JP2022052497A - Granulated silica powder and production method of granulated silica powder - Google Patents

Abstract

To provide a granulated silica powder which has high purity and good flowability and from which a formed body having high uniformity with occurrence of bubbles suppressed therein can be obtained.SOLUTION: A granulated silica powder has: a D50 particle diameter (median diameter) of 75 μm or more and 200 μm or less; a repose angle of 20 degrees or more and 35 degrees or less; and a specific surface area of 0.3 m2/g or more and 10 m2/g or less. The granulated silica powder is a particle aggregate including 15% or more and 40% or less of a particle having a particle diameter of 10 μm or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to granulated silica powder suitable for manufacturing a semiconductor jig made of quartz glass and an optical fiber.

The Verneuil method and the plasma spraying method are known as a method for producing a quartz glass molded body. These are methods in which silica powder is passed through a high-temperature region of oxyhydrogen flame or plasma by a method such as dropping or spraying, and is attached to a substrate as a molten state and laminated to produce a quartz glass molded body. As the silica powder used here, natural quartz powder having a particle size of 100 μm to 200 μm or synthetic quartz powder derived from the sol-gel method is used.
For example, in Patent Document 1, a silica gel obtained by a sol-gel method is dried in a dryer and then further calcined to obtain a synthetic quartz powder capable of providing a quartz glass molded body in which impurities and foaming are suppressed. Has been proposed.

Patent No. 4391529

However, the conventionally used natural silica powders and synthetic silica powders having a particle size of 100 μm to 200 μm have a crushed particle shape and poor fluidity, and the particle surface is melted but the central part is insufficiently melted. There is a problem that unevenness of the melt viscosity in the inside is likely to occur, which causes non-uniformity of the molded body such as veins, and improvement is desired.

That is, the characteristics of the silica powder required by the Bernui method and the plasma spraying method are (I) appropriate fluidity (which can be quantitatively fed to a high temperature region), (II) easy melting, and (III) bubble-free. A molded body can be formed, and (IV) the uniformity of the molded body can be obtained. In short, there is a demand for silica powder that can obtain a highly uniform molded product having high purity, good fluidity, and suppressed generation of bubbles.
An object of the present invention is to provide a silica powder satisfying such a requirement.

The present inventors have made diligent studies under the above circumstances, and have found that a granulated silica powder produced by granulating silica fine particle powder having a specific particle size can solve the above-mentioned problems, and have found that the present invention can be solved. Completed. The present invention includes the following.

(1) Granulated silica having a D50 particle size (median diameter) of 75 μm or more and 200 μm or less, an angle of repose of 20 degrees or more and 35 degrees or less, and a specific surface area of 0.3 m ² / g or more and 10 m ² / g or less. It ’s a powder,
The granulated silica powder is an aggregated silica powder containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less.
(2) The granulated silica powder according to (1), wherein the silanol concentration is 200 ppm or less and the adsorbed water content is 1% or less.
(3) The granulated silica powder according to (1) or (2), wherein the Fe content is 1 ppm or less, the Al content is 0.1 ppm or less, and the Ti content is 0.01 ppm or less.
(4) The granulated silica powder according to any one of (1) to (3), which has an average pore diameter of 1 μm or more and 10 μm.
(5) A preparatory step for preparing raw material silica obtained by a sol-gel method containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less.
A method for producing granulated silica powder, which comprises a granulation step in which raw material silica is slurried, a binder is added, and spray granulation is performed, and a firing step in which the obtained granulated particles are calcined at 1000 ° C. or higher and 1300 ° C. or lower.
(6) The method for producing granulated silica powder according to (5), wherein in the granulation step, the medium used for slurrying is water and the binder is polyvinylpyrrolidone.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a granulated silica powder which can obtain a highly uniform molded body having high purity and good fluidity and suppressing the generation of bubbles.

It is a graph which shows the particle size distribution of the raw material silica powder used in an Example. It is a graph which shows the particle size distribution of the raw material silica powder used in an Example. It is a graph which shows the measurement result of the particle size of the granulated silica powder obtained in an Example. The SEM image of the granulated silica powder obtained in the Example is shown (drawing substitute photograph). It is a schematic diagram which shows the Verneuil method (oxyhydrogen flame melting method) apparatus used in an Example. It is an image of the ingot manufactured in the example (photograph substitute for drawing). The SEM image of the granulated silica powder obtained in the comparative example is shown (drawing substitute photograph).

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents. It can be modified in various ways within the scope of the gist.

In one embodiment of the present invention, the D50 particle size (median diameter) is 75 μm or more and 200 μm or less, the angle of repose is 20 degrees or more and 35 degrees or less, and the specific surface area is 0.3 m ² / g or more and 10 m ² / g or less. The granulated silica powder is a granulated silica powder which is an aggregated particle containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less.
Conventionally used natural silica powders and synthetic silica powders with a particle size of 100 μm to 200 μm have a crushed particle shape and poor fluidity, and the particle surface melts but the central part melts insufficiently. However, in the present embodiment, the above-mentioned problem can be solved by using a granulated silica powder having a specific property, which has a problem that unevenness of the melt viscosity is likely to occur.

By using the granulated silica powder, it is possible to produce spherical particles having good fluidity, and since the granulated particles are granulated from the fine particles, the melting unevenness is reduced when the particles are melted.

The granulated silica powder has a D50 particle size (median diameter) of 75 μm or more and 200 μm or less, preferably 100 μm or more, and preferably 150 μm or less. The median diameter is a particle diameter at which the cumulative frequency is 50%, and can be obtained by drawing from the particle size distribution curve as shown in FIG. 2 as an example of the calculation method.
By setting the D50 particle size of the granulated silica powder in the above range, the fluidity is high and the quantitativeness of the powder transfer is good. The D50 particle size of the granulated particles can be calculated from the particle size distribution by the sieving method or the laser diffraction / scattering method, and the D50 particle size can be adjusted within the above range by classification using a sieve or the like.

The granulated silica powder has an angle of repose of 20 degrees or more and 35 degrees or less, preferably 25 degrees or more, and preferably 30 degrees or less.
By setting the angle of repose of the granulated silica powder within the above range, the fluidity is high and the quantitativeness of the powder transfer is good. As a method for measuring the angle of repose, a cylindrical rotation method angle of repose measuring device (manufactured by Tsutsui Rikagaku Kikai Co., Ltd.) can be used. The method for adjusting the angle of repose is not particularly limited, but the angle of repose can be adjusted within the above range by granulating by the spray granulation method using the raw materials having a specific particle size described in the present specification. ..

The granulated silica powder has a specific surface area of 0.3 m ² / g or more and 10 m ² / g or less, preferably 0.5 m ² / g or more, and preferably 3 m ² / g or less.
By setting the specific surface area of the granulated silica powder within the above range, a highly uniform molded body in which the generation of bubbles is suppressed can be obtained. The specific surface area can be measured with a mercury porosimeter, and the specific surface area is adjusted within the above range by granulating the granulated silica powder by the spray granulation method using the raw materials having the particle size described below. can do.

The granulated silica powder of the present embodiment is agglomerated particles granulated from silica fine particles, and is agglomerated particles containing 15% or more and 40% or less of particles having a particle size of 10 μm or less, and 20% of particles having a particle size of 10 μm or less. It is preferable to include the above, and it is preferable to include 30% or less.
When the granulated silica powder contains particles having a particle diameter of 10 μm or less in the above range, the fine particles can be appropriately used as a binder at the time of firing, and the strength of the granulated molded product can be improved, and the granulated silica powder can be used. The pore diameter and pore volume are appropriate values. Further, regarding the removal of silanol that causes bubbles existing in the molded body, the finer the particles, the faster the silanol removal rate, which is advantageous in reducing the silanol concentration of the granulated product.

The amount of particles having a particle diameter of 10 μm or less in the granulated silica powder can be determined by a sieve or a laser diffraction / scattering method before granulation, and the method after granulation. Is not limited, and it can be measured by crushing the granulated powder to the extent that the original silica is not crushed by using ultrasonic waves or the like, and measuring the particle size distribution by SEM observation or laser diffraction scattering method. If this is particularly simple, the particles may be appropriately embedded and cut, and the proportion of particles having a size of 10 μm or less may be estimated based on the particles.

The granulated silica powder of the present embodiment preferably has a silanol concentration of 200 ppm or less, more preferably 100 ppm or less. By setting the silanol concentration in the above range, the amount of water vapor generated from the silanol during melting is reduced, and the generation of water vapor-derived bubbles in the glass molded product is suppressed, which is preferable. The silanol concentration can be measured by an infrared spectrophotometer.
Further, the granulated silica powder preferably has an adsorbed water content of 1% or less, more preferably 0.1% or less. By setting the amount of adsorbed water in the above range, the generation of bubbles derived from water vapor is suppressed in the glass molded product as in silanol, which is preferable. The amount of adsorbed water can be measured with an infrared moisture meter.
The silanol concentration and the amount of adsorbed water can be set in a desired range by adjusting the firing temperature and the firing time in the production of the granulated silica powder.

The granulated silica powder preferably has an Fe content of 1 ppm or less, an Al content of 0.1 ppm or less, and a Ti content of 0.01 ppm or less. Such a low metal content makes silica powder suitable for manufacturing semiconductor jigs and optical fibers, which is preferable. The metal content can be measured by inductively coupled plasma mass spectrometry (ICP-MS) after dissolving the granulated silica powder with hydrofluoric acid.

Further, the granulated silica powder preferably has an average pore diameter of 1 μm or more and 10 μm.
It is more preferably μm or more and 7 μm. Further, the average pore volume is preferably 0.15 cc / g or more and 0.35 cc / g or less, and more preferably 0.2 cc / g or more and 0.3 cc / g or less. When the average pore diameter and the average pore volume are in the above ranges, a highly uniform molded body in which the generation of bubbles is suppressed can be obtained, which is preferable. The average pore diameter and average pore volume can be measured with a mercury porosimeter.

The granulated silica powder needs to have a breaking strength that does not disintegrate due to handling, but if the strength is too high, gas release during melting becomes poor. Therefore, it is preferably 0.5 MPa or more and 10 MPa or less, and more preferably 1 MPa or more and 5 MPa or less. Fracture strength can be measured with a microcompression tester.

The method for producing the granulated silica powder of this embodiment will be described below. The method for producing the granulated silica powder is another embodiment of the present invention.
Another embodiment of the present invention includes a preparation step of preparing a raw material silica powder obtained by a sol-gel method containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less, and slurries the raw material silica powder into a binder. It is a method for producing a granulated silica powder including a granulation step of adding and spraying granulation, and a firing step of firing the obtained granulated particles at 1000 ° C. or higher and 1300 ° C. or lower.

<Preparation step>
The preparation step is a step of preparing a raw material silica powder obtained by a sol-gel method containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less. Silica powder produced by the sol-gel method tends to have high purity and an appropriate particle size. Therefore, it has a low metal content and is preferable as a raw material for semiconductors. In addition, it is excellent in dispersibility in slurry preparation in the granulation step described later.

Further, by including the fine particles having a particle diameter of 10 μm or less in the above ratio, the fine particles appropriately serve as a binder, and the pore diameter and the pore volume of the granulated silica powder become appropriate values. Further, since the silanol removal that causes bubbles existing in the molded body can be removed, the strength of the granulated molded body can be improved.
As the sol-gel method, a known method can be used, and from the viewpoint of purity, it is preferable to hydrolyze tetramethoxysilane or tetraethoxysilane as a Si source.

<Granulation step>
The granulation step is a step in which raw material silica is slurried, a binder is added, and spray granulation is performed. By granulation, the obtained granulated silica powder can be sphericalized, and by adopting this method, contamination can be suppressed.

The solvent for slurrying is usually water, but the solvent is not limited to this as long as it can be used as a dispersion medium for granulation. The viscosity of the slurry is not particularly limited. Further, a binder may be added at the time of preparing the slurry. The binder is suitable for a substance that does not remain in the final granulated silica powder, and an organic binder that can be decomposed and removed by combustion by firing after granulation is preferable. Examples of the organic binder include natural polymers, semi-synthetic polymers, and synthetic polymers. From the viewpoint of purity, synthetic polymers such as acrylic polymers, polyacrylamide, polyvinylpyrrolidone, and polyvinyl alcohol are preferable, and polyvinylpyrrolidone is particularly preferable. When the binder is used, it is usually used in a ratio of 3 parts by weight or more to 10 parts by weight with respect to 100 parts by weight of the raw material silica.
The spraying may be a known spray (sprayer) and is not particularly limited.
The granulated silica granulated in the granulation step may be dried.

<Baking step>
The firing step is a step of firing the obtained granulated particles at 1000 ° C. or higher and 1300 ° C. or lower. If the firing temperature is low, the strength of the granulated product is low, and if the temperature is too high, the granulated powders stick to each other, which is not preferable. The firing temperature is preferably 1100 ° C. or higher, preferably 1250 ° C. or lower. The firing time has an influence on the strength, and the firing time is usually 10 hours or more and 100 hours or less, preferably 30 hours or more, preferably 60 hours or less.
The atmosphere at the time of firing is not particularly limited, but it is preferable to create a dry air atmosphere. The dry air preferably has a dew point of −40 ° C. or lower.

The granulated silica powder is melted by a known method such as the Bernui method or the plasma spraying method to form a glass molded body. Further, the melting conditions and the like at this time are not particularly limited.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

<Example>
(1) Preparation of raw material silica powder TMOS (tetramethoxysilane) and water having a molar ratio of 6 times that of TMOS (tetramethoxysilane) are added to a horizontal cylindrical reactor with a jacket having a ribbon-type stirring blade, and warm water at 50 ° C. is passed through the jacket to TMOS. Was hydrolyzed and the produced wet gel was extracted. The extracted wet gel was pulverized using a high-speed rotary mill type pulverizer (Comil manufactured by Quadro) having a pore diameter of 1 mm, and then the pulverized product was dried at 150 ° C. to obtain a dried silica gel powder. This powder was classified by a sieve having an opening of 125 μm, and the powder under the sieve was further classified by using a sieve having a fine opening to obtain a raw material silica powder. Two types of raw material silica powders, A and B, were prepared, and the particle size distributions of the powders were shown in FIGS. 1A and 1B. The proportion of particles having a particle size of 10 μm or less was 25% for A and 35% for B. ..

(2) Granulation The raw material silica powder prepared in (1) above was dispersed in water to prepare a slurry having 30% by weight of the raw material silica. Further, as a granulation binder, 5 parts by weight of polyvinylpyrrolidone was added to 100 parts by weight of the raw material silica powder. The slurry was spray-dried at a drying gas temperature of 150 ° C. using a spray dryer (manufactured by Pris) to obtain granulated particles. The granulated particles were heated at 1220 ° C. for 40 hours in an air (dew point −68 ° C.) atmosphere to obtain granulated silica powder. The physical characteristics of the obtained granulated silica powder were measured as follows.

<Particle size distribution>
FIG. 2 shows the results of measuring the particle size of the obtained granulated silica powder by sieving. The particle sizes of the granulated silica powders A and B produced from the raw material silica powders A and B were the same. The D50 particle size (median diameter) was 130 μm as shown in the figure.
For this D50 particle size (median diameter), a JIS standard sieve made of stainless steel was used, and a sieve having a mesh size of 45, 75, 106, 125, 150, 212, and 250 μm was used in order, and the passing weight was measured and passed. The cumulative weight was graphed by Excel, a smooth line was drawn, and the point at which the cumulative% was 50% was obtained using this.

<SEM image>
FIG. 3 shows an SEM image of the obtained granulated silica powder. It can be seen that the particles are spherical (A), and when expanded, small particles are present in the gaps between the large particles (B).
<Angle of repose>
As a result of measuring the angle of repose of the obtained granulated silica powder with a cylindrical rotation method angle of repose measuring device (manufactured by Tsutsui Rikagaku Kikai Co., Ltd.), both the granulated silica powders A and B were 28 degrees.

<Specific surface area>
As a result of measuring the specific surface area of the obtained granulated silica powder with a mercury porosimeter, the specific surface area was 0.68 m ^{2 / g for A, 2.2 m 2 /} g for B, and the pore volume was 0.25 cc for A. / G and B were 0.29. The pore diameters of both A and B were 3.7 μm.
<Hardness>
The measurement result of the breaking strength of the obtained granulated silica powder was 1.4 MPa for both A and B, and the hardness was sufficient for normal handling.
<Impurity concentration>
The concentrations of Fe, Al and Ti were measured by ICP-MS. As a result, the concentrations of the granulated silica powder A were 0.68, 0.04, <0.01 ppm in the order of Fe, Al, and Ti, and similarly, the granulated silica powder B was 0.55, 0.07. It was <0.01 ppm.

(3) Production of molded body A glass ingot was produced using the obtained granulated silica powder by a Verneuil method (oxyhydrogen flame melting method) apparatus shown in FIG. 4 in a schematic diagram. A photograph of the molten ingot (thumb size) is shown in FIG. Several bubbles were generated in both the granulated silica powders A and B, but they were well within the permissible range.

<Comparison example>
The silica gel powder on the 125 μm sieve of Example (1) was calcined at 1220 ° C. for 40 hours in the same manner as in Example, and further sieved with a 212 μm sieve to obtain the silica gel powder under the sieve. The D50 of the powder was consistent with the granulated powder of the example. The specific surface area was less than 0.1 m ² / g, and the pore volume was less than 0.01 cc / g. The SEM image is shown in FIG. 6, but the particles were crushed, and the fine particle agglomeration structure as shown in FIG. 3 of the granulated particles was not found.
The angle of repose of this silica powder was measured and found to be 37 degrees.
An attempt was made to fabricate a glass ingot using the same Verneuil method as in the examples, but the piping after the powder pool was clogged and the powder did not flow smoothly.

1 Powder hopper 2 Powder pool 3 Vibrator 4 Nozzle cushion 5 Quartz nozzle 6 Heat-resistant brick 7 Ingot 8 Supporting rotary rod 9 Motor 10 Elevating stage

Claims (6)

A granulated silica powder with a D50 particle size (median diameter) of 75 μm or more and 200 μm or less, an angle of repose of 20 degrees or more and 35 degrees or less, and a specific surface area of 0.3 m ² / g or more and 10 m ² / g or less. There,
The granulated silica powder is an aggregated silica powder containing 15% or more and 40% or less of particles having a particle diameter of 10 μm or less. The granulated silica powder according to claim 1, wherein the silanol concentration is 200 ppm or less and the adsorbed water content is 1% or less. The granulated silica powder according to claim 1 or 2, wherein the Fe content is 1 ppm or less, the Al content is 0.1 ppm or less, and the Ti content is 0.01 ppm or less. The granulated silica powder according to any one of claims 1 to 3, wherein the average pore diameter is 1 μm or more and 10 μm or less. Preparation step for preparing raw material silica obtained by the sol-gel method, which contains 15% or more and 40% or less of particles having a particle diameter of 10 μm or less.
A method for producing granulated silica powder, which comprises a granulation step in which raw material silica is slurried, a binder is added, and spray granulation is performed, and a firing step in which the obtained granulated particles are calcined at 1000 ° C. or higher and 1300 ° C. or lower. The method for producing granulated silica powder according to claim 5, wherein in the granulation step, the medium used for slurrying is water and the binder is polyvinylpyrrolidone.

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