JPS62100425A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To obtain the titled high-quality quartz glass in good yield by using a metallic alkoxide as the raw material, carrying out preparation of a sol and gelation at a specified temp., and synthesizing the glass at a low temp. by a sol-gel method. CONSTITUTION:In the low-temp. synthesis of quartz glass using a metallic alkoxide as the main raw material by the sol-gel method, the sol is prepared at <=15 deg.C and gelation is carried out at >=20 deg.C. Since the sintering temp. can be set in a high-temp. zone by using the org. gel obtained by the above- mentioned method and having a low bulk density, dehydroxylation and removal of org. matter can be sufficiently carried out before vitrification. Consequently, by virtue of the important facts cited above, the properties necessary for the base material of an optical fiber such as the property for preventing frothing when wiredrawing is carried out at a high temp. close to 2,000 deg.C and a high light transmissivity can be satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing quartz glass by a sol-gel method.

[Summary of the invention]

The present invention is a method for producing quartz glass using a sol-gel method using a metal alkoxide as a starting material. 1, it can be manufactured with high yield.

[Prior art]

Normally, in the production of silica-based glass using the sol-gel method, the liquid undergoes two states: a sol state that occurs during the hydrolysis process of metal alkoxides, and a gel state that occurs during the condensation polymerization process that follows the hydrolysis process. An in-phase amorphous silica gel is prepared from a phase metal alkoxide. Thereafter, the amorphous silica in the gel state undergoes a drying and sintering process to become silica glass, but the quality and yield of the obtained silica glass are significantly affected by the transition process from the sol state to the gel state.

When manufacturing quartz glass using the conventional sol-gel method,
As stated in our patent application (Japanese Unexamined Patent Publication No. 58-237577), the main content of acid salts or basic salts in the sol solution is gold,
That is, gelation was controlled by changing the hydrogen ion concentration (pH value) in the sol solution.

[Problems and objectives to be solved by the invention] The dried gel body becomes transparent silica glass through a sintering process.
This sintering process includes steps such as dehydration, organic matter removal, and hydroxyl dehydration. These treatment steps are essential to prevent foaming during high-temperature sintering, and are effective only when the bulk density of the gel body is less than a certain value.

Therefore, considering the sintering process of the gel body, in order to obtain high-quality silica-based glass, it is necessary to reduce the bulk density of the gel body, which is a precursor thereof, as much as possible. The bulk density of the gel body depends on the hydrogen ion concentration at the time of gelation.

Specifically, the larger the hydrogen ion concentration is, the lower the bulk density of the resulting gel is, and conversely, the lower the hydrogen ion concentration is, the higher the bulk density is. Therefore, in order to obtain high-quality silica-based glass gold, one of the necessary conditions is to increase the hydrogen ion concentration during gelation as high as possible. Furthermore, gels with low bulk density are highly resistant to volume changes (shrinkage process) that occur during drying.

The gel body undergoes a significant volume change during the drying process accompanying the progress of the polycondensation reaction within the gel body and the evaporation of floating water from the surface of the gel body. At this time, internal stress is generated due to local differences in reaction rate and drying rate within the gel body, but the lower the bulk density of the gel body, the easier it is to relieve internal stress and residual stress. In other words, it can be said that a gel body with a low bulk density has a high yield during drying, and therefore, from this point of view as well, it is effective to keep the bulk density of the gel body low. However, in the conventional method, since gluing is controlled by the hydrogen ion concentration as described above, there was a problem in that the hydrogen ion concentration could not be increased unnecessarily. This is because increasing the hydrogen ion concentration lowers the bulk density of the gel, but on the other hand, the gelation time becomes extremely short, making it extremely difficult to form the gel into any desired shape.

The present invention aims to solve these problems, and its purpose is to change the temperature during sol solution preparation and the temperature during gelation, control the gelation rate through temperature changes, and produce high-quality glass. The next prerequisite for obtaining a gel body with a high yield υ is to obtain a gel body with a low bulk density.

[Means to solve the problem]

Therefore, the sol based on the metal alkoxide of the present invention
In the low-temperature synthesis method of silica glass using the gel method, 1
A sol solution is prepared in a relatively low temperature range of 5°C or less, and then the temperature of the entire system is raised to a temperature range of 20°C or higher, which is higher than when preparing the sol solution, to cause gelation. do.

<Example 1> (1) Preparation of silica fine particles Purified commercially available ethyl silicate [trade name: Colcoat 28. :ffle:l-t]1c,L) 11244 g
Anhydrous ethyl alcohol (99.5L Kanto Kagaku,
) 189&7g, ammonia water (29%, Kanto Kagaku,
Mix 65 ml of ) and 389.0 g'i of water for approx.
After stirring for ~4 hours, the solution was allowed to stand in a cool place for over a day and night to stabilize the amorphous silica particles produced.

After that, the concentration of amorphous silica fine particles in the solution was
The alcohol component in the concentrate was replaced with water for the purpose of vacuum concentration to approximately rnl and to prevent rapid drying and to increase the strength of the gel body. Through the above operations, the average particle size is reduced to 0.
．． A solution of silica fine particles having a diameter of 18 μm and good dispersibility was synthesized.

(2) Preparation of hydrolysis solution Purified commercially available ethyl silicate (trade name: Colcoat 28. Colcoat ni, x,) 0.0 per 749.6 g
A colorless, transparent and homogeneous hydrolysis solution was obtained by adding 51 & 8 gi of a 2N aqueous hydrochloric acid solution and vigorously stirring in an ice bath for about 2 hours.

(3) Preparation of sol solution and gelation Hydrogen ion concentration in the silica fine particle solution (hereinafter referred to as pH value) that has been cooled in advance so that the liquid temperature is 10°C or less
After adjusting the concentration to 40 with a t-12 normal aqueous hydrochloric acid solution, the solution was mixed with a hydrolysis solution whose temperature had also been previously cooled to 10° C. or below, and stirred to prepare a homogeneous sol solution.

The pH value of this sol solution was readjusted to 5.3 using a 0.2 normal ammonia aqueous solution, and then poured into a polypropylene container (100 m + 11φ x 50 m) in 100 ml portions and sealed. The solution temperature at this time was approximately 7.
It died at 0℃. Thereafter, this polypropylene container was placed in a constant temperature bath maintained at various temperatures to cause gelation. After each gelled sample was stored at a temperature of 30°C for about 2 days after gelling, a number of holes were made in the lid of the container so that the open area ratio was 0.4%, and the sample was placed in a constant temperature dryer kept at 55°C. After about 17 days, a dry gel was obtained that did not crack even when left in the air.

Table 1 shows the atmospheric temperature and gelation time during gelation, and the bulk density of the obtained dry gel body. The higher the gelling temperature, the lower the bulk density of the dried gel. Since the dry gel body t1 having a low bulk density has a high temperature at which it becomes non-porous during sintering, organic matter, hydroxyl groups, etc. in the gel body can be sufficiently removed. Therefore, the sol solution that is the raw material at low temperature is
It can be seen that by using the present invention of iM and gelation at high temperature, it is possible to easily obtain a gel body with a low bulk density, which is very effective for obtaining a high quality sintered glass body. Four types of dry gel bodies were sintered in a quartz tubular sintering furnace, and changes in the sintering temperature and bulk density of the sintered bodies were investigated. It was confirmed that the pores did not become closed.

1 54 34
0.7782 40
42 0.7873
25 55 0.804
4 12 97 0.825
<Example 2> In a bulk gel body with a relatively large volume, it is difficult to relieve stress caused by the difference in drying rate between the bulk surface and the inside, and cracks are likely to occur during drying.

Therefore, by drying bulk gel bodies that are difficult to dry uniformly in a drying container with a large opening ratio that increases the drying speed, and comparing the yield of the resulting dried gel bodies, Strength and stress relaxation ability during drying can be easily determined.

A silica fine particle solution and a hydrolysis solution were prepared using the same composition and method as in Example 1. Furthermore, Yahashi Example 1
A sol solution in which the silica fine particle solution and the hydrolyzed solution were uniformly mixed was prepared by the same procedure as above at a liquid temperature of 7°C. After adjusting the pH value of this sol solution to 5.5 using a 0.2 normal ammonia aqueous solution, it was placed in a Teflon cylindrical container s o o wxl x 7011 IIφ.
Pour the specified amount 1 into a hole (Jx50mφ hole),
The mixture was transferred to a constant temperature bath kept at 50°C and gelatinized in about 20 minutes. On the other hand, for comparison, a similar sol solution was gelled in about 100 minutes in a constant temperature bath maintained at 10° C. using the same cylindrical container.

20 of each of the above two types of samples were made, and the aperture ratio was L5%.
The sample was placed in a drying container made of propylene (60 o. The size of the obtained rod-shaped dry gel body is 32G++mJ
The diameter was 33 mφ, and the cracks were as shown in Table 2. From Table 2, it is clear that the gel body gelled at a high temperature is more resistant to cracking during drying than the gel body gelled at a low temperature comparable to that during sol synthesis. This is because by performing gelation in an atmosphere at a relatively higher temperature than during sol synthesis, the polymerization reaction of the ranol groups proceeds more quickly, resulting in a gel body with a high porosity and a sparse structure. This is thought to be due to the excellent stress relaxation ability during drying.

Table 2 <Example 3> (1) Preparation of 7-Liquid Microparticle Solution Purified commercially available ethyl silicate (trade name: Colcoat 28.Kolcoat) was added to 11244 g of anhydrous ethyl alcohol (99, s%, Kanto). chemistry, ni,) 18
95.7g, ammonia water (29%, Kanto Kagaku x, x,
) ssml and water were mixed at 389° Og'ir and stirred for about 3 hours, and the solution was allowed to stand in a cold place for more than a day and night to form amorphous silica particles, which were completely stabilized. Thereafter, the solution was concentrated under reduced pressure to a total concentration of amorphous silica particles of about 0.4 g/ml, and the alcohol component in the concentrated solution was replaced with water in order to prevent rapid drying and increase the strength of the gel body. did. Through the above operations, a fine silica particle solution having an average particle diameter of 0.18 μm and good dispersibility was synthesized.

(2) Preparation of hydrolyzed solution for cladding To 599.7 g of purified commercially available ethyl silicate (trade name: Colcoat 28.Kolcoat), add 415°0 gff1 of a 0.02N hydrochloric acid aqueous solution, and cool on ice. Approximately 2
A colorless, transparent and homogeneous hydrolysis solution for rad was obtained by stirring vigorously for a period of time.

(3) Preparation of hydrolyzed solution for core 38.1 g of purified commercially available ethyl silicate (trade name: Colcoat 28. Colcoat x,
The mixture is ice-cooled to below 0°C, and 1&Og of a 02N aqueous solution of hydrochloric acid, which has also been ice-cooled, is added thereto and stirred for about 2 hours. After the reaction was completed and 9% was confirmed, tetraethoxygermanium (99,999%) was added.

A solution of 116 gk (Trichemical Research Institute) previously mixed with 9.5 g of anhydrous ethyl alcohol and cooled on ice was gradually added and stirred for about 40 minutes. Thereafter, 317 gr of an ice-cooled 02N hydrochloric acid aqueous solution was added thereto and stirred for about 2 hours to obtain a colorless, transparent and homogeneous hydrolyzed solution for the core.

(4) Preparation of sol solution and gelation
H value? After adjusting to Table 3 using 2N hydrochloric acid aqueous solution,
The solution is divided into two into a silica fine particle solution (A) and a silica fine particle solution (B) at a weight ratio of 4:1. The silica fine particle solution (A) was gradually added to the hydrolyzed solution for cladding which had been ice-cooled to 10° C. or lower in advance, and sufficiently stirred until uniformly mixed. The mixed solution was cooled with ice to prevent the liquid crystal from rising, and the pH value of the solution was adjusted to 47 and the volume to 1872 ml using 02N ammonia aqueous solution again. The liquid temperature after adjustment was 56°C. This solution was poured into a rotating cylindrical container (50nφxsoo) whose inner surface was coated with silicone.
A predetermined amount was poured into a tube (m/), and the mixture was attached to a rotating device. The temperature around the rotating device is kept at 1: 60℃, then 100℃
The rotating cylindrical container was rotated at a speed of 0r11 m to gel in about 21 minutes, to obtain a cylindrical clad gel having a hollow portion in the direction of the rotation axis.

Prior to gelation of the cladding sol, the silica fine particle solution is added to the core hydrolysis solution which has been ice-cooled to below 10°C. Add gradually and stir well until uniformly mixed. While cooling the mixed solution on ice, adjust the pH value of the solution to 42 and the volume to 46 using 0.2N ammonia aqueous solution.
8 ml: Adjusted, poured into the hollow part of the clad gel body immediately after gelation, and gelled in an atmosphere maintained at 60°C.

The temperature of the core sol solution during pouring was 48° C., and the gelation time was 13 minutes.

(5) Drying The obtained clad/core integral gel was placed in a dryer kept at 35° C. for about 3 days after gelation in a closed state to fully accelerate the polymerization reaction after gelation. After that, the clad-core integrated gel was dried in a polypropylene drying container (3001111X2
5 omx 150MII+), aperture ratio is 04%
A number of holes with a diameter of I II+ were made on each side so that the gel was covered with a lid and placed in a constant temperature dryer kept at 55°C to obtain a dried gel in about 23 days.

(6) Sintering Next, this dry gel was placed in a quartz tubular sintering furnace and heated from 30°C to 200°C at a heating rate of 30°C/hr, held at this temperature for 5 hours, and then heated at a heating rate of 30°C. ℃/h
Heat from 200℃ to 300℃ with r, and at this temperature 5
Desorption of water was carried out by holding for a certain period of time. Next, heating rate 3
Heating from 300°C to 1100°C at 0°C/hr,
This temperature was maintained for 30 minutes to perform all decarbonization, dechlorination ammonium treatment, and dehydration condensation reaction acceleration treatment. Subsequently, the temperature was lowered to 700℃ and He 21 / min,
Cl! 3 while flowing 1 mixed gas of 0.21 /win
Hold for 0 minutes, then increase the temperature to 6 while flowing only He.
Heated to 800 °C at 0 °C/hr. H at 800℃
e21! /min%0. l, 0.21/
The mixture was maintained for 1 hour while flowing a mixed gas of min.

Hs2J/! at 900℃! nin,,Olt 0.2A'
Hold for 1 hour while flowing a mixed gas of /win to remove OH.
Straw treatment was carried out. Next, He 273/m
While flowing a mixed gas of o and a41/rn1n to i.sub.n, it was heated to 1050.degree. C. at a temperature increase rate of 60.degree. C./hr and held at this temperature for 20 hours to perform one dechlorination treatment.

Subsequently, without flowing only He, the tube was heated to 1250.degree. C. at a temperature increase rate of 30.degree. C./hr and held at this temperature for 30 minutes to perform a pore-closing treatment. Next, the sample was heated at a rate of 60℃/
When heated to 1400° C. for 1 hour and held at this temperature for 1 hour, it became non-porous and a transparent base material for optical fiber was obtained.

In the dry gel body with a low bulk density obtained by the present invention, the sintering temperature can be set in a lower range than that of conventional dry gel bodies, so that sufficient dehydroxyl groups and deoxidation can be achieved to achieve transparent vitrification. Organic matter treatment is possible. This means that 2000℃
This is important in order to meet the various properties required for optical fiber base materials, such as not foaming when drawn at near high temperatures and the ability to obtain high light transmittance. In fact, the quality of the transparent sintered glass body obtained was extremely good, and the yield was also excellent at about 85% or more. When the OH groups of the optical fiber base material obtained by measuring the entire infrared absorption spectrum at 27 μm were quantified, no absorption peak was observed and it was less than 1 υ, indicating that hydroxyl groups were sufficiently removed. It was confirmed that this was done. When the outside of this optical fiber base material was covered with a quartz tube and fused together, and drawn at a high temperature of about 2000° C., a ngle mode optical fiber with no foaming was obtained. Furthermore, the optical loss of this optical fiber? When measured, it was found to have an excellent low optical loss of 1 dIl/- in the 1.55 μm band.

〔Effect of the invention〕

As described above, according to the present invention, by preparing the entire sol solution at low temperature, the viscosity of the sol solution can be kept low, making it easier to obtain a homogeneous sol solution and preventing local heterogeneous reactions. After that, by transferring the metal to a high temperature state, the kelization is completely promoted, so a large amount of basic salt can be used. Therefore, drying with a low bulk density is the first condition for obtaining a high quality glass body in the sintering process. A gel body can be obtained. In addition, for the purpose of strengthening and stabilizing the gel body after gelation, it is usually used at about 30°C for 3 to 4
Although the aging period is 7 days, the achievement of a low bulk density improves the ability of the gel body to relax the stress of the seeds, so this period can be shortened and the yield during drying can be improved. Furthermore, when manufacturing optical fiber base materials, it is possible to match the pH values of the cladding sol and the core sol, and the gel body manufactured under such conditions has a lower volumetric shrinkage rate in the cladding and core parts. There is no difference in the drying process, and there is little chance of splitting or cracking by the time the drying is finished.

Various functional glasses can be obtained by applying the sol-gel method, and typical examples include various optical functional materials (e.g., base materials for optical fibers, jacket tubes, thin film waveguides, etc.) and porous glasses due to their excellent properties. It can be said that the fields of application are extremely wide, including bio-related materials. Therefore, by applying the present invention to the production of left-sided glass bodies using the sol-gel method, it is possible to easily produce high-quality dry gel bodies, which is the first condition for obtaining high-quality functional glasses. You can get good results.

that's all

Claims (3)

[Claims] (1) In a low-temperature synthesis method of quartz glass using a sol-gel method using metal alkoxide as the main raw material, a sol solution is prepared at a temperature of 15°C or lower, and gelation is performed at a temperature of 20°C or higher. A method for producing quartz glass, characterized by: (2) In the method for producing quartz glass according to claim 1, the molar ratio to the metal alkoxide is 0.
A method for producing quartz glass, characterized by using 2 to 5 times the amount of ultrafine silica particles. (3) The method for producing silica-based glass according to claim 2, characterized in that amorphous silica synthesized from metal alkoxide in the presence of a basic catalyst is used as the ultrafine silica particles.