Preparation method and application of low-temperature rapid curing coil powder coating

Abstract

The application belongs to the technical field of paint, and discloses a preparation method and application of low-temperature rapid curing coiled material powder paint, and the preparation method comprises the following steps: S1, adding raw materials of the low-temperature rapid curing coiled material powder paint into a high-speed mixer, rotating at a speed of 1200-1600 r / min, and mixing for 5-8 min to ensure uniform dispersion of components; S2, adding the mixed material into a double-screw extruder for melting and extrusion, the temperature of the double-screw extruder is 80-90 DEG C in a first zone, 100-110 DEG C in a second zone, 120-130 DEG C in a third zone, and 110-120 DEG C in a fourth zone, and the rotating speed is 200-250 r / min; S3, tabletting and cooling to below 40 DEG C, coarsely crushing, and then using an ACM pulverizer and a grading screen with a mesh size of 80-120 meshes to obtain the low-temperature rapid curing coiled material powder paint, low-temperature curing and rapid film forming are realized through component synergy, the process has high adaptability, and functional fillers, i.e., modified sericite and modified nano-aluminum oxide, are added, and the two fillers synergistically enhance the corrosion resistance, mechanical strength and environmental adaptability of the powder paint film.

Description

Technical Field

[0001] This invention belongs to the field of powder coating technology, specifically relating to a method for preparing and applying a low-temperature rapid-curing roll coating powder. Background Technology

[0002] Metal coils, as a high-efficiency and energy-saving metal processing substrate, are widely used in construction, home appliances, transportation, furniture, and other fields. The performance of their surface protective coating directly determines the service life and application scenarios of the metal coils. Therefore, metal coils need to be coated during processing. Currently, liquid coatings are the main pre-coating agents for metal coils, but the large amount of volatile organic compounds they release puts significant pressure on the environment, greatly hindering their application. Powder coatings, due to their solvent-free evaporation, environmental friendliness, high coating utilization rate, and excellent performance, have become a new type of coating for the surface protection of metal coils. Powder coatings are solid powdered synthetic resin coatings composed of solid resins, pigments, fillers, and additives. Their dispersion medium is air, and they feature solvent-free pollution, 100% film formation, and low energy consumption.

[0003] Traditional metal powder coatings require high curing temperatures, making them unsuitable for coil production lines (where thin substrates deform at high temperatures). Low-temperature curing powders (such as UV curing) require specialized equipment, resulting in high costs and insufficient adhesion. Furthermore, the shortcomings of traditional metal coil powder coatings, including insufficient long-term corrosion resistance, lack of self-healing capabilities, inadequate antibacterial properties, and weak self-cleaning functions, have become key bottlenecks restricting their application in high-end fields. Therefore, developing a novel metal coil powder coating that can cure rapidly at low temperatures and possesses excellent antibacterial, anti-corrosion, and mechanical properties is of great significance for improving the service life of metal coils and expanding their application scenarios. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a method for preparing and applying a low-temperature rapid-curing coil powder coating. This method achieves low-temperature curing and rapid film formation through component synergy, with high process adaptability. Furthermore, the addition of functional fillers, modified sericite, and modified nano-alumina enhances the corrosion resistance, mechanical strength, and environmental adaptability of the powder coating film.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a low-temperature, rapid-curing coil powder coating includes the following steps:

[0007] S1. Add all raw materials of low-temperature fast-curing roll powder coating to a high-speed mixer, rotate at 1200~1600 r / min, mix for 5~8 min, and ensure that the components are evenly dispersed;

[0008] S2. Add the mixture to a twin-screw extruder for melt extrusion. The temperature of the twin-screw extruder is 80~90℃ in zone 1, 100~110℃ in zone 2, 120~130℃ in zone 3, and 110~120℃ in zone 4. The speed is 200~250r / min.

[0009] S3. After pressing and cooling to below 40°C, the powder coating is coarsely crushed and then pulverized using an ACM pulverizer with a grading screen of 80-120 mesh to obtain the low-temperature rapid curing roll coating.

[0010] Preferably, the raw materials for the low-temperature rapid-curing coil powder coating include: 45-55 parts of carboxylated polyester resin, 3-6 parts of β-hydroxyalkylamide, 5-10 parts of epoxy resin, 0.1-0.3 parts of organotin catalyst, 6-12 parts of modified sericite, 15-25 parts of barium sulfate, 1.0-1.5 parts of composite leveling agent, 0.8-1.2 parts of modified nano-alumina, and 0.3-0.6 parts of benzoin;

[0011] The modified sericite is formed by modifying sericite through cerium salt intercalation, then modifying the surface with tannic acid iron complex, and finally coating it with polydopamine and benzotriazole corrosion inhibitor through dopamine self-polymerization.

[0012] The modified nano-alumina was prepared by in-situ growth of nano-zinc oxide on the surface of nano-alumina using a hydrothermal method, followed by loading Ag and carbon quantum dots for co-modification, and finally grafting fluorosilane to achieve superhydrophobic modification.

[0013] Preferably, the carboxylated polyester resin has an acid value of 40-50 mg KOH / g, the epoxy resin has an epoxy equivalent (EEW) of 800, the organotin catalyst is dibutyltin dilaurate, and the composite leveling agent is a mixture of polybutyl acrylate, polydimethylsiloxane, and perfluoropolyether in a mass ratio of 6:3:1.

[0014] Preferably, the preparation method of modified sericite includes the following steps:

[0015] (1) Disperse sericite in deionized water, sonicate for 20-40 min, add 5% of the total mass of sericite cerium nitrate, stir at 80℃ for 4-6 h, centrifuge and wash until neutral, and vacuum dry at 80℃ to obtain cerium salt intercalated modified sericite.

[0016] (2) The intercalated modified sericite was dispersed in a 50 vol% ethanol solution, tannic acid and ferric chloride were added, the reaction was carried out at 60°C for 3-5 h, centrifuged and washed, and dried to obtain sericite with tannic acid iron complex surface modified.

[0017] (3) Disperse the surface-modified sericite in Tris buffer, add dopamine hydrochloride, stir at room temperature for 18-24 h, add benzotriazole and continue stirring for 2-4 h to allow benzotriazole to be adsorbed into the polydopamine porous structure, centrifuge and wash, and vacuum dry at 40 °C to obtain modified sericite.

[0018] Preferably, the mass ratio of the intercalated modified sericite, tannic acid and ferric chloride is 5:2:0.5.

[0019] Preferably, the mass ratio of the surface-modified sericite, dopamine hydrochloride, and benzotriazole is 6:1:0.4.

[0020] Preferably, the method for preparing modified nano-alumina includes the following steps:

[0021] A. Disperse nano-alumina in deionized water, sonicate for 20-40 min, add zinc nitrate and hexamethylenetetramine, and hydrothermally react at 90℃ for 3-5 h to grow nano-zinc oxide on the surface of alumina. Centrifuge, wash, and dry to obtain zinc oxide-coated nano-alumina.

[0022] B. Disperse zinc oxide-coated nano-alumina in deionized water, add silver nitrate and ascorbic acid, stir in the dark for 1-3 hours, add 1 mg / mL carbon quantum dot solution, stir at 60℃ for 3-5 hours to allow carbon quantum dots to adsorb in the gaps between zinc oxide, centrifuge and wash to obtain co-modified nano-alumina.

[0023] C. Disperse the co-modified nano-alumina in ethanol, add heptadecafluorodecyltrimethoxysilane, reflux at 80°C for 4-6 hours to graft fluorosilane onto the surface, centrifuge and wash, and cure at 120°C to obtain the modified nano-alumina.

[0024] Preferably, the mass ratio of nano-alumina, zinc nitrate, and hexamethylenetetramine is 5:2:1.5.

[0025] Preferably, the mass ratio of zinc oxide-coated nano-alumina, silver nitrate, and carbon quantum dots is 4:0.1:0.2.

[0026] The application of a low-temperature rapid-curing coil powder coating in continuous coating of metal coils, wherein the powder coating can be rapidly cured at a low temperature of 130~160℃ for 1~3 minutes, which significantly reduces energy consumption and improves production efficiency.

[0027] The beneficial effects of this invention are:

[0028] This invention relates to a low-temperature, rapid-curing coil powder coating. It uses carboxylated polyester resin as the main resin, β-hydroxyalkylamide as the curing agent, and epoxy resin as an auxiliary resin. An organotin catalyst significantly reduces the activation energy of the reaction between β-hydroxyalkylamide and polyester, promoting low-temperature curing. A composite leveling agent balances wetting and anti-cratering properties, while benzoin inhibits bubbles generated by the β-hydroxyalkylamide reaction. Through synergistic component action, low-temperature curing and rapid film formation are achieved. Functional fillers, modified sericite and modified nano-alumina, are added, synergistically enhancing the corrosion resistance, mechanical strength, and environmental adaptability of the powder coating film. Compared to traditional coil coatings, this invention's powder coating improves salt spray resistance by over 100% through physical barrier, chemical repair, and superhydrophobic synergy. It also possesses self-healing, antibacterial, and self-cleaning properties, making it suitable for applications such as building exteriors, appliance casings, and automotive parts requiring corrosion resistance, weather resistance, and self-cleaning. This low-temperature, rapid-curing powder coating is compatible with existing coil coating lines, requires no equipment modification, and has high process adaptability.

[0029] In this coating, the modified sericite flake structure is stacked in parallel, forming a labyrinth effect that prolongs the penetration path of corrosive media such as water, oxygen, and chloride ions, thus improving the coating's resistance to penetration. When corrosion occurs on the metal surface (local pH fluctuations between acidic and alkaline), the polydopamine coating structure is destroyed, releasing benzotriazole corrosion inhibitor, while the interlayer... Migrating to corrosion sites, the Ce-based passivation film and the triazole adsorption film work together to inhibit corrosion; the polar groups (hydroxyl and amino groups) of the tannic acid iron complex and the polydopamine coating can form hydrogen bonds with the carboxyl groups of the polyester resin, thereby enhancing the bonding force between sericite and the resin matrix and reducing interface defects.

[0030] Modified nano-alumina grafted with heptadecafluorodecyltrimethoxysilane introduces low surface energy fluorocarbon chains, which, combined with the micro-nano rough structure of nano-zinc oxide, results in a coating surface contact angle >150°, reducing moisture adhesion and penetration, and lowering the probability of corrosive media intrusion. The nano-alumina is uniformly dispersed in the resin matrix, filling the micropores of the coating and enhancing its hardness and impact resistance through a nano-reinforcement effect. Ag nanoparticles are slowly released... It inhibits bacterial growth on the coating surface (especially in humid environments), and carbon quantum dots regulate the interfacial charge to stabilize Ag nanoparticles, preventing their oxidation and aggregation, and extending the antibacterial lifespan. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A modified sericite is prepared by modifying the surface of sericite through cerium salt intercalation, followed by surface modification with an iron tannic acid complex, and finally coating it with polydopamine and benzotriazole corrosion inhibitors via dopamine self-polymerization. The preparation method includes the following steps:

[0034] (1) Disperse 10g of sericite in 200mL of deionized water, sonicate for 30min, add cerium nitrate (5% of the total mass of sericite), and stir at 80℃ for 6h. Intercalated between layers, centrifuged and washed until neutral, then vacuum dried at 80°C to obtain cerium salt intercalated modified sericite;

[0035] (2) Disperse 5g of intercalated modified sericite in 100mL of 50vol% ethanol solution, add 2g of tannic acid and 0.5g of ferric chloride, react at 60℃ for 4h, centrifuge, wash, and dry to obtain sericite with tannic acid iron complex surface modified.

[0036] (3) Disperse 3g of surface-modified sericite in 100mL Tris buffer, add 0.5g of dopamine hydrochloride, stir at room temperature for 24h, add 0.2g of benzotriazole and continue stirring for 2h to allow benzotriazole to be adsorbed into the polydopamine porous structure, centrifuge and wash, and vacuum dry at 40℃ to obtain modified sericite.

[0037] Example 2

[0038] A modified nano-alumina is prepared by in-situ growth of nano-zinc oxide on the surface of nano-alumina via a hydrothermal method, followed by loading with Ag and carbon quantum dots for co-modification, and finally grafting with fluorosilane for superhydrophobic modification. The preparation method includes the following steps:

[0039] A. Disperse 5g of nano-alumina in 100mL of deionized water, sonicate for 30min, add 2g of zinc nitrate and 1.5g of hexamethylenetetramine, and hydrothermally react at 90℃ for 4h to grow nano-zinc oxide on the surface of alumina. Centrifuge, wash, and dry to obtain zinc oxide-coated nano-alumina.

[0040] B. Disperse 2g of zinc oxide-coated nano-alumina in 50mL of deionized water, add 0.05g of silver nitrate and 0.01g of ascorbic acid, stir in the dark for 2h, add 100mL of 1mg / mL carbon quantum dot solution, stir at 60℃ for 4h to allow carbon quantum dots to adsorb in the gaps between zinc oxide, centrifuge and wash to obtain co-modified nano-alumina.

[0041] C. Disperse 1g of co-modified nano-alumina in 50mL of ethanol, add 0.5mL of heptadecafluorodecyltrimethoxysilane, reflux at 80℃ for 6h to graft fluorosilane onto the surface, centrifuge and wash, and cure at 120℃ to obtain the modified nano-alumina.

[0042] Example 3

[0043] A method for preparing a low-temperature, rapid-curing coil powder coating includes the following steps:

[0044] S1. Add all raw materials of low-temperature fast-curing roll powder coating into a high-speed mixer, rotate at 1200 r / min, mix for 8 min, and ensure that the components are evenly dispersed.

[0045] S2. Add the mixture to a twin-screw extruder for melt extrusion. The twin-screw extruder temperatures are 80℃ in zone 1, 110℃ in zone 2, 120℃ in zone 3, and 120℃ in zone 4, with a rotation speed of 200 r / min.

[0046] S3. After pressing and cooling to below 40°C, the powder coating is coarsely crushed and then pulverized using an ACM pulverizer with an 80-mesh sieve to obtain the low-temperature rapid curing roll coating.

[0047] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 45 parts of carboxylated polyester resin with an acid value of 50 mg KOH / g, 6 parts of β-hydroxyalkylamide, 5 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.3 parts of dibutyltin dilaurate, 6 parts of modified sericite, 25 parts of barium sulfate, 0.6 parts of polybutyl acrylate, 0.3 parts of polydimethylsiloxane, 0.1 parts of perfluoropolyether, 1.2 parts of modified nano-alumina, and 0.3 parts of benzoin. The modified sericite was prepared in Example 1, and the modified nano-alumina was prepared in Example 2.

[0048] Example 4

[0049] A method for preparing a low-temperature, rapid-curing coil powder coating includes the following steps:

[0050] S1. Add all raw materials of low-temperature fast-curing roll powder coating into a high-speed mixer, rotate at 1600 r / min, mix for 5 min, and ensure that the components are evenly dispersed.

[0051] S2. Add the mixture to a twin-screw extruder for melt extrusion. The twin-screw extruder temperatures are 90℃ in zone 1, 100℃ in zone 2, 130℃ in zone 3, and 110℃ in zone 4, with a rotation speed of 250 r / min.

[0052] S3. After pressing and cooling to below 40°C, the powder coating is coarsely crushed and then pulverized using an ACM mill with a 120-mesh grading screen to obtain the low-temperature rapid curing roll coating.

[0053] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 55 parts of carboxylated polyester resin with an acid value of 40 mg KOH / g, 3 parts of β-hydroxyalkylamide, 10 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.1 parts of dibutyltin dilaurate, 12 parts of modified sericite, 15 parts of barium sulfate, 0.9 parts of polybutyl acrylate, 0.45 parts of polydimethylsiloxane, 0.15 parts of perfluoropolyether, 0.8 parts of modified nano-alumina, and 0.6 parts of benzoin. The modified sericite was prepared in Example 1, and the modified nano-alumina was prepared in Example 2.

[0054] Example 5

[0055] A method for preparing a low-temperature, rapid-curing coil powder coating includes the following steps:

[0056] S1. Add all raw materials of low-temperature fast-curing roll powder coating into a high-speed mixer, rotate at 1450 r / min, mix for 6 min, and ensure that the components are evenly dispersed.

[0057] S2. Add the mixture to a twin-screw extruder for melt extrusion. The twin-screw extruder temperatures are 85℃ in zone 1, 105℃ in zone 2, 125℃ in zone 3, and 115℃ in zone 4, with a rotation speed of 225 r / min.

[0058] S3. After pressing and cooling to below 40°C, the powder coating is coarsely crushed and then pulverized using an ACM pulverizer with a 100-mesh grading screen to obtain the low-temperature rapid curing roll coating.

[0059] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 50 parts of carboxylated polyester resin with an acid value of 45 mg KOH / g, 4.5 parts of β-hydroxyalkylamide, 8 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.2 parts of dibutyltin dilaurate, 9 parts of modified sericite, 20 parts of barium sulfate, 0.72 parts of polybutyl acrylate, 0.36 parts of polydimethylsiloxane, 0.12 parts of perfluoropolyether, 1.0 part of modified nano-alumina, and 0.5 parts of benzoin. The modified sericite was prepared in Example 1, and the modified nano-alumina was prepared in Example 2.

[0060] Comparative Example 1

[0061] The preparation method of a low-temperature rapid curing roll powder coating is the same as in Example 5.

[0062] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 50 parts of carboxylated polyester resin with an acid value of 45 mg KOH / g, 4.5 parts of β-hydroxyalkylamide, 8 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.2 parts of dibutyltin dilaurate, 20 parts of barium sulfate, 0.72 parts of polybutyl acrylate, 0.36 parts of polydimethylsiloxane, 0.12 parts of perfluoropolyether, 1.0 part of modified nano-alumina, and 0.5 parts of benzoin. The modified nano-alumina was prepared in Example 2.

[0063] Comparative Example 2

[0064] The preparation method of a low-temperature rapid curing roll powder coating is the same as in Example 5.

[0065] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 50 parts of carboxylated polyester resin with an acid value of 45 mg KOH / g, 4.5 parts of β-hydroxyalkylamide, 8 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.2 parts of dibutyltin dilaurate, 9 parts of modified sericite, 20 parts of barium sulfate, 0.72 parts of polybutyl acrylate, 0.36 parts of polydimethylsiloxane, 0.12 parts of perfluoropolyether, and 0.5 parts of benzoin. The modified sericite was prepared in Example 1.

[0066] Comparative Example 3

[0067] The preparation method of a low-temperature rapid curing roll powder coating is the same as in Example 5.

[0068] The low-temperature rapid-curing roll powder coating comprises the following raw materials in parts by weight: 50 parts of carboxylated polyester resin with an acid value of 45 mg KOH / g, 4.5 parts of β-hydroxyalkylamide, 8 parts of epoxy resin with an epoxy equivalent EEW = 800, 0.2 parts of dibutyltin dilaurate, 20 parts of barium sulfate, 0.72 parts of polybutyl acrylate, 0.36 parts of polydimethylsiloxane, 0.12 parts of perfluoropolyether, and 0.5 parts of benzoin.

[0069] Performance testing

[0070] The powder coatings prepared in Example 5 and Comparative Examples 1-3 were subjected to performance testing. Cold-rolled steel plates of 150mm × 70mm × 0.8mm were used, and after degreasing, rust removal, and water washing to neutrality, they were dried for later use. Each group of powder coatings was uniformly sprayed onto the substrate surface using an electrostatic powder coating machine, controlling the coating thickness to be 60±5μm. After curing in an oven according to the process, and naturally cooling to room temperature, the following performance tests were conducted after 24 hours. The data are shown in Table 1 below:

[0071] (1) Neutral salt spray test: According to GB / T1771-2007 standard, the sample was scratched and then placed in a salt spray chamber at 35±2℃. Spray a 5% NaCl solution. Take out the sample after 500h, 800h, 900h and 1200h, rinse the surface salt frost with deionized water, dry and observe, record the blistering and rusting of the coating, and measure the corrosion spread width at the scratch.

[0072] (2) Water contact angle test: In accordance with GB / T30447-2013 standard, a contact angle measuring instrument is used to automatically analyze the water droplet profile and calculate the contact angle;

[0073] (3) Pencil hardness test: Refer to GB / T6739-2006 standard, select pencils with hardness grades from 2B to 3H for scratch test, until the pencil can make continuous visible scratches on the coating surface (without penetrating the coating), the hardness of the pencil is the coating hardness grade.

[0074] (4) Falling ball impact strength test: Refer to GB / T2423.5-1995 standard. Fix the sample with the coated surface facing up on the falling ball impact tester. The steel ball has a mass of 1000g and a diameter of 16mm. Starting from a height of 30cm, release the steel ball to fall freely and impact the coating surface (the impact point is ≥25mm from the edge of the sample). After each impact, observe whether the coating cracks or peels off. If the coating is not damaged, increase the height (increase by 10cm each time) and repeat the test until the coating shows visible cracks or peels off. Record the height at this time as the impact strength.

[0075] (5) Self-healing efficiency test: Electrochemical impedance spectroscopy (EIS) was used with a three-electrode system, and the sample was used as the working electrode (exposed area 1 cm²). 2 A platinum sheet was used as the counter electrode, a saturated calomel electrode as the reference electrode, and a 3.5% NaCl solution was used as the electrolyte. Electrochemical impedance spectroscopy (frequency range 10) was performed on the unscratched coating. -2 ~10 5 (Hz, AC signal amplitude 10mV), record the low-frequency impedance modulus |Z|0. Then, use a blade to make a 1cm long scratch in the working electrode area (penetrating the coating to the substrate). Immerse the scratched sample in the electrolyte and test the impedance spectrum at 0h, 24h, and 48h respectively. Record the low-frequency impedance modulus |Z| at 48h. t Calculate the self-repair efficiency, self-repair efficiency = (|Z|) t / |Z|0)×100%, reflecting the degree of coating impedance recovery (the higher the value, the better the self-healing effect);

[0076] (6) Antibacterial test: According to GB / T21510-2008 standard, Escherichia coli (ATCC25922) was inoculated into nutrient broth medium and cultured at 37℃ for 24 h. The culture was then diluted with physiological saline to a bacterial concentration of 10. 6 ~10 7CFU / mL, take a 2cm×2cm coated sample, sterilize with UV for 30 min, place it in a sterile petri dish, add 0.2mL of bacterial suspension, spread it evenly on the coating surface, cover with sterile polyethylene film, and incubate at 37℃ for 24 h. After incubation, add 10mL of physiological saline to rinse the coating surface, take 1mL of the rinsing solution, serially dilute it, spread it on nutrient agar medium, incubate at 37℃ for 48 h, count the colonies, and calculate the antibacterial rate. Antibacterial rate = (number of colonies in control group - number of colonies in experimental group) / number of colonies in control group × 100%.

[0077] Table 1. Performance test results of low-temperature rapid-curing coil powder coatings

[0078]

[0079] The data in Table 1 shows that:

[0080] Example 5 exhibited the best salt spray resistance and the largest water contact angle, attributed to the synergistic effect of modified sericite and nano-alumina. The sheet-like structure of the modified sericite forms a physical barrier, delaying the penetration of corrosive media; the pH-responsive release of benzotriazole and... A passivation film forms at the scratches, achieving self-repair. The modified nano-alumina, with its heptadecafluorodecyltrimethoxysilane-grafted fluorocarbon chains (low surface energy) and the micro-nano rough structure of nano-zinc oxide, synergistically achieves superhydrophobicity, further blocking corrosion pathways. Comparative Example 1's salt spray resistance decreased to 800h. Although the superhydrophobicity of the nano-alumina still blocked water, it lacked the physical barrier and self-repair function of sericite, and corrosion at the scratches could not be inhibited, with an accelerated spread rate. Comparative Example 2 withstood 900h of salt spray. The barrier and self-repair function of sericite remained effective, but the lack of a superhydrophobic layer allowed moisture to easily adhere to and penetrate the coating surface, resulting in a shorter anti-corrosion time than Example 5. Comparative Example 3 performed the worst. Lacking modified nano-alumina, the coating surface relied solely on the polar groups of the resin itself, failing to form a low surface energy and rough structure. It exhibited either hydrophobicity or hydrophilicity, allowing moisture to easily spread and penetrate, leading to rapid intrusion of corrosive media.

[0081] Example 5 and Comparative Example 1 achieved a pencil hardness of 3H, while Comparative Examples 2 and 3 only achieved 2H. This is because the modified nano-alumina is uniformly dispersed in the resin matrix, refining the coating's microstructure through the "nano-filling effect" and thus increasing hardness; while the modified sericite contributed little to the increase in hardness. Example 5 and Comparative Example 1 achieved an impact resistance of 50 cm, while Comparative Example 2 decreased to 40 cm, and Comparative Example 3 only reached 30 cm. The modified nano-alumina enhanced the toughness of the resin matrix through interfacial interactions, absorbing impact energy; although the modified sericite could enhance flexural strength, its effect on improving impact strength was relatively weak.

[0082] Example 5 and Comparative Example 2 both exhibit self-healing efficiencies >80%, and both contain modified sericite. Their polydopamine and benzotriazole coatings release benzotriazole when the pH fluctuates at the scratch site. The migration forms a passivation film, and the self-healing effect is demonstrated through electrochemical impedance recovery. The self-healing efficiency of Comparative Examples 1 and 3 is ≤10% because they lack modified sericite and have no responsive corrosion inhibitor release system, so the scratches cannot be repaired autonomously and the impedance is almost unrecovered.

[0083] Example 5 and Comparative Example 1 both exhibited antibacterial rates >98%, and both contained modified nano-alumina with slowly released nano-silver on their surface. The carbon quantum dots disrupt bacterial cell membranes and enzyme activity, achieving highly efficient antibacterial activity; their stabilizing effect extends the antibacterial lifespan of the nano-silver. The antibacterial rates of Comparative Examples 2 and 3 (<66%) are due to the lack of modified nano-alumina. The release system only has a weak antibacterial effect due to the resin itself, resulting in poor antibacterial efficacy.

[0084] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a low-temperature, rapid-curing roll coating powder, characterized in that, Includes the following steps: S1. Add all raw materials of low-temperature fast-curing roll powder coating to a high-speed mixer, rotate at 1200~1600 r / min, mix for 5~8 min, and ensure that the components are evenly dispersed; S2. Add the mixture to a twin-screw extruder for melt extrusion. The temperature of the twin-screw extruder is 80~90℃ in zone 1, 100~110℃ in zone 2, 120~130℃ in zone 3, and 110~120℃ in zone 4. The speed is 200~250r / min. S3. After pressing and cooling to below 40°C, the powder coating is coarsely crushed and then pulverized using an ACM mill with a grading screen of 80-120 mesh to obtain the low-temperature rapid curing roll material powder coating. The low-temperature rapid-curing coil powder coating comprises the following raw materials in parts by weight: 45-55 parts carboxylated polyester resin, 3-6 parts β-hydroxyalkylamide, 5-10 parts epoxy resin, 0.1-0.3 parts organotin catalyst, 6-12 parts modified sericite, 15-25 parts barium sulfate, 1.0-1.5 parts composite leveling agent, 0.8-1.2 parts modified nano-alumina, and 0.3-0.6 parts benzoin; The modified sericite is formed by modifying sericite through cerium salt intercalation, then modifying the surface with tannic acid iron complex, and finally coating it with polydopamine and benzotriazole corrosion inhibitor through dopamine self-polymerization. The modified nano-alumina is produced by growing nano-zinc oxide in situ on the surface of nano-alumina using a hydrothermal method, then loading Ag and carbon quantum dots for co-modification, and finally grafting fluorosilane for superhydrophobic modification. The acid value of the carboxylated polyester resin is 40~50 mg KOH / g, the epoxy equivalent EEW of the epoxy resin is 800, the organotin catalyst is dibutyltin dilaurate, and the composite leveling agent is a mixture of polybutyl acrylate, polydimethylsiloxane and perfluoropolyether in a mass ratio of 6:3:

1.

2. The method for preparing low-temperature rapid-curing coil powder coating according to claim 1, characterized in that, The preparation method of the modified sericite includes the following steps: (1) Disperse sericite in deionized water, sonicate for 20-40 min, add 5% of the total mass of sericite cerium nitrate, stir at 80℃ for 4-6 h, centrifuge and wash until neutral, and vacuum dry at 80℃ to obtain cerium salt intercalated modified sericite. (2) The intercalated modified sericite was dispersed in a 50 vol% ethanol solution, tannic acid and ferric chloride were added, the reaction was carried out at 60°C for 3-5 h, centrifuged and washed, and dried to obtain sericite with tannic acid iron complex surface modified. (3) Disperse the surface-modified sericite in Tris buffer, add dopamine hydrochloride, stir at room temperature for 18-24 h, add benzotriazole and continue stirring for 2-4 h to allow benzotriazole to be adsorbed into the polydopamine porous structure, centrifuge and wash, and vacuum dry at 40 °C to obtain modified sericite.

3. The method for preparing low-temperature rapid-curing coil powder coating according to claim 2, characterized in that, The mass ratio of the intercalated modified sericite, tannic acid and ferric chloride is 5:2:0.

5.

4. The method for preparing low-temperature rapid-curing coil powder coating according to claim 2, characterized in that, The mass ratio of the surface-modified sericite, dopamine hydrochloride, and benzotriazole is 6:1:0.

4.

5. The method for preparing low-temperature rapid-curing coil powder coating according to claim 1, characterized in that, The preparation method of the modified nano-alumina includes the following steps: A. Disperse nano-alumina in deionized water, sonicate for 20-40 min, add zinc nitrate and hexamethylenetetramine, and hydrothermally react at 90℃ for 3-5 h to grow nano-zinc oxide on the surface of alumina. Centrifuge, wash, and dry to obtain zinc oxide-coated nano-alumina. B. Disperse zinc oxide-coated nano-alumina in deionized water, add silver nitrate and ascorbic acid, stir in the dark for 1-3 hours, add 1 mg / mL carbon quantum dot solution, stir at 60℃ for 3-5 hours to allow carbon quantum dots to adsorb in the gaps between zinc oxide, centrifuge and wash to obtain co-modified nano-alumina. C. Disperse the co-modified nano-alumina in ethanol, add heptadecafluorodecyltrimethoxysilane, reflux at 80°C for 4-6 hours to graft fluorosilane onto the surface, centrifuge and wash, and cure at 120°C to obtain the modified nano-alumina.

6. The method for preparing low-temperature rapid-curing coil powder coating according to claim 5, characterized in that, The mass ratio of the nano-alumina, zinc nitrate, and hexamethylenetetramine is 5:2:1.

5.

7. The method for preparing low-temperature rapid-curing coil powder coating according to claim 5, characterized in that, The mass ratio of the zinc oxide-coated nano-alumina, silver nitrate, and carbon quantum dots is 4:0.1:0.

2.

8. The application of a low-temperature rapid-curing coil powder coating prepared by the method according to any one of claims 1 to 7 in continuous coating of metal coils, characterized in that, The powder coating cures rapidly in 1-3 minutes at a low temperature of 130-160℃, significantly reducing energy consumption and improving production efficiency.

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