JPS5992924A - Silica glass manufacturing method - Google Patents

Abstract

PURPOSE:To obtain a quartz glass having perfect structure free from cracking and crazing, by adding fine silica powder to a raw material composition containing a metal alkoxide as a raw material, and preparing the quartz glass by sol- gel process. CONSTITUTION:A raw material mixture composed of a metal alkoxide, Si(OH)4 (R is 1-10C alkyl), an alcohol, water and hydrochloric acid, is added with 10- 80mol%, in terms of SiO2, of fine silica powder, and the product is gelatinized to obtain a dried gel, which is sintered to quartz glass. Since the dried gel produced by this process contains a large amount of fine pores, it is resistant to cracking even by the sintering at an extremely high rate of temperature increase (200-1,000 deg.C/hr).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing quartz glass, and more specifically, in a method for producing quartz glass at low temperatures by a sol-gel method using a metal alkoxide as a raw material, the raw material composition includes: This invention relates to a method for producing dry gel and perfect quartz glass that does not cause cracks or cracks by adding finely powdered silica.

The concentration of impurities such as copper and boron in quartz glass is 0.1 p.
It has become possible to produce products with high purity below pm.
In the production of germanium, silicon, and other semiconductors, it has been used in crucibles, boards, diffusion furnaces, etc., and its usefulness has been recognized. Quartz glass is also often used as beakers for physics and chemistry and cells for optical measurements, and those with a small amount of hydroxyl groups and those with good optical uniformity have been developed and are used for various optical applications. As a result, quartz glass fiber, especially for original communications, has recently been attracting attention.

Cylindrical quartz glass, which is thus necessary, is currently manufactured generally by the following three methods.

111 A method of cleaning natural crystal and melting it.

(21 A method for producing 5ho2 using high purity E3iCIL4 or SiH as a raw material.

13+ Method of melting natural silica sand. (Quartz glass containing bubbles can be obtained.) However, in both of these methods, the raw material cost is high;
Quartz cuffs are very expensive, due in part to the high temperature processing required. Therefore, as an inexpensive method for producing quartz cufflinks, a method that has recently attracted particular attention is a method for producing quartz cufflinks at low temperatures using a sol-gel method using jormetal alkoxide as a raw material.

A brief explanation of the method for manufacturing quartz cufflinks using the sol-gel method is as follows.

Suitable metal alkoxides, such as alkyl silicates (
5j(OR4) ) (R (alkyl group having 1 to 1 carbon atoms) is dissolved in a suitable alcohol solution, for example, aqueous ethanol, to form a silica sol, or treated with a solvent such as heating to form a silica gel.

The resulting lump of silica gel is placed in a furnace and sintered to a predetermined noochrome to form a quartz cuff. The above is the method for manufacturing quartz cufflinks using the sol-gel method.

A feature of this manufacturing method is that it can be produced at a lower temperature than the high-temperature melting method using crystal as a raw material, which saves energy.

(Since raw material 21 is easily purified, cufflinks with high purity can be obtained.

+31 Because a low viscosity solution is used as a raw material, high-strength cuffs are obtained.

Because of these excellent characteristics, the synthesis of quartz cuffs using this method has been widely studied in various places.

However, according to the materials that have been published in the past, there are some problems, and the current situation is that it has not been put into practical use.

Among these problems are the difficulty of drying the dried gel without cracking, and the fact that it is difficult to heat the dried gel without cracking, and that it is difficult to heat the dried gel with heat treatment, that is, sintering, even if the heating rate is considerably slow (0. ,5℃/
hr ~ 2.6 Vhr)
You may not be able to get a perfect product at a cheap price because it may break if it is damaged. In particular, at 700°C to 1000°C, a significant body Cτ
Contraction occurs, and at this time the knee is also prone to cracking. To some extent, it is possible to create a dry gel that does not crack, by appropriately selecting a container and temperature release conditions to prevent gelation, but it is possible to create a dry gel that does not break, but it is possible to make it non-porous, which involves a dehydration reaction during sintering. A method to prevent cracks and fractures due to volumetric shrinkage and gel-cuff transition is considered essential.

As a method for producing this dry gel, it has been announced that a dry gel that has a large number of small pores of 2 OA and relatively large pores of about 50 to 20 OA is difficult to crack during sintering. A method of gelling and shrinking at high temperatures has been proposed, but this method produces a large number of bubbles during shrinkage, making it difficult to produce a uniform dry gel both optically and mechanically. However, the reproducibility is poor, and when the heating rate is slowed down (0° shallow Aγ ~ 2° 6 C/h
r), it is easy to break.

Therefore, the purpose of the present invention is to prevent cracks from occurring during the process of producing dry gel, and to achieve a sintering rate of 1. It is an object of the present invention to provide a method for producing a dry gel that does not require cracks or cracks, even when the heating rate at t is extremely fast (200 to 1000'C/Ar).

As a method for producing a dry gel that satisfies the above conditions,
We devised the following method.

That is, a raw material mixture of alkyl silicate, water, alcohol, and hydrochloric acid is mixed with finely powdered silica (e.g.
il (Degrtssa), Cab-0-Bi
t CCabot), Fransil (Fra
nso1), D, c, 5ilica (DowC
om, ing) and Arc 5ilica (P
P0 company) etc, )) is added and gelled to obtain a dry gel, which is then sintered to form quartz cufflinks. The dry gel obtained in this way contains more pores than the conventional method, so the temperature increase rate during sintering is extremely fast (20 (JC/hr ~ 1000 n/Ar)). It also has the property of being resistant to cracking.

Hereinafter, the content of the present invention will be explained in more detail by giving Examples.

Example 1 Purified commercially available ethyl silicate (Si(OE)4)4
4 mp: L-tanol 5, 4 mJ, and 0.1
1"L of hydrochloric acid was mixed in a flask under water cooling, and the mixed solution was mixed into a fine powder at room temperature with vigorous stirring. CCab-04i1 (Cabot)
) 8 ff was added gradually. After the addition, stirring was continued for 2 hours to ensure that the solution was completely homogeneous. Next, pour this solution into a Teflon Petri dish with a diameter of 10 cIn.
The temperature of the thermostatic chamber was kept at 50℃ for the first 5 days, and then the temperature of the thermostatic chamber was kept at 50℃ for the first 5 days, and then the temperature of the thermostatic chamber was kept at 50℃ for the first 5 days. to 50”C
The temperature was gradually increased to 60'C-i, and drying was performed at 60°C for 3 days. The dried gel obtained after drying was circular (6.3 cIn diameter, 0.2 cm thickness) without any cracks.
It was white and completely uniform in appearance. When this dried gel was placed in a diffusion furnace and heated and sintered at a heating rate of 200'C/Ilr, a transparent quartz glass with a diameter of 5.0 cm was obtained at 1150°C without any cracks or cracks. Ta. When this quartz glass was analyzed, it had a Vickers hardness of 800H and a specific gravity of 2.
It was 2.

The near-infrared absorption spectrum is shown in Figure 1. 2 shows the spectral characteristics of the commercially available fused silica glass, and 2 shows the spectral characteristics of the quartz glass according to this example. These analysis results, infrared absorption spectrum, refractive index, etc. completely matched those of fused silica glass, indicating that perfect silica glass had been obtained.

Example 2 Using the same raw materials as in Example 1, a dry gel was obtained in the same manner as in Example 1. Note that this dried gel was in the same state as that obtained in Example 1, and it was found that the dried gel could be produced with good reproducibility. This dried gel was placed in a diffusion furnace, heated and sintered at a heating rate of 400° C./nozzle, and heated to 1150° C. to obtain a transparent quartz glass having a diameter of 5° Ocm exactly as in Example 1. The analysis results of this quartz glass were also consistent with those of fused silica glass.

Example 3 A dried gel was prepared in exactly the same manner as in Examples 1 and 2. When this dry gel was placed in a diffusion furnace and heated and sintered at a very fast temperature increase rate of 1000°C/hr, no cracks or cracks were produced during heating, and the temperature was 1150°C as in Examples 1 and 2. A transparent quartz glass was obtained at ℃.

The analysis results of this quartz glass were also consistent with fused silica glass.

Example 4 Fine powder silica (Cab-0-8il (Cabot) was added to the same raw material mixed solution as in Examples 1 to 3 while vigorously stirring
)6F? was added gradually. After the addition, stirring was continued for an additional 2 hours to ensure that the solution was completely homogeneous. Next, this solution was poured into a Teflon petri dish with a diameter of JOα at 30 f, and a lid with a hole (diameter 1.5
(mxx8 pieces) was placed in a constant temperature bath, and dried under the same conditions as Examples 1 to 3. The dried gel obtained after drying was white and had a circular shape with a diameter of 6.0 mm and a thickness of 0.2 mm without any cracks. When this dried gel was placed in a diffusion furnace and heated and sintered at a heating rate of 400'C/Aγ, a transparent quartz glass was obtained at 1100°C without any cracks or breaks. Note that this quartz glass had a diameter of 4.8 mm. In addition, the infrared absorption spectrum of this quartz glass,
The analysis results of near-infrared absorption spectrum, refractive index, Vickers hardness, and specific gravity completely matched those of fused silica glass, indicating that it was perfect silica glass.

Example 5 Added fine powder silica (Ca, b-o-8il (Ca
bot Inc.) was set as 42, and the other operations were performed in the same manner as in Example 4. The dry gel thus obtained without any cracks or the like had a circular shape with a diameter of 5.8 cm and a thickness of 0.2 cm, and was white in color.

This dry gel was placed in a diffusion furnace and the temperature was increased at a rate of 400°C4.
When heated and sintered at 1,080° C., a transparent quartz cuff was obtained. Of course, cracks and cracks will not occur.
The analysis results were also the same as those of fused silica glass. This quartz glass had a diameter of 4° and 7 buttons.

Example 6 The same operation as in Example 5 was carried out, except that fine powder silica (Jab-0-8il (-Cabot jf
> ) was set to 27. The dry gel obtained here with few cracks, etc., was circular with a diameter of 5.7 W and a thickness of 0.2 cm.
It was white. In addition, when this dried gel was placed in a diffusion furnace and heated and sintered at a temperature increase rate of 400 C/hr, the result was 105
A quartz glass with a diameter of 4.5 (7), transparent at 0° C., was obtained, and the analysis was consistent with bath-fused silica glass. No cracks or breaks were observed in this quartz glass either.

Example 7 In Examples 1 to 6, the added fine powder silica (sz
The amount of o2) was 1() to 40wo1% of the total when converting the raw material ethyl silicate to SiO2.
Here, finely powdered silica of 55 moA (15 P) was added. That is, purified commercially available ethyl silicate (5i
(OEc)4) 44mA, ethanol 5.4me,
and 0°IN hydrochloric acid in a flask under water cooling, and while vigorously stirring this mixed solution at room temperature, fine powdered silica (Cab-0-8il, Ca, bO1
55 mof (15y) was gradually added. The operations are the same as in the previous example, but drying at 50°C.
and the time at 60°C was extended by one day each. The dried gel obtained here had a diameter of 6°7tin.

It was circular and white with a thickness of 0.25L:rn, and no cracks were observed. This dried gel was placed in a diffusion furnace and heated and sintered at a temperature increase rate of 400°C ΔLr, resulting in a transparent quartz glass at 1300°C without any cracks or breaks during heating. This quartz glass has a diameter of 5.3o
I conducted the same analysis as in the previous example, but the analysis results of the infrared absorption spectrum, near-infrared absorption spectrum, refractive index, Vickers hardness, and specific gravity obtained here are the same as those of fused silica glass. Agreed.

Example 8 The amount of fine powder silica (Bib2) to be added is 80 m in total when the raw material ethyl silicate is converted to 5io2.
oA%, and the same repetition as in the previous example was performed.

However, fine powder silica (cob-o-ail)
T"r>) The stirring time after addition was 3 hours, and the drying conditions were somewhat longer, 7 days at 50°C and 5 days at 60°C.

The dried gel i4 thus obtained had a circular shape with a diameter of 7.2 crn and a thickness of 0.28 crn, and was white in color. This dry gel was placed in a diffusion furnace and heated and sintered at an external speed of 400 C/hr. Got the glass.

This quartz glass was analyzed in the same way as in the previous example, and the results obtained were also consistent with those of fused silica glass.

Example 9 Purified commercially available methyl silicate (si(ocH8)4
33-, ,)' evening/-le 3.8 width, and 0. I
N-hydrochloric acid 36- was mixed in a flask under ice-cooling, and the mixed solution was vigorously stirred at room temperature, and then finely powdered silica (Cab-0-8il < Cabot ?b 8
? was added gradually. After the addition, stirring was continued for 2 hours to ensure that the solution was completely homogeneous. Next, this solution was poured into a Teflon Petri dish with a diameter of 10 m for 30 y of measurement, and a lid with a hole (1° 5 m in diameter x 8 pieces) that allowed the evaporation rate to be adjusted was placed.
and placed it in a constant temperature bath. The temperature of the thermostat is 1 for the first 5 days.
The temperature was maintained at 50°C, and on the 6th day, the temperature was gradually increased from 50°C to 60°C, and drying was performed at 60°C for 3 days. The dried gel obtained after drying has no cracks and is circular (diameter 6.2
The film was white in color and had a thickness of 0.0 cm (0.02 cm). When this dry gel was placed in a diffusion furnace and heated and sintered at a temperature increase rate of 400C/hγ, no cracks or cracks occurred.
A transparent quartz glass with a diameter of 4.8 (7) was obtained at 1150°C. The analysis results of the obtained quartz glass show that the Vickers hardness is 800 Kf, 2. The specific gravity was 2.2, and the infrared absorption spectrum, near-infrared absorption spectrum, and refractive index were all equal to those of fused silica glass, making it clear that it was perfect silica glass.

As shown in the examples above, by adding finely powdered silica to a mixed solution of alkyl silicate, alcohol, water, and hydrochloric acid, it is possible to prevent cracking during the dry gel manufacturing process and to prevent sintering. It has become clear that even when the heating rate is very high (200 to 1000'C/hr), it is possible to form a dry gel that is resistant to cracking. As the proportion of powdered silica increases, the gel-to-glass transition temperature during sintering also increases;
The temperature is much lower than that (around 00°C) and is energy saving.

In this way, various applications can be considered for the dried gel obtained by the present invention and the quartz glass which is its sintered body. Examples include masks, crucibles, boards, and scientific beakers. In addition, since quartz glass can be manufactured at low cost using the conventional manufacturing method (melting method), it is thought that its application will become even more widespread.

[Brief explanation of the drawing]

FIG. 1 shows near-infrared spectra of commercially available fused silica glass and quartz glass manufactured using the present invention. The thickness of each fused silica glass is 1°293μ1, and the thickness of the present invention is 1.210m5. Applicant Suwa Kozukosha Co., Ltd. Agent Mogami Patent Attorney

Claims (1)

[Claims] In a method for producing quartz glass by a sol-gel method using metal alkoxide as a raw material, metal alkoxide, 5i(O
R) 4 (R represents an alkyl group having 1 to 10 carbon atoms) Finely powdered silica is added to a liquid-resistant mixture of alcohol, water and hydrochloric acid, and S
In terms of iO2 amount, from 10 mol 'chi to 80 m
A method for producing quartz glass in which 417 is added with ola%.