Preparation method for hydrophobic silica aerogel, and silica aerogel beads and silica aerogel powder prepared by using hydrophobic silica aerogel

Abstract

The present disclosure relates to a preparation method for a hydrophobic silica aerogel, and silica aerogel beads and silica aerogel powder prepared by using the hydrophobic silica aerogel. Specifically, the present disclosure relates to a preparation method for a silica aerogel, comprising: a step of mixing silica hydrogel beads into a reaction solution comprising an alcohol solution containing propanol and butanol, a silylating agent, and a surfactant, so as to prepare a mixture; a step of pre-treating the mixture for 10-60 minutes at the temperature of 50-70°C; following the pretreatment step, a step of heating for 30-100 minutes at a temperature between the boiling point of the alcohol solution and 20°C above the boiling point; and a step of drying at the temperature of 100-120°C under atmospheric pressure.

Description

A method for manufacturing hydrophobic silica aerogels, utilizing silica aerogel beads and silica aerogel powder produced therefrom.

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411205208.7, filed on August 29, 2024, entitled “Method for manufacturing hydrophobic silica aerogel, silica aerogel beads and silica aerogel powder manufactured therefrom”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments of this disclosure relate to, but are not limited to, a method for manufacturing hydrophobic silica aerogel, silica aerogel beads and silica aerogel powder manufactured therefrom, and a method for significantly increasing process speed by using a surfactant in a solvent and performing a pretreatment step on silica hydrogel beads, as well as hydrophobic silica aerogel beads and silica aerogel powder manufactured by the method. Background Technology

[0004] Recently, with the advancement of industrial technology, the demand for thermal insulation material silica aerogel has been increasing, and the demand for processes that can effectively manufacture silica aerogel is also constantly increasing.

[0005] The process for manufacturing silica aerogels generally involves two steps: solvent replacement and surface silylation for hydrophobication, and drying without shrinkage. The drying step can be further divided into supercritical drying and room temperature drying. Among these processes, the solvent replacement step is particularly time-consuming; therefore, the ability to perform the drying step quickly significantly impacts the manufacturing efficiency and cost of aerogels.

[0006] For example, Korean Patent Application No. 2004-72145 discloses a method for manufacturing nano-sized silica particles by using n-Butanol, propanol, and mixtures thereof to remove moisture from silica. This method involves adding HCl to water glass to accelerate the reaction, causing silica to precipitate, then mixing it with butanol, filtering, and distilling to remove moisture from the silica, and finally drying it at a high temperature of 285°C to manufacture nano-sized silica particles. However, this method has the problem of complex processes and the need for equipment and energy to perform the high-temperature drying steps.

[0007] In addition, in the alcohol solvent replacement of silica hydrogels, for silica hydrogel powder, the solvent replacement is completed relatively quickly because the contact area between the solvent and the hydrogel powder is large. However, for silica hydrogel beads with a size of about 1 mm to 5 mm, due to the large size of the beads, it takes a considerable amount of time to replace water with solvent in all the pores inside the beads. Therefore, this step has a significant impact on production efficiency.

[0008] Therefore, especially in the manufacture of bead-like silica aerogels, it is necessary to develop technologies that can improve the solvent replacement rate and the surface hydrophobication reaction rate. Summary of the Invention

[0009] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0010] One aspect of this disclosure is to provide a method for manufacturing a hydrophobic silica aerogel, comprising:

[0011] The step of preparing a mixture is to mix silica hydrogel beads in an alcohol solution containing propanol and butanol, a reaction solution containing a silylating agent and a surfactant.

[0012] The mixture is pretreated at a temperature of 50°C to 70°C for 10 to 60 minutes.

[0013] Following the pretreatment step, the alcohol solution is heated at a temperature between its boiling point and 20°C above its boiling point for 30 to 100 minutes; and

[0014] The drying process involves drying at a temperature of 100°C to 120°C under atmospheric pressure.

[0015] Another aspect of this disclosure provides silica aerogel beads manufactured according to this disclosure and having a density (apparent specific gravity) of 0.08 g / m³. 3 Up to 0.15g / m 3 .

[0016] In another aspect of this disclosure, a silica aerogel powder is provided, manufactured according to this disclosure, and having a density of 0.01 g / m³. 3 Up to 0.1g / m 3 Specific surface area is 500m² 2 / g to 800m 2 / g.

[0017] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0018] Figure 1a is a photograph of the dried silica aerogel beads obtained by Example 1, and Figure 1b is a photograph confirming that the hydrophobic silica aerogel powder obtained by crushing the silica aerogel beads exhibits hydrophobicity and floats on the water.

[0019] Figure 2 is a photograph that confirms that the product obtained by Comparative Example 1 underwent severe shrinkage during the drying process and could not be used to produce an aerogel.

[0020] Figure 3 is a photograph that confirms that the product prepared by Comparative Example 4 does not exhibit the characteristics of silica aerogel, and that the beads adhere to each other and partially shrink.

[0021] Figure 4 is a photograph that confirms that the product manufactured by Comparative Example 7 shrinks due to excessive use of silylating agent, resulting in uneven shape and localized loss of transparency.

[0022] Figure 5 is a flowchart of the manufacturing method of hydrophobic silica aerogel. Detailed Implementation

[0023] The preferred embodiments of this disclosure are described below with reference to the accompanying drawings. However, the embodiments of this disclosure can be modified in various other forms, and the scope of this disclosure is not limited to the embodiments described below.

[0024] According to this disclosure, a method is provided for manufacturing bead-shaped silica aerogels and silica aerogel powders from silica hydrogel beads using a significantly faster process under ambient temperature drying conditions.

[0025] In this disclosure, “silica aerogel” refers to both bead and powder forms, while “hydrophobic silica aerogel” is understood to include the concept of “silylated silica aerogel”.

[0026] More specifically, the method for manufacturing the hydrophobic silica aerogel disclosed herein includes: a step of mixing silica hydrogel beads into an alcohol solution comprising a propanol and butanol, a reaction solution comprising a silylating agent and a surfactant, to prepare a mixture; a step of pretreating the mixture at a temperature of 50°C to 70°C for 10 to 60 minutes; a step of heating the mixture after the pretreatment step at a temperature of the boiling point of the alcohol solution to 20°C above the boiling point for 30 to 100 minutes; and a step of drying the mixture at a temperature of 100°C to 120°C under atmospheric pressure.

[0027] In the step of preparing a mixture by mixing silica hydrogel beads into an alcohol solution containing propanol and butanol, a reaction solution containing a silylating agent and a surfactant, the mixture may be 100 to 1000 parts by weight of alcohol solution, 3 to 20 parts by weight of silylating agent, and 0.01 to 5 parts by weight of surfactant per 100 parts by weight of silica hydrogel beads. For example, it may be 200 to 5000 parts by weight of alcohol solution, 5 to 7 parts by weight of silylating agent, and 0.1 to 3 parts by weight of surfactant per 100 parts by weight of silica hydrogel beads.

[0028] Alternatively, the step of manufacturing the mixture may consist of a step of mixing silica hydrogel beads into an alcohol solution containing propanol and butanol, a reaction solution containing a silylating agent and a surfactant, or it may consist of a step of first manufacturing a mixture of an alcohol solution containing propanol and butanol and silica hydrogel beads, and then performing a step of adding a surfactant to the mixture, in which case the silylating agent is contained in the alcohol solution or may be added before, during or after the step of adding the surfactant.

[0029] When the alcohol solution is below the specified range, the silica hydrogel beads used as raw materials may not be sufficiently impregnated, which may prevent the reaction from proceeding smoothly. Furthermore, when the alcohol solution exceeds the specified range, it is not preferred from a process economy perspective, and the concentration of the silylating agent may be too low, which may reduce the reaction efficiency.

[0030] In addition, if the silylating agent is below the specified range, the silylation in the silica hydrogel beads may be insufficient, resulting in insufficient hydrophobic properties of the reaction product. When the silylating agent is used beyond the specified range, the reaction product may shrink, resulting in uneven shape and local loss of transparency, and the thermal conductivity may not be low enough, thus failing to exhibit the characteristics of silica aerogel.

[0031] Furthermore, when the surfactant concentration is below the specified range, the increase in solvent displacement and surface silanization rates may become insufficient; when the surfactant concentration exceeds the specified range, excessive foaming by the surfactant necessitates an increase in reactor size, which is economically disadvantageous. Moreover, if the amount of surfactant is excessive, surfactant molecules can clog the fine pores of the silica hydrogel, hindering solvent displacement and preventing the production of silica aerogels.

[0032] When the alcohol solvent used for solvent displacement is a highly nonpolar solvent such as butanol, its nonpolarity makes it difficult to mix with and displace the polar water present in the nanopores within the silica hydrogel beads. In this case, if an appropriate surfactant is mixed in, the surfactant can increase the miscibility of the alcohol and water, thereby improving the permeability of the solvent into the micropores. This significantly increases the rate of solvent displacement within the nanopores, thus reducing the time required.

[0033] However, if pretreatment is suddenly performed at a high temperature exceeding 70°C, the surfactant in the mixture of surfactant, silylating agent and alcohol solvent will be activated too quickly, resulting in excessive foaming and making the reaction unstable. Therefore, it will hinder the rapid progress of silylation or solvent replacement.

[0034] The silica aerogel beads used in this disclosure can have a particle size of 1 mm to 5 mm, for example, a particle size of 2 mm to 4 mm. If a particle size greater than 5 mm is used, there is a tendency to require more reaction time; if the particle size is less than 1 mm, the drying process becomes more difficult as the particle size decreases. More specifically, because the specific gravity of the beads decreases during the drying process, even slight stirring or touching during drying will cause a large amount of dust to be released. Furthermore, the small beads, which become lighter due to the high-temperature airflow during drying, may accumulate in the exhaust channels of the drying equipment, causing significant inconvenience to the process.

[0035] Additionally, the alcohol solution used in this disclosure may contain propanol and butanol in a weight ratio of 1:99 to 4:6, for example, in a weight ratio of 1:9 to 3:7. For example, based on the total weight of the alcohol solution, it may contain 1% to 40% propanol and the balance being butanol.

[0036] When propanol is used in amounts below the stated range, the density of the resulting silica aerogel increases and its specific surface area decreases, potentially leading to a deterioration in the properties of the silica aerogel. If propanol is used in amounts exceeding the stated range, due to its high solubility in both water and butanol, propanol may be consumed and lost in excess during solvent replacement of the silica hydrogel, resulting in the inconvenience of having to replenish it. Furthermore, using propanol beyond the stated range confirms an increase in product density and a decrease in specific surface area, leading to a deterioration in the properties of the silica aerogel. Therefore, using the alcohol solution containing propanol and butanol disclosed herein allows for the production of an excellent silica aerogel with reduced density and increased specific surface area.

[0037] In this case, propanol is preferably n-propanol.

[0038] In addition, butanol is preferably n-butanol.

[0039] Conversely, when low molecular weight methanol, ethanol, or mixtures thereof are used for solvent replacement, these alcohols exhibit excellent miscibility with water, thereby accelerating the solvent replacement rate within the micropores. However, due to their high polarity, severe shrinkage occurs during drying due to capillary action, necessitating a supercritical process. This disclosure utilizes propanol and / or butanol to prevent shrinkage even during drying under ambient pressure, rather than supercritical conditions. This disclosure can significantly increase the silanization surface treatment speed by utilizing a slightly slower solvent replacement rate, thereby accelerating the overall process speed.

[0040] Surfactant molecules facilitate and accelerate the expulsion of water molecules from the nanopores within silica hydrogel beads, where they are replaced by alcohol solvents. This effect is further amplified when using methanol, which is relatively polar, or a mixture of two or more solvents such as propanol, butanol, and pentanol, which are more non-polar than ethanol. If solvent replacement proceeds rapidly and smoothly, the surface of the silica hydrogel beads dissolved in the alcohol solvent is simultaneously hydrophobically treated. The silylating agent then more easily and quickly contacts and reacts with the surface of the silica gel forming the micropores. Through this mechanism, OH groups attach to the surface of the nanopores inside the silica hydrogel beads. These OH groups then react with the silylating agent used in the alcohol solvent mixture, resulting in the silica surface being replaced by silanized groups, thus maintaining the hydrophobicity of the final silica aerogel product.

[0041] As a silane alkylating agent that can be used in this disclosure, a silane compound can be used. More specifically, the chemical formula is R 14-n -SiX n (where n is 1-3, and R1 is C1-C) 10 The group is selected from alkyl, C3-C8 aromatic, C3-C8 aromatic alkyl, C3-C7 heteroaromatic alkyl (the heteroatom is selected from at least one of the groups consisting of O, N, S, and P) and hydrogen, and X is a halogen selected from the group consisting of F, Cl, Br, and I, C1-C 10 The groups selected from alkoxy groups, C3-C8 aromatic alkoxy groups, and C3-C7 heteroaromatic alkoxy groups (the heteroatoms are selected from at least one of the groups consisting of O, N, S, and P), as well as R2Si-O-SiR3 (where R2 and R3 groups are halogens selected from groups consisting of F, Cl, Br, and I, C1-C 10The group can be selected from groups consisting of alkyl, C3-C8 aromatic, C3-C8 aromatic alkoxy, C3-C7 heteroaromatic alkoxy (the heteroatom is selected from at least one of the groups consisting of O, N, S, and P) and hydrogen, each of which is independently selected.

[0042] In the chemical formula of the silylating agent, the alkyl, aromatic alkyl, heteroaromatic alkyl, alkoxy, heteroaromatic alkoxy, and aromatic alkoxy groups, which are used as substitution groups, may have 1 to 10 carbon atoms in the alkyl and alkoxy groups. Specific embodiments of the silylating agent described above include, but are not limited to, at least one selected from the group consisting of methoxytrimethylsilane (MTMS), hexamethyldisiloxane (HMDSO), hexamethyldisiloxane (HMDS), trimethoxymethylsilane (TMMS), ethyltriethoxysilane, trimethoxysilane, triethylethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, trimethylchlorosilane, and triethylchlorosilane. For example, the silylating agent such as MTMS reacts with a large amount of water contained in the silica wet gel to undergo a hydrolysis reaction, ultimately silylating (hydrophobicating) the surface of the silica hydrogel.

[0043] The surfactants used in this disclosure can be anionic surfactants, nonionic surfactants, or mixtures thereof, with a mixture of anionic and nonionic surfactants being preferred. In this case, it is preferable to use anionic and nonionic surfactants mixed in a weight ratio of 8:2 to 7:3. If more nonionic surfactant is used, the effect of increasing the reaction rate will decrease; if more anionic surfactant is used, it will cause excessive foaming, thus increasing the capacity of the reaction vessel and potentially increasing costs, which is therefore not preferred. Furthermore, for high molecular weight synthetic nonionic surfactants such as polyethylene glycol and alkyl cellulose esters, there are difficulties in uniformly mixing them with alcohol solutions, and low molecular weight surfactants can lead to excessive foaming, among other process inconveniences. Therefore, it is preferable to use nonionic surfactants from natural sources.

[0044] When this mixed surfactant is used, silica aerogels with better physical properties can be obtained.

[0045] The anionic surfactant may be at least one selected from the group consisting of sodium methyl cocoyl taurate, sodium lauryl polyoxyethylene ether sulfate, sodium lauryl sulfate, sodium cocoyl glutamate, sodium cocoyl hydroxyethyl sulfonate, sodium lauroyl amphoteric acetate, carboxylates, sulfonates, sulfates and phosphates.

[0046] The nonionic surfactant may be at least one selected from the group consisting of cocoyl glucoside, lauryl glucoside, decyl glucoside, octyl / decyl glucoside (Caprylyl / Capryl Glucoside), cocobetaine, and sodium cocoyl glutamate.

[0047] Preferably, cocoyl glucoside extracted from coconut is used as a nonionic surfactant, and sodium methyl cocoyl taurate or sodium cocoyl hydroxyethyl sulfonate is used as an anionic surfactant.

[0048] In this disclosure, after the step of preparing a mixture of silica hydrogel beads in an alcoholic solution containing propanol and butanol, and a reaction solution containing a silylating agent and a surfactant, the mixture is pretreated at a temperature of 50°C to 70°C for 10 to 60 minutes (e.g., 20 to 40 minutes). This pretreatment step, with its increased temperature, makes the movement of water molecules and surfactants within the micropores more active, thereby further accelerating the solvent displacement rate.

[0049] The pretreatment step of this disclosure (especially when performed after the step of preparing the mixture of this disclosure) can be completed in a short time of 10 to 60 minutes. If the pretreatment step is carried out at a temperature below 50°C, there is a tendency for the reaction time to become longer, and if the temperature exceeds 70°C, the surfactant becomes over-activated, and excessive foaming occurs even with slight stirring of the reactants, which may lead to problems such as insufficient reaction vessel capacity, and is also not conducive to improving the solvent displacement rate. More specifically, in order to rapidly carry out solvent displacement and surface silylation of water, alcohol and silylating agent in the micropores of the silica hydrogel as reactants, the surfactant plays the role of bringing the relatively polar water and the relatively weakly polar organic solvent into close contact with each other. However, at high temperatures above 70°C, such as 80°C or 90°C, the very high vapor pressure of water in the micropores and the rapid movement of butanol, silylating agent, etc., relative to the progress of this mechanism, will lead to a chaotic situation, making it difficult to carry out solvent displacement rapidly.

[0050] Following the pretreatment step, a heating step is performed at the boiling point or at a temperature 20°C above the boiling point (e.g., 100 to 120°C) for 30 to 100 minutes. In this case, the heating step of this disclosure is the step to end solvent displacement and silanization, and therefore it can also be performed in a short time based on the mixture of this disclosure.

[0051] After performing solvent displacement and silylation reactions, the silica aerogel beads are dried. There are no particular limitations on the drying method. The method for manufacturing the hydrophobic silica aerogel disclosed herein can be carried out at atmospheric pressure, i.e., at 1 atm, and the drying step can be performed at a temperature of 100°C to 120°C at atmospheric pressure, for example, at a temperature of 105°C to 115°C. Below this temperature range, the drying time may be longer; above this temperature range, the butanol and silylating agent present on the surface and in the micropores of the silica hydrogel will turn slightly yellow, which is not only unsightly but also deepens to brown when the drying temperature is further increased, for example, to 150°C. At this point, the final product may lose its hydrophobicity due to the thermal decomposition of the mixture containing the surface-treated silylating agent and butanol, etc., therefore, care must be taken.

[0052] Alternatively, drying can be carried out, for example, by oven drying, but is not limited to this.

[0053] Furthermore, a step of pulverizing the dried silica aerogel beads can be performed. At this point, there are no particular restrictions on the pulverization method, which can be carried out by, for example, a pin mill or a jet mill.

[0054] For example, it may further include the step of pulverizing the dried hydrophobic silica aerogel beads into silica aerogel powder with a particle size of 50 μm to 200 μm, but is not limited thereto.

[0055] According to another aspect of this disclosure, a silica aerogel bead manufactured by the method for manufacturing hydrophobic silica aerogel of this disclosure as described above, and a silica aerogel powder pulverized therefrom are provided.

[0056] More specifically, according to this disclosure, a hydrophobic silica aerogel manufactured by the method of this disclosure as described above is provided, having a density (apparent specific gravity) of 0.08 g / m³. 3 Above, below 0.15g / m 3 Silica aerogel beads.

[0057] Furthermore, according to this disclosure, a hydrophobic silica aerogel with a density of 0.01 g / m³ is provided, manufactured by the method described above. 3 Up to 0.1g / m 3 Specific surface area is 500m² 2 / g to 800m 2 / g (e.g., 250m) 2 / g to 700m 2 / g) of silica aerogel powder.

[0058] The present disclosure will now be described in more detail through specific embodiments. These embodiments are merely examples to aid in understanding the present disclosure, and its scope is not limited thereto.

[0059] Example

[0060] Manufacturing of hydrophobic silica aerogel powder

[0061] Example 1

[0062] Hydrophobic silica aerogel was manufactured according to the flowchart in Figure 5. Specifically, 100g of commercially available silica hydrogel beads (average diameter 2mm) were placed in a reactor, and 300ml of an alcohol solution containing propanol and butanol mixed in a 1:9 weight ratio, along with a solution containing 10g of trimethoxymethylsilane (TMMS), was added. 0.8g of sodium cocoyl taurate as a nonionic surfactant and 0.2g of sodium methyl cocoyl taurate as an anionic surfactant were added to the solution, and the mixture was thoroughly mixed. The temperature was then raised to 70°C and allowed to stand for 30 minutes.

[0063] Then, the temperature was further increased to 105°C, and the reaction was carried out for 40 minutes while the alcohol solution was replenished to maintain the solvent volume and solvent replacement and silylation surface treatment were performed.

[0064] Then, the temperature was cooled and the resulting product was filtered, and the resulting solid was thoroughly dried in a drying oven at 110°C for 90 minutes.

[0065] The resulting dried silica aerogel beads are shown in Figure 1a, with a density (apparent specific gravity or tap density) of 0.13 g / cm³. 3 The powder is then pulverized into a fine powder with an average particle size of 100 μm and a density of 0.08 g / cm³. 3 The surface of the hydrophobic silica aerogel powder obtained in this way is shown in Figure 1b. When placed in water, it exhibits hydrophobicity and floats on the water, with a specific surface area of ​​620 m². 2 / g.

[0066] Comparative Example 1

[0067] Except for using an alcohol solution in which methanol and ethanol are mixed in a 5:5 weight ratio, raising the temperature to 70°C, and letting it stand for 40 minutes, the same process as in Example 1 was performed.

[0068] The resulting dried product, as shown in Figure 2, has a very high density (apparent specific gravity or tap density) of 1.75 g / cm³. 3Its properties are quite different from those of aerogels; its specific surface area is extremely low, at 180 m². 2 / g.

[0069] Therefore, when methanol and ethanol are used as solvents, it has been confirmed that aerogels cannot be manufactured due to severe shrinkage during the drying process.

[0070] Example 2

[0071] Silica hydrogel beads with an average diameter of 5 mm were used, along with a mixed silylating agent consisting of 5 g of TMMS and 5 g of HMDSO (hexamethyldisiloxane). The temperature was raised to 70°C and allowed to stand for 60 minutes. Then, the temperature was further increased to 105°C, and the reaction was carried out for 80 minutes while simultaneously replenishing the alcohol solution to maintain the solvent level and performing solvent displacement and silylation surface treatment. Otherwise, hydrophobic silica aerogel powder was prepared using the same method as in Example 1.

[0072] As a result, the density of the dried product was 0.12 g / cm³. 3 It was then pulverized into powder with an average particle size of 100 μm and a powder density of 0.08 g / cm³. 3 The surface is hydrophobic, and the specific surface area is 580 m². 2 / g.

[0073] However, it can be confirmed that the larger the particle size of the silica hydrogel beads in the original material, the longer the reaction time required.

[0074] Comparative Example 2

[0075] The same process as in Example 1 is performed except that no surfactant is used.

[0076] As a result, the material produced, exhibiting incomplete solvent displacement and surface treatment, did not display the properties of a complete silica aerogel. Specifically, its density was 0.32 g / cm³. 3 The powder with an average particle size of 100 μm has a density of 0.21 g / cm³. 3 The surface exhibits only partial hydrophobicity, with a specific surface area of ​​240 m². 2 / g.

[0077] Comparative Example 3

[0078] Except for not using surfactants, not heating to 70°C and letting stand for 30 minutes, and only performing the step of immediately heating to 105°C to carry out the reaction, the process is the same as in Example 1.

[0079] As a result, the final material did not exhibit the properties of silica aerogel. This is because the solvent displacement and surface treatment reactions were not fully completed within such a short reaction time, and during the drying process, shrinkage due to capillary action led to a reduction in porosity. It also exhibited weak hydrophobicity and a high density (0.39 g / cm³) in the bead product. 3 It exhibits physical properties that make it difficult to use as an aerogel.

[0080] Comparative Example 4

[0081] The same process as in Example 1 was performed except that 8g of cocoyl glucoside (a nonionic surfactant) and 6g of sodium methyl cocoyl taurate (anionic surfactant) were used.

[0082] As a result, the final material did not exhibit the properties of silica aerogel. As shown in Figure 3, the beads adhered to each other and partially shrank. At this point, the density (apparent specific gravity or tap density) was 0.34 g / cm³. 3 Its specific surface area is 190m². 2 / g, exhibiting physical properties that are difficult to classify as aerogels.

[0083] Therefore, adding too much surfactant will clog the micropores of silica hydrogel, which will hinder solvent exchange and make it impossible to manufacture silica aerogel.

[0084] Comparative Example 5

[0085] Except that 300 ml of propanol was used as the alcohol solution, the same process as in Example 1 was performed.

[0086] As a result, the density (apparent specific gravity or tap density) of the final manufactured silica aerogel was 0.19 g / cm³. 3 The density of the powder obtained by pulverizing it into powder with an average particle size of 100 μm is 0.192 g / cm³. 3 The surface is hydrophobic, and its specific surface area is 390 m². 2 / g.

[0087] Compared to the silica aerogel of Example 1, it was confirmed that the density increased and the specific surface area decreased, resulting in a deterioration in the performance of the silica aerogel.

[0088] Comparative Example 6

[0089] Except that 300 ml of butanol was used as the alcohol solution, the same process as in Example 1 was performed.

[0090] As a result, the density (apparent specific gravity or tap density) of the final manufactured silica aerogel was 0.14 g / cm³. 3The powder, obtained by crushing it into particles with an average particle size of 100 μm, has a density of 0.088 g / cm³. 3 The surface is hydrophobic, and its specific surface area is 540 m². 2 / g.

[0091] Compared with the silica aerogel of Example 1, it was confirmed that the density increased and the specific surface area decreased, resulting in the deterioration of the silica aerogel properties.

[0092] Comparative Example 7

[0093] Except for using 50g of TMMS, the same process as in Example 1 was performed.

[0094] As shown in Figure 4, the final silica aerogel was confirmed to have uneven shape and localized loss of transparency due to shrinkage caused by excessive silylating agent. This means that excessive silylating agent enters the pores and blocks them. Furthermore, when an excessive concentration of silylating agent is applied, polymerization occurs due to the hydrolysis of water, further blocking the pores on the surface of the hydrogel and inhibiting the solvent displacement reaction.

[0095] The product has a very high density (apparent specific gravity or tap density), at 2.24 g / cm³. 3 During the drying process, the silylating agent changes color, affecting the appearance, and its specific surface area is also very low, at 180m². 2 / g.

[0096] Comparative Example 8

[0097] The same process as in Example 1 was performed except that 1g of PEG (polyethylene glycol-MW 3000) was used.

[0098] As a result, the final silica aerogel produced did not meet the general properties of silica aerogels. More specifically, its density (apparent specific gravity or tap density) was high, at 0.29 g / cm³. 3 It exhibits hydrophobicity on its surface, but its specific surface area is very low, at 380 m². 2 / g.

[0099] Example 3

[0100] The same process as in Example 1 was performed except that a 300 ml alcohol solution of propanol and butanol mixed in a 2:8 weight ratio was used.

[0101] 100g of commercially available silica hydrogel beads (average diameter 2mm) were placed in a reactor, along with 100g of an alcohol solution containing propanol and butanol in a 2:8 weight ratio, and a solution containing 10g of TMMS. 0.8g of sodium cocoyl taurate as a nonionic surfactant and 0.2g of sodium methyl cocoyl taurate as an anionic surfactant were added to the solution and mixed thoroughly. The mixture was then heated to 70°C and left to stand for 30 minutes.

[0102] Then, the temperature was further increased to 105°C, and the reaction was carried out for 40 minutes while the alcohol solution was replenished to maintain the solvent volume and solvent replacement and silylation surface treatment were performed.

[0103] Then, the temperature was cooled, the product was filtered, and the resulting solid was thoroughly dried in a drying oven at 110°C for 90 minutes.

[0104] The resulting dried silica aerogel beads are shown in Figure 1a, with a density (apparent specific gravity or tap density) of 0.15 g / cm³. 3 The powder is then pulverized into a fine powder with an average particle size of 100 μm and a density of 0.087 g / cm³. 3 The surface of the hydrophobic silica aerogel powder obtained in this way is shown in Figure 1b. When placed in water, it exhibits hydrophobicity and floats on the water, with a specific surface area of ​​620 m². 2 / g.

[0105] Comparative Example 9

[0106] The same process as in Example 3 was performed, except that a 300 ml alcohol solution of propanol and butanol mixed in a 3:7 weight ratio was used.

[0107] As a result, the density (apparent specific gravity or tap density) of the dried silica aerogel beads was 0.16 g / cm³. 3 The powder is then pulverized into a fine powder with an average particle size of 100 μm and a density of 0.102 g / cm³. 3 The resulting hydrophobic silica aerogel powder exhibits a hydrophobic surface and floats on water, with a specific surface area of ​​490 m². 2 / g.

[0108] Comparative Example 10

[0109] The same process as in Example 3 was performed, except that a 300 ml alcohol solution of propanol and butanol mixed in a 5:5 weight ratio was used.

[0110] The resulting dried silica aerogel beads, as shown in Figure 1a, had a density (apparent specific gravity or tap density) of 0.18 g / cm³. 3The powder is then pulverized into a fine powder with an average particle size of 100 μm and a density of 0.13 g / cm³. 3 The resulting hydrophobic silica aerogel powder exhibits a hydrophobic surface and floats on water, with a specific surface area of ​​380 m². 2 / g.

[0111] Furthermore, approximately 60 g of added propanol was detected in the waste water after solvent replacement. This is detrimental to reaction efficiency.

[0112] Comparative Example 11

[0113] Except for using 1g of cocoyl glucoside (a nonionic surfactant), the same process as in Example 1 was performed.

[0114] As a result, the final silica aerogel produced did not meet the general properties of silica aerogels. More specifically, its density (apparent specific gravity or tap density) was high, at 0.21 g / cm³. 3 The surface is hydrophobic, but the specific surface area is low, at 408 m². 2 / g.

[0115] The reason for producing such low-quality aerogels is that solvent replacement and surface treatment were not completed in a short time.

[0116] Comparative Example 12

[0117] Except for using 1g of sodium methyl cocoyl taurate (anionic surfactant), the same process as in Example 1 was performed.

[0118] Excessive foaming occurs during the reaction, making it difficult for the mixture to mix thoroughly. This excessive foaming phenomenon poses a significant risk when applied to large-scale processing systems.

[0119] The reaction results showed that its density (apparent specific gravity - tap density) was 0.15 g / cm³. 3 Its surface is hydrophobic, but its specific surface area is 495 m². 2 / g. And it is pulverized into powder with an average particle size of 100μm and a density of 0.10g / cm³. 3 .

[0120] Comparative Example 13

[0121] The same process as in Example 1 was performed except that 0.5g of cocoyl glucoside (a nonionic surfactant) and 0.5g of sodium methyl cocoyl taurate (anionic surfactant) were used.

[0122] As a result, the density (apparent specific gravity or tap density) of the dried silica aerogel beads was 0.17 g / cm³.3 It is then pulverized into powder with an average particle size of 100 μm and a density of 0.115 g / cm³. 3 The resulting hydrophobicity is shown in Figure 1b. The surface of the silica aerogel powder exhibits hydrophobicity and floats on water, with a specific surface area of ​​430 m². 2 / g.

[0123] According to this disclosure, pretreatment with surfactants can significantly increase the alcohol solvent displacement rate, thereby enabling the rapid fabrication of hydrophobic silica aerogel beads and hydrophobic silica aerogel powder from silica hydrogel beads. Furthermore, a method for manufacturing silica aerogel that can be dried under ambient temperature conditions is provided, resulting in silica aerogel beads and silica aerogel powder with low density and high specific surface area.

[0124] Although the embodiments of this disclosure have been described in detail above, the scope of this disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the technical concept of this disclosure as set forth in the claims.

Claims

1. A method for manufacturing a hydrophobic silica aerogel, comprising: The step of preparing a mixture is to mix silica hydrogel beads in an alcohol solution containing propanol and butanol, a reaction solution containing a silylating agent and a surfactant. The mixture is pretreated at a temperature of 50°C to 70°C for 10 to 60 minutes. Following the pretreatment step, the alcohol solution is heated at a temperature between its boiling point and 20°C above its boiling point for 30 to 100 minutes; and The drying process at atmospheric pressure and a temperature of 100°C to 120°C yields dried hydrophobic silica aerogel beads.

2. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The mixture consists of 100 to 1000 parts by weight of an alcohol solution, 3 to 20 parts by weight of a silylating agent, and 0.01 to 5 parts by weight of a surfactant per 100 parts by weight of silica hydrogel beads.

3. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The silica hydrogel beads have a particle size of 1 mm to 5 mm.

4. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The alcohol solution comprises propanol and butanol in a weight ratio of 1:99 to 4:

6.

5. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The propanol mentioned is n-propanol.

6. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The butanol mentioned is n-butanol.

7. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The silylating agent is selected from at least one group consisting of methoxytrimethylsilane, hexamethyldisiloxane, hexamethyldisilane, trimethoxymethylsilane, ethyltriethoxysilane, trimethoxysilane, triethylethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, trimethylchlorosilane, and triethylchlorosilane.

8. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The surfactant is an anionic surfactant, a nonionic surfactant, or a mixture of anionic and nonionic surfactants.

9. The method for manufacturing hydrophobic silica aerogel according to claim 8, wherein, The anionic surfactant is selected from at least one of the group consisting of sodium methyl cocoyl taurate, sodium lauryl polyoxyethylene ether sulfate, sodium lauryl sulfate, sodium cocoyl glutamate, sodium cocoyl hydroxyethyl sulfonate, sodium lauroyl amphoteric acetate, carboxylates, sulfonates, sulfates and phosphates.

10. The method for manufacturing hydrophobic silica aerogel according to claim 8, wherein, The nonionic surfactant is selected from at least one of the group consisting of cocoyl glucoside, lauryl glucoside, decyl glucoside, octyl / decyl glucoside, cocobetaine, and sodium cocoyl glutamate.

11. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The surfactant is a mixed surfactant obtained by mixing the anionic surfactant and the nonionic surfactant in a weight ratio of 8:2 to 7:

3.

12. The method for manufacturing hydrophobic silica aerogel according to claim 1, wherein, The heating step is carried out at a temperature of 100°C to 120°C.

13. The method for manufacturing hydrophobic silica aerogel according to any one of claims 1 to 12 further comprises the step of pulverizing the dried hydrophobic silica aerogel beads into silica aerogel powder with a particle size of 50 μm to 200 μm.

14. A silica aerogel bead, manufactured by the method for manufacturing hydrophobic silica aerogel according to any one of claims 1 to 12, wherein the density (apparent specific gravity) of the silica aerogel bead is 0.08 g / m³. 3 Up to 0.15g / m 3 .

15. A silica aerogel powder, manufactured by the method for manufacturing hydrophobic silica aerogel according to claim 13, wherein the density of the silica aerogel powder is 0.01 g / m³. 3 Up to 0.1g / m 3 Specific surface area is 500m² 2 / g to 800m 2 / g.

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