JP2005334871A - Production method for porous material and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of efficiently producing a porous material while preventing the generation of a crack and the destruction of the porous material in a drying process, and to provide a useful production method for carrying out the above method. <P>SOLUTION: The porous material is produced by drying a wet material having a first liquid solvent while substituting the first solvent with a second solvent in a state of high pressure, wherein this operation is carried out while supplying a mixed solvent of the same or same kinds of solvents as the first solvent and the second solvent, and if necessary, the mixed solvent is supplied while gradually increasing the mixing ratio of the second solvent by changing the mixing ratio of each solvent of the mixed solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a porous body such as airgel and an apparatus therefor, and in particular, a method capable of producing a porous body while preventing cracks and the like from being generated in the porous body in the drying step, and The present invention relates to a useful device for this purpose.

  As the light-transmitting or light-semi-transmitting inorganic porous material, for example, a gel-like compound (wet gel) obtained by hydrolysis and condensation polymerization of alkoxysilane is generated, and then used to generate this gel-like compound. An airgel obtained by removing the obtained solvent and drying is known. Since this airgel is lightweight and has excellent heat insulating properties, it has attracted attention as a material for heat insulating materials useful in various fields.

  In producing an airgel, it is necessary to effectively remove the solvent used in producing the gel compound (wet gel) from the gel compound to obtain a dry gel. However, if the wet gel is dried as it is, the structure of the gel compound is destroyed and cannot be dried while maintaining the shape. This is considered to be caused by stress caused by interfacial tension generated at the interface of gas or the like.

  As a typical means for preventing such structural destruction, a method of drying under supercritical conditions is known (for example, Non-Patent Document 1). This method is based on the principle that if the atmosphere is brought into a supercritical state, gas-liquid distinction is eliminated and generation of interfacial tension at the interface is theoretically eliminated.

  As a technique applying the above principle, for example, a technique as shown in Patent Document 1 has been proposed. This technique is a method of drying while replacing a solvent (for example, alcohol) contained in a gel compound with supercritical carbon dioxide. According to this method, since the critical temperature and pressure in carbon dioxide are relatively low, a supercritical state can be realized relatively easily and inexpensively.

  However, when supplying carbon dioxide in the supercritical state, if the displacement rate of the solvent around the gel is too fast, the generation of interfacial tension in the wet gel due to rapid concentration change in the gel, diffusion of the solvent, etc. Still, there remains a problem that the stress associated with expansion increases and the airgel cracks. For this reason, a method of supplying carbon dioxide in a supercritical state over a long period of time has been adopted.

On the other hand, from the viewpoint of preventing the occurrence of cracks, a technique such as Patent Document 2 has also been proposed. In this technology, after the solvent replacement, the inside of the high-pressure vessel is maintained at a temperature equal to or higher than the boiling point of the solvent, thereby preventing the solvent remaining in the atmosphere from liquefying, thereby preventing the occurrence of an interface, This prevents the structure from being destroyed. However, even if such treatment is performed, it cannot be said that the operation efficiency is improved so much, and if the replacement speed is too high, the problem of cracking still exists.
"Science of sol-gel method", May 1, 1990, published by Agne Jofusha Co., Ltd., page 37 US Pat. No. 4,610,863 Japanese Patent No. 30428276

  The present invention has been made under such circumstances, and an object of the present invention is to provide a method capable of efficiently producing a porous body while preventing the occurrence of cracks in the drying process and the destruction of the porous body, and the like. The object is to provide a useful manufacturing apparatus for carrying out the method.

  The present invention was able to solve the above-mentioned problems, and produced a porous body by drying while replacing the first solvent in the wet body containing the first liquid solvent with the second solvent in a high-pressure state. In this method, the present invention has a gist in that it operates while supplying a mixed solution of the same or the same kind of solvent as the first solvent and the second solvent.

  In this method, it is preferable to supply by gradually increasing the mixing ratio of the second solvent by changing the mixing ratio of each solvent in the mixed solvent. In gradually increasing the mixing ratio of the second solvent, it is preferable to gradually increase the increase ratio itself of the mixing ratio of the second solvent.

  In the method of the present invention, it is preferable to gradually reduce the pressure of the mixed solvent. A typical example of the porous body targeted by the method of the present invention is airgel. Moreover, as a solvent to be used, the first solvent is preferably an alcohol and the second solvent is preferably a combination of carbon dioxide.

On the other hand, the production apparatus of the present invention capable of achieving the above object is a drying process while replacing the first solvent in the wet body containing the first liquid solvent with the second solvent in a high-pressure state. In the porous body manufacturing apparatus configured to manufacture the porous body,
A first solvent high pressure supply section for supplying the same or the same kind of solvent as the first solvent in a high pressure state;
A second solvent high pressure supply section for supplying the second solvent in a high pressure state;
A high pressure mixing section for mixing the first solvent and the second solvent in a high pressure state;
A high-pressure mixed solvent supplied from the high-pressure mixing section, and a porous body processing section for processing by bringing the high-pressure mixed solvent into contact with a porous material installed in a processing tank;
It is the manufacturing apparatus of the porous body which has a summary in the point provided with.

  The apparatus of the present invention is preferably configured to operate while changing the ratio of the supply amount of the same or the same solvent as the first solvent and the supply amount of the second solvent. Moreover, it is preferable to provide the 1st solvent separation part which isolate | separates the same or same kind of solvent as said 1st solvent from the mixed solvent after a porous body process. The first solvent storage unit stores the same or the same type of solvent as the first solvent separated by the first solvent separation unit, and is the same or the same type as the first solvent from the first solvent storage unit. It is also preferable that the solvent is recycled to the first solvent high-pressure supply unit and reused. Further, a pressure reducing means is provided after the porous body processing section, and a pressure detecting means for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing section is provided in the porous body processing section, and is detected by the pressure detecting means. It is also preferable that the pressure reducing means is controlled based on the signal so as to operate while gradually decreasing the pressure of the high pressure mixed solvent.

As another configuration of the production apparatus according to the present invention, a porous body is obtained by performing a drying treatment while replacing the first solvent in the wet body containing the first liquid solvent with the second solvent in a high-pressure state. In the porous body manufacturing apparatus configured to manufacture,
A porous body processing section in which the wet body containing the first solvent is installed and processed;
A high-pressure solvent circulation unit that circulates and supplies the high-pressure solvent discharged from the porous body processing unit;
A second solvent high pressure supply section for supplying the second solvent in a high pressure state;
A high-pressure mixing unit that mixes the solvent from the high-pressure solvent circulation unit and the second solvent from the second solvent supply unit in a high-pressure state, and then supplies a mixed solvent to the porous body processing unit;
The above object of the present invention can be achieved even with an apparatus having such a configuration.

  In this apparatus, the mixing of the second solvent in the solvent supplied from the solvent mixing unit to the porous body processing unit is controlled by controlling the supply amount of the second solvent from the second solvent supplying unit. It is preferable that the operation is performed while changing the ratio. Moreover, it is preferable to provide the 1st solvent separation part which isolate | separates said 1st solvent from a part of mixed solvent after the porous body process in the said porous body process part. A first solvent storage unit for storing the first solvent separated by the first solvent separation unit; and recycling the first solvent from the first solvent storage unit to the porous body processing unit It is also preferable to configure so as to. Further, similarly to the above apparatus, the porous body processing section includes a pressure reducing means after the porous body processing section, and pressure detecting means for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing section. It is also preferable that the pressure reducing means is controlled based on the signal detected by the pressure detecting means so that the operation is performed while gradually reducing the pressure of the high pressure mixed solvent.

  In the present invention, when the porous body is produced by drying the wet body (wet gel) while replacing the solvent, the solvent is not the same as the solvent contained in the wet body, Due to supplying a mixed solvent in which the same type of solvent and substitution solvent are mixed, a two-phase (liquid / liquid or gas / liquid) interface is formed between the two solvents, or the substitution speed is too high. The stress generated in the wet gel can be relaxed, and a porous body can be produced efficiently while preventing the generation of cracks and the destruction of the structure of the gel compound.

  The present inventors have studied from various angles in order to achieve the above object. As a result, when producing a porous body by drying the wet body (wet gel) while substituting the solvent, a mixed solvent in which the same or the same type of solvent as the solvent contained in the wet body and a replacement solvent is mixed is used. As a result, the present inventors have found that the above object can be achieved brilliantly, thereby completing the present invention. In addition, "same kind" said here is mutually compatible, for example, the combination of alcohol and water, ethanol and water, ethanol and methanol etc. is mentioned as an example. Further, “circulation and reuse” or “circulation supply and reuse” as used in the present invention includes not only the case where all are circulated but also the case where only a part is circulated.

  If only the solvent for replacement is supplied in a high-pressure state (especially in the supercritical state) in the drying process, a stress occurs in the wet gel due to the formation of a two-phase interface between the two solvents or the excessive replacement speed. It will be. In contrast, by supplying the replacement solvent in the form of the mixed solvent as described above, the concentration difference between the solvent in the porous body and the solvent supplied from the outside can be arbitrarily controlled, and the stress applied to the wet body is reduced. It can be reduced as much as possible.

  In the present invention, even if the replacement solvent is supplied in the form of the mixed solvent as described above, the effect is exhibited. However, the mixing ratio of each solvent in the mixed solvent is changed, and the second solvent is used. It is preferable to gradually increase the mixing ratio. Here, “suppliing the mixing ratio of the second solvent so as to gradually increase” means supplying the mixing ratio of the second solvent to increase as the mixed solvent is supplied. It means that. Further, the meaning is not limited to supplying the mixed solvent so that the mixing ratio of the second solvent continuously increases smoothly, so that the mixing ratio increases stepwise. A mixed solvent may be supplied. By adopting such a configuration, it is possible to promptly replace the solvent while suppressing the difference in concentration inside and outside the porous body as much as possible.

Examples of the porous body to be used in the present invention include silica aerogel, but are not limited thereto. For example, metal oxide airgel / porous body (for example, a single oxide catalyst, a composite oxide catalyst, a catalyst simple substance, etc.) _{in, TiO 2, Al 2 O 3} , MgO, SiO 2 -TiO 2, SiO 2 -Al 2 O 3, Pd-Al 2 O 3, Ni-SiO 2, _{zeolites, BaAl 12 O 19, TiCl 4} -Al 2 O ₃ etc.), polymer aerogel (eg resorcinol formaldehyde resin, copolymer containing Cu), porous material such as clay inter-layer crosslinked porous material, or brittle substance (biopolymer One kind of dried humic acid, etc.), a substance that aggregates (Y-Ba-Cu-O-based double oxide fine powder, etc.), and the like can be targeted. Even in such a porous body, similar problems occur in the drying step, and these problems can be solved by applying the present invention.

  In practicing the present invention, the first solvent contained in the wet body (for example, a wet gel) corresponds to a solvent used for the production of a porous wet gel. Generally, alcohols are used. There are many examples used. Moreover, as this alcohol, any of methanol, ethanol, isopropanol, butanol, etc. can be used, and it is not specifically limited.

  In addition, the first solvent is assumed to be an alcohol contained in the step of producing an airgel, for example, but the alcohol contained in the step of producing an airgel is temporarily substituted with another solvent and included in the production step. Solvent at the stage where the catalyst, etc. is removed, or the catalyst at the stage where the airgel has been hydrophobized, and the solvent at the stage where the solvent is replaced with a solvent having high solubility in supercritical carbon dioxide, such as organic solvents such as acetone and hexane It may be a solvent.

  On the other hand, the second solvent used to replace the first solvent in the present invention is not particularly limited as long as it can easily achieve a high-pressure state (particularly a supercritical state). Examples include carbon dioxide, nitrous oxide, propane, and ammonia. Among these, carbon dioxide is recommended as a preferable one from the viewpoint of a relatively low critical temperature and critical pressure, a safe fluid, and low cost. In particular, carbon dioxide has an advantage that the treatment can be performed at a low cost as compared with the case of using alcohol in a supercritical state.

  The second solvent may be supplied as long as the first solvent and the second solvent are not less than the two-component critical state where the two-phase state (liquid / liquid or gas-liquid coexisting phase) is not formed. It is not indispensable that it is above the critical state of one solvent or the second solvent. In addition, the first solvent in the mixed stage is not necessarily required to be higher than the critical state of the first solvent or higher than the critical state of the second solvent. In order to carry out efficiently, the pressure and temperature above the critical condition of the second solvent are more preferable. In the present invention, “more than critical state” means “supercritical state, critical state or subcritical state”.

  For example, the case where isopropanol (IPA) is employed as the first solvent and carbon dioxide is employed as the second solvent will be described with reference to FIG. 5 showing phase equilibrium at 60 ° C., 50 ° C., and 20 ° C. Note that the pressure shown on the vertical axis in FIG. 5 is expressed as a so-called gauge pressure. As understood from FIG. 5, since the two-phase coexisting phase at 60 ° C. is present at 10.5 MPa or less, the pressure at 60 ° C. may be 10.5 MPa or more. Since the critical temperature of isopropanol is 235 ° C., 60 ° C. is below the critical temperature, but it can still be replaced and dried without going through the two-phase coexisting phase. Moreover, when processing at the critical temperature of carbon dioxide of 31 degrees C or less, for example, 25 degreeC, you may replace by performing processing, such as raising temperature, before reaching a two-phase coexistence phase.

  From such a viewpoint, the mixed solvent used in the present invention is preferably a combination in which the first solvent is alcohol and the second solvent is carbon dioxide in a supercritical state.

  Next, the configuration of the apparatus according to the present invention will be described in detail based on the drawings. FIG. 1 is a schematic explanatory view showing an example of the configuration of the manufacturing apparatus of the present invention. In this apparatus, as a basic configuration, a porous body processing unit 1, a first solvent high pressure supply unit 2, a second solvent high pressure supply unit 3, and a high pressure mixing unit 4 are provided. Accompanying these basic configurations, a first solvent separation unit 5, a second solvent receiving tank 6, a cooling unit 7, heating units 8a and 8b, a decompression unit 9 are provided, and a first solvent storage unit 10a is provided if necessary. It is done. Depending on the type of first solvent and the second solvent to be handled, conditions, etc., the heating means 8a and heating means 8b may be installed at positions different from those in FIG. Or, they may not be installed.

  In such an apparatus, the first solvent high-pressure supply unit 2 has a liquid solvent of the same type as the liquid solvent (first liquid solvent) contained in the wet body (eg, wet gel) processed in the porous body processing unit 1. This liquid solvent is supplied from the first solvent high pressure supply unit 2 to the high pressure mixing unit 4 in a high pressure state. A second solvent for replacement is supplied to the second solvent high pressure supply unit 3, and this solvent is supplied from the second solvent high pressure supply unit 3 to the high pressure mixing unit 4 in a high pressure state. The second solvent high-pressure supply unit 3 is supplied with the low-pressure second solvent from the second solvent receiving tank 6 via the cooling means 7. Although not shown in FIG. 1, the second solvent discharged from the first solvent separation unit 5 is returned to the second solvent receiving tank 6 after being passed through a heat exchanger, a purifier, or the like and reused. good.

  In the high-pressure mixing unit 4, the supplied solvents (the same type of solvent as the first solvent and the second solvent) are mixed at a predetermined ratio to be a mixed solvent. Then, the mixed solvent is heated by the heating means 8 a and then sent to the porous body processing unit 1. The heating at this time is set to a temperature at which the mixed solvent becomes a supercritical state.

  The porous body processing unit 1 is provided with a wet body (for example, a wet gel) containing the first liquid solvent. The wet body is brought into contact with the supplied mixed solvent, and the first wet body is in the first position. This solvent is gradually replaced with the second solvent in the mixed solvent. In supplying the mixed solvent, by controlling the amount of each solvent supplied from the first solvent supply unit 2 and the second solvent high pressure supply unit 3, the mixing ratio of each solvent in the mixed solvent can be changed, Control can be performed so that the mixing ratio of the second solvent gradually increases.

  That is, in the porous body manufacturing apparatus shown in FIG. 1, the amount of each solvent in the mixed solvent is mixed by controlling the amount of each solvent supplied from the first solvent supply unit 2 and the second solvent high pressure supply unit 3. The operation is performed while changing the ratio of the supply amount of the first solvent and the supply amount of the second solvent to change the ratio. Note that the first solvent high-pressure supply unit 2 and the second solvent high-pressure supply unit 3 are to supply in controlling the amount of each solvent supplied from the first solvent high-pressure supply unit 2 and the second solvent high-pressure supply unit 3. It is preferable that the supply amount of each solvent is controlled by so-called feedback control or the like so that the supply amount of each solvent can be correctly supplied. For example, the first solvent high-pressure supply unit 2 and the second solvent high-pressure supply unit 3 preferably include a flow meter or the like in the vicinity of each solvent supply port. In addition, the first solvent high-pressure supply unit 2 and the second solvent high-pressure supply unit 3 are set based on the detection amount output from the flow meter and the like and the supply amount preset according to the supply process. It is preferable to control so that each solvent may be supplied. However, the present invention is not limited to such a configuration. In short, it is sufficient if the configuration is such that the mixing ratio of each solvent in the mixed solvent can be changed.

  The mixed solvent supplied to the porous body processing unit 1 is sent to the decompression unit 9, the heating unit 8b, and the first solvent separation unit 5, and is separated into the first solvent and the second solvent. The mixed solvent is supplied while increasing the ratio of the second solvent in the mixed solvent, that is, decreasing the ratio of the first solvent, then the supply of the first solvent is stopped, and only the second solvent is supplied. Among them, the mixing ratio of the first solvent in the mixed solvent becomes substantially zero, but the supply of the second solvent is continued thereafter. Accordingly, the wet body in the porous body processing unit 1 is dried while the solvent replacement is performed, and after the solvent replacement is completed, the mixed solvent in which the mixing ratio of the first solvent is approximately zero, that is, the second solvent is approximately the second. Drying is continued with the solvent alone. Finally, after the supply of the second solvent is stopped and the inside of the porous body processing unit 1 is depressurized, the dried porous body, which was originally a wet body, is taken out from the porous body processing unit 1.

  In this apparatus, a first solvent storage unit 10a is provided as necessary, and the first solvent separated by the first solvent separation unit 5 is stored in the first solvent storage unit 10a. Then, the stored first solvent is circulated to the first solvent high-pressure supply unit 2 and reused. Depending on the separation conditions of the first solvent separation unit 5, a large amount of the second solvent that should not be originally contained in the separated first solvent may be dissolved. Therefore, the first solvent storage unit 10a may be provided with a function of heating the solvent and the like, and the second solvent dissolved in the first solvent may be removed.

  FIG. 2 is a schematic explanatory view showing another configuration example of the manufacturing apparatus according to the present invention. The basic configuration of this apparatus is similar to the apparatus configuration shown in FIG. 1, and the same reference numerals are given to corresponding parts to avoid redundant description.

  In this apparatus, instead of the first solvent high-pressure supply unit 2 in the apparatus shown in FIG. 1, a high-pressure solvent circulation unit 12 is provided, and a part of the mixed solvent is circulated through the first solvent contained in the wet body. It is configured to be used as. In this apparatus, the wet body containing the first solvent is installed in the porous body processing unit 1, and the first solvent contained in the wet body is sent to the high-pressure solvent circulation unit 12 in advance to perform high-pressure mixing. It is circulated from the part 4 in the porous body processing part 1. This circulation of the solvent is carried out while the solvent is in a high pressure state. Then, by supplying the second solvent from the second solvent high-pressure supply unit 3 to the high-pressure mixing unit 4 through the heating unit 8c, the first solvent and the second solvent are predetermined in the high-pressure mixing unit 4. After being mixed at a mixing ratio to be a mixed solvent, it is sent to the porous body processing unit 1 and the same processing is performed. At this time, the mixing ratio of the second solvent in the mixed solvent supplied from the solvent mixing unit 4 to the porous body processing unit 1 by changing the supply amount of the second solvent from the second solvent high-pressure supply unit 3 Can be changed.

  Also in this apparatus, a first solvent storage unit 10b is provided if necessary, and the first solvent separated by the first solvent separation unit 5 can be stored in the first solvent storage unit 10b. The stored first solvent is circulated and reused in the porous body processing unit 1. Here, the supply of the first solvent to the porous body processing unit 1 is performed only when the porous body processing unit 1 is at normal pressure.

  The other configuration is basically the same as that of the apparatus shown in FIG. 1, but the method of the present invention can be effectively implemented by such an apparatus configuration.

  FIG. 3 is a schematic explanatory view showing still another configuration example of the manufacturing apparatus according to the present invention. The basic configuration of this apparatus is similar to the apparatus configuration shown in FIG. 1, and the same reference numerals are given to corresponding parts to avoid redundant description.

  In this apparatus, in addition to the apparatus shown in FIG. 1, the porous body processing section 1 is provided with a pressure detection means 13 for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing section. Then, based on the signal detected by the pressure detecting means 13, the pressure reducing means 9 is controlled to operate while gradually reducing the pressure of the high pressure mixed solvent. Here, “the pressure of the high-pressure mixed solvent is gradually reduced” means that the pressure of the mixed solvent is reduced as the mixed solvent is supplied. The meaning is not limited to supplying the mixed solvent so that the pressure of the mixed solvent continuously decreases smoothly, but the mixed solvent is supplied so that the pressure gradually decreases. It may be what you do.

  FIG. 4 is a schematic explanatory diagram showing another configuration example of the manufacturing apparatus according to the present invention. The basic configuration of this apparatus is similar to the apparatus configuration shown in FIG. 2, and the same reference numerals are given to corresponding parts to avoid redundant description.

  In this apparatus, in addition to the apparatus shown in FIG. 2, the porous body processing unit 1 is provided with a pressure detection means 14 for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing unit. Then, based on the signal detected by the pressure detecting means 13, the pressure reducing means 9 is controlled to operate while gradually reducing the pressure of the high pressure mixed solvent. Here, “the pressure of the high-pressure mixed solvent is gradually reduced” has the same meaning as described for the apparatus shown in FIG.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and any design changes in accordance with the gist of the preceding and following descriptions are technical aspects of the present invention. It is included in the range.

  In order to obtain silica aerogel, alkoxysilane, tetramethoxysilane, ethanol as a solvent, an ammonia aqueous solution as a catalyst and hydrolysis water are added and mixed to hydrolyze alkoxysilane, polycondensate, gel A compound was obtained. After adding isopropanol to this gel compound and heat-treating (a so-called aging step), a product in which the solvent portion was completely replaced (referred to as “alcogel”) was obtained.

  Using the thus obtained alcogel (wet gel), the atmosphere conditions were treated and dried by the methods shown in the following (A) to (G), and the formation state of the airgel at that time was investigated. The drying at this time was performed using a high-pressure vessel with a glass window while observing the inside of the vessel.

[(A) Method of supplying supercritical carbon dioxide into a high-pressure vessel]
Fill the high-pressure vessel with isopropanol (IPA), close the lid containing the one alcogel, pressurize the high-pressure vessel to 60 ° C. (A in FIG. 5), pressurize with carbon dioxide to 13 MPa (B in FIG. 5), and then Continue to supply supercritical carbon dioxide at 60 ° C. and 13 MPa, replace IPA in the high-pressure vessel with carbon dioxide (B to C in FIG. 5), and then depressurize the high-pressure vessel (C to D in FIG. 5). The gel was removed from the container.

  As a result, when all the treatments are completed in 7 hours, in the step of replacing IPA in the high-pressure vessel with supercritical carbon dioxide, a clear interface is formed between isopropanol and supercritical carbon dioxide, resulting in the gel. It was confirmed that cracks occurred. In addition, if the supply of supercritical carbon dioxide is temporarily stopped or flowed very slowly in the replacement process so that a two-phase interface does not occur due to the mutual diffusion of isopropanol and carbon dioxide, cracks will occur in the gel. It was confirmed that it did not enter. However, in that case, it took 9 hours for all the processes. In addition, when the spacer in the container is removed, the container depth is 1.6 times, and two alcoholcogels are put in the container and dried, in order to prevent the gel from cracking, in the replacement step, As described above, when supercritical carbon dioxide at 60 ° C. and 13 MPa was flowed at a flow rate of 10 cc / min, it was necessary to continue to flow for 770 minutes, and all treatments required a long time of about 14 hours. .

[(B) Method of supplying a mixed solvent of supercritical carbon dioxide and isopropanol into a high-pressure vessel]
Using the apparatus shown in FIG. 1, the high-pressure vessel (corresponding to the porous body processing unit 1) is filled with isopropanol, the alcogel is placed, the lid is closed, the high-pressure vessel is heated to 60 ° C., and then 13 MPa with carbon dioxide. Then, a mixed solvent of supercritical carbon dioxide and isopropanol at 60 ° C. and 13 MPa was supplied. At this time, isopropanol and carbon dioxide were mixed and supplied into the high-pressure vessel so that the mass ratio of isopropanol gradually decreased (for example, 95 mass% → 90 mass% → 85 mass%). In such a supply, as the mass ratio of isopropanol decreases, the concentration of isopropanol in the high-pressure vessel also decreases.

  After the mass ratio of isopropanol in the mixed fluid to be supplied was 0%, the supercritical carbon dioxide was supplied for a while, and the pressure was reduced after the isopropanol in the high-pressure vessel became 0.5% or less.

  According to such a method, in (A) above, the gel was not cracked during the drying process without forming an interface even during the treatment time (7 hours) in which the gel was cracked.

[(C) Method of circulating the solvent discharged from the high-pressure vessel and gradually mixing supercritical carbon dioxide]
Using the apparatus shown in FIG. 4, the high-pressure vessel (corresponding to the porous body processing unit 1) is filled with isopropanol, the alcogel is placed, the lid is closed, the high-pressure vessel is heated to 60 ° C., and then 13 MPa with carbon dioxide. The solvent was circulated by supplying the solvent discharged from the high-pressure vessel to the high-pressure vessel via the high-pressure mixing unit 4 by the circulation pump (high-pressure solvent circulation unit 12). Thereafter, supercritical carbon dioxide at 60 ° C. and 13 MPa was supplied while the solvent was circulated. At this time, the decompression means 9 was controlled based on the signal from the pressure detection means 14 so that the mixed solvent was discharged out of the system so that the pressure in the high-pressure vessel could be maintained at 13 MPa. As a result, the concentration of isopropanol in the high-pressure vessel gradually decreased, and finally only supercritical carbon dioxide was obtained. Thereafter, supercritical carbon dioxide was supplied for a while, and the pressure was reduced after isopropanol in the high-pressure vessel was completely removed.

  Even with such a method, in (A) above, the gel was not cracked during the drying process without forming an interface even during the treatment time (7 hours) in which the gel was cracked. That is, in the case of the above (A), it is necessary to perform the treatment under conditions that do not cause a two-phase interface depending on the mutual diffusion rate of the solvent, and for this purpose, a long time is required. On the other hand, in the case of the present invention [(B), (C)], since the concentration of the mixed solvent around the gel can be freely controlled, there is no restriction on the flow rate of the mixed solvent. The flow velocity around the gel can be freely set, and uniform processing can be performed in a short time.

[(D) Other methods of circulating the solvent discharged from the high-pressure vessel and gradually mixing the supercritical carbon dioxide]
Using the apparatus shown in FIG. 2, the high-pressure vessel (corresponding to the porous body processing unit 1) is filled with isopropanol, the alcogel is placed, the lid is closed, the high-pressure vessel is heated to 60 ° C., and then 13 MPa with carbon dioxide. The solvent was circulated by supplying the solvent discharged from the high-pressure vessel to the high-pressure vessel via the high-pressure mixing unit 4 by the circulation pump (high-pressure solvent circulation unit 12). Thereafter, supercritical carbon dioxide at 60 ° C. and 13 MPa was supplied through the high-pressure mixing unit 4 while the solvent was circulated. However, although the supply amount of supercritical carbon dioxide was initially 20 cc / min, the supply amount of supercritical carbon dioxide was increased to 35 cc / min after 180 minutes from the start of supply of supercritical carbon dioxide. That is, in gradually increasing the mixing ratio of the supercritical carbon dioxide as the second solvent, the increasing ratio itself of the supercritical carbon dioxide was increased stepwise (gradually). As a result, 100 minutes after increasing the supply amount of supercritical carbon dioxide, the isopropanol concentration in the high-pressure vessel became 0.5% or less. After the isopropanol concentration became 0.5% or less, the pressure was further reduced over 30 minutes. As a result, the time required for all treatments was about 5.7 hours.

  Also by such a method [the method (D) of the present invention], the porous body can be efficiently produced while preventing the occurrence of cracks and the like in the porous body. In this way, the operation time can be made shorter than in the case of the above (C) by operating while increasing the mixing rate of the supercritical carbon dioxide in a stepwise (gradual) manner. became.

[(E) Still another method of circulating the solvent discharged from the high-pressure vessel and gradually mixing the supercritical carbon dioxide]
Using the apparatus shown in FIG. 2, the high-pressure vessel (corresponding to the porous body processing unit 1) is filled with isopropanol, the alcogel is placed, the lid is closed, the high-pressure vessel is heated to 60 ° C., and then 13 MPa with carbon dioxide. The solvent was circulated by supplying the solvent discharged from the high-pressure vessel to the high-pressure vessel via the high-pressure mixing unit 4 by the circulation pump (high-pressure solvent circulation unit 12). Thereafter, supercritical carbon dioxide at 60 ° C. was supplied while the solvent was circulated. At this time, the pressure of the high-pressure mixed solvent (initially only isopropanol) was initially 13 MPa, but after starting the supply of supercritical carbon dioxide, it was reduced to 11.5 MPa after 40 minutes and to 10 MPa after 80 minutes. That is, the pressure was gradually reduced in the high-pressure mixed solvent. As a result, the isopropanol concentration in the high-pressure vessel after 300 minutes was 0.5% or less. As a result, the time required for all treatments was about 6 hours.

  Also by such a method [the method (E) of the present invention], the porous body can be efficiently produced while preventing the occurrence of cracks and the like in the porous body. In this way, by gradually reducing the pressure of the mixed solvent, the treatment time can be made shorter than in the case of (C).

[(F) Other methods of circulating supercritical carbon dioxide gradually by circulating solvent discharged from high-pressure vessel]
Using the apparatus shown in FIG. 4, the high-pressure vessel (corresponding to the porous body processing unit 1) is filled with isopropanol, one sheet of the alcogel is placed, the lid is closed, and the high-pressure vessel is heated to 60 ° C. Then, the pressure was increased to 13 MPa over 30 minutes, and then the solvent discharged from the high-pressure vessel was circulated by a circulation pump (high-pressure solvent circulation unit 12), and supercritical carbon dioxide was supplied at 20 cc / min. At this time, based on the signal from the pressure detection means 14, the decompression means 9 was controlled to discharge the mixed solvent discharged from the high pressure container out of the system so that the pressure in the high pressure container could be maintained at 13 MPa. As a result, the isopropanol concentration in the high-pressure vessel gradually decreased, and when the isopropanol concentration was measured after 360 minutes, it was 0.5% or less, and then the pressure was reduced over 30 minutes. As a result, the time required for all treatments was about 7 hours.

[(G) Other methods of circulating the solvent discharged from the high-pressure vessel and gradually mixing the supercritical carbon dioxide]
The procedure was substantially the same as the above method (F), but the spacer in the container was removed by this method, the container depth was increased 1.6 times, two alcogels were placed in the container, and supercritical carbon dioxide was supplied. The amount was 32 cc / min. As a result, similar to the method (F), the time required for all treatments was about 7 hours.

  Even by such a method [the present invention methods (F) and (G)], the interface is not formed even during the treatment time (7 hours) in which the gel is cracked in the above (A), and during the drying process. There was no crack in the gel. Also, as in (F) and (G) above, even if the number of alcogels is increased, the change in the concentration in the container can be set freely, so that only a single sheet can be processed, the processing in a short time This enables efficient industrial production of porous bodies.

  In the conventional method in which only the solvent for replacement is supplied, if the replacement speed is limited, the processing time increases as the size of the processing container increases. However, in the present invention, since the mixed solvent in which the same or the same type of solvent as that contained in the wet body and the solvent for substitution are mixed is supplied, the solvent concentration in the entire processing container is uniformly and continuously increased. And can be efficiently replaced with a solvent for replacement. As a result, even if the size of the processing container is increased, the processing time does not become long and the porous body can be efficiently produced.

  In addition, when the mixing ratio of the second solvent is gradually increased, the increase in the mixing ratio of the second solvent itself is gradually increased, thereby affecting the occurrence of cracks. It is possible to increase the replacement speed in the later stage of replacement while suppressing the speed. As a result, the processing time can be shortened and the porous body can be efficiently produced.

  Further, by gradually reducing the pressure of the mixed solvent, the concentration of the solvent for substitution decreases, and the concentration of the solvent contained in the wet body and the concentration of the solvent for substitution becomes relatively small, so that the substitution rate is increased. It is possible to improve the production efficiency of the porous body.

It is a schematic explanatory drawing which shows one structural example of the manufacturing apparatus of this invention. It is a schematic explanatory drawing which shows the other structural example of the manufacturing apparatus of this invention. It is a schematic explanatory drawing which shows another structural example of the manufacturing apparatus of this invention. It is a schematic explanatory drawing which shows the other structural example of the manufacturing apparatus of this invention. It is a phase equilibrium diagram of both when isopropanol is adopted as the first solvent and carbon dioxide is adopted as the second solvent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Porous body process part 2 1st solvent high pressure supply part 3 2nd solvent high pressure supply part 4 High pressure mixing part 5 1st solvent separation part 12 High pressure solvent circulation part

Claims (16)

  In the method for producing a porous body by replacing the first solvent in the wet body containing the first liquid solvent with the second solvent in a high-pressure state, the same or the same kind as the first solvent A method for producing a porous body, which is operated while supplying a mixed solvent of the above solvent and the second solvent.   The method for producing a porous body according to claim 1, wherein the mixing ratio of each solvent in the mixed solvent is changed and the mixing ratio of the second solvent is gradually increased.   3. The method for producing a porous body according to claim 2, wherein when the mixing ratio of the second solvent is gradually increased, the rate of increase of the mixing ratio of the second solvent is gradually increased.   The method for producing a porous body according to claim 1, wherein the pressure of the mixed solvent is gradually reduced.   The method for producing a porous body according to any one of claims 1 to 4, wherein the porous body is an airgel.   The method for producing a porous body according to any one of claims 1 to 5, wherein the first liquid solvent is alcohol and the second solvent is carbon dioxide. In a porous body manufacturing apparatus configured to manufacture a porous body by replacing the first solvent in a wet body containing a first liquid solvent with a second solvent in a high-pressure state to perform a drying treatment ,
A first solvent high pressure supply section for supplying the same or the same kind of solvent as the first solvent in a high pressure state;
A second solvent high pressure supply section for supplying the second solvent in a high pressure state;
A high pressure mixing section for mixing the first solvent and the second solvent in a high pressure state;
A porous body processing unit for processing the high-pressure mixed solvent supplied from the high-pressure mixing unit in contact with a wet body installed in a processing tank;
An apparatus for producing a porous body, comprising:   The apparatus for producing a porous body according to claim 7, wherein the apparatus is configured to operate while changing a ratio of a supply amount of the same or the same kind of solvent as the first solvent and a supply amount of the second solvent.   The apparatus for producing a porous body according to claim 7, further comprising a first solvent separation unit that separates the same or the same kind of solvent as the first solvent from the mixed solvent after the porous body treatment.   A first solvent storage unit that stores the same or same type of solvent as the first solvent separated by the first solvent separation unit, and the same or the same type of solvent as the first solvent from the first solvent storage unit The apparatus for producing a porous body according to claim 9, wherein the apparatus is configured to be circulated and reused in the first solvent high-pressure supply unit.   A pressure reducing means is provided after the porous body processing section, and a pressure detecting means for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing section is provided in the porous body processing section, and is detected by the pressure detecting means. The apparatus for producing a porous body according to any one of claims 7 to 10, wherein the apparatus is configured to control the pressure reducing means based on a signal and operate while gradually reducing the pressure of the high-pressure mixed solvent. In a porous body manufacturing apparatus configured to manufacture a porous body by replacing the first solvent in a wet body containing a first liquid solvent with a second solvent in a high-pressure state to perform a drying treatment ,
A porous body processing section in which the wet body containing the first solvent is installed and processed;
A high-pressure solvent circulation unit that circulates and supplies the high-pressure solvent discharged from the porous body processing unit;
A second solvent high pressure supply section for supplying the second solvent in a high pressure state;
A high-pressure mixing unit that mixes the solvent from the high-pressure solvent circulation unit and the second solvent from the second solvent high-pressure supply unit in a high-pressure state, and then supplies a mixed solvent to the porous body processing unit;
An apparatus for producing a porous body, comprising:   By controlling the supply amount of the second solvent from the second solvent supply unit, the mixing ratio of the second solvent in the solvent supplied from the solvent mixing unit to the porous body processing unit is changed. The apparatus for producing a porous body according to claim 12, wherein the apparatus is configured to operate while being operated.   The apparatus for producing a porous body according to claim 12, comprising a first solvent separation section that separates the first solvent from the mixed solvent after the porous body treatment in the porous body treatment section.   A first solvent storage unit for storing the first solvent separated by the first solvent separation unit, and circulatingly supplying the first solvent from the first solvent storage unit to the porous body processing unit; The porous body manufacturing apparatus according to claim 14, which is configured to be used.   A pressure reducing means is provided after the porous body processing section, and a pressure detecting means for detecting the pressure of the high-pressure mixed solvent supplied to the porous body processing section is provided in the porous body processing section, and is detected by the pressure detecting means. The apparatus for producing a porous body according to any one of claims 12 to 15, wherein the apparatus is configured so as to operate while gradually reducing the pressure of the high-pressure mixed solvent by controlling the decompression means based on a signal.

Images