JPH066493B2 - Method for producing low OH glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing glass, and more particularly to a method for producing glass by a sol-gel method using Si alkoxide as one of the raw materials.

[Prior Art] Currently, as a method for producing an optical fiber preform, a glass porous body obtained by depositing glass fine particles on a target by subjecting SiCl ₄ or the like in a flame to a VAD method or the like is used. The method of sintering to obtain a glass gob has become the mainstream. This is an excellent method for obtaining highly pure porous glass at a relatively low cost. However, since this method is a gas phase reaction, there is a drawback in that substances usable as additives are limited to those which can be gasified.

Therefore, in recent years, as a method of compensating for this drawback, a metal alkoxide mainly composed of Si is hydrolyzed to obtain silica gel or silica gel containing an additive element, and the silica gel is dried and then subjected to a non-porous treatment to obtain a transparent glass. The way to get is being actively researched.

As an example, an alkoxide of Si such as Si (OCH ₃ ) ₄ is
After thoroughly stirring and mixing with ethanol, water is added and further stirred to hydrolyze. At this time, it is preferable to add a pH adjusting agent such as ammonia to the water. Precipitation of particles starts with the start of the hydrolysis reaction, the reaction solution is transferred to a container coated with silicone on the inner surface, and a lid is covered with an aluminum foil or the like so that the drying time can be extended, and the reaction solution is placed in a constant temperature bath at about 60 ° C. By keeping it, the sol liquid is gelated and the gel is dried. The gel shrinks as it dries, and usually finishes drying in less than a few days. There is already known a method in which the gel thus obtained is taken out and subjected to a non-porous treatment by heating in a He atmosphere containing oxygen, for example, to obtain a transparent glass.

In addition, the inventors of the present invention have proposed that the sol liquid is mixed with powder having a size that does or does not become a colloid (Japanese Patent Application Nos. 59-192581 and 6-62).
According to this specification, it is possible to easily obtain a larger and easily sintered glass.

[Problems to be solved by the invention]

However, the above method has a drawback in that it is difficult to remove OH which adversely affects the optical characteristics of glass during sintering. Therefore, the infrared absorption of OH is large, and when heated to a high temperature, it may foam.

The present invention solves such problems of the conventional method,
That is, it is an object of the present invention to provide a method for obtaining a glass containing less OH.

[Means for solving problems]

The present invention is a low OH glass characterized in that at least one of the starting materials is a silicon alkoxide, and in the method of producing glass by the sol-gel method, the gel contains at least one of iodine, bromine and chlorine compounds. And a method for producing the above-mentioned object.

As a particularly preferred embodiment of the present invention, the above method in which the compound is an alkali metal iodide or bromide can be mentioned.

In the present invention, a compound of iodine, bromine or chlorine is contained in the gel, and the OH is lowered by utilizing the dehydrating action of these compounds.

Examples of iodine, bromine or chlorine compounds that can be used in the present invention include alkali metal iodides, bromides or chlorides, aluminum phosphorus, antimony, lead arsenide, bromides or chlorides, and the like. The compounds are not limited to these, and other iodine, bromine or chlorine compounds may be used. Particularly preferable compounds include iodides and bromides of alkali metals, and aluminum iodide, antimony, lead iodides and bromides are also preferable. The compound may be used alone or in combination of two or more kinds such as KI and KBr.

According to the method of the present invention, at least one of the raw materials is hydrolyzed as an alkoxide of silicon as described above to obtain silica gel or silica sol containing an additional element, and then the sol solution is gelled. iodine,
A compound of bromine or chlorine is included in the gel. Specifically, for example, the starting material is dissolved in water or alcohol. After gelation, the dispersion medium is replaced with a liquid containing the compound. After the gel is dried, the liquid containing the compound is soaked. However, other methods may be used.

Thus, iodine, bromine, or chlorine in the compound contained in the gel is bound to H of the OH group in the gel to become HI / HBr, HCl, etc., which scatters at the initial stage of sintering and is dehydrated by this. I think that the.

It is considered that iodide, bromide, and chloride are more likely to be appropriately decomposed than fluoride, and iodine, bromine, and chlorine are less likely to remain in the glass, which is advantageous.

Especially, iodide and bromide seem to be advantageous.

When dehydrating a porous body having a small pore size such as a gel, it is sufficient to use a dehydrating gas in the atmosphere during sintering as in the conventional case because the dehydrating gas does not easily penetrate into the gel. It is difficult to dehydrate. According to the method of the present invention, a dehydrating substance is present inside the gel, so that the gel can be dehydrated very effectively.

In the method of the present invention, the amount of the above-mentioned iodine, bromine, or chlorine compound added is not particularly limited, as the effect can be obtained even if the amount is small, and there is no particular limitation. The optimum amount may be selected according to the above.

The method of the present invention is effective when used alone, but when used in combination with other dehydration methods such as heating in a chlorine atmosphere, a greater effect can be obtained.

〔Example〕

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

Example 1 9.5 g of silicon tetramethoxide and ethanol 1
Mix 1.5g with magnetic stirrer and add 1 to it.
A solution prepared by dissolving 0.53 g of potassium iodide in 9.0 g of water containing 3 drops of 3% aqueous ammonia was added and further mixed. This was put into a test tube having a diameter of 12 mm, the inner surface of which was coated with silicone, at the 8th minute. Lightly cover this test tube with aluminum foil,
It was placed in a constant temperature bath at a temperature of 60 ° C. The gel was dry after one week.

This was sintered at a temperature of 1300 ° C. in a helium atmosphere containing 1% each of oxygen and chlorine to obtain a transparent glass. When the infrared transmittance spectrum of this glass was measured, it was as shown in FIG. 1, and the absorption of OH was extremely small.

Example 2 9.5 g of silicon tetramethoxide and ethanol 1
Mix 1.5g with magnetic stirrer and add 1 to it.
A solution prepared by dissolving 0.53 g of potassium bromide in 9.0 g of water containing 3 drops of 3% aqueous ammonia was added and further mixed. This was put into a test tube having a diameter of 12 mm, the inner surface of which was coated with silicone for 8 minutes. The test tube was lightly covered with aluminum foil and placed in a constant temperature bath at a temperature of 60 ° C. The gel was dry after one week.

This was sintered at 1300 ° C. in a helium atmosphere containing 1% each of oxygen and chlorine to obtain transparent glass. When the infrared transmittance spectrum of this glass was measured, it was as shown in FIG. 2, and the absorption of OH was extremely small.

Comparative Example 1 Silicon tetramethoxide 9.5 g and ethanol 1
Mix 1.5g with magnesium stirrer, and add 1 to it.
9.0 g of water containing 3 drops of 3% aqueous ammonia was added and further mixed. This was put into a test tube having a diameter of 12 mm, the inner surface of which was coated with silicone, at the 8th minute. The test tube was lightly covered with aluminum foil and placed in a constant temperature bath at 60 ° C. The gel was dry after one week.

This was sintered at 1300 ° C. in a helium atmosphere containing 1% each of oxygen and chlorine to obtain transparent glass. When the infrared transmittance spectrum of this glass was measured, it was as shown in FIG. 3, and the absorption of OH was extremely large.

Example 3 9.5 g of silicon tetramethoxide and ethanol 1
Mix 1.5g with magnetic stirrer and add 1 to it.
A solution prepared by dissolving 0.66 g of cesium bromide in 9.0 g of water containing 3 drops of 3% ammonia water was added and further mixed. This was put into a test tube having a diameter of 12 mm, the inner surface of which was coated with silicone for 8 minutes. Lightly cover the test tube with aluminum foil, and
It was placed in a 0 ° C. constant temperature bath. The gel was dry after one week.

130 in a He atmosphere containing 1% oxygen and chlorine.
Sintering was performed at 0 ° C. to obtain transparent glass. When the infrared transmittance spectrum of this glass was measured, the absorption of OH was small.

Example 4 9.5 g of silicon tetramethoxide and ethanol 1
Mix 1.5g with magnetic stirrer and add 1 to it.
A solution prepared by dissolving 0.81 g of cesium iodide in 9.0 g of water containing 3 drops of 3% ammonia water was added and further mixed. This was put into a test tube having a diameter of 12 mm, the inner surface of which was coated with silicone, at the 8th minute. Lightly cover this examiner with aluminum foil,
It was placed in a constant temperature bath at 60 ° C. The gel was dry after one week.

130 in a He atmosphere containing 1% oxygen and chlorine.
Sintering was performed at 0 ° C. to obtain transparent glass.

The infrared transmittance spectrum of this glass was measured. However, the absorption of OH was low.

Reference Example 1 When the same gels as in Examples 1 and 2 were calcined in air at 500 ° C. and then heated to 1100 ° C. in He atmosphere, the gel containing no potassium bromide foamed, but brominated. The gel containing potassium did not foam.

Although not mentioned in the examples, the same effect can be obtained by using a chlorine compound.

〔The invention's effect〕

According to the present invention, there is an excellent effect that a glass having a low OH can be obtained by the sol-gel method.

[Brief description of drawings]

FIG. 1 is a graph showing an infrared absorption spectrum of glass obtained by sintering silica gel containing potassium iodide, and FIG. 2 is an infrared absorption spectrum of glass obtained by sintering silica gel containing potassium bromide. Fig. 3 is a graph showing the infrared absorption spectrum of glass obtained by sintering pure silica gel, in which the horizontal axis is the wave number (cm ^-1 ) and the vertical axis is the transmittance (T%). is there.

Claims (2)

[Claims] 1. A method for producing glass by a sol-gel method, wherein at least one of the starting materials is a silicon alkoxide, and the gel contains at least one of iodine, bromine and chlorine compounds. OH glass manufacturing method. 2. The compound of iodine, bromine or chlorine is an alkali metal iodide or bromide.
The method for producing a low OH glass according to item (1).