Increase in silicon content in the preparation of quartz glass

Patent metadata

Field	Value
Publication number	US-11952303-B2
Application number	US-201616062387-A
Country	US
Kind code	B2
Filing date	Dec 16, 2016
Priority date	Dec 18, 2015
Publication date	Apr 9, 2024
Grant date	Apr 9, 2024

Abstract

A quartz glass body and a process for the preparation of a quartz glass body is disclosed. One process includes providing a silicon dioxide granulate from a pyrogenic silicon dioxide powder, making a glass melt out of the silicon dioxide granulate and making a quartz glass body out of at least part of the glass melt. In at least one process a silicon component different from silicon dioxide is added. A quartz glass body is obtainable by this process. A light guide, an illuminant and a formed body, are each obtainable by further processing of the quartz glass body.

First claim

The invention claimed is:

1. A process for the preparation of a quartz glass body comprising:
providing a silicon dioxide granulate, wherein this provision comprises:
providing a pyrogenic silicon dioxide powder; and
processing the silicon dioxide powder to obtain a silicon dioxide granulate, wherein the silicon dioxide granulate has a greater particle diameter than the silicon dioxide powder, wherein the processing of the silicon dioxide powder comprises one of spray granulation, centrifugal pulverisation, fluidized bed granulation and roll granulation and wherein the BET surface area of the silicon dioxide granulate is in a range from 25-35 m 2 /g and wherein the silicon dioxide granulate has a particle size distribution D 10 in the range from 50 to 150 μm and D 50 in the range from 150 to 300 μm;

continuously making a glass melt out of the silicon dioxide granulate in a continuous melting process; and
making a quartz glass body out of at least part of the glass melt;

wherein processing the silicon dioxide powder to obtain a silicon dioxide granulate includes adding elemental silicon in order to limit the OH content of the quartz glass body in the continuous melting process to less than 500 ppm.

2. The process according to claim 1 , wherein in the processing of the silicon dioxide powder, the silicon dioxide granulate is formed with granules, wherein the granules have a spherical morphology, wherein the processing comprises a spray granulation or a roll granulation.

3. The process according to claim 1 , wherein the elemental silicon is silicon, a silicon-hydrogen compound, a silicon-oxygen compound or a silicon-hydrogen-oxygen compound.

4. The process according to claim 1 , wherein the elemental silicon is added as powder.

5. The process according to claim 1 , wherein the addition of the elemental silicon takes place in processing the silicon dioxide powder.

6. The process according to claim 1 , wherein the elemental silicon is added as liquid or as gas.

7. The process according to claim 1 , wherein a quantity of 10 to 100,000 ppm of a silicon component is added, the ppm being based on the total weight of silicon dioxide.

8. The process according to claim 1 , wherein the glass melt is made in a melting crucible, wherein the melting crucible has at least one inlet and at least one outlet.

9. The process according to claim 1 , wherein the silicon dioxide granulate comprises at least one of the following:
a mean particle size in a range from 50 to 500 μm;
a bulk density in a range from 0.5 to 1.2 g/cm 3 ;
a carbon content of less than 50 ppm;
an aluminium content of less than 200 ppb;
a tamped density in a range from 0.7 to 1.3 g/cm 3 ;
a pore volume in a range from 0.1 to 2.5 mL/g;
an angle of repose in a range from 23 to 26°;
a particle size distribution D 10 in a range from 50 to 150 μm;
a particle size distribution D 50 in a range from 150 to 300 μm; and
a particle size distribution D 90 in a range from 250 to 620 μm,

wherein the wt.-%, ppm and ppb are each based on the total weight of the silicon dioxide granulate.

10. The process according to claim 1 , comprising:
providing a liquid;
mixing the silicon dioxide powder and optionally the silicon component with the liquid to obtain a slurry; and
spray drying the slurry to obtain the silicon dioxide granulate.

11. The process according to claim 10 , wherein the spray drying takes place through the spraying of the slurry through a nozzle into a spray tower and comprises at least one of the following:
spray granulation in the spray tower;
the presence of a pressure of the slurry at the nozzle of not more than 40 bar, in a range from 1.3 to 20 bar, wherein the pressure is given in absolute terms (relative to p=0 hPa);
a temperature of the droplets upon entering into the spray tower in a range from 10 to 50° C.;
a temperature at the side of the nozzle directed towards the spray tower in a range from 100 to 450° C.;
a throughput of slurry through the nozzle in a range from 0.05 to 1 m 3 /h;
a solids content of the slurry of at least 40 wt.-%, in a range from 50 to 80 wt.-%;
based on the total weight of the slurry;
a gas inflow into the spray tower in a range from 10 to 100 kg/min;
a temperature of the gas flow upon entering into the spray tower in a range from 100 to 450° C.;
a temperature of the gas flow at the exit out of the spray tower of less than 170° C.;
the gas is selected from the group consisting of air, nitrogen and helium, or a combination of two or more thereof;
a residual moisture content of the granulate on removal out of the spray tower of less than 5 wt.-%, in each case based on the total weight of the silicon dioxide granulate created in the spray drying;
at least 50 wt.-% of the spray granulate, based on the total weight of the silicon dioxide granulate created in the spray drying, completes a flight time in a range from 1 to 100 s;
at least 50 wt.-% of the spray granulate, based on the total weight of the silicon dioxide granulate created in the spray drying, covers a flight path of more than 20 m;
the spray tower has a cylindrical geometry;
a height of the spray tower of more than 10 m;
screening out of particles with a size of less than 90 μm before the removal of the granulate from the spray tower;
sieving out of particles with a size of more than 500 μm after the removal of the granulate from the spray tower; and
the exit of the droplets of the slurry out of the nozzle occurs at an angle of 30 to 60 degrees from vertical.

12. The process according to claim 1 , wherein the melting energy is transferred to the silicon dioxide granulate via a solid surface.

13. The process according to claim 1 , wherein the silicon dioxide powder can be prepared from a compound selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.

14. The process according to claim 1 , wherein the silicon dioxide powder comprises at least one of the following:
a BET surface area in a range from 20 to 60 m 2 /g;
a bulk density in a range from 0.01 to 0.3 g/cm 3 ;
a carbon content of less than 50 ppm;
a chlorine content of less than 200 ppm;
an aluminium content of less than 200 ppb;
a total metal content of metals different to aluminium of less than 1,000 ppb;
at least 70 wt.-% of the powder particles have a primary particle size in a range from 10 to 100 nm;
a tamped density in a range from 0.001 to 0.3 g/cm 3 ;
a residual moisture content of less than 5 wt.-%;
a particle size distribution D 10 in the range from 1 to 7 μm;
a particle size distribution D 50 in the range from 6 to 15 μm; and
a particle size distribution D 90 in the range from 10 to 40 μm;

wherein the wt.-%, ppm and ppb are each based on the total weight of the silicon dioxide powder.

15. The process according to claim 1 , comprising the following:
making a hollow body with at least one opening out of the quartz glass body.

16. A quartz glass body obtainable by a process according to claim 1 .

17. The process of forming the quartz glass body according to claim 1 , wherein the quartz glass body has at least one of the following features:
a chlorine content of less than 200 ppm;
an aluminium content of less than 200 ppb;
an ODC content of less than 5*10 15 /cm 3 ;
a metal content of metals different from aluminium of less than 1 ppm;
a viscosity (p=1013 hPa) in a range from log 10 (η (1250° C.)/dPas)=11.4 to log 10 (η (1250° C.)/dPas)=12.9 or log 10 (η (1300° C.)/dPas)=11.1 to log 10 (η (1300° C.)/dPas)=12.2 or log 10 (η

Assignees

• Heraeus Quarzglas

Inventors

• Whippey Nigel Robert
• Göbel Marcus Constantin
• Gromann Boris
• Scheich Gerrit

Classifications

• C03B20/00 Primary

  Processes specially adapted for the production of quartz or fused silica articles {, not otherwise provided for (C03B19/01, C03B19/066, C03B19/106, C03B19/12, C03B19/14, C03B37/00 take precedence)} · CPC title

• B01J2/04

  in a gaseous medium {(if combined with suspending the material in a gas, e.g. fluidised beds B01J2/16)} · CPC title

• C03B5/08

  Glass-melting pots · CPC title

• C03B17/04 Primary

  Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles · CPC title

• C03B19/106

  by chemical vapour deposition; by liquid phase reaction · CPC title