JPH0520365B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing glass by a sol-gel method, and a method for producing glass for an optical fiber base material having a core-clad structure by the sol-gel method. The method can be advantageously applied.

[Conventional technology]

In recent years, a glass manufacturing method called the sol-gel method has been developed.It is easy to dope with various substances, it is possible to obtain a glass with a chemically very uniform composition, it is possible to sinter at low temperatures, and it is easy to obtain a glass of high purity. ,
It is attracting attention because it has advantages such as no need for expensive equipment and the possibility of producing glass at low cost.

In this method, a sol solution of glass raw materials is poured into a container, gelled, and the gel is dried and sintered to obtain glass. For example, glass is produced as follows.

First, Si, Ge, P, Al, Sb, Ti, Zr, Sn, Pb,
An alkoxide such as B is mixed with an alcohol such as methanol, ethanol, propanol, butanol. Then add water and mix further. The sol thus obtained is poured into a container whose inner surface is coated with silicone, and the container is placed in a constant temperature bath to gel the sol and dry. The dried gel is then sintered to form glass.

When the gel dries, the gel shrinks, and when the gel shrinks and peels off from the inner surface of the container, the gel tends to crack if the gel dispersion medium has good wettability with the container. In the above method, silicone is applied to the inner surface of the container in order to impair wettability and prevent gel cracking (Japanese Patent Laid-Open No. 56-92135).

However, silicone is soft and easily scratched, making it difficult to use it over and over again.
In addition, containers made of Teflon or the like have been used instead of containers coated with silicone on the inside (Japanese Patent Laid-Open No. 57-22127), but with this method, the container is opaque and drying cannot be observed. I can't.

Therefore, as shown in FIG. 5, the present inventors extruded the undried gel 1 from the container 3 with the extrusion rod 2, transferred it to another container 4 in which the area of the contact part with the gel 1 was reduced, Dry in the container 4,
When an attempt was made to obtain a dry gel, it was possible to obtain a dry gel without cracking. Hereinafter, this method will be referred to as the extrusion method.

[Problem that the invention seeks to solve]

However, when trying to obtain a large gel by the above-mentioned extrusion method, a problem arose in that the gel would break under its own weight when taken out.

The present invention aims to eliminate the above-mentioned drawbacks in extrusion methods and provide a method for extracting large gels without cracking, and also to provide a method for easily obtaining gels with a core-clad structure by applying the method. The purpose is to provide.

[Means for solving problems]

In view of the current situation explained above, the present inventors
After intensive research, they came up with the idea that the problem could be solved by extracting the gel from a liquid and supporting the weight of the gel with buoyancy.

The present invention provides a method for producing glass by obtaining a sol solution of a glass raw material, gelling the sol solution, drying the gel, and sintering the dried gel, when taking out the gel that needs to be dried. This is a method for producing glass, characterized in that at least a part of the gel is taken out while remaining in a liquid.

Furthermore, the present invention provides a method for producing glass for an optical fiber base material by obtaining a sol solution of a glass raw material, gelling the sol solution, drying the gel, and sintering the dried gel. When taking out the gel, at least a part of the first gel is taken out in a second sol solution that can become a second gel, and the first gel is held in the second sol solution. to gel the second sol solution, thereby causing the first sol to gel.
The gel is the core and the second gel is the cladding.
Provided is a method for producing glass characterized by obtaining a gel having a core-clad structure.

That is, as shown in FIG. 1, for example, by extruding undried gel 1 from a container 3 with a push rod 2 into a liquid 5 in a container 4 having an inner diameter larger than that of another container 3, the weight of the gel can be reduced. is supported by buoyancy and the gel can be taken out without cracking.

Liquids include water, methanol, ethanol, propanol, butanol, dioxane, acetone,
Dimethylformamide and the like can be used, but are not limited thereto. Further, although it is desirable that the liquid has a density similar to that of the gel, it is not necessarily necessary that the density be the same. The density of the liquid can be adjusted, for example, by appropriately mixing ethanol and water.

The liquid also contains B, Ge, P, Al, Sb, Ti,
By adding elements such as Zr, Pb, and Cs and keeping the gel in the liquid for several hours, the elements can be added to the glass produced.

When taking out a gel in a liquid, it is not necessarily necessary that the entire removed gel be in the liquid, but it is effective as long as at least a portion of the gel is in the liquid. For example, it may be as shown in FIG. Note that the symbols in FIG. 2 are the same as in FIG. 1. Further, the method for removing the gel is not limited to extrusion, and any method may be used as long as it can be removed in a liquid. For example, a cylindrical container divided into three parts may be used, and the gel may be taken out by dividing the container into three parts in the liquid.

The present invention can also be used to take out gel that has dried to some extent. For example, as shown in Fig. 3, a gel 41 that has dried and shrunk to some extent in a container 43 whose inner surface is coated with silicone is placed in water 45 in a container 4 that is larger in diameter and height than the container 43, and floats due to buoyancy. You can take it out. If you don't do this, the gel will be easily damaged when you take it out.
Since this method involves soaking the gel in a liquid, it is not preferable to use it to remove even sufficiently dried gel.

So far, we have described the case where alkoxides are used as raw materials, but this is not limited to this. Glass can also be produced by obtaining a sol solution of glass raw materials, gelling the sol solution, drying the gel, and sintering the dried gel. If so, the present invention can be utilized. For example, fuming silica fine powder is first granulated and then mixed with water to form a sol solution, which is poured into a container, gelled, dried, and sintered to obtain glass (Japanese Patent Laid-Open No. 58 26048), a large gel can be taken out more easily by taking out the gel in a liquid.

When making optical fibers, the inner refractive index is high;
A glass rod with a core-clad structure is required, with a low outer refractive index. A gel with a core-clad structure can be obtained as follows. Fourth
As shown in the figure, first, a gel 1 that will become the core is prepared in a tube 3 with a small inner diameter. On the other hand, a sol liquid 55 to be clad is put into the tube 4 having a larger inner diameter. The sol liquid 5
5, the gel 1 which will become the core is pushed out and held until the sol solution 55 which will become the cladding is gelled.

By drying and sintering the gel thus obtained, a glass for optical fiber base material having a core-clad structure is obtained. Shrinkage occurs during drying and sintering of the gel, but it is necessary to keep the shrinkage rates at approximately the same level in the core and cladding parts.

〔Example〕

Hereinafter, the manufacturing method of the present invention will be specifically explained with reference to Examples.

Example 1 19.0 g of Si(OCH ₃ ) ₄ and 23.0 g of ethanol were mixed using a magnetic stirrer, and 18.0 g of water containing 6 drops of 13% aqueous ammonia was added thereto and further mixed. Pour this liquid into 4 glass tubes (length 15 cm, inner diameter 8 mm) sealed at one end with aluminum foil and silicone adhesive.
I put eight minutes into each book. The mixture was allowed to stand at room temperature to form a gel. After 1 hour of gelation, the aluminum foil was removed from one of the tubes, a ball of soft paper was placed on the reaction side of the tube, and the gel was pushed out by pressing the paper with a rod. However, the gel broke midway due to its own weight, and the gel was only about 7 cm long. I tried the same thing with another tube, but could only get about 7 cm of gel.

Next, I put ethanol in a test tube with an inner diameter of 20 mm and a length of 20 cm, and when I pushed out the gel into it, the length was about 12 mm.
I was able to take out the cm gel without breaking it. After leaving this as it is for 5 hours, discard the ethanol, cover the test tube loosely with aluminum foil, and heat it to 60°C.
A dried gel was obtained in about 5 days after being placed in a constant temperature bath.

To make the remaining gel, put a solution of 1.0 g of boric acid in 60 g of ethanol in a test tube with an inner diameter of 20 mm and a length of 20 cm, and squeeze out the gel into the test tube to a length of approximately 20 cm.
A 12 cm gel was taken out without breaking. After leaving this as it is for 5 hours, throw away the ethanol,
The test tube was lightly covered with aluminum foil and placed in a constant temperature bath at 60°C, and a dried gel was obtained in about 5 days.

The two dry gels obtained in this way were
It was sintered at ℃ to obtain transparent glass.

Example 2 A sol solution with the same composition as Example 1 was placed in a glass tube (length:
150cm, inner diameter 8mm) with a length of 130cm. This was gelled, and after 1 hour gelation, a glass tube (length 130cm, inner diameter 12mm) was sealed at one end and filled with ethanol.
The gel was extruded into the gel, and about 10 cm from both ends were removed to obtain a 95 cm gel.

Example 3 9.5 g of Si(OCH ₃ ) ₄ and 11.5 g of ethanol were mixed in a magnetic stirrer, and 0.06 g of C _S NO ₃ dissolved in 9.0 g of water containing 1 drop of 13% ammonia water was added thereto. , further mixed.

This solution was poured for 8 minutes into a glass tube (length 15 cm, inner diameter 8 mm) whose one end was sealed with aluminum foil and silicone adhesive. It was left as it was at room temperature to gel. After 1 hour of gelation, 19 g of Si(OCH ₃ ) ₄ and 23 g of ethanol were mixed using a magnetic stirrer, and 18.0 g of water containing 2 drops of 13% aqueous ammonia was added thereto and further mixed. This liquid was placed in a glass tube (length 15 cm, inner diameter 25 mm) sealed at one end. The gel was pushed out into this, leaving about 1 cm of the gel. The state at this time is as shown in FIG. The sol solution is gelled in this state, and the length of the core-clad structure is approximately
A 10 cm gel was obtained.

[Effects of the Invention] The method of the present invention is an excellent sol-gel method in which large gels can be easily extracted, and gels for optical fibers having a core-clad structure can also be easily obtained using the method of the present invention. This is a method for manufacturing glass.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams illustrating embodiments of the method of the present invention, in which Figure 1 is a diagram in which undried gel is extruded into liquid 5, and Figure 2 is a diagram in which only a portion of the gel is in the liquid. Figure 3 shows the case of taking out gel that has dried to a certain extent, and Figure 4 shows the core of the present invention.
FIG. 3 is a diagram illustrating a method for obtaining a gel having a clad structure. FIG. 5 is a diagram illustrating a conventional method for removing gel.

Claims (1)

[Claims] 1 Obtaining a sol solution of a glass raw material, gelling the sol solution, drying the gel, and sintering the dried gel,
A method for producing glass, characterized in that when a gel that needs to be dried is taken out, at least a part of the gel is in a liquid. 2. A method for producing glass for an optical fiber base material by obtaining a sol solution of a glass raw material, gelling the sol solution, drying the gel, and sintering the dried gel,
When taking out the first gel that needs to be dried, at least a part of the first gel is taken out in a second sol solution that can become the second gel, and the first gel is placed in the second sol solution. A glass characterized in that a second sol solution is gelled while held in a liquid, thereby obtaining a gel having a core-clad structure in which the first gel is the core and the second gel is the cladding. manufacturing method.