Synthetic amorphous silica powder and process for manufacturing same

Patent metadata

Field	Value
Publication number	US-9745201-B2
Application number	US-201415113570-A
Country	US
Kind code	B2
Filing date	Dec 10, 2014
Priority date	Jan 29, 2014
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

The purpose of the present invention is to provide: a synthetic amorphous silica powder which is suitable as a raw material for a synthetic silica glass product used in a high-temperature and reduced-pressure environment, which can yield a synthetic silica product such that the occurrence or expansion of air bubbles in the glass product is inhibited even in use in a high-temperature and reduced-pressure environment, and which can be obtained at a relatively low cost; and a process for manufacturing the same.

First claim

The invention claimed is:

1. A synthetic amorphous silica powder obtained by subjecting silica as a raw material to granulation and firing,
wherein a particle diameter D v50 at a cumulative frequency of 50% in a volume-based particle size distribution is 72 μm or more and 509 μm or less,
a cumulative frequency of particles having volume-based diameters of 45 μm or less is 1.8% or less,
a value obtained by dividing a difference between a particle diameter D v90 at a cumulative frequency of 90% in a volume-based particle size distribution and a particle diameter D v10 at a cumulative frequency of 10% in a volume-based particle size distribution by a particle diameter D v50 at a cumulative frequency of 50% in a volume-based particle size distribution is 0.79 or more and 1.40 or less,
F NL /F NS which is a ratio of a frequency F NL of a frequency peak in a number particle size distribution existing at a neighbor of the particle diameter D v50 at a cumulative frequency of 50% in a volume-based particle size distribution, and a frequency F NS of a frequency peak in a number-based particle size distribution existing at a particle diameter of 30 μm or less is 0.3 or more, and
a bulk density is 0.75 g/cm 3 or more and 1.5 g/cm 3 or less.

2. The synthetic amorphous silica powder according to claim 1 , wherein fumed silica having a specific surface area of 50 to 200 m 2 /g is used as a raw material, a concentration of carbon is less than 2 ppm, a concentration of a hydroxyl group is less than 70 ppm, and a concentration of chlorine is less than 2 ppm.

3. A process for manufacturing a synthetic amorphous silica powder which comprises:
a granulation step of forming a siliceous slurry and obtaining silica powder having a particle diameter D v50 at a cumulative frequency of 50% in the volume-based particle size distribution of 100 to 700 μm from the siliceous slurry,
a step of subjecting the silica powder obtained in the granulation step to a primary firing at a temperature of 900 to 1200° C.,
a step of subjecting the silica powder after the primary firing to pulverization and a secondary firing at a temperature of 1100 to 1400° C.,
a step of subjecting the silica powder after the secondary firing to pulverization and washing with a ultrasonic wave or washing by using a fluorine-based inert liquid, and
a step of subjecting the silica powder after washing to solid-liquid separation using a sieve having openings of 35 to 95 μm and drying
to obtain a synthetic amorphous silica powder having a particle diameter D v50 at a cumulative frequency of 50% in the volume-based particle size distribution of 72 μm or more and 509 μm or less, a cumulative frequency of particles having volume-based diameters of 45 μm or less of 1.8% or less, a value obtained by dividing a difference between a particle diameter D v90 at a cumulative frequency of 90% in a volume-based particle size distribution and a particle diameter D v10 at a cumulative frequency of 10% in a volume-based particle size distribution by a particle diameter D v50 at a cumulative frequency of 50% in a volume-based particle size distribution of 0.79 or more and 1.40 or less, F NL /F NS which is a ratio of a frequency F NL of a frequency peak in a number-based particle size distribution existing at a neighbor of the particle diameter D v50 at a cumulative frequency of 50% in a volume-based particle size distribution, and a frequency F NS of a frequency peak in a number-based particle size distribution existing at a particle diameter of 30 μm or less of 0.3 or more and a bulk density of 0.75 g/cm 3 or more and 1.5 g/cm 3 or less.

4. The process for manufacturing a synthetic amorphous silica powder according to claim 3 , wherein the granulation step is a step which comprises hydrolyzing silicon tetrachloride to form a siliceous slurry, drying the siliceous slurry to make a dry powder, and classifying the dry powder after pulverization or without pulverization.

5. The process for manufacturing a synthetic amorphous silica powder according to claim 3 , wherein the granulation step is a step which comprises hydrolyzing an organic silicon compound to form a siliceous slurry, drying the siliceous slurry to make a dry powder, and classifying the dry powder after pulverization or without pulverization.

6. The process for manufacturing a synthetic amorphous silica powder according to claim 3 , wherein the granulation step is a step which comprises forming a siliceous slurry by using fumed silica, drying the siliceous slurry to make a dry powder, and classifying the dry powder after pulverization or without pulverization.

Assignees

• Mitsubishi Materials Corp

Inventors

• Ueda Toshiaki

Classifications

• C01P2002/02

  Amorphous compounds · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C01P2006/10

  Solid density · CPC title

• C01B33/18 Primary

  Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof (preparation of aerogels by dehydrating gels C01B33/158; treatment to enhance the pigmenting or filling properties C09C) · CPC title

• C01P2006/12

  Surface area · CPC title