JPS5964542A - Preparation of silica glass - Google Patents

Abstract

PURPOSE:To prepare silica glass having improved quality, by bringing an alkoxyl silicone premixed with water into contact with a gas containing ammonia, and sintering the resultant homogeneous gelatinous material. CONSTITUTION:A gas, containing ammonia, and obtained by bubbling Ar into aqueus ammonia 6 in a vessel 5 is blown into a mixture solution 2 of an alkoxyl silicone, e.g. tetramethoxysilane, with an alcohol, e.g. methanol, and water contained in a reaction vessel 1, passed through a piping 4 and blown from a bubbling tube 3 into the reaction vessel 1 to solidify the mixture solution 2. The resultant solidified material (gelatinous material) is dried and sintered at about 1,400-1,500 deg.C to form a transparent silica glass material. The use of a raw material solution containing another metallic alkyl compound, e.g. an alkoxylgermanium, mixed with the alkoxyl silicone provides a silica glass material doped with the metal.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing silica glass.

When producing silica glass using alkoxyl silicon such as si(CH30) as a raw material, conventionally, water containing NT(, OH) is directly added to a Si(CHBO)4 solution diluted with CH30H while stirring. and solidify (
After gelation), drying, and sintering, a silica glass body was obtained.

However, in this conventional method, water containing NH4OH, which is a reaction catalyst, is directly added to the si(CH30)4 solution diluted with CH30H, so if the concentration of NH,OH in the added water is too high, si(CH30) CH30).

The hydrolysis reaction of is too fast, producing a white precipitate and inhibiting assimilation (gelation). On the other hand, if the NH and OH concentrations in the added water are too low, the hydrolysis reaction does not proceed and a gel body cannot be obtained. There was a drawback. That is, it is extremely difficult to obtain a uniform gel body by directly adding water containing NH, O) (to alkoxyl silicone and hydrolyzing it), resulting in a drawback that good quality silica glass cannot be obtained.

In order to eliminate these drawbacks, the present invention involves adding an appropriate amount of water to the raw material alkoxyl silicon in advance and mixing it, and then exposing this mixed solution to a gaseous body containing ammonia, which is a reaction catalyst, to solidify (gel) it. The purpose of this method is to realize a uniform hydrolysis reaction and provide a method for obtaining a uniform gel body, thereby making it possible to manufacture high-quality silica glass.

FIG. 1 is a diagram showing an embodiment of the present invention, in which 1 is a reaction vessel, 2 is a mixture of alkoxyl silicone, alcohol, and water, 3 is a foaming tube, 4 is piping, 5 is a saturator, and 6 is aqueous ammonia. It is. In the embodiment of FIG.
The mixture 2 of alkoxyl silicone, alcohol, and water placed in the tube is exposed to ammonia water vapor containing NH and OH as reaction accelerators transported by Ar gas from the saturator 5 for a certain period of time, and then 3 is taken out and the mixed liquid 2 is solidified.

Now, in the above example, 51 (cH
8o) A solution containing 4, C'H80H and H2C in a volume ratio of 1:2:30 as 10e1 and ammonia water 6 as 5
%N) (When using an OH solution, a homogeneous gel body is formed by exposing the mixed solution for 1 minute to a gas containing ammonia transported by Ar gas at 100 J/min at a temperature of 30°C. was gotten.

°At this time, contact time (exposure time) for gelation
depends on the degree of NH4OHa in the ammonia water, the reaction temperature, and the ratio of 51(an, o) in the mixture.The higher the degree of NH4OHa in the ammonia water and the higher the reaction temperature, the more The higher the proportion of S i (CH30) 4, the shorter the contact time for gelation.

Note that when the proportion of 81(C14aO)+ in the mixed solution is below a certain value, no gelation reaction occurs and no gel body is obtained even if the NH and OH concentrations are increased or the reaction temperature is increased.

FIG. 2 is a diagram showing the gelation region of the mixed liquid.

The vertical axis is the mixing ratio (volume ratio) of H2C and 5i(aH8o)4, and the horizontal axis is the NH, O in the ammonia water to be brought into contact.
The H concentration (mol%) is shown. As can be seen from Figure 2, when the proportion of Si (CH30)2 in the mixed solution is high, gelation occurs easily even if the concentration of NH4OHIAs in the contact ammonia water is low, but when the proportion of water is increased, gelation occurs. However, no gel was obtained under the conditions of the area above the curve in FIG. 2.

After drying the homogeneous gel body obtained as above,
A high-quality transparent silica glass body was obtained by sintering at a temperature of 1.00 to 1500°C.

Furthermore, in the present invention, even when a raw material solution containing alkoxyl silicone and other metal alkyl compounds such as alkoxyl germanium, alkoxyl aluminum, and "J" is mixed at a certain ratio, a gel body can be obtained by the same operation as described above. It is possible to further dry the gel body,
Upon sintering, a doped silica glass body is obtained.

As explained above, by the method for producing silica glass of the present invention, a homogeneous gel body can be easily obtained using alkoxyl silicon as a raw material, and a high-quality silica glass body can be obtained from this gel body.

Furthermore, high-quality optical fibers can be obtained using the high-quality silica glass body and doped silica glass body as raw materials.

Moreover, according to the present invention, it is easy to increase the size of the reaction vessel shown in FIG. 1 and manufacture a large amount of silica glass bodies at once, and the present invention has the advantage that an inexpensive optical fiber can be provided by implementing the present invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a gelation region of a mixed liquid. ■... Reaction container, 2... Mixed solution of alkoxyl silicone, alcohol and water, 3... Foaming tube, 4...
Piping, 5...Saturator, 6...Ammonia water. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. When producing silica glass using alkoxyl silicon as a raw material, the alkoxyl silicon is mixed with water in advance, and then this mixed solution is exposed to a gaseous body containing ammonia to solidify, and then dried and sintered. A method for producing silica glass, the method comprising: obtaining a silica glass body. λ The method for producing silica glass according to claim 1, characterized in that the alkoxyl silicon raw material contains another metal alkoxyl compound.