Household appliance color-coated sheet cured by adopting EB curing technology and preparation method of household appliance color-coated sheet

Abstract

The invention belongs to the technical field of metal material surface treatment, and particularly discloses a home appliance color-coated sheet cured by adopting an EB curing technology and a preparation method of the home appliance color-coated sheet. The home appliance color-coated sheet cured by adopting the EB curing technology comprises a hot galvanizing substrate, a UV primer layer, an EB finish paint layer and a protective film, and the protective film is prepared from the following raw materials in parts by weight: 60-65 parts of low-density polyethylene, 12-15 parts of ethylene-vinyl acetate copolymer, 6-9 parts of nano tackifying clay, 3-5 parts of chopped polyurethane fiber, 1-3 parts of antioxidant and 2-4 parts of dispersing agent. According to the protective film, multiple components are synergistically matched, so that the protective film has good mechanical strength, good flexibility, low possibility of brittle failure, high durability, damage resistance, tear resistance, puncture resistance and wear resistance, and can effectively resist scraping and collision of household appliance plates in transportation and installation processes.

Description

Technical Field

[0001] This application relates to the technical field of surface treatment of metal materials, and in particular to a color-coated sheet for home appliances cured using EB curing technology and its preparation method. Background Technology

[0002] Color-coated steel sheets for home appliances are pre-coated products made from metal coils as the substrate through surface treatment and coating processes. Their structure mainly includes a substrate layer and a coating structure. Organic coatings are uniformly applied to the surface of the substrate using a roller coating method to obtain the finished color-coated steel sheet for home appliances.

[0003] Existing color-coated steel sheets for home appliances typically consist of a substrate, a primer, and a topcoat. Common substrate materials include hot-dip galvanized steel, zinc-coated steel, aluminum, and stainless steel. The primer layer is usually an epoxy or polyester coating, which may be solvent-based or water-based, providing a dense barrier to further block moisture and corrosive media. The topcoat layer typically uses a traditional thermosetting type, offering good overall performance, high gloss, and excellent gloss and color retention.

[0004] However, the aforementioned color-coated panels for home appliances are prone to scratches on their surface during long-term exposure to sunlight or daily impacts, which in turn affects their durability. Summary of the Invention

[0005] To address the issue of scratches easily appearing on the surface of color-coated panels for home appliances, this application provides a color-coated panel for home appliances cured using EB curing technology and its preparation method.

[0006] This application provides a color-coated sheet for home appliances cured using EB curing technology, and adopts the following technical solution: A color-coated sheet for home appliances cured using EB curing technology includes a hot-dip galvanized substrate, a UV primer layer, an EB topcoat layer, and a protective film. The protective film, by weight, includes the following raw materials: 60-65 parts of low-density polyethylene, 12-15 parts of ethylene-vinyl acetate copolymer, 6-9 parts of nano-adhesive clay, 3-5 parts of chopped polyurethane fiber, 1-3 parts of antioxidant, and 2-4 parts of dispersant.

[0007] By adopting the above technical solution, the hot-dip galvanized substrate serves as the supporting framework for the entire color-coated sheet, providing basic corrosion resistance and forming the foundation for subsequent coating adhesion. The UV primer layer connects the hot-dip galvanized substrate and the EB topcoat layer, solving the adhesion problem between the substrate and the topcoat, while optimizing surface smoothness and laying the foundation for topcoat decoration. The EB topcoat layer gives the color-coated sheet for home appliances an aesthetically pleasing appearance, while providing weather resistance, scratch resistance, and chemical corrosion resistance, improving the durability of home appliances. The protective film has good abrasion resistance and mechanical strength, protecting the EB topcoat layer from damage during the production, transportation, and processing of the color-coated sheet.

[0008] In the protective film, low-density polyethylene (LDPE) serves as the main material, forming the film's framework and exhibiting excellent film-forming properties, resulting in a uniform and smooth film. The vinyl acetate segments in the ethylene-vinyl acetate copolymer provide polarity and viscosity, allowing the protective film to adhere firmly to the surface of the color-coated sheet and preventing it from easily detaching. It also improves the impact resistance and flexibility of LPE, making the protective film less prone to breakage under tension or puncture. Nano-adhesive clay particles can be uniformly dispersed in the polymer matrix, enhancing the mechanical strength (modulus, tear resistance) and dimensional stability (reducing thermal expansion and contraction) of the protective film. The layered nano-adhesive clay can extend the pathways for oxygen and moisture, providing a certain barrier effect and better protecting the underlying paint surface.

[0009] Short-cut polyurethane fibers form a network within the matrix, dispersing concentrated stress over a larger area and preventing the protective film from tearing due to localized damage. They also exhibit extremely high elongation and resilience, improving the puncture and tear resistance of the protective film. Antioxidants prevent material aging during processing and use, extending the service life and shelf life of the protective film. Dispersants ensure uniform dispersion of the nano-adhesive clay and short-cut polyurethane fibers, guaranteeing the overall performance of the protective film. The multi-component synergistic effect of this protective film results in excellent mechanical strength, good flexibility, resistance to brittleness, high durability and damage resistance, tear resistance, puncture resistance, and abrasion resistance, effectively protecting the sheet metal of household appliances from scratches and impacts encountered during transportation and installation.

[0010] Preferably, the preparation method of the nano-adhesive clay includes the following steps: (1) Disperse kaolin in sodium hydroxide solution, stir for 20-25 min, calcine at 350-360℃ for 1-2 h, and then grind it with triisopropanolamine and sodium carboxymethyl cellulose to obtain treated clay; (2) Disperse the composite nano zinc oxide into deionized water, add the treated clay from step (1), stir at 70-75℃ for 2-3 hours, dry, grind, and obtain nano-adhesive clay.

[0011] By employing the above technical solution, sodium hydroxide treatment of kaolin partially breaks the silicon-oxygen and aluminum-oxygen bonds on the kaolin surface, making the structure more porous and forming new active sites. Calcination further removes moisture and organic impurities from the kaolin, making the active sites generated by alkali treatment more stable and significantly increasing the specific surface area and porosity of the clay.

[0012] The amino and hydroxyl groups in triisopropanolamine molecules can interact with active sites on the activated clay surface, reducing the surface energy of the clay particles and resulting in better compatibility and dispersibility. This helps prevent particle re-agglomeration during subsequent grinding. Sodium carboxymethyl cellulose molecules contain numerous carboxyl and hydroxyl groups, exhibiting good water solubility. They adsorb onto the hollow cores and surface of kaolin, with polar groups forming hydrogen bonds with the hydroxyl groups on the kaolin surface, simultaneously providing sites for subsequent bonding with nano-zinc oxide. During grinding, these polar groups can tightly bind to the alkali-activated kaolin surface through hydrogen bonds. Adhering to the surface and pores of clay particles, they assist in forming a stable structure and enhance the subsequent bonding force with composite nano-zinc oxide.

[0013] Composite nano-zinc oxide can fill the pores of treated clay, and its surface hydroxyl groups can bind to the active sites of the clay, firmly loading onto the surface and pores of the activated clay with a huge specific surface area, thus improving the adhesion and mechanical properties of the nano-adhesive clay. Meanwhile, sodium carboxymethyl cellulose, which is soluble in water and has viscosity, exhibits enhanced molecular chain mobility. Through physical entanglement and hydrogen bonding, it effectively captures and fixes nano-zinc oxide particles, while also forming stronger physical entanglement with the active sites of kaolin, thereby improving the composite stability of the three components.

[0014] The obtained nano-adhesive clay has strong interfacial bonding, excellent dispersibility and mechanical properties. When applied to protective films, it improves the tear resistance and durability of the protective films and has good adhesion to the EB topcoat layer.

[0015] Preferably, the mass ratio of kaolin, composite nano zinc oxide and sodium carboxymethyl cellulose is 1:0.65-0.76:0.12-0.35.

[0016] By employing the above technical solution and further limiting the mass ratio of kaolin, composite nano-zinc oxide, and sodium carboxymethyl cellulose within a certain range, the resulting nano-adhesive clay exhibits excellent comprehensive properties. Kaolin serves as the substrate, providing a large specific surface area and numerous physical adsorption sites. The composite nano-zinc oxide possesses good mechanical strength and heat resistance, enabling it to adsorb onto the surface and within the pores of the kaolin, thus improving the strength, stiffness, and heat resistance of the composite material. Sodium carboxymethyl cellulose provides a certain degree of viscosity, ensuring a tight bond between the kaolin and the composite nano-zinc oxide, thereby enhancing the overall performance of the kaolin. When subsequently applied to protective films, the three components work synergistically to improve the high viscosity, high toughness, and high strength requirements of the protective film.

[0017] Preferably, the preparation method of the composite nano zinc oxide includes the following steps: dispersing nano zinc oxide in a modifier, stirring at a temperature of 60-65℃ for 1-2 hours, drying, and grinding to obtain composite nano zinc oxide; Modifiers include: stearic acid, silane coupling agent, deionized water, modified rice husk powder, and dispersant; The preparation method of modified rice husk powder includes the following steps: dispersing rice husk powder in modified starch solution, stirring for 30-35 min, then adding carbon nanotubes, stirring at 65-68℃ for 1-2 h, filtering, and drying to obtain modified rice husk powder.

[0018] By adopting the above technical solution, nano zinc oxide is dispersed in a modifier, and the modifier forms a film on the surface of the nano zinc oxide, resulting in a composite nano zinc oxide with superior comprehensive performance, excellent reinforcement and toughening effect, good dispersibility, and strong interfacial bonding force.

[0019] In this modifier, stearic acid reduces the surface energy of nano-zinc oxide, improving the dispersibility of the system; the silane coupling agent reacts with the hydroxyl groups on the surface of nano-zinc oxide at one end and is compatible with the organic matrix at the other end, enhancing the interfacial bonding force; modified rice husk powder has excellent dispersibility and reinforcing properties, allowing nano-zinc oxide to be adsorbed on the surface and within the pores of the modified rice husk powder, thereby improving the compatibility and mechanical properties of the composite nano-zinc oxide; the dispersant prevents the agglomeration of nano-zinc oxide during the modification process, ensuring uniform modification. Through the synergistic effect of multiple modifiers, the problems of easy agglomeration of nano-zinc oxide and poor compatibility with the organic matrix are solved, while the composite characteristics of modified rice husk powder are introduced, expanding the functional dimensions.

[0020] In the preparation method of modified rice husk powder, the hydroxyl groups of starch molecules in modified starch can form hydrogen bonds with the hydroxyl groups on the surface of rice husk powder, adhering to the surface of rice husk powder and forming an active viscous surface; carbon nanotubes have good antibacterial and mechanical properties, adhere to the surface of rice husk powder, and interact with starch molecules, so that carbon nanotubes are uniformly attached to the surface of rice husk powder, improving the mechanical, toughness and functional properties of the final material.

[0021] Preferably, the method for preparing the chopped polyurethane fiber includes the following steps: dissolving thermoplastic polyurethane in dimethylformamide solution, adding nano-silica, silane coupling agent and dispersant and stirring evenly, adjusting the pH of the mixture to 3-4 with citric acid, degassing for 6-7 hours after mixing evenly to obtain polyurethane spinning solution, spinning, cutting into segments, then dispersing into the mixture, drying to obtain chopped polyurethane fiber; The mixture includes: modified ceramic whiskers, deionized water, polyvinyl alcohol, and dispersant.

[0022] By employing the above technical solutions, thermoplastic polyurethane (TPU) offers excellent elasticity, toughness, and abrasion resistance. The addition of nano-silica to the spinning solution creates physical cross-linking points within the TPU fibers, significantly improving their strength, modulus, and thermal stability. A silane coupling agent, with one end reacting with the hydroxyl groups on the surface of the nano-silica and the other end compatible with or reacting with the organic TPU molecular chains, forms a "molecular bridge" between them, resolving compatibility issues and preventing nanoparticle aggregation. A dispersant helps to uniformly disperse the nano-silica in the dimethylformamide solution and the TPU matrix. Spinning transforms the TPU solution containing nano-SiO2 into continuous fibers, which are then cut into the desired short fibers. Compared to pure TPU fibers, this results in higher strength, stiffness, and heat resistance, while maintaining the inherent high elasticity of TPU.

[0023] The mixture is coated onto the fiber surface to form a robust composite shell. Modified ceramic whiskers possess extremely high strength, modulus, and hardness, while the PVA aqueous solution exhibits excellent film-forming properties and adhesion, firmly bonding the ceramic whiskers to the TPU fiber surface. A dispersant ensures uniform dispersion of the ceramic whiskers in water, preventing agglomeration and thus forming a uniform coating layer on the fiber surface. The resulting chopped polyurethane fibers offer flexibility, elasticity, and matrix toughness, along with extremely high surface hardness, stiffness, and abrasion resistance. Subsequent applications in protective films enhance interfacial adhesion, tear resistance, and puncture resistance.

[0024] Preferably, the mixture contains 10-15 parts modified ceramic whiskers, 50-55 parts deionized water, 6-9 parts polyvinyl alcohol, and 2-3 parts dispersant.

[0025] By adopting the above technical solution and further limiting the specific dosage range of multiple raw materials, the resulting mixture exhibits superior overall performance. Modified ceramic whiskers provide excellent rigidity, strength, and heat resistance. Polyvinyl alcohol possesses excellent film-forming and adhesive properties, resulting in a film with excellent strength and toughness after film formation. The dispersant ensures uniform and stable dispersion of the modified ceramic whiskers in the aqueous system, preventing agglomeration and sedimentation. The mixture of multiple components subsequently improves the abrasion resistance, tear resistance, and puncture resistance of the protective film.

[0026] Preferably, the method for preparing the modified ceramic whiskers includes the following steps: dispersing silicon carbide whiskers in sulfuric acid solution, soaking for 15-20 minutes, washing with water, and then spraying xanthan gum solution to obtain a composite; dispersing nano-calcium carbonate onto the surface of the composite and drying to obtain modified ceramic whiskers.

[0027] By employing the above technical solution, sulfuric acid solution corrodes the surface of silicon carbide whiskers, removing surface impurities and weak boundary layers, while simultaneously creating a micro-nano-scale rough structure on the surface. Xanthan gum solution possesses excellent adhesion and film-forming properties, enabling it to coat the surface of silicon carbide whiskers and form a dense, continuous, and tough organic film. Nano-calcium carbonate particles can be adsorbed onto the xanthan gum molecular chains through van der Waals forces and other interactions, forming a robust composite shell. The resulting modified ceramic whiskers exhibit good mechanical properties, further enhancing the overall performance of the protective film.

[0028] Preferably, the UV primer layer comprises, by weight, the following raw materials: 20-25 parts of waterborne polyurethane acrylate, 5-8 parts of tripropylene glycol diacrylate, 1-2 parts of waterborne UV leveling agent, 2-3 parts of initiator, 3-5 parts of titanium dioxide, 1-2 parts of waterborne UV defoamer, and 30-40 parts of water.

[0029] By adopting the above technical solution, waterborne polyurethane acrylate is the main continuous phase forming the paint film, encapsulating all other components. Its polar groups in its molecular structure can form a strong physical and chemical bond with the surface of the hot-dip galvanized substrate, giving the paint film excellent flexibility and impact resistance, preventing cracking and peeling of the color-coated sheet during subsequent cutting and bending processes. Tripropylene glycol diacrylate reduces the viscosity of the waterborne resin system and participates in the cross-linking reaction during UV curing, becoming part of the paint film network, effectively balancing the curing speed, hardness, and flexibility of the paint film. Waterborne UV leveling agents reduce surface tension, eliminating defects such as pinholes and fisheyes caused by surface tension differences, forming a smooth, even, and uniform paint film surface.

[0030] The initiator transforms the liquid coating into a robust and durable solid film within seconds; titanium dioxide provides excellent hiding power, enhancing the mechanical strength and durability of the film. A water-based UV defoamer effectively breaks down bubble walls, preventing bubble formation and ensuring their stability, thus avoiding defects such as pinholes and craters in the dry film and guaranteeing its integrity and aesthetics. The resulting UV primer layer ensures strong adhesion to the metal substrate, while its smooth surface provides a perfect base for the EB topcoat.

[0031] Preferably, the EB topcoat layer comprises, by weight, the following raw materials: 50-60 parts epoxy acrylate, 15-20 parts 1,6-hexanediol diacrylate, 5-9 parts rutile titanium dioxide, 1-2 parts leveling agent, 2-3 parts defoamer, and 3-4 parts dispersant.

[0032] By employing the above technical solutions, the molecular structure of epoxy acrylate endows the cured paint film with extremely high hardness, excellent chemical resistance, good adhesion, and superior heat resistance. 1,6-Hexanediol diacrylate adjusts the high viscosity of the epoxy acrylate, participates in the cross-linking reaction, effectively improving the curing speed and cross-linking density, while simultaneously imparting good flexibility and toughness to the paint film, preventing brittleness due to excessive rigidity. Rutile titanium dioxide provides excellent hiding power, covering the primer layer and giving the topcoat a pure white color and high gloss. Leveling agents, through extremely low surface tension, promote leveling of the coating before curing, eliminating construction marks such as orange peel and brush marks. Defoamers prevent the generation and stable existence of bubbles, thereby avoiding defects such as pinholes and fisheyes in the cured paint film, ensuring the density and aesthetics of the paint film. Dispersants ensure the uniform and stable dispersion of titanium dioxide in the system, achieving uniform color, gloss, and excellent paint film performance.

[0033] Secondly, this application also provides a method for preparing a color-coated steel sheet for home appliances using EB curing technology, comprising the following steps: (1) Preparation of protective film mixture: Low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant and dispersant are mixed evenly, melt extruded to obtain initial protective film; Nano-adhesive clay and short polyurethane fibers are dispersed in deionized water, coated on the surface of initial protective film, and hot-pressed to obtain protective film; (2) Preparation of UV primer coating: Waterborne polyurethane acrylate, tripropylene glycol diacrylate, waterborne UV leveling agent, initiator, titanium dioxide, waterborne UV defoamer and water are mixed evenly to obtain UV primer coating. (3) Preparation of EB topcoat: Epoxy acrylate, 1,6-hexanediol diacrylate, rutile titanium dioxide, leveling agent, defoamer and dispersant are mixed evenly to obtain EB topcoat; (4) Clean and dry the hot-dip galvanized substrate, apply the prepared UV primer coating evenly on the hot-dip galvanized substrate, and enter the UV curing equipment to form a UV primer layer; apply the prepared EB topcoat coating evenly on the cured UV primer layer, and enter the EB curing equipment to form an EB topcoat layer; apply the protective film to the surface of the prepared EB topcoat layer using a laminating machine, and dry at 80-85℃ to obtain the color-coated sheet for home appliances.

[0034] By adopting the above technical solution and manufacturing process, the operation is simple and helps to improve the wear resistance, mechanical properties and crack resistance of the color-coated panels for home appliances cured by EB curing technology. The resulting color-coated panels for home appliances cured by EB curing technology have good durability.

[0035] In summary, this application has the following beneficial effects: 1. The protective film in this application has multiple components working together to achieve good mechanical strength, good flexibility, is not easily brittle, has high durability and damage resistance, is tear-resistant and puncture-resistant, and can effectively resist scratches and collisions encountered by household appliance panels during transportation and installation.

[0036] 2. In this application, the short-cut polyurethane fibers form a network in the matrix, which can disperse the concentrated stress in a local area to a larger area, prevent the protective film from tearing as a whole due to local damage, and improve the puncture resistance and tear resistance of the protective film.

[0037] 3. In this application, the nano-adhesive clay particles can be uniformly dispersed in the polymer matrix, improving the mechanical strength and dimensional stability of the protective film, extending the path of oxygen, water vapor, etc., providing a certain barrier performance, and better protecting the underlying paint surface. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the embodiments.

[0039] The raw materials used in the examples and comparative examples are all commercially available.

[0040] Preparation Example 1-1 of Nano-Adhesive Clay The preparation method of nano-adhesive clay includes the following steps: (1) Disperse 12 kg of kaolin into 23 L of 5% sodium hydroxide solution, stir for 23 min, calcine at 355 °C for 1.5 h, and then grind with 1 kg of triisopropanolamine and 3 kg of sodium carboxymethyl cellulose to obtain treated clay; (2) Disperse the composite nano zinc oxide into 50L of deionized water, add the treated clay from step (1), stir at 72℃ for 2.5h, dry, grind, and obtain nano-adhesive clay.

[0041] The mass ratio of kaolin, composite nano zinc oxide, and sodium carboxymethyl cellulose is 1:0.65:0.12.

[0042] The preparation method of composite nano zinc oxide includes the following steps: dispersing 10 kg of nano zinc oxide in a modifier, stirring at 62℃ for 1.5 h, drying, and grinding to obtain composite nano zinc oxide; The modifiers include: 1 kg stearic acid, 2 kg silane coupling agent KH550, 25 L deionized water, 5 kg modified rice husk powder, and 2 kg dispersant, which is sodium polyacrylate. The preparation method of modified rice husk powder includes the following steps: 10 kg of rice husk powder is dispersed in a modified starch solution and stirred for 32 min. Then, 2 kg of carbon nanotubes are added and stirred at 65℃ for 1.5 h. The mixture is then filtered and dried to obtain modified rice husk powder. 5 kg of modified starch is dissolved in 20 L of deionized water and stirred evenly to obtain a modified starch solution. The modified starch was purchased from Tianjin Huiyi Technology Co., Ltd.

[0043] Preparation Examples 1-2 The difference from Preparation Example 1-1 is that sodium carboxymethyl cellulose is not added in step (1).

[0044] Preparation Examples 1-3 The difference from preparation example 1-1 is that in step (2), composite nano zinc oxide is not added.

[0045] Preparation Examples 1-4 The difference from Preparation Example 1-1 is that the mass ratio of kaolin, composite nano zinc oxide and sodium carboxymethyl cellulose is 1:0.76:0.35.

[0046] Preparation Examples 1-5 The difference from Preparation Example 1-1 is that the mass ratio of kaolin, composite nano zinc oxide and sodium carboxymethyl cellulose is 1:0.12:0.69.

[0047] Preparation Examples 1-6 The difference from Preparation Example 1-1 is that the modified starch solution is not added in the preparation method of modified rice husk powder.

[0048] Preparation Examples 1-7 The difference from Preparation Example 1-1 is that carbon nanotubes are not added in the preparation method of modified rice husk powder.

[0049] Preparation Example 2-1 of Short-Cut Polyurethane Fibers The preparation method of chopped polyurethane fibers includes the following steps: 10 kg of thermoplastic polyurethane is dissolved in 100 L of dimethylformamide solution, 8 kg of nano-silica, 1.5 kg of silane coupling agent KH-550, and 1 kg of dispersant BYK-2150 are added and stirred evenly. The pH of the mixture is adjusted to 3 with citric acid. After mixing evenly, the mixture is degassed at -0.1 MPa for 6 h to obtain a polyurethane spinning solution. The fibers are spun, cut to 1 mm, dispersed in the mixture, and dried to obtain chopped polyurethane fibers. The mixture includes: 13 kg of modified ceramic whiskers, 52 kg of deionized water, 8 kg of polyvinyl alcohol, and 2 kg of dispersant, which is sodium polyacrylate. Spinning parameters: the solidified phase is water, and the draw ratio is 15 times.

[0050] The method for preparing modified ceramic whiskers includes the following steps: dispersing 16 kg of silicon carbide whiskers in 30 L of 25% sulfuric acid solution, soaking for 18 min, washing with water, and then spraying with 1.8 kg of xanthan gum solution to obtain a composite; dispersing 7 kg of nano-calcium carbonate on the surface of the composite and drying to obtain modified ceramic whiskers; the xanthan gum solution is obtained by dissolving 1 kg of xanthan gum in 10 kg of deionized water and stirring evenly at 60 °C.

[0051] Preparation Example 2-2 The difference from preparation example 2-1 is that no nano-silica is added.

[0052] Preparation Examples 2-3 The difference from Preparation Example 2-1 is that no mixture is added.

[0053] Preparation Examples 2-4 The difference from Preparation Example 2-1 is that xanthan gum solution is not added in the preparation method of modified ceramic whiskers.

[0054] Preparation Examples 2-5 The difference from Preparation Example 2-1 is that nano-calcium carbonate is not added in the preparation method of modified ceramic whiskers. Example

[0055] Example 1 A color-coated sheet for home appliances cured using EB curing technology includes a hot-dip galvanized substrate, a UV primer layer, an EB topcoat layer, and a protective film. The protective film, by weight, comprises the following raw materials: 65 kg of low-density polyethylene, 15 kg of ethylene-vinyl acetate copolymer, 6 kg of nano-adhesive clay, 3 kg of chopped polyurethane fiber, 1 kg of antioxidant 1010, and 4 kg of dispersant BYK-P 9920. The thickness of the hot-dip galvanized substrate is 0.3 mm, and the thickness of the protective film is 30 μm.

[0056] The UV primer layer, by weight, comprises the following raw materials: 25 kg of waterborne polyurethane acrylate, 5 kg of tripropylene glycol diacrylate, 2 kg of waterborne UV leveling agent BYK-346, 2 kg of initiator Irgacure 819, 5 kg of titanium dioxide, 2 kg of waterborne UV defoamer BYK-024, and 40 kg of water. The thickness of the UV primer layer is 8 μm.

[0057] The EB topcoat layer, by weight, comprises the following raw materials: 60 kg of epoxy acrylate, 20 kg of 1,6-hexanediol diacrylate, 9 kg of rutile titanium dioxide, 2 kg of leveling agent BYK-333, 3 kg of defoamer BYK-077, and 4 kg of dispersant BYK-2050. The thickness of the topcoat layer is 2 μm.

[0058] The above-mentioned method for preparing color-coated panels for home appliances using EB curing technology includes the following steps: (1) Preparation of protective film mixture: Low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant and dispersant are mixed evenly and melt-extruded at 170°C to obtain the initial protective film; Nano-adhesive clay and short-cut polyurethane fibers are dispersed in deionized water, coated on the surface of the initial protective film, and hot-pressed at 80°C to obtain the protective film; (2) Preparation of UV primer coating: Waterborne polyurethane acrylate, tripropylene glycol diacrylate, waterborne UV leveling agent, initiator, titanium dioxide, waterborne UV defoamer and water are mixed evenly to obtain UV primer coating. (3) Preparation of EB topcoat: Epoxy acrylate, 1,6-hexanediol diacrylate, rutile titanium dioxide, leveling agent, defoamer and dispersant are mixed evenly to obtain EB topcoat; (4) Clean and dry the hot-dip galvanized substrate, then evenly coat the prepared UV primer onto the hot-dip galvanized substrate and place it into a UV curing equipment (curing energy 150 mJ / cm²). 2 A UV primer layer is formed; the prepared EB topcoat is evenly applied to the cured UV primer layer and then placed into an EB curing device (EB curing energy is 150keV, and the amount of EB curing agent is 20kGy) to form an EB topcoat layer; a protective film is then applied to the surface of the prepared EB topcoat layer using a laminating machine and dried at 80℃ to obtain a color-coated sheet for home appliances.

[0059] The nano-adhesive clay was prepared using Preparation Example 1-1, and the chopped polyurethane fiber was prepared using Preparation Example 2-1.

[0060] Example 2 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the protective film, by weight, comprises the following raw materials: 60 kg of low-density polyethylene, 12 kg of ethylene-vinyl acetate copolymer, 9 kg of nano-adhesive clay, 5 kg of chopped polyurethane fiber, 3 kg of antioxidant, and 2 kg of dispersant.

[0061] The UV primer layer, by weight, includes the following raw materials: 20 kg of waterborne polyurethane acrylate, 8 kg of tripropylene glycol diacrylate, 1 kg of waterborne UV leveling agent, 3 kg of initiator, 3 kg of titanium dioxide, 1 kg of waterborne UV defoamer, and 30 kg of water.

[0062] The EB topcoat layer, by weight, includes the following raw materials: 50 kg of epoxy acrylate, 15 kg of 1,6-hexanediol diacrylate, 5 kg of rutile titanium dioxide, 1 kg of leveling agent, 2 kg of defoamer, and 3 kg of dispersant.

[0063] Example 3 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the nano-adhesive clay is prepared using Preparation Examples 1-2.

[0064] Example 4 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the nano-adhesive clay is prepared using Preparation Examples 1-3.

[0065] Example 5 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the nano-adhesive clay is prepared using Preparation Examples 1-4.

[0066] Example 6 A color-coated sheet for home appliances cured using EB curing technology differs from Example 4 in that the nano-adhesive clay is prepared using Preparation Examples 1-5.

[0067] Example 7 A color-coated sheet for home appliances cured using EB curing technology differs from Example 4 in that the nano-adhesive clay is prepared using Preparation Examples 1-6.

[0068] Example 8 A color-coated sheet for home appliances cured using EB curing technology differs from Example 4 in that the nano-adhesive clay is prepared using Preparation Examples 1-7.

[0069] Example 9 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the short-cut polyurethane fibers are prepared using Preparation Example 2-2.

[0070] Example 10 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the short-cut polyurethane fibers are prepared using Preparation Examples 2-3.

[0071] Example 11 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the short-cut polyurethane fibers are prepared using Preparation Examples 2-4.

[0072] Example 12 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that the short-cut polyurethane fibers are prepared using Preparation Examples 2-5.

[0073] Comparative Example Comparative Example 1 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that it does not contain nano-adhesive clay.

[0074] Comparative Example 2 A color-coated sheet for home appliances cured using EB curing technology differs from Example 1 in that it does not contain chopped polyurethane fibers.

[0075] Performance testing The color-coated panels for home appliances cured using EB curing technology, prepared in Examples 1-12 and Comparative Examples 1-2, were subjected to performance tests. The tensile strength of the protective film was tested according to GB / T1040.1-2006; the adhesion strength between the protective film and the EB topcoat layer was tested according to GB / T2792; the scratch resistance was tested according to the method in standard PV3952 "Test for Scratch Resistance of Plastic Interior Parts", with the following parameters: load 10N, speed 1000mm / min, spacing 2mm, and scratch length 40mm. Using a spectrophotometer, the lightness / darkness difference (ΔL) of the surface scratch was obtained by subtracting the L value before scratching from the L value measured after scratching (L represents lightness / darkness, reflecting the depth of color). The smaller the ΔL value, the better the scratch resistance. The test results are shown in Table 1.

[0076] Table 1 Test data for the examples and comparative examples As shown in Table 1, the color-coated panels for home appliances prepared using EB curing technology in Examples 1-2 of this application exhibit good overall performance. Performance tests on the protective film revealed that Example 1 had a transverse tensile strength of 30.5 MPa, a longitudinal tensile strength of 38.7 MPa, an adhesive strength of 8.6 N / cm, and a scratch resistance ΔL of 0.54. This indicates that the multi-component synergistic effect of the protective film in this application provides excellent mechanical strength, good flexibility, resistance to brittle fracture, high durability and damage resistance, tear resistance, puncture resistance, and abrasion resistance, effectively protecting the panels from scratches and impacts encountered during transportation and installation of home appliances.

[0077] In Examples 3-4, the preparation methods of the nano-adhesive clay did not include sodium carboxymethyl cellulose or composite nano-zinc oxide. In Examples 5-6, the mass ratio of kaolin, composite nano-zinc oxide, and sodium carboxymethyl cellulose was varied. Table 1 shows that the transverse / longitudinal tensile strength, bond strength, and scratch resistance of Examples 3-4 were significantly worse than those of Examples 1-2 and Example 5. The corresponding performance of Example 6 was better than that of Examples 3-4, but worse than that of Examples 1-2 and Example 5. This indicates that the composite nano-zinc oxide has better mechanical strength and heat resistance, and the sodium carboxymethyl cellulose ensures a tight bond between the kaolin and the composite nano-zinc oxide, improving the overall performance of the kaolin. When subsequently applied to protective films, the three components work synergistically to improve the high adhesion, high toughness, and high strength requirements of the protective film.

[0078] In Examples 7-8, the modified rice husk powder was prepared without the addition of modified starch solution or carbon nanotubes. Table 1 shows that the transverse / longitudinal tensile strength, bond strength, and scratch resistance of Examples 7-8 were significantly worse than those of Examples 1-2, but better than Example 4. This indicates that the hydroxyl groups of the starch molecules in the modified starch can form hydrogen bonds with the hydroxyl groups on the surface of the rice husk powder, adhering to the surface. Carbon nanotubes, with their good antibacterial and mechanical properties, adhere to the surface of the rice husk powder and interact with the starch molecules, resulting in uniform adhesion of the carbon nanotubes to the rice husk powder surface, thus improving the mechanical, toughness, and functional properties of the final material.

[0079] In Examples 9-10, the preparation methods of chopped polyurethane fibers did not include nano-silica or the mixed solution. Table 1 shows that the transverse / longitudinal tensile strength, bond strength, and scratch resistance of Examples 9-10 were significantly worse than those of Examples 1-2. This indicates that adding nano-silica to the spinning solution can form physical cross-linking points inside the TPU fiber, greatly improving the fiber's strength, modulus, and thermal stability; coating the fiber surface with the mixed solution forms a robust composite shell; the modified ceramic whiskers possess extremely high strength, modulus, and hardness; and the PVA aqueous solution has good film-forming properties and adhesion, firmly bonding the ceramic whiskers to the surface of the TPU fiber.

[0080] In Examples 11-12, the modified ceramic whiskers were prepared without the addition of xanthan gum solution or nano-calcium carbonate. Table 1 shows that the transverse / longitudinal tensile strength, bond strength, and scratch resistance of Examples 11-12 were significantly worse than those of Examples 1-2, but better than those of Example 10. This indicates that the xanthan gum solution has excellent adhesion and film-forming properties, capable of coating the surface of silicon carbide whiskers to form a dense, continuous, and tough organic film. Nano-calcium carbonate particles can be adsorbed onto the xanthan gum molecular chains through van der Waals forces, forming a robust composite shell. The resulting modified ceramic whiskers exhibit good mechanical properties, further improving the overall performance of the protective film.

[0081] Comparative Examples 1 and 2 were prepared without nano-adhesive clay and with chopped polyurethane fibers, respectively. As shown in Table 1, the transverse / longitudinal tensile strength, bond strength, and scratch resistance of Comparative Examples 1 and 2 were significantly worse than those of Examples 1-2. This indicates that the nano-adhesive clay particles can be uniformly dispersed in the polymer matrix, improving the mechanical strength and dimensional stability of the protective film. The chopped polyurethane fibers form a network in the matrix, preventing the protective film from tearing as a whole due to local damage. They also have extremely high elongation and resilience, improving the puncture resistance and tear resistance of the protective film.

[0082] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A color-coated sheet for home appliances cured using EB curing technology, characterized in that, It includes a hot-dip galvanized substrate, a UV primer layer, an EB topcoat layer, and a protective film. The protective film, by weight, includes the following raw materials: 60-65 parts of low-density polyethylene, 12-15 parts of ethylene-vinyl acetate copolymer, 6-9 parts of nano-adhesive clay, 3-5 parts of chopped polyurethane fiber, 1-3 parts of antioxidant, and 2-4 parts of dispersant.

2. The color-coated sheet for home appliances cured using EB curing technology according to claim 1, characterized in that, The preparation method of the nano-adhesive clay includes the following steps: (1) Disperse kaolin in sodium hydroxide solution, stir for 20-25 min, calcine at 350-360℃ for 1-2 h, and then grind it with triisopropanolamine and sodium carboxymethyl cellulose to obtain treated clay; (2) Disperse the composite nano zinc oxide into deionized water, add the treated clay from step (1), stir at 70-75℃ for 2-3 hours, dry, grind, and obtain nano-adhesive clay.

3. The color-coated sheet for home appliances cured using EB curing technology according to claim 2, characterized in that, The mass ratio of kaolin, composite nano zinc oxide and sodium carboxymethyl cellulose is 1:0.65-0.76:0.12-0.

35.

4. A color-coated sheet for home appliances cured using EB curing technology according to claim 2, characterized in that, The preparation method of the composite nano zinc oxide includes the following steps: dispersing nano zinc oxide in a modifier, stirring at a temperature of 60-65℃ for 1-2 hours, drying, and grinding to obtain composite nano zinc oxide; Modifiers include: stearic acid, silane coupling agent, deionized water, modified rice husk powder, and dispersant; The preparation method of modified rice husk powder includes the following steps: dispersing rice husk powder in modified starch solution, stirring for 30-35 min, then adding carbon nanotubes, stirring at 65-68℃ for 1-2 h, filtering, and drying to obtain modified rice husk powder.

5. A color-coated sheet for home appliances cured using EB curing technology according to claim 1, characterized in that, The method for preparing the chopped polyurethane fiber includes the following steps: dissolving thermoplastic polyurethane in dimethylformamide solution, adding nano-silica, silane coupling agent and dispersant and stirring evenly, adjusting the pH of the mixture to 3-4 with citric acid, degassing for 6-7 hours after mixing evenly to obtain polyurethane spinning solution, spinning, cutting into segments, then dispersing into the mixture, drying to obtain chopped polyurethane fiber; The mixture includes: modified ceramic whiskers, deionized water, polyvinyl alcohol, and dispersant.

6. A color-coated sheet for home appliances cured using EB curing technology according to claim 5, characterized in that, 10-15 parts modified ceramic whiskers, 50-55 parts deionized water, 6-9 parts polyvinyl alcohol, and 2-3 parts dispersant.

7. A color-coated sheet for home appliances cured using EB curing technology according to claim 5, characterized in that, The method for preparing the modified ceramic whiskers includes the following steps: dispersing silicon carbide whiskers in sulfuric acid solution, soaking for 15-20 minutes, washing with water, and then spraying xanthan gum solution to obtain a composite; dispersing nano-calcium carbonate on the surface of the composite and drying to obtain modified ceramic whiskers.

8. A color-coated sheet for home appliances cured using EB curing technology according to claim 1, characterized in that, The UV primer layer comprises, by weight, the following raw materials: 20-25 parts of waterborne polyurethane acrylate, 5-8 parts of tripropylene glycol diacrylate, 1-2 parts of waterborne UV leveling agent, 2-3 parts of initiator, 3-5 parts of titanium dioxide, 1-2 parts of waterborne UV defoamer, and 30-40 parts of water.

9. A color-coated sheet for home appliances cured using EB curing technology according to claim 1, characterized in that, The EB topcoat layer, by weight, comprises the following raw materials: 50-60 parts epoxy acrylate, 15-20 parts 1,6-hexanediol diacrylate, 5-9 parts rutile titanium dioxide, 1-2 parts leveling agent, 2-3 parts defoamer, and 3-4 parts dispersant.

10. The method for preparing a color-coated sheet for home appliances using EB curing technology according to claim 1, characterized in that, Includes the following steps: (1) Preparation of protective film mixture: Low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant and dispersant are mixed evenly, melt extruded to obtain initial protective film; Nano-adhesive clay and short polyurethane fibers are dispersed in deionized water, coated on the surface of initial protective film, and hot-pressed to obtain protective film; (2) Preparation of UV primer coating: Waterborne polyurethane acrylate, tripropylene glycol diacrylate, waterborne UV leveling agent, initiator, titanium dioxide, waterborne UV defoamer and water are mixed evenly to obtain UV primer coating. (3) Preparation of EB topcoat: Epoxy acrylate, 1,6-hexanediol diacrylate, rutile titanium dioxide, leveling agent, defoamer and dispersant are mixed evenly to obtain EB topcoat; (4) Clean and dry the hot-dip galvanized substrate, apply the prepared UV primer coating evenly on the hot-dip galvanized substrate, and put it into the UV curing equipment to form a UV primer layer. The prepared EB topcoat is evenly applied onto the cured UV primer layer and then placed into the EB curing equipment to form the EB topcoat layer. A protective film is then applied to the surface of the prepared EB topcoat layer using a laminating machine and dried at 80-85℃ to obtain the color-coated sheet for home appliances.

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