Highly thermally conductive powder coating and method for its production

Abstract

The application discloses a kind of high heat-conducting powder coating and preparation method thereof, belong to heat-conducting powder coating technical field. Including: epoxy resin 50-60 parts by mass;Carboxyl-terminated saturated polyester 50-60 parts by mass;Curing agent 1-4 parts by mass;Auxiliary crosslinking agent 0.4-0.6 parts by mass;Thermal conductive filler 60-110 parts by mass;Auxiliary agent 2-3 parts by mass;The thermal conductive filler is composed of 55-85 parts by mass micron alpha-alumina and 5-25 parts by mass KH550 modified gamma-alumina / core-shell rubber particles;The shell layer of the core-shell rubber particle contains epoxy functional group;The obtained powder coating is cured after electrostatic spraying, and the coating has high thermal conductivity, good adhesion, impact resistance and corrosion resistance, and is suitable for heat-conducting protective coating on the surface of transformer radiator, oil tank and other power equipment metal components.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive powder coating technology, specifically relating to a high thermal conductivity powder coating and its preparation method. Background Technology

[0002] Transformers are core energy conversion devices in power systems, and their cores and windings generate a significant amount of heat during operation. If this heat cannot be dissipated in time, the internal temperature of the transformer will rise, accelerating the aging of insulation materials, shortening the equipment's lifespan, and in severe cases, even causing equipment failure or safety accidents. Therefore, the thermal management capability of the transformer's radiator directly determines the transformer's operational reliability, load capacity, and service life. Currently, transformer radiators and tank surfaces are generally protected with coatings, whose main functions include: preventing corrosion of the metal substrate in outdoor environments; providing a certain degree of mechanical protection; and assisting in heat dissipation through the coating's thermal conductivity.

[0003] Existing anti-corrosion coatings for transformers (including epoxy resin coatings, polyester resin coatings, etc.) are themselves high-molecular organic materials with thermal conductivity far lower than that of metal materials. When such low thermal conductivity coatings are applied to the surface of metal heat sinks, they form a significant thermal resistance layer along the heat dissipation path, hindering the transfer of heat from the metal substrate to the external environment, thereby reducing overall heat dissipation efficiency. Under the same coating thickness, heat sinks coated with conventional powder coatings have significantly lower heat dissipation performance than products without coatings or those using high thermal conductivity coatings.

[0004] To improve the thermal conductivity of coatings, the industry has explored various technical approaches: Adding high thermal conductivity inorganic fillers (such as alumina, boron nitride, graphite, etc.) directly to powder coatings can lead to poor interfacial compatibility between the filler and the resin matrix, easily causing interfacial thermal resistance. Patent document CN118308017B discloses a high thermal conductivity powder coating with modified thermally conductive fillers as its core. This is achieved by copolymerizing graphene oxide with high and low acid value saturated carboxyl polyester resins, and by selecting a combination of diols with long carbon chain side chains and straight-chain diols as the diol component for preparing the low acid value saturated carboxyl polyester resin. This results in a high and low acid value end-carboxyl polyester composite resin with uniformly dispersed graphene oxide, which is then used as the film-forming resin for the powder coating, thus ensuring uniform dispersion of the filler in the matrix resin. However, this technical solution does not address the specific needs of large power equipment (such as transformer radiators). Transformer radiators are large outdoor metal components, and the requirements for coating corrosion resistance and operational stability are far higher than those for indoor applications such as 3C electronics. The patent's technical solution focuses on improving dispersion uniformity and thermal conductivity through filler surface modification, but it does not describe a systematic solution to the deterioration of coating mechanical properties (especially toughness and impact resistance) under high filler content. According to the technical information disclosed in the patent specification, it does not introduce a specific toughening mechanism in pursuit of high thermal conductivity, which poses a risk of increased coating brittleness under high filler content.

[0005] One method is to optimize the coating packing density by adjusting the particle size of the powder coating, thereby reducing the internal porosity of the coating and lowering the thermal resistance. However, this method has limited effect on improving thermal conductivity and is insufficient to meet the actual requirements of efficient heat dissipation in transformers.

[0006] For example, solvent-based coatings with added high thermal conductivity fillers can be used, but these coatings have high volatile organic compound (VOC) content, which not only pollutes the environment and endangers the health of operators, but also requires multiple sprayings to achieve the target thickness, resulting in low production efficiency and high energy consumption.

[0007] In transformer radiator coatings, increasing filler content to enhance thermal conductivity often comes at the cost of reduced toughness and adhesion. Therefore, significantly improving coating thermal conductivity while maintaining high corrosion resistance and long-term durability has become a pressing technical challenge for the industry. Summary of the Invention

[0008] The purpose of this invention is to provide a high thermal conductivity powder coating and its preparation method, which solves the problem that it is difficult to simultaneously achieve thermal conductivity, coating toughness, adhesion and corrosion resistance in high-filler thermal conductivity powder coatings. It is especially suitable for thermally conductive protective coatings on the surfaces of transformer radiators, oil tanks and other metal components of power equipment.

[0009] The objective of this invention can be achieved through the following technical solutions: A high thermal conductivity powder coating comprises the following components: 50-60 parts by weight of epoxy resin; 50-60 parts by weight of carboxyl-terminated saturated polyester; 1-4 parts by weight of curing agent; 0.4-0.6 parts by weight of auxiliary crosslinking agent; 60-110 parts by weight of thermally conductive filler; 2-3 parts by weight of additives; The thermally conductive filler is composed of 55-85 parts by mass of micron-sized α-alumina and 5-25 parts by mass of KH550 modified γ-alumina / core-shell rubber particles; the shell of the core-shell rubber particles contains epoxy functional groups.

[0010] The coating matrix is ​​made of epoxy resin and carboxyl-terminated saturated polyester, combined with a special curing agent and auxiliary crosslinking agent to form a dense crosslinking network, which lays the foundation for the overall performance of the coating: epoxy resin has high bonding strength and excellent corrosion resistance; carboxyl-terminated saturated polyester has good flexibility and good leveling properties. The two complement each other, and the shortcomings of single resin are offset, taking into account both the adhesion of the base and the corrosion resistance.

[0011] By combining modified γ-alumina with epoxy-based core-shell rubber into a single particle, thermal conductivity and toughening are integrated, avoiding the contradiction of purely thermally conductive fillers being too rigid and purely toughening fillers reducing thermal conductivity. Furthermore, the KH550 modified γ-alumina / core-shell rubber particles are compounded with micron-sized α-alumina and uniformly distributed throughout the entire filler system, simultaneously improving the interface, toughness, and density throughout the entire system.

[0012] By adjusting the amount of curing agent, a more complete cross-linking network is formed in combination with epoxy resin and carboxyl-terminated saturated polyester.

[0013] As a preferred embodiment of the present invention, the core layer of the core-shell rubber particle is cross-linked polybutyl acrylate rubber, and the shell layer contains methyl methacrylate structural units and glycidyl methacrylate structural units.

[0014] The core-shell rubber particles, with cross-linked polybutyl acrylate as the core, can absorb stress, inhibit cracking, and stably improve the toughness of highly filled coatings. Its methyl methacrylate shell enhances compatibility and dispersibility with the resin matrix. The epoxy functional groups retained in the shell and the active groups introduced on the surface facilitate interfacial bonding with the resin matrix, enhancing interfacial compatibility and coating density. This structure balances the coating's thermal conductivity, toughness, adhesion, and corrosion resistance, exhibiting excellent processing and usage stability.

[0015] As a preferred embodiment of the present invention, the curing agent comprises a dicyandiamide curing agent and an imidazole accelerator, wherein the mass ratio of the dicyandiamide curing agent to the imidazole accelerator is 5-8:0.3-0.8; the additives are composed of a leveling agent, a degassing agent, a light stabilizer, an antistatic agent, and a lubricant in a mass ratio of 0.5-0.9:0.3-0.5:0.2-0.4:0.1-0.3:0.1-0.3.

[0016] By using a dicyandiamide-based curing agent combined with an imidazole-based accelerator, the excellent storage stability of powder coatings is preserved, while achieving more complete curing. The cured crosslinking network is uniform and dense, effectively improving the mechanical properties and corrosion resistance of the coating. At the same time, it avoids the problems of insufficient curing, poor storage, and many coating defects caused by a single curing system.

[0017] By using this specific ratio of compounded additives, a high-filler, high-thermal-conductivity powder coating formulation system can be adapted. The synergistic effect of each additive significantly improves the coating's processability and spraying effect without affecting the coating's thermal conductivity, mechanical properties, and adhesion.

[0018] As a preferred embodiment of the present invention, the micron-sized α-alumina has a particle size of 5-50 μm, specifically comprising 30-50 parts by mass of α-alumina with a particle size of 30-50 μm and 25-35 parts by mass of α-alumina with a particle size of 5-15 μm.

[0019] α-alumina with a particle size of 30-50μm is selected as the skeletal thermally conductive phase. The large particle size and high probability of interparticle contact allow for the establishment of a continuous thermally conductive main pathway, ensuring overall thermal conductivity efficiency. α-alumina itself has high thermal conductivity and stable chemical properties, making it a commonly used high-performance thermally conductive filler in powder coatings. α-alumina with a particle size of 5-15μm is used to fill the gaps between large particles, filling voids, reducing air thermal resistance, and further densifying the thermally conductive network. This avoids filler voids and increased porosity even with high filler content. The two-stage particle size distribution achieves dense packing of the filler, enabling the formation of a complete, low-thermal-resistance thermally conductive network even in high-filler systems. This addresses the shortcomings of large particles having many voids and small particles easily agglomerating and reducing thermal conductivity in high-filler systems, thus steadily improving the thermal conductivity of the coating.

[0020] As a preferred embodiment of the present invention, the preparation method of the KH550 modified γ-alumina / core-shell rubber particles includes the following steps: A1. KH550 is added to an ethanol-water mixed solution and pre-hydrolyzed under acidic conditions. Core-shell rubber particles are added and heated and stirred under neutral to weakly alkaline conditions. The solid phase is separated and washed to obtain aminated rubber particles. Under neutral to weakly alkaline conditions, KH550 hydrolyzes and condenses to form a siloxane network. It can be fixed on the surface of the core-shell rubber particles through multiple interactions such as the reaction of amino groups with epoxy functional groups in the shell of the core-shell rubber particles, hydrogen bonding, van der Waals forces and physical entanglement, thereby introducing an amino-containing silane active layer on the surface of the core-shell rubber particles. A2. KH550 was added to an ethanol-water mixture and pre-hydrolyzed under acidic conditions. γ-alumina was then added, heated, and stirred. The solid phase was separated and washed to obtain KH550-modified γ-alumina. KH550 hydrolyzes to generate silanol groups, which can undergo a condensation reaction with hydroxyl groups on the surface of γ-alumina, thus fixing KH550 onto the surface of γ-alumina. At the same time, the amino groups in the KH550 molecules are introduced into the surface of γ-alumina to improve its interfacial compatibility and dispersion stability in organic resin systems. A3. Disperse the aminated rubber particles in an isopropanol-water mixed solution, add KH550 modified γ-alumina and stir until homogeneous. Add glutaraldehyde aqueous solution under weakly alkaline conditions at 40-50℃ and stir. Separate the solid phase, wash, and dry to obtain the KH550 modified γ-alumina / core-shell rubber particles. Fully disperse the aminated core-shell rubber particles and KH550 modified γ-alumina in an isopropanol-water system, allowing KH550 modified γ-alumina to approach and adhere to the surface of the aminated core-shell rubber particles through hydrogen bonding, van der Waals forces, and physical adsorption. Subsequently, add the crosslinking agent glutaraldehyde to covalently crosslink the aminated core-shell rubber particles with KH550 modified γ-alumina, obtaining modified γ-alumina / core-shell structured rubber composite particles.

[0021] As a preferred embodiment of the present invention, in step A1, the ethanol-water mixed solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 4:1; the mass ratio of the core-shell rubber particles, the ethanol-water mixed solution, and KH550 is 1:8-15:0.010-0.015; the heating and stirring under neutral to weakly alkaline conditions refers to adjusting the pH of the system to 7.0-8.0 with 0.1 mol / L ammonia water and stirring at 60-70℃ for 4-6 hours.

[0022] As a preferred embodiment of the present invention, in step A2, the ethanol-water mixed solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; the amount of KH550 used is 2%-5% of the mass of γ-alumina.

[0023] In a preferred embodiment of the present invention, in step A3, the isopropanol-water mixed solution is prepared by mixing isopropanol and deionized water at a volume ratio of 7:3; the mass ratio of the aminated core-shell rubber particles, the isopropanol-deionized water mixed solution, the KH550 modified γ-alumina, and the glutaraldehyde aqueous solution is 5-12:100:1-4:0.2-0.6; and the mass fraction of the glutaraldehyde aqueous solution is 25%.

[0024] As a preferred embodiment of the present invention, the leveling agent is Resiflow® PL-200, the degassing agent is benzoin, the light stabilizer is a benzotriazole light stabilizer, the antistatic agent is a quaternary ammonium salt antistatic agent, and the lubricant is polyethylene wax; the auxiliary crosslinking agent is triglycidyl isocyanurate.

[0025] This application uses a limited range of additives and triglycidyl isocyanurate as an auxiliary crosslinking agent, which are highly compatible with the high-filler thermally conductive powder coating system. The components work synergistically to significantly optimize the coating's processing performance and overall coating performance. Among them, Resiflow® PL-200 leveling agent has excellent compatibility and can effectively reduce the surface tension of the coating melt system, eliminate orange peel and pinhole defects in the coating, and greatly improve the coating's smoothness and appearance. Benzoin degassing agent can efficiently remove air, moisture, and small molecule volatiles trapped in the system, avoiding pinholes and bubbles that are prone to occur in high-filler systems, and improving the coating's density and corrosion resistance.

[0026] Benzotriazole light stabilizers can absorb ultraviolet light, which helps to inhibit the photodegradation and aging of the resin matrix and improve the stability of the coating for outdoor use; quaternary ammonium salt antistatic agents can reduce the surface resistivity of the coating, reduce static electricity accumulation, avoid adsorption of dust and impurities during the spraying process, and improve the uniformity of spraying and the cleanliness of the finished product; polyethylene wax lubricant can improve the flowability and release properties of powder extrusion processing, reduce processing energy consumption, and at the same time improve the smoothness and scratch resistance of the coating surface.

[0027] Triglycidyl isocyanurate, as an auxiliary crosslinking agent, possesses multifunctional reactivity and can participate in the crosslinking reaction of the epoxy-polyester matrix, perfecting the three-dimensional crosslinking network of the system, effectively increasing the crosslinking density of the coating, and further enhancing the coating's adhesion, mechanical strength, and chemical corrosion resistance. It also compensates for the sparse crosslinking network caused by high inorganic filler content. The various additives and auxiliary crosslinking agents are synergistically formulated without antagonism, comprehensively optimizing the coating's processability, storage stability, appearance, service stability, and overall mechanical and corrosion resistance properties without weakening the coating's thermal conductivity.

[0028] Another object of the present invention is to provide a method for preparing a high thermal conductivity powder coating, comprising the following steps: S1. Epoxy resin, carboxyl-terminated saturated polyester and additives are put into a high-speed mixer for dry mixing and pre-dispersion to obtain resin premix; S2. The resin premix, curing agent, auxiliary crosslinking agent and thermally conductive filler are added to a twin-screw extruder for melt extrusion mixing, tableting and cooling, coarse crushing, air-classification grinding, sieving and magnetic separation to obtain the high thermal conductivity powder coating.

[0029] The beneficial effects of this invention are: (1) The high thermal conductivity powder coating and its preparation method disclosed in this invention adopts a composite thermally conductive filler system of micron-sized α-alumina and KH550 modified γ-alumina / core-shell rubber particles, which is conducive to forming a more continuous thermal conductivity path and improving thermal conductivity and heat dissipation performance.

[0030] (2) The high thermal conductivity powder coating and its preparation method disclosed in this invention modify γ-alumina with core-shell rubber particles to introduce rigid thermally conductive components and flexible toughening nodes into the thermally conductive filler system. The elastic core layer of the core-shell rubber particles can absorb external impact energy. The epoxy functional groups retained in the shell layer and the active groups introduced on the surface are conducive to forming an interface bond with the resin matrix, thereby improving the problem of easy cracking of the coating in the high filler filling system.

[0031] (3) The high thermal conductivity powder coating and its preparation method disclosed in this invention use KH550 to treat the surface of γ-alumina and core-shell rubber particles, and further improve the bonding stability between γ-alumina and core-shell rubber particles through glutaraldehyde crosslinking, which is beneficial to reduce filler agglomeration and interface defects, reduce interface thermal resistance, and improve the compatibility between filler and epoxy / polyester resin matrix.

[0032] (4) The high thermal conductivity powder coating and its preparation method disclosed in this invention select epoxy resin and carboxyl-terminated saturated polyester as film-forming material, and supplement it with dicyandiamide / imidazolium curing system and triglycidyl isocyanurate auxiliary crosslinking agent, which is conducive to forming a denser crosslinking network; combined with a specific ratio of leveling agent, degassing agent and antistatic agent, it can improve the processing stability, coating density, adhesion, impact resistance, heat oil resistance and corrosion resistance of the high filler system. Detailed Implementation

[0033] The claims of the present invention will be further described in detail below with reference to specific embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of protection of the claims of the present invention are still within the scope of protection of the claims of the present invention.

[0034] The source of the raw materials for this invention is explained as follows: Epoxy resin E-12, Hubei Shiteng Chemical Technology Co., Ltd.; Carboxyl-terminated saturated polyester, GH-7701, Zhejiang Guanghua Technology Co., Ltd.; Triglycidyl isocyanurate, Hubei Shiteng Chemical Technology Co., Ltd.; Dicyandiamide curing agent Ecure 14, Shanghai Merman Chemical Co., Ltd.; Imidazole accelerator 2-methylimidazole, Hubei Hongjing Chemical Co., Ltd.; Core-shell rubber particles, Metalatn W-450A, Mitsubishi Chemical (Shanghai) Trading Co., Ltd.; γ-alumina, Zhejiang Jiupeng New Materials Co., Ltd.; α-alumina, Zhejiang Zhitai Nano-Micro New Materials Co., Ltd.; Leveling agent Resiflow® PL-200, Guangzhou Siteyuan Chemical Co., Ltd.; Degassing agent benzoin, Shanghai Aidie Industrial Co., Ltd.; Benzotriazole light stabilizer 1130, Zhengzhou Huiju Chemical Co., Ltd.; Quaternary ammonium salt antistatic agent SN, Hubei Zhonglong Kangcheng Fine Chemical Co., Ltd.; Lubricant polyethylene wax, Korean 1206P, Guangzhou Haocheng Chemical Technology Co., Ltd.

[0035] Example 1 0.010 parts by mass of KH550 were added to 8 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 4:1. The pH of the system was adjusted to 4.5 with 0.1 mol / L acetic acid solution and stirred for 30 min. Then, 1 part by mass of core-shell rubber particles were added and ultrasonically dispersed for 30 min. The pH of the system was then adjusted to 7.0 with 0.1 mol / L ammonia solution and stirred under reflux at 60 °C for 6 h. The mixture was filtered, the solid phase was collected, and the solid phase was washed 5 times alternately with anhydrous ethanol and deionized water and dried to obtain amination-modified core-shell rubber particles.

[0036] 0.02 parts by mass of KH550 were added to 20 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 4 with 0.1 mol / L acetic acid solution, and the mixture was pre-hydrolyzed for 30 min to obtain a pre-hydrolyzed solution. 1 part by mass of γ-alumina with a particle size of 50 nm was added, and the mixture was ultrasonically dispersed for 20 min. The mixture was then refluxed at 60 °C and stirred for 4 h. After filtration, the solid phase was collected, washed 5 times alternately with anhydrous ethanol and deionized water, and dried to obtain KH550 modified γ-alumina.

[0037] Five parts by mass of aminated core-shell rubber particles were added to 100 parts by mass of an isopropanol-water mixed solution prepared by mixing isopropanol and deionized water in a volume ratio of 7:3. The mixture was ultrasonically dispersed for 10 min. One part by mass of KH550 modified γ-alumina was added, and the mixture was ultrasonically dispersed for another 20 min. The mixture was then stirred at 60 °C for 4 h. The temperature was lowered to 40 °C, and the pH of the system was adjusted to 7.5 using 0.1 mol / L ammonia. 0.2 parts by mass of 25 wt% glutaraldehyde aqueous solution was added, and the mixture was stirred for another 50 min. The mixture was then centrifuged, and the solid phase was collected, washed, and dried to obtain KH550 modified γ-alumina / core-shell rubber particles.

[0038] Take 50 parts by weight of epoxy resin E-12, 50 parts by weight of carboxyl-terminated saturated polyester GH-7701, and 2 parts by weight of an additive composed of Resiflow® PL-200, benzoin, light stabilizer 1130, antistatic agent SN, and polyethylene wax in a mass ratio of 0.5:0.3:0.2:0.1:0.1. Add these to a high-speed mixer and mix for 5 minutes at a stirring speed of 800 rpm. Then, feed the mixture into a co-rotating twin-screw extruder through the main feed port. Add 1 part by weight of Ecure (a compound) through the first side feed port. A curing agent composed of 14- and 2-methylimidazole in a mass ratio of 5:0.3, and 0.4 parts by mass of triglycidyl isocyanurate; a thermally conductive filler composed of 30 parts by mass of α-alumina with a particle size of 30 μm, 25 parts by mass of α-alumina with a particle size of 5 μm, and 5 parts by mass of KH550 modified γ-alumina / core-shell rubber particles is added to the second side feed port for melt extrusion compounding; the temperature of each zone of the twin-screw extruder is controlled by a stepped heating-homogenization-cooling method, with the temperature of zone 1 being 80℃, zone 2 being 95℃, zone 3 being 105℃, zone 4 being 110℃, zone 5 being 105℃, and the die head temperature being 100℃; the screw speed is 220 r / min; and the material residence time is 120 s.

[0039] After the extruded material is discharged from the die head, it immediately enters a stainless steel double-roller tablet press and cooler for cooling and tableting. The resulting cooled tablet material is coarsely crushed to obtain coarse powder. The coarse powder is then subjected to air-classification grinding, and the particle size of the powder coating is measured using a laser particle size analyzer to obtain the D value. 10 25μm, D 50 50μm, D 90 For powder coatings with a thickness of 85μm, an ultrasonic vibrating screen is used for sieving. The sieved powder is then magnetically separated by a strong magnetic grid to obtain a finished product of high thermal conductivity powder coating.

[0040] Example 2 0.011 parts by mass of KH550 were added to 10 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 4:1. The pH of the system was adjusted to 4.5 with 0.1 mol / L acetic acid solution and stirred for 40 min. Then, 1 part by mass of core-shell rubber particles were added and ultrasonically dispersed for 35 min. The pH of the system was then adjusted to 7.0 with 0.1 mol / L ammonia solution and stirred under reflux at 60 °C for 6 h. The mixture was filtered, the solid phase was collected, and the solid phase was washed 5 times alternately with anhydrous ethanol and deionized water. The solid phase was then dried to obtain amination-modified core-shell rubber particles.

[0041] 0.03 parts by mass of KH550 were added to 22 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 4.5 with 0.1 mol / L acetic acid solution, and the mixture was pre-hydrolyzed for 30 min to obtain a pre-hydrolyzed solution. 1 part by mass of γ-alumina with a particle size of 100 nm was added, and the mixture was ultrasonically dispersed for 20 min. The mixture was then refluxed at 60 °C and stirred for 4 h. After filtration, the solid phase was collected, washed 5 times alternately with anhydrous ethanol and deionized water, and dried to obtain KH550 modified γ-alumina.

[0042] Six parts by mass of aminated core-shell rubber particles were added to 100 parts by mass of an isopropanol-water mixed solution prepared by mixing isopropanol and deionized water in a volume ratio of 7:3. The mixture was ultrasonically dispersed for 15 min. Two parts by mass of KH550 modified γ-alumina were added, and the mixture was ultrasonically dispersed for another 25 min. The mixture was then stirred at 65 °C for 3 h. The temperature was lowered to 45 °C, and the pH of the system was adjusted to 7.5 using 0.1 mol / L ammonia. 0.3 parts by mass of 25 wt% glutaraldehyde aqueous solution was added, and the mixture was stirred for another 55 min. The mixture was then centrifuged, and the solid phase was collected, washed, and dried to obtain KH550 modified γ-alumina / core-shell rubber particles.

[0043] Take 52 parts by weight of epoxy resin E-12, 52 parts by weight of carboxyl-terminated saturated polyester GH-7701, and 2.3 parts by weight of an additive composed of Resiflow® PL-200, benzoin, light stabilizer 1130, antistatic agent SN, and polyethylene wax in a mass ratio of 0.6:0.4:0.25:0.15:0.15. Add these to a high-speed mixer and mix for 8 minutes at a stirring speed of 900 rpm. Then, add the mixture to a co-rotating twin-screw extruder through the main feed port and add 2 parts by weight of Ecure (a compound) through the first side feed port. A curing agent composed of 14- and 2-methylimidazole in a mass ratio of 6:0.5, and 0.45 parts by mass of triglycidyl isocyanurate; a thermally conductive filler composed of 35 parts by mass of α-alumina with a particle size of 35 μm, 28 parts by mass of α-alumina with a particle size of 8 μm, and 10 parts by mass of KH550 modified γ-alumina / core-shell rubber particles is added to the second side feed port for melt extrusion compounding; the temperature of each zone of the twin-screw extruder is controlled by a stepped heating-homogenization-cooling method, with the temperature of zone 1 being 85℃, zone 2 being 100℃, zone 3 being 110℃, zone 4 being 115℃, zone 5 being 115℃, and the die head being 105℃; the screw speed is 300 r / min; and the material residence time is 100 s.

[0044] After the extruded material is discharged from the die head, it immediately enters a stainless steel double-roller tablet press and cooler for cooling and tableting. The resulting cooled tablet material is coarsely crushed to obtain coarse powder. The coarse powder is then subjected to air-classification grinding, and the particle size of the powder coating is measured using a laser particle size analyzer to obtain the D value. 10 It is 22μm, D50 45μm, D 90 For powder coatings with a thickness of 80μm, an ultrasonic vibrating screen is used for sieving. The sieved powder is then magnetically separated by a strong magnetic grid to obtain a finished product of high thermal conductivity powder coating.

[0045] Example 3 0.013 parts by mass of KH550 were added to 12 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 4:1. The pH of the system was adjusted to 5.0 with 0.1 mol / L acetic acid solution and stirred for 45 min. Then, 1 part by mass of core-shell rubber particles were added and ultrasonically dispersed for 35 min. The pH of the system was then adjusted to 7.5 with 0.1 mol / L ammonia solution and stirred under reflux at 65 °C for 5 h. The mixture was filtered, the solid phase was collected, and the solid phase was washed 5 times alternately with anhydrous ethanol and deionized water. After drying, ammoniated core-shell rubber particles were obtained.

[0046] 0.035 parts by mass of KH550 were added to 25 parts by mass of an ethanol-water mixture prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 4.5 with 0.1 mol / L acetic acid solution, and the mixture was pre-hydrolyzed for 35 min to obtain a pre-hydrolyzed solution. 1 part by mass of γ-alumina with a particle size of 130 nm was added, and the mixture was ultrasonically dispersed for 25 min. The mixture was then refluxed at 65 °C and stirred for 3 h. After filtration, the solid phase was collected, washed 5 times alternately with anhydrous ethanol and deionized water, and dried to obtain KH550 modified γ-alumina.

[0047] Eight parts by mass of aminated core-shell rubber particles were added to 100 parts by mass of an isopropanol-water mixed solution prepared by mixing isopropanol and deionized water in a volume ratio of 7:3. The mixture was ultrasonically dispersed for 15 min. Then, 2.5 parts by mass of KH550 modified γ-alumina were added, and the mixture was ultrasonically dispersed for another 30 min. The mixture was then stirred at 65℃ for 3 h, cooled to 45℃, and the pH of the system was adjusted to 8.0 using 0.1 mol / L ammonia. Finally, 0.4 parts by mass of 25 wt% glutaraldehyde aqueous solution were added, and the mixture was stirred for another 60 min. The mixture was then centrifuged, and the solid phase was collected, washed, and dried to obtain KH550 modified γ-alumina / core-shell rubber particles.

[0048] Take 55 parts by weight of epoxy resin E-12, 55 parts by weight of carboxyl-terminated saturated polyester GH-7701, and 2.5 parts by weight of an additive composed of Resiflow® PL-200, benzoin, light stabilizer 1130, antistatic agent SN, and polyethylene wax in a mass ratio of 0.7:0.4:0.3:0.2:0.2. Add these to a high-speed mixer and mix for 8 minutes at a stirring speed of 1000 rpm. Then, add the mixture to a co-rotating twin-screw extruder through the main feed port and add 2.5 parts by weight of Ecure (a compound) through the first side feed port. A curing agent composed of 14- and 2-methylimidazole in a mass ratio of 6.5:0.5, and 0.5 parts by mass of triglycidyl isocyanurate; a thermally conductive filler composed of 40 parts by mass of α-alumina with a particle size of 40 μm, 30 parts by mass of α-alumina with a particle size of 10 μm, and 15 parts by mass of KH550 modified γ-alumina / core-shell rubber particles is added to the second side feed port for melt extrusion compounding; the temperature of each zone of the twin-screw extruder is controlled by a stepped heating-homogenization-cooling method, with the temperature of zone 1 being 90℃, zone 2 being 100℃, zone 3 being 115℃, zone 4 being 120℃, zone 5 being 110℃, and the die head being 105℃; the screw speed is 350 r / min; and the material residence time is 90 s.

[0049] After the extruded material is discharged from the die head, it immediately enters a stainless steel double-roller tablet press and cooler for cooling and tableting. The resulting cooled tablet material is coarsely crushed to obtain coarse powder. The coarse powder is then subjected to air-classification grinding, and the particle size of the powder coating is measured using a laser particle size analyzer to obtain the D value. 10 20μm, D 50 42μm, D 90 For 75μm powder coatings, an ultrasonic vibrating screen is used for sieving, and the sieved powder is then magnetically separated by a strong magnetic grid to obtain a high thermal conductivity powder coating product.

[0050] Example 4 0.014 parts by mass of KH550 were added to 13 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 4:1. The pH of the system was adjusted to 5.5 with 0.1 mol / L acetic acid solution and stirred for 55 min. Then, 1 part by mass of core-shell rubber particles were added and ultrasonically dispersed for 38 min. The pH of the system was then adjusted to 8.0 with 0.1 mol / L ammonia solution and stirred under reflux at 68 °C for 4.5 h. The mixture was filtered, the solid phase was collected, and the solid phase was washed 5 times alternately with anhydrous ethanol and deionized water and dried to obtain amination-modified core-shell rubber particles.

[0051] 0.04 parts by mass of KH550 were added to 28 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 5 with 0.1 mol / L acetic acid solution, and the mixture was pre-hydrolyzed for 38 min to obtain a pre-hydrolyzed solution. 1 part by mass of γ-alumina with a particle size of 180 nm was added, and the mixture was ultrasonically dispersed for 28 min. The mixture was then refluxed at 68 °C and stirred for 2.5 h. After filtration, the solid phase was collected, washed 5 times alternately with anhydrous ethanol and deionized water, and dried to obtain KH550 modified γ-alumina.

[0052] Take 11 parts by mass of aminated core-shell rubber particles and add them to 100 parts by mass of an isopropanol-water mixed solution prepared by mixing isopropanol and deionized water at a volume ratio of 7:3. Disperse the mixture ultrasonically for 18 min, add 3.6 parts by mass of KH550 modified γ-alumina, and continue ultrasonic dispersion for 35 min. Then stir at 68℃ for 2.5 h, cool down to 48℃, adjust the pH of the system to 8.5 with 0.1 mol / L ammonia water, add 0.5 parts by mass of 25 wt% glutaraldehyde aqueous solution and continue stirring for 65 min. Centrifuge to separate the solid phase, collect the solid phase, wash and dry it to obtain KH550 modified γ-alumina / core-shell rubber particles.

[0053] Take 58 parts by weight of epoxy resin E-12, 58 parts by weight of carboxyl-terminated saturated polyester GH-7701, and 2.9 parts by weight of an additive composed of Resiflow® PL-200, benzoin, light stabilizer 1130, antistatic agent SN, and polyethylene wax in a mass ratio of 0.8:0.45:0.35:0.25:0.25. Add these to a high-speed mixer and mix for 9 minutes at a stirring speed of 1100 r / min. Then, add the mixture to a co-rotating twin-screw extruder through the main feed port and 3.7 parts by weight of Ecure (a compound) through the first side feed port. A curing agent composed of 14- and 2-methylimidazole in a mass ratio of 7.8:0.7, and 0.55 parts by mass of triglycidyl isocyanurate; a thermally conductive filler composed of 45 parts by mass of α-alumina with a particle size of 50 μm, 32 parts by mass of α-alumina with a particle size of 15 μm, and 20 parts by mass of KH550 modified γ-alumina / core-shell rubber particles is added to the second side feed port for melt extrusion compounding; the temperature of each zone of the twin-screw extruder is controlled by a stepped heating-homogenization-cooling method, with the temperature of zone 1 being 93℃, zone 2 being 108℃, zone 3 being 118℃, zone 4 being 123℃, zone 5 being 112℃, and the die head being 108℃; the screw speed is 380 r / min; and the material residence time is 75 s.

[0054] After the extruded material is discharged from the die head, it immediately enters a stainless steel double-roller tablet press and cooler for cooling and tableting. The resulting cooled tablet material is coarsely crushed to obtain coarse powder. The coarse powder is then subjected to air-classification grinding, and the particle size of the powder coating is measured using a laser particle size analyzer to obtain the D value. 10It is 18μm, D 50 40μm, D 90 For 70μm powder coatings, an ultrasonic vibrating screen is used for sieving, and the sieved powder is then magnetically separated by a strong magnetic grid to obtain a high thermal conductivity powder coating product.

[0055] Example 5 0.015 parts by mass of KH550 were added to 15 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 4:1. The pH of the system was adjusted to 5.5 with 0.1 mol / L acetic acid solution and stirred for 60 min. Then, 1 part by mass of core-shell rubber particles were added and ultrasonically dispersed for 40 min. The pH of the system was then adjusted to 8.0 with 0.1 mol / L ammonia solution and stirred under reflux at 70 °C for 4 h. The mixture was filtered, the solid phase was collected, and the solid phase was washed 5 times alternately with anhydrous ethanol and deionized water and dried to obtain amination-modified core-shell rubber particles.

[0056] 0.05 parts by mass of KH550 were added to 30 parts by mass of an ethanol-water mixed solution prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1. The pH of the system was adjusted to 5 with 0.1 mol / L acetic acid solution, and the mixture was pre-hydrolyzed for 40 min to obtain a pre-hydrolyzed solution. 1 part by mass of γ-alumina with a particle size of 200 nm was added, and the mixture was ultrasonically dispersed for 30 min. The mixture was then refluxed at 70 °C and stirred for 2 h. After filtration, the solid phase was collected, washed 5 times alternately with anhydrous ethanol and deionized water, and dried to obtain KH550 modified γ-alumina.

[0057] Take 12 parts by mass of aminated core-shell rubber particles and add them to 100 parts by mass of an isopropanol-water mixed solution prepared by mixing isopropanol and deionized water at a volume ratio of 7:3. Disperse the mixture by sonication for 20 min, add 4 parts by mass of KH550 modified γ-alumina, continue to disperse by sonication for 40 min, then stir at 70℃ for 4 h, cool to 50℃, adjust the pH of the system to 8.5 with 0.1 mol / L ammonia water, add 0.6 parts by mass of 25 wt% glutaraldehyde aqueous solution and continue stirring for 70 min, centrifuge, collect the solid phase, wash and dry to obtain KH550 modified γ-alumina / core-shell rubber particles.

[0058] Take 60 parts by weight of epoxy resin E-12, 60 parts by weight of carboxyl-terminated saturated polyester GH-7701, and 3 parts by weight of an additive composed of Resiflow® PL-200, benzoin, light stabilizer 1130, antistatic agent SN, and polyethylene wax in a mass ratio of 0.9:0.5:0.4:0.3. Add these to a high-speed mixer and mix for 10 minutes at a stirring speed of 1200 rpm. Then, add the mixture to a co-rotating twin-screw extruder through the main feed port and add 4 parts by weight of Ecure (a compound) through the first side feed port. A curing agent composed of 14- and 2-methylimidazole in a mass ratio of 8:0.8, and 0.6 parts by mass of triglycidyl isocyanurate; a thermally conductive filler composed of 50 parts by mass of α-alumina with a particle size of 50 μm, 35 parts by mass of α-alumina with a particle size of 15 μm, and 25 parts by mass of KH550 modified γ-alumina / core-shell rubber particles is added to the second side feed port for melt extrusion compounding; the temperature of each zone of the twin-screw extruder is controlled by a stepped heating-homogenization-cooling method, with the temperature of zone 1 being 95℃, zone 2 being 110℃, zone 3 being 120℃, zone 4 being 125℃, zone 5 being 115℃, and the die head being 110℃; the screw speed is 400 r / min; and the material residence time is 60 s.

[0059] After the extruded material is discharged from the die head, it immediately enters a stainless steel double-roller tablet press and cooler for cooling and tableting. The resulting cooled tablet material is coarsely crushed to obtain coarse powder. The coarse powder is then subjected to air-classification grinding, and the particle size of the powder coating is measured using a laser particle size analyzer to obtain the D value. 10 15μm, D 50 35μm, D 90 For 65μm powder coatings, an ultrasonic vibrating screen is used for sieving, and the sieved powder is then magnetically separated by a strong magnetic grid to obtain a high thermal conductivity powder coating product.

[0060] Comparative Example 1 The difference from Example 3 is that no thermally conductive filler is added, while the composition and preparation process of the remaining resin, curing agent, auxiliary crosslinking agent and additives are the same as those in Example 3.

[0061] Comparative Example 2 The difference from Example 3 is that 40 parts by mass of α-alumina with a particle size of 40 μm and 30 parts by mass of α-alumina with a particle size of 10 μm are completely replaced with 70 parts by mass of α-alumina with a particle size of 40 μm. The remaining 15 parts by mass of KH550 modified γ-alumina / core-shell rubber particles and other components are the same as in Example 3.

[0062] Comparative Example 3 The difference from Example 3 is that 40 parts by mass of α-alumina with a particle size of 40 μm and 30 parts by mass of α-alumina with a particle size of 10 μm are completely replaced with 70 parts by mass of α-alumina with a particle size of 10 μm. The remaining 15 parts by mass of KH550 modified γ-alumina / core-shell rubber particles and other components are the same as in Example 3.

[0063] Comparative Example 4 The difference from Example 3 is that the KH550 modified γ-alumina / core-shell rubber particles are replaced with a physical mixture of unmodified γ-alumina and core-shell rubber particles. The mass ratio of γ-alumina to core-shell rubber particles is the same as that of KH550 modified γ-alumina / core-shell rubber particles in Example 3. The remaining components and preparation process are the same as in Example 3.

[0064] Comparative Example 5 The difference from Example 3 is that 15 parts by mass of KH550 modified γ-alumina / core-shell rubber particles were completely replaced with 15 parts by mass of KH550 modified γ-alumina, and no core-shell rubber particles were added. The remaining components and preparation process are the same as in Example 3.

[0065] Comparative Example 6 The difference from Example 3 is that KH550 modified γ-alumina / core-shell rubber particles are not added, and they are replaced by an equal mass of α-alumina with a particle size of 10 μm. The remaining components and preparation process are the same as in Example 3.

[0066] Comparative Example 7 The difference from Example 3 is that the thermally conductive filler is composed of 30 parts by mass of α-alumina with a particle size of 40 μm, 20 parts by mass of α-alumina with a particle size of 10 μm, and 5 parts by mass of KH550 modified γ-alumina / core-shell rubber particles. The remaining components and preparation process are the same as in Example 3.

[0067] Comparative Example 8 The difference from Example 3 is that the thermally conductive filler is composed of 60 parts by mass of α-alumina with a particle size of 40 μm, 45 parts by mass of α-alumina with a particle size of 10 μm, and 15 parts by mass of KH550 modified γ-alumina / core-shell rubber particles. The remaining components and preparation process are the same as in Example 3.

[0068] Comparative Example 9 The difference from Example 3 is that, in the preparation of KH550 modified γ-alumina / core-shell rubber particles, glutaraldehyde aqueous solution is not added in step A3, while the remaining preparation steps, components and powder coating preparation process are the same as in Example 3.

[0069] Performance testing Coating thermal conductivity test: The powder coatings obtained in Examples 1-5 and Comparative Examples 1-9 were cured in molds at 180°C for 20 min to prepare circular samples with a diameter of 12.7 mm and a thickness of 1.0 ± 0.1 mm. The thermal diffusivity was determined according to GB / T 22588-2008 "Measuring thermal diffusivity or thermal conductivity by flash method", and the thermal conductivity was calculated in combination with the sample density and specific heat capacity.

[0070] The powder coatings obtained in Examples 1-5 and Comparative Examples 1-9 were electrostatically sprayed onto the surface of cold-rolled steel sheets that had been degreased and polished. The coatings were cured at 180°C for 20 minutes, with the coating thickness controlled at 80±10 μm, to obtain coated test panels. The following performance tests were then conducted. Each sample group was tested in parallel at least three times, with the thermal conductivity and the unilateral corrosion spread width at the scribing point after 1000 hours of neutral salt spray being the average values.

[0071] Adhesion test: The test shall be conducted in accordance with GB / T 9286-2021 "Paints and Varnishes Cross-cut Test".

[0072] Impact resistance test: The test shall be conducted in accordance with GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film", and the maximum impact height when the coating has no cracks or peeling shall be recorded.

[0073] Pencil hardness test: The test shall be conducted in accordance with GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method".

[0074] Neutral salt spray resistance test: The neutral salt spray test shall be conducted in accordance with GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test" for 1000 hours. After the test, observe the blistering and rusting of the coating and measure the corrosion spread width on one side of the scribing line.

[0075] Heat-resistant oil test: Immerse the coated test plate in No. 25 transformer oil and keep it at 105℃ for 168 hours. After taking it out, cool it to room temperature and observe whether the coating blister, crack, or peel off.

[0076] The test results are shown in Table 1 below: Table 1

[0077] As shown in Table 1, Examples 1-5 of the present invention all exhibit good thermal conductivity and overall coating performance. Example 3 achieves a better balance among thermal conductivity, adhesion, impact resistance, pencil hardness, neutral salt spray resistance, and hot oil resistance, and is the preferred embodiment of the present invention. Comparative Example 1, without the addition of thermally conductive fillers, had a relatively complete resin continuity, resulting in better adhesion and impact resistance, but its thermal conductivity was significantly lower than that of Example 3. Comparative Examples 2 and 3 both used only single-size α-alumina, and their thermal conductivity, adhesion, and salt spray resistance were all lower than those of Example 3. Comparative Example 4 replaced the KH550-modified γ-alumina / core-shell rubber particles with a physical mixture of unmodified γ-alumina and core-shell rubber particles, resulting in a significant decrease in thermal conductivity, adhesion, impact resistance, and salt spray resistance. Comparative Example 5, without the addition of core-shell rubber particles, maintained a high thermal conductivity due to the higher proportion of inorganic thermally conductive components, but its impact resistance was significantly reduced. Comparative Example 6 did not add KH550-modified γ-alumina / core-shell rubber particles, but only used… Dual-particle-size α-alumina, as a thermally conductive filler, has insufficient interface regulation and toughening effects, resulting in lower overall performance than Example 3. Comparative Example 7 has a low total amount of thermally conductive filler, making it difficult to form an effective thermally conductive network, resulting in a low thermal conductivity. Although Comparative Example 8 further increases the total amount of thermally conductive filler, the excessive filler content leads to insufficient resin coating of the filler, increased local agglomeration and pore defects, resulting in a decrease in the continuity of the effective thermal conduction pathway. At the same time, the adhesion, impact resistance, and salt spray resistance are significantly deteriorated. In Comparative Example 9, no glutaraldehyde aqueous solution was added when preparing KH550 modified γ-alumina / core-shell rubber particles. The γ-alumina and core-shell rubber particles mainly rely on physical adsorption for bonding, resulting in insufficient stability of the composite particle structure. Consequently, the thermal conductivity, impact toughness, and salt spray resistance of the final coating are all lower than those of Example 3.

[0078] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, features in the embodiments of the present invention can be combined with each other unless otherwise specified.

Claims

1. A high thermal conductivity powder coating, characterized in that, Includes the following components: 50-60 parts by weight of epoxy resin; 50-60 parts by weight of carboxyl-terminated saturated polyester; 1-4 parts by weight of curing agent; 0.4-0.6 parts by weight of auxiliary crosslinking agent; 60-110 parts by weight of thermally conductive filler; 2-3 parts by weight of additives; The thermally conductive filler is composed of 55-85 parts by mass of micron-sized α-alumina and 5-25 parts by mass of KH550 modified γ-alumina / core-shell rubber particles; the shell of the core-shell rubber particles contains epoxy functional groups.

2. The high thermal conductivity powder coating according to claim 1, characterized in that, The core layer of the core-shell rubber particle is cross-linked polybutyl acrylate rubber, and the shell layer contains methyl methacrylate structural units and glycidyl methacrylate structural units.

3. The high thermal conductivity powder coating according to claim 1, characterized in that, The curing agent includes a dicyandiamide curing agent and an imidazole accelerator, wherein the mass ratio of the dicyandiamide curing agent to the imidazole accelerator is 5-8:0.3-0.8; the additives consist of a leveling agent, a degassing agent, a light stabilizer, an antistatic agent, and a lubricant in a mass ratio of 0.5-0.9:0.3-0.5:0.2-0.4:0.1-0.3:0.1-0.

3.

4. The high thermal conductivity powder coating according to claim 1, characterized in that, The micron-sized α-alumina consists of 30-50 parts by mass of α-alumina with a particle size of 30-50 μm and 25-35 parts by mass of α-alumina with a particle size of 5-15 μm.

5. The high thermal conductivity powder coating according to claim 1, characterized in that, The preparation method of the KH550 modified γ-alumina / core-shell rubber particles includes the following steps: A1. KH550 was added to an ethanol-water mixture and pre-hydrolyzed under acidic conditions. Core-shell rubber particles were added and heated and stirred under neutral to weakly alkaline conditions. The solid phase was separated and washed to obtain aminated rubber particles. A2. KH550 was added to an ethanol-water mixture and pre-hydrolyzed under acidic conditions. γ-alumina was added, heated and stirred, and the solid phase was separated and washed to obtain KH550 modified γ-alumina. A3. Disperse the aminated rubber particles in an isopropanol-water mixed solution, add KH550 modified γ-alumina and stir until uniform, add glutaraldehyde aqueous solution under weakly alkaline conditions at 40-50℃ and stir, separate the solid phase, wash and dry to obtain the KH550 modified γ-alumina / core-shell rubber particles.

6. The high thermal conductivity powder coating according to claim 5, characterized in that, In step A1, the ethanol-water mixed solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 4:1; the mass ratio of the core-shell rubber particles, the ethanol-water mixed solution, and KH550 is 1:8-15:0.010-0.015; the heating and stirring under neutral to weakly alkaline conditions refers to adjusting the pH of the system to 7.0-8.0 with 0.1 mol / L ammonia water and stirring at 60-70℃ for 4-6 hours.

7. The high thermal conductivity powder coating according to claim 5, characterized in that, In step A2, the ethanol-water mixed solution is prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 9:1; the amount of KH550 used is 2%-5% of the mass of γ-alumina.

8. The high thermal conductivity powder coating according to claim 5, characterized in that, In step A3, the isopropanol-water mixed solution is prepared by mixing isopropanol and deionized water at a volume ratio of 7:3; the mass ratio of the aminated core-shell rubber particles, the isopropanol-deionized water mixed solution, the KH550 modified γ-alumina, and the glutaraldehyde aqueous solution is 5-12:100:1-4:0.2-0.6; and the mass fraction of the glutaraldehyde aqueous solution is 25%.

9. A high thermal conductivity powder coating according to claim 3, characterized in that, The leveling agent is Resiflow® PL-200, the degassing agent is benzoin, the light stabilizer is a benzotriazole light stabilizer, the antistatic agent is a quaternary ammonium salt antistatic agent, the lubricant is polyethylene wax, and the auxiliary crosslinking agent is triglycidyl isocyanurate.

10. A method for preparing a high thermal conductivity powder coating, characterized in that, Includes the following steps: S1. Epoxy resin, carboxyl-terminated saturated polyester and additives are put into a high-speed mixer for dry mixing and pre-dispersion to obtain resin premix; S2. The resin premix, curing agent, auxiliary crosslinking agent and thermally conductive filler are added to a twin-screw extruder for melt extrusion mixing, tableting and cooling, coarse crushing, air-classification grinding, sieving and magnetic separation to obtain the high thermal conductivity powder coating.

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