JPH10231128A - Production of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a glass by a sol-gel method, capable of easily preventing the destruction of a gel and carrying out a solvent-exchanging treatment at a high speed to shorten the time required for an immersion process by performing plural immersion treatments of the gel obtained by the sol-gel method in a treating liquid at a specific temperature under a high pressure. SOLUTION: When plural immersion treatments of a gel in a treating liquid are carried out, the gel is treated at a temp. of 50-250 deg.C under a high pressure in at least either one of the immersion treatments. At least two pressure-proof vessels in whose systems temperatures and pressures can independently by controlled are connected to each other, and an immersion liquid in one vessel can be transferred to the other vessel in a state maintained at a high temperature and under a high pressure without returning the temperature and the pressure to original temperature and pressure, respectively. For example, treatment vessels 4, 9 at high temperatures and at high pressures are disposed in the A and B chambers 3, 8, respectively, of a pressure-proof vessel 1 provided with a partition 2, and the A and B chambers 3, 8 are maintained at prescribed temperatures and at prescribed pressures with heating means 6, 10 and valves 7, 11. A gel 5 is immersed in a vessel 4 and subsequently transferred to the vessel 9 through the partition 2. Thereby, the glass is rapidly obtained in a high yield without destructing the gel 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing glass by immersing a gel produced by a sol-gel method in a solution, followed by drying and firing.

[0002]

2. Description of the Related Art In order to produce glass by a sol-gel method, a sol is prepared by subjecting a silicon alkoxide serving as a glass skeleton to a hydrolysis reaction using an alcohol such as ethanol as a solvent under a catalyst such as hydrochloric acid. Is further subjected to a polycondensation reaction to produce a porous gel body (wet gel) in which alcohol, water, and the like are filled in a gap of a three-dimensional gel skeleton comprising a covalent bond of a metal atom such as silicon and an oxygen atom. Then, after removing the solvent contained in the pores in the wet gel by drying, it is densified by firing to obtain glass.

[0003] The advantage of producing glass using the sol-gel method is that the use of a liquid raw material makes it relatively easy to purify the raw material, so that high-purity glass can be produced. Glass that could not be produced by the conventional melting method, such as glass that contains a large amount of components that easily volatilize during melting and glass that uniformly contains components that easily separate during melting because glass can be obtained at a relatively low temperature Can be produced.

[0004] In spite of these advantages, firstly, there is a problem that the gel is easily broken due to a large volume shrinkage from drying and firing to a glass, resulting in poor yield. The wet gel prepared by the sol-gel method contains alcohol resulting from hydrolysis and condensation polymerization of silicon alkoxide, water resulting from the reaction, etc., and water has a large surface tension in the pores of the gel. For this reason, a large stress is generated in the pores of the gel during drying, which causes cracking.

Second, a gradient index optical element (GRI)
In the case of producing a glass in which the concentration distribution of the metal component is imparted in a medium such as N), a multi-step process is required, and there is a problem that the in-process period is long. In the refractive index distribution type optical element manufacturing step, a step of preparing a gel containing a metal salt having a large contribution to the refractive index such as lead acetate, immersing in a processing solution having a low solubility of the metal salt in the gel, A step of immobilizing the metal salt in the gel by precipitating microcrystals, a step of giving a gradient to the metal salt concentration distribution by immersing and eluting in a solution having a slightly higher solubility of the metal salt, It consists of a step of immersing in a small solution to precipitate metal salt microcrystals to fix the metal salt concentration distribution, a step of drying the solvent in the gel to obtain a dry gel, and a sintering step of heating and making the dry gel non-porous. . As described above, there are many steps of preparing a sol, gelling, fixing a metal component, imparting a distribution, and the like, followed by drying and firing after multi-stage immersion treatment. In particular, since each step of immersing the gel in the solution utilizes the diffusion of the solvent inside and outside the gel,
It is not uncommon for a single process to take hours to days.

As one of the methods for avoiding the above-described cracking during drying, which is the first problem, a method of gradually drying the gel with a lid having a small opening ratio when drying the gel is particularly featured. It is described in, for example, JP-A-60-131833.

A method of replacing the solvent in the wet gel with a solvent that is easy to dry is described in Japanese Patent Publication No. 2-39454. The gel obtained by hydrolysis of the alkoxide is heated at a high temperature in an autoclave. A method of strengthening the gel skeleton by pressure treatment and preventing cracking during drying is disclosed in Japanese Patent Publication No. Hei 8-25755. These methods have made it possible to take measures against cracking, which is the first problem in producing glass by the sol-gel method. However, there is no suitable method as a countermeasure against another problem, that is, a prolonged process.

The time required for solvent exchange increases as the size of the gel increases, and the diffusion time is proportional to the square of the diffusion distance. Therefore, if the size is simply doubled, the time required for liquid exchange is about four times When the size is tripled, the time required for liquid exchange is increased about nine times.

In particular, in the case of producing a gradient index optical element, the exchange of the solvent requires not only the step of providing the distribution but also the step of fixing the metal salt before and after the provision of the distribution.
In particular, the time required for liquid exchange requires a long time for the entire manufacturing process.

By impregnating the wet gel prepared by the sol-gel method with a metal salt solution, the solution in the wet gel is replaced with a metal salt solution, and the optical characteristics such as the refractive index, dispersion, and spectral transmittance are arbitrarily changed. Optical glass can be produced. By using a metal having a large contribution to the refractive index as a metal salt, for example, a salt of lead, barium, lanthanum, yttrium, titanium, or the like, a refractive index distribution type optical glass can be manufactured. In addition, a color filter or the like can be manufactured by using a metal having a coloring action as a metal salt, for example, a salt of copper, cobalt, iron, manganese, or the like.

In order to manufacture a gradient index optical element or a color filter, the solution in the wet gel is replaced with a metal salt solution, and the concentration distribution of the metal salt in the wet gel is adjusted to a desired concentration and a concentration distribution. Then, in order to fix the metal salt concentration distribution, it is immersed in a solvent having low solubility of the metal salt. However, since the fixing solution permeates from the outer peripheral portion of the wet gel, the metal salt is fixed from the outer peripheral portion. Since it takes time for the fixation solvent to diffuse to the vicinity of the center, it takes time before the fixation of the metal salt in the center starts, and during that time, the metal salt concentration distribution near the center collapses. there were.

[0012]

SUMMARY OF THE INVENTION In the present invention, when a glass is produced by a sol-gel method, the solvent exchange in the gel, which is performed for various purposes, requires that the solvent pass through the pores of the gel. Therefore, there is a problem that it takes a long time. The present invention has been made in view of such a problem, and has as its object to speed up the solvent exchange treatment of a gel produced by a sol-gel method.

[0013]

According to the present invention, in a method for producing a glass by a sol-gel method, when a gel is immersed in a treatment liquid a plurality of times, at least one of the immersion treatments is performed at a temperature of 50 ° C. or higher. And a method for producing glass under pressure at a temperature of 250 ° C. or lower. In the method for producing glass by the sol-gel method, when performing the immersion treatment of the gel in the treatment liquid a plurality of times, the immersion treatment is performed at 50 ° C. or more and 250 ° C.
This is a method for producing glass in which the glass is immersed in a treatment liquid having a different composition while maintaining the temperature and pressure under the following temperature. Further, in the method for producing glass by the sol-gel method, the glass is immersed in a pressure-resistant container having at least two compartments capable of individually adjusting the temperature and pressure.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Generally, a gel is immersed in a solution,
In the case of solvent exchange, the higher the temperature of the solution, the faster the solution diffuses through the gel skeleton. However, when the temperature is raised to a high temperature, the boiling point of the solvent causes the boiling of the solvent in the gel, so that a locally high pressure is generated in the gel and the gel is destroyed. Therefore, by applying pressure to the immersion treatment step as in the present invention and immersing the gel in a high-temperature and high-pressure solution while suppressing the boiling of the solvent, the solvent in the gel and the outside of the gel are not destroyed without destroying the gel. The exchange rate of the solvent can be further increased.

The immersion of the gel is performed by exchanging a solvent in the gel to prevent cracking during drying, and by doping a metal salt by immersion in a metal component-containing solution when producing a color filter, a gradient index optical element, or the like. For various purposes, such as immersion in a solution for dissolving the components of the metal salt, and immersion in a solvent that is hardly soluble in the metal component for fixing the metal component, Even if the method of the present invention is applied, the time required for the immersion step can be shortened, so that the glass manufacturing step by the sol-gel method can be shortened. In particular, since the refractive index distribution type optical element manufacturing process requires a multi-stage immersion process, the application of the present invention is particularly effective in shortening the process.

The high pressure suitable for the method of the present invention is a pressure at which the processing solvent does not boil at the processing temperature, preferably 1 kg / cm ² or more and 500 kg / cm ² or less, more preferably 5 kg / cm ² or more. , 200 kg / cm ² or less. On the other hand, if the pressurizing speed is too high, a pressure difference occurs inside the gel and the gel breaks. Therefore, the pressurizing speed is preferably low, but the processing time is too long, so that 2 kg / cm ² /
Minutes or more and 1000 kg / cm ² / minute or less. Also,
In order to speed up the process further, when immersing in the next immersion solution, do not return to the original temperature and pressure when immersing in the multistage, and transfer to the next immersion liquid while maintaining high temperature and high pressure Is valid. If it is possible to shift to the next solution while maintaining high temperature and high pressure, the time required for raising or lowering the temperature or pressure can be reduced.

Further, when the immersion solution is exchanged, the solvent in the gel expands,
Due to the shrinkage, stress may be applied to the gel skeleton that cannot follow the volume change. When the temperature is repeatedly increased, decreased, depressurized, and pressurized, stress on the gel skeleton is also repeatedly applied, so that the skeleton structure is damaged. However, according to this method of exchanging liquids at high temperature and pressure, the rise and fall of temperature and pressure are minimized,
Such damage to the gel skeleton can be minimized. As described above, in order to reduce damage to the gel skeleton and speed up the process, when immersing in the next immersion solution, do not return the temperature and pressure to the ambient temperature and pressure, and keep the high temperature and high pressure It shifts to the next immersion liquid.

In the present invention, maintaining the temperature and pressure means
It means not only maintaining the temperature and pressure constant, but also not heating the gel temperature or pressure and returning it to the state before pressurization when moving between gel processing steps or removing the processing solution. .

In the method of practicing the present invention, a plurality of immersion liquids necessary for gel treatment are prepared in advance in one pressure-resistant container, and the gel or solution is placed in the pressure-resistant container after a predetermined time has elapsed. There is a method of moving. This method is suitable when the type and number of immersion liquids are small.

When there are many types of immersion liquids, more places are required for disposing the immersion liquid containers, and a large pressure-resistant container is required. Also, when the immersion liquids have significantly different vapor pressure characteristics, if the immersion liquid is subjected to high temperature and high pressure in the same pressure vessel, the liquid having a low boiling point volatilizes and the liquid volume becomes unstable, It is not desirable to install in one pressure-resistant container because it may be mixed as impurities into other liquids.

Therefore, in order to solve such a problem, at least two pressure-resistant containers capable of independently controlling the temperature and pressure in the system are connected, and the temperature and pressure are not restored, and the high temperature and pressure are reduced. A method of transferring to another immersion liquid while maintaining the state can be given. As an example of such a pressure-resistant container, one having a configuration in which the inside of a pressure-resistant container 1 is divided into two chambers by a partition 2 as shown in FIG. First,
First, a high-temperature and high-pressure processing container 4 containing a solution to be used for high-temperature and high-pressure processing is attached to the A-room 3 in FIG. 1, a gel 5 is placed therein, and the A-room heating means 6 is connected to an external pressurizing or depressurizing means. A predetermined temperature and pressure are adjusted by a valve 7. In this state, it is immersed for a predetermined time. On the other hand, a processing container 9 containing a solution to be used for the next processing is placed in the chamber B, and when the immersion of the gel in the chamber A is completed, the heating means 10 in the chamber B and an external pressurizing or depressurizing means The same temperature and pressure as in the chamber A are reached by the valve 11 connecting When immersed for a predetermined time, the partition 2 between the room A and the room B is opened, the gel is moved to the immersion solution in the processing container 9 in the room B 8, and the partition 2 between the room A and the room B is closed. The inside of the B chamber 6 is maintained at a predetermined temperature and pressure, and immersion is continued. on the other hand,
After lowering the temperature in the A chamber 3 and returning it to normal pressure, a processing container for the next immersion solution is put in if necessary.

In order to strictly prevent the mixing of the vapors in the chambers A and B, an intermediate chamber is provided between the chambers A and B with an openable and closable partition. After separating the partition between the intermediate chambers and transferring the gel to the intermediate chamber and closing the partition between the chamber A and the intermediate chamber, the partition between the chamber B and the intermediate chamber is opened and the gel is moved to the chamber B. You can do it. In this case, in order to prevent drying of the gel during movement, it is preferable that the intermediate chamber is filled with vapor of a solvent contained in the gel, such as alcohol.

It is desirable that the temperature and pressure in both chambers immediately before opening for gel movement are the same, but in accordance with the solution having the lower vapor pressure among the vapor pressures of the processing liquids provided in both chambers, The temperature and pressure during immersion may be slightly different.
There can be various other configurations of an autoclave in which at least two pressure vessels capable of independently controlling the pressure in the processing chamber are conceivable, provided that the object of the present invention can be achieved.
Any autoclave may be used.

When the gel is immersed in the immersion liquid to elute the components in the gel, the concentration of the liquid coming out of the gel is high and the concentration of the immersion liquid is low in the vicinity of the gel. Since the exchange rate of the liquid increases as the concentration potential difference between the inside and outside of the gel increases, the exchange rate increases when the concentration of the eluate from the gel existing at a high concentration near the gel is as low as possible. be able to. Further, by sufficiently stirring the immersion solution in the pressure vessel, the solution near the gel and the solvent at a position away from the gel are mixed, so that the solvent exchange efficiency inside and outside the gel can be increased.

Further, since the temperature of the eluate greatly changes the diffusion rate, the temperature of each part of the processing solution must be made uniform so that the temperature of the processing solution does not become uneven when heating or cooling the solution. Also, the stirring of the processing solution is important. Therefore, when a gel is treated by the method of the present invention, it is very effective to use a pressure-resistant container equipped with a stirring device. As a stirring method in the pressure-resistant container, a method of rotating a stirring blade, a method of stirring a stirrer by a magnetic force, a stirring by bubbles or a liquid flow using a pump, or the like can be used.

When a refractive index distribution type optical element is manufactured, it is preferable that the temperature of the step of imparting the distribution be lower than the step of fixing the distribution thereafter. Although it is possible to speed up the distribution by performing the distribution applying step of the refractive index distribution type optical element at high temperature and high pressure, the distribution applying step requires delicate preparation as compared with the metal component fixing step before and after. If the distribution is gradually applied, the distribution shape can be formed precisely. Further, the temperature and pressure at the time of providing the distribution are preferably determined in consideration of the diameter of the gel and the size of the pores, the solubility characteristics of the immersion liquid and the metal salt used for providing the distribution, and the like. The distribution step is performed at a lower temperature than the subsequent step of fixing the distribution, and after the distribution of the metal is transferred to the distribution fixing liquid, the gel is transferred to the distribution fixing liquid. A method of increasing the diffusion rate of a solvent having a low dispersion into a gel is effective for obtaining a good distribution shape. This is because the fixing solvent quickly reaches the center of the gel, so that the difference in the arrival time of the distribution fixing solution depending on the position in the gel is reduced, and the collapse of the distribution can be reduced. In addition, after the distribution fixing step at high temperature and high pressure, the temperature and pressure are increased to a supercritical state, and the supercritical drying is performed. The process can be simplified.

[0027]

The present invention will be described below with reference to examples. Example 1 140 ml of Si (OCH ₃ ) ₄ and 140 ml of Si (OCH ₃ ) ₄
C ₂ H _{5) 4} 0.01 N hydrochloric acid 300ml and 0.25
A sol was prepared by adding 6 ml of a mol / l aqueous lead acetate solution and hydrolyzing the solution, poured into a cylindrical fluororesin container having an inner diameter of 40 mm, and gelled at room temperature to obtain a wet gel. Prepare two vessels in the autoclave, one for 5mo
500 ml of an aqueous solution in which 1 / l of potassium acetate and 0.001 mol / l of copper acetate were dissolved, and 500 ml of acetone was poured into the other container. The wet gel is immersed in a potassium acetate copper acetate aqueous solution, and the autoclave is heated at 115 ° C.
It was heated and pressurized to 180 kg / cm ² . The immersion solution was stirred by a stirrer so as to be uniform. After being immersed in this state for 12 hours, the gel surface was washed with acetone mist for 2 minutes while maintaining the temperature and pressure, and then the gel was transferred to acetone of another container and immersed for 5 hours. Fine crystals of copper acetate were precipitated. This gel was dried and fired to 670 ° C. to obtain a blue transparent glass rod having a diameter of about 7 mm. This glass had a function of cutting infrared light.

Comparative Example 1 A gel obtained in the same manner as in Example 1 was immersed in an aqueous solution in which 5 mol / l of potassium acetate and 0.001 mol / l of copper acetate were dissolved in a room at 25 ° C. under atmospheric pressure. Processed.
More than 70 hours were required to distribute copper acetate evenly inside the gel. In order to fix copper acetate and potassium acetate by sufficiently replacing the solvent in the gel with acetone, the immersion time in acetone was required to be 36 hours or more under the same conditions.

Example 2 155 ml of Si (OC ₂ H ₅ ) ₄ and 65 ml of Si
Hydrochloric acid of pH 2 was added to the mixed solution of (OCH ₃ ) _{4, and} the mixture was stirred for 1 hour to perform a partial hydrolysis reaction. In addition, 1.2
250 ml of 5 mol / l lead acetate aqueous solution and 85 ml of acetic acid
The sol obtained by adding the mixture of
After dispensing into a 0 mm gelling container, the mixture was left at 30 ° C. to gel. The gel was taken out of the gelling container, immersed in a 0.5 mol / l aqueous solution of lead acetate provided in an autoclave, and sealed. The autoclave is gradually pressurized to 20
After reaching kg / cm ² , heat to 90 ° C, 25k
After immersion for 10 hours at g / cm ² , the solution was cooled to 20 ° C. while maintaining the pressure, and then returned to normal pressure. The gel surface was wetted with ethanol and transferred to a container filled with ethanol while keeping the gel surface from drying. Seal the container, put it in an autoclave, 90 ℃, 50k
After immersion treatment at g / cm ² for 8 hours, the mixture was cooled to 20 ° C. while maintaining the pressure, and then returned to normal pressure to precipitate lead acetate microcrystals in the gel.

Next, this gel was immersed in a methanol solution containing 0.3 mol / l potassium acetate,
After immersion for 5 hours and 20 minutes in a state maintained at 10 kg / cm ² , the lead acetate was given a convex distribution, then returned to normal temperature and normal pressure again, immersed in acetone and heated to 70 ° C. and 100 ° C.
After the distribution was fixed at kg / cm ² for 6 hours, the temperature and pressure were increased and the temperature was maintained at 240 ° C. and 240 kg / cm ² for 3 hours to carry out supercritical drying to obtain an airgel. 6 of this airgel
By heating to 50 ° C and sintering, a diameter of about 1
A 7.6 mm GRIN glass rod was obtained. Conventionally, the immersion process time could be reduced to about one-eighth as compared with a case where an immersion step was performed at normal temperature and pressure to obtain a refractive index distribution type optical element.

Example 3 0.01N hydrochloric acid 1 was added to 280 ml of Si (OCH ₃ ) _4.
40 ml were added and partial hydrolysis was carried out for 1 hour.
Next, 50 mol of 0.8 mol / l barium acetate aqueous solution
1 and 65 ml of acetic acid were added and hydrolyzed to prepare a sol,
Pour into a cylindrical fluororesin container with an inner diameter of 12.4 mm,
Gelation was performed at room temperature to obtain a wet gel. The obtained gel was immersed and sealed in a container of an aqueous solution in which 0.2 mol / l of barium acetate was dissolved.

Then, the inside of the sealed container was set at 140 ° C. and 100 k
After the gel was immersed for 3 hours while maintaining the g / cm ² , the solution in the container was replaced with ethanol while maintaining the temperature and pressure, the gel was immersed in ethanol for 3 hours, and potassium acetate was immersed in the gel. And copper acetate microcrystals were precipitated. After immersion for 3 hours, the liquid temperature was cooled at a rate of 8 ° C./min.
After reaching ° C, the pressure was returned to atmospheric pressure.

The gel was immersed in a methanol / acetone mixed solution (25 ° C.) in which 0.2 M potassium acetate was dissolved for 28 hours, and barium and potassium acetate in the gel were exchanged.
The concentration distribution was such that the barium concentration was high in the center of the gel and low in the periphery. The gel after distribution was transferred into acetone and heated at 10 ° C./min while pressurizing at 20 kg / min. Finally 90 ° C, 15
The pressure was set to 0 kg / cm ^2, and the treatment was performed in this for 2 hours.
Thereafter, the resultant was again pressurized and heated, supercritically dried and baked to 670 ° C., to obtain a glass rod having a diameter of about 3.8 mm and having a colorless and transparent refractive index distribution type.

[0034]

According to the present invention, the provision of the concentration distribution under high-temperature pressurization and the fixation of the concentration distribution at a higher temperature and a higher pressure than that are performed, the distribution collapse at the time of fixing the distribution is small, and the refractive index distribution shape is reduced. It was possible to obtain a precise one with little variation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an apparatus for performing a method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pressure-resistant container, 2 ... Partition, 3 ... Room A, 4 ... High-temperature and high-pressure processing container, 5 ... Gel, 6 ... Room A heating means, 7 ... Valve, 8 ...
B chamber, 9: processing container, 10: heating means of B chamber, 11: valve

Claims (3)

[Claims] In a method for producing glass by a sol-gel method, when immersing a gel in a treatment liquid a plurality of times, at least one of the immersing treatments is performed by heating the gel to 50 ° C. or higher.
A method for producing glass, which is performed under pressure at a temperature of 50 ° C. or lower. 2. In the method for producing glass by the sol-gel method, when the gel is immersed in a treatment liquid a plurality of times, the immersion treatment is carried out under a pressure of 50 ° C. or more and 250 ° C. or less. A method for producing glass, characterized by immersing in a processing solution having a different composition while holding the glass. 3. The method for producing glass by the sol-gel method, wherein the immersion treatment of the gel is performed in a pressure-resistant container having at least two compartments whose temperature and pressure can be individually adjusted. Production method of glass.