Weather-resistant and corrosion-resistant composite powder coating and preparation method thereof

Abstract

The application discloses a weather-resistant and corrosion-resistant composite powder coating and a preparation method thereof, and relates to the technical field of weather-resistant powder coatings.The weather-resistant and corrosion-resistant composite powder coating comprises the following raw materials in parts by mass: base resin 40-60 parts, curing agent 5-10 parts, weather-resistant filler 5-15 parts, corrosion-resistant filler 10-20 parts, additive 2-8 parts, and weather-resistant agent 0.5-1.5 parts.Compared with the prior art, the weather-resistant agent is prone to migration and volatilization loss, resulting in long-term weather resistance attenuation; the weather-resistant agent is anchored by intermolecular hydrogen bonds with the base resin in the application, and the physical shielding effect of the weather-resistant filler is combined, so that a double-protection system of 'chemical absorption-anchoring + physical reflection' is constructed, the aging process of the coating in long-term ultraviolet light, high-low temperature circulation and other outdoor environments can be significantly delayed, appearance defects such as yellowing, light loss and powdering are reduced, and the physical and mechanical performance stability of the coating can be maintained for a long time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of weather-resistant powder coatings, in particular to a weather-resistant and corrosion-resistant composite powder coating and a preparation method thereof. BACKGROUND

[0002] With the continuous promotion of environmental protection policy and the popularization of green coating concept, the application proportion of solvent-free and low VOC emission powder coatings in outdoor fields (such as traffic barriers, building exterior wall components, outdoor billboards, photovoltaic supports, etc.) is increasing year by year. Such outdoor facilities need to be exposed to the natural environment for a long time, and face complex climate conditions such as strong ultraviolet radiation, high and low temperature cycles, high temperature and humidity, rainwater erosion and day and night temperature difference changes, therefore, weather resistance becomes the core index to determine the service life and protection efficiency of powder coatings - not only requires the coating to maintain the appearance integrity (no obvious yellowing, loss of luster, chalking) for a long time, but also needs to maintain the physical and mechanical properties (adhesion, hardness, flexibility) to avoid the corrosion of the substrate due to the aging failure of the coating, and shorten the product service cycle.

[0003] However, the existing outdoor powder coatings still have significant technical bottlenecks. On the one hand, traditional base resins (such as ordinary epoxy resin, low weather-resistant acrylic resin) are prone to molecular chain rupture and oxidative degradation under long-term ultraviolet radiation, resulting in obvious loss of luster (loss of luster rate > 30%), local chalking or micro-cracks in the coating within 1-2 years, especially in high-altitude strong ultraviolet regions or coastal high-temperature and high-humidity environments, the aging rate is further accelerated; on the other hand, the existing weather modification schemes have limitations: the commonly used hindered amine (HALS) and benzotriazole weathering agents can delay ultraviolet aging in the short term, but they are prone to loss over time due to strong molecular migration, resulting in the decay of long-term weather resistance; some schemes increase the amount of titanium dioxide and other weather-resistant fillers to improve the hiding property, but this easily causes the coating to lose its leveling property, the surface orange peel defect increases, or the adhesion is reduced due to poor compatibility between the filler and the resin.

[0004] In addition, the synergistic effect of "ultraviolet-humidity-temperature cycle" in outdoor environment can accelerate the aging process of the coating - the internal stress formed by rainwater penetration and day and night temperature difference can easily cause the aged coating to peel off, thereby losing its protective effect on the substrate, resulting in the need to frequently renovate municipal facilities, outdoor components, etc., which not only increases the maintenance cost, but also causes resource waste. Therefore, developing a composite powder coating with excellent weather resistance, long-term anti-aging, and good processing performance and appearance quality has become a technical problem to be solved in the field of outdoor powder coatings. SUMMARY

[0005] The application aims at solving the problems of insufficient weather resistance, easy loss of weather resistance agent and poor long-acting property of outdoor powder coatings in the prior art, and provides a weather-resistant and corrosion-resistant composite powder coating and a preparation method thereof, which is prepared by compounding base resin, weather resistance agent with structure 1 and composite filler through a segmented mixing process, can resist ultraviolet aging for a long time, has corrosion resistance and coating performance, and meets the demand of extreme outdoor environment.

[0006] To achieve the above object, the application adopts the technical scheme of a weather-resistant and corrosion-resistant composite powder coating, which comprises the following raw materials in parts by mass: base resin 40-60 parts, curing agent 5-10 parts, weather-resistant filler 5-15 parts, corrosion-resistant filler 10-20 parts, additive 2-8 parts, weather resistance agent 0.5-1.5 parts.

[0007] The additive is composed of leveling agent and defoaming agent, and the mass ratio of the two is 1:1.5.

[0008] The weather resistance agent is a compound shown in formula 1.

[0009] The formula 1 is .

[0010] R1 in the formula 1 is a substituent, and n is the number of substituents.

[0011] The n is selected from 0, 1 and 2.

[0012] The R1 is selected from any one of alkyl with carbon atom number being 1-5, fluorine and nitro.

[0013] Further, the base resin is selected from any one of hydroxyl acrylic resin MACRYNAL ® SM510n, Joncryl ® 587, Joncryl ® 550.

[0014] Further, the curing agent is selected from isocyanuric acid triglycidyl ester.

[0015] Further, the weather-resistant filler is selected from at least one of titanium dioxide, zinc oxide and silicon dioxide.

[0016] Further, the corrosion-resistant filler is selected from at least one of mica powder, glass flake and barium sulfate.

[0017] Further, the leveling agent is selected from at least one of BYK-361n, EFKA-3600 and ADDITOL ® XL490.

[0018] The defoaming agent is selected from at least one of 2-hydroxy-2-phenylphenylacetone, microcrystalline paraffin and BYK-054.

[0019] Further, the weather-resistant agent is any one of the following compounds shown in the following structure:

[0020] ;

[0021] ;

[0022] .

[0023] A preparation method of a weather-resistant and corrosion-resistant composite powder coating, comprising the following steps:

[0024] Step 1: placing the base resin, curing agent, weather-resistant filler, corrosion-resistant filler, and auxiliary agent in a mixer, mixing at a rotation speed of 500-1000 rpm for 30-45 min to obtain a premix;

[0025] Step 2: feeding the premix into a double-screw extruder, controlling the extrusion temperature to be 120-160°C and the screw rotation speed to be 30-60 rpm, and obtaining an extruded material after melt extrusion;

[0026] Step 3: cooling the extruded material to room temperature, crushing it into particles with a particle size of 5-10 mm by a crusher;

[0027] Step 4: feeding the particles obtained in Step 3 into a grinder for grinding, sieving the ground particles through a 80-120 mesh screen to obtain the weather-resistant and corrosion-resistant composite powder coating.

[0028] Further, the mixing process of the mixer in Step 1 is divided into two stages:

[0029] In the first stage, the base resin, weather-resistant filler, and corrosion-resistant filler are added and premixed at a rotation speed of 800-1000 rpm for 20 min;

[0030] In the second stage, the curing agent and auxiliary agent are added and mixed at a rotation speed of 500-800 rpm for 10-25 min;

[0031] and Step 1 is carried out in a nitrogen atmosphere.

[0032] Further, the grinder in Step 4 is an air jet mill or a mechanical crusher; and the particle size distribution of the finally obtained powder coating satisfies: D50 is 30-50 μm, and D90≤80 μm.

[0033] The triazine group and naphthyl group in the weather-resistant agent molecule constitute a heterocyclic conjugated structure, which can efficiently absorb high-energy ultraviolet light (especially in the UV-A and UV-B bands, wavelength 290-400 nm), so that the molecule jumps from the ground state (S0) to the excited state (S1). After absorbing energy, the molecule converts the light energy of ultraviolet light into harmless thermal energy (molecular vibration energy) by non-radiative transition through internal conversion and rapidly releases it to the environment, and the molecule returns to the ground state from the excited state, preparing for the next absorption. This process is reversible and cyclic, so the weather-resistant agent can persistently play a role without being consumed in large quantities. The hydrogen atoms on the amino and imino groups can act as hydrogen bond donors to form strong intermolecular hydrogen bonds with the hydrogen bond acceptors in the base resin in the powder coating system, anchoring the weather-resistant agent molecules in the resin network, greatly reducing the loss caused by small molecule migration or volatilization. Amino / imino can also capture free radicals to prevent radical oxidation.

[0034] The formula of the present application solves the problems of insufficient long-term weather resistance of outdoor powder coatings, easy loss of weather-resistant agents, and decay of coating physical properties through the synergistic design between components. Specifically, it uses hydroxyl acrylate resin and isocyanuric acid triglycidyl ester as the base and curing agent to build a three-dimensional network skeleton with high cross-linking density, effectively locking functional molecules such as weather-resistant agents while providing excellent mechanical properties and chemical medium resistance; the weather-resistant agent realizes ultraviolet light absorption-transformation mechanism through the triazine group and naphthyl group in its molecule, and is anchored by the strong hydrogen bond formed between the amino group / imino group and the carbonyl group of the resin to prevent migration and loss, while also assisting in capturing free radicals; the weather-resistant filler forms a "physical + chemical" double protection with the weather-resistant agent by reflecting and scattering ultraviolet light, and the sheet-like corrosion-resistant filler forms a dense barrier to block the penetration of corrosive media; the leveling agent and defoaming agent are compounded at a ratio of 1:1.5 to ensure a smooth and defect-free coating surface, and the segmented mixing and nitrogen protection process prevents pre-crosslinking, ensuring processing stability and final performance. Through multi-level synergy of chemical bonding, physical shielding, and morphological complementation, the entire system realizes long-term weather resistance, corrosion resistance, high mechanical strength, and appearance integrity of the coating in extreme outdoor environments.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] 1. Long-term weather resistance is significantly improved: Compared with the prior art, where the weather-resistant agent easily loses long-term weather resistance due to migration and volatilization, the present application anchors the weather-resistant agent through intermolecular hydrogen bonds between the specific structure weather-resistant agent and the base resin, combined with the physical shielding effect of the weather-resistant filler, to build a "chemical absorption-anchoring + physical reflection" double protection system, which can significantly slow down the aging process of the coating in long-term ultraviolet light, high-low temperature cycling, and other outdoor environments, reduce appearance defects such as yellowing, loss of gloss, and chalking, and maintain the stability of the coating's physical and mechanical properties over a long period of time.

[0037] 2. Corrosion resistance and coating comprehensive performance synergistic optimization: the existing technology increases the filler to improve the corrosion resistance, which easily leads to the decrease of coating leveling property and adhesion, while the present application forms a dense barrier by using sheet-shaped corrosion-resistant fillers (such as mica powder, glass flake), and cooperates with high cross-linking density of base resin-curing agent network, and at the same time, with specific proportion of leveling agent and defoaming agent, the coating surface smoothness and substrate adhesion are ensured while the corrosion resistance of the coating to the penetration of corrosive medium is strengthened, and the corrosion resistance and appearance and mechanical properties are synergistically improved.

[0038] 3. Processing stability and use reliability are enhanced: compared with the pre-crosslinking problem caused by the existing mixing process, the present application adopts segmented mixing (mixing resin and filler first, and then mixing curing agent and additives) and nitrogen protection process, and combines with precise control of extrusion, grinding parameters and particle size distribution, which effectively avoids the pre-reaction of raw materials, and ensures the stability of the processing process; the final product does not easily appear coating peeling, performance mutation and other problems when serving in extreme outdoor environment, reduces the frequency of outdoor component renovation, improves the use reliability and reduces the maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The nuclear magnetic chart of the weathering agent 1 described in the present application. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0041] Preparation Example 1

[0042] Preparation of weathering agent 1:

[0043] First step:

[0044] Under the atmosphere of flowing nitrogen, 15.00 g of compound A, 6.42 g of compound B, 7.84 g of sodium tert-butoxide and 180 ml of dichloromethane were sequentially added into the reaction system, and after stirring and mixing uniformly, 0.27 g of palladium acetate and 0.53 g of triphenylphosphine were sequentially added, the temperature of the reaction system was raised to 100℃, and the reaction was carried out for 8 h. After the reaction was completed, the reaction liquid was filtered with diatomite, the filter cake was washed with dichloromethane for 2 times, the filtered liquid was spin-dried, and was purified by silica gel column chromatography (the mobile phase was a mixed solution of n-heptane and ethyl acetate), and was spin-dried to obtain 15.16 g of compound C, and HPLC showed that the purity was 99.9%.

[0045] .

[0046] Second step:

[0047] Under the flow of nitrogen, 15.16 g of compound C, 11.71 g of compound D, 6.30 g of sodium tert-butoxide, 0.15 g of ferroferric oxide and 180 ml of DMF were sequentially added into the reaction system, and after stirring and mixing uniformly, 0.07 g of palladium-carbon and 0.43 g of triphenylphosphine were sequentially added, and the temperature of the reaction system was increased to 110°C for 20 h. After the reaction was completed, the reaction solution was filtered with diatomite, the filter cake was washed with dichloromethane for 2 times, the filtered solution was spin-dried, the powder after spin-drying was added into 80 ml of ethanol, heated to 90°C, stirred and refluxed for 3 h, after the stirring was completed, it was placed in a refrigerator at 4°C for 2 h, filtered, and the filter residue was purified by silica gel column chromatography (the mobile phase was a mixed solution of n-heptane and ethyl acetate), spin-dried, and 19.85 g of weather-resistant agent 1 was obtained, and HPLC showed that the purity was 99.9%.

[0048] .

[0049] Structure identification:

[0050] 1. Mass spectrum of compound C m / z: 463 [MS+H + ];

[0051] 2. Mass spectrum of weather-resistant agent 1 m / z: 724 [MS+H + ];

[0052] 3. H NMR of weather-resistant agent 1 1 see Figure 1 .

[0053] Preparation examples 2-6

[0054] Weather-resistant agents 2-6 were sequentially prepared in preparation examples 2-6, and the preparation method of preparation example 1 was referred to, and compound B therein was replaced, and the rest, including the feeding, post-treatment and the like, was the same as that of preparation example 1, and specific reference was made to Table 1.

[0055] Table 1.

[0056]

[0057] Example 1

[0058] Preparation of a weather-resistant and corrosion-resistant composite powder coating

[0059] 1. Raw material components:

[0060] Base resin: hydroxyl acrylate resin MACRYNAL ® SM510n 50 parts, purchased from Zhenxin Resin (China) Co., Ltd.;

[0061] Curing agent: isocyanuric acid triglycidyl ester 8 parts, purchased from Wuhan Yujing Jiasheng Pharmaceutical Co., Ltd.;

[0062] Weather-resistant filler: titanium dioxide 10 parts, zinc oxide 5 parts, titanium dioxide and zinc oxide, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0063] Corrosion-resistant filler: mica powder 12 parts, glass flake 8 parts, mica powder purchased from Wuhan Huaxiang Kejie Biological Technology Co., Ltd., glass flake purchased from Wuhan Prolav Biological Technology Co., Ltd.;

[0064] Auxiliary agent: leveling agent BYK-361n 2 parts, defoaming agent BYK-054 3 parts, BYK-361n and BYK-054 purchased from BYK Additives (Shanghai) Co., Ltd.;

[0065] Weather-resistant agent: weather-resistant agent 1 1.0 part.

[0066] 2. Preparation method:

[0067] Step 1: Put the base resin, weather-resistant filler, and corrosion-resistant filler into a high-speed mixer, and pre-mix under nitrogen atmosphere protection at a speed of 900 rpm for 20 min; add the curing agent, leveling agent, and defoaming agent, adjust the speed to 600 rpm, and continue mixing for 15 min to obtain a premix. The temperature of the material during mixing is controlled at 35°C by jacket cooling water;

[0068] Step 2: Put the premix into a twin-screw extruder (screw diameter 35 mm, L / D = 40:1), set the temperature of each zone of the extruder to 125°C, 135°C, 145°C, and 150°C, respectively, set the screw speed to 50 rpm, melt extrude, the residence time of the material in the machine is 60 seconds, the melt pressure is maintained at 1.2 MPa, and the extruded material is obtained;

[0069] Step 3: After the extruded material is cooled to room temperature by a cooling water tank (water temperature 12°C), it is crushed into particles with a particle size of 6-8 mm by a crusher;

[0070] Step 4: Put the crushed particles into an air jet mill, set the classification wheel speed to 2800 rpm and the grinding pressure to 0.75 MPa, sieve the crushed powder through a vibrating sieve machine (100 mesh screen), collect the fine powder that passes through the screen, and obtain the weather-resistant and corrosion-resistant composite powder coating.

[0071] The particle size distribution of the obtained powder coating is D50=38.2 μm and D90=74.6 μm, which meets the design requirements.

[0072] Examples 2-6

[0073] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant agent was replaced by weather-resistant agent 2-weather-resistant agent 6 in turn, and the rest was the same as Example 1.

[0074] Comparative Example 1

[0075] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant agent was replaced by 2,4,6-tris(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine (UV-1164), and the rest was the same as Example 1.

[0076] Comparative Example 2

[0077] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant agent was replaced by bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin 770), and the rest was the same as Example 1.

[0078] Comparative Example 3

[0079] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant agent was replaced by 2,6-di-tert-butyl-4-methylphenol (BHT), and the rest was the same as Example 1.

[0080] Comparative Example 4

[0081] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant agent was not added, and the rest was the same as Example 1.

[0082] Comparative Example 5

[0083] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the weather-resistant filler was not added, and the rest was the same as Example 1.

[0084] Comparative Example 6

[0085] A weather-resistant and corrosion-resistant composite powder coating was prepared according to the preparation method of Example 1, wherein the corrosion-resistant filler was not added, and the rest was the same as Example 1.

[0086] Performance test:

[0087] Test sample: According to GB / T 9286-1998 "Paints and varnishes Cross-cut test for coatings", first, the Q235 steel plate was sandblasted with quartz sand (particle size 0.8-1.2 mm) to make the surface roughness reach Ra 6.3-12.5 μm to enhance the mechanical anchoring effect of the coating. Then the powder coating was uniformly sprayed on the surface of the steel plate using an electrostatic spraying equipment, and the coating thickness was controlled at 200±10 μm. The sprayed sample was placed in an oven, and the temperature was raised to 180℃ at 10℃ / min, and the temperature was kept for 30 minutes. After cooling to room temperature, the sample was obtained.

[0088] 1. Adhesion test: the test sample was drawn with a single-blade cross-cut knife on the surface of the coating to form a 10x10 grid. The cross-cut depth should penetrate the coating to the substrate surface. A standard 3M 600 adhesive tape (adhesive force 6.2 N / 25 mm) was tightly attached to the cross-cut area, and the surface of the tape was pressed with a rubber eraser to remove air bubbles, and then the tape was quickly torn off at an angle of 90°. The coating peeling condition in the grid area was observed by 4 times magnifying glass, and the adhesion grade was evaluated according to ISO standard: 0 grade for no peeling at the cross-cut intersection, and 5 grade for peeling area >65%. The test results are shown in Table 2.

[0089] 2. UV oxidation resistance test: the test sample was placed in a QUV ultraviolet aging test box, using UVA-340 lamp, radiation intensity 0.71 W / (m 2 ・nm), ultraviolet irradiation stage (temperature 60℃, relative humidity 50%) for 8h, condensation stage (temperature 20℃, relative humidity 95%) for 4h, single cycle 12h, test period 2400h. A miniature gloss meter (60° incident angle) was used to measure the initial (0h) and gloss after each aging period (G0, G 2400 ), respectively, according to the test standard of GB / T 9754-2007, and the light loss rate was calculated according to the formula "(%)=(G0-G 2400 ) / G0x100". The test results are shown in Table 2.

[0090] 3. Weather resistance test: the test sample was placed in a xenon lamp aging test box to simulate the complex outdoor climate environment. The radiation source was an air-cooled xenon lamp, the radiation intensity was 0.51 W / (m 2 ・nm) at 340 nm wavelength, the temperature was controlled (blackboard temperature 63℃, box temperature 45℃), the relative humidity was 65%, the spraying condition was 1 time every 2h, and the spraying time was 18 min each time (deionized water, spraying pressure 0.15 MPa), and the test period was 4500h. A spectrophotometer was used to test the color difference ΔE after aging according to GB / T 11186.3-1989. The test results are shown in Table 2.

[0091] Table 2.

[0092]

[0093] In terms of UV aging resistance (light loss rate) and weather resistance (color difference ΔE), the examples (added with specific structure weathering agent and complete filler system) are significantly better than the comparative examples. Specifically, the light loss rate and color difference of the comparative examples (especially comparative examples 1-4) without the specific weathering agent of the application increase significantly, indicating that the traditional weathering agent or the lack of weathering agent results in insufficient UV aging resistance and color stability of the coating; while the comparative examples such as comparative examples 5 and 6 without weathering filler or corrosion-resistant filler also show performance decline, but the focus of the decline is different, which indicates that the weathering filler mainly contributes to UV shielding, and the corrosion-resistant filler is more focused on blocking environmental media to maintain the adhesion and color retention rate of the coating. In summary, the weathering agent and composite filler system of the application realize the comprehensive improvement of long-term weather resistance and color stability of the coating through the synergistic effect of chemical anchoring, UV absorption conversion and physical shielding.

[0094] Although embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the foregoing embodiment, and that various changes in the form and details thereof can be made by those skilled in the art without departing from the spirit or scope of the application. The scope of the application is defined by the appended claims and their equivalents.

Claims

1. A weather-resistant and corrosion-resistant composite powder coating, characterized in that, The raw materials include the following parts by weight: 40-60 parts base resin, 5-10 parts curing agent, 5-15 parts weather-resistant filler, 10-20 parts corrosion-resistant filler, 2-8 parts additives, and 0.5-1.5 parts weather-resistant agent; The additive consists of a leveling agent and a defoamer, with a mass ratio of 1:1.

5. The weather-resistant agent is a compound represented by Formula 1; Equation 1 is... ; In Formula 1, R1 is a substituent and n is the number of substituents; The n is selected from: 0, 1, 2; R1 is selected from any one of alkyl, fluorine, or nitro groups with 1-5 carbon atoms.

2. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The base resin is selected from: hydroxyl acrylic resin (MACRYNAL). ® SM510n, Joncryl ® 587, Joncryl ® Any one of 550.

3. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The curing agent is selected from triglycidyl isocyanurate.

4. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The weather-resistant filler is selected from at least one of titanium dioxide, zinc oxide, and silicon dioxide.

5. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The corrosion-resistant filler is selected from at least one of mica powder, glass flakes, and barium sulfate.

6. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The leveling agent is selected from: BYK-361n, EFKA-3600, ADDITOL. ® At least one of XL490; The defoamer is selected from at least one of the following: 2-hydroxy-2-phenylacetophenone, microcrystalline wax, and BYK-054.

7. The weather-resistant and corrosion-resistant composite powder coating according to claim 1, characterized in that, The weather-resistant agent is any one of the compounds shown in the following structures: ； ； 。 8. A method for preparing a weather-resistant and corrosion-resistant composite powder coating as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Place the base resin, curing agent, weather-resistant filler, corrosion-resistant filler, and additives into a mixer and mix at 500-1000 rpm for 30-45 minutes to obtain a premix. Step 2: Feed the premixed material into a twin-screw extruder, control the extrusion temperature to be 120-160℃ and the screw speed to be 30-60 rpm, and obtain the extruded material after melt extrusion; Step 3: After cooling the extruded material to room temperature, crush it into particles with a particle size of 5-10 mm using a crusher; Step 4: The particles obtained in Step 3 are fed into a grinder for grinding. After grinding, they are sieved through an 80-120 mesh sieve to obtain the weather-resistant and corrosion-resistant composite powder coating.

9. The method for preparing a weather-resistant and corrosion-resistant composite powder coating according to claim 8, characterized in that, The mixing process of the mixer in step 1 is divided into two stages: The first stage involves adding the base resin, weather-resistant filler, and corrosion-resistant filler, and premixing for 20 minutes at a speed of 800-1000 rpm. In the second stage, the curing agent and additives are added, and the mixture is continued to be mixed at 500-800 rpm for 10-25 minutes. Furthermore, step 1 is performed under a nitrogen atmosphere.

10. The method for preparing a weather-resistant and corrosion-resistant composite powder coating according to claim 8, characterized in that, The grinding mill in step 4 is an air jet mill or a mechanical mill; and the particle size distribution of the final powder coating satisfies: D50 is 30-50μm, D90≤80μm.

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