KR20110125773A - Manufacturing method of hydrophobic silica aerogel and hydrophobic silica aerogel manufactured therefrom - Google Patents

Abstract

PURPOSE: A method for manufacturing hydrophobic silica aerogel and hydrophobic silica aerogel manufactured by the same are provided to simultaneously implement a gelation reaction and a hydrophobication reaction without the substitution of a solvent. CONSTITUTION: A hydrophobicating agent is added in silica sol to obtain hydrophobic gel(S200). The hydrophobic gel is supercritically dried(S300). The hydrophobicating agent is basic hydrophobicating agent. The basic hydrophobicating agent is one selected from a group including hexamethyl disilazane and lithium bis(trimethylsilyl)amide. The content of the basic hydrophobicating agent is in a range between 4 and 8wt% based on 100 wt% of the silica sol. The silica sol is prepared by mixing tetra ethyl ortho silicate, alcohol, water, and an acidic catalyst.

Description

Manufacturing method of hydrophobic silica airgel and hydrophobic silica airgel manufactured by the manufacturing method TECHNICAL FIELD The present invention relates to a hydrophobic silica airgel.

The present invention relates to a method for preparing a hydrophobic silica airgel, and to a hydrophobic silica airgel prepared by the method. More specifically, the hydrophilic gel produced after a sol-gel reaction is immersed in a hydrophobic solution for several days to undergo hydrophobic gel. The present invention relates to a hydrophobic silica airgel prepared by adding a hydrophobization agent directly to a silica sol to obtain a hydrophobized gel and supercritically drying the hydrophobized gel to obtain a hydrophobic silica airgel, and to a hydrophobic silica airgel prepared by the method. .

Silica aerogel is a silica structure having a three-dimensional network structure, more than 90% is a porous material consisting of nano-sized pores. Due to its low density and high porous structure, it is attracting attention as an excellent catalyst, adsorbent, sound absorbing material, and heat insulating material. When the silica airgel is hydrophilic, the pore structure is gradually collapsed by moisture when exposed to the external environment, thereby deteriorating physical properties. In order to remove this phenomenon, the surface of the airgel is modified to be hydrophobic, so that it is manufactured not to be affected by moisture and moisture even when exposed to the external environment for a long time.

Looking at the conventional representative hydrophobic airgel synthesis technology in detail, the first step is a sol-gel process, the condensation by adding a basic catalyst to the silica sol prepared by hydrolyzing TEOS (Tetra Ethyl Ortho Silicate) and water glass raw material with an acid catalyst The reaction produces a hydrophilic wet gel. As the acid catalyst, hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, and the like are used, and as the base catalyst, sodium hydroxide, aqueous ammonia, pyridine, hydrazine, piperidine and the like are used.

The second step is a hydrophobic process, in order to hydrophobically modify the hydrogel wet gel surface by putting the wet gel in an organic solvent, replacing the water in the gel with an organic solvent, and then adding a hydrophobizing agent to make the wet gel surface hydrophobic for a long time. While reforming. Organic solvents include acetone, isopropanol, ethanol, methanol, normal hexane, normal heptane, butanol, xylene and the like. Halogen, alkyl and alkoxy, aromatic silanes such as methyltrimethoxysilane, trimethylethoxysilane, ethyltriethoxysilane, and phenyltriethoxysilane are mainly used.

The third step is a drying process in which the unreacted substance is removed by washing the modified hydrophobic gel, and the hydrophobic airgel is manufactured by supercritical drying or atmospheric pressure drying. The washing solution uses an organic solvent used for solvent replacement, and drying may be selected from high temperature and high pressure drying using a supercritical equipment, CO ₂ low temperature and high pressure drying using a supercritical equipment, and atmospheric pressure drying in air.

The prior art produces a hydrogel having hydrophobicity through a multi-step process as described above. However, this is difficult to commercialize due to the disadvantages of high production cost and low productivity and continuity of the manufacturing process, such as the consumption of a large amount of organic solvent and a long hydrophobic reaction time.

The present invention to solve the above problems, the conventional sol-gel process and hydrophobic process to improve the process to a single process to induce a hydrophobic reaction at the same time sol-gel process even if the organic solvent is not used during the hydrophobic reaction It is an object of the present invention to provide a method for preparing a hydrophobic silica airgel and a hydrophobic silica airgel prepared by the method for producing a hydrophobic reaction within a time.

According to the present invention for achieving the above object, a step of obtaining a hydrophobization gel by adding a hydrophobization agent to the silica sol; Supercritical drying the hydrophobization gel; Provided is a method for producing hydrophobic silica airgel comprising a.

The hydrophobizing agent is a basic hydrophobizing agent, and the basic hydrophobizing agent is preferably at least one selected from the group consisting of HMDZ (Hexamethyl disilazane) and Lithium bis (trimethylsilyl) amide.

Wherein the basic hydrophobizing agent is present at 4 to 8 wt% with respect to 100 wt% of the silica sol.

The silica sol is preferably prepared by mixing TEOS (Tetra Ethyl Ortho Silicate), alcohol, water, acid catalyst.

The alcohol is preferably at least one selected from the group consisting of ethanol, isopropanol, methanol and butanol.

The acidic catalyst is preferably at least one selected from the group consisting of hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, trimethyl chlorosilane (TMCS) which is an acidic hydrophobic agent, and dimethyl chlorosilane (DMCS) which is an acidic hydrophobizing agent.

The step of supercritical drying the hydrophobization gel is heated and pressurized such that the hydrophobization gel is in a state of 30 ~ 80 ℃ temperature and 80 ~ 200 bar pressure, the pressure after drying the hydrophobization gel at the temperature and pressure It is preferable to reduce the pressure to atmospheric pressure.

Here it is preferred that the pressure and pressure is adjusted to a pressure of 3 ~ 5 bar per minute.

According to another aspect of the present invention, there is provided a hydrophobic silica airgel, which is prepared by the above methods.

Here, the silica airgel preferably has a density of 50 to 250 kg / m ³ , a specific surface area of 600 to 1500 m ² / g, a pore volume of 3 to 5 cc / g, and a pore size of 3 to 30 nm.

According to the present invention as described above, by improving the existing sol-gel process and hydrophobic process to one process to induce a hydrophobic reaction at the same time sol-gel process hydrophobization within a quick time even if the organic solvent is not used during the hydrophobization reaction There can be provided a method for producing a hydrophobic silica airgel capable of causing a reaction, and a hydrophobic silica airgel prepared by the method.

Accordingly, according to the present invention, the step of solvent replacement and surface modification of the hydrophilic gel prepared through the sol-gel process using a organic solvent and a hydrophobizing agent as in the prior art can be omitted.

According to the present invention, hydrophobic silica airgel can be produced quickly and at low cost by simultaneously performing a gelation reaction and a hydrophobic reaction without solvent replacement.

1 is a flow chart showing a method for producing a hydrophobic silica airgel according to the present invention in chronological order.
Figure 2 is a graph showing the results of the FT-IR structure analysis of silica airgel prepared according to the first embodiment of the present invention.
Figure 3 is a graph showing the results of the FT-IR structure analysis of silica airgel prepared according to the second and third embodiments of the present invention.

Hereinafter, a method of preparing a hydrophobic silica airgel according to a preferred embodiment of the present invention and a hydrophobic silica airgel manufactured by the method will be described in detail with reference to the accompanying drawings.

Figure 1 is a flow chart showing a method for producing a hydrophobic silica airgel according to the present invention in chronological order. As shown in Figure 1, the method for producing a hydrophobic silica airgel according to the present invention consists of the following steps.

First Step: Preparation of Silica Sol and Gelation by Basic Hydrophobization Agent

The molar ratio of TEOS (Tetra Ethyl Ortho Silicate): alcohol: water: acidic catalyst as a component molar ratio mixed to prepare a silica sol is 1: 20 to 26: 3 to 5: 0.001 to 0.004. According to the manufacturing conditions such as TEOS (Tetra Ethyl Ortho Silicate), the mixing ratio of each component of alcohol, water, acidic catalyst, and reaction temperature, the physical properties of the silica sol may be changed little by little. Silica sol can be obtained. (S100) A basic hydrophobizing agent is added at a weight ratio of 4 to 8 wt% relative to the silica sol, and then reacted for 1 to 2 hours to prepare a gel having hydrophobicity. (S200)

The alcohol used is mainly ethanol, isopropyl alcohol, methanol and butanol, etc., and mainly corresponds to a fourth-class alcohol. The acid catalyst used is preferably selected from the group consisting of hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. However, the present invention is not limited thereto, and trimethyl chlororosilane (TMCS) or dimethyl chlorosilane (DMCS), which may also serve as a catalyst as an acidic hydrophobic agent, may be selected.

In addition, the basic hydrophobization agent may be used such as HMDZ (Hexamethyl disilazane), Lithium bis (trimethylsilyl) amide.

Second Step: Carbon Dioxide Supercritical Drying of Hydrophobized Gel

The hydrophobic gel obtained in the first step was put into a carbon dioxide supercritical drying pressure vessel and heated and pressurized at a temperature of 30 to 80 ° C. and a pressure of 80 to 200 bar, and then carbon dioxide was flowed at a flow rate of 1 to 6 L / Min. After drying for 5 hours, the solvent in the hydrophobization gel may be extracted to dry the hydrophobic gel. (S300) When drying is completed, the pressure may be reduced to atmospheric pressure to remove carbon dioxide, thereby preparing a hydrophobic silica airgel. S400) Here, it is preferable to adjust the pressure of 3 to 5 bar per minute so that no sudden change in pressure occurs during pressurization and decompression. In particular, when the temperature decreases due to a rapid pressure reduction during decompression, carbon dioxide is dried ice, and thus, carbon dioxide is not removed from the inside of the gel, and the aerogel may contract or deteriorate in physical properties.

Process conditions of the supercritical drying is set to dry for 1 to 5 hours at a temperature of 30 ~ 80 ℃ and a pressure range of 80 ~ 200 bar, preferably at a temperature of 50 ~ 60 ℃ and a pressure range of 130 ~ 170 bar 3 Can be dried for hours.

Example 1

26 moles of ethanol (99% purity) and 5 moles of distilled water were mixed with TEOS for 1 minute on the basis of 1 mole of reagent TEOS (99% purity), and then 0.0027 moles of hydrochloric acid was added based on 1 mole of TEOS. The mixture was further stirred for a minute and subjected to hydrolysis for 60 minutes to prepare a silica sol, which is a mixed solution of TEOS, ethanol, water, and an acid catalyst. HMDZ (purity 95%) was mixed and stirred at a weight ratio of 4 wt% of the prepared silica sol, and then reacted for 120 minutes to prepare a hydrophobized gel.

The hydrophobized gel was placed in a pressure vessel (ethanol extraction tank) for carbon dioxide supercritical drying, then liquid carbon dioxide was poured into the pressure vessel (ethanol extraction tank) and heated and 5 bar per minute until temperature and pressure conditions of 60 ° C and 150bar were met. After pressurization, the temperature and pressure were maintained while flowing carbon dioxide at a flow rate of 3 L / Min for 3 hours.

During the process, the carbon dioxide extracts the solvent in the hydrophobization gel for 3 hours under pressure and moves to a separation tank for recovering ethanol to separate the ethanol. After 3 hours of pressurization, the ethanol contained in the hydrophobization gel is removed, and the hydrophobic silica airgel is finally separated by separating carbon dioxide from the dried hydrophobization gel while depressurizing 3 bar per minute until the pressure of 150 bar is at atmospheric pressure. Could get

The recovered aerogels had a density of 50 to 250 kg / m ³ , and specific surface area of 600 to 1500 m ² / g, pore volume of 3 to 5 cc / g and pore of 3 to 30 nm by BET and BJH measurement Physical properties with size are shown. The prepared hydrophobic silica airgel was confirmed to have a hydrophobic surface by FT-IR structure analysis results, and the results are shown in FIG. 2.

Examples 2-6 Example 6 Preparation of Airgel According to Basic Hydrophobizing Agent Content

Example 2

In Example 1, the basic hydrophobization agent was prepared in the same manner as in Example 1, except that 1 wt% of the silica sol was added.

Example 3

In Example 1, the basic hydrophobization agent was prepared in the same manner as in Example 1, except that 2 wt% of the silica sol was added.

Example 4

In Example 1, the basic hydrophobizing agent was prepared in the same manner as in Example 1, except that 6 wt% of the silica sol was added.

Example 5

In Example 1, the basic hydrophobization agent was prepared in the same manner as in Example 1, except that 8 wt% of the silica sol was added.

Example 6

In Example 1, except that 10 wt% of the basic hydrophobizing agent content compared to the silica sol was prepared in the same manner as in Example 1.

Referring to FIG. 3 showing the results of FT-IR structure analysis of Examples 2 and 3, when the ratio of the basic hydrophobization agent is less than 4 wt%, the amount of solution required for the hydrophobic reforming reaction is weak, unlike in Example 1 It was confirmed that the hydrophobic surface was close to hydrophilicity because the OH group peak was strong.

In addition, referring to Table 1, which shows the result of measuring the bulk density of the silica airgel powder prepared according to Examples 1 to 6, the hydrophobization agent ratio is greater than 8 wt% to confirm that the silica sol is not gelled. Could.

Example HMDZ content
[Wt% compared to silica] Bulk density
[kg / m ³ ] Hydrophobicity One 4 85 o 2 One 88 x 3 2 88 x 4 6 83 o 5 8 83 o 6 10 Not gelated -

Example  7 ~ Example  9: Preparation of Airgel According to Alcohol Type

Example 7

Except for using methanol (purity 99%) instead of ethanol in Example 1 was prepared in the same manner as in Example 1.

Example 8

Except for using butanol (purity 99%) instead of ethanol in Example 1 was prepared in the same manner as in Example 1.

Example  9

Except for using isopropanol (purity 99%) instead of ethanol in Example 1 was prepared in the same manner as in Example 1.

As a result of Examples 7 to 9, gelation was smoothly performed even by changing alcohol types. However, as shown in Table 2, butanol was the longest in the time of gelation, methanol and isopropanol was confirmed to take a similar gelation time as ethanol.

Alcohol type ethanol Isopropanol Methanol Butanol Gelation time 60 minutes 80 minutes 90 mins 300 minutes

Examples 10-13: Effect of the content of the acidic hydrophobization agent

Example 10

Example 1 was prepared in the same manner as in Example 1, except that 0.14 mol of TMCS instead of hydrochloric acid was added based on 1 mol of TEOS.

Example 11

In Example 1 was prepared in the same manner as in Example 1, except that 0.28 mol of TMCS instead of hydrochloric acid based on 1 mol of TEOS.

Example 12

In Example 1 was prepared in the same manner as in Example 1, except that 0.42 mol of TMCS instead of hydrochloric acid based on 1 mol of TEOS.

Example 13

In Example 1 was prepared in the same manner as in Example 1, except that 0.56 mol of TMCS instead of hydrochloric acid based on 1 mol of TEOS was prepared.

In Examples 10 to 13, when the molar ratio of TMCS exceeds 0.28 moles, the silica sol is not gelled, and below 0.28 moles shows a stable gelation reaction, and finally the prepared airgel has a hydrophobicity.

Claims (10)

Adding a hydrophobizing agent to the silica sol to obtain a hydrophobizing gel;
Supercritical drying the hydrophobization gel;
Hydrophobic silica airgel manufacturing method comprising a. The method according to claim 1,
The hydrophobizing agent is a basic hydrophobizing agent, wherein the basic hydrophobizing agent is at least one selected from the group consisting of Hexamethyl disilazane (HMDZ) and Lithium bis (trimethylsilyl) amide. The method according to claim 2,
Wherein the basic hydrophobizing agent is present in an amount of 4 to 8 wt% based on 100 wt% of the silica sol. The method according to claim 1,
The silica sol is prepared by mixing TEOS (Tetra Ethyl Ortho Silicate), alcohol, water and acid catalyst. The method of claim 4,
The alcohol is hydrophobic silica airgel production method characterized in that at least one selected from the group consisting of ethanol, isopropanol, methanol and butanol. The method of claim 4,
The acidic catalyst is hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, hydrophobic silica airgel, characterized in that at least one selected from the group consisting of acidic hydrophobizing agent (TMCS) (trimethyl chlororosilane) and acidic hydrophobizing agent (dimethyl chlorochlorosilane). . The method according to claim 1,
The step of supercritical drying the hydrophobization gel is heated and pressurized such that the hydrophobization gel is in a state of 30 ~ 80 ℃ temperature and 80 ~ 200 bar pressure, the pressure after drying the hydrophobization gel at the temperature and pressure A method for producing a hydrophobic silica airgel, characterized in that the pressure is reduced to atmospheric pressure. The method according to claim 7,
Hydrophobic silica airgel production method characterized in that the pressure and the pressure is reduced to 3 to 5 bar per minute during pressure reduction. Hydrophobic silica airgel prepared by any one of claims 1 to 8. The method according to claim 9,
The silica airgel is hydrophobic silica, characterized in that it has a density of 50 ~ 250 kg / m ³ , a specific surface area of 600 ~ 1500 m ² / g, a pore volume of 3 ~ 5 cc / g and a pore size of 3 ~ 30 nm Aerogels.

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