Super-hydrophobic aerogel composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heat insulation materials, in particular to a super-hydrophobic aerogel composite material and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing orthosilicate and ethanol to obtain a first mixed solution, adding an acid solution to adjust the pH to be acidic, and hydrolyzing to obtain a hydrolysate; (2) mixing the hydrolysate with a solvent, then adding alkali liquor to adjust the pH to be alkaline, and then adding fibrofelt to obtain wet gel; the solvent is ethanol or a mixed solution of water and ethanol; and (3) contacting an alcoholic solution of a hydrophobic modifier with the wet gel, aging and drying to obtain the super-hydrophobic aerogel composite material, the first mixed solution does not contain water; in the hydrolysate, the volume content of water is not higher than 5%. The prepared super-hydrophobic aerogel composite material is excellent in heat insulation performance, high in flexibility and low in powder falling rate.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal insulation materials, and particularly relates to a superhydrophobic aerogel composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its unique three-dimensional network structure, silica aerogel has attracted wide attention in recent decades. Its low density, high specific surface area, and high porosity determine that silica aerogel materials can effectively inhibit gas heat transfer and reduce solid heat conduction, with low thermal conductivity. It is currently a solid material with good thermal insulation performance and is therefore widely used in the field of thermal insulation, such as for chemical plant pipelines, building exterior walls, aerospace, chemical industry, metallurgy, household appliances, etc., and has broad application prospects.

[0003] Generally, the preparation method of silica aerogel is to obtain a sol by acid catalysis of water glass, tetraethyl orthosilicate, or organosiloxane in an aqueous alcohol solution, and then through gelation, aging, surface modification, solvent replacement, and drying processes. Since pure aerogel has low mechanical strength and poor toughness, the stability of aerogel is poor, which limits its application. To solve this problem, industrially, aerogel is generally compounded with fibers to obtain an aerogel composite material, which can be used in industrial thermal insulation and other fields. However, in actual applications, the adhesion between aerogel and fiber felt is poor, resulting in problems such as powder shedding and poor flexibility during use. At the same time, it also poses a threat to the health of construction workers and reduces the performance of the aerogel felt itself. Therefore, on the premise of ensuring good thermal insulation performance of aerogel, it is very necessary to develop a powder-free aerogel composite material to ensure the health of production and use personnel and meet various market demands.

[0004] In CN111018482B, during the preparation process of the aerogel material, the fibers need to be pretreated before use, and the solvent replacement takes 12 - 36 hours. The preparation time is long and the preparation process is cumbersome, greatly increasing the time cost. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of poor adhesion between existing aerogel and fiber felt, resulting in powder shedding and poor flexibility during use. The present invention provides a superhydrophobic aerogel composite material, a preparation method thereof, and an application thereof. By using the preparation method described in the present invention, the traditional steps of aging, surface modification, and solvent replacement are optimized, shortening the preparation process, saving time costs, and the preparation method is simple and reliable.

[0006] Through in - depth research, the inventors of the present invention found that when no additional water is added during the hydrolysis of a silicon source (such as orthosilicate ester) except for the water in the acid solution, using only ethanol as the solvent and adding a mixture of water and alcohol during base - catalyzed condensation can make the sol hydrolyze more completely, strengthen the framework structure of the gel, improve the flexibility of the aerogel itself, and then compound it with a fiber felt, resulting in a stronger interfacial adhesion force between the gel and the matrix, improving the flexibility of the aerogel composite material and simultaneously reducing the powder - shedding rate of the aerogel; when aging, adding a hydrophobic modifier endows the aerogel composite material with good hydrophobicity.

[0007] To achieve the above - mentioned purpose, the first aspect of the present invention provides a method for preparing a super - hydrophobic aerogel composite material, comprising the following steps:

[0008] (1) Mix orthosilicate ester and ethanol to obtain a first mixture, add an acid solution to adjust the pH to acidic, and hydrolyze to obtain a hydrolyzate.

[0009] (2) Mix the hydrolyzate with a solvent, then add an alkali solution to adjust the pH to basic to obtain a second mixture, and then add a fiber felt to obtain a wet gel; the solvent is ethanol or a mixture of water and ethanol.

[0010] (3) Contact the wet gel with an alcohol solution of a hydrophobic modifier, age and dry to obtain a super - hydrophobic aerogel composite material.

[0011] The first mixture does not contain water.

[0012] In the hydrolyzate, the volume content of water is not higher than 5%.

[0013] The second aspect of the present invention provides a super - hydrophobic aerogel composite material prepared by the preparation method described in the present invention.

[0014] The third aspect of the present invention provides an application of the super - hydrophobic aerogel composite material described in the present invention in heat insulation.

[0015] Through the above - mentioned technical solution, when no additional water is added during the hydrolysis of orthosilicate ester except for the water in the acid solution, using only ethanol as the solvent and adding a mixture of water and alcohol during base - catalyzed condensation can make the sol hydrolyze more completely, strengthen the framework structure of the gel, improve the flexibility of the aerogel itself, and then compound it with a fiber felt, resulting in a stronger interfacial adhesion force between the gel and the matrix, improving the flexibility of the aerogel composite material and simultaneously reducing the powder - shedding rate of the aerogel; when aging, adding a hydrophobic modifier endows the aerogel composite material with good hydrophobicity. By optimizing the traditional steps of aging, surface modification and solvent replacement, the preparation process is shortened, the time cost is saved, and the preparation method is simple and reliable.

[0016] The super-hydrophobic aerogel composite material of the present invention has excellent thermal insulation performance, high flexibility, low powder loss rate, and good hydrophobicity. As a good thermal insulation material, the composite material is widely used in pipelines, furnaces and other thermal equipment in the fields of petrochemical industry, chemical industry, etc., which can reduce heat energy loss to a certain extent and improve heat energy utilization. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] A first aspect of the present invention provides a method for preparing a super-hydrophobic aerogel composite material, comprising the following steps:

[0019] (1) mixing orthosilicate and ethanol to obtain a first mixed solution, adding an acid solution to adjust the pH to acidic, and hydrolyzing to obtain a hydrolyzed solution;

[0020] (2) mixing the hydrolyzate with a solvent, then adding an alkali solution to adjust the pH to alkaline to obtain a second mixed solution, and then adding the fiber felt to obtain a wet gel; the solvent is ethanol or a mixture of water and ethanol;

[0021] (3) contacting the wet gel with an alcohol solution of a hydrophobic modifier, aging, and drying to obtain a super hydrophobic aerogel composite material;

[0022] The first mixed solution does not contain water;

[0023] The volume content of water in the hydrolyzate is not higher than 5%.

[0024] The super-hydrophobic aerogel composite material prepared by the method of the present invention has the advantages of excellent thermal insulation performance, high flexibility, low powder loss rate and good hydrophobicity.

[0025] In the present invention, in step (1), the volume ratio of orthosilicate to ethanol can be selected in a wide range, which is exemplary but not limiting. According to a preferred embodiment of the present invention, the volume ratio of orthosilicate to ethanol is 1:2-6; more preferably, the volume ratio of orthosilicate to ethanol is 1:2-4. The above preferred solution allows the sol to be further hydrolyzed more completely, thereby enhancing the skeleton structure of the gel and improving the flexibility of the aerogel itself.

[0026] In the present invention, in step (1), an acid solution is added to cause the orthosilicate to undergo a hydrolysis reaction under acidic conditions to obtain a hydrolyzed solution.

[0027] In the present invention, in step (1), according to a preferred embodiment of the present invention, by way of illustration but not limitation of the scope of the present invention, the acid solution adjusts the pH of the solution to 2-4.

[0028] According to a preferred embodiment of the present invention, in the hydrolysis solution, the volume ratio of water to ethanol is 1:20-40; which is beneficial to enhancing the framework structure of the gel and improving the flexibility of the aerogel itself.

[0029] In the present invention, in step (1), the types of the acid solution have a relatively wide optional range. By way of illustration but not limitation of the scope of the present invention, according to a preferred embodiment of the present invention, the acid solution is selected from one or more of acetic acid, hydrochloric acid, acetic acid aqueous solution and oxalic acid aqueous solution; more preferably, the acid solution is hydrochloric acid.

[0030] When the acid solution added is acetic acid, the volume content of water in the hydrolysis solution is 0.

[0031] In the present invention, in step (1), the concentration of the acid solution has a relatively wide optional range. By way of illustration but not limitation of the scope of the present invention, preferably, the concentration is 0.05-0.5 mol / L.

[0032] In the present invention, in step (1), as long as the object of the present invention can be achieved, there is no special requirement for the hydrolysis time. By way of illustration but not limitation of the scope of the present invention, according to a preferred embodiment of the present invention, the hydrolysis time is 1-3 h.

[0033] In the present invention, in step (1), the types of the tetraalkyl orthosilicate have a relatively wide optional range. By way of illustration but not limitation of the scope of the present invention, according to a preferred embodiment of the present invention, the tetraalkyl orthosilicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.

[0034] In the present invention, in step (2), by adding a water-alcohol mixture during base-catalyzed condensation, the sol is further hydrolyzed more completely, enhancing the framework structure of the gel, improving the flexibility of the aerogel itself, and then compounding with the fiber felt, so that a stronger interfacial adhesion force is generated between the gel and the matrix, improving the flexibility of the aerogel composite material, and at the same time reducing the powder loss rate of the aerogel.

[0035] In the present invention, in step (2), for the ethanol and water mixture, the optional range of the volume ratio of the amounts of water and ethanol used is relatively wide. By way of illustration but not limitation of the scope of the present invention, according to a preferred embodiment of the present invention, in the solvent, the volume ratio of ethanol to water is 1:0-3, preferably 1:0.5-2.

[0036] According to a preferred embodiment of the present invention, the volume ratio of the hydrolysis solution to the solvent is 1:0.2 - 1. According to a preferred embodiment of the present invention, in step (2), an alkali solution is added to adjust the pH of the solution to 8 - 10.

[0037] In the present invention, in step (2), the types of the alkali have a relatively wide selection range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the alkali is selected from one or more of ammonia water, ethanolamine, diethanolamine, and sodium hydroxide solution; more preferably, the alkali is ammonia water. By adopting the aforementioned preferred scheme, the sol is further hydrolyzed more completely, the framework structure of the gel is enhanced, and the flexibility of the aerogel itself is improved.

[0038] In the present invention, in step (2), there is no particular limitation on the concentration of the alkali solution. According to a preferred embodiment of the present invention, the concentration of the alkali solution is 25wt% - 28wt%. By adopting the aforementioned preferred scheme, when compounding with the fiber felt, a stronger interfacial adhesion force is generated between the gel and the matrix, the flexibility of the aerogel composite material is improved, and at the same time, the powder dropping rate of the aerogel is reduced.

[0039] In the present invention, in step (2), the types of the fiber felt have a relatively wide selection range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the fiber felt is selected from one or more of glass fiber felt, ceramic fiber felt, mullite fiber felt, carbon fiber felt, and polyester fiber felt; more preferably, the fiber felt is glass fiber felt.

[0040] In the present invention, in step (2), as long as the object of the present invention can be achieved, the addition amount of the fiber felt has a relatively wide selection range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the volume ratio of the fiber felt to the second mixed solution is 1:1.1 - 3.

[0041] In the present invention, in step (3), an alcohol solution of a hydrophobic modifier is added to age and modify the wet gel, so that the aerogel composite material has good hydrophobicity.

[0042] In the present invention, in step (3), the types of the hydrophobic modifier have a relatively wide selection range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the hydrophobic modifier is an alkyl siloxane, preferably one or more of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, polydimethylsiloxane, hexamethylsiloxane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, and diethyldimethoxysilane. By adopting the aforementioned preferred scheme, the flexibility of the aerogel composite material is improved, and at the same time, the powder dropping rate of the aerogel is reduced, so that the aerogel composite material has good hydrophobicity.

[0043] In the present invention, in step (3), the types of alcohols in the alcoholic solution of the hydrophobic modifier can be selected from a relatively wide range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the alcohol is one or more of methanol, ethanol, and isopropanol. More preferably, the alcohol is ethanol.

[0044] In the present invention, in step (3), for the alcoholic solution of the hydrophobic modifier, the volume ratio of the hydrophobic modifier to the alcohol can be selected from a relatively wide range. According to a preferred embodiment of the present invention, the volume ratio of the hydrophobic modifier to the alcohol is 1:3 - 8.

[0045] In the present invention, in step (3), the addition amount of the alcoholic solution of the hydrophobic modifier can be selected from a relatively wide range. According to a preferred embodiment of the present invention, the volume ratio of the added alcoholic solution of the hydrophobic modifier to the wet gel is 1:1 - 3. By adopting the aforementioned preferred scheme, the flexibility of the aerogel composite material is improved, and at the same time, the powder dropping rate of the aerogel is reduced, making the aerogel composite material have good hydrophobicity.

[0046] In the present invention, in step (3), the aging temperature can be selected from a relatively wide range. According to a preferred embodiment of the present invention, the aging temperature is 30 - 60 °C, and the aging time is 8 - 36 h. By adopting the aforementioned preferred scheme, the flexibility of the aerogel composite material is improved, and at the same time, the powder dropping rate of the aerogel is reduced, making the aerogel composite material have good hydrophobicity.

[0047] In the present invention, in step (3), the drying method can be selected from a relatively wide range. By way of illustration, but not limiting the scope of the present invention thereby, according to a preferred embodiment of the present invention, the drying method is supercritical drying. More preferably, it is low-temperature supercritical CO 2 drying; in the present invention, as long as it is ensured to be dried under the supercritical state of CO 2 it is fine, and there are no special limitations on the temperature and pressure of supercritical CO 2 drying. For example, the supercritical drying temperature is 35 °C, and the drying pressure is 7.5 Mpa.

[0048] According to a preferred embodiment of the present invention, the method for preparing the superhydrophobic aerogel composite material includes:

[0049] (1) Mix orthosilicate and ethanol to obtain a first mixed solution, add an acid solution to adjust the pH to 2 - 4, and hydrolyze to obtain a hydrolyzate;

[0050] (2.1) Mix the hydrolyzate with a first solvent, and then add an alkali solution to adjust the pH to neutral; the first solvent is a water-alcohol mixture and the volume ratio of water to alcohol is greater than 1;

[0051] (2.2) Add a second solvent to the material obtained in step (2.2), then add an alkali solution to adjust the pH to 8 - 10 to obtain a second mixed solution, and then add a fiber felt to obtain a wet gel; the second solvent is a water - alcohol mixed solution with a volume ratio of water to alcohol less than 1;

[0052] The volume ratio of the hydrolysis solution, the first solvent, and the second solvent is 1:0.1 - 0.8:0.1 - 0.8;

[0053] (3) Contact the alcohol solution of the hydrophobic modifier with the wet gel, age and dry to obtain a super - hydrophobic aerogel composite material;

[0054] The first mixed solution does not contain water;

[0055] In the hydrolysis solution, the volume content of water is not higher than 5%. This is beneficial to improving the heat - insulation performance and reducing the powder - dropping rate.

[0056] According to a preferred embodiment of the present invention, the volume ratio of water to alcohol in the first solvent is 2 - 5:1.

[0057] According to a preferred embodiment of the present invention, the volume ratio of water to alcohol in the second solvent is 0.1 - 0.4:1.

[0058] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0059] To illustrate the present invention more clearly, the following examples are listed, but the applicable situations of the present invention are not limited to the scope of the examples.

[0060] In the present invention, the hydrophobicity test, thermal conductivity test, and powder - dropping rate test were carried out on the super - hydrophobic aerogel composite material. Among them, the test method for hydrophobicity, i.e., the contact angle, can be seen in GB / T 30693 - 2014; the test method for thermal conductivity can be seen in the standard GB / T 10295 - 2008; the powder - dropping rate is the vibration mass loss rate (the standard can be seen in GB / T 34336 - 2017).

[0061] In the examples, the ethanol used had an analytical - pure anhydrous ethanol purity.

[0062] Example 1

[0063] (1) Add 5 mL of tetraethyl orthosilicate and 15 ml of ethanol to a beaker, then add 0.5 ml (0.1 mol / L) hydrochloric acid solution, adjust the pH of the solution to 3.5, and magnetically stir and hydrolyze for 2 h to obtain a hydrolysis solution;

[0064] (2) Add a mixture of 5 mL of water and 5 mL of ethanol to the hydrolysis solution, stir evenly, then add ammonia water (26 wt%) to adjust the pH of the solution to 8.5. After stirring evenly, add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0065] (3) According to the volume ratio of the gel obtained in step (2) to the aging solution of 3:1, add the aging solution (methyltrimethoxysilane and ethanol with a volume ratio of 1:4), and carry out aging modification at 45 °C for 24 h, and then carry out CO 2 supercritical drying (drying temperature is 35 °C, drying pressure is 7.5 Mpa) to obtain a flexible superhydrophobic aerogel composite material;

[0066] Among them, the water contact angle of the superhydrophobic aerogel composite material is 152°, the thermal conductivity is 0.025 W / mK, and the powder loss rate is 0.09%.

[0067] Example 2

[0068] (1) Add 5 mL of tetraethyl orthosilicate and 15 mL of ethanol to a beaker, then add 0.5 mL (0.1 mol / L) hydrochloric acid solution, adjust the pH of the solution to 3.5, and magnetically stir and hydrolyze for 2 h to obtain a hydrolysis solution;

[0069] (2) Add a mixture of 5 mL of water and 5 mL of ethanol to the hydrolysis solution, stir evenly, then add ammonia water (26 wt%) to adjust the pH of the solution to 8.5. After stirring evenly, add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0070] (3) According to the volume ratio of the gel obtained in step (2) to the aging solution of 3:1, add the aging solution (methyltriethoxysilane and ethanol with a volume ratio of 1:4), and carry out aging modification at 45 °C for 24 h, and then carry out CO 2 supercritical drying (drying temperature is 35 °C, drying pressure is 7.5 Mpa) to obtain a flexible superhydrophobic aerogel composite material;

[0071] Among them, the water contact angle of the superhydrophobic aerogel composite material is 151°, the thermal conductivity is 0.029 W / mK, and the powder loss rate is 0.11%.

[0072] Example 3

[0073] (1) Add 5 mL of tetraethyl orthosilicate and 12 mL of ethanol to a beaker, then add 0.5 mL (0.1 mol / L) hydrochloric acid solution, adjust the pH of the solution to 3.5, and magnetically stir and hydrolyze for 2 h to obtain a hydrolysis solution;

[0074] (2) Add a mixed solution of 5 mL of water and 7 mL of ethanol to the hydrolysis solution, stir evenly, then add ammonia water (26 wt%) to adjust the pH of the solution to 8.5. After stirring evenly, add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0075] (3) According to the volume ratio of the gel obtained in step (2): aging solution is 3:1, add the aging solution (a mixed solution of methyltrimethoxysilane and ethanol with a volume ratio of 1:4), and age and modify at 45 °C for 24 h, then perform CO 2 supercritical drying (drying temperature is 35 °C, drying pressure is 7.5 Mpa), to obtain a flexible superhydrophobic aerogel composite material;

[0076] Among them, the water contact angle of the superhydrophobic aerogel composite material is 151°, the thermal conductivity is 0.031 W / mK, and the powder loss rate is 0.15%.

[0077] Example 4

[0078] (1) Add 5 mL of tetraethyl orthosilicate and 15 mL of ethanol to a beaker, then add 0.5 mL (0.1 mol / L) hydrochloric acid solution, adjust the pH of the solution to 3.5, and magnetically stir and hydrolyze for 2 h to obtain a hydrolysis solution;

[0079] (2) Add a mixed solution of 4 mL of water and 1 mL of ethanol to the hydrolysis solution, stir evenly, add ammonia water (26 wt%) to adjust the pH to neutral, then add a mixed solution of 1 mL of water and 4 mL of ethanol, stir evenly, add ammonia water (26 wt%) to adjust the pH to 8.5, fully stir evenly and then add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0080] (3) According to the volume ratio of the gel obtained in step (2): aging solution is 3:1, add the aging solution (a mixed solution of methyltrimethoxysilane and ethanol with a volume ratio of 1:4), and age and modify at 45 °C for 24 h, then perform CO 2 supercritical drying (drying temperature is 35 °C, drying pressure is 7.5 Mpa), to obtain a flexible superhydrophobic aerogel composite material;

[0081] Among them, the water contact angle of the superhydrophobic aerogel composite material is 152°, the thermal conductivity is 0.022 W / mK, and the powder loss rate is 0.06%.

[0082] Example 5

[0083] (1) Add 4 mL of tetraethyl orthosilicate and 20 mL of ethanol to a beaker, then add acetic acid to adjust the pH of the solution to 2, and magnetically stir and hydrolyze for 2 h to obtain a hydrolysis solution;

[0084] (2) Add a mixed solution of 4 mL of water and 8 mL of ethanol to the hydrolysis solution, stir evenly, then add ammonia water (26 wt%) to adjust the pH of the solution to 10. After stirring evenly, add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0085] (3) According to the volume ratio of the gel obtained in step (2) to the aging solution of 1:1, add the aging solution (methyltrimethoxysilane and ethanol with a volume ratio of 1:4), and age and modify at 45 °C for 24 h, and then perform CO 2 supercritical drying (the drying temperature is 35 °C and the drying pressure is 7.5 Mpa) to obtain a flexible superhydrophobic aerogel composite material;

[0086] Among them, the water contact angle of the aerogel composite material is 152°, the thermal conductivity is 0.26 W / mK, and the powder loss rate is 0.14%.

[0087] Comparative Example 1

[0088] (1) Add a mixture of 1 mL of water and 15 mL of ethanol to a beaker, then add 5 mL of tetraethyl orthosilicate, adjust the pH of the solution to 2.5, then add 0.5 mL (0.1 mol / L) hydrochloric acid solution, and magnetically stir for hydrolysis for 2 h to obtain a hydrolysis solution;

[0089] (2) Add 5 mL of water and 5 mL of ethanol to the hydrolysis solution, stir evenly, add 0.5 mL of ammonia water (26 wt%), adjust the pH of the solution to 8.5, stir evenly and then add a block-shaped glass fiber mat with dimensions of 50 mm × 50 mm × 10 mm, and let it stand to wait for gelation;

[0090] (3) According to the volume ratio of the gel obtained in step (2) to the aging solution of 3:1, add the aging solution (methyltrimethoxysilane and ethanol with a volume ratio of 1:4), and age and modify at 45 °C for 24 h, and then perform CO 2 supercritical drying (the drying temperature is 35 °C and the drying pressure is 7.5 Mpa) to obtain a hard and brittle superhydrophobic aerogel composite material;

[0091] Among them, the water contact angle of the aerogel composite material is 151°, the thermal conductivity is 0.039 W / mK, and the powder loss rate is 0.3%.

[0092] Comparative Example 2

[0093] (1) Add a mixture of 5 mL of water and 10 mL of ethanol to a beaker, then add 0.5 mL (0.1 mol / L) hydrochloric acid solution, adjust the pH of the solution to 3.5, then add 5 mL of tetraethyl orthosilicate, and then magnetically stir for hydrolysis for 2 h to obtain a hydrolysis solution;

[0094] (2) Add 5 ml of ethanol to the hydrolysis solution, stir evenly, add 0.5 ml of ammonia water (26 wt%), adjust the pH of the solution to 9.5, and it becomes a white paste-like wet powder, and a gel cannot be formed.

[0095] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A preparation method of a superhydrophobic aerogel composite material, characterized in that, it comprises the following steps: (1) Mix orthosilicate and ethanol to obtain a first mixed solution, add an acid solution to adjust the pH to acidic, and hydrolyze to obtain a hydrolyzate; (2) Mix the hydrolyzate with a solvent, then add an alkali solution to adjust the pH to alkaline to obtain a second mixed solution, and then add a fiber felt to obtain a wet gel; the solvent is ethanol or a mixed solution of water and ethanol; (3) Contact the alcohol solution of the hydrophobic modifier with the wet gel, age and dry to obtain the superhydrophobic aerogel composite material; The first mixed solution does not contain water; In the hydrolyzate, the volume content of water is not higher than 5%.

2. The preparation method according to claim 1, wherein, in step (1), the volume ratio of the amount of orthosilicate to ethanol is 1:2 - 6, preferably 1:2 - 4; and / or in step (1), the pH is adjusted to 2 - 4; and / or in the hydrolyzate, the volume ratio of water to ethanol is 1:20 - 40.

3. The preparation method according to claim 1 or 2, wherein, in step (2), in the solvent, the volume ratio of ethanol to water is 1:0 - 3, preferably 1:0.5 - 2; and / or in step (2), the volume ratio of the hydrolyzate to the solvent is 1:0.2 - 1.

4. The preparation method according to claim 1 or 2, wherein, in step (2), the pH is adjusted to 8 - 10; and / or the volume ratio of the fiber felt to the second mixed solution is 1:1.1 - 3.

5. The preparation method according to claim 1 or 2, wherein, in step (1), the orthosilicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate; and / or the acidic substance in the acid solution is selected from one or more of acetic acid, HCl, oxalic acid; and / or the concentration of the acid solution is 0.05 - 0.5 mol / L; and / or the hydrolysis conditions include: the hydrolysis time is 1 - 3 h.

6. The preparation method according to claim 1 or 2, wherein, in step (2), the alkali solution is selected from one or more of ammonia water, ethanolamine, diethanolamine, sodium hydroxide solution; and / or the fiber felt is selected from one or more of glass fiber felt, ceramic fiber felt, mullite fiber felt, carbon fiber felt, polyester fiber felt.

7. The preparation method according to claim 1 or 2, wherein, in step (3), in the alcohol solution of the hydrophobic modifier, the volume ratio of the hydrophobic modifier to the alcohol is 1:3 - 8; and / or the hydrophobic modifier is an alkyl siloxane, preferably one or more of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, polydimethylsiloxane, hexamethylsiloxane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane; and / or the alcohol is one or more of methanol, ethanol, isopropanol; and / or the volume ratio of the alcohol solution of the hydrophobic modifier to the wet gel is 1:1 - 3; and / or the aging conditions include: the temperature is 30 - 60 °C, and the aging time is 8 - 36 h; and / or In step (3), the drying method is supercritical drying, preferably low-temperature supercritical CO 2 drying.

8. The preparation method according to claim 1 or 2, wherein, The preparation method of the superhydrophobic aerogel composite material comprises the following steps: (1) Mix orthosilicate and ethanol to obtain a first mixed solution, add an acid solution to adjust the pH to 2-4, and hydrolyze to obtain a hydrolyzate; (2.1) Mix the hydrolyzate with a first solvent, and then add an alkali solution to adjust the pH to neutral; the first solvent is a water-alcohol mixed solution and the volume ratio of water to alcohol is greater than 1; (2.2) Add a second solvent to the material obtained in step (2.2), then add an alkali solution to adjust the pH to 8-10 to obtain a second mixed solution, and then add a fiber felt to obtain a wet gel; the second solvent is a water-alcohol mixed solution and the volume ratio of water to alcohol is less than 1; The volume ratio of the hydrolyzate, the first solvent, and the second solvent is 1:0.1-0.8:0.1-0.8; (3) Contact the alcohol solution of the hydrophobic modifier with the wet gel, age and dry to obtain the superhydrophobic aerogel composite material; The first mixed solution does not contain water; In the hydrolyzate, the volume content of water is not higher than 5%.

9. The superhydrophobic aerogel composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of the superhydrophobic aerogel composite material according to claim 9 in heat insulation.