A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys and its preparation method.

Abstract

This invention belongs to the field of coating technology and discloses a powder coating for conductive heat dissipation and low-temperature curing of aluminum-magnesium alloys and its preparation method. The raw materials of the powder coating, by weight, include: 50-65 parts modified polyester resin, 3-8 parts triglycidyl isocyanate, 5-12 parts coupling-modified nano-alumina, 4-10 parts conductive filler, 1-3 parts adhesion promoter, 0.5-2 parts leveling agent, 0.1-1 parts gloss enhancer, and 0.3-0.5 parts benzoin. The modified polyester resin is obtained by grafting graphene onto polyester resin. The conductive filler includes an aluminum-doped zinc oxide core and a polyethylene wax shell layer. This invention constructs a conductive heat dissipation and low-temperature curing powder coating system adapted to aluminum-magnesium alloy substrates, effectively overcoming the core bottlenecks of existing technologies such as single function, poor substrate compatibility, and difficulty in balancing low-temperature curing and performance. It provides strong support for the wider application of aluminum-magnesium alloy materials and possesses significant technical value and market prospects.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a powder coating for low-temperature curing of conductive heat dissipation on aluminum-magnesium alloys and its preparation method. Background Technology

[0002] Aluminum-magnesium alloys, with their lightweight, high strength, and excellent thermal conductivity, have been widely used in various fields such as electronic communication equipment, engineering machinery, and rail transportation. As these fields continue to demand higher product performance, not only must the aluminum-magnesium alloy substrate itself maintain good mechanical and thermal conductivity, but the powder coating on its surface must also possess multiple functions such as electrical conductivity, heat dissipation, low-temperature curing, and strong adhesion.

[0003] However, existing powder coatings face numerous challenges when adapted for aluminum-magnesium alloy applications. Traditional powder coatings that combine conductivity and heat dissipation typically require high-temperature curing. Aluminum-magnesium alloys have relatively limited heat resistance, and high-temperature curing can easily lead to substrate deformation, performance degradation, and even damage to the oxide layer structure on the substrate surface, affecting overall performance. Even if some coatings claim to cure at low temperatures, the reactivity of the resin and curing agent in their curing system is insufficient, making it difficult to form a dense and stable cross-linked network at lower temperatures. This results in defects such as high porosity and poor mechanical strength in the coating, consequently affecting the continuity of the conductive pathway and heat dissipation efficiency.

[0004] Meanwhile, achieving the synergistic effect of conductivity and heat dissipation is quite challenging. Commonly used conductive fillers in existing coatings are prone to agglomeration, which not only leads to uneven distribution of conductivity within the coating but also disrupts the integrity of the heat dissipation network, preventing conductivity and heat dissipation from simultaneously meeting application requirements. Furthermore, the poor compatibility of conductive fillers with the resin matrix further exacerbates the problem of uneven dispersion and may also affect the coating's molding effect and durability. Summary of the Invention

[0005] The present invention aims to improve at least one technical problem in the prior art.

[0006] The first aspect of this invention provides a powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys. The raw materials, by weight, include: 50-65 parts of modified polyester resin, 3-8 parts of triglycidyl isocyanate, 5-12 parts of coupling-modified nano-alumina, 4-10 parts of conductive filler, 1-3 parts of adhesion promoter, 0.5-2 parts of leveling agent, 0.1-1 parts of gloss enhancer, and 0.3-0.5 parts of benzoin.

[0007] The modified polyester resin is obtained by grafting graphene onto polyester resin, and the grafting rate of the graphene is 20%-30%.

[0008] The conductive filler comprises a core and a shell with a mass ratio of 1:(0.08-0.12). The core is zinc oxide doped with aluminum at a doping amount of 1.5 at.% to 2.5 at.%, and the shell is polyethylene wax.

[0009] In the powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys provided in this application, modified polyester resin serves as the film-forming matrix. By grafting graphene onto the polyester resin molecular chain, the low-temperature curing activity of the polyester resin is retained, while the excellent thermal conductivity of graphene enhances the overall heat dissipation efficiency of the coating. Simultaneously, the layered structure of graphene also assists in constructing conductive pathways. Triglycidyl isocyanate, as a curing agent, can undergo a cross-linking reaction with the modified polyester resin, forming a dense and stable coating structure under low-temperature conditions, ensuring the mechanical strength and durability of the coating. Coupling-modified nano-alumina possesses excellent thermal conductivity. After coupling modification, its compatibility with the resin matrix is ​​significantly improved, enabling uniform dispersion and the construction of a continuous heat dissipation network, further enhancing the heat dissipation effect of the coating. The conductive filler adopts a core-shell structure design. The aluminum-doped zinc oxide core, with its appropriate aluminum doping amount, possesses excellent conductivity and can form effective conductive pathways in the coating. The polyethylene wax in the shell layer improves the dispersibility of the conductive filler in the resin matrix, preventing agglomeration that affects conductivity and heat dissipation, while also improving the processing performance of the coating. The adhesion promoter is specifically tailored to the characteristics of aluminum-magnesium alloy substrates, enhancing the adhesion between the coating and the substrate surface and preventing coating peeling or flaking. The leveling agent optimizes flow properties during the coating forming process, reducing surface defects and resulting in a smoother, more even coating. The gloss enhancer improves the coating's gloss and overall appearance. Benzoin effectively eliminates air bubbles during the coating curing process, ensuring a dense internal structure and preventing porosity from affecting electrical conductivity, heat dissipation, and mechanical strength. The synergistic effect of these components allows the coating to balance electrical conductivity, heat dissipation, and low-temperature curing properties, while simultaneously meeting the application requirements of aluminum-magnesium alloys.

[0010] The low-temperature curing performance of the coating in this application stems from the synergistic structural design and reactivity of the components in the raw materials. The core principle is the optimization of the interaction between the resin, curing agent, and additives to rapidly form a dense and stable cross-linked network at lower temperatures. During the graphene grafting process, the modified polyester resin precisely retains sufficient amounts of active groups such as carboxyl and hydroxyl groups. These groups exhibit high reactivity with the epoxy groups in the triglycidyl isocyanate ester molecule, initiating ring-opening esterification and cross-linking reactions without requiring high temperatures. At low temperatures, the epoxy groups undergo addition reactions with the carboxyl groups, while the hydroxyl groups participate in the reaction as auxiliary cross-linking sites, gradually constructing a three-dimensional network structure to achieve coating curing. The graphene grafting rate is controlled at 20%-30%, preventing excessive grafting from causing excessive rigidity and hindering the movement of the resin molecular chains. Furthermore, the interfacial interaction of the layered structure promotes contact and diffusion between the resin and curing agent molecules, reducing the activation energy of the reaction. The active groups on the surface of the coupling-modified nano-alumina can form hydrogen bonds or covalent bonds with the resin and curing agent, acting as a "bridge" to accelerate the reaction process; while the polyethylene wax shell layer of the conductive filler can reduce the frictional resistance in the system, allowing the reactants to be more evenly dispersed and contacted, reducing local reaction dead zones, and ensuring the fullness of the reaction at low temperatures.

[0011] The preparation method of the modified polyester resin includes the following steps:

[0012] The graphene was dispersed in acetone, a silane coupling agent was added, and the mixture was stirred at 70℃-80℃ for 1-2 hours to obtain mixture A.

[0013] The polyester resin was dissolved in acetone, and then adipate dihydrazide was added. The mixture was stirred for 10-20 minutes to obtain mixture B.

[0014] Add mixture A to mixture B, mix well, add dibutyltin dilaurate, heat to 80℃-85℃ under an inert gas atmosphere, stir for 2h-4h, cool to room temperature, add water, stir for 20min-30min, collect the solid product, wash, dry, and obtain the modified polyester resin.

[0015] The preparation method of the coupling-modified nano-alumina includes the following steps:

[0016] Nano-alumina was dispersed in anhydrous ethanol to obtain suspension A;

[0017] Add the silane coupling agent to water and adjust the pH to 4-5 to obtain solution B;

[0018] Solution B was added dropwise to suspension A, and the mixture was stirred at 70℃-80℃ for 1-2 hours. The solid product was collected, washed, and dried to obtain the coupled modified nano-alumina.

[0019] The mass ratio of the nano-alumina to the silane coupling agent is 1:(0.03-0.05).

[0020] Preferably, the acid value of the polyester resin is 15 mg KOH / g-35 mg KOH / g.

[0021] Preferably, the particle size of the conductive filler is 70nm-120nm.

[0022] Preferably, the adhesion promoter is Lubrizol R 2063.

[0023] Preferably, the leveling agent includes at least one of leveling agent F-400, leveling agent F-401, and leveling agent DH-4036.

[0024] Preferably, the brightening agent includes at least one of brightening agent LD-608 and brightening agent T-701.

[0025] A second aspect of the present invention provides a method for preparing the above-mentioned powder coating for conductive heat dissipation and low-temperature curing of aluminum-magnesium alloys, comprising the following steps:

[0026] The raw materials are added to a high-speed mixer and stirred, then fed into a twin-screw extruder through a feed port for melt extrusion, cooling, tableting, crushing, and sieving to obtain the powder coating for low-temperature curing of conductive heat dissipation of aluminum-magnesium alloy.

[0027] The stirring speed is 1500r / min-2500r / min, and the time is 8min-15min.

[0028] The melt extrusion temperature is 100℃-120℃, and the screw speed is 300r / min-400r / min.

[0029] The beneficial effects of this invention are as follows: This invention, through targeted formulation design and synergistic optimization of components, constructs a conductive and heat-dissipating low-temperature curing powder coating system adapted to aluminum-magnesium alloy substrates, effectively overcoming the core bottlenecks of existing technologies such as single function, poor substrate compatibility, and difficulty in balancing low-temperature curing and performance. The powder coating of this invention uses graphene-grafted modified polyester resin as the film-forming matrix, combined with core-shell structured aluminum-doped zinc oxide conductive filler and coupled modified nano-alumina, achieving a three-in-one synergistic effect of conductivity, heat dissipation, and low-temperature curing. This avoids performance damage to the aluminum-magnesium alloy substrate caused by high-temperature curing, and ensures the continuity of the conductive pathway and heat dissipation network through the modified design and dispersion optimization of each functional component. Simultaneously, the optimized interfacial interaction between the components and the adhesion promoter specifically adapted to the characteristics of aluminum-magnesium alloys significantly improves the bonding stability between the coating and the substrate. Combined with reasonable control of the graphene grafting rate and the curing system design, the coating possesses excellent conductive and heat dissipation performance while also exhibiting good mechanical strength, weather resistance, and molding quality. The overall technical solution of this invention not only meets the demand for multi-functional coating of aluminum-magnesium alloy surfaces in high-end fields, but also simplifies the preparation and construction process, conforms to the development trend of energy conservation and environmental protection, and provides strong support for the promotion and application of aluminum-magnesium alloy materials in a wider range of scenarios, possessing significant technical value and market prospects. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] Example 1

[0032] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys comprises the following raw materials by weight: 58 parts modified polyester resin, 5 parts triglycidyl isocyanate, 8 parts coupling modified nano-alumina, 7 parts conductive filler, 2 parts adhesion promoter (Lubrizol R 2063), 1.2 parts leveling agent F-401, 0.6 parts gloss enhancer LD-608, and 0.4 parts benzoin.

[0033] The modified polyester resin was obtained by grafting graphene onto polyester resin (196 unsaturated polyester resin, acid value 20 mg KOH / g), with a graphene grafting rate of 25%. The preparation method of the modified polyester resin included the following steps: dispersing graphene in acetone (mass ratio of graphene to acetone 1:80), adding γ-aminopropyltriethoxysilane (mass ratio of graphene to γ-aminopropyltriethoxysilane 1:1.5), and stirring the mixture at 75°C for 1.5 h to obtain mixture A; dissolving the polyester resin in acetone (mass ratio of polyester resin to acetone 1:0.8), and then adding adipic acid diacyl... Hydrazine was added and stirred for 15 min to obtain mixture B. Mixture A was added to mixture B and mixed well. Dibutyltin dilaurate (mass ratio of polyester resin to dibutyltin dilaurate was 100:0.05) was added. The mixture was heated to 82°C under a nitrogen atmosphere and stirred for 3 h. After cooling to room temperature, 200 parts of deionized water (mass ratio of deionized water to polyester resin was 2:1) were added. After stirring for 25 min, the solid product was collected, washed three times with anhydrous ethanol, and dried under vacuum at 80°C for 5 h to obtain modified polyester resin.

[0034] The conductive filler comprises a core and a shell with a mass ratio of 1:0.1. The core is zinc oxide doped with aluminum at a doping amount of 2.0 at.%, and the shell is polyethylene wax. The preparation method of the conductive filler includes the following steps: zinc oxide and aluminum nitrate are mixed at a mass ratio of 100:2.2, added to deionized water and ultrasonically dispersed for 30 min to form a uniform suspension. After spray drying, the suspension is placed in a muffle furnace and calcined at 550℃ for 3 h. After cooling, the suspension is pulverized to obtain the zinc oxide core doped with aluminum. The core is mixed with polyethylene wax at a mass ratio of 1:0.1, placed in a high-speed mixer, melt-coated at 125℃ for 1 h, cooled, and pulverized through a 300-mesh sieve to obtain the conductive filler. The particle size of the conductive filler is 100 nm.

[0035] The preparation method of coupling-modified nano-alumina includes the following steps: nano-alumina is dispersed in anhydrous ethanol (the mass ratio of nano-alumina to anhydrous ethanol is 1:3), and ultrasonically dispersed for 25 min to obtain suspension A; γ-glycidoxypropyltrimethoxysilane is added to deionized water (the mass ratio of nano-alumina to γ-glycidoxypropyltrimethoxysilane is 1:0.04, and the mass ratio of γ-glycidoxypropyltrimethoxysilane to deionized water is 1:5), the pH is adjusted to 4.5 with glacial acetic acid, and stirred for 10 min to obtain solution B; solution B is added dropwise to suspension A, and the reaction is stirred at 75℃ for 1.5 h, the solid product is collected by filtration, washed 4 times with anhydrous ethanol, and vacuum dried at 85℃ for 4 h to obtain coupling-modified nano-alumina.

[0036] The preparation method of the powder coating for low-temperature curing of conductive heat dissipation on aluminum-magnesium alloy includes the following steps:

[0037] The raw materials are added to a high-speed mixer and mixed (mixed at 2000 r / min for 12 min). Then, they are fed into a twin-screw extruder through the feed port for melt extrusion (melt extrusion temperature is 110℃, screw speed is 350 r / min). After cooling, the material is pressed into sheets, crushed, and sieved (200 mesh sieve) to obtain a powder coating for low-temperature curing of conductive heat dissipation of aluminum-magnesium alloy.

[0038] Example 2

[0039] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that: the raw materials, by weight, are 62 parts modified polyester resin, 6 parts triglycidyl isocyanate, 10 parts coupling-modified nano-alumina, 9 parts conductive filler, 2.5 parts adhesion promoter (Lubrizol R 2063), 1.5 parts leveling agent F-401, 0.8 parts gloss enhancer LD-608, and 0.45 parts benzoin; the graphene grafting rate in the modified polyester resin is 22%; the core-to-shell mass ratio of the conductive filler is 1:0.08, and the aluminum doping amount in the core is 1.8 at.%. All other aspects are the same as in Example 1.

[0040] Example 3

[0041] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that: the raw materials, by weight, are 52 parts modified polyester resin, 4 parts triglycidyl isocyanate, 6 parts coupling-modified nano-alumina, 5 parts conductive filler, 1.5 parts adhesion promoter (Lubrizol R 2063), 0.8 parts leveling agent F-401, 0.4 parts gloss enhancer LD-608, and 0.35 parts benzoin; the graphene grafting rate in the modified polyester resin is 30%; the core-to-shell mass ratio of the conductive filler is 1:0.12, and the aluminum doping amount in the core is 2.3 at.%. All other aspects are the same as in Example 1.

[0042] Example 4

[0043] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that: the raw materials, by weight, are 65 parts modified polyester resin, 8 parts triglycidyl isocyanate, 11 parts coupling-modified nano-alumina, 10 parts conductive filler, 3 parts adhesion promoter (Lubrizol R 2063), 2 parts leveling agent F-401, 1 part gloss enhancer LD-608, and 0.5 parts benzoin; the graphene grafting rate in the modified polyester resin is 28%; the core-to-shell mass ratio of the conductive filler is 1:0.09, and the aluminum doping amount in the core is 2.5 at.%. All other aspects are the same as in Example 1.

[0044] Comparative Example 1

[0045] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that the modified polyester resin is replaced with unmodified polyester resin (196 unsaturated polyester resin, acid value 20 mg KOH / g). All other aspects are the same as in Example 1.

[0046] Comparative Example 2

[0047] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that the conductive filler consists only of an aluminum-doped zinc oxide core, without a polyethylene wax shell layer. Otherwise, it is the same as Example 1.

[0048] Comparative Example 3

[0049] A powder coating for low-temperature curing of conductive heat dissipation coatings for aluminum-magnesium alloys differs from Example 1 in that the core of the conductive filler is zinc oxide without aluminum doping, and the mass ratio of the core to the shell remains 1:0.1. Everything else is the same as in Example 1.

[0050] Comparative Example 4

[0051] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that the coupling-modified nano-alumina is replaced with unmodified nano-alumina. Otherwise, it is the same as Example 1.

[0052] Comparative Example 5

[0053] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that the graphene grafting rate in the modified polyester resin is 10%. All other aspects are the same as in Example 1.

[0054] Comparative Example 6

[0055] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that the graphene grafting rate in the modified polyester resin is 50%. All other aspects are the same as in Example 1.

[0056] Comparative Example 7

[0057] A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys differs from Example 1 in that it does not contain an adhesion promoter (Lubrizol R 2063). Otherwise, it is the same as Example 1.

[0058] The powder coatings prepared in the examples and comparative examples were sprayed onto the surface of magnesium-aluminum alloy substrates, and the performance of the coatings obtained after curing was tested, as shown in Table 1.

[0059] Table 1

[0060]

[0061] Referring to the data in Table 1, Comparative Example 1 uses ungrafted graphene-free unsaturated polyester resin (No. 196) instead of modified polyester resin. Compared to Example 1, its conductivity and heat dissipation performance show a significant decrease. This is because the continuous conductive and heat dissipation network constructed by the graphene sheet structure is lacking. At the same time, the synergistic effect of the resin and other functional fillers is weakened, resulting in the coating not only failing to form an effective conductive path, but also significantly reducing heat transfer efficiency. The mechanical properties and appearance quality are also affected due to the insufficient compatibility of the resin itself, failing to achieve the multi-performance effect of the examples. In Comparative Example 2, the conductive filler does not have a polyethylene wax shell layer, only retaining the aluminum-doped zinc oxide core. Compared to Example 1, its conductive filler in the resin matrix... Agglomeration easily occurs, disrupting the integrity of the conductive and heat dissipation networks, resulting in a significant decrease in both electrical and thermal conductivity. Simultaneously, agglomerated filler particles form stress concentration points within the coating, leading to reduced mechanical strength. The coating appearance also exhibits obvious defects due to particle agglomeration. In Example 1, the polyethylene wax shell coating modification effectively improved the dispersion of the conductive filler, ensuring synergistic performance of all functions. In Comparative Example 3, the conductive filler core is undoped zinc oxide. Compared to the aluminum-doped design in Example 1, pure zinc oxide lacks sufficient conductive active sites, failing to form efficient conductive pathways in the coating, resulting in increased surface resistivity and loss of practical conductive function. Comparative Example 4 uses undoped zinc oxide... Compared to Example 1, the unmodified pure nano-alumina exhibits poor compatibility with the resin matrix, making it difficult to disperse uniformly and construct a continuous heat dissipation network. This results in a significant decrease in thermal conductivity. Furthermore, insufficient bonding strength between the nano-alumina and the resin interface leads to reduced coating adhesion and mechanical properties, as well as appearance defects such as localized pinholes. Example 1, through coupling modification, improved the compatibility between the nano-alumina and the resin, ensuring the continuity of the heat dissipation network and the stability of the coating structure. In Comparative Example 5, the graphene grafting rate was only 10%. Compared to Example 1, this lower grafting rate resulted in insufficient graphene bonding to the resin molecular chains, failing to fully utilize the synergistic effect of its layered structure in terms of electrical conductivity and heat dissipation. The low grafting rate resulted in lower electrical and thermal conductivity than in the example, and the coating also showed slight haze. This indicates that a low grafting rate weakens the synergistic effect between graphene and resin. In Comparative Example 6, the graphene grafting rate was as high as 50%. Compared with Example 1, the excessively high grafting rate caused the modified polyester resin molecular chain to be too rigid, hindering molecular movement. This not only disrupted the continuity of the conductive pathway and increased the surface resistivity, but also increased the brittleness of the coating and significantly reduced its mechanical properties. During the curing process, uneven heat release caused serious appearance defects such as cracking and loss of gloss. This shows that a higher graphene grafting rate is not necessarily better. The 20%-30% range specified in this invention can balance the rigidity and flexibility of the resin and ensure the synergistic optimization of various properties.Comparative Example 7 lacked an adhesion promoter. Compared to Example 1, the coating could not effectively penetrate the dense oxide layer on the aluminum-magnesium alloy surface, resulting in extremely poor adhesion between the coating and the substrate, a significant decrease in adhesion grade, and peeling at the edges. In contrast, Example 1, by adding an adhesion promoter suitable for the aluminum-magnesium alloy substrate, enabled the coating to form a strong bond with the substrate.

[0062] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys, characterized in that, The raw materials, by weight, include: 50-65 parts modified polyester resin, 3-8 parts triglycidyl isocyanate, 5-12 parts coupling modified nano alumina, 4-10 parts conductive filler, 1-3 parts adhesion promoter, 0.5-2 parts leveling agent, 0.1-1 part gloss enhancer, and 0.3-0.5 parts benzoin; The modified polyester resin is obtained by grafting graphene onto polyester resin, and the grafting rate of the graphene is 20%-30%. The conductive filler comprises a core and a shell with a mass ratio of 1:(0.08-0.12), wherein the core is zinc oxide doped with aluminum at a doping amount of 1.5 at.%-2.5 at.%, and the shell is polyethylene wax. The acid value of the polyester resin is 15 mg KOH / g - 35 mg KOH / g; The method for preparing the modified polyester resin includes the following steps: The graphene was dispersed in acetone, a silane coupling agent was added, and the mixture was stirred at 70℃-80℃ for 1-2 hours to obtain mixture A. The polyester resin was dissolved in acetone, and adipate dihydrazide was added. The mixture was stirred for 10-20 minutes to obtain mixture B. Add the mixture A to the mixture B, mix well, add dibutyltin dilaurate, heat to 80℃-85℃ under an inert gas atmosphere, stir for 2h-4h, cool to room temperature, add water, stir for 20min-30min, collect the solid product, wash, dry, and obtain the modified polyester resin. The preparation method of the coupling-modified nano-alumina includes the following steps: Nano-alumina was dispersed in anhydrous ethanol to obtain suspension A; Add the silane coupling agent to water and adjust the pH to 4-5 to obtain solution B; Solution B was added dropwise to suspension A, and the mixture was stirred at 70℃-80℃ for 1-2 hours. The solid product was collected, washed, and dried to obtain the coupled modified nano-alumina. The mass ratio of the nano-alumina to the silane coupling agent is 1:(0.03-0.05).

2. The powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys according to claim 1, characterized in that, The particle size of the conductive filler is 70nm-120nm.

3. The powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys according to claim 1, characterized in that, The adhesion promoter is Lubrizol R 2063.

4. The powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys according to claim 1, characterized in that, The leveling agent includes at least one of leveling agent F-400, leveling agent F-401, and leveling agent DH-4036.

5. The powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys according to claim 1, characterized in that, The brightening agent includes at least one of brightening agent LD-608 and brightening agent T-701.

6. A method for preparing a powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The raw materials are added to a high-speed mixer and stirred. Then, they are fed into a twin-screw extruder through a feed port for melt extrusion, cooling, tableting, crushing, and sieving to obtain the powder coating for low-temperature curing of conductive heat dissipation of aluminum-magnesium alloy.

7. The method for preparing a powder coating for low-temperature curing of conductive and heat-dissipating aluminum-magnesium alloys according to claim 6, characterized in that, The stirring speed is 1500 r / min-2500 r / min, and the time is 8 min-15 min; And / or, the melt extrusion temperature is 100℃-120℃, and the screw speed is 300r / min-400r / min.

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