Aerogel blanket monolithic gel process based on micro-pressurized impregnation

Abstract

The application discloses a kind of based on micro-pressure impregnation aerogel felt integral gel process, including substrate pretreatment and roll-shaped forming, sol preparation, micro-pressure impregnation, pressure relief gel, aging, drying and other core steps: select glass fiber mat and other various substrates (can be calcined to 500~800 DEG C impurity removal), after roll forming vertically into special equipment, 8~20wt% solid content sol is injected under-0.04~‑0.2MPa micro-pressure environment, slowly pressure relief is completed after impregnation 30~120min integral gel, after aging, drying to get finished product.Process is designed through accurate micro-pressure control, coupling agent optimization, etc.Adapt to low strength and calcined substrate, product breakage rate≤3%, sol penetration rate≥98%, the qualified rate is increased to more than 95%, thermal conductivity is as low as 0.017W / (m・K), with the advantages of high production efficiency, low cost, wide adaptability, suitable for large-scale production of thermal insulation materials in many fields.

Description

Technical Field

[0001] This invention belongs to the technical field of aerogel material production, specifically relating to an integral gelation process for aerogel felt based on micro-pressure impregnation. Background Technology

[0002] Aerogel felt is a functional thermal insulation material formed by combining aerogel materials with flexible fiber felt. It combines ultra-low thermal conductivity with flexible and cuttable properties, and its application demand is increasing in fields such as building energy conservation, industrial insulation, and aerospace. As application scenarios increase the requirements for material purity and thermal insulation stability, flexible substrates such as glass fiber felt and ceramic fiber felt have become mainstream, while the application of materials such as polymer foam and wet-laid fiber paper is gradually expanding. Some high-end fields also require the substrate to be calcined to remove impurities and harmful substances, and to improve high-temperature resistance and purity.

[0003] However, existing continuous production technologies for aerogel mats have significant shortcomings: the traditional "layout-impregnation-step gelation-winding" process easily leads to tearing and fuzzing of the flexible substrate, and uneven sol enrichment; the overall impregnation method suffers from insufficient penetration and insufficient adhesive in the roll core; and the substrate after calcination is difficult to achieve continuous overall gelation because the surface wetting functional groups are destroyed. Existing negative pressure assisted impregnation technology does not precisely define the range; strong negative pressure easily damages the substrate and compromises gel stability, while weak negative pressure results in insufficient penetration. Neither can synergistically optimize the uniformity of penetration, the integrity of the substrate, and the stability of the gel, thus restricting the large-scale application of aerogel mats in high-end fields. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a micro-pressure impregnation-based integral gelation process for aerogel felts that enables efficient, high-quality, and continuous production of various types of substrates.

[0005] This invention is achieved through the following technical solution: A monolithic gelation process for aerogel mats based on micro-pressure impregnation includes the following core steps: (1) Select an aerogel felt substrate, wherein the substrate is one or more of glass fiber felt, ceramic fiber felt, quartz fiber felt, pre-oxidized fiber felt, carbon fiber felt, alumina fiber felt, basalt fiber felt, polymer foam, wet-laid fiber paper, and chopped fiber felt; if calcination is required to remove impurities, place the substrate in a calcination furnace for heat preservation and then allow it to cool naturally. (2) Clean the surface of the pretreated substrate, lay it flat on the mesh cloth and roll it into a cylindrical roll; (3) Prepare a sol system with a solid content of 8~20wt%, wherein the sol is one or more of SiO2, Al2O3, ZrO2, silicon-aluminum composite, RF sol, and inorganic silica sol; (4) Place the roll-shaped substrate vertically into the micro-pressure impregnation-integral gelation equipment, evacuate to -0.04~-0.2MPa and maintain for 15~20min, then inject sol at a rate of 5~15L / min until the substrate is completely submerged, maintain this negative pressure environment for impregnation for 30~120min, and control the internal temperature of the equipment to 20~60℃. (5) Depressurize at a rate of ≤0.02MPa / min and let stand for 0.1~6h to complete the overall gelation; (6) Immerse the gelled roll material in a methanol or ethanol solution at 40-80°C for 12-48 hours, changing the soaking solution 2-4 times during the period; (7) Dry the aged material by means of normal pressure drying, vacuum drying or supercritical drying, and blow off the loose powder on the surface after drying to obtain the finished product.

[0006] Furthermore, the conditions for calcination and impurity removal in step (1) are: calcination temperature 500~800℃, holding time 2~6h.

[0007] Furthermore, in step (2), the surface cleaning is performed by blowing with compressed air at 0.2~0.4MPa, and the mesh fabric is non-woven fabric, nylon mesh fabric, Teflon mesh fabric or polyethylene mesh fabric.

[0008] Furthermore, in step (3), the pH value of the sol is controlled to be an acidic system of 3-5 or an alkaline system of 8-10. The acidic system is suitable for silica-based sol, and the alkaline system is suitable for aluminum-based sol.

[0009] Furthermore, in step (3), 0.5~2wt% of an inorganic silane coupling agent is added to the sol for the calcined aerogel felt substrate.

[0010] Furthermore, in step (4), a sol flow gap of 5~10mm is left between the rolled substrate and the wall of the micro-pressure impregnation-integral gelation equipment, and the negative pressure fluctuation range is ≤±0.02MPa.

[0011] Furthermore, in step (4), the impregnation pressure of the polymer foam cotton and wet-laid fiber paper substrates with low strength is controlled within -0.08MPa; and the impregnation pressure of the calcined substrate is controlled above -0.1MPa.

[0012] Further, the conditions for vacuum drying in step (7) are: temperature 60~100℃, vacuum degree -0.05~-0.09MPa, drying time 6~16h; the conditions for supercritical drying are: pressure 12~16MPa, temperature 40~60℃, drying time 5~12h.

[0013] Furthermore, the inorganic silane coupling agent is KH550.

[0014] Furthermore, in step (7), the purging after drying is carried out with compressed air of 0.2~0.3MPa, and the finished aerogel felt is a thin product with a thickness of less than 3mm or a thick product with a thickness of more than 50mm.

[0015] The beneficial effects of this invention are: 1. Avoid substrate damage: Roll forming eliminates the need for unwinding and rewinding, completely preventing tearing and fuzzing issues. The product breakage rate is ≤3%, significantly improving structural integrity.

[0016] 2. Excellent uniform impregnation effect: The -0.04~-0.2MPa micro-pressure range creates a gentle and efficient penetration force, with a solvent penetration rate of ≥98%, solving the problem of insufficient adhesive in the core.

[0017] 3. Adaptable to calcined substrates: No organic impurities need to be introduced. Through micro-pressure control and coupling agent optimization, continuous production can be achieved, increasing efficiency by more than 80% and reducing costs by 40%.

[0018] 4. Wide process adaptability: The core processes are simple, adaptable to various flexible substrates and products of different thicknesses, covering application needs in multiple fields.

[0019] 5. Stable product quality: The pass rate has been increased to over 95%, the thermal conductivity (25℃) is as low as 0.017W / (m・K), and the mechanical stability and thermal insulation performance are excellent. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings.

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] 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.

[0023] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0024] In the description of this invention, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. It should be noted that the terms "comprising," "including," or any other variations are intended to cover a 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 a process, method, article, or apparatus. Example 1

[0025] This embodiment provides a monolithic gelation process for aerogel mats based on micro-pressure impregnation, the specific steps of which are as follows: Fiber felt pretreatment: The pre-oxidized fiber felt is subjected to plasma treatment with a power of 550W for 5 minutes to improve the surface activity of the fiber. Traction step: The pretreated substrate is guided into the first set of pressure rollers. Before entering, a longitudinal tension of 150 N / m is applied through the tension control system to ensure that the fiber felt remains flat during the impregnation process and to avoid wrinkles and excessive stretching. Venting steps: Adjust the spacing of the pressure rollers to 7.5mm, introduce the traction substrate into the pressure roller device and vent it using a 1.5MPa linear pressure. The pressure roller device is set up close to the impregnation tank. Sol-gel step: Mix tetraethyl orthosilicate, ethanol, water and modifier in a certain volume ratio, adjust the pH to 4 with hydrolysis catalyst, react at a constant temperature of 55℃ for 4 hours, stir to form a uniform and stable silica sol, add a certain proportion of gel catalyst and pump into the impregnation tank. Dip coating step: Guide the drained substrate into the dip tank and immerse it for 25 seconds; Gradient dredging and roller pressing: Adjust the spacing of the dredging rollers to 7.5mm, draw the impregnated wet felt out of the impregnation tank, and after initial squeezing by the dredging rollers, enter the dredging section with an inclination angle of 10° for dredging. Then, through precise control of the gap and pressure of the pressure rollers, precise pressing and shaping are performed, and excess glue is squeezed out from the side. Gel and surface cleaning: The impregnated fiber felt is gelled using a microwave device at 35℃ and 1500W. Immediately after gelation, the surface is smoothed using a scraper with a gap of 7.5mm to remove excess colloid. Breathable mesh treatment: Cover the upper and lower surfaces of the aerogel felt with a carpet mesh to ensure air permeability between layers and to ensure uniform distribution of the adhesive on the surface. Aging, modification and drying: The aerogel felt treated with a mesh screen is subjected to aging, modification and drying steps in sequence to finally obtain a silica aerogel felt with complete structure and smooth appearance.

[0026] Comparative Example 1: This comparative example uses the traditional production line flat-laying impregnation gel method. The difference from the process in Example 1 is that the traction step in Example 1 is replaced with the relevant steps of the mesh permeability treatment. The specific process steps are as follows: ① Substrate pretreatment (same as Example 1: pre-oxidized fiber felt is subjected to plasma treatment with a power of 550W for 5 minutes to improve fiber surface activity). ②The substrate is laid flat on the production line without the need for roll forming, and the traction and emptying steps in Example 1 are not performed; ③ Prepare a sol of the same specifications (same as in Example 1: mix tetraethyl orthosilicate, ethanol, water and modifier in a certain volume ratio, adjust the pH to 4 with hydrolysis catalyst, react at a constant temperature of 55℃ for 4 hours, stir to form a uniform and stable silica sol, and add a certain proportion of gel catalyst). ④Under normal pressure, the flat substrate is immersed in the above sol without performing the dip coating steps in Example 1. The immersion time is 25 seconds, the same as in Example 1. ⑤ After applying the flat gel (not a whole gel), skip the gradient drenching and roller pressing, gel and surface cleaning, and mesh ventilation steps in Example 1, and then roll it up; ⑥ The subsequent aging, modification and drying steps are the same as in Example 1.

[0027] Comparative Example 2: This comparative example uses the conventional integral impregnation and gelation method (without negative pressure). The difference from the process in Example 1 is that the traction step in Example 1 is replaced with the relevant steps of the mesh permeability treatment. The specific process steps are as follows: ① Substrate pretreatment (same as Example 1: pre-oxidized fiber felt is subjected to plasma treatment with a power of 550W for 5 minutes to improve fiber surface activity). ②The substrate is rolled into shape (same as the roll substrate specifications in Example 1), without performing the traction and emptying steps in Example 1; ③ Prepare a sol of the same specifications (same as in Example 1: mix tetraethyl orthosilicate, ethanol, water and modifier in a certain volume ratio, adjust the pH to 4 with hydrolysis catalyst, react at a constant temperature of 55℃ for 4 hours, stir to form a uniform and stable silica sol, and add a certain proportion of gel catalyst). ④ Immerse the roll substrate in the above sol under normal pressure (without any negative pressure), and immerse the whole substrate in the sol. Do not perform the dip coating steps in Example 1. The immersion time is 25 seconds, the same as in Example 1. ⑤ The whole gel is formed without the gradient leaching and roller pressing, gelation and surface cleaning, and mesh ventilation steps in Example 1. The subsequent aging, modification and drying steps are the same as in Example 1.

[0028] Comparative Example 3: This comparative example uses a strong negative pressure method (-0.25MPa). The difference from the process in Example 1 is that the traction step in Example 1 is replaced with the relevant steps of the mesh ventilation treatment. The specific process steps are as follows: ① Substrate pretreatment, rolling and forming, and sol preparation (all the same as in Example 1: substrate pretreatment is plasma treatment, power 550W, time 5 minutes; rolling and forming is the same as in Example 1; sol preparation is the same as in Example 1 in terms of method and parameters). ② Without performing the traction step, emptying step, and dip coating step in Example 1, the roll substrate is placed into a special equipment, vacuumed to -0.25MPa, and impregnated under this negative pressure. The impregnation time is 25 seconds, the same as in Example 1. ③ The whole gel is formed without the gradient leaching and roller pressing, gelation and surface cleaning, and mesh ventilation steps in Example 1. The subsequent aging, modification and drying steps are the same as in Example 1.

[0029] Comparative Example 4: This comparative example uses a weak negative pressure method (-0.03MPa). The difference from the process in Example 1 is that the traction step in Example 1 is replaced with the relevant steps of the mesh ventilation treatment. The specific process steps are as follows: ① Substrate pretreatment, rolling and forming, and sol preparation (all the same as in Example 1: substrate pretreatment is plasma treatment, power 550W, time 5 minutes; rolling and forming is the same as in Example 1; sol preparation is the same as in Example 1 in terms of method and parameters). ② Without performing the traction step, emptying step, and dip coating step in Example 1, the roll substrate is placed into a special equipment, vacuumed to -0.03MPa, and impregnated under this negative pressure. The impregnation time is 25 seconds, the same as in Example 1. ③ The whole gel is formed without the gradient leaching and roller pressing, gelation and surface cleaning, and mesh ventilation steps in Example 1. The subsequent aging, modification and drying steps are the same as in Example 1.

[0030] The comparative experimental results of the aerogel felt examples and comparative examples are shown in Table 1 below:

[0031] Table 1 According to the table above: 1. Advantages in adapting to low-strength substrates: For low-strength substrates such as aerogel paper, the precise micro-pressure range of -0.04 to -0.2 MPa in this invention can achieve deep and uniform impregnation of the core while effectively protecting the structural integrity of the substrate. According to the table data, the breakage rate of the strong negative pressure method (-0.25 MPa) is as high as 15% to 20%, while the breakage rate of the process in this application is 0%, significantly reducing the risk of substrate breakage; the overall gel pass rate of the weak negative pressure method (-0.03 MPa) is only 70% to 76%, while this application achieves ≥98%, greatly improving the pass rate. At the same time, the thermal conductivity remains stable at 0.022 to 0.028 W / (m·K), ensuring stable thermal insulation performance and solving the pain points of easy breakage and low pass rate in the production of low-strength substrates.

[0032] 2. Advantages for adapting to calcined hydrophobic substrates: For calcined hydrophobic substrates, this invention enhances the sol wetting and penetration effect through precise control within a micro-pressure range (-0.1~-0.2MPa). Table data shows that traditional production line flat-lay impregnation gelation methods (overall gel qualification rate 65%-72%) and conventional overall impregnation and overall gelation methods (without negative pressure, overall gel qualification rate 71%-78%) both suffer from uneven penetration and easy delamination and breakage. In contrast, the process in this application achieves an overall gel qualification rate ≥98%, a breakage rate of 0%, and the optimal thermal conductivity. This not only significantly improves production efficiency and qualification rate but also completely solves the core defect of uneven penetration in such substrates, demonstrating significantly better adaptability than existing comparative processes.

[0033] 3. Creativity and Synergistic Advantages of the Micro-Pressure Range: The -0.04~-0.2MPa micro-pressure range of this invention is not a simple application of negative pressure, but rather an optimal parameter range selected through experimentation. It can simultaneously balance the three core requirements of impregnation efficiency, substrate protection, and gel stability. This synergistic effect cannot be achieved by the four conventional comparative processes. The strong negative pressure method (-0.25MPa) has excessively high negative pressure, leading to substrate breakage and gel cracking and delamination (damage rate 15%-20%, lowest pass rate); the weak negative pressure method (-0.03MPa) has insufficient negative pressure, failing to achieve effective impregnation (low pass rate, high thermal conductivity); and the atmospheric pressure process suffers from uneven impregnation. All of these demonstrate the creativity and uniqueness of the micro-pressure range optimization in this invention.

[0034] 4. Comprehensive Advantages of the Process System: This invention utilizes an integrated process system of "roll forming - precise micro-pressure impregnation - overall gelation," combined with optimized steps such as mesh fabric assistance and surface cleaning, to form a complete closed-loop process. Based on the three core indicators in the table, compared to four conventional comparative processes (highest overall gelation pass rate ≤78%, breakage rate ≥5%, thermal conductivity ≥0.030W / (m·K)), the process of this application demonstrates superior performance in all indicators (overall gelation pass rate ≥98%, breakage rate 0%, thermal conductivity 0.022-0.028W / (m·K)). The process exhibits strong controllability and wide adaptability, effectively covering various substrates such as low-strength and hydrophobic substrates after calcination, thus overcoming the adaptability limitations of existing processes.

[0035] In summary, based on the core quantitative data in the table and the above analysis, this invention, through the precise definition and optimization of the micro-pressure range of -0.04 to -0.2 MPa, constructs an integrated process system of "roll forming - precise micro-pressure impregnation - overall gelation", which fundamentally solves the core pain points (uneven impregnation, substrate damage, and low pass rate) in the overall gelation process of existing aerogel felt production and the application limitations of existing negative pressure technology (extensive application and inability to balance multiple core needs).

[0036] 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 monolithic gelation process for aerogel mats based on micro-pressure impregnation, characterized in that: The core steps include the following: (1) Select an aerogel felt substrate, wherein the substrate is one or more of glass fiber felt, ceramic fiber felt, quartz fiber felt, pre-oxidized fiber felt, carbon fiber felt, alumina fiber felt, basalt fiber felt, polymer foam, wet-laid fiber paper, and chopped fiber felt; if calcination is required to remove impurities, place the substrate in a calcination furnace for heat preservation and then allow it to cool naturally. (2) Clean the surface of the pretreated substrate, lay it flat on the mesh cloth and roll it into a cylindrical roll; (3) Prepare a sol system with a solid content of 8~20wt%, wherein the sol is one or more of SiO2, Al2O3, ZrO2, silicon-aluminum composite, RF sol, and inorganic silica sol; (4) Place the roll-shaped substrate vertically into the micro-pressure impregnation-integral gelation equipment, evacuate to -0.04~-0.2MPa and maintain for 15~20min, then inject sol at a rate of 5~15L / min until the substrate is completely submerged, maintain this negative pressure environment for impregnation for 30~120min, and control the internal temperature of the equipment to 20~60℃. (5) Depressurize at a rate of ≤0.02MPa / min and let stand for 0.1~6h to complete the overall gelation; (6) Immerse the gelled roll material in a methanol or ethanol solution at 40-80°C for 12-48 hours, changing the soaking solution 2-4 times during the period; (7) Dry the aged material by means of normal pressure drying, vacuum drying or supercritical drying, and blow off the loose powder on the surface after drying to obtain the finished product.

2. The process according to claim 1, characterized in that: The conditions for calcination and impurity removal in step (1) are: calcination temperature 500~800℃, holding time 2~6h.

3. The process according to claim 1, characterized in that: In step (2), the surface is cleaned by blowing with compressed air at 0.2~0.4MPa. The mesh fabric is non-woven fabric, nylon mesh fabric, Teflon mesh fabric or polyethylene mesh fabric.

4. The process according to claim 1, characterized in that: In step (3), the pH value of the sol is controlled to be an acidic system of 3-5 or an alkaline system of 8-10. The acidic system is suitable for silica-based sol, and the alkaline system is suitable for aluminum-based sol.

5. The process according to claim 1, characterized in that: In step (3), 0.5-2 wt% of inorganic silane coupling agent is added to the sol for the calcined aerogel felt substrate.

6. The process according to claim 1, characterized in that: In step (4), a sol flow gap of 5~10mm is left between the rolled substrate and the cylinder wall of the micro-pressure impregnation-integral gelation equipment, and the negative pressure fluctuation range is ≤±0.02MPa.

7. The process according to claim 1, characterized in that: In step (4), the impregnation pressure of the low-strength polymer foam cotton and wet-process fiber paper substrates is controlled within -0.08 MPa; the impregnation pressure of the calcined substrate is controlled above -0.1 MPa.

8. The process according to claim 1, characterized in that: The conditions for vacuum drying in step (7) are: temperature 60~100℃, vacuum degree -0.05~-0.09MPa, drying time 6~16h; the conditions for supercritical drying are: pressure 12~16MPa, temperature 40~60℃, drying time 5~12h.

9. The process according to claim 5, characterized in that: The inorganic silane coupling agent is KH550.

10. The process according to claim 1, characterized in that: In step (7), the purging after drying is carried out with compressed air of 0.2~0.3MPa. The finished aerogel felt is a thin product with a thickness of less than 3mm or a thick product with a thickness of more than 50mm.

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