Insulating weather-resistant powder coating and preparation method thereof

Abstract

The invention relates to an insulating weather-resistant powder coating and a preparation method thereof, and belongs to the technical field of coatings, and the powder coating comprises composite modified resin, a dual curing agent, a functional filler, a polyacrylate leveling agent, fumed silica, a benzotriazole ultraviolet light absorber, polytetrafluoroethylene wax powder and the like. A core-shell structure of the composite modified resin is designed, high insulativity is kept through a silane modified epoxy core layer, a weather-proof barrier is provided through an acrylic acid shell layer, and the phase separation problem is solved through interface chemical bonding; a dual-curing mechanism is designed, and isocyanate and acrylic hydroxyl react to form an interpenetrating network while an epoxy core layer is cured by anhydride; a filler synergistic effect is designed, silane coupling agent modified nano boron nitride forms a three-dimensional heat-conducting insulating network, and rutile type titanium dioxide is coated with silicon dioxide, so that ultraviolet aging is resisted. All the components cooperate with one another, so that the coating has excellent insulativity, weather resistance, adhesiveness and the like at the same time.

Description

Technical Field

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

[0002] From the development history of coatings, the emergence of polyethylene powder in the 1940s opened the chapter of powder coatings. Thermosetting epoxy powder coatings were developed in the 1950s, and the types of powder coatings have been continuously enriched since then. In the late 1990s, in order to meet new safety or weather resistance requirements, powder coatings with special properties such as low molecular weight epoxy compound cured polyester and thermosetting fluororesin powder were developed. Entering the new century, powder technology is changing with each passing day, the market scale is expanding and becoming more refined, and the growth rate of weather-resistant powder coatings is particularly significant.

[0003] Insulating weather-resistant powder coatings play an indispensable role in many application fields. In the power industry, equipment such as high-voltage switchgear, transformers, and electromagnetic wires are in a complex electrical environment for a long time. They not only need to have good insulation properties to ensure the safety and stability of power transmission, but also need to withstand harsh weather conditions such as outdoor sunlight, acid rain, and temperature changes to prevent equipment failures caused by coating damage. The new energy vehicle industry also has an urgent need for it. Key components such as battery packs and motors of new energy vehicles will generate a lot of heat and electric fields when working, requiring the coating to have insulation, temperature resistance, and chemical corrosion resistance. At the same time, vehicles are driving outdoors and face various climate challenges. Therefore, insulating weather-resistant powder coatings have become an important material to ensure the safety and service life of new energy vehicles. In addition, some outdoor electronic equipment, communication base stations, etc. also need this kind of coating with both insulation and weather resistance to protect the equipment and ensure its stable operation.

[0004] However, it is difficult for traditional powder coatings to meet the high standards of insulation and weather resistance at the same time. For example, although the commonly used epoxy powder coating has excellent insulation performance, metal adhesion, corrosion resistance, hardness, flexibility and impact strength, it has poor weather resistance, is prone to powdering and discoloration in outdoor environments, and has a short service life, which limits its wide application in the field of outdoor insulation. Acrylic resin powder coating has good weather resistance and insulation performance, but it still needs to be improved in some insulation performance indicators, and there are few reports on its application in the insulation field.

[0005] Although some curing agents, fillers and additives are mixed in order to balance various indicators, it is still not ideal. Currently, the coatings on the market have different compositions and varying performances. There is still a common problem that it is difficult to comprehensively improve insulation, weather resistance and adhesion. Summary of the invention

[0006] In view of the problem that the insulation, weather resistance and adhesion of existing powder coatings are difficult to improve comprehensively, the present invention provides an insulating weather-resistant powder coating and a preparation method thereof, designs a core-shell structure of a composite modified resin, maintains high insulation through a silane-modified epoxy core layer, provides a weather-resistant barrier through an acrylic shell layer, and solves the phase separation problem through interfacial chemical bonding; designs a dual curing mechanism, while anhydride cures the epoxy core layer, isocyanate reacts with acrylic hydroxyl groups to form an interpenetrating network; designs a filler synergistic effect, silane coupling agent-modified nano-boron nitride forms a three-dimensional thermally conductive insulating network, and silica-coated rutile titanium dioxide resists ultraviolet aging. Cooperating with other ingredients, the coating simultaneously possesses excellent insulation, weather resistance, adhesion and other properties, solving the problem that it is difficult for traditional powder coatings to comprehensively improve these properties. Its specific technical scheme is as follows: An insulating weather-resistant powder coating, the powder coating comprising 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 siloxane cross-linked network formed by modifying bisphenol A epoxy resin with 3-glycidyloxypropyltrimethoxysilane; the shell layer of the composite modified resin is a hydroxy acrylic resin and the core layer is 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, and the microcapsule wall material is polyurethane; The functional filler comprises silane coupling agent modified nano boron nitride and silicon dioxide coated rutile titanium dioxide.

[0007] In the above powder coating, the compounding mass ratio of the methyl nadic anhydride, diphenylmethane diisocyanate and latent curing accelerator is (3-4): (1-1.5): (0.5-1).

[0008] In the above powder coating, the mass ratio of the silane coupling agent modified nano boron nitride to the silicon dioxide coated rutile titanium dioxide is (3-5): (1-2).

[0009] In the above-mentioned powder coating, the preparation method of the composite modified resin comprises the following steps: adding bisphenol A type 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 and reacting for 2h to 3h to form a siloxane cross-linked network to obtain a core layer system; heating at 30°C to 40°C , add hydroxy acrylic resin and dimethyl stearylamine to ethyl acetate under stirring to prepare solution B; cool the core layer system to 70℃~80℃, add solution B to the core layer system under stirring at a volume ratio of core layer system: solution B = (8~10): (3~5), then add benzoyl peroxide initiator, stir and react for 3h~4h to form chemical bond between hydroxy acrylic resin and core layer through grafting polymerization, centrifugal atomization drying, vacuum drying to obtain composite modified resin with particle size below 50μm.

[0010] In the preparation method of the above-mentioned composite modified resin, the addition amount of the 3-glycidyloxypropyltrimethoxysilane is 4% to 6% of the mass of the bisphenol A epoxy resin; the addition amount of the aminopropyl-terminated polydimethylsiloxane is 3% to 5% of the mass of the bisphenol A epoxy resin; the addition amount of the dibutyltin dilaurate is 0.2% to 0.5% of the mass of the bisphenol A epoxy resin; the solution B contains 10wt% to 15wt% of hydroxylated acrylic resin and 3wt% to 5wt% of dimethylstearylamine; the addition amount of the benzoyl peroxide initiator is 3% to 5% of the mass of the 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] In the above-mentioned powder coating, the preparation method of the silicon dioxide-coated rutile titanium dioxide comprises the following steps: mixing rutile titanium dioxide (nanoscale) with 5wt% to 8wt% hydrogen peroxide solution in a mass ratio of 1: (10 to 12), stirring at 70°C to 80°C for 1h to 2h, centrifuging at 8000r / min to 10000r / min for 10min to 20min, taking the precipitate, washing with water to neutrality, and drying to obtain surface hydroxylated titanium dioxide; preparing a coating solution in a volume ratio of ethyl orthosilicate: anhydrous ethanol: ammonia water (concentration 20wt% to 25wt%) = 1: (10 to 12): (0.5 to 0.8); preparing a coating solution in a volume ratio of 8w t%~12wt%, the surface hydroxylated titanium dioxide is dispersed in ethanol to obtain a suspension, and then the coating liquid is added under stirring according to the volume ratio of suspension: coating liquid = (10~12): (2~3), and the reaction is stirred at 40℃~45℃ and 300r / min~500r / min for 5h~6h, and the reaction is allowed to stand for 20h~30h, and 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.

[0015] The method for preparing the above-mentioned insulating weather-resistant powder coating 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.

[0016] The present invention provides an insulating weather-resistant powder coating and a preparation method thereof, and the beneficial effects are as follows: 1. The present invention prepares a composite modified resin, in which the core layer system of the bisphenol A epoxy resin itself has good insulation properties, adhesion to metals, corrosion resistance, hardness, flexibility and impact strength. The siloxane group in 3-glycidyloxypropyltrimethoxysilane can react with active groups such as hydroxyl groups in 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, and especially significantly improve its weather resistance, because the siloxane bond has good resistance to environmental factors such as ultraviolet rays and moisture. Aminopropyl-terminated polydimethylsiloxane utilizes the silicon-oxygen segment in its molecular structure to promote the formation stability of the siloxane cross-linked network, and can also give the core layer good flexibility and hydrophobicity. Dibutyltin dilaurate is used as a catalyst to accelerate the cross-linking reaction of siloxane, ensuring that a stable cross-linked structure is formed within a specified time.

[0017] During the formation of the shell layer, the hydroxy acrylic resin has good weather resistance, glossiness and color retention. Dimethyl stearyl amine can promote the dispersion and graft polymerization of the hydroxy acrylic resin on the surface of the core layer. The benzoyl peroxide initiator decomposes to produce free radicals, which trigger the graft polymerization of the hydroxy acrylic resin and the core layer, so that the shell layer is tightly chemically bonded to the core layer. This core-shell structured composite modified resin not only retains the excellent properties of epoxy resin, but also combines the weather resistance advantages of hydroxy acrylic resin to form a synergistically enhanced system. The addition of aminopropyl-terminated polydimethylsiloxane and dimethyl stearyl amine additives effectively promotes the stability of the system structure, greatly improving the overall comprehensive performance of the coating.

[0018] 2. In the dual curing agent, both methyl nadic anhydride and diphenylmethane diisocyanate can react with the active groups in the resin to crosslink and cure the resin. After reacting with epoxy resin and other resins, methyl nadic anhydride can improve the hardness, strength and chemical stability of the coating. The anhydride groups in its structure react with the hydroxyl groups of the resin to form stable chemical bonds. Diphenylmethane diisocyanate has a high reactivity. It reacts with hydroxyl groups, amino groups, etc. in the resin to further increase the crosslinking density and improve the mechanical properties and chemical corrosion resistance of the coating. The two can be used in combination to achieve a good balance between the curing speed, curing degree and the final coating performance by adjusting the ratio.

[0019] 3. Among the dual curing agents, the latent curing accelerator is a microencapsulated imidazole compound. 2-ethyl-4-methylimidazole is a highly efficient curing accelerator that can accelerate the curing reaction. However, in order to prevent it from initiating a curing reaction during the storage stage of the coating, polyurethane is used as the wall material to microencapsulate it. Under low temperature or normal conditions, the microcapsules remain intact, and the imidazole inside is coated and will not react with other components in the coating, thus ensuring the storage stability of the coating. When the coating is in the high-temperature curing stage, the microcapsule wall material is decomposed or softened by heat, releasing imidazole, thereby promoting the cross-linking reaction between the main curing agent and the resin, improving the curing efficiency and degree, and enabling the coating to cure quickly and fully.

[0020] A certain amount of propylene glycol is added to promote the formation of polyurethane wall materials. Propylene glycol participates in the synthesis reaction of polyurethane, has a chain extension effect, and adjusts the structure and performance of the wall materials. If excessive propylene glycol is added, the wall material structure will be destroyed. Excessive propylene glycol will make the molecular chain of the polyurethane wall material too long or excessively cross-linked, causing the wall material to become brittle and the integrity of the microcapsules to be destroyed.

[0021] 4. 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, so that it can be evenly distributed in the coating, avoiding agglomeration and giving full play to its performance advantages; on the other hand, the interfacial bonding between nano boron nitride and the resin is enhanced, thereby improving the insulation performance, thermal conductivity and mechanical properties of the coating, especially in improving the insulation performance, because good dispersion and interfacial bonding help reduce defects in the electron conduction path.

[0022] 5. Rutile titanium dioxide has good light resistance and weather resistance. Through synthetic silica coating, a dense protective film is formed to further prevent ultraviolet rays from directly contacting titanium dioxide and inhibit the occurrence of photocatalytic reactions, thereby further enhancing the weather resistance of the coating. At the same time, the presence of synthetic silica also improves the dispersibility and stability of titanium dioxide in the resin matrix, further improving the overall performance of the coating.

[0023] 6. Fumed silica has a large specific surface area and a special surface structure. In coatings, fumed silica increases the viscosity and thixotropy of the system by forming hydrogen bonds or other interactions with polymer molecules in the coating.

[0024] 7. PTFE wax powder can form a protective film with low surface energy on the surface of the coating, which makes the coating smooth and not easy to be stained with dust and stains, thus improving the anti-fouling property 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.

[0025] In summary, the present invention designs a core-shell structure of a composite modified resin, wherein the epoxy core layer modified by silane maintains high insulation, the acrylic shell layer provides a weather-resistant barrier, and the interfacial chemical bonding solves the phase separation problem; a dual curing mechanism is designed, wherein the anhydride cures the epoxy core layer while the isocyanate reacts with the acrylic hydroxyl group to form an interpenetrating network; a filler synergistic effect is designed, wherein the silane coupling agent modifies the nano-boron nitride to form a three-dimensional thermally conductive insulating network, and the silica-coated rutile titanium dioxide resists ultraviolet aging.

[0026] As the main film-forming material of the coating, the composite modified resin provides the basic foundation for mechanical properties, insulation properties and weather resistance. The dual curing agent ensures that the resin can be fully cross-linked and cured to form a stable three-dimensional network structure, thereby 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 filler strengthen the coating from the aspects of improving insulation and weather resistance, while enhancing homogeneity and also having a certain enhancing effect on adhesion performance. They work together to enable the coating to have excellent insulation, weather resistance and adhesion properties at the same time, solving the problem that traditional powder coatings are difficult to comprehensively improve these properties. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0028] Embodiment 1: An insulating weather-resistant powder coating, the powder coating comprising the following raw materials in parts by weight: 65 parts of a composite modified resin, 8 parts of a dual curing agent, 25 parts of a functional filler, 0.8 parts of a polyacrylate leveling agent, 0.8 parts of a fumed silica, 0.8 parts of a benzotriazole ultraviolet absorber, 0.35 parts of a polytetrafluoroethylene wax powder, 0.3 parts of a pigment and 0.3 parts of an antioxidant 1010; wherein the core layer of the composite modified resin is a siloxane cross-linked network formed by modifying a bisphenol A type epoxy resin with 3-glycidyloxypropyltrimethoxysilane; the composite modified resin The shell layer is a hydroxy acrylic resin and the core layer is 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, and the microcapsule wall material is polyurethane; the composite mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate and 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 in a mass ratio of 4:1.5.

[0029] The preparation method of the composite modified resin includes the following steps: adding bisphenol A epoxy resin to cyclohexanone at 75°C and 400 r / min stirring to prepare a 10wt% concentration solution A, adding 5% of the mass of bisphenol A epoxy resin 3-glycidyloxypropyl trimethoxysilane and 4% of the mass of bisphenol A epoxy resin aminopropyl-terminated polydimethylsiloxane, mixing evenly, then adding 0.3% of the mass of bisphenol A epoxy resin dibutyltin dilaurate, heating to 125°C, stirring at 400 r / min for 2.5 hours to form a siloxane cross-linked network to obtain a core layer system; adding hydroxy acrylic resin and dimethyl stearylamine at 35°C and 400 r / min stirring to obtain a core layer system; Add ethyl acetate with a hydroxy acrylic resin content of 12wt% and a dimethyl stearylamine content of 4wt% to prepare solution B; cool the core layer system to 75°C, and add solution B to the core layer system at a volume ratio of core layer system: solution B = 9:4 under stirring at 400r / min, then add benzoyl peroxide initiator at a weight percentage of 4% of the weight of the hydroxy acrylic resin, and stir at 400r / min for 3.5h to form a chemical bond between the hydroxy acrylic resin and the core layer through grafting polymerization, centrifugal atomization drying, with an inlet air temperature of 170°C, an outlet air temperature of 80°C, and a centrifugal atomization speed of 11000r / min, and vacuum drying at 55°C for 26h to obtain a composite modified resin with a particle size of less than 50μm.

[0030] 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 = 100:9:4:2.5, stirring and reacting at 47°C and 300r / min for 2.5h to obtain a polyurethane wall material solution; dissolving 2-ethyl-4-methylimidazole (EMI) in ethanol to prepare an imidazole solution with a concentration of 10wt%; preparing a polyvinyl alcohol aqueous solution with a concentration of 0.9wt%; and mixing the imidazole solution: polyurethane in a volume ratio of 1:1. The ratio of ester wall material solution to polyvinyl alcohol aqueous solution is 1.5:2.5:1.8. The imidazole solution is added to the polyurethane wall material solution, and ultrasonic dispersion is performed at 40kHz for 35 minutes. Then, the polyvinyl alcohol aqueous solution is added under stirring conditions at 300r / min, and the reaction is stirred at 300r / min for 3.5 hours to form microcapsules. The microcapsules are collected by centrifugation at 4000r / min for 12 minutes, washed three times with deionized water, and vacuum dried at 55°C for 26 hours to obtain a microencapsulated latent curing accelerator.

[0031] 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 5.5wt%, adding silane coupling agent KH560 of 4% by mass of nano boron nitride under stirring, adjusting the pH value to 4.5 with acetic acid, heating to 65°C, stirring at 400r / min for 5h, centrifuging at 9000r / min for 12min, taking the precipitate, washing it with water for 3 times, and vacuum drying it at 75°C for 18h to obtain silane coupling agent modified nano boron nitride.

[0032] The preparation method of silica-coated rutile titanium dioxide comprises the following steps: mixing rutile titanium dioxide (nanoscale) with 7wt% hydrogen peroxide solution in a mass ratio of 1:11, stirring at 75°C and 400r / min for 1.5h, centrifuging at 9000r / min for 15min, taking the precipitate, washing with water until neutral, and drying to obtain surface hydroxylated titanium dioxide; preparing a coating solution in a volume ratio of ethyl orthosilicate: anhydrous ethanol: ammonia water (concentration 22wt%) = 1:11:0.6; and mixing at a solid content of 1:11:0.6. The surface hydroxylated titanium dioxide was dispersed in ethanol at a volume ratio of 11:2.5, and the coating liquid was added under stirring at 400 r / min. The mixture was stirred at 42 °C and 400 r / min for 5.5 h, aged for 25 h, and centrifuged at 9000 r / min for 15 min to obtain a solid. The solid was heated to 550 °C at a heating rate of 5 °C / min and calcined for 2.5 h to obtain a silica-coated rutile titanium dioxide.

[0033] The method for preparing the above-mentioned insulating weather-resistant powder coating comprises the following steps: The raw materials were mixed uniformly according to their mass fractions to obtain a mixture; the mixture was extruded into strips using an extruder at 110° C. and a screw speed of 180 r / min, and the strips were air-cooled and crushed to obtain a median particle size of 21 μm to obtain an insulating weather-resistant powder coating.

[0034] Example 2: An insulating weather-resistant powder coating, the powder coating comprises the following raw materials in parts by weight: 60 parts of a composite modified resin, 5 parts of a dual curing agent, 20 parts of a functional filler, 0.5 parts of a polyacrylate leveling agent, 0.5 parts of a fumed silica, 0.5 parts of a benzotriazole ultraviolet absorber, 0.2 parts of a polytetrafluoroethylene wax powder, 1 part of a pigment and 0.1 parts of an antioxidant 1010; wherein the core layer of the composite modified resin is a siloxane cross-linked network formed by modifying a bisphenol A type epoxy resin with 3-glycidyloxypropyltrimethoxysilane; the composite modified The shell layer of the resin is a hydroxy acrylic resin and the core layer is chemically bonded by grafting 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 composite mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate and latent curing accelerator is 3:1:0.5; the functional filler is a mixture of silane coupling agent modified nano boron nitride and silica-coated rutile titanium dioxide in a mass ratio of 3:1.

[0035] The preparation method of the composite modified resin includes the following steps: adding bisphenol A epoxy resin to cyclohexanone at 70°C and 300 r / min stirring to prepare a solution A with a concentration of 8wt%, adding 4% of 3-glycidyloxypropyltrimethoxysilane by weight of the bisphenol A epoxy resin and 3% of aminopropyl-terminated polydimethylsiloxane by weight of the bisphenol A epoxy resin, mixing evenly, then adding 0.2% of dibutyltin dilaurate by weight of the bisphenol A epoxy resin, heating to 120°C, stirring at 300 r / min for 2h to form a siloxane cross-linked network to obtain a core layer system; adding hydroxylated acrylic resin and dimethyl stearylamine at 30°C and 300 r / min stirring to obtain a core layer system; Add ethyl acetate with a hydroxy acrylic resin content of 10wt% and a dimethyl stearylamine content of 3wt% to prepare solution B; cool the core layer system to 70°C, and add solution B to the core layer system at a volume ratio of core layer system: solution B = 8:3 under stirring at 300r / min, and then add benzoyl peroxide initiator with a mass% of hydroxy acrylic resin, and stir at 300r / min for 3h to form a chemical bond between the hydroxy acrylic resin and the core layer through graft polymerization, and centrifugal atomization drying with an inlet air temperature of 150°C, an outlet air temperature of 70°C, and a centrifugal atomization speed of 10000r / min, and vacuum drying at 50°C for 24h to obtain a composite modified resin with a particle size of less than 50μm.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The method for preparing the above-mentioned insulating weather-resistant powder coating comprises the following steps: The raw materials were mixed uniformly according to their mass fractions to obtain a mixture; the mixture was extruded into strips by an extruder at 100° C. and a screw speed of 150 r / min, and the strips were air-cooled and crushed to obtain an insulating weather-resistant powder coating with a median particle size of 30 μm.

[0040] Embodiment 3: An insulating weather-resistant powder coating, the powder coating comprises the following raw materials in parts by weight: 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 a fumed silica, 1 part of a benzotriazole ultraviolet absorber, 0.5 parts of a polytetrafluoroethylene wax powder, 5 parts of a pigment and 0.5 parts of an antioxidant 1010; wherein the core layer of the composite modified resin is a siloxane cross-linked network formed by modifying a bisphenol A type epoxy resin with 3-glycidyloxypropyltrimethoxysilane; The shell layer is a hydroxy acrylic resin and the core layer is chemically bonded by grafting 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 composite mass ratio of methyl nadic anhydride, diphenylmethane diisocyanate and latent curing accelerator is 4:1.5:1; the functional filler is a mixture of silane coupling agent modified nano boron nitride and silica-coated rutile titanium dioxide in a mass ratio of 5:2.

[0041] The preparation method of the composite modified resin includes the following steps: adding bisphenol A epoxy resin to cyclohexanone at 80°C and 500r / min stirring to prepare a solution A with a concentration of 12wt%, adding 6% of 3-glycidyloxypropyltrimethoxysilane by weight of the bisphenol A epoxy resin and 5% of aminopropyl-terminated polydimethylsiloxane by weight of the bisphenol A epoxy resin, mixing evenly, then adding 0.5% of dibutyltin dilaurate by weight of the bisphenol A epoxy resin, heating to 130°C, stirring at 500r / min for 3h to form a siloxane cross-linked network to obtain a core layer system; adding hydroxylated acrylic resin and dimethyl stearylamine at 40°C and 500r / min stirring to obtain a core layer system; Add ethyl acetate with a hydroxy acrylic resin content of 15wt% and a dimethyl stearylamine content of 5wt% to prepare solution B; cool the core layer system to 80°C, and add solution B to the core layer system at a volume ratio of core layer system: solution B = 10:5 under stirring at 500r / min, and then add benzoyl peroxide initiator with a mass% of hydroxy acrylic resin, and stir at 500r / min for 4h to form a chemical bond between the hydroxy acrylic resin and the core layer through graft polymerization, centrifugal atomization drying, with an inlet air temperature of 180°C, an outlet air temperature of 90°C, and a centrifugal atomization speed of 12000r / min, and vacuum drying at 60°C for 30h to obtain a composite modified resin with a particle size of less than 50μm.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The method for preparing the above-mentioned insulating weather-resistant powder coating comprises the following steps: The raw materials were mixed uniformly according to their mass fractions to obtain a mixture; the mixture was extruded into strips by an extruder at 120° C. and a screw speed of 200 r / min, and the strips were air-cooled and crushed to obtain an insulating weather-resistant powder coating with a median particle size of 15 μm.

[0046] In the above embodiments: bisphenol A epoxy resin is from Linzi Shuangli Resin Factory, Zibo City, solid, brand 604. 3-Glycidyloxypropyl trimethoxysilane 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. Hydroxylated acrylic resin is from Guangzhou Tanhua New Materials Co., Ltd., solid, model 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., model 2E4MI. Polyvinyl alcohol comes from Langfang Yingen Environmental Protection Technology Co., Ltd., with a density of 50g / cm 3 . Nano boron nitride comes from Shanghai Naio Nano Technology Co., Ltd., model NO-N-003-1. Silane coupling agent KH560 comes from Dongguan Shanyi Plastic Co., Ltd. Rutile titanium dioxide comes from Beijing Wanyun Huarui Chemical Co., Ltd. Tethyl orthosilicate comes from Shandong Jinyueyuan New Materials Co., Ltd. Methyl nadic anhydride comes from Nantong Runfeng Petrochemical Co., Ltd. Polyacrylate leveling agent comes from Guangdong Nuoyi Chemical Co., Ltd., model 2170. Fumed silica comes from Shandong Jiquan Biotechnology Co., Ltd., model A220. Benzotriazole UV absorber comes from BASF, model: light stabilizer UV-326. Polytetrafluoroethylene wax powder comes from Huangshan Aoshengyuan New Materials Technology Co., Ltd., model MTF-2020. Antioxidant 1010 comes from Dongguan Shanyi Plastic Co., Ltd.

[0047] The recommended reference coating method for the powder coatings in the above-mentioned embodiments is: it is recommended to use an electrostatic spraying method, spray the powder coating through a spray gun onto the grounded surface of the object to be coated, the spray gun voltage is controlled at 60kV-80kV, the distance between the spray gun and the object surface is maintained at 15cm-25cm, the spraying environment temperature is controlled at 20℃-25℃, the relative humidity is 40%-60%, so that the powder is evenly attached to the surface of the object, and the coating thickness is controlled at 80μm-120μm.

[0048] The powder coatings of the above embodiments are recommended to be cured by reference method: the sprayed object is placed in an oven for curing, the heating rate is controlled at 5°C / min-10°C / min, the temperature is raised to 180°C-200°C, and the temperature is kept for curing, so that the coating is cross-linked and cured to form a hard paint film.

[0049] Comparative Example 1 In the powder coating, the composite modified resin is replaced by 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.

[0050] Comparative Example 2 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.

[0051] Comparative Example 3 In the preparation method of the composite modified resin, dimethyl stearylamine 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.

[0052] Comparative Example 4 In the dual curing agent, the main curing agent is all 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.

[0053] Comparative Example 5 In the dual curing agent, the main curing agent is all diphenylmethane diisocyanate; other parameters and methods are the same as in Example 1. The median particle size of the product is 22 μm.

[0054] Comparative Example 6 No latent curing accelerator was added to the dual curing agent; other parameters and methods were the same as those in Example 1. The median particle size of the product was 25 μm.

[0055] Comparative Example 7 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.

[0056] Comparative Example 8 In the preparation method of the latent curing accelerator, the mass ratio of acetone: polyether polyol: diphenylmethane diisocyanate: propylene glycol is 100:9:4:6 (ie, propylene glycol is added in excess); other parameters and methods are the same as in Example 1. The median particle size of the product is 17 μm.

[0057] Comparative Example 9 In the functional filler, the silane coupling agent modified nano boron nitride 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.

[0058] Comparative Example 10 In the functional filler, the silica-coated rutile titanium dioxide 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.

[0059] Comparative Example 11 In the functional filler, the silane coupling agent modified nano boron nitride is replaced by nano boron nitride, and the silicon dioxide coated rutile titanium dioxide is replaced by rutile titanium dioxide; other parameters and methods are the same as in Example 1. The median particle size of the product is 26 μm.

[0060] Comparative Example 12 In the preparation method of the silica-coated rutile titanium dioxide, calcination is not performed, and calcination is replaced by drying at 100° C. for 8 hours; other parameters and methods are the same as those in Example 1. The median particle size of the product is 20 μm.

[0061] For the convenience of detection, the pigments of each embodiment and each comparative example are all iron oxide red, and the performance of each of the above powder coating products is tested.

[0062] 1. Insulation performance 1. Volume resistivity: According to GB / T 1410 "Test Method for Volume Resistivity and Surface Resistivity of Solid Insulating Materials", the powder coating is placed in a mold and maintained at a pressure of 15MPa for 5 minutes to form a disc sample with a diameter of 50mm and a thickness of 2mm. The sample is placed in a constant temperature and humidity environment at a temperature of 23°C and a relative humidity of 50% for 24 hours to reach a stable state before measurement. The sample is placed on the test electrode of the high resistance meter to ensure good contact between the electrode and the sample, and a DC voltage of 500V is applied for 60 seconds before reading the volume resistivity value. The results are shown in Table 1.

[0063] 2. Electrical strength: According to GB / T 1408.1 "Electrical strength test method for insulating materials Part 1: Test under power frequency", the sample has the same specifications as the volume resistivity test sample, and is also tested at a temperature of 23°C and a relative humidity of 50%. The sample is placed between the upper and lower electrodes of the withstand voltage tester, with an electrode diameter of 25mm, and the voltage increase rate is set to 1kV / s. The voltage is continuously increased until the sample breaks down, and the breakdown voltage value at this time is recorded, and then the electrical strength is calculated according to the formula: electrical strength = breakdown voltage / sample thickness. The results are shown in Table 1.

[0064] 2. Weather resistance 1. Artificial accelerated aging: According to GB / T 1865 "Artificial weathering and artificial radiation exposure (filtered xenon arc radiation) of paints and varnishes", the powder coating is sprayed on an aluminum plate with a size of 150mm×70mm×1mm, and the coating thickness is controlled at 80μm and cured. The sample is placed in a xenon arc lamp aging test box, the irradiance is set to 0.55W / (m²·nm) (340nm), the blackboard temperature is 65℃, the relative humidity is 50%, and the test period is 1000h. The color difference ΔE before and after the test is detected by a colorimeter to evaluate the weather resistance. The results are shown in Table 1.

[0065] 2. Salt spray corrosion: According to GB / T 1771 "Determination of neutral salt spray resistance of paints and varnishes", the sample preparation is the same as that of the artificial accelerated aging test. The sample is 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 to 35°C, and the spray is continuously sprayed for 2000 hours. Take out the sample, rinse it with clean water, and observe the surface corrosion of the sample after drying at room temperature for 1 hour. Corrosion rating is carried out in accordance with GB / T 6461 "Rating of samples and test pieces of metals and other inorganic coatings on metal substrates after corrosion tests". The rating standards are divided into 0-10 levels, 10 for no corrosion, and 0 for severe corrosion. The results are shown in Table 1.

[0066] 3. Adhesion performance According to GB / T 9286 "Cross-cut test for paint and varnish film", the powder coating was sprayed on a steel plate with a size of 100mm×100mm×1mm, and the coating thickness was controlled at 100μm and cured. On the prepared coating surface, a cross-cutting device was used to penetrate the coating with uniform pressure to scratch 10×10 1mm×1mm squares, and then a 3M600 tape with a width of 25mm was pasted on the cross-cut area. The tape was pressed with fingers to make full contact with the coating. After keeping it for 30s, the tape was quickly torn off at an angle of 90°. The coating shedding in the square was observed, and the adhesion level was divided into 0-5 levels, with 0 indicating no coating shedding and the best adhesion; 5 indicating that the coating shedding area was greater than 65% and the adhesion was the worst. The results are shown in Table 1.

[0067] Table 1 Test results

[0068] It can be seen from the above results that the powder coatings of Examples 1 to 3 have good insulation, weather resistance and adhesion, overcoming the technical bottleneck that it is difficult to improve the three as a whole.

[0069] In Comparative Example 1, the composite modified resin is replaced by bisphenol A epoxy resin, and no core-shell structure and siloxane cross-linked network are formed. Bisphenol A epoxy resin itself has poor weather resistance. In artificial accelerated aging and salt spray corrosion tests, it is easily corroded by ultraviolet rays and salt, resulting in powdering, corrosion, color difference and corrosion rating of the coating. At the same time, due to the lack of synergistic enhancement of the core-shell structure, the insulation performance and adhesion performance are also affected, the volume resistivity is reduced, the electrical strength is reduced, and the adhesion grade is increased.

[0070] In comparative example 2, aminopropyl-terminated polydimethylsiloxane is not added in the preparation of the composite modified resin, which affects the perfection of the siloxane cross-linking network. Aminopropyl-terminated polydimethylsiloxane participates in the cross-linking reaction of siloxane, increases the cross-linking density, and improves the stability of the material. The lack of it will make the cross-linking network sparse, weaken the intermolecular force, and in terms of electrical properties, it will not be able to effectively block electron migration, resulting in a decrease in volume resistivity and electrical strength; in terms of weather resistance, the ability to resist external erosion becomes weaker, and the color difference and corrosion rating increase.

[0071] In Comparative Example 3, dimethyl stearylamine was not added in the preparation of the composite modified resin, which affected the grafting polymerization of the hydroxy acrylic resin and the core layer. Dimethyl stearylamine promotes the grafting reaction, so that the shell layer and the core layer are tightly combined. Without it, the grafting rate is reduced, the chemical bonding between the shell layer and the core layer is reduced, and the structural stability is deteriorated. This makes the material prone to stratification when subjected to external forces and environmental factors, resulting in decreased adhesion and weather resistance, and increased color difference and adhesion grade.

[0072] In Comparative Example 4, all the main curing agents are methyl nadic anhydride, and the curing system is changed. When methyl nadic anhydride is used alone as the main curing agent, the curing reaction rate and degree are different from those of the compound system, and an ideal cross-linking structure cannot be formed. In terms of insulation performance, the imperfect cross-linking structure will affect charge conduction and electric field distribution, resulting in a decrease in electrical strength; in terms of weather resistance, the hardness and toughness of the cured coating are insufficient, the ability to resist ultraviolet rays and chemical erosion is weakened, and the color difference and corrosion rating increase.

[0073] In Comparative Example 5, diphenylmethane diisocyanate is used as the main curing agent, and the curing system is also changed. When diphenylmethane diisocyanate is used alone, the reactivity with the resin and the performance of the cured product are different from those of the compound system. The internal stress of the coating after curing is large, and microcracks are easily generated, which affects the insulation performance and weather resistance, and the volume resistivity is slightly reduced, and the electrical strength is reduced. In the salt spray and aging tests, the microcracks become erosion channels, resulting in color difference and corrosion rating increases.

[0074] In comparative example 6, the dual curing agent does not add a latent curing accelerator, and the curing is incomplete. The latent curing accelerator activates the curing reaction under certain conditions, making the curing more complete. The lack of it will cause the curing reaction to remain at a low level, the cross-linking density is insufficient, and the mechanical properties and chemical stability of the material are reduced. In terms of insulation performance, it is manifested as a decrease in electrical strength; in terms of weather resistance, the coating is more susceptible to damage from environmental factors, and the color difference and corrosion rating increase.

[0075] In Comparative Example 7, propylene glycol is not added in the preparation of the latent curing accelerator, which affects the formation of the polyurethane wall material. Propylene glycol participates in the synthesis reaction of polyurethane and adjusts the structure and performance 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 worse. This makes the latent curing accelerator easy to be released in advance during storage and use, and the curing reaction cannot be effectively controlled, resulting in unstable performance of the curing system and a decrease in various performance indicators.

[0076] In Comparative Example 8, excessive propylene glycol was added to prepare the latent curing accelerator, which destroyed the wall material structure. Excessive propylene glycol will make the molecular chain of the polyurethane wall material too long or excessively cross-linked, causing the wall material to become brittle and the integrity of the microcapsules to be destroyed. During the extrusion process, the latent curing accelerator will leak in advance, affecting the orderly progress of the subsequent curing reaction, resulting in decreased insulation and weather resistance, reduced volume resistivity and electrical strength, and increased color difference and corrosion rating.

[0077] In Comparative Example 9, the silane coupling agent modified nano boron nitride in the functional filler is replaced by nano boron nitride, and the dispersibility and interface bonding are deteriorated. Silane coupling agent modification can improve the dispersibility of nano boron nitride in the resin matrix and enhance its interface bonding with the resin. Unmodified nano boron nitride is easy to agglomerate, forming stress concentration points in the composite material, reducing the mechanical properties and insulation properties of the material. In terms of electrical properties, the agglomerate part becomes a conductive channel, reducing the volume resistivity and electrical strength; in terms of weather resistance, stress concentration points easily cause coating cracking, resulting in an increase in corrosion rating.

[0078] In Comparative Example 10, the silica-coated rutile titanium dioxide in the functional filler is replaced by rutile titanium dioxide, and the weather resistance is reduced. Silica coating can improve the chemical stability and dispersibility of rutile titanium dioxide and enhance its shielding ability against ultraviolet rays. Uncoated rutile titanium dioxide is prone to photocatalytic reaction under ultraviolet irradiation, resulting in aging and discoloration of the coating. In the artificial accelerated aging test, the color difference is significantly increased and the weather resistance is reduced.

[0079] In Comparative Example 11, the two functional fillers were replaced at the same time, and the insulation and weather resistance performance were significantly reduced. On the one hand, the unmodified nano-boron nitride and the uncoated rutile titanium dioxide weakened the material performance from the insulation and weather resistance aspects respectively; on the other hand, the synergistic effect of 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.

[0080] In Comparative Example 12, the preparation of silica-coated rutile titanium dioxide was replaced by drying without calcination, 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 is loose, and cannot effectively block ultraviolet rays and chemical corrosion. In 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 siloxane cross-linked network formed by modifying bisphenol A epoxy resin with 3-glycidyloxypropyltrimethoxysilane; the shell layer of the composite modified resin is a hydroxy acrylic resin and the core layer is 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, and the microcapsule wall material is polyurethane; The functional filler comprises silane coupling agent modified nano boron nitride and silicon dioxide coated rutile titanium dioxide.

2. The insulating weather-resistant powder coating according to claim 1, characterized in that: The compounding mass ratio of the methyl nadic anhydride, diphenylmethane diisocyanate and latent curing accelerator is (3-4): (1-1.5): (0.5-1).

3. The insulating weather-resistant powder coating according to claim 1, characterized in that: The mass ratio of the silane coupling agent modified nano boron nitride to the silicon dioxide coated rutile titanium dioxide is (3-5): (1-2).

4. 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.

5. The insulating weather-resistant powder coating according to claim 4, 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.

6. 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.

7. The insulating weather-resistant powder coating according to claim 6, 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.

8. 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.

9. 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.

10. 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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