KR101958995B1 - Supercritical drying method for silica wetgel blanket - Google Patents

Abstract

The present invention relates to a supercritical drying method for a silica wet-gel blanket. More specifically, the present invention relates to: the supercritical drying method for the silica wet-gel blanket which, by a change in CO_2 input and discharge locations during a supercritical drying process, can improve supercritical drying efficiency to reduce a drying time, increase an ethanol recovery rate, reduce the use of CO_2 and the like, and is able to prevent a channeling phenomenon caused by the change in CO_2 input and discharge locations; and a method for manufacturing the silica wet-gel blanket comprising the same.

Description

SUPERCRITICAL DRYING METHOD FOR SILICA WETGEL BLANKET < RTI ID = 0.0 >

The present invention relates to a silica wet gel blanket supercritical drying process capable of improving the supercritical drying efficiency and a method for producing silica airgel blanks containing the same.

Aerogels are high-porosity materials composed of nanoparticles and have high porosity, specific surface area, and low thermal conductivity, and are attracting attention as high-efficiency heat insulating materials and soundproofing materials. Since such an airgel has a very low mechanical strength due to its porous structure, an airgel composite in which an airgel is impregnated and bonded to a fibrous blanket such as inorganic fiber or organic fiber, which is a conventional heat insulating fiber, has been developed. For example, in the case of a silica airgel-containing blanket using a silica airgel, it is produced through a process for producing silica sol, a gelling process, an aging process, a surface modification process and a drying process.

Drying process preserves the porosity in the airgel than atmospheric pressure process and there to the supercritical drying process using CO ₂ in the supercritical state can be used to prevent, when dry shrinkage, the supercritical drying is the CO ₂ in the supercritical state, high-pressure reactor To extract ethanol in the gelatinized blanket product and proceed to drying.

On the other hand, the CO ₂ introduced into the high-pressure reactor is generally supplied to the lower portion and discharged to the upper portion. This is to prevent the deterioration of the drying efficiency due to the channeling phenomenon of the supercritical fluid. However, in the case of the conventional drying method is from the bottom of the reactor CO ₂ is filled and ethanol is occupied by a bar, the process time for CO ₂ is fed to the upper portion being forward space in a manner that is substituted by CO ₂ prolonged increase in the amount of CO ₂ . This lowers the productivity of the aerobic blanket and causes deterioration of the properties of the aerobic blanket due to residual ethanol.

In order to solve such conventional problems the present invention is to during the supercritical drying with CO ₂ to change the CO ₂ input and discharge position supercritical improve the drying efficiency and capable of preventing the airgel blanket properties decrease silica wet gel seconds A critical drying method and a method for producing the silica airgel blanket including the same.

JP 1999-197557 A (July 27, 1999)

The problem to be solved by the present invention is to improve the supercritical drying efficiency such as shortening the drying time, increasing the ethanol recovery rate and reducing the CO ₂ usage amount by changing the CO ₂ input and discharge position, and preventing the channeling phenomenon through the perforated plate and the dispersion plate And a method for producing the silica airgel blanket including the silica wet gel supercritical drying method.

The present invention provides a method for preparing a supercritical extractor, comprising: placing a silica wet gel blanket within a supercritical extractor; And subjecting the silica wet gel blanket to supercritical drying to produce a silica airgel blanket wherein the supercritical fluid is introduced at the top of the extractor and exits to the bottom of the extractor. do.

The present invention also relates to a process for producing a silica sol, Impregnating and gelling the substrate for the blanket; A surface modification step and a drying step, wherein the drying step is by the silica wet gel blanket supercritical drying method.

The present invention also relates to a supercritical extractor in which supercritical drying is performed; A supercritical fluid supply connected to the upper portion of the extractor and supplying a supercritical fluid; And a supercritical fluid outlet connected to the bottom of the extractor for discharging the supercritical fluid,

The supercritical extractor includes a basket for receiving the silica wet gel blanket and an upper cap for sealing the basket,

Wherein the top cap comprises a perforated plate and a diffuser plate attached to the bottom of the perforated plate.

According to the method for producing a silica airgel blanket of the present invention, it is possible to shorten the process time and reduce the amount of CO _{2 to be} used by increasing the drying efficiency, to increase the amount of recovered ethanol and to reduce the manufacturing cost of the silica airgel blanket, The amount can be reduced and the deterioration of physical properties can be prevented.

Therefore, the silica airgel blanket manufacturing method of the present invention can produce the silica airgel blanket having excellent physical properties more economically.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a CO ₂ feed and discharge position in a conventional supercritical drying process. FIG.
FIG. 2 is a schematic view showing the positions of CO ₂ injection and discharge in the supercritical drying process of the silica airgel blanket manufacturing method of the present invention.
FIG. 3 is a schematic view showing an upper cap including a basket, a perforated plate, and a dispersion plate included in the supercritical drying apparatus of the present invention.
4 is a graph showing the ethanol recovery rate in the supercritical drying process of Comparative Example 1. Fig.
5 is a graph showing the ethanol recovery rate in the supercritical drying process of Example 2. Fig.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention. Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

<Silica Wet Gel Blanket Supercritical Drying Method>

The present invention provides a method for preparing a supercritical extractor, comprising: placing a silica wet gel blanket within a supercritical extractor; And

Subjecting the silica wet gel blanket to supercritical drying to produce a silica airgel blanket,

Wherein the supercritical fluid is introduced at the top of the extractor and exits to the bottom of the extractor.

In the silica airgel blanket manufacturing method, the hydrophobized silica wet gel can be prepared by a drying process in which the solvent is removed while maintaining the pore structure as it is. The drying process may be a normal-pressure drying process or a supercritical drying process. In particular, the present invention is characterized by a supercritical drying process.

The atmospheric-pressure drying process does not require high-pressure reaction conditions and special high-pressure facilities for supercritical drying, and the process is simple and economical. However, as the water or the organic solvent evaporates at high temperatures, There may be a problem that the internal pore structure is significantly collapsed and the heat insulating performance is rapidly deteriorated. The above problem can be further exacerbated when drying is performed directly without substitution with a low surface tension organic solvent.

In contrast, since the drying of the present invention can maximize the porosity by supercritical drying, the heat insulating performance of the silica airgel produced by atmospheric pressure drying can be remarkably excellent. The present invention is for producing a silica airgel blanket which is mainly used in the construction of an ultra-high temperature piping system, and it is essential that the thermal insulation performance of the silica airgel blanket is higher than that of the silica airgel blanket used for other purposes to be.

First, the silica wet gel blanket supercritical drying process of the present invention may include placing a silica wet gel blanket within the supercritical extractor.

The silica wet gel blanket refers to a hydrophobic silica wet gel blanket that is immersed in a silica sol and gelling catalyst solution into a substrate for the blanket to complete the gelling reaction, followed by an aging and surface modification step. More specifically, the method will be described below in the production of silica airgel blanket.

The supercritical extractor refers to a high pressure apparatus in which supercritical drying of a silica wet gel blanket is carried out using a supercritical fluid. Specifically, the supercritical extractor of the present invention comprises a basket for receiving a silica wet gel blanket and an upper cap for sealing the basket, the upper cap comprising a perforated plate and a diffuser plate attached to the lower portion of the perforated plate . &Lt; / RTI &gt;

More specifically, the silica wet gel blanket of the present invention is contained in a basket in a roll form, and is sealed within the supercritical extractor by being sealed by an upper cap. The silica wet gel blanket of the present invention is a sheet of up to about 10 m length and is wound in roll form. In order to fixly place the roll-type silica wet gel blanket in the supercritical extractor, a basket, which is a vessel capable of accommodating silica wet gel blanket, is essentially required.

Thereafter, the present invention includes the step of supercritically drying the silica wet gel blanket contained in the basket to produce a silica airgel blanket.

For this supercritical drying, the present invention is characterized in that supercritical fluid is injected from the upper part of the extractor and discharged to the lower part of the extractor.

As shown in FIG. 1, the conventional supercritical drying method employs a method of injecting a supercritical fluid into a lower portion of a supercritical extractor and discharging it to an upper portion. This is to prevent the drying efficiency from deteriorating due to the channeling phenomenon of the supercritical fluid. The channeling phenomenon is a phenomenon in which the flow is formed only in a region where the fluid is easily discharged. In the case of channeling phenomenon, the supercritical fluid can not flow uniformly in the extractor and the drying efficiency is lowered.

However, in the conventional drying method, supercritical fluid is filled from the bottom of the extractor, and the solvent contained in the silica wet gel blanket, especially ethanol, is replaced. As a result, the drying process time is increased and the amount of the supercritical fluid is increased, The productivity of the silica airgel blanket is lowered, and there is a limitation in that the property of the silica airgel blanket is lowered due to the residual ethanol.

2, the supercritical drying method of the silica wet gel blanket of the present invention is modified to apply the supercritical fluid to the supercritical drying system in order to solve the problems of the prior art, Is improved.

When the supercritical fluid is injected from the upper part of the extractor and discharged from the lower part as in the present invention, it is easy to extract ethanol due to gravity, and it is possible to maximize the extraction of ethanol gathered especially in the lower part. Of the supercritical fluid.

In order to prevent the channeling phenomenon that may occur due to the change of the injection and discharge positions of the supercritical fluid, the present invention is characterized in that an upper cap including a perforated plate and a dispersing plate is additionally provided.

Specifically, the upper cap includes a perforated plate and a dispersing plate attached to a lower portion of the perforated plate.

When the supercritical fluid injected from the upper portion of the extractor is introduced through the upper cap, the perforated plate serves to uniformly spread the injected supercritical fluid primarily in a roll-shaped silica wet gel blanket in the basket.

Accordingly, the present invention provides a piercing plate having a hole having a diameter of 5 to 20 mm, more preferably 5 to 15 mm, and having an open ratio of 40% or more, more preferably 50% or more, .

When the diameter of the hole and the open ratio satisfy the above range, the supercritical fluid flow can be uniformly diffused to enhance the supercritical drying efficiency.

In addition, the dispersion plate is attached to a lower portion of the perforated plate, and serves to uniformly distribute the supercritical fluid passing through the perforated plate through secondary fine pores.

Accordingly, the dispersion plate of the present invention may also include several pores, and the diameter of the pores may be 50 to 200 μm, more preferably 50 to 100 μm, and the open ratio may be 40% or more Preferably 50% or more.

When the diameter and the open ratio of the pore satisfy the above range, the supercritical fluid can be uniformly diffused to increase the supercritical drying efficiency.

The dispersing plate may be made of a sintered metal material. Specifically, the sintered metal material may be at least one selected from the group consisting of stainless steel (SUS), brass, copper and aluminum.

Thus, CO ₂ input and change the discharge position, and, CO ₂ input and silica wet gel blanket supercritical drying method of the present invention have solved the channeling phenomenon in the top cap including a perforated plate and a dispersion plate according to the change the discharge position is the supercritical drying The efficiency can be improved, the drying process time can be shortened, and the ethanol recovery rate can be improved.

Generally, when the drying is completed, the supercritical fluid is introduced into the extractor, the supercritical fluid is diffused, the solvent contained in the wet gel blanket is replaced, and then discharged out of the extractor. It is considered that the rate of increase of the solvent recovered from the bottom of the extractor is repeatedly converged to zero.

In the case of the present invention, the supercritical drying efficiency is improved, and the supercritical drying can be completed even with a few cycles.

In addition, the present invention can provide an ethanol recovery rate of 80% or more, more preferably 90% or more, recovered at the bottom of the extractor.

The ethanol recovery rate is the ratio of the amount of ethanol recovered from the lower part of the extractor to the total amount of ethanol contained in the silica wet gel blanket as the ratio of the amount of ethanol recovered in the lower part of the extractor to the amount of ethanol recovered = [(amount of ethanol discharged and recovered from the extractor) / The amount of ethanol in the Blanket)] x 100% &quot;

Since the supercritical drying efficiency is improved and the ethanol recovery rate is remarkably higher than that of the conventional supercritical drying method, the amount of ethanol to be reused is large and the cost of solvent purchase can be reduced. The amount of ethanol remaining in the silica airgel blanket is small, Can be minimized.

As the supercritical fluid, freons such as SF ₆ , CHF ₃ and CHF ₂ OCF ₃ , N ₂ O, alcohols, ketones or carbon dioxide (CO ₂ ) can be used. However, the silica wet gel blanket In the critical drying method, it is appropriate to use carbon dioxide (CO ₂ ) which is easy to handle.

Carbon dioxide (CO ₂ ) is in a gaseous state at room temperature and atmospheric pressure, but when it exceeds a certain temperature and high pressure limit, called a supercritical point, it does not evaporate and becomes a critical state in which gas and liquid can not be distinguished. Is called supercritical carbon dioxide. The supercritical carbon dioxide has a density close to that of a liquid, but has a low viscosity and a gas-like nature. The supercritical carbon dioxide has a high diffusion rate and a high thermal conductivity, which results in high drying efficiency and short drying time.

The supercritical drying method of the present invention early into the silica wet gel blanket aging in critical extraction, and then, filling up the CO ₂ in a liquid state and performs the solvent replacement step of replacing the alcohol solvent within the silica wet gel blanket to CO _2. Thereafter, the temperature is raised to 40 to 50 DEG C at a constant heating rate, specifically 0.1 DEG C / min to 1 DEG C / min. Thereafter, a pressure of at least 100 bar to 150 bar Is maintained for a certain period of time, specifically 20 minutes to 1 hour, in the supercritical state of carbon dioxide. Generally, carbon dioxide becomes supercritical at a temperature of 31 ° C and a pressure of 73.8 bar. The carbon dioxide is maintained at a constant temperature and a constant pressure for 2 hours to 12 hours, more specifically, 2 hours to 6 hours at which the carbon dioxide becomes a supercritical state, and then the pressure is gradually removed to complete the supercritical drying process to obtain a hydrophobic silica airgel blanket Can be manufactured.

Meanwhile, the silica wet gel blanket supercritical drying method of the present invention may further include an atmospheric pressure drying step after the supercritical drying step.

This can be arbitrarily added to remove a small amount of residual solvent that has not been completely removed in the supercritical drying step after the supercritical drying and to remove the hydrophilic salt that may be generated by ammonia and CO ₂ in the supercritical drying gel It is a process.

The above-mentioned atmospheric-pressure drying process is not an indispensable process, and the fact that the destruction of the pore structure is not so large, is different from the atmospheric-pressure drying process in which the entire solvent contained in the silica wet-gel blanket is removed by atmospheric- There are different sides from the side.

When the silica wet gel blanket supercritical drying method of the present invention further performs the above-described atmospheric pressure drying step, the atmospheric pressure drying loss of the present invention may be 5 wt% or less, more preferably 4 wt% or less.

The atmospheric pressure drying loss represents the rate of weight change before and after the atmospheric pressure drying, which is further carried out to remove residual ethanol present in the airgel blanket after supercritical drying. The &quot; atmospheric pressure drying loss (wt%) = Blanket weight - weight of aerogel blanket after supercritical drying followed by atmospheric pressure drying) / (weight of aerogel blanket after supercritical drying)] x 100%.

The silica wet gel blanket supercritical drying method according to the present invention has a low supercritical drying efficiency and a low residual ethanol so that the atmospheric pressure drying loss value is small and the deterioration of physical properties due to the increase in thermal conductivity due to the shrinkage of the airgel in the final product can be minimized have.

&Lt; Production method of silica airgel blanket >

The present invention relates to a process for producing a silica sol, Impregnating and gelling the substrate for the blanket; A surface modification step and a drying step,

Wherein the drying step is by the silica wet gel blanket supercritical drying method of the present invention.

1) Preparation of silica sol

The silica sol of the present invention is characterized by being prepared by mixing a silica precursor, an alcohol and an acidic aqueous solution.

The silica precursor that can be used in the preparation of the silica sol may be a silicon-containing alkoxide compound, specifically, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), methyltriethyl But are not limited to, tetraethyl orthosilicate, methyl triethyl orthosilicate, dimethyl diethyl orthosilicate, tetrapropyl orthosilicate, tetraisopropyl orthosilicate, tetrabutyl orthosilicate, ), Tetra secondary butyl orthosilicate, tetra tertiary butyl orthosilicate, tetrahexyl orthosilicate, tetracyclohexyl orthosilicate, tetracyclohexyl orthosilicate, licate, tetradodecyl orthosilicate, and the like. More particularly, in the case of the present invention, the silica precursor may be tetramethyl orthosilicate (TMOS), tetraethylorthosilicate (TEOS) or a mixture thereof.

The silica precursor may be used in an amount such that the content of silica (SiO ₂ ) contained in the silica sol is 0.1 wt% to 30 wt%. If the content of the silica is less than 0.1 wt%, the content of the silica airgel in the final blanket is too low to achieve the desired thermal insulation effect. When the content exceeds 30 wt%, excessive silica airgel is formed There is a possibility that the mechanical properties, particularly the flexibility, of the blanket may deteriorate.

The alcohols usable in the preparation of the silica sol of the present invention are specifically exemplified by monohydric alcohols such as methanol, ethanol, isopropanol, butanol and the like; Or polyhydric alcohols such as glycerol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and sorbitol, and any one or a mixture of two or more thereof may be used. Among them, monohydric alcohols having 1 to 6 carbon atoms such as methanol, ethanol, isopropanol, butanol and the like can be used in consideration of compatibility with water and an airgel.

The alcohol (polar organic solvent) as described above can be used in an appropriate amount in consideration of the degree of hydrophobization in the silica airgel which is finally produced while promoting the surface modification reaction.

Further, the acidic aqueous solution usable in the production of the silica sol of the present invention can promote the gelation of the silica sol. The acid catalyst contained in the acidic aqueous solution may specifically include at least one inorganic acid such as nitric acid, hydrochloric acid, acetic acid, sulfuric acid, and hydrofluoric acid, and may be used in an amount to promote gelation of the silica sol.

2) Impregnating and gelling the substrate for the blankets

This step is for preparing a silica gel composite, and may be carried out by adding a base catalyst to the silica sol and impregnating the base material for blanket.

The base catalyst, which can be used to prepare the silica gel of the present invention, serves to promote the gelation by increasing the pH of the silica sol.

Examples of the base catalyst include inorganic bases such as sodium hydroxide and potassium hydroxide; Or ammonium hydroxide. In the case of an inorganic base, an organic base may be preferable since metal ions contained in the compound may be coordinated to the Si-OH compound. Specifically, the organic base is ammonium hydroxide (NH ₄ OH), tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), methylamine, ethylamine, isopropylamine, monoisopropylamine, diethylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, choline, (2-aminoethyl) ethanol, 2- (methylamino) ethanol, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, nitrilotriethanol, 2 - (2-aminoethoxy) ethanol, 1-amino-2-propanol, triethanolamine, monopropanolamine or dibutanolamine, and mixtures of two or more thereof may be used. More specifically, in the case of the present invention, the base may be ammonium hydroxide (NH ₄ OH).

The base catalyst may be included in an amount such that the pH of the silica sol is 4 to 8. If the pH of the silica sol is out of the above range, the gelation is not easy or the gelation speed is too slow to lower the processability. In addition, since the base may be precipitated when it is added in a solid phase, it may be preferable to be added in the form of a solution diluted with the alcohol (polar organic solvent).

The gelation of the silica aerogel blanket manufacturing method according to an embodiment of the present invention may be to form a network structure from the silica precursor material, and the network structure may be formed of one or more kinds of atomic arrangement Dimensional mesh structure sharing a vertex, a corner, a surface, etc. of a specific polyhedron in which a specific polygon is connected.

The gelation of the silica sol of the present invention can occur in a state in which the silica sol is impregnated in the substrate for the blanket.

Specifically, the impregnation may be carried out in a reaction vessel capable of accommodating the substrate for blanket, and may be impregnated by pouring silica sol into the reaction vessel, or by wetting the substrate for blanket in a reaction vessel containing silica sol have. At this time, in order to improve the bonding between the substrate for blanket and the silica sol, the base material for blanket can be lightly impregnated sufficiently. Thereafter, the substrate for blanket may be pressed to a predetermined thickness at a constant pressure to remove excess silica sol to reduce the subsequent drying time.

The substrate for a blanket usable in the present invention may be a film, a sheet, a net, a fiber, a porous body, a foam, a nonwoven fabric, or a laminate of two or more thereof. Further, depending on the application, surface roughness may be formed or patterned on the surface thereof. More specifically, the base material for blanket may be a fiber capable of further improving the heat insulating performance by including spaces or voids into which the silica airgel can be inserted into the base material for blanket. It is also preferable that the substrate for blanket has a low thermal conductivity.

Specifically, the base material for blanket may be selected from the group consisting of polyamide, polybenzimidazole, polyaramid, acrylic resin, phenol resin, polyester, polyetheretherketone (PEEK), polyolefin (for example, polyethylene, Etc.), cellulose, carbon, cotton, wool, non-woven fabric, glass fiber or ceramic wool, etc. More specifically, the base material for blanket may include glass fiber or polyethylene.

3) Aging and surface modification step

The present invention can include a step of aging and surface modification of the silica gel composite.

The aging is an optional step, which is a step of allowing the silica gel to be left at an appropriate temperature to complete the chemical change. The step of immersing the silica gel in an organic solvent or a solution of a basic catalyst such as ammonia in an organic solvent at a concentration of 1 to 10% At a temperature of 50 to 90 DEG C for 1 to 10 hours. By carrying out the aging step of the present invention, the formed network structure can be more firmly formed, and mechanical stability can be enhanced.

In addition, the dried silica airgel maintains a low thermal conductivity immediately after drying but has a disadvantage in that it absorbs water in the air due to the hydrophilic nature of the silanol group (Si-OH) on the surface of the silica, and the thermal conductivity gradually increases. Therefore, in order to maintain a low thermal conductivity, it is necessary to modify the surface of the silica airgel to be hydrophobic. The surface modification of the present invention is performed by using trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS) At least one surface modifier selected from the group consisting of methyltrimethoxysilane, trimethylethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, and polydimethylsiloxane is added. , And more specifically, may be performed by adding hexamethyldisilazane (HMDS).

4) Supercritical drying step

The supercritical drying step of the method for producing a silica airgel blanket of the present invention is characterized by the above-mentioned silica wet gel blanket supercritical drying method of the present invention. The details are as described above.

Meanwhile, the method of manufacturing a silica airgel blanket according to an embodiment of the present invention may further include a step of washing before the drying. The washing is to obtain a high purity hydrophobic silica airgel by removing impurities (unreacted materials, by-products, etc.) generated during the reaction and residual ammonia which may react with CO _{2 in} supercritical drying to form ammonium carbonate salt, It may be carried out by a dilution process or an exchange process using an organic solvent.

<Silica wet gel blanket supercritical drying apparatus>

The present invention relates to a supercritical extractor in which supercritical drying is performed;

A supercritical fluid supply connected to the upper portion of the extractor and supplying a supercritical fluid;

And a supercritical fluid outlet connected to the bottom of the extractor for discharging the supercritical fluid,

The supercritical extractor includes a basket for receiving the silica wet gel blanket and an upper cap for sealing the basket,

Wherein the top cap comprises a perforated plate and a diffuser plate attached to the bottom of the perforated plate.

The silica wet gel blanket supercritical drying apparatus of the present invention is characterized in that supercritical drying efficiency is improved by changing and applying the equipment such that the injection and discharge positions of the supercritical fluid are opposite to the conventional ones.

As shown in FIG. 2, the supercritical fluid supply unit for supplying the supercritical fluid of the present invention is connected to the upper portion of the supercritical fluid extractor, and the supercritical fluid discharge portion for discharging the supercritical fluid is connected to the lower portion of the supercritical fluid extractor do.

A channeling phenomenon that may occur according to the change of the input and discharge positions is solved by introducing an upper cap including a pier plate and a dispersion plate attached to a lower portion of the pier plate, .

Accordingly, the ethanol recovery rate of the supercritical drying apparatus of the present invention may be 80% or more, more preferably 90% or more.

The supercritical drying apparatus of the present invention may further include a circulation pump circulating the supercritical fluid discharged from the discharge unit to a supply unit for reuse, and includes a pressure controller for controlling the pressure and temperature inside the supercritical extractor, A temperature control unit, a filtration unit provided in the circulation path of the circulated supercritical fluid, and a solvent recovery unit connected to the bottom of the extractor to recover the supercritical fluid.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example  One

The silica sol was prepared by mixing 75% hydrated tetraethylorthosilicate (HTEOS) (silica concentration 19 to 20 wt%), ethanol and water at a weight ratio of 1: 2.25: 0.35. The silica sol was mixed with a base catalyst solution at a weight ratio of ethanol: ammonia = 210: 1 in an amount of 0.44 wt% based on the HTEOS, followed by impregnation with glass fiber to induce gelation. After completion of the gelation, the mixture was allowed to stand for 1 hour at a temperature of 50 to 70 캜 using 80 to 90% ammonia solution (2 to 3 vol%) based on the volume of the silica sol and aged. Then, 80 to 90% The hydrophobic silica wet gel blanket roll was prepared by allowing the solution to stand for 4 hours at a temperature of 50 to 70 ° C using a solution of methyldisilazane (HMDS) (2 to 10 vol%).

The surface-modified wet gel blanket Roll was placed in a basket for supercritical drying and sealed with an upper cap made of a perforated plate. The lower part of the basket was also sealed with a lower cap made of a perforated plate. The perforated plate has 95 holes each having a diameter of 12 mm. The hole has a diameter of 330 mm and a thickness of 8 mm. The open ratio is 50% of the total area.

The wet gel blanket Roll sealed with the top cap consisting of the basket and perforated plate was placed in a 77 L supercritical extractor and CO ₂ was added for 15 minutes at the top of the extractor. Thereafter, the temperature in the extractor was raised to 70 ° C over 1 hour, and when the pressure reached 150 bar, the reaction was continued for 20 minutes at a rate of 5.5 L / min for 200 minutes, followed by 20 minutes for supercritical drying.

At this time, the ethanol extracted through the bottom of the extractor was recovered. After that, CO ₂ was vented from the bottom of the extractor for 1 hour, and further air-dried in an oven at 150 ° C to produce an airgel blanket.

Example  2

In Example 1, instead of the upper cap made of the perforated plate, 95 holes having a diameter of 12 mm were drilled to form a perforated plate having a diameter of 330 mm and a thickness of 8 mm and having an open ratio (ratio of the perforated area as a whole area) The same procedure as in Example 1 was carried out except that an upper cap including a dispersion plate made of SUS (stainless steel) having a diameter of 50 탆 and a diameter of 250 mm and a thickness of 2 mm and having a diameter of 50 탆 was used at the bottom of the pier A silica airgel blanket was prepared.

Comparative Example  One

A silica airgel blanket was prepared in the same manner as in Example 1, except that CO ₂ was introduced from the lower portion of the extractor in Example 1, CO ₂ was discharged from the upper portion of the extractor, and the supercritical drying cycle was performed for 7 cycles.

Comparative Example  2

In Comparative Example 1, instead of the lower cap, 95 holes having a diameter of 12 mm were drilled to form openings having a diameter of 330 mm and a thickness of 8 mm and an open ratio of 40% A silica airgel blanket was prepared in the same manner as in Comparative Example 1, except that a lower cap including a dispersion plate of SUS (stainless steel) having a diameter of 50 탆 and a diameter of 250 mm and a thickness of 2 mm was used .

Experimental Example

The physical properties of the silica airgel blanket prepared in the above Examples and Comparative Examples were measured, and the results are shown in Table 1 below.

1) ethanol recovery (%)

The ethanol recovery rate was the ratio of the amount of ethanol recovered from the bottom of the extractor in the supercritical drying step to the total amount of ethanol contained in the silica wet gel blanket. The ethanol recovery rates in the examples and comparative examples were measured as follows.

- ethanol recovery rate = [(amount of ethanol discharged and recovered from the extractor) / (amount of ethanol in the blanket fed into the extractor)] x 100%

2) Loss at atmospheric pressure (wt%)

The atmospheric pressure drying loss represents the rate of weight change before and after atmospheric pressure drying, which is further performed to remove residual ethanol present in the aerogel blanket after supercritical drying.

The higher the supercritical drying efficiency, the smaller the amount of residual ethanol and the lower the dry weight loss value. The lower the dry weight loss value, the less the deterioration of physical properties due to the increase in thermal conductivity due to the shrinkage of aerogels in the final product.

(Weight of aerogel blanket after supercritical drying) - (weight of aerogel blanket after supercritical drying) x 100%

3) Thickness (mm) and room temperature thermal conductivity (mW / mK, 25 ℃)

For each of the silica airgel blanks prepared in the Examples and Comparative Examples, a sample of 30 cm x 30 cm was prepared and the thickness and the room temperature thermal conductivity were measured using a HFM 436 Lambda machine from NETZSCH.

Supercritical drying cycle
(time) Total Drying Time
(min) Ethanol recovery rate
(%) Atmospheric dry weight loss (wt%) thickness
(mm) Room temperature thermal conductivity (mW / mK) Example 1 5 200 89.30 2.51 10.5 18.2 Example 2 5 200 92.80 1.78 10.9 17.7 Comparative Example 1 7 280 82.60 4.20 10.8 19.3 Comparative Example 2 7 280 85.70 4.00 10.1 19.0

 As shown in Table 1, it was confirmed that the Examples have low insulation loss at room temperature and low thermal conductivity at room temperature compared with Comparative Example.

In addition, as shown in FIG. 4 (Comparative Example 1) and 5 (Example 2), the ethanol recovery rate in Example 2 was significantly higher than that in Comparative Example 1, and drying was completed only after five drying cycles, .

On the other hand, it was confirmed that Example 2 using the upper cap including both the perforated plate and the dispersing plate had more excellent effect than that of Example 1 using the upper cap having no perforated plate.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (14)

Placing a silica wet gel blanket within the supercritical extractor; And
Subjecting the silica wet gel blanket to supercritical drying to produce a silica airgel blanket,
Supercritical fluid is injected at the top of the extractor, exits to the bottom of the extractor,
The silica wet gel blanket is housed in a roll in a basket, sealed by an upper cap and positioned inside the supercritical extractor,
Wherein the upper cap includes a perforated plate and a dispersing plate attached to a lower portion of the perforated plate,
Wherein the perforated plate comprises a hole and the diffuser plate comprises pores having a diameter smaller than the hole of the perforated plate.
delete delete The method according to claim 1,
Wherein the perforated plate has an open ratio of at least 40%.
The method according to claim 1,
Wherein the holes included in the perforated plate have a diameter of 5 to 20 mm.
The method according to claim 1,
Wherein the pores contained in the dispersion plate have a diameter of 50 to 200 mu m.
The method according to claim 1,
Wherein the dispersing plate is a sintered metal material.
The method according to claim 1,
Wherein the dispersing plate is at least one material selected from the group consisting of stainless steel (SUS), brass, copper and aluminum.
The method according to claim 1,
Wherein the supercritical drying step has an ethanol recovery of at least 80%.
The method according to claim 1,
Further comprising an atmospheric pressure drying step after the supercritical drying step,
Wherein said atmospheric pressure drying loss is 5 wt% or less.
Silica sol preparation step; Impregnating and gelling the blanket substrate; A surface modification step and a drying step,
Wherein the drying step is by the silica wet gel blanket supercritical drying method of any one of claims 1 to 10.
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