JPH10279318A - Manufacturing method of quartz glass - Google Patents

Abstract

(57) [Summary] [Problem] There are almost no problems such as cracks during manufacturing.
Provided is a method for manufacturing quartz glass, which can easily and inexpensively manufacture a relatively large quartz glass product. SOLUTION: A silica powder slurry containing a silica powder, a binder and a curing agent is poured into a mold to be cured, and then a silica bulk body obtained by releasing from the mold is dried and calcined to obtain quartz. In the production of glass, a reactant consisting of an alkyl silicate and / or a partial condensate thereof is partially hydrolyzed and polycondensed in the presence of a catalyst with water less than an equivalent amount of an alkoxy group in the reactant as the binder. This is a method for producing quartz glass using a silicate-based sol solution obtained by the above method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing quartz glass, which is not particularly limited, but has a high purity and is suitable for use in the fields of electronic materials, semiconductor materials, and apparatuses for producing the same. The present invention relates to a method for producing fused quartz glass.

[0002]

2. Description of the Related Art Quartz glass is a glass made of only silicon dioxide and has a high purity. Therefore, for example, glass equipment such as a single crystal pulling crucible used in a semiconductor manufacturing process, a furnace core tube for a diffusion furnace, and its surroundings. It is a material widely used in fields requiring high purity, such as jigs.

[0003] As a method for producing such quartz glass, a melting method of melting, cooling, and processing a siliceous material such as natural quartz is generally performed. In this melting method, Since the melting temperature is usually as high as 1900 ° C. or more, the material of the electric furnace to be used is limited to a special material, which makes the production equipment too expensive and increases the power cost, resulting in the production cost of quartz glass. Is too high.

Further, as another method of manufacturing quartz glass,
A silica powder (synthetic silica powder) is produced from water glass or an alkyl silicate, a silicate-based binder is mixed with the silica powder to form a silica powder slurry, and the silica powder slurry is poured into a predetermined mold and cured. Using a binder that is released from the mold, dried, and fired (JP-A-5-3456)
No. 20) or a sol which hydrolyzes an alkyl silicate to form a bulk silica and calcinates the bulk silica.
A gel method (JP-A-63-182222) has been proposed.

According to these methods, high-purity quartz glass can be produced at a low sintering temperature. However, in the former method using a binder, the silicate-based binder is more than the hydrolysis equivalent of alkyl silicate. Of water, the bonding part made of the silicate binder becomes too hard at the time of curing, cannot withstand shrinkage during curing and drying, and cracks occur especially when manufacturing a relatively large silica bulk body In addition, in the latter sol-gel method, the silica bulk obtained has a large shrinkage upon drying, and the same problem as in the former case cannot be avoided.

However, quartz glass utensils used in a semiconductor manufacturing process, for example, are required to have higher purity, more complicated shape, larger size, etc. in recent years. There is a need to develop a method that can be manufactured at low cost.

[0007]

The inventors of the present invention have conducted intensive studies on a method for producing a quartz glass which can be used to produce a relatively large quartz glass product with less problems such as cracks during production. The inventors have found that the above-mentioned conventional problems can be solved by leaving a part of the alkoxy group in a reaction product comprising an alkyl silicate and / or a partial condensate of the binder used in the binder utilization method, The present invention has been completed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing quartz glass, which can produce relatively large quartz glass products easily and inexpensively with almost no problems such as cracks during production. .

[0009]

That is, the present invention is obtained by injecting a silica powder slurry containing silica powder, a binder and a curing agent into a mold, curing the slurry, and then releasing the mold from the mold. When the silica bulk material is dried and calcined to produce quartz glass, as the binder, a reactant composed of an alkyl silicate and / or a partial condensate thereof is mixed with water having an equivalent of less than an alkoxy group in the reactant. This is a method for producing quartz glass using a silicate-based sol obtained by partial hydrolysis and polycondensation in the presence of a catalyst.

[0010] The silicate sol used as a binder in the present invention comprises a reactant comprising one or a mixture of two or more selected from alkyl silicates and partial condensates thereof, and an alkoxy group in the reactant. Is a sol-like liquid obtained by partial hydrolysis and polycondensation in the presence of a catalyst using water less than the equivalent amount of an alkoxy group so that a part of the liquid remains.

The alkyl silicate and its partial condensate used in the present invention are represented by the following general formula:

Embedded image

(Wherein, R ₁ , R ₂ , R ₃ and R ₄ are lower alkyl groups having 1 to 9 carbon atoms and may be the same or different from each other) Alkyl and partial condensates thereof are mentioned. The partial condensate has an average degree of polymerization before gelation, preferably an average degree of polymerization of alkyl silicate of 2 to 9, and preferably 3 to 6. No. Among these particularly preferred are substituents R ₁ to R ₄ is a partial condensate having an average polymerization degree of 2-9 alkyl silicate having 1 to 4 carbon atoms, more preferably a substituted group R ₁ to R ₄ It is a partial condensate of an alkyl silicate having 1 to 4 carbon atoms having an average degree of polymerization of 3 to 6. In addition, for example, a material having a bonding structure in which a carbon atom is directly bonded to a silicon atom such as trialkoxyalkylsilane, when this is used as a raw material of a silicate-based sol solution of a binder, the carbon quartz is contained in a product quartz glass. There is a possibility that a residue may remain, which is not preferable.

The catalyst used in the partial hydrolysis and polycondensation reaction of these alkyl silicates and / or their partial condensates may be selected from sodium hydroxide, An inorganic catalyst such as potassium hydroxide or the like, an alkali catalyst such as ammonia or an organic alkali, or an acid catalyst such as nitric acid can be used. However, in order to prevent contamination of metal impurities as much as possible and to promote the reaction smoothly. And preferably an organic alkali.

Preferably, the organic alkali is easily scattered from the silica bulk when the silica bulk obtained by releasing from the mold is dried and calcined.
It is preferable that no residue such as carbon remains after firing. Specifically, tetramethylammonium hydroxide (T
MAH), tetraethylammonium hydroxide, (2-hydroxyethyl) trimethylammonium hydroxide (choline), di (2-hydroxyethyl) dimethylammonium hydroxide, tri (2-hydroxyethyl) methylammonium hydroxide, tetra (ammonium hydroxide) Quaternary ammonium hydroxides such as 2-hydroxyethyl) ammonium,
Organic amines such as trimethylamine, triethylamine, ethanolamine, diethanolamine, and triethanolamine are exemplified.

The amount of reaction water used in the partial hydrolysis and polycondensation reaction of the present invention must be less than the equivalent of the alkoxy group of the reactant so that a part of the alkoxy group in the reactant remains. Preferably, 0.30 to 0.95 equivalent, more preferably 0.50 to 1 equivalent of alkoxy group.
A range of 0.90 equivalents is preferred. When the reaction water is present in an amount equal to or more than the equivalent of the alkoxy group, the alkoxy group in the reaction product is completely hydrolyzed, and then the polycondensation proceeds to form a strong three-dimensional bond by a siloxane bond (Si-O-Si), The molded silica bulk body becomes too hard and cannot cope with shrinkage due to evaporation of the solvent in the drying process,
May cause cracking. Further, when the amount of the reaction water is less than 0.30 equivalent, there is a problem that the binder structure is formed around two dimensions and is easily peeled off.

As a catalyst for preparing a silicate-based sol solution as a binder, basically, an alkali catalyst or an acid catalyst can be used, but preferably an organic alkali, such as sodium hydroxide or water. Inorganic alkali such as potassium oxide, sodium ions and potassium ions remain in the silica bulk produced using it,
Since it becomes a metal impurity and remains in the quartz glass, it becomes difficult to obtain high-purity quartz glass. Also, the use of ammonia is not preferred because the concentration may not be constant due to evaporation during the heat treatment at the time of preparing the binder.

The organic alkali used as the catalyst is desirably one which does not leave residues such as metal impurities and carbon in the fired body obtained after firing, and specifically, tetramethylammonium hydroxide (hereinafter referred to as tetramethylammonium hydroxide). ,
“TMAH”), tetraethylammonium hydroxide, (2-hydroxyethyl) trimethylammonium hydroxide (hereinafter “choline”), dihydroxide (2
Quaternary ammonium hydroxides such as -hydroxyethyl) dimethylammonium, tri (2-hydroxyethyl) methylammonium hydroxide, tetra (2-hydroxyethyl) ammonium hydroxide, trimethylamine, triethylamine, monoethanolamine, diethanolamine, Examples thereof include alkylamines such as triethanolamine.

A reactant comprising the above-mentioned alkyl silicate and / or a partial condensate thereof is partially hydrolyzed and polycondensed with water having less than an equivalent amount of an alkoxy group in the reactant in the presence of the above-mentioned catalyst to form a silicate sol solution ( The reaction conditions for preparing the (binder) are not particularly limited, but preferably the reaction product and water and a solvent that dissolves the catalyst as a solvent, more preferably when the reaction product is hydrolyzed Using the same type of alcohol as the solvent to be produced as a solvent, first, the alcohol solvent and the reactants are mixed, and a predetermined amount of a catalyst and water are added thereto with stirring, and the solvent is heated from room temperature to the reflux temperature of the solvent, The reaction is carried out preferably at 30 to 65 ° C and a reaction time of 0.1 to 16 hours, preferably 0.5 to 9 hours.

Here, the use of an alcohol solvent is not essential, but it is effective for smoothly proceeding the partial hydrolysis reaction and polycondensation reaction of the reactants. It is determined in consideration of the viscosity and the like to be obtained. For the alcohol used as a solvent or a by-product in the partial hydrolysis reaction or polycondensation reaction of the reactant, the amount does not exceed the amount of the solvent such as alcohol required for preparing the silica powder slurry. As long as it remains in this binder, it is desirable to use it as a solvent when preparing a silica powder slurry.

In the present invention, the silica powder used for preparing the silica powder slurry is not particularly limited, and the one synthesized by a sol-gel method using water glass or an alkyl silicate as a raw material is pulverized and classified. It is possible to use those obtained by pulverizing and classifying natural quartz or the like, but in order to produce high-purity quartz glass, it is preferably a product synthesized by a sol-gel method using alkyl silicate as a raw material. Is good. The particle size and shape of the silica powder is not particularly limited as long as it is a normal powder, preferably 1 to 100 μm,
More preferably, it is 3 to 50 μm. If the particle size is too small, a relatively large amount of a binder or a solvent must be used, and shrinkage tends to occur during the evaporation of the solvent or the like, so that the particle tends to crack, and conversely, the particle size is too large. Then, the contact area between the particles becomes small and the adhesive force by the binder is reduced, so that the particles are easily cracked.

Further, various alkaline substances can be used as a hardening agent used for preparing the silica powder slurry. Inorganic alkalis include sodium ions and potassium ions in a silica bulk material produced using the same. It remains and becomes a metal impurity and remains in the quartz glass, and is therefore preferably ammonia or an organic alkali, and as the organic alkali, TMAH, tetraethylammonium hydroxide, which is suitable as a catalyst used in the production of the binder, Choline, di (2-hydroxyethyl) dimethylammonium hydroxide, tri (2-hydroxyethyl) methylammonium hydroxide, tetra (2
Quaternary ammonium hydroxides such as -hydroxyethyl) ammonium; and alkylamines such as trimethylamine, triethylamine, monoethanolamine, diethanolamine, and triethanolamine.

When this hardener is used as an aqueous solution when preparing a silica powder slurry, the amount of water in the hardener aqueous solution is the sum of the amount of water used in preparing the binder and the amount of silicic acid. It is necessary that the amount of the alkoxy group in the reactant be less than the equivalent of the alkoxy group so that a part of the alkoxy group in the reactant comprising the alkyl and the partial condensate remains. In other words, when the curing agent is used as an aqueous solution, the amount of water in the curing agent aqueous solution is such that the water in the curing agent aqueous solution also participates in the partial hydrolysis and polycondensation reaction of the reactant after the preparation of the silica powder slurry. It is necessary to calculate the amount as a part of the amount and leave the amount of the alkyl silicate and a part of the alkoxy group in the partial condensate thereof in the prepared silica powder slurry. If water exceeding the equivalent of the alkoxy group of the reactant is added during the preparation of the silica powder slurry, the formed silica bulk becomes too hard and causes cracking in the drying step.

In the present invention, the mixing ratio of the silica powder, the binder and the curing agent in preparing the silica powder slurry is generally determined in consideration of the viscosity of the slurry, the curing time, the presence or absence of cracks, and the like. The binder is usually 10 to 40 parts by weight, preferably 12 to 35 parts by weight, based on 100 parts by weight of the silica powder, depending on the type of the binder and the curing agent to be used. 2% by weight
It is usually 0.3 to 1.5 parts by weight, preferably 0.5 to 1.0 parts by weight in terms of ammonia water. If the amount of the binder is too small, there is a problem that the silica powder is peeled off, and if the amount is too large, a problem that cracks easily occur, and if the amount of the curing agent is too small, it takes a long time to cure. Is required, and the silica powder is settled. If it is too large, it hardens during mixing and it becomes difficult to pour into the mold.

In the present invention, when preparing a silica powder slurry, if necessary, various adjustments may be made for the purpose of adjusting the viscosity to ensure good moldability and the drying speed to ensure crack prevention during drying. Solvents and thickeners can be added. Examples of the solvent used for such a purpose include alcohols such as methanol, ethanol, n-propanol, isopropanol and n-butanol, and various ketones and ethers. For example, glycols such as ethylene glycol, diethylene glycol, propylene glycol, and the like, and alcohols such as pentyl alcohol, hexyl alcohol, methoxyethanol, ethoxyethanol, propoxyethanol, butoxyethanol, methoxypropanol, ethoxypropanol, and propoxypropanol. it can.

The method for preparing a silica powder slurry using the above-mentioned silica powder, binder, curing agent, and optionally added solvent and thickener is particularly limited as long as the whole is uniformly mixed. Instead, the mixture may be stirred manually using a stirring rod, or an ordinary stirring mixer may be used. In this case, in order to reduce bubbles trapped in the slurry, it is desirable to perform an operation of keeping the whole slurry under reduced pressure during or after mixing.

Next, the silica powder slurry thus prepared is poured into a mold having a predetermined shape, cured in the mold, separated from the mold and dried to form a silica bulk material. It is said. In the method of the present invention, injection → curing →
The steps from release to drying may be the same as those conventionally performed, but the step of curing the silica powder slurry in the mold and the release and drying of the cured silica bulk body are performed. The steps are preferably performed by the following method.

That is, in the step of curing the silica powder slurry in the mold, the silica powder slurry is poured into the mold, and then the mold is covered with a gas-impermeable sheet such as a polyethylene sheet. The mold should be sealed. By sealing the mold in this manner, the evaporation of the solvent and the like from the slurry is prevented, thereby providing an advantage that the occurrence of cracks in the bulk body during curing can be more reliably prevented.

In the step of releasing and drying the silica bulk material, the released silica bulk material is first immersed in water or a partial condensate of alkyl silicate, preferably in water, and then in water or alkyl silicate. Is preferably removed from the partial condensate and dried. Here, regarding the method and conditions for immersing the silica bulk body in water or a partial condensate of alkyl silicate, the entire silica bulk body may be immersed in water or a partial condensate of alkyl silicate, and there is no particular limitation. However, the immersion temperature is preferably in the range from room temperature to about 50 ° C. Prior to the drying of the silica bulk body, the silica bulk body is immersed in water or a partial condensate of an alkyl silicate to dry the bulk silica body without causing cracking. Can be greatly reduced, and the productivity is significantly improved. This is because the solvent or by-product consisting of alcohols such as methanol incorporated in the bulk silica is replaced with these water or partial condensates of alkyl silicate, in other words, the solvent is exchanged. It is considered that drying can be achieved.

In the present invention, the obtained silica bulk body is immersed, if necessary, with a partial condensate of water or an alkyl silicate, dried, and then fired to produce a quartz glass product. The method and conditions for drying the silica bulk body can be the same methods and conditions as in the past, but greatly differ depending on the size of the silica bulk body and whether or not to perform the immersion treatment beforehand, When the immersion treatment is not performed, it is usually left in the air at a temperature of 50 ° C. or less for 1 day to 3 months, preferably 10 days to 3 months. The temperature is controlled at a constant temperature and humidity within a range of 3 days to 30 days, preferably at a temperature of 20 to 50 ° C. and a humidity of 60 to 90%.
Dry for 0 days.

Further, the same method and conditions as in the prior art can be employed for the firing method and the conditions for firing the dried silica bulk body into quartz glass, and usually, the air is generally used in the atmosphere. 200-2 under medium or vacuum or in an atmosphere of inert gas such as nitrogen, helium, argon, etc.
1 minute to 20 hours at a temperature of 000 ° C., preferably 1100
１1900 ° C. for 1 minute to 10 hours. The firing conditions differ depending on the particle size of the silica powder used. For example, when the average particle size is 3 to 4 μm, sintering proceeds at 1100 to 1400 ° C., and when the average particle size is 10 μm or more, a temperature of 1400 ° C. or more is required. . In addition, in order to produce quartz glass having excellent transparency, it is necessary to prepare a glass substrate under vacuum or an inert gas atmosphere.
It is desirable to fire at a temperature of 0 to 1900 ° C.

A partial condensate of methyl silicate [trade name: MS-51, manufactured by Tama Chemical Industry Co., Ltd., average degree of polymerization: 3 to 5]
Regarding the silicate-based binder prepared using 4), the sample amount: 24.70 mg, the cell: platinum, the gas type: nitrogen,
Gas flow rate: 30.00 ml / min, and heating rate 10.2
The temperature was raised to 26.61-599.34 ° C. under the conditions of ° C./min, and thermal analysis data analysis was performed. The results are as shown in FIG. 1, and the loss on heating was 5.727 mg (23.185 mg).
%), And it was found that dimethyl ether was eliminated at 360.51 ° C. From this, in the present invention, the alkoxy groups remaining in the bulk silica body effectively prevent the cracking of the bulk silica body during drying, and the alkoxy group during the heating process of the bulk silica body during firing. It is considered that the group is eliminated as an ether and scattered without leaving a residue such as carbon in the silica bulk body.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below based on examples and comparative examples.

Example 1 A partial condensate of methyl silicate [trade name: MS-51, manufactured by Tama Chemical Industry Co., Ltd., average degree of polymerization: 3-4] 218.4 g of methanol and 80 g of methanol were sufficiently mixed to obtain a product. 16.2 g of a 0.05% by weight aqueous solution of TMAH was added to the obtained solution,
The reaction was performed at 5 ° C. for 2 hours to produce a binder.

To 64 g of the obtained binder, 22 g of ethanol as a solvent and 20 g of ethylene glycol for the purpose of adjusting viscosity and drying speed were added.
m of silica powder was added, and the resulting mixture was uniformly mixed. Then, 1.7 g of 2% by weight ammonia water was added.
Was added and mixed well to obtain a silica powder slurry.

The silica powder slurry thus prepared was poured into a polypropylene mold having a circular shape, the upper part of the mold was covered with a polyethylene sheet, sealed, and left to cure overnight. Thereafter, ten holes each having a diameter of 5 mm were formed in a polyethylene sheet covering the upper part of the mold, and left for one week to dry the silica bulk material in the mold. After that, the polyethylene sheet was removed, the silica bulk body was taken out of the mold, and its appearance was observed.
The silica bulk body had a size of 105 mm in diameter × 23 mm in height and was of good quality without cracks.

Next, the obtained silica bulk body was fired in an air atmosphere at 1000 ° C. for 3 hours using a firing furnace to obtain a fired body without cracks. The fired body is further subjected to 154 vacuum.
The resultant was fired at 0 ° C. for 5 hours and at 1800 ° C. for 5 minutes in an argon atmosphere to obtain a transparent quartz glass having a size of 90 mm in diameter × 22 mm in height. Further, this quartz glass was of high purity containing no impurity metal or the like.

Table 1 shows the raw materials and the mixing ratios of the silica bulk material of Example 1 and the evaluation of its appearance and properties. Table 1 also shows the total water equivalent relative to the alkoxy group used in the production of the binder and the preparation of the silica powder slurry. The appearance properties were evaluated by observing the appearance of the obtained silica bulk body visually and judging its properties. ：: No cracks, almost no carbon or air bubbles observed, good transparency and good , Δ: almost transparent with no cracking, and ×: poor, with cracks observed and evaluated on a three-point scale.

Examples 2 to 5 Using the same binder as prepared in Example 1, the raw materials for producing a large silica bulk having a diameter of 270 mm were blended at the ratios shown in Table 1, and the silica was produced in the same manner as in Example 1. A bulk body was prepared, then dried and fired to produce quartz glass. All of the obtained quartz glasses were transparent and of good quality. For the silica bulk bodies of Examples 2 to 5, the production raw materials, the blending ratios and the evaluation of the appearance properties, and the total water equivalents to the alkoxy groups used during the production of the binder and the preparation of the silica powder slurry are shown in Table 1.

[0039]

[Table 1]

Examples 6 to 8 Partial condensate of methyl silicate used in Example 1 218.4
g of methanol and 80 g of methanol were sufficiently mixed, an organic alkali having a concentration shown in Table 2 was added to the obtained solution, and the mixture was reacted at 65 ° C. for 0.5 to 2 hours to produce a binder. Using 64 g of the obtained binder, a silica powder slurry was prepared in the same manner as in Example 1, and then a silica bulk body was formed, dried and fired to produce quartz glass. The obtained silica bulk body was of good quality without cracks as in Example 1, and transparent and high-purity quartz glass was obtained. Table 2 shows the evaluation of the appearance properties of the silica bulk bodies of Examples 6 to 8, and the total water equivalent relative to the alkoxy group used during the production of the binder and the preparation of the silica powder slurry.
Shown in

[0041]

[Table 2]

Examples 9 to 13 In a silica powder slurry containing 250 g of silica powder, 64 g of the same binder as in Example 1, and 20 g of ethylene glycol, 2 to 4% by weight of aqueous ammonia 1.4 to 1.7 were used as a curing agent.
g, 19-23 g of ethanol as a solvent and 0-added water
A silica bulk was prepared in the same manner as in Example 1 except that 2.6 g was added, and quartz glass was produced. Each of the obtained quartz glasses was transparent and of high purity.
For each of Examples 9 to 13, the amount of ethanol used, the amount of 2% by weight ammonia water used as a curing agent, the amount of added water, the total water equivalent, and the appearance properties of the obtained silica bulk body The evaluation is shown in Table 3.

[0043]

[Table 3]

Example 14 The silica bulk material cured in the mold was removed from the mold and was placed in about 350 ml of water shown in Table 4 or the partial condensate of methyl silicate (MS-51) used in Example 1. Immersion treatment at room temperature for each immersion time shown in Table 4, followed by water or MS-
A quartz glass was manufactured in exactly the same manner as in Example 1 except that the quartz glass was taken out of the room 51 and dried at room temperature in a completely open state.

Table 4 shows the results of observing the appearance properties of the silica bulk obtained at each immersion time. As is clear from the results in Table 4, when water is used as the immersion solvent, the immersion time is 2.5 hours or more, and when MS-51 is used as the immersion solvent, the immersion time is 1.0 hour. As described above, no defects such as cracks were observed on the surface of the silica bulk body. Moreover, the obtained quartz glass was excellent in transparency.

[0046]

[Table 4]

Further, the silica powder and the binder used as raw materials used in this example and the quartz glass obtained by immersing in water for 4.0 hours, and then dried and fired were subjected to flameless atomic absorption spectrometry to determine whether Na, Fe, The analysis was carried out for Al and K elements. The results are as shown in Table 5 and were high purity containing no impurity metals and the like.

[0048]

[Table 5]

Comparative Examples 1 to 3 Ethylene glycol 10 to 18 in a silica powder slurry containing 250 g of silica powder, 64 g of the same binder as in Example 1, and 1.7 g of 2% by weight aqueous ammonia as a curing agent.
g, 12 to 20 g of ethanol as solvent and added water3.
A silica bulk was prepared in the same manner as in Example 1 except that 8 to 21.4 g was added, and quartz glass was produced.

Cracks were observed in all of the silica bulk bodies obtained in Comparative Examples 1 to 3, and quartz glass obtained by sintering them also had cracks. Table 6 shows the amount of ethylene glycol used, the amount of ethanol used, the amount of added water, the total water equivalent, and the evaluation of the appearance properties of the obtained silica bulk body for each of Comparative Examples 1 to 3.

[0051]

[Table 6]

Comparative Example 4 The same partial condensate 21 of methyl silicate as used in Example 1
8.4 g and 80 g of methanol were sufficiently mixed, and 43.2 g of a 0.05% by weight aqueous TMAH solution was added to the obtained solution.
(Containing an equivalent amount of water with respect to the alkoxy group), and 6
The reaction was performed at 5 ° C. for 12 hours, and an attempt was made to produce a binder. As a result, the reaction mixture gelled during the reaction, and the desired binder was not obtained.

Comparative Example 5 The same partial condensate 21 of methyl silicate as used in Example 1
8.4 g and methanol (80 g) were sufficiently mixed, and a 0.1% by weight aqueous solution of formic acid (16.2.
g (containing 0.57 equivalent of water in total water equivalent relative to alkoxy group) was added and reacted at 65 ° C. for 2 hours to prepare a binder. A silica powder slurry was prepared in the same manner as in Example 1 using the obtained binder, and an attempt was made to produce quartz glass. As a result, cracks were observed in the dried silica bulk body, and quartz glass of good quality could not be obtained.

Comparative Example 6 A binder was prepared in the same manner as in Comparative Example 5 except that a 0.1% aqueous solution of nitric acid was used instead of 16.2 g of a 0.1% aqueous solution of formic acid as a catalyst. Was prepared to prepare a silica bulk body, and quartz glass was produced.
As a result, similarly to Comparative Example 5, cracks were observed in the dried silica bulk body, and quartz glass of good quality could not be obtained.

[0055]

According to the method of the present invention, a problem such as cracking at the time of production can be achieved by partially leaving an alkoxy group in a reaction product comprising an alkyl silicate as a binder and / or a partial condensate thereof. Few, relatively large quartz glass products can be easily and inexpensively manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing thermal analysis data of a silicate-based binder prepared using a partial condensate of methyl silicate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Yukinobu Hara 3-1-109 Koyo, Hachinohe City, Aomori Prefecture, within Nitto Chemical Industry Co., Ltd. (72) Takeshi Matsumura 3-1-109 Koyo, Hachinohe City, Aomori Prefecture, Nitto Chemical Industry Co., Ltd.

Claims (7)

[Claims] 1. A silica powder slurry containing a silica powder, a binder and a curing agent is poured into a mold to be cured, and then the silica bulk body obtained by releasing from the mold is dried and fired. In producing quartz glass, as a binder, a reactant consisting of an alkyl silicate and / or a partial condensate thereof is partially hydrolyzed and hydrolyzed in the presence of a catalyst with water having an equivalent amount of an alkoxy group in the reactant. A method for producing quartz glass, comprising using a silicate-based sol obtained by condensation. 2. The method for producing quartz glass according to claim 1, wherein the catalyst is an organic alkali. 3. The method for producing quartz glass according to claim 1, wherein the curing agent is an organic alkali or ammonia. 4. The method for producing silica glass according to claim 1, wherein the silica powder is an amorphous silica powder produced by a sol-gel method using water glass or an alkyl silicate as a raw material. 5. The silica powder has an average particle size of 1 to 100 μm.
The method for producing quartz glass according to claim 1, wherein the value is within the range of m. 6. The method for producing quartz glass according to claim 1, wherein the mold is hermetically sealed when the silica powder slurry is injected into the mold and cured. 7. The silica bulk body is immersed in water or a partial condensate of alkyl silicate before drying the silica bulk body obtained by releasing the mold from the mold.
7. The method for producing quartz glass according to any one of 6.