Preparation of a quartz glass body in a multi-chamber oven

Patent metadata

Field	Value
Publication number	US-2019062193-A1
Application number	US-201616061929-A
Country	US
Kind code	A1
Filing date	Dec 16, 2016
Priority date	Dec 18, 2015
Publication date	Feb 28, 2019
Grant date	—

Abstract

The invention relates to a process for the preparation of a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m2/g, ii.) Making a glass melt out of silicon dioxide granulate in an oven and iii.) Making a quartz glass body out of at least part of the glass melt, wherein the oven has at least a first and a further chamber connected to one another via a passage, wherein the temperature in the first chamber is lower than the temperature in the further chambers. The invention further relates to a quartz glass body which is obtainable by this process. The invention further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

First claim

1 . A process for the preparation of a quartz glass body comprising the process steps:
i) Providing a silicon dioxide granulate
wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has the following feature;
A) A BET surface area in a range from 20 to 40 m 2 /g
ii) Making a glass melt out of the silicon dioxide granulate in an oven; iii) Making a quartz glass body out of at least part of the glass melt; wherein the oven has at least a first and a further chamber connected to one another by a passage,
Wherein the first and further chambers are at different temperatures;
Wherein the temperature in the first chamber is lower than the temperature in the further chamber

2 . The process according to claim 1 , wherein there is an additive in the first chamber selected from the group consisting of halogens, inert gas, base, oxygen or a combination of two or more of them.

3 . The process according to claim 2 , wherein the halogen is selected from the group consisting of chlorine, fluorine, compounds containing chlorine, compounds containing fluorine and a combination of two or more thereof, and wherein the inert gas is selected from the group consisting of nitrogen, helium and a combination of the two.

4 . The process according to one of the preceding claims wherein in the first chamber there is a pressure of less than 500 mbar.

5 . The process according to one of the preceding claims, wherein the silicon dioxide granulate has at least one of the following features:
B) a mean particle size in a range from 50 to 500 μm C) a bulk density in a range from 0.5 to 1.2 g/cm 3 ; D) a carbon content of less than 10 ppm; E) an aluminium content of less than 200 ppb; F) a tamped density in a range from 0.7 to 1.2 g/cm 3 ; G) a pore volume in a range from 0.1 to 2.5 mL/g; H) an angle of repose in a range from 23 to 26° I) a particle size distribution D 10 in a range from 50 to 150 μm; J) a particle size distribution D 50 in a range from 150 to 300 μm; K) a particle size distribution D 90 in a range from 250 to 620 μm;
wherein the ppm and ppb are each based on the total weight of the silicon dioxide powder.

6 . The process according to one of the preceding claims, wherein the silicon dioxide is transported from the first to the further chamber as granulate.

7 . The process according to one of the preceding claims, wherein the first chamber comprises at least one element selected from the group consisting of quartz glass, a refractory metal, aluminium and a combination of two or more of them.

8 . The process according to one of the preceding claims, wherein the further chamber is a crucible of a metal sheet or a sinter material containing a sinter metal, wherein the metal sheet or the sinter metal is selected from the group consisting of molybdenum, tungsten and a combination of them.

9 . The process according to one of the preceding claims, wherein the BET surface area before step ii) is not reduced to less than 5 m 2 /g.

10 . The process according to one of the preceding claims, wherein the melt energy is transmitted to the silicon dioxide granulate via a solid surface.

11 . The process according to one of the preceding claims, wherein hydrogen, helium, nitrogen or a combination of two or more of them is present in the gas space of the oven.

12 . The process according to one of the preceding claims, wherein providing the silicon dioxide granulate comprises the following process steps:
I Providing silicon dioxide powder with the following characteristics:
a) a BET surface area in a range from 20 to 60 m 2 /g;
b) a bulk density in a range from 0.01 to 0.3 g/cm 3 .
II Processing the silicon dioxide powder to obtain a silicon dioxide granulate wherein the silicon dioxide granulate has a larger particle size than the silicon dioxide powder:

13 . The process according to claim 12 , wherein the silicon dioxide powder in step I. has at least one of the following features:
c. a carbon content of less than 50 ppm d. a chlorine content of less than 200 ppm; e. an aluminium content of less than 200 ppb; f. a total content of metals which are different from aluminium of less than 5 ppm; g. at least 70 wt.-% of the powder particles have a primary particle size in a range from 10 to 100 nm; h. a tamped density in a range from 0.001 to 1.3 g/cm 3 ; i. a residual moisture content of less than 5 wt.-%; j. a particle size distribution D 10 in the range from 1 to 7 μm; k. a particle size distribution D 50 in the range from 6 to 15 μm; l. a particle size distribution D 90 in the range from 10 to 40 μm; wherein the wt.-%, the ppm and the ppb are each based on the total weight of the silicon dioxide powder.

14 . The process according to one of the preceding claims, wherein the silicon dioxide powder can be made from an element selected from the group consisting of siloxanes, silicon alkoxides and silicon halides.

15 . The process according to one of the preceding claims, comprising the following process step:
iv) Forming a hollow body with at least one opening from the quartz glass body.

16 . A quartz glass body obtainable by a process according to one of the claims 1 to 15 .

17 . The quartz glass body according to claim 16 , at having at least one of the following features:
A] an OH content of less than 500 ppm; B] a chlorine content of less than 60 ppm; C] an aluminium content of less than 200 ppb; D] an ODC content of less than 5*10 15 /cm 3 ; E] a metal content of metals different from aluminium of less than 1 ppm; F] 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 (q (1350° C.)/dPas)=10.5 to log 10 (η (1350° C.)/dPas)=11.5; G] a standard deviation of the OH content of not more than 10%, based on the OH-content A] of the quartz glass body; H] a standard deviation of the Cl content of not more than 10%, based on the Cl content B] of the quartz glass body; I] a standard deviation of the Al content of not more than 10%, based on the Al content C] of the quartz glass body; J] a refractive index homogeneity of less than 10 4 ; K] a cylindrical form; L] a tungsten content of less than 1000 ppb; M] a molybdenum content of less than 1000 ppb, wherein the ppb and ppm are each based on the total mass of the quartz glass body.

18 . A process for the preparation of a light guide comprising the following steps:
A/ Providing:
A1/ a hollow body with at least one opening obtainable by a process according to claim 15 , or
A2/ a quartz glass body according to one of the claim 16 or 17 , wherein the quartz glass body is first processed to obtain a hollow body with at least two openings;
B/ Introducing one or multiple core rods into the quartz glass body through the at least one opening to obtain a precursor; C/ Drawing the precursor from step B/ in the warm to obtain the light guide with one or multiple cores and a jacket M 1 .

19 . A process for the preparation of an illuminant comprising the following steps
(i) Providing
(i-1) a hollow body with at least one opening obtainable by a process according to claim 15 ; or
(i-2) a quartz glass body according to one of the claim 16 or 17 , wherein the quartz glass body is first processed to obtain a hollow body;
(ii) Optionally fitting the hollow body with electrodes; (iii) Filling the hollow body with a gas.

Assignees

• Heraeus Quarzglas

Inventors

• Otter Matthias
• Lehmann Walter
• Hünermann Michael
• Nielsen Nils Christian
• Whippey Nigel Robert
• Gromann Boris
• Kpebane Abdoul-Gafar
• Söhn Matthias

Classifications

• C03C2201/40

  containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn · CPC title

• C03C2201/11

  containing chlorine · CPC title

• C03C2201/32

  containing aluminium (C03C2201/36 takes precedence) · CPC title

• C03B17/04

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

• C03B37/01211

  by inserting one or more rods or tubes into a tube · CPC title