A water-based biomass coating with self-cleaning function and preparation method thereof

Abstract

The present invention belongs to the technical field of coating preparation, and provides a kind of water-based biomass coating with self-cleaning function and preparation method thereof. After lignin is purified by alkali dissolution, modified by acrylic anhydride and grafted with dopamine, it is cross-linked with enzymatically treated soy protein by dopamine modification and glutaraldehyde to form a modified lignin protein, which is introduced into an acrylic monomer emulsion polymerization system and copolymerized with ethyl acrylate and methyl methacrylate to prepare a water-based acrylic copolymer emulsion, and simultaneously prepares PDA-metal network and low-surface-energy particles, wherein the low-surface-energy particles form a super-hydrophobic structure by an electrolyte layer and surface modification, and the water-based acrylic emulsion is compounded with chitosan-citrate, PDA-metal network and low-surface-energy particles, and a leveling agent and a defoamer are added to adjust the coating performance to prepare a water-based biomass coating with self-cleaning function.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation and relates to a water-based biomass coating with a self-cleaning function and a preparation method thereof. Background Art

[0002] Self-cleaning coatings have recently become a hot topic in functional coatings research. They enable the automatic removal of dirt through their unique physical and chemical properties. These coatings, inspired by biomimetic design concepts found in nature, such as the superhydrophobicity of lotus leaves and the superhydrophilicity of photocatalytic surfaces, have been applied to a variety of fields, including building facades, photovoltaic panels, and medical devices. However, the preparation of traditional self-cleaning coatings often relies heavily on chemicals such as fluorinated compounds or siloxanes, which can cause environmental pollution and pose challenges to eco-friendliness. With growing environmental awareness, the development of green coatings based on renewable resources has become a key research direction in materials science and environmental chemistry. Biomass materials, as renewable resources, have become a key option in green coatings research due to their rich chemical structures, diverse functional groups, and environmental friendliness. Biomass materials are not only widely available but also possess excellent film-forming properties, mechanical properties, and chemical modification potential. Using these biomass materials as coating substrates not only reduces dependence on petrochemical resources but also allows for the coatings to be endowed with various functional properties, such as stain resistance, antibacterial properties, and water repellency, through appropriate chemical or physical modification.

[0003] Water-based biomass coatings avoid the environmental and human health hazards of traditional solvent-based coatings. Compared to solvent-based coatings, their production and application processes significantly reduce volatile organic compound (VOC) emissions, contributing to improved air quality and aligning with the requirements of green chemistry and sustainable development. These coatings have broad application potential in building exteriors, industrial coatings, home furnishings, and medical device surface protection. In particular, their self-cleaning properties effectively prevent the adhesion of dust, dirt, and water stains on building exteriors and photovoltaic panels, reducing cleaning frequency and thus maintenance costs. The development of biomass coatings goes beyond environmental friendliness; it also embodies innovative material versatility and structural design. By leveraging the biodegradability and biocompatibility of biomass materials, these coatings naturally degrade after application, avoiding the environmental burden of traditional coatings that are difficult to recycle. Therefore, the development of water-based biomass coatings with self-cleaning properties is of great significance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a water-based biomass coating with a self-cleaning function and a preparation method thereof. First, lignin is treated with alkali dissolution purification, acrylic anhydride modification and dopamine grafting to prepare functionalized dopamine-grafted lignin; at the same time, soy protein is enzymatically hydrolyzed and, through dopamine modification and glutaraldehyde cross-linking, composited with lignin to form a modified lignin protein material, and the modified lignin protein is introduced into an acrylic emulsion polymerization system and copolymerized with acrylic monomer to prepare a biomass-based water-based acrylic copolymer emulsion; in order to further enhance the functionality of the coating, a PDA-metal network and low-surface-energy particles are prepared, and the low-surface-energy particles are modified by an electrolyte layer and hydrophobicity to construct a super-hydrophobic surface structure, and finally the water-based acrylic copolymer emulsion is mixed with chitosan-citrate, PDA-metal network and low-surface-energy particles, and a leveling agent and a defoaming agent are added to prepare a water-based biomass coating with a self-cleaning function, thereby meeting the needs of actual production.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a water-based biomass coating having a self-cleaning function, the preparation method comprising:

[0007] S1, dispersing lignin in a NaOH solution, stirring and dissolving, adjusting the pH to 6, filtering and washing to obtain purified lignin, dispersing the purified lignin, pyridine, and acrylic anhydride in anhydrous dichloromethane, stirring and reacting at room temperature, centrifuging and washing, and vacuum drying to obtain modified lignin, then dispersing the modified lignin, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide in deionized water, adjusting the pH to 6, stirring at room temperature, adding dopamine hydrochloride, continuing the reaction, and centrifuging and washing to obtain dopamine-grafted lignin;

[0008] S2, dispersing soy protein in a NaOH solution, adding trypsin, adjusting the pH to 8 and reacting in a water bath at 37°C, heating and inactivating after the reaction, separating the supernatant to obtain a partially hydrolyzed protein solution, mixing the partially hydrolyzed protein solution with a dopamine hydrochloride solution, adjusting the pH to 8, reacting with stirring at room temperature, and freeze-drying to obtain a modified protein, dispersing the dopamine-grafted lignin and the modified protein in deionized water, adding a glutaraldehyde solution, adjusting the pH to 8 and reacting at room temperature, filtering, washing, and drying to obtain a modified lignin protein, then dispersing sodium lauryl sulfate and the modified lignin protein in deionized water, stirring evenly, and then adding ethyl acrylate, methyl methacrylate, and acrylic acid to obtain an emulsion, adjusting the temperature to a first temperature under a nitrogen atmosphere, adding ammonium persulfate and sodium bisulfite to react, and obtaining an aqueous acrylic copolymer emulsion;

[0009] S3, adding dopamine hydrochloride, metal salt solution and CQDs dispersion into Tris-HCl buffer with a pH of 8.5, stirring for reaction and freeze-drying to obtain PDA-metal network;

[0010] S4, dispersing tetraethyl orthosilicate in anhydrous ethanol, adding hydrochloric acid solution under ice-water bath conditions, stirring to form a transparent sol, adjusting the pH of a mixed solution of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, then mixing the transparent sol and the hydroxide sol and stirring to obtain a composite sol, mixing the composite sol with a chitosan solution, adjusting the pH to 8 to obtain a precursor solution, then adding the precursor solution to Span 80@liquid paraffin, stirring evenly, adding sodium hydroxide solution, and centrifuging and washing to obtain core particles;

[0011] S5, dispersing the core particles in a PDA-PEI solution, stirring thoroughly and then centrifuging and washing, then transferring them to a PAA solution, stirring thoroughly and centrifuging and washing, and immersing them in a glutaraldehyde solution to obtain electrolyte layer particles, and then dispersing the electrolyte layer particles in a trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles;

[0012] S6, mixing the aqueous acrylic copolymer emulsion and the chitosan-citrate mixture evenly and adjusting the pH to 6, then adding the PDA-metal network, low surface energy particles, a leveling agent and a defoaming agent, and mixing evenly to obtain a water-based biomass coating with a self-cleaning function.

[0013] Lignin is a complex three-dimensional polymer composed of phenylpropane units cross-linked by ether bonds and carbon-carbon single bonds. The molecule is rich in functional groups such as phenolic hydroxyl groups, primary hydroxyl groups, secondary hydroxyl groups, and methoxy groups, which impart high chemical reactivity to lignin. First, lignin is dispersed in a sodium hydroxide solution for treatment. As a strong base, sodium hydroxide breaks down the hydrogen bonds between lignin molecules and the ester bonds within them. This disruption not only dissociates lignin from the complex matrix of the plant cell wall but also promotes its dissolution in solution. Specifically, sodium hydroxide reacts with the phenolic hydroxyl and carboxyl groups in lignin to form soluble phenol and carboxyl salts, thereby reducing lignin's aggregation and increasing its solubility. Furthermore, the alkaline environment of sodium hydroxide partially hydrolyzes the ester bonds in lignin, releasing more free phenolic hydroxyl and carboxyl groups. These reactive functional groups provide important active sites for subsequent chemical modification. After dissolution is complete, the solution pH is adjusted to 6 to precipitate the lignin, while some impurities (such as low-molecular-weight sugars, small organic acids, and other soluble impurities) remain in solution. Lignin precipitation is due to its low water solubility under neutral conditions, enabling effective separation and purification by adjusting the solution pH. At this point, the NaOH treatment not only removes most impurities, but also reduces the degree of intramolecular crosslinking and loosens the structure due to the cleavage of ester bonds and the disruption of intermolecular hydrogen bonds, exposing more phenolic hydroxyl and carboxyl groups. The purified lignin is then dispersed in anhydrous dichloromethane and chemically modified by the addition of pyridine and acrylic anhydride. Acrylic anhydride is a commonly used acylating agent containing two acylating groups that react with the hydroxyl groups in lignin. In this reaction, pyridine acts as a solvent, effectively dissolving acrylic anhydride and lignin, increasing the contact area between the reactants. Furthermore, as a basic catalyst, pyridine's nitrogen atom weakly interacts with the carbonyl oxygen of acrylic anhydride, enhancing the electropositivity of acrylic anhydride and thereby increasing its reactivity toward nucleophiles. In this system, the phenolic hydroxyl group in the lignin molecule acts as a nucleophile, attacking the carbonyl carbon atom of acrylic anhydride via nucleophilic substitution, forming an ester bond and releasing acetic acid as a byproduct. Through this reaction, the surface of the lignin molecule is modified with acrylic anhydride, introducing unsaturated structures such as propenyl groups. These propenyl groups impart increased chemical reactivity to the lignin, providing active sites for subsequent free radical polymerization or other chemical functionalization reactions. Furthermore, the surface unsaturation and hydrophilicity of the lignin are significantly enhanced, laying the foundation for its use as a matrix in composite materials.

[0014] Subsequently, the modified lignin, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, N-hydroxysuccinimide and dopamine hydrochloride are co-dispersed in water for grafting reaction. As a classic amide bond coupling system, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide have the core function of activating the carboxyl groups on the surface of the lignin molecules so that they can undergo amidation reaction with the amine groups in the dopamine molecules to form stable amide bonds. Specifically, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride first reacts with the carboxyl groups on the surface of the lignin to generate an active intermediate, which then reacts with N-hydroxysuccinimide to form a more stable N-hydroxysuccinimide ester. The carboxyl carbon atom of this N-hydroxysuccinimide ester intermediate has a high electrophilicity and can be attacked by the amine groups in the dopamine molecule, ultimately forming a stable amide bond. Dopamine molecules contain two types of functional groups: phenolic hydroxyl groups and amine groups. After being grafted onto lignin, they significantly improve the chemical functionality of lignin. First, the phenolic hydroxyl structure of the dopamine molecule introduces polyphenol functionality to lignin, which not only enhances the material's antioxidant capacity, but also improves its free radical scavenging performance, making it more stable under certain special environments. Secondly, the benzene ring structure of dopamine and the aromatic ring of lignin can further enhance the intermolecular synergy through π-π stacking, thereby improving the mechanical properties of the material. In addition, the amino group of dopamine provides more active sites for subsequent chemical modification and cross-linking reactions, thus laying the foundation for the multifunctional application of lignin.

[0015] Soy protein is a naturally derived complex polypeptide chain polymer primarily composed of various amino acids linked by amide (peptide) bonds. Soy protein contains numerous functional groups, including carboxyl, amino, and amide bonds, which impart unique chemical reactivity and structural properties. However, due to its high molecular weight and tertiary structure, soy protein has poor solubility in solution. Intermolecular hydrogen bonding and hydrophobic interactions further stabilize its structure, making it difficult to directly use for chemical modification or composite material preparation. In the present invention, soy protein is first dispersed in an alkaline solution and partially hydrolyzed using trypsin. The alkaline environment dissociates the carboxyl and amino groups in the soy protein molecules, forming carboxylates and free amino groups. The dissociation of these functional groups on the protein surface reduces intermolecular hydrogen bonding and hydrophobic interactions, thereby disrupting the protein's higher-order structure and significantly improving its solubility. Furthermore, the alkaline environment loosens the protein's molecular structure, providing a more open substrate for trypsin-catalyzed hydrolysis. Trypsin is a highly specific proteolytic enzyme that recognizes and selectively hydrolyzes peptide bonds at the carboxyl side of lysine and arginine in polypeptide chains. Its mechanism of action is nucleophilic attack by the serine residue in the active center on the carbonyl group of the peptide bond, forming an enzyme-substrate complex. This complex then binds to water molecules to cleave the peptide bond, ultimately releasing short peptides and free amino acids. Through this controlled hydrolysis process, the long-chain polypeptides in soy protein are degraded into low-molecular-weight short peptides and amino acids. This partial hydrolysis not only significantly reduces the protein's molecular weight and improves its solubility, but also exposes more carboxyl and amino groups, which provide active sites for subsequent chemical modification and cross-linking reactions. Furthermore, the reduced molecular weight of the partially hydrolyzed soy protein enhances its diffusivity and reactivity in solution, paving the way for dopamine modification and material composites. After the partial hydrolysis of the protein, the trypsin is inactivated by heat to terminate the enzymatic reaction, preventing excessive hydrolysis or degradation and ensuring protein functionality and chemical modification activity.

[0016] Next, the partially hydrolyzed soy protein was chemically modified with dopamine hydrochloride under alkaline conditions. Dopamine is a small nitrogen-containing compound with two functional groups, phenolic hydroxyl and amine, and exhibits high chemical reactivity. Under alkaline conditions, dopamine undergoes oxidation to form dopamine quinone. This oxidation process, typically catalyzed by oxygen or metal ions, is accompanied by deprotonation and structural transformation of the dopamine molecule. Dopamine quinone is a highly reactive intermediate. The quinone group in its molecule is highly electrophilic and can react chemically with amino or thiol groups in soy protein molecules. The amino group acts as a nucleophile to attack the carbonyl group of the quinone group, forming an imine bond. The carboxyl group or other nucleophilic groups then attack the double bond of the quinone group, forming a covalent bond. Furthermore, the phenolic hydroxyl group in the dopamine molecule can also interact non-covalently with the protein molecule through hydrogen bonding or π-π stacking. These non-covalent interactions not only enhance the binding stability between dopamine and the protein but also impart superior physical and chemical properties to the material. Through dopamine modification, a large number of phenolic hydroxyl groups are introduced onto the surface of soy protein. This polyphenol structure significantly enhances the antioxidant capacity and free radical scavenging properties of the protein, while also increasing the chemical activity of the protein. After dopamine modification, the dopamine-grafted lignin and the modified protein are cross-linked via glutaraldehyde. Glutaraldehyde is a commonly used bifunctional cross-linking agent that contains active aldehyde groups at both ends of its molecule. Under alkaline conditions, the aldehyde groups of glutaraldehyde can chemically react with the amino groups in the dopamine-grafted lignin and modified protein molecules to form imine bonds. In addition, the aldehyde groups of glutaraldehyde can also combine with hydroxyl groups or phenolic hydroxyl groups through acetalization reactions, further enhancing the degree of cross-linking. During the cross-linking process, the phenolic hydroxyl groups and propenyl groups of the dopamine-grafted lignin form a three-dimensional network structure with the amino and carboxyl groups in the protein molecules through the bridging effect of glutaraldehyde. This chemical cross-linking not only significantly enhances the mechanical strength of the composite material, but also improves the chemical stability, water resistance, and thermal stability of the material. Furthermore, dopamine molecules act synergistically between lignin and protein, with their phenolic hydroxyl groups and aromatic ring structures further enhancing interfacial bonding and intermolecular interactions through hydrogen bonding or π-π stacking. This process binds lignin and protein together, forming a composite structure with high strength and functionality.

[0017] The cross-linked lignin-protein complex was emulsion-polymerized with acrylic monomers. Sodium dodecyl sulfate, an emulsifier with a hydrophilic head and lipophilic tail, stabilized the interface between the aqueous and oil phases, forming a uniform emulsion. Within the emulsion system, the lignin-protein complex further enhanced the emulsion's stability through interfacial adsorption. Subsequently, ammonium persulfate and sodium bisulfite were added as initiators to initiate free radical polymerization under heating conditions. Ammonium persulfate decomposed to produce sulfate radicals, which attacked the double bonds of ethyl acrylate, methyl methacrylate, and acrylic acid, forming polymer chains. The free radical polymerization gradually polymerized the monomers into acrylic copolymers, which then bonded to the lignin-protein complex to form a highly structurally stable copolymer emulsion. A composite matrix with high chemical activity and mechanical properties was successfully constructed by partial hydrolysis of soy protein, dopamine modification, and cross-linking with lignin. This composite material exposed more reactive groups (such as amino and carboxyl groups) through protein hydrolysis. Dopamine modification significantly enhanced the antioxidant properties, while glutaraldehyde cross-linking further enhanced the structural stability of the material. The final emulsion polymerization system provides a stable and high-performance functional emulsion for the preparation of subsequent coatings.

[0018] Polydopamine (PDA) is a highly functional material formed by the oxidation and self-polymerization of dopamine molecules under alkaline conditions. Its molecular structure is rich in key functional groups, including phenolic hydroxyl and quinone groups. These groups play a crucial role in the redox and self-cleaning properties of PDA. Phenolic hydroxyl groups possess strong free radical-scavenging capabilities, effectively neutralizing reactive oxygen species (ROS) such as hydroxyl and superoxide radicals in the environment, thereby reducing environmental damage to coatings or materials. PDA's molecular structure is also rich in amine groups and aromatic rings. These structural properties enable it to strongly adsorb onto a variety of substrates through hydrogen bonding, electrostatic interactions, and π-π stacking. This strong adhesion allows PDA to form uniform and stable coatings, providing a robust substrate for the construction of functional materials. Furthermore, PDA's antioxidant properties further enhance its durability and functionality. PDA effectively captures reactive oxygen species in the environment, particularly in photocatalytic reactions or oxidative environments, preventing degradation and contamination accumulation on the material surface. By reducing the impact of oxidative pollutants in the external environment, polydopamine ensures the long-term stable use of the material. After introducing metal ions into the polydopamine network, the polydopamine-metal complex structure formed significantly improves the self-cleaning performance and functional diversity of the material. The phenolic hydroxyl and quinone groups in the polydopamine molecule can coordinate with metal ions to form stable metal complexes. This complex structure not only enhances the three-dimensional cross-linking degree and mechanical properties of the polydopamine network, but also gives the material unique photocatalytic and antibacterial properties through the introduction of metal ions. For example, the introduction of zinc ions not only improves the stability of the complex network but also provides the material with strong antibacterial capabilities. Zinc ions can inhibit the proliferation of microorganisms through various mechanisms. This antibacterial property enables the material to effectively inhibit bacterial growth in humid or polluted environments, thereby further improving the self-cleaning performance of the coating.

[0019] To further enhance the photocatalytic performance and photoresponse range of polydopamine-metal complex networks, doping them with carbon quantum dots (CQDs) is a promising modification strategy. CQDs are nanoscale carbon-based materials with unique optical properties and surface chemical activity. Doping with CQDs significantly enhances the complex network's functionality: First, CQDs absorb ultraviolet and visible light and convert the light energy into long-lived electron-hole pairs, thereby expanding the material's light absorption range and improving its photocatalytic efficiency. Traditional photocatalytic materials typically require high-energy UV light to stimulate photocatalytic reactions. However, the introduction of CQDs enables the utilization of low-energy visible light, significantly improving the practical applicability of the photocatalytic process. Second, the π-conjugated system of CQDs promotes rapid electron transfer, reducing the probability of electron-hole recombination during the photocatalytic process. This accelerated electron transfer ensures the generation of more reactive oxygen species, thereby enhancing pollutant degradation efficiency. At the same time, the hydroxyl and carboxyl groups on the surface of the carbon quantum dots can bind to polydopamine molecules and metal complexes through hydrogen bonds or covalent bonds, further enhancing the structural stability and interfacial bonding strength of the complex network. This bonding not only improves the mechanical properties of the material but also enables it to maintain excellent durability under complex environmental conditions. The high specific surface area and nanometer size of the carbon quantum dots further enhance the complex network's adsorption capacity for pollutants, providing higher reaction efficiency for photocatalytic degradation.

[0020] Under acidic conditions, tetraethyl orthosilicate (TES) serves as a silicon source, undergoing a hydrolysis reaction to generate silanol intermediates. Under acidic conditions, the ethoxy groups in the TOS molecules are gradually replaced by hydroxyl groups, forming silanol molecules. These silanol molecules further undergo polycondensation to form silanol bonds, resulting in a three-dimensional network structure. This silanol network exhibits excellent chemical stability and mechanical strength, making it a suitable core component for particles that provide durability and wear resistance. During this process, uncondensed silanol groups often remain on the surface of the silanol network. These silanol groups not only provide active sites for subsequent chemical modification, but also maintain the structural integrity of the particles during subsequent functionalization, providing long-term functional support. To further enhance the functionality of the core particles, titanium tetrachloride and zinc nitrate hexahydrate are introduced into the system and hydrolyzed under alkaline conditions to generate titanium oxide and zinc oxide sols. Under alkaline conditions, titanium tetrachloride and zinc nitrate hexahydrate generate titanium hydroxide and zinc hydroxide, respectively. These intermediates are stably dispersed in the solution, forming a uniform sol. The introduction of titanium oxide and zinc oxide into the core particles significantly enriches the material's functionality. Titanium oxide is a classic photocatalytic material. When irradiated with ultraviolet or visible light, it stimulates electron transitions, generating reactive oxygen species such as superoxide radicals and hydroxyl radicals. These reactive oxygen species possess strong oxidative activity, rapidly degrading organic pollutants such as oil, dye molecules, or microbial metabolites adhering to the particle surface. Through photocatalytic action, the particle surface remains consistently clean. Furthermore, the introduction of zinc oxide not only enhances photocatalytic performance but also imparts antimicrobial properties to the particles. Zinc ions disrupt bacterial cell membranes and enzyme activity through various mechanisms, inhibiting their growth and reproduction, thereby reducing biofouling on the particle surface. This antimicrobial property is particularly important in humid environments, as humid conditions typically promote microbial growth. A silica sol is mixed with titanium and zinc sols and stirred to form a composite sol. During this process, the silica sol and metal oxide sols bond through hydrogen bonding or electrostatic interactions, forming a uniformly dispersed composite system. Furthermore, the titanium oxide and zinc oxide impart photocatalytic and antimicrobial properties to the sol. The synergistic effect of the two significantly enhances the self-cleaning ability of the core particles, enabling them to effectively remove pollutants and microorganisms in complex application environments.

[0021] To further optimize the particle morphology and properties, the composite sol was mixed with a chitosan solution and the pH was adjusted to 8. Chitosan is a natural polysaccharide with excellent biocompatibility and chemical activity. Under alkaline conditions, chitosan molecules can dissolve and physically adsorb or chemically bind to silanol groups or metal hydroxides in the sol. This binding not only stabilizes the sol morphology but also provides a preliminary functional modification to the particle surface. The introduction of chitosan also enhances the antibacterial properties of the core particles, as chitosan itself possesses certain antibacterial properties, inhibiting bacterial proliferation by inhibiting cell wall synthesis or interfering with bacterial metabolic processes. Subsequently, the precursor solution was added to an oil phase containing Span 80 and liquid paraffin, where the particles were further controlled through emulsification. Span 80, as an emulsifier, forms a stable emulsion at the water-oil interface, dispersing the composite sol in the aqueous phase into tiny droplets. The size of these droplets can be precisely controlled by stirring speed and emulsifier concentration, thereby influencing the final particle size and morphology. Liquid paraffin provides a uniform oil phase environment, ensuring the stability of the sol droplets. To solidify the sol droplets into a granular structure, sodium hydroxide solution is gradually added to the system. Under alkaline conditions, the silica network and the metal hydroxide undergo further polycondensation or precipitation reactions to form solid particles. The polycondensation reaction further crosslinks the three-dimensional structure of the silica network, enhancing the mechanical strength and durability of the particles. Simultaneously, the metal hydroxide gradually converts to a stable oxide form, endowing the particles with photocatalytic and antimicrobial properties. These particles combine the mechanical properties of the silica network with the functionality of the metal oxide, exhibiting multiple self-cleaning properties. Furthermore, the particles' photocatalytic properties effectively degrade organic pollutants on their surfaces under illumination, while their antimicrobial properties inhibit bacterial growth. This versatility enables the core particles to adapt to a variety of complex environments, enabling them to degrade pollutants under illumination while also effectively preventing microbial contamination in humid environments.

[0022] The core particles are dispersed in a polydopamine-polyethyleneimine (PDA-PEI) solution and thoroughly coated. The exposed silanol groups on the core particle surface and the hydroxyl groups on the metal oxide provide chemically active sites for coating. These groups can strongly bond to the coating material through hydrogen bonding and electrostatic interactions, providing a foundation for the formation of a stable coating. Polydopamine is produced by the self-polymerization of dopamine molecules under alkaline conditions. The molecule is rich in a variety of reactive functional groups, including phenolic hydroxyl groups, amino groups, and quinone groups. These functional groups impart excellent adhesion to the core particle surface, allowing it to firmly attach to the core particle surface through various chemical and physical interactions. Phenolic hydroxyl groups and amino groups can hydrogen bond with hydroxyl or silanol groups on the core particle surface, while quinone groups further stabilize the bonding interface through electrostatic interactions. Furthermore, the aromatic ring structure of polydopamine can interact with any aromatic groups on the core particle surface through π-π stacking, further enhancing adhesion strength. Polyethyleneimine (PEI) is a cationic polymer with a high density of amino groups. Its abundant amino groups enable it to bond with polydopamine through hydrogen bonding and electrostatic interactions, forming a stable composite coating. The introduction of PEI significantly increases the positive charge density on the particle surface, laying an important chemical foundation for subsequent multilayer electrolyte coating. The interaction between the amino groups and the quinone or phenolic hydroxyl groups in polydopamine further enhances the stability of the coating. Furthermore, the positive surface charge of the particles provides the necessary charge driving force for electrostatic self-assembly of the negatively charged polymer. After the initial polydopamine-PEI coating, the particles are transferred to a polyacrylic acid (PAA) solution to further construct the multilayer electrolyte structure. PAA is a polymer with carboxyl groups. The carboxyl groups in its molecules partially dissociate into carboxylates at near-neutral to slightly alkaline pH. The dissociated carboxylates carry a negative charge, which allows them to form a stable bond with the positively charged PEI on the particle surface through electrostatic adsorption. This electrostatic adsorption is the core principle of the layer-by-layer self-assembly process, and its driving force comes from the Coulomb attraction between positive and negative charges.

[0023] After the electrolyte coating is completed, the particles are immersed in a glutaraldehyde solution for cross-linking. Glutaraldehyde is a compound containing two aldehyde groups. The symmetrically distributed aldehyde groups in its molecular structure can react chemically with the amino groups in the polydopamine, polyethyleneimine and polyacrylic acid molecules in the multilayer electrolyte coating. The essence of this cross-linking process is that the aldehyde groups and amino groups react through Schiff base to form imine bonds, thereby achieving intermolecular cross-linking. The cross-linking reaction makes the molecular structure inside the multilayer coating more compact, significantly enhancing the mechanical strength and chemical resistance of the coating. Another important function of glutaraldehyde cross-linking is to enhance the hydrolysis resistance of the coating. The uncross-linked coating may dissolve or peel off in water or other polar solvents, while the cross-linked coating has higher stability due to the chemical bond connection between molecules and can resist water erosion. In addition, cross-linking also reduces the risk of peeling of the coating under mechanical stress, and improves the durability and service life of the particles in the coating system. After completing the glutaraldehyde cross-linking, the electrolyte layer particles are further dispersed in a trifluoropropyltriethoxysilane ethanol solution for surface modification. Trifluoropropyltriethoxysilane is a fluorinated silane compound. The siloxy groups in its molecular structure can undergo a condensation reaction with silanol or hydroxyl groups on the particle surface to form a stable silicon-oxygen-silicon bond. This reaction firmly binds the trifluoropropyltriethoxysilane molecule to the particle surface through the formation of a covalent bond. Trifluoropropyltriethoxysilane molecules contain long-chain fluorinated groups, which have extremely low surface energy and excellent hydrophobicity and oleophobicity. During the surface modification process, the fluorinated groups of the trifluoropropyltriethoxysilane molecules are exposed to the particle surface through molecular arrangement, forming an outer layer rich in fluorinated carbon chains. This outer layer of fluorinated groups has extremely strong hydrophobicity and oleophobicity, and has extremely weak interactions with water molecules or pollutant molecules, thereby significantly reducing the surface energy of the particles. The multilayer structure of the electrolyte layer and the surface fluorination modification of trifluoropropyltriethoxysilane form a synergistic effect. The electrolyte coating provides micro-nanoscale roughness on the surface of the particles, while the fluorine-containing groups of trifluoropropyltriethoxysilane further reduce the surface energy of the particles. The combination of the two makes the particles hydrophobic, which can effectively prevent the adhesion of water to the surface of the particles, while improving the particles' anti-adhesion properties to oil and dust.

[0024] As a preferred technical solution of the present invention, in step S1, the mass volume ratio of the lignin to the NaOH solution is 1 g:10 mL.

[0025] In some optional embodiments, the mass fraction of the NaOH solution is 10 wt.%.

[0026] In some optional embodiments, the mass volume ratio of the purified lignin, pyridine and acrylic anhydride is 1 g:1 mL:1 mL.

[0027] In some optional embodiments, the mass volume ratio of the purified lignin to anhydrous dichloromethane is 1 g:10 mL.

[0028] In some optional embodiments, the stirring time at room temperature is 4-5h, for example, it can be 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In some optional embodiments, the mass ratio of the modified lignin, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and dopamine hydrochloride is 30:5:3:20.

[0030] As a preferred technical solution of the present invention, in step S2, the mass volume ratio of the soy protein, NaOH solution and trypsin is 10g:100mL:0.01g.

[0031] In some optional embodiments, the concentration of the NaOH solution is 0.1M.

[0032] In some optional embodiments, the water bath reaction time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In some optional embodiments, the volume ratio of the partially hydrolyzed protein solution to the dopamine hydrochloride solution is 2:1.

[0034] In some optional embodiments, the mass fraction of the dopamine hydrochloride solution is 10 wt.%.

[0035] In some optional embodiments, the reaction time of stirring at room temperature is 4-5h, for example, it can be 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In some optional embodiments, the mass volume ratio of the dopamine-grafted lignin, the modified protein and the glutaraldehyde solution is 5 g:5 g:2 mL.

[0037] In some optional embodiments, the mass fraction of the glutaraldehyde solution is 10 wt.%.

[0038] In some optional embodiments, the room temperature reaction time is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional embodiments, the mass ratio of sodium lauryl sulfate, modified lignin protein, ethyl acrylate, methyl methacrylate, acrylic acid, ammonium persulfate and sodium bisulfite is 5:0.5:10:5:5:0.5:0.25.

[0040] In some optional embodiments, the first temperature is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, in step S3, the mass volume ratio of the dopamine hydrochloride, the metal salt solution, the CQDs dispersion and the Tris-HCl buffer is 0.2 g:4 mL:10 mL:20 mL.

[0042] In some optional embodiments, the concentration of the metal salt solution is 0.1 M, and the solutes are FeCl3·6H2O and ZnCl2, with a molar ratio of 1:1.

[0043] In some optional embodiments, the concentration of the CQDs dispersion is 10 mg / mL.

[0044] In some optional embodiments, the stirring reaction time is 10-12h, for example, it can be 10.0h, 10.2h, 10.4h, 10.6h, 10.8h, 11.0h, 11.2h, 11.4h, 11.6h, 11.8h or 12.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] As a preferred technical solution of the present invention, in step S4, the volume ratio of the tetraethyl orthosilicate, anhydrous ethanol and hydrochloric acid solution is 2:10:1.

[0046] In some optional embodiments, the concentration of the hydrochloric acid solution is 0.1M.

[0047] In some optional embodiments, the mass ratio of titanium tetrachloride to zinc nitrate hexahydrate is 1:1.

[0048] In some optional embodiments, the mass ratio of the transparent sol to the hydroxide sol is 2:1.

[0049] In some optional embodiments, the volume ratio of the composite sol to the chitosan solution is 5:2.

[0050] In some optional embodiments, the mass fraction of the chitosan solution is 2 wt.%, and the solvent is 1 wt.% acetic acid solution.

[0051] In some optional embodiments, the volume ratio of the precursor solution, Span 80@ liquid paraffin and sodium hydroxide solution is 5:10:1.

[0052] In some optional embodiments, the mass fraction of Span 80@liquid paraffin is 3 wt.%, and the solvent is liquid paraffin.

[0053] In some optional embodiments, the concentration of the sodium hydroxide solution is 1M.

[0054] As a preferred technical solution of the present invention, in step S5, the mass volume ratio of the core particles, the PDA-PEI solution and the PAA solution is 1 g:100 mL:100 mL.

[0055] In some optional embodiments, the mass fraction of the glutaraldehyde solution is 0.5 wt.%.

[0056] In some optional embodiments, the mass fraction of the trifluoropropyltriethoxysilane ethanol solution is 0.5 wt.%.

[0057] As a preferred technical solution of the present invention, in step S6, the mass volume ratio of the aqueous acrylic copolymer emulsion, chitosan-citrate mixed solution, PDA-metal network, low surface energy particles, leveling agent and defoaming agent is 100 mL: 5 mL: 10 g: 15 g: 1 g: 1 g.

[0058] In the chitosan-citrate mixed solution, the mass fraction of chitosan is 0.5 wt.%, and the mass fraction of sodium citrate is 1 wt.%.

[0059] In a second aspect, the present invention provides a water-based biomass coating with a self-cleaning function prepared by the preparation method described in the first aspect.

[0060] Compared with the prior art, the present invention has the following advantages: (1) natural biomass materials such as lignin and protein are used, which are renewable, low-cost and environmentally friendly. Compared with the petroleum-based chemicals widely used in the prior art, the present invention is more sustainable in the selection of raw materials. Lignin and protein are endowed with multiple active sites through chemical modification, forming a strong chemical bond with the coating matrix and other components, which not only increases the added value of biomass materials but also reduces dependence on non-renewable resources; (2) the mechanical strength and chemical stability of the particles and coating are enhanced through multi-layer electrolyte coating and glutaraldehyde cross-linking treatment. The introduction of cross-linking technology also significantly improves the hydrolysis resistance of the coating, so that it can still maintain its function in humid or high humidity environments. The introduction of fluorine-containing low surface energy particles gives the coating excellent hydrophobicity. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a SEM image of the water-based biomass coating with self-cleaning function provided in Example 1 of the present invention;

[0062] Figure 2 This is a contact angle diagram of the water-based biomass coating with self-cleaning function provided in Example 1 of the present invention and water. DETAILED DESCRIPTION

[0063] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0064] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been subjected to any further purification treatment.

[0065] Example 1

[0066] This embodiment provides a method for preparing a water-based biomass coating with a self-cleaning function, and the preparation method specifically comprises the following steps:

[0067] S1, 10 g of lignin was dispersed in 100 mL of 10 wt.% NaOH solution, stirred and dissolved, and then the pH was adjusted to 6. The solution was filtered and washed to obtain purified lignin. 10 g of purified lignin, 10 mL of pyridine, and 10 mL of acrylic anhydride were dispersed in 100 mL of anhydrous dichloromethane, stirred at room temperature for 4.2 h, centrifuged and washed, and vacuum dried to obtain modified lignin. 6 g of modified lignin, 1 g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride, and 0.6 g of N-hydroxysuccinimide were dispersed in 100 mL of deionized water, the pH was adjusted to 6, stirred at room temperature, and then 4 g of dopamine hydrochloride was added to continue the reaction. After centrifugation and washing, dopamine-grafted lignin was obtained.

[0068] S2, 10g of soy protein was dispersed in 100mL of 0.1M NaOH solution, 1mL of 10mg / mL trypsin was added, the pH was adjusted to 8 and the reaction was carried out in a water bath at 37℃ for 2.3h. After the reaction was completed, the solution was heated and inactivated, and the supernatant was separated to obtain a partially hydrolyzed protein solution. 10mL of the partially hydrolyzed protein solution was mixed with 5mL of 10wt.% dopamine hydrochloride solution, the pH was adjusted to 8, the solution was stirred at room temperature for 4.1h, and the modified protein was obtained by freeze-drying. 5g of dopamine-grafted lignin and 5g of modified protein were dispersed in 50mL of deionized water and added. 2 mL of 10 wt.% glutaraldehyde solution was added, the pH was adjusted to 8, and the mixture was reacted at room temperature for 2.2 h. The mixture was filtered, washed, and dried to obtain a modified lignin protein. 10 g of sodium lauryl sulfate and 1 g of the modified lignin protein were dispersed in 100 mL of deionized water, and the mixture was stirred evenly. 20 g of ethyl acrylate, 10 g of methyl methacrylate, and 10 g of acrylic acid were added to obtain an emulsion. The temperature was adjusted to 73 ° C under a nitrogen atmosphere. 1 g of ammonium persulfate and 0.5 g of sodium bisulfite were added and reacted for 4.8 h to obtain an aqueous acrylic copolymer emulsion.

[0069] S3, 1 g of dopamine hydrochloride, 20 mL of metal salt solution, and 50 mL of CQDs dispersion were added to 100 mL of Tris-HCl buffer with a pH of 8.5, stirred for 10.5 h, and then freeze-dried to obtain a PDA-metal network; the concentration of the metal salt solution was 0.1 M, and the solutes were FeCl3·6H2O and ZnCl2 at a molar ratio of 1:1; the concentration of the CQDs dispersion was 10 mg / mL;

[0070] S4, dispersing 4 mL of tetraethyl orthosilicate in 20 mL of anhydrous ethanol, adding 2 mL of 0.1 M hydrochloric acid solution under ice-water bath conditions, stirring to form a transparent sol, adjusting the pH of a mixed solution of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, then mixing 20 g of the transparent sol with 10 g of the hydroxide sol and stirring to obtain a composite sol, mixing 20 mL of the composite sol with 8 mL of 2 wt.% chitosan solution, adjusting the pH to 8 to obtain a precursor solution, then adding 50 mL of the precursor solution to 100 mL of 3 wt.% Span 80@ liquid paraffin, stirring evenly, adding 10 mL of 1 M sodium hydroxide solution, and centrifuging and washing to obtain core particles;

[0071] S5, 1 g of core particles were dispersed in 100 mL of PDA-PEI solution, stirred thoroughly, and then centrifuged for washing. The core particles were then transferred to 100 mL of PAA solution, stirred thoroughly, and centrifuged for washing. The particles were immersed in a 0.5 wt.% glutaraldehyde solution to obtain electrolyte layer particles. The electrolyte layer particles were then dispersed in a 0.5 wt.% trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles.

[0072] S6, 100 mL of aqueous acrylic copolymer emulsion and 5 mL of chitosan-citrate mixture are mixed evenly and the pH is adjusted to 6, and then 10 g of PDA-metal network, 15 g of low surface energy particles, 1 g of leveling agent and 1 g of defoamer are added and mixed evenly to obtain a water-based biomass coating with a self-cleaning function; in the chitosan-citrate mixture, the mass fraction of chitosan is 0.5 wt.%, and the mass fraction of sodium citrate is 1 wt.%.

[0073] Figure 1 This is the SEM image of the water-based biomass coating with self-cleaning function prepared in this example; Figure 2 The contact angle of the water-based biomass coating with self-cleaning function prepared in this example with water is 162.4°, indicating that the coating has good hydrophobicity.

[0074] Example 2

[0075] This embodiment provides a method for preparing a water-based biomass coating with a self-cleaning function, and the preparation method specifically comprises the following steps:

[0076] S1, 10 g of lignin was dispersed in 100 mL of 10 wt.% NaOH solution, stirred and dissolved, and then the pH was adjusted to 6. The solution was filtered and washed to obtain purified lignin. 10 g of purified lignin, 10 mL of pyridine, and 10 mL of acrylic anhydride were dispersed in 100 mL of anhydrous dichloromethane, stirred at room temperature for 4.9 h, centrifuged and washed, and vacuum dried to obtain modified lignin. 6 g of modified lignin, 1 g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride, and 0.6 g of N-hydroxysuccinimide were dispersed in 100 mL of deionized water, the pH was adjusted to 6, stirred at room temperature, and then 4 g of dopamine hydrochloride was added to continue the reaction. After centrifugation and washing, dopamine-grafted lignin was obtained.

[0077] S2, 10g of soy protein was dispersed in 100mL of 0.1M NaOH solution, 1mL of 10mg / mL trypsin was added, the pH was adjusted to 8 and the mixture was reacted in a water bath at 37℃ for 2.8h. After the reaction was completed, the mixture was heated to inactivate, and the supernatant was separated to obtain a partially hydrolyzed protein solution. 10mL of the partially hydrolyzed protein solution was mixed with 5mL of 10wt.% dopamine hydrochloride solution, the pH was adjusted to 8, the mixture was stirred at room temperature for 4.7h, and the modified protein was obtained by freeze-drying. 5g of dopamine-grafted lignin and 5g of modified protein were dispersed in 50mL of deionized water and added. 2 mL of 10 wt.% glutaraldehyde solution was added, the pH was adjusted to 8, and the mixture was reacted at room temperature for 2.7 h. The mixture was filtered, washed, and dried to obtain a modified lignin protein. 10 g of sodium lauryl sulfate and 1 g of the modified lignin protein were dispersed in 100 mL of deionized water, and the mixture was stirred evenly. 20 g of ethyl acrylate, 10 g of methyl methacrylate, and 10 g of acrylic acid were added to obtain an emulsion. The temperature was adjusted to 77 ° C under a nitrogen atmosphere. 1 g of ammonium persulfate and 0.5 g of sodium bisulfite were added and reacted for 4.6 h to obtain an aqueous acrylic copolymer emulsion.

[0078] S3, 1 g of dopamine hydrochloride, 20 mL of metal salt solution, and 50 mL of CQDs dispersion were added to 100 mL of Tris-HCl buffer with a pH of 8.5, stirred for 10.9 h, and then freeze-dried to obtain a PDA-metal network; the concentration of the metal salt solution was 0.1 M, and the solutes were FeCl3·6H2O and ZnCl2 at a molar ratio of 1:1; the concentration of the CQDs dispersion was 10 mg / mL;

[0079] S4, dispersing 4 mL of tetraethyl orthosilicate in 20 mL of anhydrous ethanol, adding 2 mL of 0.1 M hydrochloric acid solution under ice-water bath conditions, stirring to form a transparent sol, adjusting the pH of a mixed solution of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, then mixing 20 g of the transparent sol with 10 g of the hydroxide sol and stirring to obtain a composite sol, mixing 20 mL of the composite sol with 8 mL of 2 wt.% chitosan solution, adjusting the pH to 8 to obtain a precursor solution, then adding 50 mL of the precursor solution to 100 mL of 3 wt.% Span 80@ liquid paraffin, stirring evenly, adding 10 mL of 1 M sodium hydroxide solution, and centrifuging and washing to obtain core particles;

[0080] S5, 1 g of core particles were dispersed in 100 mL of PDA-PEI solution, stirred thoroughly, and then centrifuged for washing. The core particles were then transferred to 100 mL of PAA solution, stirred thoroughly, and centrifuged for washing. The particles were immersed in a 0.5 wt.% glutaraldehyde solution to obtain electrolyte layer particles. The electrolyte layer particles were then dispersed in a 0.5 wt.% trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles.

[0081] S6, 100 mL of aqueous acrylic copolymer emulsion and 5 mL of chitosan-citrate mixture are mixed evenly and the pH is adjusted to 6, and then 10 g of PDA-metal network, 15 g of low surface energy particles, 1 g of leveling agent and 1 g of defoamer are added and mixed evenly to obtain a water-based biomass coating with a self-cleaning function; in the chitosan-citrate mixture, the mass fraction of chitosan is 0.5 wt.%, and the mass fraction of sodium citrate is 1 wt.%.

[0082] Example 3

[0083] This embodiment provides a method for preparing a water-based biomass coating with a self-cleaning function, and the preparation method specifically comprises the following steps:

[0084] S1, 10 g of lignin was dispersed in 100 mL of 10 wt.% NaOH solution, stirred and dissolved, and then the pH was adjusted to 6. The solution was filtered and washed to obtain purified lignin. 10 g of purified lignin, 10 mL of pyridine, and 10 mL of acrylic anhydride were dispersed in 100 mL of anhydrous dichloromethane, stirred at room temperature for 4.6 h, centrifuged and washed, and vacuum dried to obtain modified lignin. 6 g of modified lignin, 1 g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride, and 0.6 g of N-hydroxysuccinimide were dispersed in 100 mL of deionized water, the pH was adjusted to 6, stirred at room temperature, and then 4 g of dopamine hydrochloride was added to continue the reaction. After centrifugation and washing, dopamine-grafted lignin was obtained.

[0085] S2, 10g of soy protein was dispersed in 100mL of 0.1M NaOH solution, 1mL of 10mg / mL trypsin was added, the pH was adjusted to 8 and the reaction was carried out in a water bath at 37℃ for 2.1h. After the reaction was completed, the solution was heated and inactivated, and the supernatant was separated to obtain a partially hydrolyzed protein solution. 10mL of the partially hydrolyzed protein solution was mixed with 5mL of 10wt.% dopamine hydrochloride solution, the pH was adjusted to 8, the solution was stirred at room temperature for 4.9h, and the modified protein was obtained by freeze-drying. 5g of dopamine-grafted lignin and 5g of modified protein were dispersed in 50mL of deionized water and added. 2 mL of 10 wt.% glutaraldehyde solution was added, the pH was adjusted to 8, and the mixture was reacted at room temperature for 2.6 h. The mixture was filtered, washed, and dried to obtain a modified lignin protein. 10 g of sodium lauryl sulfate and 1 g of the modified lignin protein were dispersed in 100 mL of deionized water, and the mixture was stirred evenly. 20 g of ethyl acrylate, 10 g of methyl methacrylate, and 10 g of acrylic acid were added to obtain an emulsion. The temperature was adjusted to 79 ° C under a nitrogen atmosphere. 1 g of ammonium persulfate and 0.5 g of sodium bisulfite were added and reacted for 4.1 h to obtain an aqueous acrylic copolymer emulsion.

[0086] S3, 1 g of dopamine hydrochloride, 20 mL of metal salt solution, and 50 mL of CQDs dispersion were added to 100 mL of Tris-HCl buffer with a pH of 8.5, stirred for 11.8 h, and then freeze-dried to obtain a PDA-metal network; the concentration of the metal salt solution was 0.1 M, and the solutes were FeCl3·6H2O and ZnCl2 at a molar ratio of 1:1; the concentration of the CQDs dispersion was 10 mg / mL;

[0087] S4, dispersing 4 mL of tetraethyl orthosilicate in 20 mL of anhydrous ethanol, adding 2 mL of 0.1 M hydrochloric acid solution under ice-water bath conditions, stirring to form a transparent sol, adjusting the pH of a mixed solution of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, then mixing 20 g of the transparent sol with 10 g of the hydroxide sol and stirring to obtain a composite sol, mixing 20 mL of the composite sol with 8 mL of 2 wt.% chitosan solution, adjusting the pH to 8 to obtain a precursor solution, then adding 50 mL of the precursor solution to 100 mL of 3 wt.% Span 80@ liquid paraffin, stirring evenly, adding 10 mL of 1 M sodium hydroxide solution, and centrifuging and washing to obtain core particles;

[0088] S5, 1 g of core particles were dispersed in 100 mL of PDA-PEI solution, stirred thoroughly, and then centrifuged for washing. The core particles were then transferred to 100 mL of PAA solution, stirred thoroughly, and centrifuged for washing. The particles were immersed in a 0.5 wt.% glutaraldehyde solution to obtain electrolyte layer particles. The electrolyte layer particles were then dispersed in a 0.5 wt.% trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles.

[0089] S6, 100 mL of aqueous acrylic copolymer emulsion and 5 mL of chitosan-citrate mixture are mixed evenly and the pH is adjusted to 6, and then 10 g of PDA-metal network, 15 g of low surface energy particles, 1 g of leveling agent and 1 g of defoamer are added and mixed evenly to obtain a water-based biomass coating with a self-cleaning function; in the chitosan-citrate mixture, the mass fraction of chitosan is 0.5 wt.%, and the mass fraction of sodium citrate is 1 wt.%.

[0090] Example 4

[0091] This embodiment provides a method for preparing a water-based biomass coating with a self-cleaning function, and the preparation method specifically comprises the following steps:

[0092] S1, 10g of lignin was dispersed in 100mL of 10 wt.% NaOH solution, stirred and dissolved, and then the pH was adjusted to 6. The solution was filtered and washed to obtain purified lignin. 10g of purified lignin, 10mL of pyridine and 10mL of acrylic anhydride were dispersed in 100mL of anhydrous dichloromethane, stirred and reacted at room temperature for 4.3h, centrifuged and washed, and vacuum dried to obtain modified lignin. 6g of modified lignin, 1g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and 0.6g of N-hydroxysuccinimide were dispersed in 100mL of deionized water, the pH was adjusted to 6, stirred at room temperature, and then 4g of dopamine hydrochloride was added to continue the reaction. After centrifugation and washing, dopamine-grafted lignin was obtained.

[0093] S2, 10g of soy protein was dispersed in 100mL of 0.1M NaOH solution, 1mL of 10mg / mL trypsin was added, the pH was adjusted to 8 and the reaction was carried out in a water bath at 37℃ for 2.5h. After the reaction was completed, the solution was heated and inactivated, and the supernatant was separated to obtain a partially hydrolyzed protein solution. 10mL of the partially hydrolyzed protein solution was mixed with 5mL of 10wt.% dopamine hydrochloride solution, the pH was adjusted to 8, the solution was stirred at room temperature for 4.5h, and the modified protein was obtained by freeze-drying. 5g of dopamine-grafted lignin and 5g of modified protein were dispersed in 50mL of deionized water and added. 2 mL of 10 wt.% glutaraldehyde solution was added, the pH was adjusted to 8, and the mixture was reacted at room temperature for 2.1 h. The mixture was filtered, washed, and dried to obtain a modified lignin protein. 10 g of sodium lauryl sulfate and 1 g of the modified lignin protein were dispersed in 100 mL of deionized water, and the mixture was stirred evenly. 20 g of ethyl acrylate, 10 g of methyl methacrylate, and 10 g of acrylic acid were added to obtain an emulsion. The temperature was adjusted to 71 ° C under a nitrogen atmosphere. 1 g of ammonium persulfate and 0.5 g of sodium bisulfite were added and reacted for 4.3 h to obtain an aqueous acrylic copolymer emulsion.

[0094] S3, 1 g of dopamine hydrochloride, 20 mL of metal salt solution, and 50 mL of CQDs dispersion were added to 100 mL of Tris-HCl buffer with a pH of 8.5, stirred for 11.4 h, and then freeze-dried to obtain a PDA-metal network; the concentration of the metal salt solution was 0.1 M, and the solutes were FeCl3·6H2O and ZnCl2 at a molar ratio of 1:1; the concentration of the CQDs dispersion was 10 mg / mL;

[0095] S4, dispersing 4 mL of tetraethyl orthosilicate in 20 mL of anhydrous ethanol, adding 2 mL of 0.1 M hydrochloric acid solution under ice-water bath conditions, stirring to form a transparent sol, adjusting the pH of a mixed solution of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, then mixing 20 g of the transparent sol with 10 g of the hydroxide sol and stirring to obtain a composite sol, mixing 20 mL of the composite sol with 8 mL of 2 wt.% chitosan solution, adjusting the pH to 8 to obtain a precursor solution, then adding 50 mL of the precursor solution to 100 mL of 3 wt.% Span 80@ liquid paraffin, stirring evenly, adding 10 mL of 1 M sodium hydroxide solution, and centrifuging and washing to obtain core particles;

[0096] S5, 1 g of core particles were dispersed in 100 mL of PDA-PEI solution, stirred thoroughly, and then centrifuged for washing. The core particles were then transferred to 100 mL of PAA solution, stirred thoroughly, and centrifuged for washing. The particles were immersed in a 0.5 wt.% glutaraldehyde solution to obtain electrolyte layer particles. The electrolyte layer particles were then dispersed in a 0.5 wt.% trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles.

[0097] S6, 100 mL of aqueous acrylic copolymer emulsion and 5 mL of chitosan-citrate mixture are mixed evenly and the pH is adjusted to 6, and then 10 g of PDA-metal network, 15 g of low surface energy particles, 1 g of leveling agent and 1 g of defoamer are added and mixed evenly to obtain a water-based biomass coating with a self-cleaning function; in the chitosan-citrate mixture, the mass fraction of chitosan is 0.5 wt.%, and the mass fraction of sodium citrate is 1 wt.%.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing a water-based biomass coating with a self-cleaning function. The difference between it and Example 1 is that the mass of the PDA-metal network in S6 is 20 g, which is 10 g more than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0100] Comparative Example 2

[0101] This comparative example provides a method for preparing a water-based biomass coating with a self-cleaning function. The difference between it and Example 1 is that the mass of the PDA-metal network in S6 is 1 g, which is 9 g less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0102] Comparative Example 3

[0103] This comparative example provides a method for preparing a water-based biomass coating with a self-cleaning function. The difference between it and Example 1 is that the mass of the low surface energy particles in S6 is 30g, which is 15g more than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0104] Comparative Example 4

[0105] This comparative example provides a method for preparing a water-based biomass coating with a self-cleaning function. The difference between it and Example 1 is that the mass of the low surface energy particles in S6 is 2g, which is 13g less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0106] The stain resistance test standard is GB / T 9780-2013; the weather resistance test standard is GB / T 14522-2008; and the adhesion test standard is GB / T 9286-2021. The test results are shown in Table 1.

[0107] Table 1 Test results of a water-based biomass coating with self-cleaning function in Examples 1-4 and Comparative Examples 1-4

[0108]

[0109] As shown in Table 1, compared with Example 1, the stain resistance, weather resistance, and adhesion of Comparative Example 1 are all reduced; the stain resistance, weather resistance, and adhesion of Comparative Example 2 are all reduced. This is because the metal oxides in the PDA-metal network can generate active oxygen species under light conditions, which can degrade organic pollutants on the coating surface, thereby giving the coating stain resistance. The multifunctional functional groups of PDA can form chemical bonds or intermolecular interactions with the acrylic matrix and other components, enhancing the adhesion of the coating. The PDA-metal network in Comparative Example 1 is excessive. Under the action of excessive active oxygen species, the coating matrix may be oxidized and degraded, resulting in a decrease in coating strength and accelerated aging, thereby weakening the long-term self-cleaning performance of the coating. The excessive PDA-metal network may form a thicker inorganic layer, hindering the combination between the functional particles and the acrylic matrix, resulting in a decrease in interfacial bonding strength, thereby affecting the adhesion of the coating. In Comparative Example 2, the PDA-metal network is insufficient, the generation of active oxygen species is insufficient, the coating's ability to degrade organic pollutants is weakened, and the metal oxide's UV shielding effect is insufficient, making the coating more susceptible to damage from UV radiation in outdoor environments, thereby reducing weather resistance. Too little PDA will result in insufficient interfacial bonding with the substrate and other components, weakening the overall adhesion performance of the coating.

[0110] As shown in Table 1, compared to Example 1, the stain resistance, weather resistance, and adhesion of Comparative Example 3 were all reduced; the stain resistance, weather resistance, and adhesion of Comparative Example 4 were also reduced. The low-surface-energy particles, which have a large number of fluorinated groups exposed on their surfaces and have extremely low surface energy, can significantly reduce the adhesion between the coating and pollutants. The excessive low-surface-energy particles in Comparative Example 3 may accumulate on the coating surface, causing particle agglomeration, reducing stain resistance, weakening the integrity of the coating matrix, reducing its mechanical strength and durability, and reducing the overall strength and adhesion of the coating. In Comparative Example 4, the lack of low-surface-energy particles reduces stain resistance, significantly weakens the chemical corrosion resistance and UV resistance brought about by the fluorinated group modification, and reduces the weather resistance of the coating.

[0111] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a water-based biomass coating with a self-cleaning function, characterized in that: The preparation method comprises: S1, dispersing sodium lauryl sulfate and modified lignin protein in deionized water, adding ethyl acrylate, methyl methacrylate and acrylic acid to obtain an emulsion, adding ammonium persulfate and sodium bisulfite to react to obtain an aqueous acrylic copolymer emulsion; S2, adding dopamine hydrochloride, metal salt solution and CQDs dispersion into Tris-HCl buffer with a pH of 8.5 to react and obtain a PDA-metal network; S3, dispersing tetraethyl orthosilicate in anhydrous ethanol, adding hydrochloric acid solution to form a transparent sol, adjusting the pH of a mixture of titanium tetrachloride and zinc nitrate hexahydrate to 9 to form a hydroxide sol, mixing the transparent sol with the hydroxide sol to obtain a composite sol, mixing the composite sol with a chitosan solution, adjusting the pH to 8 to obtain a precursor solution, adding the precursor solution to Span 80@liquid paraffin, and adding sodium hydroxide solution to obtain core particles; S4, dispersing the core particles in a PDA-PEI solution, then transferring them to a PAA solution, and then immersing them in a glutaraldehyde solution to obtain electrolyte layer particles, and then dispersing the electrolyte layer particles in a trifluoropropyltriethoxysilane ethanol solution to obtain low surface energy particles; S5, mixing the aqueous acrylic copolymer emulsion and the chitosan-citrate mixture and adjusting the pH to 6, and then adding the PDA-metal network, low surface energy particles, a leveling agent, and a defoaming agent to obtain a water-based biomass coating with a self-cleaning function; The mass volume ratio of the aqueous acrylic copolymer emulsion, chitosan-citrate mixed solution, PDA-metal network, low surface energy particles, leveling agent and defoaming agent is 100 mL: 5 mL: 10 g: 15 g: 1 g: 1 g; The preparation method of the modified lignin protein includes: dispersing modified lignin, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in deionized water, adjusting the pH to 6, adding dopamine hydrochloride to react to obtain dopamine-grafted lignin, dispersing soy protein in a NaOH solution, adding trypsin, adjusting the pH to 8 and reacting in a 37°C water bath to obtain a partially hydrolyzed protein solution, mixing the partially hydrolyzed protein solution with a dopamine hydrochloride solution, adjusting the pH to 8 to obtain a modified protein, dispersing the dopamine-grafted lignin and the modified protein in deionized water, adding a glutaraldehyde solution, adjusting the pH to 8 to obtain a modified lignin protein; The preparation method of the modified lignin comprises: dispersing lignin in a NaOH solution, stirring and dissolving, and then adjusting the pH to 6 to obtain purified lignin; and dispersing the purified lignin, pyridine and acrylic anhydride in anhydrous dichloromethane to obtain modified lignin.

2. The method for preparing a water-based biomass coating with a self-cleaning function according to claim 1, characterized in that: In S1: The mass ratio of the sodium lauryl sulfate, modified lignin protein, ethyl acrylate, methyl methacrylate, acrylic acid, ammonium persulfate and sodium bisulfite is 5:0.5:10:5:5:0.5:0.

25.

3. The method for preparing a water-based biomass coating with a self-cleaning function according to claim 1, characterized in that: In S2: The mass volume ratio of the dopamine hydrochloride, metal salt solution, CQDs dispersion and Tris-HCl buffer is 0.2 g:4 mL:10 mL:20 mL.

4. The method for preparing a water-based biomass coating with a self-cleaning function according to claim 1, characterized in that: In S3: The mass ratio of titanium tetrachloride to zinc nitrate hexahydrate is 1:1; The mass ratio of the transparent sol to the hydroxide sol is 2:1; The volume ratio of the composite sol to the chitosan solution is 5:2; The volume ratio of the precursor solution, Span 80@ liquid paraffin and sodium hydroxide solution is 5:10:

1.

5. The method for preparing a water-based biomass coating with a self-cleaning function according to claim 1, characterized in that: In S4: The mass volume ratio of the core particles, the PDA-PEI solution and the PAA solution is 1 g:100 mL:100 mL.

6. The method for preparing a water-based biomass coating with a self-cleaning function according to claim 1, characterized in that: The mass ratio of the modified lignin, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and dopamine hydrochloride is 30:5:3:

20.

7. A water-based biomass coating with self-cleaning function obtained according to the preparation method according to any one of claims 1 to 6.

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