A bismuth vanadate coating and a method for preparing the same

Abstract

The present application relates to the field of paint, disclose a kind of bismuth vanadate paint and preparation method thereof.The paint includes the following components by weight parts: fluorocarbon resin emulsion: 45~55 weight parts, modified bismuth vanadate: 30~40 weight parts, nano cerium dioxide: 2~4 weight parts, nano silicon dioxide-zirconium oxide core-shell particles: 1~2 weight parts, graphene quantum dots: 0.1~0.3 weight parts, composite dispersant: 2~3 weight parts, light stabilizer: 0.5~1 weight parts, toughening agent: 3~5 weight parts.The present application realizes the comprehensive improvement of weather resistance, mechanical property and optical property of coating through the molecular level interface design of modified pigment and fluorocarbon resin, combined with the synergistic effect of a variety of nanomaterials, coating is QUV accelerated aging 3000h after ΔE≤1.2, gloss retention rate >90%;Pencil hardness ≥5H, impact resistance >50kg·cm;The adhesion to aluminum alloy substrate can reach 0 level.

Description

Technical Field

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

[0002] Automotive paints and high-end building exterior coatings need to be exposed to the outdoor environment for a long time, and must withstand strong ultraviolet radiation, high and low temperature cycles, humidity changes and industrial pollutant corrosion, which puts high demands on protective coatings.

[0003] Traditional yellow automotive paints and high-end architectural exterior coatings often use pigments containing heavy metals such as chromium and lead. However, the environmental and health hazards of heavy metal pigments are receiving increasing attention, thus limiting their use.

[0004] Bismuth vanadate (BiVO4), as an environmentally friendly inorganic yellow pigment, has great potential to replace traditional heavy metal-containing coatings (such as chrome yellow) in the field of green and environmentally friendly coatings, especially in special application scenarios with extremely high requirements for color performance and durability, such as automotive original paint and high-end building facade coatings.

[0005] However, in practical large-scale applications, coating systems using bismuth vanadate as pigment still have shortcomings in terms of weather resistance and mechanical strength.

[0006] Traditional or simply coated bismuth vanadate pigments, under the synergistic effect of high-energy ultraviolet light and water vapor and oxygen, will induce a slight photocatalytic reaction on their surface. This may not only accelerate the migration and change of ions on their own crystal lattice surface, leading to irreversible color drift (such as yellowing attenuation or graying and darkening), but also catalyze the photo-oxidative degradation of the organic resin matrix in contact with them, resulting in overall chalking and loss of gloss in the coating. Bismuth vanadate coatings prepared by existing technologies typically show significant discoloration (ΔE>3.0) after 1500~2000h in standard QUV accelerated aging tests, making it difficult to meet the stringent standards of long-term weather resistance required by high-end automotive paints (requiring 5~8 years of stable appearance) and high-end architectural coatings (requiring 15~20 years of color fidelity).

[0007] Conventional bismuth vanadate coatings suffer from weak mechanical strength and interfacial adhesion, affecting the overall performance and lifespan of the coating after formation. These specialized applications demand extremely high mechanical properties from the coating, including stone impact resistance, scratch resistance, flexibility, and excellent adhesion. However, bismuth vanadate powder without effective surface modification has high surface energy and strong polarity, resulting in poor compatibility with commonly used organic resin matrices (such as polyurethane and acrylic resins). During film formation, the physical interfacial bond between the pigment and resin is weak. This weak interfacial bond not only makes the coating prone to peeling from the substrate under conditions such as impacts from gravel during vehicle travel or thermal expansion and contraction stresses on building exteriors, becoming the origin of microcracks and reducing the coating's impact resistance and flexibility, but also directly affects the adhesion of the coating to metal or concrete substrates. When using the cross-cut adhesion test, conventional bismuth vanadate coatings often only achieve an adhesion grade of 1 or 2, failing to meet the grade 0 standard commonly required for automotive original equipment manufacturer (OEM) paints or high-end curtain wall coatings.

[0008] Furthermore, in existing technologies, bismuth vanadate surfaces are modified by coating to improve its dispersibility in coating systems. The coating process typically employs traditional wet chemical methods (such as sol-gel and liquid-phase precipitation). However, this coating method results in a rough and uneven coating layer. A rough and uneven coating layer often reduces the gloss and color purity of the pigment itself, affecting the final vibrancy and transparency of the coating, and ultimately reducing its optical performance.

[0009] Therefore, there is still much room for improvement in the existing bismuth vanadate coating system in terms of weather resistance, mechanical strength, and optical properties. Summary of the Invention

[0010] In view of the above-mentioned problems in the prior art, the main objective of the present invention is to provide a bismuth vanadate coating and its preparation method.

[0011] According to one aspect of the present invention, a bismuth vanadate coating is provided, the coating comprising the following components by weight: fluorocarbon resin emulsion: 45-55 parts by weight, modified bismuth vanadate: 30-40 parts by weight, nano-cerium dioxide: 2-4 parts by weight, nano-silica-zirconia core-shell particles: 1-2 parts by weight, graphene quantum dots: 0.1-0.3 parts by weight, composite dispersant: 2-3 parts by weight, light stabilizer: 0.5-1 parts by weight, and toughening agent: 3-5 parts by weight.

[0012] According to one embodiment of the present invention, the modified bismuth vanadate is prepared by mechanical activation and a zinc oxide-alumina composite coating layer is formed on the surface of the bismuth vanadate by plasma-assisted atomic layer deposition.

[0013] According to one embodiment of the present invention, the fluorocarbon resin emulsion is a hydroxyl-containing fluorocarbon resin emulsion, wherein the fluorine content of the hydroxyl-containing fluorocarbon resin emulsion is ≥28%, the hydroxyl value is 35~45mgKOH / g, and the solid content is 48%~52%, and a blocked isocyanate curing agent is used in conjunction, wherein the amount of the curing agent added is 15%~20% of the resin solid content.

[0014] 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.

[0015] According to one embodiment of the present invention, the nano-cerium dioxide is mesoporous nano-cerium dioxide prepared by the sol-gel method, with a pore size of 3~5 nm and a specific surface area >150 m². 2 / g, and modified with an aminosilane coupling agent.

[0016] According to one embodiment of the present invention, the nano-silica-zirconia core-shell particles have a silica core and are encapsulated with a zirconia shell by atomic layer deposition, the shell thickness being 2~3 nm.

[0017] According to one embodiment of the present invention, the graphene quantum dots have a size of 3-5 nm and their surface is carboxylated.

[0018] According to one embodiment of the present invention, the composite dispersant comprises a comb-shaped polycarboxylate ammonium salt, a hyperbranched polyesteramine, and a fluorocarbon-modified polysiloxane.

[0019] According to one embodiment of the present invention, the light stabilizer is a compound of a benzotriazole UV absorber and a hindered amine light stabilizer.

[0020] According to one embodiment of the present invention, the toughening agent is a core-shell structured acrylate particle with a particle size of 80~100nm.

[0021] According to another aspect of the present invention, a method for preparing a bismuth vanadate coating is provided, the method being used to prepare a bismuth vanadate coating as described in any of the above embodiments and comprising the following steps:

[0022] Step A: Preparation of modified bismuth vanadate;

[0023] Step B: Mix the composite dispersant with deionized water, then add nano-cerium dioxide and graphene quantum dots, and obtain a stable nano-slurry through high-pressure microfluidic treatment;

[0024] Step C: Add the modified bismuth vanadate and nano-silica-zirconia core-shell particles sequentially to the nano slurry, and then grind it;

[0025] Step D: After grinding, add a vinyl silane coupling agent to the slurry and stir to allow the silane to partially polymerize on the particle surface, forming an organic-inorganic hybrid interface layer;

[0026] Step E: Add the fluorocarbon resin emulsion, light stabilizer, and toughening agent to the slurry prepared in step D, and continue stirring and mixing.

[0027] According to one embodiment of the present invention, the preparation of modified bismuth vanadate comprises the following steps:

[0028] Bismuth oxide, vanadium salt, and sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product.

[0029] A zinc oxide layer is deposited on the surface of the activated product by atomic layer deposition.

[0030] An aluminum oxide layer is deposited on the surface of a product with a zinc oxide layer by atomic layer deposition.

[0031] 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 1.15 based on bismuth and vanadium; the sensitizer is nano-zirconia, and the amount of nano-zirconia added is 0.5% to 2% of the total mass of bismuth oxide and vanadium salt; the ball milling speed is 400 to 500 rpm, the ball-to-material ratio is 12 to 15:1, and the ball milling time is 1.5 to 3 hours.

[0032] According to one embodiment of the present invention, depositing a zinc oxide layer by atomic layer deposition includes performing a first atomic layer deposition cycle on the surface of the activated product, wherein the precursor of the first atomic layer deposition cycle is diethylzinc, the oxygen source is water, and a single cycle includes sequential diethylzinc pulse, purge and water vapor pulse, the diethylzinc pulse time is 0.05~0.2s, the purge time is 0.03~0.1s, the water vapor pulse time is 0.05~0.2s, the number of cycles is 45~55, the thickness of the zinc oxide layer is 10~15nm, and the substrate temperature is 100~180°C.

[0033] According to one embodiment of the present invention, depositing an alumina layer by atomic layer deposition includes performing a second atomic layer deposition cycle on the surface of the product on which a zinc oxide layer has been deposited, wherein the precursor of the second atomic layer deposition cycle is trimethylaluminum, and the oxidation is performed by O2 plasma. Each cycle includes a trimethylaluminum pulse, a purge, and an oxygen plasma pulse in sequence. The trimethylaluminum pulse time is 0.04~0.06s, the purge time is 0.05~0.15s, the oxygen plasma pulse time is 0.1~0.3s, the number of cycles is 25~35, and the thickness of the alumina layer is 5~10nm.

[0034] According to one embodiment of the present invention, the pressure of the high-pressure microjets in step B is 120~180MPa, and the number of cycles is 3~5.

[0035] According to one embodiment of the present invention, the grinding speed in step C is 300~500 rpm and the time is 1~3h.

[0036] According to one embodiment of the present invention, the stirring temperature in step D is 50~80℃ and the stirring time is 1~2h.

[0037] According to one embodiment of the present invention, the stirring in step E is divided into the following three stages:

[0038] First stage: Mix at 300-500 rpm for 10-30 minutes;

[0039] Second stage: Mix at 500-700 rpm for 15-25 minutes;

[0040] Third stage: Vacuum degassing at 300~500rpm for 20~40min.

[0041] Compared with the prior art, the bismuth vanadate coating and its preparation method of the present invention have at least one of the following beneficial effects: The coating system of the present invention achieves comprehensive improvement of the weather resistance, mechanical properties and optical properties of the coating through the molecular-level interface design of modified pigments and fluorocarbon resins, combined with the synergistic effect of multiple nanomaterials. After QUV accelerated aging for 3000h, the coating has ΔE≤1.2 and gloss retention rate>90%; pencil hardness≥5H and impact resistance>50kg·cm; and adhesion to aluminum alloy substrates can reach grade 0 (cross-cut test). Attached Figure Description

[0042] 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.

[0043] Figure 1 A flowchart illustrating a method for preparing a bismuth vanadate coating according to an embodiment of the present invention is shown;

[0044] Figure 2 A flowchart illustrating the preparation of modified bismuth vanadate according to an embodiment of the present invention is shown. Detailed Implementation

[0045] 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.

[0046] 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.

[0047] 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.

[0048] According to one aspect of the present invention, a bismuth vanadate coating is provided. The bismuth vanadate coating comprises the following components in parts by weight: fluorocarbon resin emulsion: 45-55 parts by weight, modified bismuth vanadate: 30-40 parts by weight, nano-cerium dioxide: 2-4 parts by weight, nano-silica-zirconia core-shell particles: 1-2 parts by weight, graphene quantum dots: 0.1-0.3 parts by weight, composite dispersant: 2-3 parts by weight, light stabilizer: 0.5-1 parts by weight, and toughening agent: 3-5 parts by weight.

[0049] The coating system of this invention achieves comprehensive improvement in the weather resistance, mechanical properties and optical properties of the coating through the molecular-level interface design of modified pigments and fluorocarbon resins, combined with the synergistic effect of various nanomaterials. After QUV accelerated aging for 3000h, the coating has ΔE≤1.2, gloss retention rate>90%; pencil hardness≥5H, impact resistance>50kg·cm; and adhesion to aluminum alloy substrates can reach grade 0 (cross-cut test).

[0050] In some embodiments of the present invention, modified bismuth vanadate is obtained by using mechanically activated bismuth vanadate as raw material and forming a zinc oxide-alumina composite coating layer on the surface of bismuth vanadate through plasma-assisted atomic layer deposition (PE-ALD). Depositing the coating layer on the surface of bismuth vanadate using ALD technology achieves thin film coating with molecular-level precision, solving the problems of uneven coating and weak interfacial bonding caused by traditional wet coating methods. The inner zinc oxide layer provides ultraviolet shielding, while the outer alumina layer enhances the chemical stability and interfacial bonding of the pigment.

[0051] In some embodiments of the present invention, the fluorocarbon resin emulsion is a hydroxyl-containing fluorocarbon resin emulsion with a fluorine content ≥28%, a hydroxyl value of 35~45 mgKOH / g, and a solid content of 48%~52%. A blocked isocyanate curing agent is used in conjunction, with the amount of curing agent added being 15%~20% of the resin solid content. Crosslinking is achieved by baking at 130~140℃ to form a dense network. This film-forming matrix provides excellent weather resistance, chemical stability, and hydrophobicity, and forms a chemical bond with the Al2O3 layer on the modified BiVO4 surface.

[0052] In some embodiments of the present invention, the nano-cerium dioxide is mesoporous nano-cerium dioxide prepared by the sol-gel method, with a pore size of 3-5 nm and a specific surface area >150 m². 2 / g, and modified with an aminosilane coupling agent. Nano-cerium dioxide has excellent ultraviolet absorption capacity, which can protect BiVO4 and coating matrix from ultraviolet degradation, delay coating chalking and discoloration. After modification with an aminosilane coupling agent, its ultraviolet absorption efficiency is increased by more than 40%.

[0053] In some embodiments of the present invention, nano-silica-zirconia core-shell particles use silica (approximately 20 nm in diameter) as the core, with a zirconia shell encapsulated by atomic layer deposition, the shell thickness being 2-3 nm. These particles can improve the wear resistance and hardness of the coating. Adding nano-silica alone has limited ability to improve the coating's hardness and wear resistance due to its low hardness. Adding nano-zirconia alone is prone to agglomeration due to its high surface energy. Using core-shell structured nano-silica-zirconia particles, the silica can interact with dispersants and other agents in the coating system, promoting dispersion, while the outer zirconia layer provides a hard, wear-resistant surface, synergistically improving the coating's wear resistance and hardness.

[0054] In some embodiments of the present invention, the graphene quantum dots have a size of 3-5 nm and their surface is carboxylated, allowing them to act as free radical scavengers and stress transfer media. Utilizing their surface defects and carboxyl groups, they efficiently quench free radicals generated by ultraviolet light, heat, and oxygen, interrupting the degradation chain reaction, delaying the photo-oxidative aging of the resin matrix, and preventing chalking, discoloration, and loss of gloss. The nanoscale size and surface carboxyl groups enable them to form a strong interfacial bond with the resin matrix, uniformly dispersing stress, preventing microcrack propagation, and enhancing the bonding strength between the coating and the substrate.

[0055] In some embodiments of the present invention, the composite dispersant includes a primary dispersant, a synergistic dispersant, and a wetting agent. The primary dispersant is a comb-structured polycarboxylate ammonium salt. The carboxylate groups on the polycarboxylate chain can interact with and bind to inorganic particles (such as bismuth vanadate, nano-silica-zirconia core-shell particles, etc.), while its hydrophilic side chains extend within the resin, achieving efficient dispersion of pigments and nanoparticles. The synergistic dispersant is a hyperbranched polyesteramine, which prevents nanoparticle aggregation through steric hindrance. The wetting agent is a fluorocarbon-modified polysiloxane, which reduces the surface tension of the coating, making the coating droplets spread more easily and achieving excellent leveling properties.

[0056] In some embodiments of the present invention, the light stabilizer is composed of a benzotriazole UV absorber and a hindered amine light stabilizer in a mass ratio of 1:1 to 4.

[0057] In some embodiments of the present invention, the toughening agent is a core-shell structured acrylate particle with a particle size of 80~100nm.

[0058] The coating of the present invention, by employing the above-mentioned innovative formulation system, achieves excellent coating performance, specifically:

[0059] Optical performance: Chromaticity can reach L=89~92.1, a=-5~+0.3, b=90.4~93.5 (CIE Lab).

[0060] Mechanical properties: Pencil hardness 5~6H (GB / T 6739), adhesion grade 0 (ISO 2409);

[0061] Weather resistance: After 3000 hours of aging, QUV-B has a ΔE of 0.8~1.2, which is significantly better than traditional bismuth vanadate coatings.

[0062] This invention also provides a method for preparing the bismuth vanadate coating described in the above embodiments. For example... Figure 1 As shown, the preparation method of bismuth vanadate coating according to an embodiment of the present invention generally includes the following steps:

[0063] Step A: Preparation of modified bismuth vanadate;

[0064] Step B: Mix the composite dispersant with deionized water, then add nano-cerium dioxide and graphene quantum dots, and obtain a stable nano-slurry through high-pressure microfluidic treatment;

[0065] Step C: Modified bismuth vanadate and nano-silica-zirconia core-shell particles are added sequentially to the nano slurry, and then ground.

[0066] Step D: After grinding, add a vinyl silane coupling agent to the slurry and stir to allow the silane to partially polymerize on the particle surface, forming an organic-inorganic hybrid interface layer;

[0067] Step E: Add the fluorocarbon resin emulsion, light stabilizer, and toughening agent to the slurry prepared in step D, and continue stirring and mixing.

[0068] The following provides a detailed example of each step.

[0069] In step A, modified bismuth vanadate is prepared.

[0070] In existing technologies, bismuth vanadate surfaces are modified by coating to improve its dispersibility in coating systems. The coating process typically employs traditional wet chemical methods (such as sol-gel and liquid-phase precipitation). However, this coating method results in a rough and uneven coating layer, with thickness variations reaching ±20 nm. This rough and uneven coating layer often reduces the gloss and color purity of the pigment itself, affecting the final vibrancy and transparency of the coating, and ultimately lowering its optical performance.

[0071] To address the aforementioned problems, this invention utilizes PE-ALD to precisely control the nanostructure of zinc-aluminum thin films to prepare modified bismuth vanadate. For example... Figure 2 As shown, the general process for preparing modified bismuth vanadate includes the following steps:

[0072] Step A1: Mix bismuth oxide, vanadium salt, and sensitizer in a set ratio, and carry out a high-energy ball milling activation reaction under a protective atmosphere to obtain the activated product;

[0073] Step A2: Deposit a zinc oxide layer on the surface of the activated product using atomic layer deposition (ALD).

[0074] Step A3: Deposit an aluminum oxide layer on the surface of the product with a zinc oxide layer by atomic layer deposition.

[0075] In step A1, bismuth oxide, vanadium salt, and sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product.

[0076] In some embodiments of the present invention, the bismuth oxide is Bi₂O₃ with a particle size of D50 = 3~5 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 = 1:1~1.15. The sensitizer is nano-zirconia with a specific surface area of ​​150 m² / m³. 2 The amount added is 0.5% to 2% of the total mass of bismuth oxide and vanadium salt, with a weight of ≥ / g.

[0077] The ball mill can be performed using a planetary ball mill with φ5mm ZrO2 grinding balls as the medium, a ball-to-material ratio of 12~15:1, and under an Ar atmosphere. The ball milling speed is 400~500 rpm, and the ball milling time is 1.5~3 hours.

[0078] XRD analysis showed that the product was pure monoclinic BiVO4 with a grain size of 60-70 nm.

[0079] In step A2, a zinc oxide layer is deposited on the surface of the activated product by atomic layer deposition.

[0080] In some embodiments of the present invention, depositing a zinc oxide layer by atomic layer deposition includes performing a first atomic layer deposition cycle on the surface of an activated product, wherein the precursor of the first atomic layer deposition cycle is diethylzinc, the oxygen source is water, and a single cycle includes sequential diethylzinc pulses, purges, and water vapor pulses, the diethylzinc pulse duration is 0.05~0.2s, the purge duration is 0.03~0.1s, the water vapor pulse duration is 0.05~0.2s, the number of cycles is 45~55, the thickness of the zinc oxide layer is 10~15nm, and the substrate temperature is 100~180°C.

[0081] In step A3, an aluminum oxide layer is deposited on the surface of the product on which a zinc oxide layer has been deposited by atomic layer deposition.

[0082] In some embodiments of the present invention, depositing an alumina layer by atomic layer deposition includes performing a second atomic layer deposition cycle on the surface of a product on which a zinc oxide layer has been deposited. The precursor of the second atomic layer deposition cycle is trimethylaluminum, which is oxidized by O2 plasma. Each cycle includes a trimethylaluminum pulse, a purge, and an oxygen plasma pulse in sequence. The trimethylaluminum pulse time is 0.04~0.06s, the purge time is 0.05~0.15s, the oxygen plasma pulse time is 0.1~0.3s, the number of cycles is 25~35, and the thickness of the alumina layer is 5~10nm.

[0083] In steps A2 and A3, PE-ALD can be performed using a fluidized bed PE-ALD system with a reaction chamber pressure of 0.1~1 Torr and equipped with a radio frequency plasma source (13.56MHz, 50W).

[0084] ALD (Alternating Deposition) technology enables molecular-level film coating on bismuth vanadate surfaces, solving the problems of uneven coating and weak interfacial bonding caused by traditional wet coating methods. The inner zinc oxide layer provides UV shielding, while the outer alumina layer enhances the chemical stability and interfacial adhesion of the pigment.

[0085] The remaining steps of the preparation method for bismuth vanadate coatings will now be described.

[0086] In step B, the composite dispersant is mixed with deionized water, and then nano-cerium dioxide and graphene quantum dots are added. The mixture is then treated with high-pressure microfluidic jet to obtain a stable nano-slurry.

[0087] In some embodiments of the present invention, a composite dispersant is mixed with deionized water at a mass ratio of 1:5 to 20, nano-CeO2 and graphene quantum dots are added at a low speed, and a stable nano-slurry is obtained by high-pressure microfluidic treatment (pressure 150 MPa, cycle 3 times).

[0088] In step C, modified bismuth vanadate and nano-silica-zirconia core-shell particles are added sequentially to the nano slurry, followed by grinding.

[0089] In some embodiments of the present invention, modified bismuth vanadate and nano-silica-zirconia core-shell particles are added sequentially to the nano slurry, and a planetary ball mill is used with zirconia beads with a particle size of 0.3 mm as the grinding media, and the milling is carried out at a speed of 300~500 rpm for 1~3 hours until the fineness is ≤10μm.

[0090] In step D, after grinding is completed, a vinyl silane coupling agent is added to the slurry, and the mixture is stirred to cause partial polymerization of the silane on the particle surface, forming an organic-inorganic hybrid interface layer.

[0091] In some embodiments of the present invention, after grinding, a vinyl silane coupling agent containing 0.5% to 1% of the mass percentage of the coating system is added to the slurry, and the mixture is stirred at 50 to 80°C for 1 to 2 hours to allow the silane to partially polymerize on the particle surface, forming an organic-inorganic hybrid interface layer.

[0092] In step E, the fluorocarbon resin emulsion, light stabilizer, and toughening agent are added to the slurry prepared in step D, and the mixture is stirred and mixed.

[0093] In some embodiments of the present invention, stirring is divided into the following three stages:

[0094] First stage: Mix at 300-500 rpm for 10-30 minutes;

[0095] Second stage: Mix at 500-700 rpm for 15-25 minutes;

[0096] Third stage: Vacuum degassing at 300~500rpm for 20~40min.

[0097] The method of this invention constructs a multi-level synergistic protection system of "ALD modified pigment-nano reinforcement-fluorocarbon crosslinking", which breaks through the bottlenecks of traditional bismuth vanadate coatings in terms of weather resistance, mechanical properties and optical properties.

[0098] The method of the present invention will be further described and illustrated below with reference to the embodiments. The coating application and performance testing operations in the following embodiments are as follows: Coating and curing: The prepared coating is sprayed onto Q235 steel plate and cured at 120~160℃ for 20~50 min, with the dry film thickness controlled at 50±5μm; optical properties are tested in accordance with CIE Lab testing standards; hardness testing is performed in accordance with GB / T6739; adhesion testing is performed in accordance with ISO 2409 standards; weathering resistance testing is performed by QUV-B aging for 3000 h.

[0099] Example 1

[0100] Preparation of modified bismuth vanadate: (1) Bi2O3 and NH4VO3 were mixed at a molar ratio of Bi / V = 1:1.1, and 1.0% nano ZrO2 sensitizer was added. The mixed raw materials were loaded into a planetary ball mill, and φ5mm zirconia grinding balls were used as the medium. The ball-to-material ratio was 14:1. The mixture was ball-milled at 450 rpm for 2 hours under Ar protection to obtain the activated product; (2) The activated product was subjected to PE-ALD deposition of zinc-aluminum composite film. Diethylzinc was used as the precursor and water was used as the substrate. Using oxygen as the source, the plasma was cyclically applied with a diethylzinc pulse time of 0.1 s, a purge time of 0.05 s, and a water vapor pulse time of 0.1 s for 50 cycles, at a substrate temperature of 150 °C. A layer of ZnO was deposited on the surface of the activated product. Then, the precursor was switched to trimethylaluminum, and O2 plasma oxidation was performed. The plasma was cyclically applied with a trimethylaluminum pulse time of 0.05 s, a purge time of 0.1 s, and an oxygen plasma pulse time of 0.2 s for 30 cycles to obtain modified bismuth vanadate.

[0101] Preparation of bismuth vanadate coating: (1) The coating formula is as follows: fluorocarbon resin emulsion: 52 parts by weight, modified bismuth vanadate: 35 parts by weight, nano cerium dioxide: 3 parts by weight, nano silica-zirconia core-shell particles: 1.5 parts by weight, graphene quantum dots: 0.2 parts by weight, composite dispersant: 2.5 parts by weight, light stabilizer: 0.8 parts by weight, toughening agent: 4 parts by weight; (2) The composite dispersant and deionized water are mixed at a mass ratio of 1:10, and then nano cerium dioxide and graphene quantum dots are added. After being subjected to high-pressure micro-jet circulation treatment at a pressure of 150 MPa for 4 times, a stable nano slurry is obtained; Modified bismuth vanadate and nano-silica-zirconia core-shell particles were added sequentially to the slurry, and then ground at 400 rpm for 2 hours. After grinding, KH570 silane coupling agent (0.8% by mass of the coating system) was added to the slurry, and stirred at 60°C for 1.5 hours to allow partial polymerization of silane on the particle surface, forming an organic-inorganic hybrid interface layer. Fluorocarbon resin emulsion, light stabilizer, and toughening agent were added to the slurry, and mixed at 400 rpm for 20 minutes, then at 600 rpm for 20 minutes, and then vacuum degassed at 400 rpm for 30 minutes to obtain the bismuth vanadate coating.

[0102] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4 with a grain size of 67 nm and a specific surface area of ​​29.2 m². 2 / g. TEM analysis showed that the ZnO layer thickness was approximately 12 nm, with a thickness difference within 2 nm, and the Al2O3 layer thickness was approximately 8 nm, with a thickness difference within 2 nm. XPS analysis detected Zn-O-Al interfacial bonds with a binding energy of approximately 1021.5 eV, indicating excellent interfacial bonding.

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

[0104] Optical properties: L=90.5, a=-1.8, b=92.3;

[0105] Mechanical properties: Pencil hardness 6H, adhesion grade 0;

[0106] Weather resistance: ΔE = 0.8 after 3000h aging of QUV-B.

[0107] Example 2

[0108] Preparation of modified bismuth vanadate: (1) Bi2O3 and NH4VO3 were mixed at a molar ratio of Bi / V = 1:1.15, and 2.0% nano ZrO2 sensitizer was added. The mixed raw materials were loaded into a planetary ball mill, and φ5mm zirconia grinding balls were used as the medium. The ball-to-material ratio was 15:1. The mixture was ball-milled at 500 rpm for 1.5 h under Ar protection to obtain the activated product; (2) The activated product was subjected to PE-ALD deposition of zinc-aluminum composite film. Diethylzinc was used as the precursor, and water was added. Using diethylzinc as the oxygen source, the process was cyclical with a pulse time of 0.2 s, a purge time of 0.1 s, and a water vapor pulse time of 0.2 s for 55 cycles, at a substrate temperature of 180 °C. A layer of ZnO was deposited on the surface of the activated product. Then, the precursor was switched to trimethylaluminum, and O2 plasma oxidation was performed. The process was cyclical with a trimethylaluminum pulse time of 0.06 s, a purge time of 0.15 s, and an oxygen plasma pulse time of 0.3 s for 35 cycles to obtain modified bismuth vanadate.

[0109] Preparation of bismuth vanadate coating: (1) The coating formula is as follows: fluorocarbon resin emulsion: 55 parts by weight, modified bismuth vanadate: 40 parts by weight, nano cerium dioxide: 4 parts by weight, nano silica-zirconia core-shell particles: 2 parts by weight, graphene quantum dots: 0.3 parts by weight, composite dispersant: 3 parts by weight, light stabilizer: 1 part by weight, toughening agent: 5 parts by weight; (2) The composite dispersant and deionized water are mixed at a mass ratio of 1:20, and then nano cerium dioxide and graphene quantum dots are added. The mixture is subjected to a high-pressure micro-jet circulation treatment at a pressure of 180 MPa for 5 times to obtain a stable nano slurry; Modified bismuth vanadate and nano-silica-zirconia core-shell particles were added sequentially, and then ground at 500 rpm for 3 hours. After grinding, KH570 silane coupling agent accounting for 1% of the coating system mass percentage was added to the slurry, and stirred at 80°C for 2 hours to allow silane to partially polymerize on the particle surface and form an organic-inorganic hybrid interface layer. Fluorocarbon resin emulsion, light stabilizer, and toughening agent were added to the slurry and mixed at 500 rpm for 30 minutes, then mixed at 700 rpm for 25 minutes, and then vacuum degassed at 500 rpm for 40 minutes to obtain the bismuth vanadate coating.

[0110] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4 with a grain size of 70 nm and a specific surface area of ​​25.8 m². 2 / g. TEM analysis showed that the ZnO layer thickness was approximately 14 nm, with a thickness difference within 2 nm, and the Al2O3 layer thickness was approximately 10 nm, with a thickness difference within 2 nm. XPS analysis detected Zn-O-Al interfacial bonds with a binding energy of approximately 1021.3 eV, indicating excellent interfacial bonding.

[0111] The prepared coating was sprayed onto a steel plate, and its performance was tested. The test results are as follows:

[0112] Optical properties: L=91.2, a=0.3, b=93.5;

[0113] Mechanical properties: Pencil hardness 6H, adhesion grade 0;

[0114] Weather resistance: ΔE=0.9 after 3000h aging of QUV-B.

[0115] Example 3

[0116] Preparation of modified bismuth vanadate: (1) Bi2O3 and NH4VO3 were mixed at a molar ratio of Bi / V = 1:1, and 0.5% nano ZrO2 sensitizer was added. The mixed raw materials were loaded into a planetary ball mill, and φ5mm zirconium oxide grinding balls were used as the medium. The ball-to-material ratio was 12:1. The mixture was ball-milled at 400 rpm for 3 hours under Ar protection to obtain the activated product; (2) The activated product was subjected to PE-ALD deposition of zinc-aluminum composite film. Diethylzinc was used as the precursor and water was used as the oxygen source. The process involved cycling the product with a diethylzinc pulse time of 0.05 s, a purge time of 0.03 s, and a water vapor pulse time of 0.05 s for 45 cycles at a substrate temperature of 100 °C. A layer of ZnO was deposited on the surface of the activated product. The process was then switched to trimethylaluminum as the precursor, followed by O2 plasma oxidation. The process was repeated 25 times with a trimethylaluminum pulse time of 0.04 s, a purge time of 0.05 s, and an oxygen plasma pulse time of 0.1 s to obtain modified bismuth vanadate.

[0117] Preparation of bismuth vanadate coating: (1) The coating formula is as follows: fluorocarbon resin emulsion: 45 parts by weight, modified bismuth vanadate: 30 parts by weight, nano cerium dioxide: 2 parts by weight, nano silica-zirconia core-shell particles: 1 part by weight, graphene quantum dots: 0.1 parts by weight, composite dispersant: 2 parts by weight, light stabilizer: 0.5 parts by weight, toughening agent: 3 parts by weight; (2) The composite dispersant and deionized water are mixed at a mass ratio of 1:5, and then nano cerium dioxide and graphene quantum dots are added. After being subjected to high-pressure micro-jet circulation treatment at a pressure of 120MPa for 3 times, a stable nano slurry is obtained; Modified bismuth vanadate and nano-silica-zirconia core-shell particles were added sequentially, and then ground at 300 rpm for 1 hour. After grinding, KH570 silane coupling agent (0.5% by mass of the coating system) was added to the slurry, and stirred at 50°C for 1 hour to allow partial polymerization of silane on the particle surface, forming an organic-inorganic hybrid interface layer. Fluorocarbon resin emulsion, light stabilizer, and toughening agent were added to the slurry and mixed at 300 rpm for 10 minutes, then at 500 rpm for 15 minutes, and then vacuum degassed at 300 rpm for 20 minutes to obtain the bismuth vanadate coating.

[0118] XRD analysis confirmed that the activation product was pure-phase monoclinic BiVO4 with a grain size of 63 nm and a specific surface area of ​​31.5 m². 2 / g. TEM analysis showed that the ZnO layer thickness was approximately 10 nm, with a thickness difference within 2 nm, and the Al2O3 layer thickness was approximately 6 nm, with a thickness difference within 2 nm. XPS analysis detected Zn-O-Al interface bonds with a binding energy of approximately 1022.0 eV, indicating that the interface bonding was weaker than in Examples 1 and 2.

[0119] The prepared coating was sprayed onto a steel plate, and its performance was tested. The test results are as follows:

[0120] Optical performance: L=90.2, a=-1.7, b=90.4 (yellowness slightly reduced);

[0121] Mechanical properties: Pencil hardness 5H, adhesion grade 0;

[0122] Weather resistance: ΔE = 1.2 after 3000h aging of QUV-B.

[0123] Comparative Example 1

[0124] 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:

[0125] Optical properties: L=89.1, a=-1.7, b=89.5;

[0126] Mechanical properties: Pencil hardness 4H, adhesion grade 2;

[0127] Weather resistance: ΔE = 3.4 after 3000h aging of QUV-B.

[0128] Comparative Example 2

[0129] The coating system of this comparative example is similar in composition to that of Example 1. The main difference is that the bismuth vanadate used in Comparative Example 2 is a conventional wet-process coated bismuth vanadate, and the specific process is as follows:

[0130] Bi₂O₃ and NH₄VO₃ were mixed at a Bi / V molar ratio of 1:1.1 and calcined at 600℃ for 2 hours.

[0131] The calcined product was mixed with deionized water (mass ratio 1:20) to form a slurry, which was heated to 60°C. Zinc oxide nanopowder (D50=100nm) at 5% by mass of the calcined product was added, and the mixture was kept warm and stirred for 2 hours. The solid was collected by centrifugation and filtration and then dried.

[0132] The dried solid was mixed with deionized water (mass ratio 1:10) to form a slurry, which was heated to 70°C. Aluminum chloride at a mass ratio of 3% to the solid was added, and sodium hydroxide solution was added dropwise to adjust the pH to 8.5. The mixture was kept warm and stirred for 2 hours. The solid was collected by centrifugation and filtration and then dried to obtain wet-coated modified bismuth vanadate.

[0133] The coating was prepared and tested using the same method as in Example 1, and the test results are as follows:

[0134] Optical performance: L=88.4, a=-1.9, b=85.3 (significantly decreased yellowness);

[0135] Mechanical properties: Pencil hardness 3H, adhesion grade 2;

[0136] Weather resistance: After 1000 hours of aging, QUV-B showed a ΔE of 3.5, indicating severe powdering.

[0137] Comparative Example 3

[0138] The composition of the coating system in Comparative Example 3 is similar to that in Example 1, the main difference being that Comparative Example 3 did not contain nano-cerium dioxide. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0139] Optical properties: L=89.4, a=-1.5, b=89.8;

[0140] Mechanical properties: Pencil hardness 4H, adhesion grade 1;

[0141] Weather resistance: ΔE = 2.4 after 1000h aging of QUV-B.

[0142] Comparative Example 4

[0143] 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 nano-silica-zirconia core-shell particles. The coating was prepared and tested using the same method as in Example 1, and the results are as follows:

[0144] Optical properties: L=89.2, a=-1.1, b=90.1;

[0145] Mechanical properties: Pencil hardness 4H, adhesion grade 2;

[0146] Weather resistance: ΔE = 3.2 after aging QUV-B for 1000 hours.

[0147] 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 embodiments of the present invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of the embodiments of the present invention as described above, 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 embodiments of the present invention should be included within the protection scope of the embodiments of the present invention.

Claims

1. A bismuth vanadate coating, characterized in that, The product comprises the following components by weight: fluorocarbon resin emulsion: 45-55 parts by weight, wherein the fluorocarbon resin emulsion is a hydroxyl-containing fluorocarbon resin emulsion; modified bismuth vanadate: 30-40 parts by weight; nano-cerium dioxide: 2-4 parts by weight; nano-silica-zirconia core-shell particles: 1-2 parts by weight, wherein the nano-silica-zirconia core-shell particles have a silica core coated with a zirconia shell by atomic layer deposition, the shell thickness being 2-3 nm; graphene quantum dots: 0.1-0.3 parts by weight; composite dispersant: 2-3 parts by weight; light stabilizer: 0.5-1 parts by weight; toughening agent: 3-5 parts by weight. The modified bismuth vanadate is obtained by forming a zinc oxide-alumina composite coating layer on the surface of bismuth vanadate using mechanically activated bismuth vanadate as raw material, through plasma-assisted atomic layer deposition. The preparation of modified bismuth vanadate includes the following steps: Bismuth oxide, vanadium salt, and sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product. A zinc oxide layer is deposited on the surface of the activated product by atomic layer deposition. An aluminum oxide layer is deposited on the surface of a product with a zinc oxide layer by atomic layer deposition, using O2 plasma oxidation during the deposition of the aluminum oxide layer.

2. The bismuth vanadate coating according to claim 1, characterized in that, The hydroxyl-containing fluorocarbon resin emulsion has a fluorine content of ≥28%, a hydroxyl value of 35~45 mgKOH / g, and a solid content of 48%~52%. It is used in conjunction with a blocked isocyanate curing agent, and the amount of the curing agent added is 15%~20% of the resin solid content.

3. The bismuth vanadate coating according to claim 1, characterized in that, The nano-cerium dioxide is mesoporous nano-cerium dioxide prepared by the sol-gel method, with a pore size of 3~5nm and a specific surface area >150m². 2 / g, and modified with an aminosilane coupling agent; and / or The graphene quantum dots have a size of 3-5 nm and their surface is carboxylated.

4. The bismuth vanadate coating according to claim 1, characterized in that, The composite dispersant comprises comb-structured polycarboxylate ammonium salt, hyperbranched polyesteramine, and fluorocarbon-modified polysiloxane; and / or The light stabilizer is a compound of benzotriazole UV absorbers and hindered amine light stabilizers; and / or The toughening agent is composed of core-shell structured acrylate particles with a particle size of 80~100nm.

5. A method for preparing a bismuth vanadate coating, characterized in that, The method is used to prepare bismuth vanadate coatings as described in any one of claims 1-4 and includes the following steps: Step A: Preparation of modified bismuth vanadate, wherein the modified bismuth vanadate is obtained by using mechanically activated bismuth vanadate as raw material, and forming a zinc oxide-alumina composite coating layer on the surface of bismuth vanadate through plasma-assisted atomic layer deposition. The preparation of modified bismuth vanadate includes the following steps: Bismuth oxide, vanadium salt, and sensitizer are mixed in a set ratio and activated by high-energy ball milling under a protective atmosphere to obtain the activated product. A zinc oxide layer is deposited on the surface of the activated product by atomic layer deposition. An aluminum oxide layer is deposited on the surface of a product with a zinc oxide layer by atomic layer deposition, with O2 plasma oxidation used during the deposition of the aluminum oxide layer. Step B: Mix the composite dispersant with deionized water, then add nano-cerium dioxide and graphene quantum dots, and obtain a stable nano-slurry through high-pressure microfluidic treatment; Step C: Add the modified bismuth vanadate and nano-silica-zirconia core-shell particles sequentially to the nano slurry, and then grind it; Step D: After grinding, add a vinyl silane coupling agent to the slurry and stir to allow the silane to partially polymerize on the particle surface, forming an organic-inorganic hybrid interface layer; Step E: Add the fluorocarbon resin emulsion, light stabilizer, and toughening agent to the slurry prepared in step D, and continue stirring and mixing.

6. The method for preparing bismuth vanadate coating according to claim 5, characterized in that, The bismuth oxide and vanadium salt have a molar ratio of Bi / V of 1:1 to 1.15 based on bismuth and vanadium, respectively; the sensitizer is nano-zirconia, and the amount of nano-zirconia added is 0.5% to 2% of the total mass of bismuth oxide and vanadium salt; the ball milling speed is 400 to 500 rpm, the ball-to-material ratio is 12 to 15:1, and the ball milling time is 1.5 to 3 hours.

7. The method for preparing bismuth vanadate coating according to claim 5, characterized in that, Depositing a zinc oxide layer by atomic layer deposition (ALD) involves performing a first ALD cycle on the surface of the activated product, wherein the precursor of the first ALD cycle is diethylzinc, the oxygen source is water, and a single cycle includes a sequential diethylzinc pulse, a purge, and a water vapor pulse. The diethylzinc pulse duration is 0.05–0.2 s, the purge duration is 0.03–0.1 s, the water vapor pulse duration is 0.05–0.2 s, the number of cycles is 45–55, the thickness of the zinc oxide layer is 10–15 nm, and the substrate temperature is 100–180 °C. The deposition of an alumina layer by atomic layer deposition (ALD) includes performing a second ALD cycle on the surface of the product on which a zinc oxide layer has been deposited. The precursor for the second ALD cycle is trimethylaluminum. Each cycle includes a trimethylaluminum pulse, a purge, and an oxygen plasma pulse in sequence. The trimethylaluminum pulse duration is 0.04–0.06 s, the purge duration is 0.05–0.15 s, the oxygen plasma pulse duration is 0.1–0.3 s, the number of cycles is 25–35, and the thickness of the alumina layer is 5–10 nm.

8. The method for preparing bismuth vanadate coating according to claim 5, characterized in that, In step B, the pressure of the high-pressure microjets is 120~180MPa, and the number of cycles is 3~5. In step C, the grinding speed is 300~500 rpm and the time is 1~3 hours; In step D, the stirring temperature is 50~80℃ and the stirring time is 1~2 hours; Step E involves stirring in three stages: First stage: Mix at 300-500 rpm for 10-30 minutes; Second stage: Mix at 500-700 rpm for 15-25 minutes; Third stage: Vacuum degassing at 300~500rpm for 20~40min.

Images