Preparation method of hollow double-shell nanofiller and application of hollow double-shell nanofiller in preparation of transparent heat-insulating coating

Abstract

The invention discloses a preparation method based on hollow double-shell nanofiller and application of the hollow double-shell nanofiller in preparation of a transparent heat-insulating coating, and belongs to the field of heat-insulating coatings. The preparation method comprises the steps that firstly, PMMA-coated TiO2 core-shell sphere powder is prepared; ultrasonically dispersing the prepared PMMA-coated TiO2 core-shell sphere powder into an aqueous solution of isopropanol, and adding acetic acid to adjust the pH value, so as to prepare a core-shell sphere PMMA-coated TiO2-coated SiO2; calcining the core-shell sphere PMMA (at) TiO2 (at) SiO2 to prepare a TiO2 (at) SiO2 sphere with a double-shell hollow structure; the preparation method comprises the following steps: mixing waterborne polyurethane, a solvent, a thickening agent, a curing agent, an auxiliary agent and DHTS, standing, and discharging bubbles to prepare the hollow double-shell nanofiller. The hollow double-shell nanofiller disclosed by the invention can realize the effects of high transmittance, heat insulation and fog prevention.

Description

Technical Field

[0001] The present invention relates to the field of heat-insulating coatings, and particularly to a preparation method based on hollow double-shell nano-fillers and their application in the preparation of transparent heat-insulating coatings. Background Art

[0002] Glass is an indispensable material in life. In the home field, glass is used in bathrooms, partitions, dining tables, etc., playing roles such as beautification and observation. In the transportation field, such as the portholes and windows of cars, trains, and airplanes, glass is required, mainly for ensuring safety. In the construction field, glass has good light transmittance, which can enhance the daylighting of buildings, allowing natural light to fully enter the interior and making the space brighter. Especially in modern architectural designs, glass curtain walls are increasingly favored by people and widely used due to their unique aesthetics, technical advantages, and environmental protection concepts. However, the heat transmission of glass is very large, and it cannot block outdoor heat radiation and ultraviolet rays, which will lead to an increase in indoor temperature. Especially with the global climate change, high-temperature weather is becoming more persistent and widespread, and the impact is becoming more serious. Commonly used air conditioners for cooling will greatly increase power consumption, which not only burdens the environment but also brings inconvenience to people's daily lives. In addition, when the temperature difference between the inside and outside of these glasses is large, white fog is extremely likely to form on the surface, such as the windshield or rearview mirror of a car, etc., affecting the working efficiency of some optical materials. In addition to considerations such as energy conservation, the impact of ultraviolet radiation on people's health cannot be ignored.

[0003] Improving from the glass material itself, for example, although insulating glass has better heat preservation effect than single-layer glass in winter, it cannot resist the infrared rays emitted by the sun in summer and is ineffective in summer. Low-E glass is a type of coated glass with good performance and good heat preservation effect both in summer and winter. However, its production investment is huge, the technical difficulty is high, and its high price makes it unacceptable to ordinary people. And the problem of glass fogging is also very difficult to improve through the material itself. Therefore, it is particularly important to prepare a transparent coating with infrared prevention, fog prevention, and heat insulation.

[0004] At present, many particles with transparent heat-insulating performance and infrared shielding ability have been reported, such as lanthanum boride (LaB6), antimony-doped tin oxide (ATO), indium tin oxide (ITO), vanadium dioxide (VO2), metal powders, conductive polymers, organic / inorganic composites, and semiconductors. These materials all have problems such as high cost and complex processes, and at the same time, they have no anti-fog effect. Summary of the Invention

[0005] One of the objectives of the present invention is to provide a preparation method of hollow double-shell nano-fillers, so as to solve the disadvantages in the prior art that the materials used in nano-insulating transparent coatings are expensive, the manufacturing process is complex, and it is difficult to achieve large-scale research and development.

[0006] The present invention is realized through the following technical solutions. A preparation method of hollow double-shell nano-fillers includes the following steps: S100. Add polymethyl methacrylate latex, ammonia water, and ethanol into a three-necked flask, and stir evenly to prepare a first mixed solution. Mix ethanol, tetrabutyl titanate, and triethanolamine evenly to prepare a second mixed solution. Drop the second mixed solution into the first mixed solution, and use ultrasonic to mix evenly for 15 - 30 min to prepare a third mixed solution. Raise the temperature of the third mixed solution to 60 - 90 °C, stir the third mixed solution at 600 - 900 r / min for 8 - 12 h, then cool to room temperature, separate the product by centrifugation, wash the separated product with ethanol 3 times, and dry it at 60 °C for 12 h to prepare PMMA@TiO 2 core-shell sphere powder; S200. Ultrasonically disperse the prepared PMMA@TiO 2 core-shell sphere powder into an aqueous solution of isopropanol, and add acetic acid to adjust the pH to 5 - 6.5 to prepare a first dispersion. Drop tetraethyl orthosilicate into the first dispersion to prepare a fourth mixed solution. Raise the temperature of the fourth mixed solution to 60 - 90 °C, stir at 600 - 900 r / min for 8 - 12 h, then cool to room temperature, separate the product by centrifugation, wash it 3 times with ethanol and dry it at 60 °C for 12 h to prepare core-shell sphere PMMA@TiO 2 @SiO 2 ; S300. Calcinate the core-shell sphere PMMA@TiO 2 @SiO 2 to prepare a double-shell hollow structure TiO 2 @SiO 2 sphere; S400. At room temperature, mix waterborne polyurethane, solvent, thickener, curing agent, additives, and DHTS, stir at 100 - 120 r / min for 30 - 50 min, then let it stand and discharge the bubbles to prepare hollow double-shell nano-fillers.

[0007] Furthermore, the mass ratio of polymethyl methacrylate latex to ammonia water in the first mixed solution is 2:1 - 10:9, and the dosage of ethanol in the first mixed solution is 50% - 80%.

[0008] Furthermore, the dosage of ethanol in the first mixed solution is 50% - 80%.

[0009] Furthermore, the dosage of ethanol in the second mixed solution is 50% - 80%.

[0010] Further, the mass ratio of tetraethyl orthosilicate to triethanolamine in the fourth mixed solution is 1:1 to 10:7, and the mass percentage of tetraethyl orthosilicate added dropwise is 0.05% to 1%.

[0011] Further, in the aqueous solution of isopropanol, the concentration of isopropanol is 0.7 to 1.2 mol / L.

[0012] Further, the calcination temperature in step S300 is 400 to 600 °C, and the calcination time is 2 to 6 h.

[0013] Further, the components of the waterborne polyurethane, solvent, thickener, curing agent, auxiliary agent, and DHTS in step S400 are: 80 to 140 parts of waterborne polyurethane, 10 to 30 parts of solvent, 5 to 20 parts of thickener, 5 to 20 parts of curing agent, 1 to 6 parts of auxiliary agent, and 1 to 10 parts of DHTS.

[0014] On the other hand, the present invention provides a hollow double-shell nano filler, which is prepared according to the preparation method described above.

[0015] The present invention also provides an application of the hollow double-shell nano filler in the preparation of a transparent heat-insulating coating. The hollow double-shell nano filler described above is sprayed on a dry and clean glass through a spray gun and cured at room temperature or under heating conditions to prepare a transparent heat-insulating coating.

[0016] Further, the thickness of the transparent heat-insulating coating is 50 to 70 μm.

[0017] Further, the transparent heat-insulating coating has the dual functions of transparent heat insulation and superhydrophilicity.

[0018] Further, the transparent heat-insulating coating is obtained by blending double-shell hollow-structured TiO 2 @SiO 2 spheres and waterborne polyurethane.

[0019] Further, the superhydrophilic effect of the transparent heat-insulating coating is caused by the hollow structure obtained after calcination of the double-shell hollow-structured TiO 2 @SiO 2 spheres and the photoinduced superhydrophilic effect.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. The hydrophilic transparent super coating based on nano heat-insulating filler prepared by the present invention can achieve the effects of high transparency, heat insulation, and anti-fogging.

[0022] 2. The present invention uses PMMA emulsion, tetrabutyl titanate, and tetraethyl orthosilicate as the main raw materials to form PMMA@TiO 2 @SiO 2 double spherical shell layer, and contains a mesoporous structure. After calcination at a relatively high temperature, the PMMA in the center of PMMA@TiO 2 @SiO 2 vaporizes, and further obtains TiO 2 @SiO 2 hollow double-shell DHTS. The high-temperature calcination improves the crystallinity of TiO 2 and SiO 2 at the same time, forms a hollow layer, and the spherical shell also shrinks and densifies due to the high temperature. The high-temperature calcination process can also reduce the defects and impurities in the double-shell structure, making the refraction of TiO 2 more uniform, thereby reducing the scattering and reflection of light and improving the transparency.

[0023] 3. The present invention utilizes the silicon atoms and oxygen atoms in the molecular structure of SiO 2 to be tightly connected by covalent bonds to form a stable network structure. This structure makes SiO 2 have a lower porosity, reducing the refraction and scattering of light inside the material, thereby also ensuring its transparency. The internal cavity structure of the TiO 2 @SiO 2 hollow double-shell DHTS can effectively reduce the heat conduction path and lower the heat conduction efficiency. At the same time, the calcined TiO 2 has better photocatalytic performance, enhancing its "photo-induced hydrophilic" performance, making the coating hydrophilic, and the adsorbed water molecules spread on the coating surface, improving the heat insulation performance of the coating.

[0024] 4. The present invention uses the optimized waterborne polyurethane resin as the resin of the coating. DHTS is well dispersed in the coating. The specific surface area of the TiO 2 @SiO 2 double shell layer is relatively large, which helps to increase its contact area with waterborne polyurethane; the surface of the SiO 2 outer shell contains abundant hydroxyl groups, and these hydroxyl groups can interact with the polar groups in waterborne polyurethane. These reasons enhance the compatibility and dispersibility between the two, and waterborne polyurethane provides many active groups, which can have good binding with DHTS and other additives; waterborne polyurethane resin has good compatibility with glass, and the resin can penetrate into the tiny pores on the glass surface, enhancing the bonding force between the coating and the glass. Brief Description of the Drawings

[0025] The accompanying drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0026] Figure 1 For the double-shell hollow structure TiO provided in Embodiment 1 of the present invention 2 @SiO 2 Electron micrograph of the sphere.

[0027] Figure 2 For the double-shell hollow structure TiO provided in Embodiment 3 of the present invention 2 @SiO 2 Electron micrograph of the sphere. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail. Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, that is, they are intended to include but not limited to. Unless otherwise clearly stated in the context, the expressions "a" and "an" used herein include plural references. It should be noted that "first", "second", "third", etc. are only for convenience of description and easy distinction, and cannot be understood as indicating or implying relative importance. The term "about" used herein represents a range of ±20% of the value thereafter. In some embodiments, the term "about" represents a range of ±10% of the value thereafter. In some embodiments, the term "about" represents a range of ±5% of the value thereafter.

[0030] Embodiment 1

[0031] (1) Add 9 g of PMMA, 7 g of ammonia water, and 70 g of absolute ethanol into a three-necked flask and stir evenly to obtain suspension A. Drop mixture B containing 11 g of ethanol, 9 g of TNBT, and 76 g of triethanolamine into the above suspension A. After mixing evenly, ultrasonicate for 30 minutes. Raise the temperature to 90 °C, stir at 800 revolutions per minute for 11 hours, then cool to room temperature. Centrifuge the product at a centrifugation rate of 4200 rpm for 6 min, wash it 3 times with ethanol, and dry it at 60 °C for 12 hours to obtain PMMA@TiO core-shell sphere powder with a particle size ranging from 40 nm to 200 nm. 2 core-shell sphere powder.

[0032] (2) Ultrasonically disperse the PMMA@TiO 2 core-shell spheres into an aqueous solution of isopropanol, and add an appropriate amount of acetic acid to adjust the pH to 5.5. After dropping 0.23 g of TEOS into the above dispersion, raise the temperature to 60 °C, stir at 800 revolutions per minute for 10 hours, then cool to room temperature. Centrifuge the product at a centrifugation rate of 4200 rpm for 6 min, wash it 3 times with ethanol, and dry it at 60 °C for 12 hours to obtain core-shell sphere PMMA@TiO 2 @SiO 2 .

[0033] (3) Calcinate the PMMA@TiO 2 @SiO 2 powder at 300 °C to obtain a double-shelled hollow structure TiO 2 @SiO 2 sphere (DHTS). Figure 1 Figure shows the electron micrograph of the double-shelled hollow structure TiO 2 @SiO 2 sphere prepared in this example.

[0034] (4) At room temperature, mix 100 g of waterborne polyurethane, 20 g of solvent, 10 g of thickener, 10 g of curing agent, 3 g of additive, and 3 g of DHTS, stir at 120 revolutions per minute for 30 minutes, then let it stand for 3 minutes to discharge air bubbles to obtain a spraying liquid.

[0035] (5) Pour the spraying liquid into a customized small spray gun for spraying, spray it on a dry and clean glass, and cure it at room temperature or under heating conditions to obtain a transparent heat-insulating coating with a hollow double-shelled nano-filler having a thickness of 50 - 70 μm.

[0036] Example 2

[0037] (1) Add 13.3 g of PMMA, 9.5 g of ammonia water, and 78 g of absolute ethanol into a three-necked flask, stir evenly to obtain suspension A. Drop mixture B containing 11.3 g of ethanol, 9.5 g of TNBT, and 70 g of triethanolamine into the above suspension A, mix well, and then sonicate for 30 minutes. Raise the temperature to 80 °C, stir at 800 revolutions per minute for 12 hours, then cool to room temperature, centrifuge the product at a centrifugation rate of 4200 rpm for 6 min, wash it with ethanol three times, and dry it at 60 °C for 12 hours to obtain PMMA@TiO core-shell spherical powder with a particle size ranging from 40 nm to 200 nm. 2 core-shell spherical powder.

[0038] (2) Ultrasonically disperse the PMMA@TiO 2 core-shell spheres into an aqueous solution of isopropanol, add an appropriate amount of acetic acid to adjust the pH to 6. After dropping 0.23 g of TEOS into the above dispersion, raise the temperature to 85 °C, stir at 800 revolutions per minute for 10 hours, then cool to room temperature, centrifuge the product at a centrifugation rate of 4000 rpm for 6 min, wash it with ethanol three times, and dry it at 60 °C for 12 hours to obtain core-shell spheres PMMA@TiO 2 @SiO 2 .

[0039] (3) Calcinate the PMMA@TiO 2 @SiO 2 powder at 400 °C to obtain double-shelled hollow-structured TiO 2 @SiO 2 spheres (DHTS).

[0040] (4) At room temperature, mix 100 g of waterborne polyurethane, 25 g of solvent, 11 g of thickener, 10 g of curing agent, 3 g of auxiliary agent, and 3 g of DHTS, stir at 120 revolutions per minute for 30 minutes, then let it stand for 3 minutes to discharge air bubbles to obtain a spraying liquid.

[0041] (5) Pour the spraying liquid into a customized small spray gun for spraying, spray it on a dry and clean glass, and cure it at room temperature or under heating conditions to obtain a transparent heat-insulating coating with a hollow double-shelled nano-filler having a thickness of 50 - 70 μm.

[0042] Example 3

[0043] (1) 13.3 g of PMMA, 9.5 g of ammonia water and 78.9 g of absolute ethanol were added to a three-necked flask and stirred evenly to obtain suspension A. A mixture B containing 11.3 g of ethanol, 9.5 g of TNBT and 75.5 g of triethanolamine was added dropwise to the above suspension A. After mixing evenly, it was sonicated for 30 minutes. The temperature was raised to 80 °C and stirred at 800 rpm for 8 hours, then cooled to room temperature. The product was separated by centrifugation at a centrifugation rate of 4000 rpm for 6 min, washed 3 times with ethanol and dried at 60 °C for 12 hours to obtain PMMA@TiO core-shell spherical powder with a particle size of 40 nm to 200 nm. 2 core-shell spherical powder.

[0044] (2) The PMMA@TiO 2 core-shell spheres were ultrasonically dispersed in an aqueous solution of isopropanol, and an appropriate amount of acetic acid was added to adjust the pH to 6. After 0.25 g of TEOS was added dropwise to the above dispersion, the temperature was raised to 85 °C and stirred at 800 rpm for 10 hours, then cooled to room temperature. The product was separated by centrifugation at a centrifugation rate of 4000 rpm for 6 min, washed 3 times with ethanol and dried at 60 °C for 12 hours to obtain core-shell spheres PMMA@TiO 2 @SiO 2 .

[0045] (3) The PMMA@TiO 2 @SiO 2 powder was calcined at 500 °C to obtain double-shelled hollow-structured TiO 2 @SiO 2 spheres (DHTS). Figure 2 The electron micrograph of the double-shelled hollow-structured TiO 2 @SiO 2 spheres prepared in this example is shown.

[0046] (4) At room temperature, 120 g of waterborne polyurethane, 25 g of solvent, 11 g of thickener, 10 g of curing agent, 3 g of additive and 4 g of DHTS were mixed, stirred at 120 rpm for 30 minutes and then left standing for 3 minutes to remove bubbles to obtain a spraying liquid.

[0047] (5) The spraying liquid was poured into a customized small spray gun for spraying, and sprayed on a dry and clean glass. It was left standing at room temperature for 6 h to obtain a transparent heat-insulating coating with a thickness of 50 - 70 μm of hollow double-shelled nano-fillers.

[0048] Comparative Example 1

[0049] (1) Add 17.1 g of PMMA, 22 g of ammonia water, and 78.9 g of absolute ethanol into a three-necked flask, stir evenly to obtain suspension A. Drop mixture B containing 17.1 g of ethanol, 9.5 g of TNBT, and 75.5 g of triethanolamine into the above suspension A, mix well, and then ultrasonicate for 30 minutes. Raise the temperature to 80 °C, stir at 800 revolutions per minute for 8 hours, then cool to room temperature, centrifuge the product at a centrifugation rate of 4000 rpm for 6 min, wash it 3 times with ethanol, and dry it at 60 °C for 12 hours to obtain PMMA@TiO core-shell sphere powder with a particle size ranging from 40 nm to 200 nm. 2 core-shell sphere powder.

[0050] (2) Ultrasonically disperse the PMMA@TiO 2 core-shell spheres into an aqueous solution of isopropanol, add an appropriate amount of acetic acid to adjust the pH to 6.5. After dropping 0.44 g of TEOS into the above dispersion, raise the temperature to 85 °C, stir at 800 revolutions per minute for 10 hours, then cool to room temperature, centrifuge the product at a centrifugation rate of 4000 rpm for 6 min, wash it 3 times with ethanol, and dry it at 60 °C for 12 hours to obtain core-shell sphere PMMA@TiO 2 @SiO 2 .

[0051] (3) Calcinate the PMMA@TiO 2 @SiO 2 powder at 500 °C to obtain double-shelled hollow structure TiO 2 @SiO 2 spheres (DHTS).

[0052] (4) At room temperature, mix 120 g of waterborne polyurethane, 25 g of solvent, 11 g of thickener, 10 g of curing agent, 3 g of auxiliary agent, and 4 g of DHTS, stir at 120 revolutions per minute for 30 minutes, then let it stand for 3 minutes to discharge air bubbles to obtain a spraying liquid.

[0053] (5) Pour the spraying liquid into a customized small spray gun and spray it on a dry and clean glass, let it stand at room temperature for 6 h to obtain a transparent heat-insulating coating with a hollow double-shelled nano-filler having a thickness of 50 - 70 μm.

[0054] Comparative Example 2

[0055] The difference between Comparative Example 2 and Example 3 lies only in step (1).

[0056] Modify step (1) to: the mass ratio of PMMA, ammonia water and absolute ethanol, and the corresponding mass ratio of tetrabutyl titanate, triethanolamine and absolute ethanol, heat to 80 °C and react for 6 h. During the reaction, add 10 ml of absolute ethanol every 15 min within 6 h; and add 0.1 g of initiator every 15 min.

[0057] Comparative Example 3

[0058] The scheme adopted in this comparative example is the one recorded in Chinese Patent CN118772672A. This Chinese patent discloses a transparent coating based on nano thermal insulation filler and its preparation method. The coating disclosed in this scheme has achieved good thermal insulation and transparency. The specific method is as follows:

[0059] First, mix ammonium bifluoride, tetraethyl titanate, niobium pentoxide and octadecanol according to the mass ratio of 0.1 - 0.15:2.4:0.5 - 0.8:27, reduce the pressure to 0.05 - 0.1 MPa, heat to 120 °C and react for 20 - 30 min, continue to heat up to 300 °C and react for 60 min, then cool to room temperature, add 13.5 mol / L acetone aqueous solution and centrifuge for 10 min, then add a mixed solution of n-hexanol and ethanol with a volume ratio of 1:3, heat up to 60 - 70 °C and centrifuge for 10 min, take out the powder, heat to 60 °C and dry for 12 - 15 h to obtain fluorine-niobium co-doped titanium dioxide powder; add toluene 50 times the mass of the fluorine-niobium co-doped titanium dioxide powder and mix ultrasonically for 30 min to prepare a modified nano dispersion, add ethyl cellulose solution, stir at 100 - 120 rpm for 30 - 50 min, and then let stand for 3 min to discharge bubbles to obtain a modified liquid.

[0060] Next, heat tetraethyl orthosilicate, ammonia water, absolute ethanol and deionized water according to the volume ratio of 2:1:40:3 to 80 - 90 °C, stir at 40 - 50 rpm for 6 h to obtain a nano-silica particle solution; heat tetraethyl orthosilicate, ammonia water, KH560, absolute ethanol and deionized water according to the volume ratio of 2:1:0.2 - 0.8:40:3 at room temperature and stir at 50 - 80 rpm for 1.5 - 2 h to obtain an alkaline organosilicon oligomer; mix the nano-silica particle solution, alkaline organosilicon oligomer, absolute ethanol and perfluorodecyltriethoxysilane evenly, stir at 30 - 50 rpm at room temperature for 10 min to obtain a spraying liquid.

[0061] Finally, ultrasonically clean the glass slide with deionized water for 30 min, heat to 60 °C and dry for 2 h, pour the spraying liquid into a spray gun, spray back and forth 10 times, let stand at room temperature for 6 h to obtain a superhydrophobic composite coating, and use the spray gun to evenly spray the prepared modified liquid on one side of the glass to obtain a composite transparent thermal insulation coating with a thickness of 0.3 - 0.5 mm.

[0062] The transparent coating based on nano thermal insulation filler prepared by this Chinese invention patent includes a composite transparent thermal insulation coating and a superhydrophobic composite coating. In this invention, by means of solvothermal method, ammonium bifluoride in situ decomposes into hydrogen fluoride at high temperature, which adsorbs on nano titanium dioxide to improve crystallinity. The lattice expands due to fluoride ions replacing oxygen ions, and niobium ions replace titanium ions, introducing free electrons and enhancing the plasma resonance absorption of titanium dioxide in the near-infrared light region, thereby improving visible light transparency and heat insulation. In this scheme, the superhydrophobic composite coating is prepared by mixing tetraethyl orthosilicate, ammonia water and KH-560 to obtain an alkaline organosilicon oligomer, which crosslinks to form a network structure, and then fluoroalkylsilane is grafted onto the organosilicon oligomer to increase the rough structure and improve hydrophobicity. Tetraethyl orthosilicate and ammonia water hydrolyze to produce silicate monomers, which are dehydrated and condensed through hydroxyl groups to form silicon dioxide with small particle size, improving light transmittance.

[0063] Experimental Examples

[0064] To more clearly illustrate the preparation method provided by this application, performance index test experiments were conducted on the 3 examples and Comparative Examples 1 to 3 disclosed in this application. The specific test methods for each index are as follows:

[0065] Light transmittance and near-infrared barrier property: Cut the transparent hard glass into 1 cm×3 cm splines, and use a UV-visible-near-infrared spectrophotometer to measure the light transmittance in the wavelength range of 200 nm to 2500 nm.

[0066] Heat insulation property: Cut a 5.5×5.5×5.5 cm groove in the polystyrene foam board, embed the hollow side of the customized 5×5×5 cm quartz glass cover into the groove, use a 5×5×0.1 cm thick transparent acrylic board to place the film sample, irradiate it with a 250 W near-infrared lamp at a distance of 15 cm from the top of the device for 30 min, record the temperature every 3 min, and control different coatings to start the heat insulation test at the same initial temperature.

[0067] Hydrophilicity: Water contact angle test. Under room temperature conditions, use a surface contact angle measuring instrument to measure the water contact angle, and finally take the average value as the final result of the contact angle.

[0068] The final test results are shown in Table 1 Performance Test Table.

[0069] Table 1. Performance Test Table

[0070]

[0071] It can be seen from the data in Table 1 that by comparing the water contact angle experimental data of the examples and the comparative examples, it is found that the contact angles of DHTS after high-temperature baking generally reach below 5°, meeting the standard of superhydrophilic coatings. This is because the photoinduced superhydrophilic effect TiO 2 acts as a photosensitive material and changes from a hydrophilic state to a superhydrophilic state under ultraviolet light irradiation.

[0072] The mechanism of photoinduced superhydrophilicity is that when the surface of the photoinduced active substance (such as TiO 2 ) is irradiated by ultraviolet light, photogenerated electrons and holes are generated on the surface. The electrons lead to the formation of Ti 3+ defect sites, and the holes react with the bridging oxygen at the lattice to leave oxygen vacancies. The Ti 3+ defect sites will react very quickly with the oxygen adsorbed on the surface, and the oxygen vacancies will adsorb water molecules, resulting in the rearrangement of hydroxyl groups to form hydrophilic regions.

[0073] Due to two-dimensional capillary action, water can quickly diffuse on the surface of TiO 2 irradiated by ultraviolet light, thus achieving a superhydrophilic state. At the same time, after high-temperature calcination, the crystallinity of TiO 2 and SiO 2 in DHTS increases, improving the overall stability of DHTS. The TiO 2 @SiO 2 hollow double-shell structure forms multiple reflection interfaces and can reflect heat multiple times. The hollow structure reduces the density of the material, reduces the heat conduction path, and at the same time increases the scattering and absorption of heat inside the material; finally, the excellent hollow mesoporous double-shell nanostructure of DHTS has an infrared-reflecting outer shell layer and an infrared-absorbing inner shell layer. After high-temperature baking, the DHTS structure is more stable, forming an inner wall cavity, further enhancing the heat insulation performance of the material.

[0074] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a hollow double-shell nanofiller, characterized in that: The preparation method comprises the following steps: S100, adding polymethyl methacrylate latex, ammonia water and ethanol into a three-necked flask, and stirring evenly to prepare a first mixed solution, A second mixed solution is prepared by uniformly mixing ethanol, tetrabutyl titanate and triethanolamine, and the second mixed solution is added dropwise to the first mixed solution, and ultrasonic mixing is performed for 15 to 30 minutes to prepare a third mixed solution, and the temperature of the third mixed solution is increased to 60 to 90 °C. The third mixed solution was stirred at 600-900 r / min for 8-12 h, cooled to room temperature, and the product was separated by centrifugation. The separated product was washed with ethanol for 3 times, and dried at 60 °C for 12 h to prepare PMMA@TiO2 core-shell sphere powder. S200, ultrasonically dispersing the prepared PMMA@TiO2 core-shell sphere powder into an aqueous solution of isopropanol, and adding acetic acid to adjust the pH to 5-6.5 to prepare a first dispersion, Adding tetraethyl orthosilicate dropwise to the first dispersion to obtain a fourth mixed solution, heating the fourth mixed solution to 60-90° C., stirring at 600-900 r / min for 8-12 hours, cooling to room temperature, centrifuging the product, washing it with ethanol three times, and drying it at 60° C. for 12 hours to obtain core-shell spheres PMMA@TiO2@SiO2; S300, calcining the core-shell PMMA@TiO2@SiO2 to prepare double-shell hollow structure TiO2@SiO2 spheres; S400. At room temperature, waterborne polyurethane, solvent, thickener, curing agent, additive and DHTS were mixed, stirred at 100-120 r / min for 30-50 min, and then allowed to stand and exhaust bubbles to prepare a hollow double-shell nanofiller.

2. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: The mass ratio of polymethyl methacrylate latex to ammonia water in the first mixed solution is 2:1 to 10:

9. The amount of ethanol in the first mixed solution is 50% to 80%.

3. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: The amount of ethanol in the second mixed solution is 50% to 80%.

4. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: The mass ratio of ethyl orthosilicate to triethanolamine in the fourth mixed solution is 1:1 to 10:

7. The mass percentage of the added ethyl orthosilicate is 0.05-1%.

5. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: In the aqueous solution of isopropanol, the concentration of isopropanol is 0.7-1.2 mol / L.

6. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: The calcination temperature in step S300 is 400-600° C., and the calcination time is 2-6 hours.

7. The method for preparing the hollow double-shell nanofiller according to claim 1, characterized in that: The components of the waterborne polyurethane, solvent, thickener, curing agent, auxiliary agent and DHTS in step S400 are: 80-140 parts of waterborne polyurethane, 10-30 parts of solvent, 5-20 parts of thickener, 5-20 parts of curing agent, 1-6 parts of auxiliary agent and 1-10 parts of DHTS.

8. A hollow double-shell nanofiller, characterized in that: The hollow double-shell nanofiller is prepared according to the preparation method as described in any one of claims 1 to 7.

9. Application of a hollow double-shell nanofiller in the preparation of a transparent thermal insulation coating, characterized in that: The hollow double-shell nanofiller described in claim 8 is sprayed onto dry and clean glass by a spray gun. The transparent heat-insulating coating is prepared by curing at room temperature or under heating conditions.

10. The use of the hollow double-shell nanofiller according to claim 9 in preparing a transparent heat-insulating coating, characterized in that: The transparent heat-insulating coating has the dual functions of transparent heat-insulating and super-hydrophilic. The thickness of the transparent heat-insulating coating is 50 to 70 μm; The transparent heat-insulating coating is obtained by blending double-shell hollow structure TiO2@SiO2 spheres and water-based polyurethane. The super-hydrophilic effect is due to the light-induced super-hydrophilic effect of the hollow structure obtained after the double-shell hollow structure TiO2@SiO2 spheres are calcined.

Images