JPH0791069B2 - Glass manufacturing method - 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 a metal alkoxide as a raw material.

[Prior Art] At present, as a method for producing a preform of an optical fiber, glass microparticles obtained by depositing glass fine particles on a target by passing SiCl _4, etc. through a flame, including the VAD method, are 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 is sufficiently stirred and mixed with a diluting liquid such as ethanol, and then 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. Transfer the reaction solution to a container coated with silicone on the inner surface, cover with an aluminum foil or the like so that the drying time can be extended, and gelate the sol solution obtained above in a constant temperature layer of, for example, about 60 ° C. Dry the gel. The gel shrinks as it dries, and usually finishes drying after a few days. A method is already known in which the gel thus obtained is taken out and subjected to a non-porous treatment, for example, by heating in a He atmosphere containing oxygen to form a transparent glass.

Such a so-called sol-gel method allows alkoxides to be produced for many elements regardless of metal or nonmetal.
It has the advantage that various elements can be added easily.

As the alkoxide of Si, for example, Si (OC
H ₃ ) ₄ , Si (OC ₂ H ₅ ) _4, etc. are often used.

[Problems to be solved by the invention]

However, when Si (OCH ₃ ) ₄ is used as the raw material, sintering of the gel is not easy because the gel foams or cracks. In addition, even if the transparent vitrification was successful, it often foamed when heated further. On the other hand, Si (OCH ₃ ) ₄
Higher alkoxides such as Si (OC ₂ H ₅ ) ₄ , Si (OC _{3
H 7) 4, Si (OC} 4 H 9) 4, Si (OC 5 H 11) when using ₄ or the like, but the sintering of the gel is easy, filed is difficult to obtain a form that wishes dry gel It was This is because the gel is extremely fragile.

The present invention intends to provide a glass manufacturing method which solves the above-mentioned difficulties.

[Means for solving problems]

The inventors of the present invention have diligently studied and found that the above-mentioned difficulties can be considered as follows.

The gel produced by hydrolyzing Si (OCH ₃ ) ₄ has a small clearance diameter and a large cohesive force. Therefore, gels are easily obtained.
However, since the clearance is small, the gas generated during sintering is not fully exhausted and is easily foamed or cracked. On the other hand, a gel made by hydrolyzing a higher alkoxide such as Si (OC ₂ H ₅ ) ₄ has a large clearance diameter and a small cohesive force. Therefore, the gel is fragile. However, the gas during sintering easily escapes to the outside of the gel, so that sintering is easy. Therefore, Si (OCH ₃ ) ₄ and Si (O ₂ H ₅ ) ₄ etc.
It was conceived to use it together with an alkoxide higher than CH ₃ ) ₄ .

That is, the present invention is a method of hydrolyzing Si alkoxide to obtain a sol liquid, gelling the sol liquid, and then forming a dry gel to sinter the gel to produce glass. OCH ₃ ) ₄ and Si (OC ₂ H ₅ ) ₄ or higher alkoxides are used, and Si (OC ₂ H ₅ ) ₄ or higher alkoxides are hydrolyzed before Si (OCH ₃ ) _4. It is a method of manufacturing glass.

In a particularly preferred embodiment of the present invention, Si (OC ₂ H
₅ ) The higher alkoxide of ₄ or more is 70%
More than mol% is hydrolyzed, and the hydrolysis is at a temperature of 40 ° C.
Above, the above method performed at 85 ° C or lower, and the sol liquid of the higher alkoxide of Si (OC ₂ H ₅ ) ₄ or higher obtained by pre-hydrolysis is concentrated to a SiO ₂ concentration of 20% by weight or more and 45% by weight or less. Then, the above method of mixing with Si (OCH ₃ ) ₄ or a sol liquid of Si (OCH ₃ ) ₄ can be mentioned. In the present invention, Si
(OC ₂ H ₅₎ as _four or more high alkoxide, Si (OC ₂
It is particularly preferred to use H ₅ ) ₄ .

The present invention is Si (OCH _{3) 4} and Si (OC ₂ H _{5) 4,} etc. Si (OCH _3)
The above difficulty is solved by using in combination with a Si alkoxide higher than _{4 in} order to prevent the gel from breaking.
(OCH ₃ ) ₄ is used as the raw material to obtain SiO ₂ , and the gap in the gel for facilitating sintering is Si (OC ₂ H ₅ ) ₄ etc.
₃ ) Obtained by SiO ₂ using an alkoxide of Si higher than ₄ as a raw material.

Results of our experimental studies, in having a strength to withstand handling for gel experiments, Si (OCH _{3) 4} and
It was found that the sum of those formed by hydrolysis of Si (OCH ₃ ) ₄ is preferably 1% or more in the sol liquid in terms of SiO ₂ .

Also, in order to have a gap in the gel that allows the gel to be easily sintered, Si (OCH ₃ ) ₄ such as Si (OC ₂ H ₅ ) ₄ should be used.
SiO ₂ generated from the alkoxide of higher Si is
It is preferable that the amount of SiO ₂ generated from (OCH ₃ ) _{4 is} larger.

Additives such as Ge, Al, Ti, B, Sn, Pb, Nd, Yb, Ce and Pr can be added to the glass by adding the compound to the raw material or by impregnating it after gelling. .

Also, Si (OCH ₃ ) ₄ has a faster hydrolysis rate than higher alkoxides of Si (OC ₂ H ₅ ) _{4 and} above. In the present invention, the higher alkoxide such as Si (OC ₂ H ₅ ) ₄ is first hydrolyzed and then mixed with Si (OCH ₃ ).

When the hydrolysis reaction of Si (OCH ₃ ) ₄ proceeds, the sol liquid gels, and after gelation, the hydrolysis reaction becomes slow. Therefore, to obtain a gel in good yield and in a short time, Si (OC
Higher alkoxides such as ₂ H ₅ ) ₄ etc.
It is desirable that 0 mol% or more is hydrolyzed. Si (O
By mixing a sol solution in which higher alkoxide such as C ₂ H ₅ ) ₄ is decomposed by 70 mol% or more with a sol solution of Si (OCH ₃ ) ₄ , the yield is improved and the time is shortened to obtain a gel. Is certain.

Hydrolysis of higher alkoxide such as Si (OC ₂ H ₅ ) ₄ is preferably carried out at 40 ° C. or higher and 85 ° C. or lower. This is 40 ℃
This is because at a temperature below 1, the hydrolysis rate is slow and the particle size becomes small. FIG. 2 shows the relationship between the time (days) and the temperature (T ° C.) required for the reaction of yield (the amount of SiO ₂ produced relative to the theoretical amount) of 50% in the present invention example shown in Example 3 described later. From FIG. 2, it can be seen that it is preferable to carry out the reaction at 40 ° C. or higher in order to obtain a high yield in a shorter period.

(Yield) 1/3 of the example of the present invention shown in FIG.
The relationship with the average particle size (nm) obtained from the specific surface area measured by the ET method is shown. A is at 23 ° C and B is at 63 ° C.

It has already been reported by Shibata et al. That, in the case of a gel using only Si (OC ₂ H ₅ ) ₄ as a raw material, if the specific surface area is 200 m ² / g or less (average particle size is 14 nm or more), it will not foam during sintering. [Reference: Proceedings of the 60th National Conference of the Institute of Electronics and Communication Engineers, Semiconductor and Materials Division, Lecture No. 385, p1-200]. According to the present invention, the particle size of the sol liquid hydrolyzed at 23 ° C. is not sufficiently large in the present invention. Regarding the particle size, those decomposed at 40 ° C or higher are superior.

On the other hand, when the temperature is high, the vapor pressure of the sol liquid increases, and in this case, the amount of evaporation becomes too large unless the system is closed. However, if the system is sealed, the internal pressure becomes high, and if a system that can withstand high pressure is made, the device will be expensive. Considering these points, it is economical and safe to hydrolyze at 40 ° C or more and 85 ° C or less.

In addition, the sol solution obtained by hydrolyzing the sol solution of a high-order alkoxide such as Si (OC ₂ H ₅ ) ₄ is concentrated after Si (OCH ₃ ) ₄ or
It is preferable to mix it with a sol liquid of Si (OCH ₃ ) ₄ . Si (OC
Higher alkoxides such as ₂ H ₅ ) ₄ are hard to mix with water,
Since it is necessary to dilute with ethanol or the like to mix, it is difficult to prepare a sol solution having a high concentration from the beginning. On the other hand, when the gel is dried, the larger the amount of SiO ₂ in the gel, the smaller the amount of evaporation of the dispersion medium required to obtain 1 g of SiO ₂ is. For the above reasons, it is preferable to concentrate the sol liquid of the raw material after hydrolysis to obtain a high concentration. The concentration of the concentrated sol liquid is preferably 20% by weight or more and 45% by weight or less. If it is less than 20% by weight, the effect of concentration is small,
When the concentration is higher than 45% by weight, the sol liquid tends to gel,
This is because it is difficult to concentrate in a range that does not gel. It is safe to concentrate with a hot water bath. However, other concentration methods such as placing the sol solution in a constant temperature bath at 60 ° C. and wiping dry air onto the sol solution may be used.

Among the higher alkoxides than Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ is generally superior. The reason is that the rate of hydrolysis is high, the amount of solvent mixed with water is small, and the concentration of the sol liquid can be increased. It is easy to obtain and the price per mole is low.

However, higher alkoxides such as Si (OC ₃ H ₇ ) ₄ and Si (OC ₄ H ₉ ) ₄ are easier to obtain a sol solution having larger particles.
For this reason, it is time-consuming and suitable for obtaining a large glass. A large gel for obtaining a large glass is difficult to release gas during sintering and is likely to foam.
This is because to prevent this, it is necessary to secure a large gap with large constituent particles.

〔Example〕

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

Experimental Example The amount of each raw material is shown in a to f of Table 1. Six types of experiments a to f were performed. The sum of the number of moles of Si alkoxide and the total amount of the raw materials are constant, and the proportion of Si (OCH ₃ ) ₄ is increased from a to f.

First, Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ and ethanol are mixed. Water containing 2 drops of 13% aqueous ammonia was added and further mixed. After degassing, place 3 tubes of each in a test tube with an inner diameter of 12 mm, the inner surface of which was wiped with silicone, and cover with aluminum foil.
It was placed in a constant temperature bath at ℃.

The next day, d, e and f were gelled, but a, b and c were not gelled. When left for one week, dry gels were obtained for c, d, e and f. However, c is easy to break 3
Two of the two were broken when I took them out. As for a and b, only gel which was broken into pieces could be obtained.

The c, d, e and f were calcined in air at 500 ° C for 24 hours and then sintered in He at a temperature of 1400 ° C. Transparent glass was obtained without cracks in all of c, d, and e, but all three of f were foamed.

Example 1 The amount of each raw material is shown in Tables 1g and 1h.

First, when dry gel was obtained and calcined and sintered in the same manner as in the experimental example, both g and h were foamed.

Next, first mix Si (OC ₂ H ₅ ) ₄ and ethanol, and add 13%
Water containing 2 drops of aqueous ammonia was added and further mixed. This was capped with a Saran lap, allowed to stand in a constant temperature bath at 60 ° C. for 24 hours, Si (OCH ₃ ) ₄ was added and mixed well, and degassed. Thereafter, in the same manner as in the experimental example, 2 out of 3 were transparent vitrified without cracking. One was a transparent glass, but it was broken into small pieces. All h were cracked.

Example 2 <Preparation of sol solution> While 130.2 g of Si (OC ₂ H ₅ ) _{4 and} 124.8 g of ethanol were mixed, 45 g of water containing 20 drops of 13% aqueous ammonia was added and further stirred. This was placed in a closed bottle and placed in a thermostatic chamber at 23 ° C., which was designated as (A). Further, the same amount of raw materials was heated to 60 ° C., mixed, put in a closed bottle, and put in a constant temperature bath at 60 ° C. as (B).

After 1/8, 1/4, 1/2, 1, 2, 4, 9 days, 10 g of each sol solution was taken from (A) and (B) and dried, and the yield at that time was obtained. The results are shown in FIG. Also the first
Fig. 2 shows the Arrhenius plot, which is obtained from the figure and shows the temperature dependence of the number of days required for 50% decomposition. Further, the average particle size (nm) of the powder obtained by drying was determined by the BET method, and its yield dependency was determined. This is shown in FIG. The vertical axis of FIG. 3 is the average particle size (nm) and the horizontal axis is (yield) 1/3. (B)
20 g of the sol solution of 1 day (yield 43%) was taken separately, cooled with liquid nitrogen, and stored as it was.

<Gelization to vitrification-1> Sol solution of (B) decomposed at 60 ° C for 9 days (hereinafter referred to as B)
To 20 g, 1.2 g of Si (OCH ₃ ) ₄ was added and mixed well. 5g of water containing 2 drops of 13% ammonia water and 3.8g of ethanol
And the mixture was stirred well. This was evacuated at room temperature until the sol solution became soft, kept in the normal state for about 5 seconds, and then taken out. Next, a test tube having silicone wiped on the inner surface was placed in a test tube which was lightly covered with aluminum foil and placed in a constant temperature bath at 60 ° C. Further, the above-mentioned one day division at 60 ° C. and cooling with liquid nitrogen was thawed at room temperature (hereinafter referred to as C). For (C), operate in the same manner as (B)
It was placed in a constant temperature bath at 60 ° C. Both (B) and (C) gelled on the next day, and a dried gel was obtained after 1 week. This was calcined in air at 500 ° C for 24 hours and then heated to 1400 ° C in He to obtain transparent glass without cracking.

Si (OCH ₃ ) ₄ yield calculated assuming 100% yield
The yield of (OC ₂ H ₅ ) ₄ is about 90% for (B) and about 40% for (C).
The yield of the sol is almost the same, and (C) is
Si (OC ₂ H ₅ ) ₄ was wasted.

<Concentration of Sol Solution> When 20 g of the sol solution of (B) was taken and heated in a fume hood and concentrated, the SiO ₂ concentration when the surface of the sol solution gelled was 47% by weight. When further concentrated and the whole gelled, the SiO ₂ concentration was 52% by weight. These SiO ₂ concentration was determined from now because SiO ₂ concentration of the sol solution before concentration were divide to be 12.2 wt%.

Separately, 50 g of the sol liquid of (B) is concentrated and the SiO ₂ concentration is 2
A 5% by weight liquid was obtained and designated as D.

<Gelization to Vitrification-2> (D) was used instead of the above (B) and (C), and the same procedure was performed. However, 10 needle holes were left in the aluminum foil lid, and a dry gel was obtained without cracking in 3 days. Also, the same test tubes were used, but glasses larger than B and C were obtained.

Example 3 40 g of Si (OC ₃ H ₇ ) ₄ and 100 g of propanol were mixed. A mixture of 50 g of 28% aqueous ammonia and 150 g of propanol was added to this, and the mixture was further stirred. This was placed in a closed container and placed in a constant temperature bath at 60 ° C. and kept for 28 days. Take out the sol liquid,
When the SiO ₂ concentration was dried and measured, it was 26%, and the yield was almost 100%. 1N hydrochloric acid was added to the sol solution until it became neutral. Thereafter, this sol solution was concentrated to a SiO ₂ concentration of 25%. This sol solution was used instead of (B), (C) and (D) in Example 2 to obtain a transparent glass in the same manner.

Example 4 40 g of Si (OC ₄ H ₉ ) ₄ and 100 g of butanol were mixed. A mixture of 50 g of 28% aqueous ammonia and 150 g of butanol was added to this, and the mixture was further stirred. Put this in a closed container
It was placed in a constant temperature bath at 60 ° C and kept for 28 days. The sol solution was taken out and dried, and the SiO ₂ concentration was measured to be 2.2%, and the yield was almost 100%. 1N hydrochloric acid was added to the sol solution until it became neutral. Thereafter, this sol solution was concentrated to a SiO ₂ concentration of 25%. This sol solution was used instead of (B), (C) and (D) in Example 2 to obtain a transparent glass in the same manner.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY The method for producing glass of the present invention has an excellent effect that gelling, drying and sintering of the sol-gel method are easy and high quality glass can be easily produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between the hydrolysis temperature and time of Si (OC ₂ H ₅ ) ₄ and the hydrolysis yield in Example 2 according to the present invention. Fig. 1 is a graph showing the temperature dependence of the number of days required for the decomposition of 50% yield obtained from Fig. 1, and Fig. 3 is a graph showing the relationship between the average particle size of the powder obtained in Example 2 and the yield. FIG.

Claims (5)

[Claims] 1. A method for producing a glass by hydrolyzing a Si alkoxide to obtain a sol liquid, gelling the sol liquid, and then sintering the gel to produce a glass. (OCH ₃ ) ₄ and Si (OC ₂ H ₅ ) ₄ or higher alkoxide are used, and the Si (OC ₂ H ₅ ) ₄ or higher alkoxide is hydrolyzed prior to Si (OCH ₃ ) _4. Characteristic glass manufacturing method. 2. Production of the glass according to claim (1), wherein 70% by mole or more of the high-order alkoxide of Si (OC ₂ H ₅ ) ₄ or more is decomposed before gelation. Method. 3. The hydrolysis of the higher alkoxide of Si (OC ₂ H ₅ ) ₄ or more is carried out at a temperature of 40 ° C. or more and 85 ° C. or less, according to claim (1) or (2). The glass manufacturing method described. 4. After concentrating a sol solution of a high-order alkoxide of Si (OC ₂ H ₅ ) ₄ or more obtained by hydrolysis in advance, Si
The method for producing glass according to any one of claims (1) to (3), wherein the glass is mixed with a sol liquid of (OCH ₃ ) ₄ or Si (OCH ₃ ) ₄ . 5. The concentrated sol liquid of the higher alkoxide of Si (OC ₂ H ₅ ) ₄ or more has a SiO ₂ concentration of 20% by weight or more and 45% by weight or less. Glass manufacturing method.