KR100710887B1 - Method for manufacturing aerogel blanket - Google Patents

Abstract

The present invention relates to a process for the preparation of a new airgel blanket comprising mixing water glass and tetraethyl orthosilicate in an appropriate blending ratio. The airgel blanket prepared by the method according to the present invention had a low density and a high porosity of 90% or more. In addition, the specific surface area was large, the pore size was large, and the thermal conductivity was low. That is, the aerogel blanket produced by the method according to the present invention is excellent in thermal insulation properties can be applied as an insulation product for industrial insulation and space suits, transportation and vehicles, power production insulation, jackets or sneakers.

Airgel Blanket, Water Glass, Tetraethyl Orthosilicate, Fiber

Description

Manufacturing method of airgel blanket {METHOD FOR MANUFACTURING AEROGEL BLANKET}

1 is a schematic view showing a method for preparing an airgel blanket according to the present invention from a colloidal silica sol and tetraethyl orthosilicate silica sol.

Figure 2 is a graph showing a comparison of the density and porosity of the airgel blanket prepared by the method according to the invention (Examples 1 to 3) and the airgel blanket prepared by the method according to Comparative Examples 1 and 2.

-□-: Density

-●-: Porosity

Figure 3 is a graph showing the pore volume and pore size of the aerogel blanket prepared by the method according to the invention (Examples 1 to 3) and the airgel blanket prepared by the method according to Comparative Examples 1 and 2.

-□-: Pore volume

-●-: Pore size

Figure 4 is a graph showing a comparison of the BET specific surface area of the airgel blanket prepared by the method according to Comparative Examples 1 and 2 and the airgel blanket prepared by the method according to the invention.

-□-: BET specific surface area

-●-: Pore volume

5 is a graph showing the thermal conductivity and thickness of the airgel blanket prepared by the method according to the invention (Examples 1 to 3) and the airgel blanket prepared by the method according to Comparative Examples 1 and 2.

-□-: Thermal conductivity

-●-: Thickness

Figure 6a is a scanning electron micrograph of the airgel blanket prepared by the method according to the present invention.

Figure 6b is a magnified scanning electron micrograph of a portion of an airgel blanket prepared by the method of the present invention.

The present invention relates to a method for producing an airgel blanket, and more particularly, by mixing water glass and tetraethyl orthosilicate in an appropriate blending ratio, a new airgel blanket can be manufactured more economically with a product having excellent thermal insulation properties. It is about a method.

Aerogel is an ultra-porous silica material having a porosity of 90% or more and a pore size of 1-50 nm. In particular, aerogel is a material that is attracting attention as a next-generation insulation material because its thermal insulation performance is several times better than existing materials. However, the manufacturing process is complicated and the manufacturing cost is high, but despite the excellent material properties are used only in extremely limited applications. In addition, there is a disadvantage that the mechanical strength is very fragile and fragile. Therefore, in recent years, an airgel blanket complexing technology has been developed to compensate for the disadvantages of the airgel itself and to be processed in various forms.

An aerogel blanket is a composite of aerogel material made into a mattress or sheet. Aerogel blankets have the flexibility to bend, fold, or cut, making them suitable for applications such as insulation of pipes, clothing, and many other industrial applications. Flexibility is possible because the airgel blanket is a composite consisting of fibers and aerogels. Fibers enhance the flexibility and mechanical strength of aerogel blankets, while aerogels provide thermal insulation properties due to porosity. The core composite technology of the airgel blanket is to combine the characteristics of the fiber and the characteristics of the airgel to make use of each other's advantages and to make up for the shortcomings.

Aerogel blanket is a new material that has better heat resistance and insulation than polystyrene or polyurethane foam, which is a conventional polymer insulation material, and is attracting attention as an advanced material that can solve future energy savings and environmental problems. aerogel) and flexible aerogel composite blankets.

 Silica aerogels are very lightweight (can be manufactured up to three times the weight of air) and have the advantage that thermal conductivity is more than 1/3 lower than that of ordinary insulation. However, due to very high porosity (95%), the mechanical strength is very weak, so there is a disadvantage that it is easily broken even in a small impact. In addition, there is a problem in that the manufacturing cost is expensive (about 10 times as large as plastic foam) because it needs to be manufactured by using an expensive raw material such as alkoxide and using a supercritical drying process.

The solution to the problem of the silica airgel is to provide flexibility and improve mechanical strength by manufacturing the composite material of the fiber and the airgel. The manufacture of flexible aerogel composite blankets is expected to replace the existing building insulation market in the future due to the excellent insulation properties, mechanical strength, and ease of processing in various forms due to the flexibility to replace the conventional polymer insulation. It is also expected to expand its applicability to life products such as spacecraft, space suits, sportswear and sneakers.

Conventional aerogel blanket synthesis technology to gel the sol (sol), such as silica first by changing the pH, temperature, catalyst, etc., and then synthesize a porous aerogel through a process such as supercritical drying (supercritical drying) It was the most common way. In the early days, water was used as a solvent, but when water was used, it was easily broken by capillary stress generated during the drying process. Therefore, the present invention has been developed into a process of drying the drying temperature at a low temperature of 30 ℃ through alcohol solvent replacement or CO ₂ solvent replacement, but has a disadvantage of using a large autoclave device, such as gas leakage and explosion due to high pressure There is the same process risk. Aerogel blankets can be dried more safely by incorporating fluidized sol and flexible fibers, and can also be subjected to atmospheric pressure / low temperature processes by solvent exchange and surface modification. It was possible to manufacture aerogel blankets.

U. S. Patent No. 5,789, 075 discloses an example of preparing an airgel blanket by the method as described above, using only tetraethyl orthosilicate or water glass alone as the sol precursor. However, when only water glass is used alone, the spring-back effect does not occur during drying, so that the thickness is reduced, so that the porosity of 90% or more is not exhibited. In addition, when only tetraethyl orthosilicate is used alone, the effect is good, but expensive tetraethyl orthosilicate is used, so there is an uneconomical problem because the finished airgel blanket product is very expensive.

On the other hand, considering our reality of relying on imports for more than 95% of the current energy, the development of a new aerogel blanket material that is more economical than existing insulation materials and is very economical, saves energy and improves efficiency. It will also be a very important study in overcoming the limitations of technology and dealing with the energy crisis wisely.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method of economically manufacturing a new kind of high performance airgel blanket.

The inventors of the present invention have been researching to develop a method for economically manufacturing a new airgel blanket which has flexibility and more than three times more heat insulating properties than existing heat insulating materials, and is suitable for mixing water glass and tetraethyl orthosilicate. The new airgel blanket manufacturing method including the step of mixing was developed, and the airgel blanket prepared in this manner was completed by confirming that the low density, high porosity, and low thermal conductivity have excellent thermal insulation properties.

In order to achieve the above technical problem, the present invention comprises the steps of synthesizing a colloidal silica sol from water glass; Preparing an airgel precursor by adding tetraethyl orthosilicate silica sol to the colloidal silica sol; Adjusting the pH of the airgel precursor; Adding fibers to the pH-adjusted airgel precursor to obtain a gelled composition; Aging the gelled composition; Surface modification and solvent replacement of the aged composition; And it provides a method for producing an airgel blanket comprising the step of drying the surface-modified and solvent-substituted composition and heat treatment.

Hereinafter, the present invention will be described in detail.

The method for preparing an airgel blanket according to the present invention comprises synthesizing a colloidal silica sol from water glass, and then adding tetraethyl orthosilicate silica sol to the colloidal silica sol to prepare an airgel precursor. It features.

As mentioned in the technical field, when the airgel blanket is manufactured by a conventional method, the spring-back effect does not occur during atmospheric pressure drying, so that the thickness is reduced, and thus the porosity of 90% or more is high. There was a problem. In addition, when only tetraethyl orthosilicate silica sol alone is used, there is a problem that is not economical. In the present invention, the tetraethyl orthosilicate (tetraethyl orthosilicate) is characterized in that this problem is solved by mixing the water glass with an appropriate mixing ratio. That is, in the present invention, the compounding ratio of the colloidal silica sol and tetraethyl orthosilicate silica sol was adjusted to 25 to 75:75 to 25 (volume ratio), but when the volume ratio is outside the above range, that is, the colloidal silica sol is If the blending ratio is higher than the springback effect, the porosity is small and the thermal conductivity is high because the thickness of the finished airgel blanket is reduced, and the tetraethyl orthosilicate silica sol is higher than the blending ratio. In this case, the reactivity with colloidal silica sol becomes low A problem arises in that the cost of the raw material is high. Accordingly, when the colloidal silica sol and the tetraethyl orthosilicate silica sol are blended in the above blending ratio, there is an advantage that an airgel blanket of the most economical and optimal performance can be prepared.

The colloidal silica sol is preferably used after removing Na ions from the water glass by the ion exchange resin method, followed by the addition of ethanol. In particular, it is preferable to add ethanol to the colloidal silica sol in an amount of 20 to 80% by volume. In the case of manufacturing an airgel blanket with only colloidal silica sol from which Na ions are removed from the water glass, the thickness of the blanket is significantly reduced and the pore volume is small, so that the thermal conductivity is almost the same as that of glass fiber. Therefore, it is most preferable to use a colloidal silica sol prepared by adding ethanol to the content in the above range.

In the method for producing an airgel blanket according to the present invention, it comprises the step of adjusting the pH of the airgel precursor prepared as described above.

It is preferable to use ammonia water, but the pH is not limited thereto. If the pH is less than 5, colloidal silica sol is slow in gelation, but tetraethyl orthosilicate silica sol is very fast in gelation, and the pH is 6 If it exceeds, the gelation time is too fast and the problem of hardening before all the sol is deposited on the fiber occurs.

In the method for producing an airgel blanket according to the present invention, the method comprises the step of gelling by adding the fiber to the pH-adjusted airgel precursor as described above, the fiber is a group consisting of glass fibers, carbon fibers and polyimide polymer fibers It is preferably at least one selected from, but is not limited thereto, and fibers which can be used in the art can be used.

The gelled composition is then subjected to aging. Aging is a method of completely chemical change by leaving the material at a suitable temperature for a long time, in the present invention, the aging is performed at 50 ~ 60 ℃ temperature in ethanol, the moisture in the gel is substituted with ethanol, Aging under these conditions is most preferred because of the advantage that the solid network of the gel is strengthened, thereby enhancing the strength of the gel.

In the method for producing an airgel blanket according to the present invention, the step of undergoing surface modification and solvent replacement of the aged composition. The surface modification and solvent replacement is any one or more surface modifiers and iso is selected from the group consisting of trimethylchlorosilane, hexamethyldisilazane, methyltrimethoxysilane, phenyltriethoxysilane, dimethylchlorosilane and trimethylethoxysilane Propyl alcohol, n-hexane, heptane, toluene and xylene may be formed by a mixed solution of any one or more solvents selected from the group consisting of, the mixing ratio of the surface modifier and the solvent is 1: 1 to 10 (volume ratio) is It is preferable. By performing surface modification and solvent replacement as described above, silane treatment is performed on the surface of the gel and the pores of the gel to show hydrophobicity. It is possible to produce a blanket, and due to the silanes treated on the surface, it is possible to produce an aerogel blanket having hydrophobicity.

The method for producing an airgel blanket according to the present invention is also characterized by comprising drying in two stages.

Typically, only one step of drying was performed in the preparation of the airgel blanket, but in the present invention, after drying 12 to 24 hours at room temperature, the solvent inside the gel is evaporated by re-drying at 50 to 60 ℃ for 2 to 6 hours. There is a great feature in that the strength of the gel is increased by strengthening the solid network.

The composition dried in two steps is then subjected to a heat treatment step, in the present invention was subjected to a heat treatment for 2 to 4 hours at 150 ~ 250 ℃. If the temperature during the heat treatment is less than 150 ℃ does not completely evaporate the solvent is difficult to form an airgel blanket, it is most preferable to heat treatment at a temperature in the above range because it becomes hydrophilic when it exceeds 250 ℃. In addition, when the heat treatment time is less than 2 hours, the porosity of the airgel blanket is not enough, and if it exceeds 4 hours, the airgel blanket is contracted to reduce the porosity, so it is most preferable to heat-treat for the above range of time.

As such, the aerogel blanket prepared according to the method of the present invention has a very excellent thermal insulation properties of 0.1 ~ 0.15g / cm ³ , porosity of 90 ~ 95% and thermal conductivity of 18 ~ 20mW / mK.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

[Examples 1-3]

Na ion was removed from the water glass using an amberlite ion exchange resin, and then 50 vol% of ethanol was added thereto to prepare a colloidal silica sol. After adding tetraethyl orthosilicate (hereinafter 'TEOS') silica sol to the colloidal silica sol and adding ammonia water (1M) to adjust pH to 5, glass fiber (Cerakwool, KCC) was deposited ( immersion) and gelled. After aging in ethanol at 60 ° C., surface modification and solvent replacement were performed by dipping in a mixed solution of a surface modifier and a solvent [trimethylchlorosilane (TMCS): isopropyl alcohol (IPA) = 1: 10 (volume ratio)]. I was. Thereafter, the mixture was dried for 24 hours at room temperature and 4 hours at 60 ° C., and then heat-treated at 230 ° C. for 2 hours at a temperature increase rate of 1 ° C./min to prepare an airgel blanket. A method for producing an aerosol blanket according to the present invention is briefly shown in FIG.

The volume ratio of the colloidal silica sol and the TEOS silica sol used in Examples 1 to 3 is shown in Table 1 below. Example 1 shows that the volume ratio of the colloidal silica sol and the TEOS silica sol is 75:25. In addition, Example 2 is 50:50, respectively, and Example 3 shows that it is 25:75. At this time, no matter what volume composition, the solids content of silica was 6%.

Colloidal Silica Sol (Volume%) TEOS Silica Sol (Volume%) SiO ₂ content (%) Example 1 75 25 6 Example 2 50 50 6 Example 3 25 75 6

Comparative Example 1

An aerosol blanket was prepared using the same method as in Examples 1 to 3 except that only 100% by volume of the colloidal silica sol was used.

Comparative Example 2

An aerosol blanket was prepared using the same method as in Examples 1 to 3, except that only 100 vol% of TEOS-based silica sol was used.

Comparative Example 3

An aerosol blanket was prepared using the same method as Example 1 except that the heat treatment was performed at 270 ° C. for 2 hours.

Test Example 1 Apparent Density and Porosity Measurement

The apparent density and porosity of each of the airgel blankets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following method, and the results are shown in FIG. 2.

)의 경우 에어로젤 블랑켓트가 표면개질에 의하여 소수성(hydrophobicity)을 가지기 때문에 에탄올에 침적시켜서 아르키메데스의 원리에 의하여 측정하였다(수학식 1). W_air 는 샘플의 건조 시 무게이고, W_wet는 젖은 상태에서의 샘플의 무게이다. W_liq는 에탄올 속에서의 샘플의 무게이고, ρ_e는 에탄올의 밀도이다. Apparent density(

), The aerogel blanket is hydrophobic (hydrophobicity) by surface modification, so that it was deposited on ethanol and measured according to Archimedes' principle (Equation 1). W _air is the weight of the sample when dry, and W _wet is the weight of the sample in the wet state. W _liq is the weight of the sample in ethanol and ρ _e is the density of ethanol.

Porosity (P) is obtained by subtracting the weight in wet from the weight in dry and the weight in wet from the weight in ethanol divided by percentage (Equation 2).

As shown in FIG. 2, in the case of Comparative Example 1 consisting of only colloidal silica sol, the density was 0.196, and the porosity was 86.5%. On the other hand, in Example 1 containing 25% of the TEOS-based silica sol density was greatly reduced to 0.115 and porosity also increased to 90%. In the case of Example 2, the density was slightly increased, showing a value of 0.14, and the porosity was slightly lowered to 89.3%. In Example 3, the density was lowered to about 0.13, respectively, and the porosity was 90.8%, showing a similar effect to that of Comparative Example 2.

That is, it was confirmed that the total density of the colloidal silica sol and TEOS-based silica sol in a compounding ratio of 25 to 75:75 to 25, the density is low and the porosity is also high.

[Test Example 2] Pore size, pore volume and specific surface area measurement

The pore size, pore volume and specific surface area of each of the airgel blankets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in FIGS. 3 and 4.

Specific surface area and pore size were measured by Brunauer-Emmett-Teller (BET) method and Barrett Joyner and Halenda (BJH) method by adsorption and desorption of nitrogen gas (Equation 3 and 4).

In Equations 3 and 4, S is a non-surface, W is a weight under a relative pressure of nitrogen, C is a BET constant, W _m is a monolayer weight, and the value obtained by the inverse of the sum of slope and intercept in the BET curve. , M is the molecular weight of nitrogen, A _cs is the molecular cross-sectional area of 16.2 kPa. w is the weight of the sample.

The volume (V) of pores per unit mass is expressed as the inverse of the apparent density multiplied by the porosity. The inverse of the apparent density represents the apparent volume of the sample per unit volume, which is multiplied by the porosity occupied by the pores to calculate the volume of pores per unit mass (Equation 5).

As shown in FIG. 3, in Comparative Example 1, the pore size was 90 ms, Example 1 was 150 ms, Example 2 was 140 ms, and Example 3 was 260 ms. These results show that the colloidal silica sol starting from water glass has a small pore size and the pore size increases as TEOS is added.

In the case of the pore volume, 1.5g / cc for Comparative Example 1, 2.2g / cc for Example 1, and 4.25g / cc for Example 3, respectively.

In addition, as shown in FIG. 4, in the case of Comparative Example 1, the specific surface area showed a value of 378m ² / g, Example 1 was 397m ² / g, Example 2 was 456m ² / g, and Example 3 436 m ² / g was shown.

That is, according to the results as described above, the pore size, pore volume and specific surface area of the airgel blanket produced by the method according to the present invention was large, thereby confirming that the porosity is high.

Test Example 3 Measurement of Thermal Conductivity and Thickness

The thermal conductivity and thickness of each of the airgel blankets prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured by the following method, and the results are shown in FIG. 5. The thickness of the airgel blanket was measured by eight places using a vernier caliper to represent the average value as the thickness. Thermal conductivity was measured by using a hot bed method (KSL 9016), the thermal conductivity of the airgel blanket of the area of 15cm × 15cm.

As shown in FIG. 5, in Comparative Example 1, the thickness was 9 mm and the thermal conductivity was 23.3 mW / mK, which was the highest value. On the other hand, as the TEOS-based silica sol was mixed according to the present invention, the thickness increased. As the thickness increases, the volume of the pores increases due to the springback effect, that is, the porosity increases, thereby lowering the thermal conductivity transmitted through the solid. In addition, the airgel blanket produced by the method according to the present invention shows a tendency to lower the thermal conductivity, the thermal conductivity of Example 1 is 20.2mW / mK, Example 2 19.2mW / mK, and Example 3 is 18.9mW Thermal conductivity of / mK is shown.

That is, it was confirmed that the airgel blanket prepared according to the method of the present invention has excellent thermal insulation property because of low thermal conductivity.

[Test Example 4] Characteristics of the airgel blanket according to the heat treatment temperature

 For each of the airgel blankets prepared in Example 1 and Comparative Example 3, the surface area, pore diameter, specific surface area, thermal conductivity and degree of hydrophilicity were measured. Surface area, pore diameter, specific surface area, and thermal conductivity were measured according to the above-mentioned method, and the degree of hydrophilicity was measured by measuring the contact angle of water droplets, and the results are shown in Table 2 below.

Example 1 Comparative Example 3 Surface area (m ² / g) 474.3 402.5 Pore diameter 113.5 82.28 BET constant 18.4 134.17 Thermal Conductivity (mW / m-K) 19.77 25.66 Hydrophilicity Hydrophobic Hydrophilic

As shown in Table 2, the airgel blanket heat-treated at 230 ℃ according to the present invention has a surface area value of 474m ² / g, the pore size has a BET constant of 113Å, 19.8, and showed hydrophobicity. In contrast, the silica airgel blanket heat-treated at 270 ° C. according to Comparative Example 3 exhibited hydrophilicity with a surface area of 400 m ² / g, a pore size of 82 μs, and a 134 BET constant. In addition, the airgel blanket according to Example 1 exhibited a thermal conductivity of 19.8 mW / mK, and the airgel blanket according to Comparative Example 3 exhibited a thermal conductivity of 25.7 mW / mK.

That is, it was confirmed that the airgel blanket prepared by the heat treatment by the method according to the present invention has excellent thermal conductivity and overall characteristics.

Test Example 5 Confirmation of Structure of Aerogel Blanket

The structure of the airgel blanket according to the present invention prepared in Example 1 was measured by scanning electron microscope (SEM), and the results are shown in FIGS. 6A and 6B.

As shown in Figure 6a and 6b, the airgel blanket prepared according to the present invention was confirmed that the airgel silica is filled in the glass fiber matrix. There are gaps between aerogels and aerogels, and between fiberglass and aerogels, which are thought to correspond to pores of tens of microns.

As described above, the airgel blanket prepared according to the method of the present invention has a density of 0.1 to 0.15 g / cm ³ , porosity of 90 to 95%, and thermal conductivity of 18 to 20 mW / mK. Have In addition, the specific surface area was large, the pore size was large, and the thermal conductivity was low. In other words, it is excellent in thermal insulation properties, it can be applied as a thermal insulation products for industrial insulation and space suits, transportation and vehicles, electrical power production insulation, jackets or sports shoes.

Claims (8)

Synthesizing a colloidal silica sol from water glass; Preparing an airgel precursor by adding tetraethyl orthosilicate silica sol to the colloidal silica sol; Adjusting the pH of the airgel precursor; Adding fibers to the pH-adjusted airgel precursor to obtain a gelled composition; Aging the gelled composition; Surface modification and solvent replacement of the aged composition; And Drying the surface-modified and solvent-substituted composition and then heat-treating Method for producing an airgel blanket comprising a. The method of claim 1, The compounding ratio of the colloidal silica sol and tetraethyl orthosilicate silica sol is 25 to 75:75 to 25 (volume ratio). Method for producing an airgel blanket. The method of claim 1, The colloidal silica sol is synthesized by adding Na to 20 to 80% by volume after removing Na from the water glass by ion exchange resin method Method for producing an airgel blanket. The method of claim 1, The fiber is any one or more selected from the group consisting of glass fiber, carbon fiber and polyimide fiber Method for producing an airgel blanket. The method of claim 1, The aging is carried out at 50 ~ 60 ℃ temperature in ethanol Method for producing an airgel blanket. The method of claim 1, The surface modification and solvent replacement is any one or more surface modifier selected from the group consisting of trimethylchlorosilane, hexamethyldisilazane, methyltrimethoxysilane, phenyltriethoxysilane, dimethylchlorosilane and trimethylethoxysilane And isopropyl alcohol, n-hexane, heptane, toluene, and xylene, which are formed by a mixed solution of any one or more solvents selected from the group consisting of 1 to 10 (volume ratio). sign Method for producing an airgel blanket. The method of claim 1, The drying is a step of drying for 12 to 24 hours at room temperature, followed by re-drying for 2 to 6 hours at 50 ~ 60 ℃ Method for producing an airgel blanket. The method of claim 1, The heat treatment is made for 2 to 4 hours at 150 ~ 250 ℃ Method for producing an airgel blanket.

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