Preparation method, product and application of weather-resistant self-healing radiation cooling roof coating

Abstract

The invention relates to the field of radiation cooling coatings, in particular to a preparation method, a product and application of a weather-proof self-healing radiation cooling roof coating. The preparation method comprises the following steps: dissolving the pH stabilizer and the emulsifier in water, and uniformly mixing to obtain a water phase; uniformly mixing a hard monomer, a soft monomer, a modified monomer, a co-stabilizer and a chain transfer agent to obtain an oil phase, adding the oil phase into the water phase, and performing ultrasonic emulsification to obtain a miniemulsion; heating the miniemulsion to 50-75 DEG C, then adding an initiator solution, and carrying out heat preservation to obtain latex A; adding a solution A containing a cross-linking agent and a catalyst into the latex A, and uniformly mixing to obtain latex B; and coating the latex B on the surface of a substrate, drying, and curing to obtain the weather-resistant self-healing radiation cooling roof coating. The cooling roof coating is wide in raw material source, simple in preparation process and easy for large-scale production and engineering application. The cooling roof coating has excellent weather resistance, mechanical property, self-repairing property and passive cooling capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiant cooling coatings, in particular to a preparation method, product and application of a weather-resistant self-healing radiant cooling roof coating. BACKGROUND

[0002] With the intensification of global climate change, building energy saving has become a key field to cope with energy crisis and slow down greenhouse gas emissions. Building energy consumption accounts for about 40% of the total global energy consumption, among which residential and commercial buildings consume about 60% of the global electricity and are the main source of greenhouse gas emissions. By implementing building energy saving measures, not only can fossil fuel consumption be effectively reduced, but also greenhouse gas emissions can be significantly reduced, which is of great significance to slow down climate change and promote sustainable development. Therefore, promoting the innovation and application of building energy saving technology has become an urgent task to cope with climate change globally.

[0003] The roof covers an area of about 20%-25% of the total surface area of the city, and the heat absorbed by it is transmitted to the indoor environment through conduction and convection, significantly affecting the indoor thermal environment. Studies have shown that replacing black asphalt roofs with white high-albedo roofs can reduce cooling energy consumption by 11%-43%. Therefore, using high-albedo roof coatings is an effective strategy to achieve building energy saving. Commonly used cooling roof materials include white paint (polyacrylate), white film (polyvinyl chloride, thermoplastic polyolefin), and reflective aluminum film, which can all achieve different degrees of cooling of the roof surface and indoor environment. However, during long-term outdoor use, due to high-intensity solar ultraviolet radiation, day and night temperature differences, mechanical damage, PM (acidic substances, organic chemicals, metals, and soil dust) deposition in the air, and rainwater erosion, the roof cooling material suffers irreversible damage, the albedo decreases, and thus its cooling and protection capabilities are significantly reduced, losing its energy-saving effect. Therefore, designing and developing a self-healing cooling roof material with high weather resistance and without the need for human intervention is a potential requirement for long-term building energy saving. SUMMARY

[0004] Based on the above, the present application provides a preparation method, product and application of a weather-resistant self-healing radiant cooling roof coating. The cooling roof coating of the present application simultaneously has weather resistance, self-healing property and passive cooling characteristics, overcoming the shortcomings of current cooling roof coatings in terms of sustainability.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions: One of the technical solutions of the present application is a preparation method of a weather-resistant self-healing radiant cooling roof coating, comprising the following steps: Step 1: Dissolve the pH stabilizer and emulsifier in water and mix to obtain an aqueous phase; Step 2, the hard monomer, soft monomer, modified monomer, auxiliary stabilizer, chain transfer agent are mixed uniformly to obtain an oil phase, the oil phase is added into the water phase, and the fine emulsion is obtained by ultrasonic emulsification; Step 3, the fine emulsion is heated to 50-75 DEG C, then the initiator solution is added, and the latex A is obtained after preservation; Step 4, the solution A containing crosslinking agent and catalyst is added into the latex A and mixed uniformly to obtain the latex B; Step 5, the latex B is coated on the surface of the substrate, then dried, and then cured to obtain the weather-resistant self-healing radiation cooling roof coating.

[0006] The second technical scheme of the present application is a weather-resistant self-healing radiation cooling roof coating prepared by the above preparation method.

[0007] The third technical scheme of the present application is the application of the above weather-resistant self-healing radiation cooling roof coating in the field of building.

[0008] The present application discloses the following technical effects: The raw material of the cooling roof coating of the present application is widely available, the preparation process is simple, and the present industrialized emulsion polymerization production process and production equipment can be adapted, so that large-scale production and engineering application are easy.

[0009] The cooling roof coating of the present application has excellent weather resistance, mechanical properties, self-repairing performance and passive cooling capacity. DETAILED DESCRIPTION

[0010] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0011] Figure 1 The esterification reaction degree of carboxyl and epoxy group in example 1, example 2 and example 3.

[0012] Figure 2 The stress-strain curve of the coating before and after ultraviolet aging in example 2.

[0013] Figure 3 The scratch self-repairing capacity of the coating without artificial intervention in example 2.

[0014] Figure 4 The surface of the coating after copper salt acetic acid accelerated corrosion and ultraviolet aging in example 2 and comparative example 2.

[0015] Figure 5Reflectance of the coatings in Example 2 and Comparative Example 2 before and after accelerated corrosion by copper acetate and UV aging.

[0016] Figure 6 Emissivity of the coatings in Example 2 and Comparative Example 2 before and after accelerated corrosion by copper acetate and UV aging.

[0017] Figure 7 Actual roof cooling effect of the coatings in Example 2 and Comparative Example 2 before and after accelerated corrosion by copper acetate and UV aging.

[0018] Figure 8 Synthetic route and preparation flow chart of the weathering self-healing radiant cooling roof coating of the present application. DETAILED DESCRIPTION

[0019] Various illustrative embodiments of the present application are described in detail below. This detailed description is not intended to restrict the application unless so indicated, but merely to explain certain aspects, features and embodiments of the application.

[0020] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and each range is inclusive of its end points.

[0021] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the present specification will control.

[0022] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0023] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" or the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0024] In the present application, "%" means mass percentage, unless otherwise specified.

[0025] The present application introduces epoxy groups into the backbone of the acrylate polymer to obtain (PBMG), and then introduces bicarboxymethyl trithiocarbonate (BCMTTC) as a dynamic covalent bond into the acrylate polymer in a post-curing manner to form a dynamic covalent polymer network (BCMTTC-PBMG), which endows the coating with good self-repairing ability and high mechanical properties. And using the reversible decomposition mechanism of BCMTTC under ultraviolet irradiation, the coating is endowed with excellent ultraviolet resistance. The composite film (BCMTTC-PBMG-Al) formed by coating the acrylate coating on the surface of 1060 aluminum foil has high reflectivity in the visible light band of the sun, and has high emissivity in the two atmospheric windows of 8-13 μm and 16-25 μm. In the actual roof cooling test, it shows good cooling effect. The coating preparation process is simple, has the functions of weather resistance, self-healing and radiation cooling, effectively balances the cooling performance and sustainability of the coating, and shows significant environmental protection and energy saving advantages.

[0026] The first aspect of the present application provides a preparation method of a weather-resistant self-healing radiation cooling roof coating, comprising the following steps: Step 1, dissolving pH stabilizer and emulsifier in water to obtain water phase; Step 2, mixing hard monomer, soft monomer, modified monomer, auxiliary stabilizer and chain transfer agent uniformly to obtain oil phase, adding the oil phase into the water phase, and ultrasonic emulsifying to obtain fine emulsion; Step 3, heating the fine emulsion to 50-75℃, then adding initiator solution, and keeping warm to obtain latex A; Step 4, mixing solution A containing crosslinking agent and catalyst into latex A to obtain latex B; Step 5, coating latex B on the surface of the substrate, drying, and then curing to obtain the weather-resistant self-healing radiation cooling roof coating.

[0027] In the preferred embodiment of the present application, in step 1, the mass ratio of pH stabilizer to emulsifier is 1: (6-12); the pH stabilizer is sodium bicarbonate; and the emulsifier is at least one of fatty alcohol polyoxyethylene ether phosphate, alkylphenol polyoxyethylene ether and sodium dodecyl sulfate.

[0028] The present application does not particularly limit the amount of water in the water phase, and the amount of water can make the pH stabilizer and emulsifier fully dissolved.

[0029] In the preferred embodiment of the present application, in step 2, the mass ratio of the hard monomer to the soft monomer, the modified monomer, the co-stabilizer and the polymerization transfer agent is (9.20-46.00):(46.00-82.80):(2.00-8.00):(4.00-5.00):(0.25-0.80); further preferably, the amount of the modified monomer is 2-8 wt% of the total mass of the monomers; the co-stabilizer accounts for 4-5 wt% of the total mass of the monomers; the chain transfer agent accounts for 0.25-0.8 wt% of the total mass of the monomers; the hard monomer is at least one of methyl methacrylate, ethyl methacrylate and styrene; the soft monomer is at least one of butyl acrylate, isooctyl acrylate and ethyl acrylate; the modified monomer is one or both of glycidyl methacrylate and allyl glycidyl ether; the co-stabilizer is at least one of styrene oligomer (weight average molecular weight M w =45000-50000, purchased from Tianjin Xinsuo Optoelectronic Technology Co., Ltd.), hexadecane, polyorganosiloxane (number average molecular weight M n =5600, purchased from Merck Life Science Co., Ltd.), at least one of 2,4-diphenyl-4-methyl-1-pentene (purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.), 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropanoic acid (purchased from Tianjin Xinsuo Optoelectronic Technology Co., Ltd.) and n-dodecyl mercaptan.

[0030] In the preferred embodiment of the present application, in step 3, the initiator in the initiator solution is at least one of ammonium persulfate, potassium persulfate, azobisdimethylaminoformamidine hydrochloride, ascorbic acid and t-butyl hydroperoxide complex system (ascorbic acid and t-butyl hydroperoxide complex system purchased from Shanghai Mayre Chemical Technology Co., Ltd.); the solvent of the initiator solution is water; the temperature of the heat preservation is 50-75℃, and the time is 100-150 min.

[0031] The amount of water in the initiator solution is not particularly limited in the present application, and the amount of water can be sufficient to dissolve the initiator.

[0032] In the preferred embodiment of the present application, the mass ratio of the pH stabilizer to the hard monomer is (0.50-1.00):(9.20-46.00); the mass ratio of the initiator to the hard monomer is (0.50-1.00):(9.20-46.00), and further preferably, the initiator accounts for 0.5wt%-0.8wt% of the total mass of the monomers.

[0033] In a preferred embodiment of the present application, in step 4, the crosslinking agent is at least one of bis-carboxymethyl trithiocarbonate (purchased from Shanghai Mclinn Biotech Co., Ltd.), bis-carboxyethyl trithiocarbonate (purchased from Belling Chem-Tech Co., Ltd.) or 2,2'-[methylthiobis(thio)]bis[2-methylpropanoic acid] (purchased from Belling Chem-Tech Co., Ltd.); the catalyst is at least one of acetylacetone chromium, acetylacetone manganese or acetylacetone aluminum; the solvent of solution A is ethanol; the mass ratio of the crosslinking agent, the catalyst and the hard monomer is (1.5-6.5):(0.07-0.3):(9.20-46.00).

[0034] In a preferred embodiment of the present application, the substrate is an aluminum foil.

[0035] In a preferred embodiment of the present application, in step 5, the temperature for curing is 70-150℃ and the time is 9h.

[0036] In some embodiments of the present application, in step 5, latex B is coated onto the surface of the substrate by a knife coater, and then cured after the temperature of the coater is raised to 60℃ to remove most of the solvent.

[0037] The second aspect of the present application provides a weather-resistant self-healing radiant cooling roof coating prepared by the above preparation method.

[0038] The third aspect of the present application provides the use of the above weather-resistant self-healing radiant cooling roof coating in the field of construction.

[0039] In some embodiments of the present application, in step 2, after the preparation of the fine emulsion by ultrasonic emulsification, the step of introducing nitrogen to remove air is further included.

[0040] In some embodiments of the present application, in step 3, the initiator solution is added in multiple times, and the amount of each addition is 1 / 5 of the total amount of the initiator, and the interval between two additions is 60min; and the initiator solution is kept after being added completely.

[0041] In some embodiments of the present application, in step 4, before solution A is added into latex A, the step of cooling latex A to below 40℃ is further included.

[0042] The technical solutions described in the present application are all conventional solutions in the field unless otherwise specified, and the reagents or raw materials used are purchased from commercial channels or are already disclosed unless otherwise specified.

[0043] In the examples of the present application, 2,4-diphenyl-4-methyl-1-pentene is purchased from Shanghai Mclinn Biotech Co., Ltd.; and bis-carboxymethyl trithiocarbonate is purchased from Shanghai Mclinn Biotech Co., Ltd.

[0044] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0045] Example 1 A preparation method of a weather-resistant self-healing radiation cooling roof coating, the steps are as follows: Step 1, 0.50 g of sodium bicarbonate, 4.00 g of sodium dodecyl sulfate (SDS), 2.00 g of alkylphenol polyoxyethylene ether (OP-10) were dissolved in 200 mL of deionized water, and a magnetic stirrer was used to stir until completely dissolved to obtain an aqueous phase; Step 2, 39.20 g of methyl methacrylate (MMA), 58.80 g of butyl acrylate (BA), 2.00 g of glycidyl methacrylate (GMA), 5.00 g of n-hexadecane (HD), and 0.25 g of 2,4-diphenyl-4-methyl-1-pentene (AMSD) were mixed uniformly to obtain an oil phase, then the oil phase was poured into the aqueous phase obtained in step 1, and then transferred to an ultrasonic cell crusher for ultrasonic emulsification for 10 min (5-15 min can be used), to obtain a fine emulsion, and nitrogen was introduced to remove air; Step 3, 0.50 g of azobisdimethylammonium hydrochloride (AIBA) was added to 5 g of deionized water and stirred uniformly to obtain an initiator solution. The fine emulsion obtained in step 2 was heated to 75℃, and 1.00 ml of the above initiator solution was added, then 1.00 ml of the initiator was added every 60 min, and after all the initiator solution was added, it was kept at 75℃ for 120 min to obtain a stable latex, and at this time the copolymer in the latex was butyl acrylate-methyl methacrylate-glycidyl methacrylate copolymer (PBMG); Step 4, the temperature of the latex obtained in step 3 was reduced to below 40℃, and 30 ml of ethanol solution containing 1.58 g of bis-carboxymethyl trithiocarbonate (BCMTTC) and 0.07 g of chromium acetylacetate (Cr(caca)3) was added to the system and stirred for 20 min, and then discharged to obtain a stable latex.

[0046] Step 5, the latex obtained in step 4 was coated on the surface of aluminum foil (Al) by a doctor blade coater, the coating film thickness was 300 μm, and after the coating machine was heated to 60℃ and dried for 24 h to remove most of the solvent, the composite film was transferred to a 90℃ oven for curing for 9 h to obtain a coating (BCMTTA-PBMG-Al).

[0047] Example 2 A preparation method of a weather-resistant self-healing radiation cooling roof coating, the steps are as follows: Step 1, 0.50 g of sodium bicarbonate, 4.00 g of sodium dodecyl sulfate (SDS), 2.00 g of alkylphenol polyoxyethylene ether (OP-10) were dissolved in 200 mL of deionized water, and the mixture was stirred to complete dissolution using a magnetic stirrer to obtain an aqueous phase; Step 2, 38.40 g of methyl methacrylate (MMA), 57.60 g of butyl acrylate (BA), 4.00 g of glycidyl methacrylate (GMA), 5.00 g of n-hexadecane (HD), and 0.25 g of 2,4-diphenyl-4-methyl-1-pentene (AMSD) were mixed uniformly to obtain an oil phase. The oil phase was poured into the aqueous phase obtained in step 1, and then transferred to an ultrasonic cell crusher for ultrasonic emulsification for 5-15 min to obtain a fine emulsion. Nitrogen was introduced to remove air; Step 3, 0.50 g of azobisdimethylaminoformate hydrochloride was added to 5 g of deionized water and stirred to obtain an initiator solution. The fine emulsion obtained in step 2 was heated to 75°C, and 1.00 ml of the above initiator solution was added. Thereafter, 1.00 ml of the initiator solution was added every 60 min. After all the initiator solution was added, the system was maintained at 75°C for 120 min to obtain a stable latex. At this time, the copolymer in the latex was a butyl acrylate-methyl methacrylate-glycidyl methacrylate copolymer (PBMG); Step 4, the temperature of the latex obtained in step 3 was reduced to below 40°C, and a 30 ml ethanol solution containing 3.16 g of biscarboxymethyl trithiocarbonate (BCMTTC) and 0.14 g of chromium acetylacetate (Cr(caca)3) was added to the system and stirred for 20 min. The latex was discharged to obtain a stable latex.

[0048] Step 5, the latex obtained in step 4 was coated onto the surface of an aluminum foil by a doctor blade coater to a film thickness of 300 μm. The coated film was dried at 60°C for 24 h on the coater to remove most of the solvent, and then transferred to a 90°C oven for curing for 9 h to obtain a coating layer (BCMTTA-PBMG-Al).

[0049] Example 3 A method for preparing a weather-resistant self-healing radiation-cooled roof coating, the steps are as follows: Step 1, 0.50 g of sodium bicarbonate, 4.00 g of sodium dodecyl sulfate (SDS), 2.00 g of alkylphenol polyoxyethylene ether (OP-10) were dissolved in 200 mL of deionized water, and the mixture was stirred to complete dissolution using a magnetic stirrer to obtain an aqueous phase; Step 2, 36.80 g of methyl methacrylate (MMA), 55.20 g of butyl acrylate (BA), 2.00 g of glycidyl methacrylate (GMA), 5.00 g of n-hexadecane (HD), 0.25 g of 2,4-diphenyl-4-methyl-1-pentene (AMSD) were mixed uniformly to obtain an oil phase, the oil phase was poured into the water phase obtained in step 1, and then transferred to an ultrasonic cell crusher for ultrasonic emulsification for 5-15 min to obtain a fine emulsion, and nitrogen was introduced to remove air; Step 3, 0.50 g of azobisdimethylaminoformate hydrochloride was added to 5 g of deionized water, and stirred uniformly to obtain an initiator solution. The fine emulsion obtained in step 2 was heated to 75°C, and 1.00 ml of the above initiator solution was added thereto, and then 1.00 ml of the initiator solution was added every 60 min, and after all the initiator solution was added, it was kept at 75°C for 120 min to obtain a stable latex, and at this time the copolymer in the latex was butyl acrylate-methyl methacrylate-glycidyl methacrylate copolymer (PBMG); Step 4, the latex obtained in step 3 was cooled to below 40°C, and then 30 ml of an ethanol solution containing 6.33 g of biscarboxymethyl trithiocarbonate (BCMTTC) and 0.3 g of chromium acetylacetate (Cr(caca)3) was added to the system and stirred for 20 min, and then discharged to obtain a stable latex.

[0050] Step 5, the latex obtained in step 4 was coated on the surface of an aluminum foil by a doctor blade coater, and the coating film thickness was 300 μm, and then the coating film was dried at 60°C on the coater for 24 h to remove most of the solvent, and then the composite film was transferred to an oven at 90°C and cured for 9 h to obtain a coating layer (BCMTTA-PBMG-Al).

[0051] Comparative Example 1 The difference between Example 2 and Comparative Example 1 is that in step 2, the addition of 2,4-diphenyl-4-methyl-1-pentene is omitted, and step 4 is omitted; the remaining steps and parameters are the same as those of Example 2. A linear butyl acrylate-methyl methacrylate-glycidyl methacrylate copolymer emulsion (PBMG) coating layer is obtained.

[0052] Comparative Example 2 A commercial BASF Acronal PLUS 7676 exterior wall emulsion was prepared into a coating layer according to step 5 of Example 2.

[0053] The weather-resistant self-healing radiant cooling roof coating of the present application provides epoxy groups to the acrylate polymer by introducing glycidyl methacrylate monomers into the butyl acrylate-methyl methacrylate copolymer. Further, dicarboxymethylthiuram disulfide (BCMTTC) and chromium acetylacetonate (Cr(caca)3) are added to the prepared emulsion, and after stirring uniformly, a stable latex is obtained. The latex is coated on an aluminum foil using a doctor blade coater, and after removing most of the water at 60°C, it is transferred to a 90°C oven for esterification of the epoxy and carboxyl groups. After curing, a coating layer (BCMTTC-PBMG-Al) is obtained. At this time, the BCMTTC has successfully entered the acrylate network, giving the coating layer self-repairing ability, and the BCMTTC that does not participate in the esterification reaction gives the coating layer ultraviolet aging resistance through its reversible cleavage mechanism under ultraviolet irradiation. Examples 1, 2, and 3 are acrylate coatings with different BCMTTC contents.

[0054] The coatings prepared in Examples 1, 2, and 3 were tested by UV-vis after 72h Soxhlet extraction with ethanol solution, and the UV absorbance of the extract was tested (λ=302nm, the maximum UV absorption wavelength of BCMTTC). It can be seen from Figure 1 that as the BCMTTC content in Examples 1, 2, and 3 increases from 2wt% to 8wt% (n(BCMTTC):n(GMA)=1:2), the esterification degree of the system increases from 40% to 50%, and the increase gradually decreases. In addition, after curing at 90°C for 9h, the esterification degree of carboxyl and epoxy is difficult to continue to increase.

[0055] Examples 2 and Comparative Example 1 were subjected to ultraviolet aging by an ultraviolet aging test chamber (PT-403), and the ultraviolet aging procedure was as follows: condensation at 50°C for 2h58min; 60°C, I=1w / m 2 UV aging for 9h; spraying for 2min, cycle for 200h and 400h. The self-repairing implementation method was as follows: the sample prepared according to the 5-type dumbbell-shaped sample in ISO 527-3-2018 was cut into two halves with scissors, and then manually spliced. After splicing, the sample was placed in an ultraviolet box simulating the UVB band of the sun for 8 hours of irradiation. After irradiation, the original sample and the repaired sample were subjected to tensile testing at 50mm / min using an electronic universal testing machine (HD-B609B-S type) equipped with a 50N sensor at 22±0.5°C and 50% humidity. It can be seen from Figure 2 that the tensile strength of the repaired sample is higher than that of the original sample, and the higher the BCMTTC content, the higher the tensile strength of the repaired sample. Figure 2The left and right figures show the stress-strain curves of the original sample and the fracture-repaired sample of Example 2, while the right figure shows the stress-strain curves of the original sample and the fracture-repaired sample of Comparative Example 1. After 400 hours of UV irradiation, the tensile strength self-healing rate and strain self-healing rate of Example 2 remained around 80% and 70%, respectively. After repair, the tensile strength and elongation at break remained at 2.2 MPa and 800%, respectively, still exhibiting good mechanical properties and meeting the tensile strength of 1.2 MPa and elongation at break of 300% specified in JCT 864-2023 for polymer emulsion building waterproof coatings. In contrast, the mechanical properties of Comparative Example 1 gradually decreased, and its self-healing performance was poor.

[0056] The coating surface was observed using an OLYMPUS CX31 microscope. Figure 3 As can be seen, after being cut by a blade, the surface of Example 2 can close the scratches autonomously without human intervention, demonstrating good surface self-healing ability.

[0057] Accelerated copper salt-acetic acid corrosion tests were conducted on Examples 2 and Comparative Example 2 using a salt spray corrosion test chamber (SY-9A). The salt solution was prepared by dissolving 250g of sodium chloride and 1.3g of copper chloride dihydrate in 5000ml of water, and the pH of the solution was adjusted to 3.0-3.1 using acetic acid. The accelerated copper salt-acetic acid corrosion test was performed using a continuous spray method, with the test chamber temperature set at 50℃ and a cycle time of 48 hours. Figure 4 It can be seen that after the coating surface was damaged, and subjected to accelerated corrosion with copper salt and acetic acid for 48 hours and UV aging for 400 hours, the surface of Example 2 remained intact, without whitening or blistering, and the bottom aluminum foil showed no obvious oxidation or blackening. In contrast, the surface scratches of Comparative Example 2 enlarged, the bottom aluminum foil oxidized and blackened, and obvious salt water stains remained. This resulted in no significant change in the average reflectance of Example 2 at 0.25-2.5 μm, while the average reflectance of Comparative Example 2 decreased by approximately 15%. Figure 5 ).from Figure 6 It can be seen that after the coating surface was damaged, and after accelerated corrosion with copper salt acetic acid and ultraviolet aging, the emissivity of Example 2 and Comparative Example 2 at 2.5-25 μm remained basically unchanged. This is because the emissivity of BCMTTC-PBMG-Al is mainly provided by the COC in the acrylate polymer. In the accelerated aging experiment, the acrylate film showed no obvious degradation, so the coating emissivity was maintained. The cooling capacity was tested using a radiation cooling performance testing device. To ensure that the test temperature was not affected by the sample temperature distribution, a 1 mm thick copper sheet connected to a thermocouple was loaded at the bottom of all samples. Figure 7It can be seen that after the surface damage and accelerated aging test, the average temperature of the roof of Example 2 is reduced by 14.4℃, which is higher than that of Comparative Example 2 by 11.2℃ during the daytime solar radiation period (11:00-17:00), and the average temperature of Example 2 is reduced by 4.6℃ during the night period (17:00-20:00) without solar radiation.

[0058] The weather-resistant self-healing radiant cooling roof coating of the present application has good weather resistance, self-healing performance and passive cooling ability. The coating provides epoxy groups to the acrylate polymer by introducing glycidyl methacrylate monomer into the acrylate coating, and the carboxyl groups in the dithiocarbonic acid ester containing trithiocarbonic acid ester group undergo esterification reaction to form a three-dimensional network structure, which gives the coating self-repairing ability, high mechanical properties and solvent resistance. And using the high-efficiency reversible decomposition mechanism of dithiocarbonic acid ester under ultraviolet radiation, the coating provides excellent ultraviolet resistance. The high emissivity of acrylate polymer in the two atmospheric windows of 8-13 μm and 16-25 μm, and the high reflectivity of aluminum foil to solar visible light band give it good passive cooling properties. The cooling roof coating has the characteristics of wide raw material sources, mature production process and equipment, easy large-scale industrial production, and is conducive to reducing building energy consumption and improving the sustainability of the cooling roof coating.

[0059] In summary, the cooling roof coating of the present application has excellent weather resistance. After 48h copper acetate accelerated corrosion and 400h ultraviolet aging (UVI-313, I=1w / m 2 ) cycle test, the coating surface is not whitened, not blistered, no cracking, and the aluminum foil is not oxidized and blackened.

[0060] The cooling roof coating of the present application has excellent mechanical properties and self-repairing properties, including excellent tensile strength (2.88MPa), high elongation at break (800%) and extremely high self-repairing efficiency (80±5%). When the surface is damaged, it can automatically close the damaged part in outdoor use environment without manual intervention, thereby protecting the aluminum foil below the coating from being oxidized and corroded.

[0061] The weather-resistant self-healing radiant cooling roof coating prepared by the present application has an average reflectivity of 77.6% in the range of 0.5-1.5 μm, and an average emissivity of nearly 92.5% in the two atmospheric windows of 8-13 μm and 16-25 μm. During the daytime solar radiation period (11:00-17:00), the coating realizes an average temperature reduction of 14.4℃ on the roof, and the peak temperature reduction can reach 19.7℃. During the night period (17:00-20:00) without solar radiation, the average temperature is reduced by 4.6℃, which has good cooling and energy saving effect.

[0062] The above-described embodiments are merely intended to describe the preferred modes of the present application, and are not intended to limit the scope of the present application. Various modifications and improvements of the present application made by those skilled in the art based on the above-described embodiments should fall within the scope of the present application defined by the claims.

Claims

1. A method for preparing a weather-resistant, self-healing, radiation-cooled roof coating, characterized in that, Includes the following steps: Step 1: Dissolve the pH stabilizer and emulsifier in water and mix well to obtain the aqueous phase; Step 2: Mix the hard monomer, soft monomer, modified monomer, stabilizer and chain transfer agent evenly to obtain the oil phase. Add the oil phase to the aqueous phase and emulsify by ultrasonication to obtain a fine emulsion. Step 3: Heat the fine emulsion to 50-75℃, then add the initiator solution and keep it warm to obtain latex A; Step 4: Add solution A containing crosslinking agent and catalyst to latex A and mix well to obtain latex B; Step 5: Apply latex B to the substrate surface and dry it, then cure it to obtain a weather-resistant, self-healing, radiation-cooled roof coating.

2. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, In step 1, the mass ratio of pH stabilizer to emulsifier is 1:(6-12); the pH stabilizer is sodium bicarbonate; the emulsifier is at least one of fatty alcohol polyoxyethylene ether phosphate, alkylphenol polyoxyethylene ether, and sodium dodecyl sulfate.

3. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, In step 2, the mass ratio of hard monomer to soft monomer, modified monomer, co-stabilizer, and polymerization transfer agent is (9.20-46.00):(46.00-82.80):(2.00-8.00):(4.00-5.00):(0.25-0.80); the hard monomer is at least one of methyl methacrylate, ethyl methacrylate, and styrene; the soft monomer is at least one of butyl acrylate, isooctyl acrylate, and ethyl acrylate; the modified monomer is one or two of glycidyl methacrylate and allyl glycidyl ether; the co-stabilizer is a styrene oligomer (weight average molecular weight M). w =45000-50000, purchased from Tianjin Xiens Aopud Technology Co., Ltd.), hexadecane, polyorganosiloxane, at least one of the following: the chain transfer agent is 2,4-diphenyl-4-methyl-1-pentene, 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, and n-dodecyl mercaptan.

4. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, In step 3, the initiator in the initiator solution is at least one of the following: ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, ascorbic acid and tert-butyl hydroperoxide complex system; the solvent of the initiator solution is water; the temperature for heat preservation is 50-75℃ and the time is 100-150 min.

5. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, The mass ratio of pH stabilizer to hard monomer is (0.50-1.00): (9.20-46.00); the mass ratio of initiator to hard monomer is (0.50-1.00): (9.20-46.00).

6. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, In step 4, the crosslinking agent is at least one of dicarboxymethyl trithiocarbonate, dicarboxyethyl trithiocarbonate, or 2,2'-[methylthiodi(thio)]bis[2-methylpropionic acid]; the catalyst is at least one of chromium acetylacetonate, manganese acetylacetonate, and aluminum acetylacetonate; the solvent of solution A is ethanol; and the mass ratio of crosslinking agent and catalyst to hard monomer is (1.5-6.5):(0.07-0.3):(9.20-46.00).

7. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, The substrate is aluminum foil.

8. The method for preparing the weather-resistant self-healing radiation-cooled roof coating according to claim 1, characterized in that, In step 5, the curing temperature is 70-150℃ and the time is 9 hours.

9. The weather-resistant, self-healing, radiation-cooled roof coating prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the weather-resistant, self-healing, radiation-cooled roofing coating as described in claim 9 in the construction field.

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