A superhydrophobic and stain-resistant wall paint and its preparation method

Abstract

This application provides a superhydrophobic and antifouling wall paint and its preparation method. The superhydrophobic and antifouling wall paint comprises the following raw materials in parts by weight: 100 parts by weight of water-based styrene-acrylate emulsion, 5-15 parts by weight of modified hollow silica microspheres, 10-30 parts by weight of pigment, 15-30 parts by weight of filler, 0.1-0.2 parts by weight of defoamer, 1-3 parts by weight of film-forming aid, 0.1-0.3 parts by weight of pH adjuster, and 10-30 parts by weight of water. One side of the modified hollow silica microspheres is grafted with a fluorosilane coupling agent, and the other side is grafted with an oxygen-based silane coupling agent. This application, by partially hydrophobically modifying the hollow silica microspheres, causes them to migrate directionally and accumulate on the coating surface during film formation, thus endowing the coating with excellent superhydrophobic self-cleaning and antifouling properties.

Description

Technical Field

[0001] This application relates to the field of wall paint, specifically to a superhydrophobic and stain-resistant wall paint and its preparation method. Background Technology

[0002] Superhydrophobic and antifouling coatings, due to their unique self-cleaning properties, have significant application value in building exteriors, interior decoration, and medical devices. Their core principle lies in constructing a low-surface-energy surface with a micro-nano rough structure, allowing water droplets to exist in a "lotus effect" state with high contact angles and low roll-off angles, thereby carrying away surface contaminants. With increasing societal demands for building durability, aesthetics, and cost control, the market demand for long-lasting, high-performance superhydrophobic wall coatings is becoming increasingly urgent.

[0003] Currently, the main technical approaches to achieving superhydrophobic properties in wall paints face the following limitations: Physical blending, which involves directly blending low surface energy additives (such as organosilicon or fluorinated small molecules) or completely hydrophobic fillers with the film-forming matrix (such as styrene-acrylate emulsions). While simple, this method has inherent drawbacks. Small molecule additives tend to migrate and volatilize during coating application, leading to rapid degradation of hydrophobicity. Completely hydrophobic fillers have poor compatibility with hydrophilic polymer matrices, resulting in weak interfacial bonding. This not only impairs the coating's adhesion and flexibility but also makes it prone to detachment under external forces, causing functional failure. Surface post-treatment involves constructing a rough structure and performing hydrophobic modification on the surface of the existing film coating using techniques such as sol-gel and vapor deposition. This method can achieve excellent performance, but it is complex, requires expensive equipment, and is generally unsuitable for large-area or on-site application. It is also significantly out of step with conventional mixing and brushing methods for architectural coatings, hindering industrial application. Functional filler methods aim to impart superhydrophobicity to the coating by adding pre-modified functional micro / nano particles. However, existing technologies mostly focus on achieving uniform hydrophobic modification of particles across the entire surface. These fillers are randomly distributed within the coating and struggle to spontaneously and systematically accumulate at the outermost air interface, resulting in a large amount of filler being "buried" within the coating and unable to effectively contribute hydrophobic properties. To achieve the desired surface effect, the filler dosage often needs to be significantly increased, which in turn leads to a surge in coating viscosity, difficulties in application, increased costs, and a series of problems such as film embrittlement and cracking. Furthermore, existing solutions generally fail to address another core challenge in the practical application of superhydrophobic coatings: the interlayer adhesion between the superhydrophobic surface and the substrate (especially existing coatings). When re-applying or repairing walls, hydrophobic materials typically have low surface energy. While imparting hydrophobicity to the coating, they also significantly reduce the bonding force between the coating and the substrate (wall) as well as between the coating's internal components, making it difficult for the new coating to spread and anchor, easily leading to serious quality problems such as peeling and flaking.

[0004] Therefore, existing technological approaches generally face a key contradiction: how to achieve and maintain the superhydrophobic function of the surface while ensuring strong interlayer adhesion between the coating and various substrates, without compromising the ease of application and mechanical properties of the coating.

[0005] To address these challenges, existing research has attempted to introduce specific structures or responsive materials, such as developing hydrophobic particles with core-shell structures or utilizing microphase separation to create roughness. However, these methods either fail to fundamentally solve the problem of filler orientation or involve cumbersome and demanding preparation processes, making them unsuitable for large-scale production and application of waterborne architectural coatings.

[0006] Therefore, developing a superhydrophobic surface that is compatible with standard waterborne coating processes and can simultaneously achieve long-term stable superhydrophobic surface and interlayer adhesion has become a key breakthrough that urgently needs to be achieved in the field of superhydrophobic architectural coatings. Summary of the Invention

[0007] This application provides a superhydrophobic and antifouling wall paint, which aims to increase the interlayer adhesion between the hydrophobic wall paint and the substrate while maintaining the hydrophobic properties of existing hydrophobic wall surfaces.

[0008] In a first aspect, a superhydrophobic and stain-resistant wall paint is characterized by comprising the following raw materials in parts by weight: 100 parts by weight of waterborne styrene-acrylate emulsion, 5-15 parts by weight of modified hollow silica microspheres, 10-30 parts by weight of pigment, 15-30 parts by weight of filler, 0.1-0.2 parts by weight of defoamer, 1-3 parts by weight of film-forming aid, 0.1-0.3 parts by weight of pH adjuster, and 10-40 parts by weight of water; The modified hollow silica microspheres have a fluorinated silane coupling agent grafted onto one side of their surface and an epoxy silane coupling agent grafted onto the other side of their surface.

[0009] According to this application, by adding asymmetrically modified hollow silica microspheres to an aqueous styrene-acrylate emulsion matrix, it is possible to impart long-lasting superhydrophobic and antifouling properties to the surface of the wall paint while maintaining its good film-forming properties and adhesion.

[0010] Specifically, the waterborne styrene-acrylate emulsion serves as the film-forming matrix, providing the coating with basic adhesion, water resistance, and mechanical strength.

[0011] The modified hollow silica microspheres introduced in this application have Janus structural features, namely, one side of the surface is grafted with a fluorinated silane coupling agent and the other side of the surface is grafted with an epoxy silane coupling agent.

[0012] The system exhibits a certain degree of fluidity after coating, even before the emulsion is completely dry. A certain interfacial energy difference exists between the hydrophobic side of the modified hollow silica microspheres and the aqueous phase. Driven by thermodynamics, the microspheres tend to migrate towards the gas-liquid interface, where the interfacial energy difference is smaller. Regions grafted with epoxy silane coupling agents show good compatibility with the aqueous emulsion matrix, binding through hydrogen bonds and other interactions. This asymmetric effect drives the microspheres to rotate and migrate directionally towards the coating-air interface (i.e., the outer surface of the coating).

[0013] When the emulsion is in a high water content stage, the aqueous phase is the continuous phase in the system. There is a significant difference in interfacial energy between the hydrophobic fluorinated portion and the aqueous phase. Therefore, the decrease in interfacial free energy becomes the dominant factor, driving the directional rotation and migration of microspheres. As the film formation process proceeds, water gradually evaporates, which may induce micro-convection within the system. This, combined with the hydrophobic repulsion of the silica microspheres, further promotes the enrichment of microspheres on the surface. As latex particles approach and merge, the system gradually transforms from an aqueous phase to a polymer phase. The interaction between particles and the polymer matrix begins to dominate. Because the hydrophilic hemispheres of the silica microspheres contain epoxy groups, they have stronger compatibility and interaction with polar groups such as carboxyl and hydroxyl groups in the polymer chains of the emulsion. Therefore, during the latex particle merging stage, the hydrophilic hemispheres preferentially contact the polymer matrix and generate physical interactions such as hydrogen bonding.

[0014] Furthermore, since the fluorinated segments are grafted onto the surface of the microspheres through stable siloxane covalent bonds, and the microspheres are anchored in the matrix through the hydrophilic side, the migration and loss of hydrophobic functional components are reduced, thereby improving the long-term effectiveness of antifouling performance.

[0015] In particular, the hollow silica structure reduces the overall density of the microspheres, making it easier for them to overcome fluid resistance in coating systems with a certain viscosity. Driven by the difference in surface energy, the microspheres are enriched and distributed on the coating surface, thus giving the coating good hydrophobic properties on a macroscopic level.

[0016] Therefore, through the synergy of the modified hollow silica microspheres and the styrene-acrylate emulsion matrix, the wall paint successfully solves the contradiction between hydrophobicity and matrix strength and long-term performance in traditional technologies, achieving excellent immediate anti-fouling ability while ensuring the long-term durability of the coating.

[0017] In some embodiments, the raw material further includes amino-terminated polyether-modified siloxane, which is obtained by introducing epoxy groups through a hydrosilylation reaction between hydrogen-containing silicone oil and allyl glycidyl ether, followed by a ring-opening reaction with the amino-terminated polyether to introduce amino and polyether segments.

[0018] In some of the above embodiments, adding the amino-terminated polyether-modified siloxane to the raw materials can further enhance the hydrophobic properties of the system. Because Janus particles have a hydrophilic / hydrophobic asymmetric structure, with the hydrophilic hemispheres containing epoxy groups and the hydrophobic hemispheres rich in fluorinated low surface energy groups, the amino groups in the amino-terminated polyether-modified siloxane preferentially anchor to the epoxy groups on the hydrophilic hemispheres, while the hydrophobic fluorinated side does not react. This unilateral anchoring effect allows the Janus particles to align during coating formation, with the hydrophobic fluorinated side facing the air interface, thus constructing a low surface energy surface structure. Simultaneously, the polyether segments in the amino-terminated polyether-modified siloxane molecules can form a flexible interfacial transition layer between the Janus particles and the aqueous styrene-acrylate emulsion. This layer reduces the interfacial tension between the particles and the emulsion, improving particle dispersion stability and promoting their migration to the air interface. Furthermore, it forms a flexible bridging structure connecting the Janus particles and the matrix resin during film formation, achieving the transfer and buffering of interfacial stress. Furthermore, the unreacted amino groups in the amino-terminated polyether-modified siloxane can form hydrogen bonds or covalent bonds with the active groups on the substrate surface, thereby further enhancing the adhesion between the coating and the substrate. Through the above-mentioned effects, the amino-terminated polyether-modified siloxane and Janus particles form a synergistic mechanism of "unilateral anchoring-interface regulation-flexible bridging" in the system, enabling the directional migration of particles, the construction of superhydrophobic surfaces, and the enhancement of coating adhesion to be achieved simultaneously.

[0019] It should be noted that in the initial stage of coating formulation and early film formation, the system has a high water content, resulting in a low reaction rate between amino and epoxy groups. Simultaneously, the polyether segments in the amino-terminated polyether-modified siloxane molecules impart good aqueous dispersibility, causing them to preferentially distribute in the continuous phase rather than immediately accumulating on the microsphere surface. Therefore, during the window period when the microspheres respond to the interfacial energy difference and migrate, the amino and epoxy groups have not yet undergone significant reaction. As the film formation process progresses, water gradually evaporates, latex particles coalesce, and the contact probability and reaction rate between amino and epoxy groups increase simultaneously. The anchoring reaction locks the microspheres in place, thereby enhancing the long-term stability of the superhydrophobic properties.

[0020] In some embodiments, the preparation method of the amino-terminated polyether modified siloxane includes the following steps: S1: Stir 100-200 parts of hydrogen-terminated silicone oil and heat to 55-65℃, then add 20-50 parts of allyl glycidyl ether and 0.0024-0.01 parts of chloroplatinic acid catalyst. After the addition is complete, heat to 90-110℃ and stir for 6-8 hours. After the reaction is complete, cool to 60-80℃ and distill under reduced pressure to obtain the epoxy-terminated modified siloxane intermediate.

[0021] S2: Heat 50-100 parts of the epoxy-terminated modified siloxane intermediate obtained in S1 to 60-80℃ and add 10-30 parts of amino-terminated polyether. Stir and react at 65-75℃ for 4-8 hours. After the reaction is completed, cool down to below 40℃ to obtain amino-terminated polyether modified siloxane.

[0022] In some of the above embodiments, the reaction conditions and dosage ratios of each step in the preparation of amino-terminated polyether-modified siloxanes are specifically described. Under these conditions, by conducting a hydrosilylation reaction between hydrogen-containing silicone oil and allyl glycidyl ether under the catalysis of chloroplatinic acid, epoxy groups can be introduced into the siloxane molecular chain, thereby obtaining an epoxy-modified siloxane intermediate. Subsequently, through the ring-opening reaction between the epoxy group and the amino-terminated polyether, amino and flexible polyether segments are introduced into the siloxane backbone structure, resulting in a multifunctional additive that simultaneously possesses amino reaction sites, flexible polyether segments, and a siloxane backbone. This additive can both achieve directional anchoring of the microspheres by reacting the amino group with the epoxy group on the hydrophilic side surface of the Janus microspheres, and form a flexible interface layer between the microspheres and the aqueous emulsion matrix by relying on the polyether segments, thereby improving the dispersion stability of the particles and promoting their directional migration to the coating surface. Therefore, the additive can work synergistically with the asymmetric microspheres to ensure that the microspheres can successfully construct a surface micro-nano rough structure, while improving the interfacial bonding strength between the microspheres and the coating substrate and the base layer, so that the resulting wall paint can maintain good adhesion and durability while obtaining superhydrophobic and antifouling properties.

[0023] In some embodiments, the particle size of the hollow silica microspheres is 1~5 μm.

[0024] In some of the above embodiments, the hollow silica microspheres of the above particle size can undergo directional migration in response to the interfacial energy difference during the coating film formation process. This may construct a scale-matched micron-scale rough structure on the surface, which can synergistically form a stable superhydrophobic composite interface with the nanoscale components, thereby providing the coating with long-lasting antifouling and weather-resistant properties.

[0025] In some embodiments, the fluorinated silane coupling agent includes a perfluorooctylsilane coupling agent.

[0026] In some of the above embodiments, when perfluorooctylsilane coupling agents are selected as fluorinated silane coupling agents to modify hollow silica microspheres, the resulting coating exhibits superior and more stable superhydrophobic properties. The reason for this may be that in the aqueous reaction system, the perfluorooctylsilane coupling agent (C8 chain length) achieves a balance between hydrophobicity and hydrolytic reactivity. If the chain length is too short, although the molecule hydrolyzes faster, its hydrophobicity is insufficient, making it difficult to effectively accumulate at the water-solid interface, resulting in a low interfacial reaction concentration and potentially an incomplete modification layer. If the chain length is too long, the molecule's hydrophobicity is too strong, making it prone to intermolecular aggregation or premature self-condensation in the aqueous phase, which also makes it difficult to fully transport to the surface of the microspheres to participate in the reaction. These properties enable the perfluorooctylsilane coupling agent to form a suitable local concentration on the exposed hemispherical surface of the microspheres. This concentration, combined with the hydrolysis rate in an aqueous environment, allows for an efficient and uniform condensation reaction with the silanol groups on the microsphere surface, forming a good monomolecular modification layer. This provides a reliable functional unit for the subsequent construction of a uniform and stable superhydrophobic coating.

[0027] In some embodiments, the modified hollow silica microspheres are prepared by the following steps: M1: Add 1-5 parts by weight of hydrophilic hollow silica microspheres to 100-200 mL of water and ultrasonically disperse for 20-40 minutes. Heat to 70-80℃ and add 40-60 parts by weight of molten paraffin. Stir and disperse at 1000-2000 rpm for 10-30 minutes. Cool to 10-20℃ in an ice-water bath to solidify the paraffin droplets. Filter to separate and collect the solid complex, and wash with cold deionized water 2-3 times to obtain SiO2 microspheres coated with paraffin. Then disperse the above microspheres in 100-200 parts by weight of ethanol aqueous solution with a volume fraction of 70%-95%. Add 0.1-2.5 parts by weight of fluorinated silane coupling agent and adjust the pH of the system to 4-6 with glacial acetic acid. The reaction was stirred at 20-40℃ for 6-12 hours. After the reaction was completed, the mixture was cooled to 20-30℃, the solid was separated by centrifugation, and washed 2-3 times each with toluene, ethanol and deionized water to obtain partially modified hollow silica microspheres. M2: Disperse the obtained modified hollow silica microspheres in 100-200 parts of toluene, add 0.1-2 parts of epoxy silane coupling agent, stir and react at 80-110℃ for 6-12 hours, centrifuge after the reaction, wash with toluene and ethanol 2-3 times each, and vacuum dry at 60-80℃ for 6-12 hours to obtain modified hollow silica microspheres.

[0028] In some of the above embodiments, the reaction conditions and dosage ratios of each step in the preparation of modified hollow silica microspheres are specifically described. Under these conditions, obtaining Janus-structured microspheres with one side containing fluorine and hydrophobicity and the other side containing epoxy and hydrophilicity is key to the directional migration, surface enrichment, and synergistic construction of micro-nano rough surfaces of the microspheres in subsequent coatings. This enables wall paints to have stable and long-lasting superhydrophobic and antifouling properties.

[0029] In some embodiments, the raw materials further include thickeners, including associative polyurethane thickeners and alkali-swellable acrylate thickeners.

[0030] In some of the above embodiments, the combined use of the two thickeners results in a better hydrophobic coating. During construction, storage, and film formation, the hydrophobic end groups of the associative polyurethane thickener can reversibly bond with the hydrophobic fluorinated surface of the microspheres. Its dynamic network is rapidly rebuilt after shearing, providing initial guidance and spatial anchoring for the directional migration of the microspheres and preventing their disordered aggregation. The alkali-swellable acrylate thickener, by regulating the medium-low shear viscosity of the system, ensures that the microspheres have sufficient time to complete the interfacial enrichment and orderly arrangement, and effectively locks the microstructure formed in the early stage of curing.

[0031] In some embodiments, the filler comprises hydrophobically treated fumed silica.

[0032] In some of the above embodiments, after dispersion in water, it can form a three-dimensional network, effectively preventing the sedimentation of modified hollow silica microspheres and other fillers, and ensuring storage stability. At the same time, its nanoscale size and hydrophobic surface do not compete for dominance on the coating surface, ensuring that the modified hollow silica microspheres can fully migrate to the surface and oriented, constructing a stable superhydrophobic structure.

[0033] In some embodiments, the pigment includes titanium dioxide. Based on the above embodiments, titanium dioxide provides the necessary hiding power and whiteness for the coating, and is a key component that satisfies the basic functions of building wall decoration.

[0034] In some embodiments, the defoamer includes a mineral oil-based defoamer. Based on the above embodiments, mineral oil-based defoamers can effectively eliminate bubbles generated during the production and application of coatings, ensuring a smooth and dense paint film appearance.

[0035] In some embodiments, the film-forming aid includes ester-based film-forming aids. Based on the above embodiments, the ester-based film-forming aids can effectively reduce the minimum film-forming temperature of waterborne styrene-acrylate emulsions and promote the fusion of latex particles after application to form a continuous and dense paint film.

[0036] In some embodiments, the pH adjuster includes an organic amine pH adjuster. Based on the above embodiments, organic amine pH adjusters can gently stabilize aqueous emulsions within a weakly alkaline range, thereby preventing corrosion of the substrate.

[0037] Secondly, this application provides a method for preparing a superhydrophobic and antifouling wall paint, comprising: Provide raw materials for the superhydrophobic and antifouling wall paint according to any one of the first aspects; The raw materials are mixed to obtain a superhydrophobic and stain-resistant wall paint.

[0038] According to this application, by using the raw materials described in any embodiment of the first aspect and mixing them in a specific sequence and under specific process conditions, an aqueous styrene-acrylate emulsion, asymmetric modified hollow silica microspheres, amino-terminated polyether modified siloxanes, pigments, fillers, and various additives can be uniformly dispersed and form a stable system. This method ensures that the asymmetrically modified hollow silica microspheres are fully dispersed in the paint and can effectively migrate to the coating surface during subsequent film formation, aligning with their hydrophobic surfaces to synergistically construct a stable micro / nano structure and a low surface energy surface. Therefore, this preparation method can successfully produce the high-performance superhydrophobic and antifouling wall paint described in the first aspect, which also possesses good durable antifouling and hydrophobic properties.

[0039] Compared with the prior art, the beneficial effects of this application are at least as follows: This application utilizes an interface confinement reaction to partially modify the surface of hollow silica microspheres with a fluorinated silane layer. This allows the hydrophilic microsphere matrix and the low surface energy modification layer to form a synergistic superhydrophobic structure in the coating film. During film formation, the modified hollow silica microspheres accumulate on the coating surface. The fluorinated silane molecular layer grafted onto the exposed side of the microspheres provides the coating surface with low surface energy chemical properties, reducing the intrinsic adhesion of the solid surface. At the same time, it reduces the solid-liquid contact area and increases the gas-liquid interface, making it easy for water droplets to roll off and carry away surface contaminants under extremely low adhesion. This endows the coating with excellent superhydrophobic self-cleaning and antifouling properties. Meanwhile, this application further introduces amino-terminated polyether-modified siloxane, whose amino groups can react with the epoxy groups on the hydrophilic side surface of Janus microspheres to anchor the microspheres that have migrated to the surface. The polyether segments can improve the interfacial compatibility and dispersion stability of the microspheres in the aqueous emulsion, and form a flexible interfacial transition layer between the microspheres and the emulsion matrix and base layer during the coating curing process. This improves the overall adhesion and long-term durability of the coating while maintaining the enrichment of the microsphere surface and the stability of the superhydrophobic structure. Detailed Implementation

[0040] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0041] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0044] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0045] Waterborne styrene-acrylate emulsion, product model RS-7702; Hollow silica microspheres with an average particle size of approximately 3 μm; Amino-terminated polyether with a number-average molecular weight of 1500; Hydrogen-containing silicone oil with a viscosity of 100 mPa·s and a hydrogen content of 0.15 wt%. Titanium dioxide, rutile type R-215; Mineral oil defoamer, model NOPCOSN1340; Fumed silica, with an average particle size of approximately 10 nm; Film-forming aid, dodecyl alcohol ester, CAS number 25265-77-4; Fluorinated silane coupling agent, tridecafluorooctyltriethoxysilane, CAS number 51851-37-7; Heptadecafluorodecyltrimethoxysilane, CAS No. 83048-65-1; Nonafluorohexyltriethoxysilane, CAS number 102390-98-7; Octyltriethoxysilane, CAS number 2943-75-1; pH adjuster, 2-amino-2-methyl-1-propanol, CAS number 124-68-5; Leveling agent RHT-1008, polyether-modified siloxane; Associative polyurethane thickener, model RM-8W; Alkali-swellable acrylate thickener, model ACRYSOLDR-50; Preparation of amino-terminated polyether-modified siloxanes: S1: 100 parts by mass of hydrogen-terminated silicone oil were added to a three-necked flask, stirred and heated to 60°C under nitrogen protection, followed by the addition of 30 parts by mass of allyl glycidyl ether and 0.005 parts by mass of chloroplatinic acid catalyst. The mixture was stirred and reacted at 90°C for 6 hours. After the reaction was completed, the system was cooled to 70°C, and unreacted small molecules and solvents were removed by distillation under reduced pressure to obtain the terminal epoxy-modified siloxane intermediate.

[0046] S2: Add 80 parts by mass of the epoxy-terminated modified siloxane intermediate obtained above to a reaction vessel, heat to 70°C and stir evenly, then add 20 parts by mass of the amino-terminated polyether, and stir and react at 70°C for 5 hours to allow the amino and epoxy groups to undergo a ring-opening reaction; after the reaction is completed, cool the system to below 40°C to obtain the amino-terminated polyether modified siloxane.

[0047] Preparation Example 1 Preparation of modified hollow silica microspheres: M1: Three parts by mass of hollow silica microspheres were added to 150 mL of deionized water and ultrasonically dispersed for 30 minutes to obtain a silica aqueous dispersion. This dispersion was heated to 75°C, and 50 parts by mass of molten paraffin were added. The mixture was stirred at 1500 rpm for 20 minutes to form an oil-in-water Pickering emulsion. Subsequently, under continuous stirring, the hot emulsion was rapidly poured into an ice-water bath and cooled to 15°C to solidify the paraffin droplets. The solid composite was collected by filtration and washed three times with cold deionized water to obtain SiO2 microspheres coated with paraffin. These microspheres were dispersed in 150 parts by mass of a water / ethanol mixture (80% ethanol by volume), and one part by mass of tridecafluorooctyltriethoxysilane was added. The pH of the system was adjusted to 5 using glacial acetic acid. The reaction was stirred at 30°C for 8 hours. After the reaction was complete, the mixture was cooled to 25°C, and the solid was separated by centrifugation and washed three times with deionized water. The solid was then added to 100 parts by mass of toluene, and the paraffin was dissolved by stirring at 45°C for 30 minutes. The solid was then separated by centrifugation. This dissolution-centrifugation process was repeated twice. Finally, the solid was washed three times each with toluene, ethanol and deionized water to obtain partially modified hollow silica microspheres.

[0048] M2: The partially modified hollow silica microspheres obtained above were dispersed in 150 mL of toluene, and 0.8 parts by mass of γ-glycidoxypropyltrimethoxysilane were added. The mixture was stirred at 90 °C for 9 hours. After the reaction was completed, the mixture was centrifuged and washed three times each with toluene and ethanol. Finally, it was vacuum dried at 70 °C for 8 hours to obtain asymmetric modified hollow silica microspheres.

[0049] Preparation Example 2 Preparation of modified hollow silica microspheres: M1: Three parts by mass of hollow silica microspheres were added to 150 mL of deionized water and ultrasonically dispersed for 30 minutes to obtain a silica aqueous dispersion. This dispersion was heated to 75°C, and 50 parts by mass of molten paraffin were added. The mixture was stirred at 1500 rpm for 20 minutes to form an oil-in-water Pickering emulsion. Subsequently, under continuous stirring, the hot emulsion was rapidly poured into an ice-water bath and quickly cooled to 15°C to solidify the paraffin droplets. The solid composite was collected by filtration and washed three times with cold deionized water to obtain SiO2 microspheres coated with paraffin. These microspheres were dispersed in 150 parts by mass of a water / ethanol mixture (80% ethanol by volume), and one part by mass of heptadecafluorodecyltrimethoxysilane was added. The pH of the system was adjusted to 5 using glacial acetic acid. The reaction was stirred at 30°C for 8 hours. After the reaction was complete, the mixture was cooled to 25°C, and the solid was separated by centrifugation and washed three times with deionized water. The solid was then added to 100 parts by mass of toluene, and the paraffin was dissolved by stirring at 45°C for 30 minutes. The solid was then separated by centrifugation. This dissolution-centrifugation process was repeated twice. Finally, the solid was washed three times each with toluene, ethanol and deionized water to obtain partially modified hollow silica microspheres.

[0050] M2: The partially modified hollow silica microspheres obtained above were dispersed in 150 mL of toluene, and 0.8 parts by mass of γ-glycidoxypropyltrimethoxysilane were added. The mixture was stirred at 90 °C for 9 hours. After the reaction was completed, the mixture was centrifuged and washed three times each with toluene and ethanol. Finally, it was vacuum dried at 70 °C for 8 hours to obtain asymmetric modified hollow silica microspheres.

[0051] Preparation Example 3 Preparation of modified hollow silica microspheres: nonafluorohexyltriethoxysilane M1: Three parts by mass of hollow silica microspheres were added to 150 mL of deionized water and ultrasonically dispersed for 30 minutes to obtain a silica aqueous dispersion. This dispersion was heated to 75°C, and 50 parts by mass of molten paraffin were added. The mixture was stirred at 1500 rpm for 20 minutes to form an oil-in-water Pickering emulsion. Subsequently, under continuous stirring, the hot emulsion was rapidly poured into an ice-water bath and quickly cooled to 15°C to solidify the paraffin droplets. The solid composite was collected by filtration and washed three times with cold deionized water to obtain SiO2 microspheres coated with paraffin. These microspheres were dispersed in 150 parts by mass of a water / ethanol mixture (80% ethanol by volume), and one part by mass of nonafluorohexyltriethoxysilane was added. The pH of the system was adjusted to 5 using glacial acetic acid. The reaction was stirred at 30°C for 8 hours. After the reaction was complete, the mixture was cooled to 25°C, and the solid was separated by centrifugation and washed three times with deionized water. The solid was then added to 100 parts by mass of toluene, and the paraffin was dissolved by stirring at 45°C for 30 minutes. The solid was then separated by centrifugation. This dissolution-centrifugation process was repeated twice. Finally, the solid was washed three times each with toluene, ethanol and deionized water to obtain partially modified hollow silica microspheres.

[0052] M2: The partially modified hollow silica microspheres obtained above were dispersed in 150 mL of toluene, and 0.8 parts by mass of γ-glycidoxypropyltrimethoxysilane were added. The mixture was stirred at 90 °C for 9 hours. After the reaction was completed, the mixture was centrifuged and washed three times each with toluene and ethanol. Finally, it was vacuum dried at 70 °C for 8 hours to obtain asymmetric modified hollow silica microspheres.

[0053] Comparative Preparation Example 1 Preparation of modified silica microspheres: M1: Add 3 parts by mass of silica microspheres to 150 mL of deionized water and sonicate for 30 minutes to obtain a silica aqueous dispersion. Heat the dispersion to 75°C, add 50 parts by mass of molten paraffin, and stir at 1500 rpm for 20 minutes to form an oil-in-water Pickering emulsion. Then, while continuously stirring, quickly pour the above hot emulsion into an ice-water bath and cool to 15°C to solidify the paraffin droplets. Filter and collect the solid composite, and wash it three times with cold deionized water to obtain SiO2 microspheres coated with paraffin. Disperse the above microspheres in 150 parts by mass of a water / ethanol mixed solution (80% ethanol by volume), add 1 part by mass of tridecafluorooctyltriethoxysilane, and adjust the pH of the system to 5 with glacial acetic acid. Stir the reaction at 30°C for 8 hours. After the reaction is complete, cool to 25°C, centrifuge to separate the solid, and wash it three times with deionized water. The solid was then added to 100 parts by mass of toluene, and the paraffin was dissolved by stirring at 45°C for 30 minutes. The solid was then separated by centrifugation. This dissolution-centrifugation process was repeated twice. Finally, the solid was washed three times each with toluene, ethanol and deionized water to obtain partially modified silica microspheres.

[0054] M2: The partially modified hollow silica microspheres obtained above were dispersed in 150 mL of toluene, and 0.8 parts by mass of γ-glycidoxypropyltrimethoxysilane were added. The mixture was stirred at 90 °C for 9 hours. After the reaction was completed, the mixture was centrifuged and washed three times each with toluene and ethanol. Finally, it was vacuum dried at 70 °C for 8 hours to obtain asymmetric modified hollow silica microspheres.

[0055] Comparative Preparation Example 2 Preparation of modified hollow silica microspheres: Three parts by mass of hydrophilic hollow silica microspheres were dispersed in 40 mL of toluene and sonicated for 20 minutes. Then, one part by mass of tridecafluorooctyltriethoxysilane was added to the system and the mixture was stirred at 60 °C for 8 hours. The system was then cooled to 20 °C and centrifuged to obtain a solid product. The product was washed three times each with toluene, ethanol and deionized water, and finally dried under vacuum at 70 °C for 8 hours to obtain modified hollow silica microspheres.

[0056] Example 1 Preparation of superhydrophobic and stain-resistant wall paint: 100 parts by weight of aqueous styrene-acrylate emulsion and 2 parts by weight of film-forming aid were added to a dispersion vessel and stirred at 300 rpm for 5 minutes. Then, 20 parts by weight of titanium dioxide, 5 parts by weight of hydrophobic fumed silica, and 20 parts by weight of deionized water were pre-dispersed at 1000 rpm and added to the vessel, and stirred at 400 rpm for 15 minutes. Next, 10 parts by weight of asymmetric modified hollow silica microspheres obtained in Preparation Example 1 were added, and the stirring speed was reduced to 200 rpm for 20 minutes. Add 1 part by weight of the amino-terminated polyether modified siloxane obtained in Preparation Example 1, 0.2 parts by weight of the pH adjuster, and 0.1 parts by weight of the defoamer, and stir at 300 r / min for 10 minutes; then add 0.3 parts by weight of the associative polyurethane thickener and 0.5 parts by weight of the alkali-swellable acrylate thickener premixed and diluted with 10 parts by weight of deionized water to the reactor; finally, add 0.05 parts by weight of the defoamer at 250 r / min, and continue stirring for 15 minutes until the system is homogeneous. After filtering through a 100-mesh filter, the superhydrophobic and antifouling wall paint is obtained.

[0057] Example 2 Preparation of superhydrophobic and stain-resistant wall paint: The preparation method is largely the same as Example 1, except that the asymmetric modified hollow silica microspheres obtained in Preparation Example 1 are replaced with the asymmetric modified hollow silica microspheres obtained in Preparation Example 2.

[0058] Example 3 Preparation of superhydrophobic and stain-resistant wall paint: The preparation method is largely the same as Example 1, except that the asymmetric modified hollow silica microspheres obtained in Preparation Example 1 are replaced with the asymmetric modified hollow silica microspheres obtained in Preparation Example 3.

[0059] Comparative Example 1 Preparation of superhydrophobic and stain-resistant wall paint: The preparation method is largely the same as Example 1, except that the asymmetric modified hollow silica microspheres obtained in Preparation Example 1 are replaced with the modified silica microspheres obtained in Comparative Preparation Example 1.

[0060] Comparative Example 2 Preparation of superhydrophobic and stain-resistant wall paint: The preparation method is largely the same as Example 1, except that the asymmetric modified hollow silica microspheres obtained in Preparation Example 1 are replaced with the modified hollow silica microspheres obtained in Comparative Preparation Example 2.

[0061] Comparative Example 3 Preparation of superhydrophobic and stain-resistant wall paint: 100 parts by weight of aqueous styrene-acrylate emulsion and 2 parts by weight of film-forming aid were added to a dispersion vessel and stirred at 300 r / min for 5 minutes. Then, 20 parts by weight of titanium dioxide, 5 parts by weight of hydrophobic fumed silica, and 20 parts by weight of deionized water were pre-dispersed in the vessel at 1000 r / min and stirred at 400 r / min for 15 minutes. Next, 10 parts by weight of asymmetric modified hollow silica microspheres obtained in Preparation Example 1 were added, and the stirring speed was reduced to 200 r / min. At a speed of 300 rpm, add 0.2 parts by weight of pH adjuster and 0.1 parts by weight of defoamer for 20 minutes, and stir for 10 minutes. Then, premix and dilute 0.3 parts by weight of associative polyurethane thickener and 0.5 parts by weight of alkali-swellable acrylate thickener with 10 parts by weight of deionized water and add them to the reactor. Finally, add 0.05 parts by weight of defoamer at a speed of 250 rpm and continue stirring for 15 minutes until the system is homogeneous. After filtering through a 100-mesh filter, the superhydrophobic and antifouling wall paint is obtained.

[0062] Comparative Example 4 Preparation of superhydrophobic and stain-resistant wall paint: 100 parts by weight of aqueous styrene-acrylate emulsion and 2 parts by weight of film-forming aid were added to a dispersion vessel and stirred at 300 r / min for 5 minutes. Then, 20 parts by weight of titanium dioxide, 5 parts by weight of hydrophobic fumed silica, and 20 parts by weight of deionized water were pre-dispersed in the vessel at 1000 r / min and added to the vessel, and stirred at 400 r / min for 15 minutes. Next, 10 parts by weight of asymmetric modified hollow silica microspheres obtained in Preparation Example 1 were added, and the stirring speed was reduced to 200 r / min for 2 minutes. Add 1 part by weight of leveling agent RH-T1008, 0.2 parts by weight of pH adjuster and 0.1 parts by weight of defoamer at 0 minutes, and stir at 300 r / min for 10 minutes; then premix and dilute 0.3 parts by weight of associative polyurethane thickener and 0.5 parts by weight of alkali-swellable acrylate thickener with 10 parts by weight of deionized water and add to the reactor; finally, add 0.05 parts by weight of defoamer at 250 r / min and continue stirring for 15 minutes until the system is homogeneous. After filtering through a 100-mesh filter, the superhydrophobic and antifouling wall paint is obtained.

[0063] Test section The wall paint samples prepared in each embodiment and comparative example were placed with 3 mL of paint on one end of a degreased glass plate and coated with a paint film applicator at a speed of 100 mm / s to form a smooth paint film. After drying naturally for 24 hours, the samples were left to stand for 168 hours at 25°C and 50% relative humidity to obtain test samples.

[0064] Anti-fouling test: The test sample was washed according to the standard state method in GB / T9780-2013. After five cycles, the reflection coefficient at the middle position of the sample was tested. The initial reflection coefficient R0, the reflection coefficient after treatment R1, and the coating reflection reduction rate were calculated as X=(R0-R1) / R0×100%.

[0065] Hydrophobicity test: After placing the samples of each embodiment and comparative example at 25°C and 50% relative humidity for 24 hours, 5 μL of deionized water was dropped onto the sample surface using a contact angle meter, and the static water contact angle at 5 seconds was recorded. Five different locations were tested for each sample, and the average value was taken.

[0066] Adhesion test: A cross-cut test was conducted according to GB / T9286-2021. A cross-cutting tool with appropriate spacing was selected based on the coating thickness (80μm coating thickness, 2mm spacing). A 6×6 grid was vertically cut into the sample surface, ensuring the cut lines penetrated the coating to the substrate. After gently brushing away debris with a soft brush, pressure-sensitive adhesive tape was applied, compacted, and then quickly peeled off at a 90° angle. The sample was rated according to the standard, with three different locations tested for each sample, and the average rating was taken.

[0067] The test results are shown in Table 1.

[0068] Table 1

[0069] As shown in Table 1, the hydrophobic and antifouling wall coatings obtained in each embodiment outperformed the comparative examples in terms of static water contact angle, reflection reduction rate, and adhesion grade. This indicates that they have better hydrophobicity, antifouling durability, and coating adhesion. The reason may be as follows: In Comparative Example 1, solid silica microspheres were used instead of hollow silica microspheres. Although the Janus structure was also constructed through the interface confinement method, the density of solid microspheres was relatively high. During the film formation process, it was difficult to overcome fluid resistance and migrate efficiently to the surface. This may result in an insufficient number of low surface energy microspheres enriched on the surface, making it impossible to construct a complete micro-nano rough structure to achieve a stable Cassie-Baxter state. Therefore, the hydrophobic angle was lower and the antifouling performance was reduced. At the same time, the reduced surface anchoring points resulted in a slightly lower adhesion than the embodiments. In Comparative Example 2, the hollow silica microspheres were uniformly modified across the entire surface, completely destroying the Janus asymmetric structure. The completely hydrophobic microspheres had poor dispersibility and were prone to aggregation in the aqueous system. They also lost the anchoring effect between the hydrophilic side and the polymer matrix, resulting in the microspheres being dispersed in the coating. Uneven distribution and inability to orient the microspheres result in a lack of a continuous low-surface-energy hydrophobic layer, leading to a significantly reduced hydrophobic angle and the worst antifouling performance. Furthermore, the absence of anchoring sites causes a severe decrease in adhesion. In Comparative Example 3, the absence of amino-terminated polyether-modified siloxane, while retaining the asymmetric structure of the Janus microspheres, resulted in a lack of chemical anchoring between amino and epoxy groups. The microspheres relied solely on physical embedding into the matrix, making them prone to detachment or orientation disorder during film formation and rinsing. This resulted in insufficient stability of the superhydrophobic surface structure, thus hindering initial adhesion. The hydrophobic angle is high, but the antifouling durability is significantly reduced, and the adhesion is poor. In Comparative Example 4, the amino-terminated polyether modified siloxane was replaced with ordinary polyether modified siloxane leveling agent. Although it can improve the dispersion and wetting of microspheres, ordinary siloxane lacks amino groups that can react with the hydrophilic epoxy groups on the Janus microspheres. It cannot achieve unilateral chemical anchoring and flexible bridging. The interfacial bonding strength between microspheres and the substrate is weak. Therefore, the stability and antifouling durability of the hydrophobic structure are still inferior to those of the example. Although the adhesion is better than that of Comparative Example 3, it is still lower than that of the example.

[0070] As shown in Examples 1-3, the chain length of the fluorinated silane coupling agent has a certain influence on the coating performance. When octyl (C8) silane is used, the overall coating performance is better. This may be because although the C6 short chain diffuses rapidly, its oleophobicity is insufficient, resulting in a weak driving force for molecule migration from the oil phase to the interface, a low interface reaction concentration, and an easy formation of an incomplete and defective modified layer. The C10 long chain has strong oleophobicity, but its solubility and diffusivity in the oil phase decrease, making it difficult for molecules to be fully transported to the interface and prone to pre-aggregation, which also leads to uneven or loose interface modification. The C8 medium chain achieves the best balance between solubility, diffusivity and oleophobicity, which can both diffuse efficiently to the interface and accumulate and stabilize at the interface, thereby undergoing a uniform and complete condensation reaction with the silanol groups on the microsphere surface to form a good monomolecular low surface energy layer, laying an ideal chemical foundation for the subsequent construction of a stable superhydrophobic surface.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A superhydrophobic and stain-resistant wall paint, characterized in that, The raw materials include the following parts by weight: 100 parts by weight of waterborne styrene-acrylate emulsion, 5-15 parts by weight of modified hollow silica microspheres, 10-30 parts by weight of pigment, 15-30 parts by weight of filler, 0.1-0.2 parts by weight of defoamer, 1-3 parts by weight of film-forming aid, 0.1-0.3 parts by weight of pH adjuster, and 10-40 parts by weight of water; The modified hollow silica microspheres have a fluorinated silane coupling agent grafted onto one side of their surface and an epoxy silane coupling agent grafted onto the other side of their surface.

2. The superhydrophobic and stain-resistant wall paint according to claim 1, characterized in that, The raw materials also include amino-terminated polyether modified siloxanes, which are obtained by introducing epoxy groups through a hydrosilylation reaction between end-hydrogen-containing silicone oil and allyl glycidyl ether, followed by a ring-opening reaction with the amino-terminated polyether to introduce amino and polyether segments.

3. The superhydrophobic and stain-resistant wall paint according to claim 2, characterized in that, The preparation method of the amino-terminated polyether modified siloxane includes the following steps: S1: Stir 100-200 parts of hydrogen-terminated silicone oil and heat to 55-65℃, then add 20-50 parts of allyl glycidyl ether and 0.0024-0.01 parts of chloroplatinic acid catalyst. After the addition is complete, heat to 90-110℃ and stir for 6-8 hours. After the reaction is complete, cool to 60-80℃ and distill under reduced pressure to obtain the epoxy-terminated modified siloxane intermediate. S2: Heat 50-100 parts of the epoxy-terminated modified siloxane intermediate obtained in S1 to 60-80℃ and add 10-30 parts of amino-terminated polyether. Stir and react at 65-75℃ for 4-8 hours. After the reaction is completed, cool down to below 40℃ to obtain amino-terminated polyether modified siloxane.

4. The superhydrophobic and stain-resistant wall paint according to claim 2, characterized in that, The hollow silica microspheres have a particle size of 1~5μm.

5. The superhydrophobic and stain-resistant wall paint according to claim 3, characterized in that, The method shall satisfy at least one of the following conditions: 1) The viscosity of the hydrogen-containing silicone oil is 50~200 mPa·s, and the hydrogen content is 0.1~0.2 wt%; 2) The number average molecular weight of the terminal amino polyether is 1000~2000.

6. The superhydrophobic and stain-resistant wall paint according to claim 1, characterized in that, The modified hollow silica microspheres were prepared through the following steps: M1: Add 1-5 parts by weight of hydrophilic hollow silica microspheres to 100-200 mL of water and ultrasonically disperse for 20-40 minutes. Heat to 70-80℃ and add 40-60 parts by weight of molten paraffin. Stir and disperse at 1000-2000 rpm for 10-30 minutes. Cool to 10-20℃ in an ice-water bath to solidify the paraffin droplets. Filter to separate and collect the solid complex, and wash with cold deionized water 2-3 times to obtain SiO2 microspheres coated with paraffin. Then disperse the above microspheres in 100-200 parts by weight of ethanol aqueous solution with a volume fraction of 70%-95%. Add 0.1-2.5 parts by weight of fluorinated silane coupling agent and adjust the pH of the system to 4-6 with glacial acetic acid. The reaction was stirred at 20-40℃ for 6-12 hours. After the reaction was completed, the mixture was cooled to 20-30℃, the solid was separated by centrifugation, and washed 2-3 times each with toluene, ethanol and deionized water to obtain partially modified hollow silica microspheres. M2: Disperse the obtained modified hollow silica microspheres in 100-200 parts of toluene, add 0.1-2 parts of epoxy silane coupling agent, stir and react at 80-110℃ for 6-12 hours, centrifuge after the reaction, wash with toluene and ethanol 2-3 times each, and vacuum dry at 60-80℃ for 6-12 hours to obtain modified hollow silica microspheres.

7. The superhydrophobic and stain-resistant wall paint according to claim 1, characterized in that, The raw materials also include thickeners, including associative polyurethane thickeners and alkali-swellable acrylate thickeners.

8. The superhydrophobic and stain-resistant wall paint according to claim 1, characterized in that, The filler comprises hydrophobically treated fumed silica, wherein the average particle size of the fumed silica is 1~20 nm.

9. The superhydrophobic and antifouling wall paint according to any one of claims 1 to 8, characterized in that, The raw materials meet at least one of the following conditions: 1) The pigment includes titanium dioxide; 2) The defoamer includes mineral oil-based defoamers; 3) The film-forming aids include ester-based film-forming aids; 4) The pH adjuster includes organic amine pH adjusters; 5) The fluorinated silane coupling agent includes perfluorooctylsilane coupling agent.

10. A method for preparing a superhydrophobic and stain-resistant wall paint, characterized in that, include: Provide the raw materials for the superhydrophobic and antifouling wall paint according to any one of claims 1 to 9; The raw materials are mixed to obtain a superhydrophobic and stain-resistant wall paint.

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