JPH0283220A - Production of glass body - Google Patents

Abstract

PURPOSE:To obtain a dry gel excellent in calcining properties without cracking in a short time by bringing a gel into contact with a basic liquid with a higher moisture content than that of the gel and then with surfactant solution in producing a glass body from an organometallic compound according to a sol-gel method. CONSTITUTION:A solution containing an organometallic compound, e.g., methyl orthosilicate, is hydrolyzed, heated and gelatinized to provide a gel substance, which is then brought into contact with a basic liquid (pH8-12) with a higher moisture content than that of a liquid in pores of the gel substance. The resultant substance is subsequently brought into contact with a solution containing a surfactant or a liquid containing the surfactant added into the basic liquid. The surfactant is preferably an ampholytic or nonionic surfactant and the concentration thereof is at least 0.0001wt.%. The upper limit thereof is 1wt.% which is higher than the critical micelle concentration. The contact temperature is preferably 20-80 deg.C and the contact time is 3-100hr. The gel substance is then dried and calcined to afford a glass body.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for producing a glass body, and in particular to a method for producing a glass body, in which a solution is gelled by hydrolysis and polycondensation of an organic metal compound raw material, and then the resulting gel body is dried and sintered to form a glass body. A method for manufacturing glass bodies called the sol-gel method was used.

[Conventional technology]

In the manufacture of glass products by the sol-gel method using organometallic compounds, there has been a major problem in that volume shrinkage is severe due to evaporation of the solvent, and cracks are likely to occur during the drying process of the gel body. To prevent this, there is a known method of slowing down the drying speed and drying slowly over several weeks to several months. However, the above method takes a long time to manufacture, making industrial use virtually impossible. In recent years, several measures have been proposed to solve this problem.The most representative ones are: 1) Adding fine silica powder to the raw material solution to suppress cracks (for example, Japanese Patent Laid-open No. 5
9-92924), (2) A crack-free gel body is obtained by drying the gel body under critical conditions. method (e.g.
(Japanese Patent Application Laid-Open No. 57-209817), (2) A method using formamide, etc., which has a slow evaporation rate as a solvent (for example, L, L, He
nch et al., Mat, Res, Soc, Symp, P
roc, 32.47 (1984)), ■ a method of replacing the alkoxyl groups remaining in the gel body with hydroxyl groups and then drying (for example, T., Mizuno et al., 4th Sol-Gel International Workshop, 1987) , Kyoto). However, in the above-mentioned conventional technology, although the method of adding fine silica powder reduces the tendency for cracks to occur, it takes time and effort to disperse the fine silica powder in the solution, and it significantly slows down the drying speed. The problem was that it was impossible to raise the In addition, the method (2) of drying the gel body under critical conditions requires a large investment in equipment due to the use of an autoclave, and has the problem of poor productivity. However, there was a problem in that a large amount of formamide remained in the gel body, which caused cracks in the gel body during the sintering process.

[Problem to be solved by the invention]

The method (2), which the present inventors are working on, is to immerse the gel body in a liquid with a water content higher than that of the liquid filling the pores of the gel to transform all the alkoxyl groups into hydroxyl groups. Although it is a simple method, it is very effective. In addition, the properties of the liquid that can be used in this method range from acidic to basic. In particular, gel bodies immersed in basic liquids have a smaller specific surface area, a larger pore size, and a higher sinterability. We are proud that we can easily obtain glass by improving the
T, Mizuno et al., J, Man-Cryst
, 5olids, out. 236 (198B)) However, subsequent research by the present inventors revealed that when the gel body is made larger, cracks are more likely to occur during drying when it is immersed in a basic liquid. In view of the above-mentioned prior art, the present invention provides a method for maintaining the sinterability of a large gel body immersed in a basic liquid and suppressing cracks during drying.

[Means to solve the problem]

The present invention has been made to solve the above-mentioned problems, and involves producing a gel body by gelling a raw material solution containing an organometallic compound, and determining the water content of the liquid in the pores of the gel body. In the method of producing a glass body by bringing the gel body into contact with a basic liquid having a high water content and then drying and vE-curing, the gel body before drying is brought into contact with a solution containing a surfactant. There is. The method of bringing the gel body into contact with a solution containing a surfactant includes (1) bringing the gel body into contact with a basic liquid having a water content higher than the water content of the liquid in the pores of the gel body; ,
A method in which a surfactant is added to the basic liquid; (2) a method in which a solution 1α containing a surfactant is brought into contact with a gel body, and then a basic liquid is brought into contact with the gel body; (2) a base. A method of bringing a basic liquid into contact with a gel body and then contacting the gel body with a solution containing a surfactant; Examples include a method of adding and bringing into contact with the gel body. The pH of the basic liquid is not particularly limited, but if it is less than 8, the effect of increasing the gel pore size will not be significant.
Moreover, if it is larger than 12, gel dissolution will occur significantly and the strength of the gel will decrease, which is not preferable. Therefore, it is preferable that the pH of the basic liquid is 8 or more and 12 or less. Contact between the gel body and the surfactant reduces the surface tension of the liquid in the striped pores of the gel body. The amount of surfactant added to the liquid 'a' is preferably greater than the critical micelle concentration, but even if the amount is greater than the critical micelle concentration, the surface tension will not drop significantly, so excess surfactant will be wasted. Furthermore, if the amount of surfactant is too large, the surfactant will remain during gel sintering and the purity of the glass will decrease. Therefore, the upper limit of the surfactant concentration is preferably lvt% equal to or higher than the critical micelle concentration. The added surfactant is also concentrated in the culm and exerts its effect. In order to obtain a really noticeable effect, at least 0. It is preferable to contain OO01vt%. Regarding the type of surfactant, surfactants such as and can also have some effect. However, anionic surfactants cause adsorption reactions with eluted gel components such as silica,
Anionic surfactants are undesirable because they inhibit the growth of gel particles; amphoteric surfactants or nonionic W surfactants are undesirable because they have a low drying yield;
It is more preferable to use these surfactants because of their high drying yield. The temperature at which the gel body is brought into contact with the basic liquid containing a surfactant is not particularly limited, but if the temperature is too low, the liquid displacement reaction and gel particle growth reaction will be slow, resulting in closure during processing. becomes longer. Moreover, if the temperature is high, the internal pressure will rise beyond the boiling point of the solvent, and an expensive pressure-resistant container will be required. Therefore 20~80℃
is preferred. In addition, the time period for which the gel body is brought into contact with the basic liquid containing a surfactant is not particularly limited, but if it is too short, the growth of the gel particles will be incomplete, resulting in non-uniformity between the surface layer and the inside of the gel. 3 hours or more is preferable.
If the contact time is too long, productivity will decrease and problems such as gradual gel dissolution will occur, so the upper limit is 10
000 hours.

[Effect]

The force that causes cracks in the drying gel body is the capillary force that occurs at the gas-liquid-solid interface, and this is the capillary force ΔP,
It is known that it can be expressed as follows using the pore radius r of the gel, the surface tension γ of the liquid filling the pores, and the contact angle θ between the liquid in the gel pores and the gel. From the above formula (1), by reducing the surface tension of the liquid in the gel pores, cracks during drying can be suppressed. Although the surface tension of a liquid with a high water content is several tens of dyn/c, it can be reduced to about 1/2 to 173 by adding a surfactant. When a gel is immersed in a basic liquid, an increase in the gel particle size is observed. As a result, the pore size of the gel becomes larger and the crack resistance of the gel during drying is improved. In addition, the sinterability of the gel is improved, and it becomes possible to vitrify it easily. The action of surfactants is to reduce the surface tension of the liquid in the gel pores, but in the context of using basic liquids in the present invention, it is especially important to use amphoteric surfactants or nonionic surfactants. If it is, it will be even more effective in suppressing cracks. As described above, according to the present invention, by bringing a gel body into contact with a basic liquid containing a surfactant, the capillary force that causes cracks can be reduced, and drying can be performed quickly without causing cracks. be able to. In addition, since the gel pore diameter becomes large, a gel body with good sinterability can be obtained. The method of the present invention can be applied to gel bodies of any composition as long as they are produced from liquids containing organometallic compounds. Hereinafter, the present invention will be explained in more detail based on Examples.

【Example】

Examples 1 to 4 Commercially available methyl orthosilicate, ethanol, and water were mixed at a volume ratio of l+o, 43:1.83, and stirred for about 30 minutes to obtain a transparent liquid. 260ml of this liquid,
- It was placed in a Teflon-coated stainless steel container with sides of 15 cm and sealed, and gelatinized and cured at 60° C. for 24 hours. This wet gel was mixed with 0.00% of the various surfactants shown in Table 1 containing 0.02vt%. IN
It was immersed in 260 ml of ammonia water at 60°C for 24 hours. Thereafter, the liquid was discarded and the product was dried at 80°C. At the beginning of drying, cover with a lid with a frontage ratio of 0.2% and hold for 24 WIt.
After that, the lid was removed and dried for 18 hours. Approximately 85 m
A dried gel measuring m square and 7 mm thick was obtained. Drying yield is the first priority
Then, the obtained dry gel ° as shown in the table is 1000 ~
When heat treated at 1100°C, all gels had a
The resulting glass was 0 mm square and 5 mm thick. Comparative Examples 1 to 2 In order to confirm the effects of the present invention, wet gels obtained in the same manner as Examples 1 to 4 were prepared in Comparative Example 1:0. IN Ammonia Water Comparative Example 2: Each sample was immersed in an aqueous solution of water + amphoteric surfactant (0.02 wt%), subjected to immersion treatment under the same conditions as in the above example, and then dried and sintered. The results are shown in Table 111. If the treatment liquid does not contain a surfactant (Comparative Example 1), the drying yield will be low, and if it does not contain ammonia (Comparative Example 2), the drying yield will be low. All foamed under these conditions. Therefore, from the above examples and comparative examples,
It can be seen that the effects of the present invention are remarkable. Example-5 Wet gel obtained in the same manner as Example-1-4,
0. Immersed in 260ml of IN ammonia water, 60℃, 1
It was treated for 2 hours. Then, add an amphoteric surfactant to a concentration of O
-02 wt% and left at 60°C for 12 hours. When this gel was dried in the same manner as in Examples 1 to 4, the drying yield was 8.
It was 5%. In addition, this dry gel was heated to 1000
When heat treated at ~1100°C, a transparent glass was obtained. Example-6 Commercially available methyl orthosilicate, ethanol, and water were
:o, 43:1.83 volume ratio, commercially available Ti(OCnH*) 4 was added so as to contain 5 wt% as titania after firing to prepare a mixed solution, and Example- Wet gels were obtained in the same manner as in 1 to 4. This wet gel was mixed with 0°002wt% of amphoteric surfactant.
Including 0. 260 ml of IN ammonia water at 60°C.
Soaked for 4 hours. Thereafter, drying was performed in the same manner as in Examples 1 to 4. The drying yield is shown in Table 2. This dried gel could be easily vitrified by heat treatment at 1100 to 1200°C (see Table 2). Table 2 Comparative Examples-3 to 4 Wet gels obtained in the same manner as in Example-6 were used in Comparative Example 3.
:0. IN Ammonia water comparative example 4: Water amphoteric surfactant (0,002wt%)
The samples were each immersed in an aqueous solution of the above, subjected to the immersion treatment under the same conditions as in Example 6, and then dried and sintered. The results are shown in Table 2. Example 7 Wet gel obtained in the same manner as Examples 1 to 4,
0. Immerse in 260 ml of IN ammonia water at 60°C.
, soaked for 24 hours. After that, discard the ammonia water and remove the ammonia water. 02wt% amphoteric surfactant aqueous solution 260ml
It was immersed in water at 60°C for 24 hours. Thereafter, the liquid was discarded and drying was performed in the same manner as in Examples 1 to 4, and the drying yield was 80%. Also,
When this dried gel was heat-treated under the same conditions as Examples 1 to 4, it became transparent glass. Example-8 A gel body was prepared using the procedure of Example-7 except that the order of (1) ammonia water treatment and (2) surfactant treatment in Example-7 was reversed. The drying yield was 50%. Moreover, when this dried gel was heat-treated under the same conditions as Examples 1 to 4, it became transparent glass. In the above examples, the raw material solution containing the organometallic compound is a normal sol to which fine silica powder etc. are not added.
Although a gel solution is used, the present invention is not limited to the above, and a raw material solution containing an organometallic compound containing fine silica powder or the like may be used.

【Effect of the invention】

According to the present invention, as is clear from the above Examples and Comparative Examples, a dry gel with very good sinterability can be obtained in a short time without generating cracks. Since the present invention has almost no restrictions on the gel body itself, it can be applied to glasses of any components and compositions. Patent applicant Nippon Sheet Glass Co., Ltd. 2nd Division 5.1

Claims (1)

[Claims] (1) After producing a gel body by gelling a raw material solution containing an organometallic compound, and bringing the gel body into contact with a basic liquid having a water content higher than the water content of the liquid in the pores of the gel body. A method for producing a glass body by drying and sintering, the method comprising bringing the gel body before drying into contact with a solution containing a surfactant.