One-part water-based metallic paint and method for preparing the same

Abstract

The application relates to the technical field of metal paint, and particularly discloses a bottom-surface integrated water-based metal paint and a preparation method thereof. The bottom-surface integrated water-based metal paint is prepared from the following raw materials in parts by weight: 40-60 parts of acrylic emulsion, 5-10 parts of zinc phosphate, 5-10 parts of aluminum tripolyphosphate, 6-12 parts of mica iron oxide, 2-6 parts of modified layered hydrotalcite, 1-4 parts of functionalized attapulgite, 0.5-2 parts of a dispersing agent, 2-6 parts of a film-forming aid, 0.3-1.2 parts of adipic acid dihydrazide, 0.1-0.5 parts of a defoaming agent, 0.2-1 part of a thickening agent and 20-30 parts of deionized water. The bottom-surface integrated water-based metal paint can significantly improve the water resistance of a paint film in an initial curing stage, effectively solves the problem of whitening and blistering caused by water in a short time after construction, and simultaneously has excellent adhesion, flexibility and impact resistance.

Description

Technical Field

[0001] This application relates to the field of metallic paint technology, and more specifically, to a base-and-top water-based metallic paint and its preparation method. Background Technology

[0002] Metal protective coatings are core materials in the field of industrial corrosion protection. Traditional metal coatings generally employ a matching system of anti-rust primer and decorative topcoat. The primer provides adhesion and corrosion inhibition to the substrate, while the topcoat imparts weather resistance, decoration, and physical shielding. However, this system suffers from drawbacks such as numerous construction steps, long cycles, and high risks associated with interlayer compatibility. Integrated primer-topcoat metal coatings combine the anti-rust and adhesion capabilities of the primer with the weather resistance and decorative properties of the topcoat into a single coating. This allows for a single coat to meet both protective and decorative requirements, significantly improving coating efficiency and reducing overall costs. Water-based integrated primer-topcoat metal coatings, with water as the dispersion medium, are gradually replacing traditional solvent-based products due to their advantages such as low VOC emissions and safe construction with no risk of combustion or explosion. They are widely used in various metal protection scenarios, including steel structures, construction machinery, and municipal facilities.

[0003] Numerous studies have been conducted on waterborne coatings that combine substrate and surface treatment in the prior art. For example, Chinese patent application CN113045942A discloses a multi-purpose waterborne coating that combines substrate and surface treatment and its preparation method. It uses self-drying waterborne acrylic emulsion as the main film-forming base material, compounded with siloxane coupling agent and epoxy phosphate polymer as adhesion promoters, and combined with zinc molybdate modified pigment and calcium ion exchange type anti-rust pigment to construct an anti-rust system. It also introduces fillers such as siloxane modified nano mica powder and talc powder to enhance the shielding performance. It aims to be compatible with various metal substrates such as cold-rolled steel, galvanized sheet, and aluminum alloy, while improving the adhesion and salt spray resistance of the coating, and achieving a single-coat substrate and surface protection effect.

[0004] However, the above-mentioned technical solutions still have obvious defects in poor initial water resistance. Since the single-component self-drying acrylic system mainly relies on the physical stacking and fusion of emulsion particles after water evaporation to form a film, a complete and continuous dense cross-linked structure has not yet been formed between the resin particles in the early stage of curing. The hydrophilic dispersants, emulsifiers and polar additives remaining in the paint film are easily swollen and precipitated by water molecules. At the same time, there are microscopic hydrophilic channels at the interface between a large number of anti-rust pigments and fillers and the resin matrix. If the system is exposed to water environments such as rain or condensation within a short period of time after construction, water molecules will quickly penetrate into the paint film, causing the paint film to turn white, lose its gloss, blister and even peel off locally. This not only causes irreversible damage to the appearance and decoration, but also destroys the integrity of the initial anti-corrosion barrier. In outdoor on-site construction scenarios, the coating is very easy to fail due to sudden weather, which restricts the construction tolerance and application range of the product. Summary of the Invention

[0005] To enhance the initial water resistance of water-based metallic paints, this application provides a base coat and top coat water-based metallic paint and its preparation method.

[0006] The technical solution for the water-based metallic paint that combines base and topcoat in this application is as follows: A water-based metallic paint that combines base and topcoat properties comprises the following raw materials in parts by weight: Acrylic emulsion 40-60 parts, zinc phosphate 5-10 parts, aluminum tripolyphosphate 5-10 parts, mica iron oxide 6-12 parts, modified layered hydrotalcite 2-6 parts, functionalized attapulgite 1-4 parts, dispersant 0.5-2 parts, film-forming aid 2-6 parts, adipic acid dihydrazide 0.3-1.2 parts, defoamer 0.1-0.5 parts, thickener 0.2-1 parts, deionized water 20-30 parts; The modified layered hydrotalcite is prepared by first achieving hydrophobic intercalation between layers via dodecylbenzenesulfonate ions, and then covalently grafting ketone-containing carbonyl organic segments onto the surface. The functionalized attapulgite is prepared by co-hydrolyzing and grafting nano-attapulgite fibers with octyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane, followed by free radical copolymerization with diacetone acrylamide.

[0007] By adopting the above technical solution, and by introducing two raw materials, modified layered hydrotalcite and functionalized attapulgite, and relying on the structural characteristics and surface reactivity of the two modified fillers, efforts are made simultaneously from three levels: physical barrier construction, bulk hydrophobic barrier and chemical cross-linking and densification. This effectively addresses the core cause of rapid water molecule penetration in the early stage of film formation, and avoids the problems of whitening, loss of gloss and blistering and peeling of the paint film caused by short-term contact with water after construction.

[0008] Modified layered hydrotalcite, with its two-dimensional lamellar structure, can form a labyrinthine shielding structure after being uniformly dispersed in the paint film matrix, significantly extending the penetration and diffusion path of water molecules and exerting a physical barrier effect during the surface drying stage of the paint film. At the same time, after undergoing interlayer hydrophobic intercalation treatment, its hydrophilicity is fundamentally transformed, avoiding the defects of conventional inorganic fillers acting as hydrophilic channels, and can repel and block water molecules penetrating into the paint film. In addition, the ketone carbonyl groups grafted on the surface can undergo cross-linking reaction with adipic acid dihydrazide in the system, so that the filler and the resin matrix form covalent bonds, eliminating the microscopic gaps and hydrophilic penetration channels at the filler-resin interface, and acting as additional cross-linking points to accelerate the initial cross-linking network construction, promoting the rapid transformation of the paint film from a physically stacked state to a dense cross-linked film.

[0009] Functionalized attapulgite, with its one-dimensional fiber structure and two-dimensional hydrotalcite sheets, forms a complementary scale and dimension. These two elements intertwine within the coating film to construct a three-dimensional composite network, enabling multi-level filling of micropores at different levels, further densifying the coating film matrix structure and improving physical shielding efficiency. After surface modification with hydrophobicity and ketone carbonyl groups, it possesses both hydrophobic barrier and cross-linking reactivity. It can inhibit the adsorption and diffusion of water molecules on the fiber surface through surface hydrophobic groups, and also participate in the ketone-hydrazine cross-linking reaction of the system, increasing the cross-linking point density and accelerating the initial densification process. Simultaneously, the one-dimensional fiber structure can exert a fiber toughening effect, offsetting the risk of coating film embrittlement that may result from increased cross-linking density, thus strengthening initial water resistance while ensuring the mechanical properties and protective integrity of the coating film.

[0010] The modified filler described above has good compatibility with the existing acrylic emulsion primer-topcoat system. It can achieve a significant improvement in initial water resistance without changing the main film-forming and rust-preventing system, thereby improving the tolerance of outdoor on-site construction to sudden rainfall, condensation and other conditions, and expanding the applicable scenarios and construction window of primer-topcoat water-based metallic paint.

[0011] Optionally, the modified layered hydrotalcite is prepared using the following method: (1) Add magnesium-aluminum type layered bimetallic hydroxide to deionized water to prepare a suspension; heat the suspension to 60-70℃, adjust the pH of the system to 8.0-9.0, slowly add sodium dodecylbenzenesulfonate aqueous solution, and then stir the reaction at a constant temperature for 4-6 hours; after the reaction is completed, centrifuge to separate, and after washing, drying and grinding, obtain interlayer hydrophobic intercalated hydrotalcite. (2) Disperse the interlayer hydrophobic intercalated hydrotalcite in an ethanol aqueous solution, adjust the pH of the system to 4.0-5.0, raise the temperature to 50-60℃, slowly add γ-methacryloxypropyltrimethoxysilane, stir the reaction at a constant temperature for 3-4h, then add diacetone acrylamide and ammonium persulfate, and react at 70-75℃ for 3-5h; then after washing, drying and grinding, the modified layered hydrotalcite is obtained.

[0012] By adopting the above technical solution, hydrophobic intercalation between layers is first achieved through ion exchange, followed by the introduction of ketone carbonyl functional groups through surface grafting and copolymerization. This stepwise reaction avoids mutual interference between the intercalation and grafting processes, ensuring the integrity of the hydrotalcite sheet structure and the precision of functional group grafting. The process path of hydrophobization followed by functionalization ensures sufficient hydrophobic modification between layers. At the same time, the covalently grafted ketone carbonyl groups on the surface have stable reactivity, enabling the filler to stably perform multiple functions of shielding, hydrophobicity, and crosslinking during the film formation process, providing a material basis for the stable improvement of initial water resistance.

[0013] Optionally, in step (1), the solid content of the suspension is 5%-8%; the mass concentration of the sodium dodecylbenzenesulfonate aqueous solution is 15%-25%; and the amount of sodium dodecylbenzenesulfonate aqueous solution added is 15%-30% of the mass of magnesium-aluminum layered bimetallic hydroxide.

[0014] By adopting the above technical solution, the above material ratio is conducive to maintaining a stable intercalation effect. A stable intercalation effect is a prerequisite for ensuring the hydrophobicity and structural stability of the filler body, which can ensure that it continues to play a hydrophobic barrier role in the paint film and avoid initial water permeability defects caused by the filler's own hydrophilicity.

[0015] Optionally, in step (2), the mass ratio of the interlayer hydrophobic intercalated hydrotalcite to the ethanol aqueous solution is 1:(10-15); the amount of γ-methacryloyloxypropyltrimethoxysilane added is 8%-15% of the mass of the interlayer hydrophobic intercalated hydrotalcite; and the mass ratio of the interlayer hydrophobic intercalated hydrotalcite, diacetone acrylamide, and ammonium persulfate is 100:(5-12):(0.1-0.4).

[0016] Optionally, the functionalized attapulgite is prepared using the following method: (a) Nano-attapulgite fibers were added to an aqueous ethanol solution to obtain a dispersion. The pH of the system was adjusted to 3.5-4.5, and the temperature was raised to 55-65℃. Octyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane were then added dropwise. After the addition was completed, the mixture was stirred at a constant temperature for 4-5 hours. After the reaction was completed, the mixture was centrifuged, and then separated by centrifugation, washed and dried to obtain silane co-modified attapulgite. (b) Silane co-modified attapulgite was dispersed in anhydrous ethanol to obtain a dispersion, diacetone acrylamide was added, and the temperature was raised to 65-70℃ under nitrogen protection. Azobisisobutyronitrile was added, and the reaction was carried out at a constant temperature for 4-6 hours. After the reaction was completed, the functionalized attapulgite was obtained by centrifugation, washing, drying and grinding.

[0017] By employing the above technical solution, hydrophobic alkyl groups and polymerizable double bonds are first introduced simultaneously through silane co-hydrolysis grafting, followed by free radical copolymerization grafting of ketone carbonyl functional groups. This stepwise reaction ensures the grafting efficiency and uniformity of each functional group, avoiding mutual interference between different reactions. This process enables attapulgite fibers to simultaneously obtain stable hydrophobic surfaces and reactive sites, ensuring that they can both play a physical filling and network-building role as one-dimensional fibers in the coating film and effectively participate in the system's cross-linking reaction, providing one-dimensional structural support for improving initial water resistance.

[0018] Optionally, in step (a), the mass concentration of the ethanol aqueous solution is 50%-60%; the mass ratio of the nano-attapulgite fiber to the ethanol aqueous solution is 1:(12-18); the amount of octyltriethoxysilane added is 5%-9% of the mass of the nano-attapulgite fiber; and the amount of γ-methacryloyloxypropyltrimethoxysilane added is 3%-5% of the mass of the nano-attapulgite fiber.

[0019] Optionally, in step (b), the mass ratio of the silane co-modified attapulgite to anhydrous ethanol is 1:(8-10); the amount of diacetone acrylamide added is 6%-10% of the mass of the silane co-modified attapulgite, and the amount of azobisisobutyronitrile added is 1.5%-3% of the mass of the diacetone acrylamide.

[0020] Optionally, the film-forming aid is a compound of dodecyl alcohol ester and propylene glycol butyl ether at a mass ratio of 1:(0.4-0.6).

[0021] By employing the above technical solution, the combination of two film-forming aids can regulate the evaporation rate and film-forming efficiency, promote the full deformation and fusion of acrylic emulsion particles at room temperature, reduce micropores caused by the initial accumulation of emulsion particles in the early stage of film formation, and improve the continuity of early film formation. The good film-forming quality can synergize with the shielding effect of the two modified fillers, further reducing the initial permeation rate of water molecules, while ensuring the uniformity of the film structure and avoiding localized water resistance failure caused by film-forming defects.

[0022] Optionally, the dispersant is an ammonium polyacrylate dispersant.

[0023] Secondly, this application provides a method for preparing a base-and-top integrated water-based metallic paint, employing the following technical solution: A method for preparing a base-and-top water-based metallic paint includes the following steps: S1. Stir deionized water and dispersant at 300-500 rpm for 3-5 min, then add zinc phosphate, aluminum tripolyphosphate, mica iron oxide, modified layered hydrotalcite and functionalized attapulgite, and continue stirring for 20-30 min to obtain a pre-dispersed slurry. S2. Add acrylic emulsion to the pre-dispersed slurry and stir at 300-500 rpm for 3-5 minutes. Then add film-forming aid, adipic acid dihydrazide and defoamer, and continue stirring for 15-20 minutes. Add thickener and continue stirring for 3-5 minutes to obtain a base and topcoat integrated water-based metallic paint.

[0024] By adopting the above technical solution, the stepwise process of pre-dispersing pigments and fillers with functional fillers, followed by mixing the paint emulsion, can achieve sufficient refinement and uniform dispersion of pigments and fillers in the pre-dispersion stage, ensuring that the fineness of the slurry meets the standards, while avoiding demulsification damage to the acrylic emulsion caused by high-shear dispersion. This process can ensure that each functional component is uniformly distributed in the final system, allowing the crosslinking reaction and shielding effect to work simultaneously throughout the paint film, stably achieving an improvement in initial water resistance, and the process conditions are mild, making it suitable for industrial mass production needs.

[0025] In summary, this application has the following beneficial effects: 1. This application uses modified layered hydrotalcite as the core functional filler, which can solve the core defect of insufficient water resistance in the early stage of water-based paint curing from multiple dimensions. Its two-dimensional layered structure can form a labyrinthine shielding barrier in the paint film matrix, which can significantly extend the water molecule penetration path and reduce the initial water permeation rate during the surface drying stage. After interlayer hydrophobic intercalation treatment, the hydrophilicity of the filler body is fundamentally changed, avoiding itself from becoming a fast channel for water molecule diffusion, and can have a repulsive and hindrance effect on the penetrating medium. The covalently grafted ketone carbonyl groups on the surface can participate in the ketone-hydrazine crosslinking reaction of the system, which not only eliminates the hydrophilic gap at the interface between the filler and the resin, but also serves as an additional crosslinking point to accelerate the densification process of the paint film, effectively improving the problems of whitening and bubbling when exposed to water in the early stage.

[0026] 2. This application introduces functionalized attapulgite as a one-dimensional reinforcing component, forming a dual complement of structure and function with two-dimensional hydrotalcite, further enhancing initial water resistance while ensuring the overall mechanical performance of the coating. Its fibrous structure can interweave with lamellar hydrotalcite to construct a three-dimensional composite network, achieving multi-level filling of micropores of different scales, improving the overall density and physical shielding efficiency of the paint film; after surface modification with hydrophobicity and ketone carbonyl functionalization, it can both inhibit the adsorption and diffusion of water molecules on the fiber surface and participate in the cross-linking reaction to increase the initial cross-linking density; at the same time, the one-dimensional fiber can exert a toughening effect, offsetting the risk of paint film embrittlement that may be caused by the improvement of cross-linking, and avoiding the trade-off between improved water resistance and mechanical properties.

[0027] 3. This application constructs an integrated initial water resistance enhancement system through the synergistic compounding of two modified inorganic fillers, which also exhibits good compatibility with existing primer-topcoat base systems. The two fillers complement each other in terms of structure, synergistically enhancing the physical barrier effect; functionally, they simultaneously achieve hydrophobicity and reactive modification, jointly accelerating the transformation of the paint film from a physically stacked state to a cross-linked, dense state. This solution significantly shortens the water resistance development cycle without altering the main film-forming and rust-preventing systems, improves the tolerance of outdoor on-site construction to sudden rainfall and condensation conditions, and effectively expands the product's application scope and construction window. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments.

[0029] Preparation example of modified layered hydrotalcite Preparation Example 1 Modified layered hydrotalcite was prepared using the following method: (1) Weigh 100g of magnesium-aluminum type layered bimetallic hydroxide, add it to deionized water to prepare a suspension with a solid content of 5%, and ultrasonically disperse it for 25min until the system is uniform. Heat the suspension to 60℃, adjust the pH of the system to 8.0 with 10% sodium hydroxide solution, and slowly add 15% sodium dodecylbenzenesulfonate aqueous solution, of which the total mass of sodium dodecylbenzenesulfonate is 15g, and the addition time is controlled at 30min. After the addition is completed, stir the reaction at a constant temperature for 4h. After the reaction is completed, centrifuge at 3000rpm, wash the precipitate repeatedly with deionized water until no foam is produced in the filtrate, vacuum dry at 60℃ for 12h, take it out, grind it and pass it through a 200-mesh sieve to obtain interlayer hydrophobic intercalated hydrotalcite.

[0030] (2) Weigh 80g of the above-mentioned hydrophobic intercalated hydrotalcite and add it to an ethanol-water mixed solvent (ethanol to water volume ratio of 7:3). The material-to-liquid mass ratio is 1:10. Disperse the mixture by ultrasonication for 30min to form a uniform dispersion. Adjust the pH of the system to 4.0 with glacial acetic acid, raise the temperature to 50℃, slowly add 6.4g of γ-methacryloyloxypropyltrimethoxysilane, add it dropwise for 20min, and stir the mixture at a constant temperature for 3h. Then add 4g of diacetone acrylamide and 0.08g of ammonium persulfate to the system, purge with nitrogen to remove oxygen for 10min, raise the temperature to 70℃, and keep the temperature for copolymerization for 3h. After the reaction is completed, centrifuge and separate the precipitate. Wash the precipitate three times with anhydrous ethanol to remove unreacted monomers and homopolymers. Dry it under vacuum at 60℃ for 12h, grind it through a 200-mesh sieve, and obtain the modified layered hydrotalcite.

[0031] Preparation Example 2 Modified layered hydrotalcite was prepared using the following method: (1) Weigh 100g of magnesium-aluminum type layered bimetallic hydroxide, add it to deionized water to prepare a suspension with a solid content of 6.5%, and ultrasonically disperse it for 25min until the system is uniform. Heat the suspension to 65℃, adjust the pH of the system to 8.5 with 10% sodium hydroxide solution, and slowly add 20% sodium dodecylbenzenesulfonate aqueous solution, of which the total mass of sodium dodecylbenzenesulfonate is 22.5g, and control the addition time to 40min. After the addition is completed, stir the reaction at a constant temperature for 5h. After the reaction is completed, centrifuge at 3000rpm, wash the precipitate repeatedly with deionized water until no foam is produced in the filtrate, vacuum dry at 65℃ for 14h, take it out, grind it and pass it through a 200-mesh sieve to obtain interlayer hydrophobic intercalated hydrotalcite.

[0032] (2) Weigh 80g of the above-mentioned hydrophobic intercalated hydrotalcite and add it to an ethanol-water mixed solvent (ethanol to water volume ratio of 7:3). The material-to-liquid mass ratio is 1:12.5. Disperse the mixture by ultrasonication for 35min to form a uniform dispersion. Adjust the pH of the system to 4.5 with glacial acetic acid, raise the temperature to 55℃, slowly add 9.2g of γ-methacryloyloxypropyltrimethoxysilane, add it dropwise for 25min, and stir the reaction at a constant temperature for 3.5h. Then add 6.8g of diacetone acrylamide and 0.2g of ammonium persulfate to the system, purge the oxygen with nitrogen for 12min, raise the temperature to 72℃, and keep the temperature for copolymerization reaction for 4h. After the reaction is completed, centrifuge the mixture, wash the precipitate three times with anhydrous ethanol to remove unreacted monomers and homopolymers, dry it under vacuum at 65℃ for 14h, grind it through a 200-mesh sieve, and obtain the modified layered hydrotalcite.

[0033] Preparation Example 3 Modified layered hydrotalcite was prepared using the following method: (1) Weigh 100g of magnesium-aluminum type layered bimetallic hydroxide, add it to deionized water to prepare a suspension with a solid content of 8%, and ultrasonically disperse it for 30min until the system is uniform. Heat the suspension to 70℃, adjust the pH of the system to 9.0 with 10% sodium hydroxide solution, and slowly add 25% sodium dodecylbenzenesulfonate aqueous solution, of which the total mass of sodium dodecylbenzenesulfonate is 30g, and the addition time is controlled at 50min. After the addition is completed, stir the reaction at a constant temperature for 6h. After the reaction is completed, centrifuge at 3000rpm, wash the precipitate repeatedly with deionized water until no foam is produced in the filtrate, vacuum dry at 70℃ for 16h, take it out, grind it and pass it through a 200-mesh sieve to obtain interlayer hydrophobic intercalated hydrotalcite.

[0034] (2) Weigh 80g of the above-mentioned hydrophobic intercalated hydrotalcite and add it to an ethanol-water mixed solvent (ethanol to water volume ratio of 7:3). The material-to-liquid mass ratio is 1:15. Disperse the mixture by ultrasonication for 40min to form a uniform dispersion. Adjust the pH of the system to 5.0 with glacial acetic acid, raise the temperature to 60℃, slowly add 12g of γ-methacryloyloxypropyltrimethoxysilane, add it dropwise for 30min, and stir the mixture at a constant temperature for 4h. Then add 9.6g of diacetone acrylamide and 0.32g of ammonium persulfate to the system, purge the oxygen with nitrogen for 15min, raise the temperature to 75℃, and keep the temperature for copolymerization for 5h. After the reaction is completed, centrifuge the mixture, wash the precipitate 4 times with anhydrous ethanol to remove unreacted monomers and homopolymers, dry it under vacuum at 70℃ for 16h, grind it through a 200-mesh sieve, and obtain the modified layered hydrotalcite.

[0035] Example of preparation of functionalized attapulgite Preparation Example 4 Functionalized attapulgite was prepared using the following method: (a) Weigh 100g of nano-attapulgite fiber and add it to a 50% ethanol aqueous solution with a material-to-liquid mass ratio of 1:12. Disperse the solution by ultrasonication for 30 min to obtain a uniform dispersion. Adjust the pH of the system to 3.5 with glacial acetic acid, raise the temperature to 55℃, and slowly add a mixture of 5g of octyltriethoxysilane and 3g of γ-methacryloyloxypropyltrimethoxysilane over a period of 30 min. After the addition is complete, stir the mixture at a constant temperature for 4 h. After the reaction is complete, centrifuge at 3500 rpm, wash the precipitate twice with anhydrous ethanol, and dry it under vacuum at 60℃ for 10 h to obtain silane co-modified attapulgite.

[0036] (b) Weigh 70g of the above-mentioned silane co-modified attapulgite and add it to anhydrous ethanol at a mass ratio of 1:8. Disperse the mixture by ultrasonication for 20min to form a uniform dispersion. Add 4.2g of diacetone acrylamide, purge with nitrogen for 10min to remove oxygen, and then heat to 65℃. Add 0.063g of azobisisobutyronitrile and react at a constant temperature for 4h. After the reaction is completed, centrifuge and wash the precipitate three times with anhydrous ethanol to remove homopolymer and residual monomers. Dry the precipitate under vacuum at 60℃ for 12h, grind it, and pass it through a 200-mesh sieve to obtain functionalized attapulgite.

[0037] Preparation Example 5 Functionalized attapulgite was prepared using the following method: (a) Weigh 100g of nano-attapulgite fiber and add it to a 55% ethanol aqueous solution with a material-to-liquid mass ratio of 1:15. Disperse the solution by ultrasonication for 35 min to obtain a uniform dispersion. Adjust the pH of the system to 4.0 with glacial acetic acid, raise the temperature to 60℃, and slowly add a mixture of 7g of octyltriethoxysilane and 4g of γ-methacryloyloxypropyltrimethoxysilane over a period of 40 min. After the addition is complete, stir the mixture at a constant temperature for 4.5 h. After the reaction is complete, centrifuge at 3500 rpm, wash the precipitate twice with anhydrous ethanol, and dry it under vacuum at 65℃ for 11 h to obtain silane co-modified attapulgite.

[0038] (b) Weigh 70g of the above-mentioned silane co-modified attapulgite and add it to anhydrous ethanol at a mass ratio of 1:9. Disperse the mixture by ultrasonication for 25min to form a uniform dispersion. Add 5.6g of diacetone acrylamide, purge with nitrogen for 12min to remove oxygen, and then heat to 67℃. Add 0.126g of azobisisobutyronitrile and react at a constant temperature for 5h. After the reaction is completed, centrifuge and wash the precipitate three times with anhydrous ethanol to remove homopolymer and residual monomers. Dry the precipitate under vacuum at 65℃ for 13h, grind it, and pass it through a 200-mesh sieve to obtain functionalized attapulgite.

[0039] Preparation Example 6 Functionalized attapulgite was prepared using the following method: (a) Weigh 100g of nano-attapulgite fiber and add it to a 60% ethanol aqueous solution with a material-to-liquid mass ratio of 1:18. Disperse the solution by ultrasonication for 40 min to obtain a uniform dispersion. Adjust the pH of the system to 4.5 with glacial acetic acid, raise the temperature to 65℃, and slowly add a mixture of 9g of octyltriethoxysilane and 5g of γ-methacryloyloxypropyltrimethoxysilane dropwise over a period of 50 min. After the addition is complete, stir the mixture at a constant temperature for 5 h. After the reaction is complete, centrifuge at 3500 rpm, wash the precipitate three times with anhydrous ethanol, and dry it under vacuum at 70℃ for 12 h to obtain silane co-modified attapulgite.

[0040] (b) Weigh 70g of the above-mentioned silane co-modified attapulgite and add it to anhydrous ethanol at a mass ratio of 1:10. Disperse the mixture by ultrasonication for 30min to form a uniform dispersion. Add 7g of diacetone acrylamide, purge with nitrogen for 15min to remove oxygen, and then heat to 70℃. Add 0.21g of azobisisobutyronitrile and react at a constant temperature for 6h. After the reaction is completed, centrifuge and wash the precipitate repeatedly with anhydrous ethanol 4 times to remove homopolymer and residual monomers. Dry the precipitate under vacuum at 70℃ for 14h, grind it, and pass it through a 200-mesh sieve to obtain functionalized attapulgite.

[0041] Example Example 1 A water-based metallic paint that combines base and topcoat properties, the raw material components and dosages of which are shown in Table 1, wherein the solid content of the acrylic emulsion is 50%; the modified layered hydrotalcite is the modified layered hydrotalcite prepared in Preparation Example 1; the functionalized attapulgite is the functionalized attapulgite prepared in Preparation Example 4; the dispersant is ammonium polyacrylate dispersant; the film-forming aid is a compound of dodecyl alcohol ester and propylene glycol butyl ether at a mass ratio of 1:0.4; the defoamer is BYK-024 defoamer; and the thickener is RM-8W thickener.

[0042] A method for preparing a base-and-top water-based metallic paint includes the following steps: S1. Stir deionized water and dispersant at 300 rpm for 3 min, then add zinc phosphate, aluminum tripolyphosphate, mica iron oxide, modified layered hydrotalcite and functionalized attapulgite, and continue stirring for 20 min to obtain a pre-dispersed slurry. S2. Add acrylic emulsion to the pre-dispersed slurry and stir at 300 rpm for 3 min. Then add film-forming aid, adipic acid dihydrazide and defoamer, and continue stirring for 15 min. Then add thickener and continue stirring for 3 min to obtain a base and top water-based metallic paint.

[0043] Example 2 A water-based metallic paint that combines base and topcoat properties, the raw material components and dosages of which are shown in Table 1, wherein the solid content of the acrylic emulsion is 50%; the modified layered hydrotalcite is the modified layered hydrotalcite prepared in Preparation Example 2; the functionalized attapulgite is the functionalized attapulgite prepared in Preparation Example 5; the dispersant is ammonium polyacrylate dispersant; the film-forming aid is a compound of dodecyl alcohol ester and propylene glycol butyl ether at a mass ratio of 1:0.5; the defoamer is BYK-024 defoamer; and the thickener is RM-8W thickener.

[0044] A method for preparing a base-and-top water-based metallic paint includes the following steps: S1. Stir deionized water and dispersant at 400 rpm for 4 min, then add zinc phosphate, aluminum tripolyphosphate, mica iron oxide, modified layered hydrotalcite and functionalized attapulgite, and continue stirring for 25 min to obtain a pre-dispersed slurry. S2. Add acrylic emulsion to the pre-dispersed slurry and stir at 400 rpm for 4 min. Then add film-forming aid, adipic acid dihydrazide and defoamer, and continue stirring for 18 min. Then add thickener and continue stirring for 4 min to obtain a base and top water-based metallic paint.

[0045] Example 3 A water-based metallic paint that combines base and topcoat properties, the raw material components and dosages of which are shown in Table 1, wherein the solid content of the acrylic emulsion is 50%; the modified layered hydrotalcite is the modified layered hydrotalcite prepared in Preparation Example 3; the functionalized attapulgite is the functionalized attapulgite prepared in Preparation Example 6; the dispersant is ammonium polyacrylate dispersant; the film-forming aid is a compound of dodecyl alcohol ester and propylene glycol butyl ether at a mass ratio of 1:0.6; the defoamer is BYK-024 defoamer; and the thickener is RM-8W thickener.

[0046] A method for preparing a base-and-top water-based metallic paint includes the following steps: S1. Stir deionized water and dispersant at 500 rpm for 5 min, then add zinc phosphate, aluminum tripolyphosphate, mica iron oxide, modified layered hydrotalcite and functionalized attapulgite, and continue stirring for 30 min to obtain a pre-dispersed slurry. S2. Add acrylic emulsion to the pre-dispersed slurry and stir at 500 rpm for 5 min. Then add film-forming aid, adipic acid dihydrazide and defoamer, and continue stirring for 20 min. Then add thickener and continue stirring for 5 min to obtain a base and top water-based metallic paint.

[0047] Table 1. Raw material components and dosages (kg) of the water-based metallic paints in Examples 1-3.

[0048] Example 4 A water-based metallic paint that combines base and surface coating differs from Example 3 in that: in this example, the modified layered hydrotalcite is selected from the modified layered hydrotalcite prepared in Preparation Example 1; and the functionalized attapulgite is selected from the functionalized attapulgite prepared in Preparation Example 6.

[0049] Example 5 A water-based metallic paint that combines base and surface coating differs from Example 3 in that: in this example, the modified layered hydrotalcite is selected from the modified layered hydrotalcite prepared in Example 3; and the functionalized attapulgite is selected from the functionalized attapulgite prepared in Example 4.

[0050] Example 6 A water-based metallic paint that combines base and topcoat is different from Example 3 in that the film-forming aid used in this example is a single alcohol ester twelve.

[0051] Example 7 A base-and-top water-based metallic paint differs from Example 3 in that: in this example, the thickener used is DIGIC thickener 3060.

[0052] Comparative Example Comparative Example 1 A base-and-surface integrated water-based coating was prepared according to Example 1 in the patent application document with publication number CN113045942A entitled "A Multi-purpose Top and Base Water-based Coating and Its Preparation Method".

[0053] Comparative Example 2 A water-based metallic paint that combines top and bottom coatings differs from Example 3 in that: no modified layered hydrotalcite and functionalized attapulgite were added in this comparative example.

[0054] Comparative Example 3 A base-and-top water-based metallic paint differs from Example 3 in that an equal amount of magnesium-aluminum type hydrotalcite is used instead of modified layered hydrotalcite in this comparative example.

[0055] Comparative Example 4 A water-based metallic paint that combines top and bottom coatings differs from Example 3 in that an equal amount of attapulgite fiber is used instead of functionalized attapulgite in this comparative example.

[0056] Performance testing Test samples: Paints prepared in Examples 1-7 and Comparative Examples 1-4.

[0057] Test items: 1. Initial water resistance The water immersion method was used in accordance with GB / T1733-2020 "Determination of Water Resistance of Paint Films". The test timing was set to allow the paint film to dry at room temperature for 24 hours (simulating an outdoor scenario where the paint film is exposed to water for a short period of time after application). Two-thirds of the test panel was immersed in room temperature deionized water for 24 hours. After immersion, the surface moisture was gently absorbed with clean filter paper. The paint film was visually observed for any abnormalities such as whitening, blistering, loss of gloss, or peeling. The gloss value of the paint film before and after immersion was measured using a 60° gloss meter. The gloss retention rate was calculated (gloss retention rate = gloss value after immersion / gloss value before immersion × 100%). A higher gloss retention rate and fewer appearance abnormalities indicate better initial water resistance.

[0058] 2. Adhesion The test was conducted according to GB / T 9286-1998 "Cross-cut test for paint and varnish film". A cross-cut tester was used to cut squares with a spacing of 1 mm. The film peeling level was used for evaluation, with level 0 being the best (no peeling). The higher the level value, the worse the adhesion.

[0059] 3. Flexibility The test was conducted according to GB / T 1731-2020 "Test Method for Flexibility of Paint Film and Putty Film". A cylindrical shaft bending tester was used to bend the test plate 180° along shafts of different diameters. The result was expressed as the smallest shaft diameter (unit: mm) that did not produce cracks, netting or peeling of the paint film. The smaller the value, the better the flexibility.

[0060] 4. Impact resistance The test was conducted according to GB / T 1732-2020 "Test Method for Impact Resistance of Paint Films". A 1kg hammer was dropped freely onto the painted surface, and the impact energy (unit: kg) corresponding to the maximum impact height from which the paint film did not crack or peel off was measured. The result is indicated by cm, with a larger value representing better impact resistance.

[0061] Experimental results: see Table 2.

[0062] Table 2 Experimental Results

[0063] As shown in Table 2, Comparative Example 1 exhibited significant whitening and localized microbubbles after immersion in water for 24 hours of drying, with a gloss retention rate of only 52%. Comparative Example 2, a basic formulation without modified layered hydrotalcite and functionalized attapulgite, showed even more pronounced whitening, with a gloss retention rate as low as 48%. Both examples exhibited typical characteristics of insufficient initial water resistance. In contrast, Examples 1-7 of this application showed no whitening or bubbling after immersion in water, with a gloss retention rate of 86%-96%, representing an improvement of over 65% compared to existing technologies. This demonstrates that the synergistic effect of modified layered hydrotalcite and functionalized attapulgite can simultaneously block the water molecule penetration pathway from three levels: physical barrier, hydrophobic barrier, and cross-linking density. This significantly shortens the establishment period of the paint film's water resistance and effectively avoids the risk of appearance damage and protective failure caused by short-term water exposure after outdoor construction.

[0064] Comparative Examples 3 and 4 were replaced with equal amounts of unmodified magnesium aluminum hydrotalcite and ordinary attapulgite fiber, respectively. Both showed some improvement in initial water resistance compared to the blank comparative example, with gloss retention rates of 71% and 68%, respectively. However, slight whitening was still visible to the naked eye, showing a significant difference from the examples. This is because, although the unmodified inorganic filler can provide a certain physical barrier effect due to its structure, its surface is rich in hydrophilic groups such as hydroxyl groups, which form new hydrophilic penetration channels within the paint film, limiting the improvement in water resistance.

[0065] In Example 6, after replacing the film-forming aid with a single film-forming aid, the gloss retention rate decreased slightly, verifying that the compound film-forming aid can optimize the early film-forming continuity and form a synergistic gain with the modified filler. In Example 7, after changing the thickener type, the performance fluctuation was minimal, indicating that the core modified filler system has good compatibility with conventional waterborne coating additives.

[0066] In terms of mechanical properties, this application achieves simultaneous gains in water resistance and mechanical reinforcement, avoiding the drawbacks of increased crosslinking leading to film embrittlement seen in conventional formulations. Comparative examples typically exhibit a flexibility of 3mm and an impact strength of only 35-40 kg·cm, while the embodiments in this application achieve a flexibility of 1-2mm and an impact strength up to 90 kg·cm, demonstrating significantly superior overall mechanical properties compared to existing technologies. This is because the one-dimensional fiber structure of functionalized attapulgite can form fiber bridging and pull-out toughening mechanisms within the film matrix, effectively dispersing external impact stress and offsetting the risk of film embrittlement that may result from increased crosslinking density. While enhancing initial water resistance, it further ensures the coating's resistance to deformation and impact, meeting the application requirements of a single-coat base coat that balances protection and mechanical properties.

[0067] 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 water-based metallic paint that combines base and topcoat properties, characterized in that, The raw materials include the following parts by weight: Acrylic emulsion 40-60 parts, zinc phosphate 5-10 parts, aluminum tripolyphosphate 5-10 parts, mica iron oxide 6-12 parts, modified layered hydrotalcite 2-6 parts, functionalized attapulgite 1-4 parts, dispersant 0.5-2 parts, film-forming aid 2-6 parts, adipic acid dihydrazide 0.3-1.2 parts, defoamer 0.1-0.5 parts, thickener 0.2-1 parts, deionized water 20-30 parts; The modified layered hydrotalcite is prepared by first achieving hydrophobic intercalation between layers via dodecylbenzenesulfonate ions, and then covalently grafting ketone-containing carbonyl organic segments onto the surface. The functionalized attapulgite is prepared by co-hydrolyzing and grafting nano-attapulgite fibers with octyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane, followed by free radical copolymerization with diacetone acrylamide.

2. The water-based metallic paint with integrated base and surface coating according to claim 1, characterized in that, The modified layered hydrotalcite was prepared using the following method: (1) Add magnesium-aluminum type layered bimetallic hydroxide to deionized water to prepare a suspension; heat the suspension to 60-70℃, adjust the pH of the system to 8.0-9.0, slowly add sodium dodecylbenzenesulfonate aqueous solution, and then stir the reaction at a constant temperature for 4-6 hours; After the reaction was completed, the mixture was centrifuged, washed, dried and ground to obtain hydrophobic intercalated hydrotalcite. (2) Disperse the interlayer hydrophobic intercalated hydrotalcite in an ethanol aqueous solution, adjust the pH of the system to 4.0-5.0, raise the temperature to 50-60℃, slowly add γ-methacryloxypropyltrimethoxysilane, stir the reaction at a constant temperature for 3-4h, then add diacetone acrylamide and ammonium persulfate, and react at 70-75℃ for 3-5h; then after washing, drying and grinding, the modified layered hydrotalcite is obtained.

3. The water-based metallic paint with integrated base and surface coating according to claim 2, characterized in that: In step (1), the solid content of the suspension is 5%-8%; the mass concentration of the sodium dodecylbenzenesulfonate aqueous solution is 15%-25%; and the amount of sodium dodecylbenzenesulfonate aqueous solution added is 15%-30% of the mass of magnesium-aluminum layered bimetallic hydroxide.

4. The water-based metallic paint with both base and topcoat as described in claim 2, characterized in that: In step (2), the mass ratio of the interlayer hydrophobic intercalated hydrotalcite to the ethanol aqueous solution is 1:(10-15); the amount of γ-methacryloyloxypropyltrimethoxysilane added is 8%-15% of the mass of the interlayer hydrophobic intercalated hydrotalcite; the mass ratio of the interlayer hydrophobic intercalated hydrotalcite, diacetone acrylamide and ammonium persulfate is 100:(5-12):(0.1-0.4).

5. The water-based metallic paint with integrated base and surface coating according to claim 1, characterized in that, The functionalized attapulgite was prepared using the following method: (a) Nano-attapulgite fibers were added to an aqueous ethanol solution to obtain a dispersion. The pH of the system was adjusted to 3.5-4.5, and the temperature was raised to 55-65℃. Octyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane were then added dropwise. After the addition was completed, the mixture was stirred at a constant temperature for 4-5 hours. After the reaction was completed, the mixture was centrifuged, and then separated by centrifugation, washed and dried to obtain silane co-modified attapulgite. (b) Silane co-modified attapulgite was dispersed in anhydrous ethanol to obtain a dispersion, diacetone acrylamide was added, and the temperature was raised to 65-70℃ under nitrogen protection. Azobisisobutyronitrile was added, and the reaction was carried out at a constant temperature for 4-6 hours. After the reaction was completed, the functionalized attapulgite was obtained by centrifugation, washing, drying and grinding.

6. The water-based metallic paint with both base and topcoat as described in claim 5, characterized in that: In step (a), the mass concentration of the ethanol aqueous solution is 50%-60%; the mass ratio of the nano-attapulgite fiber to the ethanol aqueous solution is 1:(12-18); the amount of octyltriethoxysilane added is 5%-9% of the mass of the nano-attapulgite fiber; and the amount of γ-methacryloyloxypropyltrimethoxysilane added is 3%-5% of the mass of the nano-attapulgite fiber.

7. The water-based metallic paint with both base and topcoat as described in claim 5, characterized in that: In step (b), the mass ratio of the silane co-modified attapulgite to anhydrous ethanol is 1:(8-10); the amount of diacetone acrylamide added is 6%-10% of the mass of the silane co-modified attapulgite, and the amount of azobisisobutyronitrile added is 1.5%-3% of the mass of the diacetone acrylamide.

8. The water-based metallic paint with both base and topcoat as described in claim 1, characterized in that: The film-forming aid is a compound of dodecyl alcohol ester and propylene glycol butyl ether in a mass ratio of 1:(0.4-0.6).

9. The water-based metallic paint with integrated base and topcoat as described in claim 1, characterized in that: The dispersant is an ammonium polyacrylate dispersant.

10. A method for preparing a base-and-surface integrated water-based metallic paint according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Stir deionized water and dispersant at 300-500 rpm for 3-5 min, then add zinc phosphate, aluminum tripolyphosphate, mica iron oxide, modified layered hydrotalcite and functionalized attapulgite, and continue stirring for 20-30 min to obtain a pre-dispersed slurry. S2. Add acrylic emulsion to the pre-dispersed slurry and stir at 300-500 rpm for 3-5 minutes. Then add film-forming aid, adipic acid dihydrazide and defoamer, and continue stirring for 15-20 minutes. Add thickener and continue stirring for 3-5 minutes to obtain a base and topcoat integrated water-based metallic paint.

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