WO2023249291A1

WO2023249291A1 - Aerogel preparation method

Info

Publication number: WO2023249291A1
Application number: PCT/KR2023/007844
Authority: WO
Inventors: 최익준; 장주영; 최강희; 이찬형; 강동희; 최정원; 박병제
Original assignee: 주식회사 엔에스앤티
Priority date: 2022-06-24
Filing date: 2023-06-08
Publication date: 2023-12-28
Also published as: KR20240002166A; KR102534702B1

Abstract

The present invention provides an aerogel preparation method comprising the steps of: reacting water glass and a first material in a reaction bath to obtain a hydrogel; transferring the hydrogel into a solvent replacement bath and then reacting the hydrogel and a second material in the solvent replacement bath to obtain an organogel; and transferring the organogel into a dryer and then drying the organogel in the dryer to obtain an aerogel powder, wherein the first material includes pure water, HMDS, and nitric acid, and the nitric acid is introduced into the reaction bath after HMDS.

Description

Airgel manufacturing method

The present invention relates to a method for producing airgel with a base base.

In general, aerogels have high porosity of up to 99%, low refractive index of 1.01 to 1.1, high transparency of over 90%, and high specific surface area of over 1000 m ² /g. It is an advanced material with characteristics such as very low thermal conductivity of less than 0.02 W/mK.

Airgel, which has these characteristics, is evaluated as having high applicability as an energy and environmental material, and a material for the advancement of the electronics industry due to its unique thermal, electrical, and optical properties. Therefore, this material is being attempted to be applied as an ultra-insulating material, acoustic wave delay material, catalyst carrier, and interlayer insulating material for high-speed circuits of next-generation semiconductors.

Despite these excellent properties, airgel has many difficulties in the manufacturing process when mass-producing it for commercial purposes. Manufacturing takes a long time, and a lot of money must be invested to build production facilities. Additionally, the quality of mass-produced airgel may be lower than when produced in small quantities in a laboratory.

One object of the present invention is to provide a method for manufacturing airgel that can shorten production time and improve production equipment efficiency.

Another object of the present invention is to provide a method for manufacturing airgel that can improve the quality of the final product in addition to improving productivity as described above.

1. A method for producing airgel according to an aspect of the present invention includes the steps of reacting water glass and a first material in a reaction tank to obtain a hydrogel; Moving the hydrogel to a solvent exchange tank and then reacting the hydrogel with a second material in the solvent exchange tank to obtain an organogel; And after moving the organogel to a dryer, drying the organogel in the dryer to obtain airgel powder, wherein the first material includes pure water, HMDS, and nitric acid, and the nitric acid is next to the HMDS. It can be added to the reaction tank.

2. In the first embodiment above, the solvent may be added to the solvent exchange tank without adding the solvent to the reaction tank.

3. In embodiment 1-2, no second material is added to the reaction tank, and the second material may include n-hexane.

4. In embodiments 1-3, the method includes reacting water glass and a first material in a reaction tank to obtain a hydrogel; Moving the hydrogel to a solvent exchange tank and then reacting the hydrogel with a second material in the solvent exchange tank to obtain an organogel; And after moving the organogel to a dryer, drying the organogel in the dryer to obtain airgel powder, wherein the first material includes pure water, HMDS, and nitric acid, and the nitric acid is next to the HMDS. It is added to the reaction tank, no second material is added to the reaction tank, and the second material may include n-hexane.

5. In embodiments 1-4, the nitric acid may be introduced through the bottom of the reaction tank and first mixed with the water glass and pure water mixture before reacting with the HMDS.

6. In embodiments 1-5, while the mixed solution of water glass, pure water, and HMDS is stirred in the reaction tank, the nitric acid may be introduced along the wall of the reaction tank and react with the HMDS.

7. In embodiments 1-6, after the hydrogel is moved to the solvent exchange tank, a step of cleaning the reaction tank may be further provided.

8. In embodiments 1-7, after the hydrogel is moved to the solvent exchange tank, the step of cleaning the reaction tank includes spraying pure water on the inner surface of the reaction tank while rotating the spray nozzle 360°. can do.

9. In embodiments 1-8, the second material may include n-hexane.

10. In embodiments 1-9 above, there is no organogel in the reaction tank.

11. In embodiments 1-10, the solvent substitution tank may be made of a material with lower corrosion resistance, acid resistance, and high-temperature strength than the reaction tank.

12. In embodiments 1-11, further comprising discharging wastewater generated with the organogel in the solvent displacement tank before moving the organogel to the dryer, wherein the step of discharging the wastewater includes, The controller may include controlling the opening and closing of a discharge valve for discharging the wastewater based on the level of the wastewater measured by a level sensor.

13. In embodiments 1-12, the level sensor may be a radar-type sensor that is installed in the solvent substitution tank and emits electromagnetic waves in a direction toward the interface between the organogel layer and the wastewater layer.

14. In embodiments 1-13, after the organogel is moved to the dryer, a step of washing the solvent replacement tank may be further provided.

15. In embodiments 1-14, after the organogel is moved to the dryer, the step of cleaning the solvent displacement tank includes spraying n-hexane on the inner surface of the solvent displacement tank while rotating the spray nozzle 360°. It may include steps.

16. Another aspect of the present invention relates to airgel. The airgel was manufactured by the method 1-15 above. The airgel may have a thermal conductivity of less than 0.020 W/mK and an apparent density of less than 0.09 g/cm ³ .

17. In the above 16 embodiments, the airgel has mesopores, and in SEM image analysis at 20,000 magnification, the number of mesopores of 500 nm or more per area of 3㎛ x 5㎛ may be 6 or more.

According to the airgel production method according to the present invention configured as described above, hydrogel is obtained from water glass in a reaction tank, then the hydrogel is moved to a solvent replacement tank to obtain organogel, and then airgel powder is obtained through drying in a dryer. While the substitution process is in progress for a long time in the tank, the next round of reaction takes place in the reaction tank, thereby significantly shortening the overall production time.

In addition, since the organogel is produced separately in the solvent exchange tank, disturbance of raw material mixing due to the organogel remaining in the reaction tank can be structurally prevented compared to the case where the organogel is produced in the reaction tank. Due to the absence of this disturbance, the quality of the final produced airgel can also be improved.

In addition, even when airgel is manufactured using a base base, the explosive reaction between HMDS and nitric acid can be prevented by introducing nitric acid through the lower channel or wall channel of the reaction tank. This lowers the sensitivity and risk of the reaction process and makes it possible to obtain higher quality airgel.

Figure 1 is a flowchart showing an airgel manufacturing method according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing the arrangement of the manufacturing equipment 100 and the input of materials for implementing the manufacturing method of FIG. 1.

Figure 3 is a diagram showing the chemical reaction equation for producing airgel.

FIG. 4 is a conceptual diagram showing the specific structure of the reaction tank 110 of FIG. 2.

Figure 5 is a conceptual diagram showing the specific structure of the solvent substitution tank 130 of Figure 2.

Figure 6(A) is a SEM image of the airgel powder prepared in the comparative example at x1500 magnification, and Figure 6(B) is an SEM image of the airgel powder prepared in the example at x1500 magnification.

Figure 7(A) is a SEM image of the airgel powder prepared in the comparative example at x5000 magnification, and Figure 7(B) is an SEM image of the airgel powder prepared in the example at x5000 magnification.

Figure 8(A) is a SEM image of the airgel powder prepared in the comparative example at a magnification of x20,000, and Figure 8(B) is a SEM image of the airgel powder prepared in the example at a magnification of x20,000.

Hereinafter, an airgel manufacturing method according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. In this specification, the same or similar reference numbers are assigned to the same or similar components even in different embodiments, and the description is replaced with the first description.

Figure 1 is a flowchart showing an airgel manufacturing method according to an embodiment of the present invention, and Figure 2 is a conceptual diagram showing the arrangement of the manufacturing equipment 100 and material input for implementing the manufacturing method of Figure 1.

Referring to these drawings, airgel production begins with a step (S1) of reacting water glass and the first material.

The first water glass introduced into the reaction tank 110 is sodium silicate (Na ₂ SiO ₃ ). Before the water glass is introduced from the storage tank into the reaction tank 110, the amount required for the reaction can be measured and placed on standby. Water glass can be put into the reaction tank 110 in a short time by gravity.

After the water glass is added to the reaction tank 110, the first material is added to the reaction tank 110. Specifically, the first material may include demineralized water, HMDS (Hexamethyldisilazane), and nitric acid. These must be sequentially added to the reaction tank 110.

Since water glass and pure water do not mix well due to the large difference in specific gravity, an agitator can be installed in the reaction tank 110 and stirred to ensure sufficient mixing. When adding raw materials, HMDS is added at 1-minute intervals while water glass and pure water are being stirred. After 3 minutes, nitric acid (HNO ₃ ,60%) can be done in a way that is invested. It is preferable that the stirring mechanism is continuously operated so that they are well mixed during the reaction.

As pure water is added to the water glass, the water glass is hydrolyzed to create an aqueous water glass solution. As HMDS and nitric acid are added, the property changes to a gel and the pH concentration begins to be neutralized. The total process time in the reaction tank 110 is less than 20 minutes.

For the reaction between water glass and the first material, the internal temperature of the reaction tank 110 should be about 45-50°C. To this end, a heating jacket surrounding the housing of the reaction tank 110 heats the reaction tank 110 using hot water. As the reaction proceeds smoothly, the internal temperature of the reaction tank 110 may be about 60°C.

The chemical formula for the above reaction is shown in Figure 3. Referring further to FIG. 3, when HMDS and nitric acid react, ammonia (NH ₃ ) is produced, and this gas is treated with a scrubber (190). Treated wastewater is sent to a wastewater treatment plant where it is treated. Whether the reaction in the reaction tank 110 is complete can be determined by checking the pH of the reactant.

Upon completion of the reaction, hydrogel is formed in the reaction tank 110. The generated hydrogel is discharged from the reaction tank 110.

After the reaction tank 110 is emptied, cleaning of the reaction tank 110 may be performed. For cleaning, a spray nozzle is operated within the reaction tank 110. The spray nozzle can spray pure water onto the inner surface of the reaction tank 110 while rotating 360°. As a result, the reaction tank 110 receives the next round of water glass and the first material in a cleanly cleaned state. The cleaned wastewater is sent to a wastewater treatment device for treatment.

The hydrogel discharged from the reaction tank 110 is moved to another container, that is, the solvent replacement tank 130 (S3). The solvent substitution tank 130 may be manufactured differently from the reaction tank 110 in terms of materials. Specifically, the reaction tank 110 must be made of, for example, STS316L in order to respond to corrosion and temperature decrease in response to strong acids and strong bases. On the other hand, since this is not the case for the solvent substitution tank 130, STS304, a material with lower corrosion resistance, acid resistance, and high-temperature strength than the reaction tank 110, is sufficient.

Accordingly, the solvent substitution tank 130 can be manufactured at 40% of the material cost compared to the reaction tank 110. Since the solvent displacement tank 130 must be twice the size of the reaction tank 110, even if they are manufactured separately, the overall cost is further reduced compared to the case where only the reaction tank 110 is manufactured in a larger size.

In the solvent replacement tank 130, n-hexane, for example, is added as a second material to the hydrogel (S5). Hydrogel undergoes a condensation reaction with n-hexane and is replaced with organogel and water. The substitution process is completed within about 40 minutes while maintaining the temperature of 50°C at normal pressure. This time is approximately twice that of the time in the reaction tank 110. Water (wastewater) is discharged to a wastewater treatment device, which is explained with reference to FIG. 5.

Referring again to FIGS. 1 and 2, the organogel is moved to the dryer 150 (S7). After the solvent displacement tank 130 is emptied, the solvent displacement tank 130 can be cleaned. This can be achieved by spraying n-hexane into the solvent substitution tank 130. n-hexane can be sprayed to every corner of the inner surface of the solvent replacement tank 130 by rotating the spray nozzle 360°.

Within the dryer 150, the organogel becomes airgel powder through a drying process (S9). Specifically, the organogel introduced into the dryer 150 is stirred at a temperature of about 130°C and under vacuum. Accordingly, n-hexane and residual moisture evaporate, and the organogel undergoes a phase transformation into a solid state. n-hexane may be separated and sent to the condenser 170, liquefied, separated, and reintroduced into the solvent replacement tank 130. The reuse rate of n-hexane can be around 90%, and a certain amount may need to be discharged periodically to maintain quality. To compensate for this, new n-hexane can be additionally mixed with the recycled n-hexane. Through drying, the airgel powder is subjected to shear force and its pores are homogenized. Airgel powder is sent to silos, stored, and can be shipped in required quantities.

In the above, the method of adding nitric acid to the reaction tank 110 is described with reference to FIG. 4. FIG. 4 is a conceptual diagram showing the specific structure of the reaction tank 110 of FIG. 2.

Referring to this drawing, the reaction tank 110 includes a housing 111 having an internal space. A stirring mechanism 113 is installed in the internal space. A lower input channel 115 is formed in the lower part of the housing 111. The lower input channel 115 may be provided with a valve (not shown) responsible for opening and closing the channel. An inner wall input channel 117 is formed in the upper part of the housing 111. The inner wall input channel 117 may be the inner wall of the housing 111 itself, a groove formed in the inner wall, or a pipe attached to the inner wall.

In the case of a base-based process, HMDS (H) is added to the mixture (M) of water glass and pure water. HMDS (H) is a hydrophobic liquid, so it does not easily mix with the mixed solution (M). In that state, when stirring is performed using the stirring mechanism 113, the middle part of the layer formed by HMDS (H) becomes thick according to the inertial momentum. On the other hand, the closer it is to the inner wall of the housing 111, the thinner the layer of HMDS (H) becomes.

If nitric acid is added to the middle part under these conditions, an explosive reaction will occur between nitric acid and HMDS(H), resulting in great danger. To solve this problem, the present inventor came up with the following two methods.

The first is to slowly inject nitric acid through the lower injection channel 115. In that case, nitric acid is first mixed with the mixed solution (M) before reacting with HMDS (H). Accordingly, nitric acid can react little by little with HMDS(H).

Second, nitric acid is slowly injected along the inner wall of the housing 111 through the inner wall injection channel 117. In that case, nitric acid may react slowly with the thin portion of the HMDS(H) layer.

By this method, it is possible to obtain airgel of superior quality than the acid-based process while effectively controlling the sensitivity and risk of the process in the base-based process.

The solvent substitution tank 130 will be further described with reference to FIG. 5 . Figure 5 is a conceptual diagram showing the specific structure of the solvent substitution tank 130 of Figure 2.

Referring to this figure, organogel (O) and wastewater (W) are generated within the housing 131 of the solvent substitution tank 130 according to a condensation reaction. Here, the organogel (O) is located on the upper side of the wastewater (W) due to the difference in specific gravity. Depending on the operation of the stirring mechanism within the housing 131, layer separation of the organogel (O) and the waste water (W) may occur more easily.

Wastewater (W) must be discharged to the wastewater treatment device through the discharge valve (133). The discharge valve 133 must be controlled to open only until the waste water (W) is discharged. To this end, a controller (not shown) that controls the opening and closing of the discharge valve 133 operates based on the detection result of the level sensor 135.

The level sensor 135 measures the water level of the wastewater (W) by measuring the interface (I) between the organogel (O) and the wastewater (W). For this purpose, the level sensor 135 may be a radar-type sensor installed in the housing 131. Accordingly, the level sensor 135 can measure the height of the interface I in a non-contact manner by emitting electromagnetic waves in a direction toward the interface I.

The controller controls the discharge valve 133 based on the detection result of the level sensor 135, so that the discharge valve 133 can be opened and closed according to the exact level of the wastewater (W). This prevents loss of not only wastewater (W) but also organogel (O).

After discharging the wastewater (W), the organogel (O) can be moved to the dryer (150) through another line (137). Furthermore, ammonia generated within the housing 131 may be moved to the scrubber 190 through a separate line 139.

The airgel manufacturing method as described above is not limited to the configuration and operation method of the embodiments described above. The above embodiments may be configured so that various modifications can be made by selectively combining all or part of each embodiment.

Example

24.55 kg of water glass, 117.27 kg of pure water, and 12.27 kg of HMDS were added to the reaction tank and stirred to prepare a mixture. After reacting by adding 14.73 kg of nitric acid to the mixture to prepare a hydrogel, the hydrogel was transferred to a solvent replacement tank and reacted with 90 kg of n-hexane at 50°C to obtain an organogel. The prepared organogel was dried at 130°C to prepare airgel powder. The thermal conductivity of the manufactured airgel powder was measured and was 0.01835 W/mk.

Comparative example

The same procedure as the above example was performed except that n-hexane was added to the reaction tank instead of being added to the solvent exchange tank. Thermal conductivity was measured for the manufactured airgel powder and was 0.02147 W/mK.

Thermal conductivity and apparent density of the airgel powders prepared in Examples and Comparative Examples were measured and shown in Table 1.

Table 1

In addition, the airgel powders prepared in Examples and Comparative Examples were measured at x1500 magnification, x5000 magnification, and x20000 magnification for SEM image analysis, and are shown in Figures 6, 7, and 8, respectively. Figure 6(A) is a SEM image of the airgel powder prepared in the comparative example at x1500 magnification, and Figure 6(B) is an SEM image of the airgel powder prepared in the example at x1500 magnification. In Figure 6(A), it can be seen that the gelation process and particle growth were interrupted by impurities, resulting in more small pieces compared to Figure 6(B). It appears that organic impurities inhibited the agglomeration process between airgel particles. Figure 7(A) is a SEM image of the airgel powder prepared in the comparative example at x5000 magnification, and Figure 7(B) is an SEM image of the airgel powder prepared in the example at x5000 magnification. It can be seen that the pores in Figure 7(B) are more developed than in Figure 7(A). This indicates that FIG. 7(B) was properly mesoporated. Figure 8(A) is a SEM image of the airgel powder prepared in the comparative example at a magnification of x20,000, and Figure 8(B) is a SEM image of the airgel powder prepared in the example at a magnification of x20,000. In Figure 8(B), the number of mesopores larger than 500 nm was 8 per area of 3㎛

So far, the present invention has been examined focusing on the embodiments. A person skilled in the art to which the present invention pertains will understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a restrictive perspective. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the equivalent scope should be construed as being included in the present invention.

According to the airgel production method according to the present invention, hydrogel is obtained from water glass in a reaction tank, then the hydrogel is moved to a solvent displacement tank to obtain organogel, and then airgel powder is obtained through drying in a dryer, so that the hydrogel is stored in the solvent displacement tank for a long time. As the next round of reactions takes place in the reaction tank while the substitution process is in progress, the overall production time can be significantly shortened. Since the organogel is produced separately in the solvent substitution tank, the organogel is produced separately from the reaction tank. Disturbance in the mixing of raw materials due to remaining in this reaction tank can be structurally prevented. Due to the absence of this disturbance, the quality of the final produced airgel can also be improved. Additionally, even when manufacturing airgel based on a base, the explosive reaction between HMDS and nitric acid can be prevented by introducing nitric acid through the lower channel or wall channel of the reaction tank. This lowers the sensitivity and risk of the reaction process and makes it possible to obtain higher quality airgel.

Claims

Reacting water glass and the first material in a reaction tank to obtain a hydrogel;

Moving the hydrogel to a solvent exchange tank and then reacting the hydrogel with a second material in the solvent exchange tank to obtain an organogel; and

After moving the organogel to a dryer, drying the organogel in the dryer to obtain airgel powder,

The first material includes pure water, HMDS, and nitric acid, and the nitric acid is added to the reaction tank after the HMDS.
The method of claim 1, wherein the solvent is not added to the reaction tank, but the solvent is added to the solvent exchange tank.
The method of claim 1, wherein no second material is added to the reaction tank, and the second material includes n-hexane.
The method of claim 1, wherein the silver nitrate,

A method of producing airgel, which is introduced through the lower part of the reaction tank and first mixed with the mixture of the water glass and the pure water before reacting with the HMDS.
According to paragraph 1,

While the mixed solution of the water glass, pure water, and HMDS is stirred in the reaction tank, the nitric acid is introduced along the wall of the reaction tank and reacts with the HMDS.
According to paragraph 1,

After the hydrogel is moved to the solvent exchange tank, the airgel production method further includes the step of cleaning the reaction tank.
According to clause 6,

After the hydrogel is moved to the solvent exchange tank, the step of cleaning the reaction tank is,

An airgel production method comprising the step of spraying pure water on the inner surface of the reaction tank while rotating the spray nozzle 360°.
According to paragraph 1,

An airgel production method in which organogel is not present in the reaction tank.
According to paragraph 1,

The solvent substitution tank is,

A method of producing airgel, which is made of a material with lower corrosion resistance, acid resistance, and high temperature strength than the reaction tank.
According to paragraph 1,

Further comprising the step of discharging wastewater generated with the organogel from the solvent displacement tank before moving the organogel to the dryer,

The step of discharging the wastewater is,

A method for producing airgel, comprising the step of a controller controlling the opening and closing of a discharge valve for discharging the wastewater based on the level of the wastewater measured by a level sensor.
According to clause 10,

The level sensor is,

An airgel manufacturing method, which is a radar-type sensor installed in the solvent replacement tank and emitting electromagnetic waves in a direction toward the interface between the organogel layer and the wastewater layer.
According to paragraph 1,

After the organogel is moved to the dryer, the airgel production method further comprises the step of cleaning the solvent displacement tank.
According to clause 12,

After the organogel is moved to the dryer, the step of cleaning the solvent displacement tank is,

An airgel production method comprising the step of spraying n-hexane on the inner surface of the solvent substitution tank while rotating the spray nozzle 360°.
An airgel manufactured by the method of any one of claims 1 to 13, having a thermal conductivity of less than 0.020 W/mK and an apparent density of less than 0.09 g/cm3.
According to clause 14,

The airgel has mesopores, and the number of mesopores of 500 nm or more per area of 3㎛ x 5㎛ is 6 or more in SEM image analysis at 20,000 magnification.