Preparation method of high-efficiency hydrophobic thermal insulation aerogel

Abstract

The application discloses a preparation method of high-efficiency hydrophobic heat-insulating aerogel and belongs to the field of functional heat-insulating composite materials. The high-efficiency hydrophobic heat-insulating aerogel is prepared by respectively preparing a hydrophobic monomer and a long-chain polymer skeleton structure, fully mixing the hydrophobic monomer and the long-chain polymer skeleton structure in a solvent system, and performing solvent replacement and freeze drying. The aerogel prepared by the application has excellent hydrophobicity and heat-insulating property. The hydrogel preparation method is convenient and has a wide application prospect in the field of heat-insulating materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional thermal insulation composite materials, specifically relating to a method for preparing a high-efficiency hydrophobic thermal insulation aerogel. Background Technology

[0002] Thermal insulation materials play a crucial role in modern building and industrial applications. With the continuous growth of global energy demand and increasing environmental awareness, effectively reducing energy consumption and improving energy efficiency has become a significant challenge for various industries. The application of thermal insulation materials can not only significantly reduce heat loss but also improve the overall efficiency of the system, thereby reducing negative environmental impacts. In pipeline insulation, especially in industries such as oil, gas, and chemicals, heat loss in pipelines not only leads to energy waste but can also pose safety hazards. In the construction industry, the choice of building insulation materials directly affects indoor comfort and energy consumption. Good insulation performance can effectively block external high or low temperatures, maintain a stable indoor environment, reduce the burden on air conditioning and heating equipment, and thus reduce energy consumption in residential and commercial buildings.

[0003] Aerogels, as a novel type of thermal insulation material, have attracted widespread attention due to their unique microstructure and excellent thermal insulation properties. The main component of aerogels is porous materials such as silica, filled with gas, resulting in an extremely high specific surface area and low thermal conductivity. Aerogels typically have a very low density, sometimes even lighter than air, giving them significant advantages in many applications. The thermal insulation principle of aerogels is mainly based on three heat transfer mechanisms: conduction, convection, and radiation. In the microstructure of aerogels, the thermal conductivity of gases is much lower than that of solid materials, thus effectively reducing heat transfer. Furthermore, the porous structure of aerogels greatly extends the path of gas molecules within the pores, thereby reducing the efficiency of heat conduction. The low thermal conductivity of aerogels makes them an ideal thermal insulation material, maintaining good performance under extreme temperature conditions. Due to their lightweight, low density, and good chemical stability, aerogel materials show broad application prospects in construction, aerospace, and electronic equipment.

[0004] The performance of aerogel materials is not only reflected in their excellent thermal insulation effect but is also closely related to their mechanical properties. The thermal insulation performance of aerogels mainly depends on the mechanical strength and specific surface area of ​​their skeleton. A high-strength skeleton can withstand external pressure and impact, ensuring the stability of the material during long-term use, while a larger specific surface area helps to improve the thermal insulation effect. The microstructure of aerogels allows them to maintain lightweight properties while possessing relatively high strength, making aerogel materials a preferred choice in many applications. Researchers have also begun to explore ways to improve the performance of aerogels by adding different functional monomers. For example, by adding hydrophobic monomers, not only can the waterproof performance of aerogels be enhanced, but their application capability in humid environments can also be improved. This modification method allows aerogels to maintain good performance under various environmental conditions, further broadening their application range. In addition, adding hydrophobic monomers can effectively prevent moisture from affecting the performance of aerogels, reducing the decline in thermal insulation performance caused by moisture absorption. Such modifications not only improve the durability and reliability of aerogels but also significantly extend their service life, making their application in construction, industry, and aerospace more widespread and effective. Through these innovative research and developments, the functionality of aerogel materials has been greatly enhanced, providing new possibilities for achieving more efficient thermal insulation solutions.

[0005] Based on this, this invention utilizes a mixture of hydrophobic monomers and long-chain polymer backbone structures to prepare dendritic organosilicon materials through co-hydrolysis using silane coupling agents. These materials are then composited with long carbon chains, and after solvent displacement and freeze-drying, an aerogel matrix is ​​obtained. Upon use, it can be diluted with solvent and sprayed onto various substrates. This invention fundamentally solves the problem of decreased thermal insulation performance caused by moisture absorption in existing aerogel materials. The preparation process is simple, and the application is convenient, meeting the needs of industrial-scale mass production. It can be used in building exterior walls, pipeline transportation, aerospace, and other fields. Summary of the Invention

[0006] To address the issue of decreased thermal insulation performance of aerogel materials due to moisture absorption, and to meet the demands of industrial-scale mass production, this invention aims to provide a method for preparing a highly efficient hydrophobic thermal insulation aerogel. The preparation method of this invention is simple, applicable under wide conditions, and exhibits excellent thermal insulation and hydrophobic properties, making it widely applicable to various insulation scenarios.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a highly efficient hydrophobic and thermally insulating aerogel. The aerogel material is characterized by being prepared by separately obtaining hydrophobic monomers and a long-chain polymer backbone structure, fully mixing them in a solvent system, and then undergoing solvent displacement and freeze-drying. In use, it can be sprayed onto various substrates after solvent dilution and then cured.

[0008] The freeze-dried aerogel material comprises 5-20% hydrophobic monomers and 80-95% high molecular long-chain backbone.

[0009] The hydrophobic monomers are mainly prepared by the sol-gel method, and the raw materials include at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, anilinemethyltriethoxysilane, and anilinemethyltrimethoxysilane.

[0010] The aforementioned long-chain polymer backbone includes at least one of chitosan, sodium methyl cellulose, sodium alginate, polyvinyl alcohol, polyethylene glycol, and polyimide.

[0011] The solvent substitution method specifically involves solvents including at least one selected from water, petroleum ether, n-hexane, cyclohexane, toluene, dimethyl sulfoxide, N-methylpyrrolidone (NMP), acetonitrile, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, chloroform, tetrahydrofuran, and diethyl ether.

[0012] The freeze-drying refers to the process carried out in a system with a temperature of -80 to -10°C and a vacuum degree of 0.01 to 0.2 MPa.

[0013] The aerogel material has a specific surface area of ​​100–250 m². 2 / g.

[0014] The aerogel material has a pore size of 40–150 nm.

[0015] The preparation method is as follows: select at least one silane coupling agent, dissolve it in a mixture of ethanol and water; hydrolyze it at 25-30℃ for 20-45 min, and then reflux it at 70-75℃ for 5-8 h to obtain dendritic organosilicon material; after removing the solvent by rotary evaporation, hydrophobic monomer is obtained.

[0016] The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1 is characterized in that the curing conditions refer to drying in a forced-air environment at 25-80°C for 0.5-6 hours.

[0017] By employing the above technical solution, a high-efficiency hydrophobic thermal insulation aerogel is obtained by compounding hydrophobic monomers with a long-chain polymer backbone, followed by solvent displacement and freeze-drying. This aerogel can form a uniform thermal insulation layer on substrates such as glass, metal, and cement. The preparation method is simple and convenient to use, and it offers significant advantages compared to existing technologies.

[0018] In summary, this application has the following beneficial effects: (1) Excellent thermal insulation performance Hydrophobic thermal insulating aerogels possess extremely low thermal conductivity, primarily due to their porous microstructure. The pores of the aerogel are filled with gas, whose thermal conductivity is far lower than that of solid materials, effectively preventing heat transfer. Furthermore, the high specific surface area and long-path effect of aerogels further enhance their thermal insulation performance, enabling them to maintain excellent thermal insulation properties even under extreme temperature conditions.

[0019] (2) Enhanced durability By doping with hydrophobic monomers, the durability of aerogels is significantly improved. The introduction of hydrophobic monomers effectively prevents moisture penetration and reduces performance degradation caused by humidity. This modification enables hydrophobic aerogels to exhibit good stability in humid environments, extending their service life, making them particularly suitable for building and industrial applications.

[0020] (3) Excellent hydrophobic properties The reduced hydrophilicity of the surface of hydrophobic aerogels endows them with excellent hydrophobic properties. This characteristic not only prevents moisture adsorption but also effectively resists the intrusion of water droplets, avoiding an increase in thermal conductivity caused by moisture. Furthermore, the hydrophobic properties allow aerogels to maintain their thermal insulation performance in humid environments, ensuring reliability for long-term applications.

[0021] (4) Good mechanical properties Although aerogels are generally brittle, their mechanical strength can be significantly improved through appropriate preparation processes and composite methods. The addition of hydrophobic monomers helps improve the skeletal structure of aerogels, thereby enhancing their compressive and impact resistance. This modification not only improves the durability of aerogels but also makes them more suitable for a variety of applications.

[0022] (5) Simple preparation process The preparation process of hydrophobic thermal insulating aerogels is relatively simple, typically employing a sol-gel method combined with drying and post-treatment steps. This simplified process reduces production costs, facilitates large-scale production, and enables hydrophobic aerogels to be more widely used in the market. Attached Figure Description

[0023] Figure 1 A schematic diagram of a high-efficiency hydrophobic thermal insulation aerogel provided by the present invention; Figure reference numerals: 1-Aerogel coating; 2-Substrate. Detailed Implementation Example 1

[0024] S1: Preparation of hydrophobic monomers: 10 g of γ-aminopropyltriethoxysilane (APTES) and 12 g of phenyltrimethoxysilane (PTMOS) were added to 200 mL of a mixed solvent of ethanol / deionized water (volume ratio 7:3) at a mass ratio of 1:1.2. The initial pH of the system was adjusted to 4.5 (using 0.1 mol / L glacial acetic acid solution), and the mixture was hydrolyzed by magnetic stirring at 28 °C for 30 min. After hydrolysis, the temperature was slowly increased to 72 °C, and the pH was simultaneously raised to 9.0 (using 0.1 mol / L ammonia solution), and the mixture was refluxed for 6.5 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a pale yellow, high-viscosity, hydrophobic monomer sol.

[0025] S2: Preparation of long-chain polymer backbone: Weigh 5 g of chitosan and 10 g of polyvinyl alcohol (PVA), and dissolve them in 200 mL of deionized water at 60℃ (chitosan needs to be dissolved in 1% acetic acid beforehand). Stir for 1 hour to ensure complete dissolution and the formation of a homogeneous solution.

[0026] S3: Mixing and Molding: 1.6 g of the prepared hydrophobic monomer was added dropwise to the polymer solution (dropwise addition time 50 min) while stirring. After the addition was complete, stirring was continued at 40℃ for 2 h to allow the siloxane and polymer chains to undergo a condensation crosslinking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 12 h to complete the pre-aging process.

[0027] S4: Solvent replacement: First, replace with anhydrous ethanol (3 times, 6 h each time), then replace with petroleum ether (2 times, 4 h each time) and n-hexane (1 time, 4 h each time) in a gradient.

[0028] S5: Freeze-drying: The wet gel was pre-frozen at -40℃ for 12 h, and then placed in a freeze dryer at -80℃ and 0.05MPa for 36 h to obtain hydrophobic and thermally insulating aerogel powder.

[0029] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.2 mm, and dry it at 60℃ for 2 hours.

[0030] The properties of this hydrophobic thermal insulating aerogel are shown in Table 1.

[0031] Table 1 Example 2

[0032] S1: Preparation of hydrophobic monomers: 8 g of γ-glycidyl etheroxypropyltriethoxysilane (GPTES) and 7 g of vinyltrimethoxysilane (VTMS) were dissolved in 250 mL of a mixed solvent of ethanol / water (8:2, v / v). The initial pH of the system was adjusted to 5.2 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 25 °C with magnetic stirring for 25 min. After hydrolysis, the temperature was slowly increased to 70 °C, and the pH was simultaneously raised to 8.8 (using 0.1 mol / L ammonia solution), and refluxed for 7 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a pale yellow, high-viscosity, hydrophobic monomer sol.

[0033] S2: Preparation of long-chain polymer backbone: Weigh 4 g polyethylene glycol (PEG, Mn 2000) + 8 g polyimide, add 150 mL NMP, stir for 2 h to completely dissolve and form a homogeneous solution.

[0034] S3: Mixing and Molding: 1.5 g of the prepared hydrophobic monomer was added dropwise to the polymer solution (dropwise addition time 60 min) while stirring. After the addition was complete, stirring was continued at 40℃ for 3 h to allow the siloxane and polymer chains to undergo a condensation crosslinking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 18 h to complete the pre-aging process.

[0035] S4: Solvent replacement: First, replace with anhydrous methanol (twice, 4 h each time), then replace with dichloromethane (twice, 4 h each time) and n-hexane (once, 3 h each time) in a gradient.

[0036] S5: Freeze-drying: The wet gel was first pre-frozen at -30℃ for 16 h, then placed in a freeze dryer and dried by temperature steps at -65℃ with a vacuum of 0.04 MPa for a total time of 30 h.

[0037] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm, and dry it at 55℃ for 3 hours.

[0038] The properties of this hydrophobic thermal insulating aerogel are shown in Table 2.

[0039] Table 2 Example 3

[0040] S1: Preparation of hydrophobic monomers: 6 g of γ-aminopropyltrimethoxysilane (APTMS) and 6 g of phenyltriethoxysilane (PTES) were dissolved in 100 mL of a mixed solvent of ethanol / water (6:4, v / v). The initial pH of the system was adjusted to 4 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 25 °C with magnetic stirring for 20 min. Then, 4 g of isobutyltriethoxysilane (IBTES) was hydrolyzed separately in 50 mL of ethanol (pH 4.5, 20 min). The two hydrolysates were then combined and heated to 73 °C, the pH was adjusted to 9.2 (using 0.1 mol / L ammonia solution), and refluxed for 7.5 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a transparent sol.

[0041] S2: Preparation of long-chain polymer backbone: Weigh 6g of sodium alginate and 5g of polyvinyl alcohol and dissolve them in 250 mL of aqueous solution. Stir at 80℃ for 2 hours to ensure complete dissolution and the formation of a homogeneous solution.

[0042] S3: Mixing and Molding: 1.3 g of the prepared hydrophobic monomer was slowly mixed into the polymer solution at 40℃, and 0.5 g of calcium gluconate was added to assist cross-linking (dropping time 60 min), while stirring. After the addition was complete, stirring was continued at 40℃ for 3 h to allow the siloxane and polymer chains to undergo a condensation cross-linking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 14 h to complete the pre-aging process.

[0043] S4: Solvent replacement: First, water was used for replacement (3 times, 6 hours each time), followed by a gradient replacement with methanol (3 times, 6 hours each time) and cyclohexane (3 times, 6 hours each time).

[0044] S5: Freeze-drying: The wet gel was first pre-frozen at -60℃ for 12 h, then placed in a freeze dryer and dried by temperature increments of -20℃ under a vacuum of 0.02 MPa for a total time of 48 h.

[0045] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm. Dry at 50°C for 3 hours.

[0046] The properties of this hydrophobic thermal insulating aerogel are shown in Table 3.

[0047] Table 3 Example 4

[0048] S1: Preparation of hydrophobic monomers: 8 g of γ-glycidyl etheroxypropyltriethoxysilane (GPTES) and 10 g of phenyltriethoxysilane (PTES) were dissolved in 100 mL of a mixed solvent of ethanol / water (volume ratio 7:3). The initial pH of the system was adjusted to 5 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 30 °C with magnetic stirring for 35 min. The temperature was raised to 75 °C, pH = 8.5 (adjusted with 0.1 mol / L ammonia solution), and refluxed for 7 h. The solvent was removed by rotary evaporation. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a transparent sol.

[0049] S2: Preparation of long-chain polymer backbone: Weigh 4g of chitosan (chitosan needs to be dissolved in 1% acetic acid beforehand), dissolve 6g of sodium methyl cellulose in 200 mL of aqueous solution and mix. Stir at 60℃ for 1.5 h to completely dissolve and form a homogeneous solution.

[0050] S3: Mixing and Molding: 1.2 g of the prepared hydrophobic monomer was added to the framework solution in three portions (20 min apart) and stirred for 3 h. After adjusting the pH of the system to 7.0, it was allowed to stand for 20 h to complete the pre-aging process.

[0051] S4: Solvent replacement: First, ethanol was used for replacement (twice, 4 h each time), followed by a gradient replacement with toluene (twice, 4 h each time), tetrahydrofuran (twice, 4 h each time), and n-hexane (twice, 3 h each time).

[0052] S5: Freeze-drying: The wet gel was first pre-frozen at -80℃ for 8 hours, then placed in a freeze dryer and dried by temperature increments of -20℃ under a vacuum of 0.02 MPa for a total time of 40 hours.

[0053] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm, and dry it at 55℃ for 3 hours.

[0054] The properties of this hydrophobic thermal insulating aerogel are shown in Table 4.

[0055] Table 4

[0056] Comparative Example 1 S1: Preparation of hydrophobic monomers: 10 g of γ-aminopropyltriethoxysilane (APTES) was added to 200 mL of a mixed solvent of ethanol / deionized water (volume ratio 7:3). The initial pH of the system was adjusted to 4.5 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 28 °C with magnetic stirring for 30 min. After hydrolysis, the temperature was slowly increased to 72 °C, and the pH was simultaneously raised to 9.0 (using 0.1 mol / L ammonia solution), and refluxed for 6.5 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a pale yellow, high-viscosity, hydrophobic monomer sol.

[0057] S2: Preparation of long-chain polymer backbone: Weigh 5 g of chitosan and 10 g of polyvinyl alcohol (PVA), and dissolve them in 200 mL of deionized water at 60℃ (chitosan needs to be dissolved in 1% acetic acid beforehand). Stir for 1 hour to ensure complete dissolution and the formation of a homogeneous solution.

[0058] S3: Mixing and Molding: 1.6 g of the prepared hydrophobic monomer was added dropwise to the polymer solution (dropwise addition time 50 min) while stirring. After the addition was complete, stirring was continued at 40℃ for 2 h to allow the siloxane and polymer chains to undergo a condensation crosslinking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 12 h to complete the pre-aging process.

[0059] S4: Solvent replacement: First, replace with anhydrous ethanol (3 times, 6 h each time), then replace with petroleum ether (2 times, 4 h each time) and n-hexane (1 time, 4 h each time) in a gradient.

[0060] S5: Freeze-drying: The wet gel was pre-frozen at -40℃ for 12 h, and then placed in a freeze dryer at -80℃ and 0.05MPa for 36 h to obtain hydrophobic and thermally insulating aerogel powder.

[0061] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.2 mm, and dry it at 60℃ for 2 hours.

[0062] The properties of this hydrophobic thermal insulating aerogel are shown in Table 5.

[0063] Table 5

[0064] Comparative Example 2 S1: Preparation of hydrophobic monomers: 8 g of γ-glycidyl etheroxypropyltriethoxysilane (GPTES) and 7 g of vinyltrimethoxysilane (VTMS) were dissolved in 250 mL of a mixed solvent of ethanol / water (8:2, v / v). The initial pH of the system was adjusted to 5.2 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 25 °C with magnetic stirring for 25 min. After hydrolysis, the temperature was slowly increased to 70 °C, and the pH was simultaneously raised to 8.8 (using 0.1 mol / L ammonia solution), and refluxed for 7 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a pale yellow, high-viscosity, hydrophobic monomer sol.

[0065] S2: Preparation of long-chain polymer backbone: Weigh out 4 g of polyethylene glycol (PEG, Mn 2000) and 8 g of polyimide, add 150 mL of NMP, and stir for 2 hours to completely dissolve and form a homogeneous solution.

[0066] S3: Mixing and Molding: 1.5 g of the prepared hydrophobic monomer was added dropwise to the polymer solution (dropwise addition time 60 min) while stirring. After the addition was complete, stirring was continued at 40℃ for 3 h to allow the siloxane and polymer chains to undergo a condensation crosslinking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 18 h to complete the pre-aging process.

[0067] S4: Freeze-drying: The wet gel was first pre-frozen at -30℃ for 16 h, then placed in a freeze dryer and dried by temperature steps at -65℃ with a vacuum of 0.04 MPa for a total time of 30 h.

[0068] S5: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm, and dry it at 55℃ for 3 hours.

[0069] The properties of this hydrophobic thermal insulating aerogel are shown in Table 6.

[0070] Table 6

[0071] Comparative Example 3 S1: Preparation of hydrophobic monomers: 6 g of γ-aminopropyltrimethoxysilane (APTMS) and 6 g of phenyltriethoxysilane (PTES) were dissolved in 100 mL of a mixed solvent of ethanol / water (6:4, v / v). The initial pH of the system was adjusted to 4 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 25 °C with magnetic stirring for 20 min. Then, 4 g of isobutyltriethoxysilane (IBTES) was hydrolyzed separately in 50 mL of ethanol (pH 4.5, 20 min). The two hydrolysates were then combined, heated to 50 °C, and the pH was adjusted to 9.2 (using 0.1 mol / L ammonia solution), and refluxed for 3 h. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a transparent sol.

[0072] S2: Preparation of long-chain polymer backbone: Weigh 6g of sodium alginate and 5g of polyvinyl alcohol and dissolve them in 250 mL of aqueous solution. Stir at 80℃ for 2 hours to ensure complete dissolution and the formation of a homogeneous solution.

[0073] S3: Mixing and Molding: 1.3 g of the prepared hydrophobic monomer was slowly mixed into the polymer solution at 40℃, and 0.5 g of calcium gluconate was added to assist cross-linking (dropping time 60 min), while stirring. After the addition was complete, stirring was continued at 40℃ for 3 h to allow the siloxane and polymer chains to undergo a condensation cross-linking reaction. The pH of the system was adjusted to 7.0 and then allowed to stand for 14 h to complete the pre-aging process.

[0074] S4: Solvent replacement: First, water was used for replacement (3 times, 6 hours each time), followed by a gradient replacement with methanol (3 times, 6 hours each time) and cyclohexane (3 times, 6 hours each time).

[0075] S5: Freeze-drying: The wet gel was first pre-frozen at -60℃ for 12 h, then placed in a freeze dryer and dried by temperature increments of -20℃ under a vacuum of 0.02 MPa for a total time of 48 h.

[0076] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm. Dry at 50°C for 3 hours.

[0077] The properties of this hydrophobic thermal insulating aerogel are shown in Table 7.

[0078] Table 7

[0079] Comparative Example 4 S1: Preparation of hydrophobic monomers: 8 g of γ-glycidyl etheroxypropyltriethoxysilane (GPTES) and 10 g of phenyltriethoxysilane (PTES) were dissolved in 100 mL of a mixed solvent of ethanol / water (volume ratio 7:3). The initial pH of the system was adjusted to 5 (using 0.1 mol / L glacial acetic acid solution), and hydrolysis was carried out at 30 °C with magnetic stirring for 35 min. The temperature was raised to 75 °C, pH = 8.5 (adjusted with 0.1 mol / L ammonia solution), and refluxed for 7 h. The solvent was removed by rotary evaporation. After reflux, most of the solvent was evaporated using a rotary evaporator at 50 °C and a vacuum of 0.08 MPa to obtain a transparent sol.

[0080] S2: Preparation of long-chain polymer backbone: Weigh 4g of chitosan (chitosan needs to be dissolved in 1% acetic acid beforehand), dissolve 6g of sodium methyl cellulose in 200 mL of aqueous solution and mix. Stir at 60℃ for 1.5 h to completely dissolve and form a homogeneous solution.

[0081] S3: Mixing and Molding: 1.2 g of the prepared hydrophobic monomer was added to the framework solution in three portions (20 min apart) and stirred for 3 h. After adjusting the pH of the system to 7.0, it was allowed to stand for 20 h to complete the pre-aging process.

[0082] S4: Solvent replacement: First, ethanol was used for replacement (twice, 4 h each time), followed by a gradient replacement with toluene (twice, 4 h each time), tetrahydrofuran (twice, 4 h each time), and n-hexane (twice, 3 h each time).

[0083] S5: Freeze-drying: The wet gel was first pre-frozen at -80℃ for 8 hours, then placed in a freeze dryer and dried by temperature increments of -20℃ under a vacuum of 0.02 MPa for a total time of 40 hours.

[0084] S6: Diluted spray coating: When using, dissolve 5g of hydrophobic and heat-insulating aerogel powder in 10g of ethanol, and spray the aerogel evenly onto the substrate surface using a spray gun with a nozzle diameter of 1.0 mm, and dry it at 55℃ for 10 min.

[0085] The properties of this hydrophobic thermal insulating aerogel are shown in Table 8.

[0086] Table 8

[0087] The hydrophobic thermal insulating aerogels prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance testing, and the specific process is as follows: The specific surface area of ​​hydrophobic thermal insulating aerogel was tested according to GB / T 19587-2017. The average pore size of the hydrophobic thermal insulating aerogel was tested according to GB / T 21650. The contact angle of the hydrophobic thermal insulating aerogel was tested according to GB / T 30693-2014; As can be seen from the data in Tables 1-8, the hydrophobic thermal insulating aerogels prepared in Examples 1-4 of the present invention have good hydrophobicity, large specific surface area and small average pore size.

[0088] The test results from Example 1 and Comparative Example 1 show that using multiple silane coupling agents may improve the hydrophobicity and thermal stability of the final product compared to using only a single type of silane coupling agent. Different silane compounds affect the structure, porosity, and properties of the aerogel.

[0089] The test results from Example 2 and Comparative Example 2 show that the nozzle diameter and drying temperature affect the coating uniformity and overall coating properties. The nozzle diameter directly affects the uniformity of aerogel application and the coating thickness. Smaller nozzles may result in a finer and more uniform coating, while larger nozzles may result in a thicker coating, affecting the performance of the final product. Furthermore, variations in drying temperature may affect the pore structure and density of the aerogel, thereby influencing its thermal insulation properties and mechanical strength. Higher drying temperatures may lead to faster solvent evaporation, affecting the final morphology of the aerogel.

[0090] The test results from Example 3 and Comparative Example 3 show that the reflow temperature and time during the preparation of hydrophobic monomers affect the hydrophobicity and thermal insulation properties of the aerogel. Higher reflow temperatures generally accelerate the reaction rate, promote the polymerization and cross-linking reactions of siloxanes, and longer reflow times help improve the completeness of the reaction, which may improve the final properties of the aerogel. Ultimately, this contributes to the formation of a higher degree of polymerization and a better network structure, thereby affecting the porosity, mechanical strength, and thermal conductivity of the aerogel.

[0091] The test results from Example 4 and Comparative Example 4 show that the drying time of the diluted spray coating has a significant impact on the performance of the aerogel. A longer drying time helps to remove the solvent more thoroughly, ensuring that the structure and properties of the aerogel are optimally utilized. A short drying time may result in more solvent residue in the aerogel, thus affecting its final physical and chemical properties, such as porosity, mechanical strength, and thermal conductivity. In addition, a longer drying time can promote coating uniformity and adhesion, allowing the aerogel to better bond with the substrate. A short drying time may result in an uneven coating, affecting its performance.

[0092] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-efficiency hydrophobic thermal insulating aerogel, characterized in that... The aerogel material is obtained by separately preparing hydrophobic monomers and polymer long-chain backbone structures, fully mixing them in a solvent system, and then performing solvent replacement and freeze-drying. When in use, it can be sprayed onto various substrates after solvent dilution and then cured.

2. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The freeze-dried aerogel material comprises 5-20% hydrophobic monomers and 80-95% high molecular long-chain backbone.

3. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The hydrophobic monomers are mainly prepared by the sol-gel method, and the raw materials include at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, anilinemethyltriethoxysilane, and anilinemethyltrimethoxysilane.

4. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The aforementioned long-chain polymer backbone includes at least one of chitosan, sodium methyl cellulose, sodium alginate, polyvinyl alcohol, polyethylene glycol, and polyimide.

5. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The solvent substitution method specifically involves solvents including at least one selected from water, petroleum ether, n-hexane, cyclohexane, toluene, dimethyl sulfoxide, N-methylpyrrolidone (NMP), acetonitrile, methanol, ethanol, ethylene glycol, N,N-dimethylformamide, N,N-dimethylacetamide, dichloromethane, chloroform, tetrahydrofuran, and diethyl ether.

6. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The freeze-drying refers to the process carried out in a system with a temperature of -80 to -10°C and a vacuum degree of 0.01 to 0.2 MPa.

7. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The aerogel material has a specific surface area of ​​100–250 m². 2 / g.

8. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The aerogel material has a pore size of 40–150 nm.

9. The method for preparing hydrophobic monomers using the sol-gel method according to claim 3, characterized in that, The preparation method is as follows: select at least one silane coupling agent, dissolve it in a mixture of ethanol and water; hydrolyze it at 25-30℃ for 20-45 min, and then reflux it at 70-75℃ for 5-8 h to obtain dendritic organosilicon material; after removing the solvent by rotary evaporation, hydrophobic monomer is obtained.

10. The method for preparing a high-efficiency hydrophobic thermal insulating aerogel according to claim 1, characterized in that, The curing conditions refer to drying in a forced-air environment at 25–80°C for 0.5–6 hours.

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