Preparation method of silica nano-aerogel thermal insulation paper

Abstract

The application discloses a preparation method of silica nano-aerogel heat-insulating paper, which comprises the following steps: (1) covering a permeable membrane interlayer on the surface of each fiber paper; (2) preparing a silica aerogel prepolymer mixed solution; (3) compounding the silica aerogel prepolymer mixed solution with the fiber paper to obtain wet silica aerogel paper; and (4) performing solvent replacement, hydrophobic modification and drying on the wet silica aerogel paper. The aerogel paper is prepared by covering the permeable membrane interlayer on the surface of the fiber paper and applying gravity in the gel process, so that the problems of the brittleness of the aerogel itself, the low strength of the fiber material itself, the damage of the prepared ultra-thin aerogel paper (less than or equal to 0.3 mm) and the like are solved, the gel absorption amount of the fiber paper is effectively controlled, and the flatness, thickness and thickness size deviation of the aerogel paper are ensured; and the prepared silica nano-aerogel heat-insulating paper is flat in appearance and free of defects such as wrinkles, holes and cracks which affect use.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a method for preparing silica nano-aerogel heat insulation paper. Background Technology

[0002] Silica nano-aerogel insulation paper is a thermal insulation material composed of aerogel and fiber paper. In addition to the advantages of aerogel itself, it also has the advantages of being ultra-thin, ultra-light, flexible, easy to construct, and easy to cut and process. In particular, it has both high-efficiency thermal insulation performance and ultra-thin thickness, making it especially suitable for thermal insulation of complex components and high-temperature narrow spaces. It can be widely used for cold insulation of batteries, fighter jet engines, and precision equipment.

[0003] Most aerogel papers currently on the market are produced using the following two methods:

[0004] One method involves directly blending aerogel powder and fibers, followed by drying to produce aerogel paper. In this method, to ensure uniform bonding between the aerogel powder and fibers, various additives are required, such as polyaluminum chloride, sodium silicate, silane coupling agents, or adhesives. This not only increases the cost of the aerogel paper but also, since many of these additives are high-temperature volatile components, can easily cause volatile pollution to the environment. Strict control of the aerogel powder particle size is necessary, generally below 100 nm. Although the aerogel paper produced using this method is relatively thin, its thermal insulation and stability are poor due to the structural collapse and uneven dispersion of the aerogel powder during the soaking process.

[0005] Another method involves impregnating rolls of fiber felt and fiber paper with a composite aerogel sol, followed by drying to obtain aerogel paper. This method has the following characteristics: it requires a relatively long impregnation time (generally 2-10 hours, or even longer) to ensure uniform bonding between the sol and the roll of fiber felt or fiber paper; a shorter time will not guarantee the thermal insulation performance of the aerogel paper. Drying conditions below 100℃ and at normal pressure cannot ensure drying effectiveness; therefore, drying needs to be carried out at higher temperatures (generally above 240℃) and higher pressures (generally above 7.5MPa), increasing the complexity of the process. While aerogel paper produced using this method can achieve relatively excellent thermal insulation performance, it is uneven in thickness, easily damaged, and, due to its long production time and complex process, results in a higher cost. Summary of the Invention

[0006] To address the above problems, the purpose of this invention is to provide a method for preparing silica nano-aerogel thermal insulation paper.

[0007] A method for preparing a silica nano-aerogel heat insulation paper includes the following steps:

[0008] (1) A permeable membrane is applied to the surface of each fiber paper. The permeable membrane is one or more nonwoven fabrics of polypropylene, polyester, nylon, spandex and acrylic fiber with the characteristics of water repellency, air permeability, flexibility, flame retardancy and non-toxicity. The permeable membrane is applied to the surface of the fiber paper by any physical method of roller pressing, hot pressing or vacuum pressing. The fiber paper is one or two of glass fiber, high silica fiber, ceramic fiber, alumina fiber and mullite fiber. The fiber paper can be a sheet or a roll.

[0009] (2) Preparation of silica aerogel prepolymer mixture, including the following steps:

[0010] A. Mix the silicon source, solvent, water, and weak acid catalyst, and stir for 30 minutes;

[0011] B. Add the two-phase adhesive in step A and stir for 5 minutes;

[0012] C. Add the alkaline catalyst to step B and stir for 5 minutes to obtain the final product.

[0013] (3) The silica aerogel prepolymer mixture is combined with fiber paper to obtain wet silica aerogel paper.

[0014] (4) Solvent replacement, hydrophobic modification and drying of wet silica aerogel paper can be used to obtain silica nano-aerogel heat insulation paper. Supercritical drying, atmospheric pressure drying or freeze drying can be used for drying.

[0015] Further, the ratio of the silicon source, solvent, water, weak acid catalyst, two-phase binder, and alkaline catalyst is 1:(2-10):(0.05-0.15):(0.0005-0.0015):(0.15-0.75):(0.01-0.1); the silicon source is tetraethyl orthosilicate or methyl orthosilicate; the solvent is methanol or ethanol; the water is purified water or distilled water; the weak acid catalyst is boric acid, oxalic acid, or phosphoric acid; the two-phase binder is one or two of silica gel and fumed silica; the alkaline catalyst is one or a combination of two or more of ammonia, ammonium fluoride, formamide, and dimethylformamide.

[0016] Furthermore, the composite of the silica aerogel prepolymer mixture and the fiber paper involves placing the fiber paper in a gel fixture, pumping in the silica aerogel prepolymer mixture to submerge the fiber paper using a vacuum pump, and then placing the gel fixture on an ultrasonic or mechanical vibration table with a vibration frequency of 40-80Hz. After running for 5-20 minutes, a gravity of 0.1-0.5 times the weight of the wet gel paper (i.e., the sum of the weight of the fiber paper and the weight of the silica aerogel prepolymer mixture) is applied to the fiber paper. After continuing to run for 10-30 minutes, the vibration table is turned off, and the mixture is left to stand for 2-24 hours.

[0017] When the fiber paper is a sheet and its thickness is no more than 0.5 mm, in order to ensure the flatness and integrity of the fiber material, the permeable membrane layer on the surface of the fiber paper should be removed before solvent replacement. When the fiber paper is a sheet with a thickness greater than 0.5 mm, it is not necessary to remove the permeable membrane layer. During solvent replacement, the wet silica aerogel paper is placed on a tooling partition with evenly distributed mesh. A gravity of 0.01-0.1 times its own weight is applied to the wet silica aerogel paper on each partition, and then it is placed in the solvent and replaced at 40-65℃ for 4-24 hours.

[0018] When the fiber paper is in roll form, it is not necessary to remove the permeable membrane layer. The solvent replacement involves placing the wet silica aerogel paper in a solvent and replacing it at 40-65°C for 4-24 hours.

[0019] Furthermore, the hydrophobic modification involves placing the solvent-replaced wet silica aerogel paper into a hydrophobic agent alcohol solution and reacting it at 40-65°C for 4-24 hours to carry out an in-situ alkylation chemical reaction. The hydrophobic agent is one of the alkylating reagents such as hexamethyldisilazane, trimethylmethoxysilane, and trimethylchlorosilane.

[0020] Compared with the prior art, the preparation method of silica nano-aerogel thermal insulation paper of the present invention has the following advantages: 1. The present invention prepares aerogel paper by coating the surface of fiber paper with a permeable membrane and applying gravity during the gelation process. This not only solves the problems of the brittleness of aerogel itself and the low strength of fiber materials, which make it easy to damage the preparation of ultra-thin aerogel paper (≤0.3mm), but also effectively controls the amount of adhesive absorbed by the fiber paper, improves the strength of the fiber paper, and ensures the integrity, flatness, deformation, thickness and thickness dimensional deviation of the aerogel paper.

[0021] 2. This invention enhances the permeability of silica aerogel prepolymer solution in multilayer fiber paper by adding a permeable membrane layer and interlayer mesh on the surface of fiber paper, and by using ultrasonic or mechanical wave permeation and flow enhancement technology during the aerogel paper gelation process. This results in a uniform loading of the prepolymer solution on the surface of the fiber paper. The transverse and longitudinal wave vibrations of ultrasonic or mechanical waves strengthen the collision intensity and frequency between aerogel particles, destroying the agglomeration structure between particles and allowing for perfect agglomerate growth. At the same time, it breaks the surface tension between water molecules, increases the activity of water molecules, accelerates the growth of aerogel particles to form agglomerates, and improves the composite efficiency of fiber paper and silica aerogel prepolymer, reducing the traditional impregnation time from 2-10 hours to 15-50 minutes.

[0022] 3. This invention adds a two-phase adhesive (silica gel and fumed silica) to the silica aerogel prepolymer mixture. Without affecting its thermal insulation performance, it can withstand greater tensile strength because the -OH groups in the two-phase adhesive connect with the silica aerogel particles to form a ≡Si—O—Si≡ network structure, filling the gaps between the fiber reinforcements and reducing the gaps between the silica aerogel particles and the fibers. This allows the silica aerogel particles to be tightly and reliably "anchored" to the fiber paper surface, ultimately greatly improving the compactness of the composite material's microstructure, preventing the silica aerogel from collapsing, reducing the vibration mass loss rate, and further enhancing the mechanical properties of the composite material. Furthermore, during the mixing process, the macroscopic pores of the two-phase adhesive can accommodate some silica hydrosol or aerogel particles, dividing the large pores inside the two-phase adhesive into smaller pores, ultimately strengthening the porous structure of the silica aerogel and enhancing the material's thermal insulation performance.

[0023] 4. This invention uses boric acid as a hydrolysis catalyst. Since boron in boric acid is an electron-deficient atom, it can combine with hydroxide ions from water molecules to release protons. After the silicon source hydrolyzes to form a polyhydroxy compound intermediate, this electron-deficient property enhances its acidity, which in turn promotes further hydrolysis of the silicon source. Simultaneously, during the hydrolysis of the silicon source, boric acid can reduce the viscosity and surface tension of the mixture, increase its refractive index, and improve the thermal insulation and transparency of the aerogel paper, ultimately improving its thermal insulation, chemical stability, and resistance to mechanical and thermal shock. Furthermore, boric acid does not introduce new elements into the aerogel paper and can reduce the risks associated with strong acids, which are more harmful to the human body and more corrosive to equipment.

[0024] 5. This invention can prepare aerogel paper with a minimum thickness of only 0.1 mm. By using the aerogel paper alone or in combination, it can be applied to almost all occasions that require heat insulation. At the same time, the super adsorption properties of aerogel can also be used for separation chromatography and as a carrier.

[0025] 6. The silica nano-aerogel insulation paper prepared by this invention has a smooth appearance, without defects such as wrinkles, holes, and cracks that affect its use, and the impregnation time is shortened. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings.

[0027] Figure 1 A photograph of the silica nano-aerogel insulation paper prepared in Example 1;

[0028] Figure 2 The actual sample of the silica nano-aerogel insulation paper prepared in Comparative Example 1. Figure 1 ;

[0029] Figure 3 The actual sample of the silica nano-aerogel insulation paper prepared in Comparative Example 1. Figure 2 ;

[0030] Figure 4 The actual sample of the silica nano-aerogel insulation paper prepared in Comparative Example 1. Figure 3 ;

[0031] Figure 5 This is a photograph of the silica nano-aerogel insulation paper prepared in Example 2.

[0032] Figure 6 The actual sample of the silica nano-aerogel insulation paper prepared in Comparative Example 2. Figure 1 ;

[0033] Figure 7 The actual sample of the silica nano-aerogel insulation paper prepared in Comparative Example 2. Figure 2 . Detailed Implementation

[0034] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0035] It should be noted that the term "comprising" or any other variation is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Example 1

[0036] A method for preparing a silica nano-aerogel heat insulation paper includes the following steps:

[0037] (1) Using a roll pressing method, a surface layer with a density of 30 g / m² is applied to the surface of each 0.27 mm glass fiber paper. 2 Polypropylene nonwoven fabric is cut into 400mm×400mm sheets. Then, the treated glass fiber paper is stacked in the gel fixture, and a 2mm thick polyester spiral mesh is added every 8cm. The stacking is continued until the gel fixture is 3 / 4 full.

[0038] (2) Mix 1 part tetraethyl orthosilicate, 6 parts methanol, 0.07 parts purified water and 0.00075 parts boric acid, stir for 30 min, then add 0.35 parts silica gel and mix evenly, stir for 5 min, then add 0.045 parts ammonia water and mix evenly, continue stirring for 5 min to obtain silica aerogel prepolymer mixture.

[0039] (3) The silica aerogel prepolymer mixture was pumped in by vacuum pump to cover the top layer of fiber paper. The mechanical wave vibration table was turned on and the vibration frequency was 65 Hz. After running for 15 minutes, a gravity of 0.25 times the weight of the wet gel paper was applied to the fiber paper. After running for another 15 minutes, the vibration table was turned off and left to stand for 12 hours. In order to ensure the flatness and integrity of the fiber material, the permeable membrane layer on the surface of the fiber paper was removed, and the polyester spiral wire mesh was retained.

[0040] (4) Place the wet silica aerogel paper on a tooling partition with a uniform mesh, apply a gravity of 0.1 times its own weight to the wet silica aerogel paper on each partition, and put it together with the tooling into 99% methanol solvent. Solvent replacement is carried out at 55°C for 20 hours. Then, put it into a hexamethyldisilazanol solution and carry out an in-situ alkylation chemical reaction at 55°C for 8 hours. Then, supercritical carbon dioxide drying is carried out to obtain silica nano-aerogel heat insulation paper.

[0041] The silica nano-aerogel insulation paper prepared in this embodiment has a smooth appearance, free from defects such as wrinkles, holes, and tears that would affect its use. Its thickness is 0.36-0.41 mm; its bulk density (g / cm³) is... 3 The thermal conductivity (25℃) is 0.0173-0.0183; the tensile strength (longitudinal) is 0.86-0.92; the resistance to high and low temperatures (-55-600℃, 1h) is ≥98%; the thermal weight loss at 600℃ is ≤3.0%; the bending performance is without cracks or damage; the vibration mass loss rate is ≤0.5%; and the paper product qualification rate is ≥90%. The main test results are shown in Table 1. See the attached physical sample for details. Figure 1 .

[0042] Table 1. Third-party testing data of silica nano-aerogel insulation paper (multiple sheets) – Example 1

[0043]

[0044] Comparative Example 1

[0045] Layer 0.27mm thick, 400mm×400mm glass fiber paper in the gel fixture, adding a 2mm thick polyester spiral mesh every 8cm, and continue layering until the gel fixture is 3 / 4 full. The remaining steps are the same as in Example 1.

[0046] The silica nano-aerogel insulation paper prepared in this comparative example has defects affecting its use, such as wrinkles, holes, tears, severe deformation, and uneven thickness; its thickness is 0.28-0.71 mm; its bulk density (g / cm³) is... 3 The thermal conductivity (25℃) (W / (m•K)) is 0.019-0.031; the tensile strength (longitudinal) (kN / m) is 0.58-0.76. Single sheets exhibit localized water penetration or poor hydrophobicity, with a vibration mass loss rate ≥5%. The main test results are shown in Table 2. See the attached sample for details. Figure 2 , Figure 3 , Figure 4 .

[0047] Table 2 Third-party testing data of silica nano-aerogel insulation paper (multiple sheets) – Comparative Example 1

[0048]

[0049] In Comparative Example 1, since the surface of the fiber paper was not covered with a film, the two fiber papers were stuck together. After preparation, they were difficult to separate and the fiber paper was easy to tear. In addition, since the surface of the fiber paper was not covered with a film, the amount of aerogel on the fiber paper was different. There was more aerogel near the outer layer and the surface, and less aerogel on the inner layer and the center of the fiber paper, or even local areas without glue. Example 2

[0050] A method for preparing a silica nano-aerogel heat insulation paper includes the following steps:

[0051] (1) A sheet of 0.08 mm thick glass fiber paper is coated with a surface density of 30 g / m² using a roller pressing method. 2 Polypropylene nonwoven fabric is cut into 300mm×300mm sheets, and then the treated glass fiber paper is placed into a gel fixture.

[0052] (2) Mix 1 part tetraethyl orthosilicate, 8 parts methanol, 0.05 parts purified water and 0.001 parts boric acid, stir for 30 min, then add 0.5 parts fumed silica and mix evenly, stir for 5 min, then add 0.075 parts ammonia water and mix evenly, continue stirring for 5 min to obtain silica aerogel prepolymer mixture.

[0053] (3) The silica aerogel prepolymer mixture was pumped into the fiber paper by vacuum pump, and the mechanical wave vibration table was turned on. The vibration frequency was 60 Hz. After running for 10 minutes, a gravity of 0.2 times the weight of the wet gel paper was applied to the fiber paper. After running for another 10 minutes, the vibration table was turned off and left to stand for 30 minutes. To ensure the flatness and integrity of the fiber material, the permeable membrane layer on the surface of the fiber paper was removed.

[0054] (4) Place the wet silica aerogel paper on a tooling partition with uniform mesh, apply a gravity of 0.1 times its own weight on the wet silica aerogel paper, and put it together with the tooling into 99% methanol solvent. Solvent replacement is carried out at 50°C for 4 hours. Then, put it into hexamethyldisilazanol solution and carry out alkylation in situ chemical reaction at 55°C for 4 hours. Then, supercritical carbon dioxide drying is carried out to obtain silica nano-aerogel heat insulation paper.

[0055] The silica nano-aerogel insulation paper prepared in this embodiment has a smooth appearance, free from defects such as wrinkles, holes, and tears that would affect its use; its bulk density is 0.215 g / cm³. 3 Thermal conductivity (25℃) is 0.0164 W / (m•K); tensile strength (longitudinal) is 0.28-0.32 kN / m; resistance to high and low temperatures (-55-600℃, 1h); hydrophobicity is 98.9%; thermal weight loss at 600℃ is 2.72%; bending performance shows no cracks or breakage; vibration mass loss rate is 0.5%. Samples were taken from the length, width, and center of the same sheet of paper. Thickness test results are shown in Table 3. Specific photographs are available in [link to photograph]. Figure 5 .

[0056] Table 3 Third-party test data of silica nano-aerogel insulation paper (single sheet) – Example 2

[0057]

[0058] Comparative Example 2

[0059] Place a 0.08mm thick, 300×300mm glass fiber paper into the gel tooling, and follow the same steps as in Example 2.

[0060] The silica nano-aerogel insulation paper prepared in this comparative example has defects affecting its use, such as wrinkles, holes, tears, severe deformation, and uneven thickness; its bulk density is 0.295 g / cm³. 3The thermal conductivity (25℃) is 0.0188 W / (m•K); the tensile strength (longitudinal) is 0.18-0.29 kN / m; single sheet exhibits localized water penetration or poor hydrophobicity, with a vibration mass loss rate of 4.58%. Samples were taken from the length, width, and center of the same sheet; thickness test results are shown in Table 4. Specific photographs are available in the attached image. Figure 6 , Figure 7 .

[0061] Table 4 Third-party testing data of silica nano-aerogel insulation paper (single sheet) – Comparative Example 2

[0062]

[0063] In Comparative Example 2, because the fiber paper surface was not coated, the sol deposited on the fiber paper surface, resulting in excessive and uneven colloid thickness. In addition, because the fiber paper surface was not coated, the fiber material itself was relatively brittle, leading to holes and tears in the aerogel fiber paper. Example 3

[0064] A method for preparing a silica nano-aerogel heat insulation paper includes the following steps:

[0065] (1) A high silica fiber paper with a surface density of 20 g / m² was coated onto a 70 m long and 0.26 mm thick high silica fiber paper surface using a roll pressing method. 2 The polypropylene nonwoven fabric is then rolled into a roll, and the long roll of high silica fiber paper is then placed into a gel fixture.

[0066] (2) Mix 1 part tetraethyl orthosilicate, 5 parts methanol, 0.06 parts purified water and 0.00065 parts boric acid, stir for 30 min, then add 0.25 parts fumed silica and mix evenly, stir for 5 min, then add 0.065 parts ammonia water and mix evenly, continue stirring for 5 min to obtain silica aerogel prepolymer mixture.

[0067] (3) The silica aerogel prepolymer mixture was pumped into the fiber paper by vacuum pump to cover it by about 5 mm. The mechanical wave vibration table was turned on and the vibration frequency was 80 Hz. After running for 20 min, a gravity of 0.1 times the weight of the wet gel paper was applied to the fiber paper. After running for another 30 min, the vibration table was turned off and the paper was left to stand for 18 h.

[0068] (4) The roll of wet gel paper was placed in 99% methanol solvent and solvent was replaced at 55°C for 24 hours; then it was placed in trimethylmethoxysilane alcohol solution and alkylation in situ chemical reaction was carried out at 55°C for 8 hours; then supercritical carbon dioxide drying was carried out to obtain silica nano-aerogel heat insulation paper.

[0069] The silica nano-aerogel insulation paper prepared in this embodiment has a smooth appearance, free from defects such as wrinkles, holes, and tears that affect its use; its thickness is 0.32-0.36 mm; and its bulk density (g / cm³) is... 3 ≤0.3; Thermal conductivity (25℃) (W / (m•K)) ≤0.021; Tensile strength (longitudinal) (kN / m) ≥0.35; Resistance to high and low temperatures (-55-600℃, 1h); Water repellency ≥98%; Weight loss at 600℃ ≤3.0%; Bending performance: no cracks, no breakage; Vibration mass loss rate ≤0.5%; Paper product qualification rate ≥91%. The main test results are shown in Table 5.

[0070] Table 5 Third-party testing data for silica nano-aerogel insulation paper (roll material) – Example 3

[0071]

[0072] Other aspects of this invention that are not detailed herein are all conventional techniques known to those skilled in the art.

[0073] The scope of protection of this invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing a silica nano-aerogel thermal insulation paper, characterized by: The method comprises the following steps: (1) covering a permeable membrane layer on the surface of each fiber paper by any one of physical methods such as rolling, hot pressing and vacuum pressing, wherein the permeable membrane layer is a non-woven fabric of one or more than two of propylene, polyester, cotton, spandex and acrylic; (2) preparing a silica aerogel pre-polymer mixture, wherein the silica aerogel pre-polymer mixture comprises a silicon source, a solvent, water, a weak acid catalyst, a two-phase adhesive and an alkaline catalyst, the weak acid catalyst is boric acid, oxalic acid or phosphoric acid, and the two-phase adhesive is one or both of silica gel and fumed silica; (3) combining the silica aerogel pre-polymer mixture with the fiber paper to obtain a wet silica aerogel paper; the combination is placing the fiber paper in a gel tool, pumping the silica aerogel pre-polymer mixture into the fiber paper through a vacuum pump, then placing the gel tool on an ultrasonic vibration table or a mechanical wave vibration table, vibrating at a frequency of 40-80 Hz, applying a gravity of 0.1-0.5 times the weight of the wet silica aerogel paper to the fiber paper after running for 5-20 min, then continuing to run for 10-30 min, turning off the vibration table, and standing for 2-24 h to obtain the wet silica aerogel paper; (4) performing solvent replacement, hydrophobic modification and drying on the wet silica aerogel paper to obtain a silica nano-aerogel thermal insulation paper.

2. The method for preparing silica nano-aerogel insulating paper as described in claim 1, characterized in that: The silica aerogel pre-polymer mixture is prepared by the following steps: A. mixing the silicon source, the solvent, the water and the weak acid catalyst and stirring for 30 min; B. adding the two-phase adhesive in step A and stirring for 5 min; C. adding the alkaline catalyst in step B and stirring for 5 min to obtain the silica aerogel pre-polymer mixture.

3. The method for preparing silica nano-aerogel insulating paper as described in claim 2, characterized in that: The ratio of the silicon source, the solvent, the water, the weak acid catalyst, the two-phase adhesive and the alkaline catalyst is 1:(2-10):(0.05-0.15):(0.0005-0.0015):(0.15-0.75):(0.01-0.1); the silicon source is tetraethyl orthosilicate or tetramethyl orthosilicate; the solvent is methanol or ethanol; the water is pure water or distilled water; and the alkaline catalyst is one or a combination of more than two of ammonia, ammonium fluoride, formamide and dimethylformamide.

4. The method for preparing silica nano-aerogel insulating paper as described in claim 3, characterized in that: The fiber paper is one of glass fiber paper, high-silica fiber paper and ceramic fiber paper, and has a form of a sheet or a roll.

5. The method for preparing silica nano-aerogel insulating paper as described in claim 4, characterized in that: When the fiber paper is in the form of a sheet and has a thickness of not more than 0.5 mm, the permeable membrane layer on the surface of the fiber paper is removed before the solvent replacement of the wet silica aerogel paper.

6. The method for preparing silica nano-aerogel insulating paper as described in claim 4, characterized in that: When the fiber paper is in the form of a sheet and has a thickness of more than 0.5 mm, the permeable membrane layer on the surface of the fiber paper is retained before the solvent replacement of the wet silica aerogel paper.

7. The method for preparing silica nano-aerogel insulating paper as described in claim 5 or 6, characterized in that: The solvent replacement is placing the wet silica aerogel paper on a tool partition plate with uniformly distributed mesh, applying a gravity of 0.01-0.1 times the weight of the wet silica aerogel paper on each layer of the wet silica aerogel paper, then placing in a solvent, and replacing for 4-24 h at 40-65℃.

8. The method for preparing silica nano-aerogel insulating paper as described in claim 4, characterized in that: When the fibrous paper is in the form of a roll, a through membrane barrier is retained on the surface of the fibrous paper; the solvent replacement is placing the wet silica aerogel paper into a solvent, and replacing for 4-24 h at 40-65 ℃.

9. The method for preparing silica nano-aerogel insulating paper as described in claim 4, characterized in that: The hydrophobic modification is placing the wet silica aerogel paper after the solvent replacement into a hydrophobic agent alcohol solution, and reacting for 4-24 h at 40-65 ℃ to perform in-situ chemical reaction of alkylation, and the hydrophobic agent is one of hexamethyldisilazane, trimethylmethoxysilane and trimethylchlorosilane.

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