Plant-based inorganic coating and method for its preparation

Abstract

This invention discloses a plant-based inorganic coating and its preparation method, belonging to the field of coating technology. The coating of this invention comprises the following raw materials in parts by weight: 20-40 parts potassium silicate, 10-20 parts silica sol, 10-20 parts plant extract, 10-25 parts modified corn cob biochar, 5-10 parts pigment, 15-30 parts inorganic filler, 1-5 parts additives, 1-3 parts stabilizer, and 10-20 parts water. This invention, by introducing specific plant extracts and zinc-cerium co-modified biochar, achieves a synergistic effect with the inorganic base material. While retaining the excellent fire resistance, durability, and environmental protection properties of traditional inorganic coatings, it significantly improves the flexibility and crack resistance of the coating, and endows it with efficient and long-lasting formaldehyde purification and antibacterial and antifungal functions. The product of this invention features extremely low VOC content and superior overall performance, making it suitable for interior wall decoration in building applications where indoor environmental health and sustainability are highly demanding.

Description

Technical Field

[0001] This invention relates to a plant-based inorganic coating and its preparation method, belonging to the field of coating technology. Background Technology

[0002] With the rapid development of the world economy and the continuous improvement of people's living standards, the pollution and toxicity of paints have increasingly attracted attention, and environmental protection and resource conservation have become topics of common concern to humankind. Therefore, countries around the world have formulated regulations to promote the transformation of the traditional paint industry towards green and environmentally friendly paints. Vigorously developing environmentally friendly interior wall paints is imperative, and is essential for people's health, socio-economic development, energy conservation, and sustainable development.

[0003] Traditional coatings typically refer to a class of coatings that use organic synthetic resins as the main film-forming substance, organic solvents or water as the dispersion medium, and contain a large number of chemical synthetic additives. With the tightening of environmental regulations and the increasing awareness of health among the public, traditional coatings, especially high-VOC solvent-based coatings, are gradually being replaced by more advanced and greener products.

[0004] Inorganic coatings are materials that primarily use inorganic materials as film-forming substances. They are widely used in interior and exterior wall decoration due to their excellent environmental friendliness (low VOC), durability, fire resistance (Class A), and mildew and antibacterial properties. Their film-forming substances are mainly inorganic alkali metal silicates such as potassium silicate and silica sol. However, traditional inorganic coatings have the following shortcomings: 1) Poor flexibility: The coating is hard but lacks elasticity, making it prone to cracking when the substrate experiences minor cracks or thermal expansion and contraction. 2) Poor application performance: The application feel may be rough, and the leveling properties are not as good as high-end organic latex paints, requiring high-level application techniques. 3) Insufficient raw material sustainability: Although inherently environmentally friendly, their main raw materials still originate from mining and chemical production, leaving room for improvement in terms of "green and renewable" aspects. With increasing demands for healthy indoor environments and sustainable development, developing a new type of inorganic coating with more balanced performance and greener, more environmentally friendly raw materials has become an urgent technical challenge. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a plant-based inorganic coating and its preparation method. This coating, while retaining the excellent properties of inorganic coatings, effectively improves the flexibility and workability of the coating by introducing specific plant-based components, and further enhances the product's environmental friendliness and bio-based content.

[0006] A plant-based inorganic coating comprises the following raw materials in parts by weight: 20-40 parts potassium silicate, 10-20 parts silica sol, 10-20 parts plant extract, 10-25 parts modified corn cob biochar, 5-10 parts pigment, 15-30 parts inorganic filler, 1-5 parts additives, 1-3 parts stabilizer, and 10-20 parts water.

[0007] Preferably, the plant extract is prepared by the following method: weigh pomegranate peel powder, add phosphate buffer solution with pH 7.5 according to the material-liquid ratio and mix evenly, add compound enzyme and enzymatically hydrolyze at 40-45℃ for 4 hours, after the reaction is completed, immediately inactivate the enzyme in boiling water for 10 minutes, filter, and freeze-dry the filtrate into powder under vacuum.

[0008] Preferably, the ratio of pomegranate peel powder to phosphate buffer solution is 1g:20mL.

[0009] Preferably, the amount of the compound enzyme is 2-3% of the mass of the pomegranate peel powder.

[0010] Preferably, the mass ratio of cellulase, pectinase, glucan endopeptidase, and bromelain in the composite enzyme is (1-2):1:(0.5-1):(0.6-0.8).

[0011] Preferably, the modified corn cob biochar is prepared by the following method:

[0012] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0013] (2) The corn cob biochar obtained in step (1) is immersed in a mixed solution containing zinc nitrate and cerium ammonium nitrate according to the solid-liquid ratio, stirred evenly, and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min after the reaction is completed, then placed in an oven to dry, and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral, and then dried and ground into powder to obtain the product.

[0014] Preferably, the solid-liquid ratio is 1g:30mL; the concentration of zinc nitrate in the mixed solution is 0.2mol / L, and the concentration of cerium ammonium nitrate is 0.1mol / L.

[0015] Preferably, the additive consists of 0.5-1 parts of defoamer, 3-5 parts of thickener and 1-2 parts of wetting agent.

[0016] Preferably, the inorganic filler is one or more of titanium dioxide, heavy calcium carbonate, talc, and kaolin.

[0017] Preferably, the stabilizer is composed of alkylphenol polyoxyethylene ether and triethanolamine in a mass ratio of 1:2.

[0018] This invention also provides a method for preparing the above-mentioned plant-based inorganic coating, comprising the following steps:

[0019] S1: Add potassium silicate, silica sol and water to the reactor under stirring at 300-400 rpm, mix evenly to form an inorganic base material;

[0020] S2: While stirring, add the pre-prepared plant extract powder and stabilizer to the inorganic base material, slowly increase the speed to 600 rpm, and continue stirring for 20 minutes until the system is homogeneous;

[0021] S3: Slowly add modified corn cob biochar and inorganic filler at a stirring speed of 400-500 rpm. After the addition is complete, increase the speed to 800-1000 rpm and disperse at high speed for 30 minutes. Then reduce the speed to 500 rpm and add wetting agent, defoamer, thickener and pigment in sequence. Stir for 5 minutes after each additive is added before adding the next one. After all additives are added, continue stirring for 15 minutes to make the coating system uniform. Then filter through a 200-mesh sieve to obtain the plant-based inorganic coating product.

[0022] The pigments used in this invention are selected from one of chrome green, iron oxide red, iron oxide black, cobalt blue, and cobalt green;

[0023] The thickener is selected from at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, and guar gum;

[0024] The defoamer is an organosilicon defoamer; the wetting agent is a polyoxyethylene alkyl ether.

[0025] Biochar itself has an irregular layered porous structure. These irregularly shaped nanoparticles interweave in the coating, forming a microscopic reinforcing network that effectively hinders crack propagation. This forces cracks to bypass or deflect these hard particles during propagation, thereby improving the fracture toughness and strength of the coating. The modified corn cob biochar used in this invention, after zinc-cerium modification, introduces a large number of metal oxide active sites on the surface of the biochar. These active sites chemically bond with the silanol groups in potassium silicate and silica sol (such as forming Si-O-Zn or Si-O-Ce bonds). This strong chemical bonding greatly improves the interfacial bonding between biochar and the inorganic matrix, avoiding detachment and defects caused by weak interfaces. A flexible organic-inorganic hybrid structure is formed in the rigid inorganic silicate network, allowing the coating to maintain hardness while achieving better elasticity and ductility, overcoming the weakness of poor flexibility in traditional inorganic coatings. Furthermore, the modified corn cob biochar used in this invention has a rich microporous structure and a large specific surface area, which can efficiently adsorb harmful gases such as formaldehyde. The ZnO / CeO2 nanoparticles on its surface can catalytically degrade formaldehyde under light, thereby effectively purifying indoor air and creating a healthier and safer living environment for people. It is especially suitable for newly renovated houses and public places.

[0026] The plant extracts used in this invention are rich in natural polymers such as tannins (polyphenols) and plant polysaccharides. These molecular chains contain a large number of active functional groups such as phenolic hydroxyl groups and carboxyl groups. These long-chain polymers are interwoven in a rigid inorganic siloxane network, and through hydrogen bonding and physical interactions, they effectively absorb and disperse stress, significantly improving the flexibility and impact resistance of the coating film. Simultaneously, their active functional groups can interact with the silanol groups in the inorganic matrix (potassium silicate, silica sol) and also combine with the functional groups on the surface of biochar, thus acting as a bridge between the inorganic and organic phases / carbon materials, improving interfacial compatibility and preventing phase separation. Furthermore, pomegranate peel polyphenols are broad-spectrum natural antibacterial agents, providing the coating with the first biological defense barrier, chemically inhibiting the germination of mold spores and the reproduction of bacteria. This antibacterial effect complements the physical antibacterial effect, enhancing the coating's antifungal and antibacterial properties.

[0027] The beneficial effects of this invention are:

[0028] (1) The plant extracts and modified corn cob biochar introduced in this invention are both renewable resources, which further enhances the environmental friendliness and bio-based content of the product, reduces the dependence on traditional chemical raw materials, and is more in line with the concept of green and environmentally friendly development.

[0029] (2) The addition of plant extracts and modified corn cob biochar increases the flexibility of the coating while maintaining the durability of inorganic coatings, enabling it to better adapt to the slight deformation of the substrate, reduce the generation of cracks, and extend the service life of the coating. At the same time, it improves the construction performance of the coating, making the brushing feel smoother, the leveling better, reducing the construction difficulty, and improving the construction efficiency.

[0030] (3) The plant extract of the present invention contains a variety of natural antibacterial components and has good antibacterial properties; the modified corn cob biochar surface is rich in microporous structure and a variety of active groups, which can adsorb and inhibit bacterial growth. The two work together to make the coating have stronger antibacterial and anti-corrosion properties, effectively inhibit the growth of mold and bacteria, reduce problems such as mold and discoloration of coating caused by microbial growth, keep the wall clean and beautiful, and are especially suitable for humid environments.

[0031] (4) The zinc-cerium modified biochar prepared in this invention adsorbs formaldehyde, and the metal oxide nanoparticles on the surface catalyze the degradation of formaldehyde under light; while the phenolic hydroxyl groups of pomegranate peel polyphenols can act as nucleophiles to react with formaldehyde, converting some formaldehyde molecules into stable compounds through chemical fixation, as a supplementary pathway for photocatalytic degradation; the two work together to form a triple purification network of fixation-adsorption-degradation, which improves the formaldehyde removal efficiency and reliability under no light or weak light conditions, and effectively purifies indoor air. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. The potassium silicate used in the present invention has a modulus of 2.5-4.0 and was purchased from Guangzhou Fuer Chemical Technology Co., Ltd.; the silica sol was purchased from Zhejiang Yuda Chemical Co., Ltd. as LS-30.

[0033] Example 1

[0034] A plant-based inorganic coating comprises the following raw materials in parts by weight: 20 parts potassium silicate, 10 parts silica sol, 10 parts plant extract, 10 parts modified corn cob biochar, 5 parts pigment, 15 parts inorganic filler, 1 part additive, 1 part stabilizer, and 10 parts water.

[0035] The plant extract is prepared by the following method: weigh pomegranate peel powder, add it to pH 7.5 phosphate buffer at a ratio of 1g:20mL, mix well, add compound enzyme and enzymatically hydrolyze at 40-45℃ for 4h, after the reaction is completed, immediately inactivate the enzyme in boiling water for 10min, filter, and freeze-dry the filtrate into powder under vacuum.

[0036] The amount of the compound enzyme used is 2% of the mass of pomegranate peel powder.

[0037] The mass ratio of cellulase, pectinase, glucan endopeptidase, and bromelain in the complex enzyme is 1:1:0.5:0.6.

[0038] The modified corn cob biochar is prepared using the following method:

[0039] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0040] (2) The corn cob biochar obtained in step (1) is impregnated in a mixed solution containing zinc nitrate and cerium ammonium nitrate at a solid-liquid ratio of 1g:30mL. The mixture is stirred evenly and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min after the reaction is completed. Then it is placed in an oven to dry and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral and then dried and ground into powder to obtain the product.

[0041] The concentration of zinc nitrate in the mixed solution is 0.2 mol / L, and the concentration of cerium ammonium nitrate is 0.1 mol / L.

[0042] The additive consists of 0.5 parts of defoamer, 3 parts of thickener, and 1 part of wetting agent.

[0043] The inorganic filler consists of 5 parts titanium dioxide, 5 parts heavy calcium carbonate, and 5 parts talc.

[0044] The pigment used in this invention is selected from chrome green; the thickener is hydroxymethyl cellulose; the defoamer is an organosilicon defoamer; and the wetting agent is polyoxyethylene alkyl ether.

[0045] The stabilizer is composed of alkylphenol polyoxyethylene ether and triethanolamine in a mass ratio of 1:2.

[0046] This invention also provides a method for preparing the above-mentioned plant-based inorganic coating, comprising the following steps:

[0047] S1: Add potassium silicate, silica sol and water to the reactor under stirring at 300-400 rpm, mix evenly to form an inorganic base material;

[0048] S2: While stirring, add the pre-prepared plant extract powder and stabilizer to the inorganic base material, slowly increase the speed to 600 rpm, and continue stirring for 20 minutes until the system is homogeneous;

[0049] S3: Slowly add modified corn cob biochar and inorganic filler at a stirring speed of 400-500 rpm. After the addition is complete, increase the speed to 800-1000 rpm and disperse at high speed for 30 minutes. Then reduce the speed to 500 rpm and add wetting agent, defoamer, thickener and pigment in sequence. Stir for 5 minutes after each additive is added before adding the next one. After all additives are added, continue stirring for 15 minutes to make the coating system uniform. Then filter through a 200-mesh sieve to obtain the plant-based inorganic coating product.

[0050] Example 2

[0051] A plant-based inorganic coating comprises the following raw materials in parts by weight: 30 parts potassium silicate, 15 parts silica sol, 15 parts plant extract, 20 parts modified corn cob biochar, 8 parts pigment, 20 parts inorganic filler, 3 parts additives, 2 parts stabilizer, and 15 parts water.

[0052] The plant extract is prepared by the following method: weigh pomegranate peel powder, add it to pH 7.5 phosphate buffer at a ratio of 1g:20mL, mix well, add compound enzyme and enzymatically hydrolyze at 40-45℃ for 4h, after the reaction is completed, immediately inactivate the enzyme in boiling water for 10min, filter, and freeze-dry the filtrate into powder under vacuum.

[0053] The amount of the compound enzyme used is 3% of the mass of pomegranate peel powder.

[0054] The mass ratio of cellulase, pectinase, glucan endopeptidase, and bromelain in the complex enzyme is 2:1:1:0.8.

[0055] The modified corn cob biochar is prepared using the following method:

[0056] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0057] (2) The corn cob biochar obtained in step (1) is impregnated in a mixed solution containing zinc nitrate and cerium ammonium nitrate at a solid-liquid ratio of 1g:30mL. The mixture is stirred evenly and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min after the reaction is completed. Then it is placed in an oven to dry and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral and then dried and ground into powder to obtain the product.

[0058] The concentration of zinc nitrate in the mixed solution is 0.2 mol / L, and the concentration of cerium ammonium nitrate is 0.1 mol / L.

[0059] The additive consists of 1 part defoamer, 5 parts thickener and 2 parts wetting agent.

[0060] The inorganic filler consists of 10 parts titanium dioxide, 5 parts heavy calcium carbonate, and 5 parts talc.

[0061] The pigment used in this invention is iron oxide red; the thickener is hydroxyethyl cellulose; the defoamer is an organosilicon defoamer; and the wetting agent is polyoxyethylene alkyl ether.

[0062] The stabilizer is composed of alkylphenol polyoxyethylene ether and triethanolamine in a mass ratio of 1:2.

[0063] This invention also provides a method for preparing the above-mentioned plant-based inorganic coating, comprising the following steps:

[0064] S1: Add potassium silicate, silica sol and water to the reactor under stirring at 300-400 rpm, mix evenly to form an inorganic base material;

[0065] S2: While stirring, add the pre-prepared plant extract powder and stabilizer to the inorganic base material, slowly increase the speed to 600 rpm, and continue stirring for 20 minutes until the system is homogeneous;

[0066] S3: Slowly add modified corn cob biochar and inorganic filler at a stirring speed of 400-500 rpm. After the addition is complete, increase the speed to 800-1000 rpm and disperse at high speed for 30 minutes. Then reduce the speed to 500 rpm and add wetting agent, defoamer, thickener and pigment in sequence. Stir for 5 minutes after each additive is added before adding the next one. After all additives are added, continue stirring for 15 minutes to make the coating system uniform. Then filter through a 200-mesh sieve to obtain the plant-based inorganic coating product.

[0067] Example 3

[0068] A plant-based inorganic coating comprises the following raw materials in parts by weight: 40 parts potassium silicate, 20 parts silica sol, 20 parts plant extract, 25 parts modified corn cob biochar, 10 parts pigment, 30 parts inorganic filler, 5 parts additives, 3 parts stabilizer, and 20 parts water.

[0069] The plant extract is prepared by the following method: weigh pomegranate peel powder, add it to pH 7.5 phosphate buffer at a ratio of 1g:20mL, mix well, add compound enzyme and enzymatically hydrolyze at 40-45℃ for 4h, after the reaction is completed, immediately inactivate the enzyme in boiling water for 10min, filter, and freeze-dry the filtrate into powder under vacuum.

[0070] The amount of the compound enzyme used is 2% of the mass of pomegranate peel powder.

[0071] The mass ratio of cellulase, pectinase, glucan endopeptidase, and bromelain in the complex enzyme is 1.5:1:0.6:0.7.

[0072] The modified corn cob biochar is prepared using the following method:

[0073] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0074] (2) The corn cob biochar obtained in step (1) is impregnated in a mixed solution containing zinc nitrate and cerium ammonium nitrate at a solid-liquid ratio of 1g:30mL. The mixture is stirred evenly and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min after the reaction is completed. Then it is placed in an oven to dry and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral and then dried and ground into powder to obtain the product.

[0075] The concentration of zinc nitrate in the mixed solution is 0.2 mol / L, and the concentration of cerium ammonium nitrate is 0.1 mol / L.

[0076] The additive consists of 0.6 parts of defoamer, 4 parts of thickener, and 1.5 parts of wetting agent.

[0077] The inorganic filler consists of 10 parts titanium dioxide, 5 parts heavy calcium carbonate, 5 parts kaolin, and 10 parts talc.

[0078] The pigment used in this invention is iron oxide black; the thickener is guar gum; the defoamer is an organosilicon defoamer; and the wetting agent is polyoxyethylene alkyl ether.

[0079] The stabilizer is composed of alkylphenol polyoxyethylene ether and triethanolamine in a mass ratio of 1:2.

[0080] This invention also provides a method for preparing the above-mentioned plant-based inorganic coating, comprising the following steps:

[0081] S1: Add potassium silicate, silica sol and water to the reactor under stirring at 300-400 rpm, mix evenly to form an inorganic base material;

[0082] S2: While stirring, add the pre-prepared plant extract powder and stabilizer to the inorganic base material, slowly increase the speed to 600 rpm, and continue stirring for 20 minutes until the system is homogeneous;

[0083] S3: Slowly add modified corn cob biochar and inorganic filler at a stirring speed of 400-500 rpm. After the addition is complete, increase the speed to 800-1000 rpm and disperse at high speed for 30 minutes. Then reduce the speed to 500 rpm and add wetting agent, defoamer, thickener and pigment in sequence. Stir for 5 minutes after each additive is added before adding the next one. After all additives are added, continue stirring for 15 minutes to make the coating system uniform. Then filter through a 200-mesh sieve to obtain the plant-based inorganic coating product.

[0084] Comparative Example 1

[0085] A plant-based inorganic coating has the same raw material composition as in Example 1, except that it does not contain plant extracts.

[0086] Comparative Example 2

[0087] A plant-based inorganic coating has the same raw material composition as in Example 1, except that it does not contain modified corn cob biochar.

[0088] Comparative Example 3

[0089] A plant-based inorganic coating has the same raw material composition as in Example 1, except that ordinary corn cob biochar is used instead of modified corn cob biochar.

[0090] Ordinary corn cob biochar is prepared by the following method: corn cobs are washed, dried, cooled and crushed to obtain corn cob particles. The corn cob particles are mixed with KHCO3 at a mass ratio of 1:1 and then transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0091] Comparative Example 4

[0092] A plant-based inorganic coating has a similar raw material composition to Example 1, except that the preparation method of the modified corn cob biochar is different. The modified corn cob biochar used in this comparative example was prepared by the following method:

[0093] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0094] (2) The corn cob biochar obtained in step (1) is immersed in 0.2 mol / L zinc nitrate solution at a solid-liquid ratio of 1 g: 30 mL, stirred evenly, and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min, then placed in an oven to dry, and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral, dried again and ground into powder to obtain the product.

[0095] Comparative Example 5

[0096] A plant-based inorganic coating has a similar raw material composition to Example 1, except that the preparation method of the modified corn cob biochar is different. The modified corn cob biochar used in this comparative example was prepared by the following method:

[0097] (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar.

[0098] (2) The corn cob biochar obtained in step (1) is immersed in 0.1 mol / L cerium ammonium nitrate solution at a solid-liquid ratio of 1 g: 30 mL. The mixture is stirred evenly and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min, then placed in an oven to dry, and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral, and then dried and ground into powder to obtain the product.

[0099] Performance testing

[0100] All samples prepared in Examples 1-3 and Comparative Examples 1-5 were uniformly coated onto a standard cement asbestos board. After complete curing, the following tests were performed. The results were taken as the average of three tests, as shown in the table below.

[0101] Table 1. Test results of basic physical and chemical properties of coatings

[0102]

[0103] As can be seen from the above data, all embodiments of the present invention exhibit excellent adhesion (level 0), indicating that the introduction of plant extracts did not weaken the bond between the coating and the substrate; on the contrary, it may have enhanced it due to its bridging effect. The hardness of the embodiments remained at a high level of 4H-5H, slightly lower than Comparative Example 1 without plant-based flexible components, but significantly higher than Comparative Example 2 without biochar reinforcement, demonstrating the synergistic balance between the flexibility provided by plant extracts and the reinforcement provided by biochar. The scrub resistance of Embodiments 1-3 of the present invention far exceeds that of Comparative Examples 1-5, proving that the modified corn cob biochar and plant extracts work together to form a more wear-resistant and denser coating structure. Furthermore, the VOC content of the products obtained from the embodiments of the present invention is less than 2.5 g / L, meeting the green coating standard and superior to Comparative Examples 1-5.

[0104] Table 2 Results of Coating Flexibility and Functionality Tests

[0105]

[0106] Note: The application performance is evaluated by a combination of brushing feel score (1-5 points, with 5 points being the best) and leveling performance (observe the smoothness of the coating surface after 24 hours; no brush marks or shrinkage are acceptable).

[0107] As can be seen from the data in Table 2 above, the flexibility of Examples 1-3 of the present invention all reached the 1mm level, and the application feel score was close to 5 points, significantly better than Comparative Examples 1-5. This indicates that the synergistic effect of plant extracts and zinc-cerium modified corn cob biochar effectively improved the rigidity defects of inorganic coatings and enhanced the smoothness and leveling properties of the coating. Examples 1-3 showed an antibacterial rate of over 99.2% against Escherichia coli and a mildew resistance level of 0 (no mold growth), demonstrating comprehensive and efficient biological inhibition performance. Comparative Example 1 showed a significantly reduced antibacterial rate and a mildew resistance level of 1. This fully demonstrates that natural antibacterial components such as pomegranate peel polyphenols provide an indispensable and active chemical antibacterial barrier, which is the first key line of defense against mold growth (mildew prevention). Comparative Examples 2-5 showed antibacterial rates of 80.1%-91.5% and were mildew resistant (level 0), indicating that the microporous adsorption and physical antibacterial effects of biochar were effective. However, their antibacterial rate is still generally below 99%, which highlights the synergistic effect of natural chemical antibacterial components provided by plant extracts and physical antibacterial properties of biochar, which can achieve a near-complete antibacterial effect (>99%), forming a more complete defense system.

[0108] The formaldehyde purification efficiency of Examples 1-3 of this invention is significantly higher than that of Comparative Examples 1-5. This result demonstrates the effectiveness of the "adsorption-photocatalysis-chemical fixation" triple purification network described in this invention and the synergistic effect of its components. Comparative Examples 1 and 2 have the lowest purification efficiencies, indicating that plant extracts and modified biochar constitute two indispensable components of a complete purification system; the absence of either component leads to a significant decrease in performance. The efficiency of Comparative Example 3 is significantly lower than that of the Examples, indicating that simple physical adsorption is limited, and the photocatalytically active component introduced by zinc-cerium co-modification is key to improving purification efficiency. The purification efficiencies of Comparative Examples 4 and 5 are also low, proving that the co-modification of zinc (ZnO) and cerium (CeO2) has a significant synergistic catalytic effect. The two promote each other in terms of band structure, producing stronger photocatalytic activity than single modification, achieving a better formaldehyde removal effect. Moreover, the formaldehyde purification effect persistence of Examples 1-3 all reached over 80%, far exceeding that of Comparative Examples 1-5. This also demonstrates the effectiveness of the triple purification network in this invention in improving the persistence of formaldehyde removal.

[0109] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A plant-based inorganic coating material, characterized by, It comprises the following raw materials in parts by weight: 20-40 parts potassium silicate, 10-20 parts silica sol, 10-20 parts plant extract, 10-25 parts modified corn cob biochar, 5-10 parts pigment, 15-30 parts inorganic filler, 1-5 parts additives, 1-3 parts stabilizer, and 10-20 parts water. The plant extract is prepared by the following method: weigh pomegranate peel powder, add phosphate buffer solution with pH 7.5 according to the material-liquid ratio and mix evenly, add compound enzyme and enzymatically hydrolyze at 40-45℃ for 4 hours, after the reaction is completed, immediately inactivate the enzyme in boiling water for 10 minutes, filter, and freeze-dry the filtrate into powder under vacuum. The modified corn cob biochar is prepared using the following method: (1) After washing, drying, cooling and crushing the corn cobs, corn cob particles are obtained. The corn cob particles and KHCO3 are mixed evenly at a mass ratio of 1:

1. Then, the mixture is transferred to a muffle furnace and heated to 600℃ in an oxygen-free environment and kept at that temperature for 2 hours. The resulting carbonized product is ground and sieved to remove ash. It is then repeatedly washed with water until neutral and dried at 80℃ to obtain corn cob biochar. (2) The corn cob biochar obtained in step (1) is immersed in a mixed solution containing zinc nitrate and cerium ammonium nitrate according to the solid-liquid ratio, stirred evenly, and the pH value of the solution is slowly adjusted to 9.0~10.0 with 0.1 mol / L NaOH solution. After stirring for 2 h, the mixture is ultrasonically treated for 30 min after the reaction is completed, then placed in an oven to dry, and finally transferred to a muffle furnace. The temperature is raised to 450-550℃ in an oxygen-free environment and calcined for 2 h. After cooling, the calcined product is washed with water until neutral, and then dried and ground into powder to obtain the product.

2. The plant-based inorganic coating of claim 1, wherein, The ratio of pomegranate peel powder to phosphate buffer solution is 1g:20mL.

3. The plant-based inorganic coating of claim 1, wherein, The amount of the compound enzyme used is 2-3% of the mass of pomegranate peel powder.

4. The plant-based inorganic coating according to claim 3, characterized in that, The mass ratio of cellulase, pectinase, dextran endopeptidase, and bromelain in the complex enzyme is (1-2):1:(0.5-1):(0.6-0.8).

5. The plant-based inorganic coating of claim 1, wherein, The solid-liquid ratio is 1g:30mL; the concentration of zinc nitrate in the mixed solution is 0.2mol / L, and the concentration of cerium ammonium nitrate is 0.1mol / L.

6. The plant-based inorganic coating of claim 1, wherein, The additives consist of 0.5-1 parts of defoamer, 3-5 parts of thickener, and 1-2 parts of wetting agent; the inorganic filler is one or more of titanium dioxide, heavy calcium carbonate, talc, and kaolin.

7. The plant-based inorganic coating according to claim 1, characterized in that, The stabilizer is composed of alkylphenol polyoxyethylene ether and triethanolamine in a mass ratio of 1:

2.

8. A method for preparing a plant-based inorganic coating according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Add potassium silicate, silica sol and water to the reactor under stirring at 300-400 rpm, mix evenly to form an inorganic base material; S2: While stirring, add the pre-prepared plant extract powder and stabilizer to the inorganic base material, slowly increase the speed to 600 rpm, and continue stirring for 20 minutes until the system is homogeneous; S3: Slowly add modified corn cob biochar and inorganic filler at a stirring speed of 400-500 rpm. After the addition is complete, increase the speed to 800-1000 rpm and disperse at high speed for 30 minutes. Then reduce the speed to 500 rpm and add wetting agent, defoamer, thickener and pigment in sequence. Stir for 5 minutes after each additive is added before adding the next one. After all additives are added, continue stirring for 15 minutes to make the coating system uniform. Then filter through a 200-mesh sieve to obtain the plant-based inorganic coating product.

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