Durable anti-fingerprint pollution low-density transparent silica aerogel and preparation method and application thereof

Abstract

The application relates to a low-density transparent silica aerogel with durable anti-fingerprint pollution and a preparation method and application thereof. The method comprises the following steps: sequentially performing calcination, preliminary humidification in a constant-temperature and constant-humidity box and controllable humidification treatment in a vacuum drying box on the low-density transparent silica aerogel; performing gas-phase anti-fingerprint pollution modification on the low-density transparent silica aerogel subjected to wet activation treatment and a modification liquid containing perfluorosilane reagent and ammonium methanol; and performing heat vacuum treatment on the low-density transparent silica aerogel subjected to the gas-phase anti-fingerprint pollution modification, so as to obtain the low-density transparent silica aerogel with durable anti-fingerprint pollution. The method does not cause any influence on the intrinsic structure, light weight characteristics and transparent function of the aerogel. The strong bonding of the coating and the substrate based on chemical reaction makes the coating not easy to fall off. Even if the surface layer of the aerogel is damaged, the newly exposed surface layer is still covered with a perfluoro coating, and the low-density transparent silica aerogel has excellent durable anti-fingerprint pollution effect.

Description

Technical Field

[0001] This invention belongs to the field of nanoporous materials technology, and particularly relates to a durable, fingerprint-resistant, low-density transparent silica aerogel, its preparation method, and its application. Background Technology

[0002] Low-density transparent silica aerogels are a type of high-performance aerogel material characterized by their lightweight and high transparency. Their high light transmittance makes them widely used in deep space exploration missions (such as capturing cosmic dust), high-energy physics, and transparent windows in energy-efficient buildings. However, due to their low density and high porosity, low-density transparent silica aerogels have poor mechanical properties. In practical applications, they often require careful manual assembly into protective frames, inevitably involving frequent handling. This handling inevitably leaves fingerprints and other stains on the aerogel's surface. The oily contamination from fingerprints is visually more noticeable and difficult to clean, severely impacting the aerogel's transparency and aesthetics, thus affecting its practical applications. Therefore, developing low-density transparent silica aerogels with fingerprint-resistant properties has significant economic value.

[0003] One of the key aspects of anti-fingerprint coatings lies in the fact that the constructed coating is a superhydrophobic system, making it difficult for fingerprint grease to adhere, thus achieving an anti-fingerprint effect. Many existing technologies report on the formation of anti-fingerprint coatings on substrate surfaces and their manufacturing methods. For example, Chinese patent application CN112189061A describes a novel method for coating a metal substrate with an anti-fingerprint coating by using a water-soluble silicone coating mixture. Chinese patent application CN114507475A involves an anti-fingerprint coating composition consisting of a silane-functionalized polymer, a polymer containing fluorinated polyether groups, and an organic solvent. Chinese patent application CN115079316A introduces a coating composed of perfluoropolyether chains. Chinese patent application CN115124910A describes a durable, lubricating, and fingerprint-resistant coating and its manufacturing method. It describes a fluorinated liquid coating material composed of perfluoropolyether, methyl nonafluorobutyl ether, and nano-calcium carbonate that can improve wear resistance. Chinese patent applications CN116515097A, CN115216001A, and CN113788942A respectively use complex synthesis to prepare fluorides such as fluorinated polyether siloxane, fluorinated siloxane compounds, and perfluoropolyether siloxane as fingerprint-resistant coatings to improve the anti-fouling performance of the substrate surface.

[0004] However, currently reported anti-fingerprint coating methods are not suitable for special substrates such as low-density transparent silica aerogels, especially in aerospace applications where the content of condensable volatiles must be strictly controlled. The problems with applying these methods to low-density transparent silica aerogels include: First, low-density silica aerogels have high porosity, making them susceptible to penetration when using fluorinated compounds and organic solvents as coating compounds during spraying or brushing, thus damaging the aerogel's porous structure; Second, existing methods often involve the addition of additives such as nanoparticles or thick coatings, which negatively impact the aerogel's high transparency; Third, the bonding between the coating and the silica aerogel is relatively weak, resulting in insufficient wear resistance and a decrease in anti-fingerprint performance over prolonged use; Fourth, current anti-fingerprint coatings tend to release volatiles under high vacuum conditions, which is detrimental to long-term use in sealed spacecraft systems; Fifth, once the reported methods are used, the surface coating of the aerogel is damaged, and the newly exposed surface no longer possesses anti-fingerprint properties.

[0005] Therefore, there is an urgent need to develop a durable anti-fingerprint coating for low-density transparent silica aerogel. The developed coating should not only not have any adverse effects on the material's inherent porous structure, high transparency, and lightweight properties, but also have wear-resistant and long-lasting anti-fingerprint properties, meeting the application requirements of low-density transparent silica aerogel in both conventional and certain special environments. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, this invention provides a durable, fingerprint-resistant, low-density transparent silica aerogel, its preparation method, and its application.

[0007] The present invention provides a method for preparing a durable, fingerprint-resistant, low-density transparent silica aerogel, the method comprising the following steps:

[0008] (1) Provide low-density transparent silica aerogel;

[0009] (2) The low-density transparent silica aerogel was subjected to calcination, preliminary humidification in a constant temperature and humidity chamber and controlled humidification in a vacuum drying oven in sequence to obtain the wet-activated low-density transparent silica aerogel.

[0010] (3) The wet-activated low-density transparent silica aerogel was modified with a modified liquid containing perfluorosilane reagent and ammonia methanol in the gas phase to prevent fingerprint pollution, and a fingerprint-resistant low-density transparent silica aerogel was obtained.

[0011] (4) The low-density transparent silica aerogel that is resistant to fingerprint contamination is subjected to a durability strengthening treatment to obtain a durable low-density transparent silica aerogel that is resistant to fingerprint contamination.

[0012] Preferably, in step (2): the calcination is carried out in a muffle furnace, the calcination temperature is 300-500°C, and the calcination time is 0.1-2 hours.

[0013] Preferably, in step (2): the initial humidification of the constant temperature and humidity chamber is to keep it at a temperature of 25-40℃ and a humidity of 20-50% for 5-120 minutes; preferably, the initial humidification of the constant temperature and humidity chamber is to keep it at a temperature of 25-40℃ and a humidity of 35% for 20 minutes.

[0014] Preferably, in step (2): the vacuum drying oven controllable humidification treatment is performed under the condition of a temperature of 25 to 40°C and an absolute pressure of no more than 50 Pa for 1 to 8 hours, preferably 3 hours.

[0015] Preferably, in step (3): the perfluorosilane reagent is one or more of 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane.

[0016] Preferably, in step (3): the molar ratio of the perfluorosilane reagent to ammonia in the ammonia-methanol is 1:(0.002-0.05), preferably 1:0.02; and / or the amount of the perfluorosilane reagent to the mass ratio of the low-density transparent silica aerogel is 0.001-0.03 mol / g, preferably 0.005 mol / g.

[0017] Preferably, in step (3): the vapor phase anti-fingerprint contamination modification is performed at 60-120°C for 1-48 hours; more preferably, the vapor phase anti-fingerprint contamination modification is performed at 90°C for 12 hours.

[0018] Preferably, in step (4): the durability strengthening treatment is performed for 1 to 48 hours at a temperature of 100 to 180°C and an absolute pressure of no more than 0.0007 Pa; preferably, the durability strengthening treatment is performed for 24 hours at a temperature of 150°C and an absolute pressure of no more than 0.0007 Pa.

[0019] In a second aspect, the present invention provides a durable, fingerprint-resistant, low-density transparent silica aerogel prepared by the preparation method described in the first aspect of the present invention. Preferably, the durable, fingerprint-resistant, low-density transparent silica aerogel has one or more of the following properties: the durable, fingerprint-resistant, low-density transparent silica aerogel has good hydrophobic and oleophobic properties, effectively reducing fingerprint marks or stains generated when touching the aerogel surface, exhibiting excellent fingerprint resistance; the light transmittance of the durable, fingerprint-resistant, low-density transparent silica aerogel remains essentially unchanged before and after fingerprint resistance modification; the durable, fingerprint-resistant, low-density transparent silica aerogel has anti-fouling properties from the surface to the interior, and after the aerogel surface layer is damaged, the newly exposed surface layer still has good fingerprint resistance; the durable, fingerprint-resistant, low-density transparent silica aerogel has low total mass loss and condensable volatiles in a vacuum environment, and will not cause environmental pollution in a closed environment.

[0020] In a third aspect, the present invention provides the application of a durable, fingerprint-resistant, low-density transparent silica aerogel prepared by the preparation method described in the first aspect of the present invention in the fields of next-generation deep space exploration, high-energy physics, building construction, or electronics.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) The present invention uses perfluorosilane reagents, which have extremely low surface tension and can achieve oleophobic coating, which is beneficial to the removal of fingerprint stains; they are commercial chemical reagents, and the materials are readily available, avoiding complex processes and harsh conditions in synthesis, effectively reducing material costs; they have relatively low boiling points and can undergo efficient gas-phase reactions. Unlike in-situ modification in immersion modification or sol-gel process, the present invention uses perfluorosilane reagents for gas-phase anti-fingerprint pollution modification.

[0023] (2) The durable anti-fingerprint modification coating provided by the method of the present invention has high bonding strength with the aerogel skeleton interface from the inside to the outside, giving the coating long-term durability. This is due to the following aspects: First, the selection of materials uses perfluorosilane reagents with multifunctional groups, which can form multifunctional bonds with the substrate material and have the potential advantage of strong bonding with the substrate; Second, the special activation process of calcination, humidification and vacuum treatment exposes a large number of fresh and active hydroxyl groups on the surface of the aerogel structure without being damaged by water vapor, providing reaction sites with the multifunctional perfluorosilane reagent; Third, the unique ammonia-methanol catalyst system is used in the gas phase anti-fingerprint modification, which not only strengthens the reaction between the substrate hydroxyl sites and the perfluorosilane reagent, but also effectively avoids the introduction of water with a much higher stoichiometric ratio than water and silane in the conventional alkaline catalyst aqueous solution system; Finally, since the gas phase anti-fingerprint modification occurs on the entire surface of the porous skeleton structure of the aerogel, when the coating on the surface of the aerogel is damaged for some reason, the newly exposed surface still has anti-fingerprint properties.

[0024] (3) The durable, fingerprint-resistant, low-density transparent silica aerogel of the present invention has low total mass loss and condensable volatiles in a vacuum environment and will not cause environmental pollution in a closed environment.

[0025] (4) The durable anti-fingerprint staining modification strategy of the present invention is applicable not only to low-density transparent silica aerogel, but also to high-density transparent silica aerogel, and is also applicable to other substrate materials such as inorganic glass and ceramics. It has good universality and the method is simple and easy to operate. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation process of a durable, fingerprint-resistant, low-density transparent silica aerogel according to some specific embodiments of the present invention.

[0027] Figure 2 This is an image of the durable, fingerprint-resistant, low-density transparent silica aerogel prepared in Example 1 of this invention placed on a metal mesh.

[0028] Figure 3 This is a scanning electron microscope image of the durable, fingerprint-resistant, low-density transparent silica aerogel prepared in Example 1 of this invention.

[0029] Figure 4 This is a fluorine distribution diagram at different locations inside the durable, fingerprint-resistant, low-density transparent silica aerogel prepared in Example 1 of the present invention.

[0030] Figure 5This is an image of the durable, fingerprint-resistant, low-density transparent silica aerogel prepared in Example 1 of this invention, after being cleaned with an organic solvent (n-hexane) following a fingerprint imprinting test and then placed on a metal mesh. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] The present invention provides a method for preparing a durable, fingerprint-resistant, low-density transparent silica aerogel, the method comprising the following steps:

[0033] (1) Provide low-density transparent silica aerogel; the present invention does not specifically limit the source of the low-density transparent silica aerogel, for example, it can be a product purchased on the market or prepared by existing methods;

[0034] (2) The low-density transparent silica aerogel is subjected to calcination, preliminary humidification in a constant temperature and humidity chamber and controlled humidification in a vacuum drying oven in sequence to obtain a wet-activated low-density transparent silica aerogel; this step (2) is to perform a controlled surface humidification activation treatment on the low-density transparent silica aerogel, which includes calcination, preliminary humidification in a constant temperature and humidity chamber and controlled humidification in a vacuum drying oven in sequence to obtain a low-density transparent silica aerogel with controlled humidification activation of the microstructure for later use;

[0035] (3) The wet-activated low-density transparent silica aerogel is modified with a modification liquid containing perfluorosilane reagent and ammonia methanol in the gas phase to obtain a fingerprint-resistant low-density transparent silica aerogel; Step (3) is to modify the wet-activated low-density transparent silica aerogel to prevent fingerprint contamination. Specifically, for example, the wet-activated low-density transparent silica aerogel to be used is placed on the upper metal mesh of the modification tank (the lower layer of the metal mesh is pre-filled with a modification liquid containing perfluorosilane reagent and ammonia methanol), and the fingerprint-resistant modification is carried out at a certain temperature to obtain a fingerprint-resistant low-density transparent silica aerogel with a perfluorinated coating on the skeleton surface.

[0036] (4) The low-density transparent silica aerogel with anti-fingerprint contamination is subjected to a durability strengthening treatment (thermal vacuum treatment) to obtain a durable low-density transparent silica aerogel with anti-fingerprint contamination; In this invention, the durability strengthening treatment is to put the low-density transparent silica aerogel with anti-fingerprint contamination into a thermal vacuum treatment device, control the reaction temperature and vacuum degree, so that the perfluorinated coating and the aerogel skeleton undergo an interfacial strengthening reaction to obtain a durable low-density transparent silica aerogel with anti-fingerprint contamination performance with long-term durability.

[0037] This invention develops a unique strategy for durable anti-fingerprint contamination of nanoporous optically transparent materials. The core principle involves using a vaporized perfluorosiloxane reagent to react with the active hydroxyl groups on the entire nanostructure surface of activated silica aerogel. Under the influence of trace amounts of water and ammonia as a catalyst, a high-strength condensation reaction occurs. Because the reaction occurs in a near-monolayer, high-intensity manner throughout the entire spatial structure of the aerogel, the coating exhibits strong adhesion to the aerogel matrix and is extremely thin, without affecting the aerogel's intrinsic structure, lightweight properties, or transparency. The strong chemical bond between the coating and the matrix makes the coating difficult to detach. Even if the aerogel surface is damaged, the newly exposed surface is still covered with a perfluoro coating. This perfluoro coating possesses excellent properties such as low surface energy and superhydrophobicity and superoleophobicity, thus providing superior durable anti-fingerprint contamination.

[0038] Before performing vapor-phase anti-fingerprint modification, this invention employs a special activation process involving sequential calcination, preliminary humidification in a constant temperature and humidity chamber, and controlled humidification in a vacuum drying oven on a low-density transparent silica aerogel. This process exposes a large number of fresh and active hydroxyl groups on the aerogel surface without damaging the structure with moisture, providing reaction sites for multifunctionalized perfluorosilane reagents. Furthermore, appropriate treatment facilitates better interaction between the modifying liquid and its surface, improving the uniform distribution of the modifying liquid on the aerogel and enhancing the modification effect, thereby improving the vapor-phase anti-fingerprint modification. Performance; The purpose of the calcination in this invention is to burn off the residual or adsorbed organic matter on the surface of the aerogel framework, making the aerogel surface hydrophilic and exposing a large number of fresh and active hydroxyl groups. These hydroxyl groups can subsequently undergo condensation reactions with the methylsiloxane or ethylsiloxane groups of the perfluorosilane reagent. The purpose of the initial humidification in the constant temperature and humidity chamber and the controlled humidification in the vacuum drying oven in this invention is to enable the aerogel framework surface to adsorb an appropriate amount of water molecules. On the one hand, water molecules can accelerate the condensation reaction of the methylsiloxane or ethylsiloxane groups on the perfluorosilane reagent. Pre-hydrolysis promotes the condensation reaction between the hydroxyl groups exposed on the aerogel framework and the perfluorosilane reagent. On the other hand, water molecules can promote the gradual, nearly stoichiometric hydrolysis of the three methylsiloxane groups or ethylsiloxane groups on the perfluorosilane reagent, thereby increasing the degree of binding between the aerogel framework and the perfluorosilane reagent. This invention reveals that controlling the amount of adsorbed water molecules is crucial during the aforementioned pre-humidification in a constant temperature and humidity chamber and controlled humidification in a vacuum drying oven. If only pre-humidification in the constant temperature and humidity chamber is performed, too many water molecules will be adsorbed, leading to… The three methylsiloxane groups or ethylsiloxane groups on the perfluorosilane reagent are rapidly and completely hydrolyzed simultaneously. After hydrolysis, the perfluorosilane reagent undergoes an immediate condensation reaction with each other and does not react with the hydroxyl groups on the aerogel backbone, thus failing to achieve an effective modification effect. After preliminary humidification in a constant temperature and humidity chamber, a controlled humidification treatment is performed in a vacuum drying oven. This allows for controllable water molecule content adsorbed during the preliminary humidification in the constant temperature and humidity chamber, promoting the stepwise hydrolysis of the three methylsiloxane groups or ethylsiloxane groups on the perfluorosilane reagent. After hydrolysis, these groups undergo stepwise condensation reactions with the hydroxyl groups on the aerogel backbone.

[0039] This invention involves subjecting low-density transparent silica aerogel to a special humidification activation treatment followed by vapor-phase anti-fingerprint modification with a modifying liquid containing perfluorosilane reagents and ammonia-methanol. Compared to immersion treatment of low-density transparent silica wet gel with perfluorosilane reagents, this modification method ensures that the reaction proceeds in a near-monolayer, high-intensity manner throughout the entire spatial structure of the aerogel, resulting in strong adhesion between the coating and the aerogel matrix and an extremely thin coating thickness. The perfluorosilane reagent can more uniformly modify the entire surface of the aerogel. Compared to immersion modification, this method better ensures the uniform distribution of the modifying liquid and facilitates better interaction between the modifying liquid and the aerogel, thereby improving the modification effect. Compared to adding perfluorosilane reagents during aerogel synthesis, the humidification activation treatment can be performed after aerogel preparation, thus avoiding the complexity and harsh synthesis conditions of the synthesis process and avoiding potential adverse effects on the intrinsic structure, lightweight properties, and transparency of the aerogel material.

[0040] The durable, fingerprint-resistant, low-density transparent silica aerogel of the present invention exhibits low total mass loss and condensable volatiles in a vacuum environment, thus avoiding environmental pollution in enclosed use environments. The durable fingerprint-resistant modification strategy of the present invention is applicable not only to low-density transparent silica aerogels but also to high-density transparent silica aerogels, and is also applicable to other substrate materials such as inorganic glass and ceramics, demonstrating excellent versatility. Furthermore, the method is simple and easy to operate.

[0041] According to some preferred embodiments, in step (2): the calcination is carried out in a muffle furnace, the calcination temperature is 300-500℃ (e.g., 300℃, 350℃, 400℃, 450℃ or 500℃), and the calcination time is 0.1-2h (e.g., 0.1, 0.5, 1, 1.5 or 2h), preferably 0.5-1.5h (e.g., 0.5, 1 or 1.5h); In this invention, it is preferred that the calcination temperature is 300-500℃ and the time is 0.1-2h. This invention has found that if the calcination temperature is too low or the time is too short, the organic matter remaining or adsorbed on the surface of the aerogel skeleton cannot be burned off, and the aerogel surface cannot expose a large number of fresh and active hydroxyl groups. If the calcination temperature is too high or the time is too long, the hydroxyl groups exposed by the aerogel will react and be consumed. More seriously, it may destroy the aerogel matrix structure.

[0042] According to some preferred embodiments, in step (2): the initial humidification of the constant temperature and humidity chamber is performed by holding the chamber at a temperature of 25-40°C (e.g., 25°C, 30°C, 35°C, or 40°C) and a humidity of 20-50% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, or 45%) for 5-120 minutes (e.g., 5, 15, 30, 45, 60, 75, 90, or 120 minutes); in this invention, the humidity is a relative humidity of 20-50% RH; preferably, the initial humidification of the constant temperature and humidity chamber is performed by holding the chamber at a temperature of 25-40°C (e.g., 25°C, 30°C, 35°C, or 40°C) and a humidity of 35% for 20 minutes; in this invention, it is preferred to hold the chamber at a temperature of 25-40°C and a humidity of 20-50%. The present invention found that appropriate humidity and processing time can ensure sufficient humidification and activation of the aerogel surface, providing favorable conditions for subsequent modification. Suitable humidification conditions can ensure that the entire aerogel surface is treated similarly, reducing surface inhomogeneity. If the humidity is too high, the aerogel may absorb too much moisture, leading to damage such as pulverization and collapse. If the humidification is insufficient, the aerogel surface may not be fully humidified and activated, thus affecting the effective interaction between the subsequent modifying liquid and the aerogel and reducing the modification effect. If the processing time is too long, it will increase energy consumption and will not have a beneficial effect on further improving the properties of the aerogel. If the processing time is too short, the aerogel surface will not be fully humidified and activated, thus limiting the modification effect.

[0043] According to some preferred embodiments, in step (2): the vacuum drying oven controllable humidification treatment is a heat treatment at a temperature of 25 to 40°C (e.g., 25°C, 30°C, 35°C or 40°C) and an absolute pressure not greater than 50 Pa for 1 to 8 hours (e.g., 1, 2, 3, 4, 5, 6, 7 or 8 hours), preferably 3 hours.

[0044] According to some preferred embodiments, in step (3): the perfluorosilane reagent is one or more of 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, preferably, the perfluorosilane reagent is 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0045] According to some preferred embodiments, in step (3): the molar ratio of the perfluorosilane reagent to ammonia in the ammonia-methanol is 1:(0.002-0.05) (e.g., 1:0.002, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04 or 1:0.05), preferably 1:0.02; and / or the mass ratio of the perfluorosilane reagent to the low-density transparent silica aerogel is 0.001-0.03 mol / g (e.g., 0.001, 0.002, 0.003, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02 or 0.03 mol / g), preferably 0.005 mol / g.

[0046] According to some preferred embodiments, in step (3): the vapor phase anti-fingerprint contamination modification is performed at 60-120°C (e.g., 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C) for 1-48 hours (e.g., 1, 5, 10, 12, 18, 24, 30, 36, 42 or 48 hours); preferably, the vapor phase anti-fingerprint contamination modification is performed at 90°C for 12 hours.

[0047] According to some preferred embodiments, in step (4): the durability strengthening treatment is performed at a temperature of 100-180°C (e.g., 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C) and an absolute pressure not greater than 0.0007 Pa for 1-48 hours (e.g., 1, 5, 10, 12, 18, 24, 30, 36, 42 or 48 hours); preferably, the durability strengthening treatment is performed at a temperature of 150°C and an absolute pressure not greater than 0.0007 Pa for 24 hours.

[0048] This invention discovers that by processing at a temperature of 100–180°C and an absolute pressure not exceeding 0.0007 Pa, a durability strengthening treatment can be achieved on low-density transparent silica aerogels that resist fingerprint contamination. This durability strengthening treatment is carried out under vacuum heating, where the vacuum helps maintain the clean surface of the aerogel skeleton. This invention also discovers that the perfluorosilane modifier physically adsorbed on the low-density transparent silica aerogels obtained through steps (1) to (3) will be removed, leaving only the perfluorosilanes that have partially or completely reacted with the aerogel skeleton surface. The high temperature under vacuum promotes the deep coupling between the hydroxyl groups remaining on the surface of the aerogel skeleton and the perfluorosilanes chemically grafted onto the aerogel skeleton, thereby increasing the bonding strength and achieving the purpose of durability enhancement. In this invention, it is preferred that the durability enhancement treatment is carried out at a temperature of 100-180°C and an absolute pressure of no more than 0.0007 Pa. This invention has found that if the durability enhancement temperature is too high, the perfluorosilane reagent will be destroyed; if the temperature is too low, the reaction between the hydroxyl groups remaining on the surface of the aerogel skeleton and the perfluorosilanes chemically grafted onto the aerogel skeleton is too slow and insufficient.

[0049] In a second aspect, the present invention provides a durable, fingerprint-resistant, low-density transparent silica aerogel prepared by the preparation method described in the first aspect of the present invention. Preferably, the durable, fingerprint-resistant, low-density transparent silica aerogel has one or more of the following properties: the durable, fingerprint-resistant, low-density transparent silica aerogel has good hydrophobic and oleophobic properties, effectively reducing fingerprint marks or stains generated when touching the aerogel surface, exhibiting excellent fingerprint resistance; the light transmittance of the durable, fingerprint-resistant, low-density transparent silica aerogel remains essentially unchanged before and after fingerprint resistance modification; the durable, fingerprint-resistant, low-density transparent silica aerogel has anti-fouling properties from the surface to the interior, and after the aerogel surface layer is damaged, the newly exposed surface layer still has good fingerprint resistance; the durable, fingerprint-resistant, low-density transparent silica aerogel has low total mass loss and condensable volatiles in a vacuum environment, and will not cause environmental pollution in a closed environment.

[0050] In a third aspect, this invention provides the application of durable, fingerprint-resistant, low-density transparent silica aerogel prepared by the preparation method described in the first aspect in numerous fields such as next-generation deep space exploration, high-energy physics, building construction, and electronics.

[0051] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0052] Example 1

[0053] ① Add 15.2g of methyl orthosilicate, 32g of methanol, 3.6g of water, and 10μL of 0.1mol / L dilute hydrochloric acid to a flask. Stir magnetically to mix thoroughly, heat to 70℃, and reflux at this temperature for 16h. Then, replace the reflux apparatus with a distillation apparatus and raise the temperature to 80℃ to completely evaporate the methanol from the reaction solution. After the reaction is complete, cool to room temperature to obtain a mixed solution. Then, add sufficient acetonitrile to the mixed solution to make the total mass of the mixed solution 200g. Add 4.6g of 0.03mol / L dilute ammonia water dropwise to the above mixed solution, stir evenly, and pour into a molding mold. After gelation, a low-density transparent silica wet gel was obtained. This wet gel was then immersed in anhydrous ethanol for solvent replacement. The waste liquid was discarded, and this solvent replacement operation was repeated once. The wet gel block after solvent replacement was placed in a supercritical drying vessel and immersed in ethanol. Then, under low temperature and high pressure (20℃, 13.5MPa), liquid carbon dioxide was used to replace the solvent inside and outside the wet gel block (replacement time 36h). After that, the temperature was raised to the supercritical state (48℃, 13.5MPa) and circulated for 16h. Finally, the pressure was released to atmospheric pressure and cooled to room temperature to obtain a low-density transparent silica aerogel.

[0054] ② The above-mentioned low-density transparent silica aerogel was placed in a muffle furnace and calcined at 400℃ for 1 hour. After the muffle furnace temperature cooled to room temperature, it was taken out and placed in a constant temperature and humidity chamber at 35℃ and 35%RH for preliminary humidification. The humidification time was controlled at 20 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber and immediately placed in a vacuum drying oven for subsequent controllable humidification. The temperature in the vacuum drying oven was controlled at 35℃ and the absolute pressure was ≤20Pa. The controllable humidification time was 3 hours. The resulting low-density transparent silica aerogel with controllable moisture activation of the microstructure (dimensions of 50mm (length) × 50mm (width) × 10mm (height)) was obtained, which is the moisture-activated low-density transparent silica aerogel.

[0055] ③ Place the wet-activated low-density transparent silica aerogel (0.75g) obtained in step ② in a modification tank. Place a metal mesh support at the bottom of the modification tank. The wet-activated low-density transparent silica aerogel is placed above the metal mesh. A modification solution composed of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and ammonia-methanol is placed in the lower layer of the metal mesh (the molar ratio of ammonia in 1H,1H,2H,2H-perfluorooctyltriethoxysilane and ammonia-methanol is 1:0.02, and the amount of 1H,1H,2H,2H-perfluorooctyltriethoxysilane is 0.00375mol). Perform gas-phase anti-fingerprint modification in the sealed modification tank. The temperature of the gas-phase anti-fingerprint modification is 90℃, and the modification time is 12h. After the gas-phase anti-fingerprint modification is completed, take out the low-density transparent silica aerogel with a perfluorinated coating on the skeleton surface to prevent fingerprint contamination.

[0056] ④ The above-mentioned low-density transparent silica aerogel with anti-fingerprint contamination is placed in a thermal vacuum treatment device. The thermal vacuum treatment temperature is controlled at 150℃ and the absolute pressure is ≤0.0007Pa. Under these conditions, it is treated for 24 hours to allow the perfluorinated coating to undergo an interfacial strengthening reaction with the aerogel skeleton, thereby obtaining a durable low-density transparent silica aerogel with anti-fingerprint contamination.

[0057] Example 2

[0058] Example 2 is basically the same as Example 1, except that:

[0059] ② The above-mentioned low-density transparent silica aerogel was placed in a muffle furnace and calcined at 400°C for 1 hour. After the muffle furnace temperature cooled to room temperature, it was taken out and placed in a constant temperature and humidity chamber at 35°C and 60%RH for preliminary humidification. The humidification time was controlled at 40 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber and immediately placed in a vacuum drying oven for subsequent controllable humidification. The temperature in the vacuum drying oven was controlled at 35°C and the absolute pressure was ≤20Pa. The controllable humidification time was 3 hours. The resulting low-density transparent silica aerogel with controllable moisture activation of the microstructure was obtained, which is the moisture-activated low-density transparent silica aerogel.

[0060] Example 3

[0061] Example 3 is basically the same as Example 1, except that:

[0062] ② The above-mentioned low-density transparent silica aerogel was placed in a muffle furnace and calcined at 600℃ for 2 hours. After the muffle furnace temperature cooled to room temperature, it was taken out and placed in a constant temperature and humidity chamber at 35℃ and 35%RH for preliminary humidification. The humidification time was controlled at 20 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber and immediately placed in a vacuum drying oven for subsequent controllable humidification. The temperature in the vacuum drying oven was controlled at 35℃ and the absolute pressure was ≤20Pa. The controllable humidification time was 3 hours. The resulting low-density transparent silica aerogel with controllable moisture activation of the microstructure was obtained, which is the moisture-activated low-density transparent silica aerogel.

[0063] Example 4

[0064] Example 4 is basically the same as Example 1, except that:

[0065] ② The above-mentioned low-density transparent silica aerogel was placed in a muffle furnace and calcined at 200°C for 0.5 hours. After the muffle furnace temperature cooled to room temperature, it was taken out and placed in a constant temperature and humidity chamber at 35°C and 35%RH for preliminary humidification. The humidification time was controlled at 20 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber and immediately placed in a vacuum drying oven for subsequent controllable humidification. The temperature in the vacuum drying oven was controlled at 35°C and the absolute pressure was ≤20Pa. The controllable humidification time was 3 hours. The resulting low-density transparent silica aerogel with controllable moisture activation of the microstructure was obtained, which is the moisture-activated low-density transparent silica aerogel.

[0066] Example 5

[0067] Example 5 is basically the same as Example 1, except that:

[0068] ④ The above-mentioned low-density transparent silica aerogel with anti-fingerprint contamination is placed in a thermal vacuum treatment device, and the thermal vacuum treatment temperature is controlled at 80℃ and the absolute pressure is ≤0.0007Pa. Under these conditions, it is treated for 24 hours to allow the perfluorinated coating to undergo an interfacial strengthening reaction with the aerogel skeleton, thereby obtaining a durable low-density transparent silica aerogel with anti-fingerprint contamination.

[0069] Comparative Example 1

[0070] Comparative Example 1 is basically the same as Example 1, except that:

[0071] ② The above-mentioned low-density transparent silica aerogel was placed in a constant temperature and humidity chamber at 35℃ and 35%RH for preliminary humidification. The humidification time was controlled at 20 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber and immediately placed in a vacuum drying oven for subsequent controllable humidification. The temperature in the vacuum drying oven was controlled at 35℃ and the absolute pressure ≤20Pa. The controllable humidification time was 3 hours. The wet-activated low-density transparent silica aerogel was obtained. The wet-activated low-density transparent silica aerogel was used for subsequent steps ③ and ④.

[0072] Comparative Example 2

[0073] Comparative Example 2 is basically the same as Example 1, except that:

[0074] ② The above-mentioned low-density transparent silica aerogel was placed in a muffle furnace and calcined at 400°C for 1 hour. After the muffle furnace temperature cooled to room temperature, it was taken out and placed in a constant temperature and humidity chamber at 35°C and 35%RH for preliminary humidification. The humidification time was controlled at 20 minutes. The aerogel after preliminary humidification was taken out of the constant temperature and humidity chamber to obtain the wet-activated low-density transparent silica aerogel. The wet-activated low-density transparent silica aerogel was used for subsequent steps ③ and ④.

[0075] Comparative Example 3

[0076] Comparative Example 3 is basically the same as Example 1, except that:

[0077] After obtaining a low-density transparent silica aerogel with a perfluorinated coating on the skeleton surface through step ③, which is resistant to fingerprints, step ④ is not performed.

[0078] Comparative Example 4

[0079] ①The steps are the same as in Example 1.

[0080] ② is the same as step ② in Example 1.

[0081] ③ The above-mentioned wet-activated low-density transparent silica aerogel was completely immersed in a modification solution composed of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and ammonia-methanol (the molar ratio of ammonia in 1H,1H,2H,2H-perfluorooctyltriethoxysilane and ammonia-methanol was 1:0.02) for modification. The modification temperature was 90℃ and the modification time was 12h to obtain modified low-density transparent silica aerogel.

[0082] ④ The modified low-density transparent silica aerogel was placed in a thermal vacuum treatment device, and the thermal vacuum treatment temperature was controlled at 150℃ and the absolute pressure was ≤0.0007Pa. Under these conditions, it was treated for 24 hours to obtain a pollution-resistant modified low-density transparent silica aerogel.

[0083] Comparative Example 5

[0084] ① Add 15.2g of methyl orthosilicate, 32g of methanol, 3.6g of water, and 10μL of 0.1mol / L dilute hydrochloric acid to a flask. Stir magnetically to mix thoroughly, heat to 70℃, and reflux at this temperature for 16h. Then, replace the reflux apparatus with a distillation apparatus and raise the temperature to 80℃ to completely evaporate the methanol from the reaction solution. After the reaction is complete, cool to room temperature to obtain a mixed solution. Then, add sufficient acetonitrile to the mixed solution to make the total mass of the mixed solution 200g. Add 4.6g of 0.03mol / L dilute ammonia water dropwise to the mixed solution, stir evenly, and pour into a molding mold. After gelation, a low-density transparent silica wet gel is obtained. Immerse this wet gel in anhydrous ethanol for solvent replacement, discard the waste liquid, and repeat this solvent replacement operation once. The resulting low-density transparent silica alcohol gel after solvent replacement is set aside for later use.

[0085] ② Weigh 0.004 mol of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 0.015 mol of water into a 1L volumetric flask, add acetonitrile solvent to the 1L mark, shake well and pour into a metal plate reaction vessel. Place the solvent-displaced low-density transparent silica alcohol gel obtained in step ① into the vessel. Place the metal plate reaction vessel in a 70℃ oven and react for 2 hours. After removing the metal plate reaction vessel and cooling it to room temperature, discard the waste liquid and keep the obtained modified silica wet gel for later use.

[0086] ③ Measure 11.4 mL of 7 mol / L ammonia methanol (0.08 mol) and 9 g of water (0.5 mol) into a 1 L volumetric flask, and add anhydrous ethanol to the 1 L mark. Shake well and pour into the metal plate reaction vessel containing the modified silica wet gel. Place it at room temperature (25 °C) for 48 h for interface strengthening treatment. Discard the waste liquid and keep the obtained interface-strengthened silica wet gel for later use.

[0087] ④ The interface-strengthened silica wet gel was immersed in anhydrous ethanol for solvent replacement. The waste liquid was discarded, and this solvent replacement operation was repeated once. Then, the wet gel block after solvent replacement was placed in a supercritical drying vessel and immersed in ethanol. Then, under low temperature and high pressure (15℃, 15MPa), liquid carbon dioxide was used to replace the solvent inside and outside the wet gel block (replacement time 72h). After that, the temperature was raised to the supercritical state (50℃, 15MPa) and circulated for 24h. Finally, the pressure was released to atmospheric pressure and cooled to room temperature to obtain modified low-density transparent silica aerogel.

[0088] Comparative Example 6

[0089] Comparative Example 6 refers to steps ① to ④ of Example 1 of Chinese Patent Application 202211338714.4 to obtain a modified low-density transparent silica aerogel.

[0090] Comparative Example 7

[0091] Comparative Example 7 refers to steps ① to ⑤ of Example 1 of Chinese Patent Application 202011210194.X to obtain a modified low-density transparent silica aerogel.

[0092] Comparative Example 8

[0093] Add 15.2g of methyl orthosilicate, 32g of methanol, 3.6g of water, and 10μL of 0.1mol / L dilute hydrochloric acid to a flask. Mix the mixture magnetically and heat to 70℃. Reflux the reaction at this temperature for 16 hours. Then, replace the reflux apparatus with a distillation apparatus and raise the temperature to 80℃ to completely evaporate the methanol from the reaction solution. After the reaction is complete, cool to room temperature to obtain a mixed solution. Add sufficient acetonitrile to the mixed solution to make the total mass of the mixed solution 200g. Add 4.6g of 0.03mol / L dilute ammonia solution dropwise to the mixed solution, stir well, and pour into a molding mold. After gelation, a low-density transparent silica wet gel was obtained. This wet gel was then immersed in anhydrous ethanol for solvent replacement. The waste liquid was discarded, and this solvent replacement operation was repeated once. The wet gel block after solvent replacement was placed in a supercritical drying vessel and immersed in ethanol. Then, under low temperature and high pressure (20℃, 13.5MPa), liquid carbon dioxide was used to replace the solvent inside and outside the wet gel block (replacement time 36h). After that, the temperature was raised to the supercritical state (48℃, 13.5MPa) and circulated for 16h. Finally, the pressure was released to atmospheric pressure and cooled to room temperature to obtain a low-density transparent silica aerogel.

[0094] The present invention conducted performance tests on the durable, fingerprint-resistant, low-density transparent silica aerogels prepared in each embodiment and the silica aerogels finally prepared in each comparative example. The results are shown in Table 1. Among them, the fingerprint test was conducted by attaching fingerprints to the silica aerogel materials finally prepared in each embodiment and each comparative example, and repeatedly wiping the material surface with a Kim Wipes lint-free cloth five times to observe the removal of the fingerprints. The ease of fingerprint removal was visually evaluated: A - all stains were removed after wiping; B - most stains were removed after wiping, but slight marks remained; C - stains were clearly left after wiping. The durable fingerprint resistance test results refer to the fingerprint test results conducted after the silica aerogel materials of each embodiment and each comparative example were placed for three years. The fingerprint imprinting test was conducted by pressing the sample with a hand until the fingerprint covered the surface of the silica aerogel sample. The total mass loss and condensable volatiles of the silica aerogel materials of each embodiment and each comparative example under vacuum conditions were characterized according to the aerospace standard QJ1558A-2012 "Test Method for Volatilization Performance of Materials under Vacuum Conditions". The results are shown in Table 1.

[0095]

[0096]

[0097] The transmittance mentioned in this invention refers to the transmittance of a 10mm thick silica aerogel sample at 550nm. The transmittance at 550nm is used as the indicator because the human eye is most sensitive to visible light at a wavelength of 550nm.

[0098] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a durable, fingerprint-resistant, low-density transparent silica aerogel, characterized in that, The method includes the following steps: (1) Provide low-density transparent silica aerogel; (2) The low-density transparent silica aerogel was subjected to calcination, preliminary humidification in a constant temperature and humidity chamber and controlled humidification in a vacuum drying oven in sequence to obtain the wet-activated low-density transparent silica aerogel. (3) The wet-activated low-density transparent silica aerogel was modified with a modified liquid containing perfluorosilane reagent and ammonia methanol in the gas phase to prevent fingerprint contamination, and a fingerprint-resistant low-density transparent silica aerogel was obtained. (4) The low-density transparent silica aerogel that is resistant to fingerprint contamination is subjected to a durability strengthening treatment to obtain a durable low-density transparent silica aerogel that is resistant to fingerprint contamination.

2. The preparation method according to claim 1, characterized in that, In step (2): The calcination is carried out in a muffle furnace at a temperature of 300-500°C for a duration of 0.1-2 hours.

3. The preparation method according to claim 1, characterized in that, In step (2): The initial humidification in the constant temperature and humidity chamber is performed by maintaining the temperature at 25~40℃ and the humidity at 20~50% for 5~120 minutes.

4. The preparation method according to claim 3, characterized in that, In step (2): The initial humidification of the constant temperature and humidity chamber is carried out by maintaining the temperature at 25~40℃ and the humidity at 35% for 20 minutes.

5. The preparation method according to claim 1, characterized in that, In step (2): The vacuum drying oven is used for controlled humidification treatment by maintaining the temperature at 25~40℃ and the absolute pressure at no more than 50Pa for 1~8 hours.

6. The preparation method according to claim 5, characterized in that, In step (2): The vacuum drying oven is used for controlled humidification treatment by maintaining the temperature at 25~40℃ and an absolute pressure of no more than 50Pa for 3 hours.

7. The preparation method according to claim 1, characterized in that, In step (3): The perfluorosilane reagent is one or more of the following: 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane.

8. The preparation method according to claim 1, characterized in that, In step (3): The molar ratio of the perfluorosilane reagent to ammonia in the ammonia-methanol is 1:(0.002~0.05); and / or The mass ratio of the perfluorosilane reagent to the low-density transparent silica aerogel is 0.001~0.03 mol / g.

9. The preparation method according to claim 8, characterized in that, In step (3): The molar ratio of the perfluorosilane reagent to the ammonia in the ammonia-methanol is 1:0.

02.

10. The preparation method according to claim 8, characterized in that, In step (3): The mass ratio of the perfluorosilane reagent to the low-density transparent silica aerogel is 0.005 mol / g.

11. The preparation method according to claim 1, characterized in that, In step (3): The vapor-phase anti-fingerprint contamination modification is carried out at 60~120℃ for 1~48h.

12. The preparation method according to claim 11, characterized in that, In step (3): The vapor-phase anti-fingerprint modification was performed at 90°C for 12 hours.

13. The preparation method according to claim 1, characterized in that, In step (4): The durability strengthening treatment is carried out at a temperature of 100~180℃ and an absolute pressure of no more than 0.0007Pa for 1~48 hours.

14. The preparation method according to claim 13, characterized in that, In step (4): The durability strengthening treatment is performed at a temperature of 150°C and an absolute pressure of no more than 0.0007 Pa for 24 hours.

15. A durable, fingerprint-resistant, low-density transparent silica aerogel prepared by any one of claims 1 to 14.

16. The durable, fingerprint-resistant, low-density transparent silica aerogel according to claim 15, characterized in that, The durable, fingerprint-resistant, low-density transparent silica aerogel has one or more of the following properties: The durable, fingerprint-resistant, low-density transparent silica aerogel has good hydrophobic and oleophobic properties, which can effectively reduce fingerprint marks or stains when touching the aerogel surface, and exhibit excellent fingerprint resistance. The durable, fingerprint-resistant, low-density transparent silica aerogel showed virtually no change in light transmittance before and after fingerprint-resistant modification. The durable, fingerprint-resistant, low-density transparent silica aerogel has anti-fouling properties from the surface to the interior. Even after the surface layer of the aerogel is damaged, the newly exposed surface layer still has good fingerprint resistance. The durable, fingerprint-resistant, low-density transparent silica aerogel exhibits low total mass loss and condensable volatiles in a vacuum environment, and will not cause environmental pollution in a closed environment.

17. The application of the durable, fingerprint-resistant, low-density transparent silica aerogel prepared by any one of claims 1 to 14 in the fields of next-generation deep space exploration, high-energy physics, architecture, or electronics.

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