhydride and diphenylmethane diisocyanate; the latent curing accelerator of the dual curing agent is a microencapsulated imidazole compound, and the microcapsule wall material is polyurethane;

[0010] The functional filler includes silane coupling agent-modified nano-boron nitride and silica-coated rutile titanium dioxide.

[0011] In the above powder coating, the compounding mass ratio of the methyl nadic anhydride, diphenylmethane diisocyanate and the latent curing accelerator is (3 to 4):(1 to 1.5):(0.5 to 1).

[0012] In the above powder coating, the mass ratio of the silane coupling agent-modified nano-boron nitride to the silica-coated rutile titanium dioxide is (3 to 5):(1 to 2).

[0013] In the above powder coating, the preparation method of the composite modified resin comprises the following steps: at 70°C to 80°C, under stirring, bisphenol A epoxy resin is added to cyclohexanone to prepare solution A with a concentration of 8wt% to 12wt%. Then, 3-glycidoxypropyltrimethoxysilane and aminopropyl-terminated polydimethylsiloxane are added and mixed evenly. After that, dibutyltin dilaurate is added, and the temperature is raised to 120°C to 130°C, and stirring reaction is carried out for 2h to 3h to form a silicone cross-linked network, obtaining a core layer system; at 30°C to 40°C, under stirring, hydroxy acrylic resin and dimethylstearylamine are added to ethyl acetate to prepare solution B; the core layer system is cooled to 70°C to 80°C, and under stirring, according to the volume ratio of core layer system: solution B = (8 to 10): (3 to 5), solution B is added to the core layer system. Then, benzoyl peroxide initiator is added, and stirring reaction is carried out for 3h to 4h to enable the hydroxy acrylic resin to form chemical bonding with the core layer through graft polymerization. After centrifugal atomization drying and vacuum drying, a composite modified resin with a particle size below 50μm is obtained.

[0014] In the preparation method of the above composite modified resin, the addition amount of 3-glycidoxypropyltrimethoxysilane is 4% to 6% of the mass of bisphenol A epoxy resin; the addition amount of aminopropyl-terminated polydimethylsiloxane is 3% to 5% of the mass of bisphenol A epoxy resin; the addition amount of dibutyltin dilaurate is 0.2% to 0.5% of the mass of bisphenol A epoxy resin; solution B contains 10wt% to 15wt% of hydroxy acrylic resin and 3wt% to 5wt% of dimethylstearylamine; the addition amount of benzoyl peroxide initiator is 3% to 5% of the mass of hydroxy acrylic resin; the stirring speed is 300r / min to 500r / min; the parameters of the centrifugal atomization drying are: inlet air temperature 150°C to 180°C, outlet air temperature 70°C to 90°C, and centrifugal atomization rotation speed 10000r / min to 12000r / min.

[0015] In the above-mentioned powder coating, the preparation method of the latent curing accelerator comprises the following steps: preparing the ingredients according to the mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol = 100: (8-10): (3-5): (2-3), stirring and reacting at 45°C to 50°C for 2h to 3h to obtain a polyurethane wall material solution; dissolving 2-ethyl-4-methylimidazole (EMI) in ethanol to prepare an imidazole solution with a concentration of 8wt% to 12wt%; preparing a polyvinyl alcohol aqueous solution with a concentration of 0.8wt% to 1wt%; according to the volume ratio of imidazole solution: polyurethane wall material solution: polyvinyl alcohol aqueous solution = (1-2): (2-3): (1-2), adding the imidazole solution to the polyurethane wall material solution, ultrasonically dispersing, then adding the polyvinyl alcohol aqueous solution under stirring conditions, stirring and reacting for 3h to 4h to form microcapsules, centrifuging, collecting the microcapsules, washing with deionized water, and vacuum drying to obtain a microencapsulated latent curing accelerator.

[0016] In the preparation method of the above-mentioned latent curing accelerator, the ultrasonic dispersion is 30kHz~50kHz ultrasonic dispersion for 30min~40min; the stirring speed is 200r / min~400r / min; the centrifugation is centrifugation at 3000r / min~5000r / min for 10min~15min; the number of washings is 3 times~4 times; and the vacuum drying is vacuum drying at 50℃~60℃ for 24h~30h.

[0017] In the above-mentioned powder coating, the preparation method of the silane coupling agent modified nano boron nitride comprises the following steps: dispersing nano boron nitride in anhydrous ethanol at a solid content of 5wt% to 6wt%, adding silane coupling agent KH560 of 3% to 5% by mass of the nano boron nitride under stirring, adjusting the pH value to 4 to 5 with acetic acid, heating to 60°C to 70°C, stirring at 300r / min to 500r / min for 4h to 6h, centrifuging at 8000r / min to 10000r / min for 10min to 15min, taking the precipitate, washing with water for 3 to 4 times, and vacuum drying at 70°C to 80°C for 12h to 24h to obtain silane coupling agent modified nano boron nitride.

[0018] In the above-mentioned powder coating, the preparation method of the silica-coated rutile titanium dioxide includes the following steps: Rutile titanium dioxide (nanoscale) is mixed with a 5wt% - 8wt% hydrogen peroxide solution in a mass ratio of 1:(10 - 12), stirred at 70°C - 80°C for 1h - 2h, centrifuged at 8000r / min - 10000r / min for 10min - 20min, the precipitate is taken, washed with water until neutral, and dried to obtain surface-hydroxylated titanium dioxide; According to the volume ratio, tetraethyl orthosilicate: absolute ethanol: ammonia water (concentration 20wt% - 25wt%) = 1:(10 - 12):(0.5 - 0.8), a coating solution is prepared; According to a solid content of 8wt% - 12wt%, the surface-hydroxylated titanium dioxide is dispersed in ethanol to obtain a suspension, and then, under stirring, according to the volume ratio of suspension: coating solution = (10 - 12):(2 - 3), the coating solution is added, and the mixture is stirred and reacted at 40°C - 45°C and 300r / min - 500r / min for 5h - 6h, allowed to stand and age for 20h - 30h, centrifuged at 8000r / min - 10000r / min for 10min - 20min to obtain a solid, and calcined at a heating rate of 4°C / min - 6°C / min to 500°C - 600°C for 2h - 3h to obtain silica-coated rutile titanium dioxide.

[0019] The preparation method of the above-mentioned insulating and weather-resistant powder coating includes the following steps:

[0020] By mass fraction, the raw materials are mixed evenly to obtain a mixture; The mixture is extruded into strips by an extruder at 100°C - 120°C with a screw speed of 150r / min - 200r / min, air-cooled, pulverized, and the median particle size is 15μm - 30μm to obtain the insulating and weather-resistant powder coating.

[0021] An insulating and weather-resistant powder coating and its preparation method provided by the present invention have the following beneficial effects:

[0022] I. The present invention prepares a composite modified resin. In its core layer system, bisphenol A epoxy resin itself has good insulation performance, adhesion to metals, corrosion resistance, as well as hardness, flexibility and impact strength. The siloxane group in 3-glycidoxypropyltrimethoxysilane can react with active groups such as hydroxyl groups in the epoxy resin to form a siloxane cross-linked network. This network structure can enhance the intermolecular force, improve the chemical stability and mechanical properties of the resin, especially significantly enhance its weather resistance, because the siloxane bond has good resistance to environmental factors such as ultraviolet rays and moisture. Aminopropyl-terminated polydimethylsiloxane utilizes the siloxane chain segments in its molecular structure to promote the formation stability of the siloxane cross-linked network, and can also endow the core layer with good flexibility and hydrophobicity. Dibutyltin dilaurate acts as a catalyst to accelerate the siloxane cross-linking reaction and ensure the formation of a stable cross-linked structure within a specified time.

[0023] During the formation of the shell layer, hydroxyl acrylic resin has good weather resistance, gloss and color retention. Dimethyl stearylamine can promote the dispersion and graft polymerization reaction of hydroxyl acrylic resin on the surface of the core layer. The initiator benzoyl peroxide decomposes to generate free radicals, initiating the graft polymerization of hydroxyl acrylic resin and the core layer, so that the shell layer is tightly chemically bonded to the core layer. This composite modified resin with a core-shell structure not only retains the excellent properties of epoxy resin, but also combines the weather resistance advantages of hydroxyl acrylic resin to form a synergistic enhancement system, and the addition of aminopropyl-terminated polydimethylsiloxane and dimethyl stearylamine additives effectively promotes the structural stability of the system, greatly improving the overall comprehensive performance of the coating.

[0024] II. Among the dual curing agents, methyl nadic anhydride and diphenylmethane diisocyanate can both react with the active groups in the resin to crosslink and cure the resin. After methyl nadic anhydride reacts with resins such as epoxy resin, it can improve the hardness, strength and chemical stability of the coating, and the anhydride group in its structure reacts with the hydroxyl group of the resin to form a stable chemical bond. Diphenylmethane diisocyanate has relatively high reactivity. It reacts with the hydroxyl group, amino group, etc. in the resin to further increase the crosslinking density and improve the mechanical properties and chemical corrosion resistance of the coating. When the two are used in combination and the ratio is adjusted, a better balance can be achieved among the curing speed, curing degree and the final coating properties.

[0025] III. In the dual curing agents, the latent curing accelerator is a microencapsulated imidazole compound. 2-Ethyl-4-methylimidazole is an efficient curing accelerator that can accelerate the curing reaction rate. However, to prevent it from initiating the curing reaction during the paint storage stage, it is microencapsulated using polyurethane as the wall material. At low temperatures or under normal conditions, the microcapsules remain intact, and the internal imidazole is encapsulated and will not react with other components in the paint, ensuring the storage stability of the paint. When the paint is in the high-temperature curing stage, the microcapsule wall material decomposes or softens upon heating, releasing imidazole, which thus promotes the crosslinking reaction between the main curing agent and the resin, improving the curing efficiency and degree, and enabling the coating to cure quickly and fully.

[0026] A certain amount of propylene glycol is added to promote the formation of the polyurethane wall material. Propylene glycol participates in the synthesis reaction of polyurethane, has a chain extension effect, and regulates the structure and properties of the wall material. If the addition is excessive, it will damage the wall material structure. Excessive propylene glycol will make the molecular chain of the polyurethane wall material too long or cause excessive crosslinking, resulting in the brittleness of the wall material and the destruction of the integrity of the microcapsules.

[0027] IV. Nano boron nitride itself has high thermal conductivity, high insulation, and good chemical stability. One end of the silane coupling agent KH560 can react with the surface of nano boron nitride, and the organic group at the other end can interact with the resin matrix. Through this modification, on the one hand, the dispersibility of nano boron nitride in the resin matrix is improved, enabling it to be evenly distributed in the paint, avoiding agglomeration phenomena, and giving full play to its performance advantages; on the other hand, the interfacial bonding force between nano boron nitride and the resin is enhanced, thereby improving the insulation performance, thermal conductivity, and mechanical properties of the paint, especially showing significant effects in enhancing the insulation performance, because good dispersion and interfacial bonding help reduce the defects in the electron conduction path.

[0028] V. Rutile titanium dioxide has good light resistance and weather resistance. By synthesizing silica coating, a dense protective film is formed to further prevent ultraviolet light from directly contacting the titanium dioxide and inhibit the occurrence of photocatalytic reactions, thereby further enhancing the weather resistance of the paint. At the same time, the presence of synthesized silica also improves the dispersibility and stability of titanium dioxide in the resin matrix, further enhancing the comprehensive performance of the paint.

[0029] VI. Fumed silica has a very large specific surface area and a special surface structure. In the paint, fumed silica increases the viscosity and thixotropy of the system by forming hydrogen bonds or other interactions with polymer molecules in the paint.

[0030] VII. Polytetrafluoroethylene wax powder can form a protective film with a low surface energy on the coating surface, giving the coating good slipperiness, making it not easy to stain with dust and dirt, improving the stain resistance of the coating. At the same time, its own wear resistance also helps to improve the wear resistance of the coating and extend the service life of the coating.

[0031] In summary, the present invention designs a core-shell structure of a composite modified resin. The epoxy core layer modified by silane maintains high insulation, the acrylic shell layer provides a weather resistance barrier, and the interfacial chemical bonding solves the phase separation problem. A dual-curing mechanism is designed. While the acid anhydride cures the epoxy core layer, the isocyanate reacts with the acrylic hydroxyl group to form an interpenetrating network. A filler synergistic effect is designed. The silane coupling agent-modified nano-boron nitride forms a three-dimensional thermal conductive and insulating network, and the silica-coated rutile titanium dioxide resists ultraviolet aging.

[0032] The composite modified resin, as the main film-forming substance of the coating, provides the basic mechanical properties, insulation properties and weather resistance properties. The dual curing agents ensure that the resin can be fully crosslinked and cured to form a stable three-dimensional network structure, improving the hardness, strength and chemical stability of the coating. The silane coupling agent-modified nano-boron nitride and silica-coated rutile titanium dioxide in the functional fillers strengthen the coating in terms of improving insulation properties and weather resistance respectively. At the same time, they enhance the homogeneity and also have a certain enhancing effect on the adhesion performance. They cooperate with each other to enable the coating to simultaneously possess excellent properties such as insulation, weather resistance and adhesion, solving the problem that it is difficult for traditional powder coatings to comprehensively improve these properties. Detailed implementation mode

[0033] The present invention will be further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0034] Example 1: An insulating and weather-resistant powder coating, the powder coating comprising the following raw materials in parts by mass: 65 parts of composite modified resin, 8 parts of dual curing agent, 25 parts of functional filler, 0.8 part of polyacrylate leveling agent, 0.8 part of fumed silica, 0.8 part of benzotriazole ultraviolet absorber, 0.35 part of polytetrafluoroethylene wax powder, 0.3 part of pigment and 0.3 part of antioxidant 1010; wherein, the core layer of the composite modified resin is a bisphenol A epoxy resin modified by 3-glycidoxypropyltrimethoxysilane to form a siloxane crosslinked network; the shell layer of the composite modified resin is a hydroxyl acrylic resin chemically bonded to the core layer through graft polymerization; the main curing agent of the dual curing agent is a compound of methyl nadic anhydride and diphenylmethane diisocyanate; the latent curing accelerator of the dual curing agent is a microencapsulated imidazole compound, and the microcapsule wall material is polyurethane; the compounding mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate and the latent curing accelerator is 3.5:1.2:0.8; the functional filler is a mixture of silane coupling agent-modified nano-boron nitride and silica-coated rutile titanium dioxide with a mass ratio of 4:1.5.

[0035] Among them, the preparation method of the composite modified resin comprises the following steps: at 75°C and under the stirring state of 400 r / min, bisphenol A epoxy resin is added to cyclohexanone to prepare solution A with a concentration of 10 wt%. 3-glycidoxypropyltrimethoxysilane accounting for 5% of the mass of bisphenol A epoxy resin and aminopropyl-terminated polydimethylsiloxane accounting for 4% of the mass of bisphenol A epoxy resin are added and mixed evenly. Then, dibutyltin dilaurate accounting for 0.3% of the mass of bisphenol A epoxy resin is added, and the temperature is raised to 125°C. Stirring reaction is carried out at 400 r / min for 2.5 h to form a silicone cross-linked network, obtaining a core layer system; at 35°C and under the stirring state of 400 r / min, hydroxyl acrylic resin and dimethylstearylamine are added to ethyl acetate, with the content of hydroxyl acrylic resin being 12 wt% and the content of dimethylstearylamine being 4 wt%, to prepare solution B; the core layer system is cooled to 75°C, and under the stirring state of 400 r / min, solution B is added to the core layer system according to the volume ratio of core layer system:solution B = 9:4. Then, benzoyl peroxide initiator accounting for 4% of the mass of hydroxyl acrylic resin is added, and stirring reaction is carried out at 400 r / min for 3.5 h to enable the hydroxyl acrylic resin and the core layer to form chemical bonding through graft polymerization. Centrifugal atomization drying is carried out, with the inlet air temperature being 170°C, the outlet air temperature being 80°C, and the centrifugal atomization speed being 11,000 r / min. Vacuum drying is carried out at 55°C for 26 h to obtain a composite modified resin with a particle size below 50 μm.

[0036] Among them, the preparation method of the latent curing accelerator comprises the following steps: materials are proportioned according to the mass ratio of acetone:polyether polyol:diphenylmethane diisocyanate:propylene glycol = 100:9:4:2.5, and stirring reaction is carried out at 47°C and 300 r / min for 2.5 h to obtain a polyurethane wall material solution; 2-ethyl-4-methylimidazole (EMI) is dissolved in ethanol to prepare an imidazole solution with a concentration of 10 wt%; an aqueous solution of polyvinyl alcohol with a concentration of 0.9 wt% is prepared; according to the volume ratio, imidazole solution:polyurethane wall material solution:aqueous solution of polyvinyl alcohol = 1.5:2.5:1.8, the imidazole solution is added to the polyurethane wall material solution, ultrasonic dispersion is carried out at 40 kHz for 35 min, and then, under the stirring condition of 300 r / min, the aqueous solution of polyvinyl alcohol is added, and stirring reaction is carried out at 300 r / min for 3.5 h to form microcapsules. Centrifugation is carried out at 4,000 r / min for 12 min, the microcapsules are collected, washed 3 times with deionized water, and vacuum dried at 55°C for 26 h to obtain a microencapsulated latent curing accelerator.

[0037] Among them, the preparation method of silane coupling agent modified nano boron nitride includes the following steps: Disperse nano boron nitride in absolute ethanol according to a solid content of 5.5 wt%, add silane coupling agent KH560 accounting for 4% of the mass of nano boron nitride under stirring, adjust the pH value to 4.5 with acetic acid, raise the temperature to 65 °C, stir and react at 400 r / min for 5 h, centrifuge at 9000 r / min for 12 min, take the precipitate, wash it with water three times, and vacuum dry it at 75 °C for 18 h to obtain silane coupling agent modified nano boron nitride.

[0038] Among them, the preparation method of silica-coated rutile titanium dioxide includes the following steps: Mix rutile titanium dioxide (nano-scale) and 7 wt% hydrogen peroxide solution in a mass ratio of 1:11, stir at 75 °C and 400 r / min for 1.5 h, centrifuge at 9000 r / min for 15 min, take the precipitate, wash it with water until neutral, and dry it to obtain surface-hydroxylated titanium dioxide; Prepare a coating solution according to a volume ratio of tetraethyl orthosilicate: absolute ethanol: ammonia water (concentration 22 wt%) = 1:11:0.6; Disperse the surface-hydroxylated titanium dioxide in ethanol according to a solid content of 10 wt% to obtain a suspension, and then under stirring at 400 r / min, add the coating solution according to a volume ratio of suspension: coating solution = 11:2.5, stir and react at 42 °C and 400 r / min for 5.5 h, stand and age for 25 h, centrifuge at 9000 r / min for 15 min to obtain a solid, and calcine it at a heating rate of 5 °C / min to 550 °C for 2.5 h to obtain silica-coated rutile titanium dioxide.

[0039] The preparation method of the above-mentioned insulating and weather-resistant powder coating includes the following steps:

[0040] Mix each raw material evenly by mass parts to obtain a mixture; Extrude the mixture into strips with an extruder at 110 °C and a screw speed of 180 r / min, cool it with air, crush it, and the median particle size is 21 μm to obtain the insulating and weather-resistant powder coating.

[0041] Example 2: An insulating and weather-resistant powder coating. The powder coating comprises raw materials in the following parts by mass: 60 parts of a composite modified resin, 5 parts of a dual curing agent, 20 parts of a functional filler, 0.5 part of a polyacrylate leveling agent, 0.5 part of fumed silica, 0.5 part of benzotriazole ultraviolet absorber, 0.2 part of polytetrafluoroethylene wax powder, 1 part of a pigment, and 0.1 part of antioxidant 1010; wherein, the core layer of the composite modified resin is a bisphenol A epoxy resin modified by 3-glycidoxypropyltrimethoxysilane to form a siloxane cross-linked network; the shell layer of the composite modified resin is a hydroxyl acrylic resin chemically bonded to the core layer through graft polymerization; the main curing agent of the dual curing agent is a compound of methyl nadic anhydride and diphenylmethane diisocyanate; the latent curing accelerator of the dual curing agent is a microencapsulated imidazole compound, and the microcapsule wall material is polyurethane; the compounding mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate and the latent curing accelerator is 3:1:0.5; the functional filler is a mixture of silane coupling agent-modified nano boron nitride and rutile titanium dioxide coated with silica in a mass ratio of 3:1.

[0042] Among them, the preparation method of the composite modified resin comprises the following steps: at 70 °C and under a stirring state of 300 r / min, add bisphenol A epoxy resin into cyclohexanone to prepare solution A with a concentration of 8 wt%, add 4% of 3-glycidoxypropyltrimethoxysilane based on the mass of bisphenol A epoxy resin and 3% of aminopropyl-terminated polydimethylsiloxane based on the mass of bisphenol A epoxy resin, mix evenly, then add 0.2% of dibutyltin dilaurate based on the mass of bisphenol A epoxy resin, raise the temperature to 120 °C, and stir and react for 2 h at 300 r / min to form a siloxane cross-linked network, obtaining a core layer system; at 30 °C and under a stirring state of 300 r / min, add hydroxyl acrylic resin and dimethyl stearylamine into ethyl acetate, with the content of hydroxyl acrylic resin being 10 wt% and the content of dimethyl stearylamine being 3 wt%, to prepare solution B; cool the core layer system to 70 °C, and under a stirring state of 300 r / min, add solution B to the core layer system according to a volume ratio of core layer system:solution B = 8:3, then add 3% of benzoyl peroxide initiator based on the mass of hydroxyl acrylic resin, stir and react for 3 h at 300 r / min to make the hydroxyl acrylic resin chemically bonded to the core layer through graft polymerization, centrifugally atomize and dry, with an inlet air temperature of 150 °C, an outlet air temperature of 70 °C, a centrifugal atomization speed of 10000 r / min, and vacuum dry at 50 °C for 24 h to obtain a composite modified resin with a particle size of less than 50 μm.

[0043] The preparation method of the latent curing accelerator comprises the following steps: preparing the ingredients in a mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol = 100:8:3:2, stirring and reacting at 45°C and 200r / min for 2h to obtain a polyurethane wall material solution; dissolving 2-ethyl-4-methylimidazole (EMI) in ethanol to prepare an imidazole solution with a concentration of 8wt%; preparing a polyvinyl alcohol aqueous solution with a concentration of 0.8wt%; according to the volume ratio of imidazole solution: polyurethane wall material solution: polyvinyl alcohol aqueous solution = 1:2:1, adding the imidazole solution to the polyurethane wall material solution, ultrasonically dispersing at 30kHz for 30min, then adding the polyvinyl alcohol aqueous solution under stirring conditions of 200r / min, stirring and reacting at 200r / min for 3h to form microcapsules, centrifuging at 3000r / min for 10min, collecting the microcapsules, washing them 3 times with deionized water, and vacuum drying them at 50°C for 24h to obtain a microencapsulated latent curing accelerator.

[0044] The preparation method of silane coupling agent modified nano boron nitride includes the following steps: dispersing nano boron nitride in anhydrous ethanol at a solid content of 5wt%, adding silane coupling agent KH560 of 3% by mass of nano boron nitride under stirring, adjusting the pH value to 4 with acetic acid, heating to 60°C, stirring at 300r / min for 4h, centrifuging at 8000r / min for 10min, taking the precipitate, washing it with water 3 times, and vacuum drying it at 70°C for 12h to obtain silane coupling agent modified nano boron nitride.

[0045] The preparation method of silica-coated rutile titanium dioxide comprises the following steps: mixing rutile titanium dioxide (nanoscale) with 5wt% hydrogen peroxide solution at a mass ratio of 1:10, stirring at 70°C and 300r / min for 1h, centrifuging at 8000r / min for 10min, taking the precipitate, washing with water until neutral, and drying to obtain surface hydroxylated titanium dioxide; preparing a coating solution at a volume ratio of ethyl orthosilicate: anhydrous ethanol: ammonia water (concentration 20wt%) = 1:10:0.5; The solid content is 8wt%. The surface hydroxylated titanium dioxide is dispersed in ethanol to obtain a suspension. Then, under stirring at 300r / min, the coating liquid is added according to the volume ratio of suspension: coating liquid = 10:2. The reaction is carried out at 40°C and 300r / min with stirring for 5h, and the mixture is allowed to stand for 20h. The solid is centrifuged at 8000r / min for 10min to obtain a solid. The solid is heated to 500°C at a heating rate of 4°C / min and calcined for 2h to obtain silica-coated rutile titanium dioxide.

[0046] The method for preparing the above-mentioned insulating weather-resistant powder coating comprises the following steps:

[0047] Mix the raw materials in parts by mass to obtain a mixture; extrude the mixture into strips using an extruder at 100 °C with a screw speed of 150 r / min, cool it with air, pulverize it, and obtain an insulating weather-resistant powder coating with a median particle size of 30 μm.

[0048] Example 3: An insulating weather-resistant powder coating, the powder coating comprising the following raw materials in parts by mass: 70 parts of a composite modified resin, 10 parts of a dual curing agent, 30 parts of a functional filler, 1 part of a polyacrylate leveling agent, 1 part of fumed silica, 1 part of a benzotriazole ultraviolet absorber, 0.5 part of a polytetrafluoroethylene wax powder, 5 parts of a pigment, and 0.5 part of antioxidant 1010; wherein, the core layer of the composite modified resin is a bisphenol A epoxy resin modified with 3-glycidoxypropyltrimethoxysilane to form a siloxane crosslinked network; the shell layer of the composite modified resin is a hydroxy acrylic resin chemically bonded to the core layer through graft polymerization; the main curing agent of the dual curing agent is a compound of methyl nadic anhydride and diphenylmethane diisocyanate; the latent curing accelerator of the dual curing agent is a microencapsulated imidazole compound, and the microcapsule wall material is polyurethane; the compounding mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate, and the latent curing accelerator is 4:1.5:1; the functional filler is a mixture of silane coupling agent modified nano boron nitride and rutile titanium dioxide coated with silica with a mass ratio of 5:2.

[0049] Among them, the preparation method of the composite modified resin comprises the following steps: at 80 °C and under a stirring state of 500 r / min, add bisphenol A epoxy resin into cyclohexanone to prepare solution A with a concentration of 12 wt%, add 3-glycidoxypropyltrimethoxysilane accounting for 6% of the mass of bisphenol A epoxy resin and aminopropyl-terminated polydimethylsiloxane accounting for 5% of the mass of bisphenol A epoxy resin, mix evenly, then add dibutyltin dilaurate accounting for 0.5% of the mass of bisphenol A epoxy resin, raise the temperature to 130 °C, and stir and react for 3 h to form a siloxane crosslinked network to obtain a core layer system; at 40 °C and under a stirring state of 500 r / min, add hydroxy acrylic resin and dimethyl stearylamine into ethyl acetate, with the content of hydroxy acrylic resin being 15 wt% and the content of dimethyl stearylamine being 5 wt%, to prepare solution B; cool the core layer system to 80 °C and under a stirring state of 500 r / min, add solution B to the core layer system according to a volume ratio of core layer system:solution B = 10:5, then add a benzoyl peroxide initiator accounting for 5% of the mass of hydroxy acrylic resin, stir and react for 4 h to make the hydroxy acrylic resin chemically bonded to the core layer through graft polymerization, centrifuge and atomize and dry, with an inlet air temperature of 180 °C, an outlet air temperature of 90 °C, and a centrifugal atomization speed of 12000 r / min, and vacuum dry at 60 °C for 30 h to obtain a composite modified resin with a particle size below 50 μm.

[0050] The preparation method of the latent curing accelerator comprises the following steps: preparing the ingredients in a mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol = 100:10:5:3, stirring and reacting at 50°C and 400r / min for 3h to obtain a polyurethane wall material solution; dissolving 2-ethyl-4-methylimidazole (EMI) in ethanol to prepare an imidazole solution with a concentration of 12wt%; preparing a polyvinyl alcohol aqueous solution with a concentration of 1wt%; according to the volume ratio of imidazole solution: polyurethane wall material solution: polyvinyl alcohol aqueous solution = 2:3:2, adding the imidazole solution to the polyurethane wall material solution, ultrasonically dispersing at 50kHz for 40min, then adding the polyvinyl alcohol aqueous solution under stirring at 400r / min, stirring and reacting at 400r / min for 4h to form microcapsules, centrifuging at 5000r / min for 15min, collecting the microcapsules, washing them 4 times with deionized water, and vacuum drying them at 60°C for 30h to obtain a microencapsulated latent curing accelerator.

[0051] The preparation method of silane coupling agent modified nano boron nitride includes the following steps: dispersing nano boron nitride in anhydrous ethanol at a solid content of 6wt%, adding silane coupling agent KH560 of 5% by mass of nano boron nitride under stirring, adjusting the pH value to 5 with acetic acid, heating to 70°C, stirring at 500r / min for 6h, centrifuging at 10000r / min for 15min, taking the precipitate, washing it with water for 4 times, and vacuum drying it at 80°C for 24h to obtain silane coupling agent modified nano boron nitride.

[0052] The preparation method of silica-coated rutile titanium dioxide comprises the following steps: mixing rutile titanium dioxide (nanoscale) with 8wt% hydrogen peroxide solution at a mass ratio of 1:12, stirring at 80°C and 500r / min for 2h, centrifuging at 10000r / min for 20min, taking the precipitate, washing with water until neutral, and drying to obtain surface hydroxylated titanium dioxide; preparing a coating solution at a volume ratio of ethyl orthosilicate: anhydrous ethanol: ammonia water (concentration 25wt%) = 1:12:0.8; The solid content is 12wt%. The surface hydroxylated titanium dioxide is dispersed in ethanol to obtain a suspension. Then, under stirring at 500r / min, the coating liquid is added according to the volume ratio of suspension: coating liquid = 12:3. The reaction is carried out at 45°C and 500r / min with stirring for 6h, and the mixture is allowed to stand for aging for 30h. The solid is centrifuged at 10000r / min for 20min to obtain a solid. The solid is heated to 600°C at a heating rate of 6°C / min and calcined for 3h to obtain silica-coated rutile titanium dioxide.

[0053] The method for preparing the above-mentioned insulating weather-resistant powder coating comprises the following steps:

[0054] Mix the raw materials evenly by mass parts to obtain a mixture; extrude the mixture into strips using an extruder at 120 °C with a screw speed of 200 r / min, cool it with air, pulverize it, and obtain an insulating weather-resistant powder coating with a median particle size of 15 μm.

[0055] In the above-mentioned examples: Bisphenol A epoxy resin comes from Linzi Shuangli Resin Factory in Zibo City, is solid, and the brand is 604. 3-Glycidyl etheroxypropyltrimethoxysilane is from Zhongshan Xingrui Chemical Co., Ltd. Aminopropyl-terminated polydimethylsiloxane is from Tianmen Hengchang Chemical Co., Ltd. Dibutyltin dilaurate is from Shanghai Xiangu Chemical Co., Ltd., Dibutyltin dilaurate-D12. Hydroxy acrylic resin is from Guangzhou Tanva New Materials Co., Ltd., is solid, and the model is Joncryl587. Dimethyl stearylamine is from Hubei Chushuo Biotechnology Co., Ltd. Benzoyl peroxide is from Changzhou Panwang FRP Composite Materials Co., Ltd. Polyether polyol is from Shanghai Donghui Chemical Technology Co., Ltd., Polyether polyol EP-330N. Diphenylmethane diisocyanate (MDI) is from Covestro Wanhua. Propylene glycol is from Jinan Leshan New Materials Co., Ltd. 2-Ethyl-4-methylimidazole (EMI) is from Wuhan Huaxiang Kejie Biotechnology Co., Ltd., and the model is 2E4MI. Polyvinyl alcohol is from Langfang Ying'en Environmental Protection Technology Co., Ltd., with a density of 50 g / cm 3 . Nano boron nitride is from Shanghai Naiou Nano Technology Co., Ltd., and the model is NO-N-003-1. Silane coupling agent KH560 is from Dongguan Shanyi Plastic Co., Ltd. Rutile titanium dioxide is from Beijing Wanyun Huarei Chemical Co., Ltd. Tetraethyl orthosilicate is from Shandong Jinyuanyuan New Materials Co., Ltd. Methyl nadic anhydride is from Nantong Runfeng Petrochemical Co., Ltd. Polyacrylate leveling agent is from Guangdong Nuoyi Chemical Co., Ltd., and the model is 2170. Fumed silica is from Shandong Jiquan Biotechnology Co., Ltd., and the model is A220. Benzotriazole ultraviolet absorber is from BASF, model: Light stabilizer UV-326. Polytetrafluoroethylene wax powder is from Huangshan Aoshengyuan New Materials Technology Co., Ltd., and the model is MTF-2020. Antioxidant 1010 is from Dongguan Shanyi Plastic Co., Ltd.

[0056] The recommended coating method for the powder coatings in the above examples: It is recommended to use the electrostatic spraying method. Spray the powder coating onto the surface of the grounded object to be coated through a spray gun. The voltage of the spray gun is controlled at 60 kV - 80 kV, the distance between the spray gun and the object surface is kept at 15 cm - 25 cm, the spraying environment temperature is controlled at 20 °C - 25 °C, and the relative humidity is 40% - 60%, so that the powder adheres evenly to the object surface, and the coating thickness is controlled at 80 μm - 120 μm.

[0057] The recommended curing method for the powder coatings in the above embodiments: Put the sprayed object into an oven for curing, control the heating rate at 5°C / min - 10°C / min, heat up to 180°C - 200°C, and carry out heat preservation curing to make the coating crosslink and cure to form a hard paint film.

[0058] Comparative Example 1

[0059] In the powder coating, the composite modified resin is replaced with bisphenol A epoxy resin; other parameters and methods are the same as those in Example 1. The median particle size of the product is 18 μm.

[0060] Comparative Example 2

[0061] In the preparation method of the composite modified resin, aminopropyl-terminated polydimethylsiloxane is not added; other parameters and methods are the same as those in Example 1. The median particle size of the product is 23 μm.

[0062] Comparative Example 3

[0063] In the preparation method of the composite modified resin, dimethylstearylamine is not added; other parameters and methods are the same as those in Example 1. The median particle size of the product is 28 μm.

[0064] Comparative Example 4

[0065] In the double curing agent, all the main curing agent is methyl nadic anhydride; other parameters and methods are the same as those in Example 1. The median particle size of the product is 16 μm.

[0066] Comparative Example 5

[0067] In the double curing agent, all the main curing agent is diphenylmethane diisocyanate; other parameters and methods are the same as those in Example 1. The median particle size of the product is 22 μm.

[0068] Comparative Example 6

[0069] In the double curing agent, the latent curing accelerator is not added; other parameters and methods are the same as those in Example 1. The median particle size of the product is 25 μm.

[0070] Comparative Example 7

[0071] In the preparation method of the latent curing accelerator, propylene glycol is not added; other parameters and methods are the same as those in Example 1. The median particle size of the product is 29 μm.

[0072] Comparative Example 8

[0073] In the preparation method of the latent curing accelerator, the raw materials are proportioned according to the mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol = 100:9:4:6 (i.e., the addition of propylene glycol is excessive); other parameters and methods are the same as those in Example 1. The median particle size of the product is 17 μm.

[0074] Comparative Example 9

[0075] In the functional filler, the nano boron nitride modified by silane coupling agent is replaced by nano boron nitride; other parameters and methods are the same as those in Example 1. The median particle size of the product is 21 μm.

[0076] Comparative Example 10

[0077] In the functional filler, the rutile titanium dioxide coated with silica is replaced by rutile titanium dioxide; other parameters and methods are the same as those in Example 1. The median particle size of the product is 24 μm.

[0078] Comparative Example 11

[0079] In the functional filler, the nano boron nitride modified by silane coupling agent is replaced by nano boron nitride, and the rutile titanium dioxide coated with silica is replaced by rutile titanium dioxide; other parameters and methods are the same as those in Example 1. The median particle size of the product is 26 μm.

[0080] Comparative Example 12

[0081] In the preparation method of the rutile titanium dioxide coated with silica, calcination is not carried out, and calcination is replaced by drying. Drying is carried out at 100 °C for 8 h; other parameters and methods are the same as those in Example 1. The median particle size of the product is 20 μm.

[0082] For the convenience of detection, iron oxide red is used for the pigments of each example and each comparative example, and the performance of the above powder coating products is detected.

[0083] I. Insulation performance

[0084] 1. Volume resistivity: According to GB / T 1410 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials", the powder coating is placed in a mold and kept under pressure at 15 MPa for 5 min to make a circular sample with a diameter of 50 mm and a thickness of 2 mm. In a constant temperature and humidity environment of 23 °C and 50% relative humidity, the sample is placed for 24 h to reach a stable state and then measured. The sample is placed on the test electrodes of a high resistance meter to ensure good contact between the electrodes and the sample. A DC voltage of 500 V is applied, and after 60 s, the volume resistivity value is read. The results are shown in Table 1.

[0085] 2. Electrical strength: According to GB / T 1408.1 "Test Methods for Electrical Strength of Insulating Materials - Part 1: Tests at Power Frequency", the sample has the same specifications as the sample for volume resistivity test, and is also tested in an environment of 23 °C and 50% relative humidity. The sample is placed between the upper and lower electrodes of a withstand voltage tester. The electrode diameter is 25 mm, and the voltage rising rate is set at 1 kV / s. The voltage is continuously increased until the sample breaks down, and the breakdown voltage value at this time is recorded. Then, the electrical strength is calculated according to the formula: Electrical strength = breakdown voltage / sample thickness. The results are shown in Table 1.

[0086] II. Weather Resistance

[0087] 1. Artificial accelerated aging: According to GB / T 1865 "Paints and varnishes - Artificial weathering and exposure to artificial radiation (filtered xenon - arc radiation)", the powder coating is sprayed on an aluminum plate with dimensions of 150 mm × 70 mm × 1 mm, the coating thickness is controlled at 80 μm, and then cured. The test specimens are placed in a xenon - arc lamp aging test chamber. The irradiance is set to 0.55 W / (m²·nm) (at 340 nm), the black - board temperature is 65 °C, the relative humidity is 50%, and the test cycle is 1000 h. A color - difference meter is used to detect the color - difference ΔE value before and after the test to evaluate the weather resistance. The results are shown in Table 1.

[0088] 2. Salt - spray corrosion: According to GB / T 1771 "Paints and varnishes - Determination of resistance to neutral salt - spray", the test specimens are the same as those prepared for the artificial accelerated aging test. The test specimens are placed in a salt - spray test chamber, using a 5% sodium chloride solution, the pH value of the solution is controlled at 7.0, the temperature is set at 35 °C, and continuous spraying is carried out for 2000 h. The test specimens are taken out, rinsed thoroughly with clean water, dried at room temperature for 1 h, and then the corrosion situation on the surface of the test specimens is observed. Corrosion rating is carried out according to GB / T 6461 "Metallic and other inorganic coatings on metallic substrates - Rating of specimens and test - pieces after corrosion tests". The rating standard is divided into 0 - 10 levels, where level 10 indicates no corrosion and level 0 indicates severe corrosion. The results are shown in Table 1.

[0089] III. Adhesion Performance

[0090] According to GB / T 9286 "Paints and varnishes - Cross - cut test of paint films", the powder coating is sprayed on a steel plate with dimensions of 100 mm × 100 mm × 1 mm, the coating thickness is controlled at 100 μm, and then cured. On the surface of the prepared coating, a cross - cutter is used to penetrate the coating with a uniform pressure to draw 10 × 10 squares of 1 mm × 1 mm. Then, a 3M600 tape with a width of 25 mm is pasted on the cross - cut area, and the tape is pressed firmly with fingers to make it in full contact with the coating. After maintaining for 30 s, the tape is quickly torn off at an angle of 90°. Observe the coating peeling situation within the squares. The adhesion grade is divided into 0 - 5 levels, where level 0 indicates no coating peeling and the best adhesion; level 5 indicates that the coating peeling area is greater than 65% and the worst adhesion. The results are shown in Table 1.

[0091] Table 1 Test Results

[0092]

[0093] From the above results, it can be seen that the powder coatings of Examples 1 to 3 simultaneously have good insulation, weather resistance and adhesion, overcoming the technical bottleneck that it is difficult to improve all of them as a whole.

[0094] In Comparative Example 1, the composite modified resin was replaced with bisphenol A epoxy resin, and no core-shell structure and siloxane cross-linked network were formed. Bisphenol A epoxy resin itself has poor weather resistance. In the artificial accelerated aging and salt spray corrosion tests, it is easily eroded by ultraviolet rays and salts, resulting in coating powdering, corrosion, and deterioration of color difference and corrosion rating. At the same time, due to the lack of the synergistic strengthening effect of the core-shell structure, the insulation performance and adhesion performance are also affected, the volume resistivity decreases, the electrical strength drops, and the adhesion grade increases.

[0095] In Comparative Example 2, aminopropyl-terminated polydimethylsiloxane was not added during the preparation of the composite modified resin, which affected the perfection of the siloxane cross-linked network. Aminopropyl-terminated polydimethylsiloxane participates in the siloxane cross-linking reaction, increases the cross-linking density, and improves the stability of the material. The lack of it will make the cross-linked network sparse and the intermolecular force weaken. In terms of electrical properties, it cannot effectively block electron migration, resulting in a decrease in volume resistivity and a drop in electrical strength; in terms of weather resistance, the ability to resist external erosion becomes weaker, and the color difference and corrosion rating increase.

[0096] In Comparative Example 3, dimethylstearylamine was not added during the preparation of the composite modified resin, which affected the graft polymerization of hydroxyl acrylic resin and the core layer. Dimethylstearylamine promotes the grafting reaction and makes the shell layer and the core layer closely combined. Without it, the grafting rate decreases, the chemical bonding between the shell layer and the core layer decreases, and the structural stability deteriorates. This makes the material prone to delamination when subjected to external forces and environmental factors, resulting in a decrease in adhesion performance and weather resistance, and an increase in color difference and adhesion grade.

[0097] In Comparative Example 4, all of the main curing agent was replaced with methyl nadic anhydride, changing the curing system. Methyl nadic anhydride alone as the main curing agent has different curing reaction rates and extents from the compounding system, and an ideal cross-linked structure cannot be formed. In terms of insulation performance, the imperfect cross-linked structure will affect charge conduction and electric field distribution, resulting in a drop in electrical strength; in terms of weather resistance, the cured coating has insufficient hardness and toughness, and the ability to resist ultraviolet rays and chemical erosion becomes weaker, and the color difference and corrosion rating increase.

[0098] In Comparative Example 5, all of the main curing agent was replaced with diphenylmethane diisocyanate, also changing the curing system. When diphenylmethane diisocyanate is used alone, its reaction activity with the resin and the properties of the cured product are different from those of the compounding system. The internal stress of the cured coating is relatively large, and microcracks are easily generated, affecting the insulation performance and weather resistance. The volume resistivity decreases slightly, the electrical strength drops, and in the salt spray and aging tests, the microcracks become erosion channels, resulting in an increase in color difference and corrosion rating.

[0099] In Comparative Example 6, the dual curing agent does not add a latent curing accelerator, resulting in incomplete curing. The latent curing accelerator activates the curing reaction under specific conditions to make the curing more complete. The lack of it will cause the curing reaction to stay at a lower level, with insufficient crosslinking density, leading to a decline in the mechanical properties and chemical stability of the material. In terms of insulation performance, it is manifested as a decrease in electrical strength; in terms of weather resistance, the coating is more vulnerable to environmental factors, with an increase in color difference and corrosion rating.

[0100] In Comparative Example 7, the preparation of the latent curing accelerator does not add propylene glycol, which affects the formation of the polyurethane wall material. Propylene glycol participates in the synthesis reaction of polyurethane to regulate the structure and properties of the wall material. Without propylene glycol, the crosslinking degree and flexibility of the polyurethane wall material change, and the coating effect of the microcapsule becomes poor. This makes the latent curing accelerator prone to premature release during storage and use, unable to effectively control the curing reaction, resulting in unstable performance of the curing system and a decline in various performance indicators.

[0101] In Comparative Example 8, an excessive amount of propylene glycol is added in the preparation of the latent curing accelerator, damaging the wall material structure. Excessive propylene glycol will make the molecular chain of the polyurethane wall material too long or over-crosslinked, resulting in the brittleness of the wall material and the destruction of the integrity of the microcapsule. During the extrusion process, the latent curing accelerator will leak prematurely, affecting the orderly progress of the subsequent curing reaction, leading to a decline in insulation performance and weather resistance, a decrease in volume resistivity and electrical strength, and an increase in color difference and corrosion rating.

[0102] In Comparative Example 9, the silane-coupling-agent-modified nano boron nitride in the functional filler is replaced with nano boron nitride, resulting in poor dispersibility and interfacial bonding. Silane-coupling-agent modification can improve the dispersibility of nano boron nitride in the resin matrix and enhance its interfacial bonding force with the resin. Unmodified nano boron nitride is prone to agglomeration, forming stress concentration points in the composite material, reducing the mechanical properties and insulation performance of the material. In terms of electrical properties, the agglomerates partially become conductive channels, reducing the volume resistivity and electrical strength; in terms of weather resistance, the stress concentration points are prone to cause coating cracking, leading to an increase in the corrosion rating.

[0103] In Comparative Example 10, the rutile titanium dioxide coated with silica in the functional filler is replaced with rutile titanium dioxide, resulting in a decline in weather resistance. Silica coating can improve the chemical stability and dispersibility of rutile titanium dioxide, enhancing its ability to shield ultraviolet rays. Uncoated rutile titanium dioxide is prone to photocatalytic reactions under ultraviolet irradiation, leading to coating aging and color change. In the artificial accelerated aging test, the color difference increases significantly and the weather resistance decreases.

[0104] In Comparative Example 11, when two functional fillers were replaced simultaneously, the insulation and weather resistance properties were significantly reduced. On the one hand, unmodified nano boron nitride and uncoated rutile titanium dioxide weakened the material properties in terms of insulation and weather resistance respectively; on the other hand, the synergistic effect between the two fillers and the resin matrix was destroyed, and an effective reinforcement and protection system could not be formed. In terms of insulation performance, the volume resistivity and electrical strength decreased significantly; in terms of weather resistance, the color difference and corrosion rating increased significantly, and the adhesion was also greatly affected.

[0105] In Comparative Example 12, the preparation of silica-coated rutile titanium dioxide was not calcined and replaced by drying, and the coating structure was imperfect. The calcination process can form a dense coating layer of silica on the surface of titanium dioxide, improving its stability and weather resistance. Drying cannot achieve the same effect, the coating layer is loose and cannot effectively block the erosion of ultraviolet rays and chemical substances. In the artificial accelerated aging and salt spray corrosion tests, the coating is easily damaged, the color difference and corrosion rating increase, and the weather resistance decreases.

Claims

1. An insulating weather-resistant powder coating, characterized in that: The powder coating comprises the following raw materials in parts by weight: 60 to 70 parts of a composite modified resin, 5 to 10 parts of a dual curing agent, 20 to 30 parts of a functional filler, 0.5 to 1 part of a polyacrylate leveling agent, 0.5 to 1 part of fumed silica, 0.5 to 1 part of a benzotriazole ultraviolet absorber, 0.2 to 0.5 parts of polytetrafluoroethylene wax powder, 1 to 5 parts of a pigment and 0.1 to 0.5 parts of an antioxidant 1010; The core layer of the composite modified resin is a bisphenol A epoxy resin modified by 3-glycidyloxypropyltrimethoxysilane and aminopropyl-terminated polydimethylsiloxane to form a siloxane cross-linked network; the shell layer of the composite modified resin is a hydroxy acrylic resin, dimethyl stearylamine and the core layer are chemically bonded by graft polymerization; The main curing agent of the dual curing agent is a compound of methyl nadic anhydride and diphenylmethane diisocyanate; the latent curing accelerator of the dual curing agent is a microencapsulated imidazole compound, the microcapsule wall material is polyurethane, and the polyurethane is prepared by reacting polyether polyol, diphenylmethane diisocyanate, and propylene glycol in a mass ratio of (8-10): (3-5): (2-3); The compounding mass ratio of the methyl nadic anhydride, diphenylmethane diisocyanate and latent curing accelerator is (3-4): (1-1.5): (0.5-1); The mass ratio of the functional filler components is silane coupling agent modified nano boron nitride: silica coated rutile titanium dioxide = (3-5): (1-2); the silica coated rutile titanium dioxide is prepared by coating rutile titanium dioxide with silica and calcining at 500-600°C for 2h-3h.

2. The insulating weather-resistant powder coating according to claim 1, characterized in that: The preparation method of the composite modified resin comprises the following steps: adding bisphenol A epoxy resin to cyclohexanone at 70°C to 80°C under stirring to prepare a solution A with a concentration of 8wt% to 12wt%, adding 3-glycidyloxypropyltrimethoxysilane and aminopropyl-terminated polydimethylsiloxane, mixing evenly, then adding dibutyltin dilaurate, heating to 120°C to 130°C, stirring for 2h to 3h to form a siloxane cross-linked network, and obtaining a core layer system; stirring at 30°C to 40°C, In a stirring state, hydroxy acrylic resin and dimethyl stearylamine are added to ethyl acetate to prepare solution B; the core layer system is cooled to 70°C to 80°C, and solution B is added to the core layer system at a volume ratio of core layer system: solution B = (8-10): (3-5) under stirring, and then benzoyl peroxide initiator is added, and the reaction is stirred for 3h to 4h to form a chemical bond between the hydroxy acrylic resin and the core layer through graft polymerization, and the mixture is centrifugally atomized and vacuum dried to obtain a composite modified resin with a particle size of less than 50μm.

3. The insulating weather-resistant powder coating according to claim 2, characterized in that: The amount of 3-glycidyloxypropyltrimethoxysilane added is 4% to 6% of the mass of bisphenol A epoxy resin; the amount of aminopropyl-terminated polydimethylsiloxane added is 3% to 5% of the mass of bisphenol A epoxy resin; the amount of dibutyltin dilaurate added is 0.2% to 0.5% of the mass of bisphenol A epoxy resin; the solution B contains 10wt% to 15wt% of hydroxylated acrylic resin and 3wt% to 5wt% of dimethylstearylamine; the amount of benzoyl peroxide initiator added is 3% to 5% of the mass of hydroxylated acrylic resin; the stirring speed is 300r / min to 500r / min; the parameters of the centrifugal atomization drying are: inlet air temperature 150℃ to 180℃, outlet air temperature 70℃ to 90℃, and centrifugal atomization speed 10000r / min to 12000r / min.

4. The insulating weather-resistant powder coating according to claim 1, characterized in that: The preparation method of the latent curing accelerator comprises the following steps: preparing the ingredients according to the mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol = 100: (8-10): (3-5): (2-3), stirring and reacting at 45°C-50°C for 2h-3h to obtain a polyurethane wall material solution; dissolving 2-ethyl-4-methylimidazole in ethanol to prepare an imidazole solution with a concentration of 8wt%-12wt%; preparing a polyvinyl alcohol aqueous solution with a concentration of 0.8wt%-1wt%; according to the volume ratio of imidazole solution: polyurethane wall material solution: polyvinyl alcohol aqueous solution = (1-2): (2-3): (1-2), adding the imidazole solution to the polyurethane wall material solution, ultrasonically dispersing, then adding the polyvinyl alcohol aqueous solution under stirring conditions, stirring and reacting for 3h-4h to form microcapsules, centrifuging, collecting the microcapsules, washing with deionized water, and vacuum drying to obtain a microencapsulated latent curing accelerator.

5. The insulating weather-resistant powder coating according to claim 4, characterized in that: The ultrasonic dispersion is 30kHz to 50kHz ultrasonic dispersion for 30min to 40min; the stirring speed is 200r / min to 400r / min; the centrifugation is 3000r / min to 5000r / min for 10min to 15min; the washing times is 3 to 4 times; the vacuum drying is vacuum drying at 50°C to 60°C for 24h to 30h.

6. The insulating weather-resistant powder coating according to claim 1, characterized in that: The preparation method of silane coupling agent modified nano boron nitride comprises the following steps: dispersing nano boron nitride in anhydrous ethanol at a solid content of 5wt% to 6wt%, adding silane coupling agent KH560 in an amount of 3% to 5% by mass of the nano boron nitride under stirring, adjusting the pH value to 4 to 5 with acetic acid, heating to 60°C to 70°C, stirring at 300r / min to 500r / min for 4h to 6h, centrifuging at 8000r / min to 10000r / min for 10min to 15min, taking a precipitate, washing with water for 3 to 4 times, and vacuum drying at 70°C to 80°C for 12h to 24h to obtain silane coupling agent modified nano boron nitride.

7. The insulating weather-resistant powder coating according to claim 1, characterized in that: The preparation method of the silica-coated rutile titanium dioxide comprises the following steps: mixing the rutile titanium dioxide and a 5wt% to 8wt% hydrogen peroxide solution in a mass ratio of 1:(10-12), stirring at 70°C to 80°C for 1h to 2h, centrifuging at 8000r / min to 10000r / min for 10min to 20min, taking a precipitate, washing with water until neutral, and drying to obtain a surface hydroxylated titanium dioxide; preparing a coating solution in a volume ratio of ethyl orthosilicate: anhydrous ethanol: ammonia water = 1:(10-12):(0.5-0.8); and hydroxylating the surface of the titanium dioxide at a solid content of 8wt% to 12wt%. The titanium dioxide powder is dispersed in ethanol to obtain a suspension, and then the coating liquid is added in a stirring state according to the volume ratio of suspension: coating liquid = (10-12): (2-3), and the reaction is carried out at 40℃-45℃ and 300r / min-500r / min with stirring for 5h-6h, and then the solid is aged for 20h-30h, and then the solid is centrifuged at 8000r / min-10000r / min for 10min-20min to obtain a solid, and the solid is heated to 500℃-600℃ at a heating rate of 4℃ / min-6℃ / min and calcined for 2h-3h to obtain silica-coated rutile titanium dioxide.

8. The method for preparing an insulating weather-resistant powder coating according to claim 1, characterized in that: The preparation method comprises the following steps: The raw materials are mixed uniformly according to their mass fractions to obtain a mixture; the mixture is extruded into strips by an extruder at 100° C. to 120° C. and a screw speed of 150 r / min to 200 r / min, and the strips are air-cooled and crushed to obtain a median particle size of 15 μm to 30 μm to obtain an insulating weather-resistant powder coating.

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