A high-temperature hydrophobic SiO2 aerogel felt and its preparation method

Abstract

The application discloses a high-temperature hydrophobic SiO2 aerogel felt and a preparation method thereof, and belongs to the technical field of aerogel composite materials. Triphenylhydroxysilane and diphenyldihydroxysilane are used as a hydrophobic modifier, and the prepared high-temperature hydrophobic SiO2 aerogel felt still has good hydrophobic performance after being treated at 316 DEG C for 24 hours or more, and the combustion grade can reach A1, so that the high-temperature hydrophobic SiO2 aerogel felt has a wide application prospect in the fields of city heat supply pipe networks and steam injection oil production pipes.

Description

Technical Field

[0001] This invention belongs to the field of aerogel composite material technology, specifically relating to a high-temperature hydrophobic SiO2 aerogel felt and its preparation method. Background Technology

[0002] SiO2 aerogel felts are characterized by low density, high temperature resistance, and low thermal conductivity, making them widely used in industries such as petrochemicals, heating pipelines, and construction. However, the surface of unmodified SiO2 aerogel felts is rich in -OH groups and has a nanoporous structure, making it prone to absorbing moisture from the air. This leads to increased thermal conductivity and reduced insulation performance. Furthermore, direct contact with liquid water can cause the nanoporous structure to collapse, severely impacting the application of this type of material.

[0003] Currently, commonly used R species include dimethyldichlorosilane and methyltriethoxysilane. n SiX 4-n Organosilicon compounds (n=1-3, R=CH3, C2H5, etc., X=OCH3, OC2H5 or Cl, etc.), hexamethyldisilazane or hexamethyldisiloxane are used to modify silica aerogel. The modified SiO2 aerogel felt has good hydrophobic properties at lower temperatures, but when the temperature reaches 300℃, the hydrophobic groups are decomposed and oxidized, and the hydrophobic properties are lost, which seriously affects the use of aerogel felt in high-temperature environments.

[0004] There have been relevant studies on improving the hydrophobic temperature resistance of aerogel felts. For example, CN 106829972 B describes the reaction of silica aerogel with trifluoromethane under the catalysis of ammonia at a reaction temperature of 10℃-50℃, which yields a product with good hydrophobicity and resistance to high temperatures above 900℃.

[0005] CN 114162827 B describes the use of phenyltriethoxysilane as a hydrophobic modifier to hydrophobically modify pretreated SiO2 aerogel thermal insulation composite materials. The resulting material, after drying, maintains good hydrophobic properties below 500℃.

[0006] Based on the excellent properties of magnesium hydroxide, CN 106587908 A describes the use of the sol-gel method and supercritical fluid CO2 drying technology to dope magnesium hydroxide into glass fiber composite silica aerogel, thereby preparing a high-temperature resistant hydrophobic silica aerogel insulation felt.

[0007] CN 106007652 A describes a sol-gel method using an organosilicon source as the silicon source, ethanol as the solvent, acid and alkali as catalysts, and sodium methylsilicate and potassium methylsilicate as surface modifiers to prepare a wet gel. The wet gel is then subjected to aging, solvent replacement, supercritical drying, and heat treatment to obtain a high-temperature resistant hydrophobic modified SiO2 aerogel felt. This material can maintain its hydrophobic effect for a long time at temperatures above 350℃. Summary of the Invention

[0008] To address the problem that existing aerogel felts suffer from poor hydrophobicity and temperature resistance, with hydrophobic groups decomposing and oxidizing at 300℃, leading to loss of hydrophobic properties and hindering the thermal insulation performance of aerogels, this invention provides a high-temperature hydrophobic SiO2 aerogel felt and its preparation method. The high-temperature hydrophobic SiO2 aerogel felt prepared by this invention retains good hydrophobic properties even after treatment at 316℃ for more than 24 hours, and its flammability rating can reach A1, showing broad application prospects in urban heating pipe networks, steam injection oil production pipelines, and other fields.

[0009] The objective of this invention is achieved through the following technical solution: A method for preparing a high-temperature hydrophobic SiO2 aerogel mat includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol and H2O in a volume ratio of 100:(1-5):(100-150):(15-35) and stir. Then slowly add inorganic acid to adjust the pH of the solution to 4.5-6. After stirring and hydrolyzing, obtain solution 1. S1-2. Ethanol and hydrophobic modifier are mixed at a mass ratio of 100:(10-30) and stirred at room temperature until dissolved to obtain solution 2; S1-3. Mix equal volumes of solution 1 and solution 2, and stir to obtain solution 3; S1-4. Ethanol and concentrated ammonia water are stirred at room temperature in a volume ratio of 400:(1-3) to obtain solution 4; S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. S3. The wet gel mat obtained in the previous step is transported to the microwave cavity via a transport line for rapid gelation and curing by microwave heating. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature. S5. Replace the aged wet gel mat with ethanol. S6. After supercritical drying, the replaced wet gel mat is used to obtain a high-temperature hydrophobic SiO2 aerogel mat. The obtained high-temperature hydrophobic SiO2 aerogel mat has the following properties: The volumetric water absorption rate is 1.5%-6.0%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 3.4%-9.5%, and the flammability rating is A1.

[0010] Further, S1-1 is prepared by mixing an organosilicon source, a phosphorus-containing silane coupling agent, ethanol, and H2O in a volume ratio of 100:(1-5):(100-150):(15-35), stirring at 40℃-70℃ for 30 min, then slowly adding an inorganic acid to adjust the pH of the solution to 4.5-6, and hydrolyzing at 40℃-70℃ for 1-3 h to obtain solution 1; The organosilicon source is one or two of tetraethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, and polyethyl orthosilicate, with any two being mixed in any proportion; the phosphorus-containing silane coupling agent is one of KH-560-DOPO derivative, KH-570-DOPO derivative, and 2-(diphenylphosphino)ethyltriethoxysilane; the inorganic acid is one of hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

[0011] Furthermore, in S1-2, the hydrophobic modifier is one of triphenylhydroxysilane or diphenyldihydroxysilane.

[0012] Furthermore, in S1-3, the stirring time is 2h-8h.

[0013] Furthermore, in S1-4, stir for 30 minutes at room temperature.

[0014] Furthermore, the fiber felt roll described in S2 contains one of glass fiber felt, high silica fiber felt, or quartz fiber felt.

[0015] Furthermore, in S3, the temperature inside the microwave cavity is maintained at 40℃-55℃; the rapid gelation time is 3min-8min.

[0016] Furthermore, in S4, the aging time at room temperature is 4-12 hours.

[0017] Furthermore, in S1 and S5, the volume concentration of the ethanol is ≥95%.

[0018] Furthermore, the supercritical drying described in S6 is supercritical drying of ethanol. The drying process is as follows: the aerogel is dried at a temperature of 260℃-320℃ under the protection of nitrogen gas, the pressure of the autoclave is controlled at 8MPa-14MPa, and the reaction time is 4h-10h.

[0019] This invention also relates to a high-temperature hydrophobic SiO2 aerogel felt, which is obtained by the above-mentioned preparation method of high-temperature hydrophobic SiO2 aerogel felt. The prepared high-temperature hydrophobic SiO2 aerogel felt has the following properties: The volumetric water absorption rate is 1.5%-6.0%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 3.4%-9.5%, and the flammability rating is A1.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention discloses a method for preparing a high-temperature hydrophobic SiO2 aerogel felt, using triphenylhydroxysilane and diphenyldihydroxysilane as hydrophobic modifiers. These are hydrolysis products of triphenylmethoxy(ethoxy)silane and diphenyldimethoxy(ethoxy)silane. Due to the large steric hindrance of the benzene ring, these hydrophobic modifiers may experience incomplete hydrolysis or incomplete polymerization, leaving residual -OCH3 (-OC2H5) groups during the sol-gel preparation process. These groups are unstable when exposed to air for extended periods, generating -OH groups, resulting in low surface hydrophobicity of the material. Using the hydrolysis products of these hydrophobic modifiers directly as the hydrophobic modifiers results in higher reactivity, avoiding these issues and further improving the hydrophobic properties of the material. The hydrolysis products do not contain methoxy or ethoxy groups, and therefore do not produce flammable gases such as methanol or ethanol at high temperatures, reducing the risk of material combustion.

[0021] 2. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to the present invention introduces a phosphorus-containing silane coupling agent during the sol preparation process. -OCH3 / -OC2H5 can be hydrolyzed and undergo a condensation reaction with Si-OH on the surface of the aerogel or Si-OH in the hydrophobic modifier, so that the phosphorus element is uniformly fixed on the silicon skeleton in the form of chemical bonds. At high temperature, it decomposes to generate phosphoric acid or polyphosphoric acid, which promotes the dehydration and carbonization of the substrate and forms a dense carbon layer. This carbon layer can not only isolate oxygen and heat, but also effectively prevent the decomposition of internal hydrophobic groups (phenyl). Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0023] Figure 1 This is a process flow diagram of the preparation method of a high-temperature hydrophobic SiO2 aerogel felt according to the present invention. Figure 2 This is a scanning electron microscope image of the high-temperature hydrophobic SiO2 aerogel felt prepared in Example 1 of this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] The high-temperature hydrophobic SiO2 aerogel felt prepared in the examples and the comparative examples were subjected to performance tests. The volume water absorption rate was tested according to ASTM C176320 (2025), and the flammability rating was tested according to GB8624-2012.

[0026] Example 1: A method for preparing high-temperature hydrophobic SiO2 aerogel felt, the process flow is as follows: Figure 1 As shown, it includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol (volume concentration ≥95%) and H2O in a volume ratio of 100:2:100:15 and stir at 40℃ for 30 min. Then slowly add inorganic acid to adjust the pH of the solution to 4.5. After hydrolyzing at 40℃ for 2 h, obtain solution 1. The organosilicon source is tetraethyl orthosilicate; the phosphorus-containing silane coupling agent is a KH-560-DOPO derivative; and the inorganic acid is nitric acid. S1-2. Ethanol and hydrophobic modifier are mixed at a mass ratio of 100:15 and stirred at room temperature until dissolved to obtain solution 2; The hydrophobic modifier is triphenylhydroxysilane; S1-3. Mix equal volumes of solution 1 and solution 2 and stir for 8 hours to obtain solution 3. S1-4. Ethanol and concentrated ammonia were mixed at a volume ratio of 400:1 and stirred at room temperature for 30 minutes to obtain solution 4. S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. The fiber felt roll is a glass fiber felt roll; S3. The wet gel mat obtained in the previous step is transported to the microwave cavity through a transport line for microwave heating and rapid gelation and curing. The temperature inside the microwave cavity is maintained at 55°C and the gelation time is 5 minutes. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature for 4 hours. S5. Replace the wet gel mat aged at room temperature with ethanol (volume concentration ≥95%). S6. After the replacement wet gel felt is subjected to supercritical ethanol drying, high-temperature hydrophobic SiO2 aerogel felt is obtained. The supercritical ethanol drying process is as follows: the aerogel is dried at 320℃ under the protection of nitrogen gas, the pressure of the autoclave is controlled at 12MPa, and the reaction time is 4h. The obtained high-temperature hydrophobic SiO2 aerogel mat, as shown in the scanning electron microscope image. Figure 2 As shown, it has the following properties: The volumetric water absorption rate is 1.5%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 3.4%, and the flammability rating is A1.

[0027] Example 2: A method for preparing a high-temperature hydrophobic SiO2 aerogel mat includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol (volume concentration ≥95%) and H2O in a volume ratio of 100:5:150:35 and stir at 60℃ for 30 min. Then slowly add inorganic acid to adjust the pH of the solution to 6. After hydrolyzing at 60℃ for 1 h, obtain solution 1. The organosilicon source is polyethyl silicate; the phosphorus-containing silane coupling agent is 2-(diphenylphosphino)ethyltriethoxysilane; and the inorganic acid is hydrochloric acid. S1-2. Ethanol and hydrophobic modifier are mixed at a mass ratio of 100:10 and stirred at room temperature until dissolved to obtain solution 2; The hydrophobic modifier is diphenyl dihydroxysilane; S1-3. Mix equal volumes of solution 1 and solution 2 and stir for 4 hours to obtain solution 3. S1-4. Ethanol and concentrated ammonia water are stirred at a volume ratio of 400:3 for 30 minutes at room temperature to obtain solution 4. S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. The fiber felt roll is a glass fiber felt roll; S3. The wet gel mat obtained in the previous step is transported to the microwave cavity through a transport line for microwave heating to rapidly gel and solidify. The temperature inside the microwave cavity is maintained at 40°C and the gelation time is 8 minutes. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature for 12 hours. S5. Replace the wet gel mat aged at room temperature with ethanol (volume concentration ≥95%). S6. After the replaced wet gel mat is subjected to supercritical ethanol drying, a high-temperature hydrophobic SiO2 aerogel mat is obtained. The supercritical ethanol drying process is as follows: the aerogel is dried at 300℃ under nitrogen protection, the pressure in the autoclave is controlled at 8MPa, and the reaction time is 8h. The obtained high-temperature hydrophobic SiO2 aerogel mat has the following properties: The volumetric water absorption rate is 2.0%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 8.8%, and the flammability rating is A1.

[0028] Example 3: A method for preparing a high-temperature hydrophobic SiO2 aerogel mat includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol (volume concentration ≥95%) and H2O in a volume ratio of 100:1:120:20 and stir at 70℃ for 30 min. Then slowly add inorganic acid to adjust the pH of the solution to 5.5. After hydrolyzing at 70℃ for 3 h, obtain solution 1. The organosilicon source is methyl orthosilicate or methyltriethoxysilane; the phosphorus-containing silane coupling agent is a KH-570-DOPO derivative; and the inorganic acid is sulfuric acid. S1-2. Ethanol and hydrophobic modifier are mixed at a mass ratio of 100:30 and stirred at room temperature until dissolved to obtain solution 2; The hydrophobic modifier is diphenyl dihydroxysilane; S1-3. Mix equal volumes of solution 1 and solution 2 and stir for 2 hours to obtain solution 3. S1-4. Ethanol and concentrated ammonia were mixed at a volume ratio of 400:2 and stirred at room temperature for 30 minutes to obtain solution 4. S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. The fiber felt roll is a glass fiber felt roll; S3. The wet gel mat obtained in the previous step is transported to the microwave cavity through a transport line for microwave heating to rapidly gel and solidify. The temperature inside the microwave cavity is maintained at 45°C and the gelation time is 3 minutes. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature for 5 hours. S5. Replace the wet gel mat aged at room temperature with ethanol (volume concentration ≥95%). S6. After the replaced wet gel mat is subjected to supercritical ethanol drying, a high-temperature hydrophobic SiO2 aerogel mat is obtained. The supercritical ethanol drying process is as follows: the aerogel is dried at 260℃ under nitrogen protection, the pressure in the autoclave is controlled at 14MPa, and the reaction time is 10h. The obtained high-temperature hydrophobic SiO2 aerogel mat has the following properties: The volumetric water absorption rate is 6.0%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 9.5%, and the flammability rating is A1.

[0029] Example 4: A method for preparing a high-temperature hydrophobic SiO2 aerogel mat includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol (volume concentration ≥95%) and H2O in a volume ratio of 100:3:130:25 and stir at 50℃ for 30 min. Then slowly add inorganic acid to adjust the pH of the solution to 5.0. After hydrolyzing at 50℃ for 2 h, obtain solution 1. The organosilicon source is methyltrimethoxysilane or polyethyl silicate; the phosphorus-containing silane coupling agent is 2-(diphenylphosphino)ethyltriethoxysilane; and the inorganic acid is hydrofluoric acid. S1-2. Ethanol and hydrophobic modifier are mixed at a mass ratio of 100:20 and stirred at room temperature until dissolved to obtain solution 2; The hydrophobic modifier is triphenylhydroxysilane; S1-3. Mix equal volumes of solution 1 and solution 2, stir for 4 hours to obtain solution 3; S1-4. Ethanol and concentrated ammonia water are stirred at a volume ratio of 400:1.5 for 30 minutes at room temperature to obtain solution 4; S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. The fiber felt roll is a glass fiber felt roll; S3. The wet gel mat obtained in the previous step is transported to the microwave cavity through a transport line for microwave heating to rapidly gel and solidify. The temperature inside the microwave cavity is maintained at 45°C and the gelation time is 6 minutes. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature for 6 hours. S5. Replace the wet gel mat aged at room temperature with ethanol (volume concentration ≥95%). S6. After the replaced wet gel mat is subjected to supercritical ethanol drying, a high-temperature hydrophobic SiO2 aerogel mat is obtained. The supercritical ethanol drying process is as follows: the aerogel is dried at 280℃ under nitrogen protection, the pressure in the autoclave is controlled at 10MPa, and the reaction time is 6h. The obtained high-temperature hydrophobic SiO2 aerogel mat has the following properties: The volumetric water absorption rate is 4.8%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 7.2%, and the flammability rating is A1.

[0030] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the hydrophobic modifier is diphenyldimethoxysilane, otherwise the same as Example 1; The prepared SiO2 aerogel felt has the following properties: The volumetric water absorption rate is 10.2%. After heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 86.3%, and the flammability rating is A2.

[0031] The results showed that using diphenyldimethoxysilane as a hydrophobic modifier, due to the large steric hindrance of the benzene ring, resulted in insufficient hydrolysis or incomplete polycondensation. This led to residual -OCH3 and -OH groups during the sol-gel preparation process. The -OCH3 groups, when exposed to air for extended periods, are unstable and generate -OH groups, resulting in high volumetric water absorption rates in the aerogel felt both before and after heat treatment at 316℃ for 24 hours. The residual -OCH3 and -OH groups continued to undergo a reverse polycondensation reaction at high temperatures, producing flammable methanol. This caused combustion during the flammability rating test, downgrading the flammability rating to A2, which does not meet the A1 requirement.

[0032] Comparative Example 2: The difference between Comparative Example 1 and Example 1 is that no phosphorus-containing silane coupling agent was added; otherwise, they are the same as Example 1. The prepared SiO2 aerogel felt has the following properties: The volumetric water absorption rate is 5.8%. After heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 10.0%, and the combustion rating does not meet the requirements of Class A (including Class A1 and Class A2).

[0033] The results showed that without the addition of a phosphorus-containing silane coupling agent, the benzene ring in the hydrophobic group was oxidized at high temperature, resulting in combustion and the release of a large amount of heat, leading to a decrease in combustion performance and failure to meet the A1 grade. Without the phosphorus-containing silane coupling agent to supplement the oxidation reaction between the Si-OH groups on the modified SiO2 aerogel felt surface and the Si-OH groups in the hydrophobic modifier, the volume water absorption rate of the aerogel felt increased both before and after heat treatment at 316℃ for 24 hours.

[0034] Results and Discussion: 1. Compared with Example 1, the volume water absorption rate of the SiO2 aerogel felt prepared in Comparative Example 1 increased before and after heat treatment at 316℃ for 24 hours, especially after heat treatment, and the flammability rating decreased to A2. This indicates that using diphenyldimethoxysilane as a hydrophobic modifier, due to the large steric hindrance of the benzene ring, there may be insufficient hydrolysis or incomplete condensation. In the sol preparation process, -OCH3 and -OH remain. The -OCH3 group is unstable when exposed to air for a long time and generates -OH. Moreover, the residual -OCH3 and -OH continue to undergo a reverse condensation reaction at high temperature, producing flammable methanol, which leads to combustion during the flammability rating test. In contrast, Example 1 uses triphenylhydroxysilane, a modifier with -OH, which has higher reactivity. It can avoid the problem of more Si-OH remaining on the material surface due to the large steric hindrance of the benzene ring and incomplete hydrolysis or condensation, which affects the hydrophobic effect. In addition, the hydrolysis products do not contain methoxy or ethoxy groups, and will not produce flammable gases such as methanol at high temperature, reducing the risk of material combustion.

[0035] 2. Compared with Example 1, the volume water absorption rate of the SiO2 aerogel felt prepared in Comparative Example 2 increased slightly before and after heat treatment at 316℃ for 24 hours, and the combustion rating decreased, failing to meet the Class A requirements. This indicates that Example 1 introduced a phosphorus-containing silane coupling agent during the sol preparation process. The -OCH3 / -OC2H5 can undergo a condensation reaction with the Si-OH on the aerogel surface or the Si-OH in the hydrophobic modifier after hydrolysis, uniformly fixing the phosphorus element on the silicon skeleton in the form of chemical bonds. This can reduce the number of Si-OH on the surface of the aerogel felt and improve the hydrophobic properties to a certain extent. The phosphorus-containing groups are grafted onto the structure of the aerogel felt, which decompose at high temperature to generate phosphoric acid or polyphosphoric acid, promoting the dehydration and carbonization of the substrate and forming a dense carbon layer. This carbon layer can not only isolate oxygen and heat, but also effectively prevent the decomposition of internal hydrophobic groups (phenyl), thereby improving the combustion rating of the material.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a high-temperature hydrophobic SiO2 aerogel felt, characterized in that: Includes the following steps: S1. Preparation of sol: S1-1. Mix organosilicon source, phosphorus-containing silane coupling agent, ethanol and H2O in a volume ratio of 100:(1-5):(100-150):(15-35) and stir. Then slowly add inorganic acid to adjust the pH of the solution to 4.5-6. After stirring and hydrolyzing, obtain solution 1. The organosilicon source is one or two of tetraethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, and polyethyl orthosilicate, with two sources mixed in any proportion; the phosphorus-containing silane coupling agent is one of KH-560-DOPO derivative, KH-570-DOPO derivative, and 2-(diphenylphosphino)ethyltriethoxysilane. S1-2. Ethanol and hydrophobic modifier are stirred at a mass ratio of 100:(10-30) until dissolved to obtain solution 2; the hydrophobic modifier is one of triphenylhydroxysilane and diphenyldihydroxysilane; S1-3. Mix equal volumes of solution 1 and solution 2, and stir to obtain solution 3; S1-4. Ethanol and concentrated ammonia water are stirred at room temperature in a volume ratio of 400:(1-3) to obtain solution 4; S2. The fiber felt roll is passed through the ultrasonic impregnation tank at a constant speed via a conveyor line. Equal volumes of solutions 3 and 4 are mixed in the pipe and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel felt. S3. The wet gel mat obtained in the previous step is transported to the microwave cavity via a transport line for rapid gelation and curing by microwave heating. S4. After leaving the microwave cavity, the wet gel felt is aged at room temperature. S5. Replace the aged wet gel mat with ethanol. S6. After supercritical drying, the replaced wet gel mat is used to obtain a high-temperature hydrophobic SiO2 aerogel mat. The obtained high-temperature hydrophobic SiO2 aerogel mat has the following properties: The volumetric water absorption rate is 1.5%-6.0%, and after heat treatment at 316℃ for 24 hours, the volumetric water absorption rate is 3.4%-9.5%, and the flammability rating is A1.

2. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: In S1-1, the mixing and stirring are carried out at a temperature of 40℃-70℃ for 30 minutes; the stirring and hydrolysis are carried out at a temperature of 40℃-70℃ for 1 hour-3 hours. The inorganic acid mentioned is one of hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

3. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: In S1-3, the stirring time is 2h-8h; in S1-4, the stirring time is 30min at room temperature.

4. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: The fiber felt roll described in S2 is one of glass fiber felt, high silica fiber felt, or quartz fiber felt.

5. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: In S3, the temperature inside the microwave cavity is maintained at 40℃-55℃; the rapid gelation time is 3min-8min.

6. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: In S4, the aging time at room temperature is 4h-12h.

7. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: In S1 and S5, the volume concentration of ethanol is ≥95%.

8. The method for preparing a high-temperature hydrophobic SiO2 aerogel felt according to claim 1, characterized in that: The supercritical drying described in S6 is supercritical drying of ethanol. The drying process is as follows: the aerogel is dried at a temperature of 260℃-320℃ under the protection of nitrogen gas, the pressure of the autoclave is controlled at 8MPa-14MPa, and the reaction time is 4h-10h.

9. A high-temperature hydrophobic SiO2 aerogel felt, characterized in that: The high-temperature hydrophobic SiO2 aerogel felt is obtained according to any one of claims 1-8.

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