A powder coating and a method for its production and use

Abstract

The present application relates to a kind of powder coating and its preparation method and application, the preparation method includes: after mixing thermosetting powder coating, film forming auxiliary and conductive filler, screening, obtain the powder coating.The preparation method of powder coating provided by the present application is used, and the powder coating prepared has electromagnetic shielding effect, and no solvent emission.The present application also provides a kind of coating method of the powder coating: the coating method includes the following steps: (1) heat treatment is carried out to the heat-sensitive substrate;(2) low viscosity powder coating is coated on the heat-sensitive substrate, forms adhesive layer;(3) after the powder coating is coated on the adhesive layer, solidification is carried out, obtains coating, completes the coating.After coating by the coating method, the surface resistance of the coating obtained is ≤4.5Ω, electromagnetic shielding effectiveness is ≥48dB, the hardness of coating is high, the wet heat resistance is good, and has excellent adhesion.

Description

Technical Field

[0001] This invention belongs to the field of coating composition technology, specifically relating to a powder coating, its preparation method, and its application. Background Technology

[0002] Powder coating is a solid powder coating that does not contain any organic solvents. It is usually applied using electrostatic spraying and is traditionally used for coating metal substrates. In recent years, low-temperature curing powder coatings have become a research hotspot in the coating industry, and their application scope has gradually expanded to composite materials, wood, and other heat-sensitive substrates. At the same time, new application directions such as electromagnetic shielding, antistatic properties, and conductivity have emerged.

[0003] Electromagnetic shielding coatings are a type of material that shields electromagnetic waves, blocking electromagnetic radiation from the widespread use of communication and electronic equipment, thus providing effective protection for human health and information security. Currently, electromagnetic shielding coatings typically use solvent-based or water-based coatings. Solvent-based coatings contain 60-70% solvent, causing serious environmental pollution. Water-based electromagnetic shielding coatings disclosed in CN116218292A and CN108699386A usually include film-forming resins, conductive fillers, leveling agents, film-forming aids, defoamers, etc. These water-based coatings typically form a thin film in a single application, usually requiring multiple coats and a drying and curing process, making application complex.

[0004] Achieving electromagnetic shielding typically requires adding a large amount of conductive filler to the coating. However, an excessively high proportion of conductive filler can lead to difficulties in melt extrusion. Therefore, it is difficult to prepare electromagnetic shielding powder coatings using the traditional melt extrusion method commonly used in powder coating. Thus, there is an urgent need to find a new method for preparing powder coatings with good electromagnetic shielding performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a powder coating, its preparation method, and its application. By designing the raw materials and process steps, the resulting powder coating possesses electromagnetic shielding properties and can be applied to electromagnetic protection of components such as interior and exterior trim parts and battery casings in new energy vehicles. Furthermore, the coating formed after curing exhibits excellent adhesion, a smooth and flat surface, and is free of pinholes and shrinkage cavities.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a powder coating, the method comprising: mixing a thermosetting powder coating, a film-forming aid and a conductive filler and then sieving the mixture to obtain the powder coating.

[0008] In the powder coating preparation method provided by the present invention, the film-forming aid melts first during the curing process of the powder coating, which causes the conductive fillers to bond together. As the melting process proceeds, the film-forming aid gradually volatilizes, thereby causing the conductive fillers to connect with each other to form a conductive network, giving the coating a good electromagnetic shielding effect.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0010] As a preferred technical solution, the mesh size of the sieve used for screening is 180-240 mesh, for example, it can be 180 mesh, 200 mesh, 230 mesh or 240 mesh, etc.

[0011] Preferably, the thermosetting powder coating is 5-30 parts by weight, for example, 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 15 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 25 parts by weight, 28 parts by weight or 30 parts by weight, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0012] The film-forming aid is 10-20 parts by weight, for example, it can be 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight or 20 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0013] The conductive filler is 50-100 parts by weight, for example, 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight or 100 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0014] Preferably, the thermosetting powder coating comprises the following components by weight: 50-100 parts by weight of matrix resin, 5-50 parts by weight of curing agent, and 0.1-2 parts by weight of nanofiller.

[0015] The matrix resin is 50-100 parts by weight, for example, 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight or 100 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0016] The curing agent is 5-50 parts by weight, for example, it can be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight or 50 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0017] The nanofiller is 0.1-2 parts by weight, for example, it can be 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight or 2 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0018] Preferably, the matrix resin includes any one or a combination of at least two of epoxy resin, polyester resin, polyurethane or acrylic resin.

[0019] Preferably, the epoxy resin includes any one or a combination of at least two of the following: a first bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a linear phenolic epoxy resin.

[0020] Preferably, the epoxy equivalent of the epoxy resin is 300-700 g / eq, for example, it can be 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, 500 g / eq, 550 g / eq, 600 g / eq, 650 g / eq or 700 g / eq, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0021] Preferably, the polyester resin comprises a first carboxyl polyester resin and / or a hydroxyl polyester resin.

[0022] Preferably, the acid value of the first carboxylated polyester resin is 40-70 mg KOH / g, for example, it can be 40 mg KOH / g, 43 mg KOH / g, 45 mg KOH / g, 48 mg KOH / g, 50 mg KOH / g, 55 mg KOH / g, 58 mg KOH / g, 60 mg KOH / g, 65 mg KOH / g, 68 mg KOH / g or 70 mg KOH / g, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0023] Preferably, the hydroxyl value of the hydroxyl polyester resin is 100-220 mg KOH / g, for example, it can be 100 mg KOH / g, 120 mg KOH / g, 140 mg KOH / g, 160 mg KOH / g, 180 mg KOH / g, 200 mg KOH / g or 220 mg KOH / g, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0024] Preferably, the acrylic resin includes carboxylated acrylic resin and / or epoxy acrylic resin.

[0025] Preferably, the acid value of the carboxyacrylic resin is 140-200 mg KOH / g, for example, it can be 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 170 mg KOH / g, 180 mg KOH / g, 190 mg KOH / g or 200 mg KOH / g, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] Preferably, the epoxy equivalent of the epoxy acrylate resin is 500-700 g / eq, for example, it can be 500 g / eq, 520 g / eq, 550 g / eq, 580 g / eq, 600 g / eq, 620 g / eq, 650 g / eq, 680 g / eq or 700 g / eq, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0027] Preferably, the curing agent comprises any one or a combination of at least two of the following: triglycidyl isocyanurate, substituted dicyandiamide, 2,6-xylylbiguanidine, blocked polyisocyanate, dodecanoic acid, dicarboxylic acid dihydrazide, acid anhydride, second bisphenol A type epoxy resin, second carboxylated polyester resin, linear phenolic resin, phenolic hydroxyl resin, or hydroxyalkylamide.

[0028] Preferably, the epoxy equivalent of the second bisphenol A type epoxy resin is 300-700 g / eq, for example, it can be 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, 500 g / eq, 550 g / eq, 600 g / eq, 650 g / eq or 700 g / eq, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] Preferably, the acid value of the second carboxylated polyester resin is 40-70 mg KOH / g, for example, it can be 40 mg KOH / g, 43 mg KOH / g, 45 mg KOH / g, 48 mg KOH / g, 50 mg KOH / g, 55 mg KOH / g, 58 mg KOH / g, 60 mg KOH / g, 65 mg KOH / g, 68 mg KOH / g or 70 mg KOH / g, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0030] Preferably, the nanofiller includes any one or a combination of at least two of nano-alumina, nano-titanium dioxide, nano-silica, nano-magnesium oxide, or nano-zinc oxide.

[0031] Preferably, the median particle size of the nanofiller is 30-200 nm, for example, it can be 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0032] Preferably, the thermosetting powder coating further includes 0.03-3 parts by weight of curing accelerator, for example, 0.03 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight or 3 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0033] Preferably, the curing accelerator includes any one or a combination of at least two of imidazole, imidazole derivatives, tertiary amine salts, quaternary ammonium salts, tetraalkylammonium carboxylate, or dibutyltin dilaurate.

[0034] Preferably, the thermosetting powder coating further includes 0.1-2 parts by weight of leveling agent, for example, 0.1 parts by weight, 0.15 parts by weight, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, or 2 parts by weight, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0035] Preferably, the leveling agent comprises any one or a combination of at least two acrylate leveling agents.

[0036] Preferably, the thermosetting powder coating further includes 0.5-5 parts by weight of degassing agent, for example, 0.5 parts by weight, 0.8 parts by weight, 1 part by weight, 1.5 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 3.8 parts by weight, 4 parts by weight, 4.5 parts by weight, or 5 parts by weight, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0037] Preferably, the degassing agent comprises polyamide wax.

[0038] Preferably, the thermosetting powder coating is prepared by the following method, which includes: mixing a base resin, a curing agent, a nanofiller, optionally a curing accelerator, optionally a leveling agent and optionally a degassing agent, followed by melt extrusion, and then sequentially pressing, cooling, pulverizing and sieving to obtain the thermosetting powder coating.

[0039] Preferably, the temperature of the melt extrusion is 80-110℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 95℃, 98℃, 100℃, 102℃, 105℃, 108℃ or 110℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0040] Preferably, the particle size is 10-110 μm, for example, it can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or 110 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] Preferably, the mesh size of the sieve is 160-200 mesh, for example, it can be 160 mesh, 170 mesh, 180 mesh or 200 mesh.

[0042] Preferably, the film-forming aid comprises any one or a combination of at least two of benzoin or benzoin derivatives, with benzoin being the most preferred.

[0043] Preferably, the conductive filler comprises any one or a combination of at least two of metal powder, graphite, carbon nanotubes or carbon fibers.

[0044] Preferably, the metal powder includes any one or a combination of at least two of silver powder, copper powder, nickel powder, or silver-coated copper powder.

[0045] Preferably, the shape of the metal powder includes flakes and / or spheres.

[0046] Preferably, when the metal powder is in the form of flakes, the median particle size is 2-10 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, as well as specific particle sizes between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific particle sizes included in the range.

[0047] Preferably, the median particle size of the metal powder when it is spherical is 30-80 nm, for example, it can be 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm or 80 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0048] Preferably, the mixed materials in the preparation method of the powder coating further include 0.2-1 parts by weight of dispersing agent, for example, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight or 1 part by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0049] Preferably, the dispersing agent comprises nano-gas phase metal oxide.

[0050] Preferably, the nano-vaporized metal oxide includes nano-vaporized alumina and / or nano-vaporized silicon oxide.

[0051] In a second aspect, the present invention provides a powder coating, which is prepared by the preparation method described in the first aspect.

[0052] Thirdly, the present invention provides an application of the powder coating as described in the second aspect, wherein the powder coating is used for coating a heat-sensitive substrate.

[0053] Preferably, the coating method includes the following steps:

[0054] (1) The heat-sensitive substrate is subjected to heat treatment;

[0055] (2) Apply a low-viscosity powder coating onto the heat-sensitive substrate to form an adhesive layer;

[0056] (3) The powder coating is applied to the adhesive layer and then cured to obtain a coating layer, thus completing the coating process.

[0057] Before spraying the powder coating, the present invention first applies a low-viscosity powder coating to the surface of a heat-sensitive substrate. This serves two purposes: firstly, it acts as a sealant and improves adhesion; secondly, it increases the amount of powder coating with a high conductive filler content, thereby increasing the coating thickness.

[0058] Preferably, the heat treatment temperature is 80-110℃, for example, it can be 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, 98℃, 100℃, 102℃, 105℃, 108℃ or 110℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0059] Preferably, the heat treatment time is 3-5 min, for example, it can be 3 min, 3.2 min, 3.4 min, 3.6 min, 3.8 min, 4 min, 4.2 min, 4.4 min, 4.8 min or 5 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0060] Preferably, the thickness of the adhesive layer is 10-50 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0061] Preferably, the thickness of the powder coating is 60-150 μm, for example, it can be 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm or 150 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0062] Preferably, the curing method includes infrared curing.

[0063] Preferably, the infrared curing power is 5-30 kW / m². 2 For example, it can be 5kW / m 2 8kW / m 2 10kW / m 2 12kW / m 2 15kW / m 2 18kW / m 2 20kW / m 2 22kW / m 2 25kW / m 2 28kW / m 2 Or 30kW / m 2 As well as the specific point values ​​between the above point values, due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0064] Preferably, the infrared curing time is 3-10 min, for example, it can be 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0065] Preferably, the low-viscosity powder coating comprises the following components by weight: 90-100 parts epoxy resin, 3-10 parts curing agent, 0.2-3 parts flow aid, 0.5-5 parts micron filler, 0.5-5 parts degassing agent, and 0.1-2 parts leveling agent.

[0066] The epoxy resin is 90-100 parts by weight, for example, 90 parts by weight, 91 parts by weight, 92 parts by weight, 93 parts by weight, 94 parts by weight, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, or 100 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0067] The curing agent is 3-10 parts by weight, for example, it can be 3 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, 7 parts by weight, 7.5 parts by weight, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight or 10 parts by weight, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0068] The flow aid is 0.2-3 parts by weight, for example, it can be 0.2 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 2.8 parts by weight or 3 parts by weight, and specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0069] The micron filler is 0.5-5 parts by weight, for example, it can be 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0070] The degassing agent is 0.5-5 parts by weight, for example, it can be 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0071] The leveling agent is 0.1-2 parts by weight, for example, it can be 0.1 parts by weight, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight or 2 parts by weight, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0072] Preferably, the epoxy resin comprises bisphenol A type epoxy resin.

[0073] Preferably, the curing agent comprises any one or a combination of at least two of the following: substituted dicyandiamide, imidazole, or imidazole derivatives.

[0074] Preferably, the flow aid comprises hydrogenated castor oil.

[0075] Preferably, the micron-sized filler comprises spherical silica.

[0076] Preferably, the median particle size of the micron filler is 3-10 μm (e.g., 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc.), and more preferably 5-8 μm (e.g., 5 μm, 6 μm, 7 μm or 8 μm, etc.).

[0077] Preferably, the degassing agent comprises polyamide wax.

[0078] Preferably, the leveling agent comprises any one or a combination of at least two acrylate leveling agents.

[0079] Preferably, the low-viscosity powder coating is prepared by the following method, which includes: mixing epoxy resin, curing agent, flow aid, micron filler, degassing agent and leveling agent, then melting and extruding the mixture, followed by sequential pressing, cooling, pulverizing and sieving to obtain the low-viscosity powder coating.

[0080] Preferably, the temperature of the melt extrusion is 80-110℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 95℃, 98℃, 100℃, 102℃, 105℃, 108℃ or 110℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0081] Preferably, the mesh size of the sieve is 200-300 mesh, for example, it can be 200 mesh, 230 mesh, 240 mesh, 250 mesh, 270 mesh or 300 mesh, etc.

[0082] Preferably, the particle size is 10-90μm, for example, it can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm or 90μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0083] Preferably, the melt viscosity of the low-viscosity powder coating at 150°C is 1000-3000 mPa·s, for example, it can be 1000 mPa·s, 1200 mPa·s, 1400 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, 2200 mPa·s, 2400 mPa·s, 2600 mPa·s, 2800 mPa·s, or 3000 mPa·s, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] The powder coating preparation method provided by this invention is simple. The powder coating prepared by the method provided by this invention has a smooth and flat coating without pinholes or shrinkage cavities after curing, and has excellent adhesion (adhesion grade 0). It also has good electromagnetic shielding effect, with a surface resistance ≤4.5Ω and electromagnetic shielding effectiveness ≥48dB. In addition, the coating has high hardness (H-2H) and good resistance to damp heat. After 1000h of damp heat resistance testing, no blistering, cracking, or obvious loss of gloss was observed. Detailed Implementation

[0086] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0087] The sources of some components in the examples and comparative examples are as follows:

[0088] (1) Bisphenol A type epoxy resin KD211G: purchased from Guodu Chemical, epoxy equivalent is 500g / eq;

[0089] (2) Bisphenol A type epoxy resin HY903: purchased from Anhui Hengyuan, epoxy equivalent is 700g / eq;

[0090] (3) Carboxylated polyester resin 1501: purchased from Zhanxin Resin, with an acid value of 70 mg KOH / g;

[0091] (4) Carboxylated polyester resin 2403: purchased from Zhanxin Resin, with an acid value of 40 mg KOH / g;

[0092] (5) Hydroxy polyester resin 1413: purchased from DSM, with a hydroxyl value of 100 mg KOH / g;

[0093] (6) Carboxylated acrylic resin G154: purchased from ESTRON, with an acid value of 155 mg KOH / g;

[0094] (7) Epoxy acrylic resin EP581: purchased from ESTRON, epoxy equivalent is 650g / eq;

[0095] (8) Benzoin: Purchased from Aladdin;

[0096] (9) Flake nickel powder: D50 is 10μm, purchased from NOVAMET, USA;

[0097] (10) Flake nickel powder: D50 is 2μm, purchased from Zhejiang Yamei Nanotechnology Co., Ltd.;

[0098] (11) Spherical nickel powder: D50 is 50nm, purchased from Shanghai Xiangtian Nanomaterials Co., Ltd.

[0099] (12) Nano silica: D50 is 30nm, purchased from Xuancheng Jingrui New Materials Co., Ltd.;

[0100] (13) Nano-alumina: D50 is 30nm, purchased from Xuancheng Jingrui New Materials Co., Ltd.;

[0101] (14) Micron-sized spherical silica: D50 is 5μm, purchased from Guangdong Nanhai Xinchuan Mining Co., Ltd.;

[0102] (15) Nano-sized fumed alumina AluC: purchased from Evonik;

[0103] (16) Nano-sized fumed silica A200: purchased from Evonik;

[0104] (17) Replacement of dicyandiamide: XB2632 purchased from Ciba.

[0105] (18) Blocked polyisocyanates: purchased from Degussa EP-BF 1320

[0106] (19) Leveling agent: GLP588 purchased from Ningbo Nanhai Chemical Co., Ltd.

[0107] (20) Polyamide wax: purchased from Clariant;

[0108] (21) Multi-walled carbon nanotubes: outer diameter 4-8 nm, length 10-20 μm, purchased from Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences.

[0109] Preparation Example 1

[0110] A thermosetting powder coating A comprises the following components by weight: 50 parts by weight of bisphenol A type epoxy resin HY903 (base resin), 150-150 parts by weight of carboxylated polyester resin (curing agent), 0.5 parts by weight of dimethylimidazole, 0.5 parts by weight of nano-alumina, 0.5 parts by weight of leveling agent GLP588, and 2 parts by weight of polyamide wax.

[0111] The thermosetting powder coating A is prepared by the following method, which includes: mixing the above components and then melting and extruding them at 90°C, followed by sequentially pressing, cooling, pulverizing to 10-110 μm and passing through an 180-mesh sieve to obtain the thermosetting powder coating A.

[0112] Preparation Example 2

[0113] A thermosetting powder coating B, wherein the thermosetting powder coating B comprises the following components by weight: 100 parts by weight of carboxylated polyester resin 2403 (base resin), 8 parts by weight of triglycidyl isocyanurate, 3 parts by weight of dimethylimidazole, 2 parts by weight of nano alumina, 2 parts by weight of leveling agent GLP588, and 5 parts by weight of polyamide wax.

[0114] The only difference between the preparation method of the thermosetting powder coating B and that of Preparation Example 1 is that the components of the thermosetting powder coating B are the same as those provided in this preparation example. All other process parameters and steps are the same as those in Preparation Example 1.

[0115] Preparation Example 3

[0116] A thermosetting powder coating C, wherein the thermosetting powder coating C comprises the following components by weight: 50 parts by weight of bisphenol A type epoxy resin HY903 (base resin), 130 parts by weight of carboxylated polyester resin 1501 (base resin), 20 parts by weight of carboxylated acrylic resin G1542 (base resin), 5 parts by weight of triglycidyl isocyanurate, 0.03 parts by weight of dimethylimidazole, 0.1 parts by weight of nano silica, 0.5 parts by weight of leveling agent GLP588, and 0.5 parts by weight of polyamide wax.

[0117] The difference between the preparation method of the thermosetting powder coating C and Preparation Example 1 is that the components of the thermosetting powder coating C are the same as those provided in this preparation example, while the other process parameters and steps are the same as those in Preparation Example 1.

[0118] Preparation Example 4

[0119] A thermosetting powder coating D, wherein the thermosetting powder coating D comprises the following components by weight: 240380 parts by weight of carboxylated polyester resin (base resin), 120 parts by weight of epoxy acrylic resin EP581 (base resin), 6 parts by weight of triglycidyl isocyanurate, 0.05 parts by weight of diphenylimidazoline, 0.8 parts by weight of nano silica, 0.5 parts by weight of leveling agent GLP588, and 2 parts by weight of polyamide wax.

[0120] The only difference between the preparation method of the thermosetting powder coating D and Preparation Example 1 is that the components of the thermosetting powder coating D are the components provided in this preparation example, while the other process parameters and steps are the same as those in Preparation Example 1.

[0121] Preparation Example 5

[0122] A thermosetting powder coating E, wherein the thermosetting powder coating E comprises the following components by weight: 141370 parts by weight of hydroxyl polyester resin, 18 parts by weight of blocked polyisocyanate, 1.5 parts by weight of diphenylimidazoline, 1.5 parts by weight of nano silica, 1.5 parts by weight of leveling agent GLP588, and 3 parts by weight of polyamide wax.

[0123] The only difference between the preparation method of the thermosetting powder coating E and Preparation Example 1 is that the components of the thermosetting powder coating E are the components provided in this preparation example, while the other process parameters and steps are the same as those in Preparation Example 1.

[0124] Preparation Example 6

[0125] A low-viscosity powder coating a, wherein the low-viscosity powder coating a comprises the following components by weight: 90 parts by weight of bisphenol A type epoxy resin KD211G, 5 parts by weight of diphenylimidazoline, 0.5 parts by weight of hydrogenated castor oil, 3 parts by weight of micron-sized spherical silica, 2 parts by weight of polyamide wax, and 0.5 parts by weight of leveling agent GLP588.

[0126] The low-viscosity powder coating a is prepared by the following method, which includes: mixing the above components and then melting and extruding them at 90°C, followed by sequentially pressing, cooling, pulverizing to 10-90 μm and passing through a 300-mesh sieve to obtain the low-viscosity powder coating a; the melt viscosity of the low-viscosity powder coating a is 2000 mPa·s, and the melt viscosity is tested by the ICI viscosity method. The following preparation examples use the same test method to test the melt viscosity.

[0127] Preparation Example 7

[0128] A low-viscosity powder coating b, wherein the low-viscosity powder coating b comprises the following components by weight: 100 parts by weight of bisphenol A type epoxy resin KD211G, 3 parts by weight of dimethylimidazole, 0.2 parts by weight of hydrogenated castor oil, 0.5 parts by weight of micron-sized spherical silica, 0.5 parts by weight of polyamide wax, and 0.1 parts by weight of leveling agent GLP588; the melt viscosity of the low-viscosity powder coating b is 1000 mPa·s.

[0129] The difference between the preparation method of the low-viscosity powder coating b and preparation example 6 is that the components of the low-viscosity powder coating b are the components provided in this preparation example, while the other process parameters and steps are the same as those in preparation example 6.

[0130] Preparation Example 8

[0131] A low-viscosity powder coating c, wherein the low-viscosity powder coating c comprises the following components by weight: 100 parts by weight of bisphenol A type epoxy resin KD211G, 10 parts by weight of substituted dicyandiamide, 3 parts by weight of hydrogenated castor oil, 5 parts by weight of micron-sized spherical silica, 5 parts by weight of polyamide wax, and 2 parts by weight of leveling agent GLP5882; the melt viscosity of the low-viscosity powder coating c is 3000 mPa·s.

[0132] The preparation method of the low-viscosity powder coating c differs from that of Preparation Example 6 only in that the components of the low-viscosity powder coating c are the components provided in this preparation example; all other process parameters and steps are the same as those in Preparation Example 6.

[0133] Example 1

[0134] A powder coating and its preparation method are disclosed. The preparation method includes: mixing 20 parts by weight of thermosetting powder coating A, 0.5 parts by weight of nano-fumed alumina AluC, 15 parts by weight of benzoin, 60 parts by weight of flake nickel powder (D50 of 10 μm), 5 parts by weight of flake nickel powder (D50 of 2 μm), and 5 parts by weight of spherical nickel powder by high-speed mechanical stirring, and passing the mixture through a 200-mesh sieve to obtain the powder coating.

[0135] Example 2

[0136] A powder coating and its preparation method are disclosed. The preparation method includes: mixing 30 parts by weight of thermosetting powder coating B, 1 part by weight of nano-fumed alumina AluC, 20 parts by weight of benzoin, 80 parts by weight of flake nickel powder (D50 of 10 μm), 10 parts by weight of flake nickel powder (D50 of 2 μm), and 10 parts by weight of spherical nickel powder (D50 of 50 nm) by high-speed mechanical stirring, and passing the mixture through a 200-mesh sieve to obtain the powder coating.

[0137] Example 3

[0138] A powder coating and its preparation method are disclosed. The preparation method includes: mixing 5 parts by weight of thermosetting powder coating C, 0.2 parts by weight of nano-fumed alumina AluC, 10 parts by weight of benzoin, 40 parts by weight of flake nickel powder (D50 of 10 μm), 5 parts by weight of flake nickel powder (D50 of 2 μm), and 5 parts by weight of spherical nickel powder by high-speed mechanical stirring, and passing the mixture through a 200-mesh sieve to obtain the powder coating.

[0139] Example 4

[0140] A powder coating and its preparation method are disclosed. The preparation method includes: mixing 25 parts by weight of thermosetting powder coating D, 0.8 parts by weight of nano-fumed alumina AluC, 18 parts by weight of benzoin, 70 parts by weight of flake nickel powder (D50 is 10 μm), 15 parts by weight of flake nickel powder (D50 is 2 μm), and 5 parts by weight of multi-arm carbon nanotubes by high-speed mechanical stirring, and passing the mixture through a 200-mesh sieve to obtain the powder coating.

[0141] Example 5

[0142] A powder coating and its preparation method are disclosed. The preparation method includes: mixing 30 parts by weight of thermosetting powder coating E, 6 parts by weight of nano-fumed silica A2000, 15 parts by weight of benzoin, 60 parts by weight of flake nickel powder (D50 is 10 μm), 10 parts by weight of flake nickel powder (D50 is 2 μm), and 5 parts by weight of carbon fiber (D50 is 50 nm) by high-speed mechanical stirring, and passing the mixture through a 200-mesh sieve to obtain the powder coating.

[0143] Example 6

[0144] A powder coating and its preparation method are disclosed, which differ from Example 1 only in that the amount of benzoin is 5 parts by weight, while the other raw materials, process steps and parameters are the same as in Example 1.

[0145] Comparative Example 1

[0146] A powder coating and its preparation method are disclosed, which differ from Example 1 only in that benzoin is not added, while the other raw materials, process steps and parameters are the same as those in Example 1.

[0147] Application Example 1

[0148] A method for applying powder coating according to Embodiment 1, the method comprising the following steps:

[0149] (1) The glass fiber reinforced composite material substrate was heat-treated at 110℃ for 3 min;

[0150] (2) Low-viscosity powder coating a is applied to the glass fiber reinforced composite material substrate by electrostatic spraying to form an adhesive layer; the thickness of the adhesive layer is 25 μm.

[0151] (3) The powder coating provided in Example 1 was applied to the adhesive layer by electrostatic spraying, and then placed in a container with a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 100 μm.

[0152] Application Example 2

[0153] A method for applying powder coating according to Embodiment 2 includes the following steps:

[0154] (1) The glass fiber reinforced composite material substrate was heat-treated at 100℃ for 5 min;

[0155] (2) Low-viscosity powder coating b is applied to the glass fiber reinforced composite material substrate by electrostatic spraying to form an adhesive layer; the thickness of the adhesive layer is 50 μm.

[0156] (3) The powder coating provided in Example 2 was applied to the adhesive layer by electrostatic spraying, and then placed in a container with a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 150 μm.

[0157] Application Example 3

[0158] A method for applying powder coating according to Embodiment 3 includes the following steps:

[0159] (1) Heat-treat the medium-density fiberboard substrate at 80°C for 3 minutes;

[0160] (2) Low-viscosity powder coating c is applied to the medium-density fiberboard substrate by electrostatic spraying to form an adhesive layer; the thickness of the adhesive layer is 10 μm.

[0161] (3) The powder coating provided in Example 3 was applied to the adhesive layer by electrostatic spraying, and then placed in a container with a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 60 μm.

[0162] Application Example 4

[0163] A method for applying powder coating provided in Embodiment 4, the method comprising the following steps:

[0164] (1) The glass fiber reinforced composite material substrate was heat-treated at 100℃ for 4 min;

[0165] (2) Low-viscosity powder coating a is applied to the glass fiber reinforced composite material substrate by electrostatic spraying to form an adhesive layer; the thickness of the adhesive layer is 35 μm.

[0166] (3) The powder coating provided in Example 4 was applied to the adhesive layer by electrostatic spraying, and then placed in a container with a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 120 μm.

[0167] Application Example 5

[0168] A method for applying powder coating provided in Embodiment 5, the method comprising the following steps:

[0169] (1) The glass fiber reinforced composite material substrate was heat-treated at 105℃ for 4 min;

[0170] (2) Low-viscosity powder coating a is applied to the glass fiber reinforced composite material substrate by electrostatic spraying to form an adhesive layer; the thickness of the adhesive layer is 30 μm.

[0171] (3) The powder coating provided in Example 5 was applied to the adhesive layer by electrostatic spraying, and then placed in a container with a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 100 μm.

[0172] Application Example 6

[0173] The method for applying powder coating provided in Example 6 differs from Application Example 1 only in step (3) by electrostatic spraying the powder coating provided in Example 6 onto the adhesive layer. The other raw materials, process steps and parameters are the same as in Application Example 1.

[0174] Application Comparative Example 1

[0175] A method for applying the powder coating provided in Comparative Example 1 differs from Application Example 1 only in step (3) by electrostatic spraying the powder coating provided in Comparative Example 1 onto the adhesive layer. All other raw materials, process steps and parameters are the same as in Application Example 1.

[0176] Application Comparative Example 2

[0177] An embodiment 1 provides a powder coating method, the coating method comprising the following steps:

[0178] (1) The glass fiber reinforced composite material substrate was heat-treated at 110°C for 3 min;

[0179] (3) The powder coating provided in Example 1 was applied to a glass fiber reinforced composite material substrate by electrostatic spraying, and placed in a power of 15KW / m 2 The coating is cured in a mid-wave infrared curing oven for 8 minutes to obtain the coating, thus completing the coating process; the thickness of the powder coating is 80 μm.

[0180] Coating performance testing:

[0181] (1) Coating thickness: measured according to GB / T 13452.2-2008;

[0182] (2) Curing temperature of coating: The curing temperature of uncured powder coating was obtained by non-isothermal heating test of uncured powder coating using DSC (manufacturer: TA Instruments, model: Q1000);

[0183] (3) Surface smoothness test and coating appearance: The three-dimensional morphology of the scanned area is obtained by laser confocal scanning microscope (Zeiss 710). The surface roughness Ra value (unit: nm) of the coating is calculated by software to represent the surface smoothness. The smaller the Ra value, the higher the surface smoothness of the coating. Visually observe whether there are pinholes, pores and orange peel phenomenon in the coating.

[0184] (4) Electromagnetic shielding effectiveness test: measured according to GB / T 25471-2010, with a frequency range of 10kHz-3GHz;

[0185] (5) Surface resistance of the coating: tested using an LCR meter (manufacturer: HIOKI; model: IM3536);

[0186] (6) Adhesion test: Tested according to GB / T 9286-2021;

[0187] (7) Hardness test: Tested according to GB / T 6739-2006;

[0188] (8) Moisture and heat resistance test: According to GB / T 1740-2007, the coating was treated for 1000 hours at a temperature of 47℃ and a relative humidity of 96%, and the coating was observed to show signs of loss of gloss and blistering.

[0189] The coatings provided in Application Examples 1-6 and Comparative Examples 1-2 were tested according to the above performance test methods, and the results are shown in Table 1:

[0190] Table 1

[0191]

[0192] As shown in Table 1, the powder coating prepared by the method of the present invention, when applied to a heat-sensitive substrate by the coating method provided by the present invention, results in a smooth and flat coating surface, free from pinholes and pores, free from orange peel phenomenon, high coating hardness, electromagnetic shielding effectiveness ≥48dB, surface resistance ≤4.5Ω, strong adhesion, and good resistance to damp heat.

[0193] As can be seen from the comparison of Application Example 1, Application Example 6 and Application Comparative Example 1, if the amount of film-forming aid added is too small or no film-forming aid is added, the conductive fillers can only form a small amount of conductive network or no conductive network can be formed, resulting in a significant deterioration in the electromagnetic shielding performance of the coating.

[0194] As can be seen from the comparison between Application Example 1 and Application Comparative Example 2, when powder coating is directly applied to the surface of a thermosensitive substrate, the high conductivity powder coating has poor adhesion to the thermosensitive substrate, the amount of powder applied is small, and a continuous coating cannot be formed. The surface smoothness and electromagnetic shielding effectiveness of the coating will all deteriorate.

[0195] The applicant declares that the detailed process equipment and process flow of this invention are illustrated through the above embodiments, but this invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that this invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing a powder coating, characterized in that, The preparation method includes the following steps: (1) heat-treating the heat-sensitive substrate; (2) Apply a low-viscosity powder coating onto the heat-sensitive substrate to form an adhesive layer; (3) After applying the powder coating onto the adhesive layer, it is cured to obtain a powder coating; The powder coating is prepared by the following method, which includes: mixing thermosetting powder coating, film-forming aid and conductive filler and then sieving to obtain the powder coating; By weight, the thermosetting powder coating is 5-30 parts; the film-forming aid is 10-20 parts; and the conductive filler is 50-100 parts. The film-forming aid includes any one or a combination of at least two of benzoin or benzoin derivatives; The thermosetting powder coating is prepared by the following method, which includes: mixing a matrix resin, a curing agent, a nanofiller, optionally a curing accelerator, optionally a leveling agent and optionally a degassing agent, followed by melt extrusion, and then sequentially pressing, cooling, pulverizing and sieving to obtain the thermosetting powder coating; The low-viscosity powder coating has a melt viscosity of 1000-3000 mPa·s at 150 ℃.

2. The preparation method according to claim 1, characterized in that, The sieve used in the preparation method of the powder coating has a mesh size of 180-240.

3. The preparation method according to claim 1, characterized in that, The thermosetting powder coating comprises the following components by weight: 50-100 parts by weight of matrix resin, 5-50 parts by weight of curing agent, and 0.1-2 parts by weight of nanofiller.

4. The preparation method according to claim 3, characterized in that, The matrix resin includes any one or a combination of at least two of epoxy resin, polyester resin, polyurethane or acrylic resin.

5. The preparation method according to claim 4, characterized in that, The epoxy resin includes any one or a combination of at least two of the following: a first bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a linear phenolic epoxy resin.

6. The preparation method according to claim 4, characterized in that, The epoxy equivalent of the epoxy resin is 300-700 g / eq.

7. The preparation method according to claim 4, characterized in that, The polyester resin includes a first carboxyl polyester resin and / or a hydroxyl polyester resin.

8. The preparation method according to claim 7, characterized in that, The acid value of the first carboxylated polyester resin is 40-70 mg KOH / g.

9. The preparation method according to claim 7, characterized in that, The hydroxyl value of the hydroxyl polyester resin is 100-220 mg KOH / g.

10. The preparation method according to claim 4, characterized in that, The acrylic resin includes carboxylated acrylic resin and / or epoxy acrylic resin.

11. The preparation method according to claim 10, characterized in that, The acid value of the carboxylated acrylic resin is 140-200 mg KOH / g.

12. The preparation method according to claim 10, characterized in that, The epoxy equivalent of the epoxy acrylate resin is 500-700 g / eq.

13. The preparation method according to claim 3, characterized in that, The curing agent includes any one or a combination of at least two of the following: triglycidyl isocyanurate, substituted dicyandiamide, 2,6-xylylbiguanidine, blocked polyisocyanate, dodecanoic acid, dicarboxylic acid dihydrazide, acid anhydride, second bisphenol A type epoxy resin, second carboxylated polyester resin, linear phenolic resin, phenolic hydroxyl resin, or hydroxyalkylamide.

14. The preparation method according to claim 13, characterized in that, The epoxy equivalent of the second bisphenol A type epoxy resin is 300-700 g / eq.

15. The preparation method according to claim 13, characterized in that, The acid value of the second carboxylated polyester resin is 40-70 mg KOH / g.

16. The preparation method according to claim 3, characterized in that, The nanofiller includes any one or a combination of at least two of nano-alumina, nano-titanium dioxide, nano-silicon dioxide, nano-magnesium oxide, or nano-zinc oxide.

17. The preparation method according to claim 3, characterized in that, The median particle size of the nanofiller is 30-200 nm.

18. The preparation method according to claim 3, characterized in that, The thermosetting powder coating further includes 0.03-3 parts by weight of curing accelerator.

19. The preparation method according to claim 18, characterized in that, The curing accelerator includes any one or a combination of at least two of imidazole, imidazole derivatives, tertiary amine salts, quaternary ammonium salts, or dibutyltin dilaurate.

20. The preparation method according to claim 3, characterized in that, The thermosetting powder coating also includes 0.1-2 parts by weight of leveling agent.

21. The preparation method according to claim 20, characterized in that, The leveling agent includes any one or a combination of at least two acrylate leveling agents.

22. The preparation method according to claim 3, characterized in that, The thermosetting powder coating further includes 0.5-5 parts by weight of degassing agent.

23. The preparation method according to claim 22, characterized in that, The degassing agent includes polyamide wax.

24. The preparation method according to claim 1, characterized in that, The temperature of the melt extrusion is 80-110 ℃.

25. The preparation method according to claim 1, characterized in that, The particles are pulverized to a size of 10-110 μm.

26. The preparation method according to claim 1, characterized in that, The mesh size of the sieve used in the preparation method of the thermosetting powder coating is 160-200 mesh.

27. The preparation method according to claim 1, characterized in that, The film-forming aid is benzoin.

28. The preparation method according to claim 1, characterized in that, The conductive filler includes any one or a combination of at least two of the following: metal powder, graphite, carbon nanotubes, or carbon fibers.

29. The preparation method according to claim 28, characterized in that, The metal powder includes any one or a combination of at least two of silver powder, copper powder, nickel powder, or silver-coated copper powder.

30. The preparation method according to claim 28, characterized in that, The shape of the metal powder includes flakes and / or spheres.

31. The preparation method according to claim 30, characterized in that, The median particle size of the metal powder when it is in the form of flakes is 2-10 μm.

32. The preparation method according to claim 30, characterized in that, The median particle size of the metal powder when it is spherical is 30-80 nm.

33. The preparation method according to claim 1, characterized in that, The mixed materials in the preparation method of the powder coating further include 0.2-1 parts by weight of dispersing agent.

34. The preparation method according to claim 33, characterized in that, The dispersing agent includes nano-gas phase metal oxides.

35. The preparation method according to claim 34, characterized in that, The nano-vaporized metal oxide includes nano-vaporized aluminum oxide.

36. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 80-110 ℃.

37. The preparation method according to claim 1, characterized in that, The heat treatment time is 3-5 minutes.

38. The preparation method according to claim 1, characterized in that, The thickness of the adhesive layer is 10-50 μm.

39. The preparation method according to claim 1, characterized in that, The thickness of the powder coating is 60-150 μm.

40. The preparation method according to claim 1, characterized in that, The curing method includes infrared curing.

41. The preparation method according to claim 40, characterized in that, The infrared curing power is 5-30 kW / m 2 .

42. The preparation method according to claim 40, characterized in that, The infrared curing time is 3-10 minutes.

43. The preparation method according to claim 1, characterized in that, The low-viscosity powder coating comprises the following components by weight: 90-100 parts epoxy resin, 3-10 parts curing agent, 0.2-3 parts flow aid, 0.5-5 parts micron filler, 0.5-5 parts degassing agent, and 0.1-2 parts leveling agent.

44. The preparation method according to claim 43, characterized in that, The epoxy resin includes bisphenol A type epoxy resin.

45. The preparation method according to claim 43, characterized in that, The curing agent comprises any one or a combination of at least two of the following: substituted dicyandiamide, imidazole, or imidazole derivatives.

46. ​​The preparation method according to claim 43, characterized in that, The flow aid includes hydrogenated castor oil.

47. The preparation method according to claim 43, characterized in that, The micron-filler includes micron-sized spherical silicon oxide.

48. The preparation method according to claim 43, characterized in that, The median particle size of the micron filler is 3-10 μm.

49. The preparation method according to claim 48, characterized in that, The median particle size of the micron filler is 5-8 μm.

50. The preparation method according to claim 43, characterized in that, The degassing agent includes polyamide wax.

51. The preparation method according to claim 43, characterized in that, The leveling agent includes any one or a combination of at least two acrylate leveling agents.

52. The preparation method according to claim 43, characterized in that, The low-viscosity powder coating is prepared by the following method, which includes: mixing epoxy resin, curing agent, flow aid, micron filler, degassing agent and leveling agent, then melting and extruding the mixture, followed by sequential pressing, cooling, pulverizing and sieving to obtain the low-viscosity powder coating.

53. The preparation method according to claim 52, characterized in that, The melt extrusion temperature in the preparation method of the low viscosity powder coating is 80-110 ℃.

54. The preparation method according to claim 52, characterized in that, The sieve used in the preparation method of the low-viscosity powder coating has a mesh size of 200-300.

55. The preparation method according to claim 52, characterized in that, In the preparation method of the low viscosity powder coating, the particle size is 10-90 μm by pulverization.

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