JPH01270530A - Production of formed glass body - Google Patents

Abstract

PURPOSE:To reduce alkaline metal content, improve purity and simultaneously contrive increase in density and reduction in cost by pulverizing a specific pulverizing raw material silica in the presence of a liquid dispersion medium, forming and drying the resultant fine particulate silica slurry and calcining the resultant formed product. CONSTITUTION:An aqueous solution prepared by dissolving an alkaline silicate expressed by the formula M2O.nSiO2 (M is alkaline metal element; n is 0.5-5) so as to provide >=20wt.% concentration of SiO2 is reacted with an acid, such as sulfuric acid or nitric acid, to afford silica, which is then purified to provide a pulverizing raw material silica having 20mu-1mm average particle diameter, preferably >=5 ppm alkaline metal content and 20-1000m<2>/g specific surface area (measured by the BET method). The resultant silica is subsequently pulverized in the presence of a liquid dispersion medium consisting of water and/or water-soluble liquid organic compound (e.g., methanol) with a ball mill, etc. The obtained fine particulate silica slurry with <=10 ppm alkaline metal content and <20mu average particle diameter is cast into a mold, formed, dried, then heated to 800-1800 deg.C at 300-600 deg.C/hr heating rate, kept at the temperature for 0-24hr, calcined and, as necessary, heat-treated at 1800-2000 deg.C for several sec-1min.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a glass molded body, particularly a quartz glass molded body.

The method of the present invention can be applied to the production of transparent, translucent, opaque, or porous quartz glass molded bodies, or glass molded bodies such as tempered glass and doped glass.

[Conventional technology]

Traditionally, quartz glass has been made of silica stone, silica sand, crystal, etc.
It is manufactured by a method of melting at a high temperature of ~2000°C. However, it is difficult to manufacture quartz glass due to the high viscosity of the melt, and it is also difficult to directly manufacture a quartz glass molded body by melting these raw materials as they are.

A known method for manufacturing quartz glass molded bodies is to mix pulverized quartz glass with water, cast it, dry it, and fire it, but this method avoids contamination due to impurities during the pulverization process. First, it tends to crystallize during firing, and the bulk density of the cast fused silica obtained is only 80 to 85% of the theoretical value.

(Journal of the A+nerican
Ceramic 5ocity, G6 No. 10
, 683-68B, (1983),) In addition, a sol-gel method using silicon alkoxide and ultrafine powdered silica obtained by a wet method using sodium silicate as the raw material has been proposed (Japanese Patent Application Laid-Open No. Commercially available silica obtained by a wet method using sodium silicate as a raw material contains an amount of sodium equivalent to several ppm to several thousand ppm based on the silica. However, when the gel is fired, it easily turns into Christohalai I, and in order to avoid the formation of countless cracks when the fired product is cooled to room temperature, it must be fired at a low temperature, which is a disadvantage in that sufficient sintering cannot be achieved. There is.

[Problem to be solved by the invention]

The present invention solves the problems of the prior art by firing fine particle silica obtained from an easily available alkali metal silicate aqueous solution as a raw material at a relatively low temperature, thereby reducing the content of alkali metals such as Na and other impurities. This method produces a glass molded body with high purity and high density, especially a quartz glass molded body.

An object of the present invention is to provide a method for producing a high-purity, high-density glass molded body, particularly a quartz glass molded body, using an aqueous alkali metal silicate solution as a raw material.

[Means to solve the problem]

The present inventors purified silica obtained by reacting 78 aqueous alkali metal silicate solutions with an acid, and obtained a product with a low content of alkali metals and other impurities, and an average particle size of 20 μm or more.] By using silica as a raw material and pulverizing it in a liquid dispersion medium,
Alkali metal content is 10 ppm or less, even 1 ppm
m or less, and the average particle size is less than 20 μm, and even 10
It is possible to obtain a high-purity particulate silica slurry with a small impurity content of μm or less at a high concentration without requiring a concentration operation, and furthermore, the obtained particulate silica slurry can be used as it is, or the slurry can be The present invention was completed based on the discovery that a glass molded article can be obtained by molding the dried fine silica powder obtained by drying the powder, drying it if necessary, and then firing it.

The details of the present invention will be explained below.

The raw material for crushing (hereinafter referred to as crushing material) used in the method of the present invention is an aqueous solution of alkasolinate used as a raw material for obtaining the shear force, and has the general formula: M20・n5io□ (where M is an alkali metal element, n is the number of moles in 5in2 and is 0
．． An aqueous solution of an alkali metal LJ phosphate represented by 5 to 5), a lithium salt, a potassium salt, a lithium J salt, etc. of phosphoric acid can be used.

The SiO□ concentration is 20% by weight or more, preferably 25% by weight or more.
It is desirable that the amount is at least % by weight. S+Oz! If the strength is low, the shearing force obtained by reacting with the acid may be dispersed in the form of a sol, or the reaction product may solidify into a soft shell, making it difficult to purify the shearing force. There is.

As the acid to be reacted with the aqueous alkali metal silicate solution, mineral acids such as sulfuric acid, nitric acid, and hydrochloric acid are used, with sulfuric acid and nitric acid being preferred.

In addition to mineral acids, organic acids can also be used.

The requirements for the pulverized silica used in the method of the present invention are:
The average wafer diameter is in the range of 2011 m or more to I mm or less.

It is desirable that the alkali metal content of the pulverized silica used in the method of the present invention is as low as possible, preferably 5 pp.
m or less, more preferably], ppm or less.

The crushed silica used in the method of the present invention has an average particle size of 2
The range is 0 to 300 μm, and the specific surface area is 20 to 10
00n? / g (based on the BIET method; hereinafter the same applies).

If the average particle size of the silica obtained by reacting an aqueous alkali metal silicate solution with an acid is 20 μm or more, it will not have any negative effect on the extraction of impurities in the purification process and can be washed and dehydrated. On the other hand, if the average particle size of silica is less than 20 μm, it becomes difficult to perform washing and dehydration treatments during the purification process.
Moreover, if it exceeds mm, it becomes difficult to extract impurities in the purification process, and it is difficult to obtain highly pure silica, which is not preferable.

of silica used as a grinding material in the method of the present invention.
It is desirable that the L surface area is 20 rW/g or more. Silica with a small specific surface area is difficult to crush, causes severe wear on the material of the crushing device, shortens its useful life, and increases the amount of impurities mixed into the resulting fine-particle silica slurry, which is not preferred.

The specific surface area of the silica used as the grinding material in the method of the present invention is preferably in the range of 20 to 1000 m/g,
Preferably, it is in the range of 30 to 00n (/g), and more preferably in the range of 200 to 900 rT (/g).

When using the ground silica of the method of the present invention, the specific surface area is 20
n? Compared to when using silica with a particle diameter of less than 1.5 g, the wear of the grinding device is less, and the amount of impurities mixed into the resulting fine particle silica slurry is smaller.

In addition, when pulverizing silica with a specific surface area of less than 20 rd/g, quartz glass, fused quartz,
Siliceous materials such as quartz, quartz or silica can also be used in the process of the invention as they are less abrasive.

As a method for obtaining silica as a granule used in the method of the present invention, a method is selected from among known methods that yields silica that meets the requirements as a granule in the method of the present invention. For example, the powder silica used in the method of the present invention can be obtained by the methods described in JP-A-62-3011 and JP-A-62-283809.

In an embodiment, the aqueous solution of the alkali metal silicate prepared in advance to have a viscosity of 2 to 500 poise, preferably 2 to 200 poise, is mixed with a pore size of 20 μm to 1 m.
m, preferably in the range of 30 to 300 μm, into a coagulation bath consisting of a water-soluble organic medium or an acid solution to coagulate it into a fibrous, columnar, or granular shape, and the resulting gel is poured into an acid-containing solution. It can be obtained by treating with water and then washing with water to extract and remove impurities.

By the above method, a hollow structure surrounded by walls with countless cracks on both the inside and outside surfaces is formed, and in addition to radioactive substances such as alkali metal elements, chlorine, and uranium,
High purity silica can be obtained in which the content of various impurities such as AI, Fe, and Ti is all 1 ppm or less.

The nozzle used is Al-=7 which has been gelled in a coagulation bath.
− In order to prevent problems such as potassium metal silicate adhering to the nozzle surface, the nozzle surface should be made of noble metal alloys such as gold-platinum alloy or tetrafluoroethylene resin, or the nozzle surface should be made of precious metals or tetrafluoroethylene resin. Preferably, the material is coated with a resin.

Examples of the water-soluble organic medium used in the coagulation bath include alcohols such as methanol and 5n-propanol, esters such as methyl acetate and ethyl acetate, ketones such as acetone and methyl ethyl ketone, dimethylacetamide and dimethylformamide. Amides, dimethyl sulfoxide and the like can be mentioned.

In addition, the acid used in the coagulation bath is sulfuric acid.

Among inorganic acids such as nitric acid and hydrochloric acid, it is preferable to use sulfuric acid and nitric acid, and as the acid solution, an aqueous solution of these acids is practically preferable. The acid concentration is in the range of 0.1 to 4N, preferably 0.5 to 3N, more preferably 1 to 2N.

The coagulation bath temperature is 25°C or higher, preferably 40-80°C.
It is best to keep it within the range of C.

To purify the silica obtained by reacting an aqueous alkali metal silicate solution with an acid, mineral acids such as sulfuric acid, nitric acid, and hydrochloric acid,
Known methods such as cleaning with an aqueous solution containing a substance selected from peroxides such as hydrogen peroxide and -1-rate agents can be used.

The average particle size J of crushed silica is measured using the sieve method.In addition, if the shape of the crushed silica is fibrous or columnar, and has a large deviation from a spherical shape, the particle diameter determined by an optical microscope is used. The arithmetic mean value of the diameter (minor diameter) was regarded as the "average particle diameter."

The "average particle size" of the silica particles obtained by the pulverization treatment was measured by a centrifugal sedimentation light transmission method.

In the method of the present invention, the powder is used for wet grinding.

Conventional grinding equipment can be used. For example, a transfer ball mill such as a bot mill, a tube mill, a conical ball mill, or a compartment mill, a vibrating ball mill, or a media stirring mill such as a tower type crusher or a stirred tank type mill is used. Preferably, a transfer ball mill or a vibrating ball mill is used. It will be done.

The material of the main part of the crushing device that comes into contact with the crushed material or the crushing media used as necessary may be alumina, zirconia, silicon carbide, silicon nitride, quartz glass, fused quartz, or crystal 1.
The material is appropriately selected from among silicic acid H materials such as silica or silica stone.

When obtaining the particulate silica slurry used in producing transparent quartz glass by the method of the present invention, the main parts of the crushing device and the crushing media are made of an amorphous silicic acid material such as fused silica glass 1-8. is suitable, and high-purity quartz glass is particularly preferred.

Calcining pulverized silica using a pulverizer made of a crystalline siliceous material is undesirable because crystallization of the silica is promoted.

The size of the grinding medium made of a rigid body such as a ball or Roso I used in the method of the present invention is 0.5-2 mm in diameter.
5 mm, preferably in the range from 1 to 10 mm, especially when the average particle size is 1.5 mm. // The grinding media used when trying to obtain ultrafine silica particles with a particle size of rn or less has a diameter of 1 to 5.
Preferably, it is in the range of mm.

In the method of the present invention, the pulverization treatment of pulverized silica is performed in the presence of a liquid dispersion medium, and an aqueous medium is preferably used as the liquid dispersion medium.

In addition, a water-soluble liquid organic compound can be used as the dispersion medium, and specific examples thereof include alcohols such as methanol and ethanol, volumado, dimethylformamide 1-. Examples include amides such as dimethylacetamide 1', and carbons such as acetone and nodyl ether carbon.

A mixture of water and a water-soluble organic compound can also be used as a dispersion medium, and the obtained fine particle silica slurry can be poured into a mold and molded, and when it is dried, cracking of the dried molded product can be prevented.

The pl+ of the grinding system when using an aqueous medium is preferably in the range of 2 to 11, preferably 2 to 5 or 7 to 11.

If the pH of the grinding system is less than 2, the acid content will increase, and
If it exceeds 11, the solubility of silica in the medium increases, which is not preferable. In the range Q of more than 5 and less than 7, silica pulverization progresses, but when the silica concentration exceeds 25% by weight, the obtained fine particle silica slurry becomes paste-like and has low fluidity, and the pulverization used Separation from the medium tends to be difficult.

In the case of a slurry having a silica concentration in the range of 25 to 50%, it is preferable to adjust the pl+ of the obtained slurry to a range of 7 to 11. The silica slurry prepared in this way has surprisingly good storage stability despite its high silica concentration, and the amount of precipitated silica is small. The rate of glue force settling after one month of standing was 10% or less of the weight of silica in the slurry.

Acids used for pH adjustment include sulfuric acid, hydrochloric acid, and phosphoric acid.

Inorganic acids such as boric acid are used. These have the effect of preventing the dry molded silica from cracking.

Further, as the alkali, amines such as ammonia and methylamine can be used.

Adjustment of pl+ is carried out before the first pulverization, but it can also be carried out during the pulverization process or after the pulverization process, if necessary.

The temperature during the crushing process is not limited to 4, but is usually 2
It is carried out in the range of 0 to 100°C. Using pressure-resistant equipment]
00°C or higher, even higher temperatures - e.g. 150-200°
It can also be done in the range of C.

The time required for crushing varies depending on the crushing column (1, 05 to 90 minutes).
It is in the range of 6 hours, preferably in the range of 0.2 hours to 24 hours.

According to the method of the present invention, the 5iO7 concentration is as high as 15 to 50% by weight, and the alkali metal content is 1Qppm or less, furthermore, 11"pm or less, by only wet pulverization without performing an a-condensation operation. Yes, average particle size is less than 20μIn,
Furthermore, it is possible to obtain a highly purified fine particle silica slurry with a small impurity content, which is 10 μm or less.

To obtain a glass molded body from the fine-particle silica slurry obtained in the above-mentioned pulverization process: A dry molded body obtained by molding the fine-particle silica slurry or the fine-particle silica powder obtained by drying the dirt by an appropriate method. to be fired.

Molding methods include pour molding and extrusion molding.

Examples include various methods such as push molding, tape casting such as calendar method and doctor blade method, press molding, and injection molding.

When using the fine particle silica slurry as it is, a casting method is preferred.

In the casting method, fine-particle silica slurry is poured into a mold and kept at a temperature of 10 to 100°C to solidify. Molding molds include polyethylene, polypropylene,
Various synthetic resins or synthetic rubbers such as polystyrene, fluororesin, phenolic resin, epoxy resin, silicone rubber, polyurethane, water-absorbing materials such as plaster, resin sintered bodies such as polyethylene and polypropylene, or resin sintered bodies containing aggregate, etc. A mold made of a porous material that is permeable to water or water vapor can be used.

The particulate silica slurry used for casting is degassed under reduced pressure before solidification. In addition, it is preferable to degas under reduced pressure in a state with a low viscosity before adjusting the pH, and then adjust the PL to a range of 15 to 7 and solidify it, since the dried molded product will not be easily cracked during the subsequent drying process. .

Regarding the particulate silica slurry used for casting, the particle size of the particulate silica is preferably greater than 1 μm and not more than 10 μm. If the particle size is 1 μm or less, cracks may occur when drying the molded product, while if the particle size exceeds 10 μm, high temperatures are required when firing the molded product.

When using a dry powder or granules of fine silica obtained by dehydrating and drying fine silica slurry by a method normally used, preferably a spray drying method, mold press molding, rubber press molding, isostatic press molding,
Hot press molding.

Molded by various press molding methods such as injection molding.

The pressure during molding is 10-5000 kg/afl,
Preferably it is in the range of 100 to 2000 kg/c+fl.

Furthermore, in the method of the present invention, silica powder can be further added to the fine-particle silica slurry to increase the SiO□ concentration before molding. For example, in extrusion molding, die molding, or doctor blade method, 5ro2f4
Molding is carried out as a slurry or paste with a content of 35% to 85%.

The fine-particle silica slurry-added silica powder for JJII used in the present invention is obtained by dry-pulverizing high-purity warp obtained by refining silica obtained by reacting an aqueous alkali metal silicate solution with an acid. Those having an average particle diameter of 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less are used.

In addition, prior to dry pulverization, after drying at a temperature of 50 to 300°C, preferably 100 to 200°C, the silica powder obtained by dry pulverization is added to a fine particle silica slurry and molded. This is preferable because cracks are less likely to occur when drying the molded product. In addition, after drying under the above conditions, 80
0~1800°C1 Preferably 1100~1800°C
It is preferable to add the sintered silica powder obtained by dry pulverization to the microparticle silica slurry after sintering in the range of 1,000 ml and then mold the resulting molded object, since the resulting molded object shrinks less when dried and fired.

In addition to the above-mentioned silica powder, silica powder or silica sol with few impurities produced by a known method can also be added to the fine-particle silica slurry.

In addition, in the present invention, the weight ratio per silica is 0,002 to 3%, preferably 0.01 to Flocculant in the range of 1% or 0.
By adding a binder in the range of 1 to 10%, preferably 0.2 to 3%, it is possible to avoid cracking of the molded body without reducing it.

As flocculants, tannic acid, ammonium chloride, ammonium fluoride, ammonium nitrate, ammonium sulfate,
Examples of binders include dextrin, casein, gelatin, polyvinyl alcohol, methyl cellulose, methyl ethyl cellulose, ammonium alginate, oleic acid, and wax emulsion.

In the present invention, a preferred embodiment of the drying treatment performed after pouring the particulate silica slurry into a mold is as follows.

The drying temperature is preferably in the range of 20 to 200°C, and preferably in the range of 30 to 90°C at the initial stage of drying.

When the molded article contains a large amount of water, it is preferable to adjust the drying rate in order to prevent the molded article from cracking during drying. By changing the opening and 1'X of the gas phase part of the container containing the molded body,
Alternatively, the drying speed can be adjusted by adjusting the temperature and humidity inside the dryer. The drying time varies depending on the size, thickness, moisture content, etc. of the molded body, and is from 3 minutes to 3 months.

Next, a preferred embodiment of the firing treatment of the obtained dry molded body is as follows.

The firing temperature is 800 to 1800°C, preferably 110°C.
It is in the range of 0 to 1800°C.

The required sintering temperature changes depending on the particle size and specific surface area of the silica, and the larger the average particle size of the silica particles, the higher the temperature required for sintering. When the average particle size of silica particles is about 1 μm, sintering progresses at 1000 to 1250°C, but when the average particle size is 10 μm or more, sintering progresses at 1400°C.
Temperatures above 10°C are required.

The temperature increase rate during firing is in the range of 30 to 600°C per hour, preferably 100 to 500°C.

The firing time may be short at high temperatures, but requires a long time at low temperatures. The time for maintaining a constant temperature during firing is in the range of 0 to 24 hours, preferably 0.1 to 5 hours.

In addition, if necessary, the glass molded body obtained by firing in the above-mentioned temperature range may be further subjected to a short-time treatment 5 of about several seconds to about 1 minute at a temperature exceeding 1800 ° C and about 2200 ° C. Defects such as microcrystals and bubbles can be removed.

The atmosphere in the furnace during firing may be in the presence of air, nitrogen, hydrogen, -.lium 1 argon, etc., and firing may also be performed under vacuum.

When manufacturing transparent glass or transparent quartz glass, it is preferable to fire the glass in a helium atmosphere.

Furthermore, a method of firing in a vacuum and then firing in an air atmosphere is also preferable.

〔Effect of the invention〕

By the method of the present invention, using an aqueous alkali metal silicate solution as a raw material, a fine particle silica slurry having a high purity with few impurities and an alkali metal content of 1Q ppm or less and an average particle size of 20 μm or less is obtained, and this is molded. After that, it is fired at a relatively low temperature to produce a low alkali, high purity and
A high-density quartz glass molded body can be manufactured.

Transparent, translucent, opaque, or porous quartz glass can be produced by appropriately changing the silica crushing conditions and firing conditions.

The method of the present invention J, the raw materials used are easily available, and
It has the advantage of being energy efficient and more economical than conventional methods.

〔Example〕

The method of the present invention will be specifically explained below using Examples and Comparative Examples.

Note that "1%" means "wt% J.

Example-1 Sodium phosphate #3 (equivalent to JIS K1408.3, hereafter) (SiOz: 28%, Na2O: 9%
) 20kg was heated to 5°C under reduced pressure, dehydrated and concentrated,
A processing stock solution containing 5in2: 30% and NazO: 9.8% was obtained. The viscosity of the wood solution was 41 voids at 20'C.

After filtering this stock solution, the pore size is reduced to 36 mm using an extruder.
Pass through a gold-platinum alloy nozzle with μmφ and 600 holes into a coagulation bath-2N sulfuric acid aqueous solution maintained at 50°C.
A transparent fibrous gel was obtained by extrusion at a speed of m/min.

Obtained fibrous gel (liquid content: 267%, wet basis) 1
0 kg was immersed in an acid treatment liquid-sulfuric acid 2N aqueous solution at 30°C, treated at 100°C for 1 hour without stirring, and deoxidized using a Nunche. After repeating the same process two more times, the obtained short fibrous silica was washed and filtered five times using 3ON ion-exchanged water, and then deoxidized and dehydrated using Nusoche to reduce the water content to 58%. Wet silica was obtained.

The average particle size of the obtained silica particles was 40 μm, the specific surface area was 800 po/g (by BET method), and 5 iOz (
The impurity content per dry weight basis is Na: 0.2p
p.m.

8l: 0.4ppm, Zr: 0. It was lppm.

65 g of the obtained wet silica was used as a granule, and 1.6 g of water and 4 ml of 0.1N hydrochloric acid aqueous solution were used as a dispersion medium in a quartz glass (Na content: 0.05 ppm) 5
200 g of mmφ balls were placed in a ball mill as a grinding medium, and pulverized at a rotational speed of 1100 rpm for 12 hours.

The ball mill is a transfer type and uses quartz glass (Na content.

0.05ppm) type bot (capacity 0.4N) was used.

The fine particle silica slurry obtained by the above pulverization treatment has an average particle size of 3 μm of silica particles in the slurry.
, S+C1z1 degree; 40%, pH: 3,
And the impurity content per Sin□ is Na: 0
．． 2ppm+Al: 0.4ppm, Zr: 0. l
It was ppm.

35 g of the obtained fine particle silica slurry was stirred with a magnetic cooler and heated under a pressure of 40 Torr.
Degassed for 0 minutes. 0.0% to the fine particle silica slurry after degassing.
3% aqueous ammonia was added to adjust the pH to 5.0. This was again degassed for 10 minutes under a pressure of 40 Torr.

The treated fine particle silica slurry is placed in a Teflon petri dish.
(inner diameter 80 mmφ), covered with a lid, and left standing in a thermostat at 50°C to solidify. After one day, the lid of the petri dish was replaced with a lid with holes with a porosity of 1%, and after drying in a thermostat at 50 °C for 6 days, the obtained disc-shaped silica molded body was placed in a dryer. , and dried at 150°C for 10 hours.

The obtained dry compact was placed in an electric furnace, heated to 1300°C at a rate of 200°C per hour in a helium atmosphere, maintained at this temperature for 1.5 hours, and heated to 1500°C over an additional hour. The temperature was raised to °C, maintained at this temperature for 1 hour, and then cooled.

The disc-shaped quartz glass molded body thus obtained (50
mmφX3mm) None of the five sheets had devitrification or air bubbles.
It was transparent. In addition, the bulk density of both is 2.2 g.
/cffl, and as a result of measurement by X-ray diffraction (hereinafter referred to as XRD), it was found to be amorphous.

Average particle size and specific surface area of the pulverized material; pulverization processing conditions (amounts of pulverized material and dispersion medium, p1 of the pulverization system).

Material of the main parts of the device, number of rotations per revolution and processing time); Obtained fine particle silica slurry (SiOzfi degree, average particle diameter of silica particles in the slurry and impurity content (vs. 5i);
h)) ; PL+ of the fine particle silica slurry after adjustment performed before solidification, firing conditions for the dry molded body (atmosphere, temperature, and holding time); Regarding the density and state of the obtained fired molded body, each example and comparison Table 1 shows the results of the example.
Shown below.

-23 Example-2゜About the same lot of wet silica used in Example-1,
Wet pulverization was carried out in the same manner as in Example 1, except that only water was used as the dispersion medium without adding an aqueous hydrochloric acid solution, and the resulting fine particle silica slurry was degassed and p II in the same manner as in Example 1. After gJil preparation (ammonium chloride is not generated in this example), pour molding and
Drying and firing were performed.

The disc-shaped quartz glass molded body thus obtained (50
All five pieces (mmφ×3mm) were transparent with no devitrification or bubbles. (Cracks were observed in two of the five molded bodies.) All of the obtained quartz glass molded bodies had a bulk density of 2.2.
g/cnt, and as a result of XR [l measurement, it was found to be amorphous.

Example-3゜The wet silica obtained in the same manner as in Example-1 was used as a pulverizer, and the wet pulverization treatment was carried out in the same manner as in Example-1, except that the treatment time was 24 hours as shown in Table-1. As shown in Table 1, a fine particle silica slurry containing 40% of silica particles having an average particle diameter of 1.1 μm was obtained.

Using the obtained fine particle silica slurry, deaeration and pH adjustment (3 → 5.5) were performed according to Example-1, and then
Cast molding and drying were performed.

The temperature of the obtained dried molded body was raised to 1200° C. at a rate of 200”C per hour in an electric furnace in an air atmosphere, maintained at this temperature for 1.5 hours, and then cooled.

The disc-shaped quartz glass molded body thus obtained (50
The five sheets (mmφX3mm') were translucent, but had a high density of 2.2 g/cJ, and as a result of XRD measurement, they were amorphous.

Example-4 The process was carried out in accordance with Example-1, except that a nozzle with a pore diameter of 200 μm was used as the nozzle of the extruder, and the moisture content was 54.
% wet silica was obtained.

The average particle diameter of the obtained silica particles was 220 μm, the specific surface area was 700 rf/g, and the impurity content per SiO□ (dry weight basis) was Na: 0.2 ppm + 8I: 0.5
ppm.

Zr: 0. 1020 g of the obtained wet silica was used as a grinding material, and with 155 g of water as a dispersion medium, alumina (Na content = O
622%) balls (5 mmφ) were placed in a ball mill as a grinding medium, and pulverized at a rotation speed of 60 rpm for 24 hours.

Made of alumina (Na content,
022%) Bot (volume: 7°C) was used.

The fine particle silica slurry obtained by the above pulverization treatment has an average particle size of silica particles in the slurry of 0.7 μm.
, Sin□ concentration 40%, ptl: 4, and impurity content per 5iO7 is Na:
1 ppm.

Eight I: 220ppm, Zr: 0. It was lppm.

Using the obtained particulate liquid slurry, deaeration and pH adjustment (4 → 6.0) were performed according to Example-1, and then
Cast molding and drying were performed.

The obtained dried molded body was heated to 1200''C at a rate of 200°C per hour in an air atmosphere with electricity at i, kept at that temperature for 15 hours, and then cooled.

The disc-shaped quartz glass molded body thus obtained (51
mmφx3mm) 5 sheets were translucent, but the bulk density was 2.
．． As a result of χRD measurement, it was found to be amorphous. (Cracks were observed in 2 of the 5 molded bodies.) Example 5 Regarding wet silica of the same lot as used in Example 4,
Wet pulverization was carried out according to Example 1 under the conditions shown in Table 1, and the resulting fine particle silica slurry was deaerated and PL+ adjusted in the same manner as in Example 1, followed by casting, drying, and Firing was performed.

The disc-shaped quartz glass molded body thus obtained (50
mmφx3mm) is transparent without devitrification or bubbles, and its bulk density is 2.2g/cr? As a result of XRD measurement, it was found to be amorphous.

Example 6 Example 1 was carried out under the conditions shown in Table 1, using the same Shino 1 wet silica as used in Example 4 as the crushing material, and setting the treatment time to 6 hours.
A wet pulverization treatment was performed according to 1, to obtain a fine particle silica slurry containing 40% of silica particles with an average particle size of 10 μm as shown in the table.

Using the obtained fine-particle silica slurry, deaeration and pH adjustment were performed in the same manner as in the actual measurement, followed by casting and drying.

The resulting dry compact was heated to 1500°C at a rate of 400°C per hour in an electric furnace in an air atmosphere, maintained at this temperature for 1 hour, and then cooled.

The disc-shaped quartz glass molded body thus obtained (50
mmφx3mm) was translucent with bubbles, but
The layer density was 2.2 g/cm, and as a result of χRD measurement, it was found to be amorphous.

Example 7 Wet pulverization was carried out in the same manner as in Example 6, except that the treatment time was 4 hours, and as shown in Table 1, the average particle size was 1.
A particulate silica slurry containing 40% of silica particles having a diameter of 5 μm was obtained.

Using the obtained fine particle silica slurry, deaeration and PL+ adjustment were performed in the same manner as in Example 1, followed by casting and drying.

The resulting dry compact was heated to 1400°C at a rate of 400°C per hour in an electric furnace in an air atmosphere, maintained at this temperature for 185 hours, and then cooled.

The disc-shaped quartz glass molded body thus obtained (51
mmφx3n+m) was white and opaque.

Its bulk density is 2.1g/cr? As a result of XRD measurement, it was found to be amorphous.

Example-8゜About the same lot of wet silica used in Example-4,
A wet pulverization treatment was carried out according to Example 1 under the conditions shown in Table 1 to obtain a fine particle silica slurry.

The fine particle silica slurry was heated at 150° C. for 10 hours, and the resulting dried product was lightly ground in an agate mortar to obtain a fine particle dry powder.

1 g of the obtained fine particle silica dry powder was placed in a mold press (inner diameter 1
The mixture was filled into a cylinder (3 mmφ) and pressed from both upper 1ζ directions at a pressure of 1000 kg/cM for 20 minutes to obtain a fine particle silica molded body.

The molded body is heated in an electric furnace under an air atmosphere at a rate of 40% per hour.
The temperature was raised to 1300°C at a rate of 0°C, maintained at this temperature for 3 hours, and then cooled.

The disc-shaped quartz glass molded body obtained in this way (],
OmmφX6mm) was white and opaque.

Its bulk density is 2.0 g/cJ, and XRD i'1t
As a result of determination, it was found to be amorphous.

Example-9゜Dry fine particle silica powder obtained in the same manner as Example-83.
3g in a mold press (inner diameter 40mmφ cylinder)
Fill with pressure 1000 kg/c from both top and bottom directions.
A fine particle silica molded body was obtained by pressing at f for 20 minutes.

(Two of the five press-formed bodies obtained by performing the same treatment five times had cracking.) The molded bodies were heated in an electric furnace under vacuum at a rate of 200°C per hour. The temperature was increased to 1400°C and held at this temperature for 1.5 hours, then heated at a rate of 200°C per hour under an argon atmosphere for 17 hours.
After increasing the temperature to 50 °C and maintaining this temperature for 0.5 hours,
Cooled.

The disc-shaped quartz glass molded body thus obtained (25
mmφ x 3 mm) was transparent without devitrification or bubbles, had a bulk density of 2.2 g/cffl, and was amorphous as a result of XRD measurement.

Example-10゜The dry fine particle silica powder obtained in the same manner as in Example-8 was
3.7 g of fine particle silica containing 1% polyvinyl alcohol per silica obtained by mixing with 10% polyvinyl alcohol 10% aqueous solution was pressed in the same manner as in Example 9 to obtain a fine particle silica molded body. I got it.

Five press molded bodies obtained by performing the same treatment five times had the following properties:
There were no cracks in any of them.

After heating and drying the molded body at 150°C for 10 hours, the temperature was raised to 950°C at a rate of 200°C per hour in an air atmosphere in an electric furnace and maintained at this temperature for 18 hours, and then, 14 at a rate of 200'C per hour as vacuum
The temperature was raised to 00''C and held at this temperature for 1.5 hours.

Then, the temperature was increased to 200°C per hour as an argon atmosphere.
The temperature was raised to 1750°C at a rate of 1,750°C, maintained at this temperature for 0.5 hour, and then cooled.

The disc-shaped quartz glass molded body thus obtained (25
The liver (φX 3 mm) was transparent without devitrification or bubbles, had a bulk density of 2.2 g/cJ, and was amorphous as a result of XRD measurement.

Comparative Example-1゜35g of wet silica of the same loft as used in Example-1 was placed in a quartz glass Petri dish (
(inner diameter 80 mmφ), dried according to Example-1, and then heated in an electric furnace under an air atmosphere at 20°C per hour.
The temperature was increased to 1200°C at a rate of 0°C, and 1.
After holding for 5 hours, it was cooled.

The fired product was granular and no molded product was obtained.

Comparative Example-2゜35g of wet silica from the same lot used in Example-4 was placed in a quartz glass Petri dish (
(inner diameter 80 mmφ), dried according to Example-1, and then heated in an electric furnace under an air atmosphere at 20°C per hour.
The temperature was increased to 1400°C at a rate of 0°C, and 1.
After holding for 5 hours, it was cooled.

The fired product was granular and no molded product was obtained.

Comparative Example 3 The same lot of wet silica as used in Example 4 was heated as it was at 150° C. for 10 hours without being pulverized to obtain dry silica.

1 g of the obtained dry silica was pressed in the same manner as in Example-8.

When the pressed body was taken out from the mold, it was brittle and cracked, and could not be fired, so that the desired molded body could not be obtained.

Claims (1)

[Claims] 1) Silica obtained by refining silica obtained by reacting an aqueous alkali metal silicate solution with an acid and having an average particle size in the range of 20 μm or more and 1 mm or less is used as a liquid dispersion medium. A glass molded article characterized in that a fine-particle silica slurry having an alkali metal content of 10 ppm or less and an average particle size of less than 20 μm obtained by pulverization in the presence of silica particles is molded, dried, and then fired. manufacturing method. 2) A method for manufacturing a glass molded body, which comprises drying the particulate silica slurry according to claim 1, molding the obtained particulate silica dry powder, and firing.