Method for producing hydrophobic silica aerogel blanket and silica aerogel blanket

Abstract

The present invention relates to a method for producing a silica aerogel blanket that has excellent surface modification efficiency, is free of residual chlorine, and has high hydrophobicity, and to the silica aerogel blanket free of residual chlorine produced thereby.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0091301, filed July 22, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for producing a silica aerogel blanket that has excellent surface modification efficiency, is free of residual chlorine, and has high hydrophobicity, and to the silica aerogel blanket free of residual chlorine produced thereby. [Background technology]

[0003] Aerogel is a super-porous material with a high specific surface area (≥ 500 m) with a porosity of 90-99.9% and a pore diameter in the range of 1-100 nm. 2 / g) material, and has excellent properties such as being ultra-lightweight, super-insulating, and ultra-low dielectric. Therefore, not only is research into the development of aerogel materials being conducted, but active research is also being conducted into their applications as transparent insulation materials, environmentally friendly high-temperature insulation materials, extremely low dielectric thin films for highly integrated devices, catalysts and catalyst supports, electrodes for supercapacitors, and electrode materials for seawater desalination.

[0004] The greatest advantage of aerogel is its super-insulation properties, with a thermal conductivity of less than 0.300 W / m·K, which is lower than conventional organic insulation materials such as Styrofoam. It also solves the fatal weaknesses of organic insulation materials, such as vulnerability to fire and the generation of toxic gases during a fire.

[0005] However, despite its excellent material properties, aerogel has been used in very limited applications due to its complex manufacturing process and high manufacturing costs. Furthermore, its high porosity makes it very weak mechanically, making it susceptible to cracking even with a small impact. Therefore, research has recently been conducted into aerogel blanket composite technology that can overcome these drawbacks of aerogel itself and enable it to be processed into various shapes.

[0006] An aerogel blanket is a mattress or sheet made by compounding aerogel material. It is flexible and can be bent, folded, or cut. This allows it to be used in a variety of industrial applications, including pipe insulation and clothing. Its flexibility is possible because the aerogel blanket is a composite made of fiber and aerogel. The fiber enhances the aerogel blanket's flexibility and mechanical strength, while the aerogel provides insulating properties through its porosity. The core composite technology of aerogel blankets is the combination of the characteristics of fiber and aerogel, leveraging each other's advantages and complementing their disadvantages.

[0007] This aerogel blanket is a new material that has better heat resistance and insulation properties than existing polymer insulation materials such as polytyrofoam and polyurethane foam, and is attracting attention as an advanced material that can solve energy conservation and environmental problems that will emerge in the future.

[0008] Silica aerogel blankets are manufactured by mixing fibers with silica sol derived from water glass, gelling the mixture, and then aging, surface-modifying, and drying. The surface modification is performed by adding a hydrophobizing agent and an acid catalyst after the silica sol is impregnated into the fibers. Because the hydrophobizing agent is immiscible with water and unreactive with wet gels, especially hydrogels made from water glass, solvent substitution with an amphipathic organic solvent such as ethanol has been used. Alternatively, a method using a trimethylchlorosilane (TMCS) hydrophobizing agent and the resulting HCl as a catalyst has been used. However, solvent substitution with an amphipathic organic solvent takes a long time and produces a large amount of diluted organic solvent. Using a trimethylchlorosilane (TMCS) hydrophobizing agent produces HCl, resulting in Cl remaining in the final silica aerogel blanket.

[0009] Residual chlorine in silica aerogel blankets can cause corrosion, so there is a need to develop a method for producing highly hydrophobic silica aerogel blankets that has excellent surface modification efficiency and does not generate residual chlorine. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,789,075 Summary of the Invention [Problem to be solved by the invention]

[0011] The problem to be solved by the present invention is to provide a method for producing a silica aerogel blanket that has excellent surface modification efficiency and is free of residual chlorine, thereby eliminating corrosion problems that may occur during application of the silica aerogel blanket and exhibiting excellent stability.

[0012] Another problem that the present invention aims to solve is to provide a chlorine-free silica aerogel blanket. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a method for producing a silica aerogel blanket and a silica aerogel blanket.

[0014] [1] The present invention provides a method for producing a silica aerogel blanket, comprising the steps of: 1) preparing a silica sol containing a water glass solution; 2) impregnating a blanket substrate with the silica sol; 3) gelling the silica sol while the blanket substrate is impregnated with the silica sol to produce a wet gel; 4) immersing the wet gel in an acid mixture aqueous solution containing acetic acid and an acid catalyst to surface-modify the wet gel with an alkyldisiloxane compound; and 5) drying the surface-modified wet gel, wherein in step 4), the acetic acid is used in an amount of 0.5 L to 10 L per 1 L of the wet gel, and the acetic acid concentration (w / w%) after step 4) is 30% to 90%.

[0015] [2] The present invention provides the method for producing a silica aerogel blanket according to [1] above, wherein the acid catalyst is at least one selected from the group consisting of nitric acid, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0016] [3] The present invention provides the method for producing a silica aerogel blanket according to [1] or [2] above, wherein after step 4), the concentration (w / w%) of the acid catalyst is 3% to 10%.

[0017] [4] The present invention provides the method for producing a silica aerogel blanket according to any one of [1] to [3] above, wherein the acid catalyst comprises nitric acid, sulfuric acid, or a mixture thereof, and the concentration (w / w%) of the acid catalyst after step 4) is 5% to 10%.

[0018] [5] The present invention provides the method for producing a silica aerogel blanket according to any one of [1] to [4] above, wherein the acid catalyst comprises one or more selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid, and the concentration (w / w%) of the acid catalyst after step 4) is 3% to 10%.

[0019] [6] The present invention provides a method for producing a silica aerogel blanket according to any one of the above [1] to [5], wherein in step 4), a step of further adding toluene to the wet gel is carried out before the surface modification.

[0020] [7] The present invention provides a method for producing a silica aerogel blanket in any one of the above [1] to [6], wherein in step 4), a step of immersing the wet gel in an acid mixture aqueous solution is carried out, followed by a step of surface modification with the alkyldisiloxane compound.

[0021] [8] The present invention provides a method for producing a silica aerogel blanket in any one of the above [1] to [7], wherein in step 4), the acid mixture aqueous solution and the alkyldisiloxane compound are added to the wet gel sequentially, or the acid mixture aqueous solution and the alkyldisiloxane compound are added to the wet gel simultaneously.

[0022] [9] The present invention provides a method for producing a silica aerogel blanket in any one of the above [1] to [8], wherein in step 4), the alkyldisiloxane compound is added in a volume ratio of 1 to 3 times the volume of the wet gel.

[0023]

[10] The present invention is directed to any one of the above [1] to [9], wherein the alkyldisiloxane compound is hexa(C 1-8 A method for producing silica aerogel blankets is provided.

[0024]

[11] The present invention provides the method for producing a silica aerogel blanket according to any one of the above items [1] to

[10] , wherein the method is carried out under chlorine-free (Cl-free) conditions.

[0025]

[12] The present invention provides a silica aerogel blanket having a thermal conductivity of 12 mW / mK to 19 mW / mK and a Cl content of 0 ppm to 500 ppm.

[0026]

[13] The present invention provides the silica aerogel blanket according to

[12] , wherein the silica aerogel blanket has a Cl content of 0 ppm to 200 ppm. [Effects of the Invention]

[0027] The method for producing hydrophobic silica aerogel according to the present invention can produce a highly hydrophobic silica aerogel blanket that has excellent surface modification efficiency and is free of residual chlorine, and can be usefully applied to industries that require such a silica aerogel, particularly industries that require highly hydrophobic silica aerogel or silica aerogels with various ranges of hydrophobicity. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will now be described in more detail to aid in understanding the present invention.

[0029] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0030] Generally, silica wet gels prepared using water glass have pores filled with water, which is a solvent. When the solvent is simply removed by drying, the liquid solvent evaporates into a gas phase, and the high surface tension of water at the gas / liquid interface causes shrinkage and cracks in the pore structure, resulting in a decrease in surface area and changes in the pore structure. Therefore, in order to maintain the pore structure of the wet gel, it is necessary not only to replace the water, which has a high surface tension, with an organic solvent, which has a relatively low surface tension, but also to develop a technology that can wash and dry the wet gel without shrinkage while maintaining the structure of the wet gel.

[0031] Furthermore, although dried silica aerogel maintains low thermal conductivity immediately after drying, it has the disadvantage of gradually increasing its thermal conductivity as it absorbs water from the air due to the hydrophilic nature of the silanol groups (Si-OH) on the silica surface.

[0032] Therefore, to reduce the shrinkage and cracking of the pore structure caused by the high surface tension of water at the gas / liquid interface during drying of the silica wet gel, and to reduce the water absorption rate of the dried silica aerogel and maintain its low thermal conductivity, it is necessary to modify the surface of the silica aerogel to make it hydrophobic. Therefore, methods of modifying the surface of silica aerogel to make it hydrophobic using surface modifiers are widely used.

[0033] To modify the wet gel to be hydrophobic, one or more surface modifiers selected from the group consisting of trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), dimethyldiethoxysiloxane (DMDES), hexamethyldisiloxane (HMDSO), and trimethylethoxysilane (TMES) are typically used.

[0034] Among the surface modifiers, when hexamethyldisilazane (HMDS), trimethylethoxysilane (TMES), dimethyldiethoxysiloxane (DMDES), and hexamethyldisiloxane (HMDSO) are used, they are immiscible with water and therefore unreactive with wet gels, particularly hydrogels made from water glass. Therefore, a process is performed in which the hydrogel is first converted into an organogel by solvent substitution using an amphiphilic organic solvent such as ethanol, and then reacted with the surface modifier to modify the surface to hydrophobic groups. This method has the disadvantage of taking a long time to solvent-substitution, which is necessary to convert the hydrogel into an organogel, and producing a large amount of diluted organic solvent.

[0035] On the other hand, when trimethylchlorosilane (TMCS) is used among the surface modifiers, it is reactive with wet gels or hydrogels, which makes it possible to eliminate the solvent substitution process, but it has the disadvantage that after surface modification, any remaining trimethylchlorosilane is converted to hexamethyldisiloxane (HMDSO) and becomes inactive.

[0036] Therefore, in order to overcome the disadvantages of using trimethylchlorosilane (TMCS) alone, a method was developed in which a small proportion of trimethylchlorosilane (TMCS) is mixed with hexamethyldisiloxane (HMDSO) and the HCl generated from trimethylchlorosilane is used as a catalyst to convert the inactive species hexamethyldisiloxane into trimethylchlorosilane, thereby modifying the surface.

[0037] However, in both the method using trimethylchlorosilane and the method using a mixture of hexamethyldisiloxane (HMDSO) and trimethylchlorosilane, trimethylchlorosilane generates HCl after the surface modification reaction as shown in Reaction Scheme 1 below. This means that some of the chlorine remains in the final silica aerogel blanket, which can cause corrosion (corrosion under insulation, CUI).

[0038] Alternatively, instead of mixing hexamethyldisiloxane (HMDSO) with trimethylchlorosilane, a method of separately adding HCl, which is used as a catalyst, to hexamethyldisiloxane can be used. In this method, the hexamethyldisiloxane fills the pores while simultaneously modifying the surface, converting the hydrogel into an organic gel. However, some of the added chlorine remains in the final silica aerogel blanket.

[0039] [ka]

[0040] On the other hand, the method for producing a silica aerogel blanket of the present invention does not use any chlorine (Cl)-containing compound during the production process, so the final hydrophobic silica aerogel blanket produced does not contain residual chlorine.

[0041] The method for producing a silica aerogel blanket of the present invention includes the steps of: 1) preparing a silica sol containing a water glass solution; 2) impregnating a blanket substrate with the silica sol; 3) gelling the silica sol while the blanket substrate is impregnated with the silica sol to produce a wet gel; 4) immersing the wet gel in an acid mixture aqueous solution containing acetic acid and an acid catalyst to surface-modify the wet gel with an alkyldisiloxane compound; and 5) drying the surface-modified wet gel. In step 4), the acetic acid is used in an amount of 0.5 L to 10 L per 1 L of the wet gel, and the acetic acid concentration (w / w%) after step 4) is 30% to 90%.

[0042] The method for producing a silica aerogel blanket of the present invention uses acetic acid, an amphiphilic substance soluble in both water and an alkyldisiloxane compound used as a surface modifier, and an acid catalyst for promoting protonation of the alkyldisiloxane compound. The amount of acetic acid used is determined based on the volume of the wet gel, and the amount is adjusted so that the acetic acid concentration [weight (w) / weight (w)] after the surface modification in step 4) satisfies a predetermined value. This allows for an excellent surface modification rate and prevents residual chlorine from being present in the final silica aerogel blanket.

[0043] 1) Preparing a silica sol containing a water glass solution The silica sol in step 1) can be produced by mixing a water glass solution as a silica precursor and an acid catalyst.

[0044] The water glass solution may be a diluted solution obtained by adding distilled water to water glass and mixing the water glass. The water glass may be sodium silicate (Na2SiO3), which is an alkali silicate obtained by melting silicon dioxide (SiO2) and an alkali.

[0045] The water glass dispersion may contain 1% to 13% by weight of silicon dioxide (SiO2). If the silicon dioxide content in the water glass dispersion is lower than this range, aerogel may not be properly formed, and if the silicon dioxide content is higher than this range, gelation may not occur easily or the specific surface area may decrease.

[0046] The acid catalyst may be one or more organic acids and inorganic acids that do not contain chlorine in the molecular structure in order to eliminate chlorine from the final silica aerogel blanket. For example, the acid catalyst may be one or more selected from the group consisting of acetic acid, oxalic acid, nitric acid, sulfuric acid, and hydrofluoric acid. Specifically, in consideration of the acid mixture aqueous solution used in the surface modification of step 4), acetic acid, nitric acid, sulfuric acid, or a mixture of two or more of these may be used.

[0047] The acid catalyst may be included in an amount that allows the pH of the silica sol to be 3 to 10. If the pH of the silica sol is outside this range, the gelation in step 3) may not be easy or the gelation rate may be too fast or slow, resulting in a decrease in processability.

[0048] 2) Impregnating the blanket substrate with silica sol The step 2) is a step of impregnating the silica sol into a blanket substrate.

[0049] The blanket substrate according to an embodiment of the present invention may be a porous substrate to improve the thermal insulation of the silica aerogel blanket. When a porous blanket substrate is used, the silica sol can easily penetrate into the substrate, forming a uniform aerogel inside the blanket substrate, thereby providing the manufactured silica aerogel blanket with excellent thermal insulation.

[0050] The blanket substrate usable in accordance with one embodiment of the present invention may be a film, sheet, net, fiber, foam, nonwoven fabric, or a laminate of two or more layers thereof. Furthermore, depending on the intended use, the surface may be roughened or patterned. More specifically, the blanket substrate may be a fiber that includes spaces or voids within the blanket substrate that facilitate the insertion of silica aerogel, thereby further improving the insulation performance. Furthermore, the blanket substrate preferably has low thermal conductivity.

[0051] Specifically, the blanket substrate may be polyamide, polybenzimidazole, polyaramid, acrylic resin, phenolic resin, polyester, polyether ether ketone (PEEK), polyolefin (e.g., polyethylene, polypropylene, or copolymers thereof), cellulose, carbon, cotton, wool, hemp, nonwoven fabric, glass fiber, ceramic wool, or the like. More specifically, in the present invention, the blanket substrate may be glass fiber.

[0052] According to one embodiment of the present invention, impregnation can be performed by pouring silica sol into a reaction vessel containing a blanket substrate or by wetting the blanket substrate with silica sol. Here, to ensure good bonding between the blanket substrate and the silica sol, the blanket substrate can be lightly pressed to ensure sufficient impregnation. Subsequently, the blanket substrate can be pressed to a predetermined thickness with a predetermined pressure to remove excess silica sol, thereby shortening the drying time.

[0053] 3) A step of gelling the silica sol while the silica sol is impregnated into the blanket substrate to produce a wet gel Step 3) is a step for producing a hydrophobic silica wet gel blanket, in which the silica sol impregnated in the blanket substrate is left to gel, thereby producing a wet gel blanket.

[0054] Here, the gelation may refer to a sol-gel reaction, and the sol-gel reaction may form a network structure from silicon unit precursor materials.

[0055] Here, the network structure can refer to a planar network-like structure in which certain polygons, each having one or more types of atomic arrangement, are connected, or a structure in which the vertices, corners, faces, etc. of certain polyhedra are shared to form a three-dimensional skeletal structure.

[0056] In the method according to an embodiment of the present invention, the silica wet gel blanket may be further aged after the gelation in step 3).

[0057] The aging is not particularly limited, but can be carried out, for example, by leaving the mixture at room temperature (25° C.) to 90° C. for 1 hour to 24 hours.

[0058] In the manufacturing method according to an embodiment of the present invention, after the silica wet gel blanket is manufactured, the aging process is performed, so that the network structure of the wet gel in the silica wet gel blanket can be more firmly formed, and thus the silica wet gel blanket can have excellent pore characteristics.

[0059] 4) A step of immersing the wet gel in an aqueous acid mixture containing acetic acid and an acid catalyst and surface-modifying the wet gel with an alkyldisiloxane compound. In step 4), the wet gel is immersed in an aqueous acid mixture containing acetic acid and an acid catalyst, and the surface is modified with an alkyldisiloxane compound to form a hydrophobic silica wet gel blanket.

[0060] In one example of the present invention, a step of adding the aqueous acid mixture to the wet gel, immersing the wet gel in the aqueous acid mixture, and then adding the alkyldisiloxane compound to the wet gel can be performed. In another example of the present invention, a step of simultaneously adding the aqueous acid mixture and the alkyldisiloxane compound to the wet gel can be performed.

[0061] Regardless of the time of addition of the aqueous acid mixture and the alkyldisiloxane compound to the wet gel, the aqueous acid mixture containing water, which has a higher density than the alkyldisiloxane compound, will be located at the bottom, resulting in layer separation into an upper alkyldisiloxane compound layer and a lower acid mixture aqueous layer. Even when the aqueous acid mixture and the alkyldisiloxane compound are both added to the wet gel, the hydrophobic alkyldisiloxane compound and the aqueous acid mixture containing water will separate into layers, and the wet gel containing water will be located in the aqueous acid mixture layer and will be immersed in the aqueous acid mixture.

[0062] In the process of immersing the wet gel in the acid mixture aqueous solution, the acid mixture aqueous solution enters the wet gel by diffusion, and the water present in the wet gel moves out of the wet gel into the acid mixture aqueous solution layer. Thus, when the immersion in the acid mixture aqueous solution is completed, the acid concentration inside the wet gel and the acid concentration of the acid mixture aqueous solution outside the wet gel can be equilibrated.

[0063] The amphiphilic substance acetic acid contained in the aqueous acid mixture causes a trace amount of the alkyldisiloxane compound to dissolve in the aqueous acid mixture at the interface between the alkyldisiloxane compound layer and the aqueous acid mixture layer, allowing the alkyldisiloxane compound to modify the surface of the wet gel. During the surface modification process, the aqueous solution that filled the wet gel is replaced with the alkyldisiloxane compound, filling the wet gel with the alkyldisiloxane compound, and the aqueous solution moves out of the wet gel and into the aqueous acid mixture layer. When the immersion and surface modification processes are completed, the acid concentration inside the wet gel and the acid concentration outside the wet gel reach equilibrium.

[0064] Since the wet gel contains water, it is initially located in the acid mixture aqueous solution layer. As the surface modification proceeds, the wet gel becomes filled with the alkyldisiloxane compound, and gradually rises to the surface and moves to the alkyldisiloxane compound layer.

[0065] In one embodiment of the present invention, when hexamethyldisiloxane is used as the alkyldisiloxane compound in step 4), a reaction such as that shown in Reaction Scheme 2 below can be carried out.

[0066] [ka]

[0067] In step 4), the acetic acid may be used in an amount of 0.5 L to 10 L per 1 L of the wet gel, specifically, 0.5 L to 9.5 L, 0.5 L to 9 L, 1 L to 9 L, 2 L to 9 L, or 2 L to 8 L.

[0068] Furthermore, after step 4), the acetic acid concentration (w / w%) can be 30% to 90%, specifically 40% to 80%, and more specifically 50% to 70%. When acetic acid is used in an amount that results in a concentration of 30% to 90% after step 4), the acetic acid can effectively contact the hydrophilic wet gel with the hydrophobic alkyldisiloxane compound, resulting in a smooth surface modification reaction. If the acetic acid concentration (w / w%) is too low, the reaction between the hydrophilic wet gel and the hydrophobic alkyldisiloxane compound may not occur, resulting in a smooth surface modification reaction. Furthermore, if the acetic acid concentration is too high, more acetic acid than necessary must be added, which can reduce economic efficiency.

[0069] The acetic acid concentration (w / w%) after step 4) refers to the concentration of acetic acid contained in the aqueous acid mixture layer after step 4), and can be expressed by the following Equation 1. The acetic acid concentration can be calculated by measuring the weight of water in the aqueous acid mixture layer after step 4) and measuring the weight of the acetic acid in the aqueous acid mixture layer by gas chromatography (GC). The weight of water in the aqueous acid mixture layer can be measured using a Karl Fischer moisture analyzer (Si Analytics Titro Line 7000).

[0070] [Formula 1] Acetic acid concentration (w / w%) = weight of acetic acid in the acid mixture aqueous solution layer / (weight of acetic acid in the acid mixture aqueous solution layer + total weight of water in the acid mixture aqueous solution layer) × 100

[0071] In step 4), the acid catalyst concentration (w / w%) after step 4) can be 3% to 10%, specifically 4% to 9%, and more specifically 5% to 8%.

[0072] When the acid catalyst concentration is within this range, protonation of the alkyldisiloxane compound is effectively promoted, resulting in an excellent surface modification reaction rate. If the acid catalyst concentration is too low, the surface modification reaction rate decreases, the surface modification reaction by the alkyldisiloxane compound does not proceed sufficiently, and the hydrophobicity of the wet gel decreases, which may increase the thermal conductivity of the final silica aerogel blanket. Furthermore, if the acid catalyst concentration is too high, the oxidizing power of the acid catalyst increases, which may form dangerous by-products by reacting with acetic acid, resulting in reduced stability.

[0073] The acid catalyst can be one or more selected from the group consisting of nitric acid, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

[0074] When the acid catalyst includes nitric acid, sulfuric acid, or a mixture thereof, the concentration of the acid catalyst can satisfy the above concentration range.

[0075] Furthermore, when the acid catalyst is one or more selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid, the concentration (w / w%) of the acid catalyst after step 4) can be 3% to 10%, specifically 4% to 9%, and more specifically 5% to 8%.

[0076] Meanwhile, in one example of the present invention, in step 4), a process of further adding toluene to the wet gel before the surface modification can be performed. When the toluene is further added, the toluene can be added after the aqueous acid mixture solution is added to the wet gel and before the alkyldisiloxane compound is added, or the toluene can be added simultaneously with the aqueous acid mixture solution and the alkyldisiloxane compound.

[0077] In step 4), if toluene is further added, the toluene may be included in the hydrophobic organic solution layer. When sulfuric acid is used as the acid catalyst, adding the toluene causes the reaction between sulfuric acid and toluene to form p-toluenesulfonic acid, which acts as a catalyst to activate the surface modification reaction by the alkyldisiloxane compound, resulting in a faster surface modification reaction rate.

[0078] The concentration (w / w%) of the acid catalyst after step 4) means the concentration of the acid catalyst contained in the aqueous acid mixture layer after step 4), and can be expressed by the following Equation 2. The concentration of the acid catalyst can be calculated by measuring the weight of the water in the aqueous acid mixture layer after step 4) and then measuring the weight of the acid catalyst in the aqueous acid mixture layer by gas chromatography (GC).

[0079] [Formula 2] Acid catalyst concentration (w / w%) = weight of acid catalyst / (weight of acid catalyst + total weight of water in the acid mixture aqueous solution layer) × 100

[0080] As described above, when the process of immersing in the acid mixture aqueous solution is completed, the acid concentration inside the wet gel and the acid concentration outside the wet gel are in equilibrium, and when the acid concentration of the acid mixture aqueous solution layer after the immersion is measured, the acid concentration inside the wet gel can be determined, thereby making it possible to grasp the acid concentration related to surface modification.

[0081] After step 4), the water contained in the aqueous acid mixture solution layer may be the water contained in the aqueous acetic acid solution and the acid catalyst, the water contained in the wet gel, and the water derived from the hydrophilic-to-hydrophobic reaction of the wet gel, which remains after step 4), and the total weight of these may be the total weight of water in the aqueous acid mixture solution layer.

[0082] Step 4) may be performed by a method in which the wet gel is immersed in an aqueous solution of an acid mixture and then surface-modified with the alkyldisiloxane compound.

[0083] In the method for manufacturing a silica aerogel blanket according to one embodiment of the present invention, in step 4), when the wet gel is immersed in the acid mixture aqueous solution, an acid mixture aqueous solution containing acetic acid and an acid catalyst is used, and the acetic acid fills a predetermined volume relative to the wet gel. After step 4), it is confirmed that the acetic acid concentration satisfies the above-mentioned value, thereby enabling the wet gel, especially the hydrogel manufactured using a water glass solution, to be quickly and effectively surface-modified.

[0084] The alkyldisiloxane compound may be added in a volume ratio of 1 to 3 times, specifically 1 to 2.5 times, and more specifically 1 to 2 times, the volume of the wet gel.

[0085] The alkyldisiloxane compound should be added in a volume of at least 1 times the volume of the wet gel to modify the wet gel and perform solvent substitution on the wet gel. Increasing the amount of alkyldisiloxane compound added requires an increase in the size of the equipment. Therefore, the alkyldisiloxane compound may be added in the above range based on the volume of the wet gel.

[0086] The alkyldisiloxane compound may be a hexaalkyldisiloxane compound, specifically, hexa(C 1-8 The alkyl disiloxane may be, for example, a methyl disiloxane, and more specifically, a hexamethyl disiloxane.

[0087] The surface modification reaction may be carried out at a temperature of 25° C. to 95° C. In addition, the step of immersing the wet gel in the acid mixture aqueous solution and the step of surface modifying the wet gel with the alkyldisiloxane compound may include a stirring step.

[0088] Here, the stirring is not particularly limited, but may be performed at a speed of, for example, 50 rpm to 700 rpm.

[0089] Furthermore, step 4) according to one embodiment of the present invention may be carried out for 2 to 24 hours, and is preferably carried out for 4 to 22 hours or 8 to 20 hours in terms of maintaining an excellent level of surface modification effect and improving process economy.

[0090] In a manufacturing method according to one embodiment of the present invention, when step 4) is performed by sequentially performing a process of immersing the wet gel in an aqueous acid mixture solution and then a process of surface-modifying the wet gel with an alkyldisiloxane compound, the process of immersing the wet gel in an aqueous acid mixture solution may be performed for 30 minutes to 4 hours, specifically 30 minutes to 3 hours, and more specifically 1 hour to 3 hours, and the process of surface-modifying the wet gel with an alkyldisiloxane compound may be performed for 1 hour 30 minutes to 20 hours, specifically 3 hours to 19 hours, and more specifically 6 hours to 18 hours.

[0091] 5) Drying the surface-modified wet gel Step 5) is a step of drying the hydrophobic silica wet gel blanket to produce a hydrophobic silica aerogel blanket.

[0092] Here, a washing step can be further performed before the drying step to remove impurities (sodium ions, unreacted materials, by-products, etc.) generated during the reaction to obtain a high-purity hydrophobic silica aerogel blanket. The washing step can be performed by adding a non-polar organic solvent to the hydrophobic silica wet gel and stirring for 20 minutes to 1 hour, but is not limited thereto.

[0093] The drying may be performed by methods such as atmospheric drying or supercritical drying, but is not limited thereto. For example, atmospheric drying may be a method of drying at atmospheric pressure for 1 to 12 hours at a temperature of 100 to 190°C, and supercritical drying is a method using CO2 in a supercritical state. Atmospheric drying has the advantage of being relatively simple and economical, while supercritical drying has the advantage of being able to effectively remove fluid from inside the gel.

[0094] The method for manufacturing a hydrophobic silica aerogel blanket according to one embodiment of the present invention can significantly improve the efficiency of surface modification, thereby providing excellent physical properties such as excellent porosity and high hydrophobicity, thereby ensuring excellent thermal insulation performance. In particular, the method for manufacturing a silica aerogel blanket according to one embodiment of the present invention performs hydrophobization of the aerogel under chlorine-free (Cl-free) conditions, and the final silica aerogel blanket does not contain or contains minimal chlorine, thereby eliminating the possibility of chlorine inducing corrosion at the application site of the silica aerogel blanket.

[0095] The silica aerogel blanket according to one embodiment of the present invention has a thermal conductivity of 12 mW / mK to 19 mW / mK and a Cl content of 0 ppm to 500 ppm.

[0096] Specifically, the thermal conductivity of the silica aerogel blanket according to one embodiment of the present invention may be 12 mW / mK or more, 13 mW / mK or more, 14 mW / mK or more, 15 mW / mK or more, or 16 mW / mK or more to 19 mW / mK or less, 18.5 mW / mK or less, or 18.3 mW / mK or less.

[0097] The silica aerogel blanket according to one embodiment of the present invention does not contain Cl derived from the aerogel, but may contain a small amount of Cl derived from the silica aerogel blanket substrate. The Cl content of the silica aerogel blanket according to one embodiment of the present invention may be, specifically, 0 ppm to 500 ppm, ppm to 400 ppm, 0 ppm to 300 ppm, or 0 ppm to 200 ppm.

[0098] The silica aerogel blanket manufactured by the manufacturing method according to one embodiment of the present invention can be used in a variety of applications, including thermal insulation applications, including those requiring thermal insulation at temperatures below 650°C. For example, it can be used as an insulation material for pipes such as double-casing pipes, insulation for aircraft and their components, building insulation, spacecraft insulation, automobile insulation, clothing insulation, footwear insulation, etc. The aerogel blanket can be used in the same manner as an aerogel mat or multiple aerogels.

[0099] The present invention will be described in more detail below with reference to examples and experimental examples. However, the following examples and experimental examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0100] Example 1 33.8 g of water glass was diluted with 108.1 g of water to prepare a water glass solution, to which 7.8 g of acetic acid (97%) was added to prepare a silica sol. The silica sol was impregnated into glass fibers and then allowed to stand for 10 minutes to obtain a glass fiber composite impregnated with the wet gel.

[0101] An acid mixture solution prepared by mixing 140 g of acetic acid (≥ 97%) and 15 g of 70% (w / w%) nitric acid aqueous solution was poured onto the glass fiber impregnated with the wet gel and immersed in an oven at 60°C for 2 hours while maintaining the temperature, followed by the addition of 160 g of hexamethyldisiloxane (HMDSO) and carrying out a surface modification reaction while maintaining the temperature in an oven at 75°C for 16 hours. Here, the acetic acid in the acid mixture solution was used in an amount of 1 L per 1 L of the volume of the wet gel, and the hexamethyldisiloxane was used in an amount of 1.2 L per 1 L of the volume of the wet gel.

[0102] The produced hydrophobic silica wet gel blanket was collected and then completely dried in a forced circulation dryer at 150°C for 4 hours to produce a hydrophobic silica aerogel blanket.

[0103] Example 2 A hydrophobic silica aerogel blanket was produced in the same manner as in Example 1, except that 10 g of 98% (w / w%) sulfuric acid was mixed instead of 15 g of 70% (w / w%) aqueous nitric acid solution, and 10 g of toluene and 140 g of hexamethyldisiloxane (HMDSO) were added instead of 160 g of hexamethyldisiloxane (HMDSO).

[0104] Example 3 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that 17.6 g of 98% (w / w%) p-toluenesulfonic acid was mixed instead of 15 g of 70% (w / w%) aqueous nitric acid solution.

[0105] Example 4 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that 9.8 g of 99% (w / w%) methanesulfonic acid was mixed instead of 15 g of 70% (w / w%) nitric acid aqueous solution.

[0106] Example 5 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that 15.3 g of 98% (w / w%) trifluoromethanesulfonic acid was mixed instead of 15 g of 70% (w / w%) aqueous nitric acid solution.

[0107] Example 6 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that the content of acetic acid (≧97%) was changed to 185 g when preparing the acid mixture aqueous solution, the amount of acetic acid in the acid mixture aqueous solution was changed to 1.3 L per 1 L of the volume of the wet gel, and a diluted nitric acid aqueous solution prepared by mixing 20 g of a 70% (w / w) nitric acid aqueous solution with 95 g of water was used instead of the 70% (w / w) nitric acid aqueous solution.

[0108] Example 7 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that the content of acetic acid (≧97%) was changed to 168 g when preparing the acid mixture aqueous solution, the amount of acetic acid in the acid mixture aqueous solution was changed to 0.6 L per 1 L of the volume of the wet gel, and a diluted nitric acid aqueous solution prepared by mixing 20 g of a 70% (w / w) nitric acid aqueous solution with 95 g of water was used instead of the 70% (w / w) nitric acid aqueous solution.

[0109] Example 8 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that the content of acetic acid (≧97%) was changed to 333 g when preparing the acid mixture aqueous solution, the amount of acetic acid in the acid mixture aqueous solution was changed to 4.0 L per 1 L of the volume of the wet gel, and a diluted nitric acid aqueous solution prepared by mixing 20 g of a 70% (w / w) nitric acid aqueous solution with 95 g of water was used instead of a 70% (w / w) nitric acid aqueous solution.

[0110] Example 9 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that the content of acetic acid (≧97%) was changed to 359.9 g when preparing the acid mixture aqueous solution, the amount of acetic acid in the acid mixture aqueous solution was changed to 7.0 L per 1 L of the volume of the wet gel, and a diluted nitric acid aqueous solution prepared by mixing 20 g of a 70% (w / w) nitric acid aqueous solution with 95 g of water was used instead of the 70% (w / w) nitric acid aqueous solution.

[0111] Comparative Example 1 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that 140 g of 35 wt % hydrochloric acid was used instead of the aqueous acid mixture prepared by mixing aqueous acetic acid and aqueous nitric acid solutions.

[0112] Comparative Example 2 33.8 g of water glass was diluted with 108.1 g of water to prepare a water glass solution, to which 7.8 g of acetic acid (97%) was added to prepare a silica sol. The silica sol was impregnated into glass fibers and then left for 10 minutes to obtain a glass fiber composite impregnated with the wet gel.

[0113] 107 g of trimethylchlorosilane (TMCS) was added to the glass fiber impregnated with the wet gel, and a surface modification reaction was carried out in an oven at 75° C. for 16 hours while maintaining the temperature.

[0114] The produced hydrophobic silica wet gel blanket was collected and then completely dried in a forced circulation dryer at 150°C for 4 hours to produce a hydrophobic silica aerogel blanket.

[0115] Comparative Example 3 A hydrophobic silica aerogel blanket was prepared in the same manner as in Example 1, except that the content of acetic acid (≧97%) was changed to 70 g when preparing the acid mixture aqueous solution, the amount of acetic acid in the acid mixture aqueous solution was changed to 0.5 L per 1 L of the volume of the wet gel, and a diluted nitric acid aqueous solution prepared by mixing 20 g of a 70% (w / w) nitric acid aqueous solution with 100 g of water was used instead of a 70% (w / w) nitric acid aqueous solution.

[0116] Experimental example 1) Acetic acid concentration after immersion For each of Examples 1 to 9 and Comparative Examples 1 to 3, the weight of water in the aqueous acid mixture solution after acid immersion was measured using a Karl Fischer moisture content analyzer (Si Analytics Titro Line 7000).

[0117] The amount of acetic acid in the acid mixture aqueous solution after acid immersion was obtained using gas chromatography (GC) analysis.

[0118] -Column: AT-1000 -Gas flow rate: Column (He) 4mL / min -Oven temperature: Initial Value & Time 40℃, 5 minutes -Injector temperature: 250℃ -Detector temperature: 270℃

[0119] Acetic acid concentration after acid immersion = weight of acetic acid / (weight of acetic acid + weight of water) x 100

[0120] 2) Measurement of thermal conductivity (mW / mK) The thermal conductivity of each of the silica aerogel blankets produced in Examples 1 to 9 and Comparative Examples 1 to 3 was measured at room temperature (about 23° C.) using an HFM 436 device manufactured by NETZSCH.

[0121] 3) Measurement of residual Cl The amount of residual Cl was measured for each of the silica aerogel blankets produced in Examples 1 to 9 and Comparative Examples 1 to 3 using a combustion ion chromatography (combustion IC) system (AQF-2100H, ICS-3000, manufactured by Thermo Fisher Scientific).

[0122] [Table 1]

[0123] In Examples 1 to 9, silica aerogel blankets were manufactured using an acid mixture aqueous solution containing acetic acid and an acid catalyst, the amount of acetic acid used was 0.5 L to 10 L per 1 L of wet gel, and the acetic acid concentration (w / w%) in the acid mixture aqueous solution layer after acid immersion was 30% to 90%. It was confirmed that the silica aerogel blankets manufactured had low thermal conductivity and contained only 50 ppm or less of Cl.

[0124] Comparative Example 1 uses hydrochloric acid instead of the aqueous solution of acetic acid and an acid catalyst, and Comparative Example 2 uses trimethylchlorosilane as a surface modifier. The use of a chlorine-containing compound during the silica aerogel blanket manufacturing process resulted in over 5,000 ppm of residual chlorine in the final silica aerogel blanket. Therefore, if residual chlorine is present in the silica aerogel blanket, the residual chlorine causes corrosion at the application site of the silica aerogel blanket. Therefore, Comparative Examples 1 and 2 cannot provide long-term stability and durability. In Comparative Example 3, the amount of acetic acid used was 0.5 L per 1 L of wet gel, but the acetic acid concentration (w / w%) in the aqueous solution of the acid mixture after acid immersion was too low at 22.8%, resulting in only 50 ppm or less of Cl. However, the lack of acetic acid prevented smooth surface modification, resulting in high thermal conductivity.

[0125] In contrast, the silica aerogel blankets of Examples 1 to 9 exhibited low thermal conductivity and contained only a minimal amount of Cl derived from the glass fiber used as the blanket substrate, and therefore were confirmed to provide excellent stability and durability when used.

Claims

1. 1) preparing a silica sol containing a water glass solution; 2) impregnating a blanket substrate with the silica sol; 3) gelling the silica sol while the silica sol is impregnated into the blanket substrate to produce a wet gel; 4) immersing the wet gel in an aqueous acid mixture containing acetic acid and an acid catalyst, and surface-modifying the wet gel with an alkyldisiloxane compound; 5) drying the surface-modified wet gel; In step 4), the acetic acid is used in an amount of 0.5 L to 10 L per 1 L of the wet gel, and the concentration (w / w%) of the acetic acid after step 4) is 30% to 90%.

2. 2. The method for producing a silica aerogel blanket according to claim 1, wherein the acid catalyst is at least one selected from the group consisting of nitric acid, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.

3. 2. The method for producing a silica aerogel blanket according to claim 1, wherein after step 4), the concentration (w / w%) of the acid catalyst is 3% to 10%.

4. the acid catalyst comprises nitric acid, sulfuric acid, or a mixture thereof; 2. The method for producing a silica aerogel blanket according to claim 1, wherein after step 4), the concentration (w / w%) of the acid catalyst is 5% to 10%.

5. the acid catalyst comprises one or more selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid; 2. The method for producing a silica aerogel blanket according to claim 1, wherein after step 4), the concentration (w / w%) of the acid catalyst is 3% to 10%.

6. 2. The method for producing a silica aerogel blanket according to claim 1, wherein in step 4), a step of further adding toluene to the wet gel is performed before the surface modification.

7. 2. The method for producing a silica aerogel blanket according to claim 1, wherein in step 4), the step of immersing the wet gel in an acid mixture aqueous solution is performed, and then the step of surface-modifying the wet gel with the alkyldisiloxane compound is performed in this order.

8. 2. The method for producing a silica aerogel blanket according to claim 1, wherein in step 4), the acid mixture aqueous solution and the alkyldisiloxane compound are added to the wet gel sequentially, or the acid mixture aqueous solution and the alkyldisiloxane compound are added to the wet gel simultaneously.

9. 2. The method for producing a silica aerogel blanket according to claim 1, wherein in step 4), the alkyldisiloxane compound is added in a volume ratio of 1 to 3 times the volume of the wet gel.

10. The alkyldisiloxane compound is hexa(C １－８ 2. The method for producing a silica aerogel blanket according to claim 1, wherein the silica aerogel is a (alkyl)disiloxane.

11. 2. The method for producing a silica aerogel blanket according to claim 1, wherein the method is carried out under chlorine-free (Cl-free) conditions.

12. The thermal conductivity is 12 mW / mK to 19 mW / mK, A silica aerogel blanket having a Cl content of 0 ppm to 500 ppm.

13. The silica aerogel blanket according to claim 12, wherein the silica aerogel blanket has a Cl content of 0 ppm to 200 ppm.

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