Transparent passive radiation refrigeration coating with antifouling property and preparation method thereof

Abstract

The invention belongs to the field of passive radiation refrigeration coating materials, and discloses a transparent passive radiation refrigeration coating with antifouling property and a preparation method thereof. Firstly, a silicone-acrylic polymer is prepared from an acrylate monomer and high-flexibility low-surface-energy silicone oil, then nano SiO2 particles are introduced to prepare a hybrid polymer, and the coating is endowed with passive radiation refrigeration performance by the strong absorptivity of C-O-C in the acrylate monomer and Si-O-Si in the silicone oil in a long-wave infrared region; the polarization resonance absorption characteristic of the nano silicon dioxide synergistically guarantees the cooling effect. The preparation method of the coating is simple, large-scale preparation can be achieved, the prepared antifouling coating has high transparency (larger than or equal to 85%) in a visible light area and high emissivity (larger than 85%) in an atmospheric transparent window, and the passive radiation refrigeration effect that the temperature can be averagely reduced by 5.5 DEG C is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of refrigeration coating materials, and particularly relates to a transparent anti-fouling passive radiative cooling coating and a preparation method thereof. Background Art

[0002] With the intensification of the greenhouse effect and the urban heat island effect, people's demand for cooling and refrigeration is also increasing day by day. However, currently, the realization of cooling mainly relies on air-conditioning equipment that requires active work, which consumes a large amount of petroleum energy and emits air pollutants, further exacerbating environmental deterioration. Based on the long-term consideration of human sustainable development and the proposal of the "dual-carbon" goal, there is an urgent need for energy-saving and emission-reduction refrigeration technologies. Passive radiative cooling materials achieve the purpose of cooling without energy input by reflecting sunlight (0.25 - 2.5 μm) and emitting long-wave infrared light (8 - 13 μm, 16 - 25 μm) into outer space. It is a passive technology without fuel consumption, providing a promising technical solution to overcome energy shortages and environmental pollution problems globally.

[0003] Existing passive radiative cooling materials mainly include photonic structures, metamaterials, polymer materials, and polymer-inorganic particle composites, etc. Although a large amount of research work has confirmed that thin film materials with excellent refrigeration performance can be prepared, the materials with photonic structures require complex and costly structure designs, making it difficult to be applied on a large scale; and currently, polymer-based radiative cooling materials usually fill inorganic particles in a polymer matrix to achieve a high reflectivity by enhancing Mie scattering, and then achieve the purpose of enhanced refrigeration. They do not have transparency in the visible light region, restricting the application fields.

[0004] Chinese Patent with Publication No. CN116042090B discloses a passive radiative cooling coating, a preparation method thereof, and a passive radiative cooling coating. The components of the provided passive radiative cooling coating include: octavinyl POSS, silane coupling agent, pH regulator, inorganic nanoparticles, and organic solvents. Experimental results show that: the coating formed by the passive radiative cooling coating provided by the present invention has high reflectivity in the 400 - 2500 nm band and high emissivity in the infrared atmospheric window region (wavelength 8 - 13 μm); at the same time, it has superhydrophobic ability, and the contact angle with water is about 140°; in addition, it also has good mechanical strength and is firmly bonded to the substrate; the composition of the passive radiative cooling coating provided by this invention is relatively simple, does not require complex structure design, is relatively easy to produce and prepare, and has low production costs, solving the problem of large-scale application. However, this invention does not involve the research on the transparency of the coating.

[0005] Since the solar reflectivity of white surfaces is the highest, which is conducive to suppressing the absorption of solar heat by the surface, most of the existing daytime passive radiative cooling technologies have a single white appearance so far. There are few that have high transparency in the visible light region, which limits their application fields. If we can provide a coating with low reflectivity, high transmittance, and high emissivity, it will greatly break through the limitations of application fields.

[0006] Chinese Patent No. CN118810163A discloses a low-reflection, high-transmission radiative cooling visible window and its preparation method. The PDMS film attached to the glass surface is improved to place the PDMS film between two glass layers. Since PDMS has adsorptivity, placing it on the surface will adsorb tiny particles and dust in the air, which is not conducive to the long-term use of this structure. Placing PDMS in the middle extends the service life of the structure and improves its stability at the same time. This method applies PDMS to the glass layer by means of high-pressure thermal composite and edge sealing treatment. Its preparation and construction process is cumbersome and requires specific equipment, and it cannot be applied on a large scale.

[0007] If a transparent coating can be prepared, which can significantly inhibit the heat absorption and temperature rise of the substrate under direct sunlight, it will be very beneficial. Using high-transparency passive radiative cooling materials to provide a coating with high transmittance and high emissivity will enable such materials to have great application prospects in fields such as solar photovoltaic panels and building glass windows, completely changing the energy consumption problem in urban cooling, and slowing down the trends of urban heat island effect and global warming. Summary of the Invention

[0008] To solve the above problems, the purpose of the present invention is to provide a transparent passive radiative cooling coating with antifouling properties to solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or create conditions.

[0009] The purpose of the present invention is achieved through the following technical solutions: A transparent passive radiative cooling coating with antifouling properties includes a silicone-acrylic polymer and an inorganic nanoparticle solution. Among them, the mixing mass ratio of the silicone-acrylic polymer and the inorganic nanoparticle solution is: 50 - 90 parts of the silicone-acrylic polymer, and 10 - 50 parts of the inorganic nanoparticle solution.

[0010] The silicone-acrylic polymer includes an organosilicon-modified acrylic resin obtained by solution polymerization or a silicone-acrylic emulsion obtained by emulsion polymerization.

[0011] Specifically, the organosilicon-modified acrylic resin is prepared by the following method: S001, Stir and dissolve 10 - 30% initiator in 50 - 80% solvent, then pour it into a three-necked flask and preheat to 80 - 100 °C. Mix acrylate monomers, silicone, 50 - 70% initiator and 20 - 40% solvent and stir evenly to obtain a mixed solution, then pour it into a constant pressure funnel for standby.

[0012] S002, Drop the mixed solution in the constant pressure funnel into the three-necked flask preheated to 80 - 100 °C at a feeding rate of 2 - 3 seconds per drop. After dropping, continue to keep the temperature for reaction for 1 - 2 hours.

[0013] S003, After the heat preservation ends, add 10 - 30% initiator, then make it continue to react fully for 2 - 4 hours, and finally cool to room temperature and discharge to obtain silicone-modified acrylic resin.

[0014] Preferably, the acrylate monomers include at least three of styrene, methyl (meth)acrylate, ethyl (meth)acrylate, lauryl (meth)acrylate, isooctyl methacrylate, cyclohexyl methacrylate, octadecyl (meth)acrylate, n-butyl acrylate, (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl methacrylate.

[0015] Preferably, the silicone includes at least one of unsaturated group silicone prepolymer, amino silicone prepolymer, carboxyl silicone prepolymer, epoxy group silicone prepolymer, alcohol hydroxyl group silicone prepolymer.

[0016] Preferably, the initiator includes at least one of azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide, tert-butyl peroxybenzoate. The solvent includes at least one of propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, isopropanol.

[0017] Specifically, the silicone-acrylic emulsion is prepared by the following method: S101, At room temperature, disperse acrylate monomers at a stirring speed of 450 - 650 rpm under the action of an aqueous solution of emulsifier to obtain pre-emulsion 1. Take 10% of pre-emulsion 1 as seed pre-emulsion for standby, then drop polysiloxane into the remaining pre-emulsion 1 drop by drop. Under a stirring speed of 500 - 700 rpm, continuously stir for 30 - 50 minutes to obtain milky white pre-emulsion 2. S102. At 75 - 90 °C, using the process of semi - continuous seed emulsion polymerization, simultaneously add the seed pre - emulsion and the aqueous solution of ammonium persulfate initiator into the aqueous solution of emulsifier pre - heated to 85 °C. After reacting for 30 - 60 min, simultaneously add dropwise pre - emulsion 2 and the aqueous solution of ammonium persulfate initiator, and the dropping time is 2 - 3 hours. Then keep warm for 1 - 3 hours, and then cool it to 40 - 50 °C, adjust the pH to 8 - 9, and finally filter and discharge to obtain the silicone - acrylic emulsion.

[0018] Preferably, the acrylate monomers include at least two of styrene, (meth) methyl acrylate, isooctyl methacrylate, cyclohexyl methacrylate, (meth) octadecyl acrylate, and n - butyl acrylate.

[0019] Preferably, the polysiloxane is at least one of polydimethylsiloxane, vinyl polysiloxane, mono - (meth) acrylate - terminated polysiloxane, and bis - (meth) acrylate - terminated polysiloxane.

[0020] Preferably, the emulsifier is an anionic emulsifier, a non - ionic emulsifier, or a compound emulsifier of anionic and non - ionic types; the anionic emulsifier includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium dodecyl diphenyl ether disulfonate, ammonium tridecyl polyoxyethylene ether phosphate, SR - 10, and SR - 20; the non - ionic emulsifier includes at least one of OP - 10, ER - 10, ER 20, ER 30, AEO 9, LCN287, and LCN118.

[0021] Preferably, the solid content of the silicone - acrylic emulsion is 30% - 50%, and the average particle size of the prepared silicone - acrylic emulsion is 70 - 100 nm.

[0022] Finally, mix the inorganic nanoparticle solution and the silicone - acrylic polymer evenly to prepare an organic - inorganic hybrid polymer, and then coat it on the glass surface to obtain a passive radiative cooling coating.

[0023] Preferably, the inorganic nanoparticle solution includes a hydrophilic (hydrophobic) nano - SiO 2 solution, a silane - modified nano - SiO 2 solution, or a silica sol, and its particle size is 2 - 30 nm. The silane - modified nano - SiO 2 solution includes an active aminated nano - silica solution or an active epoxidized nano - silica solution; Among them, the active amino-functionalized nano-silica solution is specifically prepared as follows: Mix nano-silica, silane coupling agent KH550, ultrapure water, and absolute ethanol, and ultrasonically disperse them evenly for 15 - 30 minutes. Then, place the dispersion at 60 °C and react for 3 - 5 hours to obtain the active amino-functionalized nano-silica solution. Among them, nano-silica, silane coupling agent KH550, ultrapure water, and absolute ethanol are mixed in a mass ratio of 1:100:10:100.

[0024] The active epoxy-functionalized nano-silica solution is specifically prepared as follows: Mix nano-silica, silane coupling agent KH560, ultrapure water, and absolute ethanol, and ultrasonically disperse them evenly for 15 - 30 minutes. Then, place the dispersion at 60 °C and react for 3 - 5 hours to obtain the active epoxy-functionalized nano-silica solution. Among them, nano-silica, silane coupling agent KH560, ultrapure water, and absolute ethanol are mixed in a mass ratio of 1:100:10:100.

[0025] Mix the silicon-propylene polymer and the inorganic nano-particle solution evenly to obtain an organic-inorganic hybrid polymer. Coat it evenly on the glass surface, pre-bake it at 50 - 60 °C for 5 - 20 minutes, and then bake it at 110 - 130 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating.

[0026] Furthermore, the average particle size of the organic-inorganic hybrid polymer emulsion is 75 - 100 nm.

[0027] Furthermore, for the transparent anti-fouling passive radiative cooling glass coating of the present invention, the visible light transmittance ≥ 85%, the emissivity in the atmospheric window > 85%, and it has good anti-adhesion performance for various aqueous and oily liquids.

[0028] The organic-inorganic hybrid polymer made of inorganic nano-particles and silicon-propylene polymer together has C - O - C in acrylate monomers and Si - O - Si in polysiloxane in the coating, which have strong absorbability in the long-wave infrared region and can achieve efficient thermal radiation. On the other hand, by utilizing the polarization resonance absorption characteristics of nano-SiO 2 There is a phonon polariton resonance effect near 9 μm, generating a strong absorption peak, which enables effective energy output in the atmospheric window. Through the superposition of various means, the infrared emissivity of the transparent coating prepared from the composite polymer material reaches nearly 88% in the atmospheric transparent window, significantly improving the emissivity of the transparent coating and achieving a cooling effect of nearly 5.5 °C during the day.

[0029] The prior art has been dedicated to researching passive cooling coatings with high reflectivity and high emissivity. These coatings are applied to opaque materials and utilize the high reflectivity of the substrate. However, due to their opacity, their application limitations are significantly restricted. Compared with the prior art, the beneficial effects of this invention are as follows: (1) This invention provides a transparent anti-fouling passive radiative cooling coating, creatively designing a transparent cooling coating with a low reflectivity and high emissivity. When the coating is applied to transparent glass, sunlight can pass through the coating and the substrate while still achieving a passive cooling effect, which is a significant improvement. This solution first utilizes the strong absorbability of C-O-C in acrylate monomers and Si-O-Si in polysiloxanes in the long-wave infrared region to achieve efficient thermal radiation. On the other hand, by utilizing the polarization resonance absorption characteristics of nano-SiO 2 or silica sol, there is a phonon polariton resonance effect near 9 μm, generating a strong absorption peak to achieve effective energy output at the atmospheric window. Finally, the infrared emissivity of the coating reaches nearly 88% at the atmospheric transparent window, significantly improving the emissivity of the transparent coating. In outdoor experimental tests, compared with a blank glass plate, it can achieve a cooling effect of nearly 5.5 °C during the day.

[0030] (2) The coating provided by this invention, its organic polymer matrix can be either an organosilicon-modified acrylic resin obtained by solution polymerization or through an emulsion polymerization process, which is economical, environmentally friendly, and can achieve large-scale production. Moreover, the resulting hybrid latex particles have the characteristics of monodisperse and small particle size. The obtained passive radiative cooling coating has a transmittance of ≥88% in the solar spectrum region, further broadening its application possibilities in fields such as solar photovoltaic panels and transparent windows compared to most existing opaque passive radiative cooling materials. At the same time, due to the formation of a liquid-like layer on the surface by the low surface energy flexible component organosilicon, this transparent coating has a low adhesion and self-cleaning function, which can effectively extend the service life of the application surface and greatly reduce its maintenance cost, and it has extremely high value in practical applications. Description of the Drawings

[0031] Figure 1 , infrared spectrum of the transparent anti-fouling passive radiative cooling coating obtained in Example 1; Figure 2 , emissivity comparison chart of glass sheets coated with passive radiative cooling coatings and blank glass sheets in Examples 1, 3, and 5; Figure 3 , outdoor experimental temperature detection comparison chart of glass sheets coated with passive radiative cooling coatings and blank glass sheets in Examples 1 - 5; Figure 4 , visible light transmittance comparison chart of glass sheets coated with passive radiative cooling coatings and blank glass sheets in Examples 1 - 5; Figure 5 , Anti-fouling function display diagram of the glass sheet coated with the passive radiative cooling coating in Example 1. Detailed implementation manners

[0032] The present invention will be further described below in conjunction with the detailed implementation manners. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content described in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application. Example 1 A transparent passive radiative cooling coating with anti-fouling properties. First, prepare a silicone-acrylic emulsion. Specifically: Add 1.60 parts of ammonium tridecyl phosphate to 17.66 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate for standby. At room temperature, add 13 parts of methyl methacrylate, 12 parts of styrene, 13 parts of isooctyl acrylate, and 2.4 parts of methacrylic acid to 19.26 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate, and disperse them at a high speed of 450 rpm for 20 minutes to obtain pre-emulsion 1. Take 6 parts of pre-emulsion 1 as the seed pre-emulsion for standby. Then, gradually add 1.5 parts of monomethacrylate-terminated polysiloxane dropwise to the remaining pre-emulsion 1. Under the stirring speed of 500 rpm, continuously stir for 50 minutes to obtain a milky white pre-emulsion 2. Add 0.24 parts of the initiator ammonium persulfate to 5.01 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the initiator ammonium persulfate. Add 1.65 g of ammonium tridecyl phosphate to 39.14 g of an aqueous solution and preheat it to 85 °C to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate. At 85 °C, adopt the semi-continuous seed emulsion polymerization process. Add the seed pre-emulsion and 1.75 parts of the aqueous solution of the initiator ammonium persulfate to 40.79 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate at 85 °C. After reacting for 60 min, simultaneously add pre-emulsion 2 and 3.5 parts of the aqueous solution of the initiator ammonium persulfate dropwise, and the dropping time is 3 hours. Then keep it warm for 2 hours, and then cool it to 45 °C, adjust the pH to 8.2, and finally filter and discharge to obtain the silicone-acrylic emulsion. The average particle size of the prepared silicone-acrylic emulsion is 72 nm.

[0033] The inorganic nanoparticle solution is silica sol, which is a commercially available transparent colloidal solution with a mass concentration of 29% of silicon dioxide, and its average particle size is 10 nm; Finally, mix the inorganic nanoparticle solution and the silicone-acrylic polymer evenly to obtain an organic-inorganic hybrid polymer, and then coat it on the glass surface to obtain the passive radiative cooling coating.

[0034] Specifically, 100 parts of silicone-acrylic emulsion and 60 parts of silica sol are taken, mixed evenly to prepare an organic-inorganic hybrid polymer, which is evenly coated on the surface of a glass plate, pre-baked at 50 °C for 10 minutes, and then baked at 120 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating with a thickness of 6 μm.

[0035] Example 2 A transparent anti-fouling passive radiative cooling coating. First, prepare the silicone-acrylic emulsion as follows: Add 1.60 parts of ammonium tridecyl phosphate to 17.66 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate for standby. At room temperature, 13 parts of methyl methacrylate, 12 parts of styrene, 13 parts of isooctyl acrylate, and 2.4 parts of methacrylic acid are dispersed at a high speed for 20 minutes at a stirring speed of 450 rpm under the action of 19.26 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate to obtain pre-emulsion 1. Take 6 parts of pre-emulsion 1 as the seed pre-emulsion for standby, and then gradually add 1.5 parts of monomethacrylate-terminated polysiloxane dropwise to the remaining pre-emulsion 1. Under a stirring speed of 700 rpm, continuously stir for 40 minutes to obtain a milky white pre-emulsion 2. Add 0.24 parts of the initiator ammonium persulfate to 5.01 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the initiator ammonium persulfate. Add 1.65 g of ammonium tridecyl phosphate to 39.14 g of an aqueous solution and preheat to 85 °C to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate. At 90 °C, using the process of semi-continuous seed emulsion polymerization, add the seed pre-emulsion and 1.75 parts of the aqueous solution of the initiator ammonium persulfate to 40.79 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate at 85 °C. After reacting for 40 min, simultaneously add pre-emulsion 2 and 3.5 parts of the aqueous solution of the initiator ammonium persulfate dropwise, and the dropping time is 3 hours. Then keep warm for 2 hours, and then cool it to 45 °C, adjust the pH to 8.5, and finally filter and discharge to obtain the silicone-acrylic emulsion. The average particle size of the prepared silicone-acrylic emulsion is 78 nm.

[0036] The inorganic nanoparticle solution is an active aminated nano-silica solution with an average particle size of 30 nm. Specifically: Mix 0.10 parts of nano-silica, 10.00 parts of silane coupling agent KH550, 1.00 part of ultrapure water, and 10.00 parts of absolute ethanol and ultrasonically disperse them evenly for 30 minutes, and then place the dispersion at 60 °C for reaction for 5 hours to obtain the active aminated nano-silica solution.

[0037] Finally, mix the active aminated nano-silica solution with the silicone-acrylic polymer evenly to prepare an organic-inorganic hybrid polymer, and then coat it on the glass surface to obtain a passive radiative cooling coating.

[0038] Specifically, 100 parts of silicone-acrylic emulsion and 15 parts of active amino-functionalized nano-silica solution are taken and mixed evenly to prepare an organic-inorganic hybrid polymer. The polymer is evenly coated on the surface of a glass plate, pre-baked at 60 °C for 15 minutes, and then baked at 130 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating with a thickness of 10 μm.

[0039] Example 3 A transparent anti-fouling passive radiative cooling coating. First, prepare the silicone-acrylic emulsion as follows: Add 1.60 parts of ammonium tridecyl phosphate to 17.66 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate for standby. At room temperature, 13 parts of methyl methacrylate, 12 parts of styrene, 13 parts of isooctyl acrylate, and 2.4 parts of methacrylic acid are dispersed at a high speed with a stirring speed of 450 rpm for 20 minutes under the action of 19.26 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate to prepare pre-emulsion 1. Take 6 parts of pre-emulsion 1 as seed pre-emulsion for standby. Then, gradually add 1.5 parts of monomethacrylate-terminated polysiloxane dropwise to the remaining pre-emulsion 1. Under a stirring speed of 650 rpm, continuously stir for 45 minutes to obtain a milky white pre-emulsion 2. Add 0.24 parts of the initiator ammonium persulfate to 5.01 parts of an aqueous solution and stir evenly to obtain an aqueous solution of the initiator ammonium persulfate. Add 1.65 g of ammonium tridecyl phosphate to 39.14 g of an aqueous solution and preheat to 85 °C to obtain an aqueous solution of the emulsifier ammonium tridecyl phosphate. At 75 - 90 °C, adopt the process of semi-continuous seed emulsion polymerization. Add the seed pre-emulsion and 1.75 parts of the aqueous solution of the initiator ammonium persulfate to 40.79 parts of the aqueous solution of the emulsifier ammonium tridecyl phosphate at 85 °C. After reacting for 30 min, simultaneously add pre-emulsion 2 and 3.5 parts of the aqueous solution of the initiator ammonium persulfate dropwise, and the dropping time is 2 hours. Then keep the temperature for 3 hours, and then cool it to 45 °C, adjust the pH to 9.0, and finally filter and discharge to obtain the silicone-acrylic emulsion. The average particle size of the prepared silicone-acrylic emulsion is 86 nm.

[0040] The inorganic nanoparticle solution is an active epoxidized nano-silica solution with an average particle size of 20 nm. Specifically, 0.10 part of nano-silica, 10.00 parts of silane coupling agent KH560, 1.00 part of ultrapure water, and 10.00 parts of absolute ethanol are mixed and ultrasonicated for 20 minutes to make it evenly dispersed. Then, the dispersion is placed at 60 °C and reacted for 5 hours to obtain the active epoxidized nano-silica solution.

[0041] Finally, mix the active epoxidized nano-silica solution with the silicone-acrylic polymer evenly to prepare an organic-inorganic hybrid polymer, and then coat it on the glass surface to obtain a passive radiative cooling coating.

[0042] Specifically, 100 parts of silicone-acrylic emulsion and 25 parts of an active epoxidized nano-silica solution are taken, mixed evenly to prepare an organic-inorganic hybrid polymer, which is evenly coated on the surface of a glass plate, pre-baked at 55 °C for 15 minutes, and then baked at 110 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating with a thickness of 11 μm.

[0043] Example 4 A transparent anti-fouling passive radiative cooling coating. First, an organosilicon-modified acrylic resin is prepared as follows: 11.00 parts of methyl methacrylate, 11.88 parts of cyclohexyl methacrylate, 17.60 parts of butyl acrylate, 2.20 parts of 2-hydroxyethyl methacrylate, 3.52 parts of epoxy group-terminated organosilicon prepolymer, 0.23 part of initiator azobisisobutyronitrile, and 27.72 parts of propylene glycol methyl ether acetate are mixed and stirred evenly. After pouring into a constant pressure funnel, it is dropped into a three-necked flask containing 0.12 part of azobisisobutyronitrile / 34.65 parts of propylene glycol methyl ether acetate preheated to 90 °C at a feeding rate of 3 drops / second. After the dropping is completed, the reaction is continued under insulation for 1 hour. Then, 0.12 part of azobisisobutyronitrile is added, and the reaction is continued for 4 hours until it reacts fully. Finally, it is cooled to room temperature and discharged to obtain the organosilicon-modified acrylic resin.

[0044] The inorganic nanoparticle solution is an active aminated nano-silica solution with an average particle size of 5 nm. Specifically: 0.10 part of nano-silica, 10.00 parts of silane coupling agent KH550, 1.00 part of ultrapure water, and 10.00 parts of absolute ethanol are mixed and ultrasonicated for 30 minutes to disperse evenly, and then the dispersion is placed at 60 °C for reaction for 5 hours to prepare the active aminated nano-silica solution.

[0045] Finally, the active aminated nano-silica solution and the silicone-acrylic polymer are mixed evenly to prepare an organic-inorganic hybrid polymer, and then coated on the glass surface to obtain a passive radiative cooling coating.

[0046] Specifically, 100 parts of organosilicon-modified acrylic resin and 15 parts of active aminated nano-silica solution are taken, mixed evenly to prepare an organic-inorganic hybrid polymer, which is evenly coated on the surface of a glass plate, pre-baked at 60 °C for 15 minutes, and then baked at 130 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating with a thickness of 9 μm.

[0047] Example 5 A transparent anti-fouling passive radiative cooling coating. First, prepare an organosilicon-modified acrylic resin. Specifically: Mix 11.00 parts of methyl methacrylate, 11.88 parts of cyclohexyl methacrylate, 17.60 parts of butyl acrylate, 2.20 parts of 2-hydroxyethyl methacrylate, 3.52 parts of epoxy group double-capped organosilicon prepolymer, 0.23 parts of initiator azobisisobutyronitrile, and 27.72 parts of propylene glycol monomethyl ether acetate evenly. After pouring into a constant pressure funnel, dropwise add it to a three-necked flask containing 0.12 parts of azobisisobutyronitrile / 34.65 parts of propylene glycol monomethyl ether acetate preheated to 90 °C at a feeding rate of 2 drops / second. After the dropping is completed, continue to keep the temperature and react for 2 hours. Then add 0.12 parts of azobisisobutyronitrile, and then make it continue to react fully for 4 hours. Finally, cool to room temperature and discharge to obtain the organosilicon-modified acrylic resin.

[0048] The inorganic nanoparticle solution is an actively epoxidized nano-silica solution with an average particle size of 15 nm. Specifically: Mix 0.10 parts of nano-silica, 10.00 parts of silane coupling agent KH560, 1.00 part of ultrapure water, and 10.00 parts of absolute ethanol and ultrasonically disperse them evenly for 20 minutes. Then place the dispersion at 60 °C and react for 5 hours to obtain the actively epoxidized nano-silica solution.

[0049] Finally, mix the actively epoxidized nano-silica solution and the silicon-acrylic polymer evenly to obtain an organic-inorganic hybrid polymer, and then coat it on the glass surface to obtain the passive radiative cooling coating.

[0050] Specifically, take 100 parts of the organosilicon-modified acrylic resin and 25 parts of the actively epoxidized nano-silica solution, mix them evenly to obtain an organic-inorganic hybrid polymer, coat it evenly on the surface of the glass plate, pre-bake it at 55 °C for 15 minutes, and then bake it at 110 °C for 4 hours to obtain a transparent anti-fouling passive radiative cooling glass coating with a thickness of 6 μm.

[0051] Comparative Example 1: Ordinary blank glass plate; Test data analysis 1. Coating molecular structure characterization Use ATR-FTIR to characterize and analyze the molecular structure of the coating, as shown in Figure 1 。 Figure 1 This is the infrared spectrum of Example 1 of the present invention. From Figure 1As can be seen, in the transparent atmospheric window band, there are strong stretching vibration overlapping peaks of C-O-C and Si-O-Si near 9.3 μm. Si-O-Si also has strong symmetric stretching vibration peaks at 12.5 μm and 21.7 μm, enabling it to have strong long-wave infrared radiation ability in the atmospheric window band. Similarly, ATR-FTIR molecular structure characterization was performed on the coatings of Examples 2-5, and they all have strong stretching vibration absorption peaks of C-O-C and Si-O-Si intrinsic groups in the atmospheric window band. Therefore, in Examples 1-5 of this aspect, by utilizing the strong absorption of C-O-C in acrylate monomers and Si-O-Si in polysiloxanes in the long-wave infrared region, efficient thermal radiation can be achieved; on the other hand, by utilizing the polarization resonance absorption characteristics of nano-SiO 2 or silica sol, there is a phonon polariton resonance effect near 9 μm, generating strong absorption peaks, enabling effective energy output at the atmospheric window.

[0052] 2. Coating emissivity measurement data The emissivities of the coatings obtained in Examples 1, 3, and 5 and Comparative Example 1 in the long-wave infrared band (2.5-25 μm) were measured using a Fourier transform infrared spectrometer, as shown in Figure 2 . Figure 2 This is a comparison chart of the emissivities of Examples 1, 3, 5 of the present invention and the comparative example. Using the integration method, the average emissivities of coatings 1, 3, and 5 in the atmospheric window are 88.21%, 88.00%, and 87.07% respectively, while that of the blank glass in the comparative example is only 77.94%. This shows that the glass coatings prepared in Examples 1, 3, and 5 have higher emissivities than the surface of the blank glass plate in Comparative Example 1, endowing them with the performance of radiative cooling.

[0053] 3. Refrigeration effect test of the coating An outdoor experiment was designed. First, a cardboard box was wrapped with aluminum foil as a radiation shield, and a layer of polystyrene thermal insulation foam was placed at the bottom inside as a thermal insulation layer. Subsequently, the glass plates with the coatings obtained in Examples 1-5 and Comparative Example 1 and the blank glass plate were placed on the foam surface. Then, two thermocouples were placed between the two glass plates and the foam board to measure the real-time temperature on the back of the glass, as shown in Figure 3 . Figure 3 This is a comparison chart of the outdoor experiment temperature detections of Examples 1-5 of the present invention and Comparative Example 1. As can be seen from the figure, during the test period, the temperatures of the glass coatings of the examples measured are significantly lower than those of the blank glass coating in the comparative example, and their average temperature drops are approximately 5.5 °C, 3.9 °C, 5.0 °C, 2.1 °C, and 3.4 °C respectively. From Figure 3It can be seen that during the test period, the temperature of the glass coating of the examples measured is significantly lower than that of the blank glass coating. Although the quality effects of Examples 3 and 4 are slightly lower, the reason is that the modified silica particle solution is used, making the compatibility of the system better, the coating life longer, and the transparency better.

[0054] 4. Visible light transmittance of the glass coating The visible light transmittance of the glass coating was measured by ultraviolet spectrophotometry. See specifically Figure 4 , Figure 4 This is a comparison chart of the visible light transmittance of Examples 1-5 of the present invention and Comparative Example 1. It can be seen from the figure that at 500 nm, the transmittance of the coated glass is slightly lower than that of the blank glass. Among them, the transmittance of Comparative Example 1 is 91.18%, and the transmittances of Examples 1-5 are 86.81%, 90.41%, 89.24%, 90.89%, and 90.65% respectively. From Figure 4 it can be seen that at 500 nm, the transmittance of the coated glass is slightly lower than that of the blank glass, but there is no obvious difference to the naked eye and it does not affect the visibility of the field of view, indicating that it has good transparency.

[0055] 5. Anti-fouling performance The anti-fouling performance was tested and evaluated by dropping ink on the surface of the glass coating. See specifically Figure 5 , Figure 5 This is a display diagram of the anti-fouling function of Example 1. Using ink as the pollution source, it can be seen from the figure that the ink drops cleanly on the inclined surface of the coated glass, indicating that it has good anti-adhesion and anti-fouling performance. The above anti-fouling performance test was also carried out on Examples 2-5, and it was also found that Examples 2-5 all showed low adhesion to ink, and the ink could cleanly slide off their surfaces without residue.

[0056] The above is only used to illustrate the technical solutions of the present invention and not to limit them. Equal modifications and changes made by ordinary technicians in the art to the technical solutions of the present invention still fall within the scope covered by the present invention as long as they do not depart from the overall concept of the present invention.

Claims

1. A transparent antifouling passive radiative cooling coating, characterized in that: The transparent antifouling passive radiation cooling coating comprises a silicone-acrylic polymer and an inorganic nanoparticle solution, wherein the mixed mass proportions of the silicone-acrylic polymer and the inorganic nanoparticle solution are: 50 to 90 parts of the silicone-acrylic polymer and 10 to 50 parts of the inorganic nanoparticle solution; The silicone-acrylic polymer includes an organosilicon-modified acrylic resin obtained by solution polymerization or a silicone-acrylic emulsion obtained by emulsion polymerization; The inorganic nanoparticle solution includes a hydrophilic (hydrophobic) nano-SiO2 solution, a silane-modified nano-SiO2 solution or a silica sol, and the particle size is 2 to 30 nm.

2. The transparent antifouling passive radiative cooling coating according to claim 1, characterized in that: The organosilicon-modified acrylic resin is prepared by the following method: S001, dissolve 10-30% of the initiator in 50-80% of the solvent by stirring, then pour it into a three-necked flask and preheat it to 80-100°C; mix and stir acrylate monomer, silicone, 50-70% of the initiator and 20-40% of the solvent to obtain a mixed solution, then pour it into a constant pressure funnel for standby use; S002, add the mixed solution in the constant pressure funnel dropwise into a three-necked flask preheated to 80-100° C. at a feeding rate of 2-3 seconds / drop, and after the addition is complete, continue to keep warm for 1-2 hours; S003, after the heat preservation is completed, 10-30% of the initiator is added, and then it is allowed to continue to fully react for 2-4 hours, and finally cooled to room temperature to obtain the organosilicon-modified acrylic resin.

3. The transparent antifouling passive radiative cooling coating according to claim 2, characterized in that: When preparing the organosilicon-modified acrylic resin, the acrylic ester monomers include at least three of styrene, methyl (meth)acrylate, ethyl (meth)acrylate, lauryl (meth)acrylate, isooctyl methacrylate, cyclohexyl methacrylate, octadecyl (meth)acrylate, n-butyl acrylate, (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and glycidyl methacrylate; The silicone includes at least one of unsaturated silicone prepolymer, amino silicone prepolymer, carboxyl silicone prepolymer, epoxy silicone prepolymer and alcohol hydroxy silicone prepolymer; the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dibenzoyl peroxide and tert-butyl perbenzoate; the solvent includes at least one of propylene glycol methyl ether acetate, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate and isopropanol.

4. The transparent antifouling passive radiative cooling coating according to claim 1, characterized in that: The silicone-acrylic emulsion is prepared by the following method: S101, at room temperature, the acrylic acid ester monomer is dispersed at a high speed of 450-650 rpm under the action of an aqueous solution of an emulsifier to obtain a pre-emulsion 1, 10% of the pre-emulsion 1 is taken as a seed pre-emulsion for standby use, and then polysiloxane is added dropwise to the remaining pre-emulsion 1, and the stirring is continued at a stirring speed of 500-700 rpm for 30-50 minutes to obtain a milky white pre-emulsion 2, S102, at 75-90°C, using a semi-continuous seed emulsion polymerization process, the seed pre-emulsion and the initiator ammonium persulfate aqueous solution are simultaneously added to the aqueous solution of the emulsifier preheated to 85°C, and after reacting for 30-60 minutes, the pre-emulsion 2 and the initiator ammonium persulfate aqueous solution are simultaneously added dropwise for 2-3 hours; then the temperature is kept warm for 1-3 hours, then the temperature is reduced to 40-50°C, the pH is adjusted to 8-9, and finally the material is filtered to obtain the silicone acrylic emulsion.

5. The transparent antifouling passive radiation cooling coating according to claim 4, characterized in that: When preparing the silicone acrylic emulsion: the acrylic ester monomers include at least two of styrene, methyl (meth)acrylate, isooctyl methacrylate, cyclohexyl methacrylate, octadecyl (meth)acrylate, and n-butyl acrylate; The polysiloxane is at least one of polydimethylsiloxane, vinyl polysiloxane, mono(meth)acrylate-terminated polysiloxane, and di(meth)acrylate-terminated polysiloxane; The emulsifier is an anionic emulsifier, a nonionic emulsifier or an anionic and nonionic composite emulsifier; the anionic emulsifier includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, tridecyl polyoxyethylene ether ammonium phosphate, SR-10, and SR-20; the nonionic emulsifier includes at least one of OP-10, ER-10, ER 20, ER 30, AEO 9, LCN287, and LCN118.

6. The transparent antifouling passive radiative cooling coating according to claim 4, characterized in that: The solid content of the silicone-acrylic emulsion is 30% to 50%; the average particle size of the silicone-acrylic emulsion is 70 to 100 nm.

7. The transparent antifouling passive radiation cooling coating according to claim 1, characterized in that: The silane-modified nano-SiO2 solution includes an active aminated nano-SiO2 solution or an active epoxidized nano-SiO2 solution. The active aminated nano-silica solution is specifically prepared by mixing nano-silica, silane coupling agent KH550, ultrapure water and anhydrous ethanol for 15 to 30 minutes to make them dispersed evenly, and then placing the dispersion at 60° C. to react for 3 to 5 hours to obtain an active aminated nano-silica solution; wherein the nano-silica, silane coupling agent KH550, ultrapure water and anhydrous ethanol are mixed in a mass ratio of 1:100:10:100; The active epoxidized nano-silica solution is specifically prepared by mixing nano-silica, silane coupling agent KH560, ultrapure water and anhydrous ethanol and ultrasonically dispersing them for 15 to 30 minutes to make them uniformly dispersed, and then placing the dispersion at 60° C. to react for 3 to 5 hours to obtain the active epoxidized nano-silica solution; wherein the nano-silica, silane coupling agent KH560, ultrapure water and anhydrous ethanol are mixed in a mass ratio of 1:100:10:

100.

8. The transparent antifouling passive radiative cooling coating according to claim 1, characterized in that: The preparation method of the transparent anti-fouling passive radiation cooling coating is as follows: a silicone-acrylic polymer and inorganic nanoparticles are uniformly mixed to obtain an organic-inorganic hybrid polymer, which is uniformly coated on a glass surface, and baked at 90 to 150° C. for 2 to 6 hours to obtain a transparent anti-fouling passive radiation cooling glass coating.

Images