UV coating as well as preparation method and application thereof

Abstract

The invention provides a UV coating as well as a preparation method and application thereof. The UV coating is prepared from the following raw materials: ultraviolet curing resin, an active monomer, thermoplastic acrylic resin, a photoinitiator, an adhesion promoter, a base material wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax anti-settling slurry, pigment and matting powder, and the UV coating disclosed by the invention reduces the influence of light absorption of the pigment on UV curing by improving the UV light intensity, so that the UV curing effect is improved, and the service life of the UV coating is prolonged. And proper coloring of the coating is realized. By improving the light intensity, the coloring proportion is improved, and the coloring property and the covering property are superior to those in the prior art. The invention further provides a preparation method and application of the UV coating.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a UV coating and a preparation method and application thereof. Background Art

[0002] In the 3C industry, the development trend of mobile phones and notebooks is to become thinner and lighter. Aluminum-magnesium alloys meet their development requirements due to their low density, high strength, and good rigidity, and have become the preferred material for high-end mobile phones and notebooks. However, due to the high chemical activity of magnesium, its corrosion resistance is poor, which limits the use of aluminum-magnesium alloys. In order to improve the corrosion resistance of aluminum-magnesium alloys, anti-corrosion treatment is usually performed on the surface of aluminum-magnesium alloys. Among them, the micro-arc oxidation process is a simple, efficient and environmentally friendly surface treatment process.

[0003] Micro-arc oxidation technology is a method that uses a combination of electrolyte and corresponding electrical parameters to grow a ceramic film layer mainly composed of matrix metal oxide on the surface of aluminum, magnesium, titanium and their alloys by relying on the instantaneous high temperature and high pressure generated by arc discharge, which greatly improves the corrosion resistance, wear resistance and insulation of magnesium alloys. At the same time, the porous structure of the metal oxide layer is conducive to the anchoring of the coating on the surface and to improving the adhesion of the coating on the metal. Generally, after the surface treatment of aluminum-magnesium alloy, the surface is smooth and the coating is difficult to adhere. The surface coating often adopts a three-coating process of PU primer + PU color paint + UV topcoat, which is complex, inefficient and energy-intensive. However, after the micro-arc oxidation treatment of aluminum-magnesium alloy, the porous structure of the surface makes it possible for a UV coating to adhere to the metal surface, greatly improving production efficiency, reducing energy consumption and saving costs.

[0004] CN110452599A discloses a method for preparing a baking-cured coating. The coating needs to be heated and baked for more than 30 minutes, which has high energy consumption and low efficiency. In addition, the wear resistance of the coating is average, and it is not suitable for fields with high wear resistance requirements such as mobile phones and notebooks. CN116515351A adopts a dual-curing system of UV+baking paint, with the baking paint part providing adhesion and the UV curing part providing performance. The coating needs to be UV cured and baked at 150°C, which also has high energy consumption and low efficiency. At present, after micro-arc oxidation treatment of aluminum-magnesium alloy, the color is single, which is not conducive to the colorfulization of mobile phones and notebooks. It is necessary to develop a coating that is easy to add color and can ensure good adhesion on the micro-arc oxidation treated substrate to meet the diverse and differentiated needs of customers. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention provides a UV coating, which reduces the influence of pigment light absorption on UV curing by increasing UV light intensity, and realizes appropriate color addition of the coating. The present invention increases the color addition ratio by increasing light intensity, and the color addition and hiding properties are better than those of the prior art.

[0006] The invention also provides a method for preparing the UV coating.

[0007] The invention also provides a surface treatment layer.

[0008] The invention also provides a method for preparing the surface treatment layer.

[0009] The invention also provides application of the surface treatment layer in 3C products.

[0010] The first aspect of the present invention provides a UV coating, wherein the raw materials for preparing the coating include ultraviolet curing resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax anti-settling slurry, pigment and matting powder.

[0011] One of the technical solutions of the present invention regarding UV coatings has at least the following beneficial effects:

[0012] The existing baking paint scheme of common coatings can add color because adding color will not affect the curing of the coating. However, for UV curing coatings, since the pigment absorbs light, it will affect the curing of the UV coating. Therefore, the existing UV coatings have the problem of difficult curing after adding color. The UV coating of the present invention reduces the influence of the pigment light absorption on UV curing by increasing the UV light intensity, and realizes the appropriate amount of color addition of the coating. The present invention increases the color addition ratio by increasing the light intensity, and the color addition and hiding properties are better than the prior art.

[0013] The present invention provides a colorable UV coating that can ensure good adhesion on a micro-arc oxidation treated substrate to protect the metal surface and at the same time provide different color effects to meet the diverse and differentiated needs of customers.

[0014] The UV coating of the present invention only needs to be baked at 50-60°C for 3-5 minutes, and then cured by UV to obtain a UV protective layer with high hardness, high wear resistance and good chemical resistance. It has good adhesion on the micro-arc oxidation substrate, and meets the adhesion of ≥4B after boiling at 85°C for 1 hour; it has high hardness, and the pencil hardness is 1000g≥6H; it has high wear resistance, and the RCA paper tape is abraded 150g≥300 times; it has good chemical resistance, and the salt spray adhesion is ≥4B for 48 hours; different color effects can be adjusted, such as black, white, silver, gold, etc. The UV coating of the present invention has the characteristics of simple process, high efficiency, energy saving, environmental protection, etc.

[0015] According to some embodiments of the present invention, the preparation raw materials include, by weight:

[0016] UV curing resin: 30-40 parts,

[0017] Active monomer: 5-10 parts,

[0018] Thermoplastic acrylic resin: 5-10 parts,

[0019] Photoinitiator: 1-4 parts,

[0020] Adhesion promoter: 1-4 parts,

[0021] Substrate wetting agent: 0.2-0.5 parts,

[0022] Ethyl acetate: 10-20 parts,

[0023] Butyl acetate: 10-20 parts,

[0024] Fumed silica: 1-5 parts,

[0025] Polyamide wax anti-settling slurry: 1-5 parts,

[0026] Pigment: 5-10 parts,

[0027] Matting powder: 0-5 parts.

[0028] For UV-curable resins, choose low-functional group resins in combination with high-functional group resins. For low-functional resins, choose epoxy-modified acrylic resins with 2-3 functional groups and good adhesion to metals to ensure the adhesion of the coating on the micro-arc oxidation substrate and adjust the flexibility of the paint film. The micro-arc oxidation substrate has a high hardness and the paint film hardness is above 6H. The coating cannot be too hard, otherwise the paint will easily collapse. It is necessary to add resins with better flexibility to adjust the flexibility and improve the paint collapse phenomenon. For high-functional resins, choose polyurethane acrylic resins with 6-12 functional groups. They have good reaction activity and high cross-linking density, which can improve the chemical resistance and wear resistance of the paint film, while ensuring deep curing and improving the adhesion of the paint film.

[0029] According to some embodiments of the present invention, the active monomer includes dipentaerythritol hexaacrylate resin, which has high functionality and good reactivity, can enhance the reactivity of the color-additive UV coating, ensure deep curing of the coating, and thus ensure the adhesion of the paint film.

[0030] According to some embodiments of the present invention, the Tg value of the thermoplastic acrylic resin is 80-120°C.

[0031] According to some embodiments of the present invention, the molecular weight of the thermoplastic acrylic resin is 100,000-200,000.

[0032] Choose a macromolecular thermoplastic acrylic resin with a Tg value of 80-120℃ and a molecular weight of 100,000-200,000. When the paint film is cured, it can reduce the volume shrinkage of the paint film, reduce the shrinkage stress, and improve adhesion. At the same time, thermoplastic acrylic resin has good solvent release and thixotropy, which can improve paint film defects such as edge accumulation and sagging during the coating construction process.

[0033] Photoinitiators absorb UV energy and generate free radicals, which initiate polymerization of monomers to crosslink and cure the compound.

[0034] According to some embodiments of the present invention, the adhesion promoter includes trifunctional methacrylate phosphate. The water boiling adhesion of the coating can be improved. It is necessary to select an adhesion promoter with high functionality and good reactivity to ensure that the adhesion promoter can participate in the reaction in the color-added UV, thereby improving the adhesion. Otherwise, the reaction speed is slow and the reaction is incomplete, which will lead to water boiling and blistering.

[0035] The surface of the micro-arc oxidation substrate is a microporous structure. After spraying the coating, tiny microbubbles are easily left on the surface of the substrate. During the water boiling test, the air in the microbubbles expands and contracts, causing the paint film to bubble when boiling. Adding a substrate wetting agent improves the wettability of the coating to the substrate. When the coating is applied to the surface of the substrate, the coating can well wet the microporous structure, ensure that the coating fills the microporous structure, and remove the air in the micropores. While solving the problem of boiling bubbles, the coating and the substrate form an anchoring effect, which improves the adhesion of the coating on the micro-arc oxidation substrate.

[0036] The surface of fumed silica contains a large number of hydroxyl groups, which allow the silica to be connected together through hydrogen bonds to form a three-dimensional network structure of silica, which can prevent the color paste and silver bead powder in the paint from agglomerating and settling, thereby improving the storage stability of the paint.

[0037] Polyamide wax is a thixotropic additive that forms a network structure in the paint and has excellent thixotropic, anti-sagging and anti-settling properties. It can effectively prevent the agglomeration and sedimentation of the color paste and silver bead powder in the paint, ensure the uniformity and storage stability of the paint, and improve the workability of the paint.

[0038] Pigments can be selected from color paste, aluminum silver paste, pearlescent powder and other pigments to meet customers' different appearance effect requirements.

[0039] According to some embodiments of the present invention, the matting powder comprises silicon dioxide.

[0040] The second aspect of the present invention provides a method for preparing the UV coating of the first aspect of the present invention, comprising the following steps:

[0041] S1: adding the thermoplastic acrylic resin and butyl acetate into a dispersion kettle for dispersion to obtain a dissolved thermoplastic acrylic resin;

[0042] S2: adding the photoinitiator into ethyl acetate to dissolve, adding the dissolved thermoplastic acrylic resin, ultraviolet light curing resin, active monomer, substrate wetting agent, adhesion promoter, adding the polyamide wax anti-settling slurry and fumed silica while dispersing to obtain a dispersion, and grinding the dispersion;

[0043] S3: adding the pigment and the matting powder into the dispersion to obtain the UV coating after dispersion.

[0044] A technical solution in the preparation method of UV coating of the present invention has at least the following beneficial effects:

[0045] The preparation method of the present invention does not require expensive equipment and complicated process control, has undemanding reaction conditions, has readily available raw materials, has low production costs, and is easy to industrialize.

[0046] In step S1:

[0047] Add thermoplastic acrylic resin and butyl acetate into a dispersion kettle and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0048] In step S2:

[0049] Dissolve the photoinitiator in ethyl acetate, then add the dissolved thermoplastic acrylic resin, UV curing resin, active monomer, substrate wetting agent, and adhesion promoter, disperse at a speed of 800-1000 rpm for 10 minutes, add polyamide wax anti-settling slurry and fumed silica while dispersing, and disperse at a speed of 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness of ≤5μm, and transfer the grinding liquid to a dispersion kettle.

[0050] In step S3:

[0051] Pigments can be added to the ground grinding liquid (the silver paste is soaked in solvent for 30 minutes before adding), and silica matting powder is added while dispersing, and then dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate with a colored UV coating.

[0052] The third aspect of the present invention provides a surface treatment layer, including a micro-arc oxidation treatment layer, wherein the surface of the micro-arc oxidation treatment layer is coated with the UV coating of the first aspect of the present invention.

[0053] One of the technical solutions of the present invention regarding the surface treatment layer has at least the following beneficial effects:

[0054] The surface treatment layer provided by the present invention, including the micro-arc oxidation treatment layer and the coated UV coating, has the following beneficial effects:

[0055] Micro-arc oxidation treatment can form a dense ceramic layer on the metal surface, providing better adhesion for UV coating. After applying UV coating, the bonding force of the coating can be further enhanced to ensure that the coating is not easy to fall off or wear under external force or harsh environment.

[0056] The micro-arc oxidation treatment layer has good corrosion resistance, and the UV coating itself has good chemical resistance (such as salt spray resistance, moisture and heat resistance, etc.). The combination of the two makes the surface treatment layer have stronger antioxidant and corrosion resistance, effectively improving the durability of the metal substrate, especially suitable for metal objects exposed to corrosive environments.

[0057] The micro-arc oxidation layer itself has high hardness and wear resistance, and the UV coating can also provide high hardness and wear resistance after curing. Especially when the hardness of the coating reaches 6H, it can effectively resist scratches and wear and increase the service life of the product.

[0058] After applying UV coating, the color effect can be adjusted (such as black, white, silver, gold, etc.), so that the metal surface not only has functional protection, but also can meet the diverse needs of consumers for appearance, and provide personalized and differentiated aesthetic effects.

[0059] The curing process of UV coatings is more energy-saving and environmentally friendly than traditional thermal baking coatings, and can reduce energy consumption and the emission of harmful substances. In addition, UV coatings have a lower volatile organic compound (VOC) content, which is conducive to reducing environmental pollution and meets the requirements of modern green environmental protection.

[0060] By using low temperature (50-60℃) baking followed by UV curing, the production cycle can be greatly shortened, energy consumption can be reduced, and the processing process is more efficient and simple. The simplicity of this process also helps to improve production efficiency and reduce manufacturing costs.

[0061] After micro-arc oxidation treatment, the substrate surface is rough and has strong hydrophilicity, which can effectively react physically and chemically with UV coatings to improve the adhesion and uniformity of the coating, making the surface treatment layer suitable for different types of metal substrates and meeting a variety of application requirements.

[0062] Therefore, the surface treatment layer of the present invention not only enhances the protective performance of the metal surface, but also improves the decorativeness by combining the characteristics of micro-arc oxidation and UV coating, thereby meeting the functional and aesthetic needs of different customers, and at the same time has the advantages of simple process, environmental protection and energy saving.

[0063] According to some embodiments of the present invention, the coating layer formed by the UV coating has a thickness of 15-20 microns.

[0064] The fourth aspect of the present invention provides a method for preparing the surface treatment layer of the third aspect of the present invention, comprising the following steps:

[0065] After the UV coating of the first aspect of the present invention is coated on the surface of the micro-arc oxidation treatment layer, it is baked at 50-60° C. for 3-5 minutes and then transferred to a UV oven for curing treatment.

[0066] A technical solution in the method for preparing a surface treatment layer of the present invention has at least the following beneficial effects:

[0067] Baking at 50-60°C for 3-5 minutes is low-temperature baking. Compared with the existing high-temperature baking process for coatings, which has high energy consumption and low efficiency, the curing process of the UV coating of the present invention is energy-saving, environmentally friendly and highly efficient.

[0068] According to some embodiments of the present invention, the UV energy of the curing process is 1000-2000 mJ / cm 2 .

[0069] According to some embodiments of the present invention, the UV light intensity of the curing process is greater than 150 mW / cm 2 .

[0070] First of all, in color-additive UV, the color is added to the pigment, which absorbs and blocks light, and will affect the UV penetration. When the UV light intensity is not enough, the UV penetration is not enough, and the UV cannot reach the bottom of the coating, and cannot stimulate the reaction of the coating, thus affecting the adhesion and other properties of the coating. Although energy can be increased by extending the time and increasing the light intensity, the effect of increasing energy is not the same as the effect of increasing light intensity.

[0071] According to some embodiments of the present invention, if the coating has a high viscosity, it needs to be diluted with a diluent and then applied by air spraying.

[0072] The fifth aspect of the present invention provides application of the surface treatment layer of the third aspect of the present invention in 3C products.

[0073] A technical solution of the present invention regarding the application of the surface treatment layer in 3C products has at least the following beneficial effects:

[0074] 3C products usually experience frequent friction and collision, such as the outer shell of mobile phones, laptops, headphones, etc. The ceramic layer formed by micro-arc oxidation treatment and the high hardness of UV coating work together to make the surface very wear-resistant, which can effectively resist scratches and wear in daily use and extend the service life of the product.

[0075] Micro-arc oxidation treatment can form a dense oxide layer on the metal surface, effectively preventing oxidation and corrosion. Combined with the anti-corrosion function of UV coating, it can enhance the corrosion resistance of 3C products in humid, high temperature or salt spray environments, ensuring the long-term stability of the product.

[0076] The shell of 3C products usually needs to be coated with multiple layers of protective coating (such as painting, electroplating, etc.), so adhesion is very important. The micro-arc oxidation treatment layer can form a uniform base on the metal surface, enhance the adhesion of the coating to the metal substrate, and avoid problems caused by peeling or shedding of the coating during use. After UV curing, the adhesion of UV coating is further enhanced, which is especially suitable for application on plastic and metal surfaces, ensuring that the coating will not fall off, fade or bubble during long-term use.

[0077] 3C products have high requirements for appearance, and consumers pursue more refined and personalized appearance. UV coatings can adjust different color effects (such as black, silver, gold, etc.), providing a rich color selection for 3C products and meeting the market demand for differentiated products. The micro-arc oxidation layer itself has a good texture, and the combination with UV coating can enhance the gloss and visual effect of the product surface, making the product not only highly functional, but also more attractive in appearance.

[0078] 3C products are easily scratched or hit by sharp objects during daily use, especially mobile phone screens, laptop cases, etc. The high hardness of UV coatings (such as pencil hardness ≥ 6H) can effectively improve the scratch resistance of the coating and avoid scratches that affect the appearance and function of the product. UV coatings themselves have strong UV resistance and can effectively prevent aging, fading and surface damage under sunlight. This is especially important for some 3C products that are often exposed to sunlight (such as smart watches, headphones, mobile phone cases, etc.), which can delay the aging process of the product and maintain its long-lasting color and appearance.

[0079] The process of using low-temperature (50-60°C) baking followed by UV curing can significantly shorten the production cycle, save a lot of energy consumption and improve production efficiency compared to traditional high-temperature baking or electroplating processes. This is particularly important for the mass production of 3C products, which helps to reduce manufacturing costs and improve market competitiveness.

[0080] 3C products have increasingly higher environmental requirements, and low VOC (volatile organic compound) emissions meet modern environmental standards. 3C products using this coating process not only meet environmental requirements and reduce harmful gas emissions, but also enhance corporate social responsibility. Reducing energy consumption and improving production efficiency through energy-saving processes not only helps reduce production costs, but also complies with the concept of sustainable development.

[0081] 3C products are often exposed to various chemicals in daily life (such as detergents, hand oil, fingerprints, sweat, etc.). UV coatings have good chemical resistance and can effectively prevent these substances from corroding and damaging the product surface, keeping the product surface clean and bright. For 3C products with high waterproof requirements, such as smart phones, smart watches, sports headphones, etc., the combination of micro-arc oxidation layer and UV coating can effectively prevent moisture from penetrating, protect the internal circuit from moisture damage, and enhance the product's waterproof performance.

[0082] Therefore, the application of the surface treatment layer (micro-arc oxidation + UV coating) of the present invention in 3C products can significantly improve the durability, appearance quality, corrosion resistance, scratch resistance and chemical resistance of the products. At the same time, this process has the characteristics of environmental protection, energy saving and simplicity, which is very suitable for the efficient production and market demand of modern 3C products. It not only improves the overall performance and appearance of the product, but also meets the consumer's demand for high quality, high cost performance and personalization. DETAILED DESCRIPTION

[0083] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0084] In the first aspect, some embodiments of the present invention provide a UV coating, wherein the raw materials for preparing the coating include ultraviolet light-curing resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax anti-settling slurry, pigment and matting powder.

[0085] The existing baking paint scheme of common coatings can add color because adding color will not affect the curing of the coating. However, for UV curing coatings, since the pigment absorbs light, it will affect the curing of the UV coating. Therefore, the existing UV coatings have the problem of difficult curing after adding color. The UV coating of the present invention reduces the influence of the pigment light absorption on UV curing by increasing the UV light intensity, and realizes the appropriate amount of color addition of the coating. The present invention increases the color addition ratio by increasing the light intensity, and the color addition and hiding properties are better than the prior art.

[0086] The present invention provides a colorable UV coating that can ensure good adhesion on a micro-arc oxidation treated substrate to protect the metal surface and at the same time provide different color effects to meet the diverse and differentiated needs of customers.

[0087] The UV coating of the present invention only needs to be baked at 50-60°C for 3-5 minutes, and then cured by UV to obtain a UV protective layer with high hardness, high wear resistance and good chemical resistance. It has good adhesion on the micro-arc oxidation substrate, and meets the adhesion of ≥4B after boiling at 85°C for 1 hour; it has high hardness, and the pencil hardness is 1000g≥6H; it has high wear resistance, and the RCA paper tape is abraded 150g≥300 times; it has good chemical resistance, and the salt spray adhesion is ≥4B for 48 hours; different color effects can be adjusted, such as black, white, silver, gold, etc. The UV coating of the present invention has the characteristics of simple process, high efficiency, energy saving, environmental protection, etc.

[0088] In combination with the first aspect, in some embodiments of the present invention, the raw materials for preparation include, by weight:

[0089] UV curing resin: 30-40 parts,

[0090] Active monomer: 5-10 parts,

[0091] Thermoplastic acrylic resin: 5-10 parts,

[0092] Photoinitiator: 1-4 parts,

[0093] Adhesion promoter: 1-4 parts,

[0094] Substrate wetting agent: 0.2-0.5 parts,

[0095] Ethyl acetate: 10-20 parts,

[0096] Butyl acetate: 10-20 parts,

[0097] Fumed silica: 1-5 parts,

[0098] Polyamide wax anti-settling slurry: 1-5 parts,

[0099] Pigment: 5-10 parts,

[0100] Matting powder: 0-5 parts.

[0101] For UV-curable resins, choose low-functional group resins in combination with high-functional group resins. For low-functional resins, choose epoxy-modified acrylic resins with 2-3 functional groups and good adhesion to metals to ensure the adhesion of the coating on the micro-arc oxidation substrate and adjust the flexibility of the paint film. The micro-arc oxidation substrate has a high hardness and the paint film hardness is above 6H. The coating cannot be too hard, otherwise the paint will easily collapse. It is necessary to add resins with better flexibility to adjust the flexibility and improve the paint collapse phenomenon. For high-functional resins, choose polyurethane acrylic resins with 6-12 functional groups. They have good reaction activity and high cross-linking density, which can improve the chemical resistance and wear resistance of the paint film, while ensuring deep curing and improving the adhesion of the paint film.

[0102] In combination with the first aspect, in some embodiments of the present invention, the active monomer includes dipentaerythritol hexaacrylate resin, which has high functionality and good reactivity, can enhance the reactivity of the color-additive UV coating, ensure deep curing of the coating, and thus ensure the adhesion of the paint film.

[0103] In combination with the first aspect, in some embodiments of the present invention, the Tg value of the thermoplastic acrylic resin is 80-120°C.

[0104] In combination with the first aspect, in some embodiments of the present invention, the molecular weight of the thermoplastic acrylic resin is 100,000-200,000.

[0105] Choose a macromolecular thermoplastic acrylic resin with a Tg value of 80-120℃ and a molecular weight of 100,000-200,000. When the paint film is cured, it can reduce the volume shrinkage of the paint film, reduce the shrinkage stress, and improve adhesion. At the same time, thermoplastic acrylic resin has good solvent release and thixotropy, which can improve paint film defects such as edge accumulation and sagging during the coating construction process.

[0106] Photoinitiators absorb UV energy and generate free radicals, which initiate polymerization of monomers to crosslink and cure the compound.

[0107] In combination with the first aspect, in some embodiments of the present invention, the adhesion promoter includes trifunctional methacrylate phosphate. The water boiling adhesion of the coating can be improved. It is necessary to select an adhesion promoter with high functionality and good reactivity to ensure that the adhesion promoter can participate in the reaction in the color-added UV, thereby improving the adhesion. Otherwise, the reaction speed is slow and the reaction is incomplete, which will lead to water boiling and blistering.

[0108] The surface of the micro-arc oxidation substrate is a microporous structure. After spraying the coating, tiny microbubbles are easily left on the surface of the substrate. During the water boiling test, the air in the microbubbles expands and contracts, causing the paint film to bubble when boiling. Adding a substrate wetting agent improves the wettability of the coating to the substrate. When the coating is applied to the surface of the substrate, the coating can well wet the microporous structure, ensure that the coating fills the microporous structure, and remove the air in the micropores. While solving the problem of boiling bubbles, the coating and the substrate form an anchoring effect, which improves the adhesion of the coating on the micro-arc oxidation substrate.

[0109] The surface of fumed silica contains a large number of hydroxyl groups, which allow the silica to be connected together through hydrogen bonds to form a three-dimensional network structure of silica, which can prevent the color paste and silver bead powder in the paint from agglomerating and settling, thereby improving the storage stability of the paint.

[0110] Polyamide wax is a thixotropic additive that forms a network structure in the paint and has excellent thixotropic, anti-sagging and anti-settling properties. It can effectively prevent the agglomeration and sedimentation of the color paste and silver bead powder in the paint, ensure the uniformity and storage stability of the paint, and improve the workability of the paint.

[0111] Pigments can be selected from color paste, aluminum silver paste, pearlescent powder and other pigments to meet customers' different appearance effect requirements.

[0112] In combination with the first aspect, in some embodiments of the present invention, the matting agent includes silicon dioxide.

[0113] In a second aspect, in some embodiments of the present invention, there is provided a method for preparing the UV coating of the first aspect of the present invention, comprising the following steps:

[0114] S1: adding thermoplastic acrylic resin and butyl acetate into a dispersion kettle for dispersion to obtain dissolved thermoplastic acrylic resin;

[0115] S2: adding a photoinitiator into ethyl acetate to dissolve, adding the dissolved thermoplastic acrylic resin, ultraviolet light curing resin, active monomer, substrate wetting agent, and adhesion promoter, while dispersing, adding polyamide wax anti-settling slurry and fumed silica to obtain a dispersion, and grinding the dispersion;

[0116] S3: Add pigment and matting powder to the dispersion to obtain UV coating after dispersion.

[0117] It is easy to understand that the preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easily available, the production cost is low, and it is easy to industrialize production.

[0118] In step S1:

[0119] Add thermoplastic acrylic resin and butyl acetate into a dispersion kettle and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0120] In step S2:

[0121] Dissolve the photoinitiator in ethyl acetate, then add the dissolved acrylic resin, UV curing resin, active monomer, substrate wetting agent, and adhesion promoter, disperse at a speed of 800-1000 rpm for 10 minutes, add polyamide wax anti-settling slurry and fumed silica while dispersing, and disperse at a speed of 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness of ≤5μm, and transfer the grinding liquid to a dispersion kettle.

[0122] In step S3:

[0123] Pigments can be added to the ground grinding liquid (the silver paste is soaked in solvent for 30 minutes before adding), and silica matting powder is added while dispersing, and then dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate with a colored UV coating.

[0124] In a third aspect, in some embodiments of the present invention, a surface treatment layer is provided, comprising a micro-arc oxidation treatment layer, the surface of the micro-arc oxidation treatment layer is coated with the UV coating of the first aspect of the present invention.

[0125] It can be understood that the surface treatment layer provided by the present invention, including the micro-arc oxidation treatment layer and the coated UV coating, has the following beneficial effects:

[0126] Micro-arc oxidation treatment can form dense ceramic micropores on the metal surface. The microporous structure can anchor the coating on the surface of the metal oxide layer and increase the adhesion of the coating. It provides better adhesion for UV coating. After applying UV coating, the bonding force of the coating can be further enhanced to ensure that the coating is not easy to fall off or wear under external force or harsh environment.

[0127] The micro-arc oxidation treatment layer has good corrosion resistance, and the UV coating itself has good chemical resistance (such as salt spray resistance, moisture and heat resistance, etc.). The combination of the two makes the surface treatment layer have stronger antioxidant and corrosion resistance, effectively improving the durability of the metal substrate, especially suitable for metal objects exposed to corrosive environments.

[0128] The micro-arc oxidation layer itself has high hardness and wear resistance, and the UV coating can also provide high hardness and wear resistance after curing. Especially when the hardness of the coating reaches 6H, it can effectively resist scratches and wear and increase the service life of the product.

[0129] After applying UV coating, the color effect can be adjusted (such as black, white, silver, gold, etc.), so that the metal surface not only has functional protection, but also can meet the diverse needs of consumers for appearance, and provide personalized and differentiated aesthetic effects.

[0130] The curing process of UV coatings is more energy-saving and environmentally friendly than traditional thermal baking coatings, and can reduce energy consumption and the emission of harmful substances. In addition, UV coatings have a lower volatile organic compound (VOC) content, which is conducive to reducing environmental pollution and meets the requirements of modern green environmental protection.

[0131] By using low temperature (50-60℃) baking followed by UV curing, the production cycle can be greatly shortened, energy consumption can be reduced, and the processing process is more efficient and simple. The simplicity of this process also helps to improve production efficiency and reduce manufacturing costs.

[0132] After micro-arc oxidation treatment, the substrate surface is rough and has strong hydrophilicity, which can effectively react physically and chemically with UV coatings to improve the adhesion and uniformity of the coating, making the surface treatment layer suitable for different types of metal substrates and meeting a variety of application requirements.

[0133] Therefore, the surface treatment layer of the present invention not only enhances the protective performance of the metal surface, but also improves the decorativeness by combining the characteristics of micro-arc oxidation and UV coating, thereby meeting the functional and aesthetic needs of different customers, and at the same time has the advantages of simple process, environmental protection and energy saving.

[0134] In combination with the third aspect, in some embodiments of the present invention, the thickness of the coating formed by the UV coating is 15-20 microns.

[0135] In a fourth aspect, in some embodiments of the present invention, there is provided a method for preparing the surface treatment layer of the third aspect of the present invention, comprising the following steps:

[0136] After the UV coating of the first aspect of the present invention is coated on the surface of the micro-arc oxidation treated layer, it is baked at 50-60° C. for 3-5 minutes and then transferred to a UV oven for curing treatment.

[0137] It should be noted that baking at 50-60°C for 3-5 minutes is low-temperature baking, which is to volatilize the organic solvents (ethyl acetate and butyl acetate) and do not participate in the reaction. The purpose of the organic solvent is to facilitate construction. Compared with the existing high-temperature baking process of coatings with high energy consumption and low efficiency, the curing process of the UV coating of the present invention is energy-saving, environmentally friendly and efficient.

[0138] In combination with the fourth aspect, in some embodiments of the present invention, the UV energy of the curing process is 1000-2000 mJ / cm 2 .

[0139] In conjunction with the fourth aspect, in some embodiments of the present invention, the UV light intensity of the curing process is greater than 150 mW / cm 2 .

[0140] First of all, in color-additive UV, the color is added to the pigment, which absorbs and blocks light, and will affect the UV penetration. When the UV light intensity is not enough, the UV penetration is not enough, and the UV cannot reach the bottom of the coating, and cannot stimulate the reaction of the coating, thus affecting the adhesion and other properties of the coating. Although energy can be increased by extending the time and increasing the light intensity, the effect of increasing energy is not the same as the effect of increasing light intensity.

[0141] In combination with the fourth aspect, in some embodiments of the present invention, if the viscosity of the coating is high, it needs to be diluted with a diluent and then applied by air spraying.

[0142] In a fifth aspect, in some embodiments of the present invention, there is provided application of the surface treatment layer of the third aspect of the present invention in 3C products.

[0143] It is understandable that 3C products usually experience frequent friction and collision, such as the outer shell of mobile phones, laptops, headphones, etc. The ceramic layer formed by micro-arc oxidation treatment and the high hardness of UV coating work together to make the surface very wear-resistant, which can effectively resist scratches and wear in daily use and extend the service life of the product.

[0144] Micro-arc oxidation treatment can form a dense oxide layer on the metal surface, effectively preventing oxidation and corrosion. Combined with the anti-corrosion function of UV coating, it can enhance the corrosion resistance of 3C products in humid, high temperature or salt spray environments, ensuring the long-term stability of the product.

[0145] The shell of 3C products usually needs to be coated with multiple layers of protective coating (such as painting, electroplating, etc.), so adhesion is very important. The micro-arc oxidation treatment layer can form a uniform base on the metal surface, enhance the adhesion of the coating to the metal substrate, and avoid problems caused by peeling or shedding of the coating during use. After UV curing, the adhesion of UV coating is further enhanced, which is especially suitable for application on plastic and metal surfaces, ensuring that the coating will not fall off, fade or bubble during long-term use.

[0146] 3C products have high requirements for appearance, and consumers pursue more refined and personalized appearance. UV coatings can adjust different color effects (such as black, silver, gold, etc.), providing a rich color selection for 3C products and meeting the market demand for differentiated products. The micro-arc oxidation layer itself has a good texture, and the combination with UV coating can enhance the gloss and visual effect of the product surface, making the product not only highly functional, but also more attractive in appearance.

[0147] 3C products are easily scratched or hit by sharp objects during daily use, especially mobile phone screens, laptop cases, etc. The high hardness of UV coatings (such as pencil hardness ≥ 6H) can effectively improve the scratch resistance of the coating and avoid scratches that affect the appearance and function of the product. UV coatings themselves have strong UV resistance and can effectively prevent aging, fading and surface damage under sunlight. This is especially important for some 3C products that are often exposed to sunlight (such as smart watches, headphones, mobile phone cases, etc.), which can delay the aging process of the product and maintain its long-lasting color and appearance.

[0148] The process of using low-temperature (50-60°C) baking followed by UV curing can significantly shorten the production cycle, save a lot of energy consumption and improve production efficiency compared to traditional high-temperature baking or electroplating processes. This is particularly important for the mass production of 3C products, which helps to reduce manufacturing costs and improve market competitiveness.

[0149] 3C products have increasingly higher requirements for environmental protection. UV coatings do not require the use of solvents when curing, and have low VOC (volatile organic compound) emissions, which meet modern environmental standards. 3C products using this coating process not only meet environmental requirements and reduce the emission of harmful gases, but also enhance the company's sense of social responsibility. Reducing energy consumption and improving production efficiency through energy-saving processes not only helps reduce production costs, but also conforms to the concept of sustainable development.

[0150] 3C products are often exposed to various chemicals in daily life (such as detergents, hand oil, fingerprints, sweat, etc.). UV coatings have good chemical resistance and can effectively prevent these substances from corroding and damaging the product surface, keeping the product surface clean and bright. For 3C products with high waterproof requirements, such as smart phones, smart watches, sports headphones, etc., the combination of micro-arc oxidation layer and UV coating can effectively prevent moisture from penetrating, protect the internal circuit from moisture damage, and enhance the product's waterproof performance.

[0151] Therefore, the application of the surface treatment layer (micro-arc oxidation + UV coating) of the present invention in 3C products can significantly improve the durability, appearance quality, corrosion resistance, scratch resistance and chemical resistance of the products. At the same time, this process has the characteristics of environmental protection, energy saving and simplicity, which is very suitable for the efficient production and market demand of modern 3C products. It not only improves the overall performance and appearance of the product, but also meets the consumer's demand for high quality, high cost performance and personalization.

[0152] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0153] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0154] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0155] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0156] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0157] In the embodiments and comparative examples of the present invention, the types and manufacturers of the raw materials used are shown in Table 1.

[0158] Table 1

[0159] raw material Manufacturer model Photoinitiator 1 IGM Omnirad 1173 Photoinitiator 2 IGM Omnirad 819 Ethyl acetate / / Butyl acetate / / Thermoplastic acrylic resin Bollier MB-18-A UV curing resin 1 Changxing Chemical 61967 UV curing resin 2 Bahe New Materials BW 8288-2 Dipentaerythritol hexaacrylate Changxing Chemical EM266 Adhesion promoter Runao Chemical R9107 Substrate wetting agent 3M FC-4430 Polyamide wax Disbaron 6900-HV Fumed Silica Degussa A380 Silver paste / color paste Love Card HP Z 1255IL Butyl acetate / / Silica matting powder Tosou K500

[0160] Example 1

[0161] Two UV coatings A and B were prepared. The raw materials are shown in Table 2. The preparation method is as follows:

[0162] S1: adding thermoplastic acrylic resin and butyl acetate into a dispersion kettle for dispersion to obtain dissolved thermoplastic acrylic resin;

[0163] S2: adding a photoinitiator into ethyl acetate to dissolve, adding the dissolved thermoplastic acrylic resin, ultraviolet light curing resin, active monomer, substrate wetting agent, and adhesion promoter, while dispersing, adding polyamide wax anti-settling slurry and fumed silica to obtain a dispersion, and grinding the dispersion;

[0164] S3: Add pigment and matting powder to the dispersion to obtain UV coating after dispersion.

[0165] In step S1:

[0166] Add thermoplastic acrylic resin and butyl acetate into a dispersion kettle and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0167] In step S2:

[0168] Dissolve the photoinitiator in ethyl acetate, then add the dissolved acrylic resin, UV curing resin, active monomer, substrate wetting agent, and adhesion promoter, disperse at a speed of 800-1000 rpm for 10 minutes, add polyamide wax anti-settling slurry and fumed silica while dispersing, and disperse at a speed of 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness of ≤5μm, and transfer the grinding liquid to a dispersion kettle.

[0169] In step S3:

[0170] Pigments can be added to the ground grinding liquid (the silver paste is soaked in solvent for 30 minutes before adding), and silica matting powder is added while dispersing, and then dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate with a colored UV coating.

[0171] The purpose of compounding photoinitiator 1173 and photoinitiator 819 is to fully absorb ultraviolet light and improve the initiation efficiency, thereby improving the bottom curing effect of the coating.

[0172] The purpose of compounding the UV-curable resin 1 and the UV-curable resin 2 is to increase the overall reaction rate of the coating and improve the bottom curing effect of the coating.

[0173] Comparative Example 1

[0174] Five UV comparison coatings, C to G, were prepared. The raw materials are shown in Table 2. The preparation method is the same as the coating preparation method in Example 1.

[0175] Table 2

[0176]

[0177]

[0178] Example 2

[0179] UV coatings A and B were prepared into coating A and coating B, and the process parameters were shown in Table 3.

[0180] Comparative Example 2

[0181] UV comparison coatings C to G were prepared into coatings C to G, and the process parameters are shown in Table 3.

[0182] Table 3

[0183] Coating A Coating B Coating C Coating D Coating E Coating F Coating G Dilute ratio 100:100 100:100 100:100 100:100 100:100 100:100 100:100 Baking temperature 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ Bake time 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes UV curing light intensity 200 200 200 200 100 200 200 UV curing energy 1500 1500 1500 1500 1500 1500 1500

[0184] The thickness of coatings A to G was 16 microns.

[0185] Performance Testing

[0186] The properties of coatings A to G were tested, including:

[0187] 1. Conventional adhesion: The adhesion test is carried out according to the method specified in GB / T 9826. 100 / 100 means that 10*10 grids are drawn on the coating, and after the test, no coating falls off in any of the 100 grids.

[0188] 2. Water resistance: Place in a constant temperature water bath at 85°C for 1 hour, take it out and wipe it clean with a rag, observe whether the paint film has discoloration, bubbling, etc., and test the adhesion.

[0189] 3. RCA abrasion resistance: RCA paper bag abrasion tester (Norman Tool RCAAbrader), 175g load, record the number of times the paint film is worn. The sample and abrasive medium should be placed in an environment of 23±2℃ and 50±10% relative humidity for 24 hours before testing.

[0190] 4. Hardness: Pencil hardness tester. Japanese Mitsubishi pencil, H, 750g.

[0191] 5. Stain resistance: Use a ZEBRA oil-based pen (model: MO-120-MC, fine tip test), with the oil-based pen at an angle of about 90° to the coating surface, apply a force of about 1-2N to uniformly draw 5 5-10mm lines on the coating surface. After standing at room temperature for 10 minutes, wipe the surface with alcohol (concentration ≥ 99.5%). No traces remain after wiping.

[0192] 6. Chemical resistance test: Apply vaseline to the surface of the paint film, and then place it in a constant temperature and humidity chamber (temperature 85°C, humidity 85%) for 96 hours. After taking it out, wipe it clean with a rag and observe whether the paint film has discoloration, bubbling, discoloration, paint peeling, etc.

[0193] 7. Salt spray: neutral salt spray, leave it for 96 hours, take it out and wipe it clean with a rag, and observe whether the paint film has discoloration, bubbling, color change, paint peeling, etc.

[0194] The test results are shown in Table 4.

[0195] Table 4

[0196]

[0197]

[0198] By comparing coating A and coating C, it can be seen that adding a substrate wetting agent can ensure that the coating fully wets the microporous structure of the micro-arc oxidation substrate, ensure that the coating fills the microporous structure, form an anchoring effect, enhance the adhesion of the coating on the micro-arc oxidation substrate, and improve the water boiling adhesion.

[0199] Comparison between coating A and coating D shows that acid phosphate adhesion promoters form a stable bridge between the coating and the substrate through chemical bonding, improving the adhesion and water resistance of the coating.

[0200] Comparison between coating B and coating E shows that: the higher the light intensity of UV curing, the higher the UV penetration ability, which can improve the deep curing effect of the color-added UV coating, thereby improving the adhesion and water resistance of the coating.

[0201] By comparing coating B with coating F, it can be seen that the use of photoinitiators can improve the utilization rate of UV energy and the curing effect of the coating, thereby improving the wear resistance and water resistance of the coating.

[0202] By comparing coating B and coating G, it can be seen that UV-curable resin 1 is a high-functionality resin (6 to 12 functional groups), and UV-curable resin 2 is a low-functionality resin (2 to 3 functional groups). The introduction of high-functionality UV resin into the formula can increase the overall reaction rate of the coating and improve the deep curing effect of the color-added UV coating, thereby improving the wear resistance and water resistance of the paint film.

[0203] It should also be noted that the one-coat color-added UV coating in the prior art is mainly suitable for plastic substrates. Plastic substrates are easily swollen by solvents and easily bitten by active monomers to form an anchoring effect, so adhesion is easy to solve. However, the metal surface has a high hardness and is not easily bitten, so the coating is difficult to adhere. At present, the color of the substrate after micro-arc oxidation treatment is generally off-white. If it is necessary to make it into black, blue, red and other colors that are very different from white, the bottom is likely to show through, which is not conducive to color control. The present invention controls the UV light intensity at 150mW / cm 2 As mentioned above, the color addition ratio of UV coating is increased to 5-10%, which can still ensure the deep curing effect of the coating, ensure the covering power of the coating, ensure the bright appearance of the coating, and facilitate color control during the production process.

[0204] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A UV coating, characterized in that: The preparation raw materials include ultraviolet light curing resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, gas phase silica, polyamide wax anti-settling slurry, pigment and matting powder.

2. The UV coating according to claim 1, characterized in that: In parts by weight, the raw materials for preparation include: UV curing resin: 30-40 parts, Active monomer: 5-10 parts, Thermoplastic acrylic resin: 5-10 parts, Photoinitiator: 1-4 parts, Adhesion promoter: 1-4 parts, Substrate wetting agent: 0.2-0.5 parts, Ethyl acetate: 10-20 parts, Butyl acetate: 10-20 parts, Fumed silica: 1-5 parts, Polyamide wax anti-settling slurry: 1-5 parts, Pigment: 5-10 parts, Matting powder: 0-5 parts.

3. The UV coating according to claim 1 or 2, characterized in that: The reactive monomer includes dipentaerythritol hexaacrylate resin.

4. The UV coating according to claim 1 or 2, characterized in that: The Tg value of the thermoplastic acrylic resin is 80-120° C.; and / or the molecular weight of the thermoplastic acrylic resin is 100,000-200,000.

5. The UV coating according to claim 1 or 2, characterized in that: The adhesion promoter includes trifunctional methacrylate phosphate.

6. The UV coating according to claim 1 or 2, characterized in that: The matting agent includes silicon dioxide.

7. A method for preparing a UV coating as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1: adding the thermoplastic acrylic resin and butyl acetate into a dispersion kettle for dispersion to obtain a dissolved thermoplastic acrylic resin; S2: adding the photoinitiator into ethyl acetate to dissolve, adding the dissolved thermoplastic acrylic resin, ultraviolet light curing resin, active monomer, substrate wetting agent, adhesion promoter, adding the polyamide wax anti-settling slurry and fumed silica while dispersing to obtain a dispersion, and grinding the dispersion; S3: adding the pigment and the matting powder into the dispersion to obtain the UV coating after dispersion.

8. A surface treatment layer, characterized in that: It comprises a micro-arc oxidation treatment layer, the surface of which is coated with the UV coating according to any one of claims 1 to 6.

9. A method for preparing the surface treatment layer according to claim 8, characterized in that: The following steps are involved: After the UV coating according to any one of claims 1 to 6 is applied on the surface of the micro-arc oxidation treatment layer, it is baked at 50-60° C. for 3-5 minutes and then transferred to a UV oven for curing treatment; and / or the UV energy of the curing treatment is 1000-2000 mJ / cm 2 ; and / or, the UV light intensity of the curing treatment is > 150mW / cm 2 .

10. Application of the surface treatment layer as claimed in claim 8 in 3C products.

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