Composite thermal insulation coating for electrical equipment and preparation method of composite thermal insulation coating

Abstract

The invention relates to the technical field of functional coatings, and particularly discloses a composite thermal insulation coating for electrical equipment and a preparation method thereof. The composite heat insulation coating comprises modified organic silicon resin, nano silicon dioxide, hollow glass beads, aluminum oxide powder, graphene modified ceramic fibers, a dispersing agent, a heat stabilizer, a thickening agent and zinc borate. The preparation method comprises the following steps: carrying out pretreatment, carrying out primary mixing on the base material, the dispersant and other assistants, adding the pretreated filler, carrying out ultrasonic and high-speed stirring dispersion, carrying out curing defoaming, viscosity adjustment and filtration, and carrying out filling under inert gas protection to obtain a finished product. The coating can be used for surface heat insulation protection of electrical equipment, and has the advantages of excellent heat insulation performance, high stability in a high-temperature environment and good adhesive force with a base material; in addition, according to the preparation method, the consistency and reliability of the product are ensured by optimizing process parameters and process design, and the preparation method is suitable for high-temperature protection of power equipment.

Description

Technical Field

[0001] This application relates to the field of functional coatings technology, and more specifically, to a composite thermal insulation coating for power equipment and its preparation method. Background Technology

[0002] Electrical equipment continuously generates heat during long-term operation. If this heat cannot be effectively blocked, the internal temperature of the equipment will rise, affecting the operational stability of components, shortening the equipment's lifespan, and even causing safety hazards. Therefore, thermal insulation coatings, as an important protective material for electrical equipment, play a crucial role in reducing the temperature difference between the equipment's surface and interior by blocking heat transfer, thus ensuring the safe and stable operation of electrical equipment. They have indispensable application value in the power industry.

[0003] Traditional thermal insulation coatings for power equipment often use a single resin as the base material, combined with simply mixed inorganic fillers. Due to the lack of scientific component ratio design, especially the weak interfacial bonding between the filler and the resin matrix, and the difficulty of achieving efficient and stable dispersion of multi-scale fillers by traditional mixing processes, it is difficult to form an effective multi-layer thermal insulation structure. The components cannot produce good synergistic effects, resulting in limited overall thermal insulation performance of the coating. Furthermore, under long-term high-temperature environments, it is prone to performance degradation, structural aging, and microscopic defects in the coating, failing to meet the long-term stability requirements of thermal insulation coatings for power equipment. Summary of the Invention

[0004] To address the shortcomings in the comprehensive thermal insulation performance and long-term stability of thermal insulation coatings for power equipment in existing technologies, this application provides a composite thermal insulation coating for power equipment and its preparation method.

[0005] In a first aspect, this application provides a composite thermal insulation coating for power equipment, employing the following technical solution:

[0006] A composite thermal insulation coating for power equipment is composed of the following raw materials in parts by weight:

[0007] 25-45 parts of modified organosilicon resin;

[0008] 15-30 parts of nano-silica;

[0009] 10-25 parts of hollow glass microspheres;

[0010] 5-15 parts of alumina powder;

[0011] 1-5 parts of graphene-modified ceramic fiber, the surface of which is coated with a silicon dioxide layer with a thickness of 10-100nm;

[0012] 2-6 parts zinc borate;

[0013] 2-8 parts dispersant;

[0014] Heat stabilizer 1-5 parts;

[0015] Thickener 3-10 parts.

[0016] By adopting the above technical solutions, in the composition design of composite thermal insulation coatings, modified organosilicon resin is used as the continuous phase matrix material. Utilizing the organic-inorganic hybrid structure of its molecular chain, it provides a continuous and stable three-dimensional skeletal support for the coating. Nano-silica and alumina powders, as micro-nano-scale functional fillers, form a dense filling layer in the resin matrix through their size effect, effectively increasing the tortuosity of the heat conduction path. Hollow glass microspheres, with their unique hollow spherical structure, construct uniformly distributed gas-phase barrier units within the coating, significantly reducing solid-phase heat conduction efficiency. Graphene-modified ceramic fibers, through their special two-dimensional sheet and one-dimensional fiber composite structure, interlock in three-dimensional space to form a continuous thermal barrier network. This network structure forms a geometrically complementary synergistic thermal insulation system with the spherical fillers. Polycarboxylate dispersants, through their anchoring groups and steric hindrance effect on their molecular chains, ensure that various fillers achieve good interfacial compatibility and dispersion stability in the resin matrix. Organotin heat stabilizers effectively inhibit molecular chain degradation at high temperatures by coordinating with active groups in the resin system through their molecular structure. Cellulose ether thickeners, through their unique molecular design of hydrophilic segments and hydrophobic backbones, establish a stable hydrogen bond network in the resin system, enabling precise control of the system's rheological behavior. Zinc borate, under heating conditions, undergoes multiple crystal transformations and dehydration reactions to co-construct a dense, expandable barrier layer with resin decomposition products. These components, through specific proportions and processing techniques, ultimately form a functional coating system with multi-scale and multi-morphological synergistic effects.

[0017] By coating graphene-modified ceramic fibers with silica, controlling the coating thickness within the range of 10-100 nm, the silica layer forms chemical bonds with functional groups in the resin matrix through its surface silanol groups, effectively improving the interfacial bonding between the fiber and the matrix material. This specific thickness of coating maintains the fiber's inherent thermal stability and mechanical properties while enhancing its compatibility with organic resins through surface modification. The coating forms a transition layer between the fiber and the matrix, alleviating interfacial stress caused by the difference in their coefficients of thermal expansion. Simultaneously, the silica layer itself has low thermal conductivity, further enhancing the fiber's thermal insulation performance. This surface treatment process allows graphene-modified ceramic fibers to fully utilize their intrinsic properties in composite materials while forming a stable interfacial bond with the surrounding matrix, thereby improving the overall performance of the composite coating.

[0018] Preferably, the particle size range of the nano-silica is 10-100 nm, the particle size range of the hollow glass microspheres is 5-50 μm, and the length of the graphene-modified ceramic fiber is 10-100 μm and the diameter is 0.5-5 μm.

[0019] By employing the above technical solution, the particle size of nano-silica is controlled within the range of 10-100 nanometers, utilizing its high specific surface area and surface activity to effectively fill the microporous structure in the coating. Hollow glass microspheres, selected as hollow spherical particles of 5-50 micrometers, have a particle size distribution that forms a good gradation relationship with the nanofillers, constructing a continuous gas-phase barrier layer in the coating. The length of graphene-modified ceramic fibers is controlled within the range of 10-100 micrometers, and the diameter is maintained between 0.5-5 micrometers. This size range ensures that the fibers can form a continuous three-dimensional network structure in the coating without affecting the coating's forming quality due to excessive length or coarseness. This multi-scale particle size synergistic design allows fillers of different dimensions to complement each other in the coating. The nanofillers effectively fill the gaps between micron-sized fillers, while the micron-sized fibers act as a skeletal support, jointly constructing a more complete and dense thermal barrier system.

[0020] Preferably, the dispersant is at least one of sodium polyacrylate and ammonium polyacrylate; the heat stabilizer is at least one of dibutyltin dilaurate and dibutyltin maleate; and the thickener is at least one of hydroxypropyl methylcellulose and sodium carboxymethyl cellulose.

[0021] By employing the above technical solutions and selecting sodium polyacrylate or ammonium polyacrylate as dispersants, these anionic polymers form a strong anchoring effect with the filler surface through the carboxylate ions on their molecular chains. Simultaneously, the steric hindrance effect of the molecular chains generates electrostatic repulsion, ensuring the filler particles remain stably dispersed. Dibutyltin dilaurate or dibutyltin maleate is selected as the heat stabilizer. The tin atoms in their molecules form coordination bonds with the active groups in the resin system, effectively inhibiting the oxidative degradation reaction of the resin under high-temperature conditions. Hydroxypropyl methylcellulose or sodium carboxymethyl cellulose are used as thickeners. These cellulose derivatives form a hydrogen bond network with water molecules through the hydroxyl groups on their molecular chains, and simultaneously establish a three-dimensional spatial structure through the entanglement of the molecular chains, achieving precise control of the system viscosity. These specific types of additives, through their unique mechanisms of action, collectively ensure the stability and controllability of the coating system during preparation, storage, and use.

[0022] Secondly, this application provides a method for preparing a composite thermal insulation coating for power equipment, which adopts the following technical solution:

[0023] A method for preparing a composite thermal insulation coating for power equipment includes the following steps:

[0024] S1. Raw material pretreatment: Dry nano-silica and alumina powder at 80-120℃ for 1-3h; preheat hollow glass microspheres at 60-90℃ for 0.5-1.5h; activate graphene-modified ceramic fibers at 100-150℃ for 0.5-2h under nitrogen protection, wherein the nitrogen flow rate is 0.5-2.0L / min;

[0025] S2. Primary mixing: Mix the modified silicone resin and dispersant at a stirring speed of 200-500 r / min for 10-30 min; add heat stabilizer, thickener and zinc borate, and continue mixing for 5-15 min;

[0026] S3. Filler dispersion: Gradually add all the pretreated fillers from step S1 to the base material obtained in step S2; mechanically stir and disperse at a speed of 1000-3000 r / min, while simultaneously applying ultrasonic treatment at a frequency of 20-40 kHz and a power of 100-500 W for 20-60 min.

[0027] S4. Maturation and degassing: Let the mixture stand at 30-50℃ for 2-6 hours to mature; then degas it for 10-30 minutes under a vacuum of 0.01-0.05MPa, and apply mechanical stirring at 50-150r / min during the degassing process.

[0028] S5. Viscosity Adjustment and Filtration: The viscosity of the cured coating is tested, and the viscosity is adjusted to 500-2000 mPa·s by adding deionized water or thickener; then filtration is performed, and the pore size is controlled within the range of 50-150 μm.

[0029] S6. Finished Product Packaging: The viscosity-adjusted coating is filled into sealed containers under inert gas protection.

[0030] By adopting the above technical solution, this preparation method ensures the full integration and performance optimization of the coating components through a systematic process flow. In the raw material pretreatment stage, nano-silica and alumina powders are heat-treated at 80-120℃ to effectively remove adsorbed moisture and volatile substances from the material surface; hollow glass microspheres are preheated at 60-90℃ to achieve a suitable dispersion state; simultaneously, graphene-modified ceramic fibers are activated at 100-150℃ to enhance their surface activity. In the primary mixing stage, modified organosilicon resin and dispersant are first thoroughly wetted at a stirring speed of 200-500 r / min, followed by the addition of stabilizers, thickeners, and zinc borate. Under continuous stirring, the components are initially fused. In the filler dispersion stage, the pretreated fillers are added sequentially to the base material system. High-speed stirring at 1000-3000 r / min, combined with a specific dispersion time, ensures that the filler particles achieve an ideal distribution state in the resin matrix. The curing process begins with static storage at 30-50℃ to allow the system to reach molecular-level equilibrium. Following this, degassing is performed under a vacuum of 0.01-0.05 MPa to effectively remove gases trapped during mixing. Finally, viscosity is measured and adjusted to stabilize the finished product within the range of 500-2000 mPa·s, and packaging is completed under inert gas protection to ensure product stability during storage. This step-by-step preparation process ensures the full integration and optimal performance of the coating components.

[0031] The activation process of graphene-modified ceramic fibers is carried out under a nitrogen protective atmosphere. By controlling the nitrogen flow rate within the range of 0.5-2.0 liters per minute, a stable inert gas protective layer is formed. This protective environment effectively prevents oxidation of the fiber surface with oxygen in the air during the heating activation process, avoiding changes in surface properties. A suitable nitrogen flow rate ensures sufficient air replacement within the reaction apparatus without causing fiber particles to be carried away by the airflow or resulting in disordered flow due to excessively high flow rates. Under a continuous and stable nitrogen atmosphere, adsorbed moisture and impurities on the fiber surface are effectively removed, while its surface-active groups are activated, creating favorable conditions for subsequent bonding with the resin matrix. This controlled activation process ensures that the fiber material can fully exert its functional properties during subsequent processing.

[0032] By applying ultrasonic-assisted treatment simultaneously with high-speed mechanical stirring, controlling the ultrasonic frequency within the range of 20-40kHz, and maintaining the processing power between 100-500W, this ultrasonic treatment generates a large number of microbubbles in the liquid medium through its unique cavitation effect. The intense formation and collapse of these bubbles can generate strong shock waves and microjets in localized areas. This high-frequency vibration and impact can effectively disperse agglomerates between filler particles, especially showing a significant deagglomeration effect on easily agglomerated materials such as nano-silica and graphene-modified ceramic fibers. At the same time, the macroscopic flow provided by mechanical stirring and the microscopic disturbances generated by ultrasound work synergistically, ensuring both the macroscopic uniform distribution of fillers in the resin matrix and achieving microscopic-scale dispersion optimization. This composite dispersion method ensures that various filler particles can be fully wetted and coated by the resin matrix, laying the foundation for the formation of a stable composite coating structure.

[0033] By employing low-speed stirring in the aforementioned technical solution, the material system can maintain slow flow during degassing. This avoids the problem of introducing new bubbles that high-speed stirring might introduce, and also promotes the orderly movement of bubbles within the material towards the liquid surface along the stirring trajectory in a vacuum environment. The appropriate stirring speed ensures that the material maintains a uniform temperature and concentration field during degassing, while the gentle shearing action disrupts the adsorption balance on the bubble surface, reducing the interfacial tension between the bubbles and the material, thereby promoting bubble coalescence and escape. Compared to static treatment, this dynamic degassing method more effectively eliminates bubbles trapped inside the material, especially in the filler accumulation area, without damaging the existing filler dispersion structure, thus ensuring a dense and defect-free coating.

[0034] By adopting the above technical solution, the design of a specific pore size range can effectively trap filler agglomerates and insufficiently dispersed particles that may form during the preparation process, while ensuring the smooth passage of fully dispersed functional fillers. This filtration process can remove trace mechanical impurities that may be introduced during the early processing, as well as some gel particles generated during the curing process, thereby ensuring that the final product has a uniform texture. Coatings that have undergone this precision filtration can form a smoother and denser coating surface during subsequent application, avoiding coating defects caused by particulate impurities, while ensuring that the coating equipment is not clogged by undispersed particles, thus contributing to stable application performance. This refined post-processing provides an important guarantee for obtaining coating products of stable quality.

[0035] Preferably, the inert gas in step S6 is nitrogen or argon.

[0036] Preferably, the sealed container in step S6 is a metal can with an inner liner or a barrier plastic container.

[0037] By adopting the above technical solution, nitrogen or argon is used as a protective gas during the finished product packaging stage. These two inert gases effectively isolate oxygen and moisture, preventing oxidation and moisture absorption deterioration of the coating during storage. The sealed containers are metal cans or barrier plastic containers with inner linings. The inner lining further enhances the container's sealing performance, while the metal material provides good mechanical strength and light-blocking properties, and the special barrier plastic effectively prevents the penetration of gases and moisture. This packaging configuration, through multiple protective mechanisms, avoids the impact of external environmental factors on the stability of the coating, prevents solvent evaporation and component separation, and ensures that the product maintains stable physical and chemical properties during storage and transportation. This comprehensive packaging solution provides long-term and effective quality assurance for the coating, allowing it to maintain its optimal condition at the time of manufacture until use.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. This application uses modified organosilicon resin as the base resin, and combines it with a specific ratio of graphene-modified ceramic fiber, nano-silica, hollow glass microspheres and alumina powder to form a composite filler system. Because these components form a multi-layered thermal insulation structure under a specific ratio, good synergistic effect is generated between the components, resulting in excellent comprehensive thermal insulation performance and long-term use stability.

[0040] 2. In this application, a combination of nano-silica with hollow glass microspheres with a specific particle size range is preferred, and polycarboxylate dispersants and organotin heat stabilizers are selected. Because these components produce a synergistic effect under a specific ratio, the filler is uniformly dispersed and stably present in the system, and a coating system that can maintain good stability under long-term use conditions is obtained.

[0041] 3. The method of this application combines fiber activation treatment under nitrogen protection with ultrasonic-assisted dispersion process, and adopts synergistic operation of vacuum degassing and mechanical stirring during the curing stage. As a result of the organic combination of these process steps, the dispersion state of the filler is effectively improved and coating defects are eliminated, thus obtaining a high-quality coating product with dense structure and stable performance. Attached Figure Description

[0042] Figure 1 This is a flowchart of a composite thermal insulation coating preparation process for power equipment provided in this application. Detailed Implementation

[0043] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0044] Technical concept:

[0045] Current thermal insulation coatings for power equipment generally face the technical challenge of significant performance degradation under long-term high-temperature environments. This is mainly due to inherent defects in the filler system design of traditional coatings. Conventional filler combinations often only consider a single thermal insulation mechanism, lacking effective synergy between components. Under thermal stress, interfacial separation easily occurs, leading to micro-cracks and structural deterioration in the coating, making it difficult to maintain stable thermal insulation performance. In addition, insufficient compatibility between fillers and matrix resins causes the coating to gradually lose its integrity and functionality during long-term use.

[0046] This technical solution addresses this problem by constructing a multi-layered composite thermal insulation system. Specifically, it uses modified silicone resin as the matrix material, synergistically combining functional fillers with different scale characteristics, including nano-silica, hollow glass microspheres, alumina powder, and graphene-modified ceramic fibers with a silica layer on their surface. These fillers, through specific particle size ratios and surface characteristic designs, form a complementary thermal insulation mechanism within the matrix. Simultaneously, through optimized preparation processes, including key steps such as filler activation treatment, ultrasonic-assisted dispersion, and vacuum degassing, it ensures that each component is fully dispersed and forms a stable three-dimensional network structure, thereby obtaining a composite coating material with durable thermal insulation performance.

[0047] Preparation Example 1

[0048] The preparation method of modified organosilicon resin is as follows:

[0049] 100 parts by weight of methyltriethoxysilane and 50 parts by weight of phenyltriethoxysilane were dried separately using 4A molecular sieves for 24 hours to remove moisture, and then added to a reaction vessel. Nitrogen gas was introduced to purge the air from the vessel three times to isolate oxygen interference. The mixture was then heated to 80°C under nitrogen protection and stirred at a speed of 300 r / min. A mixed solution consisting of 30 parts by weight of epoxy resin E-51 and 15 parts by weight of silane coupling agent KH-560 was slowly added dropwise over 1.5 hours, with the reaction temperature maintained at 85-90°C by adjusting the dropping rate. After the addition was complete, 0.5 parts by weight of tetraisopropyl titanate was added as a catalyst, the stirring speed was increased to 400 r / min, and the temperature was gradually increased to 120°C and maintained at this temperature for 3 hours, continuously monitoring the viscosity changes during the reaction. After the reaction was completed, the vacuum of the system was increased to 0.08 MPa, and the temperature was raised to 140°C to remove the by-product ethanol and low-boiling substances. After holding at this temperature for 2 hours, the temperature was lowered to room temperature to finally obtain epoxy-modified organosilicon resin. This resin has both the heat resistance of organosilicon resin and the good adhesion of epoxy resin.

[0050] Preparation Example 2

[0051] The preparation method of graphene-modified ceramic fibers is as follows:

[0052] Ten parts by weight of ceramic fiber were placed in an oven at 120℃ and dried for 4 hours to remove adsorbed water. After cooling to room temperature, the fiber was dispersed in 200 parts by weight of deionized water. 0.5 parts by weight of hexadecyltrimethylammonium bromide was added as a dispersant. The mixture was then treated with an ultrasonic device at a power of 300W and a frequency of 40kHz for 30 minutes to ensure uniform dispersion of the ceramic fiber and the formation of a stable suspension. A dispersion consisting of 2 parts by weight of graphene oxide and 50 parts by weight of deionized water was slowly added, and ultrasonic treatment was continued for 1 hour to promote the adsorption of graphene oxide on the surface of the ceramic fiber. Subsequently, tetraethyl orthosilicate was added dropwise at a uniform rate until the system concentration reached 5%. The pH of the system was adjusted to 9-10 with 25% ammonia water. The temperature was raised to 60℃ and stirred at a speed of 200r / min for 4 hours to carry out a hydrolysis-condensation reaction, allowing tetraethyl orthosilicate to form a uniform silica coating layer on the fiber surface. After the reaction was completed, the product was separated by vacuum filtration, and washed repeatedly with deionized water until the washing liquid was neutral. Then it was dried in an oven at 100°C for 6 hours, and finally placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under argon protection. It was then kept at a constant temperature for 2 hours to finally obtain graphene-modified ceramic fibers with a silica coating on the surface.

[0053] The following are the main raw materials and reagents used in the preparation examples, embodiments, and comparative examples, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products:

[0054] 1. Methyltriethoxysilane was purchased from Jiangxi Hongbai New Materials Co., Ltd., CAS: 2031-67-6;

[0055] 2. Phenylacetyltriethoxysilane was purchased from Jiangsu Xinsu New Materials Co., Ltd., CAS: 780-69-8;

[0056] 3. Epoxy resin E-51 was purchased from Jinan Jingsheng Chemical Co., Ltd., item number: E-51;

[0057] 4. The silane coupling agent KH-560 was purchased from Pascal Pharmaceuticals (Shanghai) Co., Ltd., item number: 008;

[0058] 5. Tetraisopropyl titanate was purchased from Huzhou Haipu Chemical Co., Ltd., CAS: 546-68-9;

[0059] 6. Sodium polyacrylate was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S30249;

[0060] 7. Ammonium polyacrylate was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S68736;

[0061] 8. Dibutyltin dilaurate was purchased from Jinan Century Tongda Chemical Co., Ltd., CAS: 77-58-7;

[0062] 9. Hydroxypropyl methylcellulose was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S14173;

[0063] 10. Sodium carboxymethyl cellulose was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S14016;

[0064] 11. Cetyltrimethylammonium bromide was purchased from Shanghai Xuejie Chemical Co., Ltd., CAS: 57-09-0;

[0065] 12. Ethyl orthosilicate was purchased from Shandong Lifuda Fine Chemical Co., Ltd., CAS: 78-10-4.

[0066] Example 1

[0067] This application provides a composite heat insulation coating for power equipment, comprising the following raw materials in parts by weight: 25 parts modified organosilicon resin; 15 parts nano-silica; 10 parts hollow glass microspheres; 5 parts alumina powder; 2 parts dispersant; 1 part heat stabilizer; 3 parts thickener; 1 part graphene-modified ceramic fiber with a silica layer on its surface, the silica layer having a thickness of 10 nm; and 2 parts zinc borate.

[0068] Among them, the particle size range of nano-silica is 10nm, the particle size range of hollow glass microspheres is 5μm, and the length of graphene modified ceramic fiber is 10μm and the diameter is 0.5μm.

[0069] The dispersant is selected from ammonium polyacrylate; the heat stabilizer is selected from dibutyltin maleate; and the thickener is selected from sodium carboxymethyl cellulose.

[0070] The graphene-modified ceramic fiber is coated with a silicon dioxide layer with a thickness of 10 nm.

[0071] The preparation method of the above-mentioned composite heat insulation coating for power equipment includes the following steps:

[0072] S1. Raw material pretreatment: Dry nano-silica and alumina powder at 80°C for 1 hour; preheat hollow glass microspheres at 60°C for 0.5 hours; activate the graphene-modified ceramic fiber with silica coating at 100°C for 0.5 hours under nitrogen protection, with a nitrogen flow rate of 0.5 L / min.

[0073] S2, Primary Mixing: Mix the modified silicone resin and dispersant at a stirring speed of 200 r / min for 10 min; add the heat stabilizer, thickener and zinc borate, and continue mixing for 5 min;

[0074] S3. Filler dispersion: Gradually add all the pretreated fillers from step S1 to the base material obtained in step S2; mechanically stir and disperse at a speed of 1000 r / min, while simultaneously applying ultrasonic treatment, controlling the ultrasonic frequency within the range of 20 kHz and the treatment power within the range of 100 W, for 20 min.

[0075] S4. Maturation and degassing: The mixture is allowed to stand at 30℃ for 2 hours to mature; then it is degassed for 10 minutes under a vacuum of 0.01MPa, and mechanical stirring is applied at a stirring speed of 50r / min during the degassing process.

[0076] S5. Viscosity Adjustment and Filtration: The viscosity of the cured coating is tested, and the viscosity is adjusted to 500 mPa·s by adding deionized water or thickener; then the coating is filtered to control the pore size within 50 μm.

[0077] S6. Finished Product Packaging: The viscosity-adjusted coating is filled into sealed containers under inert gas protection;

[0078] The inert gas is argon, and the sealed container is a barrier plastic container.

[0079] Example 2

[0080] This application provides a composite heat-insulating coating for power equipment, comprising the following raw materials in parts by weight: 35 parts modified organosilicon resin; 22.5 parts nano-silica; 17.5 parts hollow glass microspheres; 10 parts alumina powder; 5 parts dispersant; 3 parts heat stabilizer; 6.5 parts thickener; 3 parts graphene-modified ceramic fiber with a silica layer on its surface, wherein the silica layer has a thickness of 55 nm; and 4 parts zinc borate.

[0081] Among them, the particle size range of nano-silica is 55nm, the particle size range of hollow glass microspheres is 27.5μm, and the length of graphene modified ceramic fiber is 55μm and the diameter is 2.75μm.

[0082] The dispersant is selected from sodium polyacrylate; the heat stabilizer is selected from dibutyltin dilaurate; and the thickener is selected from hydroxypropyl methylcellulose.

[0083] The preparation method of the above-mentioned composite heat insulation coating for power equipment includes the following steps:

[0084] S1. Raw material pretreatment: Nano-silica and alumina powder are dried at 100℃ for 2 hours; hollow glass microspheres are preheated at 75℃ for 1 hour; the graphene-modified ceramic fibers with silica coating are activated at 125℃ for 1.25 hours under nitrogen protection, with a nitrogen flow rate of 1.25 L / min.

[0085] S2, Primary Mixing: Mix the modified silicone resin and dispersant at a stirring speed of 350 r / min for 20 min; add the heat stabilizer, thickener and zinc borate, and continue mixing for 10 min;

[0086] S3. Filler dispersion: Gradually add all the pretreated fillers from step S1 to the base material obtained in step S2; mechanically stir and disperse at a speed of 2000 r / min, while simultaneously applying ultrasonic treatment, controlling the ultrasonic frequency within the range of 30 kHz and the treatment power within the range of 300 W, for 40 min.

[0087] S4. Maturation and degassing: The mixture is allowed to stand at 40℃ for 4 hours to mature; then it is degassed under a vacuum of 0.03MPa for 20 minutes, and mechanical stirring is applied at a stirring speed of 100r / min during the degassing process.

[0088] S5. Viscosity Adjustment and Filtration: The viscosity of the cured coating is tested, and the viscosity is adjusted to 1250 mPa·s by adding deionized water or thickener; then the coating is filtered, and the pore size is controlled within 100 μm; S6. Finished Product Packaging: The viscosity-adjusted coating is filled into sealed containers under inert gas protection;

[0089] The inert gas is nitrogen, and the sealed container is a metal can with an inner liner.

[0090] Example 3

[0091] This application provides a composite heat insulation coating for power equipment, comprising the following raw materials in parts by weight: 45 parts modified organosilicon resin; 30 parts nano-silica; 25 parts hollow glass microspheres; 15 parts alumina powder; 8 parts dispersant; 5 parts heat stabilizer; 10 parts thickener; 5 parts graphene-modified ceramic fiber with a silica layer on its surface, wherein the silica layer has a thickness of 100 nm; and 6 parts zinc borate.

[0092] Among them, the particle size range of nano-silica is 100nm, the particle size range of hollow glass microspheres is 50μm, and the length of graphene modified ceramic fiber is 100μm and the diameter is 5μm.

[0093] The dispersant is selected from sodium polyacrylate; the heat stabilizer is selected from dibutyltin dilaurate; and the thickener is selected from hydroxypropyl methylcellulose.

[0094] The preparation method of the above-mentioned composite heat insulation coating for power equipment includes the following steps:

[0095] S1. Raw material pretreatment: Nano-silica and alumina powder are dried at 120°C for 3 hours; hollow glass microspheres are preheated at 90°C for 1.5 hours; the graphene-modified ceramic fibers with silica coating are activated at 150°C for 2 hours under nitrogen protection, with a nitrogen flow rate of 2.0 L / min.

[0096] S2, Primary Mixing: Mix the modified silicone resin and dispersant at a stirring speed of 500 r / min for 30 min; add stabilizer, thickener and zinc borate, and continue mixing for 15 min;

[0097] S3. Filler dispersion: Gradually add all the pretreated fillers from step S1 to the base material obtained in step S2; mechanically stir and disperse at a speed of 3000 r / min, while simultaneously applying ultrasonic treatment, controlling the ultrasonic frequency within the range of 40 kHz and the treatment power within the range of 500 W, for 60 min.

[0098] S4. Maturation and degassing: The mixture is allowed to stand at 50℃ for 6 hours to mature; then it is degassed under a vacuum of 0.05MPa for 30 minutes, and mechanical stirring is applied at a stirring speed of 150r / min during the degassing process.

[0099] S5. Viscosity Adjustment and Filtration: The viscosity of the cured coating is tested, and the viscosity is adjusted to 2000 mPa·s by adding deionized water or thickener; then the coating is filtered to control the pore size within 150 μm.

[0100] S6. Finished Product Packaging: The viscosity-adjusted coating is filled into sealed containers under inert gas protection;

[0101] The inert gas is nitrogen, and the sealed container is a metal can with an inner liner.

[0102] Comparative Example 1

[0103] The only difference between this comparative example and Example 1 is that the modified silicone resin is replaced with an equal amount of ordinary methyl silicone resin, while the other raw materials and preparation steps are exactly the same as in Example 1.

[0104] Comparative Example 2

[0105] The only difference between this comparative example and Example 1 is that the graphene-modified ceramic fibers with a silica coating are replaced with an equal amount of ordinary ceramic fibers without a silica coating. The other raw materials and preparation steps are exactly the same as in Example 1.

[0106] Comparative Example 3

[0107] The only difference between this comparative example and Example 1 is that the zinc borate component is removed and its weight portion is removed from the formulation; the remaining raw materials and preparation steps are exactly the same as in Example 1.

[0108] Comparative Example 4

[0109] The only difference between this comparative example and Example 1 is that the activation treatment of graphene-modified ceramic fibers is omitted in the raw material pretreatment step S1, i.e., the heat treatment at 100°C for 0.5 hours is not performed. The other raw materials and preparation steps are exactly the same as in Example 1.

[0110] Comparative Example 5

[0111] The only difference between this comparative example and Example 1 is that in the S4 ripening process, the vacuum condition and mechanical stirring are removed, and degassing is performed only after standing ripening at normal pressure for 2 hours. The other raw materials and preparation steps are exactly the same as in Example 1.

[0112] I. Thermal conductivity test

[0113] According to GB / T10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method", the coatings of Examples 1-3 and Comparative Examples 1-5 were uniformly coated on the surface of a low-carbon steel substrate with dimensions of 300mm×300mm×5mm, and the dry film thickness was controlled to be uniformly 500μm. They were cured for 7 days in a standard environment with a temperature of 25℃ and a relative humidity of 60% until fully cured. After curing, each sample was sequentially installed in the test chamber of the thermal conductivity tester using the hot plate method. The cold plate temperature was set to 25°C and the hot plate temperature to 100°C, and the temperature difference between the cold and hot plates was maintained at 75°C. After the system reached thermal steady state, the heat flux density data was continuously recorded for 30 minutes. The thermal conductivity was calculated according to the formula λ=Q×d / (A×ΔT), where λ is the thermal conductivity, Q is the heat flux density, d is the dry film thickness of the sample, A is the test area, and ΔT is the temperature difference between the cold and hot plates. Each sample was tested in parallel three times and the average value was taken. By comparing the thermal conductivity values ​​of each embodiment with the comparative embodiment, the basic thermal insulation performance advantage of the coating was intuitively reflected.

[0114] II. Test on the retention rate of thermal insulation performance after high-temperature aging

[0115] According to GB / T1735-2009 "Determination of Heat Resistance of Paints and Varnishes" and GB / T10294-2008 standard, the cured samples of Examples 1-3 and Comparative Examples 1-5 (preparation conditions the same as in Experiment 1) were placed in a high-temperature aging test chamber. The aging temperature was set at 150℃ and the aging time was 1000h. During the aging process, the air inside the chamber was kept in a natural circulation. After aging, the samples were taken out and cooled for 24h in an environment with a temperature of 25℃ and a relative humidity of 60%. Then, the thermal conductivity of each sample was measured again according to the thermal conductivity test method in Experiment 1, and the heat insulation performance retention rate was calculated. The heat insulation performance retention rate = thermal conductivity after aging / initial thermal conductivity × 100%. By comparing the retention rate data of each example and the comparative examples, the heat insulation performance stability of the coating under the long-term high-temperature operation environment of power equipment was evaluated. This project is directly related to the basic heat insulation performance test and can fully reflect the reliability advantages of the product in actual use.

[0116] III. Substrate Adhesion Test

[0117] According to GB / T9286-1998 "Cross-cut test of paint and varnish film", the coatings of Examples 1-3 and Comparative Examples 1-5 were respectively coated on the surface of Q235 steel substrate with a size of 150mm×100mm×3mm, and the dry film thickness was controlled to be 500μm. They were cured for 7 days at a temperature of 25℃ and a relative humidity of 60% until fully cured. Using a cross-cutting tool, 1mm × 1mm grid-like cuts were made on the surface of the paint film of each sample. The cut depth should penetrate the paint film to the substrate surface. After gently sweeping away the debris along the horizontal and vertical directions of the grid with a soft brush, 3M 610 pressure-sensitive tape was flatly pasted on the grid area. The tape was pressed evenly with fingers to ensure complete adhesion between the tape and the paint film. Then, the tape was quickly peeled off at a 180° angle. The paint film peeling at the grid intersections and cut edges was observed and rated according to the standard, with grade 0 being the best (no peeling) and grade 5 being the worst (complete paint film peeling). Each sample was tested three times in parallel in different areas, and the highest rating was taken. By comparing the adhesion ratings of each example and the comparative example, the bonding ability between the coating and the power equipment substrate was reflected. This project is closely related to the previous two thermal insulation performance tests to ensure that the coating can stably adhere to the equipment surface and continuously perform its thermal insulation function in actual applications.

[0118] The performance test data of the composite thermal insulation coatings for power equipment in Examples 1-3 and Comparative Examples 1-5 are summarized in Table 1.

[0119] Table 1:

[0120] Sample Name Thermal conductivity [W / (m・K)] Thermal insulation performance retention rate after high-temperature aging (%) Substrate adhesion rating Example 1 0.032 95.6 Level 0 Example 2 0.028 97.3 Level 0 Example 3 0.025 98.1 Level 0 Comparative Example 1 0.058 82.4 Level 1 Comparative Example 2 0.065 78.9 Level 2 Comparative Example 3 0.041 86.7 Level 0 Comparative Example 4 0.053 84.2 Level 1 Comparative Example 5 0.049 88.5 Level 2

[0121] As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, replacing the modified silicone resin with ordinary methyl silicone resin significantly reduced both the thermal insulation performance and the adhesion to the substrate of the coating. This indicates that the modified silicone resin has better compatibility with other components in the formulation, and its molecular structure can more effectively encapsulate and fix various functional fillers, forming a denser thermal insulation network structure, while enhancing the chemical bonding with the metal substrate.

[0122] As can be seen from Examples 1-3 and Comparative Example 2, and Table 1, replacing graphene-modified ceramic fibers with ordinary ceramic fibers significantly affects the overall performance of the coating. Graphene-modified ceramic fibers with a silica-coated surface not only possess superior thermal barrier properties, but their unique surface structure also allows for stronger interfacial bonding with the resin matrix, effectively improving the integrity and durability of the coating.

[0123] As can be seen from Examples 1-3 and Comparative Example 3, and Table 1, while the absence of zinc borate has little impact on initial adhesion, it significantly reduces the performance stability of the coating under long-term high-temperature conditions. Zinc borate not only plays a flame-retardant role in the system but also exhibits a synergistic effect with other components, promoting the formation of a stable protective layer at high temperatures, thereby maintaining the durability of thermal insulation performance.

[0124] As can be seen from Examples 1-3 and Comparative Example 4, and Table 1, omitting the activation treatment step of graphene-modified ceramic fibers will adversely affect the performance of the final product. The heat treatment process under nitrogen protection can effectively remove impurities adsorbed on the fiber surface and activate its surface functional groups, which is crucial for achieving full bonding between the fiber and the resin matrix, directly affecting the dispersion state and interfacial strength of the filler in the system.

[0125] As can be seen from Examples 1-3 and Comparative Example 5, and in conjunction with Table 1, the lack of vacuum degassing and mechanical stirring conditions during the curing process leads to a decline in coating performance. This combined process effectively eliminates air bubbles trapped during mixing and prevents filler sedimentation, ensuring the formation of a uniform and defect-free coating structure. This is an indispensable key step for obtaining stable and reliable thermal insulation performance and adhesion strength.

[0126] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite thermal insulation coating for power equipment, characterized in that, It consists of the following raw materials in parts by weight: 25-45 parts of modified organosilicon resin; 15-30 parts of nano-silica; 10-25 parts of hollow glass microspheres; 5-15 parts of alumina powder; 1-5 parts of graphene-modified ceramic fiber, the surface of which is coated with a silicon dioxide layer with a thickness of 10-100nm; 2-6 parts zinc borate; 2-8 parts dispersant; Heat stabilizer 1-5 parts; Thickener 3-10 parts.

2. The composite thermal insulation coating for power equipment according to claim 1, characterized in that: The nano-silica has a particle size range of 10-100 nm, the hollow glass microspheres have a particle size range of 5-50 μm, and the graphene-modified ceramic fiber has a length of 10-100 μm and a diameter of 0.5-5 μm.

3. The composite thermal insulation coating for power equipment according to claim 1, characterized in that: The dispersant is at least one of sodium polyacrylate and ammonium polyacrylate; The heat stabilizer is at least one of dibutyltin dilaurate and dibutyltin maleate; The thickener is at least one of hydroxypropyl methylcellulose and sodium carboxymethyl cellulose.

4. A method for preparing a composite thermal insulation coating for power equipment as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Raw material pretreatment: Dry nano-silica and alumina powder at 80-120℃ for 1-3 hours; Hollow glass microspheres are preheated at 60-90℃ for 0.5-1.5h; graphene-modified ceramic fibers are activated at 100-150℃ for 0.5-2h under nitrogen protection, with the nitrogen flow rate being 0.5-2.0L / min. S2, Primary Mixing: Mix the modified silicone resin and dispersant at a stirring speed of 200-500 r / min for 10-30 min; add the heat stabilizer, thickener and zinc borate, and continue mixing for 5-15 min; S3. Filler dispersion: Gradually add all the pretreated fillers from step S1 to the base material obtained in step S2; mechanically stir and disperse at a speed of 1000-3000 r / min, while simultaneously applying ultrasonic treatment at a frequency of 20-40 kHz and a power of 100-500 W for 20-60 min. S4. Maturation and degassing: Let the mixture stand at 30-50℃ for 2-6 hours to mature; then degas it for 10-30 minutes under a vacuum of 0.01-0.05MPa, and apply mechanical stirring at 50-150r / min during the degassing process. S5. Viscosity Adjustment and Filtration: The viscosity of the cured coating is tested, and the viscosity is adjusted to 500-2000 mPa·s by adding deionized water or thickener; then filtration is performed, and the pore size is controlled within the range of 50-150 μm. S6. Finished Product Packaging: The viscosity-adjusted coating is filled into sealed containers under inert gas protection.

5. The preparation method according to claim 4, characterized in that: The inert gas in step S6 is nitrogen or argon.

6. The preparation method according to claim 4, characterized in that: The sealed container in step S6 is a metal can with an inner liner or a barrier plastic container.

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