JPS6389420A - Production of glass product - Google Patents

Abstract

PURPOSE:To prevent both generation of a crack of gel at a time of drying and foaming thereof at a time of sintering in the production of a glass product by a gel-sol method by bringing the gelled soln. of a raw material into contact with the soln. of a cross-linked compd. having plural specified functional groups. CONSTITUTION:A glass product is produced by allowing the soln. of a raw material contg. an organic metallic compd. having alkoxyl group to gel, drying and sintering it. In this method, the soln. contg. a cross-linked compd. having two or more functional groups forming metalloxane bond by condensation reaction is brought into contact with the above-mentioned gelled soln. of the raw material before drying and thereafter it is dried and calcined. Since hydroxyl group or alkoxyl group existing on the surface of gel before drying is bonded to the compd. having >=two functional groups forming metalloxane bond by means of the contact of the above-mentioned soln. and soln., the strength of the gel itself is enhanced. As a result, shrinkage in drying is suppressed and not increased and the diameter of small holes are not decreased, thus cracks are hardly generated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing glass products, and in particular to a method of gelling a solution through a condensation reaction of organometallic compound raw materials, and then drying and firing the gel to form a glass product. This paper relates to a method for manufacturing glass products commonly known as the sol-gel method.

[Conventional technology]

In the production of glass products using the sol-gel method using organometallic compounds, cracks are likely to occur during the drying process due to volume contraction due to evaporation of the solvent, and cracks are likely to occur during firing due to the small pore size remaining in the gel after drying. The major problem was that it was easy to cause foaming.

Some countermeasures have already been proposed for each of the problems of the prior art described above. For example, as a measure to suppress cracks in (2), there is a method of adding silica powder to the raw material powder (for example, Japanese Patent Application Laid-open No. 1983-12-12), a method of drying the gel above the critical point (Tatoeha, Tokukai Showa 5y-
2oqr17), etc. Regarding the foaming during firing in (2), for example, a method of gelling at high temperature to obtain a gel with a large pore size (for example, Yamaita, Okano, Ceramics Seikaisha, -L(r)lt31) )-1). 3! > , a method in which the calcination is carried out in a helium atmosphere (for example, s, 5atoh et
al, Journal of Non-Crystall
ine 5olids, L[/913) & jj
lj-7) etc. are known.

[The problem that the invention attempts to solve]

The present invention provides a method for simultaneously solving these two problems, that is, a method for obtaining a dried gel that does not cause cracks during the drying process and has large pores and is easy to sinter. .

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a method for producing glass products in which a raw material solution containing an organometallic compound having an alkoxyl group is gelled, dried and fired to produce a glass product. A solution containing a crosslinking compound having two or more bond-forming functional groups is brought into contact with the gelled raw material solution before drying.

Various types of functional groups can be considered for forming the metalloxane bond in the present invention, but a chlorine group or an alkoxyl group is preferable in view of their stability or reactivity. Moreover, there is no particular restriction on the metal, and it can be selected arbitrarily. The compound used in the present invention must have a functional group that generates at least two metalloxane bonds in order to bind the hydroxyl or alkoxyl groups present on the surface of the gel pores, and the greater the number, the more pronounced the effect will be. .

The best way to carry out the actual operation of the present invention is to immerse the gel before drying in a solution prepared by diluting a compound with a functional group that forms a metalloxane bond with a solvent such as alcohol, and leave it at an appropriate temperature and time to allow the reaction to occur. It is simple and effective.

Here, if a compound that generates a metalloxane bond is used without being diluted with a solvent, the reaction tends to occur only near the surface of the gel, and its effect is difficult to spread to the inside. The optimum concentration of the above compound cannot be uniformly defined because it varies depending on the gel size, composition, reactivity of the compound, etc., but it is approximately 1O-jo.
vo1%.

There are no particular restrictions on the raw material solution used in the present invention, and any solution that can be gelled by hydrolysis and dehydration polycondensation of an organometallic compound containing an alkoxyl group may be used.

[For production]

Gels obtained by hydrolysis and dehydration polycondensation of organometallic compounds are porous because these reactions have not taken place completely, and their surfaces contain hydroxyl groups (-OH) or unreacted alkoxyl groups (-OR). ) is covered. In the conventional method of directly drying the gel, the shrinkage during drying is aO
It is as large as ~50%, and cracks often occur during that time. The pore diameter of the obtained gel varies depending on various conditions, but the maximum diameter is only about 3 nm, and it tends to foam during firing.

In order to solve the above problems at the same time, the present invention provides that after a raw material solution containing an organometallic compound is gelled, the gel is brought into contact with a compound having two or more functional groups capable of forming a metalloxane bond through a condensation reaction, and then dried. , is firing. By the operation of the present invention, the strength of the gel itself is increased because the hydroxyl groups or alkoxyl groups present on the surface of the gel before drying are bonded with a compound having λ or more functional groups that form metalloxane bonds. As a result, shrinkage during drying is kept small and the pore size is kept large.
Moreover, since the strength of the gel itself has increased, cracks are less likely to occur. The crosslinking compound and the gelled raw material solution before drying have a ratio of 0.5 to . In terms of effectiveness and efficiency, contacting for 200 hours is preferred.

Hereinafter, the present invention will be explained in more detail according to examples.

〔Example〕

Commercially available methyl orthosilicate, ethanol, and 0.3
The volume ratio of normal ammonia water is /:/:0. 10 ml of the starting raw material solution obtained by mixing at a ratio of 1 to 2 and stirring well was put into a Teflon container with a diameter of J and j cm, and after sealing it,
A gel was obtained by standing at ℃ for 21 hours.

This gel was treated with a treatment solution/(l
Jml and allowed to react at 60''C for 21 hours.

He then removed the lid of the Teflon container, discarded the remaining processing solution, and dried it in a dryer kept at 0''C. Observed the number of cracks that had appeared on the gel body after drying. At the same time, the pore size distribution of the gel body was determined by a nitrogen adsorption method.The results are shown in Table 1.

As is clear from Table 1, the gels obtained in the examples of the present invention did not develop cracks during the drying process, and the pore diameter of the gels after drying was extremely large.

The dry gels obtained in Examples 1 to 6 above were heated at a heating rate of
After heating between aOO℃ at C/h and holding there for 10 hours,
When further heated to 1000''C at the same temperature increase rate and held there for a long time, transparent sintered bodies were obtained.Since no peak was observed in X-ray diffraction, these sintered bodies were It can be regarded as glass, and when its properties were measured, it was not much different from commercially available silica glass.

For comparison, when an untreated gel without the treatment according to the invention was heated to 7000° C. according to the same heating program, foaming occurred and no transparent sintered body was obtained.

〔Effect of the invention〕

According to the present invention, hydroxyl groups and/or alphxyl groups on the gel surface before drying cause a crosslinking reaction with a crosslinking compound,
The strength of the gel increases, drying shrinkage is suppressed, a gel with large pores is obtained, and foaming during firing is suppressed.

Claims (5)

[Claims] (1) In a glass product production method in which a raw material solution containing an organometallic compound having an alkoxyl group is gelled, dried and fired to produce a glass product, two functional groups that produce a metalloxane bond through a condensation reaction are added. A method for manufacturing a glass product, which comprises bringing a solution containing the above-mentioned crosslinking compound into contact with the gelled raw material solution before drying. (2) The method for manufacturing a glass product according to claim 1, wherein the functional group that forms the metalloxane bond is a chlorine group or an alkoxyl group. (3) The glass product according to claim 1 or 2, wherein the crosslinking compound is at least one selected from the group consisting of diethoxydimethylsilane, dichlorodimethylsilane, triethoxysilane, and tetramethoxysilane. manufacturing method. (4) The method for manufacturing a glass product according to any one of claims 1 to 3, wherein the crosslinked compound and the gelled raw material solution before drying are brought into contact for 0.5 to 200 hours. (5) The method for manufacturing a glass product according to any one of claims 1 to 4, wherein the organometallic compound is methyl orthosilicate.