Vanadic bismuth oxide coating for building curtain wall and preparation method thereof

Abstract

The present application relates to the field of paint, disclose a kind of building curtain wall with bismuth vanadate paint and its preparation method.The paint includes the following components by mass percentage:40~60% of silicon propyl composite emulsion, 25~35% of modified bismuth vanadate, 4~6% of nano composite stabilizer, 1.0~1.5% of wet dispersing agent, 1.5~2.5% of functional adjuvant and the balance of deionized water, and functional adjuvant includes film forming aid, levelling agent and defoaming agent.The paint system of the present application realizes the excellent performance of ΔE<1.5 after QUV aging 3000h of final coating by using functional film-forming matrix, efficient stabilizer and mechanically-chemically activated-interfacial polymerization synergistic treatment pigment, with precision dispersion process, realizes the major breakthrough of long-acting weather resistance and color stability.Moreover, coating adhesion is strong, significantly better than traditional bismuth vanadate paint.

Description

Technical Field

[0001] This invention relates to the field of coatings, specifically to a bismuth vanadate coating for building curtain walls and its preparation method. Background Technology

[0002] In modern construction engineering, architectural coatings have become an indispensable functional material. Compared with coatings for other purposes, architectural coatings are used in the largest quantities. Curtain wall coatings applied to the exterior structure of buildings are exposed to the outdoor environment for a long time and must withstand complex tests such as ultraviolet radiation, temperature changes, rain erosion, and dirt adhesion. Therefore, the coating is required to have excellent weather resistance, durability, and color retention.

[0003] For a long time, lead-chromium pigments have been commonly used in architectural curtain wall coatings due to their advantages such as bright colors, good tinting strength, and high durability. However, with the increasing awareness of health and environmental protection, the potential hazards of lead-containing coatings have attracted widespread attention. Therefore, the coatings industry has been trying to find and develop alternatives to lead-chromium pigments, mainly including organic pigments and environmentally friendly inorganic pigments. Currently, relatively mature alternatives have been developed for other colors of lead-containing coatings, but lead-chromium yellow pigment is difficult to replace due to the insufficient weather resistance and lightfastness of organic pigments.

[0004] Bismuth vanadate (BiVO4), an environmentally friendly inorganic yellow pigment, exhibits promising application potential in building curtain walls, industrial equipment, and steel structure corrosion protection due to its bright color, non-toxicity, and near-infrared reflectivity. Compared to traditional pigments containing heavy metals such as chromium and lead, BiVO4 meets increasingly stringent environmental regulations and is a key candidate to replace high-performance chrome yellow and molybdenum chrome red pigments.

[0005] However, in practical large-scale applications, especially in the field of building curtain walls where long-term service performance requirements are extremely stringent, existing bismuth vanadate coatings still face several key technical bottlenecks, hindering their widespread adoption. For example, the adhesion between the coating and the substrate needs improvement. The long-term durability of the coating depends not only on the pigment itself but also on the strong interfacial bond between the coating and the metal or concrete substrate. Existing bismuth vanadate coatings exhibit unstable adhesion on complex substrates (especially commonly used curtain wall materials such as treated aluminum alloys and galvanized steel). When using the standard cross-cut test, some products only achieve Grade 1 or worse, and under stress conditions such as humid heat cycling and thermal shock, defects such as edge lifting and localized peeling are prone to occur, directly affecting their anti-corrosion protection function and overall service life. Furthermore, the coating's weather resistance is insufficient. Building curtain walls are exposed to strong ultraviolet radiation, extreme temperature changes, humidity, and polluted atmospheric environments for extended periods, which places stringent requirements on the coating's chemical stability and color durability. Under long-term aging conditions, existing bismuth vanadate coatings are prone to problems such as significant color drift, chalking, or decreased gloss, making it difficult to meet the aesthetic requirements of high-end buildings for color fidelity that can last for decades.

[0006] Therefore, there is still much room for improvement in existing bismuth vanadate coatings for building curtain walls. Summary of the Invention

[0007] In view of the above-mentioned problems in the existing technology, the main objective of the present invention is to provide a bismuth vanadate coating for building curtain walls and a method for preparing the same.

[0008] According to one aspect of the present invention, a bismuth vanadate coating for building curtain walls is provided, the coating comprising the following components by mass percentage: silicone-acrylic composite emulsion: 40%~60%, modified bismuth vanadate: 25%~35%, nanocomposite stabilizer: 4%~6%, wetting and dispersing agent: 1.0%~1.5%, functional additives: 1.5%~2.5%, and the balance being deionized water, wherein the functional additives include film-forming aids, leveling agents, and defoamers.

[0009] According to one embodiment of the present invention, the modified bismuth vanadate is bismuth vanadate prepared by mechanochemical activation and modified by interfacial polymerization, wherein the interfacial polymerization modification includes two-stage modification, the first-stage modification using 2-mercaptobenzimidazole as a grafting agent, and the second-stage modification using terminal thiol polysulfide.

[0010] According to one embodiment of the present invention, the silicone-acrylic composite emulsion is a self-crosslinking silicone-acrylic emulsion with a core-shell structure, wherein the core layer is a fluorinated acrylate, the shell layer is a copolymer of butyl acrylate and methyl methacrylate, and is grafted with γ-methacryloyloxypropyltrimethoxysilane, and the solid content of the silicone-acrylic composite emulsion is 35%~48%.

[0011] According to one embodiment of the present invention, the nanocomposite stabilizer is composed of nano-cerium oxide and acidic silica sol, wherein the mass ratio of the nano-cerium oxide to the acidic silica sol is 7:3, the particle size of the nano-cerium oxide is 20~50nm, and the particle size of the acidic silica sol is 10~50nm.

[0012] According to one embodiment of the present invention, the wetting and dispersing agent is composed of a sodium polycarboxylate dispersant and a modified polysiloxane, wherein the mass ratio of the sodium polycarboxylate dispersant to the modified polysiloxane is 7:3~8.

[0013] According to another aspect of the present invention, a method for preparing a bismuth vanadate coating for building curtain walls is provided, the method being used to prepare a bismuth vanadate coating for building curtain walls as described in any of the above embodiments and comprising the following steps:

[0014] Step A: Preparation of modified bismuth vanadate;

[0015] Step B: Add wetting and dispersing agent, a portion of defoamer and nanocomposite stabilizer sequentially to deionized water, and disperse at high speed until uniform;

[0016] Step C: Add modified bismuth vanadate under low-speed stirring, increase the speed to continue dispersing until the particle size in the slurry reaches the predetermined requirement;

[0017] Step D: Reduce the rotation speed, add silicone-acrylic composite emulsion, film-forming aid, remaining defoamer and leveling agent, and stir until the system is homogeneous and free of bubbles;

[0018] Step E: Filter through a sieve and cook under low-speed stirring.

[0019] According to one embodiment of the present invention, the preparation of modified bismuth vanadate comprises the following steps:

[0020] Bismuth oxide, vanadium salt, and composite sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product.

[0021] The activated product was refluxed with 2-mercaptobenzimidazole in a first solvent to obtain primary modified bismuth vanadate;

[0022] The terminal thiol polysulfide was dissolved in a second solvent, and primary modified bismuth vanadate was added. The mixture was reacted under predetermined temperature and pressure conditions, and then cured with ultraviolet light to obtain the interfacially polymerized modified bismuth vanadate.

[0023] According to one embodiment of the present invention, the bismuth oxide and vanadium salt have a molar ratio of Bi / V of 1:1 to 1.1 based on bismuth and vanadium; the composite sensitizer is a mixture of nano-silica and zinc oxide, with a mass ratio of nano-silica to zinc oxide of 7:3; the amount of composite sensitizer added is 1.5% to 3% of the total mass of bismuth oxide and vanadium salt; the ball milling speed is 300 to 400 rpm; the ball milling media are four types of balls with a diameter of less than 10 mm; the ball milling temperature is controlled at 70 to 80°C; the ball-to-material ratio is 10 to 15:1; and the ball milling time is 1 to 3 hours.

[0024] According to one embodiment of the present invention, the molar ratio of the activated product to 2-mercaptobenzimidazole is 1:40-55, the reflux time is 1-2 h, and the reflux temperature is 65-80 °C; and / or

[0025] The molar ratio of primary modified bismuth vanadate to terminal mercapto polysulfide is 1:1:0.05~0.1. The second solvent is a mixture of supercritical carbon dioxide and ethanol, with a volume ratio of supercritical carbon dioxide to ethanol of 3~5:1. After adding primary modified bismuth vanadate, the reaction is carried out at 55~70℃ and 8~10MPa for 2~3h, followed by UV curing for 1~1.5h.

[0026] According to one embodiment of the present invention, the high-speed dispersion rotation speed in step B is 800~1200 rpm, and the dispersion time is 15~45 min.

[0027] According to one embodiment of the present invention, the stirring speed in step C is 300~500 rpm. After adding modified bismuth vanadate, the stirring speed is increased to 1500~2000 rpm, and then the dispersion is continued for 30~40 min until the maximum particle size in the slurry is below 25 μm.

[0028] According to one embodiment of the present invention, in step D, the rotation speed is reduced to 600~800 rpm, and then stirred for 15~40 min.

[0029] According to one embodiment of the present invention, the stirring speed in step E is 300~500 rpm, and the maturation time is more than 24 hours.

[0030] Compared with existing technologies, the bismuth vanadate coating for building curtain walls and its preparation method of the present invention have at least one of the following beneficial effects: The coating system of the present invention, by employing a functional film-forming matrix, a highly efficient stabilizer, and pigments synergistically treated with mechanochemical activation and interfacial polymerization, combined with a precise dispersion process, enables the final coating to achieve excellent performance of ΔE < 1.5 after 3000 hours of QUV aging, achieving a significant breakthrough in long-term weather resistance and color stability. Furthermore, the coating exhibits strong adhesion, significantly superior to traditional bismuth vanadate coatings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating a method for preparing bismuth vanadate coatings for building curtain walls according to an embodiment of the present invention is shown;

[0033] Figure 2 A flowchart illustrating the preparation of modified bismuth vanadate according to an embodiment of the present invention is shown. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Furthermore, the reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0037] According to one aspect of the present invention, a bismuth vanadate coating for building curtain walls is provided. The bismuth vanadate coating comprises the following components by weight percentage: silicone-acrylic composite emulsion: 40%~60%, modified bismuth vanadate: 25%~35%, nanocomposite stabilizer: 4%~6%, wetting and dispersing agent: 1.0%~1.5%, functional additives: 1.5%~2.5%, and the balance being deionized water. The functional additives include film-forming aids, leveling agents, and defoamers.

[0038] The coating system of this invention, through the use of a functional film-forming matrix, a highly efficient stabilizer, and pigments synergistically treated with mechanochemical activation and interfacial polymerization, combined with a precise dispersion process, enables the final coating to achieve excellent performance with ΔE < 1.5 after 3000 hours of QUV aging, representing a significant breakthrough in long-term weather resistance and color stability. Furthermore, the coating exhibits strong adhesion, significantly superior to traditional bismuth vanadate coatings.

[0039] In some embodiments of the present invention, the silicone-acrylic composite emulsion employs a self-crosslinking silicone-acrylic emulsion with a core-shell structure. The core layer is a fluorinated acrylate, and the shell layer is a copolymer of butyl acrylate and methyl methacrylate, grafted with γ-methacryloyloxypropyltrimethoxysilane. The solid content of the silicone-acrylic composite emulsion is 35% to 48%. For example, the core layer is a fluorinated acrylate (such as dodecafluoroheptyl methacrylate, accounting for 5% to 8% of the total monomer mass) to provide excellent stain resistance and hydrophobicity; the shell layer is a copolymer of butyl acrylate (BA) and methyl methacrylate (MMA), grafted with γ-methacryloyloxypropyltrimethoxysilane (KH-570), with a solid content of 35% to 48%. After film formation, KH-570 undergoes hydrolysis and condensation to form a Si-O-Si three-dimensional network, which chemically bonds with inorganic substrates (such as cement and metal), significantly improving the adhesion (grade 0) and water resistance of the coating. Fluorine-containing core layers migrate to the coating surface, reducing surface energy and improving stain resistance. Silicone-acrylic composite emulsions constitute 40%–60% of the coating system, serving as the coating skeleton; this proportion ensures excellent coating continuity and mechanical strength.

[0040] In some embodiments of the present invention, the modified bismuth vanadate is bismuth vanadate prepared by mechanochemical activation and then modified by interfacial polymerization. Mechanochemical activation of bismuth vanadate can utilize industrial vanadium sources, such as industrial-grade ammonium metavanadate, which significantly reduces production costs and achieves high cost-effectiveness compared to using high-purity vanadium pentoxide. Interfacial polymerization modification mainly includes two stages: primary modification using 2-mercaptobenzimidazole (MBT) as a grafting agent, and secondary modification using terminal thiol polysulfide. The aim is to construct a stable functional surface layer for bismuth vanadate pigments through chemical methods to improve their agglomeration and stability in coatings.

[0041] In some embodiments of the present invention, the nanocomposite stabilizer is composed of nano-cerium oxide and acidic silica sol, with a mass ratio of nano-cerium oxide to acidic silica sol of 7:3. The particle size of the nano-cerium oxide is 20-50 nm, and the particle size of the acidic silica sol is 10-50 nm. This nanocomposite stabilizer can be prepared by ultrasonically blending and dispersing nano-cerium oxide with a particle size of 20-50 nm and acidic silica sol with a particle size of 10-50 nm at a mass ratio of 7:3 to form a stable slurry. Optionally, the nano-cerium oxide can be pre-treated with an alumina zirconate coupling agent to improve its dispersibility and enhance its compatibility with the silica sol and resin matrix. As a UV absorber and free radical scavenger, nano-cerium oxide can reduce UV penetration and inhibit free radical reactions, protecting the resin and pigments and delaying photoaging. During film formation, the acidic silica sol can promote the self-crosslinking of silicone-acrylic emulsions, fill microscopic defects in the coating, and react with metal ions on the substrate surface to enhance adhesion. The combination of these two components achieves the dual functions of chemical anti-aging and physical enhancement of density. Furthermore, pre-mixing nano-cerium oxide and acidic silica sol improves dispersion uniformity and component synergistic efficiency, reducing the risk of uneven redispersibility before application. While adding nano-cerium oxide and acidic silica sol separately offers greater process flexibility, differences in dispersion may affect performance reproducibility. Therefore, pre-forming these two components into a slurry allows the nanocomposite stabilizer to fully realize its dual functions.

[0042] In some embodiments of the present invention, the wetting and dispersing agent is a compound of sodium polycarboxylate dispersant and modified polysiloxane, with a mass ratio of sodium polycarboxylate dispersant to modified polysiloxane of 7:3-8. Specifically, a wetting and dispersing agent can be formed by compounding sodium polycarboxylate dispersant (such as Disperbyk-190) and low molecular weight modified polysiloxane wetting agent (such as BYK-346) at a mass ratio of 7:3-8. The polycarboxylate, through steric hindrance, ensures that the modified BiVO4 and nanoparticles are fully depolymerized and stably dispersed during the high-speed dispersion stage. The modified polysiloxane can significantly reduce the surface tension of the system and improve the wetting and penetration ability to pigment aggregate pores and various substrates, thereby ensuring the leveling of the coating during application and the uniformity of the final coating film.

[0043] Film-forming aids can be selected from commonly used film-forming aids in coating systems, such as, but not limited to, alcohol esters (dodecyl). Leveling agents can be selected from commonly used leveling agents in coating systems, such as, but not limited to, polyether-modified polysiloxanes. Defoamers can be selected from commonly used defoamers in coating systems, such as, but not limited to, mineral oils, silicones, and polyethers.

[0044] The coating of the present invention, by employing the above-mentioned innovative formulation system, achieves excellent coating performance, specifically:

[0045] Optical performance: Measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° viewing angle), L=91.3±0.4, a=+0.6±0.2, b=92.8±0.5, with a color gamut 35% larger than traditional products (CIE 1976 Lab space).

[0046] Chemical resistance: After immersion in 5% NaOH solution (25±1℃) for 1000h, the color difference ΔE=0.8±0.2, and the mass loss rate is only 0.15%;

[0047] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 0, the pencil hardness (GB / T6739) is 4H-5H, and the coating elastic modulus is increased to 3.8GPa (25℃).

[0048] Environmental indicators: VOC content, determined by GC-MS, was 3.2 ± 0.5 g / L; heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the ICP-OES detection limit (0.1 mg / kg);

[0049] Accelerated aging test (QUV-B, 0.55W / m) 2 After 3000 hours (at 340nm), ΔE = 1.3 ± 0.2, which is significantly better than traditional bismuth vanadate coatings.

[0050] This invention also provides a method for preparing bismuth vanadate coatings for building curtain walls as described in the above embodiments. For example... Figure 1 As shown, the preparation method of bismuth vanadate coating for building curtain walls according to an embodiment of the present invention generally includes the following steps:

[0051] Step A: Preparation of modified bismuth vanadate;

[0052] Step B: Add wetting and dispersing agent, a portion of defoamer and nanocomposite stabilizer sequentially to deionized water, and disperse at high speed until uniform;

[0053] Step C: Add modified bismuth vanadate under low-speed stirring, increase the speed to continue dispersing until the particle size in the slurry reaches the predetermined requirement;

[0054] Step D: Reduce the rotation speed, add silicone-acrylic composite emulsion, film-forming aid, remaining defoamer and leveling agent, and stir until the system is homogeneous and free of bubbles;

[0055] Step E: Filter through a sieve and cook under low-speed stirring.

[0056] The following provides a detailed example of each step.

[0057] In step A, modified bismuth vanadate is prepared.

[0058] To achieve better performance, existing technologies mostly rely on high-purity vanadium sources (such as vanadium pentoxide) or complex surface coating processes to prepare bismuth vanadate pigments. This results in high raw material costs and cumbersome preparation processes, making it difficult to apply them on a large scale in fields such as architectural curtain wall coatings that emphasize cost-effectiveness.

[0059] To address the above problems, this invention innovatively employs mechanochemical activation-interfacial polymerization modification to prepare modified bismuth vanadate. For example... Figure 2 As shown, the general process for preparing modified bismuth vanadate includes the following steps:

[0060] Step A1: Mix bismuth oxide, vanadium salt, and composite sensitizer in a set ratio, and carry out a high-energy ball milling activation reaction under a protective atmosphere to obtain the activated product;

[0061] Step A2: The activated product and 2-mercaptobenzimidazole are refluxed in the first solvent to obtain primary modified bismuth vanadate;

[0062] Step A3: Dissolve the terminal thiol polysulfide in the second solvent, add the primary modified bismuth vanadate, react under predetermined temperature and pressure conditions, and then cure with ultraviolet light to obtain the interface-polymerized modified bismuth vanadate.

[0063] In step A1, bismuth oxide, vanadium salt, and composite sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product.

[0064] In some embodiments of the present invention, the bismuth oxide is Bi₂O₃ with a particle size of D50 = 5 μm. The vanadium salt is industrial-grade ammonium metavanadate with a purity ≥ 99% and a particle size of D50 = 10~15 μm. The molar ratio of bismuth oxide to vanadium salt, calculated as bismuth and vanadium, is Bi / V = 1:1~1.1.

[0065] The ball mill uses a dedicated planetary high-energy ball mill activation system, which is equipped with a four-station synchronous operation mechanism. The rotation speed can be precisely adjusted within the range of 200~400rpm, and it integrates a high-precision temperature control system (±2℃) and a nitrogen protection device (oxygen content <50ppm).

[0066] In some embodiments of the present invention, the composite sensitizer is a mixture of nano-silica and zinc oxide, with a specific surface area ≥200m². 2 / g. The mass ratio of nano-silica to zinc oxide is 7:3, and the amount of composite sensitizer added is 1.5%~3% of the total mass of bismuth oxide and vanadium salt. As a highly efficient co-catalyst, the composite sensitizer provides abundant reaction sites with its large specific surface area, promoting the separation and migration of photogenerated carriers, thereby significantly improving the light absorption efficiency and catalytic activity of the bismuth-vanadium-based main catalyst. Bismuth vanadate has high catalytic activity, which can decompose surface stains through visible light, achieving strong self-cleaning and reducing maintenance costs; it can also degrade harmful gases such as formaldehyde, purifying the air; it has long-lasting antibacterial and antifungal properties, improving hygiene levels; and it enhances coating durability, thus bringing environmental protection, health, and long-term protection value to building and industrial coatings. The combined use of nano-silica and zinc oxide has special advantages. Nano-silica, as a highly dispersed carrier, can prevent agglomeration, while zinc oxide, as a wide bandgap semiconductor, contributes photogenerated electrons. The two work together to construct a heterojunction, optimize the charge transport path, and achieve a significant enhancement of sensitization performance.

[0067] In some embodiments of the present invention, zirconia grinding balls can be used as the grinding media, preferably balls with four particle sizes below 10 mm in diameter, such as balls with a four-level gradient distribution of diameters of 3 mm / 5 mm / 8 mm / 10 mm. This ball gradation can homogenize the energy distribution of the ball milling collisions and improve energy utilization. The ball milling speed is controlled at 300~400 rpm, the ball milling temperature at 70~80℃, the ball-to-material ratio at 10~15:1, and the ball milling time at 1~3 hours.

[0068] XRD analysis (Cu Kα radiation, scan rate 2~6° / min) revealed that the activation product was pure-phase monoclinic BiVO4 with a grain size of 80±3 nm and a specific surface area of ​​65±5 m². 2 / g.

[0069] Mechanochemical activation can be used to prepare bismuth vanadate, which can achieve efficient activation of industrial vanadium sources, reduce raw material costs by 70%, and enable large-scale production with high cost performance.

[0070] In step A2, the activated product is refluxed with 2-mercaptobenzimidazole in a first solvent to obtain primary modified bismuth vanadate.

[0071] In some embodiments, the molar ratio of the activated product to 2-mercaptobenzimidazole is 1:40-55. The first solvent can be anhydrous ethanol, the reflux time is 1-2 h, and the reflux temperature is 65-80 °C. After this primary surface modification, highly reactive thiol groups (-SH) are introduced onto the bismuth vanadate surface. These thiol groups serve as binding sites for subsequent reactions, providing anchoring sites for secondary modification.

[0072] The primary modified bismuth vanadate was detected, and Fourier transform infrared (FTIR) spectroscopy showed that it was 2560 cm⁻¹. -1The presence of a distinct SH characteristic peak indicates the introduction of highly reactive thiol groups (-SH) onto the surface of bismuth vanadate.

[0073] In step A3, the terminal thiol polysulfide is dissolved in a second solvent, primary modified bismuth vanadate is added, and the reaction is carried out under predetermined temperature and pressure conditions, followed by UV curing to obtain interface polymerization modified bismuth vanadate.

[0074] In some embodiments, the molar ratio of primary modified bismuth vanadate to terminal thiol polysulfide is 1:0.05~0.1. The second solvent is a mixture of supercritical carbon dioxide and ethanol, with a volume ratio of supercritical carbon dioxide to ethanol of 3~5:1. After adding primary modified bismuth vanadate, the reaction is carried out at 55~70℃ and 8~10MPa for 2~3h, followed by ultraviolet light (wavelength 254nm, intensity 15mW / cm²). 2 Curing time is 1-1.5 hours. Following this surface modification, a "thiol-ene" chemical reaction is used to graft terminal thiol polysulfide polymers onto the primary modified thiol groups in a unique supercritical CO2 / ethanol environment. UV curing promotes cross-linking, significantly increasing the sulfur content on the bismuth vanadate surface and forming a dense polymer shell. This polymer layer permanently isolates pigment particles through steric hindrance and chemical stability, a key step in achieving high color retention and long-term dispersion stability.

[0075] X-ray photoelectron spectroscopy (XPS) analysis of the secondary modified bismuth vanadate showed that the sulfur content on the surface of the modified material increased from 0.5–0.8 at% to 4.3–5.6 at%. Dynamic mechanical analysis (DMA) showed that polysulfide modification increased the elastic modulus of the coating from 1.2 GPa to 3.8 GPa (25 °C), which significantly improved the coating's scratch resistance, abrasion resistance, and overall stability.

[0076] The remaining steps of the preparation method for bismuth vanadate coatings for building curtain walls will be introduced.

[0077] In step B, a wetting and dispersing agent, a portion of the defoamer, and a nanocomposite stabilizer are added sequentially to deionized water and dispersed at high speed until homogeneous. In this step, the amount of defoamer can account for 40% to 60% of the total mass of the defoamer. The high-speed dispersion speed can be 800 to 1200 rpm, and the dispersion time can be 15 to 45 minutes.

[0078] In step C, modified bismuth vanadate is added under low-speed stirring, and the stirring speed is increased to continue dispersing until the particle size in the slurry reaches the predetermined requirement. For example, modified bismuth vanadate is slowly added to the slurry prepared in step B at a stirring speed of 300-500 rpm, and then the stirring speed is increased to 1500-2000 rpm, and the dispersion is continued for 30-40 minutes until the maximum particle size in the slurry is below 25 μm.

[0079] In step D, reduce the rotation speed, add the silicone-acrylic composite emulsion, film-forming aid, remaining defoamer, and leveling agent, and then stir until the system is homogeneous and bubble-free. For example, reduce the rotation speed to 600-800 rpm, slowly add the silicone-acrylic composite emulsion, film-forming aid (such as alcohol ester dodecyl), remaining defoamer, and leveling agent (such as polyether-modified polysiloxane) to the slurry obtained in step C, and stir for 15-40 minutes until the system is homogeneous and bubble-free.

[0080] In step E, the slurry obtained in step D is filtered through a filter screen and matured under low-speed stirring. For example, the slurry is filtered through a 200-mesh filter screen and matured at a low speed of 300-500 rpm for more than 24 hours to eliminate internal stress and achieve the optimal rheological state.

[0081] The preparation process is highly stable, has low raw material costs, and improves production efficiency.

[0082] The method of the present invention will be further described and illustrated below with reference to embodiments. The coating application and performance testing operations in the following embodiments are as follows:

[0083] After cleaning and sanding the substrate surface, apply the coating evenly using air spraying or scraping, controlling the wet film thickness. Allow it to stand at room temperature for 10-15 minutes to level, then place it in an oven at 80-90℃ for forced drying for 30-45 minutes, until the coating is fully cured.

[0084] Optical performance testing procedure: Take a dry, flat coated sample and test it using an X-Rite Ci7800 spectrophotometer. After calibrating the instrument, place the probe vertically against the sample surface. Under the setting of a D50 standard light source and an 8° observation angle, measure and record the L, a, and b values ​​at multiple points. Take the average value to calculate the color gamut area and compare it with the data measured under the same conditions for traditional products to calculate the percentage increase in color gamut.

[0085] Chemical resistance test procedure: Prepare a standard-sized coated sample and weigh it accurately (W1). Immerse it completely in a 5% NaOH solution, maintain a constant temperature of 25±1℃, and soak for 1000h. After removal, wash with deionized water and dry, weigh it again (W2), and calculate the mass loss rate. At the same time, use a colorimeter to measure the color change of the sample before and after immersion, and calculate the ΔE value.

[0086] Mechanical performance testing steps:

[0087] Adhesion test: Cut 1mm×1mm squares on the coating surface with a special crisscross cutter, cutting to the substrate. Attach the crisscross with tape and then quickly peel it off. The grade is determined based on the extent of coating peeling off at the edges of the squares.

[0088] Pencil hardness test: Push a pencil of known hardness at a 45° angle against the coated surface until the highest hardness pencil grade that cannot leave a permanent mark is found.

[0089] Environmental indicator testing procedures: Gases released after coating curing were collected according to standard methods. VOC content was analyzed using GC-MS: After sample processing, the sample was injected into a chromatography-mass spectrometer, and quantification was performed by comparison with a standard curve. Heavy metal content was analyzed using ICP-OES: After sample digestion, a solution was prepared, and lead (Pb), cadmium (Cd), and hexavalent chromium (Cr) were determined using inductively coupled plasma optical emission spectrometry. 6+ The concentration of ) was calculated and compared with the detection limit.

[0090] Example 1

[0091] Preparation of modified bismuth vanadate: (1) Accurately weigh industrial-grade ammonium metavanadate and bismuth trioxide to ensure that the Bi / V molar ratio is 1:1.05. To enhance the reaction activity, 2% of a composite sensitizer (nano SiO2 / ZnO=7:3) was added. This sensitizer has a high activity of up to 220m 2 / g specific surface area; (2) The mixed raw materials are loaded into a four-station planetary high-energy ball mill, and a zirconia grinding ball system (φ3 / 5 / 8 / 10mm configured in a mass ratio of 1:2:3:1) is adopted. The ball-to-material ratio is strictly controlled to be 12:1. Under nitrogen protection (oxygen content <50ppm), the ball milling is activated at a speed of 350rpm. During the process, the reaction temperature is stabilized at 78±2℃ through an integrated temperature control system. The activation is continued for 2h to obtain the activated product; (3) The activated product is subjected to primary modification. The primary modification adopts 2-mercaptobenzimidazole. Bismuth vanadate was primary modified by refluxing in anhydrous ethanol at 70°C for 1.5 h with 1:50 molar ratio of bismuth vanadate (MBT) as a grafting agent. Secondary modification was then performed using terminal thiol polysulfide. The terminal thiol polysulfide was dissolved in a supercritical CO2 / ethanol mixed solvent (volume ratio 4:1), and the primary modified bismuth vanadate was added. The molar ratio of the primary modified bismuth vanadate to the terminal thiol polysulfide was 1:0.08. The reaction was carried out at 9 MPa and 60°C for 3 h, followed by curing with 254 nm UV light for 1.2 h to obtain modified bismuth vanadate.

[0092] Preparation of bismuth vanadate coating: In deionized water (approximately 11.8% by mass of the coating system), add 1.2% wetting and dispersing agent (a mixture of sodium polycarboxylate and modified polysiloxane in a 7:5 ratio), 0.5% defoamer, and 5% nanocomposite stabilizer (a mixture of nano-cerium oxide and acidic silica sol in a 7:3 ratio). Disperse at 1000 rpm for 30 minutes until homogeneous. Reduce the stirring speed to 400 rpm and slowly add 30% (by mass) of modified bismuth vanadate from the coating system. Increase the stirring speed to 1800 rpm and continue dispersing for 35 minutes until the maximum particle size in the slurry is below 25 μm. Reduce the stirring speed to 700 rpm, and slowly add 50% of the total mass of the coating system of silicone-acrylic composite emulsion (a core-shell structured self-crosslinking silicone-acrylic emulsion with a solid content of 42%), 0.5% of alcohol ester dodecyl, 0.5% of defoamer, and 0.5% of polyether-modified polysiloxane. Stir for another 30 minutes until the system is homogeneous and bubble-free. Filter through a 200-mesh filter and mature at a low speed of 400 rpm for 24 hours to eliminate internal stress and achieve optimal rheological state.

[0093] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4 with a grain size of 80 nm and a specific surface area of ​​67 m². 2 / g. FTIR spectrum of primary modified bismuth vanadate at 2560 cm⁻¹. -1 The surface exhibits a distinct SH characteristic peak. XPS analysis of the secondary modified bismuth vanadate shows an increase in surface sulfur content to 5.1 at%.

[0094] The prepared coating was sprayed onto the substrate, and its performance was tested. The test results are as follows:

[0095] Optical performance: L=91.3, a=+0.6, b=92.8 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0096] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 0, and the pencil hardness (GB / T6739) is 5H;

[0097] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=1.3;

[0098] Environmental indicators: VOC content was determined by GC-MS to be 3.2 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0099] Example 2

[0100] Preparation of modified bismuth vanadate: (1) Accurately weigh industrial-grade ammonium metavanadate and bismuth trioxide to ensure a Bi / V molar ratio of 1:1. To enhance the reaction activity, 1.5% of a composite sensitizer (nano SiO2 / ZnO = 7:3) was added. This sensitizer has a high saturation of up to 220 μm. 2 / g specific surface area; (2) The mixed raw materials are loaded into a four-station planetary high-energy ball mill, and a zirconium oxide grinding ball system (φ3 / 5 / 8 / 10mm configured in a mass ratio of 1:2:3:1) is used. The ball-to-material ratio is strictly controlled to be 10:1. Under nitrogen protection (oxygen content <50ppm), the ball milling is activated at a speed of 300rpm. During the process, the reaction temperature is stabilized at 70±2℃ through an integrated temperature control system. The activation is continued for 3h to obtain the activated product; (3) The activated product is subjected to primary modification. The primary modification is 2-mercaptobenzo[2] Imidazole (MBT) was used as a grafting agent and refluxed in anhydrous ethanol at 65°C for 2 hours at a molar ratio of 1:40 to obtain primary modified bismuth vanadate. Secondary modification was then performed using terminal mercapto polysulfide. The terminal mercapto polysulfide was dissolved in a supercritical CO2 / ethanol mixed solvent (volume ratio of 3:1), and primary modified bismuth vanadate was added. The molar ratio of primary modified bismuth vanadate to terminal mercapto polysulfide was 1:0.05. The reaction was carried out at 8 MPa and 55°C for 3 hours, followed by curing with 254 nm ultraviolet light for 1.5 hours to obtain modified bismuth vanadate.

[0101] Preparation of bismuth vanadate coating: 1% wetting and dispersing agent (a mixture of sodium polycarboxylate and modified polysiloxane in a 7:3 ratio), 0.4% defoamer, and 6% nanocomposite stabilizer (a mixture of nano-cerium oxide and acidic silica sol in a 7:3 ratio) were sequentially added to 16.5% (by mass) of deionized water in the coating system. The mixture was dispersed at 800 rpm for 45 min until homogeneous. The stirring speed was reduced to 300 rpm, and 35% (by mass) of modified bismuth vanadate was slowly added. The stirring speed was increased to 1500 rpm, and dispersion continued for 30 min until the maximum particle size in the slurry was below 25 μm. The stirring speed was reduced to 600 rpm, and 40% (by mass) of silicone-acrylic composite emulsion (a self-crosslinking silicone-acrylic emulsion with a core-shell structure, solid content 35%), 0.4% alcohol ester dodecyl, 0.3% defoamer, and 0.4% polyether-modified polysiloxane were slowly added. The mixture was then stirred for another 40 min until the system was homogeneous and bubble-free. Filter with a 200-mesh filter and mature at a low speed of 300 rpm for 26 hours to eliminate internal stress and achieve the optimal rheological state.

[0102] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4. The FTIR spectrum of the primary modified bismuth vanadate was at 2560 cm⁻¹. -1 The surface exhibits a distinct SH characteristic peak. XPS analysis of the secondary modified bismuth vanadate shows an increase in surface sulfur content to 4.3 at%.

[0103] The prepared coating was sprayed onto the substrate, and its performance was tested. The test results are as follows:

[0104] Optical performance: L=91.1, a=+0.5, b=92.4 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0105] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 0, and the pencil hardness (GB / T6739) is 5H;

[0106] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=1.1;

[0107] Environmental indicators: VOC content was determined by GC-MS to be 2.9 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0108] Example 3

[0109] Preparation of modified bismuth vanadate: (1) Accurately weigh industrial grade ammonium metavanadate and bismuth trioxide to ensure that the Bi / V molar ratio is 1:1.1. In order to enhance the reaction activity, 3% of composite sensitizer (nano SiO2 / ZnO=7:3) was added. (2) The mixed raw materials were loaded into a four-station planetary high-energy ball mill. A zirconia grinding ball system (φ3 / 5 / 8 / 10mm configured in a mass ratio of 1:2:3:1) was adopted. The ball-to-material ratio was strictly controlled to be 15:1. Under nitrogen protection (oxygen content <50ppm), the ball milling was activated at a speed of 400rpm. During the process, the reaction temperature was stabilized at 80℃ by an integrated temperature control system for continuous activation. 1h, the activated product is obtained; (3) The activated product is subjected to primary modification. 2-mercaptobenzimidazole (MBT) is used as a grafting agent for primary modification. It is refluxed in anhydrous ethanol at 80°C for 1h at a molar ratio of 1:55 to obtain primary modified bismuth vanadate; then secondary modification is carried out. Terminal thiol polysulfide is used for secondary modification. The terminal thiol polysulfide is dissolved in a supercritical CO2 / ethanol mixed solvent (volume ratio of the two is 5:1), and primary modified bismuth vanadate is added. The molar ratio of primary modified bismuth vanadate to terminal thiol polysulfide is 1:0.1. It is reacted at 10MPa and 70°C for 2h, and then cured with 254nm ultraviolet light for 1h to obtain modified bismuth vanadate.

[0110] Preparation of bismuth vanadate coating: Add 1.5% wetting and dispersing agent (composed of sodium polycarboxylate and modified polysiloxane in a 7:8 ratio), 0.6% defoamer, and 6% nanocomposite stabilizer (composed of nano-cerium oxide and acidic silica sol in a 7:3 ratio) sequentially to 11.8% deionized water of the coating system. Disperse at 1200 rpm for 15 min until homogeneous. Reduce the stirring speed to 500 rpm, slowly add 25% modified bismuth vanadate of the coating system, increase the stirring speed to 2000 rpm and continue dispersing for 30 min until the maximum particle size in the slurry is below 25 μm. Reduce the stirring speed to 800 rpm, and slowly add 60% of the total mass of the coating system of silicone-acrylic composite emulsion (a core-shell structured self-crosslinking silicone-acrylic emulsion with a solid content of 48%), 0.6% of alcohol ester dodecyl, 0.7% of defoamer, and 0.6% of polyether-modified polysiloxane. Stir for another 40 minutes until the system is homogeneous and bubble-free. Filter through a 200-mesh filter and mature at a low speed of 500 rpm for 24 hours to eliminate internal stress and achieve optimal rheological state.

[0111] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4. The FTIR spectrum of the primary modified bismuth vanadate was at 2560 cm⁻¹. -1 The surface exhibits a distinct SH characteristic peak. XPS analysis of the secondary modified bismuth vanadate shows an increase in surface sulfur content to 5.3 at%.

[0112] The prepared coating was sprayed onto a steel plate, and its performance was tested. The test results are as follows:

[0113] Optical performance: L=91.5, a=+0.7, b=92.9 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0114] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 0, and the pencil hardness (GB / T6739) is 4H;

[0115] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=1.4;

[0116] Environmental indicators: VOC content was determined by GC-MS to be 3.1 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0117] Comparative Example 1

[0118] The composition of the coating system in this comparative example is similar to that in Example 1, the main difference being that Comparative Example 1 uses commercially available bismuth vanadate. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0119] Optical performance: L=87.3, a=+0.1, b=88.7 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0120] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level of 3, and the pencil hardness (GB / T6739) is 2H;

[0121] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000h, ΔE=4.2;

[0122] Environmental indicators: VOC content was determined by GC-MS to be 3.5 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0123] Comparative Example 2

[0124] The composition of the coating system in Comparative Example 2 is similar to that in Example 1. The main difference is that the bismuth vanadate used in Comparative Example 2 was not surface-modified with 2-mercaptobenzimidazole and terminal thiol polysulfide. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0125] Optical performance: L=90.5, a=+0.4, b=90.1 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0126] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 2, and the pencil hardness (GB / T6739) is 4H;

[0127] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=2.5;

[0128] Environmental indicators: VOC content was determined by GC-MS to be 3.1 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0129] Comparative Example 3

[0130] The composition of the coating system in this comparative example is similar to that in Example 1. The main difference is that the film-forming agent used in Comparative Example 3 is an acrylic emulsion, rather than the self-crosslinking silicone-acrylic emulsion with a core-shell structure as described in this application. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0131] Optical performance: L=89.7, a=+0.3, b=90.2 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0132] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level 2, and the pencil hardness (GB / T6739) is 3H;

[0133] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=2.2;

[0134] Environmental indicators: VOC content was determined by GC-MS to be 3.1 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0135] Comparative Example 4

[0136] The composition of the coating system in this comparative example is similar to that in Example 1. The main difference is that the coating system in Comparative Example 4 does not contain a nanocomposite stabilizer. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0137] Optical performance: L=89.8, a=+0.2, b=90.3 were measured using an X-Rite Ci7800 spectrophotometer (D50 light source, 8° observation angle);

[0138] Mechanical properties: The cross-cut adhesion test (GB / T 9286) reaches the highest level of 3, and the pencil hardness (GB / T6739) is 2H;

[0139] Accelerated aging test (QUV-B, 0.55W / m) 2 @340nm): After aging for 3000 hours, ΔE=3.6;

[0140] Environmental indicators: VOC content was determined by GC-MS to be 3.2 g / L, and heavy metal content (Pb / Cd / Cr) was [not specified]. 6+ All were below the detection limit of ICP-OES.

[0141] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of the present invention is limited to these examples. Within the framework of the present invention, technical features of the above embodiments or different embodiments can also be combined, and many other variations of different aspects of the present invention as described above exist, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bismuth vanadate coating for building curtain walls, characterized in that, The product comprises the following components by mass percentage: silicone-acrylic composite emulsion: 40%~60%, modified bismuth vanadate: 25%~35%, nanocomposite stabilizer: 4%~6%, wetting and dispersing agent: 1.0%~1.5%, functional additives: 1.5%~2.5%, and the balance being deionized water. The functional additives include film-forming aids, leveling agents, and defoamers. The silicone-acrylic composite emulsion is a self-crosslinking silicone-acrylic emulsion with a core-shell structure, the core layer being a fluorinated acrylate, and the shell layer being a mixture of butyl acrylate and methyl methacrylate. A copolymer is formed and grafted with γ-methacryloyloxypropyltrimethoxysilane. The solid content of the silicone-acrylic composite emulsion is 35%~48%. The modified bismuth vanadate is prepared by mechanochemical activation and then modified by interfacial polymerization. The interfacial polymerization modification includes two-stage modification. The primary modification uses 2-mercaptobenzimidazole as a grafting agent, and the secondary modification uses terminal thiol polysulfide. The terminal thiol polysulfide is grafted onto the thiol group of the primary modification using a "thiol-ene" chemical reaction. The preparation of modified bismuth vanadate includes the following steps: Bismuth oxide, vanadium salt, and composite sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain an activated product. The composite sensitizer is a mixture of nano-silica and zinc oxide. The activated product was refluxed with 2-mercaptobenzimidazole in a first solvent to obtain primary modified bismuth vanadate; A thiol-terminated polysulfide was dissolved in a second solvent, and primary-modified bismuth vanadate was added. The mixture was reacted under predetermined temperature and pressure conditions, followed by UV curing to obtain interfacially polymerized modified bismuth vanadate. The second solvent was a mixture of supercritical carbon dioxide and ethanol, and the UV light wavelength was 254 nm with an intensity of 15 mW / cm². 2 The nanocomposite stabilizer is composed of nano-cerium oxide and acidic silica sol, with a mass ratio of nano-cerium oxide to acidic silica sol of 7:

3. The wetting and dispersing agent is composed of sodium polycarboxylate dispersant and modified polysiloxane, with a mass ratio of sodium polycarboxylate dispersant to modified polysiloxane of 7:3 to 8.

2. The bismuth vanadate coating for building curtain walls according to claim 1, characterized in that, The nano-cerium oxide has a particle size of 20-50 nm, and the acidic silica sol has a particle size of 10-50 nm.

3. A method for preparing a bismuth vanadate coating for building curtain walls, characterized in that, The method is used to prepare the bismuth vanadate coating for building curtain walls as described in claim 1 or 2 and includes the following steps: Step A: Preparation of modified bismuth vanadate; Step B: Add wetting and dispersing agent, a portion of defoamer and nanocomposite stabilizer sequentially to deionized water, and disperse at high speed until uniform; Step C: Add modified bismuth vanadate under low-speed stirring, increase the speed to continue dispersing until the particle size in the slurry reaches the predetermined requirement; Step D: Reduce the rotation speed, add silicone-acrylic composite emulsion, film-forming aid, remaining defoamer and leveling agent, and stir until the system is homogeneous and free of bubbles; Step E: Filter through a sieve and cook under low-speed stirring.

4. The method for preparing bismuth vanadate coating for building curtain walls according to claim 3, characterized in that, The bismuth oxide and vanadium salt have a molar ratio of Bi / V of 1:1 to 1.1 based on the amount of bismuth and vanadium, respectively; the mass ratio of nano-silica to zinc oxide is 7:3; the amount of the composite sensitizer added is 1.5% to 3% of the total mass of bismuth oxide and vanadium salt; the ball milling speed is 300 to 400 rpm; the ball milling media are four types of balls with a diameter of less than 10 mm; the ball milling temperature is controlled at 70 to 80°C; the ball-to-material ratio is 10 to 15:1; and the ball milling time is 1 to 3 hours.

5. The method for preparing bismuth vanadate coating for building curtain walls according to claim 3, characterized in that, The molar ratio of the activated product to 2-mercaptobenzimidazole was 1:40-55, the reflux time was 1-2 h, and the reflux temperature was 65-80 °C; and / or The molar ratio of primary modified bismuth vanadate to terminal mercapto polysulfide is 1:0.05~0.1, and the volume ratio of supercritical carbon dioxide to ethanol is 3~5:

1. After adding primary modified bismuth vanadate, the reaction is carried out at 55~70℃ and 8~10MPa for 2~3h, and then cured with ultraviolet light for 1~1.5h.

6. The method for preparing bismuth vanadate coating for building curtain walls according to claim 3, characterized in that, In step B, the high-speed dispersion speed is 800~1200 rpm, and the dispersion time is 15~45 min; In step C, the stirring speed is 300-500 rpm. After adding modified bismuth vanadate, the stirring speed is increased to 1500-2000 rpm, and then the dispersion is continued for 30-40 minutes until the maximum particle size in the slurry is below 25 μm. In step D, reduce the rotation speed to 600-800 rpm and stir for another 15-40 minutes. In step E, the stirring speed is 300~500 rpm, and the maturation time is more than 24 hours.

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