Preparation method of spherical TiO2-coated inorganic particle composite material and light-reflecting coating thereof

Abstract

The present invention discloses a preparation method of a spherical TiO2-coated inorganic particle composite material and a light-reflective coating thereof, belonging to the technical field of composite coatings. A preparation method of a spherical TiO2-coated inorganic particle composite material comprises the following steps: preparing rutile TiO2 balls; opening a feed valve of a fluidized bed, passing an inorganic particle core material into a silo of the fluidized bed; closing the feed valve, adjusting the height of the fluidized bed, starting a bottom gas pump, adjusting the air flow velocity to a set value, so that the bed particles enter a fluidized state; adding ethanol to the spherical TiO2 to obtain a TiO2 ethanol solution, regulating the viscosity and passing it into a liquid flow bin, setting the spray pressure and spraying rate, spraying the TiO2 ethanol solution onto the surface of the inorganic particle core material, maintaining a suitable inlet and outlet temperature, stopping spraying the TiO2 ethanol solution after reaching a predetermined thickness, continuing to maintain the air flow, and completely drying the particles to obtain a spherical TiO2-coated inorganic particle composite material. The present invention is used to improve the light reflectivity of the composite material in the 400-2500nm band.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a preparation method of a spherical TiO2-coated inorganic particle composite material and a light-reflecting coating thereof. Background Art

[0002] Due to its small particle size, large specific surface area, and high proportion of interfacial atoms, TiO2 possesses unique properties, such as excellent UV shielding, transparency and non-toxicity, unique color effects, and photocatalytic activity. Therefore, TiO2 has broad application prospects in the automotive industry, sunscreen cosmetics, advanced coatings, wastewater treatment and sterilization, environmental protection, adsorbents, and functional ceramic materials. Currently, TiO2 is prepared by a variety of methods, mainly divided into gas-phase and liquid-phase methods. These methods require different process control conditions, resulting in different product properties.

[0003] In the prior art, TiO2 is often used alone as one of the components of exterior wall reflective coatings, such as CN1749331A, a solar thermal exterior wall reflective coating, CN110684411A, a TiO2 reflective thermal insulation topcoat with catalytic properties and its preparation and application, and CN103834216A, an exterior wall thermal insulation reflective coating additive.

[0004] With the development of science and technology and the diversification of needs, coatings prepared from traditional single materials can no longer meet current application requirements in terms of certain properties. To this end, TiO2 is compounded with other components with reflective properties through a specific process. For example, CN114316695A prepares microspheres with a reflective shell by combining glass powder and TiO2. The preparation steps include: S11, stirring the glass powder and TiO2 in a water bath at a temperature of 20-30°C and a rotation speed of 2000r / min-3000r / min to obtain a modified functional filler; S12, mixing a dispersion stabilizer, an emulsifier, and water to obtain a suspension polymerization liquid; S13, mixing and emulsifying the obtained filler and liquid to form a suspension solution, stirring the mixture in a high-pressure reactor to achieve suspension polymerization, and filtering and drying to obtain highly reflective microspheres. For example, CN116162387A sequentially coats the surface of glass microspheres with TiO2 layers and SiO2 layers. The preparation method is as follows: titanium tetrachloride is added to a suspension of glass microspheres, the pH is adjusted to 3-5, and the mixture is stirred to produce glass microspheres coated with a TiO2 layer. Alkali metal silicate is then added to the suspension of glass microspheres coated with the TiO2 layer, the pH is adjusted to 6-8, and the mixture is stirred to produce glass microspheres coated with a SiO2 layer. These technologies improve the light reflectivity of the coating to a certain extent by combining TiO2 with different light reflective materials and preparing the coating. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a spherical TiO2-coated inorganic particle composite material to improve the light reflection performance of the composite material in the 400-2500nm band.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for preparing a spherical TiO2-coated inorganic particle composite material comprises the following steps:

[0008] S01: Preparation of rutile TiO2 spheres: Titanium tetraisopropoxide was added to anhydrous ethanol and glacial acetic acid, stirred, and subjected to hydrothermal reaction in a reactor. After the reaction, the precipitate was centrifuged and washed twice with distilled water and anhydrous ethanol respectively. After ultrasonication, the precipitate was dried and calcined to obtain rutile TiO2 spheres;

[0009] S02: Preparation of spherical TiO2-coated inorganic particle composite materials: Open the feed valve of the fluidized bed and pass the inorganic particle core material into the silo of the fluidized bed; close the feed valve, adjust the height of the fluidized bed, start the bottom gas pump, adjust to the set air flow velocity, and make the bed particles enter a fluidized state; add the TiO2 balls to ethanol to obtain a TiO2 ethanol solution, adjust the viscosity and pass it into the liquid flow bin, set the spray pressure and spray rate, spray the TiO2 ethanol solution onto the surface of the inorganic particle core material, maintain appropriate inlet and outlet temperatures, stop spraying the TiO2 ethanol solution after reaching a predetermined thickness, continue to maintain the air flow, and completely dry the particles to obtain a spherical TiO2-coated inorganic particle composite material.

[0010] Optionally, in step S01, the weight of titanium tetraisopropoxide is 0.165-0.495 g, the volume of anhydrous ethanol is 50-100 mL, and the volume of glacial acetic acid is 5-10 mL.

[0011] Optionally, the temperature of the hydrothermal reaction in step S01 is 150° C.-200° C., and the reaction time is 2-4 hours.

[0012] Optionally, the drying temperature in step S01 is 60-80° C. and the drying time is 12-24 hours, and the calcination temperature is 900-950° C. and the drying time is 2-4 hours.

[0013] Optionally, the inorganic particle core material in step S02 is at least one of silica, alumina, and spinel, and has a particle size of 100-700 nm.

[0014] Optionally, in step S02, the height of the fluidized bed is 20-60 cm, the bed pressure is 4.5-5.5 MPa, and the air flow velocity is 0.1-0.5 m / s.

[0015] Optionally, the mass concentration of TiO2 balls in the TiO2 ethanol solution in step S02 is 60%, and the viscosity of the TiO2 ethanol solution is regulated by the following raw materials, including at least one of polyacrylate, polyacrylic amine and polyvinyl alcohol.

[0016] Optionally, in step S02, the viscosity of the TiO2 ethanol solution is adjusted to 800-1000 mPa·s, the spray pressure is 0.2-0.5 MPa, the spray rate is 10-100 L / h; the inlet temperature is 30-80°C, the outlet temperature is 80-120°C; and the spraying time is controlled at 30-40 min.

[0017] In a second aspect, the present invention provides a spherical TiO2-coated inorganic particle composite material obtained by the preparation method of the above-mentioned spherical TiO2-coated inorganic particle composite material.

[0018] In a third aspect, the present invention also provides the use of the above-mentioned spherical TiO2-coated inorganic particle composite material in light-reflective coatings.

[0019] Optionally, the preparation method of the light-reflective coating includes the following steps: providing an oligomer emulsion, a thickener, a cross-linking agent, a dispersant, a defoaming agent, tetraethyl orthosilicate, glacial acetic acid, anhydrous ethanol and water; taking the spherical TiO2-coated inorganic particle composite material and mixing it with water, a dispersant and a defoaming agent to obtain component A; mixing and reacting water, anhydrous ethanol, glacial acetic acid and tetraethyl orthosilicate to obtain component B; mixing and reacting the oligomer emulsion, a thickener and a cross-linking agent to obtain component C; mixing component A, component B and component C in a volume ratio of 6:3:1, adjusting the viscosity and pH value, and obtaining the coating.

[0020] Optionally, the ratio of the raw materials in the component A is as follows: 10-20 g of spherical TiO2-coated inorganic particle composite material, 1-5 g of dispersant, 1-10 g of defoaming agent, and 20-40 g of water;

[0021] The proportions of the raw materials in component B are as follows: 200-300 g of water, 20-40 mL of anhydrous ethanol, 1-5 mL of glacial acetic acid, and 1-5 mL of ethyl orthosilicate;

[0022] The proportions of the raw materials in the component C are as follows: 200-400 g of oligomer emulsion, 60-80 g of thickener, and 1-10 g of cross-linking agent.

[0023] Optionally, the dispersant is selected from at least one of polyethylene glycol trimethoxysilyl propyl ether, polydimethylsiloxane, epoxy silane, and aminosilane;

[0024] The defoaming agent is selected from one or a combination of two or more of hexamethylenetetramine, urea, ammonia water and ammonium carbonate;

[0025] The oligomer emulsion is selected from one or two combinations of 3-aminopropyltriethoxysilane, modified polyvinyl alcohol, and silicone-modified polyurethane;

[0026] The thickener is selected from one or a combination of lauramidopropyl betaine, sodium carboxymethyl cellulose and sodium polyacrylate;

[0027] The cross-linking agent is selected from one or a combination of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0028] Optionally, regulating the viscosity and pH value includes: adjusting the viscosity to 800-1000 mPa·s and the pH value to 7-8.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention prepares a spherical TiO2-coated inorganic particle composite material through the above-mentioned technical solution. First, rutile TiO2 balls are prepared. Then, the prepared rutile TiO2 balls are sprayed onto the surface of an inorganic particle core material through a fluidized bed to form a spherical TiO2-coated inorganic particle composite material. The TiO2-coated inorganic particle composite material has a spherical structure, which can increase the specific surface area of ​​TiO2 and improve the reflectivity of light. At the same time, the spherical structure helps to reduce light scattering and improve the directionality of light reflection. The TiO2 spherical particles are coated onto the surface of an inorganic particle core material, such as SiO2, Al2O3, spinel, etc., through fluidized bed technology. When multiple spheres are aggregated into a large sphere, the surface of the new sphere becomes smoother, the directionality of light reflection becomes stronger, and it tends to be mirror reflection, making the reflected light more concentrated. Secondly, TiO2 and inorganic particles have different refractive indices and light scattering properties. When they are compounded together, a multi-level scattering structure can be formed, which increases the scattering path of light inside the material, thereby significantly enhancing its reflection effect within a specific wavelength range; the spectral response range of a single spherical TiO2 may be narrow, while the composite material can, through the synergistic effect of different components, broaden its response range to light, including ultraviolet light, visible light and even near-infrared light regions, thereby improving overall reflection performance. In addition, the composite material prepared by the present invention coats spherical TiO2 on inorganic particles by coating, thereby improving the stability of spherical TiO2 in harsh environments, such as acid and alkali corrosion resistance, thereby maintaining its long-term reflection effect; in addition to the reflection effect, the spherical TiO2 composite material may also have other additional functions, such as photocatalytic performance, thermal insulation performance, etc., and these functional enhancements can further expand its application areas.

[0031] The present invention adopts spherical TiO2 coated inorganic particle composite material to prepare solar infrared light reflective coating and proves that the coating has a solar light reflectance of more than 80% and an infrared light reflectance of more than 80%, showing good light reflectance performance.

[0032] The present invention is with titanium tetraisopropoxide, dehydrated alcohol and glacial acetic acid as reactant, by controlling reaction condition, purification step and calcining condition thereof, obtains rutile TiO ball, gained rutile TiO ball purity is high, and granularity is suitable, is conducive to improving coating effect.In follow-up fluidized bed spraying process, suitable granularity helps to improve uniformity and the compactness of coating, as granularity is too little and may cause powder agglomeration, affects coating effect, the TiO prepared by the present invention under above-mentioned raw material composition and production condition thereof ball is more suitable, is conducive to improving coating effect, makes the effect of prepared coating more remarkable.In addition, the high-purity TiO prepared by the present invention ball can reduce the impact of impurity on coating process and final product performance.

[0033] The present invention utilizes fluidized bed technology to spray rutile TiO2 spheres onto the surface of inorganic particles, forming a spherical TiO2-coated inorganic particle composite material with the inorganic particles as the core and the spherical TiO2 as the shell. 1) The TiO2 spheres are added to ethanol to promote colloidal dispersion of the TiO2 particles. The solution is then adjusted to an appropriate viscosity using at least one of polyacrylate, polyacrylic amine, and polyvinyl alcohol, thereby enhancing the coating effect. 2) Air is used as the fluidizing gas, with the fluidized bed height adjusted to 20-60 cm and the bed pressure to 4.5-5.5 MPa. This not only prevents chemical reactions with the reactants but also maintains a well-fluidized state for the inorganic particle core, ensuring uniform coating. 3) The airflow velocity is set at 0.1-0.5 m / s. Fluidization velocity is a key parameter in fluidized bed operation. If the fluidization velocity is too low, the particles will not be fully fluidized, resulting in uneven coating. If the fluidization velocity is too high, the particles may be carried out of the fluidized bed by the gas, causing material loss and environmental pollution, while also compromising the coating effect. The fluidization velocity of the present invention represents an optimal fluidization velocity range determined through repeated experimentation. 4) Temperature also has a significant impact on the coating process, including the chemical reaction rate of the spherical TiO2 and the adhesion of the coating. If the temperature is too low, the spherical TiO2 cannot fully react with the surface of the inorganic particle core, resulting in a weak coating; if the temperature is too high, it may cause problems such as TiO2 crystal transformation, particle agglomeration, or core deformation. Therefore, based on the characteristics of the TiO2 and inorganic particle core, the present invention precisely controls the fluidized bed inlet temperature to 30-80°C and the outlet temperature to 80-120°C. This shows that the present invention uses a spraying method to spray the TiO2 sphere solution onto the surface of the fluidized inorganic particle core via a spray gun. Unlike vapor deposition methods, this method not only has milder operating conditions, but also produces a spherical TiO2-coated inorganic particle composite material that facilitates the formation of coatings with improved light reflectivity and multifunctionality. The addition of inorganic particles can make up for the objective shortcomings of the sole use of TiO2 and improve the overall performance of the coating. By compounding spherical TiO2 with inorganic particles, a coating with special structure and performance is formed. It not only retains the light reflection characteristics of spherical TiO2, but also utilizes the reinforcement, toughening, heat insulation and other functions of inorganic particles to achieve performance complementarity and improvement.

[0034] The present invention uses the prepared spherical TiO2-coated inorganic particle composite material to prepare a coating, comprising: ① mixing the spherical TiO2-coated inorganic particle composite material with a dispersant, a defoamer, and water, and sand-milling to obtain component A; the selected dispersant, upon hydrolysis, produces silanol groups, the groups carried by which have the characteristics of a polymer dispersant and can be well cross-linked with the spherical TiO2; and after sand-milling, a mixed dispersion having stable performance, a low number of solids, and a high solid content is obtained, ensuring that the spherical TiO2-coated inorganic particle composite material is uniformly dispersed in the system, providing good basic performance for the coating. ② mixing and reacting water, anhydrous ethanol, glacial acetic acid, and ethyl orthosilicate to obtain component B, wherein the ethyl orthosilicate is slowly hydrolyzed to form a stable semi-hydrolyzed liquid. In this state, the material is not prone to large-scale polymerization and precipitation, providing good film-forming properties for the coating, enabling the coating to form a uniform film on the substrate surface, ensuring the integrity and stability of the coating. ③ The oligomer emulsion, thickener, and crosslinker are mixed and reacted to obtain component C. The selected oligomer emulsion has a certain degree of polymerization and rich silanol groups. The solvent is water and the solid content is 25-35%wt. The selected thickener can reduce the surface tension of water, making the material more easily wetted. The synergistic effect of the two can increase the hydrophilicity of the coating. The increased hydrophilicity makes the coating more susceptible to water contact during use. For example, during the self-cleaning process, water can spread more quickly and fully on the coating surface, removing dirt. The crosslinker causes the oligomer emulsion and thickener to undergo a dehydration condensation reaction, fixing the highly hydrophilic thickener in the coating. Even under long-term use or in complex environments, the coating can maintain its hydrophilicity, antibacterial and antistatic properties. As a result, the hydrolysis product of the ethyl orthosilicate in component B can undergo a crosslinking polymerization reaction with the components in component A and the groups in component C, further enhancing the structural strength and stability of the coating. For example, during the curing process, the crosslinking reaction forms a three-dimensional network structure in the coating, improving the coating's hardness, wear resistance, and corrosion resistance. In summary, component A, component B and component C each play an important role in the coating system, and through cross-linking reactions, synergistic dispersion and other modes of action, they achieve synergistic enhancement of coating performance, making the coating have excellent self-cleaning function, reflective performance, hydrophilicity, stability and durability.

[0035] The light-reflecting coating prepared by the present invention has a wide range of application prospects, and its specific applications are as follows:

[0036] In the architectural field, it is primarily used as an exterior wall coating. Its high reflectivity reduces the building's absorption of solar heat and lowers indoor temperatures. The addition of inorganic particles enhances the coating's wear and corrosion resistance, extending the life of the exterior wall. It can also be used as a roof coating, where its excellent waterproof properties effectively prevent rainwater penetration and protect the roof structure.

[0037] In the field of transportation, it is mainly used as road marking paint. Its reflective properties help improve the visibility of road markings at night or in low visibility conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 : Schematic diagram of TiO2 balls prepared by the present invention;

[0040] Figure 2 : Schematic diagram of spherical TiO2-coated SiO2 composite material particles prepared by the present invention;

[0041] Figure 3 : Schematic diagram of spherical TiO2-coated Al2O3 composite material particles prepared by the present invention;

[0042] Figure 4 : Schematic diagram of spherical TiO2-coated spinel composite material particles prepared by the present invention;

[0043] Figure 5 : Flowchart of the spherical TiO2-coated inorganic particle composite material of the present invention;

[0044] Figure 6 : Spectral reflectance curves of spherical TiO2 coated Al2O3 composite material (TiO2 / Al2O3) and commercially available P25 powder. DETAILED DESCRIPTION

[0045] In order to better understand the present invention, the content of the present invention is further clearly set forth below in conjunction with the examples, but the protection content of the present invention is not limited to the following examples. In the following description, a large number of specific details are provided in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0046] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0047] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain other unspecified components except inevitable impurities.

[0048] The following examples 1-3 are specific implementation plans for preparing TiO2 balls.

[0049] Example 1: 0.165 g of titanium tetraisopropoxide was added to 80 mL of anhydrous ethanol and 8 mL of glacial acetic acid and stirred for 10 minutes. The solution was poured into a 150 mL polyethylene reactor and reacted at 180°C for 3 hours. After the reaction, the precipitate was centrifuged at 8000 rpm for 3 minutes, washed twice with distilled water and then with anhydrous ethanol. After ultrasonication, the precipitate was dried in a 70°C oven for 12 hours and calcined at 900°C for 4 hours to obtain TiO2 spheres.

[0050] Example 2: 0.330 g of titanium tetraisopropoxide was added to 80 mL of anhydrous ethanol and 8 mL of glacial acetic acid and stirred for 10 minutes. The solution was poured into a 150 mL polyethylene reactor and reacted at 150°C for 4 hours. After the reaction, the precipitate was centrifuged at 8000 rpm for 3 minutes, washed twice with distilled water and twice with anhydrous ethanol. After ultrasonication, the precipitate was dried in an oven at 65°C for 20 hours and calcined at 920°C for 3 hours to obtain TiO2 spheres.

[0051] Example 3: 0.495 g of titanium tetraisopropoxide was added to 80 mL of anhydrous ethanol and 8 mL of glacial acetic acid and stirred for 10 minutes. The solution was poured into a 150 mL polyethylene reactor and reacted at 200°C for 2 hours. After the reaction, the precipitate was centrifuged at 8000 rpm for 3 minutes, washed twice with distilled water and then with anhydrous ethanol. After ultrasonication, the precipitate was dried in a 75°C oven for 15 hours and calcined at 950°C for 2 hours to obtain TiO2 spheres.

[0052] The surface morphology of the TiO2 spheres prepared in the embodiment of the present invention was characterized by Hitachi SU8100. Figure 1 As shown in Figure 3, the TiO2 spheres are regular spherical with a diameter greater than 1000 nm.

[0053] The following Examples 4-6 are specific implementation plans for preparing spherical TiO2-coated inorganic particle composite materials.

[0054] See also Figure 5 The steps of preparing the spherical TiO2-coated inorganic particle composite material of the present invention include: feeding, feeding completion, flowing, circulating flow, spraying and loading completion. The detailed implementation plan is shown in Examples 4-6.

[0055] Example 4: SiO2 particles with a particle size of 200 nm were selected, washed and dried with distilled water and anhydrous ethanol, and set aside; the feed valve of the fluidized bed was opened, and the dried inorganic particle core material was introduced into the hopper of the fluidized bed; the feed valve was closed, the height of the fluidized bed was adjusted to 20 cm, the bottom gas pump was started, and the air flow velocity was adjusted to 0.1 m / s to fluidize the bed particles; the TiO2 prepared in Example 1 was added to ethanol to prepare a 60% TiO2 ethanol solution, and the viscosity of the solution was measured using a viscometer. The viscosity of the TiO2 solution was adjusted to 800 mPa·s using polyacrylate and then introduced into a liquid flow chamber; the spray pressure was set to 0.5 MPa and the spray rate was set to 60 L / h; when spraying the TiO2 solution, the inlet temperature was maintained at 60°C and the outlet temperature was maintained at 105°C to promote the evaporation and solidification of the solution, and the spraying of the TiO2 ethanol solution was stopped when the predetermined thickness was reached; after stopping the spraying, the air flow was continued to ensure that the particles were completely dried; after the coating was completed, the spherical TiO2-coated SiO2 composite material particles were discharged through the discharge port.

[0056] The surface morphology of the spherical TiO2-coated SiO2 composite material prepared in this example was characterized by a German ZEISS GeminiSEM 300. Figure 2 As shown, the spherical TiO2-coated SiO2 composite material particles are regular spherical and have a size of micrometer level.

[0057] Example 5: Al2O3 particles with a particle size of 400 μm were selected, washed and dried with distilled water and anhydrous ethanol, and set aside; the feed valve of the fluidized bed was opened, and the dried inorganic particle core material was introduced into the hopper of the fluidized bed; the feed valve was closed, the height of the fluidized bed was adjusted to 40 cm, the bottom gas pump was started, and the air flow velocity was adjusted to 0.3 m / s to fluidize the bed particles; the TiO2 balls prepared in Example 2 were added to ethanol to prepare a 60% TiO2 ethanol solution, and the viscosity of the solution was measured using a viscometer. The viscosity of the TiO2 solution was adjusted to 905 mPa·s using polyacrylic acid amine and then introduced into a liquid flow chamber. The spray pressure was set to 0.3 MPa and the spray rate was set to 100 L / h. When spraying the TiO2 solution, the inlet temperature was maintained at 80°C and the outlet temperature was maintained at 120°C to promote evaporation and solidification of the solution. When the predetermined thickness was reached, the spraying of the TiO2 ethanol solution was stopped. After the spraying was stopped, the air flow was continued to ensure that the particles were completely dried. After the coating was completed, the spherical TiO2-coated Al2O3 composite particles were discharged through a discharge port.

[0058] The surface morphology of the spherical TiO2-coated Al2O3 composite material prepared in this example was characterized by a German ZEISS GeminiSEM 300. Figure 3 As shown, the spherical TiO2-coated Al2O3 composite material is a regular sphere with a size of micrometer level.

[0059] Example 6: Select spinel particles with a particle size of 600nm, use distilled water and anhydrous ethanol to wash and dry them, and set them aside; open the feed valve of the fluidized bed, and pass the dried inorganic particle core material into the hopper of the fluidized bed; close the feed valve, adjust the height of the fluidized bed to 60cm, start the bottom gas pump, adjust the air flow rate to 0.1m / s, and make the bed particles enter a fluidized state; add ethanol to the TiO2 balls prepared in Example 3 to prepare a 60% TiO2 ethanol solution, and use a viscometer to measure the viscosity of the solution , use polyvinyl alcohol to adjust the viscosity to 1000mPa·s and then pass it into the liquid flow chamber; set the spray pressure to 0.2Mpa and the spray rate to 10L / h; when spraying the TiO2 solution, maintain the inlet temperature at 30℃ and the outlet temperature at 80℃ to promote the evaporation and solidification of the solution. When the predetermined thickness is reached, stop spraying the TiO2 ethanol solution; after stopping spraying, continue to maintain the air flow to ensure that the particles are completely dry; after completing the coating, the spherical TiO2 coated spinel composite material particles are discharged through the discharge port.

[0060] The surface morphology of the spherical TiO2-coated spinel composite material prepared in this example was characterized by a German ZEISS GeminiSEM 300. Figure 4 As shown, the spherical TiO2-coated spinel composite material is a regular sphere with a size of micrometer level.

[0061] The following Examples 7-10 are specific implementation plans for preparing coatings.

[0062] Example 7: 30 g of water, 3 g of polyethylene glycol trimethoxysilyl propyl ether and 5 g of hexamethylenetetramine were mixed uniformly under stirring, 10 g of the spherical TiO2-coated SiO2 composite material prepared in Example 4 was added, and after being fully dispersed, sand milled to obtain a uniform component A;

[0063] Take 250g of water, 25mL of anhydrous ethanol and 3mL of glacial acetic acid respectively, mix them evenly, and slowly add 2.7mL of ethyl orthosilicate while stirring to carry out a slow hydrolysis reaction to obtain component B with cross-linking function;

[0064] Take 300g of 3-aminopropyltriethoxysilane, add 70g of laurylamidopropyl betaine, 1.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 1.5g of N-hydroxysuccinimide under stirring, and react at 60°C for 2h to obtain component C;

[0065] The prepared component A, component B, and component C were fully stirred and mixed in a volume ratio of 6:3:1, and the viscosity of the mixture was adjusted to 800 mPa·s and the pH value was adjusted to 7.0. After mixing evenly, a finished reflective coating was obtained.

[0066] Example 8: 20 g of water, 1 g of polydimethylsiloxane, and 1 g of urea were mixed uniformly under stirring, and 12 g of the spherical TiO2-coated Al2O3 composite material prepared in Example 5 was added. After being fully dispersed, the mixture was sand-milled to obtain a uniform component A.

[0067] Take 200g of water, 20mL of anhydrous ethanol and 1mL of glacial acetic acid, mix them evenly, and slowly add 1mL of ethyl orthosilicate while stirring to carry out a slow hydrolysis reaction to obtain component B with cross-linking function;

[0068] Take 100g of 3-aminopropyltriethoxysilane and 100g of silicone-modified polyvinyl alcohol, add 40g of laurylamidopropyl betaine, 20g of sodium polyacrylate and 1g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide under stirring, and react at 60°C for 2h to obtain component C;

[0069] The prepared component A, component B, and component C were fully stirred and mixed in a volume ratio of 6:3:1, and the viscosity of the mixture was adjusted to 900 mPa·s and the pH value was adjusted to 7.8. After mixing evenly, a finished reflective coating was obtained.

[0070] Example 9: 40 g of water, 5 g of epoxy silane and 10 g of ammonia water were mixed uniformly under stirring, 20 g of the spherical TiO2-coated spinel composite material prepared in Example 6 was added, and after being fully dispersed, sand milling was performed to obtain a uniform component A;

[0071] Take 300g water, 40mL anhydrous ethanol, and 5mL glacial acetic acid and mix them evenly. Slowly add 5mL of ethyl orthosilicate while stirring to carry out a slow hydrolysis reaction to obtain component B with cross-linking function;

[0072] 400 g of silicone-modified polyurethane emulsion was added with stirring to 80 g of sodium carboxymethyl cellulose and 10 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and the mixture was reacted at 60° C. for 2 h to obtain component C.

[0073] The prepared component A, component B, and component C were fully stirred and mixed in a volume ratio of 6:3:1, and the viscosity of the mixture was adjusted to 1000 mPa·s and the pH value was adjusted to 8.5. After mixing evenly, a finished reflective coating was obtained.

[0074] Example 10: 35 g of water, 4 g of aminosilane and 8 g of ammonium carbonate were mixed uniformly under stirring, 18 g of the spherical TiO2-coated SiO2 composite material prepared in Example 4 was added, and after being fully dispersed, sand milled to obtain a uniform component A;

[0075] 280 g of water, 35 mL of anhydrous ethanol, and 4 mL of glacial acetic acid were taken respectively, mixed evenly, and 4 mL of ethyl orthosilicate was slowly added under stirring to perform a slow hydrolysis reaction to obtain component B with a cross-linking function;

[0076] Take 270g of 3-aminopropyltriethoxysilane, add 75g of sodium polyacrylate and 7g of N-hydroxysuccinimide under stirring, and react at 60°C for 2h to obtain component C;

[0077] The prepared component A, component B, and component C were fully stirred and mixed in a volume ratio of 6:3:1, and the viscosity of the mixture was adjusted to 950 mPa·s and the pH value was 8.0. After mixing evenly, a finished reflective coating was obtained.

[0078] The following Comparative Examples 1-8 are comparative implementation plans.

[0079] Comparative Example 1: This comparative example differs from Example 7 only in that the spherical TiO2-coated SiO2 composite material is replaced by the TiO2 spheres prepared in Example 1.

[0080] Comparative Example 2: This comparative example differs from Example 7 only in that the spherical TiO2-coated SiO2 composite material is replaced with commercially available P25 powder (titanium dioxide).

[0081] Comparative Example 3: This comparative example differs from Example 7 only in that the spherical TiO2-coated SiO2 composite material is replaced with SiO2 particles with a particle size of 200 nm.

[0082] Comparative Example 4: This comparative example differs from Example 8 only in that the spherical TiO2-coated SiO2 composite material is replaced with Al2O3 particles with a particle size of 400 nm.

[0083] Comparative Example 5: This comparative example differs from Example 9 only in that the spherical TiO2-coated SiO2 composite material is replaced with spinel particles with a particle size of 600 nm.

[0084] Comparative Example 6: This comparative example is different from Example 4 in that the SiO2-TiO2 composite particles are prepared by a sol-gel method, with reference to Example 1 in CN112972275A, specifically: 0.4g of polyvinylpyrrolidone (PVP) is dissolved in anhydrous ethanol, 0.3g of TiO2 balls are added, and the mixture is dispersed under an ultrasonic cell disruptor for 20min. Under electric stirring at 350r / min, 30mL of anhydrous ethanol solution of tetraethyl orthosilicate (TEOS) is added dropwise, and ammonia water is added to control the pH to 9.0. The TEOS is added dropwise within 2.5h, and the mixture is reacted in a constant temperature water bath at 35°C for 4h. After the reaction is completed, the reaction solution is cooled, centrifuged, washed several times with deionized water, and dried in a vacuum drying oven at 45°C to obtain SiO2-TiO2 composite particles.

[0085] Comparative Example 7: This comparative example differs from Example 5 in that the bed pressure is set to 3 MPa, the air flow velocity is set to 0.8 m / s, the inlet temperature is set to 120°C, and the outlet temperature is set to 150°C.

[0086] Comparative Example 8: This comparative example differs from Example 6 in that the bed pressure is set to 4 MPa, the air flow velocity is 1.0 m / s, the inlet temperature is 100°C, and the outlet temperature is 60°C.

[0087] Next, the contents of the evaluation test will be described.

[0088] 1. If Figure 6 The curve is shown in Figure 2, which is measured by UV-visible diffuse reflectance spectroscopy (UV-vis DRS) using a Shimdzu UV-3600 spectrophotometer equipped with an integrating sphere. Figure 6 As can be seen, compared to the full-band spectral reflectance of P25, the reflectance curve of the spherical TiO2 / Al2O3 composite material prepared by the present invention is significantly higher than that of P25. In the ultraviolet band of 10-400nm, the reflectance of the spherical TiO2 / Al2O3 composite material is slightly higher than that of P25; in the visible light band of 400-700nm, the reflectance of the spherical TiO2 / Al2O3 composite material is significantly increased; and in the near-infrared band of 700-2500nm, the reflectance of the spherical TiO2 / Al2O3 composite material is generally higher than that of P25. This shows that the spherical TiO2 / Al2O3 composite material prepared by the present invention can improve the material's reflectance within the 400-2500nm band.

[0089] 2. The coatings prepared in Examples 7-10 and Comparative Examples 1-8 were used to conduct reflectance test.

[0090] The spectral reflectance characteristics of the samples in the visible and ultraviolet spectral ranges were tested using a UV-Vis spectrophotometer, and the reflectance spectral characteristics of the samples in the infrared spectral range were tested using an FT-IR spectrometer.

[0091] (1) Solar reflectance: Solar reflectance ( ) is usually used to measure an object's ability to reflect sunlight, and its calculation formula is:

[0092] ,

[0093] Where: ρ represents the solar reflectance, unit is g; ρλ i Indicates wavelength is λ i Spectral reflectance, Es(λ i ) represents the wavelength λ i The spectral intensity of solar radiation at a given location, usually expressed in W / m²·μm, Δλ i Indicates the wavelength interval, usually taken as λ i+1 and λ i-1 Half the wavelength difference, in nm, Σ represents the summation, and the range covers the main wavelength region of solar radiation, such as 250nm to 2500nm.

[0094] (2) Near infrared reflectance: Near infrared reflectance (NIR) refers to the ability to reflect light under near infrared light (780-2500nm). The calculation formula is:

[0095] ,

[0096] Where: NIR represents near-infrared reflectivity, Rsample represents the reflectance value of the sample, that is, the intensity of the reflected light of the sample in the near-infrared light band, Rdark represents the dark background value, that is, the measurement value when there is no light irradiation, which is used to eliminate the influence of ambient light on the measurement results, and Rwhite represents the white standard value, that is, the value of completely reflected light, which is used as a reference standard.

[0097] The results of the above performance tests are shown in the following table:

[0098]

[0099] From the above data, it can be seen that the light-reflective coating containing spherical TiO2-coated inorganic particle composite materials prepared by the present invention has higher solar reflectance and near-infrared reflectance than comparative examples 1-8, indicating that the coating prepared by the present invention has a more significant reflective effect in the near-infrared region.

[0100] 3. The corrosion resistance and self-cleaning properties of the coatings prepared in Examples 7-10 and Comparative Examples 1-8 were measured.

[0101] The prepared coatings were sprayed on stainless steel plates (150 mm × 100 mm × 1 mm) with a thickness of 50 ± 3 μm, cured, and dried to serve as test specimens.

[0102] (1) Corrosion resistance: According to the method specified in GB / T1771-2007 "Determination of neutral salt spray resistance of paints and varnishes", the test conditions are: the concentration of NaCL solution is (50±5) g / l, the pH value of the collected liquid is 7.0, the temperature in the salt spray chamber is 35±2℃, and the test temperature is 80cm 2 The salt spray solution collection rate is 2.0 mL / h, and the test duration is 96 hours. At the end of the test, observe whether there is blistering, rusting, cracking, and peeling.

[0103] (2) Self-cleaning property: The contact angle of the sample surface to water was measured using a contact angle meter. The test method was the droplet method, where a droplet was dropped onto a glass slide through a syringe needle and the contact angle was read using the tangent method. The contact angle was measured at no less than three locations and the average value was taken. The sample surface was contaminated with oil, and the contact angle of the sample surface to water was measured. After the sample surface was exposed to ultraviolet light for 12 hours, the contact angle of the sample surface to water was measured again. The unit of contact angle is: ° (degrees).

[0104] The test results are shown in the following table:

[0105]

[0106] The test results demonstrate that the coatings prepared in accordance with the present invention exhibit excellent corrosion resistance, exhibiting no blistering, rusting, cracking, or flaking during a 96-hour neutral salt spray corrosion test. The initial static contact angles of the samples of the present invention were all greater than 150°. This contact angle decreased significantly after oil contamination. After 12 hours of UV irradiation, the static contact angles on the sample surfaces recovered and rose to greater than 120°, demonstrating excellent self-cleaning capabilities.

[0107] In summary, the light-reflective coating prepared by the present invention not only has high light-reflecting performance, but also has corrosion resistance and self-cleaning effects, and can be better applied to exterior wall or traffic marking coatings.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a spherical TiO2-coated inorganic particle composite material, characterized in that: The following steps are involved: S01: Preparation of rutile TiO2 spheres: Titanium tetraisopropoxide was added to anhydrous ethanol and glacial acetic acid, stirred, and subjected to hydrothermal reaction in a reactor. After the reaction, the precipitate was centrifuged and washed twice with distilled water and anhydrous ethanol respectively. After ultrasonication, the precipitate was dried and calcined to obtain rutile TiO2 spheres; S02: Preparation of spherical TiO2-coated inorganic particle composite materials: Open the feed valve of the fluidized bed and pass the inorganic particle core material into the silo of the fluidized bed, wherein the inorganic particle core material is at least one of silica, alumina, and spinel; Close the feed valve, adjust the height of the fluidized bed, start the bottom gas pump, adjust to the set air flow velocity, so that the bed particles enter a fluidized state, the bed pressure of the fluidized bed is 4.5~5.5MPa, and the air flow velocity is 0.1-0.5m / s; Add ethanol to the TiO2 balls to obtain a TiO2 ethanol solution, adjust the viscosity and pass it into the liquid flow bin, set the spray pressure and spray rate, spray the TiO2 ethanol solution onto the surface of the inorganic particle core material, maintain the inlet temperature at 30-80℃, and the outlet temperature at 80-120℃. After reaching the predetermined thickness, stop spraying the TiO2 ethanol solution, continue to maintain the air flow, and completely dry the particles to obtain a spherical TiO2-coated inorganic particle composite material.

2. The method for preparing a spherical TiO2-coated inorganic particle composite material according to claim 1, wherein: In step S01, the weight of titanium tetraisopropoxide is 0.165-0.495 g, the volume of anhydrous ethanol is 50-100 mL, and the volume of glacial acetic acid is 5-10 mL.

3. The method for preparing a spherical TiO2-coated inorganic particle composite material according to claim 2, wherein: The temperature of the hydrothermal reaction in step S01 is 150°C-200°C, and the reaction time is 2-4 hours. The drying temperature is 60-80°C and the drying time is 12-24 hours. The calcination temperature is 900-950° C. and the calcination time is 2-4 hours.

4. The method for preparing a spherical TiO2-coated inorganic particle composite material according to claim 3, wherein: The particle size of the inorganic particle core material in step S02 is 100-700 nm.

5. The method for preparing a composite material of spherical TiO2-coated inorganic particles according to claim 4, wherein: The height of the fluidized bed in step S02 is 20-60 cm.

6. The method for preparing a composite material of spherical TiO2-coated inorganic particles according to claim 5, wherein: The mass concentration of TiO2 balls in the TiO2 ethanol solution in step S02 is 60%, and the viscosity of the TiO2 ethanol solution is regulated by the following raw materials, including at least one of polyacrylate, polyacrylic amine and polyvinyl alcohol.

7. The method for preparing a composite material of spherical TiO2-coated inorganic particles according to claim 6, wherein: In step S02, the viscosity of the TiO2 ethanol solution is adjusted to 800-1000 mPa·s, the spray pressure is 0.2-0.5 MPa, the spray rate is 10-100 L / h; and the spraying time is controlled at 30-40 min.

8. Use of the spherical TiO2-coated inorganic particle composite material obtained by the preparation method of the spherical TiO2-coated inorganic particle composite material according to any one of claims 1 to 7 in light reflective coatings.

9. The light-reflecting coating according to claim 8, wherein: The coating is obtained by the following preparation method: providing an oligomer emulsion, a thickener, a cross-linking agent, a dispersant, a defoaming agent, tetraethyl orthosilicate, glacial acetic acid, anhydrous ethanol and water; mixing the spherical TiO2-coated inorganic particle composite material with water, the dispersant and the defoaming agent to obtain component A; mixing water, anhydrous ethanol, glacial acetic acid and tetraethyl orthosilicate and reacting them to obtain component B; mixing the oligomer emulsion, the thickener and the cross-linking agent and reacting them to obtain component C; mixing component A, component B and component C in a volume ratio of 6:3:1, adjusting the viscosity and pH value to obtain a coating; The proportions of the raw materials in component A are as follows: 10-20 g of spherical TiO2-coated inorganic particle composite material, 1-5 g of dispersant, 1-10 g of defoaming agent, and 20-40 g of water; The proportions of the raw materials in component B are as follows: 200-300 g of water, 20-40 mL of anhydrous ethanol, 1-5 mL of glacial acetic acid, and 1-5 mL of ethyl orthosilicate; The proportions of the raw materials in component C are as follows: oligomer emulsion 200-400g, thickener 60-80g, crosslinking agent 1-10g; The dispersant is selected from at least one of polyethylene glycol trimethoxysilyl propyl ether, polydimethylsiloxane, epoxy silane, and aminosilane; The defoaming agent is selected from one or a combination of two or more of hexamethylenetetramine, urea, ammonia water and ammonium carbonate; The oligomer emulsion is selected from one or two combinations of 3-aminopropyltriethoxysilane, modified polyvinyl alcohol, and silicone-modified polyurethane; The thickener is selected from one or a combination of lauramidopropyl betaine, sodium carboxymethyl cellulose and sodium polyacrylate; The cross-linking agent is selected from one or a combination of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

10. The light-reflecting paint according to claim 9, wherein: The regulating and controlling of viscosity and pH value includes: regulating the viscosity to 800-1000 mPa·s and the pH value to 7-8.

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