JPH01183421A - Production of quartz glass - Google Patents

Abstract

PURPOSE:To obtain a large-sized thick-walled transparent quartz glass in high yield with good reproducibility, by preparing a mixed sol from specific two kinds of sols, gelatinizing the sol, drying and calcining the resultant gel by a sol-gel method. CONSTITUTION:A mixture of an alkoxysilane with water is hydrolyzed in the presence of an acidic catalyst to provide a homogeneous linear polysiloxane sol solution, which is then mixed with a spherical fine particulate silica suspension sol obtained by hydrolyzing an alkoxysilane in the presence of a basic catalyst to prepare a mixed sol. The obtained mixed sol is subsequently gelatinized to afford a wet gel, which is then dried and calcined. The mixing ratio of the alkoxysilane to the water in the above-mentioned linear polysiloxane-like sol solution is preferably 0.5<=water/alkoxysilane<=3.0. Alkoxides of various metals as a dopant may be added to the alkoxysilane in hydrolyzing thereof.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing quartz glass, and particularly to a method for obtaining large-sized transparent quartz glass with good reproducibility and high yield by a sol-gel method. .

(Prior Art) Methods for producing high-purity synthetic quartz, which has recently begun to be used for optical purposes, optical communications, etc., can be roughly divided into high-temperature synthesis methods and low-temperature synthesis methods.

This high-temperature synthesis method involves flame hydrolysis of volatile silicon compounds such as 5LC1Si(OR)4 in an oxyhydrogen flame or oxidative decomposition together with oxygen in a plasma flame, and the resulting silica is transparently placed on a target. The transparent rod-shaped base material is grown in a molten state or in an opaque porous state, and then this transparent rod-shaped base material is plastically formed at high temperatures by electrical heating such as resistance heating, and is finished into the desired shape by cutting, grinding, and polishing, and is then opaque. The porous rod-shaped base material is sintered in an electric heating furnace to become transparent and vitrified, and then manufactured using the same method as the transparent rod-shaped base material. A large amount of energy is required to generate flame and plasma, and it is necessary to raise the temperature to nearly 2,000°C during plastic molding, which also requires a large amount of energy. A dopant for controlling the refractive index is added to the quartz glass obtained for this purpose, but in this case, the dopant volatilizes during the above-mentioned high-temperature process, resulting in an extremely low fixation rate. ■The disadvantage is that the process to obtain the final molded product is long, and therefore economic efficiency is poor.

For this reason, a low-temperature synthesis method called the sol-gel method has recently attracted attention. This sol-gel method is basically ■
Alkoxysilane is hydrolyzed in an alcoholic solvent in the presence of an acidic catalyst such as hydrochloric acid or a basic catalyst such as ammonia to obtain a uniform sol, which is then gelled under conditions such as heating to form a wet gel. A method of drying this to form a dry gel and then sintering it to vitrify it (Special Publications Publication No. 5)
9-9497), but regarding this
An acid or base serving as a gelling catalyst is added to a solution in which fine silica particles of 1 p or less are dispersed and suspended in water, etc., and the gel is formed into a wet gel, which is then dried and sintered to vitrify it, or A method of volatilizing the dispersion medium in this fine silica particle suspension to create a dried silica body, and sintering this to vitrify it (J, Amer, Caram, Soc,
, 66(10), 683 (1983)] has been proposed; The sol solution is mixed with the solution containing the spherical silica fine particles obtained by the hydrolysis described above, and this sol solution is rotated in the same cylindrical rotating container to form a wet gel, which is then dried to form a dry gel, and then sintered. A method of vitrification using a method (see Japanese Patent Laid-Open No. 61-91033) has been proposed.

However, in this sol-gel method, the vitrification step by sintering the dry gel can be performed at a lower temperature of 1,000-1,500°C, compared to the high-temperature synthesis method described above, so it requires much more energy than the high-temperature synthesis method. This has the advantage that the process is carried out at relatively low temperatures, so that the dopant added to the glass is immobilized with a yield of almost 100%, and the shaping of the glass body is If the gelation is performed in a container of the desired shape, the desired shape can be molded.

It has the advantage that it can be easily obtained without processing operations such as cutting or cutting. .

Therefore, although this sol-gel method is technically and economically superior to the above-mentioned high-temperature molding method, it has a 1,000 to 1,2
Although a transparent glass body can be obtained by sintering and vitrification at a relatively low temperature of 00°C, it is difficult to obtain a large glass body because cracking and foaming phenomena tend to occur in the glass body during drying and sintering. Although method (2) does not cause foaming, it is difficult to obtain large glass bodies because cracks easily occur during the drying process, and the transparent vitrification temperature is relatively high at 1,500°C. In addition, the method has the disadvantage of being less likely to crack.
Although the sintering and vitrification temperature can be relatively low at around 1.300°C, there is a disadvantage that foaming sometimes occurs during sintering and vitrification, and furthermore, the resulting glass body does not become transparent.

It can be opaque and has poor reproducibility.
There is a drawback that it is difficult to obtain a transparent glass body with a good yield.

(Structure of the Invention) The present invention relates to a method for producing quartz glass by a sol-gel method that solves the above-mentioned disadvantages.
5≦water/alkoxysilane≦3.0 in the presence of an acidic catalyst. The obtained spherical silica fine particle suspension sol is mixed to make a mixed sol, which is then gelled to form a wet gel, dried to form a dry gel, and this dried gel is sintered to vitrify it. It is characterized by:

In other words, the present inventors investigated the causes of cracking, crystallization, and foaming in the above-mentioned sol-gel method (1), and found that this was caused by the sol liquid and silica obtained by hydrolysis in the presence of an acidic catalyst. Since the mixed sol solution with a sol solution containing fine particles has a low weight concentration of 30% by weight of the silica fine particles, the resulting wet gel and dry gel have low mechanical strength. Because the particles have a particle size of 1p or less, the drying rate in a large bulk to obtain a large, thick-walled molded product becomes uneven, and as a result, the bulk cannot withstand the stress and cracks occur during the drying process. The drying rate is faster near the drying surface of the gel body and slower elsewhere, causing deformation phenomena such as warping of the gel body during the drying process. Since this is obtained by hydrolysis of H,O/alkoxysilane with a molar ratio of 4 or more, the sol obtained from this N is one in which the siloxane polymer obtained by this hydrolysis is in the form of clusters or particles. Therefore, the wet gel and dry gel obtained from this will have low mechanical strength, and because the process from wet gel to dry gel involves a large shrinkage rate, transparent quartz glass with a wall thickness of 2 cwi or more is used. When attempting to obtain a gel, the pore diameter inside the gel was small, so the strength of the gel body could not withstand the capillary force, resulting in cracking during the drying process. After investigating various countermeasures for this problem, we decided to produce an acidic hydrolyzed sol. Sometimes the molar ratio of H,O/alkoxysilane is reduced,
If this is in the range of 0.5≦H*O/1 mole of alkoxysilane, the sol obtained by this hydrolysis becomes a polymeric linear polysiloxane that exhibits stringiness. The mixed sol obtained by mixing a suspension sol of spherical silica fine particles obtained by hydrolyzing alkoxysilane in the presence of a basic catalyst, the wet gel, and the dry gel made from this are all linear in groups of spherical silica particles. By fixing and entangling the polysiloxane polymer, the strength of the gel body is dramatically improved, resulting in a strong mechanical strength. Therefore, even though the concentration of silica fine particles in the mixed sol solution is at most 30% by weight, cracking during the drying process is prevented, and white crystallization and foaming during the sintering process are also prevented. They discovered that transparent quartz glass can be obtained with good reproducibility and high yield, and completed the present invention by conducting more detailed research on each process.

The method of the present invention will be explained step by step in detail below.

The method of the present invention involves first hydrolyzing alkoxysilane in the presence of an acidic catalyst to produce a sol solution, and then hydrolyzing this alkoxysilane in the presence of a basic catalyst to obtain a suspended sol containing spherical silica particles. A mixed sol is prepared by mixing with a liquid, and this method can basically be carried out by a known method.

Therefore, the alkoxysilane used for diN has the general formula S i (OR)4 and R is alkyl having 1 to 4 carbon atoms, such as tetramethoxysilane, "tetraethoxysilane."

Tetrapropoxysilane, tetrabutoxysilane.

Methoxytriethoxysilane, dimethoxyjethoxysilane, trimethoxyethoxysilane, etc. may be used.

This acidic hydrolysis involves dissolving 1 mole of this alkoxysilane in 10 moles or less of an organic solvent that is compatible with this alkoxysilane, particularly alcohols such as methanol, ethanol, propatool, butanol, and then adding water and hydrochloric acid to this solution. , an acidic catalyst selected from inorganic acids such as nitric acid, sulfuric acid, or organic acids such as acetic acid. IX 10-3~100
x 10-3 mol and stir the mixture under atmospheric pressure or under heating in a closed state at a temperature of 0 to 50°C. However, in the method of the present invention, the water added to If the molar ratio with
Since the adhesion force with the spherical silica fine particles becomes weak and the strength of the gel decreases, the range of 0.5≦H20/alkoxysilane≦3.0, preferably 1≦H80/alkoxysilane≦2 is recommended. Needed.

This means that if the molar ratio of water and alkoxysilane is not within this range, and this molar ratio is 3 or more, especially 4 or more, the organopolysiloxane produced by hydrolysis of this alkoxysilane is where η is the specific viscosity, C is the silica concentration, ρ is the particle density, and is a constant). Since the shape is cluster-like or granular, the sol obtained from this sol has weak mechanical strength.
This molar ratio is 0.5≦H, O/alkoxysilane≦3.
When set to 0, the organopolysiloxane produced by hydrolysis of this alkoxysilane is expressed by the formula %. is a constant), and the plot of reduced viscosity vs. silica concentration is now shown as a straight line with a slope (the results of small-angle X-ray scattering measurements also support this). It has been confirmed that the polymer is a linear polysiloxane, and therefore exhibits spinnability. The sol thus obtained and the wet gel and dry gel containing the same, which will be described later, have high mechanical strength.

Note that during this hydrolysis, various metal alkoxides, such as PO (OR), are added to the alkoxysilane.

T i (OR) Al (OR),, B (OR) □.

Ge(OR), , Z r(OR), , Nd(OR), (
It is optional to add a dopant agent (R is the same as above).

In addition, to create a sol containing silica particles by hydrolyzing this alkoxysilane in the presence of a basic catalyst,
To 1 mol of alkoxysilane, 2 to 20 mol of water, 5 to 10 mol of solvent, 0.1 to 10 mol of ammonia, and the required amount of dopant are added and hydrolyzed at 0 to 50°C. In this case, Ammonia has the effect of converting the silica produced by hydrolysis of alkoxysilane into spherical particles of uniform particle size, so that a solution containing fine silica particles with a particle size of 0.1 to 2 - can be obtained. If the temperature is 20 to 45℃ and the alkoxysilane is tetramethoxysilane, the particle size can be in the range of 0.01 to 0.1 um, but if the particle size is 0.05 μs or less, the dry gel The pores become smaller and water and alcohol remain inside the gel, causing foaming and sintering during sintering and vitrification, and the strength of the gel weakens and cracks occur during the drying process. , 1.0. If it is larger, it will naturally settle before gelation, creating a distribution of silica concentration inside the gel, making the shrinkage rate uneven, and cracking during the drying process. It is better to take it as a fact. In addition, the solution containing finely divided silica obtained in this way is often concentrated to a silica concentration of about 50% by weight by distillation, and this can be done by simple distillation,
In particular, water, solvent, and ammonia may be distilled off by simple distillation under reduced pressure to adjust the pH to 8 or less, and the silica concentration to be 50% by weight or less, preferably 25 to 40% by weight.

Mixing the thus obtained sol containing linear polysiloxane hydrolyzed in the presence of an acidic catalyst with a silica fine particle-containing sol having a silica concentration of 50% by weight or less and a pH of 8 or less The sol solution containing silica fine particles may be added to the knee while stirring this acidic hydrolyzed sol solution, or the acidic hydrolyzed sol solution may be added to the knee without stirring the sol solution containing silica fine particles. In order to prevent rapid gelation, this should be done under water cooling, and this stirring should be done slowly to avoid the inclusion of air bubbles.Also, the mixing ratio of both liquids should be acidic. Let the hydrolyzed sol be liquid (a).

When the sol containing spherical silica particles is used as the liquid (b), and the respective silica weights are SiO□ (a) and 51 oz (b), Sun, (a)/SiO, (b) < 0,
In No. 1, due to the small amount of Ca) liquid, sufficient siloxane bonds were not created to bond together the spherical silica fine particles that serve as the structural reinforcement, resulting in cracks occurring during the drying process, resulting in 5in2(a)/5iOi(b ) > 6, 0, (b) liquid is too small and the number density of spherical silica fine particles becomes thin, causing cracks to occur in the drying process; b) <
It is preferable to set it in the range of 6.0.

In addition, if the silica concentration of the mixed sol solution after mixing is less than 10% by weight, sufficient siloxane bonds cannot be created to bond the spherical silica fine particles, and the mixed gel will shrink significantly during the drying process. Breaks and cracks will occur, and if it is more than 50% by weight, it will tend to gel, depending on the pH after mixing, and subsequent operations will not be possible even if mixed under water cooling, so 10 to 50% by weight. It is preferable that the p of this mixed sol be within the range of
Since the acid hydrolysis sol is acidic and the pH of one spherical particle silica sol is 6 to 8, the pH of H is approximately 2 to 6, but it does not affect the gelation time when gelling this sol. The factors involved are temperature and pH value, and although this pH value cannot be determined uniquely due to the relationship with temperature, the most preferable pH value for gelation is 3 to 5, so this is a predicted value. It is preferable to adjust this pH value by adding ammonia as a hydrochloric acid or alkali.

In the method of the present invention, the mixed sol thus obtained is gelled to obtain a wet gel, dried to form a dry gel, and this is sintered and vitrified. However, the higher the temperature, the faster this gelation will proceed, but if the temperature is too high, the solvent will boil and the wet gel will crack, so it should be heated to 30-80℃ in a closed system. It is better to let them do it.

In addition, in order to dry this wet gel into a dry gel, it is necessary to remove residual solvents such as water and alcohol contained in this wet gel, but hydrolysis inside the gel, Since it is necessary to accelerate the polycondensation reaction, it is preferable to carry out this in a closed system for as long as possible time and at as high a temperature as possible. However, if the temperature is too high, cracks will occur due to the boiling phenomenon of the solvent.
After aging for days, it is preferable to dry the glass at a temperature of 50 to 120° C. in a container having an open area ratio of 0.1 to 10% until the final glass weight becomes 105 to 130% by weight.

In addition, sintering and vitrification of this dry gel can be performed at a temperature of 1°200
This can be done by heating to ~1,400°C, but this dry gel contains surface-adsorbed water and residual organic matter, and the target quartz glass must have a low OH group content. Prior to sintering and vitrification, this product is heated to 100-300°C to desorb surface adsorbed water, and then heated to 300-500°C in an air atmosphere.
℃ to oxidize residual organic matter and decarburize it, then heat to 700 to 900℃ in the presence of CI□ gas, 5OCI gas as a chlorinating agent, deOH treatment, and then remove the oxidizer using an oxidizing agent such as 02 gas. It is preferable to carry out oxidative dechlorination treatment by heating to 900 to 1,100°C in the presence of chlorine, and it is necessary to prevent cracks from occurring due to thermal distortion during these heat treatments. 10-b It is preferable to gradually raise the temperature from room temperature to 1,100° C. and perform the various treatments described above, and then sinter and vitrify it. Note that this sintered vitrification is performed at a temperature of 1°100 to 1,200°.
℃ to close the pores, and then heating at 1,200 to 1,400℃ for 30 minutes or more under reduced pressure or He gas atmosphere. According to this method, transparent quartz glass can be It can be easily obtained with good reproducibility and efficiency.

As mentioned above, in the method of the present invention, the molar ratio is 0°5≦water/
A mixture of alkoxysilane (alkoxysilane≦3.0) and water is hydrolyzed in the presence of an acidic catalyst to prepare a polymeric linear polysiloxane sample solution, and alkoxysilane is added to this in the presence of a basic catalyst. The spherical silica fine particle suspension sol obtained by hydrolysis was mixed to make a mixed sol, which was then gelled to obtain a wet gel, which was then dried to form a dry gel.

This is then sintered and vitrified. According to this method, the acidic hydrolyzed sol contains a polymeric linear polysiloxane, so this is mixed with a sol solution containing spherical silica fine particles. The mixed sol is gelatinized to obtain a wet gel, and the dry gel obtained by drying this has a high mechanical strength.This product does not crack during the drying or sintering process, and it also has a high resistance to warping. Since foaming does not occur, this gel has the advantage of being able to easily and efficiently produce transparent quartz glass parts with good reproducibility even when molded into large, thick products.

Next, examples of the present invention will be given.

Example 1) Production of acidic hydrolysis sol A mixed solution consisting of 2,400 g of tetraethoxysilane and 672 g of anhydrous ethanol was kept at 25°C, and while stirring vigorously, 208 g of 0.04 N hydrochloric acid water was added to it.
was added and stirred vigorously for 2 hours to hydrolyze the tetraethoxysilane, then the stirring was slowed down and the mixture was left in a sealed state at 40° C. for 1 day, yielding a polymeric polysiloxy sample.

This polysiloxane sample was taken from this, diluted with ethanol to various concentrations, its viscosity was measured, and a plot of reduced viscosity vs. silica concentration was obtained, and a straight line with a slope was obtained. was confirmed to have a linear structure, but when a small amount of this material was taken out and left to stand, it showed stringiness before gelation.

2) Production of suspension of spherical silica fine particles by basic hydrolysis 4,940 g of tetraethoxysilane, 26.4 m of absolute ethanol, and aqueous ammonia (NH, concentration 29% by weight)
1,584 ■Q and 1,714 g of water were mixed, the temperature of the mixture was maintained at 35°C, and the mixture was vigorously stirred for 3 hours to hydrolyze the tetraethoxysilane.

The spherical fine particles were left in a dark place for 12 hours to stabilize them, and while adding pure water intermittently to the hydrolyzed solution using a rotary evaporator, ethanol, water, and ammonia were distilled off under N reduced pressure until the pH reached 6. 6, a suspension of spherical silica particles was obtained with a silica concentration of 36% by weight and an average silica particle size of 0.25ta.

3) Mixing and gelation of acidic hydrolyzed sol and basic hydrolyzed sol Linear polysiloxane sol obtained in step 1) above 3.1
When 40+aQ and the basic hydrolyzed spherical silica fine particle suspension 3,160a+Q obtained in 2) were mixed under water cooling (5°C) and stirred, a mixed sol solution with a pH of 5.0 was obtained. Ta.

Next, 6,300mj2 of this mixed sol liquid was made into a 20cmφ
When placed in a Teflon cylindrical container of 30cm
10 wet gel bodies of the same size were created by the steps of ) to 3).

4) Drying, sintering, and vitrification The sealing lid of the above-mentioned sealed Teflon container has an open area ratio of 0.
The 10 containers containing the wet gel replaced with the 5% lids were transferred to a constant temperature bath at 60°C and left at that temperature for 20 days, then the lids were changed to a 5% open area and kept at 100°C. When dried in a constant temperature bath for 3 days, not a single gel body cracked during this time, and the size was 14.4 cmφ x 14.5 cm.
Ten dry gels were obtained that did not crack even at room temperature of mH, and no deformation was observed in these gels.

10 of these dried gels were placed in a Matsufuru furnace and heated at a heating rate of 30°C/H from room temperature in air for desorption water treatment.
After heating to 300℃ with R and holding at this temperature for 10 hours, the heating rate was increased to 30℃ in air for rail coal treatment.
/hour from 300°C to 700°C, and further maintained at this temperature for 20 hours in order to dehydrate and condense the surface silanol while the pores were open.

Then, this product was placed in another electric furnace and heated to 7.00 to 1.0 at a heating rate of 30°C/hour in a helium gas atmosphere.
The temperature was raised to 00°C and held at this temperature for 1 hour, and then raised to 1,100°C at a heating rate of 30°C/hour and held for 5 hours to close the pores.

Next, this material was heated to 1,100°C (1,100°C)v 1 at a heating rate of 30°C/hour, and 350°C, and kept at this temperature for 5 hours to vitrify it, resulting in 10.5c + *φX 10
．． Ten cylindrical transparent quartz glass bodies with a thickness of 6cH were obtained.

Example 2 1) Production of acidic hydrolysis sol A mixed solution consisting of 5,500 g of tetramethoxysilane and 2.1 g of absolute ethanol was kept at 10°C, and while stirring vigorously, 0.02 N hydrochloric acid solution was added to it. 1.3Q was added, stirred vigorously, and when the mixture became homogeneous, the temperature was gradually raised to 45°C. After that, the stirring was slowed down and stirring was stopped after one day. A siloxane sample was obtained.

This polysiloxane sample was taken from this, diluted with ethanol to various concentrations, its viscosity was measured, and a plot of reduced viscosity vs. silica concentration was obtained, and a straight line with a slope was obtained, indicating that this polysiloxane was confirmed to have a linear structure, but when a small amount of this material was taken out and left to stand, it showed stringiness just before gelation.

2) Production of a suspension of spherical silica fine particles by basic hydrolysis 9.78 kg of tetramethoxysilane, 94.3 Q of anhydrous methanol, 6.83 Q of ammonia water (N) + 3 (concentration 29% by weight) and 24.02 kg of water The liquid temperature was maintained at 0°C, and the tetramethoxysilane was hydrolyzed by stirring vigorously for 3 hours. The spherical fine particles were stabilized by being left in a dark place for 12 hours, and the water was added using a rotary evaporator. Pure water was added intermittently to the decomposition solution, and it was concentrated under reduced pressure while distilling off methanol, water, and ammonia. After concentration, the pH was adjusted to 6.5 with 0.2 N hydrochloric acid, and the silica concentration was 36. % by weight, and the average particle size of silica is 0.20. A suspension of spherical silica particles was obtained.

3) Mixing and gelation of a-based hydrolyzed sol and basic hydrolyzed sol Linear polysiloxane sol obtained in step 1) above 8.4
When 00+mQ and 8,580 mQ of the basic hydrolyzed spherical silica fine particle suspension obtained in 2) were mixed under water cooling (5°C) and stirred, a mixed sol solution with a pH of 5.5 was obtained. Ta.

Next, this mixed sol liquid was placed in a 60 cm + φ x 30 cm H SUS cylindrical container, kept at 5°C, and sealed at 40°C.
After putting it in a constant temperature bath for 2 days, the separating water in the container was removed, and it was left standing in 0.2N hydrochloric acid for 1 day and night.Then, the hydrochloric acid water was removed and the container was washed with ultrapure water. In this example, 10 wet gel bodies of the same size were prepared by the steps 1) to 3) described above.

4) Drying, sintering, and vitrification The sealing lid of the above-mentioned sealed Teflon container has an open area ratio of 0.
The 10 containers containing the wet gel replaced with the 5% lid were transferred to a constant temperature bath at 60°C and left at that temperature for 25 days, and then the lid was changed to a 5% open area and maintained at 100°C. When dried in a constant temperature bath for 5 days, not a single gel body cracked during this time, and the size of the gel was 43.5cm x 4.3cm.
Ten dried gels that did not crack even at room temperature were obtained, and no deformation was observed in them.

10 of these dried gels were placed in a Matsufuru furnace and heated at a heating rate of 30°C/H from room temperature in air for desorption water treatment.
After heating to 300℃ with R and holding at this temperature for 10 hours, the heating rate was increased to 30℃ in air for decarburization treatment.
/hour from 300°C to 700°C, and further maintained at this temperature for 20 hours in order to dehydrate and condense the surface silanol while the pores were open.

Next, this product was placed in another electric furnace and heated to 700 to 1,000 ℃ at a heating rate of 30°C/hour in a helium gas atmosphere.
The temperature was raised to 0° C., held at this temperature for 1 hour, and then raised to 1.1° 0° C. at a heating rate of 30° C./hour and held for 5 hours to close the pores.

Next, this material was heated from 1,100°C to 1,350°C at a heating rate of 30°C/hour and kept at this temperature for 5 hours to vitrify it. Ten thick cylindrical transparent quartz glass bodies measuring Oc■φX3.2 cmH were obtained.

Example 3 1) Production of acidic hydrolysis sol 903g of tetraethoxysilane and 266g of absolute ethanol
The mixed solution consisting of mQ was kept at 30°C.

Add 82.2 g of 0.02N hydrochloric acid to this while stirring vigorously, and when the mixture becomes homogeneous, slow down the stirring and let it stand for a day, then gradually add PO32, Og again. Then, 41.1 g of 0.02N hydrochloric acid was added, and when it became homogeneous, it was left for one day.
A polymeric polysiloxane sol doped with phosphorus was obtained.

This polysiloxy sample was taken from this, diluted with ethanol to various concentrations, its viscosity was measured, and a plot of reduced viscosity vs. silica concentration was obtained, and a straight line with a slope was obtained. It was confirmed that the siloxane had a linear structure, but when a small amount of this siloxane was taken out and left to stand, it showed stringiness just before gelation.

2) Production of suspension of spherical silica fine particles by basic hydrolysis A mixture of 2,594 g of tetraethoxysilane, 91.9 g of trimethyl phosphate, 876 layers of aqueous ammonia, 14.6 g of absolute ethanol, and 947 g of water was used. was treated in the same manner as 2) of Example 1, and the silica concentration was 36.
% by weight and the average particle size of silica is 0.20 tns 3) Mixing and gelation of acidic hydrolysis sol and basic hydrolysis sol Phosphorus-doped linear obtained in 1) above Phosphorus-doped basic hydrolyzed spherical silica fine particle suspension obtained with polysiloxy samples 1,400+Q and 2) 1,75
When mixed with 0mff1 under water cooling (10°C) and stirred, a mixed sol solution with a pH of 3.5 was obtained.
This was adjusted to pH 4.5 with 0.2N ammonia water.

Next, this mixed sol liquid was poured into a S of 20cmφXIOcmH.
When placed in a US-made cylindrical container and kept at 5°C, sealed and placed in a constant temperature bath at 40°C for 3 days, this product gelled and matured, but in this example, steps 1) to 3) described above. Ten wet gel bodies of the same size were prepared by the following method.

4) Drying, sintering, and vitrification The wet gel obtained above was processed in the same manner as in Example 4) to make a dry gel.
Since a dry gel of H was obtained, this was then sintered and vitrified in the same manner as in Example 1, 4).
It was possible to obtain 10 thick cylindrical transparent quartz glass bodies having a diameter of 5.3 cmH and no cracks at all.

Example 4 1) Production of acidic hydrolysis sol 185 g of tetraethoxysilane and 103 g of absolute ethanol
A mixed solution consisting of IIQ was maintained at 20°C.

Add 21.3 g of 0.02 N hydrochloric acid to this while stirring vigorously, and when the mixture becomes homogeneous, turn the stirring slowly and leave it in a sealed container for 2 days. .5 g of 2 N hydrochloric acid was gradually added, 484.0 g of titanium isopropoxide Ti (0-iPr) was gradually added, and then 16.4 g of 0.02 N hydrochloric acid was added to make a homogeneous solution. A polymeric siloxane sol doped with

This polysiloxy sample was taken from this, diluted with ethanol to various concentrations, its viscosity was measured, and a plot of reduced viscosity vs. silica concentration was obtained, and a straight line with a slope was obtained. It was confirmed that the siloxane had a linear structure, but when a small amount of this siloxane was taken out and left to stand, it showed stringiness just before gelation.

2) Production of spherical silica fine particle suspension by basic hydrolysis 354 g of tetraethoxysilane, 161.1 g of titanium isopropoxide, 2,520 vans of absolute ethanol,
Using a mixture of 151 mA of ammonia water and 163 g of water, the treatment was carried out in the same manner as in 2) of Example 1, and the silica concentration was 34.5% by weight, and the average particle size of silica was 0.20 u.
A titanium-doped spherical silica fine particle suspension of M was obtained.

3) Mixing and gelation of acidic hydrolyzed sol and basic hydrolyzed sol 410 mfl of the titanium-doped linear polysiloxane sol obtained in 1) above and the titanium-doped basic hydrolyzed sol obtained in 2) Spherical silica fine particle suspension 340
and intestine Ω were mixed under water cooling (5°C).

Upon stirring, a mixed sol solution having a pH of 4.7 was obtained.

Next, this mixed sol liquid was poured into a 15cmφX20c tray H.
When placed in a US-made cylindrical container and kept at 5°C, sealed and placed in a constant temperature bath at 50°C for 3 days, this product gelled and matured, but in this example, steps 1) to 3) above. Ten wet gel bodies of the same size were prepared by the following method.

4) Drying, sintering, and vitrification The sealing lid of the above-mentioned sealed Teflon container has an open area ratio of 0.
The 10 containers containing the wet gel replaced with the 5% lid were transferred to a constant temperature bath at 70°C and left at that temperature for 15 days, and then the lid was changed to a 5% open area and maintained at 100°C. When dried in a constant temperature bath for 3 days, not a single gel body cracked during this time, and the size was 10.3ci + φX2.9c.
lI) 10 dry gels that do not crack even at room temperature of I were obtained,
No deformation was observed in these.

This dried gel was then sintered and vitrified in the same manner as in 4) of Example 1 above, resulting in 7.3ci+φX2.1
Ten c+*H transparent quartz glass bodies were obtained.

Comparative Example 1 1) Production of acidic hydrolysis sol A mixed solution of 2,215 g of tetraethoxysilane and 767 g of 0.02 N hydrochloric acid water was vigorously stirred and hydrolyzed to produce a sol solution, from which a sample was collected. When this was diluted with ethanol to various concentrations and its viscosity was measured, and a plot of reduced viscosity vs. silica concentration was obtained, it showed a constant reduced viscosity that was unrelated to the silica concentration. It was confirmed that the siloxane was not linear, and the measured value of the small-angle X-ray scattering intensity showed that this siloxane was a cluster-like polymer, but it did not show a string-like shape.

2) Synthesis of basic hydrolyzed silica fine particle suspension A basic hydrolyzed spherical silica fine particle suspension was prepared in the same manner as in 2) of Example 1 above.

3) Mixing of acidic hydrolyzed sol and basic hydrolyzed sol and gelation The acidic hydrolyzed sol and basic hydrolyzed sol obtained above are mixed in the same manner as in 3) of Example 1, and gelled. A wet mixed sol was made.

4) Aging, drying, sintering, vitrification Next, when the wet mixed gel obtained above was dried by the method of Example 1 and 4), the result was 14.2c+sφX14.3c+m
Ten dried gels of H were obtained, of which three were broken and five had cracks.

Therefore, when the remaining two pieces were sintered and vitrified according to the method 4) of Example 1, one piece was a crystalline body and the other one was a foamed body.

Comparative Example 2 1) Production of acidic hydrolysis sol 185 g of tetraethoxysilane and 103 g of absolute ethanol
Add 24g of 0.2N hydrochloric acid to the mixed solution of +sQ,
After partially hydrolyzing this while keeping the temperature at 5°C, 84.0 g of titanium isopropoxide was added to it, stirred vigorously, and then 61.5 g of 0°2N hydrochloric acid solution was added.
g was added to complete the hydrolysis and a sol solution was prepared.

Next, samples were taken from this sol solution, diluted with ethanol to various concentrations, the viscosity was measured, and the reduced viscosity -
When plotting the silica concentration, it showed a constant reduced viscosity regardless of the silica concentration, confirming that the polysiloxane coexisting in this material did not have a linear structure.

This material was also found to be a cluster polymer based on the small-angle X-ray scattering intensity measurements, but this material did not exhibit stringiness before gelation.

2) Preparation of basic hydrolyzed spherical silica fine particle suspension sol Etraethoxysilane and titanium isopropoxide were hydrolyzed in the same manner as in 2) of Example 4 to obtain titanium-doped spherical sol. A silica fine particle suspension sol was created.

3) Mixing of acidic hydrolysis sol and basic hydrolysis sol.

Gelation When the acidic hydrolyzed sol and basic hydrolyzed sol described above were mixed at below freezing point (5°C) and stirred, a mixed sol with a pH of 3.5 was obtained. The pH was adjusted to 4.7, and 10 wet gel bodies having the same dimensions were prepared in the same manner as in Example 4, 3).

4) Drying, sintering, and vitrification When 10 wet gel bodies made as described above were dried by the method 4) of Example 4, three of them cracked during the drying process.
Two of the pieces had cracks, so when the remaining five pieces were sintered and vitrified using the same method, two pieces became crystals, two pieces became foam bodies, and one piece became a transparent glass body. But this one also had a crack in it.

Claims (1)

[Claims] 1. Hydrolyzing alkoxysilane in the presence of a basic catalyst into a uniform linear polysiloxane sol solution obtained by hydrolyzing a mixture of alkoxysilane and water in the presence of an acidic catalyst. The resulting spherical silica fine particle suspension sol is mixed to make a mixed sol, which is then gelled to form a wet gel, dried to form a dry gel, and this dried gel is sintered to form glass. A method for producing quartz glass characterized by 2. The silica glass according to claim 1, wherein the mixing ratio of alkoxysilane and water in the linear polysiloxane-like silica sol liquid is 0.5≦water/alkoxysilane≦3.0 in terms of molar ratio. Production method. 3. The method for producing quartz glass according to claim 1 or 2, wherein the alkoxysilane contains a metal alkoxide other than silicon as a dopant.