A rice leaf structure imitated fluorine-free high-strength multifunctional super-hydrophobic coated paper and a preparation method thereof

Abstract

The application discloses a kind of paper coated with fluorine-free high-strength multifunctional super-hydrophobic coating with rice leaf structure and its preparation method.The method selects polydimethylsiloxane and natural wax as low surface energy raw materials, which are non-toxic, harmless and environmentally compatible, eliminating environmental hazards from the source.Amino silane coupling agent is used to modify silica nanoparticles, and the amino groups on the surface of the nanoparticles can form hydrogen bonds with the hydroxyl groups of PDMS, allowing the nanoparticles to be firmly anchored to the paper base, improving dispersibility and strengthening interfacial bonding.For long-term durability, a micro-nano hierarchical rough structure is constructed, and rigid silica nanoparticles and flexible wax particles work together to improve the mechanical strength of the coating, while the plastic deformation of the wax dissipates energy and avoids brittle failure.A pre-sprayed PDMS adhesive layer is used to further reinforce the coating-paper interface, making the coating have excellent wear resistance and durability, and achieving a balance between green environmental protection, structural stability and long-term durability.

Description

Technical Field

[0001] This invention belongs to the field of paper and coating preparation technology, and relates to a fluorine-free, high-strength, multifunctional superhydrophobic paper coated with a rice leaf-like structure and its preparation method. Background Technology

[0002] Paper, an indispensable basic material in daily life, food packaging, artistic creation, and cultural relic preservation, is not only an important carrier of material production but also a key medium for bearing the lineage of human civilization, with vast prospects for industrial application and cultural relic protection. However, the paper matrix is ​​mainly composed of cellulose, hemicellulose, and lignin. The inherent hydrophilic properties of these two types of polysaccharide molecules make it highly susceptible to moisture, leading to a series of damages such as deformation, cracking, brittleness, and acid aging. This is particularly pronounced for ancient paper artifacts, where long-term storage and moisture erosion cause significant deterioration, seriously threatening their long-term preservation. Based on the practical needs of paper product production, long-term cultural relic protection, and storage, there is an urgent need to perform hydrophobic modification treatment on paper to block the diffusion of moisture into the fiber matrix, thereby improving the material's mechanical durability and inhibiting the decline in mechanical properties caused by the aging process.

[0003] Numerous biological structures in nature provide natural biomimetic prototypes for interfacial wetting regulation research. The surfaces of organisms such as lotus leaves, rice leaves, butterfly wings, and water strider feet all exhibit typical superhydrophobic properties, offering biomimetic approaches to solving the hydrophilicity problem of paper. Constructing superhydrophobic coatings requires simultaneously meeting two core conditions: low surface energy chemical composition and hierarchical micro / nano rough structures. In terms of low surface energy modification materials, fluorinated compounds (perfluorinated and polyfluoroalkyl compounds) are widely used due to their extremely low surface energy; while in constructing rough morphologies, nanofillers are a commonly used technique.

[0004] Despite the progress made in the preparation of superhydrophobic coatings, several problems remain to be solved. On the one hand, while fluorinated compounds have extremely low surface energy, they exhibit poor biodegradability and pose a persistent threat to human health and ecosystems, leading to restrictions on their use in multiple industries and contradicting the trend of green development. On the other hand, nanofillers used to construct rough morphologies generally suffer from poor dispersibility, insufficient adhesion to paper substrates, and easy wear and failure of surface microstructures, significantly shortening the coating's lifespan. Therefore, developing a green, low-toxicity, structurally stable coating preparation method that combines excellent superhydrophobic properties with mechanical wear resistance and durability is both a pressing practical need and of significant research importance. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating with a rice leaf-like structure and its preparation method. This solves the problems of fluorine-containing compounds used in the superhydrophobic coatings of the prior art, which are harmful to the environment due to their poor biodegradability, and the nanofillers, which have problems such as poor dispersibility, weak bonding with the paper base, and easy wear, resulting in short coating life and difficulty in meeting the comprehensive requirements of green environmental protection, structural stability, and long-term durability.

[0006] This invention is achieved through the following technical solution: A method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves includes the following steps: S1: Mix aminosilane coupling agent, anhydrous ethanol and deionized water, and slowly add the mixture to the mixture of silica nanoparticles and anhydrous ethanol. Stir the mixture at a constant temperature to prepare silane coupling agent modified silica nanoparticles. S2: After mixing polydimethylsiloxane, curing agent and tetrahydrofuran evenly, spray it onto the paper surface and pre-cur it at room temperature to obtain paper coated with polydimethylsiloxane. S3: After uniformly mixing the silane coupling agent-modified silica nanoparticles, flake-shaped micron wax particles and tetrahydrofuran, the mixture is sprayed onto the surface of the paper coated with polydimethylsiloxane and cured at room temperature to obtain a fluorine-free, high-strength, multifunctional superhydrophobic coating paper with a rice leaf-like structure.

[0007] Optionally, the preparation of the silane coupling agent modified silica nanoparticles is as follows: aminosilane coupling agent, anhydrous ethanol, and deionized water are mixed evenly at a mass ratio of 2:(5~10):1, and then slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:(5~15). The mixture is reacted at 60°C for 2~4 h to complete the grafting modification. After centrifugation at 8000~10000 rpm, the nanoparticles are washed three times with anhydrous ethanol and dried at 80°C for 2~4 h to obtain the silane coupling agent modified silica nanoparticles.

[0008] Optionally, the preparation of the silica nanoparticles specifically includes: Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 500-1000 rpm for 12-24 h at room temperature. After the reaction was completed, the precipitate was separated by centrifugation at 8000-10000 rpm and dried at 60-80℃ for 4-8 h to obtain silica nanoparticles.

[0009] Optionally, the aminosilane coupling agent includes one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane.

[0010] Optionally, in step S2, the mass ratio of polydimethylsiloxane, curing agent, and tetrahydrofuran is 1:0.1:(5~20); the pre-curing time is 2~4 h; Optionally, in step S3, the mass ratio of the silane coupling agent modified silica nanoparticles to the sheet-like micron wax particles is (0.5~5):(5~9.5); the total mass of the silane coupling agent modified silica nanoparticles and the sheet-like micron wax particles to the mass ratio of tetrahydrofuran is 1:(10~30).

[0011] Optionally, in step S3, the curing time is 24~48 h.

[0012] Optionally, the spraying process in steps S1 and S2 is as follows: spray gun nozzle diameter 0.5 mm, spraying distance 10~20 cm, spraying pressure 0.2 MPa; each layer is sprayed 3 times, and the single spraying time is 3 s.

[0013] Optionally, the preparation of the flake-shaped micron-sized wax particles specifically involves: Weigh wax and mix it with anhydrous ethanol at a mass ratio of (1~5):150, heat it to the wax melting point to make it completely melt, let it cool naturally to precipitate wax particles, wash it three times with anhydrous ethanol, and dry it at 50℃ for 2~4 hours to obtain flaky micron wax particles; the wax includes one of beeswax, carnauba wax, candle wax and rice bran wax.

[0014] A type of paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves is prepared by the method described above.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating with a rice leaf-like structure. Firstly, regarding environmental friendliness, this method abandons poorly biodegradable fluorinated compounds and instead uses polydimethylsiloxane (PDMS) and natural wax as low surface energy materials. These raw materials are non-toxic, harmless, and environmentally compatible, fundamentally solving the environmental hazard problem. Secondly, addressing the issues of poor dispersibility and weak adhesion between nanofillers and the paper substrate, this method modifies the surface of silica nanoparticles using an aminosilane coupling agent. This allows the amino groups carried by the nanoparticles to form hydrogen bonds with the hydroxyl groups on the PDMS surface, thus firmly anchoring the nanoparticles to the paper substrate. This not only improves dispersibility but also significantly enhances the adhesion between the coating and the paper substrate. Finally, to achieve long-term durability, this method constructs a micro-nano hierarchical rough structure mimicking rice leaves. Utilizing the synergistic effect of rigid silica nanoparticles and flexible wax particles, the mechanical strength of the coating is enhanced, and energy is absorbed through the plastic deformation of the wax, preventing brittle fracture. Meanwhile, the pre-sprayed PDMS adhesion underlayer further strengthens the bond between the coating and the paper, together giving the coating excellent mechanical abrasion resistance and durability, successfully balancing the comprehensive needs of green environmental protection, structural stability and long-term durability.

[0016] Furthermore, the preparation of the silane coupling agent modified silica nanoparticles specifically involves: mixing an aminosilane coupling agent, anhydrous ethanol, and deionized water at a mass ratio of 2:(5~10):1, then slowly adding the mixture to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:(5~15). The mixture is reacted at 60°C for 2~4 h to complete the grafting modification. After centrifugation at 8000~10000 rpm, washing three times with anhydrous ethanol, and drying at 80°C for 2~4 h, the silane coupling agent modified silica nanoparticles are obtained. This step, by precisely controlling the mixing ratio of the aminosilane coupling agent, solvent, and water, as well as the temperature and time of the grafting reaction, ensures that the silane coupling agent undergoes sufficient hydrolysis and condensation reactions on the silica surface, achieving efficient grafting of organic functional groups onto the surface of inorganic nanoparticles. Meanwhile, by combining specific centrifugal speeds and cleaning and drying processes, unreacted coupling agents and byproducts are effectively removed, preventing the aggregation of nanoparticles and ensuring the purity and surface chemical activity of the modified nanoparticles. This lays a solid material foundation for the subsequent construction of stable micro-nano structures and enhanced interfacial bonding in the coating.

[0017] Furthermore, the preparation of the silica nanoparticles specifically involves: mixing tetraethyl orthosilicate, anhydrous ethanol, and ammonia in a volume ratio of 5:25:1, stirring magnetically at 500-1000 rpm for 12-24 h at room temperature, centrifuging at 8000-10000 rpm to separate the precipitate, and drying the precipitate at 60-80℃ for 4-8 h to obtain silica nanoparticles. This step utilizes the sol-gel method to prepare silica nanoparticles. By strictly controlling the volume ratio of tetraethyl orthosilicate, anhydrous ethanol, and ammonia, as well as the reaction conditions, silica nanospheres with uniform particle size and regular morphology can be synthesized simply and at low cost. These high-quality nanoparticles, serving as a rigid framework for constructing a rough structure, are not only widely available, but their size uniformity also facilitates the formation of a uniform microstructure on the coating surface, thus providing structural assurance for obtaining stable and excellent superhydrophobic properties.

[0018] Furthermore, the aminosilane coupling agent includes one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. These coupling agent molecules all contain active amino groups and hydrolyzable alkoxy groups, and none contain fluorine, meeting green and environmentally friendly requirements. The alkoxy groups can react with the hydroxyl groups on the silica surface, while the amino groups can form hydrogen bonds or chemical bonds with the polar groups on the polydimethylsiloxane (PDMS) matrix or paper fiber surface. This amphiphilic structure acts like a molecular bridge, significantly enhancing the interfacial compatibility and bonding strength between inorganic nanoparticles and the organic polymer matrix and paper base, effectively preventing coating peeling or powdering during use.

[0019] Furthermore, in step S2, the mass ratio of polydimethylsiloxane, curing agent, and tetrahydrofuran is 1:0.1:(5~20); the pre-curing time is 2~4 hours. This step defines a specific mass ratio of PDMS, curing agent, and solvent tetrahydrofuran, ensuring that the primer has suitable viscosity and leveling properties, allowing it to fully wet the paper fiber pores and form a strong anchoring layer. Simultaneously, the 2~4 hour pre-curing time control is crucial, as it keeps the primer in a semi-cured (surface dry) state, ensuring both the bonding between the primer and the paper and preserving the surface's chemical activity and physical adhesion. This facilitates the embedding and bonding of subsequent functional layers (nanoparticles and wax particles), thereby forming a tightly bonded gradient structure.

[0020] Furthermore, in step S3, the mass ratio of the silane coupling agent-modified silica nanoparticles to the flake-shaped micron-sized wax particles is (0.5~5):(5~9.5); the mass ratio of the total mass of the silane coupling agent-modified silica nanoparticles and the flake-shaped micron-sized wax particles to the mass of tetrahydrofuran is 1:(10~30). This step optimizes the mass ratio of rigid modified silica nanoparticles to flexible flake-shaped micron-sized wax particles, utilizing a strategy of combining rigidity and flexibility to construct a micro-nano hierarchical rough structure mimicking rice leaves. The rigid particles provide mechanical support, while the flexible wax flakes fill the gaps and reduce surface energy; their synergistic effect maximizes the surface roughness factor. Simultaneously, limiting the ratio of total solids content to solvent ensures the dispersion stability of the sprayed slurry, prevents nozzle clogging, and ensures uniform coating distribution on the paper surface without sagging or accumulation defects.

[0021] Furthermore, in step S3, the curing time is 24-48 hours. This step sets a room temperature curing time, providing a sufficient time window for the crosslinking reaction of the PDMS system. Sufficient curing ensures the complete formation of the polymer network within the coating, enabling the coating to achieve optimal mechanical strength and chemical stability. This process eliminates internal stress within the coating, preventing stickiness or insufficient strength caused by incomplete curing, thereby significantly improving the durability and weather resistance of the superhydrophobic paper under long-term use conditions.

[0022] Furthermore, the spraying process in steps S1 and S2 is as follows: spray gun nozzle diameter 0.5 mm, spraying distance 10-20 cm, spraying pressure 0.2 MPa; each layer is sprayed 3 times, with a single spraying time of 3 seconds. This step specifies the spraying process parameters in detail, including nozzle diameter, spraying distance, pressure, and multi-layer short-time spraying method. This process control can precisely adjust the deposition state of droplets on the paper surface, utilize airflow atomization to evenly spread the functional material, and avoid local over-thickness leading to cracking or under-thickness leading to incomplete coverage. Multiple short-time sprays help solvent evaporation and layer-by-layer coating construction, ensuring the uniform reproduction of the biomimetic micro / nano structure on the paper surface and guaranteeing the consistency of large-area preparation.

[0023] Furthermore, the preparation of the flake-like micron-sized wax particles specifically involves: weighing wax and mixing it with anhydrous ethanol at a mass ratio of (1~5):150, heating to the wax melting point to completely melt it, allowing it to cool naturally to precipitate wax particles, washing three times with anhydrous ethanol, and drying at 50℃ for 2~4 hours to obtain flake-like micron-sized wax particles. This step provides a simple solvent precipitation method for preparing flake-like micron-sized wax particles, utilizing the characteristic of wax dissolving in hot ethanol and precipitating upon cooling to generate micron-sized particles with a specific flake morphology in situ. This flake structure is similar to the papillary structure on the surface of rice leaves. Compared to spherical particles, flake-like particles are more likely to overlap on the coating surface to form multi-level voids, which can not only effectively trap air to form an air cushion, but also dissipate energy through flake slippage under stress, further enhancing the superhydrophobicity and mechanical wear resistance of the coating. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a morphology diagram of the silane coupling agent modified silica nanoparticles prepared in Example 1 of this invention. Figure 2 This is a morphology diagram of the micron-sized beeswax particles obtained in Example 1 of this invention; Figure 3 A surface morphology diagram of the original Xuan paper; Figure 4 This is a morphological image of the paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, prepared in Example 1 of the present invention. Figure 5 The water contact angle of the rice paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, prepared in Example 1 of this invention; Figure 6 The water contact angle of the original Xuan paper; Figure 7 A photograph of the original Xuan paper; Figure 8 This is a photograph of Xuan paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, obtained in Example 1 of this invention. Figure 9 This is a surface morphology image of Xuan paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, prepared according to Example 2 of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] This invention provides a method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, comprising the following steps: S1: Mix aminosilane coupling agent, anhydrous ethanol and deionized water, and slowly add the mixture to the mixture of silica nanoparticles and anhydrous ethanol. Stir the mixture at a constant temperature to prepare silane coupling agent modified silica nanoparticles. The preparation of the silane coupling agent modified silica nanoparticles is specifically as follows: Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted magnetically at 500-1000 rpm for 12-24 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 8000-10000 rpm and dried at 60-80℃ for 4-8 h to obtain silica nanoparticles. An aminosilane coupling agent, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:(5-10):1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:(5-15). The mixture was reacted at 60℃ for 2-4 h to complete the grafting modification. After centrifugation at 8000-10000 rpm, the nanoparticles were washed three times with anhydrous ethanol and dried at 80℃ for 2-4 h to obtain silane coupling agent modified silica nanoparticles.

[0032] The aminosilane coupling agent is free of fluorine and includes, but is not limited to, one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane.

[0033] S2: After mixing polydimethylsiloxane, curing agent and tetrahydrofuran evenly, spray it onto the paper surface and pre-cur it at room temperature to obtain paper coated with polydimethylsiloxane. The mass ratio of the polydimethylsiloxane, curing agent, and tetrahydrofuran is 1:0.1:(5~20); The pre-curing time is 2-4 hours; The curing agent is a curing agent used in conjunction with polydimethylsiloxane, such as Sylgard 184 curing agent (component B), which is used in combination with polydimethylsiloxane adhesive (component A).

[0034] S3: After uniformly mixing the silane coupling agent-modified silica nanoparticles, flake-shaped micron wax particles and tetrahydrofuran, the mixture is sprayed onto the surface of the paper coated with polydimethylsiloxane and cured at room temperature to obtain a fluorine-free, high-strength, multifunctional superhydrophobic coating paper with a rice leaf-like structure.

[0035] The mass ratio of the silane coupling agent modified silica nanoparticles to the sheet-like micron wax particles is (0.5~5):(5~9.5); the total mass of the silane coupling agent modified silica nanoparticles and the sheet-like micron wax particles to the mass ratio of tetrahydrofuran is 1:(10~30). The curing time is 24~48 h.

[0036] The spraying process in steps S1 and S2 is as follows: spray gun nozzle diameter 0.5 mm, spraying distance 10~20 cm, spraying pressure 0.2 MPa; each layer is sprayed 3 times, and the single spraying time is 3 s.

[0037] The preparation of the flake-shaped micron-sized wax particles is specifically as follows: Weigh wax and anhydrous ethanol at a mass ratio of (1~5):150, heat to the wax melting point to completely melt it, let it cool naturally to precipitate wax particles, wash three times with anhydrous ethanol, and dry at 50℃ for 2~4 h to obtain flaky micron wax particles.

[0038] The wax is a natural wax, including but not limited to beeswax, carnauba wax, candlewood wax, rice bran wax, etc.

[0039] This invention discloses a method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves. The method is based on the design concept of the natural superhydrophobic biomimetic system of rice leaves. It draws on the mechanism of regulating wetting behavior by the special morphology of the micron-ridge composite nano-protrusions on the surface of rice leaves. The micro-nano hierarchical structure of the biological surface is replicated to the microscale interface of the paper-based material. Using silica nanoparticles as the core construction material, a multi-level rough skeleton mimicking rice leaves is built on the surface of the paper fibers. The concave-convex structure formed by the stacking of silica nanoparticles captures the air layer. Combined with the low surface energy characteristics of natural wax, a composite superhydrophobic interface is constructed, giving the paper a stable and long-lasting superhydrophobic effect.

[0040] Existing superhydrophobic coatings involving wax materials mostly employ thermal spraying, high-temperature annealing, or substrate preheating processes to melt the wax and improve its film-forming properties. However, this is energy-intensive and unsuitable for heat-sensitive substrates, such as those used in the restoration of paper artifacts. This invention prepares micron-sized wax particles that can be directly sprayed onto paper surfaces without heating, simplifying the preparation process and reducing manufacturing costs. Furthermore, the combination of these particles with silica nanoparticles constructs a micro-nano hierarchical rough structure, significantly improving the hydrophobic properties of paper.

[0041] Aminosilane coupling agents modify silica nanoparticles with excellent compatibility with micro-cured polydimethylsiloxane. The amino groups carried by the silane coupling agent can form hydrogen bonds with the hydroxyl groups on the surface of polydimethylsiloxane, firmly anchoring the silica nanoparticles to the paper substrate surface and effectively improving the overall mechanical durability of the coating. The uniformly dispersed rigid silica nanoparticles can effectively transfer stress, and the inherent flexibility and plasticity of wax can undergo small deformations under tensile stress, thereby absorbing some energy and avoiding brittle fracture. The synergistic effect between the two enhances the tensile strength of the paper.

[0042] The Xuan paper modified with the coating prepared using the method of this invention exhibits superhydrophobicity (water contact angle greater than 150°), superior light transmittance compared to the original paper, and minimal color difference (ΔE less than 5), thus completely preserving the original color of the Xuan paper. The coating maintains its excellent hydrophobic properties even after mechanical durability tests such as friction and abrasion, tape peeling, and finger rubbing, as well as prolonged immersion in acids and alkalis. Furthermore, this coating significantly improves the tensile strength of the Xuan paper.

[0043] This invention uses a spraying method to prepare a composite coating with a bird's nest-like structure. The preparation process is simple, has a low operating threshold, can achieve large-scale preparation, has low preparation cost, and the raw materials are all natural materials that are non-toxic, harmless, and have good environmental compatibility, which is conducive to promoting the industrialization of superhydrophobic protective coatings.

[0044] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0045] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0046] Example 1 This embodiment provides a method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 500 rpm for 12 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 8000 rpm and dried at 80℃ for 6 h to prepare silica nanoparticles. 3) 3-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:7.9:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:10.5. The mixture was reacted at 60℃ for 3 h to complete the grafting modification. After centrifugation at 8000 rpm, the nanoparticles were washed three times with anhydrous ethanol and dried at 80℃ for 3 h to obtain silane coupling agent modified silica nanoparticles. 2) Weigh beeswax and anhydrous ethanol at a mass ratio of 2:150, mix them, heat to 65°C to melt them completely, let them cool naturally to precipitate beeswax particles, wash them 3 times with anhydrous ethanol, and dry them at 50°C for 2 hours to obtain micron-sized wax flake particles, i.e. flake micron wax particles. 3) Mix polydimethylsiloxane, curing agent and tetrahydrofuran at a mass ratio of 1:0.1:10 and spray it onto the surface of Xuan paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times. Each spraying time is 3 s. Pre-cur at room temperature for 4 h to obtain polydimethylsiloxane coated Xuan paper.

[0047] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran at a mass ratio of 1:9. The total mass ratio of the two to tetrahydrofuran is 1:20. Spray the mixture onto the surface of the polydimethylsiloxane-coated Xuan paper obtained in step 3). The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 48 h to obtain Xuan paper coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating.

[0048] Figure 1 The figure shows the morphology of the silane coupling agent modified silica nanoparticles prepared in Example 1 of this invention. As can be seen from the figure, the morphology of the prepared silane coupling agent modified silica nanoparticles is close to spherical, with a diameter of about 64 nm.

[0049] Figure 2 The figure shows the morphology of the micron-sized beeswax particles obtained in Example 1 of this invention. As can be seen from the figure, the obtained micron-sized beeswax particles are in the form of flakes.

[0050] Figure 3 This is a surface morphology diagram of the original Xuan paper. Figure 4 This is a morphological image of the paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, prepared in Example 1 of this invention. Figure 5 The water contact angle of the Xuan paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves, prepared in Example 1 of this invention, is shown. Figure 6 The figure shows the water contact angle of the original Xuan paper. As can be seen from the figure, compared to the disordered interweaving of fibers and abundant inter-fiber pores in the internal microstructure of Xuan paper, the paper surface coated with a rice leaf-like structure, featuring a fluorine-free, high-strength, multifunctional superhydrophobic coating, has silane coupling agent-modified silica nanoparticles and micron-sized waxy flakes uniformly filling and spreading on the Xuan paper surface. This reduces inter-fiber pores and increases roughness, allowing for stable trapping of air at the liquid-solid interface, thus endowing the paper with excellent superhydrophobic properties. The water contact angle is 152.6° (e.g., ...). Figure 5 As shown), compared to the original Xuan paper's 68.9° (as shown), Figure 6 (As shown) increased by 121.5%.

[0051] Figure 7 A photograph of the original Xuan paper. Figure 8The image shows a photograph of the Xuan paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves, prepared in Example 1 of this invention. As can be seen from the image, the light transmittance of the Xuan paper coated with the biomimetic fluorine-free, high-strength, multifunctional superhydrophobic coating prepared in this example is 37.4%, higher than the original Xuan paper's 34.8%. A photograph of the paper before coating is also shown (e.g., [image of the original paper]). Figure 7 As shown in the image, the SUST logo is clearly visible. (See the photo after painting.) Figure 8 As shown, the "SUST" lettering is clearly visible, directly confirming the transparency of the prepared coating. The coating color difference ΔE is 2.72, which is below the visual resolution threshold of 5, proving that the coating has excellent transparency and does not change the original appearance and color of the Xuan paper.

[0052] The Xuan paper coated with the biomimetic fluorine-free high-strength multifunctional superhydrophobic coating prepared in this embodiment was subjected to sandpaper abrasion, tape peeling, and finger rubbing tests. The water contact angles of the Xuan paper coated with the biomimetic fluorine-free high-strength multifunctional superhydrophobic coating prepared in this embodiment were 150.6°, 151.0°, and 150.1°, respectively, and it still maintained superhydrophobicity, proving that the coating has excellent mechanical durability.

[0053] The Xuan paper coated with the biomimetic fluorine-free high-strength multifunctional superhydrophobic coating prepared in this embodiment was soaked for 12 h under pH conditions of 5 and 10. The water contact angle of the Xuan paper coated with the biomimetic fluorine-free high-strength multifunctional superhydrophobic coating was 150.8° and 149.8°, respectively, which proves that the coating has excellent acid and alkali corrosion resistance. The tensile strength of the Xuan paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating obtained in this embodiment is 21.6 MPa, which is 36.7% higher than that of the original Xuan paper.

[0054] Example 2 This embodiment provides a method for preparing paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 500 rpm for 12 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 8000 rpm and dried at 80℃ for 6 h to prepare silica nanoparticles. 3) 3-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:7.9:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:10.5. The mixture was reacted at 60℃ for 3 h to complete the grafting modification. After centrifugation at 8000 rpm, the nanoparticles were washed three times with anhydrous ethanol and dried at 80℃ for 3 h to obtain silane coupling agent modified silica nanoparticles.

[0055] 2) Weigh beeswax and anhydrous ethanol at a mass ratio of 2:150, mix them, heat to 65°C to melt them completely, let them cool naturally to precipitate beeswax particles, wash them three times with anhydrous ethanol, and dry them at 50°C for 2 hours to obtain micron-sized wax flake particles.

[0056] 3) Mix polydimethylsiloxane, curing agent and tetrahydrofuran at a mass ratio of 1:0.1:10 and spray it onto the surface of Xuan paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times. Each spraying time is 3 s. Pre-cur at room temperature for 4 h to obtain polydimethylsiloxane coated Xuan paper.

[0057] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran at a mass ratio of 3:7. The total mass ratio of the two to tetrahydrofuran is 1:20. Spray the mixture onto the surface of the polydimethylsiloxane-coated Xuan paper obtained in step 3). The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 48 h to obtain a fluorine-free, high-strength, multifunctional superhydrophobic coating on Xuan paper with a rice leaf-like structure.

[0058] Compared to the disordered interweaving of fibers and the rich pores between fibers in the microstructure of Xuan paper (such as... Figure 3 As shown in the figure, the surface morphology of Xuan paper coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating prepared in this embodiment is as follows. Figure 9 As shown, silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles are uniformly filled and spread on the surface of Xuan paper, reducing the porosity between fibers and increasing the roughness. This can stably trap air at the liquid-solid interface, giving the paper excellent superhydrophobic properties, with a water contact angle of 151.6°, which is 120.0% higher than that of the original Xuan paper.

[0059] The light transmittance of the Xuan paper modified with this coating is 43.9%, which is higher than the original Xuan paper's 34.8%, and the color difference ΔE is 3.16, which is lower than the visual resolution threshold of 5. This proves that the coating has excellent transparency and does not change the original appearance and color of the Xuan paper. After sandpaper abrasion, tape peeling, and finger rubbing tests, the water contact angles of the coated Xuan paper were 149.3°, 149.6°, and 147.9°, respectively, still exhibiting high hydrophobicity, proving that the coating has excellent mechanical durability. After soaking for 12 hours at pH 5 and 10, the water contact angle of the coated Xuan paper was 148.3° and 149.0°, respectively, proving that the coating has excellent resistance to acid and alkali corrosion. The tensile strength of the coated Xuan paper is 17.8 MPa, which is 12.7% higher than that of the original Xuan paper.

[0060] Example 3 This embodiment provides a method for preparing paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 1000 rpm for 24 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 10000 rpm and dried at 60℃ for 8 h to prepare silica nanoparticles. 3) 3-aminopropyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:5:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:5. The grafting modification was completed by reaction at 60℃ for 2 h. After centrifugation at 10000 rpm, washing with anhydrous ethanol 3 times, and drying at 80℃ for 4 h, silane coupling agent modified silica nanoparticles were obtained.

[0061] 2) Weigh carnauba wax and anhydrous ethanol at a mass ratio of 1:150, heat to 86°C to melt completely, allow to cool naturally to precipitate carnauba wax particles, wash three times with anhydrous ethanol, and dry at 50°C for 4 hours to obtain micron-sized wax flake particles.

[0062] 3) Mix polydimethylsiloxane, curing agent and tetrahydrofuran at a mass ratio of 1:0.1:20 and spray it onto the surface of Xuan paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 10 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times. Each spraying time is 3 s. Pre-cur at room temperature for 2 h to obtain polydimethylsiloxane coated Xuan paper.

[0063] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran at a mass ratio of 0.5:9.5. The total mass ratio of the two to tetrahydrofuran is 1:30. Spray the mixture onto the surface of the polydimethylsiloxane-coated Xuan paper obtained in step 3). The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 10 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 24 h to obtain a fluorine-free, high-strength, multifunctional superhydrophobic coating on Xuan paper with a rice leaf-like structure.

[0064] The water contact angle of the Xuan paper prepared using this embodiment, coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating, is 151.4°, which is 119.7% higher than that of the original Xuan paper, exhibiting superhydrophobic properties. The light transmittance of the Xuan paper modified with this coating is 46.6%, which is higher than the original Xuan paper's 38.9%, and the color difference ΔE is 0.81, which is lower than the visual resolution threshold of 5. This proves that the coating has excellent transparency and does not change the original appearance and color of the Xuan paper. After sandpaper abrasion, tape peeling, and finger rubbing tests, the water contact angles of the coated Xuan paper were 146.9°, 147.3°, and 145.9°, respectively, still exhibiting high hydrophobicity, proving that the coating has excellent mechanical durability. After soaking for 12 hours at pH 5 and 10, the water contact angle of the coated Xuan paper was 148.4° and 148.9°, respectively, proving that the coating has excellent resistance to acid and alkali corrosion.

[0065] Example 4 This embodiment provides a method for preparing paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 800 rpm for 20 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 9000 rpm and dried at 70℃ for 4 h to prepare silica nanoparticles. 3) 3-aminopropylmethyldiethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:10:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:15. The grafting modification was completed by reaction at 60℃ for 4 h. After centrifugation at 9000 rpm, washing with anhydrous ethanol 3 times, and drying at 80℃ for 2 h, silane coupling agent modified silica nanoparticles were obtained.

[0066] 2) Weigh beeswax and anhydrous ethanol at a mass ratio of 5:150, mix them, heat to 65°C to melt them completely, let them cool naturally to precipitate beeswax particles, wash them three times with anhydrous ethanol, and dry them at 50°C for 3 hours to obtain micron-sized wax flake particles.

[0067] 3) Mix polydimethylsiloxane, curing agent and tetrahydrofuran in a mass ratio of 1:0.1:5 and spray it onto the surface of Xuan paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 15 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times. Each spraying time is 3 s. Pre-cur at room temperature for 3 h to obtain polydimethylsiloxane coated Xuan paper.

[0068] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran in a mass ratio of 5:5. The total mass ratio of the two to the tetrahydrofuran is 1:10. Spray the mixture onto the surface of the polydimethylsiloxane-coated Xuan paper obtained in step 3). The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 15 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 36 h to obtain a paper coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating.

[0069] The water contact angle of Xuan paper treated with a fluorine-free, high-strength, multifunctional superhydrophobic coating with a bird's nest-like structure prepared in this embodiment is 152.2°, which is 120.9% higher than that of the original Xuan paper, exhibiting superhydrophobic properties.

[0070] The light transmittance of the Xuan paper modified with this coating is 42.7%, which is higher than the original Xuan paper's 34.8%, and the color difference ΔE is 1.42, which is lower than the visual resolution threshold of 5. This proves that the coating has excellent transparency and does not change the original appearance and color of the Xuan paper.

[0071] After sandpaper abrasion, tape peeling, and finger rubbing tests, the water contact angles of the coated Xuan paper were 148.8°, 149.4°, and 148.7°, respectively, still exhibiting high hydrophobicity, proving that the coating has excellent mechanical durability.

[0072] After soaking for 12 hours at pH 5 and 10, the water contact angle of the coated Xuan paper was 145.4° and 148.3°, respectively, proving that the coating has excellent resistance to acid and alkali corrosion.

[0073] Example 5 This embodiment provides a method for preparing paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 800 rpm for 15 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 8000 rpm and dried at 60℃ for 5 h to prepare silica nanoparticles. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:8:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:12. The grafting modification was completed by reaction at 60℃ for 3 h. After centrifugation at 8000 rpm, washing with anhydrous ethanol 3 times, and drying at 80℃ for 3 h, silane coupling agent modified silica nanoparticles were obtained.

[0074] 2) Weigh out candle wax and anhydrous ethanol at a mass ratio of 3:150, heat to 73°C to melt completely, let cool naturally to precipitate candle wax particles, wash three times with anhydrous ethanol, and dry at 50°C for 4 hours to obtain micron-sized waxy flake particles.

[0075] 3) Mix polydimethylsiloxane, curing agent and tetrahydrofuran at a mass ratio of 1:0.1:5 and spray it onto the surface of printing paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 15 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. Pre-cur at room temperature for 4 h to obtain polydimethylsiloxane coated printing paper.

[0076] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran at a mass ratio of 4:6. The total mass ratio of the two to tetrahydrofuran is 1:15. Spray the mixture onto the surface of the polydimethylsiloxane-coated printing paper obtained in step 3). The nozzle diameter is 0.5 mm, the spraying distance is 15 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 48 h to obtain a printing paper coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating.

[0077] Example 6 This embodiment provides a method for preparing paper coated with a biomimetic, fluorine-free, high-strength, multifunctional superhydrophobic coating, specifically including the following steps: 1) Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 500 rpm for 12 h at room temperature. After the reaction, the precipitate was separated by centrifugation at 10,000 rpm and dried at 60 °C for 6 h to prepare silica nanoparticles. N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, anhydrous ethanol, and deionized water were mixed at a mass ratio of 2:9:1 and slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:7. The grafting modification was completed by reacting at 60 °C for 2 h. After centrifugation at 10,000 rpm, washing with anhydrous ethanol 3 times, and drying at 80 °C for 3 h, silane coupling agent modified silica nanoparticles were obtained.

[0078] 2) Weigh rice bran wax and anhydrous ethanol at a mass ratio of 1:150, mix them, heat to 80℃ to melt them completely, let them cool naturally to precipitate rice bran wax particles, wash them 3 times with anhydrous ethanol, and dry them at 50℃ for 2 hours to obtain micron-sized wax flake particles.

[0079] 3) After mixing polydimethylsiloxane, curing agent and tetrahydrofuran at a mass ratio of 1:0.1:13, spray it onto the surface of kraft paper. The nozzle diameter of the spray gun is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. Pre-curing at room temperature for 4 h yields polydimethylsiloxane-coated kraft paper.

[0080] 4) Mix silane coupling agent modified silica nanoparticles and micron-sized waxy flake particles with tetrahydrofuran at a mass ratio of 4:6. The total mass ratio of the two to tetrahydrofuran is 1:20. Spray the mixture onto the surface of the polydimethylsiloxane-coated kraft paper obtained in step 3). The spray gun nozzle diameter is 0.5 mm, the spraying distance is 20 cm, the spraying pressure is 0.2 MPa, and the spraying is done 3 times, with each spraying time being 3 s. The paper is cured at room temperature for 24 h to obtain kraft paper coated with a biomimetic fluorine-free high-strength multifunctional superhydrophobic coating.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, characterized in that, Includes the following steps: S1: Mix aminosilane coupling agent, anhydrous ethanol and deionized water, and slowly add the mixture to the mixture of silica nanoparticles and anhydrous ethanol. Stir the mixture at a constant temperature to prepare silane coupling agent modified silica nanoparticles. S2: After mixing polydimethylsiloxane, curing agent and tetrahydrofuran evenly, spray it onto the paper surface and pre-cur it at room temperature to obtain paper coated with polydimethylsiloxane. S3: After uniformly mixing the silane coupling agent-modified silica nanoparticles, flake-shaped micron wax particles and tetrahydrofuran, the mixture is sprayed onto the surface of the paper coated with polydimethylsiloxane and cured at room temperature to obtain a fluorine-free, high-strength, multifunctional superhydrophobic coating paper with a rice leaf-like structure.

2. The method for preparing a paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves according to claim 1, characterized in that, The preparation of the silane coupling agent modified silica nanoparticles is specifically as follows: aminosilane coupling agent, anhydrous ethanol, and deionized water are mixed evenly at a mass ratio of 2:(5~10):1, and then slowly added to a mixture of silica nanoparticles and anhydrous ethanol at a mass ratio of 1:(5~15). The grafting modification is completed by reacting at 60°C for 2~4 h. After centrifugation at 8000~10000 rpm, washing three times with anhydrous ethanol, and drying at 80°C for 2~4 h, silane coupling agent modified silica nanoparticles are obtained.

3. The method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves according to claim 2, characterized in that, The preparation of the silica nanoparticles is specifically as follows: Tetraethyl orthosilicate, anhydrous ethanol, and ammonia were mixed at a volume ratio of 5:25:1 and reacted with magnetic stirring at 500-1000 rpm for 12-24 h at room temperature. After the reaction was completed, the precipitate was separated by centrifugation at 8000-10000 rpm and dried at 60-80℃ for 4-8 h to obtain silica nanoparticles.

4. The method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves according to claim 2, characterized in that, The aminosilane coupling agent includes one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane.

5. A method for preparing a paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves, as described in claim 1, characterized in that... In step S2, the mass ratio of polydimethylsiloxane, curing agent and tetrahydrofuran is 1:0.1:(5~20); the pre-curing time is 2~4 h.

6. The method for preparing a paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves according to claim 1, characterized in that, In step S3, the mass ratio of the silane coupling agent modified silica nanoparticles to the sheet-like micron wax particles is (0.5~5):(5~9.5); the total mass of the silane coupling agent modified silica nanoparticles and the sheet-like micron wax particles to the mass ratio of tetrahydrofuran is 1:(10~30).

7. A method for preparing a paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves, as described in claim 1, characterized in that... In step S3, the curing time is 24~48 h.

8. A method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves, as described in claim 1, characterized in that... The spraying process in steps S1 and S2 is as follows: spray gun nozzle diameter 0.5 mm, spraying distance 10~20 cm, spraying pressure 0.2 MPa; each layer is sprayed 3 times, and the single spraying time is 3 s.

9. The method for preparing paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating mimicking the structure of rice leaves according to claim 1, characterized in that, The preparation of the flake-shaped micron-sized wax particles is specifically as follows: Weigh wax and mix it with anhydrous ethanol at a mass ratio of (1~5):150, heat it to the wax melting point to make it completely melt, let it cool naturally to precipitate wax particles, wash it three times with anhydrous ethanol, and dry it at 50℃ for 2~4 hours to obtain flaky micron wax particles; the wax includes one of beeswax, carnauba wax, candle wax and rice bran wax.

10. A type of paper coated with a fluorine-free, high-strength, multifunctional superhydrophobic coating that mimics the structure of rice leaves, characterized in that... It is prepared by the method described in any one of claims 1 to 9.

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