An aerogel mat vacuum pressurization synergistic impregnation system and method of making

Abstract

The application relates to the technical field of aerogel composite material preparation, and discloses an aerogel felt vacuum pressurization and impregnation system and a preparation method, which comprise a vacuum cavity, a dynamic pulsating vacuum degassing module, a sol supply module, a gradient pressurization impregnation module and an online intelligent control module; the vacuum cavity is used for accommodating a roll-shaped or sheet-shaped fiber felt base material; the dynamic pulsating vacuum degassing module is connected with the vacuum cavity and is used for performing periodic vacuum pumping and vacuum breaking circulation on the fiber felt; the sol supply module is connected with the vacuum cavity; the gradient pressurization impregnation module is connected with the vacuum cavity and is used for applying segmented incremental pressure to the fiber felt after the sol is introduced; and the online intelligent control module is respectively connected with the dynamic pulsating vacuum degassing module, the sol supply module and the gradient pressurization impregnation module in signal connection. The aerogel sol can uniformly impregnate the fiber felt in full thickness, and there is no dry core and no dead angle, so that the sol consumption is remarkably reduced and the production cycle is shortened.

Description

Technical Field

[0001] This invention relates to the field of aerogel composite material preparation technology, specifically to an aerogel felt vacuum pressure synergistic impregnation system and preparation method. Background Technology

[0002] Aerogel is a porous material with a continuous three-dimensional network structure formed by the polymerization of nanoscale particles. Its porosity can reach over 80%, and it has extremely low thermal conductivity, making it the solid material with the lowest known thermal conductivity. Due to the high brittleness and poor mechanical properties of pure aerogel, it is usually combined with fiber felt in industry to produce aerogel felt, which is widely used in aerospace, building energy conservation, new energy vehicles, and chemical pipeline insulation.

[0003] Existing aerogel felt preparation processes mainly include two methods: continuous spraying and discontinuous impregnation. Continuous production places the fiber felt on a moving element, and the sol is sprayed onto one side. This method suffers from insufficient and uneven impregnation of the fiber felt, with less sol impregnation in the core and more on the surface, leading to product performance delamination. Discontinuous production places the fiber felt in an impregnation tank, injecting sol from one side of the wound or stacked fiber felt. This also suffers from significant differences in impregnation between the core and surface, and often requires excessive sol addition to ensure thorough impregnation, resulting in significant waste of aerogel raw materials and high production costs. Furthermore, the fiber felt contains numerous closed and blind pores, making it difficult for gas to escape under normal pressure impregnation conditions. This prevents the sol from fully penetrating the micropores, resulting in slow impregnation speed, low efficiency, and products with insufficient impregnation requiring secondary repair or direct scrapping, leading to low yield and poor stability.

[0004] In existing technologies, although there are methods that involve injecting sol after evacuating the reactor, this is only a static vacuuming process and cannot effectively remove gas from the closed and blind pores inside the fiber felt. Furthermore, there is no pressurized impregnation step after injection; relying solely on vacuum negative pressure for injection makes it difficult for the sol to penetrate deep into the microporous structure. At the same time, the impregnation amount control depends on manual observation of the overflow port, which cannot achieve precise measurement and automatic adjustment, and still cannot avoid the problems of raw material waste and uneven impregnation. Summary of the Invention

[0005] The present invention aims to provide a vacuum pressurized synergistic impregnation system and preparation method for aerogel felt, in order to solve the technical problems in the existing aerogel felt impregnation process, such as the difficulty in venting gas from the closed and blind pores inside the fiber felt, resulting in uneven sol penetration and insufficient internal wetting, excessive feeding causing waste of raw materials, and low efficiency and low yield of simple atmospheric pressure impregnation.

[0006] To solve the above problems, the present invention adopts the following technical solution: Option 1: An aerogel felt vacuum pressurized synergistic impregnation system, comprising a vacuum chamber, a dynamic pulsed vacuum degassing module, a sol supply module, a gradient pressurized impregnation module, and an online intelligent control module; the vacuum chamber is used to contain roll-shaped or sheet-shaped fiber felt substrate; the dynamic pulsed vacuum degassing module is connected to the vacuum chamber and is used to periodically evacuate and break the vacuum cycle of the fiber felt to remove gas from the closed pores and blind pores inside the fiber felt; the sol supply module is connected to the vacuum chamber and is used to introduce aerogel sol into the fiber felt under vacuum; the gradient pressurized impregnation module is connected to the vacuum chamber and is used to apply segmented increasing pressure to the fiber felt after the sol is introduced, so that the sol is further pressed into the micropores; the online intelligent control module is signal-connected to the dynamic pulsed vacuum degassing module, the sol supply module, and the gradient pressurized impregnation module respectively, and is used to automatically adjust the vacuum degree, holding time, pulse parameters, and sol supply amount according to the thickness, areal density, and target sol content of the fiber felt.

[0007] Beneficial effects: By integrating four functional modules—dynamic pulsed vacuum degassing, sol supply, gradient pressure impregnation, and online intelligent control—the vacuum chamber achieves a two-step synergy between vacuum degassing and pressure impregnation. This effectively removes gas from closed and blind pores inside the fiber felt, and the sol penetrates the entire thickness of the felt under the dual action of negative pressure suction and positive pressure gradient, achieving full impregnation, no dry core, and no dead corners. At the same time, online intelligent control enables precise calculation and automatic adjustment of sol dosage, avoiding overfeeding and significantly reducing raw material costs.

[0008] This invention achieves uniform impregnation of the entire thickness of the fiber felt with aerogel sol through a two-step synergistic process of vacuum degassing and pressurized impregnation, resulting in no dry core and no dead corners. This significantly reduces the amount of sol used and shortens the production cycle while ensuring a high first-pass yield.

[0009] Furthermore, the dynamic pulsed vacuum degassing module includes a vacuum pump, a vacuum buffer tank, a pulsed control valve, and a vacuum degree sensor; the vacuum pump is connected to the vacuum chamber through the vacuum buffer tank, and the pulsed control valve is installed on the pipeline between the vacuum buffer tank and the vacuum chamber to control the periodic switching between vacuuming and vacuum breaking; the vacuum degree sensor is installed inside the vacuum chamber to monitor the vacuum degree of the chamber in real time.

[0010] Beneficial effects: By combining the vacuum buffer tank with the pulse control valve, the periodic pulsating cycle of vacuuming and vacuum breaking is achieved. The pressure fluctuations cause the gas in the closed and blind pores inside the fiber felt to be shaken out during the expansion and contraction process. The degassing efficiency is much higher than that of static vacuuming, creating the preconditions for the uniform impregnation of the sol in the subsequent process.

[0011] Furthermore, the pulsation cycle of the dynamic pulsating vacuum degassing module is 10 to 120 seconds. During a single pulsation, the vacuum level during the vacuuming phase reaches -0.05 MPa to -0.09 MPa, and the cavity pressure during the vacuum breaking phase recovers to -0.01 MPa to -0.03 MPa. The number of pulsation cycles is automatically set by the online intelligent control module according to the thickness and areal density of the fiber felt.

[0012] Beneficial effects: By limiting the pulsation period, vacuum level range, and vacuum recovery pressure range, the fiber felt undergoes sufficient gas expansion and contraction during periodic pressure fluctuations. Gas in closed and blind pores is effectively expelled, while excessive vacuum prevents fiber structure damage or premature sol gelation, balancing degassing efficiency with fiber felt structural integrity. The online intelligent control module includes a pre-defined cycle count table; the number of pulsation cycles is determined based on the corresponding fiber felt thickness and areal density in the cycle count table.

[0013] Furthermore, the gradient pressure impregnation module includes a pressure medium source, a segmented pressure valve group, and a pressure sensor; the segmented pressure valve group includes at least two pressure levels of pressure branches, used to sequentially apply a first pressure, a second pressure, and a third pressure to the fiber felt in the vacuum chamber, with each pressure dynamically increasing with the sol impregnation depth; the pressure sensor is used to monitor the chamber pressure in real time.

[0014] Beneficial effects: The segmented pressurization valve group achieves multi-stage pressure increase, so that the sol is driven by a pressure difference that matches the different penetration depths. This avoids the initial high pressure causing the sol to gel rapidly on the surface and block the pore channels, while ensuring that the deep micropores receive sufficient osmotic pressure, thus achieving gradient uniform penetration from the surface to the interior.

[0015] Furthermore, the pressure in the first stage is 0.1 MPa to 0.3 MPa, the pressure in the second stage is 0.3 MPa to 0.6 MPa, and the pressure in the third stage is 0.6 MPa to 1.0 MPa; the holding time of each stage is automatically adjusted by the online intelligent control module based on the fiber felt thickness and real-time impregnation depth feedback signal.

[0016] Beneficial effects: By limiting the specific values ​​of the three pressure gradients, the sol can slowly penetrate at a lower pressure in the surface wetting stage, accelerate diffusion at a medium pressure in the middle stage, and forcefully penetrate into the micropores at a higher pressure in the deep stage, forming a driving force distribution that matches the penetration depth, avoiding premature gelation of the surface layer, and ensuring uniform penetration throughout the entire thickness.

[0017] Option 2: A method for preparing aerogel felt by vacuum pressure synergistic impregnation, comprising the following steps: Step 1: Place the fiber felt in the vacuum chamber and start the dynamic pulsed vacuum degassing to periodically evacuate and break the vacuum cycle of the fiber felt to remove the gas in the closed pores and blind pores inside the fiber felt. Step 2: Once the vacuum level of the cavity reaches the set value, aerogel sol is introduced into the fiber felt while maintaining the vacuum. The negative pressure suction force is used to draw the sol into the interior of the felt. Step 3: After the sol is introduced, gradient pressure impregnation is started instantly to apply segmented increasing pressure to the fiber felt, so that the sol is further pressed into the micropores to achieve uniform impregnation of the entire thickness. Step four: After impregnation is completed, the online intelligent control module automatically calculates and controls the theoretical minimum amount of solvent based on the thickness, areal density and target adhesive content of the fiber felt, so as to achieve low-volume, one-time impregnation.

[0018] Beneficial effects: Through a three-step synergistic process of vacuum degassing, vacuum adhesive application, and gradient pressurization, the gas inside the fiber felt is completely eliminated. Under the synergistic drive of negative and positive pressure, the sol penetrates the entire thickness, achieving uniform impregnation without dry core or dead corners. At the same time, through the automatic calculation and control of the theoretical minimum amount of sol, overfeeding is avoided, significantly reducing raw material costs while ensuring product quality. The first-pass yield is high, and no secondary remediation is required.

[0019] Furthermore, in step one, the vacuum degree of dynamic pulsed vacuum degassing reaches -0.05MPa to -0.09MPa, the pulse period is 10 seconds to 120 seconds, the vacuuming phase in a single pulse lasts for 30 seconds to 90 seconds, and the vacuum breaking phase lasts for 10 seconds to 30 seconds; the number of pulse cycles N is determined by the formula N = k1·H + k2·ρ + c based on the fiber felt thickness H and the areal density ρ, where k1 and k2 are empirical coefficients related to the fiber type, and c is a baseline correction value.

[0020] Beneficial effects: By limiting the vacuum range, pulsation cycle, and the time ratio of vacuuming / vacuum breaking, the gas inside the fiber felt can fully expand and detach from the pore wall during periodic pressure fluctuations, and then be extracted by the vacuum pump; by establishing a quantitative relationship between the number of pulsation cycles and the thickness and areal density of the fiber felt, the degassing process parameters are automatically optimized for different product specifications to ensure thorough degassing without over-processing.

[0021] Furthermore, in step two, the aerogel sol is introduced as follows: after the vacuum level of the cavity reaches -0.05MPa to -0.09MPa and remains stable, the sol supply valve is opened after a delay of 5 to 15 seconds, so that the sol flows evenly into the fiber felt under a stable negative pressure environment; the amount of sol introduced is adjusted in real time by the online intelligent control module according to the theoretical minimum amount of sol, and the introduction rate is 0.5kg / min to 5kg / min.

[0022] Beneficial effects: By introducing the sol after the vacuum degree has stabilized, it is ensured that the gas inside the fiber felt has been fully discharged and the negative pressure field is stable. Under the action of uniform negative pressure suction, the sol quickly and evenly penetrates into the felt, avoiding impregnation defects caused by gas residue. By precisely controlling the introduction rate, it is prevented that the fiber structure will be deformed or locally accumulated due to the impact of the sol.

[0023] Furthermore, in step three, the gradient pressure impregnation is divided into three stages: the first stage has a pressure of 0.1 MPa to 0.3 MPa and a holding time of 1 to 3 minutes, allowing the sol to fully impregnate the surface and middle layers of the fiber felt; the second stage has a pressure of 0.3 MPa to 0.6 MPa and a holding time of 1 to 5 minutes, allowing the sol to diffuse into the deep pores; the third stage has a pressure of 0.6 MPa to 1.0 MPa and a holding time of 1 to 4 minutes, allowing the sol to be forced into the micro-blind pores and closed pore residual spaces; the switching of each pressure stage is automatically triggered by the online intelligent control module based on the real-time monitored sol impregnation depth signal.

[0024] Beneficial effects: By configuring a gradient of three pressures and holding times, the sol slowly penetrates the surface layer at low pressure to avoid gel blockage, accelerates diffusion in the middle layer at medium pressure, and forces it into the micropores at high pressure in the deep layer, achieving a gradual penetration from the surface to the interior; the pressure switching is automatically triggered by the penetration depth signal to avoid over-penetration of the surface layer or insufficient penetration of the deep layer caused by fixed time switching, ensuring uniformity of the entire thickness.

[0025] Furthermore, the real-time monitoring of the sol penetration depth is achieved by arranging an ultrasonic probe on the side of the fiber felt and using the difference in sound velocity between the sol-containing area and the non-sol-containing area to determine the penetration depth.

[0026] Beneficial effects: By using ultrasonic detection, the position of the sol-gel penetration front in the thickness direction of the fiber felt can be obtained in real time, providing objective data for pressure switching of gradient pressurization, realizing closed-loop control of the penetration process, avoiding errors from human experience judgment, and ensuring the consistency of penetration of each batch of products.

[0027] The advantages of this invention are as follows: By employing a two-step synergistic process of vacuum degassing and pressurized impregnation, the industry-wide problem of uneven impregnation and insufficient internal wetting during the impregnation of aerogel felt is fundamentally solved. This achieves a technological breakthrough by ensuring uniform impregnation of the entire thickness of the fiber felt, eliminating dry cores and dead corners, and significantly improving the first-pass yield. At the same time, the online intelligent control module automatically calculates the theoretical minimum amount of sol, which significantly reduces the amount of aerogel sol used while ensuring impregnation quality, thereby reducing raw material costs. Furthermore, the process is highly controllable and can be adapted to the continuous production of aerogel felts of different thicknesses and densities.

[0028] The unexpected aspect of this invention's solution to the technical problem lies in the fact that existing technologies generally believe the root cause of uneven impregnation of fiber felt is the high viscosity of the sol and the complex pore structure of the fibers. Therefore, they tend to improve this by reducing the sol viscosity or extending the impregnation time, but the effect is limited. This invention breaks away from the traditional binary relationship between sol and fiber, introducing a perspective of interaction between gas, sol, and fiber. It discovers that residual gas in the closed and blind pores inside the fiber felt is the key factor hindering the deep penetration of the sol. Under normal pressure or static vacuum, this gas is "locked" in the micropores due to surface tension, forming a barrier that the sol cannot overcome. Through dynamic pulsed vacuum degassing, the gas undergoes a cycle of expansion, contraction, and re-expansion caused by periodic pressure fluctuations, disrupting the stability of the gas-liquid-solid three-phase interface and "shaking out" the "locked" gas. This understanding of the mechanism is beyond the conventional technical knowledge in this field.

[0029] The unexpected aspect of this invention lies in the fact that while existing vacuum injection technology only uses vacuum as the driving force for sol absorption, this invention designs vacuum degassing and pressurized impregnation as a two-step sequence of "first synergistic obstacle removal, then synergistic driving." First, a dynamic pulsating vacuum removes gas obstacles; then, negative vacuum introduces the sol to establish an initial penetration field; and finally, segmented gradient pressurization provides the driving force for deep penetration. This synergistic approach, rather than simple superposition, transforms the sol's penetration behavior in the fiber felt from passive absorption to active pressure impregnation, resulting in a qualitative change in penetration depth and uniformity. Even more surprisingly, by automatically calculating the theoretical minimum sol amount through online detection of fiber felt thickness and areal density, empirical feeding is transformed into quantitative supply. This significantly reduces sol usage while ensuring full impregnation—an effect unforeseen in existing technologies. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0031] The following detailed description illustrates the specific implementation methods: The present invention provides a vacuum pressurized synergistic impregnation system for aerogel felt, comprising a vacuum chamber, a dynamic pulsed vacuum degassing module, a sol supply module, a gradient pressurized impregnation module, a sol recovery and circulation module, and an online intelligent control module. The vacuum chamber is used to contain rolls or sheets of fiber felt substrate. The vacuum chamber is a roll-to-roll continuous processing chamber, including a sealed transition chamber at the inlet end, a main processing chamber, and a sealed transition chamber at the outlet end. The fiber felt continuously passes through the main processing chamber in a roll-to-roll manner. Both the sealed transition chambers at the inlet and outlet ends are equipped with vacuum lock devices to maintain the vacuum environment of the main processing chamber while simultaneously enabling continuous entry and exit of the fiber felt. By using a roll-to-roll continuous processing chamber in conjunction with vacuum lock devices, long rolls of felt ranging from 1m × 20m to 30m can undergo vacuum degassing and pressure impregnation on a continuous production line, overcoming the length limitations of intermittent processing, significantly improving production efficiency, and adapting to the needs of industrial continuous production.

[0032] The sol recovery and recycling module includes a sol collection tank, a filtration and impurity removal device, and a viscosity compensation device located at the bottom of the vacuum chamber. The sol collection tank collects excess sol overflowing during the pressurized impregnation stage. The filtration and impurity removal device removes fiber debris and impurities from the recovered sol. The viscosity compensation device monitors and adjusts the viscosity of the recovered sol to a set range, after which the adjusted sol is returned to the sol storage tank. This sol recovery and recycling module achieves the recovery, filtration, and viscosity compensation of excess sol, further reducing raw material consumption. It also avoids fluctuations in impregnation performance caused by viscosity changes in the recovered sol, ensuring stable quality of the recycled sol and achieving green, low-cost production.

[0033] The dynamic pulsed vacuum degassing module is connected to the vacuum chamber and is used to periodically pump and break the vacuum in the fiber felt to remove gas from the closed and blind pores inside the fiber felt. The dynamic pulsed vacuum degassing module includes a vacuum pump, a vacuum buffer tank, a pulsed control valve, and a vacuum sensor. The vacuum pump is connected to the vacuum chamber through the vacuum buffer tank, and the pulsed control valve is located on the pipeline between the vacuum buffer tank and the vacuum chamber to control the periodic switching between pumping and breaking the vacuum. The vacuum sensor is located inside the vacuum chamber to monitor the vacuum level in real time. Through the cooperation of the vacuum buffer tank and the pulsed control valve, the periodic pulsed cycle of pumping and breaking the vacuum is achieved. The pressure fluctuations cause the gas in the closed and blind pores inside the fiber felt to be "shaked" out during the expansion and contraction process. The degassing efficiency is much higher than that of static vacuuming, creating the preconditions for the subsequent uniform impregnation of the sol.

[0034] The dynamic pulsating vacuum degassing module has a pulsation period of 10 to 120 seconds. During a single pulsation, the vacuum level reaches -0.05 MPa to -0.09 MPa in the vacuum-expansion phase and recovers to -0.01 MPa to -0.03 MPa in the vacuum-breaking phase. The number of pulsation cycles is automatically set by the online intelligent control module based on a pre-approved cycle limit table, according to the fiber felt thickness and areal density. By limiting the pulsation period, vacuum level range, and vacuum-breaking pressure recovery range, the fiber felt undergoes sufficient gas expansion and contraction during periodic pressure fluctuations. Closed and blind pore gases are effectively expelled, while excessive vacuum prevents fiber structure damage or premature gelation of the sol, balancing degassing efficiency with the structural integrity of the fiber felt.

[0035] The sol supply module is connected to the vacuum chamber and is used to introduce aerogel sol into the fiber felt under vacuum conditions. The sol supply module includes a sol storage tank, a metering pump, and a sol distribution pipeline. The sol distribution pipeline is located above or to the side of the fiber felt inside the vacuum chamber and has multiple evenly distributed sol injection outlets. The metering pump is signal-connected to an online intelligent control module and is used to precisely control the sol supply rate according to the theoretical minimum sol amount. By cooperating with the metering pump and the evenly distributed sol injection outlets, a precisely metered sol is evenly introduced into the fiber felt under vacuum conditions. The sol quickly penetrates into the interior of the felt under negative pressure suction, avoiding local over- or under-absence and providing a uniform sol distribution basis for subsequent gradient pressure impregnation.

[0036] The gradient pressure impregnation module is connected to the vacuum chamber and is used to apply progressively increasing pressure to the fiber felt after the sol is introduced, allowing the sol to further penetrate into the micropores. The gradient pressure impregnation module includes a pressure medium source, a segmented pressure valve assembly, and a pressure sensor. The segmented pressure valve assembly includes at least two pressure-level branches, used to sequentially apply a first-stage pressure, a second-stage pressure, and a third-stage pressure to the fiber felt in the vacuum chamber, with each stage pressure dynamically increasing with the sol impregnation depth. The pressure sensor is used to monitor the chamber pressure in real time. Beneficial effects: The segmented pressure valve assembly achieves multi-stage pressure increases, ensuring the sol receives a matching pressure differential driving force at different impregnation depth stages. This avoids the initial high pressure causing the sol to rapidly gel and block pore channels on the surface, while ensuring sufficient permeation pressure in the deep micropores, achieving uniform gradient impregnation from the surface inwards.

[0037] The pressure ranges from 0.1 MPa to 0.3 MPa in the first stage, 0.3 MPa to 0.6 MPa in the second stage, and 0.6 MPa to 1.0 MPa in the third stage. The holding time for each pressure stage is automatically adjusted by the online intelligent control module based on the fiber felt thickness and real-time impregnation depth feedback signal. By limiting the specific values ​​of the three pressure gradients, the sol penetrates slowly at a lower pressure in the surface impregnation stage, accelerates diffusion at a medium pressure in the middle stage, and forces it into the micropores at a higher pressure in the deep stage. This creates a driving force distribution that matches the impregnation depth, preventing premature gelation of the surface layer and ensuring uniform impregnation across the entire thickness.

[0038] The online intelligent control module is connected to the dynamic pulsed vacuum degassing module, the sol supply module, and the gradient pressure impregnation module, respectively, and is used to automatically adjust the vacuum degree, holding time, pulse parameters, and sol supply amount according to the thickness, areal density, and target sol content of the fiber felt.

[0039] The online intelligent control module includes a thickness detection unit, a areal density detection unit, a sol metering unit, and a central controller. The thickness detection unit measures the fiber felt thickness online, the areal density detection unit measures the fiber felt areal density online, and the sol metering unit monitors the sol supply in real time. The central controller has a built-in theoretical minimum sol quantity calculation model. Based on the input thickness, areal density, and target sol content, it automatically calculates the theoretical minimum sol quantity and outputs control signals to the dynamic pulsed vacuum degassing module, the sol supply module, and the gradient pressure impregnation module. By detecting the fiber felt thickness and areal density online and automatically calculating the theoretical minimum sol quantity based on the target sol content, the system achieves a shift from "overfeeding" to "precise metering." This minimizes sol waste and reduces raw material costs while ensuring full impregnation, while avoiding subjective errors from manual judgment and improving process stability and product consistency.

[0040] The theoretical minimum sol amount calculation model is as follows: Theoretical minimum sol amount = Fiber felt volume × Target pore filling rate × Sol solid content conversion coefficient. The fiber felt volume is calculated from the online measured thickness and width. The target pore filling rate is set according to the fiber felt type and target product performance. The sol solid content conversion coefficient is determined by the solid content and gel shrinkage rate in the sol formulation. By establishing a mathematical relationship between the sol requirement, fiber felt volume, target pore filling rate, and sol solid content conversion coefficient, the impregnation amount control is upgraded from empirical estimation to quantitative calculation. This ensures that the sol dosage meets the full impregnation requirement without being excessive, achieving an optimal balance between raw material cost and product quality.

[0041] This invention integrates four functional modules within a vacuum chamber: dynamic pulsed vacuum degassing, sol supply, gradient pressure impregnation, and online intelligent control. This achieves a two-step synergy between vacuum degassing and pressure impregnation, effectively expelling gas from closed and blind pores within the fiber felt. Under the dual action of negative pressure suction and positive pressure gradient, the sol penetrates the entire thickness of the felt, achieving full impregnation, no dry core, and no dead corners. Simultaneously, online intelligent control enables precise calculation and automatic adjustment of the sol dosage, avoiding overfeeding and significantly reducing raw material costs.

[0042] Using the above system, the present invention provides a vacuum pressure synergistic impregnation and permeation preparation method for aerogel felt, comprising the following steps: Step 1: Place the fiber felt in the vacuum chamber and start dynamic pulsed vacuum degassing. Perform periodic vacuuming and vacuum breaking cycles on the fiber felt to remove gas from the closed and blind pores inside the fiber felt. In Step 1, the vacuum degree of dynamic pulsed vacuum degassing reaches -0.05MPa to -0.09MPa, the pulse period is 10 seconds to 120 seconds, the vacuuming phase in a single pulse lasts for 30 seconds to 90 seconds, and the vacuum breaking phase lasts for 10 seconds to 30 seconds. The number of pulse cycles N is determined by the formula N = k1·H + k2·ρ + c based on the fiber felt thickness H and surface density ρ, where k1 and k2 are empirical coefficients related to the fiber type, and c is a baseline correction value. By limiting the vacuum level range, pulsation cycle, and the time ratio of vacuuming / vacuum breaking, the gas inside the fiber felt is fully expanded and detached from the pore walls during periodic pressure fluctuations, and then extracted by the vacuum pump. By establishing a quantitative relationship between the number of pulsation cycles and the thickness and areal density of the fiber felt, the degassing process parameters are automatically optimized for different product specifications to ensure thorough degassing without over-processing.

[0043] Step two: Once the cavity vacuum reaches the set value, aerogel sol is introduced into the fiber felt while maintaining the vacuum. The negative pressure suction draws the sol into the felt. In step two, the aerogel sol is introduced as follows: after the cavity vacuum reaches and stabilizes at -0.05 MPa to -0.09 MPa, the sol supply valve is opened after a delay of 5 to 15 seconds, allowing the sol to flow uniformly into the fiber felt under a stable negative pressure environment. The sol introduction rate is adjusted in real-time by the online intelligent control module based on the theoretical minimum sol amount, ranging from 0.5 kg / min to 5 kg / min. By delaying the sol introduction after the vacuum stabilizes, it ensures that the gas inside the fiber felt has been fully expelled and the negative pressure field is stable. Under the uniform negative pressure suction, the sol quickly and evenly penetrates the felt, avoiding impregnation defects caused by gas residue. Precise control of the introduction rate prevents sol impact from causing fiber structure deformation or localized accumulation.

[0044] Step three: After the sol is introduced, gradient pressure impregnation is instantly initiated, applying segmented increasing pressure to the fiber felt to further force the sol into the micropores, achieving uniform impregnation across the entire thickness. In step three, the gradient pressure impregnation is divided into three stages: the first stage uses a pressure of 0.1 MPa to 0.3 MPa, with a holding time of 1 to 3 minutes, to fully impregnate the surface and middle layers of the fiber felt; the second stage uses a pressure of 0.3 MPa to 0.6 MPa, with a holding time of 1 to 5 minutes, to allow the sol to diffuse into deeper pores; the third stage uses a pressure of 0.6 MPa to 1.0 MPa, with a holding time of 1 to 4 minutes, to force the sol into the micro-blind pores and residual closed pore spaces. The switching of pressure between each stage is automatically triggered by the online intelligent control module based on the real-time monitored sol impregnation depth signal. By using a gradient configuration of three pressure and holding time, the sol slowly penetrates the surface layer at low pressure to avoid gel blockage, accelerates diffusion in the middle layer at medium pressure, and forces it into the micropores at high pressure in the deep layer, achieving a gradual penetration from the surface to the interior. The pressure switching is automatically triggered by the penetration depth signal to avoid over-penetration of the surface layer or insufficient penetration of the deep layer caused by fixed time switching, ensuring uniformity of the entire thickness.

[0045] The real-time monitoring of the sol-soaking depth is achieved by: arranging an ultrasonic probe on the side of the fiber felt, and using the difference in sound velocity between the sol-containing and non-sol-containing areas to determine the soaking depth. By using ultrasonic detection, the position of the sol-soaking front in the fiber felt thickness direction is obtained in real time, providing objective data for pressure switching in gradient pressurization, achieving closed-loop control of the soaking process, avoiding errors from human experience judgment, and ensuring the consistency of soaking for each batch of products.

[0046] Step four: After impregnation is completed, the online intelligent control module automatically calculates and controls the theoretical minimum amount of solvent based on the thickness, areal density and target adhesive content of the fiber felt, so as to achieve low-volume, one-time impregnation.

[0047] In step four, the calculation model for the theoretical minimum sol amount is: V_min = A × H × φ × η / (C_s × (1 - α)), where V_min is the theoretical minimum sol amount, A is the area of ​​the fiber felt width, H is the online measured fiber felt thickness, φ is the target pore filling rate, η is the wetting correction coefficient of the sol on the fiber surface, C_s is the sol solid content, and α is the gel drying shrinkage rate. By introducing the wetting correction coefficient and the gel drying shrinkage rate correction, the calculation of the theoretical minimum sol amount is closer to the actual process requirements. It considers both the spreading and wetting loss of the sol on the fiber surface and the volume shrinkage during gelation and drying, ensuring that the calculated sol amount meets the sol content requirements of the final product without excessive waste, thus achieving optimal control of raw material costs.

[0048] Step 5: After impregnation, the wet gel felt is aged at 30℃ to 70℃ for 1 to 10 hours. After aging, the vacuum chamber is de-vacuumed and the pressure is released. The wet gel felt is then removed and dried to obtain the aerogel felt. The aging process promotes further cross-linking of Si-O-Si bonds in the gel network, enhances the stability of the gel structure, and ensures the maintenance of the pore structure during subsequent drying, thereby improving the mechanical and thermal insulation properties of the aerogel felt. Impregnation and aging are completed within the same vacuum chamber, reducing transfer steps and improving production efficiency.

[0049] Steps two, three, and four must take a total of 5-7 minutes, with a maximum of 5-10 minutes. The aerogel solution in step two is prepared by mixing the existing mother liquors A and B. Once the mixture begins to react, it solidifies into a gel-like consistency within 10 minutes, making impregnation impossible. Therefore, from the start of impregnation in step two to the end of impregnation in step four, only 5-7 minutes are required to complete the process.

[0050] The fiber mat is made of glass fiber, ceramic fiber, or pre-oxidized fiber. The vacuum setting and pulsation parameters for dynamic pulsed vacuum degassing differ depending on the fiber type: the vacuum setting is -0.06 MPa to -0.08 MPa for glass fiber mat, -0.07 MPa to -0.09 MPa for ceramic fiber mat, and -0.05 MPa to -0.07 MPa for pre-oxidized fiber mat. To address the differences in pore structure among the different fiber mats (glass fiber mat has relatively uniform pores, ceramic fiber mat has finer pores and a higher closed-cell rate, and pre-oxidized fiber mat has larger pores but better fiber elasticity), the vacuum setting is optimized to ensure thorough degassing while avoiding excessive vacuum that could damage the fiber structure or cause premature sol penetration, thus achieving a precise match between process parameters and material properties.

[0051] The method of this invention employs a three-step synergistic process of "vacuum degassing - vacuum adhesive application - gradient pressurization," which completely eliminates the gas inside the fiber felt. Under the synergistic drive of negative and positive pressure, the sol penetrates the entire thickness, achieving uniform impregnation without dry core or dead corners. At the same time, through the automatic calculation and control of the theoretical minimum amount of sol, overfeeding is avoided, significantly reducing raw material costs while ensuring product quality. The first-pass yield is high, and no secondary remedial measures are required.

[0052] Compared to conventional techniques in the field, this invention addresses several key differences. Conventional aerogel felt impregnation processes include three single modes: atmospheric pressure impregnation, vacuum impregnation, and pressurized impregnation, or a simple combination of two modes (e.g., vacuum followed by atmospheric pressure). While those skilled in the art understand that vacuum facilitates gas removal and pressurization promotes penetration, these are typically treated as independent processes used in different scenarios, failing to recognize the transformative effect of a synergistic three-step sequence: vacuum degassing, vacuum gel introduction, and gradient pressurization. Furthermore, those skilled in the art are unaware of the "lock-in" effect of gas in closed and blind pores within the fiber felt under static vacuum, and therefore do not consider using dynamic pulsed vacuum to "shake out" the gas. Simultaneously, the field lacks techniques for automatically calculating the minimum sol amount based on real-time fiber felt parameters; the conventional approach is to over-add material based on experience. This invention organically integrates these techniques into a synergistic process system, producing technical effects exceeding the expectations of those skilled in the art.

[0053] The specific implementation process is as follows: Example 1: Vacuum-Pressure Co-impregnation of Glass Fiber Mat A 1m wide, 5mm thick, and 300g / m² glass fiber mat is continuously fed into the vacuum chamber in a roll-to-roll manner. The dynamic pulsed vacuum degassing module is activated, with a vacuum level set to -0.07MPa and a pulse cycle of 60 seconds (45 seconds of vacuuming and 15 seconds of vacuum breaking). The vacuum breaking pressure is restored to -0.02MPa. The number of cycles is calculated using the formula N = 0.8×H + 0.05×ρ + 2, resulting in N = 0.8×5 + 0.05×300 + 2 = 21 times. The total degassing time is approximately 21 minutes. After degassing, the vacuum level of the chamber stabilizes at -0.07 MPa. After a 10-second delay, the sol supply valve is opened, and catalyzed silica sol (15% solid content) is introduced at a rate of 2 kg / min. The theoretical minimum sol volume is calculated by the online intelligent control module: V_min = A × H × φ × η / (C_s × (1 - α)), A = 1m × 20m = 20 m², H = 5mm = 0.005 m, φ = 0.85, η = 1.1, C_s = 0.15, α = 0.15, therefore (1 - α) = 0.85, V_min = 20 × 0.005 × 0.85 × 1.1 / (0.15 × 0.85) = 0.0935 / 0.1275 = 0.733 m³, which is precisely supplied by the metering pump. After the sol was introduced, gradient pressure impregnation was initiated: the first stage pressure was 0.2 MPa, held for 1 minute; the second stage pressure was 0.45 MPa, held for 1 minute; and the third stage pressure was 0.8 MPa, held for 2 minutes. The pressure switching of each stage was automatically triggered by the ultrasonic detection signal. After impregnation, the aerogel was aged at 50°C for 5 hours, removed from the vacuum, and then supercritically dried to obtain the aerogel felt.

[0054] A comparative analysis was conducted between the conventional method of impregnating glass fiber mat under normal pressure and the method described in this embodiment. The results of the two experiments are shown in Table 1. Table 1

[0055] As can be clearly seen from Table 1, the vacuum pressure synergistic impregnation of the present invention can complete the uniform impregnation of the same area of ​​glass fiber mat in a shorter time and with a smaller amount of impregnation melt.

[0056] The product obtained in this embodiment, after being cut and tested, showed no dry core or bubbles throughout the thickness direction, a thermal conductivity of 0.018 W / m·K at room temperature, a first-pass yield of 98%, and a significantly reduced amount of sol compared to traditional processes.

[0057] Example 2: Vacuum-Pressure Synergistic Impregnation of Ceramic Fiber Felt A ceramic fiber felt with a width of 1m, a thickness of 8mm, and a surface density of 500g / m² was placed in a vacuum chamber. Dynamic pulsed vacuum degassing was performed with a vacuum level set to -0.08MPa and a pulse cycle of 90 seconds (70 seconds of evacuation followed by 20 seconds of de-vacuuming), for a cycle count N = 1.0×8 + 0.03×500 + 3 = 31 times. The sol introduction rate was 1.5kg / min, and the theoretical minimum sol amount was automatically calculated and controlled by the central controller. Gradient pressure impregnation was applied: first stage 0.15MPa / 2 minutes, second stage 0.4MPa / 1 minute, and third stage 0.7MPa / 2 minutes. Aging conditions were 60℃ / 8 hours.

[0058] A comparative analysis was conducted between the conventional method of impregnating ceramic fiber felt under normal pressure and the method of this embodiment. The results of the two experiments are shown in Table 2. Table 2

[0059] As can be clearly seen from Table 2, the vacuum pressure synergistic impregnation of the present invention can complete the uniform impregnation of the same area of ​​glass fiber mat in a shorter time and with a smaller amount of impregnation melt.

[0060] Because ceramic fiber felt has finer pores and a higher closed-cell rate, traditional processes are prone to producing dry cores. The product in this embodiment is cut to show uniform impregnation throughout the entire thickness, with no dry cores, a thermal conductivity of 0.020 W / m·K, a first-pass yield of 96%, and a significant reduction in the amount of sol used compared to traditional processes.

[0061] Example 3: Vacuum-pressurized synergistic impregnation of pre-oxidized fiber mat A pre-oxidized fiber mat with a width of 1m, a thickness of 3mm, and a surface density of 200g / m² was placed in a vacuum chamber. Dynamic pulsed vacuum degassing was performed with a vacuum level of -0.06MPa and a pulse cycle of 40 seconds (30 seconds of vacuuming followed by 10 seconds of vacuum breaking), for a total of N = 0.6×3 + 0.08×200 + 1 = 19 cycles. The sol introduction rate was 3kg / min. Gradient pressure impregnation was applied: first stage 0.25MPa / 1 minute, second stage 0.5MPa / 2 minutes, and third stage 0.9MPa / 2 minutes. Aging conditions were 40℃ / 3 hours.

[0062] The experimental results of the two methods are compared and analyzed by using the conventional process of impregnating pre-oxidized fiber felt under normal pressure with the method of this embodiment. Table 3 shows the comparison of the two experimental results.

[0063] Table 3

[0064] As can be clearly seen from Table 3, the vacuum pressure synergistic impregnation of the present invention can complete the uniform impregnation of the same area of ​​glass fiber mat in a shorter time and with a smaller amount of impregnation melt.

[0065] Pre-oxidized fiber felt has large pores but good fiber elasticity. Traditional processes are prone to uneven product thickness due to excessive sol. In this embodiment, the thickness uniformity deviation of the product is less than 2%, the first pass rate is 99%, and the amount of sol used is significantly reduced compared with the traditional process.

[0066] Example 4: Sol-gel recovery and recycling Based on Example 1, a sol recovery and circulation module is activated. Excess sol overflowing during the pressurized impregnation stage is collected in a collection tank, and fiber debris is removed by a filtration and impurity removal device. A viscosity compensation device monitors the viscosity of the recovered sol and adds an appropriate amount of solvent to adjust it to the set range (viscosity deviation controlled within ±5%). The adjusted sol is returned to the sol storage tank and mixed with freshly prepared sol at a 1:1 ratio for use.

[0067] Results: The comprehensive utilization rate of sol is increased to over 95%, the raw material cost is further reduced, and the performance of products prepared from recycled sol is consistent with that of new sol products, with a thermal conductivity deviation of less than 0.001 W / (m·K).

[0068] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A vacuum pressurized synergistic impregnation system for aerogel felt, characterized in that, The system includes a vacuum chamber, a dynamic pulsed vacuum degassing module, a sol supply module, a gradient pressure impregnation module, and an online intelligent control module. The vacuum chamber is used to contain roll-shaped or sheet-shaped fiber felt substrates. The dynamic pulsed vacuum degassing module is connected to the vacuum chamber and is used to periodically evacuate and break the vacuum cycle of the fiber felt to remove gas from the closed and blind pores inside the fiber felt. The sol supply module is connected to the vacuum chamber and is used to introduce aerogel sol into the fiber felt under vacuum. The gradient pressure impregnation module is connected to the vacuum chamber and is used to apply segmented increasing pressure to the fiber felt after the sol is introduced, so that the sol is further pressed into the micropores. The online intelligent control module is connected to the dynamic pulsed vacuum degassing module, the sol supply module, and the gradient pressure impregnation module respectively, and is used to automatically adjust the vacuum degree, holding time, pulse parameters, and sol supply amount according to the thickness, areal density, and target sol content of the fiber felt.

2. The system according to claim 1, characterized in that, The dynamic pulsating vacuum degassing module includes a vacuum pump, a vacuum buffer tank, a pulsating control valve, and a vacuum degree sensor. The vacuum pump is connected to the vacuum chamber through the vacuum buffer tank. The pulsating control valve is located on the pipeline between the vacuum buffer tank and the vacuum chamber and is used to control the periodic switching between vacuuming and vacuum breaking. The vacuum degree sensor is located inside the vacuum chamber and is used to monitor the vacuum degree of the chamber in real time.

3. The system according to claim 2, characterized in that, The pulsation cycle of the dynamic pulsating vacuum degassing module is 10 to 120 seconds. During a single pulsation, the vacuum level reaches -0.05 MPa to -0.09 MPa in the vacuuming phase and the chamber pressure recovers to -0.01 MPa to -0.03 MPa in the vacuum breaking phase. The number of pulsation cycles is automatically set by the online intelligent control module according to the thickness and areal density of the fiber felt.

4. The system according to claim 1, characterized in that, The gradient pressurization impregnation module includes a pressurization medium source, a segmented pressurization valve group, and a pressure sensor; the segmented pressurization valve group includes at least two pressurization branches with pressure levels, used to sequentially apply a first-stage pressure, a second-stage pressure, and a third-stage pressure to the fiber felt in the vacuum chamber, with each stage pressure dynamically increasing with the sol impregnation depth; the pressure sensor is used to monitor the chamber pressure in real time.

5. The system according to claim 4, characterized in that, The first stage pressure is 0.1MPa to 0.3MPa, the second stage pressure is 0.3MPa to 0.6MPa, and the third stage pressure is 0.6MPa to 1.0MPa. The holding time of each stage pressure is automatically adjusted by the online intelligent control module according to the fiber felt thickness and real-time impregnation depth feedback signal.

6. A method for preparing aerogel felt by vacuum pressure synergistic impregnation, characterized in that, Includes the following steps: Step 1: Place the fiber felt in the vacuum chamber and start the dynamic pulsed vacuum degassing to periodically evacuate and break the vacuum cycle of the fiber felt to remove the gas in the closed pores and blind pores inside the fiber felt. Step 2: Once the vacuum level of the cavity reaches the set value, aerogel sol is introduced into the fiber felt while maintaining the vacuum. The negative pressure suction force is used to draw the sol into the interior of the felt. Step 3: After the sol is introduced, gradient pressure impregnation is started instantly to apply segmented increasing pressure to the fiber felt, so that the sol is further pressed into the micropores to achieve uniform impregnation of the entire thickness. Step four: After impregnation is completed, the online intelligent control module automatically calculates and controls the theoretical minimum amount of solvent based on the thickness, areal density and target adhesive content of the fiber felt, so as to achieve low-volume, one-time impregnation.

7. The preparation method according to claim 6, characterized in that, In step one, the vacuum degree of dynamic pulsed vacuum degassing reaches -0.05MPa to -0.09MPa, the pulse period is 10 seconds to 120 seconds, the vacuuming phase in a single pulse lasts for 30 seconds to 90 seconds, and the vacuum breaking phase lasts for 10 seconds to 30 seconds; the number of pulse cycles N is determined by the formula N = k1·H + k2·ρ + c based on the fiber felt thickness H and the areal density ρ, where k1 and k2 are empirical coefficients related to the fiber type, and c is a baseline correction value.

8. The preparation method according to claim 6, characterized in that, In step two, the aerogel sol is introduced as follows: after the vacuum level of the cavity reaches -0.05MPa to -0.09MPa and remains stable, the sol supply valve is opened after a delay of 5 to 15 seconds, so that the sol flows evenly into the fiber felt under a stable negative pressure environment; the amount of sol introduced is adjusted in real time by the online intelligent control module according to the theoretical minimum amount of sol, and the introduction rate is 0.5kg / min to 5kg / min.

9. The preparation method according to claim 6, characterized in that, In step three, the gradient pressure impregnation is divided into three stages: the first stage has a pressure of 0.1 MPa to 0.3 MPa and a holding time of 1 to 3 minutes, allowing the sol to fully impregnate the surface and middle layers of the fiber felt; the second stage has a pressure of 0.3 MPa to 0.6 MPa and a holding time of 1 to 5 minutes, allowing the sol to diffuse into the deep pores; the third stage has a pressure of 0.6 MPa to 1.0 MPa and a holding time of 1 to 4 minutes, allowing the sol to be forced into the micro-blind pores and closed pore residual spaces; the pressure switching of each stage is automatically triggered by the online intelligent control module based on the real-time monitored sol impregnation depth signal.

10. The preparation method according to claim 9, characterized in that, The real-time monitoring of the sol penetration depth is achieved by arranging an ultrasonic probe on the side of the fiber felt and using the difference in sound velocity between the sol-containing area and the non-sol-containing area to determine the penetration depth.

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