A radiation cooling coating for natural gas cylinders and its preparation method

Abstract

The present invention relates to the technical field of coatings, and discloses a radiative cooling coating for natural gas cylinders and a preparation method thereof. The radiative cooling coating for natural gas cylinders prepared by the present invention is mainly made of a modified polyurethane emulsion, and is mixed and stirred by adding other additives such as composite fillers and film-forming aids, and 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 radiative cooling effect; the modified polyurethane emulsion endows the coating with excellent ultraviolet resistance, so that it still has the characteristic of long service life when 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 susceptible to environmental temperature during filling, transportation, and use. Especially in high-temperature environments, the pressure inside the cylinder will increase significantly due to temperature rise, and the safety is limited. Therefore, the surface of natural gas cylinders is usually coated with heat-insulating materials, such as low-thermal-conductivity materials like polyurethane foam or aerogel felt. Although it can delay heat transfer, it has a large thickness, affects the portability of the gas cylinder, and cannot actively discharge the accumulated heat. It may also be coated with a reflective coating to reduce solar radiation absorption through a high solar reflectance, but it has insufficient thermal radiation emission ability in the mid- and far-infrared bands (8 - 13 μm), 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, while using a high solar reflectance to reduce sunlight absorption to achieve 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 rain, 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:

[0006] 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;

[0007] 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;

[0008] The composite filler is prepared by the following steps:

[0009] 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;

[0010] 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

[0011] 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;

[0012] Step A2: Add sodium hydroxide and cetyltrimethylammonium bromide into the mixed solution of ethanol and water and 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;

[0013] 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

[0014] 0.15 - 0.3 g: 0.5 - 1 g: 50 mL: 2 - 3 mL: 1 - 2 mL: 200 mL;

[0015] Further, in the hydrochloric acid ethanol solution described in step A2, the volume ratio of hydrochloric acid to ethanol is 1:7;

[0016] 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;

[0017] 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

[0018] 1 - 2 g: 0.5 - 1 g: 100 mL: 0.002 - 0.005 mol: 0.5 - 1.5 g: 200 mL;

[0019] Further, the fluorinated acrylate described in step A3 is one of 2-(perfluorobutyl)ethyl acrylate, perfluorooctylpropyl acrylate, or ethyl 2-(perfluorobutyl)acrylate.

[0020] The modified polyurethane emulsion is prepared by the following steps:

[0021] Step B1: Stir 1,8-dibromooctane and sodium hydroxide evenly in N,N-dimethylformamide, add 1H-benzotriazole, and stir and react at 35-45 °C for 24 h. Purify and distill under reduced pressure to obtain bromo-benzotriazole.

[0022] Further, in step B1, the dosage ratio of 1,8-dibromooctane, sodium hydroxide, N,N-dimethylformamide, and 1H-benzotriazole is

[0023] 0.011-0.015 mol: 1.5-2.5 g: 100 mL: 0.01 mol;

[0024] Step B2: Under argon conditions, add polyethylene glycol (number average molecular weight of 2000), isophorone diisocyanate, and 2,2-bis(hydroxymethyl)propionic acid to 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 and slowly dropwise add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 0.5-1.5 h to obtain silane-modified polyurethane.

[0025] 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

[0026] 35-45: 13-15: 2.5-3.5: 50-70: 0.5-1: 2-2.8: 2-4;

[0027] Step B3: Add sodium hydroxide solution to the silane-modified polyurethane described in step B2 and mix and stir evenly. Then add bromo-benzotriazole and stir and react at 35-45 °C for 24 h. Then add water and stir at high speed for 1 h to obtain the modified polyurethane emulsion.

[0028] Further, in step B3, the molar ratio of bromo-benzotriazole to N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in step B2 is 1-1.3: 1;

[0029] 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;

[0030] Further, in step B3, the mass ratio of water to the silane-modified polyurethane described in step B2 is 1:1.

[0031] A preparation method of a radiation cooling coating for natural gas cylinders comprises the following steps:

[0032] Weigh raw materials by weight. Mix the composite filler, film-forming aid, antioxidant, leveling agent, defoaming agent and water evenly by stirring, and 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.

[0033] Advantages of the present invention:

[0034] The radiation cooling coating for natural gas cylinders prepared in this application uses a modified polyurethane emulsion as the main raw material, and is mixed and stirred by adding other additives such as composite filler and film-forming aid. It has excellent adhesion, cooling efficiency, hydrophobicity and service life. The composite filler introduced into 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, so that it still has a long service life when exposed outdoors for a long time.

[0035] 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, which significantly improves the radiation cooling effect and cleaning ability of the coating, and further improves 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 solar light reflection and infrared radiation performance of the coating. Among them, the mesoporous structure of mesoporous silica enhances the solar light 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 the TiO2 modified by imide retains a high solar light reflectivity, and also covers the surface active sites of TiO2 through chemical bonding (imide group), reducing the generation of photoinduced electron-hole pairs and reducing 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 thus improve the service life of the coating outdoors.

[0036] The radiation cooling coating prepared in this application uses a modified polyurethane emulsion as the main component of the coating. Compared with traditional acrylate emulsions, it has better weather resistance and certain ultraviolet resistance. This is because a benzotriazole structure with ultraviolet absorption effect is introduced into the modified polyurethane emulsion, which improves the ultraviolet resistance of the coating, thereby increasing the service life of the coating outdoors. At the same time, the benzotriazole structure has strong polarity, which enables it to 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

[0037] 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Example 1: The composite filler is prepared by the following steps:

[0039] 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.

[0040] 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 and 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.

[0041] 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.

[0042] The modified polyurethane emulsion is prepared by the following steps:

[0043] Step B1: 0.011 mol of 1,8-dibromooctane and 1.5 g of sodium hydroxide are stirred evenly in 100 mL of N,N-dimethylformamide, 0.01 mol of 1H-benzotriazole is added, and the mixture is stirred and reacted at 35 °C for 24 h, then purified and distilled under reduced pressure to obtain bromobenzotriazole.

[0044] Step B2: Under argon atmosphere, 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 are added to 50 g of acetone and mixed and stirred evenly, 0.5 g of dibutyltin dilaurate is added, and the temperature is raised to 60 °C and stirred for 3 h, then cooled to 40 °C, 2 g of triethylamine is added and stirred for 1 h, and then cooled to 0 °C, 2 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is slowly added dropwise and stirred and reacted for 0.5 h to obtain silane-modified polyurethane.

[0045] Step B3: Sodium hydroxide solution is added to the silane-modified polyurethane described in Step B2 and mixed and stirred evenly, then bromobenzotriazole is added, and the mixture is stirred and reacted at 35 °C for 24 h, and then water is added and stirred 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 the mass is 10% 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 is 1:1.

[0046] Example 2: The composite filler is prepared by the following steps:

[0047] Step A1: 3 g of titanium dioxide powder, 0.15 mol of silane coupling agent KH550 and 100 mL of toluene are mixed and stirred evenly, the temperature is raised to 75 °C and reacted for 2.5 h, then 0.2 mol of maleic anhydride and 0.04 mol of anhydrous sodium acetate are added and reacted for 2 h, and then 0.025 mol of hydroquinone and 50 mL of acetic anhydride are added and reacted for another 2 h, and then filtered, washed and dried to obtain graft-modified titanium dioxide.

[0048] Step A2: 0.25 g of sodium hydroxide and 0.75 g of cetyltrimethylammonium bromide are added to a mixed solution of 50 mL of ethanol and water and stirred evenly, and the temperature is raised to 80 °C and stirred for 1 h, then 2.5 mL of tetraethyl orthosilicate and 1.5 mL of silane coupling agent KH570 are added and stirred and reacted for 4 h, centrifuged, the collected precipitate is dispersed in 200 mL of hydrochloric acid-ethanol solution and refluxed at 70 °C for 6 h, and then centrifuged, washed to neutrality and dried to obtain modified mesoporous silica. The volume ratio of hydrochloric acid to ethanol in the hydrochloric acid-ethanol solution is 1:7.

[0049] 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, raise the temperature to 80 °C and stir for 30 min, introduce nitrogen, then add 1 g of benzoyl peroxide, and then raise the temperature 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.

[0050] The modified polyurethane emulsion is prepared by the following steps:

[0051] Step B1: Stir 0.013 mol of 1,8-dibromooctane and 2 g of sodium hydroxide evenly in 100 mL of N,N-dimethylformamide, add 0.01 mol of 1H-benzotriazole, stir and react at 40 °C for 24 h, purify and distill under reduced pressure to obtain brominated benzotriazole;

[0052] Step B2: Under argon atmosphere, add 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 to 60 g of acetone, mix and stir evenly, add 0.75 g of dibutyltin dilaurate, raise the temperature to 60 °C and stir for 3.5 h, cool to 40 °C, add 2.4 g of triethylamine and stir for 1 h, then cool to 0 °C, slowly dropwise add 3 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 1 h to obtain the silane-modified polyurethane;

[0053] Step B3: Add sodium hydroxide solution to the silane-modified polyurethane described in Step B2, mix and stir evenly, then add brominated benzotriazole, stir and react at 40 °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 1.15:1, the concentration of the sodium hydroxide solution is 0.03 mol / L, the mass is 8.5% of the mass of the silane-modified polyurethane described in Step B2, and the mass ratio of water to the silane-modified polyurethane described in Step B2 is 1:1.

[0054] Example 3: The composite filler is prepared by the following steps:

[0055] Step A1: Stir 4 g of titanium dioxide powder, 0.2 mol of silane coupling agent KH550 and 100 mL of toluene evenly, raise the temperature to 80 °C and react for 3 h, then add 0.25 mol of maleic anhydride and 0.05 mol of anhydrous sodium acetate and react for 2.5 h, then add 0.03 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;

[0056] Step A2: Add 0.3 g of sodium hydroxide and 1 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 3 mL of tetraethyl orthosilicate and 2 mL of silane coupling agent KH570, stir and react for 5 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;

[0057] Step A3: Ultrasonically disperse 2 g of modified mesoporous silica and 1 g of graft-modified titanium dioxide evenly in 100 mL of N,N-dimethylformamide. Then add 0.005 mol of 2-(perfluorobutyl)ethyl acrylate, heat up to 85 °C and stir for 30 min, introduce nitrogen, then add 1.5 g of benzoyl peroxide, and then heat up 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.

[0058] The modified polyurethane emulsion is prepared by the following steps:

[0059] Step B1: Stir 0.015 mol of 1,8-dibromooctane and 2.5 g of sodium hydroxide evenly in 100 mL of N,N-dimethylformamide, add 0.01 mol of 1H-benzotriazole, stir and react at 45 °C for 24 h, purify and distill under reduced pressure to obtain bromobenzotriazole;

[0060] 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 into 70 g of acetone, mix and stir evenly, add 1 g of dibutyltin dilaurate, heat up to 60 °C and stir for 4 h, cool down to 40 °C, add 2.8 g of triethylamine and stir for 1 h, then cool down to 0 °C, slowly dropwise add 4 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 1.5 h to obtain silane-modified polyurethane;

[0061] 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 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 bromobenzotriazole 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, the mass is 7% of the mass of the silane-modified polyurethane obtained in Step B2, and the mass ratio of water to the silane-modified polyurethane obtained in Step B2 is 1:1.

[0062] Example 4: A preparation method of a radiation cooling coating for natural gas cylinders includes the following steps:

[0063] Weigh the raw materials by weight parts. 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 evenly by stirring, 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.

[0064] Example 5: A preparation method of a radiation cooling coating for natural gas cylinders comprises the following steps:

[0065] 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.

[0066] Example 6: A preparation method of a radiation cooling coating for natural gas cylinders comprises the following steps:

[0067] 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.

[0068] Comparative Example 1: This comparative example is a radiation cooling coating. The difference from Example 6 is that silica is used to replace the composite filler prepared in Example 3, and the rest are the same.

[0069] 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 to replace the modified polyurethane emulsion prepared in Example 3, and the rest are the same.

[0070] Comparative Example 3: This comparative example is a radiation cooling coating. The difference from Example 6 is that silica is used to replace the composite filler prepared in Example 3, and a commercially available polyurethane emulsion is used to replace the modified polyurethane emulsion prepared in Example 3, and the rest are the same.

[0071] Spray the radiation cooling coatings prepared in Examples 4 - 6 and Comparative Examples 1 - 3 on the surface of clean natural gas cylinders to form radiation cooling coatings with a thickness of 0.5 mm, and conduct performance tests on the coatings:

[0072] Adhesion test: The cross-cut test was carried out in accordance with the national standard GB / T 9286-2021 "Paints and varnishes".

[0073] Solar reflectance ratio test: At an incident angle of 5°, the reflectance of the coating was measured using a UV-Vis-NIR spectrophotometer Lambda950, with a wavelength range of 0.3 - 2.5 μm.

[0074] Atmospheric window emissivity test: The emissivity of the coating in the 8 - 13 μm atmospheric window was measured using an IR-2 dual-band emissivity tester.

[0075] Contact angle test: The water contact angle of the coating surface was measured using a contact angle tester THETAOptical (KSV Instruments Ltd., Finland).

[0076] UV aging resistance performance test: Referring to the standard GB / T 1865-2009, a 600h UV aging test was carried out, and the emissivity of the coating after 600h was measured.

[0077] Cooling temperature difference test: Black magnetic paint and radiation cooling coating were applied on an aluminum sheet with a dry film thickness of about 500 μm. The room temperature was fixed at (25 ± 1) °C. A 500W infrared lamp was used to simulate sunlight irradiation on the coating. By adjusting the distance between the infrared lamp and the test panel, the temperature of the black magnetic paint was controlled within the range of (37 ± 1) °C. The temperature on the back of the test panel (T1) and the temperature on the upper surface of the coating (T2) were detected using a surface thermometer, and data were recorded every 10 minutes until the temperature stabilized. The cooling temperature difference (△T) was calculated using formula 1 (△T = T2 - T1).

[0078] The test results are shown in Table 1:

[0079] Table 1: Performance test results

[0080]

[0081] As can be seen from Table 1, the radiation cooling coating prepared by the present invention has excellent adhesion on the surface of natural gas cylinders, with a solar reflectance ratio greater than 92%, an atmospheric window emissivity greater than 95% of the standard, a water contact angle greater than 130°, an emissivity greater than 95% of the standard after 600h of UV aging, and a cooling temperature difference greater than 10 °C, indicating that the coating has excellent UV resistance, hydrophobicity, and cooling effect, and has good application prospects when applied to natural gas cylinders.

[0082] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the scope defined by the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A radiation cooling coating for natural gas cylinders, characterized in that, It 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 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; The composite filler is prepared by a polymerization reaction of modified mesoporous silica, graft-modified titanium dioxide, and fluorinated acrylate. The modified mesoporous silica is prepared by the reaction of tetraethyl orthosilicate and a silane coupling agent. The graft-modified titanium dioxide is prepared by reacting titanium dioxide powder modified with a silane coupling agent with maleic anhydride; The modified polyurethane emulsion is prepared by reacting silane-modified polyurethane with bromobenzotriazole and then adding water. The bromobenzotriazole is prepared by the reaction of 1,8-dibromooctane and 1H-benzotriazole. The silane-modified polyurethane is prepared by the reaction of polyethylene glycol, isophorone diisocyanate, 2,2-bis(hydroxymethyl)propionic acid, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; 2. The radiation refrigeration coating for a natural gas cylinder according to claim 1, wherein The composite filler is prepared by the following steps: Step A1: Mix titanium dioxide powder, silane coupling agent KH550, and toluene evenly and stir, 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; 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 to react for 3 - 5 h, centrifuge, collect the precipitate, 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; Step A3: Ultrasonically disperse the modified mesoporous silica and 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.

3. The radiation cooling coating for a natural gas cylinder according to claim 2, characterized in that, 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.

4. The radiation cooling coating for natural gas cylinders according to claim 2, wherein 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.

5. A radiation cooling coating for natural gas cylinders according to claim 2, characterized in that, In step A3, the dosage ratio of the modified mesoporous silica, 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. 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, wherein 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, and stir and react at 35-45 °C for 24 h. Purify and distill under reduced pressure to obtain bromobenzotriazole. Step B2: Under argon conditions, add polyethylene glycol, isophorone diisocyanate, and 2,2-bis(hydroxymethyl)propionic acid to acetone and mix and stir evenly. Add dibutyltin dilaurate and raise the temperature to 60 °C and stir for 3-4 h. Cool to 40 °C, add triethylamine and stir for 1 h. Then cool to 0 °C and slowly dropwise add N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and stir and react for 0.5-1.5 h to obtain silane-modified polyurethane. Step B3: Add sodium hydroxide solution to the silane-modified polyurethane described in step B2 and mix and stir evenly. Then add bromobenzotriazole and stir and react at 35-45 °C for 24 h. Then add water and stir at high speed for 1 h to obtain the modified polyurethane emulsion.

7. The radiation cooling coating for natural gas cylinders according to claim 6, characterized in that, 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.

8. A 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. A radiation cooling coating for natural gas cylinders according to claim 6, characterized in that, In step B3, the molar ratio of bromobenzotriazole 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 described in step B2. The mass ratio of water to the silane-modified polyurethane described in step B2 is 1:

1.

10. A preparation method of the radiation refrigeration coating for natural gas cylinders according to any one of claims 1-9, characterized in that, It includes the following steps: Weigh the raw materials by weight, mix the composite filler, film-forming aid, antioxidant, leveling agent, defoaming agent, and water and stir evenly. 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.

Images