JPH03187933A - Production of silica glass - Google Patents

Abstract

PURPOSE:To obtain a silica glass having improved bonding strength and plasticity by adding an organic binder to a slurry of spherical silica produced by the reaction of a silicic acid ester in a specific reaction solution, forming the mixture and subjecting the formed product to drying, degreasing and heating. CONSTITUTION:A slurry of spherical silica having particle diameter of 0.03-5mum is produced by mixing and reacting (A) a silicic acid ester (e.g. tetramethroxysilane) with (B) a reaction solution having a concentration of 0.001-5mol/l and containing 1.0-7.5mol/l of a base (e.g. ammonia), 1.0-30mol/l of water and an organic solvent (e.g. methanol). The slurry is concentrated to 1-95wt.% concentration and the viscosity of the slurry is adjusted to 15-500 poise by the addition of a organic binder (e.g. methylcellulose). The slurry is formed, dried by heating at 50-200 deg.C, degreased by heating at 400-800 deg.C and finally heated at 1150-1600 deg.C to obtain a transparent glass.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing plate-shaped, rod-shaped or tubular silica glass.

[Prior Art] Conventionally, the following method is known as a method for producing silica glass.

Ingot cutting method: This method is obtained by cutting an ingot produced by an oxyhydrogen melting method, a gas phase method, or the like.

Sol-gel method: This method consists of the steps of hydrolyzing silicon alkoxide or suspending fine silica powder in a liquid to obtain a sol, turning this into a gel, drying, and fixation to remove impurities. and a non-porous process of heating to make glass.

[Problems to be Solved by the Invention] However, the prior art has the following problems.

In the ingot method, it was difficult to manufacture ultra-thin plates, and the yield was poor due to the large cutting margin.

In the sol-gel method, the gel tends to crack during the drying process, making it difficult to scale up. In addition, even in the non-porous process, cracks, warpage,
Bubbles were likely to occur. Furthermore, it took a long time to manufacture.

The present invention was made in view of the above circumstances, and it increases bonding strength and n1 plasticity, and reduces cracking and warping during drying.

It is an object of the present invention to provide a method for manufacturing silica glass in the form of a flat plate, a rod, or a tube without bubbles that can avoid bending.

[Means for Solving the Problems] The present invention in Section 1 includes a step of reacting a silicate ester in a reaction solution consisting of a basic aqueous solution and an organic solvent to produce a spherical silica slurry, and a step of reacting a silicate ester in a reaction solution consisting of a basic aqueous solution and an organic solvent, and adjusting the silica concentration in this slurry. A method for producing silica glass comprising the steps of adjusting the viscosity of the slurry by adding an organic binder after adjusting the slurry, molding the slurry, and heating after drying and degreasing. .

The invention of Section 2 of the present application includes a step of reacting a silicate ester in a reaction solution consisting of a basic aqueous solution and an organic solvent to produce a spherical silica slurry, a step of adjusting the silica concentration in this slurry, and a step of adding an organic binder. This method of producing silica glass is characterized by comprising a step of kneading the slurry while deaerating it and then molding it, and a step of heating it after drying and degreasing.

The silicic acid ester according to the present invention is not particularly limited, but it is preferable to use an ester such as a lower alcohol having 4 or less carbon atoms, such as tetramethoxysilane, tetraethoxysilane, tetraprophotoxysilane, and tetraisopropoxysilane.

The basic aqueous solution according to the present invention is not particularly limited, but in order to obtain high purity silica, ammonia, ammonium salt,
It is preferable to use organic substances such as amines.

The organic solvent according to the present invention is not particularly limited as long as it dissolves the silicate ester and the basic aqueous solution, but alcohols such as methanol, ethanol, isopropanol, butanol, and ketones such as acetone are preferable. One type or two or more types of these may be used. Since the silicate ester and the basic aqueous solution do not mix directly, the six solvents are used to dilute the two for a mixed reaction.

The organic binder according to the present invention is not particularly limited, but for example, polyvinyl butyrald (PVB).

Methylcellulose and the like are suitable. Furthermore, a plasticizer such as dibutyl phthalate may be added together with the organic binder.

[Effect] First, the operation of the invention of Section 1 of the present application will be explained.

(1) First, a silicate ester is reacted in a reaction solution consisting of a basic aqueous solution and an organic solvent to produce a spherical silica slurry (particle production step). As a result, silica (810□) particles that are perfectly spherical and have a uniform particle size are obtained. Particle size is 0.03-5 μm, preferably 0.05-1.5
μm spherical particles are preferable. When the particle size is smaller than 0.03 μm, the obtained silica glass contains many bubbles, and the particle size is less than 5 μm.
If it is larger than μm, cracks are likely to occur during manufacturing and it is also difficult to obtain a transparent body. The particles may be used alone or in combination of two or more types of particles with different particle sizes.

Note that the hydrolyzed solution containing silica particles may be concentrated if necessary. The reaction solution includes a base and water.

It consists of an organic solvent, and by adding a silicate ester to it, a spherical silica slurry is produced.

Here, the base and water concentrations in the reaction solution are each 1.0 to 7.
．． 5 mol/I, and a range of 1.0 to 80 mol/I is suitable. Moreover, the silicate ester may be added as it is, but it can be added as a solvent to o,oot~5sol/j! It is best to dilute it to a certain extent. Furthermore, since water is consumed in the reaction, water may be added simultaneously with the addition of the silicate ester.

■Next, after adjusting the silica concentration in the slurry, an organic binder is added to the slurry to adjust the viscosity (ta degree,
viscosity adjustment process). It should be noted that the concentration of the spherical silica slurry obtained in the above (2) varies depending on the composition at the time of synthesis, but is 0.
Since it is about 1 to 5 wt%, the concentration is adjusted. Here, the concentration varies depending on the target thickness of the thin plate, but in the case of a self-supporting thin plate, it is 1 to 95v[%, preferably 3
Adjust to 0-g5vL%. The concentration adjustment method is not particularly limited, but centrifugal concentration, vacuum separation, ultrafiltration, and the like are suitable. Also, by adding an organic binder, the viscosity can be increased from 15 to 500 pols, preferably from 30 to 150 pols.
Adjust to ois.

(2) Next, the slurry with adjusted silica concentration and viscosity is molded into, for example, a thin plate (molding process).

(2) Next, the molded body is dried, degreased, and then heated (drying, degreasing, and heating step). Here, drying is performed to remove solvent, water, etc. from the molded product. The drying temperature varies depending on the solvent, but is generally about 50 to 200°C.

Degreasing is performed to remove organic binders.
The temperature range is approximately 400-800°C. Dry in step ① above.

Transparent silica glass is obtained by heating after degreasing. Here, the transparency temperature varies slightly depending on the particle size of the silica, but is approximately 1150 to 1600°C.

Furthermore, a transparent body can be obtained without particularly controlling the atmosphere.

However, (a) under reduced pressure, or (b) He, or (c) H2, or (d) CN at 600 to 1000°C.
After pretreatment in an atmosphere containing 2, the pressure is reduced or He
-0□, He atmosphere ((If the 02 treatment is performed after the 12 treatment, the Cj!2 concentration can be reduced). When such an atmosphere is used, silica glass with less impurities such as alkali metals and OH can be obtained.

Next, the operation of the second invention of the present application will be explained.

(2) Particle generation step: This step is similar to that of the first invention of the present application.

(2) Slurry adjustment step: In this second step, the concentration of the spherical silica slurry obtained in (1) above is about 0.1 to 5 vt%, although it varies depending on the composition at the time of synthesis, so the concentration is adjusted. The concentration here varies depending on the target thickness of the thin plate, but in the case of freestanding thin plates or pipes, it is 1 to 90vt.
%, preferably 70 to 9 ovt%. The density adjustment method is as described in the first invention of the present application.

■Forming process: In this process, the slurry to which an organic binder has been added is kneaded while degassing under reduced pressure.
Alternatively, the molded product is molded into a rod shape or a tube shape. ①Drying, degreasing, and heating process; Here, drying is performed to remove solvent, water, etc. from the molded product. The drying temperature is approximately room temperature to 50°C. The temperature range and atmosphere for degreasing are as follows:
This is similar to the described first invention of the present application.

Examples of the present invention will be described below.

[Example 1] First, 15% of ethanol was added to a glass reaction vessel equipped with a stirrer.
00mj! , 200 mjJ of 29% aqueous ammonia was added and mixed to obtain a reaction solution. Also, ethanol 100
0m 41 and tetraethoxysilane (Sl(OC2H5
) a, Toshiba Silicone Co., Ltd. (manufactured) 250m, and Q were mixed to prepare a raw material solution. Next, the raw material solution was added to the reaction solution adjusted to 20° C. and stirred for 8 hours to obtain a spherical silica slurry containing monodispersed silica particles with a particle size of 0.4 μm.

Subsequently, this slurry was concentrated five times using a vacuum evaporator. This concentrated slurry is then injected with PVB.
(Organic binder) 4 parts by weight and dibutyl phthalate (
2 parts by weight of plasticizer) was added to reduce the viscosity of the slurry to I
Adjusted to 02 pots. Subsequently, this slurry was stretched into a film and formed into a thin plate with a thickness of 0.31 mm using a device 4 consisting of a support 2 supporting the molded body 1 and a doctor 3 as shown in FIG. 5 is slurry). Furthermore, this thin plate was dried at 50°C,
Degreased at 600℃, 5%C11295%H at 1000℃
After the treatment in an atmosphere of 300 mL, the glass was heated to 1250° C. under a reduced pressure of 0, t torr to obtain a bubble-free plate-like silica glass with a thickness of 0.2 ms.

According to Example 1 above, a raw material solution consisting of ethanol and tetraethoxysilane (silicate ester) is added to a reaction solution consisting of ethanol (organic solvent) and aqueous ammonia (basic aqueous solution) to obtain particles of a predetermined particle size. After forming a slurry containing dispersed silica particles and adjusting the concentration and viscosity of the silica in this slurry, drying, degreasing, and heating processes are performed.Therefore, there are no bubbles and the bonding strength and plasticity are increased. It is possible to obtain high-density 0 degree silica glass that can avoid cracking, warping, and bending.

[Example 2] First, the same reaction solution and raw material solution as in Example 1 were prepared. Next, the raw material solution was added to the reaction solution adjusted to 20° C. and stirred for 8 hours to obtain a spherical silica slurry containing monodispersed silica particles with a particle size of 0.7 μm. Next, this slurry was evaporated using a vacuum evaporator.
Concentrated twice. Then, PVB5i was added to this concentrated slurry.
and 2 parts by weight of dibutyl phthalate were added to adjust the viscosity of the slurry to I x 10' pols. Subsequently, this slurry was stretched into a film using the apparatus 4 shown in FIG. 1 and formed into a thin plate having a thickness of 0.5-1.

Furthermore, this thin plate was dried at 50°C, degreased at 600°C,
After processing at 1000° C. in a 5% CJ295% He atmosphere, the sample was heated to 1250° C. under a reduced pressure atmosphere of o, t torr to obtain a bubble-free plate-like silica glass with a thickness of 0.3 mm.

[Example 3] First, in a glass reaction vessel equipped with a stirrer, 500 mN of ethanol, 500 ml of isopropanol,
500 m of n-butanol and 200 m of 17 and 20% ammonia water were added and mixed to prepare a reaction solution. Further, 400 ml of ethanol, 300 mD of isopropanol, 300 mN of n-butatol, and 250 mB of the tetraethoxysilane were mixed to prepare a raw material solution. Next, the raw material solution was added to the reaction solution adjusted to 20° C. and stirred for 8 hours to obtain a slurry containing +1 dispersed silica particles with a particle size of 0.5 μm. This slurry was then concentrated five times by ultrafiltration. Next, PVB (Q machine binder) is added to this concentrated slurry.
5 parts by weight and 2 parts by weight of dibutyl phthalate (plasticizer) were added to adjust the viscosity of the slurry to I x In2pots. Subsequently, this slurry is transferred to the apparatus 4 shown in FIG.
was used to stretch it into a film and form it into a thin plate with a thickness of 0.3 mm. Furthermore, this thin plate was dried at 50°C, and
After degreasing at 00°C and processing at 1000°C in a 5% C#295% He atmosphere, 0. When heated to 1250°C in a reduced pressure atmosphere of 1 torr, a bubble-free plate-shaped silica glass with a thickness of 0.31 mm was obtained.

[Example 4] First, in the same manner as in Example 1, a reaction solution and a raw material solution were prepared, and then diffused at a predetermined temperature for 1 hour to obtain a spherical silica slurry containing monodispersed silica particles with a particle size of 0.4 μm. . Next, this slurry was concentrated 70 times using a vacuum evaporator. Subsequently, water IBg was added to this slurry,
Further, 8 g of a methylcellulose binder (trade name: Selander, manufactured by Yuken Kogyo Co., Ltd.) was added and kneaded under reduced pressure.

Next, this slurry was extruded and molded into a thin plate having a thickness of 0.8 gm. Furthermore, this thin plate was dried at 50°C and heated to 40°C.
After degreasing at 0°C, processing at 800°C in a 5%CNz95%He atmosphere, and heating to 1250°C in a reduced pressure atmosphere of 0.1 torr, a bubble-free plate-like silica glass with a thickness of 0.6I was formed. Obtained.

According to Example 4, a predetermined reaction solution and a raw material solution are added to form a slurry containing monodispersed silica particles of a predetermined particle size, the concentration of silica in this slurry is adjusted, and the slurry is further molded. After drying, degreasing, and heating, the high-density plate-shaped silica glass is produced without bubbles, increasing bonding strength and plasticity, and avoiding cracking, warping, and bending during drying. Obtainable.

[Example 5] First, 150 ml of ethanol was added to a glass reaction container equipped with a stirrer.
0mj! , 300ml of 29% aqueous ammonia was added and mixed to obtain a reaction solution. Thereafter, in the same manner as in Example 4, a bubble-free plate-shaped silica glass having a thickness of 0.6 cm was obtained.

[Example 6] In Example 4, the extruded tube with an outer diameter of 15 aug and an inner diameter of 12-1 was also used.
A bubble-free plate-like silica glass of 1- was obtained.

[Example 7] In Example 4, 5% CfI295% He at 800°C
After heat treatment in an atmosphere, bubble-free silica glass was obtained when heated to 1250° C. even in a reduced pressure atmosphere of 0.3 LOrr.

In addition, although the above-mentioned example described the case where 4 tetraethoxy was used as the silicate ester, it is not limited to this. esters may also be used.

In the above example, the case where aqueous ammonia was used as the basic aqueous solution was described, but the invention is not limited to this.
An organic substance such as ammonium salt amine described in the section ``Means'' may also be used.

In the above example, the case where ethanol was used as the organic solvent was described, but the method is not limited to this.
Methanol, n-propertool, etc. mentioned in the section above may also be used.

[Effects of the Invention] As detailed above, the method of the present invention significantly reduces the generation of bubbles, thereby increasing the bonding strength and plasticity, and forming a high-density flat plate that can avoid cracking, warping, and bending during drying. , rod-shaped, and ring-shaped silica glass can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a slurry stretching device 5 according to the present invention. 1... Molded body, 2... Support body, 3... Doctor slurry

Claims (2)

[Claims] (1) A step of reacting a silicate ester in a reaction solution consisting of a basic aqueous solution and an organic solvent to produce a spherical silica slurry, and after adjusting the silica concentration in this slurry, adding an organic binder to adjust the viscosity of the slurry. A method for producing silica glass, comprising a step of adjusting, a step of molding the slurry, and a step of heating after drying and degreasing. (2) A step of reacting a silicate ester in a reaction solution consisting of a basic aqueous solution and an organic solvent to produce a spherical silica slurry, a step of adjusting the silica concentration in this slurry, and a step of adding an organic binder to the slurry. A method for producing silica glass, comprising the steps of kneading and molding while degreasing, and heating after drying and degreasing.