A coating and a method for its preparation

Abstract

The application provides a coating and a preparation method thereof. The coating comprises a bismuth vanadate pigment modified by a plant polyphenol-protein complex, and the preparation method of the bismuth vanadate pigment comprises the following steps: A) mixing a plant polyphenol with a protein substance to obtain a complex modifier; B) mixing and stirring the complex modifier with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain a modified precursor; and C) calcining the precursor to obtain the bismuth vanadate pigment. The bismuth vanadate pigment modified by the plant polyphenol-protein complex provided by the application is applied to the coating, and by virtue of an innovative biomolecule synergistic modification technology, the acid and alkali resistance of the coating is significantly improved while the excellent chroma is maintained.

Description

Technical Field

[0001] This invention belongs to the field of functional coatings technology, specifically relating to a coating and its preparation method. Background Technology

[0002] Bismuth vanadate (BiVO4), an environmentally friendly inorganic yellow pigment, has broad application potential in high-end coatings, plastics, and ceramics due to its excellent lightfastness, high color saturation (b-value > 90), and low toxicity. However, traditional BiVO4 pigments still face three major technical bottlenecks in practical applications:

[0003] (1) Insufficient acid and alkali resistance

[0004] BiVO4 crystals readily undergo ion dissolution in strong acid (pH < 2) or strong alkaline (pH > 12) environments (e.g., Bi...). 3+ Acidic dissolution or VO4 3- The alkaline hydrolysis of HCl can cause the coating to chalk or fade. For example, commercially available BiVO4 pigments, after being soaked in 5% HCl for 240 hours, generally exhibit a color difference ΔE > 5, far exceeding the industrial standard of ΔE < 3.

[0005] (2) Limitations of surface modification technology

[0006] Existing modification methods mainly rely on two types of techniques:

[0007] Inorganic coating (such as SiO2 / Al2O3): Although it can improve weather resistance, it will lead to a decrease in color (b value decreases by 10-15%).

[0008] Single biomolecule modification (such as chitosan): Although environmentally friendly, it has poor thermal stability (decomposition temperature <300℃), making it difficult to meet the requirements of high-temperature processing.

[0009] (3) International monopoly on high-end product technology

[0010] Internationally competitive products achieve high performance through complex atomic layer deposition (ALD) technology, but their production cost is as high as $50-80 per kilogram, and the core technology patents are blocked.

[0011] Therefore, providing a bismuth vanadate coating with excellent acid and alkali resistance, color stability, and environmental friendliness has become a problem that needs to be solved. Summary of the Invention

[0012] In view of this, the technical problem to be solved by the present invention is to provide a coating and a method for preparing the same, wherein the coating provided by the present invention has excellent acid and alkali resistance, color stability and environmental friendliness.

[0013] This invention provides a coating comprising a bismuth vanadate pigment modified with a plant polyphenol-protein composite, wherein the preparation method of the bismuth vanadate pigment includes the following steps:

[0014] A) A composite modifier is obtained by mixing plant polyphenols with protein substances;

[0015] B) Mix the composite modifier with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain the modified precursor;

[0016] C) The precursor is calcined to obtain bismuth vanadate pigment.

[0017] Preferably, the plant polyphenols are selected from tannins;

[0018] The protein is selected from whey protein;

[0019] The mass ratio of plant polyphenols to protein substances is 1:1 to 1:3.

[0020] Preferably, step A) includes the following steps:

[0021] A1) Dissolve plant polyphenols and protein substances in a phosphate buffer solution to obtain a mixed solution;

[0022] A2) The mixed solution is heated in a water bath to obtain composite micelles.

[0023] Preferably, after step A2), the procedure further includes:

[0024] A3) The composite micelles are reacted with a crosslinking agent to obtain a composite modifier.

[0025] Preferably, the crosslinking agent is selected from genipin crosslinking agents;

[0026] The amount of crosslinking agent added to the composite micelles is 0.1wt% to 0.5wt%.

[0027] Preferably, in the precursor solution containing bismuth nitrate and ammonium metavanadate, the molar ratio of bismuth nitrate to ammonium metavanadate is 1:0.95-1:1.05;

[0028] The total concentration of metal ions in the precursor solution containing bismuth nitrate and ammonium metavanadate is 0.5~1.0 mol / L.

[0029] Preferably, in step B), the composite modifier is added to the precursor solution at 10-20 wt% of the theoretical yield of BiVO4;

[0030] The mixing and stirring process is carried out at a pH of 5.0-6.0, a temperature of 50-70℃, and a time of 2-3 hours.

[0031] Preferably, the calcination includes a low-temperature pretreatment stage and a high-temperature crystallization stage;

[0032] The low-temperature pretreatment stage includes: heating to 200~300℃ at a rate of 3-7℃ / min; and holding at that temperature for 1~2 hours.

[0033] The high-temperature crystallization stage includes: heating to 400~450℃ at a rate of 3-7℃ / min; calcining for 1~2 hours.

[0034] Preferably, the bismuth vanadate pigment includes a bismuth vanadate core and a coating layer covering the bismuth vanadate core;

[0035] The coating layer is formed by carbonization of a polyphenol-protein complex;

[0036] The thickness of the coating layer is 5~10nm.

[0037] Preferably, the coating comprises:

[0038] 40wt%~60wt% of base resin;

[0039] The above-mentioned bismuth vanadate pigments, at concentrations of 30wt% to 50wt%;

[0040] 5wt%~10wt% UV absorber;

[0041] 1wt%~3wt% dispersant;

[0042] Thickener at 0.5wt%~1.5wt%;

[0043] The remaining amount of solvent.

[0044] Preferably, the base resin is selected from fluorocarbon resins;

[0045] The ultraviolet absorber is selected from nano CeO2;

[0046] The dispersant is selected from biological dispersants, and the biological dispersant is selected from tea saponin dispersants;

[0047] The thickener is selected from guar gum;

[0048] The solvent is selected from water.

[0049] This invention also provides a method for preparing a coating, comprising the following steps:

[0050] Bismuth vanadate pigment, UV absorber and dispersant are added to solvent and mixed and dispersed, then base resin is added and mixed and stirred, and finally thickener is added, mixed and filtered and cured to eliminate bubbles and stabilize the system.

[0051] Compared with existing technologies, this invention provides a coating comprising a bismuth vanadate pigment based on a plant polyphenol-protein composite modification. The preparation method of the bismuth vanadate pigment includes the following steps: A) mixing plant polyphenols with protein-based substances to obtain a composite modifier; B) mixing and stirring the composite modifier with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain a modified precursor; C) calcining the precursor to obtain the bismuth vanadate pigment. The bismuth vanadate pigment based on a plant polyphenol-protein composite modification provided by this invention, through innovative biomolecular synergistic modification technology, significantly improves acid and alkali resistance while maintaining excellent color when applied to coatings. Detailed Implementation

[0052] This invention provides a coating comprising a bismuth vanadate pigment modified with a plant polyphenol-protein composite, wherein the preparation method of the bismuth vanadate pigment includes the following steps:

[0053] A) A composite modifier is obtained by mixing plant polyphenols with protein substances;

[0054] B) Mix the composite modifier with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain the modified precursor;

[0055] C) The precursor is calcined to obtain bismuth vanadate pigment.

[0056] This invention first prepares a composite modifier, specifically including the following steps:

[0057] A1) Dissolve plant polyphenols and protein substances in a phosphate buffer solution to obtain a mixed solution;

[0058] A2) The mixed solution is heated in a water bath to obtain composite micelles.

[0059] The plant polyphenols are selected from tannic acid, and the tannic acid is selected from one or more of hydrolyzable tannins, hydrolyzable tannins, and complex tannins; the protein is selected from whey protein, and the whey protein is selected from whey protein concentrate, whey protein isolate, and hydrolyzed whey protein.

[0060] The mass ratio of plant polyphenols to protein substances is 1:1 to 1:3, and can be any value between 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or 1:1 to 1:3.

[0061] The pH of the phosphate buffer solution is 5.5 to 6.5. The plant polyphenols and proteins account for 5 wt% to 10 wt% of the mixed solution, and can be any value between 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or 5 wt% to 10 wt%.

[0062] Then, the mixed solution is heated in a water bath to induce polyphenols and proteins to self-assemble into composite micelles through hydrophobic interactions and hydrogen bonds. The water bath heating temperature is 55-75°C, and can be any value between 55, 60, 65, 70, 75°C, or 55-75°C; the heating time is 1.5-3.5 hours, and can be any value between 1.5, 2, 2.5, 3, 3.5 hours, or 1.5-3.5 hours.

[0063] In some preferred embodiments of the present invention, the composite micelles are further functionalized, specifically by reacting the composite micelles with a crosslinking agent to obtain a composite modifier.

[0064] The crosslinking agent is selected from genipin crosslinking agent;

[0065] The amount of crosslinking agent added to the composite micelles is 0.1wt% to 0.5wt%, and can be any value between 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, or 0.1wt% to 0.5wt%.

[0066] The reaction temperature is 35-55℃, which can be 35, 40, 45, 50, or 55℃, or any value between 35-55℃, and the time is 30-90 min, which can be 30, 60, or 90 min, or any value between 30-90 min.

[0067] The particle size of the composite modifier was detected by dynamic light scattering (DLS) to ensure that it was distributed in the range of 50–200 nm.

[0068] Compared to unfunctionalized composite micelles, cross-linked micelles exhibit better structural stability, targeting ability, and functional diversity.

[0069] After obtaining the composite modifier, the composite modifier is mixed and stirred with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain the modified precursor.

[0070] In the precursor solution containing bismuth nitrate and ammonium metavanadate, the molar ratio of bismuth nitrate to ammonium metavanadate is 1:0.95-1:1.05, which can be any value between 1:0.95, 1:1, 1:1.05, or 1:0.95-1:1.05.

[0071] In the precursor solution containing bismuth nitrate and ammonium metavanadate, the total concentration of metal ions is 0.5~1.0 mol / L, which can be any value between 0.5, 0.6, 0.7, 0.8, 0.9, 1, or 0.5~1.0 mol / L. It is necessary to control the total concentration of metal ions to avoid excessively high concentrations that could lead to uneven precipitation.

[0072] The composite modifier is added to the precursor solution at 10-20 wt% of the theoretical yield of BiVO4, which can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or any value between 10 and 20 wt%.

[0073] The mixing and stirring process is carried out at a pH of 5.0–6.0 and a temperature of 50–70°C (which can be any value between 50, 55, 60, 65, 70, or 50–70°C) for 2–3 hours. After mixing and stirring, the phenolic hydroxyl groups of the polyphenols react with Bi... 3+ / VO4 3- Coordination bonds are formed, and the reaction process is monitored by UV-Vis spectroscopy. The reaction is terminated when the absorbance at 420 nm tends to stabilize.

[0074] The precursor was calcined to obtain bismuth vanadate pigment.

[0075] In some preferred embodiments of the present invention, the calcination includes a low-temperature pretreatment stage and a high-temperature crystallization stage;

[0076] The low-temperature pretreatment stage includes: heating to 200-300℃ at a rate of 3-7℃ / min; holding at this temperature for 1-2 hours; wherein the heating rate can be any value between 3, 4, 5, 6, 7, or 3-7℃ / min, and the low-temperature pretreatment temperature can be any value between 200, 220, 240, 250, 260, 280, 300, or 200-300℃. During the low-temperature pretreatment stage, whey protein undergoes moderate denaturation to form a three-dimensional network structure while retaining the active groups of tannins.

[0077] The high-temperature crystallization stage includes: heating to 400~450℃ at a rate of 3-7℃ / min; and calcining for 1~2 hours. The heating rate can be 3, 4, 5, 6, 7, or any value between 3-7℃ / min, and the high-temperature crystallization temperature can be 400, 410, 420, 430, 440, 450, or any value between 400~450℃. This high-temperature crystallization stage promotes complete crystallization of BiVO4, with XRD analysis showing a monoclinic phase purity >98%. During this stage, the polyphenol-protein complex carbonizes to form a 5~10 nm thick graphene-like protective layer.

[0078] In this invention, the bismuth vanadate pigment based on plant polyphenol-protein composite modification includes a bismuth vanadate core and a coating layer covering the bismuth vanadate core; the coating layer is formed by carbonization of the polyphenol-protein composite; the thickness of the coating layer is 5~10 nm.

[0079] In this invention, the coating comprises:

[0080] 40wt%~60wt% of base resin;

[0081] The above-mentioned bismuth vanadate pigments, at concentrations of 30wt% to 50wt%;

[0082] 5wt%~10wt% UV absorber;

[0083] 1wt%~3wt% dispersant;

[0084] Thickener at 0.5wt%~1.5wt%;

[0085] The remaining amount of solvent.

[0086] The coating provided by this invention comprises 40wt% to 60wt% of a base resin, which can be 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, or any value between 40wt% and 60wt%. The base resin is selected from fluorocarbon resins; the base resin is used to enhance adhesion and chemical resistance.

[0087] The coating provided by this invention further includes 30wt% to 50wt% of the aforementioned bismuth vanadate pigment, which can be 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, or any value between 30wt% and 50wt%. The bismuth vanadate pigment is used to provide color and weather resistance.

[0088] The coating provided by this invention further includes 5wt% to 10wt% of a UV absorber, which can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or any value between 5wt% and 10wt%. The UV absorber is selected from nano-CeO2. The UV absorber can improve the light stability of the coating.

[0089] The coating provided by this invention further includes 1wt% to 3wt% of a dispersant, which can be any value between 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or 1wt% to 3wt%. The dispersant is selected from biodispersants, specifically tea saponin dispersants. The dispersant can improve suspension stability.

[0090] The coating provided by this invention further includes 0.5wt% to 1.5wt% of a thickener, which can be any value between 0.5wt%, 0.7wt%, 0.9wt%, 1wt%, 1.2wt%, 1.4wt%, 1.5wt%, or 0.5wt% to 1.5wt%. The thickener is selected from guar gum. The thickener is used to adjust the rheological properties of the coating.

[0091] The coating provided by the present invention also includes a solvent, wherein the solvent is selected from water.

[0092] This invention also provides a method for preparing a coating, comprising the following steps:

[0093] Bismuth vanadate pigment, UV absorber and dispersant are added to solvent and mixed and dispersed, then base resin is added and mixed and stirred, and finally thickener is added, mixed and filtered and cured to eliminate bubbles and stabilize the system.

[0094] Specifically, bismuth vanadate pigment, ultraviolet absorber and dispersant are added to a solvent and subjected to ultrasonic treatment. The ultrasonic treatment power is 35-45 kHz, which can be any value between 35, 40, 45 or 35-45 kHz, and the time is 25-40 min, which can be any value between 25, 30, 35, 40 or 25-40 min.

[0095] Then add the base resin and mix. The stirring speed is 500-1000 rpm, which can be any value between 500, 750, 1000, or 500-1000 rpm. The time is 30-50 min, which can be any value between 30, 40, 50, or 30-50 min. The stirring temperature is controlled to be <40℃.

[0096] Next, a thickener is added. In this invention, the thickener is preferably added in stages until the viscosity reaches 2000~3000 mPa·s to obtain a mixed slurry.

[0097] Then, the mixed slurry is filtered and then sealed for maturation for 36-48 hours, which can be any value between 36, 40, 48, or 36-48 hours.

[0098] Finally, the bubbles are eliminated and the system is stabilized to obtain the coating.

[0099] In this invention, the catechol group of tannic acid forms a [Bi-O-C6H4] coordination structure with the surface of BiVO4, blocking H2O. + Erosion path; the porosity of the carbonized protein coating layer formed by gradient calcination is <5%, which can effectively block OH. - Diffusion, electrochemical impedance spectroscopy showed an increase in impedance value of 3 orders of magnitude.

[0100] Furthermore, the present invention can suppress the formation of oxygen vacancies through gradient calcination, resulting in a colorimetric b* value fluctuation of <1.5 (compared to ±3.0 in conventional processes); the synergistic effect of nano CeO2 and the carbonization products of polyphenols results in a ΔE of only 2.1 after QUV aging for 2000 hours.

[0101] This invention utilizes the catechol groups of tannic acid to chelate metal sites on the surface of BiVO4, forming an anti-H group. + / OH - The corrosion-resistant coordination protective layer, constructed by whey protein through hydrophobic interactions, creates steric hindrance, inhibiting particle aggregation (D50 < 100 nm). Combined with a gradient calcination process, the modified layer remains stable at 420℃ (TGA analysis shows a weight loss rate of < 5%). This invention fills the technological gap between extreme environmental stability and industrial production costs for bio-modified BiVO4 pigments, demonstrating excellent performance and a significant competitive advantage in the market.

[0102] To further understand the present invention, the coating and its preparation method provided by the present invention are described below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0103] Example 1: Preparation of BiVO4 coating modified with tannic acid-whey protein composite

[0104] Step 1: Preparation of biocomposite modifiers

[0105] Tannic acid and whey protein were mixed at a mass ratio of 1:3 and dissolved in phosphate buffer (8 wt%) at pH 6.0. The mixture was stirred in a water bath at 60°C for 2 h to form a composite micelle.

[0106] Add 0.3 wt% genipin crosslinking agent, react at 40℃ for 1 h, and the particle size was detected by DLS as 120±20 nm, thus obtaining the composite modifier.

[0107] Step 2: BiVO4 precursor modification

[0108] Bi(NO3)3·5H2O and NH4VO3 (1:1 molar ratio) were dissolved in deionized water (0.7 mol / L), 10 wt% composite modifier was added, the pH was adjusted to 5.5, and the mixture was stirred at 60℃ for 2.5 h. The absorbance at 420 nm was stable under UV monitoring.

[0109] Step 3: Gradient calcination

[0110] The temperature was first increased to 250℃ at 5℃ / min and held for 1.5 h, then increased to 420℃ at 5℃ / min and calcined for 1.5 h. XRD showed that the monoclinic phase BiVO4 had a purity of 98.5%, and HRTEM observed an 8 nm carbon layer.

[0111] Step 4: Coating Preparation

[0112] Mix by weight percentage: 35% modified BiVO4, 55% fluorocarbon resin, 8% nano CeO2, 2% tea saponin, 1% guar gum, and make up with deionized water. Disperse ultrasonically for 30 min, stir at 800 rpm for 40 min, adjust viscosity to 2500 mPa·s, and mature for 48 h.

[0113] Step 5: Test performance

[0114] Acid resistance (10% HCl, 24h): ΔE=1.3; Alkali resistance (10% NaOH, 24h): ΔE=1.9; QUV aging for 2000h: ΔE=2.3, b value 95.6.

[0115] Example 2: High-proportion modified and optimized weather-resistant coating

[0116] Step 1: Preparation of biocomposite modifiers

[0117] Tannic acid and whey protein were mixed at a mass ratio of 1:1 and dissolved in a pH 5.8 buffer solution (10 wt%), and stirred at 60°C for 2 h.

[0118] Add 0.5 wt% genipin for crosslinking, react at 40℃ for 1 h, and the DLS particle size is 80±15 nm to obtain the composite modifier.

[0119] Step 2: BiVO4 precursor modification

[0120] Bi(NO3)3·5H2O and NH4VO3 (1:1 molar ratio) were dissolved in deionized water to obtain a Bi / V precursor solution (1 mol / L). 20 wt% composite modifier was added, the pH was adjusted to 6.0, and the mixture was stirred at 70℃ for 3 h. The reaction endpoint was monitored by UV.

[0121] Step 3: Gradient calcination

[0122] The temperature was first increased to 300℃ at 3℃ / min and held for 2 h, then increased to 450℃ at 5℃ / min and calcined for 2 h. XRD showed that the monoclinic phase BiVO4 had a purity of 99%, and HRTEM showed a 10 nm carbon layer.

[0123] Step 4: Coating Preparation

[0124] Mix by weight percentage: 45% modified BiVO4, 45% fluorocarbon resin, 5.5% nano CeO2, 3% tea saponin, and 1.5% guar gum. Disperse ultrasonically for 35 min, stir at 800 rpm for 45 min, achieving a viscosity of 2800 mPa·s, and mature for 48 h.

[0125] Step 5: Test performance

[0126] Acid resistance (10% HCl, 24h): ΔE=1.1; Alkali resistance (10% NaOH, 24h): ΔE=1.7; QUV aging for 2000h: ΔE=1.9, b value 97.2.

[0127] Example 3: Low-cost industrial-grade coatings

[0128] Step 1: Simplification of Biocomposite Modifiers

[0129] Tannic acid and whey protein were mixed at a mass ratio of 1:2 and dissolved in phosphate buffer (6 wt%) at pH 6.0. The mixture was stirred at pH 6.5 at 60°C for 1.5 h without the addition of cross-linking agent. The particle size of the DLS was 150±30 nm.

[0130] Step 2: BiVO4 precursor modification

[0131] Bi(NO3)3·5H2O and NH4VO3 (1:1 molar ratio) were dissolved in a deionized water precursor (0.5 mol / L) and 15 wt% composite modifier were added. The mixture was stirred at pH 5.0 for 2 h at 50 °C.

[0132] Step 3: Gradient calcination

[0133] The temperature was first increased to 200℃ at 7℃ / min and held for 1 h, then increased to 400℃ at 5℃ / min and calcined for 1 h. XRD showed that the monoclinic phase BiVO4 had a purity of 98%, and HRTEM showed a carbon layer of 5 nm.

[0134] Step 4: Coating Preparation

[0135] Mix by weight percentage: 30% modified BiVO4, 60% fluorocarbon resin, 5% nano CeO2, 1% tea saponin, 0.5% guar gum, and make up with deionized water. Disperse ultrasonically for 35 min, stir at 700 rpm for 35 min, adjust viscosity to 2000 mPa·s, and mature for 36 h.

[0136] Step 5: Test performance

[0137] Acid resistance (10% HCl, 24h): ΔE=1.5; Alkali resistance (10% NaOH, 24h): ΔE=2.0; QUV aging for 2000h: ΔE=2.5, b value 96.2.

[0138] All three sets of examples are superior to traditional BiVO4 coatings (ΔE>5), and Example 2 has the best overall performance due to its high proportion of modification and optimized calcination.

[0139] Comparative Example 1 - Traditional BiVO4 Coatings

[0140] 1. Raw material mixing: Accurately weigh bismuth trioxide (Bi2O3) and vanadium pentoxide (V2O5) according to the stoichiometric ratio (2:1 molar ratio).

[0141] 2. Grinding: Grind the mixed powder in a mortar or ball mill for a long time and thoroughly to ensure that the raw materials are uniformly mixed and to increase the reaction contact area.

[0142] 3. Calcination / annealing: Place the uniformly mixed powder into a crucible and calcine it in an air atmosphere at 700°C for 4 hours in a muffle furnace.

[0143] 4. Post-processing: After the reaction is complete, the product is naturally cooled to room temperature and then ground again to obtain the final BiVO4 powder.

[0144] Comparative Example 2

[0145] Step 1: Preparation of biomodifiers

[0146] Whey protein was dissolved in pH 5.8 buffer (10 wt%) and stirred at 60°C for 2 h.

[0147] Add 0.5 wt% genipin for crosslinking, react at 40℃ for 1 h, and the DLS particle size is 80±15 nm to obtain the modifier.

[0148] Step 2: BiVO4 precursor modification

[0149] Bi(NO3)3·5H2O and NH4VO3 (1:1 molar ratio) were dissolved in deionized water to obtain a Bi / V precursor solution (1 mol / L). 20 wt% modifier was added, the pH was adjusted to 6.0, and the mixture was stirred at 70℃ for 3 h. The reaction endpoint was monitored by UV.

[0150] Step 3: Gradient calcination

[0151] The temperature was first increased to 300℃ at 3℃ / min and held for 2 h, then increased to 450℃ at 5℃ / min and calcined for 2 h. XRD showed that the monoclinic phase BiVO4 had a purity of 99%, and HRTEM showed a 10 nm carbon layer.

[0152] Step 4: Coating Preparation

[0153] Mix by weight percentage: 45% modified BiVO4, 45% fluorocarbon resin, 5.5% nano CeO2, 3% tea saponin, and 1.5% guar gum. Disperse ultrasonically for 35 min, stir at 800 rpm for 45 min, achieving a viscosity of 2800 mPa·s, and mature for 48 h.

[0154] Comparative Example 3

[0155] Step 1: Preparation of biocomposite modifiers

[0156] Tannic acid and whey protein were mixed at a mass ratio of 1:1 and dissolved in a pH 5.8 buffer solution (10 wt%), and stirred at 60°C for 2 h.

[0157] Add 0.5 wt% genipin for crosslinking, react at 40℃ for 1 h, and the DLS particle size is 80±15 nm to obtain the composite modifier.

[0158] Step 2: BiVO4 precursor modification

[0159] Bi(NO3)3·5H2O and NH4VO3 (1:1 molar ratio) were dissolved in deionized water to obtain a Bi / V precursor solution (1 mol / L). 20 wt% composite modifier was added, the pH was adjusted to 6.0, and the mixture was stirred at 70℃ for 3 h. The reaction endpoint was monitored by UV.

[0160] Step 3: Calcination

[0161] The temperature was increased to 400℃ at a heating rate of 6℃ / min and held for 3 h. XRD showed that the monoclinic phase BiVO4 purity was 99%, and HRTEM showed an 8 nm carbon layer.

[0162] Step 4: Coating Preparation

[0163] Mix by weight percentage: 45% modified BiVO4, 45% fluorocarbon resin, 5.5% nano CeO2, 3% tea saponin, and 1.5% guar gum. Disperse ultrasonically for 35 min, stir at 800 rpm for 45 min, achieving a viscosity of 2800 mPa·s, and mature for 48 h.

[0164] Test case

[0165] 1. Test method for acid resistance (10% HCl, ΔE):

[0166] (1) Sample preparation: The pigment to be tested and the base material (acrylic resin) are fully dispersed in a standard ratio to prepare a color paste or coating.

[0167] Use a bar coater or a scraper fineness meter to evenly coat the pigment onto a standard test card (white cardstock) to form a wet film of the specified thickness (100µm).

[0168] Completely cure / dry under standard conditions (23±2℃, 50±5% relative humidity).

[0169] (2) Reagent preparation: Prepare a 10% hydrochloric acid (HCl) aqueous solution using deionized water.

[0170] (3) Test procedure: Take a few drops (about 1.0 mL) of 10% HCl solution with a dropper or pipette and drop it onto the coating surface. Immediately cover with a watch glass or watch glass to form a sealed space to prevent the acid from evaporating too quickly. Let it stand at room temperature (23±2℃) for 24 hours.

[0171] At the same time, an untreated control sample was prepared.

[0172] (4) Result evaluation:

[0173] After the specified time has elapsed, gently absorb the residual acid with filter paper or cotton balls, rinse the test area gently with deionized water, and then let it air dry.

[0174] Use a colorimeter to measure the color difference ΔE between the treated area and the control sample (or the untreated area of ​​the sample).

[0175] 2. Test method for alkali resistance (10% NaOH, ΔE):

[0176] (1) Sample preparation: exactly the same as acid resistance test.

[0177] (2) Reagent preparation: Prepare a 10% sodium hydroxide (NaOH) aqueous solution using deionized water.

[0178] (3) Test process: The operation procedure is exactly the same as that of acid resistance test: add NaOH solution - cover the petri dish - let stand at room temperature for 24 hours.

[0179] (4) Result evaluation: exactly the same as the acid resistance test. After cleaning and drying, the ΔE value is measured and rated using a colorimeter.

[0180] 3. Test method for QUV aging for 2000 hours (ΔE)

[0181] (1) Sample preparation:

[0182] Make standard paint samples from the pigments and ensure there are enough of them, one portion for testing and the other portion as a control sample stored in a dark environment.

[0183] (2) Test conditions:

[0184] Equipment: QUV accelerated aging test chamber.

[0185] Light source: UVA-340 lamps are typically used, whose ultraviolet spectrum between 295nm and 365nm best simulates sunlight.

[0186] Test Cycle: A standard cycle is used, for example: Step 1 (Irradiation): Irradiate with ultraviolet light for 8 hours at a plate temperature of 60°C. Step 2 (Condensation): Condense (simulate dew) for 4 hours at 50°C. Repeat this cycle until the total duration reaches 2000 hours.

[0187] (3) Result evaluation:

[0188] Before the test begins, use a colorimeter to measure the initial color value of the sample.

[0189] At 500h, 1000h, 1500h, and finally 2000h, the samples were removed, the surfaces were cleaned, and their color values ​​were measured. The color change ΔE after 2000 hours of aging was calculated.

[0190] 4. Initial b-value testing method

[0191] (1) Sample preparation: The pigment is completely and uniformly dispersed in a neutral white base (acrylic resin). An opaque coating is prepared. This is the only method to obtain accurate and repeatable data.

[0192] (2) Measurement process: Place the prepared sample tightly against the measuring hole of the instrument.

[0193] Select the D65 standard light source (simulating sunlight) and a 10° standard observer angle. Trigger the measurement; the instrument will directly output the L*, a*, and b* values. Take at least three measurements at different locations on the sample and use the average value as the final result.

[0194] Table 1

[0195]

[0196] As shown in Table 1, this invention achieves controllable self-assembly of plant polyphenols-proteins on the surface of inorganic pigments. The gradient calcination process used is compatible with existing industrial equipment (such as rotary kilns). The results show that the obtained bismuth vanadate pigment has excellent color, acid and alkali resistance, and weather resistance. When applied to coatings, it can significantly improve the acid and alkali resistance and aging resistance of the coating while maintaining high color.

[0197] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A coating, characterized in that, The coating comprises a bismuth vanadate pigment based on plant polyphenol-protein composite modification, and the preparation method of the bismuth vanadate pigment includes the following steps: A1) Dissolve plant polyphenols and protein substances in a phosphate buffer solution to obtain a mixed solution; A2) The mixed solution is heated in a water bath to obtain composite micelles; A3) The composite micelles are reacted with a crosslinking agent to obtain a composite modifier, wherein the crosslinking agent is selected from genipin crosslinking agent; B) Mix the composite modifier with a precursor solution containing bismuth nitrate and ammonium metavanadate to obtain the modified precursor; C) The precursor is calcined to obtain bismuth vanadate pigment, wherein the calcination includes a low-temperature pretreatment stage and a high-temperature crystallization stage; The low-temperature pretreatment stage includes: heating to 200~300℃ at a rate of 3-7℃ / min; and holding at that temperature for 1~2 hours. The high-temperature crystallization stage includes: heating to 400~450℃ at a rate of 3-7℃ / min; calcining for 1~2 hours.

2. The coating according to claim 1, characterized in that, The plant polyphenols are selected from tannic acid; The protein is selected from whey protein; The mass ratio of plant polyphenols to protein substances is 1:1 to 1:

3.

3. The coating according to claim 1, characterized in that, The amount of crosslinking agent added to the composite micelles is 0.1wt% to 0.5wt%.

4. The coating according to claim 1, characterized in that, In the precursor solution containing bismuth nitrate and ammonium metavanadate, the molar ratio of bismuth nitrate to ammonium metavanadate is 1:0.95-1:1.05; The total concentration of metal ions in the precursor solution containing bismuth nitrate and ammonium metavanadate is 0.5~1.0 mol / L.

5. The coating according to claim 1, characterized in that, In step B), the composite modifier is added to the precursor solution at 10-20 wt% of the theoretical yield of BiVO4; The mixing and stirring process is carried out at a pH of 5.0-6.0, a temperature of 50-70℃, and a time of 2-3 hours.

6. The coating according to claim 1, characterized in that, The bismuth vanadate pigment includes a bismuth vanadate core and a coating layer covering the bismuth vanadate core; The coating layer is formed by carbonization of a polyphenol-protein complex; The thickness of the coating layer is 5~10nm.

7. The coating according to claim 1, characterized in that, The coating includes: 40wt%~60wt% of base resin; Bismuth vanadate pigments of 30wt%~50wt%; 5wt%~10wt% UV absorber; 1wt%~3wt% dispersant; Thickener at 0.5wt%~1.5wt%; The remaining amount of solvent.

8. The coating according to claim 7, characterized in that, The base resin is selected from fluorocarbon resins; The ultraviolet absorber is selected from nano CeO2; The dispersant is selected from biological dispersants, and the biological dispersant is selected from tea saponin dispersants; The thickener is selected from guar gum; The solvent is selected from water.

9. A method for preparing a coating as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Bismuth vanadate pigment, UV absorber and dispersant are added to solvent and mixed and dispersed, then base resin is added and mixed and stirred, and finally thickener is added, mixed and filtered and cured to eliminate bubbles and stabilize the system.

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