A heat-insulating silicone coating and its preparation method

Abstract

The invention discloses a heat-insulating silicone coating and a preparation method thereof, belonging to the technical field of thermal insulation materials. Linear hydrogel is wrapped on the surface of sepiolite fiber / alumina aerogel and used as a bridge to provide uniformly dispersed anchoring points for subsequent cage-like hybrid nanospheres. The cage-like hybrid nanospheres are then used as a cross-linking agent on the surface. Cross-linkable double bonds exist on the surface of the cage-like hybrid nanospheres, thereby forming a ball-chain composite unit structure based on the original linear hydrogel, and polymerizing and cross-linking into a network. After calcination, the cage-like hybrid nanospheres inside are transformed into core-shell carbon nanospheres, which inhibit crack propagation. Carbon chains derived from the linear hydrogel form a macroporous structure, while a mesoporous structure is generated between the cross-linking points of the cage-like balls. The microporous structure is retained inside the core-shell balls, and a better heat-insulating effect is achieved through a multi-level stepped pore structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials, and specifically relates to a thermal insulation and heat preservation organic silicon coating and a preparation method thereof. Background Art

[0002] In daily life, effective thermal insulation measures are generally taken for civil buildings, heat pipes, industrial thermal facilities, etc., and rock wool felt, inorganic thermal insulation mortar, polystyrene foam board, and foamed polyurethane are more commonly used insulation materials, but they must reach a certain thickness to have excellent thermal insulation effect, the construction is more complicated, and the waterproof performance cannot meet actual needs; thermal insulation coatings can overcome the disadvantage of complex construction, and the thickness requirement is not high.

[0003] Insulation systems, including thermal insulation coatings, are widely used in production equipment and transportation routes. However, traditional thermal insulation coatings are mostly organic insulation materials with poor toughness, which greatly limits the application of traditional building insulation materials in high-end industries. The development of water-based nano-insulation technology that combines excellent thermal insulation and high toughness involves compounding inorganic nanomaterials with thermal insulation materials to create a slurry-like insulation material with adjustable thermal properties. This energy-saving thermal insulation material can significantly improve the thermal insulation effect of the coating and possess excellent toughness.

[0004] A Chinese patent with announcement number CN116376386B discloses a nano-scale silica composite thermal insulation material and its preparation process. The scheme discloses a thermal insulation coating prepared by core-shell silica insulation filler, silicone-modified acrylate emulsion, and other fillers and additives. The coating uses silicone-modified acrylate emulsion as the main component, and grafts silicone groups on the chain segments of linear acrylic resin to improve the water resistance and waterproofing properties of the coating. In order to improve the thermal insulation performance of the coating, the scheme introduces core-shell structured silica and titanium dioxide and other materials, and has good environmental protection. However, in this scheme, the core-shell silica has a single pore structure, resulting in insufficient actual insulation performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermal insulation silicone coating and a preparation method thereof. By wrapping a linear hydrogel on the surface of sepiolite fiber / alumina aerogel and using this as a bridge, a uniformly dispersed anchoring point is provided for the subsequent cage-like hybrid nanospheres. The carbon chains derived from the linear hydrogel form a macroporous structure, while a mesoporous structure is generated between the cross-linking points of the cage-like spheres. The microporous structure is retained inside the core-shell spheres, and a better thermal insulation effect is achieved through a multi-level stepped pore structure.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a heat-insulating silicone coating comprises the following steps:

[0008] Step 1: Using a sol-gel method, the sepiolite fiber is immersed in an alumina sol, and freeze-dried to obtain a sepiolite fiber / alumina aerogel.

[0009] Step 2: Using hexadecyltrimethylammonium bromide as a cationic surfactant, micelles are formed in the solution, tetraethoxysilane is hydrolyzed and condensed to form silica nanospheres, and then under acidic conditions, vinyltriethoxysilane is condensed to form Si-O-Si bonds to obtain cage-like hybrid nanospheres.

[0010] Step 3: Using N-isopropylacrylamide as a monomer, under the action of an initiator, a chain reaction is initiated to form a linear hydrogel attached to the sepiolite fiber / alumina aerogel, thereby obtaining an aerogel-loaded linear hydrogel.

[0011] Step 4: The caged hybrid nanospheres are attached to the surface of the aerogel-loaded linear hydrogel by electrostatic adsorption. The vinyl sites on the upper surface of the caged hybrid nanospheres act as crosslinkers for N-isopropylacrylamide, and polymerization, crosslinking, and calcination are continued to obtain a multifunctional composite filler.

[0012] Step 5: Stir and mix polyurethane, acrylate, deionized water, dispersant SN-5040, defoaming agent Aksu SF-208, wetting agent alkylphenol polyoxyethylene ether, film-forming aid OE-300, sodium bicarbonate and multifunctional composite filler to obtain a heat-insulating silicone coating.

[0013] Furthermore, the usage ratio of polyurethane, acrylate, deionized water, SN-5040, Aksu SF-208, alkylphenol polyoxyethylene ether, OE-300, sodium bicarbonate and multifunctional composite filler is 500-550g:300-340g:2-4L:5-6g:1-2g:2-3g:0.8-0.9g:0.5-0.7g:30-40g.

[0014] Furthermore, the specific preparation steps of sepiolite fiber / alumina aerogel are as follows:

[0015] Alumina hydrosol and ethanol are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 minutes, then ammonium sulfate as an initiator is added, and stirring is continued for 40-60 minutes. Then, a 5-6% ammonia aqueous solution and sepiolite fibers are added to promote gel polycondensation, heated to 80-90°C, stirred for 48-50 hours, naturally cooled to room temperature, and freeze-dried with liquid nitrogen for 12-14 hours to obtain sepiolite fiber / alumina aerogel.

[0016] Furthermore, the usage ratio of alumina hydrosol, ethanol, ammonium sulfate, ammonia solution and sepiolite fiber is 100-120 g: 800-900 mL: 1-2 g: 26-28 mL: 40-50 g.

[0017] Furthermore, the specific preparation steps of the cage-like hybrid nanospheres are as follows:

[0018] Anhydrous ethanol and deionized water are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 minutes, then hexadecyltrimethylammonium bromide and ammonia water are added, and stirring is continued for 15-20 minutes. Then tetraethoxysilane is added and stirring is continued for 2-3 hours to form silica nanospheres. Then, 1 mol / L glacial acetic acid solution, vinyltriethoxysilane and acetone are added, and stirring is continued for 2-3 hours. The reaction mixture is filtered, and the filter cake is washed 2-4 times with deionized water and anhydrous ethanol, respectively, and dried in vacuo at 60-70°C for 1-2 hours to obtain cage-shaped hybrid nanospheres.

[0019] Furthermore, the usage ratio of anhydrous ethanol, deionized water, hexadecyltrimethylammonium bromide, aqueous ammonia, tetraethoxysilane, glacial acetic acid solution, vinyltriethoxysilane and acetone is 400-500 mL: 600-700 mL: 12-14 g: 8-10 mL: 36-45 mL: 4-5 mL: 45-55 mL: 80-90 mL.

[0020] Furthermore, the specific preparation steps of aerogel-loaded linear hydrogel are as follows:

[0021] N-isopropylacrylamide, sepiolite fiber / alumina aerogel, sodium dodecyl sulfate and deionized water were added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 min, ammonia was introduced at a flow rate of 10-12 min / L for 30-40 min, heated to 70-80°C, ammonium persulfate was added, and the reaction was continued with stirring for 6-7 h under a nitrogen atmosphere. The reaction was filtered, and the filter cake was washed with petroleum ether and deionized water for 2-4 times, respectively, and vacuum dried at 60-70°C for 1-2 h to obtain an aerogel-loaded linear hydrogel.

[0022] Furthermore, the usage ratio of N-isopropylacrylamide, sepiolite fiber / alumina aerogel, sodium lauryl sulfate, deionized water and ammonium persulfate is 80-90 mL: 40-50 g: 4-5 g: 1-2 L: 12-14 g.

[0023] Furthermore, the specific preparation steps of the multifunctional composite filler are as follows:

[0024] Aerogel-loaded linear hydrogel, caged hybrid nanospheres, N-isopropylacrylamide and deionized water are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 min, then sodium dodecyl sulfate is added, heated to 40-50°C, and stirred for 20-30 min. Ammonia is introduced at a flow rate of 10-12 min / L for 30-40 min, heated to 70-80°C, and ammonium persulfate is added. Under a nitrogen atmosphere, stirring is continued for 6-7 h, filtered, and the filter cake is washed with petroleum ether and deionized water for 2-3 times, respectively, and vacuum dried at 60-80°C for 1-2 h. The product is transferred to a muffle furnace and calcined at 500-550°C for 2-3 h under nitrogen protection to obtain a multifunctional composite filler.

[0025] Furthermore, the amount ratio of the aerogel-loaded linear hydrogel, caged hybrid nanospheres, N-isopropylacrylamide, deionized water, sodium lauryl sulfate and ammonium persulfate is 80-90 g: 40-50 g: 50-60 mL: 1-2 L: 6-7 g: 12-14 g.

[0026] Beneficial effects of the present invention:

[0027] 1. The thermal insulation silicone coating prepared by the present invention uses sepiolite fiber / alumina aerogel as a matrix, is covered with a stepped three-dimensional network hydrogel layer on the surface, and cage-shaped hybrid nanospheres are embedded inside the hydrogel layer to obtain a multifunctional composite filler, so that the thermal insulation silicone coating has excellent thermal insulation properties, high strength, high adhesion, is not easy to peel off, and is not easy to absorb water.

[0028] 2. The multifunctional composite filler of the present invention is prepared by first covering a layer of linear aerogel on the sepiolite fiber / alumina aerogel, using N-isopropylacrylamide as a monomer, and in the absence of a cross-linking agent, the obtained hydrogel is linear, thereby obtaining an aerogel-loaded linear hydrogel, and then using cage-like hybrid nanospheres as a cross-linking agent on the surface. The cage-like hybrid nanospheres have cross-linkable double bonds on the surface, thereby forming a ball-chain composite unit structure based on the original linear hydrogel, a secondary porous structure similar to a "grape bunch", and polymerizing and cross-linking into a network, so that the cage-like hybrid nanospheres are fixed into the three-dimensional network structure of the hydrogel. After calcination, the three-dimensional network structure on the surface of the sepiolite fiber / alumina aerogel becomes a porous carbon layer with a network structure, and the cage-like hybrid nanospheres inside are converted into core-shell nanocarbon spheres. This composite structure is applied to the coating. On the one hand, the core-shell nanospheres can disperse stress by generating relative slip inside the porous carbon layer, inhibit crack propagation, and significantly improve the impact resistance of the coating.

[0029] 3. The linear hydrogel acts as a bridge, providing uniformly dispersed anchor points for subsequent cage-like hybrid nanospheres, avoiding the agglomeration problem caused by traditional direct addition methods. The carbon chains derived from the linear hydrogel form a macroporous structure, while the crosslinks between the cage-like nanospheres create a mesoporous structure, while the core-shell nanospheres retain a microporous structure. This stepped pore structure, through a multi-level structure, better disperses stress and provides enhanced thermal insulation. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Example 1: A method for preparing a heat-insulating silicone coating, comprising the following steps:

[0032] S1: 100 g of alumina hydrosol and 800 mL of ethanol were added to a reactor, stirred at 20°C and 400 r / min for 20 min, then 1 g of initiator ammonium sulfate was added and stirring continued for 40 min. Then, 26 mL of 5% ammonia solution and 40 g of sepiolite fiber were added to promote gel polycondensation. The mixture was heated to 80°C and stirred for 48 h. The mixture was naturally cooled to room temperature and freeze-dried with liquid nitrogen for 12 h to obtain sepiolite fiber / alumina aerogel.

[0033] S2: Add 400 mL of anhydrous ethanol and 600 mL of deionized water into the reactor, stir at 20°C and 400 r / min for 20 min, then add 12 g of hexadecyltrimethylammonium bromide and 8 mL of ammonia water, continue stirring for 15 min, then add 36 mL of tetraethoxysilane, continue stirring for 2 h to form silica nanospheres, then add 4 mL of 1 mol / L glacial acetic acid solution, 45 mL of vinyltriethoxysilane and 80 mL of acetone, continue stirring for 2 h, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry in vacuo at 60°C for 1 h to obtain cage-like hybrid nanospheres.

[0034] S3: 80 mL of N-isopropylacrylamide, 40 g of sepiolite fiber / alumina aerogel, 4 g of sodium dodecyl sulfate and 1 L of deionized water were added to the reactor, stirred at 20°C and 400 r / min for 20 min, ammonia was introduced at a flow rate of 10 min / L for 30 min, heated to 70°C, 12 g of ammonium persulfate was added, and the reaction was continued with stirring for 6 h under a nitrogen atmosphere. The mixture was filtered, and the filter cake was washed twice with petroleum ether and deionized water respectively, and dried in vacuum at 60°C for 1 h to obtain aerogel-loaded linear hydrogel.

[0035] S4: 80 g of aerogel-loaded linear hydrogel, 40 g of caged hybrid nanospheres, 50 mL of N-isopropylacrylamide and 1 L of deionized water were added to the reactor, stirred at 20 ° C and 400 r / min for 20 min, then 6 g of sodium dodecyl sulfate was added, heated to 40 ° C, and continued to stir for 20 min. Ammonia was introduced at a flow rate of 10 min / L for 30 min, heated to 70 ° C, and 12 g of ammonium persulfate was added. Under a nitrogen atmosphere, the stirring reaction was continued for 6 h, filtered, and the filter cake was washed twice with petroleum ether and deionized water respectively, and vacuum dried at 60 ° C for 1 h. The product was transferred to a muffle furnace and calcined at 500 ° C for 2 h under nitrogen protection to obtain a multifunctional composite filler.

[0036] S5: Add 500g of polyurethane, 300g of acrylate and 2L of deionized water into a reactor, stir at 70°C and 400r / min for 20min, then add 5g of dispersant SN-5040, 1g of defoamer Aksu SF-208, 2g of wetting agent alkylphenol polyoxyethylene ether, 0.8g of film-forming aid OE-300, 0.5g of sodium bicarbonate and 30g of multifunctional composite filler, stir and disperse for 30min to obtain a thermal insulation silicone coating.

[0037] Example 2: A method for preparing a heat-insulating silicone coating, comprising the following steps:

[0038] S1: 110 g of alumina hydrosol and 850 mL of ethanol were added to a reactor and stirred at 22.5 °C and 450 r / min for 25 min. Then, 1.5 g of initiator ammonium sulfate was added and stirring was continued for 50 min. Then, 27 mL of 5.5% ammonia solution and 45 g of sepiolite fiber were added to promote gel polycondensation. The mixture was heated to 85 °C and stirred for 49 h. The mixture was naturally cooled to room temperature and freeze-dried with liquid nitrogen for 13 h to obtain sepiolite fiber / alumina aerogel.

[0039] S2: Add 450 mL of anhydrous ethanol and 650 mL of deionized water into the reactor, stir at 22.5 ° C and 450 r / min for 25 minutes, then add 13 g of hexadecyltrimethylammonium bromide and 9 mL of ammonia water, continue stirring for 17.5 minutes, then add 40.5 mL of tetraethoxysilane, continue stirring for 2.5 hours to form silica nanospheres, then add 4.5 mL of 1 mol / L glacial acetic acid solution, 50 mL of vinyltriethoxysilane and 85 mL of acetone, continue stirring for 2.5 hours, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and dry it in a vacuum at 65 ° C for 1.5 hours to obtain cage-like hybrid nanospheres.

[0040] S3: 85 mL of N-isopropylacrylamide, 45 g of sepiolite fiber / alumina aerogel, 4.5 g of sodium dodecyl sulfate and 1.5 L of deionized water were added to the reactor, stirred at 22.5°C and 450 r / min for 25 min, ammonia was introduced at a flow rate of 11 min / L for 35 min, heated to 75°C, 13 g of ammonium persulfate was added, and the reaction was continued with stirring for 6.5 h under a nitrogen atmosphere. The mixture was filtered, and the filter cake was washed three times with petroleum ether and deionized water respectively, and vacuum dried at 65°C for 1.5 h to obtain aerogel-loaded linear hydrogel.

[0041] S4: 85 g of aerogel-loaded linear hydrogel, 45 g of caged hybrid nanospheres, 55 mL of N-isopropylacrylamide and 1.5 L of deionized water were added to the reactor, stirred at 22.5 ° C and 450 r / min for 25 min, then 6.5 g of sodium dodecyl sulfate was added, heated to 45 ° C, and continued to stir for 25 min. Ammonia was introduced at a flow rate of 11 min / L for 35 min, heated to 75 ° C, and 13 g of ammonium persulfate was added. Under a nitrogen atmosphere, the reaction was continued to stir for 6.5 h, filtered, and the filter cake was washed with petroleum ether and deionized water 2.5 times respectively, and vacuum dried at 70 ° C for 1.5 h. The product was transferred to a muffle furnace and calcined at 525 ° C for 2.5 h under nitrogen protection to obtain a multifunctional composite filler.

[0042] S5: Add 525g of polyurethane, 320g of acrylate and 3L of deionized water into a reactor, stir at 77.5℃ and 450r / min for 25min, then add 5.5g of dispersant SN-5040, 1.5g of defoaming agent Aksu SF-208, 2.5g of wetting agent alkylphenol polyoxyethylene ether, 0.85g of film-forming aid OE-300, 0.6g of sodium bicarbonate and 35g of multifunctional composite filler, stir and disperse for 35min to obtain a thermal insulation silicone coating.

[0043] Example 3: A method for preparing a heat-insulating silicone coating, comprising the following steps:

[0044] S1: 120 g of alumina hydrosol and 900 mL of ethanol were added to a reactor and stirred at 25 °C and 500 r / min for 30 min. Then, 2 g of initiator ammonium sulfate was added and stirring was continued for 60 min. Then, 28 mL of 6% ammonia solution and 50 g of sepiolite fiber were added to promote gel polycondensation. The mixture was heated to 90 °C and stirred for 50 h. The mixture was naturally cooled to room temperature and freeze-dried with liquid nitrogen for 14 h to obtain sepiolite fiber / alumina aerogel.

[0045] S2: Add 500 mL of anhydrous ethanol and 700 mL of deionized water into the reactor, stir at 25°C and 500 r / min for 30 min, then add 14 g of hexadecyltrimethylammonium bromide and 10 mL of ammonia water, continue stirring for 20 min, then add 45 mL of tetraethoxysilane, continue stirring for 3 h to form silica nanospheres, then add 5 mL of 1 mol / L glacial acetic acid solution, 55 mL of vinyltriethoxysilane and 90 mL of acetone, continue stirring for 3 h, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and dry in vacuo at 70°C for 2 h to obtain cage-like hybrid nanospheres.

[0046] S3: Add 90 mL of N-isopropylacrylamide, 50 g of sepiolite fiber / alumina aerogel, 5 g of sodium dodecyl sulfate and 2 L of deionized water into the reactor, stir at 25 ° C and 500 r / min for 30 min, introduce ammonia at a flow rate of 12 min / L for 40 min, heat to 80 ° C, add 14 g of ammonium persulfate, continue stirring and reacting under nitrogen atmosphere for 7 h, filter, wash the filter cake with petroleum ether and deionized water four times respectively, and dry in vacuo at 70 ° C for 2 h to obtain aerogel-loaded linear hydrogel.

[0047] S4: 90 g of aerogel-loaded linear hydrogel, 50 g of caged hybrid nanospheres, 60 mL of N-isopropylacrylamide and 2 L of deionized water were added to the reactor, stirred at 25 ° C and 500 r / min for 30 min, then 7 g of sodium dodecyl sulfate was added, heated to 50 ° C, and continued to stir for 30 min. Ammonia was introduced at a flow rate of 12 min / L for 40 min, heated to 80 ° C, and 14 g of ammonium persulfate was added. Under a nitrogen atmosphere, the reaction was continued to stir for 7 h, filtered, and the filter cake was washed with petroleum ether and deionized water three times respectively, and vacuum dried at 80 ° C for 2 h. The product was transferred to a muffle furnace and calcined at 550 ° C for 3 h under nitrogen protection to obtain a multifunctional composite filler.

[0048] S5: Add 550g of polyurethane, 340g of acrylate and 4L of deionized water into a reactor, stir at 85°C and 500r / min for 30min, then add 6g of dispersant SN-5040, 2g of defoaming agent Aksu SF-208, 3g of wetting agent alkylphenol polyoxyethylene ether, 0.9g of film-forming aid OE-300, 0.7g of sodium bicarbonate and 40g of multifunctional composite filler, stir and disperse for 40min to obtain a thermal insulation silicone coating.

[0049] Comparative Example 1: Based on Example 3, the cage-like hybrid nanospheres in step S2 were replaced with silica nanospheres.

[0050] Comparative Example 2: Based on Example 3, without the treatment of step S3, the aerogel-loaded linear hydrogel in step S4 is replaced by the sepiolite fiber / alumina aerogel in step S1.

[0051] Comparative Example 3: Based on Example 3, the aerogel loaded with linear hydrogel prepared in step S3 is directly used as the multifunctional composite filler in step S5 without the treatment in step S4.

[0052] The thermal insulation silicone coatings obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were tested for their performance. The coatings were applied to the glass surface with a coating amount of 80 g / m 2 , 365nm ultraviolet light irradiation for 30s, the coating sample was prepared, and the performance was tested and the test results were recorded. Mechanical properties: GB / T2567-2008 was used as the reference standard to test the tensile strength and compressive elastic modulus of the coating sample; Water resistance: The sample was cut and weighed, and immersed in deionized water for 24 hours. The mass of the sample before and after water absorption was recorded, and the mass change rate of the sample before and after water absorption was calculated; Adhesion: GB / T9286-1998 was used as the reference standard, and a paint film cross-score was used to draw a "cross" grid to evaluate the adhesion level of the sample; Thermal insulation performance: A laser pulse flash thermal conductivity meter was used to test the thermal diffusivity of the sample, and the thermal conductivity of the sample was calculated. The results are shown in Table 1:

[0053] Table 1 Thermal insulation performance test of silicone coating

[0054] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (MPa) 35.4 36.2 37.1 28.5 24.3 17.1 Compression elastic modulus (MPa) 28.5 29.2 29. 22.6 19.7 13.2 Water absorption rate (%) 2.2 2.0 1.8 2.8 3.1 5.8 Adhesion (grade) 0 0 0 1 2 2 Thermal conductivity (W / m·K) 0.052 0.048 0.046 0.062 0.073 0.095

[0055] As can be seen from Table 1, the tensile strength, compressive elastic modulus and adhesion of the thermal insulating silicone coatings obtained in Examples 1 to 3 are significantly better than those of the comparative example, and the water absorption and thermal conductivity are significantly lower than those of the comparative example, indicating that the thermal insulating silicone coatings prepared by the present invention have thermal insulation properties, high strength, high adhesion, are not easy to peel off, and are not easy to absorb water.

[0056] In Comparative Example 1, the cage-like hybrid nanospheres are replaced with silica nanospheres, and hexadecyltrimethylammonium bromide is used as a cationic surfactant to form micelles in the solution. Tetraethoxysilane is hydrolyzed and condensed to form silica nanospheres. Then, under acidic conditions, vinyltriethoxysilane is condensed to form Si-O-Si bonds to obtain cage-like hybrid nanospheres. The cage-like hybrid nanospheres are a core-shell structure with silica as the core and cage-type polysiloxane as the shell. After calcination, core-shell nanocarbon spheres are obtained. The core-shell nanospheres can disperse stress by generating relative slip inside the porous carbon layer, inhibit crack propagation, and significantly improve the impact resistance of the coating.

[0057] In Comparative Example 2, the aerogel-loaded linear hydrogel was replaced with sepiolite fiber / alumina aerogel. The linear hydrogel served as a bridge to provide a uniformly dispersed anchor point for the subsequent cage-like hybrid nanospheres, avoiding the agglomeration problem caused by the traditional direct addition method. The carbon chain derived from the linear hydrogel formed a macroporous structure, which lost the macroporous structure and reduced the multi-level structure of the pores, resulting in a slight decrease in the performance test.

[0058] In Comparative Example 3, the aerogel loaded with linear hydrogel is directly used as a multifunctional composite filler, and the caged hybrid nanospheres are used as a cross-linking agent. There are cross-linkable double bonds on the surface of the caged hybrid nanospheres, thereby forming a ball-chain composite unit structure based on the original linear hydrogel, similar to a secondary porous structure of "grape bunches", and polymerized and cross-linked into a network, so that the caged hybrid nanospheres are fixed into the three-dimensional network structure of the hydrogel. After calcination, the three-dimensional network structure on the surface of the sepiolite fiber / alumina aerogel becomes a porous carbon layer with a network structure, and the carbon chain derived from the linear hydrogel forms a macroporous structure, while a mesoporous structure is generated between the cross-linking points of the caged balls. The microporous structure is retained inside the core-shell balls, thereby forming a stepped pore. After losing the three-dimensional network structure, the performance test shows a significant decrease.

[0059] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a heat-insulating silicone coating, characterized in that: The steps include: Step 1: Using a sol-gel method, sepiolite fibers are immersed in alumina sol, and freeze-dried to obtain sepiolite fiber / alumina aerogel; Step 2: Using hexadecyltrimethylammonium bromide as a cationic surfactant, micelles are formed in the solution, tetraethoxysilane is hydrolyzed and polycondensed to form silica nanospheres, and then vinyltriethoxysilane is polycondensed under acidic conditions to form Si-O-Si bonds to obtain cage-like hybrid nanospheres; Step 3: Using N-isopropylacrylamide as a monomer, under the action of an initiator, a chain reaction is initiated to form a linear hydrogel attached to the sepiolite fiber / alumina aerogel to obtain an aerogel-loaded linear hydrogel; Step 4: The caged hybrid nanospheres are attached to the surface of the aerogel-loaded linear hydrogel by electrostatic adsorption. The vinyl sites on the upper surface of the caged hybrid nanospheres act as a crosslinker for N-isopropylacrylamide, and polymerization, crosslinking, and calcination are continued to obtain a multifunctional composite filler. Step 5: mixing polyurethane, acrylate, deionized water, dispersant SN-5040, defoaming agent Aksu SF-208, wetting agent alkylphenol polyoxyethylene ether, film-forming aid OE-300, sodium bicarbonate and multifunctional composite filler to obtain a heat-insulating silicone coating; The specific preparation steps of the cage-shaped hybrid nanospheres are as follows: Anhydrous ethanol and deionized water are added to a reactor, stirred at 20-25°C and 400-500 rpm for 20-30 minutes, and then hexadecyltrimethylammonium bromide and ammonia water are added, and stirring is continued for 15-20 minutes. Then, tetraethoxysilane is added, and stirring is continued for 2-3 hours to form silica nanospheres. Then, a 1 mol / L glacial acetic acid solution, vinyltriethoxysilane, and acetone are added, and stirring is continued for 2-3 hours. The mixture is filtered, washed, and vacuum dried to obtain cage-like hybrid nanospheres. The specific preparation steps of the multifunctional composite filler are as follows: Aerogel-loaded linear hydrogel, caged hybrid nanospheres, N-isopropylacrylamide and deionized water are added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 min, then sodium dodecyl sulfate is added, heated to 40-50°C, and stirred for 20-30 min. Nitrogen is introduced at a flow rate of 10-12 min / L for 30-40 min, heated to 70-80°C, ammonium persulfate is added, and the reaction is continued with stirring for 6-7 h under a nitrogen atmosphere. The product is filtered, washed, and vacuum dried. The product is transferred to a muffle furnace and calcined at 500-550°C for 2-3 h under nitrogen protection to obtain a multifunctional composite filler.

2. The method for preparing a heat-insulating silicone coating according to claim 1, characterized in that: The usage ratio of the polyurethane, acrylate, deionized water, SN-5040, Aksu SF-208, alkylphenol polyoxyethylene ether, OE-300, sodium bicarbonate and multifunctional composite filler is 500-550g: 300-340g: 2-4L: 5-6g: 1-2g: 2-3g: 0.8-0.9g: 0.5-0.7g: 30-40g.

3. The method for preparing a heat-insulating silicone coating according to claim 1, wherein: The specific preparation steps of the sepiolite fiber / alumina aerogel are as follows: Alumina hydrosol and ethanol were added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 min, and then ammonium sulfate as an initiator was added, and stirring was continued for 40-60 min. Then, a 5-6% ammonia aqueous solution and sepiolite fibers were added to promote gel polycondensation. The reaction mixture was heated to 80-90°C, stirred for 48-50 h, cooled naturally, and freeze-dried with liquid nitrogen for 12-14 h to obtain sepiolite fiber / alumina aerogel.

4. The method for preparing a heat-insulating silicone coating according to claim 3, characterized in that: The usage ratio of the alumina hydrosol, ethanol, ammonium sulfate, ammonia solution and sepiolite fiber is 100-120 g: 800-900 mL: 1-2 g: 26-28 mL: 40-50 g.

5. The method for preparing a heat-insulating silicone coating according to claim 1, characterized in that: The usage ratio of the anhydrous ethanol, deionized water, hexadecyltrimethylammonium bromide, ammonia water, tetraethoxysilane, glacial acetic acid solution, vinyltriethoxysilane and acetone is 400-500 mL: 600-700 mL: 12-14 g: 8-10 mL: 36-45 mL: 4-5 mL: 45-55 mL: 80-90 mL.

6. The method for preparing a heat-insulating silicone coating according to claim 1, characterized in that: The specific preparation steps of the aerogel-loaded linear hydrogel are as follows: N-isopropylacrylamide, sepiolite fiber / alumina aerogel, sodium dodecyl sulfate and deionized water were added to a reactor, stirred at 20-25°C and 400-500 r / min for 20-30 min, nitrogen was introduced at a flow rate of 10-12 min / L for 30-40 min, heated to 70-80°C, ammonium persulfate was added, and the reaction was continued with stirring for 6-7 h under a nitrogen atmosphere. The reaction was filtered, washed and vacuum dried to obtain an aerogel-loaded linear hydrogel.

7. The method for preparing a heat-insulating organic silicon coating according to claim 6, characterized in that: The usage ratio of the N-isopropylacrylamide, sepiolite fiber / alumina aerogel, sodium lauryl sulfate, deionized water and ammonium persulfate is 80-90 mL: 40-50 g: 4-5 g: 1-2 L: 12-14 g.

8. The method for preparing a heat-insulating silicone coating according to claim 1, characterized in that: The aerogel-loaded linear hydrogel, cage-shaped hybrid nanospheres, N-isopropylacrylamide, deionized water, sodium lauryl sulfate and ammonium persulfate have a usage ratio of 80-90 g: 40-50 g: 50-60 mL: 1-2 L: 6-7 g: 12-14 g.

9. A heat-insulating silicone coating, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.