Antibacterial anti-discoloration composite coating for silver-based component and preparation method of antibacterial anti-discoloration composite coating

Abstract

The invention relates to the technical field of silver-based material surface protection, in particular to an antibacterial and anti-discoloration composite coating for a silver-based component and a preparation method of the antibacterial and anti-discoloration composite coating. The antibacterial and anti-discoloration composite coating comprises a nanometer sealing film bottom layer and an antibacterial and anti-discoloration film top layer. The coating provided by the invention adopts a composite structure of the nano sealing film bottom layer and the antibacterial anti-discoloration film top layer, can effectively prevent discoloration and bacteria, can keep gloss and has strong binding force.

Description

Technical Field

[0001] This application relates to the technical field of surface protection for silver-based materials, and in particular to an antibacterial and anti-discoloration composite coating for silver-based components and its preparation method. Background Technology

[0002] Silver-based components for personal adornment (including portable silver-based decorative pieces and silver-based parts used in high-frequency contact and close contact with the skin) have become a preferred material in the decoration field due to their unique metallic luster, excellent ductility, and chemical stability. However, in actual scenarios where they are worn on the body, they face two major challenges:

[0003] Firstly, silver-based materials are prone to oxidation and discoloration. When worn, the components frequently come into contact with human sweat (containing chloride ions and sulfides), environmental moisture, and sulfur-containing media (such as hydrogen sulfide in the air and cosmetic ingredients). Silver reacts chemically with these substances, producing black products such as silver sulfide (Ag2S) and forming a dense discolored film. This causes the components to lose their original metallic luster, severely diminishing their decorative value. Conventional cleaning methods can only temporarily restore the surface condition and easily abrade the surface of the components. In addition, the friction from frequent contact with clothing and skin further accelerates the discoloration process, making maintaining the luster a significant challenge.

[0004] Secondly, there are significant hygiene and safety risks. Because these components need to be in close contact with the body or in frequent contact with the external environment, their surfaces easily absorb sweat, dust, and microorganisms, providing a suitable breeding ground for bacteria. Long-term wear may cause skin discomfort or even cross-infection. Among them, silver-based components used close to the body have even stricter requirements for antibacterial performance.

[0005] To address the two major challenges of oxidation discoloration and hygiene safety, existing technologies have developed various surface treatment solutions, but all have significant limitations and cannot form a comprehensive solution.

[0006] In terms of anti-discoloration treatment, the shortcomings of traditional technologies are concentrated in the actual needs of wearable scenarios: chemical passivation processes (such as chromate passivation) have insufficient film density, and oxygen and moisture can easily penetrate in humid and multi-media contact conditions, which can only maintain the protection cycle for a few months and cannot achieve long-term anti-discoloration; electroplating layers (such as rhodium plating and palladium plating) can improve wear resistance in the short term, but the process is complicated and the cost is high, and it is easy to fall off in the high-frequency friction of wearing, and the exposed silver base surface will quickly discolor, and some plating layers will also change the original metallic texture of the silver base component; organic coatings have the problem of poor interface compatibility with silver base substrates, are easy to peel off and fail in wearable friction, and some coatings have poor transparency, which will directly cover the natural luster of the silver base and further reduce the decorative value.

[0007] In terms of antibacterial treatment, existing technologies mostly focus on achieving a single function and fail to meet the requirements of both anti-discoloration and gloss maintenance. For example, Chinese invention patent CN112980231A forms an antibacterial layer by mixing nanodiamond particles and silver-silicon carbide composite nanoparticles into the coating or embedding them into the surface through mechanical polishing. Although it can achieve the antibacterial effect, it cannot solve the problem of oxidation and discoloration of silver-based components. Moreover, the mechanical polishing embedding method is prone to damaging the integrity of the component surface and destroying the decorative gloss, making it unsuitable for high-precision decorative scenarios. Other silver-based antibacterial agents (such as silica / silver composite powder) have improved their own stability through the core-shell structure, but they have defects such as photochromism of the silver component and poor water resistance (unable to withstand repeated erosion by sweat). They cannot achieve the function of preventing discoloration and may further damage the gloss due to photochromism.

[0008] In summary, existing surface treatment technologies for silver-based components either focus only on a single function such as anti-discoloration or antibacterial properties, or sacrifice the substrate adhesion or the original gloss of the component when solving a certain problem. They cannot simultaneously meet the comprehensive needs of anti-discoloration, antibacterial, gloss preservation, and strong adhesion in everyday scenarios. There is an urgent need to develop suitable technologies to fill the technological gap and meet the market's demand for performance upgrades in silver-based decorative components. Summary of the Invention

[0009] This application provides an antibacterial and anti-discoloration composite coating for silver-based components and its preparation method. The coating of this application adopts a composite structure of "nano-sealed film bottom layer + antibacterial and anti-discoloration film top layer", which can effectively prevent discoloration and resist bacteria, while maintaining gloss and having strong adhesion.

[0010] In a first aspect, this application provides a silver-based antibacterial and anti-discoloration composite coating for components, employing the following technical solution:

[0011] A silver-based antibacterial and anti-discoloration composite coating for components, the antibacterial and anti-discoloration composite coating comprising a nano-sealed film bottom layer and an antibacterial and anti-discoloration film top layer.

[0012] Optionally, the nano-sealed membrane is prepared using a nano-sol; the preparation method of the nano-sol is as follows: 12-16 vol% of tetraethyl orthosilicate and 4-6 vol% of tetrabutyl titanate are added to a mixed solvent of ethanol and deionized water in a volume ratio of 2:1; 3-5 wt% of ultrasonically dispersed β-cyclodextrin encapsulating thymol microcapsules are added; then 1-2 wt% of bisphenol A type epoxy resin is added; then 0.4-0.6 g / L of silane coupling agent KH-550 and 0.3-0.5 g / L of silane coupling agent KH-570 are added; the pH value is adjusted to 3.5-4.0 with dilute hydrochloric acid, and the mixture is stirred and hydrolyzed at 35-45℃ for 90-120 min to obtain a uniform and stable nano-sol.

[0013] Optionally, the antibacterial and anti-discoloration film is prepared using an antibacterial and anti-discoloration coating; the preparation method of the antibacterial and anti-discoloration coating is as follows: Ag-Cu-MOFs@MC is added to anhydrous ethanol for ultrasonic dispersion pretreatment; the dispersed Ag-Cu-MOFs@MC is added to waterborne acrylic-polyurethane resin at an addition amount of 5~7wt%; then 0.8~1.2wt% CTS-QAS is added and stirred until uniform; 2.0~3.0wt% CeO2-x and 0.5~0.8wt% GQDs are added and stirring is continued; 0.5~1wt% polycarboxylate dispersant is added and dispersed at a speed of 1500~2000r / min for 40~60min, during which ultrasonic treatment at 280~320W is performed for 15~25min to ensure that each component is uniformly dispersed and free from agglomeration.

[0014] Secondly, this application provides a method for preparing an antibacterial and anti-discoloration composite coating for silver-based components, using the following technical solution:

[0015] A method for preparing an antibacterial and anti-discoloration composite coating for silver-based components, the method specifically comprising the following steps:

[0016] (1) Substrate pretreatment: The silver-based components are degreased and polished in sequence;

[0017] (2) Preparation of the nano-sealed film bottom layer: The pretreated silver-based component is immersed in the nano-sol and pulled at a uniform speed of 7~9cm / min to ensure that the sol uniformly covers the surface of the substrate; after coating and curing, 20~30 Al2O3 nano-layers are deposited on the film surface to obtain the nano-sealed film bottom layer; the preparation method of the nano-sol is as follows: 12~16 vol% of tetraethyl orthosilicate and 4~6 vol% of tetrabutyl titanate are added to a mixed solvent of ethanol and deionized water with a volume ratio of 2:1; 3~5 wt% of tetrabutyl titanate is added to the mixture. β-cyclodextrin, after ultrasonic dispersion, is encapsulated with thymol microcapsules; then 1-2 wt% bisphenol A type epoxy resin is added; then 0.4-0.6 g / L silane coupling agent KH-550 and 0.3-0.5 g / L silane coupling agent KH-570 are added; the pH value is adjusted to 3.5-4.0 with dilute hydrochloric acid, and the mixture is stirred and hydrolyzed at 35-45℃ for 90-120 min to obtain a uniform and stable nano-sealed membrane;

[0018] (3) Preparation of the top layer of antibacterial and anti-discoloration film: The top layer of antibacterial and anti-discoloration film is formed on the surface of the nano-sealed film by air spraying, i.e., cross spraying. The preparation method of the antibacterial and anti-discoloration coating is as follows: Ag-Cu-MOFs@MC is added to anhydrous ethanol for ultrasonic dispersion pretreatment. Ag-Cu-MOFs@MC is added to waterborne acrylic-polyurethane resin at an addition amount of 5~7wt%. Then, 0.8~1.2wt% CTS-QAS is added and stirred evenly. 2.0~3.0wt% CeO2-x and 0.5~0.8wt% GQDs are added and stirred continuously. 0.5~1wt% polycarboxylate dispersant is added and dispersed at a speed of 1500~2000r / min for 40~60min. During this period, ultrasonic treatment at 280~320W is performed for 15~25min to ensure that each component is evenly dispersed and free from agglomeration.

[0019] (4) Post-treatment: The silver-based components with the composite coating prepared are subjected to low-temperature curing and surface finishing treatment, that is, an antibacterial and anti-discoloration composite coating is obtained on the surface of the silver-based components.

[0020] This application removes the oxide layer and impurities from the surface of silver-based components through substrate pretreatment, while avoiding excessive corrosion of the silver substrate. A dense nano-sealing film underlayer is formed on the pretreated substrate surface using a nano-sol-gel process, filling the micropores on the silver surface and blocking oxygen and moisture penetration. An antibacterial and anti-discoloration film top layer is prepared by mixing antibacterial components with an anti-discoloration modified resin, and then uniformly coating the surface of the nano-sealing underlayer using a spraying process, followed by curing to form the antibacterial and anti-discoloration film top layer. Post-treatment ensures a smooth coating surface that is compatible with the decorative appearance of the silver-based components. In this application, the nano-sealing film underlayer provides basic anti-discoloration protection, while the antibacterial and anti-discoloration film top layer simultaneously provides antibacterial and enhanced anti-discoloration functions, resulting in a dual synergistic improvement in overall performance.

[0021] The bottom layer of the nano-sealed membrane breaks through the traditional "single barrier" logic and introduces a dual mechanism of "intelligent response antibacterial + dense cross-linking barrier". Corrosion-triggered antibacterial is achieved through β-cyclodextrin encapsulation microcapsules (β-CD@TP), and the interpenetrating network formed by bisphenol A epoxy resin (E51) and silane-titanium ester solves the membrane brittleness. The atomic layer deposition (ALD) Al2O3 layer seals the micropores, thus constructing a "active antibacterial + passive barrier" defense line.

[0022] Specifically, the core principle of the bottom layer of the nano-sealed membrane is as follows: The bottom layer is "responsive antibacterial": The wall material of β-CD@TP microcapsules contains pH-sensitive carboxyl groups. When corrosive media (H⁺, Cl⁻) invade, the wall material swells and ruptures to release thymol, realizing "antibacterial action is initiated as soon as corrosion occurs"; The bottom layer is "dense barrier": Bisphenol A epoxy resin (E51) and silane-titanium ester form an interpenetrating network to improve the toughness of the membrane. 20~30 layers of Al2O3 (uniform particle size, no pores) are deposited by ALD to block the penetration of oxygen / moisture / corrosive media.

[0023] The top layer of the antibacterial and anti-discoloration film breaks away from the traditional framework of "single antibacterial + single anti-discoloration". It adopts a synergistic design of "dynamic slow-release antibacterial + broad-spectrum anti-discoloration + anti-fouling carrier". Mesoporous carbon-loaded Ag⁺-Cu²⁺-MOFs (Ag-Cu-MOFs@MC) achieve long-lasting antibacterial effect, and sulfur vacancy cerium dioxide (CeO2-x) and graphene quantum dots (GQDs) form a triple anti-discoloration mechanism.

[0024] Specifically, the core principle of the top layer of the antibacterial and anti-discoloration film is as follows: Top layer "dynamic antibacterial": Ag-Cu-MOFs@MC controls the release rate of Ag⁺ / Cu²⁺ through mesoporous carbon slow-release channels. The porous structure of MOFs captures bacteria, Ag⁺ destroys the bacterial film, and Cu²⁺ inhibits enzyme activity. Combined with the contact antibacterial effect of chitosan grafted quaternary ammonium salt (CTS-QAS), it achieves "long-lasting and broad-spectrum" antibacterial effect; Top layer "broad-spectrum anti-discoloration": CeO2-x preferentially adsorbs H2S through sulfur vacancies and catalyzes its decomposition into S and H2O. GQDs use reducing properties to inhibit silver surface oxidation. The dual mechanism blocks the "sulfur-silver reaction" and "silver oxidation" pathways.

[0025] Optionally, in the preparation of the nano-sealing membrane substrate, the amount of bisphenol A type epoxy resin added is 1.5-2 wt%.

[0026] Optionally, in the preparation of the nano-sealed membrane bottom layer, the deposited Al2O3 nanolayers are 25-30 layers.

[0027] Optionally, in the preparation of the nano-sealed film substrate, the coating process utilizes electrostatic assisted spraying with a voltage of 6.5-8KV.

[0028] Optionally, in the preparation of the top layer of the antibacterial and anti-discoloration film, the amount of CeO2-x added is 2.5~3.0wt%.

[0029] Optionally, in the preparation of the top layer of the antibacterial and anti-discoloration film, the spraying process utilizes electrostatic assisted spraying with a voltage of 13-15KV.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] (1) Significant anti-discoloration effect: The nano-sealed bottom layer fills the micropores on the surface of the silver base, blocking the penetration of oxygen and moisture. Combined with the enhanced protection of the antibacterial and anti-discoloration top layer, the silver base components will not turn black or discolor for a long time when placed at room temperature, and the decorative effect is long-lasting.

[0032] (2) Excellent antibacterial properties: The top layer, which is antibacterial and anti-discoloration, contains antibacterial ingredients and has an antibacterial rate of over 99% against common pathogens, thus solving the hygiene and safety hazards of personal use.

[0033] (3) The coating is firmly bonded: the pretreatment process and composite structure design ensure that the coating is tightly bonded to the silver-based components, and it is not easy to fall off due to friction during carrying, thus providing long-lasting protection.

[0034] (4) Retaining metallic luster: The coating has good transparency and does not obscure the original metallic luster of the silver-based components, so the decorative value is not affected.

[0035] (5) Suitable for portable scenarios: The coating is thin and smooth, which does not affect the carrying feel and decorative effect of the silver-based components, and meets the usage requirements of portable decorative components. Detailed Implementation

[0036] Before describing the embodiments of this application in detail, it should be understood that the terminology used herein is for the purpose of describing a particular embodiment only. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the term pertains.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0038] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0040] This application provides an antibacterial and anti-discoloration composite coating for silver-based components. The antibacterial and anti-discoloration composite coating includes a nano-sealed film bottom layer and an antibacterial and anti-discoloration film top layer.

[0041] This application also provides a method for preparing an antibacterial and anti-discoloration composite coating for silver-based components.

[0042] In one specific embodiment, the preparation method includes the following steps:

[0043] (a) Substrate pretreatment

[0044] (1) Degreasing treatment

[0045] Immerse the silver-based components in a degreasing agent and treat them at 40-50℃ and ultrasonic power 300-500W for 5-8 minutes. For complex, irregularly shaped components, the treatment time can be extended to 8-12 minutes. During this time, gently brush the crevices manually (using a soft nylon brush) to ensure thorough removal of oil stains. After degreasing, rinse with deionized water for 2-3 minutes. The surface water film should be continuous without breaks to indicate successful degreasing; if the water film breaks, degreasing must be repeated.

[0046] The degreasing agent used is an environmentally friendly alkaline degreasing agent (composed of 50-80 g / L sodium carbonate (industrial grade, purity ≥98%), 20-30 g / L trisodium phosphate (industrial grade, purity ≥98%), and 5-10 g / L nonionic surfactant (industrial grade, polyoxyethylene ether), pH value 10-12). The use of an environmentally friendly alkaline degreasing agent to replace traditional solvent-based degreasing agents reduces VOC emissions.

[0047] (2) Surface polishing treatment

[0048] A two-step mechanical polishing process is employed, as detailed below:

[0049] Rough polishing to remove oxidation: Use 1200~1500 grit diamond polishing paste (industrial grade) with a wool polishing wheel (speed 1200~1500r / min) for dry polishing for 2~3 minutes. Control the polishing pressure at 0.1~0.15MPa to remove the oxide layer, scratches and residual impurities on the silver-based surface, ensuring that there are no yellow oxide spots or dust on the surface.

[0050] Fine polishing to enhance activity: Use 2500~3000 mesh cerium oxide polishing paste (industrial grade) and a soft sponge polishing wheel (speed 800~1000r / min) for wet polishing for 1~2 minutes (use anhydrous ethanol (analytical grade, purity ≥99.7%) as the polishing medium, with a dosage of ≤0.5mL per 10cm² of surface) to reduce surface roughness.

[0051] Immediately after polishing, ultrasonically clean with deionized water (250~300W, 4~6 min, ultrasonic frequency 40kHz) to remove polishing residue, then dry with hot air at 60~80℃ for 8~12 min. The final polished silver-based surface should achieve the following: surface roughness Ra≤0.08μm, retain the original metallic luster, and the water contact angle should be controlled at 25°~35°.

[0052] (II) Preparation of the bottom layer of the nano-sealed membrane

[0053] (1) Preparation of nanosol

[0054] Using a silane-titanium ester-β-cyclodextrin encapsulation microcapsule composite system as the core, a nanosol with "corrosion-responsive release + three-dimensional cross-linking barrier" function was prepared: 12-16 vol% of tetraethyl orthosilicate (industrial grade, purity ≥98%) and 4-6 vol% of tetrabutyl titanate (industrial grade, purity ≥98%) were added to an ethanol / deionized water mixed solvent (volume ratio 2:1) (ethanol was analytical grade, purity ≥99.7%); 3-5 wt% of... β-Cyclodextrin-encapsulated thymol microcapsules (β-CD@TP, particle size 100~150nm, inclusion rate ≥85%, added after ultrasonic dispersion at 180W for 20min); 1~2wt% bisphenol A type epoxy resin (E51, epoxy value 0.51-0.54eq / 100g); 0.4~0.6g / L silane coupling agent KH-550 (industrial grade, purity ≥95%) + 0.3~0.5g / L silane coupling agent. The binder KH-570 (industrial grade, purity ≥95%) was used; the pH value was adjusted to 3.5~4.0 with dilute hydrochloric acid (analytical grade, 36-38%), and the mixture was stirred and hydrolyzed at 35~45℃ for 90~120min (with ultrasonic dispersion at 15kHz, 120-140W for 10-20min every 30min of stirring, with a 5min interval to avoid overheating) to ensure uniform dispersion of microcapsules without rupture and to avoid sol agglomeration, thus obtaining a uniform and stable nanosol.

[0055] Through optimization of the sol composition, the antibacterial rate of the bottom layer was increased from "no antibacterial" to ≥99%. The pH-sensitive carboxyl groups of β-CD@TP microcapsules swell in corrosive media and release thymol to achieve "in-situ antibacterial". E51 forms an interpenetrating network with silane-titanium ester to make up for the brittleness of traditional sol film layers. KH-570 double bonds crosslink with E51 epoxy groups and KH-550 amino groups combine with silver-based hydroxyl groups to form double chemical bonds to enhance adhesion.

[0056] The nano sol is stored using "vacuum encapsulation + inert gas protection". The shelf life of refrigerated storage at 4~8℃ is extended from 72h to 120h. No warming is required before use. It can be directly ultrasonically dispersed for 5min (solving the problem of easy agglomeration of traditional sols when warmed).

[0057] The vacuum environment isolates oxygen, and the inert gas (such as nitrogen) prevents the oxidation of sol components and prevents premature cross-linking and aggregation. Direct ultrasonic dispersion can quickly restore the uniformity of the sol.

[0058] The specific preparation method (saturated aqueous solution method) of β-cyclodextrin-encapsulated thymol microcapsules (β-CD@TP) is as follows: Weigh 8-12g of β-cyclodextrin (analytical grade, purity ≥98%, water content ≤14%, CAS No. 7585-39-9), add 80-120ml of deionized water, heat to 45-55℃ and stir to dissolve, thus preparing a saturated aqueous solution; dissolve 0.8-1.2g of thymol (analytical grade, purity ≥98% (GC), CAS No. 89-83-8) in 8-12ml of anhydrous ethanol (analytical grade, purity ≥99.7%), and slowly add it dropwise to the β-cyclodextrin solution, stirring at 45-55℃ for 2-3 hours; cool to room temperature and refrigerate for 20-28 hours to allow complete precipitation; filter, and wash the filter cake with 5-10ml of cold water 2-3 times. The product was dried under vacuum at 35-45°C for 10-14 hours to obtain white powdery β-CD@TP microcapsules (inclusion rate approximately 70-85%).

[0059] (2) Sol-gel film formation process

[0060] Under ambient humidity of 35~55% RH, perform electrostatic elimination pretreatment (ion air gun blowing for 5~8 minutes, electrostatic voltage ≤50V) to avoid the agglomeration of sol particles due to electrostatics affecting film formation.

[0061] The coating is applied using an electrostatic assisted spraying method (spray gun pressure 0.15~0.2MPa, applied electrostatic voltage 5~8kV, distance 18~22cm). Electrostatic adsorption is used to oriented the adhesion of sol particles, improving the uniformity of film formation in complex areas.

[0062] After coating, allow to stand at room temperature for 15-20 minutes to level, then dry with hot air at 70-80℃ for 25-35 minutes; pre-cur under UV light (wavelength 365nm, power 150-180mW / cm², time 8-12s); finally, cure at 120-140℃ for 35-45 minutes (heating rate 3℃ / min) to promote complete cross-linking of the silane-titanium ester-E51 interpenetrating network; immediately after curing, deposit 20-30 Al2O3 nanolayers on the film surface (using trimethylaluminum (purity ≥99.999%) and water as precursors, deposition temperature 80-100℃) to seal the micropores of the film and form a dual barrier structure of "sol-gel layer + ALD dense layer".

[0063] Electrostatic elimination pretreatment prevents sol particles from agglomerating due to electrostatic adsorption, ensuring that the coating surface is free of particulate impurities; electrostatic assisted spraying uses a voltage of 5~8kV to direct sol particles to adhere to complex areas (such as gaps and corners), solving the problem of "uneven film thickness in complex areas" in traditional spraying.

[0064] UV pre-curing (365nm, 8~12s) rapidly activates KH-570 double bonds to form initial cross-links, avoiding film deformation during thermal curing; curing at 120~140℃ promotes complete cross-linking of the interpenetrating network; the Al2O3 nanolayer deposited by ALD (80~100℃) has uniform particle size and no pores, precisely sealing the micropores of the sol film layer, forming a dual barrier of "sol-gel layer + ALD layer".

[0065] (III) Preparation of the top layer of antibacterial and anti-discoloration film

[0066] (1) Preparation of antibacterial and anti-discoloration coating

[0067] Waterborne acrylic-polyurethane resin (solid content 25~28%, VOC emission ≤20g / L) was selected as the matrix for anti-discoloration modified resin.

[0068] Antibacterial component treatment and addition: Take 5~7wt% of mesoporous carbon-loaded Ag⁺-Cu²⁺-MOFs composite powder (Ag-Cu-MOFs@MC, particle size 120~150nm, mesoporous carbon pore size 2~4nm, Ag⁺ loading 6~9wt%, Cu²⁺ loading 3~5wt%), add anhydrous ethanol (analytical grade, purity ≥99.7%) and perform ultrasonic dispersion pretreatment (power 300W, time 15min); add the dispersed Ag-Cu-MOFs@MC to the resin matrix, and then add 0.8~1.2wt% chitosan-grafted quaternary ammonium salt (CTS-QAS), and stir to mix evenly.

[0069] Anti-discoloration additive: Add 2.0~3.0wt% of sulfur vacancy cerium dioxide (CeO2-x, sulfur vacancy concentration ≥1.2×10¹). 9 Add 0.5~0.8wt% graphene quantum dots (GQDs, particle size 3~5nm, surface containing hydroxyl and carboxyl groups) with a concentration of cm⁻³ and an adsorption capacity ≥80mg / g, and continue stirring.

[0070] Dispersant addition and dispersion treatment: Add 0.5~1wt% of polycarboxylate dispersant (industrial grade), put it into a high-speed disperser, and disperse it at a speed of 1500~2000r / min for 40~60min. During this period, it is supplemented with ultrasonic treatment at 280~320W for 15~25min to ensure that each component is uniformly dispersed and free from agglomeration.

[0071] The preparation method of Ag-Cu-MOFs@MC (silver-copper metal-organic framework@mesoporous carbon) (solventothermal method + carbon composite) is as follows: (1) Preparation of mesoporous carbon (MC): Weigh 4~6g resorcinol (analytical grade, purity ≥99%), 3.0~4.5g formaldehyde (analytical grade, 37~40% aqueous solution, based on the mass of pure formaldehyde), 0.4~0.6g Pluronic F127 (reagent grade, average molecular weight ≈12600), dissolve in 80~120ml deionized water; stir at 55~65℃ for 20~28h to form a gel, solidify at 75~85℃ for 20~28h; carbonize at 500~600℃ for 4~8h under nitrogen protection (heating rate 5℃ / min), and obtain mesoporous carbon after natural cooling. (2) Synthesis of Ag-Cu-MOFs: Weigh 1.0~1.4g silver nitrate (analytical grade, purity ≥99.8%), 1.2~1.8g copper nitrate (analytical grade, purity ≥99.0% (based on Cu)), and 1.8~2.4g trimesic acid (BTC, analytical grade, purity ≥98%), dissolve in 80~120ml N,N-dimethylformamide (DMF, analytical grade, purity ≥99.5%); add 1.5~2.5g of the above mesoporous carbon, ultrasonically disperse at 200~300W for 25~35min; transfer to a high-pressure reactor, solvothermal reaction at 110~130℃ for 20~28h; cool to room temperature and filter, the filter cake is then filtered with DMF. Wash 2-3 times, then wash 2-3 times with anhydrous ethanol (analytical grade, purity ≥99.7%); vacuum dry at 55-65℃ for 10-14h to obtain gray-black powder Ag-Cu-MOFs@MC (Ag⁺ loading 6-9wt%, Cu²⁺ loading 3-5wt%).

[0072] The specific preparation method (molten salt method) of sulfur vacancy cerium dioxide (CeO2-x) is as follows: Weigh 4~6g of cerium nitrate (Ce(NO3)3·6H2O, analytical grade, purity ≥99.0% (calculated as Ce)), 1.6~2.4g of sodium chloride (analytical grade, purity ≥99.5%), and 0.8~1.2g of potassium chloride (NaCl:KCl). The mass ratio was maintained at 2:1 (analytical grade, purity ≥99.5%). After thorough mixing, 10-20 ml of deionized water was added and stirred to form a paste. The paste was transferred to a crucible and placed in a muffle furnace. The temperature was increased to 400-500℃ at a rate of 3-7℃ / min and held for 5-7 hours. After natural cooling to room temperature, the product was transferred to a beaker, and deionized water was added for ultrasonic washing (200-300W, 15-20 min). The mixture was then filtered, and the washing-filtration process was repeated until the filtrate was tested with silver nitrate solution (analytical grade, 0.1 mol / L standard solution) and no chloride ions were detected (after acidification of the filtrate with dilute nitric acid, no white precipitate was observed upon addition of AgNO3 solution). The filtrate was then vacuum dried at 55-65℃ for 10-14 hours to obtain a pale yellow CeO2-x powder (sulfur vacancy concentration ≥1.2×10¹).9 cm⁻³, adsorption capacity ≥80mg / g).

[0073] The preparation method of graphene quantum dots (GQDs) (hydrothermal method of graphene oxide) is as follows: Weigh 0.8~1.2g of graphene oxide (GO, number of layers ≤5, oxidation degree ≥30%, reagent grade), disperse in 80~120ml of deionized water, and ultrasonically disperse at 200~300W for 40~80min to form a uniform GO dispersion; add 8~12ml of 30%... Hydrogen peroxide (analytical grade, concentration 28-30%) was stirred for 20-30 minutes until homogeneous. The mixture was then transferred to a polytetrafluoroethylene-lined high-pressure reactor (60-80% filling) and subjected to hydrothermal reaction at 160-200℃ for 10-14 hours. After cooling to room temperature, the mixture was filtered through a 0.22μm filter membrane to remove unreacted large GO particles. The filtrate was then transferred to a dialysis bag (molecular weight cutoff 800-1200 Da). The dialyzed solution was freeze-dried (-50 to -40℃, vacuum ≤10Pa) for 24-36 hours to obtain black, fluffy GQDs powder (particle size 3-5 nm, surface containing hydroxyl and carboxyl groups).

[0074] Coating performance testing: The coating particle size must meet the requirement of D90≤150nm; the coating stability must meet the requirement of no stratification or sedimentation after standing for 20~24h; if the particle size or stability does not meet the standards, high-speed dispersion must be carried out again (extending by 10~15min); after meeting the standards, the coating viscosity should be adjusted to 15~20mPa·s with deionized water to adapt to the spraying process requirements; the coating should be prepared and used immediately, and spraying should be completed within 4h after preparation.

[0075] Using Ag-Cu-MOFs@MC+CTS-QAS, Ag-Cu-MOFs@MC mesoporous carbon (pore size 2~4nm) serves as a slow-release channel to control the Ag⁺ / Cu²⁺ release rate (avoiding rapid loss). The porous structure of MOFs (ZIF-8) actively captures bacteria, Ag⁺ disrupts the bacterial membrane, and Cu²⁺ inhibits respiratory enzyme activity, achieving "long-lasting antibacterial effect". CTS-QAS interacts with the bacterial cell membrane through quaternary ammonium salt groups, supplementing "contact antibacterial effect" and covering fungi (such as Candida albicans) and viruses (such as Escherichia coli bacteriophages) that have not been acted upon by Ag⁺ / Cu²⁺.

[0076] Sulfur vacancies in CeO2-x (concentration ≥ 1.2 × 10¹) 9 GQDs preferentially adsorb H2S (adsorption capacity ≥80mg / g) and catalyze its decomposition into non-corrosive S and H2O, blocking the "silver-sulfur reaction". The hydroxyl and carboxyl groups on the surface of GQDs have reducing properties, which can inhibit the oxidation of silver surface to Ag2O, forming a triple anti-discoloration mechanism of "adsorption-catalysis-reduction" and rapidly responding to low concentrations of H2S.

[0077] A 10~15kV electrostatic voltage causes the coating particles to become negatively charged, which then adsorbs onto the positively charged bottom layer surface (the bottom layer is slightly positively charged after ALD treatment), forming a gradient structure of "dense bonding of the bottom layer + oleophobic top layer". The adjusted spray gun pressure and distance ensure uniform atomization particle size (8~15μm), avoid coating sagging or pinholes, and improve surface smoothness and adhesion.

[0078] (2) Spray coating film forming process

[0079] In a dust-free spraying environment (cleanliness level ≤ 100,000, ambient humidity 50~60% RH), air spraying is used. A 10~15kV electrostatic voltage is applied to the spray gun, the spray gun pressure is controlled at 0.28~0.32MPa, the spraying distance is 18~20cm, and the atomized particle size is controlled at 8~15μm. A "cross-hatching" spraying method is used, with 2~3 thin coats (each coat has a dry film thickness of 1~1.5μm). Pre-drying treatment: After each coat, the silver-based component is placed in a drying equipment and pre-dried at 55~65℃ for 10~15min to avoid coating sagging or pinholes.

[0080] After spraying, ensure that the thickness of the top dry film is controlled at 3~5μm to ensure both antibacterial and anti-discoloration effects, and to avoid the coating being too thick and obscuring the original metallic luster of the silver-based components.

[0081] (iv) Post-processing

[0082] (1) Low temperature curing

[0083] Place the silver-based components in a hot air circulating oven and use a stepped low-temperature curing method: first preheat at 50-60℃ for 15-20 minutes, then raise the temperature to 120-130℃ and hold for 40-50 minutes, and finally cool down to below 60℃ to remove them. This avoids oxidation and discoloration of the silver substrate caused by high-temperature curing. Nitrogen gas (oxygen content ≤0.5%) needs to be introduced into the oven for protection to further prevent silver oxidation.

[0084] (2) Surface finishing

[0085] The process employs a combination of "low-pressure micro-polishing + chemical finishing," focusing on repairing minor coating imperfections and optimizing surface smoothness and gloss.

[0086] Low-pressure micro-polishing: Use a 4500~5000 mesh ultra-fine fiber polishing wheel (speed 600~800r / min), dry polish for 30~60s without polishing paste, polishing pressure ≤0.05MPa, to remove tiny particles and drip marks on the coating surface and avoid damaging the coating.

[0087] Chemical finishing: Prepare the environmentally friendly finishing solution (components: 0.5~1g / L nonionic surfactant (industrial grade, polyoxyethylene ether), 0.3~0.5g / L silane coupling agent KH-560 hydrolysate (industrial grade, purity ≥95%), pH 6.5~7.5) and immerse the silver-based components in it at room temperature for 4~8 minutes to improve the wettability and smoothness of the coating surface.

[0088] Final washing and drying: After removal, ultrasonically clean with deionized water (180~220W, 2~4min) to remove finishing residue, and then dry with hot air at 55~65℃ for 8~12min; after final washing, check the surface contact angle deviation to ensure no residue.

[0089] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0090] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0091] The present application will be further described in detail below with reference to the embodiments and test results.

[0092] Example 1

[0093] This embodiment provides an antibacterial and anti-discoloration composite coating for silver-based components. The antibacterial and anti-discoloration composite coating includes a nano-sealed film bottom layer and an antibacterial and anti-discoloration film top layer. The preparation method of this antibacterial and anti-discoloration composite coating specifically includes the following steps (some parameters are shown in Table 1):

[0094] (a) Substrate pretreatment

[0095] (1) Degreasing treatment

[0096] Immerse the silver-based components in an environmentally friendly alkaline degreasing agent (composed of 65g / L sodium carbonate, 25g / L trisodium phosphate, and 8g / L nonionic surfactant, pH 10-12) and treat for 6 minutes at 45℃ and 400W ultrasonic power, supplementing with manual brushing of crevices to ensure thorough removal of oil stains. After degreasing, rinse with deionized water for 3 minutes. The surface water film should be continuous without breaks to indicate successful degreasing; if the water film breaks, degreasing must be repeated.

[0097] (2) Surface polishing treatment

[0098] A two-step mechanical polishing process is employed, as detailed below:

[0099] Rough polishing to remove oxidation: Use 1500-grit diamond polishing paste and a wool polishing wheel (1200 r / min) for dry polishing for 2 minutes. Control the polishing pressure at 0.1~0.15 MPa to remove the oxide layer, scratches and residual impurities on the silver-based surface, ensuring that there are no yellow oxide spots or dust on the surface.

[0100] Fine polishing to enhance activity: Switch to 2500-mesh cerium oxide polishing paste and use a soft sponge polishing wheel (1000 r / min) for wet polishing for 2 minutes (using anhydrous ethanol as the polishing medium, with a dosage of ≤0.5 mL per 10 cm² of surface) to reduce surface roughness.

[0101] Immediately after polishing, ultrasonically clean with deionized water (300W, 5 min, ultrasonic frequency 40kHz) to remove polishing residue, and then dry with hot air at 80℃ for 10 min. The final polished silver-based surface should achieve the following: surface roughness Ra≤0.08μm, retain the original metallic luster, and the water contact angle should be controlled between 25° and 35°.

[0102] (II) Preparation of the bottom layer of the nano-sealed membrane

[0103] (1) Preparation of nanosol

[0104] A nanosol with "corrosion-responsive release + three-dimensional cross-linking barrier" function was prepared using a silane-titanium ester-β-cyclodextrin encapsulation microcapsule composite system as the core: 14 vol% tetraethyl orthosilicate and 5 vol% tetrabutyl titanate were added to an ethanol / deionized water mixed solvent (volume ratio 2:1); 4 wt% β-cyclodextrin-encapsulated thymol microcapsules (β-CD@TP, particle size 120 nm, encapsulation rate ≥85%, added after ultrasonic dispersion at 180 W for 20 min) were added; 1.5 wt% bisphenol A type epoxy resin (E51) was added; and 0.5 g / L silane coupling agent KH-550+0.4 g / L was added. γ-(methacryloyloxy)propyltrimethoxysilane (KH-570) was used. The pH was adjusted to 3.5–4.0 with dilute hydrochloric acid, and the mixture was hydrolyzed at 40°C with stirring for 100 min (with ultrasonic dispersion at 15 kHz, 120–140 W for 10–20 min every 30 min of stirring, followed by a 5-min interval to avoid overheating) to ensure uniform dispersion and prevent sol agglomeration, thus obtaining a uniform and stable nanosol. It was stored using vacuum encapsulation and inert gas protection.

[0105] The specific preparation method (saturated aqueous solution method) of β-cyclodextrin-encapsulated thymol microcapsules (β-CD@TP) is as follows: Weigh 10g of β-cyclodextrin, add 100ml of deionized water, heat to 50℃ and stir to dissolve, thus preparing a saturated aqueous solution; dissolve 1g of thymol in 10ml of anhydrous ethanol, slowly add it dropwise to the β-cyclodextrin solution, and stir at 50℃ for 2.5h; cool to room temperature and refrigerate for 24h to ensure complete precipitation; filter, and wash the filter cake 2-3 times with 5-10ml of cold water each time; vacuum dry at 40℃ for 12h to obtain white powdery β-CD@TP microcapsules (encapsulation rate of about 70-85%).

[0106] (2) Sol-gel film formation process

[0107] Under ambient humidity of 45% RH, perform electrostatic elimination pretreatment (ion air gun blowing for 6 minutes, electrostatic voltage ≤50V) to avoid the agglomeration of sol particles due to electrostatics affecting film formation.

[0108] Electrostatic assisted spraying (spray gun pressure 0.15MPa, applied electrostatic voltage 6.5kV, distance 20cm) is used for coating. Electrostatic adsorption is used to make the sol particles adhere in an orientation, which improves the uniformity of film formation in complex areas.

[0109] After coating, allow to stand at room temperature for 18 minutes to level, then dry with hot air at 75°C for 30 minutes; UV pre-curing (wavelength 365nm, power 150~180mW / cm², time 10s); finally, cure at 130°C for 40 minutes (heating rate 3°C / min) to promote complete cross-linking of the silane-titanium ester-E51 interpenetrating network.

[0110] Immediately after curing, 25 Al2O3 nanolayers (using trimethylaluminum and water as precursors, deposition temperature 100℃) are deposited on the film surface to block the micropores of the film and form a dual barrier structure of "sol-gel layer + ALD dense layer".

[0111] (III) Preparation of the top layer of antibacterial and anti-discoloration film

[0112] (1) Preparation of antibacterial and anti-discoloration coating

[0113] Waterborne acrylic-polyurethane resin (solid content 25~28%, VOC emission ≤20g / L) was selected as the matrix for anti-discoloration modified resin.

[0114] Antibacterial component treatment and addition: Take 6wt% Ag-Cu-MOFs@MC (particle size 120~150nm, mesoporous carbon pore size 2~4nm, Ag⁺ loading 6~9wt%, Cu²⁺ loading 3~5wt%), add anhydrous ethanol and perform ultrasonic dispersion pretreatment (power 300W, time 15min); add the dispersed Ag-Cu-MOFs@MC to the resin matrix, then add 1.0wt% CTS-QAS, and stir to mix evenly.

[0115] Anti-discoloration additive: Add 2.5wt% sulfur vacancy cerium dioxide (CeO2-x, sulfur vacancy concentration ≥1.2×10¹). 9 Add 0.6wt% graphene quantum dots (GQDs, particle size 3~5nm, surface containing hydroxyl and carboxyl groups) with a concentration of cm⁻³ and an adsorption capacity ≥80mg / g, and continue stirring.

[0116] Dispersant addition and dispersion treatment: Add 0.6wt% polycarboxylate dispersant, put it in a high-speed disperser, and disperse at 1800r / min for 50min. During this period, it is subjected to ultrasonic treatment at 300W for 20min to ensure that each component is uniformly dispersed and free from agglomeration.

[0117] The preparation method of Ag-Cu-MOFs@MC (silver-copper metal-organic framework@mesoporous carbon) (solventothermal method + carbon composite) is as follows: (1) Preparation of mesoporous carbon (MC): 5g resorcinol, 3.7g formaldehyde and 0.5g Pluronic F127 are dissolved in 100ml deionized water; stirred at 60℃ for 24h to form a gel, and solidified at 80℃ for 24h; carbonized at 550℃ for 6h under nitrogen protection to obtain mesoporous carbon; (2) Synthesis of Ag-Cu-MOFs: 1.2g silver nitrate, 1.5g copper nitrate and 2.1g trimesic acid (BTC) are dissolved in 100ml DMF; 2g of the above mesoporous carbon is added and ultrasonically dispersed for 30min; transferred to a high-pressure reactor and reacted at 120℃ for 24h; filtered after cooling and washed with DMF and ethanol in sequence; vacuum dried at 60℃ for 12h to obtain Ag-Cu-MOFs@MC.

[0118] The preparation method of sulfur vacancy cerium dioxide (CeO2-x) (molten salt method) is as follows: 5g of cerium nitrate, 2g of sodium chloride, and 1g of potassium chloride are mixed and then 15ml of deionized water is added and stirred to form a paste. The paste is placed in a crucible and heated in a muffle furnace at 450℃ for 6h (heating rate 5℃ / min). After cooling, the paste is repeatedly washed with deionized water until no chloride ions are present. The paste is then vacuum dried at 60℃ for 12h to obtain a light yellow CeO2-x powder.

[0119] The preparation method of graphene quantum dots (GQDs) (hydrothermal method of graphene oxide) is as follows: 1g of graphene oxide (GO) is dispersed in 100ml of deionized water, sonicated at 250W for 1h, 10ml of 30% hydrogen peroxide is added, and stirred for 25min until uniformly mixed; the mixture is transferred to a high-pressure reactor and hydrothermally reacted at 180℃ for 12h; after cooling, it is filtered through a 0.22μm filter membrane and purified by dialyzing (molecular weight cutoff 1000); the dialyzed solution is freeze-dried for 30h to obtain black fluffy GQDs powder.

[0120] (2) Electrophoretic film formation process

[0121] In a dust-free spraying environment (cleanliness ≤ 100,000 class, ambient humidity 50~60% RH), air spraying is used. A 13kV electrostatic voltage is applied to the spray gun, the spray gun pressure is controlled at 0.3MPa, the spraying distance is 20cm, and the atomized particle size is controlled at 8~15μm. A "cross-hatching" spraying method is used, applying 2~3 thin coats (each coat with a dry film thickness of 1~1.5μm). Pre-drying treatment: After each coat, the silver-based component is placed in a drying device and pre-dried at 60℃ for 15min to prevent coating sagging or pinholes. After spraying, ensure the top dry film thickness is controlled at 3~5μm.

[0122] (iv) Post-processing

[0123] (1) Low temperature curing

[0124] The silver-based components are placed in a hot air circulating oven and cured using a stepped low-temperature method: first, preheat at 55°C for 15 minutes, then raise the temperature to 125°C and hold for 45 minutes, and finally cool down to below 60°C to remove them. This avoids oxidation and discoloration of the silver substrate caused by high-temperature curing. Nitrogen gas (oxygen content ≤0.5%) must be introduced into the oven for protection to further prevent silver oxidation.

[0125] (2) Surface finishing

[0126] Low-pressure micro-polishing: Use a 4500-mesh ultra-fine fiber polishing wheel (800 r / min), dry polish for 40 seconds without polishing paste, with a polishing pressure ≤0.05 MPa, to remove tiny particles and drip marks from the coating surface and avoid damaging the coating.

[0127] Chemical finishing: Prepare the environmentally friendly finishing solution (composed of 0.8g / L nonionic surfactant, 0.4g / L silane coupling agent KH-560 hydrolysate, pH 6.5~7.5) and use it immediately. Immerse the silver-based components in it at room temperature for 5 minutes to improve the wettability and smoothness of the coating surface.

[0128] Final washing and drying: After removal, ultrasonically clean with deionized water (220W, 3min) to remove finishing residue, and then dry with hot air at 60℃ for 10min; after final washing, check the surface contact angle deviation to ensure no residue.

[0129] Example 2-13

[0130] Examples 2-13 provide a silver-based antibacterial and anti-discoloration composite coating for components. The preparation method of the above antibacterial and anti-discoloration composite coating differs from that of Example 1 in that some parameters in the preparation process are different, as shown in Table 1, while the remaining operation steps are consistent with those of Example 1.

[0131] Specifically, the differences between Examples 1-13 are as follows:

[0132] The difference between Examples 1-3 is that the amount of bisphenol A type epoxy resin (E51) added is different.

[0133] The difference between Examples 1 and 4-5 is that the number of Al2O3 nanolayers is different.

[0134] The difference between Examples 1 and 6-7 is that the voltage of electrostatic spraying in the preparation of the nano-sealed film bottom layer is different.

[0135] The difference between Examples 1 and 8-9 is that the amount of CeO2-x added is different.

[0136] The difference between Examples 1 and 10-11 is that the voltage of electrostatic assisted spraying in the preparation of the top layer of the antibacterial and anti-discoloration film is different.

[0137] Comparative Examples 1-4

[0138] Comparative Examples 1-4 each provide a silver-based antibacterial and anti-discoloration composite coating. The preparation method of the above antibacterial and anti-discoloration composite coatings differs from that of Example 1 in that some parameters in the preparation process are different, as shown in Table 1, while the remaining operation steps are consistent with those of Example 1.

[0139] Specifically, the differences between Example 1 and Comparative Examples 1-4 are as follows:

[0140] The difference between Example 1 and Comparative Example 1 is that Comparative Example 1 did not add β-CD@TP.

[0141] The difference between Example 1 and Comparative Example 2 is that Comparative Example 2 did not contain bisphenol A type epoxy resin (E51).

[0142] The difference between Example 1 and Comparative Example 3 is that Comparative Example 3 did not deposit an Al2O3 nanolayer.

[0143] The difference between Example 1 and Comparative Example 4 is that Comparative Example 4 did not add Ag-Cu-MOFs@MC.

[0144] Comparative Example 5

[0145] This comparative example provides an antibacterial and anti-discoloration composite coating for silver-based components. The preparation method of the above-mentioned antibacterial and anti-discoloration composite coating differs from that of Example 1 in that the preparation processes of steps (ii) and (iii) are different. However, the remaining operation steps are consistent with those of Example 1.

[0146] (II) Preparation of the bottom layer of the nano-sealed membrane

[0147] (1) Preparation of nanosol

[0148] A nanosol was prepared using a silane-titanium ester composite system as the core: 14 vol% tetraethyl orthosilicate and 5 vol% tetrabutyl titanate were added to a mixed solvent of ethanol / deionized water (volume ratio 2:1); 0.5 g / L of silane coupling agent KH-550 was added; the pH was adjusted to 3.5-4.0 with dilute hydrochloric acid, and the mixture was stirred and hydrolyzed at 40℃ for 100 min to ensure uniform dispersion and prevent sol aggregation, thus obtaining a uniform and stable nanosol. Store in a sealed container.

[0149] (2) Sol-gel film formation process

[0150] The coating was applied using a conventional air spraying method (spray gun pressure 0.15MPa, distance 20cm).

[0151] After coating, allow to stand at room temperature for 18 minutes to level, then dry with hot air at 75°C for 30 minutes; then cure at 130°C for 40 minutes (heating rate 3°C / min).

[0152] (III) Preparation of the top layer of antibacterial and anti-discoloration film

[0153] (1) Preparation of antibacterial and anti-discoloration coating

[0154] Waterborne acrylic-polyurethane resin (solid content 25~28%, VOC emission ≤20g / L) was selected, and 6wt% Ag-ZnO powder was added; 3.1wt% traditional benzotriazole anti-discoloration agent was added, and the mixture was stirred at low speed.

[0155] (2) Electrophoretic film formation process

[0156] In a normal spraying environment, air spraying is used, with the spray gun pressure controlled at 0.3MPa, the spraying distance at 20cm, and a single thick coating (dry film thickness 3~5μm).

[0157] Table 1. Preparation methods and parameters of some examples and comparative examples

[0158]

[0159] Performance testing

[0160] The above embodiments and comparative examples were tested as follows, and the test results are shown in Table 2.

[0161] (a) Anti-discoloration

[0162] (1) Test of sulfur resistance and discoloration performance

[0163] The specific testing methods are as follows: A customized sulfur-containing environment test (50ppm H2S gas, 25℃, 60%RH) was adopted; the color difference test was conducted in accordance with "GB / T 11186.3-1989 Measurement Methods of Coating Color Part 3: Calculation of Color Difference"; the specimen was placed in a sulfur-containing environment, and the color difference (ΔE) between the coating and the original silver base was tested every 24 hours using a colorimeter (accuracy ΔE±0.01); the time when ΔE first reached 1.5 (significant color change) was recorded.

[0164] (2) Salt spray oxidation tolerance test

[0165] The specific testing method is as follows: Refer to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; place the specimen in a 5% NaCl salt spray chamber (35℃) and observe whether oxidation spots appear on the silver base every 24 hours; record the "time of the first appearance of oxidation spots".

[0166] (ii) Antibacterial

[0167] (1) Antibacterial rate test (broad spectrum)

[0168] The specific testing methods are as follows: Referring to GB / T 21866-2008 "Determination of Antibacterial Properties of Antibacterial Coatings (Films)" (shaking flask method), the 24-hour antibacterial rate of the coating against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538) was tested; referring to GB / T 24346-2009 "Evaluation of Antibacterial Properties of Industrial Products - Plastics, Rubber and Other Non-Porous Materials" (film method), the 24-hour antibacterial rate against Candida albicans (ATCC 10231) was tested.

[0169] (2) Antimicrobial cycle stability test (long-term effect)

[0170] The specific testing method is as follows: Refer to the water cycle test in GB / T 17657-2013 Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels; immerse the coating in 50℃ deionized water, change the water every 24 hours, and repeat the antibacterial rate test after 50 cycles.

[0171] (iii) Cohesion

[0172] (1) Cross-cut adhesion test

[0173] The specific testing method is as follows: Refer to "GB / T 9286-1998 Cross-cut test for paint and varnish film", use a cross-cut tester to cut 10×10 grids (1mm spacing) on ​​the coating surface, stick on the tape and then peel it off, and observe the grid detachment.

[0174] (2) Adhesion test by circling

[0175] The specific testing method is as follows: Refer to "GB / T 1720-1979 Test Method for Coating Adhesion", use a QFD type adhesion tester to draw circles on the coating surface and observe the coating peeling level inside the circle.

[0176] (iv) Gloss

[0177] (1) Gloss

[0178] The specific testing method is as follows: Refer to "GB / T 9754-2007 Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments"; use a 60° gloss meter to test the surface gloss of the coating (silver-based native gloss is about 90 GU).

[0179] (2) Surface roughness

[0180] The specific testing method is as follows: Referring to "GB / T 3505-2009 Product Geometric Specification (GPS) Surface Structure Profile Method Terminology, Definitions and Parameters" (the test basis for surface roughness parameters), the Ra value of the coating surface is tested using a stylus-type roughness meter. The lower the roughness, the more uniform the gloss.

[0181] Table 2 Test Results

[0182]

[0183] As shown in Table 2, by comparing the technical solutions and test results of Examples 1-11, it can be seen that the coating prepared on the surface of silver-based components using the technical solution provided in this application can effectively improve the anti-discoloration, antibacterial properties, adhesion, and gloss of the silver-based components. Specifically, the sulfur resistance time is ≥120h, the salt spray resistance time is ≥96h; the antibacterial rate of Escherichia coli / Staphylococcus aureus reaches 99.99%, and the antibacterial rate of Candida albicans reaches 99.9%; the antibacterial rate remains ≥99% after cyclic treatment; the adhesion reaches 4B for cross-cutting and 2 for circular cutting; the gloss reaches 93GU, and Rs ≤0.04μm. The solution before optimization in the prior art is shown in Comparative Example 5, with a sulfur resistance time of 60h and a salt spray resistance time of 24h; the antibacterial rate of Escherichia coli / Staphylococcus aureus reaches 99%, and the antibacterial rate of Candida albicans reaches 99%; the antibacterial rate after cyclic treatment is only 85%; the adhesion reaches 3B for cross-cutting and 3 for circular cutting; the gloss is 80GU, and Rs is 0.06μm. As can be clearly seen from the above, the technical solution of this application has significant advantages over the prior art.

[0184] Furthermore, the technical solutions and test results of Comparative Example 1 show that without the addition of β-CD@TP, the salt spray resistance time decreases to 24 hours, and the antibacterial rate also decreases after cycling, especially the binding strength, which only reaches grade 3B for cross-cutting and grade 3 for circular cutting; the gloss decreases to 90 GU, and the Rs decreases to 0.05 μm. The technical solutions and test results of Comparative Example 2 show that without the addition of E51, the binding strength only reaches grade 3B for cross-cutting and grade 3 for circular cutting. The technical solutions and test results of Comparative Example 3 show that without the deposition of the Al2O3 nanolayer, the salt spray resistance time decreases to 24 hours. The technical solutions and test results of Comparative Example 4 show that without the addition of Ag-Cu-MOFs@MC, the antibacterial rate of Candida albicans decreases to 85%; the antibacterial rate decreases significantly after cycling.

[0185] Based on the above, the coating of this application adopts a composite structure of "nano-sealed film bottom layer + antibacterial and anti-discoloration film top layer", which can effectively prevent discoloration and antibacterial, while maintaining gloss and having strong adhesion.

[0186] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," 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 this application. In this specification, the 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A silver-based antibacterial and anti-discoloration composite coating for components, characterized in that, The antibacterial and anti-discoloration composite coating includes a nano-sealed film bottom layer and an antibacterial and anti-discoloration film top layer.

2. The antibacterial and anti-discoloration composite coating according to claim 1, characterized in that, The nano-encapsulated membrane is prepared using a nano-sol. The preparation method of the nano-sol is as follows: 12-16 vol% of tetraethyl orthosilicate and 4-6 vol% of tetrabutyl titanate are added to a mixed solvent of ethanol and deionized water in a volume ratio of 2:1; 3-5 wt% of ultrasonically dispersed β-cyclodextrin encapsulating thymol microcapsules are added; then 1-2 wt% of bisphenol A epoxy resin is added; then 0.4-0.6 g / L of silane coupling agent KH-550 and 0.3-0.5 g / L of silane coupling agent KH-570 are added; the pH value is adjusted to 3.5-4.0 with dilute hydrochloric acid, and the mixture is stirred and hydrolyzed at 35-45℃ for 90-120 min to obtain a uniform and stable nano-sol.

3. The antibacterial and anti-discoloration composite coating according to claim 1, characterized in that, The antibacterial and anti-discoloration film is prepared using an antibacterial and anti-discoloration coating. The preparation method of the antibacterial and anti-discoloration coating is as follows: Ag-Cu-MOFs@MC is added to anhydrous ethanol for ultrasonic dispersion pretreatment. The dispersed Ag-Cu-MOFs@MC is added to waterborne acrylic-polyurethane resin at an addition amount of 5~7wt%. Then, 0.8~1.2wt% CTS-QAS is added and stirred until uniform. 2.0~3.0wt% CeO2-x and 0.5~0.8wt% GQDs are added and stirring is continued. 0.5~1wt% polycarboxylate dispersant is added and dispersed at a speed of 1500~2000r / min for 40~60min, during which ultrasonic treatment at 280~320W is performed for 15~25min to ensure that each component is uniformly dispersed and free from agglomeration.

4. A method for preparing the antibacterial and anti-discoloration composite coating for silver-based components as described in claim 1, characterized in that, The preparation method specifically includes the following steps: (1) Substrate pretreatment: The silver-based components are degreased and polished in sequence; (2) Preparation of the nano-sealed film bottom layer: The pretreated silver-based component is immersed in the nano-sol and pulled at a uniform speed of 7~9cm / min to ensure that the sol uniformly covers the surface of the substrate; after coating and curing, 20~30 Al2O3 nano-layers are deposited on the film surface to obtain the nano-sealed film bottom layer; the preparation method of the nano-sol is as follows: 12~16 vol% of tetraethyl orthosilicate and 4~6 vol% of tetrabutyl titanate are added to a mixed solvent of ethanol and deionized water with a volume ratio of 2:1; 3~5 wt% of tetrabutyl titanate is added to the mixture. β-cyclodextrin, after ultrasonic dispersion, is encapsulated with thymol microcapsules; then 1-2 wt% bisphenol A type epoxy resin is added; then 0.4-0.6 g / L silane coupling agent KH-550 and 0.3-0.5 g / L silane coupling agent KH-570 are added; the pH value is adjusted to 3.5-4.0 with dilute hydrochloric acid, and the mixture is stirred and hydrolyzed at 35-45℃ for 90-120 min to obtain a uniform and stable nano-sealed membrane; (3) Preparation of the top layer of antibacterial and anti-discoloration film: The top layer of antibacterial and anti-discoloration film is formed on the surface of the nano-sealed film by air spraying, i.e., cross spraying. The preparation method of the antibacterial and anti-discoloration coating is as follows: Ag-Cu-MOFs@MC is added to anhydrous ethanol for ultrasonic dispersion pretreatment. Ag-Cu-MOFs@MC is added to waterborne acrylic-polyurethane resin at an addition amount of 5~7wt%. Then, 0.8~1.2wt% CTS-QAS is added and stirred evenly. 2.0~3.0wt% CeO2-x and 0.5~0.8wt% GQDs are added and stirred continuously. 0.5~1wt% polycarboxylate dispersant is added and dispersed at a speed of 1500~2000r / min for 40~60min. During this period, ultrasonic treatment at 280~320W is performed for 15~25min to ensure that each component is evenly dispersed and free from agglomeration. (4) Post-treatment: The silver-based components with the composite coating prepared are subjected to low-temperature curing and surface finishing treatment, that is, an antibacterial and anti-discoloration composite coating is obtained on the surface of the silver-based components.

5. The preparation method according to claim 4, characterized in that, In the preparation of the nano-sealed membrane bottom layer, the amount of bisphenol A type epoxy resin added is 1.5-2 wt%.

6. The preparation method according to claim 4, characterized in that, In the preparation of the nano-sealed membrane bottom layer, the deposited Al2O3 nanolayers are 25-30 layers.

7. The preparation method according to claim 4, characterized in that, In the preparation of the nano-sealed film substrate, the coating process utilizes electrostatic assisted spraying with a voltage of 6.5-8KV.

8. The preparation method according to claim 4, characterized in that, In the preparation of the top layer of the antibacterial and anti-discoloration film, the amount of CeO2-x added is 2.5~3.0wt%.

9. The preparation method according to claim 4, characterized in that, In the preparation of the top layer of the antibacterial and anti-discoloration film, the spraying process utilizes electrostatic assisted spraying with a voltage of 13-15KV.

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