KR101193987B1 - Method for Preparing High-insulation Aerogel-Impregnated Fiber - Google Patents

Abstract

The present invention relates to an airgel-containing nonwoven fabric which greatly improves heat resistance. Airgel nonwoven fabrics greatly improve the sound insulation and thermal properties of existing nonwoven fabrics due to their large surface area, low density and high porosity. The present invention relates to an airgel-impregnated nonwoven fabric that can be placed between glass or plastic substrates and applied to walls, curtains, floors, windows, and the like, and can also provide thermal insulation to translucent panels. This process consists of a solvent-drying / surface modification / solvent replacement followed by atmospheric pressure drying using a sol-gel process including TEOS-IPA condensation, which is suitable for large area coating of nonwoven fabrics. The airgel particles are uniformly dispersed between the fibers. In addition, since the airgel particles used in the present invention have hydrophobic surface groups, it is possible to avoid the collapse of the airgel that is subsequently caused by condensation of moisture in the pores.

Description

Method for preparing high insulation airgel impregnated fiber {Method for Preparing High-insulation Aerogel-Impregnated Fiber}

The present invention relates to an airgel impregnated fiber, in particular a nonwoven fabric, capable of controlling humidity by simultaneously having excellent heat insulation of aerogel, high sound insulation and water absorption. The thermal insulation and high solar emissivity and reflectance of these airgel fibers can be used as internal and external building materials of buildings at low cost by increasing the insulation effect by absorbing the sound by the micro voids in the airgel impregnated into the fiber or by absorbing sound. As a result, the energy saving efficiency is increased.

The airgel of the present invention has the highest porosity (~ 90%), low density (0.03 ~ 0.1 g / cm ³ ), high specific surface area (≥800), and low dielectric constant (~ 1.1) among the existing materials having a three-dimensional network structure. It is a very fine solid powder with very low thermal conductivity (~ 0.01 W / Km) and has unique physical properties due to the mesh-like nanopore structure. Therefore, aerogel material is a new material with a wide variety of applications in energy, environment, electrical and electronic fields, such as insulation, insulating film.

On the other hand, the existing nonwoven fabric has a large gap in the interior, and this large gap has been limited to be used as interior and exterior insulation due to the defect that the insulation effect is relatively low due to the air convection and the sound insulation is not good. In other words, if the nonwoven fabric contains airgel, the thermal conductivity may be about 15% lower than that of the nonwoven fabric. The nonwoven fabric impregnated with the airgel may be easily manufactured by the supercritical drying method, but the supercritical drying method used for the supercritical drying method may be used for large area. There are high obstacles such as high price and volume limitation of glave equipment. The atmospheric pressure drying method chosen in the present invention makes it possible to solve this point. In other words, it is more advantageous if the process cost is lowered and particularly large area.

In general, aerogel-impregnated nonwoven fabric is a sol-gel process using inorganic tetraethoxysilane (TEOS) and isopropyl alcohol (IPA) as starting materials. After preparing (silica sol), it is immersed in a nonwoven fabric and then solvent-substituted first with n-butanol to form an airgel under appropriate atmospheric pressure drying conditions. Then, by changing the hydroxy group (OH) on the surface of the airgel in the nonwoven fabric with an alkyl group or an aryl group using a surface modifier, the state of the hydrophilic airgel nonwoven fabric is changed to hydrophobic, followed by atmospheric drying. Obtain airgel impregnated nonwovens.

This airgel nonwoven fabric has high thermal insulation and low thermal conductivity, and the micro voids in the aerogel formed in the nonwoven fabric can absorb not only sound but also moisture. Increase it.

It is an object of the present invention to produce airgel impregnated airgel fabrics / fibers with the aim of improving heat resistance and sound insulation properties than general nonwoven fabrics / fibers, and have high thermal insulation, low thermal conductivity, sound insulation, and energy saving compared to conventional nonwoven fabrics / fibers. It is to provide an atmospheric pressure dry airgel nonwoven fabric / fiber with improved efficiency. Conventional methods for manufacturing airgel-containing nonwoven fabrics include a needle punch method (Korean Patent Publication No. 2009-0078357) and a spraying method (Korean Patent Publication No. 2009-0065496), but the needle punch method does not uniformly distribute the airgel in the nonwoven fabric. Since the spraying method is very sensitive to the viscosity of the sol, the present invention uses a method that is relatively unaffected by the viscosity. In addition, Korean Patent No. 0896790 discloses a bulk manufacturing method of a high-strength or high-transparent airgel, but here it is aged and the first solvent replacement process, surface modification, the second solvent replacement process, the third solvent replacement process and the Samsung system azeotropy. The solvent substitution process of the wet gel using the ternary azeotropic mixing method is used, and the process time is long, and when the azeotropic azeotrope mixture is used, the atmospheric pressure drying time is longer, the temperature conditions are difficult, and the high quality airgel is manufactured. Although it may be suitable for the fabrication of low-cost nonwoven fabrics, it is expensive.

In addition, the airgel-containing nonwoven fabric can be easily manufactured by a supercritical drying method or a vacuum extraction method in addition to the atmospheric pressure drying method of the present invention, but in the case of using a supercritical drying method (Korean Patent Publication No. 2009-0078357, US Patent Publication 2009-029109) On the other hand, there are big obstacles such as large size and high equipment price and risk of using equipment. In addition, the vacuum extraction method (Korean Patent Publication No. 2009-0065496) also has difficulty in completely drying the airgel in the nonwoven fabric. Furthermore, when the size of the nonwoven fabric increases, the size of the vacuum equipment also increases, making it difficult to control the process accurately and costly. There are disadvantages. In addition, if the vacuum extraction method is used instead of the cleaning process as described in the patent (Korean Patent Publication No. 2009-0065496) (see Claims 1 and 3), it is difficult to remove by-products and the like, and the by-products remain in the powder or airgel nonwoven fabric, so that the purity is poor. Although it does not fully extract residual solvents, it takes a lot of time during drying and heat treatment, and it describes that airgel powder is manufactured by spraying airgel powder (see claim 2). Powders often fall during substitution and vacuum extraction processes, making them unsuitable for aerogel nonwovens.

Therefore, in order to solve the disadvantages of the prior art, in particular, the disadvantages of the synthesis method of the airgel nonwoven fabric, such as the conventional needle punching method and injection method, the present inventors prepared a high-pressure dry airgel-containing high-insulation nonwoven fabric by the impregnation method, the present invention As a result, a more uniform airgel nonwoven fabric can be produced.

The present invention utilizes tetraethoxysilane (TEOS) and isopropyl alcohol (IPA) as a starting material and about 0.1 M HCl and about 0.15 M NH ₄ OH as catalysts, so that the viscosity of the sol is 5 to 35, preferably 10 to It is characterized in that the sol is prepared by impregnating the sol in a non-woven matrix at 30cP. Disadvantages of the preparation of the airgel is that the viscosity increases rapidly, so that the stable hydrolysis is induced to about 0.1M HCl, and then about 0.15M NH ₄ OH can be used to properly adjust the viscosity retention time of the airgel. In general, in the case of manufacturing an airgel nonwoven fabric by substituting with a solvent composed of a mixture of three-phase azeotrope mixed during solvent replacement, it is disadvantageous in terms of mass production because it has an effect such as a process time delay in an atmospheric drying process.

In the present invention, by using n-butanol instead of commonly used IPA, it is possible to simultaneously perform the aging process and the solvent replacement process, thereby saving time and manufacturing cost. Herein, solvent-substituted with n-butanol to obtain an airgel impregnated nonwoven fabric, and then an OH group on the surface of the airgel formed in the nonwoven fabric using a mixed solution of 6 to 10% by volume of trimethylchlorosilane (TMCS) in n-butanol is used as an alkyl group or By converting to aryl groups, hydrophilic airgel nonwovens can be converted to hydrophobic. Then, the by-products remaining after the reaction was washed with an aqueous n-butanol solution to prepare a high-purity airgel nonwoven fabric. In addition, aerogel-impregnated nonwovens can be easily manufactured by super critical drying or vacuum extractive methods, but supercritical drying is limited in size to large areas and is difficult to dry completely in vacuum extraction methods. Restricted The present invention was carried out under an atmospheric pressure (restriction of size), n-butanol in an amount of 10% to 40% by volume of the airgel nonwoven fabric, and then about 1 ℃ / min to 70 ℃ ~ 100 ℃ under atmospheric pressure The speed was increased and then dried for about 24 hours to obtain a large area of complete airgel nonwoven.

It is made by impregnating the airgel of the present invention configured as described above in a nonwoven fabric or fiber. Atmospheric dry airgel nonwovens or fibers provide airgel impregnated nonwovens or fibers with high thermal insulation and low thermal conductivity (at least 15% lower thermal conductivity for the same fiber without aerogel impregnation), sound insulation and improved energy saving efficiency.

1 is a manufacturing process diagram schematically showing a manufacturing process of the airgel impregnated fiber according to the present invention.
Figure 2 is a SEM microstructure photograph and EDS analysis of the specimen nonwoven fabric impregnated with silica airgel prepared in Example 1.
Figure 3 is a graph of the FT-IR analysis to confirm the surface modification of the airgel as shown by comparing the hydrophilicity and hydrophobicity according to the surface modification.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings by way of examples and experimental examples, but the scope of the present invention is not limited to these examples.

≪ Example 1 >

As shown below, the airgel nonwoven fabric according to the present invention was prepared using a silica sol according to the manufacturing process as shown in FIG. 1.

In the present invention, TEA was used as a starting material, and IPA was mixed and mixed in a magnetic stirrer for 1 hour, and then 0.1 M HCl solution was added to induce hydrolysis for 1 hour. Then a small amount of 0.15M NH ₄ OH was added slowly to promote the polymerization of the silica sol. Stable hydrolysis can be induced with 0.1 M HCl, and the viscosity can be prevented from rapidly rising with 0.15 M NH ₄ OH. Viscosity is very important when impregnating airgel into a nonwoven fabric. If the viscosity is low, the amount attached to the nonwoven fabric is small and there is no thermal insulation effect. If the viscosity is too high, it is not uniformly synthesized on the nonwoven fabric, resulting in a heterogeneous nonwoven fabric. Therefore, in the present invention, in order to accurately control the viscosity of the sol in the gelation process (Brookfield viscometer (programmable DV-II +) using a non-woven fabric (or glass fiber at a viscosity of 10 ~ 30 cP by measuring the viscosity ) Was impregnated with aerosol. Then, the synthesized airgel nonwoven fabric (or airgel glass fiber) was placed in a container and left at room temperature for 1 hour to induce gelation. It was replaced with another container, filled with n-butanol, sealed, and aged at the same time for about 24 hours with solvent replacement in an oven at 50 ° C. Then, a wet gel sample substituted with n-butanol solvent was 6% by volume of TMCS in n-butanol. The surface was modified for about 24 hours using. At this time, the wet gel was washed to remove the by-products generated by the surface modification reaction. The silica gel after solvent replacement and surface modification was washed with n-butanol to dry at low pressure at normal pressure. The use of n-butanol not only changed the color of the nonwovens by making the airgel more transparent than other solvents, but also slightly increased the strength. In addition, it was easier to prevent breakage due to cracks during air pressure drying. Although it can be manufactured by supercritical drying method and vacuum extraction method after cleaning, supercritical drying method has a high risk of equipment price and process risk to large area, and vacuum extraction method is difficult to completely dry and the size of non-woven fabric is increased. It is expensive to adjust and manufacture. In addition, the conventional atmospheric drying takes a lot of processing time because it is dried in several steps due to the use of a solvent composed of a samsung system azeotrope. Therefore, in the present invention, in order to significantly reduce the drying time, n-butanol is added in an amount of about 10% to 40% of the weight of the airgel nonwoven fabric, and then raised at a rate of 1 ° C./min to 70 ° C. to 100 ° C., and the atmospheric pressure is maintained for only 24 hours. It was dried to prepare an airgel nonwoven fabric.

Thermal conductivity analysis was measured at 25 ° C. with EKO HC-074-314 instrument. FT-IR analysis was performed using a THERMO MATTSONMODEL INFINITY GOLD FT-IR instrument and measured in an air atmosphere. In addition, the microstructure of the airgel was observed and compared using a scanning electron microscope (SEM, JEOL JSM-35 CF).

<Example 2>

An airgel-impregnated glass fiber was made in the same manner except that the nonwoven fabric was replaced with glass fiber in Example 1.

Experimental Example 1 Observation of Microstructure

The photo shown in Figure 2 is a non-woven fabric SEM microstructure photograph of the specimen impregnated with silica airgel prepared by <Example 1>. (a) is a 800x magnification of the airgel impregnated nonwoven fabric, showing that the airgel is well adhered to the fibrous surface of the nonwoven fabric. (b) is an enlarged 100,000 times only the airgel particles attached to the nonwoven fabric (a) and has a microstructure of nanopores, which is the original form of silica airgel. In addition, (C) shows that the surface of the nonwoven fabric is enlarged 100,000 times, showing that airgel particles adhere well to the fiber surface of the nonwoven fabric. As a result of analyzing the particles attached to (C) by EDS, only C, N, and O components were detected from the nonwoven fabric, and the elements of Si, O, and C were detected from the airgel particles attached to the nonwoven fabric, and only silica airgel particles were formed into the nonwoven fabric. It adheres well to the airgel particles, which do not fall as easily as conventional airgel nonwoven fabrics.

Experimental Example 2 Comparison of Hydrophilicity and Hydrophobicity

Figure 3 is a graph of the FT-IR analysis to determine whether the surface modification of the airgel. The surface-modified lower curve shows clear C-H bonds in the aerogels. This can be explained by the fact that a part of the hydrophilic hydroxyl group is substituted with an alkyl group to show hydrophobicity.

Experimental Example 3 Comparison of Thermal Conductivity

Table 1 is a table comparing the thermal conductivity of the nonwoven fabric impregnated with the airgel and the general nonwoven fabric according to Example 1 and the thermal conductivity of the glass fiber impregnated with the airgel and the non-woven glass fiber according to Example 2. It has a sensor at the top and the bottom of the glass fiber, so it is set at 35 ℃ below and 15 ℃ above the average so that the average is 25 ℃, and then the sensor attached at the top and bottom measures the amount of heat flow passing from the bottom to the top, which is expressed as a thermal conductivity. .

As a result, it can be seen that the general nonwoven fabric has a thermal conductivity of 0.037 W / mK, and the airgel-containing nonwoven fabric has a thermal conductivity of 0.030 W / mK. That is, the nonwoven fabric containing the airgel according to the present invention exhibited a thermal conductivity value about 18% lower than that of the general nonwoven fabric. In addition, the glass fiber exhibited a thermal conductivity of 0.034 W / mK, and the glass fiber impregnated with the airgel according to the present invention had a thermal conductivity value of 0.021 W / mK, indicating a 30% improvement in heat resistance.

Comparison of thermal conductivity of nonwovens and glass fibers Thermal Conductivity of Nonwovens (W / mK) Thermal Conductivity of Glass Fibers (W / mK) Without airgel 0.037 0.034 If airgel impregnation 0.030 0.021

Claims (13)

(a) After mixing alkoxysilane and isopropyl alcohol as starting materials, an acidic solution is added to the mixed solution to proceed hydrolysis, and then a small amount of basic solution is added slowly to proceed with polymerization of the silica sol to give a silica sol. Preparing a;
(b) impregnating the silica sol of (a) onto the fiber in a state in which the sol has a viscosity of 10 to 30 cP;
(c) aging and solvent substitution of the fibers of (b) under n-butanol;
(d) surface modification after solvent replacement of (c);
(e) washing with n-butanol after surface modification of (d);
(f) atmospheric pressure drying in the range of 70 ° C to 100 ° C. The process for producing airgel impregnated fibers according to claim 1, wherein the alkoxysilane is tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS). The method of claim 1, wherein the acidic solution is HCl solution and the basic solution is NH ₄ OH solution. The method of claim 3, wherein the concentration of HCl solution and NH ₄ OH solution is 0.1M and 0.15M, respectively. The method for producing airgel impregnated fibers according to claim 1, wherein the fibers are nonwoven or glass fibers. delete delete The method of claim 1, wherein the surface modification in step (d) is to modify the airgel impregnated fiber to a hydrophobic surface with a polar solvent and a surface modifier. The method of claim 8, wherein the surface modifier is trimethylchlorosilane (TMCS) and is used in an amount of 6 to 10% by volume based on n-butanol as a polar solvent. delete delete The method for producing airgel impregnated fibers according to claim 1, wherein the atmospheric drying comprises n-butanol in an amount of 10% to 40% of the weight of the airgel impregnated fiber. An airgel impregnated fiber obtained by the manufacturing method according to any one of claims 1 to 5, 8, 9 and 12.

Images