KR20240013573A - Method for manufacturing hydrophobic silica aerogel blanket - Google Patents

Abstract

The present invention relates to a method for producing a silica airgel blanket with excellent surface modification efficiency and high hydrophobicity that does not contain residual chlorine, and to a silica airgel blanket that does not contain residual chlorine produced thereby.

Description

Method for manufacturing hydrophobic silica airgel blanket {METHOD FOR MANUFACTURING HYDROPHOBIC SILICA AEROGEL BLANKET}

The present invention relates to a method for producing a silica airgel blanket with excellent surface modification efficiency and high hydrophobicity that does not contain residual chlorine, and to a silica airgel blanket that does not contain residual chlorine produced thereby.

Aerogel is an ultraporous, high-specific surface area (≥500 m ² /g) material with a porosity of about 90 to 99.9% and a pore size in the 1 to 100 nm range, and has excellent properties such as ultra-light weight, ultra-insulation, and ultra-low dielectric properties. Since it is a material that has airgel material development research, as well as application research on transparent insulation and environmentally friendly high-temperature insulation, ultra-low dielectric thin films for highly integrated devices, catalysts and catalyst carriers, electrodes for super capacitors, and electrode materials for seawater desalination, are also actively being conducted. .

The biggest advantage of airgel is its super-insulation property, which shows a thermal conductivity of less than 0.300 W/m·K, which is lower than conventional organic insulation materials such as Styrofoam. In addition, it can solve the fatal weaknesses of organic insulation materials such as fire vulnerability and harmful gas generation during fire.

However, airgel has a complex manufacturing process and high manufacturing cost, so despite having such excellent material properties, it is used only for extremely limited purposes. In addition, due to the high porosity, the mechanical strength is very weak, so it has the disadvantage of being easily broken by even a small impact. Therefore, recently, airgel blanket composite technology has been studied to compensate for the shortcomings of airgel itself and enable processing into various forms.

An airgel blanket refers to a product made by combining airgel materials into a mattress or sheet form, and is flexible and can be bent, folded, or cut. Accordingly, it can be applied to pipe insulation, clothing, etc., and various industrial applications are also possible. Flexibility is possible because the airgel blanket is a composite composed of fiber and airgel. Fibers play a role in strengthening the flexibility and mechanical strength of the airgel blanket, and airgel provides insulation properties due to its porosity. The core composite technology of airgel blankets is to combine the characteristics of fiber and airgel to take advantage of each other's strengths and complement their weaknesses.

Airgel blankets are a new material with better heat resistance and insulation than existing polymer insulators such as polystyrofoam or polyurethane foam, and are attracting attention as a cutting-edge material that can solve future energy saving and environmental problems.

Silica airgel blankets are manufactured by mixing fibers with silica sol obtained from water glass or alkoxide-based precursors and gelling them, followed by aging, surface modification, and drying. The surface modification is performed by impregnating the fibers with silica sol and then adding acid with a hydrophobizer. It is carried out by adding a catalyst. At this time, the hydrophobizing agent is not miscible with water and has no reactivity with wet gels, especially hydrogels made by gelling water glass, so a method of solvent replacement with an amphiphilic organic solvent such as ethanol is used, or trimethylchlorosilane (TMCS) is used. ) A method of reacting using a hydrophobizing agent and the resulting HCl as a catalyst has been developed, but when solvent replacement is performed with an amphiphilic organic solvent, a lot of time is required for solvent replacement, and a large amount of diluted organic solvent is generated. , the method of using trimethylchlorosilane (TMCS) hydrophobizing agent generates HCl, resulting in Cl remaining in the final silica airgel blanket.

Since chlorine remaining in the silica airgel blanket causes corrosion, there is a need to develop a method for producing a silica airgel blanket with high hydrophobicity in a way that has excellent surface modification efficiency and does not generate residual chlorine.

US 5,789,075 B

The problem to be solved by the present invention is to provide a silica airgel blanket that has excellent surface modification efficiency and does not contain residual chlorine, thereby eliminating corrosion problems that may arise when applying the silica airgel blanket, thereby demonstrating excellent stability. It provides a manufacturing method.

Another problem to be solved by the present invention is to provide a silica airgel blanket that does not contain chlorine.

In order to solve the above problems, the present invention provides a method for manufacturing a silica airgel blanket and a silica airgel blanket.

[1] The present invention includes the steps of 1) preparing silica sol containing a water glass solution; 2) impregnating the blanket substrate with the silica sol; 3) preparing a wet gel by gelling the silica sol while impregnating the blanket substrate with the silica sol; 4) immersing the wet gel in an aqueous acid mixture solution containing acetic acid and an acid catalyst and surface modifying the wet gel with an alkyldisiloxane-based compound; and 5) drying the surface-modified wet gel, wherein in step 4), the alkyldisiloxane-based compound is used in an amount of 1 L to 3 L per 1 L of the wet gel. A method for producing a silica airgel blanket is provided wherein the acetic acid concentration (w/w) is 30% to 90%.

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

[3] The present invention provides a method for producing a silica airgel blanket according to [1] or [2] above, wherein the acetic acid concentration (w/w) is 40% to 80%.

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

[5] The present invention is according to any one of [1] to [4] above, wherein in step 4), after the process of immersing the wet gel in an aqueous acid mixture solution, the surface is modified with the alkyldisiloxane-based compound. A method for manufacturing a silica airgel blanket in which the processes are performed sequentially is provided.

[6] In the present invention, in any one of the above [1] to [5], in step 4), the acid mixture aqueous solution and the alkyldisiloxane-based compound are sequentially added to the wet gel, or the acid mixture A method for producing a silica airgel blanket is provided in which an aqueous solution and the alkyldisiloxane-based compound are simultaneously added to the wet gel.

[7] The present invention provides a method for producing a silica airgel blanket according to any one of [1] to [6] above, wherein the alkyldisiloxane-based compound is hexa(C _1-8 alkyl)disiloxane.

[8] The present invention provides a method for producing a silica airgel blanket according to any one of [1] to [7] above, wherein the method for producing a silica airgel blanket is performed under chlorine-free (Cl-free) conditions.

[9] The present invention provides a silica airgel blanket produced by the manufacturing method of any one of [1] to [8] above, and does not contain Cl.

The method for producing hydrophobic silica airgel according to the present invention has excellent surface modification efficiency and can produce a silica airgel blanket with high hydrophobicity that does not contain residual chlorine, so it is used in industries that require it, especially silica with high hydrophobicity. It can be usefully applied to industries that require airgel or industries that require silica airgel with the above-mentioned range of hydrophobization degrees.

Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.

Terms or words used in this specification and claims should not be construed as limited to their common or dictionary meanings, and the inventor may appropriately define the concept of terms in order to explain his or her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it is.

In general, silica wet gel manufactured using water glass has pores filled with water as a solvent. When the solvent is simply dried and removed, the liquid solvent evaporates into the gas phase and forms a pore at the gas/liquid interface. Due to the high surface tension of water, shrinkage and cracking of the pore structure are likely to occur, 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 not only necessary to replace water with a high surface tension with an organic solvent with a relatively low surface tension, but also to maintain the structure of the wet gel without shrinkage. Skills for cleaning and drying are required.

In addition, dried silica airgel maintains low thermal conductivity immediately after drying, but has the disadvantage of absorbing water in the air due to the hydrophilic nature of the silanol group (Si-OH) on the silica surface, which gradually increases thermal conductivity.

Therefore, in order to reduce the shrinkage and occurrence of cracks in the pore structure due to the high surface tension of water at the gas/liquid interface when drying the silica wet gel, and to maintain low thermal conductivity by reducing the water absorption rate of the dried silica airgel, silica There is a need to modify the airgel surface to make it hydrophobic. Accordingly, a method of modifying the surface of silica airgel to make it hydrophobic using a surface modifier is widely used.

In order to modify the wet gel to be hydrophobic, it is usually treated with trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), dimethyldiethoxysiloxane (DMDES), hexamethylsiloxane (HMDSO), and trimethylethoxysilane (TMES). At least one surface modifier selected from the group consisting of is used.

When using hexamethyldisilazane (HMDS), trimethylethoxysilane (TMES), dimethyldiethoxysiloxane (DMDES), and hexamethylsiloxane (HMDSO) among the surface modifiers, the surface modifier does not mix with water, so wet gel, In particular, since it is not reactive with hydrogel made by gelling water glass, it is first converted into an organic gel (organogel) by solvent replacement using an amphiphilic organic solvent such as ethanol, and then reacted with the surface modifier to modify the surface with a hydrophobizer. This comes true. This method has the disadvantage of requiring a long time for solvent replacement to convert hydrogel to organic gel and producing a large amount of diluted organic solvent.

On the other hand, when trimethylchlorosilane (TMCS) is used among the surface modifiers, it is reactive with wet gel or hydrogel, so a solvent replacement process can be excluded. However, after surface modification, all remaining trimethylchlorosilane is converted to hexamethyldisiloxane (HMDSO). It has the disadvantage of being switched to and deactivated.

Therefore, in order to solve the disadvantages of using trimethylchlorosilane (TMCS) alone, trimethylchlorosilane (TMCS) is mixed with hexamethyldisiloxane (HMDSO) in a small ratio to use HCl generated from trimethylchlorosilane as a catalyst. A method was developed to modify the surface by converting hexamethyldisiloxane, an inactive species, to trimethylchlorosilane.

However, in both the method of using trimethylchlorosilane and the method of mixing trimethylchlorosilane with hexamethyldisiloxane (HMDSO), trimethylchlorosilane generates HCl after surface modification reaction as shown in Scheme 1 below, so chlorine There is a problem that some remains in the ultimately obtained silica airgel blanket, causing corrosion (corrosion under insulation, CUI).

Meanwhile, instead of using a method of mixing trimethylchlorosilane with hexamethyldisiloxane (HMDSO), a method of separately adding HCl, which is used as a catalyst, to hexamethyldisiloxane is also used. This method is used to modify the surface and simultaneously produce hexamethyl Disiloxane fills the pores to convert the hydrogel into an organic gel, but similarly, some of the added chlorine remains in the silica airgel blanket that is ultimately obtained.

[Scheme 1]

On the other hand, the silica airgel blanket manufacturing method of the present invention does not use a compound containing chlorine (Cl) during the manufacturing process, so the final hydrophobic silica airgel blanket produced does not contain residual chlorine.

The silica airgel blanket manufacturing method of the present invention does not use compounds containing chlorine (Cl) during the manufacturing process, so the final hydrophobic silica airgel blanket produced does not contain residual chlorine. 1) preparing silica sol containing a water glass solution; 2) impregnating the blanket substrate with the silica sol; 3) preparing a wet gel by gelling the silica sol while impregnating the blanket substrate with the silica sol; 4) immersing the wet gel in an aqueous acid mixture solution containing acetic acid and an acid catalyst and surface modifying the wet gel with an alkyldisiloxane-based compound; and 5) drying the surface-modified wet gel, wherein in step 4), the alkyldisiloxane-based compound is used in an amount of 1 L to 3 L per 1 L of the wet gel. The subsequent acetic acid concentration (w/w) is characterized in that it is 30% to 90%.

The method for producing a silica airgel blanket of the present invention is to promote the protonation of acetic acid and alkyldisiloxane-based compounds, which are amphiphilic substances that can dissolve both water and alkyldisiloxane-based compounds used as surface modifiers. While using an acid catalyst, a certain amount of acetic acid is used based on the volume of the wet gel, and the acetic acid concentration [weight (w) / weight (w)] satisfies a certain value after the surface modification in step 4). By using the alkyldisiloxane compound in a certain amount based on the volume of the wet gel, residual chlorine is maintained in the final manufactured silica airgel blanket while exhibiting an excellent surface modification rate. You can choose not to include it.

1) Preparing silica sol containing water glass solution

The silica sol of step 1) can be prepared by mixing a water glass solution and an acid catalyst as a silica precursor.

The acid catalyst in the silica sol may be included in a molar ratio of 1 to 3 relative to the water glass in the water glass solution.

The water glass solution may be a diluted solution obtained by adding and mixing distilled water to water glass, and the water glass may be sodium silicate (Na ₂ SiO ₃ ), which is an alkali silicate salt obtained by melting silicon dioxide (SiO ₂ ) and an alkali. there is.

The water glass dispersion may contain 1% to 13% by weight of silicon dioxide (SiO ₂ ). If the water glass dispersion contains silicon dioxide in a content lower than the above range, the airgel may not be properly formed, and if the silicon dioxide is contained in a content higher than the above range, gelation does not proceed easily or does not proceed easily. Surface area may be reduced.

As the acid catalyst, any one or more of organic acids and inorganic acids that do not contain chlorine in the compound molecular structure can be used to exclude chlorine from the final manufactured silica airgel blanket, and include, for example, acetic acid, oxalic acid, nitric acid, sulfuric acid, and hydrofluoric acid. It may be one or more types selected from the group, and specifically, considering the aqueous acid mixture solution used in the surface modification in step 4), acetic acid, nitric acid, sulfuric acid, or a mixture of two or more of them may be used.

The acid catalyst may be included in an amount such that the pH of the silica sol is 3 to 10. If the pH of the silica sol is outside the above range, gelation in step 3) may not be easy, or the gelation rate may be too fast or too slow, which may reduce processability.

2) Impregnating the blanket substrate with silica sol

Step 2) is a step of impregnating the blanket substrate with the silica sol.

The blanket substrate according to an embodiment of the present invention may be specifically a porous substrate in terms of improving the thermal insulation of the silica airgel blanket. When a porous blanket substrate is used, the silica sol easily penetrates into the substrate and forms airgel uniformly inside the blanket substrate, allowing the manufactured silica airgel blanket to have excellent thermal insulation properties.

The blanket substrate that can be used according to an embodiment of the present invention may be a film, sheet, net, fiber, foam, non-woven fabric, or a laminate of two or more layers thereof. Additionally, depending on the use, surface roughness may be formed or patterned on the surface. More specifically, the blanket substrate may be a fiber that can further improve thermal insulation performance by including a space or void that facilitates insertion of silica airgel into the blanket substrate. Additionally, it may be desirable for the blanket substrate to have low thermal conductivity.

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

Additionally, according to one embodiment of the present invention, impregnation may be performed by pouring silica sol into a reaction vessel containing a blanket substrate or by wetting the blanket substrate with silica sol. At this time, in order to improve the bond between the blanket substrate and the silica sol, the blanket substrate can be lightly pressed to ensure sufficient impregnation. Afterwards, the blanket substrate can be pressed to a certain thickness with a certain pressure to remove excess silica sol, thereby reducing the drying time.

3) A step of preparing a wet gel by gelling the silica sol while impregnating the blanket substrate with the silica sol.

Step 3) is a step for producing a hydrophobic silica wet gel blanket. The wet gel blanket can be produced by allowing the silica sol impregnated in the blanket substrate to undergo gelation.

Here, the gelation may represent a sol-gel reaction, and the “sol-gel reaction” may be the formation of a network structure from a silicon unit precursor material.

Here, the network structure is a flat network-shaped structure in which certain polygons of one or more types of atomic arrangements are connected, or a three-dimensional skeletal structure by sharing vertices, edges, faces, etc. of a specific polyhedron. It may represent the structure forming the .

The manufacturing method according to an embodiment of the present invention may further include aging the silica wet gel blanket prepared after gelation in step 3).

The maturation is not particularly limited, but may be performed, for example, by leaving it at room temperature (25°C) to 90°C for 1 hour to 24 hours.

The manufacturing method according to an embodiment of the present invention can form the network structure of the wet gel in the silica wet gel blanket more firmly by subjecting the silica wet gel blanket to the above-described aging process, and thus have excellent pore characteristics. there is.

4) Immersing the wet gel in an aqueous acid mixture containing acetic acid and an acid catalyst and surface modifying it with an alkyldisiloxane-based 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-based compound to form a hydrophobic silica wet gel blanket.

In one example of the present invention, the process of adding the aqueous acid mixture solution to the wet gel to immerse the wet gel in the aqueous acid mixture solution and then adding the alkyldisiloxane-based compound to the wet gel may be performed, and In another example of the present invention, a process of simultaneously adding the acid mixture aqueous solution and the alkyldisiloxane-based compound to the wet gel may be performed.

Regardless of the time of addition of the acid mixture aqueous solution and the alkyldisiloxane-based compound added to the wet gel, the acid mixture aqueous solution containing water having a higher density than the alkyldisiloxane-based compound is positioned downward. , the layers are separated into an organic solution layer containing an alkyldisiloxane-based compound in the upper layer and an aqueous acid mixture solution layer in the lower layer. Even when the process of adding the acid mixture aqueous solution and the alkyldisiloxane-based compound together to the wet gel is performed, the hydrophobic alkyldisiloxane-based compound and the acid mixture aqueous solution containing water are separated into layers, and moisture The wet gel containing is placed in the acid mixture aqueous solution layer and immersed in the acid mixture aqueous solution.

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 moisture present in the wet gel comes out of the wet gel and moves to the acid mixture aqueous solution layer. In this way, when immersion with 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 may be in equilibrium.

Acetic acid, an amphiphilic substance contained in the acid mixture aqueous solution, allows a trace amount of the alkyldisiloxane-based compound to be dissolved into the acid mixture aqueous solution at the interface between the organic solution layer and the acid mixture aqueous solution layer, thereby dissolving the alkyldisiloxane-based compound. The surface of the wet gel is modified by the compound. In the process of surface modification of the wet gel, the aqueous solution filling the wet gel is replaced with the alkyldisiloxane-based compound, and the wet gel is filled with the alkyldisiloxane-based compound, and the aqueous solution flows out of the wet gel. comes out and moves to the acid mixture aqueous solution layer. When the immersion process is completed, the acid concentration inside the wet gel and the acid concentration outside the wet gel reach equilibrium.

Since the wet gel contains moisture, it is initially located in the acid mixture aqueous solution layer, and as surface modification occurs and the wet gel is filled with the alkyldisiloxane-based compound, it gradually rises and moves to the alkyldisiloxane-based compound layer. do.

In one embodiment of the present invention, when hexamethyldisiloxane, for example, is used as the alkyldisiloxane-based compound in step 4), a reaction as shown in Scheme 2 below may be performed.

[Scheme 2]

After step 4), the acetic acid concentration (w/w) may be 30% to 90%, specifically 40% to 80%, and more specifically 50% to 70%. After step 4), when acetic acid is used in an amount such that the concentration of acetic acid is 30% or more to 90%, the acetic acid enables effective contact between the hydrophilic wet gel and the hydrophobic alkyldisiloxane-based compound, resulting in smooth surface modification. A reaction can occur. If the acetic acid concentration (w/w) is too low, the reaction between the hydrophilic wet gel and the hydrophobic alkyldisiloxane-based compound may not occur, so the surface modification reaction may not proceed smoothly. Additionally, if the acetic acid concentration is excessive, more acetic acid than necessary must be added, which may reduce economic efficiency.

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

[Equation 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)

In step 4), the acid catalyst concentration (w/w) after step 4) may satisfy 3% to 10%, specifically 4 to 9%, and more specifically 5% to 8%. there is.

When the acid catalyst concentration satisfies the above range, protonation of the alkyldisiloxane-based 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 is reduced, and the surface modification reaction by the alkyldisiloxane-based compound is not sufficiently achieved, so that the degree of hydrophobization of the wet gel decreases and thus the heat conduction of the final manufactured silica airgel blanket degree may increase. Additionally, if the acid catalyst concentration is excessive, the oxidizing power of the acid catalyst increases and dangerous side reactants may be formed through reaction with acetic acid, thereby reducing stability.

The acid catalyst may be at least one 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) refers to the concentration of the acid catalyst contained in the acid mixture aqueous solution layer after step 4), and can be expressed by Equation 2 below. The concentration of the acid catalyst can be calculated by measuring the weight of water in the acid mixture aqueous solution layer after step 4) and then measuring the weight of the acid catalyst in the acid mixture aqueous solution layer using gas chromatography (GC).

[Equation 2]

Concentration of acid catalyst (w/w) = weight of acid catalyst / (weight of acid catalyst + total weight of water in the acid mixture aqueous solution layer)

As described above, when the process of immersion 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, so the acid concentration of the acid mixture aqueous solution layer after immersion can be measured. In this case, the acid concentration inside the wet gel can be known, and thus the acid concentration involved in surface modification can be determined.

After step 4), the water contained in the acid mixture aqueous solution layer is water contained in the acetic acid aqueous solution and the acid catalyst, water contained in the wet gel, and water derived from the hydrophilic hydrophobization reaction of the wet gel. Among them, they may remain after step 4), and their total weight may be the total weight of water in the acid mixture aqueous solution layer.

Step 4) can be performed by sequentially immersing the wet gel in an aqueous acid mixture solution and then sequentially modifying the surface with the alkyldisiloxane-based compound.

The method for manufacturing a silica airgel blanket according to an embodiment of the present invention uses an aqueous acid mixture solution containing acetic acid and an acid catalyst when immersing the wet gel in the aqueous acid mixture solution in step 4), and the acetic acid is used as the wet gel. While satisfying a certain volume for the gel, after step 4), check whether the acetic acid concentration satisfies the above-mentioned value, and also ensure that the alkyldisiloxane-based compound satisfies a certain volume for the wet gel, thereby producing a wet gel. , In particular, surface modification can be achieved quickly, sufficiently and effectively for hydrogels manufactured using a water glass solution.

The alkyldisiloxane-based compound may be used in an amount of 1 L to 3 L per 1 L of wet gel, specifically 1 L to 2.5 L, and more specifically 1 L to 2 L.

The alkyldisiloxane-based compound needs to be added in a volume of at least 1 time based on the volume of the wet gel to modify the wet gel and replace the solvent of the wet gel, and the amount of the alkyldisiloxane-based compound added is If it is insufficient, water or acetic acid may remain in the wet gel, causing shrinkage of the silica airgel blanket when the wet gel is dried. In addition, when increasing the amount of the alkyldisiloxane-based compound, the size of the equipment needs to be increased, so the alkyldisiloxane-based compound may be added within the above range based on the volume of the wet gel.

The alkyldisiloxane-based compound may be a hexaalkyldisiloxane-based compound, specifically hexa(C _1-8 alkyl)disiloxane, and more specifically hexamethyldisiloxane.

The surface modification reaction may be performed at a temperature of 25°C to 95°C. Additionally, a stirring process may be performed in the process of immersing the wet gel in an aqueous acid mixture solution and the process of surface modifying the wet gel with an alkoxydisiloxane-based compound.

At this time, the stirring is not particularly limited, but may be stirred at a speed of, for example, 50 rpm to 700 rpm.

In addition, step 4) according to an embodiment of the present invention may be performed for 2 to 24 hours, and is preferably performed for 4 to 22 hours or 8 in terms of improving the economics of the process while maintaining the surface modification effect at an excellent level. It can be performed for up to 20 hours.

In the manufacturing method according to an embodiment of the present invention, step 4) involves immersing the wet gel in an aqueous acid mixture solution, and then sequentially performing surface modification with the alkyldisiloxane-based compound. When carried out, the process of immersing in the acid mixture aqueous solution may be performed for 30 minutes to 4 hours, specifically 30 minutes to 3 hours, more specifically 1 hour to 3 hours, and surface modification with the alkyldisiloxane-based compound. The process may be carried out for 1 hour and 30 minutes to 20 hours, specifically 3 hours to 19 hours, and more specifically 6 hours to 18 hours.

When the wet gel is immersed in an aqueous acid mixture solution containing acetic acid and an acid catalyst and the alkyldisiloxane-based compound is reacted with a surface modification solution, decomposition of the alkyldisiloxane-based compound may be activated by the acid mixture. , Through this, the surface modification reaction is promoted and can be performed effectively. After the surface modification step, the alkyldisiloxane-based compound is separated from the acid mixture aqueous solution layer containing the acid catalyst, so it can be reused without a separate purification process.

The silica airgel blanket manufacturing method of the present invention can simultaneously perform solvent substitution and surface modification in one step, thereby shortening the process steps and process time, thereby improving productivity and economic efficiency.

5) Drying the surface-modified wet gel

Step 5) is a step of manufacturing a hydrophobic silica airgel blanket by drying the hydrophobic silica wet gel blanket.

At this time, the step of washing before drying may be further performed. The washing is to remove impurities (sodium ions, unreacted products, by-products, etc.) generated during the reaction to obtain a high-purity, hydrophobic silica airgel blanket. The hydrophobic silica wet gel is added with a non-polar organic solvent, and washed for 20 minutes. It can be performed by stirring for 1 hour, but is not limited to this.

The drying may be performed through methods such as normal pressure drying and supercritical drying, but is not limited thereto. For example, normal pressure drying may be a method of drying at normal pressure for 1 to 12 hours under temperature conditions of 100°C to 190°C, and supercritical drying may be a method performed using CO ₂ in a supercritical state. Normal pressure drying In the case of , it has the advantage of being relatively simple and economical, and in the case of supercritical drying, it may have the advantage of effectively removing the fluid inside the gel.

The method for manufacturing the hydrophobic silica airgel blanket according to an embodiment of the present invention can greatly improve the surface modification efficiency, and thus has physical properties such as excellent pore characteristics and high hydrophobicity, thereby improving the thermal insulation performance to an excellent level. It can be secured. In particular, since the method for producing the silica airgel blanket according to an embodiment of the present invention is performed under chlorine-free (Cl-free) conditions, chlorine is not included in the final silica airgel blanket produced, so the silica airgel blanket caused by chlorine The possibility of causing corrosion at the application site can be excluded.

The silica airgel blanket manufactured according to the manufacturing method according to an embodiment of the present invention can be used for a variety of purposes, including thermal insulation applications, including applications requiring insulation, for example, at a temperature of 650°C or lower. For example, it can be used as an insulation material for pipes such as double-casing pipes, insulation of aircraft and its parts, insulation of buildings, insulation of spacecraft, insulation of automobiles, insulation of clothing, insulation of shoes, etc. The airgel blanket can be used in the same way as when an airgel mat or a plurality of airgels are used.

Hereinafter, the present invention will be described in more detail through examples and experimental examples. However, the following examples and experimental examples are for illustrative purposes only and do not limit the scope of the present invention.

Example 1

33.8 g of water glass was diluted in 108.1 g of water to prepare a water glass solution, and 7.8 g of acetic acid (97%) was added to prepare silica sol. The silica sol was impregnated into glass fiber and left for 10 minutes to obtain a glass fiber composite impregnated with wet gel.

An aqueous acid mixture solution prepared by mixing 150 g of 90% (w/w) acetic acid aqueous solution and 20 g of 98% (w/w) p-toluenesulfonic acid was poured onto the glass fiber impregnated with the wet gel and placed in an oven at 60°C. After maintaining the temperature for 2 hours, 200 mL of hexamethyldisiloxane (HMDSO) was added, and the temperature was maintained in an oven at 75°C for 16 hours to proceed with the surface modification reaction. At this time, the acetic acid in the acid mixture aqueous solution was used in an amount of 1 L based on the volume of 1 L of the wet gel, and the hexamethyldisiloxane was used in an amount of 1.2 L based on the volume of 1 L of the wet gel. It has been done.

The prepared hydrophobic silica wet gel blanket was recovered and completely dried in a forced circulation dryer at 150°C for 4 hours to prepare a hydrophobic silica airgel blanket.

Example 2

A hydrophobic silica airgel blanket was prepared in the same manner as Example 1, except that 9.8 g of 99% (w/w) methanesulfonic acid was mixed instead of p-toluenesulfonic acid.

Example 3

A hydrophobic silica airgel blanket was prepared in the same manner as Example 1, except that 15.3 g of 98% (w/w) trifluoromethanesulfonic acid was mixed instead of p-toluenesulfonic acid.

Comparative Example 1

A hydrophobic silica airgel blanket was prepared in the same manner as Example 1, except that only 140 g of 35 wt% hydrochloric acid was used instead of the aqueous acid mixture solution of acetic acid and p-toluenesulfonic acid. did.

Comparative Example 2

A hydrophobic silica airgel blanket was prepared in the same manner as Example 1, except that only 140 g of acetic acid (≥97%) was used instead of the acid mixture of acetic acid and p-toluenesulfonic acid in Example 1. did.

Experiment example

1) Acetic acid concentration after immersion

In each of Examples 1 to 3 and Comparative Examples 1 and 2, the weight of water in the acid mixture aqueous solution after acid immersion was measured using a Karl Fischer moisture meter (Si Analytics Titro Line 7000).

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

- Column: AT-1000

- Gas flow rate: Column(He) 4 mL/min

- Oven Temperature: Initial Value & Time 40℃, 5 minutes

- Injector temperature: 250℃

- Detector temperature: 270℃

Acetic acid concentration after acid immersion = weight of acetic acid / (weight of acetic acid + weight of water

2) Thermal conductivity measurement (mW/mK)

The thermal conductivity of the silica airgel blankets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was measured at room temperature (about 23°C) using HFM 436 equipment from NETZSCH.

3) Measurement of Cl residual amount

The residual silica airgel blankets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were analyzed using a combustion ion chromatography (combusion IC) system (AQF-2100H, ICS-3000, Thermo Fisher Scientific). The amount of Cl was measured.

division acetic acid
usage Acetic acid concentration after soaking (%) Types of acid catalysts Alkyldisiloxane-based compounds Thermal conductivity (mW/mK) Cl detection type usage Example 1 1L/1L-gel 51.2 p-toluenesulfonic acid Hexamethyldisiloxane 1.2 L/1 L-gel 17.4 X Example 2 1L/1L-gel 51.2 Methanesulfonic acid Hexamethyldisiloxane 1.2 L/1 L-gel 17.5 X Example 3 1L/1L-gel 51.2 Trifluorosulfonic acid Hexamethyldisiloxane 1.2 L/1 L-gel 17.7 X Comparative Example 1 - - Hydrochloric acid Hexamethyldisiloxane 1.2 L/1 L-gel 17.5 >5000 ppm Comparative Example 2 - 51.2 - Hexamethyldisiloxane 1.2 L/1 L-gel 20.5 X

Examples 1 to 3 use an aqueous acid mixture solution using acetic acid and an acid catalyst, and after acid immersion, the acetic acid concentration (w/w) of the aqueous acid mixture solution layer satisfies 30% to 90%, and the alkyldisiloxane-based compound It was confirmed that a silica airgel blanket was manufactured using a manufacturing method that satisfies the condition that the amount of used is 1 L to 3 L per 1 L of wet gel, and that a silica airgel blanket that has low thermal conductivity and does not contain Cl was manufactured.

In Comparative Example 1, the silica airgel blanket manufactured using hydrochloric acid (HCl) as the acid showed relatively low thermal conductivity, but more than 5,000 ppm of Cl was detected therefrom. Comparative Example 2 is an example in which only acetic acid was used without using an acid catalyst, and it showed a slow surface modification rate, and it was confirmed that the thermal conductivity increased for this reason and the physical properties decreased.

When the silica airgel blanket contains residual chlorine as in Comparative Example 1, when the silica airgel blanket is applied, the residual chlorine causes corrosion in the area to which the silica airgel blanket is applied. Therefore, Comparative Example 1 has long-term stability and durability. It was confirmed that it would not be provided. In contrast, the silica airgel blankets of Examples 1 to 3 showed low thermal conductivity and did not contain residual chlorine, so it was confirmed that they could provide excellent stability and durability when applied.

Claims (9)

1) Preparing silica sol containing a water glass solution;
2) impregnating the blanket substrate with the silica sol;
3) preparing a wet gel by gelling the silica sol while impregnating the blanket substrate with the silica sol;
4) immersing the wet gel in an aqueous acid mixture solution containing acetic acid and an acid catalyst and surface modifying the wet gel with an alkyldisiloxane-based compound; and
5) comprising drying the surface-modified wet gel,
In step 4), the alkyldisiloxane-based compound is used in an amount of 1 L to 3 L per 1 L of the wet gel,
A method for producing a silica airgel blanket wherein the acetic acid concentration (w/w) after step 4) is 30% to 90%.
According to claim 1,
A method of producing a silica airgel blanket wherein the acid catalyst is at least one selected from the group consisting of p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.
According to claim 1,
A method for producing a silica airgel blanket wherein the acetic acid concentration (w/w) is 40% to 80%.
According to claim 1,
The method of producing a silica airgel blanket wherein the acid catalyst concentration (w/w) after step 4) is 3% to 10%.
According to claim 1,
A method of manufacturing a silica airgel blanket in which the process of immersing the wet gel in an aqueous acid mixture solution in step 4) is followed by the process of surface modification with the alkyldisiloxane-based compound.
According to claim 1,
In step 4), the acid mixture aqueous solution and the alkyldisiloxane-based compound are sequentially added to the wet gel, or the acid mixture aqueous solution and the alkyldisiloxane-based compound are simultaneously added to the wet gel. Manufacturing method.
According to claim 1,
A method of producing a silica airgel blanket wherein the alkyldisiloxane-based compound is hexa(C _1-8 alkyl)disiloxane.
According to claim 1,
The silica airgel blanket manufacturing method is a silica airgel blanket manufacturing method performed under chlorine-free (Cl-free) conditions.
A silica airgel blanket manufactured by the manufacturing method according to claim 1, wherein the silica airgel blanket does not contain Cl.