JPH02302332A - Production of platy silica glass - Google Patents

Abstract

PURPOSE:To obtain high-density platy silica glass capable of avoiding cracking, warping and bending in drying by hydrolyzing a silicic acid ester in the presence of a basic catalyst, separating the resultant silica particles from a liquid, providing a silica cake, then drying and heat-treating the formed cake. CONSTITUTION:A silicic acid ester, such as tetramethoxysilane, is mixed with water and a water-soluble organic solvent, such as methanol, in the presence of a basic catalyst and hydrolyzed. NH3 and an organic substance, such as amines, are preferred as the abovementioned basic catalyst. Spherical silica particles, formed by the hydrolysis and having 0.03 to 5mum particle diameter are then naturally settled, filtered or centrifuged and separated from a liquid to afford a silica cake, which is then sufficiently dried, then heat-treated up to 1150 to 1500 deg.C in an He atmosphere or under reduced pressure and transparentized. Thereby, the objective platy silica glass is obtained.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a method for manufacturing flat silica glass.

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

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

(2) Sol-gel method: This method involves hydrolyzing silicon alkoxide or suspending fine silica powder in a liquid to obtain a sol, gelling it, drying it, and removing impurities. process, and a nonporous process of heating to make glass.

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

In the ingot method, it is difficult to manufacture extremely thin plates, and the yield is low because the cutting edges are large.

In the sol-gel method, the gel tends to crack during the drying process, and thin plates tend to warp. Furthermore, even in the non-porous process, cracks, warping, and bubbles are likely to occur. Moreover, it requires a very long manufacturing time.

For this reason, there has been a need to develop an efficient method for producing flat silica glass.

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

An object of the present invention is to provide a method for manufacturing high-density flat silica glass that can avoid bending.

[Means for Solving the Problems] The present invention involves mixing and hydrolyzing a silicate ester with water and a solvent in the presence of a basic catalyst to produce silica particles;
The method for producing flat silica glass is characterized by separating the obtained silica particles from a liquid to obtain a silica cake, and further drying and heat-treating the obtained silica cake.

In the present invention, a binder may be added during hydrolysis of the silicate ester, or a binder may be added to the liquid containing the silica particles after hydrolysis. Here, the binder used is not particularly limited as long as it is a substance that dissolves in water or the organic solvent used to increase the bonding strength of particles and increase reversibility, but polyvinyl alcohol (hereinafter referred to as PvA) or polyvinyl butylade (hereinafter referred to as PVB) is used. Organic compounds such as (called ) are preferred. The amount of binder added varies depending on the type of binder, but it is 0.01% or more, preferably 0.1% or more by weight of the hydrolyzed liquid, and the upper limit is the amount of melon that dissolves in the hydrolyzed liquid. .

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 catalyst according to the present invention is not particularly limited, but in order to obtain high purity silica, it is preferable to use organic substances such as ammonia and amines.

The organic solvent according to the present invention is not particularly limited as long as it is soluble in water, but one or more types of lower alcohols having 4 or less carbon atoms such as methanol, ethanol, n-propanol, and 1-propanol It is preferable to use

[Effect] The operation of the present invention will be explained.

(1) First, silicate ester is mixed with water and an organic solvent in the presence of a basic catalyst and hydrolyzed to produce spherical silica particles. In this reaction, spherical silica (S+02) particles are obtained which are perfectly spherical and have a very uniform particle size.

The particle size is 0.03-5 μm, preferably 0.05-1.
Spherical particles of 5 μm are preferable. If the particle size is smaller than 0.03 μm, the obtained silica glass will contain many bubbles, and if the particle size is larger than 5 μm, cracks will easily occur during production and it will be difficult to obtain a transparent body. Particles can be used alone or in pairs.
A mixture of more than one type of particles with different particle sizes is used.

Note that the hydrolyzed solution containing silica particles may be concentrated if necessary.

(2) Next, the liquid is allowed to stand still to allow the silica particles to settle naturally, or is filtered or centrifuged to separate the silica particles from the liquid. In the case of natural sedimentation, the standing time varies depending on the particle size of the silica particles, the degree of concentration of the liquid, etc., but sedimentation ends when the liquid part becomes transparent and the boundary between solid and liquid becomes clear. However, if the standing time is too short, it is difficult to obtain a high-density silica cake. Further, in the case of filtration, it is preferable to select the opening diameter of the filter depending on the particle size of the obtained particles.

(2) Next, the obtained silica cake is dried, and after being thoroughly dried, it is heat-treated to 1150 to 1500°C to make it transparent. Here, the heat treatment temperature varies depending on the particle size of the silica particles used, but if it is less than 1150°C, it is difficult to obtain a transparent body. The heat treatment atmosphere is not particularly limited, but in order to obtain high-purity silica glass, heat treatment is performed in a He atmosphere or under reduced pressure, or after pretreatment is performed at 600 to 1000°C in an atmosphere containing 6g2.

It is preferable to perform the heat treatment in a He atmosphere or under reduced pressure.

By obtaining the above process, cracking during drying can be avoided.

It is possible to obtain a high-density flat silica glass that can avoid warping.

In addition, in the above step, by adding a binder to the hydrolysis solution containing silica particles, or by adding a binder in advance to the reaction solution when hydrolyzing the silicate ester, and hydrolyzing the silicate ester. , the above effects can be further improved.

Examples of the present invention will be described below.

[Example 1] First, 150 ml of ethanol was added to a glass reaction container equipped with a stirrer.
mg, ammonia water (20 weight 96) 40ml
was added and mixed to obtain a reaction solution. Also, ethanol 1
00mΩ and tetraethoxysilane (St(OC2H5)
4. 25 mg of Toshiba Silicone Co., Ltd. (manufactured by Toshiba Silicone Co., Ltd.) were mixed to prepare a raw material solution. Next, when the raw material solution was added to the reaction solution adjusted to 20° C., monodisperse silica particles with a particle size of 0.48 μm were obtained. Subsequently, this solution was transferred to a polypropylene container (φ30), sealed and allowed to stand, whereby the silica particles precipitated and a silica cake was obtained. Next, the silica cake obtained by separating this liquid was
℃.

It was dried at 60°C and 200°C for 1 hour each. After this,
When this was heat-treated to 1300℃ under reduced pressure, the diameter was 25.
A plate-like silica glass having a thickness of 5 mm and a thickness of 5 cm was obtained.

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 (solvent) and aqueous ammonia (catalyst) to obtain monodispersed silica particles of a predetermined particle size. After forming the mixed solution, the silica particles are allowed to settle to form a silica cake, which is then subjected to a drying and heat treatment process, thereby increasing the bonding strength and drying without passing through the sol and gel states. It is possible to obtain flat silica glass that can avoid cracking, 2 warping, and 1 bending.

[Example 2] A hydrolyzed solution obtained in the same manner as in Example 1 was heated to 0.3 μm.
Filtered under reduced pressure with a membrane filter of 30ffl in diameter.
A silica cake of No. 111 was obtained. When the obtained silica cake was heat treated in the same manner as in Example 1, it had a diameter of 25) and a thickness of 50
A 1I11 plate-like silica glass was obtained.

[Example 3] The solution obtained in the same manner as in Example 1 was divided into 5 equal parts, and 500
Centrifugation was performed at 0 rpm for 30 minutes. When the obtained silica cake was heat treated in the same manner as in Example 1, it had a diameter of 25 m.
A tabular silica glass of mSIfsII was obtained.

[Example 4] First, 150 ml of ethanol was added to a glass reaction container equipped with a stirrer.
mg and 40 mg of aqueous ammonia (20% by weight) were added and mixed to prepare a reaction solution. Also, ethanol 100mΩ
and 25 mg of tetraethoxysilane were mixed to prepare a raw material solution. Furthermore, another set of reaction solutions and raw material solutions with the same composition as these were prepared.

Next, one of the reaction solutions was adjusted to 10° C. and the raw material solution was added to obtain monodispersed silica particles with a particle size of 0.5 μm (solution A). Further, when the other reaction solution was adjusted to 30° C. and the raw material solution was added, monodispersed silica particles with a particle size of 0.3 μm were obtained (solution B). Next, both solutions A and B were combined and filtered under reduced pressure using a 0.2 μm membrane filter. When the obtained silica cake was heat-treated in the same manner as in Example 1, it had a diameter of 2511 and a thickness of 1OIII.
A flat silica glass of I was obtained.

[Example 5] First, 15% of ethanol was added to a glass reaction vessel equipped with a stirrer.
0 iΩ, aqueous ammonia (20% by weight) 40 mJ) was added and mixed to prepare a reaction solution. Also ethanol 100mΩ
and 25 mg of tetraethoxysilane were mixed to prepare a raw material solution. Next, the raw material solution was added dropwise to the reaction solution adjusted to 20° C. with stirring to synthesize monodisperse silica particles.

Next, PVBl and Og were mixed with this hydrolyzed solution and stirred to dissolve PVB.

Thereafter, this was transferred to a polypropylene container (Φ30 mm), tightly sealed, and allowed to stand at room temperature for 5 days. After standing still, solid (
The silica cake) and the liquid were separated, and the obtained silica cake was dried at 30°C and 200°C for one day each. When this was heated to 1300° C., a flat silica glass having a thickness of 31Il11 was obtained.

According to the above Example 5, since PVB as a binder is added to the hydrolyzed solution containing monodispersed silica particles, the bonding strength and plasticity are further increased compared to Example 1, and cracks, warping, and bending during drying are reduced. It is possible to obtain a flat silica glass that can be avoided.

[Example 6] First, 150 ml of ethanol was added to a glass reaction container equipped with a stirrer.
ml and 40 ml of aqueous ammonia (20% by weight) were added and mixed to prepare a reaction solution. Also, ethanol 100
mg and 25 m fl of tetraethoxysilane,
A raw material solution was prepared. Furthermore, another set of reaction solutions and raw material solutions with the same composition as these were prepared.

Next, one of the reaction solutions was adjusted to 10°C, and the raw material solution was added dropwise to synthesize monodispersed silica particles with a particle size of 0.5 μm (
Hydrolyzate A). Further, the other reaction solution was adjusted to 30° C., and the raw material solution was added dropwise to synthesize monodispersed silica particles with a particle size of 0.3 μm (hydrolysis solution B). Next, the above A
After mixing both liquids B and B, 2.0 g of PVB was added and stirred to dissolve. After this, this is placed in a polypropylene container (Φ3
After the solid was separated from the liquid and heat treated in the same manner as in Example 5, a flat silica glass having a thickness of 3 cm was obtained.

According to Example 6, PVB is added as a binder to the hydrolysis solutions A and B containing monodispersed silica particles after hydrolysis, so that the same effects as in Example 5 can be obtained.

[Example 7] First, add 15 liters of ethanol to a glass reaction vessel equipped with a stirrer. and PVBl. Og was added and mixed to obtain a reaction solution.

Also, 100 mg of ethanol and 2 ml of tetraethoxysilane
5 mg were mixed to prepare a raw material solution. Next, the raw material solution was added dropwise to the reaction solution adjusted to 20° C. with stirring to synthesize monodisperse silica particles. Next, the hydrolyzed solution containing the binder was transferred to a polypropylene container (φ30 mm), sealed and allowed to stand at room temperature for 5 days. After standing still, the solid (silica cake) and liquid were separated and heat treated in the same manner as in Example 5 to obtain a flat silica glass with a thickness of 3 mm.

In the above example, a case was described in which tetraethoxysilane was used as the silicate ester, but the invention is not limited to this, and lower alcohols having 4 or less carbon atoms such as tetramethoxy described in the column of [Means] mentioned above can also be used. Esters such as may also be used.

In the above embodiment, a case was described in which ammonia was used as the basic catalyst, but the present invention is not limited to this, and organic substances such as amines described in the section [Means] described above 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, according to the present invention, flat silica glass is produced which can increase bonding strength and plasticity and avoid cracking, warping, and bending during drying without passing through the sol and gel states. can provide a manufacturing method.

Claims (2)

[Claims] (1) After mixing silicate ester with water and a solvent in the presence of a basic catalyst and hydrolyzing it to produce silica particles, the obtained silica particles are separated from the liquid to obtain a silica cake, and further A method for producing flat silica glass, which comprises drying and heat-treating a silica cake. (2) The method for producing flat silica glass according to claim 1, characterized in that a binder is added during hydrolysis of the silicate ester, or a binder is added to the liquid containing the silica particles after hydrolysis.