WO2016195380A1 - Method for preparing metal oxide-silica composite aerogel and metal oxide-silica composite aerogel prepared by means of same - Google Patents

Abstract

The present invention provides a method for preparing metal oxide-silica composite aerogel and metal oxide-silica composite aerogel which is prepared by means of same and has excellent porous properties as well as excellent properties such as a low tap density, a high specific surface area and the like. The method comprises the steps of: preparing a metal oxide-silica composite precipitate by adding a metal salt solution to a silicate solution and reacting same; and drying the metal oxide-silica composite precipitate by irradiating infrared rays having a wavelength region from 2 ㎛ to 8 ㎛.

Description

Method for preparing metal oxide-silica composite airgel and metal oxide-silica composite airgel prepared using the same

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 2015-0077280 dated June 1, 2015 and Korean Patent Application No. 2016-0067867 dated June 1, 2016. The contents are included as part of this specification.

Technical Field

The present invention minimizes the shrinkage occurring during the drying process in the preparation of the metal oxide-silica composite airgel, a method for producing a metal oxide-silica composite airgel having low tap density and high specific surface area with excellent pore properties and using the same It relates to a metal oxide-silica composite airgel prepared by.

Recently, as industrial technologies are advanced, interest in aerogels having excellent thermal insulation properties is increasing. The aerogels developed so far include organic aerogels such as resorcinol-formaldehyde or melamine-formaldehyde aerogel particles, silica (Silica, SiO ₂ ), alumina (Alumina, Al ₂ O ₃ ), titania (Titania, TiO _2). Or inorganic aerogels containing metal oxides such as carbon (C) aerogels.

Among them, silica airgel is a highly porous material, and has high porosity, specific surface area, and low thermal conductivity, and thus can exhibit excellent thermal insulation effect. Therefore, silica airgel has various fields such as insulation, catalyst, sound absorbing material, filler, and interlayer insulating material of semiconductor circuit. Application in is expected.

Since silica airgel has a low mechanical strength due to its porous structure, the silica airgel is usually combined with a substrate such as glass fiber, ceramic fiber, or polymer fiber to produce a product such as an airgel blanket or airgel sheet. However, since the silica airgel structurally contains 90% by volume or more of air in the internal pores, the density is too low, there is a severe scattering during processing, difficult to impregnate the substrate. In addition, even if impregnated in part, the difference in density from the substrate is too large and does not mix well, resulting in problems such as poor appearance and physical properties. In addition, a volume fraction of 50% by volume or more must be mixed to effectively block heat transfer to exert an insulating effect by filling, but the powder itself is not easy to process at such a high level of mixing ratio.

Accordingly, a method of mixing an additive with an airgel has been proposed to enhance the processability of the silica airgel, and to enhance the properties of the airgel such as heat insulating property, suction ability, catalytic activity, or to impart additionally required properties. Specifically, the additives are added to the sol before the silica airgel is polymerized, or the prepared silica airgel is contacted with a liquid or gaseous stream containing the additive. The method of introducing the elements to strengthen the structure and increase the density, and the method of forming a composite with the plate-like inorganic material has been proposed.

However, the conventional methods are not easy to control the size, particle size distribution, etc. of the additive materials, and there is a problem such as deformation and reduction of the pore structure in the manufacturing process of the silica airgel.

SUMMARY OF THE INVENTION An object of the present invention is to minimize the shrinkage of silica gel generated during the drying process of a metal oxide-silica composite airgel, thereby facilitating a metal oxide-silica composite aerogel having low tap density and high specific surface area with excellent pore properties. It is to provide a manufacturing method that can be manufactured.

Still another object of the present invention is to provide a metal oxide-silica composite airgel prepared by the above production method.

In order to solve the above problems, according to an embodiment of the present invention, adding a metal salt solution to the silicate solution and reacting to prepare a metal oxide-silica composite precipitate; And it provides a method for producing a metal oxide-silica composite airgel comprising the step of drying the metal oxide-silica composite precipitate by irradiating infrared rays in the wavelength range of 2㎛ 8㎛.

According to another embodiment of the present invention, there is provided a metal oxide-silica composite aerogel prepared by the above production method.

In the manufacturing method of the metal oxide-silica composite airgel according to the present invention, the drying of the metal oxide-silica composite precipitates is carried out simultaneously in the pores of the airgel and on the particle surface, so that the shrinkage of the airgel generated in the drying process occurs. The phenomenon can be minimized. As a result, metal oxide-silica composite aerogels having excellent physical properties such as low tap density and high specific surface area can be prepared. Accordingly, the metal oxide-silica composite aerogel prepared by the above manufacturing method is applicable to various industrial fields such as catalysts or heat insulating materials due to the pore and physical properties described above.

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

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

In the preparation of the conventional metal oxide-silica composite airgel, the drying process for the particles of the composite airgel is usually performed in a drying oven. Since the drying process is performed by the temperature of the ambient atmosphere in the oven, in the case of a solvent present inside the pores of the silica gel particles, the solvent is diffused to the surface and then evaporated from the surface. At this time, the capillary phenomenon due to the surface tension of the solvent amplifies the shrinkage of the pores, increases the tap density of the aerogel, decreases the specific surface area and porosity, and consequently increases the thermal conductivity.

On the other hand, in the present invention, the middle range infrared ray (MIR) in the middle region corresponding to the wavelength range that can resonate with the water or the hydroxyl group used as the solvent so that drying inside the pores of the silica gel particles and the particle surface proceed simultaneously. By performing the drying process by irradiating to minimize the shrinkage of the airgel particles, and for the metal oxide can exhibit a quick drying effect according to the MIR absorption. As a result, metal oxide-silica composite aerogels having improved tap density, specific surface area and pore properties can be prepared.

That is, in the method of preparing a metal oxide-silica composite airgel (hereinafter, simply referred to as a 'composite aerogel') according to an embodiment of the present invention, a metal salt solution and optionally an acid catalyst are added to the silicate solution to react with the metal oxide-silica composite. Preparing a precipitate (step 1); And drying the metal oxide-silica composite precipitate by irradiating infrared rays in a wavelength range of 2 μm to 8 μm (step 2). Hereinafter, each step will be described in more detail.

Step 1

In the method of manufacturing a composite airgel according to an embodiment of the present invention, step 1 is a step of forming a metal oxide-silica composite precipitate by adding and reacting a metal salt solution and optionally an acid catalyst to the silicate solution.

The silicate solution may be prepared by dissolving water glass (Na ₂ SiO ₃ ) in a solvent, specifically water, at a concentration of 0.125M to 3.0M. If the concentration of the water glass is less than 0.125M, the silica content in the final composite airgel is low, and if it exceeds 3.0M, there is a fear of increasing the tap density due to the formation of excessive composite airgel. More specifically, when considering the tap density reduction effect, the silicate solution may include water glass at a concentration of 0.75M to 3.0M, and more specifically, at a concentration of 1.5M to 2.0M. At this time, the water glass is not particularly limited, but may contain 28 wt% to 35 wt%, more specifically 28 wt% to 30 wt% silica (SiO ₂ ) based on the total weight of the water glass.

In addition, the silicate solution may include the water glass (Na ₂ SiO ₃ ) in an amount to include 0.04M to 6.0M silica when based on silica (SiO ₂ ) included in the water glass.

The metal salt solution is prepared by dissolving a metal salt, which is a raw material, to form a metal oxide in a final composite aerogel in a solvent. Specifically, the metal salt may be a salt including one or two or more metals selected from the group consisting of alkali metals, alkaline earth metals, lanthanides, actinides, transition metals, and metals of Group 13 (IIIA), and more specifically, Calcium (Ca), Magnesium (Mg), Copper (Cu), Zinc (Zn), Manganese (Mn), Cadmium (Cd), Lead (Pb), Nickel (Ni), Chromium (Cr), Silver (Ag ), Titanium (Ti), vanadium (V), cobalt (Co), molybdenum (Mo), tin (Sn), antimony (Sb), strontium (Sr), barium (Ba), and tungsten (W) It may be a chloride containing any one or two or more metal elements selected from the group. In addition, among the above metals may be appropriately selected according to the use of the composite aerogel, for example, when considering the application to the application that requires a thermal insulation effect on the composite aerogel, the metal salt includes magnesium, calcium or mixed metals thereof May be chloride.

In addition, when the metal salt includes two metal salts, it is preferable to adjust the concentration ratio of each metal ion so as to satisfy the ratio of the metal element in the metal oxide in the composite aerogel to be finally prepared. For example, in the case of a composite aerogel required to have excellent thermal insulation performance, the metal oxide may include MgO and CaO, in which case MgO and CaO may be included in a molar ratio of 2: 1 to 1: 2.

In addition, the metal salt may be used in an amount such that the concentration of metal ions derived from the metal salt in the metal salt solution is 0.125M to 3.0M. If the concentration of metal ions is less than 0.125M, the amount of metal oxide formed in the composite aerogel may be Less, the improvement effect according to the metal oxide formation is insignificant, and if it exceeds 3.0M there is a fear that the physical properties of the composite aerogel, including the tap density due to the excessive metal oxide formation rather deteriorate. More specifically, the metal salt may be used in a concentration of metal ions in the metal salt solution of 0.25M to 1.0M, even more specifically 0.25M to 0.5M.

In addition, the metal salt may be used in an amount such that the molar ratio of water glass: metal ion is 1: 1 to 3: 1, compared to the concentration of water glass in the silicate solution within the above concentration range. If the molar ratio is out of range, there is a fear that the tap density of the composite airgel to be manufactured is increased. More specifically, the molar ratio of water glass: metal ion may be used in a molar ratio of 1.5: 1 to 3: 1, and more specifically 3: 1.

Further, the solvent used for forming the metal salt solution can be used without particular limitation as long as it can dissolve the metal salt. Specific examples thereof include water or a hydrophilic polar organic solvent, and any one or a mixture of two or more thereof may be used. Of these, the hydrophilic polar organic solvent is excellent in miscibility with the above-described silicate solution, and may then be uniformly present in the gel during gelation.

The hydrophilic polar organic solvent may be specifically an alcohol solvent. In addition, the alcohol solvent is specifically a monohydric alcohol such as methanol, ethanol, isopropanol, butanol and the like; Or polyhydric alcohols such as glycerol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, sorbitol, and the like, and any one or a mixture of two or more thereof may be used. In consideration of the miscibility with water and the uniform dispersibility in silica gel, the alcohol-based compound may be an alcohol having 1 to 8 carbon atoms. In addition to the above effects, when considering the efficiency of the modification reaction on the surface of the silica later, the alcohol-based compound may be a linear alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, propanol, or n-butanol, One kind alone or a mixture of two or more kinds may be used. More specifically, the alcohol-based compound may be methanol, ethanol or a mixture thereof.

After mixing the silicate solution and the metal salt solution, the pH of the mixture obtained as a result of the mixing process may further comprise the step of adjusting the pH to 1.5 to 10, more specifically 3 to 9.5. At this time, when the pH of the mixture is out of the above range, the tap density of the final composite aerogel is increased, and there is a fear that the specific surface area and pore characteristics are lowered.

The pH of the mixed solution may be adjusted through controlling the mixing ratio of the silicate and the metal salt, or may be controlled by selectively adding an acid catalyst.

The acid catalyst serves to increase the production rate of the composite precipitate by promoting the reaction of the silicate solution and the metal salt solution in the formation of the composite precipitate. Specifically, the acid catalyst may be hydrochloric acid, acetic acid, citric acid, sulfuric acid, phosphoric acid, nitric acid, or the like, any one or a mixture of two or more thereof may be used, and among these, an inorganic acid such as hydrochloric acid may be used.

Balance of tap density, specific surface area and pore characteristics according to pH adjustment To obtain a good improvement effect, the pH of the mixed solution can be adjusted to 3 to 9 through the addition of acid catalyst, and considering the remarkable improvement effect, the pH is 3 to 8 More specifically, it may be 5 or more and less than 7.5.

When the silicate solution, the metal salt solution, and the acid catalyst are mixed and reacted, a metal oxide-silica composite precipitate is formed and precipitated. For example, when MgCl ₂ and CaCl ₂ are used as the metal salt, a composite precipitate of MgO—CaO—SiO ₂ is precipitated by the same reaction as in Scheme 1 below.

Scheme 1

Na ₂ O.nSiO ₂ (I) + 1 / 2Mg ²⁺ + 1 / 2Ca ²⁺ -> (Mg, Ca) O.nSiO ₂ (s) + 2Na ⁺

After the formation of the metal oxide-silica composite precipitate, a separation process of separating the precipitate from the solvent using a conventional method, specifically, a vacuum filter or the like may optionally be further performed. In this case, the method of manufacturing a composite airgel according to an embodiment of the present invention may further include a separation process with a solvent after the formation of the metal oxide-silica composite precipitate.

After the formation and / or separation of the metal oxide-silica composite precipitate, the unreacted reactant (eg, Si ^{4 +} , Mg ^{2 +} or Ca ^{2 +} ) and the added ions (Na) remaining in the precipitate are carried out. Washing process for removal of ⁺ or Cl ^−, etc.) may optionally be further performed. In this case, the manufacturing method of the composite airgel according to an embodiment of the present invention may further include a washing step after the formation of the metal oxide-silica composite precipitate.

The washing process may be performed according to a conventional method such as dipping, spraying, or spraying using a washing solvent. Specifically, the washing solvent is water; Alcohol compounds such as methanol, ethanol, isopropanol or propanol; Hydrocarbon-based compounds such as hexane, octane, n-decane, n-heptane, n-undodecane, cyclohexane or toluene; Or ketone compounds such as methyl ethyl ketone or acetone, and any one or a mixture of two or more thereof may be used. Among these, alcohol-based compounds having excellent miscibility with water as a reaction solvent, easy penetration into pores inside silica gel particles, and no drying effect and subsequent pore shrinkage and deformation when combined with subsequent drying processes, More specifically ethanol can be used.

The washing process may be performed once or twice or more, specifically, 3 to 5 times. In addition, when the washing process is performed two or more times, it may be performed using the same washing solvent, it may be carried out using a different heterogeneous washing solvent.

In addition, prior to the subsequent drying process, after the separation of the metal oxide-silica composite precipitate, or after performing the washing process, a water content control process through the solid / liquid separation may be performed.

The water content control process may be performed by a conventional solid / liquid separation method such as a vacuum filter, more specifically, the water content in the metal oxide-silica composite precipitate is 110% by weight or less based on the total weight of the metal oxide-silica composite precipitate. More specifically, it may be performed to be 85% by weight or less. This moisture content control can shorten the drying time during the drying process and at the same time increase the fairness.

Step 2

In the method of manufacturing a composite airgel according to an embodiment of the present invention, step 2 is a step of preparing a composite airgel by drying the metal oxide-silica composite precipitate formed in step 1.

The drying process may be performed using infrared rays in the wavelength range of 2 ㎛ to 8 ㎛. The wavelength within the above-mentioned range is resonated in the wavelength range of 2 μm to 8 μm with the water used as the solvent and penetrated into the silica airgel particles, or the hydroxyl group (-OH) in the solvent molecule. As a result, energy is applied directly to the solvent present in the silica airgel particles to allow drying to occur inside the airgel, and at the same time, the drying of the airgel particles is performed at the surface of the airgel particles by increasing the ambient temperature, thereby minimizing pore shrinkage in the airgel particles. Can be. More specifically, the average wavelength value of the main peak at the time of infrared rays or infrared irradiation of 2 micrometers-4 micrometers wavelength range can be used.

In addition, it is possible to easily control the temperature of the atmosphere in which the drying process is performed by adjusting the intensity during infrared irradiation of the wavelength range as described above. Specifically, the infrared radiation may be irradiated with an intensity such that the ambient temperature is 130 ℃ to 300 ℃. Accordingly, the drying process may be completely completed by the infrared irradiation. Considering the remarkable effect of the improvement according to the intensity control during the infrared irradiation, it can be irradiated with an intensity such that the ambient temperature during the infrared irradiation is 190 ℃ to 300 ℃, or 220 ℃ to 300 ℃. Or after the primary drying process of 80% or more, more specifically 80% to 95% by infrared irradiation, is carried out, and the remainder is dried by the ambient temperature increased by the infrared intensity during the infrared irradiation, that is, secondary drying The process may be performed.

The infrared irradiation as described above may be performed using a device equipped with an infrared lamp capable of generating infrared rays in the wavelength range. Specifically, the metal oxide-silica composite precipitate to be dried may be placed on a substrate and then irradiated with infrared rays by adjusting the wavelength and intensity of the infrared lamp. At this time, the concentration of the solvent evaporated inside the apparatus may be further provided with a venting device (venting) so as not to reduce the drying efficiency.

In addition, the method for producing the metal oxide-silica composite airgel according to an embodiment of the present invention, in order to improve the balance of the tap density and BET specific surface area of the metal oxide-silica composite airgel to be produced finally, during the washing process It can be performed by further optimizing the combination of the conditions of the solvent and the drying conditions in the drying process. Specifically, the method for producing a metal oxide-silica composite aerogel, comprising: preparing a metal oxide-silica composite precipitate by adding and reacting a metal salt solution and an acid catalyst to the silicate solution; And washing the metal oxide-silica composite precipitate with a washing solvent of an alcohol-based compound, and then irradiating infrared rays of infrared rays in a wavelength range capable of resonating with water molecules or hydroxyl groups in the solvent used in the preparation of the silicate solution and the metal salt solution. And irradiating with an intensity to be in the range of from 0.degree. C. to 300.degree. C., more specifically from 190.degree. C. to 300.degree. At this time, the type and content of the materials used in each step, the specific process conditions are the same as described above.

By minimizing the shrinkage of the silica gel generated during the drying process, the metal oxide-silica composite airgel having excellent physical properties such as low tap density, high specific surface area and porosity can be prepared by the above manufacturing process. .

Accordingly, according to another embodiment of the present invention there is provided a metal oxide-silica composite aerogel prepared by the above-described manufacturing method.

The metal oxide-silica composite airgel is a composite in which a silica airgel and a metal oxide are mixed in the composite airgel structure. The metal oxide-silica composite airgel has a low tap density, a high specific surface area, and a low thermal conductivity through controlling the conditions in the manufacturing process.

Specifically, the metal oxide-silica composite airgel may be 0.2g / ml or less, more specifically 0.055g / ml or less, and more specifically 0.009g / ml to 0.055g / ml. In this case, the tap density of the metal oxide-silica composite airgel may be measured using a tap density meter (TAP-2S, Logan Instruments co.).

In addition, the metal oxide-silica composite airgel is more specifically 450m than with the above-described tap density, BET specific surface area (specific surface area), and the number is more than 400m ² / g, more particularly to 450m ² / g or more, It may be from ² / g to 600 m ² / g. In the present invention, the specific surface area of the metal oxide-silica composite airgel can be measured by the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p _o <1) using the ASAP 2010 device of Micrometrics.

In addition, the metal oxide-silica composite airgel may have an average particle diameter (D ₅₀ ) of 7 μm to 15 μm, more specifically 7 μm to 12 μm. In the present invention, the average particle diameter (D ₅₀ ) of the metal oxide-silica composite airgel may be defined as the particle size based on 50% of the particle size distribution, wherein the average particle diameter of the metal oxide-silica composite airgel is laser diffraction method (laser) diffraction method) or as a dry analysis model, a particle size analyzer (Macrotrac Particle Size Analyzer S3500) was used to calculate the average particle diameter (D ₅₀ ) at 50% of the particle size distribution in the measuring device. can do.

In addition, due to the volume occupied by the pores within the tap density, the specific surface area, and the particle size, it may exhibit low thermal conductivity and improved thermal insulation effect. Specifically, the metal oxide-silica composite airgel may exhibit a thermal conductivity of 30 mW / mK or less. In this case, the thermal conductivity may be measured at 25 ° C. using a thermal conductivity meter (NETZSCH, HFM436 Lambda).

Furthermore, the metal oxide-silica composite airgel has excellent pore properties through a characteristic drying process in its manufacturing process. Specifically, the metal oxide-silica composite airgel may have a porosity of 80% by volume or more, or 90% by volume to 98% by volume, and an average pore diameter of 20nm or less, or 5nm to 15nm. In this case, the average pore diameter and porosity of the metal oxide-silica composite aerogel can be measured by the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p _o <1) using an ASAP 2010 device of Micrometrics. .

In addition, the metal oxide-silica composite airgel may have a pore volume of 0.4 cm ³ / g to 1.0 cm ³ / g, more specifically 0.4 cm ³ / g to 0.7cm ³ / g. At this time, the pore volume in the metal oxide-silica composite airgel can be determined from the amount of mercury intrusion into the pores measured by mercury porosimeter analysis.

On the other hand, in the metal oxide-silica composite airgel, the silica airgel is a particulate porous structure containing a plurality of micropores, the nano-sized primary particles, specifically, the average particle diameter (D ₅₀ ) is 100nm or less, Alternatively, the nanoparticle may include a microstructure, that is, a three-dimensional network structure, in which primary particles of 1 nm to 50 nm are combined to form a network-shaped cluster.

In addition, since the metal oxide is fixed by the silanol groups present on the surface of the silica airgel, the silanol groups present on the surface of the silica airgel in order to increase the immobilization efficiency between the negative charge on the surface of the silica airgel and the positive charge of the metal oxide. It is preferable to appropriately control the density of. Specifically, the density of silanol groups present on the surface of the silica airgel may be 10 / nm ² or less, or 5 / nm ² to 7 / nm ² .

Accordingly, the silica airgel has a BET (Brunauer-Emmett-Teller) surface area of 50 m ² / g to 700 m ² / g, an average particle diameter (D ₅₀ ) of 10 μm to 150 μm, and a porosity of 0.5 cm 3 / g to 2.4 Cm 3 / g, and the average pore diameter of pores included in the silica airgel may be 0.5nm to 40nm. If the BET specific surface area, average particle diameter, porosity or average pore diameter of the silica airgel is outside the above-mentioned ranges, for example, if the average pore diameter is less than 0.5 nm, the density of silanol groups is relatively increased and the absolute value of negative charge is greatly increased. As a result, the immobilization efficiency with the positively charged metal oxide is increased, but the hydrophilicity is also increased, thereby reducing the dispersibility of the metal oxide-silica composite aerogel. In addition, when the average pore diameter exceeds 40 nm, the silanol group density is relatively low, so that there is no fear of lowering the dispersibility of the metal oxide-silica composite aerogel, but the absolute value of the negative charge is low, so that the immobilization efficiency may be lowered.

In the metal oxide-silica composite airgel, the metal oxide may be used without particular limitation as long as it is fixed by silanol groups on the surface of the silica airgel and used to form the composite airgel. Specifically, the metal oxide may be an oxide containing any one or two or more metals selected from the group consisting of alkali metals, alkaline earth metals, lanthanides, actinides, transition metals, and metals of Group 13 (IIIA), More specifically, calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), silver (Ag), titanium (Ti), vanadium (V), cobalt (Co), molybdenum (Mo), tin (Sn), antimony (Sb), strontium (Sr), barium (Ba), and tungsten (W) It may be an oxide containing any one or two or more metal elements selected from the group consisting of, and more specifically may be magnesium oxide, calcium oxide or a mixture thereof.

The metal oxides are discontinuously physically immobilized on the surface of the silica by electrical attraction occurring between the negatively charged and relatively positively charged metal oxides resulting from the silanol groups present on the surface of the silica. Accordingly, in order to be easily and efficiently fixed on the surface of the silica airgel and to exhibit a sufficient effect by the metal oxide, the metal oxide preferably has an appropriate particle size and specific surface area. Specifically, the metal oxide may have a specific surface area of 20 m ² / g to 100 m ² / g and an average particle diameter (D ₅₀ ) of 5 nm to 300 nm.

In addition, the metal oxide may be adjusted in the content of the metal oxide contained in the composite airgel according to the use of the metal oxide-silica composite airgel, specifically, the metal oxide is 5 to 80% by weight based on the total weight of the composite airgel May be included as a%. In addition, the metal oxide is a silicon oxide (Si) contained in the metal oxide-silica composite aerogel and a metal (Me) contained in the metal oxide (mole ratio of 1: 1 to 3: 1 (molar ratio of Si / Me)), more specifically May be included in an amount such that 1.5: 1 to 3: 1, and more specifically 3: 1.

More specifically, according to another embodiment of the present invention, through the manufacturing process configured by more optimal combination of the type of the washing solvent and the conditions of the drying process in the manufacturing process, particulate porous including a plurality of micropores A silica airgel, and a metal oxide dispersed in the porous silica airgel, and having an average particle diameter (D ₅₀ ) of 7 μm to 15 μm, more specifically 7 μm to 12 μm, and a tap density of 0.055 g / ml. Hereinafter, more specifically, the metal oxide-silica composite aerogel provided with 0.009 g / ml to 0.055 g / ml and having a BET specific surface area of 450 m ² / g or more, and more specifically 450 m ² / g to 600 m ² / g do.

As described above, the metal oxide-silica composite aerogel prepared by the manufacturing method according to the present invention has excellent physical properties such as low tap density and high specific surface area, and thus, catalysts or industrial furnace pipes or industrial furnaces. Insulation facilities such as thermal insulation, such as aircraft, ships, automobiles, building structures, such as insulation, insulation, or non-combustible materials are useful.

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.

Example 1

Distilled water was added to the water glass (Na ₂ SiO ₃ ) and mixed to prepare a silicate solution having a concentration of 1.5 M of Na ₂ SiO ₃ . Additionally, MgCl ₂ and CaCl ₂ were dissolved in the distilled water, the metal salt solution (total concentration of the metal ion = 0.5M, Mg ^{+ 2:} 1 molar ratio of Ca ^{+ 2:} 1) was prepared by adding the silicate solution and mixed It was. HCl acid catalyst was added to the resulting mixture until the pH of the mixture was 7.3. A white precipitate formed immediately upon reaction of the metal salt solution with the silicate solution.

The precipitate was spontaneously precipitated and then the transparent solvent was removed. The separated precipitate was washed three times with ethanol and then vacuum filtered. The resulting cake (water content of about 85% by weight) was placed on a substrate of a MIR drying apparatus equipped with a MIR lamp, and irradiated with MIR under the conditions described in Table 1 below, thereby containing a plurality of micropores. To prepare a metal oxide-silica composite aerogel comprising a porous porous silica, and a metal oxide dispersed in the porous silica. The amount of each compound was used as described in Table 1 below.

Examples 2 and 3

A metal oxide-silica composite aerogel was prepared in the same manner as in Example 1 except that the washing and drying processes were performed under the conditions described in Table 1 below.

Comparative Examples 1 to 8

A metal oxide-silica composite aerogel was prepared in the same manner as in Example 1 except that the washing and drying processes were performed under the conditions described in Table 1 below.

Experimental Example

Using the metal oxide-silica composite airgel prepared in Examples 1 to 3 and Comparative Examples 1 to 8, the tap density and the average particle diameter of the metal oxide-silica composite airgel according to the drying method were evaluated, respectively.

At this time, the tap density was measured using a tap density meter (TAP-2S, Logan Istruments co.). The results are shown in Table 1 below.

In addition, the average particle diameter (D ₅₀ ) is a dry analysis model, represented as the average value after three repeated measurements using a particle size analyzer (Macrotrac Particle Size Analyzer S3500).

	Solvent	Drying method	Drying condition	Wavelength range (㎛)	Wavelength range of main peak	Average wavelength of main peak (㎛)	Atmosphere temperature (℃)	Tap Density (g / ml)	Average particle size (D 50 , ㎛)
Example 1	ethanol	MIR survey	IR 90% *	2 ~ 8	2 ~ 4	3	190	0.051	8.5
Example 2	Water and ethanol mixture (mixed weight ratio = 60:40)	MIR survey	IR 90%	2 ~ 8	2 ~ 4	3	190	0.054	8.8
Example 3	ethanol	MIR investigation	IR 100%	2 ~ 8	2 ~ 4	3	220	0.045	7.8
Comparative Example 1	ethanol	Oven drying	-	-	-	-	105	0.084	10.5
Comparative Example 2	Water and ethanol mixture (mixed weight ratio = 60:40)	Oven drying	-	-	-	-	105	0.110	12.1
Comparative Example 3	ethanol	Oven drying	-	-	-	-	150	0.080	9.4
Comparative Example 4	ethanol	Oven drying	-	-		-	190	0.078	8.9
Comparative Example 5	ethanol	NIR investigation	IR 90%	0.75 ~ 2	0.8-1.5	1.15	95	0.071	9.7
Comparative Example 6	ethanol	NIR investigation	IR 100%	0.75 ~ 2	0.8-1.5	1.15	110	0.067	8.6
Comparative Example 7	ethanol	FIR investigation	IR 90%	9-15	9-15	12	125	0.073	9.3
Comparative Example 8	ethanol	FIR investigation	IR 100%	9-15	9-15	12	140	0.063	8.7

Drying condition 'IR 90%' in Table 1 means performing by adjusting the intensity (intensity) of the infrared irradiation device to 90%, and as a result, the drying temperature at IR 90% is lower than when the IR 100% do.

As shown in Table 1, the composite aerogels of Examples 1 to 3, in which solvent evaporation occurred simultaneously on the inside and the surface of silica gel particles through MIR irradiation, were reduced compared to Comparative Examples 1 to 4 dried using a drying oven. Tap density is shown. Specifically, in the case of Example 3, there was a decrease in tap density of 46.4% compared to Comparative Example 1, 59.1% compared to Comparative Example 2, 43.8% compared to Comparative Example 3, 42.3% compared to Comparative Example 4.

The result is that the MIR wavelength penetrates inside the aerogel structure and directly resonates energy by resonating in the wavelength range of 2 ~ 4㎛ with the hydroxyl group (-OH) included in the molecular structure of water and ethanol used as reaction solvent and washing solvent. The drying of the solvent may proceed within the pores of the gel structure, and at the same time, the surface of the gel particles is dried by increasing the ambient temperature by the MIR lamp, thereby minimizing shrinkage of the airgel particles during the drying process compared to the conventional oven drying. Because. Accordingly, it can be seen that the tap density of the composite airgel finally prepared during drying by MIR irradiation can significantly increase the specific surface area.

In addition, Examples 1 to 3 irradiated with MIR in the wavelength range of 2 μm to 8 μm differed only from the wavelength range under the use of the same washing solvent and under the same IR 90% or IR 100% drying conditions. ), Or compared with Comparative Examples 5 to 8 irradiated with NIR (Near Infrared Ray, NIR), the tap density was greatly reduced. From these results, it can be seen that only the control of the infrared wavelength during drying can significantly improve the tap density of the final composite aerogel.

In addition, Example 1 using the ethanol single solvent as the washing solvent, the tap density reduction effect was greater than in Example 2 using a mixed solvent of water and ethanol as the washing solvent under the same IR 90% conditions. From these results, it can be seen that the tap density of the metal oxide-silica composite aerogel can be further lowered through simultaneous control of the washing solvent together with the drying process by infrared irradiation.

In addition, for the metal oxide-silica composite aerogels prepared in Example 1 and Comparative Example 1, the adsorption / desorption amount of nitrogen according to the partial pressure (0.11 <p / p _o <1) using an ASAP 2010 device of Micrometrics Was measured, and from this, the BET specific surface area of the composite airgel was evaluated.

	BET specific surface area of composite airgels (m 2 / g)
Example 1	540
Comparative Example 1	400

As a result, Example 1 subjected to the drying process by MIR irradiation showed a BET specific surface area increased by about 25.9% or more compared with Comparative Example 1 subjected to the oven drying process. From these results, it can be seen that the specific surface area of the final composite airgel with the tap density during drying through infrared irradiation can be significantly improved.

Claims (17)

1. Adding a metal salt solution to the silicate solution and reacting to prepare a metal oxide-silica composite precipitate; And

   Drying the metal oxide-silica composite precipitate by irradiating infrared rays in a wavelength range of 2 μm to 8 μm

   Method for producing a metal oxide-silica composite airgel comprising a.
2. The method of claim 1,

   The drying is a method of producing a metal oxide-silica composite aerogel is carried out by irradiating infrared rays in the wavelength range resonating with water molecules or hydroxyl groups in the solvent used in the preparation of the silicate solution and the metal salt solution.
3. The method of claim 1,

   The drying is a method of producing a metal oxide-silica composite aerogel is to be carried out by irradiating infrared rays in the wavelength range of 2㎛ 4㎛.
4. The method of claim 1,

   The drying is a method of producing a metal oxide-silica composite aerogel is to be carried out by irradiating infrared rays with an intensity such that the ambient temperature is 130 ℃ to 300 ℃.
5. The method of claim 1,

   After the drying step by the infrared irradiation, the method of producing a metal oxide-silica composite aerogel further comprising a further drying step at an ambient temperature of 130 ℃ to 300 ℃.
6. The method of claim 1,

   The silicate solution is prepared by dissolving the water glass in water at a concentration of 0.125M to 3.0M metal oxide-silica composite airgel.
7. The method of claim 1,

   The metal salt solution is a method of producing a metal oxide-silica composite aerogel is a metal ion concentration of 0.125M to 3.0M.
8. The method of claim 1,

   The metal salt is a metal oxide-silica which is one or two or more chlorides selected from the group consisting of alkali metals, alkaline earth metals, lanthanides, actinides, transition metals and metals of Group 13 (IIIA). Method for producing a composite airgel.
9. The method of claim 1,

   The metal salt is a method of producing a metal oxide-silica composite aerogel which comprises any one or a mixture thereof selected from the group consisting of MgCl ₂ and CaCl ₂ .
10. The method of claim 1,

    The metal salt is a method of producing a metal oxide-silica composite airgel containing MgCl ₂ and CaCl ₂ in a content such that the molar ratio of magnesium ions and calcium ions is 2: 1 to 1: 2.
11. The method of claim 1,

    The reaction of the silicate solution and the metal salt solution is a method of producing a metal oxide-silica composite aerogel is performed at pH 3 to 9.5.
12. The method of claim 1,

    The method of producing a metal oxide-silica composite aerogel is to react at a pH of 5 or more and less than 7.5 by further adding an acid catalyst when the silicate solution and the metal salt solution.
13. The method of claim 12,

    The acid catalyst is a method of producing a metal oxide-silica composite airgel is hydrochloric acid.
14. The method of claim 1,

    Before the drying step, further comprising the step of washing the metal oxide-silica composite precipitate using a washing solvent,

    The washing solvent is water, an alcohol compound, a hydrocarbon compound, and a method of producing a metal oxide-silica composite aerogel comprising a mixture of one or two or more selected from the group consisting of ketone compounds.
15. The method of claim 14,

    The washing solvent is a method for producing a metal oxide-silica composite airgel containing an alcohol compound.
16. Metal oxide-silica composite airgel prepared by the method of claim 1.
17. The method of claim 16.

    A metal oxide-silica composite airgel having an average particle diameter (D ₅₀ ) of 7 µm to 15 µm, a tap density of 0.055 g / ml or less, and a BET specific surface area of 450 m ² / g or more.