Moisture and heat resistant insulating silicone coating, method of making and use thereof

Abstract

This invention relates to a moisture- and heat-resistant insulating silicone coating, its preparation method, and its application, belonging to the technical field of silicone coatings. The technical problem solved by this invention is to provide a moisture- and heat-resistant insulating silicone coating with good moisture resistance and insulation properties. The coating comprises α,ω-dihydroxypolydimethylsiloxane, surface-modified nano-silica, mica powder, aluminum hydroxide, modifier, pigment, crosslinking agent, moisture- and heat-resistant tackifier, catalyst, heat-resistant flame retardant, and solvent. This coating exhibits excellent moisture resistance, adhesion durability, and insulation retention; breakdown strength ≥30 kV / mm; arc resistance ≥200 s; resistance to tracking and electrical erosion not less than 1A 3.5 grade; after aging in high temperature and high humidity (85℃, 85%RH) for 1000 h, the change rate of breakdown strength, volume resistivity, and shear strength is less than 20%; hydrophobicity remains at HC1~HC2 grade; after boiling in water for 100 h, there are no bubbles at the interface between the coating and the insulator surface. When applied to the surface of electrical equipment in humid and hot areas, it provides long-term insulation and anti-flashover protection.

Description

Technical Field

[0001] This invention relates to moisture- and heat-resistant insulating silicone coatings, their preparation methods, and applications, belonging to the field of silicone coating technology. Background Technology

[0002] Silicone coatings, with their excellent electrical insulation, hydrophobicity, and weather resistance, are often used for surface protection of electrical equipment such as power transmission (transformation) equipment (lines), electric locomotives, dry-type transformers, and electronic circuit boards, serving functions such as hydrophobicity prevention, flashover protection, insulation, and moisture protection. In high-humidity and hot regions, higher requirements are placed on the insulation and moisture-heat resistance of silicone rubber materials commonly used for equipment insulation protection.

[0003] Currently, several patent documents disclose technical solutions for improving the adhesion, insulation, or bird damage resistance of silicone rubber materials. For example, Chinese patent CN10258870 discloses a single-component deketoxime type silicone rubber sealant and its preparation method. It introduces a self-made coupling agent with a special structure, giving the sealant excellent adhesion durability, especially high adhesion strength retention under high temperature and humidity conditions and boiling water conditions. It can also improve the curing speed of the silicone rubber sealant and can be widely used in bonding and sealing in industries such as electronics, automobiles, and home appliances. However, this patent aims to improve the adhesion durability of silicone rubber sealants and does not address the insulation properties of materials in the power industry (such as breakdown strength, arc resistance, and resistance to tracking), nor does it provide solutions for the damp heat aging problem of transmission line insulators.

[0004] For example, Chinese patent CN120795794 discloses an environmentally friendly, low-viscosity insulating silicone rubber coating for bird protection of power equipment. It employs a low-viscosity matrix design and utilizes the synergistic effect of branched vinyl silicone rubber molecular chains and bio-based plasticizers, making it suitable for spraying or dipping. This coating utilizes nano-alumina and modified fumed silica to form a three-dimensional insulating network, achieving a breakdown strength ≥25kV / mm and resistance to tracking and electrical erosion reaching 1A 2.5 level. However, this patent does not address the coating's resistance to damp heat, nor does it study the insulation retention of the coating after high-temperature and high-humidity aging or the interfacial blistering problem between the coating and the substrate.

[0005] In summary, existing technologies lack silicone coatings that possess both excellent insulation properties and outstanding resistance to damp heat. Therefore, developing a damp-heat resistant, high-insulation silicone coating suitable for power transmission lines in high-humidity and hot regions has significant practical importance and application value. Summary of the Invention

[0006] To address the above deficiencies, the first technical problem solved by this invention is to provide a moisture-resistant and insulating silicone coating with good moisture resistance and insulation properties.

[0007] This invention relates to a moisture- and heat-resistant insulating silicone coating, comprising the following components in parts by weight: 40-60 parts of α,ω-dihydroxypolydimethylsiloxane, 1-10 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 0.5-2.5 parts of modifier, 0-10 parts of pigment, 2-5 parts of crosslinking agent, 1-3 parts of moisture- and heat-resistant tackifier, 0.01-0.1 parts of catalyst, 0.1-0.6 parts of heat-resistant flame retardant, and 20-40 parts of solvent; wherein the surface-modified nano-silica is obtained by hydrophobic surface treatment of nano-silica; the modifier has the structural formula C m H 2m+1 COOH or (C n H 2n+1 SiR 1 x (OR 2 ) (3-x) m≥20, n≥12, R 1 R 2 Each is independently CH3 or C2H5, and x is 0, 1 or 2; the crosslinking agent includes tetrabutanone oxime silane; the humid heat resistant tackifier is a bissilane coupling agent containing secondary amino and ester groups.

[0008] In some embodiments of the present invention, the moisture-resistant and heat-insulating silicone coating comprises the following components in parts by weight: 45-55 parts of α,ω-dihydroxypolydimethylsiloxane, 3-7 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 1-2 parts of modifier, 3 parts of pigment, 4-5 parts of crosslinking agent, 2-3 parts of moisture-resistant and heat-resistant tackifier, 0.02 parts of catalyst, 0.2-0.6 parts of heat-resistant and flame-retardant agent, and 30-40 parts of solvent.

[0009] In some embodiments of the present invention, the viscosity of α,ω-dihydroxypolydimethylsiloxane at 25°C is 10,000 to 20,000 mPa·s.

[0010] In some embodiments of the present invention, the specific surface area of ​​the surface-modified nano-silica is 150–400 m². 2 / g. Preferably, the surface-modified nano-silica has a specific surface area of ​​190–250 m² / g. 2 / g, surface treated with hexamethyldisilazane.

[0011] In some embodiments of the present invention, the particle size D50 of mica powder is 2 to 6 μm; the particle size D50 of aluminum hydroxide is 1 to 5 μm.

[0012] In some specific embodiments, the pigment is one or more of iron oxide, titanium dioxide, carbon black, phthalocyanine green, iron yellow, and iron blue.

[0013] In some specific embodiments, the modifier is one or more of dodecanoic acid, dodecanoic acid, dodecyltrimethoxysilane, and dodecyltriethoxysilane.

[0014] In some embodiments of the present invention, the crosslinking agent is tetrabutylone oxime silane, a combination of tetrabutylone oxime silane and vinyltributanone oxime silane, or a combination of tetrabutylone oxime silane and methyltributanone oxime silane.

[0015] In some embodiments of the present invention, the catalyst is a tin-containing catalyst. Preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin acetate, and dioctyltin dilaurate.

[0016] In some embodiments of the present invention, the heat-resistant flame retardant is a platinum complex Karstedt type platinum catalyst.

[0017] In some embodiments of the present invention, the solvent is one or more of petroleum ether, 120# solvent gasoline, 200# solvent gasoline, isoparaffin, and toluene.

[0018] In some embodiments of the present invention, the humid heat tackifier has the structural formula (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3.

[0019] In some specific embodiments of the present invention, the moisture-resistant tackifier is synthesized from silane coupling agent S1 and silane coupling agent S2, wherein S1 is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and S2 is γ-acryloyloxypropyltrimethoxysilane.

[0020] In some specific embodiments of the present invention, the molar ratio of S1 to S2 is 1:(1~1.2), and preferably, the molar ratio of S1 to S2 is 1:1.1.

[0021] The second technical problem solved by the present invention is to provide a method for preparing the moisture-resistant and heat-insulating silicone coating described in the present invention.

[0022] The method for preparing the moisture- and heat-resistant insulating silicone coating of the present invention includes the following steps:

[0023] a. Mixing process: α,ω-dihydroxypolydimethylsiloxane, surface-modified nano-silica, mica powder, and aluminum hydroxide are stirred, kneaded and mixed evenly to obtain the base adhesive.

[0024] b. Grinding or sanding process: Grind or sand the base adhesive 1 to 3 times;

[0025] c. Modification process: Heat and stir the base adhesive after grinding or sand milling. When the material temperature reaches 80℃, add the modifier and keep the material temperature at 80~100℃ for 2 hours.

[0026] d. Drying process: Maintain the material temperature at 100-130℃ and the vacuum degree at no less than -0.08 MPa, and vacuum dry for 3-5 hours to obtain the dried base material;

[0027] e. Adhesive preparation process: First, add pigment to the dried base adhesive and stir in a sealed container until uniform; after the base adhesive cools to below 50°C, add crosslinking agent and stir for 20-30 minutes; then add moisture-resistant tackifier, catalyst, and heat-resistant flame retardant, stir for 20-30 minutes, and finally add solvent and stir until uniform to obtain the final product.

[0028] This invention also provides the application of the moisture- and heat-resistant insulating silicone coating described herein in the surface protection of electrical equipment.

[0029] This invention relates to a moisture- and heat-resistant insulating silicone coating, which has excellent moisture resistance and insulation properties and can be used for surface protection of electrical equipment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention utilizes a combination of mica powder filler and aluminum hydroxide filler to hinder the growth of electrical trees and suppress the formation of conductive channels, thereby improving the breakdown strength of organosilicon coatings.

[0032] 2. The base rubber compound undergoes surface treatment with a long-chain modifier, improving the hydrophobicity of the coating. A tetrafunctional crosslinking agent increases the crosslinking density of the silicone rubber, preventing moisture penetration into the coating. A moisture-resistant tackifier eliminates the presence of active hydrogen atoms in the ammonia group, ensuring the coating's adhesive durability. Through the synergistic effect of the long-chain modifier surface treatment, the tetrafunctional crosslinking agent, and the moisture-resistant tackifier, the coating exhibits excellent moisture resistance, adhesive durability, and insulation retention. Its breakdown strength is ≥30 kV / mm, arc resistance is ≥200 s, and resistance to tracking and electrical erosion is not less than 1A 3.5 grade. After aging in high temperature and humidity (85℃, 85%RH) for 1000 h, the change rate of breakdown strength, volume resistivity, and shear strength is less than 20%. Hydrophobicity remains at HC1~HC2 grade. After boiling in water for 100 h, there are no bubbles at the interface between the coating and the insulator surface. When applied to the surface of electrical equipment in humid and hot regions, it provides long-term insulation and protection against flashover.

[0033] 3. The tackifier synthesis method and coating modification method of the present invention are simple and feasible, the raw materials are common and readily available, and the synthesis method of the moisture-resistant and heat-insulating silicone coating is also simple and easy to implement, suitable for industrial production. Attached Figure Description

[0034] Figure 1 The infrared spectrum of the moisture-resistant tackifier H3 of this invention is shown.

[0035] Figure 2 The 1H NMR spectrum of the moisture-resistant tackifier H3 of this invention is shown.

[0036] Figure 3 This is the carbon NMR spectrum of the moisture-resistant tackifier H3 of the present invention. Detailed Implementation

[0037] This invention relates to a moisture- and heat-resistant insulating silicone coating, comprising the following components in parts by weight: 40-60 parts of α,ω-dihydroxypolydimethylsiloxane, 1-10 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 0.5-2.5 parts of modifier, 0-10 parts of pigment, 2-5 parts of crosslinking agent, 1-3 parts of moisture- and heat-resistant tackifier, 0.01-0.1 parts of catalyst, 0.1-0.6 parts of heat-resistant flame retardant, and 20-40 parts of solvent; wherein the surface-modified nano-silica is obtained by hydrophobic surface treatment of nano-silica; the modifier has the structural formula C m H 2m+1 COOH or (C n H 2n+1 SiR 1 x (OR 2 ) (3-x) m≥20, n≥12, R 1 R 2 Each is independently CH3 or C2H5, and x is 0, 1 or 2; the crosslinking agent includes tetrabutanone oxime silane; the humid heat resistant tackifier is a bissilane coupling agent containing secondary amino and ester groups.

[0038] This invention relates to a moisture- and heat-resistant insulating silicone coating, which has excellent insulation and moisture- and heat-resistant properties. Its breakdown strength is ≥30kV / mm, arc resistance is ≥200 s, and resistance to tracking and electrical erosion is not less than 1A3.5 level. After aging in high temperature and high humidity (85℃, 85%RH) for 1000 h, the breakdown strength, volume resistivity, and shear strength change rate are less than 20%. The hydrophobicity remains at HC1~HC2 level. After boiling in water for 100 h, there are no bubbles at the interface between the coating and the insulator surface.

[0039] In some embodiments of the present invention, the moisture-resistant and heat-insulating silicone coating comprises the following components in parts by weight: 45-55 parts of α,ω-dihydroxypolydimethylsiloxane, 3-7 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 1-2 parts of modifier, 3 parts of pigment; 4-5 parts of crosslinking agent, 2-3 parts of moisture-resistant tackifier, 0.02 parts of catalyst, 0.2-0.6 parts of heat-resistant flame retardant, and 30-40 parts of solvent.

[0040] In some embodiments of the present invention, the viscosity of α,ω-dihydroxypolydimethylsiloxane at 25°C is 10,000 to 20,000 mPa·s.

[0041] Surface-modified nano-silica is obtained by hydrophobic surface treatment of nano-silica. Commonly used hydrophobic treatment methods in the art are applicable to this invention. For example, hexamethyldisilazane is used for surface treatment. In some embodiments of this invention, the specific surface area of ​​the surface-modified nano-silica is 150–400 m². 2 / g. Preferably, the surface-modified nano-silica has a specific surface area of ​​190–250 m² / g. 2 / g, with a surface treated with hexamethyldisilazane, exhibiting hydrophobicity. Surface-modified nano-silica can be commercially available, such as Evonik's AEROSIL® R 812 S, Wacker Chemie's HDK® H2000, and Cabot's CAB-O-SIL® TS-530.

[0042] In some embodiments of the present invention, the particle size D50 of mica powder is 2 to 6 μm; the particle size D50 of aluminum hydroxide is 1 to 5 μm.

[0043] Commonly used pigments in this field are applicable to this invention. In some specific embodiments, the pigment is one or more of iron oxide, titanium dioxide, carbon black, phthalocyanine green, iron yellow, and iron blue.

[0044] The modifier is a reagent requiring a boiling point greater than 200℃, and can be a reagent with the structural formula C. m H 2m+1 COOH is a long-chain organic carboxylic acid with m ≥ 20; it can also be a long-chain alkylsiloxane with the structure C n H 2n+1 SiR 1 x (OR 2 ) (3-x) n≥12, R 1 R 2 Each is independently CH3 or C2H5, and x is 0, 1, or 2. In some specific embodiments, the modifier is at least one of organic carboxylic acids such as docosanoic acid and docosanoic acid, long-chain alkylsiloxanes such as dodecyltrimethoxysilane and dodecyltriethoxysilane.

[0045] The crosslinking agent includes tetrabutylone oxime silane; the crosslinking agent can be a single component or a multi-component composition. In some embodiments of the present invention, the crosslinking agent is tetrabutylone oxime silane. In other embodiments of the present invention, the crosslinking agent is a composition of tetrabutylone oxime silane and vinyltributanone oxime silane. In still other embodiments of the present invention, the crosslinking agent is a composition of tetrabutylone oxime silane and methyltributanone oxime silane.

[0046] In the moisture- and heat-resistant high-insulation silicone coating of this invention, the moisture- and heat-resistant tackifier is a bissilane coupling agent containing secondary amino and ester groups. In some embodiments of this invention, the structural formula of the moisture- and heat-resistant tackifier is (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3.

[0047] In some specific embodiments of the present invention, the moisture-resistant tackifier is synthesized from silane coupling agent S1 and silane coupling agent S2, wherein S1 is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and S2 is γ-acryloyloxypropyltrimethoxysilane. That is, the moisture-resistant tackifier is synthesized from N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and γ-acryloyloxypropyltrimethoxysilane.

[0048] In some specific embodiments of the present invention, the molar ratio of S1 to S2 is 1:(1~1.2), and preferably, the molar ratio of S1 to S2 is 1:1.1.

[0049] Commonly used synthesis methods in this field are applicable to this invention. In some specific embodiments, the method for synthesizing the moisture-resistant tackifier is as follows: In a four-necked flask equipped with a condenser, a stirring device, a nitrogen purging device, and an atmospheric distillation apparatus, 222 g (1 mol) of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 257 g (1.1 mol) of γ-acryloyloxypropyltrimethoxysilane are added. After nitrogen purging, the mixture is heated to 80°C with stirring, and the reaction mixture is maintained at 80°C for 5 h. The reaction is then terminated to obtain the pale yellow transparent liquid product (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3.

[0050] In some embodiments of the present invention, the catalyst is a tin-containing catalyst. Preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin acetate, and dioctyltin dilaurate.

[0051] In some embodiments of the present invention, the heat-resistant flame retardant is a platinum complex Karstedt type platinum catalyst.

[0052] In some embodiments of the present invention, the solvent is one or more of petroleum ether, 120# solvent gasoline, 200# solvent gasoline, isoparaffin, and toluene.

[0053] The method for preparing the moisture- and heat-resistant insulating silicone coating of the present invention includes the following steps:

[0054] a. Mixing process: α,ω-dihydroxypolydimethylsiloxane, surface-modified nano-silica, mica powder, and aluminum hydroxide are stirred, kneaded and mixed evenly to obtain the base adhesive.

[0055] b. Grinding or sanding process: Grind or sand the base adhesive 1 to 3 times;

[0056] c. Modification process: Heat and stir the base adhesive after grinding or sand milling. When the material temperature reaches 80℃, add the modifier and keep the material temperature at 80~100℃ for 2 hours.

[0057] d. Drying process: Maintain the material temperature at 100-130℃ and the vacuum degree at no less than -0.08 MPa, and vacuum dry for 3-5 hours to obtain the dried base material;

[0058] e. Adhesive preparation process: First, add pigment to the dried base adhesive and stir in a sealed container until uniform; after the base adhesive cools to below 50°C, add crosslinking agent and stir for 20-30 minutes; then add moisture-resistant tackifier, catalyst, and heat-resistant flame retardant, stir for 20-30 minutes, and finally add solvent and stir until uniform to obtain the final product.

[0059] Specifically, the preparation method of the moisture- and heat-resistant insulating silicone coating of the present invention includes the following steps:

[0060] a. Mixing process: α,ω-dihydroxy polydimethylsiloxane, surface-modified nano-silica, mica powder, and aluminum hydroxide are sequentially added to a kneader and mixed for 10-30 minutes to obtain the base material.

[0061] b. Grinding or sanding process: Grind or sand the base adhesive 1 to 3 times;

[0062] c. Modification process: Heat and stir the base adhesive after grinding or sand milling. When the material temperature reaches 80℃, add the modifier and keep the material temperature at 80-100℃ for 2 hours.

[0063] d. Drying process: Further increase the material temperature and maintain it at 100-130℃, with a vacuum degree not lower than -0.08MPa, and vacuum dry for 3-5 hours;

[0064] e. Adhesive preparation process: First, add pigment to the base adhesive and stir in a sealed container for 10 minutes until homogeneous. After the base adhesive cools to below 50°C, add crosslinking agent and stir for 20-30 minutes. Then add moisture-resistant tackifier, catalyst, and heat-resistant flame retardant, and stir for 20-30 minutes. Add solvent in batches, stirring for 20-30 minutes after each addition. Once the adhesive is homogeneous, filter and package to obtain the finished product.

[0065] This invention relates to a moisture- and heat-resistant insulating silicone coating, which has excellent moisture resistance and insulation properties and can be used for surface protection of electrical equipment.

[0066] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0067] The raw materials used in the embodiments and comparative examples of this invention are as follows:

[0068] A: α,ω-dihydroxypolydimethylsiloxane, 107 glue, viscosity at 25℃ 20000 mPa.s, Hoshine Silicon Industry Co., Ltd.

[0069] B: Fumed silica treated with hexamethyldihexamethyldisilazane, AEROSIL® R 812 S, with a specific surface area of ​​195–245 m² / g, Evonik Chemicals.

[0070] C: Mica powder with a particle size D50 of 2-6 μm, from Guangdong Sanbao New Materials.

[0071] D: Aluminum hydroxide, with a particle size D50 of 1-5 μm, from Shandong Zhonglv.

[0072] E1: Modifier, docosanoic acid, Jiangsu Runfeng.

[0073] E2: Modifier, dodecyltrimethoxysilane, Jingzhou Jianghan.

[0074] F: Pigment, iron oxide red, Bayer.

[0075] G1: Crosslinking agent, a combination of tetrabutylone oxime silane and vinyltributylone oxime silane, Hangzhou Sibao.

[0076] G2: Crosslinking agent, vinyltributylone oxime silane, Hubei Lantian.

[0077] H1: Raw material for tackifier synthesis, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, Jingzhou Jianghan.

[0078] H2: Raw material for the synthesis of tackifier, γ-acryloyloxypropyltrimethoxysilane, Jingzhou Jianghan.

[0079] H3: Moisture-resistant tackifier, with the structural formula (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3, self-made.

[0080] I: Catalyst, dibutyltin dilaurate, Jianyi Chemical.

[0081] J: Heat-resistant flame retardant, Karstedt type platinum catalyst (5000ppm), Heraeus.

[0082] K: Solvent, 120# gasoline, Changling Refining & Chemical.

[0083] The synthesis method of the moisture-resistant tackifier (H3) is as follows:

[0084] In a four-necked flask equipped with a condenser, stirrer, nitrogen purging device, and atmospheric distillation apparatus, 222 g (1 mol) of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (H1) and 257 g (1.1 mol) of γ-acryloyloxypropyltrimethoxysilane (H2) were added. After nitrogen purging, the mixture was heated to 80 °C with stirring, and the reaction mixture was maintained at 80 °C for 5 h. The reaction was then terminated, yielding a pale yellow, transparent liquid product. Infrared and nuclear magnetic resonance analysis confirmed the product structure as: (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3.

[0085] The performance testing methods for the embodiments and comparative examples of this invention are as follows:

[0086] (1) Test method for initial hydrophobicity classification characteristics: Appendix C of DL / T 627 Room temperature curing silicone rubber anti-pollution flashover coating for insulators.

[0087] (2) Shear strength test method: Appendix E of DL / T 627 Room temperature curing silicone rubber anti-pollution flashover coating for insulators.

[0088] (3) Breakdown strength test method: GB / T 1408.1 Electrical strength test method for insulating materials.

[0089] (4) Volume resistivity test method: GB / T 1692 Determination of the resistivity of vulcanized rubber insulation

[0090] (5) Arc resistance: GB / T 1411 Test of dry solid insulating materials for high voltage and low current arc discharge resistance

[0091] (6) Resistance to tracking and corrosion: GB / T 6553 Test methods for evaluating the resistance to tracking and corrosion of electrical insulating materials used in harsh environments.

[0092] (7) Boiling water test: IEEE Std. 1523 IEEE Guide for the Application, Maintenance, and Evaluation of Room-Temperature Vulcanizing (RTV) SiliconeRubber Coatings for Outdoor Ceramic Insulators

[0093] The preparation methods of the embodiments and comparative examples of this invention are as follows:

[0094] a. Mixing process: α,ω-dihydroxypolydimethylsiloxane (A), surface-modified nano-silica (B), mica powder (C), and aluminum hydroxide (D) are sequentially added to a kneader and mixed for 20 minutes to obtain the base material.

[0095] b. Grinding or sanding process: Grind or sand the base adhesive material twice;

[0096] c. Modification process: Heat and stir the base rubber material after grinding or sand milling. When the material temperature reaches 80℃, add the modifier (E1 or E2) and keep the material temperature at 80-100℃ for 2 hours.

[0097] d. Drying process: Further increase the material temperature and maintain it at 100-130℃, with a vacuum degree not lower than -0.08MPa, and vacuum dry for 4 hours;

[0098] e. Adhesive preparation process: First, add pigment (F) to the base adhesive and stir in a sealed container for 10 minutes until homogeneous. After the base adhesive cools to below 50°C, add crosslinking agent (G1 or G2) and stir for 25 minutes. Then add moisture-resistant tackifier (H1 or H3), catalyst (I), and heat-resistant flame retardant (J), and stir for 25 minutes. Add solvent (K) in batches, stirring for 25 minutes after each addition. Once the adhesive is homogeneous, filter and package to obtain the finished product.

[0099] The proportions of raw materials used in each embodiment and comparative example, by weight, are shown in Table 1.

[0100] Table 1

[0101]

[0102] The silicone coatings prepared in the examples and comparative examples were tested for hydrophobicity, shear strength, breakdown strength, volume resistivity, arc resistance, tracking resistance, and electro-erosion resistance according to various standards. They were then aged at 85°C and 85% humidity for 1000 hours, and the changes in hydrophobicity, shear strength, breakdown strength, and volume resistivity were observed. Simultaneously, the silicone coating was applied to the surface of the insulator with a thickness of 0.4 mm. After complete curing, a boiling water test (100°C, 100 h) was conducted according to standards to observe the blistering of the coating. The performance test results are shown in Table 2.

[0103] Table 2

[0104]

[0105] As shown in Examples 1-5 of Table 2, the comprehensive performance of the moisture-heat resistant, high-insulation silicone coating of the present invention can achieve the following: breakdown strength ≥30 kV / mm, arc resistance ≥200 s, and resistance to tracking and electrical erosion not less than 1A 3.5 level. After aging in high temperature and high humidity (85℃, 85%RH) for 1000 h, the change rate of breakdown strength, volume resistivity, and shear strength is less than 20%, and the hydrophobicity remains at HC1-HC2 level. After boiling in water for 100 h, there are no bubbles at the interface between the coating and the insulator surface, demonstrating excellent moisture-heat resistance and insulation.

[0106] The moisture- and heat-resistant, highly insulating silicone coating of Example 1 has an initial hydrophobicity of HCl, a shear strength of 3.4 MPa, a breakdown strength of 37.4 kV / mm, and a volume resistivity of 1.3 × 10⁻⁶. 15 Ω·cm, arc resistance 216 s, resistance to tracking and electrolytic corrosion is 1A 3.5 grade. After aging in high temperature and high humidity (85℃, 85%RH) for 1000 h, the hydrophobicity remains at HC1, and the shear strength, breakdown strength, and volume resistivity change rate are 15%, 10%, and 15%, respectively. After boiling in water for 100 h, there are no bubbles at the interface between the coating and the insulator surface.

[0107] Comparative Example 1, based on Example 1, omits the mica powder insulating filler. Its breakdown strength is 28.9 kV / mm. The initial breakdown strength in Comparative Example 1 is lower than that in Example 1. The combination of mica powder and aluminum hydroxide helps improve its breakdown strength. Comparative Example 2, based on Example 1, uses an unmodified base adhesive. After aging in high temperature and humidity (85℃, 85%RH) for 1000 h, the shear strength, breakdown strength, and volume resistivity change rates are 33%, 28%, and 29%, respectively. After boiling in water for 100 h, bubbles appear at the interface between the coating and the insulator surface. Surface treatment with a long-chain modifier improves the moisture and heat resistance of the silicone coating. Comparative Example 3, based on Example 1, does not use a tetrafunctional crosslinking agent. Its resistance to tracking and electrical erosion is 1A3.0. After aging in high temperature and humidity (85℃, 85%RH) for 1000 h, the shear strength, breakdown strength, and volume resistivity change rates are 31%, 25%, and 24%, respectively. After boiling in water for 100 hours, bubbles appeared at the interface between the coating and the insulator surface. The introduction of the tetrafunctional crosslinking agent increased the crosslinking density of the silicone coating, thereby improving its resistance to tracking, electro-erosion, and damp heat. Comparative Example 4, based on Example 1, did not use a damp heat resistant tackifier. After aging at high temperature and high humidity (85°C, 85%RH) for 1000 hours, the shear strength, breakdown strength, and volume resistivity change rates were 35%, 29%, and 32%, respectively. After boiling in water for 100 hours, bubbles appeared at the interface between the coating and the insulator surface. The introduction of the damp heat resistant tackifier improved the adhesion durability of the silicone coating, thereby improving its damp heat resistance. Comparative Example 5, based on Example 1, did not add mica powder, had no base adhesive treatment, and did not use a tetrafunctional crosslinking agent or a moisture-resistant tackifier. Its initial breakdown strength was only 27.4 kV / mm, and its resistance to tracking and electrical erosion was 1A 3.0. After aging in high temperature and high humidity (85℃, 85%RH) for 1000 h, the changes in shear strength, breakdown strength, and volume resistivity were 41%, 35%, and 38%, respectively. After boiling in water for 100 h, bubbles appeared at the interface between the coating and the insulator surface. The combined use of mica powder and aluminum hydroxide is beneficial for improving the initial breakdown strength of the coating. The synergistic effect of the base adhesive surface treatment, the tetrafunctional crosslinking agent, and the moisture-resistant tackifier significantly improves the coating's resistance to moisture and heat, ensuring the coating's adhesion durability and insulation retention.

[0108] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the above embodiments have described the present invention in detail, those skilled in the art should understand that modifications or equivalent substitutions can be made to the present invention, but any modifications and partial substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A moisture- and heat-resistant insulating silicone coating, characterized in that: The product comprises the following components in parts by weight: 40-60 parts of α,ω-dihydroxypolydimethylsiloxane, 1-10 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 0.5-2.5 parts of modifier, 0-10 parts of pigment, 2-5 parts of crosslinking agent, 1-3 parts of moisture-resistant tackifier, 0.01-0.1 parts of catalyst, 0.1-0.6 parts of heat-resistant flame retardant, and 20-40 parts of solvent; Among them, the surface-modified nano-silica is obtained by hydrophobic surface treatment of nano-silica. The structural formula of the modifier is C m H 2m+1 COOH or (C n H 2n+1 SiR 1 x (OR 2 ) (3-x) m≥20, n≥12, R 1 R 2 Each can be independently CH3 or C2H5, and x is 0, 1 or 2; Crosslinking agents include tetrabutylone oxime silane; The humid heat resistant tackifier is a bissilane coupling agent containing secondary amino and ester groups.

2. The moisture-resistant and heat-insulating silicone coating according to claim 1, characterized in that: It comprises the following components in parts by weight: 45-55 parts of α,ω-dihydroxypolydimethylsiloxane, 3-7 parts of surface-modified nano-silica, 5-10 parts of mica powder, 30-40 parts of aluminum hydroxide, 1-2 parts of modifier, 3 parts of pigment, 4-5 parts of crosslinking agent, 2-3 parts of moisture-resistant tackifier, 0.02 parts of catalyst, 0.2-0.6 parts of heat-resistant flame retardant, and 30-40 parts of solvent.

3. The moisture- and heat-resistant insulating silicone coating according to claim 1, characterized in that: The viscosity of α,ω-dihydroxypolydimethylsiloxane at 25°C is 10,000–20,000 mPa·s; The specific surface area of ​​surface-modified nano-silica is 150–400 m². 2 / g; preferably, the specific surface area of ​​the surface-modified nano-silica is 190–250 m². 2 / g, surface treated with hexamethyldisilazane; The particle size D50 of mica powder is 2–6 μm; the particle size D50 of aluminum hydroxide is 1–5 μm.

4. The moisture- and heat-resistant insulating silicone coating according to claim 1, characterized in that: The pigment is one or more of iron oxide, titanium dioxide, carbon black, phthalocyanine green, iron yellow, and iron blue; The modifier is one or more of dodecanoic acid, dodecanoic acid, dodecyltrimethoxysilane, and dodecyltriethoxysilane; The crosslinking agent is tetrabutylone oxime silane, a combination of tetrabutylone oxime silane and vinyltributanone oxime silane, or a combination of tetrabutylone oxime silane and methyltributanone oxime silane; The catalyst is a tin-containing catalyst; preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dibutyltin acetate, and dioctyltin dilaurate. The heat-resistant flame retardant is a platinum complex, a Karstedt-type platinum catalyst; The solvent is one or more of petroleum ether, 120# solvent gasoline, 200# solvent gasoline, isoalkanes, and toluene.

5. The moisture- and heat-resistant insulating silicone coating according to claim 1, characterized in that: The structural formula of the moisture-resistant tackifier is (CH3O)3SiC3H6NHC2H4NHC2H4COOC3H6Si(OCH3)3.

6. The moisture- and heat-resistant insulating silicone coating according to claim 5, characterized in that: The humid heat resistant tackifier is synthesized from silane coupling agents S1 and S2, wherein S1 is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and S2 is γ-acryloyloxypropyltrimethoxysilane.

7. The moisture- and heat-resistant insulating silicone coating according to claim 6, characterized in that: The molar ratio of S1 to S2 is 1:(1~1.2), preferably 1:1.

1.

8. The method for preparing the moisture-resistant and heat-insulating silicone coating according to any one of claims 1 to 7, characterized in that, Includes the following steps: a. Mixing process: α,ω-dihydroxypolydimethylsiloxane, surface-modified nano-silica, mica powder, and aluminum hydroxide are stirred, kneaded and mixed evenly to obtain the base adhesive. b. Grinding or sanding process: Grind or sand the base adhesive 1 to 3 times; c. Modification process: Heat and stir the base adhesive after grinding or sand milling. When the material temperature reaches 80℃, add the modifier and keep the material temperature at 80~100℃ for 2 hours. d. Drying process: Maintain the material temperature at 100-130℃ and the vacuum degree at no less than -0.08 MPa, and vacuum dry for 3-5 hours to obtain the dried base material; e. Adhesive preparation process: First, add pigment to the dried base adhesive and stir in a sealed container until uniform; after the base adhesive cools to below 50°C, add crosslinking agent and stir for 20-30 minutes; then add moisture-resistant tackifier, catalyst, and heat-resistant flame retardant, stir for 20-30 minutes, and finally add solvent and stir until uniform to obtain the final product.

9. The application of the moisture- and heat-resistant insulating silicone coating according to any one of claims 1 to 7 in the surface protection of electrical equipment.

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