Method and device for continuous preparation of highly dispersed superhydrophobic nanosilica

Abstract

The application belongs to the technical field of functional nanomaterial preparation and surface modification, and particularly relates to a continuous preparation method and device of high-dispersibility super-hydrophobic nanosilica. The application adopts an integrated process of "acid-catalyzed pre-hydrolysis-alkali-catalyzed condensation growth-in-situ long-chain alkyl silane grafting modification". Firstly, tetraethyl orthosilicate is pre-hydrolyzed under acid condition, then is transferred into an alkaline system to perform controllable condensation, monodisperse nanosilica sol is generated, then long-chain alkyl silane coupling agent is used for in-situ surface modification without separation, and finally the final product is obtained through washing and drying. Through ingenious process design, the application realizes uniform and high-density grafting of the modifier on the surface of the nanoparticles, and the prepared nanosilica has the outstanding advantages of spherical regularity, good monodispersity, and excellent dispersion stability in organic medium. The product can be widely applied to the fields of super-hydrophobic coating, self-cleaning material, oil-water separation, high-performance composite material and the like as a functional filler.

Description

Technical Field

[0001] This invention belongs to the field of functional nanomaterial preparation and surface modification technology, specifically relating to a method and apparatus for continuous preparation of highly dispersed superhydrophobic nano-silica. Background Technology

[0002] Nano-silica is an important inorganic nanomaterial that plays a crucial role in many fields due to its excellent mechanical properties, thermal stability, and large specific surface area. However, the abundance of silanol groups on its surface makes it hydrophilic, and the strong hydrogen bonding between particles leads to its easy aggregation in organic media and polymer matrices, which severely restricts the realization of its nano-effects and the improvement of its application performance.

[0003] Hydrophobic surface modification of nano-silica is key to solving the aforementioned problems. Existing hydrophobic modification methods mainly include physical adsorption and chemical grafting. Physical adsorption is unstable, and the modifier is prone to desorption. Chemical grafting, especially using silane coupling agents, is more reliable due to its ability to form strong covalent bonds (Si-O-Si). However, existing chemical modification methods still have many shortcomings: Post-modification method: First, silica is prepared, and then it is dispersed and modified. This method is complicated, and the dried nano-silica will undergo irreversible hard agglomeration during the redispersion process, resulting in uneven modification and the modifier cannot effectively contact the silanol groups encapsulated in the agglomerates.

[0004] Vapor phase modification method: The equipment is complex and the cost is high, making it difficult to apply on a large scale.

[0005] Insufficient selection of modifiers and process optimization: Many methods use short-chain silanes, which can provide hydrophobicity, but it is difficult to achieve a superhydrophobic state, and the modified particles have poor long-term dispersion stability in complex organic systems.

[0006] Coarse process control: Insufficient precision in controlling reaction conditions for key steps such as hydrolysis, condensation, and modification leads to wide particle size distribution, uneven morphology, and poor performance repeatability of the products. Especially in batch reactors, uneven micro-mixing of materials, low mass and heat transfer efficiency, and gradients and fluctuations in reaction parameters (such as pH and concentration) make it difficult to precisely control the nucleation, growth, and surface modification processes of nanoparticles, resulting in poor batch-to-batch product quality stability.

[0007] Furthermore, existing nano-silica surfaces are rich in hydroxyl groups, exhibiting strong hydrophilicity and a tendency to aggregate, resulting in poor dispersibility in organic systems. Traditional modification methods include gas-phase methods, post-modification methods, and one-step co-condensation methods, but these suffer from problems such as complex processes, uneven modification, wide particle size distribution, high energy consumption, and poor reproducibility. Especially in batch systems, the uncontrollable hydrolysis and condensation rates often lead to uneven particle morphology and fluctuations in hydrophobic properties. Summary of the Invention

[0008] The purpose of this invention is to provide a method and apparatus for the continuous preparation of highly dispersible superhydrophobic nano-silica.

[0009] The first aspect of this application provides a method for the continuous preparation of highly dispersible superhydrophobic nano-silica, comprising the following steps: (1) Preparation of silicon source prehydrolysate: Tetraethyl orthosilicate, anhydrous ethanol (part 1), deionized water (part 1) and acid catalyst are mixed and prehydrolyzed to obtain prehydrolysate; (2) Synthesis of nano silica sol: Ammonia water, anhydrous ethanol in the second part and deionized water in the second part are mixed to prepare an alkaline catalytic system; under strong stirring, the pre-hydrolyzed solution obtained in step (1) is slowly added dropwise to the alkaline catalytic system, and monodisperse nano silica sol is obtained after the reaction. (3) In-situ hydrophobic modification: Add an ethanol solution of a long-chain alkyl silane coupling agent to the nano silica sol obtained in step (2) to carry out a surface grafting reaction; (4) Post-treatment and activation: After the reaction is completed, the solid product is separated and washed several times with a mixed solvent of anhydrous ethanol and n-hexane. Finally, it is dried to obtain the highly dispersed superhydrophobic nano silica.

[0010] In one embodiment of this application, in step (1): The acid catalyst is hydrochloric acid, acetic acid, or nitric acid with a concentration of 0.01–0.1 mol / L; The molar ratio of the tetraethyl orthosilicate, the first portion of anhydrous ethanol, and the first portion of deionized water is 1:(40-60):(15-25); wherein The acid catalyst is added at the catalytic level and does not participate in the stoichiometry of the main reaction; when it is added in the form of an aqueous solution, the water introduced must be included in the total molar amount of deionized water in the first part of the formula to ensure that the molar ratio of the main raw materials meets the specified requirements.

[0011] Optionally, the solution can be pre-hydrolyzed by stirring at 30–50°C for 0.5–2 hours to obtain a transparent and clear pre-hydrolyzed solution.

[0012] In one embodiment of this application, in step (2): The concentration of the ammonia solution is 25-28%; The molar ratio of tetraethyl orthosilicate to NH3 in ammonia water is 1:(2.5-4); in the alkaline catalytic system, the total volume ratio of the second part of anhydrous ethanol and the second part of deionized water to the volume ratio of tetraethyl orthosilicate is (8-15):1; that is, the amount of NH3 used is determined by the molar ratio with tetraethyl orthosilicate, and the total volume of the second part of anhydrous ethanol and the second part of deionized water is determined by the volume ratio with tetraethyl orthosilicate.

[0013] Optionally, the reaction can be carried out at 40–70°C for 2–6 hours to obtain monodisperse nano-silica sol.

[0014] In one embodiment of this application, in step (3), the long-chain alkylsilane coupling agent is a compound with the general formula R-Si-(OR')3, wherein R is a C12-C18 straight-chain alkyl group and R' is a methyl or ethyl group.

[0015] In one embodiment of this application, the amount of the long-chain alkylsilane coupling agent is 15% to 35% of the mass of the tetraethyl orthosilicate.

[0016] In one embodiment of this application, the long-chain alkylsilane coupling agent is selected from at least one of hexadecyltrimethoxysilane, octadecyltriethoxysilane, and dodecyltrimethoxysilane.

[0017] In one embodiment of this application, the concentration of the ethanol solution of the long-chain alkylsilane coupling agent is 5% to 15% (w / v).

[0018] In one embodiment of this application, the surface grafting reaction temperature is 60–85°C, and the reaction time is 4–10 hours. Preferably, the surface grafting reaction temperature is 70–80°C, and the reaction time is 6–8 hours.

[0019] In one embodiment of this application, in step (4), the volume ratio of the mixed solvent of anhydrous ethanol and n-hexane is 1:1. The number of washing cycles can be at least 3.

[0020] In one embodiment of this application, the vacuum drying temperature is 60–90°C and the time is 8–16 hours.

[0021] The second aspect of this application provides a highly dispersed superhydrophobic nano-silica prepared by the preparation method described above, with an average particle size of 20-100 nm, PDI≤0.15, water contact angle≥155°, and no sedimentation in toluene after 24 hours.

[0022] A second aspect of this application provides a continuous preparation apparatus for highly dispersed superhydrophobic nano-silica, comprising: The following components are connected in sequence: acidic pre-hydrolysis module (R-101), micro mixer (MX-201), tubular aging-growth reactor (R-202), in-situ grafting module (R-301), solid-liquid separation and countercurrent washing unit (F-401, W-402), vacuum drying unit (VBD-501 / FB-502), and solvent recovery module (D-601); among which... The acidic pre-hydrolysis module is used to mix and pre-hydrolyze tetraethyl orthosilicate, anhydrous ethanol, deionized water and acid catalyst to obtain a pre-hydrolysate; The tubular aging-growth reactor is used to contain an alkaline catalytic system, and the micromixer is used to inject the pre-hydrolyzed solution into the tubular aging-growth reactor to obtain nano-silica sol. The in-situ grafting module is used to receive nano-silica sol and add an ethanol solution of long-chain alkylsilane coupling agent to carry out a surface grafting reaction. The solid-liquid separation and countercurrent washing unit is used to separate solids and perform washing.

[0023] In one embodiment, the device is equipped with turbidity, moisture, conductivity, DLS particle size sensors and a PLC closed-loop control system.

[0024] In one embodiment of this application, the mixing time of the micromixer is ≤50 ms, and the residence time of the tubular aging-growth reactor is 2-20 min.

[0025] In one embodiment of this application, the in-situ grafting module is equipped with a humidity control unit to maintain the water activity a_w of the reaction system at 0.20-0.50.

[0026] In one embodiment of this application, the vacuum drying unit operates at 60-90℃ and ≤5 kPa to achieve Si-O-Si bond bridging and curing.

[0027] The beneficial effects of this invention are: Excellent superhydrophobic properties: Due to the use of long-chain alkylsilanes (C12~C18) and the achievement of high-density grafting, the resulting product has a stable contact angle with water of more than 155° and a roll-off angle of less than 10°, which meets the superhydrophobic standard.

[0028] Extremely high organic phase dispersibility: The modification is uniform and thorough, with strong interparticle repulsion, and it can be stably dispersed in organic media such as toluene, cyclohexane, and epoxy resin for a long time without sedimentation.

[0029] Excellent monodispersity and particle size controllability: The "acid-base two-step method" effectively controls the nucleation and growth kinetics of particles. Combined with the instantaneous uniform mixing of the micro-mixer in the continuous device, the resulting nano-silica spheres are regular in shape, with a narrow particle size distribution (PDI≤0.15) and an average particle size that can be adjusted in the range of 20 to 100 nm.

[0030] Stable and repeatable process: In continuous production, the high consistency of product performance between batches can be ensured by precisely limiting the material ratio, reaction temperature, time and feeding method of each step and PLC closed-loop control, thus solving the problem of fluctuation in batch process.

[0031] High production efficiency and easy to scale up: Continuous production equipment achieves seamless connection from raw materials to products, reduces batch-to-batch operations, improves production efficiency, and has significant potential for industrial scale-up.

[0032] Broad application prospects: This product can be used as a high-performance additive to prepare self-cleaning coatings, anti-icing coatings, oil-water separation materials, high-performance composite materials, etc., significantly improving the performance of the matrix material.

[0033] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the chemical equation for the preparation of the present invention; Figure 2 This is a schematic diagram of the preparation apparatus of the present invention; Figure 3 XRD curves of nano-silica Figure 4 Nitrogen adsorption-desorption isotherm of nano-silica Figure 5 Infrared spectrum of nano-silica Figure 6 SEM image of nano-silica Figure 7 TEM image of nano-silica. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Figure 1 This is a schematic diagram of the chemical equation for the preparation of this invention. Specifically: Step 1: Complete hydrolysis of tetraethoxysilane. Tetraethoxysilane undergoes a hydrolysis reaction with 4 molecules of water, and the ethoxy group (-OC2H5) is completely replaced by the hydroxyl group (-OH), producing orthosilicic acid (Si(OH)4) and 4 molecules of ethanol (C2H5OH).

[0039] Step 2: Condensation reaction between silanol groups. Two orthosilicic acid molecules undergo dehydration condensation to form Si-O-Si covalent bonds, generating dimer silicic acid, while simultaneously losing one molecule of water.

[0040] Step 3: Cocondensation reaction of partially hydrolyzed silanes. The completely hydrolyzed orthosilicic acid undergoes cocondensation with the silane intermediate that still retains some ethoxy groups, and Si-O-Si bonds are formed through dehydration. Example 1:

[0041] (1) Preparation of silicon source pre-hydrolysate: 74 mL of anhydrous ethanol, 10 mL of deionized water and 0.2 mL of 0.1 mol / L hydrochloric acid solution were added to a round-bottom flask and stirred until homogeneous. Then 6 mL of tetraethyl orthosilicate was slowly added. The system was heated to 40 °C and stirred at a constant temperature for 1 hour to obtain a clear and transparent pre-hydrolysate.

[0042] (2) Synthesis of nano-silica sol: In another round-bottom flask, add 80 mL of anhydrous ethanol, 10 mL of deionized water and 6 mL of ammonia solution with a concentration of 25-28%, and mix well. Under mechanical stirring, use a constant pressure dropping funnel to slowly add the pre-hydrolyzed solution from step (1) to this alkaline system at a rate of about 1 drop / second. After the addition is complete, heat the reaction system to 60°C and continue the reaction for 4 hours to obtain monodisperse nano-silica sol.

[0043] (3) In-situ hydrophobic modification: Weigh 2.5 g of hexadecyltrimethoxysilane and dissolve it in 20 mL of anhydrous ethanol. Add this solution slowly dropwise to the sol in step (2) at a rate of 2 mL / min through a dropping funnel. After the addition is complete, raise the reaction temperature to 75 °C and reflux the reaction under constant temperature and stirring for 7 hours.

[0044] (4) Post-treatment and activation: After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The reaction mixture was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 15 minutes. The precipitate was redispersed with 50 mL of anhydrous ethanol / n-hexane mixed solvent (1:1 volume ratio) and washed by centrifugation. This process was repeated 3 times. The washed white precipitate was transferred to a petri dish and dried in a vacuum drying oven at 75°C for 12 hours to obtain a loose white powder product (referred to as sample 1). Example 2:

[0045] The continuous preparation apparatus described in this invention is used for: (1) In the acidic prehydrolysis module (R-101): Tetraethyl orthosilicate, anhydrous ethanol, deionized water and dilute hydrochloric acid are mixed in a molar ratio of 1:10:2:0.05 and stirred at 40°C for 1 hour to generate a clear prehydrolysis solution; (2) Alkali-catalyzed growth reaction: A mixture of ammonia / ethanol / water (ammonia concentration 1 mol / L) was injected into a tubular aging-growth reactor (R-202) and kept at a constant temperature of 60℃. The pre-hydrolyzed solution was injected at a rate of 0.5 mL / min through a micro-mixer (MX-201), with a mixing time of <50 ms; (3) In-situ grafting modification: In the unseparated state of the system, 20 mL of hexadecyltrimethoxysilane (HDTMS) ethanol solution (concentration 13.7%) was added dropwise to the sol at 2 mL / min in the in-situ grafting module (R-301), and the reaction was carried out at 75 °C for 6 hours, with the water activity a_w = 0.3. (4) Separation and drying: After high-speed centrifugation in the solid-liquid separation unit (F-401), the filtrate is washed three times with alternating EtOH / n-hexane in the countercurrent washing unit (W-402) until the conductivity of the filtrate is ≤20 μS / cm; finally, it is vacuum dried in the vacuum drying unit (VBD-501) at 75℃ and 5 kPa for 12 hours.

[0046] The resulting product is a white, free-flowing powder. Example 3:

[0047] Only steps (1) and (2) of Example 1 were performed. After the reaction was completed, the sample was centrifuged directly, washed three times with anhydrous ethanol, and then dried to obtain unmodified hydrophilic nano-silica (referred to as Sample 2).

[0048] Performance testing and characterization All samples prepared above were subjected to the following tests: Morphology and particle size: Observed using scanning electron microscopy and transmission electron microscopy.

[0049] Crystal structure: Analyzed using X-ray diffraction.

[0050] Chemical structure: Analyzed using Fourier transform infrared spectroscopy.

[0051] Pore ​​size and pore volume: analyzed using a nitrogen adsorption-desorption tester.

[0052] Figure 3 The results are qualitative characterization of the crystal structure of the target sample in Example 1. X-ray diffraction (XRD) directly verifies that the sample prepared in this example is high-purity amorphous nano-silica without crystalline impurities.

[0053] Figure 4 This is a quantitative characterization result of the pore structure and specific surface area of ​​the target sample in Example 1. The nitrogen adsorption-desorption test verified that the pore structure of the sample prepared in this example is controllable and the pore size distribution is narrow. The measured BET specific surface area deviates from the theoretical value by less than 10%.

[0054] Figure 5 This is a comparative characterization of the surface chemical structure of the modified sample from Example 1 and the blank control sample from Example 3. The upper figure shows the infrared spectrum of the unmodified sample from Example 3, verifying the inorganic framework core structure of silica and serving as a reference. The lower figure shows the infrared spectrum of the modified sample from Example 1. In addition to retaining the characteristic peaks of the silica framework, characteristic peaks of long-chain alkyl groups and Si-C bonds were detected, directly proving that the in-situ modification process of Example 1 successfully grafted the long-chain alkylsilane coupling agent onto the silica surface through covalent bonds, rather than through physical adsorption.

[0055] Figure 6 This is a direct characterization of the microstructure, particle size and dispersibility of the target sample in Example 1. The scanning electron microscope (SEM) observation verified that the sample prepared in this example has regular spherical shape, no obvious hard agglomerates, excellent monodispersity, and particle size RSD < 5%.

[0056] Figure 7 The results are high-resolution characterizations of the internal microstructure of the target sample in Example 1. Observation by transmission electron microscopy (TEM) verified that the sample prepared in this example is a solid, dense, homogeneous structure without core-shell delamination, proving that the in-situ modification process of this application achieves uniform grafting of the modifier on the entire surface of the nanoparticles, rather than local modification.

[0057] How technical effects are manifested: The samples presented in this application exhibit perfect spherical shape, clear particle boundaries, no obvious hard agglomeration, and independent dispersion of individual particles, with a particle size RSD < 5% (meeting the monodispersity standard). TEM revealed a solid, dense, homogeneous structure of SiO2 particles, demonstrating that in-situ modification achieved uniform grafting across the entire surface, rather than localized modification.

[0058] The sample from this application only showed the characteristic broad peaks of amorphous SiO2, without any sharp crystalline peaks, indicating that the prepared sample was high-purity amorphous nano-SiO2.

[0059] The sample from this application exhibited extremely strong long-chain alkyl characteristic peaks and Si-C bond characteristic peaks, while the unmodified blank sample did not show these peaks, proving that the long-chain alkylsilane coupling agent was successfully grafted onto the SiO2 surface via covalent bonds, rather than through physical adsorption.

[0060] The measured BET specific surface area of ​​the sample in this application is in high agreement with the theoretical value, with a deviation of less than 10%. The sample has a narrow pore size distribution and controllable pore structure. The specific surface area and pore structure can be precisely adjusted through process parameters, making it suitable for different application scenarios such as superhydrophobic coatings, rubber reinforcement, and ink matting. This is superior to the shortcomings of traditional processes, which have uncontrollable structures and poor adaptability.

[0061] In summary, this invention provides an efficient, reliable, and scalable method and apparatus for preparing high-performance superhydrophobic nano-silica, and the product has great application potential.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A continuous preparation method for highly dispersible superhydrophobic nano-silica, characterized in that, Includes the following steps: (1) Preparation of silicon source prehydrolysate: Tetraethyl orthosilicate, anhydrous ethanol (part 1), deionized water (part 1) and acid catalyst are mixed and prehydrolyzed to obtain prehydrolysate; (2) Synthesis of nano silica sol: Ammonia water, anhydrous ethanol in the second part and deionized water in the second part are mixed to prepare an alkaline catalytic system; under strong stirring, the pre-hydrolyzed solution obtained in step (1) is slowly added dropwise to the alkaline catalytic system, and monodisperse nano silica sol is obtained after the reaction. (3) In-situ hydrophobic modification: Add an ethanol solution of a long-chain alkyl silane coupling agent to the nano silica sol obtained in step (2) to carry out a surface grafting reaction; (4) Post-treatment and activation: After the reaction is completed, the solid product is separated and washed several times with a mixed solvent of anhydrous ethanol and n-hexane. Finally, it is dried to obtain the highly dispersed superhydrophobic nano silica.

2. The preparation method according to claim 1, characterized in that, In step (1): The acid catalyst is hydrochloric acid, acetic acid, or nitric acid with a concentration of 0.01–0.1 mol / L; The molar ratio of the tetraethyl orthosilicate, the first part of anhydrous ethanol, and the first part of deionized water is 1: (40-60): (15-25).

3. The preparation method according to claim 1, characterized in that, In step (2): The concentration of the ammonia water is 25-28%; The molar ratio of tetraethyl orthosilicate to NH3 in ammonia water is 1:(2.5-4); In the alkaline catalytic system, the total volume ratio of the second part of anhydrous ethanol and the second part of deionized water to the volume ratio of tetraethyl orthosilicate is (8-15):

1.

4. The preparation method according to claim 1, characterized in that, In step (3), the long-chain alkylsilane coupling agent is a compound with the general formula R-Si-(OR')3, wherein R is a C12-C18 straight-chain alkyl group, and R' is methyl or ethyl; and / or The amount of the long-chain alkylsilane coupling agent is 15% to 35% of the mass of the tetraethyl orthosilicate.

5. The preparation method according to claim 4, characterized in that, The long-chain alkylsilane coupling agent is selected from at least one of hexadecyltrimethoxysilane, octadecyltriethoxysilane, and dodecyltrimethoxysilane.

6. The preparation method according to claim 4, characterized in that, The concentration of the ethanol solution of the long-chain alkylsilane coupling agent is 5%–15% (w / v); and / or The surface grafting reaction is carried out at a temperature of 60–85°C for 4–10 hours.

7. The preparation method according to claim 1, characterized in that, In step (4), the volume ratio of the mixed solvent of anhydrous ethanol and n-hexane is 1:1; and / or The vacuum drying temperature is 60–90°C, and the time is 8–16 hours.

8. A highly dispersed superhydrophobic nano-silica prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The average particle size is 20-100 nm, PDI≤0.15, water contact angle≥155°, and there is no sedimentation in toluene after 24 hours.

9. A continuous preparation apparatus for highly dispersible superhydrophobic nano-silica, characterized in that, include: The system consists of, in sequence, an acidic pre-hydrolysis module, a micromixer, a tubular aging-growth reactor, an in-situ grafting module, a solid-liquid separation and countercurrent washing unit, a vacuum drying unit, and a solvent recovery module; among which... The acidic pre-hydrolysis module is used to mix and pre-hydrolyze tetraethyl orthosilicate, anhydrous ethanol, deionized water and acid catalyst to obtain a pre-hydrolysate; The tubular aging-growth reactor is used to contain an alkaline catalytic system, and the micromixer is used to inject the pre-hydrolyzed solution into the tubular aging-growth reactor to obtain nano-silica sol. The in-situ grafting module is used to receive nano-silica sol and add an ethanol solution of long-chain alkylsilane coupling agent to carry out a surface grafting reaction. The solid-liquid separation and countercurrent washing unit is used to separate solids and perform washing.

10. The continuous preparation apparatus as described in claim 9, characterized in that, include: The mixing time of the micro mixer is ≤50 ms, and the residence time of the tubular aging-growth reactor is 2-20 min; The in-situ grafting module is equipped with a humidity control unit to maintain the water activity a_w of the reaction system at 0.20-0.

50. The vacuum drying unit operates at 60-90℃ and ≤5 kPa to achieve Si-O-Si bond bridging and curing.

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