Insulating nano ceramic coating and preparation method thereof

Abstract

The invention discloses an insulating nano ceramic coating and a preparation method thereof, relates to the technical field of coatings, and belongs to the patent classification number C09D1 / 00. The preparation method comprises the following steps: firstly, carrying out hydroxylation activation and silane modification treatment on nano aluminum oxide and nano zirconium oxide, and grafting polymer chains on the surfaces of the nano aluminum oxide and the nano zirconium oxide through a polymerization reaction to obtain grafted modified nano ceramic powder so as to enhance the dispersity and compatibility of the grafted modified nano ceramic powder in a resin matrix; meanwhile, the acrylic polysiloxane resin is subjected to epoxy modification and is subjected to a cross-linking reaction with 3-aminopropyltriethoxysilane and polyethylene glycol diglycidyl ether, so that resin with a cross-linked network structure is synthesized; and finally, mixing the modified resin, the grafted modified nano ceramic powder, a mixed solvent, polyamide wax, an organic silicon defoaming agent, an acrylate film-forming agent, gamma-aminopropyltriethoxysilane hydrolysate and other auxiliaries, stirring and fusing to obtain the final insulating nano ceramic coating. The nano ceramic coating disclosed by the invention has excellent insulating property.

Description

Technical Field

[0001] This invention relates to the field of coating technology, belonging to patent classification number C09D1 / 00, specifically to an insulating nano-ceramic coating and its preparation method. Background Technology

[0002] Nano-ceramic coatings are a new type of high-performance coating with nano-sized inorganic ceramic powders as the core functional component. The core powders used are mostly inorganic oxides or nitrides with excellent physicochemical properties. The preparation of these coatings requires a precise multi-step process: first, the nano-ceramic powders are uniformly dispersed in an aqueous or inorganic solvent system using a combination of mechanical stirring and ultrasonic dispersion. Simultaneously, dispersants, coupling agents, and other additives are added to inhibit powder agglomeration. Then, specific film-forming processes such as sol-gel method, spraying, brushing, or dip coating are used to form a continuous coating on the substrate surface. Finally, room temperature curing or low-temperature sintering treatment is performed to form a dense three-dimensional network ceramic structure. Relying on the unique high specific surface area and high surface activity of nanoparticles, this type of coating exhibits many outstanding characteristics: in terms of temperature adaptability, it can withstand extreme low temperatures of 60℃ to high temperatures of 800℃, and is not prone to cracking or peeling even under repeated thermal cycling conditions. Leveraging these advantages, nano-ceramic coatings have been widely applied in various fields such as electronics, power, aerospace, chemical equipment, and building protection. They provide long-lasting protection for various substrates, including metals, concrete, and plastics, resisting environmental erosion. Furthermore, they can impart special functional properties such as insulation, thermal conductivity, and wear resistance to substrates according to specific needs, making them a promising new material in the coatings industry. Although nano-ceramic coatings inherently possess the dielectric properties of zirconia—inorganic ceramic powders themselves have the fundamental advantages of high resistivity and low dielectric loss, theoretically possessing the potential to become high-performance zirconia—existing commercial products still face significant bottlenecks in insulation performance, making it difficult to meet the stringent requirements of high-end applications such as high-voltage electronic equipment, integrated circuit substrates, and high-voltage insulators. Summary of the Invention

[0003] The purpose of this invention is to provide an insulating nano-ceramic coating and its preparation method, thereby solving the technical problems mentioned in the background section. The nano-ceramic coating prepared by this invention has excellent insulating properties.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an insulating nano-ceramic coating includes the following steps: S1. Nano-alumina and nano-zirconia are added to deionized water, ultrasonically dispersed, pH adjusted to weak alkalinity, activated under heating and stirring, and then centrifuged, washed and dried to obtain hydroxylated activated nano-ceramic powder. S2. The hydroxylated activated nano-ceramic powder was dispersed in anhydrous ethanol, water and glacial acetic acid, and γ-methacryloxypropyltrimethoxysilane was added to react. After the reaction, the powder was precipitated, filtered and dried to obtain silane-modified nano-ceramic powder. S3. Mix silane-modified nano-ceramic powder with glycidyl methacrylate under nitrogen protection, add benzoyl peroxide, and after heating and polymerization, wash with acetone, centrifuge and dry to obtain grafted modified nano-ceramic powder. S4. Dissolve acrylic polysiloxane resin in xylene, add epichlorohydrin and tetrabutylammonium bromide, heat to react, then cool down, add triethylamine dropwise, continue the reaction, and after standing to separate layers, wash and distill to obtain epoxy modified acrylic polysiloxane resin. S5. Epoxy-modified acrylic polysiloxane resin is dissolved in N,N-dimethylformamide, and 3-aminopropyltriethoxysilane is added under nitrogen protection to react. Then polyethylene glycol diglycidyl ether is added, the mixture is heated and reacted, and then diluted to obtain crosslinked modified acrylic polysiloxane resin. S6. Heat the mixed solvent of xylene and butyl acetate, add polyamide wax and organosilicon defoamer, stir to form an auxiliary agent system, then add cross-linked modified acrylic polysiloxane resin, heat and stir at high speed to form a resin base, add grafted modified nano-ceramic powder to the resin base in batches, mix under heating and high speed to obtain a premixed system. S7. Add acrylate film-forming agent and γ-aminopropyltriethoxysilane hydrolysate to the premixed system, heat and stir at high speed to obtain insulating nano-ceramic coating.

[0005] In this invention, the insulation performance of nano-ceramic coatings is improved synergistically from two aspects. Firstly, active sites are constructed on the powder surface through hydroxylation activation, followed by silane modification to introduce organic functional groups, breaking the agglomeration of the nano-ceramic powder and achieving uniform dispersion of the powder in the resin matrix. This avoids weak channels for charge transport caused by local filler agglomeration. Secondly, the graft polymerization of glycidyl methacrylate forms a dense organic insulating shell on the powder surface. This not only further enhances the interfacial compatibility between the nano-ceramic powder and the acrylic polysiloxane resin, eliminating interfacial defects between inorganic fillers and organic resin, and reducing charge accumulation and leakage at the interface, but also improves insulation performance. From the perspectives of filler dispersion uniformity and self-insulation, a robust inorganic filler insulating phase is constructed for the coating, significantly reducing the risk of localized breakdown caused by uneven filler distribution or interfacial defects.

[0006] On the other hand, epoxy groups are introduced into the acrylic polysiloxane resin molecular chain through epoxy modification, providing sites for subsequent crosslinking reactions. Then, through the amino crosslinking of 3-aminopropyltriethoxysilane and the chain extension effect of polyethylene glycol diglycidyl ether, the resin forms a high-density three-dimensional crosslinked network structure. This structure significantly reduces the free volume and molecular chain movement space in the resin matrix, reduces the probability of charge migration in the resin, and significantly improves the breakdown voltage of the resin matrix. At the same time, the introduction of aminosilane can also further strengthen the interfacial bonding force between the resin and the grafted modified nano-ceramic powder through chemical bonding, eliminate interfacial voids and defects, and avoid charge breakdown at the interface. In addition, the high-density crosslinked network also enhances the rigidity and thermal stability of the resin molecular chain, enabling the resin to maintain a stable insulating structure under high-temperature service conditions, preventing the decrease in insulation performance caused by resin thermal deformation or molecular chain relaxation. From the three dimensions of resin matrix structural stability, interfacial bonding, and high-temperature insulation, a high-performance organic resin insulating phase is constructed for the coating, forming a synergistic effect with the nano-ceramic powder modification, ultimately achieving a significant improvement in the overall insulation performance of the coating.

[0007] Preferably, in step S1, the mass ratio of nano-alumina to nano-zirconia is 3:(1-2).

[0008] Preferably, in step S2, the mass ratio of hydroxylated activated nano-ceramic powder to γ-methacryloyloxypropyltrimethoxysilane is 10:(0.5-1.0).

[0009] Preferably, in step S3, the mass ratio of silane-modified nano-ceramic powder to glycidyl methacrylate is 3:(4-5).

[0010] Preferably, in step S4, the mass ratio of acrylic polysiloxane resin to epichlorohydrin is 7:1 to 3.

[0011] Preferably, in step S5, the mass ratio of epoxy-modified acrylic polysiloxane resin to 3-aminopropyltriethoxysilane is 6:(1-2).

[0012] Preferably, in step S6, the grafted modified nano-ceramic powder undergoes pretreatment, including the following steps: The grafted modified nano-ceramic powder was added to anhydrous ethanol, ultrasonically dispersed, and then hydroxyl-terminated hyperbranched polysiloxane and triethylamine catalyst were added. The mixture was heated to react, and then centrifuged, washed and dried to obtain the final product.

[0013] In the technical solution of this invention, the invention team discovered through in-depth research that the high-density three-dimensional cross-linked network formed by epoxy modification and amino cross-linking of acrylic polysiloxane resin will generate internal stress. This internal stress will exert a squeezing effect on the organic graft layer around the nano-ceramic powder, causing the graft layer to deform or even break locally, ultimately destroying the integrity of the insulating shell layer on the powder surface, and thus affecting the improvement and stability of the overall insulation performance of the coating. To address this technical challenge, the research team employed hyperbranched polysiloxanes with terminal hydroxyl groups grafted onto the surface of the original nano-ceramic powder graft layer. Hyperbranched polysiloxanes possess a unique three-dimensional spherical topology, and their numerous branched end groups can form multi-point weak interactions such as hydrogen bonds and van der Waals forces with the functional groups of the resin crosslinking network. This effectively disperses internal stress, originally concentrated at a single site, to multiple points of action, significantly reducing local stress intensity. Simultaneously, this hyperbranched structure generates a steric hindrance buffering effect, reducing direct compression and collision between the resin crosslinking segments and the graft layer. Furthermore, the siloxane segments of the hyperbranched polysiloxane exhibit good compatibility with the siloxane bonds in the acrylic polysiloxane resin, further optimizing the stress distribution at the powder-resin interface. This approach, addressing both stress dispersion and interface compatibility, prevents damage to the graft layer due to internal stress, ensuring the integrity of the insulating shell on the powder surface.

[0014] Preferably, the heating and stirring reaction temperature is 50-60°C, and the heating and stirring reaction time is 3-5 hours.

[0015] An insulating nano-ceramic coating is prepared by the method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Through surface modification and graft polymerization, a dense insulating shell is formed on the surface of nano-ceramic powder, and a high-density three-dimensional cross-linked network is formed with the resin, which together greatly improves the breakdown voltage and overall insulation performance of the coating.

[0017] 2. The high-density cross-linked network formed by the resin reduces the space for molecular chain movement, improves the rigidity and thermal stability of the matrix, and enables the coating to maintain a stable insulation structure even at high temperatures.

[0018] 3. Through multi-step modification, the interfacial compatibility between inorganic fillers and organic resins is greatly improved, and interfacial defects are eliminated. In addition, the introduction of hyperbranched polysiloxane can effectively disperse internal stress, protect the integrity of the insulating shell on the powder surface, and ensure long-lasting and reliable insulation performance. Attached Figure Description

[0019] Figure 1 This is a surface SEM image of the coating obtained in Example 1 of the present invention after being coated to form a coating layer. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The acrylic polysiloxane resin used in the specific embodiments is model SH-3010A, manufactured by Quark New Materials Co., Ltd.

[0021] Example 1 A method for preparing an insulating nano-ceramic coating includes the following steps: Step 1: Weigh 6g of nano-alumina and 3.5g of nano-zirconia, add them to 50mL of deionized water, and ultrasonically disperse them at 300W for 30min. Adjust the pH of the system to 8.5 (weakly alkaline) with 5% ammonia water, then transfer it to a three-necked flask and heat it at 80℃ and 500rpm for 2h. After activation, centrifuge the suspension at 4000rpm for 10min, collect the precipitate and wash it 3 times with deionized water. Finally, dry it in a vacuum drying oven at 60℃ for 12h to obtain hydroxylated activated nano-ceramic powder.

[0022] Step 2: Take 10g of hydroxylated activated nano-ceramic powder, add it to a mixture of 60mL anhydrous ethanol, 5mL deionized water and 0.5mL glacial acetic acid, and ultrasonically disperse for 20min; then add 0.9g of γ-methacryloyloxypropyltrimethoxysilane, and react for 3h at 60℃ and 400rpm; after the reaction is completed, let it stand to precipitate, filter and collect the solid, wash it twice with anhydrous ethanol, and dry it in a vacuum drying oven at 60℃ for 8h to obtain silane-modified nano-ceramic powder.

[0023] Step 3: Take 6g of silane-modified nano-ceramic powder and 9.5g of glycidyl methacrylate and add them to a three-necked flask. After purging with nitrogen for 15min, add 0.07g of benzoyl peroxide (initiator). Heat to 85℃ and polymerize at 500rpm for 6h. After the reaction, wash the precipitate three times with acetone, centrifuge at 4000rpm for 10min, and finally dry in a vacuum drying oven at 70℃ for 10h to obtain grafted modified nano-ceramic powder.

[0024] Step 4: Weigh 21g of acrylic polysiloxane resin, dissolve it in 50mL of xylene, add 8g of epichlorohydrin and 0.105g of tetrabutylammonium bromide (catalyst), heat to 100℃ and react for 3h; after the reaction, cool to 50℃, slowly add 5mL of triethylamine, and continue stirring for 1h; after standing, separate the aqueous phase, wash the organic phase with deionized water until neutral, and remove the solvent by vacuum distillation at 80℃ and -0.09MPa to obtain epoxy-modified acrylic polysiloxane resin.

[0025] Step 5: Take 18g of epoxy-modified acrylic polysiloxane resin, dissolve it in 40mL of N,N-dimethylformamide, purge with nitrogen for protection, add 5g of 3-aminopropyltriethoxysilane, and react at 60℃ and 400rpm for 2h; then add 3g of polyethylene glycol diglycidyl ether, raise the temperature to 80℃ and continue the reaction for 3h; after the reaction is completed, add 10mL of N,N-dimethylformamide to dilute, and obtain crosslinked modified acrylic polysiloxane resin.

[0026] Step 6: Take 6g of grafted modified nano-ceramic powder, add it to 20mL of anhydrous ethanol and ultrasonically disperse it for 20min. Add 0.6g of terminal hydroxyl hyperbranched polysiloxane and 0.03g of triethylamine catalyst, and react at 55℃ and 400rpm for 4h. After the reaction, centrifuge at 4000rpm for 10min, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain the pretreated powder.

[0027] Heat a mixture of 20 mL xylene and 20 mL butyl acetate to 70 °C, add 1 g polyamide wax and 0.2 g silicone defoamer, and stir at 800 rpm for 30 min to form an additive system. Add 20 g crosslinked modified acrylic polysiloxane resin to the system, heat to 80 °C, and stir at 1500 rpm for 30 min to form a resin base. Add 5 g of pretreated powder in three equal batches to the base, and stir at 80 °C and 1500 rpm for 2 h to obtain a premixed system.

[0028] Step 7: Add 2g of acrylate film-forming agent (polybutyl methacrylate) to the premixed system, heat to 85℃ and stir at 1500rpm for 30min; separately take 0.5g of γ-aminopropyltriethoxysilane (KH550), add a mixture of 2mL of deionized water and 1mL of anhydrous ethanol, stir at room temperature for 10min for pre-hydrolysis, slowly add the pre-hydrolyzed KH550 solution dropwise to the premixed system, heat to 85℃ and stir at 2000rpm for 1h. After the system is mixed evenly and there are no obvious bubbles, cool to room temperature to obtain the insulating nano-ceramic coating.

[0029] Example 2 A method for preparing an insulating nano-ceramic coating includes the following steps: Step 1: Weigh 6g of nano-alumina and 2.5g of nano-zirconia, add them to 50mL of deionized water, and ultrasonically disperse them at 300W for 30min. Adjust the pH of the system to 8.5 (weakly alkaline) with 5% ammonia water, then transfer it to a three-necked flask and heat it at 80℃ and 500rpm for 2h. After activation, centrifuge the suspension at 4000rpm for 10min, collect the precipitate and wash it 3 times with deionized water. Finally, dry it in a vacuum drying oven at 60℃ for 12h to obtain hydroxylated activated nano-ceramic powder.

[0030] Step 2: Take 10g of hydroxylated activated nano-ceramic powder, add it to a mixture of 60mL anhydrous ethanol, 5mL deionized water and 0.5mL glacial acetic acid, and ultrasonically disperse for 20min; then add 0.6g of γ-methacryloyloxypropyltrimethoxysilane, and react for 3h at 60℃ and 400rpm; after the reaction is completed, let it stand to precipitate, filter and collect the solid, wash it twice with anhydrous ethanol, and dry it in a vacuum drying oven at 60℃ for 8h to obtain silane-modified nano-ceramic powder.

[0031] Step 3: Take 6g of silane-modified nano-ceramic powder and 8.5g of glycidyl methacrylate and add them to a three-necked flask. After purging with nitrogen for 15min, add 0.07g of benzoyl peroxide (initiator). Heat to 85℃ and polymerize at 500rpm for 6h. After the reaction, wash the precipitate three times with acetone, centrifuge at 4000rpm for 10min, and finally dry in a vacuum drying oven at 70℃ for 10h to obtain grafted modified nano-ceramic powder.

[0032] Step 4: Weigh 21g of acrylic polysiloxane resin, dissolve it in 50mL of xylene, add 4g of epichlorohydrin and 0.105g of tetrabutylammonium bromide (catalyst), heat to 100℃ and react for 3h; after the reaction, cool to 50℃, slowly add 5mL of triethylamine, and continue stirring for 1h; after standing, separate the aqueous phase, wash the organic phase with deionized water until neutral, and remove the solvent by vacuum distillation at 80℃ and -0.09MPa to obtain epoxy-modified acrylic polysiloxane resin.

[0033] Step 5: Take 18g of epoxy-modified acrylic polysiloxane resin, dissolve it in 40mL of N,N-dimethylformamide, purge with nitrogen for protection, add 4g of 3-aminopropyltriethoxysilane, and react at 60℃ and 400rpm for 2h; then add 3g of polyethylene glycol diglycidyl ether, heat to 80℃ and continue the reaction for 3h; after the reaction is completed, add 10mL of N,N-dimethylformamide to dilute and obtain crosslinked modified acrylic polysiloxane resin.

[0034] Step 6: Take 6g of grafted modified nano-ceramic powder, add it to 20mL of anhydrous ethanol and ultrasonically disperse it for 20min. Add 0.6g of terminal hydroxyl hyperbranched polysiloxane and 0.03g of triethylamine catalyst, and react at 55℃ and 400rpm for 4h. After the reaction, centrifuge at 4000rpm for 10min, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain the pretreated powder.

[0035] Heat a mixture of 20 mL xylene and 20 mL butyl acetate to 70 °C, add 1 g polyamide wax and 0.2 g silicone defoamer, and stir at 800 rpm for 30 min to form an additive system. Add 20 g crosslinked modified acrylic polysiloxane resin to the system, heat to 80 °C, and stir at 1500 rpm for 30 min to form a resin base. Add 5 g of pretreated powder in three equal batches to the base, and stir at 80 °C and 1500 rpm for 2 h to obtain a premixed system.

[0036] Step 7: Add 2g of acrylate film-forming agent (polybutyl methacrylate) to the premixed system, heat to 85℃ and stir at 1500rpm for 30min; separately take 0.5g of γ-aminopropyltriethoxysilane (KH550), add a mixture of 2mL of deionized water and 1mL of anhydrous ethanol, stir at room temperature for 10min for pre-hydrolysis, slowly add the pre-hydrolyzed KH550 solution dropwise to the premixed system, heat to 85℃ and stir at 2000rpm for 1h. After the system is mixed evenly and there are no obvious bubbles, cool to room temperature to obtain the insulating nano-ceramic coating.

[0037] Example 3 A method for preparing an insulating nano-ceramic coating includes the following steps: Step 1: Weigh 6g of nano-alumina and 3g of nano-zirconia, add them to 50mL of deionized water, and ultrasonically disperse them at 300W for 30min. Adjust the pH of the system to 8.5 (weakly alkaline) with 5% ammonia water, then transfer it to a three-necked flask and heat it at 80℃ and 500rpm for 2h. After activation, centrifuge the suspension at 4000rpm for 10min, collect the precipitate and wash it 3 times with deionized water. Finally, dry it in a vacuum drying oven at 60℃ for 12h to obtain hydroxylated activated nano-ceramic powder.

[0038] Step 2: Take 10g of hydroxylated activated nano-ceramic powder, add it to a mixture of 60mL anhydrous ethanol, 5mL deionized water and 0.5mL glacial acetic acid, and ultrasonically disperse for 20min; then add 0.7g of γ-methacryloyloxypropyltrimethoxysilane, and react for 3h at 60℃ and 400rpm; after the reaction is completed, let it stand to precipitate, filter and collect the solid, wash it twice with anhydrous ethanol, and dry it in a vacuum drying oven at 60℃ for 8h to obtain silane-modified nano-ceramic powder.

[0039] Step 3: Take 6g of silane-modified nano-ceramic powder and 9g of glycidyl methacrylate and add them to a three-necked flask. After purging with nitrogen for 15min, add 0.07g of benzoyl peroxide (initiator). Heat to 85℃ and polymerize at 500rpm for 6h. After the reaction, wash the precipitate three times with acetone, centrifuge at 4000rpm for 10min, and finally dry in a vacuum drying oven at 70℃ for 10h to obtain grafted modified nano-ceramic powder.

[0040] Step 4: Weigh 21g of acrylic polysiloxane resin, dissolve it in 50mL of xylene, add 6g of epichlorohydrin and 0.105g of tetrabutylammonium bromide (catalyst), heat to 100℃ and react for 3h; after the reaction, cool to 50℃, slowly add 5mL of triethylamine, and continue stirring for 1h; after standing, separate the aqueous phase, wash the organic phase with deionized water until neutral, and remove the solvent by vacuum distillation at 80℃ and -0.09MPa to obtain epoxy-modified acrylic polysiloxane resin.

[0041] Step 5: Take 18g of epoxy-modified acrylic polysiloxane resin, dissolve it in 40mL of N,N-dimethylformamide, purge with nitrogen for protection, then add 4.5g of 3-aminopropyltriethoxysilane, and react at 60℃ and 400rpm for 2h; then add 3g of polyethylene glycol diglycidyl ether, raise the temperature to 80℃ and continue the reaction for 3h; after the reaction is completed, add 10mL of N,N-dimethylformamide to dilute, and obtain crosslinked modified acrylic polysiloxane resin.

[0042] Step 6: Take 6g of grafted modified nano-ceramic powder, add it to 20mL of anhydrous ethanol and ultrasonically disperse it for 20min. Add 0.6g of terminal hydroxyl hyperbranched polysiloxane and 0.03g of triethylamine catalyst, and react at 55℃ and 400rpm for 4h. After the reaction, centrifuge at 4000rpm for 10min, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain the pretreated powder.

[0043] Heat a mixture of 20 mL xylene and 20 mL butyl acetate to 70 °C, add 1 g polyamide wax and 0.2 g silicone defoamer, and stir at 800 rpm for 30 min to form an additive system. Add 20 g crosslinked modified acrylic polysiloxane resin to the system, heat to 80 °C, and stir at 1500 rpm for 30 min to form a resin base. Add 5 g of pretreated powder in three equal batches to the base, and stir at 80 °C and 1500 rpm for 2 h to obtain a premixed system.

[0044] Step 7: Add 2g of acrylate film-forming agent (polybutyl methacrylate) to the premixed system, heat to 85℃ and stir at 1500rpm for 30min; separately take 0.5g of γ-aminopropyltriethoxysilane (KH550), add a mixture of 2mL of deionized water and 1mL of anhydrous ethanol, stir at room temperature for 10min for pre-hydrolysis, slowly add the pre-hydrolyzed KH550 solution dropwise to the premixed system, heat to 85℃ and stir at 2000rpm for 1h. After the system is mixed evenly and there are no obvious bubbles, cool to room temperature to obtain the insulating nano-ceramic coating.

[0045] Example 4 A method for preparing an insulating nano-ceramic coating includes the following steps: Step 1: Weigh 6g of nano-alumina and 4g of nano-zirconia, add them to 50mL of deionized water, and ultrasonically disperse them for 30min at 300W power; adjust the pH of the system to 8.5 (weakly alkaline) with 5% ammonia water, then transfer it to a three-necked flask and heat it at 80℃ and 500rpm for 2h for activation; after activation, centrifuge the suspension at 4000rpm for 10min, collect the precipitate and wash it 3 times with deionized water, and finally dry it in a vacuum drying oven at 60℃ for 12h to obtain hydroxylated activated nano-ceramic powder.

[0046] Step 2: Take 10g of hydroxylated activated nano-ceramic powder, add it to a mixture of 60mL anhydrous ethanol, 5mL deionized water and 0.5mL glacial acetic acid, and sonicate for 20min; then add 1.0g of γ-methacryloyloxypropyltrimethoxysilane, and react for 3h at 60℃ and 400rpm; after the reaction is completed, let it stand to precipitate, filter and collect the solid, wash it twice with anhydrous ethanol, and dry it in a vacuum drying oven at 60℃ for 8h to obtain silane-modified nano-ceramic powder.

[0047] Step 3: Take 6g of silane-modified nano-ceramic powder and 10g of glycidyl methacrylate and add them to a three-necked flask. After purging with nitrogen for 15min, add 0.07g of benzoyl peroxide (initiator). Heat to 85℃ and polymerize at 500rpm for 6h. After the reaction, wash the precipitate three times with acetone, centrifuge at 4000rpm for 10min, and finally dry in a vacuum drying oven at 70℃ for 10h to obtain grafted modified nano-ceramic powder.

[0048] Step 4: Weigh 21g of acrylic polysiloxane resin, dissolve it in 50mL of xylene, add 9g of epichlorohydrin and 0.105g of tetrabutylammonium bromide (catalyst), heat to 100℃ and react for 3h; after the reaction, cool to 50℃, slowly add 5mL of triethylamine, and continue stirring for 1h; after standing, separate the aqueous phase, wash the organic phase with deionized water until neutral, and remove the solvent by vacuum distillation at 80℃ and -0.09MPa to obtain epoxy-modified acrylic polysiloxane resin.

[0049] Step 5: Take 18g of epoxy-modified acrylic polysiloxane resin, dissolve it in 40mL of N,N-dimethylformamide, purge with nitrogen for protection, add 6g of 3-aminopropyltriethoxysilane, and react at 60℃ and 400rpm for 2h; then add 3g of polyethylene glycol diglycidyl ether, raise the temperature to 80℃ and continue the reaction for 3h; after the reaction is completed, add 10mL of N,N-dimethylformamide to dilute, and obtain crosslinked modified acrylic polysiloxane resin.

[0050] Step 6: Take 6g of grafted modified nano-ceramic powder, add it to 20mL of anhydrous ethanol and ultrasonically disperse it for 20min. Add 0.6g of terminal hydroxyl hyperbranched polysiloxane and 0.03g of triethylamine catalyst, and react at 60℃ and 400rpm for 5h. After the reaction, centrifuge at 4000rpm for 10min, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain the pretreated powder.

[0051] Heat a mixture of 20 mL xylene and 20 mL butyl acetate to 70 °C, add 1 g polyamide wax and 0.2 g silicone defoamer, and stir at 800 rpm for 30 min to form an additive system. Add 20 g crosslinked modified acrylic polysiloxane resin to the system, heat to 80 °C, and stir at 1500 rpm for 30 min to form a resin base. Add 5 g of pretreated powder in three equal batches to the base, and stir at 80 °C and 1500 rpm for 2 h to obtain a premixed system.

[0052] Step 7: Add 2g of acrylate film-forming agent (polybutyl methacrylate) to the premixed system, heat to 85℃ and stir at 1500rpm for 30min; separately take 0.5g of γ-aminopropyltriethoxysilane (KH550), add a mixture of 2mL of deionized water and 1mL of anhydrous ethanol, stir at room temperature for 10min for pre-hydrolysis, slowly add the pre-hydrolyzed KH550 solution dropwise to the premixed system, heat to 85℃ and stir at 2000rpm for 1h. After the system is mixed evenly and there are no obvious bubbles, cool to room temperature to obtain the insulating nano-ceramic coating.

[0053] Example 5 A method for preparing an insulating nano-ceramic coating includes the following steps: Step 1: Weigh 6g of nano-alumina and 2g of nano-zirconia, add them to 50mL of deionized water, and ultrasonically disperse them at 300W for 30min. Adjust the pH of the system to 8.5 (weakly alkaline) with 5% ammonia water, then transfer it to a three-necked flask and heat it at 80℃ and 500rpm for 2h. After activation, centrifuge the suspension at 4000rpm for 10min, collect the precipitate and wash it 3 times with deionized water. Finally, dry it in a vacuum drying oven at 60℃ for 12h to obtain hydroxylated activated nano-ceramic powder.

[0054] Step 2: Take 10g of hydroxylated activated nano-ceramic powder, add it to a mixture of 60mL anhydrous ethanol, 5mL deionized water and 0.5mL glacial acetic acid, and sonicate for 20min; then add 0.5g of γ-methacryloyloxypropyltrimethoxysilane, and react for 3h at 60℃ and 400rpm; after the reaction is completed, let it stand to precipitate, filter and collect the solid, wash it twice with anhydrous ethanol, and dry it in a vacuum drying oven at 60℃ for 8h to obtain silane-modified nano-ceramic powder.

[0055] Step 3: Take 6g of silane-modified nano-ceramic powder and 8g of glycidyl methacrylate and add them to a three-necked flask. After purging with nitrogen for 15min, add 0.07g of benzoyl peroxide (initiator). Heat to 85℃ and polymerize at 500rpm for 6h. After the reaction, wash the precipitate three times with acetone, centrifuge at 4000rpm for 10min, and finally dry in a vacuum drying oven at 70℃ for 10h to obtain grafted modified nano-ceramic powder.

[0056] Step 4: Weigh 21g of acrylic polysiloxane resin, dissolve it in 50mL of xylene, add 3g of epichlorohydrin and 0.105g of tetrabutylammonium bromide (catalyst), heat to 100℃ and react for 3h; after the reaction, cool to 50℃, slowly add 5mL of triethylamine, and continue stirring for 1h; after standing, separate the aqueous phase, wash the organic phase with deionized water until neutral, and remove the solvent by vacuum distillation at 80℃ and -0.09MPa to obtain epoxy-modified acrylic polysiloxane resin.

[0057] Step 5: Take 18g of epoxy-modified acrylic polysiloxane resin, dissolve it in 40mL of N,N-dimethylformamide, purge with nitrogen for protection, add 3g of 3-aminopropyltriethoxysilane, and react at 60℃ and 400rpm for 2h; then add 3g of polyethylene glycol diglycidyl ether, raise the temperature to 80℃ and continue the reaction for 3h; after the reaction is completed, add 10mL of N,N-dimethylformamide to dilute, and obtain crosslinked modified acrylic polysiloxane resin.

[0058] Step 6: Take 6g of grafted modified nano-ceramic powder, add it to 20mL of anhydrous ethanol and ultrasonically disperse it for 20min. Add 0.6g of terminal hydroxyl hyperbranched polysiloxane and 0.03g of triethylamine catalyst, and react at 50℃ and 400rpm for 3h. After the reaction, centrifuge at 4000rpm for 10min, wash twice with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain the pretreated powder.

[0059] Heat a mixture of 20 mL xylene and 20 mL butyl acetate to 70 °C, add 1 g polyamide wax and 0.2 g silicone defoamer, and stir at 800 rpm for 30 min to form an additive system. Add 20 g crosslinked modified acrylic polysiloxane resin to the system, heat to 80 °C, and stir at 1500 rpm for 30 min to form a resin base. Add 5 g of pretreated powder in three equal batches to the base, and stir at 80 °C and 1500 rpm for 2 h to obtain a premixed system.

[0060] Step 7: Add 2g of acrylate film-forming agent (polybutyl methacrylate) to the premixed system, heat to 85℃ and stir at 1500rpm for 30min; separately take 0.5g of γ-aminopropyltriethoxysilane (KH550), add a mixture of 2mL of deionized water and 1mL of anhydrous ethanol, stir at room temperature for 10min for pre-hydrolysis, slowly add the pre-hydrolyzed KH550 solution dropwise to the premixed system, heat to 85℃ and stir at 2000rpm for 1h. After the system is mixed evenly and there are no obvious bubbles, cool to room temperature to obtain the insulating nano-ceramic coating.

[0061] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps 1-3 are omitted in the preparation process of the nano-ceramic coating, and the pretreated powder in step 6 is replaced with a mixture of 6g nano-alumina and 3.5g nano-zirconia particles.

[0062] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that steps 4 and 5 are omitted in the preparation process of the nano-ceramic coating, and the crosslinked modified acrylic polysiloxane resin in step 6 is replaced with ordinary acrylic polysiloxane resin.

[0063] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the grafted modified nano-ceramic powder in step 6 of the preparation process of the nano-ceramic coating was not pretreated.

[0064] Performance testing: 1. Volume resistivity test: The coating was applied to a 50mm×50mm×2mm quartz glass substrate using the dip-coating method and cured at 80℃ for 24 hours, with the dry film thickness controlled at 40±5μm. Using a high resistivity meter, a 500V DC voltage was applied using a three-electrode system at room temperature (25℃) and relative humidity of 50%±5%. After stabilizing the voltage for 1 minute, the volume resistivity was measured. Each sample was tested three times, and the arithmetic mean was taken. The test results are shown in Table 1.

[0065] 2. Breakdown Voltage Test: The coating was sprayed onto a 100mm×100mm×1mm cold-rolled steel plate and cured at 80℃ for 24 hours, resulting in a dry film thickness of 50±5μm. A breakdown voltage tester was used with AC voltage and a boost rate of 2kV / s at room temperature to test the breakdown voltage of the sample. Five different areas were tested for each sample, and the average value was converted into the breakdown field strength (kV / mm). The test results are shown in Table 1.

[0066] 3. Dielectric constant and dielectric loss test: The coating was applied to a circular ceramic substrate with a diameter of 50 mm. After curing, the dry film thickness was 30 ± 3 μm. Using a precision impedance analyzer, the dielectric constant and dielectric loss tangent of the sample were measured at a frequency of 1 kHz and a room temperature of 25 °C. Each sample was tested three times, and the average value was taken. The test results are shown in Table 1.

[0067] Table 1: Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an insulating nanoceramic coating, characterized in that, The method comprises the following steps: S1, adding nano-alumina and nano-zirconia into deionized water, ultrasonic dispersion, pH adjustment to weak alkaline, activation under heating and stirring, then centrifugation, washing and drying to obtain hydroxylated activated nano-ceramic powder; S2, dispersing the hydroxylated activated nano-ceramic powder in anhydrous ethanol, water and glacial acetic acid, adding γ-methacryloyloxypropyltrimethoxysilane for reaction, then precipitating, filtering and drying to obtain silane modified nano-ceramic powder; S3, mixing the silane modified nano-ceramic powder with glycidyl methacrylate under nitrogen protection, adding benzoyl peroxide, polymerizing after heating, then washing with acetone, centrifugation and drying to obtain grafted modified nano-ceramic powder; S4, dissolving the acrylic polysiloxane resin in xylene, adding epichlorohydrin and tetrabutylammonium bromide, heating and reacting, then cooling, adding triethylamine dropwise, continuing to react, then standing and separating, washing and distilling to obtain epoxy modified acrylic polysiloxane resin; S5, dissolving the epoxy modified acrylic polysiloxane resin in N,N-dimethylformamide, adding 3-aminopropyltriethoxysilane under nitrogen protection for reaction, then adding polyethylene glycol diglycidyl ether, heating and reacting, then diluting to obtain crosslinking modified acrylic polysiloxane resin; S6, heating the mixed solvent of xylene and butyl acetate, adding polyamide wax and silicone defoaming agent, stirring to form an auxiliary system, then adding the crosslinking modified acrylic polysiloxane resin, heating and high-speed stirring to form a resin base, adding the grafted modified nano-ceramic powder into the resin base, mixing under heating and high-speed stirring to obtain a premixing system; S7, adding acrylic ester film forming agent and γ-aminopropyltriethoxysilane hydrolysate into the premixing system, heating and high-speed stirring to fuse to obtain an insulating nano-ceramic coating.

2. The method of claim 1, wherein the insulation nanoceramic coating is prepared by the steps of: In the step S1, the mass ratio of nano-alumina to nano-zirconia is 3:(1-2).

3. The method for preparing an insulating nano-ceramic coating according to claim 1, characterized in that, In the step S2, the mass ratio of hydroxylated activated nano-ceramic powder to γ-methacryloyloxypropyltrimethoxysilane is 10:(0.5-1.0).

4. The method of claim 1, wherein the insulation nanoceramic coating is prepared by the steps of: In the step S3, the mass ratio of silane modified nano-ceramic powder to glycidyl methacrylate is 3:(4-5).

5. The method for preparing an insulating nano-ceramic coating according to claim 1, characterized in that, In the step S4, the mass ratio of acrylic polysiloxane resin to epichlorohydrin is 7:(1-3).

6. The method of claim 1, wherein the insulation nanoceramic coating is prepared by the steps of: In the step S5, the mass ratio of epoxy modified acrylic polysiloxane resin to 3-aminopropyltriethoxysilane is 6:(1-2).

7. The method for preparing an insulating nano-ceramic coating according to claim 1, characterized in that, In the step S6, the grafted modified nano-ceramic powder is pretreated, comprising the following steps: adding the grafted modified nano-ceramic powder into anhydrous ethanol, ultrasonic dispersion, adding hydroxyl-terminated hyperbranched polysiloxane and triethylamine catalyst, heating and reacting, then centrifugation, washing and drying.

8. The method of claim 8, wherein the insulation nanoceramic coating is prepared by the steps of: The heating and stirring reaction temperature is 50-60℃, and the heating and stirring reaction time is 3-5h.

9. An insulating nanoceramic coating, characterized in that, Prepared by the method of any one of the above claims 1-8.

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