WO2018030796A1 - Aerogel precursor, preparation method therefor, aerogel prepared therefrom, and aerogel preparation method using same - Google Patents

Abstract

The present invention relates to: an aerogel precursor, which comprises, in a molar ratio of 100:1 to 100:20, a structural unit represented by the following chemical formula 1, and one or more selected from the group consisting of structural units represented by the following chemical formulas 2-4, has a weight average molecular weight of 1,000-6,000 g/mol, and has a viscosity of 2.0-4.0 cps after being heated at 45-60°C for 24 hours or longer; a preparation method therefor; an aerogel prepared therefrom; and an aerogel preparation method using the same.

Description

Airgel precursor, preparation method thereof, airgel manufactured therefrom and preparation method of airgel using same

[Citations with Related Applications]

The present invention claims the benefit of priority based on Korean Patent Application No. 10-2016-0101072 filed on August 09, 2016 and Korean Patent Application No. 10-2017-0101114 filed on 2017.08.09, All content disclosed in the literature is included as part of this specification.

[Technical Field]

The present invention relates to an airgel precursor, a method for preparing the same, an airgel prepared therefrom, and a method for preparing an airgel using the same. It relates to a manufacturing method.

Aerogels are porous materials with 98% of the total volume of air in which SiO ₂ nanostructures are coarsely woven like a nonwoven fabric. Aerogels have high porosity, nano-level micropores, and high specific surface area, resulting in ultra-light weight, high thermal insulation, and low dielectric properties. As a result, researches are being actively conducted as insulation materials and environmentally friendly high-temperature insulation materials, ultra-low dielectric thin films for highly integrated devices, catalysts and catalyst carriers, electrodes for supercapacitors or seawater desalination.

The biggest advantage of airgel is super-insulation, which shows a thermal conductivity of 0.300 W / m · K or lower, which is lower than that of conventional thermal insulation such as styrofoam. In addition, airgel has been used as a high temperature insulation material because there is no fear of fire vulnerabilities and the generation of harmful gases in case of fire, which is a fatal weakness of the organic insulation material.

However, in the case of high temperature insulation material, durability is an important factor along with low thermal conductivity, and for the durability, thermal denaturation due to moisture infiltration should be prevented.

For this purpose, surface hydrophobization treatment is essential to prevent moisture penetration. As the hydrophobic group on the surface of the airgel is not oxidized by heat, it may exhibit excellent durability.

Conventionally, tetraethoxysilane (TEOS) or hydrolyzed TEOS is used as a precursor when synthesizing aerogels, and water, alcohol, and acid or base catalysts are used to control the porosity of the wet gel, and after hydrophobic surface modification, Aerogels having hydrophobicity were prepared through supercritical drying and atmospheric pressure drying.

However, when the hydrogel is hydrophobic to the surface of the wet gel after the preparation of the wet gel, the reaction efficiency is lower than that of the liquid phase which is a single phase because it is a liquid / solid two phase. Therefore, a large amount of surface hydrophobization agent is used in the surface hydrophobization treatment of the wet gel, and as a result, the surface hydrophobization agent is easily oxidized by heat, thereby deteriorating high temperature durability.

It is an object of the present invention to provide an airgel precursor having excellent durability at room temperature and high temperature as well as excellent durability.

Another object of the present invention is to provide an airgel excellent in both room temperature and high temperature hydrophobicity, high temperature stability and heat insulation.

Still another object of the present invention is to provide an airgel blanket having excellent room temperature and high temperature hydrophobicity, high temperature stability, and thermal insulation.

Still another object of the present invention is to provide a method for preparing an airgel that does not undergo a separate solvent replacement process.

The present invention comprises at least one selected from the group consisting of structural units represented by the following formula (1) and structural units represented by the following formulas (2) to (4) in a molar ratio of 100: 1 to 100: 20, and the weight average molecular weight An airgel precursor is characterized in that it is 1,000 to 6,000 g / mol and has a viscosity of 2.0 to 4.0 cps after heating at 45 to 60 ° C. for 24 hours:

<Formula 1>

<Formula 2>

<Formula 3>

<Formula 4>

In Chemical Formulas 1 to 4,

L ₁ to L ₄ are the same as or different from each other, and each independently, a direct bond or O,

X is Si, Ti, Zr, Hf or Rf,

R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, Substituted or unsubstituted C ₄ to C ₂₀ linear alkenyl group, substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or substituted or unsubstituted C ₅ to C ₂₀ aryl group,

R ₂ is a halogen, hydroxyl group, substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, substituted or unsubstituted C ₁ to C ₂₀ alkyloocta It's time.

The present invention is a first step of preparing a mixture by mixing a compound represented by the formula (21) and a compound represented by the formula (22) with an alcohol in a molar ratio of 100: 1 to 100: 20; And a second step of hydrolyzing and polycondensing the mixture.

<Formula 21>

<Formula 22>

In Chemical Formulas 21 and 22,

R is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group,

X is Si, Ti, Zr, Hf or Rf,

R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, A substituted or unsubstituted C ₄ to C ₂₀ branched alkenyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or a substituted or unsubstituted C ₅ to C ₂₀ aryl group,

R ₂ is a halogen, hydroxyl group, substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, substituted or unsubstituted C ₁ to C ₂₀ alkyloocta It's time.

The present invention comprises the steps of mixing the airgel precursor and the base catalyst to form a wet gel at pH≥3; Surface modification by mixing the wet gel and a hydrophobic agent; And it provides a method for producing an airgel comprising the step of drying the surface modification gel.

The airgel precursor according to the present invention has excellent room temperature and high temperature hydrophobicity, excellent durability, and can be used while mass storage for a long time. In addition, the airgel precursor of the present invention is imparted hydrophobicity to the wet gel produced during the preparation of the airgel, so that compatibility of the wet gel and the organic solvent can be improved, thereby increasing the efficiency during surface modification, surface modification You can also reduce the amount of material you use.

The airgel and the airgel blanket of the present invention may be excellent in both room temperature and high temperature hydrophobicity, high temperature stability and thermal insulation.

1 is a graph measuring the viscosity change with time at 50 ° C of the airgel precursor of Synthesis Example 4.

Figure 2 is a graph showing the distribution of pores in the airgel of Example 5 and Comparative Example 3.

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

The words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the principle that the inventor may appropriately define the concept of terms in order to best describe his or her invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

In the present specification, 'substituted or unsubstituted' is deuterium; Cyano group; C ₁ to C ₂₀ linear alkyl group; C ₃ to C ₂₀ branched alkyl group; C _{2 Through} C ₂₀ Linear alkenyl group; Branched alkenyl groups of C ₄ to C ₂₀ ; C ₂ to C ₂₀ linear alkynyl group; It means unsubstituted or substituted with one or more substituents selected from the group consisting of a C ₃ to C ₂₀ cycloalkyl group and a C ₆ to C ₂₀ aryl group.

로 표시되는 것은 다른 치환기 또는 구조 단위와 연결되는 사이트를 의미한다. In the formula described in the present invention

Denoted by site means a site linked with other substituents or structural units.

One. Airgel  Precursor

Airgel precursor according to an embodiment of the present invention is a structural unit represented by the following formula (1) and at least one selected from the group consisting of structural units represented by the formula 2 to 4 in a molar ratio of 100: 1 to 100: 20 The weight average molecular weight is 1,000 to 6,000 g / mol, and the viscosity is 2.0 to 4.0 cps after heating at 45 to 60 ° C for 24 hours.

<Formula 1>

<Formula 2>

<Formula 3>

<Formula 4>

In Chemical Formulas 1 to 4,

L ₁ to L ₄ are the same as or different from each other, and each independently, a direct bond or O,

X may be Si, Ti, Zr, Hf or Rf, more specifically Si.

R ₁ is a hydrophobic functional group which imparts hydrophobicity to the airgel precursor. Substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, substituted or unsubstituted C ₄ to C ₂₀ branched alkenyl group, substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or substituted or unsubstituted C ₅ To C ₂₀ aryl group, specifically substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, substituted or unsubstituted C ₃ to C ₂₀ branched alkyl group, or substituted or unsubstituted C ₅ to C ₂₀ may be an aryl group.

The alkyl group may be a substituted or unsubstituted C ₁ to C ₁₀ linear alkyl group or a substituted or unsubstituted C ₃ to C ₁₀ branched alkyl group, specific examples thereof include methyl group, ethyl group, propyl group, butyl group, Pentyl, hexyl, heptyl, octyl, nonyl, decyl, isopropyl, isobutyl, sec-butyl and tert-butyl, isopentyl, neopentyl, isohexyl, isoheptyl, isooctyl, isononyl, Or isodecyl.

The cyclic alkyl group includes C ₃ to C ₂₀ monocyclic or polycyclic, and the polycyclic may mean a group directly connected or condensed with another ring group. The other ring group here may be a cyclo alkyl group, hetero cyclo alkyl group, aryl group or heteroaryl group. The cycloalkyl group may be a substituted or unsubstituted C ₃ to C ₁₀ cycloalkyl group, specific examples thereof include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, Cyclononyl group, a cyclodecyl group, etc. are mentioned.

The alkenyl group may be a substituted or unsubstituted C ₂ to C ₁₀ linear alkenyl group, a substituted or unsubstituted C ₄ to C ₁₀ branched alkenyl group, specific examples thereof may be an ethenyl group, propenyl group, butene And a vinyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, or decenyl group.

The alkynyl group may be a substituted or unsubstituted C ₂ to C ₁₀ linear alkynyl group, and specific examples thereof include ethynyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, heptynyl group, octinyl group, and noninyl group. Or a decinyl group.

The aryl group includes monocyclic or polycyclic, and the polycyclic means a group in which aryl is directly connected or condensed with another ring group. Specific examples of the aryl group include phenyl group, biphenyl group, triphenyl, naphthyl group, anthryl group, phenanthrenyl group, pyrenyl group or fluorenyl group.

R ₁ may be a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched group, and more specifically, may be a methyl group.

R ₂ are each independently the same as or different from each other and are a halogen, a hydroxyl group, a substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, a substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, a substituted or unsubstituted It may be a C ₁ to C ₂₀ alkylooxy group, specifically, it may be a halogen, a hydroxyl group or an unsubstituted C ₁ to C ₂₀ alkoxy group.

The halogen may be one selected from the group consisting of F, Cl, Br, I, and At, and specifically, the halogen may be one selected from the group consisting of F, Cl, Br, and I.

The alkoxy group may be a C ₁ to C ₁₀ alkoxy group, and specific examples thereof include methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group, hexoxy group, octoxy group, nonoxy group or dodecyloxy, and the like. Can be.

Specific examples of the alkylooxy group include an acetyl group, propionyl group, n-butyryloxy group or stearooxy group.

Specific examples of the alkyloyloxy group include propionyloxy group, n-butyryloxy group, stearoyloxy group, and the like.

R ₂ may be specifically an unsubstituted C ₁ to C ₂₀ alkoxy group, and more specifically, may be a methoxy group.

The airgel precursor is preferably at least one selected from the group consisting of a structural unit represented by the formula (1) and a structural unit represented by the following formulas 2 to 4 100: 1 to 100: 15, more preferably 100: It may be included in a molar ratio of 4 to 100: 10, the weight average molecular weight is preferably 1,000 to 5,500g / mol, more preferably 1,000 to 3,500g / mol.

When the molar ratio and the weight average molecular weight of the structural units are satisfied, the airgel precursor may have excellent hydrophobicity by itself. In addition, it is excellent in durability and can be mass-produced, and can be used in an airgel manufacturing process while storing for a long time after mass production. In addition, the airgel precursor may impart hydrophobicity to the wet gel produced during the preparation of the airgel or the airgel blanket. In addition, the wet gel imparted with hydrophobicity may improve compatibility with an organic solvent, thereby increasing efficiency in the surface modification process during the aerogel or airgel blanket manufacturing process, and reducing the amount of surface modifier used. The airgel or airgel blanket prepared from the airgel precursor of the present invention is not only excellent in room temperature and high temperature hydrophobicity, but also in high temperature thermal stability and heat insulation.

The airgel precursor has a viscosity of 2.0 to 4.0 cps after heating at 45 to 60 ° C. for 24 hours, preferably 2.5 to 3.5 cps, more preferably 2.8 to 2.9 cps. The airgel precursor may maintain the above-described viscosity range not only after heating but also before and during heating.

In general, leaving the airgel precursor at 45 to 60 ° C. for 1 hour means to leave it at room temperature (23 ± 3 ° C.) for 1 hour. The airgel precursor satisfies all of the above-mentioned viscosity conditions at a temperature of 6 months or more at a viscosity of 2.0 to 4.0 cps, preferably 2.5 to 3.5 cps, more preferably 2.8 to 2.9 cps, and excellent durability. it means.

Meanwhile, Si of the structural unit represented by Chemical Formula 1 in the airgel precursor may be connected to Si of the structural unit represented by Chemical Formula 1 via O (oxygen). Specifically, the airgel precursor may include a structural unit represented by Formula 5 below.

<Formula 5>

Definitions for L ₁ to L ₄ are as described in formula (I).

Si of the structural unit represented by Formula 1 and at least one X selected from the group consisting of the structural units represented by Formulas 2 to 4 may be connected to each other via O (oxygen). Specifically, the airgel precursor may include one or more selected from the group consisting of structural units represented by the following Chemical Formulas 6 to 8.

<Formula 6>

<Formula 7>

<Formula 8>

Definitions for X, L ₁ , L ₃ , L ₄ , R ₁ and R ₂ are as described in Chemical Formulas 1 to 4 above.

The structural unit represented by Chemical Formula 6 may include one or more selected from the group consisting of structural units represented by the following Chemical Formulas 6-1 to 6-3.

<Formula 6-1>

<Formula 6-2>

<Formula 6-3>

The structural unit represented by Chemical Formula 7 may include one or more types from the group consisting of the structural units represented by the following Chemical Formulas 7-1 to 7-3.

<Formula 7-1>

<Formula 7-2>

<Formula 7-3>

The structural unit represented by Formula 8 may be at least one selected from the group consisting of structural units represented by the following Formulas 8-1 to 8-3.

<Formula 8-1>

<Formula 8-2>

<Formula 8-3>

In Chemical Formulas 6-1 to 6-3, 7-1 to 7-3, and 8-1 to 8-3,

R is a substituted or unsubstituted C ₁ to C ₃ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, specifically, a substituted or unsubstituted C ₁ to C ₃ linear alkyl group It may be, and more specifically may be an ethyl group.

Definitions for X and R ₁ and R ₂ are as described in Chemical Formulas 2 to 4 above.

On the other hand, the airgel precursor may include two or more selected from the group consisting of structural units represented by the formula (2) to (4). When two or more kinds of the structural units are included, the high temperature hydrophobization thermal stability of the airgel, which is the final product, may be more excellent. When two or more kinds of the structural units are included, two or more of the same structural units may be included, or two or more different structural units may be included. When two or more of the same structural units are included, the Xs of the structural units represented by Formulas 2 to 4 may be connected to each other via O. Specifically, it may be represented by one or more selected from the group consisting of structural units represented by the following formulas (9) and (10).

<Formula 9>

<Formula 10>

In Chemical Formulas 9 and 10,

Definitions for X and R ₁ and R ₂ are as described in Chemical Formulas 2 to 4 above.

When two or more different structural units are included, X in the structural units represented by Formulas 2 to 4 may be connected to each other through O. Specifically, it may be represented by one or more selected from the group consisting of structural units represented by the following formulas (11) to (13).

<Formula 11>

<Formula 12>

<Formula 13>

In Chemical Formulas 11 to 13,

Definitions for X and R ₁ and R ₂ are as described in Chemical Formulas 2 to 4 above.

Si of the structural unit represented by Formula 1 and X or more of the structural units represented by Formulas 9 to 13 in the airgel precursor may be connected to each other via O (oxygen). Specifically, the airgel precursor is a structural unit represented by the formula (1); And it may include one or more selected from the group consisting of structural units represented by the formula (14) to formula (18).

<Formula 14>

<Formula 15>

<Formula 16>

<Formula 17>

<Formula 18>

In Chemical Formulas 14 to 18,

Definitions for X and R ₁ and R ₂ are as described in Chemical Formulas 2 to 4 above.

The structural unit represented by Chemical Formula 14 may include one or more types from the group consisting of structural units represented by the following Chemical Formulas 14-1 to 14-3.

<Formula 14-1>

<Formula 14-2>

<Formula 14-3>

The structural unit represented by Chemical Formula 15 may include one or more types from the group consisting of structural units represented by the following Chemical Formulas 15-1 to 15-3.

<Formula 15-1>

<Formula 15-2>

<Formula 15-3>

The structural unit represented by Chemical Formula 16 may include one or more types from the group consisting of structural units represented by the following Chemical Formulas 16-1 to 16-3.

<Formula 16-1>

<Formula 16-2>

<Formula 16-3>

The structural unit represented by Chemical Formula 17 may include one or more types from the group consisting of structural units represented by Chemical Formulas 17-1 to 17-3.

<Formula 17-1>

<Formula 17-2>

<Formula 17-3>

The structural unit represented by Chemical Formula 18 may include one or more types from the group consisting of structural units represented by the following Chemical Formulas 18-1 to 18-3.

<Formula 18-1>

<Formula 18-2>

<Formula 18-3>

In Formula 14-1 to 14-3, 15-1 to 15-3, 16-1 to 16-3, 17-1 to 17-3, 18-1 to Formula 18-3,

R is a substituted or unsubstituted C ₁ to C ₃ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, specifically, a substituted or unsubstituted C ₁ to C ₃ linear alkyl group It may be, and more specifically may be an ethyl group.

Definitions for X and R ₁ and R ₂ are as described in Chemical Formulas 2 to 4 above.

Meanwhile, the structural unit represented by Chemical Formula 1 may be derived from a compound represented by Chemical Formula 21, and the structural unit represented by Chemical Formulas 2 to 4 may be derived from a compound represented by Chemical Formula 22.

<Formula 21>

<Formula 22>

In Chemical Formulas 21 and 22,

The definitions of R, X, R ₁ and R ₂ are as described in the description of Formula 6-1.

Specifically, R may be an ethyl group, X may be Si, R ₁ may be a methyl group, and R ₂ may be methoxy.

Hydrolysis degree of the airgel precursor according to an embodiment of the present invention may be 60% to 95%. If the above range is satisfied, the wet gel formed using the same may be formed in a short time. If the degree of hydrolysis is less than the above-mentioned range, the wet gel formation time may be long, and transparency and heat resistance of the airgel may be reduced. When the degree of hydrolysis exceeds the above-mentioned range, durability of the airgel precursor prepared therefrom may be lowered.

On the other hand, the airgel precursor according to an embodiment of the present invention is a first step of preparing a mixture by mixing a compound represented by the formula (21) and a compound represented by the following formula 22 with alcohol in a molar ratio of 100: 1 to 100: 20 ; And a second step of hydrolyzing and polycondensing the mixture.

<Formula 21>

<Formula 22>

In Chemical Formulas 21 and 22,

The definitions of R, X, R ₁ and R ₂ are as described in the description of the above airgel precursor.

In the first step, the alcohol is not particularly limited as long as it is compatible with water and can dissolve the compounds represented by Formulas 21 and 22. The alcohol may be at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol and butanol.

The alcohol may be included in an amount of 1 to 40 parts by weight based on 100 parts by weight of the total of the compounds represented by Formulas 21 and 22. If the above range is satisfied, the silica content in the airgel precursor can be appropriately controlled.

The second step specifically includes a second step of hydrolyzing the mixture using an acid catalyst and water to form a reactant; And it may include a step 2-2 to prepare an airgel precursor by polycondensing the reactants.

In the step 2-1, the acid catalyst may be at least one selected from the group consisting of hydrochloric acid, nitric acid, acetic acid, citric acid and oxalic acid. The acid catalyst may be included in an amount of 0.01 to 0.1 parts by weight based on 100 parts by weight of the total of the compounds represented by Formulas 21 and 22.

The water may be included in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the total of the compounds represented by Chemical Formulas 21 and 22, and when the above-mentioned content is satisfied, the degree of hydrolysis is controlled to control the above-described weight average molecular weight and viscosity conditions. It can be prepared an airgel precursor that satisfies.

Here, the water and the acid catalyst may be in the form of an acid catalyst aqueous solution. The acid catalyst aqueous solution may be included in the mixture in a dropwise dropwise manner in a dropwise manner.

When the reactant is completed in the step 2-1, the color may be blurred and the temperature may be higher than room temperature, but the color of the reactant is clear, and the temperature is lowered to room temperature, and then the step 2-2 is performed. Can be done.

Step 2-2 may be a step of preparing an airgel precursor by heating and refluxing the reactant at 70 to 100 ° C. for 1 to 30 hours, cooling to room temperature, and filtration under reduced pressure using a filter. When the temperature and time conditions described above are satisfied, an airgel precursor that satisfies the above-described weight average molecular weight and viscosity conditions may be prepared.

2. Airgel

An airgel according to another embodiment of the present invention may be prepared using an airgel precursor according to an embodiment of the present invention.

Since the airgel according to another embodiment of the present invention is all hydrophobized to small pores in the airgel precursor, it may have excellent hydrophobicity at room temperature and high temperature. In addition, the airgel may have high porosity, low thermal conductivity, and excellent mechanical flexibility.

In addition, the airgel may have a carbon content of 10 to 15% by weight relative to the total weight of the airgel at room temperature, and may have a carbon content of 1 to 4% with respect to the total weight of the airgel at high temperature. That is, due to the high carbon content in the airgel, not only excellent hydrophobicity at room temperature, but also high temperature hydrophobicity may be excellent because more carbon may remain at a higher temperature than a conventional airgel.

In addition, the airgel may have a specific surface area of 500 m 2 / g to 800 m 2 / g.

In addition, the aerogel is a porous porous structure comprising a plurality of micropores, nano-sized primary particle particles, specifically, the average particle diameter (D ₅₀ ) of 100 nm or less primary particles are combined to form a mesh It may be formed as a fine structure, that is, a three-dimensional network structure forming a cluster (cluster) of.

In the present invention, the carbon content can be measured using Eltra's Carbon / Sulfur Analyzer (CS-800). In addition, the specific surface area can be measured by the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p0 <1) using the ASAP 2020 instrument of Micrometrics.

On the other hand, the airgel according to another embodiment of the present invention comprises the steps of preparing a wet gel by adding a base to a silica sol containing an airgel precursor according to an embodiment of the present invention; Aging the wet gel; Surface modification of the matured wet gel; And it can be prepared by a manufacturing method comprising the step of supercritical drying the wet gel.

The silica sol may be prepared by further mixing water and alcohol with the airgel precursor. Description of the alcohol is as described above in the description of the airgel precursor.

Examples of the base include inorganic bases such as sodium hydroxide and potassium hydroxide; Or an organic base such as ammonium hydroxide, but in the case of the inorganic base, since the metal ion contained in the compound may be coordinated (coordination) to the Si-OH compound, the organic base may be preferable. Specifically, the organic base is ammonium hydroxide (NH ₄ OH), tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), methylamine, ethylamine, isopropylamine, monoisopropylamine, diethylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, choline, Monoethanolamine, diethanol amine, 2-aminoethanol, 2- (ethyl amino) ethanol, 2- (methyl amino) ethanol, N-methyl diethanolamine, dimethylaminoethanol, diethylaminoethanol, nitrilotriethanol, 2 -(2-aminoethoxy) ethanol, 1-amino-2-propanol, triethanolamine, monopropanolamine, or dibutanolamine, and the like, and any one or a mixture of two or more thereof may be used. More specifically, the base may be ammonium hydroxide (NH ₄ OH).

Since the base may be precipitated when it is added to the solid phase, it may be preferable to be added in a solution phase diluted with the polar organic solvent described above.

The aging step is a process for allowing the wet gel to stand at an appropriate temperature so that the chemical change is completely made, and by the aging process for the wet gel, it is possible to strengthen the network structure inside the wet gel. In addition, the moisture inside the wet gel may be substituted with a polar organic solvent during the aging process, and as a result, it is possible to prevent the pore structure deformation and reduction of the silica gel due to evaporation of the moisture inside the wet gel in a subsequent supercritical drying process.

The aging step may be carried out until the chemical change in the wet gel is completed, specifically, the wet gel-based composite at 50 to 80 ℃ 1 hour to 6 hours, more specifically to 60 to 75 ℃ It can be carried out by immersing in a aging solution for 2 to 4 hours.

The aging solution may be alcohol, the description of the alcohol is as described above.

The surface deformation may be performed for 1 to 6 hours at 40 to 80 ° C. after the wet gel is immersed in the surface modification solution. Specifically, the surface modification solution is at least one selected from the group consisting of hexamethyldisilazane, tetramethylchlorosilane, silicone oil, amino silane, alkyl silane, polydimethyl siloxane, and dimethyldichlorosilane and alcohol It may be a solution containing. Description of the alcohol is as described above.

By performing the surface deformation step, the pores of the wet gel may be hydrophobized to facilitate water removal of the pores during supercritical drying.

The supercritical drying step may be a supercritical drying step using supercritical carbon dioxide. Carbon dioxide (CO ₂ ) is a gaseous state at room temperature and atmospheric pressure, but if it exceeds a certain temperature and high pressure limit called the supercritical point, the evaporation process does not occur, so it becomes a critical state in which gas and liquid cannot be distinguished. Carbon dioxide in the state is called supercritical carbon dioxide. Supercritical carbon dioxide has a molecular density close to a liquid, but has a low viscosity, close to a gas, high diffusion efficiency, high drying efficiency, and short drying time.

In the supercritical drying step, the surface-modified wet gel may be put in a supercritical drying reactor, and then a solvent replacement process may be performed in which a liquid CO ₂ is filled and a solvent inside the silica aerogel is replaced with CO ₂ . Thereafter, the temperature is raised to 30 to 80 ° C., preferably 40 to 70 ° C. at a constant temperature increase rate, specifically 0.1 / min to 1 / min, and then the pressure is equal to or higher than the pressure at which carbon dioxide becomes a supercritical state. Maintaining a pressure of 300 bar, preferably 80 to 200 bar, more preferably 100 bar to 150 bar can be maintained for a predetermined time, specifically 20 minutes to 1 hour in the supercritical state of carbon dioxide. In general, carbon dioxide is supercritical at a temperature of 31 ° C. and a pressure of 73.8 bar. The carbon dioxide may be maintained at a constant temperature and a constant pressure for 2 hours to 12 hours, more specifically, 2 hours to 6 hours at which the carbon dioxide becomes a supercritical state, and then the pressure may be gradually removed to complete the supercritical drying step.

On the other hand, the airgel according to another embodiment of the present invention comprises the steps of mixing the airgel precursor and the base catalyst according to an embodiment of the present invention to form a wet gel at pH≥3; Surface modification by mixing with the wet gel and a hydrophobic agent; And it may be prepared by a manufacturing method comprising the step of drying the surface-modified wet gel.

The forming of the wet gel is as described in the above-described method for preparing an airgel.

The step of modifying the surface by mixing the wet gel and the hydrophobic agent may be a step of silylating the surface of the wet gel using a silylating agent which is a hydrophobic agent.

In addition, by performing the silylation, predetermined water in the pores of the wet gel and the used silylating agent can react to form an insoluble compound in water, and water present in the pores by the molar volume of the formed compound. This can be substituted automatically. During the silylation of the wet gel, water and water in the pores of the wet gel may be easily separated from the wet gel by a compound that is insoluble in water. This silylation may not require a separate solvent replacement process.

The silylating agent is preferably (R ₃ ) _{4- n} SiCl _n , (R ₄ ) _{4- m} Si (OR ₅ ) _m , (R ₆ ) ₃ Si-O-Si (R ₆ ) ₃ , and ( R ₇ ) ₃ Si-O-Si (R ₇ ) _{3 It} may be one or more selected from the group consisting of, wherein R ₃ to R ₇ are the same as or different from each other, and each independently, hydrogen, substituted or unsubstituted A C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₅ to C ₂₀ aryl group, n and m are the same as each other Different, and may each independently be 1-4.

More preferably, the silylating agent may be at least one selected from the group consisting of silazane, hexamethyldisilazane, trimethylchlorosilane, hexamethyldisiloxane, trimethylsiloxane and isopropoxytrimethylsilane.

The silylating agent may be used in a liquid state or a gaseous state. The liquid state may be a silylating agent alone or a state dissolved in alcohol.

The temperature in the step of drying the surface-modified wet gel may be -30 to 200 ℃, preferably 0 to 150 ℃, the pressure is 0.001 to 20bar, preferably 0.01 to 5bar, more preferably 0.1 to It can be 2 bar and can be dried by radiation, convection and contact drying.

The airgel produced by the above-described method for producing an airgel may be 90% or more of the theoretically possible coverage of the inner surface by the organic surface group coated by the surface silylation.

In the present invention, coverage means the number of organic surface groups per square nanometer of the inner surface area of the airgel. Surface modification of the porous SiO ₂ material with trimethylchlorosilane can theoretically yield coverage of trimethylsilyl groups (TMS) of up to 2.8 nm ⁻² . This can be calculated from the steric bulk of the TMS unit, which is described in the literature as the umbrella effect. The required space from the Si-C (0.189 nm) and CH (0.108 nm) bond lengths and the van der Waals radius of the TMS molecules is estimated to be about 0.36 nm ² per TMS molecule. In conversion, this corresponds to the coverage of TMS per nm ² (W. Urbaniak, F. Janowski, B. Marciniec, F. Wolf, React. Kinet. Catal, Lett, 1987, 34, 129; KK Unger, Journal of Chromatography Library 1979, 16, 64; EV Broun, A. Ya. Korolev, LM Vinogradova, RV Artamonova, TV Men'kova, Russ. J. Phys. Chem. 1970, 44, 442).

The coverage can be calculated using the following formula.

Coverage = ([C] / [BET] × K; unit: [nm ⁻² ]

^{K = 6.022 × 10 23/100} × 12 × 3 × 10 18 = 167.28; Unit: [g ^-1 ]

[C]: C content in weight percent

[BET]: BET surface area; Unit: [m ² / g]

3. Airgel Blanket

An airgel blanket according to another embodiment of the present invention may be prepared using an airgel precursor according to an embodiment of the present invention.

The airgel blanket according to another embodiment of the present invention is also hydrophobic to all the small pores in the airgel precursor, and thus may have excellent hydrophobicity at room temperature and high temperature. In addition, the airgel contained in the airgel blanket may also have high porosity, low thermal conductivity, and excellent mechanical strength.

The airgel blanket according to another embodiment of the present invention may be an airgel blanket having excellent thermal insulation having a thermal conductivity of 20 kW / mK or less.

In the present invention, the thermal conductivity can be measured using HFM436 Lambda equipment of NETZSCH.

On the other hand, the airgel blanket according to another embodiment of the present invention, after immersing the substrate for the blanket in a silica sol containing the airgel precursor according to an embodiment of the present invention, by adding a base to prepare a wet gel-based composite Making; Aging the wet gel-based composite; Surface modifying the aged wet gel-based composite; And it may be prepared by a manufacturing method comprising the step of supercritical drying the wet gel-based composite.

The blanket substrate may be a film, a sheet, a net, a fiber, a porous body, a foam, a nonwoven fabric, or a laminate of two or more thereof. In addition, depending on the application, the surface roughness may be formed or patterned. More specifically, the blanket substrate may be a fiber capable of further improving the thermal insulation performance by including a space or a space in which an airgel is easily inserted into the blanket substrate. In addition, the blanket base material may have a low thermal conductivity.

Specifically, the blanket base material may be polyamide, polybenzimidazole, polyaramid, acrylic resin, phenol resin, polyester, polyether ether ketone (PEEK), polyolefin (for example, polyethylene, polypropylene, or copolymers thereof). Etc.), cellulose, carbon, cotton, wool, hemp, nonwoven fabric, glass fiber or ceramic wool, and the like, but are not limited thereto. More specifically, the substrate may include glass fiber or polyethylene.

On the other hand, in the manufacturing method of the airgel blanket, except for immersing the substrate for the blanket in a silica sol containing an airgel precursor can be prepared in the same manner as the manufacturing method of the airgel described above.

Example

Hereinafter, the present invention will be described in more detail with reference to the following Examples and Experimental Examples. However, the following Examples and Experimental Examples are for illustrating the present invention and the scope of the present invention is not limited by these Examples and Experimental Examples.

< Airgel  Preparation of Precursors>

Synthesis Example  1 to Synthesis Example  4 and Comparative Synthesis Example  One

Tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS) and ethanol (C ₂ H ₅ OH) (industrial, 94-96% by volume) at room temperature (23 ± 3 ℃) in the amounts shown in Table 1 After the reactor was added, the first reactant was prepared by dropwise dropwise addition of an aqueous hydrochloric acid solution of PH 1.0 dropwise for 1 hour while stirring at a speed of 130 rpm for 1 hour. After the first reactant was refluxed at a temperature of 80 ° C. for 20 hours or more, the reaction was terminated and cooled to room temperature to prepare a second reactant. The second reactant was filtered under reduced pressure using a filter to prepare an airgel precursor having a molar ratio and weight molecular weight of the TEOS-derived structural unit and MTMS-derived structural unit shown in Table 1.

division TEOS MTMS Molar ratio of TEOS-derived and MTMS-derived structural units Weight average molecular weight (g / mol) Synthesis Example 1 100 mol 4 mol 20: 1 About 2,250 Synthesis Example 2 100 mol 6 mol 50: 3 5,200 Synthesis Example 3 100 mol 8 mol 25: 4 About 3,030 Synthesis Example 4 100 mol 10 mol 10: 1 About 1,300 Comparative Synthesis Example 1 100 mol - 10: 0 About 1,150

Comparative Synthesis Example  2

At room temperature, silica alcohol was prepared by mixing TEOS, ethanol, and an aqueous solution of oxalic acid (oxalic acid: 0.001 M) in a molar ratio of 1: 5: 7. While stirring the silica alcohol, MTMS was added at a molar ratio of 0.1 to TEOS (TEOS: MTMS = 100: 10) to prepare an airgel precursor. However, spontaneous gelation proceeded immediately after preparation and the weight average molecular weight could not be measured.

Experimental Example  One: Airgel  Characterization of the precursor

Since leaving the airgel precursor at 50 ° C. for 1 hour may realize the same effect as leaving the airgel precursor at room temperature for 1 week, the airgel precursor of Synthesis Example 4 was heated in an oven at 50 ° C. for 24 hours. Viscosity change was measured. And the result is shown in FIG.

1) Viscosity measuring method: It measured at 100 rpm and 20 degreeC using Viscometer TV-22 (Disk Type, TOKISANGYO Co. LTD).

As shown in Figure 1, the airgel precursor of Synthesis Example 4 was confirmed to maintain a relatively constant viscosity even when heated at 50 ℃ for 24 hours. From these results, it can be inferred that the airgel precursor of Synthesis Example 4 according to the present invention can maintain a constant viscosity even after 6 months at room temperature and has excellent durability.

< Airgel  Manufacture

Example  1 to Example  4 and Comparative example  One

The airgel precursor, ethanol and water of Synthesis Example 1 to Synthesis Example 4 and Comparative Synthesis Example 1 shown in Table 2 were mixed at a weight ratio of 1: 0.5: 0.3 to prepare an airgel precursor solution. At room temperature, the aerogel precursor solution was mixed with a catalyst (volume ratio NH ₄ OH: C ₂ H ₅ OH = 1: 12.65) in a weight ratio of 1: 0.12, and gelled to form a wet gel. The wet gel was aged at 60 ° C. for 1 hour. The aged wet gel was surface modified using a mixture of ethanol and hexamethyldisilazane (HMDS) (ethanol: HMDS = 95: 5 volume ratio solution for 4 hours at 60 ° C.). The gel was subjected to supercritical drying for 8 hours using CO ₂ at 50 ° C. and 100 bar, and dried for 1 hour at 150 ° C. and atmospheric pressure to prepare an airgel.

Example  5

An airgel was prepared in the same manner as in Example 4 except that surface modification was not performed.

division Airgel precursor Surface modification Example 1 Synthesis Example 1 ○ Example 2 Synthesis Example 2 ○ Example 3 Synthesis Example 3 ○ Example 4 Synthesis Example 4 ○ Example 5 Synthesis Example 4 × Comparative Example 1 Comparative Synthesis Example 1 ○

Example  6

An airgel precursor solution of Synthesis Example 4 was mixed with ethanol and water in a weight ratio of 1: 0.5: 0.3 to prepare an airgel precursor solution. At room temperature, the aerogel precursor solution was mixed with a catalyst (NH ₄ OH: C ₂ H ₅ OH = 1: 12.65 by volume ratio) in a weight ratio of 1: 0.12 and gelated to form a wet gel having a pH of 5. The wet gel was aged at 60 ° C. for 1 hour. The aged wet gel was acidified with an aqueous hydrochloric acid solution, hexamethyldisiloxane and ethanol were added thereto, and stirred at room temperature for 5 hours to separate the aqueous phase. Stir at room temperature for 24 hours, and separate the aqueous phase. After adding ethanol, the mixture was stirred for 3 days at room temperature, and the aqueous phase was separated three times. The gel was dried in a hot nitrogen stream for 1 hour to prepare an aerogel.

Comparative example  2

An airgel precursor solution was prepared by mixing TEOS and MTMS in a molar ratio of 1: 3, ethanol and water in a weight ratio of 1: 0.5: 0.3. At room temperature, the aerogel precursor solution was mixed with a catalyst (volume ratio of NH ₄ OH: C ₂ H ₅ OH = 1: 12.65) in a weight ratio of 1: 0.12, but gelation did not proceed during the gelling time of Examples 1-6. Thus no airgel was produced.

Comparative example  3

The wet gel was prepared by naturally gelling the airgel precursor prepared in Comparative Synthesis Example 2. The wet gel was aged at 60 ° C. for 24 hours. The aged wet gel was subjected to supercritical drying for 8 hours using CO ₂ at 50 ° C. and 100 bar, and dried for 1 hour at 150 ° C. and atmospheric pressure to prepare an airgel.

Experimental Example  2: Airgel  Property evaluation 1

The pore distribution in the airgel of Example 5 and Comparative Example 3 was measured and the results are shown in FIG. 2. In FIG. 2, the x-axis denotes pore diameter (unit: mm), and the y-axis denotes pore volume (cm 3 / g).

As shown in FIG. 2, the pores in the airgel of Example 5 were found to have a uniform diameter and volume compared to the pores in the airgel of Comparative Example 3.

Experimental Example  3: Airgel  Physical property evaluation 2

The room temperature and high temperature hydrophobicity of the airgel of Examples 1 to 5, Comparative Example 1 and Comparative Example 3 were evaluated and the results are shown in Table 3 below.

1) Hydrophobicity evaluation method: The carbon content of the airgel before and after heating was measured using a carbon analyzer (manufacturer: Eltra, model name: Carbon / Sulfur Analyzer (CS-800)). Heating was carried out for 6 hours at 450 ℃ after the airgel was put into the furnace (furnace), the carbon content was to measure the carbon weight to the total weight of the airgel.

division Carbon content before heating (% by weight) Carbon content after heating (% by weight) % Carbon reduction Example 1 10.3 2.5 75.72 Example 2 11.4 2.7 76.31 Example 3 12.2 3.3 72.95 Example 4 12.9 3.6 72.09 Example 5 3.9 1.1 71.79 Comparative Example 1 8.0 0.5 93.75 Comparative Example 3 2.5 0.6 76.00

As shown in Table 3, since the airgel of Examples 1 to 4 has a carbon content of 10% by weight or more before heating, it was confirmed that the room temperature hydrophobicity was excellent. Since the carbon content of the airgel of Examples 1 to 4 after heating was 2.5 to 3.6 weight%, it was confirmed that high temperature hydrophobicity is also comparatively excellent. In addition, since the carbon reduction rate is 70 to 80% at a high temperature, it can be seen that the high temperature stability is also relatively excellent.

The airgel of Example 5 used the same airgel precursor as that of Example 4, except that only the surface modification process was not performed. Since the airgel of Example 5 had a carbon reduction rate of 71.79% after heating, it was confirmed that the high temperature stability was the best.

On the other hand, the airgel of Comparative Example 1 was not hydrophobized because the airgel precursor, even if the airgel was prepared under the same conditions as the embodiment was not superior to the room temperature hydrophobicity compared to the examples. In addition, after heating, the carbon content was reduced by 93.75% and the carbon content reached 0.5%. From these results, it was confirmed that Comparative Example 1 was not excellent in high-temperature hydrophobicity and poor in high temperature stability. In Comparative Example 3, an airgel was prepared using an aerogel precursor using TEOS and MTMS in the same molar ratio as in Example 4, except that the airgel precursor prepared by the acid catalyst condensation reaction was different from the hydrolysis and polycondensation reactions. there was. However, the room temperature, high temperature hydrophobicity, and high temperature stability of Comparative Example 3 were significantly lower than those of Example 4. From these results, it was confirmed that the difference in the method of manufacturing the airgel precursor has a great influence on the physical properties of the airgel, that is, the hydrophobicity.

< Airgel Blanket  Manufacture

Example  7

An airgel precursor solution of Synthesis Example 4 was mixed with ethanol and water in a weight ratio of 1: 0.5: 0.3 to prepare an airgel precursor solution. At room temperature, a catalyst (NH ₄ OH: C ₂ H ₅ OH = 1: 12.65 by volume ratio) was mixed in the airgel precursor solution at a weight ratio of 1: 0.12, glass fibers were deposited, and then gelled to gel the wet gel-based composite. Prepared. The wet gel-based composite was aged at 60 ° C. for 1 hour. The aged wet gel-based composite was surface modified at 60 ° C. for 4 hours. The surface-modified wet gel-based composite was subjected to supercritical drying for 8 hours using CO ₂ at 50 ° C. and 100 bar, and dried for 1 hour at 150 ° C. and atmospheric pressure to prepare an airgel blanket.

Example  8

An airgel blanket was prepared in the same manner as in Example 7, except that surface modification was not performed.

Comparative example  4

A glass gel was deposited on the airgel precursor prepared in Comparative Synthesis Example 2, followed by natural gelation to prepare a wet gel-based composite. The wet gel-based composite was aged at 60 ° C. for 1 hour. The aged wet gel-based composite was surface modified at 60 ° C. for 4 hours. The surface-modified wet gel-based composite was subjected to supercritical drying for 8 hours using CO ₂ at 50 ° C. and 100 bar, and dried for 1 hour at 150 ° C. and atmospheric pressure to prepare an airgel blanket.

Comparative example  5

An airgel blanket was prepared in the same manner as in Comparative Example 4 except that surface modification was not performed.

Experimental Example  4: Airgel Blanket  Property evaluation

The thermal insulation properties of the airgel blanket of Example 7, Example 8, Comparative Example 4 and Comparative Example 5 were evaluated and the results are shown in Table 4 below.

2) Insulation evaluation method: Measured by using NETZSCH HFM436 Lambda equipment.

division Thermal insulation (heat conductivity: 전 / mK) Example 7 18.0 Example 8 19.0 Comparative Example 4 25.0 Comparative Example 5 27.0

As shown in Table 4, since the airgel blanket of Examples 7 and 8 has a thermal conductivity of 18 to 19 kW / mK, it is confirmed that 6 to 9 kW / mK or thermal conductivity is higher than that of Comparative Example 4 and Comparative Example 5. Could. In addition, it was confirmed that the surface deformation during the manufacture of the airgel blanket has a positive effect on the improvement of the thermal insulation of the airgel blanket.

Meanwhile, in the case of Comparative Example 4 and Comparative Example 5, an airgel blanket was prepared using an airgel precursor using TEOS and MTMS in the same molar ratio as in Examples 7 and 8, but the acid catalyst condensation was not hydrolysis and polycondensation reaction. An airgel precursor prepared by the reaction was used. From these results, it was confirmed that the difference in the manufacturing method of the airgel precursor has a great influence on the physical properties of the airgel blanket, that is, the degree of thermal insulation.

Claims (19)

To include at least one selected from the group consisting of a structural unit represented by the formula (1) and a structural unit represented by the formula (2) to 4 in a molar ratio of 100: 1 to 100: 20, The weight average molecular weight is 1,000 to 6,000 g / mol, Aerogel precursor, characterized in that the viscosity is 2.0 to 4.0cps after 24 hours heating at 45 to 60 ℃: <Formula 1>

<Formula 2>

<Formula 3>

<Formula 4>

In Chemical Formulas 1 to 4, L ₁ to L ₄ are the same as or different from each other, and each independently, a direct bond or O, X is Si, Ti, Zr, Hf or Rf, R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, A substituted or unsubstituted C ₄ to C ₂₀ branched alkenyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or a substituted or unsubstituted C ₅ to C ₂₀ aryl group, R ₂ is a halogen, hydroxyl group, substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, substituted or unsubstituted C ₁ to C ₂₀ alkyloocta It's time. The method according to claim 1, At least one selected from the group consisting of the structural units represented by Formula 1 and the structural units represented by Formulas 2 to 4 includes a molar ratio of 100: 4 to 100: 10, An airgel precursor having a weight average molecular weight of 1,000 g / mol to 2,000 g / mol. The method according to claim 1, The airgel precursor is aerogel precursor having a viscosity of 2.5 to 3.5cps after heating for 24 hours at 45 to 60 ℃. The method according to claim 1, The airgel precursor is an airgel precursor, characterized in that the viscosity is maintained at 2.0 to 4.0 cps for at least 6 months at room temperature. The method according to claim 4, The airgel precursor is an airgel precursor, characterized in that the viscosity is maintained at 2.5 to 3.5cps at least 6 months at room temperature. The method according to claim 1, Si of the structural unit represented by Chemical Formula 1 is connected to Si of the structural unit represented by Chemical Formula 1 via O. An airgel precursor. The method according to claim 1, Si of the structural unit represented by Formula 1 is connected to at least one X selected from the group consisting of the structural units represented by Formulas 2 to 4 via O as an airgel precursor. The method according to claim 1, The structural unit represented by Formula 1 is an airgel precursor, characterized in that derived from the compound represented by Formula 21: <Formula 21>

In Chemical Formula 21, R is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group. The method according to claim 8, The R is an airgel precursor, characterized in that the ethyl group. The method according to claim 1, The structural unit represented by Formulas 2 to 4 is an airgel precursor, characterized in that derived from the compound represented by the formula (22). <Formula 22>

In Chemical Formula 22, X is Si, Ti, Zr, Hf or Rf, R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, A substituted or unsubstituted C ₄ to C ₂₀ branched alkenyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or a substituted or unsubstituted C ₅ to C ₂₀ aryl group, R ₂ is a halogen, hydroxyl group, substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, substituted or unsubstituted C ₁ to C ₂₀ alkyloocta It's time. The method according to claim 10, Wherein X is Si, R ₁ is a methyl group, and R ₂ is methoxy. A first step of preparing a mixture by mixing a compound represented by Formula 21 with a compound represented by Formula 22 with an alcohol in a molar ratio of 100: 1 to 100: 20; And A method for preparing an airgel precursor according to claim 1, comprising the step of hydrolyzing and polycondensing the mixture: <Formula 21>

<Formula 22>

In Chemical Formulas 21 and 22, R is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group or a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, X is Si, Ti, Zr, Hf or Rf, R ₁ is a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkenyl group, A substituted or unsubstituted C ₄ to C ₂₀ branched alkenyl group, a substituted or unsubstituted C ₂ to C ₂₀ linear alkynyl group, or a substituted or unsubstituted C ₅ to C ₂₀ aryl group, R ₂ is a halogen, hydroxyl group, substituted or unsubstituted C ₁ to C ₂₀ alkoxy group, substituted or unsubstituted C ₁ to C ₂₀ alkyloyl group, substituted or unsubstituted C ₁ to C ₂₀ alkyloocta It's time. The method according to claim 12, The second step may include a step 2-1 of preparing a reactant by hydrolyzing the mixture using an acid catalyst and water; And And a second step of preparing the airgel precursor by polycondensing the reactants. The method according to claim 13, The acid catalyst is a method for producing an airgel precursor, characterized in that at least one selected from the group consisting of hydrochloric acid, nitric acid, acetic acid, citric acid and oxalic acid. Mixing the aerogel precursor according to any one of claims 1 to 11 with a base catalyst to form a wet gel at pH ≧ 3; Surface modification by mixing the wet gel and a hydrophobic agent; And Method for producing an aerogel, characterized in that it comprises the step of drying the surface-modified gel. The method according to claim 15, The surface-modifying gel is a method of producing an airgel, characterized in that the surface of the wet gel silylated. The method according to claim 15, The hydrophobic agent is (R ₃ ) _{4- n} SiCl _n , (R ₄ ) _{4- m} Si (OR ₅ ) _m , (R ₆ ) ₃ Si-O-Si (R ₆ ) ₃ , and (R ₇ ) ₃ At least one member selected from the group consisting of Si-O-Si (R ₇ ) ₃ , R ₃ to R ₇ are the same as or different from each other, and each independently hydrogen, a substituted or unsubstituted C ₁ to C ₂₀ linear alkyl group, a substituted or unsubstituted C ₃ to C ₂₀ branched or cyclic alkyl group, substituted Or an unsubstituted C ₅ to C ₂₀ aryl group, n and m are the same as or different from each other, and each independently a method for producing an airgel, characterized in that 1 to 4. The method according to claim 17, The hydrophobic agent is a method for producing an aerogel, characterized in that at least one selected from the group consisting of silazane, hexamethyldisilanic acid, trimethylchlorosilane, hexamethyldisiloxane, trimethylsiloxane and isopropoxytrimethylsilane. The method according to claim 15, A part of the water present in the wet gel is a method for producing an airgel, characterized in that the reaction with a hydrophobic agent.

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