Preparation method of flexible silica aerogel composite thermal insulation material

Abstract

The application discloses a preparation method of a flexible silica aerogel composite thermal insulation material, and the method takes tetraethyl orthosilicate as a silicon source, adopts anhydrous ethanol and deionized water as solvents, carries out a hydrolysis reaction under an acidic condition to prepare a sol, and introduces a flexible glass fiber into the sol system, and then induces the sol to occur a gelation reaction under an alkaline condition to form a wet gel composite material. The wet gel is subjected to aging treatment to enhance the stability of a skeleton structure of the wet gel, and then is subjected to surface modification through solvent exchange and a silane reagent, and finally is dried under a normal pressure condition to obtain the flexible silica aerogel composite thermal insulation material. The composite material prepared by the method has a continuous nano-porous structure and good flexibility, is not prone to structural damage under bending or compression conditions, has excellent thermal insulation performance and fireproof performance, and can be widely applied to the fields of building thermal insulation, industrial pipeline thermal insulation and flexible protection.

Description

Technical Field

[0001] This invention belongs to the field of advanced thermal insulation materials technology, specifically relating to a method for preparing a flexible silica aerogel composite thermal insulation material. Background Technology

[0002] Silica aerogel is a lightweight inorganic material with a three-dimensional nanoporous network structure. Due to its small pore size, large specific surface area, and limited gas thermal conduction, it exhibits an extremely low thermal conductivity and is considered one of the best-performing solid materials known to date. It has broad application potential in building energy conservation, aerospace, industrial equipment, and pipeline insulation.

[0003] However, traditional silica aerogels are typically formed by a sol-gel reaction, with their framework consisting of nanoscale particles connected by necks, resulting in a loose structure and low mechanical strength. During the drying process, the evaporation of solvent in the pores of the wet gel generates significant capillary stress, which can easily lead to significant shrinkage or even structural failure of the aerogel. This results in a material that exhibits obvious brittleness, making it difficult to meet the requirements of flexibility and mechanical stability for practical engineering applications.

[0004] To reduce the damage to the structure caused by capillary forces during the drying process, existing technologies often employ supercritical drying methods, where the solvent directly transforms from a liquid phase to a gas phase in a supercritical state, thereby avoiding capillary stress generated at the liquid-gas interface. Although this method can better maintain the integrity of the aerogel's nanostructure, the process requires high temperature and pressure conditions, placing high demands on equipment and operation, consuming a lot of energy, posing significant safety risks, and making continuous and large-scale production difficult, which severely restricts the industrial application of silica aerogel materials.

[0005] On the other hand, to improve the mechanical properties of aerogel materials, researchers have attempted to composite aerogels with reinforcements such as glass fibers, ceramic fibers, or polymer fibers. However, existing composite methods mostly involve simply introducing fibers into the sol system or attaching aerogel particles to the fiber surface through post-coating. The interfacial bonding mainly relies on physical adsorption or mechanical interlocking, resulting in limited interfacial bonding strength. These fibers are prone to detachment or pulverization during bending, compression, or long-term use, making it difficult to fully utilize the synergistic reinforcement and toughening effect of the fiber reinforcement on the aerogel skeleton.

[0006] Therefore, how to form a continuous and stable nanoporous structure of silica aerogel in situ within a flexible fiber-reinforced skeleton through reasonable process design without relying on supercritical drying conditions, and how to prepare aerogel composite materials with good flexibility, structural integrity and excellent thermal insulation performance under normal pressure drying conditions, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the problems of high brittleness, poor mechanical properties, reliance on supercritical drying, and difficulty in large-scale preparation of existing silica aerogel materials, this invention aims to provide a method for preparing a flexible silica aerogel composite insulation material. This method uses flexible fiber tapes as a reinforcing skeleton and prepares a flexible silica aerogel composite insulation material through a sol-gel process combined with atmospheric pressure drying technology. This material possesses excellent flexibility, thermal insulation performance, and fire resistance.

[0008] This method introduces flexible glass fiber tape into the sol-gel reaction system, enabling the in-situ construction of a silica aerogel network within the fiber-reinforced framework. Combined with solvent modification and atmospheric pressure drying, this significantly improves the flexibility and structural stability of the material while ensuring the integrity of the aerogel nanoporous structure. As a result, a flexible silica aerogel composite insulation material that is crack-free, non-pulverizing, bendable, cuttable, and possesses excellent thermal insulation and fire resistance properties is prepared.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a flexible silica aerogel composite thermal insulation material includes the following steps: (1) Sol preparation: Tetraethyl orthosilicate (TEOS) is used as the silicon source. It is mixed with anhydrous ethanol, deionized water and catalyst hydrochloric acid (HCl) in a certain proportion and stirred at room temperature to carry out hydrolysis reaction to form a uniform and stable silica sol.

[0010] (2) Impregnation and gelation: The flexible glass fiber tape is impregnated in the sol prepared in the above steps to ensure full wetting. Then, ammonia water (NH3·H2O) is added to the system as a gel catalyst to adjust the pH value of the system. Under alkaline conditions, the silica sol is induced to undergo hydrolysis-condensation reaction, so that the silica gel network is formed in situ on the surface and inside of the flexible fiber tape, and fiber-reinforced wet gel composite material is obtained.

[0011] (3) Aging: The wet gel composite material obtained above is placed in a specific aging solution (such as a mixed solution of ethanol and ammonia) and aged at a certain temperature. This process helps the gel network to further condense and strengthen, forming a more robust skeleton structure, thereby reducing shrinkage and cracking during the subsequent drying process.

[0012] (4) Solvent Modification: The aged gel composite material was subjected to surface modification through solvent exchange and silane reagents in sequence. The solvent exchange involved immersion in anhydrous ethanol and n-hexane in sequence, while the surface modification involved immersion in a trimethylchlorosilane (TMCS)-n-hexane mixture. The hydrophobic groups in the modifier react with the hydrophilic groups (such as hydroxyl groups -OH) on the gel skeleton, replacing them with hydrophobic groups. This step is crucial, as it changes the gel skeleton from hydrophilic to hydrophobic, greatly eliminating the huge capillary forces generated by water evaporation during atmospheric pressure drying. This is key to achieving atmospheric pressure drying and obtaining a good product.

[0013] (5) Drying under normal pressure: The modified gel composite material is dried in an oven at a certain temperature under normal pressure. Solvents and water evaporate slowly during this process, and finally a silica aerogel / fiber tape composite material with low density, high porosity, flexibility and excellent thermal insulation properties is obtained.

[0014] Further, in step (1), the volume ratio of anhydrous ethanol to deionized water is 2-6:1, and the volume ratio of tetraethyl orthosilicate to solvent is 0.3-0.6:1; step (1) involves adding hydrochloric acid to adjust the acidic conditions for hydrolysis, and the final concentration of hydrochloric acid in the mixed system in step (1) is 0.02-0.05M.

[0015] Furthermore, in step (2), the flexible fiber strip is a glass fiber fabric.

[0016] Furthermore, in step (2), the amount of ammonia added is such that the pH value of the entire reaction system is adjusted to the range of 8 to 9.

[0017] Further, in step (3), the wet gel composite material is immersed in an aging solvent for aging treatment. The aging solvent is an ethanol-ammonia solution with a volume ratio of 0.8-1.2:1, the ammonia concentration in the aging solvent is 0.2-0.3M, the aging temperature is 40-60℃, and the aging time is 12-24 hours.

[0018] Furthermore, in step (4), the specific process is as follows: S1: The aged gel composite material is first immersed in anhydrous ethanol and solvent exchange is carried out at room temperature for 10-30 hours. S2: Then immerse in n-hexane and perform solvent exchange at room temperature for 10-30 hours; S3: Finally, immerse in a trimethylchlorosilane-n-hexane mixture with a volume ratio of 1:8-10 and carry out modification treatment at room temperature for 10-30 hours.

[0019] Furthermore, in step (5), the temperature of the atmospheric pressure drying is 60-80℃, and the drying time is 4-6 hours.

[0020] To verify the rationality of the process parameters of this invention, in addition to adjusting the amount of ammonia, a comparative analysis was conducted by examining the gelation behavior under different conditions and the final product state. The study found that introducing an appropriate amount of ammonia-ethanol solution during the aging process helps promote further condensation and structural strengthening of the gel skeleton, thereby effectively reducing the risk of shrinkage and structural damage during subsequent atmospheric pressure drying. Compared to samples that were not aged or were subjected to unsuitable aging conditions, the composite material prepared using the aging system of this invention exhibits superior structural integrity and flexibility.

[0021] Compared with the prior art, the present invention has the following significant advantages: (1) Excellent flexibility and mechanical properties: The present invention adopts the fiber-reinforced in-situ gel construction method, so that the silica aerogel network and the flexible fiber belt form a stable three-dimensional composite structure. The fiber skeleton can effectively share the external load, thereby significantly improving the brittleness of the aerogel material and making the resulting composite material have good bending and anti-destruction ability.

[0022] (2) Simple process, low cost and high safety: This invention successfully replaces the supercritical drying process with the atmospheric pressure drying process through the key "solvent modification" step. This avoids the use of expensive and dangerous high-pressure equipment, significantly reduces production costs and energy consumption, and makes large-scale industrial production possible.

[0023] (3) Excellent heat insulation and fire resistance: The prepared composite material retains the nanoporous structure characteristics of silica aerogel, has a low thermal conductivity, and has excellent heat insulation performance; at the same time, its main components are silica and refractory fiber, which gives the material good high temperature resistance and flame retardant properties.

[0024] (4) Broad application prospects: The flexible silica aerogel composite insulation material prepared by this invention is lightweight, flexible, easy to cut and install, and is suitable for applications such as insulation of irregular pipes, building energy conservation, heat insulation and flexible protection of new energy equipment, thus expanding the engineering application scope of aerogel materials. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the implementation of this invention; Figure 2 This is a 200μm SEM image of the fiber-coating effect of the flexible silica aerogel prepared in Example 1 of this invention; Figure 3 This is the XRD pattern of the silica aerogel powder in Example 1 of the present invention; Figure 4This is a high-temperature thermal infrared image of the flexible silica aerogel composite material prepared in Example 1 of the present invention; Figure 5 These are the thermal conductivity test data of the flexible silica aerogel composite material prepared in Example 1 of this invention; Figure 6 This is a flame-retardant and heat-resistant optical image of the flexible silica aerogel composite material prepared in Example 1 of this invention; Figure 7 These are Fourier transform infrared (FT-IR) analysis images of the flexible silica aerogel composite materials prepared in Examples 1-3 of this invention; Figure 8 This refers to the hydrophobic angle of the flexible silica aerogel composite material prepared in Example 1 of this invention; Figure 9 This is a stress-strain curve of the flexible silica aerogel composite material prepared in Example 1 of the present invention.

[0026] Figure 10 This is a 50μm SEM image of the fiber-coating effect of the flexible silica aerogel prepared in Example 1 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Example 1: Preparation of a flexible silica aerogel composite insulation material, including the following steps (control). Figure 1 ): (1) Sol preparation: In a beaker, add 44 ml of anhydrous ethanol, 26 ml of tetraethyl orthosilicate (TEOS) and 10.8 ml of deionized water in sequence and stir until homogeneous. Then, use a dropper to slowly add 2.8 mL of 1 mol / L hydrochloric acid (HCl) as a catalyst and continue to stir magnetically for 60 minutes to form a homogeneous and transparent silica sol.

[0028] (2) Impregnation and gelation: Take a piece of glass fiber tape measuring 10cm × 10cm and completely impregnate it in the prepared sol. After standing at room temperature for about 30 minutes, slowly add 7ml of 0.5mol / L ammonia water (NH3·H2O) to the system. Adjust the pH of the mixture to about 8 with ammonia water, and gently shake the container to mix it evenly. After standing, it can be observed that the sol gradually transforms into a non-flowing wet gel wrapped with fiber cloth within 30 minutes.

[0029] (3) Aging: The formed wet gel composite material, along with its container, was transferred to a sealed environment containing a 1:1 volume ratio of ethanol and ammonia (0.5 mol / L) as the aging solution. The mixture was aged in a constant temperature oven at 40°C for 12 hours.

[0030] (4) Solvent modification: After aging, the gel composite material was taken out and first immersed in anhydrous ethanol for solvent exchange at room temperature for 24 hours; then immersed in n-hexane for solvent exchange at room temperature for 24 hours; then immersed in a hexane solution of trimethylchlorosilane (TMCS) (volume ratio 1:9) for modification treatment at room temperature for 24 hours.

[0031] (5) Drying under normal pressure: After modification, the composite material is taken out and the surface of the modified agent is gently rinsed with n-hexane. Then, it is placed in an 80°C forced-air drying oven and dried under normal pressure for 4 hours to obtain the flexible silica aerogel composite insulation material.

[0032] SEM images of the fiber-coating effect of the flexible silica aerogel prepared in Example 1 of this invention are shown below. Figure 2 and Figure 10 As shown, silica aerogel grows uniformly in situ on the surface of glass fibers and in the gaps between fibers, forming a continuous three-dimensional nanoporous network. This indicates that the method of the present invention can achieve a tight composite of aerogel and fiber reinforcement, rather than a simple physical adhesion.

[0033] The XRD pattern of the silica aerogel powder in Example 1 is shown below. Figure 3 As shown, the sample exhibits typical broad dispersion peaks, indicating that the prepared silica aerogel has an amorphous structure, which is consistent with the structural characteristics of aerogel materials.

[0034] The high-temperature thermal infrared image of the flexible silica aerogel composite material prepared in Example 1 of this invention is as follows: Figure 4 As shown, the temperature rise on the back side of the composite material is significantly limited under the action of a high-temperature heat source, indicating that the material has excellent thermal insulation capabilities and stable transient thermal protection performance.

[0035] The thermal conductivity test data of the flexible silica aerogel composite material prepared in Example 1 of this invention are as follows: Figure 5 As shown, the composite material prepared by this invention can still maintain a low thermal conductivity under normal pressure drying conditions, demonstrating the effectiveness of solvent modification and synergistic control of process parameters.

[0036] Flame-retardant and heat-resistant optical images of the flexible silica aerogel composite material prepared in Example 1 of this invention are shown below. Figure 6As shown, the material did not exhibit significant combustion or structural collapse under open flame or high temperature conditions, verifying its excellent high-temperature resistance and flame-retardant properties. From Figures 4-6 The test results show that the composite material of this invention has good high-temperature resistance.

[0037] The Fourier transform infrared (FT-IR) analysis diagram of the flexible silica aerogel composite material prepared in Example 1 of this invention is shown below. Figure 7 As shown, characteristic absorption peaks of Si-O-Si and related absorption peaks of hydrophobic groups can be observed, indicating that the aerogel framework was successfully formed and the surface modification reaction was effectively carried out.

[0038] The hydrophobic angle results of the flexible silica aerogel composite material prepared in Example 1 of this invention are shown in the figure. Figure 8 The data shows that the contact angle of the composite material surface is greater than 140°, indicating that the material has significant hydrophobicity, which is beneficial to reducing capillary stress during the normal pressure drying process and improving environmental stability.

[0039] The stress-strain curve of the flexible silica aerogel composite material prepared in Example 1 of this invention is shown in the figure below. Figure 9 As shown, Example 2 describes the preparation of a flexible silica aerogel composite insulation material, comprising the following steps: (1) Sol preparation: In a beaker, add 44 ml of anhydrous ethanol, 26 ml of tetraethyl orthosilicate (TEOS) and 10.8 ml of deionized water in sequence and stir until homogeneous. Then, use a dropper to slowly add 2.8 mL of 1 mol / L hydrochloric acid (HCl) as a catalyst and continue to stir magnetically for 60 minutes to form a homogeneous and transparent silica sol.

[0040] (2) Impregnation and gelation: Take a piece of glass fiber tape measuring 10cm × 10cm and completely impregnate it in the prepared sol. After standing at room temperature for about 30 minutes, slowly add 8.5ml of 0.5mol / L ammonia water (NH3·H2O) to the system. Adjust the pH of the mixture to about 8.5 with ammonia water, and gently shake the container to mix it evenly. After standing, it can be observed that the sol gradually transforms into a non-flowing wet gel wrapped with fiber cloth within 20 minutes.

[0041] (3) Aging: The formed wet gel composite material, along with its container, was transferred to a sealed environment containing a 1:1 volume ratio of ethanol and ammonia (0.5 mol / L) as the aging solution. The mixture was aged in a constant temperature oven at 40°C for 12 hours.

[0042] (4) Solvent modification: After aging, the gel composite material was taken out and first immersed in anhydrous ethanol for solvent exchange at room temperature for 24 hours; then immersed in n-hexane for solvent exchange at room temperature for 24 hours; then immersed in a hexane solution of trimethylchlorosilane (TMCS) (volume ratio 1:9) for modification treatment at room temperature for 24 hours.

[0043] (5) Drying under normal pressure: After modification, the composite material is taken out and the surface of the modified agent is gently rinsed with n-hexane. Then, it is placed in an 80°C forced-air drying oven and dried under normal pressure for 4 hours to obtain the flexible silica aerogel composite insulation material.

[0044] Example 3: Preparation of a flexible silica aerogel composite insulation material, including the following steps: (1) Sol preparation: In a beaker, add 44 ml of anhydrous ethanol, 26 ml of tetraethyl orthosilicate (TEOS) and 10.8 ml of deionized water in sequence and stir until homogeneous. Then, use a dropper to slowly add 2.8 mL of 1 mol / L hydrochloric acid (HCl) as a catalyst and continue to stir magnetically for 60 minutes to form a homogeneous and transparent silica sol.

[0045] (2) Impregnation and gelation: Take a piece of glass fiber tape measuring 10cm × 10cm and completely impregnate it in the prepared sol. After standing at room temperature for about 30 minutes, slowly add 10.0 ml of 0.5mol / L ammonia water (NH3·H2O) to the system. Adjust the pH of the mixture to about 9.0 with ammonia water and gently shake the container to mix it evenly. After standing, it can be observed that the sol gradually transforms into a non-flowing wet gel wrapped with fiber cloth within 10 minutes.

[0046] (3) Aging: The formed wet gel composite material, along with its container, was transferred to a sealed environment containing a 1:1 volume ratio of ethanol and ammonia (0.5 mol / L) as the aging solution. The mixture was aged in a constant temperature oven at 40°C for 12 hours.

[0047] (4) Solvent modification: After aging, the gel composite material was taken out and first immersed in anhydrous ethanol for solvent exchange at room temperature for 24 hours; then immersed in n-hexane for solvent exchange at room temperature for 24 hours; then immersed in a hexane solution of trimethylchlorosilane (TMCS) (volume ratio 1:9) for modification treatment at room temperature for 24 hours.

[0048] (5) Drying under normal pressure: After modification, the composite material is taken out and the surface of the modified agent is gently rinsed with n-hexane. Then, it is placed in an 80°C forced-air drying oven and dried under normal pressure for 4 hours to obtain the flexible silica aerogel composite insulation material.

[0049] Fourier transform infrared (FT-IR) analysis images of the flexible silica aerogel composite materials prepared in Examples 1-3 of this invention are shown below. Figure 7 As shown, based on the provided infrared spectral data, the spectral characteristics of this composite material are consistent with the expected results of silica + glass fiber modified with TMCS hydrophobicity, for the following reasons: Si-O-Si characteristic peaks: in the 1000-1100 cm⁻¹ range -1 There should be strong absorption nearby, corresponding to the silicon-oxygen bond framework in silica and glass fiber.

[0050] Si-CH3 characteristic peak: at 2950 cm⁻¹ -1 and 2850 cm -1 There is a distinct absorption peak nearby, corresponding to the methyl (-CH3) functional group introduced by TMCS modification, proving that the hydrophobic modification was successful.

[0051] Comparative Example 1: A flexible silica aerogel composite insulation material was prepared, comprising the following steps: (1) Sol preparation: In a beaker, add 44 ml of anhydrous ethanol, 26 ml of tetraethyl orthosilicate (TEOS) and 10.8 ml of deionized water in sequence and stir until homogeneous. Then, use a dropper to slowly add 2.8 mL of 1 mol / L hydrochloric acid (HCl) as a catalyst and continue to stir magnetically for 60 minutes to form a homogeneous and transparent silica sol.

[0052] (2) Impregnation and gelation: Take a piece of glass fiber tape measuring 10cm × 10cm and completely impregnate it in the prepared sol. After standing at room temperature for about 30 minutes, slowly add 5.0 ml of 0.5mol / L ammonia water (NH3·H2O) to the system and gently shake the container to mix it evenly. After standing, it can be observed that the sol gradually transforms into a non-flowing wet gel wrapped with fiber cloth within 120 minutes.

[0053] (3) Aging: The formed wet gel composite material, along with its container, was transferred to a sealed environment containing a 1:1 volume ratio of ethanol and ammonia (0.5 mol / L) as the aging solution. The mixture was aged in a constant temperature oven at 40°C for 12 hours.

[0054] (4) Solvent modification: After aging, the gel composite material was taken out and first immersed in anhydrous ethanol for solvent exchange at room temperature for 24 hours; then immersed in n-hexane for solvent exchange at room temperature for 24 hours; then immersed in a hexane solution of trimethylchlorosilane (TMCS) (volume ratio 1:9) for modification treatment at room temperature for 24 hours.

[0055] (5) Drying under normal pressure: After modification, the composite material is taken out and the surface of the modified agent is gently rinsed with n-hexane. Then, it is placed in a forced-air drying oven at 80°C and dried under normal pressure for 4 hours.

[0056] Comparative Example 2: A flexible silica aerogel composite insulation material was prepared, comprising the following steps: (1) Sol preparation: In a beaker, add 44 ml of anhydrous ethanol, 26 ml of tetraethyl orthosilicate (TEOS) and 10.8 ml of deionized water in sequence and stir until homogeneous. Then, use a dropper to slowly add 2.8 mL of 1 mol / L hydrochloric acid (HCl) as a catalyst and continue to stir magnetically for 60 minutes to form a homogeneous and transparent silica sol.

[0057] (2) Impregnation and gelation: Take a piece of glass fiber tape measuring 10cm × 10cm and completely impregnate it in the prepared sol. After standing at room temperature for about 30 minutes, slowly add 12.0 ml of 0.5mol / L ammonia water (NH3·H2O) to the system and gently shake the container to mix it evenly. After standing, it can be observed that the sol gradually transforms into a non-flowing wet gel wrapped with fiber cloth within 5 minutes.

[0058] (3) Aging: The formed wet gel composite material, along with its container, was transferred to a sealed environment containing a 1:1 volume ratio of ethanol and ammonia (0.5 mol / L) as the aging solution. The mixture was aged in a constant temperature oven at 40°C for 12 hours.

[0059] (4) Solvent modification: After aging, the gel composite material was taken out and first immersed in anhydrous ethanol for solvent exchange at room temperature for 24 hours; then immersed in n-hexane for solvent exchange at room temperature for 24 hours; then immersed in a hexane solution of trimethylchlorosilane (TMCS) (volume ratio 1:9) for modification treatment at room temperature for 24 hours.

[0060] (5) Drying under normal pressure: After modification, the composite material is taken out and the surface of the modified agent is gently rinsed with n-hexane. Then, it is placed in a forced-air drying oven at 80°C and dried under normal pressure for 4 hours.

[0061] The performance parameters of the flexible silica aerogel composite insulation material obtained in this embodiment were measured, as shown in Table 1.

[0062] Table 1. Performance parameters of flexible silica aerogel composite insulation materials .

[0063] Comparing the above examples and comparative examples, it can be seen that the preparation method provided by the present invention effectively regulates the gel properties and composite process by controlling the concentration of ammonia (NH3·H2O). The key lies in the use of a "solvent modification" step, which allows for the acquisition of a structurally intact and highly flexible silica aerogel composite material under normal pressure. This material combines the inherent low density, low thermal conductivity, and high hydrophobicity of aerogels with excellent flexibility and mechanical integrity, exhibiting outstanding comprehensive performance and making it suitable for use as a high-efficiency flexible thermal insulation material. Furthermore, this method requires simple equipment and has low raw material costs, which is conducive to large-scale production.

[0064] In this invention, ammonia water acts as an alkaline catalyst, and its amount directly determines the pH value of the sol-gel system, thus significantly affecting the condensation rate, gelation behavior, and the uniformity and stability of the final gel network structure of the silica sol. When the amount of ammonia water is low and the system pH is low, the silanol condensation reaction rate is slow, making it difficult to form a continuous and complete gel network within the fiber skeleton, resulting in excessively long gelation times or even failure to gel (as in Comparative Example 1). Conversely, when the amount of ammonia water is too high and the system pH is too high, the condensation reaction is too fast, easily leading to rapid local nucleation and particle coarsening, resulting in a loose gel skeleton, insufficient interfacial bonding, and easy powdering or structural damage after drying (as in Comparative Example 2). Therefore, by controlling the amount of ammonia water added to maintain a system pH of approximately 8-9, this invention can obtain a uniform, continuous skeleton, and firmly bonded aerogel network with fiber reinforcement while ensuring gelation efficiency. This is one of the key factors for achieving high flexibility and atmospheric pressure drying molding.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention. The protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a flexible silica aerogel composite thermal insulation material, characterized in that, Includes the following steps: (1) Preparation of sol: Using tetraethyl orthosilicate as the silicon source, anhydrous ethanol and deionized water as solvents, a hydrolysis reaction was carried out under acidic conditions to prepare the sol; (2) Impregnation and gelation: The flexible glass fiber tape is impregnated in the sol obtained in step (1), and then ammonia is added to adjust the alkalinity of the system, so that the sol undergoes a gelation reaction on the surface and inside of the flexible fiber tape to form a wet gel composite material. (3) Aging: The wet gel composite material obtained in step (2) is subjected to aging treatment to strengthen its network structure; (4) Solvent modification: The gel composite material aged in step (3) is subjected to surface modification by solvent exchange and silane reagents in sequence; (5) Drying: The gel composite material modified in step (4) is dried under normal pressure to finally obtain the flexible silica aerogel composite insulation material.

2. The method according to claim 1, characterized in that... In step (1), the volume ratio of anhydrous ethanol to deionized water is 2-6:1, and the volume ratio of tetraethyl orthosilicate to solvent is 0.3-0.6:

1. Step (1) involves adding hydrochloric acid to adjust the acidic conditions for hydrolysis. The final concentration of hydrochloric acid in the mixed system in step (1) is 0.02-0.05M.

3. The method according to claim 1, characterized in that, In step (2), the flexible fiber tape is a glass fiber fabric.

4. The method according to claim 1, characterized in that, In step (2), the amount of ammonia added is such that the pH value of the entire reaction system is adjusted to the range of 8 to 9.

5. The method according to claim 1, characterized in that... In step (3), the wet gel composite material is immersed in an aging solvent for aging treatment. The aging solvent is an ethanol-ammonia solution with a volume ratio of 0.8-1.2:1, the ammonia concentration in the aging solvent is 0.2-0.3M, the aging temperature is 40-60℃, and the aging time is 12-24 hours.

6. The method according to claim 1, characterized in that... In step (4), the specific process is as follows: S1: The aged gel composite material is first immersed in anhydrous ethanol and solvent exchange is carried out at room temperature for 10-30 hours. S2: Then immerse in n-hexane and perform solvent exchange at room temperature for 10-30 hours; S3: Finally, immerse in a trimethylchlorosilane-n-hexane mixture with a volume ratio of 1:8-10 and carry out modification treatment at room temperature for 10-30 hours.

7. The method according to claim 1, characterized in that... In step (5), the temperature of the atmospheric pressure drying is 60-80℃ and the drying time is 4-6 hours.

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