Single-layer anti-ultraviolet heavy anti-corrosion powder coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials and protective coatings, and discloses a single-layer anti-ultraviolet heavy-duty powder coating as well as a preparation method and application thereof. The preparation method of the single-layer anti-ultraviolet heavy anti-corrosion powder coating comprises the following steps: adding carboxyl polyester resin, triglycidyl isocyanurate, modified nano silicon dioxide, modified chitosan, 2-(2H-benzotriazole-2-yl)-4, 6-di-tert-pentylphenol, bis (2, 2, 6, 6-tetramethyl-4-piperidinyl) sebacate, flaky aluminum powder, zinc phosphate, BYK-3920, 2-hydroxy-1, 2, 4-triazole-2-yl)-1, 3, 4-triazole-2-yl)-1, 3, 5-triazole-2-yl)-1, 3, 5-triazole-2-yl)-1, 3, 5-triazole-2-yl)-1, 3, 5-triazole-2-yl)-1, 3, 5- The preparation method comprises the following steps: stirring and mixing 2, 2-diphenylethanone and gamma-aminopropyltriethoxysilane at room temperature at 300-350rpm for 10-15min to obtain a mixture, extruding the mixture through a double-screw extruder at the extrusion temperature of 110-120 DEG C and the screw rotation speed of 450-500rpm, and grinding to obtain the single-layer anti-ultraviolet heavy-duty anticorrosive powder coating. The single-layer anti-ultraviolet heavy anti-corrosion powder coating can be applied to metal base material protection. The coating prepared by the invention has good ultraviolet resistance and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer materials and protective coating, in particular to a formula design, a preparation process and an application of a high-performance powder coating, and particularly to a high-durability heavy-duty powder coating capable of realizing excellent anti-ultraviolet aging performance and meeting the requirements of severe corrosion environment (C4-C5 grade) through single coating. BACKGROUND

[0002] Traditional protective systems have various limitations in application. For example, a multi-layer coating system has good protection, but has disadvantages such as complex construction process, long cycle, high VOC emission, poor compatibility between coating layers, difficult quality control, and high total cost. Although a single-layer powder coating mainly composed of epoxy and epoxy polyester has good corrosion resistance and mechanical properties, it has poor weather resistance, and is easy to powder, discolor, and lose luster outdoors, and cannot be used as a long-acting protective topcoat. Therefore, how to avoid this phenomenon is the key to solving the problem, and there is an urgent need in the market for a coating solution that can simplify construction, is environmentally friendly and efficient, has long-term anti-ultraviolet aging and excellent heavy-duty corrosion resistance, effectively combines high corrosion resistance and high weather resistance components in a single layer, and ensures processing stability, leveling, mechanical properties, etc. Patent No. CN120310435A discloses an environmentally friendly epoxy asphalt anticorrosive coating. The coating is simple and convenient to prepare, and has the characteristics of green environmental protection and corrosion resistance, but the anti-ultraviolet aging performance needs to be improved. SUMMARY

[0003] (I) Technical problems solved In view of the deficiencies of the prior art, the present application provides a single-layer anti-ultraviolet heavy-duty powder coating and a preparation method and application thereof. The coating prepared by the present application has good anti-ultraviolet performance and corrosion resistance, and can be applied in metal substrate protection.

[0004] (II) Technical solutions To achieve the above-mentioned object, the present application provides the following technical solution: a single-layer anti-ultraviolet heavy-duty powder coating, comprising the following components by weight: 55-60 parts by weight of carboxyl polyester resin, 8-12 parts by weight of isocyanuric acid triglycidyl ester, 3-5 parts by weight of modified nano-silicon dioxide, 2-4 parts by weight of modified chitosan, 1-2 parts by weight of 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol, 1-1.5 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 8-10 parts by weight of flaky aluminum powder, 3-6 parts by weight of zinc phosphate, 0.6-1 part by weight of BYK-3920, 0.3-0.5 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.2-0.3 parts by weight of gamma-aminopropyl triethoxysilane.

[0005] Further, the preparation method of the modified nanosilica is: Step one: 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 3-mercaptopropionic acid, and p-toluenesulfonic acid were added to tetrahydrofuran solvent, stirred and mixed, then p-toluenesulfonic acid was added, and the reaction was carried out at 65-75℃ for 6-8h. After the reaction was completed, washing and drying were performed, and purification was carried out to obtain intermediate 1. Step two: under the protection of nitrogen gas, intermediate 1 and vinyltriethoxysilane were added to N,N-dimethylformamide solvent, stirred and dispersed, then benzoin dimethyl ether photoinitiator was added, and the reaction was carried out under 365nm ultraviolet light at 30-45℃ for 3-4h. After the reaction was completed, centrifugal separation, washing and drying were performed to obtain intermediate 2. Step three: nanosilica was dispersed in deionized water, ultrasonic treatment was carried out at 55-60℃ for 20-30min, then intermediate 2 was added, stirred and mixed, and the reaction was carried out for 3-4h. After the reaction was completed, centrifugal, suction filtration and drying were performed to obtain modified nanosilica.

[0006] Further, the amount ratio of tetrahydrofuran, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 3-mercaptopropionic acid, and p-toluenesulfonic acid in step one is 40-50mL:2.25-2.28g:1.06-1.08g:0.04-0.05g.

[0007] Further, the amount ratio of N,N-dimethylformamide, intermediate 1, vinyltriethoxysilane, and benzoin dimethyl ether in step two is 22-25mL:2.14-2.18g:2.41-2.45g:0.03-0.05g.

[0008] Further, the amount ratio of nanosilica, deionized water, and intermediate 2 in step three is 3.62-3.66g:28-30mL:2.32-2.38g.

[0009] Further, the preparation method of the modified chitosan is: S1: chitosan was swelled in 3% acetic acid solution for 1-2h, then N,N-diisopropylethylamine and pyrazole-1-carboxamide were added, stirred and mixed, and the reaction was carried out at room temperature for 20-24h. After the reaction was completed, filtration, washing and drying were performed, and column chromatography purification was carried out to obtain guanidylated chitosan. S2: guanidylated chitosan was swelled in 3% acetic acid solution for 2-3h, then stearic acid and p-toluenesulfonic acid were added, stirred at 50-60℃ for 5-8h, and after the reaction was completed, suction filtration, washing and drying were performed to obtain modified chitosan.

[0010] Further, the S1 chitosan, acetic acid, N,N-diisopropyl ethylamine, pyrazole-1-carbamidine are used in a ratio of 1.12-1.15g:18-20mL:4.32-4.36mL:3.83-3.87g.

[0011] Further, the S2 guanidination chitosan, acetic acid, stearic acid, p-toluenesulfonic acid are used in a ratio of 2.03-2.05g:22-25mL:1.65-1.68g:0.04-0.06g.

[0012] Further, the preparation method of the single-layer anti-ultraviolet heavy anti-corrosion powder coating is as follows: carboxyl polyester resin, isocyanuric acid triglycidyl ester, modified nano silicon dioxide, modified chitosan, 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentyl phenol, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, flaky aluminum powder, zinc phosphate, BYK-3920, 2-hydroxy-1,2-diphenyl ethanone, gamma-aminopropyl triethoxysilane are mixed at room temperature under stirring at 300-350rpm for 10-15min to obtain a mixture, the mixture is extruded through a double screw extruder, the extrusion temperature is 110-120 DEG C, the screw rotation speed is 450-500rpm, and grinding is performed to obtain the single-layer anti-ultraviolet heavy anti-corrosion powder coating.

[0013] Further, the single-layer anti-ultraviolet heavy anti-corrosion powder coating is applied in metal substrate protection.

[0014] (Three) beneficial technical effects The present application modifies the nano silicon dioxide by 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, introduces benzotriazole groups, benzotriazole groups can effectively absorb ultraviolet light, and convert light energy into heat energy through intramolecular structure conversion, thereby reducing the damage of ultraviolet light to the coating; and the nano silicon dioxide particles can be uniformly dispersed in the coating due to small size, thereby reducing the penetration depth of ultraviolet light through scattering and reflection of ultraviolet light, improving the anti-ultraviolet aging performance of the coating, and the nano silicon dioxide itself is chemically stable, resistant to acid, alkali and solvent, and not easy to react with corrosive medium, thereby protecting the coating matrix from erosion, improving the corrosion resistance of the coating; the guanidino group is introduced by the reaction of chitosan and N,N-diisopropyl ethylamine, the electron-rich nitrogen atom in the guanidino group can be combined with the empty orbital of the metal substrate surface to form a dense coordination compound film, thereby inhibiting the anodic dissolution reaction and improving the corrosion resistance of the coating, and the conjugated structure in the guanidino group can absorb part of the ultraviolet wave band, and can synergistically enhance the benzotriazole ultraviolet absorber, and then esterification reaction occurs with stearic acid, stearic acid is a fatty acid containing a long carbon chain and a low surface energy, and the introduction of a low surface energy material on the metal surface to prepare a hydrophobic coating can effectively enhance the corrosion resistance of the coating to prevent corrosive ions from etching the metal. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a synthetic reaction formula of intermediate 2.

[0016] Figure 2 is a synthetic reaction formula of modified chitosan. DETAILED DESCRIPTION

[0017] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are 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 fall within the scope of protection of the present application.

[0018] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0019] According to the reference "Research and Application of 2,2,4,4-Tetramethyl-1,3-Cyclobutanediol in Polyester Resin Synthesis and Powder Coatings": with the finished product quality, the formula is as follows: neopentyl glycol: 38-42%, 2,2,4,4-tetramethyl-1,3-cyclobutanediol: 0-5%, terephthalic acid: 58-60%, acidolysis agent: 10-11%, monobutyl tin oxide: 0.06%, other raw materials (triphenyl phosphite, antioxidant and BETP): 0.5%, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, monobutyl tin oxide and a small amount of distilled water are put into a 6L glass reactor, and the temperature is raised to complete dissolution; then terephthalic acid is put in, nitrogen is introduced, and the temperature is raised to 240℃ within 4-5h. During this period, the temperature at the top of the distillation column is kept ≤101℃; sample test acid value after the material is clear and transparent; when the acid value reaches 8-15mg KOH / g, add triphenyl phosphite, acidolysis agent, and raise the temperature to 245℃ again, and keep for 2-3h. During this period, the temperature at the top of the distillation column is kept ≤101℃, and after the temperature at the top of the distillation column is lower than 55℃, the acid value is measured, and when the acid value reaches 45-48mg KOH / g, vacuum polycondensation is carried out at -0.01MPa until the acid value reaches 33-36mg KOH / g, and then the temperature is lowered to about 200℃, antioxidant and BETP are added, stirred uniformly, and then poured out and cooled naturally to obtain a carboxyl polyester resin.

[0020] Example 1 (1) 2.25 g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 1.06 g of 3- mercaptopropionic acid, 0.04 g of p-toluenesulfonic acid were added to 40 mL of tetrahydrofuran solvent, stirred and mixed, and then reacted at 65°C for 6 h. After the reaction was completed, it was washed and dried, purified to obtain intermediate 1; (2) 2.14 g of intermediate 1, 2.41 g of vinyltriethoxysilane were added to 22 mL of N,N-dimethylformamide solvent, stirred and dispersed, and then 0.03 g of benzoin dimethyl ether photoinitiator was added thereto. It was irradiated with ultraviolet light of 365 nm at 30°C for 3 h, and after the completion, it was centrifugally separated, washed and dried to obtain intermediate 2; (3) 3.62 g of nano-silica was dispersed in 28 mL of deionized water, and then ultrasonically treated at 55°C for 20 min. Then, 2.32 g of intermediate 2 was added thereto, stirred and mixed, and then reacted for 3 h. After the reaction was completed, it was centrifuged, suction filtered and dried to obtain modified nano-silica. (4) 1.12 g of chitosan was swelled in 18 mL of 3% acetic acid solution for 1 h, and then 4.32 mL of N,N-diisopropylethylamine, 3.83 g of pyrazole-1-carboxamidine were added thereto, stirred and mixed, and then reacted at room temperature for 20 h. After the reaction was completed, it was filtered, washed and dried, and then column chromatography purified to obtain guanidylated chitosan; (5) 2.03 g of guanidylated chitosan was swelled in 22 mL of 3% acetic acid solution for 2 h, and then 1.65 g of stearic acid, 0.04 g of p-toluenesulfonic acid were added thereto, stirred at 50°C for 5 h, and then after the reaction was completed, it was suction filtered, washed and dried to obtain modified chitosan; (6) 55 parts by weight of carboxyl polyester resin, 8 parts by weight of isocyanuric acid triglycidyl ester, 3 parts by weight of modified nano-silica, 2 parts by weight of modified chitosan, 1 part by weight of 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol, 1 part by weight of bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, 8 parts by weight of flaky aluminum powder, 3 parts by weight of zinc phosphate, 0.6 parts by weight of BYK-3920, 0.3 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.2 parts by weight of γ-aminopropyl triethoxysilane were stirred and mixed at 300 rpm for 10 min at room temperature to obtain a mixture. The mixture was extruded through a twin-screw extruder at an extrusion temperature of 110°C and a screw rotation speed of 450 rpm, and then ground to obtain a single-layer ultraviolet-resistant heavy-duty powder coating.

[0021] Example 2 (1) 2.28 g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 1.08 g of 3- mercaptopropionic acid, 0.05 g of p-toluenesulfonic acid were added to 50 mL of tetrahydrofuran solvent, and the mixture was stirred and mixed, and then reacted at 75°C for 8 h. After the reaction was completed, it was washed and dried, and purified to obtain intermediate 1; (2) 2.18 g of intermediate 1, 2.45 g of vinyltriethoxysilane were added to 25 mL of N,N-dimethylformamide solvent, and the mixture was stirred and dispersed, and then 0.05 g of benzoin dimethyl ether photoinitiator was added thereto, and irradiated with 365 nm ultraviolet light at 45°C for 4 h. After the irradiation was completed, it was centrifuged, washed and dried to obtain intermediate 2; (3) 3.66 g of nano-silica was dispersed in 30 mL of deionized water, and ultrasonically treated at 60°C for 30 min. Then, 2.38 g of intermediate 2 was added thereto, and the mixture was stirred and mixed, and then reacted for 4 h. After the reaction was completed, it was centrifuged, suction filtered and dried to obtain modified nano-silica; (4) 1.15 g of chitosan was swelled in 20 mL of 3% acetic acid solution for 2 h, and then 4.36 mL of N,N-diisopropylethylamine, 3.87 g of pyrazole-1-carboxamidine were added thereto, and the mixture was stirred and mixed, and then reacted at room temperature for 24 h. After the reaction was completed, it was filtered, washed and dried, and column chromatography purified to obtain guanidylated chitosan; (5) 2.05 g of guanidylated chitosan was swelled in 25 mL of 3% acetic acid solution for 3 h, and then 1.68 g of stearic acid, 0.06 g of p-toluenesulfonic acid were added thereto, and the mixture was stirred at 60°C for 8 h. After the reaction was completed, it was suction filtered, washed and dried to obtain modified chitosan; (6) 60 parts by weight of carboxyl polyester resin, 12 parts by weight of isocyanuric acid triglycidyl ester, 5 parts by weight of modified nano-silica, 4 parts by weight of modified chitosan, 2 parts by weight of 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol, 1.5 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 10 parts by weight of flaky aluminum powder, 6 parts by weight of zinc phosphate, 1 part by weight of BYK-3920, 0.5 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.3 parts by weight of γ-aminopropyl triethoxysilane were mixed at room temperature for 15 min with stirring at 350 rpm to obtain a mixture. The mixture was extruded through a twin-screw extruder at an extrusion temperature of 120°C and a screw rotation speed of 500 rpm, and then ground to obtain a single-layer ultraviolet-resistant heavy-duty powder coating.

[0022] Example 3 (1) 2.27 g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 1.07 g of 3-mercaptopropionic acid, 0.04 g of p-toluenesulfonic acid were added to 45 mL of tetrahydrofuran solvent, stirred and mixed, and then reacted at 70°C for 7 h. After the reaction was completed, it was washed and dried, purified, and then intermediate 1 was obtained. (2) 2.16 g of intermediate 1, 2.43 g of vinyltriethoxysilane, and 0.04 g of benzoin dimethyl ether photoinitiator were added to 24 mL of N,N-dimethylformamide solvent, stirred and dispersed, and then irradiated with 365 nm ultraviolet light at 40°C for 3.5 h. After centrifugal separation, washing, and drying, intermediate 2 was obtained. (3) 3.64 g of nanosilica was dispersed in 29 mL of deionized water, ultrasonically treated at 58°C for 25 min, and then 2.35 g of intermediate 2 was added thereto, stirred and mixed, and reacted for 3.5 h. After the reaction was completed, it was centrifuged, suction filtered, and dried to obtain modified nanosilica. (4) 1.14 g of chitosan was swelled in 19 mL of a 3% by mass acetic acid solution for 1.5 h, and then 4.34 mL of N,N-diisopropylethylamine, 3.85 g of pyrazole-1-carboxamidine were added thereto, stirred and mixed, and reacted at room temperature for 22 h. After the reaction was completed, it was filtered, washed, and dried, and then column chromatography purification was performed to obtain guanidylated chitosan. (5) 2.04 g of guanidylated chitosan was swelled in 24 mL of a 3% by mass acetic acid solution for 2.5 h, and then 1.67 g of stearic acid, 0.05 g of p-toluenesulfonic acid were added thereto, stirred at 55°C for 7 h, and then suction filtered, washed, and dried to obtain modified chitosan. (6) 58 parts by weight of carboxyl polyester resin, 10 parts by weight of isocyanuric acid triglycidyl ester, 4 parts by weight of modified nanosilica, 3 parts by weight of modified chitosan, 1 part by weight of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, 1.2 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 9 parts by weight of flaky aluminum powder, 5 parts by weight of zinc phosphate, 0.8 parts by weight of BYK-3920, 0.4 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.2 parts by weight of γ-aminopropyl triethoxysilane were stirred and mixed at 325 rpm for 13 min at room temperature to obtain a mixture. The mixture was extruded through a twin-screw extruder at an extrusion temperature of 115°C and a screw rotation speed of 475 rpm, and then ground to obtain a single-layer ultraviolet-resistant heavy-duty powder coating.

[0023] Example 4 (1) 2.26 g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 1.06 g of 3- mercaptopropionic acid, 0.04 g of p-toluenesulfonic acid were added to 42 mL of tetrahydrofuran solvent, stirred and mixed, and then reacted at 70°C for 7 h. After the reaction was completed, it was washed and dried, purified, and then intermediate 1 was obtained. (2) 2.15 g of intermediate 1, 2.42 g of vinyltriethoxysilane, and 0.03 g of benzoin dimethyl ether photoinitiator were added to 23 mL of N,N-dimethylformamide solvent, stirred and dispersed, and then irradiated with 365 nm ultraviolet light at 35°C for 3 h. After the irradiation was completed, it was centrifuged, washed, and dried to obtain intermediate 2. (3) 3.63 g of nanosilica was dispersed in 28 mL of deionized water, and then ultrasonically treated at 56°C for 22 min. Then, 2.33 g of intermediate 2 was added thereto, stirred and mixed, and then reacted for 3 h. After the reaction was completed, it was centrifuged, suction-filtered, and dried to obtain modified nanosilica. (4) 1.13 g of chitosan was swelled in 18 mL of 3% acetic acid solution for 1 h, and then 4.33 mL of N,N-diisopropylethylamine, 3.84 g of pyrazole-1-carboxamidine were added thereto, stirred and mixed, and then reacted at room temperature for 21 h. After the reaction was completed, it was filtered, washed, and dried, and then column chromatography-purified to obtain guanidylated chitosan. (5) 2.03 g of guanidylated chitosan was swelled in 23 mL of 3% acetic acid solution for 2 h, and then 1.66 g of stearic acid, 0.04 g of p-toluenesulfonic acid were added thereto, stirred at 52°C for 6 h, and then suction-filtered, washed, and dried to obtain modified chitosan. (6) 56 parts by weight of carboxyl polyester resin, 9 parts by weight of isocyanuric acid triglycidyl ester, 3 parts by weight of modified nanosilica, 3 parts by weight of modified chitosan, 1 part by weight of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, 1 part by weight of bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, 8 parts by weight of flaky aluminum powder, 4 parts by weight of zinc phosphate, 0.7 parts by weight of BYK-3920, 0.3 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.2 parts by weight of γ-aminopropyl triethoxysilane were stirred and mixed at 310 rpm for 11 min at room temperature to obtain a mixture. The mixture was extruded through a twin-screw extruder at an extrusion temperature of 112°C and a screw rotation speed of 460 rpm, and then ground to obtain a single-layer ultraviolet-resistant heavy-duty powder coating.

[0024] Example 5 (1) 2.27 g of 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 1.08 g of 3-mercaptopropionic acid, and 0.05 g of p-toluenesulfonic acid were added to 48 mL of tetrahydrofuran solvent, and the mixture was stirred and mixed, followed by reaction at 72°C for 8 h. After the reaction was completed, the product was washed and dried, and purified to obtain intermediate 1; (2) 2.17 g of intermediate 1 and 2.44 g of vinyltriethoxysilane were added to 24 mL of N,N-dimethylformamide solvent, and the mixture was stirred and dispersed, followed by addition of 0.05 g of benzoin dimethyl ether photoinitiator. The mixture was irradiated with ultraviolet light of 365 nm at 42°C for 4 h. After the irradiation was completed, the product was centrifuged, washed, and dried to obtain intermediate 2; (3) 3.65 g of nanosilica was dispersed in 30 mL of deionized water, and the mixture was ultrasonically treated at 58°C for 25 min. Then, 2.36 g of intermediate 2 was added to the mixture, and the mixture was stirred and mixed for 4 h. After the reaction was completed, the product was centrifuged, filtered, and dried to obtain modified nanosilica. (4) 1.14 g of chitosan was swelled in 20 mL of 3% acetic acid solution for 2 h, and then 4.35 mL of N,N-diisopropylethylamine, 3.86 g of pyrazole-1-carboxamidine were added to the mixture, which was stirred and mixed. The mixture was reacted at room temperature for 23 h. After the reaction was completed, the product was filtered, washed, and dried, and column chromatography was performed to obtain guanidylated chitosan. (5) 2.05 g of guanidylated chitosan was swelled in 24 mL of 3% acetic acid solution for 3 h, and then 1.67 g of stearic acid and 0.06 g of p-toluenesulfonic acid were added to the mixture, which was stirred at 58°C for 8 h. After the reaction was completed, the product was filtered, washed, and dried to obtain modified chitosan. (6) 60 parts by weight of carboxyl polyester resin, 11 parts by weight of isocyanuric acid triglycidyl ester, 5 parts by weight of modified nanosilica, 3 parts by weight of modified chitosan, 2 parts by weight of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol, 1.5 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 9 parts by weight of flaky aluminum powder, 5 parts by weight of zinc phosphate, 1 part by weight of BYK-3920, 0.5 parts by weight of 2-hydroxy-1,2-diphenyl ethanone, and 0.3 parts by weight of γ-aminopropyl triethoxysilane were mixed at room temperature for 15 min at 340 rpm to obtain a mixture. The mixture was extruded through a twin-screw extruder at an extrusion temperature of 118°C and a screw rotation speed of 500 rpm, and then ground to obtain a single-layer ultraviolet-resistant heavy-duty powder coating.

[0025] Comparative Example 1 In the present comparative example, nanosilica was used instead of modified nanosilica, as compared with Example 5.

[0026] Comparative Example 2 This comparative example is different from Example 5 in that chitosan is used instead of modified chitosan.

[0027] Performance test: The powder coatings prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests.

[0028] Preparation of coating: seven pieces of plywood with a size of 100 mm x 100 mm x 5 mm were taken as substrates, dried in a drying oven at 60°C for 2 h for standby, and the powder coatings prepared in Examples 1-5 and Comparative Examples 1-2 were evenly brushed on the surface of the plywood for 3 times with an interval of about 10 min, and dried at room temperature for 24 h. After being coated on the surface of the plywood, the final thickness of the dried composite coating reached 0.5 mm ± 0.001 mm.

[0029] (1) Anti-UV aging test: the anti-UV performance of the epoxy resin coating was detected according to GB / T14522-93 "Paints. Test method for UV resistance of epoxy coatings", and the detailed operation was as follows: the coated and dried plywood was placed in a UV aging test box to ensure that the surface of the plywood could uniformly receive UV radiation. The UV radiation intensity should be controlled between 0.35 W / m 2 and 0.55 W / m 2 , the temperature was set to (60±3) °C, the relative humidity was set to (65±5) %, and the test time was 800 h. The gloss change of the coating was recorded, and the test results are shown in Table 1.

[0030] Table 1: Anti-UV aging test.

[0031] As can be seen from Table 1, the powder coatings prepared in Examples 1-5 have better anti-UV aging performance than the powder coatings prepared in Comparative Examples 1-2.

[0032] (2) Corrosion resistance test: the prepared plywood coating was subjected to corrosion resistance test, and the test conditions were 20% sulfuric acid immersion, 20% sodium hydroxide immersion, and 5% sodium chloride salt spray. The test results are shown in Table 2.

[0033] Table 2: Corrosion resistance test.

[0034] As can be seen from Table 2, the powder coatings prepared in Examples 1-5 have better corrosion resistance than the powder coatings prepared in Comparative Examples 1-2.

[0035] It should be noted that, in the present document, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0036] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0037] Those skilled in the art should understand that the above only describes several specific embodiments of the present application, rather than all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications and improvements that do not exceed the scope of the claims should be considered as the protection scope of the present application.

Claims

1. A single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating, characterized in that: The invention comprises the following components by weight: 55-60 parts by weight of carboxyl polyester resin, 8-12 parts by weight of triglycidyl isocyanurate, 3-5 parts by weight of modified nano-silica, 2-4 parts by weight of modified chitosan, 1-2 parts by weight of 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol, 1-1.5 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, 8-10 parts by weight of flaky aluminum powder, 3-6 parts by weight of zinc phosphate, 0.6-1 parts by weight of BYK-3920, 0.3-0.5 parts by weight of 2-hydroxy-1,2-diphenylacetone, and 0.2-0.3 parts by weight of gamma-aminopropyltriethoxysilane.

2. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 1, characterized in that: The preparation method of the modified nano-silica is: Step 1: Add 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and 3-mercaptopropionic acid to tetrahydrofuran solvent, stir and mix, then add p-toluenesulfonic acid, react at 65-75°C for 6-8 hours. After the reaction is completed, wash, dry, and purify to obtain intermediate 1; Step 2: Under nitrogen protection, add intermediate 1 and vinyl triethoxysilane to N,N-dimethylformamide solvent, stir and disperse, then add benzoin dimethyl ether photoinitiator, irradiate with 365nm ultraviolet light at 30-45°C for 3-4h, centrifuge, wash and dry to obtain intermediate 2; Step 3: Disperse the nano-silica in deionized water, ultrasonically treat at 55-60°C for 20-30 minutes, then add the intermediate 2, stir and mix, and continue the reaction for 3-4 hours. After the reaction is completed, centrifuge, filter, and dry to obtain modified nano-silica.

3. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 2, characterized in that: In the step 1, the usage ratio of tetrahydrofuran, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 3-mercaptopropionic acid, and p-toluenesulfonic acid is 40-50 mL: 2.25-2.28 g: 1.06-1.08 g: 0.04-0.05 g.

4. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 2, characterized in that: In the step 2, the usage ratio of N,N-dimethylformamide, intermediate 1, vinyltriethoxysilane, and benzoin dimethyl ether is 22-25 mL: 2.14-2.18 g: 2.41-2.45 g: 0.03-0.05 g.

5. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 2, characterized in that: In the step 3, the usage ratio of nano-silica, deionized water, and intermediate 2 is 3.62-3.66 g: 28-30 mL: 2.32-2.38 g.

6. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 1, characterized in that: The preparation method of the modified chitosan is: S1: Chitosan is swelled in a 3% by mass acetic acid solution for 1-2 hours, and then N,N-diisopropylethylamine and pyrazole-1-carboxamidine are added thereto, stirred and mixed, and reacted at room temperature for 20-24 hours. After the reaction is completed, the mixture is filtered, washed, dried, and purified by column chromatography to obtain guanylated chitosan; S2: The guanidinated chitosan is swelled in a 3% by mass acetic acid solution for 2-3 hours, and then stearic acid and p-toluenesulfonic acid are added. The mixture is stirred at 50-60°C for 5-8 hours. After the reaction is completed, the mixture is filtered, washed and dried to obtain the modified chitosan.

7. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 6, characterized in that: The usage ratio of chitosan, acetic acid, N,N-diisopropylethylamine, and pyrazole-1-carboxamidine in S1 is 1.12-1.15 g: 18-20 mL: 4.32-4.36 mL: 3.83-3.87 g.

8. The single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating according to claim 6, characterized in that: The usage ratio of guanidinated chitosan, acetic acid, stearic acid and p-toluenesulfonic acid in S2 is 2.03-2.05 g:22-25 mL:1.65-1.68 g:0.04-0.06 g.

9. A method for preparing a single-layer UV-resistant heavy-duty anti-corrosion powder coating according to any one of claims 1 to 8, characterized in that: The preparation method of the single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating comprises the following steps: carboxyl polyester resin, triglycidyl isocyanurate, modified nano-silica, modified chitosan, 2-(2H-benzotriazole-2-yl)-4,6-di-tert-amylphenol, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, flaky aluminum powder, zinc phosphate, BYK-3920, 2-hydroxy-1,2-diphenylacetone, and γ-aminopropyltriethoxysilane are stirred and mixed at room temperature at 300-350 rpm for 10-15 minutes to obtain a mixture; the mixture is extruded through a twin-screw extruder at an extrusion temperature of 110-120° C. and a screw speed of 450-500 rpm; and the mixture is ground to obtain a single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating.

10. An application of a single-layer UV-resistant heavy-duty anti-corrosion powder coating according to any one of claims 1 to 8, characterized in that: Application of the single-layer anti-ultraviolet heavy-duty anti-corrosion powder coating in metal substrate protection.

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