Method for producing hydrophobic silica aerogel, silica aerogel beads produced using same, and silica aerogel powder

Abstract

The present invention relates to a method for manufacturing a hydrophobic silica aerogel, and silica aerogel beads and silica aerogel powder manufactured using the same, and more particularly, to a method for manufacturing a silica aerogel, the method comprises: a step of preparing a mixture by mixing silica hydrogel beads into a reaction solution comprising an alcoholic solution containing propanol and butanol, a silylating agent, and a surfactant; a step of pretreating the mixture at a temperature of 50 to 70 DEG C for 10 to 60 minutes; a step of heating for 30 to 100 minutes at a temperature from the boiling point of the alcoholic solution to 20 DEG C higher than the boiling point after the pretreatment step; and a step of drying at a temperature of 100 to 120 DEG C under atmospheric pressure, and to silica aerogel beads having a density (apparent specific gravity) of 0.08 g / m3 or more and less than 0.15 g / m3 manufactured according to this method, and a silica aerogel powder having a density of 0.01 to 0.1 g / m3 and a specific surface area of 500 to 800 m2 / g.

Description

Technical Field

[0001] This invention relates to a method for manufacturing hydrophobic silica aerogel, silica aerogel beads and silica aerogel powder manufactured therefrom, and to a method for significantly increasing process speed by using a surfactant in a solvent and pretreating silica hydrogel beads, as well as the hydrophobic silica aerogel beads and silica aerogel powder manufactured by this method. Background Technology

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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

[0007] (The problem to be solved)

[0008] One aspect of the present invention is to provide a method for manufacturing bead-shaped silica aerogels with a significantly faster process under ambient temperature drying conditions.

[0009] Another aspect of the present invention is to provide a low-density silica aerogel bead manufactured according to this process.

[0010] Another aspect of the present invention is to provide a low-density and high specific surface area silica aerogel powder manufactured according to this process.

[0011] (Methods for solving problems)

[0012] According to one aspect of the present invention, a method for manufacturing silica aerogel is provided, comprising: mixing silica hydrogel beads into a reaction solution comprising an alcohol solution containing propanol and butanol, a silylating agent, and a surfactant to form a mixture; pretreating the mixture at a temperature of 50 to 70°C for 10 to 60 minutes; heating the mixture at a temperature from the boiling point of the alcohol solution to 20°C above the boiling point for 30 to 100 minutes after the pretreatment step; and drying the mixture at a temperature of 100 to 120°C under atmospheric pressure.

[0013] According to another aspect of the present invention, silica aerogel beads are provided, manufactured according to the present invention, and having a density (apparent specific gravity) of 0.08 g / m³. 3 Above, below 0.15g / m 3 .

[0014] According to another aspect of the present invention, a silica aerogel powder is provided, manufactured according to the present invention, 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.

[0015] (Invention Effects)

[0016] According to the present invention, pretreatment with surfactants can significantly improve the alcohol solvent displacement rate, thereby enabling the rapid production 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 drying conditions is provided, resulting in silica aerogel beads and silica aerogel powder with low density and high specific surface area. Attached Figure Description

[0017] Figure 1a This is a photograph of the dried silica aerogel beads obtained through Example 1. Figure 1bThe photograph confirms that the hydrophobic silica aerogel powder obtained by crushing the silica aerogel beads is placed in water and exhibits hydrophobicity and floats on the water.

[0018] Figure 2 The photograph confirms that the product obtained by Comparative Example 1 underwent severe shrinkage during the drying process, thus making it impossible to produce an aerogel.

[0019] Figure 3 The photograph confirms that the product manufactured by Comparative Example 4 did not exhibit the characteristics of silica aerogel, and that the beads adhered to each other and partially shrank.

[0020] Figure 4 The photograph 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. Detailed Implementation

[0021] Preferred embodiments of the present invention are described below with reference to the accompanying drawings. However, embodiments of the present invention can be modified in various other ways, and the scope of the present invention is not limited to the embodiments described below.

[0022] The present invention provides a method for manufacturing bead-shaped silica aerogel and silica aerogel powder from silica hydrogel beads under ambient temperature drying conditions with a significantly faster process.

[0023] In the present invention, “silica aerogel” refers to both bead and powder forms, while “hydrophobic silica aerogel” is understood to include the concept of “silylated silica aerogel”.

[0024] More specifically, the method for manufacturing the hydrophobic silica aerogel of the present invention includes: 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 to form 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In addition, when the surfactant content is below the specified range, the increase in solvent displacement and surface silylation rate may become insufficient. When the surfactant content exceeds the specified range, excessive foaming by the surfactant necessitates an increase in reactor size, which is economically disadvantageous. Furthermore, if the amount of surfactant is excessive, surfactant molecules will clog the fine pores of the silica hydrogel, which will hinder solvent displacement and make it impossible to manufacture silica aerogels.

[0030] When the alcohol solvent used for solvent replacement is a nonpolar solvent such as butanol, its nonpolarity makes it difficult to mix with and be replaced by 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. Therefore, the solvent replacement rate within the nanopores can be significantly increased, thus shortening the time required.

[0031] 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.

[0032] The silica aerogel beads used in this invention can have a particle size of 1 mm to 5 mm, for example, 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 scatter. 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.

[0033] Additionally, the alcohol solution used in this invention contains propanol and butanol in a weight ratio of 1:99 to 4:6, for example, it may contain propanol and butanol 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.

[0034] 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 deterioration of the silica aerogel's properties. 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 deterioration of the silica aerogel's properties. Therefore, using the alcohol solution containing propanol and butanol of the present invention allows for the production of an excellent silica aerogel with reduced density and increased specific surface area.

[0035] In this case, propanol is preferably n-propanol.

[0036] In addition, butanol is preferably n-butanol.

[0037] Conversely, when using low molecular weight methanol, ethanol, or mixtures thereof 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 invention, by using propanol and / or butanol, prevents shrinkage even during drying under normal pressure conditions, rather than supercritical conditions. This invention can significantly increase the speed of silanization surface treatment by utilizing a slightly slower solvent replacement rate, thereby accelerating the overall process speed.

[0038] 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.

[0039] As a silane alkylating agent that can be used in this invention, a silane compound, more specifically, having the chemical formula R1, can be used. 4-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 include alkoxy groups, C3-C8 aromatic alkoxy groups, and C3-C7 heteroaromatic alkoxy groups (the heteroatom is selected from at least one of the groups composed of O, N, S, and P), as well as R2Si-O-SiR3 (where R2 and R3 groups are halogens selected from groups composed 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, P) and hydrogen, each of which is independently selected.

[0040] 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.

[0041] The surfactants used in this invention 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.

[0042] When this mixed surfactant is used, silica aerogels with better physical properties can be obtained.

[0043] 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.

[0044] The nonionic surfactant may be at least one selected from the group consisting of cocoyl glucoside, lauryl glucoside, decyl glucoside, octyl / octyl glucoside, cocobetaine, and sodium cocoyl glutamate.

[0045] 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.

[0046] In this invention, 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.

[0047] The pretreatment step of the present invention (especially when performed after the step of manufacturing the mixture of the present invention) can be completed in a short time of 10 to 60 minutes. If the pretreatment step is performed 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 enable the rapid 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 quickly.

[0048] Following the pretreatment step, a heating step is performed at the boiling point or at a temperature 20°C higher than the boiling point (e.g., 100 to 120°C) for 30 to 100 minutes. In this case, the heating step of the present invention is the step to end solvent displacement and silylation. Therefore, based on the mixture of the present invention, it can also be carried out in a short time.

[0049] 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 of the present invention 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, when the drying temperature is further increased to, for example, 150°C, the color will become darker to brown. At this point, due to the thermal decomposition of the mixture containing the surface-treated silylating agent and the alcohol solvent such as butanol, the final product may lose its hydrophobicity; therefore, this must be carefully considered.

[0050] Alternatively, drying can be carried out, for example, by oven drying, but is not limited to this.

[0051] 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.

[0052] 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.

[0053] According to another aspect of the present invention, silica aerogel beads manufactured by the method for manufacturing hydrophobic silica aerogel of the present invention as described above, and silica aerogel powder pulverized therefrom are provided.

[0054] More specifically, according to the present invention, a hydrophobic silica aerogel manufactured by the method of the present invention 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.

[0055] Furthermore, according to the present invention, a hydrophobic silica aerogel manufactured by the method described above is provided, 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 (e.g., 250m) 2 / g to 700m 2 / g) of silica aerogel powder.

[0056] The present invention will now be described in more detail through specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto.

[0057] Example

[0058] 1. Preparation of hydrophobic silica aerogel powder

[0059] Example 1

[0060] 100g of commercially available silica hydrogel beads (average diameter 2mm) were placed in a reactor, along with 300ml of an alcohol solution containing propanol and butanol in a 1:9 weight ratio, and a solution containing 10g of TMMS (Trimethoxymethylsilan). 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 allowed to stand for 30 minutes.

[0061] Then, the temperature was further increased to 105°C, and alcohol solution was added to maintain the solvent level for 40 minutes while the reaction was carried out, solvent replacement and silylation surface treatment were performed.

[0062] 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.

[0063] The resulting dried silica aerogel beads are as follows: Figure 1a As shown, its density (apparent specific gravity or tap density) is 0.13 g / cm³. 3 It is then pulverized into powder with an average 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 like... Figure 1b As shown, when placed in water, it exhibits hydrophobicity and floats on the surface, with a specific surface area of ​​620 m². 2 / g.

[0064] Comparative Example 1

[0065] 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.

[0066] The resulting dried product is as follows Figure 2 As shown, its density (apparent specific gravity or tap density) is very high, at 1.75 g / cm³. 3 Its properties are quite different from those of aerogels; its specific surface area is extremely low, at 180 m². 2 / g.

[0067] 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.

[0068] Example 2

[0069] Silica hydrogel beads with an average diameter of 5 mm were used, along with a mixed silylating agent consisting of 5 g of TMMS (Trimethoxymethylsilan) and 5 g of HMDSO (hexamethyldisiloxane). The temperature was raised to 70°C and left to stand for 60 minutes. Then, in a step where the temperature was further raised to 105°C, an alcohol solution was added to maintain the solvent level for 80 minutes while the reaction proceeded, and solvent displacement and silylation surface treatment were performed. Otherwise, hydrophobic silica aerogel powder was prepared using the same method as in Example 1.

[0070] As a result, the density of the dried product was 0.12 g / cm³. 3 It was then pulverized into powder with an average size of 100 μm and a density of 0.08 g / cm³. 3 The surface is hydrophobic, and the specific surface area is 580 m². 2 / g.

[0071] 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.

[0072] Comparative Example 2

[0073] The same process as in Example 1 is performed except that no surfactant is used.

[0074] As a result, a material with incomplete solvent displacement and surface treatment was produced, and consequently, it did not exhibit the properties of a complete silica aerogel. Specifically, its density was 0.32 g / cm³. 3 The average powder density at 100μm is 0.21g / cm³. 3 The surface exhibits only partial hydrophobicity, and its specific surface area is 240 m². 2 / g.

[0075] Comparative Example 3

[0076] 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.

[0077] 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, resulting in reduced porosity due to capillary shrinkage during drying. It also exhibits 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.

[0078] Comparative Example 4

[0079] 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.

[0080] As a result, the final material did not exhibit the properties of silica aerogel. Its shape... Figure 3 As can be seen, the beads are stuck together and partially shrunk. At this point, the density (apparent specific gravity or tap density) is 0.34 g / cm³. 3 Its specific surface area is 190m². 2 / g, exhibiting physical properties that are difficult to classify as aerogels.

[0081] 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.

[0082] Comparative Example 5

[0083] Except that 300 ml of propanol was used as the alcohol solution, the same process as in Example 1 was performed.

[0084] 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 size of 100 μm is 0.192 g / cm³. 3 The surface is hydrophobic, and its specific surface area is 390 m². 2 / g.

[0085] 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.

[0086] Comparative Example 6

[0087] Except that 300 ml of butanol was used as the alcohol solution, the same process as in Example 1 was performed.

[0088] As a result, the density (apparent specific gravity or tap density) of the final manufactured silica aerogel was 0.14 g / cm³. 3The powder, which was pulverized to an average size of 100 μm, had a density of 0.088 g / cm³. 3 The surface is hydrophobic, and its specific surface area is 540 m². 2 / g.

[0089] 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.

[0090] Comparative Example 7

[0091] The same process as in Example 1 was performed except that 50g of MMS (trimethoxymethylsilan) was used.

[0092] As a result, Figure 4 As shown, the final manufactured silica aerogel exhibited uneven shape and localized loss of transparency due to shrinkage caused by excessive silylating agent. This indicates that excessive silylating agent enters the pores and blocks them. Furthermore, when an excessive concentration of silylating agent is applied, polymerization occurs due to water hydrolysis, further blocking the pores on the surface of the hydrogel and inhibiting the solvent displacement reaction.

[0093] 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.

[0094] Comparative Example 8

[0095] The same process as in Example 1 was performed except that 1g of PEG (polyethylene glycol-MW 3000) was used.

[0096] As a result, the final silica aerogel produced did not meet the general properties of silica aerogels. More specifically, its density (apparent specific gravity - 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.

[0097] Example 3

[0098] 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.

[0099] 100g of commercially available silica hydrogel beads (average diameter 2mm) were placed in a reactor. 100g of an alcohol solution containing propanol and butanol in a 2:8 weight ratio, along with 10g of a solution containing TMMS (Trimethoxymethylsilan), were 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 mixed thoroughly. The mixture was then heated to 70°C and left to stand for 30 minutes.

[0100] Then, the temperature was further increased to 105°C, and the alcohol solution was replenished to maintain the solvent volume for 40 minutes while the reaction was carried out, and solvent replacement and silylation surface treatment were performed.

[0101] 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.

[0102] The resulting dried silica aerogel beads are as follows: Figure 1a As shown, its density (apparent specific gravity or tap density) is 0.15 g / cm³. 3 It is then pulverized into powder with an average 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 like... Figure 1b As shown, when placed in water, it exhibits hydrophobicity and floats on the surface, with a specific surface area of ​​620 m². 2 / g.

[0103] Comparative Example 9

[0104] 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.

[0105] As a result, the density (apparent specific gravity or tap density) of the dried silica aerogel beads was 0.16 g / cm³. 3 The silica aerogel powder was pulverized into a powder with an average size of 100 μm and a density of 0.102 g / μm. The resulting hydrophobic silica aerogel powder exhibited a hydrophobic surface and floated on water, with a specific surface area of ​​490 m². 2 / g.

[0106] Comparative Example 10

[0107] 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.

[0108] As a result, the dried silica aerogel beads obtained were as follows: Figure 1aAs shown, its density (apparent specific gravity or tap density) is 0.18 g / μm. When pulverized into powder with an average size of 100 μm, the density of the powder is 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.

[0109] Furthermore, approximately 60 g of added propanol was detected in the waste water after solvent replacement. This is detrimental to reaction efficiency.

[0110] Comparative Example 11

[0111] The same process as in Example 1 was performed except that 1g of cocoyl glucoside (a nonionic surfactant) was used.

[0112] As a result, the final silica aerogel produced did not meet the general properties of silica aerogels. More specifically, its density (apparent specific gravity - 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.

[0113] The reason for producing such low-quality aerogels is that solvent replacement and surface treatment were not completed in a short time.

[0114] Comparative Example 12

[0115] Except for using 1g of sodium methyl cocoyl taurate (anionic surfactant), the same process as in Example 1 was performed.

[0116] 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.

[0117] 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 size of 100μm and a density of 0.10g / μm.

[0118] Comparative Example 13

[0119] 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.

[0120] As a result, the density (apparent specific gravity or tap density) of the obtained dried silica aerogel beads was 0.17 g / μm, and when pulverized into powder with an average size of 100 μm, the density of the powder was 0.115 g / cm³. 3 The resulting hydrophobicity is as follows Figure 1b As shown, the surface of the silica aerogel powder is hydrophobic and floats on water, with a specific surface area of ​​430 m². 2 / g.

[0121] Although embodiments of the present invention have been described in detail above, the scope of the present invention 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 the present invention as set forth in the claims.

Claims

1. A method for producing a hydrophobic silica aerogel, comprising: a step of mixing silica hydrogel beads in an alcohol solution containing propanol and butanol, a reaction solution containing a silylating agent, and a surfactant, to produce a mixture; a step of subjecting the mixture to a pretreatment at a temperature of 50°C to 70°C for 10 minutes to 60 minutes; a step of heating at a temperature of the boiling point of the alcohol solution to 20°C higher than the boiling point for 30 minutes to 100 minutes after the pretreatment step; and a step of drying at a temperature of 100°C to 120°C under atmospheric pressure.

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

3. The method for producing a 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 producing a hydrophobic silica aerogel according to claim 1, wherein, The alcohol solution contains propanol and butanol, and the weight ratio of the propanol to the butanol is 1:99 to 4:

6.

5. The method of manufacturing hydrophobic silica aerogels according to claim 1, wherein, The propanol is n-propanol.

6. The method for producing a hydrophobic silica aerogel according to claim 1, wherein the butanol is n-butanol.

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

8. The method of manufacturing hydrophobic silica aerogels according to claim 1, wherein, The surfactant is an anionic surfactant, a nonionic surfactant, or a mixed surfactant of an anionic surfactant and a nonionic surfactant.

9. The method for producing a hydrophobic silica aerogel according to claim 8, wherein, The anionic surfactant is 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 isethionate, sodium lauroamphoacetate, carboxylate, sulfonate, sulfate, and phosphate.

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

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

3.

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

13. The method of manufacturing hydrophobic silica aerogels according to claim 1, wherein, Further comprising a step of pulverizing the dried hydrophobic silica aerogel beads into a silica aerogel powder having a particle size of 50 μm to 200 μm. Further comprising a step of pulverizing the dried hydrophobic silica aerogel beads into a silica aerogel powder having a particle size of 50 μm to 200 μm.

14. A silica aerogel bead having a density (apparent specific gravity) of 0.08 g / cm3 or less, which is produced by the production method of the hydrophobic silica aerogel bead described in any one of claims 1 to 12. 3 Hereinbefore, the density (apparent specific gravity) is less than 0.15 g / cm3. 3 Hereinbefore, the density (apparent specific gravity) is less than 0.15 g / cm3. 3 15. A silica aerogel powder, manufactured by the method of manufacturing a hydrophobic silica aerogel bead according to claim 13, having a density of 0.01 g / m 3 to 0.1 g / m 3 and a specific surface area of 500 m2 / g to 800 m2 / g.

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