KR100975432B1 - Method of hydrophobic silica powders with low density - Google Patents

Abstract

The present invention relates to a process for producing low density hydrophobic silica powder. According to the preparation method of the present invention, an organic additive such as an acid / base catalyst, an emulsifier and a dispersant, which induces a gelation reaction by excluding the sol preparation step of acid or ion exchange treatment by obtaining a gel directly from an inexpensive water glass using alcohol. High porosity of more than 95% and low density of less than 0.1g / mL by completing the hydrophobization reaction in a short time without using a small amount of modifier and organic solvent and drying for a short time at low temperature below 200 ° C under normal pressure The hydrophobic silica powder having the composition can be prepared, and thus the silica powder can be prepared very economically and quickly and simply.

Water glass, alcohol, low density, hydrophobic, silica, airgel

Description

METHOD OF HYDROPHOBIC SILICA POWDERS WITH LOW DENSITY

The present invention relates to a method for producing a low density hydrophobic silica powder, and more particularly, an acid that induces a gelation reaction by excluding a sol preparation step of adding an acidic solution by obtaining a gel directly from an inexpensive water glass using alcohol. After drying the hydrophobization reaction in a short time without using additives such as emulsifiers and dispersants that stabilize the base catalyst and particles, and using a small amount of modifier and organic solvent, drying at a low temperature of less than 200 ° C. under normal pressure for a short time. The present invention relates to a method for producing a hydrophobic silica powder having a high porosity and low density of 95% or more.

Conventional silica powder synthesis technology is typically a wet process of acid-precipitated water glass to precipitate precipitated silica (precipitated silica) and hydrolyzed to a flame of high temperature 1000 ℃ or more using tetrachloride silane to fumed silica (fumed silica) It is divided into dry process to synthesize. In the case of the wet process, the acid treatment is required to neutralize the water glass and remove the salt. After drying, the powder has a relatively high density of about 0.3 g / mL and has a hydrophilic property on the surface. The dry process produces high purity silica with a low powder density of 0.05 g / mL, but uses toxic tetrachloride silane and requires high temperature thermal energy of at least 1,000 ° C. Since the silica obtained by the dry method and the wet method is a hydrophilic surface, a hydrophobic powder may be obtained by additionally performing a hydrophobic treatment process.

Although the silica powder has a hydrophilic surface having a hydroxyl group inherently, it is easy to modify the hydrophobic surface having a functional group such as a methyl group or a phenyl group on the surface through a hydrophobic reaction. Recently developed hydrophobic silica has been made from porous materials, commonly referred to as 'aerogels', and silica aerogels contain nano-sized pores in more than 90% of their interior space, resulting in very low densities of 0.1g / mL and below. It is attracting attention because of its high thermal insulation performance. In particular, the hydrophobic surface of the silica airgel powder is resistant to water, thereby preventing the collapse of the pore structure due to moisture when exposed to the external environment, and exhibits fluid-like fluidity, and is processed into a free shape according to the shape of the molded body. Contribute to

The production of hydrophobic silica powder containing pores varies slightly from producer to manufacturer, but the basic method of preparation is the same. A raw material solution made of silica is prepared, and a powder is obtained by performing a gelation reaction, a hydrophobization reforming reaction, and a final drying step.

Specifically, the first step obtains a sol (liquid phase) whose main component is silica from precursor raw materials such as metal alkoxide or water glass. The silica sol is divided into very small primary particles by hydrolysis, and when water glass is used as a precursor raw material, the silica sol is mixed with an acid solution or a cation exchange treatment to remove impurities Na ⁺ ions. The second step promotes the gelation reaction by changing the acidity of the total solution to gel the silica sol. To this end, acidic or basic catalyst materials are added, in particular surfactants, emulsifiers and the like are added for the purpose of stably maintaining the particles in powder form to obtain a wet gel having a hydrophilic surface in the form of particles. Hydrochloric acid, sulfuric acid, nitric acid, and the like are used as the acid catalyst, and ammonia water, pyridine, hydrazine, piperidine and the like are used as the base catalyst. Surfactant to stabilize particles, sorbitan monolaurate (span 20) sorbitan monooleate (span 80), polyoxyethylenesorbitan monooleate (Tween 80), lanolin (lanolin), metallic soap, rosin, cholesterin, lecithin, etc. are used, and the HLB value is designed according to the manufacturing purpose and one or more additives are used together. . In the third step, a reaction for reforming the hydrophilic surface into a hydrophobic surface is carried out, and solvent replacement / surface modification is performed in which water filling the mesh inside the gel is replaced with an organic solvent. For hydrophobic modification, a modifier having hydrophobic end groups such as methyl group and phenol group is added to react with hydroxyl end groups on the silica surface. Solvents used in this reaction are hexane (n-hexane), heptane (n-heptane), 2-propanol, and modifiers are chlorotrimethylsilane, hexamethyldisilazane, methyl Trimethoxysilane (methyltrimethoxysilane), trimethylethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, acrylated silane compound and the like are used. The fourth step is a drying step of volatilizing the organic solvent without destroying the pore structure formed inside the hydrophobic gel. Water molecules in the pores cause capillary forces during drying to shrink the gel structure, resulting in a small porosity solid. Therefore, the temperature increase rate, temperature range, holding time, etc. are important variables when drying under atmospheric pressure, and depending on the choice of the solvent of the previous step, it is very sensitive to physicochemical properties such as boiling point. Alternatively, the hydrophobic reforming and atmospheric drying of the third stage can be replaced by supercritical drying. The supercritical drying process is a process of removing pore water in a supercritical state in which there is no difference in interfacial tension between liquid and gas phase using a medium such as methanol or carbon dioxide (CO ₂ ). As it is operated at a high pressure of 70 bar or higher, a special apparatus such as an autoclave is required. As such a limited manufacturing method for the device, there is a problem to limit the mass production due to the increase in cost, and to increase the initial investment and operating costs. Therefore, in order to solve this problem, recently, an atmospheric pressure drying technique for drying hydrophobic gel in the air has been developed.

The present invention has been made to solve the above problems of the prior art, an object of the present invention is to provide a method for producing a simple and economical hydrophobic silica powder capable of mass production at a low cost without being limited to the apparatus. .

In particular, the silica powder manufacturing method provided according to the present invention can omit the pretreatment (acid solution mixing or ion exchange) for removing impurities in the water glass, as in the prior art, and to stabilize the gelation reaction and particles inside the solution. Alternatively, a low density hydrophobic powder can be produced quickly and at low cost without using an inorganic additive.

The above object of the present invention can be achieved by the present invention described below.

In order to achieve the above object, it has been devised,

The present invention comprises the steps of preparing an alcohol / water / n- hexane mixed solvent by stirring alcohol, water and n-hexane; Adding a water glass solution to the alcohol / water / n-hexane mixed solvent, stirring and gelling to obtain a wet gel; A surface modification / solvent replacement step of modifying the wet gel with a nonpolar organic solvent and an organosilane compound; It provides a method for producing a silica powder comprising a; drying step of drying the surface-modified gel for 1 to 6 hours at a temperature of 20 ~ 190 ℃ under atmospheric pressure.

The alcohol is a volume ratio (v / v) of 0.6 to 2 relative to the water glass, the water is a volume ratio of 0.5 to 1.4 (v / v) relative to the water glass, and the n-hexane is mixed in a volume ratio of 0 to 2 relative to the water glass (v / v) can be. Alcohol does not gel when the volume ratio of water glass is less than 0.6, and water does not gel when the volume ratio of water glass is greater than 1.4. In the case of n-hexane, even if the volume ratio with respect to the water glass does not affect the gelation progress.

The alcohol may be selected from one or more selected from the group consisting of ethanol, isopropyl alcohol, methanol and acetone, but is not limited thereto.

The method of preparing the silica powder may further include washing the wet gel one or more times with an acidic solution between the wet gel obtaining step and the surface modification / solvent replacement step.

The acid is preferably one or more selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and acetic acid, but is not limited thereto.

The non-polar organic solvent is at least one selected from the group consisting of isopropyl alcohol, n-hexane, n-heptane, xylene and cyclohexane, the organosilane compound is trimethylchlorosilane, hexamethyldisilazane, alkyltrialkoxy Silane (where the alkyl group may be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl, etc., the alkoxy group may be methoxy or ethoxy), trialkylalkoxysilane (where the alkyl group is methyl , Ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl and the like can be selected, the alkoxy group can be methoxy or ethoxy), acrylated silane compound (where acrylate is methacrylate, acryl Rate, and the like, and alkoxy group may be selected from the group consisting of methoxy or ethoxy, etc.), but is not limited thereto.

The amount of the non-polar organic solvent is preferably mixed at a volume ratio of 4 to 10 with respect to the wet gel, and the organosilane compound is mixed at a volume ratio of 2 to 4 with respect to the wet gel.

The drying step is preferably dried for 1 to 5 hours at a temperature of 20 ~ 70 ℃ and further drying for 0.2 ~ 1 hour at a solvent boiling point ~ 190 ℃, most preferred embodiment for 3 hours at 70 ℃ Dry and further dry at 150 ° C. for 1 hour. When the hydrophobized gel is drastically dried at a high temperature, cracking, shrinkage, or cracking occurs, such a problem is solved by heating in multiple stages to the boiling point of the solvent. If the heating is performed at a temperature below 20 ℃, the drying time becomes longer, the pores shrink and cracks may occur at temperatures above 190 ℃ .The heat treatment at a temperature of 400 to 500 ℃ causes the powder surface to become hydrophilic. Depends on the bonding strength of the hydrophobic surface groups. The same result can be obtained by drying for more than 4 hours, but the long drying process results in increasing the overall process time, thereby lowering the production yield.

The present invention also provides a silica powder prepared by the method for producing a silica powder described above. This silica powder may have a density of 0.03 to 0.10 g / mL and a porosity of 95 to 99%.

Hereinafter, the present invention will be described in detail.

Silica powder production method according to the present invention is composed of the following steps.

First step: alcohol / water / n- Hexane  By mixed solvent Gelation reaction

Alcohol, water, and n-hexane are mixed by stirring at a volume ratio of 0.6 to 2.0, 0.5 to 1.4, and 0 to 2.0, respectively, with respect to the volume of the water glass. The low density silica powder may be synthesized according to the process conditions such as the mixing ratio and stirring speed for each component of the mixed solvent of alcohol, water and n-hexane. The alcohol may be used one or more lower alcohols in the group consisting of ethanol, isopropyl alcohol, methanol and acetone.

Conventionally, the water glass solution was subjected to ion exchange or acid treatment to form a sol from which the sodium component was removed and then gelled. However, the present invention eliminates the sodium removal process drastically and allows the gel to be obtained directly from the water glass.

Second Step: Hydrophobic Reforming / Solvent Replacement Step

The wet gel obtained in the first step is modified with a nonpolar organic solvent and an organosilane compound and solvent-substituted. As the solvent used, non-polar organic solvents such as isopropyl alcohol, n-hexane, n-heptane, xylene or cyclohexane can be used, and the organosilane compound is trimethylchlorosilane, hexamethyldisilazane, alkyltrialkoxysilane (The alkyl group may be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl, etc., the alkoxy group may be methoxy or ethoxy), trialkylalkoxysilane (alkyl group is methyl, ethyl, Propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl and the like can be selected, the alkoxy group can be methoxy or ethoxy), acrylated silane compound (acrylate is selected from methacrylate, acrylate, etc.) And alkoxy groups may be combined with methoxy or ethoxy).

In addition, the amount of the solvent is preferably mixed in a volume ratio of 4 to 10 with respect to the wet gel, the organosilane compound in a volume ratio of 2 to 4 with respect to the wet gel. When the volume ratio of the solvent is greater than 10 and when the volume ratio of the organic silane compound is less than 2, the reaction time is long and does not occur in a complete surface modification reaction within 3 hours, and when the volume ratio of the solvent is less than 4 and the volume ratio of the organic silane compound is If it is greater than 4, the pore structure of the wet gel shrinks due to a sudden reaction, and the density increases, or cracks occur due to dry shrinkage.

Between the first step of obtaining the wet gel and the surface modification / solvent replacement step of the two steps, may further comprise the step of washing the wet gel with an acidic solution one or more times.

The acid is preferably one or more selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and acetic acid, but is not limited thereto.

Step 3: drying

The surface modified gel is dried for 1 to 6 hours at a temperature of 20 ~ 190 ℃ under atmospheric pressure. Moreover, when drying for 3 hours at a temperature of 70 ℃ and further drying for 1 hour at a temperature of 150 ℃, it is possible to further prevent cracking or cracking that may occur when drying the hydrophobized gel. Since the substituted solvent shrinks the silica structure while being volatilized at a rapid rate in the wet gel for a short time, internal cracks may be generated, cracked, or broken, and may be prevented by drying through the multi-step drying process. If the heating is performed at a temperature below 20 ℃, the drying time becomes longer, the pores shrink and cracks may occur at temperatures above 190 ℃ .The heat treatment at a temperature of 400 to 500 ℃ causes the powder surface to become hydrophilic. Depends on the bonding strength of the hydrophobic surface groups. The same result can be obtained by drying for more than 4 hours, but the long drying process results in extending the overall process time, thereby lowering the production yield.

As described above, the method for producing silica powder according to the present invention is a hydrophobic silica powder, in particular 0.1 g in the process of obtaining a gel directly from the water glass using a cheap alcohol without the sol-gel process hydrophobic silica powder A powder having a low density of less than / mL and a very high porosity of more than 95% and nanopores can be synthesized. Thus, a process for preparing a liquid sol which is a silica main component without using an acid or ion exchange resin to remove sodium The organic additives such as emulsifiers and dispersants necessary for the formation of powders may not be used, and pH adjusting agents and base catalysts that induce gelation reactions are not used. Using organic solvent, the overall process for powder synthesis such as sol-gel, hydrophobization, atmospheric drying It is a fast process that can be completed.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

Example  One

Commercial water glass (manufacturer: one mythology, No. 3, SiO ₂ 29.8% by weight) and water was added to 566.67㎖ 71㎖ was prepared a water-glass solution containing SiO ₂ of 4.35% by weight, by taking a part of the next step 60㎖ Used for. 40 ml of ethanol corresponding to 2/3 and 60 ml of water corresponding to 1/1 were first mixed and then stirred at a high speed of 6,000 rpm using a dispenser to prepare a mixed solvent of ethanol and water. 60 ml of the water glass prepared above was added thereto, followed by further stirring for 2 minutes to proceed the gelation reaction to produce a wet gel.

The resulting wet gel was observed to separate layer with an organic solvent over time, and the wet gel was separated and recovered. The entire process of obtaining the gel from the water glass did not exceed 30 minutes. Isopropyl alcohol, n-hexane, trimethylchlorosilane was mixed in order to prepare a solvent to modify the hydrophobic surface, the gel was added to the surface modification and solvent replacement reaction for 3 hours at room temperature. The surface-modified gel was dried at 70 ° C. for 3 hours at atmospheric pressure using a drying oven and then at 150 ° C. for 1 hour to obtain a powder.

As a result of measuring the bulk density according to the KS test standard (L 1621: 2003), the obtained powder obtained a low density silica powder of 0.053 g / mL. Since the theoretical density of amorphous silica is 2.2g / mL, it could be confirmed that the synthesized silica was a porous material filled with air of 97.6% (porosity). The prepared powder was confirmed to have a hydrophobic surface by Fourier Transformation Infrared Spectroscopy (FTIR) spectroscopy, and the results are shown in FIG. 1.

Example  2 to Example  7: Preparation of Silica Powder According to Alcohol (Ethanol) Content

Example  2

In Example 1, 20 ml (corresponding to 1/3 based on water glass volume) was further added to the ethanol / water mixture solution to prepare a mixed solution, and hydrochloric acid was removed to remove Na from the gel. After the second washing was carried out in the same manner as in Example 1 except that the silica powder was prepared.

Example  3

A water / n-hexane mixed solution was prepared in the same manner as in Example 2, except that silica powder was prepared without using ethanol in Example 2.

Example  4

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 20 ml of ethanol (volume corresponding to 1/3 of water glass volume).

Example  5

In Example 2, the same procedure as in Example 2 was carried out except that silica powder was prepared using 50 ml of ethanol (volume corresponding to 5/6 based on water glass volume).

Example  6

A silica powder was prepared in Example 2 except that 60 ml of ethanol (volume corresponding to 1/1 based on the volume of water glass) was prepared in the same manner as in Example 2.

Example  7

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 120 mL of ethanol (volume corresponding to 2/1 based on water glass volume).

As in Example 3 and Example 4, the gelation reaction did not occur under process conditions without ethanol or very small amount of ethanol, and thus powder could not be synthesized. The prepared powder was confirmed to have a hydrophobic surface by Fourier Transformation Infrared Spectroscopy (FTIR) spectroscopy, and the results are shown in FIG. 1. In addition, the bulk density of the silica powders prepared in Examples 2 to 7 was measured and the results are shown in Table 1. As a result of EDAX component analysis of the powder using the scanning electron microscope of FIG. 2, the silica powder prepared using 1/1 of ethanol relative to the volume of water glass did not show sodium (Na) component in the water glass, and was made of silica only. It was confirmed that.

Example  8 to Example  12: Preparation of Silica Powder According to Alcohol (Isopropyl Alcohol) Content

Example  8

In Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 40 ml (volume equivalent to 2/3 of water glass volume) in place of ethanol.

Example  9

It was prepared in the same manner as in Example 8, except that silica powder was prepared using 20 mL of isopropyl alcohol (volume corresponding to 1/3 of water glass volume) in Example 8 at all times.

Example  10

It was prepared in the same manner as in Example 8, except that silica powder was prepared by using 30 ml of isopropyl alcohol (volume equivalent to 1/2 of water glass volume) in Example 8 at all times.

Example  11

It was prepared in the same manner as in Example 8, except that silica powder was prepared by using 50 ml of isopropyl alcohol (volume corresponding to 5/6 based on water glass volume) in Example 8 at all times.

Example  12

It was prepared in the same manner as in Example 8, except that silica powder was prepared by using 60 ml of isopropyl alcohol (volume corresponding to 1/1 on the basis of water glass volume) in Example 8 at all times.

Example  13

It was prepared in the same manner as in Example 8, except that silica powder was prepared by using 120 mL of isopropyl alcohol (volume corresponding to 2/1 based on water glass volume) in Example 8 at all times.

As in Example 9, the gelation reaction did not occur under the process conditions where the amount of isopropyl alcohol was very small, and thus powder could not be synthesized. In addition, the bulk density of the silica powder prepared in Examples 9 to 13 was measured and the results are shown in Table 1.

Example  14- Example  19: Preparation of Silica Powder According to Water Content

Example  14

Except for using a ethanol / n-hexane mixed solution without using water in Example 2 was prepared in the same manner as in Example 2 except that the silica powder was prepared.

Example  15

In Example 2, except that the silica powder was prepared using 30 ml of water (volume equivalent to 1/2 based on the volume of water glass) was prepared in the same manner as in Example 2.

Example  16

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 70 ml of water (volume corresponding to 7/6 based on water glass volume).

Example  17

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 80 ml of water (volume corresponding to 4/3 of water glass volume).

Example  18

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 90 ml of water (volume corresponding to 3/2 of water glass volume).

Example  19

Example 2 was prepared in the same manner as in Example 2, except that silica powder was prepared using 120 mL of water (volume corresponding to 2/1 based on the volume of water glass).

In the composition regions in Examples 18 and 19, no gelation reaction occurred, and thus powder could not be synthesized. In addition, the bulk density of the silica powder prepared in Examples 14 to 17, which are the following conditions, was measured, and the results are shown in Table 1.

Example  20 ~ Example  24: Preparation of Silica Powder with and without Hydrochloric Acid

Example  20

In Example 2, the silica powder was synthesized by omitting the process of washing with hydrochloric acid to remove the Na component of the gel and performing the same process as in Example 2.

Example  21

Example 20 was prepared in the same manner as in Example 20, except that silica powder was prepared using 20 ml of ethanol (volume corresponding to 1/3 of water glass volume).

Example  22

Example 20 was prepared in the same manner as in Example 20, except that silica powder was prepared using 50 ml of ethanol (volume corresponding to 5/6 based on water glass volume).

Example  23

Example 20 was prepared in the same manner as in Example 20, except that silica powder was prepared using 60 ml of ethanol (volume corresponding to 1/1 based on water glass volume).

Example  24

Example 20 was prepared in the same manner as in Example 20, except that the silica powder was prepared using 120 mL of ethanol (volume corresponding to 2/1 based on the volume of water glass).

In Example 21, a gelation reaction did not occur, and thus powder could not be synthesized, but in Example 20 and Examples 22 to 24, low density silica powder of 0.1 g / mL or less was obtained. As a result of EDAX component analysis using the scanning electron microscope of FIG. 3, the silica powder prepared without the wet gel after the gelation reaction as in Example 2 did not show sodium (Na) component present in the water glass. I could confirm it. Table 1 shows the density measurement results of the synthesized silica powder.

Example  25- Example  27: n- Hexane  Preparation of Silica Powder According to Content

Example  25

In Example 20 was prepared in the same manner as in Example 20, except that the silica powder was prepared using 40 mL (volume corresponding to 2/3 of the water glass volume).

Example  26

In Example 20 was prepared in the same manner as in Example 20, except that the silica powder was prepared using 60 mL (volume corresponding to 1/1 on the basis of water glass volume).

Example  27

In Example 20 was prepared in the same manner as in Example 20, except that the silica powder was prepared using 120 mL (volume corresponding to 2/1 on the basis of water glass volume).

Although n-hexane is added in Examples 25 to 27 to form fine bubbles in the water / alcohol / n-hexane mixed solution to prevent agglomeration during the gelation process, n-hexane in Example 1 It can be seen that even without the addition of silica powder of low density without affecting the gelation of water glass. As a result, it was confirmed that low density silica powder of 0.1 g / mL or less could be prepared regardless of the content of n-hexane.

Example  28 and Example  29: At the stirring speed  Of silica powder according to

Example  28

The preparation was carried out in the same manner as in Example 20, except that silica powder was prepared by using a stirring speed of 600 rpm to prepare a mixed solvent of ethanol, water, and n-hexane in Example 20.

Example  29

The preparation was carried out in the same manner as in Example 20, except that silica powder was prepared at the stirring speed of 9000 rpm in the preparation of a mixed solvent of ethanol, water, and n-hexane in Example 20.

The silica powders prepared in Examples 28 and 29 both had a low density and a hydrophobic surface of 0.1 g / mL or less.

Comparative example

To remove the sodium (Na) component from commercial water glass (manufactured by Ilshin Chemical, No. 3, 29.8 wt.% SiO ₂ ), Na cation using a cation exchange resin Amberlite (Amberlite IR-120H +, Rohm and Haas, France) was used. ^Through the ion exchange process between ⁺ ions and H ⁺ ions, a liquid sol mainly composed of silica was prepared. To 60 ml of a mixed solvent of isopropyl alcohol and n-hexane (2: 1 (v / v)) was added 60 ml of a silica sol prepared by stirring at a high speed of 9,000 rpm using a dispenser. In order to induce the gelation reaction, 2 ml of ammonia water was added, followed by further stirring for 2 minutes to obtain a gelled wet gel. Thereafter, silica powder was prepared in the same manner as in Example 1 by hydrophobic modification, solvent substitution, and drying under atmospheric pressure. The bulk density of the silica powder was 0.120 g / mL, and it was confirmed that it was modified hydrophobicly. As a result of EDAX component analysis of the powder using a scanning electron microscope, it was confirmed that the sodium (Na) component present in the water glass in Figure 4 does not appear.

Comparative example  2

In the same manner as in Example 1, a cation exchange treatment was performed to prepare a silica sol. 300 ml of a mixed solution containing lanolin as a dispersant and pyridine as a basic substance was prepared in n-hexane, and the amount of lanolin was mixed in 0.3 weight ratio with respect to n-hexane and pyridine in 0.13 volume ratio. 40 ml of silica sol was added to the n-hexane / lanolin / pyridine mixed solution and stirred to obtain a gelled wet gel. Thereafter, the surface modification reaction was carried out in the same manner as in Example 1 except that the surface modification reaction was carried out for atmospheric pressure drying in the air. The bulk density of the silica powder was 0.127 g / mL, and it was confirmed that the silica powder was hydrophobically modified.

Comparative example  3

In the same manner as in Example 1, a cation exchange treatment was performed to prepare a silica sol. 300 ml of a mixed solution containing span80 as an emulsifier and ammonia water as a basic catalyst was prepared in n-hexane. 20 ml of silica sol was added to the n-hexane / span80 / ammonia water solution and stirred to obtain a gelled wet gel. Then, it was prepared by performing the surface modification and atmospheric pressure drying in the same manner as in Example 1. The bulk density of the silica powder was 0.094 g / mL, and it was confirmed that the silica powder was hydrophobically modified.

Very low 0.054 g / mL according to Example 1 of the present invention, even if the ion exchange process of Comparative Example 1 was omitted or no additives such as lanolin and pyridine or lanolin and ammonia water were used compared to Comparative Examples 2 and 3 It can be seen that hydrophobic silica powder having a density can be prepared.

The bulk density of the silica powders prepared in Examples 1 to 29 and Comparative Examples 1 to 3 are collectively shown in Table 1 below.

Example No. Bulk density (g / mL) Example 1 0.054 Example 2 0.086 Example 3 Gelation does not proceed Example 4 Gelation does not proceed Example 5 0.072 Example 6 0.034 Example 7 0.052 Example 8 0.062 Example 9 Gelation does not proceed Example 10 0.055 Example 11 0.057 Example 12 0.051 Example 13 0.072 Example 14 0.233 Example 15 0.114 Example 16 0.081 Example 17 0.146 Example 18 Gelation does not proceed Example 19 Gelation does not proceed Example 20 0.055 Example 21 Gelation does not proceed Example 22 0.066 Example 23 0.042 Example 24 0.062 Example 25 0.088 Example 26 0.054 Example 27 0.079 Example 28 0.053 Example 29 0.094 Comparative Example 1 0.120 Comparative Example 2 0.127 Comparative Example 3 0.094

1 is a view showing the results measured by the FTIR spectroscopy of the silica powder prepared according to Examples 1 and 2 of the present invention.

2 is a graph of EDAX component analysis of a silica powder prepared according to Example 6 of the present invention using a scanning electron microscope.

3 is a graph showing the results of EDAX component analysis of a silica powder prepared according to Example 20 of the present invention using a scanning electron microscope.

4 is a graph of EDAX component analysis of a silica powder prepared according to the prior art using a scanning electron microscope.

Claims (11)

Stirring the alcohol and water to prepare an alcohol / water mixed solvent; Adding a water glass solution to the alcohol / water mixed solvent and stirring to gelate to obtain a wet gel; A surface modification / solvent replacement step of modifying the wet gel with a nonpolar organic solvent and an organosilane compound; Drying step of drying the surface-modified gel for 1 to 6 hours at a temperature of 20 ~ 190 ℃ under atmospheric pressure; Method for producing a silica powder comprising the. The method of claim 1, The alcohol is a method of producing a silica powder, characterized in that mixed in a volume ratio (v / v) of 0.6 to 2 with respect to the water glass, the water ratio of the volume ratio (v / v) of 0.5 to 1.4 with respect to the water glass. The method of claim 1, The alcohol is a method of producing a silica powder, characterized in that at least one selected from the group consisting of ethanol, isopropyl alcohol, methanol and acetone. The method of claim 1, The nonpolar organic solvent is at least one selected from the group consisting of isopropyl alcohol, n-hexane, n-heptane, xylene and cyclohexane, Wherein said organosilane compound is selected from the group consisting of trimethylchlorosilane, hexamethyldisilazane, alkyltrialkoxysilane, trialkylalkoxysilane, and acrylated silane compound. The method of claim 1, The non-polar organic solvent is used in a volume ratio of 4 to 10 with respect to the wet gel, and the organosilane compound is mixed with a volume ratio of 2 to 4 with respect to the wet gel. The method of claim 1, The drying step is a method for producing a silica powder, characterized in that the drying for 1 to 5 hours at a temperature of 20 ~ 70 ℃ and further drying for 0.2 ~ 1 hour at a solvent boiling point ~ 190 ℃ temperature. The method of claim 1, Between the step of obtaining the wet gel and the surface modification / solvent replacement step, the method of producing a silica powder further comprising the step of washing the wet gel with an acidic solution one or more times. The method of claim 7, wherein The acid is a method of producing a silica powder, characterized in that at least one selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and acetic acid. A silica powder prepared by the method for producing a silica powder according to claim 1, wherein the silica powder has a density of 0.03 to 0.10 g / mL and a porosity of 95% to 99%. delete The method of claim 1, The alcohol / water mixed solvent is n- hexane prepared by the silica powder, characterized in that further comprising a volume ratio of more than 0 ~ 2 compared to the water glass.

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