KR20130051304A - Super hydrophobic silica aerogel powders - Google Patents

Abstract

PURPOSE: A superhydrophobic aerogel powder is provided to manufacture a lightweight insulating body or an insulator by having a low dielectric coefficient, a large specific size, a low thermal conductivity, a low density, and high porosity. CONSTITUTION: A superhydrophobic aerogel powder has an average particle diameter of 100-10,000 nm, an average pore size of 5-10 nm, a dielectric coefficient of 1.1-1.5, a specific surface area of 900-1300m^2/g, a thermal conductivity of 0.01-0.03W/m·K, a density of 0.02-0.04g/cm^3, and a porosity of 95-99.9%. A manufacturing method of the superhydrophobic aerogel powder comprises a step of adding 40-60 wt% of water glass solution as a precursor material, together with an inorganic acid; a step of generating hydrogel by adding residual organosilane compound; a step of removing Na+ ion by dipping the hydrogel into a nonpolar solvent, and conducting solvent exchanges; and a step of drying the hydrogel at atmospheric pressure. The organosilane compound has an alkaline pH. [Reference numerals] (AA) Water glass; (BB) Deionized water; (CC) Inorganic acid; (DD) Primarily inject an organosilane compound; (EE) Secondarily inject the organosilane compound; (FF) Modify surface, Manufacture hydrogel; (GG) Non-polar solvent; (HH) Exchange a solvent, Remove sodium ions; (II) First drying step; (JJ) Second drying step; (KK) Third drying step; (LL) Silica aerogel

Description

Super hydrophobic Silica aerogel powders

The present invention relates to superhydrophobic silica airgel powder.

Aerogel (aerogel) is a highly porous material having the highest porosity among the solids known to date, a representative inorganic aerogel, silica airgel is a gel sol-gel polymerization reaction of a silica precursor solution, and then dried under supercritical or atmospheric conditions To obtain an airgel with a pore structure filled with air. Therefore, due to the unique pore structure in which most of the inner space is empty, physical properties such as super insulation, low weight, sound absorption, and low dielectric constant that are attracting airgel are expressed.

The biggest advantage of the airgel is super-insulation, which exhibits a thermal conductivity of 0.300 W / m · K or lower, which is lower than that of conventional thermal insulation materials such as styrofoam. At present, the thermal conductivity of the bead-based styrofoam insulation board specified by the Korean Industrial Standard (KS) is less than 0.036W / m · K at 20 ℃. Silica aerogels have been reported in various technical literatures with lower thermal conductivity, and the flame retardancy of the inorganic components is super flame retardant like silica aerogels because it can solve the fire fragility and the harmful gas generated in the fire, which are fatal weaknesses of organic insulating materials. There is an urgent need for the development of inorganic insulating materials.

The super insulation performance of aerogels is known to be due to the formation of mesoporous-sized pore structures that prevent the convective heat transfer by air and the solid (silica) heat transfer effect of very small 2 ~ 5 wt% content. The average free path of the air gas molecules is 65 nm and the average pore size of the airgel is formed to be smaller than that of the mesopore, which interferes with the heat transfer of the gas molecules. The pore structure of aerogels filled with mesopores shows very high porosity, resulting in very low density with macroscopic properties. Until now, many literatures have reported various manufacturing methods to realize pore structure and low density characteristics of airgel, but airgel with sufficient low dielectric constant, large specific surface area, low thermal conductivity, low density and high porosity has not been reported. The research on this is urgently needed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object thereof is to provide a superhydrophobic silica airgel having sufficient low dielectric constant, large specific surface area, low thermal conductivity, low density, and high porosity.

The present invention provides a superhydrophobic silica airgel powder having an average particle diameter of 100 to 10,000 nm, an average pore size of 5 to 10 nm, and a dielectric constant of 1.1 to 1.5.

The specific surface area of the superhydrophobic silica airgel powder is 900 ~ 1300m ² / g, thermal conductivity is 0.01 ~ 0.03W / m · K, density is 0.02 ~ 0.04g / cm ³ , porosity can be 95 ~ 99.9% However, the present invention is not limited thereto.

The superhydrophobic silica airgel powder is a precursor of water glass solution without ion exchange, and 40 to 60% by weight of the total amount of the organosilane compound having an alkaline pH is added together with the inorganic acid, and then the organosilane A first step of surface modification and gelation by adding the remaining 40-60 wt% of the total amount of the compound to generate a hydrogel; Dipping the hydrogel in a nonpolar solvent to remove solvent and Na ⁺ ions; And it can be prepared through a third step of drying the solvent-exchanged hydrogel under atmospheric pressure.

The water glass solution may include 1 to 30% by volume of water glass and 70 to 99% by volume of distilled water, compared to 100% by volume of the total water glass solution, but is not limited thereto.

The organosilane compound may be hexamethyldisilazane (HMDS), but is not limited thereto.

The inorganic acid may be at least one selected from the group consisting of acetic acid, nitric acid, and hydrochloric acid, but is not limited thereto.

The solvent exchange and removal of Na ⁺ ions may be made within 10 hours at room temperature or more and less than 60 ℃, but is not limited thereto.

The nonpolar solvent may be hexane or heptane or a mixture thereof, but is not limited thereto.

The drying is a first drying step of stirring for 20 to 80 minutes at a temperature of 80 ~ 110 ℃; A second drying step of stirring at a temperature of 140 to 160 ° C. for 30 to 50 minutes; And a third drying step of generating and drying a dryer, but is not limited thereto.

The nonpolar solvent may be recollected by condensation of steam during the drying process.

Washing the hydrogel with water between the second step and the third step or removing water by applying a vacuum to the hydrogel between the second step and the third step, or the second step and the It is possible to further include the step of removing the water by washing the hydrogel with water between the third step and then applying a vacuum.

The superhydrophobic silica airgel powder according to the present invention can provide a lightweight insulator or insulator due to sufficient low dielectric constant, large specific surface area, low thermal conductivity, low density, and high porosity, and is lightweight using the superhydrophobic silica airgel powder. Insulator or insulator of Styrofoam can replace the existing Styrofoam, which can solve the problem of fire vulnerabilities and harmful gases generated during ignition, which is very important from an industrial point of view.

1 is a flowchart illustrating a method of preparing a superhydrophobic silica airgel powder according to an embodiment of the present invention.
Figure 2 is a graph showing the analysis results of the FT-IR for the superhydrophobic silica airgel powder according to an embodiment of the present invention.
3 is an SEM image of a superhydrophobic silica airgel powder according to one embodiment of the present invention.

The present invention provides a superhydrophobic silica airgel powder having a dielectric constant of 1.1 to 1.5.

Due to the superhydrophobic silica airgel powder having the above dielectric constant range, silica airgel excellent in flame retardancy and heat insulation can be used as an insulator, and its industrial meaning is very large.

The specific surface area of the superhydrophobic silica airgel powder is in the range of 900 ~ 1300m ² / g to obtain a lightweight airgel powder due to low density and high porosity in this range.

The thermal conductivity of the superhydrophobic silica airgel powder is significantly lower than that of the conventional silica airgel powder in the range of 0.01 to 0.03 W / m · K, and the superhydrophobic silica airgel powder having such thermal conductivity By using it is possible to provide a lightweight insulator excellent in flame retardancy and insulation.

The density of the superhydrophobic silica airgel powder is in the range of 0.02 ~ 0.04g / cm ³ , it is possible to make products such as ultra-light insulators or heat insulators in this range.

The average particle diameter of the superhydrophobic silica airgel powder is in the range of 100 ~ 10,000nm, the average pore size is in the range of 5 ~ 10nm is appropriate, in this range to provide a superhydrophobic silica airgel powder with sufficiently low dielectric constant and thermal conductivity. Can be.

The porosity of the superhydrophobic silica airgel powder is 95 to 99.9% in this range, it is possible to provide a superhydrophobic silica airgel powder having a large specific surface area.

Hereinafter, with reference to Figure 1, a method for producing a superhydrophobic silica airgel powder according to the present invention will be described in detail.

Superhydrophobic silica airgel powder according to the present invention,

A water glass solution without ion exchange is used as a precursor, and 40 to 60% by weight of the total amount of the organosilane compound having an alkaline pH is added together with the inorganic acid, followed by the remaining 40 to 30% of the total amount of the organosilane compound. Adding a 60% by weight to surface modification and gelation to produce a hydrogel;

Dipping the hydrogel in a nonpolar solvent to remove solvent and Na ⁺ ions; And

The solvent exchanged hydrogel is prepared through a third step of drying under normal pressure.

The present invention is characterized in that the first step in preparing the superhydrophobic silica airgel powder is divided into two times the organosilane compound added for the surface modification and gelation of water glass.

Specifically, in the first step, the total amount of inorganic acid for making the water glass into silicic acid is added, and at the same time, a part of the total amount of the organosilane compound is added, and the remaining organosilane compound is added at regular intervals. do.

When the organosilane compound is added in two portions as described above, a large amount of inorganic acid and water glass initially introduced are sufficiently stirred to generate a sufficient amount of silicic acid, and the silicic acid reacts with the organosilane compound to modify the surface and To produce a gelled hydrogel, there is an effect that the gelation rate and degree of gelation of the hydrogel is improved.

For example, in the first step, the inorganic acid and the organosilane compound are first added to the water glass solution, and then stirred for about 5 to 10 minutes at a speed of about 120 to 500 rpm, followed by the second addition of the remaining organosilane compound. , But may proceed by stirring for about 3 minutes at a speed of about 70 ~ 90 rpm, but is not limited thereto.

The water glass solution uses a water glass solution that is not ion exchanged, as shown in FIG. 1, in the present invention, the surface modification of the water glass is removed without removing sodium ions through ion exchange performed before the surface modification step of the conventional water glass. In a second step, which is later, it is configured to remove sodium ions from the hydrogel through solvent exchange.

That is, the present invention adds an inorganic acid and an organosilane compound to the water glass solution that is not ion-exchanged, and prepares hydrogels using a co-precursor method. The organosilane compound used at this time has an alkaline pH and performs surface modification and gelling.

The water glass solution is preferably 1 to 30% by volume of water glass and 70 to 99% by volume of distilled water relative to 100% by volume of the total water glass solution, preferably 10 to 20% by volume of water glass and 80 to 90% by volume of distilled water. It is suitable to be. If the content of the water glass and distilled water is out of the range it is not preferable because the gelation of the water glass surface-modified with the organosilane compound is not easy.

As the organosilane compound having an alkaline pH, hexamethyldisilazane (HMDS) may be used, but is not limited thereto.

The inorganic acid may be used one or more selected from the group consisting of acetic acid, nitric acid, and hydrochloric acid, but is not limited thereto.

In the second step, the pore water present in the reticular tissue of the hydrogel is exchanged with a nonpolar solvent which is not mixed with water. In this case, Na ⁺ ions contained in the hydrogel have a better affinity with water, thus making the pore water easier. Accordingly the removal is made from the hydrogel.

Specifically, the hydrogel is immersed in the nonpolar solvent in the second step. Then, water is discharged from the network of the hydrogel, and a nonpolar solvent penetrates into pores, so that solvent exchange and removal of sodium ions are completed in one step.

As the nonpolar solvent, n-hexane (n-hexane) or heptane may be used, or a mixture thereof may be used, but is not limited thereto.

Such solvent exchange and removal of sodium ions are carried out within 10 hours under conditions of less than 60 ° C above room temperature. If 10 hours or more is required at room temperature, volatile solvents such as hexane, which are used as nonpolar solvents, are left for a long time, and the nonpolar solvent to replace the pore water must be evaporated, or a very large amount of nonpolar solvent must be used. If the solvent exchange and the sodium ions are removed at 60 ° C. or higher, the boiling point of hexane, which is mainly used as the non-polar solvent, is 69 ° C., so that the non-polar solvent does not participate in the solvent substitution and is not preferable. Preferably, it is suitable to carry out within 3 hours at 40 ° C. in consideration of the properties of a nonvolatile solvent having high volatility and low boiling point.

In the present invention, by further performing a process of washing the hydrogel with water after the second step, it is possible to more reliably remove some sodium ions that may be present in the hydrogel.

In addition, after the second step, the hydrogel may be subjected to a vacuum to remove moisture, or the hydrogel may be washed with water and then vacuumed to remove the moisture. That is, the hydrogel can be dried more easily by applying vacuum in advance before performing the drying process to be described later, and additionally, there is an effect of removing some hexane.

In the third step to dry the hydrogel with a gap substituted with a non-polar solvent to prepare a superhydrophobic silica airgel powder, the drying is a first drying step of stirring for 20 to 80 minutes at a temperature of 80 ~ 110 ℃; A second drying step of stirring at a temperature of 140 to 160 ° C. for 30 to 50 minutes; And a third drying step of drying and generating a dryer, and when the drying is performed in this way, the drying efficiency may be improved, and the density of the silica airgel powder may be lowered. Do.

The first drying step is to secure the space of the pores formed during the removal and solvent exchange of the residual solvent remaining in the hydrogel in which the gap is replaced with a non-polar solvent.

The second drying step is for removing water remaining after the first drying step or any organic matter (such as organic solvent) remaining.

The present invention avoids the drying process for a long time at a high temperature of 170 ~ 200 ℃ or more through the first drying step and the second drying step, and economic efficiency and energy saving silica airgel powder by reducing the drying temperature and drying time Increased productivity.

After the first drying step and the second drying step proceeds to the third drying step of generating and drying the dryer, the third drying step may be performed by generating a jet stream at the bottom of the reactor, but is not limited thereto. no.

In the present invention, after the third drying step, a stabilization process commonly used in the art may be further added.

In addition, the nonpolar solvent vapor evaporated during the drying process may be recollected by condensation to reuse the nonpolar solvent.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited by the following Examples.

Example

A water glass solution containing 75 ml of water glass and 425 ml of distilled water, which had not been subjected to the ion exchange process, was added to 30 ml of hexamethyldisilazane and 44 ml of nitric acid under constant stirring conditions, and stirred at 250 to 450 rpm for 5 to 10 minutes. After surface modification of a portion of the water glass, an additional 30 ml of hexamethyldisilazane is added again to form a completely surface modified hydrogel.

Thereafter, for solvent exchange of the obtained hydrogel and removal of sodium ions, the hydrogel is immersed in n-hexane (600 ml), and then left at a temperature of 40 ° C. for 3 to 5 hours.

Thereafter, the drying process is stirred for 1 hour at a temperature of 100 ℃ in the primary drying furnace, and dried for 40 minutes at a temperature of 150 ℃ in the secondary drying furnace. Finally, jet streams are generated at the bottom of the reactor for tertiary drying.

Through this process, 68.3 g of superhydrophobic silica airgel powder was obtained.

Experimental Example

1.Fourier Transform Infrared Spectroscopy (FT-IR) Analysis

Fourier Transform Infrared Spectroscopy (FT-IR) analysis was performed to confirm the surface modification by the co-precursor method of the hydrogel prepared as described above. Figure 2 is a graph showing the analysis results of the FT-IR for the superhydrophobic silica airgel powder according to the embodiment, as shown in Figure 2, the Si-CH ₃ peak (Peak), which is due to the coprecursor ( Surface modification by co-precursor) method was confirmed.

2. Evaluation of Superhydrophobic Silica Airgel Powder

(1) permittivity

In order to measure the dielectric constant of the superhydrophobic silica airgel powder prepared according to the above embodiment, a copper substrate was formed in a monolithic form, and used as a lower electrode, and an Ag electrode was sputtered on the airgel monolith to form an M-I-M structure. The dielectric constant was measured using an HP 4155 Semiconductor Parameter Analyzer. The measurement results are shown in Table 1.

(2) specific surface area

The specific surface area of the superhydrophobic silica airgel powder prepared according to the above example was measured by BET analysis. The measurement results are shown in Table 1.

(3) thermal conductivity

The thermal conductivity of the superhydrophobic silica airgel powder prepared according to the above example was measured by KSL1016. The measurement results are shown in Table 1.

(4) density

The density of the superhydrophobic silica airgel powder prepared according to the above example was measured by KSL1621. The measurement results are shown in Table 1.

(5) average particle diameter

The average particle diameter of the superhydrophobic silica airgel powder prepared according to the above example was measured by particle size analysis. The measurement results are shown in Table 1.

(6) average pore size

The average pore size of the superhydrophobic silica airgel powder prepared according to the above example was measured by BET analysis. The measurement results are shown in Table 1.

(7) porosity

Since the density of the superhydrophobic silica airgel powder prepared according to the above example is 0.022 g / mL and the theoretical density of amorphous silica is 2.2 g / mL, the porosity of the superhydrophobic silica airgel powder can be calculated, and the table 1 is shown.

Measurement result (1) dielectric constant (unitless) 1.1 to 1.5 (2) specific surface area (m ² / g) 900-1300 (3) Thermal Conductivity (W / mK) 0.01 ~ 0.03 (4) density (g / cm ³ ) 0.022 (5) Average particle diameter (nm) 100 to 10,000 (6) Average pore size (nm) 5 to 10 (7) Porosity (%) 99

3. SEM (Scanning Electron Microscopy) Analysis

The superhydrophobic silica airgel powder prepared according to the above example confirmed the nanoporous structure of the airgel through SEM (Scanning Electron Microscopy). 3 is an SEM image of a superhydrophobic silica airgel powder prepared according to the above embodiment.

Although the technical details of the superhydrophobic silica airgel powder of the present invention have been described together with the accompanying drawings, this is illustrative of the best embodiment of the present invention and is not intended to limit the present invention.

In addition, it is obvious that any person skilled in the art can make various modifications and imitations within the scope of the appended claims without departing from the scope of the technical idea of the present invention.

The present invention can be variously used in the energy field, the environment field, the electric / electronic field, and other fields. In other words, it can be used as transparent / translucent insulator, polyurethane substitute, building interior and exterior materials in the energy field, and can be applied to gas / liquid separation filter and catalyst device for VOC / NOx removal in the environmental field. It can be used as an interlayer insulating film for semiconductors, microwave circuit materials, and in other fields, it can be used as sound absorbing paints, sound absorbing panels, other sound absorbing materials, and cold light raw materials.

Claims (16)

A superhydrophobic silica airgel powder having an average particle diameter of 100 to 10,000 nm and an average pore size of 5 to 10 nm, and having a dielectric constant of 1.1 to 1.5.
The method of claim 1,
The specific surface area of the superhydrophobic silica airgel powder is a super hydrophobic silica airgel powder, characterized in that 900 ~ 1300m ² / g.
The method of claim 1,
The superhydrophobic silica airgel powder has a thermal conductivity of 0.01 to 0.03 W / m · K.
The method of claim 1,
The superhydrophobic silica airgel powder has a density of 0.02 to 0.04 g / cm ³ , the superhydrophobic silica airgel powder.
The method of claim 1,
The superhydrophobic silica airgel powder has a porosity of 95 to 99.9%, the superhydrophobic silica airgel powder.
The method of claim 1, wherein the superhydrophobic silica airgel powder,
A water glass solution without ion exchange is used as a precursor, and 40 to 60% by weight of the total amount of the organosilane compound having an alkaline pH is added together with the inorganic acid, followed by the remaining 40 to 30% of the total amount of the organosilane compound. Adding a 60% by weight to surface modification and gelation to produce a hydrogel;
Dipping the hydrogel in a nonpolar solvent to remove solvent and Na ⁺ ions; And
Superhydrophobic silica airgel powder, characterized in that prepared by the third step of drying the solvent-exchanged hydrogel under normal pressure.
The method according to claim 6,
The water glass solution is superhydrophobic silica airgel powder, characterized in that 1 to 30% by volume of water glass and 70 to 99% by volume of distilled water compared to 100% by volume of the total water glass solution.
The method according to claim 6,
The organosilane compound is hexamethyldisilazane (hexamethyldisilazane; HMDS), characterized in that the superhydrophobic silica airgel powder.
The method according to claim 6,
The inorganic acid is superhydrophobic silica airgel powder, characterized in that at least one selected from the group consisting of acetic acid, nitric acid, and hydrochloric acid.
The method according to claim 6,
The solvent exchange and the removal of Na ⁺ ions is superhydrophobic silica airgel powder, characterized in that made in 10 hours or more under a condition of less than 60 ℃.
The method according to claim 6,
The non-polar solvent is superhydrophobic silica airgel powder, characterized in that hexane or heptane or a mixture thereof.
The method of claim 6, wherein the drying
A first drying step of stirring at a temperature of 80 to 110 ° C. for 20 to 80 minutes;
A second drying step of stirring at a temperature of 140 to 160 ° C. for 30 to 50 minutes; And
A superhydrophobic silica airgel powder, comprising a separate process comprising a third drying step of generating and drying a dryer.
The method according to claim 6,
Wherein said nonpolar solvent is recollected by condensation of steam during said drying process.
The method according to claim 6,
The superhydrophobic silica airgel powder, further comprising the step of washing the hydrogel with water between the second step and the third step.
The method according to claim 6,
The hydrophobic silica airgel powder of claim 2, further comprising the step of removing moisture by applying a vacuum to the hydrogel between the second step and the third step.
The method according to claim 6,
The hydrophobic silica airgel powder further comprises the step of washing the hydrogel with water between the second step and the third step and then applying a vacuum to remove water.

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