Acid-alkali-resistant anti-ultraviolet high-fastness daytime radiation cooling coating as well as preparation method and application thereof

Abstract

The invention discloses an acid and alkali resistant anti-ultraviolet high-fastness daytime radiation cooling coating and a preparation method and application thereof, the daytime radiation cooling coating covers the surface of a base material, and is formed by curing a water-based environment-friendly emulsion containing inorganic nanoparticles under the action of a curing agent; the water-based environment-friendly emulsion comprises an emulsifier, a bonding polymer and an organic silicon material; the base material is made of at least one of metal, concrete, ceramic, wood, plastic and glass. The daytime radiation cooling coating disclosed by the invention has the advantages of high sunlight reflectivity, high atmospheric window emissivity and strong cooling performance, meanwhile, the adhesion fastness with a base material is high, the acid and alkali resistance and the ultraviolet resistance are excellent, the service life of the daytime radiation cooling coating can be prolonged, and the cooling performance of the daytime radiation cooling coating can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, and in particular to a kind of acid and alkali resistant and ultraviolet resistant high fastness daytime radiative cooling coating and its preparation method and application. BACKGROUND

[0002] The continuous development of population growth and social economy and the acceleration of urbanization process have caused many negative impacts on global climate and environment, one of which is urban heat island effect. The urban heat island effect not only brings discomfort to urban residents and even threatens their life safety, but also shortens the service life of outdoor equipment. Heat acts on the urban environment, leading to increased energy consumption and accelerating the process of global warming. Energy crisis and global warming are major global challenges that are currently attracting much attention and need to be addressed urgently. About 15% of global energy consumption is used for cooling every year. However, the efficiency and energy conversion rate of traditional cooling methods are generally low. Passive radiative cooling, as a new type of environmentally friendly and zero-energy cooling technology, has become an important means to solve this problem.

[0003] Daytime radiative cooling materials achieve cooling effect by reflecting most of the energy in sunlight, and the main reflected wave band covers from visible light to near-infrared light (wavelength range of 0.3-2.5 μm). At the same time, the material can also transfer the heat generated by itself to the absolute zero environment of outer space through the atmospheric window band (wavelength range of 8-13 μm) by radiation, thereby ensuring effective reduction of its own temperature. This feature enables daytime radiative cooling materials to significantly reduce the temperature of the surface of outdoor workers, building walls, tanks, and iron sheets. Chinese patent document CN118374199A uses a hydrophobic modifier to modify inorganic particles, and mixes the modified inorganic particles with an organic polymer to prepare a self-cleaning daytime radiative cooling coating. The coating has high solar reflectance and mid-infrared emissivity, and the preparation method is simple and easy to industrialize. Chinese patent document CN114634727B discloses a radiative cooling coating for the outer surface of a building. The infrared emission layer of the coating is mainly composed of polyvinylidene fluoride-hexafluoropropylene copolymer and polymethyl methacrylate, and the reflective material is selected from one of silver powder or aluminum powder. This invention achieves effective reflection of sunlight by a solar spectrum radiation total reflection layer, reducing the absorption of solar energy. At the same time, the infrared emission layer radiates the heat of the building outward. This technology not only reduces the absorption of solar radiation during the day, but also enhances the infrared radiation release in the wavelength range of 8-13 μm at night, thereby effectively reducing the overall temperature of the building.

[0004] However, the daytime radiative cooling coatings at the present stage generally do not have high fastness performance in terms of acid and alkali resistance and ultraviolet resistance, and the cooling performance may decrease in the face of harsh environment. SUMMARY

[0005] The present application provides a high-fastness acid and alkali resistant ultraviolet resistant daytime radiant cooling coating, which has the advantages of high solar reflectance, high atmospheric window emissivity, strong cooling performance, high adhesion to the substrate, acid and alkali resistance, excellent ultraviolet resistance, and can prolong the service life and cooling performance.

[0006] The technical scheme of the present application is as follows: A high-fastness acid and alkali resistant ultraviolet resistant daytime radiant cooling coating is covered on the surface of a substrate and is formed by curing a water-based environmentally friendly emulsion containing inorganic nanoparticles under the action of a curing agent; the water-based environmentally friendly emulsion contains an emulsifier, a bonding polymer and an organic silicon material. The material of the substrate is at least one of metal, concrete, ceramic, wood, plastic and glass.

[0007] The present application adopts a method of combining inorganic particles with resin emulsion, wraps inorganic particles into resin emulsion, and obtains a high-fastness acid and alkali resistant ultraviolet resistant daytime radiant cooling coating. The coating prepared on the surface of a specific substrate has good adhesion to the substrate surface, acid and alkali resistance, ultraviolet resistance, and the raw materials are economical and easy to obtain, and are suitable for industrial production.

[0008] Preferably, the thickness of the daytime radiant cooling coating is 100-600 μm; or the coating amount of the daytime radiant cooling coating per square centimeter of the substrate surface is 1-30 mg.

[0009] With the increase of the coating amount and thickness of the coating, the inorganic particles on the surface accumulate more and form a relatively flat reflective layer, which improves the reflection of sunlight. However, when the coating amount and thickness of the coating are further increased, the reflectivity and emissivity no longer increase, but slightly decrease.

[0010] Further preferably, the thickness of the daytime radiant cooling coating is 250-350 μm; or the coating amount of the daytime radiant cooling coating per square centimeter of the substrate surface is 15-25 mg.

[0011] Preferably, the inorganic nanoparticles are at least one of silicon dioxide, barium sulfate, zinc oxide, titanium dioxide, zirconium oxide, zinc sulfide, calcium carbonate, aluminum oxide and barium titanate.

[0012] The particle size of the inorganic nanoparticles is 800-1500 nm.

[0013] Preferably, the content of the inorganic nanoparticles in the water-based environmentally friendly emulsion is 70-90 wt%; most preferably 83 wt%.

[0014] The curing agent is an epoxy resin curing agent.

[0015] The epoxy resin curing agent includes an amine curing agent, an acid anhydride curing agent, a phenolic resin curing agent, a latent curing agent and a catalytic curing agent.

[0016] Preferably, the emulsifier is prepared by condensation of a hydrophilic polymer and a lipophilic polymer under the action of a catalyst; the hydrophilic polymer is at least one of polyethylene glycol, polyvinyl alcohol, polypropylene oxide and polyhydroxyethyl methacrylate; and the lipophilic polymer is an epoxy resin.

[0017] In the radiation cooling coating of the present application, the epoxy groups at both ends of the molecular chain of the epoxy resin have very high reactivity. The epoxy groups can chemically react with active groups on the surface of various substrates (especially metals, concrete, ceramics, wood, plastics, glass, etc.), such as hydroxyl groups (-OH), amine groups (-NH2) and carboxyl groups (-COOH) on the surface of metals, to form chemical bonds; the epoxy groups can also crosslink with amine curing agents (such as F0716) to form a dense crosslinked network, thereby making the radiation cooling coating have excellent fastness.

[0018] Further, the lipophilic polymer is one of bisphenol A type epoxy resin, alicyclic epoxy resin and phenolic type epoxy resin.

[0019] Further preferably, the hydrophilic polymer is polyethylene glycol, and the lipophilic polymer is bisphenol A type epoxy resin.

[0020] The ratio of the hydrophilic polymer to the lipophilic polymer determines the HLB value of the macromolecular emulsifier. When the emulsifier is synthesized, the more the hydrophilic polymer, the more the hydrophilic segment, and the better the hydrophilicity of the emulsifier. Preferably, the mass ratio of the hydrophilic polymer to the lipophilic polymer is 3-5:1.

[0021] The type of catalyst determines whether the reaction can proceed smoothly and the reaction rate. The catalyst is one of triphenylphosphine, dibutyltin dilaurate, potassium persulfate and boron trifluoride etherate.

[0022] The bonding polymer is an epoxy resin; further, the bonding polymer is at least one of bisphenol A type epoxy resin, alicyclic epoxy resin and phenolic type epoxy resin.

[0023] The organic silicon material is at least one of polyether modified silicone oil, amino silicone oil, phosphate ester modified silicone oil, carboxyl modified silicone oil and betaine type organic silicon.

[0024] The application prepares an acid and alkali resistant, ultraviolet resistant and high fastness radiation cooling coating by mixing water-based resin emulsion and nano inorganic particles, and the introduction of silicone material improves the atmospheric window emissivity of the coating and provides better ultraviolet resistance for the coating, so that the coating is not damaged by ultraviolet rays, the radiation cooling performance is not affected, and the outdoor service life is prolonged.

[0025] The application also provides a preparation method of the acid and alkali resistant, ultraviolet resistant and high fastness daytime radiation cooling coating. (1) hydrophilic polymer and lipophilic polymer are added to a cosolvent, and are uniformly mixed and stirred at 50-100 DEG C under an inert atmosphere to obtain a mixed solution; (2) a catalyst solution is added dropwise to the mixed solution, the temperature is increased to 150-200 DEG C, and reaction is carried out for 1-5 h to obtain an emulsifier; (3) the emulsifier, silicone material, adhesive polymer and water are emulsified to obtain a silicone modified water-based emulsion; (4) the water-based emulsion is uniformly mixed with nano inorganic particles, a curing agent is added, and the mixture is arranged on the surface of a base material, so that an acid and alkali resistant, ultraviolet resistant and high fastness daytime radiation cooling coating is obtained after curing.

[0026] The cosolvent can help the hydrophilic polymer and the lipophilic polymer to be mixed.

[0027] Preferably, in step (3), the emulsification comprises: obtaining a coarse emulsion by mechanical stirring or ultrasonic assisted method; and then homogenizing by using a homogenizer to obtain a stable water-based emulsion.

[0028] In step (3), the emulsification process involves using high shear force stirring or shearing equipment such as a high-speed stirrer and a homogenizer to deeply stir and shear the mixed solution. Under the action of shear force, the emulsifier can further disperse droplets, so that the oil droplets or water droplets become smaller and more uniform, thereby forming a stable emulsion structure.

[0029] In step (4), the water-based emulsion is arranged on the surface of the base material by means of blade coating, dip coating, spraying or spin coating.

[0030] The application also provides an acid and alkali resistant, ultraviolet resistant and high fastness daytime radiation cooling product, which comprises a base material and the daytime radiation cooling coating arranged on the surface of the base material; and the material of the base material is at least one of iron, aluminum, wood, plastic and glass.

[0031] Compared with the prior art, the application has the following beneficial effects: (1) the water-based emulsion used in the application has an environmentally friendly curing process without VOC emission, and does not pollute the environment.

[0032] (2) The nano inorganic particle adopted in the application has high reflectivity, and the selectivity is wide.

[0033] (3) The introduction of the silicone material improves the atmospheric window emissivity of the coating, and increases the ultraviolet resistance.

[0034] (4) The radiation cooling coating prepared by the application has good acid and alkali resistance, excellent ultraviolet resistance, and can maintain good radiation cooling capacity in harsh environments.

[0035] (5) The raw materials used in the application are cheap and easy to obtain, the preparation method is simple, and the application is suitable for industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The solar reflectivity curve diagram of the radiation cooling coating with different thicknesses in Example 6.

[0037] Figure 2 The mid-infrared emissivity curve diagram of the radiation cooling coating with different thicknesses in Example 6.

[0038] Figure 3 The adhesion test result diagram of the radiation cooling coating in Example 6.

[0039] Figure 4 The acid and alkali resistance test result diagram of the radiation cooling coating in Example 6.

[0040] Figure 5 The ultraviolet resistance test result diagram of the radiation cooling coating in Example 6. DETAILED DESCRIPTION

[0041] The application will be described in further detail below in conjunction with the drawings and examples, and it should be pointed out that the following examples are intended to facilitate the understanding of the application and do not limit the application in any way.

[0042] The same amine curing agent (F0716) is used in the following implementation examples.

[0043] Example 1 (1) Place 400 parts of polyethylene glycol-6000 and 100 parts of epoxy resin E-51 in a three-necked flask, add a small amount of cosolvent, and stir uniformly at 70°C under nitrogen. until the polyethylene glycol and the epoxy resin are completely dissolved, add 4 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly drop into the mixed solution, the temperature rises to 180°C, and the reaction is carried out for 3 hours to obtain a light yellow transparent macromolecular emulsifier.

[0044] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 100 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0045] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add silica (1 μm) 72 parts, stir and mix uniformly, to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is applied to the iron sheet substrate, and after drying, the thickness is 350 μm.

[0046] Example 2 (1) According to the mass fraction, 400 parts of polyethylene glycol-6000 and 100 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 4 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixed solution, the temperature rises to 180°C, and the reaction is carried out for 3 hours to obtain a light yellow transparent macromolecular emulsifier.

[0047] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 100 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0048] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add silica (1 μm) 80 parts, stir and mix uniformly, to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is applied to the polyester fabric substrate, and the coating amount is 20.1 mg·cm -2 .

[0049] Example 3 (1) According to the mass fraction, 400 parts of polyethylene glycol-6000 and 100 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 4 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixed solution, the temperature rises to 180°C, and the reaction is carried out for 3 hours to obtain a light yellow transparent macromolecular emulsifier.

[0050] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 100 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0051] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add calcium carbonate (1 μm) 72 parts, stir and mix uniformly to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation and cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation and cooling paint is dip-coated on the aluminum can substrate, and dried to a thickness of 300 μm.

[0052] Example 4 (1) According to the mass fraction, 400 parts of polyethylene glycol-6000 and 100 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 4 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixture, the temperature rises to 180°C, and react for 3 hours to obtain a light yellow transparent macromolecular emulsifier.

[0053] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 100 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0054] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add calcium carbonate (1 μm) 80 parts, stir and mix uniformly to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation and cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation and cooling paint is dip-coated on the aluminum can substrate, and dried to a thickness of 350 μm.

[0055] Example 5 (1) According to the mass fraction, 420 parts of polyethylene glycol-6000 and 110 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 6 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixture, the temperature rises to 180°C, and react for 3.5 hours to obtain a light yellow transparent macromolecular emulsifier.

[0056] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First, slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 110 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0057] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add silica (1 μm) 80 parts, stir and mix uniformly, to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is applied to the surface of the polyester fabric substrate by scraping, and the coating amount is 21.2 mg·cm -2 .

[0058] Example 6 (1) According to the mass fraction, 420 parts of polyethylene glycol-6000 and 110 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 6 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixed solution, the temperature rises to 180°C, and the reaction is carried out for 3.5 hours to obtain a light yellow transparent macromolecular emulsifier.

[0059] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and mixed at 60°C in a three-necked flask. First, slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 110 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0060] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add barium sulfate (1 μm) 78 parts, stir and mix uniformly, to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is applied to the surface of the iron sheet substrate by scraping, and the thickness is 120~300 μm.

[0061] Example 7 (1) According to the mass fraction, 420 parts of polyethylene glycol-6000 and 110 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out at 70°C until the polyethylene glycol and epoxy resin are completely dissolved. Add 6 parts of potassium persulfate catalyst and a small amount of cosolvent, slowly add to the mixed solution, the temperature rises to 180°C, and the reaction is carried out for 3.5 hours to obtain a light yellow transparent macromolecular emulsifier.

[0062] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and uniformly at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 110 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0063] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add zinc oxide (800 nm) 80 parts, stir and mix uniformly to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is scraped and arranged on the iron sheet substrate, with a thickness of 305 μm.

[0064] Example 8 (1) According to the mass fraction, 420 parts of polyethylene glycol-6000 and 110 parts of epoxy resin E-51 are placed in a three-necked flask, a small amount of cosolvent is added, nitrogen is introduced, and stirring is carried out uniformly at 70°C. Until the polyethylene glycol and epoxy resin are completely dissolved, 6 parts of potassium persulfate catalyst and a small amount of cosolvent are added, slowly added to the mixed solution, the temperature is raised to 180°C, and the reaction is carried out for 3.5 hours to obtain a light yellow transparent macromolecular emulsifier.

[0065] (2) Take the above 10 parts of emulsifier, 30 parts of epoxy resin E-51, 5 parts of epoxy-terminated polyether silicone oil (Xt-12k) hydrophilic silicone resin, fully stirred and uniformly at 60°C in a three-necked flask. First slowly add deionized water, then speed up the dropwise addition rate, the total amount of deionized water is 110 parts. The emulsion is dispersed by high-speed stirring for 30 min, then homogenized by homogenizer for 30 min, and filtered by gauze to obtain a stable silicone-modified epoxy resin emulsion.

[0066] (3) Take the above emulsion 60 parts, curing agent 5 parts, stir and mix uniformly, then add zinc oxide (800 nm) 75 parts, stir and mix uniformly to obtain acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint. The acid and alkali resistant, ultraviolet resistant, high fastness, radiation cooling paint is scraped and arranged on the iron sheet substrate, with a thickness of 305 μm.

[0067] Test: 1. Test the solar reflectivity curve and the mid-infrared emissivity curve of the radiation cooling coating prepared in Examples 1-8.

[0068] Figure 1The solar reflectance curves of the radiation cooling coating with different thicknesses in Example 6 are shown in the following table. When the thicknesses are 120, 200, and 300 μm, the average solar reflectance is 88.5%, 92.1%, and 94.2%, respectively, which can effectively reflect solar energy. Figure 2 The mid-infrared emissivity curves of the radiation cooling coating with different thicknesses in Example 6 are shown in the following table. When the thicknesses are 120, 200, and 300 μm, the average emissivity in the atmospheric window is 0.894, 0.901, and 0.903, respectively, which can effectively emit heat to the outside space, thereby achieving cooling.

[0069] 2. Adhesion test of the radiation cooling coating to the substrate The coating is divided into 10x10 squares using a cross-cut knife, and then the squares are adhered using transparent tape. Whether the edges of the squares fall off is observed.

[0070] Figure 3 The adhesion test results of Example 6 are shown in the following table. When the thickness of the coating is 300 μm, the adhesion is level 2. The adhesion of the coating is good, as shown in the following table. Figure 3 Good adhesion can improve the durability of the coating. If the adhesion of the coating is poor, the coating may fall off under external environmental changes (external force impact, humidity, temperature, wind speed, etc.).

[0071] In the radiation cooling coating of the present application, the epoxy groups at both ends of the epoxy resin molecular chain have very high reactivity. The epoxy groups can chemically react with active groups (such as hydroxyl (-OH), amine (-NH2), carboxyl (-COOH), etc.) on the surface of various substrates (especially metals, concrete, ceramics, etc.), forming chemical bonds (covalent bonds), which is the strongest binding force; the epoxy groups can also crosslink with the molecules of the curing agent, forming a dense crosslinked network, thereby making the radiation cooling coating have excellent fastness performance.

[0072] 3. Acid and alkali resistance test The coating is applied to the substrate and immersed in a solution with a pH range of 1-14 for 24 h. After wiping off the surface moisture, the coating is dried in an oven. The average reflectivity, average emissivity, and mass change are tested and calculated.

[0073] Figure 4 The acid and alkali resistance test results of the radiation cooling coating prepared in Example 6 are shown in the following table. The coating has high reflectivity and emissivity in both acidic and alkaline environments, and the mass of the coating is basically not lost.

[0074] 4. Anti-ultraviolet performance test The K / S value change of the coating before and after aging was tested by using a UV light accelerated aging tester to accelerate the aging of the coating for 24 h. Figure 5 The K / S value of the coating before and after aging of Example 6 did not change substantially after 24 h of UV accelerated aging. The introduction of the silicone material increased the anti-UV performance of the coating. The silicon-oxygen bond has a high bond energy and is not easily broken and decomposed under UV irradiation. At the same time, the inorganic particles reflect most of the UV light to avoid being absorbed by the substrate, thus having good anti-UV performance.

[0075] The performance of the radiation cooling coating prepared in other examples is consistent with the performance of the radiation cooling coating prepared in Example 6.

[0076] The above examples have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, supplement, and equivalent replacement within the principle range of the present application should be included in the protection scope of the present application.

Claims

1. A daytime radiation cooling coating with high acid, alkali and UV resistance, characterized by: The adhesive is covered on the surface of the substrate and is formed by solidifying an aqueous environmentally friendly emulsion containing inorganic nanoparticles under the action of a curing agent; the aqueous environmentally friendly emulsion contains an emulsifier, an adhesive polymer, and an organic silicon material; The material of the substrate is at least one of metal, concrete, ceramic, wood, plastic and glass.

2. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1, characterized in that: The thickness of the daytime radiation cooling coating is 100-600 μm.

3. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1, characterized in that: The inorganic nanoparticles are at least one of silicon dioxide, barium sulfate, zinc oxide, titanium dioxide, zirconium oxide, zinc sulfide, calcium carbonate, aluminum oxide, and barium titanate.

4. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1 or 3, characterized in that: The content of inorganic nanoparticles in the water-based environmentally friendly emulsion is 70~90wt%.

5. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1, characterized in that: The emulsifier is formed by polycondensation of a hydrophilic polymer and a lipophilic polymer under the action of a catalyst; the hydrophilic polymer is at least one of polyethylene glycol, polyvinyl alcohol, polypropylene oxide, and polyhydroxyethyl methacrylate; and the lipophilic polymer is epoxy resin.

6. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1, characterized in that: The adhesive polymer is epoxy resin.

7. The acid-base resistant, UV-resistant, high-fastness daytime radiation cooling coating according to claim 1, characterized in that: The organic silicon material is at least one of polyether modified silicone oil, amino silicone oil, phosphate modified silicone oil, carboxyl modified silicone oil and betaine type organic silicon.

8. A method for preparing a daytime radiation cooling coating according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Adding a hydrophilic polymer and a lipophilic polymer to a cosolvent, mixing and stirring them uniformly at 50-100°C under an inert atmosphere to obtain a mixed solution; (2) Add the catalyst solution dropwise to the mixed solution, raise the temperature to 150-200°C and react for 1-5 hours to obtain an emulsifier; (3) emulsifying the emulsifier, the silicone material, the adhesive polymer and water to obtain a silicone-modified aqueous emulsion; (4) The aqueous emulsion and the nano inorganic particles are mixed and stirred evenly, a curing agent is added, and the mixture is applied to the surface of the substrate. After curing, a daytime radiation cooling coating with high fastness, acid and alkali resistance, and UV resistance is obtained.

9. The method for preparing the daytime radiation cooling coating according to claim 8, characterized in that: The cosolvent is at least one of acetone, butanone, ethyl acetate, butyl acetate, n-butanol, ethylene glycol ethyl ether and propylene glycol methyl ether.

10. A daytime radiation cooling product with high acid, alkali and UV resistance, characterized by: The invention comprises a substrate and a daytime radiation cooling coating as claimed in any one of claims 1 to 7 covering the surface of the substrate.

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