Radiation refrigeration coating for natural gas bottle and preparation method of radiation refrigeration coating

Abstract

The invention relates to the technical field of coatings, and discloses a radiation refrigeration coating for a natural gas bottle and a preparation method of the radiation refrigeration coating. The prepared radiation refrigeration coating for the natural gas bottle is prepared by taking the modified polyurethane emulsion as a main raw material, adding the composite filler, the coalescing agent and other auxiliaries, mixing and stirring, and has excellent adhesive force, cooling efficiency and hydrophobicity and long service life. The composite filler introduced into the coating utilizes the synergistic effect of mesoporous silica and titanium dioxide to endow the coating with an excellent radiation refrigeration effect; and the modified polyurethane emulsion endows the coating with excellent ultraviolet resistance, so that the coating still has the characteristic of long service life after being exposed outdoors for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly relates to a radiation cooling coating for natural gas cylinders and a preparation method thereof. Background Art

[0002] As a clean energy source, natural gas is widely used in fields such as industrial fuel, transportation, and distributed energy. As the core container for storing and transporting natural gas, the safety of gas cylinders is directly related to energy utilization efficiency and public safety. However, natural gas cylinders are vulnerable to environmental temperature during filling, transportation, and use. Especially in high-temperature environments, the pressure inside the cylinders will increase significantly due to temperature rise, and the safety is limited. Therefore, heat insulation materials such as polyurethane foam or aerogel felt, which are low-thermal-conductivity materials, are usually coated on the surface of natural gas cylinders. Although they can delay heat transfer, they have a large thickness, affect the portability of the cylinders, and cannot actively discharge the accumulated heat. A reflective coating may also be applied to reduce solar radiation absorption through a high solar reflectance, but the thermal radiation emission ability in the medium and far infrared band (8 - 13 μm) is insufficient, resulting in low radiation heat dissipation efficiency during the day.

[0003] Radiation cooling is a passive heat dissipation technology based on the principle of thermal radiation. Through the high emissivity of materials in the "atmospheric window", heat is directly dissipated into the low-temperature cosmic space in the form of infrared radiation, and at the same time, the high solar reflectivity is used to reduce sunlight absorption, achieving all-weather zero-energy consumption cooling. For traditional radiation cooling coatings used on natural gas cylinders outdoors, they are easily affected by outdoor environments such as ultraviolet rays, air dust, and rainwater, resulting in a reduction in the cooling effect of the radiation cooling coating and a decrease in service life. Therefore, it is necessary to develop a radiation cooling coating with excellent ultraviolet resistance and hydrophobicity to meet the actual application requirements. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a radiation cooling coating for natural gas cylinders and a preparation method thereof.

[0005] The object of the present invention can be achieved by the following technical solutions: A radiation cooling coating for natural gas cylinders, comprising the following raw materials in parts by weight: 40 - 60 parts of modified polyurethane emulsion, 20 - 30 parts of composite filler, 0.5 - 1 part of film-forming aid, 0.5 - 1.5 parts of antioxidant, 0.5 - 1 part of leveling agent, 0.5 - 1 part of defoaming agent, and 15 - 25 parts of water; Further, the film-forming aid is propylene glycol monomethyl ether, the antioxidant is antioxidant 1010, the leveling agent is BYK381, and the defoaming agent is BYK057; The composite filler is prepared by the following steps: Step A1: Mix titanium dioxide powder, silane coupling agent KH550 and toluene evenly, heat up to 70 - 80 °C and react for 2 - 3 h, then add maleic anhydride and sodium acetate anhydrous and react for 1.5 - 2.5 h, then add hydroquinone and acetic anhydride and continue to react for 2 h, filter, wash and dry to obtain graft-modified titanium dioxide; Further, in step A1, the dosage ratio of titanium dioxide powder, silane coupling agent KH550, toluene, maleic anhydride, sodium acetate anhydrous, hydroquinone and acetic anhydride is 2 - 4 g: 0.1 - 0.2 mol: 100 mL: 0.15 - 0.25 mol: 0.03 - 0.05 mol: 0.02 - 0.03 mol: 50 mL; Step A2: Add sodium hydroxide and cetyltrimethylammonium bromide to the mixed solution of ethanol and water, stir evenly, heat up to 80 °C and stir for 1 h, then add tetraethyl orthosilicate and silane coupling agent KH570 and stir and react for 3 - 5 h, centrifuge, collect the precipitate and disperse it in hydrochloric acid ethanol solution, and reflux at 70 °C for 6 h, centrifuge, wash until neutral and dry to obtain modified mesoporous silica; Further, in step A2, the dosage ratio of sodium hydroxide, cetyltrimethylammonium bromide, the mixed solution of ethanol and water, tetraethyl orthosilicate, silane coupling agent KH570 and hydrochloric acid ethanol solution is 0.15 - 0.3 g: 0.5 - 1 g: 50 mL: 2 - 3 mL: 1 - 2 mL: 200 mL; Further, in the hydrochloric acid ethanol solution described in step A2, the volume ratio of hydrochloric acid to ethanol is 1:7; Step A3: Ultrasonically disperse the modified mesoporous silica and the graft-modified titanium dioxide evenly in N,N-dimethylformamide, then add fluorinated acrylate, heat up to 75 - 85 °C and stir for 30 min, introduce nitrogen, then add benzoyl peroxide, then heat up to 110 °C and react for 3 - 5 h, add petroleum ether and stir for 20 min, wash and dry to obtain the composite filler; Further, in step A3, the dosage ratio of the modified mesoporous silica, the graft-modified titanium dioxide, N,N-dimethylformamide, fluorinated acrylate, benzoyl peroxide and petroleum ether is 1 - 2 g: 0.5 - 1 g: 100 mL: 0.002 - 0.005 mol: 0.5 - 1.5 g: 200 mL; Further, the fluorinated acrylate described in step A3 is one of 2-(perfluorobutyl)ethyl acrylate, perfluorooctylpropyl acrylate or 2-(perfluorobutyl)ethyl acrylate.

[0006] The modified polyurethane emulsion is prepared by the following steps: Step B1: Stir 1,8-dibromooctane and sodium hydroxide evenly in N,N-dimethylformamide, add 1H-benzotriazole, stir and react at 35 - 45 °C for 24 h, then purify and distill under reduced pressure to obtain bromobenzotriazole; Further, in step B1, the dosage ratio of 1,8-dibromooctane, sodium hydroxide, N,N-dimethylformamide and 1H-benzotriazole is 0.011 - 0.015 mol: 1.5 - 2.5 g: 100 mL: 0.01 mol; Step B2: Under argon atmosphere, add polyethylene glycol (number average molecular weight of 2000), isophorone diisocyanate and 2,2-bis(hydroxymethyl)propionic acid into acetone and mix and stir evenly, add dibutyltin dilaurate, and heat up to 60 °C and stir for 3 - 4 h, cool down to 40 °C, add triethylamine and stir for 1 h, then cool down to 0 °C, slowly dropwise add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 0.5 - 1.5 h to obtain silane-modified polyurethane; Further, in step B2, the mass ratio of polyethylene glycol, isophorone diisocyanate, 2,2-bis(hydroxymethyl)propionic acid, acetone, dibutyltin dilaurate, triethylamine and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is 35 - 45: 13 - 15: 2.5 - 3.5: 50 - 70: 0.5 - 1: 2 - 2.8: 2 - 4; Step B3: Add sodium hydroxide solution to the silane-modified polyurethane obtained in step B2 and mix and stir evenly, then add bromobenzotriazole, stir and react at 35 - 45 °C for 24 h, then add water and stir at high speed for 1 h to obtain modified polyurethane emulsion; Further, in step B3, the molar ratio of bromobenzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in step B2 is 1 - 1.3: 1; Further, in step B3, the concentration of the sodium hydroxide solution is 0.025 - 0.035 mol / L, and the mass is 7% - 10% of the mass of the silane-modified polyurethane described in step B2; Further, in step B3, the mass ratio of water to the silane-modified polyurethane described in step B2 is 1: 1.

[0007] A preparation method of a radiation cooling coating for natural gas cylinders comprises the following steps: Weigh the raw materials by weight, mix and stir evenly the composite filler, film-forming auxiliary, antioxidant, leveling agent, defoaming agent and water, then slowly add the modified polyurethane emulsion, and stir at a speed of 500 - 800 rpm for 30 - 50 min to obtain the radiation cooling coating for natural gas cylinders.

[0008] The beneficial effects of the present invention: The radiation cooling coating for natural gas cylinders prepared in this application is mainly made of modified polyurethane emulsion, and is mixed and stirred by adding composite fillers, film-forming aids and other additives. It has excellent adhesion, cooling efficiency, hydrophobicity and service life. The composite filler introduced in the coating utilizes the synergistic effect of mesoporous silica and titanium dioxide to endow the coating with excellent radiation cooling effect; the modified polyurethane emulsion endows the coating with excellent ultraviolet resistance, making it still have a long service life when exposed outdoors for a long time.

[0009] After the composite filler in this application is introduced into the coating, it has the function of "reflection-radiation-protection" integration, and has a certain dispersibility, significantly improving the radiation cooling effect and cleaning ability of the coating, and then improving the service life of the coating on the surface of natural gas cylinders. The composite filler utilizes the synergistic effect between titanium dioxide and mesoporous silica to enhance the sunlight reflection and infrared radiation performance of the coating. Among them, the mesoporous structure of mesoporous silica enhances sunlight reflection through light scattering, and its high specific surface area and porosity can improve the infrared emission efficiency of the coating, forming an efficient "radiation channel", while TiO modified by imide 2 retains a high sunlight reflectivity, and also covers the surface active sites of TiO through chemical bonding (imide group) 2 to reduce the generation of photo-generated electron-hole pairs and reduce the risk of photocatalytic degradation of the polymer molecular chain in the coating. In addition, the fluorinated acrylate chains embedded through free radical copolymerization can form an organic-inorganic hybrid network in the composite filler to prevent particle agglomeration. At the same time, the presence of fluorine elements can reduce the surface energy of the coating, endow the coating with excellent hydrophobicity, reduce the adhesion of pollutants (dust, water) when the coating is used outdoors, maintain high reflectivity and radiation efficiency, and then improve the service life of the coating outdoors.

[0010] The radiation cooling coating prepared in this application uses modified polyurethane emulsion as the main component of the coating, which has better weather resistance than traditional acrylate emulsions, and also has certain ultraviolet resistance. This is because a benzotriazole structure with ultraviolet absorption function is introduced into the modified polyurethane emulsion, improving the ultraviolet resistance of the coating, and then improving the service life of the coating outdoors. At the same time, the benzotriazole structure has strong polarity, making it have a certain adsorption effect on metal ions on the surface of natural gas cylinders, and can improve the adhesion of the coating on the surface of natural gas cylinders. In addition, the introduced silane structure can reduce the surface tension of the coating after the coating is formed, further improving the hydrophobicity of the coating. Detailed implementation mode

[0011] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0012] Embodiment 1: The composite filler is prepared by the following steps: Step A1: Mix 2 g of titanium dioxide powder, 0.1 mol of silane coupling agent KH550, and 100 mL of toluene and stir evenly. Heat up to 70 °C and react for 2 h. Then add 0.15 mol of maleic anhydride and 0.03 mol of anhydrous sodium acetate and react for 1.5 h. Then add 0.02 mol of hydroquinone and 50 mL of acetic anhydride and continue to react for 2 h. Filter, wash, and dry to obtain graft-modified titanium dioxide. Step A2: Add 0.15 g of sodium hydroxide and 0.5 g of cetyltrimethylammonium bromide to a mixed solution of 50 mL of ethanol and water and stir evenly. Heat up to 80 °C and stir for 1 h. Then add 3 mL of tetraethyl orthosilicate and 1 mL of silane coupling agent KH570 and stir and react for 3 h. Centrifuge, collect the precipitate, disperse it in 200 mL of hydrochloric acid-ethanol solution, and reflux at 70 °C for 6 h. Centrifuge, wash until neutral, and dry to obtain modified mesoporous silica. The volume ratio of hydrochloric acid to ethanol in the hydrochloric acid-ethanol solution is 1:7. Step A3: Ultrasonically disperse 1 g of modified mesoporous silica and 0.5 g of graft-modified titanium dioxide evenly in 100 mL of N,N-dimethylformamide. Then add 0.002 mol of 2-(perfluorobutyl)ethyl acrylate, heat up to 75 °C, and stir for 30 min. Pass in nitrogen, then add 0.5 g of benzoyl peroxide, and then heat up to 110 °C and react for 3 h. Add 200 mL of petroleum ether and stir for 20 min. Wash and dry to obtain the composite filler.

[0013] The modified polyurethane emulsion is prepared by the following steps: Step B1: Mix 0.011 mol of 1,8-dibromooctane and 1.5 g of sodium hydroxide evenly in 100 mL of N,N-dimethylformamide. Add 0.01 mol of 1H-benzotriazole, and stir and react at 35 °C for 24 h. Purify and distill under reduced pressure to obtain bromobenzotriazole. Step B2: Under argon atmosphere, add 35 g of polyethylene glycol (number average molecular weight of 2000), 13 g of isophorone diisocyanate, and 2.5 g of 2,2-bis(hydroxymethyl)propionic acid into 50 g of acetone, mix and stir evenly. Add 0.5 g of dibutyltin dilaurate, heat up to 60 °C and stir for 3 h. Cool down to 40 °C, add 2 g of triethylamine and stir for 1 h. Then cool down to 0 °C, slowly dropwise add 2 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir for 0.5 h to obtain the silane-modified polyurethane. Step B3: Add sodium hydroxide solution to the silane-modified polyurethane obtained in Step B2, mix and stir evenly. Then add bromobenzotriazole, stir and react at 35 °C for 24 h. Then add water and stir at high speed for 1 h to obtain the modified polyurethane emulsion. The molar ratio of bromobenzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in Step B2 is 1:1. The concentration of the sodium hydroxide solution is 0.025 mol / L, and its mass is 10% of the mass of the silane-modified polyurethane obtained in Step B2. The mass ratio of water to the silane-modified polyurethane obtained in Step B2 is 1:1.

[0014] Example 2: The composite filler is prepared by the following steps: Step A1: Mix 3 g of titanium dioxide powder, 0.15 mol of silane coupling agent KH550, and 100 mL of toluene evenly, heat up to 75 °C and react for 2.5 h. Then add 0.2 mol of maleic anhydride and 0.04 mol of anhydrous sodium acetate and react for 2 h. Then add 0.025 mol of hydroquinone and 50 mL of acetic anhydride and continue to react for 2 h. Filter, wash, and dry to obtain the graft-modified titanium dioxide. Step A2: Add 0.25 g of sodium hydroxide and 0.75 g of cetyltrimethylammonium bromide into a mixed solution of 50 mL of ethanol and water, stir evenly, heat up to 80 °C and stir for 1 h. Then add 2.5 mL of tetraethyl orthosilicate and 1.5 mL of silane coupling agent KH570 and stir and react for 4 h. Centrifuge, collect the precipitate, disperse it in 200 mL of hydrochloric acid-ethanol solution, and reflux at 70 °C for 6 h. Centrifuge, wash until neutral, and dry to obtain the modified mesoporous silica. The volume ratio of hydrochloric acid to ethanol in the hydrochloric acid-ethanol solution is 1:7. Step A3: Ultrasonically disperse 1.5 g of modified mesoporous silica and 0.75 g of graft-modified titanium dioxide evenly in 100 mL of N,N-dimethylformamide. Then add 0.0035 mol of perfluorooctylpropyl acrylate, heat up to 80 °C and stir for 30 min. Pass in nitrogen, then add 1 g of benzoyl peroxide, and then heat up to 110 °C and react for 4 h. Add 200 mL of petroleum ether and stir for 20 min. Wash and dry to obtain the composite filler.

[0015] The modified polyurethane emulsion is prepared by the following steps: Step B1: 0.013 mol of 1,8-dibromooctane and 2 g of sodium hydroxide were stirred evenly in 100 mL of N,N-dimethylformamide. 0.01 mol of 1H-benzotriazole was added, and the mixture was stirred and reacted at 40 °C for 24 h. After purification and vacuum distillation, bromobenzotriazole was obtained. Step B2: Under argon atmosphere, 40 g of polyethylene glycol (number-average molecular weight of 2000), 14 g of isophorone diisocyanate and 3 g of 2,2-bis(hydroxymethyl)propionic acid were added to 60 g of acetone and mixed and stirred evenly. 0.75 g of dibutyltin dilaurate was added, and the temperature was raised to 60 °C and stirred for 3.5 h. Then the temperature was lowered to 40 °C, 2.4 g of triethylamine was added and stirred for 1 h. Then the temperature was lowered to 0 °C, and 3 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was slowly added dropwise and stirred and reacted for 1 h to obtain silane-modified polyurethane. Step B3: Sodium hydroxide solution was added to the silane-modified polyurethane described in Step B2 and mixed and stirred evenly. Then bromobenzotriazole was added, and the mixture was stirred and reacted at 40 °C for 24 h. Then water was added and stirred at high speed for 1 h to obtain a modified polyurethane emulsion. The molar ratio of bromobenzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in Step B2 was 1.15:1. The concentration of the sodium hydroxide solution was 0.03 mol / L, and the mass was 8.5% of the mass of the silane-modified polyurethane described in Step B2. The mass ratio of water to the silane-modified polyurethane described in Step B2 was 1:1.

[0016] Example 3: The composite filler was prepared by the following steps: Step A1: 4 g of titanium dioxide powder, 0.2 mol of silane coupling agent KH550 and 100 mL of toluene were mixed and stirred evenly. The temperature was raised to 80 °C and reacted for 3 h. Then 0.25 mol of maleic anhydride and 0.05 mol of anhydrous sodium acetate were added and reacted for 2.5 h. Then 0.03 mol of hydroquinone and 50 mL of acetic anhydride were added and reacted for another 2 h. After filtration, washing and drying, graft-modified titanium dioxide was obtained. Step A2: 0.3 g of sodium hydroxide and 1 g of cetyltrimethylammonium bromide were added to a mixed solution of 50 mL of ethanol and water and stirred evenly. The temperature was raised to 80 °C and stirred for 1 h. Then 3 mL of tetraethyl orthosilicate and 2 mL of silane coupling agent KH570 were added and stirred and reacted for 5 h. After centrifugation, the precipitate was collected and dispersed in 200 mL of hydrochloric acid ethanol solution and refluxed at 70 °C for 6 h. After centrifugation, washing until neutral and drying, modified mesoporous silica was obtained. The volume ratio of hydrochloric acid to ethanol in the hydrochloric acid ethanol solution was 1:7. Step A3: Ultrasonically disperse 2 g of modified mesoporous silica and 1 g of graft-modified titanium dioxide uniformly in 100 mL of N,N-dimethylformamide. Then add 0.005 mol of 2-(perfluorobutyl)ethyl acrylate, and raise the temperature to 85 °C and stir for 30 min. Pass in nitrogen, then add 1.5 g of benzoyl peroxide, and then raise the temperature to 110 °C and react for 5 h. Add 200 mL of petroleum ether and stir for 20 min, wash and dry to obtain the composite filler.

[0017] The modified polyurethane emulsion is prepared by the following steps: Step B1: Stir 0.015 mol of 1,8-dibromooctane and 2.5 g of sodium hydroxide uniformly in 100 mL of N,N-dimethylformamide. Add 0.01 mol of 1H-benzotriazole, and stir and react at 45 °C for 24 h. Purify and distill under reduced pressure to obtain brominated benzotriazole. Step B2: Under argon atmosphere, add 45 g of polyethylene glycol (number-average molecular weight of 2000), 15 g of isophorone diisocyanate and 3.5 g of 2,2-bis(hydroxymethyl)propionic acid to 70 g of acetone and mix and stir uniformly. Add 1 g of dibutyltin dilaurate, and raise the temperature to 60 °C and stir for 4 h. Cool to 40 °C, add 2.8 g of triethylamine and stir for 1 h, then cool to 0 °C, and slowly dropwise add 4 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 1.5 h to obtain the silane-modified polyurethane. Step B3: Add a sodium hydroxide solution to the silane-modified polyurethane obtained in Step B2 and mix and stir uniformly. Then add brominated benzotriazole, and stir and react at 45 °C for 24 h. Then add water and stir at high speed for 1 h to obtain the modified polyurethane emulsion. The molar ratio of brominated benzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in Step B2 is 1.3:1. The concentration of the sodium hydroxide solution is 0.035 mol / L, and the mass is 7% of the mass of the silane-modified polyurethane obtained in Step B2. The mass ratio of water to the silane-modified polyurethane obtained in Step B2 is 1:1.

[0018] Example 4: A preparation method of a radiation cooling coating for natural gas cylinders includes the following steps: Weigh the raw materials by weight. Mix 20 parts of the composite filler prepared in Example 1, 0.5 part of propylene glycol monomethyl ether, 0.5 part of antioxidant 1010, 0.5 part of leveling agent BYK381, 0.5 part of defoaming agent BYK057 and 15 parts of water uniformly, and then slowly add 40 parts of the modified polyurethane emulsion prepared in Example 1, and stir at a speed of 500 rpm for 30 min to obtain the radiation cooling coating for natural gas cylinders.

[0019] Example 5: A preparation method of a radiation cooling coating for natural gas cylinders includes the following steps: Weigh the raw materials by weight parts. Mix 25 parts of the composite filler prepared in Example 2, 0.7 part of propylene glycol monomethyl ether, 1 part of antioxidant 1010, 0.8 part of leveling agent BYK381, 0.7 part of defoaming agent BYK057 and 20 parts of water evenly by stirring, and then slowly add 50 parts of the modified polyurethane emulsion prepared in Example 2, and stir at a speed of 700 rpm for 40 min to obtain the radiation cooling coating for natural gas cylinders.

[0020] Example 6: A preparation method of a radiation cooling coating for natural gas cylinders includes the following steps: Weigh the raw materials by weight parts. Mix 30 parts of the composite filler prepared in Example 3, 1 part of propylene glycol monomethyl ether, 1.5 parts of antioxidant 1010, 1 part of leveling agent BYK381, 1 part of defoaming agent BYK057 and 25 parts of water evenly by stirring, and then slowly add 60 parts of the modified polyurethane emulsion prepared in Example 3, and stir at a speed of 800 rpm for 50 min to obtain the radiation cooling coating for natural gas cylinders.

[0021] Comparative Example 1: This comparative example is a radiation cooling coating. The difference from Example 6 is that silica is used instead of the composite filler prepared in Example 3, and the rest are the same.

[0022] Comparative Example 2: This comparative example is a radiation cooling coating. The difference from Example 6 is that a commercially available polyurethane emulsion is used instead of the modified polyurethane emulsion prepared in Example 3, and the rest are the same.

[0023] Comparative Example 3: This comparative example is a radiation cooling coating. The difference from Example 6 is that silica is used instead of the composite filler prepared in Example 3, and a commercially available polyurethane emulsion is used instead of the modified polyurethane emulsion prepared in Example 3, and the rest are the same.

[0024] Spray the radiation cooling coatings prepared in Examples 4 - 6 and Comparative Examples 1 - 3 on the surface of a clean natural gas cylinder to form a radiation cooling coating with a thickness of 0.5 mm, and conduct performance tests on the coating: Adhesion test: Conduct a cross - cut test in accordance with the national standard GB / T 9286 - 2021 "Paints and varnishes". Solar reflectance test: At an incident angle of 5°, use a UV - Vis - NIR spectrophotometer Lambda950 to measure the reflectance of the coating, and the wavelength range is 0.3 - 2.5 μm. Atmospheric window emissivity test: Use an IR - 2 dual - band emissivity tester to measure the emissivity of the coating in the atmospheric window of 8 - 13 μm. Contact angle test: Use a contact angle tester THETAOptical (KSV Instruments Ltd., Finland) to test the water contact angle on the surface of the coating. Ultraviolet aging resistance performance test: Refer to the standard of GB / T 1865-2009 to conduct a 600h ultraviolet aging test, and test the emissivity of the coating after 600h; Cooling temperature difference test: Apply black magnetic paint and radiative cooling coating on an aluminum sheet with a dry film thickness of about 500μm. Fix the room temperature at (25±1)°C. Use a 500W infrared lamp to simulate sunlight irradiating the coating. Control the temperature of the black magnetic paint within the range of (37±1)°C by adjusting the distance between the infrared lamp and the test plate. Use a surface thermometer to detect the temperature on the back of the test plate (T1) and the temperature on the upper surface of the coating (T2), and record the data every 10 minutes until the temperature is stable. Calculate the cooling temperature difference (△T) through formula 1 (△T = T2 - T1).

[0025] The test results are shown in Table 1: Table 1: Performance test results

[0026] It can be seen from Table 1 that the radiative cooling coating prepared by the present invention has excellent adhesion on the surface of natural gas cylinders, the solar reflectance ratio is greater than 92%, the emissivity in the atmospheric window is greater than the standard of 95%, the water contact angle is greater than 130°, the emissivity after 600h of ultraviolet aging is greater than the standard of 95%, and the cooling temperature difference is greater than 10°C, indicating that the coating has excellent ultraviolet resistance, hydrophobicity, and cooling effect, and has good application prospects when applied to natural gas cylinders.

[0027] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the scope defined by the concept of the invention, they should all belong to the protection scope of the present invention.

Claims

1. A radiation cooling coating for a natural gas cylinder, characterized in that: The invention comprises the following raw materials in parts by weight: 40-60 parts of modified polyurethane emulsion, 20-30 parts of composite filler, 0.5-1 parts of film-forming aid, 0.5-1.5 parts of antioxidant, 0.5-1 parts of leveling agent, 0.5-1 parts of defoaming agent and 15-25 parts of water; The composite filler is prepared by polymerization reaction of modified mesoporous silica, grafted modified titanium dioxide and fluorine-containing acrylate, wherein the modified mesoporous silica is prepared by reaction of tetraethyl orthosilicate and silane coupling agent, and the grafted modified titanium dioxide is prepared by reaction of titanium dioxide powder modified by silane coupling agent and maleic anhydride; The modified polyurethane emulsion is prepared by adding water after reacting silane-modified polyurethane and brominated benzotriazole, the brominated benzotriazole is prepared by reacting 1,8-dibromooctane and 1H-benzotriazole, and the silane-modified polyurethane is prepared by reacting polyethylene glycol, isophorone diisocyanate, 2,2-bis(hydroxymethyl)propionic acid and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

2. The radiation cooling coating for natural gas cylinders according to claim 1, characterized in that: The composite filler is prepared by the following steps: Step A1, titanium dioxide powder, silane coupling agent KH550 and toluene are mixed and stirred evenly, heated to 70-80°C for reaction for 2-3h, then maleic anhydride and anhydrous sodium acetate are added for reaction for 1.5-2.5h, then hydroquinone and acetic anhydride are added for further reaction for 2h, filtered, washed and dried to obtain grafted modified titanium dioxide; Step A2, adding sodium hydroxide and hexadecyltrimethylammonium bromide to a mixture of ethanol and water, stirring evenly, heating to 80°C and stirring for 1 hour, then adding tetraethyl orthosilicate and silane coupling agent KH570 and stirring for 3-5 hours, centrifuging, collecting the precipitate and dispersing it in a hydrochloric acid ethanol solution, and refluxing at 70°C for 6 hours, centrifuging, washing until neutral, and drying to obtain modified mesoporous silica; Step A3, uniformly disperse the modified mesoporous silica and grafted modified titanium dioxide in N,N-dimethylformamide by ultrasonic dispersion, add fluorinated acrylate, heat to 75-85°C and stir for 30 minutes, introduce nitrogen, add benzoyl peroxide, heat to 110°C and react for 3-5 hours, add petroleum ether and stir for 20 minutes, wash and dry to obtain a composite filler.

3. The radiation cooling coating for natural gas cylinders according to claim 2, characterized in that: In step A1, the usage ratio of titanium dioxide powder, silane coupling agent KH550, toluene, maleic anhydride, anhydrous sodium acetate, hydroquinone and acetic anhydride is 2-4g:0.1-0.2mol:100mL:0.15-0.25mol:0.03-0.05mol:0.02-0.03mol:50mL.

4. The radiation cooling coating for natural gas cylinders according to claim 2, characterized in that: In step A2, the dosage ratio of sodium hydroxide, hexadecyltrimethylammonium bromide, a mixture of ethanol and water, tetraethyl orthosilicate, silane coupling agent KH570 and hydrochloric acid ethanol solution is 0.15-0.3 g: 0.5-1 g: 50 mL: 2-3 mL: 1-2 mL: 200 mL.

5. The radiation cooling coating for natural gas cylinders according to claim 2, characterized in that: In step A3, the amount ratio of modified mesoporous silica, grafted modified titanium dioxide, N,N-dimethylformamide, fluorinated acrylate, benzoyl peroxide and petroleum ether is 1-2g:0.5-1g:100mL:0.002-0.005mol:0.5-1.5g:200mL, and the fluorinated acrylate is one of 2-(perfluorobutyl) ethyl acrylate, perfluorooctylpropyl acrylate or 2-(perfluorobutyl) ethyl acrylate.

6. The radiation cooling coating for natural gas cylinders according to claim 1, characterized in that: The modified polyurethane emulsion is prepared by the following steps: Step B1, 1,8-dibromooctane and sodium hydroxide are stirred evenly in N,N-dimethylformamide, 1H-benzotriazole is added, and the mixture is stirred and reacted at 35-45° C. for 24 hours, and purified and distilled under reduced pressure to obtain bromobenzotriazole; Step B2, under argon conditions, polyethylene glycol, isophorone diisocyanate and 2,2-bis(hydroxymethyl)propionic acid are added to acetone and mixed and stirred evenly, dibutyltin dilaurate is added, and the temperature is raised to 60°C and stirred for 3-4h, then cooled to 40°C, triethylamine is added and stirred for 1h, then cooled to 0°C, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is slowly added dropwise and stirred for 0.5-1.5h to obtain silane-modified polyurethane; Step B3, add sodium hydroxide solution to the silane-modified polyurethane in step B2 and stir evenly, then add brominated benzotriazole, stir and react at 35-45° C. for 24 hours, then add water and stir at high speed for 1 hour to obtain a modified polyurethane emulsion.

7. The radiation cooling coating for natural gas cylinders according to claim 6, characterized in that: In step B1, the usage ratio of 1,8-dibromooctane, sodium hydroxide, N,N-dimethylformamide and 1H-benzotriazole is 0.011-0.015 mol:1.5-2.5 g:100 mL:0.01 mol.

8. The radiation cooling coating for natural gas cylinders according to claim 6, characterized in that: In step B2, the mass ratio of polyethylene glycol, isophorone diisocyanate, 2,2-bis(hydroxymethyl)propionic acid, acetone, dibutyltin dilaurate, triethylamine and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is 35-45:13-15:2.5-3.5:50-70:0.5-1:2-2.8:2-4.

9. The radiation cooling coating for natural gas cylinders according to claim 6, characterized in that: In step B3, the molar ratio of brominated benzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in step B2 is 1-1.3:1, the concentration of the sodium hydroxide solution is 0.025-0.035 mol / L, and the mass is 7%-10% of the mass of the silane-modified polyurethane in step B2, and the mass ratio of water to the silane-modified polyurethane in step B2 is 1:

1.

10. A method for preparing the radiation cooling coating for natural gas cylinders according to any one of claims 1 to 9, characterized in that: The following steps are involved: Weigh the raw materials by weight, mix and stir the composite filler, film-forming aid, antioxidant, leveling agent, defoamer and water evenly, then slowly add the modified polyurethane emulsion, stir at a speed of 500-800rpm for 30-50min, and obtain the radiation refrigeration coating for natural gas cylinders.

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